Mutagenesis, Vol. 14, No. 2, 153-172,
March 1999
© 1999 UK Environmental Mutagen Society/Oxford University Press
Review |
Modulation of genotoxic and related effects by carotenoids and vitamin A in experimental models: mechanistic issues
1 Department of Health Sciences, Section of Hygiene and Preventive Medicine, University of Genoa, via A.Pastore 1, I-16132 Genoa, Italy and 2 International Agency for Research on Cancer, Lyon, France
 |
Abstract |
|---|
 Top Abstract IntroductionMethodological approachAnalysis of the database...Concluding remarksReferences |
|---|
The mechanisms involved in the modulation of genotoxic and related effects by carotenoids and vitamin A were inferred from a critical review of an ad hoc constructed database. Almost 500 results were generated in experimental models evaluating the activity of 32 structurally, metabolically and functionally related nutrients, including ß-carotene and 26 other carotenoids, retinol, retinal, all-trans-retinoic acid and retinyl esters. As many as 67 experimental test systems, either in vitro or in vivo, used a variety of cellular targets and/or end-points suggestive of distinctive mechanisms of action. The bulk of available data support the view that carotenoids and vitamin A do not induce genotoxic effects per se. Even in the absence of any genotoxic agent, these nutrients appeared, on the contrary, to display some mechanisms which play protective roles in tumor promotion and progression, such as inhibition of N-myc gene expression resulting in antiproliferative effects, up-regulation of cell-to-cell communication, an increase in connexin 43 gene expression, a decrease in the `spontaneous' cell transformation frequency and induction of differentiation in vitro. A large number of studies investigated the modulation by carotenoids and vitamin A of genotoxic and related effects produced by 69 genotoxicants, including biological agents, physical agents, chemical compounds and complex mixtures. In spite of some discrepant data, the general trend was that both carotenoids and vitamin A are poorly effective in acting as nucleophiles, nor do they appear to substantially interfere with the induction or repair of DNA damage produced by direct-acting agents. In contrast, vitamin A and carotenoids, irrespective of their provitamin A role, in most studies inhibited those genotoxicants which require metabolic activation to electrophilic derivatives in either bacterial or mammalian cells. Coupled with biochemical data, the distinctive patterns observed with genotoxic agents belonging to different chemical classes suggest a complex modulation of both phase I and phase II enzymes involved in the metabolism of xenobiotics. Furthermore, carotenoids and vitamin A shared other protective mechanisms, such as scavenging of genotoxic oxygen species, modulation of signal transduction pathways, inhibition of cell transformation induced by physical and chemical agents, and facilitation of intercellular communication inhibited by genotoxic compounds. Therefore, carotenoids and vitamin A appear to work via multiple mechanisms, which would support a potential protective role in cancer initiation and in the pathogenesis of other mutation-related diseases. These conclusions are consistent with the recognized cancerpreventive activity of these nutrients in certain animal models and with the evidence provided by observational epidemiological studies, which suggested cancer-protective effects at many sites as related to their dietary intake or plasma levels. However, all these lines of evidence and mechanistically based premises contrast with the unexpected outcome of recent clinical intervention trials, which raised the concern that supplemental use of ß-carotene and vitamin A may increase the risk of lung cancer amongst high risk individuals such as tobacco smokers and asbestos-exposed workers.
|
Introduction |
|---|
|
TopAbstractIntroductionMethodological approachAnalysis of the database...Concluding remarksReferences |
|---|
Vitamin A is an essential nutrient for humans and other vertebrates (Olson, 1994
). Dietary sources of vitamin A are provided either by retinol esters, which are present in foods of animal origin and are hydrolyzed in the intestine to form retinol, or by plant carotenoids. More than 600 carotenoids have been identified in nature, of which 50–60 possess provitamin A properties and ~10 have nutritional relevance (Pfander, 1987). In addition to natural sources, vitamin A and carotenoids are produced synthetically for pharmaceutical and cosmetic uses (IARC, 1998a,b). Provitamin A carotenoids may be converted by central cleavage through a 15,15'-dioxygenase present in the intestinal mucosa to yield one or two molecules of retinaldehyde (retinal), which is then reduced by an aldehyde reductase to retinol. Retinoic acid may be formed by eccentric cleavage of such carotenoids as ß-carotene (Olson, 1983; Blaner and Olson, 1994). A central feature of vitamin A physiology is the strong mechanism of homeostatic control of the circulating concentrations of retinol in blood across a broad range of intake of preformed vitamin A and provitamin A. Circulating retinol concentrations remain fairly constant until liver reserves fall to very low levels. This is in contrast to concentrations of carotenoids in blood, which are mainly determined by the levels of carotenoids in the diet.
The antigenotoxic and anticarcinogenic effects of carotenoids or vitamin A have been reviewed (Krinsky, 1993a,b, 1994; Odin, 1997) and they have recently been evaluated in IARC Handbooks of Cancer Prevention (IARC, 1998a,b). Antimutagenicity profiles have also been prepared with compounds falling within this functional family (Waters et al., 1990, 1996a,Waters et al., b; Brockman et al., 1992). The purpose of the present article was to provide an up-to-date and comprehensive overview of the literature covering these nutrients as modulators of genotoxic and related effects, as investigated during the last 20 years using a large variety of in vitro and in vivo test systems. Experimental models are very useful to predict both safety and efficacy of putative chemopreventive agents. Even more, they provide essential tools for understanding their mechanisms of action. Therefore, the database we constructed not only provides quite an extensive compilation of literature results, but its critical analysis is also a valuable source of information on the possible modes of action of carotenoids and vitamin A. Virtually every step involved in mutagenesis and carcinogenesis can be modulated exogenously and, in principle, a large number of mechansisms are expected to account for the possible effects of inhibitors of mutagenesis and carcinogenesis (Wattenberg, 1981; De Flora and Ramel 1988; Kelloff et al., 1996; De Flora, 1998). The example of carotenoids and vitamin A is in line with the notion that potential chemopreventive agents possess pleiotropic properties and are capable of working via multiple mechanisms, which affect different stages of these biological processes (Wattenberg, 1981; De Flora and Ramel 1988; Kelloff et al., 1996; De Flora, 1998).
Genotoxic effects include a variety of end-points which can be evaluated both in vitro and in animal models, such as DNA damage, point mutations of differential specificity, numerical and structural chromosomal alterations and impairment of DNA repair mechanisms. DNA adducts, unless removed by excision repair, are progenotoxic lesions. Progenotoxic and genotoxic effects have been implicated as key mechanisms in the pathogenesis of those diseases which are the leading causes of death in the population, including cancer and possibly other chronic degenerative diseases (De Flora et al., 1996), such as atherosclerosis (De Flora et al., 1997). The term `related effects', as used in the present article, refers to certain end-points which can be either mimicked in vitro or evaluated as intermediate biomarkers in vivo. These effects are not genuine genotoxic alterations but include pathogenetically related changes. As inferred from the data available for carotenoids and vitamin A, they cover the expression of oncogenes, which regulate the cellular cycle and accordingly the cell proliferation rate, gap junctional intercellular communication and associated mechanisms, cell transformation or differentiation and other mechanisms which may contribute to tumor promotion and progression to malignancy.
|
Methodological approach |
|---|
|
TopAbstractIntroductionMethodological approachAnalysis of the database...Concluding remarksReferences |
|---|
Preparation of the database
A database on modulation of genotoxic and related effects in experimental test systems was prepared following a systematic survey of the pertinent literature published in the English language until the end of 1997. Although as exhaustive as possible, the database does not pretend to cover the whole existing literature. A total of 489 results were available, 205 of which related to carotenoids and 284 to vitamin A (Table I
). As specified in the footnotes to Table I, the results are presented in a semi-quantitative way.
|
Outline and nomenclature of the reviewed carotenoids and vitamin A compounds
The available data covered the activity of ß-carotene and of 26 other carotenoids (see Table I
), some of which have a provitamin A function. The term vitamin A, as used in the present article, refers to preformed vitamin A, which occurs in the form of retinol (all-trans-retinol) and of its esters retinyl acetate (all-trans-retinol acetate) and retinyl palmitate (all-trans-retinol palmitate). The activities of the related compounds retinal (all-trans-retinal, retinaldehyde) and retinoic acid (all-trans-retinoic acid) were also reviewed.
Outline of the reviewed genotoxic agents
The ability of carotenoids and vitamin A to modulate genotoxic and related effects was evaluated either with respect to `spontaneous' effects influenced by these nutrients, in the absence of any genotoxic agent or in the presence of a variety of genotoxic agents. As shown in Table I, these included three biological agents, four physical agents, 54 compounds belonging to various chemical or functional families and eight complex mixtures.
Outline of the reviewed experimental test systems
A total of 67 experimental test systems were available in the database. These systems used a variety of cellular targets and/or end-points suggestive of distinctive mechanisms of action.
In vitro models often employed exogenous metabolic systems, which were coupled with target cells in order to mimic the metabolism of genotoxicants. The metabolic patterns, along with biochemical analyses, provided information on the ability of carotenoids and vitamin A to interfere with the biotransformation of genotoxic agents and with oxidative mechanisms. Studies in prokaryotes investigated the modulation of mutagenicity, DNA damage and DNA repair in strains of Bacillus subtilis, Escherichia coli and Salmonella typhimurium differing in their susceptibility to agents working via distinctive genetic mechanisms. Assays in eukaryotes in one study used yeast cells of Saccharomyces cerevisiae which are sensitive to mutations, either genomic or mitochondrial. A large number of studies used organ cultures, primary cultured cells or continuous cell lines from a variety of organs, tissues and cells from mice, hamsters, rats, woodchucks or humans. The investigated end-points included DNA binding, expression of oncogenes (N-myc), DNA fragmentation (single-strand breaks), unscheduled DNA synthesis (UDS), mutations at various loci, numerical and structural chromosomal alterations (sister chromatid exchanges, micronuclei and chromosomal aberrations), regulation of gap junctional intercellular communication, expression of genes encoding gap junction proteins (connexin 43), cell transformation and morphological differentiation. Therefore, the evaluated end-points covered a sequence of mechanisms involved in the induction and fixation of the genotoxic damage and in cancer initiation, as well as in subsequent steps of the carcinogenesis process.
Studies in animal models were designed in order to assess the modulation of intermediate biomarkers. Some of them, such as RNA binding or DNA binding, measure the biologically effective dose at the molecular level. Other biomarkers evaluate early biological alterations, such as mutations or DNA fragmentation, or chromosomal changes, which may be predictive of the final pathological events, including cancer or other chronic degenerative diseases.
|
Analysis of the database and mechanistic inferences |
|---|
|
TopAbstractIntroductionMethodological approachAnalysis of the database...Concluding remarksReferences |
|---|
Table I
provides a synthetic overview of the data available in the database and shows at a glance, often on a comparative basis, the results obtained in studies evaluating the ability of carotenoids and vitamin A to modulate genotoxic and related effects in experimental models. For technical details we refer to the original papers referenced in the table and to the pertinent IARC Handbooks of Cancer Prevention (1998a,b).
Modulation of spontaneous events
As many as 135 negative results, generated in the large majority of studies using experimental test systems, support the view that carotenoids and vitamin A do not per se induce genotoxic effects. A genotoxic role for these nutrients was only suggested by nine results. In particular, in the yeast S.cerevisiae retinol was not mutagenic with respect to nuclear genes but induced a mitochondrial mutation to respiratory deficiency known as the petite mutation (Cheng and Wilkie, 1991). A single laboratory reported the induction of mutations in strain TA104 of S.typhimurium by ß-carotene and retinol, but not by retinoic acid (Han, 1992). However, this result contrasted with 64 negative results obtained with carotenoids and vitamin A in various S.typhimurium his– strains, including TA104 itself and TA102, which, like TA104, is reverted by oxidative mutagens. Similarly, induction by retinol of sister chromatid exchanges in cultured mammalian cells as reported in a single study (Dozi-Vassiliades et al., 1985) contrasted with the lack of influence on the same end-point or other chromosomal alterations as reported in many other in vitro studies (Table I).
The studies evaluating the modulation of intermediate biomarkers in rodents receiving oral administration of carotenoids or vitamin A led to conflicting results. In particular, ß-carotene failed to induce mutations in rat spleen lymphocytes (Aidoo et al., 1995) and retinyl palmitate did not induce DNA damage in rat hepatocytes (Decoudu et al., 1992). The frequency of micronuclei in peripheral blood erythrocytes was not significantly affected in mice receiving a diet supplemented with either retinyl palmitate (Sinha and Kumari, 1994) or Dunaliella bardawil as a source of ß-carotene (Umegaki et al., 1994). Although one laboratory reported the induction by ß-carotene of micronuclei in mouse bone marrow cells (Mukherjee et al., 1991), other studies failed to show this clastogenic effect with ß-carotene itself (Raj and Katz, 1985; Salvadori et al., 1992; Lahiri et al., 1993) or retinyl palmitate (Busk et al., 1984, Rao et al., 1986). The results generated in a single laboratory suggested, however, the possibility that retinyl palmitate may enhance the frequency of chromosomal aberrations in mouse bone marrow cells and in spermatocytes (Kumari and Sinha, 1994; Sinha and Kumari, 1994).
Therefore, on the whole, in spite of some suspicions raised by a minority of in vivo studies, the bulk of the experiments carried out in vitro or in animal models suggest a lack of genotoxic properties for carotenoids and vitamin A. On the other hand, even in the absence of any genotoxic agent, these nutrients appeared to display protective effects towards some mechanisms, reproduced in vitro, which are involved in tumor promotion and progression to malignancy. Thus, the carotenoid fucoxanthin inhibited the growth of cultured human neuroblastoma cells, caused an arrest in the G0–G1 phase of the cell cycle and inhibited expression of the N-myc gene, which may represent an important mechanism involved in the antiproliferative action of carotenoids (Okuzumi et al., 1990).
Extensive studies in mouse C3H 10T1/2 fibroblasts provided evidence that certain carotenoids and vitamin A enhance gap junctional intercellular communication, which plays an important protective role in cell growth control and carcinogenesis (Zhang et al., 1991). As shown in Table I, intercellular communication was up-regulated by vitamin A (retinol and retinoic acid), ß-carotene and other carotenoids, including 3-hydroxy-ß-carotene, 4-hydroxy-ß-carotene, canthaxanthin, dinor-canthaxanthin, lutein, lycopene, echinenone, violerythrin and retrodehydro-ß-carotene. In comparative experiments, methylbixin, capsorubicin and C-20, C-30 or C-40 dialdehydes were conversely inactive (Zhang et al., 1991; Stahl et al., 1997). Since methylbixin is an antioxidant, its inactivity in these test systems also implies that up-regulation of intercellular communication and the increased expression of connexin 43 by carotenoids are independent of their antioxidant properties (Zhang et al., 1992). The same carotenoids which up-regulated intercellular communications also increased the expression of connexin 43, a gene that encodes a major gap junction protein (Zhang et al., 1992).
In a comparative study, ß-carotene was confirmed to up-regulate intercellular communication and increase connexin 43 gene expression in C3H 10T1/2 fibroblasts, but these end-points were unaffected in mouse lung epithelial cells. Based on this study, the effects of ß-carotene appear to be cell-specific and perhaps may be limited to mesenchymal cells. This tentative hypothesis may in part explain why this nutrient is an ineffective lung cancer chemopreventive agent in humans (Banoub et al., 1996).
Enhancement of gap junctional permeability by retinol and retinoic acid was accompanied by their ability to inhibit neoplastic transformation, as assessed by evaluating anchorage-independent growth in a C3H 10T1/2 cell clone which had previously been `initiated' with 3-methylcholanthrene (Hossain et al., 1989). In addition, ß-carotene but not retinol caused morphological differentiation in cultured mouse melanoma cells (Hazuka et al., 1990). The ability of carotenoids and vitamin A to induce cell differentiation was further supported by other in vitro studies. For instance, ß-carotene, canthaxanthin and, even more efficiently, retinoic acid stimulated the RAR-ß reporter gene, collagen expression and morphological differentiation in cultured embryonal cells (Nikawa et al., 1995) and the same agents decreased the expression of the keratin 10 and fillagrin genes in human keratinocytes in organotypic culture (Bertram and Bortkiewicz, 1995).
Modulation of effects produced by biological agents
ß-Carotene inhibited the induction of sister chromatid exchange in cultured hamster cells treated with human leukocytes, whose oxidative metabolism was stimulated by adding 12-O-tetradecanoylphorbol-13-acetate (TPA). Generation of hydroxyl radicals appeared to be involved in this biologically induced DNA damage (Weitberg et al., 1985). The ability of vitamin A to modulate signal transduction pathways was demonstrated by inhibition of anchorage-independent growth induced by platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF) in human diploid fibroblasts as well as in a human fibrosarcoma-derived cell line (Palmer et al., 1989).
Modulation of effects produced by physical agents
An in vitro study failed to show any effect of retinol and retinoic acid on UDS, which is indicative of DNA excision repair, in primary rat hepatocytes exposed to UV-C light (Budroe et al., 1987). Both ß-carotene and canthaxanthin inhibited the mutagenic effects produced in strain TA102 of S.typhimurium by 8-methoxypsoralen, phoactivated following UV-A irradiation. TA102 is sensitive to oxidative mutagens, and singlet oxygen (1O2) is likely to be produced during the photo-crosslinking reaction of 8-methoxypsoralen with DNA (Santamaria et al., 1988). The same carotenoids inhibited the development of transformed foci of C3H 10T1/2 fibroblasts induced by X-rays, but only when added 1 week after irradiation. Canthaxanthin was even more potent than ß-carotene in this protective effect. Since canthaxanthin is not converted to vitamin A in mammalian cells, it was postulated that carotenoids and vitamin A have distinct mechanisms of action as inhibitors of transformation in these cells, although they share the ability to inhibit the peroxidation of unsaturated lipids (Pung et al., 1988).
In vivo studies demonstrated that the frequency of micronuclei in polychromatic erythrocytes was decreased in mice exposed to 
-rays and X-rays, treated by gavage with ß-carotene (Abraham et al., 1993) and ß-carotene-containing Dunaliella bardawil (Umegaki et al., 1994), respectively.
Modulation of effects produced by chemical oxidants
ß-Carotene inhibited the induction of sister chromatid exchanges by reactive oxygen species generated by electron transfer reactions following exposure of cells to hypoxanthine plus xanthine oxidase (Weitberg et al., 1985). Less consistent were the results obtained with hydrogen peroxide. In fact, using the same cellular system, ß-carotene inhibited sister chromatid exchanges, but, surprisingly, enhanced chromosomal aberrations, although parallel cytofluorimetric analyses proved the ability of ß-carotene to scavenge endogenous and H2O2-induced oxygen species (Cozzi et al., 1997). In another laboratory, both end-points were unaffected by ß-carotene (Stich and Dunn, 1986). In the same study in which ß-carotene and retinol had been found to enhance the `spontaneous' number of revertants, ß-carotene, retinol and retinoic acid did not influence the hydrogen peroxide-induced mutagenicity in strain TA104 of S.typhimurium (Han, 1992).
Using S. typhimurium (TA1535) as a target for mutagenicity, ß-carotene potently inhibited the induction of GC
AT transition mutations by nitric oxide (NO) or its combination with nitrogen dioxide (NO2). Since reactive oxygen species may contribute to NOx mutagenicity, this effect was ascribed to the antioxidant properties of ß-carotene, although quenching of hydroxyl radicals was ruled out. Due to the complexity of the action of NOx, other mechanisms could have been involved as well in the antimutagenic effect of ß-carotene. For instance, inhibition of mutagenicity correlated with the ability to block in vitro the nitrosation reaction. Nitrosation of primary amines by NOx, as found on DNA bases, results in immediate deamination and DNA codon alterations (Arroyo et al., 1992).
The pathways of oxygen generation and its modulation by vitamin A were investigated by means of 32P-post-labeling of diastereomeric DNA adducts in mouse epidermis following topical application of (7S,8S)-dihydroxy-7,8-dihydrobenzo[a]pyrene (benzo[a]pyrene-7,8-diol) and TPA. When co-treated with the TPA application, topically administered retinoic acid inhibited the formation of the (–)-anti-benzo[a]pyrene diolepoxide–deoxyguanosine adduct but not that of its (–)-syn isomer. This finding demonstrates that the tumor promoter TPA stimulates oxygen radical generation in mouse skin, an effect which is inhibited by retinoic acid (Marnett and Ji, 1994).
Modulation of effects produced by direct-acting chemicals
As shown in Table I, carotenoids and vitamin A did not inhibit genotoxic effects in the large majority of the studies carried out with direct-acting chemicals (51 negative results out of 65, i.e. 78.5%), irrespective of the nature of the test system used.
In particular, vitamin A was consistently ineffective (14 negative results) towards the direct-acting alkylating agents N-methyl-N'-nitro-N-nitrosoguanidine, N-methyl-N'-nitrosourea, N-ethyl-N'-nitrosourea, methyl methanesulfonate and ethyl methanesulfonate, with the exception of one study reporting a weak inhibition by retinyl acetate of 6TGR mutations induced by ethyl methanesulfonate in cultured hamster cells (Kuroda, 1990). Conversely, carotenoids yielded conflicting results within this class of mutagens, with seven negative results out of 14. In a comparative in vivo study, ß-carotene was effective but retinol was ineffective in decreasing the chromosomal aberrations induced by methyl methanesulfonate in hamster bone marrow cells (Renner, 1985).
Within direct-acting cytostatic agents, 21 results out of 27 were negative. Only three in vivo results showed inhibition by ß-carotene of micronuclei induced by mitomycin C in mouse bone marrow cells (Raj and Katz, 1985) and of chromosomal aberrations induced by busulfan and thio-TEPA in hamster bone marrow cells (Renner, 1985). Again, retinol was ineffective in the latter in vivo study. On the other hand, three studies in vitro even suggested an enhancement of certain end-points modulated by ß-carotene or vitamin A, including induction of micronuclei by bleomycin in cultured hamster cells in the presence of ß-carotene (Salvadori et al., 1994), induction of sister chromatid exchanges by melphalan in cultured human lymphocytes in the presence of retinol (Dozi-Vassiliades et al., 1985) and DNA binding of cisplatin in cultured human ovarian carcinoma cells in the presence of retinoic acid (Caliaro et al., 1997). Adriamycin (doxorubicin) genotoxicity in bacteria was unaffected by ß-carotene, retinol, retinoic acid and retinyl acetate (Baird and Birnbaum, 1979; Okai et al., 1996).
ß-Carotene failed to affect the induction of micronuclei and chromosomal aberrations by the phenols tannic acid and gallic acid in cultured hamster cells (Stich and Dunn, 1986). Retinol did not affect the mutagenicity in S.typhimurium strains of the direct-acting compounds diepoxybutane (Busk and Ahlborg, 1980) and photoactivated 2-azido-9-fluorenone oxime (White and Rock, 1981), but was successful in inhibiting the mutagenicity of methylazoxymethanol (Tavan et al., 1997). Moreover, retinol did not significantly change the frequency of micronuclei induced by caffeine in cultured human lymphocytes (Dozi-Vassiliades et al., 1985). Retinyl acetate inhibited the bacterial mutagenicity of high, non-physiological doses of cysteine (Stark et al., 1994).
On the whole, with some notable exceptions in the case of ß-carotene, carotenoids and vitamin A do not appear to behave as nucleophiles, capable of blocking reactive genotoxicants, nor do they appear to interfere with the induction or repair of DNA damage produced by direct-acting agents.
Modulation of effects produced by nitroarenes
Enterobacteria, including the S.typhimurium strains used in the Ames test, contain high amounts of nitroreductases which activate certain nitroaromatic compounds. Accordingly, these compounds exert a direct mutagenic activity in bacteria. Sensitivity of S.typhimurium strains (TA series) to nitroaromatic and other mutagens, which are often present in complex mixtures such as urban air, water, food and cigarette smoke, was considerably enhanced by engineering new strains (YG series) with elevated levels of nitroreductases (NR) or acetyl-CoA:N-hydroxyarylamine O-acetyltransferase (OAT) (Einistö et al., 1991). Carotenoids and vitamin A effectively decreased the mutagenicity of nitroaromatics, including 1-nitropyrene, 2-nitrofluorene, 3-nitrofluoranthene, 1,6-dinitropyrene and 1,8-dinitropyrene, in the `classical' strain TA98 and in its OAT-overproducing derivative YG1024. Almost all results, some of which were generated in comparative studies, indicated that this protective effect is shared by carotenoids, such as ß-carotene, lutein, marigold extract and xanthophyllin plus extracted from Tagetes erecta, and vitamin A, including retinol, retinal, retinoic acid and retinyl palmitate (Table I). These patterns suggest that carotenoids and vitamin A interfere with the metabolic activation of tricyclic and tetracyclic nitroaromatics to ultimate mutagens. It has also been suggested that lutein may form an extracellular complex with 1-nitropyrene, which could limit the bioavailability of this compound to target cells (González de Mejía et al., 1997a).
A different situation was envisaged with 4-nitroquinoline 1-oxide, whose bacterial mutagenicity was affected neither in NR- or OAT-overproducing agents (Einistö et al., 1991) nor by challenge with ß-carotene, retinoic acid or retinyl palmitate (Camoirano et al., 1994). On the other hand, ß-carotene inhibited the formation of micronuclei and chromosomal aberrations induced by this dicyclic compound in cultured hamster cells (Stich and Dunn, 1986). Besides its greater propensity to induce base pair substitutions rather than frameshift mutations, 4-nitroquinoline 1-oxide differs from other nitroaromatics in that its metabolic activation is catalyzed by the cytosolic enzyme DT diaphorase (Sugimura et al., 1966; De Flora et al., 1988). However, the possible influence of carotenoids and vitamin A on this enzyme activity in cultured hamster cells remains to be established.
A study with 4-nitro-o-phenylenediamine showed that retinol does not affect the frameshift mutagenicity of this monocyclic nitroarene. In addition, retinol did not influence its detoxification in the presence of rat liver post-mitochondrial (S9) fractions (Balbinder et al., 1983).
Modulation of effects produced by genotoxic compounds bioactivated in mammalian cells
It is well known that a large proportion of genotoxicants require bioactivation via metabolic pathways which occur in mammalian cells, mainly in the endoplasmic reticulum. Carotenoids and vitamin A were much more effective in inhibiting the genotoxicity of this category of compounds, as compared with direct-acting agents. However, efficacy of inhibition and consistency of results varied depending on the chemical nature of the genotoxic compounds.
An overwhelming proportion of in vitro and in vivo studies provided evidence for the efficiency of these nutrients in inhibiting the genotoxicity of aflatoxin B1. As shown in Table I, almost invariably the S9-mediated mutagenicity of this mycotoxin was inhibited by ß-carotene, canthaxanthin, carrot carotenoids, cryptoxanthin, lutein, marigold extract, xanthophyllin plus, retinol, retinal, retinoic acid, retinyl acetate and retinyl palmitate. Among carotenoids, only lycopene was found to be inactive. The antimutagenic effect was more evident when carotenoids (He and Campbell, 1990) or retinoic acid (Raina and Gurtoo, 1985) were added at the start of the metabolic activation reaction rather than when added after the reaction was terminated with menadione, thereby suggesting an effect of these nutrients on aflatoxin B1 metabolism. This mechanism was further supported by the finding that the mutagenicity of aflatoxin B1 was lower in the presence of S9 fractions from mice maintained on a diet supplemented with retinyl esters as compared with mice maintained on a vitamin A-deficient diet (Decoudu et al., 1992; Qin and Huang, 1986). Studies in cultured rodent cells showed a protective role towards certain effects produced by aflatoxin B1. These included inhibition by crocetin of DNA binding and inhibition by retinol of sister chromatid exchanges and chromosomal aberrations. Again, occurrence of these effects required the presence of an exogenous metabolic system coupled with the cellular system, with the exception of cultured woodchuck hepatocytes, which retain their metabolic capacity (Sirianni et al., 1981; Qin et al., 1985; Wang,C.-J. et al., 1991a; González de Mejía et al., 1997b).
The large majority of in vivo studies were also consistent with the conclusion that the oral administration of carotenoids or vitamin A inhibits the induction by aflatoxin B1 of progenotoxic and genotoxic effects, including DNA binding, DNA fragmentation, sister chromatid exchanges, micronuclei and chromosomal aberrations in various rodent cell types (Table I). ß-Carotene failed to decrease the formation of DNA single-strand breaks in rat liver in one study only, which contrasted with the inhibition produced by canthaxanthin, 8'-apo-ß-carotenal and anthaxanthin in parallel experiments. This protective effect correlated with the selective ability of these carotenoids to stimulate the metabolism of aflatoxin B1 to aflatoxin M1, a less genotoxic hydroxylated metabolite formed by CYP1A isozymes (Gradelet et al., 1997). Besides inducing these phase I enzymes, the same carotenoids were shown to stimulate the activity of phase II enzymes, such as uridine diphosphate glucuronyl transferase and DT diaphorase, in rat liver and intestine (Gradelet et al., 1996). Retinol was also found to induce the activity of DT diaphorase in cultured colon cancer cells (Wang,W. and Higuchi, 1995). In addition, treatment with crocetin of C3H 10T1/2 fibroblasts, in parallel with inhibition of DNA binding by S9-activated aflatoxin B1, resulted in an elevation of reduced glutathione (GSH) in the cell cytosol and in a stimulation of GSH S-transferase and GSH peroxidase activities (Balbinder et al., 1983).
Vitamin A also inhibited in vivo effects of ochratoxin, another mycotoxin, as shown by the decrease in DNA binding in kidney cells of mice receiving oral retinol (Grosse et al., 1997) and by the decrease in chromosomal aberrations in bone marrow cells and spermatocytes of mice receiving oral retinyl palmitate (Kumari and Sinha, 1994).
Among cytostatic agents requiring metabolic activation, ß-carotene and vitamin A were quite effective in inhibiting the genotoxicity of cyclophosphamide in in vitro test systems, including inhibition of base repair substitutions in S.typhimurium and of sister chromatid exchanges, micronuclei and chromosomal aberrations in cultured mammalian cells (Table I). The protective role towards this alkylating agent, producing highly active carbonium ions, was less consistent in animal models. In fact, ß-carotene inhibited the induction of sister chromatid exchanges and chromosomal aberrations in mouse bone marrow cells (Mukherjee et al., 1991; Salvadori et al., 1992), but, like retinol, did not exert protective effects against the induction of chromosomal aberrations in hamster bone marrow cells (Renner, 1985). Moreover, retinyl esters failed to decrease the induction by cyclophosphamide of sister chromatid exchanges (Qin and Huang, 1986) and micronuclei (Busk et al., 1984) in mouse bone marrow cells.
Polycyclic aromatic hydrocarbons represent one of the major families of genotoxic and carcinogenic chemical compounds, which typically need metabolic activation. The majority of results (46 out of 68, i.e. 67.6%) are indicative of protective effects of carotenoids and vitamin A toward this class of compounds. Nevertheless, as shown at a glance in Table I, the overall picture is rather intricate, with several inconsistent results obtained in different laboratories. Thus, the ability of these nutrients to prevent point mutations produced by benzo[a]pyrene in bacteria, as reported in five studies (Calle and Sullivan, 1982; Alzieu et al., 1987; Colin et al., 1991; Azuine et al., 1992; Balansky et al., 1994), is counterbalanced by the negative results obtained in three other studies (Qin and Huang, 1985, 1986; Terwel and van der Hoeven, 1985). The ability of cantaxanthin, ß-carotene and its intermediate metabolites 8'-apo-ß-carotenal and 8'-apo-ß-carotene methylester to inhibit the bacterial mutagenicity of benzo[a]pyrene correlated with the ability of the same compounds to inhibit the development of forestomach tumors induced by benzo[a]pyrene given by gavage in mice (Azuine et al., 1992).
Both ß-carotene and retinol were found to decrease binding of benzo[a]pyrene to DNA in organ cultures of tracheal epithelium, which was accompanied by a stimulation of UDS in these cells. This finding was interpreted by the authors as an inhibition of DNA adduct levels due to an enhancement of DNA repair activity (Wolterbeek et al., 1995). Retinyl palmitate inhibited the mutagenicity of benzo[a]pyrene in cultured human cells (Rocchi et al., 1983). Retinol failed to affect sister chromatid exchanges in cultured hamster cells and, like 7,12-dimethylbenz[a]anthracene, even enhanced chromosomal aberrations, which contrasted with the protective effect towards aflatoxin B1 and cyclophosphamide shown in the same study (Qin et al., 1985). An in vivo study showed that ß-carotene decreases benzo[a]pyrene-induced DNA damage in the mouse forestomach mucosa but not the induction of micronuclei in mouse bone marrow cells (Lahiri et al., 1993). However, in another laboratory a protective effect was observed towards the latter end-point (Raj and Katz, 1985). The oral administration of retinyl esters inhibited DNA binding of benzo[a]pyrene metabolites in rat hepatocytes and stomach cells, but not in lung and kidney cells (McCarthy et al., 1987). Moreover, this treatment inhibited the induction of micronuclei (Rao et al., 1986) but not that of sister chromatid exchanges (Qin and Huang, 1986) in mouse bone marrow cells. In studies with benzo[a]pyrene derivatives, retinol inhibited the S9-mediated bacterial mutagenicity of 6-methylbenzo[a]pyrene and 6-hydroxymethylbenzo[a]pyrene, but failed to affect the direct mutagenicity of 6-acetoxymethylbenzo[a]pyrene (Bayless et al., 1986), a result which once more is consistent with the differential effects of vitamin A towards promutagens and direct-acting mutagens.
Retinol failed to affect the bacterial mutagenicity (Qin and Huang, 1985) and sister chromatid exchanges in hamster cultured cells (Qin et al., 1985) induced by both benz[a]anthracene and 7,12-dimethylbenz[a]anthracene. However, all remaining studies (Table I) showed protective effects of ß-carotene and vitamin A towards a variety of end-points altered by 7,12-dimethylbenz[a]anthracene, including UDS, mutations, sister chromatid exchanges and chromosomal aberrations in mammalian cultured cells and appearance of nodule-like alveolar lesions in mouse mammary organ cultures, as well as binding to mammary cells and DNA single-strand breaks in hepatocytes and mammary cells of rats orally receiving retinyl esters. 7,12-Dimethylbenz[a]anthracene-induced transformation of mammary epithelial cells in the whole mammary organ, kept in a hormone-supplemented medium, was inhibited by ß-carotene, added either during or after exposure to the carcinogen. This suggested the occurrence of protective effects both at the initiation and the promotional stages (Som et al., 1984).
Similarly, most studies with 3-methylcholanthrene were consistent with protective effects of several carotenoids and vitamin A, with the exception of a study on sister chromatid exchanges in hamster cultured cells (Qin et al., 1985). It is noteworthy that, at variance with the results obtained with benzo[a]pyrene, benz[a]anthracene and 7,12-dimethylbenz[a]anthracene, retinol was successful in decreasing the bacterial mutagenicity of 3-methylcholanthrene, a result which suggested the involvement of some peculiar metabolic pathway for this polycyclic aromatic hydrocarbon (Qin and Haung, 1985). The mutagenicity of 3-methylcholanthrene was also decreased by retinyl palmitate in human cultured cells (Rocchi et al., 1983). In addition, several studies performed by a single research group provided sound evidence that most carotenoids and vitamin A can inhibit 3-methylcholanthrene-induced cell transformation in C3H 10T11/2 mouse fibroblasts. This protective effect was shared by ß-carotene, chanthaxanthin, 
-carotene, lutein, lycopene, retinol, retinal, retinoic acid and retinyl acetate. Bixin and renierapurpurin were the only ineffective carotenoids (Table I).
The aromatic amines 2-aminofluorene and 2-acetylaminofluorene are among the most extensively investigated and best-characterized chemical compounds in the areas of mutation research and cancer research. The mutagenicity of 2-aminofluorene in the frameshift S.typhimurium strain TA98, in the presence of an exogenous metabolic activation system (S9 mix), was found in one laboratory to be inhibited by both retinol and retinyl acetate (Baird and Birnbaum, 1979). However, two independent studies drew the conclusion that retinol enhances 2-aminofluorene mutagenicity when added at low doses, whereas at high doses a protective effect was observed. The modulating effect depended not only on the amount of retinol but also on the concentration of S9 (Busk and Ahlborg, 1982a; Balbinder et al., 1983). In the case of 2-acetylaminofluorene, an enhancement of mutagenicity was observed, irrespective of retinol dose (Busk and Ahlborg, 1982a), which could not be explained as the result of stimulated N-hydroxylation, deacetylation or ring hydroxylation, which on the contrary appeared to be diminished in the presence of either retinol or retinoic acid (Rondahl et al., 1985). The direct mutagenicity of the proximal metabolite N-hydroxy-2-acetylaminofluorene was not affected by retinol. In the presence of S9 mix, its mutagenicity was enhanced and was further increased by retinol, which suggested a stimulation of 2-acetylaminofluorene metabolism at a metabolic step following the initial N-hydroxylation (Rondahl et al., 1985). This hypothesis was not substantiated by the finding, reported in the same paper, that binding to hepatic DNA and RNA of [14C]2-acetylaminofluorene, given i.p. to rats, was not affected in animals receiving retinyl palmitate in the diet for 12 weeks. Presumably, 2-acetylaminofluorene metabolism in bacteria in the presence of rat liver preparations was affected by vitamin A to a higher degree than in vivo metabolism in rat liver (Rondahl et al., 1985).
In other studies from the same group, the bacterial mutagenicity of the carcinogenic aminoazo dye o-aminoazotoluene was found to be inhibited by retinol, retinyl acetate and retinyl palmitate (Busk and Ahlborg, 1982b). Inhibition by retinol occurred in the presence of liver S9 preparations from either hamster, mouse, gerbil or rat (Victorin et al., 1987).
Heterocyclic amines are present in food pyrolysis products and other combustion products. They are very potent mutagens, mainly inducing frameshift mutations in strain TA98 of S.typhimurium in the presence of an exogenous metabolic activation system. Carotenoids and vitamin A were consistently effective in decreasing the mutagenicity of several compounds belonging to this family. In particular, retinol decreased the mutagenicity in strain TA98 of the imidazoles 2-amino-6-methylpyrido [1,2-a:3',2'-d]imidazole (Glu-P-1) and 2-aminodipyrido[1,2-a:3',2'-d]imidazole (Glu-P-2) and of the indoles 3-amino-3,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) (Busk et al., 1982) and both retinol and retinal decreased the mutagenic potency of the aminoimidazoarenes 2-amino-3-methylimidazo[4,5-f]quinoxaline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoxaline (MelQ) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MelQx) (Ioannides et al., 1990). Inhibition of IQ mutagenicity by retinol also occurred in the presence of purified liver microsomal fractions, indicating that vitamin A inhibits the microsomal metabolism of IQ, presumably its hydroxylation. Conversely, no effect was observed when retinol was added after termination of microsomal metabolism, showing that vitamin A does not scavenge the reactive metabolites, or when bacteria were exposed to retinol prior to the mutagenicity assay, indicating that no interaction takes place between the vitamin and bacterial DNA capable of protecting it from IQ genotoxic metabolites (Ioannides et al., 1990).
In a comparative study, vitamin A and carotenoids were assayed for the ability to modulate the genotoxicity of Trp-P-1 by evaluating the umuC gene expression system in strain TA1535/pSK 1002 of S.typhimurium. The umuC gene contributes to the SOS response, which provides a major DNA system as a response to genotoxic damage. Trp-P-1 genotoxicity in this test system was inhibited, in order of potency, by retinol, retinyl acetate, retinoic acid, canthaxanthin, ß-carotene and retinyl palmitate. As previously reported, the same nutrients did not affect the direct genotoxicity of the direct-acting cytostatic agents adriamycin and mitomycin C (Okai et al., 1996).
N-Nitrosamines constitute a further important class of mutagens/carcinogens requiring metabolic activation whose genotoxic effects were consistently inhibited by vitamin A (Table I). The investigated compounds were dimethylnitrosamine (N-nitrosodimethylamine), diethylnitrosamine (N-nitrosodiethylamine) and N-nitrosopyrrolidine, which are volatile N-nitrosamines, and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), which is a tobacco-specific nitrosamine formed during the curing and smoking of tobacco following N-nitrosation of nicotine. Retinol was invariably effective in decreasing a variety of genotoxic effects produced by these compounds, including non-reparable DNA damage in E.coli, either in vitro or following a host-mediated assay, base pair substitutions in S.typhimurium and DNA single-strand breaks or sister chromatid exchanges in cultured mammalian cells (Huang, 1987; Alaoui-Jamali et al., 1991a; Knasmüller et al., 1992). ß-Carotene was also found to inhibit the induction of sister chromatid exchanges by diethylnitrosamine in mouse mammary organ cultures (Manoharan and Banerjee, 1985). In in vivo studies, the oral administration of retinyl palmitate decreased the induction of DNA single-strand breaks by dimethylnitrosamine (Webster et al., 1996) and induction of micronuclei by NNK (Alaoui-Jamali et al., 1991b) in rat hepatocytes.
Modulation of effects produced by complex mixtures
Some studies evaluated the modulation by ß-carotene and vitamin A of genotoxic and related effects produced in vitro by a variety of complex mixtures. ß-Carotene did not decrease the induction of chromosomal aberrations by extracts of areca nut, which is an ingredient of betel quid, in cultured hamster cells (Stich and Dunn, 1986). However, as shown in the same laboratory, retinol inhibited the ability of areca nut to produce transformed foci in cultured CH3 10T1/2 cells transfected with bovine papillomavirus (BPV) DNA. This assay was designed to mimic in vitro tumor promotion mechanisms (Stich and Tsang, 1989).
As evaluated in a comparative study (Ong et al., 1989), retinol decreased the direct mutagenicity in S.typhimurium TA98 of extracts of coal dust, diesel emission particles, tobacco snuff and airborne particles and the S9-mediated mutagenicity of fried beef extracts. ß-Carotene was only effective towards airborne particle extracts.
ß-Carotene, retinoic acid and retinyl palmitate did not affect the S9-mediated mutagenicity of cigarette smoke in S.typhimurium TA98 in one study (Camoirano et al., 1994), but in another study retinyl acetate exerted a protective effect (Balansky et al., 1994). At variance with ß-carotene, retinyl palmitate decreased the mutagenicity of cigarette smoke condensates in both TA98 and TA100 (Romert et al., 1994). However, negative data were reported in other studies not only for ß-carotene (Terwel and van der Hoeven, 1985), but also for retinol, retinoic acid and retinyl acetate (Wilmer and Spit, 1986). These conflicting results probably reflect the fact that the mutagenicity of cigarette smoke and its condensates is mainly due to aromatic amines (De Flora et al., 1995) whose mutagenicity, as previously discussed, is modulated in a peculiar manner by retinol. In any case, the finding that retinol can enhance gap junctional intercellular communication in hamster tracheal cells exposed to cigarette smoke (Rutten et al., 1988) suggests that vitamin A may interfere with subsequent steps of smoke-related carcinogenesis.
|
Concluding remarks |
|---|
|
TopAbstractIntroductionMethodological approachAnalysis of the database...Concluding remarksReferences |
|---|
First of all, a substantial proportion of the data presented in Table I
suggests that carotenoids and vitamin A do not per se possess genotoxic properties. In contrast, they appear to favor protective mechanisms involved in degenerative processes, such as the stimulation of gap junctional intercellular communication, at least in fibroblasts, up-regulation of the connexin 43 gene, inhibition of N-myc expression, a decrease in cell transformation frequency and induction of morphological differentiation.
Although it was not a general rule, carotenoids and vitamin A appeared to share similar mechanisms in the protection towards the genotoxic and related effects induced in a variety of test systems by physical agents, biological agents, chemical oxidants, direct-acting genotoxicants, genotoxicants requiring metabolic activation in bacterial or mammalian cells and complex mixtures. As evaluated in comparative studies addressing this point, modulation of certain in vitro end-points by carotenoids seems to be independent of their conversion into vitamin A. In fact, modulation was effected not only by ß-carotene, whose molecule can be converted to vitamin A in appropriate tissues and under appropriate conditions (Olson, 1983, 1994; Sporn, 1984), but also by other carotenoids, such as canthaxanthin, which do not have a provitamin A role. In addition, the enzyme 15,15'-dioxygenase, which splits the symmetrical molecule of ß-carotene to retinal after cleavage of the central double bond (Olson, 1983), is not detectable in cultured cells (Rundhaug et al., 1988). Even in in vivo experiments it should be noted that this enzyme is primarily located in the intestine, liver and corpus luteum (Sporn, 1984).
The scenario pictured in Table I is extremely complex. Some conflicting findings reported in different studies can be ascribed to several variability factors, such as the type of nutrient, its solubility, mode of application, dosage, schedule of administration, sequence of treatment with respect to the challenged genotoxic agent, cellular substrate, investigated end-point, interlaboratory variations, etc. Nevertheless, the bulk of the data are consistent with the conclusion that interference with the metabolism of xenobiotics is the major mechanism involved in modulation of genotoxicity by carotenoids and vitamin A. This can be clearly inferred from the poor influence of these agents on direct-acting genotoxicants as opposed to the frequent protective effects exerted towards genotoxicants which require metabolic activation. Carotenoids and vitamin A appear to inhibit the cytochrome P450 (CYP) system, which is involved in the metabolism of a broad variety of genotoxicants and which, in addition, appears to metabolize vitamin A itself (Leo and Lieber, 1985). Within the CYP superfamily, individual forms are specifically involved in the metabolism of certain genotoxic agents. For instance, by picking up some of the genotoxicants considered in Table I, and with reference to human isozymes, benzo[a]pyrene is mainly metabolized by CYP1A1, its 7,8-diol by CYP3A4, aflatoxin B1 by CYP1A2, CYP2B7 and CYP3A4, aromatic amines and heterocyclic amines by CYP1A2, N-nitrosodimethylamine and N-nitrosodiethylamine by CYP2A3 and CYP2E1, and NNK by CYP2D6 (Gonzales and Gelboin, 1991). Therefore, one could argue that the variable consistency of results and the degree of efficacy of carotenoids and vitamin A in inhibiting the genotoxicity of different procarcinogens may depend on a selective inhibition of specifically involved CYP isoforms. However, the molecular shape of retinol, having an area/depth ratio of 234 nm, suggests that this compound is poorly selective in inhibiting the various CYP isoforms (Lewis et al., 1986). It should be kept in mind that this system is not only involved in activation pathways but also in detoxification of genotoxicants, and, therefore, different effects may be expected to ensue depending on the metabolic pathways involved in the metabolism of each genotoxicant. Since a delicate balance exists between activating and detoxifying mechanisms, it is also possible that inhibition of certain CYP isoforms may favor the activity of other isoforms. For instance, as previously reported, it was shown that certain carotenoids can orient the microsomal pathways of aflatoxin B1 metabolism towards formation of the less genotoxic derivative aflatoxin M1 (Gradelet et al., 1997).
In addition to modulation of CYP isozymes involved in phase I reactions, studies in cultured cells or whole animals have indicated that carotenoids and vitamin A can induce phase II enzyme activities, such as GSH S-transferase, GSH peroxidase, uridine diphosphate glucuronyl transferase and DT diaphorase (Wang,C.-J. et al., 1991a; Wang,W. and Higuchi, 1995; Gradelet et al., 1996). Again, although these enzymes bear a predominantly detoxifying role, all of them are double-edged swords that under certain circumstances may trigger opposite effects. For instance, DT diaphorase plays a protective role with most substrates, but with certain compounds, such as 4-nitroquinoline 1-oxide, this enzyme catalyzes the activation to proximal metabolites (Sugimura et al., 1966; De Flora et al., 1988). A carotenoid (crocetin) was also shown to enhance, in cultured fibroblasts, the levels of GSH, a nucleophilic and antioxidant tripeptide which constitutes one of the major defense systems of the cell against genotoxicants (Wang,C.-K. et al., 1991a). Studies showing the ability of carotenoids and vitamin A to inhibit the bacterial mutagenicity of nitroarenes (Espinosa-Aguirre et al., 1993; González de Mejía et al., 1997a; Tang and Edenharder, 1997), which is mediated by nitroreductases and acetyl-CoA:N-hydroxyarylamine O-acetyltransferase, suggest an inhibition of these enzymes. On the whole, it appears that carotenoids and vitamin A can interfere with several pathways involved in the metabolism of xenobiotics, which appears to be the key mechanism explaining the protective activity of these nutrients towards a variety of genotoxicants. Genotoxic damage represents the crucial initiating event in carcinogenesis and possibly in the pathogenesis of other chronic degenerative diseases (De Flora et al., 1996).
In addition, a number of experimental studies indicate that carotenoids and vitamin A share certain properties which suggest a potential protective role of these nutrients in later stages of the carcinogenesis process. For instance, their ability to scavenge reactive oxygen species, which are involved throughout all stages of the carcinogenesis process, is supported by previously reported results (Weitberg et al., 1985; Pung et al., 1988; Santamaria et al., 1988; Arroyo et al., 1992; Marnett and Ji, 1994). Cell proliferation represents an intrinsically essential mechanism in tumor promotion and progression and, additionally, affects fixation of the genotoxic damage, since lack of proliferation allows more time to repair DNA alterations. The antiproliferative properties of carotenoids and vitamin A are well established (IARC, 1998a,b) and are supported by the findings that a carotenoid (fucoxanthin) inhibited expression of the N-myc gene (Okuzumi et al., 1990) and vitamin A modulated signal transduction pathways resulting in inhibition of anchorage-independent growth (Palmer et al., 1989). Other studies provided evidence for the ability of these nutrients to inhibit cell transformation in cultured mammalian cells, either in a 3-methylcholanthrene-initiated cell clone mimicking tumor promotion (Mordan et al., 1982) or in cells exposed to X-rays (Pung et al., 1988), polycyclic aromatic hydrocarbons (Merriman and Bertram, 1979; Som et al., 1984; Pung et al., 1988; Hossain et al., 1989; Bertram et al., 1991) or complex mixtures (Merriman and Bertram, 1979). This protective effect often correlated with the enhancement of gap junctional cell-to-cell communication in cultured mouse fibroblasts (Hossain et al., 1989; Zhang et al., 1991; Banoub et al., 1996; Stahl et al., 1997) and with parallel up-regulation of the connexin 43 gene (Zhang et al., 1992; Banoub et al., 1996). Interestingly, an enhancement of intercellular communication by retinol was also observed in hamster tracheal epithelial cells exposed to a cigarette smoke condensate (Rutten et al., 1988), although no effect of ß-carotene was detected in untreated mouse lung epithelial cells (Banoub et al., 1996). Both ß-carotene and retinol were capable of inducing morphological differentiation in in vitro studies (Hazuka et al., 1990; Bertram and Bortkiewicz, 1995; Nikawa et al., 1995).
The reported data lend solid support to the conclusion that carotenoids and vitamin A possess antigenotoxic properties and share multiple mechanisms suggesting a possible role of these nutrients in cancer prevention. These mechanistic premises are consistent with a wealth of results generated in preclinical studies, which provided evidence for the chemopreventive efficacy of both ß-carotene and canthaxanthin in models of skin carcinogenesis in mice and buccal pouch carcinogenesis in hamsters, of ß-carotene in models of liver and colon carcinogenesis in rats and pancreatic carcinogenesis in both rats and hamsters, of canthaxanthin in models of tongue and stomach carcinogenesis in rats and of vitamin A in rodent mammary cancer models (IARC 1998a,b). Many observational epidemiological studies carried out in the 1970s and 1980s showed negative associations between estimated intakes of vitamin A or ß-carotene and the risk of developing cancer at various sites. In well-nourished populations, however, no consistent relationship was found between cancer risk and plasma retinol cancentrations. Thus, in the early 1980s, carotenoids, mostly ß-carotene, and vitamin A, were considered as primary candidates for chemoprevention of cancer, especially cancer of the lung. Several large-scale intervention trials with ß-carotene and/or retinol were launched. Unfortunately, the major lung cancer chemoprevention trials turned out to be disappointing. Not only did they show no benefit, but they even produced small but significant increases in lung cancer incidence amongst high risk individuals such as tobacco smokers and asbestos-exposed workers. An increased mortality for all causes and cardiovascular diseases was also recorded (reviewed in IARC 1998a,b). The mechanisms of these adverse modulations are not yet understood and the findings from the reviewed literature on genotoxic and related effects do not, as present, give a satisfactory explanation for the biological effects observed.
|
Acknowledgments |
|---|
Preparation of this article was supported by AIRC (Associazione Italiana per la Ricerca sul Cancro).
|
Notes |
|---|
3 To whom correspondence should be addressed. Phone: +39 010 353 8500; Fax: +39 010 353 8504; Email: sdf{at}unige.it
|
References |
|---|
|
TopAbstractIntroductionMethodological approachAnalysis of the database...Concluding remarksReferences |
|---|
-
Abraham,S.K., Sarma,L. and Kevasan,P.C. (1993) Protective effects of chlorogenic acid, curcumin and ß-carotene against
-radiation-induced in vivo chromosomal damage. Mutat. Res., 303, 109–112.[Web of Science][Medline]
Aidoo,A., Lyn-Cook,L.E., Lensing,S., Bishop,M.E. and Warmer,W. (1995) In vivo antimutagenic activity of beta-carotene in rat spleen lymphocytes. Carcinogenesis, 16, 2237–2241.
Alaoui-Jamali,M.A., Bélanger,P.M., Rossignol,G. and Castonguay,A. (1991a) Metabolism, sister chromatid exchanges and DNA single-strand breaks induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and their modulation by vitamin A in vitro. Cancer Res., 51, 3946–3950.
Alaoui-Jamali,M.A., Rossignol,G. and Castonguay,A. (1991b) Protective effects of vitamin A against the genotoxicity of NNK, a nicotine-derived N-nitrosamine. Carcinogenesis, 12, 379–384.
Althaus,F.R., Lawrence,S.D., Sattler,G.L., Longfellow,D.G. and Pitot,H.C. (1982) Chemical quantification of unscheduled DNA synthesis in cultured hepatocytes as an assay for the rapid screening of potential chemical carcinogens. Cancer Res., 42, 3010–3015.
Alzieu,P., Cassand P., Colin,C., Grolier P. and Narbonne J.F. (1987) Effect of vitamins A, C and glutathione on the mutagenicity of benzo[a]pyrene mediated by S9 from vitamin A-deficient rats. Mutat. Res., 192, 227–231.[Web of Science][Medline]
Amagase,H., Schaffer,E.M. and Milner,J.A. (1996) Dietary components modify the ability of garlic to suppress 7,12-dimethylbenz[a]anthracene-induced mammary DNA adducts. J. Nutr., 126, 817–824.
Arroyo,P.L., Hatch-Pigott,V., Mower,H.F. and Cooney,R.V. (1992) Mutagenicity of nitric oxide and its inhibition by antioxidants. Mutat. Res., 281, 193–202.[Web of Science][Medline]
Azuine,M.A., Goswami,U.C., Kayal,J.J. and Bhide,S.V. (1992) Antimutagenic and anticarcinogenic effects of carotenoids and dietary palm oil. Nutr. Cancer, 17, 287–295.[Web of Science][Medline]
Baird,M.B. and Birnbaum,L.S. (1979) Inhibition of 2-fluorenamine-induced mutagenesis in Salmonella typhimurium by vitamin A. J. Natl Cancer Inst., 63, 1093–1096.
Balansky,R., Mircheva,Z. and Blagoeva P. (1994) Modulation of the mutagenic activity of cigarette smoke, cigarette smoke condensate and benzo[a]pyrene in vitro and in vivo. Mutagenesis, 9, 107–112.
Balbinder,E., Stick,S.M. and Sharma,O.K. (1983) Complex effects of retinol on the metabolic activation of 2-aminofluorene. Environ. Mutagen., 5, 665–678.[Web of Science][Medline]
Banoub,R.W., Fernstrom,M. and Ruch,R.J. (1996) Lack of growth inhibition or enhancement of gap junctional intercellular communication and connexin 43 expression by ß-carotene in murine lung epithelial cells in vitro. Cancer Lett., 108, 35–40.[Web of Science][Medline]
Bayless,J.H., Jablonski,J.E., Roach,S.M. and Sullivan,P.D. (1986) Inhibition of the mutagenicity and metabolism of 6-methyl-benzo[a]pyrene and 6-hydroxymethyl-benzo[a]pyrene. Biochem. Pharmacol., 35, 2313–2322.[Web of Science][Medline]
Belisario,M.A., Pecce,R., Battista,C., Panza,N. and Pacilio,G. (1985) Inhibition of cyclophosphamide mutagenicity by ß-carotene. Biomed. Pharmacother., 39, 445–448.[Medline]
Bertram,J.S. and Bortkiewicz,H. (1995) Dietary carotenoids inhibit neoplastic transformation and modulate gene expression in mouse and human cells. Am. J. Clin. Nutr., 62, 1327S–1336S.
Bertram,J.S., Pung,A., Churley,M., Kappock,T.J., Wilkins,L.R. and Cooney,R.V. (1991) Diverse carotenoids protect against chemically induced neoplastic transformation. Carcinogenesis, 12, 671–678.
Bhattacharya,R.K., Francis,A.R. and Shetty,T.K. (1987) Modifying role of dietary factors on the mutagenicity of aflatoxin B1: in vitro effect of vitamins. Mutat. Res., 188, 121–128.[Web of Science][Medline]
Blaner,W.S. and Olson,J.A. (1994) Retinol and retinoic acid metabolism. In Sporn,M.B., Roberts,A.B. and Goodman,D.S. (eds), The Retinoids: Biology, Chemistry and Medicine, 2nd Edn. Raven Press, New York, NY, pp. 229–255.
Bolognesi,C., Ognio,E., Ferreri–Santi,L. and Rossi,L. (1992) Modulation of DNA damage by vitamin A in developing Sprague–Dawley rats. Anticancer Res., 12, 1587–1592.[Web of Science][Medline]
Brockman,H.E., Stack,H.F. and Waters,M.D. (1992) Antimutagenicity profiles of some natural substances. Mutat. Res., 267, 157–172.[Web of Science][Medline]
Budroe,J.D., Shaddock,J.G. and Casciano D.A. (1987) Modulation of ultraviolet light-, ethyl methanesulfonate- and 7,12-dimethylbenz[a]anthracene-induced unscheduled DNA synthesis by retinol and retinoic acid in the primary rat hepatocyte. Environ. Mol. Mutagen., 10, 129–139.[Web of Science][Medline]
Budroe,J.D., Schol,H.M., Shaddock,J.G. and Casciano,D.A. (1988) Inhibition of 7,12-dimethylbenz[a]anthracene-induced genotoxicity in Chinese hamster ovary cells by retinol and retinoic acid. Carcinogenesis, 9, 1307–1311.
Busk,L. and Ahlborg,U.G. (1980) Retinol (vitamin A) as an inhibitor of the mutagenicity of aflatoxin B1. Toxicol. Lett., 6, 243–249.[Web of Science][Medline]
Busk,L. and Ahlborg,U.G. (1982a) Retinol (vitamin A) as a modifier of 2-aminofluorene and 2-acetyl-aminofluorene mutagenesis in the Salmonella/microsome assay. Arch. Toxicol., 49, 169–174.[Web of Science][Medline]
Busk,L. and Ahlborg,U.G. (1982b) Retinoids as inhibitors of ortho-aminoazotoluene-induced mutagenesis in the Salmonella/liver microsome test. Mutat. Res., 104, 225–231.[Web of Science][Medline]
Busk,L., Ahlborg,U.G. and Albanus,L. (1982) Inhibition of protein pyrolisate mutagenicity by retinol (vitamin A). Fd Chem. Toxicol., 20, 535–539.[Web of Science][Medline]
Busk,L., Sjöström,B. and Ahlborg,U.G. (1984) Effects of vitamin A on cyclophosphamide mutagenicity in vitro (Ames test) and in vivo (mouse micronucleus test). Fd Chem. Toxicol., 22, 725–730.[Web of Science][Medline]
Caliaro,M.J., Vitaux,P., Lafon,C., Lochon,I., Néhmé,A., Valette,A., Canal,P., Bugat,R. and Jozan,S. (1997) Multifactorial mechanism for the potentiation of cisplatin (CDDP) cytotoxicity by all-trans-retinoic acid (ATRA) in human ovarian carcinoma cell lines. Br. J. Cancer, 75, 333–340.[Web of Science][Medline]
Calle,L.M. and Sullivan,P.D. (1982) Screening of antioxidants and other compounds for antimutagenic properties towards benzo[a]pyrene-induced mutagenicity in strain TA98 of Salmonella typhimurium. Mutat. Res., 101, 99–114.[Web of Science][Medline]
Camoirano,A., Balansky,R.M., Bennicelli,C., Izzotti,A., D'Agostini,F. and De Flora,S. (1994) Experimental databases on inhibition of the bacterial mutagenicity of 4-nitroquinoline 1-oxide and cigarette smoke. Mutat. Res., 317, 89–109.[Web of Science][Medline]
Cheng,L.L. and Wilkie,D. (1991) Mitochondrial activity and cytotoxicity of vitamin A (retinol) in yeast and human cell cultures. Biochem. Pharmacol., 42, 1237–1240.[Web of Science][Medline]
Colin,C., Narbonne,J.F., Migaud,M.L., Grolier,P., Cassand,P. and Pellissier M.A. (1991) Lipid peroxidation and benzo[a]pyrene activation to mutagenic metabolites: in vivo influence of vitamins A, E and C and glutathione in both dietary vitamin A sufficiency and deficiency. Mutat. Res., 246, 159–168.[Web of Science][Medline]
Cozzi,R., Bona,R., Polani,S. and De Salvia,R. (1990) Retinoids as modulators of metabolism: their inhibitory effect on cyclophosphamide and 7,12-dimethylbenz[a]anthracene induced sister chromatid exchanges in a metabolically competent cell line. Mutagenesis, 5, 397–401.
Cozzi,R., Ricordy,R., Aglitti,T., Gatta,V., Perticone,P. and De Salvia,R. (1997) Ascorbic acid and ß-carotene as modulators of oxidative damage. Carcinogenesis, 18, 223–228.
De Flora,S. (1998) Mechanisms of inhibitors of mutagenesis and carcinogenesis. Mutat. Res., 402, 151–158.[Web of Science][Medline]
De Flora,S. and Ramel,C. (1988) Mechanisms of inhibitors of mutagenesis and carcinogenesis. Classification and overview. Mutat. Res., 202, 285–306.[Web of Science][Medline]
De Flora,S., Bennicelli,C., Camoirano,A., Serra,D. and Hochstein,P. (1988) Influence of DT diaphorase on the mutagenicity of organic and inorganic compounds. Carcinogenesis, 9, 611–617.
De Flora,S., Bennicelli,C., Rovida,A., Scatolini,L. and Camoirano,A. (1994) Inhibition of the `spontaneous' mutagenicity in Salmonella typhimurium TA102 and TA104. Mutat. Res., 307, 157–167.[Web of Science][Medline]
De Flora,S., Balansky,R., Gasparini,L. and Camoirano,A. (1995) Bacterial mutagenicity of cigarette smoke and its interactions with ethanol. Mutagenesis, 10, 47–52.
De Flora,S. et al. (1996) DNA adducts in chronic degenerative diseases. Pathogenetic relevance and implications in preventive medicine. Mutat. Res., 366, 197–238.[Web of Science][Medline]
De Flora,S., Izzotti,A., Walsh,D., Degan,P., Petrilli,G.L. and Lewtas,J. (1997) Molecular epidemiology of atherosclerosis. FASEB J., 11, 1021–1031.[Abstract]
Decoudu,S., Cassand,P., Daubèze,M., Frayssinet,C. and Narbonne,J.F (1992) Effect of vitamin A dietary intake on in vitro and in vivo activation of aflatoxin B1. Mutat. Res., 269, 269–278.[Web of Science][Medline]
Dozi-Vassiliades,J., Myrtsiotis,A., Granitsas,A. and Mourelatos D. (1985) Induction of sister-chromatid exchanges and cell-cycle delays in human lymphocytes by vitamin A alone or in combination with melphalan and caffeine. Eur. J. Cancer Clin. Oncol., 21, 1089–1092.[Web of Science][Medline]
Einistö,P., Watanabe,M., Ishidate,M.,Jr and Nohmi,T. (1991) Mutagenicity of 30 chemicals in Salmonella typhimurium strains possessing different nitroreductase or O-acetyltransferase activities. Mutat. Res., 259, 95–102.[Web of Science][Medline]
Espinosa-Aguirre,J.J., Reyes,R.E., Rubio,J., Ostrosky-Wegman,P. and Martinez,G. (1993) Mutagenic activity of urban air samples and its modulation by chili extracts. Mutat. Res., 303, 55–61.[Web of Science][Medline]
Ferrari,N., Rocco,M., Aprile,A., Fassina,G. and Vidali,G. (1989) Interaction retinol–chromatin: an analysis of DNA from vitamin A-treated V79 Chinese hamster cells. Biochim. Biophys. Acta, 1007, 30–35.[Medline]
Ferreri,A.M., Grilli,M.P., Capucci,A., Prodi,G., Rocchi,P. and Bianucci,F. (1986) Effect of antioxidants on mutagenesis induced by DMBA in human cells. Nutr. Cancer, 8, 267–272.[Medline]
Gonzales,F.J. and Gelboin,H.V. (1991) Human cytochromes P450: evolution, catalytic activities and interindividual variations in expression. In Gledhill,B.L. and Mauro,F. (eds), New Horizons in Biological Dosimetry. Wiley Liss, New York, NY, pp. 11–20.
González de Mejía,E., Loarca-Piña,G. and Ramos-Gómez,M. (1997a) Antimutagenicity of xanthophylls present in Aztec Marigold (Tagetes erecta) against 1-nitropyrene. Mutat. Res., 389, 219–226.[Web of Science][Medline]
González de Mejía,E., Ramos-Gómez,M. and Loarca-Piña,G. (1997b) Antimutagenic activity of natural xanthophyllins against aflatoxin B1 in Salmonella typhimurium. Environ. Mol. Mutagen., 30, 346–353.[Web of Science][Medline]
Gradelet,S., Leclerc,J., Siess,M.H. and Astorg,P.O. (1996) ß-Apo-8'-carotenal, but not ß-carotene, is a strong inducer of liver citochromes P4501A1 and 1A2 in rat. Xenobiotica, 26, 909–919.[Web of Science][Medline]
Gradelet,S., Astorg,P., Le Bon,A.-M., Bergès,R. and Suschetet,M. (1997) Modulation of aflatoxin B1 carcinogenicity, genotoxicity and metabolism in rat liver by dietary carotenoids: evidence for a protective effect of CYP1A inducers. Cancer Lett., 114, 221–223.[Web of Science][Medline]
Grosse,Y., Chekir-Ghedira,L., Huc,A., Obrecht-Pflumio,S., Dirheimer,G., Bacha,H. and Pfohl-Leszkowicz,A. (1997) Retinol, ascorbic acid and -tocopherol prevent DNA adduct formation in mice treated with the mycotoxins ochratoxin A and zearalenone. Cancer Lett., 114, 225–229.[Web of Science][Medline]
Han,J.-S. (1992) Effects of various chemical compounds on spontaneous and hydrogen peroxide-induced reversion in strain TA104 of Salmonella typhimurium. Mutat. Res., 266, 77–84.[Web of Science][Medline]
Haveland-Smith,R.B. (1981) Evaluation of genotoxicity of some natural food colors. Mutat. Res., 91, 285–290.[Web of Science][Medline]
Hazuka,M.B., Edwards Prasad,J., Newman,F., Kinzie,J.J. and Prasad,K.N. (1990) Beta-carotene induces morphological differentiation and decreases adenylate cyclase activity in melanoma cells in culture. J. Am. Coll. Nutr., 9, 143–149.[Abstract]
He,Y. and Campbell,C. (1990) Effects of carotenoids on aflatoxin B1-induced mutagenesis in S. typhimurium TA100 and TA98. Nutr. Cancer, 13, 243–253.[Web of Science][Medline]
Heywood,R., Palmer,A.K., Gregson,R.L. and Hummler,H. (1985) The toxicity of beta-carotene. Toxicology, 36, 91–100.[Web of Science][Medline]
Hossain,M.Z., Wilkens,L.R., Metha,P.P., Lowenstein,W. and Bertram,J.S. (1989) Enhancement of gap junctional communication by retinoids correlates with their ability to inhibit neoplastic transformation. Carcinogenesis, 10, 1743–1748.
Huang,C.C. (1987) Retinol (vitamin A) inhibition of dimethylnitrosamine (DMN) and diethylnitrosamine (DEN) induced sister-chromatid exchanges in V79 cells and mutations in Salmonella/microsome assays. Mutat. Res., 187, 133–140.[Web of Science][Medline]
Huang,C.C., Hsueh,J.L., Chen,H.H. and Batt,T.R. (1982) Retinol (vitamin A) inhibits sister chromatid exchanges and cell cycle delay induced by cyclophosphamide and aflatoxin B1 in Chinese hamster V79 cells. Carcinogenesis, 3, 1–5.
IARC (1998a) IARC Handbooks of Cancer Prevention, Vol. 2, Carotenoids. International Agency for Research on Cancer, Lyon, France.
IARC (1998b) IARC Handbooks of Cancer Prevention, Vol. 3, Vitamin A. International Agency for Research on Cancer, Lyon, France.
Ioannides,C., Ayrton,A.D., Keele,A., Lewis,D.F.V., Flatt,P.R. and Walker,R. (1990) Mechanism of the in vitro antimutagenic action of retinol. Mutagenesis, 5, 257–262.
Kada,T.K., Tulikawa,K. and Sadaie Y. (1972) In vitro and host-mediated `rec-assay' procedures for screening chemical mutagens; and phloxine, a mutagenic red dye detected. Mutat. Res., 16, 165–174.[Web of Science][Medline]
Kelloff,G.J., Boone,C.W., Steele,V.E., Crowell,J.A., Lubet,R.A., Greenwald,P., Hawk,E.T., Fay,J.R., Sigman,C.C. (1996) Mechanistic considerations in the evaluation of chemopreventive data. In Stewart,B.W., McGregor,D. and Kleihues,P. (eds), Principles of Chemoprevention. IARC Scientific Publication no. 139, International Agency for Research on Cancer, Lyon, France, pp. 203–219.
Knasmüller,S., Huber,W.W., Kienzl,H. and Schulte-Hermann,R. (1992) Inhibition of repairable DNA-damage in Escherichia coli K-12 cells recovered from various organs of nitrosamine-treated mice by vitamin A, phenethylisothiocyanate, oleic acid and triolein. Carcinogenesis, 13, 1643–1650.
Krinsky,N.I. (1993a) Micronutrients and their influence on mutagenicity and malignant transformation. Ann. NY Acad. Sci., 686, 229–242.[Web of Science][Medline]
Krinsky,N.I. (1993b) Actions of carotenoids in biological systems. Annu. Rev. Nutr., 13, 561–587.[Web of Science][Medline]
Krinsky,N.I. (1994) Carotenoids and cancer: basic research studies. In Frei,B. (ed.), Natural Antioxidants in Human Health and Disease. Academic Press, New York, NY, pp. 239–261.
Kumari,D. and Sinha,P. (1994) Effect of retinol on ochratoxin-produced genotoxicity in mice. Fd Chem. Toxicol., 32, 471–475.[Web of Science][Medline]
Kuroda,Y. (1990) Antimutagenic activity of vitamins in cultured mammalian cells. In Kuroda,Y., Shankel,D.M. and Waters,M.D. (eds), Antimutagenesis and Anticarcinogenesis Mechanisms II. Plenum Publishing, New York, NY, pp. 233–256.
Lahiri,M., Maru,G.B. and Bhide,S.V. (1993) Effect of plant phenols, ß-carotene and -tocopherol on benzo[a]pyrene-induced damage in the mouse forestomach mucosa (target organ) and bone marrow polychromatic erythrocytes (non-target organ). Mutat. Res., 303, 97–100.[Web of Science][Medline]
Leo,M.A. and Lieber,C.S. (1985) New pathways for retinol metabolism in liver microsomes. J. Biol. Chem., 260, 5228–5231.
Lewis,D.F.V., Ioannides,C. and Parke,D.V. (1986) Molecular dimensions of the substrate binding site of cytochrome P-448. Biochem. Pharmacol., 35, 2179–2185.[Web of Science][Medline]
Manoharan,K. and Banerjee,M.R. (1985) Beta-carotene reduces sister chromatid exchanges induced by chemical carcinogens in mouse mammmary cells in organ culture. Cell. Biol. Int. Rep., 9, 783–789.[Web of Science][Medline]
Marnett,L.J. and Ji,C. (1994) Modulation of oxidant formation in mouse skin in vivo by tumor-promoting phorbol esters. Cancer Res., 54, 1886s–1889s.
McCarthy,D.J., Lindamood,C. and Hill,D.L. (1987) Effects of retinoids on metabolizing enzymes and on binding of benzo(a)pyrene to rat tissue DNA. Cancer Res., 47, 5014–5020.
Merriman,R.L. and Bertram,J.S. (1979) Reversible inhibition by retinoids of 3-methylcholanthrene-induced neoplastic transformation in CH3/10T1/2 clone cells. Cancer Res., 39, 1661–1666.
Mordan,L.J., Bergin,L.M., Budnick,J.E.L., Meegan,R.R. and Bertram,J.S. (1982) Isolation of methylcholanthrene-`initiated' CH3/10T1/2 cells by inhibiting neoplastic progression with retinyl acetate. Carcinogenesis, 3, 279–285.
Mukherjee,A., Agarwal,K., Aguilar,M.A. and Sharma,A. (1991) Anticlastogenic activity of ß-carotene against cyclophosphamide in mice in vivo. Mutat. Res., 263, 41–46.[Web of Science][Medline]
Nikawa,T., Schulz,W.A., van den Brink,C.E., Hanusch,M., van der Saag,P., Stahl,W. and Sies,H. (1995) Efficacy of all-trans-ß-carotene, canthaxanthin and all-trans-, 9-cis- and 4-oxoretinoic acids in inducing differentiation of an F9 embryonal carcinoma RARß-lacZ reporter cell line. Arch. Biochem. Biophys, 316, 665–672.[Web of Science][Medline]
Odin,A.P. (1997) Vitamins as antimutagens: advantages and some possible mechanisms of antimutagenic action. Mutat. Res., 386, 39–67.[Web of Science][Medline]
Okai,Y., Higashi-Okai,K., Nakamura,S.-I., Yano,Y. and Otani,S. (1996) Suppressive effects of retinoids, carotenoids and antioxidant vitamins on heterocyclic amine-induced umu C gene expression in Salmonella typhimurium (TA1535/pSK 1002). Mutat. Res., 368, 133–140.[Web of Science][Medline]
Okuzumi,J., Nishino,H., Murakoshi,M., Iwashima,A., Tanaka,Y., Yamane,T., Fujita,Y. and Takahashi,T. (1990) Inhibitory effects of fucoxanthin, a natural carotenoid, on N-myc expression and cell cycle progression in human malignant tumor cells. Cancer Lett., 55, 75–81.[Web of Science][Medline]
Olson,J.A. (1983) Formation and function of vitamin A. In Porter,J.W. and Spurgeon,D.L. (eds), Biosynthesis of Isoprenoid Compounds. John Wiley & Sons, New York, NY, pp. 371–412.
Olson,J.A. (1994) Vitamin A, retinoids and carotenoids. In Shils,M.E., Olson,J.A and Shike,M. (eds), Modern Nutrition in Health and Disease, 8th Edn. Lea & Febiger, Philadelphia, PA, pp. 371–412.
Ong,T., Whong,W.-Z., Stewart,J.D. and Brockman,H.E. (1989) Comparative antimutagenicity of 5 compounds against 5 mutagenic complex mixtures in Salmonella typhimurium strain TA98. Mutat. Res., 222, 19–25.[Web of Science][Medline]
Palmer,H.J., Maher,V.M. and McCormick,J.J. (1989) Effect of retinoids on growth factor-induced anchorage independent growth of human fibroblasts. In Vitro Cell. Dev. Biol., 25, 1009–1015.[Web of Science][Medline]
Pfander,H. (1987) Key to Carotenoids, 2nd Edn. Birkhäuser, Basel, Switzerland.
Pung,A., Rundhaug,J.E., Yoshizawa,C.N. and Bertram,J.S. (1988) ß-Carotene and canthaxanthin inhibit chemically- and physically-induced neoplastic transformation in 10T1/2 cells. Carcinogenesis, 9, 1533–1539.
Qin,S. and Huang,C.C. (1985) Effect of retinoids on carcinogen-induced mutagenesis in Salmonella tester strains. Mutat. Res., 142, 115–120.[Web of Science][Medline]
Qin,S. and Huang,C.C. (1986) Influence of mouse liver stored vitamin A on the induction of mutations (Ames test) and SCE of bone marrow cells by aflatoxin B1, benzo[a]pyrene, or cyclophosphamide. Environ. Mutagen., 8, 839–847.[Web of Science][Medline]
Qin,S., Batt,T. and Huang,C.C. (1985) Influence of retinol on carcinogen-induced sister chromatid exchanges and chromosome aberrations in V79 cells. Environ. Mutagen., 7, 137–146.[Web of Science][Medline]
Raina,V. and Gurtoo,H.L. (1985) Effects of vitamins A, C and E on aflatoxin B1-induced mutagenesis in Salmonella typhimurium TA98 and TA100. Teratogen. Carcinogen. Mutagen., 5, 29–40.[Web of Science][Medline]
Raj,A.S. and Katz,M. (1985) ß-Carotene as an inhibitor of benzo(a)pyrene and mytomicin C induced chromosomal breaks in the bone marrow of mice. Can. J. Genet. Cytol., 27, 598–602.[Web of Science][Medline]
Rao,K.P., Ramadevi,G. and Das,U.N. (1986) Vitamin A can prevent genetic damage induced by benzo(a)pyrene to the bone marrow cells of mice. Int. J. Tissue React., 8, 219–223.[Web of Science][Medline]
Renner,H.W. (1985) Anticlastogenic effect of ß-carotene in Chinese hamsters. Time and dose response studies with different mutagens Mutat. Res., 144, 251–256.[Web of Science][Medline]
Rocchi,P., Arfellini,G., Capucci,A., Grilli,M.P. and Prodi,G. (1983) Effect of vitamin A palmitate on mutagenesis induced by polycyclic aromatic hydrocarbons in human cells. Carcinogenesis, 4, 245–247.
Romert,L., Jansson,T., Curvall,M. and Jenssen,D. (1994) Screening for agents inhibiting the mutagenicity of extracts and constituents of tobacco products. Mutat. Res., 322, 97–110.[Web of Science][Medline]
Rondahl,L., Busk,L., Ahlborg,U.G. and Bergman,K. (1985) Effects of vitamin A on the metabolism and mutagenicity of 2AAF in vitro and on the covalent binding to rat liver DNA/RNA in vivo. Arch. Toxicol., 57, 178–183.[Web of Science][Medline]
Rundhaug,J.E., Pung,A., Read,C.M. and Bertram,J.S. (1988) Uptake and metabolism of ß-carotene and retinol by CH310T1/2 cells. Carcinogenesis, 9, 1541–1545.
Rutten,A.A.J.J.L., Jongen,W.M.F., de Haan,L.H.J., Hendriksen,E.G.J. and Koeman,J.H. (1988) Effect of retinol and cigarette-smoke condensate on dye-coupled intercellular communication between hamster tracheal epithelial cells. Carcinogenesis, 9, 315–320.
Salvadori,D.M.F., Ribeiro,L.R., Oliveira,M.D.M., Pereira,C.A.B. and Becan,W. (1992) The protective effect of ß-carotene on genotoxicity induced by cyclophosphamide. Mutat. Res., 265, 237–244.[Web of Science][Medline]
Salvadori,D.M.F., Ribeiro,L.R. and Natarajan,A.T. (1993) The anticlastogenicity of ß-carotene evaluated on human hepatoma cells. Mutat. Res., 303, 151–156.[Web of Science][Medline]
Salvadori,D.M.F., Ribeiro,L.R. and Natarajan,A.T. (1994) Effect of ß-carotene on clastogenic effects of mitomycin C, methyl methanesulphonate and bleomycin in Chinese hamster ovary cells. Mutagenesis, 9, 53–57.
Santamaria,L., Bianchi,A., Arnaboldi,A., Ravetto,C., Bianchi,L., Pizzala,R., Andreoni,L., Santagati,G. and Bermond,P. (1988) Chemoprevention of indirect and direct chemical carcinogenesis by carotenoids as oxygen radical quenchers. Ann. NY Acad. Sci., 534, 584–596.[Web of Science][Medline]
Shetty,T.K., Francis,A.R. and Bhattacharya,R.K. (1988) Modifying role of vitamins on the mutagenic action of N-methyl-N'-nitro-N-nitrosoguanidine. Carcinogenesis, 9, 1513–1515.
Sinha,S.P. and Kumari,D. (1994) Vitamin A ameliorates the genotoxicity in mice of aflatoxin B1-containing Aspergillus flavus infested food. Cytobios, 79, 85–95.[Medline]
Sirianni,S.R., Chen,H.H. and Huang,C.C. (1981) Effect of retinoids on plating efficiency, sister-chromatid exchanges (SCE) and mitomycin-C-induced SCE in cultured Chinese hamster cells. Mutat. Res., 90, 175–182.[Web of Science][Medline]
Som,S., Chatterjee,M. and Banerjee,M. (1984) ß-Carotene inhibition of 7,12-dimethylbenz[a]anthracene-induced transformation of murine mammary cells in vitro. Carcinogenesis, 5, 937–940.
Sporn,M.B. (1984) The Retinoids. Academic Press, New York, NY.
Stahl,W., Nicolai,S., Briviba,K., Hanusch,M., Broszeit,G., Peters,M., Martin,H.-D. and Sies,H. (1997) Biological activities of natural and synthetic carotenoids: induction of gap junctional communication and singlet oxygen quenching. Carcinogenesis, 18, 89–92.
Stark,A.-A., Pagano,D.A., Glass,G., Kamin-Belsky,N. and Zeiger,R. (1994) The effects of antioxidants and enzymes involved in glutathione metabolism on mutagenesis by glutathione and L-cysteine. Mutat. Res., 308, 215–222.[Web of Science][Medline]
Stich,H.F. and Dunn,B.P. (1986) Relationship between cellular levels of beta-carotene and sensitivity to genotoxic agents. Int. J. Cancer, 38, 713–717.[Web of Science][Medline]
Stich,H.F. and Tsang,S.S. (1989) Promoting activity of betel quid ingredients and their inhibition by retinol. Cancer Lett., 45, 71–77.[Web of Science][Medline]
Stich,H.F., Tsang,S.S. and Palcic,B. (1990) The effect of retinoids, carotenoids and phenolics on chromosomal instability of bovine papillomavirus DNA-carrying cells. Mutat. Res., 241, 387–393.[Web of Science][Medline]
Sugimura,T., Okabe,K. and Nagao,M. (1966) The metabolism of 4-nitroquinoline-1-oxide, a carcinogen. III. An enzyme catalyzing the conversion of 4-nitroquinoline-1-oxide to 4-hydroxyaminoquinoline in rat liver and hepatomas. Cancer Res., 26, 1717–1721.
Tang,X. and Edenharder,R. (1997) Inhibition of the mutagenicity of 2-nitrofluorene, 3-nitrofluoranthene and 1-nitropyrene by vitamins, porphyrins and related compounds and vegetable and fruit juices and solvent extracts. Fd Chem. Toxicol., 35, 373–378.[Web of Science][Medline]
Tavan,E., Maziere,S., Narbonne,J.F. and Cassand,P. (1997) Effects of vitamins A and E on methylazoxymethanol-induced mutagenesis in Salmonella typhimurium strain TA100. Mutat. Res., 377, 231–237.[Web of Science][Medline]
Terwel,L. and van der Hoeven,J.C.M. (1985) Antimutagenic activity of some naturally occurring compounds towards cigarette-smoke condensate and benzo[a]pyrene in the Salmonella/microsome assay. Mutat. Res., 152, 1–4.[Web of Science][Medline]
Umegaki,K., Tacheuchi,N., Ikegami,S. and Ichikawa,T. (1994) Effect of ß-carotene on spontaneous and X-ray-induced chromosomal damage in bone marrow cells of mice. Nutr. Cancer, 22, 277–284.[Web of Science][Medline]
Victorin,K., Busk,L. and Ahlborg,U.G. (1987) Retinol (vitamin A) inhibits the mutagenicity of o-aminoazotoluene activated by liver microsomes from several species in the Ames test. Mutat. Res., 179, 41–48.[Web of Science][Medline]
Wang,C.-J., Shiah,H.-S. and Lin,J.-K. (1991a) Modulatory effect of crocetin on aflatoxin B1 cytotoxicity and DNA adduct formation in C3H10T1/2 fibroblast cell. Cancer Lett., 56, 1–10.[Web of Science][Medline]
Wang,C.-J., Shiow,S.-J. and Lin,J.-K. (1991b) Effects of crocetin on the hepatotoxicity and hepatic DNA binding of aflatoxin B1 in rats. Carcinogenesis, 12, 459–462.
Wang,W. and Higuchi,C.M. (1995) Induction of NAD(P)H:quinone reductase by vitamins A, E and C in Colo205 colon cancer cells. Cancer Lett., 98, 63–69.[Web of Science][Medline]
Waters,M.D., Brady,A.L., Stack,H.F. and Brockman,H.E. (1990) Antimutagenicity profiles for some model compounds. Mutat. Res., 238, 57–85.[Web of Science][Medline]
Waters,M.D., Stack,H.F., Jackson,M.A. and Brockman,H.E (1996a) Interpretation of short-term test data: implications for assessment of chemopreventive activity. In Stewart,B.W., McGregor,D. and Kleihues,P. (eds), Principles of Chemoprevention. IARC Scientific Publication no. 139, International Agency for Research on Cancer, Lyon, France, pp. 313–332.
Waters,M.D., Stack,H.F., Jackson,M.A., Brockman,H.E. and De Flora,S. (1996b) Activity profiles of antimutagens: in vitro and in vivo data. Mutat. Res., 350, 109–129.[Web of Science][Medline]
Wattenberg,L.W. (1981) Inhibitors of chemical carcinogens. In Burchenal,J.H. and Oettgen,H.F. (eds), Cancer. Achievements, Challenges and Prospects for the 1980s. Grune & Stratton, New York, NY, pp. 517–540.
Webster,R.P., Gawde,M.D. and Bhattacharya,R.K. (1996) Effect of different vitamin A status on carcinogen-induced DNA damage in repair enzymes in rats. In Vivo, 10, 113–118.[Web of Science][Medline]
Weitberg,A.B., Weitzman,S.A., Clark,E.P. and Stossel,T.P. (1985) Effects of antioxidants on antioxidant-induced sister chromatid exchange formation. J. Clin. Invest., 75, 1835–1841.
White,W.E.,Jr and Rock,S.G. (1981) Lack of comutagenicity by norharman and other compounds on revertants induced by photolabeling with 2-azido-9-fluorenone oxime. Mutat. Res., 84, 263–271.[Web of Science][Medline]
Whong,W.-Z., Stewart,J., Brockman,H.E. and Ong,T.-M. (1988) Comparative antimutagenicity of chlorophyllin and five other agents against aflatoxin B1-induced reversion in Salmonella typhimurium strain TA98. Teratogen. Carcinogen. Mutagen., 8, 215–224.[Web of Science][Medline]
Wilmer,J.W.G.M. and Spit,B.J. (1986) Influence of retinoids on the mutagenicity of cigarette-smoke condensate in Salmonella typhimurium TA98. Mutat. Res., 173, 9–11.[Web of Science][Medline]
Wolterbeek,A.P.M., Roggeband,R., van Morsel,C.J.A., Baan,R.A., Koeman,J.H., Feron,V.J. and Rutten,A.A.J.J.L. (1995) Vitamin A and ß-carotene influence the level of benzo[a]pyrene-induced DNA adducts and DNA-repair activities in hamster tracheal epithelium in organ culture. Cancer Lett., 91, 205–214.[Web of Science][Medline]
Yu,M.-W., Zhang,Y.-J., Blaner,W.-S. and Santella,R.M. (1994) Influence of vitamins A, C and E and ß-carotene on aflatoxin B1, binding to DNA in woodchucks hepatocytes. Cancer, 73, 596–604.[Web of Science][Medline]
Zhang,L.-X., Cooney,R.V. and Bertram,J.-S. (1991) Carotenoids enhance gap junctional communication and inhibit lipid peroxidation in C3H/10T1/2 cells: relationship to their cancer chemopreventive action. Carcinogenesis, 12, 2109–2114.
Zhang,L.-X., Cooney,R.V. and Bertram,J.-S. (1992) Carotenoids up-regulate connexin 43 gene expression independent of their provitamin A or antioxidant properties. Cancer Res., 52, 5707–5712.
Received on July 17, 1998; accepted on September 25, 1998.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  S.-K. Myung, Y. Kim, W. Ju, H. J. Choi, and W. K. Bae Effects of antioxidant supplements on cancer prevention: meta-analysis of randomized controlled trials Ann. Onc., July 21, 2009; (2009) mdp286v1. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Witschi Carcinogenic Activity of Cigarette Smoke Gas Phase and Its Modulation by Beta-Carotene and N-Acetylcysteine Toxicol. Sci., March 1, 2005; 84(1): 81 - 87. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. D. Gulkac, G. Akpinar, H. Ustun, and A. Ozon Kanli Effects of vitamin A on doxorubicin-induced chromosomal aberrations in bone marrow cells of rats Mutagenesis, May 1, 2004; 19(3): 231 - 236. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. M. Russell The Enigma of {beta}-Carotene in Carcinogenesis: What Can Be Learned from Animal Studies J. Nutr., January 1, 2004; 134(1): 262S - 268. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 The ATBC Study Group Incidence of Cancer and Mortality Following {alpha}-Tocopherol and {beta}-Carotene Supplementation: A Postintervention Follow-up JAMA, July 23, 2003; 290(4): 476 - 485. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. A. Koutsos, A. J. Clifford, C. C. Calvert, and K. C. Klasing Maternal Carotenoid Status Modifies the Incorporation of Dietary Carotenoids into Immune Tissues of Growing Chickens (Gallus gallus domesticus) J. Nutr., April 1, 2003; 133(4): 1132 - 1138. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
U. C. Obermueller-Jevic, I. Espiritu, A. M. Corbacho, C. E. Cross, and H. Witschi Lung Tumor Development in Mice Exposed to Tobacco Smoke and Fed {beta}-Carotene Diets Toxicol. Sci., September 1, 2002; 69(1): 23 - 29. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Liu, X.-D. Wang, R. T. Bronson, D. E. Smith, N. I. Krinsky, and R. M. Russell Effects of physiological versus pharmacological {beta}-carotene supplementation on cell proliferation and histopathological changes in the lungs of cigarette smoke-exposed ferrets Carcinogenesis, December 1, 2000; 21(12): 2245 - 2253. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Bianchini, S. Elmstahl, C. Martinez-Garcia, A.-L. van Kappel, T. Douki, J. Cadet, H. Ohshima, E. Riboli, and R. Kaaks Oxidative DNA damage in human lymphocytes: correlations with plasma levels of {alpha}-tocopherol and carotenoids Carcinogenesis, February 1, 2000; 21(2): 321 - 324. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||