Mutagenesis Advance Access originally published online on August 24, 2009
Mutagenesis 2009 24(6):481-493; doi:10.1093/mutage/gep032
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Signalling pathways involved in 1-nitropyrene (1-NP)-induced and 3-nitrofluoranthene (3-NF)-induced cell death in Hepa1c1c7 cells
Division of Environmental Medicine, Norwegian Institute of Public Health, PO Box 4404 Nydalen, N-0403 Oslo, Norway 1INSERM U620, Group ‘Toxicity of Environmental Contaminants’ labellisée Ligue contre le Cancer, 2 av Pr. Léon Bernard, 35043 Rennes Cédex, France 2EA 4427 SeRAIC, Université Rennes 1, IFR 140, 2 av Pr. Léon Bernard, 35043 Rennes Cédex, France 3Section of Chemistry and Toxicology, National Veterinary Institute, PO Box 8156 Dep., N-0033 Oslo, Norway 4Department of Biological and Chemical Working Environment, The National Institute of Occupational Health, PO Box 8149 Dep., N-0033 Oslo, Norway
We previously reported that 1-nitropyrene (1-NP) and 3-nitrofluoranthene (3-NF) elicited apoptotic cell death as well as non-apoptotic programmed cell deaths (PCDs) with paraptotic and necroptotic characteristics, respectively. In the present study, we have further confirmed and extended these findings. Flow cytometric analyses of 1-NP-exposed/3NF-exposed Hepa1c1c7 cells revealed that caspase-3 was only activated in the subpopulation of cells corresponding to that with classic apoptotic morphology. Immunocytochemical analysis indicated that leucocyte elastase inhibitor-derived DNaseII (LEI/L-DNaseII), apoptosis-inducing factor (AIF) and endonuclease G (EndoG) were more clearly translocated to the nucleus following 3-NF exposure than after 1-NP. These 3-NF-induced changes in AIF and EndoG translocation were reduced by necrostatin-1, an inhibitor of necroptotic cell death. Both compounds lead to accumulation of lipid droplets and induced DNA damage. Activation of checkpoint kinase (CHK) 1 and H2AX, but not ataxia telangiectasia mutated and CHK2, were observed. Furthermore, inhibition of p53 using pifithrin-
reduced the cell death induced by both compounds, suggesting a role of DNA damage/CHK1/p53 pathway in the death process. 1-NP-induced cell death was in addition characterized by increased oxidative damage and intracellular accumulation of Ca2+. These findings further support the notion that 1-NP elicited apoptotic cell death and PCD with paraptotic characteristics, while 3-NF induced apoptosis and a PCD with necroptotic features.
* To whom correspondence should be addressed. Tel: +47 21 07 62 47; Fax: +47 21 07 66 86; Email: jorn.holme{at}fhi.no
Received on February 13, 2009; revised on July 13, 2009; accepted on July 16, 2009.