Comparison of oxidative stress response parameters in newborn mouse liver versus simian virus 40 (SV40)-transformed hepatocyte cell lines

Abstract

Induction of approximately one dozen genes and/or enzyme activities in liver of the untreated newborn c 14CoS /c 14CoS mouse—when compared with the c ch /c 14CoS heterozygote or the c ch /c ch wild-type—is the result of enhanced levels of reactive oxygenated metabolites originating from a block in the tyrosine degradation pathway. Oxidative stress activates genes via the electrophile response element, whereas dioxin activates genes via the receptor-mediated aromatic hydrocarbon response element. Here, we compared several parameters in 14CoS/14CoS versus ch/ch newborn mouse liver with that in simian virus 40 (SV40)-transformed hepatocyte lines that had been derived from newborn liver. We showed in this study that: (a) NADP(H):quinone oxidoreductase and UDP glucuronosyltransferase 1A6 mRNA levels were increased in both the (untreated) 14CoS/14CoS newborn liver and cell line; (b) aldehyde dehydrogenase 3A1 mRNA was increased by both oxidative stress and dioxin in hepatocyte cultures, but was not detectable in liver of the intact mouse; (c) the glutathione S-transferase GSTA1, GSTP1, GSTA3, and GSTM1 mRNA levels were increased by oxidative stress in 14CoS/14CoS newborn liver, but these transcripts were either low or undetectable in the cell lines; (d) GSTA1 mRNA was up-regulated by the absence of cytochrome P450 1A1 (CYP1A1) activity (i.e. the Gsta1 gene is a member of the aromatic hydrocarbon [ Ah] battery); and (e) GSTP1 mRNA was not up-regulated by the absence of CYP1A1 activity (i.e. Gstp1 is not a member of the [ Ah] battery). The 14CoS/14CoS and ch/ch hepatocyte established cell lines were transformed with SV40, which expresses large T antigen; this gene product is known to bind to, and interact with, several cell cycle regulatory proteins such as p53 and the retinoblastoma protein–E2F complex. It is therefore likely that differences in the oxidative stress responses between the 14CoS/14CoS newborn liver and the immortalized hepatocyte cell line might be explained by the presence of large T antigen in the established cell line.