Transcriptional‐ and post‐transcriptional‐dependent regulation of glutathione S‐transferase expression in rat hepatocytes as a function of culture conditions

Abstract

Transcriptional activity of the glutathlone S-transfemse (GST) ~t (subumt~ 1 and 2),/~ (.~ubunit~ 3 and 4) :rod rt (~ubumt 7) gent fam~hes has been analyzed u~mg the nuclear "run-on' technique on adult rat hepatoeyte~ ,naintained for 4 days m convenuonal culture and for 4 and 12 days in co-culture with rat liver epithehal cells. Several medium conditions are included m tlus utudy, namely with or without fetal calf ~rum and with meotmamide or dlmethylnulphoxlde. Hepatocyte~ co-cultured for 4 days maintain approximatdy 30-70% of the a t~ene family transcriptional acuvity, whatever the medium conditions, when compared to freshly isolated hepatocytes. A marked decrease is observed after 12 days ofeo-culture or when hepatoeytes are maintained in convenuonal culture. The tmn~npuonal activity of the/~ gene family is saammiugd at 40-160% when hepatocytes are cultured with or without fetal calf serum, and is inducible by nicotinamidc (approximately 4-fold) and d:meth]llsulphoxlde (approximately 2-fold) m conventional culture and/or in co-culture. In contrast to freshly ~solated hepatocyte.% GST ~ gene transcriptional activity is observed in eouventLonal and go-cultured hepatoeytes, trrespeetive of the medium conditions. Dlmcthylsulphoxidc treatment however, represses the expression of GST 7 in vitro. These rehultn demonbtrate that the expression of GST 0~,/~ and rt genes m conventional and eo.eultured rat hepatoeytgs is controlled primarily at the level of transerq)tion. It cannot be excluded, however, that dimethylsulphoxide ntablllze~ the GST mRNA levels m vitro,

Regulation of the Major Detoxication Functions by Phenobarbital and 3‐Methylcholanthrene in Co‐Cultures of Rat Hepatocytes and Liver Epithelial Cells

“…It has been shown that the level of transcription of the aldolase B, albumin and GST genes was increased in co-cultures, whereas it disappeared in pure hepatocyte cultures (Fraslin et al, 1985;Vandenberghe et al, 1992). Although we have not determined the actual transcription rate of the genes surveyed in the present study, it seems likely that active transcription could account for most, if not all, of the mRNA levels we have analysed, especially as a result of phenobarbital or 3-methylcholanthrene treatment, similarly to results in vivo.…”

Nicotinamide, a missing link in the early stress response in eukaryotic cells: A hypothesis with special reference to oxidative stress in plants

“…Other observations also point to an effect of NIC on gene expression, e.g. an increased rate of glutathione transferase gene transcription in hepatocytes [20], increased transcription of membrane-bound alkaline phosphodiesterase in human tumor-derived fibroblasts [21], increased expression of the growth hormone (GH) gene and an increase in its response to triiodothyronine (T3) in human pituitary cells [22] and Friend erythroleukemia cell differentiation [23]. A compilation of NIC effects in animal tissues is shown in Table 1.…”

“…$ cyt P-450, glutathione transferase (GT) (rat liver) [17] $ glutathione (GSH), glutathione reductase (GR) (rat liver) [18] q" GT gene transcription (hepatocyte) [20] 1" membrane bound alkaline phosphodiesterase (human fibroblasts) […”

Defensive and secondary metabolism in plant tissue cultures, with special reference to nicotinamide, glutathione and oxidative stress

“…1989). Recent investigations with animal cell cultures show an effect of NIC at the level of gene expression, e.g., increased glutathione transferase gene transcription in hepatocytes (Vandenberghe et al 1992) and an increase in the activity of membrane-bound alkaline phosphodiesterase I in fibroblast cell cultures (Maruyama et al 1992). In human pituitary cells NIC caused increased expression of the growth hormone (GH) gene and an increase in its response to triiodothyronine (T3) (S~chez-Pacheco & Aranda 1992).…”