Hepatocellular response to chemical stress in CD-1 mice: induction of early genes and gamma-glutamylcysteine synthetase.
Exposure of cells to toxic chemical species can result in reduced glutathione (GSH) depletion, generation of free radicals, and/or binding to critical cell determinants. Chemical stress is usually followed by a concerted cellular response aimed at restoring homeostasis, although the precise initial stimulus for the response is unclear. We have focused on one component of this stress response, the up-regulation of gamma-glutamylcysteine synthetase (gamma-GCS) and the preceding molecular events involved in its regulation in an in vivo mouse model. Male CD-1 mice received buthionine sulphoximine (BSO; 7.2 mmol/kg), diethyl maleate (DEM; 4.2 mmol/kg), paracetamol (APAP; 3.5 and 1.0 mmol/kg), or carbon tetrachloride (CCl(4); 1.0 and 0.2 mmol/kg). Biochemical (serum transaminase and hepatic GSH levels) and molecular (c-jun and c-fos messenger RNA [mRNA] levels and activator protein 1 [AP-1] DNA binding activity) parameters were measured, as well as the consequent effects on gamma-GCS levels and activity. All compounds produced GSH depletion, but only the higher doses of APAP and CCl(4) caused liver damage. DEM, APAP, and CCl(4) increased c-jun and c-fos mRNA levels, together with an increase in AP-1 binding; BSO failed to induce AP-1 despite an increase in c-fos. Interestingly, the effects on gamma-GCS varied markedly according to the compound: BSO and DEM increased gamma-GCS enzyme activity, although only DEM, but not BSO, resulted in an increase in gamma-GCS(h) mRNA and protein. In contrast, APAP and CCl(4) both increased gamma-GCS(h) mRNA and protein; however, there was a marked dose-dependent decrease in gamma-GCS activity. These data indicate that the effect of chemical stress on the liver is compound specific and is not merely dependent on depletion of GSH.
Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool, Merseyside, UK.
N R
NR
Kitteringham
H
H
Powell
Y N
YN
Clement
C C
CC
Dodd
J N
JN
Tettey
M
M
Pirmohamed
D A
DA
Smith
L I
LI
McLellan
B
B
Kevin Park
D000082:Acetaminophen / Q000633:toxicity; D000818:Animals; D019328:Buthionine Sulfoximine / Q000633:toxicity; D002251:Carbon Tetrachloride / Q000633:toxicity; D005786:Gene Expression Regulation / Q000187:drug effects*; D016762:Genes, fos; D016758:Genes, jun; D005721:Glutamate-Cysteine Ligase / Q000096:biosynthesis* / Q000235:genetics; D008099:Liver / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008297:Male; D008298:Maleates / Q000633:toxicity; D051379:Mice; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018808:Transcription Factor AP-1 / Q000378:metabolism
D008298:Maleates; D018808:Transcription Factor AP-1; D000082:Acetaminophen; D019328:Buthionine Sulfoximine; D002251:Carbon Tetrachloride; D005721:Glutamate-Cysteine Ligase; C014476:diethyl maleate