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.
Kitteringham
N R
NR
Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool, Merseyside, UK.
Powell
H
H
Clement
Y N
YN
Dodd
C C
CC
Tettey
J N
JN
Pirmohamed
M
M
Smith
D A
DA
McLellan
L I
LI
Kevin Park
B
B
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