Interleukin-1-induced nitric oxide production modulates glutathione synthesis in cultured rat hepatocytes.
In cultured rat hepatocytes, we have previously demonstrated that inhibition of interleukin-1 (IL-1)-mediated nitric oxide (NO) synthesis is associated with depletion of intracellular reduced glutathione (GSH) in toxin-mediated oxidative injury. To further examine NO's effects on GSH metabolism in rat hepatocytes, IL-1-mediated NO synthesis was examined in the context of 1) cysteine, cystine, and methionine uptake; 2) gene transcription and enzyme activities for gamma-glutamylcysteine synthetase, the rate-limiting enzyme in GSH synthesis, glutathione reductase, and glutathione peroxidase; and 3) GSH and oxidized glutathione (GSSG) levels. Inhibition of NO synthesis decreased the GSH content and GSH/GSSG ratio in a guanylyl cyclase-independent fashion. Enzyme activity and steady-state levels of mRNA for gamma-glutamylcysteine synthetase were also depressed. Nuclear run-on analysis demonstrated ablation of gamma-glutamylcysteine synthetase gene transcription. Hepatocellular uptake of cysteine, cystine, and methionine was not altered. Activity and steady-state mRNA levels for glutathione reductase and glutathione peroxidase were not affected. These results indicate that IL-1-mediated NO synthesis regulates hepatocyte GSH synthesis through a mechanism that is dependent on transcriptional regulation of the rate-limiting enzyme in GSH synthesis. In the setting of oxidative stress and IL-1 exposure, hepatocyte synthesis of NO may be protective through regulation of GSH synthesis.
Kuo
P C
PC
Department of Surgery, University of Maryland, Baltimore 21201, USA.
Abe
K Y
KY
Schroeder
R A
RA
D000818:Animals; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D005978:Glutathione / Q000096:biosynthesis*; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D008099:Liver / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D051381:Rats; D011917:Rats, Inbred Lew; D011994:Recombinant Proteins / Q000494:pharmacology
D007375:Interleukin-1; D011994:Recombinant Proteins; D009569:Nitric Oxide; D005978:Glutathione