Ethanol plus the Jo2 Fas agonistic antibody-induced liver injury is attenuated in mice with partial ablation of argininosuccinate synthase.
BACKGROUND
Argininosuccinate synthase (ASS) is an enzyme shared by the urea cycle and the l-citrulline/nitric oxide (NO·) cycle. ASS is the rate-limiting enzyme in the urea cycle and along with nitric oxide synthase 2 (NOS2), it endows cells with the l-citrulline/NO· salvage pathway to continuously supply l-arginine from l-citrulline for sustained NO· generation. Thus, ASS conditions NO· synthesis by NOS2. Because of the relevance of NOS2 activation for liver injury, we examined the contribution of ASS to NO· generation and how it impacts liver injury.


METHODS
Wild-type (WT) mice and Ass(+/-) mice (Ass(-/-) mice are lethal) were intraperitoneally injected with ethanol (EtOH) at a dose of 2.5 g/kg of body weight twice a day for 3 days. Two hours after the last dose of EtOH, mice were administered the agonistic Jo2 anti-mouse Fas monoclonal antibody (Ab) at a dose of 0.2 μg/g of body weight. Mice were sacrificed 8 hours after the Jo2 Ab injection. Markers of nitrosative and oxidative stress as well as liver damage were analyzed.


RESULTS
EtOH plus Jo2 injection induced liver injury as shown by serum alanine aminotransferase and aspartate aminotransferase activity, liver pathology, TUNEL, and cleaved caspase-3 were lower in Ass(+/-) mice compared with WT mice, suggesting that ASS contributes to EtOH plus Jo2-mediated liver injury. CYP2E1 induction, glutathione depletion, and elevated thiobarbituric acid reactive substances were comparable in both groups of mice, suggesting that CYP2E1-mediated oxidative stress is not linked to ASS-induced liver injury. In contrast, NOS2 induction, 3-nitrotyrosine adducts formation and elevated nitrites, nitrates, and S-nitrosothiols were higher in livers from WT mice than from Ass(+/-) mice.


CONCLUSIONS
Decreased nitrosative stress causes lower EtOH plus Jo2-induced liver injury in Ass(+/-) mice.
Division of Liver Diseases , Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York.
Yongke
Y
Lu
Stephen C
SC
Ward
Natalia
N
Nieto
D000818:Animals; D001124:Argininosuccinate Synthase / Q000378:metabolism*; D002492:Central Nervous System Depressants / Q000009:adverse effects*; D056486:Chemical and Drug Induced Liver Injury / Q000201:enzymology* / Q000209:etiology / Q000473:pathology; D019392:Cytochrome P-450 CYP2E1 / Q000378:metabolism; D000431:Ethanol / Q000009:adverse effects*; D008099:Liver / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D018384:Oxidative Stress; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D019014:fas Receptor / Q000819:agonists*
D002492:Central Nervous System Depressants; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor; D000431:Ethanol; D019392:Cytochrome P-450 CYP2E1; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D001124:Argininosuccinate Synthase
Nitric Oxide Synthase 2; Nitrosative Stress; Urea Cycle; l-Citrulline/NO· Cycle