Protection against concanavalin A-induced hepatocyte apoptosis by molsidomine is time-dependent.
BACKGROUND
Viral hepatitis and autoimmune liver diseases cause hepatocyte apoptosis. Concanavalin A (Con A)-induced hepatitis resembles human viral hepatitis and autoimmune hepatitis. The role of nitric oxide (NO) in liver injury was controversial in different liver injury models. We hypothesize both endogenous and exogenous NO protect liver against Con A-induced liver injury. Molsidomine is metabolized into SIN-1 by the liver, and SIN-1 subsequently generates NO. So, molsidomine was used as a NO donor in this study.


METHODS
To study a protective role of endogenous NO in Con A-induced liver injury, mice were pretreated with a specific inducible nitric oxide synthase (iNOS) inhibitor, L-N(6)-(1-iminoethyl)-lysine (L-NIL), before Con A challenge. To study a time-dependent protection against Con A-induced liver injury, animals were either given molsidomine, a NO donor, before or after Con A administration. Serum alanine aminotranferase (ALT) was analyzed. Liver samples were subjected to DNA fragmentation assay, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling stain, Western blot analysis, and caspase activity assays.


RESULTS
Animals pretreated with L-NIL had significantly increased serum ALT levels compared with those challenged with Con A alone; but pretreatment with molsidomine dramatically decreased ALT levels in L-NIL-pretreated animals or in animals that received Con A alone. Administration of molsidomine 30 minutes before or 1, 2, and 3 hours after Con A injection significantly reduced serum ALT levels and attenuated hepatocyte apoptosis from caspase inactivation. The ALT reduction was associated with inhibition of both caspase-3 and caspase-8 activation and reduction of hepatocyte apoptosis.


CONCLUSIONS
Endogenous NO plays an important protective role against Con A-induced liver injury by reducing hepatocyte apoptosis. Administration of a NO donor early after Con A injection protects the liver from injury. This is the first study demonstrating a time-dependent inhibition of liver injury induced by Con A administration.
Ding
Jin Wen
JW
Department of Surgery, Loyola University Medical Center, Maywood, IL 60607, USA.
Wang
Kewei
K
Brems
John J
JJ
Gamelli
Richard L
RL
D000410:Alanine Transaminase / Q000097:blood; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000097:blood; D056486:Chemical and Drug Induced Liver Injury / Q000209:etiology*; D003208:Concanavalin A / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D022781:Hepatocytes / Q000187:drug effects*; D008239:Lysine / Q000031:analogs & derivatives* / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D008981:Molsidomine / Q000494:pharmacology*; D009569:Nitric Oxide / Q000502:physiology; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000502:physiology*; D052247:Nitric Oxide Synthase Type II; D013997:Time Factors
D004791:Enzyme Inhibitors; C090663:N(6)-(1-iminoethyl)lysine; D020030:Nitric Oxide Donors; D003208:Concanavalin A; D009569:Nitric Oxide; D008981:Molsidomine; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D000410:Alanine Transaminase; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; C505409:Casp3 protein, mouse; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D008239:Lysine