title: Nitric oxide ameliorates hydrophobic bile acid-induced apoptosis in isolated rat hepatocytes by non-mitochondrial pathways.
abstract: Hydrophobic bile acids are toxic to isolated rat hepatocytes by mechanisms involving mitochondrial dysfunction and oxidative stress. In the current study we examined the role of nitric oxide (NO), a potential mediator of apoptosis, during bile acid-induced apoptosis. Freshly isolated rat hepatocytes and hepatic mitochondria generated NO and peroxynitrite (ONOO(-)) in a concentration- and time-dependent manner when exposed to the toxic bile salt glycochenodeoxycholate (GCDC) (25-500 microm), which was prevented by the nitric-oxide synthase (NOS) inhibitors N(G)-monomethyl-N-arginine monoacetate (l-NMMA) and 1400W. Relationships between hepatocyte NO production and apoptosis were examined by comparing the effects of NOS inhibitors with other inhibitors of GCDC-induced apoptosis. Inhibitors of caspases 8 and 9, the mitochondrial permeability transition blocker cyclosporin A, and the antioxidant idebenone reduced NO generation and apoptosis in GCDC-treated hepatocytes. In contrast, NOS inhibitors had no effect on GCDC-induced apoptosis despite marked reduction of NO and ONOO(-). However, treatment with the NO donors S-nitroso-N-acetylpenicillamine and spermine NONOate [N-(-aminoethyl)N-(2-hydroxy-2-nitrohydrazino)-1,2-ethylenediamine) inhibited apoptosis and caspase 3 activity while significantly elevating NO levels above GCDC-stimulated levels. Neither NO donors nor NOS inhibitors affected GCDC-induced mitochondrial permeability transition or cytochrome c release from liver mitochondria or GCDC-induced mitochondrial depolarization from isolated hepatocytes, suggesting that NO inhibits bile acid-induced hepatocyte apoptosis by a non-mitochondrial-dependent pathway. In conclusion, whereas NO produced from GCDC-treated hepatocytes neither mediates nor protects against bile acid-induced apoptosis, higher levels of NO inhibit GCDC-induced hepatocyte apoptosis by caspase-dependent pathways.
authors: Pediatric Liver Center and Liver Transplantation Program, Section of Pediatric Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, University of Colorado School of Medicine, Denver 80262, USA.
authors: Eric
authors: E
authors: Gumpricht
authors: Rolf
authors: R
authors: Dahl
authors: Baruch
authors: B
authors: Yerushalmi
authors: Michael W
authors: MW
authors: Devereaux
authors: Ronald J
authors: RJ
authors: Sokol
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D005999:Glycochenodeoxycholic Acid / Q000494:pharmacology*; D022781:Hepatocytes / Q000187:drug effects*; D008297:Male; D008930:Mitochondria, Liver / Q000378:metabolism*; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D005999:Glycochenodeoxycholic Acid; D019001:Nitric Oxide Synthase