title: Signal pathway responsible for hepatocyte preconditioning by nitric oxide.
abstract: Nitric oxide (NO) improves liver resistance to hypoxia/reperfusion injury acting as a mediator of hepatic preconditioning. However, the mechanisms involved are still poorly understood. In this study, we have investigated the mechanisms by which short-term exposure to the NO donor (Z)-1-(N-methyl-N-[6-(N-methylammoniohexyl)amino])-diazen-1-ium-1,2-diolate (NOC-9) increases hepatocyte tolerance to hypoxic injury. Isolated rat hepatocytes preincubated 15 min with NOC-9 (0.250 mM) became resistant to the killing caused by hypoxia. NOC-9 cytoprotection did not involve the activation of protein kinase C, but was instead blocked by inhibiting soluble guanylate cyclase with 1H-(1,2,4)-oxadiazolo-(4,3) quinoxalin-1-one (ODQ) (50 microM) or cGMP-dependent kinase (cGK) with KT 5823 (5 microM). Conversely, cGMP analogue, 8Br-cGMP (50 microM) mimicked the effect of NOC-9. Western blot analysis revealed that hepatocyte treatment with NOC-9 or 8Br-cGMP significantly increased dual phosphorylation of p38 MAPK. The activation of p38 MAPK was abolished by inhibiting guanylate cyclase or cGK. Pretreatment with NO significantly reduced intracellular Na(+) accumulation in hypoxic hepatocytes. This effect was reverted by KT 5823 as well as by the p38 MAPK inhibitor SB203580. SB203580 also reverted NOC-9 protection against hypoxic injury. Altogether, these results demonstrated that NO can induce hepatic preconditioning by activating p38 MAPK through a guanylate cyclase/cGK-mediated pathway.
authors.affiliation: Department of Medical Science, University "A Avogadro" of East Piedmont, Novara, Italy. carini@med.no.unipmn.it
authors.forename: Rita
authors.initials: R
authors.lastname: Carini
authors.forename: Maria
authors.initials: M
authors.lastname: Grazia De Cesaris
authors.forename: Roberta
authors.initials: R
authors.lastname: Splendore
authors.forename: Cinzia
authors.initials: C
authors.lastname: Domenicotti
authors.forename: Maria Paola
authors.initials: MP
authors.lastname: Nitti
authors.forename: Maria Adelaide
authors.initials: MA
authors.lastname: Pronzato
authors.forename: Emanuele
authors.initials: E
authors.lastname: Albano
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002227:Carbazoles / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005609:Free Radicals; D006162:Guanylate Cyclase / Q000378:metabolism; D022781:Hepatocytes / Q000378:metabolism*; D000860:Hypoxia; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D019194:Ischemic Preconditioning; D008099:Liver / Q000293:injuries / Q000473:pathology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D009569:Nitric Oxide / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D015398:Signal Transduction; D012964:Sodium / Q000378:metabolism; D013997:Time Factors; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D002227:Carbazoles; D004791:Enzyme Inhibitors; D005609:Free Radicals; D007093:Imidazoles; D007211:Indoles; D011725:Pyridines; C073601:KT 5823; D009569:Nitric Oxide; D012964:Sodium; D017869:Cyclic GMP-Dependent Protein Kinases; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D006162:Guanylate Cyclase; C093642:SB 203580