Nitric oxide is not involved in hepatocyte killing by neutrophils activated by N-formyl-methionyl-leucyl-phenylalanine or phorbol myristate acetate in vitro
✍ Scribed by J G Wagner; P E Ganey; R A Roth
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 252 KB
- Volume
- 23
- Category
- Article
- ISSN
- 0270-9139
No coin nor oath required. For personal study only.
✦ Synopsis
hepatocytes in coculture with activated PMNs. Thus, Polymorphonuclear leukocytes (PMNs) have been im-PMNs and hepatocytes produced NO in vitro, but neiplicated as cellular mediators of hepatic injury in models ther suppression nor elevation of NO production afof inflammation in vivo. In vitro, hepatocyte killing by fected PMN-mediated hepatocyte killing. Accordingly, activated PMNs is mediated in part by proteases, but NO is not involved in the mechanisms by which FMLPthe role of nitric oxide is unknown. NO is produced by or PMA-stimulated PMNs mediate hepatocyte injury PMNs and hepatocytes and can act either to damage or in vitro. (HEPATOLOGY 1996;23:803-810.) protect in various models of toxicity. Therefore, we tested the hypothesis that NO is important in PMN-mediated hepatocyte killing in vitro. Freshly isolated hepato-Polymorphonuclear leukocytes (PMNs) are versatile cytes from rat liver and PMNs elicited from rat perito-
cells that combat pathogens by phagocytosis and proneum were cultured together or alone for 16 hours. Both duction of cytotoxic mediators. Extracellular release of cell types spontaneously released NO, estimated as its stable breakdown product, nitrite. Accumulation of ni-the same toxic messengers can have injurious consetrite in medium from hepatocyte cultures was augquences to host tissue. Tissue damage spawned by actimented threefold by incubation with L-arginine and was vated PMNs can make a substantial, detrimental concompletely inhibited by treatment with the nitric oxide tribution to the sequelae of various diseases. For synthase (NOS) inhibitor N G -methyl-L-arginine (NMA). example, PMNs have been implicated in models of com-Nitrite release in PMN cultures was unaffected by L-argiplement-mediated 1 and endotoxin-induced 2 lung injunine addition and only partially inhibited by NMA. In ries and ischemia-reperfusion damage to the heart. 3 PMN:hepatocyte cocultures (10:1), accumulation of ni-Evidence exists for PMN involvement in certain modtrite was additive relative to cells cultured separately.
els of liver injury in the rat. Both endotoxin-and a-Incubation with NMA blocked nitrite production comnaphthylisothiocyanate-induced hepatotoxicities are pletely in cocultures, whereas L-arginine caused a twofold increase in nitrite. Addition of PMN stimulants, prevented by prior depletion of PMNs. 4,5 In vitro, stim-N-formyl-methionyl-leucyl-phenylalanine (FMLP), or ulated rat PMNs injure hepatic parenchymal cells, 6,7 phorbol myristate acetate (PMA), caused increased rebut the specific mechanisms by which cytotoxicity oclease of alanine aminotransferase (ALT) activity into curs have not been revealed fully. Initial results sugmedium from hepatocytes cultured with PMNs but not gested a role for proteases and little or no participation from hepatocytes cultured alone; this indicated that by oxygen-derived free radicals. [6][7][8] We considered the injury to hepatocytes was due to activated PMNs. Howpotential for involvement of nitric oxide. Production of ever, neither FMLP nor PMA significantly altered nicytotoxic concentrations of NO by host defense cells is trite release from cocultures. Despite the alterations an important mechanism for eliminating pathogens. in NO production induced by addition of NMA or L-NO can be produced in copious amounts by rat PMNs arginine, neither agent altered the release of ALT from in vitro 9,10 and participates in bacterial cell killing by human PMNs. 11 Macrophages produce NO as a cyto-Abbreviations: PMN, polymorphonuclear leukocyte; NOS, nitric oxide syntoxic mediator in the killing of tumor cells 12 and parathase; FMLP, N-formyl-methionyl-leucyl-phenylalanine; PMA, phorbol myrissites. 13 tate acetate; NMA, N G -methyl-L-arginine; ALT, alanine aminotransferase.