Nitric Oxide Inhibits Apoptosis by Preventing Increases in Caspase-3-like Activity via Two Distinct Mechanisms

• Published in: The Journal of biological chemistry Vol. 272; no. 49; pp. 31138 - 31148
• Main Authors: Kim, Young-Myeong, Talanian, Robert V., Billiar, Timothy R.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 05.12.1997; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Apoptosis - drug effects; Caspase 3; Caspases; Cells, Cultured; Cyclic GMP - metabolism; Cysteine Endopeptidases - metabolism; Cysteine Proteinase Inhibitors - pharmacology; DNA Fragmentation - drug effects; Enzyme Activation; Enzyme Inhibitors - pharmacology; Enzyme Precursors - metabolism; Interleukin-1 - pharmacology; Liver - cytology; Liver - drug effects; Male; Membrane Glycoproteins - metabolism; Nitric Oxide - pharmacology; Rats; Rats, Sprague-Dawley; Tumor Necrosis Factor-alpha - pharmacology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.272.49.31138

Nitric oxide (NO) has emerged as an important endogenous inhibitor of apoptosis, and here we report that NO prevents hepatocyte apoptosis initiated by the removal of growth factors or exposure to TNFα or anti-Fas antibody. We postulated that the mechanism of the inhibition of apoptosis by NO would include an effect on caspase-3-like protease activity. Caspase-3-like activity increased coincident with apoptosis due to all three stimuli, and treatment with the caspase-3-like protease inhibitorN-acetyl-Asp-Glu-Val-Asp-aldehyde inhibited both proteolytic activity and apoptosis. Endogenous or exogenous sources of NO prevented the increase in caspase-3-like activity in hepatocytes. Exposure of purified recombinant caspase-3 to an NO or NO+donor inhibited proteolytic activity. Dithiothreitol (DTT), but not glutathione, reversed the inhibition of recombinant caspase-3 by NO. When lysates from cells stimulated to express inducible NO synthase or cells exposed to NO donors were incubated in DTT, caspase-3-like activity increased to about 55% of cells not exposed to a source of NO. Similarly, administration of an NO donor to rats treated with TNFα and d-galactosamine also prevented the increase in caspase-3-like activity as measured in liver homogenates. The effect of the NO donor was reversed by about 50% if the homogenate was incubated with DTT. TNFα-induced apoptosis and caspase-3-like activity were also reduced in cultured hepatocytes exposed to 8-bromo-cGMP, and both effects were inhibited by the cGMP-dependent kinase inhibitor KT5823. The suppression in caspase-3-like activity in hepatocytes exposed to an NO donor was partially blocked by an inhibitor of soluble guanylyl cyclase, 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one, (ODQ), while the incubation of these lysates in DTT almost completely restored caspase-3-like activity to the level of TNFα-treated controls. These data indicate that NO prevents apoptosis in hepatocytes by either directly or indirectly inhibiting caspase-3-like activation via a cGMP-dependent mechanism and by direct inhibition of caspase-3-like activity through proteinS-nitrosylation.