Sodium Nitroprusside-Induced Mitochondrial Apoptotic Events in Insulin-Secreting RINm5F Cells Are Associated with MAP Kinases Activation

• Published in: Experimental cell research 2001-10, Vol.269 (2), p.222-229
• Main Authors: Bernabé, Julio C., Tejedo, Juan R., Rincón, Pilar, Cahuana, Gladys M., Ramı́rez, Remedios, Sobrino, Francisco, Bedoya, Francisco J.
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Bcl-2; Blotting, Western; Caspase 3; Caspases - metabolism; Catalase - metabolism; Cell Line; Cell Survival; Cells, Cultured; Cytochrome c Group - metabolism; Enzyme Activation; Enzyme Inhibitors - pharmacology; Free Radicals; Imidazoles - pharmacology; Indicators and Reagents - pharmacology; Insulin - metabolism; Islets of Langerhans - metabolism; MAP Kinase Signaling System; MAPKs; Mitochondria - pathology; Mitogen-Activated Protein Kinases - metabolism; nitric oxide; Nitric Oxide - metabolism; Nitroprusside - pharmacology; pancreatic beta cell; Phosphatidylinositol 3-Kinases - antagonists & inhibitors; Phosphorylation; Precipitin Tests; Protein Binding; Proto-Oncogene Proteins c-bcl-2 - metabolism; Pyridines - pharmacology; Rats; Signal Transduction; Superoxide Dismutase - metabolism; Time Factors; Transfection
• ISSN: 0014-4827; 1090-2422
• DOI: 10.1006/excr.2001.5315

Exposure of insulin-secreting RINm5F cells to the chemical nitric oxide donor sodium nitroprusside (SNP) resulted in apoptotic cell death, as detected by cytochrome c release from mitochondria and caspase 3 activation. SNP exposure also leads to phosphorylation and activation of enzymes involved in cellular response to stress such as signal-regulated kinase 2 (ERK2) and c-Jun NH2-terminal kinase 46 (JNK46). Both cytochrome c release and caspase 3 activation were abrogated in cells exposed to MEK and p38 inhibitors. Treatment of cells with the NO donors SNP, DETA–NO, GEA 5024, and SNAP resulted in phosphorylation of the antiapoptotic protein Bcl-2, which was resistant to blockade of MEK, p38, and JNK pathways and sensitive to phosphoinositide 3-kinase (PI3K) inhibition. In addition, transient transfection of cells with the wild-type PI3K γ gene mimics the increased rate of Bcl-2 phosphorylation detected in NO-treated cells. The generation of phosphoinositides seems to participate in the process since Bcl-2 phosphorylation was not observed in cells overexpressing lipid-kinase-deficient PI3Kγ. The potential of SNP toxicity directly from NO was supported by our finding that the NO scavenger carboxy-PTIO prevented cell death. We found no evidence to support the contention that oxygen radicals generated during cellular SNP metabolism mediate cell toxicity in RINm5F cells, since neither addition of catalase/superoxide dismutase nor transfection with superoxide dismutase prevented SNP-induced cell death. Thus, we propose that exposure to apoptotic concentrations of NO triggers ERK- and p38-dependent cytochrome c release, caspase 3 activation, and PI3K-dependent Bcl-2 phosphorylation.