iNOS/NO signaling regulates apoptosis induced by glycochenodeoxycholate in hepatocytes.

Inducible nitric oxide synthase (iNOS) and nitric oxide (NO) can ameliorate apoptosis induced by toxic glycochenodeoxycholate (GCDC) in hepatocytes. However, the underlying molecular mechanisms are not yet understood in detail. This study is to clarify the function of iNOS/NO and its mechanisms during the apoptotic process. The apoptosis was brought about by GCDC in rat primary hepatocytes. iNOS/NO signaling was then investigated. iNOS inhibitor 1400W enhanced the GCDC-induced apoptosis as reflected by caspase-3 activity and TUNEL assay. Exogenous NO regulated the apoptosis subsequent to NO donor S-nitroso-N-acetyl-penicillamine (SNAP) or sodium nitroprusside (SNP). The GCDC-induced apoptosis was decreased with 0.1mM SNAP or 0.15mM SNP, while it was increased with 0.8mM SNAP or 1.2mM SNP. The endogenous iNOS inhibited apoptosis, but the exogenous NO played a dual role during the GCDC-induced apoptosis. There was a potential iNOS/Akt/survivin axis that inhibited the hepatocyte apoptosis in low doses of NO donors. In contrast, high doses of NO donors activated CHOP through p38MAP-kinase (p38MAPK), upregulated TRAIL receptor DR5, and suppressed survivin. Consequently the high doses of NO donors promoted the apoptosis in hepatocytes. Our data suggest that the iNOS/NO signaling can modulate Akt/survivin and p38MAPK/CHOP pathways to mediate the GCDC-induced the apoptosis in hepatocytes. These signaling pathways may serve as targets for therapeutic intervention in cholestatic liver disease.

Wang K ，Brems JJ ，Gamelli RL ，Holterman AX ... -  《-》

Inducible NO synthase confers chemoresistance in head and neck cancer by modulating survivin.

The dual role of the inducible NO synthase (iNOS) and NO signaling in head and neck squamous cell carcinoma (HNSCC) is a complex and can both promote or inhibit tumor progression. However, the underlying molecular mechanisms are not yet resolved in detail. We show for the first time that conditions, favoring low NO levels conferred resistance against cisplatin/taxol-induced apoptosis in HNSCC cell lines. Cytoprotection was mediated by survivin, because we observed its upregulation subsequent to low doses of the NO donors S-nitroso-N-acetyl-penicillamine (SNAP) and sodium nitroprusside (SNP) or ectopic expression of physiologic amounts of iNOS. Also, RNAi-mediated depletion of survivin blocked NOs anti-apoptotic effects. Induction of survivin involves activation of the phosphatidylinositol-3-kinase/Akt (PI3K/Akt) pathway, which was antagonized by the PI3K-inhibitor LY294002. Importantly, application of the iNOS-specific inhibitor 1400W combined with RNAi-mediated downregulation of survivin cooperatively enhanced drug-induced cell death. The iNOS/survivin-axis appears to be also of clinical relevance since immunohistochemistry revealed that iNOS expression correlated with enhanced survivin levels in HNSCC specimens. In contrast, high NO concentrations suppressed survivin levels in HNSCC but also in non-malignant cells resulting in apoptosis. Cell death induced by high amounts of SNAP/SNP or by strong overexpression of iNOS involved activation of p38MAP-kinase, which was counteracted by the p38MAP-kinase inhibitor SB202190. Here, we provide evidence for a novel molecular mechanism how NO signaling may contribute to therapy resistance in HNSCC by modulating survivin expression. Our data further suggest pursuing pharmacogenetic iNOS/survivin-targeting approaches as potential therapeutic strategies in head and neck cancer.

Fetz V ，Bier C ，Habtemichael N ，Schuon R ，Schweitzer A ，Kunkel M ，Engels K ，Kovács AF ，Schneider S ，Mann W ，Stauber RH ，Knauer SK ... -  《-》

Glycochenodeoxycholate (GCDC) inhibits cytokine induced iNOS expression in rat hepatocytes.

Bucher BT ，Feng X ，Jeyabalan G ，Zhang B ，Shao L ，Guo Z ，Geller DA ... -  《JOURNAL OF SURGICAL RESEARCH》

NO signaling confers cytoprotectivity through the survivin network in ovarian carcinomas.

Engels K ，Knauer SK ，Loibl S ，Fetz V ，Harter P ，Schweitzer A ，Fisseler-Eckhoff A ，Kommoss F ，Hanker L ，Nekljudova V ，Hermanns I ，Kleinert H ，Mann W ，du Bois A ，Stauber RH ... -  《-》

Nitric oxide ameliorates hydrophobic bile acid-induced apoptosis in isolated rat hepatocytes by non-mitochondrial pathways.

Gumpricht E ，Dahl R ，Yerushalmi B ，Devereaux MW ，Sokol RJ ... -  《JOURNAL OF BIOLOGICAL CHEMISTRY》