RT Journal Article SR Electronic T1 Post-Transcriptional Regulation of Human Inducible Nitric-Oxide Synthase Expression by the Jun N-terminal Kinase JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 1427 OP 1434 DO 10.1124/mol.106.033449 VO 71 IS 5 A1 Riku Korhonen A1 Katrin Linker A1 Andrea Pautz A1 Ulrich Förstermann A1 Eeva Moilanen A1 Hartmut Kleinert YR 2007 UL http://molpharm.aspetjournals.org/content/71/5/1427.abstract AB Human inducible nitric-oxide synthase (iNOS) expression is regulated both at transcriptional and post-transcriptional levels. In the present study, the effect of Jun N-terminal kinase (JNK) on human iNOS expression was investigated. In A549/8 human alveolar epithelial cells, both the inhibition of JNK by a pharmacological inhibitor anthra[1,9-cd]pyrazol-6(2H)-one1,9-pyrazoloanthrone (SP600125) and small interfering RNA (siRNA)-mediated down-regulation of JNK led to a reduction of iNOS mRNA and protein expression. iNOS promoter activity was not affected by these treatments. Hence, JNK seems to regulate iNOS expression through post-transcriptional mechanisms by stabilizing iNOS mRNA. Our laboratory has shown recently that a cytokine-induced RNA binding protein tristetraprolin (TTP) is a major positive regulator of human iNOS expression by stabilizing iNOS mRNA. Therefore, the effect of JNK inhibition by SP600125 or down-regulation by siRNA on TTP expression was investigated. Both SP600125 and siRNA targeted at JNK resulted in a reduction of TTP protein expression without affecting the amount of TTP mRNA. These data suggest a post-transcriptional control of TTP expression by JNK. Moreover, the modulation of JNK signaling by SP600125 or siRNA did not change p38 phosphorylation. In summary, the results suggest that JNK regulates human iNOS expression by stabilizing iNOS mRNA possibly by a TTP-dependent mechanism. The American Society for Pharmacology and Experimental Therapeutics