title: Interleukin-6 impairs the insulin signaling pathway, promoting production of nitric oxide in human umbilical vein endothelial cells.
abstract: Interleukin 6 (IL-6) is an independent predictor of type 2 diabetes and cardiovascular disease and is correlated with insulin resistance. Insulin stimulates nitric oxide (NO) production through the IRS-1/PI3-kinase/Akt/eNOS pathway (where IRS-1 is insulin receptor substrate 1, PI3-kinase is phosphatidylinositol 3-kinase, and eNOS is endothelial NO synthase). We asked if IL-6 affects insulin vasodilator action both in human umbilical vein endothelial cells (HUVEC) and in the aortas of C57BL/6J mice and whether this inhibitory effect was caused by increased Ser phosphorylation of IRS-1. We observed that IL-6 increased IRS-1 phosphorylation at Ser(312) and Ser(616); these effects were paralleled by increased Jun N-terminal protein kinase (JNK) and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and reversed by JNK and ERK1/2 inhibition. In addition, IL-6 treatment resulted in impaired IRS-1 phosphorylation at Tyr(612), a site essential for engaging PI3-kinase. Furthermore, IL-6 treatment reduced insulin-stimulated phosphorylation of eNOS at the stimulatory Ser(1177) site and impaired insulin-stimulated eNOS dephosphorylation at the inhibitory Thr(495) site. Insulin-stimulated eNOS activation and NO production were also inhibited by IL-6; these effects were reversed by inhibition of JNK and ERK1/2. Treatment of C57BL/6J mice with IL-6 resulted in impaired insulin-dependent activation of the Akt/eNOS pathway in the aorta as a result of JNK and ERK1/2 activation. Our data suggest that IL-6 impairs the vasodilator effects of insulin that are mediated by the IRS-1/PI3-kinase/Akt/eNOS pathway through activation of JNK and ERK1/2.
authors.affiliation: Department of Clinical and Experimental Medicine, University Magna Graecia of Catanzaro, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Andreozzi
authors.forename: Emanuela
authors.initials: E
authors.lastname: Laratta
authors.forename: Cristina
authors.initials: C
authors.lastname: Procopio
authors.forename: Marta Letizia
authors.initials: ML
authors.lastname: Hribal
authors.forename: Angela
authors.initials: A
authors.lastname: Sciacqua
authors.forename: Maria
authors.initials: M
authors.lastname: Perticone
authors.forename: Claudia
authors.initials: C
authors.lastname: Miele
authors.forename: Francesco
authors.initials: F
authors.lastname: Perticone
authors.forename: Giorgio
authors.initials: G
authors.lastname: Sesti
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins; D015850:Interleukin-6 / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009569:Nitric Oxide / Q000096:biosynthesis*; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010768:Phosphoserine / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011972:Receptor, Insulin / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D014471:Umbilical Veins / Q000166:cytology*
chemical_list: C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D015850:Interleukin-6; C526295:Irs1 protein, mouse; D010750:Phosphoproteins; D010768:Phosphoserine; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases; D011972:Receptor, Insulin; D051057:Proto-Oncogene Proteins c-akt; D010749:Phosphoprotein Phosphatases