title: Insulin generates free radicals in human fibroblasts ex vivo by a protein kinase C-dependent mechanism, which is inhibited by pravastatin.
abstract: Insulin can generate oxygen free radicals. Statins, 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors, exert a powerful antioxidant effect. The present study aimed to clarify the mechanisms through which insulin generates free radicals and to assess whether pravastatin modulates such effects. In cultured skin fibroblasts from human volunteers exposed to high insulin concentration, either in the presence or in the absence of pravastatin, insulin induced translocation of the p47(phox) subunit of NAD(P)H oxidase from the cytosol to the membrane and generation of radical oxygen species through a PKC delta-dependent mechanism. The insulin-induced translocation of p47(phox) was PKC delta dependent and attenuated by pravastatin, but independent of the activation of Akt and Rac1. Insulin-induced Akt phosphorylation was increased by pravastatin and ERK1/2 phosphorylation attenuated. The present study demonstrates a novel mechanism by which insulin stimulates the generation of free radicals in human fibroblasts, ex vivo. It involves phosphatidylinositol 3-kinase, PKC delta, and p47(phox) translocation and promotes ERK1/2 phosphorylation. Pravastatin inhibited radical oxygen species production by inhibiting PKC delta. These observations offer a robust explanation for the positive effects of pravastatin treatment in patients with insulin resistance syndrome.
authors.affiliation: Department of Clinical and Experimental Medicine, University of Padova Medical School, Via Giustiniani 2, 35128 Padova, Italy.
authors.forename: Giulio
authors.initials: G
authors.lastname: Ceolotto
authors.forename: Italia
authors.initials: I
authors.lastname: Papparella
authors.forename: Livia
authors.initials: L
authors.lastname: Lenzini
authors.forename: Michelangelo
authors.initials: M
authors.lastname: Sartori
authors.forename: Martina
authors.initials: M
authors.lastname: Mazzoni
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Iori
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Franco
authors.forename: Alessandra
authors.initials: A
authors.lastname: Gallo
authors.forename: Saula Vigili
authors.initials: SV
authors.lastname: de Kreutzenberg
authors.forename: Antonio
authors.initials: A
authors.lastname: Tiengo
authors.forename: Achille C
authors.initials: AC
authors.lastname: Pessina
authors.forename: Angelo
authors.initials: A
authors.lastname: Avogaro
authors.forename: Andrea
authors.initials: A
authors.lastname: Semplicini
mesh_terms: D002478:Cells, Cultured; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005347:Fibroblasts; D005609:Free Radicals / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D019255:NADPH Oxidases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017035:Pravastatin / Q000494:pharmacology*; D051745:Protein Kinase C-delta / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D012867:Skin / Q000187:drug effects / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D005609:Free Radicals; D007328:Insulin; D007527:Isoenzymes; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1; D051057:Proto-Oncogene Proteins c-akt; D051745:Protein Kinase C-delta; D048049:Extracellular Signal-Regulated MAP Kinases; D020830:rac1 GTP-Binding Protein; D017035:Pravastatin