title: Leptin enhances alpha1(I) collagen gene expression in LX-2 human hepatic stellate cells through JAK-mediated H2O2-dependent MAPK pathways.
abstract: Leptin, a liver profibrogenic cytokine, induces oxidative stress in hepatic stellate cells (HSCs), with increased formation of the oxidant H2O2, which signals through p38 and extracellular signal-regulated kinase 1/2 (ERK1/2) pathways, stimulating tissue inhibitor of metalloproteinase-1 production. Since oxidative stress is a pathogenic mechanism of liver fibrosis and activation of collagen gene is a marker of fibrogenesis, we evaluated the effects of leptin on collagen I expression. We report here that, in LX-2 human HSCs, leptin enhances the levels of alpha1(I) collagen mRNA, promoter activity and protein. Janus kinase (JAK)1 and JAK2 were activated. H2O2 formation was increased; this was prevented by the JAK inhibitor AG490, suggesting a JAK-mediated process. ERK1/2 and p38 were activated, and the activation was blocked by catalase, consistent with an H2O2-dependent mechanism. AG490 and catalase also prevented leptin-stimulated alpha1(I) collagen mRNA expression. PD098059, an ERK1/2 inhibitor, abrogated ERK1/2 activation and suppressed alpha1(I) collagen promoter activity, resulting in mRNA down-regulation. The p38 inhibitor SB203580 and overexpression of dominant negative p38 mutants abrogated p38 activation and down-regulated the mRNA. While SB203580 had no effect on the promoter activity, it reduced the mRNA half-life from 24 to 4 h, contributing to the decreased mRNA level. We conclude that leptin stimulates collagen production through the H2O2-dependent and ERK1/2 and p38 pathways via activated JAK1 and JAK2. ERK1/2 stimulates alpha1(I) collagen promoter activity, whereas p38 stabilizes its mRNA. Accordingly, interference with leptin-induced oxidative stress by antioxidants provides an opportunity for the prevention of liver fibrosis.
authors.affiliation: Alcohol Research and Treatment Center, Bronx Veterans Affairs Medical Center, and Mount Sinai School of Medicine, New York, NY, USA.
authors.forename: Qi
authors.initials: Q
authors.lastname: Cao
authors.forename: Ki M
authors.initials: KM
authors.lastname: Mak
authors.forename: Charles S
authors.initials: CS
authors.lastname: Lieber
mesh_terms: D024042:Collagen Type I / Q000235:genetics*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D053613:Janus Kinase 1; D053614:Janus Kinase 2; D020738:Leptin / Q000502:physiology*; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D017382:Reactive Oxygen Species
chemical_list: D024042:Collagen Type I; D004791:Enzyme Inhibitors; D020738:Leptin; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D011505:Protein-Tyrosine Kinases; C507904:JAK1 protein, human; C507924:JAK2 protein, human; D053613:Janus Kinase 1; D053614:Janus Kinase 2