title: Epigenetic Regulation of Caveolin-1 Gene Expression in Lung Fibroblasts.
abstract: Fibrotic disorders are associated with tissue accumulation of fibroblasts. We recently showed that caveolin (Cav)-1 gene suppression by a profibrotic cytokine, transforming growth factor (TGF)-β1, contributes to fibroblast proliferation and apoptosis resistance. Cav-1 has been shown to be constitutively suppressed in idiopathic pulmonary fibrosis (IPF), but mechanisms for this suppression are incompletely understood. We hypothesized that epigenetic processes contribute to Cav-1 down-regulation in IPF lung fibroblasts, and after fibrogenic stimuli. Cav-1 expression levels, DNA methylation status, and histone modifications associated with the Cav-1 promoter were examined by PCR, Western blots, pyrosequencing, or chromatin immunoprecipitation assays in IPF lung fibroblasts, normal fibroblasts after TGF-β1 stimulation, or in murine lung fibroblasts after bleomycin injury. Methylation-specific PCR demonstrated methylated and unmethylated Cav-1 DNA copies in all groups. Despite significant changes in Cav-1 expression, no changes in DNA methylation were observed in CpG islands or CpG island shores of the Cav-1 promoter by pyrosequencing of lung fibroblasts from IPF lungs, in response to TGF-β1, or after bleomycin-induced murine lung injury, when compared with respective controls. In contrast, the association of Cav-1 promoter with the active histone modification mark, H3 lysine 4 trimethylation, correlated with Cav-1 down-regulation in activated/fibrotic lung fibroblasts. Our data indicate that Cav-1 gene silencing in lung fibroblasts is actively regulated by epigenetic mechanisms that involve histone modifications, in particular H3 lysine 4 trimethylation, whereas DNA methylation does not appear to be a primary mechanism. These findings support therapeutic strategies that target histone modifications to restore Cav-1 expression in fibroblasts participating in pathogenic tissue remodeling.
authors: 1 Division of Pulmonary, Allergy, and Critical Care, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and.
authors: Yan Y
authors: YY
authors: Sanders
authors: 1 Division of Pulmonary, Allergy, and Critical Care, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and.
authors: Hui
authors: H
authors: Liu
authors: 2 Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan.
authors: Anne M
authors: AM
authors: Scruggs
authors: 1 Division of Pulmonary, Allergy, and Critical Care, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and.
authors: Steven R
authors: SR
authors: Duncan
authors: 2 Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan.
authors: Steven K
authors: SK
authors: Huang
authors: 1 Division of Pulmonary, Allergy, and Critical Care, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama; and.
authors: Victor J
authors: VJ
authors: Thannickal
mesh_terms: D000818:Animals; D001483:Base Sequence; D051242:Caveolin 1 / Q000235:genetics* / Q000378:metabolism; D002469:Cell Separation; D002478:Cells, Cultured; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation / Q000187:drug effects / Q000235:genetics; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D044127:Epigenesis, Genetic / Q000187:drug effects; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D042421:Histone Code / Q000187:drug effects; D006657:Histones / Q000378:metabolism; D006801:Humans; D008168:Lung / Q000166:cytology*; D008239:Lysine / Q000378:metabolism; D008810:Mice, Inbred C57BL; D011401:Promoter Regions, Genetic; D011499:Protein Processing, Post-Translational / Q000235:genetics; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology
chemical_list: D051242:Caveolin 1; D006657:Histones; D053773:Transforming Growth Factor beta1; D008239:Lysine
keywords: DNA methylation; caveolin-1; fibrosis; histone modification; lung fibroblasts