title: Novel fibrogenic pathways are activated in response to endothelial apoptosis: implications in the pathophysiology of systemic sclerosis.
abstract: Apoptosis of endothelial cells (EC) is appreciated as a primary pathogenic event in systemic sclerosis. Yet, how apoptosis of EC leads to fibrosis remains to be determined. We report that apoptosis of EC triggers the release of novel fibrogenic mediators. Medium conditioned by apoptotic EC (SSC) was found to inhibit apoptosis of fibroblasts, whereas medium conditioned by EC in which apoptosis was blocked (with either pan-caspase inhibition or Bcl-x(L) overexpression) did not. PI3K was activated in fibroblasts exposed to SSC. This was associated with downstream repression of Bim-EL and long-term up-regulation of Bcl-x(L) protein levels. RNA interference for Bim-EL in fibroblasts blocked apoptosis. SSC also induced PI3K-dependent myofibroblast differentiation with expression of alpha-smooth muscle actin, formation of stress fibers, and production of collagen I. A C-terminal fragment of the domain V of perlecan was identified as one of the fibrogenic mediators present in SSC. A synthetic peptide containing an EGF motif present on the perlecan fragment and chondroitin 4-sulfate, a glycosaminoglycan anchored on the domain V of perlecan, induced PI3K-dependent resistance to apoptosis in fibroblasts and myofibroblast differentiation. Human fibroblasts derived from sclerodermic skin lesions were more sensitive to the antiapoptotic activities of the synthetic peptide and chondroitin 4-sulfate than fibroblasts derived from normal controls. Hence, we propose that a chronic increase in endothelial apoptosis and/or increased sensitivity of fibroblasts to mediators produced by apoptotic EC could form the basis of a fibrotic response characterized by sustained induction of an antiapoptotic phenotype in fibroblasts and persistent myofibroblast differentiation.
authors.affiliation: Research Centre Centre Hospitalier de l'Université de Montréal (CHUM), University of Montreal, Quebec, Canada.
authors.forename: Patrick
authors.initials: P
authors.lastname: Laplante
authors.forename: Marc-André
authors.initials: MA
authors.lastname: Raymond
authors.forename: Gabrielle
authors.initials: G
authors.lastname: Gagnon
authors.forename: Normand
authors.initials: N
authors.lastname: Vigneault
authors.forename: A Marie-Josée
authors.initials: AM
authors.lastname: Sasseville
authors.forename: Yves
authors.initials: Y
authors.lastname: Langelier
authors.forename: Monique
authors.initials: M
authors.lastname: Bernard
authors.forename: Yves
authors.initials: Y
authors.lastname: Raymond
authors.forename: Marie-Josée
authors.initials: MJ
authors.lastname: Hébert
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D017209:Apoptosis / Q000276:immunology*; D002454:Cell Differentiation / Q000276:immunology; D002460:Cell Line; D002809:Chondroitin Sulfates / Q000494:pharmacology; D017077:Culture Media, Conditioned; D004730:Endothelium, Vascular / Q000201:enzymology / Q000276:immunology / Q000473:pathology* / Q000503:physiopathology*; D005347:Fibroblasts / Q000276:immunology / Q000378:metabolism* / Q000473:pathology*; D019812:Heparan Sulfate Proteoglycans / Q000502:physiology; D006801:Humans; D007113:Immunity, Innate; D018836:Inflammation Mediators / Q000378:metabolism / Q000502:physiology; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D017434:Protein Structure, Tertiary; D012595:Scleroderma, Systemic / Q000276:immunology / Q000473:pathology* / Q000503:physiopathology*; D015398:Signal Transduction / Q000276:immunology*
chemical_list: D017077:Culture Media, Conditioned; D019812:Heparan Sulfate Proteoglycans; D018836:Inflammation Mediators; D010446:Peptide Fragments; C071927:perlecan; D002809:Chondroitin Sulfates; D019869:Phosphatidylinositol 3-Kinases