title: Inhibition of host connective tissue growth factor expression: a novel Trypanosoma cruzi-mediated response.
abstract: Connective tissue growth factor (CTGF) is a secreted cytokine that plays a fundamental role in the development of tissue fibrosis by mediating many of the profibrotic effects of TGF-beta. We present the novel finding that the intracellular pathogen Trypanosoma cruzi elicits immediate and sustained repression of basal CTGF expression in dermal fibroblasts, followed by down-regulation of the extracellular matrix proteins, fibronectin, and collagen I alpha1. To address mechanisms underlying this response, the major CTGF-regulating pathways were investigated. We report that both T. cruzi trypomastigotes and secreted parasite factor(s) antagonize TGF-beta-dependent induction of CTGF in fibroblasts. Of the TGF-beta-dependent signaling pathways required for CTGF expression, we demonstrate that T. cruzi interferes with cellular Erk1/2 phosphorylation but not Smad3 signaling. While increased stimulation of Erk phosphorylation alone was insufficient to override the parasite-mediated repression of CTGF, stimulation of fibroblasts with increased concentrations of TGF-beta, which activates both Smad3 and Erk1/2, completely abrogated this inhibition. Together with the finding that T. cruzi-mediated down-regulation of CTGF expression requires de novo host cell protein synthesis, our data indicate that the unique ability of T. cruzi to interfere with the host fibrogenic response is a complex process requiring input from multiple host cell signaling pathways.
authors.affiliation: Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts 02115, USA.
authors.forename: Meera
authors.initials: M
authors.lastname: Unnikrishnan
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Burleigh
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D055513:Connective Tissue Growth Factor; D015536:Down-Regulation; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism / Q000469:parasitology; D005786:Gene Expression Regulation; D006801:Humans; D017874:Immediate-Early Proteins / Q000096:biosynthesis* / Q000235:genetics; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis* / Q000235:genetics; D014176:Protein Biosynthesis; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors* / Q000502:physiology; D014349:Trypanosoma cruzi / Q000502:physiology*
chemical_list: C526317:CCN2 protein, human; D016326:Extracellular Matrix Proteins; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D016212:Transforming Growth Factor beta; D055513:Connective Tissue Growth Factor