Project description:Members of the NADPH oxidase (NOX) family of enzymes, which catalyze the reduction of O2 to reactive oxygen species, have increased in number during eukaryotic evolution. Seven isoforms of the NOX gene family have been identified in mammals; however, specific roles of NOX enzymes in mammalian physiology and pathophysiology have not been fully elucidated. The best established physiological role of NOX enzymes is in host defense against pathogen invasion in diverse species, including plants. The prototypical member of this family, NOX-2 (gp91phox), is expressed in phagocytic cells and mediates microbicidal activities. Here we report a role for the NOX4 isoform in tissue repair functions of myofibroblasts and fibrogenesis. Transforming growth factor-β1 (TGF-β1) induces NOX-4 expression in lung mesenchymal cells by a SMAD-3–dependent mechanism. NOX-4–dependent generation of hydrogen peroxide (H2O2) is required for TGF-β1–induced myofibroblast differentiation, extracellular matrix (ECM) production and contractility. NOX-4 is upregulated in lungs of mice subjected to noninfectious injury and in cases of human idiopathic pulmonary fibrosis (IPF). Genetic or pharmacologic targeting of NOX-4 abrogates fibrogenesis in two murine models of lung injury. These studies support a function for NOX4 in tissue fibrogenesis and provide proof of concept for therapeutic targeting of NOX-4 in recalcitrant fibrotic disorders. Experiment Overall Design: mRNA expression of genes in human fetal lung mesenchymal cells (IMR-90) treated with or without TGF-β1, as analyzed by Affymetrix (U133A) microarrays. Control (C0, C2, C3) = cells without TGF-β1 treatment (n=3). Experimental (T0, T5, T7) = cells treated with TGF-β1 (2ng/ml) (n=3). mRNA was collected for all 6 samples for 48 hours post treatment.
Project description:The etiology of autoimmune hepatitis is poorly understood but likely involves Th1 cells producing IFN-γ. BALB/c background TGF-β1-/- mice rapidly develop fulminant Th1-mediated autoimmune hepatitis. Our aims are to profile liver gene expression in TGF-β1-/- mice, to identify gene expression pathways dependent on IFN-γ as possible targets for rational therapy, and to test potential targets directly in vivo in mice. Keywords: Comparative analysis of gene expression in livers of WT, TGFB1 & IFN knockout mice DNA microarray analyses were applied to liver RNA from TGF-β1-/- mice, TGF-β1-/- /IFN-γ-/- mice, and TGF-β1+/+ littermate controls. 3 mice from each group were analyzed in this study.
Project description:Venkatraman2012 - Interplay between PLS and TSP1 in TGF-β1 activation
The interplay between PLS (Plasmin) and TSP1 (Thrombospondin-1) in TGF-β1 (Transforming growth factor-β1)is shown using mathematical modelling and in vitro
experimentents.
This model is described in the article:
Plasmin triggers a switch-like decrease in thrombospondin-dependent activation of TGF-β1.
Venkatraman L, Chia SM, Narmada BC, White JK, Bhowmick SS, Forbes Dewey C Jr, So PT, Tucker-Kellogg L, Yu H.
Biophys J. 2012 Sep 5;103(5):1060-8.
Abstract:
Transforming growth factor-β1 (TGF-β1) is a potent regulator of extracellular matrix production, wound healing, differentiation, and immune response, and is implicated in the progression of fibrotic diseases and cancer. Extracellular activation of TGF-β1 from its latent form provides spatiotemporal control over TGF-β1 signaling, but the current understanding of TGF-β1 activation does not emphasize cross talk between activators. Plasmin (PLS) and thrombospondin-1 (TSP1) have been studied individually as activators of TGF-β1, and in this work we used a systems-level approach with mathematical modeling and in vitro experiments to study the interplay between PLS and TSP1 in TGF-β1 activation. Simulations and steady-state analysis predicted a switch-like bistable transition between two levels of active TGF-β1, with an inverse correlation between PLS and TSP1. In particular, the model predicted that increasing PLS breaks a TSP1-TGF-β1 positive feedback loop and causes an unexpected net decrease in TGF-β1 activation. To test these predictions in vitro, we treated rat hepatocytes and hepatic stellate cells with PLS, which caused proteolytic cleavage of TSP1 and decreased activation of TGF-β1. The TGF-β1 activation levels showed a cooperative dose response, and a test of hysteresis in the cocultured cells validated that TGF-β1 activation is bistable. We conclude that switch-like behavior arises from natural competition between two distinct modes of TGF-β1 activation: a TSP1-mediated mode of high activation and a PLS-mediated mode of low activation. This switch suggests an explanation for the unexpected effects of the plasminogen activation system on TGF-β1 in fibrotic diseases in vivo, as well as novel prognostic and therapeutic approaches for diseases with TGF-β dysregulation.
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