View Abstract

A4364 - Tyrosine Phosphatase SHP-1 Regulates Pulmonary Fibrosis Through Inhibition of β-Catenin Activation in Lung Epithelial Cells
Author Block: Z. Chen1, S. Oh2, P. Fang2, Q. Li3, F. Zhang1, H. Tang1, R. Homer4, X. Zhang4, N. Kaminski3, T. Zheng1, Z. Zhu5; 1Section of Allergy and Clinical Immunology, Yale University School of Medicine, New Haven, CT, United States, 2Division of Allergy and Clinical Immunology, Johns Hopkins University School of Medicine, Baltimore, MD, United States, 3Section of Pulmonary and Critical Care Medicine, Yale University School of Medicine, New Haven, CT, United States, 4Pathology, Yale University School of Medicine, New Haven, CT, United States, 5Molecular Microbiology and Immunology, Brown Univ Med School, Providence, RI, United States.
The mechanisms in pulmonary fibrosis, such as in idiopathic pulmonary fibrosis (IPF), are not completely clear. The Wnt/β-Catenin signaling pathway has been implicated in pulmonary fibrosis. Tyrosine phosphorylation of β-Catenin is one potential mechanism for its activation. However, the regulatory mechanisms that regulate β-Catenin activation are not defined. Tyrosine phosphatase SHP-1 regulates cytokine and growth factor signaling and plays a role in allergic inflammation in the lung. SHP-1 deficient mice develop severe lung inflammation and fibrosis. We investigated whether SHP-1 expression is altered in pulmonary fibrosis and sought to define the role of SHP-1 in regulating β-Catenin in fibrogenesis. Microarray data from control subjects (CTRL) and IPF patients were analyzed for SHP-1 mRNA expression and immunostain was performed to determine SHP-1 protein expression in lung tissues. SHP-1 deficient mev-/- mice were compared with wild type (WT) mice. Sftpc-CreERT2 (tamoxifen inducible Cre) and SHP-1 flox/flox mice were cross-bred to generate SPC-SHP-1 mice with type II alveolar epithelial cell-specific deletion of SHP-1. WT, heterozygous mev+/-, and SPC-SHP-1 mice were challenged with Bleomycin (BLM 1.5mg/kg, i.t.) for 7-28 days. Lung samples were analyzed for inflammation and fibrosis. Immunostain, immunoblot and qPCR were used to determine the expression and activation of fibrogenic factors and signaling molecules. Microarray analysis showed that SHP-1 expression was significantly decreased in IPF patients compared to CTRL. By immunostain, SHP-1 protein was readily seen in lung epithelial cells of CTRL but low to undetectable in IPF samples. Decreased E-Cadherin but increased α-smooth muscle actin (α-SMA) and β-catenin-Tyr654 were seen in the IPF lung by immunostain and immunoblot. Histology showed that mev-/- mice developed severe lung fibrosis, while no abnormalities in WT mice. Immunostain and immunoblot of lung tissues and proteins showed that p-STAT3, p-Akt, α-SMA, collagen-1, fibrinogen, and vimentin were significantly upregulated, but E-Cadherin was downregulated. Further analysis showed increased β-Catenin-Tyr654. qPCR analysis showed differential mRNA expression of E-Cadherin, collagen-1, Twist and Snail in the mev-/- lung. BLM challenged mev+/- mice showed enhanced inflammation and fibrosis compared to WT mice. After tamoxifen induction, SHP-1 expression in the lung epithelial cells was undetectable in SPC-SHP-1 mice and BLM challenge resulted in significantly exaggerated inflammation and fibrosis with increased β-Catenin-Tyr654 and α-SMA but decreased E-Cadherin in the lung. These findings demonstrate that SHP-1 is down-regulated in human IPF; SHP-1 plays a critical role in lung epithelial cells; and SHP-1 inhibition of β-Catenin activation is a novel mechanism in regulation of pulmonary fibrosis.