C71-15 gα12 Is Involved in Tgf-β-Induced Extracellular Matrix Production by Human Lung Fibroblasts

Rationale Abnormal tissue repair and excessive extracellular matrix (ECM) deposition driven by the transition of fibroblasts into myofibroblasts characterizes idiopathic pulmonary fibrosis (IPF), a progressive fibrosing interstitial pneumonia. IPF carries a poor prognosis due to limited therapeutic options. Several G-protein coupled receptors (GPCRs) are impugned in the pathogenesis of IPF. In this study, we posit an interplay between G-protein families and TGF-β, a key regulator of ECM remodeling and fibrosis in human lung fibroblasts (HLF). Methods As a model of lung fibrosis, primary HLF were stimulated with TGF-β; collagen 1A1 and plasminogen activator inhibitor-1 (PAI) expression were then measured in the presence and absence of soluble receptor inhibitors (Gαq inhibitors) and decreased receptor expression with siRNA (Gα12 and Gαs siRNA). All experiments were performed in n ≥ 3 unique cell lines. Results TGF-β significantly induced collagen 1A1 (p = 0.03) and PAI (p = 0.02) in HLF. TGF-β induced collagen 1A1 (n = 9; p = 0.03) and PAI (n = 6; p = 0.03) was unaffected by Gαs knockdown. Treatment with the Gαs agonist (treprostinil) significantly inhibited TGF-β-induced collagen 1A1 (n = 6, p = 0.04). The treprostinil inhibitory effects was partially reversed following Gαs knockdown (n = 6, p = 0.05), suggesting that Gαs mediates treprostinil’s suppression of collagen 1A1. In contrast, Gαs was not required for treprostinil-mediated inhibition of PAI (n = 6, p = 0.03). The efficiency of Gαs knockdown exceeded 90%. A dose-response of the soluble Gαq inhibitor (100nM to 1µM) failed to alter TGF-β-induced collagen 1A1 or PAI expression (n = 4). In contrast, TGF-β-induced collagen 1A1 expression was reduced by Gα12 knockdown (n = 3, p = 0.05) while PAI remained unaffected. These findings suggest that Gα12 specifically mediates TGF-β-induced collagen 1A1 expression but not PAI. Conclusions Gα12 functions as a profibrotic G protein involved in TGF-β-induced collagen 1A1 expression. Elucidating the interplay between GPCR signaling, particularly the Gα12 subunit, and TGF-β may identify novel therapeutic strategies for IPF. This abstract is funded by: None