Activation of transforming growth factor-β1 by thrombin via integrins αvβ1, αvβ3, and αvβ5 in buccal fibroblasts: Suppression by epigallocatechin-3-gallate.

BACKGROUND: Transforming growth factor-beta (TGF-β) plays a central role in the pathogenesis of oral submucous fibrosis (OSF). Thrombin is a key player in tissue repair, inflammation, and fibrosis after injury.

METHODS: Effects of thrombin on activated-TGF-β1 levels, Smad3 phosphorylation, and connective tissue growth factor (CTGF/CCN2) synthesis in primary human buccal mucosal fibroblasts (BMFs) were assessed by enzyme-linked immunosorbent assay or Western blot analysis.

RESULTS: Thrombin and protease-activated receptor-1 (PAR-1) agonist induced TGF-β1 activation and Smad3 phosphorylation. Pretreatment with TGF-β-neutralizing antibody completely inhibited thrombin-induced CCN2 synthesis. Neutralizing antibodies to integrin αv, β1, αvβ3, αvβ5, and Rho-associated coiled-coil forming protein kinase (ROCK) inhibitor Y27632 completely blocked thrombin-induced TGF-β1 activation, Smad3 phosphorylation, and CCN2 synthesis. Epigallocatechin-3-gallate (EGCG) dose-dependently inhibited thrombin-induced TGF-β1 activation.

CONCLUSION: Thrombin induces αvβ1, αvβ3, and αvβ5 integrins-mediated TGF-β1 activations via ROCK signaling. EGCG inhibits thrombin-induced CCN2 synthesis in BMFs by suppressing latent TGF-β1 activation.