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.