Sphingosine-1-phosphate stimulated connective tissue growth factor expression in human buccal fibroblasts: Inhibition by epigallocatechin-3-gallate

Connective tissue growth factor (CCN2) has been associated with the pathogenesis of various fibrotic diseases, including oral submucous fibrosis (OSF). The chemical constituents of areca nut along with the mechanical trauma cause OSF. The coarse fibers of areca nut injure the mucosa and hence sphingosine-1-phosphate (S1P) is released at the wounded sites. Recent studies have shown that S1P is involved in wound healing and the development of fibrosis. The aims of this study were to investigate the effects of S1P on CCN2 expression in human buccal fibroblasts (HBFs) and identify the potential targets for drug intervention or chemoprevention of OSF. Methods: Western blot analyses were used to study the effects of S1P on CCN2 expression and its signaling pathways in HBFs and whether epigallocatechin-3-gallate (EGCG), the main and most significant polyphenol in green tea, could inhibit this pathway. Results: S1P significantly enhanced CCN2 synthesis in HBFs. This effect can be inhibited by c-Jun NH2-terminal kinase (JNK) inhibitor and extracellular signal-regulated kinase inhibitor but not by P38 mitogen-activated protein kinase inhibitor. Interestingly, EGCG completely blocked S1P-induced CCN2 expression via suppressing S1P-induced JNK phosphorylation. Conclusion: S1P released by repetitive mechanical trauma during AN chewing may contribute to the pathogenesis of OSF through upregulating CCN2 expression in HBFs. EGCG could be an adjuvant to the current offered therapy options or the prevention of OSF through suppression of JNK activation