(−)-Epigallocatechin-3-gallate inhibits matrix metalloproteinases in oral ulcers

Abstract

The overexpression of matrix metalloproteinases (MMPs) results in excessive extracellular matrix degradation and oral ulcer healing delay. This study investigated the inhibitory effect of (−)-epigallocatechin-3-gallate (EGCG) on MMPs, the possible molecular mechanism and its implications for oral ulcers. MMP-1 and MMP-9 inhibition was detected using fluorometric and colorimetric assays after incubating EGCG (at concentrations of 25, 50, 100 and 200 μM) with the MMPs, along with their specific substrates. The recombinant human (rh) interleukin-1β (rhIL-1β)-induced MMP-1 and MMP-9 production by macrophages was measured by enzyme-linked immunosorbent assays (ELISAs). 75% acetic acid was used to prepare the experimental oral ulcer animal model. The expression of MMP-1 and MMP-9 was observed by an immunohistochemical assay and western blot analysis. The expression and activity of activator protein (AP-1) were determined using real-time PCR and luciferase assay, respectively. The results revealed that, in vitro, EGCG inhibited the activity of the MMPs and the rhIL-1β-induced MMP production in a concentration-dependent manner. The inhibition constants (K_i) of MMP-1 and MMP-9 were 9.56 ± 1.67 and 26.36 ± 1.85 μM, respectively. In vivo, the means of positive integrated optic density (IOD) and the protein expressions of the MMPs in the control group were significantly higher than those in the large dose group. The results of the real-time PCR and luciferase assays showed that EGCG inhibited the rhIL-1β-induced c-fos and c-jun expression, as well as AP-1 transcriptional activity, in a dose-dependent manner. Thus, EGCG has the capability to accelerate the healing of oral ulcers by inhibiting MMP-1 and MMP-9. The mechanism may involve deactivation of AP-1.