Mechanisms of the Inhibitory Effect of Epigallocatechin-3-Gallate on Cultured Human Vascular Smooth Muscle Cell Invasion

OBJECTIVE: Although we recently showed that the administration of catechins reduced the neointimal formation in a rat balloon-injury model, the precise molecular mechanisms are largely unknown. In the present study, we tried to determine these mechanisms using an in vitro SMC invasion system. METHODS AND RESULTS: Boyden chamber assay was used to examine the effect of catechins on the invasive behavior of SMCs. The invasive activity of SMCs through collagen gel was restrained by EGCG in a concentration-dependent manner. The data from gelatin and collagen zymography and Western blot revealed that EGCG blocks the activation of pro-matrix metalloproteinase (MMP)-2 during an invasion assay and in the conditioned medium of cultured SMCs as well as the activities of MMP-2 and membrane type 1-MMP (MT1-MMP) even at 0.1 to 0.3 micromol/L of EGCG. EGCG was found to restrain MT1-MMPcat-dependent pro-MMP-2 activation. EGCG upregulated the expression of tissue inhibitor of MMP-2 (TIMP-2) protein. Reverse zymography showed that the increased TIMP-2 to expression was validated by an increased activity. The data from decreased TIMP-2 activity using its siRNA suggested that upregulation of TIMP-2 expression may be one of the major mechanisms for inhibition of SMC invasion by EGCG. CONCLUSIONS: These results indicate that EGCG targets multiple MMP-mediated SMC cellular events and provides a new major mechanism for the SMC invasion through upregulation of TIMP-2 expression to modulate MMP activity.