Epigallocatechin-3-gallate prevents heat shock-induced MMP-1 expression by inhibiting AP-1 activity in human dermal fibroblasts

The anti-skin aging effects of epigallocatechin-3-gallate (EGCG) have been studied extensively in vitro and in vivo models. Accumulating data suggest that EGCG possesses important antioxidant and photoprotective properties. Our previous study demonstrated that heat exposure induces cutaneous angiogenesis and inflammatory cellular infiltration, disrupts the dermal extracellular matrix by inducing matrix metalloproteinases, and alters dermal structural proteins, thereby causing premature skin aging. In the present study, we examined whether EGCG may inhibit expression of MMP-1 in heat-stimulated human dermal fibroblasts. Furthermore, we investigated the inhibitory mechanism of EGCG on heat-induced MMP-1 expression. Western blot analysis and MMP-1 promoter assay revealed that EGCG markedly inhibited heat shock-induced MMP-1 expression in human dermal fibroblasts. In addition, we found that heat shock increased AP-1 DNA binding activity, and c-Jun was found to be increased mostly by heat stimulation in a supershift assay, which were suppressed by EGCG treatment. Also, in Western blotting, EGCG significantly inhibited the heat-induced expression of AP-1 constituent proteins, c-Jun, JunB and c-Fos. These results demonstrated that EGCG has abilities to inhibit heat-induced collagenolytic MMP-1 production via interfering with AP-1 pathways. Therefore, we propose that EGCG may be a potential agent for the prevention and treatment for heat shock-induced skin aging (thermal skin aging).