Epigallocatechin-3-Gallate Attenuates the Effects of TNF-α in Vascular Endothelial Cells by Causing Ectodomain Shedding of TNF Receptor 1

Abstract

Background/Aims: We investigated the mechanism underlying anti-tumor necrosis factor-α (TNF-α) effects of epigallocatechin-3-gallate (EGCG) in human aortic endothelial cells. Methods: Tumor necrosis factor receptor 1 (TNFR1) was assessed by Western blot analysis. Cytosolic Ca2+ was measured using Fluo-4 AM. A disintegrin and metalloprotease 10 (ADAM10) was localized by immunofluorescence staining. Results: EGCG caused ectodomain shedding of TNFR1 within 30 min and attenuated TNF-α-induced endothelin-1 (ET-1) expression. EGCG-induced TNFR1 ectodomain shedding was prevented by BAPTA-AM (intracellular Ca2+ chelator), but not by the absence of extracellular Ca2+. In physiologic extracellular Ca2+ concentration, EGCG markedly increased cytosolic Ca2+. Even in the absence of extracellular Ca2+, EGCG raised cytosolic Ca2+, though less potently. siRNA depletion of ADAM10 prevented EGCG-induced ectodomain shedding of TNFR1 and also diminished the inhibitory effect of EGCG on TNF-α-induced ET-1 expression. EGCG caused translocation of ADAM10 to the plasma membrane, and this effect was prevented by BAPTA-AM. Besides extracellular Ca2+ influx, release of intracellular stored Ca2+ caused ADAM10-dependent ectodomain shedding of TNFR1. Conclusion: EGCG decreases the responsiveness of cells to TNF-α by causing ADAM10-dependent ectodomain shedding of TNFR1. This effect was attributed to its property to increase cytosolic Ca2+ through both extracellular Ca2+ influx and release of stored Ca2+.