Tannic acid, a vasodilator present in wines and beverages, stimulates Ca²⁺ influx via TRP channels in bEND.3 endothelial cells

Tannic acid (TA) is a polyphenol compound present in wines and many beverages. Although previous works have shown that TA could cause vasodilation in an endothelial cell (EC)-dependent manner, there is hitherto no report showing whether TA could raise EC cytosolic Ca²⁺ concentration. In this work we examined the effects of TA on cytosolic Ca²⁺ of mouse brain bEND.3 EC. TA (1–30 μM) caused a slow elevation in cytosolic Ca²⁺ level in a concentration-dependent manner. At 30 μM, TA triggered Ca²⁺ influx without causing intracellular Ca²⁺ release. TA-triggered Ca²⁺ influx was suppressed by Ni²⁺ (a non-specific Ca²⁺ channel blocker), ruthenium red and SKF 96365 (non-specific TRP channel blockers), CBA (a selective TRPM4 inhibitor) and M 084 (a selective TRPC4/C5 blocker). However, TA-triggered Ca²⁺ influx pathway was not permeable to Mn²⁺. Our results suggest TA activated TRP channels, possibly TRPM4 and TRPC4/C5, to promote influx of Ca²⁺.