(-)-Epicatechin and related procyanidins modulate intracellular calcium and prevent oxidation in Jurkat T cells

This study investigated the effects of (-)-epicatechin (EC), its oligomers, dimer B2 (B2) and trimer C1 (C1), on calcium-dependent cell oxidation. Jurkat T cells were subjected to a Ca²⁺ mobilization challenge by replacing Na⁺ with K⁺ in the incubation media. A 249±38% increase in intracellular Ca²⁺ concentration ([Ca²⁺]_i) was observed and that effect was prevented by the presence of inhibitors of Ca²⁺ mobilization and entrance. The pre-incubation of the cells in the presence of EC, B2 or C1 prevented K²⁺-mediated increase in [Ca²⁺]_i. IC₅₀ were 10, 24 and 196 nm for EC, B2 and C1, respectively. Cell membrane depolarization was affected by K²⁺, but neither inhibitors of Ca²⁺ mobilization nor EC, B2 or C1 modified the increase in membrane potential. An 84±7% increase in cell oxidants was observed after cell exposure to K⁺. This increase was prevented by the inhibition of Ca²⁺ mobilization, NADPH oxidase and protein kinase C, as well as by 10 nm EC, 10 nm B2 or 100 nm C1. In addition, EC and B2 (100 nm) significantly inhibited the activation of the [Ca²⁺]_i-regulated transcription factor NFAT. These results indicate that EC and related oligomers, assayed at physiologically achievable concentrations, can modulate [Ca²⁺] _i and then prevent cell oxidation and other Ca²⁺ -regulated events.