Effects of antioxidants on calcium influx through TRPM2 channels in transfected cells activated by hydrogen peroxide

Melastatin-like transient receptor potential 2 (TRPM2) channel is a redox sensitive Ca2+-permeable cation channel that can be gated by H2O2 binding to the channel's enzymatic Nudix domain. Since the mechanisms that lead to TRPM2 action in response to H2O2 are not understood, we examined the effects of various antioxidants on H2O2-induced TRPM2 cation channel currents in transfected Chinese hamster ovary (CHO) cells.The CHO cells were transfected with cDNA coding for TRPM2. Membrane currents were measured with the conventional whole cell patch-clamp technique. The intracellular solution contained ethylenediamine tetraacetic acid (EDTA) as a chelator for Ca2+ and heavy metal ions instead of ethylene glycol tetraacetic acid (EGTA). Moreover, we chose an intracellular Ca2+ concentration calculated to be in the range of 1 μM. H2O2 (10 mM) was added extracellularly to the bath chamber. With these conditions, we were able to evoke TRPM2 currents consistently with H2O2. We next tested whether vitamins C and E or glutathione (GSH) would prevent or attenuate the induction of TRPM2 currents by H2O2 when applied extracellularly or intracellularly. Unexpectedly, administration of these antioxidants did not inhibit activation of TRPM2 by H2O2.In conclusion, TRPM2 channels were constitutively activated by H2O2 although we could not detect any inhibitory effect of the antioxidants on H2O2-induced TRPM2 cation channel currents in CHO cells.