Role of TRPM2 Channel in Mediating H 2 O 2 -Induced Ca 2+ Entry and Endothelial Hyperpermeability

Abstract

Oxidative stress through the production of oxygen metabolites such as hydrogen peroxide (H 2 O 2 ) increases vascular endothelial permeability. H 2 O 2 stimulates ADP-ribose formation, which in turn opens transient receptor potential melastatin (TRPM)2 channels. Here, in endothelial cells, we demonstrate transcript and protein expression of TRPM2, a Ca 2+ -permeable, nonselective cation channel. We further show the importance of TRPM2 expression in signaling of increased endothelial permeability by oxidative stress. Exposure of endothelial cell monolayers to sublytic concentrations of H 2 O 2 induced a cationic current measured by patch-clamp recording and Ca 2+ entry detected by intracellular fura-2 fluorescence. H 2 O 2 in a concentration-dependent manner also decreased trans-monolayer transendothelial electrical resistance for 3 hours (with maximal effect seen at 300 μmol/L H 2 O 2 ), indicating opening of interendothelial junctions. The cationic current, Ca 2+ entry, and transendothelial electrical resistance decrease elicited by H 2 O 2 were inhibited by siRNA depleting TRPM2 or antibody blocking of TRPM2. H 2 O 2 responses were attenuated by overexpression of the dominant-negative splice variant of TRPM2 or inhibition of ADP-ribose formation. Overexpression of the full-length TRPM2 enhanced H 2 O 2 -mediated Ca 2+ entry, cationic current, and the transendothelial electrical resistance decrease. Thus, TRPM2 mediates H 2 O 2 -induced increase in endothelial permeability through the activation of Ca 2+ entry via TRPM2. TRPM2 represents a novel therapeutic target directed against oxidant-induced endothelial barrier disruption.