Role of TRPM2 Channels in Endothelial Ca2+ signaling and Transendothelial Migration of Neutrophil

Abstract

Adhesion of PMNs (polymorphonuclear leukocytes) to endothelial cells (ECs) may induce cross‐talk that contributes to inter‐cellular cooperation required for complex processes such as transendothelial PMN migration. Here we addressed the role of PMN activation of redox‐sensitive TRPM2 (transient receptor potential melastatin‐2) channels in activating Ca2+ signaling in ECs. ECs were loaded with Ca2+ indicator Fura‐2 and PMN‐specific agonist fMLP was used to induce adhesion and activation of PMNs applied to confluent EC monolayers. We observed an immediate PMN adhesion‐dependent spike in Ca2+ concentration [Ca2+]i in ECs lasting 2–3 min. TRPM2 siRNA‐suppression of TRPM2 in ECs reduced Ca2+ entry whereas TRPM2 overexpression augmented the response. Pretreatment of PMNs with superoxide dismutase or NADPH oxidase inhibitor DPI (dibenziodolium chloride) prevented the increase in EC [Ca2+]i. Inhibitors of adenosine diphosphate ribose (ADPR) generation (the endogenous TRPM2 activating agonist), DPQ (3,4‐dihydro‐5‐[4‐(1‐piperidinyl)butoxyl]‐1(2H)‐isoquinolinone, 100 μM) and 3‐AB (3‐aminobenzamide, 1 mM), also prevented the rise in [Ca2+]i induced by PMNs. Measurement of inward current through EC TRPM2 channels showed that injecting ADPR into ECs or extracellular application of H2O2 both induced TRPM2‐sensitive cationic currents. siRNA‐suppression of TRPM2 in ECs reduced the transendothelial migration of neutrophil (TEM) comparing with control EC. Thus, PMN interaction with ECs activates Ca2+ entry through redox‐sensitive TRPM2 channels suggesting their critical role in transendothelial migration of neutrophils.