Abstract TP286: The Study of the Role and Mechanism of TRPM7 in Acute Cerebral Ischemia-Reperfusion Injury

Abstract

Although the NMDA receptor was identified to mediate excitotoxicity for ischemia-reperfusion (IR) injury, its antagonists have not shown clinical efficacy. Unrelated to NMDA, the transient receptor potential cation channel, subfamily M, member 7 (TRPM7) has been reported to cause intracellular Ca 2+ overloading, oxidative stress and neuronal apoptosis. We postulated that TRPM7 could be a target for treatment of IR injury. To investigate the potential neuroprotective role of TRPM7 in IR injury, 1) qRT-PCR, Western blot and immuno-staining were used to identify the expression and localization of TRPM7 in normal rat forebrain cortex and cultured primary cortical neurons; 2) the oxygen glucose deprivation and reperfusion (OGD/R) model of primary cortical neurons was used to detect changes in TRPM7 expression and study the effect of two TRPM7 ion channel inhibitors, carvacrol and 2-Aminoethoxydiphenyl borate (2-APB), on neurons in OGD/R; 3) the rat middle cerebral artery (MCAO/R) model was used to study TRPM7 involvement and the effect of its inhibitor during the course of IR. Our results showed that: 1) TRPM7 was expressed in normal neurons and astrocytes mainly as a cell membrane protein in the rat cortex; 2) TRPM7 expression was enhanced in OGD/R treated neurons; treatment with carvacrol or 2-APB reversed the overexpression of TRPM7 in OGD/R neurons and reduced the level of Ca 2+ overload in neuronal IR injury and neuronal apoptosis; 3) TRPM7 expression was also augmented in rat cortical tissues during MCAO/R and peaked between 24-48 hours during the reperfusion stage; 4) treatment with TRPM7 inhibitors reversed TRPM7 overexpression, alleviated neuronal apoptosis, and improved neurobehavioral scores in MCAO/R rats. Our conclusions are: 1) TRPM7 is expressed in normal rat forebrain cortex and functions mainly as a cell membrane protein in neurons and astrocytes; 2) TRPM7 is overexpressed during cerebral ischemia-reperfusion in rats; 3) TRPM7 ion channel inhibitors carvacrol and 2-APB can alleviate OGD/R injury in neurons in vitro as well as cortical damage by MCAO/R in rat forebrain; 4) the mechanism of TRPM7 on neuronal injury in OGD/R and MCAO/R can contribute to its role in neuronal apoptosis and Ca 2+ influx toxicity.