TRPM2 channel activation following in vitro ischemia contributes to male hippocampal cell death

Abstract

Hippocampal CA1 neurons are particularly sensitive to ischemic damage, such as experienced following cardiac arrest and cardiopulmonary resuscitation. In recent years transient receptor potential M2 (TRPM2) channels have been identified as mediators of ischemic damage. We previously demonstrated that neuroprotective strategies targeting TRPM2 channels preferentially protect male cortical neurons from ischemic injury both in vitro and in vivo. It is important to determine the role of TRPM2 in ischemic injury of hippocampal neurons as this population of neurons are particularly sensitive to ischemic injury and are therapeutic targets. Here we report significantly decreased neuronal cell death following in vitro ischemia preferentially in male hippocampal neurons using TRPM2 inhibitors or knockdown of TRPM2 expression. Electrophysiological characterization of sex-stratified cultures shows similar levels of functional TRPM2 channel expression in male and female hippocampal neurons under basal conditions. In contrast, recordings made during reperfusion following in vitro ischemia revealed that TRPM2 channels are activated only in male neurons, resulting in rapid and complete depolarization. These findings provide strong evidence for TRPM2 as a target for protection against cerebral ischemia in male brain and helps define a molecular cell death pathway that is differentially engaged in male and female neurons.

Sirtuin-2 mediates male specific neuronal injury following experimental cardiac arrest through activation of TRPM2 ion channels

“…The mechanism of neuroprotection by female sex steroids is primarily through inhibition of caspase dependent cell death, which is the dominant form of cell death in females (Liu et al, 2009; Liu et al, 2011). Our results obtained with TRPM2 KO demonstrating neuroprotection in male but not female mice are consistent with our previously published observations that activation of TRPM2-mediated cell death following cerebral ischemia is male specific (Jia et al, 2011; Verma et al, 2012; Nakayama et al, 2013; Shimizu et al, 2013; Quillinan et al, 2014). These results demonstrate for the first time male specificity of TRPM2 using genetic knockouts in global ischemia, and are consistent male specific neuroprotection with administration of AGK2 following CA/CPR.…”

“…Relevant to the male-specific PARP-mediated cell death pathway, we have recently demonstrated that the calcium-permeable ion channel transient receptor potential channels, M2 (TRPM2) contributes to male-specific injury following cerebral ischemia in a PARP-dependent manner (Shimizu et al, 2013). Inhibition or knock-down of TRPM2 is protective in males, but not females using in vitro and in vivo models of cerebral ischemia (Jia et al, 2011; Verma et al, 2012; Nakayama et al, 2013; Quillinan et al, 2014). A distinguishing property of TRPM2 channels is that they are gated by ADP ribose (ADPr), likely generated following the activation of PARP (Fonfria et al, 2004).…”

Transient Receptor Potential Channels as Drug Targets: From the Science of Basic Research to the Art of Medicine

“…TRPM2 (Verma et al, 2012), TRPM4 (Loh et al, 2014), and TRPM7 have been implicated in ischemic brain injury (reviewed in Aarts and Tymianski, 2005;Bae and Sun, 2013). In vivo siRNA-mediated silencing of TRPM4 reduces brain infarct volume by half and facilitates functional recovery in rats with middle cerebral artery occlusion (Loh et al, 2014).…”

Sex differences in mitochondrial (dys)function: Implications for neuroprotection

“…TRPM2 channels are present in both males and females at similar levels in cultured hippocampal neurons. However, electrophysiological evidence (Verma et al 2012) and reductions in cell death by TRPM2 pharmacological or shRNA inhibition in an in vivo model of stroke, (Jia et al 2011) or shRNA knockdown following in vitro oxygen glucose deprivation (OGD), (Verma et al 2012) indicate that TRPM2 channels are only activated in males following injury. Contrarily, peroxide mediated in vitro toxicity shows no sex difference in cell death and TRPM2 inhibition is neuroprotective in both sexes (Verma et al 2012) suggesting greater oxidative stress and/or PAR/ADPr generation in males following injury contributes to sex differences in TRPM2 mediated cell death.…”