A critical role of the transient receptor potential melastatin 2 channel in a positive feedback mechanism for reactive oxygen species‐induced delayed cell death

Abstract Transient receptor potential melastatin 2 (TRPM2) channel activation by reactive oxygen species (ROS) plays a critical role in delayed neuronal cell death, responsible for postischemia brain damage via altering intracellular Zn 2+ homeostasis, but a mechanistic understanding is still lacking. Here, we showed that H 2 O 2 induced neuroblastoma SH‐SY5Y cell death with a significant delay, dependently of the TRPM2 channel and increased [Zn 2+ ] i , and therefore used this cell model to investigate the mechanisms underlying ROS‐induced TRPM2‐mediated delayed cell death. H 2 O 2 increased concentration‐dependently the [Zn 2+ ] i and caused lysosomal dysfunction and Zn 2+ loss and, furthermore, mitochondrial Zn 2+ accumulation, fragmentation, and ROS generation. Such effects were suppressed by preventing poly(adenosine diphosphate ribose, ADPR) polymerase‐1‐dependent TRPM2 channel activation with PJ34 and 3,3′,5,5′‐tetra‐tert‐butyldiphenoquinone, inhibiting the TRPM2 channel with 2‐aminoethoxydiphenyl borate (2‐APB) and N ‐( p ‐amylcinnamoyl)anthranilic acid, or chelating Zn 2+ with N , N , N , N ‐tetrakis(2‐pyridylmethyl)‐ethylenediamine (TPEN). Bafilomycin‐induced lysosomal dysfunction also resulted in mitochondrial Zn 2+ accumulation, fragmentation, and ROS generation that were inhibited by PJ34 or 2‐APB, suggesting that these mitochondrial events are TRPM2 dependent and sequela of lysosomal dysfunction. Mitochondrial TRPM2 expression was detected and exposure to ADPR‐induced Zn 2+ uptake in isolated mitochondria, which was prevented by TPEN. H 2 O 2 ‐induced delayed cell death was inhibited by apocynin and diphenyleneiodonium, nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) oxidase (NOX) inhibitors, GKT137831, an NOX1/4‐specific inhibitor, or Gö6983, a protein kinase C (PKC) inhibitor. Moreover, inhibition of PKC/NOX prevented H 2 O 2 ‐induced ROS generation, lysosomal dysfunction and Zn 2+ release, and mitochondrial Zn 2+ accumulation, fragmentation and ROS generation. Collectively, these results support a critical role for the TRPM2 channel in coupling PKC/NOX‐mediated ROS generation, lysosomal Zn 2+ release, and mitochondrial Zn 2+ accumulation, and ROS generation to form a vicious positive feedback signaling mechanism for ROS‐induced delayed cell death.