A differential role of macrophage TRPM2 channels in Ca²âº signaling and cell death in early responses to H2O2.

ABSTRACT

Reactive oxygen species such as H2O2 elevates the cytosolic Ca²âº concentration ([Ca²âº]c) and causes cell death via poly(ADPR) polymerase (PARP) activation, which also represents the primary mechanism by which H2O2 activate the transient receptor potential melastatin-related 2 (TRPM2) channel as a Ca²âº-permeable channel present in the plasma membrane or an intracellular Ca²âº-release channel. The present study aimed to define the contribution and mechanisms of the TRPM2 channels in macrophage cells in mediating Ca²âº signaling and cell death during initial response to H2O2, using mouse peritoneal macrophage, RAW264.7, and differentiated THP-1 cells. H2O2 evoked robust increases in the [Ca²âº]c, and such Ca²âº responses were significantly greater at body temperature than room temperature. H2O2-induced Ca²âº responses were strongly inhibited by pretreatment with PJ-34, a PARP inhibitor, and largely prevented by removal of extracellular Ca²âº. Furthermore, H2O2-induced increases in the [Ca²âº]c were completely abolished in macrophage cells isolated from trpm2-/- mice. H2O2 reduced macrophage cell viability in a duration- and concentration-dependent manner. H2O2-induced cell death was significantly attenuated by pretreatment with PJ-34 and TRPM2 channel deficiency but remained significant and persistent. Taken together, these results show that the TRPM2 channel in macrophage cells functions as a cell surface Ca²âº-permeable channel that mediates Ca²âº influx and constitutes the principal Ca²âº signaling mechanism but has a limited, albeit significant, role in cell death during early exposure to H2O2.