H₂O₂‐induced Ca²⁺ influx and its inhibition by N‐(p‐amylcinnamoyl) anthranilic acid in the β‐cells: involvement of TRPM2 channels

Abstract

Type 2 melastatin-related transient receptor potential channel (TRPM2), a member of the melastatin-related TRP (transient receptor potential) subfamily is a Ca2+-permeable channel activated by hydrogen peroxide (H2O2). We have investigated the role of TRPM2 channels in mediating the H2O2-induced increase in the cytoplasmic free Ca2+ concentration ([Ca2+]i) in insulin-secreting cells. In fura-2 loaded INS-1E cells, a widely used model of β-cells, and in human β-cells, H2O2 increased [Ca2+]i, in the presence of 3 mM glucose, by inducing Ca2+ influx across the plasma membrane. H2O2-induced Ca2+ influx was not blocked by nimodipine, a blocker of the L-type voltage-gated Ca2+ channels nor by 2-aminoethoxydiphenyl borate, a blocker of several TRP channels and store-operated channels, but it was completely blocked by N-(p-amylcinnamoyl)anthranilic acid (ACA), a potent inhibitor of TRPM2. Adenosine diphosphate phosphate ribose, a specific activator of TRPM2 channel and H2O2, induced inward cation currents that were blocked by ACA. Western blot using antibodies directed to the epitopes on the N-terminal and on the C-terminal parts of TRPM2 identified the full length TRPM2 (TRPM2-L), and the C-terminally truncated TRPM2 (TRPM2-S) in human islets. We conclude that functional TRPM2 channels mediate H2O2-induced Ca2+ entry in β-cells, a process potently inhibited by ACA.

Transient Receptor Potential Melastatin Subfamily Member 2 Cation Channel Regulates Detrimental Immune Cell Invasion in Ischemic Stroke

“…16 Indeed, although 5 mg/kg body weight ACA was not effective, administration of a single-dose 25 mg/kg body weight ACA 2 hours after stroke induction resulted in a significant reduction (P<0.001) in infarct size and improvement in clinical outcome compared with the injection of vehicle control ( Figure 6A-6C). Furthermore, ACA treatment significantly suppressed neutrophil infiltration into the ischemic hemisphere ( Figure 6D).…”

“…We dissolved the TRPM2 channel blocker, N-(p-amylcinnamoyl)anthranilic acid (ACA; Sigma, St Louis, MO), in dimethylsulfoxide and then further diluted it in PBS and injected it intraperitoneally 2 hours after tM-CAO in wild-type (WT) littermate controls and Trpm2 -/-mice at 5 or 25 mg/kg body weight. 16 We administered PBS-diluted dimethylsulfoxide by intraperitoneal injections in sham-treated mice. Sample size calculation was performed (stroke size from pilot experiments, significance level 0.05, power 90%) and resulted in 9 animals per group to see a difference of 23% in stroke size.…”

β Cell Store-Operated Ion Channels

“…In addition to full-length TRPM2, a short, 846-amino-acid variant is expressed that is truncated after the second transmembrane domain and is able to interact with TRPM2-L and regulate its activity (Zhang et al 2003). Both long and short forms of TRPM2 are expressed in human islets (Bari et al 2009). Several other splice variants of TRPM2 also occur (Perraud et al 2003), but their expression in islets is unknown.…”

“…TRPM2 is expressed in human islets in both long (TRPM2-L) and short forms (TRPM2-S) where it mediates H 2 O 2 -induced Ca 2+ influx (Bari et al 2009;Fig. 5).…”

Temperature-Sensitive Transient Receptor Potential Channels in Corneal Tissue Layers and Cells

“…Besides voltage-operated Ca 2+ channels, the non-temperature-sensitive TRPM2 channel is putatively expressed in this tissue [23,24]. Given that TRPM2 is activated by oxidative stress (H 2 O 2 ), this suggests that corneal endothelial cells can withstand some levels of oxidative stress [25]. In a study, it was shown that a block of voltage-operated Ca 2+ channels (L-type) could only partially suppress the H 2 O 2 -induced Ca 2+ influx [24].…”