标题：Inositol 1,4,5-Trisphosphate Receptor-Mediated Initial Ca2+ Mobilization Constitutes a Triggering Signal for Hydrogen Peroxide-Induced Apoptosis in INS-1 β-Cells
摘要：Reactive oxygen species, including hydrogen peroxide (H2O2), are known to induce β-cell apoptosis. The present study investigated the role of Ca2+ in H2O2-induced apoptosis of the β-cell line INS-1. Annexin V assay with flow cytometry and DNA ladder assay demonstrated that treatment of INS-1 cells with 100 μ M H2O2 for 18 h significantly increased apoptotic cells. A comparable level of apoptosis was also observed after 18 h when the cells were treated with 100 μ M H2O2 only for initial 30 min. The H2O2-induced apoptosis was abolished by 1,2-bis( o -aminophenoxy)ethane- N , N , N ′, N ′-tetraacetic acid tetra(acetoxymethyl)ester (BAPTA/AM), a chelator of intracellular Ca2+, by 2-aminoethoxydiphenylborate (2-APB), a blocker of inositol 1,4,5-trisphosphate (IP3) receptors and cation channels, and by xestospongin D, a blocker of IP3 receptors, and was partially blocked by SKF-96365, a non-selective cation channel blocker. However, nicardipine, an L-type voltage-dependent Ca2+ channel blocker, or N -( p -amylcinnamoyl)anthranilic acid (ACA), a TRPM2 blocker, had little effect on the apoptosis. The inhibitory effect of BAPTA/AM or 2-APB on the H2O2-induced apoptosis was largely attenuated when the drug was added 30 min or 1 h after start of the treatment with H2O2. These results suggest that the initial intracellular Ca2+ elevation induced by H2O2, which is mediated via IP3 receptors and store-operated cation channels, plays an obligatory role in the induction of β-cell apoptosis.
