title: Involvement of TRPM2 and L-type Ca²⁺ channels in Ca²⁺ entry and cell death induced by hydrogen peroxide in rat β-cell line RIN-5F.
abstract: Ca²⁺ overload is one of the mechanisms for H₂O₂-induced cell death in rat pancreatic β-cell line RIN-5F cells. RIN-5F cells express TRPM2, which is a Ca²⁺-permeable channel activated by H₂O₂, and voltage-dependent L-type Ca²⁺ channels, both of which induce Ca²⁺ entry by H₂O₂. This study examined the contribution of these channels to H₂O₂-induced Ca²⁺ entry and cell death in RIN-5F cells. Cytosolic Ca²⁺ concentration was measured using fura-2 as a Ca²⁺ indicator. Cell death was estimated by trypan blue exclusion. Pre-treatment with poly(ADP-ribose) polymerase (PARP) inhibitors, which inhibit TRPM2 activation, strongly reduced Ca²⁺ entry by H₂O₂. The PARP inhibitors used had no effect on the Ca²⁺ elevation by voltage-dependent L-type Ca²⁺ channels. On the other hand, pre-treatment with L-type Ca²⁺ channel blockers, which did not affect TRPM2 activation, partly reduced H₂O₂-induced Ca²⁺ entry. Treatment with PARP inhibitors but not L-type Ca²⁺ channel blockers, around the early phase in H₂O₂-induced Ca²⁺ elevation, also reduced the late phase. Moreover, H₂O₂-induced RIN-5F cell death was strongly attenuated by PARP inhibitors, in compared to L-type Ca²⁺ channel blockers. Our results suggest that TRPM2 channels rather than L-type Ca²⁺ channels primarily contribute to H₂O₂-induced Ca²⁺ entry and cell death.
authors.affiliation: Department of Pharmacology, Toxicology and Therapeutics, Division of Physiology and Pathology, Showa University School of Pharmacy.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Ishii
authors.forename: Tamio
authors.initials: T
authors.lastname: Hagiwara
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Mori
authors.forename: Shunichi
authors.initials: S
authors.lastname: Shimizu
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000502:physiology*; D016923:Cell Death / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000009:adverse effects*; D050417:Insulin-Secreting Cells / Q000378:metabolism* / Q000473:pathology*; D007340:Insulinoma / Q000378:metabolism* / Q000473:pathology; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D051381:Rats; D050053:TRPM Cation Channels / Q000378:metabolism / Q000502:physiology*
chemical_list: D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D004791:Enzyme Inhibitors; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D050053:TRPM Cation Channels; C121934:TRPM2 protein, human; D006861:Hydrogen Peroxide; D002118:Calcium