title: Nicorandil regulates Bcl-2 family proteins and protects cardiac myocytes against hypoxia-induced apoptosis.
abstract: Nicorandil has been shown to inhibit myocyte apoptosis by opening of mitochondrial ATP-sensitive potassium (mitoK(ATP)) channels and nitrate-like effect against oxidative stress. However, the detailed mechanism of nicorandil-mediated cardioprotection under hypoxic conditions remains to be largely unknown. The present study examined whether nicorandil can inhibit apoptosis via regulation of Bcl-2 family proteins in hypoxic myocytes. Neonatal rat cardiac myocytes were exposed to hypoxia for 7 hours. Hypoxia-induced myocyte apoptosis (13.9+/-0.9%) under glucose-rich conditions. Myocyte apoptosis was accompanied by loss of mitochondrial membrane potential (Deltapsi(m)), cytochrome c release from mitochondria into cytosol, and activation of caspase-3. Hypoxia also significantly increased Bax and decreased Bcl-2 mRNA and protein expression, thereby increasing Bax/Bcl-2 ratio. Nicorandil 100 micromol/l significantly decreased the percentage of apoptotic myocytes (7.2+/-0.5%) by inhibiting loss of Deltapsi(m) and translocation of cytochrome c. These effects of nicorandil were partially but significantly inhibited by cotreatment of either 500 micromol/l 5-hydroxydecanoate, a selective mitoK(ATP) channel antagonist, or 10 micromol/l 1H-[1,2,4]oxidazolo[4,3-a]quinoxalin-1-one (ODQ), an inhibitor of soluble guanylate cyclase. Moreover, nicorandil significantly inhibited the hypoxia-induced changes in Bax and Bcl-2 expression, and concomitant increased Bax and decreased Bcl-2 immunoreactivity in mitochondria. These effects of nicorandil in Bax and Bcl-2 expression were significantly blunted by cotreatment of ODQ and 5-HD, respectively. Cotreatment of KT5823, an inhibitor of protein kinase G, significantly blocked the effect of nicorandil on Bax expression and 8-bromo-cyclic guanosine 3',5' monophosphate (8-bromo-cGMP), a cGMP analog, mimicked the effect of nicorandil on Bax expression. The present study demonstrates that nicorandil regulates Bcl-2 family proteins via opening of mitoK(ATP) channels and nitric oxide-cGMP signaling and inhibits hypoxia-induced mitochondrial death pathway.
authors.affiliation: Department of Cardiology and Vascular Regenerative Medicine, Kyoto Prefectural University of Medicine, Kyoto, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602-8566, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Nishikawa
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Tatsumi
authors.forename: Jun
authors.initials: J
authors.lastname: Shiraishi
authors.forename: Shinsaku
authors.initials: S
authors.lastname: Matsunaga
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Takeda
authors.forename: Akiko
authors.initials: A
authors.lastname: Mano
authors.forename: Miyuki
authors.initials: M
authors.lastname: Kobara
authors.forename: Natsuya
authors.initials: N
authors.lastname: Keira
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Okigaki
authors.forename: Tomosaburo
authors.initials: T
authors.lastname: Takahashi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Matsubara
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects*; D002227:Carbazoles / Q000494:pharmacology; D027682:Cation Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D015687:Cell Hypoxia / Q000187:drug effects; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D007211:Indoles / Q000494:pharmacology; D008928:Mitochondria / Q000201:enzymology; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000473:pathology; D020108:Nicorandil / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D002227:Carbazoles; D027682:Cation Transport Proteins; D007211:Indoles; D047428:Protein Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D014665:Vasodilator Agents; C073601:KT 5823; D020108:Nicorandil; D009569:Nitric Oxide; D006152:Cyclic GMP