title: Schisandrin B stereoisomers protect against hypoxia/reoxygenation-induced apoptosis and inhibit associated changes in Ca2+-induced mitochondrial permeability transition and mitochondrial membrane potential in H9c2 cardiomyocytes.
abstract: The effects of schisandrin B stereoisomers, (+/-)gamma-schisandrin [(+/-)gamma-Sch] and (-)schisandrin B [(-)Sch B], on hypoxia/reoxygenation-induced apoptosis were investigated in H9c2 cardiomyocytes. Changes in cellular reduced glutathione (GSH) levels, Ca(2+)-induced mitochondrial permeability transition (MPT), and mitochondrial membrane potential (Deltapsi(m)) values, were examined in (+/-)gamma-Sch-pretreated and (-)Sch B-pretreated cells, without or with hypoxia/reoxygenation challenge. The (+/-)gamma-Sch and (-)Sch B (2.5-5.0 microM) pretreatments protected against hypoxia/reoxygenation-induced apoptosis of H9c2 cells in a concentration-dependent manner, with (-)Sch B being more potent. The degrees of protection decreased, however, at the higher drug concentrations of 7.5 microM in both (+/-)gamma-Sch-pretreated and (-)Sch B-pretreated cells. The anti-apoptotic effects of the drugs were further evidenced by the suppression of hypoxia/reoxygenation-induced mitochondrial cytochrome c release and the subsequent cleavage of caspase 3 and poly-ADP-ribose polymerase after (-)Sch B pretreatment. Both (+/-)gamma-Sch and (-)Sch B pretreatments increased GSH levels in H9c2 cells, with (-)Sch B being more potent. Hypoxia/reoxygenation challenge caused a depletion in cellular GSH and the cytoprotection afforded by (+/-)gamma-Sch/(-)Sch B was associated with enhancement of cellular GSH in H9c2 cells, as compared to the drug-unpretreated control. Whereas hypoxia/reoxygenation challenge increased the extent of Ca(2+)-induced MPT pore opening and decreased Deltapsi(m) in H9c2 cardiomyocytes, cytoprotection against hypoxia/reoxygenation-induced apoptosis afforded by (+/-)gamma-Sch/(-)Sch B pretreatments was associated with a decreased sensitivity to Ca(2+)-induced MPT and an increased Deltapsi(m) in both unchallenged and challenged cells, as compared to the respective drug-unpretreated controls. The degrees of protection against apoptosis correlated negatively with the extents of Ca(2+)-induced MPT (r=-0.615, P<0.01) and positively with the values of Deltapsi(m) (r=0.703, P<0.01) in (+/-)gamma-Sch/(-)Sch B-pretreated and hypoxia/reoxygenation challenged cells. The results indicate that (+/-)gamma-Sch/(-)Sch B pretreatment protected against hypoxia/reoxygenation-induced apoptosis in H9c2 cardiomyocytes and that the cytoprotection afforded by (+/-)gamma-Sch/(-)Sch B may at least in part be mediated by a decrease in cellular sensitivity to Ca(2+)-induced MPT, which may in turn result from enhancement of cellular GSH levels by drug pretreatments.
authors.affiliation: Department of Biochemistry, The Hong Kong University of Science & Technology, Clear Water Bay, Hong Kong SAR, China.
authors.forename: Po Yee
authors.initials: PY
authors.lastname: Chiu
authors.forename: Ka Fai
authors.initials: KF
authors.lastname: Luk
authors.forename: Hoi Yan
authors.initials: HY
authors.lastname: Leung
authors.forename: Ka Ming
authors.initials: KM
authors.lastname: Ng
authors.forename: Kam Ming
authors.initials: KM
authors.lastname: Ko
mesh_terms: D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D053148:Caspase 3 / Q000378:metabolism; D015687:Cell Hypoxia / Q000187:drug effects*; D002460:Cell Line; D034242:Cyclooctanes / Q000737:chemistry / Q000494:pharmacology; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D017705:Lignans / Q000737:chemistry / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D008929:Mitochondria, Heart / Q000187:drug effects*; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D010539:Permeability; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011083:Polycyclic Compounds / Q000737:chemistry / Q000494:pharmacology*; D013237:Stereoisomerism
chemical_list: D017304:Annexin A5; D034242:Cyclooctanes; D005456:Fluorescent Dyes; D017705:Lignans; D011083:Polycyclic Compounds; C015499:schizandrin B; D011065:Poly(ADP-ribose) Polymerases; D053148:Caspase 3; D005978:Glutathione; D016650:Fluorescein-5-isothiocyanate; D002118:Calcium