Schisandrin B stereoisomers protect against hypoxia/reoxygenation-induced apoptosis and associated changes in the Ca(2+)-induced mitochondrial permeability transition and mitochondrial membrane potential in AML12 hepatocytes.
The effects of the schisandrin B stereoisomers, (+/-)gamma-schisandrin [(+/-)gamma-Sch] and (-)schisandrin B [(-)Sch B], on hypoxia/reoxygenation-induced apoptosis were investigated in AML12 hepatocytes. Changes in cellular reduced glutathione (GSH) levels, Ca(2+)-induced mitochondrial permeability transitions (MPTs) and mitochondrial membrane potentials (Deltapsi(m) values) were also examined in (+/-)gamma-Sch- and (-)Sch B-treated cells, without or with hypoxia/reoxygenation challenge. The (+/-)gamma-Sch/(-)Sch B pretreatments (2.5-5.0 microm) protected against hypoxia/reoxygenation-induced apoptosis in AML12 cells in a concentration-dependent manner, with the (-)Sch B effect being more potent. Drug antiapoptotic effects were further evidenced by suppression of hypoxia/reoxygenation-induced mitochondrial cytochrome c release and subsequent cleavage of caspase 3 and poly-ADP-ribose polymerase by (-)Sch B pretreatment. Whereas hypoxia/reoxygenation challenge increased the extent of Ca(2+)-induced MPT pore opening, and Deltapsi(m), in AML12 hepatocytes, cytoprotection afforded by (+/-)gamma-Sch/(-)Sch B pretreatment against hypoxia/reoxygenation-induced apoptosis was associated with a decreased sensitivity to Ca(2+)-induced MPT and an increased Deltapsi(m) in both unchallenged and challenged cells, compared with the drug-free control. The results indicate that (+/-)gamma-Sch/(-)Sch B pretreatment protected against hypoxia/reoxygenation-induced apoptosis in AML12 hepatocytes and that the cytoprotection afforded by (+/-)gamma-Sch/(-)Sch B may at least in part be mediated by a decrease in sensitivity to Ca(2+)-induced MPT, which may in turn result from enhancement of cellular GSH levels by drug pretreatments.
Department of Biochemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong SAR, China.
Po Yee
PY
Chiu
Ka Fai
KF
Luk
Hoi Yan
HY
Leung
Ka Ming
KM
Ng
Kam Ming
KM
Ko
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D015687:Cell Hypoxia; D002460:Cell Line; D034242:Cyclooctanes / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects*; D017705:Lignans / Q000494:pharmacology*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects*; D051379:Mice; D015394:Molecular Structure; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011083:Polycyclic Compounds / Q000494:pharmacology*
D034242:Cyclooctanes; D017705:Lignans; D011083:Polycyclic Compounds; C015499:schizandrin B; D045304:Cytochromes c; D011065:Poly(ADP-ribose) Polymerases; D053148:Caspase 3; D005978:Glutathione