title: Cytochrome P450-catalysed reactive oxygen species production mediates the (-)schisandrin B-induced glutathione and heat shock responses in AML12 hepatocytes.
abstract: Sch B (schisandrin B), the most abundant dibenzocyclooctadiene lignan in Fructus schisandrae, can induce glutathione antioxidant and heat shock responses, as well as protect against oxidant-induced injury in various tissues, including the liver in rodents and AML12 (alpha mouse liver 12) hepatocytes. (-)Sch B is the most potent stereoisomer of Sch B in its cytoprotective action on AML12 hepatocytes. To define the role of ROS (reactive oxygen species) arising from CYP (cytochrome P450)-catalysed metabolism of (-)Sch B in triggering glutathione antioxidant and heat shock responses, the effects of a CYP inhibitor [ABT (aminobenzotriazole)] and antioxidants [DMTU (dimethylthiouracil) and TRX (trolox)] on (-)Sch B-induced ROS production and associated increases in cellular GSH level, as well as Hsp25/70 (heat-shock protein 25/70) production, were investigated in AML12 hepatocytes. The results indicated that (-)Sch B causes a dose dependent and sustained increase in ROS production over 6 h in AML12 hepatocytes, which was completely suppressed by pre-/co-treatment with ABT or DTMU/TRX. Incubation with (-)Sch B for 6 h caused optimal and dose-dependent increases in cellular GSH level and Hsp25/70 production at 16 h post-drug exposure in AML12 hepatocytes. These cellular responses were associated with protection against menadione-induced apoptosis. Pre-/co-treatment with ABT or antioxidants completely abrogated the (-)Sch B-induced glutathione antioxidant and heat shock responses, as well as protection against menadione-induced apoptosis. Experimental evidence obtained thus far supports the causal role of ROS arising from the CYP-catalysed metabolism of (-)Sch B in eliciting glutathione antioxidant and heat shock responses in AML12 hepatocytes.
authors: Department of Biochemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong SAR, Peoples Republic of China.
authors: Pou Kuan
authors: PK
authors: Leong
authors: Po Yee
authors: PY
authors: Chiu
authors: Hoi Yan
authors: HY
authors: Leung
authors: Kam Ming
authors: KM
authors: Ko
mesh_terms: D000818:Animals; D002384:Catalysis; D034242:Cyclooctanes / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D018869:Heat-Shock Response / Q000502:physiology*; D022781:Hepatocytes / Q000378:metabolism*; D017705:Lignans / Q000378:metabolism*; D051379:Mice; D011083:Polycyclic Compounds / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: D034242:Cyclooctanes; D017705:Lignans; D011083:Polycyclic Compounds; D017382:Reactive Oxygen Species; C015499:schizandrin B; D003577:Cytochrome P-450 Enzyme System; D005978:Glutathione