title: Intracellular glutathione depletion by oridonin leads to apoptosis in hepatic stellate cells.
abstract: Proliferation of hepatic stellate cells (HSCs) plays a key role in the pathogenesis of liver fibrosis. Induction of HSC apoptosis by natural products is considered an effective strategy for treating liver fibrosis. Herein, the apoptotic effects of 7,20-epoxy-ent-kaurane (oridonin), a diterpenoid isolated from Rabdosia rubescens, and its underlying mechanisms were investigated in rat HSC cell line, HSC-T6. We found that oridonin inhibited cell viability of HSC-T6 in a concentration-dependent manner. Oridonin induced a reduction in mitochondrial membrane potential and increases in caspase 3 activation, subG1 phase, and DNA fragmentation. These apoptotic effects of oridonin were completely reversed by thiol antioxidants, N-acetylcysteine (NAC) and glutathione monoethyl ester. Moreover, oridonin increased production of reactive oxygen species (ROS), which was also inhibited by NAC. Significantly, oridonin reduced intracellular glutathione (GSH) level in a concentration- and time-dependent fashion. Additionally, oridonin induced phosphorylations of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (MAPK). NAC prevented the activation of MAPKs in oridonin-induced cells. However, selective inhibitors of MAPKs failed to alter oridonin-induced cell death. In summary, these results demonstrate that induction of apoptosis in HSC-T6 by oridonin is associated with a decrease in cellular GSH level and increase in ROS production.
authors.affiliation: Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan. kuo33410@yahoo.com.tw.
authors.forename: Liang-Mou
authors.initials: LM
authors.lastname: Kuo
authors.affiliation: Graduate Institute of Natural Products, School of Traditional Chinese Medicine, Collage of Medicine, Chang Gung University, Taoyuan 333, Taiwan. cykuo@thu.edu.tw.
authors.forename: Chan-Yen
authors.initials: CY
authors.lastname: Kuo
authors.affiliation: Graduate Institute of Natural Products, School of Traditional Chinese Medicine, Collage of Medicine, Chang Gung University, Taoyuan 333, Taiwan. m9709108@stmail.cgu.edu.tw.
authors.forename: Chen-Yu
authors.initials: CY
authors.lastname: Lin
authors.affiliation: Graduate Institute of Natural Products, School of Traditional Chinese Medicine, Collage of Medicine, Chang Gung University, Taoyuan 333, Taiwan. g902302@yahoo.com.tw.
authors.forename: Min-Fa
authors.initials: MF
authors.lastname: Hung
authors.affiliation: Graduate Institute of Natural Products, School of Traditional Chinese Medicine, Collage of Medicine, Chang Gung University, Taoyuan 333, Taiwan. s0429@mail.cgu.edu.tw.
authors.forename: Jiann-Jong
authors.initials: JJ
authors.lastname: Shen
authors.affiliation: Graduate Institute of Natural Products, School of Traditional Chinese Medicine, Collage of Medicine, Chang Gung University, Taoyuan 333, Taiwan. htl@mail.cgu.edu.tw.
authors.forename: Tsong-Long
authors.initials: TL
authors.lastname: Hwang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D045786:Diterpenes, Kaurane / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005978:Glutathione / Q000378:metabolism*; D055166:Hepatic Stellate Cells / Q000187:drug effects* / Q000378:metabolism*; D020128:Inhibitory Concentration 50; D042541:Intracellular Space / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D018384:Oxidative Stress; D010766:Phosphorylation; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D045786:Diterpenes, Kaurane; D017382:Reactive Oxygen Species; C011959:oridonin; D020928:Mitogen-Activated Protein Kinases; D053148:Caspase 3; D005978:Glutathione