Reactive oxygen species mediate oridonin-induced HepG2 apoptosis through p53, MAPK, and mitochondrial signaling pathways.
Oridonin, a diterpenoid isolated from Rabdosia rubescences, could induce apoptosis through the generation of reactive oxygen species (ROS) in human hepatoma HepG2 cells. p53, a specific inhibitor of pifithrin alpha (PFT alpha), markedly inhibited ROS generation and apoptosis, showing that p53 was responsible for the cytotoxity of oridonin through mediation by ROS. Moreover, the ROS activated the p38 kinase, which in turn promoted the activation of p53, as verified by evidence showing that the ROS scavenger N-acetyl-cysteine (NAC) not only blocked the phosphorylation of p38 but also partially inhibited the activation of p53, and the p38 inhibitor SB203580 reduced the activation of p53 as well. Mitochondria were either the sources or the targets of ROS. This study showed that oridonin stimulated mitochondrial transmembrane permeabilization in a ROS-dependent manner because NAC almost thoroughly reversed the drop of mitochondrial transmembrane potential (Deltapsim) and the release of cytochrome c from the mitochondrial inter-membrane space into cytosol. Furthermore, as a result of mitochondrial permeability transition, procaspases-9 and -3 were cleaved into 37- and 17-kDa proteolytic products, respectively, which acted as executors of oridonin-induced apoptosis.
Huang
Jian
J
Department of Phytochemistry, Shenyang Pharmaceutical University, Shenyang, P.R. China.
Wu
Lijun
L
Tashiro
Shin-ichi
S
Onodera
Satoshi
S
Ikejima
Takashi
T
D017209:Apoptosis / Q000187:drug effects*; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy / Q000473:pathology; D053148:Caspase 3 / Q000187:drug effects / Q000378:metabolism; D053453:Caspase 9 / Q000187:drug effects / Q000378:metabolism; D045744:Cell Line, Tumor; D045304:Cytochromes c / Q000187:drug effects / Q000378:metabolism; D045786:Diterpenes, Kaurane / Q000494:pharmacology*; D006801:Humans; D037602:Isodon / Q000737:chemistry; D008113:Liver Neoplasms / Q000188:drug therapy / Q000473:pathology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000187:drug effects / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism
D045786:Diterpenes, Kaurane; D017382:Reactive Oxygen Species; D016159:Tumor Suppressor Protein p53; C011959:oridonin; D045304:Cytochromes c; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D053148:Caspase 3; D053453:Caspase 9