Oridonin induces a caspase-independent but mitochondria- and MAPK-dependent cell death in the murine fibrosarcoma cell line L929.
Oridonin, an active component isolated from Rabdosia rubescences, has been reported to exhibit antitumor effects, but little is known about its molecular mechanisms of action. In this study, the growth-inhibitory activity of oridonin for L929 cells is in time- and dose-dependent manner. After treatment with various concentrations of oridonin for 12 h, the majority of L929 cells underwent apoptosis as measured by an LDH activity-based assay. Although apoptotic bodies were observed in oridonin-treated L929 cells, DNA fragmentation as a hallmark of apoptosis was not found. The pan-caspase inhibitor, z-VAD, and caspase-3 inhibitor, z-DEVD, sensitized L929 cells to oridonin, however, a PARP inhibitor (DPQ) effectively blocked oridonin-induced cell death. After 12 h treatment, PARP proenzyme was significantly cleaved. This result indicated that oridonin-induced L929 cell death required PARP degradation in a caspase-independent manner. In addition, an MEK/ERK inhibitor (PD98059) markedly blocked oridonin-induced cell death, whereas a p38 inhibitor (SB203580) and JNK inhibitor (SP600125) weakly protected the cells against death. Treatment with 41.2 microM oridonin for 12 h induced significant and persistent ERK activation and p38 inactivation in L929 cells without evident changes in the protein levels. The responsiveness of ERK and p38 to oridonin suggests the involvement of these kinases in this apoptotic process. Moreover, oridonin increased the ratio of Bax/Bcl-2 protein expression, whereas it had no effect on the expression of Bcl-xL. These results indicate that regulation of the Bcl-2 and MAPK families maybe the effector mechanisms of oridonin-induced L929 cell death, independent of the caspase pathway.
China-Japan Research Institute of Medical and Pharmaceutical Sciences, Shenyang Pharmaceutical University, China.
Chun-Ling
CL
Zhang
Li-Jun
LJ
Wu
Shin-ichi
S
Tashiro
Satoshi
S
Onodera
Takashi
T
Ikejima
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D061945:Caspase Inhibitors; D020169:Caspases / Q000502:physiology*; D045744:Cell Line, Tumor; D004224:Diterpenes / Q000494:pharmacology*; D045786:Diterpenes, Kaurane; D004305:Dose-Response Relationship, Drug; D005354:Fibrosarcoma; D037602:Isodon; D051379:Mice; D008928:Mitochondria / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D009336:Necrosis; D010936:Plant Extracts / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases / Q000502:physiology
D000970:Antineoplastic Agents; D061945:Caspase Inhibitors; D004224:Diterpenes; D045786:Diterpenes, Kaurane; D010936:Plant Extracts; D019253:Proto-Oncogene Proteins c-bcl-2; C011959:oridonin; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020169:Caspases