Fas/FasL signaling allows extracelluar-signal regulated kinase to regulate cytochrome c release in oridonin-induced apoptotic U937 cells.
Previously, we found that human histocytic lymphoma U937 cells possessed high susceptibility to oridonin-induced cell death, but the molecular mechanisms in response to oridonin remain unclear. In this study, U937 cells showed susceptible to apoptosis induced by 27 microM oridonin and an agonistic anti-Fas IgM mAb (CH-11) (500 ng/ml) as a Fas-sensitized positive control. Caspase 8 inhibitor z-IETD, but neither caspase 1 inhibitor Ac-YVAD nor caspase 10 inhibitor z-AEVD, effectively blocked oridonin-induced cell death as well as DNA fragmentation. Western blot analysis showed the up-regulated expression of Fas, FasL, and FADD, and down-regulated expression of procaspase 8, suggesting that Fas/FasL pathway was activated in oridonin-induced cell apoptosis. Further, stimulation of U937 cells with oridonin and CH11 resulted in significant ERK MAPK activation. However, inhibition of ERK by PD98059 reversed oridonin-induced cell death as well as the activation of caspase 8, indicating that ERK-mediated control occured upstream of caspase 8. Simultaneously, ERK activation accounted for the release of cytochrome c, but failed to influence decreased Bcl-2 expression induced by oridonin. Taken together, these results suggest that Fas/FasL signaling pathway-mediated ERK activation sensitized U937 cells to mitochondrial pathway-mediated apoptosis induced by oridonin.
Liu
Yan-Qiu
YQ
China-Japan Research Institute of Medical and Pharmaceutical Sciences, Shenyang Pharmaceutical University, Shenyang, China.
Mu
Zhen-Qiang
ZQ
You
Song
S
Tashiro
Shin-ichi
S
Onodera
Satoshi
S
Ikejima
Takashi
T
D048868:Adaptor Proteins, Signal Transducing / Q000096:biosynthesis; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000502:physiology; D045304:Cytochromes c / Q000378:metabolism*; D004224:Diterpenes / Q000494:pharmacology*; D045786:Diterpenes, Kaurane; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology*; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D006801:Humans; D008562:Membrane Glycoproteins / Q000502:physiology*; D011493:Protein Kinase C / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D048069:Tumor Necrosis Factors / Q000502:physiology*; D020298:U937 Cells; D019014:fas Receptor / Q000502:physiology*
D048868:Adaptor Proteins, Signal Transducing; D004224:Diterpenes; D045786:Diterpenes, Kaurane; C505533:FADD protein, human; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D008562:Membrane Glycoproteins; D048069:Tumor Necrosis Factors; D019014:fas Receptor; C011959:oridonin; D045304:Cytochromes c; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; D020169:Caspases