Activation of neutral sphingomyelinase participates in ethanol-induced apoptosis in Hep G2 cells.
The mechanism underlying ethanol-induced apoptosis in liver cells is not clear. Sphingomyelin (SM) metabolism is a novel signal transduction pathway that has an impact on apoptosis in many cell types. We investigated whether the SM pathway is involved in ethanol-induced apoptosis in the liver. Hep G2 cells were treated with ethanol followed by assaying apoptosis, sphingomyelinase (SMase) activity, caspase-3 activity, and the changes of SM content in the cells. We found that ethanol dose-dependently increased apoptosis and the effect was accompanied by increases of caspase-3 activity and neutral SMase activity. At concentrations of 80 and 160 mM, ethanol significantly increased caspase-3 activity by 120% and neutral SMase activity by 24%. The activity of acid SMase was only slightly increased without statistical significance. C(2)-ceramide, the exogenous SM metabolite, mimicked the effects of ethanol on apoptosis and caspase-3 activation. When the SM content was determined 24 h after treatment with ethanol, its level was 15% lower than that of controls. The results indicate that metabolism of SM triggered by neutral SMase participates in ethanol-induced apoptosis in Hep G2 cells and activation of caspase-3 is involved in the apoptotic pathway.
Liu
J J
JJ
Department of Gastroenterology, Zhongshan Hospital, Shanghai Medical University, Shanghai, People's Republic of China.
Wang
J Y
JY
Hertervig
E
E
Cheng
Y
Y
Nilsson
A
A
Duan
R D
RD
D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D000431:Ethanol / Q000494:pharmacology*; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D015398:Signal Transduction; D013108:Sphingomyelin Phosphodiesterase / Q000187:drug effects / Q000378:metabolism*; D018709:Statistics, Nonparametric; D014407:Tumor Cells, Cultured
D000431:Ethanol; D013108:Sphingomyelin Phosphodiesterase; D053148:Caspase 3; D020169:Caspases