Influence of Sphingomyelin Synthase Knockdown on Cell Apoptosis

HEK293 cells were uesd to investigate the relationship between sphingomyelin synthase (SMS) activity and cell apoptosis. SMS1siRNA and SMS2siRNA were transfected HEK293 cells, respectively, or simultaneously. SMS activity was monitored by thin layer chromatographic assay. Sphingomyelin, ceramide, and phosphatidylcholine levels were determined by an established method. Cell apoptosis was measured by flow cytomertry. The results show that SMS1 and SMS2 knockdown reduces SMS activity(17%, 20%, 49%, respectively), sphingomyelin levels were significantly reduced (P < 0.05), ceramide was significantly increased (P < 0.05), compared with control group. We then performed cell apoptosis, and found that SMS1, SMS2, and SMS1/SMS2 knockdown significantly induced by TNF-alpha mediated apoptosis [58% (P < 0.01), 24% (P < 0.05), 77% (P < 0.01), respectively], suggesting monitoring SMS activity plays an important role on cell apoptosis, thus may have impact on the development of atherosclerosis.