Sphingosine kinase-1 mediates TNF-alpha-induced MCP-1 gene expression in endothelial cells: upregulation by oscillatory flow.
Atherosclerosis is a focal inflammatory disease and preferentially occurs in areas of low fluid shear stress and oscillatory flow, whereas the risk of atherosclerosis is decreased in regions of high fluid shear stress and steady laminar flow. Sphingosine kinase-1 (SphK1) catalyzes the conversion of sphingosine to sphingosine-1 phosphate (S1P), a sphingolipid metabolite that plays important roles in angiogenesis, inflammation, and cell growth. In the present study, we demonstrated that exposure of human aortic endothelial cells to oscillatory flow (shear stress, +/-5 dyn/cm(2) for 48 h) resulted in a marked increase in SphK1 mRNA levels compared with endothelial cells kept in static culture. In contrast, laminar flow (shear stress, 20 dyn/cm(2) for 48 h) decreased SphK1 mRNA levels. We further investigated the role of SphK1 in TNF-alpha-induced expression of inflammatory genes, such as monocyte chemoattractant protein-1 (MCP-1) and VCAM-1 by using small interfering RNA (siRNA) specifically for SphK1. Treatment of endothelial cells with SphK1 siRNA suppressed TNF-alpha-induced increase in MCP-1 mRNA levels, MCP-1 protein secretion, and activation of p38 MAPK. SphK1 siRNA also inhibited TNF-alpha-induced cell surface expression of VCAM-1, but not ICAM-1, protein. Exposure of endothelial cells to S1P led to an increase in MCP-1 protein secretion and MCP-1 mRNA levels and activation of NF-kappaB-mediated transcriptional activity. Treatment of endothelial cells with the p38 MAPK inhibitor SB-203580 suppressed S1P-induced MCP-1 protein secretion. These data suggest that SphK1 mediates TNF-alpha-induced MCP-1 gene expression through a p38 MAPK-dependent pathway and may participate in oscillatory flow-mediated proinflammatory signaling pathway in the vasculature.
Chen
Xi-Lin
XL
Discovery Research, AtheroGenics, Inc., 8995 Westside Parkway, Alpharetta, GA 30004, USA. xchen@atherogenics.com
Grey
Janice Y
JY
Thomas
Suzanne
S
Qiu
Fei-Hua
FH
Medford
Russell M
RM
Wasserman
Martin A
MA
Kunsch
Charles
C
D000970:Antineoplastic Agents / Q000494:pharmacology*; D001011:Aorta / Q000166:cytology; D001161:Arteriosclerosis / Q000276:immunology / Q000378:metabolism / Q000503:physiopathology; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000235:genetics* / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D013314:Stress, Mechanical; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases; D000099157:Sphingosine Kinase
D000970:Antineoplastic Agents; D018932:Chemokine CCL2; D020928:Mitogen-Activated Protein Kinases; D016328:NF-kappa B; D017853:Phosphotransferases (Alcohol Group Acceptor); D012333:RNA, Messenger; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases; D000099157:Sphingosine Kinase