title: Sphingosine-1-phosphate induces COX-2 expression via PI3K/Akt and p42/p44 MAPK pathways in rat vascular smooth muscle cells.
abstract: Sphingosine 1-phosphate (S1P) has been shown to regulate smooth muscle cell proliferation, migration, and vascular maturation. S1P increases the expression of several proteins including COX-2 in vascular smooth muscle cells (VSMCs) and contributes to arteriosclerosis. However, the mechanisms regulating COX-2 expression by S1P in VSMCs remain unclear. Western blotting and RT-PCR analyses showed that S1P induced the expression of COX-2 mRNA and protein in a time- and concentration-dependent manner, which was attenuated by inhibitors of MEK1/2 (U0126) and PI3K (wortmannin), and transfection with dominant negative mutants of p42/p44 mitogen-activated protein kinases (ERK2) or Akt. These results suggested that both p42/p44 MAPK and PI3K/Akt pathways participated in COX-2 expression induced by S1P in VSMCs. In accordance with these findings, S1P stimulated phosphorylation of p42/p44 MAPK and Akt, which was attenuated by U0126, LY294002, or wortmannin, respectively. Furthermore, this up-regulation of COX-2 mRNA and protein was blocked by a selective NF-kappaB inhibitor helenalin. Consistently, S1P-stimulated translocation of NF-kappaB into the nucleus was revealed by immnofluorescence staining. Moreover, S1P-stimulated activation of NF-kappaB promoter activity was blocked by phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 and helenalin, but not by U0126, suggesting that involvement of PI3K/Akt in the activation of NF-kappaB. COX-2 promoter assay showed that S1P induced COX-2 promoter activity mediated through p42/p44 MAPK, PI3K/Akt, and NF-kappaB. These results suggested that in VSMCs, activation of p42/p44 MAPK, Akt and NF-kappaB pathways was essential for S1P-induced COX-2 gene expression. Understanding the mechanisms involved in S1P-induced COX-2 expression on VSMCs may provide potential therapeutic targets in the treatment of arteriosclerosis.
authors.affiliation: Department of Physiology and Pharmacology, Chang Gung University, Tao-Yuan, Taiwan.
authors.forename: Hsi-Lung
authors.initials: HL
authors.lastname: Hsieh
authors.forename: Chou-Bing
authors.initials: CB
authors.lastname: Wu
authors.forename: Chi-Chin
authors.initials: CC
authors.lastname: Sun
authors.forename: Chang-Hui
authors.initials: CH
authors.lastname: Liao
authors.forename: Ying-Tung
authors.initials: YT
authors.lastname: Lau
authors.forename: Chuen-Mao
authors.initials: CM
authors.lastname: Yang
mesh_terms: D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D008246:Lysophospholipids / Q000494:pharmacology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000201:enzymology*; D016328:NF-kappa B / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011401:Promoter Regions, Genetic / Q000235:genetics; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D002070:Butadienes; D051546:Cyclooxygenase 2; D048049:Extracellular Signal-Regulated MAP Kinases; D008246:Lysophospholipids; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D016328:NF-kappa B; D009570:Nitriles; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D013110:Sphingosine; C113580:U 0126; C060506:sphingosine 1-phosphate