Sphingosine-1-phosphate induces COX-2 expression via PI3K/Akt and p42/p44 MAPK pathways in rat vascular smooth muscle cells

✍ Scribed by Hsi-Lung Hsieh; Chou-Bing Wu; Chi-Chin Sun; Chang-Hui Liao; Ying-Tung Lau; Chuen-Mao Yang

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 540 KB
• Volume: 207
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.20621

✦ Synopsis

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‐κB inhibitor helenalin. Consistently, S1P‐stimulated translocation of NF‐κB into the nucleus was revealed by immnofluorescence staining. Moreover, S1P‐stimulated activation of NF‐κB 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‐κB. COX‐2 promoter assay showed that S1P induced COX‐2 promoter activity mediated through p42/p44 MAPK, PI3K/Akt, and NF‐κB. These results suggested that in VSMCs, activation of p42/p44 MAPK, Akt and NF‐κB 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. J. Cell. Physiol. © 2006 Wiley‐Liss, Inc.