Sphingosine 1-phosphate receptors mediate the lipid-induced cAMP accumulation through cyclooxygenase-2/prostaglandin I2 pathway in human coronary artery smooth muscle cells.
Sphingosine 1-phosphate (S1P) has been shown to exert a variety of biological responses through extracellular specific receptors or intracellular mechanisms. In the present study, we characterized a signaling pathway of S1P-induced cAMP accumulation in human coronary artery smooth muscle cells (CASMCs). S1P induced biphasic cAMP accumulation composed of a short-term and transient response (a peak at 2.5 min) and a late and sustained response ( approximately 4-6 h). The late phase of cAMP accumulation was parallel to the increment of cyclooxygenase-2 protein expression and was inhibited by N-[2-(cyclohexyloxyl)-4-nitrophenyl]-methane sulfonamide (NS398), a cyclooxygenase-2-specific inhibitor. We were surprised to find that the cyclooxygenase-2 inhibitor also inhibited short-term cAMP accumulation even when cyclooxygenase-2 protein expression was not yet increased. More interestingly, the short-term cAMP accumulation was also completely inhibited by pertussis toxin, an inhibitor of G(i/o) proteins. JTE-013, a specific antagonist for S1P(2) receptors, inhibited the S1P-induced cAMP accumulation. Furthermore, small interfering RNAs targeted for S1P(2) receptors significantly inhibited the S1P-induced cAMP accumulation. The cAMP response was also inhibited by specific inhibitors for phospholipase C, extracellular signal-regulated kinase pathways, and cytosolic phospholipase A(2). S1P actually activated these enzyme activities and stimulated prostaglandin I(2) (PGI(2)) synthesis. Finally, exogenously applied arachidonic acid and PGI(2) induced cAMP accumulation to a similar extent as S1P. In conclusion, S1P induced cAMP accumulation through S1P receptors, including S1P(2) receptor and G(i/o) protein-mediated stimulation of intracellular signaling pathways involving cyclooxygenase-2-dependent PGI(2) synthesis.
Damirin
Alatangaole
A
Laboratory of Signal Transduction, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi 371-8512, Japan.
Tomura
Hideaki
H
Komachi
Mayumi
M
Tobo
Masayuki
M
Sato
Koichi
K
Mogi
Chihiro
C
Nochi
Hiromi
H
Tamoto
Koichi
K
Okajima
Fumikazu
F
D002478:Cells, Cultured; D003331:Coronary Vessels / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D051546:Cyclooxygenase 2; D011464:Epoprostenol / Q000502:physiology*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000502:physiology; D006801:Humans; D008075:Lipoproteins, HDL / Q000502:physiology; D008246:Lysophospholipids / Q000494:pharmacology*; D008565:Membrane Proteins; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D011451:Prostaglandin-Endoperoxide Synthases / Q000502:physiology*; D049349:Receptors, Lysosphingolipid / Q000502:physiology*; D015398:Signal Transduction; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology*
D008075:Lipoproteins, HDL; D008246:Lysophospholipids; D008565:Membrane Proteins; D049349:Receptors, Lysosphingolipid; C060506:sphingosine 1-phosphate; D011464:Epoprostenol; D000242:Cyclic AMP; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D013110:Sphingosine