Sphingosine 1-phosphate inhibits nitric oxide production induced by interleukin-1beta in rat vascular smooth muscle cells.

Sphingosine 1-phosphate (S1P) is a lipid mediator that exerts potent and diverse biological effects on several cardiovascular cells. We investigated the effect of S1P on interleukin (IL)-1beta-induced nitric oxide (NO) production and inducible NO synthase (iNOS) expression in rat vascular smooth muscle cells (VSMCs). S1P inhibited NO production at concentrations higher than 0.1 muM; this was associated with the inhibition of iNOS protein and mRNA expression. S1P also inhibited IL-1beta-induced GTP cyclohydrolase I (GTPCH) mRNA expression. Pertussis toxin (PTX) partially attenuated the inhibitory effects of S1P on NO production and iNOS protein induction, whereas it completely blocked the inhibitory effects on iNOS and GTPCH mRNA expression. S1P inhibited iNOS expression in Ca(2+)-depleted conditions; PTX did not modify this effect. The Rho kinase inhibitor Y 27632 partially but significantly attenuated the inhibitory effect of S1P on iNOS expression in Ca(2+)-depleted condition but did not affect it in the presence of Ca(2+). S1P significantly inhibited IL-1beta-induced persistent activation of extracellular signal-regulated kinase (ERK) but had no effect in Ca(2+)-depleted conditions. Thus, S1P inhibits IL-1beta induction of NO production and iNOS expression in rat VSMCs through multiple mechanisms involving both PTX-sensitive and -insensitive G proteins coupled to S1P receptors. Furthermore, Ca(2+)-dependent ERK inhibition and Ca(2+)-independent Rho kinase activation might be involved in the inhibitory mechanism of iNOS expression. Through its action on NO production by VSMCs, S1P may play an important role in the progression of local vascular injury associated with thrombosis, atherosclerosis, and hypertension.

[Modulation of sphingosine 1-phosphate, a new lipid mediator, on nitric oxide production by vascular smooth muscle cells].

The effects of sphingosine 1-phosphate (S1P) on nitric oxide (NO) production induced by interleukin (IL)-1 beta in cultured rat vascular smooth muscle cells (VSMCs) have been investigated. Rat VSMCs abundantly expressed mRNA of Edg-3 and Edg-5 receptor subtypes in both unstimulated and IL-1 beta-stimulated cells. S1P at higher than 0.1 microM inhibited the NO production induced by IL-1 beta in a concentration-dependent manner, in which S1P at 10 microM caused over 90% inhibition. S1P also inhibited inducible NO synthase (iNOS) protein and mRNA expressions induced by IL-1 beta in a concentration-dependent manner, which effects were smaller than that in the NO production. S1P also significantly inhibited GTP cyclohydrolase I (GTPCH) mRNA expression induced by IL-1 beta. PTX pretreatment partially prevented the inhibitory effects of S1P on the NO production and iNOS induction, while completely prevented the inhibitory effects on iNOS and GTPCH mRNA expressions. In PTX-pretreated VSMC, S1P showed a bell-shaped enhancing and inhibitory effect on iNOS protein expression. These results suggest that S1P modulates IL-1 beta induction of NO production by rat VSMCs through multiple mechanisms, partially via Edg-3 and Edg-5 receptor subtypes coupled to PTX-sensitive G proteins.