Review: novel insights into the regulation of vascular tone by sphingosine 1-phosphate

Endothelial dysfunction leading to increased vascular tone is implicated in the pathogenesis of cardiovascular disease, hypertension and pregnancy-related complications like preeclampsia and intrauterine growth restriction. Vascular tone is regulated by a balance between vasoconstrictor and vasodilator signals. Some vascular mediators circulate in blood, whereas others are produced by the endothelium and are delivered to the underlying vascular smooth muscle cells (VSMCs). It is proposed that increased permeability of resistance arteries in preeclampsia allows access of circulating vasoactive factors to VSMCs leading to increased vascular tone. This review focuses on the role of sphingosine 1-phosphate (SIP). This sphingolipid enhances the endothelial barrier, but it can also disrupt the barrier under certain conditions. These SIP-mediated effects on the endothelial barrier have been demonstrated in cultured endothelial cells and in isolated venules. They depend on SIP concentrations, the SIP receptors expressed and the vascular bed. However, no studies have examined if vascular tone is regulated by SIP in resistance arteries through changes in endothelial permeability and the leakage of circulating vasoconstrictors. Our recent studies using the pressure myograph system show that access of infused vasoconstrictors to VSMCs is blocked under low SW concentrations. Pathophysiological levels of infused SW disrupt the barrier and maximally increase vascular tone by facilitating access of itself and a coinfused vasoconstrictor to the VSMCs. Interestingly, infusion of an intermediate physiological concentration of SIP showed a small increase in endothelial permeability with controlled leakage of a coinfused vasoconstrictor that led to sub-maximal vascular tone development. These and other studies delineate the important role of SIP in the regulation of vascular tone and emphasize how dysfunction of this regulation can lead to pregnancy-related disorders. (C) 2013 Published by IFPA and Elsevier Ltd