Sphingosine‐1‐phosphate and sphingosylphosphorylcholine constrict renal and mesenteric microvessels in vitro

Abstract

1 Sphingolipids such as sphingosine-1-phosphate (SPP) and sphingosylphosphorylcholine (SPPC) can act both intracellularly and at G-protein-coupled receptors, some of which were cloned and designated as Edg-receptors. 2 Sphingolipid-induced vascular e ects were determined in isolated rat mesenteric and intrarenal microvessels. Additionally, sphingolipid-induced elevations in intracellular Ca 2+ concentration were measured in cultured rat aortic smooth muscle cells. 3 SPPC and SPP (0.1 ± 100 mmol l 71 ) caused concentration-dependent contraction of mesenteric and intrarenal microvessels (e.g. SPPC in mesenteric microvessels pEC 50 5.63+0.17 and E max 49+3% of noradrenaline), with other sphingolipids being less active. The vasoconstrictor e ect of SPPC in mesenteric microvessels was stereospeci®c (pEC 50 D-erythro-SPPC 5.69+0.08, L-threo-SPPC 5.31+0.06) and inhibited by pretreatment with pertussis toxin (E max from 44+5 to 19+4%), by chelation of extracellular Ca 2+ with EGTA and by nitrendipine (E max from 40+6 to 6+1 and 29+6%, respectively). Mechanical endothelial denudation or NO synthase inhibition did not alter the SPPC e ects, while indomethacin reduced them (E max from 87+3 to 70+4%). 4 SPP and SPPC caused transient increases in intracellular Ca 2+ concentrations in rat aortic smooth muscle cells in a pertussis toxin-sensitive manner. 5 Our data demonstrate that SPP and SPPC cause vasoconstriction of isolated rat microvessels and increase intracellular Ca 2+ concentrations in cultured rat aortic smooth muscle cells. These e ects appear to occur via receptors coupled to pertussis toxin-sensitive G-proteins. This is the ®rst demonstration of e ects of SPP and SPPC on vascular tone and suggests that sphingolipids may be an hitherto unrecognized class of endogenous regulators of vascular tone.

Sphingosine-1-phosphate and modulation of vascular tone

“…59 S1P also induces pertussis toxin-sensitive transient calcium mobilization in cultured smooth muscle cells derived from rat aorta. 69 Thus, S1P appears to modulate calcium-mobilizing pathways in smooth muscle cells in a manner similar to other classical G-protein-coupled receptor agonists.…”

Effects of Sphingosine-1-Phosphate on Pacemaker Activity of Interstitial Cells of Cajal from Mouse Small Intestine

“…The actions of many G-protein coupled receptors are mediated by release of PLC-dependent IP 3 -gated Ca 2+ from the ER (Fukata et al, 2001). S1P receptors also have a role in mobilization of intracellular Ca 2+ in various cell types (Bischoff et al, 2000;Spiegel and Merrill, 1996;Young and Nahorski, 2002). The pacemaking mechanisms of intestinal ICC are driven by activation of Ca 2+ -dependent pacemaker channels, such as TRP or Ca 2+ -activated Cl -channels, which are coupled with release of IP 3 -gated Ca 2+ from the endoplasmic reticulum (Huizinga et al, 2002;Kim et al, 2005;Nakayama et al, 2007;Ward et al, 2000).…”

Potential Roles of Magnesium Deficiency in Inflammation and Atherogenesis: Importance and Cross-talk of Platelet-Activating Factor and Ceramide

“…There are some reports that both PAF and ceramides may result in transformation of VSM cells from one phenotype to another, as is typical in the atherosclerotic process [53,54,72,73]. In addition, like we see in MgD, PAF produces vasoconstriction of blood vessels and a variety of VSM types [for recent review, see 69], as do several of the ceramides [69,74,75]. A number of investigators employing intravital microscopy techniques, similar to those used by our laboratories [76][77][78][79][80], have demonstrated that PAF increased the number of white blood cells in the microvessels concomitant with intense vasoconstriction-spasms with increasing concentrations of the putative lipid mediator (i.e., PAF), less leukocyte rolling, and increased adherence of the leukocytes to the endothelial surfaces with increases in vascular-capillary permeability [78][79][80].…”