VEGF induces S1P ₁ receptors in endothelial cells: Implications for cross-talk between sphingolipid and growth factor receptors

Abstract

Sphingosine 1-phosphate (S1P) is a platelet-derived sphingolipid that binds to S1P 1 (EDG-1) receptors and activates the endothelial isoform of NO synthase (eNOS). S1P and the polypeptide growth factor vascular endothelial growth factor (VEGF) act independently to modulate angiogenesis and activate eNOS. In these studies, we explored the cross-talk between S1P and VEGF signaling pathways. When cultured bovine aortic endothelial cells were treated with VEGF (10 ng͞ml), the expression of S1P 1 protein and mRNA increased by Ϸ4-fold. S1P1 up-regulation by VEGF was seen within 30 min of VEGF addition and reached a maximum after 1.5 h. By contrast, expression of neither bradykinin B2 receptors nor the scaffolding protein caveolin-1 was altered by VEGF treatment. The EC 50 for VEGF-promoted induction of S1P 1 expression was Ϸ2 ng͞ml, within its physiological concentration range. S1P1 induction by VEGF was attenuated by the tyrosine kinase inhibitor genistein and by the PKC inhibitor calphostin C. Preincubation of bovine aortic endothelial cells with VEGF (10 ng͞ml for 90 min) markedly enhanced subsequent S1P-dependent eNOS activation. VEGF pretreatment of cultured endothelial cells also markedly potentiated S1P-promoted eNOS phosphorylation at Ser-1179, as well as S1P-mediated activation of kinase Akt. In isolated rat arteries, VEGF pretreatment markedly potentiated S1P-mediated vasorelaxation and eNOS Ser-1179 phosphorylation. Taken together, these data indicate that VEGF specifically induces expression of S1P 1 receptors, associated with enhanced intracellular signaling responses to S1P and the potentiation of S1P-mediated vasorelaxation. We suggest that VEGF acts to sensitize the vascular endothelium to the effects of lipid mediators by promoting the induction of S1P 1 receptors, representing a potentially important point of cross-talk between receptor-regulated eNOS signaling pathways in the vasculature.

Heme Oxygenase-1 Contributes to an Alternative Macrophage Activation Profile Induced by Apoptotic Cell Supernatants

“…Besides mechanisms such as tumor hypoxia, the interaction of tumor-associated macrophages (TAMs) with dying tumor cells could then promote VEGFA release to stimulate tumor angiogenesis. Our unexpected observation of elevated S1P 1 expression after the treatment with AC-CM might also be attributed to autocrine VEGF, because S1P 1 expression was increased in bovine aortic endothelial cells after their exposure to authentic VEGF (Igarashi et al, 2003).…”

Sphingosine-1-phosphate and modulation of vascular tone

“…In BAEC, VEGF up-regulates expression of S1P 1 receptors at both levels of mRNA and protein, in a manner sensitive to pharmacological inhibition of protein kinase C (PKC) pathways. 32 Increases in S1P 1 expression levels are associated with enhanced eNOS phosphorylation/activation of cultured ECs as well as those of isolated blood vessels in response to subsequent stimulation with S1P, suggesting that at least some of the newly synthesized S1P 1 receptor molecules are functional. Thus, VEGF may dynamically regulate the expression levels of S1P 1 receptors and the magnitudes of eNOS responses to S1P by way of PKC pathways.…”

Steroidogenic factor-1 is a sphingolipid binding protein

“…Due to the large concentration of sphingolipids such as sphingomyelin in the plasma membrane, it was held that these molecules only served structural roles. However, over the past few decades, many studies have demonstrated that these molecules, notably ceramide and sphingosine-1-phosphate (S1P), play integral roles in mediating varied cellular processes (Hannun and Obeid, 2002;Igarashi et al, 2003;Merrill Jr. et al, 1997;Spiegel and Milstien, 2002;Spiegel and Milstien, 2003;Strasberg and Callahan, 1988;Tilly and Kolesnick, 2002;Vesper et al, 1999). Ceramide is a second messenger for events as diverse as differentiation, senescence, proliferation, cell cycle arrest, and apoptosis (Hannun, 1994;Hannun et al, 2001;Kolesnick, 2002).…”