Sphingosine-1-Phosphate/Protein Kinase Cβ2 Signaling Mediates Hypercontraction of Mesenteric Arterial Smooth Muscle in Spontaneously Hypertensive Rats

Protein kinase C (PKC) isoforms are crucial in hypertension-associated vascular dysfunction. Our previous study suggested that upregulated PKCβ2 contributed to aorta hypercontraction in spontaneously hypertensive rats (SHR). However, its role in resistance arteries remains unclear. Considering the implications of sphingosine 1-phosphate (S1P) and its receptors (S1PRs) in hypertensive vascular dysfunction, we investigated whether PKCβ2 is regulated by S1P in SHR mesenteric arteries and elucidated its underlying mechanisms. Functional studies were performed on endothelium-denuded mesenteric arteries isolated from SHR and Wistar-Kyoto (WKY) rats. Expression of PKCβ2, S1P2, S1P3, and phosphorylation levels of PKCβ2 and key proteins in calcium sensitization pathway were assessed by Western blotting using mesenteric arteries and mesenteric arterial smooth muscle cells (MASMCs). PKCβ2 expression was significantly elevated in SHR. LY333531, a PKCβ inhibitor, attenuated contraction induced by norepinephrine and S1P in SHR. S1P significantly increased PKCβ2 phosphorylation in SHR, an effect suppressed by sphingosine kinase 1 inhibitor PF-543. Inhibition or silencing of PKCβ2 significantly suppressed S1P-induced calcium sensitization. The expression levels of S1P2 and S1P3 were markedly higher in SHR, and the inhibitory effect of LY333531 on S1P-induced contraction was not altered by JTE-013 (an S1P2 antagonist) or TY-52156 (an S1P3 antagonist). Furthermore, inhibition or silencing of S1P2 or S1P3 suppressed the activation of PKCβ2 and downstream calcium sensitization pathway. These findings demonstrate that S1P activates PKCβ2 via S1P2 and S1P3, enhancing calcium sensitization pathway and promoting hypercontraction in SHR. Thus, the S1P/PKCβ2 pathway is a potential therapeutic target for hypertensive vascular dysfunction.