Abstract
The bioactive lipid sphingosine-1-phosphate (S1P) regulates smooth muscle (SM) contractility predominantly via three G protein-coupled receptors. The S1P1 receptor is associated with nitric oxide (NO)-mediated SM relaxation, while S1P2 & S1P3 receptors are linked to SM contraction via activation of the Rho-kinase pathway. This study is to determine testosterone (T) modulating the expression and functional activity of S1P receptors in corpus cavernosum (CC). Adult male Sprague-Dawley rats were randomly divided into three groups: sham-operated controls, surgical castration and T supplemented group. Serum S1P levels were detected by high-performance liquid chromatography. The expression of S1P1-3 receptors and sphingosine kinases was detected by real-time RT-PCR. In vitro organ bath contractility and in vivo intracavernous pressure (ICP) measurement were also performed. T deprivation significantly decreased ICP rise. Meanwhile, surgical castration induced a significant increase in serum S1P level and the expression of S1P2-3 receptors by twofold (P < 0.05) but a decrease in the expression of S1P1 receptor. Castration also augmented exogenous phenylephrine (PE), S1P, S1P1,3 receptor agonist FTY720-P contractility and S1P2-specific antagonist JTE013 relaxation effect. T supplemented could restore the aforementioned changes. We provide novel data that castration increased serum S1P concentration and up-regulated the expression of S1P2-3 receptors in CC. Consistently, agonizing S1P receptors induced CCSM contraction and antagonizing mediated relaxation were augmented. This provides the first clear evidence that S1P system dysregulation may contribute to hypogonadism-related erectile dysfunction (ED), and S1P receptors may be expected as a potential target for treating ED.