Sphingosine‐1‐phosphate stimulation of bladder smooth muscle contraction and signaling

Abstract

The purpose of this study was to determine the effect of sphingosine-1-phosphate (S1P) on myosin light chain (MLC) phosphorylation in bladder smooth muscle and on the activation of calcium sensitization pathways. Additionally, the effect of increases in extracellular glucose on S1P-stimulated bladder smooth muscle contraction was determined. Bladder smooth muscle strips were stimulated in response to S1P in the presence or absence of the protein kinase C inhibitor, bisindolylmaleimide-I (Bis), or the Rho kinase (ROK) inhibitor, H-1152. Force of contraction and MLC phosphorylation levels were measured at various points during stimulation with S1P. S1P increased MLC phosphorylation levels at Ser19 but not the dual phosphorylation of Thr18 and Ser19. Additionally, there was greater inhibition of S1P stimulated force by H-1152 as compared to Bis suggesting that ROK plays a more prominent role in S1P-induced contraction. The greater inhibition by H-1152 coupled with the data that S1P increased MLC phosphorylation levels at Ser19 together suggest that S1P-induced contractions signal through the ROK pathway preferentially. Lastly, bladder smooth muscle contraction in response to S1P stimulation is enhanced by increases in extracellular glucose suggesting this contraction could be modified in diseases such as diabetes-induced hyperglycemia. This study was funded by NIH grant DK 85734.