Sphingosine 1-Phosphate (S1P) Induces S1P2 Receptor-Dependent Tonic Contraction in Murine Iliac Lymph Vessels

摘要

Objective: We studied the effects of S1P on the diameter and spontaneous contraction of murine iliac collecting lymph vessels. Methods: The isolated lymph vessel was cannulated with two glass micropipettes and then pressurized to 4 cmH2O at the intraluminal pressure. The changes in lymph vessel diameter were measured using a custom-made diameter-detection device. Immunohistochemical studies were also performed to confirm S1P receptors on the lymph vessels. Results: S1P (10-7 M) had no significant effect on the frequency or amplitude of the lymph vessels' spontaneous contractions. In contrast, S1P (10-8-10-6 M) produced a concentration-related reduction in lymph vessel diameter (tonic contraction). Pretreatment with 10-4 M l-NAME or 10-5 M aspirin had no significant effect on the S1P-induced tonic contraction of the lymph vessels. To evaluate the intracellular signal transduction pathway responsible for the S1P-induced tonic contractions and their Ca2+-dependence, we investigated the effects of JTE013, VPC23019, U-73122, xestospongin C, and nifedipine on the S1P-induced tonic contractions. All of these inhibitors except VPC23019 and nifedipine significantly reduced the S1P-induced tonic contractions. S1P (5x10-7 M) also induced significant tonic contractions in the lymph vessels that had been superfused with high K+ Krebs-bicarbonate solution or Ca2+-free high K+ Krebs solution containing 1 mM EGTA. S1P2 receptors were immunohistochemically detected in the lymph vessels. Conclusion: These findings suggest that neither endogenous NO nor prostaglandins are involved in the S1P-induced tonic contraction of lymph vessels, which is mainly caused by Ca2+ release from intracellular Ca2+ stores through the activation of S1P2 and 1,4,5 IP3 receptors.