S1P1 receptor modulation preserves vascular function in mesenteric and coronary arteries after CPB in the rat independent of depletion of lymphocytes

Abstract

Background: Cardiopulmonary bypass (CPB) may induce systemic inflammation and vascular dysfunction. Sphingosine 1-phosphate (S1P) modulates various vascular and immune responses. Here we explored whether agonists of the S1P receptors, FTY720 and SEW2871 improve vascular reactivity after CPB in the rat.

Methods: Experiments were done in male Wistar rats (total n = 127). Anesthesia was induced by isoflurane (2.5-3%) and maintained by fentanyl and midazolam during CPB. After catheterization of the left femoral artery, carotid artery and the right atrium, normothermic extracorporeal circulation was instituted for 60 minutes. In the first part of the study animals were euthanized after either 1 hour, 1 day, 2 or 5 days of the recovery period. In second part of the study animals were euthanized after 1 day of postoperative period. We evaluated the contractile response to phenylephrine (mesenteric arteries) or to serotonin (coronary artery) and vasodilatory response to acethylcholine (both arteries).

Results: Contractile responses to phenylephrine were reduced at 1 day recovery after CPB and Sham as compared to healthy control animals (Emax, mN: 7.9 ± 1.9, 6.5 ± 1.5, and 11.3 ± 1.3, respectively). Mainly FTY720, but not SEW2871, caused lymphopenia in both Sham and CPB groups. In coronary and mesenteric arteries, both FTY720 and SEW2871 normalized serotonin and phenylephrine-mediated vascular reactivity after CPB (p<0.05) and FTY720 increased relaxation to acetylcholine as compared with untreated rats that underwent CPB.

Conclusion: Pretreatment with FTY720 or SEW2871 preserves vascular function in mesenteric and coronary artery after CPB. Therefore, pharmacological activation of S1P1 receptors may provide a promising therapeutic intervention to prevent CPB-related vascular dysfunction in patients.

Figure 1. Data on mean arterial pressure in Sham and CPB groups during the experimental protocol.

Abbreviations: MAP, mean arterial pressure; CPB, cardiopulmonary bypass. Data are mean±SEM. a- indicates P<0.05, t-test; b- indicates P<0.05, Repeated Measurements Anova, Bonferroni test.

Figure 2. Contractile reactivity after short and long-term recovery following Sham or CPB.

Left panels: contractile reactivity of mesenteric arteries to PE. A: concentration-response curves for Sham groups, mN; B: concentration-response curves for CPB groups, mN; C: AUC values of the contractile responses to PE, au. Right panels: contractile reactivity of coronary arteries to SE. D: concentration-response curves for Sham groups, mN; E: concentration-response curves for CPB groups, mN; F: AUC values of the contractile responses to SE, au. Abbreviations: CBP, cardiopulmonary bypass; PE, phenylephrine; SE, serotonin. Data are mean±SEM. a- indicates P<0.05 vs Control-Vehicle, Repeated measurements ANOVA, Bonferroni test; b- indicates P<0.05 vs CPB-Vehicle, One Way ANOVA, Bonferroni test.

Figure 3. Effect of S1P receptor agonist pretreatment with FTY720 and SEW2871 on contractile responses at 1 day following recovery from Sham or CPB.

Left Panels: responses to PE in mesenteric arteries. Right panels: responses to SE in coronary arteries. Abbreviations: CPB, cardiopulmonary bypass; PE, phenylephrine; SE, serotonin. Data are mean±SEM. a- indicates P<0.05 SEW2871 vs Vehicle, Repeated Measurements ANOVA, Bonferroni test (P = 0.007 for coronary artery and P = 0.037 for mesenteric artery); b- indicates P = 0.018 FTY720 vs Vehicle, Repeated Measurements ANOVA, Bonferroni test; c- indicates P = 0.04, SEW2871 vs Vehicle, t-test; d- indicates P = 0.028 SEW2871 vs Vehicle, t-test; e- indicates P = 0.01 FTY720 vs Vehicle, t-test.

Figure 4. Relaxant reactivity after short and long-term recovery following Sham or CPB.

Left panels: relaxant reactivity of mesenteric arteries to ACh. A: concentration-response curves for Sham groups, % of relaxation; B: concentration-response curves for CPB groups, % of relaxation; C: AUC values of the relaxant responses to ACh, au. Right panels: relaxant reactivity of coronary arteries to ACh. D: concentration-response curves for Sham groups, % of relaxation; E: concentration-response curves for CPB groups, % of relaxation; F: AUC values of the relaxant responses to ACh, au. Abbreviations: CBP, cardiopulmonary bypass; PE, phenylephrine; SE, serotonin. Data are mean±SEM. a- indicates P<0.05 vs Control-Vehicle, t-test. b- indicates P<0.05 vs Sham 2 days, t-test.

Figure 5. Effect of S1P receptor agonist pretreatment with FTY720 and SEW2871 on relaxant reactivity at 1 day following recovery from Sham or CPB.

ACh-induced relaxation was studied in mesenteric arteries (left panels A and B) and coronary arteries (right panels C and D). Abbreviations: CPB, cardiopulmonary bypass, ACh, acetylcholine. Data are mean±SEM. a- indicates P = 0.026 SEW2871 vs Vehicle, Repeated Measurements ANOVA, Bonferroni test; b- indicates P = 0.018 FTY720 vs Vehicle Repeated Measurements ANOVA, Bonferroni test; c- indicates P = 0.03 SEW2871 vs Vehicle, t-test; d- indicates P = 0.03 FTY720 vs Vehicle, t-test.