Abstract 214: Sphingosine Kinase-1 Knockout Mice Have Increased Cardiac Arrest Mortality That is Rescued by Sphingosine-1-Phosphate Lyase Inhibition
Introduction: Sphingosine-1-phosphate (S1P) is an important regulator of pro-survival signaling. Two sphingosine kinases (SK), SK1 and SK2, form S1P in cells while S1P lyase irreversibly degrades S1P and controls the total pool of cellular sphingolipids. Deletion of the SK1 gene is detrimental in both in vitro and in vivo heart models of ischemia/reperfusion (I/R) injury. Using our mouse model of cardiac arrest and return of spontaneous circulation (CA/ROSC), we tested the hypothesis that SK1 knockout (SK1-KO) mice will demonstrate decreased survival after CA/ROSC, and that upregulation of S1P levels via pharmacologic S1P lyase inhibition will rescue the effect of SK1 gene deletion in this model.
Methods: Control C57Bl/6 and SK1-KO mice were subjected to an established potassium-induced CA protocol. After 8 min CA, CPR was performed for 1.5 min, followed by an epinephrine bolus (1.5 μg/mouse) with continued CPR for an additional 3 min or until ROSC. Blood pressure, ETCO2, body temperature and ECG monitoring were continued until 4 h post-ROSC. SK1-KO mice were compared to control C57Bl/6 mice and to SK1-KO mice pre-treated with the S1P lyase inhibitor tetrahydroxybutylimidazole (THI) given orally (10 μg/mouse twice daily for 3 days). The effect of SK1-KO and THI on blood and heart tissue S1P levels were determined by LC/MS/MS.
Results: LC/MS/MS analysis of heart tissue and plasma showed significant reductions in S1P levels in SK1-KO compared to C57Bl/6 mice (p<0.05). Inhibition of S1P lyase by THI almost doubled S1P levels in the hearts of SK1-KO and C57Bl/6 mice compared to non-treated animals (p<0.01). 5 of 9 C57Bl/6 mice (56%) demonstrated ROSC, and 3 of these 5 resuscitated mice (60%) survived 4 h post-ROSC. By comparison, 4 of 8 SK1-KO mice demonstrated ROSC (50%), while 0 of 4 (0%) resuscitated mice achieved 4 h survival. Inhibition of S1P lyase by THI significantly improved the ROSC rate of SK1-KO mice to 83% (5/6 mice) and 4 h survival to 80% (4/5 mice).
Conclusions: SK1 and S1P lyase appear to be critical mediators of early cardiac arrest outcomes in a mouse model of cardiac arrest. S1P lyase inhibition is a pharmacologic strategy in this model that increases cardiac S1P levels, and significantly improves both ROSC and 4-hour survival after cardiac arrest.
- © 2010 by American Heart Association, Inc.