PGE2 and NO Mediate the Inhibitory Effect Exerted by FTY720P at 15 Minutes on Colonic Na+/K+ ATPase

Abstract

Inflammatory Bowel Disease was shown to be accompaniedwith higher levels of sphingosine‐1‐ phosphate (S1P) and lower Na+/K+ ATPase activity. This work was undertaken to see if a cause‐effect relationship exists between S1P and the ATPase, and in case it does to determine the main mediators involved, using Caco‐2 cells as a model and fingolimod phosphate (FTY720P), a S1P analogue. The activity of the Na+/K+ ATPase was assayed by measuring the amount of inorganic phosphate liberated in presence and absence of ouabain, a specific inhibitor of the Na+/K+ATPase. Western blot analysis showed that sphingosine‐1‐phosphate receptor 2 (S1PR2) is the mostly expressed receptor in Caco‐2 cells. FTY720P, applied for 15 min, reduced significantly the activity of the Na+/K+ ATPase, with a maximal inhibition observed at a concentration of 7.5nM. The effect of FTY720P disappeared completely in presence of JTE‐013 (a specific blocker of S1PR2) and indomethacin (an inhibitor of cyclooxygenase enzymes), and was mimicked by CYM5520 (a S1PR2 agonist), prostaglandin E2 (PGE2), and sulprostone (an agonist of E prostanoid receptor 3 (EP3)). Carboxy‐PTIO a nitric oxide scavenger, abrogated the effect of FTY720P as well as that of PGE2. Treating the cells with Glyco‐SNAP (nitric oxide donor) reduced significantly the ATPase activity. It was concluded that FTY720‐P inhibits the ATPase by binding to S1PR2 leading to PGE2 production. PGE2 binds to EP3 receptors and increases nitric oxide levels resulting in an inhibitory effect on the Na+/K+ ATPase.Support or Funding InformationUniversity Research BoardThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.