Abstract 424: Activation of the S1P3 Receptors is Responsible for S1P-mediated RhoA Activation and Cardioprotection
Sphingosine-1-phoshpate (S1P) is a bioactive lysophospholipid, generated and released at sites of tissue injury. S1P signals through a variety of G-protein coupled receptor subtypes and there are three major sub-types, S1P1, S1P2, and S1P3, to mediate cardiovascular responses. S1P2 and S1P3 receptors couple to Gαi, Gα12, Gα13 and Gαq and we first examined the contribution of S1P2 and S1P3 to cardiac hypertrophy using S1P2and S1P3 knockout (KO) mice and found that there is no difference in hypertrophy induced by pressure-overload. We previously showed that S1P provides cardioprotection against oxidative stress such as ischemia/reperfusion in which RhoA activation and its downstream effector PKD1 play an important role. It has not, however, been determined which S1P receptor subtype is responsible for S1P mediated cardioprotection. We knocked down the three major S1P receptors using siRNA in neonatal rat ventricular myocytes (NRVMs) and assessed RhoA and PKD1 activation induced by S1P. Knockdown of S1P3abolished RhoA activation and largely attenuated phosphorylation of PKD1 while knockdown of S1P1 and S1P2 did not. Using siRNA or pertussis toxin to inhibit different G-proteins, we further established that S1Pregulates RhoA activation through Gα13, but not Gα12, Gαq,or Gαi. To investigate the role of S1P3 receptors in the adult heart, hearts were isolated from wild-type or S1P3 KO adult mice, perfused in the Langendorff mode and subjected to ex vivo ischemia/reperfusion. As previously reported, S1P perfusion significantly reduced infarct size induced by ischemia/reperfusion in WT hearts (by 50%), but this protection was abolished in the S1P3 KO mouse heart. To further confirm the role of S1P3 in cardioprotection we perfused WT mouse hearts with an S1P3-specific agonist CYM-51736. We observed that CYM-51736 attenuated the infarct size to a similar degree as that observed with S1P. Our findings reveal that activation of the S1P3 receptor coupling to Gα13 and subsequent RhoA activation is responsible for cardioprotection against ischemia/reperfusion. Accordingly specific drug targeting of S1P3 receptors could provide therapeutic benefits in ischemic heart disease without the undesirable effects of global activation of other cardiac S1P receptors.
Author Disclosures: B.S. Yung: None. S.Y. Xiang: None. N. Purcell: None. H. Rosen: None. J. Chun: None. J. Heller Brown: None. S. Miyamoto: None.
- © 2015 by American Heart Association, Inc.