We previously reported the anti-allergic effect of rocaglamide-A (roc-A). Molecular docking analysis showed the binding of roc-A to sphingosine-1-phospahe receptor 2 (S1PR2). This led us to hypothesize that S1PR2 might play a role in allergic reactions. Antigen stimulation increased the expression of S1PR2 in rat basophilic leukemia (RBL2H3 cells). Sphingosine-1-phosphate (S1P) increased the expression of S1PR2 in an antigen-independent manner. S1PR2 was necessary for both allergic reactions in vitro and anaphylaxis. Sphingosine prevented the antigen (DNP-HSA) from increasing the expression of S1PR2 and hallmarks of allergic reactions in RBL2H3 cells. Sphingosine also prevented antigen from increasing the level of reactive oxygen species (ROS). Animal model of passive systemic anaphylaxis (PSA) showed the increased expression of CXCL1. CXCL1 was shown to mediate allergic reactions in vitro. TargetScan predicted the binding of miR-212 to the 3 ´ UTR of S1PR2. The downregulation of S1PR2 prevented antigen from increasing the expression of CXCL1 at the transcriptional level. cmiR-212 was found to decrease the expression of S1PR2 in antigen stimulated RBL2H3 cells. miR-212 mimic decreased the luciferase activity associated with 3 ´ UTR of S1PR2. The miR-212 mimic exerted a negative effect on the passive cutaneous anaphylaxis (PCA). The downregulation of S1PR2 increased the expression of miR-212 in antigen stimulated RBL2H3 cells. This suggests that miR-212 and S1PR2 form negative feedback loops to regulate allergic reactions. Our results show that S1PR2-miR-212 negative feedback loop regulates allergic reactions in vitro and in vivo.
