Rocaglamide Suppresses Allergic Reactions by Regulating IL-4 Receptor Signaling

Abstract

Rocaglamide (Roc-A), a natural phytochemical isolated from Aglaia species, is known to exert anticancer effects. Allergic inflammation can enhance the tumorigenic potential of cancer cells. We hypothesized that Roc-A could regulate allergic inflammation. Roc-A prevented an antigen from increasing the hallmarks of allergic reactions in vitro. Roc-A suppressed passive cutaneous anaphylaxis (PCA) and passive systemic anaphylaxis (PSA). RNA sequencing analysis showed that Roc-A prevented the antigen from increasing the expression of IL-4 in RBL2H3 cells. Roc-A also prevented the antigen from increasing the expression of interleukin-4 receptor (IL-4R). Roc-A was found to form a hydrogen-bonding network with residues N92 and L64 of IL-4R in a molecular docking simulation. Roc-A prevented the antigen from inducing the binding of IL-4R to JAK1. Chromatin immunoprecipitation (ChIP) assays showed that C-Jun could bind to promoter sequences of IL-4 and IL-4R. Mouse recombinant IL-4 protein increased β-hexosaminidase activity, IL-4R expression, and the hallmarks of allergic inflammation in the antigen-independent manner. Mouse recombinant IL-4 protein increased the expressions of CD163 and arghinase-1 and markers of M2 macrophages, but decreased the expression of iNOS, a marker of M1 macrophages in lung macrophages. Roc-A regulated the effects of a culture medium of antigen-stimulated RBL2H3 cells on the expressions of iNOS and arginase-1 in RAW264.7 macrophages. The blocking of IL-4 or downregulation of IL-4R exerted negative effects on the hallmarks of allergic reactions in vitro. The blocking of IL-4 or downregulation of IL-4R also exerted negative effects on PCA, and the downregulation of IL-4R exerted negative effects on PSA. An miR-34a mimic exerted negative effects on allergic reactions in vitro. The downregulation of IL-4R prevented the antigen from decreasing the expression of miR-34a in RBL2H3 cells. We identified chemicals that could bind to IL-4R via molecular docking analysis. The IL-4R docking chemical 1536801 prevented the antigen from increasing β-hexosaminidase activity and the hallmarks of allergic reactions. The IL-4R docking chemical 1536801 also exerted a negative effect on PCA. TargetScan analysis predicted miR-34a as a negative regulator of IL-4R. We found that the anti-allergic effect of Roc-A and its mechanisms were associated with miR-34a. Taken together, our results show that understanding IL-4R-mediated allergic reactions can provide clues for the development of anti-allergy therapeutics.

Keywords

• allergic reactions
• interleukin-4 receptor
• miR-34a
• molecular docking
• Rocaglamide