Involvement of the Negative Feedback of IL-33 Signaling in the Anti-Inflammatory Effect of Electro-acupuncture on Allergic Contact Dermatitis via Targeting MicroRNA-155 in Mast Cells

In this study, we aimed to investigate the effect of electro-acupuncture (EA) at the Zusanli acupoint (ST36) on interleukin (IL)-33-mediated mast cell activation. Firstly, 2,4-dinitrofluorobenzene (DNFB)-induced allergic contact dermatitis (ACD) in rats was developed with or without EA treatment. Then, rat peritoneal mast cells (RPMCs) were obtained and cultured in the presence of IL-33. EA treatment relieved ear swelling and reduced mast cell infiltration in the local inflammation area with DNFB challenge, accompanying the decrement of IL-33 production. RPMCs isolated from ACD rats with EA treatment showed significant downregulation of IL-6, TNF-α, IL-13, and MCP-1 production following IL-33 stimulation. However, there was no obvious difference in surface ST2 receptor expression among different groups. In addition, EA selectively altered IL-33 signaling, suppressing p38 phosphorylation as well as NF-κB- and AP-1-mediated transcription but not Akt phosphorylation. Importantly, EA lowered microRNA (miR)-155 expression in the RPMCs, which presented a positive correlation with IL-33-induced IL-6 production. Furthermore, overexpression of miR-155 in the RPMCs was established following miR-155 mimic transfection. RPMCs with the overexpressed miR-155 displayed an obvious increment of inflammatory cytokine and abrogated the inhibitive effect of EA on NF-κB- and AP-1-regulated transcription in response to IL-33 compared with those without transfected-miR-155. These findings demonstrate EA treatment inhibits NF-κB and AP-1 activation as well as promotes the negative feedback regulation of IL-33 signaling via targeting miR-155 in mast cells, which contribute to the anti-inflammatory effect of EA on DNFB-induced ACD in rats.