ORIGINAL RESEARCH article
Front. Immunol.
Sec. Inflammation
This article is part of the Research TopicNeuroimmune Interactions in Pain: From Central and Peripheral Neuroinflammation to Novel Therapeutic StrategiesView all 4 articles
Electroacupuncture Alleviates Pain by Activating the MD2/TLR4/NF-κB Pathway in the ST36 Acupoint
Provisionally accepted
Jiangjiang FuGangchen Cheng
Zhongxi Lu
Feiyang Li
ZeZhi Fan
Zhifang Xu
Bo ChenYongming GuoYuhan LiuHui Zhang
Yuan Xu*
Yi Guo*- Graduate School of Tianjin University of Traditional Chinese Medicine, Tianjin, China
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The acupuncture acupoint is the key initial component for the efficacy of electroacupuncture (EA). Previous studies have confirmed that the NF-κB pathway in the acupoint region mediates the therapeutic effects of acupuncture. Therefore, this study focuses on further in-depth research on the MD2/TLR4/NF-κB axis. This study utilized the mouse model of adjuvant-induced arthritis (AIA) established by intraplantar injection of Complete Freund's Adjuvant (CFA). Low-frequency EA intervention was applied at both sides of the Zusanli (ST36) acupoint, and behavioral, molecular, and immunological approaches were integrated to investigate the role of MD2 in EA-mediated analgesia. Results demonstrated that EA increased paw thermal withdrawal thresholds (PTWTs) in AIA mice (P<0.05), accompanied by higher levels of MD2, TLR4, p65, and the phosphorylated form of p65 (p-p65) at the acupoint. Co-immunoprecipitation (Co-IP) confirmed binding between MD2 and TLR4 in ST36 acupoint, while immunofluorescence (IF) revealed co-localization of TLR4 with fibroblasts and mast cells in ST36, suggesting these immune cells are critical targets for signal activation. Lentivirus-mediated knockdown of MD2 at the acupoint partially reversed EA's analgesic effects and suppressed downstream TLR4/NF-κB pathway activation, indicating that altering MD2 in the acupoint can modulate spinal cord-related signaling pathways. Mechanistically, EA dynamically regulates the equilibrium of the Grem1/BMP4/COX2 axis in the spinal dorsal horn via activation of the MD2/TLR4/NF-κB pathway cascade, achieving systemic analgesia. This study provides molecular evidence supporting the "acupoint priming" theory in acupuncture and highlights MD2 as a potential therapeutic target for pain management.
Keywords: Electroacupuncture, Analgesia, ST36 acupoint, MD2/TLR4/NF-κB pathway, Grem1/BMP4/COX2 pathway
Received: 25 Jun 2025; Accepted: 26 Nov 2025.
Copyright: © 2025 Fu, Cheng, Lu, Li, Fan, Xu, Chen, Guo, Liu, Zhang, Xu and Guo. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Yuan Xu
Yi Guo
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