MicroRNA Let-7b-5p Induces Electroacupuncture Tolerance by Downregulating the MKP-1 Gene in Rats Subjected to CFA-induced Inflammatory Nociception

Abstract

Electroacupuncture (EA) treatment has proved to significantly decrease nociception in inflammatory nociception model by suppressing the phosphorylation of p38 mitogen-activated protein kinase (p38MAPK). However, repeated EA treatment results in gradual attenuation of its analgesic effects, which was defined as "EA tolerance." Recent studies have shown that let-7b-5p microRNA (miRNA) contributes to the EA tolerance. The present study aimed to explore the function of let-7b-5p in p38MAPK pathway and the development of EA tolerance in the inflammatory nociception. Dual luciferase reporter gene experiments were used in cortical neurons to determine the target gene locus of let-7b-5p. The threshold of nociception was assessed by tail flick latency (TFL) and paw withdrawal threshold (PWT). Western blots were used to measure the expression of mitogen-activated protein kinase phosphatase 1 (MKP-1) and phosphorylation level of p38MAPK after intracerebroventricular (ICV) injections of let-7b-5p agomir, antagomir, and controls. In vitro dual luciferase experiments demonstrated that the MKP-1-3′ untranslated region (UTR) is a target of let-7b-5p. In vivo experiment, rat with repeated EA treatment exhibits gradual decrease in TFL and PWT, which showed formation of EA tolerance. This trend was delayed after IVC injection of let-7b-5p antagomir and facilitated after IVC injection of let-7b-5p agomir. The protein levels of MKP-1 in the EA+let-7b-5p antagomir group were significantly higher than in the EA + let-7b-5p agomir group. However, P-p38MAPK in the EA+let-7b-5p antagomir group was significantly lower than in the EA+let-7b-5p agomir group. By upregulating the p38MAPK pathway through the inactivation of the MKP-1 gene, let-7b-5p contributes to EA tolerance in complete Freund's adjuvant (CFA)-induced inflammatory nociception rats. Our work revealed the mechanism of EA tolerance and indicated that let-7b-5p could be targeted to improve the long-term effects of EA.

Acupuncture for brain diseases: Conception, application, and exploration

“…worth mentioning that EA is stemmed from MA, in which electrodes are attached to the inserted needles to deliver electrical stimulation at the acupoints (Tang et al, 2020;Zhang, Abouelfetouh, et al, 2020). EA has been widely used for its better efficacy, objectivity, and controllability than MA (Zhang, Gong, et al, 2020).…”

“…The innovative acupuncture techniques include electroacupuncture (EA; Li, Wang, et al, 2019), transcutaneous electrical acupoint stimulation (TEAS; Ao et al, 2021), and laser acupuncture (Chon et al, 2019). It is worth mentioning that EA is stemmed from MA, in which electrodes are attached to the inserted needles to deliver electrical stimulation at the acupoints (Tang et al, 2020; Zhang, Abouelfetouh, et al, 2020). EA has been widely used for its better efficacy, objectivity, and controllability than MA (Zhang, Gong, et al, 2020).…”