Electroacupuncture promotes macrophage/microglial M2 polarization and suppresses inflammatory pain through AMPK.

Inflammatory pain, the most prevalent disease globally, remains challenging to manage. Electroacupuncture emerges as an effective therapy, yet its underlying mechanisms are not fully understood. This study investigates whether adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK)-regulated silent information regulator 1 (SIRT1) contributes to electroacupuncture's antinociceptive effects by modulating macrophage/microglial polarization in the spinal dorsal horn of a mouse model of inflammatory pain. In this study, mice, introduced to inflammatory pain through subcutaneous injections of complete freund's adjuvant (CFA) in the plantar area, underwent electroacupuncture therapy every alternate day for 30-min sessions. The assessment of mechanical allodynia and thermal hyperalgesia in these subjects was carried out using paw withdrawal frequency and paw withdrawal latency measurements, respectively. Western blot analysis measured levels of AMPK, phosphorylation-adenosine 5'-monophosphate (AMP)-activated protein kinase, SIRT1, inducible nitric oxide synthase, cluster of differentiation 86, arginase 1, and interleukin 10. In contrast to the group treated solely with CFA, the cohort receiving both CFA and electroacupuncture demonstrated notable decreases in both thermal hyperalgesia and mechanical allodynia. This was accompanied by a marked enhancement in AMPK phosphorylation levels. AMPK knockdown reversed electroacupuncture's analgesic effects and reduced M2 macrophage/microglial polarization enhancement. Additionally, AMPK knockdown significantly weakened electroacupuncture-induced SIRT1 upregulation, and EX-527 injection attenuated electroacupuncture's facilitation of M2 macrophage/microglial polarization without affecting AMPK phosphorylation levels. Furthermore, combining electroacupuncture with SRT1720 enhanced the analgesic effect of SRT1720. Our findings suggest that AMPK regulation of SIRT1 plays a critical role in electroacupuncture's antinociceptive effect through the promotion of M2 macrophage/microglial polarization.

[Involvement of miR-34a and p53 protein of cerebral cortex in electroacpuncture analgesia in mice with neuropathic pain].

OBJECTIVE: To explore the involvement of miR-34a in cerebral cortex mediated anti-hyperalgesic effect of electroacupuncture (EA) in mice with neuropathic pain induced by chronic constriction injury (CCI) of sciatic nerve, so as to reveal its mechanisms underlying improvement of neuropathic pain. METHODS: A total of 75 male C57BL/6 mice were equally randomized into 3 groups: sham, CCI model and CCI+EA (n=25 in each group). Mice of the sham group received simple separation of the right sciatic nerve without ligation. The CCI model was established by liagation of the right sciatic nerve. EA (2 Hz /15 Hz, 1 mA) was applied to bilateral "Zusanli" (ST36) and "Sanyinjiao" (SP9) for 30 min, once every other day. The mechanical and thermal pain threshold of the bilateral hind-paws was detected at the 3rd, 5th and 7th day after modeling, and the expression of miR-34a of bilateral cerebral cortex tissues and that of p53 protein of the left cerebral cortex were determined by using quantitive real time PCR and Western blot, respectively. RESULTS: The mechnical paw withdrawal frequency were significantly higher and the thermal paw withdrawal latencies (PWLs) were significantly shorter at the affected hind-limb (rather than at the healthy hind limb) on day 3, 5 and 7 in the CCI model group than those in the sham group (P<0.05), and considerably reversed at the affected hind-limb (rather than at the healthy hind limb) in the EA group than in the CCI model group (P<0.05), suggesting an analgesic effect of EA intervention. After modeling, the expression levels of miR-34a and p53 on day 3, 5 and 7 were significantly up-regulated in the left cerebral cortex tissue (rather than in the right cerebral cortex) of the CCI model group in comparison with the sham group (P<0.05). After EA intervention, the up-regulated expression levels of miR-34a and p53 in the left cerebral cortex tissue (rather than in the right cerebral cortex) were obviously suppressed in the EA group relevant to the CCI model group (P<0.05). CONCLUSION: EA stimulation of ST36 and SP9 can down-regulate the expression of miR-34a and p53 in the contra-lateral cerebral cortex tissue of the CCI mice, which may contribute to its anti-hyperalgesic effect.