Manual acupuncture at ST36 attenuates rheumatoid arthritis by inhibiting M1 macrophage polarization and enhancing Treg cell populations in adjuvant-induced arthritic rats

Abstract

Objectives: Acupuncture has been found to be effective at relieving many inflammatory pain conditions, including rheumatoid arthritis (RA). We aimed to assess the anti-inflammatory potential of manual acupuncture (MA) treatment of RA using adjuvant-induced arthritic (AIA) rats and to explore the underlying mechanisms. Methods: The anti-inflammatory and analgesic actions of MA at ST36 ( Zusanli) in AIA rats were assessed using paw withdrawal latency and swelling, histological examination and cytokine detection by enzyme-linked immunoassay (ELISA). The cell–cell communication (CCC) network was analyzed with a multiplex immunoassay of 24 immune factors expressed in the inflamed joints, and the macrophage and Treg populations and associated cytokines regulated by MA were investigated using reverse-transcription quantitative polymerase chain reaction (RT-qPCR), ELISA and flow cytometry. Results: MA markedly decreased heat hyperalgesia and paw swelling in AIA rats. MA-treated rats also exhibited decreased levels of pro-inflammatory cytokines (tumor necrosis factor (TNF)-α, interleukin (IL)-1β) coupled with increased anti-inflammatory cytokines (IL-10, transforming growth factor (TGF)-β1) in the ankle joints at protein and mRNA levels. CCC network analysis confirmed that macrophages are of critical importance and are potential therapeutic targets in RA. Repeated treatment with MA triggered a macrophage phenotypic switch in the paws, with fewer M1 macrophages. Prominent increases in the Treg cell population and TGF-β1 in the popliteal lymph nodes demonstrated the immunomodulatory effects of MA. Furthermore, a selective TGF-β1-receptor inhibitor, SB431542, attenuated the anti-inflammatory effects of MA and MA-induced suppression of the levels of M1-released cytokines. Conclusion: These findings provide novel evidence that the anti-inflammatory and analgesic effects of MA on RA act through phenotypic modulation involving the inhibition of M1 macrophage polarization and an increase in the Treg cell population, highlighting the potential therapeutic advantages of acupuncture in controlling pain and ameliorating inflammatory conditions.

The effect of acupuncture on pain and swelling of arthritis animal models: A systematic review and meta-analysis

“…The quality assessments of the 21 studies are summarized in Figure 2 . 13 studies were rated as having a low risk for the sequence generation bias, as they mentioned the rats were randomly grouped ( Yu et al, 2009 ; He et al, 2011 ; Qiao et al, 2012 ; Shou et al, 2013 ; Zhu et al, 2015 ; Dong et al, 2018 ; Ma et al, 2018 ; Xu et al, 2018 ; Su et al, 2019 ; Zhu et al, 2019 ; Gusmao et al, 2021 ; Shen et al, 2021 ; Yang et al, 2021 ; Zheng et al, 2021 ; Yu et al, 2022 ); the remaining 8 studies did not mention the criteria for grouping. All the studies started with rats of similar weights, and they were kept under similar environmental conditions.…”

“…The baselines of groups were similar except in 1 study ( Park et al, 2006 ); the initial PWL, PWT or the paw volume values after disease induction were similar. 10 studies informed that the behavioral tests were taken by examiners blinded from the experiments ( Sun et al, 2006 ; Shan et al, 2007 ; Sun et al, 2008 ; Mi et al, 2011 ; Shou et al, 2013 ; Zhu et al, 2015 ; Chai et al, 2018 ; Xu et al, 2018 ; Yang et al, 2021 ; Yu et al, 2022 ). The statistical analyses were taken in blind manner in one study ( Shou et al, 2013 ).…”

“…Various mechanisms have been proposed in this section. Most of the studies focused on the immune regulation: changes in cytokine levels were measured in 4 studies ( Xu et al, 2018 ; Gusmao et al, 2021 ; Yang et al, 2021 ; Yu et al, 2022 ); NF-kB signaling was investigated in 2 studies ( Dong et al, 2018 ; Gusmao et al, 2021 ); changes in immune cell proportions were assessed in 2 studies ( Zhu et al, 2015 ; Yu et al, 2022 ). Expression levels of vasoactive intestinal peptide (VIP) and its binding receptors were measured in 2 studies ( He et al, 2011 ; Zhu et al, 2015 ); VIP is a neuropeptide with pleiotropic functions, like vasodilation and immune regulation ( Delgado and Ganea, 2013 ).…”

“…Acupuncture treatment tends to lower the pro-inflammatory cytokine (e.g., TNF-α, IL-1β, IL-4, IL-6, IL-17, IL-18) levels at the inflammatory sites ( Xu et al, 2018 ; Gusmao et al, 2021 ; Yu et al, 2022 ). In consistent with these findings, NF-κB signaling was inhibited by acupuncture ( Dong et al, 2018 ; Gusmao et al, 2021 ).…”

“…In consistent with these findings, NF-κB signaling was inhibited by acupuncture ( Dong et al, 2018 ; Gusmao et al, 2021 ). Acupuncture also seems to promote the pro-resolving inflammation by reducing M1 macrophage polarization and increasing regulatory T cell population ( Zhu et al, 2015 ; Yu et al, 2022 ). Other factors like increased apoptosis and inhibited angiogenesis may also help to control inflammation ( Su et al, 2019 ; Zhu et al, 2019 ).…”