Effect of Electroacupuncture on Synovial M 1/M 2 Macrophage Polarization in Rats with Acute Gouty Arthritis

Abstract

To explore the effect of electroacupuncture (EA) on the expression of synovial AMP-activated protein kinase (AMPK) protein α， arginase-1 mRNA, nitric oxide synthase 2 (NOS 2) mRNA, NOD-like receptor protein 3 (NLRP 3) mRNA, and interleukin-1 β (IL-1 β) mRNA in acute gouty arthritis (AGA) rats, so as to explore its mechanisms underlying improvement of AGA via M 1/M 2 macrophage polarization. Male Wistar rats were randomly divided into normal control, model, medication (colchicine) and EA groups (n＝15 rats in each group). The AGA model was established by injection of sodium urate crystal (MSU) suspension (0.2 mL) into the articular cavity of the left knee. The rats of the normal control group received articular injection of normal saline (0.2 mL) of the left knee, and those of the medication group were treated by gavage of the colchicine (0.3 mg•kg－1•d－1) once daily for 7 days. EA (2 Hz/10 Hz, 1.0 mA) was applied to "Zusanli"(ST 36) and "Sanyinjiao" (SP 6) of the left hind limb for 10 min, once daily for 7 days. The inflammatory conditions of the synovial membrane tissue of the left knee joint were observed by H．E. staining. The expression levels of phosphorylated AMPKα (p-AMPKα) protein, and arginase-1 (a maker of M 2 macrophages) mRNA, NOS 2 (a maker of M 1 macrophages) mRNA, NLRP 3 mRNA, and IL-1 β mRNA in the knee joint synovial tissue were detected by Western blot and quantitative real-time PCR, respectively. Compared with the normal group, the inflammatory cell infiltration of the synovial tissue was more severe, the expression of p-AMPKα protein was significantly decreased (P<0.01), and the expression levels of arginase-1, NOS 2, IL-1 β and NLRP 3 mRNAs were considerably increased in the model group (P<0.01). The expression levels of p-AMPKα protein and arginase-1 mRNA were significantly up-regulated, and those of NOS 2, IL-1 β and NLRP 3 mRNAs obviously down-regulated in both EA and medication groups relevant to the model group (P<0.01, P<0.05), suggesting an increase of M 2 macrophage and a decrease of M 1 macrophage activity after EA. No significant differences were found between the EA and medication groups in up-regulating p-AMPKα expression and in down-regulating NOS 2, IL-1 β and NLRP 3 mRNA expression (P>0.05), except higher up-regulation of arginase-1 mRNA in the medication group (P<0.05)．. EA intervention can up-regulate the expression of arginase-1 mRNA and p-AMPKα protein, and down-regulate the expression of NOS 2, IL-1 β and NLRP 3 mRNAs in synovial tissues in AGA rats, which may contribute to its anti-inflammatory effect by promoting conversion of macrophages from M 1 pro-inflammatory phenotype to M 2 anti-inflammatory phenotype.