Effect of electroacupuncture of "Zusanli"(ST36) and "Guanyuan" (CV4) on apoptosis and expression of apoptosis-related proteins of synoviocytes in adjuvant-induced arthritis rats

Abstract

To observe the effect of electroacupuncture (EA) of "Zusanli"(ST36) and "Guanyuan"(CV4) on the apoptosis rate of synoviocytes and protein expression of Fas, FasL and Caspase-3 in synovial tissue of adjuvant-induced arthritis (AIA) rats, so as to explore its mechanisms underlying improvement of rheumatoid arthritis （RA）. A total of 24 rats were randomly divided into normal, model, medication and EA groups, with 6 rats in each group. The AIA model was established by injection of complete Freund's adjuvant (CFA, 0.1 mL) into the left hindlimb paw. The rats in the medication group received intraperitoneal injection of 0.35 mg/kg of methotrexate, twice a week for 4 weeks. The rats in the EA group received EA stimulation of ST36 and CV4 (20 Hz/50 Hz, 1 mA) for 20 min, 6 times a week for 4 weeks. The left hind paw volume was measured using a paw volume meter, and histopathological changes of synovial tissue were observed by light microscope after H.E. staining. The serum contents of tumor necrosis factor-α（TNF-α） and interleukin-1 （IL-1） were measured by ELISA. The apoptosis of synoviocytes was detected by terminal-deoxynucleoitidyl transferase mediated nick end labeling (TUNEL), and the expression of apoptosis-associated proteins Fas, FasL and Caspase-3 in synovium were detected by Western blot. Compared with the normal group, the left hind paw volume from day 3 to 24 after administration of CFA, serum IL-1 and TNF-α contents were significantly increased (P<0.01), while the expressions of Fas, FasL and Caspase-3 proteins and apoptotic rate of synoviocytes were significantly decreased in the model group (P<0.01). In comparison with the model group, the paw volume from day 17 to 24 after modeling, the serum IL-1 and TNF-α contents were significantly reduced (P<0.01), while the apoptotic rate of synoviocytes, expressions of Fas protein in both medication and EA groups, Caspase-3 protein in the acupuncture group and FasL protein in the medication group were increased (P<0.01, P<0.05). Compared with the medication group, the expression of FasL protein was decreased in EA group (P<0.05). H.E. stain showed obvious hyperplasia of the synovial lining layer, and disordered arrangement of synovial cells, with edema and enlargement in some cells in the model group, which was relatively milder in both medication and EA groups. EA of ST36 and CV4 can promote the apoptosis of synoviocytes and the expressions of Fas and FasL proteins in AIA rats, which may contribute to its role in relieving synovitis through activating Fas/FasL signaling.