Imbalance between T-helper 17 (Th17) cells and regulatory T (Treg) cells is causally linked to the development of rheumatoid arthritis (RA). In this study, we tested the hypothesis that electroacupuncture (EA) confers therapeutic benefits in RA through activation of vasoactive intestinal peptide (VIP)-dependent signalling and restoration of the Th17/Treg cell balance.
A collagen-induced arthritis (CIA) model was induced in Sprague-Dawley rats by injection of bovine type II collagen in incomplete Freund's adjuvant on day 0 and day 7. Three days after the second injection, EA was given at acupuncture points GB39 and ST36 three times per week for 4 weeks. To block VIP signalling, [D-P-Cl-Phe(6)-Leu(17)]-VIP, a VIP receptor antagonist, was administered intraperitoneally 30 min before EA. Inflammatory and pathological responses in the joint were assessed. Synovial VIP receptor mRNA levels and Treg and Th17 cell frequencies in the spleen were determined.
EA significantly reduced the severity of CIA, as evidenced by reduced paw volumes, arthritis scores and inflammation scores. EA significantly increased mRNA expression of the VIP receptor VPAC1 and led to an elevation in CD4(+)FOXP3(+) Treg cell frequency and a reduction in CD4(+)IL17(+) Th17 cell frequency. Pre-injection of a VIP receptor antagonist significantly reversed EA-induced expansion of Treg cells, but did not alter the frequencies of Th17 cells.
EA exerts anti-inflammatory effects in a collagen-induced rat model of arthritis. These effects appear to be mediated through activation of VIP signalling and re-establishment of the Th17/Treg cell balance.