Ginsenoside Metabolite Compound K Alleviates Adjuvant-Induced Arthritis by Suppressing T Cell Activation

Ginsenoside metabolite compound K (CK) is the degradation product of ginsenosides in the intestine by bacteria and has many pharmacological activities including anti-inflammatory effects. Rheumatoid arthritis (RA) is an inflammatory and autoimmune disease characterized by chronic synovial inflammation and articular damage in multiple joints. However, the effect of CK on RA remains unclear. In this study, the effect of CK on adjuvant arthritis (AA) and the underlying mechanisms that focused on T cell activation were investigated. Complete Freund’s adjuvant was used to induce AA rats. After the onset of arthritis, rats were given CK (10, 40, and 160 mg/kg) or MTX (0.5 mg/kg). To evaluate the severity of arthritis, arthritis index and paw swelling were evaluated every 3 days. Histopathology of joint and spleen were assayed. Subsets of T cells including CD4 + CD62L+ (naïve T cells), CD4 + CD25+ (activated T cells), and CD4 + CD25 + Foxp3+ cells (Treg) and CD25 expression were assayed by flow cytometry. Proliferation of T cell was evaluated by ³H-TdR. IL-2 level was assayed by ELISA. We found that CK attenuated arthritis index and paw swelling, restored the histopathological change of joint and spleen, downregulated the percentage of activated T cells, and upregulated naïve T cells and Treg cells in spleen. CK significantly suppressed T cell activation (as indicated by T cell proliferation, CD25 expression, and IL-2 production). In conclusion, our results suggest that CK alleviates autoimmune arthritis by suppressing T cell activation.