Immunomodulatory activity of the aqueous extract from rhizome of Smilax glabra in the later phase of adjuvant-induced arthritis in rats

Our previous paper has reported that the aqueous extract from Rhizoma Smilacis Glabrae (RSG) remarkably inhibited the primary inflammation of adjuvant arthritis (AA) in rats. In the present study, we further examined the activity of RSG and its mechanism on the secondary inflammation of AA. The administration of RSG (400 and 800mg/kg) during the later phase significantly inhibited the swelling of the adjuvant-non-injected footpad of AA rats. The lipopolysaccharide-induced production of IL-1, TNF and NO by peritoneal macrophages was significantly reduced. In contrast, the extract significantly recovered the decrease in weight gain of the AA rats and Concanavalin A-induced T lymphocyte proliferation and IL-2 production by their splenocytes, while prednisolone (10mg/kg) showed a significant aggravation. Furthermore, RSG significantly recovered the picryl chloride-induced delayed-type hypersensitivity to almost normal levels from the higher or lower levels induced by different treatments of cyclophosphamide with a normalization of CD4/CD8 ratio. These results suggest that RSG exhibit an improvement on AA through down-regulating over-activated macrophages and up-regulating the dysfunctional T lymphocytes during the later phase of arthritis. Such characteristics of RSG on AA may be advantageous to the long-term treatment of clinical rheumatoid arthritis.