Liposomes encapsulated dimethyl curcumin regulates dipeptidyl peptidase I activity, gelatinase release and cell cycle of spleen lymphocytes in-vivo to attenuate collagen induced arthritis in rats.

Rheumatoid arthritis (RA) is an autoimmune disease and characterized by the excessive cell proliferation, abnormal cell cycle of lymphocytes and synovial cells. The therapeutic effects of curcumin in active RA patients were reported, but limited by its insolubility and rapid systemic elimination. Dimethyl curcumin (DiMC) is a metabolically stable analogue of curcum with anti-inflammatory property. In this study, liposomes encapsulated dimethyl curcumin (Lipo-DiMC) was prepared to improve the bioavailability and metabolic-stability; collagen induced arthritis (CIA) rat model was employed to investigate the effects of Lipo-DiMC treatments during CIA progress. Physical assessments and routine-blood-test were performed. Fresh spleen lymphocytes were isolated from normal, CIA and Lipo-DiMC-treated CIA rats; flow-cytometry for cell-cycle analysis, western-blotting for intracellular signal pathway protein expressions, gelatin-zymography for matrix-metalloproteases 2/9 (MMP-2/9) and GF-AFC for dipeptidyl-peptidase I (DPPI) activity assay. Compared with untreated CIA rats, Lipo-DiMC treatments relieved paw-swellings, suppressed the increments of immunocytes numbers and inhibited DPPI and MMP-2/9 over-activity in blood. Lipo-DiMC adjusted CIA-induced cell cycle dysfunction at G0/G1-phase and S-phase of spleen lymphocytes for CIA rats. The intracellular expression-trends of P38, P21, Bcl-2, JNK-1 and DPPI of spleen lymphocytes were observed during CIA progress with and without Lipo-DiMC administrations. Lipo-DiMC exhibited its therapeutic functions by attenuating CIA development in rats, associated with down-regulating CIA-induced lymphocytes numbers, inhibiting over-expressed of DPPI and MMP-2/9, and adjusting cell cycles. These findings provide a new insight into the mechanism of Lipo-DiMC treatment in CIA rat model and suggest that Lipo-DiMC could be considered as a potential drug for RA treatment.