Cardiac glycoside digoxin ameliorates pro-inflammatory cytokines in PBMCs of rheumatoid arthritis patients in vitro

Rheumatoid arthritis (RA) is a systemic autoimmune disorder characterized by hyperplasia of the synovial membrane along with persistent inflammation of joints. Earlier studies suggest the crucial role of Th1 and Th17 subsets of T-helper cells in the pathogenesis of RA. Digoxin, a cardiac glycoside, is widely used in the treatment of heart failure. Keeping into consideration the potential of digoxin to regulate inflammatory responses in the host, we assessed its effect on the peripheral blood mononuclear cells (PBMCs) of RA patients. The PBMCs were incubated with a varying amount (10-500 nM) of digoxin for 24 h at 37 degrees C. There was a significant reduction in the population of Th17 cells upon treatment with digoxin. On the other hand, the digoxin treatment failed to modify the expression of T-bet and IFN-gamma at both proteins as well as mRNA level in the treated PBMCs. The cardiac glycoside also inhibited transcription factor ROR-gamma t in the Th17 cells. We also found a decrease in the levels of IL-1 beta, IL-6, IL-17, and IL-23 cytokines in the culture supernatant of digoxin treated PBMCs isolated from RA patients. The data of the present study suggest the preferential role of digoxin in suppressing the differentiation of Th17 cells in RA patients.