Efficient new cationic liposome formulation for systemic delivery of small interfering RNA silencing tumor necrosis factor α in experimental arthritis

Objective. Tumor necrosis factor alpha (TNF alpha) is among the most prominent cytokines in rheumatoid arthritis (RA) and is secreted mainly by macrophages. A direct method for restoring the immunologic balance in RA is use of small interfering RNA (siRNA) for silencing the TNFa transcript. The aim of this study was to determine the therapeutic effect of systemic administration of TNF alpha ARNA in an experimental model of RA, optimizing its delivery using new liposome formulations. Methods. Murine macrophages were transfected with ARNA targeting TNF alpha, and expression was measured. The therapeutic effect in collagen-induced arthritis (CIA) was assessed after intravenous delivery of TNF alpha ARNA. Delivery was optimized using a carrier DNA for complexation with the cationic liposome RPR209120/DOPE. Levels of TNF alpha and other cytokines were measured in sera and joint tissue-conditioned media. Biodistribution was determined using a fluorescent siRNA. Results. In vitro, TNF alpha ARNA efficiently and specifically modulated the expression of TNF alpha at both the messenger RNA and protein levels. In vivo, complete cure of CIA was observed when TNF alpha ARNA was administered weekly, complexed with the liposome and combined with carrier DNA. Inhibition (50-70%) of articular and systemic TNF alpha secretion was detected in the siRNA-injected groups, which correlated with a decrease in the levels of interleukin-6 and monocyte chemotactic protein 1. The main organs targeted by ARNA were the liver and spleen; the addition of liposome RPR209120 and carrier DNA significantly increased organ uptake. Conclusion. We demonstrated the efficiency of systemic delivery of ARNA designed to silence TNF alpha in CIA, using a liposome carrier system as a way to address the methodologic limitations in vivo.