Tumor necrosis factor alpha small interfering RNA decreases herpes simplex virus-induced inflammation in a mouse model.

BACKGROUND: Anti-TNFalpha antibodies have been used for treating inflammation in patients. But, more effective and safer drugs need to be developed for improved future therapeutic use. OBJECTIVES: To inhibit the expression of TNFalpha, we used small interfering RNAs (siRNAs) to reduce over expression of TNFalpha in vitro in cell cultures and in an in vivo Behcet's disease-like (BD) mouse model for amelioration of chronic inflammation. METHODS: TNFalpha siRNA was injected intraperitoneally twice with a 1-week interval. To compare the efficacy of TNFalpha siRNA versus an anti-TNFalpha antibody, Infliximab and Etanercept were administered to symptomatic mice with inflamed tissue. RESULTS: Intraperitoneal delivery of TNFalpha siRNA effectively decreased BD symptoms in 18 of 32 cases (56.3%). Scrambled siRNA treatment decreased BD symptoms in 2 of 19 cases (10.5%). Infliximab was effective in 11 of 27 cases (40.7%) and Etanercept was also effective in 9 of 25 cases (36.0%) at the end of the second week after treatment. TNFalpha siRNA reduced serum levels of TNFalpha (1.57 +/- 0.43pg/ml), compared to levels in mice not injected (84.02 +/- 24.59pg/ml) (p<0.01) or scramble injected (118.89 +/- 20.08pg/ml) (p<0.01). After single injection of TNFalpha siRNA, improvement of BD symptoms showed at 9 +/- 7th day on an average, contrary, in Infliximab injected group, improvement was apparent at 15 +/- 4th day after injection (p<0.05). CONCLUSION: We show that siRNAs can be employed to inhibit cytokine gene expression in an in vivo disease mouse model. This inhibition may, therefore, be attributed to the improvement of inflammatory symptoms.