Functional TNFα gene silencing mediated by polyethyleneimine/TNFα siRNA nanocomplexes in inflamed colon

During inflammatory bowel disease, TNF alpha is the major pro-inflammatory cytokine mainly secreted from macrophages and dendritic cells. Here, we have demonstrated that TNF alpha siRNA/polyethyleneimine loaded into polylactide at an optimal concentration of 20 g/L nanoparticles covered with polyvinyl alcohol are efficiently taken up by inflamed macrophages and inhibit TNF alpha secretion by the macrophages. Those nanoparticles have a diameter of similar to 380 nm and zeta potential of -8 mV at pH 7.2, and are non-cytotoxic. Complexation, interactions and protection from RNAse between TNF alpha siRNA and polyethyleneimine were higher than those using chitosan. Importantly, complexation between TNF alpha siRNA and polyethyleneimine facilitated higher rates of siRNA loading into nanoparticles, compared to Chi or free siRNA mixed with Lipofectamine. Oral administration of encapsulated TNF alpha siRNA-loaded nanoparticles specifically reduced the TNF alpha expression/secretion in colonic tissue in LPS-treated mice. In conclusion, we have shown: (1) that proposed TNF alpha siRNA-loaded NPs are prepared via a non-denaturing synthetic process; (2) a high encapsulation rate of TNF alpha siRNA complexed to polyethyleneimine into NPs; (3) effective enzymatic protection of TNF alpha siRNA by polyethyleneimine; (4) non-cytotoxicity and biodegradability of nanoparticles loaded with polyethyleneimine/TNF alpha siRNA; and (5) in vitro and in vivo significant anti-inflammatory effects at low TNF alpha siRNA dose that is specific and restricted to the colonic cells. Our results collectively indicate that polyethyleneimine/TNF alpha siRNA nanocomplexes represent an efficient therapeutic option for diseases such as IBD. (C) 2010 Elsevier Ltd. All rights reserved.