Evaluation of proinflammatory cytokine production induced by linear and branched polyethylenimine/plasmid DNA complexes in mice

The purpose of this study was to evaluate the cytokine response induced by linear and branched polyethylenimine (PEI)/plasmid DNA (pDNA) complex (polyplex) in relation to the ratio of PEI nitrogen and DNA phosphate (N/P ratio) of the polyplex, dose of pDNA, and structure and molecular weight of PEI, which are important for transfection efficacy of PEI polyplex. As a control, a N-[1-(2,3-dioleyloxy)propyl]-n,n,n-trimethylammonium chloride/cholesterol liposome/pDNA complex (lipoplex) was selected for its high transfection efficacy in vivo. The concentration of proinflammatory cytokines such as tumor necrosis factor (TNF)-alpha were much lower after the administration of polyplex than lipoplex irrespective of the N/P ratio, dose of pDNA, or structure and molecular weight of PEI, although these factors affected the transfection efficacy in vivo. We demonstrated that the amount of activated nuclear factor-kappa B, which contributes substantially to the production of cytokines, was comparable with the control (no treatment) level, and significantly less than that obtained with lipoplex. Although the production of proinflammatory cytokines (TNF-alpha, interferon-gamma, and interleukin-12) was reduced on the administration of the linear PEI polyplex, serum alanine aminotransferase levels were significantly enhanced by pDNA in a dose-dependent manner, suggesting that such hepatic damage is not induced by proinflammatory cytokines.