Evaluation of proinflammatory cytokine production and liver injury induced by plasmid DNA/cationic liposome complexes with various mixing ratios in mice

The purpose of this study was to investigate the cytokine production and liver injury induced by lipoplexes prepared with DOTMA/cholesterol and DOTAP/cholesterol liposomes with various mixing ratios in mice. Lipoplexes were prepared with pCMV-Luc and DOTMA/cholesterol or DOTAP/cholesterol liposomes. After intravenous administration into the mice, organ luciferase activity and serum TNFα and ALT were measured to evaluate the transfection efficacy, cytokine production and liver injury. After intravenous administration of these lipoplexes, basically the serum TNFα and ALT levels were in agreement with the transfection efficacy of the lipoplexes. The cytokine production and liver injury were markedly suppressed by reducing the pDNA dose, and achieved normal levels at a pDNA dose of 0.47 mg/kg. As far as the effects of the charge ratio at this low pDNA dose are concerned, the charge ratios of the lipoplexes affected the transfection efficacy, but not the cytokine production and liver injury. After intravenous administration of either DOTAP/cholesterol or DOTMA/cholesterol liposomes, serum TNFα and ALT levels were normal, suggesting that liver injury as well as cytokine production was caused by lipoplexes, but not by cationic liposomes. This information will be valuable for the future optimization of the preparation conditions of lipoplexes for use in clinical gene therapy.