Use of lipoplex-induced nuclear factor-kappaB activation to enhance transgene expression by lipoplex in mouse lung.

Background: Although lipofection-induced TNF-alpha can activate nuclear factor kappaB (NF-kappaB), which, in turn, increases the transgene expression from plasmid DNA in which any NF-kappaB responsive element is incorporated, no attempts have been made to use such biological responses as NF-kappaB activation against a vector to enhance vector-mediated gene transfer.

Methods: A lipoplex composed of N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium and cholesterol liposome and plasmid DNA encoding firefly luciferase under the control of the cytomegalovirus immediate early promoter (pCMV-Luc) was intravenously injected into mice. Luciferase activity as well as NF-kappaB activation in the lung were evaluated. Then, a novel plasmid DNA, pCMV-kappaB-Luc, was constructed by inserting 5 repeats of NF-kappaB-binding sequences into the pCMV-Luc.

Results: NF-kappaB in the lung was activated by injection of the lipoplex and its nuclear localization was observed. An injection of lipopolysaccharide 30 min prior to the lipofection further activated NF-kappaB. At the same time, the treatment significantly increased the transgene expression by lipoplex, suggesting a positive correlation between expression and NF-kappaB activity. Based on these findings, we tried to enhance the lipoplex-based transgene expression by using NF-kappaB activation. The lipoplex consisting of pCMV-kappaB-Luc showed a 4.7-fold increase in transgene expression in the lung compared with that with pCMV-Luc.

Conclusions: We demonstrated that NF-kappaB activation by lipoplex can be used to enhance lipoplex-mediated transgene expression by inserting NF-kappaB-binding sequences into plasmid DNA. These findings offer a novel method for designing a vector for gene transfer in conjunction with biological responses to it.