Free cationic liposomes inhibit the inflammatory response to cationic lipid–DNA complex injected intravenously and enhance its transfection efficiency

Abstract

In this report, we show that intravenous (i.v.) injection into mice of a complex made of the cationic lipid diC14-amidine and the luciferase reporter plasmid (pCMV-luc) results in efficient gene expression in several organs but elicits an inflammatory response characterized by a release of tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) into the serum of treated animals. A single preinjection of free diC14-amidine liposomes improves the i.v. transfection efficiency of the diC14-amidine/protamine/pCMV-luc complex as much as 40 times. This improvement is correlated with the ability of free liposomes to inhibit TNF-alpha but not IFN-gamma production resulting from complex injection. TNF-alpha-rich serum obtained from mice injected with diC14-amidine/protamine/pCMV-luc complex inhibits luciferase expression in transfected mouse lung endothelial (MLE) cells cultured in vitro, whereas IFN-gamma has no effect. This inhibitory effect can be partly abolished by treating the mouse serum with a specific anti-TNF-alpha antibody. These data point out that cationic lipids are potent inhibitors of the inflammatory response to the CpG motifs in plasmid DNA. This property is shown to enhance the in vivo transfection efficiency.

Effect of Methylated Adenine in Plasmid DNA on Transgene Expression in Mice

“…These results are contrast to the previous reports on decrease in cytokine production and increase in transgene expression by preinjection of free liposomes and coinjection of NF-kB decoy ODNs. [10][11][12] When we preinjected lipopolysaccharide which induces the inflammatory responses into mice, it suppressed transgene expression from the same plasmid DNA as used in this study by ca. 80-fold (data not shown).…”

“…[5][6][7][8][9] To overcome the inflammatory response associated with the cationic lipid-mediated gene transfer, preinjection of free liposomes and coinjection of NFkB decoy oligodeoxyribonucleotides (ODNs) have been attempted. [10][11][12] These treatments decrease cytokine production and increase transgene expression. The inflammatory response elicited by the DNA-cationic lipid complexes is thought to be due to unmethylated CpG sequences, because the unmethylated CpG dinucleotides in ODNs effectively induce cytokine production.…”

Higly fusogenic cationic liposomes transiently permeabilize the plasma membrane of HeLa cells

“…Short-chained lipids are more fusogenic than long-chained ones, and liposomes composed of cationic lipids of different acyl chain lengths fuse more easily than those made up of lipids with identical acyl chains [12]. DiC14-amidine, a shortchained cationic lipid, has been reported to posses a high level of transfection activity even in the absence of helper lipids in vitro and in vivo [13,14]. It was also recently successfully used as an immunoadjuvant [15].…”

Immune responses of therapeutic lipid nanoparticles

“…In addition, Liu et al [26,27] incorporated non-steroidal anti-inflammatory drugs (dexamethasone and prednisone) and agents that inhibit NF-κ B (capsaicin) and MAPK (PD9805) inflammatory pathways into the lipid bilayer of lipoplex, and showed that the levels of inflammatory cytokines (TNF-α , IL-12 and IFN-γ ) were reduced by 2-to 10-fold. Elouahabi et al [22] showed that a single pre-injection of empty DiC14-amidine liposomes reduced TNF-α production by 2-to 3-fold induced by the subsequent DiC14-amidine/protamine/pDNA complex, which in turn increased the transgene expression by 40-fold. This interesting result, however, was contradictory to their earlier report indicating that the DiC14-amidine liposomes induced significant production of inflammatory cytokines, including TNF-α [14] .…”