Delivery of oligonucleotides into mammalian cells by anionic peptides: comparison between monomeric and dimeric peptides.

The use of antisense oligonucleotides as putative therapeutic agents is limited by their poor delivery into the cytosol and/or the nucleus because they are not able to efficiently cross lipid bilayers. To circumvent this pitfall, anionic amphipathic peptides derived from the influenza virus fusogenic peptide have been used to destabilize membranes in an acidic environment. In this paper, we compare the ability of a monomeric and a dimeric peptide to introduce oligonucleotides into the cytosol and nuclei of several types of cultured cells. Cells incubated at pH 6.2 or at a slightly lower pH in the presence of the monomeric peptide but not the dimeric peptide were efficiently permeabilized. The location of fluorescent derivatives of peptides and of oligonucleotides was assessed by confocal microscopy. Both the peptides and oligonucleotides remained entrapped in vesicular compartments at neutral pH; at acidic pH, oligonucleotides in the presence of the monomeric peptide were mainly in the nucleus, while in the presence of the dimeric peptide they co-localized with the peptide into vesicles. The data are interpreted on the basis of the spectroscopic behaviour of monomeric and dimeric peptides in relation to the environmental pH.

Spacer length dependence on the efficiency of dimeric anionic peptides in gene transfer by glycosylated polylysine/plasmid complexes.

Amphiphilic anionic peptides have been used to enhance the efficiency of transfection by helping plasmids to escape from endosomes to the cytosol. It has been shown that efficiency of an eicosamers containing five glutamyl residues (E5), can be considerably enhanced either by transforming it into a dimer or by adding a tripeptide WYG in a C-terminal position (E5WYG). The dimerization of the peptide E5WYG leads to a more efficient tool when the dimerization device includes the tripeptide WYG unit and a longer spacer arm made of Gly-betaAla-betaAla residues, but to a 10-fold less efficient tool when the dimerization device includes a shorter spacer, a glycyl residue. Both dimers are taken up by the cells to a similar extent. Both dimers seem to be surrounded similarly as far as the environmental pH is concerned. In contrast, we found a correlation between the propensity of the peptides to adopt a helical structure at neutral pH and the gene transfer efficiency.

Glycofection in the presence of anionic fusogenic peptides: a study of the parameters affecting the peptide-mediated enhancement of the transfection efficiency.

Gene delivery mediated by polyplexes such as DNA complexed with polylysine conjugates is limited by the low efficiency of escape of DNA from the endosomes. One of the strategies which favors the transmembrane passage of polyplexes consists of adding anionic amphipathic peptides capable of destabilizing membranes in an acidic medium. Although less efficient than replication-defective adenoviruses, fusogenic peptides increase the expression of the reporter gene by a factor between 100 and 1000 depending on the cell line. However, the activity of a given peptide depends on the composition of the lipid bilayer. We were interested in developing a polyplex (glycoplex) formulation comprising a glycosylated polylysine, a fusogenic peptide and a plasmid which would be useful for efficient transfection (glycofection) of a large panel of cells, even in the presence of serum. We synthesized several peptides and tested their efficiency in combination with different glycoplex formulations. We found that glycofection with a quaternary complex (called one pot formulation) made of lactosylated-polylysine, polylysine, DNA, and the dimeric peptide (E5-WYGG)2-KA was less cell-type dependent than other peptide-based formulations. In addition, its efficiency was not affected by the presence of serum (up to 20%).

Cytosolic and nuclear delivery of oligonucleotides mediated by an amphiphilic anionic peptide.

Antisense oligonucleotides (ODN) were easily introduced into the cytosol of mammalian cells on permeabilization of the plasma membrane by an amphiphilic anionic peptide. The E5CA peptide (GLFEAIAEFIEGGWEGLIEGCA) is an E5 peptide analog derived from the N-terminal segment of the HA2 subunit of influenza virus hemagglutinin. This peptide undergoes a conformational change when the pH shifts from neutral to around 6.0, inducing a transient permeabilization of the plasma membrane. In the presence of the E5CA peptide at pH close to 6.0, fluoresceinylated ODN were rapidly taken up by cells and diffused into the nucleus. The uptake of ODN was dependent on the E5CA peptide concentration and on the duration of the incubation at low pH, as shown by confocal microscopy and flow cytometry analyses. This procedure is suitable for loading adherent cells as well as nonadherent cells with single-stranded or double-stranded ODN. Under optimal conditions, a high percentage of cells were nuclei loaded, and the viability was not affected. This method makes use of a well-defined chemical product without the requirement of any special equipment. It will be useful to study the interactions of single-stranded or double-stranded ODN used as antisense, antigenes, or decoys.