How to make siRNA lipoplexes efficient? Add a DNA cargo

Viscous Core Liposomes Increase siRNA Encapsulation and Provides Gene Inhibition When Slightly Positively Charged

Since its discovery, evidence that siRNA was able to act as an RNA interference effector, led to its acceptation as a novel medicine. The siRNA approach is very effective, due to its catalytic mechanism, but still the limitations of its cellular delivery should be addressed. One promising form of non-viral gene delivery system is liposomes. The variable and versatile nature of the lipids keeps the possibility to upgrade the liposomal structure, which makes them suitable for encapsulation and delivery of drugs. However, to avoid the limitation of fast release for the hydrophilic drug, we previously designed viscous core liposomes. We aimed in this work to evaluate if these viscous core liposomes (NvcLs) could be of interest for siRNA encapsulation. Then, we sought to add a limited amount of positive charges to provide cell interaction and transfection. Cationic lipid dimyristoylaminopropylaminopropyl or the polymer poly(ethylenimine) were incorporated in NvcL to produce positively charged viscous core liposomes (PvcL) by a customized microfluidic device. We found that NvcLs increased the encapsulation efficiency and loading content with regards to the neutral liposome. Both PvcL_PEI and PvcL_DMAPAP exhibited transfection and GFP knock-down (≈40%) in both 2D and 3D cell cultures. Finally, the addition of slight positive charges did not induce cell toxicity.

Compression of Vectors for Small Interfering RNAs Delivery: Toward Oral Administration of siRNA Lipoplexes in Tablet Forms

Currently, most nonviral nucleic acid vectors are in the form of colloidal suspensions administered primarily parenterally. This type of formulation and the mode of administration impose strong constraints such as the size of the administered vectors or the production of sterile preparations. The tablet form provides access to easy oral administration, well accepted by patients; As regards nucleic acid vectors, a dry form represents an advance in terms of stability. Using an optimized lipid-based small interfering RNA-delivery system, we studied the tabletability of a liquid suspension of these vectors. We optimized the conditions of freeze-drying by choosing excipients and process, allowing for the conservation of both the gene-silencing efficacy of the formulated siRNAs and the supramolecular structure of the lipid particulate system. Gene-silencing efficacy was assayed on luciferase-expressing cells and the structure of the siRNA vector in freeze-dried and tablet forms was examined using small-angle X-ray scattering (SAXS) synchrotron radiation. The freeze-dried powders were then mixed with excipients necessary for the good progress of the compression by allowing for a regular supply of the matrix and the reduction of friction. The compression was carried out using a rotary press simulator that allows for complete monitoring of the compression conditions. After compression, formulated siRNAs retained more than 60% of their gene-silencing efficacy. Within the tablets, a specific SAXS signal was detectable and the lamellar and cubic phases of the initial liquid suspension were restored after resuspension of siRNA vectors by disintegration of the tablets. These results show that the bilayer lipid structures of the particles were preserved despite the mechanical constraints imposed by the compression. If such a result could be expected after the freeze-drying step, it was never shown, to our knowledge, that siRNA-delivery systems could retain their efficacy and structure after mechanical stress such as compression. This opens promising perspectives to oral administration of siRNA as an alternative to parenteral administration.

Modifying internal organization and surface morphology of siRNA lipoplexes by sodium alginate addition for efficient siRNA delivery

Vectorized small interfering RNAs (siRNAs) are widely used to induce specific mRNA degradation in the intracellular compartment of eukaryotic cells. Recently, we developed efficient cationic lipid-based siRNA vectors (siRNA lipoplexes or siLex) containing sodium alginate (Nalg-siLex) with superior efficiency and stability properties than siLex. In this study, we assessed the physicochemical and some biological properties of Nalg-siLex compared to siLex. While no significant differences in size, ζ potential and siRNA compaction were detected, the addition of sodium alginate modified the particle morphology, producing smoother and heterogeneous particles characterized by transmission electron microscopy. We also noted that Nalg-siLex have surface differences observed by X-ray photoelectron spectroscopy. These differences could arise from an internal reorganization of components induced by the addition of sodium alginate, that is indicated by Small-Angle X-ray Scattering results. Moreover, Nalg-siLex did not trigger significant hepatotoxicity nor inflammatory cytokine secretion compared to siLex. Taken together these results suggest that sodium alginate played a key role by structuring and reinforcing siRNA lipoplexes, leading to more stable and efficient delivery vector.

Cationic lipids as one-component vaccine adjuvants: A promising alternative to alum

Effective vaccine formulations consist of several components: an antigen carrier, the antigen, a stimulator of cellular immunity such as a Toll-like Receptors (TLRs) ligand, and a stimulator of humoral response such as an inflammasome activator. Here, we investigated the immunostimulatory and adjuvant properties of lipopolyamines, cationic lipids used as gene carriers. We identified new lipopolyamines able to activate both TLR2 and TLR4 and showed that lipopolyamines interact with TLRs via a mechanism different from the one used by bacterial ligands, activating a strong type-I IFN response, pro-inflammatory cytokines and IL-1β secretion. The TLR and inflammasome stimulations, together with the antigen carrier properties of lipopolyamines, resulted in both humoral and cellular immunity in mice vaccinated against OVA and make lipopolyamines promising one-component vaccine adjuvants.

Genetic pharmacology: progresses in siRNA delivery and therapeutic applications

In the RNA interference process, the catalytic degradation of an endogenous mRNA results from the Watson-Crick complementary recognition by either a small silencing synthetic double-stranded ribonucleotide (siRNA) or by a small hairpin RNA (shRNA) produced in the cell by transcription from a DNA template. This interference process ideally results in an exquisitely specific mRNA suppression. The present review is dedicated to siRNAs. It describes the mechanism of RNA silencing and the main siRNA delivery techniques, with a focus on siRNA self-complexing to cationic lipids to form nanoparticles, which are called lipoplexes. The addition to lipoplexes of an anionic polymer leads to the ternary formulation APIRL (Anionic-Polymer-Interfering-RNA-Lipoplexes) with increased in vivo stability and biological efficacy. In terms of clinical development, the review focuses on therapeutic applications by intravenous delivery to the liver and inflammatory joints, and to localized siRNA delivery to the ocular sphere.

Toll-like receptor 2 promiscuity is responsible for the immunostimulatory activity of nucleic acid nanocarriers

Lipopolyamines (LPAs) are cationic lipids; they interact spontaneously with nucleic acids to form lipoplexes used for gene delivery. The main hurdle to using lipoplexes in gene therapy lies in their immunostimulatory properties, so far attributed to the nucleic acid cargo, while cationic lipids were considered as inert to the immune system. Here we demonstrate for the first time that di-C18 LPAs trigger pro-inflammatory responses through Toll-like receptor 2 (TLR2) activation, and this whether they are bound to nucleic acids or not. Molecular docking experiments suggest potential TLR2 binding modes reminiscent of bacterial lipopeptide sensing. The di-C18 LPAs share the ability of burying their lipid chains in the hydrophobic cavity of TLR2 and, in some cases, TLR1, at the vicinity of the dimerization interface; the cationic headgroups form multiple hydrogen bonds, thus crosslinking TLRs into functional complexes. Unravelling the molecular basis of TLR1 and TLR6-driven heterodimerization upon LPA binding underlines the highly collaborative and promiscuous ligand binding mechanism. The prevalence of non-specific main chain-mediated interactions demonstrates that potentially any saturated LPA currently used or proposed as transfection agent is likely to activate TLR2 during transfection. Hence our study emphasizes the urgent need to test the inflammatory properties of transfection agents and proposes the use of docking analysis as a preliminary screening tool for the synthesis of new non-immunostimulatory nanocarriers.

SLAP displays tumour suppressor functions in colorectal cancer via destabilization of the SRC substrate EPHA2

The adaptor SLAP is a negative regulator of receptor signalling in immune cells but its role in human cancer is ill defined. Here we report that SLAP is abundantly expressed in healthy epithelial intestine but strongly downregulated in 50% of colorectal cancer. SLAP overexpression suppresses cell tumorigenicity and invasiveness while SLAP silencing enhances these transforming properties. Mechanistically, SLAP controls SRC/EPHA2/AKT signalling via destabilization of the SRC substrate and receptor tyrosine kinase EPHA2. This activity is independent from CBL but requires SLAP SH3 interaction with the ubiquitination factor UBE4A and SLAP SH2 interaction with pTyr594-EPHA2. SRC phosphorylates EPHA2 on Tyr594, thus creating a feedback loop that promotes EPHA2 destruction and thereby self-regulates its transforming potential. SLAP silencing enhances SRC oncogenicity and sensitizes colorectal tumour cells to SRC inhibitors. Collectively, these data establish a tumour-suppressive role for SLAP in colorectal cancer and a mechanism of SRC oncogenic induction through stabilization of its cognate substrates.

Lipoplexes Strengthened by Anionic Polymers: Easy Preparation of Highly Effective siRNA Vectors Based on Cationic Lipids and Anionic Polymers

RNA interference is an invaluable tool in biology to specifically silence a given gene. Synthetic duplexes of RNA oligonucleotides are widely used to induce mRNA degradation in cultured cells or in whole organisms. They have to be vectorized to reach their target site. Here, we describe the preparation of highly efficient siRNA vectors based on cationic liposomes and polyanionic polymers and their application in cultured cells to silence reporter and/or endogenous genes.

Inhibition of replication of hepatitis B virus in transgenic mice following administration of hepatotropic lipoplexes containing guanidinopropyl-modified siRNAs

Chronic infection with hepatitis B virus (HBV) occurs commonly and complications that arise from persistence of the virus are associated with high mortality. Available licensed drugs have modest curative efficacy and advancing new therapeutic strategies to eliminate the virus is therefore a priority. HBV is susceptible to inactivation by exogenous gene silencers that harness RNA interference (RNAi) and the approach has therapeutic potential. To advance RNAi-based treatment for HBV infection, use in vivo of hepatotropic lipoplexes containing siRNAs with guanidinopropyl (GP) modifications is reported here. Lipoplexes contained polyglutamate, which has previously been shown to facilitate formulation and improve efficiency of the non-viral vectors. GP moieties were included in a previously described anti-HBV siRNA that effectively targeted the conserved viral X sequence. Particles had physical properties that were suitable for use in vivo: average diameter was approximately 50-200 nm and surface charge (zeta potential) was +65 mV. Efficient hepatotropic delivery of labeled siRNA was observed following systemic intravenous injection of the particles into HBV transgenic mice. Good inhibition of markers of viral replication was observed without evidence of toxicity. Efficacy of the GP-modified siRNAs was significantly more durable and formulations made up with chemically modified siRNAs were less immunostimulatory. An RNAi-mediated mechanism was confirmed by demonstrating that HBV mRNA cleavage occurred in vivo at the intended target site. Collectively these data indicate that GP-modified siRNAs formulated in anionic polymer-containing lipoplexes are effective silencers of HBV replication in vivo and have therapeutic potential.

Inhibition of osteolysis and increase of bone formation after local administration of siRNA-targeting RANK in a polyethylene particle-induced osteolysis model

Receptor activator of nuclear factor kappa-B (RANK) and RANK-ligand are relevant targets for the treatment of polyethylene particle-induced osteolysis. This study assessed the local administration of siRNA, targeting both human RANK and mouse Rank transcripts in a mouse model. Four groups of mice were implanted with polyethylene (PE) particles in the calvaria and treated locally with 2.5, 5 and 10 μg of RANK siRNA or a control siRNA delivered by the cationic liposome DMAPAP/DOPE. The tissues were harvested at day 9 after surgery and evaluated by micro-computed tomography, tartrate-resistant acid phosphatase (TRAP) immunohistochemistry for macrophages and osteoblasts, and gene relative expression of inflammatory and osteolytic markers. 10 μg of RANK siRNA exerted a protective effect against PE particle-induced osteolysis, decreasing the bone loss and the osteoclastogenesis, demonstrated by the significant increase in the bone volume (P<0.001) and by the reduction in both the number of TRAP(+) cells and osteoclast activity (P<0.01). A bone anabolic effect demonstrated by the formation of new trabecular bone was confirmed by the increased immunopositive staining for osteoblast-specific proteins. In addition, 5 and 10 μg of RANK siRNA downregulated the expression of pro-inflammatory cytokines (P<0.01) without depletion of macrophages. Our findings show that RANK siRNA delivered locally by a synthetic vector may be an effective approach for reducing osteolysis and may even stimulate bone formation in aseptic loosening of prosthetic implants.

Dimethylaminoethyl methacrylate copolymer-siRNA nanoparticles for silencing a therapeutically relevant gene in macrophages

DMC nanoparticles target Bfl1/A1 gene in lung macrophages and effective silencing of Bfl1/A1 gene by DMC nanoparticles paves the way for research on alternative treatment strategies for tuberculosis.

Enhanced uptake and siRNA-mediated knockdown of a biologically relevant gene using cyclodextrin polyrotaxane

Cellular investigations confirm the ability of cyclodextrin polyrotaxane nanoplexes to deliver siRNA for down-regulating genes relevant to the pathogenesis of tuberculosis.

Development of dual-activity vectors by co-envelopment of adenovirus and SiRNA in artificial lipid bilayers

Gene therapy with human adenovirus type 5 (Ad5) has been extensively explored for the treatment of diseases resistant to traditional therapies. Intravenous administration leads to rapid clearance from blood circulation and high liver accumulation, which restrict the use of Ad-based vectors in clinical gene therapy protocols that involve systemic administration. We have previously proposed that such limitations can be improved by engineering artificial lipid envelopes around Ad and designed a variety of artificial lipid bilayer envelopes around the viral capsid. In this study, we sought to explore further opportunities that the artificially enveloped virus constructs could offer, by designing a previously unreported gene therapy vector by simultaneous envelopment of Ad and siRNA within the same lipid bilayer. Such a dual-activity vector can offer efficacious therapy for different genetic disorders where both turning on and switching off genes would be needed. Dynamic light scattering, transmission electron microscopy and atomic force microscopy were used to characterize these vectors. Agarose gel electrophoresis, Ribo green and dot blot assays showed that siRNA and Ad virions can be enveloped together within lipid bilayers at high envelopment efficiency. Cellular uptake and in vitro transfection experiments were carried out to show the feasibility of combining siRNA-mediated gene silencing with viral gene transfer using these newly designed dual-activity vectors.

Nonionic surfactant vesicles for delivery of RNAi therapeutics

RNAi is a promising potential therapeutic approach for many diseases. A major barrier to its clinical translation is the lack of efficient delivery systems for siRNA. Among nonviral vectors, nonionic surfactant vesicles (niosomes) have shown a great deal of promise in terms of their efficacy and toxicity profiles. Nonionic surfactants have been shown to be a superior alternative to phospholipids in several studies. There is a large selection of surfactants with various properties that have been incorporated into niosomes. Therefore, there is great potential for innovation in terms of nisome composition. This article summarizes recent advancements in niosome technology for the delivery of siRNA.

Targeting monocytes/macrophages in the treatment of rheumatoid arthritis

Biotherapies have revolutionized the treatment of RA. However, much work is needed to understand all the mechanisms of these biotherapies, and alternatives are needed to circumvent adverse effects and the high cost of these long-lasting treatments. In this article we outline some of the approaches we have used to target monocytes/macrophages as major components of inflammation and bone homeostasis. We also discuss how anti-TNF-α antibodies target monocytes/macrophages in the complex mechanisms contributing to inhibition of inflammation.

Reduced in vitro and in vivo toxicity of siRNA-lipoplexes with addition of polyglutamate

We previously designed a new siRNA vector that efficiently silences genes in vitro and in vivo. The vector originality is based on the fact that, in addition to the siRNA molecule, it contains two components: 1) a cationic liposome that auto-associates with the siRNA to form particles called "lipoplexes" and, 2) an anionic polymer which enhances the lipoplex's efficiency. This anionic polymer can be a nucleic acid, a polypeptide or a polysaccharide. We show here how the nature of the added anionic polymer into our siRNA delivery system impacts the toxic effects induced by siRNA lipoplexes. We first observed that: (i) siRNA lipoplexes-induced toxicity was cell line dependent, tumoral cell lines being the more sensitive; and (ii) plasmid DNA-containing siRNA lipoplexes were more toxic than polyglutamate-containing ones or cationic liposomes. We next determined that the toxicity induced by plasmid-containing lipoplexes is a long-lasting effect that decreased cell survival capacity for several generations. We also found that treated cells underwent death following apoptosis pathway. Systemic injection to mice of siRNA lipoplexes, rather than of cationic liposome, triggered a production of several cytokines in mice and replacement of plasmid by polyglutamate reduced the elevation of all assayed cytokines. In order to enhance siRNA lipoplexes efficiency, the addition of polyglutamate as anionic polymer should be preferred to plasmid DNA as far as in vitro as well as in vivo toxicity is concerned.

Essential requirement for β-arrestin2 in mouse intestinal tumors with elevated Wnt signaling

β-Arrestins (Arrb) participate in the regulation of multiple signaling pathways, including Wnt/β-catenin, the major actor in human colorectal cancer initiation. To better understand the roles of Arrb in intestinal tumorigenesis, a reverse genetic approach (Arrb(-/-)) and in vivo siRNA treatment were used in Apc(Δ14/+) mice. Mice with Arrb2 depletion (knockout and siRNA) developed only 33% of the tumors detected in their Arrb2-WT littermates, whereas Arrb1 depletion remained without significant effect. These remaining tumors grow normally and are essentially Arrb2-independent. Unsupervised hierarchical clustering analysis showed that they clustered with 25% of Apc(Δ14/+);Arrb2(+/+) tumors. Genes overexpressed in this subset reflect a high interaction with the immune system, whereas those overexpressed in Arrb2-dependent tumors are predominantly involved in Wnt signaling, cell adhesion, migration, and extracellular matrix remodeling. The involvement of Arrb2 in intestinal tumor development via the regulation of the Wnt pathway is supported by ex vivo and in vitro experiments using either tumors from Apc(Δ14/+) mice or murine Apc(Min/+) cells. Indeed, Arrb2 siRNAs decreased the expression of Wnt target genes in cells isolated from 12 of 18 tumors from Apc(Δ14/+) mice. In Apc(Min/+) cells, Arrb2 siRNAs completely reversed the increased Wnt activity and colony formation in soft agar induced by Apc siRNA treatment, whereas they did not affect these parameters in basal conditions or in cells expressing constitutively active β-catenin. We demonstrate that Arrb2 is essential for the initiation and growth of intestinal tumors displaying elevated Wnt pathway activity and identify a previously unsuspected molecular heterogeneity among tumors induced by truncating Apc mutations.

Therapeutic plasmid DNA versus siRNA delivery: common and different tasks for synthetic carriers

Gene therapy offers great opportunities for the treatment of severe diseases including cancer. In recent years the design of synthetic carriers for nucleic acid delivery has become a research field of increasing interest. Studies on the delivery of plasmid DNA (pDNA) have brought up a variety of gene delivery vehicles. The more recently emerged gene silencing strategy by the intracellular delivery of small interfering RNA (siRNA) takes benefit from existing expertise in pDNA transfer. Despite common properties however, delivery of siRNA also faces distinct challenges due to apparent differences in size, stability of the formed nucleic acid complexes, the location and mechanism of action. This review emphasizes the common aspects and main differences between pDNA and siRNA delivery, taking into consideration a wide spectrum of polymer-based, lipidic and peptide carriers. Challenges and opportunities which result from these differences as well as the recent progress made in the optimization of carrier design are presented.

Lipothioureas as Lipids for Gene Transfection: A Review

Non-viral gene therapy requires innovative strategies to achieve higher transfection efficacy. A few years ago, our group proposed bioinspired lipids whose interaction with DNA was not based on ionic interactions, but on hydrogen bonds. We thus developed lipids bearing a thiourea head which allowed an interaction with DNA phosphates through hydrogen bonds. After a proof of concept with a lipid bearing three thiourea functions, a molecular and cellular screening was performed by varying all parts of the lipids: the hydrophobic anchor, the spacer, the linker, and the thiourea head. Two lipothiourea-based structures were identified as highly efficient in vitro transfecting agents. The lipothioureas were shown to reduce non specific interactions with cell membranes and deliver their DNA content intracellularly more efficiently, as compared to cationic lipoplexes. These lipids could deliver siRNA efficiently and allowed specific cell targeting in vitro. In vivo, thiourea lipoplexes presented a longer retention time in the blood and less accumulation in the lungs after an intravenous injection in mice. They also induced luciferase gene expression in muscle and tumor after local administration in mice. Therefore, these novel lipoplexes represent an excellent alternative to cationic lipoplexes as transfecting agents. In this review we will focus on the structure activity studies that permitted the identification of the two most efficient thiourea lipids.

Using drug-excipient interactions for siRNA delivery

SiRNA is the trigger of RNA interference, a mechanism discovered in the late 1990s. To release the therapeutic potential of this versatile but large and fragile molecule, excipients are used which either interact by electrostatic interaction, passively encapsulate siRNA or are covalently attached to enable specific and safe delivery of the drug substance. Controlling the delicate balance between protective complexation and release of siRNA at the right point and time is done by understanding excipients–siRNA interactions. These can be lipids, polymers such as PEI, PLGA, Chitosans, Cyclodextrins, as well as aptamers and peptides. This review describes the mechanisms of interaction of the most commonly used siRNA delivery vehicles, and looks at the results of their clinical and preclinical studies.

Anionic polymers for decreased toxicity and enhanced in vivo delivery of siRNA complexed with cationic liposomes

We recently reported a cationic lipid-based vector of siRNA, termed siRNA lipoplex that was very efficient in specific gene silencing, both in cell culture and in mouse disease models. To be more efficient, this vector included the addition of a plasmid DNA as an anionic "cargo." Although this plasmid DNA was devoid of any eukaryotic expression cassette, we decided to replace it by an anionic polymer that would be more acceptable for clinical applications. We identified seven anionic polymers, regarded as non-toxic, biodegradable, of various characteristics and nature. The addition of polymers to siRNA lipoplexes led to the formation of particles with similar characteristics to crude siRNA lipoplexes, decreased cellular toxicity and variable in vitro gene silencing efficiency depending on the type of polymer used. Upon i.v. injection in mice, siRNA lipoplexes prepared with the best polymer, polyglutamate, led to significantly increased recovery of siRNA in liver and lung compared with lipoplexes without polymer.

Optimization of poly(amido amine)s as vectors for siRNA delivery

By Michael addition polymerization of N,N'-cystaminebisacrylamide (CBA) with variable ratios of 4-amino-1-butanol (ABOL) and ethylene diamine (EDA) or triethylenetetramine (TETA), poly(amido amine) copolymers could be obtained with tunable charge densities. The copolymers were optimized to serve as nonviral vectors in RNA interference (RNAi) to form stable, nanosized polyplexes with siRNA with maximum transfection efficacy. It was observed that at least 20-30% EDA or TETA amino units in the copolymers is necessary to encapsulate siRNA into small and stable polyplexes (< 200 nm). Incorporation of higher amounts of EDA or TETA in the copolymers did not further improve polyplex formation and stability, but the increased cationic charge in these copolymers resulted in increased cytotoxicity and hemolytic activity. Copolymers with 20% EDA showed excellent gene silencing properties in vitro (70% luciferase knockdown in H1299 cells) with negligible cytotoxicity.

In vivo RNAi-mediated silencing of TAK1 decreases inflammatory Th1 and Th17 cells through targeting of myeloid cells

Cells from the mononuclear phagocyte system (MPS) act as systemic and local amplifiers that contribute to the progression of chronic inflammatory disorders. Transforming growth factor-β–activated kinase 1 (TAK1) is a pivotal upstream mitogen-activated protein kinase-kinase-kinase acting as a mediator of cytokine expression. It remains critical to determine in vivo the implication of TAK1 in controlling the innate immune system. Here, we describe a vehicle tailored to selectively deliver siRNAs into MPS cells after intravenous administration, and validate in vivo the potential of the RNAi-mediated TAK1 knock down for immunomodulation. In a mouse model of immune-mediated inflammatory disorder, we show that anti-TAK1 siRNA lipoplexes efficiently alleviate inflammation, severely impair the downstream c-Jun N-terminal kinase and nuclear factor-κB signaling pathways, and decrease the expression of proinflammatory mediators. Importantly, the systemic TAK1 gene silencing decreases the frequency of Th1 and Th17 cells, both mediating autoimmunity in experimental arthritis, demonstrating the immunomodulatory potential of TAK1. Finally, in vitro inhibition of TAK1 in myeloid cells decreases interferon-γ–producing T cells, suggesting that a delivery sys-tem able to target MPS cells and to silence TAK1 impacts on pathogenic T effector cells in autoimmunity.

Design and evaluation of histidine-rich amphipathic peptides for siRNA delivery

PURPOSE

Short linear peptides have a high potential for delivering various drugs with therapeutic potential, including nucleic acids. Recently, we have shown that the cationic amphipathic histidine-rich peptide LAH4 (KKALLALALHHLAHLALHLALALKKA) possesses high plasmid DNA delivery capacities. Since such peptides are thought to efficiently disrupt endosomal membranes, we have tested their ability to deliver small interfering RNA (siRNA) into mammalian cells.

METHODS

Using a human cell line stably transfected with a luciferase-encoding expression vector, we have evaluated the ability of LAH4 and five derivatives thereof to deliver siRNAs and silence gene expression.

RESULTS

The six peptides are all efficient siRNA delivery vehicles whose efficiency in mediating gene silencing in 911-Luc cells was greater than that of commercially available compounds including Lipofectamine, DOTAP and polyethylenimine. In addition, by using the proton pump inhibitor bafilomycin A1, we show that efficient siRNA delivery to the cytosol requires acidification of the endosomes.

CONCLUSIONS

The LAH4 histidine-rich cationic amphipathic peptides represent an interesting and promising family of compounds for siRNA delivery.