Full deacylation of polyethylenimine dramatically boosts its gene delivery efficiency and specificity to mouse lung

Chimeric capsid protein as a nanocarrier for siRNA delivery: stability and cellular uptake of encapsulated siRNA

For the efficient cytoplasmic delivery of siRNA, we designed a chimeric capsid protein composed of a capsid shell, integrin targeting peptide, and p19 RNA binding protein. This recombinant protein assembled into a macromolecular container-like structure with capsid shell and provided a nanocarrier for siRNA delivery. Our capsid nanocarriers had dual affinity both for siRNA within the interior and integin receptors on the exterior, and the capsid shell structure allowed the encapsulated siRNAs to be protected from the external nucleases, leading to the enhanced stability of siRNA in serum conditions. The capsid nanocarriers could complex with siRNA in a size-dependent and sequence-independent manner and showed the pH-dependent complexing/dissocation behaviors with siRNA. Moreover, RGD peptides on the exterior surface of the capsid shell enabled the capsid nanocarriers to deliver siRNA into the cytosol of the target cells. Here, we demonstrated the superior efficiency of our siRNA/capsid nanocarrier complexes in RFP gene silencing, compared to untreated cells. These results provide an alternative approach to enhancing the stability of siRNA as well as to achieving targeted siRNA delivery.

Strategies and advances in nanomedicine for targeted siRNA delivery

siRNA are a rapidly emerging class of new therapeutic molecules for the treatment of inherited and acquired diseases. However, poor cellular uptake and instability in physiological conditions limits its therapeutic potential, hence a need to develop a delivery system that can protect and efficiently transport siRNA to the target cells has arisen. Nanoparticles have been proposed as suitable delivery vectors with reduced cytotoxicity and enhanced efficacy. These delivery vectors form condensed complexes with siRNA which, in turn, provides protection to siRNA against enzymatic degradation and further leads to tissue and cellular targeting. Nanoparticles derived from polymers, such as chitosan and polyethylenimine have found numerous applications owing to ease of manipulation, high stability, low cost and high gene carrying capability. This article focuses on various aspects of nanomedicine based siRNA delivery with emphasis on targeted delivery to tumors.

Elucidating the interplay between DNA-condensing and free polycations in gene transfection through a mechanistic study of linear and branched PEI

In the present study we compare LPEI and BPEI characteristics related to DNA condensation and their role as free polycation chains in gene transfection. Using radioactive (32)P labeled DNA, we investigated the effect of free PEI chains on the cellular uptake of polyplexes. Our investigations show different properties of BPEI and LPEI polyplexes in condensation and de-condensation processes as well as in cellular uptake, which was tightly correlated with transfection efficiency. In agreement with earlier reports we find all DNA to be condensed at N/P = 3. Further added PEI chains remain free in solution. We found that both the cellular uptake and gene transfection of BPEI polyplexes is much more efficient than LPEI polyplexes at a low N/P ratio of 3 (i.e., without free PEI chains). When N/P is high (10, with 7 portions of free PEI), the LPEI and BPEI polyplexes have similar transfection efficiency even though the cellular uptake of the LPEI polyplexes is significantly lower. In addition, we found that addition of free short or long PEI chains (2.5 and 25 kDa) leads to a comparable gene transfection efficiency.

One-step photochemical synthesis of permanent, nonleaching, ultrathin antimicrobial coatings for textiles and plastics

Antimicrobial copolymers of hydrophobic N-alkyl and benzophenone containing polyethylenimines were synthesized from commercially available linear poly(2-ethyl-2-oxazoline), and covalently attached to surfaces of synthetic polymers, cotton, and modified silicon oxide using mild photo-cross-linking. Specifically, these polymers were applied to polypropylene, poly(vinyl chloride), polyethylene, cotton, and alkyl-coated oxide surfaces using solution casting or spray coating and then covalently cross-linked rendering permanent, nonleaching antimicrobial surfaces. The photochemical grafting of pendant benzophenones allows immobilization to any surface that contains a C-H bond. Incubating the modified materials with either Staphylococcus aureus or Escherichia coli demonstrated that the modified surfaces had substantial antimicrobial capacity against both Gram-positive and Gram-negative bacteria (>98% microbial death).

Association between adherens junctions and tight junctions via Rap1 promotes barrier protective effects of oxidized phospholipids

Previous studies showed that cyclopenthenone-containing products resulting from oxidation of a natural phospholipid, 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (OxPAPC) exhibit potent barrier-protective effects in the in vitro and in vivo models of lung endothelial cell (EC) barrier dysfunction, and these effects are associated with enhancement of peripheral actin cytoskeleton, cell-cell and cell-substrate contacts driven by activation of Rac and Cdc42 GTPases. Rap1 GTPase is another member of small GTPase family involved in control of cell-cell interactions; however, its involvement in EC barrier-protective effects by OxPAPC remains unknown. This study examined a role of Rap1 in regulation of OxPAPC-induced interactions in adherens junctions (AJ) and tight junctions (TJ) as a novel mechanism of EC barrier preservation in vitro and in vivo. Immunofluorescence analysis, subcellular fractionation, and co-immunoprecipitation assays indicate that OxPAPC promoted accumulation of AJ proteins: VE-cadherin, p120-catenin, and β-catenin; and TJ proteins: ZO-1, occludin, and JAM-A in the cell membrane, and induced novel cross-interactions between AJ and TJ protein complexes, that were dependent on OxPAPC-induced Rap1 activation. Inhibition of Rap1 function suppressed OxPAPC-mediated pulmonary EC barrier enhancement and AJ and TJ interactions in vitro, as well as inhibited protective effects of OxPAPC against ventilator-induced lung injury in vivo. These results show for the first time a role of Rap1-mediated association between adherens junctions and tight junction complexes in the OxPAPC-induced pulmonary vascular EC barrier protection.

Application of magnetic nanoparticles to gene delivery

Nanoparticle technology is being incorporated into many areas of molecular science and biomedicine. Because nanoparticles are small enough to enter almost all areas of the body, including the circulatory system and cells, they have been and continue to be exploited for basic biomedical research as well as clinical diagnostic and therapeutic applications. For example, nanoparticles hold great promise for enabling gene therapy to reach its full potential by facilitating targeted delivery of DNA into tissues and cells. Substantial progress has been made in binding DNA to nanoparticles and controlling the behavior of these complexes. In this article, we review research on binding DNAs to nanoparticles as well as our latest study on non-viral gene delivery using polyethylenimine-coated magnetic nanoparticles.

Comparisons of three polyethyleneimine-derived nanoparticles as a gene therapy delivery system for renal cell carcinoma

Background

Polyethyleneimine (PEI), which can interact with negatively charged DNA through electrostatic interaction to form nanocomplexes, has been widely attempted to use as a gene delivery system. However, PEI has some defects that are not fit for keeping on gene expression. Therefore, some modifications against PEI properties have been done to improve their application value in gene delivery. In this study, three modified PEI derivatives, including poly(ε-caprolactone)-pluronic-poly(ε-caprolactone) grafted PEI (PCFC-g-PEI), folic acid-PCFC-isophorone diidocyanate-PEI (FA-PEAs) and heparin-PEI (HPEI), were evaluated in terms of their cytotoxicity and transfection efficiency in vitro and in vivo in order to ascertain their potential application in gene therapy.

Methods

MTT assay and a marker GFP gene, encoding green fluorescent protein, were used to evaluate cell toxicity and transfection activity of the three modified PEI in vitro. Renal cell carcinoma (RCC) models were established in BALB/c nude mice inoculated with OS-RC-2 cells to detect the gene therapy effects using the three PEI-derived nanoparticles as gene delivery vehicles. The expression status of a target gene Von Hippel-Lindau (VHL) in treated tumor tissues was analyzed by semiquantitative RT-PCR and immunohistochemistry.

Results

Each of three modified PEI-derived biomaterials had an increased transfection efficiency and a lower cytotoxicity compared with its precursor PEI with 25-kD or 2-kD molecule weight in vitro. And the mean tumor volume was obviously decreased 30% by using FA-PEAs to transfer VHL plasmids to treat mice RCC models. The VHL gene expression was greatly improved in the VHL-treated group. While there was no obvious tumor inhibition treated by PCFC-g-PEI:VHL and HPEI:VHL complexes.

Conclusions

The three modified PEI-derived biomaterials, including PCFC-g-PEI, FA-PEAs and HPEI, had an increased transfection efficiency in vitro and obviously lower toxicities compared with their precursor PEI molecules. The FA-PEAs probably provide a potential gene delivery system to treat RCC even other cancers in future.

Bioanalysis of siRNA and oligonucleotide therapeutics in biological fluids and tissues

This article summarizes bioanalytical avenues for the determination of siRNA and oligonucleotide therapeutics, with an emphasis on hybridization methods. Aspects of the chemistry and delivery of investigational oligonucleotide therapeutics are considered. The nature of the oligonucleotide under investigation will dictate the best analytical course of action; each method has its advantages and disadvantages, depending upon the oligonucleotide test article and the anticipated toxicokinetic and pharmacokinetic study parameters. Stringent method development and specific validation criteria are essential to attain the best quality results in support of a regulatory filing.

Highly effective gene transfection in vivo by alkylated polyethylenimine

We mechanistically explored the effect of increased hydrophobicity of the polycation on the efficacy and specificity of gene delivery in mice. N-Alkylated linear PEIs with varying alkyl chain lengths and extent of substitution were synthesized and characterized by biophysical methods. Their in vivo transfection efficiency, specificity, and biodistribution were investigated. N-Ethylation improves the in vivo efficacy of gene expression in the mouse lung 26-fold relative to the parent polycation and more than quadruples the ratio of expression in the lung to that in all other organs. N-Propyl-PEI was the best performer in the liver and heart (581- and 3.5-fold enhancements, resp.) while N-octyl-PEI improved expression in the kidneys over the parent polymer 221-fold. As these enhancements in gene expression occur without changing the plasmid biodistribution, alkylation does not alter the cellular uptake but rather enhances transfection subsequent to cellular uptake.

Ciliary transition zone activation of phosphorylated Tctex-1 controls ciliary resorption, S-phase entry and fate of neural progenitors

Primary cilia are displayed during the G₀/G₁ phase of many cell types. Cilia are reabsorbed as cells prepare to re-enter the cell cycle, but the causal and molecular link between these two cellular events remains unclear. We show that phospho(T94)Tctex-1 is recruited to ciliary transition zones prior to S-phase entry and plays a pivotal role in both ciliary disassembly and cell cycle progression. Tctex-1’s role in S-phase entry, however, is dispensable in non-ciliated cells. Exogenously added phosphomimic Tctex-1 T94E accelerates cilium disassembly and S-phase entry. These results support a model in which the cilia act as a brake to prevent cell cycle progression. Mechanistic studies show the involvement of actin dynamics in Tctex-1 regulated cilium resorption. Phospho(T94)Tctex-1 is also selectively enriched at the ciliary transition zones of cortical neural progenitors, and plays a key role in controlling G₁ length, cell cycle entry, and fate determination of these cells during corticogenesis.

A Biocompatible Arginine-based Polycation

Self assembly between cations and anions is ubiquitous throughout nature. Important biological structures such as chromatin often use polyvalent assembly between a polycation and a polyaninon. Biomedical importance of synthetic polycations arises from their affinity to polyanions such as nucleic acid and heparan sulfate. However, the limited biocompatibility of synthetic polycations hampers the realization of their immense potential. By examining biocompatible cationic peptides, we hypothesize that a biocompatible polycation should be biodegradable and made from endogenous cations. We designed an arginine-based biodegradable polycation and demonstrated that it was orders of magnitude more compatible than conventional polycations in vitro and in vivo. This biocompatibility diminishes when L-arginine is substituted with D-arginine or when the biodegradable ester linker changes to a biostable ether linker. We believe this design can lead to many biocompatible polycations that can significantly advance a wide range of applications including controlled release, tissue engineering, biosensing, and medical devices.

Polymer-related off-target effects in non-viral siRNA delivery

Since off-target effects in non-viral siRNA delivery are quite common but not well understood, in this study various polymer-related effects observed in transfection studies were described and their mechanisms of toxicity were investigated. A variety of stably luciferase-expressing cell lines was compared concerning polymer-mediated effects after transfection with polyplexes of siRNA and poly(ethylene imine) (PEI) or poly(ethylene glycol)-grafted PEI (PEG-PEI). Cell viability, LDH release, gene expression profiles of apoptosis-related genes and promoter activation were investigated. Interestingly, PEG-PEI, which is generally better tolerated than PEI, was found to activate apoptosis in a cell line- and concentration-dependent manner. While both polymers showed sigmoidal dose-response of cell viability in L929 cells (IC(50)(PEI) = 6 μg/ml, IC(50)(PEG-PEI) = 11 μg/ml), H1299/Luc cells exhibited biphasic dose-response for PEG-PEI and stronger apoptosis at 2 μg/ml than at 20 μg/ml PEG-PEI, as shown in TUNEL assays. Gene expression profiling confirmed that H1299/Luc cells underwent apoptosis via thousand-fold activation of TNF receptor-associated factors. Additionally, it was demonstrated that NFkB-mediated CMV promoter activation in stably transfected cells can lead to increased target gene levels after transfection instead of siRNA-mediated knockdown. With these results, polymeric vectors were shown not to be inert substances. Therefore, alterations in gene expression caused by the delivery agent must be known to correctly interpret gene-silencing experiments, to understand the mechanisms of off-target effects, and most of all to further develop vectors with reduced side effects. Taking these observations into account, one established cell line was eventually identified to be suitable for RNAi experiments. As shown by these experiments, materials that have been used for many years can elicit unexpected off-target effects. Therefore, non-viral vectors must be screened for several levels of toxicity to make them promising candidates.

Dual functional polyelectrolyte multilayer coatings for implants: permanent microbicidal base with controlled release of therapeutic agents

Here we present a new bifunctional layer-by-layer (LbL) construct made by combining a permanent microbicidal polyelectrolyte multilayered (PEM) base film with a hydrolytically degradable PEM top film that offers controlled and localized delivery of therapeutics. Two degradable film architectures are presented: (1) bolus release of an antibiotic (gentamicin) to eradicate initial infection at the implant site, or (2) sustained delivery of an anti-inflammatory drug (diclofenac) to cope with inflammation at the site of implantation due to tissue injury. Each degradable film was built on top of a permanent base film that imparts the implantable device surface with microbicidal functionality that prevents the formation of biofilms. Controlled-delivery of gentamicin was demonstrated over hours and that of diclofenac over days. Both drugs retained their efficacy upon release. The permanent microbicidal base film was biocompatible with A549 epithelial cancer cells and MC3T3-E1 osteoprogenitor cells, while also preventing bacteria attachment from turbid media for the entire duration of the two weeks studied. The microbicidal base film retains its functionality after the biodegradable films have completely degraded. The versatility of these PEM films and their ability to prevent biofilm formation make them attractive as coatings for implantable devices.

Efficient and targeted delivery of siRNA in vivo

RNA interference (RNAi) has been regarded as a revolutionary tool for manipulating target biological processes as well as an emerging and promising therapeutic strategy. In contrast to the tangible and obvious effectiveness of RNAi in vitro, silencing target gene expression in vivo using small interfering RNA (siRNA) has been a very challenging task due to multiscale barriers, including rapid excretion, low stability in blood serum, nonspecific accumulation in tissues, poor cellular uptake and inefficient intracellular release. This minireview introduces major challenges in achieving efficient siRNA delivery in vivo and discusses recent advances in overcoming them using chemically modified siRNA, viral siRNA vectors and nonviral siRNA carriers. Enhanced specificity and efficiency of RNAi in vivo via selective accumulations in desired tissues, specific binding to target cells and facilitated intracellular trafficking are also commonly attempted utilizing targeting moieties, cell-penetrating peptides, fusogenic peptides and stimuli-responsive polymers. Overall, the crucial roles of the interdisciplinary approaches to optimizing RNAi in vivo, by efficiently and specifically delivering siRNA to target tissues and cells, are highlighted.

Mechanism of inactivation of influenza viruses by immobilized hydrophobic polycations

N,N-dodecyl,methyl-polyethylenimine coatings applied to solid surfaces have been shown by us to disinfect aqueous solutions of influenza viruses. Herein we elucidate the mechanism of this phenomenon. Infectivity-, protein-, RNA-, and scanning electron microscopy-based experiments reveal that, upon contact with the hydrophobic polycationic coating, influenza viruses (including pathogenic human and avian, both wild-type and drug-resistant, strains) irreversibly adhere to it, followed by structural damage and inactivation; subsequently, viral RNA is released into solution, while proteins remain adsorbed.

Tailorable thiolated trimethyl chitosans for covalently stabilized nanoparticles

A novel four-step method is presented to synthesize partially thiolated trimethylated chitosan (TMC) with a tailorable degree of quaternization and thiolation. First, chitosan was partially N-carboxylated with glyoxylic acid and sodium borohydride. Next, the remaining amines were quantitatively dimethylated with formaldehyde and sodium borohydride and then quaternized with iodomethane in NMP. Subsequently, these partially carboxylated TMCs dissolved in water were reacted with cystamine at pH 5.5 using EDC as coupling agent. After addition of DTT and dialysis, thiolated TMCs were obtained, varying in degree of quaternization (25-54%) and degree of thiolation (5-7%), as determined with (1)H NMR and Ellman's assay. Gel permeation chromatography with light scattering detection indicated limited intermolecular cross-linking. All thiolated TMCs showed rapid oxidation to yield disulfide cross-linked TMC at pH 7.4, while the thiolated polymers were rather stable at pH 4.0. When Calu-3 cells were used, XTT and LDH cell viability tests showed a slight reduction in cytotoxicity for thiolated TMCs as compared to the nonthiolated polymers with similar DQs. Positively charged nanoparticles loaded with fluorescently labeled ovalbumin were made from thiolated TMCs and thiolated hyaluronic acid. The stability of these particles was confirmed in 0.8 M NaCl, in contrast to particles made from nonthiolated polymers that dissociated under these conditions, demonstrating that the particles were held together by intermolecular disulfide bonds.

Polyethylenimines for RNAi-mediated gene targeting in vivo and siRNA delivery to the lung

RNA interference (RNAi) is a promising strategy to inhibit the expression of pathologically relevant genes, which show aberrant (over-)expression, e.g. in tumors or other pathologies. The induction of RNAi relies on small interfering RNAs (siRNAs), which trigger the specific mRNA degradation. Their instability and poor delivery into target tissues including the lung, however, so far severely limits the therapeutic use of siRNAs and requires the development of nanoscale delivery systems. Polyethylenimines (PEIs) are synthetic polymers, which are able to form non-covalent complexes with siRNAs. These nanoscale complexes ('nanoplexes') allow the protection of siRNAs from nucleolytic degradation, their efficient cellular uptake through endocytosis and intracellular release through the 'proton sponge effect'. Chemical modifications of PEIs as well as the coupling of cell/tissue-specific ligands are promising approaches to increase the biocompatibility, specificity and efficacy of PEI-based nanoparticles. This review article gives a comprehensive overview of pre-clinical in vivo studies on the PEI-mediated delivery of therapeutic siRNAs in various animal models. It discusses the chemical properties of PEIs and PEI modifications, and their influences on siRNA knockdown efficacy, on adverse effects of the polymer or the nanoplex and on siRNA biodistribution in vivo. Beyond systemic application, PEI-based complexation allows the local siRNA application to the lung. Biodistribution studies demonstrate cellular uptake of PEI-complexed, but not of naked siRNAs in the lung with little systemic availability of the siRNAs, indicating the usefulness of this approach for the targeting of genes, which are pathologically relevant in lung tumors or lung metastases. Taken together, (i) PEI and PEI derivatives may represent an efficient delivery platform for siRNAs, (ii) siRNA-mediated induction of RNAi is a promising approach for the knockdown of pathologically relevant genes, and (iii) when sufficiently addressing biocompatibility issues, the locoregional delivery of PEI/siRNA complexes may become an attractive therapeutic strategy for the treatment of lung diseases with little systemic side effects.

Regulation of Ack1 localization and activity by the amino-terminal SAM domain

Background

The mechanisms that regulate the activity of the nonreceptor tyrosine kinase Ack1 (activated Cdc42-associated kinase) are poorly understood. The amino-terminal region of Ack1 is predicted to contain a sterile alpha motif (SAM) domain. SAM domains share a common fold and mediate protein-protein interactions in a wide variety of proteins. Here, we addressed the importance of the Ack1 SAM domain in kinase activity.

Results

We used immunofluorescence and Western blotting to show that Ack1 deletion mutants lacking the N-terminus displayed significantly reduced autophosphorylation in cells. A minimal construct comprising the N-terminus and kinase domain (NKD) was autophosphorylated, while the kinase domain alone (KD) was not. When expressed in mammalian cells, NKD localized to the plasma membrane, while KD showed a more diffuse cytosolic localization. Co-immunoprecipitation experiments showed a stronger interaction between full length Ack1 and NKD than between full length Ack1 and KD, indicating that the N-terminus was important for Ack1 dimerization. Increasing the local concentration of purified Ack1 kinase domain at the surface of lipid vesicles stimulated autophosphorylation and catalytic activity, consistent with a requirement for dimerization and trans-phosphorylation for activity.

Conclusions

Collectively, the data suggest that the N-terminus of Ack1 promotes membrane localization and dimerization to allow for autophosphorylation.

Bioresponsive small molecule polyamines as noncytotoxic alternative to polyethylenimine

Nonviral gene therapy continues to require novel synthetic vectors to deliver therapeutic nucleic acids effectively and safely. The majority of synthetic nonviral vectors employed in clinical trials to date have been cationic liposomes; however, cationic polymers are attracting increasing attention. One of the few cationic polymers to enter clinical trials has been polyethylenimine (PEI); however, doubts remain over its cytotoxicity, and in addition it displays lower levels of transfection than viral systems. Herein, we report on the development of a series of small molecule analogues of PEI that are bioresponsive to the presence of pDNA, forming poly(disulfide)s that are capable of efficacious transfection with no associated toxicity. The most effective small molecule developed, a cyclic disulfide based upon a spermine backbone, is shown to form very well-defined polyplexes (100-200 nm in diameter) that mediate murine lung transfection in vivo to within an order of magnitude of in vivo jetPEI, and at the same time display a much improved cytotoxicity profile.

On structural damage incurred by bacteria upon exposure to hydrophobic polycationic coatings

Hydrophobic polycations previously developed by us efficiently kill E. coli and Staphylococcus aureus on contact. As visualized by electron microscopy herein, these pathogenic bacteria incur marked morphological damage from the exposure to these N-alkylated-polyethylenimine "paints" which results in the leakage of an appreciable fraction of the total cellular protein. The quantity and composition of that leaked protein is similar to that released upon traditional lysozyme/EDTA treatment, thus providing insights into the mechanism of action of our microbicidal coatings.

Toll-like receptor 4 mediates lipopolysaccharide-induced muscle catabolism via coordinate activation of ubiquitin-proteasome and autophagy-lysosome pathways

Cachectic muscle wasting is a frequent complication of many inflammatory conditions, due primarily to excessive muscle catabolism. However, the pathogenesis and intervention strategies against it remain to be established. Here, we tested the hypothesis that Toll-like receptor 4 (TLR4) is a master regulator of inflammatory muscle catabolism. We demonstrate that TLR4 activation by lipopolysaccharide (LPS) induces C2C12 myotube atrophy via up-regulating autophagosome formation and the expression of ubiquitin ligase atrogin-1/MAFbx and MuRF1. TLR4-mediated activation of p38 MAPK is necessary and sufficient for the up-regulation of atrogin1/MAFbx and autophagosomes, resulting in myotube atrophy. Similarly, LPS up-regulates muscle autophagosome formation and ubiquitin ligase expression in mice. Importantly, autophagy inhibitor 3-methyladenine completely abolishes LPS-induced muscle proteolysis, while proteasome inhibitor lactacystin partially blocks it. Furthermore, TLR4 knockout or p38 MAPK inhibition abolishes LPS-induced muscle proteolysis. Thus, TLR4 mediates LPS-induced muscle catabolism via coordinate activation of the ubiquitin-proteasome and the autophagy-lysosomal pathways.

Atrial natriuretic peptide attenuates LPS-induced lung vascular leak: role of PAK1

Increased levels of atrial natriuretic peptide (ANP) in the models of sepsis, pulmonary edema, and acute respiratory distress syndrome (ARDS) suggest its potential role in the modulation of acute lung injury. We have recently described ANP-protective effects against thrombin-induced barrier dysfunction in pulmonary endothelial cells (EC). The current study examined involvement of the Rac effector p21-activated kinase (PAK1) in ANP-protective effects in the model of lung vascular permeability induced by bacterial wall LPS. C57BL/6J mice or ANP knockout mice (Nppa(-/-)) were treated with LPS (0.63 mg/kg intratracheal) with or without ANP (2 μg/kg iv). Lung injury was monitored by measurements of bronchoalveolar lavage protein content, cell count, Evans blue extravasation, and lung histology. Endothelial barrier properties were assessed by morphological analysis and measurements of transendothelial electrical resistance. ANP treatment stimulated Rac-dependent PAK1 phosphorylation, attenuated endothelial permeability caused by LPS, TNF-α, and IL-6, decreased LPS-induced cell and protein accumulation in bronchoalveolar lavage fluid, and suppressed Evans blue extravasation in the murine model of acute lung injury. More severe LPS-induced lung injury and vascular leak were observed in ANP knockout mice. In rescue experiments, ANP injection significantly reduced lung injury in Nppa(-/-) mice caused by LPS. Molecular inhibition of PAK1 suppressed the protective effects of ANP treatment against LPS-induced lung injury and endothelial barrier dysfunction. This study shows that the protective effects of ANP against LPS-induced vascular leak are mediated at least in part by PAK1-dependent signaling leading to EC barrier enhancement. Our data suggest a direct role for ANP in endothelial barrier regulation via modulation of small GTPase signaling.

Poly(I:C)-mediated tumor growth suppression in EGF-receptor overexpressing tumors using EGF-polyethylene glycol-linear polyethylenimine as carrier

PURPOSE

To develop a novel polyethylenimine (PEI)-based polymeric carrier for tumor-targeted delivery of cytotoxic double-stranded RNA polyinosinic:polycytidylic acid, poly(I:C). The novel carrier should be chemically less complex but at least as effective as a previously developed tetra-conjugate containing epidermal growth factor (EGF) as targeting ligand, polyethylene glycol (PEG) as shielding spacer, 25 kDa branched PEI as RNA binding and endosomal buffering agent, and melittin as endosomal escape agent.

METHODS

Novel conjugates were designed employing a simplified synthetic strategy based on 22 kDa linear polyethylenimine (LPEI), PEG spacers, and recombinant EGF. The efficacy of various conjugates (different PEG spacers, with and without targeting EGF) in poly(I:C)-mediated cell killing was evaluated in vitro using two human U87MG glioma cell lines. The most effective polyplex was tested for in vivo activity in A431 tumor xenografts.

RESULTS

Targeting conjugate LPEI-PEG2 kDa-EGF was found as most effective in poly(I:C)-triggered killing of tumor cells in vitro. The efficacy correlated with glioma cell EGFR levels. Repeated intravenous administration of poly(I:C) polypexes strongly retarded growth of A431 human tumor xenograft in mice.

CONCLUSIONS

The optimized LPEI-PEG2 kDa-EGF conjugate displays reduced chemical complexity and efficient poly(I:C)-mediated killing of EGFR overexpressing tumors in vitro and in vivo.

Hypo-osmotic stress enhances the uptake of polyethylenimine/oligonucleotide complexes in A549 cells via Ca(2+) mobilization from intracellular stores

To determine the mechanism of osmolarity involved in polyethylenimine (PEI)/oligonucleotide (ON) complex transfection in cells, we measured the fluorescence intensities of fluorescein isothiocyanate-labeled ONs complexed with PEI and the changes in cytosolic Ca(2+) concentration ([Ca(2+)](c)) in A549 cells, and we found that uptake of PEI/ON complexes was improved in the cells along with a rise of [Ca(2+)](c) in A549 cells challenged by 50% hypotonic medium. Further experiments showed that the enhanced uptake efficiency and the rise in [Ca(2+)](c) in A549 cells were almost completely abolished from cells loaded with the intracellular calcium chelator 1,2-bis(2-aminophenoxy)-N,N,N,N-tetraacetic acid-acetoxymethyl ester. 2-Aminoethoxydiphenyl borate or 8-(N,N-diethylamino) octyl-3,4,5-trimethoxybenzoate, two potent antagonists of inositol 1,4,5-trisphosphate-mediated Ca(2+) release that blunt [Ca(2+)](c) elevation via Ca(2+) release from endoplasmic reticulum, inhibited the enhanced uptake of PEI/ON complexes induced by Ca(2+)-free hypo-osmotic stress. In summary, the results strongly suggest that calcium-dependent transfection is responsible for the uptake of PEI/ON complexes into A549 cells under hypotonic conditions.

Potential c-myc antisense oligonucleotide carriers: PCl/PEG/PEI and PLL/PEG/PEI

In this work, positively charged, micelle-forming polymers were synthesized and used as a model vector to deliver antisense oligodeoxynucleotide (ASODN) into melanoma cells. Polymers and polymer/ASODN complexes were characterized by DLS according to size, charge, and critical micelle concentration. Nanosize and spherical complexes were observed by AFM. Complexes did not reveal significant toxicity to melanoma cells. Antiproliferative effect of the complexes was observed by immunocytochemical staining and estimated as 56.8% with N/P:9. High amount of apoptosis and very small amount of necrosis were estimated. According to the results, these positively charged polymers forming micelle-like structures seem promising as ASODN carriers.

Electrostatic surface modifications to improve gene delivery

IMPORTANCE OF THE FIELD

Gene therapy has the potential to treat a wide variety of diseases, including genetic diseases and cancer.

AREAS COVERED IN THIS REVIEW

This review introduces biomaterials used for gene delivery and then focuses on the use of electrostatic surface modifications to improve gene delivery materials. These modifications have been used to stabilize therapeutics in vivo, add cell-specific targeting ligands, and promote controlled release. Coatings of nanoparticles and microparticles as well as non-particulate surface coatings are covered in this review. Electrostatic principles are crucial for the development of multilayer delivery structures fabricated by the layer-by-layer method.

WHAT THE READER WILL GAIN

The reader will gain knowledge about the composition of biomaterials used for surface modifications and how these coatings and multilayers can be utilized to improve spatial control and efficiency of delivery. Examples are shown for the delivery of nucleic acids, including DNA and siRNA, to in vitro and in vivo systems.

TAKE HOME MESSAGE

The versatile and powerful approach of electrostatic coatings and multilayers will lead to the development of enhanced gene therapies.

RNAi-based strategies for cyclooxygenase-2 inhibition in cancer

Cyclooxygenase-2 (COX-2) enzyme has been involved in the tumorigenesis and in the progression of colorectal cancer (CRC). The use of traditional nonsteroidal anti-inflammatory drugs (NSAIDs) or selective COX-2 inhibitors has been proposed for the prevention and the treatment of this relevant neoplastic disease. In the light of an innovative alternative to these pharmacological approaches, we review here the possible strategies to achieve a strong and selective inhibition of COX-2 enzyme by using the mechanism of RNA Interference (RNAi) targeted against its mRNA. Anti-COX-2 siRNA molecules (siCOX-2) can be generated in CRC cells from short hairpin RNA (shRNA) precursors, delivered in vitro by a retroviral expression system, and induce a significant and stable silencing of overexpressed COX-2 in human colon cancer cells. As a safer alternative to viral approach, nonpathogenic bacteria (E. coli) can be engineered to invade eukaryotic cells and to generate siCOX-2 molecules in cancer cells. Moreover, the involvement of miRNAs in COX-2 posttranscriptional regulation opens up the possibility to exploit an endogenous silencing mechanism to knockdown overexpressed COX-2. Thus, these recent strategies disclose new challenging perspectives for the development of clinically compatible siRNA or miRNA capable of selectively inhibiting COX-2 enzyme.

One-pot synthesis of linear-like and photoluminescent polyethylenimines for intracellular imaging and siRNA delivery

Linear-like and photoluminescent polyethylenimines (LPEIs) were synthesized through a one-pot reaction within 5 min using synchrotron radiation for intracellular imaging and siRNA delivery.

Intracellular trafficking and unpacking of siRNA/quantum dot-PEI complexes modified with and without cell penetrating peptide: confocal and flow cytometric FRET analysis

Cationic quantum dots (QDs) were utilized to complex small interfering RNA (siRNA) for studying intracellular trafficking, unpacking, and gene silencing. Positively charged polyethylenimine (PEI) was covalently conjugated on the surface of QDs to complex with cyanine dye labeled vascular endothelial growth factor siRNA (cy5-VEGF siRNA) for the formation of nanosized polyelectrolyte complexes (PEC). Fluorescence resonance energy transfer (FRET) was achieved between cy5-VEGF siRNA and PEI conjugated QDs (QD625) in the complex. From confocal microscopic analysis, intracellular uptake and release of siRNA from the PEC were visualized as a function of incubation time. The extent of cy5-siRNA release from the PEC was quantitatively evaluated by flow cytometric analysis. In addition, PEI conjugated QDs were further modified with a protein transduction domain (PTD) from human transcriptional factor, Hph-1. The two siRNA/QD-PEI complexes with and without Hph-1 have shown markedly different intracellular uptake behaviors and unpacking kinetics of cy5-siRNA. However, they exhibited similar extent of VEGF gene knockout regardless of Hph-1, but showed much higher gene silencing efficiency than siRNA/PEI complexes. The present study demonstrates that PEI conjugated QDs can be utilized as a useful siRNA carrier to analyze intracellular trafficking and unpacking pathway as well as to effectively silence a target gene.

Engineering RNA for targeted siRNA delivery and medical application

RNA engineering for nanotechnology and medical applications is an exciting emerging research field. RNA has intrinsically defined features on the nanometre scale and is a particularly interesting candidate for such applications due to its amazing diversity, flexibility and versatility in structure and function. Specifically, the current use of siRNA to silence target genes involved in disease has generated much excitement in the scientific community. The intrinsic ability to sequence-specifically downregulate gene expression in a temporally- and spatially controlled fashion has led to heightened interest and rapid development of siRNA-based therapeutics. Although methods for gene silencing have been achieved with high efficacy and specificity in vitro, the effective delivery of nucleic acids to specific cells in vivo has been a hurdle for RNA therapeutics. This article covers different RNA-based approaches for diagnosis, prevention and treatment of human disease, with a focus on the latest developments of non-viral carriers of siRNA for delivery in vivo. The applications and challenges of siRNA therapy, as well as potential solutions to these problems, the approaches for using phi29 pRNA-based vectors as polyvalent vehicles for specific delivery of siRNA, ribozymes, drugs or other therapeutic agents to specific cells for therapy will also be addressed.

Cost-effective gene transfection by DNA compaction at pH 4.0 using acidified, long shelf-life polyethylenimine

Introduction of genetic material into cells is an essential prerequisite for current research in molecular cell biology. Although transfection with commercially available reagents results in excellent gene expression, their high costs are obstacles to experimentation with a large number or large scales of transfection. The cationic polymer linear-polyethylenimine (MW 25,000) (PEI), one of the most cost-effective vehicles, facilitates DNA compaction by polyplex formation, which leads to efficient delivery of DNA into cells by endocytosis. However, the use of PEI is still limited because of substantial cytotoxicity and intolerable deterioration in transfection efficiency by its low stability. Here, we show that acidification of PEI is important for its transfection activity. Dissolving PEI powder in 0.2N HCl confers a long shelf-life for PEI storage at 4 and -80 degrees C, and the polyplex formation of plasmid DNA with PEI is optimized in lactate-buffered saline at pH 4.0. Furthermore, changing the culture medium at 8-12 h posttransfection can minimize the cytotoxicity of PEI without sacrificing the high transfection efficiency comparable to that of commercial reagents. The cost per test using acidified PEI is drastically reduced to approximately 1:10,000, compared with commercial reagents. Thus, we conclude that acidification of PEI satisfactorily accomplishes cost-effective, high-efficiency transfection.

Cancer-associated mutations activate the nonreceptor tyrosine kinase Ack1

Ack1 is a nonreceptor tyrosine kinase that participates in tumorigenesis, cell survival, and migration. Relatively little is known about the mechanisms that regulate Ack1 activity. Recently, four somatic missense mutations of Ack1 were identified in cancer tissue samples, but the effects on Ack1 activity, and function have not been described. These mutations occur in the N-terminal region, the C-lobe of the kinase domain, and the SH3 domain. Here, we show that the cancer-associated mutations increase Ack1 autophosphorylation in mammalian cells without affecting localization and increase Ack1 activity in immune complex kinase assays. The cancer-associated mutations potentiate the ability of Ack1 to promote proliferation and migration, suggesting that point mutation is a mechanism for Ack1 deregulation. We propose that the C-terminal Mig6 homology region (MHR) (residues 802-990) participates in inhibitory intramolecular interactions. The isolated kinase domain of Ack1 interacts directly with the MHR, and the cancer-associated E346K mutation prevents binding. Likewise, mutation of a key hydrophobic residue in the MHR (Phe(820)) prevents the MHR-kinase interaction, activates Ack1, and increases cell migration. Thus, the cancer-associated mutation E346K appears to destabilize an autoinhibited conformation of Ack1, leading to constitutively high Ack1 activity.

Identification of inhibitors of Plasmodium falciparum phosphoethanolamine methyltransferase using an enzyme-coupled transmethylation assay

BACKGROUND

The phosphoethanolamine methyltransferase, PfPMT, of the human malaria parasite Plasmodium falciparum, a member of a newly identified family of phosphoethanolamine methyltransferases (PMT) found solely in some protozoa, nematodes, frogs, and plants, is involved in the synthesis of the major membrane phospholipid, phosphatidylcholine. PMT enzymes catalyze a three-step S-adenosylmethionine-dependent methylation of the nitrogen atom of phosphoethanolamine to form phosphocholine. In P. falciparum, this activity is a limiting step in the pathway of synthesis of phosphatidylcholine from serine and plays an important role in the development, replication and survival of the parasite within human red blood cells.

RESULTS

We have employed an enzyme-coupled methylation assay to screen for potential inhibitors of PfPMT. In addition to hexadecyltrimethylammonium, previously known to inhibit PfPMT, two compounds dodecyltrimethylammonium and amodiaquine were also found to inhibit PfPMT activity in vitro. Interestingly, PfPMT activity was not inhibited by the amodiaquine analog, chloroquine, or other aminoquinolines, amino alcohols, or histamine methyltransferase inhibitors. Using yeast as a surrogate system we found that unlike wild-type cells, yeast mutants that rely on PfPMT for survival were sensitive to amodiaquine, and their phosphatidylcholine biosynthesis was inhibited by this compound. Furthermore NMR titration studies to characterize the interaction between amoidaquine and PfPMT demonstrated a specific and concentration dependent binding of the compound to the enzyme.

CONCLUSION

The identification of amodiaquine as an inhibitor of PfPMT in vitro and in yeast, and the biophysical evidence for the specific interaction of the compound with the enzyme will set the stage for the development of analogs of this drug that specifically inhibit this enzyme and possibly other PMTs.

A potential therapeutic for pandemic influenza using RNA interference

RNA interference (RNAi) involves sequence-specific downregulation of target genes, leading to gene silencing in vitro and in vivo. Synthetic small interfering RNAs (siRNAs), formulated with appropriate delivery agents, can serve as effective tools for RNAi-based therapeutics. The potential of siRNA to provide antiviral activity has been studied extensively in many respiratory viruses, including influenza virus, wherein specific siRNAs target highly-conserved regions of influenza viral genome, leading to potent inhibition of viral RNA replication. Despite various delivery strategies, such as polycations and liposomes that have been employed to formulate siRNAs, effective delivery modalities are still needed. Although current strategies can provide significant biodistribution and delivery into lungs allowing gene silencing, complete protection and prolonged survival rates against multiple strains of influenza virus still remains a key challenge. Here, we describe methods and procedures pertaining to screening and selection of highly effective influenza-specific siRNAs in cell culture, in mice, and in the ferret model. This will be potentially useful to evaluate RNAi as a therapeutic modality for future clinical application.

Photochemical internalization (PCI): a technology for drug delivery

The utilization of macromolecules in therapy of cancer and other diseases is becoming increasingly relevant. Recent advances in molecular biology and biotechnology have made it possible to improve targeting and design of cytotoxic agents, DNA complexes, and other macromolecules for clinical applications. To achieve the expected biological effect of these macromolecules, in many cases, internalization to the cell cytosol is crucial. At an intracellular level, the most fundamental obstruction for cytosolic release of the therapeutic molecule is the membrane-barrier of the endocytic vesicles. Photochemical internalization (PCI) is a novel technology for release of endocytosed macromolecules into the cytosol. The technology is based on the use of photosensitizers located in endocytic vesicles that upon activation by light induces a release of macromolecules from their compartmentalization in endocytic vesicles. PCI has been shown to potentiate the biological activity of a large variety of macromolecules and other molecules that do not readily penetrate the plasma membrane, including type I ribosome-inactivating proteins (RIPs), gene-encoding plasmids, adenovirus, oligonucleotides, and the chemotherapeutic bleomycin. PCI has also been shown to enhance the treatment effect of targeted therapeutic macromolecules. The present protocol describes PCI of an epidermal growth factor receptor (EGFR)-targeted protein toxin (Cetuximab-saporin) linked via streptavidin-biotin for screening of targeted toxins as well as PCI of nonviral polyplex-based gene therapy. Although describing in detail PCI of targeted protein toxins and DNA polyplexes, the methodology presented in these protocols are also applicable for PCI of other gene therapy vectors (e.g., viral vectors), peptide nucleic acids (PNA), small interfering RNA (siRNA), polymers, nanoparticles, and some chemotherapeutic agents.

Gold nanoparticles capped with polyethyleneimine for enhanced siRNA delivery

An efficient and safe delivery system for small interfering RNA (siRNA) is required for clinical application of RNA interfering therapeutics. Polyethyleneimine (PEI)-capped gold nanoparticles (AuNPs) are successfully manufactured using PEI as the reductant and stabilizer, which bind siRNA at an appropriate weight ratio by electrostatic interaction and result in well-dispersed nanoparticles with uniform structure and narrow size distribution. With siRNA binding, PEI-capped AuNPs induce more significant and enhanced reduction in targeted green fluorescent protein expression in MDA-MB-435s cells, though more internalized PEI/siRNA complexes in cells are evidenced by confocal laser scanning microscopy observation and fluorescence-activated cell sorting analyses. PEI-capped AuNPs/siRNA targeting endogenous cell-cycle kinase, an oncogene polo-like kinase 1 (PLK1), display significant gene expression knockdown and induce enhanced cell apoptosis, whereas it is not obvious when the cells are treated with PLK1 siRNA using PEI as the carrier. Without exhibiting cellular toxicity, PEI-capped AuNPs appear to be suitable as a potential carrier for intracellular siRNA delivery.

Alkylcarboxylate grafting to polyethylenimine: a simple approach to producing a DNA nanocarrier with low toxicity

BACKGROUND

Various strategies have been examined to improve both transfection efficiency and cytotoxicity of polyethylenimine (PEI), a widely used polycationic nonviral gene vector. In the present study, we sought to improve PEI transfection efficiency by combining the osmotic burst mechanism for lysing endocytotic vesicles with the lipid depletion mechanism, which was accomplished by maintaining buffering capacity at the same time as adding a lipid-absorbing hydrophobic shell.

METHODS

PEI was altered via the substitution of various percentages of its primary amines with carboxylate-terminated short, moderate and long alkyl chains, by reaction with bromoacetic, 6-bromohexanoic, 10-bromodecanoic and 16-bromohexadecanoic acids. Modified polymers were complexed with plasmid and the particle size and zeta potential of the polyplexes were determined. Ethidium bromide dye exclusion was used to show the DNA-binding ability of the polymers and their transfection activity and cytotoxicity was evaluated in Neuro2A mammalian cells.

RESULTS

Decreased DNA-binding ability resulted from increases in either the degree of substitution or hydrocarbon chain length. Particle size and zeta potential measurements demonstrated that modified PEI polymers were able to form nanoparticles in the size range 60-195 nm, and surface charge decreased with an increasing degree of substitution. Higher degrees of substitution resulted in decreased cytotoxicity of polymers. Alkylcarboxylate substitution of primary amines on PEI enhanced transfection efficiencies by up to approximately five-fold relative to underivatized PEI, with the greatest increases occurring with 6-bromohexanoic acid derivatives at degrees of substitution below 10%.

CONCLUSIONS

The results obtained suggest that an appropriate balance between cationic and hydrophobic regions of alkylated PEI yields the optimal nonviral vector with high transfection efficiency and low toxicity.

Strategies for targeted nonviral delivery of siRNAs in vivo

Silencing specific gene expression by RNA interference (RNAi) has rapidly become a standard tool for the reverse genetic analysis of gene functions. It also has tremendous potential for managing diseases for which effective treatment is currently unavailable or suboptimal. However, the poor cellular uptake of synthetic small interfering RNAs (siRNAs) is a major impediment for their clinical use. Great progress has been made in recent years to overcome this barrier, and several methods have been described for the in vivo delivery of siRNA. Moreover, the latest advances have focused on achieving targeted siRNA delivery restricted to relevant tissues and cell types in vivo. These approaches are expected to reduce the dose requirement as well as minimize siRNA-induced toxicities, thereby advancing the field of siRNA therapy towards clinical use.

Rapid modification of proteins using a rapamycin-inducible tobacco etch virus protease system

Background

The ability to disrupt the function of a specific protein on a rapid time scale provides a powerful tool for biomedical research. Specific proteases provide a potential method to selectively cleave a chosen protein, but rapid control of protease activity is difficult.

Methodology/Principal Findings

A heterologous expression system for rapid target-directed proteolysis in mammalian cells was developed. The system consists of an inducible NIa protease from the tobacco etch virus (TEVp) and a chosen protein into which a TEVp substrate recognition sequence (TRS) has been inserted. Inducible activity was conferred to the TEVp using rapamycin-controlled TEVp fragment complementation. TEVp activity was assayed using a FRET-based reporter construct. TEVp expression was well tolerated by mammalian cells and complete cleavage of the substrate was possible. Cleavage at 37°C proceeded exponentially with a time constant of approximately 150 minutes. Attempts to improve cleavage efficiency were hampered by substantial background activity, which was attributed to inherent affinity between the TEVp fragments. A second TEVp assay, based on changes in inactivation of a modified K_V3.4 channel, showed that functional properties of a channel can be using altered using an inducible TEVp system. Similar levels of background activity and variability were observed in both electrophysiological and FRET assays.

Conclusions/Significance

The results suggested that an optimum level of TEVp expression leading to sufficient inducible activity (with minimal background activity) exists but the variability in expression levels between cells makes the present system rather impractical for single cell experiments. The system is likely to be more suitable for experiments in which the cell-to-cell variability is less of an issue; for example, in experiments involving large populations of cells.