Effects of complement depletion on the pharmacokinetics and gene delivery mediated by cationic lipid-DNA complexes

Engineering PEGylated Polyester Nanoparticles to Reduce Complement-Mediated Infusion Reaction

Translation of intravenously administered nanomaterials to the clinic is limited due to adverse infusion reactions. While these reactions are infrequent, with up to 10% prone to experiencing infusion reactions, the reactions can be severe and life-threatening. One of the innate immune pathways, the complement activation pathway, plays a significant role in mediating this response. Nanoparticle surface properties are a relevant design feature, as they control the blood proteins the nanoparticles interact with and allow the nanoparticles to evade the immune reaction. PEGylation of nanosurfaces is critical in improving the blood circulation of nanoparticles and reducing opsonization. Our goal was to understand whether modifying the surface architecture by varying the PEG density and architecture can impact the complement response in vitro. We utilized block copolymers of poly(lactic acid)-b-poly(ethylene glycol) prepared with poly(ethylene glycol) macroinitiators of molecular weights 3400 and 5000 Da. Tracking the complement biomarker C5a, we monitored the impact of changing PEGylation of the nanoparticles. We also investigated how the changing PEG length on the nanoparticle surface impacts further strengthening the stealth properties. Lastly, we determined which cytokines change upon blood incubation with nanoparticles in vitro to understand the extent to which inflammation may occur and the crosstalk between the complement and immune responses. Increasing PEGylation reduced the generation of complement-mediated anaphylatoxin C5a in vitro, with 5000 Da PEG more effectively reducing levels of C5a generated compared to 3400 Da PEG. The insights gathered regarding the impact of PEG density and PEG chain length would be critical in developing stealth nanoparticles that do not lead to infusion reactions upon intravenous administration.

P-selectin targeted RAGE-shRNA lipoplexes alleviate atherosclerosis-associated inflammation

The receptor for advanced glycation end products (RAGE) plays a central role in the chronic inflammatory process associated with atherosclerosis development. We aimed to develop lipoplexes carrying RAGE-short hairpin (sh) RNA, targeted to the adhesion molecule P-selectin, selectively expressed on the surface of activated endothelium (Psel-lipo/shRAGE) to down-regulate RAGE expression as a therapeutic strategy for atherosclerosis. In vitro, Psel-lipo/shRAGE lipoplexes were efficiently taken up by activated endothelial cells (EC), decreased the expression of RAGE protein, and proved to be functional by reducing the monocyte adhesion to activated EC. In ApoE-deficient mice, the targeted lipoplexes accumulated specifically and efficiently transfected the aorta. The repeated administration of Psel-lipo/shRAGE lipoplexes, twice per week for one month: i) reduced the expression of RAGE protein in the aorta by decreasing the expression of NF-kB and TNF-α; ii) diminished the plasma levels of TNF-α, IL6, IL-1β, and MCP-1; iii) inhibited the atherosclerotic plaque development and iv) had no significant adverse effects. In conclusion, the newly developed Psel-lipo/shRAGE lipoplexes reduce the inflammatory processes associated with RAGE signaling and the progression of atherosclerosis in ApoE-deficient mice. Downregulation of RAGE employing these lipoplexes may represent a promising new targeted therapy to block atherosclerosis progression.

Innate and adaptive immune responses toward nanomedicines

Since the commercialization of the first liposomes used for drug delivery, Doxil/Caelyx® and Myocet®, tremendous progress has been made in understanding interactions between nanomedicines and biological systems. Fundamental work at the interface of engineering and medicine has allowed nanomedicines to deliver therapeutic small molecules and nucleic acids more efficiently. While nanomedicines are used in oncology for immunotherapy or to deliver combinations of cytotoxics, the clinical successes of gene silencing approaches like patisiran lipid complexes (Onpattro®) have paved the way for a variety of therapies beyond cancer. In parallel, the global severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has highlighted the potential of mRNA vaccines to develop immunization strategies at unprecedented speed. To rationally design therapeutic and vaccines, chemists, materials scientists, and drug delivery experts need to better understand how nanotechnologies interact with the immune system. This review presents a comprehensive overview of the innate and adaptative immune systems and emphasizes the intricate mechanisms through which nanomedicines interact with these biological functions.

In Vivo Calpain Knockdown Using Delivery of siRNA

Calpain is an intracellular Ca²⁺-dependent non-lysosomal cysteine protease expressed ubiquitously in mammals. In endothelial cells, dysregulation of calpain has been shown to be involved in a wide variety of pathological conditions such as angiogenesis, vascular inflammation, and diabetes. Cell- or tissue-targeted in vivo delivery of small interfering RNA (siRNA) is a powerful research tool in the analysis of protein function and has been proposed as an attractive therapeutic modality that is applicable against a large number of human diseases including cancer. In this chapter we describe a method to knockdown calpain 1 in mouse pulmonary vascular endothelium using delivery of siRNA/cationic liposome complex. This technique results in a greater than 80% reduction in calpain 1 protein levels 48 h after a single i.v. injection of calpain 1 siRNA (0.5 mg siRNA/kg)/cationic liposome complex. We also describe confocal imaging to verify the loss of calpain 1 expression in pulmonary microvessel endothelial cells and application of this technique in the mouse model of ventilator-induced lung injury.

Polyquaternium-mediated delivery of morpholino oligonucleotides for exon-skipping in vitro and in mdx mice

Antisense oligonucleotide therapy for Duchenne muscular dystrophy has shown great potential in preclinical and clinical trials, but its therapeutic applications are still limited due to inefficient delivery. In this study, we investigated a few polyquaterniums (PQs) with different size and composition for their potential to improve delivery performance of an antisense phosphorodiamidate morpholino oligomer (PMO) both in vitro and in vivo. The results showed that LuviquatTM series, especially PQ-1 and PQ-3, promoted the exon-skipping efficiency comparable to Endoporter-mediated PMO delivery in vitro. Significant enhancement in skipping dystrophin exon 23 has also been achieved with PQ-3 up to seven-fold when compared to PMO alone in mdx mice. Cytotoxicity of the PQs was lower than Endoporter and PEI 25 K in vitro and muscle damage not clearly detected in vivo under the tested concentrations. These results together demonstrate that the optimization of PQ in molecular size, composition and distribution of positive charges is the key factor to achieve enhanced PMO exon-skipping efficiency. The higher efficiency and lower toxicity endow polyquaternium series as AO delivery enhancing agents for treating muscular dystrophy and other diseases.

Assessing the effect of a nude mouse model on nanoparticle-mediated gene delivery

The relevance of using nude mouse models for evaluating drug delivery to human tumors has recently been questioned by numerous researchers. While the immune response is known to play a critical role in cancer, this study assesses the effect of using immunocompromised "nude" mice on drug delivery. By inoculating both nude and immunocompetent mice with a mouse mammary carcinoma cell line (4T1), differences in the "first pass effect", distribution, and reporter gene expression due to the use of the nude mouse model could be elucidated. Our results indicate that initial tumor deposition (5 min) was slightly lower in nude mice but comparable after 24 h. In addition, some small differences in tissue deposition/accumulation and reporter gene expression were observed between the two mouse models. The results with this one tumor model suggest that delivery studies conducted in nude mice can provide comparable results to those in immunocompetent mouse models.

Cationic polyelectrolyte-mediated delivery of antisense morpholino oligonucleotides for exon-skipping in vitro and in mdx mice

In this study, we investigated a series of cationic polyelectrolytes (PEs) with different size and composition for their potential to improve delivery of an antisense phosphorodiamidate morpholino oligomer (PMO) both in vitro and in vivo. The results showed that the poly(diallyldimethylammonium chloride) (PDDAC) polymer series, especially PE-3 and PE-4, improves the delivery efficiency of PMO, comparable with Endoporter-mediated PMO delivery in vitro. The enhanced PMO delivery and targeting to dystrophin exon 23 was further observed in mdx mice, up to fourfold with the PE-4, compared with PMO alone. The cytotoxicity of the PEs was lower than that of Endoporter and polyethylenimine 25,000 Da in vitro, and was not clearly detected in muscle in vivo under the tested concentrations. Together, these results demonstrate that optimization of PE molecular size, composition, and distribution of cationic charge are key factors to achieve enhanced PMO exon-skipping efficiency. The increased efficiency and lower toxicity show this PDDAC series to be capable gene/antisense oligonucleotide delivery-enhancing agents for treating muscular dystrophy and other diseases.

Poly(propylacrylic acid)-mediated serum stabilization of cationic lipoplexes

The serum instability associated with cationic lipoplexes represents one of the major obstacles for the in vivo delivery of nonviral gene therapy vectors. Recently, we have shown that poly(propylacrylic acid) (PPAA), a pH-sensitive polyanionic polymer, can significantly improve the in vitro serum stability of DOTAP lipoplexes and enhance transfection (Cheung et al., Bioconjug. Chem. 12, 906 (2001)). We investigated this serum-stabilizing effect provided by PPAA using methods to identify the specific serum proteins that interact with DOTAP/DNA and DOTAP/DNA/PPAA lipoplexes and determined their modes of interaction with these lipoplexes. Studies showed that only low-density lipoprotein (LDL) caused significant decondensation of DNA from lipoplexes lacking PPAA, but that fully condensed DNA was retained within lipoplexes incorporating PPAA. Another major factor in the loss of transfection activity was due to the reduced cellular uptake of DOTAP lipoplexes upon exposure to serum, with bovine serum albumin (BSA) and high-density lipoprotein (HDL) acting as major contributors to this reduction in vector internalization. In contrast, lipoplexes containing PPAA maintained high levels of uptake into cells in the presence of these proteins. Transfection results generally concurred with the mechanistic studies, suggesting that maintaining effective cellular delivery of intact lipoplexes in the presence of serum proteins is important to retain high transfection efficiencies. These results indicate that the addition of PPAA as a ternary component in DOTAP lipoplexes can overcome some of the serum-related deficiencies encountered with these lipoplexes to provide efficient transfection.

Multiple components in serum contribute to hepatic transgene expression by lipoplex in mice

BACKGROUND

Interaction of cationic liposome/plasmid DNA complex (lipoplex) with serum was not a limiting factor for in vivo transfection. After intraportal injection of lipoplex, hepatic transgene expression was enhanced by interaction with serum in mice. In the present study, we analyzed the mechanism of enhanced hepatic transgene expression of lipoplex by interaction with serum components.

METHODS

Lipoplexes were incubated with several serum components for 5  min at 37  ° C before administration. Transfection efficiency of lipoplexes was measured 6  h after intraportal injection of lipoplex in mice.

RESULTS

Depletion of divalent cation from serum decreased hepatic transgene expression. The addition of calcium ion to divalent cation-depleted serum restored transgene expression. Heat-inactivated serum and bovine serum albumin diminished the enhancing effect of serum on hepatic transgene expression. On the other hand, removal of anionic proteins from serum using an anion-exchanging column was critical for the enhancing effect of serum on transgene expression. Among the serum components tested, fibronectin and complement component C3 enhanced hepatic transgene expression.

CONCLUSIONS

Hepatic transgene expression by lipoplex was enhanced by interaction with multiple components in serum. Interaction of lipoplex with serum could be an important factor for successful in vivo gene transfer. Hence, the information obtained in the present study is valuable for the future development of effective gene carriers.

In vitro and in vivo complement activation and related anaphylactic effects associated with polyethylenimine and polyethylenimine-graft-poly(ethylene glycol) block copolymers

Complement activation by polymeric gene and drug delivery systems has been overlooked in the past. As more reports appear in the literature concerning immunogenicity of polymers and their impact on gene expression patterns, it is important to address possible immune side effects of polymers, namely complement activation. Therefore, in this study the activity of low and high molecular weight poly(ethylene imine) and two PEGylated derivatives to induce complement activation were investigated in human serum. These in vitro results revealed that PEI 25 kDa caused significant and concentration dependent complement activation, whereas none of the other polymers induced such effects at their IC(50) concentrations determined by MTT-assays. To verify these in vitro results, additionally, studies were carried out in a swine model after intravenous administration, showing complement activation-related pseudoallergy (CARPA), reflected in symptoms of transient cardiopulmonary distress. Injections of PEI 25 kDa or PEI(25k)-PEG(2k)(10) at a dose of 0.05 and 0.1 mg/kg caused strong reactivity, while PEI 5 kDa and with PEI(25k)-PEG(20k)(1) were also reactogenic at 0.1 mg/kg. It was found that PEI 25 kDa caused both self- and cross-tolerance, whereas the PEG-PEIs were neither self- nor cross-reactively tachyphylactic. As a result of this study, it was shown that PEGylation of polycations with PEG of 20 kDa or higher molecular weight may be favorable. However, potential safety concerns in the development of PEI-based polymeric carriers for drugs and nucleic acids and their translation from bench to bedside need to be taken into consideration for human application.

Comparison between a multifunctional envelope-type nano device and lipoplex for delivery to the liver

The utility of using a multifunctional envelope-type nano device (MEND) for delivering a gene to the liver was examined. Lipotrust, a commercially available transfection reagent whose lipid composition is DC6- 14 :DOPE: cholesterol=4 : 3 : 3, was used as a reference. When Lipotrust was administrated intravenously, luciferase activity of the lung was 25 times higher than that of the liver. The luciferase activity of the lung was greatly reduced when a MEND was administered, even though the lipid composition of the lipid envelope was the same in both devices. Furthermore, the luciferase activity of the liver was 5 times higher than that for lipotrust, suggesting that the encapsulation of plasmid DNA (pDNA) in liposomes is more advantageous for delivering pDNA to the liver than complex formation. The isolation of parenchymal cells (PCs) and non-parenchymal cells (NPCs) showed that the MEND system is capable of expressing the luciferase protein more preferentially in NPCs than the lipoplex system. In addition, when the surface was modified with a pH-sensitive fusogenic peptide (GALA) used as a device for endosomal escape, overall liver luciferase activity was greatly enhanced. This suggests that endosomal escape is a limiting step for the MEND system. In the case of the GALA-modified MEND, the luciferase activity of PCs and NPCs was 18 times and 11 times higher than MEND system, while the transfection efficiency of NPCs was significantly higher compared to that of PCs. Collectively, these data show that a GALA-modified MEND prepared with DC6-14 :DOPE: cholesterol represents a promising device for NPCtargeting gene delivery in vivo.

Investigation of polyethylenimine-grafted-triamcinolone acetonide as nucleus-targeting gene delivery systems

BACKGROUND

Nuclear membrane is one of the main barriers in polymer mediated intracellular gene delivery. To improve the transgenic activity and safety of nonviral vector, triamcinolone acetonide (TA) as a nuclear localization signal was conjugated with different molecular weight polyethylenimine (PEI).

METHODS

Different molecular weight PEI [600, 1800, 25,000 (25k)] was conjugated with TA to synthesize PEI-TA by two-step reaction. Their physicochemical characteristics, in vitro cytotoxicity and transfection efficiency were evaluated. To investigate the difference of transfection efficiency of various molecular weight PEI-TA, their transfection mechanism was further investigated by confocal microscopy and competition assay. Transgenic expression in vivo was evaluated by injection into hepatic portal vein of mice.

RESULTS

All PEI-TA could form nanosize polyplexes with DNA and their physicochemical properties resemble each other. Their cytotoxicities were negligible compared to PEI 25k. The order of transfection efficiency was PEI 1800-TA > PEI 600-TA > PEI 25k-TA. A transfection mechanism study displayed that TA could inhibit considerably the transgenic activity of PEI 1800-TA and PEI 600-TA, but that of PEI 25k-TA was not inhibited. It was suggested that PEI 1800-TA and PEI 600-TA might translocate into the nucleus. Confocal microscopy investigation verified this suggestion. The data strongly suggested that the transfection efficiency of PEI 1800-TA in vivo was much higher than that of PEI 25k, which was consistent with the results obtained in vitro.

CONCLUSIONS

Low molecular weight PEI-TA could translocate into the nucleus efficiently. PEI 1800-TA presented higher transgenic activity and it has a great potential for gene therapy as a nonviral carrier.

Triazine dendrimers as nonviral vectors for in vitro and in vivo RNAi: the effects of peripheral groups and core structure on biological activity

A family of triazine dendrimers, differing in their core flexibility, generation number, and surface functionality, was prepared and evaluated for its ability to accomplish RNAi. The dendriplexes were analyzed with respect to their physicochemical and biological properties, including condensation of siRNA, complex size, surface charge, cellular uptake and subcellular distribution, their potential for reporter gene knockdown in HeLa/Luc cells, and ultimately their stability, biodistribution, pharmacokinetics and intracellular uptake in mice after intravenous (iv) administration. The structure of the backbone was found to significantly influence siRNA transfection efficiency, with rigid, second generation dendrimers displaying higher gene knockdown than the flexible analogues while maintaining less off-target effects than Lipofectamine. Additionally, among the rigid, second generation dendrimers, those with either arginine-like exteriors or peripheries containing hydrophobic functionalities mediated the most effective gene knockdown, thus showing that dendrimer surface groups also affect transfection efficiency. Moreover, these two most effective dendriplexes were stable in circulation upon intravenous administration and showed passive targeting to the lung. Both dendriplex formulations were taken up into the alveolar epithelium, making them promising candidates for RNAi in the lung. The ability to correlate the effects of triazine dendrimer core scaffolds, generation number, and surface functionality with siRNA transfection efficiency yields valuable information for further modifying this nonviral delivery system and stresses the importance of only loosely correlating effective gene delivery vectors with siRNA transfection agents.

Nonviral vectors for the delivery of small interfering RNAs to the CNS

While efficient methods for cell line transfection are well described, for primary neurons a high-yield method different from those relying on viral vectors is lacking. Viral vector-based primary neuronal infection has several drawbacks, including complexity of vector preparation, safety concerns and the generation of immune and inflammatory responses, when used in vivo. This article will cover the different approaches that are being used to efficiently deliver genetic material (both DNA and small interfering RNA) to neuronal tissue using nonviral vectors, including the use of cationic lipids, polyethylenimine derivatives, dendrimers, carbon nanotubes and the combination of carbon-made nanoparticles with dendrimers. The effectiveness, both in vivo and in vitro, of the different methods to deliver genetic material to neural tissue is discussed.

Lipid-based delivery of CpG oligonucleotides enhances immunotherapeutic efficacy

There has been significant interest in the potential of cytosine-guanine (CpG) containing oligodeoxynucleotides (ODN) as an immunotherapy for malignant, infectious and allergic diseases. While human trials have yielded promising results, clinical use of free CpG ODN still faces several challenges which limit their effectiveness. These include suboptimal in vivo stability, toxicity, unfavorable pharmacokinetic/biodistribution characteristics, lack of specificity for target cells and the requirement for intracellular uptake. To overcome these challenges, optimized lipid-based delivery systems have been developed to protect the CpG ODN payload, modify their circulation/distribution so as to enhance immune cell targeting and facilitate intracellular uptake. Ultimately, lipid-mediated delivery has the capacity to increase the immunopotency of CpG ODN and enhance their prophylactic or therapeutic efficacy in a range of diseases. Lipid-encapsulation provides a feasible strategy to optimize the immunostimulatory activity and immunotherapeutic efficacy of CpG ODN, thereby allowing their full clinical potential to be realized.

The encapsulation of DNA molecules within biomimetic lipid nanocapsules

Most of DNA synthetic complexes result from the self-assembly of DNA molecules with cationic lipids or polymers in an aqueous controlled medium. However, injection of such self-assembled complexes in medium like blood that differ from that of their formulation leads to strong instability. Therefore, DNA vectors that have physico-chemical properties and structural organisation that will not be sensitive to a completely different medium in terms of ionic and protein composition are actively sought. To this end, the goal here was to discover and optimize a nanostructured system where DNA molecules would be encapsulated in nanocapsules consisting in an oily core and a shell covered by PEG stretches obtained through a nanoemulsion process in the absence of organic solvent. This encapsulation form of DNA molecules would prevent interactions with external hostile biological fluid. The results show the entrapment of lipoplexes into lipid nanocapsules, leading to the formation of neutral 110 nm-DNA nanocapsules. They were weakly removed by the immune system, displaying an increased blood half-life, and improved carcinoma cell transfection, in comparison to the parent lipoplexes. Our results demonstrate that the fabrication of nanocapsules encapsulating hydrophilic DNA in an oily core that meet criteria for blood injection is possible.

The location of the left-handedly curved DNA sequence affects exogenous DNA expression in vivo

The intranuclear disposition of a plasmid is extremely important for transgene expression. The effects of a left-handedly curved sequence with high histone affinity on plasmid expression were examined in vivo. A naked luciferase-plasmid was delivered into mouse liver by a hydrodynamics-based injection, and the luciferase activities were quantitated at various time points. The location of the left-handedly curved sequence determined the transgene expression, without affecting the amount of intranuclear exogenous DNA. The plasmid containing the curved sequence at the location that results in the exposure of the TATA box out of the nucleosome core showed the highest expression. These results suggest that sequences with high histone affinity could control transgene expression from plasmids in vivo.

Targeted gene delivery to cancer cells with nanometric DNA particles enveloped with folic acid using a polymerisable anchor

Progress in the design of gene delivery system is vital for cancer gene therapy since many physiological and intracellular barriers remain. We have developed a technology for condensing genes into nanometric delivery systems. In this paper, we present a novel strategy for decorating 30 nm DNA particles with folic acid for cancer cell recognition. Physicochemical and biological experiments show that these DNA complexes selectively bind to cells expressing the corresponding folic acid receptor.

Targeted delivery of oligodeoxynucleotides to mouse lung endothelial cells in vitro and in vivo

Pulmonary endothelium plays an important role in the maintenance of normal pulmonary physiology and its dysfunction is involved in a number of pulmonary diseases. Correction of endothelial dysfunction via antisense oligodeoxynucleotides (ODN) is dependent on the development of a delivery vehicle that can efficiently deliver the ODN to pulmonary endothelium with minimal toxicity. To this end, we have developed a novel lipidic vector that is highly efficient in targeted delivery of ODN to pulmonary endothelium. This is based on a method that utilizes an ionizable aminolipid (1,2-dioleoyl-3-dimethylammonium propane) and an ethanol-containing buffer system for encapsulating large quantities of polyanionic ODN in lipid vesicles. An endothelium-specific antibody (273-34A) is incorporated into the lipid vesicles via a distearoylphosphatidylethanolamine-poly(ethylene glycol) spacer. The 273-34A antibody efficiently mediated delivery of ODN to mouse lung endothelial cells in vitro and in vivo. Furthermore, systemic administration of this formulation is associated with minimal hematological toxicities and induces little acute change in systemic and pulmonary hemodynamics. These results provide a basis for lipid-mediated delivery of ODN for the treatment of pulmonary diseases. They also suggest the utility of this approach as a research tool to characterize the function of genes in the pulmonary endothelium.

Interaction with Blood Components Plays a Crucial Role in Asialoglycoprotein Receptor-Mediated in Vivo Gene Transfer by Galactosylated Lipoplex

In this study, we evaluated the effect of blood components (whole blood and serum) on asialoglycoprotein receptor-mediated in vivo gene transfer. The hepatic transfection activity of galactosylated lipoplex preincubated with serum was approximately 10 times higher than that without incubation after intraportal injection in mice. However, preincubation with whole blood significantly reduced hepatic transfection activity. Fluorescent resonance energy transfer analysis and agarose gel electrophoresis revealed that preincubation with serum reduced the degree of destabilization of the galactosylated lipoplex in blood, partially supporting enhanced hepatic transfection activity by preincubation with serum. Inhibition of hepatic transfection activity by predosing galactosylated bovine serum albumin indicated that the galactosylated lipoplex exposed to serum is recognized by asialoglycoprotein-receptors on hepatocytes. Inactivation of serum prior to mixing with galactosylated lipoplex reduced liver accumulation and completely abolished enhancement of hepatic transfection activity by preincubation with active serum, suggesting that not only the stability of the lipoplex in blood but also the serum opsonin activity plays important roles. Alternatively, preincubation with inactivated serum reduced the lung accumulation and inflammatory cytokine production of galactosylated lipoplex. The information provided by this study will be valuable for the future use, design, and development of galactosylated lipoplex for in vivo asialoglycoprotein receptor-mediated gene transfer.

Nanoparticle-mediated gene delivery: state of the art

With the development of genomic and proteomic technologies, the prospect for gene therapy has progressed rapidly. This has been partly possible due to the emergence of a diverse array of polymeric and non-polymeric nanoparticles that are being investigated for their ability to deliver genes and drugs. In this review, particles have been pragmatically divided as chitosan-related and chitosan-unrelated nanomaterials. The state of the art in terms of the development, characterisation and evaluation of their in vitro and/or in vivo potential is discussed for each of these various particles. Although substantial progress has been made, the potential of these particles in the clinical arena and human responses remain to be evaluated. It is hoped that this review will provide an impetus for further studies of these particles, with the ultimate intent that one or more of these diverse nanoparticle-based non-viral approaches for gene transfer will translate from 'bench to bedside' in the future.

Cationic lipids enhance siRNA-mediated interferon response in mice

RNA interference mediated by small interfering RNAs (siRNAs) shows promise as a powerful research tool for gene function studies. However, controversy exists over the potential of siRNA-induced interferon response in vitro and in vivo. In this study, we showed that although intravenous administration of siRNA alone is essentially inert, injection of siRNA complexed with cationic liposomes resulted in a potent induction of both type I and type II interferon responses. Furthermore, i.v. administration of cationic lipid/siRNA complexes led to activation of STAT1. This study suggests caution in data interpretation and the potential toxicity with in vivo use of siRNA, particularly when delivered via a cationic lipid vector. This study also suggests the potential of siRNA as an immunostimulatory agent for immunotherapy.

Pharmacokinetics of Plasmid DNA-Based Non-viral Gene Medicine

Non-viral gene therapy can be realized by optimization of the pharmacokinetic properties of both the vector and the encoded therapeutic protein. A major obstacle to its successful clinical application is the limited ability of plasmid DNA, the most convenient gene-coding compound, to distribute within the body after in vivo administration. Under normal conditions, plasmid DNA and its non-viral vector complexes have difficulty in passing through various anatomical and biological barriers. These characteristics greatly limit the number and distribution of cells transduced with the vector, because transgene expression only occurs in cells that are reached by the vector. New approaches to the design of vectors as well as the methods of administration, such as electroporation and a hydrodynamic delivery, have increased the transgene expression in vivo, suggesting that improved distribution of plasmid DNA is possible by these approaches. In this chapter, the basic pharmacokinetic properties of naked plasmid DNA under normal conditions are first reviewed, then the properties of both naked and complexed plasmid DNA are discussed under conditions where significant transgene expression takes place.

Toxicity of Cationic Lipid‐DNA Complexes

As with any conventional drug, the body's response to cationic lipid-DNA complexes is highly dependent on both the dose administered and the route of delivery. At relatively low doses there is little to no effect on organ function or tissue architecture, but at higher doses, acute inflammation and tissue damage can occur that is sometimes quite profound. Of the two most common routes of delivery, intravenous (IV) or intrapulmonary, IV administration tends to cause more severe adverse effects and can be lethal at higher doses of complex. Both routes activate an innate immune response that includes the induction of proinflammatory cytokines and immune cell activation, a major portion of which has been attributed to the presence of immunostimulatory CpG motifs within the plasmid DNA vector. Removing CpGs from the plasmid vector reduces several, but not all of the acute inflammatory responses to cationic lipid-DNA complexes. Therefore, other strategies are required to improve the therapeutic potential of these vectors, such as transient immune suppression, aerosolization of the complex, and novel formulations that have increased efficiency of transduction and decreased interaction with immune cells.

Inhibition of B16BL6 tumor progression by coadministration of recombinant angiostatin K1-3 and endostatin genes with cationic liposomes

Transfection of the antiangiogenic angiostatin and endostatin genes was shown to be an alternative to high-dose administration of angiostatin or endostatin proteins for cancer therapy. We have systematically investigated whether coadministration of the mouse angiostatin kringle 1-3 gene (pFLAG-AngioK1/3) and the endostatin gene (pFLAG-Endo) complexed with cationic liposomes exhibits enhanced therapeutic efficacy. In vitro, the coexpressed mixture of angiostatin K1-3 and endostatin more effectively reduced angiogenesis in chorioallantoic membranes than either angiostatin K1-3 or endostatin alone. In vivo, subcutaneous co-administration of pFLAG-AngioK1/3 and pFLAG-Endo lipoplexes more effectively inhibited vascularization in Matrigel plugs implanted in mice than either one alone. Additionally, subcutaneous administration of these genes inhibited the growth and formation of pulmonary metastases of B16BL6 melanoma cells in mice. Compared to treatment with an empty vector, treatment with pFLAG-AngioK1/3 plus pFLAG-Endo inhibited 81% of tumor growth, while treatment with pFLAG-AngioK1/3 or pFLAG-Endo inhibited tumor growth 70 and 69%, respectively. Cotreatment with the two plasmids after primary tumor excision induced a 90% inhibition of pulmonary metastases versus 79% for pFLAG-AngioK1/3 or 80% for pFLAG-Endo individually. These results suggest that combined administration of angiostatin K1-3 and endostatin genes complexed with cationic liposomes may be an innovated antiangiogenic strategy for cancer therapy.

A sterically stabilized immunolipoplex for systemic administration of a therapeutic gene

A sterically stabilized immunolipoplex (TsPLP), containing an antitransferrin receptor single-chain antibody fragment (TfRscFv)-PEG molecule, has been developed to specifically and efficiently deliver a therapeutic gene to tumor cells. A postcoating preparation strategy was employed in which a DNA/lipid complex (lipoplex) was formed first and then sequentially conjugated with PEG and TfRscFv. The complex prepared by this method was shown to be superior in ability to deliver genes to tumor cells than when prepared by a common precoating strategy, in which DNA is mixed with TfRscFv-PEG conjugated liposome. Using prostate cancer cell line DU145, a comparison was made between the in vitro and in vivo gene delivery efficiencies of four complexes, Lipoplex (LP), PEG-Lipoplex (PLP), TfRscFv-PEG-Lipoplex (TsPLP) and our standard TfRscFv-Lipoplex (TsLP). In vitro, the order of transfection efficiency was TsLP>LP approximately TsPLP>PLP. However, in vivo the order of transfection efficiency, after systemic administration via the tail vein, was TsPLP>TsLP>LP or PLP with TsPLP-mediated exogenous gene expression in tumor being two-fold higher than when mediated by TsLP. This suggests that the in vitro transfection efficiency of TsPLP was not indicative of its in vivo efficiency. In addition, it was found that the level of exogenous gene expression in the tumor mediated by TsPLP was higher than that mediated by TsLP and did not decrease over the time. More importantly, high exogenous gene expression in tumor, but low expression in liver, was observed after an i.v. delivery of TsPLP carrying either the GFP reporter gene or the p53 gene, indicating that tumor preferential targeting was maintained by this complex in the presence of PEG. These findings show that incorporation of PEG into our targeted lipoplex results in a more efficient delivery of the complex to the tumor cells, possibly by inhibiting the first pass clearance observed with non-PEG containing liposomes. Therefore, these data demonstrate that TsPLP is a improvement over our previously established tumor targeted gene delivery complex for systemic gene therapy of cancer.

Intravenous fate of poly(2-(dimethylamino)ethyl methacrylate)-based polyplexes

The objective of this study was to assess the in vivo fate of poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA)-based polyplexes after intravenous administration into mice. Circulation kinetics and tissue distribution in terms of plasmid localization and transfection efficiency were assessed. To gain more insight into the observed biodistribution and gene expression profile, the interaction of pDMAEMA-based polyplexes with blood components (erythrocytes and albumin) was investigated in vitro. In the case of i.v. injection of positively charged polyplexes at a dose of 30 microg DNA most of the radioactivity was found in the lungs and the liver 60 min after injection. In the case of pDMAEMA/DNA polyplexes with a negative charge, uptake occurred mainly by the liver. Administration of positively charged complexes at a 30 microg DNA dose resulted in reporter gene expression primarily in the lungs. Injection of negatively charged complexes and naked plasmid did not result in luciferase expression in any of the organs examined. In vitro turbidity experiments showed the induction of a charge dependent aggregation process upon addition of albumin to the polyplexes pointing out to the involvement of aggregate formation in the dominant lung uptake of the positively charged polyplexes. Also, incubations of polyplexes after pre-incubation with a physiological concentration of albumin with washed erythrocytes confirmed that polyplexes induce the formation of extremely large structures. This paper underlines the need for the design of systems with reduced interaction with blood components to promote the delivery of DNA to target tissues outside the lungs.

DNA sequences in cationic lipid:pDNA-mediated systemic toxicities

Systemic delivery of synthetic gene transfer vectors such as cationic lipid:plasmid DNA (pDNA) complexes elicits a range of acute physiologic responses, which in the context of therapeutic gene delivery represent dose-limiting toxicities. The most prominent responses are transient leukopenia, thrombocytopenia, serum transaminase elevations, and elevations of proinflammatory cytokines such as interferon-gamma (IFN-gamma), interleukin-12 (IL-12), and tumor necrosis factor-alpha (TNF-alpha). The unmethylated CpG sequences present in plasmid DNA have been implicated as a major cause of the robust cytokine response that follows systemic administration of cationic lipid:pDNA complexes. However, the factors causing the additional significant toxicities (leukopenia, thrombocytopenia, and serum transaminase elevations) recently shown to be associated with vector administration have not been defined. We show here that DNA sequences, such as immune stimulatory CpG sequences, play a significant role in inducing the additional acute toxicities associated with cationic lipid:pDNA complex administration. Importantly, while methylating these CpG sequences results in greatly reduced cytokine levels, this modification does not eliminate their ability to generate the other systemic toxicities. Examples of non-CpG DNA sequences that induce distinct toxicity profiles when administered systemically in the form of cationic lipid:DNA complexes are also identified. Taken together, these results imply that specific DNA sequences are responsible for a significant portion of the systemic toxicities observed after administration of cationic lipid:pDNA complexes.

Molecular weight-dependent gene transfection activity of unmodified and galactosylated polyethyleneimine on hepatoma cells and mouse liver

To optimize a receptor-mediated and cell-selective gene transfer with polyethyleneimine (PEI)-based vector, we synthesized three galactosylated PEIs (Gal-PEI) with different molecular weights (PEI(1800), PEI(10,000), and PEI(70,000)) and investigated their potential as a targetable vector to asialoglycoprotein receptor-positive cells. All PEI derivatives formed complexes with plasmid DNA (pDNA), whereas the particle size of the complex became smaller on increasing the molecular weight of PEI. Transfection efficiency in HepG2 cells with PEI was highest with PEI(1800); efficiency was next highest with PEI(10,000), although the cellular association was similar. After galactosylation, Gal(19)-PEI(10,000)/pDNA and Gal(120)-PEI(70,000)/pDNA showed considerable agglutination with a galactose-recognizing lectin, but Gal(9)-PEI(1800) did not, suggesting that galactose units on the Gal(9)-PEI(1800)-pDNA complex are not sufficiently available for recognition. Gal(19)-PEI(10,000)-pDNA and Gal(120)-PEI(70,000)-pDNA complexes showed galactose-inhibitable transgene expression in HepG2 cells. Transfection efficiency was greatest with Gal(19)-PEI(10,000)/pDNA, a result that highlights the importance of obtaining a balance between the cytotoxicity and the transfection activity, both of which are found to be a function of the molecular weight of PEI. After intraportal injection, however, Gal(153)-PEI(70,000)/pDNA having a low N/P ratio was most effective, suggesting that additional variables, such as the size of the complex, are important for in vivo gene transfer to hepatocytes.

Prolonged gene expression in mouse lung endothelial cells following transfection with Epstein-Barr virus-based episomal plasmid

The development of a strategy to deliver a gene to pulmonary endothelium will be useful for gene function study and for pulmonary gene therapy. Cationic lipidic vectors are efficient in gene transfer to pulmonary endothelium via the vascular route; however, gene expression is transient and lasts for only a few days. In this study, we show that pulmonary gene transfer via cationic lipidic vectors can be significantly improved using an Epstein-Barr virus (EBV)-based expression plasmid. Systemic administration of cationic liposomes followed by the EBV-based plasmid led to gene expression in the lung that lasted for more than 3 weeks. Prolonged and high levels of gene expression can also be obtained in primary mouse lung endothelial cells (MLEC) following lipofection with an EBV-based plasmid. These results suggest the utility of this gene transfer protocol in studying the expression of cloned genes in lung endothelial cells and in pulmonary gene therapy.

Lipid-mediated delivery of oligonucleotide to pulmonary endothelium

Pulmonary endothelium plays an important role in the maintenance of normal pulmonary physiology and its dysfunction is involved in a number of pulmonary diseases. Correction of endothelial dysfunction via antisense oligodeoxyonucleotides (ODN) is dependent on the development of a delivery vehicle that can efficiently deliver the ODN to pulmonary endothelium with minimal toxicity. To this end, we have developed a lipidic vector (LPD) that is composed of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) liposomes, protamine, and ODN. This formulation is highly efficient in delivering ODN to the lung via the vascular route. The efficiency of delivery is a function of lipid composition and of the charge ratio between lipid and ODN. Immunofluorescence staining of BrdU-labeled ODN suggested efficient accumulation of ODN in the alveolar capillary region. Transmission electron microscopy of immunogold localization of BrdU-labeled ODN confirmed that pulmonary endothelial cells were indeed targeted by the vector. Furthermore, this formulation is associated with minimal proinflammatory cytokine response and other hematologic toxicities when the ODN lack a potent unmethylated CpG motif. Pretreatment of mice with LPD containing an ODN against intercellular adhesion molecule-1 (ICAM-1) significantly decreased ICAM-1 expression in the lung following LPS challenge. These results provide a basis for lipid-mediated delivery of ODN for the treatment of pulmonary diseases.

Importance of lateral and steric stabilization of polyelectrolyte gene delivery vectors for extended systemic circulation

Gene therapy for systemic diseases requires intravenous administration, but existing vectors are not suitable for systemic delivery, often showing rapid elimination from the bloodstream that restricts potential transfection sites to "first-pass" organs. To develop long-circulating vectors, here we have compared polyplexes containing DNA and poly-L-lysine (PLL) or polyethylenimine (PEI), surface-modified with either monovalent polyethylene glycol (PEG) or multivalent copolymers of N-(2-hydroxypropyl)methacrylamide (PHPMA), correlating their biophysical properties with their distribution following intravenous injection. A key difference between the two types of coating is the introduction of lateral stabilization by surface attachment of multivalent PHPMA, in addition to the steric stabilization provided by both types of polymers. The alpha-half-life for bloodstream clearance of polycation/DNA polyplexes (typically <5 minutes in mice) could be extended using multivalent PHPMA coating to >90 minutes. We found that the dose administered, as well as the amount and molecular weight of the coating PHPMA, had important effects on circulation properties. Multivalent PHPMA coating allows, for the first time, considerably extended circulation time using polyplex systems-a prerequisite for systemic gene delivery.

Strain-based genetic differences regulate the efficiency of systemic gene delivery as well as expression

We have characterized the impact of strain-based genetic differences on the efficiency of the intravenous cationic liposome-DNA complex (CLDC)-based gene transfer and expression in mice. We also investigated what steps in the gene delivery and expression pathway appeared responsible for these strain-related differences and whether such differences could be compensated for either by agents that alter host pathways important in CLDC-mediated gene transfer and expression, or by changes in CLDC formulation. We found that different mouse strains can exhibit different expression levels and/or differences in the amount of plasmid DNA delivered to the organs where the DNA is expressed. Furthermore, drug pretreatment or reformulation of the CLDC could improve DNA delivery and/or gene expression in a strain-specific fashion. We conclude that genetic factors critically modify both the tissue deposition and the expression of genetic materials delivered by CLDC. Because manipulation of either the host or the CLDC could at least partially compensate for these strain-related differences, such strategies may be required to effectively use non-viral gene transfer approaches in genetically diverse populations.

A simple method to overcome the interference of hemoglobin in the detection of reporter genes in vivo

The determination of chemiluminescent intensity of reporter gene expression in vivo is generally disturbed by the presence of hemoglobin. Current methods consist in using perfusion to eliminate blood from investigated tumors or organs. In this work we propose a simple method to overcome this difficulty. The method consists in establishing an absorbance-dependence plot of the ratio R% = phi/phi(0) between the chemiluminescent intensities measured when hemoglobin is present or absent. For every measurement of the luminescent intensity phi on sample containing blood, if the absorbance A of the hemoglobin is determined, it allows one to have the intensity ratio R% which in turn gives the corrected intensity phi(0) when the absorption by hemoglobin is eliminated. The method is particularly adapted for comparative measurements of transfection levels in tumors where perfusion cannot be easily performed.

Nonviral gene transfer strategies for the vasculature

Major attention has been focused on the development of gene therapy approaches for the treatment of vascular diseases. In this review, we focus on an alternative use of gene therapy: the use of genetic means to study vascular cell biology and physiology. Both viral and nonviral gene transfer strategies have limitations, but because of the overwhelming inflammatory responses associated with the use of viral vectors, nonviral gene transfer methods are likely to be used more abundantly for future applications in the vasculature. Researchers have made great strides in the advancement of gene delivery to the vasculature in vivo. However, the efficiency of gene transfer seen with most nonviral approaches has been exceedingly low. We discuss how to circumvent and take advantage of a number of the barriers that limit efficient gene delivery to the vasculature to achieve high-level gene expression in appropriate cell types within the vessel wall. With such levels of expression, gene transfer offers the ability to alter pathways at the molecular level by genetically modulating the activity of a gene product, thus obviating the need to rely on pharmacological agents and their foreseen and unforeseen side effects. This genetic ability to alter distinct gene products within a signaling or biosynthetic pathway or to alter structural interactions within and between cells is extremely useful and technologically possible today. Hopefully, with the availability of these tools, new advances in cardiovascular physiology will emerge.

Evaluation of the role of lipoprotein metabolism genes in systemic cationic liposome-mediated gene transfer in vivo

Germ line gene disruption and gene insertion are often used to study the function of selected genes in vivo. We used selected knockout and transgenic mouse models to attempt to identify lipoprotein-related genes and gene products that regulate the process of intravenous cationic liposome-DNA complex (CLDC)-based gene delivery. Several observations suggested that proteins involved in lipoprotein metabolism might be important in influencing the delivery and/or expression of CLDC. First, in vitro transfection of either K562 or CHO cells by CLDCs was enhanced by the presence of a functional low-density lipoprotein receptor (LDLR). Second, pretreatment of mice with 4-aminopyrazolopyrimidine (4APP), an agent that alters lipoprotein profiles in mice, significantly decreased expression of luciferase (luc) after intravenous injection of CLDC-luc complexes in mice. Therefore, we tested mouse model systems either deficient for, or overexpressing, selected genes involved in lipoprotein metabolism, for their potential to regulate intravenous, CLDC-based gene delivery. Although homozygous knockout mutation in the apoE gene caused a significant decrease in gene expression in many tissues of apoE-deficient mice, mice with homozygous deletion of both the apoE and LDLR genes showed wild-type levels of gene transfer efficiency. Thus, a secondary event, produced by homozygous deletion of apoE, but compensated for by the concomitant deletion of LDLR, and/or effects resulting from strain-related, genetic background differences, appeared to play a significant role in mediating intravenous, CLDC-based gene delivery. Secondary alterations resulting from germ line knockouts, as well as epigenetic effects produced by strain differences, may limit the ability to assign specific, gene transfer-related functions to the deleted gene.

Effects of erythrocytes and serum proteins on lung accumulation of lipoplexes containing cholesterol or DOPE as a helper lipid in the single-pass rat lung perfusion system

Plasmid DNA-cationic liposome complexes (lipoplexes) accumulate in the lung to a great extent immediately after intravenous administration, and gene expression occurs predominantly in the lung. However, the detailed mechanisms underlying the lung accumulation of lipoplexes are not fully understood. In this study, we investigated the effect of blood components on the lung accumulation of lipoplexes using a single-pass rat lung perfusion system. Two types of lipoplexes, Chol-containing lipoplex ([(32)P]DNA-DOTMA/Chol liposome complex) and DOPE-containing lipoplex ([(32)P]DNA-DOTMA/DOPE liposome complex), pre-incubated with whole blood, serum, or erythrocytes, were injected into the perfused lung via an artery. Similarly to in vivo observations, extensive lung accumulation was observed for both types of lipoplexes after incubation with whole blood during a single passage. The (32)P-labeled lipoplexes pre-incubated with erythrocytes showed similar lung accumulation, whereas their lung accumulation after incubation with serum was significantly reduced, suggesting that erythrocytes would be more responsible blood components for extensive uptake by the perfused lung. However, there was a clear difference in the amounts of the accumulated erythrocytes after intra-arterial injection between the two lipoplex formulations. A significant degree of erythrocyte accumulation was observed when the DOPE-containing lipoplex was injected, whereas the Chol-containing lipoplex failed to induce any significant erythrocyte accumulation in the lung. In vitro experiments showed that the major fraction of both lipoplexes was bound to erythrocytes. These data suggested that Chol-containing lipoplexes bound to erythrocytes before injection dissociate from the erythrocytes and are transferred to the lung capillary endothelial cells during their passage through the lung. In contrast, DOPE-containing lipoplexes bound to erythrocytes cause aggregation and are embolized in the lung capillary with erythrocytes. Thus, the present study demonstrated that the interaction with erythrocytes plays an important role in the lung accumulation of lipoplexes and that neutral helper lipid significantly affects this interaction.

Mechanism of lipoplex gene delivery in mouse lung: binding and internalization of fluorescent lipid and DNA components

We introduce a lung inflation-fixation protocol to examine the distribution and gene transfer efficiency of fluorescently tagged lipoplexes using fluorescence confocal microscopy within thick lung tissue sections. Using this technique, we tested the hypothesis that factors related to lipoplex distribution were the predominant reason that intravenous (i.v.) administration of lipoplex was superior to intratracheal (i.t.) administration for gene transfer in the murine lung. Lipoplex distribution was analyzed using digitized images of overlapping fields, reconstructed to view an entire lung lobe. Intravenously administered lipoplexes were confined to the capillary network and homogenously distributed throughout the lung lobe. In contrast, i.t. administration resulted in regional distribution of lipoplex, concentrated around bronchioles and distal airways. Not all the bronchioles were stained with lipoplex, suggesting that the airway-administered solution became channeled through certain bronchiolar pathways. A fluorescent oligonucleotide was used as a marker for cytoplasmic release of nucleic acids. Quantification of the resulting fluorescent nuclei was used to define the relationship between cytoplasmic release of nucleic acids and gene expression. Endothelial cells were stained after i.v. administration, and epithelial cells were stained after i.t. administration. The delivery of nucleic acids was also more homogeneous with i.v. administration of lipoplex than with i.t. administration. After i.t. administration, it was notable that high concentrations of fluorescent nuclei correlated with low GFP expression. This suggested that toxicity was associated with high local concentrations of cationic lipoplexes. The ratio of GFP-expressing cells to fluorescent nuclei indicated that capillary endothelial cells were more efficient in gene expression per delivery event than were pulmonary epithelial cells. Thus, the greater gene expression efficiency of i.v. administered lipoplexes was due not only to the initial distribution but also to the greater efficiency of the vascular endothelial cells to appropriately traffic and express the foreign gene.

Specific recognition of protein carboxy-terminal sequences by natural IgM antibodies in normal serum

Our previous study indicated that normal serum contains complement-fixing natural IgM antibodies reacting with a large variety of randomly generated protein carboxy-termini. Here we show that the "carboxy-terminal" IgM (C-IgM) antibodies specifically react with short peptide sequences located immediately at the protein carboxy-terminus. The specificity of C-IgM-peptide interactions is tentatively defined by three to four amino acid residues. All carboxy-terminal peptides in a large peptide library apparently react with C-IgM antibodies. Immobilized synthetic peptides also react with C-IgM antibodies. No interaction of C-IgM antibodies with internal peptide sequences has been observed. C-IgM antibodies are present in germ-free and in athymic adult rats and are absent in newborn rats. The natural ubiquity of protein carboxy-termini in biological structures suggests that C-IgM could play an important role in antigen clearance and presentation to the immune system. From a practical viewpoint, the recognition of carboxy-terminal peptides by complement-fixing C-IgM antibodies has profound implications for the use of peptide- and protein-derivatized delivery vehicles and artificial materials.