Novel polyaminolipids enhance the cellular uptake of oligonucleotides

Optimizing Transfection Efficiency of Spermine Polar Head Cholesterol-Based Cationic Lipids with Amino Acid Linker

In this work, a series of spermine polar head cholesterol-based cationic lipids with various amino acid spacers were synthesized and evaluated as non-viral gene delivery systems. The physicochemical properties of the resulting lipoplexes, formed from these lipids and DOPE, were assessed, including zeta-potential, DNA binding and DNA protection from serum. Transfection efficiency and cytotoxicity were examined under serum-free and 10-40 % serum-containing conditions. The results showed that the physicochemical properties of cationic lipids, both with and without amino acid spacers, were not significantly different. Cationic liposomes composed of lipid Sper-Ahx-Chol, which has a 6-aminohexanoic acid spacer, and DOPE exhibited greater transfection efficiency in HeLa cells compared to Lipofectamine3000, both in the absence and presence of 10-40 % serum. Additionally, lipid Sper-His-Chol with a histidine spacer and Sper-Ahx-Chol showed higher efficiency than Lipofectamine3000 against HEK293T under 40 % serum conditions. These results suggest that the incorporation of amino acids into the cationic lipids can significantly enhance their DNA delivery efficiency. Specifically, certain amino acid modifications improved transfection efficiency while maintaining low cytotoxicity. Our findings highlight the potential of amino acid-tailored cationic lipids as promising vectors for enhanced DNA delivery.

Polyene-based cationic lipids as visually traceable siRNA transfer reagents

Cationic lipids are promising non-viral vectors for the cellular delivery of nucleic acids. Important considerations for the development of new delivery vectors are enhanced uptake efficiency, low toxicity and traceability. Traceable gene transfer systems however typically require the inclusion of a labeled excipient, and highly sensitive imaging instrumentation to detect the presence of the label. Recently, we reported the synthesis and characterization of colored, polyene cationic phospholipidoids composed of a rigid, polyenoic acid of predetermined dimension (C20:5 and C30:9) paired with flexible saturated alkyl chains of varying lengths (12:0, 14:0, 16:0, 18:0, 20:0 carbons). Herein, the potential of these cationic phospholipids as siRNA carriers was evaluated through standard liposomal formulations in combination with a neutral helper lipid DOPE. The polyene-based lipids were compared with a standard cationic lipid for siRNA-delivery into luciferase expressing HR5-CL11 cells. Within the series of lipids screened, knockdown results indicated that polyene cationic phospholipids paired with longer saturated alkyl chains are more effective as gene transfer agents, and perform comparably with the commercial lipid EPC. Furthermore, the chromophore associated with the polyene chain allowed tracking of the siRNA delivery using direct observation. The polyene lipoplexes were tracked on both a macroscopic and microscopic level either as a single-component or as a multi-component lipoplex formulation. When combined with a reference EPC, effective knockdown and tracking abilities were combined in a single preparation.

Assessment of the cellular internalization of thermolytic phosphorothioate DNA oligonucleotide prodrugs

The bioactivity of a CpG-containing phosphorothioate DNA oligonucleotide with thermolytic 2-(N-formyl-N-methylamino)ethyl (fma) thiophosphate groups in mice led us to investigate the parameters affecting the internalization of these thermosensitive DNA prodrugs in various cell lines. Flow cytometry and confocal microscopy analyses indicate that 5'-fluoresceinated fma-phosphorothioate DNA sequences are poorly internalized in Vero, HeLa and GC-2 cells. However, when four fma-thiophosphate groups of a 15-nucleotide long oligothymidylate prodrug are replaced with 3-(N,N-dimethylamino)prop-1-yl thiophosphate functions, internalization of the positively charged prodrug, under physiological conditions, increased fourfold in HeLa and 40-fold in Vero or GC-2 cells. No cytotoxic effects are observed in Vero cells even at an extracellular prodrug concentration of 50 μM over a period of 72 h. Confocal microscopy studies show that internalization of the positively charged oligothymidylate prodrug in Vero cells is time-dependent with early trafficking of the DNA sequence through endosomal vesicles and, eventually, to the nucleus of the cells. Thus, the incorporation of four 3-(N,N-dimethylamino)prop-1-yl thiophosphate groups into thermosentive fma-phosphorothioate DNA prodrugs is an attractive strategy for efficient cellular internalization of these nucleic acid-based drugs for potential therapeutic indications.

Peptoids and polyamines going sweet: Modular synthesis of glycosylated peptoids and polyamines using click chemistry

Sugar moieties are present in a wide range of bioactive molecules. Thus, having versatile and fast methods for the decoration of biomimetic molecules with sugars is of fundamental importance. The glycosylation of peptoids and polyamines as examples of such biomimetic molecules is reported here. The method uses Cu-catalyzed azide alkyne cycloaddition to promote the reaction of azidosugars with either polyamines or peptoids. In addition, functionalized nucleic acids were attached to polyamines via the same route. Based on a modular solid-phase synthesis of peralkynylated peptoids with up to six alkyne groups, the latter were modified with azidosugar building blocks by using copper-catalyzed azide alkyne cycloadditions. In addition, the up-scaling of some particular azide-modified sugars is described.

A molecular beacon strategy for real-time monitoring of triplex DNA formation kinetics

We used a molecular beacon (MB) containing a 15-mer triplex-forming oligonucleotide (TFO) to probe in real-time the kinetics of triplex DNA formation in the left side of the TCl tract (502-516) of the c-src proto-oncogene in vitro. The metal ions Na+, K+, and Mg2+ stabilized triplex DNA at this site. The pseudo-first-order rate constant (kpsi) and the second-order association rate constant (k1) for the binding of the MB to the target duplex in 10 mM sodium phosphate buffer, pH 7.3, increased from 3.2 +/- 0.9 to 15 +/- 2.8 x 10(-3) s(-1) and 6.4 +/- 1.8 to 30 +/- 5.6 x 102 M(-1) s(-1), respectively, on increasing the MgCl2 concentration from 1 to 2.5 mM. Similar values were obtained for the triplex DNA stabilized by NaCl (100-250 mM). Surprisingly, the values were around 2 times higher in the presence of KCl. The AG of triplex formation in the presence of 1 mM MgCl2, 150 mM NaCl, and 150 mM KCl were -7.8 +/- 0.3, -8.2 +/- 0.3 and -8.7 +/- 0.7 kcal/mol respectively, despite significant differences in the values of deltaH and deltaS, suggesting enthalpy-entropy compensation in the stabilization of the triplex DNA by these metal ions. These results show the utility of MBs ih probing triplex DNA formation and in evaluating kinetic and thermodynamic parameters important for the design and development of TFOs as triplex DNA-based therapeutic agents.

Non-viral vector-mediated uptake, distribution, and stability of chimeraplasts in human airway epithelial cells

BACKGROUND

Chimeraplasty is a novel methodology that uses chimeric RNA/DNA oligonucleotides (chimeraplasts) to stimulate genomic DNA repair. Efficient uptake and nuclear localization of intact chimeraplasts are key parameters to achieve optimal correction of mutation defects into specific cell types.

METHODS

A 5'-end FITC-labeled 68-mer RNA/DNA oligonucleotide was complexed with the polycation polyethylenimine (PEI) and the cationic lipids Cytofectin and GenePorter. Flow cytometry was employed to evaluate chimeraplast uptake under different conditions. Intracellular chimeraplast distribution and co-localization with endocytosis markers were assessed by confocal microscopy. Relative quantification of chimeraplast metabolism was performed by denaturing PAGE and GeneScan(trade mark) analysis.

RESULTS

In airway epithelial cells, optimized chimeraplast uptake reached near 100% efficiency with the carriers tested. However, chimeraplast nuclear localization could only be achieved using PEI or Cytofectin. Chimeraplast/GenePorter lipoplexes were retained in the cytoplasm. PEI polyplexes and Cytofectin lipoplexes displayed different uptake rates and internalization mechanisms. Chimeraplast/PEI polyplexes were internalized at least partially by fluid-phase endocytosis. In contrast, phagocytosis may have contributed to the internalization process of large-sized chimeraplast/Cytofectin lipoplexes. Moreover, significant chimeraplast degradation was detected 24 h after transfection with both PEI polyplexes and Cytofectin lipoplexes, although the latter seemed to confer a higher degree of protection against nuclease degradation.

CONCLUSION

Both Cytofectin and PEI are efficient for chimeraplast nuclear uptake into airway epithelial cells. However, despite the distinct structures and trafficking pathways of the corresponding complexes, none of them could prevent nuclease-mediated metabolism of the chimeric oligonucleotides. These findings should be taken into account for future investigations of chimeraplast-mediated gene repair in airway epithelial cells.

Use of perfluorocarbon (fluorinert) to enhance reporter gene expression following intratracheal instillation into the lungs of Balb/c mice: implications for nebulized delivery of plasmids

Perfluorocarbons combine high respiratory gas dissolving capabilities with extreme chemical and biological inertness and therefore offer an attractive option as an excipient in the area of pulmonary therapeutics. Perfluorocarbons have also been shown to "float" mucus, because of their high densities (1.9-2.5 g/mL), which may hold potential in gene delivery for cystic fibrosis patients, in terms of enhancing penetration through highly viscous mucus and thereby providing access to target epithelial cells to correct the gene defect. Additionally, their low surface tension allows for better dispersion. A commonly available perflurocarbon, heptacosafluorotributylamine (Fluorinert), was used to deliver either plasmid DNA (pDNA) alone or cationic-lipid-complexed plasmid DNA to the lungs of Balb/c mice by direct intratracheal instillation. The complexes consisted of supercoiled (SC) plasmid DNA (4.7 Kb, 0.625 mg/mL) and lipid (ethyldimyristoyl phosphatidylcholine [EDMPC]/cholesterol [1:1 mole ratio], with pDNA (3:1 mg pDNA/mM EDMPC in 20 mM Tris-HCl pH 8.0) expressing chloramphenicol acetyl transferase (CAT) or beta-galactosidase (beta-Gal). pDNA alone was supplemented with 14% w/v Fluorinert. Cationic lipid/pDNA complexes were supplemented with 3, 8, and 14% w/v Fluorinert. Results showed that the CAT expression from pDNA alone was enhanced 24 x using 14% w/v Fluorinert, whereas that from the cationic-lipid-formulated pDNA was enhanced 7 x using 14% w/v Fluorinert. Immunohistochemistry showed that beta-Gal expression was primarily from epithelial cells and not from F4/80 or MAC3 antigen-stained cells (predominantly macrophages), indicating efficient delivery.

Enhanced delivery of antisense oligonucleotides with fluorophore-conjugated PAMAM dendrimers

PAMAM dendrimers are cationic polymers that have been used for the delivery of genes and oligonucleotides to cells. However, little is known about the behavior of dendrimer-nucleic acid complexes once they reach the cell interior. To pursue this issue, we prepared dendrimers conjugated with the fluorescent dye Oregon green 488. These were used in conjunction with oligonucleotides labeled with a red (TAMRA) fluorophore in order to visualize the sub-cellular distribution of the dendrimer-oligonucleotide complex and of its components by two-color digital fluorescence microscopy. The 2'-O:-methyl antisense oligonucleotide sequence used in these studies was designed to correct splicing at an aberrant intron inserted into a luciferase reporter gene; thus effective delivery of the antisense agent results in the expression of the reporter gene product. The dendrimer-oligonucleotide complex remained associated during the process of uptake into vesicular compartments and eventual entry into the nucleus. Since the pharmacological activity of the antisense compound was manifest under these conditions, it suggests that the dendrimer-oligonucleotide complex is functionally active. A surprising result of these studies was that the Oregon green 488-conjugated dendrimer was a much better delivery agent for antisense compounds than unmodified dendrimer. This suggests that coupling of relatively hydrophobic small molecules to PAMAM dendrimers may provide a useful means of enhancing their capabilities as delivery agents for nucleic acids.

Delivery systems for antisense oligonucleotides

In vitro, the efficacy of the antisense approach is strongly increased by systems delivering oligodeoxyribonucleotides (ODNs) to cells. Up to now, most of the developed vectors favor ODN entrance by a mechanism based on endocytosis. Such is the case for particulate systems, including liposomes (cationic or non-cationic), cationic polyelectrolytes, and delivery systems targeted to specific receptors. Under these conditions, endosomal compartments may represent a dead end for ODNs. Current research attempts to develop conditions for escaping from these compartments. A new class of vectors acts by passive permeabilization of the plasma membrane. It includes peptides, streptolysin O, and cationic derivatives of polyene antibiotics. In vivo, the interest of a delivery system, up to now, has appeared limited. Development of vectors insensitive to the presence of serum seems to be a prerequisite for future improvements.

Nature of linkage between the cationic headgroup and cholesteryl skeleton controls gene transfection efficiency

Three novel cationic cholesterol derivatives with different modes of linkage between the cationic headgroup and the cholesteryl backbone have been synthesized and used as mixtures with 1, 2-dioleoyl-L-alpha-glycero-3-phosphatidyl ethanolamine (DOPE) for liposome-mediated gene transfection. A pronounced improvement in gene transfer efficiency was observed when the cationic center was appended to the cholesteryl backbone using an ether linkage as opposed to when the linkages were based on either ester or urethane groups. Amphiphiles with ether links such as cholest-5-en-3beta-oxyethane-N,N,N-trimethyl ammonium bromide (2) and cholest-5-en-3beta-oxyethane-N,N-dimethyl-N-2-hydroxyethyl ammonium bromide (3) showed transfection efficiencies considerably greater than commercially available gene transfer reagents. Notably, the transfection ability of 2 with DOPE in the presence of serum was significantly greater than Lipofectamine((R)) and Lipofectin((R)). Interestingly, 3 did not require the helper lipid DOPE for transfection. This suggests that these newly described cholesterol-based amphiphiles should be very promising in liposome-mediated gene transfection. The advantage that the ether linkage possesses would be important in the design of newer, more efficient cholesterol-based delivery reagents.

Studies on uptake, sub-cellular trafficking and efflux of antisense oligodeoxynucleotides in glioma cells using self-assembling cationic lipoplexes as delivery systems

The cellular uptake of antisense oligodeoxynucleotides (ODNs) may be enhanced by the use of carriers such as cationic liposomes or lipoplexes, but little is known about the intracellular fate and subcellular trafficking of these systems in target cells. In this study, we report on the cellular uptake and biodistribution of ODNs in the presence and absence of optimised self-assembled cationic lipoplexes using the C6 glioma cell line as an in vitro model. Biotin or radiolabelled 15-mer phosphorothioate (PS) ODNs were synthesised and their cellular uptake and subcellular biodistribution characterised in the presence and absence of an optimised cationic lipoplex delivery system using studies ranging from cellular association, cellular efflux and transmission electron microscopy (TEM). Ultrastructural studies clearly showed PS ODNs in the absence of liposomal delivery to be sequestered within endosomal and lysosomal vesicular bodies indicative of endocytic uptake. ODNs were also visible, to a lesser extent, in the nucleus and cytoplasm. By employing DOSPA (2'-(1",2"-dioleoyloxypropyldimethyl-ammonium bromide)-N-ethyl-6-amidospermine tetra trifluoroacetic acid) and DOPE (dioleoylphosphatidylethanolamine) complex in a 3 : 1 ratio, as a delivery system for ODNs at a optimal lipid/DNA charge ratio of 1 : 1, the level of ODN cellular association was significantly increased by approximately 10-12 fold with a concomitant change in subcellular distribution of PS ODN. TEM studies indicated enhanced penetration of ODN within the cytosol and the cell nucleus with reduced presence in vesicular compartments. Efflux studies confirmed that cationic lipoplexes promoted entry of ODNs into 'deeper' cellular compartments, consistent with endosomal release. Optimised cationic lipoplexes improved cellular delivery of ODNs by enhancing cell association, uptake and by favourably modulating the intracellular trafficking and distribution of ODNs into non-vesicular compartments including the cytosol and nucleus.

The regiochemical distribution of positive charges along cholesterol polyamine carbamates plays significant roles in modulating DNA binding affinity and lipofection

We have quantified the effects of the regiochemical distribution of positive charges along the polyamine moiety in lipopolyamines for DNA molecular recognition. High affinity binding leads to charge neutralisation, DNA condensation and ultimately to lipofection. Binding affinities for calf thymus DNA were determined using an ethidium bromide displacement assay and condensation was detected by changes in turbidity using light scattering. The in vitro transfection competence of cholesterol polyamine carbamates was measured in CHO cells. In the design of DNA condensing and transfecting agents for non-viral gene therapy, the interrelationship of ammonium ions, not just their number, must be considered.

Decreased bone resorption, osteoclast differentiation, and expression of vacuolar H+-ATPase in antisense DNA-treated mouse metacarpal and calvaria cultures ex vivo

Expression and function of vacuolar H(+)-ATPase, a key enzyme in bone resorption, were monitored in antisense DNA-treated bone organ cultures ex vivo. A novel fluoroimmunoassay was used to quantitate mRNA levels after treatment with various antisense, sense, or random DNA oligonucleotides. Conventional slot blots and in vitro translation experiments were used to monitor the efficiency of the antisense molecules. In cell cultures, the used antisense molecules were transported into osteoclasts and a population of mononuclear cells. A significant decrease in bone resorption and in the expression of the 16 kDa, 31 kDa, 42 kDa, 60 kDa, 70 kDa, and 116 kDa subunits of V-ATPase was seen after antisense treatment. Also, osteoclast differentiation was decreased in antisense-treated mouse metacarpal cultures. These data show that the proper function of V-ATPase in osteoclasts requires expression of the 16 kDa, 31 kDa, 42 kDa, 60 kDa, 70 kDa, and 116 kDa subunits of V-ATPase. Antisense DNA molecules can be used to inhibit osteoclast differentiation and function in tissue cultures, in which the physical and chemical cellular environment resembles that in vivo. However, more studies are needed to learn if antisense DNA molecules can be used for inhibiting bone resorption also in vivo.

Selectivity of spermine homologs on triplex DNA stabilization

We synthesized seven homologs of spermine (H2N(CH2)3NH(CH2)nNH(CH2)3NH2, where n = 2-9; n = 4 for spermine) and studied their effects on melting temperature (Tm), conformation, and precipitation of poly(dA).2poly(dT). The triplex DNA melting temperature, Tm1 was 34.4 degrees C in the presence of 150 mM KCl. Addition of spermine homologs increased Tm1 in a concentration-dependent and structure-dependent manner, with 3-6-3 (n = 6) exerting optimal stabilization. The dTm1/dlog[polyamine] values were 9-24 for these compounds. The duplex melting temperature, Tm2 was insensitive to homolog concentration and structure, suggesting their ability to stabilize triplex DNA without altering the stability of the underlying duplex. Circular dichroism spectral studies revealed psi-DNA formation in a concentration-dependent and structure-dependent manner. Phase diagrams were constructed showing the critical ionic/polyamine concentrations stabilizing different structures. These compounds also exerted structural specificity effects on precipitating triplex DNA. These data provide new insights into the ionic/structural determinants affecting triplex DNA stability and indicate that 3-6-3 is an excellent ligand to stabilize poly(dA).2poly(dT) triplex DNA under physiologic ionic conditions for antigene therapeutics.

Phosphorothioate oligodeoxyribonucleotides dissociate from cationic lipids before entering the nucleus

Antisense oligonucleotides complementary to specific mRNA sequences are widely used inhibitors of gene expression in vitro and in vivo . In vitro cationic lipids have been demonstrated to increase the pharmacological activity of antisense oligonucleotides by increasing cellular uptake and facilitating nuclear accumulation. We have investigated the intracellular fate of oligonucleotide/cationic lipid complexes using fluorescently labeled lipids and oligonucleotides targeted to protein kinase C-alpha. After addition to cells the lipids initially co-localized with the oligonucleotide on the cell surface and in fine punctate structures within the cytoplasm. At later times the oligonucleotide began to accumulate in the nucleus as well as the cytoplasm. In contrast, the cationic lipid remained localized to the cell surface and the cytoplasm and was never found in the nucleus. Expression of protein kinase C-alpha mRNA did not begin to decline until after oligonucleotide was seen in the nucleus. This was also coincident with the transient appearance of a smaller mRNA transcript believed to result from RNase H cleavage of protein kinase C-alpha mRNA. These data suggest that although cationic lipids facilitate uptake of oligonucleotides, the complex must disassociate before the oligonucleotide can gain access to the nucleus and induce degradation of targeted mRNA.

Gene transfer with lipospermines and polyethylenimines

It is an obvious and basic principle that to be efficient, gene therapy requires effective gene transfer followed by adequate gene expression. However, getting DNA, a pro-drug, into the cell and into the nucleus, remains a crucially limiting factor. Even recombinant viral methods still show poor performances in clinical situations and non-viral methods are considered classically to be of yet lower efficiency. Here, we consider the mode of action, the nature of the complexes formed with DNA and the transfection potentials of two categories of inert, cationic vectors, the lipospermines and polyethylenimine. Both are among the best vectors currently available for in vitro work. Moreover, polyethylenimine is proving to be a versatile and effective carrier for different in vivo situations, especially for delivering genes into the mammalian brain.

Effect of serum components on the physico-chemical properties of cationic lipid/oligonucleotide complexes and on their interactions with cells

The interactions among serum components and cationic lipid-nucleic acid complexes are central to the understanding of how serum inhibits cellular delivery of oligonucleotides in vitro and in vivo. In this study, we show that several serum proteins, in particular bovine serum albumin (BSA), lipoproteins (HDL and LDL) and macroglobulin, interact with cationic lipid/oligonucleotide complexes, alter the complex diameter and zeta potential (from positive to negative values), and significantly interfere with the ability of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) to deliver phosphorothioate oligonucleotides (ODN) into cells. Serum and BSA do not dissociate the ODN and lipid components, therefore inhibition of delivery cannot be attributed to a displacement of cationic lipid from the ODN. Rather BSA at 2.5 mg/ml, comparable to the amount found in 10% serum, decreases the cell association of ODN by about 5-fold and nuclear uptake of ODN by greater than 20-fold. In contrast, immunoglobulin G, the other major serum component, alters the zeta potential from positive to near neutral, has a modest effect on the diameter of the complex but does not affect cell association or nuclear delivery of the ODN at amounts found in 10% serum. Other molecules found in serum, specifically oleic acid and heparin, displace the ODN from the complex and thus interfere with delivery. This displacement is attenuated by first incubating the complex with BSA. Another manifestation of serum-complex interactions is that ODN significantly and cationic liposomes slightly, activate complement. However, formation of the complex markedly reduces the complement activation of the ODN. Finally, the effect of serum can be partially counteracted by the selection of the helper lipid (DOPE or cholesterol). Inclusion of a helper lipid reduces the effective charge ratio (cationic groups/anionic thioates) required to deliver ODN into cells and permits delivery in the presence of greater percentages of serum in the culture medium. These results support the current view that the binding of serum proteins to the complex is a significant factor in modulating the activity of cationic lipid-ODN complexes in culture and after intravenous administration.

Transfection of myoblasts in primary culture with isomeric cationic cholesterol derivatives

Transfection of satellite cells from dog muscle (myoblasts) in primary culture has been optimized with respect to the position of the cholesteryl moiety along the polyamine chain of spermidine or spermine. Spermidine or spermine were derivatized with cholesterylchloroformate giving rise to three isomers in the case of spermidine and two isomers for spermine that were separated by reversed-phase high-performance liquid chromatography (rp-HPLC). The position of the cholesteryl moiety was assigned by 13C-NMR and coelution with synthetic isomers of defined structure. The isomeric cationic lipids were evaluated for their transfection activity in myoblasts from dog muscle and a human lung epithelial cell line (A549) using plasmid DNA expressing the luciferase reporter gene. The results showed that the position of the cholesteryl moiety is of critical importance for efficient transfection of myoblasts in primary culture with isomers having a derivatized secondary amine being significantly more effective than those with a derivatized primary amine. On the contrary, differences in the A549 cell line were less pronounced and did not follow the same pattern. The results show that slight structural differences between cationic lipids lead to significantly different transfection efficiencies for myoblasts in primary culture. This may also represent an advantage in view of cell or organ targeting.

Transfection by cationic liposomes using simultaneous single cell measurements of plasmid delivery and transgene expression

Cationic liposomes are potentially important gene transfer vehicles, although their application has been limited by relatively low efficiency of transgene expression. Single cell quantitative methods, such as those used in this study, should permit a more detailed understanding of the relationships between delivered plasmid and transgene expression. Intracellular plasmid delivery and transgene expression were measured simultaneously using photoconjugated ethidium monoazide as an intracellular plasmid delivery marker and green fluorescent protein (GFP(S65T)) as a transgene expression marker. Quantitative flow cytometry was used to estimate plasmid copy number and GFP(S65T) molecules in single cells. The plasmid was delivered to HeLa cells with a cationic liposome vehicle containing 1,2-dioleoyloxy-3-trimethylammonium-propane and dioleoylphosphatidylethanolamine (1:1 mol/mol). Treatment was carried out continuously for 24 h. Flow cytometry measurements on 20, 000 cells were performed during treatment and for 48 h post-treatment. On a single cell basis, transgene expression efficiency and average GFP(S65T) expression level increased with intracellular plasmid copy number. After 3-h exposure to the liposomal vector, more than 95% of the cells were positive for plasmid entry, but none had detectable transgene expression. Maximum transgene expression was achieved at 24 h and remained unchanged at the 72-h measurement. At 24 h, the average positive cell contained 1.6 x 10(5) plasmid copies and 2.3 x 10(6) GFP(S65T) molecules. Importantly, the measurement strategies revealed that transgene expression varied widely within the entire cell population. Although only 30% of all cells expressed transgene, the subpopulation of cells that rapidly incorporated the vector demonstrated 100% efficiency in transgene expression. This study identifies parameters that modulate highly efficient transgene expression from plasmid delivery by cationic liposomes.

Sequence-specific inhibition of the tumor necrosis factor-alpha receptor I gene by oligodeoxynucleotides containing N7 modified 2'-deoxyguanosine

Tumor necrosis factor-alpha (TNF-alpha) is a highly pleiotropic cytokine produced mainly by activated macrophages. This cytokine has been found to mediate the growth of certain tumors, the replication of HIV-1, septic shock, cachexia, graft-versus-host disease, and autoimmune diseases. The binding of TNF-alpha to the p55 tumor necrosis factor receptor type I (TNFRI) is considered one of the initial steps responsible for the multiple physiologic effects mediated by TNF-alpha. The role of TNF-alpha as an inflammatory mediator through TNFRI makes both of these genes attractive targets for intervention in both acute and chronic inflammatory diseases. We have designed antisense oligodeoxynucleotides (ODNs) containing chemically modified purine and pyrimidine bases that specifically inhibit TNFRI expression and functions. These ODNs were designed to hybridize to the 3'-polyadenylation signal region of the TNFRI gene. In cell-based assays, gene-specific antisense inhibition occurred in a dose-dependent fashion at submicromolar concentrations in the presence of cellular uptake enhancing agents. Within ODN sets with a common pattern of stabilizing backbone substitution, the inhibition of the gene expression is found to be correlated with the affinity of the ODNs for their cognate mRNA target sites, providing direct evidence for an antisense mechanism of action. In addition, events triggered by the binding of TNF-alpha to TNFRI, such as the production of IL-6 and IL-8, were significantly reduced by treatment of cells with the anti-TNFRI ODN. Therefore, antisense ODNs can be used to control biologic processes mediated by TNF-alpha and may be useful as therapeutic agents to treat conditions resulting from overproduction of TNF-alpha.

Deoxyribonucleic acid triplex formation inhibits granulocyte macrophage colony-stimulating factor gene expression and suppresses growth in juvenile myelomonocytic leukemic cells

Juvenile myelomonocytic leukemia (JMML) is a severe childhood malignancy. The autocrine production of GMCSF is believed to be responsible for the spontaneous proliferation of JMML cells. A nuclear factor-kappaB (NF-kappaB)/Rel binding site within the GM-CSF gene promoter, termed the kappaB element, plays an important role in controlling transcription from the GM-CSF gene. We investigated the effect of an oligonucleotide GM3, directed to form a DNA triple helix across this kappaB element, on growth and GM-CSF production by JMML cells. Treatment of these cells, either unstimulated or induced by TNFalpha, with GM3 led to a significant and specific inhibition of both GM-CSF production and spontaneous colony formation. This constitutes the first report linking specific triplex-mediated inhibition of gene transcription with a functional outcome; i.e., cell growth. We observed the constitutive presence of NF-kappaB/Rel proteins in the nucleus of JMML cells. The constitutive and TNFalpha-induced NF-kappaB/Rel complexes were identical and were composed mainly of p50 and c-Rel proteins. Treatment of the cells with a neutralizing anti-TNFalpha monoclonal antibody completely abrogated constitutive nuclear expression of NF-kappaB/Rel proteins. These results indicate that the aberrant, constitutive GM-CSF gene activation in JMML is maintained by TNFalpha-mediated activation of NF-kappaB/Rel proteins. Our findings identify the molecular basis for the autocrine TNFalpha activation of the GM-CSF gene in JMML and suggest potential novel and specific approaches for the treatment of this aggressive childhood leukemia.

Basis of pulmonary toxicity associated with cationic lipid-mediated gene transfer to the mammalian lung

Studies have indicated that although abundant levels of transgene expression could be achieved in the lungs of mice instilled with cationic lipid:pDNA complexes, the efficiency of gene transfer is low. As a consequence, a relatively large amount of the complex will need to be administered to the human lungs to achieve therapeutic efficacy for indications such as cystic fibrosis. Because all cationic lipids exhibit some level of cytotoxicity in vitro, we assessed the safety profile of one such cationic lipid, GL-67, following administration into the lungs of BALB/c mice. Dose-dependent pulmonary inflammation was observed that was characterized by infiltrates of neutrophils, and, to a lesser extent, macrophages and lymphocytes. The lesions in the lung were multifocal in nature and were manifested primarily at the junction of the terminal bronchioles and alveolar ducts. The degree of inflammation abated with time and there were no apparent permanent fibrotic lesions, even in animals that were treated at the highest doses. Analysis of the individual components of the complex revealed that the pulmonary inflammation was primarily cationic lipid-mediated with a minor contribution from the neutral co-lipid DOPE. Associated with the lesions in the lungs were elevated levels of the pro-inflammatory cytokines interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma) that peaked at days 1-2 post-instillation but resolved to normal limits by day 14. Total cell counts, primarily of neutrophils, were also significantly elevated in the bronchoalveolar lavage fluids of GL-67:pDNA-treated mice between days 1 and 3 but returned to normal limits by day 14. No specific immune responses were detected against the cationic lipid or plasmid DNA in mice that had been either instilled or immunized with the individual components or complex, nor was there any evidence of complement activation. These studies indicate that a significant improvement in the potency of cationic lipid:pDNA formulations is desirable to minimize the toxicity associated with cationic lipids.

Optimization of plasmid vectors for high-level expression in lung epithelial cells

Nonviral gene therapy approaches use a plasmid vector to express the desired transgene. We have systematically examined several regulatory elements within plasmid vectors that govern gene expression, e.g., the promoter, enhancer, intron, and polyadenylation signal, by constructing a series of plasmids that differed only in the particular sequence element being evaluated. Of the several promoters and polyadenylation signal sequences that were tested, the human cytomegalovirus (CMV) immediate early gene promoter and the addition of polyadenylation signal sequences from the bovine growth hormone (BGH) gene or rabbit beta-globin gene produced the highest levels of expression in vitro. The inclusion of a hybrid intron 3 to the promoter further increased expression 1.6-fold. The addition of a region of the CMV enhancer 5' to several weak promoters increased expression 8- to 67-fold, and co-transfection with a second plasmid encoding a chimeric transcription factor also enhanced expression. On the basis of these results, the CMV promoter, the hybrid intron, and the BGH polyadenylation signal were selected for consistent high level expression in vitro and in the mouse lung. However, expression was transient, with greater than 60% loss of activity in the first 7 days. This transient expression was not specific to CMV promoter-containing plasmids, because plasmids containing other heterologous promoters showed a similar profile of transient expression in vivo. These comparative analyses begin to provide a basis for the development of optimized expression plasmids for gene therapy of lung diseases.

Detailed analysis of structures and formulations of cationic lipids for efficient gene transfer to the lung

Cationic lipid-mediated gene transfer of cystic fibrosis transmembrane conductance regulator (CFTR) cDNA represents a promising approach for treatment of cystic fibrosis (CF). Here, we report on the structures of several novel cationic lipids that are effective for gene delivery to the lungs of mice. An amphiphile (#67) consisting of a cholesterol anchor linked to a spermine headgroup in a "T-shape" configuration was shown to be particularly efficacious. An optimized formulation of #67 and plasmid vector encoding chloramphenicol acetyl-transferase (CAT) was capable of generating up to 1 microgram of CAT enzyme/lung following intranasal instillation into BALB/c mice. This represents a 1,000-fold increase in expression above that obtained in animals instilled with naked pDNA alone and is greater than 100-fold more active than cationic lipids used previously for CFTR gene expression. When directly compared with adenovirus-based vectors containing similar transcription units, the number of molecules of gene product expressed using lipid-mediated transfer was equivalent to vector administration at multiplicities of infection ranging from 1 to 20. The level of transgene expression in the lungs of BALB/c mice peaked between days 1 and 4 post-instillation, followed by a rapid decline to approximately 20% of the maximal value by day 7. Undiminished levels of transgene expression in the lung could be obtained following repeated intranasal administration of #67:DOPE:pCF1-CAT in nude mice. Transfection of cells with formulations of #67:DOPE:pCF1-CFTR generated cAMP-stimulated CFTR chloride channel and fluid transport activities, two well-characterized defects associated with CF cells. Taken together, the data demonstrate that cationic lipid-mediated gene delivery and expression of CFTR in CF lungs is a viable and promising approach for treatment of the disease.