Lipofectin enhances cellular uptake of antisense DNA while inhibiting tumor cell growth

Transfection of cultured eukaryotic cells using cationic lipid reagents

The development of high-efficiency methods for the introduction of functional genetic material into eukaryotic cells using cationic lipid-based transfection reagents has accelerated biology research in studies of gene expression, control of cell growth, and cell lineage. In this unit, DNA transfection is described for adherent mammalian cells (both cells and primary cultures) along with an alternate procedure for enhanced transfection. A protocol is also described for transfection of suspension cells (lymphoid, myeloid and leukemic-derived cells). In addition, transfection of RNA into adherent mammalian cells and DNA transfection into insect cells are presented. Importantly, a detailed procedure is described for optimization of reagents and transfection conditions.

Transfection of cultured eukaryotic cells using cationic lipid reagents

The development of high-efficiency methods for the introduction of functional genetic material into eukaryotic cells using cationic lipids has accelerated biological research in the studies of gene expression, control of cell growth, and cell lineage. Transfection mediated by cationic lipids is commonly used in industrial protein production as well as in some clinical gene therapy protocols. Replacing our previous unit on this topic, this new version describes how to perform transfection of adherent and suspension cells, insect cells, and RNA transfection using the cationic lipid system.

What sense lies in antisense inhibition of inducible nitric oxide synthase expression?

The impact of nitric oxide (NO) synthesized after activation by proinflammatory cytokines and/or bacterial products by an inducible NO synthase (iNOS) is still contradictory. Expression of iNOS in inflammatory reactions is often found predominantly in cells of epithelial origin, and in these cases NO may serve as a protective agent limiting pathogen spreading, downregulating local inflammatory reactions by inducing production of Th2-like responses in a classical feedback circle, or limiting tissue damage during stress conditions. However, an abundant amount of data on chronic human disorders with predominant proinflammatory Th1-like reactions points to a destructive role of iNOS activity calling for a specific inhibition. Various methods to inhibit iNOS have been established to elucidate a protective versus a destructive role of NO during various stresses. In this review, we focus on antisense (AS)-mediated gene knock-down as a relatively new method to inhibit NO production and summarize the techniques applied and their successes. At least in theory, it provides a specific, rapid, and potentially high-throughput method for inhibiting gene expression and function. We here discuss the opportunities of iNOS-directed AS-ODN, and extensively deal with limitations and experimental problems.

Optimization of functional efficacy of phosphorothioate-modified oligonucleotides in a human CD8+ T-cell ex vivo expansion model

Antisense oligodeoxyribonucleotides (ODNs) can specifically inhibit gene expression, but their application to fresh human CD8+ T cells is limited by poor spontaneous uptake (<2%). We have examined and optimized the uptake of phosphorothioate-modified oligodeoxyribonucleotides (PS-ODNs) into these cells in an ex vivo expansion model. Optimal antisense treatments were found to be, for fresh CD8+ T cells, 1 micro m PS-ODNs complexed with lipofectin (LF), which resulted in 35% uptake and 10 micro m PS-ODNs in the absence of LF, for cultured cells, which resulted in 95% uptake. The delivered antisenses were functional, as determined by the inhibition of protein expression. In this respect, partially phosphorothioate-modified ODNs (PS-ODNs-P) were twice as effective as completely modified (PS-ODNs-C), and the antisense specific for the cap site showed the highest protein suppression of those tested (68%). Uptake mechanisms were also investigated. To our knowledge, this is the first optimization of the delivery of antisense oligonucleotides into human CD8+ T cells. This protocol could be used to study the function of a particular gene in cytotoxic T lymphocytes and also by those looking for a method to deliver short interfering RNA into cell lines to specifically suppress a gene of interest.

Modulation of human interferon-gamma biosynthesis by antisense oligodeoxynucleotides

We investigated the inhibition of human interferon-gamma (HuIFN-gamma) production in cultures of lymphocytes with the use of the antisense strategy. Out of a series of antisense oligodeoxynucleotides (ODN) complementary to different regions of the HuIFN-gamma gene, a 16-mer specific for a sequence including the translation initiation codon was the most effective. Here we describe a detailed protocol for the isolation of lymphocytes from buffy coats, the rational design of antisense ODN, and the monitoring of HuIFN-gamma production of the antisense ODN-treated cells.

Liposomes as a gene delivery system

Gene therapy is an active field that has progressed rapidly into clinical trials in a relatively short time. The key to success for any gene therapy strategy is to design a vector able to serve as a safe and efficient gene delivery vehicle. This has encouraged the development of nonviral DNA-mediated gene transfer techniques such as liposomes. Many liposome-based DNA delivery systems have been described, including molecular components for targeting given cell surface receptors or for escaping from the lysosomal compartment. Another recent technology using cationic lipids has been evaluated and has generated substantial interest in this approach to gene transfer.

Effects of oligodeoxynucleotides on the physicochemical characteristics and cellular uptake of liposomes

We studied the effects of a phosphodiester oligodeoxynucleotide (ODN), which is antisense to the site in the neighborhood of the AUG initiation codon of the mouse tumor necrosis factor alpha gene (TNF-alpha), on the physicochemical characteristics and the cellular association of three types of liposomes with different surface charges. The physicochemical characteristics of the liposomes changed after adding ODN. When the ODN/lipid molar ratio was approximately 0.15 in cationic (TMAG) liposomes [consisting of N-(alpha-trimethylammonioacetyl)didodecyl-D-glutamate chloride (TMAG), dilauroylphosphatidylcholine (DLPC), and dioleolylphosphatidylethanolamine (DOPE) in a 1:2:2 ratio], but not in neutral and negatively charged liposomes, then the liposomes aggregated and fused. At higher molar ratios, these changes in TMA liposomes were not evident. In addition, ODN inverted the zeta-potential of TMAG liposomes from positive to negative at an ODN/lipid molar ratio of approximately 0.15. Therefore, the aggregation and fusion induced by ODN could be explained by a lower surface charge repulsion between TMAG liposomes. On the other hand, the association of ODN with RAW264.7 cells, a mouse macrophage-like cell line, was very slight. The cellular association of ODN was significantly enhanced compared with neutral and negatively charged liposomes by encapsulation in TMAG liposomes. The ODN added to liposome suspensions did not affect the rate and extent of TMAG liposome cellular association, even at an ODN/lipid molar ratio of approximately 0.15. These results indicate that the lipid composition and ODN/lipid molar ratio are critical for the physicochemical characteristics of cationic liposomes. However, the changes had less influence on the cellular uptake properties of cationic liposomes.

Improved oligonucleotide uptake and stability by a new drug carrier, the SupraMolecular Bio Vector (SMBV)

Antisense oligodeoxynucleotides are potential therapeutic agents, but their development is still limited by both a poor cellular uptake and a high degradation rate in biological media. The strategy that we propose to face these problems is to use small synthetic carriers, around 30 nm diameter, the SupraMolecular Bio Vectors (SMBV). We used positively charged SMBV and settled the ionic incorporation of negatively charged oligonucleotides into these carriers. A minimal leakage of 10% of total incorporated oligonucleotides was then measured during two months. Both protection and uptake of oligonucleotides were then analyzed. On the one hand, we showed that the incorporation of oligonucleotides into the selected SMBV allows to significantly increase, 8 times, their half-life, in cell growth medium. On the other hand, the internalization of the SMBV, into cells, by an endosomal pathway has been characterized. The essential point is that the SMBV uptake elicits the simultaneous oligonucleotide uptake. The oligonucleotide amount that goes through cells within 5 h can be up to 30 times higher than for free oligonucleotides and the fraction of oligonucleotides that is present in the cytosol is increased up to 10 fold after incorporation into the SMBV. This study demonstrates the ability of SMBV to improve oligonucleotide cellular behaviour.

Reversible permeabilization. A novel technique for the intracellular introduction of antisense oligodeoxynucleotides into intact smooth muscle

Antisense oligodeoxynucleotides (ODNs) have been used to modify gene expression in vitro and are also promising therapeutic agents. Although there are numerous reports of antisense ODN-mediated changes in protein expression of cultured cells, use of these compounds to achieve antisense regulation of specific proteins in intact tissue has been limited. The aims of this study were (1) to define organ culture conditions for ileum smooth muscle that would permit long-term maintenance of force-generating capabilities and normal ultrastructure and (2) to develop a method for efficient introduction of antisense ODNs into intact tissue. Sheets of ODN-containing, reversibly permeabilized rat outer longitudinal ileum were maintained in a serum-free organ culture medium for 1 week without significant decreases in tension response to membrane depolarization or carbachol stimulation; the G protein-coupled calcium sensitization pathway was also intact after 7 days. Reversible permeabilization, a method previously used to load smooth and cardiac muscle with aequorin and heparin, was effective for loading > 95% of ileum smooth muscle cells with a fluorescein-conjugated antisense ODN (5'-AAGGGCCATTTTGTT-FITC-3'). Confocal microscopy of reversibly permeabilized smooth muscle loaded with fluorescent antisense ODNs revealed intense nuclear fluorescence and less intense, homogeneous, cytoplasmic fluorescence. Internally radiolabeled ODNs (homologous to the above sequence) showed complete degradation between 4 and 16 hours after introduction into the cells. In summary, we have demonstrated methods for long-term organ culture and high-efficiency introduction of antisense ODNs into intact smooth muscle sheets. Such methods have broad potential utility for investigating many questions in smooth muscle biology. At present, however, a major limitation of this approach is the short half-life of phosphorothioated ODNs.

Use of cyclodextrin and its derivatives as carriers for oligonucleotide delivery

The use of antisense phosphorothioate oligodeoxynucleotides as tools for modulating gene expression represents a novel strategy for designing drugs to treat a variety of diseases. Several factors, including cellular uptake and internalization of the phosphorothioate oligodeoxynucleotide, are important parameters in determining the effectiveness of antisense agents as therapies. We have used cyclodextrin and its analogs as carriers to increase cellular uptake of phosphorothioate oligodeoxynucleotides. The studies were carried out using 35S-labeled and fluorescent-labeled phosphorothioate oligodeoxynucleotide in human T cell leukemia H9 cell line. Cellular uptake of phosphorothioate oligodeoxynucleotide in the presence of cyclodextrin was found to be concentration and time dependent. Using various cyclodextrin analogs, e.g., 2-hydroxypropyl beta-cyclodextrin (HPCD), hydroxyethyl beta-cyclodextrin (HECD), and a mixture of various hydroxypropyl beta-cyclodextrins (Encapsin), we observed increases in phosphorothioate oligodeoxynucleotide uptake, up to twofold to threefold in 48 hours. Confocal microscopy studies confirmed that oligonucleotide was present intracellularly. Cyclodextrin itself was not toxic at the concentration used. Cyclodextrins did not seem to affect the efflux of phosphorothioate oligodeoxynucleotide from cells. Stability of phosphorothioate oligodeoxynucleotide against endogenous cellular nucleases remained unchanged in the presence of cyclodextrins. These studies suggest that cyclodextrin and its analogs might be used successfully as carriers for oligonucleotide and analogs.

Antisense oligonucleotides as therapeutic agents--is the bullet really magical?

Because of the specificity of Watson-Crick base pairing, attempts are now being made to use oligodeoxynucleotides (oligos) in the therapy of human disease. However, for a successful outcome, the oligo must meet at least six criteria: (i) the oligos can be synthesized easily and in bulk; (ii) the oligos must be stable in vivo; (iii) the oligos must be able to enter the target cell; (iv) the oligos must be retained by the target cell; (v) the oligos must be able to interact with their cellular targets; and (vi) the oligos should not interact in a non-sequence-specific manner with other macromolecules. Phosphorothioate oligos are examples of oligos that are being considered for clinical therapeutic trials and meet some, but not all, of these criteria. The potential use of phosphorothioate oligos as inhibitors of viral replication is highlighted.

Internalization of oligodeoxyribonucleotides by Vibrio parahaemolyticus

The bacterium Vibrio parahaemolyticus was tested for its ability to internalize unmodified as well as modified DNA oligomers without attempting to permeabilize the cells. These experiments were conducted to establish whether it may be feasible to employ antisense oligomers for control of gene expression in Vibrio species without heat-shocking or electroporating the cells. The bacterium was found to bind radiolabeled synthetic oligodeoxyribonucleotides that were added to culture media. Incorporation of a phosphorothioate oligomer into subcellular regions was determined following cellular fractionation. The phosphorothioate was recovered primarily from the periplasm and peptidoglycan layer of the bacterium; however, a significant fraction was recovered from the bacterial cytosol. The extent of uptake depended on both the concentration of oligomer as well as culture medium selected. A maximum of 2.1 x 10(6) oligomers/cell was achieved when a 12-mer phosphorothioate oligomer (10 microM) was added to bacterial cultures in an artificial seawater (Instant Ocean) medium. Several terminally modified oligomers were found to become associated with bacterial cells, albeit less efficiently than the phosphorothioate. None of the oligomers tested was toxic to the bacteria at 0.1 microM, and the phosphorothioate was only marginally toxic at 10 microM. Stability of the oligomers in extracellular and cell-associated fractions was evaluated by PAGE; even after 8 hr of incubation intact phosphorothioate oligomer could be found in both components.