A simple approach to DOTAP and its analogs bearing different fatty acids

A simple synthesis of N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methyl sulfate (DOTAP) and its analogs differing in the fatty acids is presented. The synthesis is designed as quasi-one-pot reaction and the precipitating products are purified by simple recrystallization.

Probing the size of a hydrophobic binding pocket within the allosteric site of muscarinic acetylcholine M2-receptors

Hexane-bisammonium-type compounds containing lateral phthalimide moieties are known to have a rather high affinity for the allosteric site of muscarinic M2 receptors. In order to get more insight into the contribution of the lateral substituents for alloster binding affinity, a series of compounds with unilaterally varying imide substituents were synthesized and tested for their ability to retard allosterically the dissociation of [3H]N-methylscopolamine from the receptor protein (control t1/2 = 2 min; 3 mM MgHCO4, 50 mM Tris, pH 7.3, 37 degrees C). Among the test compounds, the naphthalimide containing agent (half maximum effect at ECs5,diss = 60 nM) revealed the highest potency. Apparently, its affinity for the allosteric site in NMS-occupied receptors is 20fold higher compared with the phthalimide containing parent compound W 84. Analysis of quantitative structure-activity relationships yielded a parabolic correlation between the volume of the lateral substituents and the allosteric potency. The maximal volume was determined to be approximately 600 A3 suggesting that the allosteric binding site contains a binding pocket of a defined size for the imide moiety.

Antimalarial activity of compounds interfering with Plasmodium falciparum phospholipid metabolism: comparison between mono- and bisquaternary ammonium salts

On the basis of a previous structure-activity relationship study, we identified some essential parameters, e.g. electronegativity and lipophilicity, required for polar head analogues to inhibit Plasmodium falciparum phospholipid metabolism, leading to parasite death. To improve the in vitro antimalarial activity, 36 cationic choline analogues consisting of mono-, bis-, and triquaternary ammonium salts with distinct substituents of increasing lipophilicity were synthesized. For monoquaternary ammonium salts, an increase in the lipophilicity around nitrogen was beneficial for antimalarial activity: IC(50) decreased by 1 order of magnitude from trimethyl to tripropyl substituents. Irrespective of the polar head substitution (methyl, ethyl, hydroxyethyl, pyrrolidinium), increasing the alkyl chain length from 6 to 12 methylene groups always led to increased activity. The highest activity was obtained for the N,N,N-tripropyl-N-dodecyl substitution of nitrogen (IC(50) 33 nM). Beyond 12 methylene groups, the antimalarial activities of the compounds decreased slightly. The structural requirements for bisquaternary ammonium salts in antimalarial activity were very similar to those of monoquaternary ammonium salts, i.e. polar head steric hindrance and lipophilicity around nitrogen (methyl, hydroxyethyl, ethyl, pyrrolidinium, etc.). In contrast, with bisquaternary ammonium salts, increasing the lipophilicity of the alkyl chain between the two nitrogen atoms (from 5 to 21 methylene groups) constantly and dramatically increased the activity. Most of these duplicated molecules had activity around 1 nM, and the most lipophilic compound synthesized exhibited an IC(50) as low as 3 pM (21 methylene groups). Globally, this oriented synthesis produced 28 compounds out of 36 with an IC(50) lower than 1 microM, and 9 of them had an IC(50) in the nanomolar range, with 1 compound in the picomolar range. This indicates that developing a pharmacological model for antimalarial compounds through choline analogues is a promising strategy.

Polycations as displacer in high-performance bioseparation

Displacement chromatography is an interesting but up to now rarely used type of preparative biochromatography. The lack of well-engineered and accessible displacer contributes to this phenomenon. In this paper a novel type of displacer is introduced for cation-exchange displacement chromatography, which will soon become commercially available. The molecule is a well-defined PolyDADMAC [poly(diallyldimethylammonium chloride)] with a molar mass of less than 35000 g/mol, an exclusively linear structure and a molar mass polydispersity of less than 1.5. A method for synthesizing such a polymer at high yields is described. The PolyDADMAC is shown to be an efficient displacer of basic proteins from strong cation-exchange columns.

New quaternary ammonium oxicam derivatives targeted toward cartilage: synthesis, pharmacokinetic studies, and antiinflammatory potency

Analogues of nonsteroidal antiinflammatory drugs (NSAIDs) oxicams, in which the active group was linked to a quaternary ammonium function [(4-hydroxy-2-methyl-2H-1,2-benzothiazine-1, 1-dioxide-3-carboxamido)2-methylpyridinium iodide or piroxicam-N(+) and [3-(4-hydroxy-2-methyl-2H-1,2-benzothiazine-1, 1-dioxide-3-carboxamido)propyl]trimethylammonium iodide or propoxicam-N(+)] were synthesized. Compounds were labeled with tritium for piroxicam-N(+) and carbon-14 for propoxicam-N(+). Pharmacokinetic studies conducted on rats showed that these molecules were able to highly concentrate in joint cartilages but their bioavailability by the oral way was low. Only propoxicam-N(+) exhibited a sufficient water solubility to be administered intravenously. This molecule was able to restore proteoglycans biosynthesis in cultured articular chondrocytes treated with Interleukin-1beta with an efficiency identical to that of indomethacin. These results suggest that the functionalization of oxicam derivatives by a quaternary ammonium group greatly increases their affinity toward articular cartilage without eliminating their pharmacological activity. New drugs synthesized according to this scheme could be useful to obtain a significant decrease of the efficient administered dose and consequently an attenuation of adverse effects such as digestive toxicity.

In vitro and in vivo study of water-soluble prodrugs of dexanabinol

Trialkylammonium acetoxymethyl esters of dexanabinol were synthesized and evaluated as water-soluble prodrugs. Syntheses were performed by conventional methods; solubility in water and stability in buffers and human plasma were determined by HPLC, and in vivo tissue distribution studies were performed in a rat model. Most of the new derivatives were soluble in water (approximately 50 mg/mL). They were relatively stable in water, while rapidly hydrolyzed in human plasma. Distribution studies indicated that peak concentrations of drug both in blood (30 microg/mL) and brain (2 microg/mL) were rapidly (5 min) achieved after iv administration of a selected prodrug to rats. The blood concentration decreased faster than brain levels which were detectable even after 24 h. Some of the examined esters could be further developed as water soluble prodrugs of dexanabinol.

Novel series of non-glycerol-based cationic transfection lipids for use in liposomal gene delivery

A novel series of nontoxic and non-glycerol-based simple monocationic transfection lipids containing one or two hydroxyethyl groups directly linked to the positively charged nitrogen atom were synthesized. The in vitro transfection efficiencies of these new liposomal gene delivery reagents were better than that of lipofectamine, a widely used transfection agent in cationic lipid-mediated gene transfer. The most efficient transfection formulation was observed to be a 1:1:0.3 mol ratio of DHDEAB (N, N-di-n-hexadecyl-N,N-dihydroxyethylammonium bromide):cholesterol:HDEAB (N-n-hexadecyl-N,N-dihydroxyethylammonium bromide) using a DHDEAB-to-DNA charge ratio (+/-) of 0.3:1. Observation of good transfection at charge ratios lower than 1 suggests that the amphiphile-DNA complex may have net negative charge. Our results reemphasize the important point that in cationic lipid-mediated gene delivery, the overall charge of the lipid-DNA complex need not always be positive. In addition, our transfection results also imply that favorable hydrogen-bonding interactions between the lipid headgroups and the cell surface of biological membranes may have some role for improving the transfection efficiency in cationic lipid-mediated gene delivery.

Stereoselective synthesis of a conformationally defined cyclohexyl carnitine analogue that binds CPT-1 with high affinity

Carnitine (1, 3-hydroxy-4-trimethylammoniobutyrate) is important in mammalian tissue as a carrier of acyl groups. In order to explore the binding requirements of the carnitine acyltransferases for carnitine, we designed conformationally defined cyclohexyl carnitine analogues. These diastereomers contain the required gauche conformation between the trimethylammonium and hydroxy groups but vary the conformation between the hydroxy and carboxylic acid groups. Here we describe the synthesis and biological activity of the all-trans diastereomer (2), which was prepared by the ring opening of trans-methyl 2,3-epoxycylohexanecarboxylate with NaN3. Racemic 2 was a competitive inhibitor of neonatal rat cardiac myocyte CPT-1 (K(i) 0.5 mM for racemic 2; K(m) 0.2 mM for L-carnitine) and a noncompetitive inhibitor of neonatal rat cardiac myocyte CPT-2 (K(i) 0.67 mM). These results suggest that 2 represents the bound conformation of carnitine for CPT-1.

Synthesis and biological activities of dibenzyl dipiperazine diquaternary ammonium salts

Twenty new 4,4'-dibenzoyl-1,1'-dibenzyl-1,1'-(decane-1,5-diyl)-piperazi nium dihalides 5a-l and 1,1'-dibenzyl-1,1'-(decane-1,5-diyl)piperazinium dihydrochloride dihalides 6a-l were prepared and evaluated for their analgesic, sedative and anti-inflammatory activities. Structure-activity relationship studies indicated that the compounds 6c (Ar = 4-NO2C6H5) and 6k (Ar = 3-Me-C6H5) exhibited higher activities than others. Compared with the corresponding compounds 6k and 6l, the presence of benzoyl in the compound 5k and 5l exerted a contrary influence on the activities. 5h and 6h show the highest anti-inflammatory activity (59%, dose 20 mg/kg and 48%, dose 1 mg/kg) in the series 5 and 6, respectively.

Ionic and structural specificity effects of natural and synthetic polyamines on the aggregation and resolubilization of single-, double-, and triple-stranded DNA

DNA condensation, precipitation, and aggregation are related phenomena involving DNA-DNA interactions in the presence of multivalent cations, and studied for their potential implications in DNA packaging in the cell. Recent studies have shown that the condensation/aggregation is a prerequisite for the cellular uptake of DNA for gene therapy applications. To elucidate the ionic and structural factors involved in DNA aggregation, we studied the precipitation and resolubilization of high molecular weight and sonicated calf thymus DNA, two therapeutic oligonucleotides, and poly(dA).2Poly(dT) triplex DNA in the presence of the tetravalent polyamine spermine using a centrifugation assay, Tm measurements, and CD spectroscopy. The ability of spermine to provoke DNA precipitation was in the following order: triplex DNA > duplex DNA > single-stranded DNA. In contrast, their resolubilization at high polyamine concentrations followed a reverse order. The effective concentration of spermine to precipitate DNA increased with Na+ in the medium. Tm data indicated the DNA stabilizing effect of spermine even in the resolubilized state. CD spectroscopy revealed a series of sequential conformational alterations of duplex and triplex DNA, with the duplex form regaining the B-DNA conformation at high concentrations (approximately 200 mM) of spermine. The triplex DNA, however, remained in a Psi-DNA conformation in the resolubilized state. Chemical structural specificity effects were exerted by spermidine and spermine analogues in precipitating and resolubilizing sonicated calf thymus DNA, with N4-methyl substitution of spermidine and a heptamethylene separation of the imino groups of spermine having the maximal difference in the precipitating ability of the analogues compared to spermidine and spermine, respectively. Therapeutically important bis(ethyl) substitution reduced the precipitating ability of the analogues compared to spermine. The effect of the cationicity of polyamines was evident with the pentamines being much more efficacious than the tetramines and triamines. These results provide new insights into the mechanism of DNA precipitation by polyamines, and suggest the importance of polyamine structure in developing gene delivery vehicles for therapeutic applications.

Interfacial indazolization: novel chemical evidence for remarkably high exo-surface pH of cationic liposomes used in gene transfection

Cationic liposomes are used as the carriers of polyanionic genes for combating against hereditary diseases in gene therapy. Studies directed to careful biophysical characterizations of the cationic liposomes commonly used in gene delivery have just begun. Herein, we report on a novel liposomal exo-surface bound indazolization reaction of an amphiphilic arenediazonium salt as evidence for the existence of remarkably alkaline exo-surface of cationic liposomes commonly used in gene transfection. Our results demonstrate that formation of 5-hexadecyl-7-methylindazole in thermal indazolization of 2,6-dimethyl-4-hexadecylbenzenediazonium tetrafluoroborate bound to liposome surface is a strong indication for the existence of significantly high exo-surface pH for cationic liposomes commonly used in gene delivery. The present method can be used in determining the relative exo-surface basicities of various cationic liposomes used in gene transfection and subsequently to find any possible correlation between the transfection efficiencies of these liposomes and their exo-surface basicities.

DNA damage by tert-butoxyl radicals generated in the photolysis of a water-soluble, DNA-binding peroxyester acting as a radical source

The photolysis of the water-soluble perester 1 leads to tert-butoxyl radicals as confirmed by EPR studies with the spin trap 5, 5-dimethylpyrroline N-oxide (DMPO). In the presence of DNA, oxidative cleavage of the latter was demonstrated by the formation of strand breaks in supercoiled pBR 322 DNA and by a substantial decrease of the melting temperature of salmon testes DNA. Guanidine, released from, for example, oxazolone and oxoimidazolidine on base treatment, was observed with calf thymus DNA and 2'-deoxyguanosine. These DNA modifications were effectively inhibited by the radical scavenger di-tert-butylcresol or the hydrogen atom donor glutathione. Photosensitization by the arene chromophore was excluded since the corresponding ester 2 caused no DNA damage, nor were the photoproducts of the perester 1 active. The efficacy of the perester 1 in oxidizing DNA derives from the fact that the tert-butoxyl radicals are photolytically generated in the immediate vicinity of the DNA, due to electrostatic binding of the cationic perester to the DNA, as confirmed by fluorescence measurements. These results demonstrate that the photolysis of perester 1 provides a suitable source of tert-butoxyl radicals in aqueous media, a necessary prerequisite for biochemical investigations.

L-carnitine esters as "soft", broad-spectrum antimicrobial amphiphiles

A new class of antimicrobial, "soft", quaternary ammonium l-carnitine esters, of the type (CH3)3N+-CH2-CHOCO(R1)-CH2-COO(R2) Cl-, has been designed, with R1 and R2 being in general long-chain alkyl substituents. The series shows good activity against a wide range of bacteria, yeasts, and fungi. Lipophilicity has been measured by RP-HPLC method to give the logarithm of the experimental capacity factor (log k'), and a quantitative relationship has been determined between log k' and the theoretical partition coefficient (CLOGP); also, bond-dipole descriptors have been introduced into calculations by accounting for polar moieties present within the apolar cores of the molecules, giving a more refined calculated capacity factor (log k'calcd). Finally the latter has been related to the antimicrobial activity (MIC values). The proposed models are predictive for the best broad-spectrum antimicrobial compound within the series.

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.

Synthesis, activity, and structure--activity relationship studies of novel cationic lipids for DNA transfer

We have designed and synthesized original cationic lipids for gene delivery. A synthetic method on solid support allowed easy access to unsymmetrically monofunctionalized polyamine building blocks of variable geometries. These polyamine building blocks were introduced into cationic lipids. To optimize the transfection efficiency in the novel series, we have carried out structure-activity relationship studies by introduction of variable-length lipids, of variable-length linkers between lipid and cationic moiety, and of substituted linkers. We introduce the concept of using the linkers within cationic lipids molecules as carriers of side groups harboring various functionalities (side chain entity), as assessed by the introduction of a library composed of cationic entities, additional lipid chains, targeting groups, and finally the molecular probes rhodamine and biotin for cellular traffic studies. The transfection activity of the products was assayed in vitro on Hela carcinoma, on NIH3T3, and on CV1 fibroblasts and in vivo on the Lewis Lung carcinoma model. Products from the series displayed high transfection activities. Results indicated that the introduction of a targeting side chain moiety into the cationic lipid is permitted. A primary physicochemical characterization of the DNA/lipid complexes was demonstrated with this leading compound. Selected products from the series are currently being developed for preclinical studies, and the labeled lipopolyamines can be used to study the intracellular traffic of DNA/cationic lipid complexes.

Estimating the electrostatic potential at the acetylcholine receptor agonist site using power saturation EPR

Continuous wave EPR power saturation was used to measure electrostatic potentials at spin-labeled sites. Membrane surface potentials were estimated by power saturating the EPR spectrum of a membrane bound 14N spin-labeled amphiphile in the presence of a neutral or positively charged 15N labeled aqueous spin probe. The potentials that are measured are in good agreement with other probe measurements and with the predictions of the Gouy-Chapman-Stern theory, indicating that this is a valid approach to determine electrostatic potentials. A spin-labeled affinity probe based on maleimidobenzyltrimethylammonium was synthesized and could be derivatized to a sulfhydryl near either agonist site on the nicotinic acetylcholine receptor. The amplitudes of motion of the spin-probe on the ns time scale are significantly different when the two labeled sites are compared, and the probe is more restricted in its motion when attached to the more easily labeled site. When attached to this agonist site, power saturation EPR yields an electrostatic potential of -15 mV. Two other sulfhydryl-specific probes were used to label this site in reconstituted receptor containing membranes. These probes show less contact with the receptor and reduced electrostatic potentials, indicating that there is a strong spatial dependence to the potential at the agonist site. This work demonstrates that power saturation EPR provides a general method that can be used to estimate electrostatic potentials at any specifically spin-labeled macromolecular site.

Optimization of transfection of human endothelial cells

Recently developed transfection methods for mammalian cells provide a powerful means for the study of gene function. Unfortunately, human endothelial cells were relative refractory to the classic transfection techniques. In this study we compared the usability of calcium phosphate, DEAE-dextran transfection, transferrinfection, lipofection, and electroporation for the transfection of early passage HUVECs and for the human endothelial cell lines ECV 304 and EA.hy 926. The classic transfection methods resulted in no or only marginal expression of the reporter gene E. coli beta-galactosidase. For lipofection experiments we compared the commercially available liposome formulations DOTAP and Transfectam with liposomes prepared of dimethyldioctadecylammoniumbromide (DDAB) or 1,2-dimyristyloxypropyl-3-dimethylhydroxyethyl ammonium bromide (DMRIE) as the cationic lipid compound and dioleylphosphatidylethanolamine (DOPE) or Azolectin (a crude fraction of soybean lipids, commercially available as phosphatidylcholine II) as neutral co-lipid. Because the protocol for the chemical synthesis of DMRIE has not been published yet, we developed a protocol for the chemical synthesis of this cationic lipid. With transfection protocols optimized for each cell line, we could achieve transfection efficiencies up to 2%. Compared to the other methods used, the lipofection proved to be a reliable technique for the efficient transfection of the human endothelial cell lines ECV 304 and EA.hy 926. Although we achieved a maximum transfection efficiency of 0.45% for the lipofection of HUVEC, the electroporation seemed to be the better choice for these cells.

A novel cationic lipid greatly enhances plasmid DNA delivery and expression in mouse lung

Effective gene therapy for lung tissue requires the use of efficient vehicles to deliver the gene of interest into lung cells. When plasmid DNA encoding chloramphenicol acetyltransferase (CAT) was administered intranasally to BALB/c mice without carrier lipids, CAT activity was detected in mouse lung extracts. Plasmid DNA delivered with optimally formulated commercially available transfection reagents expressed up to 10-fold more CAT activity in lung than observed with naked DNA alone. Liposome formulations consisting of (+/-)-N-(3-aminopropyl)-N,N-dimethyl-2,3-bis (dodecyloxy)-1-propanaminium bromide (GAP-DLRIE) plus the neutral colipid dioleoylphosphatidylethanolamine (DOPE) enhanced CAT expression by more than 100-fold relative to plasmid DNA alone. A single administration of GAP-DLRIE liposome-CAT DNA complexes to mouse lung elicited peak expression at days 1-4 posttransfection, followed by a gradual return to baseline by day 21 postadministration. Readministration of GAP-DLRIE liposome CAT complexes at day 21 led to another transient peak of reporter gene expression. Histological examination of lungs treated with GAP-DLRIE complexed beta-galactosidase DNA revealed that alveolar epithelial cells were the primary locus of expression and that up to 1% of all alveoli contained epithelial cells expressing the transgene.

Synthesis and antimicrobial activity of new quaternary ammonium chlorides

Decyldimethylamine reacts readily with chloromethylalkyl ethers of sulfides, chloromethylbenzyl ethers or sulfides and chloromethylcycloalkyl ethers to give quaternary ammonium chlorides in very good yields. All the chlorides studied showed antimicrobial activity. The relationship between the chemical structure and antimicrobial activity was analyzed by rough sets.

2,6,6-Trimethyl-2-oxo-1,3-dioxa-6-azonia-2-phosphocyclooctane iodide

The eight-membered ring in the title compound, C7H17NO3P+.I-, has a boat-chair conformation, with the local mirror plane passing through the cyclic O atom and methylene C atom adjacent to the N atom. The P = O bond is pseudo-axial and the P-CH3 bond is pseudo-equatorial. The P-N distance is 3.821 (2) A.