Acid-labile mPEG-vinyl ether-1,2-dioleylglycerol lipids with tunable pH sensitivity: synthesis and structural effects on hydrolysis rates, DOPE liposome release performance, and pharmacokinetics.

A family of 3-methoxypoly(ethylene glycol)-vinyl ether-1,2-dioleylglycerol (mPEG-VE-DOG) lipopolymer conjugates, designed on the basis of DFT calculations to possess a wide range of proton affinities, was synthesized and tested for their hydrolysis kinetics in neutral and acidic buffers. Extruded ∼100 nm liposomes containing these constructs in ≥90 mol % 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) produced dispersions that retained their calcein cargo for more than 2 days at pH 7.5, but released the encapsulated contents over a wide range of time scales as a function of the electronic properties of the vinyl ether linkage, the solution pH, and the mPEG-VE-DOG composition in the membrane. The in vivo performance of two different 90:10 DOPE:mPEG-VE-DOG compositions was also evaluated for blood circulation time and biodistribution in mice, using (125)I-tyraminylinulin as a label. The pharmacokinetic profiles gave a t(1/2) of 7 and 3 h for 90:10 DOPE:ST302 and 90:10 DOPE:ST502, respectively, with the liposomes being cleared predominantly by liver and spleen uptake. The behavior of these DOPE:mPEG-VE-DOG formulations is consistent with their relative rates of vinyl ether hydrolysis, i.e., the more acid-sensitive mPEG-VE-DOG derivatives produced faster leakage rates from DOPE:mPEG-VE-DOG liposomes, but decreased the blood circulation times in mice. These findings suggest that the vinyl ether-based PEG-lipid derivatives are promising agents for stabilizing acid-sensitive DOPE liposomes to produce formulations with a priori control over their pH responsiveness in vitro. Our data also suggest, however, that the same factors that contribute to enhanced acid sensitivity of the DOPE:mPEG-VE-DOG dispersions are also likely responsible for their reduced pharmacokinetic profiles.

Oral bioavailability of the ether lipid plasmalogen precursor, PPI-1011, in the rabbit: a new therapeutic strategy for Alzheimer's disease.

INTRODUCTION: Docosahexaenoic acid (DHA) and DHA-containing ethanolamine plasmalogens (PlsEtn) are decreased in the brain, liver and the circulation in Alzheimer's disease. Decreased supply of plasmalogen precursors to the brain by the liver, as a result of peroxisomal deficits is a process that probably starts early in the AD disease process. To overcome this metabolic compromise, we have designed an orally bioavailable DHA-containing ether lipid precursor of plasmalogens. PPI-1011 is an alkyl-diacyl plasmalogen precursor with palmitic acid at sn-1, DHA at sn-2 and lipoic acid at sn-3. This study outlines the oral pharmacokinetics of this precursor and its conversion to PlsEtn and phosphatidylethanolamines (PtdEtn). METHODS: Rabbits were dosed orally with PPI-1011 in hard gelatin capsules for time-course and dose response studies. Incorporation into PlsEtn and PtdEtn was monitored by LC-MS/MS. Metabolism of released lipoic acid was monitored by GC-MS. To monitor the metabolic fate of different components of PPI-1011, we labeled the sn-1 palmitic acid, sn-2 DHA and glycerol backbone with (13)C and monitored their metabolic fates by LC-MS/MS. RESULTS: PPI-1011 was not detected in plasma suggesting rapid release of sn-3 lipoic acid via gut lipases. This conclusion was supported by peak levels of lipoic acid metabolites in the plasma 3 hours after dosing. While PPI-1011 did not gain access to the plasma, it increased circulating levels of DHA-containing PlsEtn and PtdEtn. Labeling experiments demonstrated that the PtdEtn increases resulted from increased availability of DHA released via remodeling at sn-2 of phospholipids derived from PPI-1011. This release of DHA peaked at 6 hrs while increases in phospholipids peaked at 12 hr. Increases in circulating PlsEtn were more complex. Labeling experiments demonstrated that increases in the target PlsEtn, 16:0/22:6, consisted of 2 pools. In one pool, the intact precursor received a sn-3 phosphoethanolamine group and desaturation at sn-1 to generate the target plasmalogen. The second pool, like the PtdEtn, resulted from increased availability of DHA released during remodeling of sn-2. In the case of sn-1 18:0 and 18:1 plasmalogens with [(13)C(3)]DHA at sn-2, labeling was the result of increased availability of [(13)C(3)]DHA from lipid remodeling. Isotope and repeated dosing (2 weeks) experiments also demonstrated that plasmalogens and/or plasmalogen precursors derived from PPI-1011 are able to cross both the blood-retinal and blood-brain barriers. CONCLUSIONS: Our data demonstrate that PPI-1011, an ether lipid precursor of plasmalogens is orally bioavailable in the rabbit, augmenting the circulating levels of unesterified DHA and DHA-containing PlsEtn and PtdEtn. Other ethanolamine plasmalogens were generated from the precursor via lipid remodeling (de-acylation/re-acylation reactions at sn-2) and phosphatidylethanolamines were generated via de-alkylation/re-acylation reactions at sn-1. Repeated oral dosing for 2 weeks with PPI-1011 resulted in dose-dependent increases in circulating DHA and DHA-containing plasmalogens. These products and/or precursors were also able to cross the blood-retinal and blood-brain barriers.

Enhancing the oral bioavailability of simvastatin with silica-lipid hybrid particles: The effect of supersaturation and silica geometry.

Silica-lipid hybrid (SLH) microparticles are a solidified lipid-based drug delivery system under investigation for their aptitude to enhance the oral bioavailability of poorly water-soluble drugs. The cholesterol-lowering agent, simvastatin (SIM), is poorly water-soluble and undergoes extensive first pass metabolism, resulting in a low oral bioavailability of approximately 5%. Hence, the current pre-clinical studies investigated the application of SLH technology to SIM with a supersaturation approach, aiming to enhance bioavailability and drug loading capacity. Additionally, the effect of silica was explored by evaluating the performance of SLH fabricated with silica of different particle geometries. SLH microparticles with supersaturated SIM loading levels ranging from 100% to 400% above the equilibrium solubility were successfully fabricated using either Aerosil® 300 or Syloid® 244 silica. All SLH formulations existed as white free-flowing powders, consisting of spherical porous microparticles for Aerosil® 300, and aggregated irregular microparticles for Syloid® 244. During in vitro dissolution in pH 7.0 media, the SLH formulations performed up to 4.4-fold greater than pure SIM powder. Furthermore, in vivo oral pharmacokinetics in male Sprague-Dawley rats revealed that the SLH formulations enhanced the oral bioavailability of SIM up to 6.1-fold and 2.9-fold, in comparison to pure SIM powder and a commercially available formulation (Simvastatin Sandoz®), respectively. The greatest in vivo performance enhancement was observed for the SLH formulation manufactured with Syloid® 244 silica with a supersaturation level of 200%. SLH technology demonstrated to be a successful formulation strategy to significantly improve the oral bioavailability of SIM in rodents and therefore, has a strong potential to also improve the oral bioavailability of SIM in humans.

Degradation kinetics study of 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG) by a validated stability-indicating RP-HPLC method.

The chemical stability of 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG), a therapeutic agent for neutropenia, was investigated using a validated stability-indicating reversed phase high-performance liquid chromatographic (RP-HPLC) method. The forced degradation of PLAG was carried out under the stress conditions of hydrolysis (alkaline, acidic and various pH buffers), oxidation, photolysis and heat. A simple, sensitive, specific, robust, precise and accurate RP-HPLC method was developed and validated for evaluating the degradation kinetics of PLAG. The chromatographic validation of various parameters, such as system suitability, detection limit, quantification limit, linearity, accuracy, precision, specificity, robustness and stability, was achieved. The method was validated for linearity, accuracy and precision over the concentration range of 0.7813-100µg/mL (r2=0.9999). The proposed method provided excellent stability study of PLAG indicated by the resolution of degradation products from the drug. Degradation of PLAG provided first order kinetics under all experimental conditions. PLAG was catalysed more rapidly in alkaline and acidic conditions than in neutral conditions. PLAG was relatively stable in photolytic and oxidative conditions compared to hydrolysis and thermal conditions, although this drug was not also stable in these conditions. Exposed to high temperature, PLAG was more rapidly catalysed. The activation energy evaluated from the Arrhenius plot was about 110kJ/mol in the thermal conditions. Additionally, PLAG with a t1/2 of about 400h was very stable at room temperature. Therefore, PLAG was considerably influenced by alkaline and acidic hydrolysis, and thermal degradation.

Effect of inorganic mesoporous carriers on 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol-loaded solid self-emulsifying drug delivery system: Physicochemical characterization and bioavailability in rats.

The purpose of this study was to assess the impact of inorganic mesoporous carriers on the physicochemical properties and oral bioavailability of 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG)-loaded solid self-emulsifying drug delivery system (solid SEDDS). Numerous PLAG-loaded solid SEDDS formulations were prepared by spray drying technique with sodium laurylsulfate (SLS), butylated hydroxyanisole (BHA) and inorganic mesoporous materials as a surfactant, antioxidant and solid carrier, respectively. The mesoporous materials, such as calcium silicate, silicon dioxide and magnesium aluminosilicate were used as the solid carriers. Their physicochemical properties, solubility, dissolution and pharmacokinetic studies in rats were performed compared with drug alone. Three solid SEDDSs composed of PLAG/BHA/SLS/mesopous carrier at the weight ratio of 1:0.0002:0.25:0.5 resulted in a small emulsion droplet and excellent drug loading efficiency. The solid SEDDS formulations prepared with calcium silicate and silicon dioxide showed a rough-surfaced irregular shape and rough-surfaced spheres, respectively. Magnesium aluminosilicate generated a sticky powder, due to its relatively low specific surface area, resulting in insufficient adsorption of PLAG. These solid SEDDSs improved the solubility, dissolution and oral bioavailability of PLAG. Ultimately, the solid SEDDS prepared with silicon dioxide resulted in the best drug loading efficiency, shape, solubility, dissolution and oral bioavailability due to its great specific surface area. Therefore, mesoporous carriers with different specific surface areas markedly influenced the physicochemical properties, solubility, dissolution and oral bioavailability of PLAG-loaded solid SEDDS.

Dietary diacylglycerol in a typical meal suppresses postprandial increases in serum lipid levels compared with dietary triacylglycerol.

OBJECTIVE: The objective of the present study was to verify the effect of a dietary oil, consisting mainly of diacylglycerol (DAG) oil, in a typical meal on postprandial changes in serum triacylglycerol (TAG) and remnant-like particle cholesterol (RLP-C) compared with dietary triacylglycerol (TAG) oil. METHODS: In a double-blind, randomized, crossover design, 43 healthy Japanese men and women ingested test meals (2093 kJ of energy, 30 g of protein, 19 g of lipids, and 51 g of carbohydrates) containing 10 g of DAG oil (DAG meal) or TAG oil (TAG meal). Blood samples were collected in a fasting state (0 h) and at 2, 3, 4, and 6 h after ingestion of the meal. RESULTS: Postprandial TAG, RLP-C, and chylomicron TAG concentrations were significantly lower after the DAG meal compared with the TAG meal. In 29 subjects with fasting serum TAG levels of at least 1.13 mmol/L (100 mg/dL), differences in postprandial serum changes between meal types were even more remarkable and the incremental areas under the response curve (0 to 6 h) for serum TAG and RLP-C concentrations after the DAG meal were significantly smaller than those after the TAG meal. CONCLUSIONS: These results suggest that DAG oil in the daily diet is useful for the prevention of postprandial hyperlipidemia and related disorders.

Development of solid lipid nanoparticles as carriers for improving oral bioavailability of glibenclamide.

A solid lipid nanoparticle (SLN) formulation was developed with the aim of improving the oral bioavailability and the therapeutic effectiveness of glibenclamide (GLI), a poorly water-soluble drug used in the treatment of type 2 diabetes. The SLN was prepared using different lipid components (Precirol® and Compritol®) and preparation procedures. Precirol-based SLN, obtained with the emulsion of solvent evaporation technique gave the best results and was selected for drug loading. Addition of lecithin to the SLN core or PEG coating was effective in increasing the nanoparticles stability in simulated gastric solution. Both such formulations were stable after one month storage at 5±3°C, exhibited the absence of in vitro cytotoxicity, and presented a similar in vitro prolonged-release, reaching 100% release after 24h. The lecithin-containing GLI-loaded SLN formulation, selected for in vivo studies in virtue of its higher EE% than the PEG-coated formulation (70.3% vs 19.6%), showed a significantly stronger hypoglycemic effect with respect to the drug alone, in terms of both shorter onset time and longer duration of the effect. These positive results indicated that the proposed SLN approach was successful in improving GLI oral bioavailability, confirming its potential as an effective delivery system for a suitable therapy of diabetes.

D609-phosphatidylcholine-specific phospholipase C inhibitor attenuates thapsigargin-induced sodium influx in human lymphocytes.

Previously, we reported that the phosphatidylcholine-specific phospholipase C (PC-PLC) inhibitor tricyclodecan-9-yl xanthogenate (D609) potentiates thapsigargin-induced Ca(2+) influx in human lymphocytes. In the present study we examined the effect of D609 on the thapsigargin-induced Na(+) entry. We found that the early phase of the thapsigargin-induced increase in the intracellular Na(+) concentration (approx. 1-2 min after stimulation) was attenuated after preincubation of lymphocytes with D609. By contrast, thapsigargin-induced Na(+) influx was not affected in the presence butan-1-ol, which inhibits phosphatidylcholine-specific phospholipase D (PC-PLD). The thapsigargin-induced Na(+) influx could be mimicked by PC-PLC exogenously added to the lymphocyte suspension, whereas addition of PC-PLD had no effect. In addition, thapsigargin stimulated formation of the physiological PC-PLC products, diacylglycerol. Cell-permeable diacylglycerol analogue, dioctanoyl-glycerol (DOG), produced time- and concentration-dependent increase in the intracellular Na(+) concentration. Both thapsigargin- and DOG-induced Na(+) increases were not affected in the presence of Na(+)/H(+) antiport inhibitor, HOE609, or Na(+)/Ca(2+) antiport inhibitor, dimethylthiourea, as well as in the presence of Co(2+) and Ni(2+), which block store-operated Ca(2+) entry. By contrast, markedly reduced thapsigargin- and DOG-induced Na(+) influx were noted in the presence of flufenamic acid, which blocks the non-selective cation current (I(CRANC)). In conclusion, our results suggest that diacylglycerol released due to the PC-PLC activation contributes to the thapsigargin-induced Na(+) entry.

Dietary diacylglycerol reduces postprandial hyperlipidemia and ameliorates glucose intolerance in Otsuka Long-Evans Tokushima Fatty (OLETF) rats.

OBJECTIVE: The aim of the present study was to determine the effects of dietary diacylglycerol (DG) on the metabolism of lipids and glucose in type II diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats. METHODS: In experiment 1, the rats were orally administered 10 mL/kg of a triacylglycerol (TG) or DG emulsion (15% [w/v] oil), and the subsequent changes in the serum lipid levels were compared. In experiment 2, the rats were fed diets containing 15% DG or TG oil. After 22 weeks, the serum levels of lipids, glucose, and cytokines were determined. In addition, an oral glucose tolerance test (OGTT) was performed on the rats. RESULTS: Administration of an oral fat load caused marked hypertriglyceridemia with a peak at 2 h. Oral DG loading reduced the serum TG increase; the difference between the groups was significant at 4 and 6 h (P < 0.05). Diacylglycerol also markedly reduced the serum free fatty acid concentration increase due to the fat load. After 22 weeks of feeding, dietary DG reduced serum TG levels in the non-fasting state. Moreover, an OGTT revealed enhanced glucose disposal in the DG-fed rats compared with the TG-fed rats. Serum levels of adiponectin, an important insulin-sensitizing adipocytokine, were higher in the DG-fed rats than in the TG-fed rats (P < 0.05). In addition, DG-feeding reduced serum levels of C-reactive protein, a cardiovascular risk factor (P < 0.05). CONCLUSION: These results suggested that dietary DG improves lipid metabolism and glucose tolerance, and retards the progress of diabetes mellitus in OLETF rats.

The metabolism of the xenobiotic triacylglycerols, rac-1- and sn-2- (3-phenoxybenzoyl)-dipalmitoylglycerol, following intravenous administration to the rat.

The metabolism of 3-phenoxybenzoic acid (3PBA) in the form of triacylglycerol conjugates was compared with that of non-esterified 3PBA. Three radiolabeled triacylglycerols (rac-1-(3-phenoxy-[ring-14C]-benzoyl)-2,3-dipalmitoylglycerol (1(3PBA)DPG), sn-2-(3-phenoxy-[ring-14C]benzoyl)-1,3-dipalmitoylglycerol (2(3PBA)DPG) and the "natural" tri-[1-14C]oleoylglycerol) were incorporated into rat VLDL. Nonesterified 3PBA was prepared in rat serum albumin solution. Each preparation was administered i.v. to rats and serial blood samples were taken during the subsequent 6 hr. Urine and faeces were collected and tissue residues determined at 6 hr and 48 hr after administration. Biphasic elimination of 3PBA was observed with half-lives of 18 min and 2 hr. The triacylglycerols showed a rapid first phase and a longer second phase half-life: trioleoylglycerol 26 hr, 1(3PBA)DPG 7.6 hr and 2(3PBA)DPG 17.3 hr. The majority (63-76%) of 3PBA (whether esterified or not) was eliminated within 24 hr in urine, which contained similar profiles of metabolites. The triacylglycerols gave rise to higher tissue residues than did non-esterified 3PBA, particularly in adipose tissue which alone was not significantly depleted of radioactivity between 6 and 48 hr. The results accord with the rapid association of the VLDL-(3PBA)DPG complexes with lipoprotein lipase of the capillary epithelium, followed by hydrolysis to 3PBA, metabolism and elimination but with a proportion being redistributed into adipose tissue, re-esterified and then eliminated relatively slowly.

Activation of nerve growth factor synthesis in primary glial cells by phorbol 12-myristate 13-acetate: role of protein kinase C.

Phorbol 12-myristate 13-acetate (PMA) induces a dramatic production of nerve growth factor (NGF) in primary cultures of newborn mouse astrocytes maintained in a serum-free medium. This stimulation is dose-dependent and a maximal effect on the levels of cell-secreted factor was observed at a concentration of 10 nM. At this concentration, the promoting effect of PMA appears much more important than that elicited by 10% fetal calf serum (FCS) under the same culture conditions. PMA acts primarily on the accumulation of NGF mRNA, which was detected by northern blot analysis after 6 h of treatment. This accumulation may be totally or partially prevented when PMA-treated glial cells are concomitantly exposed to the protein kinase inhibitors H-7, H-9, and to a lesser degree, HA-1004. The known specificity of these inhibitors agrees with the possibility that protein kinase C (PKC), which constitutes so far the sole known target of PMA, represents a key element involved in the stimulation of NGF gene. The role of PKC is further supported by the observation that alpha phorbol didecanoate, which has no activity on PKC, is depleted of effect on the synthesis of NGF. Likewise, 1,2-dioctanoylglycerol (1,2-DOG) has a weak, but significant promoting action on the production of NGF, unlike the 1,3-isomer which is not active on PKC. Finally, a treatment of 15 min with 100 nM PMA is sufficient to stimulate the cells, suggesting that the activation phase of PKC, rather than its down regulation, constitutes an important trigger leading to an increased expression of the NGF gene.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of a novel diolein-based LPDII vector for gene delivery.

LPDII vectors are non-viral vehicles for gene delivery comprised of polycation-condensed plasmid DNA (polyplexes) complexed with anionic pH-sensitive liposomes. Here, we describe a novel LPDII formulation containing polyethylenimine (PEI) polyplexes complexed with anionic pH-sensitive liposomes composed of diolein/cholesteryl hemisuccinate (CHEMS) (6:4 mol/mol). The pH-sensitivity of diolein/CHEMS liposomes was evaluated through quantitative fluorescence measurements of calcein release and particle size analysis. The results indicated that diolein/CHEMS liposomes are stable at physiological pH, but undergo rapid aggregation and fluorescence dequenching at pH values < or =5.0. Using a luciferase reporter gene, in vitro transfection of KB oral cancer cells showed that the transfection efficiency of LPDII vectors was superior to other well-characterized polyplexes and lipoplexes. Results further showed that gene delivery using diolein-containing LPDII vectors was dependent on the PEI nitrogen/DNA phosphate (N/P) ratio, the lipid/DNA weight ratio and the cell line being transfected. Replacing PEI with poly-L-lysine as the DNA condensing agent resulted in only a moderate reduction in transfection activity. Moreover, in contrast to LPDII formulations incorporating dioleoylphosphatidylethanolamine (DOPE), the transfection efficiency of diolein-based LPDII vectors was sustained in media containing up to 50% fetal bovine serum. Since diolein-based LPDII vectors mediate efficient gene transfer and retain their transfection activity in the presence of serum, diolein may be a promising alternative to DOPE for the construction of non-viral vectors for in vivo gene delivery.

Comparison of the lymphatic transport of radiolabeled 1,3-dioleoylglycerol and trioleoylglycerol in rats.

It has been reported that, compared with TAG, DAG suppresses postprandial hypertriacylglycerolemia and reduces visceral fat levels in experimental animals and humans. To clarify the mechanism responsible for these beneficial effects, we compared the lymphatic transport of 1,3-DAG, a major isomer of DAG, and TAG in rats. Male SD rats, after insertion of a cannula into the thoracic duct, were given 1,3-di[1-14C]oleoylglycerol or tri[1-14C]oleoylglycerol via a stomach tube. The 24-h recovery of the radioactivity from 1,3-di[14C]oleoylglycerol in the lymph was slightly but significantly lower than that from tri[14C]oleoylglycerol (81.3+/-1.0 vs. 86.5+/-1.2%, respectively). However, in the first 1-h interval after administration, the recovery of radioactivity from 1,3-dioleoylglycerol was almost half of that from trioleoylglycerol (17.5+/-2.0 vs. 31.1+/-1.4%). The amount of TAG and phospholipids secreted into the lymph was significantly lower 1 h after the administration of 1,3-dioleoylglycerol compared with that after the administration of trioleoylglycerol. More than 90% of the radioactivity recovered in the lymph in the first 3 h was distributed in the TAG fraction for both 1,3-dioleoylglycerol and trioleoylglycerol. These results suggest that slower lymphatic transport of 1,3-DAG compared with TAG could be a factor in the suppression of postprandial hypertriacylglycerolemia. The possibility that the slower lymphatic transport of DAG contributes to the anti-obesity action observed in the feeding of 1,3-DAG cannot be excluded.

Absorption and effects of 3-(N-phenylamino)-1,2-propanediol esters in relation to toxic oil syndrome.

Toxic Oil Syndrome (TOS) was an epidemic disease related to the consumption of rapeseed oil denatured with aniline that made its sudden appearance in Spain in 1981. The fatty acid esters of 3-(N-phenylamino)-1,2-propanediol (PAP), which is a chemical class of by-products resulting from the reaction of aniline with oil components, have shown a strong association with TOS-related oils. These compounds also show some structural similarities to platelet-activating factor (PAF). In search of a toxic agent that could explain the widespread systemic effects observed in TOS patients, we investigated the intestinal absorption and biotransformation of the different PAP esters found in TOS-related oil samples and the possible pathophysiological effect of these mediators and their metabolic products if acting as PAF analogs. Results indicate that PAP esters are absorbed in the gastrointestinal tract and are distributed and stored in different organs, particularly in the liver and brown adipose tissue. PAP in these organs showed different patterns of fatty acids, indicating the ability of the gastrointestinal tract to modify the fatty acid composition of the parent PAP. Thus, the fatty acid profile of the PAP esters found in intestine appears to be related to the type of oil used as vehicle. Some of these PAP esters, when a long acyl chain was present in the sn-1 position of the molecule, showed an inhibitory effect on the PAF synthesis. This is an important observation in line with the systemic nature of the disease.

Diacyl glyceryl ester prodrugs for slow release in the skin: synthesis and in vitro degradation and absorption studies for naproxen derivatives.

Diacyl glyceryl ester derivatives of naproxen were synthesized and tested for transdermal and dermal administration. Diacyl derivatives of aliphatic acids of various chain length were compared. The pharmaceutical properties of these compounds, such as lipophilicity, hydrolysis in a buffer solution at various pH values and degradation in human serum and hairless mouse skin homogenate, were investigated. All the diacyl derivatives were relatively stable in a neutral buffer solution, but were rapidly degraded to release naproxen in human serum and hairless mouse skin homogenate. The diacyl compounds could not penetrate hairless mouse skin in vitro. However, significant absorption into the skin could be measured, and this increased with increasing lipophilicity. A more than 100-fold difference in absorption was observed. The prodrugs were slowly hydrolyzed to naproxen inside the skin. The release of naproxen to the receptor compartment of diffusion cells showed that this type of prodrug could be used for controlled drug delivery.

[Carbon-11 labeled diacylglycerol for signal transduction imaging: effect of the solubilizer on the distribution and radiation dosimetry].

Carbon-11 labeled diacylglycerol (11C-DAG) has been developed as a signal transduction imaging agent for the CNS, and it can visualize the second messenger. For clinical application by positron CT (PET), the 11C-DAG solution must be prepared for intravenous injection. However, the 11C-DAG does not dissolve in water because of its lipophilicity and requires a solubilizer such as human serum albumin (HSA) and Tween 80 (TW-80). We examined the influence of these solubilizers on the tissue distribution of 11C-DAG, and estimated the radiation dosimetry. In the brain, uptake of 11C-DAG dissolved with HSA was 1.3-1.8 times higher than that of dissolved with TW-80. On the other hand, the lung and spleen showed a higher uptake of 11C-DAG using TW-80 than when using HSA. Especially, the lungs showed 20-40 times higher uptake than when using HSA. Also, the washout of radioactivity from tissue was slower, and the dose of radiation exposure was estimated to be higher, with TW-80 than with HSA. Therefore, between TW-80 and HSA with different solubilizing mechanisms, the later was suggested to be a better solubilizer of 11C-DAG.

Solid lipid nanoparticles-loaded topical gel containing combination drugs: an approach to offset psoriasis.

AIM: The primary aim of present work was to develop effective combination drug therapy for topical treatment of psoriasis. METHODS: Betamethasone dipropionate and calcipotriol loaded solid lipid nanoparticles (CT-BD-SLNs) were prepared by hot melt high shear homogenization technique, which were then incorporated in Carbopol gel matrix. The anti-psoriatic potential was tested by sequential in vitro (skin permeation and dermal distribution, anti-proliferative effect in HaCaT cells) and in vivo (Draize patch irritation, transepidermal water loss (TEWL) and anti-psoriatic mouse tail studies) experiments. RESULTS: A negligible amount in receptor compartment, yet confined distribution of drugs to epidermal and dermal region of skin was observed in case of SLNs, which is essential for safe and effective anti-psoriatic therapy. Draize patch test and TEWL demonstrated negligible skin irritation and better skin tolerability of SLNs. The in vitro HaCaT cell line study demonstrated that SLNs delayed the abrupt growth of keratinocytes, while in vivo mouse tail model showed that SLNs gel significantly decreased the epidermal thickness and increased melanocyte count in comparison to commercial Daivobet® ointment. CONCLUSIONS: The developed SLNs gel is expected to be potential strategies for treatment of psoriasis and other topical diseases.

Complete inhibition of extranodal dissemination of lymphoma by edelfosine-loaded lipid nanoparticles.

BACKGROUND: Lipid nanoparticles (LNs) made of synthetic lipids Compritol(®) 888 ATO and Precirol(®) ATO 5 were developed with an average size of 110.4 ± 2.1 and 103.1 ± 2.9 nm, and an encapsulation efficiency above 85% for both type of lipids. These LNs decrease the hemolytic toxicity of the drug by 90%. MATERIALS & METHODS: Pharmacokinetic and biodistribution profiles of the drug were studied after intravenous and oral administration of edelfosine-containing LNs. RESULTS: This provided an increase in relative oral bioavailability of 1500% after a single oral administration of drug-loaded LNs, maintaining edelfosine plasma levels over 7 days in contrast to a single oral administration of edelfosine solution, which presented a relative oral bioavailability of 10%. Moreover, edelfosine-loaded LNs showed a high accumulation of the drug in lymph nodes and resulted in slower tumor growth than the free drug in a murine lymphoma xenograft model, as well as potent extranodal dissemination inhibition.

Oral peptide delivery by tetraether lipid liposomes.

The aim of this study is to improve of oral peptide delivery by a novel type of liposomes containing tetraether lipids (TELs) derived from archaea bacteria. Liposomes were used for the oral delivery of the somatostatin analogue octreotide. TELs were extracted from Sulfolobus acidocaldarius and subsequently purified to single compounds. Liposomes were prepared by the film method followed by extrusion. Vesicles in size between 130 and 207 nm were obtained as confirmed by photon correlation spectroscopy. The pharmacokinetics of radiolabeled TELs in liposomes was investigated after oral administration to rats. 1.6% of the applied radioactivity in fed and 1.5% in fasted rats was recovered in the blood and inner organs after 2h, while most of the radioactivity remained in the gastro-intestinal tract. After 24h the percentage of radioactivity in inner organs was reduced to 0.6% in fed rats, respectively 1.0% in fasted animals. Several liposomal formulations containing dipalmitoyl phosphatidylcholine (DPPC) and TELs in different ratios were loaded with octreotide and orally administered. Liposomes with 25% TEL could improve the oral bioavailability of octreotide 4.1-fold and one formulation with a cationic TEL derivative 4.6-fold. TEL-liposomes probably act by protecting the peptide in the gastro-intestinal tract.

In vitro intestinal bioaccessibility of alkylglycerols versus triacylglycerols as vehicles of butyric acid.

Butyric acid has been the subject of much attention last years due to its bioactivity. However, the potential advantages of butyrate are limited by the problem to reach enough plasma concentrations; therefore, pro-drugs have been proposed as an alternative to natural butyrate. A comparative study on in vitro intestinal digestion of 2,3-dibutyroil-1-O-octadecyl glycerol (D-SCAKG) and tributyrin (TB), as potential pro-drugs of butyric acid, was performed. Aliquots were taken at different times of digestion for studying the extent and rate of hydrolysis of both substrates. The micellar phase (MP) and oily phase (OP) formed in the digestion media were separated and their composition in lipid products was analyzed. Initially, it was confirmed that the in vitro model reproduced physiological results by testing against olive oil as a standard lipid. The progress of in vitro intestinal digestion of D-SCAKG was slower than that of TB. TB hydrolyzed completely to butyric acid, whereas D-SCAKG mainly yielded 2-butyroil-1-O-octadecyl glycerol (M-SCAKG), followed by butyric acid and 1-O-octadecyl glycerol (AKG). The MP from both substrates mainly consisted of butyric acid. Minor levels of M-SCAKG and AKG were also found in the MP after hydrolysis of D-SCAKG, the M-SCAKG being mainly distributed in the OP. Therefore, D-SCAKG produced a stable form of esterified butyric acid as M-SCAKG after in vitro intestinal digestion, unlike TB. Additionally, such a product would integrate both bioactive compounds, butyric acid and alkylglycerol, within the same molecule. Free butyric acid and AKG would be also released, which are lipid products of interest as well.