4-Aminopyridyl-based CYP51 inhibitors as anti-Trypanosoma cruzi drug leads with improved pharmacokinetic profile and in vivo potency

CYP51 is a P450 enzyme involved in the biosynthesis of the sterol components of eukaryotic cell membranes. CYP51 inhibitors have been developed to treat infections caused by fungi, and more recently the protozoan parasite Trypanosoma cruzi, the causative agent of Chagas disease. To specifically optimize drug candidates for T. cruzi CYP51 (TcCYP51), we explored the structure-activity relationship (SAR) of a N-indolyl-oxopyridinyl-4-aminopropanyl-based scaffold originally identified in a target-based screen. This scaffold evolved via medicinal chemistry to yield orally bioavailable leads with potent anti-T. cruzi activity in vivo. Using an animal model of infection with a transgenic T. cruzi Y luc strain expressing firefly luciferase, we prioritized the biaryl and N-arylpiperazine analogues by oral bioavailability and potency. The drug-target complexes for both scaffold variants were characterized by X-ray structure analysis. Optimization of both binding mode and pharmacokinetic properties of these compounds led to potent inhibitors against experimental T. cruzi infection.

Synthesis and application of 188Re-MN-16ET/Lipiodol in a hepatocellular carcinoma animal model

INTRODUCTION

Hepatocellular carcinoma is the most common form of primary hepatic carcinoma. A new N(2)S(2) tetradentate ligand, N-[2-(triphenylmethyl)thioethyl]-3-aza-19-ethyloxycarbonyl-3-[2-(triphenylmethyl)thioethyl]octadecanoate (H(3)MN-16ET), was introduced and labeled with (188)Re to create (188)Re-MN-16ET in the Lipiodol phase. The potential of (188)Re-MN-16ET/Lipiodol for hepatoma therapy was evaluated in a hepatocellular carcinoma animal model of Sprague-Dawley rats implanted with the N1S1 cell line.

METHODS

Synthesis of H(3)MN-16ET was described, and characterization was identified by infrared, nuclear magnetic resonance and mass spectra. We compared the effects of transchelating agents (glucoheptonate or tartaric acid) and a reducing agent (stannous chloride) on the complexing of (188)Re-perrhenate and H(3)MN-16ET. Twenty-four rats implanted with hepatoma were injected with 3.7 MBq/0.1 ml of (188)Re-MN-16ET/Lipiodol or (188)Re-MN-16ET via transcatheter arterial embolization. Biodistribution experiments and single-photon emission computed tomography imaging were performed to investigate tumor accumulation.

RESULTS

H(3)MN-16ET was proved to easily conjugate with the Re isotope and showed good solubility in Lipiodol. The radiochemical purity of (188)Re-MN-16ET/Lipiodol with 10 mg tartaric acid and stannous chloride was shown to be more than 90%. The major distribution sites of (188)Re-MN-16ET in Sprague-Dawley rats were hepatoma and the liver. However, the radioactivity at the tumor site postadministered with (188)Re-MN-16ET was quickly decreased from 9.15±0.23 (at 1 h) to 2.71%±0.18% of injected dose/g (at 48 h). The biodistribution and micro-single-photon emission computed tomography/computed tomography image data showed that (188)Re-MN-16ET/Lipiodol was selectively retained at the tumor site, with 11.55±1.44, 13.16±1.46 and 10.67%±0.95% of injected dose/g at 1, 24 and 48 h postinjection, respectively. The radioactivity in normal liver tissue was high but significantly lower than that of the tumors.

CONCLUSION

H(3)MN-16ET is a suitable tetradentate ligand for (188)Re labeling. From the animal data, we suggest that (188)Re-MN-16ET/Lipiodol has the potential to be a therapeutic radiopharmaceutical for hepatoma treatment.

Antitumor activity and pharmacokinetics of liposomes containing lipophilic gemcitabine prodrugs

BACKGROUND

Gemcitabine is a deoxycytidine analogue that exhibits antitumoral activity against adenocarcinomas of the colon, lung and pancreas. After intravenous injection, gemcitabine is rapidly converted to the inactive metabolite 2'-deoxy-2',2'-difluorouridine by cytidine deaminase.

MATERIALS AND METHODS

To improve the pharmacokinetic behavior and the antitumor activity of the drug, the gemcitabine prodrug, 4-(N)-stearoylgemcitabine (C18gem) was incorporated in liposomes and both the pharmacokinetic and the in vivo activity of this formulation intravenously or peritumorally administered in nude female CR1:Nu/Nu(CD-1)BR mice grafted with HT-29 and KB 396p cells were studied.

RESULTS

The C18gem-liposomes showed both higher plasma half life and tumor regression than control and gemcitabine.

CONCLUSION

The incorporation of C18gem-prodrug in liposomes increased the plasma half life of the drug resulting in increased accumulation in the tumor cells and a higher level of antitumoral efficacy. The results obtained with different tumors sensitive to gemcitabine support the efficacy of this proposed drug delivery system.

Dynamics and partitioning of spin-labeled stearates into the lipid domain of stratum corneum

The EPR spectra of the positional isomers n-doxyl stearic acids (n-DSA), with n=5, 12 and 16, and 5-doxyl methyl stearate (5-DMS) structured in the lipid domain of intact stratum corneum (SC), are characterized by the thermodynamic equilibrium of two distinct spectral components provided by two different motional states of the spin-labeled chains. A two-component model used in the EPR spectra simulations provided the relative populations of the components, allowing for the calculation of the thermodynamic profile. Based on a detailed investigation, the more motionally restricted population of spin labels (component 1) is found to arise when the spin label is hydrogen-bonded to the polar surfaces of the membranes, while the less motionally restricted population (component 2) is generated by spin labels nonhydrogen-bonded and more deeply inserted in the hydrophobic core. The 5-DSA is bound tightly to the polar surfaces (DeltaG(o)2 --> 1=-1.75 kcal/mol and DeltaH(o)2 --> 1=-13.8 kcal/mol), whereas the more lipophilic 5-DMS has a major spin population stabilized in the hydrophobic core (DeltaG(o)2 --> 10.57 kcal/mol and DeltaH(o)2 --> 1=-9.1 kcal/mol). Upon lipid-depleting SC increases the interactions of the probe with the polar surfaces, thereby decreasing its rotational diffusion. In contrast, the treatment of SC with oleic acid, a permeation enhancer, drastically increases the mobility of the spin labels, particularly that of component 1, and the thermodynamic equilibrium shifts towards the formation of component 2. A mechanism for water permeation in SC is also proposed.

Effect of Terplex/VEGF-165 gene therapy on left ventricular function and structure following myocardial infarction. VEGF gene therapy for myocardial infarction

BACKGROUND

We used a novel lipopolymeric gene delivery system, TeplexDNA, to transfect myocardium with plasmid vascular endothelial growth factor-165 (pVEGF) and evaluated the ability of pVEGF to preserve left ventricular function and structure after coronary ligation in a rabbit model.

METHODS

New Zealand white rabbits underwent circumflex coronary ligation after direct intramyocardial injection of either Terplex alone or Terplex + 50 microg pVEGF-165. Serial echocardiography and histologic studies were performed (n = 12/group). Mortality did not differ between groups. The data is reported as the mean +/- standard deviation.

RESULTS

Over the 21 days following coronary ligation, pVEGF-165-treated animals demonstrated significant improvement in fractional shortening (20-25%, p = 0.02), long axis two-dimensional ejection fraction (42-51%, p=0.02) and short axis m-mode ejection fraction (46-54%, p = 0.02). No significant improvements were noted in the control group. VEGF-treated animals had a 50% increase in peri-infarct vessel density and a trend towards a smaller infarct size (20% vs. 29%, p = 0.10). In animals receiving pVEGF-165, the diastolic ventricular area increased from 1.87 +/- 0.24 cm2 prior to ligation to 2.19 +/- 0.23 cm2 at 21 days following ligation, compared to an increase from 1.84 +/- 0.38 to 2.54 +/- 0.55 cm2 over the same period in control animals (p = 0.03). Similarly, the systolic ventricular area in VEGF-165 animals increased from 1.06 +/- 0.26 cm2 prior to ligation to 1.50 +/- 0.29 cm2 at 21 days following ligation, compared to an increase from 1.16 +/- 0.30 to 1.86 +/- 0.43 cm2 over the same period in the control animals (p = 0.04).

CONCLUSION

TerplexDNA mediated delivery of plasmid VEGF administered at the time of coronary occlusion improves left ventricular function and reduces left ventricular dilation following myocardial infarction.

The microencapsulated ascorbic acid releasein vitro and its effect on iron bioavailability

The present study was carried out to examine the stability of microencapsulated ascorbic acid in simulated-gastric and intestinal situation in vitro and the effect of microencapsulated ascorbic acid on iron bioavailability. Coating materials used were polyglycerol monostearate (PGMS) and medium-chain triacylglycerol (MCT), and core materials were L-ascorbic acid and ferric ammonium sulfate. When ascorbic acid was microencapsulated by MCT, the release of ascorbic acid was 6.3% at pH 5 and 1.32% at pH 2 in simulated-gastric fluids during 60 min. When ascorbic acid was microencapsulated by PGMS, the more ascorbic acid was released in the range of 9.5 to 16.0%. Comparatively, ascorbic acid release increased significantly as 94.7% and 83.8% coated by MCT and PGMS, respectively, for 60 min incubation in simulated-intestinal fluid. In the subsequent study, we tested whether ascorbic acid enhanced the iron bioavailability or not. In results, serum iron content and transferring saturation increased dramatically when subjects consumed milks containing both encapsulated iron and encapsulated ascorbic acid, compared with those when consumed uncapsulated iron or encapsulated iron without ascorbic acid. Therefore, the present data indicated that microencapsulated ascorbic acid with both PGMS and MCT were effective means for fortifying ascorbic acid into milk and for enhancing the iron bioavailability.

Minoxidil-containing dosage forms: skin retention and after-rinsing hair-growth promotion

Three kinds of topical dosage forms of minoxidil (MXD), namely vesicles, double emulsions, and an inclusion complex with hydoxypropyl-beta-cyclodextrin (HP-beta-CD), were prepared. The skin retention of MXD in the preparations was evaluated in vitro using hairless mouse skins. After applying the preparations onto the skin and rinsing it, the amount of the drug left on the skin was determined using HPLC. Retention was the highest when the drug was encapsulated in cationic vesicles. Nonionic vehicle, the double emulsion, and HP-beta-CD left no significant amount of the drug after rinsing the skin. Thus, an ionic interaction between the cationic vehicle and negatively charged skin is likely responsible for the relatively high skin retention. In vivo hair growth-promotion effect of each dosage form was investigated, in which the sample application onto the clipped backs of female mice (C57BL6) and the subsequent rinsing of the backs were done once a day for 30 days. Only MXD in the cationic vesicles had hair growth promotion effect, possibly due to significant skin retention.

Preparation of albumin preferential surfaces on poly(vinyl chloride) membranes via surface self-segregation

Poly(vinyl chlorides)-graft-[omega-stearyl-poly(ethylene oxide)] (PVC-g-SPEO), which has a poly(vinyl chloride) (PVC) backbone, poly(ethylene oxide) (PEO) side chain, and stearyl end groups, has been synthesized. Self-organizing blends of the amphiphilic comb polymer in poly(vinyl chlorides) have been examined as a means to create albumin preferential surfaces on polymer films. X-ray photoelectron spectroscopy (XPS) analysis indicates substantial surface segregation of the PVC-g-SPEO. A surface concentration of 59.9 EO wt % is achieved by the solution casting and heat treatment of a film with a bulk concentration of only 3.78 EO wt %. In the aqueous environment, the surface rearrangement of PVC-g-SPEO/PVC blend film is limited and presents a high interfacial energy and high depolar component of interfacial energy due to the "tail-like" SPEO side chain. Protein adsorption tests confirm that PVC-g-SPEO/PVC blend films absorb high levels of albumin and dramatically resist fibrinogen adsorption. Surfaces to attract and reversibly bind albumin, which might diminish the occurrence of thrombosis, inflammation, and infection, are developed by self-organizing blends of the amphiphilic comb polymer in poly(vinyl chlorides).

The effect of fatty acid substitution on the in vitro release of amphotericin B from micelles composed of poly(ethylene oxide)-block-poly(N-hexyl stearate-L-aspartamide)

The effect of fatty acid substitution on the in vitro release of amphotericin B (AmB) from micelles composed of poly(ethylene oxide)-block-poly[N-(6-hexyl stearate)-L-aspartamide] (PEO-b-PHSA) was investigated. PEO-b-PHSA at 11, 50 and 70% of stearic acid substitution self assembled into micelles that effectively encapsulate AmB by solvent evaporation and dialysis methods. The sustained release of AmB from PEO-b-PHSA micelles was evidenced, by measuring the transfer of the drug to lipid vesicles [dipalmitoyl phosphatidylcholine:cholesterol:dimyristoyl phosphatidyglycerol (3:1:0.25)]. The release of AmB for PEO-b-PHSA micelles was markedly influenced by the degree of fatty acid substitution--as it increased, the release of AmB slowed. Accordingly, drug release was found to correlate with haemolysis induced by AmB encapsulated in PEO-b-PHSA micelles. At 11% stearic acid substitution, encapsulation of AmB had little effect on the drug's ability to induce untoward haemolysis. In contrast, AmB stably encapsulated in PEO-b-PHSA micelles at 50 and 70% caused no hemolysis up to 20 microg/ml. Lastly, PEO-b-PHSA micelles at 50 and 70% were able to elute entirely as micelles during size-exclusion chromatography, indicating their stability toward dissociation after dilution. The results point to a nanoscopic drug depot that may release AmB at controlled rates.

Influence of neutron activation factors on matrix tablets for site specific delivery to the colon

The impact of the neutron activation procedure, i.e. incorporation of samarium oxide (Sm(2)O(3)) and neutron irradiation, on the compression properties (including the crushing strength) and in vitro dissolution of potential colonic delivery systems based on matrix tablets of amidated pectin (Am.P) or two types of hydroxypropyl methylcellulose (HPMC) was investigated. The neutron activation factors did not influence the compression properties of the tablets. Replacement of magnesium stearate with samarium stearate in directly compressed Am.P tablets to achieve both radiolabelling and lubrication resulted in a greater extent of concentration-dependent reduction of the crushing strength. Dissolution tests demonstrated that irradiation increased the release of the model drug ropivacaine from the tablets. The extent of this increase was unexpectedly low considering the previously observed degradation of the polymer expressed as an irradiation-induced viscosity reduction in solutions prepared from the polymers. Delayed-release coating with Eudragit L 100 protected the HPMC tablets against the release-increasing effect of irradiation until the late phases of release. Sm(2)O(3) retarded the release to a varying extent depending on particle characteristics. Incorporation of Sm(2)O(3) in the coating layer did not influence the release. However, one-third of the radioactivity leached from the coating within 60 min in 0.1 M HCl.

Electrogenicity of hepatocellular fatty acid uptake

Sensitivity of cellular fatty acids uptake to the membrane potential difference is still a matter of controversy. For direct evaluation of potential sensitivity the effect of changing membrane potential on uptake of a fluorescent long chain fatty acid derivative, 12-NBD-stearate, in isolated rat hepatocytes, was examined. Changes in membrane potential were achieved by patch clamp procedures. Fatty acid influx was simultaneously determined by recording of cell fluorescence. Hyperpolarization from -30 to -70 mV accelerated fatty acid influx whereas depolarization to +50 mV reduced uptake. After obtaining equilibrium hyperpolarization increased cell fluorescence, whereas depolarization pushed NBD-stearate out of cells. Potential sensitivity of uptake was dependent on the fatty acid concentrations in the medium with most prominent effects at low unbound concentrations. These data show that, at low fatty acid concentrations, uptake is, in part, driven by an intracellular negative electric membrane potential.

Sterol carrier protein-2 expression increases NBD-stearate uptake and cytoplasmic diffusion in L cells

The effects of sterol carrier protein-2 (SCP-2) expression on fatty acid uptake and cytoplasmic diffusion were determined using L cell fibroblasts transfected with cDNA encoding either the 15- or 13. 2-kDa form of SCP-2. Cis-parinarate and 12-N-methyl-(7-nitrobenz-2-oxa-1,3-diazol)aminostearate (NBD-stearate) were used as nonesterifiable fluorescent fatty acid probes. NBD-stearate and cis-parinarate uptake was rapid and saturable. In 15-kDa SCP-2-expressing cells, the extent of NBD-stearate and cis-parinarate uptake was increased 1.4- and 1. 2-fold, respectively, compared with control. In the 13.2-kDa SCP-2-expressing cells, the extent of NBD-stearate and cis-parinarate uptake was increased 1.3- and 1.1-fold, respectively, compared with control cells. NBD-stearate cytoplasmic diffusion was increased 1.5-fold in 15-kDa SCP-2-expressing cells, but not in 13. 2-kDa SCP-2-expressing cells, compared with control cells. After incubation with NBD-stearate for 30 min at 37 degrees C, fluorescence imaging indicated that NBD-stearate was localized primarily in lipid droplets in all cell lines. These results suggest that SCP-2 may be involved not only in fatty acid uptake but also in intracellular fatty acid trafficking.

L-FABP and I-FABP expression increase NBD-stearate uptake and cytoplasmic diffusion in L cells

The effects of intestinal and liver fatty acid binding protein (I- and L-FABP, respectively) expression on single-cell fatty acid uptake, internalization, and cytoplasmic diffusion were determined in transfected L cell fibroblasts. These parameters were measured using the nonesterifiable fluorescent fatty acid probe 12-N-methyl-(7-nitrobenz-2-oxa-1,3-diazol)aminostearate (NBD-stearate) and fluorescence digital imaging. In single-cell fluorescence imaging experiments, L-FABP-expressing cells, but not I-FABP-expressing cells, increased NBD-stearate uptake 1.7-fold compared with control cells. Both I- and L-FABP increased the cytoplasmic diffusion rate of the internalized NBD-stearate 2.6- and 1.9-fold, respectively, compared with control cells. However, increased NBD-stearate lateral membrane mobility was observed only in L-FABP-expressing cells. After incubation of the cells with 4 microM NBD-stearate at 37 degrees C for 30 min, fluorescence deconvolution imaging indicated that NBD-stearate was localized primarily into lipid droplets in all cell lines. The differential effect of these proteins on fatty acid uptake and intracellular trafficking in single cells illustrates a possible difference in the physiological function of I- and L-FABP in intact cells.

Long-chain fatty acid uptake by skeletal myocytes: a confocal laser scanning microscopy study

Studies of regulation of free fatty acid (FFA) utilization by skeletal muscles have focused on plasma FFA delivery and on intracellular factors affecting FFA metabolism. The present study was conducted to directly analyse the uptake process of fatty acids into single myocytes. Cells were isolated from the rat flexor digitorum brevis muscle. Confocal laser scanning microscopy was utilized to analyse the uptake of the fluorescent fatty acid derivative 12-NBD-stearate, which is not metabolized by muscle tissue. Uptake represented a saturable function of the unbound fatty acid concentration in the medium (K(m) 366 +/- 118 nM, Vmax 2.1 +/- 0.3 AU/s) and depended on the medium sodium concentration. Reduced buffer pH increased initial uptake rates, whereas lactate (10 mM) had no effect. Membrane hyper- and depolarization decreased uptake rates. This study demonstrates for the first time kinetic data from isolated myocytes with evidence for a carrier-mediated transport mechanism for long-chain fatty acids.

Cellular differentiation and I-FABP protein expression modulate fatty acid uptake and diffusion

The effect of cellular differentiation on fatty acid uptake and intracellular diffusion was examined in transfected pluripotent mouse embryonic stem (ES) cells stably expressing intestinal fatty acid binding protein (I-FABP). Control ES cells, whether differentiated or undifferentiated, did not express I-FABP. The initial rate and maximal uptake of the fluorescent fatty acid, 12-(N-methyl)-N-[(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-octadec anoic acid (NBD-stearic acid), was measured in single cells by kinetic digital fluorescence imaging. I-FABP expression in undifferentiated ES cells increased the initial rate and maximal uptake of NBD-stearic acid 1.7- and 1.6-fold, respectively, as well as increased its effective intracellular diffusion constant (Deff) 1.8-fold as measured by the fluorescence recovery after photobleaching technique. In contrast, ES cell differentiation decreased I-FABP expression up to 3-fold and decreased the NBD-stearic acid initial rate of uptake, maximal uptake, and Deff by 10-, 4.7-, and 2-fold, respectively. There were no significant differences in these parameters between the differentiated control and differentiated I-FABP-expressing ES cell lines. In summary, differentiation and expression of I-FABP oppositely modulated NBD-stearic acid uptake parameters and intracellular diffusion in ES cells.

Confocal analysis of hepatocellular long-chain fatty acid uptake

Transmembrane transport and cytosolic accumulation of fatty acids were investigated using confocal laser scanning microscopy (cLSM). A Zeiss LSM 310 system was used to determine the uptake of the fluorescent fatty acid derivative 12-(N-methyl)-N-[(7-nitrobenz-2-oxa-1,3- diazol-4-yl)amino]octadecanoic acid (12-NBD stearate) (C18) in single rat hepatocytes. Uptake was a saturable process with a Michaelis-Menten constant value of 68 nM. Initial uptake velocity was dependent on extracellular presence of albumin and beta-lactoglobulin. Absence of albumin reduced uptake to 32 +/- 16% (P < 0.01) of control values. In the presence of unlabeled stearate, uptake of 12-NBD stearate was lowered to 49 +/- 12% (P < 0.01). Ion substitution experiments showed no sodium dependency of uptake. Increase in membrane potential led to a pronounced accumulation of the fatty acid derivative within the plasma membrane and in the adjacent cytoplasmic compartment, whereas membrane depolarization had no effect on uptake rates. In separate experiments line scans through representative hepatocytes were analyzed to generate "x-t" plots. 12-NBD stearate showed a fluorescence pattern with prominent staining of the area of the plasma membrane and the adjacent cytoplasm, dependent on the presence of extracellular albumin. For the hepatocellular cytosolic accumulation process of 12-NBD stearate a diffusion constant of 22.2 +/- 6.2 x 10(-9) cm2/s was calculated. In contrast to the long-chain fatty acid derivative 12-NBD stearate, short (C5)- and medium (C11)-chain fatty acids revealed no membrane interaction with hepatocytes. Erythrocytes also lacked a membrane interaction process for 12-NBD stearate. In conclusion, it was demonstrated that cLSM is capable of directly evaluating the cellular fatty acid uptake process at a subcellular level.

Stereostructure of plagiochiline A and conversion of plagiochiline A and stearoylvelutinal into hot-tasting compounds by human saliva

The stereostructure of plagiochiline A (1) isolated from the liverwort Plagiochila fruticosa has been established by X-ray crystallographic analysis. Plagiochiline A was converted into plagiochilal B (2) and furanoplagiochilal (3) by human saliva, and stearoylvelutinal (4) isolated from the fungus Lactarius vellerus was converted into velleral (5), also by human saliva.