Pharmacokinetics,Tissue Distribution,and Anti-Lipogenic/Adipogenic Effects of Allyl-Isothiocyanate Metabolites

Allyl-isothiocyanate (AITC) is an organosulfur phytochemical found in abundance in common cruciferous vegetables such as mustard, wasabi, and cabbage. Although AITC is metabolized primarily through the mercapturic acid pathway, its exact pharmacokinetics remains undefined and the biological function of AITC metabolites is still largely unknown. In this study, we evaluated the inhibitory effects of AITC metabolites on lipid accumulation in vitro and elucidated the pharmacokinetics and tissue distribution of AITC metabolites in rats. We found that AITC metabolites generally conjugate with glutathione (GSH) or N-acetylcysteine (NAC) and are distributed in most organs and tissues. Pharmacokinetic analysis showed a rapid uptake and complete metabolism of AITC following oral administration to rats. Although AITC has been reported to exhibit anti-tumor activity in bladder cancer, the potential bioactivity of its metabolites has not been explored. We found that GSH-AITC and NAC-AITC effectively inhibit adipogenic differentiation of 3T3-L1 preadipocytes and suppress expression of PPAR-γ, C/EBPα, and FAS, which are up-regulated during adipogenesis. GSH-AITC and NAC-AITC also suppressed oleic acid-induced lipid accumulation and lipogenesis in hepatocytes. Our findings suggest that AITC is almost completely metabolized in the liver and rapidly excreted in urine through the mercapturic acid pathway following administration in rats. AITC metabolites may exert anti-obesity effects through suppression of adipogenesis or lipogenesis.     

Preparation and Characterization of Lyophilized Liposomes with Incorporated Quercetin

Liposomes composed of egg-phosphatidylcholine (EPC) incorporating quercetin (QR) were prepared by the thin-film hydration method (TFHM) and the monophase solution method (MSM). A rapid and slow freeze-drying process was applied for both laboratory and industrial scales. The purpose of this study was to compare the two methods of liposome preparation, and further determine whether the lyophilization process affects the liposome physicochemical characteristics (size, polydispersity index, and ζ-potential) and incorporation of quercetin.     

Pharmacokinetics,Tissue Distribution and Metabolism of Intravenously Administered Digalactosyldiacylglycerol and Monogalactosyldiacylglycerol in the Rat

Abstract

A bilayer forming galactolipid, digalactosyldiacylglycerol (DGalDG) has been identified as a tool with suitable physicochemichal properties for pharmaceutical formulation work. One possible application is as a carrier for liposome entrapped drugs for intravenous administration. The fate of intravenously administered galactolipids is not known. In this study liposomal dispersions of galactolipids, containing [³H]fatty acid labelled DGalDG or monogalactosyldiacylglycerol (MGalDG) were injected intravenously in the rat and the disappearance from blood and uptake by tissues were examined. The T1/2 of [³H]DGalDG in plasma was 3 to 5 minutes. Of the tissues examined (liver, spleen, kidneys, lung, heart, stomach, upper and lower small intestine and colon), the liver contained the highest radioactivity per g tissue after both 15 min. and 4 h. Autoradiographic examinations after 15 min, 1 h and 4 h showed that the uptake of radiolabeled DGalDG and MGalDG occurred mainly to the hepatocytes. Less than 6 % of the injected [³H]DGalDG remained in liver and plasma as [³H]DGalDG after 4 h. [³H]MGalDG exhibited a similar pattern of metabolism although the initial disappearance rate was faster than for [³H]DGalDG. The study thus shows that the hepatocytes take up and hydrolyse galactolipids after intravenous administration.     

Effect of Macrophage Elimination Using Liposome-Encapsulated Dichloromethylene Diphosphonate on Tissue Distribution of Liposomes

Abstract

Effect of macrophage elimination using liposomal dichloromethylene diphosphonate (C1₂MDP)1 on tissue distribution of different types of liposomes was examined in mice. Intravenously administration into mice with CI2MDP encapsulated in liposomes composed of phosphatidylcholine, cholesterol and phosphatidylserine exhibits a temporary blockade of liver and spleen function for liposome uptake. At a low dose of 90 (ig/mouse, the liposome uptake by the liver was significantly decreased. Such decrease was accompanied by an increase in liposome accumulation in either spleen or blood depending on liposome composition and size. Direct correlation between the administration dose of liposomal CI2MDP and the liposome circulation time in blood was also obtained even for liposomes with an average diameter of more than 500 nm. These results indicate that temporary elimination of macrophages of the liver and spleen using liposomal CI2MDP may prove to be useful to enhance the drug delivery efficiency of liposomes.     

Preparation,Safety, Pharmacokinetics,and Pharmacodynamics of Liposomes Containing <Emphasis Type="Italic">Brucea javanica</Emphasis> Oil

Brucea javanica oil-loaded liposomes (BJOL) were prepared through thin film hydration method and characterized by transmission electron microscope, dynamic light scattering, and differential scanning calorimetry. Acute toxicity of B. javanica oil (BJO) in liposomes was assessed by determining the number of deaths of Kunming mice over intravenous treatment for 2 weeks. The pharmacokinetic behavior of the main active component (oleic acid) was studied in SD rats. The pharmacodynamics of BJOL was investigated using MMC-7721 cell lines and mice with Lewis lung cancer. The commercial emulsion of BJO (BJOE) was used as a reference. The data showed that BJOL had an average diameter of 108.2 nm with a zeta potential of −57.0 mV, drug loading of 3.60%, and entrapment efficiency of 92.40%. The area under curve of BJO in liposomes and emulsions were 2.31 and 1.15 mg min/ml, respectively. Compared with BJOE, mean residence time and elimination half-time (t _1/2) increased 2.8- and 4.0-fold, respectively, and the clearance (CL) decreased 0.5-fold. In the acute toxicity test, the median lethal dose (LD₅₀) of BJOE was 7.35 g/kg. In contrast, all mice treated with liposomes survived even at the highest dosage (12.70 g/kg). The IC₅₀ value of BJOL group was one third of that of BJOE group (p < 0.01), and a less weight loss was observed in the BJOL-treated animals (p < 0.05). In conclusion, the present study suggests that BJOL significantly decreased toxicity of BJO and enhance the antitumor activity. Therefore, liposomes may be a potential effective delivery vehicle for this lipophilic antitumor drug.     

Neighborhood Safety and Adipose Tissue Distribution in African Americans: The Jackson Heart Study

Objective

Patterns of fat distribution are heavily influenced by psychological stress, sex, and among women, by menopause status. Emerging evidence suggests the lack of perceived neighborhood safety due to crime may contribute to psychological stress and obesity among exposed residents. Our objective is to determine if perceived neighborhood safety is associated with abdominal adiposity among African-American men and women, and among pre- and postmenopausal women in the Jackson Heart Study.

Design and Methods

We examined associations between perceived neighborhood safety, fat distribution, and other individual-level covariates among Jackson Heart Study participants (N = 2,881). Abdominal adiposity was measured via computed tomography scans measuring the volumes of visceral, subcutaneous and total adipose tissue. We also measured body mass index (BMI), and waist circumference. Multivariable regression models estimated associations between perceived neighborhood safety, adiposity, and covariates by sex and menopause status.

Results

Adjusting for all covariates, women who strongly disagreed their neighborhood was safe from crime had a higher BMI compared to women who felt safe [Std B 0.083 95% CI (0.010, 0.156)]. Premenopausal women who felt most unsafe had higher BMI, waist circumference, and volumes of visceral and total adipose tissue than those who felt safe [Std B 0.160 (0.021, 0.299), Std B 0.142 (0.003, 0.280), Std B 0.150 (0.014, 0.285), Std B 0.154 (0.019, 0.290), respectively]. We did not identify associations between neighborhood safety and adiposity among men and postmenopausal women.

Conclusions

Our data suggest that abdominal adipose tissue distribution patterns are associated with perceived neighborhood safety in some groups, and that patterns may differ by sex and menopause status, with most associations observed among pre-menopausal women. Further research is needed to elucidate whether there are causal mechanisms underlying sex and menopause-status differences that may mediate associations between perceived safety and abdominal adiposity and potential protective factors that may modify this risk.     

Antibodies to Lipids and Liposomes: Immunology and Safety

Naturally occurring antibodies to phospholipids and cholesterol are widespread; they occur commonly during the course of acute infections; they are not causally related to the anti-phospholipid syndrome; they have been associated with other clinical entities only as an epiphenomenon; and they have not been implicated as causing any clinical syndrome or disease. There are theoretical and experimental reasons to believe that normal cells and tissues are protected from binding of antibodies to bilayer lipids by steric hindrance due to adjacent larger molecules, such as large or charged adjacent glycolipids or proteins on the cell surface. There are also reasons to believe that certain natural antibodies to lipids can even serve useful normal functions. Antibodies to liposomal lipids induced by liposomes containing lipid A appear to have characteristics that are similar or identical to naturally occurring antibodies to lipids, and it is therefore believed that such antibodies would not cause adverse clinical effects. Numerous Phase I and II human clinical trials of experimental vaccines containing liposomes and lipid A have shown a high level of safety.     

Pharmacokinetics, Tissue Distribution, and Plasma Protein Binding Study of Platinum Originating from Dicycloplatin, a Novel Antitumor Supramolecule, in Rats and Dogs by ICP-MS

Dicycloplatin, as a new antitumor supramolecule, was considered to have higher solubility and higher stability compared with carboplatin. The aim of the present study was to evaluate the pharmacokinetic characteristics of platinum originating from dicycloplatin. A rapid, sensitive, and specific method with inductively coupled plasma mass spectrometry (ICP-MS) has been developed for the determination of platinum in bio-samples. The study was performed in male rats and dogs at a single dose of 10 and 5 mg kg(-1) separately by intravenous injection. Pharmacokinetic parameters were calculated by non-compartmental method, and the dose of platinum was used in the calculation of these parameters. Results showed that plasma concentrations of platinum began to decrease rapidly initially but decline slowly with a long terminal phase. The mean half-life was 27.39 and 100.98 and clearance was 0.77 and 0.08 L/h/kg for rats and dogs separately. Tissue distribution showed that platinum originating from dicycloplatin had a certain distribution in testis and prostate. Plasma protein binding proportion of platinum was increased with time. In conclusion, this research investigated the pharmacokinetic characteristics including plasma kinetics, tissue distribution, and plasma protein binding of platinum originating from dicycloplatin in rats and dogs in detail for the first time by ICP-MS.     

Pharmacokinetics,Safety and Efficacy of Voriconazole in Pediatric Patients: An Update

Opportunistic invasive fungal infections are important infectious complications in severely immunocompromised children with hematological malignancies and/or hematopoietic stem cell transplantation, and are causes of considerable morbidity and mortality. Voriconazole is a broad-spectrum, second generation antifungal triazole with activity against yeast and filamentous fungi and first line indications against invasive aspergillosis and invasive candidiasis. While the compound has been approved in children and adolescents for several years, the dose finding in this population is ongoing and data on safety and efficacy continue to be accrued. The purpose of this article is to provide an update on the pharmacokinetics, safety and efficacy of voriconazole in pediatric patients.     

Fibrin Targeting of Echogenic Liposomes with Inactivated Tissue Plasminogen Activator

Fibrin-specific molecular targeting strategies are desirable for site-specific imaging and treatment of late stage atheroma, but fibrin-specific antibodies are difficult to produce and present immunogenicity problems. Tissue plasminogen activator (tPA) is an endogenous protein that has been shown to bind fibrin with high affinity and may circumvent antibody difficulties. Use of tPA-derived proteins or peptides, however, requires that the plasminogen-activating proteolytic activity be neutralized or removed. As an initial step in determining the feasibility of this targeting strategy, human recombinant tPA (Activase®) was irreversibly inhibited with D-phe-L-pro-L-arg-chloromethyl ketone (PPACK) and conjugated to intrinsically echogenic liposomes (ELIP) by a thioether coupling protocol. Fibrin-binding affinities were assessed with a novel two‐stage fibrin pad ELISA. We achieved 95–99% inactivation, while retaining both tPA fibrin-binding activities of K_D ～ 2 nM and 33 nM. Thermodynamic analysis of the PPACK-inactivated tPA (tPA(P)) revealed highly exothermic interactions, indicative of ionic associations, especially for the higher affinity. The conjugation efficiency of tPA(P) to ELIP was within the range of that previously achieved for IgG and exhibited satisfactory fibrin targeting, characterized by striking increases of enthalpy and entropy increments. Evidence for coupling of noncovalent association energetics with the phosphatidylethanolamine major phase transition, observed in previous IgG antibody conjugations, was also evident in this case, but the nature of the transduction mechanism was different. These results demonstrate that tPA-derived components lacking proteolytic activity can be employed as fibrin-targeting agents for delivery of therapeutic and diagnostic formulations.     

Uptake and Intracellular Distribution of Oligonucleotides Vectorized by a PAMAM Dendrimer

Abstract

We studied the uptake and intracellular distribution of an FITC labelled phosphodiester oligodeoxynucleotide (ODN) vectorized by a dendrimeric structure in cell culture.     

Electrophysiological Properties of Ion Channels in Ascaris suum Tissue Incorporated into Planar Lipid Bilayers

Ion channels are important targets of anthelmintic agents. In this study, we identified 3 types of ion channels in Ascaris suum tissue incorporated into planar lipid bilayers using an electrophysiological technique. The most frequent channel was a large-conductance cation channel (209 pS), which accounted for 64.5% of channels incorporated (n=60). Its open-state probability (P_o) was ~0.3 in the voltage range of −60~+60 mV. A substate was observed at 55% of the main-state. The permeability ratio of Cl⁻ to K⁺ (P_Cl/P_K) was ~0.5 and P_Na/P_K was 0.81 in both states. Another type of cation channel was recorded in 7.5% of channels incorporated (n=7) and discriminated from the large-conductance cation channel by its smaller conductance (55.3 pS). Its Po was low at all voltages tested (~0.1). The third type was an anion channel recorded in 27.9% of channels incorporated (n=26). Its conductance was 39.0 pS and P_Cl/P_K was 8.6±0.8. P_o was ~1.0 at all tested potentials. In summary, we identified 2 types of cation and 1 type of anion channels in Ascaris suum. Gating of these channels did not much vary with voltage and their ionic selectivity is rather low. Their molecular nature, functions, and potentials as anthelmintic drug targets remain to be studied further.     

Comparison of Conventional Chemotherapy,Stealth Liposomes and Temperature-Sensitive Liposomes in a Mathematical Model

Various liposomal drug carriers have been developed to overcome short plasma half-life and toxicity related side effects of chemotherapeutic agents. We developed a mathematical model to compare different liposome formulations of doxorubicin (DOX): conventional chemotherapy (Free-DOX), Stealth liposomes (Stealth-DOX), temperature sensitive liposomes (TSL) with intra-vascular triggered release (TSL-i), and TSL with extra-vascular triggered release (TSL-e). All formulations were administered as bolus at a dose of 9 mg/kg. For TSL, we assumed locally triggered release due to hyperthermia for 30 min. Drug concentrations were determined in systemic plasma, aggregate body tissue, cardiac tissue, tumor plasma, tumor interstitial space, and tumor cells. All compartments were assumed perfectly mixed, and represented by ordinary differential equations. Contribution of liposomal extravasation was negligible in the case of TSL-i, but was the major delivery mechanism for Stealth-DOX and for TSL-e. The dominant delivery mechanism for TSL-i was release within the tumor plasma compartment with subsequent tissue- and cell uptake of released DOX. Maximum intracellular tumor drug concentrations for Free-DOX, Stealth-DOX, TSL-i, and TSL-e were 3.4, 0.4, 100.6, and 15.9 µg/g, respectively. TSL-i and TSL-e allowed for high local tumor drug concentrations with reduced systemic exposure compared to Free-DOX. While Stealth-DOX resulted in high tumor tissue concentrations compared to Free-DOX, only a small fraction was bioavailable, resulting in little cellular uptake. Consistent with clinical data, Stealth-DOX resulted in similar tumor intracellular concentrations as Free-DOX, but with reduced systemic exposure. Optimal release time constants for maximum cellular uptake for Stealth-DOX, TSL-e, and TSL-i were 45 min, 11 min, and <3 s, respectively. Optimal release time constants were shorter for MDR cells, with ∼4 min for Stealth-DOX and for TSL-e. Tissue concentrations correlated well quantitatively with a prior in-vivo study. Mathematical models may thus allow optimization of drug delivery systems to achieve a better therapeutic index.     

Tissue Safety in View of CJD and Variant CJD

Epidemiological studies on human transmissible spongiform encephalopathies (Creutzfeldt–Jakob Disease, CJD) have shown that the agent could be transmitted by highly infectious tissues like brain, spinal cord or retina and medicinal products derived from these tissues (i.e. human growth hormone, dura mater). A few cases of transmission of CJD by neurosurgical instruments have been reported. The transmission of the agent of variant CJD, which is suspected to be transmitted by BSE-contaminated food, by blood transfusion implies that in contrast to the agent of classical CJD this agent can also be transmitted by organs and tissues other than nerve tissues. Health authorities have implemented guidelines to reduce the risk of transmission of human and animal TSE by human and veterinary medicinal products. The high resistance of TSE agents against physical or chemical treatment hamper the development of highly efficient inactivation steps in the production of medicinal products. Donor selection is considered as an efficient measure to reduce the risk of TSE transmission. However, the development of rapid, sensitive and specific diagnostic test systems is urgently required to test blood, organs and tissue of donors.     

Addition of Block Copolymers to Liposomes Prepared Using Soybean Lecithin. Effects on Formation,Stability and the Specific Localization of the Incorporated Surfactants Investigated

Abstract

Soybean lecithin disperses into water forming multilamellar liposomes, which on sonication produce vesicles of the order of 40–50nm (diameter), as determined by Photon Correlation Spectroscopy (PCS). The effect of concentration of lecithin and sonication time was systematically investigated. Vesicles were then prepared by incorporation of A – B – A block copolymers of polyethylene oxide (PEO) and polypropylene oxide(PPO), i.e.(PEO-PPO-PEO), in order to construct systems of increased steric stability. The effect of the molecular weight of the PEO and PPO chains on the vesicle size was systematically studied by using various molecules to prepare the vesicles. Initial addition of these (tri-)block copolymers causes an increase in the size of the vesicles. This increase continues until a certain concentration of block copolymer is reached, after which a decrease in size is observed. The initial increase was thought to be due to the incorporation of the block copolymer onto the vesicle bilayer. The reduction at high surfactant concentration is thought to be due to solubilization of the bilayer and the ultimate breakdown of the vesicles. Electrophoresis experiments showed a reduction in the ξ-potential of the vesicles on incorporation of the block copolymer which can be attributed to the shift of the shear plane. Various models are presented to describe this incorporation. The vesicles prepared using the block copolymers are believed to enhance the steric effects and so lead to more stable and pharmaceutically optimum systems.     

Montmorillonite,Oligonucleotides, RNA and Origin of Life

Na-montmorillonite prepared from Volclay by the titration method facilitates the self-condensation of ImpA, the 5'-phosphorimidazolide derivative of adenosine. As was shown by AE-HPLC analysis and selective enzymatic hydrolysis of products, oligo(A)s formed in this reaction are 10 monomer units long and contain 67% 3',5'-phosphodiester bonds (Ferris and Ertem, 1992a). Under the same reaction conditions, 5'-phosphorimidazolide derivatives of cytidine, uridine and guanosine also undergo self-condensation producing oligomers containing up to 12-14 monomer units for oligo(C)s to 6 monomer units for oligo(G)s. In oligo(C)s and oligo(U)s, 75-80% of the monomers are linked by 2',5'-phosphodiester bonds. Hexamer and higher oligomers isolated from synthetic oligo(C)s formed by montmorillonite catalysis, which contain both 3',5'- and 2',5'-linkages, serve as catalysts for the non-enzymatic template directed synthesis of oligo(G)s from activated monomer 2-MeImpG, guanosine 5'-phospho-2-methylimidazolide (Ertem and Ferris, 1996). Pentamer and higher oligomers containing exclusively 2',5'-linkages, which were isolated from the synthetic oligo(C)s, also serve as templates and produce oligo(G)s with both 2',5'- and 3',5'-phosphodiester bonds. Kinetic studies on montmorillonite catalyzed elongation rates of oligomers using the computer program SIMFIT demonstrated that the rate constants for the formation of oligo(A)s increased in the order of 2-mer < 3-mer < 4-mer ... < 7-mer (Kawamura and Ferris, 1994). A decameric primer, dA(pdA)8pA bound to montmorillonite was elongated to contain up to 50 monomer units by daily addition of activated monomer ImpA to the reaction mixture (Ferris, Hill and Orgel, 1996). Analysis of dimer fractions formed in the montmorillonite catalyzed reaction of binary and quaternary mixtures of ImpA, ImpC, 2-MeImpG and ImpU suggested that only a limited number of oligomers could have formed on the primitive Earth rather than equal amounts of all possible isomers (Ertem and Ferris, 2000). Formation of phosphodiester bonds between mononucleotides by montmorillonite catalysis is a fascinating discovery, and a significant step forward in efforts to find out how the first RNA-like oligomers might have formed in the course of chemical evolution. However, as has been pointed out in several publications, these systems should be regarded as models rather than a literal representation of prebiotic chemistry (Orgel, 1998; Joyce and Orgel, 1999; Schwartz, 1999).