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Molecular pharmaceutics [journal]
- Functional Analysis of Novel Variants in the Organic Cation/ Ergothioneine Transporter 1 (hOCTN1) identified in Singapore Populations. [JOURNAL ARTICLE]
- Mol Pharm 2013 May 11.
The human Organic Cation/ Ergothioneine Transporter1 (hOCTN1, gene symbol SLC22A4) is responsible for the cellular uptake of substances, such as L-ergothioneine, which is an important antioxidant in mammalian cells. The common-function-altered variant L503F-hOCTN1 has been associated with susceptibility to Crohn's disease in certain populations. Previously we identified eight novel nonsynonymous single nucleotide polymorphisms (SNPs) in the SLC22A4 gene in the Chinese and Indian populations of Singapore. The present study evaluated the impact of these novel SNPs on hOCTN1 transport function in HEK-293 cells. Transport uptake assays with L-ergothioneine were used to assess the function of the variant transporters. Cell surface biotinylation and western blot analysis were used to characterize cellular transporter expression. Comparative modelling was used to locate amino acid substitutions in the topology of hOCTN1 in order to account for altered transport function. Transporter activity was markedly impaired in four of the naturally occurring hOCTN1 variants (R63H, R83P, G482D and I500N). Multiple glycosylated isoforms of hOCTN1 proteins were identified in the plasma membrane and in the whole cell. Either the total cellular or membrane expression of the functionally deficient transporter variants was lower than that of the wild-type hOCTN1. The underlying mechanism involves both impaired transporter-substrate binding affinity and turn-over rate. Considered together, several naturally occurring SNPs in the SLC22A4 gene encode variant hOCTN1 transporters that may impact on the cellular uptake of L-ergothioneine and other substrates, with the potential to influence the antioxidant capacity of human cells.
- A strategy for the improvement of the bioavailability and anti-osteoporosis activity of BCS IV flavonoid glycosides through the formulation of their lipophilic aglycone into nanocrystals. [JOURNAL ARTICLE]
- Mol Pharm 2013 May 9.
Epidemium-derived flavonoid glycosides are widely used for preventing osteoporosis, but they generally showed poor membrane permeability and oral absorption. To solve above problems, their bioactive lipophilic aglycone (ICT) was selected and successfully developed into nanocrystal (ICTN) by antisolvent-precipitation method. Parameters in preparation of ICTN were firstly optimized, followed by morphology, crystallinity, adsorption of stabilizers on ICT surface and dissolution characterizations. Pharmacokinetic study in rat and anti-osteoporosis activities of serum withdrawn after oral administration of ICTN to rat were evaluated on mouse osteoblastic cell in vitro. Consistent with its good performance in stabilizing the ICT nanosuspension, atomic force microscope showed that HPMC has adequate adsorption on ICT surface than other stabilizers. Needle-shaped crystals (~ 220 nm in diameter) with good short-term stability at 4°C and high drug loading (~90%) were produced when 0.16 ml of the ICT acetone solution (10 mg/ml) was injected quickly into 2 ml of HPMC solution (0.02%, w/w) under ultrasonication for 10 sec at room temperature. Thermal analysis demonstrated that the majority of the particles are in the crystalline forms similar to the unformulated ICT. ICTN showed faster dissolution rate, significantly increased and faster absorption, supported by the increased AUC0-36h, Cmax and reduced Tmax than raw suspension after oral administration (p<0.05). Compared to blank serum, enhanced proliferation and differentiation activities were observed when incubation serum withdrawn after oral administration of ICTN in rat with osteoblast MC3T3-E1 cells. The present delivery system could provide a new promising strategy for BCS IV glycoside of flavonoids or other natural products by formulation of their bioactive lipophilic aglycone forms to enhance oral absorption and in-vivo bioactivity.
- Cell-Penetrating Peptide Enhanced Intracellular Raman Imaging and Photodynamic Therapy. [JOURNAL ARTICLE]
- Mol Pharm 2013 May 9.
We present the application of a theranostic system combining Raman imaging and the photodynamic therapy (PDT) effect. The theranostic nanoplatform was created by loading the photosensitizer, protoporphyrin IX, onto a Raman-labeled gold nanostar. A cell-penetrating peptide, TAT, enhanced intracellular accumulation of the nanoparticles in order to improve their delivery and efficacy. The plasmonic gold nanostar platform was designed to increase the Raman signal via the surface-enhanced resonance Raman scattering (SERRS) effect. Theranostic SERS imaging and photodynamic therapy using this construct were demonstrated on BT-549 breast cancer cells. The TAT peptide allowed for effective Raman imaging and photosensitization with the nanoparticle construct after a 1 h incubation period. In the absence of the TAT peptide, nanoparticle accumulation in the cells was not sufficient to be observed by Raman imaging or to produce any photosensitization effect after this short incubation period. There was no cytotoxic effect observed after nanoparticle incubation, prior to light activation of the photosensitizer. This report shows the first application of combined SERS imaging and photosensitization from a theranostic nanoparticle construct.
- Simulating the Postprandial Stomach: Biorelevant Test Methods for the Estimation of Intragastric Drug Dissolution. [JOURNAL ARTICLE]
- Mol Pharm 2013 May 8.
Intragastric drug release from solid oral dosage forms can be affected by altered physicochemical and mechanical conditions in the upper gastrointestinal (GI) tract. Food effects may lead to changes of one or more pharmacokinetic parameters and, hence, influence drug plasma levels. This can result in severe consequences such as adverse drug reactions or even therapy failure. This review highlights different examples of drug performance under fed conditions. Various reasons such as delayed gastric emptying and pH-dependent solubility of the API as well as intragastric location and movement profiles of solid dosage forms can account for changed drug dissolution. Over the past years, several biorelevant media (e.g., fed state simulated gastric fluid) have been developed with the aim to approach the physiological situation regarding parameters such as pH, buffer capacity, surface tension, and osmolality. It was shown in different in vitro experiments that all of these factors can have an impact on drug dissolution. Besides the application of complex media such as milk or nutritional drinks, the dynamic changes of the gastric content were depicted in recent studies. The capabilities, limitations, and applicability of newly established test setups for the biorelevant simulation of intragastric drug delivery behavior are discussed. Simple test devices (e.g., rotating beaker or dissolution stress test) are mainly used for the biopharmaceutical evaluation of certain problems such as the impact of pressure or shear forces. On the other hand, complex biorelevant test devices (e.g., TNO TIM-1, Dynamic Gastric Model) have recently been introduced aiming at the simulation of multiple parameters characteristic for the postprandial upper GI tract. The different test methods are reviewed with respect to the spectrum of the simulated physiological factors and the degree of complexity.
- Ischemia/Reperfusion-Inducible Protein Modulates the Function of Organic Cation Transporter 1 and Multidrug and Toxin Extrusion 1. [JOURNAL ARTICLE]
- Mol Pharm 2013 May 7.
The recently identified ischemia/reperfusion-inducible protein (IRIP) has been reported to negatively modulate the activities of several transporters in cell culture systems. The goal of this study is to determine whether IRIP regulates the activities of OCT1 and MATE1, and hence the disposition in vivo of their substrate metformin, a therapeutic drug for diabetes and other obesity-related syndromes. In the uptake studies in the human embryonic kidney 293 cells overexpressing IRIP with and without OCT1 or MATE1, IRIP overexpression was found to significantly inhibit the uptake of 1-methyl-4-phenylpyridinium mediated by OCT1 or MATE1. In contrast, knockdown of IRIP by small hairpin RNA (shRNA) increased the transporter activities in vitro. IRIP overexpression decreased the membrane localization of transporter proteins without any changes in transcript levels in cells. By overexpressing IRIP in mouse liver via hydrodynamic tail vein injection, we demonstrated that increased IRIP expression could cause a significant reduction in hepatic accumulation of metformin (P < 0.01). In addition, we observed that the expression of IRIP was approximately half (P < 0.01) in ob/ob mice when compared to their lean littermates, with significant increases in hepatic Oct1 protein expression and metformin accumulation. In conclusion, IRIP negatively modulates the function of OCT1 and MATE1 in cells. Importantly, we provide in vivo evidence for such modulation that may cause an alteration in drug disposition. The regulation by IRIP on transporter activities likely occurs at a post-transcriptional level, and future studies are needed to characterize the exact mechanism.
- Synergistic Promotion of Blood Vessel Regeneration by Astragaloside IV and Ferulic Acid from Electrospun Fibrous Mats. [JOURNAL ARTICLE]
- Mol Pharm 2013 May 8.
The promotion of blood vessel initiation and growth plays an important role in the realization of therapeutic vascularization and regeneration of functional tissues. Astragalus membranaceus and angelica sinensis are commonly used traditional Chinese medicines for enriching the blood. In the current study astragaloside IV (AT, the main active ingredient of astragalus) and ferulic acid (FA, the main ingredient of angelica) were loaded into electrospun fibrous scaffolds to provide abundant and sustained biological factors required to initiate vascularization and bring it to maturity. The cell viability after AT and FA treatment was dose-dependent with an optimal concentration of around 50 μg/mL, and the most significant synergistic effect was demonstrated for the combined treatment with AT and FA with the ratio of 7/3 on both primary endothelial and smooth muscle cells. The in vitro release study showed that the amount of AT and FA release could be regulated by their loading amount and ratios in electrospun fibers. The localized and sustained codelivery of AT and FA indicated significantly high cell viability and secretion of extracellular matrices for both endothelial and smooth muscle cells, and induced significantly high densities of vascular structures after subcutaneous implantation. The most significant angiogenesis promotion with few inflammatory reactions was demonstrated for electrospun fibers containing AT and FA with the ratio of 7/3. It was suggested that the integration of the synergistic effect of Chinese medicine into electrospun fibrous scaffolds should provide clinical relevance for therapeutic vascularization, full vascularization in engineered tissues, and regeneration of blood vessel substitutes.
- Multistep Targeted Nano Drug Delivery System Aiming at Leukemic Stem Cells and Minimal Residual Disease. [JOURNAL ARTICLE]
- Mol Pharm 2013 May 20.
Refractory leukemia remains the most common therapeutic problem in clinical treatment of leukemia. The key therapy of refractory leukemia is to kill, thoroughly, the minimal residual disease and leukemia stem cells in the highly vascularized red marrow areas. In this study, two new conjugates, alendronate-polyethylene glycol (100) monostearate and folate-polyethylene glycol (100) monostearate, were synthesized to develop a multistep targeting nanostructured lipid carriers by enhancing drug transport to the high bone turnover areas adjacent to the red marrow and targeting the minimal residual disease and leukemia stem cells. This dual targeting system demonstrated a great binding affinity to hydroxyapatite, a model component of bone minerals, and higher cell uptake (in the form of carriers but not drug) and cytotoxicity in the K562 cell line, a leukemia cell line with overexpressed folate receptors, were observed in vitro compared to unmodified carriers, especially when the cells were pretreated and the receptors were up-regulated by all-trans retinoic acid. The comodel test of K562 cells and HA showed that this dual targeting system could desorb from bone surface and be taken up by leukemia cells. For the in vivo study, this dual targeting system exhibited a significant increase in plasma half-life and could specifically accumulate in the bone tissue of rats or mice after intravenous injection. Ex vivo imaging of mice femurs and confocal laser scanning microscope imaging of mice femur slices further confirmed that this dual targeting system could favorably deposit to the osteoblast-enriched areas of high bone turnover in regions of trabecular bone surrounded by red marrow. In vivo antitumor activity in K562/BALB/c-nu leukemia mice showed that the treatment of this dual targeting system significantly reduced the white blood cell (WBC) number in peripheral blood and bone marrow to the normal level. In conclusion, this dual targeting system could precisely target to the regions where the minimal residual disease and leukemia stem cells are located and then be specifically uptaken in large amounts, which is a valuable target for refractory leukemia therapy.
- Studies of Bicalutamide-Excipients Interaction by Combination of Molecular Docking and Molecular Dynamics Simulation. [JOURNAL ARTICLE]
- Mol Pharm 2013 May 6.
While the effects of hydrophilic excipients in enhancing the dissolution rate of water-insoluble drugs have been validated, the underlying mechanism remains poorly understood, particularly at a molecular level. In this work, a combination of docking calculations and MD simulations was applied to investigate the molecular interactions between bicalutamide (BIC) and each of three excipients: lactose (LAC), hydroxypropyl methylcellulose (HPMC), and mannitol (MAN). The calculated results indicated that BIC interacted with HPMC and MAN mainly by Lennard-Jones (LJ) interactions but with LAC mainly by Coulomb (Coul) interactions. There was no hydrogen bond formed between BIC and excipient. It was shown that BIC/LAC had the biggest total solvent accessible surface area with the biggest hydrophilic area and formed the most hydrogen bonds between excipient and water. In addition to the structure analyses, BIC/LAC had both the lowest interaction energy between BIC and excipient and the lowest interaction energy between BIC/excipient and water. All these led to the best dissolution performance of BIC/LAC, which could correspond to the experimental results of dissolution test. The present study suggests that a combination of docking calculations and MD simulations, which aims at complementing the experimental work, could provide a molecular insight into the interaction between drug and excipient. It also holds the great potential to simplify the optimization process of drug delivery system and reduce both time and costs.
- Use of folate-conjugated imaging agents to target alternatively activated macrophages in a murine model of asthma. [Journal Article]
- Mol Pharm 2013 May 6; 10(5):1918-27.
Pro-inflammatory macrophages play a prominent role in such autoimmune diseases as rheumatoid arthritis, Crohn's disease, psoriasis, sarcoidosis, and atherosclerosis. Because pro-inflammatory macrophages have also been shown to overexpress a receptor for the vitamin folic acid (i.e., folate receptor beta; FR-β), folate-linked drugs have been explored for use in imaging and treatment of these same diseases. To determine whether allergic inflammatory disorders might be similarly targeted with folate-linked drugs, we have examined the characteristics of macrophages that are prominent in the pathogenesis of asthma. We report here that macrophages from the lungs of mice with experimental allergic asthma express FR-β. We further document that these FR-β(+) macrophages coexpress markers of alternatively activated (M2-type) macrophages, including the mannose receptor and arginase-1. Finally, we demonstrate that folate-conjugated fluorescent dyes and radioimaging agents can be specifically targeted to these asthmatic lung macrophages, with little uptake by macrophages present in healthy lung tissue. These data suggest strategies for the development of novel diagnostic agents for the imaging of asthma and other diseases involving alternatively activated macrophages.
- Drug Delivery across the Blood-Brain Barrier. [Journal Article]
- Mol Pharm 2013 May 6; 10(5):1471-2.