Design, synthesis, and bioactivity evaluation of novel indole-selenide derivatives as P-glycoprotein inhibitors against multi-drug resistance in MCF-7/ADR cell.

The inhibition of P-glycoprotein (P-gp) has emerged as an intriguing strategy for circumventing multidrug resistance (MDR) in anticancer chemotherapy. In this study, we have designed and synthesized 30 indole-selenides as a new class of P-gp inhibitors based on the scaffold hopping strategy. Among them, the preferred compound H27 showed slightly stronger reversal activity (reversal fold: 271.7 vs 261.6) but weaker cytotoxicity (inhibition ratio: 33.7% vs 45.1%) than the third-generation P-gp inhibitor tariquidar on the tested MCF-7/ADR cells. Rh123 accumulation experiments and Western blot analysis demonstrated that H27 displayed excellent MDR reversal activity by dose-dependently inhibiting the efflux function of P-gp rather than its expression. Besides, UIC-2 reactivity shift assay revealed that H27 could bind to P-gp directly and induced a conformation change of P-gp. Moreover, docking study revealed that H27 matched well in the active pockets of P-gp by forming some key H-bonding interactions, arene-H interactions and hydrophobic contacts. These results suggested that H27 is worth to be a starting point for the development of novel Se-containing P-gp inhibitors for clinic use.

Protein-Based Films as Antifouling and Drug-Eluting Antimicrobial Coatings for Medical Implants.

Nosocomial infections, caused by bacterial contamination of medical devices and implants, are a serious healthcare concern. We demonstrate here, the use of fluorous-cured protein nanofilm coatings for generating antimicrobial surfaces. In this approach, bacteria-repelling films are created by heat-curing proteins in fluorous media. These films are then loaded with antibiotics, with release controlled via electrostatic interactions between therapeutic and protein film building blocks to provide bactericidal surfaces. This film fabrication process is additive-free, biocompatible, biodegradable, and can be used to provide antimicrobial coatings for both three-dimensional (2D) and 3D objects for use in indwelling devices.

Biocompatible Superparamagnetic Europium-Doped Iron Oxide Nanoparticle Clusters as Multifunctional Nanoprobes for Multimodal In Vivo Imaging.

Magnetic nanoparticle clusters composed of primary magnetic nanoparticles can not only significantly enhance the magnetic properties of the assembly but also retain the superparamagnetic properties of the individual primary nanoparticle, which is of great significance for promoting the development of multifunctional advanced materials. Herein, water-soluble biocompatible and superparamagnetic europium-doped iron oxide nanoparticle clusters (EuIO NCs) were directly synthesized by a simple one-pot method. The obtained EuIO NCs have excellent water solubility, colloidal stability, and biocompatibility. Europium doping significantly improved the contrast enhancement effect of EuIO NCs in T1-weighted MR imaging. In addition, EuIO NCs can be functionalized by active molecules, and the rhodamine123-functionalized EuIO NCs have long circulation time and excellent fluorescence imaging performance in vivo. This study provides a simple strategy for the design and construction of a novel multifunctional magnetic nanoplatform and provides solutions for the development of multimodal imaging probes and the diagnosis of disease.

Gradient radiation breeding and culture domestication of menaquinone producing strains.

By comparing the survival rate and positive mutation rate of the primary mutagenic strain and progeny mutagenic strain under different radiation doses, the results showed that the tolerance of the mutagenic strain to radiation dose increased with the increase of the mutagenic generations. We adopted an improved gradient radiation breeding strategy to improve the breeding efficiency. The strains were treated with radiation in four stages. The first stage was low energy N+ ion implantation (ion energy 15 keV, dose 80 × 2.6 × 1013 cm-2). In the second stage, the energy and dose of N+ ion reached to 20 keV, 90 × 2.6 × 1013 cm-2. In the third stage, 60Co-γ radiation (dose of 1.56 kGy) was used. In the fourth stage, the radiation dose of 60Co-γ increased to 1.82 kGy. After each stage of radiation, the MK (Menaquinone) precursor 1, 4-dihydroxy-2-naphthalate (DHNA) was used as the stress factor to domesticate the mutant strains. By gradually increasing the concentration of DHNA in the culture medium, the substrate tolerance of Flavobacterium sp. was effectively improved. By measuring SOD (superoxide dismutase) activity and malondialdehyde, it showed that the cell damage caused by radiation mutagenesis to the offspring mutant was less than that of the primary mutant. Changes in membrane permeability and membrane potential of the mutant strains were reflected in changes in fluorescence intensity of luciferin diacetate and rhodamine 123, which could explain the enhanced substrate tolerance of strain F-2. After gradient radiation breeding and culture acclimation, the biomass of mutant Strain F-2 was 6.59 g/L, and the MK yield was 9.59 mg/L.

Computational Insights into Allosteric Conformational Modulation of P-Glycoprotein by Substrate and Inhibitor Binding.

The ATP-binding cassette (ABC) transporter P-glycoprotein (P-gp) is a physiologically essential membrane protein that protects many tissues against xenobiotic molecules, but limits the access of chemotherapeutics into tumor cells, thus contributing to multidrug resistance. The atomic-level mechanism of how substrates and inhibitors differentially affect the ATP hydrolysis by P-gp remains to be elucidated. In this work, atomistic molecular dynamics simulations in an explicit membrane/water environment were performed to explore the effects of substrate and inhibitor binding on the conformational dynamics of P-gp. Distinct differences in conformational changes that mainly occurred in the nucleotide-binding domains (NBDs) were observed from the substrate- and inhibitor-bound simulations. The binding of rhodamine-123 can increase the probability of the formation of an intermediate conformation, in which the NBDs were closer and better aligned, suggesting that substrate binding may prime the transporter for ATP hydrolysis. By contrast, the inhibitor QZ-Leu stabilized NBDs in a much more separated and misaligned conformation, which may result in the deficiency of ATP hydrolysis. The significant differences in conformational modulation of P-gp by substrate and inhibitor binding provided a molecular explanation of how these small molecules exert opposite effects on the ATPase activity. A further structural analysis suggested that the allosteric communication between transmembrane domains (TMDs) and NBDs was primarily mediated by two intracellular coupling helices. Our computational simulations provide not only valuable insights into the transport mechanism of P-gp substrates, but also for the molecular design of P-gp inhibitors.

Comparison of Chemotherapeutic Activities of Rhodamine-Based GUMBOS and NanoGUMBOS.

Rhodamine derivatives have been widely investigated for their mitochondrial targeting and chemotherapeutic properties that result from their lipophilic cationic structures. In previous research, we have found that conversion of Rhodamine 6G into nanoGUMBOS, i.e., nanomaterials derived from a group of uniform materials based on organic salts (GUMBOS), led to selective chemotherapeutic toxicity for cancer cells over normal cells. Herein, we investigate the chemotherapeutic activity of GUMBOS derived from four different rhodamine derivatives, two bearing an ester group, i.e., Rhodamine 123 (R123) and SNAFR-5, and two bearing a carboxylic acid group, i.e., rhodamine 110 (R110) and rhodamine B (RB). In this study, we evaluate (1) relative hydrophobicity via octanol-water partition coefficients, (2) cytotoxicity, and (3) cellular uptake in order to evaluate possible structure-activity relationships between these different compounds. Intriguingly, we found that while GUMBOS derived from R123 and SNAFR-5 formed nanoGUMBOS in aqueous medium, no distinct nanoparticles are observed for RB and R110 GUMBOS. Further investigation revealed that the relatively high water solubility of R110 and RB GUMBOS hinders nanoparticle formation. Subsequently, while R123 and SNAFR-5 displayed selective chemotherapeutic toxicity similar to that of previously investigated R6G nanoGUMBOS, the R110 and RB GUMBOS were lacking in this property. Additionally, the chemotherapeutic toxicities of R123 and SNAFR-5 nanoGUMBOS were also significantly greater than R110 and RB GUMBOS. Observed results were consistent with decreased cellular uptake of R110 and RB as compared to R123 and SNAFR-5 compounds. Moreover, these results are also consistent with previous observations that suggest that nanoparticle formation is critical to the observed selective chemotherapeutic properties as well as the chemotherapeutic efficacy of rhodamine nanoGUMBOS.

Influene of Pharmaceutical Excipients on the Membrane Transport of a P-glycoprotein Substrate in the Rat Small Intestine.

BACKGROUND AND OBJECTIVES: Generic drugs are generally used worldwide because of affordability compared to brand-name drugs. One of the main differences between brand-name and generic drugs is pharmaceutical excipients. We previously reported the effects of pharmaceutical excipients on the membrane permeation of drugs via the paracellular and transcellular routes, which are passive transport routes. P-glycoprotein (P-gp) is a typical ATP-binding cassette transporter and is mostly responsible for drug-drug interactions involving transporters. In the present study, rhodamine 123 (Rho123) was selected as the P-gp substrate, and the effects of pharmaceutical excipients on its membrane transport in the rat jejunum and ileum were examined. METHODS: Twenty major pharmaceutical excipients widely used in the pharmaceutical industry were selected. The in vitro diffusion chamber method using the rat jejunum and ileum was employed to investigate the effects of pharmaceutical excipients on the membrane permeation of Rho123. RESULTS: The results obtained showed that the membrane permeability of Rho123 significantly (P < 0.05) changed under certain dosage conditions of pharmaceutical excipients such as sodium carboxymethyl starch, pullulan, glyceryl monostearate and so on. Furthermore, the effects of pharmaceutical excipients were site specific in the small intestine. CONCLUSION: The present results demonstrated that some pharmaceutical excipients altered the membrane permeability of Rho123 in the rat small intestine.

Release kinetics of fluorescent dyes from PLGA nanoparticles in retinal blood vessels: In vivo monitoring and ex vivo localization.

PLGA (poly(lactic-co-glycolic acid))-based nanoparticles (NPs) are promising drug carrier systems because of their excellent biocompatibility and ability for sustained drug release. However, it is not well understood how the kinetics of such drug delivery system perform in the retinal blood circulation as imaged in vivo and in real time. To answer this question, PLGA NPs were loaded either with lipophilic carbocyanine perchlorate (DiI) or hydrophilic Rhodamine 123 (Rho123) and coated with poloxamer 188 (P188): PLGA-DiI/P188 and PLGA-Rho123/P188. All particles had narrow size distributions around 130 nm, spherical shape and negative potential. Subsequently, we performed in vivo real-time imaging of retinal blood vessels, combined with ex vivo microscopy to monitor the kinetics and to detect location of those two fluorescent markers. We found that DiI signals were long lasting, detectable >90 min in blood vessels after intravenous injection as visible by homogeneous labelling of the vessel wall as well as by spots in the lumen of blood vessels. In contrast, Rho123 signals mostly disappeared after 15 min post intravenous injection in such compartment. To explore how PLGA NP-loaded cargoes are released in the retina in vivo, we thereafter monitored the Cyanine5.5 amine (Cy5.5) covalently linked PLGA polymer (Cy5.5-PLGA) in parallel to DiI and Rho123. The Cy5.5 signal from PLGA polymer was detectable in the retina vessels >90 min for both, the Cy5.5-PLGA-DiI/P188 and Cy5.5-PLGA-Rho123/P188 groups. Microscopy of the ex vivo retina tissue revealed partial level of colocalization of PLGA with DiI but no colocalization between PLGA and Rho123 at 2 h post injection. This indicates that at least a fraction of the lipophilic DiI was preserved within NPs, whereas no hydrophilic Rho123 was associated with NPs at that time point. In conclusion, the properties of PLGA carrier-cargo system in the blood circulation of the retina might be strongly influenced by the combination of factors, including the individual properties of loaded compounds and blood milieu. Thus, it is unlikely that a single nanoparticle formulation will be identified that is universally effective for the delivery of different compounds.

Phototoxic effectiveness of zinc phthalocyanine tetrasulfonic acid on MCF-7 cells with overexpressed P-glycoprotein.

The development of multidrug resistance is often associated with the over-expression of P-glycoprotein (P-gp). This protein prevents drug accumulation and extrudes them out of the cell before they reach the intended target. The aim of this study was to develop an in vitro MCF-7 cell line with increased expression of P-gp and test the phototoxicity of a novel photoactivated zinc phthalocyanine tetrasulfonic acid (ZnPcS4) on these cells. The over-expressed P-gp MCF-7 cells (MCF-7/DOX) were developed from wildtype (WT) MCF-7 cells by a stepwise continuous exposure of the WT cells to different concentrations of Doxorubicin (DOX) (0.1 - 1 µM) over a period of 4 months. The P-gp expression was measured using flow cytometry, immunofluorescence and enzyme immunoassay. To verify whether zinc phthalocyanine-mediated photodynamic therapy (ZnPcS4 - PDT) is effective in MCF-7/DOX, we studied the subcellular localization, phototoxicity and nuclear damage. The flow cytometry result showed two distinct peaks of P-gp positive and negative expression in MCF-7/DOX cell population, which correlates with the ELISA-based assay (p˂0.001). The ME16C (Normal breast cells) was used as control. The localization studies showed that ZnPcS4 have greater affinity for lysosome than mitochondria. Phototoxicity results indicated that photoactivated zinc phthalocyanine decreased the cell proliferation and viability as the drug and laser light dosages increased to 16 µM and 20 J/cm2 respectively. PDT-induced cytotoxicity using lactose dehydrogenase (LDH) enzyme leakage as measure did not increase likewise. The ZnPcS4-induced PDT was less effective for MCF-7/DOX cells which could be attributed to decreased retention of ZnPcS4 in major cellular organelles due to the presence of increased drug efflux P-gp. The current findings suggest that, increased P-gp expression, a characteristic of multidrug resistance together with other related intrinsic mechanisms might contribute to render MCF-7/DOX cells less sensitive to ZnPcS4-induced phototoxicity.

Testosterone and androstenedione are endogenous substrates of P-glycoprotein.

Raised brain levels of testosterone (Tes), as well as single nucleotide polymorphisms of P-glycoprotein (P-gp) that cause impaired transport function, are associated with increased risk of suicide. Here, we examined whether Tes and its precursors and metabolites are substrates of P-gp, using several in vitro methods. In ATPase assay, increased ATP consumption was observed as the concentrations of Tes, dihydroepiandrosterone (Dhea), androstenedione (Ado), and dihydrotestosterone (Dht), but not androstenediol (Adol), were increased, suggesting that these four androgens are transported by P-gp. Furthermore, Tes and Ado, though not Dhea or Dht, increased the intracellular accumulation of Rhodamine 123 (Rho123), a typical substrate of P-gp, in a P-gp-overexpressing cell line, suggesting that they inhibit Rho123 efflux and thus are substrates or inhibitors of P-gp. A membrane permeability study using P-gp-overexpressing cells in Transwell inserts indicated that the permeability coefficients of both Ado and Tes in the basal-to-apical direction (excretion) are significantly higher than those in the apical-to-basal direction. Moreover, transport of both Ado and Tes was significantly suppressed by verapamil, a typical P-gp inhibitor. These results indicate that Tes and Ado are endogenous substrates of P-gp. These findings provide a physiological basis for understanding previously reported associations of P-gp dysfunction and raised brain levels of Tes with suicidal behavior, and may open up new possibilities for treating patients at risk of suicide.

Delayed Blood Processing Leads to Rapid Deterioration in the Measurement of the Neutrophil Respiratory Burst by the Dihydrorhodamine-123 Reduction Assay.

BACKGROUND: Neutrophils ex vivo in whole blood specimens are widely understood to decay rapidly when compared to other leukocytes, requiring assessment of neutrophil activity to be performed shortly after blood collection. There is a disparity in evidence for decay rates in measurements and recommended time-frames for assaying neutrophil parameters in particular assays following blood collection. We, therefore, evaluated the decline in the neutrophil respiratory burst, typically screened for assessing congenital NADPH oxidase defects, over a shorter time-course than previously published experiments. METHODS: The neutrophil respiratory burst was assessed by flow cytometric detection of DHR-123 oxidation to rhodamine-123 (Rho123), following stimulation of neutrophils by phorbol myristate acetate (PMA), in heparinized healthy donor blood specimens immediately following venipuncture, and then at 3 and 5 h later with ambient temperature or refrigerated specimen storage. RESULTS: A consistent time-dependent decline in the Rho123 fluorescence of PMA-stimulated neutrophils was detected in the healthy donor specimens, indicating a decay in respiratory burst activity. Neutrophil oxidative indexes calculated for half of the specimens at 3 and 5 h of age, fell below our normal laboratory lower limit. We also found that Rho123 histograms of PMA-stimulated neutrophils from stored healthy donor specimens have a risk of misinterpretation due to mimicking the appearance of histograms from carriers of CGD and other NADPH oxidase defects. Refrigeration of specimens did not significantly minimize decay. CONCLUSIONS: DHR assay of the neutrophil respiratory burst from blood specimens at 3 h post-venipuncture and beyond can generate unreliable clinical measurements due to decay. © 2019 International Clinical Cytometry Society.

A Noncovalent Fluorescence Turn-on Strategy for Hypoxia Imaging.

Hypoxia plays crucial roles in many diseases and is a central target for them. Present hypoxia imaging is restricted to the covalent approach, which needs tedious synthesis. In this work, a new supramolecular host-guest approach, based on the complexation of a hypoxia-responsive macrocycle with a commercial dye, is proposed. To exemplify the strategy, a carboxyl-modified azocalix[4]arene (CAC4A) was designed that binds to rhodamine 123 (Rho123) and quenches its fluorescence. The azo groups of CAC4A were selectively reduced under hypoxia, leading to the release of Rho123 and recovery of its fluorescence. The noncovalent strategy was validated through hypoxia imaging in living cells treated with the CAC4A-Rho123 reporter pair.

ROS-Responsive N-Alkylaminoferrocenes for Cancer-Cell-Specific Targeting of Mitochondria.

Mitochondrial membrane potential is more negative in cancer cells than in normal cells, allowing cancer targeting by delocalized lipophilic cations (DLCs). However, as the difference is rather small, these drugs affect also normal cells. Now a concept of pro-DLCs is proposed based on an N-alkylaminoferrocene structure. These prodrugs are activated by the reaction with reactive oxygen species (ROS) forming ferrocenium-based DLCs. Since ROS are overproduced in cancer, the high-efficiency cancer-cell-specific targeting of mitochondria could be achieved as demonstrated by fluorescence microscopy in combination with two fluorogenic pro-DLCs in vitro and in vivo. We prepared a conjugate of another pro-DLC with a clinically approved drug carboplatin and confirmed that its accumulation in mitochondria was higher than that of the free drug. This was reflected in the substantially higher anticancer effect of the conjugate.

Fluorescence Measurement of Mitochondrial Membrane Potential Changes in Cultured Cells.

The mitochondrial membrane potential is the dominant component of the proton-motive force that is the potential term in the proton circuit linking electron transport to ATP synthesis and other energy-dependent mitochondrial processes. Cationic fluorescent probes have been used for many years to detect gross qualitative changes in mitochondrial membrane potentials in intact cell culture. In this chapter I describe how these fluorescence signals may be used to obtain a semiquantitative measure of changes in mitochondrial membrane potential.

Reconstitution and functional studies of hamster P-glycoprotein in giant liposomes.

This paper describes the preparation of giant unilamellar vesicles with reconstituted hamster P-glycoprotein (Pgp, ABCB1) for studying the transport activity of this efflux pump in individual liposomes using optical microscopy. Pgp, a member of ABC (ATP-binding cassette) transporter family, is known to contribute to the cellular multidrug resistance (MDR) against variety of drugs. The efficacy of many therapeutics is, thus, hampered by this efflux pump, leading to a high demand for simple and effective strategies to monitor the interactions of candidate drugs with this protein. Here, we applied small Pgp proteoliposomes to prepare giant Pgp-bearing liposomes via modified electroformation techniques. The presence of Pgp in the membrane of giant proteoliposomes was confirmed using immunohistochemistry. Assessment of Pgp ATPase activity suggested that this transporter retained its activity upon reconstitution into giant liposomes, with an ATPase specific activity of 439 ± 103 nmol/mg protein/min. For further confirmation, we assessed the transport activity of Pgp in these proteoliposomes by monitoring the translocation of rhodamine 123 (Rho123) across the membrane using confocal microscopy at various ATP concentrations (0-2 mM) and in the presence of Pgp inhibitors. Rate of change in Rho123 concentration inside the liposomal lumen was used to estimate the Rho123 transport rates (1/s) for various ATP concentrations, which were then applied to retrieve the Michaelis-Menten constant (Km) of ATP in Rho123 transport (0.42 ± 0.75 mM). Similarly, inhibitory effects of verapamil, colchicine, and cyclosporin A on Pgp were studied in this system and the IC50 values for these Pgp inhibitors were found 26.6 ± 6.1 µM, 94.6 ± 47.6 µM, and 0.21 ± 0.07 µM, respectively. We further analyzed the transport data using a kinetic model that enabled dissecting the passive diffusion of Rho123 from its Pgp-mediated transport across the membrane. Based on this model, the permeability coefficient of Rho123 across the liposomal membrane was approximately 1.25×10-7 cm/s. Comparing the membrane permeability in liposomes with and without Pgp revealed that the presence of this protein did not have a significant impact on membrane integrity and permeability. Furthermore, we used this model to obtain transport rate constants for the Pgp-mediated transport of Rho123 (m3/mol/s) at various ATP and inhibitor concentrations, which were then applied to estimate values of 0.53 ± 0.66 mM for Km of ATP and 25.2 ± 5.0 µM for verapamil IC50, 61.8 ± 34.8 µM for colchicine IC50, and 0.23 ± 0.09 µM for cyclosporin A IC50. The kinetic parameters obtained from the two analyses were comparable, suggesting a minimal contribution from the passive Rho123 diffusion across the membrane. This approach may, therefore, be applied for screening the transport activity of Pgp against potential drug candidates.

Excipient-drug pharmacokinetic interactions: Effect of disintegrants on efflux across excised pig intestinal tissues.

Pharmaceutical excipients were designed originally to be pharmacologically inert. However, certain excipients were found to have altering effects on drug pharmacodynamics and/or pharmacokinetics. Pharmacokinetic interactions may be caused by modulation of efflux transporter proteins, intercellular tight junctions and/or metabolic enzyme amongst others. In this study, five disintegrants from different chemical classes were evaluated for P-glycoprotein (P-gp) related inhibition and tight junction modulation effects. Bi-directional transport studies of the model compound, Rhodamine 123 (R123) were conducted in the absence (control group) and presence (experimental groups) of four concentrations of each selected disintegrant across excised pig jejunum tissue. The results showed that some of the selected disintegrants (e.g. Ac-di-sol® and Kollidon® CL-M) increased R123 absorptive transport due to inhibition of P-gp related efflux, while another disintegrant (e.g. sodium alginate) changed R123 transport due to inhibition of P-gp in conjunction with a transient opening of the tight junctions in a concentration dependent way. It may be concluded that the co-application of some disintegrants to the intestinal epithelium may lead to pharmacokinetic interactions with drugs that are susceptible to P-gp related efflux. However, the clinical significance of these in vitro permeation findings should be confirmed by means of in vivo studies.

Metformin enhances doxorubicin sensitivity via inhibition of doxorubicin efflux in P-gp-overexpressing MCF-7 cells.

Resistance against chemotherapy is still a major problem in successful cancer treatment in the clinic. Therefore, identifying new compounds with lower side-effects and higher efficacy is an important approach to overcome multidrug resistance (MDR). Here, we investigated the activity and possible mechanism of the antidiabetic drug, metformin, in human doxorubicin (DOX)-resistant breast cancer (MCF-7/DOX) cells. The effect of metformin on the cytotoxicity of DOX was evaluated by MTT assay. The P-gp mRNA/protein expression levels following treatment with metformin were determined using real-time polymerase chain reaction and Western blot analysis, respectively. Intracellular rhodamine 123 accumulation assay was performed to evaluate the P-gp function. Cellular ATP content was determined using ATP assay kit. The effect of metformin on DOX-induced apoptosis was evaluated by annexin V/FITC assay. Exposure to metformin considerably enhanced the cytotoxicity of DOX. Metformin had no substantial effect on P-gp expression, while the activity of P-gp and intracellular ATP content decreased with metformin treatment in a dose-dependent manner. Furthermore, metformin significantly increased the DOX-induced apoptosis. These results indicate that metformin could reverse MDR in breast cancer cells by reducing P-gp activity. Therefore, metformin can be suggested as a potent adjuvant in breast cancer chemotherapy.

Pharmacokinetic interaction of green tea beverage containing cyclodextrins and high concentration catechins with P-glycoprotein substrates in LLC-GA5-COL150 cells in vitro and in the small intestine of rats in vivo.

OBJECTIVES: Possible interaction of green tea beverage (GT) containing cyclodextrins and high concentration catechins, a drinking water, with P-glycoprotein (P-gp) substrates was examined in vitro and in vivo. METHODS: Effects of GT on the uptake of rhodamine 123 by LLC-GA5-COL150 cells and intestinal efflux of rhodamine 123 from blood, intestinal absorption of quinidine from ileum loop and oral absorption of digoxin were examined in rats. Effects of GT and GT components on digoxin solubility were also examined. KEY FINDINGS: Green tea increased the uptake of rhodamine 123 by LLC-GA5-COL150 cells, suppressed the intestinal efflux of rhodamine 123 from blood and increased the absorption of quinidine in the ileum of rats. Also, GT increased the solubility of digoxin, and ingestion of GT significantly increased the oral absorption of digoxin given at a high dose in rats. CONCLUSIONS: Green tea suppressed the P-gp-mediated efflux transport of hydrophilic compounds and increased the solubility of lipophilic compounds. Thus, GT may cause interaction with various P-gp substrates, due to the combined effects of catechins and cyclodextrins. Especially, cyclodextrin alone can cause interaction with various low-solubility compounds in vivo. In taking low-solubility drugs including low-solubility P-gp substrates, cyclodextrin-containing foods and beverages such as GT should be avoided.

Nonequilibrium fluctuations of lipid membranes by the rotating motor protein F1F0-ATP synthase.

ATP synthase is a rotating membrane protein that synthesizes ATP through proton-pumping activity across the membrane. To unveil the mechanical impact of this molecular active pump on the bending properties of its lipid environment, we have functionally reconstituted the ATP synthase in giant unilamellar vesicles and tracked the membrane fluctuations by means of flickering spectroscopy. We find that ATP synthase rotates at a frequency of about 20 Hz, promoting large nonequilibrium deformations at discrete hot spots in lipid vesicles and thus inducing an overall membrane softening. The enhanced nonequilibrium fluctuations are compatible with an accumulation of active proteins at highly curved membrane sites through a curvature-protein coupling mechanism that supports the emergence of collective effects of rotating ATP synthases in lipid membranes.

Evaluation of chemical modified hydrogel formulation for topical suitability.

BACKGROUND: Skin delivery and transdermal delivery are key ambitions of the pharmaceutical and cosmetically researchers. AIM: The study aimed to chemically modify well-known polymeric gelling agents in order to boost their topical suitability by fostering their dermal adhesiveness. METHODS: Conventional chitosan was modified via amide bound formation with sulfhydryl compound thioglycolic acid. Subsequently, preactivated chitosan conjugate was established by preactivation of chitosan-thioglycolic acid with mercaptonicotinamide being covalently attached via disulfide bond linkage. All conjugates were examined due to their dermal adhesiveness and controlled drug release properties. RESULTS: Preactivated chitosan conjugates Exhibit 7.46-fold dermal adhesiveness on skin due to tensile adhesion strength. Furthermore a 1.9-fold controlled release of Rhodamine123 as model drug was determined in comparison to unmodified chitosan. CONCLUSION: Taken together, preactivated chitosan gels show a promising platform for topical application.