Efflux Assay Research Articles

Pilot Study of 64Cu(I) for PET Imaging of Melanoma

At present, 64Cu(II) labeled tracers including 64CuCl2 have been widely applied in the research of molecular imaging and therapy. Human copper transporter 1 (hCTR1) is the major high affinity copper influx transporter in mammalian cells, and specially responsible for the transportation of Cu(I) not Cu(II). Thus, we investigated the feasible application of 64Cu(I) for PET imaging. 64Cu(II) was reduced to 64Cu(I) with the existence of sodium L-ascorbate, DL-Dithiothreitol or cysteine. Cell uptake and efflux assay was investigated using B16F10 and A375 cell lines, respectively. Small animal PET and biodistribution studies were performed in both B16F10 and A375 tumor-bearing mice. Compared with 64Cu(II), 64Cu(I) exhibited higher cellular uptake by melanoma, which testified CTR1 specially influx of Cu(I). However, due to oxidation reaction in vivo, no significant difference between 64Cu(I) and 64Cu(II) was observed through PET images and biodistribution. Additionally, radiation absorbed doses for major tissues of human were calculated based on the mouse biodistribution. Radiodosimetry calculations for 64/67Cu(I) and 64/67Cu(II) were similar, which suggested that although melanoma were with high radiation absorbed doses, high radioactivity accumulation by liver and kidney should be noticed for the further application. Thus, 64Cu(I) should be further studied to evaluate it as a PET imaging radiotracer.

Plasma metabolite profiles, cellular cholesterol efflux, and non-traditional cardiovascular risk in patients with CKD

BackgroundPatients with chronic kidney disease (CKD) experience high rates of atherosclerotic cardiovascular disease and death that are not fully explained by traditional risk factors. In animal studies, defective cellular cholesterol efflux pathways which are mediated by the ATP binding cassette transporters ABCA1 and ABCG1 are associated with accelerated atherosclerosis. We hypothesized that cholesterol efflux in humans would vary in terms of cellular components, with potential implications for cardiovascular disease. MethodsWe recruited 120 CKD patients (eGFR<30mL/min/1.73m2) and 120 control subjects (eGFR ≥60mL/min/1.73m2) in order to measure cholesterol efflux using either patients' HDL and THP-1 macrophages or patients' monocytes and a flow cytometry based cholesterol efflux assay. We also measured cell-surface levels of the common β subunit of the IL-3/GM-CSF receptor (IL-3Rβ) which has been linked to defective cholesterol homeostasis and may promote monocytosis. In addition, we measured plasma inflammatory cytokines and plasma metabolite profiles. ResultsThere was a strong positive correlation between cell-surface IL-3Rβ levels and monocyte counts in CKD (P<0.001). ABCA1 mRNA was reduced in CKD vs. control monocytes (P<0.05), across various etiologies of CKD. Cholesterol efflux to apolipoprotein A1 was impaired in monocytes from CKD patients with diabetic nephropathy (P<0.05), but we found no evidence for a circulating HDL-mediated defect in cholesterol efflux in CKD. Profiling of plasma metabolites showed that medium-chain acylcarnitines were both independently associated with lower levels of cholesterol transporter mRNA in CKD monocytes at baseline (P<0.05), and with cardiovascular events in CKD patients after median 2.6years of follow-up. ConclusionsCholesterol efflux in humans varies in terms of cellular components. We report a cellular defect in ABCA1-mediated cholesterol efflux in monocytes from CKD patients with diabetic nephropathy. Unlike several traditional risk factors for atherosclerotic cardiovascular disease, plasma metabolites inversely associated with endogenous cholesterol transporters predicted cardiovascular events in CKD patients. (Funded by the National Institute of Diabetes and Digestive and Kidney DiseasesK23DK097288 and others.)

Development of an assay for cellular efflux of pharmaceutically active agents and its relevance to understanding drug interactions.

Drug interactions may dictate the failure or success of a treatment. Patients undergoing hematopoietic stem cell transplantation (HSCT) are exposed to various types of drugs, and understanding how these drugs interact is of the utmost importance. The pharmacokinetics of busulfan, melphalan, and cyclophosphamide, drugs commonly used for HSCT, are known to be affected by a variety of other drugs with differing molecular structures. We hypothesized that these structurally unrelated drugs affect the transport of DNA-alkylating agents. To test this hypothesis, we developed a flow cytometry assay that used 5-carboxyfluorescein diacetate acetoxymethyl ester, which is cleaved by nonspecific intracellular esterases to 5-carboxyfluorescein (5-CF), a fluorescent ligand for the drug transporter MRP1. A decreased 5-CF efflux in the presence of a test compound suggests competitive inhibition. We demonstrated that chlorambucil, 4-hydroperoxycyclophosphamide, ketoconazole, ethacrynic acid, everolimus, and sirolimus strongly inhibited 5-CF efflux in lymphoma and leukemia cell lines. The efflux of these drugs partially depends on the glutathione (GSH) level, and their cytotoxicity is synergistic with inhibited GSH synthesis. This is consistent with the hypothesis that their GSH-conjugated products are ligands of a common cellular drug transporter. Our results may explain clinical observations on the effects of various drugs on the pharmacokinetics and pharmacodynamics of alkylating agents, and the assay may be used to deduce interaction mechanisms of drugs transported by a common system.

SIRT6 reduces macrophage foam cell formation by inducing autophagy and cholesterol efflux under ox-LDL condition.

SIRT6 is a pivotal regulator of lipid metabolism. It is also closely connected to cardiovascular diseases, which are the main cause of death in diabetic patients. We observed a decrease in the expression of SIRT6 and key autophagy effectors (ATG5, LC3B, and LAMP1) in ox-LDL-induced foam cells, a special form of lipid-laden macrophages. In these cells, SIRT6 WT but not SIRT6 H133Y overexpression markedly reduced foam cell formation, as shown by Oil Red O staining, while inducing autophagy flux, as determined by both mRFP-GFP-LC3 labeling and transmission electron microscopy. Silencing the key autophagy initiation gene ATG5, reversed the autophagy-promoting effect of SIRT6 in ox-LDL-treated THP1 cells, as evidenced by an increase in foam cells. Cholesterol efflux assays indicated that SIRT6 overexpression in foam cells promoted cholesterol efflux, increased the levels of ABCA1 and ABCG1, and reduced miR-33 levels. By transfecting miR-33 into cells overexpressing SIRT6, we observed that reduced foam cell formation and autophagy flux induction were largely reversed. These data imply that SIRT6 plays an essential role in protecting against atherosclerosis by reducing foam cell formation through an autophagy-dependent pathway.

Reversal of multidrug resistance by Marsdenia tenacissima and its main active ingredients polyoxypregnanes

Ethnopharmacological relevanceMultidrug resistance (MDR) of cancer is often associated with the overexpression of ATP-binding cassette (ABC) transporters, such as P-glycoprotein (P-gp), multidrug resistance-associated protein-1 (MRP-1) and breast cancer resistance protein (BCRP or ABCG2), in cancer cells, which facilitates the active efflux of a wide variety of chemotherapeutic drugs out of the cells. Marsdenia tenacissima is a traditional Chinese medicinal herb that has long been clinically used for treatment of cancers, particularly in combinational use with anticancer drugs. Polyoxypregnanes (POPs) are identified as main constituents of this herb, and three of them have been reported to exhibit P-gp modulatory effect and thus reverse MDR. Therefore, it is of great necessity to investigate more POPs that have potential to reverse transporters-mediated MDR. Aim of the studyWe aimed to identify POPs as the chemical basis responsible for circumventing ABC transporters-mediated MDR by M. tenacissima. Materials and methodsThe MDR reversal effects of M. tenacissima crude extract together with a series of isolated POPs were evaluated on several MDR cancer cell lines that overexpress P-gp, MRP1 or ABCG2. The activities of P-gp, MRP1 and ABCG2 were determined by the flow cytometry-based substrate efflux assay. Molecular docking of POPs to a three-dimensional human P-gp homology structure was also performed. ResultsThe crude extract of M. tenacissima was firstly found to circumvent P-gp-mediated MDR. Then, 11 polyoxypregnane compounds (POPs) isolated from this herb were found to overcome P-gp-, MRP1- and/or ABCG2-mediated MDR. Further mechanistic study delineated that the reversal of MDR by these POPs was due to significant increase in the intracellular concentrations of the substrate anticancer drugs via their inhibition of different ABC transporter-mediated efflux activities. Furthermore, molecular docking revealed that POPs with P-gp modulatory effect bound to P-gp and fitted well into the cavity between the alpha and beta subunit of P-gp via forming hydrogen bonds. In addition, several key structural determinants for inhibition of P-gp, MRP1 or ABCG2 by POPs were illustrated. ConclusionsOur findings advocated the rational use of M. tenacissima to enhance efficacies of conventional anticancer drugs in tumors with ABC drug transporters-mediated MDR. Furthermore, 11 POPs were found to contribute to MDR reversal effect of M. tenacissima via inhibition of different ABC efflux transporters.

Biophysical and Pharmacological Characterization of Energy-Dependent Efflux of Sb in Laboratory-Selected Resistant Strains of Leishmania (Viannia) Subgenus.

The growing resistance of leishmaniasis to first-line drugs like antimonials in some regions limits the control of this parasitic disease. The precise mechanisms involved in Leishmania antimony resistance are still subject to debate. The reduction of intracellular SbIII accumulation is a common change observed in both laboratory-selected and field isolated resistant Leishmania strains, but the exact transport pathways involved in antimony resistance have not yet been elucidated. In order to functionally characterize the antimony transport routes responsible for resistance, we performed systematic transport studies of SbIII in wild-type and resistant strains of L. (Viannia) guyanensis and L. (V.) braziliensis. Those include influx and efflux assays and the influence of ABC transporters and metabolism inhibitors: prochlorperazine, probenecid, verapamil, BSO, and sodium azide. The mRNA levels of genes associated with antimony resistance (MRPA, GSH1, ODC, AQP1, ABCI4, and ARM58) were also investigated in addition to intracellular thiol levels. A strong reduction of Sb influx was observed in L. guyanensis resistant mutant (LgSbR), but not in L. braziliensis (LbSbR). Both mutants showed increased energy-dependent efflux of SbIII, when compared to their respective parental strains. In LgSbR, BSO and prochlorperazine inhibited antimony efflux and resistance was associated with increased MRPA and GSH1 mRNA levels, while in LbSbR antimony efflux was inhibited by probenicid and prochlorperazine in absence of resistance-associated gene modulation. Intracellular thiol levels were increased in both Sb-resistant mutants. An energy-dependent SbIII efflux pathway sensitive to prochlorperazine was clearly evidenced in both Sb-resistant mutants. In conclusion, the present study allowed the biophysical and pharmacological characterization of energy-dependent Sb efflux pathway apparently independent of MRPA, ABCI4, and ARM58 upregulation, in Leishmania (Vianna) mutant selected in vitro for resistance to SbIII. Prochlorperazine has also been identified as an effective chemosensitizer in both Sb resistant mutants, which acts through inhibition of the active efflux of Sb.

Role of STARD4 in sterol transport between the endocytic recycling compartment and the plasma membrane.

Cholesterol is an essential constituent of membranes in mammalian cells. The plasma membrane and the endocytic recycling compartment (ERC) are both highly enriched in cholesterol. The abundance and distribution of cholesterol among organelles are tightly controlled by a combination of mechanisms involving vesicular and nonvesicular sterol transport processes. Using the fluorescent cholesterol analogue dehydroergosterol, we examined sterol transport between the plasma membrane and the ERC using fluorescence recovery after photobleaching and a novel sterol efflux assay. We found that sterol transport between these organelles in a U2OS cell line has a t1/2 =12-15 min. Approximately 70% of sterol transport is ATP independent and therefore is nonvesicular. Increasing cellular cholesterol levels dramatically increases bidirectional transport rate constants, but decreases in cholesterol levels have only a modest effect. A soluble sterol transport protein, STARD4, accounts for ∼25% of total sterol transport and ∼33% of nonvesicular sterol transport between the plasma membrane and ERC. This study shows that nonvesicular sterol transport mechanisms and STARD4 in particular account for a large fraction of sterol transport between the plasma membrane and the ERC.

Serum cholesterol acceptor capacity in intrauterine growth restricted fetuses.

Intrauterine growth restriction (IUGR) is an independent risk factor for the development of cardiovascular diseases later in life. The mechanisms whereby slowed intrauterine growth confers vascular risk are not clearly established. In general, a disturbed cholesterol efflux has been linked to atherosclerosis. The capacity of serum to accept cholesterol has been repeatedly evaluated in clinical studies by the use of macrophage-based cholesterol efflux assays and, if disturbed, precedes atherosclerotic diseases years before the clinical diagnosis. We now hypothesized that circulating cholesterol acceptors in IUGR sera specifically interfere with cholesterol transport mechanisms leading to diminished cholesterol efflux. RAW264.7 cells were used to determine efflux of [3H]-cholesterol in response to [umbilical cord serum (IUGR), n=20; controls (CTRL), n=20]. Cholesterol efflux was lower in IUGR as compared to controls [controls: mean 7.7% fractional [3H]-cholesterol efflux, standard deviation (SD)=0.98; IUGR: mean 6.3%, SD=0.79; P<0.0001]. Values strongly correlated to HDL (ρ=0.655, P<0.0001) and apoE (ρ=0.510, P=0.0008), and mildly to apoA1 (ρ=0.3926, P=0.0122) concentrations. Reduced cholesterol efflux in IUGR could account for the enhanced risk of developing cardiovascular diseases later in life.

High-Throughput Simulations Reveal Membrane-Mediated Effects of Alcohols on MscL Gating.

The mechanosensitive channels of large conductance (MscL) are bacterial membrane proteins that serve as last resort emergency release valves in case of severe osmotic downshock. Sensing bilayer tension, MscL channels are sensitive to changes in the bilayer environment and are, therefore, an ideal test case for exploring membrane protein coupling. Here, we use high-throughput coarse-grained molecular dynamics simulations to characterize MscL gating kinetics in different bilayer environments under the influence of alcohols. We performed over five hundred simulations to obtain sufficient statistics to reveal the subtle effects of changes in the membrane environment on MscL gating. MscL opening times were found to increase with the addition of the straight-chain alcohols ethanol, octanol, and to some extent dodecanol but not with hexadecanol. Increasing concentration of octanol increased the impeding effect, but only up to 10–20 mol %. Our in silico predictions were experimentally confirmed using reconstituted MscL in a liposomal fluorescent efflux assay. Our combined data reveal that the effect of alcohols on MscL gating arises not through specific binding sites but through a combination of the alcohol-induced changes to a number of bilayer properties and their alteration of the MscL–bilayer interface. Our work provides a key example of how extensive molecular simulations can be used to predict the functional modification of membrane proteins by subtle changes in their bilayer environment.

Efflux inhibitor suppresses Streptococcus mutans virulence properties.

It is well established that efflux pumps play important roles in bacterial pathogenicity and efflux inhibitors (EIs) have been proved to be effective in suppressing bacterial virulence properties. However, little is known regarding the EI of Streptococcus mutans, a well-known caries-inducing bacterium. In this study, we identified the EI of S. mutans through ethidium bromide efflux assay and investigated how EI affected S. mutans virulence regarding the cariogenicity and stress response. Results indicated that reserpine, the identified EI, suppressed acid tolerance, mutacin production and transformation efficiency of S. mutans, and modified biofilm architecture and extracellular polysaccharide distribution. Suppressed glycosyltransferase activity was also noted after reserpine exposure. The data from quantitative real-time-PCR demonstrated that reserpine significantly altered the expression profile of quorum-sensing and virulence-associated genes. These findings suggest that reserpine represents a promising adjunct anticariogenic agent in that it suppresses virulence properties of S. mutans.

Molecular characterization of ABC transporters in marine ciliate, Euplotes crassus: Identification and response to cadmium and benzo[a]pyrene

ATP-binding cassette (ABC) transporters participate in transporting various substances, including xenobiotics, in or out of cells. However, their genetic information and function in ciliates remain still unclear. In this study, we sequenced and characterized two ABC transporter genes (EcABCB and EcABCC), and investigated the effect of cadmium (Cd) and benzo[a]pyrene (B[a]P) on their function and gene expression, using efflux assay and real-time reverse transcription-polymerase chain reaction (qRT-PCR), respectively, in the marine ciliate, Euplotes crassus. Sequencing analysis and efflux assay showed that EcABCB and EcABCC are typical ABC transporters, possessing conserved function. Exposure to Cd (≥5mg/L) and B[a]P (≥50.5μg/L) enhanced accumulation of a substrate. A significant increase in the expression of EcABCB and EcABC mRNA was observed at lower concentration in response to Cd and B[a]P. Our findings indicate that Cd and B[a]P could inhibit the efflux function of ABC transporters, leading to cellular toxicity in the ciliate.

Polymorphisms in the multidrug-resistance 1 gene related to glucocorticoid response in rheumatoid arthritis treatment

A substantial proportion of rheumatoid arthritis (RA)-patients experience an insufficient response to glucocorticoids, an important therapeutic agent in RA. The multidrug-resistance 1 (MDR1) gene product P-glycoprotein (P-gp) is an efflux pump that actively transports substrates, such as glucocorticoids, out of the cell. We investigated if the variation in response might be explained by single-nucleotide polymorphisms (SNPs) in the MDR1 gene. RA-patients treated with intravenous methylprednisolone pulses (n = 18) or oral prednisone/prednisolone (n = 22) were included in a prospective cohort, and clinical response was measured after 5 and 30 days, respectively. The C1236T, G2677A/T, and C3435T SNPs were determined, and the functionality of P-gp was assessed by flow cytometry (Rhodamine efflux assay). Carriage of the G2677A/T SNP was significantly associated with response (OR = 6.18, p = 0.035), the other SNPs showed trends. Stratified for received treatment, the effect was only present in methylprednisolone treated patients. Mutant allele carriage significantly decreased functionality of P-gp in B cells, though had a smaller impact in other PBMC subtypes. Carriage of a MDR1 SNP was related to a response to methylprednisolone in this study, which his suggests that RA-patients carrying wild-type alleles might benefit from P-gp inhibition or administration of glucocorticoid analogues that are non-P-gp substrates.

Preparation and biological evaluation of 111In-triphenylphosphonium cations

Objective To synthesize 4 kinds of 111In-TPP cations and evaluate their properties as tumor cationic radiotracers in vivo and in vitro. Methods DO3A-xy-TPP, DO3A-xy-mTPP, DO3A-xy-dmTPP and DO3A-xy-tmTPP were radiolabeled with 111In; their lipid-water partition coefficients and in vivo and in vitro stability were evaluated. The binding affinities of 4 kinds of 111In-radiotracers were determined in cell uptake and cell efflux assay using U87MG tumor cells. Biodistribution studies and γ imaging studies were performed using the athymic nude mice bearing U87MG human glioma xenografts to explore the biological properties of 4 kinds of 111In-radiotracers. One-way analysis of variance was used. Results The labeling yields of 4 kinds of 111In-radiotracers were all above 85%, and the radiochemical purity were all greater than 99% after purification. Binding assay in U87MG cells showed that 4 kinds of radiotracers had great binding affinity and cell retention ability, and 111In-DO3A-xy-mTPP had the best binding ratio (1.49%; F=177.8, P<0.05). Gamma imaging and biodistribution results showed that the U87MG tumors could be clearly visualized by 111In-DO3A-xy-mTPP, 111In-DO3A-xy-dmTPP and 111In-DO3A-xy-tmTPP, and the liver uptake of the 3 tracers was lower than that of 111In-DO3A-xy-TPP. In particular, 111In-DO3A-xy-mTPP had the best tumor/liver ratio (0.13±0.05, 2 h postinjection; F=9.4, P<0.05). Conclusions The tumor-targeted ability of 111In-DO3A-xy-mTPP is better than those of 111In-DO3A-xy-dmTPP, 111In-DO3A-xy-tmTPP and 111In-DO3A-xy-TPP, suggesting that it has the potential to be a promising tumor cationic radiotracer. Key words: Triphenylphosphonium; Isotope labeling; Indium radioisotopes; Glioma; Radionuclide imaging; Mice, nude

G004, a synthetic sulfonylurea compound, exerts anti-atherosclerosis effects by targeting SIRT1 in ApoE−/− mice

Atherosclerosis attracts increasing global attention because of its morbidity and mortality. G004, as a synthetic sulfonylurea compound, has been confirmed to have anti-hyperglycaemia, anti-platelet and anti-thrombus effects. The aim of the present study was to investigate whether G004 suppress the onset and development of atherosclerosis and illuminate its probable mechanism of action. ApoE−/− mice that were fed a high-fat diet were randomly divided into five groups by weight; subsequently, they were treated with vehicle, G004, at different doses or atorvastatin once daily for 12weeks. Meanwhile, C57BL/6 mice with the same diet served as the normal controls. Then, the serum lipid profiles and histopathological damage to the liver, kidney, aortic arch and aortic root were analysed. The activation of endothelial nitric oxide synthase (eNOS) and levels of inflammatory markers were detected. Reverse cholesterol transport (RCT) was assessed in vivo by intraperitoneal injection of RAW264.7 cells that were radiolabelled with 3H-cholesterol. The results indicated that G004 ameliorated the serum lipid accumulation, atherosclerotic lesions and liver steatosis. Additionally, this compound increased the expression of SIRT1 and eNOS as well as the phosphorylation and deacetylation of eNOS in the aorta, alleviating the inflammatory state. RCT was promoted in ApoE−/− mice, which was accompanied by increased expression of SIRT1/LXRα/ABCA1/G1 in the liver, and similar results appeared in the cholesterol efflux assay in RAW264.7 cells. The results provide a strong rationale for G004 to be an efficient anti-atherosclerosis agent that improved vascular endothelial dysfunction by stimulating SIRT1/eNOS and promoted RCT by stimulating SIRT1/LXRα/ABCA1/G1.

Discrimination of the Effects of Doxorubicin on Two Different Breast Cancer Cell Lines on Account of Multidrug Resistance and Apoptosis

Breast cancer is one of the most common cancer types and malfunctioning proteins in apoptotic pathways are known to be the main contributors of cancer development. In this study MCF-7 and MDA-MB-231 breast cancer cell lines were treated with a potent chemotherapeutic agent, Doxorubicin. IC50 values were calculated to be 8306 and 6602 nM, respectively. Percentage of the cells in cell cycle arrest increased in a dose-dependent manner and was more evident in MDA-MB-231 cells. Apoptotic cell number increased in MCF-7 and Bax/Bcl-2 ratio was measured to be ~ 7 fold higher in cells treated with 200 nM of doxorubicin when compared to the control. Likewise, apoptotic cell rate increased in MDA-MB-231 cells and Bax/Bcl-2 ratio was increased by 2 fold compared to the control. Doxorubicin was also found to suppress Mdr-1 in a concentration-dependent manner and the outcome was more evident in MCF-7 cells. Drug efflux assay results were also shown to be consistent with Mdr-1 gene expression levels in both cell lines. Consequently it was concluded that doxorubicin directly influences apoptotic pathway and multidrug resistance in both MCF-7 and MDA-MB-231 cells even though data all together suggest that the effect is more significant on MDA-MB-231.

Fluorescent Ion Efflux Screening Assay for Determining Membrane-Active Peptides

A major global health threat is the emergence of antibiotic-resistant microbes. Coupled with a lack of development of modified antibiotics, there is a need to develop new antimicrobial molecules and screening assays for them. In this study, we provide proof of concept that a large unilamellar vesicle (LUV) method used to study chloride ion efflux facilitated by ionophores and surfactant-like molecules that disrupt membrane integrity can be adapted to identify membrane-interactive antimicrobial peptides (AMPs) and to screen relative activity of AMPs. Lucigenin was encapsulated in LUVs in the presence of Cl– ion (NaCl), which quenches fluorescence, and then incubated with AMPs in 100 mM NaNO3 buffer. Upon AMP membrane interaction or disruption, the Cl– ion is exchanged with the NO3– ion, and the resultant lucigenin fluorescence is indicative of relative AMP activity. Seven AMPs were synthesized by solid-phase peptide chemistry and incubated with LUVs of different phospholipid compositions. Each AMP resulted in lucigenin fluorescence, which was dose dependent, and the relative fluorescence correlated with the minimum inhibitory concentration and minimum bactericidal concentration values for the corresponding peptide. Furthermore, using mammalian model phospholipid LUVs, lucigenin-induced fluorescence also correlated with the AMP cytotoxicity half-maximal inhibitory concentration values. The proline-rich AMP, Chex1-Arg20, which is non-lytic but interacts with the bacterial membrane resulted in lucigenin fluorescence of bacterial membrane model LUVs but not of mammalian membrane model LUVs. The fluorescent ion efflux assay developed here should have applicability for most AMPs and could be tailored to target particular bacterial species membrane composition, potentially leading to the identification of novel membrane-interactive AMPs. The rapid high-throughput method also allows for screening of relative AMP activity and toxicity before biological testing.

ANTICANCER DRUGS AS PROSPECTIVE EFFLUX PUMP INHIBITORS FOR SALMONELLA TYPHI PRODUCE CONFLICTING RESULTS IN IN SILICO AND IN VITRO STUDIES

&lt;p&gt;&lt;strong&gt;Objective: &lt;/strong&gt;Anticancer drugs paclitaxel and vinblastine were tested for their potential as efflux pump inhibitors for &lt;em&gt;Salmonella&lt;/em&gt; Typhi-based on &lt;em&gt;in silico&lt;/em&gt; and &lt;em&gt;in vitro&lt;/em&gt; studies.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Methods: &lt;/strong&gt;Three-dimensional protein models of AcrAB-TolC of &lt;em&gt;Salmonella&lt;/em&gt; Typhi were generated by online server PHYRE-2. The quality of 3D structures was assessed by PROCHECK, SWISS MODEL. Docking analysis of anticancer drugs with AcrA, AcrB and TolC subunits were performed after refining the homology models with Modrefiner. &lt;em&gt;Salmonella&lt;/em&gt; Typhi (&lt;em&gt;S&lt;/em&gt;. Typhi) efflux pump activity was measured by ethidium bromide (EtBr) cartwheel and semi-automated fluorometry methods respectively. Fluorescence intensity in bacterial colonies was measured under different treatment conditions (with or without drugs) on Muller Hinton agar (MHA) plates containing EtBr in cartwheel assay. EtBr efflux assay was determined following the loading of bacteria with EtBr and fluorescence was recorded over fixed time period with the help of fluorescent spectrophotometer. The results obtained were compared with the control.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;Efflux pump inhibitor (EPIs) activity of paclitaxel and vinblastine determined by EtBr cartwheel assay registered no activity whereas semi-automated fluorescent assay revealed marginal activity when compared to control.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusion: &lt;/strong&gt;We report the conflicting result of &lt;em&gt;in silico&lt;/em&gt; and &lt;em&gt;in vitro&lt;/em&gt; studies in predicting the antimicrobial effect of mainstream anticancer drugs as efflux pump inhibitors for &lt;em&gt;Salmonella&lt;/em&gt; Typhi.&lt;/p&gt;

&lt;i&gt;In vitro&lt;/i&gt; and &lt;i&gt;in situ&lt;/i&gt; effects of atorvastatin and ezetimibe on P-glycoprotein expression and function

&lt;p class="Abstract"&gt;P-glycoprotein (P-gp) is a membrane transporter responsible for the active efflux from the cell. Inhibition of the activity may lead to clinically significant drug-drug interactions. This study was performed to investigate the effects of atorvastatin and ezetimibe on the function and expression of P-gp. The &lt;em&gt;in vitro&lt;/em&gt; rhodamine-123 (Rho123) efflux assay and Western blot in Caco-2 cells, and the &lt;em&gt;in situ&lt;/em&gt; rat single-pass intestinal permeability model followed by high performance liquid chromatography were developed. Rho123 intracellular accumulation in 100 µM of atorvastatin- and ezetimibe-treated cells was significantly higher than that in control cells (p&amp;lt;0.05). P-gp expression was decreased by 100 µM atorvastatin and ezetimibe. Intestinal effective permeability of digoxin in the presence of atorvastatin (3 and 100 µM), ezetimibe (10 and 100 µM) was significantly increased (p&amp;lt;0.05). Both drugs inhibited P-gp activity in vitro and&lt;em&gt; in situ&lt;/em&gt;. Atorvastatin and ezetimibe down-regulated the expression of P-gp &lt;em&gt;in vitro&lt;/em&gt;. &lt;/p&gt;&lt;p class="Abstract"&gt;&lt;strong&gt;Video Clip of Methodology&lt;/strong&gt;:&lt;/p&gt;&lt;p class="Abstract"&gt;&lt;a href="https://youtube.com/v/BQuz1ER3_NQ"&gt;Single-pass intestinal permeability&lt;/a&gt;: 17 min 26 sec&lt;/p&gt;&lt;p&gt; &lt;/p&gt;

MtTdp1α-depleted Medicago truncatula plants show reduced cuticle permeability and altered expression of defense genes

The link between the MtTdp1α (tyrosyl-DNA phosphodiesterase) gene, involved in the repair of DNA topoisomerase I mediated DNA damage, and the plant defense response has been investigated in MtTdp1α-depleted Medicago truncatula transgenic lines obtained by intron-spliced hairpin RNA approach, compared to the control line (CTRL, empty vector). Reduction of cuticle permeability highlighted by chlorophyll efflux assays positively correlated with the level of MtTdp1α gene silencing. The increased cuticle thickness was confirmed by transmission electron microscopy, which revealed an apparent expansion of the epicuticular waxes deposited on the outer surface. RNA-Seq analysis, carried out in the MtTdp1α-depleted plants, revealed the different expression of resistance (R) genes, PAMP (pathogen-associated-molecular pattern) triggered immunity (PTI) genes and transcription factors (TFs) involved in the regulation of the plant defense response.

Cholesterol Efflux and Reverse Cholesterol Transport: Experimental Approaches.

Cholesterol efflux as a key event in reverse cholesterol transport (RCT) is considered now as both diagnostic tool and a promising target for the treatment of atherosclerosis. Radioactive in vitro cholesterol efflux assay (CEA) is the gold standard for determination of efflux at cellular level. Fluorescent tracers and stable isotope-labeled cholesterol gradually come into use as convenient tools for non-radioactive CEAs. We review the use of various tracer-based and tracer-free methods for CEAs and for measuring RCT with focus on macrophage-specific cholesterol efflux. CEA utilizing stable isotope-labeled cholesterol is equally reliable with radioactive assay and especially well suited for the determination of both cholesterol efflux and net cholesterol flux. Fluorescent tracers cannot fully mimic cholesterol; however, they are successfully applied in CEA in specific well-defined conditions. Fluorescent CEAs can be high throughput and can provide unique information on efflux from fast cholesterol pools or with single cell resolution. Enzymatic and chromatographic CEAs are net cholesterol flux assays, and they can be applied as efflux assays when used with specific acceptors only. In vivo tests are suited for studies of cholesterol efflux and RCT at the level of the organism. They include injection of tracer-loaded macrophages, a method suitable at present for animal models only, and recently invented modification of whole body tracer kinetics with multicompartment modeling that is capable to determine cholesterol efflux from macrophages. Despite the decisive role of in vitro assays in our understanding of cholesterol efflux mechanism, the in vivo assays are highly desired to study cholesterol efflux in atherosclerotic lesions and RCT in whole body.