Plant-derived secondary metabolites as the main source of efflux pump inhibitors and methods for identification

The upsurge of multiple drug resistance(MDR)bacteria substantially diminishes the effectiveness of antibiotic arsenal and therefore intensifies the rate of therapeutic failure.The major factor in MDR is efflux pump-mediated resistance.A unique pump can make bacteria withstand a wide range of structurally diverse compounds.Therefore,their inhibition is a promising route to eliminate resistance phenomenon in bacteria.Phytochemicals are excellent alternatives as resistance-modifying agents.They can directly kill bacteria or interact with the crucial events of pathogenicity,thereby decreasing the ability of bacteria to develop resistance.Numerous botanicals display noteworthy efflux pumps inhibitory activities.Edible plants are of growing interest.Likewise,some plant families would be excellent sources of efflux pump inhibitors(EPIs)including Apocynaceae,Berberidaceae,Convolvulaceae,Cucurbitaceae,Fabaceae,Lamiaceae,and Zingiberaceae.Easily applicable methods for screening plant-derived EPIs include checkerboard synergy test,berberine uptake assay and ethidium bromide test.In silico highthroughput virtual detection can be evaluated as a criterion of excluding compounds with efflux substrate-like characteristics,thereby improving the selection process and extending the identification of EPIs.To ascertain the efflux activity inhibition,real-time PCR and quantitative mass spectrometry can be applied.This review emphasizes on efflux pumps and their roles in transmitting bacterial resistance and an update plant-derived EPIs and strategies for identification.

Influence of efflux pump inhibitors on the multidrug resistance of Helicobacter pylori

AIM:To evaluate the effect of efflux pump inhibitors (EPIs) on multidrug resistance of Helicobacter pylori (H. pylori).METHODS: H. pylori strains were isolated and cultured on Brucella agar plates with 10% sheep's blood. The multidrug resistant (MDR) H. pylori were obtained with the inducer chloramphenicol by repeated doubling of the concentration until no colony was seen, then the susceptibilities of the MDR strains and their parents to 9 antibiotics were assessed with agar dilution tests. The present study included periods before and after the advent of the EPIs, carbonyl cyanide m-chlorophenyl hydrazone (CCCP), reserpine and pantoprazole), and the minimum inhibitory concentrations (MICs) were determined accordingly. In the same way, the effects of 5 proton pump inhibitors (PPIs), used in treatment of H. pylori infection, on MICs of antibiotics were evaluated.RESULTS: Four strains of MDR H. pylori were induced successfully, and the antibiotic susceptibilities of MDR strains were partly restored by CCCP and pantoprazole, but there was little effect of reserpine. Rabeprazole was the most effective of the 5 PPIs which could decrease the MICs of antibiotics for MDR H. pylori significantly.CONCLUSION: In vitro, some EPIs can strengthen the activities of different antibiotics which are the putative substrates of the efflux pump system in H. pylori.

ABC efflux transporters at blood-central nervous system barriers and their implications for treating spinal cord disorders

The barriers present in the interfaces between the blood and the central nervous system form a major hurdle for the pharmacological treatment of central nervous system injuries and diseases.The family of ATP-binding cassette(ABC)transporters has been widely studied regarding efflux of medications at blood-central nervous system barriers.These efflux transporters include P-glycoprotein(abcb1),‘breast cancer resistance protein'(abcg2)and the various‘multidrug resistance-associated proteins'(abccs).Understanding which efflux transporters are present at the blood-spinal cord,blood-cerebrospinal fluid and cerebrospinal fluid-spinal cord barriers is necessary to determine their involvement in limiting drug transfer from blood to the spinal cord tissue.Recent developments in the blood-brain barrier field have shown that barrier systems are dynamic and the profile of barrier defenses can alter due to conditions such as age,disease and environmental challenge.This means that a true understanding of ABC efflux transporter expression and localization should not be one static value but instead a range that represents the complex patient subpopulations that exist.In the present review,the blood-central nervous system barrier literature is discussed with a focus on the impact of ABC efflux transporters on:(i)protecting the spinal cord from adverse effects of systemically directed drugs,and(ii)limiting centrally directed drugs from accessing their active sites within the spinal cord.

Effects of two efflux pump inhibitors on the drug susceptibility of Riemerella anatipestifer isolates from China

The objective of this study was to verify the supposition that efflux might be involved in the drug resistance of Riemerella anatipestifer isolates. Two broad-spectrum effiux pump inhibitors, carbonyl cyanide 3-chlorophenylhydrazone （CCCP） and Phe-Arg-β-naphthylamide （PAL3N）, on the contribution of minimum inhibitory concentrations of amikacin, streptomycin, chloramphenicol, tetracycline, ceftdaxone, ceftazidime, nalidixic acid, levofloxacin, enrofloxacin, as well as ciprofloxacin against 69 clinical R. anatipestifer isolates were investigated. We first reported that the two efflux pump inhibitors could restore the antimicrobial susceptibility of R. anatipestiferisolates. It is suggested that active efflux system is possible to be linked with the development of resistance in R. anatipestifer isolates.

Winter soil CO_2 efflux in two contrasting forest ecosystems on the eastern Tibetan Plateau, China

Significant CO2 fluxes from snow-covered soils occur in cold biomes. However, little is known about winter soil respiration on the eastern Tibetan Plateau of China. We therefore measured winter soil CO2 fluxes and estimated annual soil respiration in two contrasting coniferous forest ecosystems （a Picea asperata plantation and a natural forest）. Mean winter soil CO2 effluxes were 1.08 μmol m-2 s-1 in the plantation and 1.16 μmol m-2 s-1 in the natural forest. These values are higher than most reported winter soil CO2 efflux values for temperate or boreal forest ecosystems. Winter soil respiration rates were similar for our two forest ecosystems but mean soil CO2 efflux over the growing sea- son was higher in the natural forest than in the plantation. The estimated winter and annual soil effluxes for the natural forest were 176.3 and 1070.3 g m-2, respectively, based on the relationship between soil respiration and soil temperature, which were 17.2 and 9.7 % greater than their counterparts in the plantation. The contributions of winter soil respiration toannual soil efflux were 15.4 % tor the plantation and 16.5R for the natural forest and were statistically similar. Our results indicate that winter soil CO2 efflux from frozen soils in the alpine coniferous forest ecosystems of the eastern Tibetan Plateau was considerable and was an important component of annual soil respiration. Moreover, reforesta- tion （natural coniferous forests were deforested and refor- ested with P. asperata plantation） may reduce soil respiration by reducing soil carbon substrate availability and input.

Isolation and functional analysis of a Brassica junea gene encoding a component of auxin efflux carrier

Polar auxin transport plays a divergent role in plant growth and developmental processes including rootand embryo development, vascular pattern formation and cell elongation. Recently isolated Arabidopsispin gene family was believed to encode a component of auxin efflux carrier (Galweiler et al, 1998). Basedon the Arabidopsis pin1 sequence we have isolated a Brassica juncea cDNA (designated Bjpinl), whichencoded a 70-kDa putative auxin efflux carrier. Deduced BjPIN1 shared 65% identities at protein level withAtPIN1 and was highly homologous to other putative PIN proteins of Arabidopsis (with highest homologyto AtPIN3). Hydrophobic analysis showed similar structures between BjPIN1 and AtPIN proteins. Presenceof 6 exons (varying in size between 65 bp and 1229 bp) and 5 introns (sizes between 89 bp and 463 bp)in the genomic fragment was revealed by comparing the genomic and cDNA sequences. Northern blotanalysis indicated that Bjpinl was expressed in most of the tissues tested, with a relatively higher levelof transcript in flowers and a lower level in root tissues. Promoter-reporter gene fusion studies furtherrevealed the expression of Bjpinl in the mature pollen grains, young seeds, root tip, leaf vascular tissue andtrace bundle, stem epidermis, cortex and vascular cells. BjPIN1 was localized on the plasma membraneas demonstrated through fusion expression of green fluorescent protein (GFP). Auxin efflux carrier activitywas elevated in transgenic Arabidopsis expressing BjPIN1.

A Pin gene families encoding components of auxin efflux carriers in Brassica juncea

Based on the sequence information of Arabidopsis PIN1, two cDNAs encoding PIN homologues fromBrassica juncea, Bjpin2 and Bjpin3, were isolated through cDNA library screening. Bjpin2 and Bjpin3encoded proteins containing 640 and 635 amino acid residues, respectively, which shared 97.5% identities witheach other and were highly homologous to Arabidopsis PIN1, PIN2 and other putative PIN proteins. BjPIN2and BjPIN3 had similar structures as AtPIN proteins. Northern blot analysis indicated that Bjpin2 wasexpressed in stem, leaf and floral tissues, while Bjpin3 was expressed predominantly in stem and hypocotyls.Two promoter fragments of pin genes, Bjpin-X and Bjpin-Z, were isolated by 'genome walking' techniqueusing primers at 5'-end of pin cDNA. Promoter-gus fusion studies revealed the GUS activities driven byBjpin-X were at internal side of xylem and petal; while those driven by Bjpin-Z were detected at leaf vein,epidermal cell and cortex of stem, vascular tissues and anther. Results of the pin genes with differentexpression patterns in B. juncea suggested the presence of a gene family.

Rice Heavy Metal P-type ATPase OsHMA6 Is Likely a Copper Efflux Protein

P1B-type heavy metal ATPases(HMAs)are transmembrane metal-transporting proteins that play a key role in metal homeostasis.We here reported the characterization of rice OsHMA6,a member of the P1B-type ATPase family.Phylogenetic tree analysis showed that OsHMA6 belonged to the Cu/Ag subgroup of the HMA family and had a close evolutionary relationship with OsHMA9.Amino acid sequence alignment showed 82.78%consistency between OsHMA6 and OsHMA9.OsHMA6 expressed in all organs at different growth stages,including spikelet,and abundant in leaf blades,however,OsHMA9 most strongly expressed in roots,but very low in spikelet.Excessive Cu^2+can up-regulate the expression of OsHMA6 and OsHMA9 in rice seedlings.The heterologous expression in yeast showed that OsHMA6 can significantly rescue the growth of yeast strain CM52 when supplied with 3 or 6 mmol/L Cu^2+.Compared with the empty vector pYES2,the Cu concentration in OsHMA6-pYES2 decreased by 23.4%and 30.3%under 3 or 6 mmol/L Cu2+,respectively.Subcellular localization revealed that OsHMA6 was located in the plasma membrane.These results suggested that OsHMA6,similar to OsHMA9,is likely a copper efflux protein located in the plasma membrane.

Role of MexA-MexB-OprM Efflux Pump System in Chronic Pseudomonas Aeruginosa Pulmonary Infection in Mice

In order to investigate the role of the MexA-MexB-OprM efflux pump system in the pathogenesis of Pseudomonas aeruginosa(PA)-induced pulmonary infection,pulmonary infection models were established by intratracheal injection of K767(wild type),nalB(MexA-MexB-OprM up-regulated mutant),and △m exB(knockout) strains,separately.All mice were treated with Meropenem(intraperitoneal injection,100 mg/kg body weight,twice every day),and strain-related pathology,bacteria count,cytokine level,myeloperoxidase(MPO,indicator of neutrophil recruitment) activity,and macrophage inflammatory protein-2(MIP-2) expression were evaluated at early(3rd day post-infection) and late(7th and 14th day post-infection) stages of infection.E-test showed that △mexB was more significantly sensitive to panipenan(ETP),meropenem(MP) and imipenem(IP) than K767 and nalB strains.There was no significant difference in sensitivity to cefepime(TM) among the three stains.In contrast to the K767 and nalB groups,the △ mexB group showed decreased bacteria burden over time and less extensive pathological change.Additionally,MPO activity and levels of inflammatory cytokines(IL-1b,IL-12,and TNF-α) were increased at the early stage(day 3) and decreased at the later stage(day 14).Serum MIP-2 expression level was steadily increased in all three groups from early to late stages,but significantly higher in △m exB group than in K767 and nalB groups(P<0.05).In conclusion,the MexA-MexB-OprM efflux pump system might play an important role in PA-induced chronic pulmonary infection.High expression of the MexA-MexB-OprM efflux pump could increase antibacterial resistance and promote infection.

Non-growing season soil CO_2 efflux and its changes in an alpine meadow ecosystem of the Qilian Mountains,Northwest China

Most soil respiration measurements are conducted during the growing season.In tundra and boreal forest ecosystems,cumulative,non-growing season soil CO2 fluxes are reported to be a significant component of these systems＇ annual carbon budgets.However,little information exists on soil CO2 efflux during the non-growing season from alpine ecosystems.Therefore,comparing measurements of soil respiration taken annually versus during the growing season will improve the accuracy of estimating ecosystem carbon budgets,as well as predicting the response of soil CO2 efflux to climate changes.In this study,we measured soil CO2 efflux and its spatial and temporal changes for different altitudes during the non-growing season in an alpine meadow located in the Qilian Mountains,Northwest China.Field experiments on the soil CO2 efflux of alpine meadow from the Qilian Mountains were conducted along an elevation gradient from October 2010 to April 2011.We measured the soil CO2 efflux,and analyzed the effects of soil water content and soil temperature on this measure.The results show that soil CO2 efflux gradually decreased along the elevation gradient during the non-growing season.The daily variation of soil CO2 efflux appeared as a single-peak curve.The soil CO2 efflux was low at night,with the lowest value occurring between 02：00-06：00.Then,values started to rise rapidly between 07：00-08：30,and then descend again between 16：00-18：30.The peak soil CO2 efflux appeared from 11：00 to 16：00.The soil CO2 efflux values gradually decreased from October to February of the next year and started to increase in March.Non-growing season Q10 （the multiplier to the respiration rate for a 10℃ increase in temperature） was increased with raising altitude and average Q10 of the Qilian Mountains was generally higher than the average growing season Q10 of the Heihe River Basin.Seasonally,non-growing season soil CO2 efflux was relatively high in October and early spring and low in the winter.The soil CO2 efflux was positively correlated with soil temperature and soil water content.Our results indicate that in alpine ecosystems,soil CO2 efflux continues throughout the non-growing season,and soil respiration is an important component of annual soil CO2 efflux.

Characterization and frequency of antibiotic resistance related to membrane porin and efflux pump genes among Acinetobacter baumannii strains obtained from burn patients in Tehran, Iran

Objective: To explore the characterization and frequency of antibiotic resistance related to membrane porin and efflux pump genes among Acinetobacter baumannii (A. baumannii) strains obtained from burn patients in Tehran, Iran. Methods: In this cross-sectional descriptive study, 100 strains of A. baumannii isolated from burn patients visiting teaching hospitals of Tehran were collected from January 2016 to November 2017. After A. baumannii strains were confirmed, antimicrobial susceptibility testing was done via Kirby-Bauer disc diffusion method according to the Clinical and Laboratory Standards Institute guidelines. PCR amplification was performed for detection of β-lactamase adeR, OprD, adeS genes among A. baumannii strains. Results: All isolates (100%) were resistant to ceftazidime, cefotaxime, cefepime, ciprofloxacin, and piperacillin, and most isolates indicated high resistance (95%-97%) to meropenem, imipenem, gentamicin, ceftriaxone, trimethoprim-sulfamethoxazole, piperacillin-tazobactam, amikacin, and tetracycline. The most effective antibiotic against A. baumannii isolates was colistin (97% sensitivity), followed by tigecycline. The frequency of OprD, adeS, and adeR genes were 98%, 91%, and 77%, respectively. Conclusions: This study shows that the majority of A. baumannii isolates are highly resistant to the antibiotics most commonly used in burn patients. Also, high distribution of OprD and adeRS genes may be responsible for the observed resistances among A. baumannii isolates that demonstrate the possible role of both efflux pumps in simultaneous of carbapenemase production during antibiotic resistance.

Effect of thinning intensity on the stem CO_(2) efflux of Larix principis-rupprechtii Mayr

Background:Stem CO_(2) efflux(E_(S))plays a critical role in the carbon budget of forest ecosystems.Thinning is a core practice for sustainable management of plantations.It is therefore necessary and urgent to study the effect and mechanism of thinning intensity(TI)on E_(S).Methods:In this study,five TIs were applied in Larix principis-rupprechtii Mayr 21-,25-,and 41-year-old stands in North China in 2010.Portable infrared gas analyzer(Li-8100 A)was used to measure ES and its association with environmental factors at monthly intervals from May to October in 2013 to 2015.In addition,nutrients,wood structure and nonstructural carbon(NSC)data were measured in August 2016.Results:The results show that ES increased with increasing TI.The maximum ES values occurred at a TI of 35%(3.29,4.57 and 2.98μmol·m^(-2)·s^(-1))and were 1.54-,1.94-and 2.89-fold greater than the minimum E_(S) value in the CK stands(2.14,2.35 and 1.03μmol·m^(-2)·s^(-1))in July for the 21-,25-and 41-year-old forests,respectively.The E_(S) of the trees in low-density stands was more sensitive to temperature than that of the trees in high-density stands.Soluble sugars(SS)and temperature are the main factors affecting ES.When the stand density is low enough as 41-year-old L.principis-rupprechtii forests with TI 35%,bark thickness(BT)and humidity should be considered in addition to air temperature(T_(a)),wood temperature(T_(w)),sapwood width(SW),nitrogen concentration(N)and SS in the evaluation of ES.If a change in stand density is ignored,the CO_(2) released from individual 21-,25-and 41-year-old trees could be underestimated by 168.89%,101.94% and 200.49%,respectively.CO_(2) release was estimated based on the stem equation in combination with the factors influencing ES for reference.Conclusions:We suggest that it is not sufficient to conventional models which quantify ES only by temperature and that incorporating the associated drivers(e.g.density,SS,SW and N)based on stand density into conventional models can improve the accuracy of ES estimates.

Influence of environmental,root,and stand parameters on soil surface CO_2 efflux in a Populus euphratica of desert forest in extreme arid region

Spatial variation in soil surface CO2 efflux was measured in a stand of Populus euphratica in the Ejina Oasis of desert riparian forest in the extreme arid region in northwestern China from April 2007 through October 2007.Measurements were taken with a gas-exchange analyzer linked to a soil-respiration chamber.The mean soil CO2 efflux in the stand was 2.71 μmol/(m2·s) during the growing season and 1.38 μmol/(m2·s) in the nongrowing season.The seasonal maximum (end of May through early June) andminimum (October) CO2 efflux were 3.38 and 0.69 μmol/(m2·s),respectively.The diurnal fluctuation of CO2 efflux was relatively small (< 20 percent),with theminimum appearing around 05:00 and the maximum around 15:00.Linear regression analysis showed soil-surface CO2 efflux to be most highly correlated with soil temperature (R2=0.435) and soil moisture (R2=0.213).When all variables were considered simultaneously,only soil temperature (R2=0.378),soil moisture (R2=0.147),and root volume density (R2=0.021) explained a significant amount of variance in soil surface CO2 efflux.Stand volumes were not correlated with soil CO2 efflux on our sites.

From blood to gut: Direct secretion of cholesterol via transintestinal cholesterol efflux

The reverse cholesterol transport pathway (RCT) is the focus of many cholesterol-lowering therapies. By way of this pathway, excess cholesterol is collected from peripheral tissues and delivered back to the liver and gastrointestinal tract for excretion from the body. For a long time this removal via the hepatobiliary secretion was considered to be the sole route involved in the RCT. However, observations from early studies in animals and humans already pointed towards the possibility of another route. In the last few years it has become evident that a nonbiliary cholesterol secretion pathway exists in which the intestine plays a central role. This transintestinal cholesterol efflux (TICE) pathway contributes significantly to the total fecal neutral sterol excretion. Moreover, recent studies have shown that TICE is also sensitive to stimulation. As a consequence, the direct role of cholesterol secretion from blood via TICE makes the intestine a suitable and approachable target for cholesterol removal from the body and possibly reduction of atherosclerosis. In this review, the discovery and recent findings contributing to understanding the mechanism of TICE will be discussed.

Mechanisms Efflux Pumps of <i>Acinetobacter baumannii</i>(MDR): Increasing Resistance to Antibiotics

Acinetobacter baumannii has greatly increased its degree of resistance to become multidrug resistant (MDR) over the past 30 years and is on the red line of the most widely replicated bacteria according to World Health Organization (WHO). The efflux pumps are the main cause for the increasing antibiotic resistance of A. baumannii originated from nosocomial infection. The progressive resistance of A. baumannii even on the recent drugs (tigecycline and fosfomycin) reduces to very effective antibiotic scale. With attention focused on MDR and pan-drug-resistant (PDR) in A. baumannii multiple works on efflux pumps chemical inhibitor (NMP, PAβN, omeprazole, verapamil, reserpine, CCCP) are still in progress. Certain inhibitors from plants (Biricodar and timcodar, Falvone, Mahonia, Dalea versicolor, Lycopus europaeus, and Rosmarinus officinalis) have the capability to have such compounds according to their very significant synergistic effect with antibiotics. In this review we focused on the growth of antibiotic resistance to explain the mechanism of efflux pumps into these different super families and a comprehensive understanding of the extrusion, regulation and physiology role of drug efflux pumps in the essential development of anti-resistivity drugs. We recapitulated the evolution of the work carried out in these fields during the last years and in the course of elaboration, with the aim of increasing the chances of decreasing bacterial resistivity to antibiotics.

Antibacterial activity and inhibition against Staphylococcus aureus NorA efflux pump by ferulic acid and its esterified derivatives

Objective:To evaluate the inhibitory activity of ferulic acid and four of its esterified derivatives(methyl,ethyl,propyl,and butyl)against resistance mechanisms in Staphylococcus aureus strains.Methods:Ferulic acid derivatives were obtained by esterification with methanol,ethanol,propanol,and butanol,and then characterized by hydrogen and carbon-13 nuclear magnetic resonance analysis.The minimum inhibitory concentrations(MIC)of ferulic acid and its esterified derivatives,ethidium bromide,and norfloxacin were obtained using the microdilution test,while the efflux pump inhibition test was conducted by examining reduction in the MICs of norfloxacin and ethidium bromide.Molecular docking was also carried out using the Schrodinger Suite 2015 molecular modeling software.A three-dimensional model of NorA efflux pump was generated using I-TASSER.The best scoring model was used as a receptor for ligand-receptor docking.Results:The methyl and butyl ester derivatives did not demonstrate significant antimicrobial activity.However,a significant synergic effect was evidenced when norfloxacin was combined with the ethyl and propyl esterified derivatives.The docking study demonstrated favorable energy of interaction between ferulate derivatives and NorA,and amino acid residues TYR57,TYR58,and LEU255 were present commonly in stabilizing all complexes.The PCA analysis corroborated the docking hypothesis that the lipophilic character and hydrogen bond interactions were the most relevant characteristics involved with NorA inhibitors.The pharmacokinetic parameters of ferulic acid derivatives showed good ADMET properties,demonstrating that they can be easily absorbed and have no effect or inhibit the cytochrome P450 enzyme complex,revealing their potential as drug candidates.Conclusions:This study provides strong evidence that the molecular basis for this activity is potentially due to the NorA efflux pump.

The influence of stocking levels,clone,fertilization,and weed control on surface CO_(2)efflux in a mid-rotation Pinus radiata D.Don plantation in Canterbury,New Zealand

Silvicultural practices applied in managed forest plantations may help counteract the effects of climate change by influencing soil surface CO_(2)efflux(Fs).Understanding the effects of silvicultural practices on Fs will provide unbiased estimates of carbon fluxes and allow better silvicultural decisions for carbon sequestration.Therefore,we assessed how Fs differed seasonally across silvicultural practices(i.e.,stocking levels,clone,fertilization and weed control treatments)and evaluated the effects of soil temperature(Ts)and soil volumetric water content(θv)on Fs across these practices for a mid-rotation(14 year-old)Pinus radiata plantation in the Canterbury region of New Zealand.There were significant differences in Fs(p<0.05)over the four seasons,three levels of stocking,and five clones.The effects of fertilization and weed control applied 12 years previously on Fs were insignificant.Annual estimate of Fs(mean±1 standard deviation)from the study site was 22.7±7.1 t ha^(-1)a^(-1)in the form of CO_(2)(6.2±2.1 t ha^(-1)a^(-1)in the form of C).Fs values were consistently higher in plots with 1250 stems ha^(-1)compared to 2500 stems ha^(-1),which may be related to a strong soil resource limitation because of the close spacing in the latter plantation.Significant differences in Fs across clones suggest that variations in carbon partitioning might explain their growth performance.Silvicultural treatments influenced Fs response to soil temperature(p<0.05),resulting in models explaining 28-49%of the total variance in Fs.These findings provide insights into how silvicultural management decisions may impact Fs in mid-rotation radiata pine plantations,contributing towards developing more precise and unbiased plantation carbon budgets.

Drug interactions of dipeptidyl peptidase 4 inhibitors involving CYP enzymes and P-gp efflux pump

Dipeptidyl peptidase 4(DPP4) inhibitors are oral antidiabetic drugs approved to manage type 2 diabetes mellitus. Saxagliptin is a substrate of CYP3A4/5 enzymes while other DPP4 inhibitors such as sitagliptin, linagliptin, gemigliptin and teneligliptin are weak substrates of CYP3A4. DPP4 inhibitors have also been identified as substrates of P-gp. Hence, the drugs inhibiting or inducing CYP3A4/5 enzymes and/or P-gp can alter the pharmacokinetics of DPP4 inhibitors. This review is aimed to identify the drugs interacting with DPP4 inhibitors. The plasma concentrations of saxagliptin have been reported to be increased significantly by the concomitant administration of ketoconazole or diltiazem while no significant interactions between various DPP4 inhibitors and drugs like warfarin, digoxin or cyclosporine have been identified.

Are Drug Efflux Genes Present among <i>Mycobacterium tuberculosis</i>Isolates from Patients in Lagos, Nigeria?

A major challenge in the treatment of Tuberculosis (TB) is emergence of Multi-Drug Resistant Mycobacterium tuberculosis (MDRTB) strains. Efflux genes have been established to be among factors for drug resistance in Mycobacterium tuberculosis (M. tuberculosis) pulmonary infections by conferring bacterial ability to pump-out drugs from intracellular compartment, making it impossible for drugs to attain intracellular concentration lethal to the organism. There is paucity of data on the role of efflux pump in MDRTB in Nigerian strains of M. tuberculosis. Hence, the aim of this study was to detect the carriage, distribution and frequency of efflux pump genes among MDRTB and non-MDRTB isolates from participants with pulmonary tuberculosis in Lagos, Nigeria. This study was carried out on M. tuberculosis isolated from 1020 participants suspected of pulmonary tuberculosis in Lagos State, Nigeria. A total of 78 M. tuberculosis isolates were obtained from the participants suspected of pulmonary tuberculosis. Forty Eight isolates were confirmed as MDRTB and 30 non-MDRTB. Efflux pump genes were investigated in the isolates using the conventional polymerase chain reaction. Statistical analysis was carried out using the Statistical Package for Social Science (SPSS version 20) to compare the efflux pump gene results between MDRTB and non- MDRTB isolates. Different efflux genes types and frequency were detected in MDRTB and non-MDRTB isolates. Carriage of 2 or more alleles of efflux gene types Rv2486c (efpA), Rv2459c (jefA), Rv1877, Rv1002c, Rv0342, Rv2686c and drrC associated with MDR were detected. Additionally, the frequency of efflux genes alleles in MDRTB was significantly different from those in non- MDRTB isolates.

A Fluorescent Cell-Based Technique for Monitoring Efflux of MRP4

Background: Overexpression of efflux pumps is the drug resistance and adaptation mechanism employed by some eukaryotes and bacteria to transport endogenous and chemotherapeutic compounds from the intracellular to the extracellular environment. Aim: The study aimed at establishing a fluorescent cell-based assay to monitor the efflux activities of an ABC-transporter, multi-drug resistance protein 4 (MRP4). Methods: DH5α competent E. coli cells were transformed with pcDNA-MRP4 by the heat-shock process. The presence of the MRP4 gene was analyzed by the digestion of plasmid using EcoRI and analyzed on a 1% agarose gel. HEK 293 cells were transfected with purified pcDNA-MRP4 under optimized conditions using a Polyethylenimine (PEI) protocol. The level of MRP4 in the HEK 293 cells was characterized by western blotting analysis using M4I-10 anti-MRP4 and anti-Rat IgG (whole molecule)-Alkaline phosphatase antibodies. The fluorescent uptake study was performed by the incubation of 0.02 mM 8-[fluo-cAMP] with the MRP4-transfected and control HEK 293 cells for 1 h. The level of fluorescence was analyzed using fluorescence microscopy and spectrometer. Results: The agarose gel analysis showed a plasmid of 9.4 kb and restriction product of 5 kb, which correspond with the pcDNA and MRP4 sizes respectively. The western blot results of the transfection showed 4 μg pcDNA-MRP4 and the N/P ratio of 9 was the optimized condition to transfect our HEK 293 cells as it showed the broadest band. In the efflux studies, the fluorescence images of the MRP4-transfected HEK 293 cells were very low compared to the untransfected control. The level of fluorescence accumulation was significantly (P ≤ 0.0001) higher 228.6 ± 13.1 RFU in the untransfected cells than the MRP4-transfected cells 8.6 ± 1.8 RFU. Conclusion: The higher levels of fluorescence detected in the control in both the fluorescent microscopy and spectrophotometer showed that MRP4-transfected cells had effluxed the 8-[fluo-cAMP] substrate out of the cell. This method could be employed in the detection of MRP4 functions in bacteria and cancer cells.