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Lopez D, Martinez-Luis S. Marine natural products with P-glycoprotein inhibitor properties. Mar Drugs 2014; 12:525-46. [PMID: 24451193 PMCID: PMC3917285 DOI: 10.3390/md12010525] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 01/06/2014] [Accepted: 01/07/2014] [Indexed: 12/25/2022] Open
Abstract
P-glycoprotein (P-gp) is a protein belonging to the ATP-binding cassette (ABC) transporters superfamily that has clinical relevance due to its role in drug metabolism and multi-drug resistance (MDR) in several human pathogens and diseases. P-gp is a major cause of drug resistance in cancer, parasitic diseases, epilepsy and other disorders. This review article aims to summarize the research findings on the marine natural products with P-glycoprotein inhibitor properties. Natural compounds that modulate P-gp offer great possibilities for semi-synthetic modification to create new drugs and are valuable research tools to understand the function of complex ABC transporters.
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Affiliation(s)
- Dioxelis Lopez
- Center for Drug Discovery and Biodiversity, Institute for Scientific Research and Technology Services (INDICASAT), Clayton, City of Knowledge, P.O. Box 0843-01103, Panama.
| | - Sergio Martinez-Luis
- Center for Drug Discovery and Biodiversity, Institute for Scientific Research and Technology Services (INDICASAT), Clayton, City of Knowledge, P.O. Box 0843-01103, Panama.
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52
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Tillotson GS, Theriault N. New and alternative approaches to tackling antibiotic resistance. F1000PRIME REPORTS 2013; 5:51. [PMID: 24381727 PMCID: PMC3854692 DOI: 10.12703/p5-51] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Multidrug-resistant bacteria are becoming more common and due to their multiplicity of mechanisms, they are frequently resistant to many if not all of the current antibiotics. This daunting spectre has been the target of many research efforts into conventional antibiotics and alternative approaches. This review focuses on the more recent advances in these fields with an overview on peptidomimetics, nanoparticles and their derivatives, FimH inhibitors, quorum sensing inhibition molecules, neoglycosides and phage therapies. These various approaches are at different stages of development, some are closer to the clinic than others, but recent regulatory guidance and re-awakened interest from the pharmaceutical companies gives us some optimism for the future.
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53
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Xu ZQ, Flavin MT, Flavin J. Combating multidrug-resistant Gram-negative bacterial infections. Expert Opin Investig Drugs 2013; 23:163-82. [PMID: 24215473 DOI: 10.1517/13543784.2014.848853] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
INTRODUCTION Multidrug-resistant (MDR) bacterial infections, especially those caused by Gram-negative pathogens, have emerged as one of the world's greatest health threats. The development of novel antibiotics to treat MDR Gram-negative bacteria has, however, stagnated over the last half century. AREAS COVERED This review provides an overview of recent R&D activities in the search for novel antibiotics against MDR Gram-negatives. It provides emphasis in three key areas. First, the article looks at new analogs of existing antibiotic molecules such as β-lactams, tetracyclines, and aminoglycoside as well as agents against novel bacterial targets such as aminoacyl-tRNA synthetase and peptide deformylase. Second, it also examines alternative strategies to conventional approaches including cationic antimicrobial peptides, siderophores, efflux pump inhibitors, therapeutic antibodies, and renewed interest in abandoned treatments or those with limited indications. Third, the authors aim to provide an update on the current clinical development status for each drug candidate. EXPERT OPINION The traditional analog approach is insufficient to meet the formidable challenge brought forth by MDR superbugs. With the disappointing results of the genomics approach for delivering novel targets and drug candidates, alternative strategies to permeate the bacterial cell membrane, enhance influx, disrupt efflux, and target specific pathogens via therapeutic antibodies are attractive and promising. Coupled with incentivized business models, governmental policies, and a clarified regulatory pathway, it is hoped that the antibiotic pipeline will be filled with an effective armamentarium to safeguard global health.
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Affiliation(s)
- Ze-Qi Xu
- SynChem, Inc. , 1400 Chase Avenue, Elk Grove Village, IL 60007 , USA +1 847 298 2436 ;
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54
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Schindler BD, Jacinto P, Kaatz GW. Inhibition of drug efflux pumps in Staphylococcus aureus: current status of potentiating existing antibiotics. Future Microbiol 2013; 8:491-507. [PMID: 23534361 DOI: 10.2217/fmb.13.16] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The emergence of multidrug-resistant Staphylococcus aureus coupled with a declining output of new antibiotic treatment options from the pharmaceutical industry is a growing worldwide healthcare problem. Multidrug efflux pumps are known to play a role in antibiotic and biocide resistance in S. aureus. These membrane transporters are capable of extruding drugs and other structurally unrelated compounds, hence decreasing intracellular concentration and increasing survival. Coadministration of efflux pump inhibitors (EPIs) with antibiotics that are pump substrates could increase intracellular drug levels, thus bringing renewed efficacy to existing antistaphylococcal agents. Numerous EPIs have been identified or synthesized over the past two decades; these include existing pharmacologic drugs, naturally occurring compounds, and synthetic derivatives thereof. This review describes the current progress in EPI development for use against S. aureus.
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Affiliation(s)
- Bryan D Schindler
- John D Dingell Veterans Affairs Medical Center, Wayne State University, Detroit, MI 48201, USA
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55
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Taylor PW. Alternative natural sources for a new generation of antibacterial agents. Int J Antimicrob Agents 2013; 42:195-201. [DOI: 10.1016/j.ijantimicag.2013.05.004] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 05/13/2013] [Indexed: 10/26/2022]
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56
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Abstract
P-glycoprotein (P-gp), an efflux membrane transporter, is widely distributed throughout the body and is responsible for limiting cellular uptake and the distribution of xenobiotics and toxic substances. Hundreds of structurally diverse therapeutic agents are substrates to it and it impedes the absorption, permeability, and retention of the drugs, extruding them out of the cells. It is overexpressed in cancer cells and accountable for obstructing cell internalization of chemotherapeutic agents and for developing transporter mediated resistance by cancer cells during anti-tumor treatments. As it jeopardizes the success of drug delivery and cancer targeting, strategies are being developed to overcome P-gp mediated drug transport. This concise review represents a brief discussion on P-gp mediated drug transport and how it hinders the success of various therapies. Its main focus is on various strategies used to tackle this curb in the field of drug delivery and targeting.
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Affiliation(s)
- Md Lutful Amin
- Department of Pharmacy, Stamford University Bangladesh, Dhaka, Bangladesh
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57
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Holler TP, Evdokimov AG, Narasimhan L. Structural biology approaches to antibacterial drug discovery. Expert Opin Drug Discov 2013; 2:1085-101. [PMID: 23484874 DOI: 10.1517/17460441.2.8.1085] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Antibacterial drug discovery has undertaken a major experiment in the 12 years since the first bacterial genomes were sequenced. Genome mining has identified hundreds of potential targets that have been distilled to a relatively small number of broad-spectrum targets ('low-hanging fruit') using the genetics tools of modern microbiology. Prosecuting these targets with high-throughput screens has led to a disappointingly small number of lead series that have mostly evaporated under closer scrutiny. In the meantime, multi-drug resistant pathogens are becoming a serious challenge in the clinic and the community and the number of pharmaceutical firms pursuing antibacterial discovery has declined. Filling the antibacterial development pipeline with novel chemical series is a significant challenge that will require the collaboration of scientists from many disciplines. Fortunately, advancements in the tools of structural biology and of in silico modeling are opening up new avenues of research that may help deal with the problems associated with discovering novel antibiotics.
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Affiliation(s)
- Tod P Holler
- Pfizer Global Research and Development, 2800 Plymouth Road, Ann Arbor, MI 48105, USA +1 734 622 5954 ; +1 734 622 2963 ; Tod.Holler@pfizer. com
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58
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Buivydas A, Pasanen T, Senčilo A, Daugelavičius R, Vaara M, Bamford DH. Clinical isolates of Pseudomonas aeruginosa from superficial skin infections have different physiological patterns. FEMS Microbiol Lett 2013; 343:183-9. [PMID: 23590530 DOI: 10.1111/1574-6968.12148] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 03/22/2013] [Accepted: 03/28/2013] [Indexed: 12/01/2022] Open
Abstract
Pseudomonas aeruginosa are known to have a wide physiological potential allowing them to constantly populate diverse environments leading to severe infections of humans such as septicemia, leg ulcers, and burn wounds. We set out to probe physiological characteristics of P. aeruginosa isolates from diabetic leg ulcers collected from Helsinki metropolitan area. A total of 61 clinical isolates were obtained. Detailed phenotypic (physiological) characteristics [outer membrane (OM) permeability, membrane voltage, and activity of multidrug resistance pumps] were determined in several growth phases leading to the division of the analyzed set of P. aeruginosa strains into five distinct clusters including cells with similar physiological properties. In addition, their antibiotic resistance patterns and genetic heterogeneity were determined. Multiple isolates from the same patient were genetically very closely related and belonged to the same phenotypic cluster. However, genetically close isolates from different patients expressed very different phenotypic properties. The characteristics of infected patients seem to determine the growth environments for microorganisms that adapt by changing their physiological and/or genetic properties.
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Affiliation(s)
- Andrius Buivydas
- Department of Biosciences, University of Helsinki, Helsinki, Finland; Institute of Biotechnology, University of Helsinki, Helsinki, Finland
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59
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Gould IM, Bal AM. New antibiotic agents in the pipeline and how they can help overcome microbial resistance. Virulence 2013; 4:185-91. [PMID: 23302792 PMCID: PMC3654619 DOI: 10.4161/viru.22507] [Citation(s) in RCA: 184] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Bacterial resistance is a growing threat and yet few new antibiotics active against multi-resistant bacteria are being explored. A combination of falling profits, regulatory mechanisms and irrational and injudicious use of antibiotics has led to an alarming situation where some infections have no cure. In this article, we summarize the new developments that have been suggested to incentivize the pharmaceutical industries toward the field of infections. We also briefly mention the new compounds on the horizon and some newly approved compounds that might help us tide over this crisis.
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60
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Tikhonova EB, Zgurskaya HI. Assessment of multidrug efflux assemblies by surface plasmon resonance. Methods Mol Biol 2013; 966:133-155. [PMID: 23299733 DOI: 10.1007/978-1-62703-245-2_9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Surface plasmon resonance (SPR) is a powerful tool for kinetic analyses of protein-protein interactions. Here we describe the application of this method to study interactions of membrane proteins involved in multidrug efflux in Escherichia coli.These so-called multidrug efflux pumps comprise an inner membrane transporter, a periplasmic membrane fusion protein and an outer membrane channel. The three components are assembled into a protein conduit that enables bacteria to expel multiple drugs directly into the external medium bypassing the periplasm. The "across-two-membranes" transport mechanism makes tripartite transporters poorly amenable to biochemical analyses. Two out of three components are located in different membranes and must be studied in detergents or reconstituted into lipid bilayers to retain their functionality. Furthermore, cytoplasmic and exoplasmic domains of all three components perform different functions and must be oriented in a specific way to assemble functional complexes. The SPR approach provides means to overcome some of these problems in studies of protein assemblies that function in the context of two membranes.
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Affiliation(s)
- Elena B Tikhonova
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK, USA
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61
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Search for new tools to combat Gram-negative resistant bacteria among amine derivatives of 5-arylidenehydantoin. Bioorg Med Chem 2013; 21:135-45. [DOI: 10.1016/j.bmc.2012.10.053] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Revised: 10/30/2012] [Accepted: 10/31/2012] [Indexed: 11/23/2022]
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62
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The promiscuous binding of pharmaceutical drugs and their transporter-mediated uptake into cells: what we (need to) know and how we can do so. Drug Discov Today 2012. [PMID: 23207804 DOI: 10.1016/j.drudis.2012.11.008] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A recent paper in this journal sought to counter evidence for the role of transport proteins in effecting drug uptake into cells, and questions that transporters can recognize drug molecules in addition to their endogenous substrates. However, there is abundant evidence that both drugs and proteins are highly promiscuous. Most proteins bind to many drugs and most drugs bind to multiple proteins (on average more than six), including transporters (mutations in these can determine resistance); most drugs are known to recognise at least one transporter. In this response, we alert readers to the relevant evidence that exists or is required. This needs to be acquired in cells that contain the relevant proteins, and we highlight an experimental system for simultaneous genome-wide assessment of carrier-mediated uptake in a eukaryotic cell (yeast).
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63
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Collu F, Vargiu AV, Dreier J, Cascella M, Ruggerone P. Recognition of imipenem and meropenem by the RND-transporter MexB studied by computer simulations. J Am Chem Soc 2012; 134:19146-58. [PMID: 23146101 DOI: 10.1021/ja307803m] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Basic understanding of the means by which multidrug efflux systems can efficiently recognize and transport drugs constitutes a fundamental step toward development of compounds able to tackle the continuous outbreak of new bacterial strains resistant to traditional antibiotics. We applied a series of computational techniques, from molecular docking to molecular dynamics simulations and free energy estimate methods, to determine the differences in the binding properties of imipenem and meropenem, two potent antibiotics of the carbapenem family, to MexB, the RND transporter of the major efflux system of Pseudomonas aeruginosa. We identified and characterized two affinity sites in the periplasmic domain of the transporter, sharing strong similarities with the distal and proximal binding pockets identified in AcrB, the homologue of MexB in Escherichia coli. According to our results, meropenem has a higher affinity to the distal binding pocket than imipenem while both compounds are weakly bound to the proximal pocket. This different behavior is mainly due to the hydration properties of the nonpharmacophore part of the two compounds, being that of imipenem less bulky and hydrophobic. Our data provide for the first time a rationale at molecular level for the experimental evidence indicating meropenem as a compound strongly affected by MexB contrary to imipenem, which is apparently poorly transported by the same pump.
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Affiliation(s)
- Francesca Collu
- Departement für Chemie und Biochemie, Universität Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
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64
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Kurinčič M, Klančnik A, Smole Možina S. Epigallocatechin gallate as a modulator of Campylobacter resistance to macrolide antibiotics. Int J Antimicrob Agents 2012; 40:467-71. [DOI: 10.1016/j.ijantimicag.2012.07.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 06/18/2012] [Accepted: 07/20/2012] [Indexed: 12/11/2022]
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65
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Conserved small protein associates with the multidrug efflux pump AcrB and differentially affects antibiotic resistance. Proc Natl Acad Sci U S A 2012; 109:16696-701. [PMID: 23010927 DOI: 10.1073/pnas.1210093109] [Citation(s) in RCA: 151] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The AcrAB-TolC multidrug efflux pump confers resistance to a wide variety of antibiotics and other compounds in Escherichia coli. Here we show that AcrZ (formerly named YbhT), a 49-amino-acid inner membrane protein, associates with the AcrAB-TolC complex. Co-purification of AcrZ with AcrB, in the absence of both AcrA and TolC, two-hybrid assays and suppressor mutations indicate that this interaction occurs through the inner membrane protein AcrB. The highly conserved acrZ gene is coregulated with acrAB through induction by the MarA, Rob, and SoxS transcription regulators. In addition, mutants lacking AcrZ are sensitive to many, but not all, of the antibiotics transported by AcrAB-TolC. This differential antibiotic sensitivity suggests that AcrZ may enhance the ability of the AcrAB-TolC pump to export certain classes of substrates.
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66
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Schweizer HP. Understanding efflux in Gram-negative bacteria: opportunities for drug discovery. Expert Opin Drug Discov 2012; 7:633-42. [PMID: 22607346 DOI: 10.1517/17460441.2012.688949] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
INTRODUCTION Bacteria evolved an arsenal of mechanisms to deal with toxic compounds and metabolic stresses, including antimicrobial agents. Efflux pumps are major players in the multidrug resistance of Gram-negative bacteria and pose major hurdles in the drug discovery process. However, recent advances in our understanding of efflux in these bacteria provide opportunities and assets for drug discovery. AREAS COVERED This review provides an overview of drug efflux in Gram-negative bacteria and its role in antimicrobial resistance, stress responses and other biological processes such as biofilm formation, and virulence. The discussion includes comments on the significance of synergy between a low-permeability outer membrane and efflux, notably the role of porins and lipopolysaccharide. The author then summarizes efforts aimed at inhibiting efflux pumps as a means to extend the utility of clinically useful antibiotics. This includes highlights of identification and characterization of small molecule efflux pump inhibitors (EPIs) from natural and synthetic sources, as well as novel strategies such as gene silencing and inhibitory antibodies. EXPERT OPINION Options for treating infections caused by multidrug-resistant bacteria are limited. Given the attractiveness of the therapeutic potential of efflux pump inhibition, further studies exploring novel strategies to interfere with efflux pump expression and function are warranted. This includes rational EPI design facilitated by pump structure information, exploitation of genetically defined efflux-proficient and efflux-compromised strain panels and non-traditional approaches such as pump inhibition by gene silencing, antibodies and perhaps even phage.
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Affiliation(s)
- Herbert P Schweizer
- Colorado State University, IDRC at Foothills Campus, Department of Microbiology, Immunology and Pathology, Fort Collins, CO 80523-0922, USA.
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67
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Efflux pumps of Mycobacterium tuberculosis play a significant role in antituberculosis activity of potential drug candidates. Antimicrob Agents Chemother 2012; 56:2643-51. [PMID: 22314527 DOI: 10.1128/aac.06003-11] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Active efflux of drugs mediated by efflux pumps that confer drug resistance is one of the mechanisms developed by bacteria to counter the adverse effects of antibiotics and chemicals. To understand these efflux mechanisms in Mycobacterium tuberculosis, we generated knockout (KO) mutants of four efflux pumps of the pathogen belonging to different classes. We measured the MICs and kill values of two different compound classes on the wild type (WT) and the efflux pump (EP) KO mutants in the presence and absence of the efflux inhibitors verapamil and l-phenylalanyl-l-arginyl-β-naphthylamide (PAβN). Among the pumps studied, the efflux pumps belonging to the ABC (ATP-binding cassette) class, encoded by Rv1218c, and the SMR (small multidrug resistance) class, encoded by Rv3065, appear to play important roles in mediating the efflux of different chemical classes and antibiotics. Efflux pumps encoded by Rv0849 and Rv1258c also mediate the efflux of these compounds, but to a lesser extent. Increased killing is observed in WT M. tuberculosis cells by these compounds in the presence of either verapamil or PAβN. The efflux pump KO mutants were more susceptible to these compounds in the presence of efflux inhibitors. We have shown that these four efflux pumps of M. tuberculosis play a vital role in mediating efflux of different chemical scaffolds. Inhibitors of one or several of these efflux pumps could have a significant impact in the treatment of tuberculosis. The identification and characterization of Rv0849, a new efflux pump belonging to the MFS (major facilitator superfamily) class, are reported.
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68
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Brown MF, Reilly U, Abramite JA, Arcari JT, Oliver R, Barham RA, Che Y, Chen JM, Collantes EM, Chung SW, Desbonnet C, Doty J, Doroski M, Engtrakul JJ, Harris TM, Huband M, Knafels JD, Leach KL, Liu S, Marfat A, Marra A, McElroy E, Melnick M, Menard CA, Montgomery JI, Mullins L, Noe MC, O'Donnell J, Penzien J, Plummer MS, Price LM, Shanmugasundaram V, Thoma C, Uccello DP, Warmus JS, Wishka DG. Potent inhibitors of LpxC for the treatment of Gram-negative infections. J Med Chem 2012; 55:914-23. [PMID: 22175825 DOI: 10.1021/jm2014748] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this paper, we present the synthesis and SAR as well as selectivity, pharmacokinetic, and infection model data for representative analogues of a novel series of potent antibacterial LpxC inhibitors represented by hydroxamic acid.
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Affiliation(s)
- Matthew F Brown
- Worldwide Medicinal Chemistry, Pfizer Global Research and Development, Eastern Point Road, Groton, Connecticut 06340, United States.
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69
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Mealman TD, Blackburn NJ, McEvoy MM. Metal export by CusCFBA, the periplasmic Cu(I)/Ag(I) transport system of Escherichia coli. CURRENT TOPICS IN MEMBRANES 2012; 69:163-96. [PMID: 23046651 DOI: 10.1016/b978-0-12-394390-3.00007-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
High levels of metal ions have the potential to cause cellular toxicity through a variety of mechanisms; therefore, cells have developed numerous systems that regulate their intracellular concentrations. The Cus resistance system aids in protection of Escherichia coli from high levels of Cu(I) and Ag(I) by actively transporting these metal ions to the extracellular environment. The Cus system forms a continuous complex, CusCBA, that spans the inner membrane, periplasm, and outer membrane of Gram-negative bacteria, together with a novel fourth component, the periplasmic metallochaperone, CusF. The metal-binding sites of CusA, CusB, and CusF are exquisitely tuned for Cu(I) and Ag(I), and thus effectively discriminate these ions for transport from other metals that may be required in the cell. Furthermore, direct transfer of metal from protein to protein within the Cus system during the transport process is likely to reduce the potential toxicity posed by the free metal ions. Here we review the wealth of structural, biochemical, and genetic information on the Cus system, which demonstrates the many intriguing aspects of function for metal-transporting efflux systems.
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Affiliation(s)
- Tiffany D Mealman
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
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70
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Okandeji BO, Greenwald DM, Wroten J, Sello JK. Synthesis and evaluation of inhibitors of bacterial drug efflux pumps of the major facilitator superfamily. Bioorg Med Chem 2011; 19:7679-89. [PMID: 22055717 DOI: 10.1016/j.bmc.2011.10.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2011] [Revised: 09/26/2011] [Accepted: 10/05/2011] [Indexed: 11/26/2022]
Abstract
Inhibitors of drug efflux pumps have great potential as pharmacological agents that restore the drug susceptibility of multidrug resistant bacterial pathogens. Most attention has been focused on the discovery of small molecules that inhibit the resistance nodulation division (RND) family drug efflux pumps in Gram-negative bacteria. The prototypical inhibitor of RND-family efflux pumps in Gram-negative bacteria is MC-207,110 (Phe-Arg-β-naphthylamide), a C-capped dipeptide. Here, we report that C-capped dipeptides inhibit two chloramphenicol-specific efflux pumps in Streptomyces coelicolor, a Gram-positive bacterium that is a relative of the human pathogen Mycobacterium tuberculosis. Diversity-oriented synthesis of a library of structurally related C-capped dipeptides via an Ugi four component reaction and screening of the resulting compounds resulted in the discovery of a compound that is threefold more potent as a suppressor of chloramphenicol resistance in S. coelicolor than MC-207,110. Since chloramphenicol resistance in S. coelicolor is mediated by major facilitator superfamily drug efflux pumps, our findings provide the first evidence that C-capped dipeptides can inhibit drug efflux pumps outside of the RND superfamily.
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Affiliation(s)
- Babajide O Okandeji
- Department of Chemistry, Brown University, 324 Brook Street, Providence, RI 02912, United States
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71
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Bush K, Pucci MJ. New antimicrobial agents on the horizon. Biochem Pharmacol 2011; 82:1528-39. [PMID: 21798250 DOI: 10.1016/j.bcp.2011.07.077] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Revised: 07/08/2011] [Accepted: 07/11/2011] [Indexed: 12/18/2022]
Abstract
Antibiotic resistance issues necessitate the continued discovery and development of new antibacterial agents. Efforts are ongoing in two approaches to find new compounds that are effective against antibiotic-resistant pathogens. These efforts involve modification of existing classes including fluoroquinolones, tetracyclines, aminoglycosides, and β-lactams and identification of inhibitors against previously unexploited antibacterial targets. Examples of both approaches are described here with emphasis on compounds in late pre-clinical or clinical stages of development.
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Affiliation(s)
- Karen Bush
- Department of Biology, Jordan Hall, 1001 E. Third Street, Indiana University, Bloomington, IN 47405, United States.
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72
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Vargiu AV, Collu F, Schulz R, Pos KM, Zacharias M, Kleinekathöfer U, Ruggerone P. Effect of the F610A mutation on substrate extrusion in the AcrB transporter: explanation and rationale by molecular dynamics simulations. J Am Chem Soc 2011; 133:10704-7. [PMID: 21707050 DOI: 10.1021/ja202666x] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The tripartite efflux pump AcrAB-TolC is responsible for the intrinsic and acquired multidrug resistance in Escherichia coli. Its active part, the homotrimeric transporter AcrB, is in charge of the selective binding of substrates and energy transduction. The mutation F610A has been shown to significantly reduce the minimum inhibitory concentration of doxorubicin and many other substrates, although F610 does not appear to interact strongly with them. Biochemical study of transport kinetics in AcrB is not yet possible, except for some β-lactams, and other techniques should supply this important information. Therefore, in this work, we assess the impact of the F610A mutation on the functionality of AcrB by means of computational techniques, using doxorubicin as substrate. We found that the compound slides deeply inside the binding pocket after mutation, increasing the strength of the interaction. During subsequent conformational alterations of the transporter, doxorubicin was either not extruded from the binding site or displaced along a direction other than the one associated with extrusion. Our study indicates how subtle interactions determine the functionality of multidrug transporters, since decreased transport might not be simplistically correlated to decreased substrate binding affinity.
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Affiliation(s)
- Attilio V Vargiu
- CNR-IOM, Unità SLACS, S.P. Monserrato-Sestu Km 0.700, I-09042 Monserrato (CA), Italy.
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73
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Schulz R, Vargiu AV, Ruggerone P, Kleinekathöfer U. Role of Water during the Extrusion of Substrates by the Efflux Transporter AcrB. J Phys Chem B 2011; 115:8278-87. [DOI: 10.1021/jp200996x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Robert Schulz
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen,
Germany
| | - Attilio V. Vargiu
- CNR-IOM, Unità SLACS,
c/o Dipartimento di Fisica, Università di Cagliari, s.p. Monserrato-Sestu km 0.7, I-09042 Monserrato (CA), Italy
| | - Paolo Ruggerone
- CNR-IOM, Unità SLACS,
c/o Dipartimento di Fisica, Università di Cagliari, s.p. Monserrato-Sestu km 0.7, I-09042 Monserrato (CA), Italy
| | - Ulrich Kleinekathöfer
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen,
Germany
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74
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Askoura M, Mottawea W, Abujamel T, Taher I. Efflux pump inhibitors (EPIs) as new antimicrobial agents against Pseudomonas aeruginosa. Libyan J Med 2011; 6:LJM-6-5870. [PMID: 21594004 PMCID: PMC3096568 DOI: 10.3402/ljm.v6i0.5870] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Accepted: 04/20/2011] [Indexed: 11/19/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic human pathogen and one of the leading causes of nosocomial infections worldwide. The difficulty in treatment of pseudomonas infections arises from being multidrug resistant (MDR) and exhibits resistance to most antimicrobial agents due to the expression of different mechanisms overcoming their effects. Of these resistance mechanisms, the active efflux pumps in Pseudomonas aeruginosa that belong to the resistance nodulation division (RND) plays a very important role in extruding the antibiotics outside the bacterial cells providing a protective means against their antibacterial activity. Beside its role against the antimicrobial agents, these pumps can extrude biocides, detergents, and other metabolic inhibitors. It is clear that efflux pumps can be targets for new antimicrobial agents. Peptidomimetic compounds such as phenylalanine arginyl β-naphthylamide (PAβN) have been introduced as efflux pump inhibitors (EPIs); their mechanism of action is through competitive inhibition with antibiotics on the efflux pump resulting in increased intracellular concentration of antibiotic, hence, restoring its antibacterial activity. The advantage of EPIs is the difficulty to develop bacterial resistance against them, but the disadvantage is their toxic property hindering their clinical application. The structure activity relationship of these compounds showed other derivatives from PAβN that are higher in their activity with higher solubility in biological fluids and decreased toxicity level. This raises further questions on how can we compact Pseudomonas infections. Of particular importance, the recent resurgence in the use of older antibiotics such as polymyxins and probably applying stricter control measures in order to prevent their spread in clinical sittings.
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Affiliation(s)
- Momen Askoura
- Biochemistry, Immunology and Microbiology (BMI) Department, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
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75
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Bolla JM, Alibert-Franco S, Handzlik J, Chevalier J, Mahamoud A, Boyer G, Kieć-Kononowicz K, Pagès JM. Strategies for bypassing the membrane barrier in multidrug resistant Gram-negative bacteria. FEBS Lett 2011; 585:1682-90. [DOI: 10.1016/j.febslet.2011.04.054] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Revised: 04/20/2011] [Accepted: 04/21/2011] [Indexed: 10/18/2022]
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76
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Fiamegos YC, Kastritis PL, Exarchou V, Han H, Bonvin AMJJ, Vervoort J, Lewis K, Hamblin MR, Tegos GP. Antimicrobial and efflux pump inhibitory activity of caffeoylquinic acids from Artemisia absinthium against gram-positive pathogenic bacteria. PLoS One 2011; 6:e18127. [PMID: 21483731 PMCID: PMC3070693 DOI: 10.1371/journal.pone.0018127] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Accepted: 02/25/2011] [Indexed: 12/05/2022] Open
Abstract
Background Traditional antibiotics are increasingly suffering from the emergence of multidrug resistance amongst pathogenic bacteria leading to a range of novel approaches to control microbial infections being investigated as potential alternative treatments. One plausible antimicrobial alternative could be the combination of conventional antimicrobial agents/antibiotics with small molecules which block multidrug efflux systems known as efflux pump inhibitors. Bioassay-driven purification and structural determination of compounds from plant sources have yielded a number of pump inhibitors which acted against gram positive bacteria. Methodology/Principal Findings In this study we report the identification and characterization of 4′,5′-O-dicaffeoylquinic acid (4′,5′-ODCQA) from Artemisia absinthium as a pump inhibitor with a potential of targeting efflux systems in a wide panel of Gram-positive human pathogenic bacteria. Separation and identification of phenolic compounds (chlorogenic acid, 3′,5′-ODCQA, 4′,5′-ODCQA) was based on hyphenated chromatographic techniques such as liquid chromatography with post column solid-phase extraction coupled with nuclear magnetic resonance spectroscopy and mass spectroscopy. Microbial susceptibility testing and potentiation of well know pump substrates revealed at least two active compounds; chlorogenic acid with weak antimicrobial activity and 4′,5′-ODCQA with pump inhibitory activity whereas 3′,5′-ODCQA was ineffective. These intitial findings were further validated with checkerboard, berberine accumulation efflux assays using efflux-related phenotypes and clinical isolates as well as molecular modeling methodology. Conclusions/Significance These techniques facilitated the direct analysis of the active components from plant extracts, as well as dramatically reduced the time needed to analyze the compounds, without the need for prior isolation. The calculated energetics of the docking poses supported the biological information for the inhibitory capabilities of 4′,5′-ODCQA and furthermore contributed evidence that CQAs show a preferential binding to Major Facilitator Super family efflux systems, a key multidrug resistance determinant in gram-positive bacteria.
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Affiliation(s)
- Yiannis C. Fiamegos
- Laboratory of Analytical Chemistry, University of Ioannina, Ioannina, Greece
| | - Panagiotis L. Kastritis
- Bijvoet Center for Biomolecular Research, Science Faculty, Utrecht University, Utrecht, The Netherlands
| | | | - Haley Han
- Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Alexandre M. J. J. Bonvin
- Bijvoet Center for Biomolecular Research, Science Faculty, Utrecht University, Utrecht, The Netherlands
| | - Jacques Vervoort
- Wageningen NMR Center, Laboratory of Biophysics, Wageningen, The Netherlands
| | - Kim Lewis
- Department of Biology and Antimicrobial Drug Discovery Center, Northeastern University, Boston, Massachusetts, United States of America
| | - Michael R. Hamblin
- Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Dermatology, Harvard Medical School, Boston, Massachusetts, United States of America
- Harvard-MIT Division of Health Sciences and Technology, Cambridge, Massachusetts, United States of America
| | - George P. Tegos
- Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Dermatology, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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77
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Fighting bacterial infections—Future treatment options. Drug Resist Updat 2011; 14:125-39. [DOI: 10.1016/j.drup.2011.02.001] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Revised: 01/31/2011] [Accepted: 01/31/2011] [Indexed: 12/13/2022]
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78
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Freire-Moran L, Aronsson B, Manz C, Gyssens IC, So AD, Monnet DL, Cars O. Critical shortage of new antibiotics in development against multidrug-resistant bacteria-Time to react is now. Drug Resist Updat 2011; 14:118-24. [PMID: 21435939 DOI: 10.1016/j.drup.2011.02.003] [Citation(s) in RCA: 202] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Revised: 02/11/2011] [Accepted: 02/15/2011] [Indexed: 11/30/2022]
Abstract
Two commercial databases (Pharmaprojects and Adis Insight R&D) were queried for antibacterial agents in clinical development. Particular attention was given to antibacterial agents for systemic administration. For each agent, reviewers were requested to indicate whether its spectrum of activity covered a set of selected multidrug-resistant bacteria, and whether it had a new mechanism of action or a new target. In addition, PubMed was searched for antibacterial agents in development that appeared in review articles. Out of 90 agents that were considered to fulfil the inclusion criteria for the analysis, 66 were new active substances. Fifteen of these could be systemically administered and were assessed as acting via a new or possibly new mechanism of action or on a new or possibly new target. Out of these, 12 agents were assessed as having documented in vitro activity against antibiotic-resistant Gram-positive bacteria and only four had documented in vitro activity against antibiotic-resistant Gram-negative bacteria. Of these four, two acted on new or possibly new targets and, crucially, none acted via new mechanisms of action. There is an urgent need to address the lack of effective treatments to meet the increasing public health burden caused by multidrug-resistant bacteria, in particular against Gram-negative bacteria.
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79
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Amaral L, Fanning S, Pagès JM. Efflux pumps of gram-negative bacteria: genetic responses to stress and the modulation of their activity by pH, inhibitors, and phenothiazines. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2011; 77:61-108. [PMID: 21692367 DOI: 10.1002/9780470920541.ch2] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Affiliation(s)
- Leonard Amaral
- Unit of Mycobacteriology, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Lisbon, Portugal
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80
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Aathithan S, French GL. Prevalence and role of efflux pump activity in ciprofloxacin resistance in clinical isolates of Klebsiella pneumoniae. Eur J Clin Microbiol Infect Dis 2011; 30:745-52. [DOI: 10.1007/s10096-010-1147-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Accepted: 12/23/2010] [Indexed: 10/18/2022]
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81
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Leitner I, Nemeth J, Feurstein T, Abrahim A, Matzneller P, Lagler H, Erker T, Langer O, Zeitlinger M. The third-generation P-glycoprotein inhibitor tariquidar may overcome bacterial multidrug resistance by increasing intracellular drug concentration. J Antimicrob Chemother 2011; 66:834-9. [PMID: 21393173 DOI: 10.1093/jac/dkq526] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
OBJECTIVES The use of efflux pump inhibitors may be a powerful strategy to overcome transporter-mediated bacterial multidrug resistance. In the present study, we set out to investigate the potency of tariquidar, a third-generation P-glycoprotein inhibitor in clinical development, for overcoming bacterial resistance towards ciprofloxacin. METHODS Staphylococcus aureus 29213 (SA29213) and S. aureus 1199B (SA1199B), which overexpresses the multidrug transporter NorA, as well as Pseudomonas aeruginosa 27853 and Stenotrophomonas maltophilia BAA-85, which expresses SmeDEF, were exposed to ciprofloxacin in the presence and absence of tariquidar or, for comparative reasons, elacridar. Activity of both P-glycoprotein inhibitors was evaluated by determination of MICs and time-kill curves, and by quantification of uptake of ciprofloxacin into bacterial cells. RESULTS Activity of tariquidar and elacridar was comparable for S. aureus strains, and both dose-dependently increased susceptibility towards ciprofloxacin. Highest effects were observed for SA1199B, where the addition of tariquidar resulted in a 10-fold reduction of the ciprofloxacin MIC, while no effect was observed for P. aeruginosa. For S. maltophilia, elacridar but not tariquidar improved susceptibility. Uptake of [14C]ciprofloxacin and modification of susceptibility showed significant correlations (r=0.89, P<0.0001). Tariquidar had no intrinsic activity against any strain tested. CONCLUSIONS We conclude that tariquidar has potent inhibitory effect against certain bacterial efflux pumps in vitro. Their high activity at clinically achievable concentrations might yield this class of drugs promising for future applications in infectious diseases.
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Affiliation(s)
- I Leitner
- Department of Clinical Pharmacology, Medical University Vienna, Vienna, Austria
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82
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Gwynn MN, Portnoy A, Rittenhouse SF, Payne DJ. Challenges of antibacterial discovery revisited. Ann N Y Acad Sci 2010; 1213:5-19. [PMID: 21058956 DOI: 10.1111/j.1749-6632.2010.05828.x] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The discovery of novel antibiotic classes has not kept pace with the growing threat of bacterial resistance. Antibiotic candidates that act at new targets or via distinct mechanisms have the greatest potential to overcome resistance; however, novel approaches are also associated with higher attrition and longer timelines. This uncertainty has contributed to the withdrawal from antibiotic programs by many pharmaceutical companies. Genomic approaches have not yielded satisfactory results, in part due to nascent knowledge about unprecedented molecular targets, the challenge of achieving antibacterial activity by lead optimization of enzyme inhibitors, and the limitations of compound screening libraries for antibacterial discovery. Enhanced diversity of compound screening banks, entry into new chemical space, and new screening technologies are currently being exploited to improve hit rates for antibacterial discovery. Antibacterial compound lead optimization faces hurdles associated with the high plasma exposures required for efficacy. Lead optimization would be enhanced by the identification of new antibiotic classes with improved tractability and by expanding the predictability of in vitro safety assays. Implementing multiple screening and target identification strategies is recommended for improving the likelihood of discovering new antibacterial compounds that address unmet needs.
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Affiliation(s)
- Michael N Gwynn
- Antibacterial Discovery Performance Unit, Infectious Diseases Center of Excellence for Drug Discovery, GlaxoSmithKline, Collegeville, Pennsylvania, USA
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83
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Jin J, Zhang J, Guo N, Feng H, Li L, Liang J, Sun K, Wu X, Wang X, Liu M, Deng X, Yu L. The plant alkaloid piperine as a potential inhibitor of ethidium bromide efflux in Mycobacterium smegmatis. J Med Microbiol 2010; 60:223-229. [PMID: 21051548 DOI: 10.1099/jmm.0.025734-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Piperine, a major plant alkaloid found in black pepper (Piper nigrum) and long pepper (Piper longum), has shown potential for inhibiting the efflux pump (EP) of Staphylococcus aureus. In this study, a modulation assay showed that piperine could decrease the MIC of ethidium bromide (EtBr) twofold at 32 μg ml(-1) and fourfold at 64 μg ml(-1) against Mycobacterium smegmatis mc(2) 155 ATCC 700084. A real-time, 96-well plate fluorometric method was employed to evaluate the EP inhibition ability of piperine in M. smegmatis. Reserpine, chlorpromazine, verapamil and carbonyl cyanide m-chlorophenylhydrazone were used as positive controls. Piperine significantly enhanced accumulation and decreased the efflux of EtBr in M. smegmatis, which suggests that it has the ability to inhibit mycobacterial EPs.
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Affiliation(s)
- Jing Jin
- Key Laboratory of Zoonosis Research, Ministry of Education, Institute of Zoonosis, College of Animal Science and Veterinary Medicine, Jilin University, Changchun 130062, PR China
| | - Jiyu Zhang
- Key and Open Laboratory of Veterinary Pharmaceutical Engineering, Lanzhou Institute of Animal Science and Veterinary Pharmaceutics, Chinese Academy of Agricultural Sciences, Lanzhou 730050, PR China
| | - Na Guo
- Laboratory of Nutrition and Functional Food, Jilin University, Changchun 130062, PR China
| | - Haihua Feng
- Key Laboratory of Zoonosis Research, Ministry of Education, Institute of Zoonosis, College of Animal Science and Veterinary Medicine, Jilin University, Changchun 130062, PR China
| | - Lei Li
- Key Laboratory of Zoonosis Research, Ministry of Education, Institute of Zoonosis, College of Animal Science and Veterinary Medicine, Jilin University, Changchun 130062, PR China
| | - Junchao Liang
- Key Laboratory of Zoonosis Research, Ministry of Education, Institute of Zoonosis, College of Animal Science and Veterinary Medicine, Jilin University, Changchun 130062, PR China
| | - Kai Sun
- Institute of Theoretical Chemistry, Jilin University, Changchun 130023, PR China
| | - Xiuping Wu
- Key Laboratory of Zoonosis Research, Ministry of Education, Institute of Zoonosis, College of Animal Science and Veterinary Medicine, Jilin University, Changchun 130062, PR China
| | - Xuelin Wang
- Key Laboratory of Zoonosis Research, Ministry of Education, Institute of Zoonosis, College of Animal Science and Veterinary Medicine, Jilin University, Changchun 130062, PR China
| | - Mingyuan Liu
- Key Laboratory of Zoonosis Research, Ministry of Education, Institute of Zoonosis, College of Animal Science and Veterinary Medicine, Jilin University, Changchun 130062, PR China
| | - Xuming Deng
- Key Laboratory of Zoonosis Research, Ministry of Education, Institute of Zoonosis, College of Animal Science and Veterinary Medicine, Jilin University, Changchun 130062, PR China
| | - Lu Yu
- Key Laboratory of Zoonosis Research, Ministry of Education, Institute of Zoonosis, College of Animal Science and Veterinary Medicine, Jilin University, Changchun 130062, PR China
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84
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Brötz-Oesterhelt H, Sass P. Postgenomic strategies in antibacterial drug discovery. Future Microbiol 2010; 5:1553-79. [DOI: 10.2217/fmb.10.119] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
During the last decade the field of antibacterial drug discovery has changed in many aspects including bacterial organisms of primary interest, discovery strategies applied and pharmaceutical companies involved. Target-based high-throughput screening had been disappointingly unsuccessful for antibiotic research. Understanding of this lack of success has increased substantially and the lessons learned refer to characteristics of targets, screening libraries and screening strategies. The ‘genomics’ approach was replaced by a diverse array of discovery strategies, for example, searching for new natural product leads among previously abandoned compounds or new microbial sources, screening for synthetic inhibitors by targeted approaches including structure-based design and analyses of focused libraries and designing resistance-breaking properties into antibiotics of established classes. Furthermore, alternative treatment options are being pursued including anti-virulence strategies and immunotherapeutic approaches. This article summarizes the lessons learned from the genomics era and describes discovery strategies resulting from that knowledge.
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Affiliation(s)
- Heike Brötz-Oesterhelt
- AiCuris, Wuppertal, Germany, Institute for Pharmaceutical Biology, University of Duesseldorf, Universitätsstrasse 1, Building 26.23.U1, Germany
| | - Peter Sass
- Institute of Medical Microbiology, Immunology & Parasitology, Pharmaceutical Microbiology Section, University of Bonn, Germany
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85
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Bijlsma MF, Roelink H. Non-cell-autonomous signaling by Shh in tumors: challenges and opportunities for therapeutic targets. Expert Opin Ther Targets 2010; 14:693-702. [PMID: 20515293 DOI: 10.1517/14728222.2010.497488] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
IMPORTANCE OF THE FIELD The Hedgehog (Hh) pathway is required during many developmental events; in adults the Hedgehog pathway is involved in the maintenance of several stem cell niches. It is therefore not surprising that aberrantly regulated Hh pathway activity can cause birth defects in the developing organism, as well as neoplastic disease later in life. AREAS COVERED IN THIS REVIEW As a consequence of the involvement in pathogenesis, the Hh pathway components are subject to an intense scrutiny as potential targets for therapeutic agents. We aim to provide an overview of the biology of the Hh proteins and the cellular response, in conjunction with potential therapeutic interventions. WHAT THE READER WILL GAIN Specifically, we focus on the recently discovered non-cell-autonomous Shh signaling used by tumors and the implications of this for the design of treatment strategies. This should provide the reader with up-to-date knowledge on the role of the Hh pathway in tumor progression and the options to treat these malignancies. TAKE HOME MESSAGE An important concept that we advocate in this review is the need to recognize the need to target both the stromal and the tumor compartment in malignancies that rely on paracrine Shh signaling.
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Affiliation(s)
- Maarten F Bijlsma
- University of California Berkeley, Department of Molecular and Cell Biology, Berkeley, CA 94720-3204, USA
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86
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Abstract
Antibiotics have always been considered one of the wonder discoveries of the 20th century. This is true, but the real wonder is the rise of antibiotic resistance in hospitals, communities, and the environment concomitant with their use. The extraordinary genetic capacities of microbes have benefitted from man's overuse of antibiotics to exploit every source of resistance genes and every means of horizontal gene transmission to develop multiple mechanisms of resistance for each and every antibiotic introduced into practice clinically, agriculturally, or otherwise. This review presents the salient aspects of antibiotic resistance development over the past half-century, with the oft-restated conclusion that it is time to act. To achieve complete restitution of therapeutic applications of antibiotics, there is a need for more information on the role of environmental microbiomes in the rise of antibiotic resistance. In particular, creative approaches to the discovery of novel antibiotics and their expedited and controlled introduction to therapy are obligatory.
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87
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Abstract
Antibiotics have always been considered one of the wonder discoveries of the 20th century. This is true, but the real wonder is the rise of antibiotic resistance in hospitals, communities, and the environment concomitant with their use. The extraordinary genetic capacities of microbes have benefitted from man's overuse of antibiotics to exploit every source of resistance genes and every means of horizontal gene transmission to develop multiple mechanisms of resistance for each and every antibiotic introduced into practice clinically, agriculturally, or otherwise. This review presents the salient aspects of antibiotic resistance development over the past half-century, with the oft-restated conclusion that it is time to act. To achieve complete restitution of therapeutic applications of antibiotics, there is a need for more information on the role of environmental microbiomes in the rise of antibiotic resistance. In particular, creative approaches to the discovery of novel antibiotics and their expedited and controlled introduction to therapy are obligatory.
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Affiliation(s)
- Julian Davies
- Department of Microbiology and Immunology, Life Sciences Institute, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada.
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88
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Martins A, Spengler G, Martins M, Rodrigues L, Viveiros M, Davin-Regli A, Chevalier J, Couto I, Pagès JM, Amaral L. Physiological characterisation of the efflux pump system of antibiotic-susceptible and multidrug-resistant Enterobacter aerogenes. Int J Antimicrob Agents 2010; 36:313-8. [PMID: 20688487 DOI: 10.1016/j.ijantimicag.2010.06.036] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Revised: 06/13/2010] [Accepted: 06/14/2010] [Indexed: 10/19/2022]
Abstract
Enterobacter aerogenes predominates amongst Enterobacteriaceae species that are increasingly reported as producers of extended-spectrum beta-lactamases. Although this mechanism of resistance to beta-lactams is important, other mechanisms bestowing a multidrug-resistant (MDR) phenotype in this species are now well documented. Amongst these mechanisms is the overexpression of efflux pumps that extrude structurally unrelated antibiotics prior to their reaching their targets. Interestingly, although knowledge of the genetic background behind efflux pumps is rapidly advancing, few studies assess the physiological nature of the overall efflux pump system of this, or for that matter any other, bacterium. The study reported here evaluates physiologically the efflux pump system of an E. aerogenes ATCC reference as well as two strains whose MDR phenotypes are mediated by overexpressed efflux pumps. The activities of the efflux pumps in these strains are modulated by pH and glucose, although the effects of the latter are essentially restricted to pH 8, suggesting the presence of two general efflux pump systems, i.e. proton-motive force-dependent and ABC transporter types, respectively.
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Affiliation(s)
- A Martins
- Unit of Mycobacteriology, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira 96, 1349-008 Lisboa, Portugal
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89
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Pieroni M, Dimovska M, Brincat JP, Sabatini S, Carosati E, Massari S, Kaatz GW, Fravolini A. From 6-aminoquinolone antibacterials to 6-amino-7-thiopyranopyridinylquinolone ethyl esters as inhibitors of Staphylococcus aureus multidrug efflux pumps. J Med Chem 2010; 53:4466-80. [PMID: 20446747 DOI: 10.1021/jm1003304] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The thiopyranopyridine moiety was synthesized as a new heterocyclic base to be inserted at the C-7 position of selected quinolone nuclei followed by a determination of antibacterial activity against strains of Staphylococcus aureus. Selected thiopyranopyridinylquinolones showed significant antimicrobial activity, including strains having mutations in gyrA and grlA as well as other strains overexpressing the NorA multidrug (MDR) efflux pump. Most derivatives did not appear to be NorA substrates. The effect of the thiopyranopyridinyl substituent on making these quinolones poor substrates for NorA was investigated further. Several quinolone ester intermediates, devoid of any intrinsic antibacterial activity, were tested for their abilities to inhibit the activities of NorA (MFS family) and MepA (MATE family) S. aureus MDR efflux pumps. Selected quinolone esters were capable of inhibiting both MDR pumps more efficiently than the reference compound reserpine. Moreover, they also were able to restore, and even enhance, the activity of ciprofloxacin toward some genetically modified resistant S. aureus strains.
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Affiliation(s)
- Marco Pieroni
- Dipartimento di Chimica e Tecnologia del Farmaco, Università degli Studi di Perugia, 06123 Perugia, Italy
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90
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Schulz R, Vargiu AV, Collu F, Kleinekathöfer U, Ruggerone P. Functional rotation of the transporter AcrB: insights into drug extrusion from simulations. PLoS Comput Biol 2010; 6:e1000806. [PMID: 20548943 PMCID: PMC2883587 DOI: 10.1371/journal.pcbi.1000806] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Accepted: 05/05/2010] [Indexed: 01/16/2023] Open
Abstract
The tripartite complex AcrAB-TolC is the major efflux system in Escherichia coli. It extrudes a wide spectrum of noxious compounds out of the bacterium, including many antibiotics. Its active part, the homotrimeric transporter AcrB, is responsible for the selective binding of substrates and energy transduction. Based on available crystal structures and biochemical data, the transport of substrates by AcrB has been proposed to take place via a functional rotation, in which each monomer assumes a particular conformation. However, there is no molecular-level description of the conformational changes associated with the rotation and their connection to drug extrusion. To obtain insights thereon, we have performed extensive targeted molecular dynamics simulations mimicking the functional rotation of AcrB containing doxorubicin, one of the two substrates that were co-crystallized so far. The simulations, including almost half a million atoms, have been used to test several hypotheses concerning the structure-dynamics-function relationship of this transporter. Our results indicate that, upon induction of conformational changes, the substrate detaches from the binding pocket and approaches the gate to the central funnel. Furthermore, we provide strong evidence for the proposed peristaltic transport involving a zipper-like closure of the binding pocket, responsible for the displacement of the drug. A concerted opening of the channel between the binding pocket and the gate further favors the displacement of the drug. This microscopically well-funded information allows one to identify the role of specific amino acids during the transitions and to shed light on the functioning of AcrB. In nature, bacteria have to resist several toxic threats to be able to survive, from bile acids in intestines up to antibiotics. The Escherichia coli bacterium, which usually is a commensal inhabitant of human intestines, can also acquire pathogenic properties which would harm the human body. To dispose of toxic compounds, E. coli has developed a protein machinery which is called “efflux pump”. Here, we studied the dynamics of the transporter protein AcrB, a component of the E. coli major efflux system, in complex with an antibiotic (doxorubicin). We used computer simulations to complement the existing experimental data. Our purpose was to gain more detailed insights into the pumping mechanism at the molecular level. In our simulations the drug leaves the binding pocket upon induction of functional rotation in the protein, although a complete extrusion was never observed. A peristaltic motion, which starts with a zipper-like closure of the interior of the protein, is an important step for the extrusion of the drug. Interestingly, such a peristaltic mechanism of pumping has been suggested before on the basis of structural data. The molecular details obtained in this study shall deepen the understanding of the functioning of the efflux pump.
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Affiliation(s)
- Robert Schulz
- School of Engineering and Science, Jacobs University Bremen, Bremen, Germany
| | - Attilio V. Vargiu
- Istituto Officina dei Materiali del CNR, UOS SLACS and Dipartimento di Fisica, Universita' degli Studi di Cagliari, Monserrato, Italy
- * E-mail:
| | - Francesca Collu
- Istituto Officina dei Materiali del CNR, UOS SLACS and Dipartimento di Fisica, Universita' degli Studi di Cagliari, Monserrato, Italy
| | | | - Paolo Ruggerone
- Istituto Officina dei Materiali del CNR, UOS SLACS and Dipartimento di Fisica, Universita' degli Studi di Cagliari, Monserrato, Italy
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91
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Conroy O, Kim EH, McEvoy MM, Rensing C. Differing ability to transport nonmetal substrates by two RND-type metal exporters. FEMS Microbiol Lett 2010; 308:115-22. [PMID: 20497225 DOI: 10.1111/j.1574-6968.2010.02006.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The metal-exporting systems CusCFBA of Escherichia coli and GesABC of Salmonella are resistance-nodulation-division (RND)-type multiprotein systems responsible for detoxification during metal stress. In this study, the substrate range was determined for each metal transport system and possible amino acid residues important in substrate specificity were identified. The Ges system, previously identified as a gold-efflux system, conferred resistance to the greatest number and variety of organic chemicals including chloramphenicol, not recognized previously as a substrate. Phylogenetic analysis showed that GesB is most closely related to a class of RND transporters including MexF that have been shown to be responsible for exporting fluoroquinolones, chloramphenicol, and biocides. However, many of the closest homologs of GesABC appear to play a role in metal resistance judging from the genetic context. In contrast, CusCFBA belongs to a distinct family of RND-type monovalent metal-exporter systems containing a number of essential metal-binding methionines, resulting in a much narrower substrate range.
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Affiliation(s)
- Otakuye Conroy
- Department of Soil, Water, and Environmental Science, University of Arizona, Tucson, AZ 85721, USA
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92
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Kim EH, Rensing C, McEvoy MM. Chaperone-mediated copper handling in the periplasm. Nat Prod Rep 2010; 27:711-9. [PMID: 20442961 DOI: 10.1039/b906681k] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Eun-Hae Kim
- Department of Soil, Water, and Environmental Science, University of Arizona, Tucson, AZ 85721, USA
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93
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Lomovskaya O, Zgurskaya HI, Bostian K. Bacterial Multidrug Transporters: Molecular and Clinical Aspects. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/9783527627424.ch5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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94
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The relative contribution of efflux and target gene mutations to fluoroquinolone resistance in recent clinical isolates of Pseudomonas aeruginosa. Eur J Clin Microbiol Infect Dis 2010; 29:279-88. [DOI: 10.1007/s10096-009-0852-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Accepted: 11/29/2009] [Indexed: 11/26/2022]
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95
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Abstract
A semi-automated method that uses the common efflux pump (EP) substrate ethidium bromide (EB) is described for the assessment of EP systems of bacteria. The method employs the Rotor-Gene(TM) 3000 thermocycler (Corbett Research) for the real-time assessment of accumulation and efflux of EB in Phosphate-Buffered Solution (PBS) under varying physiological conditions, such as temperature, pH, presence and absence of the energy source, and presence of efflux pumps inhibitors (EPIs). The method is sufficiently sensitive to characterize intrinsic EP systems of reference strains, a prime necessity if there is a need for assessment of EP-mediated multi-drug resistance (MDR). The method has been successfully applied by us to characterize intrinsic and over-expressed EP systems of Escherichia coli, Salmonella Enteritidis, Enterobacter aerogenes, Enterococcus faecalis and Enterococcus faecium, Staphylococcus aureus, and Mycobacterium smegmatis and Mycobacterium avium, suggesting that if the organism can be maintained in PBS, the system described may suffice for the evaluation and assessment of its EP system.
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96
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Altenkämper M, Bechem B, Perruchon J, Heinrich S, Mädel A, Ortmann R, Dahse HM, Freunscht E, Wang Y, Rath J, Stich A, Hitzler M, Chiba P, Lanzer M, Schlitzer M. Antimalarial and antitrypanosomal activity of a series of amide and sulfonamide derivatives of a 2,5-diaminobenzophenone. Bioorg Med Chem 2009; 17:7690-7. [DOI: 10.1016/j.bmc.2009.09.043] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2009] [Revised: 09/18/2009] [Accepted: 09/21/2009] [Indexed: 11/29/2022]
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97
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Zgurskaya HI. Multicomponent drug efflux complexes: architecture and mechanism of assembly. Future Microbiol 2009; 4:919-32. [PMID: 19722844 DOI: 10.2217/fmb.09.62] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Multidrug efflux pumps are major contributors to intrinsic antibiotic resistance in Gram-negative pathogens. The basic structure of these pumps comprises an inner membrane transporter, a periplasmic membrane fusion protein and an outer membrane channel. However, the architecture and composition of multidrug efflux complexes vary significantly because of the topological and functional diversity of the inner membrane transporters. This article presents the current views on architecture and assembly of multicomponent drug efflux transporters from Gram-negative bacteria.
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Affiliation(s)
- Helen I Zgurskaya
- Department of Chemistry & Biochemistry, University of Oklahoma, 620 Parrington Oval, Room 208, Norman, OK 73019, USA.
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98
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Paixão L, Rodrigues L, Couto I, Martins M, Fernandes P, de Carvalho CCCR, Monteiro GA, Sansonetty F, Amaral L, Viveiros M. Fluorometric determination of ethidium bromide efflux kinetics in Escherichia coli. J Biol Eng 2009; 3:18. [PMID: 19835592 PMCID: PMC2774284 DOI: 10.1186/1754-1611-3-18] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Accepted: 10/16/2009] [Indexed: 11/24/2022] Open
Abstract
Background Efflux pump activity has been associated with multidrug resistance phenotypes in bacteria, compromising the effectiveness of antimicrobial therapy. The development of methods for the early detection and quantification of drug transport across the bacterial cell wall is a tool essential to understand and overcome this type of drug resistance mechanism. This approach was developed to study the transport of the efflux pump substrate ethidium bromide (EtBr) across the cell envelope of Escherichia coli K-12 and derivatives, differing in the expression of their efflux systems. Results EtBr transport across the cell envelope of E. coli K-12 and derivatives was analysed by a semi-automated fluorometric method. Accumulation and efflux of EtBr was studied under limiting energy supply (absence of glucose and low temperature) and in the presence and absence of the efflux pump inhibitor, chlorpromazine. The bulk fluorescence variations were also observed by single-cell flow cytometry analysis, revealing that once inside the cells, leakage of EtBr does not occur and that efflux is mediated by active transport. The importance of AcrAB-TolC, the main efflux system of E. coli, in the extrusion of EtBr was evidenced by comparing strains with different levels of AcrAB expression. An experimental model was developed to describe the transport kinetics in the three strains. The model integrates passive entry (influx) and active efflux of EtBr, and discriminates different degrees of efflux between the studied strains that vary in the activity of their efflux systems, as evident from the calculated efflux rates: = 0.0173 ± 0.0057 min-1; = 0.0106 ± 0.0033 min-1; and = 0.0230 ± 0.0075 min-1. Conclusion The combined use of a semi-automated fluorometric method and an experimental model allowed quantifying EtBr transport in E. coli strains that differ in their overall efflux activity. This methodology can be used for the early detection of differences in the drug efflux capacity in bacteria accounting for antibiotic resistance, as well as for expedite screening of new drug efflux inhibitors libraries and transport studies across the bacterial cell wall.
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Affiliation(s)
- Laura Paixão
- Unit of Mycobacteriology, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa (IHMT/UNL), Rua da Junqueira 100, 1349-008 Lisboa, Portugal. laurapaixao@iol
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99
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Blair JMA, Piddock LJV. Structure, function and inhibition of RND efflux pumps in Gram-negative bacteria: an update. Curr Opin Microbiol 2009; 12:512-9. [DOI: 10.1016/j.mib.2009.07.003] [Citation(s) in RCA: 168] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2009] [Revised: 07/02/2009] [Accepted: 07/08/2009] [Indexed: 01/07/2023]
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100
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Kinetic control of TolC recruitment by multidrug efflux complexes. Proc Natl Acad Sci U S A 2009; 106:16416-21. [PMID: 19805313 DOI: 10.1073/pnas.0906601106] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In Gram-negative pathogens, multidrug efflux pumps that provide clinically significant levels of antibiotic resistance function as three-component complexes. They are composed of the inner membrane transporters belonging to one of three superfamilies of proteins, RND, ABC, or MF; periplasmic proteins belonging to the membrane fusion protein (MFP) family; and outer membrane channels exemplified by the Escherichia coli TolC. The three-component complexes span the entire two-membrane envelope of Gram-negative bacteria and expel toxic molecules from the cytoplasmic membrane to the medium. The architecture of these complexes is expected to vary significantly because of the structural diversity of the inner membrane transporters. How the three-component pumps are assembled, their architecture, and their dynamics remain unclear. In this study, we reconstituted interactions and compared binding kinetics of the E. coli TolC with AcrA, MacA, and EmrA, the periplasmic MFPs that function in multidrug efflux with transporters from the RND, ABC, and MF superfamilies, respectively. By using surface plasmon resonance, we demonstrate that TolC interactions with MFPs are highly dynamic and sensitive to pH. The affinity of TolC to MFPs decreases in the order MacA > EmrA > AcrA. We further show that MFPs are prone to oligomerization, but differ dramatically from each other in oligomerization kinetics and stability of oligomers. The propensity of MFPs to oligomerize correlates with the stability of MFP-TolC complexes and structural features of inner membrane transporters. We propose that recruitment of TolC by various MFPs is determined not only by kinetics of MFP-TolC interactions but also by oligomerization kinetics of MFPs and pH.
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