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Alamri MA, Tariq MH, Tahir Ul Qamar M, Alabbas AB, Alqahtani SM, Ahmad S. Discovery of potential phytochemicals as inhibitors of TcdB, a major virulence factors of Clostridioides difficile. J Biomol Struct Dyn 2023; 41:12768-12776. [PMID: 36644848 DOI: 10.1080/07391102.2023.2167120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 01/06/2023] [Indexed: 01/17/2023]
Abstract
Clostridioides difficile is a gram-positive bacterium which is associated with different gastrointestinal related infections, and the numbers of cases related to it are continuously increasing in the past few years. Owing to high prevalence and development of resistance towards available antibiotics, it is required to develop new therapeutics to combat C. difficile infection. The current study was aimed to identify novel phytochemicals that could bind and inhibits the TcdB, an exotoxin which is required for the pathogenesis of bacteria, and hence can be considered as the future drug candidates against C. difficile. ∼2500 therapeutically important phyto-compounds were docked against the active sites of TcdB protein by using AutoDock-Vina software. The interactions between the ligands and the binding site of the top five docked complexes, based on the docking scores, were further elucidated by Molecular Dynamics Simulations of 500 ns, Molecular Mechanics Energies combined with the Poisson-Boltzmann and Surface Area (MMPBSA) or Generalized Born and Surface Area (MMGBSA), and WaterSwap Analysis. Findings of molecular docking suggested that natural compounds A183, A704, A1528, A2083, and A2129 with distinct chemical scaffolds are best docked in the binding site of TcdB and their bonding remained stable throughout the simulation studies of 500 ns. Compounds A2129 and A704 can be considered as prospective drug candidates against Clostridioides difficile, however, further wet lab experiments are needed to confirm our study.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Mubarak A Alamri
- Department of Pharmaceutical Chemistry, College of Pharmacy, Prince Sattam Bin Abdulaziz University, Al-Kharj, Saudi Arabia
| | | | - Muhammad Tahir Ul Qamar
- Integrative Omics and Molecular Modeling Laboratory, Department of Bioinformatics and Biotechnology, Government College University Faisalabad, Faisalabad, Pakistan
| | - Alhumaidi B Alabbas
- Department of Pharmaceutical Chemistry, College of Pharmacy, Prince Sattam Bin Abdulaziz University, Al-Kharj, Saudi Arabia
| | - Safar M Alqahtani
- Department of Pharmaceutical Chemistry, College of Pharmacy, Prince Sattam Bin Abdulaziz University, Al-Kharj, Saudi Arabia
| | - Sajjad Ahmad
- Department of Health and Biological Sciences, Abasyn University, Peshawar, Pakistan
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Paparella A, Cahill SM, Aboulache BL, Schramm VL. Clostridioides difficile TcdB Toxin Glucosylates Rho GTPase by an S Ni Mechanism and Ion Pair Transition State. ACS Chem Biol 2022; 17:2507-2518. [PMID: 36038138 PMCID: PMC9486934 DOI: 10.1021/acschembio.2c00408] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Toxins TcdA and TcdB from Clostridioides difficile glucosylate human colon Rho GTPases. TcdA and TcdB glucosylation of RhoGTPases results in cytoskeletal changes, causing cell rounding and loss of intestinal integrity. Clostridial toxins TcdA and TcdB are proposed to catalyze glucosylation of Rho GTPases with retention of stereochemistry from UDP-glucose. We used kinetic isotope effects to analyze the mechanisms and transition-state structures of the glucohydrolase and glucosyltransferase activities of TcdB. TcdB catalyzes Rho GTPase glucosylation with retention of stereochemistry, while hydrolysis of UDP-glucose by TcdB causes inversion of stereochemistry. Kinetic analysis revealed TcdB glucosylation via the formation of a ternary complex with no intermediate, supporting an SNi mechanism with nucleophilic attack and leaving group departure occurring on the same face of the glucose ring. Kinetic isotope effects combined with quantum mechanical calculations revealed that the transition states of both glucohydrolase and glucosyltransferase activities of TcdB are highly dissociative. Specifically, the TcdB glucosyltransferase reaction proceeds via an SNi mechanism with the formation of a distinct oxocarbenium phosphate ion pair transition state where the glycosidic bond to the UDP leaving group breaks prior to attack of the threonine nucleophile from Rho GTPase.
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Abstract
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The paradigm of antivirulence
therapy dictates that bacterial pathogens
are specifically disarmed but not killed by neutralizing their virulence
factors. Clearance of the invading pathogen by the immune system is
promoted. As compared to antibiotics, the pathogen-selective antivirulence
drugs hold promise to minimize collateral damage to the beneficial
microbiome. Also, selective pressure for resistance is expected to
be lower because bacterial viability is not directly affected. Antivirulence
drugs are being developed for stand-alone prophylactic and therapeutic
treatments but also for combinatorial use with antibiotics. This Review
focuses on drug modalities that target bacterial exotoxins after the
secretion or release-upon-lysis. Exotoxins have a significant and
sometimes the primary role as the disease-causing virulence factor,
and thereby they are attractive targets for drug development. We describe
the key pre-clinical and clinical trial data that have led to the
approval of currently used exotoxin-targeted drugs, namely the monoclonal
antibodies bezlotoxumab (toxin B/TcdB, Clostridioides difficile), raxibacumab (anthrax toxin, Bacillus anthracis), and obiltoxaximab (anthrax toxin, Bacillus anthracis), but also to challenges with some of the promising leads. We also
highlight the recent developments in pre-clinical research sector
to develop exotoxin-targeted drug modalities, i.e., monoclonal antibodies,
antibody fragments, antibody mimetics, receptor analogs, neutralizing
scaffolds, dominant-negative mutants, and small molecules. We describe
how these exotoxin-targeted drug modalities work with high-resolution
structural knowledge and highlight their advantages and disadvantages
as antibiotic alternatives.
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Affiliation(s)
- Moona Sakari
- Institute of Biomedicine, Research Unit for Infection and Immunity, University of Turku, Kiinamyllynkatu 10, FI-20520 Turku, Finland
| | - Arttu Laisi
- Institute of Biomedicine, Research Unit for Infection and Immunity, University of Turku, Kiinamyllynkatu 10, FI-20520 Turku, Finland
| | - Arto T. Pulliainen
- Institute of Biomedicine, Research Unit for Infection and Immunity, University of Turku, Kiinamyllynkatu 10, FI-20520 Turku, Finland
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Inhibition of Clostridium difficile TcdA and TcdB toxins with transition state analogues. Nat Commun 2021; 12:6285. [PMID: 34725358 PMCID: PMC8560925 DOI: 10.1038/s41467-021-26580-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Accepted: 10/11/2021] [Indexed: 12/20/2022] Open
Abstract
Clostridium difficile causes life-threatening diarrhea and is the leading cause of healthcare-associated bacterial infections in the United States. TcdA and TcdB bacterial toxins are primary determinants of disease pathogenesis and are attractive therapeutic targets. TcdA and TcdB contain domains that use UDP-glucose to glucosylate and inactivate host Rho GTPases, resulting in cytoskeletal changes causing cell rounding and loss of intestinal integrity. Transition state analysis revealed glucocationic character for the TcdA and TcdB transition states. We identified transition state analogue inhibitors and characterized them by kinetic, thermodynamic and structural analysis. Iminosugars, isofagomine and noeuromycin mimic the transition state and inhibit both TcdA and TcdB by forming ternary complexes with Tcd and UDP, a product of the TcdA- and TcdB-catalyzed reactions. Both iminosugars prevent TcdA- and TcdB-induced cytotoxicity in cultured mammalian cells by preventing glucosylation of Rho GTPases. Iminosugar transition state analogues of the Tcd toxins show potential as therapeutics for C. difficile pathology. The Clostridium difficile virulence factors TcdA and TcdB contain a glucosyltransferase domain (GTD), which has both glucohydrolase (GH) and glucosyltransferase (GT) activities. Here, the authors characterize the transition state features of the TcdA and TcdB GH reactions by measuring kinetic isotope effects and they identify two transition state analogues, isofagomine and noeuromycin that inhibit TcdA and TcdB. They also present the crystal structures of TcdB-GTD bound to these inhibitors and the reaction product UDP.
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Shao X, AbdelKhalek A, Abutaleb NS, Velagapudi UK, Yoganathan S, Seleem MN, Talele TT. Chemical Space Exploration around Thieno[3,2- d]pyrimidin-4(3 H)-one Scaffold Led to a Novel Class of Highly Active Clostridium difficile Inhibitors. J Med Chem 2019; 62:9772-9791. [PMID: 31584822 DOI: 10.1021/acs.jmedchem.9b01198] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Clostridium difficile infection (CDI) is the leading cause of healthcare-associated infection in the United States. Therefore, development of novel treatments for CDI is a high priority. Toward this goal, we began in vitro screening of a structurally diverse in-house library of 67 compounds against two pathogenic C. difficile strains (ATCC BAA 1870 and ATCC 43255), which yielded a hit compound, 2-methyl-8-nitroquinazolin-4(3H)-one (2) with moderate potency (MIC = 312/156 μM). Optimization of 2 gave lead compound 6a (2-methyl-7-nitrothieno[3,2-d]pyrimidin-4(3H)-one) with improved potency (MIC = 19/38 μM), selectivity over normal gut microflora, CC50s > 606 μM against mammalian cell lines, and acceptable stability in simulated gastric and intestinal fluid. Further optimization of 6a at C2-, N3-, C4-, and C7-positions resulted in a library of >50 compounds with MICs ranging from 3 to 800 μM against clinical isolates of C. difficile. Compound 8f (MIC = 3/6 μM) was identified as a promising lead for further optimization.
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Affiliation(s)
- Xuwei Shao
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences , St. John's University , Queens , New York 11439-0001 , United States
| | - Ahmed AbdelKhalek
- Department of Comparative Pathobiology , Purdue University College of Veterinary Medicine , West Lafayette , Indiana 47907-2027 , United States
| | - Nader S Abutaleb
- Department of Comparative Pathobiology , Purdue University College of Veterinary Medicine , West Lafayette , Indiana 47907-2027 , United States
| | - Uday Kiran Velagapudi
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences , St. John's University , Queens , New York 11439-0001 , United States
| | - Sabesan Yoganathan
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences , St. John's University , Queens , New York 11439-0001 , United States
| | - Mohamed N Seleem
- Department of Comparative Pathobiology , Purdue University College of Veterinary Medicine , West Lafayette , Indiana 47907-2027 , United States.,Purdue Institute of Inflammation, Immunology, and Infectious Disease , West Lafayette , Indiana 47907-2027 , United States
| | - Tanaji T Talele
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences , St. John's University , Queens , New York 11439-0001 , United States
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Giau VV, Lee H, An SSA, Hulme J. Recent advances in the treatment of C. difficile using biotherapeutic agents. Infect Drug Resist 2019; 12:1597-1615. [PMID: 31354309 PMCID: PMC6579870 DOI: 10.2147/idr.s207572] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 05/03/2019] [Indexed: 12/12/2022] Open
Abstract
Clostridium difficile (C. difficile) is rapidly becoming one of the most prevalent health care–associated bacterial infections in the developed world. The emergence of new, more virulent strains has led to greater morbidity and resistance to standard therapies. The bacterium is readily transmitted between people where it can asymptomatically colonize the gut environment, and clinical manifestations ranging from frequent watery diarrhea to toxic megacolon can arise depending on the age of the individual or their state of gut dysbiosis. Several inexpensive approaches are shown to be effective against virulent C. difficile in research settings such as probiotics, fecal microbiota transfer and immunotherapies. This review aims to highlight the current advantages and limitations of the aforementioned approaches with an emphasis on recent studies.
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Affiliation(s)
- Vo Van Giau
- Department of BioNano Technology, Gachon University, Seongnam-si 461-701, Republic of Korea
| | - Hyon Lee
- Department of Neurology, Gachon University Gil Medical Center, Incheon, South Korea
| | - Seong Soo A An
- Department of BioNano Technology, Gachon University, Seongnam-si 461-701, Republic of Korea
| | - John Hulme
- Department of BioNano Technology, Gachon University, Seongnam-si 461-701, Republic of Korea
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