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Zhang Y, Liu Y, Qiu J, Luo ZQ, Deng X. The Herbal Compound Thymol Protects Mice From Lethal Infection by Salmonella Typhimurium. Front Microbiol 2018; 9:1022. [PMID: 29867906 PMCID: PMC5968388 DOI: 10.3389/fmicb.2018.01022] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Accepted: 04/30/2018] [Indexed: 12/23/2022] Open
Abstract
Type III secretion system (T3SS) is an essential pathogenic determinant for many important bacterial pathogens; it functions to thwart immune defense by delivering effectors into host cells. Because of its essential role in bacterial virulence, this machinery is an important target in the development of novel anti-virulence therapeutics. By using an effector-lactamase fusion reporter, we identified thymol, a monoterpene phenol derivative of cymene, as an effective inhibitor of the T3SS-1 of Salmonella Typhimurium. Our results indicate that thymol effectively protected mice against S. Typhimurium-induced mortality and pathological damages, suggesting that this compound can be developed for the control of infections caused by Salmonella species.
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Affiliation(s)
- Yong Zhang
- Key Laboratory of Zoonosis, Ministry of Education, Institute of Zoonosis, College of Veterinary Medicine, Jilin University, Changchun, China.,Center of Infection and Immunity, The First Hospital, Jilin University, Changchun, China
| | - Yan Liu
- Key Laboratory of Zoonosis, Ministry of Education, Institute of Zoonosis, College of Veterinary Medicine, Jilin University, Changchun, China
| | - Jiazhang Qiu
- Key Laboratory of Zoonosis, Ministry of Education, Institute of Zoonosis, College of Veterinary Medicine, Jilin University, Changchun, China.,Center of Infection and Immunity, The First Hospital, Jilin University, Changchun, China
| | - Zhao-Qing Luo
- Center of Infection and Immunity, The First Hospital, Jilin University, Changchun, China.,Department of Biological Sciences, Purdue Institute for Inflammation, Immunology and Infectious Diseases and Purdue University, West Lafayette, IN, United States
| | - Xuming Deng
- Key Laboratory of Zoonosis, Ministry of Education, Institute of Zoonosis, College of Veterinary Medicine, Jilin University, Changchun, China
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52
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Grishin AV, Luyksaar SI, Kapotina LN, Kirsanov DD, Zayakin ES, Karyagina AS, Zigangirova NA. Identification of chlamydial T3SS inhibitors through virtual screening against T3SS ATPase. Chem Biol Drug Des 2017; 91:717-727. [PMID: 29068165 DOI: 10.1111/cbdd.13130] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 06/26/2017] [Accepted: 08/11/2017] [Indexed: 01/20/2023]
Abstract
Chlamydia trachomatis is a widespread sexually transmitted pathogen that resides within a special vacuole inside host cells. Although acute infection can be treated with antibiotics, chlamydia can enter persistent state, leading to chronic infection that is difficult to cure. Thus, novel anti-chlamydial compounds active against persistent chlamydia are required. Chlamydiae rely upon type III secretion system (T3SS) to inject effector proteins into host cell cytoplasm, and T3SS inhibitors are viewed as promising compounds for treatment of chlamydial infections. C. trachomatis ATPase SctN is an important T3SS component and has not been targeted before. We thus used virtual screening against homology modeled SctN structure to search for SctN inhibitors. Selected compounds were tested for their ability to inhibit chlamydial survival and development within eukaryotic cells, and for the ability to suppress normal T3SS functioning. We identified two compounds that were able to block normal protein translocation through T3SS and inhibit chlamydial survival within eukaryotic cells in 50-100 μm concentrations. These two novel T3SS inhibitors also possessed relatively low toxicity toward eukaryotic cells. A small series of derivatives was further synthesized for the most active of two inhibitors to probe SAR properties.
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Affiliation(s)
- Alexander V Grishin
- N.F. Gamaleya National Research Center of Epidemiology and Microbiology, Moscow, Russia.,Institute of Agricultural Biotechnology, Moscow, Russia
| | - Sergey I Luyksaar
- N.F. Gamaleya National Research Center of Epidemiology and Microbiology, Moscow, Russia
| | - Lidiya N Kapotina
- N.F. Gamaleya National Research Center of Epidemiology and Microbiology, Moscow, Russia
| | - Dmitry D Kirsanov
- N.F. Gamaleya National Research Center of Epidemiology and Microbiology, Moscow, Russia
| | - Egor S Zayakin
- N.F. Gamaleya National Research Center of Epidemiology and Microbiology, Moscow, Russia
| | - Anna S Karyagina
- N.F. Gamaleya National Research Center of Epidemiology and Microbiology, Moscow, Russia.,Institute of Agricultural Biotechnology, Moscow, Russia.,A.N. Belozersky Institute of Physical and Chemical Biology, M.V. Lomonosov Moscow State University, Moscow, Russia
| | - Naylia A Zigangirova
- N.F. Gamaleya National Research Center of Epidemiology and Microbiology, Moscow, Russia
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53
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Impact of Type III Secretion Effectors and of Phenoxyacetamide Inhibitors of Type III Secretion on Abscess Formation in a Mouse Model of Pseudomonas aeruginosa Infection. Antimicrob Agents Chemother 2017; 61:AAC.01202-17. [PMID: 28807906 DOI: 10.1128/aac.01202-17] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Accepted: 08/04/2017] [Indexed: 12/20/2022] Open
Abstract
Pseudomonas aeruginosa is a leading cause of intra-abdominal infections, wound infections, and community-acquired folliculitis, each of which may involve macro- or microabscess formation. The rising incidence of multidrug resistance among P. aeruginosa isolates has increased both the economic burden and the morbidity and mortality associated with P. aeruginosa disease and necessitates a search for novel therapeutics. Previous work from our group detailed novel phenoxyacetamide inhibitors that block type III secretion and injection into host cells in vitro In this study, we used a mouse model of P. aeruginosa abscess formation to test the in vivo efficacy of these compounds against the P. aeruginosa type III secretion system (T3SS). Bacteria used the T3SS to intoxicate infiltrating neutrophils to establish abscesses. Despite this antagonism, sufficient numbers of functioning neutrophils remained for proper containment of the abscesses, as neutrophil depletion resulted in an increased abscess size, the formation of dermonecrotic lesions on the skin, and the dissemination of P. aeruginosa to internal organs. Consistent with the specificity of the T3SS-neutrophil interaction, P. aeruginosa bacteria lacking a functional T3SS were fully capable of causing abscesses in a neutropenic host. Phenoxyacetamide inhibitors attenuated abscess formation and aided in the immune clearance of the bacteria. Finally, a P. aeruginosa strain resistant to the phenoxyacetamide compound was fully capable of causing abscess formation even in the presence of the T3SS inhibitors. Together, our results further define the role of type III secretion in murine abscess formation and demonstrate the in vivo efficacy of phenoxyacetamide inhibitors in P. aeruginosa infection.
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54
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Synthetic Cyclic Peptomers as Type III Secretion System Inhibitors. Antimicrob Agents Chemother 2017; 61:AAC.00060-17. [PMID: 28652236 DOI: 10.1128/aac.00060-17] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Accepted: 06/10/2017] [Indexed: 12/12/2022] Open
Abstract
Antibiotic-resistant bacteria are an emerging threat to global public health. New classes of antibiotics and tools for antimicrobial discovery are urgently needed. Type III secretion systems (T3SS), which are required by dozens of Gram-negative bacteria for virulence but largely absent from nonpathogenic bacteria, are promising virulence blocker targets. The ability of mammalian cells to recognize the presence of a functional T3SS and trigger NF-κB activation provides a rapid and sensitive method for identifying chemical inhibitors of T3SS activity. In this study, we generated a HEK293 stable cell line expressing green fluorescent protein (GFP) driven by a promoter containing NF-κB enhancer elements to serve as a readout of T3SS function. We identified a family of synthetic cyclic peptide-peptoid hybrid molecules (peptomers) that exhibited dose-dependent inhibition of T3SS effector secretion in Yersinia pseudotuberculosis and Pseudomonas aeruginosa without affecting bacterial growth or motility. Among these inhibitors, EpD-3'N, EpD-1,2N, EpD-1,3'N, EpD-1,2,3'N, and EpD-1,2,4'N exhibited strong inhibitory effects on translocation of the Yersinia YopM effector protein into mammalian cells (>40% translocation inhibition at 7.5 μM) and showed no toxicity to mammalian cells at 240 μM. In addition, EpD-3'N and EpD-1,2,4'N reduced the rounding of HeLa cells caused by the activity of Yersinia effector proteins that target the actin cytoskeleton. In summary, we have discovered a family of novel cyclic peptomers that inhibit the injectisome T3SS but not the flagellar T3SS.
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55
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Yang L, Li S, Qin X, Jiang G, Chen J, Li B, Yao X, Liang P, Zhang Y, Ding W. Exposure to Umbelliferone Reduces Ralstonia solanacearum Biofilm Formation, Transcription of Type III Secretion System Regulators and Effectors and Virulence on Tobacco. Front Microbiol 2017; 8:1234. [PMID: 28713361 PMCID: PMC5492427 DOI: 10.3389/fmicb.2017.01234] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Accepted: 06/19/2017] [Indexed: 12/04/2022] Open
Abstract
Ralstonia solanacearum is one of the most devastating phytopathogens and causes bacterial wilt, which leads to severe economic loss due to its worldwide distribution and broad host range. Certain plant-derived compounds (PDCs) can impair bacterial virulence by suppressing pathogenic factors of R. solanacearum. However, the inhibitory mechanisms of PDCs in bacterial virulence remain largely unknown. In this study, we screened a library of coumarins and derivatives, natural PDCs with fused benzene and α-pyrone rings, for their effects on expression of the type III secretion system (T3SS) of R. solanacearum. Here, we show that umbelliferone (UM), a 7-hydroxycoumarin, suppressed T3SS regulator gene expression through HrpG–HrpB and PrhG–HrpB pathways. UM decreased gene expression of six type III effectors (RipX, RipD, RipP1, RipR, RipTAL, and RipW) of 10 representative effector genes but did not alter T2SS expression. In addition, biofilm formation of R. solanacearum was significantly reduced by UM, though swimming activity was not affected. We then observed that UM suppressed the wilting disease process by reducing colonization and proliferation in tobacco roots and stems. In summary, the findings reveal that UM may serve as a plant-derived inhibitor to manipulate R. solanacearum T3SS and biofilm formation, providing proof of concept that these key virulence factors are potential targets for the integrated control of bacterial wilt.
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Affiliation(s)
- Liang Yang
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest UniversityChongqing, China
| | - Shili Li
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest UniversityChongqing, China
| | - Xiyun Qin
- Yunnan Academy of Tobacco Agricultural ResearchYuxi, China
| | - Gaofei Jiang
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest UniversityChongqing, China.,Laboratoire des Interactions Plantes-Microorganismes, UMR441, Institut National de la Recherche AgronomiqueCastanet-Tolosan, France
| | - Juanni Chen
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest UniversityChongqing, China
| | - Bide Li
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest UniversityChongqing, China
| | - Xiaoyuan Yao
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest UniversityChongqing, China
| | - Peibo Liang
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest UniversityChongqing, China
| | - Yong Zhang
- College of Resources and Environment, Southwest UniversityChongqing, China
| | - Wei Ding
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest UniversityChongqing, China
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56
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The salicylidene acylhydrazide INP0341 attenuates Pseudomonas aeruginosa virulence in vitro and in vivo. J Antibiot (Tokyo) 2017; 70:937-943. [PMID: 28588224 DOI: 10.1038/ja.2017.64] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2017] [Revised: 04/19/2017] [Accepted: 04/23/2017] [Indexed: 11/08/2022]
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that can be very hard to treat because of high resistance to different antibiotics and alternative treatment regimens are greatly needed. An alternative or a complement to traditional antibiotic is to inhibit virulence of the bacteria. The salicylidene acylhydrazide, INP0341, belongs to a class of compounds that has previously been shown to inhibit virulence in a number of Gram-negative bacteria. In this study, the virulence blocking effect of INP0341 on P. aeruginosa was studied in vitro and in vivo. Two important and closely related virulence system were examined, the type III secretion system (T3SS) that translocates virulence effectors into the cytosol of the host cell to evade immune defense and facilitate colonization and the flagella system, needed for motility and biofilm formation. INP0341 was shown to inhibit expression and secretion of the T3SS toxin exoenzyme S (ExoS) and to prevent bacterial motility on agar plates and biofilm formation. In addition, INP0341 showed an increased survival of P. aeruginosa-infected mice. In conclusion, INP0341 attenuates P. aeruginosa virulence.
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57
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Buschor S, Cuenca M, Uster SS, Schären OP, Balmer ML, Terrazos MA, Schürch CM, Hapfelmeier S. Innate immunity restricts Citrobacter rodentium A/E pathogenesis initiation to an early window of opportunity. PLoS Pathog 2017; 13:e1006476. [PMID: 28662171 PMCID: PMC5507559 DOI: 10.1371/journal.ppat.1006476] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 07/12/2017] [Accepted: 06/16/2017] [Indexed: 11/30/2022] Open
Abstract
Citrobacter rodentium infection is a mouse model for the important human diarrheal infection caused by enteropathogenic E. coli (EPEC). The pathogenesis of both species is very similar and depends on their unique ability to form intimately epithelium-adherent microcolonies, also known as "attachment/effacement" (A/E) lesions. These microcolonies must be dynamic and able to self-renew by continuous re-infection of the rapidly regenerating epithelium. It is unknown whether sustained epithelial A/E lesion pathogenesis is achieved through re-infection by planktonic bacteria from the luminal compartment or local spread of sessile bacteria without a planktonic phase. Focusing on the earliest events as C. rodentium becomes established, we show here that all colonic epithelial A/E microcolonies are clonal bacterial populations, and thus depend on local clonal growth to persist. In wild-type mice, microcolonies are established exclusively within the first 18 hours of infection. These early events shape the ongoing intestinal geography and severity of infection despite the continuous presence of phenotypically virulent luminal bacteria. Mechanistically, induced resistance to A/E lesion de-novo formation is mediated by TLR-MyD88/Trif-dependent signaling and is induced specifically by virulent C. rodentium in a virulence gene-dependent manner. Our data demonstrate that the establishment phase of C. rodentium pathogenesis in vivo is restricted to a very short window of opportunity that determines both disease geography and severity.
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Affiliation(s)
- Stefanie Buschor
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
- Graduate School GCB, University of Bern, Bern, Switzerland
| | - Miguelangel Cuenca
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
- Graduate School GCB, University of Bern, Bern, Switzerland
| | - Stephanie S. Uster
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Olivier P. Schären
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
- Graduate School GCB, University of Bern, Bern, Switzerland
| | - Maria L. Balmer
- Department of Biomedicine, Immunobiology, University of Basel, Basel, Switzerland
| | - Miguel A. Terrazos
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
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58
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Thanabalasuriar A, Surewaard BG, Willson ME, Neupane AS, Stover CK, Warrener P, Wilson G, Keller AE, Sellman BR, DiGiandomenico A, Kubes P. Bispecific antibody targets multiple Pseudomonas aeruginosa evasion mechanisms in the lung vasculature. J Clin Invest 2017; 127:2249-2261. [PMID: 28463232 DOI: 10.1172/jci89652] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 03/02/2017] [Indexed: 12/19/2022] Open
Abstract
Pseudomonas aeruginosa is a major cause of severe infections that lead to bacteremia and high patient mortality. P. aeruginosa has evolved numerous evasion and subversion mechanisms that work in concert to overcome immune recognition and effector functions in hospitalized and immunosuppressed individuals. Here, we have used multilaser spinning-disk intravital microscopy to monitor the blood-borne stage in a murine bacteremic model of P. aeruginosa infection. P. aeruginosa adhered avidly to lung vasculature, where patrolling neutrophils and other immune cells were virtually blind to the pathogen's presence. This cloaking phenomenon was attributed to expression of Psl exopolysaccharide. Although an anti-Psl mAb activated complement and enhanced neutrophil recognition of P. aeruginosa, neutrophil-mediated clearance of the pathogen was suboptimal owing to a second subversion mechanism, namely the type 3 secretion (T3S) injectisome. Indeed, T3S prevented phagosome acidification and resisted killing inside these compartments. Antibody-mediated inhibition of the T3S protein PcrV did not enhance bacterial phagocytosis but did enhance killing of the few bacteria ingested by neutrophils. A bispecific mAb targeting both Psl and PcrV enhanced neutrophil uptake of P. aeruginosa and also greatly increased inhibition of T3S function, allowing for phagosome acidification and bacterial killing. These data highlight the need to block multiple evasion and subversion mechanisms in tandem to kill P. aeruginosa.
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Affiliation(s)
- Ajitha Thanabalasuriar
- Department of Physiology and Pharmacology, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Alberta, Canada
| | - Bas Gj Surewaard
- Department of Physiology and Pharmacology, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Alberta, Canada
| | - Michelle E Willson
- Department of Physiology and Pharmacology, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Alberta, Canada
| | - Arpan S Neupane
- Department of Physiology and Pharmacology, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Alberta, Canada
| | | | | | | | | | | | | | - Paul Kubes
- Department of Physiology and Pharmacology, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Alberta, Canada
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59
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Bacterial thiol oxidoreductases - from basic research to new antibacterial strategies. Appl Microbiol Biotechnol 2017; 101:3977-3989. [PMID: 28409380 PMCID: PMC5403849 DOI: 10.1007/s00253-017-8291-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 04/03/2017] [Accepted: 04/04/2017] [Indexed: 12/15/2022]
Abstract
The recent, rapid increase in bacterial antimicrobial resistance has become a major public health concern. One approach to generate new classes of antibacterials is targeting virulence rather than the viability of bacteria. Proteins of the Dsb system, which play a key role in the virulence of many pathogenic microorganisms, represent potential new drug targets. The first part of the article presents current knowledge of how the Dsb system impacts function of various protein secretion systems that influence the virulence of many pathogenic bacteria. Next, the review describes methods used to study the structure, biochemistry, and microbiology of the Dsb proteins and shows how these experiments broaden our knowledge about their function. The lessons gained from basic research have led to a specific search for inhibitors blocking the Dsb networks.
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60
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Small Molecules That Sabotage Bacterial Virulence. Trends Pharmacol Sci 2017; 38:339-362. [PMID: 28209403 DOI: 10.1016/j.tips.2017.01.004] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 01/01/2017] [Accepted: 01/06/2017] [Indexed: 02/08/2023]
Abstract
The continued rise of antibiotic-resistant bacterial infections has motivated alternative strategies for target discovery and treatment of infections. Antivirulence therapies function through inhibition of in vivo required virulence factors to disarm the pathogen instead of directly targeting viability or growth. This approach to treating bacteria-mediated diseases may have advantages over traditional antibiotics because it targets factors specific for pathogenesis, potentially reducing selection for resistance and limiting collateral damage to the resident microbiota. This review examines vulnerable molecular mechanisms used by bacteria to cause disease and the antivirulence compounds that sabotage these virulence pathways. By expanding the study of antimicrobial targets beyond those that are essential for growth, antivirulence strategies offer new and innovative opportunities to combat infectious diseases.
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61
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Cornejo-Granados F, Zatarain-Barrón ZL, Cantu-Robles VA, Mendoza-Vargas A, Molina-Romero C, Sánchez F, Del Pozo-Yauner L, Hernández-Pando R, Ochoa-Leyva A. Secretome Prediction of Two M. tuberculosis Clinical Isolates Reveals Their High Antigenic Density and Potential Drug Targets. Front Microbiol 2017; 8:128. [PMID: 28223967 PMCID: PMC5293778 DOI: 10.3389/fmicb.2017.00128] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 01/18/2017] [Indexed: 12/15/2022] Open
Abstract
The Excreted/Secreted (ES) proteins play important roles during Mycobacterium tuberculosis invasion, virulence, and survival inside the host and they are a major source of immunogenic proteins. However, the molecular complexity of the bacillus cell wall has made difficult the experimental isolation of the total bacterial ES proteins. Here, we reported the genomes of two Beijing genotype M. tuberculosis clinical isolates obtained from patients from Vietnam (isolate 46) and South Africa (isolate 48). We developed a bioinformatics pipeline to predict their secretomes and observed that ~12% of the genome-encoded proteins are ES, being PE, PE-PGRS, and PPE the most abundant protein domains. Additionally, the Gene Ontology, KEGG pathways and Enzyme Classes annotations supported the expected functions for the secretomes. The ~70% of an experimental secretome compiled from literature was contained in our predicted secretomes, while only the 34–41% of the experimental secretome was contained in the two previously reported secretomes for H37Rv. These results suggest that our bioinformatics pipeline is better to predict a more complete set of ES proteins in M. tuberculosis genomes. The predicted ES proteins showed a significant higher antigenic density measured by Abundance of Antigenic Regions (AAR) value than the non-ES proteins and also compared to random constructed secretomes. Additionally, we predicted the secretomes for H37Rv, H37Ra, and two M. bovis BCG genomes. The antigenic density for BGG and for isolates 46 and 48 was higher than the observed for H37Rv and H37Ra secretomes. In addition, two sets of immunogenic proteins previously reported in patients with tuberculosis also showed a high antigenic density. Interestingly, mice infected with isolate 46 showed a significant lower survival rate than the ones infected with isolate 48 and both survival rates were lower than the one previously reported for the H37Rv in the same murine model. Finally, after a druggability analysis of the secretomes, we found potential drug targets such as cytochrome P450, thiol peroxidase, the Ag85C, and Ribonucleoside Reductase in the secreted proteins that could be used as drug targets for novel treatments against Tuberculosis.
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Affiliation(s)
- Fernanda Cornejo-Granados
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México Cuernavaca, Mexico
| | - Zyanya L Zatarain-Barrón
- Experimental Pathology Laboratory, Department of Pathology, National Institute of Medical Science and Nutrition "Salvador Zubirán" Mexico City, Mexico
| | - Vito A Cantu-Robles
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México Cuernavaca, Mexico
| | | | | | - Filiberto Sánchez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México Cuernavaca, Mexico
| | - Luis Del Pozo-Yauner
- Laboratorio de Estructura de Proteínas, National Institute of Genomic Medicine Mexico City, Mexico
| | - Rogelio Hernández-Pando
- Experimental Pathology Laboratory, Department of Pathology, National Institute of Medical Science and Nutrition "Salvador Zubirán" Mexico City, Mexico
| | - Adrián Ochoa-Leyva
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México Cuernavaca, Mexico
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62
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New antibiotics from Nature’s chemical inventory. Bioorg Med Chem 2016; 24:6227-6252. [DOI: 10.1016/j.bmc.2016.09.014] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 09/07/2016] [Indexed: 01/07/2023]
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63
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Gaytán MO, Martínez-Santos VI, Soto E, González-Pedrajo B. Type Three Secretion System in Attaching and Effacing Pathogens. Front Cell Infect Microbiol 2016; 6:129. [PMID: 27818950 PMCID: PMC5073101 DOI: 10.3389/fcimb.2016.00129] [Citation(s) in RCA: 115] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 09/27/2016] [Indexed: 02/06/2023] Open
Abstract
Enteropathogenic Escherichia coli and enterohemorrhagic E. coli are diarrheagenic bacterial human pathogens that cause severe gastroenteritis. These enteric pathotypes, together with the mouse pathogen Citrobacter rodentium, belong to the family of attaching and effacing pathogens that form a distinctive histological lesion in the intestinal epithelium. The virulence of these bacteria depends on a type III secretion system (T3SS), which mediates the translocation of effector proteins from the bacterial cytosol into the infected cells. The core architecture of the T3SS consists of a multi-ring basal body embedded in the bacterial membranes, a periplasmic inner rod, a transmembrane export apparatus in the inner membrane, and cytosolic components including an ATPase complex and the C-ring. In addition, two distinct hollow appendages are assembled on the extracellular face of the basal body creating a channel for protein secretion: an approximately 23 nm needle, and a filament that extends up to 600 nm. This filamentous structure allows these pathogens to get through the host cells mucus barrier. Upon contact with the target cell, a translocation pore is assembled in the host membrane through which the effector proteins are injected. Assembly of the T3SS is strictly regulated to ensure proper timing of substrate secretion. The different type III substrates coexist in the bacterial cytoplasm, and their hierarchical secretion is determined by specialized chaperones in coordination with two molecular switches and the so-called sorting platform. In this review, we present recent advances in the understanding of the T3SS in attaching and effacing pathogens.
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Affiliation(s)
- Meztlli O Gaytán
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México Ciudad de México, Mexico
| | - Verónica I Martínez-Santos
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México Ciudad de México, Mexico
| | - Eduardo Soto
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México Ciudad de México, Mexico
| | - Bertha González-Pedrajo
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México Ciudad de México, Mexico
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64
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Guo Z, Li X, Li J, Yang X, Zhou Y, Lu C, Shen Y. Licoflavonol is an inhibitor of the type three secretion system of Salmonella enterica serovar Typhimurium. Biochem Biophys Res Commun 2016; 477:998-1004. [DOI: 10.1016/j.bbrc.2016.07.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 07/03/2016] [Indexed: 10/21/2022]
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65
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Guo Q, Wei Y, Xia B, Jin Y, Liu C, Pan X, Shi J, Zhu F, Li J, Qian L, Liu X, Cheng Z, Jin S, Lin J, Wu W. Identification of a small molecule that simultaneously suppresses virulence and antibiotic resistance of Pseudomonas aeruginosa. Sci Rep 2016; 6:19141. [PMID: 26751736 PMCID: PMC4707474 DOI: 10.1038/srep19141] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Accepted: 12/07/2015] [Indexed: 12/20/2022] Open
Abstract
The rising antibiotic resistance of bacteria imposes a severe threat on human health. Inhibition of bacterial virulence is an alternative approach to develop new antimicrobials. Molecules targeting antibiotic resistant enzymes have been used in combination with cognate antibiotics. It might be ideal that a molecule can simultaneously suppress virulence factors and antibiotic resistance. Here we combined genetic and computer-aided inhibitor screening to search for such molecules against the bacterial pathogen Pseudomonas aeruginosa. To identify target proteins that control both virulence and antibiotic resistance, we screened for mutants with defective cytotoxicity and biofilm formation from 93 transposon insertion mutants previously reported with increased antibiotic susceptibility. A pyrD mutant displayed defects in cytotoxicity, biofilm formation, quorum sensing and virulence in an acute mouse pneumonia model. Next, we employed a computer-aided screening to identify potential inhibitors of the PyrD protein, a dihydroorotate dehydrogenase (DHODase) involved in pyrimidine biosynthesis. One of the predicted inhibitors was able to suppress the enzymatic activity of PyrD as well as bacterial cytotoxicity, biofilm formation and antibiotic resistance. A single administration of the compound reduced the bacterial colonization in the acute mouse pneumonia model. Therefore, we have developed a strategy to identify novel treatment targets and antimicrobial molecules.
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Affiliation(s)
- Qiaoyun Guo
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Yu Wei
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin 300071, China
| | - Bin Xia
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Yongxin Jin
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Chang Liu
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Xiaolei Pan
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Jing Shi
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Feng Zhu
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Jinlong Li
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin 300071, China
| | - Lei Qian
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Xinqi Liu
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Zhihui Cheng
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Shouguang Jin
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Jianping Lin
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
- State Key Laboratory of Medicinal Chemical Biology and College of Pharmacy, Nankai University, Tianjin 300071, China
| | - Weihui Wu
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
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66
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Wu D, Ding W, Zhang Y, Liu X, Yang L. Oleanolic Acid Induces the Type III Secretion System of Ralstonia solanacearum. Front Microbiol 2015; 6:1466. [PMID: 26732647 PMCID: PMC4686671 DOI: 10.3389/fmicb.2015.01466] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2015] [Accepted: 12/07/2015] [Indexed: 12/18/2022] Open
Abstract
Ralstonia solanacearum, the causal agent of bacterial wilt, can naturally infect a wide range of host plants. The type III secretion system (T3SS) is a major virulence determinant in this bacterium. Studies have shown that plant-derived compounds are able to inhibit or induce the T3SS in some plant pathogenic bacteria, though no specific T3SS inhibitor or inducer has yet been identified in R. solanacearum. In this study, a total of 50 different compounds were screened and almost half of them (22 of 50) significantly inhibited or induced the T3SS expression of R. solanacearum. Based on the strong induction activity on T3SS, the T3SS inducer oleanolic acid (OA) was chosen for further study. We found that OA induced the expression of T3SS through the HrpG-HrpB pathway. Some type III effector genes were induced in T3SS inducing medium supplemented with OA. In addition, OA targeted only the T3SS and did not affect other virulence determinants. Finally, we observed that induction of T3SS by OA accelerated disease progress on tobacco. Overall our results suggest that plant-derived compounds are an abundant source of R. solanacearum T3SS regulators, which could prove useful as tools to interrogate the regulation of this key virulence pathway.
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Affiliation(s)
- Dousheng Wu
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest University Chongqing, China
| | - Wei Ding
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest University Chongqing, China
| | - Yong Zhang
- Research Center of Bioenergy and Bioremediation, College of Resources and Environment, Southwest University Chongqing, China
| | - Xuejiao Liu
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest University Chongqing, China
| | - Liang Yang
- Laboratory of Natural Products Pesticides, College of Plant Protection, Southwest University Chongqing, China
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References. Antibiotics (Basel) 2015. [DOI: 10.1128/9781555819316.refs] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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68
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Heras B, Scanlon MJ, Martin JL. Targeting virulence not viability in the search for future antibacterials. Br J Clin Pharmacol 2015; 79:208-15. [PMID: 24552512 DOI: 10.1111/bcp.12356] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Accepted: 12/09/2013] [Indexed: 01/01/2023] Open
Abstract
New antibacterials need new approaches to overcome the problem of rapid antibiotic resistance. Here we review the development of potential new antibacterial drugs that do not kill bacteria or inhibit their growth, but combat disease instead by targeting bacterial virulence.
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Affiliation(s)
- Begoña Heras
- La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Vic
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69
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McShan AC, De Guzman RN. The bacterial type III secretion system as a target for developing new antibiotics. Chem Biol Drug Des 2015; 85:30-42. [PMID: 25521643 DOI: 10.1111/cbdd.12422] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 08/25/2014] [Accepted: 08/26/2014] [Indexed: 01/14/2023]
Abstract
Antibiotic resistance in pathogens requires new targets for developing novel antibacterials. The bacterial type III secretion system (T3SS) is an attractive target for developing antibacterials as it is essential in the pathogenesis of many Gram-negative bacteria. The T3SS consists of structural proteins, effectors, and chaperones. Over 20 different structural proteins assemble into a complex nanoinjector that punctures a hole on the eukaryotic cell membrane to allow the delivery of effectors directly into the host cell cytoplasm. Defects in the assembly and function of the T3SS render bacteria non-infective. Two major classes of small molecules, salicylidene acylhydrazides and thiazolidinones, have been shown to inhibit multiple genera of bacteria through the T3SS. Many additional chemically and structurally diverse classes of small molecule inhibitors of the T3SS have been identified as well. While specific targets within the T3SS of a few inhibitors have been suggested, the vast majority of specific protein targets within the T3SS remain to be identified or characterized. Other T3SS inhibitors include polymers, proteins, and polypeptides mimics. In addition, T3SS activity is regulated by its interaction with biologically relevant molecules, such as bile salts and sterols, which could serve as scaffolds for drug design.
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Affiliation(s)
- Andrew C McShan
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS, 66045, USA
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70
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Computational Analysis and Binding Site Identification of Type III Secretion System ATPase from Pseudomonas aeruginosa. Interdiscip Sci 2015; 8:403-411. [DOI: 10.1007/s12539-015-0121-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2015] [Revised: 06/10/2015] [Accepted: 07/16/2015] [Indexed: 01/18/2023]
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71
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Costa TRD, Felisberto-Rodrigues C, Meir A, Prevost MS, Redzej A, Trokter M, Waksman G. Secretion systems in Gram-negative bacteria: structural and mechanistic insights. Nat Rev Microbiol 2015; 13:343-59. [DOI: 10.1038/nrmicro3456] [Citation(s) in RCA: 655] [Impact Index Per Article: 72.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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72
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Gong L, Lai SC, Treerat P, Prescott M, Adler B, Boyce JD, Devenish RJ. Burkholderia pseudomallei type III secretion system cluster 3 ATPase BsaS, a chemotherapeutic target for small-molecule ATPase inhibitors. Infect Immun 2015; 83:1276-85. [PMID: 25605762 PMCID: PMC4363454 DOI: 10.1128/iai.03070-14] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 01/05/2015] [Indexed: 12/18/2022] Open
Abstract
Melioidosis is an infectious disease of high mortality for humans and other animal species; it is prevalent in tropical regions worldwide. The pathogenesis of melioidosis depends on the ability of its causative agent, the Gram-negative bacterium Burkholderia pseudomallei, to enter and survive in host cells. B. pseudomallei can escape from the phagosome into the cytosol of phagocytic cells where it replicates and acquires actin-mediated motility, avoiding killing by the autophagy-dependent process, LC3 (microtubule-associated protein light chain 3)-associated phagocytosis (LAP). The type III secretion system cluster 3 (TTSS3) facilitates bacterial escape from phagosomes, although the mechanism has not been fully elucidated. Given the recent identification of small-molecule inhibitors of the TTSS ATPase, we sought to determine the potential of the predicted TTSS3 ATPase, encoded by bsaS, as a target for chemotherapeutic treatment of infection. A B. pseudomallei bsaS deletion mutant was generated and used as a control against which to assess the effect of inhibitor treatment. Infection of RAW 264.7 cells with wild-type bacteria and subsequent treatment with the ATPase inhibitor compound 939 resulted in reduced intracellular bacterial survival, reduced escape from phagosomes, and increased colocalization with both LC3 and the lysosomal marker LAMP1 (lysosome-associated membrane protein 1). These changes were similar to those observed for infection of RAW 264.7 cells with the bsaS deletion mutant. We propose that treatment with the ATPase inhibitor compound 939 decreased intracellular bacterial survival through a reduced ability of bacteria to escape from phagosomes and increased killing via LAP. Therefore, small-molecule inhibitors of the TTSS3 ATPase have potential as therapeutic treatments against melioidosis.
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Affiliation(s)
- Lan Gong
- Department of Biochemistry and Molecular Biology, Monash University, Victoria, Clayton, Australia Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Victoria, Clayton, Australia
| | - Shu-Chin Lai
- Department of Biochemistry and Molecular Biology, Monash University, Victoria, Clayton, Australia
| | - Puthayalai Treerat
- Department of Microbiology, Monash University, Victoria, Clayton, Australia Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Victoria, Clayton, Australia
| | - Mark Prescott
- Department of Biochemistry and Molecular Biology, Monash University, Victoria, Clayton, Australia
| | - Ben Adler
- Department of Microbiology, Monash University, Victoria, Clayton, Australia Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Victoria, Clayton, Australia
| | - John D Boyce
- Department of Microbiology, Monash University, Victoria, Clayton, Australia Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Victoria, Clayton, Australia
| | - Rodney J Devenish
- Department of Biochemistry and Molecular Biology, Monash University, Victoria, Clayton, Australia Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Victoria, Clayton, Australia
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Williams JD, Torhan MC, Neelagiri VR, Brown C, Bowlin NO, Di M, McCarthy CT, Aiello D, Peet NP, Bowlin TL, Moir DT. Synthesis and structure-activity relationships of novel phenoxyacetamide inhibitors of the Pseudomonas aeruginosa type III secretion system (T3SS). Bioorg Med Chem 2015; 23:1027-43. [PMID: 25638499 PMCID: PMC4339527 DOI: 10.1016/j.bmc.2015.01.011] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 12/29/2014] [Accepted: 01/06/2015] [Indexed: 01/01/2023]
Abstract
The increasing prevalence of drug-resistant bacterial infections is driving the discovery and development not only of new antibiotics, but also of inhibitors of virulence factors that are crucial for in vivo pathogenicity. One such virulence factor is the type III secretion system (T3SS), which plays a critical role in the establishment and dissemination of Pseudomonas aeruginosa infections. We have recently described the discovery and characterization of a series of inhibitors of P. aeruginosa T3SS based on a phenoxyacetamide scaffold. To better characterize the factors involved in potent T3SS inhibition, we have conducted a systematic exploration of this structure, revealing several highly responsive structure-activity relationships indicative of interaction with a specific target. Most of the structural features contributing to potency were additive, and combination of those features produced optimized inhibitors with IC50 values <1μM.
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Affiliation(s)
| | | | | | - Carson Brown
- Microbiotix, Inc., Worcester, MA 01605, United States
| | | | - Ming Di
- Microbiotix, Inc., Worcester, MA 01605, United States
| | | | - Daniel Aiello
- Microbiotix, Inc., Worcester, MA 01605, United States
| | - Norton P Peet
- Microbiotix, Inc., Worcester, MA 01605, United States
| | | | - Donald T Moir
- Microbiotix, Inc., Worcester, MA 01605, United States
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74
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Charro N, Mota LJ. Approaches targeting the type III secretion system to treat or prevent bacterial infections. Expert Opin Drug Discov 2015; 10:373-87. [DOI: 10.1517/17460441.2015.1019860] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Nuno Charro
- 1UCIBIO, REQUIMTE, Departmento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica 2829-516, Portugal
| | - Luís Jaime Mota
- 2UCIBIO, REQUIMTE, Departmento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica 2829-516, Portugal ;
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75
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Li Y, Hutchins W, Wu X, Liang C, Zhang C, Yuan X, Khokhani D, Chen X, Che Y, Wang Q, Yang CH. Derivative of plant phenolic compound inhibits the type III secretion system of Dickeya dadantii via HrpX/HrpY two-component signal transduction and Rsm systems. MOLECULAR PLANT PATHOLOGY 2015; 16:150-63. [PMID: 24986378 PMCID: PMC6638520 DOI: 10.1111/mpp.12168] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The type III secretion system (T3SS) is a major virulence factor in many Gram-negative bacterial pathogens and represents a particularly appealing target for antimicrobial agents. Previous studies have shown that the plant phenolic compound p-coumaric acid (PCA) plays a role in the inhibition of T3SS expression of the phytopathogen Dickeya dadantii 3937. This study screened a series of derivatives of plant phenolic compounds and identified that trans-4-hydroxycinnamohydroxamic acid (TS103) has an eight-fold higher inhibitory potency than PCA on the T3SS of D. dadantii. The effect of TS103 on regulatory components of the T3SS was further elucidated. Our results suggest that TS103 inhibits HrpY phosphorylation and leads to reduced levels of hrpS and hrpL transcripts. In addition, through a reduction in the RNA levels of the regulatory small RNA RsmB, TS103 also inhibits hrpL at the post-transcriptional level via the rsmB-RsmA regulatory pathway. Finally, TS103 inhibits hrpL transcription and mRNA stability, which leads to reduced expression of HrpL regulon genes, such as hrpA and hrpN. To our knowledge, this is the first inhibitor to affect the T3SS through both the transcriptional and post-transcriptional pathways in the soft-rot phytopathogen D. dadantii 3937.
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Affiliation(s)
- Yan Li
- The MOA Key Laboratory of Plant Pathology, Department of Plant Pathology, College of Agronomy & Biotechnology, China Agricultural University, Beijing, 100193, China
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The structure of the Slrp-Trx1 complex sheds light on the autoinhibition mechanism of the type III secretion system effectors of the NEL family. Biochem J 2015; 464:135-44. [PMID: 25184225 DOI: 10.1042/bj20140587] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Salmonella infections are a leading cause of bacterial foodborne illness in the U.S.A. and the European Union Antimicrobial therapy is often administered to treat the infection, but increasingly isolates are being detected that demonstrate resistance to multiple antibiotics. Salmonella enterica contains two virulence-related T3SS (type III secretion systems): one promotes invasion of the intestine and the other one mediates systemic disease. Both of them secrete the SlrP protein acting as E3 ubiquitin ligase in human host cells where it targets Trx1 (thioredoxin-1). SlrP belongs to the NEL family of bacterial E3 ubiquitin ligases that have been observed in two distinct autoinhibitory conformations. We solved the 3D structure of the SlrP-Trx1 complex and determined the Trx1 ubiquitination site. The description of the substrate-binding mode sheds light on the first step of the activation mechanism of SlrP. Comparison with the available structural data of other NEL effectors allowed us to gain new insights into their autoinhibitory mechanism. We propose a molecular mechanism for the regulation of SlrP in which structural constraints sequestrating the NEL domain would be sequentially released. This work thus constitutes a new milestone in the understanding of how these T3SS effectors influence pathogen virulence. It also provides the fundamental basis for future development of new antimicrobials.
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77
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Di Pietro M, Filardo S, De Santis F, Mastromarino P, Sessa R. Chlamydia pneumoniae and oxidative stress in cardiovascular disease: state of the art and prevention strategies. Int J Mol Sci 2014; 16:724-35. [PMID: 25561227 PMCID: PMC4307271 DOI: 10.3390/ijms16010724] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 12/26/2014] [Indexed: 12/15/2022] Open
Abstract
Chlamydia pneumoniae, a pathogenic bacteria responsible for respiratory tract infections, is known as the most implicated infectious agent in atherosclerotic cardiovascular diseases (CVDs). Accumulating evidence suggests that C. pneumoniae-induced oxidative stress may play a critical role in the pathogenesis of CVDs. Indeed, the overproduction of reactive oxygen species (ROS) within macrophages, endothelial cells, platelets and vascular smooth muscle cells (VSMCs) after C. pneumoniae exposure, has been shown to cause low density lipoprotein oxidation, foam cell formation, endothelial dysfunction, platelet adhesion and aggregation, and VSMC proliferation and migration, all responsible for the typical pathological changes of atherosclerotic plaque. The aim of this review is to improve our insight into C. pneumoniae-induced oxidative stress in order to suggest potential strategies for CVD prevention. Several antioxidants, acting on multi-enzymatic targets related to ROS production induced by C. pneumoniae, have been discussed. A future strategy for the prevention of C. pneumoniae-associated CVDs will be to target chlamydial HSP60, involved in oxidative stress.
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Affiliation(s)
- Marisa Di Pietro
- Department of Public Health and Infectious Diseases, "Sapienza" University, Rome 00185, Italy.
| | - Simone Filardo
- Department of Public Health and Infectious Diseases, "Sapienza" University, Rome 00185, Italy.
| | - Fiorenzo De Santis
- Department of Public Health and Infectious Diseases, "Sapienza" University, Rome 00185, Italy.
| | - Paola Mastromarino
- Department of Public Health and Infectious Diseases, "Sapienza" University, Rome 00185, Italy.
| | - Rosa Sessa
- Department of Public Health and Infectious Diseases, "Sapienza" University, Rome 00185, Italy.
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Davis RA, Beattie KD, Xu M, Yang X, Yin S, Holla H, Healy PC, Sykes M, Shelper T, Avery VM, Elofsson M, Sundin C, Quinn RJ. Solving the supply of resveratrol tetramers from Papua New Guinean rainforest anisoptera species that inhibit bacterial type III secretion systems. JOURNAL OF NATURAL PRODUCTS 2014; 77:2633-2640. [PMID: 25405587 DOI: 10.1021/np500433z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The supply of (-)-hopeaphenol (1) was achieved via enzymatic biotransformation in order to provide material for preclinical investigation. High-throughput screening of a prefractionated natural product library aimed to identify compounds that inhibit the bacterial virulence type III secretion system (T3SS) identified several fractions derived from two Papua New Guinean Anisoptera species, showing activity against Yersinia pseudotuberculosis outer proteins E and H (YopE and YopH). Bioassay-directed isolation from the leaves of A. thurifera, and similarly A. polyandra, resulted in three known resveratrol tetramers, (-)-hopeaphenol (1), vatalbinoside A (2), and vaticanol B (3). Compounds 1-3 displayed IC50 values of 8.8, 12.5, and 9.9 μM in a luminescent reporter-gene assay (YopE) and IC50 values of 2.9, 4.5, and 3.3 μM in an enzyme-based YopH assay, respectively, which suggested that they could potentially act against the T3SS in Yersinia. The structures of 1-3 were confirmed through a combination of spectrometric, chemical methods, and single-crystal X-ray structure determinations of the natural product 1 and the permethyl ether analogue of 3. The enzymatic hydrolysis of the β-glycoside 2 to the aglycone 1 was achieved through biotransformation using the endogenous leaf enzymes. This significantly enhanced the yield of the target bioactive natural product from 0.08% to 1.3% and facilitates ADMET studies of (-)-hopeaphenol (1).
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Affiliation(s)
- Rohan A Davis
- Eskitis Institute for Drug Discovery, Griffith University , Brisbane, QLD 4111, Australia
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79
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Parvege MM, Rahman M, Hossain MS. Genome-wide Analysis of Mycoplasma hominis for the Identification of Putative Therapeutic Targets. Drug Target Insights 2014; 8:51-62. [PMID: 25574133 PMCID: PMC4263438 DOI: 10.4137/dti.s19728] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Revised: 11/06/2014] [Accepted: 11/10/2014] [Indexed: 01/14/2023] Open
Abstract
Ever increasing propensity of antibiotic resistance among pathogenic bacteria raises the demand for the development of novel therapeutic agents to control this grave problem. Advances in the field of bioinformatics, genomics, and proteomics have greatly facilitated the discovery of alternative drugs by swift identification of new drug targets. In the present study, we employed comparative genomics and metabolic pathway analysis with an aim of identifying therapeutic targets in Mycoplasma hominis. Our study has revealed 40 annotated metabolic pathways, including five unique pathways of M. hominis. Our study also identified 179 essential proteins, including 59 proteins having no similarity with human proteins. Further filtering by molecular weight, subcellular localization, functional analysis, and protein network interaction, we identified 57 putative candidates for which new drugs can be developed. Druggability analysis for each of the identified targets has prioritized 16 proteins as suitable for potential drug development.
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Affiliation(s)
- Md Masud Parvege
- Department of Genetic Engineering & Biotechnology, University of Dhaka, Dhaka, Bangladesh
| | - Monzilur Rahman
- Department of Genetic Engineering & Biotechnology, University of Dhaka, Dhaka, Bangladesh
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80
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Steadman D, Lo A, Waksman G, Remaut H. Bacterial surface appendages as targets for novel antibacterial therapeutics. Future Microbiol 2014; 9:887-900. [DOI: 10.2217/fmb.14.46] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The rise of multidrug resistant bacteria is a major worldwide health concern. There is currently an unmet need for the development of new and selective antibacterial drugs. Therapies that target and disarm the crucial virulence factors of pathogenic bacteria, while not actually killing the cells themselves, could prove to be vital for the treatment of numerous diseases. This article discusses the main surface architectures of pathogenic Gram-negative bacteria and the small molecules that have been discovered, which target their specific biogenesis pathways and/or actively block their virulence. The future perspective for the use of antivirulence compounds is also assessed.
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Affiliation(s)
- David Steadman
- Institute of Structural & Molecular Biology, Birkbeck & University College London, Malet Street, London, WC1E 7HX, UK
| | - Alvin Lo
- Structural & Molecular Microbiology, Structural Biology Research Center, VIB, Pleinlaan 2, 1050 Brussels, Belgium
| | - Gabriel Waksman
- Institute of Structural & Molecular Biology, Birkbeck & University College London, Malet Street, London, WC1E 7HX, UK
| | - Han Remaut
- Structural & Molecular Microbiology, Structural Biology Research Center, VIB, Pleinlaan 2, 1050 Brussels, Belgium
- Structural Biology Brussels, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
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81
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Rao C V S, De Waelheyns E, Economou A, Anné J. Antibiotic targeting of the bacterial secretory pathway. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1762-83. [PMID: 24534745 DOI: 10.1016/j.bbamcr.2014.02.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 01/27/2014] [Accepted: 02/06/2014] [Indexed: 02/06/2023]
Abstract
Finding new, effective antibiotics is a challenging research area driven by novel approaches required to tackle unconventional targets. In this review we focus on the bacterial protein secretion pathway as a target for eliminating or disarming pathogens. We discuss the latest developments in targeting the Sec-pathway for novel antibiotics focusing on two key components: SecA, the ATP-driven motor protein responsible for driving preproteins across the cytoplasmic membrane and the Type I signal peptidase that is responsible for the removal of the signal peptide allowing the release of the mature protein from the membrane. We take a bird's-eye view of other potential targets in the Sec-pathway as well as other Sec-dependent or Sec-independent protein secretion pathways as targets for the development of novel antibiotics. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
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Affiliation(s)
- Smitha Rao C V
- Laboratory of Molecular Bacteriology, Rega Institute, Department of Microbiology and Immunology, KU Leuven, O&N1, 6th floor, Herestraat 49, P.O. Box 1037, B-3000 Leuven, Belgium.
| | - Evelien De Waelheyns
- Laboratory of Molecular Bacteriology, Rega Institute, Department of Microbiology and Immunology, KU Leuven, O&N1, 6th floor, Herestraat 49, P.O. Box 1037, B-3000 Leuven, Belgium.
| | - Anastassios Economou
- Laboratory of Molecular Bacteriology, Rega Institute, Department of Microbiology and Immunology, KU Leuven, O&N1, 6th floor, Herestraat 49, P.O. Box 1037, B-3000 Leuven, Belgium; Institute of Molecular Biology and Biotechnology, FORTH, University of Crete, P.O. Box 1385, GR-711 10 Iraklio, Crete, Greece; Department of Biology, University of Crete, P.O. Box 1385, GR-71110 Iraklio, Crete, Greece.
| | - Jozef Anné
- Laboratory of Molecular Bacteriology, Rega Institute, Department of Microbiology and Immunology, KU Leuven, O&N1, 6th floor, Herestraat 49, P.O. Box 1037, B-3000 Leuven, Belgium.
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Lo AWH, Van de Water K, Gane PJ, Chan AWE, Steadman D, Stevens K, Selwood DL, Waksman G, Remaut H. Suppression of type 1 pilus assembly in uropathogenic Escherichia coli by chemical inhibition of subunit polymerization. J Antimicrob Chemother 2013; 69:1017-26. [PMID: 24324225 PMCID: PMC3956373 DOI: 10.1093/jac/dkt467] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Objectives To identify and to characterize small-molecule inhibitors that target the subunit polymerization of the type 1 pilus assembly in uropathogenic Escherichia coli (UPEC). Methods Using an SDS–PAGE-based assay, in silico pre-filtered small-molecule compounds were screened for specific inhibitory activity against the critical subunit polymerization step of the chaperone–usher pathway during pilus biogenesis. The biological activity of one of the compounds was validated in assays monitoring UPEC type 1 pilus biogenesis, type 1 pilus-dependent biofilm formation and adherence to human bladder epithelial cells. The time dependence of the in vivo inhibitory activity and the overall effect of the compound on UPEC growth were determined. Results N-(4-chloro-phenyl)-2-{5-[4-(pyrrolidine-1-sulfonyl)-phenyl]-[1,3,4]oxadiazol-2-yl sulfanyl}-acetamide (AL1) inhibited in vitro pilus subunit polymerization. In bacterial cultures, AL1 disrupted UPEC type 1 pilus biogenesis and pilus-dependent biofilm formation, and resulted in the reduction of bacterial adherence to human bladder epithelial cells, without affecting bacterial cell growth. Bacterial exposure to the inhibitor led to an almost instantaneous loss of type 1 pili. Conclusions We have identified and characterized a small molecule that interferes with the assembly of type 1 pili. The molecule targets the polymerization step during the subunit incorporation cycle of the chaperone–usher pathway. Our discovery provides new insight into the design and development of novel anti-virulence therapies targeting key virulence factors of bacterial pathogens.
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Affiliation(s)
- Alvin W H Lo
- Structural and Molecular Microbiology, VIB Department of Structural Biology, VIB, Pleinlaan 2, 1050 Brussels, Belgium
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The resveratrol tetramer (-)-hopeaphenol inhibits type III secretion in the gram-negative pathogens Yersinia pseudotuberculosis and Pseudomonas aeruginosa. PLoS One 2013; 8:e81969. [PMID: 24324737 PMCID: PMC3853165 DOI: 10.1371/journal.pone.0081969] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Accepted: 10/18/2013] [Indexed: 11/19/2022] Open
Abstract
Society faces huge challenges, as a large number of bacteria have developed resistance towards many or all of the antibiotics currently available. Novel strategies that can help solve this problem are urgently needed. One such strategy is to target bacterial virulence, the ability to cause disease e.g., by inhibition of type III secretion systems (T3SSs) utilized by many clinically relevant gram-negative pathogens. Many of the antibiotics used today originate from natural sources. In contrast, most virulence-blocking compounds towards the T3SS identified so far are small organic molecules. A recent high-throughput screening of a prefractionated natural product library identified the resveratrol tetramer (-)-hopeaphenol as an inhibitor of the T3SS in Yersinia pseudotuberculosis. In this study we have investigated the virulence blocking properties of (-)-hopeaphenol in three different gram-negative bacteria. (-)-Hopeaphenol was found to have micromolar activity towards the T3SSs in Yersinia pseudotuberculosis and Pseudomonas aeruginosa in cell-based infection models. In addition (-)-hopeaphenol reduced cell entry and subsequent intracellular growth of Chlamydia trachomatis.
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An NF-κB-based high-throughput screen identifies piericidins as inhibitors of the Yersinia pseudotuberculosis type III secretion system. Antimicrob Agents Chemother 2013; 58:1118-26. [PMID: 24295981 DOI: 10.1128/aac.02025-13] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The type III secretion system (T3SS) is a bacterial appendage used by dozens of Gram-negative pathogens to subvert host defenses and cause disease, making it an ideal target for pathogen-specific antimicrobials. Here, we report the discovery and initial characterization of two related natural products with T3SS-inhibitory activity that were derived from a marine actinobacterium. Bacterial extracts containing piericidin A1 and the piericidin derivative Mer-A 2026B inhibited Yersinia pseudotuberculosis from triggering T3SS-dependent activation of the host transcription factor NF-κB in HEK293T cells but were not toxic to mammalian cells. As the Yersinia T3SS must be functional in order to trigger NF-κB activation, these data indicate that piericidin A1 and Mer-A 2026B block T3SS function. Consistent with this, purified piericidin A1 and Mer-A 2026B dose-dependently inhibited translocation of the Y. pseudotuberculosis T3SS effector protein YopM inside CHO cells. In contrast, neither compound perturbed bacterial growth in vitro, indicating that piericidin A1 and Mer-A 2026B do not function as general antibiotics in Yersinia. In addition, when Yersinia was incubated under T3SS-inducing culture conditions in the absence of host cells, Mer-A 2026B and piericidin A1 inhibited secretion of T3SS cargo as effectively as or better than several previously described T3SS inhibitors, such as MBX-1641 and aurodox. This suggests that Mer-A 2026B and piericidin A1 do not block type III secretion by blocking the bacterium-host cell interaction, but rather inhibit an earlier stage, such as T3SS needle assembly. In summary, the marine-derived natural products Mer-A 2026B and piericidin A1 possess previously uncharacterized activity against the bacterial T3SS.
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Laxminarayan R, Duse A, Wattal C, Zaidi AKM, Wertheim HFL, Sumpradit N, Vlieghe E, Hara GL, Gould IM, Goossens H, Greko C, So AD, Bigdeli M, Tomson G, Woodhouse W, Ombaka E, Peralta AQ, Qamar FN, Mir F, Kariuki S, Bhutta ZA, Coates A, Bergstrom R, Wright GD, Brown ED, Cars O. Antibiotic resistance-the need for global solutions. THE LANCET. INFECTIOUS DISEASES 2013; 13:1057-98. [PMID: 24252483 DOI: 10.1016/s1473-3099(13)70318-9] [Citation(s) in RCA: 2541] [Impact Index Per Article: 231.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The causes of antibiotic resistance are complex and include human behaviour at many levels of society; the consequences affect everybody in the world. Similarities with climate change are evident. Many efforts have been made to describe the many different facets of antibiotic resistance and the interventions needed to meet the challenge. However, coordinated action is largely absent, especially at the political level, both nationally and internationally. Antibiotics paved the way for unprecedented medical and societal developments, and are today indispensible in all health systems. Achievements in modern medicine, such as major surgery, organ transplantation, treatment of preterm babies, and cancer chemotherapy, which we today take for granted, would not be possible without access to effective treatment for bacterial infections. Within just a few years, we might be faced with dire setbacks, medically, socially, and economically, unless real and unprecedented global coordinated actions are immediately taken. Here, we describe the global situation of antibiotic resistance, its major causes and consequences, and identify key areas in which action is urgently needed.
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Affiliation(s)
- Ramanan Laxminarayan
- Center for Disease Dynamics, Economics and Policy, Washington, DC, USA; Princeton University, Princeton NJ, USA; Public Health Foundation of India, New Delhi, India
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Vanden Bergh P, Frey J. Aeromonas salmonicida subsp. salmonicida in the light of its type-three secretion system. Microb Biotechnol 2013; 7:381-400. [PMID: 24119189 PMCID: PMC4229320 DOI: 10.1111/1751-7915.12091] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Revised: 08/27/2013] [Accepted: 08/28/2013] [Indexed: 11/30/2022] Open
Abstract
Aeromonas salmonicida subsp. salmonicida is an important pathogen in salmonid aquaculture and is responsible for the typical furunculosis. The type-three secretion system (T3SS) is a major virulence system. In this work, we review structure and function of this highly sophisticated nanosyringe in A. salmonicida. Based on the literature as well as personal experimental observations, we document the genetic (re)organization, expression regulation, anatomy, putative functional origin and roles in the infectious process of this T3SS. We propose a model of pathogenesis where A. salmonicida induces a temporary immunosuppression state in fish in order to acquire free access to host tissues. Finally, we highlight putative important therapeutic and vaccine strategies to prevent furunculosis of salmonid fish.
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Affiliation(s)
- Philippe Vanden Bergh
- Institute of Veterinary Bacteriology, University of Bern, Länggassstrasse 122, Bern, Switzerland
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Abstract
INTRODUCTION Natural products have long been instrumental for discovering antibiotics, but many pharmaceutical companies abandoned this field and new antibiotics declined. In contrast, microbial resistance to current antibiotics has approached critical levels. AREAS COVERED This article gives historical perspectives by providing background about present-day economic realities and medical needs for antibiotic research, whose pipeline is mostly focused toward older known agents and newer semi-synthetic derivatives. Future research trends and projected technological developments open many innovative opportunities to discover novel antibacterials and find ways to control pathogenic bacteria without conventional antibiotics that provoke resistance. EXPERT OPINION The successful registration of daptomycin, retapamulin and fidaxomicin indicate the re-emergence of natural products has already begun. Semi-synthetic derivatives from other under-explored classes are progressing. More effort is being put into approaches such as total synthesis, discovery of new structural scaffolds for synthesis, alterations of biosynthetic pathways, combinatorial biosynthesis, new screening targets and new resources from which to isolate natural products. A return to successful screening of actinomycetes depends on solving the rate-limiting dereplication obstacle. Long-term solutions need to come from greater exploration of the massive numbers of uncultured microbes. An ultimate solution to the antibiotic-promoted microbial resistance cycle may lie in finding ways to control bacteria by non-lethal means.
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Lo AW, Moonens K, Remaut H. Chemical attenuation of pilus function and assembly in Gram-negative bacteria. Curr Opin Microbiol 2013; 16:85-92. [DOI: 10.1016/j.mib.2013.02.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Revised: 01/30/2013] [Accepted: 02/03/2013] [Indexed: 10/27/2022]
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