1
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Glenn SJ, Gentry-Lear Z, Shavlik M, Harms MJ, Asaki TJ, Baylink A. Bacterial vampirism mediated through taxis to serum. eLife 2024; 12:RP93178. [PMID: 38820052 PMCID: PMC11142651 DOI: 10.7554/elife.93178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2024] Open
Abstract
Bacteria of the family Enterobacteriaceae are associated with gastrointestinal (GI) bleeding and bacteremia and are a leading cause of death, from sepsis, for individuals with inflammatory bowel diseases. The bacterial behaviors and mechanisms underlying why these bacteria are prone to bloodstream entry remain poorly understood. Herein, we report that clinical isolates of non-typhoidal Salmonella enterica serovars, Escherichia coli, and Citrobacter koseri are rapidly attracted toward sources of human serum. To simulate GI bleeding, we utilized an injection-based microfluidics device and found that femtoliter volumes of human serum are sufficient to induce bacterial attraction to the serum source. This response is orchestrated through chemotaxis and the chemoattractant L-serine, an amino acid abundant in serum that is recognized through direct binding by the chemoreceptor Tsr. We report the first crystal structures of Salmonella Typhimurium Tsr in complex with L-serine and identify a conserved amino acid recognition motif for L-serine shared among Tsr orthologues. We find Tsr to be widely conserved among Enterobacteriaceae and numerous World Health Organization priority pathogens associated with bloodstream infections. Lastly, we find that Enterobacteriaceae use human serum as a source of nutrients for growth and that chemotaxis and the chemoreceptor Tsr provide a competitive advantage for migration into enterohemorrhagic lesions. We define this bacterial behavior of taxis toward serum, colonization of hemorrhagic lesions, and the consumption of serum nutrients as 'bacterial vampirism', which may relate to the proclivity of Enterobacteriaceae for bloodstream infections.
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Affiliation(s)
- Siena J Glenn
- Washington State University, Department of Veterinary Microbiology and PathologyPullmanUnited States
| | | | - Michael Shavlik
- University of Oregon, Institute of Molecular BiologyEugeneUnited States
| | - Michael J Harms
- University of Oregon, Institute of Molecular BiologyEugeneUnited States
- University of Oregon, Department of Chemistry & BiochemistryEugeneUnited States
| | - Thomas J Asaki
- Washington State University, Department of Mathematics and StatisticsPullmanUnited States
| | - Arden Baylink
- Washington State University, Department of Veterinary Microbiology and PathologyPullmanUnited States
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2
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Garg A, Karhana S, Khan MA. Nanomedicine for the eradication of Helicobacter pylori: recent advances, challenges and future perspective. Future Microbiol 2024; 19:431-447. [PMID: 38381027 DOI: 10.2217/fmb-2023-0189] [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: 08/23/2023] [Accepted: 10/31/2023] [Indexed: 02/22/2024] Open
Abstract
Helicobacter pylori infection is linked to gastritis, ulcers and gastric cancer. Nanomedicine offers a promising solution by utilizing nanoparticles for precise drug delivery, countering antibiotic resistance and delivery issues. Nanocarriers such as liposomes and nanoparticles enhance drug stability and circulation, targeting infection sites through gastric mucosa characteristics. Challenges include biocompatibility, stability, scalability and personalized therapies. Despite obstacles, nanomedicine's potential for reshaping H. pylori eradication is significant and showcased in this review focusing on benefits, limitations and future prospects of nanomedicine-based strategies.
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Affiliation(s)
- Aakriti Garg
- Department of Pharmacology, School of Pharmaceutical Education & Research, Jamia Hamdard, New Delhi, 110062, India
- Centre for Translational & Clinical Research, School of Chemical & Life Sciences, Jamia Hamdard, New Delhi, 110062, India
| | - Sonali Karhana
- Centre for Translational & Clinical Research, School of Chemical & Life Sciences, Jamia Hamdard, New Delhi, 110062, India
| | - Mohd A Khan
- Centre for Translational & Clinical Research, School of Chemical & Life Sciences, Jamia Hamdard, New Delhi, 110062, India
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3
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Ciarambino T, Crispino P, Minervini G, Giordano M. Role of Helicobacter pylori Infection in Pathogenesis, Evolution, and Complication of Atherosclerotic Plaque. Biomedicines 2024; 12:400. [PMID: 38398002 PMCID: PMC10886498 DOI: 10.3390/biomedicines12020400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 09/11/2023] [Accepted: 02/07/2024] [Indexed: 02/25/2024] Open
Abstract
The therapeutic management of atherosclerosis focuses almost exclusively on the reduction of plasma cholesterol levels. An important role in the genesis and evolution of atherosclerosis is played by chronic inflammation in promoting thrombosis phenomena after atheroma rupture. This review aims to take stock of the knowledge so far accumulated on the role of endemic HP infection in atherosclerosis. The studies produced so far have demonstrated a causal relationship between Helicobacter pylori (HP) and CVD. In a previous study, we demonstrated in HP-positive patients that thrombin and plasma fragment 1 + 2 production was proportionally related to tumor necrosis factor-alpha levels and that eradication of the infection resulted in a reduction of inflammation. At the end of our review, we can state that HP slightly affects the risk of CVD, particularly if the infection is associated with cytotoxic damage, and HP screening could have a clinically significant role in patients with a high risk of CVD. Considering the high prevalence of HP infection, an infection screening could be of great clinical utility in patients at high risk of CVD.
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Affiliation(s)
- Tiziana Ciarambino
- Internal Medicine Department, Hospital of Marcianise, ASL Caserta, 81037 Caserta, Italy
| | - Pietro Crispino
- Internal Medicine Department, Hospital of Latina, ASL Latina, 04100 Latina, Italy;
| | - Giovanni Minervini
- Internal Medicine Department, Hospital of Lagonegro, AOR San Carlo, 85042 Lagonegro, Italy;
| | - Mauro Giordano
- Department of Advanced Medical and Surgical Sciences, University of Campania “L. Vanvitelli”, 81100 Naples, Italy;
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4
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Zhou X, Rahman MM, Bonny SQ, Xin Y, Liddelow N, Khan MF, Tikhomirova A, Homman-Ludiye J, Roujeinikova A. Pal power: Demonstration of the functional association of the Helicobacter pylori flagellar motor with peptidoglycan-associated lipoprotein (Pal) and its preliminary crystallographic analysis. Biosci Trends 2024; 17:491-498. [PMID: 38072447 DOI: 10.5582/bst.2023.01278] [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] [Indexed: 02/02/2024]
Abstract
The bacterial flagellar motor is a molecular nanomachine, the assembly and regulation of which requires many accessory proteins. Their identity, structure and function are often discovered through characterisation of mutants with impaired motility. Here, we demonstrate the functional association of the Helicobacter pylori peptidoglycan-associated lipoprotein (HpPal) with the flagellar motor by analysing the motility phenotype of the ∆pal mutant, and present the results of the preliminary X-ray crystallographic analysis of its globular C-terminal domain HpPal-C. Purified HpPal-C behaved as a dimer in solution. Crystals of HpPal-C were grown by the hanging drop vapour diffusion method using medium molecular weight polyethylene glycol (PEG) Smear as the precipitating agent. The crystals belong to the primitive orthorhombic space group P1 with unit cell parameters a = 50.7, b = 63.0, c = 75.1 Å. X-ray diffraction data were collected to 1.8 Å resolution on the Australian Synchrotron beamline MX2. Calculation of the Matthews coefficient (VM=2.24 Å3/Da) and molecular replacement showed that the asymmetric unit contains two protein subunits. This study is an important step towards elucidation of the non-canonical role of H. pylori Pal in the regulation, or function of, the flagellar motor.
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Affiliation(s)
- Xiaotian Zhou
- Department of Microbiology, Infection and Immunity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
| | - Mohammad M Rahman
- Department of Microbiology, Infection and Immunity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
| | - Sharmin Q Bonny
- Department of Microbiology, Infection and Immunity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
| | - Yue Xin
- Department of Microbiology, Infection and Immunity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
| | - Nikki Liddelow
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria, Australia
| | - Mohammad F Khan
- Department of Microbiology, Infection and Immunity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
| | - Alexandra Tikhomirova
- Department of Microbiology, Infection and Immunity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
| | - Jihane Homman-Ludiye
- Monash Micro Imaging, Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
| | - Anna Roujeinikova
- Department of Microbiology, Infection and Immunity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, Australia
- Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria, Australia
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5
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Zhou B, Szymanski CM, Baylink A. Bacterial chemotaxis in human diseases. Trends Microbiol 2023; 31:453-467. [PMID: 36411201 PMCID: PMC11238666 DOI: 10.1016/j.tim.2022.10.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 10/16/2022] [Accepted: 10/18/2022] [Indexed: 11/21/2022]
Abstract
To infect and cause disease, bacterial pathogens must localize to specific regions of the host where they possess the metabolic and defensive acumen for survival. Motile flagellated pathogens exercise control over their localization through chemotaxis to direct motility based on the landscape of exogenous nutrients, toxins, and molecular cues sensed within the host. Here, we review advances in understanding the roles chemotaxis plays in human diseases. Chemotaxis drives pathogen colonization to sites of inflammation and injury and mediates fitness advantages through accessing host-derived nutrients from damaged tissue. Injury tropism may worsen clinical outcomes through instigating chronic inflammation and subsequent cancer development. Inhibiting bacterial chemotactic systems could act synergistically with antibacterial medicines for more effective and specific eradication.
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Affiliation(s)
- Bibi Zhou
- University of Georgia, Department of Microbiology and Complex Carbohydrate Research Center, Athens, GA 30602, USA
| | - Christine M Szymanski
- University of Georgia, Department of Microbiology and Complex Carbohydrate Research Center, Athens, GA 30602, USA
| | - Arden Baylink
- Washington State University, Department of Veterinary Microbiology and Pathology, Pullman, WA 99164, USA.
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6
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Helicobacter pylori Infection: Current Status and Future Prospects on Diagnostic, Therapeutic and Control Challenges. Antibiotics (Basel) 2023; 12:antibiotics12020191. [PMID: 36830102 PMCID: PMC9952126 DOI: 10.3390/antibiotics12020191] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 12/26/2022] [Accepted: 01/06/2023] [Indexed: 01/20/2023] Open
Abstract
Helicobacter pylori (H. pylori) infection, which affects approximately half of the world's population, remains a serious public health problem. As H. pylori infection leads to a number of gastric pathologies, including inflammation, gastroduodenal ulcers, and malignancies, early detection and treatment are crucial to preventing the spread of the infection. Multiple extragastric complications, such as iron deficiency anaemia, immune thrombocytopenic purpura, vitamin B12 deficiency, diabetes mellitus, cardiovascular diseases, and certain neurological disorders, have also been linked to H. pylori infection. An awareness of H. pylori and associated health hazards is necessary to minimize or even eradicate the infection. Therefore, there is an urgent need to raise the standards for the currently employed diagnostic, eradication, alternative treatment strategies. In addition, a brief overview of traditional and cutting-edge approaches that have proven effective in identifying and managing H. pylori is needed. Based on the test and laboratory equipment available and patient clinical characteristics, the optimal diagnostic approach requires weighing several factors. The pathophysiology and pathogenic mechanisms of H. pylori should also be studied, focusing more on the infection-causing virulence factors of this bacterium. Accordingly, this review aims to demonstrate the various diagnostic, pathophysiological, therapeutic, and eradication tactics available for H. pylori, emphasizing both their advantages and disadvantages. Invasive methods (such as quick urease testing, biopsy, or culture) or noninvasive methods (such as breath tests, stool investigations, or serological tests) can be used. We also present the most recent worldwide recommendations along with scientific evidence for treating H. pylori. In addition to the current antibiotic regimens, alternative therapies may also be considered. It is imperative to eradicate the infections caused by H. pylori as soon as possible to prevent problems and the development of stomach cancer. In conclusion, significant advances have been made in identifying and treating H. pylori. To improve eradication rates, peptide mass fingerprinting can be used as a diagnostic tool, and vaccines can also eliminate the infection.
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7
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Shatila M, Thomas AS. Current and Future Perspectives in the Diagnosis and Management of Helicobacter pylori Infection. J Clin Med 2022; 11:jcm11175086. [PMID: 36079015 PMCID: PMC9456682 DOI: 10.3390/jcm11175086] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Revised: 08/24/2022] [Accepted: 08/25/2022] [Indexed: 12/03/2022] Open
Abstract
Helicobacter pylori (Hp) is a prevalent organism infecting almost half the global population. It is a significant concern, given its associated risk of gastric cancer, which is the third leading cause of cancer death globally. Infection can be asymptomatic or present with dyspeptic symptoms. It may also present with alarm symptoms in the case of progression to cancer. Diagnosis can be achieved non-invasively (breath tests, stool studies, or serology) or invasively (rapid urease test, biopsy, or culture). Treatment involves acid suppression and regimens containing several antibiotics and is guided by resistance rates. Eradication is essential, as it lowers the risk of complications and progression to cancer. Follow-up after eradication is similarly important, as the risk of cancer progression remains. There have been many recent advances in both diagnosis and treatment of Hp. In particular, biosensors may be effective diagnostic tools, and nanotechnology, vaccines, and potassium-competitive acid blockers may prove effective in enhancing eradication rates.
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8
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Idowu S, Bertrand PP, Walduck AK. Gastric organoids: Advancing the study of H. pylori pathogenesis and inflammation. Helicobacter 2022; 27:e12891. [PMID: 35384141 PMCID: PMC9287064 DOI: 10.1111/hel.12891] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 03/14/2022] [Accepted: 03/20/2022] [Indexed: 12/13/2022]
Abstract
For decades, traditional in vitro and in vivo models used for the study of Helicobacter pylori infection have relied heavily on the use of gastric cancer cell lines and rodents. Major challenges faced by these methods have been the inability to study cancer initiation in already cancerous cell lines, and the difficulty in translating results obtained in animal models due to genetic differences. These challenges have prevented a thorough understanding of the pathogenesis of disease and slowed the development of cancer therapies and a suitable vaccine against the pathogen. In recent years, the development of gastric organoids has provided great advantages over the traditional in vivo and in vitro models due to their similarities to the human stomach in vivo, their ease of use, and the capacity for long-term culture. This review discusses the advantages and limitations of existing in vivo and in vitro models of H. pylori infection, and how gastric organoids have been applied to study H. pylori pathogenesis, with a focus on how the pathogen interacts with the gastric epithelium, inflammatory processes, epithelial repair, and cancer initiation. The potential applications of organoids to address more complex questions on the role of hormones, vaccine-induced immunity are also discussed.
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9
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Akahoshi DT, Bevins CL. Flagella at the Host-Microbe Interface: Key Functions Intersect With Redundant Responses. Front Immunol 2022; 13:828758. [PMID: 35401545 PMCID: PMC8987104 DOI: 10.3389/fimmu.2022.828758] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 02/21/2022] [Indexed: 12/15/2022] Open
Abstract
Many bacteria and other microbes achieve locomotion via flagella, which are organelles that function as a swimming motor. Depending on the environment, flagellar motility can serve a variety of beneficial functions and confer a fitness advantage. For example, within a mammalian host, flagellar motility can provide bacteria the ability to resist clearance by flow, facilitate access to host epithelial cells, and enable travel to nutrient niches. From the host’s perspective, the mobility that flagella impart to bacteria can be associated with harmful activities that can disrupt homeostasis, such as invasion of epithelial cells, translocation across epithelial barriers, and biofilm formation, which ultimately can decrease a host’s reproductive fitness from a perspective of natural selection. Thus, over an evolutionary timescale, the host developed a repertoire of innate and adaptive immune countermeasures that target and mitigate this microbial threat. These countermeasures are wide-ranging and include structural components of the mucosa that maintain spatial segregation of bacteria from the epithelium, mechanisms of molecular recognition and inducible responses to flagellin, and secreted effector molecules of the innate and adaptive immune systems that directly inhibit flagellar motility. While much of our understanding of the dynamics of host-microbe interaction regarding flagella is derived from studies of enteric bacterial pathogens where flagella are a recognized virulence factor, newer studies have delved into host interaction with flagellated members of the commensal microbiota during homeostasis. Even though many aspects of flagellar motility may seem innocuous, the host’s redundant efforts to stop bacteria in their tracks highlights the importance of this host-microbe interaction.
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10
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Abstract
Acetylcholine is a central biological signal molecule present in all kingdoms of life. In humans, acetylcholine is the primary neurotransmitter of the peripheral nervous system; it mediates signal transmission at neuromuscular junctions. Here, we show that the opportunistic human pathogen Pseudomonas aeruginosa exhibits chemoattraction toward acetylcholine over a concentration range of 1 μM to 100 mM. The maximal magnitude of the response was superior to that of many other P. aeruginosa chemoeffectors. We demonstrate that this chemoattraction is mediated by the PctD (PA4633) chemoreceptor. Using microcalorimetry, we show that the PctD ligand-binding domain (LBD) binds acetylcholine with a equilibrium dissociation constant (KD) of 23 μM. It also binds choline and with lower affinity betaine. Highly sensitive responses to acetylcholine and choline, and less sensitive responses to betaine and l-carnitine, were observed in Escherichia coli expressing a chimeric receptor comprising the PctD-LBD fused to the Tar chemoreceptor signaling domain. We also identified the PacA (ECA_RS10935) chemoreceptor of the phytopathogen Pectobacterium atrosepticum, which binds choline and betaine but fails to recognize acetylcholine. To identify the molecular determinants for acetylcholine recognition, we report high-resolution structures of PctD-LBD (with bound acetylcholine and choline) and PacA-LBD (with bound betaine). We identified an amino acid motif in PctD-LBD that interacts with the acetylcholine tail. This motif is absent in PacA-LBD. Significant acetylcholine chemotaxis was also detected in the plant pathogens Agrobacterium tumefaciens and Dickeya solani. To the best of our knowledge, this is the first report of acetylcholine chemotaxis and extends the range of host signals perceived by bacterial chemoreceptors.
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11
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Yang H, Hu B. Immunological Perspective: Helicobacter pylori Infection and Gastritis. Mediators Inflamm 2022; 2022:2944156. [PMID: 35300405 PMCID: PMC8923794 DOI: 10.1155/2022/2944156] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2022] [Accepted: 03/02/2022] [Indexed: 02/07/2023] Open
Abstract
Helicobacter pylori is a spiral-shaped gram-negative bacterium. Its infection is mainly transmitted via oral-oral and fecal-oral routes usually during early childhood. It can achieve persistent colonization by manipulating the host immune responses, which also causes mucosal damage and inflammation. H. pylori gastritis is an infectious disease and results in chronic gastritis of different severity in near all patients with infection. It may develop from acute/chronic inflammation, chronic atrophic gastritis, intestinal metaplasia, dysplasia, and intraepithelial neoplasia, eventually to gastric cancer. This review attempts to cover recent studies which provide important insights into how H. pylori causes chronic inflammation and what the characteristic is, which will immunologically explain H. pylori gastritis.
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Affiliation(s)
- Hang Yang
- Department of Gastroenterology, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Bing Hu
- Department of Gastroenterology, West China Hospital, Sichuan University, Chengdu, Sichuan, China
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12
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MicroRNAs Encoded by Virus and Small RNAs Encoded by Bacteria Associated with Oncogenic Processes. Processes (Basel) 2021. [DOI: 10.3390/pr9122234] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Cancer is a deadly disease and, globally, represents the second leading cause of death in the world. Although it is a disease where several factors can help its development, virus induced infections have been associated with different types of neoplasms. However, in bacterial infections, their participation is not known for certain. Among the proposed approaches to oncogenesis risks in different infections are microRNAs (miRNAs). These are small molecules composed of RNA with a length of 22 nucleotides capable of regulating gene expression by directing protein complexes that suppress the untranslated region of mRNA. These miRNAs and other recently described, such as small RNAs (sRNAs), are deregulated in the development of cancer, becoming promising biomarkers. Thus, resulting in a study possibility, searching for new tools with diagnostic and therapeutic approaches to multiple oncological diseases, as miRNAs and sRNAs are main players of gene expression and host–infectious agent interaction. Moreover, sRNAs with limited complementarity are similar to eukaryotic miRNAs in their ability to modulate the activity and stability of multiple mRNAs. Here, we will describe the regulatory RNAs from viruses that have been associated with cancer and how sRNAs in bacteria can be related to this disease.
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13
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Colin R, Ni B, Laganenka L, Sourjik V. Multiple functions of flagellar motility and chemotaxis in bacterial physiology. FEMS Microbiol Rev 2021; 45:fuab038. [PMID: 34227665 PMCID: PMC8632791 DOI: 10.1093/femsre/fuab038] [Citation(s) in RCA: 90] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 07/02/2021] [Indexed: 12/13/2022] Open
Abstract
Most swimming bacteria are capable of following gradients of nutrients, signaling molecules and other environmental factors that affect bacterial physiology. This tactic behavior became one of the most-studied model systems for signal transduction and quantitative biology, and underlying molecular mechanisms are well characterized in Escherichia coli and several other model bacteria. In this review, we focus primarily on less understood aspect of bacterial chemotaxis, namely its physiological relevance for individual bacterial cells and for bacterial populations. As evident from multiple recent studies, even for the same bacterial species flagellar motility and chemotaxis might serve multiple roles, depending on the physiological and environmental conditions. Among these, finding sources of nutrients and more generally locating niches that are optimal for growth appear to be one of the major functions of bacterial chemotaxis, which could explain many chemoeffector preferences as well as flagellar gene regulation. Chemotaxis might also generally enhance efficiency of environmental colonization by motile bacteria, which involves intricate interplay between individual and collective behaviors and trade-offs between growth and motility. Finally, motility and chemotaxis play multiple roles in collective behaviors of bacteria including swarming, biofilm formation and autoaggregation, as well as in their interactions with animal and plant hosts.
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Affiliation(s)
- Remy Colin
- Max Planck Institute for Terrestrial Microbiology & Center for Synthetic Microbiology (SYNMIKRO), Karl-von-Frisch Strasse 16, Marburg D-35043, Germany
| | - Bin Ni
- Max Planck Institute for Terrestrial Microbiology & Center for Synthetic Microbiology (SYNMIKRO), Karl-von-Frisch Strasse 16, Marburg D-35043, Germany
- College of Resources and Environmental Science, National Academy of Agriculture Green Development, China Agricultural University, Yuanmingyuan Xilu No. 2, Beijing 100193, China
| | - Leanid Laganenka
- Institute of Microbiology, D-BIOL, ETH Zürich, Vladimir-Prelog-Weg 4, Zürich 8093, Switzerland
| | - Victor Sourjik
- Max Planck Institute for Terrestrial Microbiology & Center for Synthetic Microbiology (SYNMIKRO), Karl-von-Frisch Strasse 16, Marburg D-35043, Germany
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14
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Prashar A, Capurro MI, Jones NL. Under the Radar: Strategies Used by Helicobacter pylori to Evade Host Responses. Annu Rev Physiol 2021; 84:485-506. [PMID: 34672717 DOI: 10.1146/annurev-physiol-061121-035930] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The body depends on its physical barriers and innate and adaptive immune responses to defend against the constant assault of potentially harmful microbes. In turn, successful pathogens have evolved unique mechanisms to adapt to the host environment and manipulate host defenses. Helicobacter pylori (Hp), a human gastric pathogen that is acquired in childhood and persists throughout life, is an example of a bacterium that is very successful at remodeling the host-pathogen interface to promote a long-term persistent infection. Using a combination of secreted virulence factors, immune subversion, and manipulation of cellular mechanisms, Hp can colonize and persist in the hostile environment of the human stomach. Here, we review the most recent and relevant information regarding how this successful pathogen overcomes gastric epithelial host defense responses to facilitate its own survival and establish a chronic infection. Expected final online publication date for the Annual Review of Physiology, Volume 84 is February 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Akriti Prashar
- Program in Cell Biology, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, Ontario, Canada;
| | - Mariana I Capurro
- Program in Cell Biology, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, Ontario, Canada;
| | - Nicola L Jones
- Program in Cell Biology, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, Ontario, Canada; .,Division of Gastroenterology, Hepatology and Nutrition, The Hospital for Sick Children, Toronto, Ontario, Canada.,Departments of Paediatrics and Physiology, University of Toronto, Toronto, Ontario, Canada
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15
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Abstract
Helicobacter pylori infection remains one of the most prevalent infections worldwide, causing significant morbidity and mortality from gastric malignancies and peptic ulcers. This article provides a summary of the microbiology and pathogenesis of this bacterium, emphasizing the complex and protean effects of H pylori on gastric epithelial cells, including stem and progenitor populations, and evasion of host immune defenses. Increasing antibiotic resistance has made management more challenging. This article discusses the appropriate diagnostic modality for different clinical scenarios, and the evolving treatment of H pylori infections, including the use of antibiotic susceptibility testing to aid regimen selection.
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Affiliation(s)
- Jaehoon Cho
- Division of Gastroenterology, Brown University, 593 Eddy Street, POB 240, Providence, RI 02903, USA
| | - Akriti Prashar
- Department of Gastroenterology, Hepatology and Nutrition, University of Toronto, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada; Cell Biology Program, The Hospital for Sick Children, 686 Bay Street, Toronto, Ontario M5G0A4, Canada
| | - Nicola L Jones
- Department of Gastroenterology, Hepatology and Nutrition, University of Toronto, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada; Cell Biology Program, The Hospital for Sick Children, 686 Bay Street, Toronto, Ontario M5G0A4, Canada; Department of Paediatrics, University of Toronto, Toronto, Ontario, Canada
| | - Steven F Moss
- Division of Gastroenterology, Brown University, 593 Eddy Street, POB 240, Providence, RI 02903, USA.
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16
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Traulsen J, Zagami C, Daddi AA, Boccellato F. Molecular modelling of the gastric barrier response, from infection to carcinogenesis. Best Pract Res Clin Gastroenterol 2021; 50-51:101737. [PMID: 33975688 DOI: 10.1016/j.bpg.2021.101737] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 02/15/2021] [Accepted: 02/18/2021] [Indexed: 02/07/2023]
Abstract
The lining of the stomach is a tight monolayer of epithelial cells performing functions in digestion and a protective barrier against gastric acid, toxic metabolites and infectious agents, including Helicobacter pylori. The response of the epithelial barrier to infections underlies gastric pathologies, including gastric cancer. H. pylori has the unique capacity to colonise the gastric mucosa while evading the immune system. The colonised mucosa initiates an inflammatory response to fight the infection and a strong regenerative program to avoid barrier failure and ulceration. This response changes the morphology and cell composition of the gastric epithelium and in parallel it might contribute to the accumulation of somatic mutations leading to cellular transformation. Genetically modified mice, cell lines and human-derived organoids are the main biological models to study the gastric epithelial barrier. With these models it is possible to dissect the stepwise process of tissue adaptation to infection that places the epithelium at risk of malignant transformation.
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Affiliation(s)
- Jan Traulsen
- Ludwig Institute for Cancer Research, Nuffield Department of Medicine, University of Oxford, United Kingdom.
| | - Claudia Zagami
- Ludwig Institute for Cancer Research, Nuffield Department of Medicine, University of Oxford, United Kingdom.
| | - Alice Anna Daddi
- Ludwig Institute for Cancer Research, Nuffield Department of Medicine, University of Oxford, United Kingdom.
| | - Francesco Boccellato
- Ludwig Institute for Cancer Research, Nuffield Department of Medicine, University of Oxford, United Kingdom.
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17
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Liu L, Bi XY, Sheng S, Gong YY, Pu WX, Ke J, Huang PJ, Liang YL, Liu LH. Evidence that exogenous urea acts as a potent cue to alleviate ammonium-inhibition of root system growth of cotton plant (Gossypium hirsutum). PHYSIOLOGIA PLANTARUM 2021; 171:137-150. [PMID: 32997341 DOI: 10.1111/ppl.13222] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2020] [Revised: 09/28/2020] [Accepted: 09/29/2020] [Indexed: 05/24/2023]
Abstract
Many plants grown with low-millimolar concentration of NH4 + as a sole nitrogen source develop NH4 + -toxicity symptoms. To date, crucial molecular identities and a practical approach involved in the improvement of plant NH4 + -tolerance remain largely unknown. By phenotyping of upland cotton grown on varied nitrogen forms, we came across a phenomenon that caused sub-millimolar concentrations of urea (e.g., up 50 μM) to repress the growth inhibition of roots and whole plant cultivated in a NH4 + -containing nutrient solution. A growth-recovery assay revealed that the relief in NH4 + -inhibited growth required only a short-term exposure (≧12 h) of the roots to urea, implying that urea could elicit an internal signaling and be involved in antagonizing NH4 + -sensitivity. Intriguingly, split-root experiments demonstrated that low urea occurrence in one root-half could efficaciously stimulate not only supplied root but also the root-half grown in NH4 + -solution without urea, indicating the existence of urea-triggered local and systemic long-distance signaling. In the split-root experiment we also observed high arginase activity, strong arginine reduction and remarkable upregulation of polyamine biosynthesis-related genes (ADC1/2, SPDS and SPMS). Therefore, we suggest that external urea might serve as an effective cue (signal molecule) in an arginine-/polyamine-related process for ameliorating NH4 + -suppressed root growth, providing a novel aspect for deeper exploring and understanding plant NH4 + -tolerance.
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Affiliation(s)
- Lu Liu
- College of Resources and Environmental Sciences, Key Lab of Plant-Soil Interaction, MOE, Centre for Resources, Environment and Food Security, China Agricultural University, Beijing, China
| | - Xin-Yuan Bi
- Institute of Agricultural Resources and Economics, Shanxi Agricultural University, Taiyuan, China
| | - Song Sheng
- College of Resources and Environmental Sciences, Key Lab of Plant-Soil Interaction, MOE, Centre for Resources, Environment and Food Security, China Agricultural University, Beijing, China
| | - Yuan-Yong Gong
- Biological and Chemical Engineering College, Panzhihua University, Panzhihua, China
| | - Wen-Xuan Pu
- Tobacco Research Institute of Technology Centre, China Tobacco Hunan Industrial Corporation, Changsha, China
| | - Jie Ke
- College of Resources and Environmental Sciences, Key Lab of Plant-Soil Interaction, MOE, Centre for Resources, Environment and Food Security, China Agricultural University, Beijing, China
| | - Ping-Jun Huang
- Tobacco Research Institute of Technology Centre, China Tobacco Hunan Industrial Corporation, Changsha, China
| | - Yi-Long Liang
- Chongqing Key Laboratory of Big Data for Bio Intelligence, Chongqing University of Posts and Telecommunications, Chongqing, China
| | - Lai-Hua Liu
- College of Resources and Environmental Sciences, Key Lab of Plant-Soil Interaction, MOE, Centre for Resources, Environment and Food Security, China Agricultural University, Beijing, China
- Chongqing Key Laboratory of Big Data for Bio Intelligence, Chongqing University of Posts and Telecommunications, Chongqing, China
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18
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Ke J, Pu WX, Wang H, Liu LH, Sheng S. Phenotypical evidence of effective amelioration of ammonium-inhibited plant (root) growth by exogenous low urea. JOURNAL OF PLANT PHYSIOLOGY 2020; 255:153306. [PMID: 33129078 DOI: 10.1016/j.jplph.2020.153306] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 10/08/2020] [Accepted: 10/09/2020] [Indexed: 05/27/2023]
Abstract
Ammonium and nitrate are major soil inorganic-nitrogen sources for plant growth, but many species cultivated with even low millimolar NH4+ as a sole N form display a growth retardation. To date, critical biological components and applicable approaches involved in the effective enhancement of NH4+ tolerance remain to be thoroughly explored. Here, we report phenotypical traits of urea-dependent improvement of NH4+-suppressed plant/root growth. Urea at 0.1 mM was sufficient to remarkably stimulate NH4+ (3 mM)-fed cotton growth, showing a 2.5∼4-fold increase in shoot- and root-biomass and total root-length, 20 % higher GS activity, 18 % less NH4+-accumulation in roots, and a comparable plant total-N content compared to the control, implying a novel role for urea in cotton NH4+detoxification. A similar phenomenon was observed in tobacco and rice. Moreover, comparisons between twelve NH4+-grown Arabidopsis accessions revealed a great degree of natural variation in their root-growth response to low urea, with WAR and Blh-1 exhibiting the most significant increase in primary- and lateral-root length and numbers, and Sav-0 and Edi-0 being the most insensitive. Such phenotypical evidence suggests a common ability of plants to accommodate NH4+-stress by responding to exogenous urea, providing a novel aspect for further understanding the process of urea-dependent plant NH4+ tolerance.
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Affiliation(s)
- Jie Ke
- College of Resources and Environmental Sciences, Key Lab of Plant-Soil Interaction, MOE, Centre for Resources, Environment and Food Security, China Agricultural University, Beijing 100193, China
| | - Wen-Xuan Pu
- Tobacco Research Institute of Technology Centre, China Tobacco Hunan Industrial Corporation, Changsha 410007, China
| | - Hui Wang
- College of Resources and Environmental Sciences, Key Lab of Plant-Soil Interaction, MOE, Centre for Resources, Environment and Food Security, China Agricultural University, Beijing 100193, China
| | - Lai-Hua Liu
- College of Resources and Environmental Sciences, Key Lab of Plant-Soil Interaction, MOE, Centre for Resources, Environment and Food Security, China Agricultural University, Beijing 100193, China.
| | - Song Sheng
- College of Resources and Environmental Sciences, Key Lab of Plant-Soil Interaction, MOE, Centre for Resources, Environment and Food Security, China Agricultural University, Beijing 100193, China.
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19
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Ballweg R, Engevik KA, Montrose MH, Aihara E, Zhang T. Extracting Insights From Temporal Data by Integrating Dynamic Modeling and Machine Learning. Front Physiol 2020; 11:1012. [PMID: 32903488 PMCID: PMC7435055 DOI: 10.3389/fphys.2020.01012] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 07/24/2020] [Indexed: 12/14/2022] Open
Abstract
Biological processes are dynamic. As a result, temporal analyses are necessary to fully understand the complex interactions that occurs within these systems. One example of a multifaceted biological process is restitution: the initial step in complex wound repair. Restitution is a dynamic process that depends on an elegant orchestration between damaged cells and their intact neighbors. Such orchestration enables the quick repair of the damaged area, which is essential to preserve epithelial integrity and prevent further injury. High quality dynamic data of the cellular and molecular events that make up the gastric restitution process has been documented. However, comprehensive dynamic models that connect all relevant molecular interactions to cellular behaviors are challenging to construct and experimentally validate. In order to efficiently provide feedback to ongoing experimental work, we have integrated dynamical modeling and machine learning to efficiently extract data-driven insights without incorporating detailed mechanisms. Dynamical models convert time course data into a set of static features, which are then subjected to machine learning analysis. The integrated analysis provides data-driven insights into how repair might be regulated in individual gastric organoids. We have provided a “proof of concept” of how such an analysis pipeline can be used to analyze any temporal dataset and provide timely data-driven insights.
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Affiliation(s)
- Richard Ballweg
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, United States
| | - Kristen A Engevik
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, United States
| | - Marshall H Montrose
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, United States
| | - Eitaro Aihara
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, United States
| | - Tongli Zhang
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, OH, United States
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20
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Abstract
The original strategies developed by Helicobacter pylori to persistently colonise its host and to deregulate its cellular functions make this bacterium an outstanding model to study host-pathogen interaction and the mechanisms responsible for bacterial-induced carcinogenesis. During the last year, significant results were obtained on the role of bacterial factors essential for gastric colonisation such as spiral shape maintenance, orientation through chemotaxis and the formation of bacteria clonal population islands inside the gastric glands. Particularities of the H pylori cell surface, a structure important for immune escape, were demonstrated. New insights in the bacterial stress response revealed the importance of DNA methylation-mediated regulation. Further findings were reported on H pylori components that mediate natural transformation and mechanisms of bacterial DNA horizontal transfer which maintain a high level of H pylori genetic variability. Within-host evolution was found to be niche-specific and probably associated with physiological differences between the antral and oxyntic gastric mucosa. In addition, with the progress of CryoEM, high-resolution structures of the major virulence factors, VacA and CagT4SS, were obtained. The use of gastric organoid models fostered research revealing, preferential accumulation of bacteria at the site of injury during infection. Several studies further characterised the role of CagA in the oncogenic properties of H pylori, identifying the activation of novel CagA-dependent pathways, leading to the promotion of genetic instabilities, epithelial-to-mesenchymal transition and finally carcinogenesis. Recent studies also highlight that microRNA-mediated regulation and epigenetic modifications, through DNA methylation, are key events in the H pylori-induced tumorigenesis process.
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Affiliation(s)
- Milica Denic
- Département de Microbiologie, Institut Pasteur, UMR CNRS 2001, Unité Pathogenèse de Helicobacter, Paris, France.,Sorbonne Paris Cité, Cellule Pasteur, Université Paris Diderot, Paris, France
| | - Eliette Touati
- Département de Microbiologie, Institut Pasteur, UMR CNRS 2001, Unité Pathogenèse de Helicobacter, Paris, France
| | - Hilde De Reuse
- Département de Microbiologie, Institut Pasteur, UMR CNRS 2001, Unité Pathogenèse de Helicobacter, Paris, France
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21
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Wizenty J, Tacke F, Sigal M. Responses of gastric epithelial stem cells and their niche to Helicobacter pylori infection. ANNALS OF TRANSLATIONAL MEDICINE 2020; 8:568. [PMID: 32775369 PMCID: PMC7347775 DOI: 10.21037/atm.2020.02.178] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Helicobacter pylori (H. pylori) are gram-negative bacteria that are able to colonize and persist in the stomach. Gastric cancer is tightly linked to chronic infection with this bacterium. Research over the last decades has illuminated the molecular interactions between H. pylori and host cells. It is now well established that H. pylori have multiple sophisticated means to adhere to epithelial cells and to manipulate their behavior. This interaction with the epithelium can lead to altered cell signaling, DNA damage and aberrant epithelial immunity. H. pylori are known to colonize the mucus layer of the stomach and surface epithelial cells. In addition, it has recently become clear that they can also penetrate the glands and directly interact with specialized epithelial cells deep in the glands. Understanding the biogeography of infection is important because gastric epithelial glands are composed of various types of short-lived differentiated cells that are constantly regenerated by a limited pool of long-lived stem cells located in base of gastric glands. Recent advances in gastric stem cell research not only led to identification of stem cell populations using specific markers but has also uncovered specific regulatory pathways and principles that govern gastric stem cell behavior and regeneration. Particularly, the stem cell state is largely dependent on signals from the niche cells that surround the stem cell compartment. The subpopulation of H. pylori that colonizes in the stem cell compartment triggers specific inflammatory responses and drives epithelial pathology. Colonization of gastric glands induces responses of the stem cell niche, simultaneously enhancing the cell turnover kinetics and driving the formation of antimicrobial cells in the gland base. These data reveal the high plasticity of the epithelium and its ability to adapt to the environment, which is necessary to regenerate and counterbalance infection, but simultaneously lays the grounds for development of gastric pathology and carcinogenesis.
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Affiliation(s)
- Jonas Wizenty
- Department of Hepatology & Gastroenterology, Charité - Universitätsmedizin Berlin, Berlin, Germany.,Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
| | - Frank Tacke
- Department of Hepatology & Gastroenterology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Michael Sigal
- Department of Hepatology & Gastroenterology, Charité - Universitätsmedizin Berlin, Berlin, Germany.,Department of Molecular Biology, Max Planck Institute for Infection Biology, Berlin, Germany
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22
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Seeger AY, Ringling MD, Zohair H, Blanke SR. Risk factors associated with gastric malignancy during chronic Helicobacter pylori Infection. MEDICAL RESEARCH ARCHIVES 2020; 8:2068. [PMID: 37655156 PMCID: PMC10470974 DOI: 10.18103/mra.v8i3.2068] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
Chronic Helicobacter pylori (Hp) infection is considered to be the single most important risk factor for the development of gastric adenocarcinoma in humans, which is a leading cause of cancer-related death worldwide. Nonetheless, Hp infection does not always progress to malignancy, and, gastric adenocarcinoma can occur in the absence of detectable Hp carriage, highlighting the complex and multifactorial nature of gastric cancer. Here we review known contributors to gastric malignancy, including Hp virulence factors, host genetic variation, and multiple environmental variables. In addition, we assess emerging evidence that resident gastric microflora in humans might impact disease progression in Hp-infected individuals. Molecular approaches for microbe identification have revealed differences in the gastric microbiota composition between cancer and non-cancerous patients, as well as infected and uninfected individuals. Although the reasons underlying differences in microbial community structures are not entirely understood, gastric atrophy and hypochlorhydria that accompany chronic Hp infection may be a critical driver of gastric dysbiosis that promote colonization of microbes that contribute to increased risk of malignancy. Defining the importance and role of the gastric microbiota as a potential risk factor for Hp-associated gastric cancer is a vital and exciting area of current research.
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Affiliation(s)
- Ami Y. Seeger
- Department of Microbiology, School of Molecular and Cellular Biology, College of Liberal Arts and Sciences, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801
| | - Megan D. Ringling
- Department of Microbiology, School of Molecular and Cellular Biology, College of Liberal Arts and Sciences, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801
| | - Huzaifa Zohair
- Department of Microbiology, School of Molecular and Cellular Biology, College of Liberal Arts and Sciences, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801
| | - Steven R. Blanke
- Department of Microbiology, School of Molecular and Cellular Biology, College of Liberal Arts and Sciences, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801
- Biomedical and Translational Sciences Department, Carle Illinois College of Medicine, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801
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23
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Liu X, Zhang K, Liu Y, Xie Z, Zhang C. Oxalic Acid From Sesbania rostrata Seed Exudates Mediates the Chemotactic Response of Azorhizobium caulinodans ORS571 Using Multiple Strategies. Front Microbiol 2019; 10:2727. [PMID: 31849879 PMCID: PMC6901664 DOI: 10.3389/fmicb.2019.02727] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 11/08/2019] [Indexed: 12/14/2022] Open
Abstract
Chemotaxis toward seed exudates is important in the establishment of microbe-plant associations. The objective of this work was to explore whether organic acids from the seed exudates of Sesbania rostrata play a role in recruiting Azorhizobium caulinodans ORS571 in the plant rhizosphere. High-performance liquid chromatography (HPLC) was used to analyze the organic acid content in seed exudates of S. rostrata and to further determine their roles in A. caulinodans growth and chemotactic response. Succinic, acetic, citric, oxalic, and lactic acids were the most abundant, and, except for oxalic acid, they could support A. caulinodans growth as the sole carbon source. TlpA1, a transmembrane chemoreceptor, was found to be involved in the chemotactic response to these organic acids. Oxalic acid played a direct role in the chemotactic response, but it also played an indirect role by promoting or inhibiting the chemotactic response toward other chemoeffectors. Furthermore, the indirect role of oxalic acid on other chemoeffectors was concentration-dependent. The effect of oxalic acid at different concentrations on host root colonization was also determined. By using different strategies, oxalic acid appears to play a major role in the early steps of the association of A. caulinodans and its host plant.
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Affiliation(s)
- Xiaolin Liu
- Key Laboratory of Coastal Biology and Bioresource Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Kaiye Zhang
- Key Laboratory of Coastal Biology and Bioresource Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China
- College of Agriculture, Shanxi Agricultural University, Taigu, China
| | - Yanan Liu
- Key Laboratory of Coastal Biology and Bioresource Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Zhihong Xie
- Key Laboratory of Coastal Biology and Bioresource Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China
- Center for Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
| | - Chengsheng Zhang
- Marine Agriculture Research Center, Tobacco Research Institute of Chinese Academy of Agricultural Sciences, Qingdao, China
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