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Awad K, Barmeyer C, Bojarski C, Nagel O, Lee IFM, Schweiger MR, Schulzke JD, Bücker R. Epithelial Barrier Dysfunction in Diarrhea-Predominant Irritable Bowel Syndrome (IBS-D) via Downregulation of Claudin-1. Cells 2023; 12:2846. [PMID: 38132165 PMCID: PMC10741936 DOI: 10.3390/cells12242846] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 12/05/2023] [Accepted: 12/07/2023] [Indexed: 12/23/2023] Open
Abstract
BACKGROUND In patients with diarrhea-predominant irritable bowel syndrome (IBS-D), the diarrheal mechanisms are largely unknown, and they were examined in this study on colon biopsies. METHODS Electrophysiological measurements were used for monitoring functional changes in the diarrheic colon specimens. In parallel, tight junction protein expression was analyzed by Western blot and confocal laser-scanning microscopy, and signaling pathway analysis was performed using RNA sequencing and bioinformatics. RESULTS Epithelial resistance was decreased, indicating an epithelial leak flux diarrheal mechanism with a molecular correlate of decreased claudin-1 expression, while induction of active anion secretion and impairment of active sodium absorption via the epithelial sodium channel, ENaC, were not detected. The pathway analysis revealed activation of barrier-affecting cytokines TNF-α, IFN-γ, IL-1β and IL-4. CONCLUSIONS Barrier dysfunction as a result of epithelial tight junction changes plays a role in IBS-D as a pathomechanism inducing a leak flux type of diarrhea.
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Affiliation(s)
- Karem Awad
- Clinical Physiology/Nutritional Medicine, Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany (O.N.)
| | - Christian Barmeyer
- Clinical Physiology/Nutritional Medicine, Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany (O.N.)
| | - Christian Bojarski
- Clinical Physiology/Nutritional Medicine, Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany (O.N.)
| | - Oliver Nagel
- Clinical Physiology/Nutritional Medicine, Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany (O.N.)
| | - In-Fah M. Lee
- Clinical Physiology/Nutritional Medicine, Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany (O.N.)
| | - Michal R. Schweiger
- Institute for Translational Epigenetics, Medical Faculty, University of Cologne, 50931 Cologne, Germany
| | - Jörg-Dieter Schulzke
- Clinical Physiology/Nutritional Medicine, Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany (O.N.)
| | - Roland Bücker
- Clinical Physiology/Nutritional Medicine, Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany (O.N.)
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2
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Hader H, Hering NA, Schulzke JD, Bücker R, Rosenthal R. Myrrh protects against IL-13-induced epithelial barrier breakdown in HT-29/B6 cells. Front Pharmacol 2023; 14:1301800. [PMID: 38044939 PMCID: PMC10691275 DOI: 10.3389/fphar.2023.1301800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 11/03/2023] [Indexed: 12/05/2023] Open
Abstract
The oleoresin myrrh has been used for centuries as an anti-inflammatory remedy for a variety of diseases and is said to have a protective effect on the intestinal epithelium. An intact epithelial barrier function is the prerequisite for a healthy gut. Inflammatory and infectious diseases of the intestine, in particular, lead to barrier impairment resulting in leak-flux diarrhea and mucosal immune responses. Therefore, the aim of the present study was to investigate the protective effect of myrrh in an experimental inflammatory situation, namely, under the influence of IL-13, one of the key cytokines in ulcerative colitis. We used human intestinal epithelial HT-29/B6 cell monolayers for functional and molecular assessment of the epithelial barrier under IL-13 and myrrh treatment. IL-13 induced a loss in barrier function that was fully restored with myrrh treatment, as shown by transepithelial electrical resistance measurements. The molecular correlate of the IL-13-mediated barrier dysfunction could be assigned to an upregulation of the channel-forming tight junction (TJ) protein claudin-2 and to a subcellular redistribution of the TJ protein tricellulin, loosening the sealing of tricellular TJs. Moreover, IL-13 exposure leads to an increase in the number of apoptotic cells, contributing to the leak pathway of barrier dysfunction. Myrrh protected against changes in TJ deregulation and decreased the elevated apoptotic ratio under IL-13. The protective effects are mediated through the inhibition of the STAT3 and STAT6 pathway. In conclusion, our results demonstrate that myrrh exhibits antagonizing effects against IL-13-induced barrier impairment in a human intestinal cell model. These data suggest the use of myrrh as a promising option in the treatment of inflammatory bowel disease.
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Affiliation(s)
- Helena Hader
- Department of Gastroenterology, Rheumatology and Infectious Diseases, Clinical Physiology/Nutritional Medicine, Charité—Universitätsmedizin Berlin, Berlin, Germany
| | - Nina A. Hering
- Department of General and Visceral Surgery, Charité—Universitätsmedizin Berlin, Berlin, Germany
| | - Jörg-Dieter Schulzke
- Department of Gastroenterology, Rheumatology and Infectious Diseases, Clinical Physiology/Nutritional Medicine, Charité—Universitätsmedizin Berlin, Berlin, Germany
| | - Roland Bücker
- Department of Gastroenterology, Rheumatology and Infectious Diseases, Clinical Physiology/Nutritional Medicine, Charité—Universitätsmedizin Berlin, Berlin, Germany
| | - Rita Rosenthal
- Department of Gastroenterology, Rheumatology and Infectious Diseases, Clinical Physiology/Nutritional Medicine, Charité—Universitätsmedizin Berlin, Berlin, Germany
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3
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Schneemann M, Heils L, Moos V, Weiß F, Krug SM, Weiner J, Beule D, Gerhard R, Schulzke JD, Bücker R. A Colonic Organoid Model Challenged with the Large Toxins of Clostridioides difficile TcdA and TcdB Exhibit Deregulated Tight Junction Proteins. Toxins (Basel) 2023; 15:643. [PMID: 37999506 PMCID: PMC10674794 DOI: 10.3390/toxins15110643] [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] [Received: 10/05/2023] [Revised: 10/25/2023] [Accepted: 11/01/2023] [Indexed: 11/25/2023] Open
Abstract
BACKGROUND Clostridioides difficile toxins TcdA and TcdB are responsible for diarrhea and colitis. Lack of functional studies in organoid models of the gut prompted us to elucidate the toxin's effects on epithelial barrier function and the molecular mechanisms for diarrhea and inflammation. METHODS Human adult colon organoids were cultured on membrane inserts. Tight junction (TJ) proteins and actin cytoskeleton were analyzed for expression via Western blotting and via confocal laser-scanning microscopy for subcellular localization. RESULTS Polarized intestinal organoid monolayers were established from stem cell-containing colon organoids to apply toxins from the apical side and to perform functional measurements in the organoid model. The toxins caused a reduction in transepithelial electrical resistance in human colonic organoid monolayers with sublethal concentrations. Concomitantly, we detected increased paracellular permeability fluorescein and FITC-dextran-4000. Human colonic organoid monolayers exposed to the toxins exhibited redistribution of barrier-forming TJ proteins claudin-1, -4 and tricellulin, whereas channel-forming claudin-2 expression was increased. Perijunctional F-actin cytoskeleton organization was affected. CONCLUSIONS Adult stem cell-derived human colonic organoid monolayers were applicable as a colon infection model for electrophysiological measurements. The TJ changes noted can explain the epithelial barrier dysfunction and diarrhea in patients, as well as increased entry of luminal antigens triggering inflammation.
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Affiliation(s)
- Martina Schneemann
- Clinical Physiology, Nutritional Medicine, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany
| | - Lucas Heils
- Clinical Physiology, Nutritional Medicine, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany
| | - Verena Moos
- Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany
| | - Franziska Weiß
- Clinical Physiology, Nutritional Medicine, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany
| | - Susanne M. Krug
- Clinical Physiology, Nutritional Medicine, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany
| | - January Weiner
- Core Unit Bioinformatics (CUBI), Berlin Institute of Health at Charité—Universitätsmedizin Berlin, 10117 Berlin, Germany
| | - Dieter Beule
- Core Unit Bioinformatics (CUBI), Berlin Institute of Health at Charité—Universitätsmedizin Berlin, 10117 Berlin, Germany
| | - Ralf Gerhard
- Institute of Toxicology, Hannover Medical School, 30625 Hannover, Germany
| | - Jörg-Dieter Schulzke
- Clinical Physiology, Nutritional Medicine, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany
| | - Roland Bücker
- Clinical Physiology, Nutritional Medicine, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany
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4
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Chaukimath P, Frankel G, Visweswariah SS. The metabolic impact of bacterial infection in the gut. FEBS J 2023; 290:3928-3945. [PMID: 35731686 DOI: 10.1111/febs.16562] [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: 11/11/2021] [Revised: 06/02/2022] [Accepted: 06/21/2022] [Indexed: 08/17/2023]
Abstract
Bacterial infections of the gut are one of the major causes of morbidity and mortality worldwide. The interplay between the pathogen and the host is finely balanced, with the bacteria evolving to proliferate and establish infection. In contrast, the host mounts a response to first restrict and then eliminate the infection. The intestine is a rapidly proliferating tissue, and metabolism is tuned to cater to the demands of proliferation and differentiation along the crypt-villus axis (CVA) in the gut. As bacterial pathogens encounter the intestinal epithelium, they elicit changes in the host cell, and core metabolic pathways such as the tricarboxylic acid (TCA) cycle, lipid metabolism and glycolysis are affected. This review highlights the mechanisms utilized by diverse gut bacterial pathogens to subvert host metabolism and describes host responses to the infection.
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Affiliation(s)
- Pooja Chaukimath
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, India
| | - Gad Frankel
- Centre for Molecular Bacteriology and Infection and Department of Life Sciences, Imperial College, London, UK
| | - Sandhya S Visweswariah
- Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, India
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5
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Chen Y, Yu X, Yan Z, Zhang S, Zhang J, Guo W. Role of epithelial sodium channel-related inflammation in human diseases. Front Immunol 2023; 14:1178410. [PMID: 37559717 PMCID: PMC10407551 DOI: 10.3389/fimmu.2023.1178410] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 06/29/2023] [Indexed: 08/11/2023] Open
Abstract
The epithelial sodium channel (ENaC) is a heterotrimer and is widely distributed throughout the kidneys, blood vessels, lungs, colons, and many other organs. The basic role of the ENaC is to mediate the entry of Na+ into cells; the ENaC also has an important regulatory function in blood pressure, airway surface liquid (ASL), and endothelial cell function. Aldosterone, serum/glucocorticoid kinase 1 (SGK1), shear stress, and posttranslational modifications can regulate the activity of the ENaC; some ion channels also interact with the ENaC. In recent years, it has been found that the ENaC can lead to immune cell activation, endothelial cell dysfunction, aggravated inflammation involved in high salt-induced hypertension, cystic fibrosis, pseudohypoaldosteronism (PHA), and tumors; some inflammatory cytokines have been reported to have a regulatory role on the ENaC. The ENaC hyperfunction mediates the increase of intracellular Na+, and the elevated exchange of Na+ with Ca2+ leads to an intracellular calcium overload, which is an important mechanism for ENaC-related inflammation. Some of the research on the ENaC is controversial or unclear; we therefore reviewed the progress of studies on the role of ENaC-related inflammation in human diseases and their mechanisms.
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Affiliation(s)
- Yabin Chen
- Department of Hepatobiliary and Pancreatic Surgery, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
- National Organ Transplantation (Liver &Kidney Transplantation) Physician Training Centre, Zhengzhou, China
- National Regional Medical Treatment Centre of Henan Organ Transplantation, Zhengzhou, China
| | - Xiao Yu
- Department of Hepatobiliary and Pancreatic Surgery, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
- National Organ Transplantation (Liver &Kidney Transplantation) Physician Training Centre, Zhengzhou, China
- National Regional Medical Treatment Centre of Henan Organ Transplantation, Zhengzhou, China
| | - Zhiping Yan
- Henan Organ Transplantation Centre, Zhengzhou, China
- Henan Engineering and Research Center for Diagnosis and Treatment of Hepatobiliary and Pancreatic Surgical Diseases, Zhengzhou, China
| | - Shuijun Zhang
- Henan Research Centre for Organ Transplantation, Zhengzhou, China
| | - Jiacheng Zhang
- Henan Key Laboratory for Digestive Organ Transplantation, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Wenzhi Guo
- Department of Hepatobiliary and Pancreatic Surgery, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
- Open and Key Laboratory for Hepatobiliary and Pancreatic Surgery and Digestive Organ Transplantation at Henan Universities, Zhengzhou, China
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6
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Kato I, Minkevitch J, Sun J. Oncogenic potential of Campylobacter infection in the gastrointestinal tract: narrative review. Scand J Gastroenterol 2023; 58:1453-1465. [PMID: 37366241 DOI: 10.1080/00365521.2023.2228954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 05/26/2023] [Accepted: 06/16/2023] [Indexed: 06/28/2023]
Abstract
BACKGROUND Campylobacter jejuni is the leading cause of zoonotic gastroenteritis. The other emerging group of Campylobacters spp. are part of human oral commensal, represented by C. concisus (CC), which has been recently linked to non-oral conditions. Although long-term gastrointestinal (GI) complications from these two groups of Campylobacters have been previously reviewed individually, overall impact of Campylobacter infection on GI carcinogenesis and their inflammatory precursor lesions has not been assessed collectively. AIMS To evaluate the available evidence concerning the association between Campylobacter infection/colonization and inflammatory bowel disease (IBD), reflux esophagitis/metaplasia colorectal cancer (CRC) and esophageal cancer (EC). METHODS We performed a comprehensive literature search of PubMed for relevant original publications and systematic reviews/meta-analyses of epidemiological and clinical studies. In addition, we gathered additional information concerning microbiological data, animal models and mechanistic data from in vitro studies. RESULTS Both retrospective and prospective studies on IBD showed relatively consistent increased risk associated with Campylobacter infection. Despite lack of supporting prospective studies, retrospective studies based on tissue/fecal microbiome revealed consistent enrichment of Campylobacter in CRC samples. Studies on EC precursor lesions (esophagitis and metaplasia) were generally supportive for the association with Campylobacter, while inconsistent observations on EC. Studies on both IBD and EC precursors suggested the predominant role of CC, but studies on CRC were not informative of species. CONCLUSIONS There is sufficient evidence calling for concerted effort in unveiling direct and indirect connection of this organism to colorectal and esophageal cancer in humans.
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Affiliation(s)
- Ikuko Kato
- Department of Oncology and Pathology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Julia Minkevitch
- Rosalind Franklin University of Medicine and Science, Chicago, IL, USA
| | - Jun Sun
- Department of Microbiology/Immunology, University of Illinois at Chicago (UIC), Chicago, IL, USA
- UIC Cancer Center, Chicago, IL, USA
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7
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Therapeutic Oral Application of Carvacrol Alleviates Acute Campylobacteriosis in Mice Harboring a Human Gut Microbiota. Biomolecules 2023; 13:biom13020320. [PMID: 36830689 PMCID: PMC9953218 DOI: 10.3390/biom13020320] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/05/2023] [Accepted: 02/06/2023] [Indexed: 02/11/2023] Open
Abstract
Human Campylobacter jejuni infections are rising globally. Since antibiotics are usually not indicated in acute campylobacteriosis, antibiotic-independent intervention measures are desirable. The phenolic compound carvacrol constitutes a promising candidate molecule given its antimicrobial and immune-modulatory features. To test the disease-alleviating effects of oral carvacrol treatment in acute murine campylobacteriosis, IL-10-/- mice harboring a human gut microbiota were perorally infected with C. jejuni and treated with carvacrol via the drinking water. Whereas C. jejuni stably established in the gastrointestinal tract of mice from the placebo cohort, carvacrol treatment resulted in lower pathogen loads in the small intestines on day 6 post infection. When compared to placebo, carvacrol ameliorated pathogen-induced symptoms including bloody diarrhea that was accompanied by less distinct histopathological and apoptotic cell responses in the colon. Furthermore, innate and adaptive immune cell numbers were lower in the colon of carvacrol- versus placebo-treated mice. Notably, carvacrol application dampened C. jejuni-induced secretion of pro-inflammatory mediators in intestinal, extra-intestinal and systemic organs to naive levels and furthermore, resulted in distinct shifts in the fecal microbiota composition. In conclusion, our preclinical placebo-controlled intervention study provides evidence that therapeutic carvacrol application constitutes a promising option to alleviate campylobacteriosis in the infected vertebrate host.
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Awad K, Barmeyer C, Bojarski C, Nagel O, Lee IFM, Schweiger MR, Schulzke JD, Bücker R. Impaired Intestinal Permeability of Tricellular Tight Junctions in Patients with Irritable Bowel Syndrome with Mixed Bowel Habits (IBS-M). Cells 2023; 12:236. [PMID: 36672170 PMCID: PMC9856377 DOI: 10.3390/cells12020236] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 12/27/2022] [Accepted: 01/03/2023] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND The underlying pathophysiology of irritable bowel syndrome (IBS) is still unclear. Our aim was to investigate the pathophysiological mechanisms of diarrhea, constipation, and antigen uptake in mixed-type IBS (IBS-M). METHODS Colonoscopic biopsies were obtained from IBS-M patients. Epithelial transport and barrier function of colonic mucosae were characterized in Ussing chambers using impedance spectroscopy. Mucosal permeability to macromolecules was measured. Western blotting for tight junction (TJ) proteins was performed and their subcellular localization was visualized by confocal microscopy. RNA-sequencing was performed for gene expression and signaling pathway analysis. RESULTS In IBS-M, epithelial resistance and ENaC-dependent sodium absorption were unchanged, while short-circuit current reflecting chloride secretion was reduced. Concomitantly, epithelial permeability for fluorescein and FITC-dextran-4000 increased. TJ protein expression of occludin decreased, whereas claudins were unaltered. Confocal microscopy revealed the de-localization of tricellulin from tricellular TJs. Involved pathways were detected as proinflammatory cytokine pathways, LPS, PGE2, NGF, and vitamin D. CONCLUSIONS Decreased anion secretion explains constipation in IBS-M, while ion permeability and sodium absorption were unaltered. Reduced occludin expression resulted in the delocalization of tricellulin from the tricellular TJ, leading to increased macromolecular permeability that contributes to antigen influx into the mucosa and perpetuates a low-grade inflammatory process.
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Affiliation(s)
- Karem Awad
- Clinical Physiology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany
| | - Christian Barmeyer
- Clinical Physiology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany
| | - Christian Bojarski
- Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany
| | - Oliver Nagel
- Clinical Physiology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany
| | - In-Fah M. Lee
- Clinical Physiology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany
| | - Michal R. Schweiger
- Institute for Translational Epigenetics, Medical Faculty, University of Cologne, 50931 Cologne, Germany
| | - Jörg-Dieter Schulzke
- Clinical Physiology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany
- Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany
| | - Roland Bücker
- Clinical Physiology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 12203 Berlin, Germany
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Herzog MKM, Cazzaniga M, Peters A, Shayya N, Beldi L, Hapfelmeier S, Heimesaat MM, Bereswill S, Frankel G, Gahan CG, Hardt WD. Mouse models for bacterial enteropathogen infections: insights into the role of colonization resistance. Gut Microbes 2023; 15:2172667. [PMID: 36794831 PMCID: PMC9980611 DOI: 10.1080/19490976.2023.2172667] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 01/18/2023] [Indexed: 02/17/2023] Open
Abstract
Globally, enteropathogenic bacteria are a major cause of morbidity and mortality.1-3 Campylobacter, Salmonella, Shiga-toxin-producing Escherichia coli, and Listeria are among the top five most commonly reported zoonotic pathogens in the European Union.4 However, not all individuals naturally exposed to enteropathogens go on to develop disease. This protection is attributable to colonization resistance (CR) conferred by the gut microbiota, as well as an array of physical, chemical, and immunological barriers that limit infection. Despite their importance for human health, a detailed understanding of gastrointestinal barriers to infection is lacking, and further research is required to investigate the mechanisms that underpin inter-individual differences in resistance to gastrointestinal infection. Here, we discuss the current mouse models available to study infections by non-typhoidal Salmonella strains, Citrobacter rodentium (as a model for enteropathogenic and enterohemorrhagic E. coli), Listeria monocytogenes, and Campylobacter jejuni. Clostridioides difficile is included as another important cause of enteric disease in which resistance is dependent upon CR. We outline which parameters of human infection are recapitulated in these mouse models, including the impact of CR, disease pathology, disease progression, and mucosal immune response. This will showcase common virulence strategies, highlight mechanistic differences, and help researchers from microbiology, infectiology, microbiome research, and mucosal immunology to select the optimal mouse model.
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Affiliation(s)
- Mathias K.-M. Herzog
- Department of Biology, Institute of Microbiology, ETH Zurich, Zurich, Switzerland
| | - Monica Cazzaniga
- APC Microbiome Ireland, University College Cork, Cork, Ireland
- School of Microbiology, University College Cork, Cork, Ireland
| | - Audrey Peters
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
| | - Nizar Shayya
- Institute of Microbiology, Infectious Diseases and Immunology, Charité - University Medicine Berlin, Berlin, Germany
| | - Luca Beldi
- Institute for Infectious Diseases, University of Bern, Bern, Switzerland
| | | | - Markus M. Heimesaat
- Institute of Microbiology, Infectious Diseases and Immunology, Charité - University Medicine Berlin, Berlin, Germany
| | - Stefan Bereswill
- Institute of Microbiology, Infectious Diseases and Immunology, Charité - University Medicine Berlin, Berlin, Germany
| | - Gad Frankel
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
| | - Cormac G.M. Gahan
- APC Microbiome Ireland, University College Cork, Cork, Ireland
- School of Microbiology, University College Cork, Cork, Ireland
- School of Pharmacy, University College Cork, Cork, Ireland
| | - Wolf-Dietrich Hardt
- Department of Biology, Institute of Microbiology, ETH Zurich, Zurich, Switzerland
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Du K, Foote MS, Mousavi S, Buczkowski A, Schmidt S, Bereswill S, Heimesaat MM. Less Pronounced Immunopathological Responses Following Oral Butyrate Treatment of Campylobacter jejuni-Infected Mice. Microorganisms 2022; 10:1953. [PMID: 36296229 PMCID: PMC9609162 DOI: 10.3390/microorganisms10101953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 09/23/2022] [Accepted: 09/29/2022] [Indexed: 11/05/2022] Open
Abstract
Given that human Campylobacter jejuni infections are rising globally and antibiotic treatment is not recommended, infected patients would substantially benefit from alternative therapeutic strategies. Short-chain fatty acids such as butyrate are known for their health benefits, including anti-microbial and anti-inflammatory effects. This prompted us to investigate potential disease-alleviating properties of butyrate treatment during acute murine C. jejuni-induced enterocolitis. Therefore, following gut microbiota depletion IL-10-/- mice were challenged with 109 viable C. jejuni cells by oral gavage and treated with butyrate via the drinking water (22 g/L) starting on day 2 post-infection. As early as day 3 post-infection, butyrate reduced diarrheal severity and frequency in treated mice, whereas on day 6 post-infection, gastrointestinal C. jejuni burdens and the overall clinical outcomes were comparable in butyrate- and placebo-treated cohorts. Most importantly, butyrate treatment dampened intestinal pro-inflammatory immune responses given lower colonic numbers of apoptotic cells and neutrophils, less distinct TNF-α secretion in mesenteric lymph nodes and lower IL-6 and MCP-1 concentrations in the ileum. In conclusion, results of our preclinical intervention study provide evidence that butyrate represents a promising candidate molecule for the treatment of acute campylobacteriosis.
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Affiliation(s)
- Ke Du
- Gastrointestinal Microbiology Research Group, Institute of Microbiology, Infectious Diseases and Immunology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin and Berlin Institute of Health, 12203 Berlin, Germany
| | - Minnja S. Foote
- Gastrointestinal Microbiology Research Group, Institute of Microbiology, Infectious Diseases and Immunology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin and Berlin Institute of Health, 12203 Berlin, Germany
| | - Soraya Mousavi
- Gastrointestinal Microbiology Research Group, Institute of Microbiology, Infectious Diseases and Immunology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin and Berlin Institute of Health, 12203 Berlin, Germany
| | - Agnes Buczkowski
- Gastrointestinal Microbiology Research Group, Institute of Microbiology, Infectious Diseases and Immunology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin and Berlin Institute of Health, 12203 Berlin, Germany
- Hofmann & Sommer GmbH und Co., KG, Büro Berlin, 12489 Berlin, Germany
| | - Sebastian Schmidt
- Gastrointestinal Microbiology Research Group, Institute of Microbiology, Infectious Diseases and Immunology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin and Berlin Institute of Health, 12203 Berlin, Germany
- Hofmann & Sommer GmbH und Co., KG, Büro Berlin, 12489 Berlin, Germany
| | - Stefan Bereswill
- Gastrointestinal Microbiology Research Group, Institute of Microbiology, Infectious Diseases and Immunology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin and Berlin Institute of Health, 12203 Berlin, Germany
| | - Markus M. Heimesaat
- Gastrointestinal Microbiology Research Group, Institute of Microbiology, Infectious Diseases and Immunology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin and Berlin Institute of Health, 12203 Berlin, Germany
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Ma L, Feng J, Zhang J, Lu X. Campylobacter biofilms. Microbiol Res 2022; 264:127149. [DOI: 10.1016/j.micres.2022.127149] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 07/26/2022] [Accepted: 07/26/2022] [Indexed: 11/27/2022]
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12
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Wang Y, Hong C, Wu Z, Li S, Xia Y, Liang Y, He X, Xiao X, Tang W. Resveratrol in Intestinal Health and Disease: Focusing on Intestinal Barrier. Front Nutr 2022; 9:848400. [PMID: 35369090 PMCID: PMC8966610 DOI: 10.3389/fnut.2022.848400] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Accepted: 02/07/2022] [Indexed: 12/14/2022] Open
Abstract
The integrity of intestinal barrier determines intestinal homeostasis, which could be affected by various factors, like physical, chemical, and biological stimuli. Therefore, it is of considerable interest and importance to maintain intestinal barrier function. Fortunately, many plant polyphenols, including resveratrol, could affect the health of intestinal barrier. Resveratrol has many biological functions, such as antioxidant, anti-inflammation, anti-tumor, and anti-cardiovascular diseases. Accumulating studies have shown that resveratrol affects intestinal tight junction, microbial composition, and inflammation. In this review, we summarize the effects of resveratrol on intestinal barriers as well as the potential mechanisms (e.g., inhibiting the growth of pathogenic bacteria and fungi, regulating the expression of tight junction proteins, and increasing anti-inflammatory T cells while reducing pro-inflammatory T cells), and highlight the applications of resveratrol in ameliorating various intestinal diseases.
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Affiliation(s)
- Youxia Wang
- College of Animal Science, South China Agricultural University, Guangzhou, China
| | - Changming Hong
- College of Animal Science, South China Agricultural University, Guangzhou, China
| | - Zebiao Wu
- College of Animal Science, South China Agricultural University, Guangzhou, China
| | - Shuwei Li
- Animal Breeding and Genetics Key Laboratory of Sichuan Province, Sichuan Animal Science Academy, Chengdu, China
- Livestock and Poultry Biological Products Key Laboratory of Sichuan Province, Sichuan Animtech Feed Co., Ltd., Chengdu, China
| | - Yaoyao Xia
- College of Animal Science, South China Agricultural University, Guangzhou, China
| | - Yuying Liang
- College of Animal Science, South China Agricultural University, Guangzhou, China
| | - Xiaohua He
- College of Animal Science, South China Agricultural University, Guangzhou, China
| | - Xinyu Xiao
- College of Animal Science, South China Agricultural University, Guangzhou, China
| | - Wenjie Tang
- Animal Breeding and Genetics Key Laboratory of Sichuan Province, Sichuan Animal Science Academy, Chengdu, China
- Livestock and Poultry Biological Products Key Laboratory of Sichuan Province, Sichuan Animtech Feed Co., Ltd., Chengdu, China
- *Correspondence: Wenjie Tang
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13
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Micronutrient Improvement of Epithelial Barrier Function in Various Disease States: A Case for Adjuvant Therapy. Int J Mol Sci 2022; 23:ijms23062995. [PMID: 35328419 PMCID: PMC8951934 DOI: 10.3390/ijms23062995] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 03/01/2022] [Indexed: 02/04/2023] Open
Abstract
The published literature makes a very strong case that a wide range of disease morbidity associates with and may in part be due to epithelial barrier leak. An equally large body of published literature substantiates that a diverse group of micronutrients can reduce barrier leak across a wide array of epithelial tissue types, stemming from both cell culture as well as animal and human tissue models. Conversely, micronutrient deficiencies can exacerbate both barrier leak and morbidity. Focusing on zinc, Vitamin A and Vitamin D, this review shows that at concentrations above RDA levels but well below toxicity limits, these micronutrients can induce cell- and tissue-specific molecular-level changes in tight junctional complexes (and by other mechanisms) that reduce barrier leak. An opportunity now exists in critical care—but also medical prophylactic and therapeutic care in general—to consider implementation of select micronutrients at elevated dosages as adjuvant therapeutics in a variety of disease management. This consideration is particularly pointed amidst the COVID-19 pandemic.
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14
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OUP accepted manuscript. Pathog Dis 2022; 80:6521441. [DOI: 10.1093/femspd/ftac003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 10/30/2021] [Accepted: 02/01/2022] [Indexed: 11/15/2022] Open
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15
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Painong San, a Traditional Chinese Compound Herbal Medicine, Restores Colon Barrier Function on DSS-Induced Colitis in Mice. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2021; 2021:2810915. [PMID: 34966434 PMCID: PMC8712168 DOI: 10.1155/2021/2810915] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 10/10/2021] [Accepted: 12/01/2021] [Indexed: 12/17/2022]
Abstract
Objective The intestinal barrier decreases in colitis and restores the integrity of the mucosal barriers that could be used for the treatment of colitis. Painong San (PNS), a traditional Chinese compound herbal medicine originally recorded in “Jingui Yaolve” by Zhongjing Zhang in the Later Han Dynasty, is often used in China and Japan to treat various purulent diseases including intestinal carbuncle. This study was to investigate the effect of PNS on mucosal barrier function in mice with DSS-induced colitis and its related mechanisms. Methods BALB/C mice were given 3% DSS to induce colitis. The body weight and stool status of the mice were recorded daily, and the histopathological changes of the colon were observed after execution. The permeability of the intestinal mucosa was measured by fluorescein isothiocyanate-dextran 4000, the change of intestinal microbiota was measured by 16S rDNA, and the tight junction-related proteins and Muc-2 were investigated by immunohistochemical or immunofluorescence. The possible signaling pathways were detected by western blot. Results Compared with the control group, the composition of the microbiota in the PNS group was close to that of the normal group, the number of goblet cells was improved, and the mucosal permeability was significantly reduced. PNS could upregulate the expression of tight junction-related proteins (ZO-1, claudin-1, and occludin) and Muc-2, and at the same time, regulate the Notch pathway. Conclusion PNS could effectively improve the mucosal barrier function through multiple ways, including restoring the balance of intestine flora, enhancement of the mucous layer barrier, and mechanical barrier function. These protective effects may relate to inhibiting the Notch signaling pathway activated by DSS.
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16
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Criss ZK, Bhasin N, Di Rienzi SC, Rajan A, Deans-Fielder K, Swaminathan G, Kamyabi N, Zeng XL, Doddapaneni H, Menon VK, Chakravarti D, Estrella C, Yu X, Patil K, Petrosino JF, Fleet JC, Verzi MP, Christakos S, Helmrath MA, Arimura S, DePinho RA, Britton RA, Maresso AW, Grande-Allen KJ, Blutt SE, Crawford SE, Estes MK, Ramani S, Shroyer NF. Drivers of transcriptional variance in human intestinal epithelial organoids. Physiol Genomics 2021; 53:486-508. [PMID: 34612061 DOI: 10.1152/physiolgenomics.00061.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Human intestinal epithelial organoids (enteroids and colonoids) are tissue cultures used for understanding the physiology of the human intestinal epithelium. Here, we explored the effect on the transcriptome of common variations in culture methods, including extracellular matrix substrate, format, tissue segment, differentiation status, and patient heterogeneity. RNA-sequencing datasets from 276 experiments performed on 37 human enteroid and colonoid lines from 29 patients were aggregated from several groups in the Texas Medical Center. DESeq2 and gene set enrichment analysis (GSEA) were used to identify differentially expressed genes and enriched pathways. PERMANOVA, Pearson's correlation, and dendrogram analysis of the data originally indicated three tiers of influence of culture methods on transcriptomic variation: substrate (collagen vs. Matrigel) and format (3-D, transwell, and monolayer) had the largest effect; segment of origin (duodenum, jejunum, ileum, colon) and differentiation status had a moderate effect; and patient heterogeneity and specific experimental manipulations (e.g., pathogen infection) had the smallest effect. GSEA identified hundreds of pathways that varied between culture methods, such as IL1 cytokine signaling enriched in transwell versus monolayer cultures and E2F target genes enriched in collagen versus Matrigel cultures. The transcriptional influence of the format was furthermore validated in a synchronized experiment performed with various format-substrate combinations. Surprisingly, large differences in organoid transcriptome were driven by variations in culture methods such as format, whereas experimental manipulations such as infection had modest effects. These results show that common variations in culture conditions can have large effects on intestinal organoids and should be accounted for when designing experiments and comparing results between laboratories. Our data constitute the largest RNA-seq dataset interrogating human intestinal epithelial organoids.
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Affiliation(s)
- Zachary K Criss
- Section of Gastroenterology and Hepatology, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Nobel Bhasin
- Section of Gastroenterology and Hepatology, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Sara C Di Rienzi
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Anubama Rajan
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Kali Deans-Fielder
- Section of Gastroenterology and Hepatology, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | | | | | - Xi-Lei Zeng
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Harsha Doddapaneni
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas
| | - Vipin K Menon
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas
| | - Deepavali Chakravarti
- Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Clarissa Estrella
- Section of Gastroenterology and Hepatology, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Xiaomin Yu
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Ketki Patil
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Joseph F Petrosino
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - James C Fleet
- Department of Nutrition Sciences, The University of Texas, Austin, Texas
| | - Michael P Verzi
- Department of Genetics, Rutgers University, Piscataway, New Jersey
| | - Sylvia Christakos
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers-New Jersey Medical School, Newark, New Jersey
| | - Michael A Helmrath
- Department of Pediatric General and Thoracic Surgery, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Sumimasa Arimura
- Section of Gastroenterology and Hepatology, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Ronald A DePinho
- Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Robert A Britton
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Anthony W Maresso
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | | | - Sarah E Blutt
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Sue E Crawford
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Mary K Estes
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Sasirekha Ramani
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas
| | - Noah F Shroyer
- Section of Gastroenterology and Hepatology, Department of Medicine, Baylor College of Medicine, Houston, Texas
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Abundant Monovalent Ions as Environmental Signposts for Pathogens during Host Colonization. Infect Immun 2021; 89:IAI.00641-20. [PMID: 33526568 DOI: 10.1128/iai.00641-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Host colonization by a pathogen requires proper sensing and response to local environmental cues, to ensure adaptation and continued survival within the host. The ionic milieu represents a critical potential source of environmental cues, and indeed, there has been extensive study of the interplay between host and pathogen in the context of metals such as iron, zinc, and manganese, vital ions that are actively sequestered by the host. The inherent non-uniformity of the ionic milieu also extends, however, to "abundant" ions such as chloride and potassium, whose concentrations vary greatly between tissue and cellular locations, and with the immune response. Despite this, the concept of abundant ions as environmental cues and key players in host-pathogen interactions is only just emerging. Focusing on chloride and potassium, this review brings together studies across multiple bacterial and parasitic species that have begun to define both how these abundant ions are exploited as cues during host infection, and how they can be actively manipulated by pathogens during host colonization. The close links between ion homeostasis and sensing/response to different ionic signals, and the importance of studying pathogen response to cues in combination, are also discussed, while considering the fundamental insight still to be uncovered from further studies in this nascent area of inquiry.
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Lobo de Sá FD, Schulzke JD, Bücker R. Diarrheal Mechanisms and the Role of Intestinal Barrier Dysfunction in Campylobacter Infections. Curr Top Microbiol Immunol 2021; 431:203-231. [PMID: 33620653 DOI: 10.1007/978-3-030-65481-8_8] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Campylobacter enteritis is the most common cause of foodborne bacterial diarrhea in humans. Although various studies have been performed to clarify the pathomechanism in Campylobacter infection, the mechanism itself and bacterial virulence factors are yet not completely understood. The purpose of this chapter is to (i) give an overview on Campylobacter-induced diarrheal mechanisms, (ii) illustrate underlying barrier defects, (iii) explain the role of the mucosal immune response and (iv) weigh preventive and therapeutic approaches. Our present knowledge of pathogenetic and diarrheal mechanisms of Campylobacter jejuni is explained in the first part of this chapter. In the second part, the molecular basis for the Campylobacter-induced barrier dysfunction is compared with that of other species in the Campylobacter genus. The bacteria are capable of overcoming the intestinal epithelial barrier. The invasion into the intestinal mucosa is the initial step of the infection, followed by a second step, the epithelial barrier impairment. The extent of the impairment depends on various factors, including tight junction dysregulation and epithelial apoptosis. The disturbed intestinal epithelium leads to a loss of water and solutes, the leak flux type of diarrhea, and facilitates the uptake of harmful antigens, the leaky gut phenomenon. The barrier dysfunction is accompanied by increased pro-inflammatory cytokine secretion, which is partially responsible for the dysfunction. Moreover, cytokines also mediate ion channel dysregulation (e.g., epithelial sodium channel, ENaC), leading to another diarrheal mechanism, which is sodium malabsorption. Future perspectives of Campylobacter research are the clarification of molecular pathomechanisms and the characterization of therapeutic and preventive compounds to combat and prevent Campylobacter infections.
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Affiliation(s)
- Fábia Daniela Lobo de Sá
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology, Rheumatology, Charité - University Medicine Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, 12203, Berlin, Germany
| | - Jörg-Dieter Schulzke
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology, Rheumatology, Charité - University Medicine Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, 12203, Berlin, Germany
| | - Roland Bücker
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology, Rheumatology, Charité - University Medicine Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, 12203, Berlin, Germany.
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Abstract
Campylobacter jejuni and Campylobacter coli can be frequently isolated from poultry and poultry-derived products, and in combination these two species cause a large portion of human bacterial gastroenteritis cases. While birds are typically colonized by these Campylobacter species without clinical symptoms, in humans they cause (foodborne) infections at high frequencies, estimated to cost billions of dollars worldwide every year. The clinical outcome of Campylobacter infections comprises malaise, diarrhea, abdominal pain and fever. Symptoms may continue for up to two weeks and are generally self-limiting, though occasionally the disease can be more severe or result in post-infection sequelae. The virulence properties of these pathogens have been best-characterized for C. jejuni, and their actions are reviewed here. Various virulence-associated bacterial determinants include the flagellum, numerous flagellar secreted factors, protein adhesins, cytolethal distending toxin (CDT), lipooligosaccharide (LOS), serine protease HtrA and others. These factors are involved in several pathogenicity-linked properties that can be divided into bacterial chemotaxis, motility, attachment, invasion, survival, cellular transmigration and spread to deeper tissue. All of these steps require intimate interactions between bacteria and host cells (including immune cells), enabled by the collection of bacterial and host factors that have already been identified. The assortment of pathogenicity-associated factors now recognized for C. jejuni, their function and the proposed host cell factors that are involved in crucial steps leading to disease are discussed in detail.
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20
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Nattramilarasu PK, Lobo de Sá FD, Schulzke JD, Bücker R. Immune-Mediated Aggravation of the Campylobacter concisus-Induced Epithelial Barrier Dysfunction. Int J Mol Sci 2021; 22:ijms22042043. [PMID: 33669494 PMCID: PMC7922099 DOI: 10.3390/ijms22042043] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 02/09/2021] [Accepted: 02/15/2021] [Indexed: 12/17/2022] Open
Abstract
Campylobacter concisus is a human-pathogenic bacterium of the gastrointestinal tract. This study aimed at the contribution of the mucosal immune system in the context of intestinal epithelial barrier dysfunction induced by C. concisus. As an experimental leaky gut model, we used in vitro co-cultures of colonic epithelial cell monolayers (HT-29/B6-GR/MR) with M1-macrophage-like THP-1 cells on the basal side. Forty-eight hours after C. concisus infection, the decrease in the transepithelial electrical resistance in cell monolayers was more pronounced in co-culture condition and 22 ± 2% (p < 0.001) higher than the monoculture condition without THP-1 cells. Concomitantly, we observed a reduction in the expression of the tight junction proteins occludin and tricellulin. We also detected a profound increase in 4 kDa FITC-dextran permeability in C. concisus-infected cell monolayers only in co-culture conditions. This is explained by loss of tricellulin from tricellular tight junctions (tTJs) after C. concisus infection. As an underlying mechanism, we observed an inflammatory response after C. concisus infection through pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) released from THP-1 cells in the co-culture condition. In conclusion, the activation of subepithelial immune cells exacerbates colonic epithelial barrier dysfunction by C. concisus through tricellulin disruption in tTJs, leading to increased antigen permeability (leaky gut concept).
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21
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Mårtensson T, Szakos A, Mellgren K, Toporski J, Arvidson J, Mattsson J, Gustafsson B, Casswall TH. Diagnostic disagreement between clinical standard histopathological- and retrospective assessment of histopathology-based gastrointestinal graft-versus-host disease in children. Pediatr Transplant 2020; 24:e13824. [PMID: 33085820 DOI: 10.1111/petr.13824] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 07/20/2020] [Accepted: 07/23/2020] [Indexed: 01/11/2023]
Abstract
BACKGROUND No previous paediatric study has evaluated the frequency of diagnostic disagreement between clinical standard histopathological assessment (CSHA) and retrospective, independent, histopathological assessment (RIHA) of gastrointestinal Graft-Versus-Host Disease (GI-GVHD) METHODS: In a retrospective cohort study, based on gastrointestinal biopsies collected from allogeneic HSCT-treated children (<18 years) with symptom-based GI-GVHD, we evaluated; disagreement of histopathology-based GI-GVHD diagnosis in CSHA vs RIHA, and potential clinical consequences of differences between the assessments. The CSHA-based diagnoses were retrieved from histopathology reports. The RIHA was performed by one pathologist, blinded to the CSHA outcomes and based on the minimal criteria for histopathology-based GI-GVHD diagnosis by the NIH 2014. RESULTS Seventy children with 92 endoscopic occasions (including 22 re-endoscopies) were enrolled. GI-GVHD was observed in 73% (67/92) of the endoscopies in the RIHA and in 54% (50/92) in the CSHA (P = .014). The RIHA confirmed 94% (47/50) with GI-GVHD and 52% (22/42) with non-GI-GVHD diagnoses, established in the CSHA. Disagreement, that is endoscopic occasions with GI-GVHD solely detected in RIHA or detection of GI-GVHD in CSHA but not in RIHA, was observed in 20/42 (48%) and 3/50 (6%), respectively (McNemar's test, P = .0008). The risk of a subsequent re-endoscopy was higher in endoscopic occasions with GI-GVHD detected in RIHA but not in CSHA vs if non-GI-GVHD were detected in both readings (P = .005). CONCLUSION Our results suggest that in children with symptom-based GI-GVHD without histopathological confirmation in CSHA, a second, NIH 2014 based histopathological assessment should be considered before performing a re-endoscopy.
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Affiliation(s)
- Thomas Mårtensson
- Department of Clinical Science, Intervention and Technology (CLINTEC), Karolinska Institutet, Stockholm, Sweden
| | - Attila Szakos
- Department of Clinical Pathology and Cytology, Karolinska University Hospital, Stockholm, Sweden
| | - Karin Mellgren
- Department of Pediatric Oncology, Region Västra Götaland, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Jacek Toporski
- Department of Pediatrics, Skåne University Hospital, Lund, Sweden
| | - Johan Arvidson
- Department of Women´s and Children´s Health, Uppsala University Children´s Hospital, Uppsala, Sweden
| | - Jonas Mattsson
- Department of Oncology and Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Britt Gustafsson
- Department of Clinical Science, Intervention and Technology (CLINTEC), Karolinska Institutet, Stockholm, Sweden
| | - Thomas H Casswall
- Department of Clinical Science, Intervention and Technology (CLINTEC), Karolinska Institutet, Stockholm, Sweden
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Butkevych E, Lobo de Sá FD, Nattramilarasu PK, Bücker R. Contribution of Epithelial Apoptosis and Subepithelial Immune Responses in Campylobacter jejuni- Induced Barrier Disruption. Front Microbiol 2020; 11:344. [PMID: 32210941 PMCID: PMC7067706 DOI: 10.3389/fmicb.2020.00344] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 02/17/2020] [Indexed: 12/17/2022] Open
Abstract
Campylobacter jejuni is a widespread zoonotic pathogen and the leading bacterial cause of foodborne gastroenteritis in humans. Previous infection studies showed disruption of intercellular contacts, induction of epithelial apoptosis, and immune activation, all three contributing to intestinal barrier dysfunction leading to diarrhea. The present study aims to determine the impact of subepithelial immune cells on intestinal barrier dysfunction during Campylobacter jejuni infection and the underlying pathological mechanisms. Infection was performed in a co-culture of confluent monolayers of the human colon cell line HT-29/B6-GR/MR and THP-1 immune cells. Twenty-two hours after infection, transepithelial electrical resistance (TER) was decreased by 58 ± 6% compared to controls. The infection resulted in an increase in permeability for fluorescein (332 Da; 4.5-fold) and for FITC-dextran (4 kDa; 3.5-fold), respectively. In contrast, incubation of the co-culture with the pan-caspase inhibitor Q-VD-OPh during the infection resulted in a complete recovery of the decrease in TER and a normalization of flux values. Fluorescence microscopy showed apoptotic fragmentation in infected cell monolayers resulting in a 5-fold increase of the apoptotic ratio, accompanied by an increased caspase-3 cleavage and caspase-3/7 activity, which both were not present after Q-VD-OPh treatment. Western blot analysis revealed increased claudin-1 and claudin-2 protein expression. Inhibition of apoptosis induction did not normalize these tight junction changes. TNFα concentration was increased during the infection in the co-culture. In conclusion, Campylobacter jejuni infection and the consequent subepithelial immune activation cause intestinal barrier dysfunction mainly through caspase-3-dependent epithelial apoptosis. Concomitant tight junction changes were caspase-independent. Anti-apoptotic and immune-modulatory substances appear to be promising agents for treatment of campylobacteriosis.
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Affiliation(s)
- Eduard Butkevych
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology and Rheumatology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Fábia Daniela Lobo de Sá
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology and Rheumatology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Praveen Kumar Nattramilarasu
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology and Rheumatology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Roland Bücker
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology and Rheumatology, Charité-Universitätsmedizin Berlin, Berlin, Germany
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23
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Nattramilarasu PK, Bücker R, Lobo de Sá FD, Fromm A, Nagel O, Lee IFM, Butkevych E, Mousavi S, Genger C, Kløve S, Heimesaat MM, Bereswill S, Schweiger MR, Nielsen HL, Troeger H, Schulzke JD. Campylobacter concisus Impairs Sodium Absorption in Colonic Epithelium via ENaC Dysfunction and Claudin-8 Disruption. Int J Mol Sci 2020; 21:ijms21020373. [PMID: 31936044 PMCID: PMC7013563 DOI: 10.3390/ijms21020373] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 12/31/2019] [Accepted: 12/31/2019] [Indexed: 12/12/2022] Open
Abstract
The epithelial sodium channel (ENaC) can increase the colonic absorptive capacity for salt and water. Campylobacter concisus is a common pathogenic epsilonproteobacterium, causing enteritis and diarrhea. It can induce barrier dysfunction in the intestine, but its influence on intestinal transport function is still unknown. Therefore, our study aimed to characterize C. concisus effects on ENaC using the HT-29/B6-GR/MR (epithelial cell line HT-29/B6 transfected with glucocorticoid and mineralocorticoid receptors) cell model and mouse colon. In Ussing chambers, C. concisus infection inhibited ENaC-dependent Na+ transport as indicated by a reduction in amiloride-sensitive short circuit current (−55%, n = 15, p < 0.001). This occurred via down-regulation of β- and γ-ENaC mRNA expression and ENaC ubiquitination due to extracellular signal-regulated kinase (ERK)1/2 activation, predicted by Ingenuity Pathway Analysis (IPA). In parallel, C. concisus reduced the expression of the sealing tight junction (TJ) protein claudin-8 and induced claudin-8 redistribution off the TJ domain of the enterocytes, which facilitates the back leakage of Na+ ions into the intestinal lumen. In conclusion, C. concisus caused ENaC dysfunction via interleukin-32-regulated ERK1/2, as well as claudin-8-dependent barrier dysfunction—both of which contribute to Na+ malabsorption and diarrhea.
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Affiliation(s)
- Praveen Kumar Nattramilarasu
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology and Rheumatology, Charité—Universitätsmedizin Berlin, 12203 Berlin, Germany
| | - Roland Bücker
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology and Rheumatology, Charité—Universitätsmedizin Berlin, 12203 Berlin, Germany
| | - Fábia Daniela Lobo de Sá
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology and Rheumatology, Charité—Universitätsmedizin Berlin, 12203 Berlin, Germany
| | - Anja Fromm
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology and Rheumatology, Charité—Universitätsmedizin Berlin, 12203 Berlin, Germany
| | - Oliver Nagel
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology and Rheumatology, Charité—Universitätsmedizin Berlin, 12203 Berlin, Germany
| | - In-Fah Maria Lee
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology and Rheumatology, Charité—Universitätsmedizin Berlin, 12203 Berlin, Germany
| | - Eduard Butkevych
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology and Rheumatology, Charité—Universitätsmedizin Berlin, 12203 Berlin, Germany
| | - Soraya Mousavi
- Institute of Microbiology, Infectious Diseases and Immunology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 14195 Berlin, Germany
| | - Claudia Genger
- Institute of Microbiology, Infectious Diseases and Immunology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 14195 Berlin, Germany
| | - Sigri Kløve
- Institute of Microbiology, Infectious Diseases and Immunology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 14195 Berlin, Germany
| | - Markus M. Heimesaat
- Institute of Microbiology, Infectious Diseases and Immunology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 14195 Berlin, Germany
| | - Stefan Bereswill
- Institute of Microbiology, Infectious Diseases and Immunology, Charité—Universitätsmedizin Berlin, Campus Benjamin Franklin, 14195 Berlin, Germany
| | - Michal R. Schweiger
- Laboratory for Epigenetics and Tumour genetics, University Hospital Cologne and Centre for Molecular Medicine Cologne, 50931 Cologne, Germany
| | - Hans Linde Nielsen
- Department of Clinical Microbiology, Aalborg University Hospital, 9000 Aalborg, Denmark
- Department of Clinical Medicine, Aalborg University, 9000 Aalborg, Denmark
| | - Hanno Troeger
- Medical Department, Division of Gastroenterology, Infectiology and Rheumatology, Charité—Universitätsmedizin Berlin, 12203 Berlin, Germany
| | - Jörg-Dieter Schulzke
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology and Rheumatology, Charité—Universitätsmedizin Berlin, 12203 Berlin, Germany
- Correspondence:
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Nielsen HL, Dalager-Pedersen M, Nielsen H. Risk of inflammatory bowel disease after Campylobacter jejuni and Campylobacter concisus infection: a population-based cohort study. Scand J Gastroenterol 2019; 54:265-272. [PMID: 30905214 DOI: 10.1080/00365521.2019.1578406] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Objectives: In this population-based cohort study, we aimed to examine the risk of IBD following a positive stool culture with Campylobacter jejuni or Campylobacter concisus, as well as following culture-negative stool testing. Materials and methods: Patients with a first-time positive stool culture with C. jejuni or C. concisus, as well as negative stool testing, from 2009 through 2013 in North Denmark Region, Denmark, were identified. Patients diagnosed with IBD during follow-up (to 1 March 2018) were identified using national registries. For each case, we selected ten population comparisons matched by age, gender, and calendar-time. Results: We identified 1693 patients with C. jejuni, 910 C. concisus-positive patients, and 11,383 patients with culture-negative stools. During the first year of follow-up C. jejuni-positive patients had higher risk of IBD (HR 2.2, 95% CI 1.3-3.7) compared to population comparisons, but not after exclusion of the first year (HR 1.1, 95% CI 0.5-2.3). Campylobacter concisus-positive patients and culture-negative patients had similar risk of IBD (HR 12.9, 95% CI 7.2-22.9 and HR 8.7, 95% CI 7.5-10.2), during the first year, which decreased to (HR 3.3, 95% CI 1.3-8.5 and HR 3.2, 95% CI 2.6-4.0) after exclusion of the first year. Conclusions: This study does not support exposure of C. jejuni or C. concisus infection as a causal trigger in subsequent development of IBD, since culture-negative patients had similar risk for IBD on long term follow-up. Additional studies including C. concisus exposures for an evaluation of the specific risk of IBD are needed.
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Affiliation(s)
- Hans Linde Nielsen
- a Department of Clinical Microbiology , Aalborg University Hospital , Aalborg , Denmark.,b Department of Clinical Medicine , Aalborg University , Aalborg , Denmark
| | - Michael Dalager-Pedersen
- b Department of Clinical Medicine , Aalborg University , Aalborg , Denmark.,c Department of Infectious Diseases , Aalborg University Hospital , Aalborg , Denmark
| | - Henrik Nielsen
- b Department of Clinical Medicine , Aalborg University , Aalborg , Denmark.,c Department of Infectious Diseases , Aalborg University Hospital , Aalborg , Denmark
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Harrer A, Bücker R, Boehm M, Zarzecka U, Tegtmeyer N, Sticht H, Schulzke JD, Backert S. Campylobacter jejuni enters gut epithelial cells and impairs intestinal barrier function through cleavage of occludin by serine protease HtrA. Gut Pathog 2019; 11:4. [PMID: 30805031 PMCID: PMC6373145 DOI: 10.1186/s13099-019-0283-z] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 02/01/2019] [Indexed: 01/17/2023] Open
Abstract
Campylobacter jejuni secretes HtrA (high temperature requirement protein A), a serine protease that is involved in virulence. Here, we investigated the interaction of HtrA with the host protein occludin, a tight junction strand component. Immunofluorescence studies demonstrated that infection of polarized intestinal Caco-2 cells with C. jejuni strain 81-176 resulted in a redistribution of occludin away from the tight junctions into the cytoplasm, an effect that was also observed in human biopsies during acute campylobacteriosis. Occludin knockout Caco-2 cells were generated by CRISPR/Cas9 technology. Inactivation of this gene affected the polarization of the cells in monolayers and transepithelial electrical resistance (TER) was reduced, compared to wild-type Caco-2 cells. Although tight junctions were still being formed, occludin deficiency resulted in a slight decrease of the tight junction plaque protein ZO-1, which was redistributed off the tight junction into the lateral plasma membrane. Adherence of C. jejuni to Caco-2 cell monolayers was similar between the occludin knockout compared to wild-type cells, but invasion was enhanced, indicating that deletion of occludin allowed larger numbers of bacteria to pass the tight junctions and to reach basal membranes to target the fibronectin receptor followed by cell entry. Finally, we discovered that purified C. jejuni HtrA cleaves recombinant occludin in vitro to release a 37 kDa carboxy-terminal fragment. The same cleavage fragment was observed in Western blots upon infection of polarized Caco-2 cells with wild-type C. jejuni, but not with isogenic ΔhtrA mutants. HtrA cleavage was mapped to the second extracellular loop of occludin, and a putative cleavage site was identified. In conclusion, HtrA functions as a secreted protease targeting the tight junctions, which enables the bacteria by cleaving occludin and subcellular redistribution of other tight junction proteins to transmigrate using a paracellular mechanism and subsequently invade epithelial cells.
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Affiliation(s)
- Aileen Harrer
- 1Division of Microbiology, Dept. of Biology, University of Erlangen-Nuremberg, Staudtstr. 5, 91058 Erlangen, Germany
| | - Roland Bücker
- 2Institut für Klinische Physiologie, Med. Klinik m.S. Gastroenterologie, Infektiologie und Rheumatologie, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Manja Boehm
- 1Division of Microbiology, Dept. of Biology, University of Erlangen-Nuremberg, Staudtstr. 5, 91058 Erlangen, Germany
| | - Urszula Zarzecka
- 1Division of Microbiology, Dept. of Biology, University of Erlangen-Nuremberg, Staudtstr. 5, 91058 Erlangen, Germany.,4Department of General and Medical Biochemistry, Faculty of Biology, University of Gdansk, 80-308 Gdansk, Poland
| | - Nicole Tegtmeyer
- 1Division of Microbiology, Dept. of Biology, University of Erlangen-Nuremberg, Staudtstr. 5, 91058 Erlangen, Germany
| | - Heinrich Sticht
- 3Division of Bioinformatics, Institute of Biochemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Jörg D Schulzke
- 2Institut für Klinische Physiologie, Med. Klinik m.S. Gastroenterologie, Infektiologie und Rheumatologie, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Steffen Backert
- 1Division of Microbiology, Dept. of Biology, University of Erlangen-Nuremberg, Staudtstr. 5, 91058 Erlangen, Germany
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Abstract
BACKGROUND Persistent diarrhoea (PD), defined as diarrhoeal symptoms for longer than 2 weeks, still forms a substantial disease burden in children under 5 years of age. This article provides an overview of the current knowledge of PD and discusses novel concepts. METHODS A literature search on PD was performed which focused on evidence on epidemiology, pathophysiology and management of the disease. RESULTS The prevalence of PD has potentially decreased over the last decades. Debate remains around the role of specific bacterial, viral and parasitic infections with PD. PD is associated with malnutrition and a compromised immune system, including that caused by HIV infection. Management includes fluid resuscitation and improving nutritional status. There is a lack of evidence on the use of antibiotic therapy for PD. There is increasing interest in nutrient-based interventions, including pre- and/or probiotics that can modify the microbiome and thereby potentially prevent or improve the outcome of PD in children. CONCLUSION As PD remains a significant health burden, multicentre clinical trials are needed to inform future treatment guidelines. ABBREVIATIONS PD, persistent diarrhoea; EED, environmental enteric dysfunction; IBD, inflammatory bowel disease; WHO, World Health Organization.
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Affiliation(s)
- Robert H J Bandsma
- a Division of Gastroenterology, Hepatology and Nutrition , Hospital for Sick Children , Toronto , Canada.,b Translational Medicine Program, Hospital for Sick Children , Toronto , Canada.,c Centre for Global Child Health, Hospital for Sick Children , Toronto , Canada.,d Department of Nutrition Sciences , University of Toronto , Toronto , Canada
| | - Kamran Sadiq
- e Department of Paediatrics and Child Health , Aga Khan University , Karachi , Pakistan
| | - Zulfiqar A Bhutta
- c Centre for Global Child Health, Hospital for Sick Children , Toronto , Canada.,d Department of Nutrition Sciences , University of Toronto , Toronto , Canada.,e Department of Paediatrics and Child Health , Aga Khan University , Karachi , Pakistan
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