| 1. |
- Küchler, Robert, et al.
(författare)
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Antimicrobial activity of high-mobility-group box 2 : a new function to a well-known protein.
- 2013
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Ingår i: Antimicrobial Agents and Chemotherapy. - 0066-4804 .- 1098-6596. ; 57:10, s. 4782-93
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Tidskriftsartikel (refereegranskat)abstract
- The human intestinal tract is highly colonized by a vast number of microorganisms. Despite this permanent challenge, infections remain rare, due to a very effective barrier defense system. Essential effectors of this system are antimicrobial peptides and proteins (AMPs), which are secreted by intestinal epithelial and lymphoid cells, balance the gut microbial community, and prevent the translocation of microorganisms. Several antimicrobial proteins have already been identified in the gut. Nonetheless, we hypothesized that additional AMPs are yet to be discovered in this setting. Using biological screening based on antimicrobial function, here we identified competent antibacterial activity of high-mobility-group box 2 (HMGB2) against Escherichia coli. By recombinant expression, we confirmed this biologically new antimicrobial activity against different commensal and pathogenic bacteria. In addition, we demonstrated that the two DNA-binding domains (HMG boxes A and B) are crucial for the antibiotic function. We detected HMGB2 in several gastrointestinal tissues by mRNA analysis and immunohistochemical staining. In addition to the nuclei, we also observed HMGB2 in the cytoplasm of intestinal epithelial cells. Furthermore, HMGB2 was detectable in vitro in the supernatants of two different cell types, supporting an extracellular function. HMGB2 expression was not changed in inflammatory bowel disease but was detected in certain stool samples of patients, whereas it was absent from control individuals. Taken together, we characterized HMGB2 as an antimicrobial protein in intestinal tissue, complementing the diverse repertoire of gut mucosal defense molecules.
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| 2. |
- Nuding, Sabine, et al.
(författare)
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Gastric Antimicrobial Peptides Fail to Eradicate Helicobacter pylori Infection Due to Selective Induction and Resistance
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 8:9
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Tidskriftsartikel (refereegranskat)abstract
- Background: Although antimicrobial peptides protect mucus and mucosa from bacteria, Helicobacter pylori is able to colonize the gastric mucus. To clarify in which extend Helicobacter escapes the antimicrobial defense, we systematically assessed susceptibility and expression levels of different antimicrobial host factors in gastric mucosa with and without H. pylori infection.Materials and Methods: We investigated the expression levels of HBD1 (gene name DEFB1), HBD2 (DEFB4A), HBD3 (DEFB103A), HBD4 (DEFB104A), LL37 (CAMP) and elafin (PI3) by real time PCR in gastric biopsy samples in a total of 20 controls versus 12 patients colonized with H. pylori. Immunostaining was performed for HBD2 and HBD3. We assessed antimicrobial susceptibility by flow cytometry, growth on blood agar, radial diffusion assay and electron microscopy.Results: H. pylori infection was associated with increased gastric levels of the inducible defensin HBD2 and of the antiprotease elafin, whereas the expression levels of the constitutive defensin HBD1, inducible HBD3 and LL37 remained unchanged. HBD4 was not expressed in significant levels in gastric mucosa. H. pylori strains were resistant to the defensins HBD1 as well as to elafin, and strain specific minimally susceptible to HBD2, whereas HBD3 and LL37 killed all H. pylori strains effectively. We demonstrated the binding of HBD2 and LL37 on the surface of H. pylori cells. Comparing the antibacterial activity of extracts from H. pylori negative and positive biopsies, we found only a minimal killing against H. pylori that was not increased by the induction of HBD2 in H. pylori positive samples.Conclusion: These data support the hypothesis that gastric H. pylori evades the host defense shield to allow colonization.
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| 3. |
- Schröder, Björn O., et al.
(författare)
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Waking the wimp : Redox-modulation activates human beta-defensin 1
- 2011
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Ingår i: Gut microbes. - : Taylor & Francis. - 1949-0976 .- 1949-0984. ; 2:4, s. 262-266
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Tidskriftsartikel (refereegranskat)abstract
- Antimicrobial peptides are key players of the innate immune system and form a primary barrier against infection by microorganisms. In humans, several classes of antimicrobial peptides are produced, including the defensins. These small, cationic peptides show broad spectrum antimicrobial activity against bacteria, some fungi and some viruses. Defensins are characterized by six conserved cysteine residues which are connected via three disulphide bridges. Depending on the pattern of connectivity, human defensins are either classified as α- or β-defensins. Human β-defensin 1 (hBD-1) is constitutively expressed by epithelia, but in comparison with other antimicrobial peptides the antimicrobial activity of hBD-1 was comparably low. We recently found that after reduction of hBD-1's three disulphide bonds its antimicrobial activity is strongly enhanced. Reduction can be either performed by a reducing environment, as it is present in parts of the human intestine, the oral cavity and other locations, or enzymatically by the thioredoxin-system, which is one of the major redox regulators. Reduced hBD-1 is able to kill Gram-positive anaerobic bacteria of the human normal flora as well as an opportunistic pathogenic fungus, whereas the oxidized peptide does not show activity against these microorganisms. Herein we provide additional data about reduced hBD-1 and discuss the biological context of our findings.
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| 4. |
- Schröder, Björn, et al.
(författare)
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Reduction of disulphide bonds unmasks potent antimicrobial activity of human β-defensin 1
- 2011
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Ingår i: Nature. - : Macmillan Publishers Ltd.. - 0028-0836 .- 1476-4687. ; 469:7330, s. 419-423
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Tidskriftsartikel (refereegranskat)abstract
- Human epithelia are permanently challenged by bacteria and fungi, including commensal and pathogenic microbiota. In the gut, the fraction of strict anaerobes increases from proximal to distal, reaching 99% of bacterial species in the colon. At colonic mucosa, oxygen partial pressure is below 25% of airborne oxygen content, moreover microbial metabolism causes reduction to a low redox potential of -200 mV to -300 mV in the colon. Defensins, characterized by three intramolecular disulphide-bridges, are key effector molecules of innate immunity that protect the host from infectious microbes and shape the composition of microbiota at mucosal surfaces. Human β-defensin 1 (hBD-1) is one of the most prominent peptides of its class but despite ubiquitous expression by all human epithelia, comparison with other defensins suggested only minor antibiotic killing activity. Whereas much is known about the activity of antimicrobial peptides in aerobic environments, data about reducing environments are limited. Herein we show that after reduction of disulphide-bridges hBD-1 becomes a potent antimicrobial peptide against the opportunistic pathogenic fungus Candida albicans and against anaerobic, Gram-positive commensals of Bifidobacterium and Lactobacillus species. Reduced hBD-1 differs structurally from oxidized hBD-1 and free cysteines in the carboxy terminus seem important for the bactericidal effect. In vitro, the thioredoxin (TRX) system is able to reduce hBD-1 and TRX co-localizes with reduced hBD-1 in human epithelia. Hence our study indicates that reduced hBD-1 shields the healthy epithelium against colonisation by commensal bacteria and opportunistic fungi. Accordingly, an intimate interplay between redox-regulation and innate immune defence seems crucial for an effective barrier protecting human epithelia.
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| 5. |
- Troge, Anja, et al.
(författare)
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More than a marine propeller--the flagellum of the probiotic Escherichia coli strain Nissle 1917 is the major adhesin mediating binding to human mucus.
- 2012
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Ingår i: International Journal of Medical Microbiology. - : Elsevier BV. - 1438-4221 .- 1618-0607. ; 302:7-8, s. 304-14
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Tidskriftsartikel (refereegranskat)abstract
- The flagellum of the probiotic Escherichia coli strain Nissle 1917 (EcN) is not just responsible for motility, but also for EcN's ability to induce the production of human β-defensin 2. Here, we report a third function of this EcN organell. In this study we investigated the role of the EcN flagellum in adhesion to different host tissues by ex vivo and in vitro studies. Ex vivo studies with cryosections of human gut biopsies revealed that the flagellum of EcN is most likely important for efficient adhesion to the human intestinal tract. These results and in vitro studies with different epithelial cells indicated that the presence of mucus is important for efficient mediation of adhesion by the flagellum of EcN. We observed direct interaction between isolated flagella from EcN wild type and porcine mucin 2 as well as human mucus. However, we could not observe any interaction of the flagella with murine mucus. For the first time, we identified the mucus component gluconate as one receptor for the binding of flagella from EcN and were able to exclude the flagellin domain D3 as a responsible interaction partner. We propose that the flagellum of EcN is its major adhesin in vivo, which enables this probiotic strain to compete efficiently for binding sites on host tissue with several bacterial pathogens.
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| 6. |
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