| 1. |
- Hein, Kyaw Zaw, et al.
(författare)
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Disulphide-reduced psoriasin is a human apoptosis-inducing broad-spectrum fungicide.
- 2015
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 112:42, s. 13039-44
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Tidskriftsartikel (refereegranskat)abstract
- The unexpected resistance of psoriasis lesions to fungal infections suggests local production of an antifungal factor. We purified Trichophyton rubrum-inhibiting activity from lesional psoriasis scale extracts and identified the Cys-reduced form of S100A7/psoriasin (redS100A7) as a principal antifungal factor. redS100A7 inhibits various filamentous fungi, including the mold Aspergillus fumigatus, but not Candida albicans. Antifungal activity was inhibited by Zn(2+), suggesting that redS100A7 interferes with fungal zinc homeostasis. Because S100A7-mutants lacking a single cysteine are no longer antifungals, we hypothesized that redS100A7 is acting as a Zn(2+)-chelator. Immunogold electron microscopy studies revealed that it penetrates fungal cells, implicating possible intracellular actions. In support with our hypothesis, the cell-penetrating Zn(2+)-chelator TPEN was found to function as a broad-spectrum antifungal. Ultrastructural analyses of redS100A7-treated T. rubrum revealed marked signs of apoptosis, suggesting that its mode of action is induction of programmed cell death. TUNEL, SYTOX-green analyses, and caspase-inhibition studies supported this for both T. rubrum and A. fumigatus. Whereas redS100A7 can be generated from oxidized S100A7 by action of thioredoxin or glutathione, elevated redS100A7 levels in fungal skin infection indicate induction of both S100A7 and its reducing agent in vivo. To investigate whether redS100A7 and TPEN are antifungals in vivo, we used a guinea pig tinea pedes model for fungal skin infections and a lethal mouse Aspergillus infection model for lung infection and found antifungal activity in both in vivo animal systems. Thus, selective fungal cell-penetrating Zn(2+)-chelators could be useful as an urgently needed novel antifungal therapeutic, which induces programmed cell death in numerous fungi.
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| 2. |
- Huhn, Stefanie, et al.
(författare)
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Coding variants in NOD-like receptors : An association study on risk and survival of colorectal cancer
- 2018
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 13:6
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Tidskriftsartikel (refereegranskat)abstract
- Nod-like receptors (NLRs) are important innate pattern recognition receptors and regulators of inflammation or play a role during development. We systematically analysed 41 non-synonymous single nucleotide polymorphisms (SNPs) in 21 NLR genes in a Czech discovery cohort of sporadic colorectal cancer (CRC) (1237 cases, 787 controls) for their association with CRC risk and survival. Five SNPs were found to be associated with CRC risk and eight with survival at 5% significance level. In a replication analysis using data of two large genome-wide association studies (GWASs) from Germany (DACHS: 1798 cases and 1810 controls) and Scotland (2210 cases and 9350 controls) the associations found in the Czech discovery set were not confirmed. However, expression analysis in human gut-related tissues and immune cells revealed that the NLRs associated with CRC risk or survival in the discovery set were expressed in primary human colon or rectum cells, CRC tissue and/or cell lines, providing preliminary evidence for a potential involvement of NLRs in general in CRC development and/or progression. Most interesting was the finding that the enigmatic development-related NLRP5 (also known as MATER) was not expressed in normal colon tissue but in colon cancer tissue and cell lines. Future studies may show whether regulatory variants instead of coding variants might affect the expression of NLRs and contribute to CRC risk and survival.
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| 3. |
- 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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| 4. |
- 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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| 5. |
- Raschig, Judith, et al.
(författare)
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Ubiquitously expressed Human Beta Defensin 1 (hBD1) forms bacteria-entrapping nets in a redox dependent mode of action
- 2017
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Ingår i: PLoS Pathogens. - : PUBLIC LIBRARY SCIENCE. - 1553-7366 .- 1553-7374. ; 13:3
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Tidskriftsartikel (refereegranskat)abstract
- Ever since the discovery of endogenous host defense antimicrobial peptides it has been discussed how these evolutionary conserved molecules avoid to induce resistance and to remain effective. Human beta-defensin 1 (hBD1) is an ubiquitously expressed endogenous antimicrobial peptide that exhibits qualitatively distinct activities between its oxidized and reduced forms. Here, we explore these antimicrobial mechanisms. Surprisingly, using electron microscopy we detected a so far unknown net-like structure surrounding bacteria, which were treated with the reduced but not the oxidized form of hBD1. A transmigration assay demonstrated that hBD1-derived nets capture bacteria and inhibit bacterial transmigration independent of bacterial killing. The presence of nets could completely prevent migration of hBD1 resistant pathogens and are stable in the presence of human duodenal secretion with a high amount of proteases. In contrast to HD6, cysteins are necessary for net formation. This redox-dependent function serves as an additional mechanism of action for hBD1 and differs from net formation by other defensins such as Paneth cell-derived human alpha-defensin 6 (HD6). While hBD1red and hBD1ox have distinct antimicrobial profiles and functions, only the reduced form provides additional host protection by entrapping bacteria in extracellular net structures preventing bacterial invasion. Better understanding of the modes of action of endogenous host peptides will help to find new antimicrobial strategies.
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| 6. |
- 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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| 7. |
- 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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| 8. |
- 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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| 9. |
- Wendler, Judith, et al.
(författare)
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Proteolytic Degradation of reduced Human Beta Defensin 1 generates a Novel Antibiotic Octapeptide
- 2019
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Microbial resistance against clinical used antibiotics is on the rise. Accordingly, there is a high demand for new innovative antimicrobial strategies. The host-defense peptide human beta-defensin 1 (hBD-1) is produced continuously by epithelial cells and exhibits compelling antimicrobial activity after reduction of its disulphide bridges. Here we report that proteolysis of reduced hBD-1 by gastrointestinal proteases as well as human duodenal secretions produces an eight-amino acid carboxy-terminal fragment. The generated octapeptide retains antibiotic activity, yet with distinct characteristics differing from the full-length peptide. We modified the octapeptide by stabilizing its termini and by using non-natural D-amino acids. The native and modified peptide variants showed antibiotic activity against pathogenic as well as antibiotic-resistant microorganisms, including E. coli, P. aeruginosa and C. albicans. Moreover, in an in vitro C. albicans infection model the tested peptides demonstrated effective amelioration of C. albicans infection without showing cytotoxity on human cells. In summary, protease degradation of hBD-1 provides a yet unknown mechanism to broaden antimicrobial host defense, which could be used to develop defensin-derived therapeutic applications.
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