1.
Frick, Inga-Maria, et al.
(författare)
Interactions between M proteins of Streptococcus pyogenes and glycosaminoglycans promote bacterial adhesion to host cells.
2003
Ingår i: European Journal of Biochemistry. - : Wiley. - 0014-2956. ; 270:10, s. 2303-2311
Tidskriftsartikel (refereegranskat) abstract
Several microbial pathogens have been reported to interact with glycosaminoglycans (GAGs) on cell surfaces and in the extracellular matrix. Here we demonstrate that M protein, a major surface-expressed virulence factor of the human bacterial pathogen, Streptococcus pyogenes, mediates binding to various forms of GAGs. Hence, S. pyogenes strains expressing a large number of different types of M proteins bound to dermatan sulfate (DS), highly sulfated fractions of heparan sulfate (HS) and heparin, whereas strains deficient in M protein surface expression failed to interact with these GAGs. Soluble M protein bound DS directly and could also inhibit the interaction between DS and S. pyogenes. Experiments with M protein fragments and with streptococci expressing deletion constructs of M protein, showed that determinants located in the NH2-terminal part as well as in the C-repeat region of the streptococcal proteins are required for full binding to GAGs. Treatment with ABC-chondroitinase and HS lyase that specifically remove DS and HS chains from cell surfaces, resulted in significantly reduced adhesion of S. pyogenes bacteria to human epithelial cells and skin fibroblasts. Together with the finding that exogenous DS and HS could inhibit streptococcal adhesion, these data suggest that GAGs function as receptors in M protein-mediated adhesion of S. pyogenes.
2.
3.
Hansen, Finja, et al.
(författare)
The Thrombin-Derived Host Defense Peptide GKY25 Inhibits Endotoxin-Induced Responses through Interactions with Lipopolysaccharide and Macrophages/Monocytes
2015
Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 1550-6606 .- 0022-1767. ; 194:11, s. 5397-5406
Tidskriftsartikel (refereegranskat) abstract
Host defense peptides have recently gained much interest as novel anti-infectives owing to their ability to kill bacteria and simultaneously modulate host cell responses. The cationic host defense peptide GKY25 (GKYGFYTHVFRLKKWIQKVIDQFGE), derived from the C terminus of human thrombin, inhibits proinflammatory responses in vitro and in vivo, but the mode of action is unclear. In this study, we show that GKY25, apart from binding bacterial LPS, also interacts directly with monocytes and macrophages in vitro, ex vivo, and in vivo. Moreover, GKY25 inhibits TLR4-and TLR2-induced NF-kappa B activation in response to several microbe-derived agonists. Furthermore, GKY25 reduces LPS-induced phosphorylation of MAPKs p38 alpha and JNK1/2/3. FACS and electron microscopy analyses showed that GKY25 interferes with TLR4/myeloid differentiation protein-2 dimerization. The results demonstrate a previously undisclosed activity of the host defense peptide GKY25, based on combined LPS and cell interactions leading to inhibition of TLR4 dimerization and subsequent reduction of NF-kappa B activity and proinflammatory cytokine production in monocytes and macrophages.
4.
Papareddy, Praveen, et al.
(författare)
NLF20: an antimicrobial peptide with therapeutic potential against invasive Pseudomonas aeruginosa infection.
2016
Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press (OUP). - 1460-2091 .- 0305-7453. ; 71:1, s. 170-180
Tidskriftsartikel (refereegranskat) abstract
Increasing resistance to antibiotics makes antimicrobial peptides interesting as novel therapeutics. Here, we report on studies of the peptide NLF20 (NLFRKLTHRLFRRNFGYTLR), corresponding to an epitope of the D helix of heparin cofactor II (HCII), a plasma protein mediating bacterial clearance.
5.
Malmström, Erik, et al.
(författare)
Protein C inhibitor - a novel antimicrobial agent
2009
Ingår i: PLoS Pathogens. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 5:12, s. e1000698-
Tidskriftsartikel (refereegranskat) abstract
Protein C inhibitor (PCI) is a heparin-binding serine proteinase inhibitor belonging to the family of serpin proteins. Here we describe that PCI exerts broad antimicrobial activity against bacterial pathogens. This ability is mediated by the interaction of PCI with lipid membranes, which subsequently leads to their permeabilization. As shown by negative staining electron microscopy, treatment of Escherichia coli or Streptococcus pyogenes bacteria with PCI triggers membrane disruption followed by the efflux of bacterial cytosolic contents and bacterial killing. The antimicrobial activity of PCI is located to the heparin-binding site of the protein and a peptide spanning this region was found to mimic the antimicrobial activity of PCI, without causing lysis or membrane destruction of eukaryotic cells. Finally, we show that platelets can assemble PCI on their surface upon activation. As platelets are recruited to the site of a bacterial infection, these results may explain our finding that PCI levels are increased in tissue biopsies from patients suffering from necrotizing fasciitis caused by S. pyogenes. Taken together, our data describe a new function for PCI in innate immunity.
6.
Papareddy, Praveen, et al.
(författare)
Proteolysis of Human Thrombin Generates Novel Host Defense Peptides
2010
Ingår i: PLoS pathogens. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 6:4, s. e1000857-
Tidskriftsartikel (refereegranskat) abstract
The coagulation system is characterized by the sequential and highly localized activation of a series of serine proteases, culminating in the conversion of fibrinogen into fibrin, and formation of a fibrin clot. Here we show that C-terminal peptides of thrombin, a key enzyme in the coagulation cascade, constitute a novel class of host defense peptides, released upon proteolysis of thrombin in vitro, and detected in human wounds in vivo. Under physiological conditions, these peptides exert antimicrobial effects against Gram-positive and Gram-negative bacteria, mediated by membrane lysis, as well as immunomodulatory functions, by inhibiting macrophage responses to bacterial lipopolysaccharide. In mice, they are protective against P. aeruginosa sepsis, as well as lipopolysaccharide-induced shock. Moreover, the thrombin-derived peptides exhibit helical structures upon binding to lipopolysaccharide and can also permeabilize liposomes, features typical of "classical" helical antimicrobial peptides. These findings provide a novel link between the coagulation system and host-defense peptides, two fundamental biological systems activated in response to injury and microbial invasion.
7.
Rydengård, Victoria, et al.
(författare)
Histidine-rich glycoprotein protects from systemic Candida infection
2008
Ingår i: PLoS pathogens. - : Public Library of Science (PLoS). - 1553-7374 .- 1553-7366. ; 4:8, s. e1000116-
Tidskriftsartikel (refereegranskat) abstract
Fungi, such as Candida spp., are commonly found on the skin and at mucosal surfaces. Yet, they rarely cause invasive infections in immunocompetent individuals, an observation reflecting the ability of our innate immune system to control potentially invasive microbes found at biological boundaries. Antimicrobial proteins and peptides are becoming increasingly recognized as important effectors of innate immunity. This is illustrated further by the present investigation, demonstrating a novel antifungal role of histidine-rich glycoprotein (HRG), an abundant and multimodular plasma protein. HRG bound to Candida cells, and induced breaks in the cell walls of the organisms. Correspondingly, HRG preferentially lysed ergosterol-containing liposomes but not cholesterol-containing ones, indicating a specificity for fungal versus other types of eukaryotic membranes. Both antifungal and membrane-rupturing activities of HRG were enhanced at low pH, and mapped to the histidine-rich region of the protein. Ex vivo, HRG-containing plasma as well as fibrin clots exerted antifungal effects. In vivo, Hrg(-/-) mice were susceptible to infection by C. albicans, in contrast to wild-type mice, which were highly resistant to infection. The results demonstrate a key and previously unknown antifungal role of HRG in innate immunity.
8.
Malekkhaiat Häffner, Sara, et al.
(författare)
Interaction of Laponite with Membrane Components - Consequences for Bacterial Aggregation and Infection Confinement
2019
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 11:17, s. 15389-15400
Tidskriftsartikel (refereegranskat) abstract
The antimicrobial effects of Laponite nanoparticles with or without loading of the antimicrobial peptide LL-37 was investigated along with their membrane interactions. The study combines data from ellipsometry, circular dichroism, fluorescence spectroscopy, particle size/ζ potential measurements, and confocal microscopy. As a result of the net negative charge of Laponite, loading of net positively charged LL-37 increases with increasing pH. The peptide was found to bind primarily to the outer surface of the Laponite nanoparticles in a predominantly helical conformation, leading to charge reversal. Despite their net positive charge, peptide-loaded Laponite nanoparticles did not kill Gram-negative Escherichia coli bacteria or disrupt anionic model liposomes. They did however cause bacteria flocculation, originating from the interaction of Laponite and bacterial lipopolysaccharide (LPS). Free LL-37, in contrast, is potently antimicrobial through membrane disruption but does not induce bacterial aggregation in the concentration range investigated. Through LL-37 loading of Laponite nanoparticles, the combined effects of bacterial flocculation and membrane lysis are observed. However, bacteria aggregation seems to be limited to Gram-negative bacteria as Laponite did not cause flocculation of Gram-positive Bacillus subtilis bacteria nor did it bind to lipoteichoic acid from bacterial envelopes. Taken together, the present investigation reports several novel phenomena by demonstrating that nanoparticle charge does not invariably control membrane destabilization and by identifying the ability of anionic Laponite nanoparticles to effectively flocculate Gram-negative bacteria through LPS binding. As demonstrated in cell experiments, such aggregation results in diminished LPS-induced cell activation, thus outlining a promising approach for confinement of infection and inflammation caused by such pathogens.
9.
Dahlman, Anna, et al.
(författare)
Thrombin-derived C-terminal peptide reduces Candida-induced inflammation and infection in vitro and in vivo
2021
Ingår i: Antimicrobial Agents and Chemotherapy. - 0066-4804. ; 65:11
Tidskriftsartikel (refereegranskat) abstract
Infections due to the opportunistic fungus Candida have been on the rise in the last decades, especially in immunocompromised individuals and hospital settings. Unfortunately, the treatments available today are limited. Thrombin-derived C-terminal peptide (TCP-25) is an antimicrobial peptide (AMP) with antibacterial and immunomodulatory effects. In this work, we, for the first time, demonstrate the ability of TCP-25 ability to counteract Candida in vitro and in vivo. Using a combination of viable count assay (VCA), radial diffusion assay (RDA), and fluorescence and transmission electron microscopy analyses, TCP-25 was found to exert a direct fungicidal activity. An inhibitory activity of TCP-25 on NF-kB activation induced by both zymosan alone and heat-killed C. albicans was demonstrated in vitro using THP-1 cells, and in vivo using NF-kB reporter mice. Moreover, the immunomodulatory property of TCP-25 was further substantiated in vitro by analyzing cytokine responses in human blood stimulated with zymosan, and in vivo employing a zymosan-induced peritonitis model in C57BL/6 mice. The therapeutic potential of TCP-25 was demonstrated in mice infected with luminescent C. albicans. Finally, the binding between TCP-25 and zymosan was investigated using circular dichroism spectroscopy and intrinsic fluorescence analysis. Taken together, our results show that TCP-25 has a dual function by inhibiting Candida as well as the associated zymosan-induced inflammation. The latter function is accompanied by a change in secondary structure upon binding to zymosan. TCP-25, therefore, shows promise as a novel drug candidate against Candida infections.
10.
Pihl, Maria, et al.
(författare)
Effects of clinical isolates of Pseudomonas aeruginosa on Staphylococcus epidermidis biofilm formation
2010
Ingår i: FEMS Immunology and Medical Microbiology. - : Wiley-Blackwell. - 0928-8244 .- 1574-695X. ; 59:3, s. 504-512
Tidskriftsartikel (refereegranskat) abstract
Pseudomonas aeruginosa is often found in chronic infections, including cystic fibrosis lung infections and those related to chronic wounds and venous ulcers. At the latter sites, P. aeruginosa can be isolated together with Staphylococcus epidermidis, and we have therefore explored the effect of clinical isolates and laboratory strains of P. aeruginosa strains on colonisation by S. epidermidis in dual-species biofilms. Biofilm formation was assayed using 16S rRNA fluorescence in situ hybridization and confocal laser scanning microscopy. Amongst the six P. aeruginosa strains tested, one particular strain, denoted 14:2, exerted a significant inhibitory effect and even after six hours, S. epidermidis levels in dual-species biofilms were reduced by more than 85% compared to biofilms without P. aeruginosa. Interestingly strain 14:2 was found to be negative for classical virulence determinants including pyocyanin, elastase and alkaline protease. Therefore, we suggest that less virulent phenotypes of P. aeruginosa which may develop over time in chronic infections, could counteract colonisation by S. epidermidis, ensuring persistence and dominance by P. aeruginosa in the host micro-habitat. Further studies are required to explain the inhibitory effect on S. epidermidis, although, extracellular polysaccharides produced by P. aeruginosa might play a role in this phenomenon.
