| 1. |
- Hedlund, Maria, et al.
(author)
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Sphingomyelin, glycosphingolipids, and ceramide signalling in cells exposed to p-fimbriated Escherichia coli
- 1998
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In: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 29:5, s. 1297-1306
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Research review (peer-reviewed)abstract
- Uropathogenic Escherichia coli attach to epithelial cells through P fimbriae that bind Galα1‐4Galβ‐oligosaccharide sequences in cell surface glycosphingolipids. The binding of P‐fimbriated E. coli to uroepithelial cells causes the release of ceramide, activation of the ceramide signalling pathway and a cytokine response in the epithelial cells. The present study examined the molecular source of ceramide in human kidney A498 cells exposed to P‐fimbriated E. coli. Agonists such as TNF‐α and IL‐1β released ceramide from sphingomyelin by the activation of endogenous sphingomyelinases and hydrolysis of sphingomyelin, and triggered an IL‐6 response. P‐fimbriated E. coli caused a slight increase in endogenous sphingomyelinase activity, but there was no associated sphingomyelin hydrolysis. Instead, the concentration of galactose‐containing glycolipids decreased. We propose that P‐fimbriated E. coli differ from other activators of the ceramide pathway, in that release of ceramide is from receptor glycolipids and not from sphingomyelin. Receptor breakdown may be an efficient host defence strategy, as it reduces the concentration of cell surface receptors, releases soluble receptor analogues and activates an inflammatory response.
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| 2. |
- Hedlund, Maria, et al.
(author)
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Type 1 fimbriae deliver an LPS- and TLR4-dependent activation signal to CD14-negative cells
- 2001
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In: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 39:3, s. 542-552
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Journal article (peer-reviewed)abstract
- Fimbriae target bacteria to different mucosal surfaces and enhance the inflammatory response at these sites. Inflammation may be triggered by the fimbriae themselves or by fimbriae-dependent delivery of other host activating molecules such as lipopolysaccharide (LPS). Although LPS activates systemic inflammation through the CD14 and Toll-like receptor 4 (TLR4) pathways, mechanisms of epithelial cell activation by LPS are not well understood. These cells lack CD14 receptors and are unresponsive to pure LPS, but fimbriated Escherichia coli overcome this refractoriness and trigger epithelial cytokine responses. We now show that type 1 fimbriae can present an LPS- and TLR4-dependent signal to the CD14-negative epithelial cells. Human uroepithelial cells were shown to express TLR4, and type 1 fimbriated E. coli strains triggered an LPS-dependent response in those cells. A similar LPS- and fimbriae-dependent response was observed in the urinary tract of TLR4-proficient mice, but not in TLR4-defective mice. The moderate inflammatory response in the TLR4-defective mice was fimbriae dependent but LPS independent. The results demonstrate that type 1 fimbriae present LPS to CD14-negative cells and that the TLR4 genotype determines this response despite the absence of CD14 on the target cells. The results illustrate how the host "sees" LPS and other microbial products not as purified molecules but as complexes, and that fimbriae determine the molecular context in which LPS is presented to host cells.
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| 3. |
- Wullt, Björn, et al.
(author)
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P fimbriae enhance the early establishment of Escherichia coli in the human urinary tract
- 2000
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In: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 38:3, s. 456-464
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Journal article (peer-reviewed)abstract
- This study examined the role of P fimbriae in the establishment of bacteriuria. Patients (n = 17) were subjected to intravesical inoculation with an asymptomatic bacteriuria strain, Escherichia coli 83972, or its P-fimbriated (pap+/prs+) transformants. As shown by groupwise analysis, the pap+/prs+ transformants established bacteriuria more rapidly than E. coli 83972 (P = 0.021) and required a lower number of inoculations to reach 105 cfu ml-1 (P=0.018). Intraindividual analysis showed that the pap+/prs+ transformants established bacteriuria more rapidly than E. coli 83972 in the patients who subsequently became carriers of both strains. Finally, bacterial establishment was shown to vary with the in vivo expression of P fimbriae. Bacterial counts were higher when P-fimbrial expression was detected than when the pap+/prs+ strain showed a negative phenotype. The results suggested that P fimbriae enhance the establishment of bacteriuria and fulfil the molecular Koch postulates as a colonization factor in the human urinary tract.
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| 4. |
- Frendeus, Björn, et al.
(author)
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Escherichia coli P fimbriae utilize the Toll-like receptor 4 pathway for cell activation
- 2001
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In: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 40:1, s. 37-51
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Journal article (peer-reviewed)abstract
- Fimbriae mediate bacterial attachment to host cells and provide a mechanism for tissue attack. They activate a host response by delivery of microbial products such as lipopolysaccharide (LPS) or through direct fimbriae-dependent signalling mechanisms. By coupling to glycosphingolipid (GSL) receptors, P fimbriae trigger cytokine responses in CD14 negative host cells. Here we show that P fimbriae utilize the Toll-like receptor 4 (TLR4)-dependent pathway to trigger mucosal inflammation. Escherichia coli strains expressing P fimbriae as their only virulence factor stimulated chemokine and neutrophil responses in the urinary tract of TLR4 proficient mice, but TLR4 defective mice failed to respond to infection. Mucosal cells were CD14 negative but expressed several TLR species including TLR4, and TLR4 protein was detected. Infection with P fimbriated bacteria stimulated an increase in TLR4 mRNA levels. The activation signal did not involve the LPS-CD14 pathway and was independent of lipid A myristoylation, as shown by mutational inactivation of the msbB gene. Co-staining experiments revealed that TLR4 and the GSL receptors for P fimbriae co-localized in the cell membrane. The results demonstrate that P fimbriae activate epithelial cells by means of a TLR4-dependent signalling pathway, and suggest that GSL receptors for P fimbriae can recruit TLR4 as co-receptors.
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| 5. |
- Godaly, Gabriela, et al.
(author)
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Role of fimbriae-mediated adherence for neutrophil migration across Escherichia coli-infected epithelial cell layers
- 1998
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In: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 30:4, s. 725-735
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Journal article (peer-reviewed)abstract
- This study examined the role of P and type 1 fimbriae for neutrophil migration across Escherichia coli-infected uroepithelial cell layers in vitro and for neutrophil recruitment to the urinary tract in vivo. Recombinant E. coli K-12 strains differing in P or type 1 fimbrial expression were used to infect confluent epithelial layers on the underside of transwell inserts. Neutrophils were added to the upper well, and their passage across the epithelial cell layers was quantified. Infection with the P- and type 1-fimbriated recombinant E. coli strains stimulated neutrophil migration to the same extent as a fully virulent clinical E. coli isolate, but the isogenic non-fimbriated vector control strains had no stimulatory effect. The enhancement of neutrophil migration was adhesion dependent; it was inhibited by soluble receptor analogues blocking the binding of P fimbriae to the globoseries of glycosphingolipids or of type 1 fimbriae to mannosylated glycoprotein receptors. P- and type 1-fimbriated E. coli triggered higher interleukin (IL) 8 secretion and expression of functional IL-8 receptors than non-fimbriated controls, and the increase in neutrophil migration across infected cell layers was inhibited by anti-IL-8 antibodies. In a mouse infection model, P- or type 1-fimbriated E. coli stimulated higher chemokine (MIP-2) and neutrophil responses than the non-fimbriated vector controls. The results demonstrated that transformation with the pap or fim DNA sequences is sufficient to convert an E. coli K-12 strain to a host response inducer, and that fimbriation enhances neutrophil recruitment in vitro and in vivo. Epithelial chemokine production provides a molecular link between the fimbriated bacteria that adhere to epithelial cells and tissue inflammation.
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| 6. |
- Svensson, Majlis, et al.
(author)
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Glycolipid depletion in antimicrobial therapy
- 2003
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In: Molecular Microbiology. - : Wiley. - 1365-2958 .- 0950-382X. ; 47:2, s. 453-461
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Journal article (peer-reviewed)abstract
- Mucosal pathogens target sites of infection through specific adherence to host glycoconjugate receptors. As a consequence, depletion of such receptors from the cell surface may be expected to inhibit attachment, impair bacterial colonization and reduce the activation of mucosal inflammation. We have used the glucose analogue and glycosphingolipid (GSL) biosynthesis inhibitor N-butyldeoxynojirimycin (NB-DNJ) to deplete human uroepithelial cells and the murine urinary tract mucosa of receptors for P-fimbriated Escherichia coli. NB-DNJ blocks the ceramide-specific glucosyltransferase, which catalyses the formation of glucosyl ceramide (GlcCer), the precursor for GSLs. The inhibitor was shown to decrease the GSL content in a dose-dependent way, and depletion markedly inhibited P-fimbriated bacterial attachment in vitro. NB-DNJ-fed C3H/HeN mice were depleted of GSLs in vivo and showed reduced susceptibility to experimental urinary tract infection with P-fimbriated E. coli. The mucosal inflammatory response was impaired, as shown by reduced chemokine secretion and lower neutrophil recruitment, and the bacteria colonized the urinary tract less efficiently than in normal mice. These results confirmed the role of P fimbriae-mediated adherence for colonization and inflammation and point to an interesting alternative to antibiotic treatment for urinary tract infection.
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