Mucins in the host defence against Naegleria fowleri and mucinolytic activity as a possible means of evasion (original) (raw)
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Soft Matter, 2013
In this highlight, we discuss the multifaceted biology of mucins, where molecular architecture meets function, and especially the collective properties of mucin networks and gels that select adherent bacteria and restrict penetration.
Host Invasion by Pathogenic Amoebae: Epithelial Disruption by Parasite Proteins
Genes
The epithelium represents the first and most extensive line of defence against pathogens, toxins and pollutant agents in humans. In general, pathogens have developed strategies to overcome this barrier and use it as an entrance to the organism. Entamoeba histolytica, Naegleria fowleri and Acanthamoeba spp. are amoebae mainly responsible for intestinal dysentery, meningoencephalitis and keratitis, respectively. These amoebae cause significant morbidity and mortality rates. Thus, the identification, characterization and validation of molecules participating in host-parasite interactions can provide attractive targets to timely intervene disease progress. In this work, we present a compendium of the parasite adhesins, lectins, proteases, hydrolases, kinases, and others, that participate in key pathogenic events. Special focus is made for the analysis of assorted molecules and mechanisms involved in the interaction of the parasites with epithelial surface receptors, changes in epithelia...
International Journal for Parasitology, 2007
Invasive intestinal amebiasis, caused by Entamoeba histolytica, is initiated with attachment of trophozoites to the colonic mucous layer, mucous disruption and/or depletion, and adherence to and cytolysis of host epithelial and inflammatory cells. A current working model of intestinal amebiasis suggests that the microenvironment of the host intestine, particularly intestinal mucins and the bacterial biofilm, may influence the behavior of pathogenic amebae. The invasive phenotype is dependent on expression of a number of virulence factors of which cysteine proteases provide the most convenient experimental probe because their activity is readily monitored. In the present study, we examined the interaction of E. histolytica with GalNAc, mucin, different epithelial cell lines and bacteria both by biochemical assays of protease release and transcriptional profiling using a previously validated genomic microarray. A significant downregulation of released cysteine protease activity was observed when amebic trophozoites were grown with GalNAc, specific colonic cell lines and bacteria. Transcriptional profiling during GalNAc interaction revealed enhanced expression of the 170-kDa Gal/GalNAc lectin. Decreased protease activity during GalNAc interaction and enhanced expression of the Gal/GalNAc lectin gene are consistent with a program of commensal infection and mucus coat colonization mediated by the lectin. The down-regulation of cysteine protease activity following interaction with a colonic epithelial cell line parallels the presence of secretory mucin having a complex carbohydrate structure rich in Gal and GalNAc. In contrast, interaction of E. histolytica trophozoites with stomach porcine mucin enhanced cysteine protease (EhCP1 and EhCP2) secretion 3-fold. This suggests the specific composition of mucins may affect the Entamoeba phenotype. Transcriptional profiling revealed interaction of Entamoeba with intestinal bacteria induced protein kinase, ABC transporter, Rab family GTPase and hsp 90 gene expression. The enhanced expression of this gene cluster is consistent with enhanced phagocytosis of E. histolytica during interaction with bacteria.
Disruption of MDCK cell tight junctions by the free-living amoeba Naegleria fowleri
Microbiology, 2013
Naegleria fowleri is the aetiological agent of primary amoebic meningoencephalitis. This parasite invades its host by penetrating the olfactory mucosa. However, the mechanism of epithelium penetration is not well understood. In the present study, we evaluated the effect of N. fowleri trophozoites and the non-pathogenic Naegleria gruberi on Madin-Darby canine kidney (MDCK) tight junction proteins, including claudin-1, occludin and ZO-1, as well as on the actin cytoskeleton. Trophozoites from each of the free-living amoeba species were co-cultured with MDCK cells in a 1 : 1 ratio for 1, 3, 6 or 10 h. Light microscopy revealed that N. fowleri caused morphological changes as early as 3 h post-infection in an epithelial MDCK monolayer. Confocal microscopy analysis revealed that after 10 h of co-culture, N. fowleri trophozoites induced epithelial cell damage, which was characterized by changes in the actin apical ring and disruption of the ZO-1 and claudin-1 proteins but not occludin. Western blot assays revealed gradual degradation of ZO-1 and claudin-1 as early as 3 h post-infection. Likewise, there was a drop in transepithelial electrical resistance that resulted in increased epithelial permeability and facilitated the invasion of N. fowleri trophozoites by a paracellular route. In contrast, N. gruberi did not induce alterations in MDCK cells even at 10 h post-infection. Based on these results, we suggest that N. fowleri trophozoites disrupt epithelial monolayers, which could enable their penetration of the olfactory epithelium and subsequent invasion of the central nervous system.
Frontiers in Bioscience, 2001
Introduction 3. Mammalian mucins-an overview 4. Mucin/mucin-like molecules in protozoan parasites 4.1. Occurrence 4.2. Composition and structure 4.3. Mucin genes 4.4. Functions 4.4.1. Role in cellular interaction and parasite protection 4.4.2. Immunomodulatory effects 5. Perspective 6. Acknowledgements 7. References
Microbiology, 2009
Naegleria fowleri is an amoeboflagellate responsible for the fatal central nervous system (CNS) disease primary amoebic meningoencephalitis (PAM). This amoeba gains access to the CNS by invading the olfactory mucosa and crossing the cribriform plate. Studies using a mouse model of infection have shown that the host secretes mucus during the very early stages of infection, and this event is followed by an infiltration of neutrophils into the nasal cavity. In this study, we investigated the role of N. fowleri trophozoites in inducing the expression and secretion of airway mucin and pro-inflammatory mediators. Using the human mucoepidermal cell line NCI-H292, we demonstrated that N. fowleri induced the expression of the MUC5AC gene and protein and the pro-inflammatory mediators interleukin-8 (IL-8) and interleukin-1β (IL-1β), but not tumour necrosis factor-α or chemokine c-c motif ligand 11 (eotaxin). Since the production of reactive oxygen species (ROS) is a common phenomenon involved...
The Journal of Eukaryotic Microbiology, 1998
Mucins secreted from the gastrointestinal epithelium form the basis of the adherent mucus layer which is the host's first line of defense against invasion by Entamoeba histol.ytica. Galactose and N-acetyl-D-galactosamine residues of mucins specifically inhibit binding of the amebic 170 kDa heavy subunit Gal-lectin to target cells, an absolute prerequisite for pathogenesis. Herein we characterized the secretory mucins isolated from the human colon and from three human colonic adenocarcinoma cell lines: two with goblet cell-like (LS174T and T84) and one with absorptive cell-like morphology (Caco-2). By Northern blot analysis the intestinal mucin genes MUC2 and MUC3 were constitutively expressed by confluent LS174T and Caco-2 cells, whereas T84 cells only transcribed MUC2 and not MUC3 mRNA. ?H-glucosamine and 'H-threonine metabolically labeled proteins separated as high M, mucins in the void (V,, > loh Da) of Sepharose-4B column chromatography and remained in the stacking gel of SDS-PAGE as depicted by fluorography. All mucin preparations contained high amounts of N-acetyl-glucosamine, galactose, N-acetyl-galactosamine, fucose and sialic acid, saccharides typical of the 0-linked carbohydrate side chains. Mucin samples from the human colon and from LS174T and Caco-2 cells inhibited E. histolyticu adherence to Chinese hamster ovary cells, whereas mucins from T84 cells did not. These results suggest that genetic heterogeneity andor posttranslational modification in glycosylation of colonic mucins can affect specific epithelial barrier function against intestinal pathogens.
Future microbiology, 2017
The aim of this work was to identify, characterize and evaluate the pathogenic role of mucinolytic activity released by Naegleria fowleri. Zymograms, protease inhibitors, anion exchange chromatography, MALDI-TOF-MS, enzymatic assays, Western blot, and confocal microscopy were used to identify and characterize a secreted mucinase; inhibition assays using antibodies, dot-blots and mouse survival tests were used to evaluate the mucinase as a virulence factor. A 94-kDa protein with mucinolytic activity was inducible and abolished by p-hydroxymercuribenzoate. MALDI-TOF-MS identified a glycoside hydrolase. Specific antibodies against N. fowleri-glycoside hydrolase inhibit cellular damage and MUC5AC degradation, and delay mouse mortality. Our findings suggest that secretory products from N. fowleri play an important role in mucus degradation during the invasion process.
Mucins in the mucosal barrier to infection
Mucosal Immunology, 2008
nature publishing group REVIEW MUCINS-AN INTEGRAL PART OF THE MUCOSAL BARRIER Mucosal epithelial tissues have evolved multiple mechanisms of defense in response to their vulnerability to microbial attack due to their exposure to the external environment. The mucosal epithelial cells form a contiguous lining that acts as a barrier between the moist exterior environment and the remainder of the host. In addition, these cells, both constitutively and in response to microbes, together with underlying leukocytes, secrete many defensive compounds into the mucosal fluid, including mucins, antibodies, defensins, protegrins, collectins, cathlecidins, lysozyme, histatins, and nitric oxide. 1-3 Together, these different defensive compounds form a physical barrier and have direct antimicrobial activity, and the ability to opsonize microbes to aid clearance. Mucin glycoproteins, however, can fulfill all of these roles individually. Mucosal pathogens, almost by definition, have evolved mechanisms to subvert these mucosal defensive measures. The first barrier the pathogen encounters is the highly hydrated mucus gel that covers the mucosal surface and protects the epithelial cells against chemical, enzymatic, microbial, and mechanical insult. Mucosal surfaces are coated with a layer of viscous mucus ranging in thickness from 10 m in the eye 4 and trachea 5 to 300 m in the stomach and 700 m in the intestine. 6-8 This mucus layer is not static but moves to clear trapped material. In the gastrointestinal tract, the outer mucus layer is continually removed by movement of the luminal contents, whereas in the