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- Keita, Åsa, 1973-, et al.
(författare)
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Increased uptake of non-pathogenic E. coli via the follicle-associated epithelium in longstanding ileal Crohn's disease
- 2008
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Ingår i: Journal of Pathology. - : Wiley. - 0022-3417 .- 1096-9896. ; 215:2, s. 135-144
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Tidskriftsartikel (refereegranskat)abstract
- In Crohn's disease (CD), inflammation is driven by luminal commensal micro-organisms, however, mechanisms of early phases of inflammation need further clarification. The earliest observable lesions of recurrent CD are microscopic erosions at the specialized follicle-associated epithelium (FAE), which lines the Peyer's patches. Therefore, our aim was to investigate the mucosal barrier to non-pathogenic bacteria in FAE of CD. The FAE of macroscopically normal ileum from patients with longstanding CD, ulcerative colitis, and controls was studied in Ussing chambers regarding electrophysiology and permeability to 51Cr-EDTA, horseradish peroxidase, and non-pathogenic E. coli strains. Transepithelial passage routes and uptake into dendritic cells were studied by confocal and electron microscopy. FAE of CD showed increased numbers of adherent bacteria, after E. coli exposure in Ussing chambers, as well as spontaneously in non-exposed archival surgical tissues. Further, we found increased uptake of fluorescent E. coli K-12 and HB101 across FAE of CD, but not in ulcerative colitis. Microscopy demonstrated intercellular and transcellular uptake of E. coli in CD, but only transcellular in controls. FAE exposed to E. coli demonstrated changes in conductance and 51Cr-EDTA permeability, suggesting that bacteria affected the paracellular pathway in CD mucosa. Following bacterial uptake, CD mucosa also demonstrated an increased percentage of E. coli co-localizing with dendritic cells, and augmented tissue release of TNF-α. Our data present novel insights into the pathophysiology of CD by demonstrating a previously unrecognized defect of FAE barrier to bacteria in ileal CD, leading to increased load of commensal bacteria to the inductive sites of mucosal immunity. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
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| 3. |
- Schoultz, Ida, et al.
(författare)
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Combined polymorphisms in genes encoding the inflammasome components NALP3 and CARD8 confer susceptibility to Crohn's disease in Swedish men
- 2009
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Ingår i: American Journal of Gastroenterology. - : Wolters Kluwer. - 0002-9270 .- 1572-0241. ; 104:5, s. 1180-1188
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: Crohn's disease (CD) is characterized by overproduction of proinflammatory cytokines like interleukin (IL)-1beta. Production of mature IL-1beta is dependent on a caspase-1-activating protein complex called the NALP3 inflammasome, composed of NALP3, ASC, and CARD8. NALP3 shares structural similarities with Nod2, and both of these proteins are required for bacteria-induced IL-1beta secretion. The combination of the polymorphisms CARD8 (C10X)and NALP3 (Q705K) was recently shown to be associated with rheumatoid arthritis.Our aim was to investigate whether these combined polymorphisms play a role in the susceptibility to CD. METHODS: The study included 498 CD patients in two cohorts from different regions and 742 control individuals from a Swedish population. DNA was isolated from whole blood. Polymorphisms of (Q705K) NALP3 and (C10X) CARD8, as well as the Nod2 variants, R702W and G908R, were genotyped using the Taqman single nucleotide polymorphism assay. The Nod2 frameshift mutation, L1007fs, was detected by Megabace SNuPe genotyping. RESULTS: Our results show that men who have both the C10X and Q705K alleles in CARD8 and NALP3, and who express wild-type alleles of Nod2 are at an increased risk of developing CD (odds ratio, OR: 3.40 range: 1.32-8.76); P = 0.011). No association with these polymorphisms was found in women (OR: 0.89 (range: 0.44-1.77); P = 0.74). CONCLUSIONS: We suggest a role for combined polymorphisms in CARD8 and NALP3 in the development of CD in men, with obvious sex differences in the genetic susceptibility pattern. These findings give further support to the importance of innate immune responses in CD.
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| 5. |
- Schoultz, Ida, 1979-, et al.
(författare)
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Ubiquitination and degradation of the Crohn’s Disease associated protein Nod2involves the E2 enzyme UBE2G2
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Background: Mutations predisposing to Crohn’s disease (CD) have been mapped to the CARD15/Nod2 locus,which encodes a cytoplasmic receptor hereafter referred to as Nod2, a member of the NACHT-LRR (NLR) familyof pattern recognition receptors. The binding of bacterial muramyl dipeptide (MDP) to Nod2 triggers theactivation of the nuclear factor-κB (NFκB) pathway, thereby inducing a number of pro-inflammatory genes. Themost common variant of Nod2 associated with CD is the frame shift mutation L1007fs, which results in atruncated form of the protein unable to respond to MDP. Despite active research, little is known about howNod2 is regulated. The aim of this study was to investigate if the cellular Nod2 protein level is regulated by theubiquitin-proteasome pathway. Material and Methods/Results: Nod2 was shown to be subjected to rapid turnover in the colorectal cancer cellline SW480 as measured by immunoprecipitation following inhibition of protein synthesis with cyklohexamide.Immunoprecipitation of Nod2 also revealed co-precipitation of ubiquitin, suggesting that Nod2 wasubiquitinated. In line with this observation, inhibition of the proteasome using MG-132 or lactacystin, resultedin increased levels of Nod2 in the cells. UBE2G2, an E2 enzyme, thus conferring specificity of ubiquitin binding,was identified to have affinity for the CARD domain of Nod2. Activation of Nod2 with MDP enhanced itsubiquitination, and increasing amounts of UBE2G2 in the cells abrogated NF-κB-activation, suggesting thatubiquitination of Nod2 may be important for the resolution of the inflammatory signal. Conclusion: Taken together, our results show that the cellular level of Nod2 protein is regulated via theubiquitin-proteasome pathway, suggesting that Nod2-driven inflammation may be resolved through rapiddegradation of Nod2. Consequently, not only polymorphisms in Nod2 directly, but also in genes regulatingNod2 protein levels may contribute to the susceptibility to Crohn’s disease.
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