eprintid: 18990
rev_number: 16
eprint_status: archive
userid: 602
dir: disk0/00/01/89/90
datestamp: 2010-03-29 15:42:25
lastmod: 2015-07-19 03:12:38
status_changed: 2010-03-29 15:42:25
type: thesis
metadata_visibility: show
item_issues_count: 0
creators_name: Chalmers-Watson, T.A.
title: The role of the NOD2 gene in the pathogenesis of Crohn’s disease
ispublished: unpub
subjects: 3900
abstract: Introduction: Crohn’s disease is characterised by an abnormal inflammatory response
possibly induced by components of enteric bacteria, in genetically susceptible individuals.
Mutations in the NOD2 gene are strongly associated with Crohn's disease, although the
mechanisms by which these mutations cause Crohn’s disease remain unknown. Peripheral
blood monocytes (PBMC), a key component of the innate immune system, highly express
NOD2, as do intestinal epithelial Paneth cells. The ligand for NOD2 is Muramyl dipeptide
(MDP), a component of bacterial peptidoglycan. MDP has been shown to be a powerful
priming agent for subsequent stimulation by lipopolysaccharide (LPS) in cell lines and this
effect has been linked to NOD2. Studies of primary mononuclear cells in Crohn’s disease
comparing the functional effects of the NOD2 mutations had not previously been reported.
Aims: To determine the effect of inherited mutations in the NOD2 gene on the cellular
responses of freshly extracted PBMC to MDP and other bacterial ligands including
mycobacteria. To examine the effect of MDP pre treatment ‘priming’ on PBMC responses
to subsequent LPS stimulation in both normal and Crohn’s disease affected patients
expressing wild type and mutant NOD2 proteins.
Methods: PBMC from healthy controls (n=12), and Crohn’s disease affected patients who
were genotypically either wild type (n=12), heterozygous (n=11) or homozygous (n=5) for
the common disease-causing NOD2 mutations. PBMC were stimulated with bacterial
products in vitro, with or without prior stimulation or ‘priming’ with MDP. The
transcription of selected cytokine genes was determined by real time quantitative RT-PCR
Results: MDP is a weak stimulant of inflammatory responses in PBMC whereas LPS
evoked much stronger responses. Responses to MDP were particularly reduced in PBMC
homozygous for the NOD2 mutations. Priming with MDP reduced the inflammatory
response of normal PBMC to subsequent LPS stimulation. In PBMC carrying two mutant
NOD2 alleles this modulatory effect was reversed and MDP priming caused the
inflammatory response to be enhanced.
Conclusion: MDP priming significantly modulates responses of monocytes to LPS. This
effect is altered in patients with Crohn’s disease – possibly related to mutations in the
NOD2 gene. This modulatory effect may explain in part the pro-inflammatory consequence
of mutations in the NOD2 gene and could provide mechanistic understanding of how
mutations in the NOD2 gene may cause Crohn’s disease.
date: 2009-12
oa_status: green
thesis_class: doctoral_open
language: eng
thesis_view: UCL_Thesis
dart: DART-Europe
primo: open
primo_central: open_green
full_text_status: public
pages: 149
institution: UCL (University College London)
department: Department of Medicine
thesis_type: Doctoral
citation:        Chalmers-Watson, T.A.;      (2009)    The role of the NOD2 gene in the pathogenesis of Crohn’s disease.                   Doctoral thesis , UCL (University College London).     Green open access   
 
document_url: https://discovery.ucl.ac.uk/id/eprint/18990/1/18990.pdf