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MIP-3α expression in macrophages is NOD dependent
M Hausmann1, C Zeitler, A Weber
1Division of Gastroenterology and Hepatology, University Hospital of Zurich, Zurich, Switzerland. martin.hausmann@usz.ch
Background:
The first identified susceptibility gene for Crohn's disease, NOD2, acts as a sensor for the bacterial-wall peptidoglycan fragment muramyl dipeptide (MDP) and activates the transcription factor nuclear factor-κB (NF-κB). Upon NF-κB activation, intestinal macrophages (IMACs) induce expression of macrophage inflammatory protein (MIP)-3α to attract memory T lymphocytes. We therefore investigated the influence of NOD2 ligation of IMAC differentiation and functional MIP-3α induction.
Methods:
Human embryonal kidney HEK293 cells were transfected with NOD2 wild-type (NOD2(WT)) and the NOD2 SNP13 variant (NOD2(L1007fsinsC)) and stimulated with MDP. Recruitment of CD45R0+ and Th17 cells was determined by immunohistochemistry.
Results:
Endogenous NOD2 stimulation was followed by a dose-dependent increase in MIP-3α secretion in MONO-MAC-6 (MM6) cells. MIP-3α mRNA was also significantly (*p < 0.05) induced in HEK293 transfected with NOD2(WT) via MDP ligation. In vivo cell-cell contacts between IMACs and CD45R0+ memory T cells as well as recruitment of Th17 cells in patients of NOD2 variants were unchanged as compared to wild-type patients.
Conclusion:
Our data demonstrate a dose-dependent increase in MIP-3α secretion in the human myeloid cell line MM6 upon MDP. However, MIP-3α-driven recruitment of Th17 cells or CD45R0+ memory T lymphocytes is not affected in patients carrying heterozygous NOD2 variants.
Insights
NOD2 ligation increases macrophage inflammatory protein (MIP)-3α secretion, but does not affect T cell recruitment in Crohn's disease patients with NOD2 variants. This suggests NOD2's role in immune cell attraction may be independent of these specific variants.
Area of Science:
- Immunology
- Genetics
- Cell Biology
Background:
- NOD2 is a key susceptibility gene for Crohn's disease, sensing bacterial peptidoglycan and activating NF-κB.
- NF-κB activation in intestinal macrophages (IMACs) leads to MIP-3α production, attracting memory T lymphocytes.
- The study investigates how NOD2 ligation affects IMAC differentiation and MIP-3α induction.
Purpose of the Study:
- To determine the impact of NOD2 ligation on IMAC differentiation.
- To assess the functional consequence of NOD2 ligation on MIP-3α induction.
- To investigate the role of NOD2 variants in T cell recruitment in Crohn's disease.
Main Methods:
- HEK293 cells were transfected with wild-type NOD2 (NOD2(WT)) or a variant (NOD2(L1007fsinsC)) and stimulated with MDP.
- MIP-3α secretion and mRNA induction were measured in MM6 and HEK293 cells.
- In vivo immunohistochemistry assessed cell-cell contacts and Th17 cell recruitment in patients with NOD2 variants.
Main Results:
- NOD2 stimulation with MDP resulted in a dose-dependent increase in MIP-3α secretion in MM6 cells.
- MIP-3α mRNA was significantly induced in HEK293 cells transfected with NOD2(WT) upon MDP ligation.
- In patients with NOD2 variants, in vivo cell-cell contacts and Th17 cell recruitment were comparable to wild-type patients.
Conclusions:
- NOD2 ligation induces a dose-dependent increase in MIP-3α secretion in human myeloid cells (MM6).
- Despite increased MIP-3α, the recruitment of Th17 cells and CD45R0+ memory T lymphocytes is not altered in patients with heterozygous NOD2 variants.
- These findings suggest that NOD2 variants may not impact the inflammatory response mediated by MIP-3α-driven T cell recruitment in Crohn's disease.
