Complementary Roles of Nod2 in Hematopoietic and Nonhematopoietic Cells in Preventing Gut Barrier Dysfunction
Ziad Al Nabhani1, Nicolas Montcuquet, Maryline Roy
1*Laboratoire d'excellence Inflamex, Université Paris-Diderot Sorbonne Paris-Cité, UMR 1149, Paris, France; †INSERM, UMR 1149, Paris, France; ‡INSERM, UMR 989, Paris, France; §Université Paris Descartes-Sorbonne Paris Cité, Institut IMAGINE, Paris, France; ‖Assistance Publique Hôpitaux de Paris, Services des Maladies Digestives et Respiratoires de l'Enfant et Service d'Anatomie Pathologique, Hôpital Robert Debré, Paris, France; and ¶Institut de Recherche en Santé Digestive IRSD, Université de Toulouse, INSERM, INRA, ENVT, UPS, 31024 Toulouse, France.
Background:
Crohn's disease (CD) pathogenesis is multifactorial involving genetic and environmental factors. Loss of function mutations in the nucleotide oligomerization domain 2 (NOD2) gene are the main genetic risk factor for CD. Like patients with CD, Nod2 mice are characterized by an enhanced Th1 immune response and a defective mucosal barrier function evidenced by increased intestinal permeability. We previously showed that the latter is related to hematopoietic Nod2 deficiency. Our aim was to explore the mechanisms by which Nod2 expressed in the hematopoietic and in the nonhematopoietic compartments interplay to control epithelial paracellular permeability.
Methods:
Depletion of CD4 T cells in Nod2 mice and treatments with inhibitors were conducted in chimeric mice transplanted with bone marrow cells from Nod2-deficient donors into Nod2-sufficient recipients or vice versa. Caco-2 cells overexpressing a NOD2 gene which did or did not include a CD-associated polymorphism were treated with inhibitors or siRNAs and cocultured with hematopoietic cells from Peyer's patches.
Results:
In vivo and in vitro Nod2 in hematopoietic cells regulates epithelial paracellular permeability through cytokine production influencing myosin light chain kinase (MLCK) activity. Indeed, tumor necrosis factor-α and interferon-γ secretion by CD4 T cells upregulated expression and activity of epithelial MLCK leading to increased epithelial tight junction opening. When stimulated by muramyl dipeptide, Nod2 in the nonhematopoietic compartment normalized the permeability and T-cell cytokine secretion and regulated MLCK activity. This MLCK regulation is mediated by TAK1 and RICK-dependent mechanisms.
Conclusions:
Our study demonstrates how hematopoietic and nonhematopoietic Nod2 regulate intestinal barrier function, improving our knowledge on the mechanisms involved in CD pathogenesis.
Insights
Loss of function mutations in the nucleotide oligomerization domain 2 (NOD2) gene impact Crohn's disease (CD) pathogenesis. This study reveals how NOD2 in immune and non-immune cells controls intestinal barrier function, offering insights into CD mechanisms.
Area of Science:
- Immunology
- Gastroenterology
- Cell Biology
Background:
- Crohn's disease (CD) pathogenesis is complex, involving genetic and environmental factors.
- Loss-of-function mutations in nucleotide oligomerization domain 2 (NOD2) are a primary genetic risk factor for CD.
- Nod2-deficient mice exhibit heightened Th1 immune responses and impaired mucosal barrier function, similar to CD patients.
Purpose of the Study:
- To investigate the interplay between Nod2 expression in hematopoietic and nonhematopoietic cells.
- To elucidate the mechanisms by which these compartments control epithelial paracellular permeability.
Main Methods:
- Utilized chimeric mice with reciprocal bone marrow transplants between Nod2-deficient and -sufficient donors.
- Employed Caco-2 cells with NOD2 overexpression, treated with inhibitors/siRNAs, and co-cultured with hematopoietic cells.
- Depleted CD4 T cells and used inhibitors in vivo and in vitro.
Main Results:
- Hematopoietic Nod2 regulates epithelial permeability via cytokine production (TNF-α, IFN-γ) that affects myosin light chain kinase (MLCK) activity.
- CD4 T cell cytokines upregulate epithelial MLCK, increasing tight junction permeability.
- Nonhematopoietic Nod2, upon stimulation, normalizes permeability and T-cell cytokine secretion by regulating MLCK activity through TAK1 and RICK pathways.
Conclusions:
- Hematopoietic and nonhematopoietic Nod2 play distinct but coordinated roles in maintaining intestinal barrier function.
- This study enhances understanding of the molecular mechanisms underlying CD pathogenesis.
- Targeting Nod2-mediated pathways could offer therapeutic strategies for CD.
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