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Evidence for impaired CARD15 signalling in Crohn's disease without disease linked variants

Jakob Benedict Seidelin1, Oliver Jay Broom, Jørgen Olsen

  • 1Department of Gastroenterology, Medical Section, Herlev Hospital, University of Copenhagen, Denmark. jseidelin@dadlnet.dk

Plos One
|November 13, 2009
PubMed

Insights

Crohn's disease patients without CARD15 variants show impaired muramyl dipeptide (MDP) sensing, indicating a dysfunctional immune response. This suggests a potential role for these inhibited MDP pathways in Crohn's disease development.

Area of Science:

  • Immunology
  • Gastroenterology
  • Genetics

Background:

  • Crohn's disease (CD) is linked to impaired sensing of muramyl dipeptide (MDP) in patients with CARD15 gene variants.
  • While CARD15 signaling is implicated in preventing inflammatory bowel disease, only a subset of CD patients carry disease-associated variants.
  • This study investigates CARD15 signaling in CD patients lacking these specific variants.

Purpose of the Study:

  • To determine if CARD15 signaling is altered in Crohn's disease patients without known disease-associated CARD15 variants.
  • To explore the functional consequences of impaired muramyl dipeptide (MDP) sensing in these patients.

Main Methods:

  • Monocytes from Crohn's disease (CD) patients in remission (without immunosuppressants) and healthy controls were analyzed.
  • Response to muramyl dipeptide (MDP) was measured, focusing on IkappaB kinase (IKK) and mitogen-activated protein (MAP) kinase pathways.
  • Inflammasome activation was assessed in response to MDP.

Main Results:

  • Patients with CD but without disease-linked CARD15 variants exhibited impaired MDP response in peripheral monocytes.
  • This impairment correlated with decreased activation of IkappaB kinase alpha/beta (IKKalpha/beta), a key step in the nuclear factor kappaB (NFkappaB) pathway.
  • While MAP-kinase activation was unaffected, the inflammasome showed constitutive activation in CD patients but was unresponsive to MDP in both CD and control monocytes.

Conclusions:

  • Inhibited MDP-dependent pathways may contribute to Crohn's disease pathogenesis, even in patients without the common CARD15 variants.
  • CD patients display a dysfunctional immune response characterized by impaired sensing of stimuli and constitutively active cytokine processing.
  • These findings highlight a broader immune dysregulation in CD beyond specific CARD15 mutations.
Abstract

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