Role of GM-CSF in the inflammatory cytokine network that regulates neutrophil influx into the colonic mucosa duringClostridium difficileinfection in mice

Abstract

Clostridium difficile infection in antibiotic-treated mice results in acute colitis characterized by severe intestinal histopathology, robust neutrophil influx, and increased expression of numerous inflammatory cytokines, including GM-CS F. We utilized a neutralizing monoclonal antibody (mAb) against GM-CS F in a murine model to study the role of GM-CS F during acute C. difficile colitis. Cefoperazone-treated mice were challenged with C. difficile (strain 630) spores. Expression of GM-CS F was significantly increased in animals challenged with C. difficile. Treatment with an anti-GM-CS F mAb did not alter C. difficile colonization levels, weight loss, or expression of IL-22 and RegIIIγ. However, expression of the inflammatory cytokines TNFα and IL-1β, as well as iNOS, was significantly reduced following anti-GM-CS F treatment. Expression of the neutrophil chemokines CXCL1 and CXCL2, but not the chemokines CC L2, CC L4, CXCL9, and CXCL10, was significantly reduced by anti-GM-CS F treatment. Consistent with a decrease in neutrophil-attractant chemokine expression, there were fewer neutrophils in histology sections and a reduction in the expression of secretory leukocyte protease inhibitor (SLPI), a tissue anti-protease that protects against damage by secreted neutrophil elastase. These data indicate that GM-CS F plays a role in the inflammatory signaling network that drives neutrophil recruitment in response to C. difficile infection but does not appear to play a role in clearance of the infection.

Clostridium difficile colitis: pathogenesis and host defence

“…The pro-inflammatory cytokines IL-23 and granulocyte–macrophage-colony stimulating factor (GM-CSF) contribute to neutrophil migration to the site of infection by augmenting the expression of neutrophil chemotactic factors CXCL1 and CXCL2 (REFS 147,148). Once in the intestinal mucosa, neutrophils have several host protective functions, including the production of ROS in response to the activation of the N -formyl peptide receptor by TcdB 149 and the secretion of IFNγ 150 , potentially acting in concert with ILC1s to enhance phagocytosis and bacterial killing by macrophages.…”

Neutrophil-mediated inflammation in the pathogenesis of Clostridium difficile infections

“…After C. difficile infection, multiple signaling cascades and neutrophil chemo-attractant proteins are involved in neutrophil recruitment (Table 1). For example, interventions to completely abrogate or diminish P2Y6-CXCL8/IL-8 [40], MyD88-CXCL1 [37], NOD1-CXCL1 [39] and IL-22-STAT3 [41] signaling pathways or neutrophil chemo-attractant proteins GM-CSF [42], CXCL1, CXCL2 (MIP2) [22], IL-23 [43], IL-17 [44], IL-8 [45] and leptin [46] all lead to significantly decreased neutrophil recruitment in mouse models of C. difficile infection.…”

“…Recent studies have shown an important role for GM-CSF in C. difficile infection as well. Antibody-mediated neutralization of GM-CSF in C. difficile infected mice reduced both colonic neutrophil infiltration and expression of pro-inflammatory cytokines (IFNγ, IL-1β, IL-6, TNFα) and chemokines (CXCL1 and CXCL2) [42]. Whilst this data indicates that GM-CSF is involved in neutrophil recruitment, it is also possible that neutralization of GM-CSF causes extra-intestinal effects such as defective granulopoiesis resulting in a reduction of total available neutrophils.…”

Role of interferon‐γ and inflammatory monocytes in driving colonic inflammation during acute Clostridium difficile infection in mice

“…Clostridium difficile infection in mice results in innate large bowel inflammation, characterized by increased inflammatory cytokine expression, marked histopathology, and rapid, robust recruitment of innate immune cells including monocytes to the large bowel . MyD88 signalling is crucial for monocyte recruitment to the large intestine in response to C. difficile colitis, and CCR2‐deficient mice show a significant defect in monocyte recruitment when challenged with C. difficile .…”