Crohn’s & Colitis Congress™

Sessions Speakers Exhibitors Floor Plan Buzz

P092 - PHYSIOLOGIC HYPOXIA AND LIPID PEROXIDATION PRODUCTS MODULATE GRANULOCYTE-MACROPHAGE COLONY STIMULATING FACTOR-DEPENDENT NEUTROPHIL BACTERIAL KILLING IN PEDIATRIC CROHN’S DISEASE (Room Poster Hall)

Background. Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF) enhances neutrophil regulation of gut bacteria. Crohn’s Disease (CD) patients with reduced neutrophil GM-CSF signaling are more likely to experience stricturing complications requiring surgery. We aimed to determine whether bacterial killing by GM-CSF primed neutrophils is enhanced by physiologic hypoxia and suppressed by lipid peroxidation products including 4-hydroxynonenal (4-HNE). Methods: HL-60 human promyelocytic leukemia cells were differentiated to a neutrophil phenotype via 7-day incubation in DMSO. Primary human control or CD patient neutrophils or differentiated HL-60 cells were exposed to GM-CSF and/or 4-HNE, at 5% O2 (physiologic distal gut hypoxia) and atmospheric O2, exposed to S. Aureus, and the frequency of bacterial killing was determined via light microscopy. Results. The frequency of intra-cellular bacterial killing increased in CD patient primary neutrophils when exposed to hypoxia (99(3)) vs. atmospheric oxygen tension (92(6), p<0.0001) as well as in non-IBD control primary neutrophils when exposed to hypoxia (99.75(1)) vs. atmospheric oxygen tension (93(3), p<0.0001). Bacterial killing also increased in HL-60 cells when exposed to hypoxia (88(11)) vs. atmospheric oxygen tension (80(10), p=0.0089) and when primed with GM-CSF (80(4)) vs. basal conditions (73(8), p=0.0446). Bacterial killing was markedly suppressed in HL-60 cells stimulated with GM-CSF under hypoxic conditions in the presence of 4-HNE (68(7)) vs. HL-60 cells stimulated with GM-CSF under hypoxic conditions in the absence of 4-HNE (84(4), p=0.0171). Conclusions. Physiologic hypoxia in the distal gut boosts GM-CSF primed neutrophil bacterial killing which is in turn inhibited by lipid peroxidation products. These data have implications for therapeutic approaches to boost neutrophil function in CD patients with reduced GM-CSF signaling and stricturing complications.