Hyperbaric oxygen enhances neutrophil apoptosis and their clearance by monocyte-derived macrophages

摘要

Neutrophil apoptosis and clearance by macrophages are essential for wound healing. Evidence suggests that hyperbaric oxygen (HBO) exposure may enhance neutrophil apoptosis, but HBO effects leading to neutrophil clearance by macrophages are still unclear. In the current study, bovine neutrophils and monocyte-derived macrophages(MDM Phi) were co-cultured under HBO (97.9% O-2, 2.1% CO2 at 2.4 atm absolute (ATA)) (1 atm = 101.325 kPa), hyperbaric normoxia (8.8% O-2 at 2.4 ATA), normobaric hyperoxia (95% O-2, 5% CO2), normoxia (air), and normobaric hypoxia (5% O-2, 5% CO2). Phagocytosis of fresh and 22 h aged neutrophils by MDM Phi was increased after HBO pre-treatment, assessed using flow cytometry and light microscopy. Enhanced clearance of neutrophils was accompanied by an increase in H2O2 levels following HBO pre-treatment with upregulation of IL-10 (anti-inflammatory cytokine) mRNA expression in LPS-stimulated MDM Phi that had ingested aged neutrophils. TNF-alpha (pro-inflammatory cytokine) gene expression did not change in LPS-stimulated MDM Phi that had ingested fresh or aged neutrophils after HBO, pressure, and hyperoxia. These findings suggest that HBO-activated MDM Phi participate in the clearance of apoptotic cells. Uptake of neutrophils by MDM Phi exposed to HBO may contribute to resolution of inflammation, because HBO induced up-regulation of IL-10 mRNA expression.