Hyperoxia- and hypoxia-mediated activation of polymorphonuclear leukocytes: a comparison of cord and adult venous blood

Abstract

Background: Among the most prominent changes occurring in newborn infants is the exposure of tissues and blood cells to increased oxygen tension. This increase is even more pronounced in neonatal resuscitation using 100% oxygen, currently recommended in the published guidelines. Objective: To analyse the response of neonatal and adult polymorphonuclear neutrophils (PMN) to high or low oxygen tension in vitro. Materials: Neonatal cord blood and adult venous blood without previous contact to ambient air was exposed to 0, 21, or 100% oxygen for 30 min followed by incubation for up to 24 h. Methods: Flow cytometry was used to assess PMN activation as indicated by downregulation of L-selectin expression. Cell viability was quantified by the amount of propidium iodide uptake. Results: In adult PMN, L-selectin downregulation was greatly accelerated by hypoxia (PO2=27.2±3.4 mmHg) compared with both normoxia (PO2=71.0±11.0 mmHg) or hyperoxia (PO2=653.2±9.4) (P<0.05). In contrast, hyperoxia was the most potent stimulus for cord blood PMN, compared with both normoxia and hypoxia (P<0.05). Evidence of necrosis as indicated by positive staining for propidium iodide was similar in cord blood (10 h: 5.83% in oxygen) and in adult blood (10 h: 6.45% in oxygen). No differences were found between exposure to hypoxia, normoxia, or hyperoxia. Conclusion: Oxygen exposure of neonatal PMN leads to a more pronounced activation as compared with adult cells. Exposure towards high concentrations of oxygen may contribute to inflammatory processes during early neonatal life.