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An increase in polymorphonuclear leukocytes (PMNs) and proinflammatory chemokines, such as IL-8 and macrophage inflammatory protein-1a (MIP), are found in the airways during early stages of bronchopulmonary dysplasia. We determined whether IL-10 produces a dose-related inhibition of proinflammatory chemokine release from stimulated neutrophils of the newborn and whether the mechanism involves the pivotal transcription factor, nuclear factor-?B. PMNs isolated from the cord blood of healthy newborns were stimulated submaximally with either lipopolysaccharide (n = 5) or tumor necrosis factor (n = 4), with and without IL-10 (0.01–1000 ng/mL). IL-8 and MIP release were measured in cell culture supernatants at 18 h. The presence or absence of nuclear factor-?B activity and inhibitor-?Ba degradation was measured at 30 min and 3 h after PMN stimulation began. During lipopolysaccharide stimulation, IL-10 significantly reduced IL-8 levels from 50 ± 16 ng/mL to 7 ± 3 ng/mL, and MIP levels from 14 ± 5 to 0.7 ± 0.1 ng/mL (mean ± SEM, p < 0.01). IL-10 produced an insignificant reduction in IL-8 and MIP levels after stimulation of PMNs with tumor necrosis factor. IL-10 did not inhibit nuclear factor-?B activation and inhibitor-?Ba degradation in PMNs stimulated with tumor necrosis factor or lipopolysaccharide for 30 min. After PMN stimulation for 3 h, inhibitor-?Ba cytoplasmic levels were restored; however, they were unaffected by IL-10. We conclude that IL-10 is a potent inhibitor of lipopolysaccharide-stimulated release of IL-8 and MIP from neutrophils of the newborn via a mechanism not involving nuclear factor-?B activity. Further work is needed to determine whether exogenous IL-10 may be useful for suppressing inflammation in bronchopulmonary dysplasia.

Polymorphonuclear leukocytes (PMN) of the newborn, to a greater extent than those of the adult, have the ability to amplify PMN recruitment to an inflammatory site by their own release of IL-8, and this process is inhibited by dexamethasone. The aim of the present study was to determine whether the regulation of nuclear factor-?B (NF-?B) could explain the previous observations. NF-?B is a transcription factor pivotal for expression of genes encoding inflammatory cytokines such as IL-8, but NF-?B has not been previously studied in the PMN of the newborn. NF-?B activation was measured by an electrophoretic mobility shift assay in nuclear extracts prepared from PMN isolated from adults and cord blood from newborns. Two distinct molecular forms of NF-?B were identified after tumor necrosis factor-a stimulation; this included the previously characterized p50/65 heterodimer and a newly identified p50/50 homodimer. Both NF-?B dimers were activated by tumor necrosis factor-a to significantly higher levels in the neutrophil of the newborn versus adult. An additional new finding was that pretreatment of PMN with dexamethasone (10-7M, therapeutic range) inhibited activation of both NF-?B complexes in both the newborn and the adult PMN. We conclude that the increased activation of NF-?B by the PMN of the newborn may play an important role in neonatal inflammatory reactions. Eventually, specific targeting of NF-?B activation in the neutrophil may be an effective molecular approach for the treatment of neutrophil-mediated disorders in the newborn.