Interleukin-10 inhibits proinflammatory chemokine release by neutrophils of the newborn without suppression of nuclear factor-κB

Abstract

An increase in polymorphonuclear leukocytes (PMNs) and proinflammatory chemokines, such as IL-8 and macrophage inflammatory protein-1α (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-κB. 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-κB activity and inhibitor-κBα 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-κB activation and inhibitor-κBα degradation in PMNs stimulated with tumor necrosis factor or lipopolysaccharide for 30 min. After PMN stimulation for 3 h, inhibitor-κBα 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-κB activity. Further work is needed to determine whether exogenous IL-10 may be useful for suppressing inflammation in bronchopulmonary dysplasia.