Dexamethasone suppresses expression of Nuclear Factor-kappaB in the cells of tracheobronchial lavage fluid in premature neonates with respiratory distress.

Nuclear Factor-kappaB (NF-kappaB) plays a central role in regulating the key mediators of inflammation involved in acute lung injury. The anti-inflammatory effect of steroids by suppressing pro-inflammatory cytokines may be mediated by inhibition of transcription factor NF-kappaB. The objective of this study was to determine the effect of glucocorticoid therapy on the expression of NF-kappaB in the cells of tracheobronchial lavage fluid (TBLF) in premature neonates with respiratory distress. Nineteen premature neonates requiring mechanical ventilation and receiving glucocorticoids were enrolled. Their gestational age (mean +/- SD) was 25.0 +/- 1.2 wk, birth weight 714 +/- 105 g and age of starting dexamethasone was 33 +/- 15 d. Tracheobronchial lavage fluid was collected before and 48-72 h after starting dexamethasone. NF-kappaB expression was measured by immunocytochemistry using mouse MAb against the p65 subunit of NF-kappaB on cytospin slides. The percent of cells stained and the intensity staining index were significantly higher before starting dexamethasone compared with after steroid therapy. Localization of NF-kappaB was significantly decreased in the cytoplasm and nuclei of mononuclear cells after initiation of dexamethasone therapy. The concentration of IL-8 was also significantly lower after starting dexamethasone. In conclusion, dexamethasone suppressed the expression of NF-kappaB in the cytoplasm and nuclei of mononuclear cells and decreased levels of IL-8 in TBLF from premature neonates with respiratory distress. The anti-inflammatory effects of corticosteroids may be mediated through NF-kappaB.