Inhibitory effect of retinoic acid on the respiratory burst of adult and cord blood neutrophils and macrophages: Potential implication to bronchopulmonary dysplasia

Infants suffering from bronchopulmonary dysplasia (BPD) are knwon to have low levels of vitamin A, a factor which may be implicated in the pathogenesis of the condition. The ability of retinoic acid (RA) (one of the active forms of vitamin A) to influence the production of superoxide anion (O₂^-) and hydrogen peroxide (H₂O₂) by stimulated human adult or cord blood neutrophils and macrophages has been studied. RA was found to inhibit the O₂^- and H₂O₂ production in a dose-dependent manner. The time required for maximal inhibition was 30 min for neutrophils and 24 h for macrophages. Although cord blood neutrophils produced larger quantities of O₂^- and H₂O₂ both with and without RA, the degree of inhibition was similar in both adult and neonatal cells (40-60%). The results suggest that retinoic acid may prevent neutrophil and macrophage mediated lung damage by inhibiting the production of toxic oxygen compounds, especially in BPD conditions.