Meconium-induced lung injury mediated by activation of alveolar macrophages

To clarify the mechanism of meconium-induced cellular injury, we examined the effect of meconium on the alveolar macrophages (AM) and bronchial epithelial cells (AK-D). Meconium obtained from healthy newborns was added to culture medium of AM and/or AK-D, which were cultured for 1 hour. Superoxide anion production of AM and the expression of intercellular adhesion molecule-1 (ICAM-1) on AK-D stimulated by meconium or oxygen radicals were determined. As a result, superoxide anion production of AM significantly increased when AM was cultured with meconium. Expression of ICAM-1 on AK-D appeared when AK-D was stimulated by hydroxyl radical but did not when AK-D was cultured with meconium. These results suggest that meconium-induced lung injury may occur through an activation of alveolar macrophages and the macrophage-epithelial cell axis may be important for the pathogenesis of meconium aspiration syndrome.