title: Amplified nitric oxide production by pulmonary alveolar macrophages of newborn rats.
abstract: Oxygen (O2)-dependent and O2-independent antimicrobial mechanisms are used by alveolar macrophages (AM) to maintain lung sterility, but these mechanisms are underdeveloped in neonatal AM. Nitric oxide (NO(.)), a more recently described antimicrobial and immunomodulating molecule, has not been studied in neonatal AM. Lavaged AM from 3-day-old, 10-day-old, maternal and adult rats were treated with or without lipopolysaccharide (LPS) and/or interferon-γ (IFN-γ) and NO(.) synthase activity was measured as its L-arginine metabolites: NO2(-), NO3(-), and citrulline. Superoxide anion (O2(.-)) production by suspended macrophages, initiated by either opsonized zymosan or phorbol, was used as a marker of O2-dependent antimicrobial activity. Lysozyme content of AM was measured as a component of O2-independent antimicrobial activity. Unstimulated 3-day-old macrophages generated >10-fold more NO2(-) + NO3(-) than did 10-day-old, maternal or adult AM. Twenty hours after LPS and IFN-γ stimulation, 3-day-old AM produced > 2 times more NO2(-) and NO3(-) than did the more mature macrophages. Basal and stimulated O2(.-) release was similar among 3-day-old, 10-day-old and adult AM, while lysozyme concentrations were > 4-fold higher in adult macrophages compared to AM from 3-day-old pups. Rather than having a role in NO(.)-dependent antimicrobial activity, we propose that newborn AM have amplified NO(.) production to modulate their own differentiation and replication after birth. The age-dependent differences in NO(.) synthase expression by AM may lend insight into the regulation of this important enzyme.
authors.affiliation: a Department of Pediatrics , Baylor College of Medicine , Houston , Texas , USA.
authors.forename: M P
authors.initials: MP
authors.lastname: Sherman
authors.affiliation: b Departments of Pediatrics , University of California , Los Angeles; Los Angeles , California , USA.
authors.forename: V Z
authors.initials: VZ
authors.lastname: Wong
authors.affiliation: b Departments of Pediatrics , University of California , Los Angeles; Los Angeles , California , USA.
authors.forename: E E
authors.initials: EE
authors.lastname: Aeberhard
authors.affiliation: c Departments of Molecular and Medical Pharmacology , University of California , Los Angeles , California , USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Fukuto
authors.affiliation: c Departments of Molecular and Medical Pharmacology , University of California , Los Angeles , California , USA.
authors.forename: L J
authors.initials: LJ
authors.lastname: Ignarro