Fetal Alcohol Exposure Impairs Alveolar Macrophage Function via Decreased Glutathione Availability

Abstract

Immature function of the alveolar macrophage increases the risk of pulmonary infections in premature newborns. In utero alcohol increases fetal systemic oxidative stress. Because the premature lung is deficient in glutathione (GSH), we hypothesized that chronic in utero alcohol (ethanol) exposure exacerbates the oxidative stress within the developing lung, thereby impairing alveolar macrophage function. Additionally, we evaluated the effects of in vivo and in vitro GSH availability on ethanol-exposed macrophage function. Using a guinea pig model of chronic in utero ethanol exposure, fetal epithelial lining fluid (ELF) and alveolar macrophage GSH were decreased with increased markers of oxidative stress. Ethanol-exposed macrophage exhibited impaired phagocytosis and increased apoptosis compared with gestational control. When the GSH precursor S-adenosyl-methionine (SAM) was added to the maternal drinking water containing ethanol, fetal ELF and macrophage GSH were maintained and ELF oxidative stress diminished. In vivo maternal SAM therapy maintained macrophage phagocytosis and decreased apoptosis. In vitro GSH supplements also improved phagocytosis and viability in both premature and ethanolexposed macrophage. This suggested that in utero ethanol impaired premature macrophage function and viability via decreased GSH availability. Furthermore, GSH supplementation during and after ethanol exposure improved fetal macrophage function and viability. These results add a new dimension to the detrimental effects of fetal alcohol exposure on the developing alveolar macrophage, raising the possibility of GSH therapy to augment premature alveolar macrophage function. Fetal alcohol exposure remains a significant problem in our society. Alcohol abuse and binge drinking by pregnant women has been estimated at an alarming 35% of pregnancies (1-3). Fetal alcohol syndrome or alcohol-related neurodevelopmental disorder has been estimated to occur in ‫0001/1ف‬ pregnancies (4). Because there is a strong relationship between cocaine abuse and concurrent alcohol ingestion (5-7), and both substances may increase the risk of premature delivery (7,8), a significant population of premature infants is exposed to alcohol in utero.In animal models of fetal alcohol exposure, alcohol increases systemic oxidative stress in the developing fetus (9 -14). A decrease in the antioxidant GSH has been demonstrated, particularly in the alcohol-exposed fetal liver (9,15,16). As an essential antioxidant in the body, GSH is normally present in high concentrations in the ELF of the lung (17). The fetal lung is at risk for increased oxidative stress during development, because maturation of antioxidant systems, including GSH, is gestationally dependent (18,19). A reduction in alveolar GSH, as seen in the premature infant, leaves the preterm lung susceptible to increased pulmonary oxidative injury (20,21) and chronic lung disease (18,22). The impact of the oxidative stress of fetal alcohol exposure superimposed on the low GSH environment of the developing lu...

Maternal alcohol ingestion reduces surfactant protein A expression by preterm fetal lung epithelia

“…Maternal alcohol consumption during pregnancy and its effects on fetal immunity remains a largely unexplored area of clinical significance. Several studies have already demonstrated that newborns exposed to ethanol during prenatal life have a higher incidence of infection (Gauthier et al, 2004;Gauthier et al, 2005b). The exact mechanism by which this occurs is not fully understood but it is possible that reduction in tracheal CBF and SP-A may increase susceptibility to infections.…”

“…The exact mechanism by which this occurs is not fully understood but it is possible that reduction in tracheal CBF and SP-A may increase susceptibility to infections. Ethanol consumption has been shown to have a suppressive effect on cellular components of the innate immune system such as macrophages (Gauthier et al, 2005b) and/or neutrophils (Vinson et al, 1998), all of which may occur concurrently with reductions in CBF and SPA.…”

“…Most studies have focused on neurodevelopmental (Riley and McGee, 2005;West and Blake, 2005) and behavioral anomalies (Mattson et al, 2001;Sood et al, 2001) in infants born from mothers who drank during pregnancy. Recently it has been suggested that in addition to neurodevelopmental effects, ethanol may play a significant role in immunomodulation and consequential increase in susceptibility to various infectious in newborn infants (Gauthier et al, 2005a;Gauthier et al, 2004;Gauthier et al, 2005b). It is our hypothesis that ethanol consumption in moderation during pregnancy alters mucociliary clearance and expression of SP-A and SP-D by fetal lung epithelia.…”

Glutathione availability modulates alveolar macrophage function in the chronic ethanol-fed rat

“…Alveolar macrophages were fixed with 3.7% paraformaldehyde, and nonspecific binding was blocked with bovine serum albumin. Apoptosis was determined by staining for the cleaved moiety of the DNA repair enzyme poly(ADP-ribose) polymerase (PARP), an indicator of the apoptosis pathway (10,17). The primary antibody for cleaved PARP (Oncogene, Cambridge, MA) was added in a 1:100 dilution, and the sample was incubated for 2 h. Cells were serially rinsed with phosphate-buffered saline, and the secondary antibody (anti-rabbit IgG; AlexaFluor) was added in a 1:200 dilution for 1 h. Apoptosis was also evaluated after staining with the ApopTag Plus kit (Oncor, Gaithersburg, MD), which stains TdT-mediated dUTP nick end labeling (TUNEL)-positive cells.…”

Exposure Memory and Lung Regeneration

“…The process involves immune cells, proliferation of remaining epithelial cells, and recruitment of different progenitor populations. Prior research shows that fetal alcohol exposure or vitamin C deficiency affects lung cell populations and function in postnatal life (15)(16)(17), implying that the character of the scaffold influences regeneration. Systematic knowledge of exposure memory (3,18) is needed to determine whether conditioning to reverse exposure memory will promote lung regeneration.…”