Role of zinc insufficiency in fetal alveolar macrophage dysfunction and RSV exacerbation associated with fetal ethanol exposure.

BACKGROUND: We previously reported that maternal alcohol use significantly increases the risk of sepsis in premature and term newborns. In the mouse, fetal ethanol exposure results in an immunosuppressed phenotype for the alveolar macrophage (AM) and decreases bacterial phagocytosis. In pregnant mice, ethanol decreased AM zinc homeostasis, which contributed to immunosuppression and impaired AM phagocytosis. In this study, we explored whether ethanol-induced zinc insufficiency extended to the pup AMs and contributed to immunosuppression and exacerbated viral lung infections. METHODS: C57BL/6 female mice were fed a liquid diet with 25% ethanol-derived calories or pair-fed a control diet with 25% of calories as maltose-dextrin. Some pup AMs were treated in vitro with zinc acetate before measuring zinc pools or transporter expression and bacteria phagocytosis. Some dams were fed additional zinc supplements in the ethanol or control diets, and then we assessed pup AM zinc pools, zinc transporters, and the immunosuppressant TGFß1. On postnatal day 10, some pups were given intranasal saline or respiratory syncytial virus (RSV), and then AM RSV phagocytosis and the RSV burden in the airway lining fluid were assessed. RESULTS: Fetal ethanol exposure decreased pup AM zinc pools, zinc transporter expression, and bacterial clearance, but in vitro zinc treatments reversed these alterations. In addition, the expected ethanol-induced increase in TGFß1 and immunosuppression were associated with decreased RSV phagocytosis and exacerbated RSV infections. However, additional maternal zinc supplements blocked the ethanol-induced perturbations in the pup AM zinc homeostasis and TGFß1 immunosuppression, thereby improving RSV phagocytosis and attenuating the RSV burden in the lung. CONCLUSION: These studies suggest that, despite normal maternal dietary zinc intake, in utero alcohol exposure results in zinc insufficiency, which contributes to compromised neonatal AM immune functions, thereby increasing the risk of bacterial and viral infections.

In utero ethanol exposure impairs defenses against experimental group B streptococcus in the term Guinea pig lung.

BACKGROUND: The effects of fetal alcohol exposure on the risks of neonatal lung injury and infection remain under investigation. The resident alveolar macrophage (AM) is the first line of immune defense against pulmonary infections. In utero ethanol (ETOH) exposure deranges the function of both premature and term guinea pig AM. We hypothesized that fetal ETOH exposure would increase the risk of pulmonary infection in vivo. METHODS: We developed a novel in vivo model of group B Streptococcus (GBS) pneumonia using our established guinea pig model of fetal ETOH exposure. Timed-pregnant guinea pigs were pair fed +/-ETOH and some were supplemented with the glutathione (GSH) precursor S-adenosyl-methionine (SAM-e). Term pups were given GBS intratracheally while some were pretreated with inhaled GSH prior to the experimental GBS. Neonatal lung and whole blood were evaluated for GBS while isolated AM were evaluated using fluorescent microscopy for GBS phagocytosis. RESULTS: Ethanol-exposed pups demonstrated increased lung infection and sepsis while AM phagocytosis of GBS was deficient compared with control. When SAM-e was added to the maternal diet containing ETOH, neonatal lung and systemic infection from GBS was attenuated and AM phagocytosis was improved. Inhaled GSH therapy prior to GBS similarly protected the ETOH-exposed pup from lung and systemic infection. CONCLUSIONS: In utero ETOH exposure impaired the neonatal lung's defense against experimental GBS, while maintaining GSH availability protected the ETOH-exposed lung. This study suggested that fetal alcohol exposure deranges the neonatal lung's defense against bacterial infection, and support further investigations into the potential therapeutic role for exogenous GSH to augment neonatal AM function.

Fetal alcohol exposure impairs alveolar macrophage function via decreased glutathione availability.

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 ethanol-exposed 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.