Surfactant deficiency with decreased opsonic activity in a guinea pig model of alcoholism

A critical review of recent knowledge of alcohol's effects on the immunological response in different tissues

Alcohol misuse contributes to the dysregulation of immune responses and multiorgan dysfunction across various tissues, which are associated with higher risk of morbidity and mortality in people with alcohol use disorders. Organ-specific immune cells, including microglia in the brain, alveolar macrophages in the lungs, and Kupffer cells in the liver, play vital functions in host immune defense through tissue repair and maintenance of homeostasis. However, binge drinking and chronic alcohol misuse impair these immune cells' abilities to regulate inflammatory signaling and metabolism, thus contributing to multiorgan dysfunction. Further complicating these delicate systems, immune cell dysfunction associated with alcohol misuse is exacerbated by aging and gut barrier leakage. This critical review describes recent advances in elucidating the potential mechanisms by which alcohol misuse leads to derangements in host immunity and highlights current gaps in knowledge that may be the focus of future investigations.

Hyaladherins May be Implicated in Alcohol-Induced Susceptibility to Bacterial Pneumonia

Although the epidemiology of bacterial pneumonia and excessive alcohol use is well established, the mechanisms by which alcohol induces risk of pneumonia are less clear. Patterns of alcohol misuse, termed alcohol use disorders (AUD), affect about 15 million people in the United States. Compared to otherwise healthy individuals, AUD increase the risk of respiratory infections and acute respiratory distress syndrome (ARDS) by 2-4-fold. Levels and fragmentation of hyaluronic acid (HA), an extracellular glycosaminoglycan of variable molecular weight, are increased in chronic respiratory diseases, including ARDS. HA is largely involved in immune-assisted wound repair and cell migration. Levels of fragmented, low molecular weight HA are increased during inflammation and decrease concomitant with leukocyte levels following injury. In chronic respiratory diseases, levels of fragmented HA and leukocytes remain elevated, inflammation persists, and respiratory infections are not cleared efficiently, suggesting a possible pathological mechanism for prolonged bacterial pneumonia. However, the role of HA in alcohol-induced immune dysfunction is largely unknown. This mini literature review provides insights into understanding the role of HA signaling in host immune defense following excessive alcohol use. Potential therapeutic strategies to mitigate alcohol-induced immune suppression in bacterial pneumonia and HA dysregulation are also discussed.

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.

Epidemiology of sepsis: race, sex, and chronic alcohol abuse

The annual incidences of severe sepsis in several industrialized nations have recently been reported to be 50-100 cases per 100,000 persons. These numbers exceed the estimated rates for other diseases that hold a heightened public awareness, including breast cancer and acquired immune deficiency syndrome. There are also sex and race differences in the incidence of sepsis. Men are more likely than women to develop sepsis, with a mean annual relative risk of 1.28. Nonwhites are nearly twice as likely to develop sepsis as whites. These race and sex disparities in the incidence of sepsis are likely explained by differences in a variety of factors, including the presence of comorbid conditions. For example, chronic alcohol abuse is associated with a persistent fever, delayed resolution of symptoms, increased rates of bacteremia, increased use of intensive care, prolonged duration of hospital stay, and increased cost of hospitalization for infected patients.

In Vivo Dysfunction of the Term Alveolar Macrophage After in Utero Ethanol Exposure

BACKGROUND

The effects of in utero alcohol exposure on the immune function of the newborn remain under investigation. Fetal ethanol (ETOH) exposure increases oxidative stress in the developing lung, in part due to decreased availability of the antioxidant glutathione (GSH). We have previously shown that in utero ETOH impairs alveolar macrophage phagocytosis and viability in the premature pup, while maintaining GSH availability with maternal supplementation of S-adenosyl-methionine (SAM) during ETOH ingestion improves macrophage function and viability. We hypothesized that dysfunction of the neonatal alveolar macrophage exposed to ETOH in utero would persist at term gestation.

METHODS

Using a guinea-pig model of fetal ETOH exposure, timed-pregnant guinea-pigs were pair-fed ETOH+/-the GSH precursor SAM and the diet continued until spontaneous delivery. Term alveolar macrophages were evaluated using fluorescent microscopy for phagocytosis and apoptosis after in vitro incubation with Staphalococcus aureus. Using an in vivo model of intranasal Staph. aureus inoculation, the in vivo function of the term alveolar macrophage was also investigated using confocal fluorescent analysis.

RESULTS

In utero ETOH exposure increased oxidant stress in the alveolar macrophage and decreased phagocytosis and viability in vitro and in vivo. Confocal analysis of phagocytosis in vivo demonstrated a marked impairment of internalization of the bacteria by the ETOH-exposed alveolar macrophage. The addition of SAM during maternal ETOH ingestion prevented loss of alveolar macrophage function and viability in vitro and in vivo.

CONCLUSIONS

In utero ETOH exposure impairs alveolar macrophage function and viability in vitro and in vivo even at term gestation. The ETOH-induced changes in macrophage function and viability can be ablated with maternal SAM supplementation. Further investigations are required to identify the mechanisms of ETOH-induced derangement of phagocytosis in the neonatal alveolar macrophage and the clinical ramifications of altered immune function after in utero alcohol exposure for the newborn.

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

We have previously demonstrated that chronic alcohol exposure decreases glutathione in the alveolar space. Although alcohol use is associated with decreased alveolar macrophage function, the mechanism by which alcohol impairs macrophage phagocytosis is unknown. In the current study, we examined the possibility that ethanol-induced alveolar macrophage dysfunction was secondary to decreased glutathione and subsequent chronic oxidative stress in the alveolar space. After 6 wk of ethanol ingestion, oxidant stress in the alveolar macrophages was evidenced by a 30-mV oxidation of the GSH/GSSG redox potential (P <or= 0.05). For control macrophages, approximately 80% internalized fluorescent Staphylococcus aureus were added in vitro. In contrast, only 20% of the macrophages from the ethanol-fed rats were able to bind and internalize fluorescent S. aureus. This ethanol-induced decreased capacity for phagocytosis was paralleled by increased apoptosis. When added to the ethanol diet, the glutathione precursors procysteine or N-acetyl cysteine normalized glutathione and oxidant stress in the epithelial lining fluid as well as the alveolar macrophages to control values. This attenuation of oxidant stress was associated with normalization of macrophage phagocytosis and viability. These results suggested that decreased glutathione availability in the alcoholic lung contribute to alveolar macrophage dysfunction via oxidative stress, resulting in not only decreased function but decreased viability.

Acute and chronic alcohol abuse modulate immunity

This article represents the proceedings of the Alcohol and Immunology Research Interest Group (AIRIG) meeting, a satellite workshop held at the 37th Annual Meeting of the Society for Leukocyte Biology. The meeting was sponsored by the AIRIG and the National Institute on Alcohol Abuse and Alcoholism. The presentations were as follows: (1) Effects of Ethanol on Immune Response to Hepatitis C Virus by Jack R. Wands, (2) Alcohol and Alveolar Macrophage Dysfunction: The Role of Chronic Oxidant Stress by Lou Ann S. Brown, (3) T Cell Responses to Listeria monocytogenes in Mice on a Chronic Ethanol Exposure Protocol by Robert T. Cook, (4) Mechanisms of Acute and Chronic Alcohol Consumption on Severity of Viral Infections by the Liver and Pancreas by Thomas R. Jerrells, (5) Acute and Chronic Effects on Macrophage Ectodomain Shedding: Implications for Lung Host Defenses by Jay K. Kolls, (6) Increased Susceptibility to Pseudomonas Infection of Burn-Injured Mice Given Alcohol Before Injury by Elizabeth J. Kovacs, (7) Regulation of Tumor Necrosis Factor alpha Expression in Macrophages by Chronic Ethanol by Laura E. Nagy, and (8) Hepatitis C Virus Infection and Alcohol Use by Gyongyi Szabo. Meeting coorganizers were Elizabeth J. Kovacs, Lou Ann S. Brown, Thomas R. Jerrells, and Robert T. Cook.

Maternal Alcohol Abuse and Neonatal Infection

BACKGROUND

Since chronic alcohol use suppresses the adult immune system, we tested the hypothesis that maternal alcohol ingestion increases the risk of infection in term newborns.

METHODS

Analysis of a large case-control study of birth weight for gestational age was performed focusing on maternal alcohol ingestion and the development of infection in term newborns > or =36 weeks gestation. After delivery, mothers were asked about alcohol and tobacco use in the 3 months prior to conception, the 1st, 2nd, and 3rd trimester of pregnancy.

RESULTS

Eight hundred and seventy-two singleton newborns (872) > or = 36 weeks gestation were identified for analysis. A total of 51 (5.8%) had newborn infections. Gestational age, sex, and small for gestational age (SGA) were similar in the newborns with and without infection (p = NS). Infants whose mothers reported alcohol use, excessive drinking or smoking in pregnancy were more likely to have a newborn diagnosed with an infection than were mothers who reported abstaining from alcohol or cigarettes (p < 0.05). When controlling for race and smoking, SGA infants whose mothers used any alcohol had a 2.5-fold increase risk of infection, while excessive alcohol use increased the risk 3-4-fold. In a multivariable logistic regression analysis controlling for low maternal income, smoking, and SGA, excessive alcohol use during the 2 trimester increased the risk of newborn infection (OR 3.7 [1.1,12.8], p < 0.05).

CONCLUSIONS

Excessive maternal alcohol use is associated with an increased risk of newborn infection in this patient sample. Increased awareness and further clinical investigations are warranted to address the detrimental effects of fetal alcohol exposure on the developing immune system.

Chronic ethanol ingestion and the risk of acute lung injury: a role for glutathione availability?

Although pulmonary function is not altered, a history of alcohol abuse is an independent outcome variable in the development of acute respiratory distress syndrome. In the absence of cirrhosis, alcohol abuse decreased glutathione, the key antioxidant lining the alveolar space, by 80% and is associated with alveolar barrier leak. Neither the glutathione pool nor barrier leak was corrected by abstinence for 1 week. This aberrant glutathione homeostasis may contribute to enhanced alveolar permeability, thereby increasing susceptibility to the development of acute respiratory distress syndrome. In a rat model, chronic ingestion of ethanol decreased pulmonary glutathione concentration, increased alveolar barrier permeability, and increased the risk of acute lung injury. In alveolar type II cells, chronic ingestion of ethanol altered cellular functions such as decreased surfactant processing, decreased barrier integrity, and increased sensitivity to cytotoxin-induced apoptosis in vitro and in vivo. In alveolar macrophages, chronic ingestion of ethanol decreased phagocytosis of microorganisms and decreased cell viability, events that would increase the risk of pneumonia. A central role for glutathione availability was demonstrated by the normalization of cellular function and viability of type II cells and macrophages as well as decreased sensitivity to endotoxemia-induced acute lung injury when glutathione precursors were added to the ethanol diet. These results support the suggestion that chronic ingestion of ethanol increased the risk of acute lung injury not through ethanol per se but through the chronic oxidative stress that resulted from ethanol-induced glutathione depletion. Because chronic oxidative stress alters cellular functions and viability, the lung becomes more susceptible when a second hit such as sepsis occurs.

The effects of chronic alcohol abuse on pulmonary glutathione homeostasis

The incidence and severity of the acute respiratory distress syndrome (ARDS) is increased in critically ill patients with a prior history of chronic alcohol abuse; however, the specific mechanisms responsible for this association are unknown. Recently, we determined that chronic ethanol ingestion in rats decreased the alveolar epithelial lining fluid (ELF) concentration of the antioxidant glutathione (GSH), which is a characteristic finding in patients with ARDS. However, the effects of chronic alcohol abuse on the human alveolar epithelium are essentially unknown. Therefore, as a first step we asked if chronic alcohol abuse, independent of other comorbid conditions, decreases the concentration of GSH in the human lung. We determined that otherwise healthy chronic alcoholics had significantly decreased ELF concentrations of GSH compared with nonalcoholic control subjects (79 micromol [48 to 118 micromol] versus 576 micromol [493 to 728 mmol], p < 0.001). Furthermore, the percentage of GSH in the oxidized form was higher in the chronic alcoholics (9.8% [2.2 to 14.8%] versus 2.8% [0.4 to 4.0%] p = 0.05), indicative of increased utilization of GSH. This is the first report that chronic alcohol abuse alters GSH homeostasis in the human lung, and suggests a potential mechanism by which chronic alcohol abuse predisposes susceptible patients to develop ARDS.