David M. Guidot

Chronic alcohol abuse is associated with an increased incidence of acute respiratory distress syndrome and severity of multiple organ dysfunction in patients with septic shock.

ObjectiveAlcohol is one of the most commonly used drugs in the world and causes dysfunction in many vital organs. However, the effects of chronic alcohol abuse on acute lung injury and nonpulmonary organ dysfunction are relatively unexplored. The goal of this study was to determine the effects of chronic alcohol abuse on the incidence and severity of the acute respiratory distress syndrome and multiple organ dysfunction syndrome in patients with septic shock. DesignMulticenter prospective epidemiologic study. SettingIntensive care units of four university urban hospitals. PatientsA total of 220 critically ill patients with septic shock. Measurements and Main FindingsThirty percent of the patients (66 of 220) were identified as having a history of chronic alcohol abuse based on a positive response to an alcohol screening questionnaire. The incidence of acute respiratory distress syndrome in patients with a positive history of chronic alcohol abuse was 70% (46 of 66), compared with 31% (47 of 154) in individuals without a history of chronic alcohol abuse (p < .001). After adjusting for differences in the source of infection, sex, age, chronic hepatic dysfunction, diabetes, severity of illness, nutritional status, and smoking status, the effects of chronic alcohol abuse on the incidence of acute respiratory distress syndrome remained significant (p < .001; odds ratio, 3.70; 95% confidence interval, 1.83–7.71). The effect of the source of infection (pulmonary vs. nonpulmonary) on the development of acute respiratory distress syndrome also remained significant in this multivariable analysis (p < .001; odds ratio, 3.68; 95% confidence interval, 1.95–7.18). Based on the highest daily Sequential Organ Failure Assessment score, patients with a history of chronic alcohol abuse had more severe nonpulmonary organ dysfunction when compared with nonalcoholics (9.42 ± 3.89 vs. 8.05 ± 4.10, p = .01). After adjusting for source of infection, sex, age, nutritional status, history of diabetes, and smoking status, the effects of chronic alcohol abuse on the incidence of nonpulmonary organ dysfunction also remained significant (p = .03; odds ratio, 2.07; 95% confidence interval, 1.09–3.97). ConclusionsWe conclude that chronic alcohol abuse is an independent risk factor for acute respiratory distress syndrome and increases the severity of nonpulmonary organ dysfunction in patients with septic shock.

Diabetic patients have a decreased incidence of acute respiratory distress syndrome

Objective Our ability to predict which critically ill patients will develop acute respiratory distress syndrome (ARDS) is imprecise. Based on the effects of diabetes mellitus on the inflammatory cascade, we hypothesized that a history of diabetes might alter the incidence of ARDS. Design A prospective multicenter study. Setting Intensive care units at four university medical centers. Patients One hundred thirteen consecutive patients with septic shock. Interventions None. Measurements and Main Results All patients were prospectively followed during their intensive care course for the development of ARDS. A history of diabetes was identified in 28% (32/113) of the patients. In this study, nondiabetics were more likely to develop septic shock from a pulmonary source (48%, 39/81) compared with diabetics (25%, 8/32) (p = .02). Forty-one percent (46/113) of the patients with septic shock developed ARDS. Forty-seven percent of the nondiabetic patients developed ARDS compared with only 25% of those with diabetes (p = .03, relative risk = 0.53, 95% confidence interval = 0.28–0.98). In a multivariate logistic regression analysis, when we adjusted for several variables including source of infection, the effect of diabetes on the incidence of ARDS remained significant (p = .03, odds ratio = 0.33, 95% confidence interval = 0.12–0.90). Conclusions In patients with septic shock, a history of diabetes is associated with a lower risk of developing ARDS compared with nondiabetics.

Chronic ethanol ingestion impairs alveolar type II cell glutathione homeostasis and function and predisposes to endotoxin-mediated acute edematous lung injury in rats.

Chronic alcohol abuse increases the incidence and mortality of the acute respiratory distress syndrome (ARDS) in septic patients. To examine a potential mechanism, we hypothesized that ethanol ingestion predisposes to sepsis-mediated acute lung injury by decreasing alveolar type II cell glutathione homeostasis and function. Lungs isolated from rats fed ethanol (20% in water for >/= 3 wk), compared with lungs from control-fed rats, had greater (P < 0. 05) edematous injury (reflected by nonhydrostatic weight gain) after endotoxin (2 mg/kg intraperitoneally) and subsequent perfusion ex vivo with n-formylmethionylleucylphenylalanine (fMLP, 10(-7) M). Ethanol ingestion decreased (P < 0.05) glutathione levels in the plasma, lung tissue, and lung lavage fluid, and increased (P < 0.05) oxidized glutathione levels in the lung lavage fluid. Furthermore, ethanol ingestion decreased type II cell glutathione content by 95% (P < 0.05), decreased (P < 0.05) type II cell surfactant synthesis and secretion, and decreased (P < 0.05) type II cell viability, in vitro. Finally, treatment with the glutathione precursors S-adenosyl-L-methionine and N-acetylcysteine in the final week of ethanol ingestion significantly reduced lung edema during perfusion ex vivo. We conclude that ethanol ingestion in rats alters alveolar type II cell glutathione levels and function, thereby predisposing the lung to acute edematous injury after endotoxemia. We speculate that chronic alcohol abuse in humans predisposes to ARDS through similar mechanisms.

Alterations in the immuno-skeletal interface drive bone destruction in HIV-1 transgenic rats.

Osteoporosis and bone fractures are increasingly recognized complications of HIV-1 infection. Although antiretroviral therapy itself has complex effects on bone turnover, it is now evident that the majority of HIV-infected individuals already exhibit reduced bone mineral density before therapy. The mechanisms responsible are likely multifactorial and have been difficult to delineate in humans. The HIV-1 transgenic rat recapitulates many key features of human AIDS. We now demonstrate that, like their human counterparts, HIV-1 transgenic rats undergo severe osteoclastic bone resorption, a consequence of an imbalance in the ratio of receptor activator of NF-κB ligand, the key osteoclastogenic cytokine, to that of its physiological decoy receptor osteoprotegerin. This imbalance stemmed from a switch in production of osteoprotegerin to that of receptor activator of NF-κB ligand by B cells, and was further compounded by a significantly elevated number of osteoclast precursors. With the advancing age of individuals living with HIV/AIDS, low bone mineral density associated with HIV infection is likely to collide with the pathophysiology of skeletal aging, leading to increased fracture risk. Understanding the mechanisms driving bone loss in HIV-infected individuals will be critical to developing effective therapeutic strategies.

Mitochondrial respiration scavenges extramitochondrial superoxide anion via a nonenzymatic mechanism.

We determined that mitochondrial respiration reduced cytosolic oxidant stress in vivo and scavenged extramitochondrial superoxide anion (O2-.) in vitro. First, Saccharomyces cerevisiae deficient in both the cytosolic antioxidant cupro-zinc superoxide dismutase (Cu,Zn-SOD) and electron transport (Rho0 state) grew poorly (P < 0.05) in 21% O2 compared with parent yeast and yeast deficient only in electron transport or Cu,Zn-SOD, whereas anaerobic growth was the same (P > 0.05) in all yeast. Second, isolated yeast and mammalian mitochondria scavenged extramitochondrial O2-. generated by xanthine/xanthine oxidase. Yeast mitochondria scavenged 42% more (P < 0.05) extramitochondrial O2-. during pyruvate/malate-induced respiration than in the resting state. Addition of either antimycin (respiratory chain inhibitor) or FCCP (respiratory chain uncoupler) prevented increased O2-. scavenging. Mitochondria isolated from yeast deficient in the mitochondrial manganous superoxide dismutase (Mn-SOD) increased (P < 0.05) O2-. scavenging 56% during respiration. This apparent SOD activity, expressed in units of SOD activity per milligram of mitochondrial protein, was the same (9 +/- 0.6 vs. 10 +/- 1.0; P = 0.43) as the O2-. scavenging of mitochondria with Mn-SOD, suggesting that respiration-dependent mitochondrial O2-. scavenging was nonenzymatic. Finally, isolated rat liver and lung mitochondria also increased (P < 0.05) O2-. scavenging during respiration. We speculate that respiring mitochondria, via the protonmotive pump, present a polarized, proton-rich surface that enhances nonenzymatic dismutation of extramitochondrial O2-. and that this is a previously unrecognized function of mitochondrial respiration with potential physiological ramifications.

Chronic Ethanol Ingestion in Rats Decreases Granulocyte-Macrophage Colony-Stimulating Factor Receptor Expression and Downstream Signaling in the Alveolar Macrophage

Although it is well recognized that alcohol abuse impairs alveolar macrophage immune function and renders patients susceptible to pneumonia, the mechanisms are incompletely understood. Alveolar macrophage maturation and function requires priming by GM-CSF, which is produced and secreted into the alveolar space by the alveolar epithelium. In this study, we determined that although chronic ethanol ingestion (6 wk) in rats had no effect on GM-CSF expression within the alveolar space, it significantly decreased membrane expression of the GM-CSF receptor in alveolar macrophages. In parallel, ethanol ingestion decreased cellular expression and nuclear binding of PU.1, the master transcription factor that activates GM-CSF-dependent macrophage functions. Furthermore, treatment of ethanol-fed rats in vivo with rGM-CSF via the upper airway restored GM-CSF receptor membrane expression as well as PU.1 protein expression and nuclear binding in alveolar macrophages. Importantly, GM-CSF treatment also restored alveolar macrophage function in ethanol-fed rats, as reflected by endotoxin-stimulated release of TNF-α and bacterial phagocytosis. We conclude that ethanol ingestion dampens alveolar macrophage immune function by decreasing GM-CSF receptor expression and downstream PU.1 nuclear binding and that these chronic defects can be reversed relatively quickly with rGM-CSF treatment in vivo.

Predisposition for disrepair in the aged lung.

Introduction: Idiopathic pulmonary fibrosis (IPF) is a devastating progressive lung disease with an average survival of only 3 to 5 years. The mechanisms underlying the initiation and progression of IPF are poorly understood, and treatments available have only modest effect on disease progression. Interestingly, the incidence of IPF is approximately 60 times more common in individuals aged 75 years and older, but the mechanism by which aging promotes fibrosis is unclear. The authors hypothesized that aged lungs have a profibrotic phenotype that render it susceptible to disrepair after injury. Methods: Young and old mice were treated with bleomycin to examine disrepair in the aged lung. In addition, uninjured young and old mouse lungs were analyzed for transforming growth factor-beta 1 (TGF-&bgr;1) production, extracellular matrix composition and lung fibroblast phenotype. Lung fibroblasts were treated with a DNA methyltransferase inhibitor to examine the potential epigenetic mechanisms involved in age-associated phenotypic alterations. Results: The lungs of old mice showed worse fibrosis after bleomycin-induced injury compared with the lungs from young mice. At baseline, aged lungs expressed a profibrotic phenotype characterized by increased mRNA expression for fibronectin extracellular domain A (Fn-EDA) and the matrix metalloproteinases (MMPs) MMP-2 and MMP-9. Old lungs also expressed higher levels of TGF-&bgr; receptor 1 and TGF-&bgr;1 mRNA, protein and activity as determined by increased Smad3 expression, protein phosphorylation and DNA binding. Lung fibroblasts harvested from aged lungs showed reduced expression of the surface molecule Thy-1, a finding also implicated in lung fibrosis; the latter did not seem related to Thy-1 gene methylation. Conclusion: Altogether, aged lungs manifest a profibrotic phenotype characterized by enhanced fibronectin extracellular domain A and MMP expression and increased TGF-&bgr;1 expression and signaling and are populated by Thy-1–negative fibroblasts, all implicated in the pathogenesis of lung fibrosis.

Zinc Deficiency Mediates Alcohol-Induced Alveolar Epithelial and Macrophage Dysfunction in Rats

Chronic alcohol abuse impairs both alveolar epithelial and macrophage function, and renders individuals susceptible to acute lung injury, pneumonia, and other serious lung diseases. Zinc deficiency, which is known to impact both epithelial and immune cell functions, is also associated with alcohol abuse. In this study, chronic alcohol ingestion (6 wk) in rats altered expression of key zinc transporters and storage proteins in the small intestine and the lung, and decreased zinc levels in the alveolar compartment. Zinc supplementation of alveolar epithelial monolayers derived from alcohol-fed rats in vitro, or of the diets of alcohol-fed rats in vivo, restored alveolar epithelial barrier function, and these improvements were associated with salutary changes in tight junction protein expression and membrane localization. In parallel, dietary zinc supplementation increased intracellular zinc levels, GM-CSF receptor expression, and bacterial phagocytic capacity in the alveolar macrophages of alcohol-fed rats. Together, these studies implicate zinc deficiency as a novel mechanism mediating alcohol-induced alveolar epithelial and macrophage dysfunction. Importantly, these findings argue that dietary supplementation can overcome alcohol-induced zinc deficiency and restore alveolar epithelial and macrophage function, and therefore could be an effective treatment for the susceptible alcoholic lung phenotype.

Alcohol abuse and acute lung injury: epidemiology and pathophysiology of a recently recognized association.

ABSTRACT Alcohol is the most commonly used and abused drug in the United States. The deleterious health effects of alcohol can be attributed both to its acute intoxicating effects, which result in temporary impairment of judgment and motor skills, and to its more chronic and toxic effects on the liver, pancreas, heart, and brain, all of which may result in irreversible organ damage. Although recognized for more than a century as a major risk factor for pneumonia, alcohol abuse was until recently perceived to have no significant effects on lung structure and/or function. However, within the past decade, epidemiologic studies have revealed that alcohol abuse independently increases the risk of acute respiratory distress syndrome (ARDS) two- to fourfold in patients with sepsis or trauma and may play a role in ARDS pathogenesis in as many as half of all patients with the syndrome. Although alcohol abuse alone does not cause acute lung injury, it renders the lung susceptible to dysfunction in response to the inflammatory stresses of sepsis, trauma, and other clinical conditions recognized to cause ARDS. Recent investigations in both animal models of chronic ethanol ingestion and in human subjects with a history of alcohol abuse have explored this previously unrecognized connection between alcohol and acute lung injury and have uncovered multiple derangements, which we now characterize as the “alcoholic lung.” This review summarizes the epidemiologic association between alcohol abuse and acute lung injury and the recent experimental findings that are unraveling the underlying pathophysiology.

HIV-1 transgene expression in rats causes oxidant stress and alveolar epithelial barrier dysfunction

BackgroundHIV-infected individuals are at increased risk for acute and chronic airway disease even though there is no evidence that the virus can infect the lung epithelium. Although HIV-related proteins including gp120 and Tat can directly cause oxidant stress and cellular dysfunction, their effects in the lung are unknown. The goal of this study was to determine the effects of HIV-1 transgene expression in rats on alveolar epithelial barrier function. Alveolar epithelial barrier function was assessed by determining lung liquid clearance in vivo and alveolar epithelial monolayer permeability in vitro. Oxidant stress in the alveolar space was determined by measuring the glutathione redox couple by high performance liquid chromatography, and the expression and membrane localization of key tight junction proteins were assessed. Finally, the direct effects of the HIV-related proteins gp120 and Tat on alveolar epithelial barrier formation and tight junction protein expression were determined.ResultsHIV-1 transgene expression caused oxidant stress within the alveolar space and impaired epithelial barrier function even though there was no evidence of overt inflammation within the airways. The expression and membrane localization of the tight junction proteins zonula occludens-1 and occludin were decreased in alveolar epithelial cells from HIV-1 transgenic rats. Further, treating alveolar epithelial monolayers from wild type rats in vitro with recombinant gp120 or Tat for 24 hours reproduced many of the effects on zonula occludens-1 and occludin expression and membrane localization.ConclusionTaken together, these data indicate that HIV-related proteins cause oxidant stress and alter the expression of critical tight junction proteins in the alveolar epithelium, resulting in barrier dysfunction.