Ethanol Inhibits Lung Clearance of Pseudomonas aeruginosa by a Neutrophil and Nitric Oxide‐Dependent Mechanism, In Vivo

Abstract

Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic pathogen that can be found in individuals in which the immune system has been suppressed by HIV/AIDS or chronic alcoholism. We evaluated the role of inducible nitric oxide synthase (NOS II) as a modulator of lung concentrations of P. aeruginosa in normal rats and rats given a single dose of ethanol (ETOH). Rats were pretreated with either sterile saline (PBS, 0.1 ml/kg, i.v.) or the NOS II inhibitor L-N6-iminoethyl lysine (LNIL, 10 mg/kg, i.v.) 15 min before intraperitoneal administration of either PBS (4.5 ml/kg) or ETOH (4.5 g/kg). Thirty min after administration of PBS or ETOH the rats were placed in inhalation chambers and exposed to 45 min of an aerosol containing P. aeruginosa (5 x 10(4) colony forming units, CFU). A group of rats (n = 5-6/treatment/time period) were killed immediately (0 hr) or 4 hr after inhalation of P. aeruginosa. The lungs were homogenized and the P. aeruginosa were grown in nutrient broth to determine the number of viable CFU remaining in the lung. The NOS II and TNFalpha mRNA and protein content lung alveolar macrophages (AM) and neutrophils (PMN) were measured with RT-PCR and Western blot. The concentration of nitrate and nitrite anion in the bronchoalveolar lavage fluid (BALf) and ex vivo incubates of PMN were also measured. The CFU of P. aeruginosa present in the lungs of the four groups of rats at 0 hr did not differ. The CFU of P. aeruginosa in the lung increased (p < 0.05) in rats pretreated with ETOH when compared with that obtained from rats pretreated with PBS. However, pretreatment of rats with LNIL decreased (p < 0.05) the 4 hr lung content of P. aeruginosa. Coadministration of LNIL and ETOH to rats augmented the CFU of P. aeruginosa in lungs to amounts which did not differ from that of rats pretreated with ETOH. Inhalation of P. aeruginosa increased NOS II mRNA and protein in rat AM and PMN. Pretreatment of rats with ETOH alone, or in combination with LNIL, inhibited P. aeruginosa-induced NOS II transcription and translation and AM and PMN nitrate and nitrite generation whereas pretreatment with LNIL alone only inhibited nitrate and nitrite generation. Pretreatment of rats with ETOH suppressed P. aeruginosa stimulated PMN recruitment into the lung whereas LNIL enhanced (p < 0.05) P. aeruginosa-stimulated PMN recruitment into the lung. ETOH-induced increases of the lung content of P. aeruginosa were associated with increased PKC delta isozyme in the membrane of the PMN but could not be explained by altered plasma concentrations of hydrocortisone or ETOH. The data demonstrate that selective inhibition of NOS II-derived NO by LNIL decreases the lung content of P. aeruginosa whereas ETOH inhibits the lung clearance of P. aeruginosa. Speculatively, the difference between these effects of LNIL and ETOH may result from differences in drug-induced changes in lung recruitment of PMN.

Pathophysiology of Acute Lung Injury and the Acute Respiratory Distress Syndrome

“…139,140 In addition to alterations in glutathione homeostasis, chronic alcohol abuse may alter surfactant synthesis and secretion, 136 alveolar epithelial cell apoptosis, 141,142 alveolar capillary barrier permeability, 143,144 alveolar epithelial fluid transport function, 143 and alveolar macrophage function. [145][146][147] Transfusion-Related Acute Lung Injury Transfusion-related ALI (TRALI) is defined as the development of noncardiogenic pulmonary edema that is temporally related to the transfusion of blood products. 148 TRALI most commonly occurs with transfusion of packed red blood cells, fresh-frozen plasma, platelets, and whole blood.…”

Repeated ethanol exposure during late gestation alters the maturation and innate immune status of the ovine fetal lung

“…Alcoholic adults are known to have an increased risk of acute respiratory distress syndrome (ARDS) and pulmonary infections (1,41). Furthermore, adult lungs exposed to ethanol have been shown to have increased type-II alveolar epithelial cell apoptosis, as well as decreased surfactant synthesis and expression of proinflammatory cytokines (7,17,(27)(28)(29). If similar effects occurred in the fetus, functional development of the lungs could be impaired, contributing to respiratory distress after birth.…”

“…In the present study, we examined the effects of repeated ethanol exposure during the third-trimester equivalent on fetal lung growth, parenchymal architecture, and the surfactant system. Because there is evidence that ethanol can affect proinflammatory cytokines in the lung (17,27), we also examined the expression of major proinflammatory cytokines.…”

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

“…Although many mechanisms are undoubtedly involved, the increased risk of respiratory infections by alcoholics is partially due to an impaired immune response of the resident alveolar inflammatory cell, the alveolar macrophage. This impaired response is due in part to decreased ability of alveolar macrophages to phagocytose and clear infectious particles from the airways (3,11). Equally important is impaired release of proinflammatory cytokines, chemokines, and oxidant radicals required for microbial killing (28).…”