Alveolar Macrophage Release of Tumor Necrosis Factor-alpha in Chronic Alcoholics without Liver Disease


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Abstract

Alcohol is an immunosuppressive drug, and chronic abuse has been associated with increased susceptibility to a variety of infections, including bacterial pneumonia and tuberculosis. Alveolar macrophages are the resident phagocytes of the lung and play a central role in lung host defenses against infection ranging from direct antibacterial activity to the release of proinflammatory cytokines such as tumor necrosis factor-alpha (TNFalpha). TNFalpha, in particular, plays a key role in the development of the early inflammatory response. In this study, we investigated the effects of chronic alcohol consumption on alveolar macrophage release of TNFalpha in vitro. We prospectively studied lipopolysaccharide (LPS)-stimulated release of TNFalpha from alveolar macrophages obtained from bronchoalveolar lavage fluid (BALF) in 22 alcoholic (18 smokers, 4 nonsmokers) and 7 nondrinking healthy volunteers (3 smokers, 4 nonsmokers). The total number of cells recovered by bronchoalveolar lavage (BAL) and their differential distribution were not significantly different in alcoholics versus controls (43 ± 8 × 10 and 39 ± 13 × 10, respectively). However, the total number of cells recovered from BALF was significantly higher in smokers (51 ± 8 × 10) than in nonsmokers (19 ± 5 × 10). Spontaneous (basal) release of TNFalpha by alveolar macrophages was the same in alcoholics and controls. In contrast, LPS-stimulated release of TNFalpha was significantly suppressed in alcoholics compared with that of controls (1343 ± 271 vs. 3806 ± 926 U TNF/ml/10 cells, respectively, p < 0.015). When controlled for smoking, LPS-stimulated TNFalpha production was suppressed in alcoholic nonsmokers (563 ± 413 U TNF/ml/10) compared with control nonsmokers (5113 ± 1264 U TNF/ml/10). LPS-stimulated TNFalpha production was also less in control smokers (2063 ± 386 U TNF/ml/10 cells) than in control nonsmokers (5113 ± 1264 U TNF/ml/10 cells). There was no difference in TNFalpha production between smoking alcoholics and smoking control subjects. We conclude that chronic alcohol consumption significantly suppresses LPS-stimulated alveolar macrophage production of TNFalpha. This effect is obscured if the subject also smokes. Because TNFalpha production is an important element in host defense, this may explain, in part, the susceptibility of chronic alcohol abusers to a variety of infections.

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