Background: It is suggested that endotoxin, proinflammatory cytokines, and lipopolysaccharide-binding protein (LBP) play an important role in the development of alcoholic liver disease. Our previous study showed that splenic macrophages were important for endotoxin uptake and excessive production of tumor necrosis factor (TNF) in rats given large amounts of alcohol. To determine the pathophysiological roles of macrophages in alcoholic liver disease, we examined the effect of ethanol on TNF-alpha secretion of rat Kupffer cells, alveolar macrophages, and peritoneal macrophages in the presence or absence of LBP.
Methods: Kupffer cells, alveolar macrophages, and peritoneal macrophages were isolated from male Sprague Dawley rats. After the preculture in the medium containing 0, 10, 50, and 100 mmol/liter of ethanol, TNF-alpha secretion by these cells incubated with 100 ng/ml of endotoxin in the presence or absence of LBP (1% rat serum) was determined.
Results: In the absence of LBP, an addition of ethanol to the medium suppressed TNF-alpha secretion of alveolar macrophages. Kupffer cells and peritoneal macrophages were less affected. Addition of LBP led to marked enhancement (7- to 24-fold) of TNF-alpha secretion of macrophages either with or without ethanol in the medium. Although ethanol tended to suppress TNF-alpha secretion of these cells, alveolar macrophages were less affected in the presence of LBP.
Conclusions: Serum LBP enhances the secretion of TNF-alpha by macrophages. Alveolar macrophages may be important for excessive production of TNF-alpha in chronic alcoholics with endotoxemia.