Relation of Endotoxin, Endotoxin Binding Proteins and Macrophages to Severe Alcoholic Liver Injury and Multiple Organ Failure

Abstract

Our retrospective analysis of 105 patients with alcoholic liver injury confirmed that patients with severe alcoholic hepatitis (SAH) showed severe hyperbilirubinemia, reduced hepatic biosynthetic capacity, and marked acute inflammatory reactions, and developed multiple organ failure (MOF). Multivariate analysis using the Cox proportional hazards model showed serum C-reactive protein and DIC as significant independent prognostic factors among SAH, LC+AH, and AH groups. Improved assay showed an increase of plasma endotoxin with the progression of alcoholic liver injury. In most survivors, plasma Et levels decreased in the recovery phase. Serum interleukin (IL)-6 and IL-8 levels in the acute phase were high in patients with AH and LC+AH, especially in non-survivors and in patients with SAH. In the recovery phase, these cytokine levels in survivors tended to decrease, but in non-survivors, IL-6 remained high, and IL-8 further increased. Serum levels of HDL and albumin, which are protective against endotoxicity by inhibiting endotoxin uptake and TNF production by macrophages, were decreased with the progression of alcoholic liver injury. Animal experiments supported that the increase in endotoxin-binding capacity of HDL and albumin may serve as a protective mechanism against endotoxin in chronic ethanol-loaded rats and that an addition of high-dose ethanol to these rats may lead to impaired binding and inactivation of endotoxin. Lipopolysaccharide-binding protein (LBP) which enhances endotoxin uptake and TNF production by macrophages, was generally increased in patients with alcoholic liver injury. This imbalance among endotoxin binding proteins in the blood may induce overproduction of cytokines by macrophages in patients with severe alcoholic liver injury. Our animal experiments further revealed that an additional administration of a high-dose ethanol to chronic alcohol-fed rats led to decrease of endotoxin clearance, increased extrahepatic accumulation of endotoxin and elevation of plasma TNF. The splenic macrophages and pulmonary alveolar macrophages are demonstrated to be important for endotoxin uptake, and excessive production of TNF in rats given large amounts of alcohol. An in vitro culture experiment in the presence of rat LBP suggested a role of these macrophages in excessive production of TNF-alpha. When the functions of various macrophages were compared in rats given alcohol, maximum TNF-alpha secretion was noted in alveolar macrophages, In conclusion, endotoxemia and its effects on extrahepatic macrophages may play key roles in the progression of severe alcoholic liver injury and MOF.