Augmentation of aflatoxin B1 hepatotoxicity by endotoxin: Involvement of endothelium and the coagulation system

Abstract

Aflatoxin B1 (AFB1) is a fungal toxin that causes both acute hepatotoxicity and liver carcinoma in exposed humans and animals. Previous studies have shown that exposure of rats to nontoxic doses of bacterial lipopolysaccharide (LPS) augments AFB1 acute hepatotoxicity, resulting in enhanced injury to hepatic parenchymal cells and bile ducts. At larger doses, LPS causes damage to sinusoidal endothelial cells (SECs) and activation of the coagulation system. Accordingly, we tested the hypothesis that treatment of rats with AFB1 and LPS damages SECs and activates the coagulation system, which is critical for potentiation of AFB1 hepatotoxicity by LPS. Male, Sprague-Dawley rats were given 1 mg/kg AFB1 (ip), then 4 hours later 7.4 × 106 EU/kg LPS was administered (iv). A time-dependent injury to SECs and parenchymal cells was observed in AFB1/LPS-cotreated animals that became significant by 12 h, as estimated by increases in plasma hyaluronic acid (HA) and alanine aminotransferase (ALT) activities, respectively. Immunohistochemical analysis revealed that endothelial cell immunostaining was decreased in both centrilobular and periportal regions after AFB1/LPS treatment. Immunohistochemical evidence of fibrin deposition was found in both centrilobular and periportal regions by 12 h, but these deposits persisted only in periportal regions by 24 h. Administration of the anticoagulant heparin to AFB1/LPS-cotreated animals markedly attenuated increases in markers of hepatic parenchymal cell injury but provided only minimal amelioration of bile duct injury. These results suggest that AFB1/LPS coexposure results in SEC injury and activation of the coagulation system, and that the coagulation system is required for the development of hepatic parenchymal cell injury but not bile duct injury in this model.