Clinicopathological significance of oxidative cellular damage in non-alcoholic fatty liver diseases

Abstract

Oxidative stress may play an important role in the progression of simple steatosis to non-alcoholic steatohepatitis (NASH). Oxidative stress is generated through multiple sources, including oxidation of free fatty acids, cytochrome P4502E1, iron overload, and necro-inflammatory cytokines including tumor necrosis factor-alpha. Oxidative stress may trigger damage to cellular membranes and nuclear DNA, which results in lipid peroxidation and oxidative DNA damage, respectively. Here, we present our data on intrahepatic localization and clinico-pathological significance of oxidative stress-induced cellular damage in the patients with non-alcoholic fatty liver diseases (NAFLD). Our subjects were 23 patients with non-alcoholic simple fatty liver, 17 with NASH, and 7 with normal liver (control). Hepatic expression of 4-hydroxy-2'-nonenal (HNE) and 8-hydroxydeoxyguanosine (8-OHdG), as reliable markers of lipid peroxidation and oxidative DNA damage, was in situ detected by using commercially available monoclonal antibodies. While no HNE adducts were observed in control livers, they were frequently detected in NAFLD. In NASH, the localization of the HNE adducts was in the cytoplasm of sinusoidal cells and hepatocytes with a predominance in zone 3. The grade of necro-inflammation as well as the stage of fibrosis significantly correlated with the HNE labeling index. With respect to 8-OHdG, although no 8-OHdG expression was observed in normal liver and only a few in non-alcoholic simple fatty liver, 11 of 17 patients with NASH (65%) exhibited nuclear expression of 8-OHdG in hepatocytes and sinusoidal cells in areas of active inflammation. The 8-OHdG index significantly correlated with the grade of necro-inflammation, but not with the stage of fibrosis. Our observations suggest that oxidative cellular damage occurs frequently in livers with NAFLD and may be associated with some clinico-pathological features of NAFLD including liver fibrosis and possibly, hepatocarcinogenesis.