Erythrophagocytosis by Liver Macrophages (Kupffer Cells) Promotes Oxidative Stress, Inflammation, and Fibrosis in a Rabbit Model of Steatohepatitis

• DOI: 10.2353/ajpath.2007.060441
• Publication Date: 2007-02-23T20:31:52Z
• Authors: Kohji Otogawa; Kohji Kinoshita; Hideki Fujii; Masahide Sakabe; Ryoko Shiga; Kazuki Nakatani; Kazuo Ikeda; Yuji Nakajima; Yoshihiro Ikura; Makiko Ueda; Tetsuo Arakawa; Fumihiko Hato; Norifumi Kawada
• Keywords: Adult; Aged, 80 and over; Inflammation; 0301 basic medicine; Erythrocytes; Iron; Immunoblotting; Apoptosis; Flow Cytometry; Fibrosis; Immunohistochemistry; Cell Line; Hepatitis; Disease Models, Animal; 03 medical and health sciences; In Situ Nick-End Labeling; Animals; Cytokines; Humans; Female; Aged; DNA Primers

Nonalcoholic steatohepatitis (NASH) is a progressive fibrotic disease, the pathogenesis of which has not been fully elucidated. Here, we report a molecular aspect of this disease elucidated using rabbits fed a cholesterol-rich high-fat diet and exhibiting insulin resistance. The liver in this model showed steatohepatitis with fibrosis and high mRNA expression for some cytokines, heme oxygenase-1, transforming growth factor-beta1, and collagen alpha1(I). Erythrocytes isolated from the model showed marked fragility and the externalization of phosphatidylserine (PS) on the outer leaflet of the membrane and were frequently engulfed by Kupffer cells/macrophages in the hepatic sinusoids. Expression of milk fat globule-epidermal growth factor (EGF)-factor 8, a PS-binding protein, was augmented in the liver. In culture, RAW 264.7 cells engulfed erythrocytes oxidized by tert-butyl hydroperoxide, a process that was inhibited by anti-milk fat globule-EGF-factor 8 antibody. In addition, PS-positive erythrocytes appeared entrapped in the model liver in ex vivo perfusion experiments. Finally, in specimens from NASH patients, the aggregation of erythrocytes in inflammatory hepatic sinusoids was notable. These results indicate that the engulfment of PS-externalized, apoptotic signal-positive, erythrocytes by hepatic macrophages may lead to the deposition of iron derived from hemoglobin in the liver and be involved in the pathogenesis of steatohepatitis.