Erythrophagocytosis by liver macrophages (Kupffer cells) promotes oxidative stress, inflammation, and fibrosis in a rabbit model of steatohepatitis: implications for the pathogenesis of human nonalcoholic steatohepatitis.
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.
Otogawa
Kohji
K
Department of Hepatology, Graduate School of Medicine, Osaka City University, 1-4-3, Asahimachi, Abeno, Osaka 545-8585, Japan.
Kinoshita
Kohji
K
Fujii
Hideki
H
Sakabe
Masahide
M
Shiga
Ryoko
R
Nakatani
Kazuki
K
Ikeda
Kazuo
K
Nakajima
Yuji
Y
Ikura
Yoshihiro
Y
Ueda
Makiko
M
Arakawa
Tetsuo
T
Hato
Fumihiko
F
Kawada
Norifumi
N
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002460:Cell Line; D016207:Cytokines / Q000032:analysis; D017931:DNA Primers; D004195:Disease Models, Animal; D004912:Erythrocytes / Q000378:metabolism* / Q000473:pathology; D005260:Female; D005355:Fibrosis; D005434:Flow Cytometry; D006505:Hepatitis / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D007249:Inflammation / Q000378:metabolism* / Q000473:pathology; D007501:Iron / Q000378:metabolism; D007728:Kupffer Cells / Q000378:metabolism*; D008099:Liver / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D046529:Microscopy, Electron, Transmission; D008875:Middle Aged; D018384:Oxidative Stress / Q000502:physiology*; D010587:Phagocytosis / Q000502:physiology*; D010718:Phosphatidylserines / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction
D016207:Cytokines; D017931:DNA Primers; D010718:Phosphatidylserines; D012333:RNA, Messenger; D007501:Iron