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Suppression of autophagy sensitizes Kupffer cells to endotoxin
Author(s) -
Fukada Hiroo,
Yamashina Shunhei,
Izumi Kousuke,
Komatsu Masaaki,
Tanaka Keiji,
Ikejima Kenichi,
Watanabe Sumio
Publication year - 2012
Publication title -
hepatology research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.123
H-Index - 75
eISSN - 1872-034X
pISSN - 1386-6346
DOI - 10.1111/j.1872-034x.2012.01024.x
Subject(s) - autophagy , kupffer cell , tumor necrosis factor alpha , lipopolysaccharide , biology , tlr4 , western blot , inflammation , endocrinology , medicine , lysosome , microbiology and biotechnology , chemistry , immunology , apoptosis , enzyme , biochemistry , gene
Aim: Recent evidence suggests that protein degradation system autophagy is implicated in a component of innate immunity. We report here that suppression of autophagy in Kupffer cells due to hepatic steatosis enhances an inflammatory response to endotoxin. Methods: Kupffer cells were isolated from C57BL/6J mice fed chow diet (control) or high‐fat diet (HFD) for 12 weeks, liver‐specific autophagy‐deficient mice (Atg7 F/F :Mx1‐Cre) and wild‐type mice (Atg7 F/F ). Kupffer cells were incubated with 100 ng/mL lipopolysaccharide (LPS). The concentration of tumor necrosis factor (TNF)‐α in media was measured by enzyme‐linked immunoassay. Expression of Toll‐like receptor (TLR)4, IκB kinase (IKK)‐α/β, p38, p62 and LC3 in Kupffer cells was evaluated by western blot analysis. Results: Incubation with LPS increased LC3‐II expression of Kupffer cells from control mice; however, an increase in LC3‐II expression due to LPS was suppressed in Kupffer cells from HFD mice. Moreover, both p62 expression and TNF‐α production in Kupffer cells from HFD mice was higher than control mice. On the other hand, LPS exposure increased TNF‐α production from autophagy‐deficient Kupffer cells more than wild type. There was no significant difference in expression of TLR4 between wild and autophagy‐deficient Kupffer cells. Nevertheless, activation of p38 or IKK in Kupffer cells due to LPS was augmented by autophagy deficiency. The addition of the p38 inhibitor SB203580 attenuated TNF‐α production in both wild and autophagy‐deficient Kupffer cells. Conclusion: These results suggest that suppression of autophagy observed in Kupffer cells from steatotic liver sensitizes to endotoxin. In conclusion, suppression of autophagy may play a pivotal role on progression of NAFLD.