c-Jun N-terminal kinase-mediated Rubicon expression enhances hepatocyte lipoapoptosis and promotes hepatocyte ballooning.
OBJECTIVE
To clarify the relationship between autophagy and lipotoxicity-induced apoptosis, which is termed "lipoapoptosis," in non-alcoholic steatohepatitis.


METHODS
Male C57BL/6J mice were fed a high-fat diet (HFD) for 12 wk, after which the liver histology and expression of proteins such as p62 or LC3 were evaluated. Alpha mouse liver 12 (AML12) cells treated with palmitate (PA) were used as an in vitro model.


RESULTS
LC3-II, p62, and Run domain Beclin-1 interacting and cysteine-rich containing (Rubicon) proteins increased in both the HFD mice and in AML12 cells in response to PA treatment. Rubicon expression was decreased upon c-Jun N-terminal kinase (JNK) inhibition at both the mRNA and the protein level in AML12 cells. Rubicon knockdown in AML12 cells with PA decreased the protein levels of both LC3-II and p62. Rubicon expression peaked at 4 h of PA treatment in AML12, and then decreased. Treatment with caspase-9 inhibitor ameliorated the decrease in Rubicon protein expression at 10 h of PA and resulted in enlarged AML12 cells under PA treatment. The enlargement of AML12 cells by PA with caspase-9 inhibition was canceled by Rubicon knockdown.


CONCLUSIONS
The JNK-Rubicon axis enhanced lipoapoptosis, and caspase-9 inhibition and Rubicon had effects that were cytologically similar to hepatocyte ballooning. As ballooned hepatocytes secrete fibrogenic signals and thus might promote fibrosis in the liver, the inhibition of hepatocyte ballooning might provide anti-fibrosis in the NASH liver.
Akiko Suzuki, Keisuke Kakisaka, Yuji Suzuki, Ting Wang, Yasuhiro Takikawa, Division of Hepatology, Department of Internal Medicine, Iwate Medical University, Morioka 0208505, Japan.
Akiko
A
Suzuki
Akiko Suzuki, Keisuke Kakisaka, Yuji Suzuki, Ting Wang, Yasuhiro Takikawa, Division of Hepatology, Department of Internal Medicine, Iwate Medical University, Morioka 0208505, Japan.
Keisuke
K
Kakisaka
Akiko Suzuki, Keisuke Kakisaka, Yuji Suzuki, Ting Wang, Yasuhiro Takikawa, Division of Hepatology, Department of Internal Medicine, Iwate Medical University, Morioka 0208505, Japan.
Yuji
Y
Suzuki
Akiko Suzuki, Keisuke Kakisaka, Yuji Suzuki, Ting Wang, Yasuhiro Takikawa, Division of Hepatology, Department of Internal Medicine, Iwate Medical University, Morioka 0208505, Japan.
Ting
T
Wang
Akiko Suzuki, Keisuke Kakisaka, Yuji Suzuki, Ting Wang, Yasuhiro Takikawa, Division of Hepatology, Department of Internal Medicine, Iwate Medical University, Morioka 0208505, Japan.
Yasuhiro
Y
Takikawa
D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D017209:Apoptosis; D001343:Autophagy; D053453:Caspase 9 / Q000378:metabolism; D061945:Caspase Inhibitors / Q000494:pharmacology; D002460:Cell Line; D049109:Cell Proliferation; D059305:Diet, High-Fat; D022781:Hepatocytes / Q000378:metabolism* / Q000473:pathology; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D008055:Lipids; D048670:MAP Kinase Kinase 4 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008869:Microtubule-Associated Proteins / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D010168:Palmitates / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism*; D000071456:Sequestosome-1 Protein / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism
D000873:Anthracenes; D061945:Caspase Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D008055:Lipids; C480860:Map1lc3b protein, mouse; D008869:Microtubule-Associated Proteins; D010168:Palmitates; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; C000601571:Rubcn protein, mouse; D000071456:Sequestosome-1 Protein; C101343:Sqstm1 protein, mouse; C432165:pyrazolanthrone; D048670:MAP Kinase Kinase 4; D053453:Caspase 9
Ballooned hepatocyte; Caspase 9; Rubicon; SP600125; c-Jun N-terminal kinase