Removal of acetaminophen protein adducts by autophagy protects against acetaminophen-induced liver injury in mice.

Abstract

BACKGROUND & AIMS:

Acetaminophen (APAP)-induced liver injury is the most frequent cause of acute liver failure in the US and many other countries. Metabolism of APAP results in formation of APAP protein adducts (APAP-AD) in hepatocytes and triggers mitochondrial dysfunction and necrosis. However, the mechanisms for how APAP-AD are removed from hepatocytes remain unknown.

METHODS:

Mice or primary hepatocytes were treated with APAP. APAP-AD were determined by immunoblot, immunostaining and high pressure liquid chomatography with electrochemical detection analysis.

RESULTS:

We found that APAP-AD were detected at 1h, peaked at approximately 2h, declined at 6h and almost full removed at 24h post treatment with APAP in mouse livers and in primary mouse hepatocytes. APAP-AD displayed a punctate pattern and were colocalized with GFP-LC3 positive autophagosomes and Lamp1 positive lysosomes in APAP-treated primary hepatocytes. Moreover, isolated autophagosomes and autolysosomes from APAP-treated mouse livers contained APAP-AD, suggesting autophagy may selectively remove APAP-AD. APAP-AD were detected in both detergent soluble and insoluble pools in APAP-treated mouse livers and hepatocytes. More importantly, pharmacological inhibition of autophagy by leupeptin or chloroquine increased whereas induction of autophagy by Torin 1 decreased serum APAP-AD levels in APAP-treated mice, which correlated with alanine aminotransferase levels and liver necrosis. Furthermore, SQSTM1/p62, an autophagy receptor protein, was recruited to APAP-AD. Adenovirus-mediated shRNA knockdown of SQSTM1/p62 led to increased APAP-AD and necrosis in primary hepatocytes.

CONCLUSIONS:

Our data indicate that APAP-AD are removed though selective autophagy. Pharmacological induction of autophagy may be a novel promising approach for treating APAP-induced liver injury.

LAY SUMMARY:

Acetaminophen overdose can form acetaminophen protein adducts and mitochondria damage in hepatocytes resulting in liver injury. Activation of autophagy-lysosomal degradation pathway can help to remove acetaminophen protein adducts. Pharmacological induction of autophagy may be a novel promising approach for treating APAP-induced liver injury.

• Authors: Hong-Min Ni, Mitchell R McGill, Xiaojuan Chao, Kuo Du, Jessica A Williams, Yuchao Xie, Hartmut Jaeschke, Wen-Xing Ding
• Journal: Journal of hepatology (J Hepatol) Vol. 65 Issue 2 Pg. 354-62 (08 2016) ISSN: 1600-0641 [Electronic] Netherlands
• PMID: 27151180 (Publication Type: Journal Article)
• Copyright: Copyright © 2016 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Chemical References

• Acetaminophen

Topics

• Acetaminophen
• Animals
• Autophagy
• Chemical and Drug Induced Liver Injury
• Hepatocytes
• Liver
• Mice
• Mice, Inbred C57BL