Acetaminophen‐induced Liver Injury Induces DNA Damage and Activation of Ataxia Telangiectasia Mutated in Mice
Authors: Chu Christopher , Grant Stephanie , Williams Elaina , Petrescu Anca , DeMorrow Sharon 
Published: April 2020

Acetaminophen (APAP) is a common analgesic/antipyretic that is widely used throughout the world. At therapeutic doses it is safe but at higher dosages APAP causes acute liver failure (ALF). Drug‐induced liver toxicity is the most common cause of liver damage, accounting for 50% of the cases of liver failure. With the only efficacious form of treatment being liver transplant, it is imperative to find alternative forms of treatment. Gaining a greater understanding of the molecular pathology contributing to the progression of liver failure, we allow insights on methods to enhance patient care and quality of life. Acute liver injury from APAP is associated with increased levels of inflammation, oxidative stress, and hepatic cell death. High levels of oxidative stress damages multiple systems within the cell, most notability the DNA. In response to DNA damage, DNA damage response (DDR) markers are activated leading to cell cycle arrest, DNA repair and the eventual death of the cell if damage is unable to be repaired. Our hypothesis is that the accumulation of DNA damage results in the activation of the DDR, which then aids in driving further progression of APAP‐induced liver injury.

Methods

C57Bl/6 mice were injected with APAP (300mg/kg) do induce liver injury. Liver tissue was collected after 1, 2, 4, 6, 12, and 24 hours. Histology was performed on paraffin‐embedded sections using antibodies specific for phospho‐ATM (ser 1981) and γH2AX (ser 139). Replication protein A (RPA), Ataxia Telangiectasia mutated (ATM) and 53BP were assessed by qPCR. Phospho‐ATM and RPA were assessed by immunoblotting.

Results

APAP injected mice showed a marked increase in the accumulation of DNA damage when compared to saline injected mice in the liver. Markers for DNA double strand breaks (DSB), γH2AX and 53BP, were shown to be elevated 2 hours after APAP injection followed by a gradual decrease. RPA, a single stranded DNA‐binding protein, was also shown to be elevated 4 hours after APAP injection indicating an accumulation of single strand breaks. ATM, a DDR maker, and the phosphorylated form of ATM were shown to also be elevated after APAP injection after onset of DSB, with peak expression at 4 hours.

Conclusion

During APAP‐induced liver injury, there is an elevated level of DNA damage found within the liver. This elevated amount of DNA damage results in the activation of ATM and the DDR. ATM‐mediated signaling may be a potential driver for hepatocellular death and ALF. Agents designed to inhibit ATM‐mediated signaling or the DDR response need to be assessed as potential therapeutic targets for the treatment of APAP‐induced liver damage.

Support or Funding Information

This study was funded by NIH R01 awards (DK082435 and DK112803) and a VA Merit award (BX002638) from the United States Department of Veterans Affairs Biomedical Laboratory Research and Development Service to Dr. DeMorrow. This work was completed with support from the Veterans Health Administration and with resources and the use of facilities at the Central Texas Veterans Health Care System, Temple, Texas. The contents do not represent the views of the U.S. Department of Veterans Affairs or the United States Government.