The mechanism underlying acetaminophen-induced hepatotoxicity in humans and mice involves mitochondrial damage and nuclear DNA fragmentation
Mitchell R. McGill, Matthew R. Sharpe, C. David Williams, Mohammad Taha, Steven C. Curry, Hartmut Jaeschke
Mitchell R. McGill, Matthew R. Sharpe, C. David Williams, Mohammad Taha, Steven C. Curry, Hartmut Jaeschke
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Research Article Hepatology

The mechanism underlying acetaminophen-induced hepatotoxicity in humans and mice involves mitochondrial damage and nuclear DNA fragmentation

Abstract

Acetaminophen (APAP) overdose is the predominant cause of acute liver failure in the United States. Toxicity begins with a reactive metabolite that binds to proteins. In rodents, this leads to mitochondrial dysfunction and nuclear DNA fragmentation, resulting in necrotic cell death. While APAP metabolism is similar in humans, the later events resulting in toxicity have not been investigated in patients. In this study, levels of biomarkers of mitochondrial damage (glutamate dehydrogenase [GDH] and mitochondrial DNA [mtDNA]) and nuclear DNA fragments were measured in plasma from APAP-overdose patients. Overdose patients with no or minimal hepatic injury who had normal liver function tests (LTs) (referred to herein as the normal LT group) and healthy volunteers served as controls. Peak GDH activity and mtDNA concentration were increased in plasma from patients with abnormal LT. Peak nuclear DNA fragmentation in the abnormal LT cohort was also increased over that of controls. Parallel studies in mice revealed that these plasma biomarkers correlated well with tissue injury. Caspase-3 activity and cleaved caspase-3 were not detectable in plasma from overdose patients or mice, but were elevated after TNF-induced apoptosis, indicating that APAP overdose does not cause apoptosis. Thus, our results suggest that mitochondrial damage and nuclear DNA fragmentation are likely to be critical events in APAP hepatotoxicity in humans, resulting in necrotic cell death.

Authors

Mitchell R. McGill, Matthew R. Sharpe, C. David Williams, Mohammad Taha, Steven C. Curry, Hartmut Jaeschke

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Figure 4

Caspase-3 activation is not detectable in plasma from APAP-overdose patients.

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Caspase-3 activation is not detectable in plasma from APAP-overdose pati...
(A) Caspase-3 processing was assessed by immunoblot in plasma from patients or from mice treated with either APAP or G/E or from control mice. The human and mouse samples were run on different gels but probed with the same antibody. Full-length (32 kDa) pro–caspase-3 was detectable in samples from the abnormal LT patient group, as well as from mice treated with APAP or G/E. Cleaved active caspase-3 fragment (17 kDa) was detectable only in plasma from the positive control G/E-treated mice. (B) Average caspase-3 activity in plasma from G/E-treated mice (n = 3), healthy volunteers (n = 6), normal LT group (n = 20), and abnormal LT group (n = 20) based on cleavage of the caspase-3 substrate Ac-DEVD-AMC. Expressed as mean ± SEM. *P < 0.05 compared with healthy volunteers.