A Role for CHAC1 in Acetaminophen Hepatotoxicity

Abstract

Acetaminophen (APAP) is a commonly used pain reliever and a well‐established, dose‐related hepatotoxin. Hepatotoxicity occurs when metabolism of excessive APAP generates high concentrations of the reactive metabolite N‐acetyl‐p‐benzoquinone imine (NAPQI). NAPQI depletes cellular glutathione (GSH) and forms protein adducts leading to cellular stress, mitochondrial dysfunction, and, ultimately, oncotic necrosis of Zone 3 hepatocytes. The endoplasmic reticulum (ER) stress pathway is important to maintain cellular protein folding abilities in times of stress. However, extended or aberrant ER stress signaling can lead to apoptosis through the PERK‐ATF4‐CHOP pathway. Our research explores the regulation and contribution of CHAC1, an enzyme within this pathway, in response to APAP overdose.As purified mouse and yeast CHAC1 was shown to degrade GSH, the consequences of CHAC1 overexpression on GSH levels in human liver was explored in a human hepatoma cell line (HepG2). Overexpression of CHAC1 by transient transfection leads to a ~50% reduction in total GSH levels. As depletion of GSH is an important step in the pathology of APAP hepatotoxicity, the expression of CHAC1 mRNA in HepG2 cells was examined following 24‐hour treatment with 30mM APAP. CHAC1 mRNA was induced five‐fold by APAP, along with other components of the PERK‐ATF4‐CHOP pathway. Interestingly, overexpression of CHAC1 in HepG2 cells treated with APAP led to increased toxicity versus APAP alone, implicating a role for CHAC1 in response to APAP. Overall, these data implicate a new role for CHAC1 in the pathology of drug‐induced liver injury.

Activation of the eIF2α-ATF4 Pathway by Chronic Paracetamol Treatment Is Prevented by Dietary Supplementation with Cysteine

“…This is in favor of intracellular degradation of GSH in the liver of APAP-treated mice. Our result extends a single previous preliminary work reporting that overexpression of CHAC1 in HepG2 cells reduced GSH and increased APAP toxicity [28]. Further evaluation of the quantitative contribution of Chac1 to the APAP-induced GSH decrease is of interest because Chac1 could be a novel target to rescue hepatic GSH and reduce APAP toxicity.…”

Identification of a global gene expression signature associated with the genetic risk of catastrophic fracture in iPSC-derived osteoblasts from Thoroughbred horses

“…PLA2G4D also appears in the STRING network and interacts with CHAC1. Knock-out of CHAC1 in mice leads to decreased osteoblast differentiation and bone density (Crawford et al, 2016). PLA2G4D is part of the phospholipase A2 family, and it is present in the enriched gene set for the overrepresented pathway phospholipase-C pathway.…”

Ferroptosis Contributed Genes in the Soleus Muscle After Endurance Training in Older Rats

“…Current results showed that regular exercise could signi cantly reduce "CHAC1" mRNA expression. It is an enzyme that could be upregulated in response to ER stress through "PERK/elF2α/ATF4/CHOP" signaling, Nrf2, ATF3 and P53 pathways [17]. CHAC1 is an enzyme that degrades GSH, which is an important antioxidant molecule.…”

“…Crawford et al (2018) stated that genetic inhibition of CHAC1 in mice leads to numerous Modi cations in body con guration, including decreased amount of muscle tissue and changes in bone growth, which shows the importance of CHAC1 in muscles and bones proper regulation. In addition, CHAC1 could be a crucial factor in the development of muscle and bone pathology in conditions such as osteoporosis, aging, and muscle wasting [17]. Glutamate-cysteine ligase (GCL) as the rst rate-limiting enzyme of GSH biosynthesis is considered as well.…”