4-Methylpyrazole protects against acetaminophen hepatotoxicity in mice and in primary human hepatocytes

Abstract

Liver injury due to acetaminophen (APAP) overdose is the major cause of acute liver failure in the United States. While treatment with N-acetylcysteine is the current standard of care for APAP overdose, anecdotal evidence suggests that administration of 4-methylpyrazole (4MP) may be beneficial in the clinic. The objective of the current study was to examine the protective effect of 4MP and its mechanism of action. Male C57BL/6J mice were co-treated with 300 mg/kg of APAP and 50 mg/kg of 4MP. The severe liver injury induced by APAP at 6 h as indicated by elevated plasma alanine aminotransferase activities, centrilobular necrosis, and nuclear DNA fragmentation was almost completely eliminated by 4MP. In addition, 4MP largely prevented APAP-induced activation of c-Jun N-terminal kinase (JNK), mitochondrial translocation of phospho-JNK and Bax, and the release of mitochondrial intermembrane proteins. Importantly, 4MP inhibited the generation of APAP protein adducts and formation of APAP-glutathione (GSH) conjugates and attenuated the depletion of the hepatic GSH content. These findings are relevant to humans because 4MP also prevented APAP-induced cell death in primary human hepatocytes. In conclusion, early treatment with 4MP can completely prevent liver injury after APAP overdose by inhibiting cytochrome P450 and preventing generation of the reactive metabolite.

Acetaminophen Hepatotoxicity

“…Recently, 4methylpyrazole (Fomepizole), an antidote against methanol poisoning, has been shown to be highly effective against APAP-induced liver injury by inhibiting P450 enzyme when given early in mice and human hepato-cytes 180 or by inhibiting of JNK activation when administered after the drug metabolism phase. 181 In addition, metformin, a first-line drug to treat type 2 diabetes mellitus, substantially attenuated APAP hepatotoxicity 57,182 mainly by inhibiting complex I-mediated superoxide formation. 57 A caveat for any new drug is that it has to be beneficial in the presence of NAC, the current standard of care.…”

Acetaminophen hepatotoxicity: A mitochondrial perspective

“…Studies to better understand these roles, such as the influence of mitochondrial dynamics and biogenesis in mediating recovery and regeneration are ongoing with the ultimate hope to develop mitochondrial targeted therapeutics to prevent APAPinduced acute liver failure. Our unpublished data indicate that drugs such as 4methylpyrazole, which provides protection against APAP-induced injury (Akakpo et al, 2018), inhibits not only cytochrome P450 enzymes but also prevents JNK activation and its mitochondrial translocation and could thus be a useful therapeutic with similar potency as the current standard of care N-acetylcysteine. The SOD mimetics Calmangafodipir and Mito-TEMPO were also shown to have beneficial effects in APAP overdose in mice (Bedda et al, 2003;Du et al, 2018) and Calmangafodipir is currently in clinical trials (Dear et al, 2017).…”

A Case Report of Massive Acetaminophen Poisoning Treated with a Novel “Triple Therapy”: N-Acetylcysteine, 4-Methylpyrazole, and Hemodialysis

“…The 50 mg/kg 4-MP dose used in the mice by Akakpo et al is approximately equivalent to 4 mg/kg in humans; theoretically, 15 mg/kg 4-MP is several times higher than the effective dose in mice and is also the approved dose for humans in toxic alcohol poisoning. However, a therapeutic dose of 4-MP in humans for APAP poisoning would need to be elucidated [ 10 ]. In the presence of 4-MP, NAPQI formation via CYP450 2E1 is reduced [ 11 ].…”