Loss of LKB1 protects against acetaminophen hepatotoxicity in mice through sex-specific mechanisms.

Abstract

Acetaminophen (APAP) overdose is a major cause of acute liver failure (ALF). We previously observed activation of liver kinase B1 (LKB1) in non-surviving patients with APAP-induced ALF. Thus, we hypothesized LKB1 is detrimental in APAP hepatotoxicity. To test our hypothesis, we overdosed hepatocyte-specific LKB1 knockout (KO) mice and wildtype (WT) littermates with APAP and measured liver injury 2, 6, and 24 h later. Consistent with our hypothesis, LKB1 KO protected against APAP hepatotoxicity. However, the mechanisms of protection were sex-specific. Male KOs had lower NAPQI formation due to lower mitochondrial CYP2E1. In contrast, NAPQI formation was similar between female KO and WT mice, but female KOs still had reduced oxidative stress. The pentose phosphate pathway (PPP) is a major source of NADPH to counter oxidative stress, so we hypothesized that female KO mice have increased PPP enzymes. To test that, we measured hepatic glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme in the oxidative PPP. Importantly, G6PD was increased in female WT mice compared to male WT animals and even further increased in the female KO mice. Furthermore, 1.5 h post-treatment with the G6PD activator AG1 protected against APAP and increased hepatic NADPH in WT animals. Finally, re-analysis of our prior proteomics data revealed LKB1 activation occurred in both male and female ALF non-survivors, though it was greater in males. We conclude LKB1 regulates CYP2E1 and the PPP, that mitochondrial CYP2E1 is critical in APAP toxicity, and PPP activation is a potential therapeutic approach in liver injury in men and women.