miR-122 protects mice and human hepatocytes from acetaminophen toxicity by regulating CYP1A2 and CYP2E1 expression.

Acetaminophen (APAP) toxicity is a leading cause of acute liver failure (ALF). Here, we show that miR-122 is downregulated in liver biopsies of ALF patients and in APAP treated mice. A dramatic decrease in the primary-miR-122 expression occurs in mice upon APAP overdose due to suppression of its key trans-activators, HNF4α and HNF6. More importantly, the mortality rates of both male and female liver-specific miR-122 knockout (LKO) mice were significantly higher than control mice when injected intraperitoneally with an APAP dose not lethal to the control. LKO livers exhibited higher basal expression of CYP2E1 and CYP1A2 that convert APAP to highly reactive N-acetyl-p-benzoquinone imine (NAPQI). Upregulation of Cyp1a2 primary transcript and mRNA in LKO mice correlated with the elevation of AHR and MED1, two trans-activators of Cyp1a2. Analysis of ChIP-seq data in the ENCODE database identified association of CTCF with Ahr promoter in mouse livers. Both MED1 and CTCF are validated conserved miR-122 targets. Furthermore, depletion of Ahr, Med1 or Ctcf in Mir122(-/-) hepatocytes reduced Cyp1a2 expression. Pulse-chase studies showed that Cyp2e1 protein level is upregulated in LKO hepatocytes. Notably, miR-122 depletion sensitized differentiated human HepaRG cells to APAP toxicity that correlated with upregulation of AHR, MED1 and CYP1A2 expression. Collectively, these results demonstrate a critical role of miR-122 in acetaminophen detoxification and implicate its therapeutic potential in ALF patients.