miRNA-122 Protects Mice and Human Hepatocytes from Acetaminophen Toxicity by Regulating Cytochrome P450 Family 1 Subfamily A Member 2 and Family 2 Subfamily E Member 1 Expression.

Acetaminophen toxicity is a leading cause of acute liver failure (ALF). We found that miRNA-122 (miR-122) is down-regulated in liver biopsy specimens of patients with ALF and in acetaminophen-treated mice. A marked decrease in the primary miR-122 expression occurs in mice on acetaminophen overdose because of suppression of its key transactivators, hepatocyte nuclear factor (HNF)-4α and HNF6. More importantly, the mortality rates of male and female liver-specific miR-122 knockout (LKO) mice were significantly higher than control mice when injected i.p. with an acetaminophen dose not lethal to the control. LKO livers exhibited higher basal expression of cytochrome P450 family 2 subfamily E member 1 (CYP2E1) and cytochrome P450 family 1 subfamily A member 2 (CYP1A2) that convert acetaminophen to highly reactive N-acetyl-p-benzoquinone imine. Upregulation of Cyp1a2 primary transcript and mRNA in LKO mice correlated with the elevation of aryl hydrocarbon receptor (AHR) and mediator 1 (MED1), two transactivators of Cyp1a2. Analysis of ChIP-seq data in the ENCODE (Encyclopedia of DNA Element) database identified association of CCCTC-binding factor (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 found that CYP2E1 protein level is upregulated in LKO hepatocytes. Notably, miR-122 depletion sensitized differentiated human HepaRG cells to acetaminophen toxicity that correlated with upregulation of AHR, MED1, and CYP1A2 expression. Collectively, these results reveal a critical role of miR-122 in acetaminophen detoxification and implicate its therapeutic potential in patients with ALF.

Prominent dysautonomia in a patient with POEMS syndrome.

POEMS syndrome is a rare, multisystem disorder characterized by polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, and/or skin changes. Here we present an unusual case of a patient with POEMS syndrome who exhibited a prominent autonomic neuropathy.

miR-122 is a unique molecule with great potential in diagnosis, prognosis of liver disease, and therapy both as miRNA mimic and antimir.

miR-122, a completely conserved liver-specific miRNA in vertebrates, is essential for the maintenance of liver homeostasis. This 22 nucleotide RNA regulates diverse functions such as cholesterol, glucose and iron homeostasis, lipid metabolism and infection of hepatitis C virus (HCV) and of the parasitic protozoa, Leishmania donovani. It is the first miRNA that underwent successful clinical trials in HCV infected patients. In contrast, miR-122 expression is reduced in nonalcoholic steatohepatitis (NASH) patients, and in a subset of hepatocellular carcinoma (HCC) patients including hepatitis B virus (HBV) positive patients with highly invasive and metastatic cancer. Studies in mice genetically depleted of miR-122 have highlighted its critical role in liver biology. These mice progressively develop steatohepatitis, fibrosis and hepatocellular cancer, establishing it as a bona fide tumor suppressor. Additionally, delivery of miR-122 using a viral vector or liposomal nanoparticles resulted in liver tumor suppression in animal models. These results suggest miR-122 supplementation might be beneficial in NASH or HBV positive HCC patients. Furthermore, circulating miR-122 has emerged as a sensitive biomarker for liver injury. The ability of miR-122 to promote differentiation of embryonic and adult stem cells to hepatocyte-like cells in vitro suggests its potential role in driving the hepatic differentiation program. In this review, we will discuss the role of miR-122 in liver physiology and the deleterious consequences of its loss of function, its role as a sensitive biomarker for liver injury and therapeutic target. Development of novel technologies for targeted delivery of miR-122 to tumor cells and for direct monitoring of miR-122 in biological fluids is urgently needed for translating the basic research to the bedside. This review focuses on miR-122, the most abundant hepatic miRNA, in the context of liver health and diseases.