Acetaminophen (APAP) is the active component of many medications used to treat pain and fever worldwide. Its overuse provokes liver injury and it is the second most common cause of liver failure. Mitochondrial dysfunction contributes to APAP-induced liver injury but the mechanism by which APAP causes hepatocyte toxicity is not completely understood. Therefore, we lack efficient therapeutic strategies to treat this pathology. Here we show that APAP interferes with the formation of mitochondrial respiratory supercomplexes via the mitochondrial negative regulator MCJ, and leads to decreased production of ATP and increased generation of ROS. In vivo treatment with an inhibitor of MCJ expression protects liver from acetaminophen-induced liver injury at a time when N-acetylcysteine, the standard therapy, has no efficacy. We also show elevated levels of MCJ in the liver of patients with acetaminophen overdose. We suggest that MCJ may represent a therapeutic target to prevent and rescue liver injury caused by acetaminophen.

Hepatic fibrosis is a global health problem currently without effective therapeutic approaches. Even though the ubiquitin-like post-translational modification of neddylation, that conjugates Nedd8 to specific targets, is aberrant in many pathologies, its relevance in liver fibrosis remained unexplored. Our results show deregulated neddylation in clinical fibrosis and both in mouse bileduct ligation (BDL)-and carbon tetrachloride (CCl 4 )-induced fibrosis. Importantly, neddylation inhibition, by using the pharmacological inhibitor MLN4924 reduced liver injury, apoptosis, inflammation and fibrosis by targeting different hepatic cell types. On one hand, increased neddylation was associated with augmented caspase-3-activity in bile acid-induced apoptosis in mouse hepatocytes whereas neddylation inhibition ameliorated apoptosis through reduction of the † Joint Corresponding authors: María Luz Martínez-Chantar, CIC bioGUNE, Ed. 801A Parque Tecnológico de Bizkaia, 48160 Derio, Bizkaia, Spain. mlmartinez@cicbiogune.es; Tel: +34-944-061318; Fax: +34-944-061301. Teresa Cardoso Delgado, CIC bioGUNE, Ed. 801A Parque Tecnológico de Bizkaia, 48160 Derio, Bizkaia, Spain. tcardoso@cicbiogune.es; Tel: +34-944-061318; Fax: +34-944-061301. HHS Public Access Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript expression of the Cxcl1 and Ccl2 chemokines. On the other hand, chemokine receptors and cytokines, usually induced in activated macrophages, were reduced after neddylation inhibition in mouse Kupffer cells. Under these circumstances, decreased hepatocyte cell death and inflammation after neddylation inhibition could partly account for reduction of hepatic stellate cell activation. In spite of this, we provide evidence that augmented neddylation characterizes activated hepatic stellate cells suggesting that neddylation inhibition could be important for resolving liver fibrosis by directly targeting these fibrogenic cells. Indeed, neddylation inhibition in activated hepatic stellate cells induces apoptosis in a process partly mediated by the accumulation of c-Jun, whose cullin-mediated degradation is impaired under these circumstances.Conclusions-Overall, neddylation inhibition reduces fibrosis, suggesting neddylation as a potential and attractive therapeutic target in liver fibrosis. KeywordsFibrosis; Nedd8; Post-translational modification; Kupffer cell; Hepatic stellate cell Liver fibrosis is a global health problem and a critical process in liver disease as well as a major risk factor for progression to cirrhosis and hepatocellular carcinoma (HCC), one of the commonest and deadliest solid organ tumors (1). The progression and resolution of fibrosis is a complex process involving the interaction between parenchymal and nonparenchymal cells where chronic hepatocyte death often acts as a triggering event (2). For example, during cholestasis, a condition where bile efflux is disrupted, the accumulation of bile acids (BA) in the liver directly activates a signaling network in hepatocytes that promotes in...