Hydrogen sulfide protects against acetaminophen-induced acute liver injury by inhibiting apoptosis via the JNK/MAPK signaling pathway.

Acetaminophen (APAP) is a widely used over-the-counter analgesic and antipyretic. It can cause hepatotoxicity. Recent studies demonstrated that hydrogen sulfide (H2 S) exhibits cell protection in several cell types. This study was designed to investigate whether H 2 S ameliorated APAP-induced acute liver injury and to elucidate its mechanisms. In this study, we analyzed the detailed biological and molecular processes of APAP-induced hepatotoxicity using a bioinformatics analysis, which showed that apoptosis and the c-Jun N-terminal kinase (JNK)/mitogen-activated protein kinase pathway were confirmed to play critical roles in these processes. We further investigated the protective effects of H 2 S on APAP-induced hepatotoxicity. In vivo, we observed that the exogenous supplement of H 2 S ameliorated APAP-induced liver injury. Cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE) systems were the endogenous pathway of H 2 S. The expression of CBS/CSE was decreased in APAP-treated mice, while H 2 S could significantly restore it. In addition, APAP-induced JNK activation was inhibited by H 2 S in vivo. In vitro, H 2 S abolished the active effects of APAP on caspase3, Bax, and Bcl-2 expressions as well as JNK phosphorylation in hepatocytes. It was found through flow cytometry that the amount of APAP-induced apoptotic hepatocytes was decreased in the presence of H 2 S. In conclusion, our results suggested that H 2 S attenuated APAP-induced apoptosis in hepatocytes through JNK/MAPK siganaling pathway.

Li X ，Lin J ，Lin Y ，Huang Z ，Pan Y ，Cui P ，Yu C ，Cai C ，Xia J ... -  《-》

Interaction of RIPK1 and A20 modulates MAPK signaling in murine acetaminophen toxicity.

Acetaminophen (APAP)-induced liver necrosis is a form of regulated cell death (RCD) in which APAP activates the mitogen-activated protein kinases (MAPKs) and specifically the c-Jun-N-terminal kinase (JNK) pathway, leading to necrotic cell death. Previously, we have shown that receptor interacting protein kinase-1 (RIPK1) knockdown is also protective against APAP RCD upstream of JNK. However, whether the kinase or platform function of RIPK1 is involved in APAP RCD is not known. To answer this question, we used genetic mouse models of targeted hepatocyte RIPK1 knockout (RIPK1HepCKO) or kinase dead knock-in (RIPK1D138N) and adult hepatocyte specific knockout of the cytoprotective protein A20 (A20HepCKO), known to interact with RIPK1, to study its potential involvement in MAPK signaling. We observed no difference in injury between WT and RIPK1D138N mice post APAP. However, RIPK1HepCKO was protective. We found that RIPK1HepCKO mice had attenuated pJNK activation, while A20 was simultaneously upregulated. Conversely, A20HepCKO markedly worsened liver injury from APAP. Mechanistically, we observed a significant upregulation of apoptosis signal-regulating kinase 1 (ASK1) and increased JNK activation in A20HepCKO mice compared with littermate controls. We also demonstrated that A20 coimmunoprecipitated (co-IP) with both RIPK1 and ASK1, and that in the presence of RIPK1, there was less A20-ASK1 association than in its absence. We conclude that the kinase-independent platform function of RIPK1 is involved in APAP toxicity. Adult RIPK1HepCKO mice are protected against APAP by upregulating A20 and attenuating JNK signaling through ASK1, conversely, A20HepCKO worsens injury from APAP.

Iorga A ，Donovan K ，Shojaie L ，Johnson H ，Kwok J ，Suda J ，Lee BT ，Aghajan M ，Shao L ，Liu ZX ，Dara L ... -  《-》

Protein tyrosine phosphatase 1B modulates GSK3β/Nrf2 and IGFIR signaling pathways in acetaminophen-induced hepatotoxicity.

Mobasher MA ，González-Rodriguez A ，Santamaría B ，Ramos S ，Martín MÁ ，Goya L ，Rada P ，Letzig L ，James LP ，Cuadrado A ，Martín-Pérez J ，Simpson KJ ，Muntané J ，Valverde AM ... -  《Cell Death & Disease》

Thymoquinone Attenuates Acetaminophen Overdose-Induced Acute Liver Injury and Inflammation Via Regulation of JNK and AMPK Signaling Pathway.

Cui BW ，Bai T ，Yang Y ，Zhang Y ，Jiang M ，Yang HX ，Wu M ，Liu J ，Qiao CY ，Zhan ZY ，Wu YL ，Kang DZ ，Lian LH ，Nan JX ... -  《-》

Editor's Highlight: Metformin Protects Against Acetaminophen Hepatotoxicity by Attenuation of Mitochondrial Oxidant Stress and Dysfunction.

Overdose of acetaminophen (APAP) causes severe liver injury and even acute liver failure in both mice and human. A recent study by Kim et al. (2015, Metformin ameliorates acetaminophen hepatotoxicity via Gadd45β-dependent regulation of JNK signaling in mice. J. Hepatol. 63, 75-82) showed that metformin, a first-line drug to treat type 2 diabetes mellitus, protected against APAP hepatotoxicity in mice. However, its exact protective mechanism has not been well clarified. To investigate this, C57BL/6J mice were treated with 400 mg/kg APAP and 350 mg/kg metformin was given 0.5 h pre- or 2 h post-APAP. Our data showed that pretreatment with metformin protected against APAP hepatotoxicity, as indicated by the over 80% reduction in plasma alanine aminotransferase (ALT) activities and significant decrease in centrilobular necrosis. Metabolic activation of APAP, as indicated by glutathione depletion and APAP-protein adducts formation, was also slightly inhibited. However, 2 h post-treatment with metformin still reduced liver injury by 50%, without inhibition of adduct formation. Interestingly, neither pre- nor post-treatment of metformin inhibited c-jun N-terminal kinase (JNK) activation or its mitochondrial translocation. In contrast, APAP-induced mitochondrial oxidant stress and dysfunction were greatly attenuated in these mice. In addition, mice with 2 h post-treatment with metformin also showed significant inhibition of complex I activity, which may contribute to the decreased mitochondrial oxidant stress. Furthermore, the protection was reproduced in JNK activation-absent HepaRG cells treated with 20 mM APAP followed by 0.5 or 1 mM metformin 6 h later, confirming JNK-independent protection mechanisms. Thus, metformin protects against APAP hepatotoxicity by attenuating the mitochondrial oxidant stress and subsequent mitochondrial dysfunction, and may be a potential therapeutic option for APAP overdose patients.

Du K ，Ramachandran A ，Weemhoff JL ，Chavan H ，Xie Y ，Krishnamurthy P ，Jaeschke H ... -  《-》