Hepatology
Abstract
Non-alcoholic fatty liver disease (NAFLD) is prevalent in the majority of obese individuals, but in a subset, this progresses to non-alcoholic steatohepatitis (NASH) and fibrosis. The mechanisms that prevent NASH and fibrosis in the majority of NAFLD patients remain unclear. Here we report that NAD(P)H oxidase (NOX)-4 and nuclear factor erythroid 2-related factor 2 (NFE2L2) were elevated in hepatocytes early in disease progression to prevent NASH/fibrosis. Mitochondrial-derived reactive oxygen species (ROS) activated NFE2L2 to induce the expression of NOX4, which in turn generated H2O2 to exacerbate the NFE2L2 antioxidant defense response. The deletion or inhibition of NOX4 in hepatocytes decreased ROS and attenuated antioxidant defense to promote mitochondrial oxidative stress, damage proteins and lipids, diminish insulin signalling and promote cell death upon oxidant challenge. Hepatocyte NOX4 deletion in high fat fed obese mice, which otherwise develop steatosis, but not NASH, resulted in hepatic oxidative damage, inflammation and T cell recruitment to drive NASH and fibrosis, whereas NOX4 overexpression tempered the development of NASH/fibrosis in mice fed a NASH-promoting diet. Thus, mitochondrial- and NOX4-derived ROS function in concert to drive a NFE2L2 antioxidant defense response to attenuate oxidative liver damage and the progression to NASH/fibrosis in obesity.
Authors
Spencer Greatorex, Supreet Kaur, Chrysovalantou E. Xirouchaki, Pei Kee Goh, Florian Wiede, Amanda J. Genders, Melanie Tran, YaoYao Jia, Arthe Raajendiran, Wendy A. Brown, Catriona A. McLean, Junichi Sadoshima, Matthew J. Watt, Tony Tiganis
Abstract
Many cancers harbour homologous recombination defect (HRD), the therapeutic target being successfully applied in treating breast/ovarian cancer via synthetic lethality. However, canonical HRD caused by BRCAness mutations is not explicit in liver cancer. Here we report a subtype of HRD caused by the perturbation of a proteasome variant (CDW19S) in hepatitis B virus (HBV) bearing cells. This amalgamate protein complex contained the 19S proteasome decorated with CRL4WDR70 ubiquitin ligase, and assembled at broken chromatin in a PSMD4Rpn10 and ATM- MDC1-RNF8 dependent manner. CDW19S promoted DNA end processing via segregated modules that promote nuclease activities of MRE11 and EXO1. Contrarily, a proteasomal component, ADRM1Rpn13, inhibited resection and was removed by CRL4WDR70-catalysed ubiquitination upon commitment of extensive resection. HBx interfered with ADRM1Rpn13 degradation, leading to the imposition of ADRM1Rpn13-dependent resection barrier and consequent viral HRD subtype distinguishable from that caused by BRCA1 defect. Finally, we demonstrated that viral HRD in HBV-associated hepatocellular carcinoma (HBVHCC) can be exploited to restrict tumor progression. Our work clarifies the underlying mechanism of a viral-induced HRD subtype.
Authors
Ming Zeng, Zizhi Tang, Laifeng Ren, Haibin Wang, Xiaojun Wang, Wenyuan Zhu, Xiaobing Mao, Zeyang Li, Xianming Mo, Jun Chen, Junhong Han, Daochun Kong, Jianguo Ji, Antony M. Carr, Cong Liu
Abstract
X-linked myotubular myopathy (XLMTM) is a fatal congenital disorder caused by mutations in the MTM1 gene. Currently, there are no approved treatments, though AAV8-mediated gene transfer therapy has shown promise in animal models and preliminarily in patients. However, four patients with XLMTM treated with gene therapy have died from progressive liver failure, and hepatobiliary disease has now been recognized more broadly in association with XLMTM. In an attempt to understand whether loss of MTM1 itself is associated with liver pathology, we have characterized a novel liver phenotype in a zebrafish model of this disease. Specifically, we have found that loss-of-function mutations in mtm1 lead to severe liver abnormalities including impaired bile flux, structural abnormalities of the bile canaliculus, and improper endosomal-mediated trafficking of canalicular transporters. Using a reporter tagged Mtm1 zebrafish line, we have established localization of Mtm1 in the liver in association with Rab11 and canalicular transport proteins, and demonstrated that hepatocyte specific re-expression of Mtm1 can rescue the cholestatic phenotype. Lastly, we completed a targeted chemical screen, and found that Dynasore, a dynamin II inhibitor, is able to partially restore bile flow and transporter localization to the canalicular membrane. In summary, we demonstrate for the first time liver abnormalities that are directly caused by MTM1 mutation in a pre-clinical model, thus establishing the critical framework for better understanding and comprehensive treatment of the human disease.
Authors
Sophie Karolczak, Ashish R. Deshwar, Evangelina Aristegui, Binita M. Kamath, Michael W. Lawlor, Gaia Andreoletti, Jonathan R. Volpatti, Jillian L. Ellis, Chunyue Yin, James J. Dowling
Abstract
The liver has a high demand for phosphatidylcholine (PC) particularly in overnutrition where reduced phospholipid levels have been implicated in the development of non-alcoholic fatty liver disease (NAFLD). Whether other pathways exist in addition to de novo PC synthesis that contribute to hepatic PC pools remains unknown. Here, we identified the lysophosphatidylcholine (LPC) transporter Mfsd2a as critical for maintaining hepatic phospholipid pools. Hepatic Mfsd2a expression was induced in patients having NAFLD and in mice in response to dietary fat via glucocorticoid receptor action. Mfsd2a liver-specific deficiency in mice (L2aKO) led to a robust NASH-like phenotype within just two weeks of dietary fat challenge associated with reduced hepatic phospholipids containing linoleic acid. Reducing dietary choline intake in L2aKO mice exacerbated liver pathology and deficiency of liver phospholipids containing polyunsaturated fatty acids (PUFA). Treating hepatocytes with LPC containing oleate and linoleate, two abundant blood-derived LPCs, specifically induced lipid droplet biogenesis and contributed to phospholipid pools, while LPC containing the omega-3 fatty acid DHA promoted lipid droplet formation and suppressed lipogenesis. This study revealed that PUFA containing LPCs drive both hepatic lipid droplet formation, suppress lipogenesis and sustain hepatic phospholipid pools--processes that are critical for protecting the liver from excess dietary fat.
Authors
Cheen Fei Chin, Dwight L.A. Galam, Liang Gao, Bryan C. Tan, Bernice H. Wong, Geok-Lin Chua, Randy Y.J. Loke, Yen Ching Lim, Markus R. Wenk, Miao Shan Lim, Wei-Qiang Leow, George B.B. Goh, Federico Torta, David L. Silver
Abstract
The liver can fully regenerate after partial resection and its underlying mechanisms have been extensively studied. The liver can also rapidly regenerate after injury with most studies focusing on hepatocyte proliferation; however, how hepatic necrotic lesions during acute or chronic liver diseases are eliminated and repaired remains obscure. Here we demonstrated that monocyte-derived macrophages (MoMFs) were rapidly recruited to and encapsulate necrotic areas during immune-mediated liver injury, and this feature was essential in repairing necrotic lesions. At the early stage of injury, infiltrating MoMFs activated the JAG1-NOTCH2 axis to induce cell death-resistant SOX9+ hepatocytes near the necrotic lesions, which acted as a barrier from further injury. Subsequently, necrotic environment (hypoxia and dead cells) induced a cluster of C1q+MoMFs that promoted necrotic removal and liver repair, while Pdgfb+MoMFs activated hepatic stellate cells (HSCs) to express -smooth muscle actin and induce a strong contraction signal (YAP, pMLC) to squeeze and finally eliminate the necrotic lesions. In conclusion, MoMFs play a key role in repairing the necrotic lesions not only by removing necrotic tissues but also by inducing cell death resistant hepatocytes to form a perinecrotic capsule and by activating α-smooth actin expressing HSCs to facilitate necrotic lesion resolution.
Authors
Dechun Feng, Xiaogang Xiang, Yukun Guan, Adrien Guillot, Hongkun Lu, Chingwen Chang, Yong He, Hua Wang, Hongna Pan, Cynthia Ju, Sean P. Colgan, Frank Tacke, Xin Wei Wang, George Kunos, Bin Gao
Abstract
Rhythmic intraorgan communication coordinates environmental signals and the cell-intrinsic clock to maintain organ homeostasis. Hepatocyte-specific KO of core components of the molecular clock Rev-erbα and -β (Reverb-hDKO) alters cholesterol and lipid metabolism in hepatocytes as well as rhythmic gene expression in nonparenchymal cells (NPCs) of the liver. Here, we report that in fatty liver caused by diet-induced obesity (DIO), hepatocyte SREBP cleavage–activating protein (SCAP) was required for Reverb-hDKO–induced diurnal rhythmic remodeling and epigenomic reprogramming in liver macrophages (LMs). Integrative analyses of isolated hepatocytes and LMs revealed that SCAP-dependent lipidomic changes in REV-ERB–depleted hepatocytes led to the enhancement of LM metabolic rhythms. Hepatocytic loss of REV-ERBα and β (REV-ERBs) also attenuated LM rhythms via SCAP-independent polypeptide secretion. These results shed light on the signaling mechanisms by which hepatocytes regulate diurnal rhythms in NPCs in fatty liver disease caused by DIO.
Authors
Dongyin Guan, Hosung Bae, Dishu Zhou, Ying Chen, Chunjie Jiang, Cam Mong La, Yang Xiao, Kun Zhu, Wenxiang Hu, Trang Minh Trinh, Panpan Liu, Ying Xiong, Bishuang Cai, Cholsoon Jang, Mitchell A. Lazar
Abstract
Many hepatocellular carcinoma (HCC) patients do not respond to the first-line immune checkpoint inhibitor treatment. Immunization with effective cancer vaccines is an attractive alternative approach to immunotherapy. However, its efficacy remains insufficiently evaluated in preclinical studies. Here, we investigated HCC-associated self/tumor antigen, α-fetoprotein (AFP) based vaccine immunization for treating AFP (+) HCC mouse models. We found that AFP immunization effectively induced AFP-specific CD8+ T cells in vivo. However, these CD8+ T cells expressed exhaustion markers, including PD1, LAG3, and Tim3. Furthermore, the AFP vaccine effectively prevented c-MYC/Mcl1 HCC initiation when administrated before tumor formation, while it was ineffective against full-blown c-MYC/Mcl1 tumors. Similarly, anti-PD1 and anti-PD-L1 monotherapy showed no efficacy in this murine HCC model. In striking contrast, AFP immunization combined with anti-PD-L1 treatment triggered significant inhibition of HCC progression in most liver tumor nodules, while combining with anti-PD1 induced slower tumor progression. Mechanistically, we demonstrated that HCC intrinsic PD-L1 expression was the primary target of anti-PD-L1 in this combination therapy. Notably, the combination therapy had a similar therapeutic effect in the cMet/β-Catenin mouse HCC model. These findings suggest that combining the AFP vaccine and immune checkpoint inhibitors may be effective for AFP (+) HCC treatment.
Authors
Xinjun Lu, Shanshan Deng, Jiejie Xu, Benjamin L. Green, Honghua Zhang, Guofei Cui, Yi Zhou, Yi Zhang, Hongwei Xu, Fapeng Zhang, Rui Mao, Sheng Zhong, Thorsten Cramer, Matthias Evert, Diego F. Calvisi, Yukai He, Chao Liu, Xin Chen
Abstract
BACKGROUND. Hepatic de novo lipogenesis (DNL) and β-oxidation are tightly coordinated, and their dysregulation is thought to contribute to the pathogenesis of non-alcoholic fatty liver (NAFL). Fasting normally relaxes DNL-mediated inhibition of hepatic β-oxidation, dramatically increasing ketogenesis and decreasing reliance on the TCA cycle. Thus, we tested whether aberrant oxidative metabolism in fasting NAFL subjects is related to the inability to halt fasting DNL. METHODS. Forty consecutive non-diabetic individuals with and without a history of NAFL were recruited for this observational study. After phenotyping, subjects fasted for 24-hr, and hepatic metabolism was interrogated using a combination of 2H2O and 13C tracers, magnetic resonance spectroscopy, and high-resolution mass spectrometry. RESULTS. Within a subset of subjects, DNL was detectable after a 24-hr fast and was more prominent in those with NAFL, though it was poorly correlated with steatosis. However, fasting DNL negatively correlated with hepatic β-oxidation and ketogenesis and positively correlated with citrate synthesis. Subjects with NAFL but undetectable fasting DNL (25th percentile) were comparatively normal. However, those with the highest fasting DNL (75th percentile) were intransigent to the effects of fasting on the concentration of insulin, NEFA, and ketones. Additionally, they sustained glycogenolysis and spared the loss of oxaloacetate to gluconeogenesis in favor of citrate synthesis, which correlated with DNL and diminished ketogenesis. CONCLUSION. Metabolic flux analysis in fasted subjects indicates that shared metabolic mechanisms link the dysregulations of hepatic DNL, ketogenesis, and the TCA cycle in NAFL. TRIAL REGISTRATION. Data obtained during the enrollment/non-intervention phase of Effect of Vitamin E on Non-Alcoholic Fatty Liver Disease; ClinicalTrials.gov NCT02690792.
Authors
Xiaorong Fu, Justin A. Fletcher, Stanisław Deja, Melissa Inigo-Vollmer, Shawn C. Burgess, Jeffrey D. Browning
Abstract
Liver metastasis represents one of the most frequent malignant diseases with no effective treatment. As the largest population of hepatic macrophages, functional reprogramming of Kupffer cells (KCs) holds promise for treating liver cancer but remains seldom exploited. Taking advantage of the superior capacity of KCs to capture circulating bacteria, we report that a single administration of attenuated Escherichia coli producing CRISPR‒CasΦ machinery enables efficient editing of genes of interest in KCs. Using intravital microscopy, we observed a failure of tumor control by KCs at the late stage of liver metastasis due to KC loss preferentially in the tumor core and periphery, resulting in inaccessibility of these highly phagocytic macrophages to cancer cells. Simultaneous disruption of MafB and c-Maf expression using the aforementioned engineered bacteria could overcome KC dysfunction and elicit remarkable curative effects against several types of metastatic liver cancer in mice. Mechanistically, bacterial treatment induced massive proliferation and functional reprogramming of KCs. These cells infiltrated into the tumor, dismantled macrometastases by nibbling cancer cells, and skewed toward proinflammatory macrophages to unleash antitumor T-cell responses. These findings provide an immunotherapy strategy that could be applicable for treating liver metastasis and highlight the therapeutic potential of targeting tissue-resident macrophages in cancer.
Authors
Wei Liu, Xia Zhou, Qi Yao, Chen Chen, Qing Zhang, Keshuo Ding, Lu Li, Zhutian Zeng
Abstract
The non-essential amino acid asparagine can only be synthesized de novo by the enzymatic activity of asparagine synthetase (ASNS). While ASNS and asparagine have been implicated in the response to numerous metabolic stressors in cultured cells, the in vivo relevance of this enzyme in stress-related pathways remains unexplored. Here, we found ASNS to be expressed in pericentral hepatocytes, a population of hepatic cells specialized in xenobiotic detoxification. ASNS expression was strongly enhanced in two models of acute liver injury: carbon tetrachloride (CCl4) and acetaminophen (APAP). We found that mice with hepatocyte-specific Asns deletion (Asnshep-/-) were more prone to pericentral liver damage than their control (Asnshep+/+) littermates after toxin exposure. This phenotype could be reverted by intravenous administration of asparagine. Unexpectedly, the stress-induced upregulation of ASNS involved an ATF4-independent, non-canonical pathway mediated by the nuclear receptor, liver receptor homolog 1 (LRH-1; NR5A2). Altogether, our data indicate that the induction of the asparagine-producing enzyme ASNS acts as an adaptive mechanism to constrain the necrotic wave that follows toxin administration and provide proof of concept that intravenous delivery of asparagine can dampen hepatotoxin-induced pericentral hepatocellular death.
Authors
Yu Sun, Hadrien Demagny, Adrien Faure, Francesca Pontanari, Antoine Jalil, Nadia Bresciani, Ece Yildiz, Melanie Korbelius, Alessia Perino, Kristina Schoonjans
Copyright © 2024 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)