Hepatology
Abstract
Nonalcoholic fatty liver disease (NAFLD) represents a spectrum of chronic liver disease ranging from simple steatosis (NAFL) to nonalcoholic steatohepatitis (NASH). However, the molecular mechanisms of NASH progression remain incompletely understood. White adipose tissue (WAT) has emerged as an important endocrine organ and contributes not only to the initial stage of NAFLD, but also to its severity. In the current study, through transcriptomic analysis we identified increased expression of Sparcl1, a secreted glycoprotein, in the WAT from NASH mice. Plasma Sparcl1 levels were similarly elevated and positively correlated with hepatic pathological features in NASH patients. Functional studies showed that both chronic injection of recombinant Sparcl1 protein and overexpression of Sparcl1 exaggerated hepatic inflammation and liver injury in mice. In contrast, genetic ablation of Sparcl1, knockdown of Sparcl1 in WAT, and treatment with a Sparcl1-neutralizing antibody dramatically alleviated diet-induced NASH pathogenesis. Mechanistically, Sparcl1 promoted the expression of C-C motif chemokine ligand 2 (CCL2) in hepatocytes through binding to Toll-like receptor 4 (TLR4) and activation of the NF-κB/p65 signaling pathway. Genetically or pharmacologically blocking the CCL2/CCR2 pathway attenuated the hepatic inflammatory response evoked by Sparcl1. Thus, our results demonstrated an important role for Sparcl1 in NASH progression, suggesting a potential target for therapeutic intervention.
Authors
Bin Liu, Liping Xiang, Jing Ji, Wei Liu, Ying Chen, Mingfeng Xia, Yuejun Liu, Wenyue Liu, Peiwu Zhu, Yi Jin, Yu Han, Jieli Lu, Xiaoying Li, Minghua Zheng, Yan Lu
Abstract
The endocannabinoid system regulates appetite and energy expenditure and inhibitors of the cannabinoid receptor-1 (CB-1) induce weight loss with improvement in components of the metabolic syndrome. While CB-1 blockage in brain is responsible for weight loss, many of the metabolic benefits associated with CB-1 blockade have been attributed to inhibition of CB-1 signaling in the periphery. As a result, there has been interest in developing a peripherally restricted CB-1 inhibitor for the treatment of nonalcoholic fatty liver disease (NAFLD) that would lack the unwanted centrally mediated side effects. Here, we produced mice that lacked CB-1 receptors in hepatocytes or stellate cells to determine if CB-1 signaling contributes to the development of NAFLD or liver fibrosis. Deletion of CB-1 receptors in hepatocytes did not alter the development of NAFLD in mice fed a high sucrose high fat diet or high fat diet (HFD). Similarly, deletion of CB-1 deletion specifically in stellate cells also did not prevent the development of NAFLD in mice fed the HFD nor did it protect mice for carbon tetrachloride (CCl4)-induced fibrosis. Combined, these studies do not support a direct role for hepatocyte or stellate cell CB-1 signaling in the development of NAFLD or liver fibrosis.
Authors
Simeng Wang, Qingzhang Zhu, Guosheng Liang, Tania Franks, Magalie Boucher, Kendra K. Bence, Mingjian Lu, Carlos M. Castorena, Shangang Zhao, Joel K. Elmquist, Philipp E. Scherer, Jay D. Horton
Abstract
Hepatic uptake and biosynthesis of fatty acids (FA), as well as the partitioning of FA into oxidative, storage, and secretory pathways are tightly regulated processes. Dysregulation of one or more of these processes can promote excess hepatic lipid accumulation, ultimately leading to systemic metabolic dysfunction. Angiopoietin-like-4 (ANGPTL4) is a secretory protein that inhibits lipoprotein lipase (LPL) and modulates triacylglycerol (TAG) homeostasis. To understand the role of ANGPTL4 in liver lipid metabolism under normal and high-fat fed conditions, we generated hepatocyte specific Angptl4 mutant mice (Hmut). Using metabolic turnover studies, we demonstrate that hepatic Angptl4 deficiency facilitates catabolism of TAG-rich lipoprotein (TRL) remnants in the liver via increased hepatic lipase (HL) activity, which results in a significant reduction in circulating TAG and cholesterol levels. Consequently, depletion of hepatocyte Angptl4 protects against diet-induce obesity, glucose intolerance, liver steatosis, and atherogenesis. Mechanistically, we demonstrate that loss of Angptl4 in hepatocytes promotes FA uptake which results in increased FA oxidation, ROS production, and AMPK activation. Finally, we demonstrate the utility of a targeted pharmacologic therapy that specifically inhibits Angptl4 gene expression in the liver and protects against diet-induced obesity, dyslipidemia, glucose intolerance, and liver damage, which likely occurs via increased HL activity. Notably, this novel inhibition strategy does not cause any of the deleterious effects previously observed with neutralizing antibodies.
Authors
Abhishek K. Singh, Balkrishna Chaube, Xinbo Zhang, Jonathan Sun, Kathryn M. Citrin, Alberto Canfrán-Duque, Binod Aryal, Noemi Rotllan, Luis Varela, Richard G. Lee, Tamas L. Horvath, Nathan Price, Yajaira Suárez, Carlos Fernandez-Hernando
Abstract
Cancer-associated fibroblasts (CAF) may exert tumor-promoting and tumor-suppressive functions, but the mechanisms underlying these opposing effects remain elusive. Here, we sought to understand these potentially opposing functions by interrogating functional relationships between CAF subtypes, their mediators, desmoplasia and tumor growth in wide range of tumor types metastasizing to the liver, the most common organ site for metastasis. Depletion of hepatic stellate cells (HSC), which represented main source of CAF in mice and patients in our study, or depletion of all CAF decreased tumor growth and mortality in desmoplastic colorectal and pancreatic metastasis, but not in non-desmoplastic metastatic tumors. Single cell RNA-sequencing in conjunction with CellPhoneDB ligand-receptor analysis, as well as studies in immune cell-depleted and HSC-selective knockout mice uncovered direct CAF-tumor interactions as tumor-promoting mechanism, mediated by myofibroblastic CAF (myCAF)-secreted hyaluronan and inflammatory CAF (iCAF)-secreted HGF. These effects were opposed by myCAF-expressed type-I collagen, which suppressed tumor growth by mechanically restraining tumor spread, overriding its own stiffness-induced mechanosignals. In summary, mechanical restriction by type-I collagen opposes the overall tumor-promoting effects of CAF, thus providing a mechanistic explanation for their dual functions in cancer. Therapeutic targeting of tumor-promoting CAF mediators while preserving type-I collagen may convert CAF from tumor-promoting to tumor-restricting.
Authors
Sonakshi Bhattacharjee, Florian Hamberger, Aashreya Ravichandra, Maximilian Miller, Ajay Nair, Silvia Affo, Aveline Filliol, LiKang Chin, Thomas M. Savage, Deqi Yin, Naita Maren Wirsik, Adam Mehal, Nicholas Arpaia, Ekihiro Seki, Matthias Mack, Di Zhu, Peter A. Sims, Ben Z. Stanger, Kenneth P. Olive, Thomas Schmidt, Rebecca G. Wells, Ingmar Mederacke, Robert F. Schwabe
Abstract
Cholangiopathies caused by biliary epithelial cell (BEC) injury represent a leading cause of liver failure. No effective pharmacologic therapies exist, and the underlying mechanisms remain obscure. We aimed to explore the mechanisms of bile duct repair after targeted BEC injury. Injection of intermedilysin into BEC-specific human CD59 (hCD59) transgenic mice induced acute and specific BEC death, representing a model to study the early signals that drive bile duct repair. Acute BEC injury induced cholestasis followed by CCR2+ monocyte recruitment and BEC proliferation. By using microdissection and next generation RNA sequencing, we identified five genes that were most upregulated in proliferating BECs after acute injury including Mapk8ip2, Cdkn1a, Itgb6, Rgs4, and Ccl2. Immunohistochemistry analyses confirmed robust upregulation of integrin αvβ6 (ITGβ6) expression in this BEC injury model, after bile duct ligation, and in patients with chronic cholangiopathies. Deletion of Itgb6 gene attenuated BEC proliferation post-acute bile duct injury. Macrophage depletion or Ccr2-deficiency impaired ITGβ6 expression and BEC proliferation. In vitro experiments revealed that bile-acid activated monocytes promoted BEC proliferation through ITGβ6. Our data suggest that BEC injury induces cholestasis, monocyte recruitment, and induction of ITGβ6, which work together to promote BEC proliferation, and that therefore represent potential therapeutic targets for cholangiopathies.
Authors
Adrien Guillot, Lucia Guerri, Dechun Feng, Seung-Jin Kim, Yeni Ait Ahmed, Janos Paloczi, Yong He, Kornel Schuebel, Shen Dai, Fengming Liu, Pal Pacher, Tatiana Kisseleva, Xuebin Qin, David Goldman, Frank Tacke, Bin Gao
Abstract
Sepsis is a leading cause of death in critical illness, and its pathophysiology varies depending on preexisting medical conditions. Here we identified nonalcoholic fatty liver disease (NAFLD) as an independent risk factor for sepsis in a large clinical cohort and showed a link between mortality in NAFLD-associated sepsis and hepatic mitochondrial and energetic metabolism dysfunction. Using in vivo and in vitro models of liver lipid overload, we discovered a metabolic coordination between hepatocyte mitochondria and liver macrophages that express triggering receptor expressed on myeloid cells-2 (TREM2). Trem2-deficient macrophages released exosomes that impaired hepatocytic mitochondrial structure and energy supply because of their high content of miR-106b-5p, which blocks Mitofusin 2 (Mfn2). In a mouse model of NAFLD-associated sepsis, TREM2 deficiency accelerated the initial progression of NAFLD and subsequent susceptibility to sepsis. Conversely, overexpression of TREM2 in liver macrophages improved hepatic energy supply and sepsis outcome. This study demonstrates that NAFLD is a risk factor for sepsis, providing a basis for precision treatment, and identifies hepatocyte-macrophage metabolic coordination and TREM2 as potential targets for future clinical trials.
Authors
Jinchao Hou, Jue Zhang, Ping Cui, Yingyue Zhou, Can Liu, Xiaoliang Wu, Yun Ji, Sicong Wang, Baoli Cheng, Hui Ye, Liqi Shu, Kai Zhang, Di Wang, Jielin Xu, Qiang Shu, Marco Colonna, Xiangming Fang
Abstract
Monocyte homing to the liver and adhesion to the liver sinusoidal endothelial cells (LSEC) are key elements in nonalcoholic steatohepatitis (NASH) pathogenesis. We reported previously that vascular cell adhesion molecule 1 (VCAM-1) mediates monocyte adhesion to LSEC. However, the pathogenic role of VCAM-1 in NASH is unclear. Herein, we report that VCAM-1 was a top upregulated adhesion molecule in the NASH mouse liver transcriptome. Open chromatin landscape profiling combined with genome-wide transcriptome analysis showed robust transcriptional upregulation of LSEC-VCAM-1 in murine NASH. Moreover, LSEC-VCAM-1 expression was significantly increased in human NASH. LSEC-VCAM-1 expression was upregulated by palmitate treatment in vitro, and reduced with inhibition of the mitogen-activated protein 3 kinase, mixed lineage kinase 3 (MLK3). Likewise, LSEC-VCAM-1 expression was reduced in the Mlk3-/- mice with diet-induced NASH. Furthermore, VCAM-1 neutralizing antibody or pharmacological inhibition attenuated diet-induced NASH in mice, mainly via reducing the proinflammatory monocyte hepatic population as examined by mass cytometry by time of flight (CyTOF). Moreover, endothelium-specific Vcam1 knockout mice were also protected against NASH. In summary, lipotoxic stress enhances the expression of LSEC-VCAM-1, in part, through MLK3 signaling. Inhibition of VCAM-1 was salutary in murine NASH, and might serve as a potential therapeutic strategy for human NASH.
Authors
Kunimaro Furuta, Qianqian Guo, Kevin D. Pavelko, Jeong-Heon Lee, Keith D. Robertson, Yasuhiko Nakao, Jan Melek, Vijay H. Shah, Petra Hirsova, Samar H. Ibrahim
Abstract
Acute liver failure (ALF) patients display systemic innate immune suppression and increased susceptibility to infections. PD-1 expression by macrophages has been associated with immune suppression during sepsis and cancer. We therefore examined the role of PD-1/PD-L1 pathway in regulating Kupffer cell inflammatory and antimicrobial responses in acetaminophen (APAP) induced acute liver injury. Using intravital imaging and flow cytometry we found impaired Kupffer cell bacterial clearance and systemic bacterial dissemination in mice with liver injury. Increased PD-1 and PD-L1 expression was detected in Kupffer cells and lymphocyte subsets, respectively, during resolution of injury. Gene expression profiling of PD-1+ Kupffer cells revealed an immune-suppressive profile and reduced pathogen responses. Compared to wild-type, PD-1 deficient or anti-PD-1 treated mice with liver injury showed improved Kupffer cell bacterial clearance, reduced tissue bacterial load and protection from sepsis. Blood sample analyses of ALF patients revealed enhanced PD-1 and PD-L1 expression of monocytes and lymphocytes, respectively, and that plasma soluble PD-L1 levels predict patient outcome and sepsis. PD-1 in vitro blockade restored monocyte functionality. Our study describes a role for PD-1/PD-L1 axis in suppressing Kupffer cell and monocyte antimicrobial responses after liver injury and suggests anti-PD-1 immunotherapy as a strategy to reduce infection susceptibility in ALF.
Authors
Evangelos Triantafyllou, Cathrin L. C. Gudd, Marie-Anne Mawhin, Hannah C. Husbyn, Francesca M. Trovato, Matthew K. Siggins, Thomas O'Connor, Hiromi Kudo, Sujit K. Mukherjee, Julia A. Wendon, Christine Bernsmeier, Robert D. Goldin, Marina Botto, Wafa Khamri, Mark J.W. McPhail, Lucia A. Possamai, Kevin J. Woollard, Charalambos G. Antoniades, Mark R. Thursz
Abstract
Neutrophil infiltration around lipotoxic hepatocytes is a hallmark of nonalcoholic steatohepatitis (NASH); however, how these two types of cells communicate remain obscure. We have previously demonstrated that neutrophil-specific microRNA-223 (miR-223) is elevated in hepatocytes to limit NASH progression in obese mice. Here we demonstrated that this elevation of miR-223 in hepatocytes was due to preferential uptake of miR-223-enriched extracellular vesicles (EVs) derived from neutrophils as well other types of cells albeit to a lesser extent. This selective uptake was dependent on the expression of low-density lipoprotein receptor (LDLR) on hepatocytes and apolipoprotein E (APOE) on neutrophil-derived EVs, which was enhanced by free fatty acids. Once internalized by hepatocytes, the EV-derived miR-223 acted to inhibit hepatic inflammatory and fibrogenic gene expression. In the absence of this LDLR-APOE dependent uptake of miR-223-enriched EVs, the progression of steatosis to NASH was accelerated. In contrast, augmentation of this transfer by treatment with an inhibitor of proprotein convertase subtilisin/kexin type 9, a drug used to lower blood cholesterol by upregulating LDLR, ameliorated NASH in mice. This specific role of LDLR and APOE in the selective control of miR-223-enriched EV transfer from neutrophils to hepatocytes may serve as a potential therapeutic target for NASH.
Authors
Yong He, Robim M. Rodrigues, Xiaolin Wang, Wonhyo Seo, Jing Ma, Seonghwan Hwang, Yaojie Fu, Eszter Trojnar, Csaba Matyas, Suxian Zhao, Ruixue Ren, Dechun Feng, Pal Pacher, George Kunos, Bin Gao
Abstract
ABSTRACTIndividuals harboring the loss-of-function (LOF) proprotein convertase subtilising/kexin type 9 Gln152His variation (PCSK9Q152H) have low circulating low-density lipoprotein (LDL) cholesterol levels and are therefore protected against cardiovascular disease (CVD). This uncleavable form of pro-PCSK9, however, is retained in the endoplasmic reticulum (ER) of liver hepatocytes where it would be expected to contribute to ER storage disease (ERSD); a heritable condition known to cause systemic ER stress and liver injury. Here, we examined liver function in members of several French-Canadian families known to carry the PCSK9Q152H variation. We report that PCSK9Q152H carriers exhibited marked hypocholesterolemia and normal liver function despite their lifelong state of ER PCSK9 retention. Mechanistically, hepatic overexpression of PCSK9Q152H using adeno-associated viruses in male mice greatly increased the stability of key ER stress response chaperones in liver hepatocytes and unexpectedly protected against ER stress and liver injury rather than to induce them. Our findings show that ER retention of PCSK9 not only reduced CVD risk in patients but may also protect against ERSD and other ER stress-driven conditions of the liver. In summary, we have uncovered a co-chaperone function for PCSK9Q152H that explains its hepatoprotective effects and generated a translational mouse model for further mechanistic insights into this clinically relevant LOF PCSK9 variant.
Authors
Paul F. Lebeau, Hanny Wassef, Jae Hyun Byun, Khrystyna Platko, Brandon Ason, Simon Jackson, Joshua Dobroff, Susan Shetterly, William G. Richards, Ali A. Al-Hashimi, Kevin D. Won, Majambu Mbikay, Annik Prat, An Tang, Guillaume Paré, Renata Pasqualini, Nabil G. Seidah, Wadih Arap, Michel Chretien, Richard C. Austin
Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)