Interventional Potential of Recombinant Feline Hepatocyte Growth Factor in a Mouse Model of Non-alcoholic Steatohepatitis

Designing receptor agonists with enhanced pharmacokinetics by grafting macrocyclic peptides into fragment crystallizable regions

Short half-lives in circulation and poor transport across the blood-brain barrier limit the utility of cytokines and growth factors acting as receptor agonists. Here we show that surrogate receptor agonists with longer half-lives in circulation and enhanced transport rates across the blood-brain barrier can be generated by genetically inserting macrocyclic peptide pharmacophores into the structural loops of the fragment crystallizable (Fc) region of a human immunoglobulin. We used such 'lasso-grafting' approach, which preserves the expression levels of the Fc region and its affinity for the neonatal Fc receptor, to generate Fc-based protein scaffolds with macrocyclic peptides binding to the receptor tyrosine protein kinase Met. The Met agonists dimerized Met, inducing biological responses that were similar to those induced by its natural ligand. Moreover, lasso-grafting of the Fc region of the mouse anti-transferrin-receptor antibody with Met-binding macrocyclic peptides enhanced the accumulation of the resulting Met agonists in brain parenchyma in mice. Lasso-grafting may allow for designer protein therapeutics with enhanced stability and pharmacokinetics.

Liver Fibrosis-From Mechanisms of Injury to Modulation of Disease

The Transregional Collaborative Research Center "Organ Fibrosis: From Mechanisms of Injury to Modulation of Disease" (referred to as SFB/TRR57) was funded for 13 years (2009-2021) by the German Research Council (DFG). This consortium was hosted by the Medical Schools of the RWTH Aachen University and Bonn University in Germany. The SFB/TRR57 implemented combined basic and clinical research to achieve detailed knowledge in three selected key questions: (i) What are the relevant mechanisms and signal pathways required for initiating organ fibrosis? (ii) Which immunological mechanisms and molecules contribute to organ fibrosis? and (iii) How can organ fibrosis be modulated, e.g., by interventional strategies including imaging and pharmacological approaches? In this review we will summarize the liver-related key findings of this consortium gained within the last 12 years on these three aspects of liver fibrogenesis. We will highlight the role of cell death and cell cycle pathways as well as nutritional and iron-related mechanisms for liver fibrosis initiation. Moreover, we will define and characterize the major immune cell compartments relevant for liver fibrogenesis, and finally point to potential signaling pathways and pharmacological targets that turned out to be suitable to develop novel approaches for improved therapy and diagnosis of liver fibrosis. In summary, this review will provide a comprehensive overview about the knowledge on liver fibrogenesis and its potential therapy gained by the SFB/TRR57 consortium within the last decade. The kidney-related research results obtained by the same consortium are highlighted in an article published back-to-back in Frontiers in Medicine.

Exploring the Gamut of Receptor Tyrosine Kinases for Their Promise in the Management of Non-Alcoholic Fatty Liver Disease

Recently, non-alcoholic fatty liver disease (NAFLD) has emerged as a predominant health concern affecting approximately a quarter of the world’s population. NAFLD is a spectrum of liver ailments arising from nascent lipid accumulation and leading to inflammation, fibrosis or even carcinogenesis. Despite its prevalence and severity, no targeted pharmacological intervention is approved to date. Thus, it is imperative to identify suitable drug targets critical to the development and progression of NAFLD. In this quest, a ray of hope is nestled within a group of proteins, receptor tyrosine kinases (RTKs), as targets to contain or even reverse NAFLD. RTKs control numerous vital biological processes and their selective expression and activity in specific diseases have rendered them useful as drug targets. In this review, we discuss the recent advancements in characterizing the role of RTKs in NAFLD progression and qualify their suitability as pharmacological targets. Available data suggests inhibition of Epidermal Growth Factor Receptor, AXL, Fibroblast Growth Factor Receptor 4 and Vascular Endothelial Growth Factor Receptor, and activation of cellular mesenchymal-epithelial transition factor and Fibroblast Growth Factor Receptor 1 could pave the way for novel NAFLD therapeutics. Thus, it is important to characterize these RTKs for target validation and proof-of-concept through clinical trials.

Nobiletin mitigates hepatocytes death, liver inflammation, and fibrosis in a murine model of NASH through modulating hepatic oxidative stress and mitochondrial dysfunction

This study aimed to investigate the therapeutic effects of nobiletin (NOB) on nonalcoholic steatohepatitis (NASH) and liver fibrosis in mice and to elucidate its underlying molecular mechanisms. BALB/c mice were fed a normal chow diet or a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD) for 8 wks and treated with NOB (50 mg/kg) or vehicle by daily intraperitoneally injection for the last 4 wks. In vitro, we used palmitate (PA) stimulated AML12 cells as the model of hepatocyte lipotoxicity to dissect the effect and molecular mechanisms of NOB' action. Our results exhibited that NOB dramatically reduced hepatic steatosis, lipid accumulation and hepatocyte apoptosis, and inhibited the infiltration of F4/80⁺ macrophages into the NASH livers. Furthermore, NOB limited liver fibrosis and hepatic stellate cells activation in NASH mice. In parallel, NOB alleviated hepatocytes apoptosis and lipid accumulation in PA-treated AML12 cells. Most importantly, these histological ameliorations in NASH and fibrosis in NOB-treated NASH mice were associated with improvement hepatic oxidative stress, lipid peroxidation product, mitochondrial respiratory chain complexes I and restored ATP production. Similarly, NOB attenuated PA-induced reactive oxygen species (ROS) generation and mitochondrial disfunction in cultured AML12 cells. Additionally, NOB diminished the expression of mitochondrial Ca²⁺ uniporter (MCU) both in NASH livers and in PA-treated AML12. Taken together, our results indicate that NOB mitigated NASH development and fibrosis through modulating hepatic oxidative stress and attenuating mitochondrial dysfunction. Therefore, NOB might be a novel and promising agent for treatment of NASH and liver fibrosis.

A Review of CXCL1 in Cardiac Fibrosis

Chemokine C-X-C motif ligand-1 (CXCL1), principally expressed in neutrophils, macrophages and epithelial cells, is a valid pro-inflammatory factor which performs an important role in mediating the infiltration of neutrophils and monocytes/macrophages. Elevated serum level of CXCL1 is considered a pro-inflammatory reaction by the organism. CXCL1 is also related to diverse organs fibrosis according to relevant studies. A growing body of evidence suggests that CXCL1 promotes the process of cardiac remodeling and fibrosis. Here, we review structure and physiological functions of CXCL1 and recent progress on the effects and mechanisms of CXCL1 in cardiac fibrosis. In addition, we explore the role of CXCL1 in the fibrosis of other organs. Besides, we probe the possibility that CXCL1 can be a therapeutic target for the treatment of cardiac fibrosis in cardiovascular diseases.

Sevoflurane preconditioning activates HGF/Met-mediated autophagy to attenuate hepatic ischemia-reperfusion injury in mice

Sevoflurane (SEV) preconditioning plays a protective effect against liver ischemia reperfusion (IR) injury, while the role of autophagy in SEV-mediated hepatoprotection and the precise mechanism is unclear. In the current study, mice were pretreated with SEV or autophagy inhibitor before liver IR injury. In vitro, primary rat hepatocytes were pretreated with SEV and then exposed to hypoxia/reoxygenation (H/R). Liver function was measured by biochemical and histopathological examinations, and markers associated with inflammation, oxidation, apoptosis and autophagy were subsequently measured. We found that SEV preconditioning dramatically reduced hepatic damage, alleviated cell inflammatory response, oxidative stress and apoptosis in mice suffering hepatic IR injury, whereas these protective effects were abolished by the autophagy inhibitor 3-MA. In addition, pretreatment with SEV markedly activated HGF/Met signaling pathway regulation. Besides, pretreatment with an hepatocyte growth factor (HGF) inhibitor or knocking down HGF expression significantly downregulated phosphorylated met (p-met) and autophagy levels, and abolished the protective effects of SEV against hepatic IR or hepatocyte H/R injury. Conversely, HGF overexpression efficiently increased the p-met and autophagy levels and strengthened the protective effects of SEV. These results indicated that sevoflurane preconditioning ameliorates hepatic IR injury by activating HGF/Met-mediated autophagy.

Inhibition of hyaluronan synthesis by 4-methylumbelliferone ameliorates non-alcoholic steatohepatitis in choline-deficient L-amino acid-defined diet-induced murine model

Hyaluronan (HA) as a glycosaminoglycan can bind to cell-surface receptors, such as TLR4, to regulate inflammation, tissue injury, repair, and fibrosis. 4-methylumbelliferone (4-MU), an inhibitor of HA synthesis, is a drug used for the treatment of biliary spasms. Currently, therapeutic interventions are not available for non-alcoholic steatohepatitis (NASH). In this study, we investigated the effects of 4-MU on NASH using a choline-deficient amino acid (CDAA) diet model. CDAA diet-fed mice showed NASH characteristics, including hepatocyte injury, hepatic steatosis, inflammation, and fibrogenesis. 4-MU treatment significantly reduced hepatic lipid contents in CDAA diet-fed mice. 4-MU reversed CDAA diet-mediated inhibition of Ppara and induction of Srebf1 and Slc27a2. Analysis of serum ALT and AST levels revealed that 4-MU treatment protected against hepatocellular damage induced by CDAA diet feeding. TLR4 regulates low molecular weight-HA-induced chemokine expression in hepatocytes. In CDAA diet-fed, 4-MU-treated mice, the upregulated chemokine/cytokine expression, such as Cxcl1, Cxcl2, and Tnf was attenuated with the decrease of macrophage infiltration into the liver. Moreover, HA inhibition repressed CDAA diet-induced mRNA expression of fibrogenic genes, Notch1, and Hes1 in the liver. In conclusion, 4-MU treatment inhibited liver steatosis and steatohepatitis in a mouse model of NASH, implicating that 4-MU may have therapeutic potential for NASH.

The endothelial dysfunction blocker CU06-1004 ameliorates choline-deficient L-amino acid diet-induced non-alcoholic steatohepatitis in mice

Non-alcoholic steatohepatitis (NASH) is a severe, advanced form of non-alcoholic fatty liver disease (NAFLD) that is associated with features of metabolic syndrome and characterized by hepatic steatosis, inflammation, and fibrosis. In addition, NASH is associated with endothelial dysfunction within the hepatic vasculature. Treatment with CU06-1004 (previously called Sac-1004) ameliorates endothelial dysfunction by inhibiting hyperpermeability and inflammation. In this study, we investigated the protective effects of CU06-1004 in a choline-deficient L-amino acid (CDAA)-induced mouse model of NASH for 3 or 6 weeks. Specifically, we evaluated the effects of CU06-1004 on lipid accumulation, inflammation, hepatic fibrosis, and liver sinusoidal endothelial cell (LSEC) capillarization through biochemical analysis, immunohistochemistry, and real-time PCR. We found that the administration of CU06-1004 to mice improved liver triglyceride (TG) and serum alanine aminotransferase (ALT) in this CDAA-induced model of NASH for 6 weeks. In groups of NASH induced mice for both 3 and 6 weeks, CU06-1004 significantly reduced the hepatic expression of genes related to lipogenesis, inflammation, and cell adhesion. However, expression of genes related to hepatic fibrosis and vascular endothelial changes were only decreased in animals with mild NASH. These results suggest that the administration of CU06-1004 suppresses hepatic steatosis, inflammation, fibrosis, and LSEC capillarization in a CDAA-induced mouse model of NASH. This suggests that CU06-1004 has therapeutic potential for the treatment of mild NASH.

Bok-choy promotes growth performance, lipid metabolism and related gene expression in Syrian golden hamsters fed with a high-fat diet

Broadly, bok-choy is known for its potential benefits as part of a human diet. However, the effects and deeper investigations of bok-choy on human health are still insufficient. This study aimed to investigate the beneficial effects of two cultivars of bok-choy, 'Suzhouqing' (green cultivar) and 'Ziluolan' (purple cultivar), on growth performance, lipid metabolism and related gene expressions in Syrian golden hamsters. Fifty six male Syrian golden hamsters (6-months-old) were randomly assigned into 6 groups: normal diet (A), high-fat diet (B), high-fat diet + 5% 'Suzhouqing' (C), high-fat diet + 7% 'Suzhouqing' (D), high-fat diet + 5% 'Ziluolan' (E), and high-fat diet + 7% 'Ziluolan' (F), fed for 56 consecutive days. On day 0, 28 and 56, blood and liver samples were collected to examine the lipid profile, liver enzymes, histomorphology and related gene expressions. The results showed that group B had significantly increased levels of total cholesterol, triglycerides, low-density lipoprotein cholesterol, alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase, while (P < 0.05) showed impaired levels of high-density lipoprotein cholesterol compared with group A. Group D, E and F had significantly reduced levels of total cholesterol, triglycerides, low-density lipoprotein cholesterol, alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase, while the level of high-density lipoprotein cholesterol was significantly increased compared with group B. Remarkably, the mRNA expressions of CEBP-α, DGAT1, lipoprotein lipase (LPL), FASN and 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA) were significantly up-regulated and carnitine palmitoyl transferase 2 (CPT2), Cyp27A1 and proliferator activated receptor alpha (PPAR-α) were significantly down-regulated in group B compared with group A. However, in group D, E and F, the mRNA expression levels of CCAAT enhancer binding protein alpha, DGAT1, LPL, FASN and HMG-CoA were significantly down-regulated and CPT2, Cyp27A1 and PPAR-α were significantly up-regulated compared with group B. In conclusion, different amounts of bok-choy added to the diets incredibly improved the lipid-profile, enhanced liver enzyme activities and related gene expression. The hamsters supplemented with 7% 'Ziluolan' exhibited the best performance among all the other high-fat groups, which shows that Ziluolan could be a great alternative for the reduction of fat accumulation and conserving health.

Hepatic ferroptosis plays an important role as the trigger for initiating inflammation in nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a metabolic liver disease that progresses from simple steatosis to the disease state of inflammation and fibrosis. Previous studies suggest that apoptosis and necroptosis may contribute to the pathogenesis of NASH, based on several murine models. However, the mechanisms underlying the transition of simple steatosis to steatohepatitis remain unclear, because it is difficult to identify when and where such cell deaths begin to occur in the pathophysiological process of NASH. In the present study, our aim is to investigate which type of cell death plays a role as the trigger for initiating inflammation in fatty liver. By establishing a simple method of discriminating between apoptosis and necrosis in the liver, we found that necrosis occurred prior to apoptosis at the onset of steatohepatitis in the choline-deficient, ethionine-supplemented (CDE) diet model. To further investigate what type of necrosis is involved in the initial necrotic cell death, we examined the effect of necroptosis and ferroptosis inhibition by administering inhibitors to wild-type mice in the CDE diet model. In addition, necroptosis was evaluated using mixed lineage kinase domain-like protein (MLKL) knockout mice, which is lacking in a terminal executor of necroptosis. Consequently, necroptosis inhibition failed to block the onset of necrotic cell death, while ferroptosis inhibition protected hepatocytes from necrotic death almost completely, and suppressed the subsequent infiltration of immune cells and inflammatory reaction. Furthermore, the amount of oxidized phosphatidylethanolamine, which is involved in ferroptosis pathway, was increased in the liver sample of the CDE diet-fed mice. These findings suggest that hepatic ferroptosis plays an important role as the trigger for initiating inflammation in steatohepatitis and may be a therapeutic target for preventing the onset of steatohepatitis.

Genistein can ameliorate hepatic inflammatory reaction in nonalcoholic steatohepatitis rats

Genistein plays an active role in improving nonalcoholic fatty liver disease (NAFLD). This study is designed to investigate the effect of genistein on liver inflammation in rats with nonalcoholic steatohepatitis (NASH). Forty SPF male SD rats were randomly divided into normal group, model group, genistein low-dose group (0.1% wt/wt) and high-dose group (0.2% wt/wt) with 10 rats in each group. After 12 weeks' feeding, liver tissues and serum samples of rats were taken, and HE staining was used to perform pathological examination of liver tissues, then the degree of inflammatory infiltration was observed and NAFLD activity score(NAS) was calculated. With corresponding kits, several indicators were detected, namely, serum triglyceride (TG), total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), liver TC and TG, and serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood glucose and serum endotoxin. The levels of tumor necrosis factor (TNFα) in liver and insulin in blood of rats were detected by enzyme linked immunosorbent assay (ELISA), then the HOMA-IR index was calculated. Immunohistochemistry staining was used to observe the expression level of TLR4 protein and the RT-PCR was used to detect Tlr4 mRNA expression in liver tissue. The results showed that genistein could reduce TLR4 protein and gene expression, decrease the endotoxin and TNFα, alleviate the inflammatory reaction and make the indicators detected in blood and liver stay near normal in NASH rats. In conclusion, genistein can ameliorate hepatic inflammatory reaction in nonalcoholic steatohepatitis rats.

Liver Regeneration: Different Sub-Populations of Parenchymal Cells at Play Choreographed by an Injury-Specific Microenvironment

Liver regeneration is crucial for the maintenance of liver functional mass during homeostasis and diseases. In a disease context-dependent manner, liver regeneration is contributed to by hepatocytes or progenitor cells. As long as they are replicatively competent, hepatocytes are the main cell type responsible for supporting liver size homeostasisand regeneration. The concept that all hepatocytes within the lobule have the same proliferative capacity but are differentially recruited according to the localization of the wound, or whether a yet to be defined sub-population of hepatocytes supports regeneration is still debated. In a chronically or severely injured liver, hepatocytes may enter a state of replicative senescence. In such conditions, small biliary cells activate and expand, a process called ductular reaction (DR). Work in the last few decades has demonstrated that DR cells can differentiate into hepatocytes and thereby contribute to parenchymal reconstitution. In this study we will review the molecular mechanisms supporting these two processes to determine potential targets that would be amenable for therapeutic manipulation to enhance liver regeneration.

Advancing the understanding of NAFLD to hepatocellular carcinoma development: From experimental models to humans

Nonalcoholic fatty liver disease (NAFLD) has recently been recognized as an important etiology contributing to the increased incidence of hepatocellular carcinoma (HCC). NAFLD, characterized by fat accumulation in the liver, is affecting at least one-third of the global population. The more aggressive form, nonalcoholic steatohepatitis (NASH), is characterized by hepatocyte necrosis and inflammation. The development of effective approaches for disease prevention and/or treatment heavily relies on deep understanding of the mechanisms underlying NAFLD to HCC development. However, this has been largely hampered by the lack of robust experimental models that recapitulate the full disease spectrum. This review will comprehensively describe the current in vitro and mouse models for studying NAFLD/NASH/HCC, and further emphasize their applications and possible future improvement for better understanding the molecular mechanisms involved in the cascade of NAFLD to HCC progression.