Mechanism and Therapeutic Targets of c-Jun-N-Terminal Kinases Activation in Nonalcoholic Fatty Liver Disease

Compound J27 alleviates high-fat diet-induced metabolic dysfunction-associated steatotic liver disease by targeting JNK

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most characteristic form of liver diseases. As the member of MAPK family, the cJun-N-terminal-kinase (JNK) plays a crucial role in the pathogenesis of MASLD. A small molecule compound, J27, has demonstrated strong anti-inflammatory effects by inhibiting JNK phosphorylation, but its therapeutic potential in MASLD remains unclear.

METHODS

To evaluate the effect of J27, we used a high-fat diet (HFD)-induced MASLD mouse model with or without J27 treatment. Pathological changes were assessed through tissue staining, biochemical analysis, and other assays. In vitro, J27's effects were tested on macrophages, hepatocytes, and co-culture systems under palmitic acid stimulation.

RESULTS

J27 significantly reduced HFD-induced hepatic steatosis, liver injury, insulin resistance, and inflammatory responses by targeting JNK both in vivo and in vitro. On one hand, J27 blocked JNK activation, thereby improving insulin signaling and alleviating metabolic dysfunction in hepatocytes. On the other hand, J27 inhibited the inflammatory response in macrophages by disrupting the JNK/NF-κB axis, which, through cell-cell communication, further reduced hepatocyte injury.

CONCLUSIONS

J27, as a potent JNK inhibitor, markedly reduced HFD-induced MASLD, suggesting it as a promising therapeutic candidate for this disease.

Integrated liver-secreted and plasma proteomics identify a predictive model that stratifies MASH

Obesity is a major risk factor for metabolic-associated steatotic liver disease (MASLD), which can progress to metabolic-associated steatohepatitis (MASH). There are no validated non-invasive tests to stratify persons with obesity with a greater risk for MASH. Herein, we assess plasma and liver from 266 obese individuals spanning the MASLD spectrum. Ninety-six human livers were precision-cut, and mass spectrometry-based proteomics identifies 3,333 proteins in the liver-secretion medium, of which 107 are differentially secreted in MASH compared with no pathology. The plasma proteome is markedly remodeled in MASH but is not different between patients with steatosis and no pathology. The APASHA model, comprising plasma apolipoprotein F (APOF), proprotein convertase subtilisin/kexin type 9 (PCSK9), afamin (AFM), S100 calcium-binding protein A6 (S100A6), HbA1c, and zinc-alpha-2-glycoprotein (AZGP1), stratifies MASH (area under receiver operating characteristic [AUROC] = 0.88). Our investigations detail the evolution of liver-secreted and plasma proteins with MASLD progression, providing a rich resource defining human liver-secreted proteins and creating a predictive model to stratify patients with obesity at risk of MASH.

Angelica sinensis polysaccharides mitigate cadmium-induced apoptosis in layer chicken chondrocytes by inhibiting the JNK signaling pathway

Cadmium (Cd), a toxic heavy metal pollutant, inflicts widespread damage on various organs and tissues, including cartilage, where it induces chondrocyte apoptosis. Angelica sinensis polysaccharides (ASP), a key active component of the traditional Chinese medicine Angelica sinensis, have been shown to possess anti-apoptotic effects on chondrocytes. This study investigates the in vitro effects of ASP on alleviating Cd-induced apoptosis in layer chicken chondrocytes, focusing on the mitochondrial apoptosis pathway mediated by the c-Jun N-terminal kinase (JNK) signaling pathway. Chondrocytes were isolated from layer chicken embryos and confirmed to express collagen type II alpha 1 (Col2a1). We found that Cd triggered apoptosis in the chondrocytes; however, the use of the JNK inhibitor SP 600125 mitigated mitochondrial structural damage casused by Cd, indicating the involvement of JNK signaling in this process. Furthermore, ASP effectively alleviated Cd-induced apoptosis in layer chicken chondrocytes by inhibiting JNK signaling in vitro. Our findings provide a theoretical foundation for the clinical application of ASP in preventing Cd-induced cartilage diseases in poultry.

Insulin-Heart Axis: Bridging Physiology to Insulin Resistance

Insulin signaling is vital for regulating cellular metabolism, growth, and survival pathways, particularly in tissues such as adipose, skeletal muscle, liver, and brain. Its role in the heart, however, is less well-explored. The heart, requiring significant ATP to fuel its contractile machinery, relies on insulin signaling to manage myocardial substrate supply and directly affect cardiac muscle metabolism. This review investigates the insulin-heart axis, focusing on insulin's multifaceted influence on cardiac function, from metabolic regulation to the development of physiological cardiac hypertrophy. A central theme of this review is the pathophysiology of insulin resistance and its profound implications for cardiac health. We discuss the intricate molecular mechanisms by which insulin signaling modulates glucose and fatty acid metabolism in cardiomyocytes, emphasizing its pivotal role in maintaining cardiac energy homeostasis. Insulin resistance disrupts these processes, leading to significant cardiac metabolic disturbances, autonomic dysfunction, subcellular signaling abnormalities, and activation of the renin-angiotensin-aldosterone system. These factors collectively contribute to the progression of diabetic cardiomyopathy and other cardiovascular diseases. Insulin resistance is linked to hypertrophy, fibrosis, diastolic dysfunction, and systolic heart failure, exacerbating the risk of coronary artery disease and heart failure. Understanding the insulin-heart axis is crucial for developing therapeutic strategies to mitigate the cardiovascular complications associated with insulin resistance and diabetes.

Dynamics of cellular plasticity in non-alcoholic steatohepatitis (NASH)

Non-alcoholic steatohepatitis (NASH) is a pathogenic stage of the broader non-alcoholic fatty liver disease (NAFLD). Histological presentation of NASH includes hepatocyte ballooning, macrophage polarization, ductular reaction, and hepatic stellate cell (HSCs) activation. At a cellular level, a heterogenous population of cells such as hepatocytes, macrophages, cholangiocytes, and HSCs undergo dramatic intra-cellular changes in response to extracellular triggers, which are termed "cellular plasticity. This dynamic switch in the cellular structure and function of hepatic parenchymal and non-parenchymal cells and their crosstalk culminates in the perpetuation of inflammation and fibrosis in NASH. This review presents an overview of our current understanding of cellular plasticity in NASH and its molecular mechanisms, along with possible targeting to develop cell-specific NASH therapies.

Underlying Mechanisms behind the Brain-Gut-Liver Axis and Metabolic-Associated Fatty Liver Disease (MAFLD): An Update

Metabolic-associated fatty liver disease (MAFLD) includes several metabolic dysfunctions caused by dysregulation in the brain-gut-liver axis and, consequently, increases cardiovascular risks and fatty liver dysfunction. In MAFLD, type 2 diabetes mellitus, obesity, and metabolic syndrome are frequently present; these conditions are related to liver lipogenesis and systemic inflammation. This study aimed to review the connection between the brain-gut-liver axis and MAFLD. The inflammatory process, cellular alterations in hepatocytes and stellate cells, hypercaloric diet, and sedentarism aggravate the prognosis of patients with MAFLD. Thus, to understand the modulation of the physiopathology of MAFLD, it is necessary to include the organokines involved in this process (adipokines, myokines, osteokines, and hepatokines) and their clinical relevance to project future perspectives of this condition and bring to light new possibilities in therapeutic approaches. Adipokines are responsible for the activation of distinct cellular signaling in different tissues, such as insulin and pro-inflammatory cytokines, which is important for balancing substances to avoid MAFLD and its progression. Myokines improve the quantity and quality of adipose tissues, contributing to avoiding the development of MAFLD. Finally, hepatokines are decisive in improving or not improving the progression of this disease through the regulation of pro-inflammatory and anti-inflammatory organokines.

Expression of immune related genes and possible regulatory mechanisms in different stages of non-alcoholic fatty liver disease

Background

Non-alcoholic fatty liver disease (NAFLD), which includes simple steatosis (SS) and non-alcoholic steatohepatitis (NASH), is a significant contributor to liver disease on a global scale. The change of immunity-related genes (IRGs) expression level leads to different immune infiltrations. However, the expression of IRGs and possible regulatory mechanisms involved in NAFLD remain unclear. The objective of our research is to investigate crucial genes linked to the development of NAFLD and the transition from SS to NASH.

Methods

Dataset GSE89632, which includes healthy controls, SS patients, and NASH patients, was obtained using the GEO database. To examine the correlation between sets of genes and clinical characteristics, we employed weighted gene co-expression network analysis (WGCNA) and differential expression analysis. Hub genes were extracted using a network of protein-protein interactions (PPI) and three different machine learning algorithms. To validate the findings, another dataset that is publicly accessible and mice that were subjected to a high-fat diet (HFD) or MCD diet were utilized. Furthermore, the ESTIMATE algorithm and ssGSEA were employed to investigate the immune landscape in the normal versus SS group and SS versus NASH group, additionally, the relationship between immune infiltration and the expression of hub genes was also examined.

Results

A total of 28 immune related key genes were selected. Most of these genes expressed reverse patterns in the initial and progressive stages of NAFLD. GO and KEGG analyses showed that they were focused on the cytokine related pathways and immune cell activation and chemotaxis. After screening by various algorithms, we obtained two hub genes, including JUN and CCL20. Validation of these findings was confirmed by analyzing gene expression patterns in both the validation dataset and the mouse model. Ultimately, two hub genes were discovered to have a significant correlation with the infiltration of immune cells.

Conclusion

We proposed that there were dynamic changes in the expression levels of IRGs in different stages of NAFLD disease, which led to different immune landscapes in SS and NASH. The findings of our research could serve as a guide for the accurate management of various phases of NAFLD.

The Role of the Dysregulated JNK Signaling Pathway in the Pathogenesis of Human Diseases and Its Potential Therapeutic Strategies: A Comprehensive Review

JNK is named after c-Jun N-terminal kinase, as it is responsible for phosphorylating c-Jun. As a member of the mitogen-activated protein kinase (MAPK) family, JNK is also known as stress-activated kinase (SAPK) because it can be activated by extracellular stresses including growth factor, UV irradiation, and virus infection. Functionally, JNK regulates various cell behaviors such as cell differentiation, proliferation, survival, and metabolic reprogramming. Dysregulated JNK signaling contributes to several types of human diseases. Although the role of the JNK pathway in a single disease has been summarized in several previous publications, a comprehensive review of its role in multiple kinds of human diseases is missing. In this review, we begin by introducing the landmark discoveries, structures, tissue expression, and activation mechanisms of the JNK pathway. Next, we come to the focus of this work: a comprehensive summary of the role of the deregulated JNK pathway in multiple kinds of diseases. Beyond that, we also discuss the current strategies for targeting the JNK pathway for therapeutic intervention and summarize the application of JNK inhibitors as well as several challenges now faced. We expect that this review can provide a more comprehensive insight into the critical role of the JNK pathway in the pathogenesis of human diseases and hope that it also provides important clues for ameliorating disease conditions.

Hepatocyte-specific mitogen-activated protein kinase phosphatase 1 in sexual dimorphism and susceptibility to alcohol induced liver injury

Background

It is well established that females are more susceptible to the toxic effects of alcohol, although the exact mechanisms are still poorly understood. Previous studies noted that alcohol reduces the expression of mitogen-activated protein kinase phosphatase 1 (MKP1), a negative regulator of mitogen-activated protein kinases (MAPK) in the liver. However, the role of hepatocyte- specific MKP1 in the pathogenesis of alcohol-associated liver disease (ALD) remains uncharacterized. This study aimed to evaluate the role of hepatocyte-specific MKP1 in the susceptibility and sexual dimorphism in alcohol-induced liver injury.

Methods

C57Bl/6 mice were used in an intragastric ethanol feeding model of alcohol-associated steatohepatitis (ASH). Hepatocyte-specific Mkp1-/- knockout and (Mkp1+/+ "f/f" male and female mice were subjected to the NIAAA chronic plus binge model. Primary mouse hepatocytes were used for in vitro studies. Liver RNA sequencing was performed on an Illumina NextSeq 500. Liver injury was evaluated by plasma alanine transaminase (ALT), hepatic ER stress and inflammation markers. Statistical analysis was carried out using ANOVA and the unpaired Student's t-test.

Results

ASH was associated with the severe injury accompanied by increased endoplasmic reticulum (ER) stress and significant downregulation of Dusp1 mRNA expression. In vitro, ethanol treatment resulted in a time-dependent decrease in Dusp1 mRNA and protein expression in primary hepatocytes in both males and females; however, this effect was significantly more pronounced in hepatocytes from females. In vivo, female mice developed more liver injury in a chronic plus binge model which was accompanied by a significant decrease in liver Dusp1 mRNA expression. In comparison, liver Dusp1 was not changed in male mice, while they developed milder injury to alcohol. Mkp1 deletion in hepatocytes led to increased alcohol induced liver injury, ER stress and inflammation in both sexes.

Conclusion

Hepatocyte Mkp1 plays a significant role in alcohol induced liver injury. Alcohol downregulates Mkp1 expression in hepatocytes in a sex dependent manner and could play a role in sexual dimorphism in increased female susceptibility to alcohol.

Integrating network analysis and pharmacokinetics to investigate the mechanisms of Danzhi Tiaozhi Decoction in metabolic-associated fatty liver disease (MAFLD)

ETHNOPHARMACOLOGICAL RELEVANCE

Based on ancient classics, Danzhi Tiaozhi Decoction has been successfully used to treat nonalcoholic fatty liver disease for decades. However, its therapeutic mechanisms remain unclear.

AIM OF THE STUDY

This study aimed to investigate the effects of Danzhi Tiaozhi Decoction (DZTZD) on metabolic-associated fatty liver disease (MAFLD).

MATERIALS AND METHODS

First, we identified the active ingredients of DZTZD and their potential targets in the Traditional Chinese Medicine System Pharmacology database. Using the overlapped genes, we selected the key MAFLD-associated genes, then conducted GO and KEGG pathway enrichment analyses. Furthermore, DZTZD was administered orally to rats, and their serum and liver tissues were examined for absorbed compounds using pharmacochemistry. UPLC-Q-Exactive Orbitrap/MS was used to determine the main compounds. Then, we validated the binding association of the key targets with their active compounds with AutoDock Tools and other software. Finally, the predicted hub targets were experimentally validated.

RESULTS

We found 254 active compounds in DZTZD corresponding to 208 targets. Sixteen key genes were identified, and the enrichment analysis revealed multiple signaling pathways, including the AGE-RAGE pathway in diabetic complications and the lipid and atherosclerosis signaling pathway. Next, 160 absorbed components and metabolites were characterized in vivo, and 53 absorbed components and metabolites were characterized in liver tissue. Thirteen parent compounds were identified, including coptisine, quercetin, luteolin, and aloe-emodin. The molecular docking data demonstrated the strongest binding between the active compounds and the core proteins. Moreover, the animal experiments showed that DZTZD decreased body weight, liver weight, lipid accumulation, and ALT, AST, CRP, FFA, IL-6, PEPCK, G6P, TG, TC, and LDL-c serum levels, and increased serum HDL-c levels compared to high-fat induced rats. Besides, the RT-PCR and Western blot showed that DZTZD inhibited the SREBP1c and FAS and increased hyperlipidemia-induced CPT-1A levels. In the high-fat group, JNK phosphorylation increased, and AKT protein phosphorylation decreased, while DZTZD reversed these effects.

CONCLUSION

Based on the pharmacological network analysis, pharmacochemistry, and experimental validation, DZTZD can potentially improve MAFLD via the JNK/AKT pathway.

Anti-inflammatory and immunomodulating effects of rilpivirine: Relevance for the therapeutics of chronic liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease (CLD) worldwide and inflammation is key to its progression/resolution. As we have previously described that rilpivirine (RPV) is hepatoprotective in murine models of CLD, here we determine the molecular mechanisms involved, focusing on its anti-inflammatory and immunomodulating properties. They were evaluated in vitro (human hepatic cell lines of the major hepatic cell types), in vivo (liver samples from a murine nutritional model of NAFLD) and ex vivo (peripheral blood mononuclear cells -PBMC- from patients with CLD). Transcriptomic analysis of liver samples from NAFLD mice showed RPV down-regulated biological processes associated with the inflammatory response (NF-κB/IκB signaling and mitogen-activated protein kinase -MAPK- activity) and leukocyte chemotaxis and migration. We observed a decrease in Adgre1 and Ccr2 expression and in the number of CCR2 + cells in the periportal areas of RPV-treated NAFLD mice. This RPV-induced effect on the CCL2/CCR2 axis was confirmed in vitro. A similar result was also obtained with CXCL10/IP10, one of the main chemokines in the liver. RPV also diminished activation of MAP kinases p38 and JNK. In addition, RPV inhibited the NLRP3 inflammasome pathway in vitro, decreasing NLRP3 protein expression, caspase-1 activation and IL-1β gene expression. RPV was also proven anti-inflammatory in PBMC from patients with CLD treated ex vivo. In conclusion, beyond its well-described role in antiretroviral therapy, RPV manifests anti-inflammatory and immunoregulatory effects, a finding that could be of great relevance for the search of novel targets or repositioning strategies for CLD.

Coagulation Dysfunctions in Non-Alcoholic Fatty Liver Disease-Oxidative Stress and Inflammation Relevance

Non-alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases. Its incidence is progressively rising and it is possibly becoming a worldwide epidemic. NAFLD encompasses a spectrum of diseases accounting for the chronic accumulation of fat within the hepatocytes due to various causes, excluding excessive alcohol consumption. In this study, we aimed to focus on finding evidence regarding the implications of oxidative stress and inflammatory processes that form the multifaceted pathophysiological tableau in relation to thrombotic events that co-occur in NAFLD and associated chronic liver diseases. Recent evidence on the pathophysiology of NAFLD suggests that a complex pattern of multidirectional components, such as prooxidative, proinflammatory, and prothrombotic components, better explains the multiple factors that promote the mechanisms underlying the fatty acid excess and subsequent processes. As there is extensive evidence on the multi-component nature of NAFLD pathophysiology, further studies could address the complex interactions that underlie the development and progression of the disease. Therefore, this study aimed to describe possible pathophysiological mechanisms connecting the molecular impairments with the various clinical manifestations, focusing especially on the interactions among oxidative stress, inflammation, and coagulation dysfunctions. Thus, we described the possible bidirectional modulation among coagulation homeostasis, oxidative stress, and inflammation that occurs in the various stages of NAFLD.

Endoplasmic Reticulum Stress and Mitochondrial Stress in Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is a widespread and harmful disease closely linked to mitochondrial and endoplasmic reticulum stress (ERS). Globally, severe drug-induced hepatitis, cirrhosis, and liver cancer are the primary causes of liver-related morbidity and mortality. A hallmark of DILI is ERS and changes in mitochondrial morphology and function, which increase the production of reactive oxygen species (ROS) in a vicious cycle of mutually reinforcing stress responses. Several pathways are maladapted to maintain homeostasis during DILI. Here, we discuss the processes of liver injury caused by several types of drugs that induce hepatocyte stress, focusing primarily on DILI by ERS and mitochondrial stress. Importantly, both ERS and mitochondrial stress are mediated by the overproduction of ROS, destruction of Ca2+ homeostasis, and unfolded protein response (UPR). Additionally, we review new pathways and potential pharmacological targets for DILI to highlight new possibilities for DILI treatment and mitigation.

Mechanistic insights into the peroxisome proliferator-activated receptor alpha as a transcriptional suppressor

Non-alcoholic fatty liver disease (NAFLD) is one of the most prevalent hepatic disorders that 20-30% of the world population suffers from. The feature of NAFLD is excess lipid accumulation in the liver, exacerbating multiple metabolic syndromes such as hyperlipidemia, hypercholesterolemia, hypertension, and type 2 diabetes. Approximately 20-30% of NAFLD cases progress to more severe chronic hepatitis, known as non-alcoholic steatohepatitis (NASH), showing deterioration of hepatic functions and liver fibrosis followed by cirrhosis and cancer. Previous studies uncovered that several metabolic regulators had roles in disease progression as key factors. Peroxisome proliferator-activated receptor alpha (PPARα) has been identified as one of the main players in hepatic lipid homeostasis. PPARα is abundantly expressed in hepatocytes, and is a ligand-dependent nuclear receptor belonging to the NR1C nuclear receptor subfamily, orchestrating lipid/glucose metabolism, inflammation, cell proliferation, and carcinogenesis. PPARα agonists are expected to be novel prescription drugs for NASH treatment, and some of them (e.g., Lanifibranor) are currently under clinical trials. These potential novel drugs are developed based on the knowledge of PPARα-activating target genes related to NAFLD and NASH. Intriguingly, PPARα is known to suppress the expression of subsets of target genes under agonist treatment; however, the mechanisms of PPARα-mediated gene suppression and functions of these genes are not well understood. In this review, we summarize and discuss the mechanisms of target gene repression by PPARα and the roles of repressed target genes on hepatic lipid metabolism, fibrosis and carcinogenesis related to NALFD and NASH, and provide future perspectives for PPARα pharmaceutical potentials.