The role of neutrophils in innate immunity-driven nonalcoholic steatohepatitis: lessons learned and future promise

NPR is an independent risk factor for predicting all-cause mortality in patients with metabolic dysfunction-associated steatotic liver disease: evidence from NHANES 2007-2020

BACKGROUND

Neutrophil-associated inflammatory markers (NPR, NHR, SII, and SIRI) have been implicated in various metabolic diseases. However, studies on these markers with metabolic dysfunction-associated steatotic liver disease (MASLD) and advanced liver fibrosis (ALF), as well as their impact on all-cause mortality, remain limited.

METHODS

In this historical cohort study, data from 8051 adults aged 20 years and older were analysed. Weighted logistic regression was used to investigate the associations of neutrophil-associated inflammatory markers with MASLD and ALF. Nonlinear associations were described via restricted cubic spline regression. The diagnostic utility was assessed via receiver operating characteristic (ROC) curves. Furthermore, weighted Kaplan‒Meier survival curves and Cox proportional hazards models were employed to assess all-cause mortality risk. Sensitivity analyses were employed to guarantee the robustness of the findings.

RESULTS

Following adjustment for confounding factors, there was a significant positive association between the ln-transformed NPR, NHR, SII, and SIRI and the risk of MASLD (P < 0.001). Conversely, an inverse association was noted between the ln-transformed SII, SIRI and ALF (P < 0.05). Nonlinear relationships were identified between ln-transformed NPR, NHR, and SIRI and the risk of MASLD (P < 0.001), as well as between ln-transformed NPR, SII, and SIRI and the risk of ALF (P < 0.001). Furthermore, the ln-transformed NHR (cut-off value: - 2.571) exhibited the highest diagnostic accuracy for MASLD (AUC 0.71, 95% CI = 0.70, 0.72), whereas the NPR (cut-off value: - 3.857) demonstrated the highest diagnostic value for ALF (AUC 0.73, 95% CI = 0.70, 0.75). The results of the present study revealed an independent association between the ln-transformed NPR and an elevated risk of all-cause mortality in subjects diagnosed with MASLD. Subgroup analyses highlighted the underrepresentation of neutrophil-associated inflammatory markers in lean individuals with MASLD and ALF (BMI < 25 kg/m2).

CONCLUSIONS

Neutrophil-associated inflammatory markers are independently associated with MASLD and ALF. Specifically, the ln-transformed NHR and SII show promise as diagnostic markers for MASLD and ALF, respectively. Moreover, elevated ln-transformed NPR is independently associated with an increased risk of all-cause mortality in individuals with MASLD, highlighting the potential clinical relevance of these inflammatory markers in the context of steatotic liver disease.

Metabolic Dysfunction-Associated Steatotic Liver Disease Increases the Risk of Severe Infection: A Population-Based Cohort Study

BACKGROUND AND AIMS

Metabolic dysfunction-associated steatotic liver disease (MASLD) is linked to various intrahepatic and extrahepatic diseases, but its association with severe infectious disease remains to be investigated.

METHODS

We analysed data from the Shanghai Suburban Adult Cohort and Biobank, encompassing participants enrolled in 2016 and 2017 with available abdominal ultrasonography data, and followed them up until December 2022 (median follow-up = 5.71 years). We categorised the participants into the MASLD group and those without steatotic liver disease (non-SLD). Multivariable-adjusted Cox regression was used to estimate hazard ratios (HR) for severe infections in patients with MASLD compared to the non-SLD group. Cumulative incidences were calculated while accounting for competing risks (non-infection-related deaths). Mediation analyses were performed to explore the roles of cardiometabolic risk factors in the association between MASLD and severe infections.

RESULTS

Among the 33 072 eligible participants (mean age 56.37 years; 38.20% male), 11 908 (36.01%) were diagnosed with MASLD at baseline. Severe infections occurred in 912 (7.66%) MASLD patients and 1258 (5.94%) non-SLD. The rate of severe infections per 1000 person-years was higher in MASLD patients (13.58) than in comparators (10.48) (fully adjusted HR 1.18, 95% CI 1.07-1.30). The most frequent infections in MASLD were respiratory (7.25/1000 person-years) and urinary tract infections (2.61/1000 person-years). The 5-year cumulative incidence of severe infections was 6.79% (95% CI 6.36-7.26) in MASLD and 5.08% (95% CI 4.79-5.38) in comparators. Cardiometabolic risk factors, including waist circumference, triglycerides and HbA1C, partially mediate the association between MASLD and severe infections.

CONCLUSIONS

Patients with MASLD were at significantly higher risk of incident severe infections compared to the non-SLD group. Future studies are needed to elucidate the mechanisms linking MASLD to severe infections.

Beyond Genes: Epiregulomes as Molecular Commanders in Innate Immunity

The natural fastest way to deal with pathogens or danger signals is the innate immune system. This system prevents too much inflammation and tissue damage and efficiently eliminates pathogens. The epiregulome is the chromatin structure influenced by epigenetic factors and linked to cis-regulatory elements (CREs). The epiregulome helps to end the inflammatory response and also assists innate immune cells to show specific action by making cell-specific gene expression patterns. This inspection unfolds two concepts: (1) how epiregulomes are shaped by switching the expression levels of genes, manoeuvre enzyme activity and earmark of chromatin modifiers on specific genes; during and after the infection, and (2) how the expression of specific genes (aids in prompt management of innate cell growth, or the reaction to aggravation and illness) command by epiregulomes that formed during the above process. In this review, the consequences of intrinsic immuno-metabolic remodelling on epiregulomes and potential difficulties in identifying the master epiregulome that regulates innate immunity and inflammation have been discussed.

Immunological dynamics in MASH: from landscape analysis to therapeutic intervention

Metabolic dysfunction-associated steatohepatitis (MASH), previously known as nonalcoholic steatohepatitis (NASH), is a multifaceted liver disease characterized by inflammation and fibrosis that develops from simple steatosis. Immune and inflammatory pathways have a central role in the pathogenesis of MASH, yet, how to target immune pathways to treat MASH remains perplexed. This review emphasizes the intricate role that immune cells play in the etiology and pathophysiology of MASH and highlights their significance as targets for therapeutic approaches. It discusses both current strategies and novel therapies aimed at modulating the immune response in MASH. It also highlights challenges in liver-specific drug delivery, potential off-target effects, and difficulties in targeting diverse immune cell populations within the liver. This review is a comprehensive resource that integrates current knowledge with future perspectives in the evolving field of MASH, with the goal of driving forward progress in medical therapies designed to treat this complex liver disease.

Transfer from ciliate to zebrafish: Unveiling mechanisms and combined effects of microplastics and heavy metals

The impacts and toxicological mechanisms of microplastics (MPs) or heavy metals on aquatic ecosystems have been the subject of extensive research and initial understanding. However, the combined toxicity of co-pollutants on organisms and cumulative toxic effects along the food chain are still underexplored. In this study, the ciliate protozoan Paramecium caudatum and zebrafish Danio rerio were used to represent the microbial loop and the higher trophic level, respectively, to illustrate the progressive exposure of MPs and cadmium (Cd2+). The findings indicate that MPs (ca. 1 ×105 items/L) containing with Cd2+ (below 0.1 µg/L) could permeate the bodies of zebrafish through trophic levels after primary ingestion by ciliates. This could cause adverse effects on zebrafish, including alterations in bioindicators (total sugar, triglycerides, lactate, and glycogen) associated with metabolism, delayed hepatic development, disruption of intestinal microbiota, DNA damage, inflammatory responses, and abnormal cellular apoptosis. In addition, the potential risks associated with the transfer of composite pollutants through the microbial loop into traditional food chain were examined, offering novel insights on the evaluation of the ecological risks associated with MPs. As observed, understanding the bioaccumulation and toxic effects of combined pollutants in zebrafish holds crucial implications for food safety and human health.

Neutrophil Extracellular Trap Scores Predict 90-Day Mortality in Hepatitis B-Related Acute-on-Chronic Liver Failure

Hepatitis B virus (HBV)-related acute-on-chronic liver failure (ACLF) is associated with pronounced systemic inflammation, and neutrophil extracellular traps (NETs) are key components of this response. The primary objective of this study was to establish an NET-related scoring system for patients with HBV-ACLF. A prospective training cohort of 81 patients from the Beijing Ditan Hospital was included. The concentrations of NET markers (cell-free DNA, myeloperoxidase DNA [MPO-DNA], and citrullinated histone H3) in peripheral blood were quantified. Random survival forest, LASSO regression, and multivariate Cox regression analyses were used to identify prognostic factors associated with 90-day mortality in ACLF patients and develop a nomogram for visualization, which was followed by evaluation in a validation cohort (n = 40). NET-related marker levels were significantly higher in the non-survival group than in the survival group (p < 0.05). The NET score was constructed by combining MPO-DNA, neutrophil-to-lymphocyte ratio, and age data. The score's diagnostic effectiveness, assessed by the area under the curve, yielded values of 0.83 and 0.77 in the training and validation sets, respectively, markedly surpassing those of other established models (p < 0.05). In both groups, the 90-day mortality rates were 88.8% and 75.0%, respectively, for patients categorized as high risk and 18.0% and 12.5%, respectively, for those classified as low risk.

Metabolic Dysfunction-Associated Steatohepatitis Detected by Neutrophilic Crown-Like Structures in Morbidly Obese Patients: A Multicenter and Clinicopathological Study

Metabolic dysfunction-associated steatohepatitis (MASH) is the progressive form of metabolic dysfunction-associated steatotic liver disease (MASLD), and closely associated with a high risk of liver-related morbidity and mortality. Although enhanced neutrophil infiltration of the liver is a histological hallmark of MASH, the morphological pattern of hepatic neutrophils and their relevance to the definition of MASH remain unknown. This clinicopathological study aimed to determine the association of neutrophilic crown-like structures (CLSs) in liver biopsies and evaluate their relevance to the histological diagnosis of MASH. A total of 483 morbidly obese adults who underwent bariatric surgery were recruited. Neutrophilic CLSs in liver biopsies were detected by immunohistochemistry for neutrophil elastase and proteinase 3. All participants were classified into 4 histological subgroups: no MASLD (118, 24.4%), MASLD (76, 15.7%), borderline MASH (185, 38.3%), and definite MASH (104, 21.5%). In the discovery cohort (n = 379), the frequency of neutrophilic CLSs increased in line with the severity of liver disease. The number of neutrophilic CLSs was positively correlated with established histological characteristics of MASH. At a cutoff value of <0.3 per 20× microscopic field, the number of neutrophilic CLSs yielded a robust diagnostic accuracy to discriminate no MASLD and MASLD from borderline MASH and definite MASH; a cutoff at >1.3 per 20× microscopic field exhibited a statistically significant accuracy to distinguish definite MASH from other groups (no MASLD, MASLD, and borderline MASH). The significance of neutrophilic CLSs in identifying borderline MASH and definite MASH was confirmed in an external validation cohort (n = 104). The frequency of neutrophilic CLSs was significantly higher than that of macrophagic CLSs. In conclusion, neutrophilic CLSs in the liver represent a typical histological characteristic of MASH and may serve as a promising indicator to improve the diagnostic accuracy of MASH during histological assessment of liver biopsies.

Circulating Neutrophil Profiles Undergo a Dynamic Shift during Metabolic Dysfunction-Associated Steatohepatitis (MASH) Progression

Neutrophils play a crucial role in host defense against infection. Aberrant neutrophil activation may induce tissue damage via sterile inflammation. Neutrophil accumulation has been identified as a feature of the inflammatory response observed in metabolic dysfunction-associated steatohepatitis (MASH) and has been associated with liver fibrosis and cirrhosis. Here, we performed the transcriptomic analysis of circulating neutrophils from mild and advanced MASH patients to identify the potential mechanism behind neutrophil contribution to MASH progression. Our findings demonstrated that circulating neutrophils from mild and advanced MASH display an increased activated transcriptional program, with the expression of pro-inflammatory factors and an amplified lifespan compared to cells from non-diseased controls. Our results also suggest that MASH progression is associated with a dynamic shift in the profile of circulating neutrophils. In the early stages of MASH, mature neutrophils predominate in the bloodstream. As hepatic inflammation and fibrosis progress, the premature release of immature neutrophils into the circulation occurs. These immature neutrophils exhibit a pro-inflammatory profile that may exacerbate inflammation and promote fibrosis in MASH.

Emerging Insights into the Role of BDNF on Health and Disease in Periphery

Brain-derived neurotrophic factor (BDNF) is a growth factor that promotes the survival and growth of developing neurons. It also enhances circuit formation to synaptic transmission for mature neurons in the brain. However, reduced BDNF expression and single nucleotide polymorphisms (SNP) are reported to be associated with functional deficit and disease development in the brain, suggesting that BDNF is a crucial molecule for brain health. Interestingly, BDNF is also expressed in the hypothalamus in appetite and energy metabolism. Previous reports demonstrated that BDNF knockout mice exhibited overeating and obesity phenotypes remarkably. Therefore, we could raise a hypothesis that the loss of function of BDNF may be associated with metabolic syndrome and peripheral diseases. In this review, we describe our recent finding that BDNF knockout mice develop metabolic dysfunction-associated steatohepatitis and recent reports demonstrating the role of one of the BDNF receptors, TrkB-T1, in some peripheral organ functions and diseases, and would provide an insight into the role of BDNF beyond the brain.

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.

Molecular mechanisms in MASLD/MASH-related HCC

Liver cancer is the third leading cause of cancer-related deaths and ranks as the sixth most prevalent cancer type globally. NAFLD or metabolic dysfunction-associated steatotic liver disease, and its more severe manifestation, NASH or metabolic dysfunction-associated steatohepatitis (MASH), pose a significant global health concern, affecting approximately 20%-25% of the population. The increased prevalence of metabolic dysfunction-associated steatotic liver disease and MASH is parallel to the increasing rates of obesity-associated metabolic diseases, including type 2 diabetes, insulin resistance, and fatty liver diseases. MASH can progress to MASH-related HCC (MASH-HCC) in about 2% of cases each year, influenced by various factors such as genetic mutations, carcinogen exposure, immune microenvironment, and microbiome. MASH-HCC exhibits distinct molecular and immune characteristics compared to other causes of HCC and affects both men and women equally. The management of early to intermediate-stage MASH-HCC typically involves surgery and locoregional therapies, while advanced HCC is treated with systemic therapies, including anti-angiogenic therapies and immune checkpoint inhibitors. In this comprehensive review, we consolidate previous research findings while also providing the most current insights into the intricate molecular processes underlying MASH-HCC development. We delve into MASH-HCC-associated genetic variations and somatic mutations, disease progression and research models, multiomics analysis, immunological and microenvironmental impacts, and discuss targeted/combined therapies to overcome immune evasion and the biomarkers to recognize treatment responders. By furthering our comprehension of the molecular mechanisms underlying MASH-HCC, our goal is to catalyze the advancement of more potent treatment strategies, ultimately leading to enhanced patient outcomes.

Human APOE4 Protects High-Fat and High-Sucrose Diet Fed Targeted Replacement Mice against Fatty Liver Disease Compared to APOE3

Recent genome- and exome-wide association studies suggest that the human APOE ε4 allele protects against non-alcoholic fatty liver disease (NAFLD), while ε3 promotes hepatic steatosis and steatohepatitis. The present study aimed at examining the APOE genotype-dependent development of fatty liver disease and its underlying mechanisms in a targeted replacement mouse model. Male mice expressing the human APOE3 or APOE4 protein isoforms on a C57BL/6J background and unmodified C57BL/6J mice were chronically fed a high-fat and high-sucrose diet to induce obesity. After 7 months, body weight gain was more pronounced in human APOE than endogenous APOE expressing mice with elevated plasma biomarkers suggesting aggravated metabolic dysfunction. APOE3 mice exhibited the highest liver weights and, compared to APOE4, massive hepatic steatosis. An untargeted quantitative proteome analysis of the liver identified a high number of proteins differentially abundant in APOE3 versus APOE4 mice. The majority of the higher abundant proteins in APOE3 mice could be grouped to inflammation and damage-associated response, and lipid storage, amongst others. Results of the targeted qRT-PCR and Western blot analyses contribute to the overall finding that APOE3 as opposed to APOE4 promotes hepatic steatosis, inflammatory- and damage-associated response signaling and fibrosis in the liver of obese mice. Our experimental data substantiate the observation of an increased NAFLD-risk associated with the human APOEε3 allele, while APOEε4 appears protective. The underlying mechanisms of the protection possibly involve a higher capacity of nonectopic lipid deposition in subcutaneous adipose tissue and lower hepatic pathogen recognition in the APOE4 mice.

Protectin D1 inhibits TLR4 signaling pathway to alleviate non-alcoholic steatohepatitis via upregulating IRAK-M

Non-alcoholic steatohepatitis (NASH) is a prevalent metabolic disease, characterized by the hepatic steatosis, inflammation, and fibrosis, which is lack of effective treatment currently. Protectin D1 (PTD1), a lipid mediator from omega-3 fatty acid docosahexaenoic acid (DHA), has displayed wide pharmacological actions including anti-inflammation in a variety of diseases, but the role of PTD1 on NASH remains unclear. In this study, using the methionine and choline deficient (MCD) fed NASH model, we explored the effect and underlying mechanism of PTD1 on NASH in mice. Our results showed PTD1 improved MCD-induced steatosis, hepatocellular injury, inflammation and fibrosis. Furthermore, PTD1 inhibited MCD-induced activation of TLR4 downstream molecules (TAK1, p38 and p65) without affecting the levels of TLR4 and phosphorylated IRAK-1. Notably, the levels of IRAK-M protein and the binding between IRAK-M and TRAF6 in the liver were also increased by PTD1 in NASH mice. Moreover, IRAK-M knockout remarkedly reverted the beneficial effects of PTD1 on the NASH in mice. Thus, these results demonstrated that PTD1 could protect mice from NASH by inhibiting the activation of TLR4 downstream signaling pathway, which might be related to the upregulation of IRAK-M, indicating that PTD1 may provide a new treatment for NASH.

The Multicomponent Medicinal Product Hepar Compositum Reduces Hepatic Inflammation and Fibrosis in a Streptozotocin- and High-Fat Diet-Induced Model of Metabolic Dysfunction-Associated Steatotic Liver Disease/Metabolic Dysfunction-Associated Steatohepatitis

Metabolic dysfunction-associated steatotic liver disease (MASLD)-formerly known as non-alcoholic fatty liver disease (NAFLD)-is the most common chronic liver disease worldwide. Since there is currently no approved pharmacotherapy for MASLD, there is an urgent unmet need for efficacious therapeutics for this disease. Hepar compositum (HC-24) is a multicomponent medicinal product that consists of 24 natural ingredients. It has been shown to have anti-inflammatory properties in an obesity-associated MASLD mouse model, but its potential to reduce MASLD-associated fibrosis had not been explored before this study. Here, we investigated the hepatic anti-inflammatory and anti-fibrotic potential of HC-24 in a streptozotocin (STZ)- and high-fat diet (HFD)-induced model of MASLD. Mice received a single injection of low-dose STZ at 2 days of age, followed by HFD feeding from 4 to 9 weeks of age. Mice were treated every second day with HC-24 or daily with the positive control telmisartan from 6 to 9 weeks of age. A non-diseased control group was included as a healthy reference. An explorative small-scale pilot study demonstrated that HC-24 improved liver histology, resulting in a lower NAFLD activity score and reduced liver fibrosis. A subsequent full study confirmed these effects and showed that HC-24 reduced hepatic inflammation, specifically reducing T helper cell and neutrophil influx, and decreased hepatic fibrosis (with qualitatively reduced collagen type I and type III immunopositivity) in the absence of an effect on body and liver weight, blood glucose or liver steatosis. These results show that HC-24 has hepatoprotective, anti-inflammatory, and anti-fibrotic properties in an STZ- and HFD-induced model of MASLD/MASH, suggesting that this multicomponent medicine has therapeutic potential for MASLD patients.

Brain-derived neurotrophic factor knock-out mice develop non-alcoholic steatohepatitis

While brain-derived neurotrophic factor (BDNF), which is a growth factor associated with cognitive improvement and the alleviation of depression symptoms, is known to regulate food intake and body weight, the role of BDNF in peripheral disease is not fully understood. Here, we show that reduced BDNF expression is associated with weight gain and the chronic liver disease non-alcoholic steatohepatitis (NASH). At 10 months of age, BDNF-heterozygous (BDNF+/- ) mice developed symptoms of NASH: centrilobular/perivenular steatosis, lobular inflammation with infiltration of neutrophils, ballooning hepatocytes, and fibrosis of the liver. Obesity and higher serum levels of glucose and insulin - major pathologic features in human NASH - were dramatic. Dying adipocytes were surrounded by macrophages in visceral fat, suggesting that chronic inflammation occurs in peripheral organs. RNA sequencing (RNA-seq) studies of the liver revealed that the most significantly enriched Gene Ontology term involved fatty acid metabolic processes and the modulation of neutrophil aggregation, pathologies that well characterise NASH. Gene expression analysis by RNA-seq also support the notion that BDNF+/- mice are under oxidative stress, as indicated by alterations in the expression of the cytochrome P450 family and a reduction in glutathione S-transferase p, an antioxidant enzyme. Histopathologic phenotypes of NASH were also observed in a knock-in mouse (BDNF+/pro ), in which the precursor BDNF is inefficiently converted into the mature form of BDNF. Lastly, as BDNF reduction causes overeating and subsequent obesity, a food restriction study was conducted in BDNF+/pro mice. Pair-fed BDNF+/pro mice developed hepatocellular damage and showed infiltration of inflammatory cells, including neutrophils in the liver, despite having body weights and blood parameters that were comparable to those of controls. This is the first report demonstrating that reduced BDNF expression plays a role in the pathogenic mechanism of NASH, which is a hepatic manifestation of metabolic syndrome. © 2023 The Pathological Society of Great Britain and Ireland.

From NAFLD to HCC: Advances in noninvasive diagnosis

Non-alcoholic fatty liver disease (NAFLD) has gradually become one of the major liver health problems in the world. The dynamic course of the disease goes through steatosis, inflammation, fibrosis, and carcinoma. Before progressing to carcinoma, timely and effective intervention will make the condition better, which highlights the importance of early diagnosis. With the further study of the biological mechanism in the pathogenesis and progression of NAFLD, some potential biomarkers have been discovered, and the possibility of their clinical application is gradually being discussed. At the same time, the progress of imaging technology and the emergence of new materials and methods also provide more possibilities for the diagnosis of NAFLD. This article reviews the diagnostic markers and advanced diagnostic methods of NAFLD in recent years.

Neutrophil subsets in noncancer liver diseases: Cellular crosstalk and therapeutic targets

Neutrophils are the most abundant circulating granulocytes, linking innate and adaptive immunity. Neutrophils can regulate inflammatory and immune responses through degranulation, reactive oxygen species generation, the production of cytokines and chemokines, and NETosis. Emerging evidence has indicated that neutrophils contribute to the pathogenesis of various noncancer liver diseases, including nonalcoholic fatty liver disease, alcohol-associated liver disease, hepatic ischemia-reperfusion injury, and liver fibrosis. Cellular interactions among neutrophils, other immune cells, and nonimmune cells constitute a complex network that regulates the immune microenvironment of the liver. This review summarizes novel neutrophil subtypes, including CD177+ neutrophils and low-density neutrophils. Moreover, we provide an overview of the cellular cros stalk of neutrophils in noncancer liver diseases, aiming to shed new light on mechanistic studies of novel neutrophil subtypes. In addition, we discuss the potential of neutrophils as therapeutic targets in noncancer liver diseases, including inhibitors targeting NETosis, granule proteins, and chemokines.

Coral calcium carried hydrogen ameliorates the severity of non-alcoholic steatohepatitis induced by a choline deficient high carbohydrate fat-free diet in elderly rats

Hydrogen has been reported to act as an antioxidant, anti-apoptosis and anti-inflammatory agent. Coral calcium carried hydrogen (G2-SUISO) is a safer and more convenient form of hydrogen agent than others. The mechanism underlying the hepatoprotective effects of G2-SUISO using an elderly non-alcoholic steatohepatitis (NASH) rat model was investigated. Two days after fasting, six-month-old elderly male F344/NSlc rats were given a choline deficient high carbohydrate fat-free (CDHCFF) diet from day 0 to day 3 as CDHCFF control group, and then switched to a normal diet from days 4 to 7 with or without 300 mg/kg G2-SUISO. Rats in each group were finally being sacrificed on day 3 or day 7. In the CDHCFF diet group, G2-SUISO decreased the liver weight-to-body weight ratio, the serum AST, ALT, total cholesterol levels, inflammatory infiltration, pro-inflammatory cytokine expression and lipid droplets with inhibiting lipogenic pathways by reducing sterol regulatory element-binding protein-1c, acetyl-CoA carboxylase and fatty acid synthase gene expression compared with the CDHCFF diet alone. G2-SUISO had beneficial effects of anti-apoptosis as well the down-regulation of pro-apoptotic molecules including NF-κB, caspase-3, caspase-9 and Bax. These findings suggest that G2-SUISO treatment exerts a significant hepatoprotective effect against steatosis, inflammation and apoptosis in elderly NASH rats.

The microglial innate immune receptors TREM-1 and TREM-2 in the anterior cingulate cortex (ACC) drive visceral hypersensitivity and depressive-like behaviors following DSS-induced colitis

Inflammatory bowel disease (IBD) is a chronic condition with a high recurrence rate. To date, the clinical treatment of IBD mainly focuses on inflammation and gastrointestinal symptoms while ignoring the accompanying visceral pain, anxiety, depression, and other emotional symptoms. Evidence is accumulating that bi-directional communication between the gut and the brain is indispensable in the pathophysiology of IBD and its comorbidities. Increasing efforts have been focused on elucidating the central immune mechanisms in visceral hypersensitivity and depression following colitis. The triggering receptors expressed on myeloid cells-1/2 (TREM-1/2) are newly identified receptors that can be expressed on microglia. In particular, TREM-1 acts as an immune and inflammatory response amplifier, while TREM-2 may function as a molecule with a putative antagonist role to TREM-1. In the present study, using the dextran sulfate sodium (DSS)-induced colitis model, we found that peripheral inflammation induced microglial and glutamatergic neuronal activation in the anterior cingulate cortex (ACC). Microglial ablation mitigated visceral hypersensitivity in the inflammation phase rather than in the remission phase, subsequently preventing the emergence of depressive-like behaviors in the remission phase. Moreover, a further mechanistic study revealed that overexpression of TREM-1 and TREM-2 remarkably aggravated DSS-induced neuropathology. The improved outcome was achieved by modifying the balance of TREM-1 and TREM-2 via genetic and pharmacological means. Specifically, a deficiency of TREM-1 attenuated visceral hyperpathia in the inflammatory phase, and a TREM-2 deficiency improved depression-like symptoms in the remission phase. Taken together, our findings provide insights into mechanism-based therapy for inflammatory disorders and establish that microglial innate immune receptors TREM-1 and TREM-2 may represent a therapeutic target for the treatment of pain and psychological comorbidities associated with chronic inflammatory diseases by modulating neuroinflammatory responses.

Synergistic Effect of Diet and Physical Activity on a NAFLD Cohort: Metabolomics Profile and Clinical Variable Evaluation

Together with its comorbidities, nonalcoholic fatty liver disease (NAFLD) is likely to rise further with the obesity epidemic. However, the literature's evidence shows how its progression can be reduced by the administration of calorie-restrictive dietary interventions and physical activity regimens. The liver function and the gut microbiota have been demonstrated to be closely related. With the aim of ascertaining the impact of a treatment based on the combination of diet and physical activity (versus physical activity alone), we recruited 46 NAFLD patients who were divided into two groups. As a result, we traced the connection between volatile organic compounds (VOCs) from fecal metabolomics and a set of statistically filtered clinical variables. Additionally, we identified the relative abundances of gut microbiota taxa obtained from 16S rRNA gene sequencing. Statistically significant correlations emerged between VOCs and clinical parameters, as well as between VOCs and gut microbiota taxa. In comparison with a physical activity regimen alone, we disclose how ethyl valerate and pentanoic acid butyl ester, methyl valerate, and 5-hepten-2-one, 6-methyl changed because of the positive synergistic effect exerted by the combination of the Mediterranean diet and physical activity regimens. Moreover, 5-hepten-2-one, 6-methyl positively correlated with Sanguinobacteroides, as well as the two genera Oscillospiraceae-UCG002 and Ruminococcaceae UCG010 genera.

Role of immune responses for development of NAFLD-associated liver cancer and prospects for therapeutic modulation

The liver is the central metabolic organ of the body regulating energy and lipid metabolism and at the same time has potent immunological functions. Overwhelming the metabolic capacity of the liver by obesity and sedentary lifestyle leads to hepatic lipid accumulation, chronic necro-inflammation, enhanced mitochondrial/ER-stress and development of non-alcoholic fatty liver disease (NAFLD), with its pathologic form nonalcoholic steatohepatitis (NASH). Based on knowledge on pathophysiological mechanisms, specifically targeting metabolic diseases to prevent or slow down progression of NAFLD to liver cancer will become possible. Genetic/environmental factors contribute to development of NASH and liver cancer progression. The complex pathophysiology of NAFLD-NASH is reflected by environmental factors, particularly the gut microbiome and its metabolic products. NAFLD-associated HCC occurs in most of the cases in the context of a chronically inflamed liver and cirrhosis. Recognition of environmental alarmins or metabolites derived from the gut microbiota and the metabolically injured liver create a strong inflammatory milieu supported by innate and adaptive immunity. Several recent studies indicate that the chronic hepatic microenvironment of steatosis induces auto-aggressive CD8+CXCR6+PD1+ T cells secreting TNF and upregulating FasL to eliminate parenchymal and non-parenchymal cells in an antigen independent manner. This promotes chronic liver damage and a pro-tumorigenic environment. CD8+CXCR6+PD1+ T cells possess an exhausted, hyperactivated, resident phenotype and trigger NASH to HCC transition, and might be responsible for a less efficient treatment response to immune-check-point inhibitors - in particular atezolizumab/bevacizumab. Here, we provide an overview of NASH-related inflammation/pathogenesis focusing on new discoveries on the role of T cells in NASH-immunopathology and therapy response. This review discusses preventive measures to halt disease progression to liver cancer and therapeutic strategies to manage NASH-HCC patients.

Translational characterization of the temporal dynamics of metabolic dysfunctions in liver, adipose tissue and the gut during diet-induced NASH development in Ldlr-/-.Leiden mice

Background

NAFLD progression, from steatosis to inflammation and fibrosis, results from an interplay of intra- and extrahepatic mechanisms. Disease drivers likely include signals from white adipose tissue (WAT) and gut. However, the temporal dynamics of disease development remain poorly understood.

Methods

High-fat-diet (HFD)-fed Ldlr-/-.Leiden mice were compared to chow-fed controls. At t = 0, 8, 16, 28 and 38w mice were euthanized, and liver, WAT depots and gut were analyzed biochemically, histologically and by lipidomics and transcriptomics together with circulating factors to investigate the sequence of pathogenic events and organ cross-talk during NAFLD development.

Results

HFD-induced obesity was associated with an increase in visceral fat, plasma lipids and hyperinsulinemia at t = 8w, along with increased liver steatosis and circulating liver damage biomarkers. In parallel, upstream regulator analysis predicted that lipid catabolism regulators were deactivated and lipid synthesis regulators were activated. Subsequently, hepatocyte hypertrophy, oxidative stress and hepatic inflammation developed. Hepatic collagen accumulated from t = 16 w and became pronounced at t = 28-38 w. Epididymal WAT was maximally hypertrophic from t = 8 w, which coincided with inflammation development. Mesenteric and subcutaneous WAT hypertrophy developed slower and did not appear to reach a maximum, with minimal inflammation. In gut, HFD significantly increased permeability, induced a shift in microbiota composition from t = 8 w and changed circulating gut-derived metabolites.

Conclusion

HFD-fed Ldlr-/-.Leiden mice develop obesity, dyslipidemia and insulin resistance, essentially as observed in obese NAFLD patients, underlining their translational value. We demonstrate that marked epididymal-WAT inflammation, and gut permeability and dysbiosis precede the development of NAFLD stressing the importance of a multiple-organ approach in the prevention and treatment of NAFLD.

Myeloperoxidase-Sensitive T1 and T2 Switchable MR Imaging for Diagnosis of Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is the critical stage in the development of nonalcoholic fatty liver disease (NAFLD) from simple and reversible steatosis to irreversible cirrhosis and even hepatocellular carcinoma (HCC). Thus, the diagnosis of NASH is important for preventing the progress of NAFLD into a fatal condition. The oxidative enzyme myeloperoxidase (MPO), which is mostly produced by polymorphonuclear neutrophil granulocytes (NEU), has been identified as a key player in lipid peroxidation in inflamed tissues. Considering that the expression of MPO was much higher in NASH than in the nonalcoholic fatty liver (NAFL) with steatosis, we designed a nanoparticle platform based on ultrasmall iron oxide (USIO) nanoparticles to realize MPO-sensitive NASH diagnosis. After modification of USIO nanoparticles with amphiphilic poly(ethylene glycol) (PEG) and conjugation with 5-hydroxytryptamine (5HT), a physiological substrate for MPO, the final nanocomposite (USIO-DA-PEG-5HT) revealed MPO-mediated aggregation at the inflammatory site of NASH. Meanwhile, the intrinsic T₁-weighted magnetic resonance (MR) signal of dispersed USIO-DA-PEG-5HT nanoparticles diminishes, while the T₂-weighted MR signal is amplified owing to the aggregation effect. These USIO-DA-PEG-5HT nanoprobes offer great potential for improving NASH MR imaging diagnostic accuracy and sensitivity compared to existing molecular MR contrast agents with a single imaging modality.

Overview of Cellular and Soluble Mediators in Systemic Inflammation Associated with Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is currently the most prevalent chronic liver disease in Western countries, affecting approximately 25% of the adult population. This condition encompasses a spectrum of liver diseases characterized by abnormal accumulation of fat in liver tissue (non-alcoholic fatty liver, NAFL) that can progress to non-alcoholic steatohepatitis (NASH), characterized by the presence of liver inflammation and damage. The latter form often coexists with liver fibrosis which, in turn, may progress to a state of cirrhosis and, potentially, hepatocarcinoma, both irreversible processes that often lead to the patient's death and/or the need for liver transplantation. Along with the high associated economic burden, the high mortality rate among NAFLD patients raises interest, not only in the search for novel therapeutic approaches, but also in early diagnosis and prevention to reduce the incidence of NAFLD-related complications. In this line, an exhaustive characterization of the immune status of patients with NAFLD is mandatory. Herein, we attempted to gather and compare the current and relevant scientific evidence on this matter, mainly on human reports. We addressed the current knowledge related to circulating cellular and soluble mediators, particularly platelets, different leukocyte subsets and relevant inflammatory soluble mediators.

Neutrophil extracellular traps and complications of liver transplantation

Many end-stage liver disease etiologies are attributed to robust inflammatory cell recruitment. Neutrophils play an important role in inflammatory infiltration and neutrophil phagocytosis, oxidative burst, and degranulation. It has also been suggested that neutrophils may release neutrophil extracellular traps (NETs) to kill pathogens. It has been proven that neutrophil infiltration within the liver contributes to an inflammatory microenvironment and immune cell activation. Growing evidence implies that NETs are involved in the progression of numerous complications of liver transplantation, including ischemia-reperfusion injury, acute rejection, thrombosis, and hepatocellular carcinoma recurrence. NETs are discussed in this comprehensive review, focusing on their effects on liver transplantation complications. Furthermore, we discuss NETs as potential targets for liver transplantation therapy.

Asparagus cochinchinensis alleviates disturbances of lipid metabolism and gut microbiota in high-fat diet-induced obesity mice

Asparagus cochinchinensis is a valuable traditional Chinese medicine that has anti-inflammatory ability and effectively regulates the dysbiosis within the body. Obesity is usually characterized by chronic low-grade inflammation with aberrant gut microbiota. However, the role of Asparagus cochinchinensis against obesity remains unknown. Therefore, a high-fat diet (HFD)-induced obese mouse model with or without aqueous extract from Asparagus cochinchinensis root (ACE) treatment was established herein to determine whether ACE alleviated obesity and its involved mechanisms. Our results showed that ACE administration significantly decreased the weight gain and relieved dyslipidemia induced by HFD Treatment of ACE also improved glucose tolerance and insulin resistance in obese animal model, and remarkably decreased inflammation and lipogenesis in the liver and adipose. Moreover, administration of ACE significantly reshaped the gut microbiota of obese mice. These findings together suggest that ACE has beneficial effect against HFD-induced obesity and will provide valuable insights for the therapeutic potential of ACE against obesity and may aid in strategy-making for weight loss.

Therapeutic Intervention with Anti-Complement Component 5 Antibody Does Not Reduce NASH but Does Attenuate Atherosclerosis and MIF Concentrations in Ldlr-/-.Leiden Mice

Background: Chronic inflammation is an important driver in the progression of non-alcoholic steatohepatitis (NASH) and atherosclerosis. The complement system, one of the first lines of defense in innate immunity, has been implicated in both diseases. However, the potential therapeutic value of complement inhibition in the ongoing disease remains unclear. Methods: After 20 weeks of high-fat diet (HFD) feeding, obese Ldlr-/-.Leiden mice were treated twice a week with an established anti-C5 antibody (BB5.1) or vehicle control. A separate group of mice was kept on a chow diet as a healthy reference. After 12 weeks of treatment, NASH was analyzed histopathologically, and genome-wide hepatic gene expression was analyzed by next-generation sequencing and pathway analysis. Atherosclerotic lesion area and severity were quantified histopathologically in the aortic roots. Results: Anti-C5 treatment considerably reduced complement system activity in plasma and MAC deposition in the liver but did not affect NASH. Anti-C5 did, however, reduce the development of atherosclerosis, limiting the total lesion size and severity independently of an effect on plasma cholesterol but with reductions in oxidized LDL (oxLDL) and macrophage migration inhibitory factor (MIF). Conclusion: We show, for the first time, that treatment with an anti-C5 antibody in advanced stages of NASH is not sufficient to reduce the disease, while therapeutic intervention against established atherosclerosis is beneficial to limit further progression.

Tanshinone IIA Ameliorates Nonalcoholic Steatohepatitis in Mice by Modulating Neutrophil Extracellular Traps and Hepatocyte Apoptosis

Salvia miltiorrhiza Bunge, a traditional Chinese medicine, is widely used in the treatment of a variety of diseases and syndromes. Tanshinone IIA (TIIA), a phenanthrenequinone-class derivative extracted from S. miltiorrhiza, is one of its main active components and has anti-inflammatory effects on various tissues and cells. This study aimed to investigate the beneficial effects of TIIA on nonalcoholic steatohepatitis (NASH) induced in mice using a methionine choline deficiency (MCD) diet and the underlying mechanism of these. Our results reveal that TIIA remarkably ameliorated hepatic steatosis and inflammation and decreased the serum levels of liver dysfunction markers while increasing the levels of serum total cholesterol and triglycerides in MCD-fed mice. TIIA significantly reduced mRNA levels of the inflammatory factors TNF-α, IL-6, and TGF-β. Similarly, TIIA inhibited caspase-3 and Bax-mediated apoptosis in MCD-fed mice. Together, our data indicate that TIIA inhibits the formation of MPO and CitH3 in neutrophil extracellular traps and inhibits apoptosis mediated by caspase-3 and Bax in hepatocytes, thereby mitigating inflammatory progression in an MCD diet-induced NASH mouse model.

Mesenchymal stem cells-based therapy in liver diseases

Multiple immune cells and their products in the liver together form a complex and unique immune microenvironment, and preclinical models have demonstrated the importance of imbalances in the hepatic immune microenvironment in liver inflammatory diseases and immunocompromised liver diseases. Various immunotherapies have been attempted to modulate the hepatic immune microenvironment for the purpose of treating liver diseases. Mesenchymal stem cells (MSCs) have a comprehensive and plastic immunomodulatory capacity. On the one hand, they have been tried for the treatment of inflammatory liver diseases because of their excellent immunosuppressive capacity; On the other hand, MSCs have immune-enhancing properties in immunocompromised settings and can be modified into cellular carriers for targeted transport of immune enhancers by genetic modification, physical and chemical loading, and thus they are also used in the treatment of immunocompromised liver diseases such as chronic viral infections and hepatocellular carcinoma. In this review, we discuss the immunological basis and recent strategies of MSCs for the treatment of the aforementioned liver diseases. Specifically, we update the immune microenvironment of the liver and summarize the distinct mechanisms of immune microenvironment imbalance in inflammatory diseases and immunocompromised liver diseases, and how MSCs can fully exploit their immunotherapeutic role in liver diseases with both immune imbalance patterns.

Endoplasmic reticulum stress in innate immune cells - a significant contribution to non-alcoholic fatty liver disease

Liver disease and its complications affect millions of people worldwide. NAFLD (non-alcoholic fatty liver disease) is the liver disease associated with metabolic dysfunction and consists of four stages: steatosis with or without mild inflammation (NAFLD), non-alcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. With increased necroinflammation and progression of liver fibrosis, NAFLD may progress to cirrhosis or even hepatocellular carcinoma. Although the underlying mechanisms have not been clearly elucidated in detail, what is clear is that complex immune responses are involved in the pathogenesis of NASH, activation of the innate immune system is critically involved in triggering and amplifying hepatic inflammation and fibrosis in NAFLD/NASH. Additionally, disruption of endoplasmic reticulum (ER) homeostasis in cells, also known as ER stress, triggers the unfolded protein response (UPR) which has been shown to be involved to inflammation and apoptosis. To further develop the prevention and treatment of NAFLD/NASH, it is imperative to clarify the relationship between NAFLD/NASH and innate immune cells and ER stress. As such, this review focuses on innate immune cells and their ER stress in the occurrence of NAFLD and the progression of cirrhosis.

Neutrophil Extracellular Traps Mediate Acute Liver Failure in Regulation of miR-223/Neutrophil Elastase Signaling in Mice

BACKGROUND & AIMS

Marked enhancement of neutrophil infiltration in the liver is a hallmark of acute liver failure (ALF), a severe life-threatening disease with varying etiologies. However, the mechanisms and pathophysiological role corresponding to hepatic neutrophil infiltration during ALF development remain poorly characterized.

METHODS

Experimental ALF was induced in 10-week-old male microRNA-223 (miR-223) knockout (KO) mice, neutrophil elastase (NE) KO mice, and wild-type controls by intraperitoneal injection of galactosamine hydrochloride and lipopolysaccharide. Age-matched mice were injected with phosphate-buffered saline and served as vehicle controls.

RESULTS

Mouse liver with ALF showed evident formation of neutrophil extracellular traps (NETs), which were enhanced markedly in miR-223 KO mice. The blockade of NETs by pharmacologic inhibitor GSK484 significantly attenuated neutrophil infiltration and massive necrosis in mouse liver with ALF. ALF-related hepatocellular damage and mortality in miR-223 KO mice were aggravated significantly and accompanied by potentiated neutrophil infiltration in the liver when compared with wild-type controls. Transcriptomic analyses showed that miR-223 deficiency in bone marrow predominantly caused the enrichment of pathways involved in neutrophil degranulation. Likewise, ALF-induced hepatic NE enrichment was potentiated in miR-223 KO mice. Genetic ablation of NE blunted the formation of NETs in parallel with significant attenuation of ALF in mice. Pharmaceutically, pretreatment with the NE inhibitor sivelestat protected mice against ALF.

CONCLUSIONS

The present study showed the miR-223/NE axis as a key modulator of NETs, thereby exacerbating oxidative stress and neutrophilic inflammation to potentiate hepatocellular damage and liver necrosis in ALF development, and offering potential targets against ALF.

Peripheral immune cells in NAFLD patients: A spyhole to disease progression

Nonalcoholic fatty liver disease (NAFLD) is a worldwide leading cause of chronic liver disease, but we still lack ideal non-invasive tools for diagnosis and evaluation of nonalcoholic steatohepatitis (NASH) and related liver fibrosis in NAFLD population. Systemic immune dysregulations such as metabolic inflammation are believed to play central role in the development of NAFLD, signifying the hope of utilizing quantitative and phenotypic changes in peripheral immune cells among NAFLD patients as a diagnostic tool of NASH and fibrosis. In this review, we summarize the known changes in peripheral immune cells from NAFLD/NASH patients and their potential relationship with NAFLD and NASH progression. Potential challenges and possible solutions for further clinical translation are also discussed.

Dual role of neutrophils in modulating liver injury and fibrosis during development and resolution of diet-induced murine steatohepatitis

Inflammatory changes in the liver represent a key feature of non-alcoholic steatohepatitis (NASH), the progressive form of non-alcoholic fatty liver disease (NAFLD). Innate immune activation including hepatic neutrophilic infiltration acts as an important inflammatory trigger as well as a potential mediator of inflammation resolution. In this study, we dissected the effects of neutrophil depletion via anti-lymphocyte antigen 6 complex locus G6D (Ly6G) antibodies administration during ongoing high fat-fructose-cholesterol (FFC) diet-induced murine NASH and during inflammation resolution by switching into a low-fat control diet. During NASH progression, protective effects were shown as HSC activation, cell infiltration and activation of pro-inflammatory macrophages were ameliorated. Furthermore, these changes were contrasted with the effects observed when neutrophil depletion was performed during the resolution phase. Impaired resolving mechanisms, such as a failure to balance the pro and anti-inflammatory cytokines ratio, deficient macrophage phenotypic switch into a pro-restorative profile, and defective repair and remodeling processes were observed when neutrophils were depleted in this scenario. This study described phase-dependent contrasting roles of neutrophils as triggers and pro-resolutive mediators of liver injury and fibrosis associated with diet-induced NASH in mice. These findings have important translational implications at the time of designing NASH therapeutic strategies.

Analysis of Common Pathways and Markers From Non-Alcoholic Fatty Liver Disease to Immune-Mediated Diseases

Metabolic associated fatty liver disease (MAFLD) is the most prevalent form of liver disease worldwide, accounting for a high liver-related mortality and morbidity with extensive multi-organ involvement. This entity has displaced viral hepatitis as the main cause of severe forms of hepatic diseases, although the onset and transition of MAFLD stages still remains unclear. Nevertheless, innate and adaptive immune responses seem to play an essential role in the establishment and further progression of this disease. The immune system is responsible of safeguard and preserves organs and systems function, and might be altered under different stimuli. Thus, the liver suffers from metabolic and immune changes leading to different injuries and loss of function. It has been stablished that cell-cell crosstalk is a key process in the hepatic homeostasis maintenance. There is mounting evidence suggesting that MAFLD pathogenesis is determined by a complex interaction of environmental, genetic and host factors that leads to a full plethora of outcomes. Therefore, herein we will revisit and discuss the interplay between immune mechanisms and MAFLD, highlighting the potential role of immunological markers in an attempt to clarify its relationship.

Tim-1 Deficiency Aggravates High-Fat Diet-Induced Steatohepatitis in Mice

Non-alcoholic fatty liver disease (NAFLD)/non-alcoholic steatohepatitis (NASH) is commonly associated with obesity and characterized by excessive lipid accumulation and liver inflammation. The T cell immunoglobulin and mucin domain 1 (Tim-1), also known as hepatitis A virus cellular receptor 1 (Havcr-1) and kidney injury molecule 1 (Kim-1), has been shown to affect innate immunity-driven proinflammatory cascade in liver ischemia-reperfusion injury. However, its contribution to obesity-related NAFLD/NASH remains unknown. Thus, this study was designed to evaluate the role of Tim-1 in obesity-related liver inflammation and injury in wild-type (WT) and Tim-1-deficient (Tim-1^-/-) C57BL/6J mice fed a high-fat diet (HFD) for 5-6 months. HFD feeding induced steatosis and upregulated Tim-1 gene expression in the liver of WT mice. Surprisingly, Tim-1^-/- mice on HFD diet exhibited an exacerbation of hepatic steatosis, accompanied with an elevation of protein levels of fatty acid translocase CD36 and sterol regulatory element binding protein 1 (SREBP1). Tim-1 deficiency also enhanced HFD-induced liver inflammation and injury, as evidenced by augmented increase in hepatic expression of pro-inflammatory factor lipocalin 2 and elevated serum alanine transaminase (ALT). In addition, gene expression of type I, III and IV collagens and liver fibrosis were greatly enhanced in HFD Tim-1^-/- mice compared with HFD WT mice. HFD-induced hepatic expression of YM-1, a specific mouse M2 macrophage marker, was further upregulated by deletion of Tim-1. Together, these results show that Tim-1 deficiency aggravates the effects of HFD diet on lipid accumulation and liver fibrosis, most likely through enhanced infiltration and activation of inflammatory cells.

Identification of a 17-gene-signature in Non-alcoholic Steatohepatitis and Its Relationship with Immune Cell Infiltration

Background: Non-alcoholic steatohepatitis (NASH) is a risk factor for hepatocellular carcinoma, but the understanding of the regulatory mechanisms driving NASH is not comprehensive. Objectives: We aimed to identify the potential markers of NASH and explore their relationship with immune cell populations. Methods: Five gene expression datasets for NASH were downloaded from the Gene Expression Omnibus and European Bioinformatics Institute Array Express databases. Differentially expressed genes (DEGs) between NASH and controls were screened. Gene Ontology-Biological Process (GO-BP) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed for functional enrichment analysis of DEGs. Among the candidate genes selected from the protein-protein interaction (PPI) network and module analysis, DEG signatures were further identified using least absolute shrinkage and selection operator regression analysis. The Spearman correlation coefficient was calculated to assess the correlation between DEG signatures and immune cell abundance based on the CIBERSORT algorithm. Results: We screened 403 upregulated, and 158 downregulated DEGs for NASH, and they were mainly enriched in GO-BP, including the inflammatory response, innate immune response, signal transduction, and KEGG pathways, such as the pathways involved in cancer (e.g., the PI3K-Akt signaling pathway), and focal adhesion. We then screened 73 candidate genes from the PPI network and module analysis and finally identified 17 DEG signatures. By evaluating their relationship with immune cell populations, 12 DEG signatures were found to correlate with activated dendritic cells, resting dendritic cells, M2 macrophages, monocytes, neutrophils, and resting memory CD4 T cells, which were significantly different between the NASH and control tissues. Conclusions: We identified a 17-DEG-signature as a candidate biomarker for NASH and analyzed its relationship with immune infiltration in NASH.

The Role of Innate Immune Cells in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a very common hepatic pathology featuring steatosis and is linked to obesity and related conditions, such as the metabolic syndrome. When hepatic steatosis is accompanied by inflammation, the disorder is defined as nonalcoholic steatohepatitis (NASH), which in turn can progress toward fibrosis development that can ultimately result in cirrhosis. Cells of innate immunity, such as neutrophils or macrophages, are central regulators of NASH-related inflammation. Recent studies utilizing new experimental technologies, such as single-cell RNA sequencing, have revealed substantial heterogeneity within the macrophage populations of the liver, suggesting distinct functions of liver-resident Kupffer cells and recruited monocyte-derived macrophages with regards to regulation of liver inflammation and progression of NASH pathogenesis. Herein, we discuss recent developments concerning the function of innate immune cell subsets in NAFLD and NASH.

Therapeutic effects of myocardin-related transcription factor A (MRTF-A) knockout on experimental mice with nonalcoholic steatohepatitis induced by high-fat diet

OBJECTIVE

To explore the effects of myocardin-related transcription factor A (MRTF-A) knockout on mice with nonalcoholic steatohepatitis (NASH) induced by high-fat diet (HFD).

METHODS

Normal-fat diet (NFD) or HFD was fed to MRTF-A-knockout (MRTF-A^-/-) and wild-type (WT) mice for 16 weeks. Liver histopathological status was observed using Hematoxylin and Eosin (HE) staining, Oil Red O staining, Sirius Red staining, and Immunohistochemical staining. The mRNA and protein levels in liver tissues were measured through quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blot.

RESULTS

Compared with WT + HFD group, mice in MRTF-A^-/- + HFD group were decreased in body weight, blood glucose, plasma insulin, liver TG and NAFLD activity score (NAS), with liver function recovery. Besides, compared with HFD-fed WT mice, HFD-fed MRTF-A^-/- mice were improved in hepatic fibrosis, accompanied by decreased collagen content (%) and down-regulated expressions of α-SMA, COL1A2, TGFβ1, and SMAD3. In mice fed with HFD, the expression of MCP-1, CCR2, F4/80 and CD68 declined in liver tissues of MRTF-A^-/- mice as compared with WT mice. Besides, in hepatic macrophages isolated from HFD-fed mice, the observed increased expression of TNF-α, IL-1β, MCP-1, as well as decreased expression of CCR2. Compared with WT + HFD group, MRTF-A^-/- + HFD group mice were decreased regarding NF-κB p65 in liver tissues.

CONCLUSION

MRTF-A knockout reduced macrophage infiltration, down-regulated NF-κB p65 expression, and ameliorated inflammation and fibrosis of liver tissues in mice, thereby becoming a potential therapeutic target for NASH treatment.

Controversies and Opportunities in the Use of Inflammatory Markers for Diagnosis or Risk Prediction in Fatty Liver Disease

In the Western society, non-alcoholic fatty liver disease (NAFLD), characterized by the excessive accumulation of fat in the liver, represents the most common cause of chronic liver disease. If left untreated, approximately 15%-20% of patients with NAFLD will progress to non-alcoholic steatohepatitis (NASH), in which lobular inflammation, hepatocyte ballooning and fibrogenesis further contribute to a distorted liver architecture and function. NASH initiation has significant effects on liver-related mortality, as even the presence of early stage fibrosis increases the chances of adverse patient outcome. Therefore, adequate diagnostic tools for NASH are needed, to ensure that relevant therapeutic actions can be taken as soon as necessary. To date, the diagnostic gold standard remains the invasive liver biopsy, which is associated with several drawbacks such as high financial costs, procedural risks, and inter/intra-observer variability in histology analysis. As liver inflammation is a major hallmark of disease progression, inflammation-related circulating markers may represent an interesting source of non-invasive biomarkers for NAFLD/NASH. Examples for such markers include cytokines, chemokines or shed receptors from immune cells, circulating exosomes related to inflammation, and changing proportions of peripheral blood mononuclear cell (PBMC) subtypes. This review aims at documenting and critically discussing the utility of such novel inflammatory markers for NAFLD/NASH-diagnosis, patient stratification and risk prediction.

Role of Neutrophils in the Pathogenesis of Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) includes a spectrum of liver disorders, from fatty liver to nonalcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma. Compared with fatty liver, NASH is characterized by increased liver injury and inflammation, in which liver-infiltrating immune cells, with neutrophil infiltration as a hallmark of NASH, play a critical role in promoting the progression of fatty liver to NASH. Neutrophils are the first responders to injury and infection in various tissues, establishing the first line of defense through multiple mechanisms such as phagocytosis, cytokine secretion, reactive oxygen species production, and neutrophil extracellular trap formation; however, their roles in the pathogenesis of NASH remain obscure. The current review summarizes the roles of neutrophils that facilitate the progression of fatty liver to NASH and their involvement in inflammation resolution during NASH pathogenesis. The notion that neutrophils are potential therapeutic targets for the treatment of NASH is also discussed.

Function of TREM1 and TREM2 in Liver-Related Diseases

TREM1 and TREM2 are members of the triggering receptors expressed on myeloid cells (TREM) family. Both TREM1 and TREM2 are immunoglobulin superfamily receptors. Their main function is to identify foreign antigens and toxic substances, thereby adjusting the inflammatory response. In the liver, TREM1 and TREM2 are expressed on non-parenchymal cells, such as liver sinusoidal endothelial cells, Kupffer cells, and hepatic stellate cells, and cells which infiltrate the liver in response to injury including monocyte-derived macrophages and neutrophils. The function of TREM1 and TREM2 in inflammatory response depends on Toll-like receptor 4. TREM1 mainly augments inflammation during acute inflammation, while TREM2 mainly inhibits chronic inflammation to protect the liver from pathological changes. Chronic inflammation often induces metabolic abnormalities, fibrosis, and tumorigenesis. The above physiological changes lead to liver-related diseases, such as liver injury, nonalcoholic steatohepatitis, hepatic fibrosis, and hepatocellular carcinoma. Here, we review the function of TREM1 and TREM2 in different liver diseases based on inflammation, providing a more comprehensive perspective for the treatment of liver-related diseases.