Signalling via the osteopontin and high mobility group box-1 axis drives the fibrogenic response to liver injury

New insights into biomarkers and risk stratification to predict hepatocellular cancer

Hepatocellular carcinoma (HCC) is the third major cause of cancer death worldwide, with more than a doubling of incidence over the past two decades in the United States. Yet, the survival rate remains less than 20%, often due to late diagnosis at advanced stages. Current HCC screening approaches are serum alpha-fetoprotein (AFP) testing and ultrasound (US) of cirrhotic patients. However, these remain suboptimal, particularly in the setting of underlying obesity and metabolic dysfunction-associated steatotic liver disease/steatohepatitis (MASLD/MASH), which are also rising in incidence. Therefore, there is an urgent need for novel biomarkers that can stratify risk and predict early diagnosis of HCC, which is curable. Advances in liver cancer biology, multi-omics technologies, artificial intelligence, and precision algorithms have facilitated the development of promising candidates, with several emerging from completed phase 2 and 3 clinical trials. This review highlights the performance of these novel biomarkers and algorithms from a mechanistic perspective and provides new insight into how pathological processes can be detected through blood-based biomarkers. Through human studies compiled with animal models and mechanistic insight in pathways such as the TGF-β pathway, the biological progression from chronic liver disease to cirrhosis and HCC can be delineated. This integrated approach with new biomarkers merit further validation to refine HCC screening and improve early detection and risk stratification.

Myeloid cell path to malignancy: insights into liver cancer

Clinically approved treatments for advanced liver cancer often lack potency because of the heterogeneous characteristics of hepatocellular carcinoma (HCC). This complexity is largely driven by context-dependent inflammatory responses brought on by diverse etiologies, such as metabolic dysfunction-associated steatohepatitis (MASH), the genetic makeup of cancer cells, and the versatile adaptability of immune cells, such as myeloid cells. In this review, we discuss the evolutionary dynamics of the immune landscape, particularly that of liver-resident Kupffer cells (KCs), TREM2+, and SPP1+ macrophages with an active role during liver disease progression, which eventually fuels hepatocarcinogenesis. We highlight exploitable immunomodulatory avenues amenable to mitigate both the inherent pathological characteristics of liver cancers and the associated external factors that favor malignancy, paving a roadmap toward improving the management and therapeutic outcome for patients with HCC.

Intra and inter-organ communication through extracellular vesicles in obesity: functional role of obesesomes and steatosomes

BACKGROUND

Extracellular vesicles (EVs) represent a sophisticated mechanism of intercellular communication that is implicated in health and disease. Specifically, the role of EVs in metabolic regulation and their implications in metabolic pathologies, such as obesity and its comorbidities, remain unclear.

METHODS

Extracellular vesicles (EVs) were isolated through serial ultracentrifugation from murine adipocytes treated with palmitate or oleic acid, whole visceral and subcutaneous adipose tissue (obesesomes) of bariatric surgery obese donors, and human hepatocytes under steatosis (steatosomes) for functional in vitro experiments. Functional effects on inflammation and glucose and lipid metabolism of target cells (human and murine macrophages and hepatocytes) were assessed using ELISA, RT-PCR, and immunodetection. Isolated EVs from human steatotic (steatosomes) and control hepatocytes (hepatosomes) were characterized for quantity, size, and tetraspanin profile by NTA and Single Particle Interferometric Reflectance Imaging Sensor (SP-IRIS), and their protein cargo analyzed by qualitative (DDA) and quantitative (DIA-SWATH) proteomics using LC-MS/MS. Proteins identified by proteomics were validated by capturing EVs on functionalized chips by SP-IRIS.

RESULTS AND CONCLUSIONS

In this study, we investigated the role of EVs in the local communication between obese adipocytes and immune cells within adipose tissue, and the interaction of steatotic and healthy hepatocytes in the context of fatty liver disease progression. Furthermore, we analyzed obese adipose tissue-to-liver interactions through EV-obesesomes to elucidate their role in obesity-associated hepatic metabolic dysregulation. Our findings reveal that obesesomes promote inflammation and the secretion of pro-inflammatory cytokines upon interaction with macrophages, exerting a significant impact on reducing insulin resistance and altering lipid and glucose metabolism upon interaction with hepatocytes; in both cases, EVs from palmitate-loaded adipocytes and obesesomes from human visceral adipose depots demonstrated the most deleterious effect. Additionally, EVs secreted by steatotic hepatocytes (steatosomes) induced insulin resistance and altered lipid and glucose metabolism in healthy hepatocytes, suggesting their involvement in MASLD development. Proteomic analysis of steatosomes revealed that these vesicles contain liver disease-associated proteins, rendering them significant repositories of real-time biomarkers for the early stages and progression of MASLD.

Spatially restricted and ontogenically distinct hepatic macrophages are required for tissue repair

Our understanding of the functional heterogeneity of resident versus recruited macrophages in the diseased liver is limited. A population of recruited lipid-associated macrophages (LAMs) has been reported to populate the diseased liver alongside resident Kupffer cells (KCs). However, the precise roles of these distinct macrophage subsets remain elusive. Here, using proteogenomics, we have identified LAMs in multiple models of liver injury. Moreover, we found that this phenotype is not specific to recruited macrophages, as a subset of resident KCs can also adopt a LAM-like phenotype in the mouse and human liver. By combining genetic mouse models targeting the distinct populations, we determined that both recruited LAMs and resident LAM-like KCs play crucial roles in tissue repair. Specifically, triggering receptor expressed on myeloid cells 2 (TREM2) expression on either resident or recruited macrophages is required for the efficient clearance of dying cells, enhancing repair and preventing exacerbated fibrosis.

Immune Dysfunction and Infection Risk in Advanced Liver Disease

The risk of microbial infections is increased in cirrhosis and other forms of advanced liver disease such as alcohol-associated hepatitis. Such infections may precipitate new or further decompensation and death, especially in patients with clinical features of acute-on-chronic liver failure. The severe immune dysfunction or "immune paralysis" caused by advanced liver disease is associated with high short-term mortality. However, the pathogenic mechanisms underlying immune dysfunction and immunodeficiency are incompletely understood. Evidence to date suggests a complex, dynamic process that perturbs the physiological roles of the liver as a master regulator of systemic immunity and protector against noxious effects of exogenous molecules in the portal vein flowing from the gut. Thus, in cirrhosis and severe alcohol-associated hepatitis, the ability of hepatocytes and intrahepatic immune cells to balance normal context-dependent dichotomous responses of tolerance vs immune activation is lost. Contributing factors include loss of the gut barrier with translocation of microbial products through the portal vein, culminating in development of functional defects in innate and adaptive immune cells, and generation of immune-regulatory myeloid cells that permit microbial colonization and infection. This review addresses key evidence supporting the paradigm of immune dysfunction as a risk for microbial infections and identifies potential therapeutic targets for intervention. The primary focus is on cirrhosis-associated immune dysfunction and alcohol-associated liver disease, because the bulk of available data are from these 2 conditions.

HMGB1: key mediator in digestive system diseases

High Mobility Group Box 1 (HMGB1), a multifunctional non-histone protein, and its involvement in various physiological and pathological contexts has garnered significant attention. Given HMGB1's central function in modulating key biological activities, such as inflammatory responses and cellular death, its contribution to the pathogenesis of digestive system diseases has become a focus of growing interest. This review aims to comprehensively explore the mechanisms by which HMGB1 contributes to the progression of inflammatory bowel disease (IBD), liver disorders, and pancreatitis. Furthermore, we explore the prospective clinical applications and outline future research directions for HMGB1 in digestive diseases, providing fresh perspectives that highlight the necessity of ongoing studies to understand its role in these conditions.

Confrontation with kidney inflammation through a HMGB1-targeted peptide augments anti-fibrosis therapy

Damage to the renal tubular epithelial cells (TEC) is a key cellular event in kidney inflammation and subsequent fibrosis. However, drugs targeting renal TEC (RTEC) are limited to the alleviation of kidney fibrosis. Lethal giant larvae 1 (Lgl1) plays a key role in epithelial cell polarity and proliferation. Here, we report that the renal tubule epithelial-specific deletion of Lgl1 significantly ameliorated intrarenal inflammation and kidney fibrosis. Mechanistically, Lgl1 suppressed the activity of the deacetylase sirtuin 1 (SIRT1) and augmented the acetylation of high-mobility group box 1 (HMGB1) at the lysine 90 (K90) site. Consequently, HMGB1 migrated from the nucleus to the cytoplasm, activating an inflammatory cascade. Our renoprotective strategy was to construct a mimic peptide, TAT-K90WT, that targets HMGB1 K90 acetylation. Administration of this peptide significantly ameliorated inflammation and fibrosis in the kidneys. In summary, the Lgl1-HMGB1 axis plays an important role in renal fibrosis, and targeting HMGB1 acetylation by mimicking peptides is a potential strategy to prevent fibrosis.

Emerging Roles of High-mobility Group Box-1 in Liver Disease

High-mobility group box-1 (HMGB1) is an architectural chromosomal protein with various roles depending on its cellular localization. Extracellular HMGB1 functions as a prototypical damage-associated molecular pattern that triggers inflammation and adaptive immune responses, mediated by specific cell surface receptors, including receptors for advanced glycation end products and toll-like receptors. Post-translational modifications of HMGB1 significantly impact various cellular processes that contribute to the pathogenesis of liver diseases. Recent studies have highlighted the close relationship between HMGB1 and the pathogenesis of acute liver injuries, including acetaminophen-induced liver injury, hepatic ischemia-reperfusion injury, and acute liver failure. In chronic liver diseases, HMGB1 plays a role in nonalcoholic fatty liver disease, alcohol-associated liver disease, liver fibrosis, and hepatocellular carcinoma. Targeting HMGB1 as a therapeutic approach, either by inhibiting its release or blocking its extracellular function, is a promising strategy for treating liver diseases. This review aimed to summarize the available evidence on HMGB1's role in liver disease, focusing on its multifaceted signaling pathways, impact on disease progression, and the translation of these findings into clinical interventions.

Inflammatory biomarkers as cost-effective predictive tools in metabolic dysfunction-associated fatty liver disease

Qu and Li emphasize a fundamental aspect of metabolic dysfunction-associated fatty liver disease in their manuscript, focusing on the critical need for non-invasive diagnostic tools to improve risk stratification and predict the progression to severe liver complications. Affecting approximately 25% of the global population, metabolic dysfunction-associated fatty liver disease is the most common chronic liver condition, with higher prevalence among those with obesity. This letter stresses the importance of early diagnosis and intervention, especially given the rising incidence of obesity and metabolic syndrome. Research advancements provide insight into the potential of biomarkers (particularly inflammation-related) as predictive tools for disease progression and treatment response. This overview addresses pleiotropic biomarkers linked to chronic inflammation and cardiometabolic disorders, which may aid in risk stratification and treatment efficacy monitoring. Despite progress, significant knowledge gaps remain in the clinical application of these biomarkers, necessitating further research to establish standardized protocols and validate their utility in clinical practice. Understanding the complex interactions among these factors opens new avenues to enhance risk assessment, leading to better patient outcomes and addressing the public health burden of this worldwide condition.

Osteokines in Nonalcoholic Fatty Liver Disease

PURPOSE OF REVIEW

To critically summarize evidence on the potential role of osteokines in the pathogenesis and progression of nonalcoholic fatty liver disease (NAFLD).

RECENT FINDINGS

There are emerging data supporting that certain osteokines, which are specific bone-derived proteins, may beneficially or adversely affect hepatic metabolism, and their alterations in the setting of osteoporosis or other bone metabolic diseases may possibly contribute to the development and progression of NAFLD. There is evidence showing a potential bidirectional association between NAFLD and bone metabolism, which may imply the existence of a liver-bone axis. In this regard, osteocalcin, osteoprotegerin, bone morphogenic protein 4 (BMP4) and BMP6 appear to have a positive impact on the liver, thus possibly alleviating NAFLD, whereas osteopontin, receptor activator of nuclear factor kappa Β ligand (RANKL), sclerostin, periostin, BMP8B, and fibroblast growth factor 23 (FGF23) appear to have a negative impact on the liver, thus possibly exacerbating NAFLD. The potential implication of osteokines in NAFLD warrants further animal and clinical research in the field that may possibly result in novel therapeutic targets for NAFLD in the future.

OPN-Mediated Crosstalk Between Hepatocyte E4BP4 and Hepatic Stellate Cells Promotes MASH-Associated Liver Fibrosis

Stressed hepatocytes promote liver fibrosis through communications with hepatic stellate cells (HSCs) during chronic liver injury. However, intra-hepatocyte players that facilitate such cell-to-cell communications are largely undefined. It is previously reported that hepatocyte E4BP4 is potently induced by ER stress and hepatocyte deletion of E4bp4 protects mice from high-fat diet-induced liver steatosis. Here how hepatocyte E4bp4 deficiency impacts the activation of HSCs and the progression toward MASH-associated liver fibrosis is examined. Hepatic E4BP4 is increased in mouse models of NASH diet- or CCl4-induced liver fibrosis. Hepatocyte-specific E4bp4 deletion protected mice against NASH diet-induced liver injury, inflammation, and fibrosis without impacting liver steatosis. Hepatocyte E4BP4 overexpression activated HSCs in a medium transfer experiment, whereas hepatocyte E4bp4 depletion did the opposite. RNA-Seq analysis identified the pro-fibrogenic factor OPN as a critical target of E4BP4 within hepatocytes. Antibody neutralization or shRNA depletion of Opn abrogated hepatocyte E4BP4-induced HSC activation. E4BP4 interacted with and stabilized YAP, an established activator of OPN. Loss of hepatic Yap blocked OPN induction in the liver of Ad-E4bp4-injected mice. Hepatocyte E4BP4 induces OPN via YAP to activate HSCs and promote liver fibrosis during diet-induced MASH. Inhibition of the hepatocyte E4BP4-OPN pathway could offer a novel therapeutic avenue for treating MASLD/MASH.

High Mobility Group Box 1 (HMGB1): Molecular Signaling and Potential Therapeutic Strategies

High Mobility Group Box 1 (HMGB1) is a highly conserved non-histone chromatin-associated protein across species, primarily recognized for its regulatory impact on vital cellular processes, like autophagy, cell survival, and apoptosis. HMGB1 exhibits dual functionality based on its localization: both as a non-histone protein in the nucleus and as an inducer of inflammatory cytokines upon extracellular release. Pathophysiological insights reveal that HMGB1 plays a significant role in the onset and progression of a vast array of diseases, viz., atherosclerosis, kidney damage, cancer, and neurodegeneration. However, a clear mechanistic understanding of HMGB1 release, translocation, and associated signaling cascades in mediating such physiological dysfunctions remains obscure. This review presents a detailed outline of HMGB1 structure-function relationship and its regulatory role in disease onset and progression from a signaling perspective. This review also presents an insight into the status of HMGB1 druggability, potential limitations in understanding HMGB1 pathophysiology, and future perspective of studies that can be undertaken to address the existing scientific gap. Based on existing paradigm of various studies, HMGB1 is a critical regulator of inflammatory cascades and drives the onset and progression of a broad spectrum of dysfunctions. Studies focusing on HMGB1 druggability have enabled the development of biologics with potential clinical benefits. However, deeper understanding of post-translational modifications, redox states, translocation mechanisms, and mitochondrial interactions can potentially enable the development of better courses of therapy against HMGB1-mediated physiological dysfunctions.

Understanding the complex macrophage landscape in MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD) represents a spectrum of disease states ranging from simple steatosis to metabolic dysfunction-associated steatohepatitis (MASH), which can eventually lead to the development of cirrhosis and hepatocellular carcinoma. Macrophages have long been implicated in driving the progression from steatosis to end-stage disease, yet we still know relatively little about the precise involvement of these cells in MASLD progression and/or regression. Rather, there are a considerable number of conflicting reports regarding the precise roles of these cells. This confusion stems from the fact that, until recently, macrophages in the liver were considered a homogenous population. However, thanks to recent technological advances including multi-parameter flow cytometry, single-cell RNA sequencing and spatial proteogenomics, we now know that this is not the case. Rather hepatic macrophages, even in the healthy liver, are heterogenous, existing in multiple subsets with distinct transcriptional profiles and hence likely functions. This heterogeneity is even more prominent in MASLD, where the macrophage pool consists of multiple different subsets of resident and recruited cells. To probe the unique functions of these cells and determine if targeting macrophages may be a viable therapeutic strategy in MASLD, we first need to unravel this complexity and decipher which populations and/or activation states are present and what functions each of these may play in driving MASLD progression. In this review, we summarise recent advances in the field, highlighting what is currently known about the hepatic macrophage landscape in MASLD and the questions that remain to be tackled.

Post-translational modifications drive the effects of HMGB1 in alcohol-associated liver disease

BACKGROUND

We previously identified that high-mobility group box-1 (HMGB1) is increased and undergoes post-translational modifications (PTMs) in response to alcohol consumption. Here, we hypothesized that specific PTMs, occurring mostly in hepatocytes and myeloid cells, could contribute to the pathogenesis of alcohol-associated liver disease (AALD).

METHODS

We used the Lieber-DeCarli (LD) model of early alcohol-induced liver injury, combined with engineered viral vectors and genetic approaches to regulate the expression of HMGB1, its PTMs (reduced [H], oxidized [O], acetylated [Ac], both [O + Ac]), and its receptors (RAGE, TLR4) in a cell-specific manner (hepatocytes and/or myeloid cells).

RESULTS

Hmgb1 ablation in hepatocytes or myeloid cells partially protected, while ablation in both prevented steatosis, inflammation, IL1B production, and alcohol-induced liver injury. Hepatocytes were a major source of [H], [O], and [Ac] HMGB1, whereas myeloid cells produced only [H] and [Ac] HMGB1. Neutralization of HMGB1 prevented, whereas injection of [H] HMGB1 increased AALD, which was worsened by injection of [O] HMGB1. While [O] HMGB1 induced liver injury, [Ac] HMGB1 protected and counteracted the effects of [O] HMGB1 in AALD. [O] HMGB1 stimulated macrophage (MF) migration, activation, IL1B production, and secretion. Ethanol-fed RageΔMye but not Tlr4ΔMye, RageΔHep, or Tlr4ΔHep mice were protected from AALD, indicating a crucial role of RAGE in myeloid cells for AALD. [O] HMGB1 recruited and activated myeloid cells through RAGE and contributed to steatosis, inflammation, and IL1B production in AALD.

CONCLUSIONS

These results provide evidence for targeting [O] HMGB1 of hepatocyte origin as a ligand for RAGE signaling in myeloid cells and a driver of steatosis, inflammatory cell infiltration, and IL1B production in AALD. Importantly, we reveal that [Ac] HMGB1 offsets the noxious effects of [O] HMGB1 in AALD.

Hepatic stearoyl-CoA desaturase-1 deficiency induces fibrosis and hepatocellular carcinoma-related gene activation under a high carbohydrate low fat diet

Stearoyl-CoA desaturase-1 (SCD1) is a pivotal enzyme in lipogenesis, which catalyzes the synthesis of monounsaturated fatty acids (MUFA) from saturated fatty acids, whose ablation downregulates lipid synthesis, preventing steatosis and obesity. Yet deletion of SCD1 promotes hepatic inflammation and endoplasmic reticulum stress, raising the question of whether hepatic SCD1 deficiency promotes further liver damage, including fibrosis. To delineate whether SCD1 deficiency predisposes the liver to fibrosis, cirrhosis, and hepatocellular carcinoma (HCC), we employed in vivo SCD1 deficient global and liver-specific mouse models fed a high carbohydrate low-fat diet and in vitro established AML12 mouse cells. The absence of liver SCD1 remarkably increased the saturation of liver lipid species, as indicated by lipidomic analysis, and led to hepatic fibrosis. Consistently, SCD1 deficiency promoted hepatic gene expression related to fibrosis, cirrhosis, and HCC. Deletion of SCD1 increased the circulating levels of Osteopontin, known to be increased in fibrosis, and alpha-fetoprotein, often used as an early marker and a prognostic marker for patients with HCC. De novo lipogenesis or dietary supplementation of oleate, an SCD1-generated MUFA, restored the gene expression related to fibrosis, cirrhosis, and HCC. Although SCD1 deficient mice are protected against obesity and fatty liver, our results show that MUFA deprivation results in liver injury, including fibrosis, thus providing novel insights between MUFA insufficiency and pathways leading to fibrosis, cirrhosis, and HCC under lean non-steatotic conditions.

HMGB1 as an extracellular pro-inflammatory cytokine: Implications for drug-induced organic damage

Drug-induced organic damage encompasses various intricate mechanisms, wherein HMGB1, a non-histone chromosome-binding protein, assumes a significant role as a pivotal hub gene. The regulatory functions of HMGB1 within the nucleus and extracellular milieu are interlinked. HMGB1 exerts a crucial regulatory influence on key biological processes including cell survival, inflammatory regulation, and immune response. HMGB1 can be released extracellularly from the cell during these processes, where it functions as a pro-inflammation cytokine. HMGB1 interacts with multiple cell membrane receptors, primarily Toll-like receptors (TLRs) and receptor for advanced glycation end products (RAGE), to stimulate immune cells and trigger inflammatory response. The excessive or uncontrolled HMGB1 release leads to heightened inflammatory responses and cellular demise, instigating inflammatory damage or exacerbating inflammation and cellular demise in different diseases. Therefore, a thorough review on the significance of HMGB1 in drug-induced organic damage is highly important for the advancement of pharmaceuticals, ensuring their effectiveness and safety in treating inflammation as well as immune-related diseases. In this review, we initially outline the characteristics and functions of HMGB1, emphasizing their relevance in disease pathology. Then, we comprehensively summarize the prospect of HMGB1 as a promising therapeutic target for treating drug-induced toxicity. Lastly, we discuss major challenges and propose potential avenues for advancing the development of HMGB1-based therapeutics.

Oligonucleotide therapies for nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) represents a severe disease subtype of nonalcoholic fatty liver disease (NAFLD) that is thought to be highly associated with systemic metabolic abnormalities. It is characterized by a series of substantial liver damage, including hepatocellular steatosis, inflammation, and fibrosis. The end stage of NASH, in some cases, may result in cirrhosis and hepatocellular carcinoma (HCC). Nowadays a large number of investigations are actively under way to test various therapeutic strategies, including emerging oligonucleotide drugs (e.g., antisense oligonucleotide, small interfering RNA, microRNA, mimic/inhibitor RNA, and small activating RNA) that have shown high potential in treating this fatal liver disease. This article systematically reviews the pathogenesis of NASH/NAFLD, the promising druggable targets proven by current studies in chemical compounds or biological drug development, and the feasibility and limitations of oligonucleotide-based therapeutic approaches under clinical or pre-clinical studies.

A Protein Complex of Liver Origin Activates a Pro-inflammatory Program That Drives Hepatic and Intestinal Injury in Alcohol-Associated Liver Disease

BACKGROUND & AIMS

There is limited information on how the liver-to-gut axis contributes to alcohol-associated liver disease (AALD). We previously identified that high-mobility group box-1 (HMGB1) undergoes oxidation in hepatocytes and demonstrated elevated serum levels of oxidized HMGB1 ([O] HMGB1) in alcoholic patients. Since interleukin-1 beta (IL-1B) increases in AALD, we hypothesized hepatocyte-derived [O] HMGB1 could interact with IL-1B to activate a pro-inflammatory program that, besides being detrimental to the liver, drives intestinal barrier dysfunction.

RESULTS

Alcohol-fed RageΔMye mice exhibited decreased nuclear factor kappa B signaling, a pro-inflammatory signature, and reduced total intestinal permeability, resulting in protection from AALD. In addition, [O] HMGB1 bound and signaled through the receptor for advanced-glycation end-products (RAGE) in myeloid cells, driving hepatic inflammation, intestinal permeability, and increased portal blood lipopolysaccharide in AALD. We identified that [O] HMGB1 formed a complex with IL-1B, which was found in the livers of patients with acute alcoholic hepatitis and mice with AALD. This complex originated from the liver, because it was absent in the intestine when hepatocytes did not produce [O] HMGB1. Mechanistically, the complex bound RAGE in Kupffer cells and macrophages induced a pro-inflammatory program. Moreover, it bound RAGE in intestinal macrophages and epithelial cells, leading to intestinal inflammation, altered intestinal epithelial cell tight junction protein expression, increased intestinal permeability, and elevated portal blood lipopolysaccharide, enhancing AALD pathogenesis.

CONCLUSIONS

We identified a protein complex of liver origin that amplifies the pro-inflammatory feedback loop in AALD; therefore, targeting this complex could have significant therapeutic potential.

Ablation of secreted phosphoprotein-1 in hepatocytes increases fatty acid oxidation and ameliorates alcohol-associated liver disease

BACKGROUND

Previously, we demonstrated that Spp1-/- mice exhibit a greater susceptibility to alcohol-induced liver injury than wild-type (WT) mice. Notably, alcohol triggers the expression of osteopontin (encoded by SPP1) in hepatocytes. However, the specific role of hepatocyte-derived SPP1 in either mitigating or exacerbating alcohol-associated liver disease (AALD) has yet to be elucidated. We hypothesized that hepatocyte-derived SPP1 plays a role in AALD by modulating the regulation of steatosis.

METHODS

We analyzed hepatic SPP1 expression using four publicly available datasets from patients with alcoholic hepatitis (AH). Additionally, we examined SPP1 expression in the livers of WT mice subjected to either a control or ethanol Lieber-DeCarli (LDC) diet for 6 weeks. We compared the relationship between SPP1 expression and significantly dysregulated genes in AH with controls using correlation and enrichment analyses. To investigate the specific impact of hepatocyte-derived SPP1, we generated hepatocyte-specific Spp1 knock-out (Spp1ΔHep) mice and subjected them to either a control or ethanol Lieber-DeCarli diet for 6 weeks.

RESULTS

Alcohol induced hepatic SPP1 expression in both humans and mice. Our analysis, focusing on genes correlated with SPP1, revealed an enrichment of fatty acid oxidation (FAO) in three datasets, and peroxisome proliferator-activated receptor signaling in one dataset. Notably, FAO genes correlating with SPP1 were downregulated in patients with AH. Ethanol-fed WT mice exhibited higher serum-free fatty acids (FFAs), adipose tissue lipolysis, and hepatic fatty acid (FA) transporters. In contrast, ethanol-fed Spp1ΔHep mice displayed lower liver triglycerides, FFAs, and serum alanine transaminase and greater FAO gene expression than WT mice, indicating a protective effect against AALD. Primary hepatocytes from Spp1∆Hep mice exhibited heightened expression of genes encoding proteins involved in FAO.

CONCLUSIONS

Alcohol induces the expression of SPP1 in hepatocytes, leading to impaired FAO and contributing to the development of AALD.

Redox-sensitive high-mobility group box-1 isoforms contribute to liver fibrosis progression and resolution in mice

BACKGROUND & AIMS

High-mobility group box-1 (HMGB1) significantly increases and undergoes post-translational modifications (PTMs) in response to liver injury. Since oxidative stress plays a major role in liver fibrosis and induces PTMs in proteins, we hypothesized that redox-sensitive HMGB1 isoforms contribute to liver fibrosis progression and resolution.

METHODS

We used ESI-LC-MS (electrospray ionization-liquid chromatography-mass spectrometry) to study PTMs of HMGB1 during fibrosis progression and resolution. Conditional knockout mice were used for functional analyses.

RESULTS

We identified that disulfide ([O]) and sulfonated ([SO3]) HMGB1 increase during carbon tetrachloride-induced liver fibrosis progression, however, while [O] HMGB1 declines, [SO3] HMGB1 drops but remains, during fibrosis resolution. Conditional knockout of Hmgb1 revealed that production of [O] and [SO3] HMGB1 occurs mostly in hepatocytes. Co-injection of [O] HMGB1 worsens carbon tetrachloride-induced liver fibrosis more than co-injection of [H] HMGB1. Conversely, ablation of [O] Hmgb1 in hepatocytes reduces liver fibrosis. Moreover, ablation of the receptor for advanced-glycation end-products (Rage) reveals that the profibrogenic effect of [O] HMGB1 is mediated by RAGE signaling in hepatic stellate cells (HSCs). Notably, injection of [SO3] HMGB1 accelerates fibrosis resolution due to RAGE-dependent stimulation of HSC apoptosis. Importantly, gene signatures activated by redox-sensitive HMGB1 isoforms in mice, classify patients with fibrosis according to fibrosis and inflammation scores.

CONCLUSION

Dynamic changes in hepatocyte-derived [O] and [SO3] HMGB1 signal through RAGE-dependent mechanisms on HSCs to drive their profibrogenic phenotype and fate, contributing to progression and resolution of liver fibrosis.

IMPACT AND IMPLICATIONS

Since oxidative stress plays a major role in liver fibrosis and induces post-translational modifications of proteins, we hypothesized that redox-sensitive HMGB1 isoforms contribute to liver fibrosis progression and resolution. This study is significant because a rise in [H] HMGB1 could flag 'patient at risk', the presence of [O] HMGB1 could suggest 'disease in progress or active scarring', while the appearance of [SO3] HMGB1 could point at 'resolution under way'. The latter could be used as a readout for response to pharmacological intervention with anti-fibrotic agents.

A patent review on HMGB1 inhibitors for the treatment of liver diseases

INTRODUCTION

HMGB1 is a non-histone chromatin protein released or secreted in response to tissue damage or infection. Extracellular HMGB1, as a crucial immunomodulatory factor, binds with several different receptors to innate inflammatory responses that aggravate acute and chronic liver diseases. The increased levels of HMGB1 have been reported in various liver diseases, highlighting that it represents a potential biomarker and druggable target for therapeutic development.

AREAS COVERED

This review summarizes the current knowledge on the structure, function, and interacting receptors of HMGB1 and its significance in multiple liver diseases. The latest patented and preclinical studies of HMGB1 inhibitors (antibodies, peptides, and small molecules) for liver diseases are summarized by using the keywords 'HMGB1,' 'HMGB1 antagonist, HMGB1-inhibitor,' 'liver disease' in Web of Science, Google Scholar, Google Patents, and PubMed databases in the year from 2017 to 2023.

EXPERT OPINIONS

In recent years, extensive research on HMGB1-dependent inflammatory signaling has discovered potent inhibitors of HMGB1 to reduce the severity of liver injury. Despite significant progress in the development of HMGB1 antagonists, few of them are approved for clinical treatment of liver-related diseases. Developing safe and effective specific inhibitors for different HMGB1 isoforms and their interaction with receptors is the focus of future research.

Drug targets regulate systemic metabolism and provide new horizons to treat nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH), is the advanced stage of nonalcoholic fatty liver disease (NAFLD) with rapidly rising global prevalence. It is featured with severe hepatocyte apoptosis, inflammation and hepatic lipogenesis. The drugs directly targeting the processes of steatosis, inflammation and fibrosis are currently under clinical investigation. Nevertheless, the long-term ineffectiveness and remarkable adverse effects are well documented, and new concepts are required to tackle with the root causes of NASH progression. We critically assess the recently validated drug targets that regulate the systemic metabolism to ameliorate NASH. Thermogenesis promoted by mitochondrial uncouplers restores systemic energy expenditure. Furthermore, regulation of mitochondrial proteases and proteins that are pivotal for intracellular metabolic homeostasis normalize mitochondrial function. Secreted proteins also improve systemic metabolism, and NASH is ameliorated by agonizing receptors of secreted proteins with small molecules. We analyze the drug design, the advantages and shortcomings of these novel drug candidates. Meanwhile, the structural modification of current NASH therapeutics significantly increased their selectivity, efficacy and safety. Furthermore, the arising CRISPR-Cas9 screen strategy on liver organoids has enabled the identification of new genes that mediate lipid metabolism, which may serve as promising drug targets. In summary, this article discusses the in-depth novel mechanisms and the multidisciplinary approaches, and they provide new horizons to treat NASH.

Liver fibrosis: pathological features, clinical treatment and application of therapeutic nanoagents

Liver fibrosis is a reversible damage-repair response, the pathological features of which mainly include damage to hepatocytes, sinusoid capillarization, hepatic stellate cells activation, excessive accumulation of extracellular matrix and inflammatory response. Although some treatments (including drugs and stem cell therapy) for these pathological features have been shown to be effective, more clinical trials are needed to confirm their effectiveness. In recent years, nanomaterials-based therapies have emerged as an innovative and promising alternative to traditional drugs, being explored for the treatment of liver fibrosis diseases. Natural nanomaterials (including extracellular vesicles) and synthetic nanomaterials (including inorganic nanomaterials and organic nanomaterials) are developed to facilitate drug targeting delivery and combination therapy. In this review, the pathological features of liver fibrosis and the current anti-fibrosis drugs in clinical trials are briefly introduced, followed by a detailed introduction of the therapeutic nanoagents for the precise delivery of anti-fibrosis drugs. Finally, the future development trend in this field is discussed.

Kindlin-2 maintains liver homeostasis by regulating GSTP1-OPN-mediated oxidative stress and inflammation in mice

Hepatocyte plays a principal role in preserving integrity of the liver homeostasis. Our recent study demonstrated that Kindlin-2, a focal adhesion protein that activates integrins and regulates cell-extracellular matrix interactions, plays an important role in regulation of liver homeostasis by inhibiting inflammation pathway; however, the molecular mechanism of how Kindlin-2 KO activates inflammation is unknown. Here, we show that Kindlin-2 loss largely downregulates the antioxidant glutathione-S-transferase P1 in hepatocytes by promoting its ubiquitination and degradation via a mechanism involving protein-protein interaction. This causes overproduction of intracellular reactive oxygen species and excessive oxidative stress in hepatocytes. Kindlin-2 loss upregulates osteopontin in hepatocytes partially because of upregulation of reactive oxygen species and consequently stimulates overproduction of inflammatory cytokines and infiltration in liver. The molecular and histological deteriorations caused by Kindlin-2 deficiency are markedly reversed by systemic administration of an antioxidant N-acetylcysteine in mice. Taken together, Kindlin-2 plays a pivotal role in preserving integrity of liver function.

The critical role of osteopontin (OPN) in fibrotic diseases

Fibrosis is a pathological condition characterized by the excessive deposition of extracellular matrix components in tissues and organs, leading to progressive architectural remodelling and contributing to the development of various diseases. Osteopontin (OPN), a highly phosphorylated glycoprotein, has been increasingly recognized for its involvement in the progression of tissue fibrosis. This review provides a comprehensive overview of the genetic and protein structure of OPN and focuses on our current understanding of the role of OPN in the development of fibrosis in the lungs and other tissues. Additionally, special attention is given to the potential of OPN as a biomarker and a novel therapeutic target in the treatment of fibrosis.

Overexpression of HMGB1 in hepatocytes accelerates PTEN inactivation-induced liver cancer

BACKGROUND

Liver cancer is increasing due to the rise in metabolic dysfunction-associated steatohepatitis (MASH). High-mobility group box-1 (HMGB1) is involved in the pathogenesis of chronic liver disease, but its role in MASH-associated liver cancer is unknown. We hypothesized that an increase in hepatocyte-derived HMGB1 in a mouse model of inactivation of PTEN that causes MASH could promote MASH-induced tumorigenesis.

METHODS

We analyzed publicly available transcriptomics datasets, and to explore the effect of overexpressing HMGB1 in cancer progression, we injected 1.5-month-old Pten∆Hep mice with adeno-associated virus serotype-8 (AAV8) vectors to overexpress HMGB1-EGFP or EGFP, and sacrificed them at 3, 9 and 11 months of age.

RESULTS

We found that HMGB1 mRNA increases in human MASH and MASH-induced hepatocellular carcinoma (MASH-HCC) compared to healthy livers. Male and female Pten∆Hep mice overexpressing HMGB1 showed accelerated liver tumor development at 9 and 11 months, respectively, with increased tumor size and volume, compared to control Pten∆Hep mice. Moreover, Pten∆Hep mice overexpressing HMGB1, had increased incidence of mixed HCC-intrahepatic cholangiocarcinoma (iCCA). All iCCAs were positive for nuclear YAP and SOX9. Male Pten∆Hep mice overexpressing HMGB1 showed increased cell proliferation and F4/80+ cells at 3 and 9 months.

CONCLUSION

Overexpression of HMGB1 in hepatocytes accelerates liver tumorigenesis in Pten∆Hep mice, enhancing cell proliferation and F4/80+ cells to drive MASH-induced liver cancer.

Hepatic Macrophages as Targets for the MSC-Based Cell Therapy in Non-Alcoholic Steatohepatitis

Non-alcoholic steatohepatitis (NASH) is a serious public health issue associated with the obesity pandemic. Obesity is the main risk factor for the non-alcoholic fatty liver disease (NAFLD), which progresses to NASH and then to end-stage liver disease. Currently, there are no specific pharmacotherapies of NAFLD/NASH approved by the FDA or other national regulatory bodies and the treatment includes lifestyle adjustment and medicines for improving lipid metabolism, enhancing sensitivity to insulin, balancing oxidation, and counteracting fibrosis. Accordingly, further basic research and development of new therapeutic approaches are greatly needed. Mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles prevent induced hepatocyte death in vitro and attenuate NASH symptoms in animal models of the disease. They interact with hepatocytes directly, but also target other liver cells, including Kupffer cells and macrophages recruited from the blood flow. This review provides an update on the pathogenesis of NAFLD/NASH and the key role of macrophages in the development of the disease. We examine in detail the mechanisms of the cross-talk between the MSCs and the macrophages, which are likely to be among the key targets of MSCs and their derivatives in the course of NAFLD/NASH cell therapy.

Found in translation-Fibrosis in metabolic dysfunction-associated steatohepatitis (MASH)

Metabolic dysfunction-associated steatohepatitis (MASH) is a severe form of liver disease that poses a global health threat because of its potential to progress to advanced fibrosis, leading to cirrhosis and liver cancer. Recent advances in single-cell methodologies, refined disease models, and genetic and epigenetic insights have provided a nuanced understanding of MASH fibrogenesis, with substantial cellular heterogeneity in MASH livers providing potentially targetable cell-cell interactions and behavior. Unlike fibrogenesis, mechanisms underlying fibrosis regression in MASH are still inadequately understood, although antifibrotic targets have been recently identified. A refined antifibrotic treatment framework could lead to noninvasive assessment and targeted therapies that preserve hepatocellular function and restore the liver's architectural integrity.

Macrophage-derived Osteopontin (SPP1) Protects From Nonalcoholic Steatohepatitis

BACKGROUND & AIMS

Nonalcoholic steatohepatitis (NASH) is characterized by steatosis, lobular inflammation, hepatocyte ballooning degeneration, and fibrosis, all of which increase the risk of progression to end-stage liver disease. Osteopontin (OPN, SPP1) plays an important role in macrophage (MF) biology, but whether MF-derived OPN affects NASH progression is unknown.

METHODS

We analyzed publicly available transcriptomic datasets from patients with NASH, and used mice with conditional overexpression or ablation of Spp1 in myeloid cells and liver MFs, and fed them a high-fat, fructose, and cholesterol diet mimicking the Western diet, to induce NASH.

RESULTS

This study demonstrated that MFs with high expression of SPP1 are enriched in patients and mice with nonalcoholic fatty liver disease (NAFLD), and show metabolic but not pro-inflammatory properties. Conditional knockin of Spp1 in myeloid cells (Spp1KI Mye) or in hepatic macrophages (Spp1KI LvMF) conferred protection, whereas conditional knockout of Spp1 in myeloid cells (Spp1ΔMye) worsened NASH. The protective effect was mediated by induction of arginase-2 (ARG2), which enhanced fatty acid oxidation (FAO) in hepatocytes. Induction of ARG2 stemmed from enhanced production of oncostatin-M (OSM) in MFs from Spp1KI Mye mice. OSM activated STAT3 signaling, which upregulated ARG2. In addition to hepatic effects, Spp1KI Mye also protected through sex-specific extrahepatic mechanisms.

CONCLUSION

MF-derived OPN protects from NASH, by upregulating OSM, which increases ARG2 through STAT3 signaling. Further, the ARG2-mediated increase in FAO reduces steatosis. Therefore, enhancing the OPN-OSM-ARG2 crosstalk between MFs and hepatocytes may be beneficial for patients with NASH.

Mechanisms of liver fibrosis in metabolic syndrome

The understanding of the mechanisms of liver fibrosis has been dominated by models in which chronic hepatocellular injury is the initiating step as is seen with viral infections. The increased prevalence of the metabolic syndrome, and the increases in liver fibrosis due to metabolic syndrome driven non-alcoholic steatohepatitis (NASH), has made it a priority to understand how this type of liver fibrosis is similar to, and different from, pure hepatocellular injury driven liver fibrosis. Both types of liver fibrosis have the transformation of the hepatic stellate cell (HSC) into a myofibroblast as a key step. In metabolic syndrome, there is little evidence that metabolite changes such as high levels of glucose and free fatty acids are directly inducing HSC transdifferentiation, however, metabolite changes may lead to reductions in immunomodulatory and hepatoprotective molecules such as lipoxins, resolvins and Interleukin (IL)-22. Cells of the innate immune system are known to be important intermediaries between hepatocellular damage and HSC transdifferentiation, primarily by producing cytokines such as transforming growth factor-β (TGF-β) and platelet derived growth factor (PDGF). Resident and infiltrating macrophages are the dominant innate immune cells, but others (dendritic cells, neutrophils, natural killer T cells and mucosal-associated invariant T cells) also have important roles in inducing and resolving liver fibrosis. CD8+ and CD4+ T cells of the adaptive immune system have been identified to have greater profibrotic roles than previously realised by inducing hepatocyte death (auto-aggressive CD8+T) cells and cytokines producing (TH17 producing CD4+T) cells. Finally, the cellular networks present in NASH fibrosis are being identified and suggest that once fibrosis has developed cell-to-cell communication is dominated by myofibroblasts autocrine signalling followed by communication with cholangiocytes and endothelial cells, with myofibroblast-hepatocyte, and myofibroblast-macrophage signalling having minor roles. Such information is essential to the development of antifibrotic strategies for different stages of fibrosis.

Advanced Biomarkers of Hepatotoxicity in Psychiatry: A Narrative Review and Recommendations for New Psychoactive Substances

One of the factors that increase the effectiveness of the pharmacotherapy used in patients abusing various types of new psychoactive substances (NPSs) is the proper functioning of the liver. However, the articles published to date on NPS hepatotoxicity only address non-specific hepatic parameters. The aim of this manuscript was to review three advanced markers of hepatotoxicity in psychiatry, namely, osteopontin (OPN), high-mobility group box 1 protein (HMGB1) and glutathione dehydrogenase (GDH, GLDH), and, on this basis, to identify recommendations that should be included in future studies in patients abusing NPSs. This will make it possible to determine whether NPSs do indeed have a hepatotoxic effect or whether other factors, such as additional substances taken or hepatitis C virus (HCV) infection, are responsible. NPS abusers are at particular risk of HCV infection, and for this reason, it is all the more important to determine what factors actually show a hepatotoxic effect in them.

From liver fibrosis to hepatocarcinogenesis: Role of excessive liver H2O2 and targeting nanotherapeutics

Liver fibrosis and hepatocellular carcinoma (HCC) have been worldwide threats nowadays. Liver fibrosis is reversible in early stages but will develop precancerosis of HCC in cirrhotic stage. In pathological liver, excessive H₂O₂ is generated and accumulated, which impacts the functionality of hepatocytes, Kupffer cells (KCs) and hepatic stellate cells (HSCs), leading to genesis of fibrosis and HCC. H₂O₂ accumulation is associated with overproduction of superoxide anion (O₂^•−) and abolished antioxidant enzyme systems. Plenty of therapeutics focused on H₂O₂ have shown satisfactory effects against liver fibrosis or HCC in different ways. This review summarized the reasons of liver H₂O₂ accumulation, and the role of H₂O₂ in genesis of liver fibrosis and HCC. Additionally, nanotherapeutics targeting H₂O₂ were summarized for further consideration of antifibrotic or antitumor therapy.

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Liver fibrosis and HCC are closely related because ROS induced liver damage and inflammation, especially over-cumulated H₂O₂.

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Excess H₂O₂ diffusion in pathological liver was due to increased metabolic rate and diminished cellular antioxidant systems.

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Freely diffused H₂O₂ damaged liver-specific cells, thereby leading to fibrogenesis and hepatocarcinogenesis.

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Nanotherapeutics targeting H₂O₂ are summarized for treatment of liver fibrosis and HCC, and also challenges are proposed.

Pro-fibrogenic role of alarmin high mobility group box 1 in HIV-hepatitis B virus coinfection

OBJECTIVE

Liver disease is accelerated in people with HIV (PWH) with hepatitis B virus (HBV) coinfection. We hypothesized that liver fibrosis in HIV-HBV is triggered by increased hepatocyte apoptosis, microbial translocation and/or HIV/HBV viral products.

DESIGN

Sera from PWH with HBV coinfection versus from those with HBV only or putative mediators were used to examine the pathogenesis of liver disease in HIV-HBV.

METHODS

We applied sera from PWH and HBV coinfection versus HBV alone, or putative mediators (including HMGB1), to primary human hepatic stellate cells (hHSC) and examined pro-fibrogenic changes at the single cell level using flow cytometry. High mobility group box 1 (HMGB1) levels in the applied sera were assessed according to donor fibrosis stage.

RESULTS

Quantitative flow cytometric assessment of pro-fibrogenic and inflammatory changes at the single cell level revealed an enhanced capacity for sera from PWH with HBV coinfection to activate hHSC. This effect was recapitulated by lipopolysaccharide, HIV-gp120, hepatocyte conditioned-media and the alarmin HMGB1. Induction of hepatocyte cell death increased their pro-fibrogenic potential, an effect blocked by HMGB1 antagonist glycyrrhizic acid. Consistent with a role for this alarmin, HMGB1 levels were elevated in sera from PWH and hepatitis B coinfection compared to HBV alone and higher in those with HIV-HBV with liver fibrosis compared to those without.

CONCLUSIONS

Sera from PWH and HBV coinfection have an enhanced capacity to activate primary hHSC. We identified an increase in circulating HMGB1 which, in addition to HIV-gp120 and translocated microbial products, drove pro-fibrogenic changes in hHSC, as mechanisms contributing to accelerated liver disease in HIV-HBV.

Decoding liver fibrogenesis with single-cell technologies

Liver fibrogenesis is a highly dynamic and complex process that drives the progression of chronic liver disease toward liver failure and end-stage liver diseases. Despite decades of intense studies, the cellular and molecular mechanisms underlying liver fibrogenesis remain elusive, and no approved therapies to treat liver fibrosis are currently available. The rapid development of single-cell RNA sequencing (scRNA-seq) technologies allows the characterization of cellular alterations under healthy and diseased conditions at an unprecedented resolution. In this Review, we discuss how the scRNA-seq studies are transforming our understanding of the regulatory mechanisms of liver fibrosis. We specifically emphasize discoveries on disease-relevant cell subpopulations, molecular events, and cell interactions on cell types including hepatocytes, liver sinusoidal endothelial cells, myofibroblasts, and macrophages. These discoveries have uncovered critical pathophysiological changes during liver fibrogenesis. Further efforts are urged to fully understand the functional contributions of these changes to liver fibrogenesis, and to translate the new knowledge into effective therapeutic approaches.

Liver macrophages in health and disease

Single-cell and spatial transcriptomic technologies have revealed an underappreciated heterogeneity of liver macrophages. This has led us to rethink the involvement of macrophages in liver homeostasis and disease. Identification of conserved gene signatures within these cells across species and diseases is enabling the correct identification of specific macrophage subsets and the generation of more specific tools to track and study the functions of these cells. Here, we discuss what is currently known about the definitions of these different macrophage populations, the markers that can be used to identify them, how they are wired within the liver, and their functional specializations in health and disease.

Effective delivery of osteopontin small interference RNA using exosomes suppresses liver fibrosis via TGF-β1 signaling

Objective and aims: Osteopontin (OPN), an oxidant stress sensitive cytokine, plays a central role in liver fibrosis. While OPN expression can be reduced by small interfering RNA (siRNA), the challenge to deliver siRNA safely and effectively into liver remains unresolved. Exosomes are promising natural nanocarriers for drug delivery that are able to enter cells with different biological barriers efficiently. In this study, we used exosomes as a delivery vehicle to target OPN in liver fibrosis.

Methods: Exosomes selectively home to fibrotic liver according to small animal imaging system. Electroporation technique was used to engineer exosomes to carry siRNA targeting OPN (Exo^siRNA−OPN). Primary hepatic stellate cells (HSCs) were isolated and treated with Exo^siRNA−OPN to assess the effect on activated HSCs (aHSCs). Immunofluorescence for α−SMA, an aHSCs marker, and sirius red staining were performed to assess ECM deposition. Finally, plasma OPN from patients with liver fibrosis was identified by ELISA assay.

Results: Exosome-mediated siRNA delivery systems show high uptake and low toxicity. Besides, Exo^siRNA−OPN suppressed HSCs activation and ECM deposition and more efficiently improved liver function when compared to naked siRNA-OPN. Moreover, Exo^siRNA−OPN was assumed inhibiting TGF-β1 signaling activation, along with other fibrotic-related genes based on a GEO datasheet of liver fibrosis samples for correlation analyzes. Exo^siRNA−OPN inhibited TGF-β1 signaling by decreasing high-mobility group box-1 (HMGB1). Plasma proteins from chronic HBV-induced fibrosis patients were identified that patients with high OPN expression correlates with more advanced fibrosis progression.

Discussion: This study shows that exosome-mediated siRNA-OPN delivery may be an effective option for the treatment of liver fibrosis.

Examination of the role of necroptotic damage-associated molecular patterns in tissue fibrosis

Fibrosis is defined as the abnormal and excessive deposition of extracellular matrix (ECM) components, which leads to tissue or organ dysfunction and failure. However, the pathological mechanisms underlying fibrosis remain unclear. The inflammatory response induced by tissue injury is closely associated with tissue fibrosis. Recently, an increasing number of studies have linked necroptosis to inflammation and fibrosis. Necroptosis is a type of preprogrammed death caused by death receptors, interferons, Toll-like receptors, intracellular RNA and DNA sensors, and other mediators. These activate receptor-interacting protein kinase (RIPK) 1, which recruits and phosphorylates RIPK3. RIPK3 then phosphorylates a mixed lineage kinase domain-like protein and causes its oligomerization, leading to rapid plasma membrane permeabilization, the release of cellular contents, and exposure of damage-associated molecular patterns (DAMPs). DAMPs, as inflammatory mediators, are involved in the loss of balance between extensive inflammation and tissue regeneration, leading to remodeling, the hallmark of fibrosis. In this review, we discuss the role of necroptotic DAMPs in tissue fibrosis and highlight the inflammatory responses induced by DAMPs in tissue ECM remodeling. By summarizing the existing literature on this topic, we underscore the gaps in the current research, providing a framework for future investigations into the relationship among necroptosis, DAMPs, and fibrosis, as well as a reference for later transformation into clinical treatment.

Spatially resolved deconvolution of the fibrotic niche in lung fibrosis

A defining pathological feature of human lung fibrosis is localized tissue heterogeneity, which challenges the interpretation of transcriptomic studies that typically lose spatial information. Here we investigate spatial gene expression in diagnostic tissue using digital profiling technology. We identify distinct, region-specific gene expression signatures as well as shared gene signatures. By integration with single-cell data, we spatially map the cellular composition within and distant from the fibrotic niche, demonstrating discrete changes in homeostatic and pathologic cell populations even in morphologically preserved lung, while through ligand-receptor analysis, we investigate cellular cross-talk within the fibrotic niche. We confirm findings through bioinformatic, tissue, and in vitro analyses, identifying that loss of NFKB inhibitor zeta in alveolar epithelial cells dysregulates the TGFβ/IL-6 signaling axis, which may impair homeostatic responses to environmental stress. Thus, spatially resolved deconvolution advances understanding of cell composition and microenvironment in human lung fibrogenesis.

Intestinal Osteopontin Protects From Alcohol-induced Liver Injury by Preserving the Gut Microbiome and the Intestinal Barrier Function

BACKGROUND & AIMS

The gut-liver axis plays a key role in the pathogenesis of alcohol-associated liver disease (ALD). We demonstrated that Opn^-/- develop worse ALD than wild-type (WT) mice; however, the role of intestinal osteopontin (OPN) in ALD remains unknown. We hypothesized that overexpression of OPN in intestinal epithelial cells (IECs) could ameliorate ALD by preserving the gut microbiome and the intestinal barrier function.

METHODS

Opn^{KI IEC}, Opn^ΔIEC, and WT mice were fed control or ethanol Lieber-DeCarli diet for 6 weeks.

RESULTS

Opn^{KI IEC} but not Opn^ΔIEC mice showed improved intestinal barrier function and protection from ALD. There were less pathogenic and more beneficial bacteria in ethanol-fed Opn^{KI IEC} than in WT mice. Fecal microbiome transplant (FMT) from Opn^{KI IEC} to WT mice protected from ALD. FMT from ethanol-fed WT to Opn^{KI IEC} mice failed to induce ALD. Antimicrobial peptides, Il33, pSTAT3, aryl hydrocarbon receptor (Ahr), and tight-junction protein expression were higher in IECs from jejunum of ethanol-fed Opn^{KI IEC} than of WT mice. Ethanol-fed Opn^{KI IEC} showed more tryptophan metabolites and short-chain fatty acids in portal serum than WT mice. FMT from Opn^{KI IEC} to WT mice enhanced IECs Ahr and tight-junction protein expression. Oral administration of milk OPN replicated the protective effect of Opn^{KI IEC} mice in ALD.

CONCLUSION

Overexpression of OPN in IECs or administration of milk OPN maintain the intestinal microbiome by intestinal antimicrobial peptides. The increase in tryptophan metabolites and short-chain fatty acids signaling through the Ahr in IECs, preserve the intestinal barrier function and protect from ALD.

Fibrogenic Pathways in Metabolic Dysfunction Associated Fatty Liver Disease (MAFLD)

The prevalence of nonalcoholic fatty liver disease (NAFLD), recently also re-defined as metabolic dysfunction associated fatty liver disease (MAFLD), is rapidly increasing, affecting ~25% of the world population. MALFD/NAFLD represents a spectrum of liver pathologies including the more benign hepatic steatosis and the more advanced non-alcoholic steatohepatitis (NASH). NASH is associated with enhanced risk for liver fibrosis and progression to cirrhosis and hepatocellular carcinoma. Hepatic stellate cells (HSC) activation underlies NASH-related fibrosis. Here, we discuss the profibrogenic pathways, which lead to HSC activation and fibrogenesis, with a particular focus on the intercellular hepatocyte–HSC and macrophage–HSC crosstalk.

Reprogramming of Hepatic Metabolism and Microenvironment in Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease (NAFLD), a spectrum of metabolic liver disease associated with obesity, ranges from relatively benign hepatic steatosis to nonalcoholic steatohepatitis (NASH). The latter is characterized by persistent liver injury, inflammation, and liver fibrosis, which collectively increase the risk for end-stage liver diseases such as cirrhosis and hepatocellular carcinoma. Recent work has shed new light on the pathophysiology of NAFLD/NASH, particularly the role of genetic, epigenetic, and dietary factors and metabolic dysfunctions in other tissues in driving excess hepatic fat accumulation and liver injury. In parallel, single-cell RNA sequencing studies have revealed unprecedented details of the molecular nature of liver cell heterogeneity, intrahepatic cross talk, and disease-associated reprogramming of the liver immune and stromal vascular microenvironment. This review covers the recent advances in these areas, the emerging concepts of NASH pathogenesis, and potential new therapeutic opportunities. Expected final online publication date for the Annual Review of Nutrition, Volume 42 is August 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Pathophysiological mechanisms of hepatic stellate cells activation in liver fibrosis

Liver fibrosis is a complex pathological process controlled by a variety of cells, mediators and signaling pathways. Hepatic stellate cells play a central role in the development of liver fibrosis. In chronic liver disease, hepatic stellate cells undergo dramatic phenotypic activation and acquire fibrogenic properties. This review focuses on the pathophysiological mechanisms of hepatic stellate cells activation in liver fibrosis. They enter the cell cycle under the influence of various triggers. The "Initiation" phase of hepatic stellate cells activation overlaps and continues with the "Perpetuation" phase, which is characterized by a pronounced inflammatory and fibrogenic reaction. This is followed by a resolution phase if the injury subsides. Knowledge of these pathophysiological mechanisms paved the way for drugs aimed at preventing the development and progression of liver fibrosis. In this respect, impairments in intracellular signaling, epigenetic changes and cellular stress response can be the targets of therapy where the goal is to deactivate hepatic stellate cells. Potential antifibrotic therapy may focus on inducing hepatic stellate cells to return to an inactive state through cellular aging, apoptosis, and/or clearance by immune cells, and serve as potential antifibrotic therapy. It is especially important to prevent the formation of liver cirrhosis since the only radical approach to its treatment is liver transplantation which can be performed in only a limited number of countries.

The Annexin A2-Notch regulatory loop in hepatocytes promotes liver fibrosis in NAFLD by increasing osteopontin expression

BACKGROUND

The mechanisms underlying the progression of liver disease from simple hepatic steatosis to advanced nonalcoholic steatohepatitis (NASH) and liver fibrosis warrant further investigation. Increased mRNA levels of Annexin A2 protein (Anxa2) have been observed in patients with NASH. However, the role of Anxa2 in NASH remains unclear.

METHODS

The protein levels of Anxa2 were analyzed in the livers of mice and patients with NASH. Anxa2-knockout and -knockdown mice were generated, and NASH was induced through a high fructose, palmitate, and cholesterol (FPC) diet or methionine- and choline-deficient (MCD) diet.

FINDINGS

We found elevated expression of Anxa2 in the livers of patients and mice with NASH. Anxa2 knockdown but not knockout ameliorated liver fibrosis in both FPC and MCD diet-fed mice. Liver-specific Anxa2 overexpression increased collagen deposition in mice fed a normal diet. Mechanistically, Anxa2 overexpression in hepatocytes promoted hepatic stellate cell activation in a paracrine manner by increasing osteopontin expression. Notch inhibition suppressed the exogenous overexpression of Anxa2-induced osteopontin and endogenous Anxa2 expression. Additionally, Anxa2 overexpression accelerated the progression of nonalcoholic fatty liver disease (NAFLD) in mice fed a high-fat diet. Moreover, Anxa2 levels were higher in NAFLD patients with advanced liver fibrosis than in those with mild liver fibrosis, as determined using the Gene Expression Omnibus database.

INTERPRETATION

In conclusion, we found increased Anxa2 expression in hepatocytes promoted liver fibrosis in NASH mice by increasing osteopontin expression. The Anxa2-Notch positive regulatory loop contributes to this process and represents a novel target for the treatment of NASH-related liver fibrosis.

From Inflammation to Fibrosis: Novel Insights into the Roles of High Mobility Group Protein Box 1 in Schistosome-Induced Liver Damage

Schistosomiasis is a chronic helminthic disease of both humans and animals and the second most prevalent parasitic disease after malaria. Through a complex migration process, schistosome eggs trapped in the liver can lead to the formation of granulomas and subsequent schistosome-induced liver damage, which results in high mortality and morbidity. Although praziquantel can eliminate mature worms and prevent egg deposition, effective drugs to reverse schistosome-induced liver damage are scarce. High mobility group box 1 (HMGB1) is a multifunctional cytokine contributing to liver injury, inflammation, and immune responses in schistosomiasis by binding to cell-surface Toll-like receptors and receptors for advanced glycation end products. HMGB1 is increased in the serum of patients with schistosomiasis and enables hepatic stellate cells to adopt a proliferative myofibroblast-like phenotype, which is crucial to schistosome-induced granuloma formation. Inhibition of HMGB1 was found to generate protective responses against fibrotic diseases in animal models. Clinically, HMGB1 presents a potential target for treatment of the chronic sequelae of schistosomiasis. Here, the pivotal role of HMGB1 in granuloma formation and schistosome-induced liver damage, as well the potential of HMGB1 as a therapeutic target, are discussed.

Immunomodulatory Effect of Lycium barbarum Polysaccharides against Liver Fibrosis Based on the Intelligent Medical Internet of Things

Lycium barbarum polysaccharide (LBP) is the main active component of Lycium barbarum and has many beneficial effects, including neuroprotection, antiaging, and antioxidation. This study mainly explores the immunomodulatory effect of Lycium barbarum polysaccharides against liver fibrosis based on the intelligent medical Internet of Things. This measure emphasizes that the current effective methods and methods for the treatment of liver cancer are mainly combined treatments of Western medicine and Chinese medicine. These treatments have a certain effect in preventing liver cancer, reducing recurrence, and reducing side effects. Among them, chemotherapy has unique advantages in improving the quality of life and prolonging survival. With the development of medical science and technology, the clinical efficacy and efficacy of traditional Chinese medicine in the treatment of liver cancer are constantly improving. The mechanism is also studied from many aspects. The treatment time of LBPs on fibrotic hepatocytes was set to 24 h. Take liver fiber cells in logarithmic growth phase and incubate them at 37°C for 24 h. The whole process uses a temperature sensor for intelligent temperature control. In the experiment, groups of LBPs with different concentrations and different molecular weight ranges were set up and each group had 6 multiple holes. The original medium was aspirated and replaced with a medium containing different concentrations of LBPs (12.5, 25, 50, 100, and 200 μg/mL) and cultured for 24 h. Based on the previous research, this study used in vitro cell experiments, microscopic observation, and MTT method to verify whether Lycium barbarum polysaccharides inhibit the proliferation of human liver cancer cells in vitro and whether they cooperate with the chemotherapy drug fluorouracil to play a tumor-killing effect. Animal experiments, using ELISA, HE staining, and other methods, explore the molecular and immunological mechanisms of LBP's antiliver cancer effect from the perspective of Th/Th2 differentiation balance and DC function, in order to provide experimental evidence for Chinese medicine polysaccharides in cancer immunotherapy and application. At different LBP concentrations (0 μmol/L, 5 μmol/L, 10 μmol/L, and 15 μmol/L), the inhibition rates were 0.80%, 20.06%, 35.44%, and 55.39%, respectively. This study provides a new method for large-scale expansion of hepatocytes in vitro, laying a stronger foundation for biological treatment of liver fibrosis.

The Integrated "Multiomics" Landscape at Peak Injury and Resolution From Alcohol-Associated Liver Disease

Alcohol-associated liver disease (ALD) is a significant clinical problem for which the most effective therapy is alcohol abstinence. The two aims of this study were, first, to identify the liver transcriptome, fecal microbiome, and portal serum metabolome at peak injury and during early and late resolution from ALD; and second, to integrate their interactions and understand better the pathogenesis of ALD. To provoke alcohol-induced liver injury, female and male wild-type mice were fed the control or ethanol Lieber-DeCarli diets for 6 weeks. To study early and late resolution, alcohol was withdrawn from the diet and mice were sacrificed after 3 and 14 days, respectively. At peak injury, there was increased signal transducer and activator of transcription (Stat3), Rho-GTPases, Tec kinase and glycoprotein VI (Gp6), and decreased peroxisome proliferator-activated receptor signaling. During resolution from ALD, there was up-regulation of vitamin D receptor/retinoid X receptor, toll-like receptor, p38 and Stat3, and down-regulation of liver X receptor signaling. Females showed significant changes in catabolic pathways, whereas males increased cellular stress, injury, and immune-response pathways that decreased during resolution. The bacterial genus Alistipes and the metabolite dipeptide glycyl-L-leucine increased at peak but decreased during resolution from ALD in both genders. Hepatic induction of mitogen-activated protein kinase (Map3k1) correlated with changes in the microbiome and metabolome at peak but was restored during ALD resolution. Inhibition of MAP3K1 protected from ALD in mice. Conclusion: Alcohol abstinence restores the liver transcriptome, fecal microbiome, and portal serum metabolome in a gender-specific manner. Integration of multiomics data identified Map3k1 as a key gene driving pathogenesis and resolution from ALD.

Hepatic Stellate Cell-Immune Interactions in NASH

Nonalcoholic fatty liver disease (NAFLD) is the dominant cause of liver disease worldwide. Nonalcoholic steatohepatitis (NASH), a more aggressive presentation of NAFLD, is characterized by severe hepatocellular injury, inflammation, and fibrosis. Chronic inflammation and heightened immune cell activity have emerged as hallmark features of NASH and key drivers of fibrosis through the activation of hepatic stellate cells (HSCs). Recent advances in our understanding of the molecular and cellular pathways in NASH have highlighted extensive crosstalk between HSCs and hepatic immune populations that strongly influences disease activity. Here, we review these findings, emphasizing the roles of HSCs in liver immunity and inflammation, key cell-cell interactions, and exciting areas for future investigation.

Intestine-liver crosstalk in Type 2 Diabetes and non-alcoholic fatty liver disease

Type 2 diabetes (T2D) and Non-Alcoholic Fatty Liver Disease (NAFLD) are pathologies whose prevalence continues to increase worldwide. Both diseases are precipitated by an excessive caloric intake, which promotes insulin resistance and fatty liver. The role of the intestine and its crosstalk with the liver in the development of these metabolic diseases is receiving increasing attention. Alterations in diet-intestinal microbiota interactions lead to the dysregulation of intestinal functions, resulting in altered metabolite and energy substrate production and increased intestinal permeability. Connected through the portal circulation, these changes in intestinal functions impact the liver and other metabolic organs, such as visceral adipose tissue, hence participating in the development of insulin resistance, and worsening T2D and NAFLD. Thus, targeting the intestine may be an efficient therapeutic approach to cure T2D and NAFLD. In this review, we will first introduce the signaling pathways linking T2D and NAFLD. Next, we will address the role of the gut-liver crosstalk in the development of T2D and NAFLD, with a particular focus on the gut microbiota and the molecular pathways behind the increased intestinal permeability and inflammation. Finally, we will summarize the therapeutic strategies which target the gut and its functions and are currently used or under development to treat T2D and NAFLD.

Liver-fibrosis-activated transcriptional networks govern hepatocyte reprogramming and intra-hepatic communication

Liver fibrosis is a strong predictor of long-term mortality in individuals with metabolic-associated fatty liver disease; yet, the mechanisms underlying the progression from the comparatively benign fatty liver state to advanced non-alcoholic steatohepatitis (NASH) and liver fibrosis are incompletely understood. Using cell-type-resolved genomics, we show that comprehensive alterations in hepatocyte genomic and transcriptional settings during NASH progression, led to a loss of hepatocyte identity. The hepatocyte reprogramming was under tight cooperative control of a network of fibrosis-activated transcription factors, as exemplified by the transcription factor Elf-3 (ELF3) and zinc finger protein GLIS2 (GLIS2). Indeed, ELF3- and GLIS2-controlled fibrosis-dependent hepatokine genes targeting disease-associated hepatic stellate cell gene programs. Thus, interconnected transcription factor networks not only promoted hepatocyte dysfunction but also directed the intra-hepatic crosstalk necessary for NASH and fibrosis progression, implying that molecular "hub-centered" targeting strategies are superior to existing mono-target approaches as currently used in NASH therapy.

Osteopontin silencing attenuates bleomycin-induced murine pulmonary fibrosis by regulating epithelial-mesenchymal transition

Idiopathic pulmonary fibrosis (IPF) is the most common and most deadly form of interstitial lung disease. Osteopontin (OPN), a matricellular protein with proinflammatory and profibrotic properties, plays a major role in several fibrotic diseases, including IPF; OPN is highly upregulated in patients' lung samples. In this study, we knocked down OPN in a bleomycin (BLM)-induced pulmonary fibrosis (PF) mouse model using small interfering RNA (siRNA) to determine whether the use of OPN siRNA is an effective therapeutic strategy for IPF. We found that fibrosing areas were significantly smaller in specimens from OPN siRNA-treated mice. The number of alveolar macrophages, neutrophils, and lymphocytes in bronchoalveolar lavage fluid was also reduced in OPN siRNA-treated mice. Regarding the expression of epithelial-mesenchymal transition (EMT)-related proteins, the administration of OPN-siRNA to BLM-treated mice upregulated E-cadherin expression and downregulated vimentin expression. Moreover, in vitro, we incubated the human alveolar adenocarcinoma cell line A549 with transforming growth factor (TGF)-β1 and subsequently transfected the cells with OPN siRNA. We found a significant upregulation of Col1A1, fibronectin, and vimentin after TGF-β1 stimulation in A549 cells. In contrast, a downregulation of Col1A1, fibronectin, and vimentin mRNA levels was observed in TGF-β1-stimulated OPN knockdown A549 cells. Therefore, the downregulation of OPN effectively reduced pulmonary fibrotic and EMT changes both in vitro and in vivo. Altogether, our results indicate that OPN siRNA exerts a protective effect on BLM-induced PF in mice. Our results provide a basis for the development of novel targeted therapeutic strategies for IPF.