Hepatocyte mitochondria-derived danger signals directly activate hepatic stellate cells and drive progression of liver fibrosis

TREM2 protects against inflammation by regulating the release of mito-DAMPs from hepatocytes during liver fibrosis

BACKGROUND

Liver fibrosis typically develops as a result of chronic liver injury, which involves inflammatory and regenerative processes. The triggering receptor expressed on myeloid cells 2 (TREM2), predominantly expressing in hepatic non-parenchymal cells, plays a crucial role in regulating the function of macrophages. However, its mechanism in liver fibrosis remains poorly defined.

METHODS

Experimental liver fibrosis models in wild type and TREM2-/- mice, and in vitro studies with AML-12 cells and Raw264.7 cells were conducted. The expression of TREM2 and related molecular mechanism were evaluated by using samples from patients with liver fibrosis.

RESULTS

We demonstrated that TREM2 was upregulated in murine model with liver fibrosis. Mice lacking TREM2 exhibited reduced phagocytosis activity in macrophages following carbon tetrachloride (CCl4) intoxication. As a result, there was an increased accumulation of necrotic apoptotic hepatocytes. Additionally, TREM2 knockout aggravated the release of mitochondrial damage-associated molecular patterns (mito-DAMPs) from dead hepatocytes during CCl4 exposure, and further promoted the occurrence of macrophage-mediated M1 polarization. Then, TREM2-/- mice showed more serious fibrosis pathological changes. In vitro, the necrotic apoptosis inhibitor GSK872 effectively alleviated the release of mito-DAMPs in AML-12 cells after CCl4 intoxication, which confirmed that mito-DAMPs originated from dead liver cells. Moreover, direct stimulation of Raw264.7 cells by mito-DAMPs from liver tissue can induce intracellular inflammatory response. More importantly, TREM2 was elevated and inflammatory factors were markedly accumulated surrounding dead cells in the livers of human patients with liver fibrosis.

CONCLUSION

Our study highlights that TREM2 serves as a negative regulator of liver fibrosis, suggesting its potential as a novel therapeutic target.

Ba-Qi-Rougan formula alleviates hepatic fibrosis by suppressing hepatic stellate cell activation via the MSMP/CCR2/PI3K pathway

ETHNOPHARMACOLOGICAL RELEVANCE

The Ba-Qi-Rougan formula (BQRGF) is a traditional and effective compound prescription from Traditional Chinese Medicine (TCM) utilized in treating hepatic fibrosis (HF).

AIM OF THE STUDY

We aimed to evaluate the therapeutic efficacy of BQRGF on HF and explore the underlying mechanisms of action.

MATERIALS AND METHODS

UPLC-Q-TOF-MS technology was employed to identify the material basis of BQRGF. Mice with carbon tetrachloride (CCl4)-induced HF received BQRGF at three doses (3.87, 7.74, and 15.48 g/kg per day). We examined serum and liver biochemical indicators and liver histology to assess the therapeutic impact. Primary mouse cells were isolated and utilized for experimental analysis. MSMP expression levels were examined in vitro and in vivo experimental models, including human and mouse tissue. Furthermore, lentivirus and small interfering RNA (siRNA) transfections were employed to manipulate microseminoprotein (MSMP) expression in LO2 cells (human normal liver cells). These manipulated LO2 cells were then co-cultured with LX2 human hepatic stellate cells (HSCs). Through the modulation of MSMP expression in co-cultured cells, administering recombinant MSMP (rMSMP) with or without BQRGF-medicated serum, and using specific pathway inhibitors or agonists in LX2 cells, we elucidated the underlying mechanisms.

RESULTS

A total of 48 compounds were identified from BQRGF, with 12 compounds being absorbed into the bloodstream and 9 compounds being absorbed into the liver. Four weeks of BQRGF treatment in the HF mouse model led to significant improvements in biochemical and molecular assays and histopathology, particularly in the medium and high-dose groups. These improvements included a reduction in the level of liver injury and fibrosis-related factors. MSMP levels were elevated in human and mouse fibrotic liver tissues, and this increase was mitigated in HF mice treated with BQRGF. Moreover, primary cells and co-culture studies revealed that BQRGF reduced MSMP expression, decreased the expression of the hepatic stellate cell (HSC) activation markers, and suppressed critical phosphorylated protein levels in the CCR2/PI3K/AKT pathway. These findings were further validated using CCR2/PI3K/AKT signaling inhibitors and agonists in MSMP-activated LX2 cells.

CONCLUSIONS

Collectively, our results suggest that BQRGF combats HF by diminishing MSMP levels and inhibiting MSMP-induced HSC activation through the CCR2/PI3K/AKT pathway.

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.

Stiffness sensing via Piezo1 enhances macrophage efferocytosis and promotes the resolution of liver fibrosis

Tissue stiffening is a predominant feature of fibrotic disorders, but the response of macrophages to changes in tissue stiffness and cellular context in fibrotic diseases remains unclear. Here, we found that the mechanosensitive ion channel Piezo1 was up-regulated in hepatic fibrosis. Macrophages lacking Piezo1 showed sustained inflammation and impaired spontaneous resolution of early liver fibrosis. Further analysis revealed an impairment of clearance of apoptotic cells by macrophages in the fibrotic liver. Macrophages showed enhanced efferocytosis when cultured on rigid substrates but not soft ones, suggesting stiffness-dependent efferocytosis of macrophages required Piezo1 activation. Besides, Piezo1 was involved in the efficient acidification of the engulfed cargo in the phagolysosomes and affected the subsequent expression of anti-inflammation genes after efferocytosis. Pharmacological activation of Piezo1 increased the efferocytosis capacity of macrophages and accelerated the resolution of inflammation and fibrosis. Our study supports the antifibrotic role of Piezo1-mediated mechanical sensation in liver fibrosis, suggesting that targeting PIEZO1 to enhance macrophage efferocytosis could induce fibrosis regression.

Mitophagy in relation to chronic inflammation/ROS in aging

Various assaults on mitochondria occur during the human aging process, contributing to mitochondrial dysfunction. This mitochondrial dysfunction is intricately connected with aging and diseases associated with it. In vivo, the accumulation of defective mitochondria can precipitate inflammatory and oxidative stress, thereby accelerating aging. Mitophagy, an essential selective autophagy process, plays a crucial role in managing mitochondrial quality control and homeostasis. It is a highly specialized mechanism that systematically removes damaged or impaired mitochondria from cells, ensuring their optimal functioning and survival. By engaging in mitophagy, cells are able to maintain a balanced and stable environment, free from the potentially harmful effects of dysfunctional mitochondria. An ever-growing body of research highlights the significance of mitophagy in both aging and age-related diseases. Nonetheless, the association between mitophagy and inflammation or oxidative stress induced by mitochondrial dysfunction remains ambiguous. We review the fundamental mechanisms of mitophagy in this paper, delve into its relationship with age-related stress, and propose suggestions for future research directions.

Metabolism and bioenergetics in the pathophysiology of organ fibrosis

Fibrosis is the tissue scarring characterized by excess deposition of extracellular matrix (ECM) proteins, mainly collagens. A fibrotic response can take place in any tissue of the body and is the result of an imbalanced reaction to inflammation and wound healing. Metabolism has emerged as a major driver of fibrotic diseases. While glycolytic shifts appear to be a key metabolic switch in activated stromal ECM-producing cells, several other cell types such as immune cells, whose functions are intricately connected to their metabolic characteristics, form a complex network of pro-fibrotic cellular crosstalk. This review purports to clarify shared and particular cellular responses and mechanisms across organs and etiologies. We discuss the impact of the cell-type specific metabolic reprogramming in fibrotic diseases in both experimental and human pathology settings, providing a rationale for new therapeutic interventions based on metabolism-targeted antifibrotic agents.

Role of pattern recognition receptors in the development of MASLD and potential therapeutic applications

Metabolic dysfunction-associated steatotic liver disease (MASLD) has become one of the most prevalent liver diseases worldwide, and its occurrence is strongly associated with obesity, insulin resistance (IR), genetics, and metabolic stress. Ranging from simple fatty liver to metabolic dysfunction-associated steatohepatitis (MASH), even to severe complications such as liver fibrosis and advanced cirrhosis or hepatocellular carcinoma, the underlying mechanisms of MASLD progression are complex and involve multiple cellular mediators and related signaling pathways. Pattern recognition receptors (PRRs) from the innate immune system, including Toll-like receptors (TLRs), C-type lectin receptors (CLRs), NOD-like receptors (NLRs), RIG-like receptors (RLRs), and DNA receptors, have been demonstrated to potentially contribute to the pathogenesis for MASLD. Their signaling pathways can induce inflammation, mediate oxidative stress, and affect the gut microbiota balance, ultimately resulting in hepatic steatosis, inflammatory injury and fibrosis. Here we review the available literature regarding the involvement of PRR-associated signals in the pathogenic and clinical features of MASLD, in vitro and in animal models of MASLD. We also discuss the emerging targets from PRRs for drug developments that involved agent therapies intended to arrest or reverse disease progression, thus enabling the refinement of therapeutic targets that can accelerate drug development.

Forsythiaside-A improved bile-duct-ligation-induced liver fibrosis in mice: The involvement of alleviating mitochondrial damage and ferroptosis in hepatocytes via activating Nrf2

Liver fibrosis is a key and reversible stage in the progression of many chronic liver diseases to cirrhosis or hepatocellular carcinoma. Forsythiaside-A (FTA), a main compound isolated from Forsythiae Fructus, has an excellent liver protective activity. This study aims to investigate the efficacy of FTA in improving cholestatic liver fibrosis. Bile-duct-ligation (BDL) was conducted to induce liver fibrosis in mice. Hepatic collagen deposition was evaluated by Masson and Sirus red staining. The bile acid spectrum in the liver and serum was analyzed by mass spectrometry. Liver oxidative stress injury and mitochondria damage were observed by using Mito-Tracker Red fluorescence staining, transmission electron microscopy, etc. The level of ferrous iron (Fe2+) and the expression of ferroptosis-associated molecules were detected. The binding between FTA and its target protein was confirmed by Co-immunoprecipitation (Co-IP), cellular thermal shift assay (CETSA), drug affinity responsive target stability (DARTS) and surface plasmon resonance (SPR). Our results demonstrated that FTA alleviated BDL-induced liver fibrosis in mice. FTA did not decrease the elevated amount of bile acids in BDL-treated mice, but reduced the bile acid-induced mitochondrial damage, oxidative stress and ferroptosis in hepatocytes, and also induced nuclear factor erythroid 2-related factor-2 (Nrf2) activation. In Nrf2 knock-out mice, the FTA-provided protection against BDL-induced liver fibrosis was disappeared, and FTA's inhibition on mitochondrial damage, oxidative stress and ferroptosis were lowered. Further results displayed that FTA could directly bind to Kelch-like ECH-associated protein-1 (Keap1), thereby activating Nrf2. Moreover, the BDL-induced liver fibrosis was markedly weakened in liver-specific Keap1 knockout mice. Hence, this study suggests that FTA alleviated the BDL-induced liver fibrosis through attenuating mitochondrial damage and ferroptosis in hepatocytes by activating Nrf2 via directly binding to Keap1.

From NAFLD to NASH: Understanding the spectrum of non-alcoholic liver diseases and their consequences

Non-alcoholic fatty liver disease (NAFLD) has become one of the most frequent chronic liver diseases worldwide in recent decades. Metabolic diseases like excessive blood glucose, central obesity, dyslipidemia, hypertension, and liver function abnormalities cause NAFLD. NAFLD significantly increases the likelihood of liver cancer, heart disease, and mortality, making it a leading cause of liver transplants. Non-alcoholic steatohepatitis (NASH) is a more advanced form of the disease that causes scarring and inflammation of the liver over time and can ultimately result in cirrhosis and hepatocellular carcinoma. In this review, we briefly discuss NAFLD's pathogenic mechanisms, their progression into NASH and afterward to NASH-related cirrhosis. It also covers disease epidemiology, metabolic mechanisms, glucose and lipid metabolism in the liver, macrophage dysfunction, bile acid toxicity, and liver stellate cell stimulation. Additionally, we consider the contribution of intestinal microbiota, genetics, epigenetics, and ecological factors to fibrosis progression and hepatocellular carcinoma risk in NAFLD and NASH patients.

Can Nutraceuticals Support the Treatment of MASLD/MASH, and thus Affect the Process of Liver Fibrosis?

Currently, metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH) are considered to be the main causes of fibrosis. In turn, fibrosis may lead to the development of hepatocellular carcinoma or advanced cirrhosis, i.e., potentially life-threatening conditions. It is likely that therapy aimed at reducing the risk of developing hepatic steatosis and inflammation could be helpful in minimizing the threat/probability of organ fibrosis. In recent years, increasing attention has been paid to the influence of nutraceuticals in the prevention and treatment of liver diseases. Therefore, the aim of this review was to describe the precise role of selected ingredients such as vitamin C, beta-carotene, omega-3 fatty acids, and curcumin. It is likely that the use of these ingredients in the treatment of patients with MASLD/MASH, along with behavioral and pharmacological therapy, may have a beneficial effect on combating inflammation, reducing oxidative stress, and thereby preventing liver damage.

Emerging role of immunogenic cell death in cancer immunotherapy

Cancer immunotherapy, such as immune checkpoint blockade (ICB), has emerged as a groundbreaking approach for effective cancer treatment. Despite its considerable potential, clinical studies have indicated that the current response rate to cancer immunotherapy is suboptimal, primarily attributed to low immunogenicity in certain types of malignant tumors. Immunogenic cell death (ICD) represents a form of regulated cell death (RCD) capable of enhancing tumor immunogenicity and activating tumor-specific innate and adaptive immune responses in immunocompetent hosts. Therefore, gaining a deeper understanding of ICD and its evolution is crucial for developing more effective cancer therapeutic strategies. This review focuses exclusively on both historical and recent discoveries related to ICD modes and their mechanistic insights, particularly within the context of cancer immunotherapy. Our recent findings are also highlighted, revealing a mode of ICD induction facilitated by atypical interferon (IFN)-stimulated genes (ISGs), including polo-like kinase 2 (PLK2), during hyperactive type I IFN signaling. The review concludes by discussing the therapeutic potential of ICD, with special attention to its relevance in both preclinical and clinical settings within the field of cancer immunotherapy.

Mitochondrial dysfunction: A promising therapeutic target for liver diseases

The liver is an important metabolic and detoxification organ and hence demands a large amount of energy, which is mainly produced by the mitochondria. Liver tissues of patients with alcohol-related or non-alcohol-related liver diseases contain ultrastructural mitochondrial lesions, mitochondrial DNA damage, disturbed mitochondrial dynamics, and compromised ATP production. Overproduction of mitochondrial reactive oxygen species induces oxidative damage to mitochondrial proteins and mitochondrial DNA, decreases mitochondrial membrane potential, triggers hepatocyte inflammation, and promotes programmed cell death, all of which impair liver function. Mitochondrial DNA may be a potential novel non-invasive biomarker of the risk of progression to liver cirrhosis and hepatocellular carcinoma in patients infected with the hepatitis B virus. We herein present a review of the mechanisms of mitochondrial dysfunction in the development of acute liver injury and chronic liver diseases, such as hepatocellular carcinoma, viral hepatitis, drug-induced liver injury, alcoholic liver disease, and non-alcoholic fatty liver disease. This review also discusses mitochondrion-centric therapies for treating liver diseases.

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

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

Mitochondrial DNA levels in perfusate and bile during ex vivo normothermic machine correspond with donor liver quality

Ex vivo normothermic machine perfusion (NMP) preserves donor organs and permits real-time assessment of allograft health, but the most effective indicators of graft viability are uncertain. Mitochondrial DNA (mtDNA), released consequent to traumatic cell injury and death, including the ischemia-reperfusion injury inherent in transplantation, may meet the need for a biomarker in this context. We describe a real time PCR-based approach to assess cell-free mtDNA during NMP as a universal biomarker of allograft quality. Measured in the perfusate fluid of 29 livers, the quantity of mtDNA correlated with metrics of donor liver health including International Normalized Ratio (INR), lactate, and warm ischemia time, and inversely correlated with inferior vena cava (IVC) flow during perfusion. Our findings endorse mtDNA as a simple and rapidly measured feature that can inform donor liver health, opening the possibility to better assess livers acquired from extended criteria donors to improve organ supply.

Hepatic danger signaling triggers TREM2+ macrophage induction and drives steatohepatitis via MS4A7-dependent inflammasome activation

Metabolic dysfunction-associated steatohepatitis (MASH), formerly known as nonalcoholic steatohepatitis (NASH), is an advanced stage of metabolic fatty liver disease. The pathogenic mechanisms of MASH center on hepatocyte injury and the ensuing immune response within the liver microenvironment. Recent work has implicated TREM2+ macrophages in various disease conditions, and substantial induction of TREM2+ NASH-associated macrophages (NAMs) serves as a hallmark of metabolic liver disease. Despite this, the mechanisms through which NAMs contribute to MASH pathogenesis remain poorly understood. Here, we identify membrane-spanning 4-domains a7 (MS4A7) as a NAM-specific pathogenic factor that exacerbates MASH progression in mice. Hepatic MS4A7 expression was strongly induced in mouse and human MASH and associated with the severity of liver injury. Whole-body and myeloid-specific ablation of Ms4a7 alleviated diet-induced MASH pathologies in male mice. We demonstrate that exposure to lipid droplets (LDs), released upon injury of steatotic hepatocytes, triggered NAM induction and exacerbated MASH-associated liver injury in an MS4A7-dependent manner. Mechanistically, MS4A7 drove NLRP3 inflammasome activation via direct physical interaction and shaped disease-associated cell states within the liver microenvironment. This work reveals the LD-MS4A7-NLRP3 inflammasome axis as a pathogenic driver of MASH progression and provides insights into the role of TREM2+ macrophages in disease pathogenesis.

A novel network pharmacology strategy to decode mechanism of Wuling Powder in treating liver cirrhosis

BACKGROUND

Liver cirrhosis is a chronic liver disease with hepatocyte necrosis and lesion. As one of the TCM formulas Wuling Powder (WLP) is widely used in the treatment of liver cirrhosis. However, it's key functional components and action mechanism still remain unclear. We attempted to explore the Key Group of Effective Components (KGEC) of WLP in the treatment of Liver cirrhosis through integrative pharmacology combined with experiments.

METHODS

The components and potential target genes of WLP were extracted from published databases. A novel node importance calculation model considering both node control force and node bridging force is designed to construct the Function Response Space (FRS) and obtain key effector proteins. The genetic knapsack algorithm was employed to select KGEC. The effectiveness and reliability of KGEC were evaluated at the functional level by using gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Finally, the effectiveness and potential mechanism of KGEC were confirmed by CCK-8, qPCR and Western blot.

RESULTS

940 effective proteins were obtained in FRS. KEGG pathways and GO terms enrichments analysis suggested that effective proteins well reflect liver cirrhosis characteristics at the functional level. 29 components of WLP were defined as KGEC, which covered 100% of the targets of the effective proteins. Additionally, the pathways enriched for the KGEC targets accounted for 83.33% of the shared genes between the targets and the pathogenic genes enrichment pathways. Three components scopoletin, caryophyllene oxide, and hydroxyzinamic acid from KGEC were selected for in vivo verification. The qPCR results demonstrated that all three components significantly reduced the mRNA levels of COL1A1 in TGF-β1-induced liver cirrhosis model. Furthermore, the Western blot assay indicated that these components acted synergistically to target the NF-κB, AMPK/p38, cAMP, and PI3K/AKT pathways, thus inhibiting the progression of liver cirrhosis.

CONCLUSION

In summary, we have developed a new model that reveals the key components and potential mechanisms of WLP for the treatment of liver cirrhosis. This model provides a reference for the secondary development of WLP and offers a methodological strategy for studying TCM formulas.

Therapeutic potential and mechanisms of Rifaximin in ameliorating iron overload-induced ferroptosis and liver fibrosis in vivo and in vitro

Liver fibrosis could progress to liver cirrhosis with several contributing factors, one being iron overload which triggers ferroptosis, a form of regulated cell death. Rifaximin, a non-absorbable antibiotic, has shown promise in mitigating fibrosis, primarily by modulating gut microbiota. This study investigated the effects and mechanisms of rifaximin on iron overload-related hepatic fibrosis and ferroptosis. In an iron overload-induced liver fibrosis model in mice and in ferric ammonium citrate (FAC)-stimulated primary hepatocytes, treatment with rifaximin showed significant therapeutic effects. Specifically, it ameliorated the processes of ferroptosis triggered by iron overload, reduced liver injury, and alleviated fibrosis. This was demonstrated by decreased iron accumulation in the liver, improved liver function, and reduced fibrotic area and collagen deposition. Rifaximin also modulated key proteins related to iron homeostasis and ferroptosis, including reduced expression of TFR1, a protein facilitating cellular iron uptake, and increased expression of Fpn and FTH, proteins involved in iron export and storage. In the context of oxidative stress, rifaximin treatment led to a decrease in lipid peroxidation, evidenced by reduced levels of reactive oxygen species (ROS) and malondialdehyde (MDA), and an increase in the reduced glutathione (GSH) and decrease in oxidized glutathione (GSSG). Notably, rifaximin's potential functions were associated with the TGF-β pathway, evidenced by suppressed Tgfb1 protein levels and ratios of phosphorylated to total Smad2 and Smad3, whereas increased Smad7 phosphorylation. These findings indicate rifaximin's therapeutic potential in managing liver fibrosis by modulating the TGF-β pathway and reducing iron overload-induced damage. Further research is required to confirm these results and explore their clinical implications.

Mitochondrial quality control in liver fibrosis: Epigenetic hallmarks and therapeutic strategies

BACKGROUND AND AIM

Mitochondrial quality control (MQC) plays a significant role in the progression of liver fibrosis, with key processes such as mitochondrial fission, fusion, mitophagy and biogenesis maintaining mitochondrial homeostasis. To understand the molecular mechanisms underlying epigenetic regulation of mitochondrial quality control in liver fibrosis, with the aim of uncovering novel therapeutic targets for treating, mitigating, and potentially reversing liver fibrosis, in light of the most recent advances in this field.

METHODS

We searched PubMed, Web of Science, and Scopus for published manuscripts using terms "mitochondrial quality control" "mitochondrial fission" "mitochondrial fusion" "mitochondrial biogenesis" "mitophagy" "liver fibrosis" "epigenetic regulation" "DNA methylation" "RNA methylation" "histone modification" and "non-coding RNA". Manuscripts were collated, studied and carried forward for discussion where appropriate.

RESULTS

Mitochondrial fission, fusion, biogenesis, and mitophagy regulate the homeostasis of mitochondria, and the imbalance of mitochondrial homeostasis can induce liver fibrosis. Epigenetic regulation, including DNA methylation, RNA methylation, histone modifications, and non-coding RNAs, plays a significant role in regulating the processes of mitochondrial homeostasis.

CONCLUSION

Mitochondrial quality control and epigenetic mechanisms are intricately linked to the pathogenesis of liver fibrosis. Understanding these molecular interactions provides insight into potential therapeutic strategies. Further research is necessary to translate these findings into clinical applications, with a focus on developing epigenetic drugs to ameliorate liver fibrosis by modulating MQC and epigenetic pathways.

Multiscale transport and 4D time-lapse imaging in precision-cut liver slices (PCLS)

Background

Monitoring cellular processes across different levels of complexity, from the cellular to the tissue scale, is important for understanding tissue structure and function. However, it is challenging to monitor and estimate these structural and dynamic interactions within three-dimensional (3D) tissue models.

Objective

The aim of this study was to design a method for imaging, tracking, and quantifying 3D changes in cell morphology (shape and size) within liver tissue, specifically a precision-cut liver slice (PCLS). A PCLS is a 3D model of the liver that allows the study of the structure and function of liver cells in their native microenvironment.

Methods

Here, we present a method for imaging liver tissue during anisosmotic exposure in a multispectral four-dimensional manner. Three metrics of tissue morphology were measured to quantify the effects of osmotic stress on liver tissue. We estimated the changes in the volume of whole precision cut liver slices, quantified the changes in nuclei position, and calculated the changes in volumetric responses of tissue-embedded cells.

Results

During equilibration with cell-membrane-permeating and non-permeating solutes, the whole tissue experiences shrinkage and expansion. As nuclei showed a change in position and directional displacement under osmotic stress, we demonstrate that nuclei could be used as a probe to measure local osmotic and mechanical stress. Moreover, we demonstrate that cells change their volume within tissue slices as a result of osmotic perturbation and that this change in volume is dependent on the position of the cell within the tissue and the duration of the exposure.

Conclusion

The results of this study have implications for a better understanding of multiscale transport, mechanobiology, and triggered biological responses within complex biological structures.

ASK1/ p38 axis inhibition blocks the release of mitochondrial "danger signals" from hepatocytes and suppresses progression to cirrhosis and liver cancer

BACKGROUND AND AIMS

Apoptosis Signal-regulating Kinase 1 (ASK1) is activated by various pathological stimuli and induces cell apoptosis through downstream p38 activation. We studied the effect of pharmacological ASK1 inhibition on cirrhosis and its sequelae using comprehensive preclinical in vivo and in vitro systems.

APPROACH AND RESULTS

Short-term (4-6 wk) and long-term (24-44 wk) ASK1 inhibition using small molecule GS-444217 was tested in thioacetamide-induced and BALB/c. Mdr2-/- murine models of cirrhosis and HCC, and in vitro using primary hepatocyte cell death assays. Short-term GS-444217 therapy in both models strongly reduced phosphorylated p38, hepatocyte death, and fibrosis by up to 50%. Profibrogenic release of mitochondrial DAMP mitochondrial deoxyribonucleic acid from dying hepatocytes was blocked by ASK1 or p38 inhibition. Long-term (24 wk) therapy in BALBc.Mdr2 - / - model resulted in a moderate 25% reduction in bridging fibrosis, but not in net collagen deposition. Despite this, the development of cirrhosis was effectively prevented, with strongly reduced p21 + hepatocyte staining (by 72%), serum ammonia levels (by 46%), and portal pressure (average 6.07 vs. 8.53 mm Hg in controls). Extended ASK1 inhibition for 44 wk in aged BALB/c. Mdr2-/- mice resulted in markedly reduced tumor number and size by ~50% compared to the control group.

CONCLUSIONS

ASK1 inhibition suppresses the profibrogenic release of mitochondrial deoxyribonucleic acid from dying hepatocytes in a p38-dependent manner and protects from liver fibrosis. Long-term ASK1 targeting resulted in diminished net antifibrotic effect, but the progression to liver cirrhosis and cancer in BALBc/ Mdr2- / - mice was effectively inhibited. These data support the clinical evaluation of ASK1 inhibitors in fibrotic liver diseases.

Inhibiting Liver Autophagy and Promoting Hepatocyte Apoptosis by Schistosoma Japonicum Infection

We established a mouse model of Schistosoma japonicum infection in order to study the effects of the infection on hepatocyte autophagy and apoptosis. We also stimulated HepG2 cells with soluble egg antigens (SEA) in vitro. At two, four, and six weeks post-infection, quantitative real-time PCR and Western blot (WB) were used to detect liver expression levels of autophagy and apoptosis-related proteins. HepG2 cells were treated with different concentrations of SEA. The changes in the levels of autophagy-related proteins and HepG2 cell apoptosis were detected. The Lc3b, Beclin1, Atg7, and Atg12 mRNA levels were significantly lower at four and six weeks after infection than those in the uninfected group. At four and six weeks following infection, the levels of Beclin1, LC3BII/I, Atg7, and p62 proteins were considerably lower than those in the uninfected group. The protein levels of pro-apoptotic Bax and cleaved caspase 3 and fibrosis-related proteins α-SMA and collagen 3 in the liver post-infection were significantly higher than those in uninfected mice. HepG2 cells stimulated with SEA showed decreased levels of Beclin1, p62, and Atg7 proteins and significantly increased apoptosis rates. The findings demonstrated that following infection with S. japonicum, mice's liver fibrosis worsened, hepatic autophagy was suppressed, and hepatocyte apoptosis was encouraged.

Organelle stress and alterations in interorganelle crosstalk during liver fibrosis

The synchronous functioning and quality control of organelles ensure cell survival and function and are essential for maintaining homeostasis. Prolonged exposure to stressors (viruses, bacteria, parasitic infections, alcohol, drugs) or genetic mutations often disrupt the functional integrity of organelles which plays a critical role in the initiation and progression of several diseases including chronic liver diseases. One of the most important pathologic consequences of chronic liver diseases is liver fibrosis, characterized by tissue scarring due to the progressive accumulation of extracellular matrix components. Left untreated, fibrosis may advance to life-threatening complications such as cirrhosis, hepatic decompensation, and HCC, which collectively accounts for ∼1 million deaths per year worldwide. Owing to the lack of treatment options that can regress or reverse cirrhosis, liver transplantation is currently the only available treatment for end-stage liver disease. However, the limited supply of usable donor organs, adverse effects of lifelong immunosuppressive regimes, and financial considerations pose major challenges and limit its application. Hence, effective therapeutic strategies are urgently needed. An improved understanding of the organelle-level regulation of fibrosis can help devise effective antifibrotic therapies focused on reducing organelle stress, limiting organelle damage, improving interorganelle crosstalk, and restoring organelle homeostasis; and could be a potential clinical option to avoid transplantation. This review provides a timely update on the recent findings and mechanisms covering organelle-specific dysfunctions in liver fibrosis, highlights how correction of organelle functions opens new treatment avenues and discusses the potential challenges to clinical application.

The mitochondrial genome-encoded peptide MOTS-c interacts with Bcl-2 to alleviate nonalcoholic steatohepatitis progression

Nonalcoholic steatohepatitis (NASH) is a metabolism-associated fatty liver disease with accumulated mitochondrial stress, and targeting mitochondrial function is a potential therapy. The mitochondrial genome-encoded bioactive peptide MOTS-c plays broad physiological roles, but its effectiveness and direct targets in NASH treatment are still unclear. Here, we show that long-term preventive and short-term therapeutic effects of MOTS-c treatments alleviate NASH-diet-induced liver steatosis, cellular apoptosis, inflammation, and fibrosis. Mitochondrial oxidative capacity and metabolites profiling analysis show that MOTS-c significantly reverses NASH-induced mitochondrial metabolic deficiency. Moreover, we identify that MOTS-c directly interacts with the BH3 domain of antiapoptotic B cell lymphoma-2 (Bcl-2), increases Bcl-2 protein stability, and suppresses Bcl-2 ubiquitination. By using a Bcl-2 inhibitor or adeno-associated virus (AAV)-mediated Bcl-2 knockdown, we further confirm that MOTS-c improves NASH-induced mitochondrial dysfunction, inflammation, and fibrosis, which are dependent on Bcl-2 function. Therefore, our findings show that MOTS-c is a potential therapeutic agent to inhibit the progression of NASH.

Association between low-normal thyroid function and advanced liver fibrosis in metabolic dysfunction-associated fatty liver disease patients: a retrospective cohort study

Background

Recent studies have found that thyroid function may be associated with the occurrence and development of advanced liver fibrosis in patients with metabolic dysfunction-associated fatty liver disease (MAFLD). However, the majority of such research has consisted of cross-sectional studies. This retrospective cohort study aimed to investigate the effect of low-normal thyroid function on advanced liver fibrosis in MAFLD patients over a 5-year period.

Methods

This retrospective cohort study enrolled 825 outpatients and inpatients with MAFLD who attended the Third Affiliated Hospital of Sun Yat-sen University (Guangzhou, China) between January 2011 and December 2018. Based on plasma thyroid hormone and thyroid-stimulating hormone levels, these patients were divided into two groups, namely a low-normal thyroid function group and a strict-normal thyroid function group. The fibrosis-4 score was used to assess advanced liver fibrosis. A chi-square test was conducted to compare the occurrence of advanced fibrosis between the groups.

Results

Among the 825 MAFLD patients, 117 and 708 were defined as having low-normal thyroid function and strict-normal thyroid function, respectively. Follow-up data were available for 767 patients (93.0%) during a 5-year period. Eight (7.5%) MAFLD patients with low-normal thyroid function and 26 (3.9%) with strict-normal thyroid function developed advanced liver fibrosis and the cumulative incidence was not significantly different (P = 0.163). Stratification analysis showed that the lean MAFLD patients (body mass index ≤ 23 kg/m2) with low-normal thyroid function had a higher risk of advanced liver fibrosis than the lean MAFLD patients with strict-normal thyroid function (P < 0.05).

Conclusion

Low-normal thyroid function is associated with advanced liver fibrosis among lean MAFLD patients.

Combined quercetin and simvastatin attenuate hepatic fibrosis in rats by modulating SphK1/NLRP3 pathways

Liver fibrosis involves several signalling pathways working in concert regulating the deposition of extracellular matrix. In this study, we evaluated the effect of quercetin and simvastatin alone and their combination on the treatment of experimentally induced hepatic fibrosis in rats. To decipher the potential mechanisms involved, liver fibrosis was induced in rats by administration of 40 % carbon tetrachloride (CCl4) (1 μl/g rat, i.p., twice weekly) for 6 weeks. Quercetin (50 mg/kg, orally), simvastatin (40 mg/kg, orally) either individually or combined were administered for another 4 weeks. The three treatment groups ameliorated hepatic dysfunction and altered parameters of sphingolipid and pyroptosis pathways. Yet, the combined group showed a more pronounced effect. Treatments lowered serum levels of GOT, GPT, ALP and elevated albumin and total protein levels. Histopathological and electron microscope examination of liver tissue revealed diminished fibrosis and inflammation. Protein expression levels of α-SMA, IL-1β, PPAR-γ, TGF-β1, caspase-1 and caspase-3 expression in liver tissues were reduced. Additionally, hepatic mRNA levels of SphK1 and NLRP3 decreased after treatment. Furthermore, the three groups lowered MDA levels and elevated total antioxidant capacity, GSH and Nrf2 expression levels. Treatments downregulated sphingolipid pathway and NLRP3-mediated pyroptosis and stimulated an anti-apoptotic, anti-proliferative and antioxidant activity. This suggests that targeting the SphK1/NLRP3 pathway could be a prospective therapeutic strategy against liver fibrosis.

A landscape of mouse mitochondrial small non-coding RNAs

Small non-coding RNAs (ncRNAs), particularly miRNAs, play key roles in a plethora of biological processes both in health and disease. Although largely operative in the cytoplasm, emerging data indicate their shuttling in different subcellular compartments. Given the central role of mitochondria in cellular homeostasis, here we systematically profiled their small ncRNAs content across mouse tissues that largely rely on mitochondria functioning. The ubiquitous presence of piRNAs in mitochondria (mitopiRNA) of somatic tissues is reported for the first time, supporting the idea of a strong and general connection between mitochondria biology and piRNA pathways. Then, we found groups of tissue-shared and tissue-specific mitochondrial miRNAs (mitomiRs), potentially related to the "basic" or "cell context dependent" biology of mitochondria. Overall, this large data platform will be useful to deepen the knowledge about small ncRNAs processing and their governed regulatory networks contributing to mitochondria functions.

Cancer Nanobombs Delivering Artoxplatin with a Polyigniter Bearing Hydrophobic Ferrocene Units Upregulate PD-L1 Expression and Stimulate Stronger Anticancer Immunity

Poor immunogenicity seriously hampers the broader implementation of antitumor immunotherapy. Enhanced immunogenicity capable of achieving greater antitumor immunity is urgently required. Here, a novel polymer that contains hydrophobic ferrocene (Fc) units and thioketal bonds in the main chain, which further delivered a prodrug of oxaliplatin and artesunate, i.e., Artoxplatin, to cancer cells is described. This polymer with Fc units in the nanoparticle can work as a polyigniter to spark the peroxide bonds in Artoxplatin and generate abundant reactive oxygen species (ROS) to kill cancers as nanobombig for cancer therapy. Moreover, ROS can trigger the breakdown of thioketal bonds in the polymer, resulting in the biodegradation of the polymer. Importantly, nanobombig can facilitate the maturation of dendritic cells and promote the activation of antitumor immunity, through the enhanced immunogenic cell death effect by ROS generated in situ. Furthermore, metabolomics analysis reveals a decrease in glutamine in nanobombig -treated cancer cells, resulting in the upregulation of programmed death ligand 1 (PD-L1). Consequently, it is further demonstrated enhanced tumor inhibitory effects when using nanobombig combined with anti-PD-L1 therapy. Overall, the nanosystem offers a rational design of an efficient chemo-immunotherapy regimen to promote antitumor immunity by improving tumor immunogenicity, addressing the key challenges cancer immunotherapy faced.

Efferocytosis in liver disease

The process of dead cell clearance by phagocytic cells, called efferocytosis, prevents inflammatory cell necrosis and promotes resolution and repair. Defective efferocytosis contributes to the progression of numerous diseases in which cell death is prominent, including liver disease. Many gaps remain in our understanding of how hepatic macrophages carry out efferocytosis and how this process goes awry in various types of liver diseases. Thus far, studies have suggested that, upon liver injury, liver-resident Kupffer cells and infiltrating monocyte-derived macrophages clear dead cells, limit inflammation, and, through macrophage reprogramming, repair liver damage. However, in unusual settings, efferocytosis can promote liver disease. In this review, we will focus on efferocytosis in various types of acute and chronic liver diseases, including metabolic dysfunction-associated steatohepatitis. Understanding the mechanisms and consequences of efferocytosis by hepatic macrophages has the potential to shed new light on liver disease pathophysiology and to guide new treatment strategies to prevent disease progression.

Mitochondrial Dysfunction in Metabolic Dysfunction Fatty Liver Disease (MAFLD)

Nonalcoholic fatty liver disease (NAFLD) has become an increasingly common disease in Western countries and has become the major cause of liver cirrhosis or hepatocellular carcinoma (HCC) in addition to viral hepatitis in recent decades. Furthermore, studies have shown that NAFLD is inextricably linked to the development of extrahepatic diseases. However, there is currently no effective treatment to cure NAFLD. In addition, in 2020, NAFLD was renamed metabolic dysfunction fatty liver disease (MAFLD) to show that its pathogenesis is closely related to metabolic disorders. Recent studies have reported that the development of MAFLD is inextricably associated with mitochondrial dysfunction in hepatocytes and hepatic stellate cells (HSCs). Simultaneously, mitochondrial stress caused by structural and functional disorders stimulates the occurrence and accumulation of fat and lipo-toxicity in hepatocytes and HSCs. In addition, the interaction between mitochondrial dysfunction and the liver-gut axis has also become a new point during the development of MAFLD. In this review, we summarize the effects of several potential treatment strategies for MAFLD, including antioxidants, reagents, and intestinal microorganisms and metabolites.

Macrophages and platelets in liver fibrosis and hepatocellular carcinoma

During fibrosis, (myo)fibroblasts deposit large amounts of extracellular matrix proteins, thereby replacing healthy functional tissue. In liver fibrosis, this leads to the loss of hepatocyte function, portal hypertension, variceal bleeding, and increased susceptibility to infection. At an early stage, liver fibrosis is a dynamic and reversible process, however, from the cirrhotic stage, there is significant progression to hepatocellular carcinoma. Both liver-resident macrophages (Kupffer cells) and monocyte-derived macrophages are important drivers of fibrosis progression, but can also induce its regression once triggers of chronic inflammation are eliminated. In liver cancer, they are attracted to the tumor site to become tumor-associated macrophages (TAMs) polarized towards a M2- anti-inflammatory/tumor-promoting phenotype. Besides their role in thrombosis and hemostasis, platelets can also stimulate fibrosis and tumor development by secreting profibrogenic factors and regulating the innate immune response, e.g., by interacting with monocytes and macrophages. Here, we review recent literature on the role of macrophages and platelets and their interplay in liver fibrosis and hepatocellular carcinoma.

The role of hepatocyte mitochondrial DNA in liver injury

Hepatocytes, the predominant cellular constituents of the liver, exhibit the highest mitochondrial density within the human body. Remarkably, experimental insights from the latter part of the previous century involving extracellular injection of mitochondrial DNA (mtDNA) elucidated its potential to incite autoimmune disorders. Consequently, in instances of liver injury, the substantial release of mtDNA has the potential to trigger the activation of the innate immune response, thereby inducing sustained pathogenic consequences within the organism. This article provides a comprehensive retrospective analysis of recent literature pertaining to the impact of mtDNA release on various hepatic cell populations, elucidating its role and potential mechanisms in liver injury. The findings underscore the central role of mtDNA in modulating the immune system, primarily through the orchestration of a cytokine storm, further exacerbating the occurrence of liver injury.

Cuproptosis as the new kryptonite of cancer: a copper-dependent novel cell death mechanism with promising implications for the treatment of hepatocellular carcinoma

Copper is an essential element for critical cellular functions such as mitochondrial respiration, cholesterol biosynthesis and immune response. Altered copper homeostasis has been associated with various disorders, including cancer. The copper overload is known to contribute to tumorigenesis, angiogenesis and metastasis, and recently it has been suggested that the elevated level of this element may also create vulnerability to a novel cell death mechanism, named cuproptosis. Excessive amount of copper in mitochondria binds to lipoylated enzymes of the TCA cycle and forms insoluble oligomers. The aggregation of these oligomers and subsequent iron-sulfur cluster protein loss results in proteotoxic stress and eventual cell death. Hepatocellular carcinoma is a common malignancy with a low survival rate, despite the available treatment options. The discovery of cuproptosis led many researchers to explore its potential use in hepatocellular cancer therapy due to the rich mitochondria content of hepatic cells. In this regard, a number of genomic studies were conducted to discover several cuproptosis-related genes and explored their association with prognosis, survival and immunotherapy response. This review brings together the available data on the relationship between cuproptosis and hepatocellular cancer for the first time, and highlights some of the potential biomarkers or target molecules that may be useful in the treatment.

Correction to: YY1 inactivated transcription co-regulator PGC-1α to promote mitochondrial dysfunction of early diabetic nephropathy-associated tubulointerstitial fibrosis

The development of diabetic nephropathy (DN) could be promoted by the occurrence of tubulointerstitial fibrosis (TIF), which has a close relationship with mitochondrial dysfunction of renal tubular epithelial cells (RTECs). As a key regulator of metabolic homeostasis, Yin Yang 1 (YY1) plays an important role not only in regulating the fibrosis process but also in maintaining the mitochondrial function of pancreatic β-cells. However, it was not clear whether YY1 participated in maintaining mitochondrial function of RTECs in early DN-associated TIF. In this study, we dynamically detected mitochondrial functions and protein expression of YY1 in db/db mice and high glucose (HG)-cultured HK-2 cells. Our results showed that comparing with the occurrence of TIF, the emergence of mitochondrial dysfunction of RTECs was an earlier even, besides the up-regulated and nuclear translocated YY1. Correlation analysis showed YY1 expressions were negatively associated with PGC-1α in vitro and in vivo. Further mechanism research demonstrated the formation of mTOR-YY1 heterodimer induced by HG up-regulated YY1, the nuclear translocation of which inactivated PGC-1α by binding to the PGC-1α promoter. Overexpression of YY1 induced mitochondrial dysfunctions in normal glucose-cultured HK-2 cells and 8-weeks-old db/m mice. While, dysfunctional mitochondria induced by HG could be improved by knockdown of YY1. Finally, downregulation of YY1 could retard the progression of TIF by preventing mitochondrial functions, resulting in the improvement of epithelial-mesenchymal transition (EMT) in early DN. These findings suggested that YY1 was a novel regulator of mitochondrial function of RTECs and contributed to the occurrence of early DN-associated TIF.

COVID-19-associated liver injury: Adding fuel to the flame

COVID-19 is mainly characterized by respiratory disorders and progresses to multiple organ involvement in severe cases. With expansion of COVID-19 and SARS-CoV-2 research, correlative liver injury has been revealed. It is speculated that COVID-19 patients exhibited abnormal liver function, as previously observed in the SARS and MERS pandemics. Furthermore, patients with underlying diseases such as chronic liver disease are more susceptible to SARS-CoV-2 and indicate a poor prognosis accompanied by respiratory symptoms, systemic inflammation, or metabolic diseases. Therefore, COVID-19 has the potential to impair liver function, while individuals with preexisting liver disease suffer from much worse infected conditions. COVID-19 related liver injury may be owing to direct cytopathic effect, immune dysfunction, gut-liver axis interaction, and inappropriate medication use. However, discussions on these issues are infancy. Expanding research have revealed that angiotensin converting enzyme 2 (ACE2) expression mediated the combination of virus and target cells, iron metabolism participated in the virus life cycle and the fate of target cells, and amino acid metabolism regulated immune response in the host cells, which are all closely related to liver health. Further exploration holds great significance in elucidating the pathogenesis, facilitating drug development, and advancing clinical treatment of COVID-19-related liver injury. This article provides a review of the clinical and laboratory hepatic characteristics in COVID-19 patients, describes the etiology and impact of liver injury, and discusses potential pathophysiological mechanisms.

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.

Effects and potential mechanisms of IGF1/IGF1R in the liver fibrosis: A review

Liver fibrosis is a wound-healing response due to persistent liver damage and it may progress to cirrhosis and even liver cancer if no intervention is given. In the current cognition, liver fibrosis is reversible. So, it is of great significance to explore the related gene targets or biomarker for anti-fibrosis of liver. Insulin like growth factor 1 (IGF1) and IGF1 receptor (IGF1R) are mainly expressed in the liver tissues and play critical roles in the liver function. The present review summarized the role of IGF1/IGF1R and its signaling system in liver fibrosis and illustrated the potential mechanisms including DNA damage repair, cell senescence, lipid metabolism and oxidative stress that may be involved in this process according to the studies on the fibrosis of liver or other organs. In particular, the roles of IGF1 and IGF1R in DNA damage repair were elaborated, including membrane-localized and nucleus-localized IGF1R. In addition, for each of the potential mechanism in anti-fibrosis of liver, the signaling pathways of the IGF1/IGF1R mediated and the cell species in liver acted by IGF1 and IGF1R under different conditions were included. The data in this review will support for the study about the effect of IGF1/IGF1R on liver fibrosis induced by various factors, meanwhile, provide a basis for the study of liver fibrosis to focus on the communications between the different kinds of liver cells.

Evaluation of the efficacy of mitochondrial fission inhibitor (Mdivi-1) using non-alcoholic steatohepatitis (NASH) liver organoids

Non-alcoholic steatohepatitis (NASH) is known to progress to cirrhosis and hepatocellular carcinoma in some patients. Although NASH is associated with abnormal mitochondrial function related to lipid metabolism, mechanisms for the development and effective treatments are still unclear. Therefore, new approaches to elucidate the pathophysiology are needed. In the previous study, we generated liver organoids from different stages of NASH model mice that could recapitulate the part of NASH pathology. In the present study, we investigated the relationship between mitochondrial function and NASH disease by comparing NASH liver organoids (NLO) and control liver organoids (CLO). Compared with CLO, mitochondrial and organoid morphology was abnormal in NLO, with increased expression of mitochondrial mitogen protein, DRP1, and mitochondria-derived reactive oxygen species (ROS) production. Treatment of NLO with a DPR1 inhibitor, Mdivi-1 resulted in the improvement of morphology and the decreased expression of fibrosis-related markers, Col1a1 and Acta2. In addition, treatment of NASH model mice with Mdivi-1 showed a decrease in fatty liver. Mdivi-1 treatment also prevented fibrosis and ROS production in the liver. These results indicate that NLO undergoes enhanced metabolism and abnormal mitochondrial morphology compared with CLO. It was also suggested that Mdivi-1 may be useful as a therapeutic agent to ameliorate NASH pathology.

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.

Parkin-Mediated Mitophagy by TGF-β Is Connected with Hepatic Stellate Cell Activation

Hepatic stellate cells (HSCs) are the main contributors to the development and progression of liver fibrosis. Parkin is an E3 ligase involved in mitophagy mediated by lysosomes that maintains mitochondrial homeostasis. Unfortunately, there is little information regarding the regulation of parkin by transforming growth factor-β (TGF-β) and its association with HSC trans-differentiation. This study showed that parkin is upregulated in fibrotic conditions and elucidated the underlying mechanism. Parkin was observed in the cirrhotic region of the patient liver tissues and visualized using immunostaining and immunoblotting of mouse fibrotic liver samples and primary HSCs. The role of parkin-mediated mitophagy in hepatic fibrogenesis was examined using TGF-β-treated LX-2 cells with mitophagy inhibitor, mitochondrial division inhibitor 1. Parkin overexpression and its colocalization with desmin in human tissues were found. Increased parkin in fibrotic liver homogenates of mice was observed. Parkin was expressed more abundantly in HSCs than in hepatocytes and was upregulated under TGF-β. TGF-β-induced parkin was due to Smad3. TGF-β facilitated mitochondrial translocation, leading to mitophagy activation, reversed by mitophagy inhibitor. However, TGF-β did not change mitochondrial function. Mitophagy inhibitor suppressed profibrotic genes and HSC migration mediated by TGF-β. Collectively, parkin-involved mitophagy by TGF-β facilitates HSC activation, suggesting mitophagy may utilize targets for liver fibrosis.

microRNAs in parasite-induced liver fibrosis: from mechanisms to diagnostics and therapeutics

Chronic parasite infections in the liver pose a global threat to human and animal health, often occurring with liver fibrosis that leads to cirrhosis, liver failure, and even cancer. Hepatic fibrogenesis is a complex yet reversible process of tissue repair and is associated with various factors, including immune cells, microenvironment, gut microbiome, and interactions of the different liver cells. As a profibrogenic or antifibrogenic driver, microRNAs (miRNAs) are closely involved in parasite-induced hepatic fibrosis. This article updates the current understanding of the roles of miRNAs in hepatic fibrogenesis by parasite infections and discusses the strategies using miRNAs as candidates for diagnostics and therapeutics.

Hepatic inflammatory responses in liver fibrosis

Chronic liver diseases such as nonalcoholic fatty liver disease (NAFLD) or viral hepatitis are characterized by persistent inflammation and subsequent liver fibrosis. Liver fibrosis critically determines long-term morbidity (for example, cirrhosis or liver cancer) and mortality in NAFLD and nonalcoholic steatohepatitis (NASH). Inflammation represents the concerted response of various hepatic cell types to hepatocellular death and inflammatory signals, which are related to intrahepatic injury pathways or extrahepatic mediators from the gut-liver axis and the circulation. Single-cell technologies have revealed the heterogeneity of immune cell activation concerning disease states and the spatial organization within the liver, including resident and recruited macrophages, neutrophils as mediators of tissue repair, auto-aggressive features of T cells as well as various innate lymphoid cell and unconventional T cell populations. Inflammatory responses drive the activation of hepatic stellate cells (HSCs), and HSC subsets, in turn, modulate immune mechanisms via chemokines and cytokines or transdifferentiate into matrix-producing myofibroblasts. Current advances in understanding the pathogenesis of inflammation and fibrosis in the liver, mainly focused on NAFLD or NASH owing to the high unmet medical need, have led to the identification of several therapeutic targets. In this Review, we summarize the inflammatory mediators and cells in the diseased liver, fibrogenic pathways and their therapeutic implications.

Cellular stress in the pathogenesis of nonalcoholic steatohepatitis and liver fibrosis

The burden of chronic liver disease is rising substantially worldwide. Fibrosis, characterized by excessive deposition of extracellular matrix proteins, is the common pathway leading to cirrhosis, and limited treatment options are available. There is increasing evidence suggesting the role of cellular stress responses contributing to fibrogenesis. This Review provides an overview of studies that analyse the role of cellular stress in different cell types involved in fibrogenesis, including hepatocytes, hepatic stellate cells, liver sinusoidal endothelial cells and macrophages.

Immunomodulatory role of mitochondrial DAMPs: a missing link in pathology?

In accordance with the endosymbiotic theory, mitochondrial components bear characteristic prokaryotic signatures, which act as immunomodulatory molecules when released into the extramitochondrial compartment. These endogenous immune triggers, called mitochondrial damage-associated molecular patterns (mtDAMPs), have been implicated in the pathogenesis of various diseases, yet their role remains largely unexplored. In this review, we summarise the available literature on mtDAMPs in diseases, with a special focus on respiratory diseases. We highlight the need to bolster mtDAMP research using a multipronged approach, to study their effect on specific cell types, receptors and machinery in pathologies. We emphasise the lacunae in the current understanding of mtDAMPs, particularly in their cellular release and the chemical modifications they undergo. Finally, we conclude by proposing additional effects of mtDAMPs in diseases, specifically their role in modulating the immune system.

Protective role of cGAS in NASH is related to the maintenance of intestinal homeostasis

BACKGROUND & AIMS

Various intracellular pathways regulate inflammation in NASH. Cyclic GMP-AMP synthase (cGAS) is a DNA sensor that activates STING and plays a role in inflammatory diseases. Here, we explored the role of cGAS in hepatic damage, steatosis, inflammation, and liver fibrosis in mouse models of NASH.

METHODS

cGAS deficient (cGAS-KO) and STING deficient (STING-KO) mice received high fat-high cholesterol-high sugar diet (HF-HC-HSD) or relevant control diets. Livers were evaluated after 16 or 30 weeks.

RESULTS

HF-HC-HSD diet, both at 16 and 30 weeks, resulted in increased cGAS protein expression as well as in increased ALT, IL-1β, TNF-α and MCP-1 in wild-type (WT) mice compared to controls. Surprisingly, liver injury, triglyceride accumulation, and inflammasome activation were greater in HF-HC-HSD cGAS-KO compared to WT mice at 16 and to a lesser extent at 30 weeks. STING, a downstream target of cGAS was significantly increased in WT mice after HF-HC-HSD. In STING-KO mice after HF-HC-HSD feeding, we found increased ALT and attenuated MCP1 and IL-1β expression compared to WT mice. Markers of liver fibrosis were increased in cGAS- and STING-KO mice compared to WT on HF-HC-HSD. We discovered that cGAS-KO mice had a significant increase in circulating endotoxin levels on HF-HC-HSD that correlated with changes in intestinal morphology which was exacerbated by HF-HC-HSD compared to WT mice.

CONCLUSION

Our findings indicate that cGAS or STING deficiency exacerbate liver damage, steatosis, and inflammation in HF-HC-HSD diet-induced NASH, which might be linked to the disruption of the gut barrier.

Programmed Cell Death in Liver Fibrosis

Programmed cell death (PCD) is a comprehensive term that encompasses various forms of cell death, such as apoptosis, necroptosis, pyroptosis, ferroptosis, and autophagy, which play a crucial role in the pathogenesis of liver fibrosis. PCD facilitates the elimination of aberrant cells, particularly activated hepatic stellate cells (HSCs), which are the primary producers of extracellular matrix (ECM). The removal of HSCs may impede ECM synthesis, thereby mitigating liver fibrosis. As such, PCD has emerged as a promising therapeutic target for the development of novel drugs to treat liver fibrosis. Numerous studies have been conducted to investigate the underlying mechanisms of PCD in the elimination of activated HSCs and other aberrant liver cells in fibrotic liver tissue, including hepatocytes, hepatic sinusoid endothelial cells (LSECs), and Kupffer cells (KCs). The induction of PCD, the interplay between different forms of PCD, and the potential harm or benefit of PCD in liver fibrosis are topics of ongoing research. Evidences suggest that PCD is a complex process with dual effects on liver fibrosis. The purpose of this review is to summarize the most recent advances in PCD and liver fibrosis research.

SIRT3 regulates mitophagy in liver fibrosis through deacetylation of PINK1/NIPSNAP1

Damaged mitochondria, a key factor in liver fibrosis, can be removed by the mitophagy pathway to maintain homeostasis of the intracellular environment to alleviate the development of fibrosis. PINK1 (PTEN-induced kinase 1) and NIPSNAP1 (nonneuronal SNAP25-like protein 1), which cooperatively regulate mitophagy, have been predicted to include the sites of lysine acetylation related to SIRT3 (mitochondrial deacetylase sirtuin 3). Our study aimed to discuss whether SIRT3 deacetylates PINK1 and NIPSNAP1 to regulate mitophagy in liver fibrosis. Carbon tetrachloride (CCl4 )-induced liver fibrosis as an in vivo model and LX-2 cells as activated cells were used to simulate liver fibrosis. SIRT3 expression was significantly decreased in mice in response to CCl4 , and SIRT3 knockout in vivo significantly deepened the severity of liver fibrosis, as indicated by increased α-SMA and Col1a1 levels both in vivo and in vitro. SIRT3 overexpression decreased α-SMA and Col1a1 levels. Furthermore, SIRT3 significantly regulated mitophagy in liver fibrosis, as demonstrated by LC3-Ⅱ/Ⅰ and p62 expression and colocalization between TOM20 and LAMP1. Importantly, PINK1 and NIPSNAP1 expression was also decreased in liver fibrosis, and PINK1 and NIPSNAP1 overexpression significantly improved mitophagy and attenuated ECM production. Furthermore, after simultaneously interfering with PINK1 or NIPSNAP1 and overexpressing SIRT3, the effect of SIRT3 on improving mitophagy and alleviating liver fibrosis was disrupted. Mechanistically, we show that SIRT3, as a mitochondrial deacetylase, specifically regulates the acetylation of PINK1 and NIPSNAP1 to mediate the mitophagy pathway in liver fibrosis. SIRT3-mediated PINK1 and NIPSNAP1 deacetylation is a novel molecular mechanism in liver fibrosis.

Oxidative Stress in Liver Pathophysiology and Disease

The liver is an organ that is particularly exposed to reactive oxygen species (ROS), which not only arise during metabolic functions but also during the biotransformation of xenobiotics. The disruption of redox balance causes oxidative stress, which affects liver function, modulates inflammatory pathways and contributes to disease. Thus, oxidative stress is implicated in acute liver injury and in the pathogenesis of prevalent infectious or metabolic chronic liver diseases such as viral hepatitis B or C, alcoholic fatty liver disease, non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). Moreover, oxidative stress plays a crucial role in liver disease progression to liver fibrosis, cirrhosis and hepatocellular carcinoma (HCC). Herein, we provide an overview on the effects of oxidative stress on liver pathophysiology and the mechanisms by which oxidative stress promotes liver disease.

Cellular heterogeneity and plasticity during NAFLD progression

Nonalcoholic fatty liver disease (NAFLD) is a progressive liver disease that can progress to nonalcoholic steatohepatitis (NASH), NASH-related cirrhosis, and hepatocellular carcinoma (HCC). NAFLD ranges from simple steatosis (or nonalcoholic fatty liver [NAFL]) to NASH as a progressive form of NAFL, which is characterized by steatosis, lobular inflammation, and hepatocellular ballooning with or without fibrosis. Because of the complex pathophysiological mechanism and the heterogeneity of NAFLD, including its wide spectrum of clinical and histological characteristics, no specific therapeutic drugs have been approved for NAFLD. The heterogeneity of NAFLD is closely associated with cellular plasticity, which describes the ability of cells to acquire new identities or change their phenotypes in response to environmental stimuli. The liver consists of parenchymal cells including hepatocytes and cholangiocytes and nonparenchymal cells including Kupffer cells, hepatic stellate cells, and endothelial cells, all of which have specialized functions. This heterogeneous cell population has cellular plasticity to adapt to environmental changes. During NAFLD progression, these cells can exert diverse and complex responses at multiple levels following exposure to a variety of stimuli, including fatty acids, inflammation, and oxidative stress. Therefore, this review provides insights into NAFLD heterogeneity by addressing the cellular plasticity and metabolic adaptation of hepatocytes, cholangiocytes, hepatic stellate cells, and Kupffer cells during NAFLD progression.

Novel Therapeutic Approaches to Liver Fibrosis Based on Targeting Oxidative Stress

Chronic liver disease (CLD) constitutes a growing global health issue, with no effective treatments currently available. Oxidative stress closely interacts with other cellular and molecular processes to trigger stress pathways in different hepatic cells and fuel the development of liver fibrosis. Therefore, inhibition of reactive oxygen species (ROS)-mediated effects and modulation of major antioxidant responses to counteract oxidative stress-induced damage have emerged as interesting targets to prevent or ameliorate liver injury. Although many preclinical studies have shown that dietary supplements with antioxidant properties can significantly prevent CLD progression in animal models, this strategy has not proved effective to significantly reduce fibrosis when translated into clinical trials. Novel and more specific therapeutic approaches are thus required to alleviate oxidative stress and reduce liver fibrosis. We have reviewed the relevant literature concerning the crucial role of alterations in redox homeostasis in different hepatic cell types during the progression of CLD and discussed current pharmacological approaches to ameliorate fibrosis by reducing oxidative stress focusing on selective modulation of enzymatic oxidant sources, antioxidant systems and ROS-mediated pathogenic processes.

Mechanisms of organ fibrosis: Emerging concepts and implications for novel treatment strategies

Fibrosis, or tissue scarring, develops as a pathological deviation from the physiological wound healing response and can occur in various organs such as the heart, lung, liver, kidney, skin, and bone marrow. Organ fibrosis significantly contributes to global morbidity and mortality. A broad spectrum of etiologies can cause fibrosis, including acute and chronic ischemia, hypertension, chronic viral infection (e.g., viral hepatitis), environmental exposure (e.g., pneumoconiosis, alcohol, nutrition, smoking) and genetic diseases (e.g., cystic fibrosis, alpha-1-antitrypsin deficiency). Common mechanisms across organs and disease etiologies involve a sustained injury to parenchymal cells that triggers a wound healing response, which becomes deregulated in the disease process. A transformation of resting fibroblasts into myofibroblasts with excessive extracellular matrix production constitutes the hallmark of disease, however, multiple other cell types such as immune cells, predominantly monocytes/macrophages, endothelial cells, and parenchymal cells form a complex network of profibrotic cellular crosstalk. Across organs, leading mediators include growth factors like transforming growth factor-β and platelet-derived growth factor, cytokines like interleukin-10, interleukin-13, interleukin-17, and danger-associated molecular patterns. More recently, insights into fibrosis regression and resolution of chronic conditions have deepened our understanding of beneficial, protective effects of immune cells, soluble mediators and intracellular signaling. Further in-depth insights into the mechanisms of fibrogenesis can provide the rationale for therapeutic interventions and the development of targeted antifibrotic agents. This review gives insight into shared responses and cellular mechanisms across organs and etiologies, aiming to paint a comprehensive picture of fibrotic diseases in both experimental settings and in human pathology.