Kupffer cells in the liver

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.

Polymer-Based Designer Particles as Drug Carriers: Strategies to Construct and Modify

Biological barriers present remarkable challenges for therapeutics delivery, requiring an advanced drug delivery system that can navigate through the complex physiological environment. Polymeric particles provide remarkable versatility due to their adaptable physiochemical properties, facilitating new designs that address complex delivery issues. This review focuses on recent advancements in the morphology of polymeric particles that emulate biological barriers to improve drug efficacy. It includes how structural engineering─such as designing rod-shaped particles for improved cellular uptake, red-blood-cell-shaped particles for prolonged circulation, worm-shaped carriers for improved tissue penetration, and multicompartmental systems for providing combination therapies─profoundly alters drug delivery capabilities. These designer particles exhibit enhanced target specificity, controlled release kinetics, and improved therapeutic outcomes relative to traditional spherical carriers. This particular review also emphasizes how a combination of polymer chemistry and fabrication methods facilitates achieving these advanced structures, while highlighting ongoing challenges in scale-up, reproducibility, and clinical translations. Through the analysis of structure-functional property correlations in various biomimetic designs, we have also attempted to provide insight into future advancements in polymeric delivery systems that have the potential to transform treatment strategies for complicated diseases via shape-directed biological interactions for better therapeutic outcomes.

Protective role of hepatic non-parenchymal cells against drug-induced hepatocyte toxicity using perfluoropolyether-based microfluidic devices

The role of hepatic non-parenchymal cells (NPCs) in drug-induced liver injury has been controversial. Utilizing our previously developed perfluoropolyether-based microfluidic devices-characterized by significantly reduced chemical absorption compared to conventional polydimethylsiloxane (PDMS)-we investigated the interactions between primary hepatocytes (PCs) and NPCs under physiologically relevant conditions. When exposed to coumarin or acetaminophen, PCs underwent severe cytotoxicity and showed glutathione (GSH) depletion. Notably, co-culture with NPCs restored drug-induced cytotoxicity and cellular GSH levels, accompanied by increased interleukin-6 (IL-6) secretion. Given previous reports linking IL-6 to cytochrome P450 expression modulation and glutathione synthesis, these findings suggest that IL-6 might be a critical mediator of protective effects exerted by NPCs. Using these microfluidic devices, we clearly demonstrated the protective roles of NPCs without interference from innate immune systems, offering novel insights into hepatocellular protection mechanisms.

Cell therapy for liver disorders: past, present and future

The liver fulfils a plethora of vital functions and, due to their importance, liver dysfunction has life-threatening consequences. Liver disorders currently account for more than two million deaths annually worldwide and can be classified broadly into three groups, considering their onset and aetiology, as acute liver diseases, inherited metabolic disorders and chronic liver diseases. In the most advanced and severe forms leading to liver failure, liver transplantation is the only treatment available, which has many associated drawbacks, including a shortage of organ donors. Cell therapy via fully mature cell transplantation is an advantageous alternative that may be able to restore a damaged organ's functionality or serve as a bridge until regeneration can occur. Pioneering work has shown that transplanting adult hepatocytes can support liver recovery. However, primary hepatocytes cannot be grown extensively in vitro as they rapidly lose their metabolic activity. Therefore, different cell sources are currently being tested as alternatives to primary cells. Human pluripotent stem cell-derived cells, chemically induced liver progenitors, or 'liver' organoids, hold great promise for developing new cell therapies for acute and chronic liver diseases. This Review focuses on the advantages and drawbacks of distinct cell sources and the relative strategies to address different therapeutic needs in distinct liver diseases.

Targeting Polymeric Nanoparticles to Specific Cell Populations in the Liver

Nanoparticles (NPs) are beneficial for delivery of drugs in a variety of settings, serving to protect their cargo and allow for sustained release. Polymeric NPs offer several advantages as therapeutics carriers due to their tunable characteristics like size and shape, ease of manufacturing, and biocompatibility. Despite this, there are no polymeric NPs that are approved for treatment of liver diseases. This is surprising since─when administered intravenously─the majority of NPs accumulate in cells in the liver. NP characteristics like size and surface charge can be altered to affect distribution to the liver, and even cellular distribution, but the conjugation of targeting ligands onto the NP surface for specific receptors on the cells is an important approach for enhancing cell specific delivery. Enhancing cell-specific targeting of conjugated NPs in the liver has two major hurdles: 1) avoiding accumulation of NPs in the liver resident macrophages known as Kupffer cells, which are optimized to phagocytose particulates, and 2) overcoming the transport barriers associated with architectural changes of the diseased liver. To identify the structures and mechanisms most important in NP design, NP administration during ex vivo perfusion (EVP)─achieved by anatomically isolating an organ by perfusing it outside the body─may be the most important and efficient approach. However, EVP is currently underutilized in the NP field, with limited research published on NPs delivered during liver EVP, and therefore representing an opportunity for future investigations.

An in vivo systemic massively parallel platform for deciphering animal tissue-specific regulatory function

Introduction: Transcriptional regulation is an important process wherein non-protein coding enhancer sequences play a key role in determining cell type identity and phenotypic diversity. In neural tissue, these gene regulatory processes are crucial for coordinating a plethora of interconnected and regionally specialized cell types, ensuring their synchronized activity in generating behavior. Recognizing the intricate interplay of gene regulatory processes in the brain is imperative, as mounting evidence links neurodevelopment and neurological disorders to non-coding genome regions. While genome-wide association studies are swiftly identifying non-coding human disease-associated loci, decoding regulatory mechanisms is challenging due to causal variant ambiguity and their specific tissue impacts. Methods: Massively parallel reporter assays (MPRAs) are widely used in cell culture to study the non-coding enhancer regions, linking genome sequence differences to tissue-specific regulatory function. However, widespread use in animals encounters significant challenges, including insufficient viral library delivery and library quantification, irregular viral transduction rates, and injection site inflammation disrupting gene expression. Here, we introduce a systemic MPRA (sysMPRA) to address these challenges through systemic intravenous AAV viral delivery. Results: We demonstrate successful transduction of the MPRA library into diverse mouse tissues, efficiently identifying tissue specificity in candidate enhancers and aligning well with predictions from machine learning models. We highlight that sysMPRA effectively uncovers regulatory effects stemming from the disruption of MEF2C transcription factor binding sites, single-nucleotide polymorphisms, and the consequences of genetic variations associated with late-onset Alzheimer's disease. Conclusion: SysMPRA is an effective library delivering method that simultaneously determines the transcriptional functions of hundreds of enhancers in vivo across multiple tissues.

Unveiling the nexus: pyroptosis and its crucial implications in liver diseases

Pyroptosis, a distinctive form of programmed cell death orchestrated by gasdermin proteins, manifests as cellular rupture, accompanied by the release of inflammatory factors. While pyroptosis is integral to anti-infection immunity, its aberrant activation has been implicated in tumorigenesis. The liver, as the body's largest metabolic organ, is rich in various enzymes and governs metabolism. It is also the primary site for protein synthesis. Recent years have witnessed the emergence of pyroptosis as a significant player in the pathogenesis of specific liver diseases, exerting a pivotal role in both physiological and pathological processes. A comprehensive exploration of pyroptosis can unveil its contributions to the development and regression of conditions such as hepatitis, cirrhosis, and hepatocellular carcinoma, offering innovative perspectives for clinical prevention and treatment. This review consolidates current knowledge on key molecules involved in cellular pyroptosis and delineates their roles in liver diseases. Furthermore, we discuss the potential of leveraging pyroptosis as a novel or existing anti-cancer strategy.

Discovery of a novel regulator, 3β-sulfate-5-cholestenoic acid, of lipid metabolism and inflammation

Mitochondrial oxysterols, cholestenoic acid (CA), 25-hydroxycholesterol (25HC), and 27-hydroxycholesterol (27HC), are potent regulators involved in many important biological events. This study aimed to investigate the metabolic pathways of these oxysterols and their roles between hepatocytes and macrophages. LC-MS/MS analysis showed a novel regulatory molecule, 3β-sulfate-5-cholestenoic acid (3SCA), following the addition of CA in media culturing hepatocytes. Further study showed that 3SCA could also be derived from 27HC. In comparison, 25HC was converted to 25HC3S, which mostly remained in the cells and nuclei. The functional study showed that 3SCA significantly downregulated the expression of genes involved in lipid metabolism in hepatocytes and suppressed gene expression of proinflammatory cytokines induced by lipopolysaccharide in human macrophages. Based on the results, we conclude that 3SCA acts as a secretory regulator for the regulation of lipid metabolism and inflammatory responses in hepatocytes and macrophages. These findings shed light on understanding the unique metabolic pathways of these oxysterols and their possible roles in liver tissues.NEW & NOTEWORTHY This study identifies a novel oxysterol metabolite, 3β-sulfate-5-cholestenoic acid (3SCA), secreted by hepatocytes, which regulates lipid metabolism and inflammatory responses in hepatocytes and macrophages. These findings reveal previously unknown metabolic pathways of mitochondrial oxysterols and their roles in the progression and recovery of metabolic dysfunction-associated steatotic liver disease (MASLD), offering novel insights into potential therapeutic targets.

Unlocking exosome therapeutics: The critical role of pharmacokinetics in clinical applications

Exosomes are microscopic vesicles released by cells that transport various biological materials and play a vital role in intercellular communication. When they are engineered, they serve as efficient delivery systems for therapeutic agents, making it possible to precisely deliver active pharmaceutical ingredients to organs, tissues, and cells. Exosomes' pharmacokinetics, or how they are transported and metabolized inside the body, is affected by several factors, including their source of origination and the proteins in their cell membranes. The pharmacokinetics and mobility of both native and modified exosomes are being observed in living organisms using advanced imaging modalities such as in vitro-in vivo simulation, magnetic resonance imaging, and positron emission tomography. Establishing comprehensive criteria for the investigation of exosomal pharmacokinetic is essential, given its increasing significance in both therapy and diagnostics. To obtain a thorough understanding of exosome intake, distribution, metabolism, and excretion, molecular imaging methods are crucial. The development of industrial processes and therapeutic applications depends on the precise measurement of exosome concentration in biological samples. To ensure a seamless incorporation of exosomes into clinical practice, as their role in therapeutics grows, it is imperative to conduct a complete assessment of their pharmacokinetics. This review provides a brief on how exosome-based research is evolving and the need for pharmacokinetic consideration to realize the full potential of these promising new therapeutic approaches.

Single-cell transcriptomic analysis reveals dynamic changes in the liver microenvironment during colorectal cancer metastatic progression

BACKGROUND

Metastasis is a leading cause of cancer-related deaths, with the liver being the most frequent site of metastasis in colorectal cancer. Previous studies have predominantly focused on the influence of the primary tumor itself on metastasis, with relatively limited research examining the changes within target organs.

METHODS

Using an orthotopic mouse model of colorectal cancer, single-cell sequencing was employed to profile the transcriptomic landscape of pre-metastatic and metastatic livers. The analysis focused on identifying cellular and molecular changes within the hepatic microenvironment, with particular emphasis on inflammatory pathways and immune cell populations.

RESULTS

A neutrophil subpopulation with high Prok2 expression was identified, showing elevated levels in the pre-metastatic and metastatic liver. Increased infiltration of Prok2⁺ neutrophils correlated with poor prognosis in liver metastatic colorectal cancer patients. In the liver metastatic niche (MN), these neutrophils showed high App and Cd274 (PD-L1) expression, suppressing macrophage phagocytosis and promoting T-cell exhaustion.

CONCLUSION

A Prok2⁺ neutrophil subpopulation infiltrated both pre-metastatic and macro-metastatic liver environments, potentially driving immunosuppression through macrophage inhibition and T-cell exhaustion. Targeting Prok2⁺ neutrophils could represent a novel therapeutic strategy for preventing liver metastasis in colorectal cancer patients.

The multifaceted roles of macrophages in the transition from hepatitis to hepatocellular carcinoma: From mechanisms to therapeutic strategies

Macrophages are central to the progression from hepatitis to hepatocellular carcinoma (HCC), with their remarkable plasticity and ability to adapt to the changing liver microenvironment. Chronic inflammation, fibrosis, and ultimately tumorigenesis are driven by macrophage activation, making them key regulators of liver disease progression. This review explores the diverse roles of macrophages in the transition from hepatitis to HCC. In the early stages of hepatitis, macrophages are essential for pathogen clearance and tissue repair. However, chronic activation leads to prolonged inflammation, which exacerbates liver damage and promotes fibrosis. As the disease progresses to liver fibrosis, macrophages interact with hepatic stellate cells, fostering a pro-tumorigenic microenvironment that supports HCC development. In hepatocarcinogenesis, macrophages contribute to tumor initiation, growth, metastasis, immune evasion, cancer stem cell maintenance, and angiogenesis. Their functional plasticity enables them to adapt to the tumor microenvironment, thereby promoting tumor progression and resistance to therapy. Targeting macrophages represents a promising strategy for preventing and treating HCC. Therapeutic approaches, including reprogramming macrophage phenotypes to enhance anti-tumor immunity, blocking macrophage recruitment and activation, and utilizing nanoparticle-based drug delivery systems, may provide new avenues for combating HCC by modulating macrophage functions and tumor microenvironment dynamics.

A new human autologous hepatocyte/macrophage co-culture system that mimics drug-induced liver injury-like inflammation

The development of in vitro hepatocyte cell culture systems is crucial for investigating drug-induced liver injury (DILI). One prerequisite for monitoring DILI related immunologic reactions is the extension of primary human hepatocyte (PHH) cultures towards the inclusion of macrophages. Therefore, we developed and characterized an autologous co-culture system of PHH and primary human hepatic macrophages (hepM) (CoC1). We compared CoC1 with a co-culture of the same PHH batch + M0 macrophages derived from THP1 cells (CoC2) in order to represent a donor independent macrophage reaction. Then, we treated the mono- and co-cultures with drugs that cause DILI-menadione (MEN, 1 or 10 µM, 3 h), diclofenac (DIC, 0.5 or 5 mM, 6 h), or acetaminophen (APAP, 0.5 or 5 mM, 6 h)-and assessed culture stability, cell activity, macrophage differentiation, cytokine production and cell viability. Without drug treatment, CoC1 was the most stable over a culture time of up to 60 h. Cytokine array analysis revealed a proinflammatory profile of PHH mono-cultures due to isolation stress but showed different influences of hepM and M0 on the cytokine profile in the co-cultures. MEN, DIC and APAP treatment led to donor-dependent signs of cell stress and toxicity. HepM can either promote or reduce the DILI effects donor dependently in CoC1. CoC2 are slightly less sensitive than CoC1 in representing DILI. In summary, we present a new autologous co-culture system that can mimic DILI in a donor-dependent manner. This cellular system could be useful for new drug testing strategies and reducing animal testing.

Lipopolysaccharide, arbiter of the gut-liver axis, modulates hepatic cell pathophysiology in alcoholism

Over the last four decades, clinical research and experimental studies have established that lipopolysaccharide (LPS)-a component of the outer membrane of gram-negative bacteria-is a potent hepatotoxic molecule in humans and animals. Alcohol abuse is commonly associated with LPS endotoxemia. This review highlights LPS molecular structures and modes of release from bacteria, plasma LPS concentrations, induction of microbiota dysbiosis, disruption of gut epithelial barrier, and translocation of LPS into the portal circulation impacting the pathophysiology of hepatic cells via the gut-liver axis. We describe and illustrate the portal vein circulation and its distributaries draining the gastrointestinal tract. We also elaborate on the gut-liver axis coupled with enterohepatic circulation that represents a bidirectional communication between the gut and liver. The review also updates the data on how circulating LPS is cleared in a coordinated effort between Kupffer cells, hepatocytes, and liver sinusoidal endothelial cells. Significantly, the article reviews and updates the modes/mechanisms of action by which LPS mediates the diverse pathophysiology of Kupffer cells, hepatocytes, sinusoidal endothelial cells, and hepatic stellate cells primarily in association with alcohol consumption. Specifically, we review the intricate linkages between ethanol, microbiota dysbiosis, LPS production, gut-liver axis, and pathophysiology of various hepatic cells. The maintenance of the gut barrier structural and functional integrity and microbiome homeostasis is essential in mitigating alcoholic liver disease and improving liver health.

Clusterin inhibits lipopolysaccharide induced liver injury

Lipopolysaccharide (LPS) exacerbates liver injury by activating various inflammatory pathways. Clusterin, a glycoprotein involved in lipid transport, and cytoprotection, is known to have inhibitory effects on liver steatosis and fibrosis. In this study, we investigated the role of clusterin in regulating LPS-induced liver injury and its effects on liver injury in C57BL/6 mice and clusterin knockout mice injected with LPS for 3 h. Primary Kupffer cells (KCs) and hepatocytes (HCs) were isolated from these mice and examined using immunohistochemistry, real-time RT-PCR, ELISA, and western blot analysis to assess the effects of clusterin. Clusterin deficiency significantly exacerbated LPS-induced liver injury, as evidenced by increased inflammatory cell infiltration, elevated serum alanine aminotransferase and aspartate aminotransferase levels, and upregulated expression of pro-inflammatory cytokines and components of the NLRP3 inflammasome. By contrast, overexpression of clusterin in primary Kupffer cells and hepatocytes significantly reduced these inflammatory markers. Furthermore, the protective mechanism of clusterin involved inhibition of the STAT3 signaling pathway. These findings suggest that clusterin is a useful therapeutic target to modulate cytokine production and key inflammatory signaling pathways in inflammatory liver diseases.

Safety evaluation of ethanolic extract from aerial flowering part of spiny globe thistle (Echinops spinosus) in mice: Phytochemical screening and genotoxicity

Echinops spinosus is widely used by the population due to its therapeutic potential; however, there is no evidence in the literature that substantiates its safety. Therefore, this study aimed to identify the chemical constituents of E. spinosus extract via GC/MS analysis and evaluate its cytotoxicity and genotoxicity. Male mice were orally given three doses of E. spinosus extract (250, 500, and 1000 mg/kg) for four weeks. Blood and tissue samples were collected after the end of treatment. GC-MS results revealed 73 compounds in the E. spinosus extract, including sugars, sugar alcohols, fatty acids, organic acids, amino acids, and nitrogenous compounds. In vitro experiments revealed that E. spinosus was not cytotoxic to human colon, prostate, or breast cancer cells. In vivo experiments showed that E. spinosus extract did not significantly induce chromosomal damage in the bone marrow, primary spermatocyte, or sperm morphology abnormalities at doses up to 1000 mg/kg/day. This extract also did not induce DNA damage at doses ≤ 500 mg/kg/day in the bone marrow, spleen, testis, or spermatozoa and at 250 mg/kg/day in the liver or kidney. However, treatment with a high dose of E. spinosus caused significant disturbances in liver and kidney functions, oxidative stress indicators, comet tail formation, and histological architecture of the liver, kidney, and testis. In conclusion, E. spinosus extract is nontoxic, with an oral LD50 > 5000 mg/kg. The extract showed negative genotoxicity within the safety threshold of ≤ 500 mg/kg/day and positive genotoxicity at a dose of 1000 mg/kg/day.

Maternal milk cell components are uptaken by infant liver macrophages via extracellular vesicle mediated transport

Milk is a multifaceted biofluid that is essential for infant nutrition and development, yet its cellular and bioactive components, particularly maternal milk cells, remain understudied. Early research on milk cells indicated that they cross the infant's intestinal barrier and accumulate within systemic organs. However, due to the absence of modern analytical techniques, these studies were limited in scope and mechanistic analysis. To overcome this knowledge gap, we have investigated the transintestinal transport of milk cells and components in pups over a 21-day period. Studies employed a mT/mG foster nursing model in which milk cells express a membrane-bound fluorophore, tdTomato. Using flow cytometry, we tracked the transport of milk cell-derived components across local and systemic tissues, including the intestines, blood, thymus, mesenteric lymph nodes, and liver. These experiments identified milk-derived fluorescent signals in intestinal epithelial and immune cells as well as liver macrophages in 7-day-old pups. However, the minute numbers of macrophages in mouse milk suggest that maternal cells are not systemically accumulating in the infant; instead, pup macrophages are consuming milk cell membrane components, such as apoptotic bodies or extracellular vesicles (EVs). Ex vivo experiments using primary macrophages support this hypothesis, showing that immune cells preferentially consumed EVs over milk cells. Together, these data suggest a more complex interplay between milk cells and the infant's immune and digestive systems than previously recognized and highlight the need for future research on the role of milk cells in infant health.

Smad4 deficiency in hepatocytes attenuates NAFLD progression via inhibition of lipogenesis and macrophage polarization

Nonalcoholic fatty liver disease (NAFLD), a major cause of chronic liver disorders, has become a serious public health issue. Although the Smad4 signaling pathway has been implicated in the progression of NAFLD, the specific role of Smad4 in hepatocytes in NAFLD pathogenesis remains unclear. Hepatocyte-specific knockout Smad4 mice (AlbSmad4-/-) were first constructed using the Cre-Loxp recombinant system to establish a high-fat diet induced NAFLD model. The role of Smad4 in the occurrence and development of NAFLD was determined by monitoring the body weight of mice, detecting triglycerides and free fatty acids in serum and liver tissue homogenates, staining the tissue sections to observe the accumulation of liver fat, and RT-qPCR detecting the expression of genes related to lipogenesis, fatty acid intake, and fatty acid β oxidation. The molecular mechanism of Smad4 in hepatocytes affecting NAFLD was therefore investigated through combining in vitro and in vivo experiments. Smad4 deficiency in hepatocytes mitigated NAFLD progression and decreased inflammatory cell infiltration. Moreover, Smad4 deficiency inhibited CXCL1 secretion by suppressing the activation of the ASK1/P38/JNK signaling pathway. Furthermore, targeting CXCL1 using CXCR2 inhibitors diminished hepatocyte lipogenesis and inhibited the polarization of M1-type macrophages. Collectively, these results suggested that Smad4 plays a vital role in exacerbating NAFLD and may be a promising candidate for anti-NAFLD therapy.

Glutathione Depletion Exacerbates Hepatic Mycobacterium tuberculosis Infection

Extrapulmonary tuberculosis (EPTB) accounts for approximately 17% of all Mycobacterium tuberculosis (M.tb) infections globally. Immunocompromised individuals, such as those with HIV infection or type 2 diabetes mellitus (T2DM), are at an increased risk for EPTB. Previous studies have demonstrated that patients with HIV and T2DM exhibit diminished synthesis of glutathione (GSH) synthesizing enzymes. In a murine model, we showed that the diethyl maleate (DEM)-induced depletion of GSH in the lungs led to increased M.tb burden and an impaired pulmonary granulomatous response to M.tb infection. However, the effects of GSH depletion during active EPTB in the liver and spleen have yet to be elucidated. In this study, we evaluated hepatic GSH and malondialdehyde (MDA) levels, as well as cytokine profiles, in untreated and DEM-treated M.tb-infected wild-type (WT) C57BL/6 mice. Additionally, we assessed hepatic and splenic M.tb burdens and tissue pathologies. DEM treatment resulted in a significant decrease in the levels of the reduced form of GSH and an increase in MDA, oxidized GSH, and interleukin (IL)-6 levels. Furthermore, DEM-induced GSH decrease was associated with decreased production of IL-12 and IL-17 and elevated production of interferon-gamma (IFN-γ), tumor necrosis factor (TNF)-α, and transforming growth factor (TGF)-β. A significant increase in M.tb growth was detected in the liver and spleen in DEM-treated M.tb-infected mice. Large, disorganized lymphocyte infiltrates were detected in the hepatic tissues of DEM-treated mice. Overall, GSH diminishment impaired the granulomatous response to M.tb in the liver and exacerbated M.tb growth in both the liver and spleen. These findings provide critical insights into the immunomodulatory role of GSH in TB pathogenesis and suggest potential therapeutic avenues for the treatment of extrapulmonary M.tb infections.

Kupffer cells, the limelight in the liver regeneration

Kupffer cells are pivotal in initiating hepatocyte proliferation and establishing connections between different cell types during liver regeneration following partial hepatectomy. As resident macrophages within the liver, Kupffer cells collaborate with hepatocytes and non-parenchymal cells to release various inflammatory mediators that promote hepatocyte proliferation through induction signals like STAT3 phosphorylation. Additionally, the regeneration and replenishment of Kupffer cells themselves are integral components of liver regeneration. The supplementation of the Kupffer cell pool primarily occurs through two pathways: one involves local proliferation of Kupffer cells in their original location, while the other entails infiltration of circulating monocytes into the liver, followed by acquiring Kupffer cell phenotypes under the combined influence of multiple inducing factors. Extensive research has focused on intercellular crosstalk among various types of liver cells during liver regeneration, highlighting the crucial role played by Kupffer cells. This article aims to introduce Kupffer cells and their involvement in liver regeneration, as well as discuss the steady-state balance of Kupffer cell pools during this process.

ANGPTL4 induces Kupffer cell M2 polarization to mitigate acute rejection in liver transplantation

Acute rejection (AR) is a significant complication in liver transplantation, impacting graft function and patient survival. Kupffer cells (KCs), liver-specific macrophages, can polarize into pro-inflammatory M1 or anti-inflammatory M2 phenotypes, both of which critically influence AR outcomes. Angiopoietin-like 4 (ANGPTL4), a secretory protein, is recognized for its function in regulating inflammation and macrophage polarization. This study investigates the effects of ANGPTL4 on KC polarization through cellular interactions between hepatocytes (HCs) and KCs. Using a rat orthotopic liver transplantation model, we observed reduced ANGPTL4 expression during AR, whereas increased ANGPTL4 levels were linked to immune tolerance. Administration of ANGPTL4 recombinant protein improved liver function, suppressed inflammation, and promoted M2 polarization of KCs. Co-culture experiments demonstrated that hepatocyte-derived ANGPTL4 significantly modulates KC polarization and inflammatory responses, mainly by inhibiting the NF-κB signaling pathway. The results emphasize the promise of ANGPTL4 as a therapeutic target to reduce AR and improve liver transplant outcomes by influencing hepatocyte-KC interactions.

Nicotinamide riboside targets mitochondrial unfolded protein response to reduce alcohol-induced damage in Kupffer cells

The pathogenesis of alcohol-related liver disease (ALD) is closely linked to mitochondrial dysfunction and impaired cellular energy metabolism. In this study, we explored how ethanol triggers inflammation, oxidative stress, and mitochondrial dysfunction in Kupffer cells, i.e.hepatic resident macrophages, primarily focusing on the mitochondrial unfolded protein response (UPRmt) using immortalized mouse Kupffer cells (ImKCs) and mouse primary KCs. The UPRmt is a cellular defense mechanism activated in response to the perturbation of mitochondrial proteostasis to maintain mitochondrial integrity and function by upregulating the expression of mitochondrial chaperones and proteases. We also determined whether nicotinamide riboside (NR), a NAD+ precursor, could mitigate ethanol-triggered cellular damage. When ImKCs were exposed to 80 mm ethanol for 72 h, they displayed inflammation, oxidative stress, and impaired mitochondrial function with decreased mitochondrial content and deformed mitochondrial crista structure. NR, however, counteracted the effects of ethanol. Furthermore, ethanol increased mRNA and protein levels of UPRmt genes, such as mitochondrial chaperones and proteases, which were attenuated by NR. Notably, the ethanol-induced shift in the entry of activating transcription factor 5 (ATF5), a putative transcriptional regulator of UPRmt, to the nucleus from the mitochondria was abolished by NR. The induction of UPRmt genes by ethanol was significantly repressed when Atf5 was knocked down, indicating the role of ATF5 in the induction of UPRmt genes in ImKCs exposed to ethanol. We also confirmed the induction of UPRmt gene expression in mouse and human livers exposed to alcohol. Our findings demonstrate the ability of NR to alleviate ethanol-induced oxidative stress, inflammation, and mitochondrial dysfunction, partly by modulating the ATF5-dependent UPRmt pathway in ImKCs, suggesting its potential for ALD therapy. © 2024 The Pathological Society of Great Britain and Ireland.

Sinusoidal communication in chronic liver disease

The liver sinusoid, mainly composed of liver sinusoidal endothelial cells, hepatic macrophages and hepatic stellate cells, shapes the hepatic vasculature and is key to maintaining liver homeostasis and function. During chronic liver disease (CLD), the function of sinusoidal cells is impaired, being directly involved in the progression of liver fibrosis, cirrhosis, and main clinical complications including portal hypertension and hepatocellular carcinoma. In addition to their roles in liver diseases pathobiology, sinusoidal cells' paracrine communication or cross-talk is being studied as a mechanism of disease but also as a remarkable target for treatment. The aim of this review is to gather current knowledge of intercellular signalling in the hepatic sinusoid during the progression of liver disease. We summarise studies developed in pre-clinical models of CLD, especially emphasizing those pathways characterized in human-based clinically relevant models. Finally, we describe pharmacological treatments targeting sinusoidal communication as promising options to treat CLD and its clinical complications.

Kupffer Cell-derived IL6 Promotes Hepatocellular Carcinoma Metastasis Via the JAK1-ACAP4 Pathway

Tumor-associated macrophages (TAMs), which differentiate from tissue-resident macrophages, are recognized for their ability to influence cancer progression and metastasis. However, the specific role of Kupffer cells (KCs), the intrinsic macrophages of the liver, in the progression of hepatocellular carcinoma (HCC) remains unclear. In this study, we describe a novel mechanism by which exosomes derived from HCC cells induce KCs to transition into TAMs, thereby facilitating the metastasis of HCC in an IL6-JAK1-ACAP4 axis-dependent manner. Mechanistically, the exosome-mediated domestication of KCs by hepatoma cells constitutes one of the primary sources of IL6 production in the HCC microenvironment. IL6 then activates JAK1 to phosphorylate its downstream effector ACAP4 at Tyr843, a novel phosphorylation site identified in this context, which in turn promotes ARF6-GTPase activity and hepatoma cell migration. Furthermore, we found that the levels of IL6, as well as the phosphorylation of JAK1 and ACAP4 at Tyr843, were significantly greater in tumor tissues from HCC patients than in adjacent tissues. These findings suggest that the IL6-JAK1-ACAP4 axis may be a promising therapeutic target for HCC. Importantly, we screened bufalin, an active ingredient derived from Venenum Bufonis, and discovered that it inhibits JAK1 and disrupts the IL6-induced phosphorylation of ACAP4. This inhibition not only impairs hepatoma cell migration but also prevents the metastasis of HCC. These findings demonstrate the interplay between hepatoma cells and KCs through the IL6-JAK1-ACAP4 axis, thereby promoting HCC metastasis, and reveal the therapeutic potential of bufalin for the treatment of HCC through JAK1 inhibition.

NK cell exhaustion in Wilson's disease revealed by single-cell RNA sequencing predicts the prognosis of cholecystitis

Metabolic abnormalities associated with liver disease have a significant impact on the risk and prognosis of cholecystitis. However, the underlying mechanism remains to be elucidated. Here, we investigated this issue using Wilson's disease (WD) as a model, which is a genetic disorder characterized by impaired mitochondrial function and copper metabolism. Our retrospective clinical study found that WD patients have a significantly higher incidence of cholecystitis and a poorer prognosis. The hepatic immune cell landscape using single-cell RNA sequencing showed that the tissue immune microenvironment is altered in WD, mainly a major change in the constitution and function of the innate immune system. Exhaustion of natural killer (NK) cells is the fundamental factor, supported by the upregulated expression of inhibitory receptors and the downregulated expression of cytotoxic molecules, which was verified in clinical samples. Further bioinformatic analysis confirmed a positive correlation between NK cell exhaustion and poor prognosis in cholecystitis and other inflammatory diseases. The study demonstrated dysfunction of liver immune cells triggered by specific metabolic abnormalities in WD, with a focus on the correlation between NK cell exhaustion and poor healing of cholecystitis, providing new insights into the improvement of inflammatory diseases by assessing immune cell function.

Gram-negative bacteria-driven increase of cytosolic phospholipase A2 leads to activation of Kupffer cells

Bacterial infections are prevalent and the major cause of morbidity and mortality in cirrhosis. Activation of human Kupffer cells (HKCs) from livers is essential for human innate immunity. Cytosolic phospholipase A2 (cPLA2) plays a crucial role in the control and balance of innate immune and inflammatory reactions. Uncharacterized is the role of cPLA2 in HKC activation by bacterial infection. This work aimed to determine the function and mechanism of cPLA2 in gram-negative bacteria (GNB)-induced HKC activation. In this study, we found that Escherichia coli (E. coli)-induced activation of HKCs led to a rise in cPLA2 mRNA and protein expression, where the ERK and NF-κB pathways were concurrently triggered. Luciferase activity of cPLA2' promoters, PLA2G4A promoters, was enhanced with the stimulation of E. coli or co-transfection with STAT3 or RelB in HKCs. E. coli massively boosted the binding activity of STAT3 and RelB to the specific regions of the PLA2G4A promoter as measured by ChIP-qPCR. The E. coli-ERK-STAT3 and E. coli-non-canonical NF-κB-RelB signaling axes were then identified using pathway inhibitors and transcription factors in the rescue experiments during E. coli-induced HKC activation. In conclusion, we discovered that cPLA2 is necessary for E. coli-induced HKC activation, and the underlying mechanism could be the transcriptional regulation of STAT3 and RelB on the PLA2G4A promoter following the ERK and non-canonical NF-κB signaling activation, implying that the regulation of cPLA2 expression via the E. coli-ERK/non-canonical NF-κB-STAT3/RelB signaling axis could be effective for controlling GNB-induced HKC activation in cirrhotic patients.

Single-cell transcriptomics reveals tumor microenvironment changes and prognostic gene signatures in hepatocellular carcinoma

BACKGROUND

Hepatocellular Carcinoma (HCC) is the most common type of primary liver cancer, accounting for the majority of liver cancer cases. Hepatocellular Carcinoma not only exhibits high heterogeneity but also possesses an immune-suppressive tumor microenvironment that promotes tumor evasion, posing substantial difficulties for efficient therapy. Our aim is to utilize single-cell RNA transcriptome data to investigate the dynamic changes in the tumor microenvironment during the malignant progression of HCC, the communication among immune cells, and the marker genes associated with patient prognosis.

METHODS

We constructed expression matrices from open single-cell RNA transcriptome data (GSE149614) of HCC patients (representing stages I-IV), establishing single-cell RNA transcriptional atlases for different stages of HCC progression. For each stage, we conducted cell subgroup analysis to identify cell types at each stage. Horizontally, we explored the dynamic changes of the same cell type across different stages, performing trajectory analysis and prognosis analysis. Vertically, we investigated pairwise comparisons of different stages of HCC progression, probing the dynamic alterations in tumor microenvironment immune cell signaling pathways. Finally, potential drugs for the treatment of HCC were predicted based on relevant genes.

FINDINGS

As the HCC advances towards increased malignancy, there is a shift in the predominant composition of the tumor microenvironment, with a decline in the dominance of hepatic cells. Tumor-infiltrating immune cells migrate and accumulate within the tumor microenvironment, where T cells and myeloid cells display distinct patterns of change. Genes associated with cancer-associated fibroblasts (CAFs) and T cells are correlated with adverse patient outcomes. In the late stages of HCC, the tumor microenvironment is infiltrated by more myeloid-derived suppressor cells (MDSCs), and a prognostic model constructed based on genes related to myeloid cells can predict patient outcomes. Additionally, in the analysis of transcription factors, YY1 and MYC are found to be highly expressed. Cell communication analysis among tumor-infiltrating immune cells reveals significant differences in the main signaling pathways at different stages of HCC progression. Finally, drug sensitivity analysis based on key genes identifies Acetalax, Allopurinol, and Amonafide as potential candidates for HCC treatment.

Navigating the complex role of senescence in liver disease

ABSTRACT

Cellular senescence, an irreversible state of cell cycle arrest characterized by phenotypic changes and a specific secretory profile, plays a dual role in liver health and disease. Under physiological conditions, senescence aids organ repair and regeneration, but its accumulation due to aging or pathological stress significantly contributes to chronic liver diseases, including alcoholic liver disease, metabolic dysfunction-associated steatohepatitis, liver fibrosis, and hepatocellular carcinoma. Senescence is identified by a range of cellular and molecular changes, such as morphological alterations, expression of cell cycle inhibitors, senescence-associated β-galactosidase activity, and nuclear membrane changes. The onset of senescence in organ cells can affect the entire organism, primarily through the senescence-associated secretory phenotype, which has autocrine, paracrine, and endocrine effects on tissue microenvironments. The objective of this review is to offer a contemporary overview of the pathophysiological events involving hepatic senescent cells and to elucidate their role in the onset and progression of liver diseases, particularly through mechanisms like telomere shortening, genomic and mitochondrial DNA damage, and inflammation. Additionally, this review discusses the emerging senolytic therapies aimed at targeting senescent cells to delay or mitigate liver disease progression. The therapeutic potential of these interventions, alongside their safety and effectiveness, highlights the need for further research to refine these approaches and address unresolved problems in the field of hepatic cellular senescence.

Sparstolonin B potentiates the antitumor activity of nanovesicle-loaded drugs by suppressing the phagocytosis of macrophages in vivo

BACKGROUND

Extracellular vesicles (EVs) and extruded nanovesicles (ENVs) are promising nanovesicles (NVs) for drug delivery. However, the application of these NVs is strongly hindered by their short half-life in the circulation. Macrophages (Mφs) in the liver and spleen contribute to the rapid depletion of NVs, but the underlying mechanism is unclear.

METHODS

By collecting the supernatant of PANC-1 cells and squeezing PANC-1 cells, EVs and ENVs derived from PANC-1 cells were prepared via ultracentrifugation. NVs were subsequently identified via western blot, particle size measurement, and electron microscopy. The distribution of NVs in mouse bodies was observed with a live animal imaging system. Liver Mφs were extracted and isolated after NVs were administered, and transcriptome profiling was applied to determine differentially expressed genes (DEGs). siRNAs targeting interested genes were designed and synthesized. In vitro experiments, Mφs were transfected with siRNA or treated with the corresponding inhibitor, after which NV uptake was recorded. Doxorubicin (DOX) was encapsulated in ENVs using an ultrasound method. PANC-1 cell-derived tumors were established in nude mice in vivo, inhibitor pretreatment or no treatment was administered before intravenous injection of ENVs-DOX, and the therapeutic efficacy of ENVs-DOX was evaluated.

RESULTS

NVs derived from PANC-1 cells were first prepared and identified. After intravenous injection, most NVs were engulfed by Mφs in the liver and spleen. Seven genes of interest were selected via transcriptome sequencing and validated via RT‒PCR. These results confirmed that the TLR2 signaling pathway is responsible for phagocytosis. siTLR2 and its inhibitor sparstolonin B (SpB) significantly inhibited the internalization of NVs by Mφs and downregulated the activity of the TLR2 pathway. The accumulation of ENVs-DOX in the liver was inhibited in vivo by pretreatment with SpB 40 min before intravenous injection, ultimately delaying tumor progression.

CONCLUSION

The TLR2 pathway plays a crucial role in the sequestration of NVs by Mφs. A novel antiphagocytic strategy in which pretreatment of mice with SpB inhibits the clearance of NVs and prolongs their half-life in vivo, thereby improving delivery efficiency, was identified.

Vitamin D 1,25-Dihydroxyvitamin D3 reduces lipid accumulation in hepatocytes by inhibiting M1 macrophage polarization

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD), which is a significant liver condition associated with metabolic syndrome, is the leading cause of liver diseases globally and its prevalence is on the rise in most nations. The protective impact of vitamin D on NAFLD and its specific mechanism remains unclear.

AIM

To examine the role of vitamin D in NAFLD and how vitamin D affects the polarization of hepatic macrophages in NAFLD through the vitamin D receptor (VDR)-peroxisome proliferator activated receptor (PPAR)γ pathway.

METHODS

Wild-type C57BL/6 mice were provided with a high-fat diet to trigger NAFLD model and administered 1,25-dihydroxy-vitamin D [1,25(OH)2D3] supplementation. 1,25(OH)2D3 was given to RAW264.7 macrophages that had been treated with lipid, and a co-culture with AML12 hepatocytes was set up. Lipid accumulation, lipid metabolism enzymes, M1/M2 phenotype markers, proinflammatory cytokines and VDR-PPARγ pathway were determined.

RESULTS

Supplementation with 1,25(OH)2D3 relieved hepatic steatosis and decreased the proinflammatory M1 polarization of hepatic macrophages in NAFLD. Administration of 1,25(OH)2D3 suppressed the proinflammatory M1 polarization of macrophages induced by fatty acids, thereby directly relieving lipid accumulation and metabolism in hepatocytes. The VDR-PPARγ pathway had a notable impact on reversing lipid-induced proinflammatory M1 polarization of macrophages regulated by the administration of 1,25(OH)2D3.

CONCLUSION

Supplementation with 1,25(OH)2D3 improved hepatic steatosis and lipid metabolism in NAFLD, linked to its capacity to reverse the proinflammatory M1 polarization of hepatic macrophages, partially by regulating the VDR-PPARγ pathway. The involvement of 1,25(OH)2D3 in inhibiting fatty-acid-induced proinflammatory M1 polarization of macrophages played a direct role in relieving lipid accumulation and metabolism in hepatocytes.

Metabolic disorders, inter-organ crosstalk, and inflammation in the progression of metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) represents a global health concern, affecting over 30 % of adults. It is a principal driver in the development of cirrhosis and hepatocellular carcinoma. The complex pathogenesis of MASLD involves an excessive accumulation of lipids, subsequently disrupting lipid metabolism and prompting inflammation within the liver. This review synthesizes the recent research progress in understanding the mechanisms contributing to MASLD progression, with particular emphasis on metabolic disorders and interorgan crosstalk. We highlight the molecular mechanisms linked to these factors and explore their potential as novel targets for pharmacological intervention. The insights gleaned from this article have important implications for both the prevention and therapeutic management of MASLD.

Immunological dynamics in MASH: from landscape analysis to therapeutic intervention

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

A Multicellular Mechanochemical Model to Investigate Tumor Microenvironment Remodeling and Pre-Metastatic Niche Formation

Introduction

Colorectal cancer (CRC) is a major cause of cancer related deaths in the United States, with CRC metastasis to the liver being a common occurrence. The development of an optimal metastatic environment is essential process prior to tumor metastasis. This process, called pre-metastatic niche (PMN) formation, involves activation of key resident liver cells, including fibroblast-like stellate cells and macrophages such as Kupffer cells. Tumor-mediated factors introduced to this environment transform resident cells that secrete additional growth factors and remodel the extracellular matrix (ECM), which is thought to promote tumor colonization and metastasis in the secondary environment.

Methods

To investigate the underlying mechanisms of these dynamics, we developed a multicellular computational model to characterize the spatiotemporal dynamics of the PMN formation in tissue. This modeling framework integrates intracellular and extracellular signaling, and traction and junctional forces into a Cellular Potts model, and represents multiple cell types with varying levels of cellular activation. We perform numerical experiments to investigate the role of key factors in PMN formation and tumor invasiveness, including growth factor concentration, timing of tumor arrival, relative composition of resident cells, and the size of invading tumor cluster.

Results

These parameter studies identified growth factor availability and ECM concentration in the environment as two of the key determinants of tumor invasiveness. We further predict that both the ECM concentration potential and growth factor sensitivity of the stellate cells are key drivers of the PMN formation and associated ECM concentration.

Conclusions

Overall, this modeling framework represents a significant step towards simulating cancer metastasis and investigating the role of key factors on PMN formation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-024-00831-0.

Assessment of cell death in the liver of Labeo rohita on exposure to an emerging contaminant aspirin: an immunofluorescent, flow cytometric and biochemical investigation

Aspirin is one of the most frequently detected non-steroidal anti-inflammatory drugs in aquatic environments. Despite its prevalence, toxicity possessed by aspirin to non-target organisms like fish is poorly explored. In the present study, cell death induced by different concentrations of aspirin (1, 10, and 100 µg/L) has been investigated in the liver of fish, Labeo rohita exposed for 28 days. A significant increase (p < 0.05) in the density of caspase-3 positive cells in a dose and duration-dependent manner assessed through immunofluorescent staining indicates caspase-dependent pathway of cell death which may be either through intrinsic or extrinsic pathway. The flow cytometric analysis, in addition, revealed a significant (p < 0.05) decline in the live cells and an increase in apoptotic cells in the liver of fish exposed to aspirin. Cell death due to apoptosis is further indicated by a significant increase (p < 0.05) in the Kupffer cells and tumor necrosis factor-α. The decrease in the activity of cyclooxygenase (COX) enzyme significantly (p < 0.05) in all three exposure concentrations of aspirin suggests COX-dependent pathway of cell death. The present study provides in-depth insights into aspirin-induced cell death in the liver of fish at environmentally realistic concentrations.

The Long-Term Impact of Polysaccharide-Coated Iron Oxide Nanoparticles on Inflammatory-Stressed Mice

Since iron oxide nanoparticles (IONPs) are expected to be important tools in medical care, patients with inflammatory diseases will be increasingly exposed to IONPs in the future. Here, we assessed the short- and long-term impact of polysaccharide (PS)-coated IONPs on mice with persistent systemic inflammation. To this end, PS-IONPs were synthetized by a core-shell method. Mice were regularly injected with sterile zymosan. PS-IONPs were administered intravenously. At specific nanoparticle injection post-observation times, the organ iron concentration was determined via atomic absorption spectrometry, the expression of NF-κB-related proteins using SDS-PAGE and immunoblotting, as well as body weight and haemograms. Finally, the mediator secretion in blood plasma was analysed using multiplexed ELISA. Our data show that PS-IONPs induce short-term changes of iron levels in distinct organs and of NF-κB p65 and p50, p100, COX-2s, and Bcl-2 protein expression in the liver of inflammatory stressed mice. In the long term, there was an attenuated expression of several NF-κB-related proteins and attenuated features of inflammatory-based anaemia in blood. PS-IONPs weakly influenced the blood cytokine levels. PS-IONPs are biocompatible, but given their short-term pro-inflammatory impact, they should prospectively be applied with caution in patients with inflammatory diseases of the liver.

Intraperitoneal hepatorenal toxicity of zinc oxide and nickel oxide nanoparticles in rats: a systematic review

Zinc oxide (ZnO) and nickel oxide (NiO) nanoparticles (NPs) are widely used in various industries due to their distinctive physico-chemical and biological properties. However, concerns have been raised about their potential toxicity in humans. While many studies have reviewed their effects on visceral organs upon ingestion, inhalation, or skin contact, limited reviews are available regarding their adverse consequences on the liver and kidneys resulting from intraperitoneal administration in rats. Hence, this systematic review is the first to uniquely address this issue. A systematic search was performed on PubMed and Google scholar to identify articles that explored the toxic effects of ZnO-NPs and NiO-NPs in rats following intraperitoneal injection. The quality of the articles was assessed using SYCLE's risk of bias tool, leading to the selection of 16 articles; 14 for ZnO-NPs, 1 for NiO-NPs and 1 for both NPs. This review revealed that ZnO-NPs induces an acute toxicity in liver and kidney that is dose dependent. The impairments were marked by changes in organs functional markers, lipid and glucose levels and antioxidant deficiencies and lipid peroxidation. NiO-NPs also showed considerable toxicity, despite the limited studies. Further, variability of physico-chemical properties among studies complicated the toxicity assessment. To conclude, this study provides a novel contribution by summarizing the literature findings that suggest potential adverse intraperitoneal hepatorenal toxic outcomes associated with ZnO-NPs and NiO-NPs. Future research should focus on long-term effects and standardizing protocols to ensure the safe use of ZnO-NPs and NiO-NPs in industrial and clinical practices.

Dissection of molecular mechanisms of liver injury induced by microcystin-leucine arginine via single-cell RNA-sequencing

The occurrence of poisoning incidents caused by cyanobacterial blooms has aroused wide public concern. Microcystin-leucine arginine (MC-LR) is a well-established toxin produced by cyanobacterial blooms, which is widely distributed in eutrophic waters. MC-LR is not only hazardous to the water environment but also exerts multiple toxic effects including liver toxicity in both humans and animals. However, the underlying mechanisms of MC-LR-induced liver toxicity are unclear. Herein, we used advanced single-cell RNA sequencing technology to characterize MC-LR-induced liver injury in mice. We established the first single-cell atlas of mouse livers in response to MC-LR. Our results showed that the differentially expressed genes and pathways in diverse cell types of liver tissues of mice treated with MC-LR are highly heterogeneous. Deep analysis showed that MC-LR induced an increase in a subpopulation of hepatocytes that highly express Gstm3, which potentially contributed to hepatocyte apoptosis in response to MC-LR. Moreover, MC-LR increased the proportion and multiple subtypes of Kupffer cells with M1 phenotypes and highly expressed proinflammatory genes. Furthermore, the MC-LR increased several subtypes of CD8+ T cells with highly expressed multiple cytokines and chemokines. Overall, apart from directly inducing hepatocytes apoptosis, MC-LR activated proinflammatory Kupffer cell and CD8+ T cells, and their interaction may constitute a hostile microenvironment that contributes to liver injury. Our findings not only present novel insight into underlying molecular mechanisms but also provide a valuable resource and foundation for additional discovery of MC-LR-induced liver toxicity.

Mechanistic role of long non-coding RNAs in the pathogenesis of metabolic dysfunction-associated steatotic liver disease and fibrosis

Metabolic dysfunction-associated steatotic liver disease (MASLD), previously referred to as non-alcoholic fatty liver disease, encompasses a broad range of hepatic metabolic disorders primarily characterised by the disruption of hepatic lipid metabolism, hepatic lipid accumulation and steatosis. Severe cases of MASLD might progress to metabolic dysfunction-associated steatohepatitis, characterised by hepatic inflammation, hepatocyte ballooning degeneration, activation of hepatic stellate cells (HSCs) and fibrogenesis. It may further progress to hepatocellular carcinoma. In the liver, long non-coding RNAs (lncRNAs) target multiple metabolic pathways in hepatocytes, HSCs, and Kupffer cells at different stages of MASLD and liver fibrosis. In this study, we overview recent findings on the potential role of lncRNAs in the pathogenesis of MASLD and liver fibrosis via modulation of de novo lipid synthesis, fatty acid β-oxidation, lipotoxicity, oxidative stress, metabolic inflammation, mammalian target of rapamycin signalling, apoptosis, ubiquitination and fibrogenesis. We critically assess the literature reports that investigate the complex interplay between lncRNA, microRNA and key mediators in liver injury, in both human participants and animal models of MASLD and liver fibrosis. We also highlight the therapeutic potential of lncRNAs in chronic liver diseases.

The influence of biophysical niche on tumor-associated macrophages in liver cancer

HCC, the most common type of primary liver cancer, is a leading cause of cancer-related mortality worldwide. Although the advancement of immunotherapies by immune checkpoint inhibitors (ICIs) that target programmed cell death 1 or programmed cell death 1-ligand 1 has revolutionized the treatment for HCC, the majority is still not beneficial. Accumulating evidence has pointed out that the potent immunosuppressive tumor microenvironment in HCC poses a great challenge to ICI therapeutic efficacy. As a key component in tumor microenvironment, tumor-associated macrophages (TAMs) play vital roles in HCC development, progression, and ICI low responsiveness. Mechanistically, TAM can promote cancer invasion and metastasis, angiogenesis, epithelial-mesenchymal transition, maintenance of stemness, and most importantly, immunosuppression. Targeting TAMs, therefore, represents an opportunity to enhance the ICI therapeutic efficacy in patients with HCC. While previous research has primarily focused on biochemical cues influencing macrophages, emerging evidence highlights the critical role of biophysical signals, such as substrate stiffness, topography, and external forces. In this review, we summarize the influence of biophysical characteristics within the tumor microenvironment that regulate the phenotype and function of TAMs in HCC pathogenesis and progression. We also explore the possible mechanisms and discuss the potential of manipulating biophysical cues in regulating TAM for HCC therapy. By gaining a deeper understanding of how macrophages sense and respond to mechanical forces, we may potentially usher in a path toward a curative approach for combinatory cancer immunotherapies.

Artemisia argyi ethanol extract ameliorates nonalcoholic steatohepatitis-induced liver fibrosis by modulating gut microbiota and hepatic signaling

ETHNOPHARMACOLOGICAL RELEVANCE

Artemisia argyi (AA), a herbal medicine traditionally used in Asian countries, to treat inflammatory conditions such as eczema, dermatitis, arthritis, allergic asthma and colitis. However, the mechanism of action of this plant with regard to hepatitis and other liver-related diseases is still unclear.

AIM

This study aimed to investigate the effects of AA ethanol extract on NASH-related fibrosis and gut microbiota in a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD)-induced mouse model.

METHODS

Male C57BL/6J mice were fed CDAHFD, with or without AA ethanol extract treatment. Biochemical markers, lipid profiles, hepatic mRNA expression levels of key genes, and the fibrosis area were assessed. In vitro, TGF-β-stimulated human hepatic stellate LX-2 cells and mouse primary hepatic stellate cells (mHSCs) were used to elucidate the effects of AA ethanol extract on fibrosis and steatosis. 16S rRNA sequencing, QIIME2, and PICRUST2 were employed to analyze gut microbial diversity, composition, and functional pathways.

RESULTS

Treatment with the AA ethanol extract improved plasma and liver lipid profiles, modulated hepatic mRNA expression levels of antioxidant, lipolytic, and fibrosis-related genes, and significantly reduced CDAHFD-induced hepatic fibrosis. Gut microbiota analysis revealed a marked decrease in Acetivibrio ethanolgignens abundance upon treatment with the AA ethanol extract, and its functional pathways were significantly correlated with NASH/fibrosis markers. The AA ethanol extract and its active components (jaceosidin, eupatilin, and chlorogenic acid) inhibited fibrosis-related markers in LX-2 and mHSC.

CONCLUSION

The AA ethanol extract exerted therapeutic effects on CDAHFD-induced liver disease by modulating NASH/fibrosis-related factors and gut microbiota composition. Notably, AA treatment reduced the abundance of the potentially profibrotic bacterium (A. ethanolgignens). These findings suggest that AA is a promising candidate for treating NASH-induced fibrosis.

Curdlan-Mediated Syngeneic RNAi against NF-κB in Glial Cells Protects Cerebral Vessels in the TBI Mouse Model

Traumatic brain injury (TBI) activates the NF-κB pathway in microglia and astrocytes, which secrete pro-inflammatory cytokines that disrupt the blood-brain barrier (BBB). Curdlan derivatives are promising carriers for the delivery of siRNA drugs. Herein, we evaluated the glial cell specificity, siRNA delivery efficiency, and the subsequent phenotypic regulation of glial cells by the Curdlan derivatives in the TBI mouse model. Our in vitro and in vivo studies confirmed that the (1) pAVC4 or CuMAN polymer encapsulating siRNA were internalized by astrocytes and microglia in a receptor-dependent manner; (2) systemic administration of the pAVC4 or CuMAN polymer encapsulating siRNA resulted in significant gene silencing efficiency, altered the phenotypic polarization of glial cells, and regulated the secretion of inflammatory cytokines; (3) this lessened neuroinflammation, ameliorated BBB destruction, and improved vascular recovery. These data suggested that pAVC4 and CuMAN polymers are promising RNA delivery vehicles that can efficiently deliver siRNA to the target cells.

Macrophage variants in laboratory research: most are well done, but some are RAW

Macrophages play a pivotal role in the innate immune response. While their most characteristic function is phagocytosis, it is important not to solely characterize macrophages by this activity. Their crucial roles in body development, homeostasis, repair, and immune responses against pathogens necessitate a broader understanding. Macrophages exhibit remarkable plasticity, allowing them to modify their functional characteristics in response to the tissue microenvironment (tissue type, presence of pathogens or inflammation, and specific signals from neighboring cells) swiftly. While there is no single defined "macrophage" entity, there is a diverse array of macrophage types because macrophage ontogeny involves the differentiation of progenitor cells into tissue-resident macrophages, as well as the recruitment and differentiation of circulating monocytes in response to tissue-specific cues. In addition, macrophages continuously sense and respond to environmental cues and tissue conditions, adjusting their functional and metabolic states accordingly. Consequently, it is of paramount importance to comprehend the heterogeneous origins and functions of macrophages employed in in vitro studies, as each available in vitro macrophage model is associated with specific sets of strengths and limitations. This review centers its attention on a comprehensive comparison between immortalized mouse macrophage cell lines and primary mouse macrophages. It provides a detailed analysis of the strengths and weaknesses inherent in these in vitro models. Finally, it explores the subtle distinctions between diverse macrophage cell lines, offering insights into numerous factors beyond the model type that can profoundly influence macrophage function.

Neutrophil extracellular traps activate hepatic stellate cells and monocytes via NLRP3 sensing in alcohol-induced acceleration of MASH fibrosis

OBJECTIVE

Alcohol use in metabolic dysfunction-associated steatohepatitis (MASH) is associated with an increased risk of fibrosis and liver-related death. Here, we aimed to identify a mechanism through which repeated alcohol binges exacerbate liver injury in a high fat-cholesterol-sugar diet (MASH diet)-induced model of MASH.

DESIGN

C57BL/6 mice received either chow or the MASH diet for 3 months with or without weekly alcohol binges. Neutrophil infiltration, neutrophil extracellular traps (NETs) and fibrosis were evaluated.

RESULTS

We found that alcohol binges in MASH increase liver injury and fibrosis. Liver transcriptomic profiling revealed differential expression of genes involved in extracellular matrix reorganisation, neutrophil activation and inflammation compared with alcohol or the MASH diet alone. Alcohol binges specifically increased NET formation in MASH livers in mice, and NETs were also increased in human livers with MASH plus alcohol use. We discovered that cell-free NETs are sensed via Nod-like receptor protein 3 (NLRP3). Furthermore, we show that cell-free NETs in vitro induce a profibrotic phenotype in hepatic stellate cells (HSCs) and proinflammatory monocytes. In vivo, neutrophil depletion using anti-Ly6G antibody or NET disruption with deoxyribonuclease treatment abrogated monocyte and HSC activation and ameliorated liver damage and fibrosis. In vivo, inhibition of NLRP3 using MCC950 or NLRP3 deficiency attenuated NET formation, liver injury and fibrosis in MASH plus alcohol diet-fed mice (graphical abstract).

CONCLUSION

Alcohol binges promote liver fibrosis via NET-induced activation of HSCs and monocytes in MASH. Our study highlights the potential of inhibition of NETs and/or NLRP3, as novel therapeutic strategies to combat the profibrotic effects of alcohol in MASH.

DNA 5mC and RNA m6A Collaborate to Upregulate Phosphoenolpyruvate Carboxykinase 2 for Kupffer Cell Activation

Both DNA 5-methylcytosine (5mC) and RNA N6-methyladenosine (m6A) modifications are reported to participate in cellular stress responses including inflammation. Phosphoenolpyruvate carboxykinase 2 (PCK2) is upregulated in Kupffer cells (KCs) to facilitate the proinflammatory phosphorylation signaling cascades upon LPS stimulation, yet the role of 5mC and m6A in PCK2 upregulation remain elusive. Here, we report that the significantly augmented PCK2 mRNA and protein levels are associated with global 5mC demethylation coupled with m6A hypermethylation in LPS-activated KCs. The suppression of 5mC demethylation or m6A hypermethylation significantly alleviates the upregulation of PCK2 and proinflammatory cytokines in LPS-challenged KCs. Further reciprocal tests indicate 5mC demethylation is upstream of m6A hypermethylation. Specifically, CpG islands in the promoters of PCK2 and RNA methyltransferase (METTL3 and METTL14) genes are demethylated, while the 3'UTR of PCK2 mRNA is m6A hypermethylated, in LPS-stimulated KCs. These modifications contribute to the transactivation of the PCK2 gene as well as increased PCK2 mRNA stability and protein production via a m6A-mediated mechanism with IGF2BP1 as the reader protein. These results indicate that DNA 5mC and RNA m6A collaborate to upregulate PCK2 expression, respectively, at the transcriptional and post-transcriptional levels during KC activation.

Targeting hepatic macrophages for non-alcoholic fatty liver disease therapy

Non-alcoholic fatty liver disease (NAFLD) and its more advanced form, non-alcoholic steatohepatitis (NASH), have become global health challenges with significant morbidity and mortality rates. NAFLD encompasses several liver diseases, ranging from simple steatosis to more severe inflammatory and fibrotic forms. Ultimately, this can lead to liver cirrhosis and hepatocellular carcinoma. The intricate role of hepatic macrophages, particularly Kupffer cells (KCs) and monocyte-derived macrophages (MoMFs), in the pathogenesis of NAFLD and NASH, has received increasing attention. Hepatic macrophages can interact with hepatocytes, hepatic stellate cells, and endothelial cells, playing a crucial role in maintaining homeostasis. Paradoxically, they also participate in the pathogenesis of some liver diseases. This review highlights the fundamental role of hepatic macrophages in the pathogenesis of NAFLD and NASH, emphasizing their plasticity and contribution to inflammation and fibrosis, and hopes to provide ideas for subsequent experimental research and clinical treatment.

Therapeutic potential of rifaximin in liver diseases

Rifaximin, derived from rifamycin, is a broad-spectrum antibiotic by inhibiting bacterial RNA synthesis. Rifaximin has a very low intestinal absorption and exerts its antimicrobial activity primarily in the intestinal tract. It regulates the gut microbiota with limited side effects systemically. Rifaximin has been recommended for the treatment of hepatic encephalopathy but some studies shed light on its medicinal effects in many other diseases. For instance, rifaximin may suppress the progression of liver fibrosis and its related complications, and ameliorate metabolic dysfunction-associated steatotic liver disease and alcohol-associated liver disease, etc. Rifaximin can also mediate anti-inflammation, antiproliferation, and proapoptotic events by activating pregnane X receptor, which is efficious in cancers such as colon cancer. In addition, some investigations have shown rifaximin may play a therapeutic role in various autoimmune and neurological disorders. However, these findings still need more real-world practices and in-depth investigations to obtain more precise indications and fully elucidate the multifaceted potentials of rifaximin.

Mechanisms of Tolerance Induction in Liver Transplantation: Lessons Learned from Fetomaternal Tolerance, Autoimmunity and Tumor Immunity

Since the first published report of experimental kidney transplantation in dogs in 1902, there were many experimental and clinical trials of organ transplantation, with many sacrifices. After the establishment of the surgical technique and the discovery of immunosuppressive drugs, transplantation became the definitive treatment strategy for patients with terminal organ failure. However, this is not a common therapy method due to the difficulty of solving the fundamental issues behind organ transplantation, including the shortage of donor graft, potential risks of transplant surgery and economic capability. The pre- and post-transplant management of recipients is another critical issue that may affect transplant outcome. Most liver transplant recipients experience post-transplant complications, including infection, acute/chronic rejection, metabolic syndrome and the recurrence of hepatocellular carcinoma. Therefore, the early prediction and diagnosis of these complications may improve overall and disease-free survival. Furthermore, how to induce operational tolerance is the key to achieving the ultimate goal of transplantation. In this review, we focus on liver transplantation, which is known to achieve operational tolerance in some circumstances, and the mechanical similarities and differences between liver transplant immunology and fetomaternal tolerance, autoimmunity or tumor immunity are discussed.

In Vivo Polymer Mechanochemistry with Polynucleotides

Polymer mechanochemistry utilizes mechanical force to activate latent functionalities in macromolecules and widely relies on ultrasonication techniques. Fundamental constraints of frequency and power intensity have prohibited the application of the polymer mechanochemistry principles in a biomedical context up to now, although medical ultrasound is a clinically established modality. Here, a universal polynucleotide framework is presented that allows the binding and release of therapeutic oligonucleotides, both DNA- and RNA-based, as cargo by biocompatible medical imaging ultrasound. It is shown that the high molar mass, colloidal assembly, and a distinct mechanochemical mechanism enable the force-induced release of cargo and subsequent activation of biological function in vitro and in vivo. Thereby, this work introduces a platform for the exploration of biological questions and therapeutics development steered by mechanical force.

Crosstalk in extrahepatic and hepatic system in NAFLD/NASH

Non-alcoholic fatty liver disease (NAFLD) has emerged as the most prevalent chronic liver disease globally. Non-alcoholic steatohepatitis (NASH) represents an extremely progressive form of NAFLD, which, without timely intervention, may progress to cirrhosis or hepatocellular carcinoma. Presently, a definitive comprehension of the pathogenesis of NAFLD/NASH eludes us, and pharmacological interventions targeting NASH specifically remain constrained. The aetiology of NAFLD encompasses a myriad of external factors including environmental influences, dietary habits and gender disparities. More significantly, inter-organ and cellular interactions within the human body play a role in the development or regression of the disease. In this review, we categorize the influences affecting NAFLD both intra- and extrahepatically, elaborating meticulously on the mechanisms governing the onset and progression of NAFLD/NASH. This exploration delves into progress in aetiology and promising therapeutic targets. As a metabolic disorder, the development of NAFLD involves complexities related to nutrient metabolism, liver-gut axis interactions and insulin resistance, among other regulatory functions of extraneous organs. It further encompasses intra-hepatic interactions among hepatic cells, Kupffer cells (KCs) and hepatic stellate cells (HSCs). A comprehensive understanding of the pathogenesis of NAFLD/NASH from a macroscopic standpoint is instrumental in the formulation of future therapies for NASH.

Farnesoid X receptor: From Structure to Function and Its Pharmacology in Liver Fibrosis

The farnesoid X receptor (FXR), a ligand-activated transcription factor, plays a crucial role in regulating bile acid metabolism within the enterohepatic circulation. Beyond its involvement in metabolic disorders and immune imbalances affecting various tissues, FXR is implicated in microbiota modulation, gut-to-brain communication, and liver disease. The liver, as a pivotal metabolic and detoxification organ, is susceptible to damage from factors such as alcohol, viruses, drugs, and high-fat diets. Chronic or recurrent liver injury can culminate in liver fibrosis, which, if left untreated, may progress to cirrhosis and even liver cancer, posing significant health risks. However, therapeutic options for liver fibrosis remain limited in terms of FDA-approved drugs. Recent insights into the structure of FXR, coupled with animal and clinical investigations, have shed light on its potential pharmacological role in hepatic fibrosis. Progress has been achieved in both fundamental research and clinical applications. This review critically examines recent advancements in FXR research, highlighting challenges and potential mechanisms underlying its role in liver fibrosis treatment.

Restoring SRSF3 in Kupffer cells attenuates obesity-related insulin resistance

BACKGROUND AND AIMS

In obesity, depletion of KCs expressing CRIg (complement receptor of the Ig superfamily) leads to microbial DNA accumulation, which subsequently triggers tissue inflammation and insulin resistance. However, the mechanism underlying obesity-mediated changes in KC complement immune functions is largely unknown.

APPROACH AND RESULTS

Using KC-specific deactivated Cas9 transgenic mice treated with guide RNA, we assessed the effects of restoring CRIg or the serine/arginine-rich splicing factor 3 (SRSF3) abundance on KC functions and metabolic phenotypes in obese mice. The impacts of weight loss on KC responses were evaluated in a diet switch mouse model. The role of SRSF3 in regulating KC functions was also evaluated using KC-specific SRSF3 knockout mice. Here, we report that overexpression of CRIg in KCs of obese mice protects against bacterial DNA accumulation in metabolic tissues. Mechanistically, SRSF3 regulates CRIg expression, which is essential for maintaining the CRIg+ KC population. During obesity, SRSF3 expression decreases, but it is restored with weight loss through a diet switch, normalizing CRIg+ KCs. KC SRSF3 is also repressed in obese human livers. Lack of SRSF3 in KCs in lean and obese mice decreases their CRIg+ population, impairing metabolic parameters. During the diet switch, the benefits of weight loss are compromised due to SRSF3 deficiency. Conversely, SRSF3 overexpression in obese mice preserves CRIg+ KCs and improves metabolic responses.

CONCLUSIONS

Restoring SRSF3 abundance in KCs offers a strategy against obesity-associated tissue inflammation and insulin resistance by preventing bacterial DNA accumulation.