The role of neutrophils in alcohol-related hepatitis

Microbiota in Alcohol-Associated Organ Damage

Alcohol-associated organ damage is a major cause of morbidity and mortality worldwide, with the liver being the primarily affected organ. Emerging evidence highlights the gut microbiota as a key driver in alcohol-associated liver disease. Changes in the microbiota composition, microbial translocation, and a dysregulated immune response culminate in inflammation and tissue injury. Persistent liver injury eventually promotes disease progression from steatohepatitis to fibrosis and cirrhosis. In this review, we provide an overview of microbiota alterations observed in patients with chronic alcohol consumption and explore the mechanisms by which microbiota contributes to alcohol-associated damage across various organ systems. Emphasis is placed on changes in the gut microbiota and its role in alcohol-associated liver disease, the disease condition with the most robust evidence linking microbiota-related changes to organ injury. Additionally, we highlight key areas where further research is needed to address unresolved questions. Finally, we discuss emerging therapeutic strategies targeting the microbiota to treat alcohol use disorders and prevent alcohol-associated liver diseases.

Immunological mechanisms and emerging therapeutic targets in alcohol-associated liver disease

Alcohol-associated liver disease (ALD) is a major global health challenge, with inflammation playing a central role in its progression. As inflammation emerges as a critical therapeutic target, ongoing research aims to unravel its underlying mechanisms. This review explores the immunological pathways of ALD, highlighting the roles of immune cells and their inflammatory mediators in disease onset and progression. We also examine the complex interactions between inflammatory cells and non-parenchymal liver cells, as well as their crosstalk with extra-hepatic organs, including the gut, adipose tissue, and nervous system. Furthermore, we summarize current clinical research on anti-inflammatory therapies and discuss promising therapeutic targets. Given the heterogeneity of ALD-associated inflammation, we emphasize the need for precision medicine to optimize treatment strategies and improve patient outcomes.

Current insights into pathogenesis and anti-inflammatory treatment strategies for severe alcohol-associated hepatitis: focus on neutrophil-targeted therapies

Alcohol-associated hepatitis (AH) is the leading cause of liver-related mortality, with severe alcohol-associated hepatitis (SAH) showing a short-term mortality rate of 20%-50% even in developed countries. Corticosteroids are the only evidence-based pharmacologic treatment, but their efficacy is limited to short-term survival, with 30%-40% of patients achieving a complete response. Early liver transplantation (LT) has been explored as a salvage therapy for steroid-refractory SAH, but its feasibility is restricted by ethical concerns and donor shortages, particularly in Japan. In the absence of LT eligibility, patients are often left with the best supportive care, underscoring the urgent need for alternative salvage therapies. Recent studies have explored selective anti-inflammatory strategies targeting proinflammatory cytokines, such as TNFα and IL-1β. However, clinical trials have yet to demonstrate sufficient efficacy to outweigh the increased risk of infection. Granulocyte colony-stimulating factor (G-CSF) therapy has been investigated for its potential to promote liver regeneration, but its efficacy remains inconsistent across populations. Neutrophil-targeted therapies, including granulocyte-monocyte/macrophage apheresis (GMA), have emerged as a novel approach. Our recent pilot study demonstrated improved survival in patients with steroid-refractory SAH treated with GMA, supporting its potential as a safe and effective anti-inflammatory therapy. This review summarizes the latest advances in the treatment of SAH and emphasizes the need for novel salvage therapies to address unmet needs in steroid-refractory cases. Further research is essential to validate these new therapies and to optimize treatment strategies to improve the long-term prognosis of SAH.

Phytochemicals Targeting Inflammatory Pathways in Alcohol-Induced Liver Disease: A Mechanistic Review

Alcoholic beverages play a significant role in social engagement worldwide. Excessive alcohol causes a variety of health complications. Alcohol-induced liver disease (ALD) is responsible for the bulk of linked fatalities. The activation of immune mechanisms has a crucial role in developing ALD. No effective medication promotes liver function, shields the liver from harm, or aids in hepatic cell regeneration. Alcohol withdrawal is one of the most beneficial therapies for ALD patients, which improves the patient's chances of survival. There is a crucial demand for safe and reasonably priced approaches to treating it. Exploring naturally derived phytochemicals has been a fascinating path, and it has drawn attention in recent years to modulators of inflammatory pathways for the prevention and management of ALD. In this review, we have discussed the roles of various immune mechanisms in ALD, highlighting the importance of intestinal barrier integrity and gut microbiota, as well as the roles of immune cells and hepatic inflammation, and other pathways, including cGAS-STING, NLRP3, MAPK, JAK-STAT, and NF-kB. Further, this review also outlines the possible role of phytochemicals in targeting these inflammatory pathways to safeguard the liver from alcohol-induced injury. We highlighted that targeting immunological mechanisms using phytochemicals or herbal medicine may find a place to counteract ALD. Preclinical in vitro and in vivo investigations have shown promising results; nonetheless, more extensive work is required to properly understand these compounds' mechanisms of action. Clinical investigations are very crucial in transferring laboratory knowledge into effective patient therapy.

Neutrophil extracellular traps (NETs) and NETosis in alcohol-associated diseases: A systematic review

Heavy alcohol consumption is implicated in the alteration of the antimicrobial function of neutrophils, such as phagocytosis, chemotaxis, the formation of neutrophil extracellular traps (NETs), and the occurrence of NETosis. NETosis is an endogenous process of elimination of invading microbes, autoantibodies, and inflammatory elements such as danger-associated molecular patterns (DAMPs) and pathogen-associated patterns (PAMPs). However, both exaggeration and suppression of NETosis modulate normal physiological and metabolic processes by influencing events at the molecular and cellular levels. Recent research shows that binge alcohol consumption induces NETosis, leading to tissue damage and inflammation. Binge alcohol consumption, chronic alcohol intake, and alcohol use disorder (AUD) can affect immunity and often lead to alcohol-associated liver disease (ALD) and/or other organ damage. Alcohol can lead to detrimental consequences in multiple organs, including the brain, liver, pancreas, and gut. Gut-derived microbial substances, such as endotoxins in the circulation, induce systemic inflammation. Sterile danger signals from damaged cells, cytokines, and prostaglandins act as proinflammatory stimuli and are involved in multiple signaling pathways. The alcohol-induced proinflammatory cytokines chemoattract neutrophils, which interact and coordinate with other immune cells to exaggerate or suppress inflammation within the inflammatory milieu, depending on the alcohol effects. Several proteins, including different receptors, play important roles in the activation and formation of NETs as well as the initiation and execution of NETosis. This review article specifically gathers the current information on NETosis, its biological components, and signaling pathways relating to the formation of NETs and the occurrence of NETosis associated with ALD and AUD in multiorgans, specifically in the brain, liver, and gut. We also briefly describe various therapeutic strategies against AUD-associated NETosis in experimental models and human disease states.

Targeting the HDAC6/Hint2/MICU1 axis to ameliorate acute liver failure via inhibiting NETosis

AIMS

Acute liver failure (ALF) is marked by extensive inflammation and immune dysregulation, which are closely associated with neutrophil infiltration and NETosis. However, the specific mechanisms that drive NETosis in ALF remain poorly understood.

MATERIALS AND METHODS

We employed flow cytometry, western blot, qRT-PCR, and cf-DNA assay to investigate the link between NETosis and ALF. The role of HDAC6-mediated deacetylation of histidine triad nucleotide-binding protein 2 (Hint2) was assessed, along with the effects of lentiviral vector-based overexpression and knockdown of Hint2 on mitochondrial function and NETosis. Additionally, CO-IP, IF, protein docking analysis, mCa2+ uptake assay, and mtROS measurement were used to explore the interaction between Hint2 and mitochondrial calcium uniporter complex (MCUc). Finally, experimental neutrophil depletion in mice was conducted to confirm the protective effect of NETosis inhibition in ALF.

KEY FINDINGS

Our study demonstrated that Hint2 undergoes HDAC6-mediated deacetylation, disrupting mitochondrial dynamics and triggering NETosis during ALF. Furthermore, MICU1 bridges Hint2 and NETosis by regulating mCa2+ homeostasis and mtROS production. Activation of Hint2, either through the HDAC6 inhibitor ACY1215 or via overexpression, increased the level of MICU1 to suppress the opening of the MCUc and the associated mtROS release, thereby inhibiting NETosis. Conversely, Hint2 knockdown induced NETosis by surging mCa2+ overload and mtROS production, while the MCUc inhibitor RU265 mitigates NETosis by blocking mCa2+ influx.

SIGNIFICANCE

Our findings recognized the HDAC6/Hint2/MICU1 axis as a novel pathway in neutrophils, the inhibition of which intercepts mCa2+ overload and mtROS accumulation, thereby reducing NETosis and facilitating liver recovery during ALF.

Stressed hepatocyte sustains alcohol-associated hepatitis progression by producing leukocyte cell-derived chemotaxin 2

BACKGROUND

Neutrophil infiltration and hepatocyte damage are indispensable hallmarks in alcohol-associated hepatitis (AH), yet the underlying crosstalk between neutrophils and hepatocytes and its role in AH pathogenesis remain unclear.

OBJECTIVE

We investigate the regulatory role of leucocyte cell-derived chemotaxin 2 (LECT2) in hepatocyte-neutrophil interaction and its impact on AH progression.

DESIGN

We used bulk and single-cell RNA sequencing to identify hepatocyte-secreted factors targeting neutrophils. We analysed serum and liver samples from AH patients and employed genetically modified mice alongside in vitro studies.

RESULTS

RNA-sequencing analysis identified several neutrophil chemokines that are elevated in hepatocytes from AH patients, including LECT2 whose role in AH remains largely unknown. AH patients exhibited increased levels of LECT2 in hepatocytes, positively correlating with the severity of AH. Ethanol-fed mice also exhibited elevated liver LECT2, which was abolished by inhibiting endoplasmic reticulum stress. Functional studies revealed that ethanol-induced liver injury was ameliorated in Lect2-deficient mice but was exacerbated in mice with hepatic overexpression of Lect2. Furthermore, LECT2 exacerbated ethanol-induced liver injury by promoting reactive oxygen species (ROS) through its interaction with prohibitin 2 (PHB2), a neutrophil membrane protein. By directly binding to PHB2, LECT2 disrupts the stable structure of PHB1/PHB2 heterodimerisation, consequently leading to PHB2 degradation, ROS accumulation, neutrophil activation and neutrophil extracellular trap formation. Moreover, therapeutic intervention of LECT2 via Lect2 shRNA ameliorated ethanol-induced liver injury.

CONCLUSION

Our studies identified a novel vicious cycle between neutrophils and hepatocytes through the LECT2-PHB2 interaction, presenting a promising therapeutic intervention by targeting LECT2 to mitigate AH in patients.

The Role of Yes-Associated Protein in Inflammatory Diseases and Cancer

Yes-associated protein (YAP) plays a central role in the Hippo pathway, primarily governing cell proliferation, differentiation, and apoptosis. Its significance extends to tumorigenesis and inflammatory conditions, impacting disease initiation and progression. Given the increasing relevance of YAP in inflammatory disorders and cancer, this study aims to elucidate its pathological regulatory functions in these contexts. Specifically, we aim to investigate the involvement and molecular mechanisms of YAP in various inflammatory diseases and cancers. We particularly focus on how YAP activation, whether through Hippo-dependent or independent pathways, triggers the release of inflammation and inflammatory mediators in respiratory, cardiovascular, and digestive inflammatory conditions. In cancer, YAP not only promotes tumor cell proliferation and differentiation but also modulates the tumor immune microenvironment, thereby fostering tumor metastasis and progression. Additionally, we provide an overview of current YAP-targeted therapies. By emphasizing YAP's role in inflammatory diseases and cancer, this study aims to enhance our understanding of the protein's pivotal involvement in disease processes, elucidate the intricate pathological mechanisms of related diseases, and contribute to future drug development strategies targeting YAP.

Therapeutic Effects of DNase I on Peripheral and Local Markers of Liver Injury and Neutrophil Extracellular Traps in a Model of Alcohol-Related Liver Disease

Alcohol-related liver disease (ALD) is a leading cause of chronic liver conditions globally. Chronic alcohol consumption induces liver damage through various mechanisms, including neutrophil extracellular trap (NET) formation. Extracellular DNA (ecDNA), released from damaged hepatocytes and NETotic neutrophils, has emerged as a potential biomarker and contributor to liver disease pathology. Enzyme DNases could be an effective therapy for the denaturation of immunogenic ecDNA. This study investigated the circulating ecDNA and NET markers in ALD and therapeutic effect of DNase I in a murine model of ALD. Female C57BL/6J mice were fed a control diet (n = 13) or Lieber-DeCarli ethanol diet for 10 days followed by a binge ethanol dose to mimic acute-on-chronic alcoholic liver injury. From day 5, mice fed ethanol were randomized into an ethanol diet group (n = 17) and ethanol + DNase group (n = 5), which received additional DNase I treatment every 12 h. Liver damage markers were analyzed. Circulating ecDNA and NETosis were measured by fluorometry and cytometry, respectively. DNase I activity was analyzed with single radial enzyme dispersion assay. The ethanol-fed mice exhibited increased mortality, neutrophil infiltration and structural damage in the liver. Total circulating ecDNA levels and NET markers did not differ between groups. DNase activity was higher in ethanol-fed mice compared to controls and additional daily administration of DNase prevented liver injury. These findings suggest that alcohol-induced liver injury modestly influences systemic NETosis and ecDNA levels. However, increased DNase activity can prevent disease progression and enhanced systemic degradation of ecDNA using DNase I.

The interaction between central and peripheral immune systems in methamphetamine use disorder: current status and future directions

Methamphetamine (METH) use disorder (MUD) is characterized by compulsive drug-seeking behavior and substantial neurotoxicity, posing a considerable burden on individuals and society. Traditionally perceived as a localized central nervous system disorder, recent preclinical and clinical studies have elucidated that MUD is a multifaceted disorder influenced by various biological systems, particularly the immune system. Emerging evidence suggests that both central and peripheral immune responses play a crucial role in the initiation and persistence of MUD. Conceptualizing it as a systemic immune process prompts significant inquiries regarding the mechanisms of communication between peripheral and central compartments. Also, whether this intercommunication could serve as diagnostic biomarkers or therapeutic targets. This review begins by offering an overview of mechanistic studies pertaining to the neuroimmune and peripheral immune systems. Finally, future directions are suggested through the integration of innovative technologies and multidimensional data to promote the translation of basic mechanistic research into clinical diagnostic and therapeutic interventions.

Molecular mechanisms in liver repair and regeneration: from physiology to therapeutics

Liver repair and regeneration are crucial physiological responses to hepatic injury and are orchestrated through intricate cellular and molecular networks. This review systematically delineates advancements in the field, emphasizing the essential roles played by diverse liver cell types. Their coordinated actions, supported by complex crosstalk within the liver microenvironment, are pivotal to enhancing regenerative outcomes. Recent molecular investigations have elucidated key signaling pathways involved in liver injury and regeneration. Viewed through the lens of metabolic reprogramming, these pathways highlight how shifts in glucose, lipid, and amino acid metabolism support the cellular functions essential for liver repair and regeneration. An analysis of regenerative variability across pathological states reveals how disease conditions influence these dynamics, guiding the development of novel therapeutic strategies and advanced techniques to enhance liver repair and regeneration. Bridging laboratory findings with practical applications, recent clinical trials highlight the potential of optimizing liver regeneration strategies. These trials offer valuable insights into the effectiveness of novel therapies and underscore significant progress in translational research. In conclusion, this review intricately links molecular insights to therapeutic frontiers, systematically charting the trajectory from fundamental physiological mechanisms to innovative clinical applications in liver repair and regeneration.

Mechanism of triiodothyronine alleviating acute alcoholic liver injury and delaying alcoholic liver fibrosis progression

IntroductionAlcoholic liver disease poses a severe threat to human health. The thyroid hormone Triiodothyronine (T3) is closely related to liver metabolism. This study investigated the effect and mechanism of T3 in alcoholic liver injury.MethodsAcute alcoholic liver injury model was established in mice by alcohol administration. Alcoholic liver fibrosis models were established in vivo and in vitro using hepatic stellate cells (HSC)-T6 cells and mice. The role and regulatory mechanism of T3 in the occurrence and progression of alcoholic acute liver injury and fibrosis were analyzed by evaluating key factors involved in cell proliferation and apoptosis, inflammatory response, oxidative stress, and autophagy using histopathological staining.ResultsThe results showed that T3 at low and medium concentrations reduced inflammation and oxidative damage in acute alcoholic liver injury and inhibited HSC activation and delayed the onset and progression of alcoholic liver fibrosis in mice. T3 inhibited the PI3K/AKT and NF-κB signal pathway, increased Nrf2 expression levels, and restored liver autophagy. However, high T3 concentrations had the opposite effect.DiscussionOptimal T3 concentrations protects the liver from alcoholic liver injury by inhibiting inflammatory response and oxidative stress injury and by restoring hepatocyte proliferation, apoptosis, and autophagy.

Faecal proteomics links neutrophil degranulation with mortality in patients with alcohol-associated hepatitis

OBJECTIVE

Patients with alcohol-associated hepatitis (AH) have a high mortality. Alcohol exacerbates liver damage by inducing gut dysbiosis, bacterial translocation and inflammation, which is characterised by increased numbers of circulating and hepatic neutrophils.

DESIGN

In this study, we performed tandem mass tag (TMT) proteomics to analyse proteins in the faeces of controls (n=19), patients with alcohol-use disorder (AUD; n=20) and AH (n=80) from a multicentre cohort (InTeam). To identify protein groups that are disproportionately represented, we conducted over-representation analysis using Reactome pathway analysis and Gene Ontology to determine the proteins with the most significant impact. A faecal biomarker and its prognostic effect were validated by ELISA in faecal samples from patients with AH (n=70), who were recruited in a second and independent multicentre cohort (AlcHepNet).

RESULT

Faecal proteomic profiles were overall significantly different between controls, patients with AUD and AH (principal component analysis p=0.001, dissimilarity index calculated by the method of Bray-Curtis). Proteins that showed notable differences across all three groups and displayed a progressive increase in accordance with the severity of alcohol-associated liver disease were predominantly those located in neutrophil granules. Over-representation and Reactome analyses confirmed that differentially regulated proteins are part of granules in neutrophils and the neutrophil degranulation pathway. Myeloperoxidase (MPO), the marker protein of neutrophil granules, correlates with disease severity and predicts 60-day mortality. Using an independent validation cohort, we confirmed that faecal MPO levels can predict short-term survival at 60 days.

CONCLUSIONS

We found an increased abundance of faecal proteins linked to neutrophil degranulation in patients with AH, which is predictive of short-term survival and could serve as a prognostic non-invasive marker.

Alcohol-associated liver cancer

Heavy alcohol intake induces a wide spectrum of liver diseases ranging from steatosis, steatohepatitis, cirrhosis, and HCC. Although alcohol consumption is a well-known risk factor for the development, morbidity, and mortality of HCC globally, alcohol-associated hepatocellular carcinoma (A-HCC) is poorly characterized compared to viral hepatitis-associated HCC. Most A-HCCs develop after alcohol-associated cirrhosis (AC), but the direct carcinogenesis from ethanol and its metabolites to A-HCC remains obscure. The differences between A-HCC and HCCs caused by other etiologies have not been well investigated in terms of clinical prognosis, genetic or epigenetic landscape, molecular mechanisms, and heterogeneity. Moreover, there is a huge gap between basic research and clinical practice due to the lack of preclinical models of A-HCC. In the current review, we discuss the pathogenesis, heterogeneity, preclinical approaches, epigenetic, and genetic profiles of A-HCC, and discuss the current insights into and the prospects for future research on A-HCC. The potential effect of alcohol on cholangiocarcinoma and liver metastasis is also discussed.

Alcohol-related liver disease (ALD): current perspectives on pathogenesis, therapeutic strategies, and animal models

Alcohol-related liver disease (ALD) is a major cause of morbidity and mortality worldwide. It encompasses conditions such as fatty liver, alcoholic hepatitis, chronic hepatitis with liver fibrosis or cirrhosis, and hepatocellular carcinoma. Numerous recent studies have demonstrated the critical role of oxidative stress, abnormal lipid metabolism, endoplasmic reticulum stress, various forms of cell death (including apoptosis, necroptosis, and ferroptosis), intestinal microbiota dysbiosis, liver immune response, cell autophagy, and epigenetic abnormalities in the pathogenesis of ALD. Currently, abstinence, corticosteroids, and nutritional therapy are the traditional therapeutic interventions for ALD. Emerging therapies for ALD mainly include the blockade of inflammatory pathways, the promotion of liver regeneration, and the restoration of normal microbiota. Summarizing the advances in animal models of ALD will facilitate a more systematic investigation of the pathogenesis of ALD and the exploration of therapeutic targets. This review summarizes the latest insight into the pathogenesis and molecular mechanisms of ALD, as well as the pros and cons of ALD rodent models, providing a basis for further research on therapeutic strategies for ALD.

Low-Density Neutrophil Levels Are Correlated with Sporotrichosis Severity: Insights into Subcutaneous Fungal Infection

Low-density neutrophils (LDNs) constitute a distinct subset of neutrophils among PBMCs. They are key mediators in systemic infections, amplifying inflammatory responses and potentially influencing disease severity and chronicity. However, their roles in subcutaneous fungal infections have not been previously investigated. In this study, we observed increased neutrophil counts in the blood and tissues of patients with sporotrichosis through automated blood analysis, histology, and immunohistochemistry. In addition, we found elevated granulocyte colony-stimulating factor levels by ELISAs. Flow cytometry analysis revealed a significant increase in CD16+CD66b+ LDNs compared with that in healthy controls. In vitro stimulation with Sporothrix globosa induced LDN generation. We observed positive correlations of LDN frequency with levels of CRP and myeloperoxidase. Conversely, granulocyte colony-stimulating factor levels were negatively correlated with LDN frequency. LDNs exhibited a combined mature/immature phenotype. Notably, transcriptomic analysis showed downregulation of pro-inflammatory signaling pathways in LDNs; functional assays also demonstrated reduced phagocytosis, ROS production, and neutrophil extracellular trap formation after stimulation with Sporothrix globosa. Degranulation did not exhibit significant changes, suggesting that LDNs constitute an impaired subpopulation. Our findings in the context of subcutaneous fungal infections indicate that LDN levels are significantly elevated in sporotrichosis and positively correlated with disease severity.

Disrupted balance between pro-inflammatory lipid mediators and anti-inflammatory specialized pro-resolving mediators is linked to hyperinflammation in patients with alcoholic hepatitis

Background

Alcoholic hepatitis (AH) is characterized by intense systemic and liver inflammation, posing significant risks of health complications and mortality. While inflammation is a crucial defense mechanism against injury and infection, its timely resolution is essential to prevent tissue damage and restore tissue homeostasis. The resolution of inflammation is primarily governed by specialized pro-resolving mediators (SPMs), lipid metabolites derived from w-6 and w-3 poly-unsaturated fatty acids (PUFAs). Currently, the balance between pro-inflammatory lipid mediators (PLMs) and SPMs in the w-6 and w-3 PUFA metabolic pathways and the impact of alcohol abstinence on profiles of PLMs and SPMs in AH patients are not well studied.

Methods

In this study, we used LC-MS/MS and ELISA to quantify levels of lipid mediators (LMs) and their precursors in the plasma samples from 58 AH patients, 29 heavy drinkers without overt liver diseases (HDCs), and 35 healthy controls (HCs). Subsequently, we assessed correlations of altered LMs with clinical parameters and inflammatory mediators. Furthermore, we conducted a longitudinal study to analyze the effects of alcohol abstinence on LMs over 6- and 12-month follow-ups.

Results

AH patients exhibited significantly higher plasma levels of w-6 PLMs (PGD2 and LTB4) and SPM RvE1 compared to HDCs or HCs. Conversely, the SPM LXA4 was significantly downregulated in AH patients. Some of these altered LMs were found to correlate with AH disease severity and various inflammatory cytokines. Particularly, the LTB4/LXA4 ratio was substantially elevated in AH patients relative to HDCs and HCs. This altered ratio displayed a positive correlation with the MELD score. Importantly, the majority of dysregulated LMs, particularly PLMs, were normalized following alcohol abstinence.

Pathogenesis of Alcohol-Associated Liver Disease

The pathogenesis of alcohol-associated liver disease (ALD) is complex and multifactorial. Several intracellular, intrahepatic, and extrahepatic factors influence development of early fatty liver injury leading to inflammation and fibrosis. Alcohol metabolism, cellular stress, and gut-derived factors contribute to hepatocyte and immune cell injury leading to cytokine and chemokine production. The pathogenesis of alcohol-associated hepatitis (AH), an advanced form of acute-on-chronic liver failure due to excessive chronic intake in patients with underlying liver disease, is not well understood. While pathogenic mechanisms in early ALD are studied, the pathogenesis of AH requires further investigation to help design effective drugs for patients.

Chronic Alcohol Intake Compromises Lung Immunity by Altering Immunometabolism in Humans and Mouse Models

Chronic alcohol consumption disrupts lung immunity and host defense mechanisms, rendering individuals with alcohol use disorder more susceptible to developing inflammatory lung conditions with poor prognoses. Here, we focused on investigating the molecular and cellular effects of alcohol ingestion on lung immunity in male and female subjects using population-based human lung transcriptomics analysis and an experimental mouse model of chronic alcohol drinking using the National Institute on Alcohol Abuse and Alcoholism alcohol feeding model. Flow cytometry and transcriptomics analyses in lungs revealed a sexually dimorphic effect of chronic alcohol drinking on lung immunity in both human and mouse. Male lungs were more sensitive to chronic alcohol drinking-induced dysregulation of lung immunity compared with female lungs. Furthermore, comparative transcriptomics analysis using lungs and liver samples from matched human and mouse subjects demonstrated that lungs were more sensitive than liver to the effects of alcohol in downregulating immune-related genes and pathways. Furthermore, the transcriptomics analysis provided evidence that immunometabolic change is a central driver in lung alteration by downregulating the immune pathways and upregulating metabolic pathways. Chronic alcohol consumption resulted in reduced mTOR signaling and decreased immune cell populations. The mTOR signaling axis may serve as an upstream regulator of alcohol-induced dysregulation in lung immunity.

Cell-to-cell and organ-to-organ crosstalk in the pathogenesis of alcohol-associated liver disease

Alcohol-associated liver disease (ALD) is a growing global health concern and its prevalence and severity are increasing steadily. While bacterial endotoxin translocation into the portal circulation is a well-established key factor, recent evidence highlights the critical role of sterile inflammation, triggered by diverse stimuli, in alcohol-induced liver injury. This review provides a comprehensive analysis of the complex interactions within the hepatic microenvironment in ALD. It examines the contributions of both parenchymal cells, like hepatocytes, and non-parenchymal cells, such as hepatic stellate cells, Kupffer cells, neutrophils, and liver sinusoidal endothelial cells, in driving the progression of the disease. Additionally, we explored the involvement of key mediators, including cytokines, chemokines and inflammasomes, which regulate inflammatory responses and promote liver injury and fibrosis. A particular focus has been placed on extracellular vesicles (EVs) as essential mediators of intercellular communication both within and beyond the liver. These vesicles facilitate the transfer of signalling molecules, such as microRNAs and proteins, which modulate immune responses, fibrogenesis and lipid metabolism, thereby influencing disease progression. Moreover, we underscore the importance of organ-to-organ crosstalk, particularly in the gut-liver axis, where dysbiosis and increased intestinal permeability lead to microbial translocation, exacerbating hepatic inflammation. The adipose-liver axis is also highlighted, particularly the impact of adipokines and free fatty acids from adipose tissue on hepatic steatosis and inflammation in the context of alcohol consumption.

Role of Neutrophils in the Development of Steatotic Liver Disease

This review explores the biological aspects of neutrophils, their contributions to the development of steatotic liver disease, and their potential as therapeutic targets for the disease. Although alcohol-associated and metabolic dysfunction-associated liver diseases originate from distinct etiological factors, the two diseases frequently share excessive lipid accumulation as a common contributor to their pathogenesis, thereby classifying them as types of steatotic liver disease. Dysregulated lipid deposition in the liver induces hepatic injury, triggering the activation of the innate immunity, partially through neutrophil recruitment. Traditionally recognized for their role in microbial clearance, neutrophils have recently garnered attention for their involvement in sterile inflammation, a pivotal component of steatotic liver disease pathogenesis. In conclusion, technological innovations, including single-cell RNA sequencing, have gradually disclosed the existence of various neutrophil subsets; however, how the distinct subsets of neutrophil population contribute differentially to the development of steatotic liver disease remains unclear.

Inflammation in Steatotic Liver Diseases: Pathogenesis and Therapeutic Targets

Alcohol-related liver disease (ALD) and metabolic dysfunction-associated steatotic liver disease (MASLD), two main types of steatotic liver disease (SLDs), are characterized by a wide spectrum of several different liver disorders, including simple steatosis, steatohepatitis, cirrhosis, and hepatocellular carcinoma. Multiple immune cell-mediated inflammatory responses not only orchestrate the killing and removal of infected/damaged cells but also exacerbate the development of SLDs when excessive or persistent inflammation occurs. In recent years, single-cell and spatial transcriptome analyses have revealed the heterogeneity of liver-infiltrated immune cells in ALD and MASLD, revealing a new immunopathological picture of SLDs. In this review, we will emphasize the roles of several key immune cells in the pathogenesis of ALD and MASLD and discuss inflammation-based approaches for effective SLD intervention. In conclusion, the study of immunological mechanisms, especially highly specific immune cell population functions, may provide novel therapeutic opportunities for this life-threatening disease.

Inflammation in Alcohol-Associated Hepatitis: Pathogenesis and Therapeutic Targets

Alcohol-associated hepatitis (AH) is an acute-on-chronic liver injury that occurs in patients with chronic alcohol-associated liver disease (ALD). Patients with severe AH have high short-term mortality and lack effective pharmacologic therapies. Inflammation is believed to be one of the key factors promoting AH progression and has been actively investigated as therapeutic targets over the last several decades, but no effective inflammatory targets have been identified so far. In this review, we discuss how inflammatory cells and the inflammatory mediators produced by these cells contribute to the development and progression of AH, with focus on neutrophils and macrophages. The crosstalk between inflammatory cells and liver nonparenchymal cells in the pathogenesis of AH is elaborated. We also deliberate the application of recent cutting-edge technologies in characterizing liver inflammation in AH. Finally, the potential therapeutic targets of inflammatory mediators for AH are briefly summarized.

Platelets in Alcohol-Associated Liver Disease: Interaction With Neutrophils

Alcohol-associated liver disease (ALD) is a major contributor to liver-related mortality globally. An increasing body of evidence underscores the pivotal role of platelets throughout the spectrum of liver injury and recovery, offering unique insights into liver homeostasis and pathobiology. Alcoholic-associated steatohepatitis is characterized by the infiltration of hepatic neutrophils. Recent studies have highlighted the extensive distance neutrophils travel through sinusoids to reach the liver injury site, relying on a platelet-paved endothelium for efficient crawling. The adherence of platelets to neutrophils is crucial for accurate migration from circulation to the inflammatory site. A gradual decline in platelet levels leads to diminished neutrophil recruitment. Platelets exhibit the ability to activate neutrophils. Platelet activation is heightened upon the release of platelet granule contents, which synergistically activate neutrophils through their respective receptors. The sequence culminates in the formation of platelet-neutrophil complexes and the release of neutrophil extracellular traps intensifies liver damage, fosters inflammatory immune responses, and triggers hepatotoxic processes. Neutrophil infiltration is a hallmark of alcohol-associated steatohepatitis, and the roles of neutrophils in ALD pathogenesis have been studied extensively, however, the involvement of platelets in ALD has received little attention. The current review consolidates recent findings on the intricate and diverse roles of platelets and neutrophils in liver pathophysiology and in ALD. Potential therapeutic strategies are highlighted, focusing on targeting platelet-neutrophil interactions and activation in ALD. The anticipation is that innovative methods for manipulating platelet and neutrophil functions will open promising avenues for future ALD therapy.

Beyond host defense and tissue injury: the emerging role of neutrophils in tissue repair

Neutrophils, the most abundant immune cells in human blood, play a fundamental role in host defense against invading pathogens and tissue injury. Neutrophils carry potentially lethal weaponry to the affected site. Inadvertent and perpetual neutrophil activation could lead to nonresolving inflammation and tissue damage, a unifying mechanism of many common diseases. The prevailing view emphasizes the dichotomy of their function, host defense versus tissue damage. However, tissue injury may also persist during neutropenia, which is associated with disease severity and poor outcome. Numerous studies highlight neutrophil phenotypic heterogeneity and functional versatility, indicating that neutrophils play more complex roles than previously thought. Emerging evidence indicates that neutrophils actively orchestrate resolution of inflammation and tissue repair and facilitate return to homeostasis. Thus, neutrophils mobilize multiple mechanisms to limit the inflammatory reaction, assure debris removal, matrix remodeling, cytokine scavenging, macrophage reprogramming, and angiogenesis. In this review, we will summarize the homeostatic and tissue-reparative functions and mechanisms of neutrophils across organs. We will also discuss how the healing power of neutrophils might be harnessed to develop novel resolution and repair-promoting therapies while maintaining their defense functions.

Management of alcoholic hepatitis: A clinical perspective

Alcohol-associated liver disease is the primary cause of liver-related mortality worldwide and one of the most common indications for liver transplantation. Alcoholic hepatitis represents the most acute and severe manifestation of alcohol-associated liver disease and is characterized by a rapid onset of jaundice with progressive inflammatory liver injury, worsening of portal hypertension, and an increased risk for multiorgan failure in patients with excessive alcohol consumption. Severe alcoholic hepatitis is associated with a poor prognosis and high short-term mortality. During the COVID-19 pandemic, rates of alcohol-associated hepatitis have increased significantly, underscoring that it is a serious and growing health problem. However, adequate management of alcohol-associated hepatitis and its complications in everyday clinical practice remains a major challenge. Currently, pharmacotherapy is limited to corticosteroids, although these have only a moderate effect on reducing short-term mortality. In recent years, translational studies deciphering key mechanisms of disease development and progression have led to important advances in the understanding of the pathogenesis of alcoholic hepatitis. Emerging pathophysiology-based therapeutic approaches include anti-inflammatory agents, modifications of the gut-liver axis and intestinal dysbiosis, epigenetic modulation, antioxidants, and drugs targeting liver regeneration. Concurrently, evidence is increasing that early liver transplantation is a safe treatment option with important survival benefits in selected patients with severe alcoholic hepatitis not responding to medical treatment. This narrative review describes current pathophysiology and management concepts of alcoholic hepatitis, provides an update on emerging treatment options, and focuses on the need for holistic and patient-centred treatment approaches to improve prognosis.