Apoptosis of enterocytes and nitration of junctional complex proteins promote alcohol-induced gut leakiness and liver injury

Advances in the acting mechanism and treatment of gut microbiota in metabolic dysfunction-associated steatotic liver disease

Metabolic Dysfunction-Associated Steatotic Liver Disease(MASLD) is increasing in prevalence worldwide and has become the greatest potential risk for cirrhosis and hepatocellular liver cancer. Currently, the role of gut microbiota in the development of MASLD has become a research hotspot. The development of MASLD can affect the homeostasis of gut microbiota, and significant changes in the composition or abundance of gut microbiota and its metabolite abnormalities can influence disease progression. The regulation of gut microbiota is an important strategy and novel target for the treatment of MASLD with good prospects. In this paper, we summarize the role of gut microbiota and its metabolites in the pathogenesis of MASLD, and describe the potential preventive and therapeutic efficacy of gut microbiota as a noninvasive marker to regulate the pathogenesis of MASLD based on the "gut-hepatic axis", which will provide new therapeutic ideas for the clinic.

Exploration of the optimal concentration of quercetin liposome nanoparticles for the treatment of liver damage

BACKGROUND

Hepatic injury is a common pathological process for a wide spectrum of liver diseases. Quercetin has been found to counteract this process by scavenging free radicals, but its therapeutic effect is limited due to poor water-solubility. Thus, the question of how to deliver quercetin to a target organ effectively with minimal side effects has remained a clinical challenge. Our previous research findings indicate that when quercetin is delivered in the form of liposomal nanoparticles, its targeting efficiency to the liver is significantly enhanced. Although quercetin liposomal nanoparticles have been shown to improve the therapeutic effect on liver damage compared to traditional quercetin treatment, the optimal dosage of liposomal quercetin still warrants further exploration. The aim of this study was therefore to ascertain whether there are differences in the therapeutic effects on liver damage at different dosages of quercetin liposomes and to determine the optimal dosage.

METHODS

62 rats modeled with liver injury were enrolled and distributed into 4 groups, where they were treated with quercetin liposome nanoparticles, blank liposome nanoparticles, simple quercetin, and normal saline accordingly. Serum samples were measured for liver function indicators, and tissue samples were analyzed by pathohistological examination. Statistical analysis was performed to quantify the difference between the experimental and control groups.

RESULTS

Both liver function and histopathological examinations demonstrated enhanced therapeutic effects as the concentration of quercetin liposome drugs increased. Moreover, compared to traditional quercetin treatments, liposomal quercetin nanoparticles of varying concentrations uniformly provide better liver protection, with the highest dose group showing the best therapeutic effect. In addition, low concentration carrier liposome nanoparticles also showed a certain protective effect on the liver damage in rats.

CONCLUSION

Liposomal quercetin nanoparticles exhibit superior efficacy in liver protection and repair compared to pure quercetin, with the highest dose group showing the best therapeutic effect.

Alcoholic cirrhosis-associated immune dysfunction: What does it imply for us?

Alcoholic cirrhosis is a leading cause of chronic advanced liver disease. With the gradual eradication of viral hepatitis and the rising levels of alcohol consumption, the incidence of alcoholic cirrhosis is expected to increase steadily. Alcohol is primarily metabolized in the gastrointestinal tract, producing toxic metabolites that enter the portal vein circulation and are subsequently transported to the liver. Excessive alcohol intake activates the microsomal ethanol oxidation system and disrupts the intestinal microbiota-driven microenvironment dictated by intestinal microbiota, and increase intestinal permeability, all of which trigger severe systemic inflammatory responses and impaired immune function. This phenomenon, known as cirrhosis-associated immune dysfunction (CAID), is closely linked to the severity of cirrhosis and can significantly influence disease progression, potentially leading to multi-organ failure. This narrative review sheds light on the relationship between alcoholic cirrhosis and CAID, focusing on tailored interventions to modify immune response and modulate gut microbiota composition in hopes of mitigating the development and deterioration of alcoholic cirrhosis.

Influence of Alcohol on the Intestinal Immune System

PURPOSE

Alcohol misuse is associated with disruption of the microbial homeostasis (dysbiosis) and microbial overgrowth in the gut, gut barrier disruption, and translocation of microbes into the systemic circulation. It also induces changes in regulatory mechanisms of the gut, which is the largest peripheral immune organ. The gut-liver axis is important for health and disease, and alterations in the intestinal immune system contribute to alcohol-associated liver disease (ALD). Understanding these changes might help discover new targets for drugs and therapeutic approaches.

SEARCH METHODS

A systematic literature search was conducted in PubMed, Medline, and Embase of manuscripts published between January 2000 and November 2023 using the terms ("alcohol" or "ethanol") AND ("immune" or "immunol") AND ("intestine," "colon," or "gut"). Eligible manuscripts included studies and reviews that discussed the effects of ethanol on immune cells in the intestine.

SEARCH RESULTS

A total of 506 publications were found in the databases on November 20, 2023. After excluding duplicates and research not covering ALD (415 articles), 91 studies were reviewed. Also included were manuscripts covering specific immune cells in the context of ALD.

DISCUSSION AND CONCLUSIONS

Balancing immune tolerance vs. initiating an immune response challenges the intestinal immune system. Alcohol induces disruption of the intestinal barrier, which is accompanied by a thicker mucus layer and reduced anti-microbial peptides. This leads to longer attachment of bacteria to epithelial cells and consequently greater translocation into the circulation. Bacterial translocation activates the immune system, reducing the activity of regulatory T cells and inducing T helper 17 response via a variety of pathways. The role of innate immune cells, especially Type 3 innate lymphoid cells, and of specific B- and T-cell subsets in ALD remains elusive. Gut dysbiosis, translocation of viable bacteria and bacterial products into the circulation, and changes in the intestinal barrier have been linked to immune deficiency and infections in patients with cirrhosis. Modifying the intestinal immune system could reduce intestinal inflammation and alcohol-induced liver injury. Understanding the underlying pathophysiology can help to detect new targets for drugs and design therapeutic strategies.

Angelica sinensis polysaccharide could alleviate the gastrointestinal damage in alcoholic fatty liver disease mice: Regulation of alcohol metabolism and enhancement of short-chain fatty acids utilization

ETHNOPHARMACOLOGICAL RELEVANCE

Dysfunction of the intestinal barrier was an important trigger for alcoholic liver damage and alcohol had brought about intestinal damage before causing liver damage. The root of Angelica sinensis (Oliv.) Diels, crucial traditional medicinal material, was widely utilized for its blood-invigorating, intestinal-lubricating and gynecological benefits. Angelica sinensis polysaccharide (ASP) was an essential natural active ingredient of Angelica sinensis and exhibited considerable potential for gastrointestinal protection. Nevertheless, the systematic research of ASP on the gastrointestinal tract remained insufficient.

AIM OF THIS STUDY

To systematically explore the protective effect and underlying mechanisms of ASP against alcohol-induced gastrointestinal injury, including the stomach, ileum and colon.

MATERIALS AND METHODS

The AFLD mice model was established via the intragastric administration of alcohol twice a day for one week. The protective effect of ASP on the representative segments of the gastrointestinal tract (stomach, ileum and colon) was subsequently studied after confirming its hepatoprotective activity. The impact of ASP on gastrointestinal alcohol metabolism was examined to explain its antioxidant and antiapoptotic activities. Furthermore, the effect of ASP on short-chain fatty acids (SCFA) in the colon and colonic contents was investigated to further enhance the understanding of the underlying mechanisms.

RESULTS

ASP could reduce oxidative stress and apoptosis in the gastrointestinal tract via regulating CYP2E1-mediated alcohol metabolism. Additionally, ASP could significantly increase the levels of FFAR2, FFAR3 and HCAR2 in colon, thereby promoting the utilization of SCFA.

CONCLUSION

ASP was proven for the first time to improve gastrointestinal damage caused by alcohol, indicating its enormous potential as a candidate medicine for the treatment of alcohol related gastrointestinal injury.

Pathogenesis and treatment of colitis-associated colorectal cancer: Insights from Traditional Chinese Medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Inflammatory Bowel Disease (IBD) is an inflammatory intestinal disease, and with prolonged illness duration, the annual risk of IBD progressing to colitis-associated colorectal cancer (CAC) gradually increases. In recent years, there has been a noticeable trend towards the application of traditional Chinese medicine (TCM) in the treatment of CAC.

AIM OF THIS REVIEW

This comprehensive review summarizes the pathogenesis of CAC and details the therapeutic benefits of TCM in treating CAC, including various TCM prescriptions and ingredients, establishing the theoretical foundation for the application of TCM in CAC treatment.

METHODS

We assessed literature published before March 24, 2024, from several databases, including Web of Science, PubMed, Scopus and Google Scholar. The keywords used include "traditional Chinese medicine", "traditional Chinese medicine prescriptions", "traditional Chinese medicine ingredients", "herbal medicine", "colitis-associated colorectal cancer", "inflammatory bowel disease", "colorectal cancer" and "colitis-cancer transformation". We conducted a comprehensive collection and collation of pertinent scientific articles from various databases, focusing on the efficacy of TCM in the prevention and treatment of "colitis-cancer transformation".

RESULTS

This paper provides a concise summary and thorough analysis of twenty-eight prescriptions and ingredients of TCM for the prevention and treatment of CAC, based on existing experimental and clinical research. There are positive signs that TCM can effectively prevent and treat the "colitis-cancer transformation" through repairing the intestinal mucosal barrier, correcting intestinal flora imbalance, and regulating intestinal immune responses.

CONCLUSION

TCM possesses comprehensive regulatory advantages that are multifaceted, multilevel, and multitarget. It has a definite curative effect in the prevention and treatment of CAC. It is essential to enhance the clinical efficacy of TCM in the prevention and treatment of CAC based on syndrome differentiation and treatment, with the assistance of modern medicine.

Co-administration of polyethylene glycol with binge ethanol reduces markers of intestinal and hepatic inflammation in C57BL/6J mice by diminishing ethanol absorption through the intestinal wall

BACKGROUND

Therapeutic options for managing intestinal and hepatic inflammation associated with alcohol consumption, a prevalent health problem worldwide, remain unavailable. This study examines the potential efficacy of polyethylene glycol (PEG) in mitigating the intestinal and hepatic damage, employing a mouse model for assessment.

METHODS

First, the mixture of ethanol (4 g/kg body weight) and PEG (2 g/kg body weight) or an equivalent volume of vehicle was administered orally alcohol consumption.

RESULTS

Acute alcohol consumption was found to damage not only the liver but also the small intestine, as evidenced by histological findings and mRNA expression analysis of inflammatory cytokines. We also identified impaired motor function in the mouse model of binge drinking. Interestingly, PEG significantly mitigated both the impaired motor function and the injury and inflammation of the small intestine following binge drinking in mice. Furthermore, PEG exhibited hepatoprotective effects, as indicated by reduced hepatic enzyme levels in serum, less liver injury observed through H & E staining, and decreased neutrophil infiltration within the liver.

CONCLUSIONS

Collectively, these findings suggest that co-administration of PEG with binge ethanol could serve as an effective therapeutic strategy to prevent intestinal and hepatic inflammation.

Gut-liver axis: Recent concepts in pathophysiology in alcohol-associated liver disease

The growing recognition of the role of the gut microbiome's impact on alcohol-associated diseases, especially in alcohol-associated liver disease, emphasizes the need to understand molecular mechanisms involved in governing organ-organ communication to identify novel avenues to combat alcohol-associated diseases. The gut-liver axis refers to the bidirectional communication and interaction between the gut and the liver. Intestinal microbiota plays a pivotal role in maintaining homeostasis within the gut-liver axis, and this axis plays a significant role in alcohol-associated liver disease. The intricate communication between intestine and liver involves communication between multiple cellular components in each organ that enable them to carry out their physiological functions. In this review, we focus on novel approaches to understanding how chronic alcohol exposure impacts the microbiome and individual cells within the liver and intestine, as well as the impact of ethanol on the molecular machinery required for intraorgan and interorgan communication.

Therapeutic Effects of Zanthoxyli Pericarpium on Intestinal Inflammation and Network Pharmacological Mechanism Analysis in a Dextran Sodium Sulfate-Induced Colitis Mouse Model

(1) Background: IBD (inflammatory bowel disease) is characterized by chronic intestinal inflammation leading to persistent symptoms and a lack of effective treatments. ZP (Zanthoxyli Pericarpium) has been used in traditional Chinese medicine for its anti-inflammatory and antioxidant properties for the management of intestinal disorders. (2) Methods: This study aimed to investigate the components of ZP, their specific targets, and associated diseases using the TCMSP (Traditional Chinese Medicine Systems Pharmacology) analysis platform, TCMBank database, and ETCM2.0 (Encyclopedia of Traditional Chinese Medicine 2.0) database. Additionally, we explored the protective effects of ZP on the colon and the underlying molecular mechanisms in the treatment of IBD. (3) Results: We identified 59 compounds in ZP that target 38 genes related to IBD, including PTGS2, PPARG, and GPBAR1. In a mice model of DSS (dextran sodium sulfate)-induced colitis, ZP significantly reduced colonic epithelial damage and oxidative stress markers, such as iNOS and nitrotyrosine, demonstrating its antioxidant properties. (4) Conclusions: These findings suggest that ZP has protective effects against DSS-induced colonic damage owing to its anti-inflammatory and antioxidant properties, making it a potential candidate for IBD treatment. However, further research and clinical trials are required to confirm its therapeutic potential and safety in humans.

New insights into the intestinal barrier through "gut-organ" axes and a glimpse of the microgravity's effects on intestinal barrier

Gut serves as the largest interface between humans and the environment, playing a crucial role in nutrient absorption and protection against harmful substances. The intestinal barrier acts as the initial defense mechanism against non-specific infections, with its integrity directly impacting the homeostasis and health of the human body. The primary factor attributed to the impairment of the intestinal barrier in previous studies has always centered on the gastrointestinal tract itself. In recent years, the concept of the "gut-organ" axis has gained significant popularity, revealing a profound interconnection between the gut and other organs. It speculates that disruption of these axes plays a crucial role in the pathogenesis and progression of intestinal barrier damage. The evaluation of intestinal barrier function and detection of enterogenic endotoxins can serve as "detecting agents" for identifying early functional alterations in the heart, kidney, and liver, thereby facilitating timely intervention in the disorders. Simultaneously, consolidating intestinal barrier integrity may also present a potential therapeutic approach to attenuate damage in other organs. Studies have demonstrated that diverse signaling pathways and their corresponding key molecules are extensively involved in the pathophysiological regulation of the intestinal barrier. Aberrant activation of these signaling pathways and dysregulated expression of key molecules play a pivotal role in the process of intestinal barrier impairment. Microgravity, being the predominant characteristic of space, can potentially exert a significant influence on diverse intestinal barriers. We will discuss the interaction between the "gut-organ" axes and intestinal barrier damage, further elucidate the signaling pathways underlying intestinal barrier damage, and summarize alterations in various components of the intestinal barrier under microgravity. This review aims to offer a novel perspective for comprehending the etiology and molecular mechanisms of intestinal barrier injury as well as the prevention and management of intestinal barrier injury under microgravity environment.

Oxidative stress in alcoholic liver disease, focusing on proteins, nucleic acids, and lipids: A review

Oxidative stress is one of the important factors in the development of alcoholic liver disease. The production of reactive oxygen species and other free radicals is an important feature of alcohol metabolism in the liver and an important substance in liver injury. When large amounts of ROS are produced, the homeostasis of the liver REDOX system will be disrupted and liver injury will be caused. Oxidative stress can damage proteins, nucleic acids and lipids, liver dysfunction. In addition, damaging factors produced by oxidative damage to liver tissue can induce the occurrence of inflammation, thereby aggravating the development of ALD. This article reviews the oxidative damage of alcohol on liver proteins, nucleic acids, and lipids, and provides new insights and summaries of the oxidative stress process. We also discussed the relationship between oxidative stress and inflammation in alcoholic liver disease from different perspectives. Finally, the research status of antioxidant therapy in alcoholic liver disease was summarized, hoping to provide better help for learning and developing the understanding of alcoholic liver disease.

Melatonin Prevents Thioacetamide-Induced Gut Leakiness and Liver Fibrosis Through the Gut-Liver Axis via Modulating Sirt1-Related Deacetylation of Gut Junctional Complex and Hepatic Proteins

Intestinal barrier dysfunction with high serum endotoxin is common in patients with liver fibrosis, but the mechanisms underlying liver fibrosis remain unclear. Melatonin is a well-recognized antioxidant and an anti-inflammatory agent that benefits multiple organs. However, the beneficial effects of melatonin on gut leakiness-associated liver fibrosis have not been systemically studied. Here, we investigated the protective mechanisms of melatonin against thioacetamide (TAA)-induced gut barrier dysfunction and hepatic fibrosis by focusing on posttranslational protein modifications through the gut-liver axis. Our results showed that gut leakiness markers, including decreased gut tight/adherens junction proteins (TJ/AJs) with increased intestinal deformation, apoptosis, and serum endotoxin, were observed early at 1 week after TAA exposure. Liver injury, apoptosis, and fibrosis were prominent at 2 and 4 weeks. Mechanistically, we found that gut TJ/AJs were hyper-acetylated, followed by ubiquitin-dependent proteolysis, leading to their degradation and gut leakiness. Gut dysbiosis, hepatic protein hyper-acetylation, and SIRT1 downregulation were also observed. Consistently, intestinal Sirt1 deficiency greatly enhanced protein hyper-acetylation, gut leakiness, endotoxemia, and liver fibrosis. Pretreatment with melatonin prevented or improved all these changes in both the gut and liver. Furthermore, melatonin blunted protein acetylation and injury in TAA-exposed T84 human intestinal and AML12 mouse liver cells. Overall, this study demonstrated novel mechanisms by which melatonin prevents gut leakiness and liver fibrosis through the gut-liver axis by attenuating the acetylation of intestinal and hepatic proteins. Thus, melatonin consumption can become a potentially safe supplement for liver fibrosis patients by preventing protein hyper-acetylation and gut leakiness.

IFN-β Overexpressing Adipose-Derived Mesenchymal Stem Cells Mitigate Alcohol-Induced Liver Damage and Gut Permeability

Alcoholic liver disease (ALD) is a form of hepatic inflammation. ALD is mediated by gut leakiness. This study evaluates the anti-inflammatory effects of ASCs overexpressing interferon-beta (ASC-IFN-β) on binge alcohol-induced liver injury and intestinal permeability. In vitro, ASCs were transfected with a non-viral vector carrying the human IFN-β gene, which promoted hepatocyte growth factor (HGF) secretion in the cells. To assess the potential effects of ASC-IFN-β, C57BL/6 mice were treated with three oral doses of binge alcohol and were administered intraperitoneal injections of ASC-IFN-β. Mice treated with binge alcohol and administered ASC-IFN-β showed reduced liver injury and inflammation compared to those administered a control ASC. Analysis of intestinal tissue from ethanol-treated mice administered ASC-IFN-β also indicated decreased inflammation. Additionally, fecal albumin, blood endotoxin, and bacterial colony levels were reduced, indicating less gut leakiness in the binge alcohol-exposed mice. Treatment with HGF, but not IFN-β or TRAIL, mitigated the ethanol-induced down-regulation of cell death and permeability in Caco-2 cells. These results demonstrate that ASCs transfected with a non-viral vector to induce IFN-β overexpression have protective effects against binge alcohol-mediated liver injury and gut leakiness via HGF.

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.

Endogenous ethanol production in health and disease

The gut microbiome exerts metabolic actions on distal tissues and organs outside the intestine, partly through microbial metabolites that diffuse into the circulation. The disruption of gut homeostasis results in changes to microbial metabolites, and more than half of the variance in the plasma metabolome can be explained by the gut microbiome. Ethanol is a major microbial metabolite that is produced in the intestine of nearly all individuals; however, elevated ethanol production is associated with pathological conditions such as metabolic dysfunction-associated steatotic liver disease and auto-brewery syndrome, in which the liver's capacity to metabolize ethanol is surpassed. In this Review, we describe the mechanisms underlying excessive ethanol production in the gut and the role of ethanol catabolism in mediating pathogenic effects of ethanol on the liver and host metabolism. We conclude by discussing approaches to target excessive ethanol production by gut bacteria.

Direct effects of alcohol on gut-epithelial barrier: Unraveling the disruption of physical and chemical barrier of the gut-epithelial barrier that compromises the host-microbiota interface upon alcohol exposure

The development of alcohol-associated diseases is multifactorial, mechanism of which involves metabolic alteration, dysregulated immune response, and a perturbed intestinal host-environment interface. Emerging evidence has pinpointed the critical role of the intestinal host-microbiota interaction in alcohol-induced injuries, suggesting its contribution to disease initiation and development. To maintain homeostasis in the gut, the intestinal mucosa serves as the first-line defense against exogenous factors in the gastrointestinal tract, including dietary contents and the commensal microbiota. The gut-epithelial barrier comprises a physical barrier lined with a single layer of intestinal epithelial cells and a chemical barrier with mucus trapping host regulatory factors and gut commensal bacteria. In this article, we review recent studies pertaining to the disrupted gut-epithelial barrier upon alcohol exposure and examine how alcohol and its metabolism can affect the regulatory ability of intestinal epithelium.

Musculus senhousei peptides alleviated alcoholic liver injury via the gut-liver axis

Alcoholic liver injury has become a leading threat to human health, with complicated pathogenesis and limited therapeutic options. Our previous study showed that Musculus senhousei peptides (MSPs) exhibit protective potential against early-stage alcoholic liver injury, although the underlying mechanism is not yet clear. In this study, histopathological analysis, mRNA abundance of injury-associated biomarkers, the gut microbiota, and faecal metabolome were evaluated using a mouse model subjected to acute alcohol exposure, aiming to identify the mechanism by which MSP can alleviate alcoholic hepatotoxicity. The results showed that MSP intervention significantly ameliorated symptoms of liver injury (suppressed serum ALT increment, hepatic lipid accumulation, and neutrophil infiltration in liver tissue), and reversed the abnormal mRNA abundance of biomarkers associated with oxidative stress (iNOS), inflammation (TNF-α, IL-1β, MCP-1, TNF-R1, and TLR4), and apoptosis (Bax and Casp. 3) in the liver. Moreover, MSP improved intestinal barrier function by increasing the expression of tight junction proteins (Claudin-1 and Claudin-3). Further analysis of faecal microbiota and metabolome revealed that MSP promoted the growth of tryptophan-metabolizing bacteria (Clostridiales, Alistipes, and Odoribacter), leading to increased production of indole derivatives (indole-3-lactic acid and N-acetyltryptophan). These results suggested that MSPs may alleviate alcohol-induced liver injury targeting the gut-liver axis, and could be an effective option for the prevention of alcoholic liver injury.

Mitochondrial Aldehyde Dehydrogenase 2 (ALDH2) Protects against Binge Alcohol-Mediated Gut and Brain Injury

Mitochondrial aldehyde dehydrogenase-2 (ALDH2) metabolizes acetaldehyde to acetate. People with ALDH2 deficiency and Aldh2-knockout (KO) mice are more susceptible to alcohol-induced tissue damage. However, the underlying mechanisms behind ALDH2-related gut-associated brain damage remain unclear. Age-matched young female Aldh2-KO and C57BL/6J wild-type (WT) mice were gavaged with binge alcohol (4 g/kg/dose, three doses) or dextrose (control) at 12 h intervals. Tissues and sera were collected 1 h after the last ethanol dose and evaluated by histological and biochemical analyses of the gut and hippocampus and their extracts. For the mechanistic study, mouse neuroblast Neuro2A cells were exposed to ethanol with or without an Aldh2 inhibitor (Daidzin). Binge alcohol decreased intestinal tight/adherens junction proteins but increased oxidative stress-mediated post-translational modifications (PTMs) and enterocyte apoptosis, leading to elevated gut leakiness and endotoxemia in Aldh2-KO mice compared to corresponding WT mice. Alcohol-exposed Aldh2-KO mice also showed higher levels of hippocampal brain injury, oxidative stress-related PTMs, and neuronal apoptosis than the WT mice. Additionally, alcohol exposure reduced Neuro2A cell viability with elevated oxidative stress-related PTMs and apoptosis, all of which were exacerbated by Aldh2 inhibition. Our results show for the first time that ALDH2 plays a protective role in binge alcohol-induced brain injury partly through the gut-brain axis, suggesting that ALDH2 is a potential target for attenuating alcohol-induced tissue injury.

18Beta-Glycyrrhetinic Acid Attenuates H2O2-Induced Oxidative Damage and Apoptosis in Intestinal Epithelial Cells via Activating the PI3K/Akt Signaling Pathway

Oxidative stress causes gut dysfunction and is a contributing factor in several intestinal disorders. Intestinal epithelial cell survival is essential for maintaining human and animal health under oxidative stress. 18beta-Glycyrrhetinic acid (GA) is known to have multiple beneficial effects, including antioxidant activity; however, the underlying molecular mechanisms have not been well established. Thus, the present study evaluated the therapeutic effects of GA on H2O2-induced oxidative stress in intestinal porcine epithelial cells. The results showed that pretreatment with GA (100 nM for 16 h) significantly increased the levels of several antioxidant enzymes and reduced corresponding intracellular levels of reactive oxidative species and malondialdehyde. GA inhibited cell apoptosis via activating the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) signaling pathway, as confirmed by RNA sequencing. Further analyses demonstrated that GA upregulated the phosphorylation levels of PI3K and Akt and the protein level of B cell lymphoma 2, whereas it downregulated Cytochrome c and tumor suppressor protein p53 levels. Moreover, molecular docking analysis predicted the binding of GA to Vasoactive intestinal peptide receptor 1, a primary membrane receptor, to activate the PI3K/Akt signaling pathway. Collectively, these results revealed that GA protected against H2O2-induced oxidative damage and cell apoptosis via activating the PI3K/Akt signaling pathway, suggesting the potential therapeutic use of GA to alleviate oxidative stress in humans/animals.

Polysaccharides from Eucommia ulmoides Oliv. Leaves Alleviate Acute Alcoholic Liver Injury by Modulating the Microbiota-Gut-Liver Axis in Mice

The interplay among gut microbiota, intestines, and liver is crucial in preventing acute alcoholic liver injury. In this study, the hepatoprotective potential of polysaccharides from Eucommia ulmoides Oliv. leaves (EULP) on acute alcoholic liver injury in Kunming male mice was investigated. The structural features suggested that the EULP appeared as a heterogeneous mixture of polysaccharides with a molecular weight of 186132 Da. A 14-day pretreatment of EULP ameliorated acute alcoholic-induced hepatic inflam mation (TNF-α, IL-6, and IL-10), oxidative stress (GSH, SOD, and T-AOC), and liver damage (ALT and AST) via enhancing intestinal barrier (Occludin, Claudin 1, and ZO-1) and modulating microbiome, which subsequently inhibiting endotoxemia and balancing the homeostasis of the gut-liver axis. EULP restored the composition of intestinal flora with an increase in the relative abundance of Lactobacillaceae and a decrease in Lachnospiraceae and Verrucomicrobiaceae. Notably, prolonged EULP pretreatment (14 days) but no single gavage of EULP achieved excellent hepatoprotection. These findings endorsed the potential of EULP as a functional food for mitigating acute alcoholic-induce d liver damage, attributed to its anti-inflammatory, antioxidant, and prebiotic properties facilitated by the microbiota-gut-liver axis.

Contributing roles of mitochondrial dysfunction and hepatocyte apoptosis in liver diseases through oxidative stress, post-translational modifications, inflammation, and intestinal barrier dysfunction

This review provides an update on recent findings from basic, translational, and clinical studies on the molecular mechanisms of mitochondrial dysfunction and apoptosis of hepatocytes in multiple liver diseases, including but not limited to alcohol-associated liver disease (ALD), metabolic dysfunction-associated steatotic liver disease (MASLD), and drug-induced liver injury (DILI). While the ethanol-inducible cytochrome P450-2E1 (CYP2E1) is mainly responsible for oxidizing binge alcohol via the microsomal ethanol oxidizing system, it is also responsible for metabolizing many xenobiotics, including pollutants, chemicals, drugs, and specific diets abundant in n-6 fatty acids, into toxic metabolites in many organs, including the liver, causing pathological insults through organelles such as mitochondria and endoplasmic reticula. Oxidative imbalances (oxidative stress) in mitochondria promote the covalent modifications of lipids, proteins, and nucleic acids through enzymatic and non-enzymatic mechanisms. Excessive changes stimulate various post-translational modifications (PTMs) of mitochondrial proteins, transcription factors, and histones. Increased PTMs of mitochondrial proteins inactivate many enzymes involved in the reduction of oxidative species, fatty acid metabolism, and mitophagy pathways, leading to mitochondrial dysfunction, energy depletion, and apoptosis. Unique from other organelles, mitochondria control many signaling cascades involved in bioenergetics (fat metabolism), inflammation, and apoptosis/necrosis of hepatocytes. When mitochondrial homeostasis is shifted, these pathways become altered or shut down, likely contributing to the death of hepatocytes with activation of inflammation and hepatic stellate cells, causing liver fibrosis and cirrhosis. This review will encapsulate how mitochondrial dysfunction contributes to hepatocyte apoptosis in several types of liver diseases in order to provide recommendations for targeted therapeutics.

Melatonin Prevents Alcohol- and Metabolic Dysfunction- Associated Steatotic Liver Disease by Mitigating Gut Dysbiosis, Intestinal Barrier Dysfunction, and Endotoxemia

Melatonin (MT) has often been used to support good sleep quality, especially during the COVID-19 pandemic, as many have suffered from stress-related disrupted sleep patterns. It is less known that MT is an antioxidant, anti-inflammatory compound, and modulator of gut barrier dysfunction, which plays a significant role in many disease states. Furthermore, MT is produced at 400-500 times greater concentrations in intestinal enterochromaffin cells, supporting the role of MT in maintaining the functions of the intestines and gut-organ axes. Given this information, the focus of this article is to review the functions of MT and the molecular mechanisms by which it prevents alcohol-associated liver disease (ALD) and metabolic dysfunction-associated steatotic liver disease (MASLD), including its metabolism and interactions with mitochondria to exert its antioxidant and anti-inflammatory activities in the gut-liver axis. We detail various mechanisms by which MT acts as an antioxidant, anti-inflammatory compound, and modulator of intestinal barrier function to prevent the progression of ALD and MASLD via the gut-liver axis, with a focus on how these conditions are modeled in animal studies. Using the mechanisms of MT prevention and animal studies described, we suggest behavioral modifications and several exogenous sources of MT, including food and supplements. Further clinical research should be performed to develop the field of MT in preventing the progression of liver diseases via the gut-liver axis, so we mention a few considerations regarding MT supplementation in the context of clinical trials in order to advance this field of research.

Post-translational modifications of histone and non-histone proteins in epigenetic regulation and translational applications in alcohol-associated liver disease: Challenges and research opportunities

Epigenetic regulation is a process that takes place through adaptive cellular pathways influenced by environmental factors and metabolic changes to modulate gene activity with heritable phenotypic variations without altering the DNA sequences of many target genes. Epigenetic regulation can be facilitated by diverse mechanisms: many different types of post-translational modifications (PTMs) of histone and non-histone nuclear proteins, DNA methylation, altered levels of noncoding RNAs, incorporation of histone variants, nucleosomal positioning, chromatin remodeling, etc. These factors modulate chromatin structure and stability with or without the involvement of metabolic products, depending on the cellular context of target cells or environmental stimuli, such as intake of alcohol (ethanol) or Western-style high-fat diets. Alterations of epigenetics have been actively studied, since they are frequently associated with multiple disease states. Consequently, explorations of epigenetic regulation have recently shed light on the pathogenesis and progression of alcohol-associated disorders. In this review, we highlight the roles of various types of PTMs, including less-characterized modifications of nuclear histone and non-histone proteins, in the epigenetic regulation of alcohol-associated liver disease (ALD) and other disorders. We also describe challenges in characterizing specific PTMs and suggest future opportunities for basic and translational research to prevent or treat ALD and many other disease states.

Ellagic Acid Prevented Dextran-Sodium-Sulfate-Induced Colitis, Liver, and Brain Injury through Gut Microbiome Changes

Inflammatory bowel disease (IBD) affects millions of people worldwide and is considered a significant risk factor for colorectal cancer. Recent in vivo and in vitro studies reported that ellagic acid (EA) exhibits important antioxidant and anti-inflammatory properties. In this study, we investigated the preventive effects of EA against dextran sulfate sodium (DSS)-induced acute colitis, liver, and brain injury in mice through the gut-liver-brain axis. Acute colitis, liver, and brain injury were induced by treatment with 5% (w/v) DSS in the drinking water for 7 days. Freshly prepared EA (60 mg/kg/day) was orally administered, while control (CON) group mice were treated similarly by daily oral administrations with a vehicle (water). All the mice were euthanized 24 h after the final treatment with EA. The blood, liver, colon, and brain samples were collected for further histological and biochemical analyses. Co-treatment with a physiologically relevant dose (60 mg/kg/day) of EA for 7 days significantly reduced the DSS-induced gut barrier dysfunction; endotoxemia; and inflammatory gut, liver, and brain injury in mice by modulating gut microbiota composition and inhibiting the elevated oxidative and nitrative stress marker proteins. Our results further demonstrated that the preventive effect of EA on the DSS-induced IBD mouse model was mediated by blocking the NF-κB and mitogen-activated protein kinase (MAPK) pathway. Therefore, EA co-treatment significantly attenuated the pro-inflammatory and oxidative stress markers by suppressing the activation of NF-κB/MAPK pathways in gut, liver, and brain injury. These results suggest that EA, effective in attenuating IBD in a mouse model, deserves further consideration as a potential therapeutic for the treatment of inflammatory diseases.

The role of NADPH oxidase 1 in alcohol-induced oxidative stress injury of intestinal epithelial cells

Alcohol-mediated reactive oxygen species (ROS) play a vital role in intestinal barrier injury. However, the mechanism of ROS accumulation in enterocytes needs to be explored further. In our study, we found that chronic-binge ethanol-fed mice had increased levels of gut oxidative stress and high intestinal permeability. The transcription profiles of the colonic epithelial cells showed that the level of NADPH oxidase 1 (NOX1) was significantly elevated in alcohol-exposed mice compared with isocaloric-exposed mice. In vitro, NOX1 silencing alleviated ROS accumulation and the apoptosis of human colonic epithelial cells (NCM460), while NOX1 overexpression accelerated oxidative stress injury of NCM460 cells. Propionic acid was reduced in the gut of chronic-binge ethanol-fed mice, compared with isocaloric-fed mice, as observed through untargeted metabolomic analysis. Supplementation with propionate relieved ethanol-induced liver and intestinal barrier injuries and reduced the level of ROS accumulation and apoptosis of ethanol-induced colonic epithelial cells. Propionate alleviating NOX1 induced ROS injury of colonic epithelial cells, independent of G protein-coupled receptors. Propionate significantly inhibited histone deacetylase 2 (HDAC2) expressions both in ethanol-exposed colonic epithelial cells and TNF-α-treated NCM460. Chromatin immunoprecipitation (ChIP) assays showed that propionate suppressed the NOX1 expression by regulating histone acetylation in the gene promoter region. In conclusion, NOX1 induces oxidative stress injury of colonic epithelial cells in alcohol-related liver disease. Propionate, which can act as an endogenous HDAC2 inhibitor, can decrease levels of apoptosis of intestinal epithelial cells caused by oxidative stress.

Pomegranate-Derived Exosome-Like Nanovesicles Alleviate Binge Alcohol-Induced Leaky Gut and Liver Injury

Alcoholic liver disease (ALD) is damage to the liver and mainly caused by binge alcohol. ALD have decreased junctional protein expression and modulated intestinal permeability. We investigated whether plant-releasing exosome-like nanovesicles can prevent liver damage and leaky gut from binge alcohol. In this study, we characterized the exosome-like nanovesicles from pomegranate juice and confirmed the round shape of a lipid bilayer. After 14 days of pomegranate-derived exosome-like nanovesicle (PNVs) pretreatment, binge alcohol (6 g/kg/dose) was administered to mice three times orally every 12 h. Exposure to binge alcohol increased levels of oxidative and nitric oxide stress marker proteins such as CYP2E1, 3-Nitrotyrosine, and inducible nitric oxide synthase in both liver and gut damage. Also, binge alcohol significantly elevated the plasma endotoxemia, inflammatory fatty liver, and leaky gut. However, PNVs reduced the oxidative stress and apoptosis marker proteins and prevented the leaky gut and endotoxemia. Markedly, PNV treatment significantly prevented a decrease in the amount of intestinal junctional proteins and an increase in leaky gut in mice exposed to alcohol. These results showed that PNVs can prevent leaky gut and liver damage caused by binge alcohol and suggest that it may be useful hepatoprotective or intestinal protective agents for the first time.

Roles of Gut Microbiota in Alcoholic Liver Disease

Alcoholic liver disease (ALD)-one of the most common liver diseases - involves a wide range of disorders, including asymptomatic hepatic steatosis, alcoholic hepatitis (AH), liver fibrosis, and cirrhosis. Alcohol consumption induces a weakened gut barrier and changes in the composition of the gut microbiota. The presence of CYP2E1 and its elevated levels in the gastrointestinal tract after alcohol exposure lead to elevated levels of ROS and acetaldehyde, inducing inflammation and oxidative damage in the gut. At the same time, the influx of harmful molecules such as the bacterial endotoxin LPS and peptidogly from gut dysbiosis can induce intestinal inflammation and oxidative damage, further compromising the intestinal mucosal barrier. In this process, various oxidative stress-mediated post-translational modifications (PTMs) play an important role in the integrity of the barrier, eg, the presence of acetaldehyde will result in the sustained phosphorylation of several paracellular proteins (occludin and zona occludens-1), which can lead to intestinal leakage. Eventually, persistent oxidative stress, LPS infiltration and hepatocyte damage through the enterohepatic circulation will lead to hepatic stellate cell activation and hepatic fibrosis. In addition, probiotics, prebiotics, synbiotics, fecal microbial transplantation (FMT), bioengineered bacteria, gut-restricted FXR agonists and others are promising therapeutic approaches that can alter gut microbiota composition to improve ALD. In the future, there will be new challenges to study the interactions between the genetics of individuals with ALD and their gut microbiome, to provide personalized interventions targeting the gut-liver axis, and to develop better techniques to measure microbial communities and metabolites in the body.

CHRONIC ETHANOL USE WORSENS GUT PERMEABILITY AND ALTERS TIGHT JUNCTION EXPRESSION IN A MURINE SEPSIS MODEL

ABSTRACT

Alcohol use disorder is associated with increased mortality in septic patients. Murine studies demonstrate that ethanol/sepsis is associated with changes in gut integrity. This study examined intestinal permeability after ethanol/sepsis and investigated mechanisms responsible for alterations in barrier function. Mice were randomized to drink either 20% ethanol or water for 12 weeks and then were subjected to either sham laparotomy or cecal ligation and puncture (CLP). Intestinal permeability was disproportionately increased in ethanol/septic mice via the pore, leak, and unrestricted pathways. Consistent with increased permeability in the leak pathway, jejunal myosin light chain (MLC) kinase (MLCK) expression and the ratio of phospho-MLC to total MLC were both increased in ethanol/CLP. Gut permeability was altered in MLCK -/- mice in water/CLP; however, permeability was not different between WT and MLCK -/- mice in ethanol/CLP. Similarly, jejunal IL-1β levels were decreased while systemic IL-6 levels were increased in MLCK -/- mice in water/CLP but no differences were identified in ethanol/CLP. While we have previously shown that mortality is improved in MLCK -/- mice after water/CLP, mortality was significantly worse in MLCK -/- mice after ethanol/CLP. Consistent with an increase in the pore pathway, claudin 4 levels were also selectively decreased in ethanol/CLP WT mice. Furthermore, mRNA expression of jejunal TNF and IFN-γ were both significantly increased in ethanol/CLP. The frequency of CD4 + cells expressing TNF and IL-17A and the frequency of CD8 + cells expressing IFN-γ in Peyer's Patches were also increased in ethanol/CLP. Thus, there is an ethanol-specific worsening of gut barrier function after CLP that impacts all pathways of intestinal permeability, mediated, in part, via changes to the tight junction. Differences in the host response in the setting of chronic alcohol use may play a role in future precision medicine approaches toward the treatment of sepsis.

Therapeutic strategies of small molecules in the microbiota-gut-brain axis for alcohol use disorder

The microbiota-gut-brain axis (MGBA) is important in maintaining the structure and function of the central nervous system (CNS) and is regulated by the CNS environment and signals from the peripheral tissues. However, the mechanism and function of the MGBA in alcohol use disorder (AUD) are still not completely understood. In this review, we investigate the underlying mechanisms involved in the onset of AUD and/or associated neuronal deficits and create a foundation for better treatment (and prevention) strategies. We summarize recent reports focusing on the alteration of the MGBA in AUD. Importantly, we highlight the properties of small-molecule short-chain fatty acids (SCFAs), neurotransmitters, hormones, and peptides in the MGBA and discusses their usage as therapeutic agents against AUD.

Identification of biomarkers co-associated with M1 macrophages, ferroptosis and cuproptosis in alcoholic hepatitis by bioinformatics and experimental verification

Backgrounds

Alcoholic hepatitis (AH) is a major health problem worldwide. There is increasing evidence that immune cells, iron metabolism and copper metabolism play important roles in the development of AH. We aimed to explore biomarkers that are co-associated with M1 macrophages, ferroptosis and cuproptosis in AH patients.

Methods

GSE28619 and GSE103580 datasets were integrated, CIBERSORT algorithm was used to analyze the infiltration of 22 types of immune cells and GSVA algorithm was used to calculate ferroptosis and cuproptosis scores. Using the "WGCNA" R package, we established a gene co-expression network and analyzed the correlation between M1 macrophages, ferroptosis and cuproptosis scores and module characteristic genes. Subsequently, candidate genes were screened by WGCNA and differential expression gene analysis. The LASSO-SVM analysis was used to identify biomarkers co-associated with M1 macrophages, ferroptosis and cuproptosis. Finally, we validated these potential biomarkers using GEO datasets (GSE155907, GSE142530 and GSE97234) and a mouse model of AH.

Results

The infiltration level of M1 macrophages was significantly increased in AH patients. Ferroptosis and cuproptosis scores were also increased in AH patients. In addition, M1 macrophages, ferroptosis and cuproptosis were positively correlated with each other. Combining bioinformatics analysis with a mouse model of AH, we found that ALDOA, COL3A1, LUM, THBS2 and TIMP1 may be potential biomarkers co-associated with M1 macrophages, ferroptosis and cuproptosis in AH patients.

Conclusion

We identified 5 potential biomarkers that are promising new targets for the treatment and diagnosis of AH patients.

ALDH2 deficiency increases susceptibility to binge alcohol-induced gut leakiness, endotoxemia, and acute liver injury in mice through the gut-liver axis

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is the major enzyme responsible for metabolizing toxic acetaldehyde to acetate and acts as a protective or defensive protein against various disease states associated with alcohol use disorder (AUD), including alcohol-related liver disease (ARLD). We hypothesized that Aldh2-knockout (KO) mice are more susceptible to binge alcohol-mediated liver injury than wild-type (WT) mice through increased oxidative stress, gut leakiness and endotoxemia. Therefore, this study aimed to investigate the protective role of ALDH2 in binge alcohol-induced gut permeability, endotoxemia, and acute inflammatory liver injury by exposing Aldh2-KO or WT mice to a single oral dose of binge alcohol 3.5, 4.0, or 5.0 g/kg. Our findings showed for the first time that ALDH2 deficiency in Aldh2-KO mice increases their sensitivity to binge alcohol-induced oxidative and nitrative stress, enterocyte apoptosis, and nitration of gut tight junction (TJ) and adherent junction (AJ) proteins, leading to their degradation. These resulted in gut leakiness and endotoxemia in Aldh2-KO mice after exposure to a single dose of ethanol even at 3.5 g/kg, while no changes were observed in the corresponding WT mice. The elevated serum endotoxin (lipopolysaccharide, LPS) and bacterial translocation contributed to systemic inflammation, hepatocyte apoptosis, and subsequently acute liver injury through the gut-liver axis. Treatment with Daidzin, an ALDH2 inhibitor, exacerbated ethanol-induced cell permeability and reduced TJ/AJ proteins in T84 human colon cells. These changes were reversed by Alda-1, an ALDH2 activator. Furthermore, CRISPR/Cas9-mediated knockout of ALDH2 in T84 cells increased alcohol-mediated cell damage and paracellular permeability. All these findings demonstrate the critical role of ALDH2 in alcohol-induced epithelial barrier dysfunction and suggest that ALDH2 deficiency or gene mutation in humans is a risk factor for alcohol-mediated gut and liver injury, and that ALDH2 could be an important therapeutic target against alcohol-associated tissue or organ damage.

Inflammatory signaling on cytochrome P450-mediated drug metabolism in hepatocytes

Cytochrome P450 (CYP450) enzymes are membrane-bound blood proteins that are vital to drug detoxification, cell metabolism, and homeostasis. CYP450s belonging to CYP families 1-3 are responsible for nearly 80% of oxidative metabolism and complete elimination of approximately 50% of all common clinical drugs in humans liver hepatocytes. CYP450s can affect the body's response to drugs by altering the reaction, safety, bioavailability, and toxicity. They can also regulate metabolic organs and the body's local action sites to produce drug resistance through altered drug metabolism. Genetic polymorphisms in the CYP gene alone do not explain ethnic and individual differences in drug efficacy in the context of complex diseases. The purpose of this review is to summarize the impact of new inflammatory-response signaling pathways on the activity and expression of CYP drug-metabolizing enzymes. Included is a summary of recent studies that have identified drugs with the potential to regulate drug-metabolizing enzyme activity. Our goal is to inspire the development of clinical drug treatment processes that consider the impact of the inflammatory environment on drug treatment, as well as provide research targets for those studying drug metabolism.

Role of Intestinal Microbes in Chronic Liver Diseases

With the recent availability and upgrading of many emerging intestinal microbes sequencing technologies, our research on intestinal microbes is changing rapidly. A variety of investigations have found that intestinal microbes are essential for immune system regulation and energy metabolism homeostasis, which impacts many critical organs. The liver is the first organ to be traversed by the intestinal portal vein, and there is a strong bidirectional link between the liver and intestine. Many intestinal factors, such as intestinal microbes, bacterial composition, and intestinal bacterial metabolites, are deeply involved in liver homeostasis. Intestinal microbial dysbiosis and increased intestinal permeability are associated with the pathogenesis of many chronic liver diseases, such as alcoholic fatty liver disease (AFLD), non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), chronic hepatitis B (CHB), chronic hepatitis C (CHC), autoimmune liver disease (AIH) and the development of hepatocellular carcinoma (HCC). Intestinal permeability and dysbacteriosis often lead to Lipopolysaccharide (LPS) and metabolites entering in serum. Then, Toll-like receptors activation in the liver induces the exposure of the intestine and liver to many small molecules with pro-inflammatory properties. And all of these eventually result in various liver diseases. In this paper, we have discussed the current evidence on the role of various intestinal microbes in different chronic liver diseases. As well as potential new therapeutic approaches are proposed in this review, such as antibiotics, probiotics, and prebiotics, which may have an improvement in liver diseases.

Chronic Exposure to Environmentally Relevant Concentrations of Microcystin-Leucine Arginine Causes Lung Barrier Damage through PP2A Activity Inhibition and Claudin1 Ubiquitination

Microcystin-leucine arginine (MC-LR), ubiquitous in water and food, is a threat to public health. In the present study, after C57BL/6J mice were fed with environmental concentrations of MC-LR (0, 1, 30, 60, 90, and 120 μg/L) for 6, 9, and 12 months, it was found that MC-LR could enter into mouse lung tissues and cause microstructural damage, as shown by western blotting and HE staining. Electron microscopy examination showed that MC-LR could damage the lung barrier by disruption of the tight junctions, which was confirmed by the decreased expression of tight junction markers, including Occludin, Claudin1, and ZO-1. In addition, MC-LR also increased the ubiquitination of Claudin1, indicating that MC-LR could disrupt tight junctions by promoting the degradation of Claudin1. Furthermore, MC-LR increased the levels of TNF-α and IL-6 in mouse lung tissues, leading to pneumonia. Importantly, pretreatment with PP2A activator D-erythro-sphingosine (DES) was found to significantly alleviate MC-LR-induced decrease of Occludin and Claudin1 by inhibiting the P-AKT/Snail pathway in vitro. Together, this study revealed that chronic exposure to MC-LR causes lung barrier damage, which involves PP2A activity inhibition and enhancement of Claudin1 ubiquitination. This study broadens the awareness of the toxic effects of MC-LR on the respiratory system, which has deep implications for public health.

Plum Prevents Intestinal and Hepatic Inflammation in the Acute and Chronic Models of Dextran Sulfate Sodium-Induced Mouse Colitis

SCOPE

Inflammatory bowel disease (IBD), including ulcerative colitis (UC), is a chronic recurrent inflammatory disease of the digestive tract and increases the risk of colon cancer.

METHOD AND RESULTS

This study evaluates the effects of dietary intervention with freeze-dried plum (FDP), a natural antioxidant and anti-inflammatory fruit with no toxicity on dextran sulfate sodium (DSS)-induced acute and chronic experimental colitis in a mouse model and studies the molecular mechanisms of protection through the gut-liver axis. The results show that FDP decreases the levels of inflammatory mediators, which is a nitrative stress biomarker in both acute and chronic models. FDP markedly reduces DSS-induced injury to the colonic epithelium in both acute and chronic models. In addition, FDP significantly decreases the levels of pro-oxidant markers such as CYP2E1, iNOS, and nitrated proteins (detected by anti-3-NT antibody) in DSS-induced acute and chronic colonic injury models. Furthermore, FDP markedly reduces markers of liver injury such as serum ALT/AST, antioxidant markers, and inflammatory mediators in DSS-induced acute and chronic colonic injury.

CONCLUSION

These results demonstrate that the FDP exhibits a protective effect on DSS-induced acute and chronic colonic and liver injury through the gut-liver axis via antioxidant and anti-inflammatory properties.

Gut Microbiota Targeted Approach in the Management of Chronic Liver Diseases

The liver is directly connected to the intestines through the portal vein, which enables the gut microbiota and gut-derived products to influence liver health. There is accumulating evidence of decreased gut flora diversity and alcohol sensitivity in patients with various chronic liver diseases, including non-alcoholic/alcoholic liver disease, chronic hepatitis virus infection, primary sclerosing cholangitis and liver cirrhosis. Increased intestinal mucosal permeability and decline in barrier function were also found in these patients. Followed by bacteria translocation and endotoxin uptake, these will lead to systemic inflammation. Specific microbiota and microbiota-derived metabolites are altered in various chronic liver diseases studies, but the complex interaction between the gut microbiota and liver is missing. This review article discussed the bidirectional relationship between the gut and the liver, and explained the mechanisms of how the gut microbiota ecosystem alteration affects the pathogenesis of chronic liver diseases. We presented gut-microbiota targeted interventions that could be the new promising method to manage chronic liver diseases.

The Role of Gut Bacteria and Fungi in Alcohol-Associated Liver Disease

Cirrhosis and liver cancer caused by alcohol-associated liver disease (ALD) are serious threats to people's health. In addition to hepatic cell apoptosis and liver inflammation caused by oxidative stress during alcohol metabolism, intestinal microbiota disorders are also involved in the onset and development of ALD. Ethanol and its' oxidative and non-oxidative metabolites, together with dysbiosis-caused-inflammation, destroys the intestinal barrier. Changes of several microbial metabolites, such as bile acids, short-chain fatty acids, and amino acid, are closely associated with gut dysbiosis in ALD. The alcohol-caused dysbiosis can further influence intestinal barrier-related proteins, such as mucin2, bile acid-related receptors, and aryl hydrocarbon receptor (AhR), and these abnormal changes also participate in the injury of the intestinal barrier and hepatic steatosis. Gut-derived bacteria, fungi, and their toxins, such as lipopolysaccharide (LPS) and β-glucan translocate into the liver through the damaged intestinal barrier and promote the progression of inflammation and fibrosis of ALD. Thus, the prevention of alcohol-induced disruption of intestinal permeability has a beneficial effect on ALD. Currently, multiple therapeutic treatments have been applied to restore the gut microbiota of patients with ALD. Fecal microbial transplantation, probiotics, antibiotics, and many other elements has already shown their ability of restoring the gut microbiota. Targeted approaches, such as using bacteriophages to remove cytolytic Enterococcus faecalis, and supplement with Lactobacillus, Bifidobacterium, or boulardii are also powerful therapeutic options for ALD.

The Intestinal Barrier Dysfunction as Driving Factor of Inflammaging

The intestinal barrier, composed of the luminal microbiota, the mucus layer, and the physical barrier consisting of epithelial cells and immune cells, the latter residing underneath and within the epithelial cells, plays a special role in health and disease. While there is growing knowledge on the changes to the different layers associated with disease development, the barrier function also plays an important role during aging. Besides changes in the composition and function of cellular junctions, the entire gastrointestinal physiology contributes to essential age-related changes. This is also reflected by substantial differences in the microbial composition throughout the life span. Even though it remains difficult to define physiological age-related changes and to distinguish them from early signs of pathologies, studies in centenarians provide insights into the intestinal barrier features associated with longevity. The knowledge reviewed in this narrative review article might contribute to the definition of strategies to prevent the development of diseases in the elderly. Thus, targeted interventions to improve overall barrier function will be important disease prevention strategies for healthy aging in the future.

Skeletal muscle satellite cell-derived mesenchymal stem cells ameliorate acute alcohol-induced liver injury

Cultured human skeletal-muscle satellite cells have properties of mesenchymal stem cells (skeletal muscle satellite cell-derived mesenchymal stem cells, SkMSCs) and play anti-inflammatory roles by secreting prostaglandin E2 and hepatocyte growth factor (HGF). To evaluate the utility of SkMSCs in treating liver diseases, we determined whether SkMSCs could ameliorate acute liver and gut inflammation induced by binge ethanol administration. Binge drinking of ethanol led to weight loss in the body and spleen, liver inflammation and steatosis, and increased serum ALT and AST levels (markers of liver injury), along with increased IL-1β, TNF-α, and iNOS expression levels in mice. However, levels of these binge-drinking-induced indicators were reduced by a single intraperitoneal treatment of SkMSCs. Furthermore, levels of bacteria-derived lipopolysaccharide decreased in the livers and sera of ethanol-exposed mice after SkMSC administration. SkMSCs decreased the extent of tissue inflammation and reduced villus and crypt lengths in the small intestine after alcohol binge drinking. SkMSCs also reduced the leakage of blood albumin, an indicator of leaky gut, in the stool of ethanol-exposed mice. Alcohol-induced damage to human colonic Caco-2/tc7 cells was also alleviated by HGF. Therefore, a single treatment with SkMSCs can attenuate alcoholic liver damage by reducing inflammatory responses in the liver and gut, suggesting that SkMSCs could be used in cell therapy to treat alcoholic liver diseases.

Alcohol Use and Abuse Conspires With HIV Infection to Aggravate Intestinal Dysbiosis and Increase Microbial Translocation in People Living With HIV: A Review

The intestinal microbiome is an essential so-called human "organ", vital for the induction of innate immunity, for metabolizing nutrients, and for maintenance of the structural integrity of the intestinal barrier. HIV infection adversely influences the richness and diversity of the intestinal microbiome, resulting in structural and functional impairment of the intestinal barrier and an increased intestinal permeability. Pathogens and metabolites may thus cross the "leaky" intestinal barrier and enter the systemic circulation, which is a significant factor accounting for the persistent underlying chronic inflammatory state present in people living with HIV (PLWH). Additionally, alcohol use and abuse has been found to be prevalent in PLWH and has been strongly associated with the incidence and progression of HIV/AIDS. Recently, converging evidence has indicated that the mechanism underlying this phenomenon is related to intestinal microbiome and barrier function through numerous pathways. Alcohol acts as a "partner" with HIV in disrupting microbiome ecology, and thus impairing of the intestinal barrier. Optimizing the microbiome and restoring the integrity of the intestinal barrier is likely to be an effective adjunctive therapeutic strategy for PLWH. We herein critically review the interplay among HIV, alcohol, and the gut barrier, thus setting the scene with regards to development of effective strategies to counteract the dysregulated gut microbiome and the reduction of microbial translocation and inflammation in PLWH.

Ellagic Acid Prevents Binge Alcohol-Induced Leaky Gut and Liver Injury through Inhibiting Gut Dysbiosis and Oxidative Stress

Alcoholic liver disease (ALD) is a major liver disease worldwide and can range from simple steatosis or inflammation to fibrosis/cirrhosis, possibly through leaky gut and systemic endotoxemia. Many patients with alcoholic steatohepatitis (ASH) die within 60 days after clinical diagnosis due to the lack of an approved drug, and thus, synthetic and/or dietary agents to prevent ASH and premature deaths are urgently needed. We recently reported that a pharmacologically high dose of pomegranate extract prevented binge alcohol-induced gut leakiness and hepatic inflammation by suppressing oxidative and nitrative stress. Herein, we investigate whether a dietary antioxidant ellagic acid (EA) contained in many fruits, including pomegranate and vegetables, can protect against binge alcohol-induced leaky gut, endotoxemia, and liver inflammation. Pretreatment with a physiologically-relevant dose of EA for 14 days significantly reduced the binge alcohol-induced gut barrier dysfunction, endotoxemia, and inflammatory liver injury in mice by inhibiting gut dysbiosis and the elevated oxidative stress and apoptosis marker proteins. Pretreatment with EA significantly prevented the decreased amounts of gut tight junction/adherent junction proteins and the elevated gut leakiness in alcohol-exposed mice. Taken together, our results suggest that EA could be used as a dietary supplement for alcoholic hepatitis patients.

Protective Property of Scutellarin Against Liver Injury Induced by Carbon Tetrachloride in Mice

Liver injury is a clinical disorder caused by toxins, drugs, and alcohol stimulation without effective therapeutic approaches thus far. Scutellarin (SCU), isolated from the edible herb Erigeron breviscapus (Vant.) Hand. -Mazz. showed potential hepatoprotective effects, but the mechanisms remain unknown. In this study, transcriptomics combined with nontargeted metabolomics and 16S rRNA amplicon sequencing were performed to elucidate the functional mechanisms of SCU in carbon tetrachloride (CCl₄)–induced liver injury in mice. The results showed that SCU exerted potential hepatoprotective effects against CCl₄-induced liver injury by repressing CYP2E1 and IκBα/NF-κB signaling pathways, modulating the gut microbiota (especially enriching Lactobacillus), and regulating the endogenous metabolites involved in lipid metabolism and bile acid homeostasis. SCU originates from a functional food that appears to be a promising agent to guard against liver injury.

Enterically derived high-density lipoprotein restrains liver injury through the portal vein

The biogenesis of high-density lipoprotein (HDL) requires apoA1 and the cholesterol transporter ABCA1. Although the liver generates most of the HDL in the blood, HDL synthesis also occurs in the small intestine. Here, we show that intestine-derived HDL traverses the portal vein in the HDL3 subspecies form, in complex with lipopolysaccharide (LPS)-binding protein (LBP). HDL3, but not HDL2 or low-density lipoprotein, prevented LPS binding to and inflammatory activation of liver macrophages and instead supported extracellular inactivation of LPS. In mouse models involving surgical, dietary, or alcoholic intestinal insult, loss of intestine-derived HDL worsened liver injury, whereas outcomes were improved by therapeutics that elevated and depended upon raising intestinal HDL. Thus, protection of the liver from injury in response to gut-derived LPS is a major function of intestinally synthesized HDL.

Lactobacillus acidophilus and vitamin C attenuate ethanol-induced intestinal and liver injury in mice

Ethanol exposure frequently induces intestinal and liver injury, dysbiosis of the gut microbiota and vitamin C (VC) deficiency. Gut microbiota-targeted therapy is emerging as an important adjuvant method for protecting the body against ethanol-induced injury, particularly probiotics containing Lactobacillus acidophilus (LA). However, the feasibility and efficiency of using synbiotics containing LA and VC against ethanol-induced injury remained largely undetermined. To examine the advantages of LA+VC, their effect was evaluated in an ethanol-fed mouse model. The results suggested that LA+VC restored gut microbiota homeostasis and reinstated the immune balance of colonic T-regulatory cells (CD4⁺CD45⁺forkhead box p3⁺). In addition, intestinal barrier disorders were improved via upregulating tight junction proteins (claudin-2, zona occludens-1 and occludin) and mucus secretion, which prevented the translocation of lipopolysaccharide into circulatory systems and subsequently reduced the expression of Toll-like receptor 4 in liver tissues. In this context, LA+VC treatment reduced the inflammatory response in the liver, which was likely responsible for the improved liver function in ethanol-challenged mice. Collectively, these results indicated that LA+VC treatment significantly protected the intestine and liver from ethanol damage by enhancing intestinal barrier function and reducing systemic inflammation. The present study paved the way for further exploration of synbiotics based on Lactobacillus species and VC.

Role of microbiota and related metabolites in gastrointestinal tract barrier function in NAFLD

The Gastrointestinal (GI) tract is composed of four main barriers: microbiological, chemical, physical and immunological. These barriers play important roles in maintaining GI tract homeostasis. In the crosstalk between these barriers, microbiota and related metabolites have been shown to influence GI tract barrier integrity, and alterations of the gut microbiome might lead to an increase in intestinal permeability. As a consequence, translocation of bacteria and their products into the circulatory system increases, reaching proximal and distal tissues, such as the liver. One of the most prevalent chronic liver diseases, Nonalcoholic Fatty Liver Disease (NAFLD), has been associated with an altered gut microbiota and barrier integrity. However, the causal link between them has not been fully elucidated yet. In this review, we aim to highlight relevant bacterial taxa and their related metabolites affecting the GI tract barriers in the context of NAFLD, discussing their implications in gut homeostasis and in disease.

Fructose Promotes Leaky Gut, Endotoxemia, and Liver Fibrosis Through Ethanol-Inducible Cytochrome P450-2E1-Mediated Oxidative and Nitrative Stress

Fructose intake is known to induce obesity, insulin resistance, metabolic syndrome, and nonalcoholic fatty liver disease (NAFLD). We aimed to evaluate the effects of fructose drinking on gut leakiness, endotoxemia, and NAFLD and study the underlying mechanisms in rats, mice, and T84 colon cells. Levels of ileum junctional proteins, oxidative stress markers, and apoptosis-related proteins in rodents, T84 colonic cells, and human ileums were determined by immunoblotting, immunoprecipitation, and immunofluorescence analyses. Fructose drinking caused microbiome change, leaky gut, and hepatic inflammation/fibrosis with increased levels of nitroxidative stress marker proteins cytochrome P450-2E1 (CYP2E1), inducible nitric oxide synthase, and nitrated proteins in small intestine and liver of rodents. Fructose drinking significantly elevated plasma bacterial endotoxin levels, likely resulting from decreased levels of intestinal tight junction (TJ) proteins (zonula occludens 1, occludin, claudin-1, and claudin-4), adherent junction (AJ) proteins (β-catenin and E-cadherin), and desmosome plakoglobin, along with α-tubulin, in wild-type rodents, but not in fructose-exposed Cyp2e1-null mice. Consistently, decreased intestinal TJ/AJ proteins and increased hepatic inflammation with fibrosis were observed in autopsied obese people compared to lean individuals. Furthermore, histological and biochemical analyses showed markedly elevated hepatic fibrosis marker proteins in fructose-exposed rats compared to controls. Immunoprecipitation followed by immunoblot analyses revealed that intestinal TJ proteins were nitrated and ubiquitinated, leading to their decreased levels in fructose-exposed rats. Conclusion: These results showed that fructose intake causes protein nitration of intestinal TJ and AJ proteins, resulting in increased gut leakiness, endotoxemia, and steatohepatitis with liver fibrosis, at least partly, through a CYP2E1-dependent manner.

Markers of Intestinal Permeability Are Rapidly Improved by Alcohol Withdrawal in Patients with Alcohol-Related Liver Disease

Changes in intestinal microbiome and barrier function are critical in the development of alcohol-related liver disease (ALD). Here, we determined the effects of a one-week alcohol withdrawal on parameters of intestinal barrier function in heavy drinkers with ALD in comparison to healthy non-drinkers (controls). In serum samples of 17 controls (m = 10/f = 7) and 37 age-matched ALD patients (m = 26/f = 11) undergoing a one-week alcohol withdrawal, markers of liver health and intestinal barrier function were assessed. Liver damage, e.g., fibrosis and hepatic steatosis, were assessed using FibroScan. Before alcohol withdrawal, markers of liver damage, lipopolysaccharide binding protein (LBP) and overall TLR4/TLR2 ligands in serum were significantly higher in ALD patients than in controls, whereas intestinal fatty acid binding protein (I-FABP) and zonulin protein concentrations in serum were lower. All parameters, with the exception of LBP, were significantly improved after alcohol withdrawal; however, not to the level of controls. Our data suggest that one-week of abstinence improves markers of intestinal barrier function and liver health in ALD patients.

Foodborne TiO2 Nanoparticles Induced More Severe Hepatotoxicity in Fructose-Induced Metabolic Syndrome Mice via Exacerbating Oxidative Stress-Mediated Intestinal Barrier Damage

The hazard of titanium dioxide nanoparticles (TiO₂ NPs) in diseased population should be given focus due to the huge number of these NPs in foods and medicine. This study aimed to evaluate the stronger biological adverse effect of oral exposure to TiO₂ NPs in a fructose-induced metabolic syndrome mouse model. Compared to the normal mice, low-dose (2 mg/kg) TiO₂ NPs did not cause severe hepatotoxicity. However, high-dose (20 mg/kg) TiO₂ NPs induced aggravated hepatic inflammation, fibrosis, and apoptosis, with substantial alteration of related biochemical parameters in the mouse model. Moreover, significantly increased Ti and lipopolysaccharide burden were observed in metabolic syndrome murine liver and serum, which possibly worsened the portend intestinal leakage. The expression of tight junction-related protein showed that TiO₂ NPs induced further increase in serious intestinal permeability. The intestinal inflammatory and oxidative stress response in the model were also assessed. Results showed that TiO₂ NPs caused more severe intestinal inflammatory injury by intensifying the oxidative stress in metabolic syndrome mice and then induced further liver injury. This work provides information on the insights into the toxic effect of TiO₂ NPs in sub-healthy population.

Protective effect of glutamine and alanyl-glutamine against zearalenone-induced intestinal epithelial barrier dysfunction in IPEC-J2 cells

Zearalenone (ZEN), a nonsteroidal estrogenic mycotoxin, has a negative effect on porcine intestine. Glutamine (Gln) and alanyl-glutamine (Ala-Gln) are nutrients with potential preservation functions similar to those of the intestinal epithelial barrier. The protective role of Gln and Ala-Gln on ZEN-induced intestinal barrier dysfunction was evaluated in this study. Additionally, the ability of Gln and Ala-Gln to protect the intestinal barrier was investigated. Our results showed that lactate dehydrogenase (LDH) activity, paracellular permeability and reactive oxygen species (ROS) level were increased by ZEN, while the glutathione (GSH) level was decreased by ZEN. Gln and Ala-Gln promoted the proliferation of cells and attenuated the ZEN-induced increase in cytotoxicity, cell apoptosis and paracellular permeability. Gln and Ala-Gln alleviated barrier function damage, which was additionally induced by ZEN by increasing the antioxidant capacity of cells. In addition, Gln and Ala-Gln upregulated intestinal barrier associated gene expressions including pBD-1, pBD-2, MUC-2, ZO-1, occludin and claudin-3. This study revealed that Gln and Ala-Gln had similar effects in protecting intestinal epithelial barrier function against ZEN exposure in IPEC-J2 cells. A new treatment for alleviating ZEN-induced injury to the intestine through nutritional intervention is provided.