Hyperglycemic environments directly compromise intestinal epithelial barrier function in an organoid model and hyaluronan (∼35kDa) protects via a layilin dependent mechanism

BACKGROUND

Metabolic syndrome and diabetes in obese individuals are strong risk factors for development of inflammatory bowel disease (IBD) and colorectal cancer. The pathogenic mechanisms of low-grade metabolic inflammation, including chronic hyperglycemic stress, in disrupting gut homeostasis are poorly understood. In this study, we sought to understand the impact of a hyperglycemic environment on intestinal barrier integrity and the protective effects of small molecular weight (35 kDa) hyaluronan on epithelial barrier function.

METHODS

Intestinal organoids derived from mouse colon were grown in normal glucose media (5 mM) or high glucose media (25 mM) to study the impact of hyperglycemic stress on the intestinal barrier. Additionally, organoids were pretreated with 35 kDa hyaluronan (HA35) to investigate the effect of hyaluronan on epithelial barrier under high glucose stress. Immunoblotting as well as confocal imaging was used to understand changes in barrier proteins, quantitative as well as spatial distribution, respectively. Alterations in barrier function were measured using trans-epithelial electrical resistance and fluorescein isothiocyanate flux assays. Untargeted proteomics analysis was performed to elucidate mechanisms by which HA35 exerts a protective effect on the barrier. Intestinal organoids derived from receptor knockout mice specific to various HA receptors were utilized to understand the role of HA receptors in barrier protection under high glucose conditions.

RESULTS

We found that high glucose stress decreased the protein expression as well as spatial distribution of two key barrier proteins, zona occludens-1 (ZO-1) and occludin. HA35 prevented the degradation or loss of ZO-1 and maintained the spatial distribution of both ZO-1 and occludin under hyperglycemic stress. Functionally, we also observed a protective effect of HA35 on the epithelial barrier under high glucose conditions. We found that HA receptor, layilin, was involved in preventing barrier protein loss (ZO-1) as well as maintaining spatial distribution of ZO-1 and occludin. Additionally, proteomics analysis showed that cell death and survival was the primary pathway upregulated in organoids treated with HA35 under high glucose stress. We found that XIAP associated factor 1 (Xaf1) was modulated by HA35 thereby regulating apoptotic cell death in the intestinal organoid system. Finally, we observed that spatial organization of both focal adhesion kinase (FAK) as well as F-actin was mediated by HA35 via layilin.

CONCLUSION

Our results highlight the impact of hyperglycemic stress on the intestinal barrier function. This is of clinical relevance, as impaired barrier function has been observed in individuals with metabolic syndrome. Additionally, we demonstrate barrier protective effects of HA35 through its receptor layilin and modulation of cellular apoptosis under high glucose stress.

Exome-wide association analysis identifies novel risk loci for alcohol-associated hepatitis

BACKGROUND AND AIMS

Alcohol-associated hepatitis (AH) is a clinically severe, acute disease that afflicts only a fraction of patients with alcohol use disorder (AUD). Genomic studies of alcohol-associated cirrhosis (AC) have identified several genes of large effect, but the genetic and environmental factors that lead to AH and AC, and their degree of genetic overlap, remain largely unknown. This study aims to identify genes and genetic variation that contribute to the development of AH.

APPROACH AND RESULTS

Exome-sequencing of patients with AH (N=784) and heavy drinking controls (N=951) identified exome-wide significant association for AH at PNPLA3, as previously observed for AC in GWAS, although with a much lower effect-size. SNPs of large effect-size at ICOSLG (Chr 21) and TOX4/RAB2B (Chr 14), were also exome-wide significant. ICOSLG encodes a co-stimulatory signal for T-cell proliferation and cytokine secretion and induces B-cell proliferation and differentiation. TOX4 was previously implicated in diabetes and immune system function. Other genes previously implicated in AC did not strongly contribute to AH, and the only prominently implicated (but not exome wide significant) gene overlapping with AUD was ADH1B. Polygenic signals for AH were observed in both common and rare variant analysis and identified genes with roles associated with inflammation.

CONCLUSIONS

This study has identified two new genes of high effect size with a previously unknown contribution to ALD, and highlights both the overlap in etiology between liver diseases, and the unique origins of AH.

Acute kidney injury in severe alcohol-associated hepatitis treated with anakinra plus zinc or prednisone

BACKGROUND AND AIMS

In a recent trial, patients with severe alcohol-associated hepatitis treated with anakinra plus zinc (A+Z) had lower survival and higher acute kidney injury (AKI) rates versus prednisone (PRED). We characterize the clinical factors and potential mechanisms associated with AKI development in that trial.

APPROACH AND RESULTS

Data from 147 participants in a multicenter randomized clinical trial (74 A+Z, 73 PRED) were analyzed. AKI, AKI phenotypes, and kidney injury biomarkers were compared between participants who did/did not develop AKI in the 2 treatment arms. Multivariable competing risk analyses were performed to identify baseline risk factors for incident AKI, with death treated as a competing event. Risk factors considered were age, sex, mean arterial pressure, white blood cell count, albumin, MELD, ascites, HE, and treatment arm. At baseline, no participants had AKI; 33% (n=49) developed AKI during follow-up. AKI incidence was higher in A+Z than in PRED (45% [n=33] versus 22% [n=16], p =0.001). AKI phenotypes were similar between the 2 treatment arms ( p =0.361), but peak AKI severity was greater in A+Z than PRED (stage 3 n=21 [63.6%] vs. n=8 [50.0%], p =0.035). At baseline, urine-neutrophil-gelatinase-associated lipocalin levels were similar between participants who developed AKI in both treatment arms ( p =0.319). However, day 7 and 14 urine-neutrophil-gelatinase-associated lipocalin levels were significantly elevated in participants treated with A+Z who developed AKI versus participants treated with PRED who developed AKI ( p =0.002 and 0.032, respectively). On multivariable competing risk analysis, only A+Z was independently associated with incident AKI (subdistribution hazard ratio 2.35, p =0.005).

CONCLUSIONS

AKI occurred more frequently and was more severe in participants treated with A+Z. A+Z-treated participants with AKI had higher urine-neutrophil-gelatinase-associated lipocalin, suggesting that A+Z maybe nephrotoxic in patients with severe alcohol-associated hepatitis.

Designing clinical trials to address alcohol use and alcohol-associated liver disease: an expert panel Consensus Statement

Most patients with alcohol-associated liver disease (ALD) engage in heavy drinking defined as 4 or more drinks per day (56 g) or 8 (112 g) or more drinks per week for women and 5 or more drinks per day (70 g) or 15 (210 g) or more drinks per week for men. Although abstinence from alcohol after diagnosis of ALD improves life expectancy and reduces the risk of decompensation of liver disease, few studies have evaluated whether treatment of alcohol use disorders will reduce progression of liver disease and improve liver-related outcomes. In November 2021, the National Institute of Alcohol Abuse and Alcoholism commissioned a task force that included hepatologists, addiction medicine specialists, statisticians, clinical trialists and members of regulatory agencies to develop recommendations for the design and conduct of clinical trials to evaluate the effect of alcohol use, particularly treatment to reduce or eliminate alcohol use in patients with ALD. The task force conducted extensive reviews of relevant literature on alcohol use disorders and ALD. Findings were presented at one in-person meeting and discussed over the next 16 months to develop the final recommendations. As few clinical trials directly address this topic, the 28 recommendations approved by all members of the task force represent a consensus of expert opinions.

A polygenic risk score for alcohol-associated cirrhosis among heavy drinkers with European ancestry

BACKGROUND

Polygenic Risk Scores (PRS) based on results from genome-wide association studies offer the prospect of risk stratification for many common and complex diseases. We developed a PRS for alcohol-associated cirrhosis by comparing single-nucleotide polymorphisms among patients with alcohol-associated cirrhosis (ALC) versus drinkers who did not have evidence of liver fibrosis/cirrhosis.

METHODS

Using a data-driven approach, a PRS for ALC was generated using a meta-genome-wide association study of ALC (N=4305) and an independent cohort of heavy drinkers with ALC and without significant liver disease (N=3037). It was validated in 2 additional independent cohorts from the UK Biobank with diagnosed ALC (N=467) and high-risk drinking controls (N=8981) and participants in the Indiana Biobank Liver cohort with alcohol-associated liver disease (N=121) and controls without liver disease (N=3239).

RESULTS

A 20-single-nucleotide polymorphisms PRS for ALC (PRSALC) was generated that stratified risk for ALC comparing the top and bottom deciles of PRS in the 2 validation cohorts (ORs: 2.83 [95% CI: 1.82 -4.39] in UK Biobank; 4.40 [1.56 -12.44] in Indiana Biobank Liver cohort). Furthermore, PRSALC improved the prediction of ALC risk when added to the models of clinically known predictors of ALC risk. It also stratified the risk for metabolic dysfunction -associated steatotic liver disease -cirrhosis (3.94 [2.23 -6.95]) in the Indiana Biobank Liver cohort -based exploratory analysis.

CONCLUSIONS

PRSALC incorporates 20 single-nucleotide polymorphisms, predicts increased risk for ALC, and improves risk stratification for ALC compared with the models that only include clinical risk factors. This new score has the potential for early detection of heavy drinking patients who are at high risk for ALC.

Randomized trial of anakinra plus zinc vs. prednisone for severe alcohol-associated hepatitis

BACKGROUND & AIMS

Severe alcohol-associated hepatitis (SAH) is associated with high 90-day mortality. Glucocorticoid therapy for 28 days improves 30- but not 90-day survival. We assessed the efficacy and safety of a combination of anakinra, an IL-1 antagonist, plus zinc (A+Z) compared to prednisone using the Day-7 Lille score as a stopping rule in patients with SAH.

METHODS

In this phase IIb double-blind randomized trial in adults with SAH and MELD scores of 20-35, participants were randomized to receive either daily anakinra 100 mg subcutaneously for 14 days plus daily zinc sulfate 220 mg orally for 90 days, or daily prednisone 40 mg orally for 30 days. Prednisone or prednisone placebo was stopped if Day-7 Lille score was >0.45. All study drugs were stopped for uncontrolled infection or ≥5 point increase in MELD score. The primary endpoint was overall survival at 90 days.

RESULTS

Seventy-three participants were randomized to prednisone and 74 to A+Z. The trial was stopped early after a prespecified interim analysis showed prednisone was associated with higher 90-day overall survival (90% vs. 70%; hazard ratio for death = 0.34, 95% CI 0.14-0.83, p = 0.018) and transplant-free survival (88% vs. 64%; hazard ratio for transplant or death = 0.30, 95% CI 0.13-0.69, p = 0.004) than A+Z. Acute kidney injury was more frequent with A+Z (45%) than prednisone (22%) (p = 0.001), but rates of infection were similar (31% in A+Z vs. 27% in prednisone, p = 0.389).

CONCLUSIONS

Participants with SAH treated with prednisone using the Day-7 Lille score as a stopping rule had significantly higher overall and transplant-free 90-day survival and lower incidence of acute kidney injury than those treated with A+Z.

IMPACT AND IMPLICATIONS

There is no approved treatment for severe alcohol-associated hepatitis (SAH). In this double-blind randomized trial, patients with SAH treated with prednisone using the Lille stopping rule on Day 7 had higher 90-day overall and transplant-free survival and lower rates of acute kidney injury compared to patients treated with a combination of anakinra and zinc. The data support continued use of glucocorticoids for patients with SAH, with treatment discontinuation for those with a Lille score >0.45 on Day 7.

TRIAL REGISTRATION

NCT04072822.

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.

Membrane-bound O-acyltransferase 7 (MBOAT7) shapes lysosomal lipid homeostasis and function to control alcohol-associated liver injury

Recent genome-wide association studies (GWAS) have identified a link between single-nucleotide polymorphisms (SNPs) near the MBOAT7 gene and advanced liver diseases. Specifically, the common MBOAT7 variant (rs641738) associated with reduced MBOAT7 expression is implicated in non-alcoholic fatty liver disease (NAFLD), alcohol-associated liver disease (ALD), and liver fibrosis. However, the precise mechanism underlying MBOAT7-driven liver disease progression remains elusive. Previously, we identified MBOAT7-driven acylation of lysophosphatidylinositol lipids as key mechanism suppressing the progression of NAFLD (Gwag et al., 2019). Here, we show that MBOAT7 loss of function promotes ALD via reorganization of lysosomal lipid homeostasis. Circulating levels of MBOAT7 metabolic products are significantly reduced in heavy drinkers compared to healthy controls. Hepatocyte- (Mboat7-HSKO), but not myeloid-specific (Mboat7-MSKO), deletion of Mboat7 exacerbates ethanol-induced liver injury. Lipidomic profiling reveals a reorganization of the hepatic lipidome in Mboat7-HSKO mice, characterized by increased endosomal/lysosomal lipids. Ethanol-exposed Mboat7-HSKO mice exhibit dysregulated autophagic flux and lysosomal biogenesis, associated with impaired transcription factor EB-mediated lysosomal biogenesis and autophagosome accumulation. This study provides mechanistic insights into how MBOAT7 influences ALD progression through dysregulation of lysosomal biogenesis and autophagic flux, highlighting hepatocyte-specific MBOAT7 loss as a key driver of ethanol-induced liver injury.

Proteomics identifies complement protein signatures in patients with alcohol-associated hepatitis

Diagnostic challenges continue to impede development of effective therapies for successful management of alcohol-associated hepatitis (AH), creating an unmet need to identify noninvasive biomarkers for AH. In murine models, complement contributes to ethanol-induced liver injury. Therefore, we hypothesized that complement proteins could be rational diagnostic/prognostic biomarkers in AH. Here, we performed a comparative analysis of data derived from human hepatic and serum proteome to identify and characterize complement protein signatures in severe AH (sAH). The quantity of multiple complement proteins was perturbed in liver and serum proteome of patients with sAH. Multiple complement proteins differentiated patients with sAH from those with alcohol cirrhosis (AC) or alcohol use disorder (AUD) and healthy controls (HCs). Serum collectin 11 and C1q binding protein were strongly associated with sAH and exhibited good discriminatory performance among patients with sAH, AC, or AUD and HCs. Furthermore, complement component receptor 1-like protein was negatively associated with pro-inflammatory cytokines. Additionally, lower serum MBL associated serine protease 1 and coagulation factor II independently predicted 90-day mortality. In summary, meta-analysis of proteomic profiles from liver and circulation revealed complement protein signatures of sAH, highlighting a complex perturbation of complement and identifying potential diagnostic and prognostic biomarkers for patients with sAH.

Hepatic protein tyrosine phosphatase Shp2 disruption mitigates the adverse effects of ethanol in the liver by modulating oxidative stress and ERK signaling

AIMS

Chronic excessive alcohol intake is a significant cause of alcohol-associated liver disease (ALD), a leading contributor to liver-related morbidity and mortality. The Src homology phosphatase 2 (Shp2; encoded by Ptpn11) is a widely expressed protein tyrosine phosphatase that modulates hepatic functions, but its role in ALD is mostly uncharted.

MAIN METHODS

Herein, we explore the effects of liver-specific Shp2 genetic disruption using the established chronic-plus-binge mouse model of ALD.

KEY FINDINGS

We report that the hepatic Shp2 disruption had beneficial effects and partially ameliorated ethanol-induced injury, inflammation, and steatosis in the liver. Consistently, Shp2 deficiency was associated with decreased ethanol-evoked activation of extracellular signal-regulated kinase (ERK) and oxidative stress in the liver. Moreover, primary hepatocytes with Shp2 deficiency exhibited similar outcomes to those observed upon Shp2 disruption in vivo, including diminished ethanol-induced ERK activation, inflammation, and oxidative stress. Furthermore, pharmacological inhibition of ERK in primary hepatocytes mimicked the effects of Shp2 deficiency and attenuated oxidative stress caused by ethanol.

SIGNIFICANCE

Collectively, these findings highlight Shp2 as a modulator of hepatic oxidative stress upon ethanol challenge and suggest the evaluation of this phosphatase as a potential therapeutic target for ALD.

Mediators of necroptosis: from cell death to metabolic regulation

Necroptosis, a programmed cell death mechanism distinct from apoptosis, has garnered attention for its role in various pathological conditions. While initially recognized for its involvement in cell death, recent research has revealed that key necroptotic mediators, including receptor-interacting protein kinases (RIPKs) and mixed lineage kinase domain-like protein (MLKL), possess additional functions that go beyond inducing cell demise. These functions encompass influencing critical aspects of metabolic regulation, such as energy metabolism, glucose homeostasis, and lipid metabolism. Dysregulated necroptosis has been implicated in metabolic diseases, including obesity, diabetes, metabolic dysfunction-associated steatotic liver disease (MASLD) and alcohol-associated liver disease (ALD), contributing to chronic inflammation and tissue damage. This review provides insight into the multifaceted role of necroptosis, encompassing both cell death and these extra-necroptotic functions, in the context of metabolic diseases. Understanding this intricate interplay is crucial for developing targeted therapeutic strategies in diseases that currently lack effective treatments.

Membrane Bound O-Acyltransferase 7 (MBOAT7) Shapes Lysosomal Lipid Homeostasis and Function to Control Alcohol-Associated Liver Injury

Several recent genome-wide association studies (GWAS) have identified single nucleotide polymorphism (SNPs) near the gene encoding membrane-bound O -acyltransferase 7 ( MBOAT7 ) that is associated with advanced liver diseases. In fact, a common MBOAT7 variant (rs641738), which is associated with reduced MBOAT7 expression, confers increased susceptibility to non-alcoholic fatty liver disease (NAFLD), alcohol-associated liver disease (ALD), and liver fibrosis in those chronically infected with hepatitis viruses B and C. The MBOAT7 gene encodes a lysophosphatidylinositol (LPI) acyltransferase enzyme that produces the most abundant form of phosphatidylinositol 38:4 (PI 18:0/20:4). Although these recent genetic studies clearly implicate MBOAT7 function in liver disease progression, the mechanism(s) by which MBOAT7-driven LPI acylation regulates liver disease is currently unknown. Previously we showed that antisense oligonucleotide (ASO)-mediated knockdown of Mboat7 promoted non-alcoholic fatty liver disease (NAFLD) in mice (Helsley et al., 2019). Here, we provide mechanistic insights into how MBOAT7 loss of function promotes alcohol-associated liver disease (ALD). In agreement with GWAS studies, we find that circulating levels of metabolic product of MBOAT7 (PI 38:4) are significantly reduced in heavy drinkers compared to age-matched healthy controls. Hepatocyte specific genetic deletion ( Mboat7 HSKO ), but not myeloid-specific deletion ( Mboat7 MSKO ), of Mboat7 in mice results in enhanced ethanol-induced hepatic steatosis and high concentrations of plasma alanine aminotransferase (ALT). Given MBOAT7 is a lipid metabolic enzyme, we performed comprehensive lipidomic profiling of the liver and identified a striking reorganization of the hepatic lipidome upon ethanol feeding in Mboat7 HSKO mice. Specifically, we observed large increases in the levels of endosomal/lysosomal lipids including bis(monoacylglycero)phosphates (BMP) and phosphatidylglycerols (PGs) in ethanol-exposed Mboat7 HSKO mice. In parallel, ethanol-fed Mboat7 HSKO mice exhibited marked dysregulation of autophagic flux and lysosomal biogenesis when exposed to ethanol. This was associated with impaired transcription factor EB (TFEB)-mediated lysosomal biogenesis and accumulation of autophagosomes. Collectively, this works provides new molecular insights into how genetic variation in MBOAT7 impacts ALD progression in humans and mice. This work is the first to causally link MBOAT7 loss of function in hepatocytes, but not myeloid cells, to ethanol-induced liver injury via dysregulation of lysosomal biogenesis and autophagic flux.

Receptor-interacting protein 1 and 3 kinase activity are required for high-fat diet induced liver injury in mice

Background

The RIP1-RIP3-MLKL-mediated cell death pathway is associated with progression of non-alcohol-associated fatty liver/steatohepatitis (NAFL/NASH). Previous work identified a critical role for MLKL, the key effector regulating necroptosis, but not RIP3, in mediating high fat diet-induced liver injury in mice. RIP1 and RIP3 have active N-terminus kinase domains essential for activation of MLKL and subsequent necroptosis. However, little is known regarding domain-specific roles of RIP1/RIP3 kinase in liver diseases. Here, we hypothesized that RIP1/RIP3 kinase activity are required for the development of high fat diet-induced liver injury.

Methods

Rip1K45A/K45A and Rip3K51A/K51A kinase-dead mice on a C57BL/6J background and their littermate controls (WT) were allowed free access to a diet high in fat, fructose and cholesterol (FFC diet) or chow diet.

Results

Both Rip1K45A/K45A and Rip3K51A/K51A mice were protected against FFC diet-induced steatosis, hepatocyte injury and expression of hepatic inflammatory cytokines and chemokines. FFC diet increased phosphorylation and oligomerization of MLKL and hepatocyte death in livers of WT, but not in Rip3K51A/K51A, mice. Consistent with in vivo data, RIP3 kinase deficiency in primary hepatocytes prevented palmitic acid-induced translocation of MLKL to the cell surface and cytotoxicity. Additionally, loss of Rip1 or Rip3 kinase suppressed FFC diet-mediated formation of crown-like structures (indicators of dead adipocytes) and expression of mRNA for inflammatory response genes in epididymal adipose tissue. Moreover, FFC diet increased expression of multiple adipokines, including leptin and plasminogen activator inhibitor 1, in WT mice, which was abrogated by Rip3 kinase deficiency.

Discussion

The current data indicate that both RIP1 and RIP3 kinase activity contribute to FFC diet-induced liver injury. This effect of RIP1 and RIP3 kinase deficiency on injury is consistent with the protection of Mlkl-/- mice from high fat diet-induced liver injury, but not the reported lack of protection in Rip3-/- mice. Taken together with previous reports, our data suggest that other domains of RIP3 likely counteract the effect of RIP3 kinase in response to high fat diets.

Dysregulated meta-organismal metabolism of aromatic amino acids in alcohol-associated liver disease

BACKGROUND

Chronic alcohol consumption impairs gut barrier function and perturbs the gut microbiome. Although shifts in bacterial communities in patients with alcohol-associated liver disease (ALD) have been characterized, less is known about the interactions between host metabolism and circulating microbe-derived metabolites during the progression of ALD.

METHODS

A large panel of gut microbiome-derived metabolites of aromatic amino acids was quantified by stable isotope dilution liquid chromatography with online tandem mass spectrometry in plasma from healthy controls (n = 29), heavy drinkers (n = 10), patients with moderate (n = 16) or severe alcohol-associated hepatitis (n = 40), and alcohol-associated cirrhosis (n = 10).

RESULTS

The tryptophan metabolites, serotonin and indole-3-propionic acid, and tyrosine metabolites, p-cresol sulfate, and p-cresol glucuronide, were decreased in patients with ALD. Patients with severe alcohol-associated hepatitis and alcohol-associated cirrhosis had the largest decrease in concentrations of tryptophan and tyrosine-derived metabolites compared to healthy control. Western blot analysis and interrogation of bulk RNA sequencing data from patients with various liver pathologies revealed perturbations in hepatic expression of phase II metabolism enzymes involved in sulfonation and glucuronidation in patients with severe forms of ALD.

CONCLUSIONS

We identified several metabolites decreased in ALD and disruptions of hepatic phase II metabolism. These results indicate that patients with more advanced stages of ALD, including severe alcohol-associated hepatitis and alcohol-associated cirrhosis, had complex perturbations in metabolite concentrations that likely reflect both changes in the composition of the gut microbiome community and the ability of the host to enzymatically modify the gut-derived metabolites.

Genomic approaches to explore susceptibility and pathogenesis of alcohol use disorder and alcohol-associated liver disease

Excessive alcohol use is a major risk factor for the development of an alcohol use disorder (AUD) and contributes to a wide variety of other medical illnesses, including alcohol-associated liver disease (ALD). Both AUD and ALD are complex and causally interrelated diseases, and multiple factors other than alcohol consumption are implicated in the disease pathogenesis. While the underlying pathophysiology of AUD and ALD is complex, there is substantial evidence for a genetic susceptibility of both diseases. Current genome-wide association studies indicate that the genes associated with clinical AUD only poorly overlap with the genes identified for heavy drinking and, in turn, neither overlap with the genes identified for ALD. Uncovering the main genetic factors will enable us to identify molecular drivers underlying the pathogenesis, discover potential targets for therapy, and implement patient care early in disease progression. In this review, we described multiple genomic approaches and their implications to investigate the susceptibility and pathogenesis of both AUD and ALD. We concluded our review with a discussion of the knowledge gaps and future research on genomic studies in these 2 diseases.

The Beneficial Effects of Lactobacillus GG Therapy on Liver and Drinking Assessments in Patients with Moderate Alcohol-Associated Hepatitis

INTRODUCTION

We investigated the effect of daily oral Lactobacillus rhamnosus GG (LGG) in reducing liver injury/severity and drinking in patients with alcohol use disorder and moderately severe alcohol-associated hepatitis.

METHODS

Forty-six male and female individuals with alcohol use disorder and moderate alcohol-associated hepatitis (12 ≤ model for end-stage liver disease score < 20, aged 21-67 years) received either LGG (n = 24) or placebo (n = 22). Data were collected/assessed at baseline and at 1, 3, and 6 months.

RESULTS

LGG treatment was associated with a significant reduction in liver injury after 1 month. Six months of LGG treatment reduced heavy drinking levels to social or abstinence levels.

DISCUSSION

LGG treatment was associated with an improvement in both liver injury and drinking.

Alcohol-induced extracellular ASC specks perpetuate liver inflammation and damage in alcohol-associated hepatitis even after alcohol cessation

BACKGROUND AIMS

Prolonged systemic inflammation contributes to poor clinical outcomes in severe alcohol-associated hepatitis (AH) even after the cessation of alcohol use. However, mechanisms leading to this persistent inflammation remain to be understood.

APPROACH RESULTS

We show that while chronic alcohol induces nucleotide-binding oligomerization domain-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome activation in the liver, alcohol binge results not only in NLRP3 inflammasome activation but also in increased circulating extracellular apoptosis-associated speck-like protein containing a caspase recruitment domain (ex-ASC) specks and hepatic ASC aggregates both in patients with AH and in mouse models of AH. These ex-ASC specks persist in circulation even after the cessation of alcohol use. Administration of alcohol-induced-ex-ASC specks in vivo in alcohol-naive mice results in sustained inflammation in the liver and circulation and causes liver damage. Consistent with the key role of ex-ASC specks in mediating liver injury and inflammation, alcohol binge failed to induce liver damage or IL-1β release in ASC-deficient mice. Our data show that alcohol induces ex-ASC specks in liver macrophages and hepatocytes, and these ex-ASC specks can trigger IL-1β release in alcohol-naive monocytes, a process that can be prevented by the NLRP3 inhibitor, MCC950. In vivo administration of MCC950 reduced hepatic and ex-ASC specks, caspase-1 activation, IL-1β production, and steatohepatitis in a murine model of AH.

CONCLUSIONS

Our study demonstrates the central role of NLRP3 and ASC in alcohol-induced liver inflammation and unravels the critical role of ex-ASC specks in the propagation of systemic and liver inflammation in AH. Our data also identify NLRP3 as a potential therapeutic target in AH.

Altered Anti-Viral Immune Responses in Monocytes in Overweight Heavy Drinkers

Alcohol abuse causes increased susceptibility to respiratory syndromes like bacterial pneumonia and viral infections like SARS-CoV-2. Heavy drinkers (HD) are at higher risk of severe COVID-19 if they are also overweight, yet the molecular mechanisms are unexplored. Single-cell RNA-seq (scRNA-seq) was performed on peripheral blood mononuclear cells from lean or overweight HD and healthy controls (HC) after challenge with a dsRNA homopolymer (PolyI:C) to mimic a viral infection and/or with lipopolysaccharide (LPS). All monocyte populations responded to both PolyI:C and LPS with pro-inflammatory gene expression. However, expression of interferon stimulated genes, essential for inhibiting viral pathogenesis, was greatly reduced in overweight patients. Interestingly, the number of upregulated genes in response to PolyI:C challenge was far greater in monocytes from HD compared to HC, including much stronger pro-inflammatory cytokine and interferon-γ signaling responses. These results suggest increased body weight reduced anti-viral responses while heavy drinking increased pro-inflammatory cytokines.

5S rRNA pseudogene transcripts are associated with interferon production and inflammatory responses in alcohol-associated hepatitis

BACKGROUND AND AIMS

Interferon (IFN) signaling is critical to the pathogenesis of alcohol-associated hepatitis (AH), yet the mechanisms for activation of this system are elusive. We hypothesize that host-derived 5S rRNA pseudogene (RNA5SP) transcripts regulate IFN production and modify immunity in AH.

APPROACH AND RESULTS

Mining of transcriptomic datasets revealed that in patients with severe alcohol-associated hepatitis (sAH), hepatic expression of genes regulated by IFNs was perturbed and gene sets involved in IFN production were enriched. RNA5SP transcripts were also increased and correlated with expression of type I IFNs. Interestingly, inflammatory mediators upregulated in sAH, but not in other liver diseases, were positively correlated with certain RNA5SP transcripts. Real-time quantitative PCR demonstrated that RNA5SP transcripts were upregulated in peripheral blood mononuclear cells (PBMCs) from patients with sAH. In sAH livers, increased 5S rRNA and reduced nuclear MAF1 (MAF1 homolog, negative regulator of RNA polymerase III) protein suggested a higher activity of RNA polymerase III (Pol III); inhibition of Pol III reduced RNA5SP expression in monocytic THP-1 cells. Expression of several RNA5SP transcript-interacting proteins was downregulated in sAH, potentially unmasking transcripts to immunosensors. Indeed, siRNA knockdown of interacting proteins potentiated the immunostimulatory activity of RNA5SP transcripts. Molecular interaction and cell viability assays demonstrated that RNA5SP transcripts adopted Z-conformation and contributed to ZBP1-mediated caspase-independent cell death.

CONCLUSIONS

Increased expression and binding availability of RNA5SP transcripts was associated with hepatic IFN production and inflammation in sAH. These data identify RNA5SP transcripts as a potential target to mitigate inflammation and hepatocellular injury in AH.

Peripheral blood mononuclear cell mitochondrial dysfunction in acute alcohol-associated hepatitis

BACKGROUND

Patients with acute alcohol-associated hepatitis (AH) have immune dysfunction. Mitochondrial function is critical for immune cell responses and regulates senescence. Clinical translational studies using complementary bioinformatics-experimental validation of mitochondrial responses were performed in peripheral blood mononuclear cells (PBMC) from patients with AH, healthy controls (HC), and heavy drinkers without evidence of liver disease (HD).

METHODS

Feature extraction for differentially expressed genes (DEG) in mitochondrial components and telomere regulatory pathways from single-cell RNAseq (scRNAseq) and integrated 'pseudobulk' transcriptomics from PBMC from AH and HC (n = 4 each) were performed. After optimising isolation and processing protocols for functional studies in PBMC, mitochondrial oxidative responses to substrates, uncoupler, and inhibitors were quantified in independent discovery (AH n = 12; HD n = 6; HC n = 12) and validation cohorts (AH n = 10; HC n = 7). Intermediary metabolites (gas-chromatography/mass-spectrometry) and telomere length (real-time PCR) were quantified in subsets of subjects (PBMC/plasma AH n = 69/59; HD n = 8/8; HC n = 14/27 for metabolites; HC n = 13; HD n = 8; AH n = 72 for telomere length).

RESULTS

Mitochondrial, intermediary metabolite, and senescence-regulatory genes were differentially expressed in PBMC from AH and HC in a cell type-specific manner at baseline and with lipopolysaccharide (LPS). Fresh PBMC isolated using the cell preparation tube generated optimum mitochondrial responses. Intact cell and maximal respiration were lower (p ≤ .05) in AH than HC/HD in the discovery and validation cohorts. In permeabilised PBMC, maximum respiration, complex I and II function were lower in AH than HC. Most tricarboxylic acid (TCA) cycle intermediates in plasma were higher while those in PBMC were lower in patients with AH than those from HC. Lower telomere length, a measure of cellular senescence, was associated with higher mortality in AH.

CONCLUSION

Patients with AH have lower mitochondrial oxidative function, higher plasma TCA cycle intermediates, with telomere shortening in nonsurvivors.

Mincle-GSDMD-mediated release of IL-1β small extracellular vesicles from hepatic macrophages in ethanol-induced liver injury

BACKGROUND

Macrophage-inducible C-type lectin (Mincle) is expressed on hepatic macrophages and senses ethanol (EtOH)-induced danger signals released from dying hepatocytes and promotes IL-1β production. However, it remains unclear what and how EtOH-induced Mincle ligands activate downstream signaling events to mediate IL-1β release and contribute to alcohol-associated liver disease (ALD). In this study, we investigated the association of circulating β-glucosylceramide (β-GluCer), an endogenous Mincle ligand, with severity of ALD and examined the mechanism by which β-GluCer engages Mincle on hepatic macrophages to release IL-1β in the absence of cell death and exacerbates ALD.

METHOD AND RESULTS

Concentrations of β-GluCer were increased in serum of patients with severe AH and correlated with disease severity. Challenge of hepatic macrophages with lipopolysaccharide and β-GluCer induced formation of a Mincle and Gsdmd-dependent secretory complex containing chaperoned full-length gasdermin D (Hsp90-CDC37-NEDD4) with polyubiquitinated pro-IL-1β and components of the Caspase 8-NLRP3 inflammasome loaded as cargo in small extracellular vesicles (sEVs). Gao-binge EtOH exposure to wild-type, but not Mincle-/- and Gsdmd-/-, mice increased release of IL-1β-containing sEVs from liver explant cultures. Myeloid-specific deletion of Gsdmd similarly decreased the formation of sEVs by liver explant cultures and protected mice from EtOH-induced liver injury. sEVs collected from EtOH-fed wild-type, but not Gsdmd-/-, mice promoted injury of cultured hepatocytes and, when injected into wild-type mice, aggravated Gao-binge EtOH-induced liver injury.

CONCLUSION

β-GluCer functions as a danger-associated molecular pattern activating Mincle-dependent gasdermin D-mediated formation and release of IL-1β-containing sEVs, which in turn exacerbate hepatocyte cell death and contribute to the pathogenesis of ALD.

Macrophage-derived MLKL in alcohol-associated liver disease: Regulation of phagocytosis

BACKGROUND AND AIMS

Mixed lineage kinase domain-like pseudokinase (MLKL), a key terminal effector of necroptosis, also plays a role in intracellular vesicle trafficking that is critical for regulating liver inflammation and injury in alcohol-associated liver disease (ALD). Although receptor interacting protein kinase 3 (Rip3)-/- mice are completely protected from ethanol-induced liver injury, Mlkl-/- mice are only partially protected. Therefore, we hypothesized that cell-specific functions of MLKL may contribute to ethanol-induced injury.

APPROACH AND RESULTS

Bone marrow transplants between Mlkl-/- mice and littermates were conducted to distinguish the role of myeloid versus nonmyeloid Mlkl in the Gao-binge model of ALD. Ethanol-induced hepatic injury, steatosis, and inflammation were exacerbated in Mlkl-/- →wild-type (WT) mice, whereas Mlkl deficiency in nonmyeloid cells (WT→ Mlkl-/- ) had no effect on Gao-binge ethanol-induced injury. Importantly, Mlkl deficiency in myeloid cells exacerbated ethanol-mediated bacterial burden and accumulation of immune cells in livers. Mechanistically, challenging macrophages with lipopolysaccharide (LPS) induced signal transducer and activator of transcription 1-mediated expression and phosphorylation of MLKL, as well as translocation and oligomerization of MLKL to intracellular compartments, including phagosomes and lysosomes but not plasma membrane. Importantly, pharmacological or genetic inhibition of MLKL suppressed the phagocytic capability of primary mouse Kupffer cells (KCs) at baseline and in response to LPS with/without ethanol as well as peripheral monocytes isolated from both healthy controls and patients with alcohol-associated hepatitis. Further, in vivo studies revealed that KCs of Mlkl-/- mice phagocytosed fewer bioparticles than KCs of WT mice.

CONCLUSION

Together, these data indicate that myeloid MLKL restricts ethanol-induced liver inflammation and injury by regulating hepatic immune cell homeostasis and macrophage phagocytosis.

Myeloid-cell-specific role of Gasdermin D in promoting lung cancer progression in mice

The activities of the NLRP3 and AIM2 inflammasomes and Gasdermin D (GsdmD) are implicated in lung cancer pathophysiology but it's not clear if their contributions promote or retard lung cancer progression. Using a metastatic Lewis lung carcinoma (LLC) cell model, we show that GsdmD knockout (GsdmD^-/-) mice form significantly fewer cancer foci in lungs, exhibit markedly decreased lung cancer metastasis, and show a significant ∼50% increase in median survival rate. The cleaved forms of GsdmD and IL-1β were detected in lung tumor tissue, indicating inflammasome activity in lung tumor microenvironment (TME). Increased migration and growth of LLC cells was observed upon exposure to the conditioned media derived from inflammasome-induced wild type, but not the GsdmD^-/-, macrophages. Using bone marrow transplantations, we show a myeloid-specific contribution of GsdmD in lung cancer metastasis. Taken together, our data show that GsdmD plays a myeloid-specific role in lung cancer progression.