Ethanol and Other Short-Chain Alcohols Inhibit NLRP3 Inflammasome Activation through Protein Tyrosine Phosphatase Stimulation

Effect of ethanol exposure on innate immune response in sepsis

Alcohol use disorder, reported by 1 in 8 critically ill patients, is a risk factor for death in sepsis patients. Sepsis, the leading cause of death, kills over 270,000 patients in the United States alone and remains without targeted therapy. Immune response in sepsis transitions from an early hyperinflammation to persistent inflammation and immunosuppression and multiple organ dysfunction during late sepsis. Innate immunity is the first line of defense against pathogen invasion. Ethanol exposure is known to impair innate and adaptive immune response and bacterial clearance in sepsis patients. Specifically, ethanol exposure is known to modulate every aspect of innate immune response with and without sepsis. Multiple molecular mechanisms are implicated in causing dysregulated immune response in ethanol exposure with sepsis, but targeted treatments have remained elusive. In this article, we outline the effects of ethanol exposure on various innate immune cell types in general and during sepsis.

Obesity-associated inflammatory macrophage polarization is inhibited by capsaicin and phytolignans

Obesity is often accompanied by increased adipose tissue inflammation, a process that is partially driven by adipose tissue-resident macrophages. In this study, we explored the potential for plant-derived dietary compounds to exert anti-inflammatory effects in macrophages that alleviate obesity-associated adipocyte dysfunction. Capsaicin (CAP), schisandrin A (SA), enterodiol (END), and enterolactone (ENL) treatment polarized J774 macrophages to an "M2" or anti-inflammatory phenotype and inhibited responses to stimulation with lipopolysaccharide (LPS). Furthermore, these compounds blocked inflammasome activation when administered just before ATP-induced NLRP3 activation, as evidenced by the abrogation of IL-1β release in mouse macrophages and human peripheral blood monocytes. The addition of CAP, SA, or ENL during the differentiation of bone marrow-derived macrophages was also sufficient to inhibit LPS-induced IL-6 and TNFα production. Finally, CAP, END, and ENL treatment during differentiation of 3T3-L1 adipocytes induced an adiponectin-high phenotype accompanied by increases in thermogenic gene expression, and conditioned media from these adipocytes inhibited LPS-induced production of IL-1β, IL-6, and TNFα from J774 macrophages. These polarizing effects were partially mediated by the elevated adiponectin and decreased syndecan-4 in the adipocyte-conditioned media. These results implicate the contribution of plant-derived dietary components to the modulation of macrophages and adipocytes in obesity.NEW & NOTEWORTHY The utility of food-based products to prevent or alleviate chronic conditions such as obesity and its associated comorbidities is an attractive approach. Capsaicin, schisandrin A, enterodiol, and enterolactone, phytochemicals present in traditional medicinal food, decreased proinflammatory cytokine production from macrophages that, in turn, reduced obesity-associated adipocyte dysfunction. These results implicate the contribution of plant-derived dietary components to the modulation of macrophages and adipocytes in obesity.

A Membrane Biophysics Perspective on the Mechanism of Alcohol Toxicity

Motivations for understanding the underlying mechanisms of alcohol toxicity range from economical to toxicological and clinical. On the one hand, acute alcohol toxicity limits biofuel yields, and on the other hand, acute alcohol toxicity provides a vital defense mechanism to prevent the spread of disease. Herein the role that stored curvature elastic energy (SCE) in biological membranes might play in alcohol toxicity is discussed, for both short and long-chain alcohols. Structure-toxicity relationships for alcohols ranging from methanol to hexadecanol are collated, and estimates of alcohol toxicity per alcohol molecule in the cell membrane are made. The latter reveal a minimum toxicity value per molecule around butanol before alcohol toxicity per molecule increases to a maximum around decanol and subsequently decreases again. The impact of alcohol molecules on the lamellar to inverse hexagonal phase transition temperature (T_H) is then presented and used as a metric to assess the impact of alcohol molecules on SCE. This approach suggests the nonmonotonic relationship between alcohol toxicity and chain length is consistent with SCE being a target of alcohol toxicity. Finally, in vivo evidence for SCE-driven adaptations to alcohol toxicity in the literature are discussed.

Alcohol use disorder as a potential risk factor for COVID-19 severity: A narrative review

In Dec. 2019-January 2020, a pneumonia illness originating in Wuhan, China, designated as coronavirus disease 2019 (COVID-19) was shown to be caused by a novel RNA coronavirus designated as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). People with advanced age, male sex, and/or underlying health conditions (obesity, type 2 diabetes, cardiovascular disease, hypertension, chronic kidney disease, and chronic lung disease) are especially vulnerable to severe COVID-19 symptoms and death. These risk factors impact the immune system and are also associated with poor health, chronic illness, and shortened longevity. However, a large percent of patients without these known risk factors also develops severe COVID-19 disease that can result in death. Thus, there must exist risk factors that promote exaggerated inflammatory and immune response to the SARS-CoV-2 virus leading to death. One such risk factor may be alcohol misuse and alcohol use disorder because these can exacerbate viral lung infections like SARS, influenza, and pneumonia. Thus, it is highly plausible that alcohol misuse is a risk factor for either increased infection rate when individuals are exposed to SARS-CoV-2 virus and/or more severe COVID-19 in infected patients. Alcohol use is a well-known risk factor for lung diseases and ARDS in SARS patients. We propose that alcohol has three key pathogenic elements in common with other COVID-19 severity risk factors: namely, inflammatory microbiota dysbiosis, leaky gut, and systemic activation of the NLRP3 inflammasome. We also propose that these three elements represent targets for therapy for severe COVID-19.

Ketone body augmentation decreases methacholine hyperresponsiveness in mouse models of allergic asthma

Background

Individuals with allergic asthma exhibit lung inflammation and remodeling accompanied by methacholine hyperresponsiveness manifesting in proximal airway narrowing and distal lung tissue collapsibility, and they can present with a range of mild-to-severe disease amenable or resistant to therapeutic intervention, respectively. There remains a need for alternatives or complements to existing treatments that could control the physiologic manifestations of allergic asthma.

Objectives

Our aim was to examine the hypothesis that because ketone bodies elicit anti-inflammatory activity and are effective in mitigating the methacholine hyperresponsiveness associated with obese asthma, increasing systemic concentrations of ketone bodies would diminish pathologic outcomes in asthma-relevant cell types and in mouse models of allergic asthma.

Methods

We explored the effects of ketone bodies on allergic asthma-relevant cell types (macrophages, airway epithelial cells, CD4 T cells, and bronchial smooth muscle cells) in vitro as well as in vivo by using preclinical models representative of several endotypes of allergic asthma to determine whether promotion of ketosis through feeding a ketogenic diet or providing a ketone precursor or a ketone ester dietary supplement could affect immune and inflammatory parameters as well as methacholine hyperresponsiveness.

Results

In a dose-dependent manner, the ketone bodies acetoacetate and β-hydroxybutyrate (BHB) decreased proinflammatory cytokine secretion from mouse macrophages and airway epithelial cells, decreased house dust mite (HDM) extract-induced IL-8 secretion from human airway epithelial cells, and decreased cytokine production from polyclonally and HDM-activated T cells. Feeding a ketogenic diet, providing a ketone body precursor, or supplementing the diet with a ketone ester increased serum BHB concentrations and decreased methacholine hyperresponsiveness in several acute HDM sensitization and challenge models of allergic asthma. A ketogenic diet or ketone ester supplementation decreased methacholine hyperresponsiveness in an HDM rechallenge model of chronic allergic asthma. Ketone ester supplementation synergized with corticosteroid treatment to decrease methacholine hyperresponsiveness in an HDM-driven model of mixed-granulocytic severe asthma. HDM-induced morphologic changes in bronchial smooth muscle cells were inhibited in a dose-dependent manner by BHB, as was HDM protease activity.

Conclusions

Increasing systemic BHB concentrations through dietary interventions could provide symptom relief for several endotypes of allergic asthmatic individuals through effects on multiple asthma-relevant cells.

Changes in Alcohol Consumption following Direct-Acting Antiviral Treatment for Hepatitis C in VA Patients with Comorbid Alcohol Use Disorder and PTSD

OBJECTIVE

To investigate whether direct-acting antivirals (DAA) for hepatitis C viral infection (HCV): glecaprevir/pibrentasvir (GLE/PIB), ledipasvir/sofosbuvir (LDV/SOF), and sofosbuvir/velpatasvir (SOF/VEL) are associated with reduced alcohol consumption among veterans with alcohol use disorder (AUD) and co-occurring post-traumatic stress disorder (PTSD).

METHODS

We measured change in Alcohol Use Disorder Identification Test-Consumption Module (AUDIT-C) scores in a retrospective cohort of veterans with PTSD and AUD receiving DAAs for HCV.

RESULTS

One thousand two hundred and eleven patients were included (GLE/PIB n = 174, LDV/SOF n = 808, SOF/VEL n = 229). Adjusted frequencies of clinically meaningful improvement were 30.5% for GLE/PIB, 45.5% for LDV/SOF, and 40.5% for SOF/VEL. The frequency was lower for GLE/PIB than for LDV/SOF (OR = 0.59; 95% CI [0.40, 0.87]) or SOF/VEL (OR = 0.66; 95% CI [0.42, 1.04]).

CONCLUSIONS

DAA treatment for HCV was associated with a substantial reduction in alcohol use in patients with AUD and co-occurring PTSD. Further exploration of the role of DAAs in AUD treatment is warranted.

Moderate Beer Intake Downregulates Inflammasome Pathway Gene Expression in Human Macrophages

Simple Summary

Moderate consumption of fermented beverages is associated with prevention against diseases involving inflammation and immunity. Conversely, for high drinking levels, an increase of inflammatory mediators and the susceptibility to infections occur, which tend to offset the benefits in terms of health. Unfortunately, this area remains poorly understood. Inflammation is now recognized as an overwhelming burden for public health. Thus, subcellular molecular complexes such as the “inflammasomes” have been identified as key players in cellular stress and tissue damage, and as regulators of immune and inflammatory responses. Here, we investigated the impact of moderate intake of alcohol-free and traditional beer in humans on the inflammasome pathway of activated pro-inflammatory human macrophages. The results of this study showed that macrophages submitted to a pro-inflammatory stimulus to activate the inflammosome had a mitigated inflammatory response in the presence of blood serum obtained from healthy volunteers after consuming alcohol-free or traditional beer for four weeks (women one can and men two cans per day) compared to the response found in the presence of blood serum obtained before beer intake. This was shown by a decrease in end components of the inflammasome cascade (IL-1β and TNF) at gene expression and protein level as found with alcohol-free and traditional beer, respectively.

Abstract

Inflammasomes are key components of the innate immunity system that trigger the inflammatory response. Inappropriate activity of the inflammasome system has been linked to onset and perpetuation of inflammation in atherosclerotic plaques and cardiovascular disease. Low-to-moderate beer consumption is inversely associated with cardiovascular event presentation, while high levels of alcohol intake are associated with increased cardiovascular risk. Although fermented beverages have been suggested to exert their beneficial effects through their anti-oxidant and anti-inflammatory properties, little is known regarding the capacity of beer to modulate innate immunity cell responses. To this aim, primed or activated THP-1 macrophages were conditioned with human serum obtained from a prospective two-arms longitudinal crossover study to investigate the effect of a moderate and regular daily intake of beer, either alcohol-free or traditional, in the regulation of TLR-mediated inflammatory responses in healthy but overweight individuals. Conditioned macrophages with serum obtained after four-week intervention with alcohol-free beer significantly reduced the transcription of pro-inflammatory interleukins such as IL-1β and TNF. The serum of traditional beer consumers did not exhibit the same capacity as the serum of alcohol-free beer consumers to reduce gene expression of pro-inflammatory interleukins; however, serum from traditional beer consumers showed a regulatory effect at the protein level by significantly decreasing the intracellular protein levels of pro-IL-1β in primed macrophages and preventing cleaved-IL-1β protein release.

Gut Microbial Changes and their Contribution to Post-Burn Pathology

ABSTRACT

Burn injuries are a common form of traumatic injury that leads to significant morbidity and mortality worldwide. Burn injuries are characterized by inflammatory processes and alterations in numerous organ systems and functions. Recently, it has become apparent that the gastrointestinal bacterial microbiome is a key component of regulating the immune response and recovery from burn and can also contribute to significant detrimental sequelae after injury, such as sepsis and multiple organ failure. Microbial dysbiosis has been linked to multiple disease states; however, its role in exacerbating acute traumatic injuries, such as burn, is poorly understood. In this article, we review studies that document changes in the intestinal microbiome after burn injury, assess the implications in post-burn pathogenesis, and the potential for further discovery and research.

The Purinergic P2X7 Receptor-NLRP3 Inflammasome Pathway: A New Target in Alcoholic Liver Disease?

The World Health Organization has estimated that approximately 3 million deaths are attributable to alcohol consumption each year. Alcohol consumption is notably associated with the development and/or progression of many non-communicable inflammatory diseases-particularly in the liver. Although these alcoholic liver diseases were initially thought to be caused by the toxicity of ethanol on hepatocytes, the latest research indicates Kupffer cells (the liver macrophages) are at the heart of this "inflammatory shift". Purinergic signaling (notably through P2X7 receptors and the NLRP3 inflammasome) by Kupffer cells appears to be a decisive factor in the pathophysiology of alcoholic liver disease. Hence, the modulation of purinergic signaling might represent a new means of treating alcoholic liver disease. Here, we review current knowledge on the pathophysiology of alcoholic liver diseases and therapeutic perspectives for targeting these inflammatory pathways.

[Hepatocellular damage and inflammation in various forms of alcoholic liver disease]

AIM

The aim of the study was to evaluate hepatocellular damage and immune inflammation in various forms of alcoholic liver disease (ALD).

MATERIALS AND METHODS

104 patients with ALD were examined: 15 (14.4%) with liver steatosis (LS), 19 (18.3%) with steatohepatitis and 70 (67.3%) with liver cirrhosis (LC); men 50 (48.1%), women 54 (51.9%); age 45.78.4 years. Traditional clinical, laboratory, instrumental studies were performed, the levels of fragments of cytokeratin-18 (FCK-18), cytokines IL-1, TNF-, IL-4, IL-6, IL-8 were determined by ELISA. The control group consisted of 39 healthy individuals: men 20 (51.2%), women 19 (48.7%), age 48.58.3 years.

RESULTS

In LS, an increase in the level of FCK-18 was noted with normal aminotransferase activity, the content of TNF-, IL-6, IL-1, IL-8 increased and the level of IL-4 decreased compared to those in healthy individuals. In steatohepatitis, a triple increase in aminotransferases and FCK-18 was observed compared with LS, as well as an increase in the level of inflammatory mediators, to a greater extent IL-6, to a lesser extent IL-8, TNF-, a decrease in IL-4, IL-1 remained at the same level. In LC, there was a further increase in FCK-18, significantly more pronounced than an increase in AST, and the increase in cytokines continued to the same extent, the levels of IL-6 and IL-8, to a lesser extent IL-1 and TNF-, and the level of IL-4.

CONCLUSION

With the progression of ALD from LS to steatohepatitis, hepatic cell damage was carried out by equally pronounced processes of hepatocyte necrosis and apoptosis, with the development of cirrhosis of the liver, parenchyma damage occurred mainly due to hepatocyte apoptosis. The immuno-inflammatory process progressively increased from the stage of LS to LC with IL-6 and IL-8 undergoing the greatest dynamics. FCK-18 can serve as a non-invasive marker of hepatic cell damage, and IL-6 and IL-8 markers of immune inflammation in ALD.

Pyroptotic cell death by exposure to 1-butanol in H9c2 cardiomyoblastoma cells

The aim of this study is to examine the molecular mechanism of cytotoxicity caused by direct exposure to short chain alcohol. We showed previously that exposing H9c2 cardiomyoblastoma cells to 150 mM 1-butanol results in cell death within 1 h through an intrinsic apoptotic pathway. The cell death is accompanied by plasma membrane blebbing and caspase-3 activation. Here we show that a higher concentration (200 mM) of 1-butanol, as well as prolonged exposure (3-6 h) to 150 mM 1-butanol, induces plasma membrane ballooning, a characteristic feature of pyroptosis. Although gasderminD (GSDMD) cleavage by caspase-1 was not observed, GSDME cleavage by caspase-3 was observed during exposure to 150 mM 1-butanol for 6 h. We conclude that pyroptotic cell death by 1-butanol in H9c2 cardiomyoblastoma cells should occur via the caspase-3-GSDME pathway, revealing that 1-butanol could induce not only apoptosis but also pyroptosis in the cells.

Ethanol Intoxication Alleviates the Inflammatory Response of Remote Organs to Experimental Traumatic Brain Injury

Traumatic brain injury (TBI) may cause damage to distant organs. Acute ethanol intoxication (EI) induces complex local and systemic anti-inflammatory effects and influences the early outcomes of traumatized patients. Here, we evaluated its effects on the BI-induced expression of local inflammatory mediators in the trauma-remote organs the lungs and liver. Male mice were exposed to ethanol as a single oral dose (5g·kg^–1, 32%) before inducing a moderate blunt TBI. Sham groups underwent the same procedures without TBI. Ether 3 or 6h after the TBI, the lung and liver were collected. The gene expression of HMGB1, IL-6, MMP9, IL-1β, and TNF as well as the homogenate protein levels of receptor for advanced glycation end products (RAGE), IL-6, IL-1β, and IL-10 were analyzed. Liver samples were immunohistologically stained for HMGB1. EI decreased the gene expressions of the proinflammatory markers HMGB1, IL-6, and MMP9 in the liver upon TBI. In line with the reduced gene expression, the TBI-induced protein expression of IL-6 in liver tissue homogenates was significantly reduced by EI at 3h after TBI. While the histological HMGB1 expression was enhanced by TBI, the RAGE protein expression in the liver tissue homogenates was diminished after TBI. EI reduced the histological HMGB1 expression and enhanced the hepatic RAGE protein expression at 6h post TBI. With regard to the lungs, EI significantly reduced the gene expressions of HMGB1, IL-6, IL-1β, and TNF upon TBI, without significantly affecting the protein expression levels of inflammatory markers (RAGE, IL-6, IL-1β, and IL-10). At the early stage of TBI-induced inflammation, the gene expression of inflammatory mediators in both the lungs and liver is susceptible to ethanol-induced remote effects. Taken together, EI may alleviate the TBI-induced pro-inflammatory response in the trauma-distant organs, the lungs and liver, via the HMGB1-RAGE axis.

Incidence of and risk factors for perioperative or periprocedural anaphylaxis in the United States from 2005 to 2014

BACKGROUND

The estimated worldwide incidence of perioperative or periprocedural anaphylaxis (PA) is between 1 in 1250 and 1 in 20,000 procedures.

OBJECTIVE

To evaluate the incidence of PA in the United States and compare patient characteristics and underlying risk factors using a large national database.

METHODS

Using deidentified data from the nationwide inpatient sample from 2005 to 2014, we identified cases of PA through the International Classification of Diseases, Ninth Revision, Clinical Modification codes and conducted a retrospective analysis.

RESULTS

Among 35,647,347 surgeries and procedures, there were 5458 (0.015%) PA cases identified. The incidence of PA was 15.3 cases per 100,000 procedures. When compared with controls, PA cases had an increased mortality (3.4% vs 1.4%; P < .001), median length of stay (5 vs 3 days; P < .001), and median hospital cost ($45,155 vs $24,734; P < .001). The age group between 18 and 34 years (odds ratio [OR], 1.34; 95% confidence interval [CI], 1.13-1.58; P < .001) and female sex (OR, 1.40; 95% CI, 1.31-1.49; P < .001) were associated with increased odds of PA. Transplant (OR, 3.35; 95% CI, 2.59-4.34; P < .001), hematologic (OR, 1.63; 95% CI, 1.30-2.05; P < .001), vascular (OR, 1.49; 95% CI, 1.30-1.67; P < .001), and cardiac (OR, 1.47; 95% CI, 1.30-1.67; P < .001) procedures were at increased risk for PA. Several comorbidities were associated with PA including chronic pulmonary disease (OR, 1.41; 95% CI, 1.31-1.51; P < .001).

CONCLUSION

The incidence of PA is 1 in 6531 procedures, with a mortality of 1 in 191,652 procedures. PA has worsening outcomes compared with controls. The risk factors of PA include age, sex, procedure type, and comorbidities.

The NLRP3 Inflammasome in Alcoholic and Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) and alcoholic hepatitis (ASH) are advanced forms of fatty liver diseases that are associated with a high morbidity and mortality worldwide. Patients with ASH or NASH are more susceptible to the progression of fibrosis and cirrhosis up to the development of hepatocellular carcinoma. Currently, there are limited medical therapies available. Accompanied by the asymptomatic disease progression, the demand for liver transplants is high. This review provides an overview about the growing evidence for a central role of NLR family pyrin domain containing 3 (NLRP3) inflammasome, a multiprotein complex that acts as a central driver of inflammation via activation of caspase 1, maturation and release of pro-inflammatory cytokines including interleukin-1β, and trigger of inflammatory pyroptotic cell death in both NASH and ASH. We also discuss potential therapeutic approaches targeting NLRP3 inflammasome and related upstream and downstream pathways to develop prognostic biomarkers and medical treatments for both liver diseases.

Pro-inflammatory signalling and gut-liver axis in non-alcoholic and alcoholic steatohepatitis: Differences and similarities along the path

Non-alcoholic fatty liver disease (NAFLD) and alcohol-associated liver disease (ALD) represent a spectrum of injury, ranging from simple steatosis to steatohepatitis and cirrhosis. In humans, in fact, fatty changes in the liver, possibly leading to end-stage disease, were observed after chronic alcohol intake or in conditions of metabolic impairment. In this article, we examined the features and the pro-inflammatory pathways leading to non-alcoholic and alcoholic steatohepatitis. The involvement of several events (hits) and multiple inter-related pathways in the pathogenesis of these diseases suggest that a single therapeutic agent is unlikely to be an effective treatment strategy. Hence, a combination treatment towards multiple pro-inflammatory targets would eventually be required. Gut-liver crosstalk is involved not only in the impairment of lipid and glucose homoeostasis leading to steatogenesis, but also in the initiation of inflammation and fibrogenesis in both NAFLD and ALD. Modulation of the gut-liver axis has been suggested as a possible therapeutic approach since gut-derived components are likely to be involved in both the onset and the progression of liver damage. This review summarizes the translational mechanisms underlying pro-inflammatory signalling and gut-liver axis in non-alcoholic and alcoholic steatohepatitis. With a multitude of people being affected by liver diseases, identification of possible treatments and the elucidation of pathogenic mechanisms are elements of paramount importance.

Ethanol Augments Monosodium Urate-Induced NLRP3 Inflammasome Activation via Regulation of AhR and TXNIP in Human Macrophages

PURPOSE

Ethanol elicits several inflammatory responses and affects the innate immune response. The aim of this study was to identify the mechanism by which ethanol affects uric acid-induced NLR family pyrin domain-containing 3 (NLRP3) inflammasome activation by regulation of aryl hydrocarbon receptor (AhR) and thioredoxin-interacting protein (TXNIP).

MATERIALS AND METHODS

Human myeloid leukemia cells (U937 cells) were used to assess the role of ethanol in NLRP3 inflammasome activation induced by monosodium urate (MSU) crystals. Expression of target molecules, such as NLRP3 inflammasome components, AhR, and TXNIP, were measured using quantitative real-time PCR and Western blot analyses. The effect of ethanol-induced TXNIP on the NLRP3 inflammasome was assessed in human macrophages transfected with TXNIP siRNA.

RESULTS

U937 cells treated with 100 mM ethanol for 24 h induced NLRP3 and interleukin (IL)-1β expression. Ethanol increased reactive oxygen species generation in a time- and dose-dependent manner. AhR mRNA expression was downregulated in U937 cells treated with 100 mM ethanol, whereas CYP1A1 mRNA expression increased. Treatment with ethanol increased NLRP3 and IL-1β mRNA and protein expression in U937 cells exposed to 1.0 mg/mL of MSU crystals for 24 h. TXNIP expression in U937 cells incubated with both 100 mM ethanol and 1.0 mg/mL of MSU crystals was significantly higher than in cells incubated with MSU crystals alone. Treatment with 100mM ethanol for 24 h downregulated NLRP3 and IL-1β expression in MSU crystal-activated U937 cells transfected with TXNIP siRNA, compared to those with scramble siRNA.

CONCLUSION

Ethanol stimulates uric acid-induced NLRP3 inflammasome activation through regression of AhR and upregulation of TXNIP.

Short Exposure to Ethanol Diminishes Caspase-1 and ASC Activation in Human HepG2 Cells In Vitro

This paper discusses how the assembly of pro-caspase-1 and apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) in macromolecular protein complexes, inflammasomes, activates caspase-1. The present study investigates the molecular mechanisms of inflammasome activation in HepG2 cells and examines how short exposures to ethanol (EtOH) affect inflammasome activation. HepG2 cells were treated with lipopolysaccharide (LPS), ATP or nigericin (NIG) in a two-step model. After LPS priming, ATP or NIG were added. As inhibitors, sodium orthovanadate (general inhibitor of tyrosine phosphatases), AC-YVAD-CMK (caspase-1 inhibitor) or AZ10606120 (purinergic receptor P2X7R inhibitor) were applied after LPS priming. To monitor the inflammasome activation, the caspase-1 activity, ASC speck formation, reactive oxygen species (ROS) production and cell death were analyzed. To elucidate the mechanistical approach of EtOH to the inflammasome assembly, the cells were treated with EtOH either under simultaneous LPS administration or concurrently with ATP or NIG application. The co-stimulation with LPS and ATP induced a significant ASC speck formation, caspase-1 activation, cell death and ROS generation. The inhibition of the ATP-dependent purinoreceptor P2X7 decreased the caspase-1 activation, whereas sodium orthovanadate significantly induced caspase-1. Additional treatment with EtOH reversed the LPS and ATP-induced caspase-1 activation, ASC speck formation and ROS production. The ASC speck formation and caspase-1 induction require a two-step signaling with LPS and ATP in HepG2 cells. Inflammasome activation may depend on P2X7. The molecular pathway of an acute effect of EtOH on inflammasomes may involve a reduction in ROS generation, which in turn may increase the activity of tyrosine phosphatases.

Short-Chain Alcohols Upregulate GILZ Gene Expression and Attenuate LPS-Induced Septic Immune Response

Alcohol differentially affects human health, depending on the pattern of exposure. Moderate intake provides beneficial mood modulation and an anti-inflammatory effect, while excessive consumption leads to immunosuppression and various alcohol use disorders. The mechanism underlying this bi-phasic action mode of alcohol has not been clearly defined. Our previous publication demonstrated that ethanol, in the absence of glucocorticoids (GCs), induces expression of Glucocorticoid-Induced Leucine Zipper (GILZ), a key molecule that transduces GC anti-inflammatory effect through a non-canonical activation of glucocorticoid receptor (1). Here we report that similar short-chain alcohols, such as ethanol, propanol and isopropanol, share the same property of upregulating GILZ gene expression, and blunt cell inflammatory response in vitro. When mice were exposed to these alcohols, GILZ gene expression in immune cells was augmented in a dose-dependent manner. Monocytes and neutrophils were most affected. The short-chain alcohols suppressed host inflammatory response to lipopolysaccharide (LPS) and significantly reduced LPS-induced mortality. Intriguingly, propanol and isopropanol displayed more potent protection than ethanol at the same dose. Inhibition of ethanol metabolism enhanced the ethanol protective effect, suggesting that it is ethanol, not its derivatives or metabolites, that induces immune suppression. Taken together, short-chain alcohols per se upregulate GILZ gene expression and provide immune protection against LPS toxicity, suggesting a potential measure to counter LPS septic shock in a resource limited situation.

Innate Immunity and Alcohol

The innate immunity has evolved during millions of years, and thus, equivalent or comparable components are found in most vertebrates, invertebrates, and even plants. It constitutes the first line of defense against molecules, which are either pathogen-derived or a danger signal themselves, and not seldom both. These molecular patterns are comprised of highly conserved structures, a common trait in innate immunity, and constitute very potent triggers for inflammation mediated via extracellular or intracellular pattern recognition receptors. Human culture is often interweaved with the consumption of alcohol, in both drinking habits, its acute or chronical misuse. Apart from behavioral effects as often observed in intoxicated individuals, alcohol consumption also leads to immunological modulation on the humoral and cellular levels. In the last 20 years, major advances in this field of research have been made in clinical studies, as well as in vitro and in vivo research. As every physician will experience intoxicated patients, it is important to be aware of the changes that this cohort undergoes. This review will provide a summary of the current knowledge on the influence of alcohol consumption on certain factors of innate immunity after a hit, followed by the current studies that display the effect of alcohol with a description of the model, the mode of alcohol administration, as well as its dose. This will provide a way for the reader to evaluate the findings presented.

Ethanol and its metabolites: update on toxicity, benefits, and focus on immunomodulatory effects

This article summarizes recent experimental and epidemiological data on the toxic and beneficial effects of ethanol and its metabolites (acetaldehyde), and focuses on their immunomodulatory effects. The section dealing with the toxic effects of alcohol focuses on its chronic toxicity (liver disorders, carcinogenic effects, cardiovascular disorders, neuropsychic disorders, addiction and withdrawal syndrome, hematologic disorders, reprotoxicity, osteoporosis) although acute toxicity is considered. The role of oxidative metabolism of ethanol by alcohol dehydrogenase, cytochrome P450 2E1, and aldehyde dehydrogenase, as well as the impact of genetic polymorphism in its physiopathology are also highlighted. The section dealing with the beneficial effects of low to moderate alcohol consumption (on cardiovascular system, diabetes, the nervous system and sensory organs, autoimmune diseases, and rheumatology) highlights the importance of anti-inflammatory and immunomodulatory effects in these observations. This knowledge, enriched by a focus on the immunomodulatory effects of ethanol and its metabolites, in particular on the NLRP3 inflammasome pathway, might facilitate the development of treatments that can reduce ethanol's harmful effects or accentuate its beneficial effects.

Chrysanthemum indicum extract inhibits NLRP3 and AIM2 inflammasome activation via regulating ASC phosphorylation

ETHNOPHARMACOLOGICAL RELEVANCE

Chrysanthemum indicum (C. indicum), a perennial plant, has long been used to treat inflammation-related disorders, such as pneumonia, hypertension, gastritis, and gastroenteritis.

AIM OF THE STUDY

The inhibitory effect of C. indicum extract (C.I) on inflammasome activation was investigated to validate its potential in treating inflammation related disorders.

MATERIALS AND METHODS

LPS-primed bone marrow-derived macrophages (BMDMs) were used to confirm the inhibitory effect of C.I on selective inflammasome activation in vitro. A monosodium urate (MSU)-induced murine peritonitis model was employed to study the effect of C.I in vivo.

RESULTS

C.I inhibited activation of NLRP3 and AIM2 inflammasomes, leading to suppression of interleukin-1β secretion in vitro. Further, C.I regulates the phosphorylation of apoptosis-associated speck-like protein containing a CARD (ASC), which could be the main contribution to attenuate these inflammasomes activation. C.I also suppressed secretion of pro-inflammatory cytokines and neutrophils recruitment in MSU-induced murine peritonitis model.

CONCLUSIONS

This study provides scientific evidence substantiating the traditional use of C. indicum in the treatment of inflammatory diseases, including gout, which is induced by physiologically analogous cause to MSU-induced peritonitis.

Tyrosine Dephosphorylation of ASC Modulates the Activation of the NLRP3 and AIM2 Inflammasomes

The inflammasome is an intracellular multi-protein complex that orchestrates the release of the pro-inflammatory cytokines IL-1β and IL-18, and a form of cell death known as pyroptosis. Tyrosine phosphorylation of the inflammasome sensors NLRP3, AIM2, NLRC4, and the adaptor protein, apoptosis-associated speck-like protein (ASC) has previously been demonstrated to be essential in the regulation of the inflammasome. By using the pharmacological protein tyrosine phosphatase (PTPase) inhibitor, phenylarsine oxide (PAO), we have demonstrated that tyrosine dephosphorylation is an essential step for the activation of the NLRP3 and AIM2 inflammasomes in human and murine macrophages. We have also shown that PTPase activity is required for ASC nucleation leading to caspase-1 activation, IL-1β, and IL-18 processing and release, and cell death. Furthermore, by site-directed mutagenesis of ASC tyrosine residues, we have identified the phosphorylation of tyrosine Y60 and Y137 of ASC as critical for inflammasome assembly and function. Therefore, we report that ASC tyrosine dephosphorylation and phosphorylation are crucial events for inflammasome activation.

Acetate Mediates Alcohol Excitotoxicity in Dopaminergic-like PC12 Cells

Neuronal excitotoxicity is the major cause of alcohol-related brain damage, yet the underlying mechanism remains poorly understood. Using dopaminergic-like PC12 cells, we evaluated the effect of N-methyl-d-aspartate receptors (NMDAR) on acetate-induced changes in PC12 cells: cell death, cytosolic calcium, and expression levels of the pro-inflammatory cytokine tumor necrosis factor alpha (TNFα). Treatment of PC12 cells with increasing concentrations of acetate for 4 h caused a dose-dependent increase in the percentage of cells staining positive for cell death using propidium iodide (PI) exclusion and cytosolic reactive oxygen species (ROS) using cell ROX detection analyzed via flow cytometry. The EC₅₀ value for acetate was calculated and found to be 4.40 mM for PI and 1.81 mM for ROS. Ethanol up to 100 mM had no apparent changes in the percent of cells staining positive for PI or ROS. Acetate (6 mM) treatment caused an increase in cytosolic calcium measured in real-time with Fluo-4AM, which was abolished by coapplication with the NMDAR blocker memantine (10 μM). Furthermore, cells treated with acetate (6 mM) for 4 h had increased expression levels of TNFα relative to control, which was abolished by coapplication of memantine (10 μM). Co-application of acetate (6 mM) and memantine had no apparent reduction in acetate-induced cell death. These findings suggest that acetate is capable of increasing cytosolic calcium concentrations and expression levels of the pro-inflammatory cytokine TNFα through an NMDAR-dependent mechanism. Cell death from acetate was not reduced through NMDAR blockade, suggesting alternative pathways independent of NMDAR activation for excitotoxicity.

Ethanol upregulates the P2X7 purinergic receptor in human macrophages

Alcohol consumption is considered to be the third leading cause of death in the United States. In addition to its direct toxicity, ethanol has two contrasting effects on the immune system: the nucleotide oligomerization domain-like receptor pyrin domain-containing-3 (NLRP3) inflammasome is inhibited by acute ethanol exposure but activated by chronic ethanol exposure. Purinergic receptors (especially the P2X7 receptor) are able to activate the NLRP3 inflammasome and are involved in many ethanol-related diseases (such as gout, pulmonary fibrosis, alcoholic steatohepatitis, and certain cancers). We hypothesized that ethanol regulates purinergic receptors and thus modulates the NLRP3 inflammasome's activity. In experiments with monocyte-derived macrophages, we found that interleukin (IL)-1β secretion was inhibited after 7 h of exposure (but not 48 h of exposure) to ethanol. The disappearance of ethanol's inhibitory effect on IL-1β secretion after 48 h was not mediated by the upregulated production of IL-1β, IL-1α, IL-6 or the inflammasome components NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain, and caspase 1. P2X7R expression was upregulated by ethanol, whereas expression of the P2X4 and P2X1 receptors was not. Taken as a whole, our results suggest that ethanol induces NLRP3 inflammasome activation by upregulating the P2X7 receptor. This observation might have revealed a new mechanism for inflammation in ethanol-related diseases.

Inhibition of ER stress-related IRE1α/CREB/NLRP1 pathway promotes the apoptosis of human chronic myelogenous leukemia cell

Endoplasmic reticulum (ER) stress is induced in chronic myelogenous leukemia (CML) cells. As an important sensor of ER stress, inositol-requiring protein-1α (IRE1α) promotes the survival of acute myeloid leukemia. NLRP1 inflammasome activation promotes metastatic melanoma growth and that IRE1α can increase NLRP1 inflammasome gene expression. This study aimed to investigate the role and molecular mechanism of IRE1α in CML cell growth. We found that overexpression of IRE1α or NLRP1 significantly promoted the proliferation and decreased the apoptosis of CML cells, whereas downregulation of these two genes showed the opposite effects. 4-phenylbutyric acid (4-PBA), an ER stress inhibitor, reduced the expression of IRE1α and NLRP1. IRE1α elevated NLRP1 expression via cAMP responsive element binding protein (CREB) phosphorylation. NLRP1 inflammasome was activated in CML cells and its activation partly reversed ER stress inhibitor-induced cell apoptosis. Furthermore, inhibition of IRE1α/NLRP1 pathway sensitized CML cells to imatinib-mediated apoptosis. Additionally, IRE1α expression was elevated and NLRP1 inflammasome was activated in primary cells from CML patients. Downregulation of IRE1α or NLRP1 suppressed the proliferation and elevated the apoptosis of primary CML cells. Collectively, this study demonstrated that the IRE1α/CREB/NLRP1 pathway contributes to the progression of CML and the development of imatinib resistance. Hence, targeting ER stress-related IRE1α expression or NLRP1 inflammasome activation may block CML development.

Artemisia Extract Suppresses NLRP3 and AIM2 Inflammasome Activation by Inhibition of ASC Phosphorylation

Artemisia princeps var. orientalis (Asteraceae, A. princeps) is a well-known traditional medicinal herb used for treating various inflammatory disorders in Korea, Japan, China, and other Asian countries. In the present study, we investigated the effects of A. princeps extract (APO) on interleukin- (IL-) 1β regulation and inflammasome activation in bone marrow-derived macrophages (BMDMs) and monosodium urate- (MSU-) induced peritonitis mouse model in vivo. The APO treatment to BMDMs primed with lipopolysaccharide (LPS) attenuated the NLRP3 and AIM2 inflammasome activation induced by danger signals, such as ATP, nigericin, silica crystals, and poly (dA:dT), respectively. Mechanistic study revealed that APO suppressed the ASC oligomerization and speck formation, which are required for inflammasome activation. APO treatment also reduced the ASC phosphorylation induced by the combination of LPS and a tyrosine phosphatase inhibitor. In vivo evaluation revealed that intraperitoneal administration of APO reduced IL-1β levels, significantly (p < 0.05) and dose dependently, in the MSU-induced peritonitis mouse model. In conclusion, our study is the first to report that the extract of A. princeps inhibits inflammasome activation through the modulation of ASC phosphorylation. Therefore, APO might be developed as therapeutic potential in the treatment of inflammasome-mediated inflammatory disorders, such as gouty arthritis.

Alcohol abuse is associated with enhanced pulmonary and systemic xanthine oxidoreductase activity

Acute respiratory distress syndrome (ARDS) is a common and devastating disorder. Alcohol use disorders (AUDs) increase ARDS risk and worsen outcomes through mechanisms that may include enhancement of pulmonary oxidative stress. Alcohol consumption increases activity of the enzyme xanthine oxidoreductase (XOR) that contributes to production of both reactive oxygen species (ROS) and uric acid, a damage-associated molecular pattern. These by-products have the potential to modulate proinflammatory pathways, such as those involving cyclooxygenase (COX)-2, and to activate the nucleotide-binding domain, leucine-rich-containing family, pyrin-domain containing-3 (NLRP3) inflammasome. We sought to determine if pulmonary and systemic XOR activity was altered by AUDs. Bronchoscopy with bronchoalveolar lavage (BAL) and blood sampling was performed in otherwise healthy human subjects with AUDs and controls. Uric acid in epithelial-lining fluid, derived from BAL, was substantially higher among individuals with AUDs and did not normalize after 7 days of abstinence; serum uric acid did not differ across groups. XOR enzyme activity in fresh BAL cells and serum was significantly increased in subjects with AUDs. XOR protein in BAL cells from AUD subjects was increased in parallel with COX-2 expression, and furthermore, mRNA expression of NLRP3 inflammasome components was sustained in LPS-stimulated BAL cells from AUD subjects in conjunction with increased IL-1β. Our data suggest that AUDs augment pulmonary and systemic XOR activity that may contribute to ROS and uric acid generation, promoting inflammation. Further investigations will be necessary to determine if XOR inhibition can mitigate alcohol-associated pulmonary oxidative stress, diminish inflammation, and improve ARDS outcomes.

Hyperthermia and associated changes in membrane fluidity potentiate P2X7 activation to promote tumor cell death

Extracellular ATP (eATP) accumulation within the tumor microenvironment (TME) has the potential to activate purinergic signaling. The eATP evoked signaling effects bolster antitumor immune responses while exerting direct cytotoxicity on tumor cells and vascular endothelial cells, mediated at least in part through P2X7 receptors. Approaches to augment purinergic signaling in TME e.g. by ectonucleotidase CD39 blockade, and/or boosting P2X7 functional responses, might be used as immunomodulatory therapies in cancer treatment. In this study, we delineated the translatable strategy of hyperthermia to demonstrate impacts on P2X7 responsiveness to eATP. Hyperthermia (40°C) was noted to enhance eATP-mediated cytotoxicity on MCA38 colon cancer cells. Increased membrane fluidity induced by hyperthermia boosted P2X7 functionality, potentiating pore opening and modulating downstream AKT/PRAS40/mTOR signaling events. When combined with cisplatin or mitomycin C, hyperthermia and eATP together markedly potentiate cancer cell death. Our data indicate that clinically tolerable hyperthermia with modulated P2X7-purinergic signaling will boost efficacy of conventional cancer treatments.

Alcohol, aging, and innate immunity

The global population is aging: in 2010, 8% of the population was older than 65 y, and that is expected to double to 16% by 2050. With advanced age comes a heightened prevalence of chronic diseases. Moreover, elderly humans fair worse after acute diseases, namely infection, leading to higher rates of infection-mediated mortality. Advanced age alters many aspects of both the innate and adaptive immune systems, leading to impaired responses to primary infection and poor development of immunologic memory. An often overlooked, yet increasingly common, behavior in older individuals is alcohol consumption. In fact, it has been estimated that >40% of older adults consume alcohol, and evidence reveals that >10% of this group is drinking more than the recommended limit by the National Institute on Alcohol Abuse and Alcoholism. Alcohol consumption, at any level, alters host immune responses, including changes in the number, phenotype, and function of innate and adaptive immune cells. Thus, understanding the effect of alcohol ingestion on the immune system of older individuals, who are already less capable of combating infection, merits further study. However, there is currently almost nothing known about how drinking alters innate immunity in older subjects, despite innate immune cells being critical for host defense, resolution of inflammation, and maintenance of immune homeostasis. Here, we review the effects of aging and alcohol consumption on innate immune cells independently and highlight the few studies that have examined the effects of alcohol ingestion in aged individuals.

Mitochondrial ROS induced by chronic ethanol exposure promote hyper-activation of the NLRP3 inflammasome

Alcohol use disorders are common both in the United States and globally, and are associated with a variety of co-morbid, inflammation-linked diseases. The pathogenesis of many of these ailments are driven by the activation of the NLRP3 inflammasome, a multi-protein intracellular pattern recognition receptor complex that facilitates the cleavage and secretion of the pro-inflammatory cytokines IL-1β and IL-18. We hypothesized that protracted exposure of leukocytes to ethanol would amplify inflammasome activation, which would help to implicate mechanisms involved in diseases associated with both alcoholism and aberrant NLRP3 inflammasome activation. Here we show that long-term ethanol exposure of human peripheral blood mononuclear cells and a mouse macrophage cell line (J774) amplifies IL-1β secretion following stimulation with NLRP3 agonists, but not with AIM2 or NLRP1b agonists. The augmented NRLP3 activation was mediated by increases in iNOS expression and NO production, in conjunction with increases in mitochondrial membrane depolarization, oxygen consumption rate, and ROS generation in J774 cells chronically exposed to ethanol (CE cells), effects that could be inhibited by the iNOS inhibitor SEITU, the NO scavenger carboxy-PTIO, and the mitochondrial ROS scavenger MitoQ. Chronic ethanol exposure did not alter K⁺ efflux or Zn²⁺ homeostasis in CE cells, although it did result in a lower intracellular concentration of NAD⁺. Prolonged administration of acetaldehyde, the product of alcohol dehydrogenase (ADH) mediated metabolism of ethanol, mimicked chronic ethanol exposure, whereas ADH inhibition prevented ethanol-induced IL-1β hypersecretion. Together, these results indicate that increases in iNOS and mitochondrial ROS production are critical for chronic ethanol-induced IL-1β hypersecretion, and that protracted exposure to the products of ethanol metabolism are probable mediators of NLRP3 inflammasome hyperactivation.

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Chronic ethanol exposure amplifies NLRP3 inflammasome-induced IL-1β secretion.

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NO and mitochondrial ROS mediate chronic ethanol-augmented IL-1β secretion.

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Alcohol dehydrogenase-generated metabolites cause NLRP3 inflammasome over-activation.

Quercetin Inhibits Inflammasome Activation by Interfering with ASC Oligomerization and Prevents Interleukin-1 Mediated Mouse Vasculitis

Interleukin-1β (IL-1β) is a highly inflammatory cytokine that significantly contributes to both acute and chronic inflammatory diseases. The secretion of IL-1β requires a unique protease, caspase-1, which is activated by various protein platforms called inflammasomes. Data suggests a key role for mitochondrial reactive oxygen species for inflammasome activation. Flavonoids constitute a group of naturally occurring polyphenolic molecules with many biological activities, including antioxidant effects. In this study, we investigated the effect of three flavonoids, quercetin (QUC), naringenin, and silymarim on inflammasome activation. We found that QUC inhibits IL-1β secretion by both the NLRP3 and AIM2 inflammasome in a dose dependent manner, but not the NLRC4 inflammasome. QUC inhibition of the inflammasome was still observed in Atg16l1 knockout macrophages, indicating that QUC’s effect was autophagy independent. Since QUC inhibited both NLRP3 and AIM2 inflammasomes but not NLRC4, we assessed ASC speck formation. QUC reduced ASC speck formation and ASC oligomerization compared with controls. Additionally, QUC inhibited IL-1β in Cryopyrin-Associated Periodic Syndromes (CAPS) macrophages, where NLRP3 inflammasome is constitutively activated. In conclusion, QUC inhibits both the NLRP3 and AIM2 inflammasome by preventing ASC oligomerization and may be a potential therapeutic candidate for Kawasaki disease vasculitis and other IL-1 mediated inflammatory diseases.