Oxidative products from alcohol metabolism differentially modulate pro-inflammatory cytokine expression in Kupffer cells and hepatocytes

Neurotensin modulation of lipopolysaccharide induced inflammation of gut-liver axis: Evaluation using neurotensin receptor agonist and antagonist

Lipopolysaccharide (LPS), a toxic component of the cell wall of Gram-negative bacteria, is a potent immune stressor. LPS-induced inflammation of the gut-liver axis is well demonstrated. Neurotensin (NTS), a tri-decapeptide present in the gastrointestinal tract, has anti-inflammatory, anti-oxidative, and growth-promoting properties. This study elucidated the efficacy of PD149163, the type I NTS receptor agonist (NTS₁) in the modulation of LPS-induced inflammation of the gut-liver axis of mice. Young-adult female mice (Age: 8 weeks; BW: 25 ± 2.5 g) were maintained in six groups (6/group); Group I as control and Group II, III & IV were exposed to LPS (1 mg/kg BW/Day; i.p.) for five days. LPS pre-exposed Group III and Group IV mice were treated with NTS₁ agonist PD149163 (100 μg/kg BW i.p.) and antagonist SR48692 (0.5 mg/kg BW i.p.) respectively for 28 days. Group V and Group VI mice were exposed to only PD149163 and only SR48692 respectively with the doses as mentioned above for 28 days. Group I and LPS-exposed Group II mice were also maintained four weeks without further treatment. Histopathology revealed LPS-induced inflammation of the gut and liver. Significant elevation of plasma TNF-α and IL-6 and serum ALT and AST reflected as biomarkers of inflammation. Oxidative stress on both organs was distinct from decreased glutathione reductase and increased lipid peroxidation. PD149163 but not SR48692 ameliorated LPS-induced inflammation in both gut and liver counteracting inflammatory responses and oxidative stress. The use of NTS agonists including PD149163 could be exploited for therapeutic intervention of inflammatory diseases including that of the gut-liver axis.

Cytokine Production in Whole Blood Cells Culture of Patients with Alcohol Dependence and Autologous Plasma Oxidative Stress Markers

We studied spontaneous production of a spectrum of proinflammatory cytokines by cultured whole blood cells from men with alcohol dependence at the stage of withdrawal syndrome and oxidative stress markers (carbonylated proteins and TBA-reactive substances) in the plasma of these blood samples. Enhanced production of cytokines by blood cells and increased concentrations of oxidative stress markers in the autologous plasma were revealed in comparison with the corresponding parameters in the control (blood from healthy men). Direct correlations were found between the levels of spontaneous cytokine production by blood cells from subjects with alcohol dependence and the concentration of oxidized proteins and lipids in autologous plasma.

Alcohol consumption and obesity: The hidden scare with COVID-19 severity

Obese individuals seem to be at the highest risk of contracting COVID-19 infection. Furthermore, severity of morbidity and mortality rates are higher in the developed world as compared to the developing world. One probable reason for this difference could be the difference in living conditions and exposure to other infections. Secondly, the difference in food especially, alcohol use may have deteriorating effects superimposed with obesity. Our hypothesis suggests that a combination of alcohol consumption and obesity causes low immunity and makes the individual prone to develop 'cytokine storm' and 'acute respiratory distress syndrome'; the hallmark of COVID-19 mortality and morbidity. Thus, we propose that reducing any one trigger can have a beneficial effect in combating the disease severity.

Redox Control of the Immune Response in the Hepatic Progenitor Cell Niche

The liver commonly self-regenerates by a proliferation of mature cell types. Nevertheless, in case of severe or protracted damage, the organ renewal is mediated by the hepatic progenitor cells (HPCs), adult progenitors capable of differentiating toward the biliary and the hepatocyte lineages. This regeneration process is determined by the formation of a stereotypical niche surrounding the emerging progenitors. The organization of the HPC niche microenvironment is crucial to drive biliary or hepatocyte regeneration. Furthermore, this is the site of a complex immunological activity mediated by several immune and non-immune cells. Indeed, several cytokines produced by monocytes, macrophages and T-lymphocytes may promote the activation of HPCs in the niche. On the other side, HPCs may produce pro-inflammatory cytokines induced by liver inflammation. The inflamed liver is characterized by high generation of reactive oxygen and nitrogen species, which in turn lead to the oxidation of macromolecules and the alteration of signaling pathways. Reactive species and redox signaling are involved in both the immunological and the adult stem cell regeneration processes. It is then conceivable that redox balance may finely regulate the immune response in the HPC niche, modulating the regeneration process and the immune activity of HPCs. In this perspective article, we summarize the current knowledge on the role of reactive species in the regulation of hepatic immunity, suggesting future research directions for the study of redox signaling on the immunomodulatory properties of HPCs.

Tumor Microenvironment Regulation by the Endoplasmic Reticulum Stress Transmission Mediator Golgi Protein 73 in Mice

The unfolded protein response (UPR) signal in tumor cells activates UPR signaling in neighboring macrophages, which leads to tumor-promoting inflammation by up-regulating UPR target genes and proinflammatory cytokines. However, the molecular basis of this endoplasmic reticulum (ER) stress transmission remains largely unclear. Here, we identified the secreted form of Golgi protein 73 (GP73), a Golgi-associated protein functional critical for hepatocellular carcinoma (HCC) growth and metastasis, is indispensable for ER stress transmission. Notably, ER stressors increased the cellular secretion of GP73. Through GRP78, the secreted GP73 stimulated ER stress activation in neighboring macrophages, which then released cytokines and chemokines involved in the tumor-associated macrophage (TAM) phenotype. Analysis of HCC patients revealed a positive correlation of GP73 with glucose-regulated protein 78 (GRP78) expression and TAM density. High GP73 and CD206 expression was associated with poor prognosis. Blockade of GP73 decreased the density of TAMs, inhibited tumor growth, and prolonged survival in two mouse HCC models. Conclusion: Our findings provide insight into the molecular mechanisms of extracellular GP73 in the amplification and transmission of ER stress signals.

Oxidative stress-induced IL-15 trans-presentation in keratinocytes contributes to CD8+ T cells activation via JAK-STAT pathway in vitiligo

Oxidative stress and effector memory CD8⁺ T cells have been greatly implicated in vitiligo pathogenesis. However, the crosstalk between these two crucial pathogenic factors has been merely investigated. IL-15 has been regarded as an important cytokine exerting its facilitative effect on memory CD8⁺ T cells function in various autoimmune diseases. In the present study, we initially discovered that the IL-15 expression was significantly increased in vitiligo epidermis and highly associated with epidermal H₂O₂ content. In addition, epidermal IL-15 expression was mainly derived from keratinocytes. Then, we showed that oxidative stress promoted IL-15 and IL-15Rα expression as well as IL-15 trans-presentation by activating NF-κB signaling in keratinocytes. What's more, the trans-presented IL-15, rather than the secreted one, was accounted for the potentiation of CD8⁺ T_EMs activation. We further investigated the mechanism underlying trans-presented IL-15 in potentiating CD8⁺ T_EMs activation and found that the blockage of IL-15-JAK-STAT signaling could be a potent therapeutic approach. Taken together, our results demonstrate that oxidative stress-induced IL-15 trans-presentation in keratinocytes contributes to the activation of CD8⁺ T_EMs, providing a novel mechanism by which oxidative stress initiates autoimmunity in vitiligo.

Influence of Alcohol Consumption on Body Mass Gain and Liver Antioxidant Defense in Adolescent Growing Male Rats

The World Health Organization (WHO) reported that alcohol consumption is a serious problem in adolescents. The aim of the study was to assess the influence of the time of exposure of various alcoholic beverages on body mass as well as on select parameters of liver antioxidant defense in adolescent Wistar rats. Thirty-day-old animals were divided into 12 groups (six animals in each): control and groups receiving various beverages containing 10% of alcohol (ethanol, red wine, beer), observed for two, four, and six weeks. The body weight gain and energy supply were analyzed for body mass assessment. The catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase, transferase (GST), reductase activities, total antioxidant status, and glutathione level (GSH) were analyzed, for a liver antioxidant defense assessment. Group receiving red wine was characterized by the highest alcohol intake, lowest dietary intake, and highest total energy supply (p < 0.05). However, this did not influence body weight gain (p > 0.05). Reduced diet intake in groups receiving alcohol was counterbalanced by its energy value. Therefore, the energy supply was not lower than for the control (p > 0.05). Alcohol consumption and the experiment duration influenced CAT, SOD, and GST activities and GSH level. Alcohol consumption may influence hepatic antioxidant defense in adolescent male rats, but without influence on body weight gain.

Mangiferin improves hepatic damage-associated molecular patterns, lipid metabolic disorder and mitochondrial dysfunction in alcohol hepatitis rats

This study was conducted to investigate the beneficial effects and possible mechanism of action of mangiferin (MF) in alcohol hepatitis (AH) rats. Building on our previous study, the damage-associated molecular patterns (DAMPs), lipid metabolic disorder and mitochondrial dysfunction were investigated. MF effectively regulated the abnormal liver function, the levels of alcohol, FFAs and metal elements in serum. More importantly, MF improved the expression levels of mRNA and protein of PPAR-γ, OPA-1, Cav-1, EB1, NF-κB p65, NLRP3, Cas-1 and IL-1β, and decreased the positive protein expression rates of HSP90, HMGB1, SYK, CCL20, C-CAS-3, C-PARP and STARD1. Additionally, MF decreased the levels of fumarate, cAMP, xanthurenic acid and d-glucurone-6,3-lactone, and increased the levels of hippuric acid and phenylacetylglycine, and then adjusted the changes of phenylalanine metabolism, TCA cycle and ascorbate and aldarate metabolic pathways. The above results suggested that MF can effectively prevent AH by modulating specific AH-associated genes, potential biomarkers and metabolic pathways in AH rats, etc.

Inhibition of Hepatotoxicity by a LXR Inverse Agonist in a Model of Alcoholic Liver Disease

Alcohol abuse is a major cause of liver disease and mortality worldwide and is a significant public health issue. Patients with alcoholic liver disease (ALD) have severe hepatic lipid accumulation, inflammation, and fibrosis. Therapies for ALD are very limited and even abstinence from alcohol consumption does not necessarily protect patients from progression of the disease. We sought to evaluate the efficacy of a liver X receptor (LXR) inverse agonist, SR9238, in an animal model of ALD. SR9238 suppresses hepatic lipogenesis, a pathological hallmark of ALD, and we hypothesized that targeting suppression of hepatic metabolic pathways that are activated in ALD may be an effective treatment for the disease. A chronic ethanol diet with or without a final ethanol binge treatment was used to induce ALD in mice. Mice were administered the liver specific LXR inverse agonist SR9238 for 4 weeks after the mice had been maintained on the ethanol diet for 14 days. Mice developed all the hallmarks of advanced ALD demonstrating significant pathophysiology and hepatotoxicity. SR9238 significantly attenuated liver injury and hepatic steatosis and fibrosis was nearly eliminated in SR9238 treated mice. SR9238 treatment reversed the damage associated with chronic ethanol use returning the liver to near normal morphology. These results indicate that inhibiting LXR activity using the inverse agonist has a hepatoprotective effect in rodent models of ALD; thus, this pharmacological approach may be efficacious for treatment of ALD in humans.

Mitochondria-targeted ubiquinone (MitoQ) enhances acetaldehyde clearance by reversing alcohol-induced posttranslational modification of aldehyde dehydrogenase 2: A molecular mechanism of protection against alcoholic liver disease

Alcohol metabolism in the liver generates highly toxic acetaldehyde. Breakdown of acetaldehyde by aldehyde dehydrogenase 2 (ALDH2) in the mitochondria consumes NAD⁺ and generates reactive oxygen/nitrogen species, which represents a fundamental mechanism in the pathogenesis of alcoholic liver disease (ALD). A mitochondria-targeted lipophilic ubiquinone (MitoQ) has been shown to confer greater protection against oxidative damage in the mitochondria compared to untargeted antioxidants. The present study aimed to investigate if MitoQ could preserve mitochondrial ALDH2 activity and speed up acetaldehyde clearance, thereby protects against ALD. Male C57BL/6 J mice were exposed to alcohol for 8 weeks with MitoQ supplementation (5 mg/kg/d) for the last 4 weeks. MitoQ ameliorated alcohol-induced oxidative/nitrosative stress and glutathione deficiency. It also reversed alcohol-reduced hepatic ALDH activity and accelerated acetaldehyde clearance through modulating ALDH2 cysteine S-nitrosylation, tyrosine nitration and 4-hydroxynonenol adducts formation. MitoQ ameliorated nitric oxide (NO) donor-mediated ADLH2 S-nitrosylation and nitration in Hepa-1c1c7 cells under glutathion depletion condition. In addition, alcohol-increased circulating acetaldehyde levels were accompanied by reduced intestinal ALDH activity and impaired intestinal barrier. In accordance, MitoQ reversed alcohol-increased plasma endotoxin levels and hepatic toll-like receptor 4 (TLR4)-NF-κB signaling along with subsequent inhibition of inflammatory cell infiltration. MitoQ also reversed alcohol-induced hepatic lipid accumulation through enhancing fatty acid β-oxidation. Alcohol-induced ER stress and apoptotic cell death signaling were reversed by MitoQ. This study demonstrated that speeding up acetaldehyde clearance by preserving ALDH2 activity critically mediates the beneficial effect of MitoQ on alcohol-induced pathogenesis at the gut-liver axis.

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PTMs of ALDH2 participated in the pathogenesis of alcoholic liver disease.

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MitoQ treatment accelerated acetaldehyde detoxification.

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MitoQ ameliorated acetaldehyde-related tight junction disruption.

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MitoQ reversed TLR4-mediated inflammatory response in alcoholic liver disease.

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MitoQ counteracts alcohol-induced ER stress and cell apoptosis.

Antioxidants and HNE in redox homeostasis

Under physiological conditions, cells are in a stable state known as redox homeostasis, which is maintained by the balance between continuous ROS/RNS generation and several mechanisms involved in antioxidant activity. ROS overproduction results in alterations in the redox homeostasis that promote oxidative damage to major components of the cell, including the biomembrane phospholipids. Lipid peroxidation subsequently generates a diverse set of products, including α,β-unsaturated aldehydes. Of these products, 4-hydroxy-2-nonenal (HNE) is the most studied aldehyde on the basis of its involvement in cellular physiology and pathology. This review summarizes the current knowledge in the field of HNE generation, metabolism, and detoxification, as well as its interactions with various cellular macromolecules (protein, phospholipid, and nucleic acid). The formation of HNE-protein adducts enables HNE to participate in multi-step regulation of cellular metabolic pathways that include signaling and transcription of antioxidant enzymes, pro-inflammatory factors, and anti-apoptotic proteins. The most widely described roles for HNE in the signaling pathways are associated with its activation of kinases, as well as transcription factors that are responsible for redox homeostasis (Ref-1, Nrf2, p53, NFκB, and Hsf1). Depending on its level, HNE exerts harmful or protective effects associated with the induction of antioxidant defense mechanisms. These effects make HNE a key player in maintaining redox homeostasis, as well as producing imbalances in this system that participate in aging and the development of pathological conditions.

In Utero Alcohol Exposure and the Alteration of Histone Marks in the Developing Fetus: An Epigenetic Phenomenon of Maternal Drinking

Ethanol is well known for its teratogenic effects during fetal development. Maternal alcohol consumption allows the developing fetus to experience the detrimental effects of alcohol exposure. Alcohol-mediated teratogenic effects can vary based on the dosage and the length of exposure. The specific mechanism of action behind this teratogenic effect is still unknown. Previous reports demonstrated that alcohol participates in epigenetic alterations, especially histone modifications during fetal development. Additional research is necessary to understand the correlation between major epigenetic events and alcohol-mediated teratogenesis such as that observed in fetal alcohol spectrum disorder (FASD). Here, we attempted to collect all the available information concerning alcohol-mediated histone modifications during gestational fetal development. We hope that this review will aid researchers to further examine the issues associated with ethanol exposure.

Insights into the Role and Interdependence of Oxidative Stress and Inflammation in Liver Diseases

The crucial roles of oxidative stress and inflammation in the development of hepatic diseases have been unraveled and emphasized for decades. From steatosis to fibrosis, cirrhosis and liver cancer, hepatic oxidative stress, and inflammation are sustained and participated in this pathological progressive process. Notably, increasing evidences showed that oxidative stress and inflammation are tightly related, which are regarded as essential partners that present simultaneously and interact with each other in various pathological conditions, creating a vicious cycle to aggravate the hepatic diseases. Clarifying the interaction of oxidative stress and inflammation is of great importance to provide new directions and targets for developing therapeutic intervention. Herein, this review is concerned with the regulation and interdependence of oxidative stress and inflammation in a variety of liver diseases. In addition to classical mediators and signaling, particular emphasis is placed upon immune suppression, a potential linkage of oxidative stress and inflammation, to provide new inspiration for the treatment of liver diseases. Furthermore, since antioxidation and anti-inflammation have been extensively attempted as the strategies for treatment of liver diseases, the application of herbal medicines and their derived compounds that protect liver from injury via regulating oxidative stress and inflammation collectively were reviewed and discussed.