Ethanol metabolism, oxidative stress, and endoplasmic reticulum stress responses in the lungs of hepatic alcohol dehydrogenase deficient deer mice after chronic ethanol feeding

Alcohol and its metabolites dysregulate cellular bioenergetics and induce oxidative and endoplasmic reticulum stress in primary human bronchial epithelial cells

BACKGROUND

Chronic alcohol consumption/misuse is a significant risk factor for pneumonia and lung infection leading to the development of chronic pulmonary disorders such as chronic obstructive pulmonary disease (COPD) and lung fibrosis. In this study, we sought to delineate the mechanism of alcohol-associated lung disease. We did so by measuring in vitro mitochondrial, endoplasmic reticulum (ER) oxidative stress in human bronchial epithelial cells (hBECs) treated with ethanol and its oxidative (acetaldehyde) and nonoxidative (fatty acid ethyl esters or FAEEs) metabolites.

METHODS

Primary hBECs from a normal subject were treated with relevant concentrations of ethanol and its metabolites and incubated at 37°C for 24 h. Viability and cytotoxicity were determined using cell viability and lactate dehydrogenase (LDH) assay kits, respectively. Oxidized glutathione (GSSG) and reduced glutathione (GSH) were measured by colorimetric reaction, and 4-hydroxynenonal (4HNE) by immunohistochemistry. Endoplasmic reticulum stress and dysregulated cellular bioenergetics were determined by western blot analysis. Mitochondrial stress and real-time ATP production rates were determined using a Seahorse Extracellular Flux analyzer. Amelioration of ethanol-induced oxidative/ER stress and mitochondrial energetics was determined using an AMPKα agonist.

RESULTS

Human bronchial epithelial cells treated with ethanol, acetaldehyde, and FAEEs showed a concentration-dependent increase in the secretion of LDH, oxidative/ER stress, deactivation of AMPKα phosphorylation and mitochondrial stress (decreased spare respiratory capacity) with concomitant decreases in mitochondrial and glycolytic ATP production rates. FAEEs caused greater cytotoxicity, ER stress, and dysregulated cellular bioenergetics than those ethanol and its oxidative metabolite. AMPKα agonist-pretreated cells significantly ameliorated ethanol-induced oxidative/ER stress, deactivation of AMPKα, and dysregulated cellular bioenergetics.

CONCLUSIONS

Findings of this study suggest that ethanol and its metabolites contribute to cytotoxicity, oxidative/ER stress, and dysregulation of cellular bioenergetics in hBECs. The attenuation of ethanol-induced ER/oxidative stress and mitochondrial respiration by an AMPKα agonist may reflect a potential for it to be developed as a therapeutic agent for chronic alcohol-associated lung disease.

Red raspberry supplementation mitigates alcohol-induced liver injury associated with gut microbiota alteration and intestinal barrier dysfunction in mice

Alcoholic liver disease (ALD) is still a global health concern. Long-term alcohol intake alters the gut microbiota diversity and metabolic activity, and causes intestinal barrier dysfunction, leading to the development of ALD. This research explored the protective effects and underlying mechanisms of red raspberry (RR) on alcohol-related disorders in mice. Male C57BL/6J mice were fed a standard diet or a standard diet supplemented with 2%, 4%, and 8% weight/weight RR. Meanwhile, mice were administered 35% (v/v) ethanol (EtOH, 10 mL per kg body weight) intragastrically once daily for six weeks, except the control group mice. The results showed that RR supplementation decreased liver injury markers (alanine and aspartate transaminases) in the serum, reduced triglyceride level in the liver and downregulated hepatic cytochrome P450 2E1 mRNA expression in mice administered EtOH. In addition, EtOH-mediated oxidative stress in the liver was attenuated by RR supplementation through decreased hepatic malondialdehyde content and increased antioxidant (glutathione, glutathione peroxidase, and catalase) levels and activities in mice exposed to EtOH. Moreover, RR supplementation reversed EtOH-induced alteration in the cecal microbial composition at the phylum, order, genus, and species levels and improved the intestinal barrier function associated with the inhibition of the NF-κB/MLCK pathway, which was accompanied by upregulation of tight junctions (zonula occludens 1, occludin, claudin-1, and claudin-4) and E-cadherin mRNA and protein expressions. Accordingly, RR supplementation resulted in a decreased level of endotoxins in the serum and attenuation of the inflammatory response in the liver, illustrated by a significant decrease in tumor necrosis factor-alpha, interleukin (IL)-1β, and IL-6 levels. Overall, RR supplementation alleviated the adverse effects of chronic alcohol intake in C57BL/6J mice and could be a potential supplement for improving ALD.

Chronic and Binge Alcohol Ingestion Increases Truncated Oxidized Phosphatidylcholines in Mice Lungs Due to Increased Oxidative Stress

Heavy alcohol drinking has negative health effects in multiple organs. It predisposes lungs to inflammatory conditions associated with acute lung injury and increased incidence of pneumonia and sepsis, which may lead to death due to acute respiratory distress syndrome in some individuals with alcohol use disorder (AUD). In general, rodent models of alcohol exposure either do not recapitulate multiple organ injuries as seen in humans or require longer duration to establish tissue injury and inflammation. The recently introduced NIAAA model of alcohol-induced liver injury, characterized by a marked increase in steatosis and liver damage with 10 days of a liquid diet containing 5% ethanol followed by a single ethanol binge (5 g/kg). Therefore, we employed this model to explore the status of surfactant phospholipids, oxidative stress, tissue injury markers and inflammatory cytokines in lungs. In lungs of C57BL/6J mice, the alcohol feeding significantly increased levels of the surfactant phospholipid dipalmitoyl phosphatidylcholine (DPPC) as well as the truncated oxidized phosphatidylcholines palmitoyl oxovaleryl phosphatidyl-choline (POVPC), palmitoyl glutaryl phosphatidyl-choline (PGPC), palmitoyl oxo-nonanoyl phosphatidyl-choline (ALDO-PC), and palmitoyl azelaoyl phosphatidyl-choline (PAzePC) at 9 h post-binge. Additionally, gene expression of the enzymes catalyzing lipid oxidation, such as arachidonate 15-lipoxygenase (Alox15), prostaglandin synthase 2 (Ptgs2), Cytochrome P450 2E1 (Cyp2E1) and NADPH oxidase 1 (Nox1) were significantly increased. Furthermore, ethanol increased levels of the inflammatory cytokine Interleukin-17 in bronchoalveolar lavage fluid. In conclusion, the NIAAA alcohol feeding model might be suitable to study alcohol-induced lung injury and inflammation.

Alcohol dehydrogenase expression patterns in normal prostate, benign prostatic hyperplasia, and prostatic adenocarcinoma in African American and Caucasian men

BACKGROUND

In situ metabolism of ethanol by alcohol dehydrogenases (ADHs) contributes to oxidative damage of cells and DNA and has been linked to carcinogenesis in numerous epithelial tissues. The goal of this study was to determine expression patterns of ADH1 and ADH7 isozymes in normal, hyperplastic (benign prostatic hyperplasia [BPH]) and neoplastic (prostate cancer [PCa]) prostate. Furthermore, racial differences in ADH expression between African Americans and Caucasians were investigated.

METHODS

ADH expression patterns were characterized by density analysis of ADH immunohistochemistry (n = 21) and real-time RT-PCR of total RNAs by laser-capture microdissection (n = 10) and whole tissue formalin-fixed paraffin embedded prostate biopsies (n = 63).

RESULTS

ADH protein is found in normal prostate and is primarily associated with glandular epithelium. Transcripts of ADH1B are suppressed in PCa compared to BPH (p = 0.0095). Racial differences in ADH7 transcripts exist between African American and Caucasian men. A total of 57.6% of biopsies from African American prostates have detectable ADH7 messenger RNA (mRNA) transcripts compared to the 13.3% of Caucasian prostate biopsies with detectable transcripts (p = 0.0005). This increased frequency of detection contributes to higher mean ADH7 mRNA transcript levels in African Americans (p = 0.001).

CONCLUSIONS

To our knowledge this study is the first to report downregulation of ADH1B in neoplastic prostate at the transcriptional level, suggesting protective regulatory functions. ADH7 transcripts were not detectable in all samples and was found in higher frequency and amount in our African American samples. Racial differences in ADH7 within the prostate is a novel finding and should be investigated further.

Alcohol-Associated Tissue Injury: Current Views on Pathophysiological Mechanisms

At-risk alcohol use is a major contributor to the global health care burden and leads to preventable deaths and diseases including alcohol addiction, alcoholic liver disease, cardiovascular disease, diabetes, traumatic injuries, gastrointestinal diseases, cancers, and fetal alcohol syndrome. Excessive and frequent alcohol consumption has increasingly been linked to alcohol-associated tissue injury and pathophysiology, which have significant adverse effects on multiple organ systems. Extensive research in animal and in vitro models has elucidated the salient mechanisms involved in alcohol-induced tissue and organ injury. In some cases, these pathophysiological mechanisms are shared across organ systems. The major alcohol- and alcohol metabolite-mediated mechanisms include oxidative stress, inflammation and immunometabolic dysregulation, gut leak and dysbiosis, cell death, extracellular matrix remodeling, endoplasmic reticulum stress, mitochondrial dysfunction, and epigenomic modifications. These mechanisms are complex and interrelated, and determining the interplay among them will make it possible to identify how they synergistically or additively interact to cause alcohol-mediated multiorgan injury. In this article, we review the current understanding of pathophysiological mechanisms involved in alcohol-induced tissue injury.

Astaxanthin attenuates alcoholic cardiomyopathy via inhibition of endoplasmic reticulum stress-mediated cardiac apoptosis

Chronic excessive ethanol consumption is associated with a high incidence of mortality due to ethanol-induced dilated cardiomyopathy, known as alcoholic cardiomyopathy (ACM). Mechanistic studies have demonstrated that apoptosis is key to the pathogenesis of ACM, and endoplasmic reticulum (ER) stress-associated apoptosis contributes to various ethanol-related diseases. Astaxanthin (AST) is a natural carotenoid that exerts an anti-ER stress effect. Importantly, strong evidence has shown that AST induces beneficial effects in various cardiovascular diseases. The present study aimed to investigate whether AST induces beneficial effects on ACM by suppressing cardiac apoptosis mediated by ER stress. We showed that after 2 months of chronic excessive ethanol consumption, mice displayed obvious cardiac dysfunction and morphological changes associated with increased fibrosis, oxidative stress, ER stress and apoptosis. However, cardiac damage above was attenuated in response to AST treatment. The cardioprotective effect of AST against ethanol toxicity was also confirmed in both H9c2 cells and primary cardiomyocytes, indicating that AST-induced protection directly targets cardiomyocytes. Both in vivo and in vitro studies showed that AST inhibited all three ER stress signaling pathways activated by ethanol. Furthermore, administration of the ER stress inhibitor sodium 4-phenylbutyrate (4-PBA) strongly suppressed ethanol-induced cardiomyocyte damage. Interestingly, AST induced further anti-apoptotic effects once co-treated with 4-PBA, indicating that AST protects the heart from ACM partially by attenuating ER stress, but other mechanisms still exist. This study highlights that administration of AST ablated chronic excessive ethanol consumption-induced cardiomyopathy by suppressing cardiac ER stress and subsequent apoptosis.

Protective effects of curcumin against chronic alcohol-induced liver injury in mice through modulating mitochondrial dysfunction and inhibiting endoplasmic reticulum stress

Background

Curcumin is a major active ingredient extracted from powdered dry rhizome of Curcuma longa. In Ayurveda and traditional Chinese medicine, it has been used as a hepatoprotective agent for centuries. However, the underlying mechanisms are not clear.

Objective

The present study is to investigate the hepatoprotective effects of curcumin in chronic alcohol-induced liver injury and explore its mechanism.

Design

Alcohol-exposed Balb/c mice were treated with curcumin (75 and 150 mg/kg) once per day for 8 weeks. Tissue from individual was fixed with formaldehyde for pathological examination. The activities of mitochondrial antioxidant enzymes, Na⁺/k⁺-ATPase, Ca²⁺-ATPase, and Ca²⁺Mg²⁺-ATPase, were determined. The level of mitochondrial membrane potential (MMP) and mitochondrial permeability transition pore (MPTP) opening was also determined. The expression of PGC-1α, NRF1, Mn-SOD, GRP78, PERK, IRE1α, nuclear NF-κB, and phosphorylated IκBα was quantified by western blot. The contents of TNF-α, IL-1β, and IL-6 in the liver were measured using the ELISA method.

Results

Curcumin significantly promoted hepatic mitochondrial function by reducing the opening of MPTP, thus increasing the MMP, promoting the activity of Na⁺/k⁺-ATPase, Ca²⁺-ATPase, and Ca²⁺/Mg²⁺-ATPase, and attenuating oxidative stress. Curcumin upregulated the expression of PGC-1α, NRF1, and Mn-SOD, and downregulated the expression of GRP78, PERK, and IRE1α in hepatic tissue. Curcumin also attenuated inflammation by inhibiting the IκBα–NF-κB pathway, which reduced the production of TNF, IL-1β, and IL-6.

Conclusion

Curcumin attenuates alcohol-induced liver injury via improving mitochondrial function and attenuating endoplasmic reticulum stress and inflammation. This study provides strong evidence for the beneficial effects of curcumin in the treatment of chronic alcohol-induced liver injury.

Ethanol Exposure Impairs AMPK Signaling and Phagocytosis in Human Alveolar Macrophages: Role of Ethanol Metabolism

BACKGROUND

Chronic alcohol consumption impairs alveolar macrophage's (AM) function and increases risk for developing lung infection and pneumonia. However, the mechanism and metabolic basis of alcohol-induced AM dysfunction leading to lung infection are not well defined, but may include altered ethanol (EtOH) and reactive oxygen species metabolism and cellular energetics. Therefore, oxidative stress, endoplasmic reticulum (ER) stress, the formation of fatty acid ethyl esters [FAEEs, nonoxidative metabolites of EtOH], AMP-activated protein kinase (AMPK) signaling, and phagocytic function were examined in freshly isolated AM incubated with EtOH.

METHODS

AMs separated from bronchoalveolar lavage fluid samples obtained from normal volunteers were incubated with EtOH for 24 hours. AMPK signaling and ER stress were assessed using Western blotting, FAEEs by GC-MS, oxidative stress by immunofluorescence using antibodies to 4-hydroxynonenal, and phagocytosis by latex beads. Oxidative stress was also measured in EtOH-treated AMs with/without AMPK activator [5-aminoimidazole-4-carboxamide ribonucleotide (AICAR)] or inhibitor (Compound C), and in AMs incubated with FAEEs. mRNA expression for interleukins (IL-6 and IL-8), monocyte chemoattractant protein (MCP)-1, and transforming growth factor (TGF)-β was measured in AM treated with EtOH or FAEEs using RT-PCR.

RESULTS

EtOH exposure to AM increased oxidative stress, ER stress, and synthesis of FAEEs, decreased phosphorylated AMPK, and impaired phagocytosis. Attenuation or exacerbation of EtOH-induced oxidative stress by AICAR or Compound C, respectively, suggests a link between AMPK signaling, EtOH metabolism, and related oxidative stress. The formation of FAEEs may contribute to EtOH-induced oxidative stress as FAEEs also produced concentration-dependent oxidative stress. An increased mRNA expression of IL-6, IL-8, and MCP-1 by FAEEs is key finding to suggest a metabolic basis of EtOH-induced inflammatory response.

CONCLUSIONS

EtOH-induced impaired phagocytosis, oxidative stress, ER stress, and dysregulated AMPK signaling are plausibly associated with the formation of FAEEs and may participate in the pathogenesis of nonspecific pulmonary inflammation.

Oxidative stress and DNA damage in a long-term hexavalent chromium-exposed population in North China: a cross-sectional study

OBJECTIVE

The International Agency for Research on Cancer classifies hexavalent chromium (Cr(VI)) as a human carcinogen. As reported, cancer mortality was higher in Cr(VI)-contaminated areas. Scientists have recommended studying its health impact on people living in contaminated areas. This study aims to evaluate the health risk for people living in Cr(VI)-contaminated areas.

DESIGN

We conducted a cross-sectional study in rural areas of north-eastern China. Malondialdehyde (MDA), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT) were used as oxidative stress parameters, and 8-hydroxy-2 deoxyguanosine (8-OHdG) as a DNA damage biomarker. We collected information on demographics, lifestyles and length of residence from all participants using a questionnaire. Biological specimens and environmental media samples were collected on the same day as the survey was done. We used t-test, χ² test, Wilcoxon rank-sum test and multivariate linear regression analysis.

PARTICIPANTS

The study included 319 participants exposed to Cr(VI) and 307 unexposed participants, with 447 women and 179 men. These participants met the following criteria: (1) living in the areas for more than 10 years; (2) age older than 18 years; and (3) without occupational chromium exposure.

RESULTS

Our study revealed that serum concentration of MDA (p<0.001), serum activities of CAT (p<0.001) and GSH-Px (p<0.001), as well as urine concentration of 8-OHdG (p=0.008) in the exposed group were significantly higher than those in the unexposed group. However, serum SOD activity was significantly lower in the exposed group, compared with that in the unexposed group (p<0.001). Cr(VI) exposure and smoking have an interaction effect on GSH-Px activity (p<0.05). Cr(VI) exposure and alcohol drinking also have an interaction effect on GSH-Px activity (p<0.05). Longer residence in the exposed areas increased the oxidative levels (p<0.05).

CONCLUSIONS

The findings of this study showed elevated oxidative stress and DNA damage in people exposed to Cr(VI).

Salvianolic acid A alleviates chronic ethanol-induced liver injury via promotion of β-catenin nuclear accumulation by restoring SIRT1 in rats

In recent years, alcoholic liver disease (ALD) has emerged as a growing public health problem worldwide. β-catenin plays an important role in the growth, development, regeneration and metabolic activity of the liver. Salvianolic acid A (SalA) is a water-soluble component from the root extract of Salvia miltiorrhiza Bunge, and its effect on ALD has not yet been investigated. This study aimed to investigate the effect of SalA on chronic alcohol-induced liver injury and to explore the role of SIRT1-mediated β-catenin deacetylation in such an effect. In this study, SalA treatment significantly alleviated the accumulation of lipid droplets and reduced the plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), total cholesterol (TC), triglyceride (TG), alcohol and ammonia levels in rats. SalA enhanced ethanol and ammonia metabolism and maintained mitochondrial homeostasis. Moreover, SalA restored the activity of the major ethanol-metabolizing enzymes and oxidative stress functions in the liver. Importantly, we found that SalA treatment effectively inhibited the ethanol-mediated decrease in nuclear β-catenin by upregulating SIRT1 in the liver. SIRT1 then deacetylated β-catenin to promote its accumulation in the nucleus, thereby preventing alcohol-induced liver injury. The results demonstrate that the SIRT1/β-catenin pathway is a key therapeutic target in liver injury caused by chronic alcohol exposure and that SalA protects against alcohol-induced liver injury via the SIRT1-mediated deacetylation of β-catenin.

Effects of Tobacco Nicotine-Derived Nitrosamine Ketone (NNK) Exposures on Brain Alcohol Metabolizing Enzyme Activities

BACKGROUND

The high levels of blood alcohol achieved with chronic plus binge alcohol exposures are somewhat reduced by co-administration of tobacco-specific Nicotine-Derived Nitrosamine Ketone (NNK) suggesting that NNK may alter alcohol metabolism.

OBJECTIVE

We examined ethanol and acetaldehyde-metabolizing enzyme activities and malondialdehyde adduct formation in rats exposed to ethanol (chronic + binge), NNK, or both.

METHODS

4-week old Long Evans rats were fed liquid diets containing 0% or 26% caloric ethanol for 8 weeks. Ethanol-fed rats were binge-administered ethanol (2 g/kg; on Mondays, Wednesdays, and Fridays) by intraperitoneal (i.p.) injection, while control group administered saline in weeks 7 and 8 (n=12/group). Six rats from each group were administered i.p. injections of NNK (2 mg/kg) or saline on Tuesdays, Thursdays, and Saturdays of weeks 3 through 8. Alcohol dehydrogenase, catalase, and aldehyde dehydrogenase activities were measured using commercial assays. Cytochrome P450 mRNA levels (17 isoforms) were measured by quantitative reverse transcription-polymerase chain reaction. Malondialdehyde immunoreactivity was measured by enzyme-linked immunosorbent assay.

RESULTS

Dual exposures to ethanol and NNK significantly increased frontal lobe ADH activity relative to control (P=0.01) and ethanol only (P=0.04) treatments, and ALDH relative to control (P=0.02). In contrast, malondialdehyde-protein expression was not significantly altered by ethanol+NNK. Ethanol decreased CYP1A1 mRNA expression relative to control (P=0.02), and combined ethanol+NNK exposures decreased the expression of CYP1A1 (P=0.01) and CYP2C6 (P=0.03).

CONCLUSION

Dual exposures to ethanol and NNK increase brain ethanol metabolism and inhibit the expression of CYP450s that regulate xenobiotic metabolism.

Proteomic Profiling of Liver and Plasma in Chronic Ethanol Feeding Model of Hepatic Alcohol Dehydrogenase-Deficient Deer Mice

BACKGROUND

Chronic alcohol abuse, a major risk factor for such diseases as hepatitis and cirrhosis, impairs hepatic alcohol dehydrogenase (ADH; key ethanol [EtOH]-metabolizing enzyme). Therefore, differentially altered hepatic and plasma proteomes were identified in chronic EtOH feeding model of hepatic ADH-deficient (ADH^- ) deer mice to understand the metabolic basis of alcoholic liver disease (ALD).

METHODS

ADH^- deer mice were fed 3.5 g% EtOH via Lieber-DeCarli liquid diet daily for 3 months and histology of the liver assessed. Liver and plasma proteins were separated by 2-dimensional gel electrophoresis. The proteins differentially expressed were identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry.

RESULTS

Histology of the liver showed panlobular steatosis and infiltration of T lymphocytes. Using the criteria of ≥1.5 for fold change (p-value ≤0.05) with expectation value (E ≤10^-3 ) and protein score (≥64), 18 proteins in the livers and 5 in the plasma of EtOH-fed mice were differentially expressed and identified. Prolyl 4-hydroxylase, cytochrome b-5, endo A cytokeratin, ATP synthase, heat-shock 70 kD proteins, enoyl CoA hydratase, stress-70 protein, peroxiredoxin 1, and ornithine carbamoyl transferase were up-regulated in the livers. However, carbonic anhydrase 3, mitochondrial ATP synthase, aldolase 2, actin γ, laminin receptor, and carbamoyl phosphate synthase were down-regulated. Contrary to the increased expression of creatine kinase M-type, a decreased expression of serine protease inhibitor A3A precursor, sulfated glycoprotein-2 (clusterin), and apolipoprotein E isoforms were found in the plasma of EtOH group.

CONCLUSIONS

Chronic EtOH feeding in ADH^- deer mice causes steatosis and infiltration of T lymphocytes in the livers along with increased expression of proteins involved in endoplasmic reticulum (ER) stress, fibrosis, fatty acid β oxidation and biogenesis, and decreased expression of proteins involved in ATP synthesis, carbohydrate metabolism, in cell regulation and architecture. Reduced expression of various carrier proteins as found in the plasma of EtOH group has a biomarker potential.

Proteins Differentially Expressed in the Pancreas of Hepatic Alcohol Dehydrogenase-Deficient Deer Mice Fed Ethanol For 3 Months

OBJECTIVES

The aim of this study was to identify differentially expressed proteins in the pancreatic tissue of hepatic alcohol dehydrogenase-deficient deer mice fed ethanol to understand metabolic basis and mechanism of alcoholic chronic pancreatitis.

METHODS

Mice were fed liquid diet containing 3.5 g% ethanol daily for 3 months, and differentially expressed pancreatic proteins were identified by protein separation using 2-dimensional gel electrophoresis and identification by mass spectrometry.

RESULTS

Nineteen differentially expressed proteins were identified by applying criteria established for protein identification in proteomics. An increased abundance was found for ribosome-binding protein 1, 60S ribosomal protein L31-like isoform 1, histone 4, calcium, and adenosine triphosphate (ATP) binding proteins and the proteins involved in antiapoptotic processes and endoplasmic reticulum function, stress, and/or homeostasis. Low abundance was found for endoA cytokeratin, 40S ribosomal protein SA, amylase 2b isoform precursor, serum albumin, and ATP synthase subunit β and the proteins involved in cell motility, structure, and conformation.

CONCLUSIONS

Chronic ethanol feeding in alcohol dehydrogenase-deficient deer mice differentially expresses pancreatic functional and structural proteins, which can be used to develop biomarker(s) of alcoholic chronic pancreatitis, particularly amylase 2b precursor, and 60 kDa heat shock protein and those involved in ATP synthesis and blood osmotic pressure.

Calcium Channels and Oxidative Stress Mediate a Synergistic Disruption of Tight Junctions by Ethanol and Acetaldehyde in Caco-2 Cell Monolayers

Ethanol is metabolized into acetaldehyde in most tissues. In this study, we investigated the synergistic effect of ethanol and acetaldehyde on the tight junction integrity in Caco-2 cell monolayers. Expression of alcohol dehydrogenase sensitized Caco-2 cells to ethanol-induced tight junction disruption and barrier dysfunction, whereas aldehyde dehydrogenase attenuated acetaldehyde-induced tight junction disruption. Ethanol up to 150 mM did not affect tight junction integrity or barrier function, but it dose-dependently increased acetaldehyde-mediated tight junction disruption and barrier dysfunction. Src kinase and MLCK inhibitors blocked this synergistic effect of ethanol and acetaldehyde on tight junction. Ethanol and acetaldehyde caused a rapid and synergistic elevation of intracellular calcium. Calcium depletion by BAPTA or Ca²⁺-free medium blocked ethanol and acetaldehyde-induced barrier dysfunction and tight junction disruption. Diltiazem and selective knockdown of TRPV6 or Ca_V1.3 channels, by shRNA blocked ethanol and acetaldehyde-induced tight junction disruption and barrier dysfunction. Ethanol and acetaldehyde induced a rapid and synergistic increase in reactive oxygen species by a calcium-dependent mechanism. N-acetyl-L-cysteine and cyclosporine A, blocked ethanol and acetaldehyde-induced barrier dysfunction and tight junction disruption. These results demonstrate that ethanol and acetaldehyde synergistically disrupt tight junctions by a mechanism involving calcium, oxidative stress, Src kinase and MLCK.

Interactions between ethanol and cigarette smoke in a mouse lung carcinogenesis model

Both ethanol and cigarette smoke are classified as human carcinogens. They can synergize, especially in tissues of the upper aerodigestive tract that are targeted by both agents. The main objective of the present study was to evaluate the individual and combined effects of ethanol and smoke in the respiratory tract, either following transplacental exposure and/or postnatal exposure. We designed two consecutive studies in mouse models by exposing Swiss H mice to oral ethanol and/or inhaled mainstream cigarette smoke for up to 4 months, at various prenatal and postnatal life stages. Clastogenic effects and histopathological alterations were evaluated after 4 and 8 months, respectively. Ethanol was per se devoid of clastogenic effects in mouse peripheral blood erythrocytes. However, especially in mice exposed both transplacentally throughout pregnancy and in the postnatal life, ethanol administration was associated not only with liver damage but also with pro-angiogenetic effects in the lung by stimulating the proliferation of blood vessels. In addition, these mice developed pulmonary emphysema, alveolar epithelial hyperplasias, microadenomas, and benign tumors. On the other hand, ethanol interfered in the lung carcinogenesis process resulting from the concomitant exposure of mice to smoke. In fact, ethanol significantly attenuated some smoke-related preneoplastic and neoplastic lesions in the respiratory tract, such as alveolar epithelial hyperplasia, microadenomas, and even malignant tumors. In addition, ethanol attenuated cigarette smoke clastogenicity. In conclusion, preclinical studies provide evidence that, in spite of its pulmonary toxicity, ethanol may mitigate some noxious effects of cigarette smoke in the respiratory tract.

The MET Receptor Tyrosine Kinase Confers Repair of Murine Pancreatic Acinar Cells following Acute and Chronic Injury

Acinar cells represent the primary target in necroinflammatory diseases of the pancreas, including pancreatitis. The signaling pathways guiding acinar cell repair and regeneration following injury remain poorly understood. The purpose of this study was to determine the importance of Hepatocyte Growth Factor Receptor/MET signaling as an intrinsic repair mechanism for acinar cells following acute damage and chronic alcohol-associated injury. Here, we generated mice with targeted deletion of MET in adult acinar cells (MET^-/-). Acute and repetitive pancreatic injury was induced in MET^-/- and control mice with cerulein, and chronic injury by feeding mice Lieber-DeCarli diets containing alcohol with or without enhancement of repetitive pancreatic injury. We examined the exocrine pancreas of these mice histologically for acinar death, edema, inflammation and collagen deposition and changes in the transcriptional program. We show that MET expression is relatively low in normal adult pancreas. However, MET levels were elevated in ductal and acinar cells in human pancreatitis specimens, consistent with a role for MET in an adaptive repair mechanism. We report that genetic deletion of MET in adult murine acinar cells was linked to increased acinar cell death, chronic inflammation and delayed recovery (regeneration) of pancreatic exocrine tissue. Notably, increased pancreatic collagen deposition was detected in MET knockout mice following repetitive injury as well alcohol-associated injury. Finally, we identified specific alterations of the pancreatic transcriptome associated with MET signaling during injury, involved in tissue repair, inflammation and endoplasmic reticulum stress. Together, these data demonstrate the importance of MET signaling for acinar repair and regeneration, a novel finding that could attenuate the symptomology of pancreatic injury.

Alcohol Vapor Inhalation as a Model of Alcohol-Induced Organ Disease

BACKGROUND

Chronic intermittent ethanol vapor (CIEV) exposure has been used extensively to produce rodent models of alcohol dependence, but unlike other models of alcohol abuse, CIEV has not been assessed as a model of end-organ damage. The purpose of this study was to characterize the effects of CIEV on peripheral organ systems affected by alcohol abuse, including the liver, lungs, and cardiovascular system.

METHODS

Adult male Sprague-Dawley rats were exposed to daily CIEV for a period of 8 weeks (14HR ON/10HR OFF), producing blood alcohol levels of ~200 mg/dl. Controls were exposed to room air. After 8 weeks, echocardiography was performed to assess cardiac function. Indices of liver injury (alanine and aspartate aminotransferases [ALT and AST]; cytochrome p450 2E1 [CYP2E1]; alcohol dehydrogenase [ADH]; Oil Red O and triglyceride content; lipid peroxidation; inflammatory cytokine expression; and macrophage infiltration), and lung inflammatory cell count, proinflammatory cytokine expression, and lipid peroxidation were measured.

RESULTS

Left ventricular posterior wall thickness was significantly decreased, and systolic blood pressure was significantly elevated by CIEV compared with air controls. CIEV led to a significant increase in plasma ALT and triglycerides compared with room air controls. CIEV did not affect liver triglyceride content, lipid staining or peroxidation, but increased CYP2E1 and chemokine (C-C motif) ligand 2 (CCL2) protein expression, while decreasing ADH expression. CIEV significantly increased numbers of both polymorphonuclear neutrophils and lymphocytes in the bronchoalveolar lavage fluid, indicative of pulmonary inflammation. However, CIEV did not produce significant changes in lung mass, pulmonary lipid peroxidation, inflammatory cytokine expression, or edema.

CONCLUSIONS

These results show that CIEV produces hepatic, pulmonary, and cardiovascular effects in rats similar to those found in other models of chronic alcohol administration. Alcohol vapor administration is a novel method of alcohol-induced tissue injury with high potential for widespread use in alcohol toxicology research.

Peromyscus as a model of human disease

Animals of the genus Peromyscus have been a particularly informative model for many areas of study, including behavior, evolution, anatomy, physiology and genetics. While their use in modeling human disease and pathology has been relatively restricted, certain qualities of Peromyscine mice may make them a good candidate for such studies. Pathophysiological conditions where Peromyscus may be of particular value involve aging, reactive oxygen species-associated pathologies, metabolism and detoxification, diabetes, and certain cancers. In this review article we will summarize pathological conditions where Peromyscus have been used effectively, we will discuss factors limiting the use of Peromyscus in studying pathology and we will indicate areas at which the use of this model may be of special value.

Effects of acute ethanol exposure on cytokine production by primary airway smooth muscle cells

Both chronic and binge alcohol abuse can be significant risk factors for inflammatory lung diseases such as acute respiratory distress syndrome and chronic obstructive pulmonary disease. However, metabolic basis of alcohol-related lung disease is not well defined, and may include key metabolites of ethanol [EtOH] in addition to EtOH itself. Therefore, we investigated the effects of EtOH, acetaldehyde [ACE], and fatty acid ethyl esters [FAEEs] on oxidative stress, endoplasmic reticulum (ER) stress, AMP-activated protein kinase (AMPK) signaling and nuclear translocation of phosphorylated (p)-NF-κB p65 in primary human airway smooth muscle (HASM) cells stimulated to produce cytokines using LPS exposure. Both FAEEs and ACE induced evidence of cellular oxidative stress and ER stress, and increased p-NF-κB in nuclear extracts. EtOH and its metabolites decreased p-AMPKα activation, and induced expression of fatty acid synthase, and decreased expression of sirtuin 1. In general, EtOH decreased secretion of IP-10, IL-6, eotaxin, GCSF, and MCP-1. However, FAEEs and ACE increased these cytokines, suggesting that both FAEEs and ACE as compared to EtOH itself are proinflammatory. A direct effect of EtOH could be consistent with blunted immune response. Collectively, these two features of EtOH exposure, coupled with the known inhibition of innate immune response in our model might explain some clinical manifestations of EtOH exposure in the lung.

Alcohol, Aldehydes, Adducts and Airways

Drinking alcohol and smoking cigarettes results in the formation of reactive aldehydes in the lung, which are capable of forming adducts with several proteins and DNA. Acetaldehyde and malondialdehyde are the major aldehydes generated in high levels in the lung of subjects with alcohol use disorder who smoke cigarettes. In addition to the above aldehydes, several other aldehydes like 4-hydroxynonenal, formaldehyde and acrolein are also detected in the lung due to exposure to toxic gases, vapors and chemicals. These aldehydes react with nucleophilic targets in cells such as DNA, lipids and proteins to form both stable and unstable adducts. This adduction may disturb cellular functions as well as damage proteins, nucleic acids and lipids. Among several adducts formed in the lung, malondialdehyde DNA (MDA-DNA) adduct and hybrid malondialdehyde-acetaldehyde (MAA) protein adducts have been shown to initiate several pathological conditions in the lung. MDA-DNA adducts are pre-mutagenic in mammalian cells and induce frame shift and base-pair substitution mutations, whereas MAA protein adducts have been shown to induce inflammation and inhibit wound healing. This review provides an insight into different reactive aldehyde adducts and their role in the pathogenesis of lung disease.

Metabolic methanol: molecular pathways and physiological roles

Methanol has been historically considered an exogenous product that leads only to pathological changes in the human body when consumed. However, in normal, healthy individuals, methanol and its short-lived oxidized product, formaldehyde, are naturally occurring compounds whose functions and origins have received limited attention. There are several sources of human physiological methanol. Fruits, vegetables, and alcoholic beverages are likely the main sources of exogenous methanol in the healthy human body. Metabolic methanol may occur as a result of fermentation by gut bacteria and metabolic processes involving S-adenosyl methionine. Regardless of its source, low levels of methanol in the body are maintained by physiological and metabolic clearance mechanisms. Although human blood contains small amounts of methanol and formaldehyde, the content of these molecules increases sharply after receiving even methanol-free ethanol, indicating an endogenous source of the metabolic methanol present at low levels in the blood regulated by a cluster of genes. Recent studies of the pathogenesis of neurological disorders indicate metabolic formaldehyde as a putative causative agent. The detection of increased formaldehyde content in the blood of both neurological patients and the elderly indicates the important role of genetic and biochemical mechanisms of maintaining low levels of methanol and formaldehyde.

New Insights into the Pathogenesis of Alcohol-Induced ER Stress and Liver Diseases

Alcohol-induced liver disease increasingly contributes to human mortality worldwide. Alcohol-induced endoplasmic reticulum (ER) stress and disruption of cellular protein homeostasis have recently been established as a significant mechanism contributing to liver diseases. The alcohol-induced ER stress occurs not only in cultured hepatocytes but also  in vivo  in the livers of several species including mouse, rat, minipigs, zebrafish, and humans. Identified causes for the ER stress include acetaldehyde, oxidative stress, impaired one carbon metabolism, toxic lipid species, insulin resistance, disrupted calcium homeostasis, and aberrant epigenetic modifications. Importance of each of the causes in alcohol-induced liver injury depends on doses, duration and patterns of alcohol exposure, genetic disposition, environmental factors, cross-talks with other pathogenic pathways, and stages of liver disease. The ER stress may occur more or less all the time during alcohol consumption, which interferes with hepatic protein homeostasis, proliferation, and cell cycle progression promoting development of advanced liver diseases. Emerging evidence indicates that long-term alcohol consumption and ER stress may directly be involved in hepatocellular carcinogenesis (HCC). Dissecting ER stress signaling pathways leading to tumorigenesis will uncover potential therapeutic targets for intervention and treatment of human alcoholics with liver cancer.