Ethanol disrupts intestinal epithelial tight junction integrity through intracellular calcium-mediated Rho/ROCK activation

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

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

Disrupted balance between pro-inflammatory lipid mediators and anti-inflammatory specialized pro-resolving mediators is linked to hyperinflammation in patients with alcoholic hepatitis

Background

Chronic excessive alcohol consumption leads to a spectrum of alcohol-associated liver diseases (ALD), including alcoholic hepatitis (AH). AH is characterized by intense systemic and liver inflammation, posing significant risks of health complications and mortality. While inflammation is a crucial defense mechanism against injury and infection, its timely resolution is essential to prevent tissue damage and restore tissue homeostasis. The resolution of inflammation is an actively regulated process, primarily governed by specialized pro-resolving mediators (SPMs), lipid metabolites derived from ω-6 and ω-3 poly-unsaturated fatty acids (PUFAs). We investigated the balance between pro-inflammatory lipid mediators (PLMs) and SPMs in the ω-6 and ω-3 PUFA metabolic pathways and examined the impact of alcohol abstinence on rectifying the dysregulated biosynthesis of PLMs and SPMs in AH patients.

Methods

LC-MS/MS and ELISA were used to quantify levels of bioactive lipid mediators (LMs) and their precursors in the plasma samples from 58 AH patients, 29 heavy drinkers without overt liver diseases (HDCs), and 35 healthy controls (HCs). Subsequently, we assessed correlations of altered LMs with clinical parameters and various markers of inflammatory cascade andmicrobial translocation. Furthermore, we conducted a longitudinal study to track changes in levels of LMs over 6- and 12-month follow-ups in AH patients who underwent alcohol abstinence.

Results

AH patients exhibited significantly higher plasma levels of ω-6 PLMs (PGD 2 and LTB 4 ) and SPM RvE1 compared to HDCs and/or HCs. Conversely, key SPMs such as LXA4, RvD1, and several precursors in the ω-3 pathway were significantly downregulated in AH patients. Some of these altered LMs were found to correlate with AH disease severity, clinical parameters, and various inflammatory cytokines. In particular, the LTB4/LXA4 ratio was substantially elevated in AH patients relative to HDCs and HCs. This altered ratio displayed a positive correlation with the MELD score, suggesting its potential utility as an indicator of disease severity in AH patients. Importantly, the majority of dysregulated LMs, particularly PLMs, were normalized following alcohol abstinence.

Conclusion

Our study reveals significant dysregulation in the levels of PLM metabolites and anti-inflammatory SPMs in both ω-6 and ω-3 PUFA pathways in AH patients. This disrupted biosynthesis, characterized by an overabundance of PLMs and a deficiency in SPMs, is linked to the heightened inflammation observed in AH patients. Importantly, our findings suggest an important role of alcohol abstinence in restoring the balance of these LMs and the potential therapeutic benefits of SPM supplements in alleviating the inflammatory cascade in AH patients.

Fluoride disrupts intestinal epithelial tight junction integrity through intracellular calcium-mediated RhoA/ROCK signaling and myosin light chain kinase

Fluoride is a common contaminant of groundwater and agricultural commodity, which poses challenges to animal and human health. A wealth of research has demonstrated its detrimental effects on intestinal mucosal integrity; however, the underlying mechanisms remain obscure. This study aimed to investigate the role of the cytoskeleton in fluoride-induced barrier dysfunction. After sodium fluoride (NaF) treatment of the cultured Caco-2 cells, both cytotoxicity and cytomorphological changes (internal vacuoles or massive ablation) were observed. NaF lowered transepithelial electrical resistance (TEER) and enhanced paracellular permeation of fluorescein isothiocyanate dextran 4 (FD-4), indicating Caco-2 monolayers hyperpermeability. In the meantime, NaF treatment altered both the expression and distribution of the tight junction protein ZO-1. Fluoride exposure increased myosin light chain II (MLC2) phosphorylation and triggered actin filament (F-actin) remodeling. While inhibition of myosin II by Blebbistatin blocked NaF-induced barrier failure and ZO-1 discontinuity, the corresponding agonist Ionomycin had effects comparable to those of fluoride, suggesting that MLC2 serves as an effector. Given the mechanisms upstream of p-MLC2 regulation, further studies demonstrated that NaF activated RhoA/ROCK signaling pathway and myosin light chain kinase (MLCK), strikingly increasing the expression of both. Pharmacological inhibitors (Rhosin, Y-27632 and ML-7) reversed NaF-induced barrier breakdown and stress fiber formation. The role of intracellular calcium ions ([Ca²⁺]_i) in NaF effects on Rho/ROCK pathway and MLCK was investigated. We found that NaF elevated [Ca²⁺]_i, whereas chelator BAPTA-AM attenuated increased RhoA and MLCK expression as well as ZO-1 rupture, thus, restoring barrier function. Collectively, abovementioned results suggest that NaF induces barrier impairment via Ca²⁺-dependent RhoA/ROCK pathway and MLCK, which in turn triggers MLC2 phosphorylation and rearrangement of ZO-1 and F-actin. These results provide potential therapeutic targets for fluoride-induced intestinal injury.

Role of Intestinal Microbes in Chronic Liver Diseases

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

Mechanosensitive calcium flashes promote sustained RhoA activation during tight junction remodeling

Epithelial cell–cell junctions remodel in response to mechanical stimuli to maintain barrier function. Previously, we found that local leaks in tight junctions (TJs) are rapidly repaired by local, transient RhoA activation, termed “Rho flares,” but how Rho flares are regulated is unknown. Here, we discovered that intracellular calcium flashes and junction elongation are early events in the Rho flare pathway. Both laser-induced and naturally occurring TJ breaks lead to local calcium flashes at the site of leaks. Additionally, junction elongation induced by optogenetics increases Rho flare frequency, suggesting that Rho flares are mechanically triggered. Depletion of intracellular calcium or inhibition of mechanosensitive calcium channels (MSCs) reduces the amplitude of calcium flashes and diminishes the sustained activation of Rho flares. MSC-dependent calcium influx is necessary to maintain global barrier function by regulating reinforcement of local TJ proteins via junction contraction. In all, we uncovered a novel role for MSC-dependent calcium flashes in TJ remodeling, allowing epithelial cells to repair local leaks induced by mechanical stimuli.

Propolis Ameliorates Alcohol-Induced Depressive Symptoms in C57BL/6J Mice by Regulating Intestinal Mucosal Barrier Function and Inflammatory Reaction

Accumulating evidence points to a critical role of the brain gut axis as an important paradigm for many central nervous system diseases. Recent studies suggest that propolis has obvious neuroprotective properties and functionality in regulating intestinal bacteria flora, hinting at a potential key effect at both terminals of this axis regulation. However, currently no clear evidence confirms the effects of propolis on alcohol-induced depression. Here, we establish an alcoholic depression model with C57BL/6J mice and demonstrate that treatment with propolis protects against alcohol-induced depressive symptoms by behavioral tests. In addition, propolis attenuates the injury of nerve cells in the hippocampal region and restores the serum levels of brain-derived neurotrophic factor (BDNF) and dopamine (DA) in mice with alcohol-induced depression. Pathology and biotin tracer assays show that propolis repairs the intestinal leakage caused by alcohol. Additionally, propolis treatment increases the expression levels of intestinal intercellular tight junctions’ (TJs’) structural proteins Claudin-1, Occludin and zona occludens-1 (ZO-1), as well as the activation state of the liver kinase B1/AMP-activated protein kinase (LKB1/AMPK) signaling pathway, which is closely related to the intestinal permeability. Furthermore, propolis can reduce the levels of pro-inflammatory, lipopolysaccharide (LPS) and fatty-acid-binding protein 2 (FABP2), suggesting the significance of the inflammatory response in alcoholic depression. Collectively, our findings indicate that propolis exerted an improving effect on alcohol-induced depressive symptoms by ameliorating brain gut dysfunction.

Soluble Immune Checkpoints Are Dysregulated in COVID-19 and Heavy Alcohol Users With HIV Infection

Immune checkpoints (ICPs) consist of paired receptor-ligand molecules that exert inhibitory or stimulatory effects on immune defense, surveillance, regulation, and self-tolerance. ICPs exist in both membrane and soluble forms in vivo and in vitro. Imbalances between inhibitory and stimulatory membrane-bound ICPs (mICPs) in malignant cells and immune cells in the tumor immune microenvironment (TIME) have been well documented. Blockades of inhibitory mICPs have emerged as an immense breakthrough in cancer therapeutics. However, the origin, structure, production regulation, and biological significance of soluble ICPs (sICPs) in health and disease largely remains elusive. Soluble ICPs can be generated through either alternative mRNA splicing and secretion or protease-mediated shedding from mICPs. Since sICPs are found in the bloodstream, they likely form a circulating immune regulatory system. In fact, there is increasing evidence that sICPs exhibit biological functions including (1) regulation of antibacterial immunity, (2) interaction with their mICP compartments to positively or negatively regulate immune responses, and (3) competition with their mICP compartments for binding to the ICP blocking antibodies, thereby reducing the efficacy of ICP blockade therapies. Here, we summarize current data of sICPs in cancer and infectious diseases. We particularly focus on sICPs in COVID-19 and HIV infection as they are the two ongoing global pandemics and have created the world's most serious public health challenges. A "storm" of sICPs occurs in the peripheral circulation of COVID-19 patients and is associated with the severity of COVID-19. Similarly, sICPs are highly dysregulated in people living with HIV (PLHIV) and some sICPs remain dysregulated in PLHIV on antiretroviral therapy (ART), indicating these sICPs may serve as biomarkers of incomplete immune reconstitution in PLHIV on ART. We reveal that HIV infection in the setting of alcohol misuse exacerbates sICP dysregulation as PLHIV with heavy alcohol consumption have significantly elevated plasma levels of many sICPs. Thus, both stimulatory and inhibitory sICPs are present in the bloodstream of healthy people and their balance can be disrupted under pathophysiological conditions such as cancer, COVID-19, HIV infection, and alcohol misuse. There is an urgent need to study the role of sICPs in immune regulation in health and disease.

ERK1/2 mitogen-activated protein kinase mediates downregulation of intestinal tight junction proteins in heat stress-induced IBD model in pig

In many mammalian species, including pigs, heat stress (HS) detrimentally leads to epithelium damage and increases intestinal permeability. However, the underlying molecular mechanisms are not thoroughly investigated yet. This study aimed to examine the RIP1/RIP3-ERK1/2 signaling pathway that regulates the expression of tight junction proteins in HS-treated pigs. In in vitro cultured intestinal porcine epithelial cells (IPEC-J2), HS induced the expression of tight junction proteins, ZO-1, claudin-1, and claudin-4, that are regulated by the ERK1/2-MAPK signaling pathway. Further, high expression of HSP70 in IPEC-J2 cells induced a significant decrease in receptor-interacting protein 1/3 (RIP1/3), phosphorylated ERK, and tight junction protein claudin-1 (P < 0.05). Necrostatin-1 (A selective inhibitor of RIPK1) suppressed the upregulation of phosphorylated ERK1/2 induced by HS, indicating that the RIP1/RIP3 regulates ERK1/2 phosphorylation in IPEC-J2 under heat stress. In addition, HS significantly damaged the intestinal morphology characterized by reduction of villus length and crypt depth in in vivo porcine model. Moreover, the expression of tight junction, ZO-1, and claudin-4 were downregulated, whereas phosphorylated p38 and ERK1/2 were upregulated in the duodenum of heat-stressed pigs. Interestingly, a decrease in ZO-1 and claudin-1 was observed in the colon, where phosphorylated ERK1/2 was similar to that in the duodenum. Our results demonstrate that RIP1/RIP3-ERK1/2 signaling pathway regulates the expression of tight junction proteins in HS-pigs. This finding further advances the intestinal barrier function's underlying mechanisms associated with signaling regulation.

Brusatol-Enriched Brucea javanica Oil Ameliorated Dextran Sulfate Sodium-Induced Colitis in Mice: Involvement of NF-κB and RhoA/ROCK Signaling Pathways

Brucea javanica oil (BJO) is beneficial for the treatment of ulcerative colitis (UC), and that quassinoids in particular brusatol are bioactive components. However, it is still uncertain whether or not other components in BJO, such as oleic acid and fatty acids, have an anti-UC effect. The present study is aimed at comparing the anti-UC effects between brusatol-enriched BJO (BE-BJO) and brusatol-free BJO (BF-BJO) and at exploring the effects and mechanisms of BE-BJO on colon inflammation and intestinal epithelial barrier function. Balb/C mice received 3% (wt/vol) DSS for one week to establish the UC model. Different doses of BE-BJO, BF-BJO, or BJO were treated. The result illustrated that BE-BJO alleviated DSS-induced loss of body weight, an increase of disease activity index (DAI), and a shortening of colon, whereas BF-BJO did not have these protective effects. BE-BJO treatment improved the morphology of colon tissue, inhibited the production and release of TNF-α, IFN-γ, IL-6, and IL-1β in the colon tissue, and reversed the decreased expressions of ZO-1, occludin, claudin-1, and E-cadherin induced by DSS but augmented claudin-2 expression. Mechanistically, BE-BJO repressed phosphorylation of NF-κB subunit p65, suppressed RhoA activation, downregulated ROCK, and prevented phosphorylation of myosin light chain (MLC) in DSS-treated mice, indicating that the protective effect of BE-BJO is attributed to suppression of NF-κB and RhoA/ROCK signaling pathways. These findings confirm that brusatol is an active component from BJO in the treatment of UC.

Uncovering the signalling, structure and function of the 20-HETE-GPR75 pairing: Identifying the chemokine CCL5 as a negative regulator of GPR75

BACKGROUND AND PURPOSE

The G-protein-coupled receptor GPR75 (Gq) and its ligand, the cytochrome P450-derived vasoactive eicosanoid 20-hydroxyeicosatetraenoic acid (20-HETE), are involved in the activation of pro-inflammatory and hypertensive signalling cascades contributing to diabetes, obesity, vascular dysfunction/remodelling, hypertension and cardiovascular disease. Little is known as to how, where and with what affinity 20-HETE interacts with GPR75.

EXPERIMENTAL APPROACH

To better understand the pairing of 20-HETE and its receptor (GPR75), we used surface plasmon resonance (SPR) to determine binding affinity/kinetics. The PRESTO-Tango receptor-ome methodology for GPR75 overexpression was coupled with FLIPR Calcium 6 assays, homogeneous time-resolved fluorescence (HTRF) IP-1 and β-arrestin recruitment assays to determine receptor activation and downstream signalling events.

KEY RESULTS

SPR confirmed 20-HETE binding to GPR75 with an estimated K_D of 1.56 × 10^-10  M. In GPR75-transfected HTLA cells, 20-HETE stimulated intracellular Ca²⁺ levels, IP-1 accumulation and β-arrestin recruitment, all of which were negated by known 20-HETE functional antagonists. Computational modelling of the putative ligand-binding pocket and mutation of Thr212 within the putative 20-HETE binding site abolished 20-HETE's ability to stimulate GPR75 activation. Knockdown of GPR75 in human endothelial cells nullified 20-HETE-stimulated intracellular Ca²⁺ . The chemokine CCL5, a suggested GPR75 ligand, binds to GPR75 (K_D of 5.85 × 10^-10  M) yet fails to activate GPR75; however, it inhibited 20-HETE's ability to activate GPR75 signalling.

CONCLUSIONS AND IMPLICATIONS

We have identified 20-HETE as a high-affinity ligand for GPR75 and CCL5 as a low-affinity negative regulator of GPR75, providing additional evidence for the deorphanization of GPR75 as a 20-HETE receptor.

Blood Biomarkers of Intestinal Epithelium Damage Regenerating Islet-derived Protein 3α and Trefoil Factor 3 Are Persistently Elevated in Patients with Alcoholic Hepatitis

BACKGROUND

Heavy alcohol consumption disrupts gut epithelial integrity, leading to increased permeability of the gastrointestinal tract and subsequent translocation of microbes. Regenerating islet-derived protein 3α (REG3α) and Trefoil factor 3 (TFF3) are mainly secreted to the gut lumen by Paneth and Goblet cells, respectively, and are functionally linked to gut barrier integrity. Circulating levels of REG3α and TFF3 have been identified as biomarkers for gut damage in several human diseases. We examined whether plasma levels of REG3α and TFF3 were dysregulated and correlated with conventional markers of microbial translocation (MT) and pro-inflammatory mediators in heavy drinkers with and without alcoholic hepatitis (AH).

METHODS

Cross-sectional and longitudinal studies were performed to monitor plasma levels of REG3α and TFF3 in 79 AH patients, 66 heavy drinkers without liver disease (HDC), and 46 healthy controls (HC) at enrollment and at 6- and 12-month follow-ups. Spearman correlation was used to measure the relationships of REG3α and TFF3 levels with MT, disease severity, inflammation, and effects of abstinence from alcohol.

RESULTS

At enrollment, AH patients had significantly higher levels of REG3α and TFF3 than HDC and HC. The elevated REG3α levels were positively correlated with the 30-day fatality rate. Plasma levels of REG3α and TFF3 in AH patients differentially correlated with conventional MT markers (sCD14, sCD163, and LBP) and several highly up-regulated inflammatory cytokines/chemokines/growth factors. At follow-ups, although REG3α and TFF3 levels were decreased in AH patients with alcohol abstinence, they did not fully return to baseline levels.

CONCLUSIONS

Circulating levels of REG3α and TFF3 were highly elevated in AH patients and differentially correlated with AH disease severity, MT, and inflammation, thereby serving as potential biomarkers of MT and gut epithelial damage in AH patients.

Narrative review on potential role of gut microbiota in certain substance addiction

As a neuropsychiatric disorder, substance addiction represents a major public health issue with high prevalence and mortality in many countries. Recently, gut microbiota has been certified to play a part in substance addiction through various mechanisms. Hence, we mainly focused on three substance including alcohol, cocaine and methamphetamine in this review, and summarized their relationships with gut microbiota, respectively. Besides, we also concluded the possible treatments for substance addiction from the perspective of applying gut microbiota. This review aims to build a bridge between substance addiction and gut microbiota according to existing evidences, so as to excavate the possible bi-directional function of microbiota-gut-brain axis in substance addiction for developing therapeutic strategies in the future.

Piezo1 regulates intestinal epithelial function by affecting the tight junction protein claudin-1 via the ROCK pathway

AIMS

Defective tight junctions (TJs) can induce intestinal epithelial dysfunction, which participates in various diseases such as irritable bowel syndrome. However, the mechanisms of TJ defects remain unclear. Our study revealed the role of Piezo1 in regulating intestinal epithelial function and TJs.

MATERIALS AND METHODS

The human colonic adenocarcinoma cell line Caco-2 were cultured on Transwell plate to form an epithelial barrier in vitro, and Piezo1 expression was manipulated using a lentivirus vector. Epithelial function was evaluated by measuring transepithelial electronic resistance (TEER) and 4-kDa FITC-dextran (FD4) transmission. TJ proteins (claudin-1, occludin, ZO-1) were evaluated by RT-PCR, western blot, and immunostaining analysis. Potential signal pathways, including the ROCK and Erk pathways, were detected. Moreover, to explore the regulatory effect of Piezo1 activity on epithelial function, inhibitors (ruthenium red, GsMTx4) and an agonist (Yoda1) were introduced both ex vivo and in vitro.

KEY FINDINGS

Alteration of Piezo1 expression altered epithelial function and the expression of the tight junction protein claudin-1. Piezo1 expression regulated phosphorylated ROCK1/2 expression, whereas interference on ROCK1/2 prevented the regulation of claudin-1 by Piezo1. In both Caco-2 monolayer and mouse colon epithelium, Piezo1 activity directly modulated epithelial function and permeability.

SIGNIFICANCE

Piezo1 negatively regulates epithelial barrier function by affecting the expression of claudin-1. Such regulation may be achieved partially via the ROCK1/2 pathway. Moreover, activating Piezo1 can induce epithelial dysfunction.

Changes in intestinal barrier functions and gut microbiota in rats exposed to zearalenone

Zearalenone (ZEN) is a mycotoxin that causes serious health problems in humans and animals. However, few studies have focused on the destruction of the intestinal barrier caused by ZEN. In this study, rats were exposed to different dosages of ZEN (0, 0.2, 1.0 and 5.0 mg/kg bw) by gavage for 4 weeks. The results showed that 1.0 and 5.0 mg/kg ZEN impaired gut morphology, induced the inflammatory response, reduced mucin expression, increased intestinal permeability, decreased the expression of TJ proteins and activated the RhoA/ROCK pathway. However, 0.2 mg/kg ZEN had no significant effect on intestinal barrier except for reducing the expression of some TJ proteins and mucins. Moreover, exposure to ZEN led to slight imbalance in microbiota. In conclusion, ZEN exposure resulted in intestinal barrier dysfunction by inducing intestinal microbiota dysbiosis, decreasing the expression of TJ proteins, activating the RhoA/ROCK pathway, and inducing the inflammatory response.

Contribution of the Intestinal Microbiome and Gut Barrier to Hepatic Disorders

Intestinal barrier dysfunction and dysbiosis contribute to development of diseases in liver and other organs. Physical, immunologic, and microbiologic (bacterial, fungal, archaeal, viral, and protozoal) features of the intestine separate its nearly 100 trillion microbes from the rest of the human body. Failure of any aspect of this barrier can result in translocation of microbes into the blood and sustained inflammatory response that promote liver injury, fibrosis, cirrhosis, and oncogenic transformation. Alterations in intestinal microbial populations or their functions can also affect health. We review the mechanisms that regulate intestinal permeability and how changes in the intestinal microbiome contribute to development of acute and chronic liver diseases. We discuss individual components of the intestinal barrier and how these are disrupted during development of different liver diseases. Learning more about these processes will increase our understanding of the interactions among the liver, intestine, and its flora.

Lemon balm and dandelion leaf extract synergistically alleviate ethanol-induced hepatotoxicity by enhancing antioxidant and anti-inflammatory activity

We investigated the effect of a 2:1 (w/w) mixture of lemon balm and dandelion extracts (LD) on ethanol (EtOH)-mediated liver injury and explored the underlying mechanisms. Administration of LD synergistically reduced relative liver weight and decreased the levels of serum biomarkers of hepatic injury. Histopathological and biochemical analyses indicated that LD synergistically attenuated hepatic accumulation of triacylglycerides (TGs) and restored the levels of mRNAs related to fatty acid metabolism. In addition, LD significantly reduced EtOH-induced hepatic oxidative stress by attenuating the reduction in levels of nuclear factor E2-related factor 2 (Nrf2) mRNA and enhancing antioxidant activity. Moreover, LD decreased the EtOH-mediated increase in levels of hepatic tumor necrosis factor-α (TNF-α) mRNA. In vitro, LD significantly scavenged free radicals, increased cell viability against tert-butylhydroperoxide (tBHP), and transactivated Nrf2 target genes in HepG2 cells. Furthermore, LD decreased levels of pro-inflammatory mediators in lipopolysaccharide-stimulated Raw264.7 cells. Therefore, LD shows promise for preventing EtOH-mediated liver injury. PRACTICAL APPLICATIONS: There were no approved therapeutic agents for preventing and/or treating alcoholic liver diseases. In this study, a 2:1 (w/w) mixture of lemon balm and dandelion leaf extract (DL) synergistically ameliorated EtOH-induced hepatic injury by inhibiting lipid accumulation, oxidative stress, and inflammation. Our findings will enable the development of a novel food supplement for the prevention or treatment of alcohol-mediated liver injury.

Dietary Synbiotic Supplementation Protects Barrier Integrity of Hepatocytes and Liver Sinusoidal Endothelium in a Mouse Model of Chronic-Binge Ethanol Exposure

Alcohol overconsumption disrupts the gut microbiota and intestinal barrier, which decreases the production of beneficial microbial metabolic byproducts and allows for translocation of pathogenic bacterial-derived byproducts into the portal-hepatic circulation. As ethanol is known to damage liver sinusoidal endothelial cells (LSEC), here we evaluated dietary supplementation with a previously studied synbiotic on gut microbial composition, and hepatocyte and LSEC integrity in mice exposed to ethanol. We tested a chronic-binge ethanol feeding mouse model in which C57BL/6 female mice were fed ethanol (5% vol/vol) for 10 days and provided a single ethanol gavage (5 g/kg body weight) on day 11, 6 h before euthanasia. An ethanol-treatment group also received oral supplementation daily with a synbiotic; and an ethanol-control group received saline. Control mice were pair-fed and isocalorically substituted maltose dextran for ethanol over the entire exposure period; they received a saline gavage daily. Ethanol exposure decreased gut microbial abundance and diversity. This was linked with diminished expression of adherens junction proteins in hepatocytes and dysregulated expression of receptors for advanced glycation end-products; and this coincided with reduced expression of endothelial barrier proteins. Synbiotic supplementation mitigated these effects. These results demonstrate synbiotic supplementation, as a means to modulate ethanol-induced gut dysbiosis, is effective in attenuating injury to hepatocyte and liver endothelial barrier integrity, highlighting a link between the gut microbiome and early stages of acute liver injury in ethanol-exposed mice.

Microbiota and Alcohol Use Disorder: Are Psychobiotics a Novel Therapeutic Strategy?

In recent years, there has been an exciting focus of research attempting to understand neuropsychiatric disorders from a holistic perspective in order to determine the role of gut microbiota in the aetiology and pathogenesis of such disorders. Thus, the possible therapeutic benefits of targeting gut microbiota are being explored for conditions such as stress, depression or schizophrenia. Growing evidence indicates that there is bidirectional communication between gut microbiota and the brain that has an effect on normal CNS functioning and behavioural responses. Alcohol abuse damages the gastrointestinal tract, alters gut microbiota and induces neuroinflammation and cognitive decline. The relationship between alcohol abuse and hypothalamic-pituitary-adrenal axis activation, inflammation and immune regulation has been well documented. In this review, we explore the connection between microbiota, brain function and behaviour, as well as the mechanisms through which alcohol induces microbiota dysbiosis and intestinal barrier dysfunction. Finally, we propose the study of psychobiotics as a novel pharmaceutical strategy to treat alcohol use disorders.

Valsartan inhibits RhoA-ROCK2-MYL pathway in rat model of alcoholic cardiomyopathy

The present study aimed to investigate variations in the Ras homolog gene family, member A (RhoA)-Rho-associated protein kinase 2 (ROCK2)-myosin light chain (MYL) pathway in a rat model of alcoholic cardiomyopathy (ACM) and the role of angiotensin-converting enzyme inhibitor drugs. Rat models of ACM were established via alcoholic gavage + free access to alcohol. The structural and functional changes of the heart were analyzed by hematoxylin-eosin staining, Masson's trichrome staining, immunohistochemistry staining, western blotting and fluorescence quantitative polymerase chain reaction. A total of 16 weeks later, a decreased ejection fraction and left ventricular fractional shortening in the alcohol group compared with the control group were demonstrated resulting in an increased left ventricular end diastolic diameter. These adverse effects were ameliorated following treatment with valsartan. In addition, the alcohol group revealed a disorganized arrangement of myocardial filaments, which was improved upon treatment with valsartan. RhoA and ROCK2 protein expression significantly increased in myocardial cells in the alcohol compared with the control group. Following drug intervention with valsartan, expression of RhoA and ROCK2 proteins were inhibited in the alcohol group. Furthermore, significantly elevated RhoA and ROCK2 and decreased MYL protein and mRNA expression in the alcohol group was demonstrated compared with the control group. Administration of valsartan reversed the expression profile of RhoA, ROCK and MYL in ACM. Expression of RhoA and ROCK were elevated with downregulation of MYL resulting in heart failure. However, the angiotensin receptor antagonist diminished the expression of RhoA and ROCK and enhanced the expression of MYL. The results of the present study suggest a curative effect of valsartan in ACM.

Occludin endocytosis is involved in the disruption of the intestinal epithelial barrier in a mouse model of alcoholic steatohepatitis

OBJECTIVE

We aimed to investigate the involvement of the endocytosis of occludin, a key component of tight junction (TJ), in the ethanol-induced disassembly of TJ in a model of alcoholic steatohepatitis.

METHODS

Wild-type mice were fed an ethanol-containing or isocaloric liquid diet for 8 weeks and then assessed for liver injury (histopathology and measurement of serum enzymes), gut permeability (in vivo lactulose/mannitol and ex vivo dye leakage assays), intestinal epithelium ultrastructure (transmission electron microscopy), and intestinal occludin localization (immunofluorescence microscopy). The human intestinal epithelial cell line Caco-2 was also analyzed in vitro for the effects of ethanol on the barrier function (transepithelial electrical resistance), occludin localization (immunofluorescence microscopy and Western blotting), and endocytosis pathways (double-labeling immunofluorescence microscopy with selective pathway inhibitors).

RESULTS

The ethanol-fed mice developed steatohepatitis and displayed intestinal barrier dysfunction, the disruption of intestinal TJ, and enhanced intestinal endocytosis of occluding compared with the control mice. In the Caco-2 monolayers, ethanol treatment decreased transepithelial electrical resistance, disrupted TJ formation, and enhanced occludin endocytosis in a dose- and time-dependent manner. These deleterious events were reversed by pretreating the Caco-2 cells with a selective pharmacological inhibitor of macropinocytosis, but not with the inhibitors of clathrin or caveolin-mediated endocytic pathways.

CONCLUSION

Chronic ethanol exposure may increase intestinal permeability by inducing the micropinocytosis of occludin, resulting in the disruption of intestinal TJ.

Specifically Sized Hyaluronan (35 kDa) Prevents Ethanol-Induced Disruption of Epithelial Tight Junctions Through a layilin-Dependent Mechanism in Caco-2 Cells

BACKGROUND

Specific-sized species of the carbohydrate hyaluronan elicit a variety of cellular responses mediating tissue integrity and repair, as well as regulating inflammatory responses. Orally provided hyaluronan with an average molecular weight of 35 kDa (HA35) protects mice from short-term ethanol (EtOH)-induced liver injury. This protection was associated with maintenance of the colocalization of zonula occludens-1 (ZO-1) and occludin at tight junctions in the proximal colon. However, it is not known whether HA35 also protects other regions of the intestine or whether protection is due to a direct and/or indirect interaction of HA35 with the intestinal epithelium.

METHODS

Female C57BL/6J mice were fed an EtOH containing diet or pair-fed control diet (4 days) and treated with or without HA35 via daily gavage during the last 3 days of EtOH feeding. Intestinal morphology and tight junction integrity were assessed. Differentiated Caco-2 cells were transfected or not with scrambled siRNA or siRNA targeting layilin, a hyaluronan receptor. Caco-2 cells were treated with or without HA35 prior to challenge with EtOH. Localization of tight junction proteins, fluorescein isothiocyanate (FITC)-dextran permeability, and transepithelial electrical resistance (TEER) were evaluated.

RESULTS

While short-term EtOH did not result in any apparent changes in the gross morphology of the intestine, colocalization of ZO-1 and occludin at tight junctions was decreased in the proximal and distal colon. HA35 prevented these effects of EtOH. In differentiated Caco-2 cells, EtOH decreased the localization of ZO-1 and occludin at tight junctions and increased permeability of FITC-dextran. At higher concentrations, EtOH also decreased TEER. Pretreatment with HA35 prevented these changes. When the hyaluronan receptor layilin was knocked down in Caco-2 cells, HA35 no longer protected cells from EtOH-induced loss of tight junctions.

CONCLUSIONS

Taken together, these data indicate that HA35 interacts with layilin on intestinal epithelial cells and maintains intestinal tight junction integrity during short-term EtOH exposure.

Osteopontin Protects Colonic Mucosa from Dextran Sodium Sulfate-Induced Acute Colitis in Mice by Regulating Junctional Distribution of Occludin

BACKGROUND

Osteopontin (OPN) has been reported to play an important role in intestinal mucosal protection. Although OPN may have positive effects on tight junctions, the exact relationship between OPN and tight junctions has yet to be elucidated.

AIMS

To investigate the role of OPN on tight junctions.

METHODS

We evaluated clinical signs and histopathology of acute colitis induced by dextran sodium sulfate (DSS) in OPN knockout and wild-type (WT) mice in vivo. Expression levels of occludin and zonula occludens-1 were examined using immunofluorescence. For in vitro analysis, an siRNA-mediated OPN-suppressed Caco-2 monolayer was used. Expression levels and patterns of occludin were analyzed by immunofluorescence, and transepithelial electrical resistance (TER) was measured to evaluate barrier function. Triton X-100 fractionation was used to analyze phosphorylated occludin associated with tight junctional localization.

RESULTS

OPN deficiency resulted in an elevated disease activity index, shortened colon length, and aggravated histological signs in mice with DSS-induced acute colitis compared to WT mice. OPN deficiency decreased occludin expression in the colonic mucosa. In Caco-2 monolayers, OPN suppression reduced junctional occludin and redistributed it into the intracellular compartment with decreased TER. Furthermore, western blot for occludin from Triton X-100 insoluble fraction revealed that OPN suppression reduced the phosphorylated form of occludin, which is actually distributed in the tight junction.

CONCLUSIONS

Our study showed that OPN is essential for maintaining the tight junction complex by allowing occludin to localize at tight junctions. This could constitute additional evidence that OPN plays a crucial role in intestinal mucosal protection.

OTA induces intestinal epithelial barrier dysfunction and tight junction disruption in IPEC-J2 cells through ROS/Ca2+-mediated MLCK activation

Ochratoxin A (OTA) is a frequent contaminant of feed and food worldwide. The toxicity of OTA on intestinal barrier was investigated in porcine intestinal epithelial cells (IPEC-J2). We observed that OTA induced intestinal barrier dysfunction as indicated by the reduction in transepithelial electrical resistance (TEER) and elevation in paracellular permeability to 4 kDa dextran. The barrier dysfunction was accompanied with tight junction disruption including a down-regulation in ZO-1 expression and redistribution of Occludin and ZO-1. Moreover, OTA exposure increased reactive oxygen species (ROS) generation, elevated the intracellular calcium level ([Ca²⁺]_c) and activated myosin light chain kinase (MLCK). Simultaneously, NAC, a ROS scavenger, blocked OTA-induced ROS generation, [Ca²⁺]_c elevation, barrier dysfunction and tight junction disruption, suggesting that OTA-induced ROS generation may act as a trigger. Next, we found that OTA-induced MLCK activation was inhibited by BAPTA-AM, the cytosolic Ca²⁺ chelator, demonstrating that OTA-induced MLCK activation is dependent on [Ca²⁺]_c elevation. Furthermore, inhibition of MLCK with ML-7 or inhibition of [Ca²⁺]_c elevation with BAPTA-AM markedly prevented OTA-induced barrier dysfunction and tight junction disruption. Taken together, our results indicated that OTA induces ROS generation, and then elevates the [Ca²⁺]_c and MLCK activity in turn, which finally induces barrier dysfunction and disrupts tight junction in IPEC-J2 cell monolayers.

Dysregulation of junctional adhesion molecule-A contributes to ethanol-induced barrier disruption in intestinal epithelial cell monolayers

Alcohol consumption promotes loss of intestinal barrier function. However, mechanisms by which ethanol affects the tight junction (TJ), the cellular structure responsible for maintaining the gut epithelial barrier, are not well understood. Three classes of transmembrane proteins comprise TJs: occludin, claudins, and junctional adhesion molecules (JAMs). It has recently been postulated that JAM‐A (F11R), the most abundant JAM expressed in intestinal epithelium, regulates “leak” pathway flux, a paracellular route for the nonselective permeation of large solutes. Since transluminal flux of many gut‐derived antigens occurs through this pathway, we investigated the role of JAM‐A in ethanol‐induced disruption of the intestinal epithelial barrier. Using Caco‐2 and SK‐CO15 monolayers, we found that ethanol induced a dose‐ and time‐dependent decrease in JAM‐A protein expression to about 70% of baseline levels. Alcohol also reduced Ras‐related protein 2 (Rap2) activity, and enhanced myosin light chain kinase (MLCK) activity, changes consistent with impaired JAM‐A signaling. Stable overexpression and shRNA‐mediated knockdown of JAM‐A were employed to investigate the role of JAM‐A in paracellular‐mediated flux following alcohol exposure. The paracellular flux of 40‐kDa fluorescein isothiocynate (FITC)‐dextran following ethanol treatment was decreased by the overexpression of JAM‐A; conversely, flux was enhanced by JAM‐A knockdown. Thus, we conclude that ethanol‐mediated control of JAM‐A expression and function contributes to mechanisms by which this chemical induces intestinal epithelial leakiness.

Concurrent gut transcriptome and microbiota profiling following chronic ethanol consumption in nonhuman primates

Alcohol use disorder (AUD) results in increased intestinal permeability, nutrient malabsorption, and increased risk of colorectal cancer (CRC). Our understanding of the mechanisms underlying these morbidities remains limited because studies to date have relied almost exclusively on short-term heavy/binge drinking rodent models and colonic biopsies/fecal samples collected from AUD subjects with alcoholic liver disease (ALD). Consequently, the dose- and site-dependent impact of chronic alcohol consumption in the absence of overt liver disease remains poorly understood. In this study, we addressed this knowledge gap using a nonhuman primate model of voluntary ethanol self-administration where rhesus macaques consume varying amounts of 4% ethanol in water for 12 months. Specifically, we performed RNA-Seq and 16S rRNA gene sequencing on duodenum, jejunum, ileum, and colon biopsies collected from 4 controls and 8 ethanol-consuming male macaques. Our analysis revealed that chronic ethanol consumption leads to changes in the expression of genes involved in protein trafficking, metabolism, inflammation, and CRC development. Additionally, we observed differences in the relative abundance of putatively beneficial bacteria as well as those associated with inflammation and CRC. Given that the animals studied in this manuscript did not exhibit signs of ALD or CRC, our data suggest that alterations in gene expression and bacterial communities precede clinical disease and could serve as biomarkers as well as facilitate future studies aimed at developing interventions to restore gut homeostasis.

Staphylococcus aureus impairs sinonasal epithelial repair: Effects in patients with chronic rhinosinusitis with nasal polyps and control subjects

BACKGROUND

The effect of Staphylococcus aureus on nasal epithelial repair has never been assessed in patients with chronic rhinosinusitis with nasal polyps (CRSwNP).

OBJECTIVE

This study aimed to determine whether (1) nasal epithelial cell cultures from patients with CRSwNP and control subjects repair differently; (2) S aureus exoproducts compromise nasal epithelial repair; (3) S aureus alters lamellipodial dynamics; and (4) deleterious effects could be counteracted by the Rho-associated coiled-coil kinase inhibitor Y-27632.

METHODS

Primary nasal epithelial cells (pNECs) collected during surgeries were cultured and injured under 3 conditions: (1) basal conditions, (2) exposed to S aureus exoproducts, and (3) exposed to S aureus exoproducts and Y-27632. Epithelial repair, lamellipodial dynamics, and cytoskeletal organization were assessed.

RESULTS

Under basal conditions, pNEC cultures from patients with CRSwNP presented significantly lower repair rates and reduced lamellipodial protrusion length and velocity than those from control subjects. S aureus exoproducts significantly decreased repair rates and protrusion dynamics in both control subjects and patients with CRSwNP; however, the effect of S aureus on cell protrusions was more sustained over time in patients with CRSwNP. Under basal conditions, immunofluorescence assays showed significantly reduced percentages of cells with lamellipodia at the wound edge in patients with CRSwNP compared with control subjects. S aureus altered cell polarity and decreased the percentage of cells with lamellipodia in both groups. Finally, Y-27632 prevented the deleterious effects of S aureus exoproducts on CRSwNP repair rates, as well as on lamellipodial dynamics and formation.

CONCLUSIONS

S aureus exoproducts significantly alter epithelial repair and lamellipodial dynamics on pNECs, and this impairment was more pronounced in patients with CRSwNP. Importantly, Y-27632 restored epithelial repair and lamellipodial dynamics in the presence of S aureus exoproducts.

Protective Effect of Aplysin Supplementation on Intestinal Permeability and Microbiota in Rats Treated with Ethanol and Iron

Aplysin, a kind of phytochemicals or phytonutrients, is purified from red alga Laurencia tristicha. The present study aims to investigate the influence of aplysin on changes of intestinal permeability and microbiota induced by excessive ethanol and iron. Thirty male rats were randomly divided into three groups (10/group): control group (normal saline); ethanol + iron group as EI treated with ethanol (8–12 mL/kg/day) and iron (1000 mg/kg) in diet; EI supplemented with aplysin (150 mg/kg/day) group as AEI; the trial lasts for 12 weeks. The result showed that levels of plasma endotoxin, fatty acid-binding protein 2, D-lactic acid, diamine oxidase were increased in rats in the EI group; and significantly decreased by 14%, 17%, 26%, 16%, respectively (p < 0.05) in the AEI group after the 12-week aplysin treatment. Moreover, in the AEI group the amount of Escherichia coli and Bacteroides fragilis were higher, while the amount of Lactobacillus, Bifidobacterium and Clostridium were lower than those in the EI group. The expressions of iron transporters divalent-metal transporter 1(DMT1) and ferroportin 1(FPN1) were significantly upregulated in the EI group compared to those in the control group. In conclusion, aplysin could effectively improve intestinal permeability and intestinal flora disorder induced with excessive ethanol and iron.

Deoxycholic Acid-Mediated Sphingosine-1-Phosphate Receptor 2 Signaling Exacerbates DSS-Induced Colitis through Promoting Cathepsin B Release

We recently have proved that excessive fecal DCA caused by high-fat diet may serve as an endogenous danger-associated molecular pattern to activate NLRP3 inflammasome and thus contributes to the development of inflammatory bowel disease (IBD). Moreover, the effect of DCA on inflammasome activation is mainly mediated through bile acid receptor sphingosine-1-phosphate receptor 2 (S1PR2); however, the intermediate process remains unclear. Here, we sought to explore the detailed molecular mechanism involved and examine the effect of S1PR2 blockage in a colitis mouse model. In this study, we found that DCA could dose dependently upregulate S1PR2 expression. Meanwhile, DCA-induced NLRP3 inflammasome activation is at least partially achieved through stimulating extracellular regulated protein kinases (ERK) signaling pathway downstream of S1PR2 followed by promoting of lysosomal cathepsin B release. DCA enema significantly aggravated DSS-induced colitis in mice and S1PR2 inhibitor as well as inflammasome inhibition by cathepsin B antagonist substantially reducing the mature IL-1β production and alleviated colonic inflammation superimposed by DCA. Therefore, our findings suggest that S1PR2/ERK1/2/cathepsin B signaling plays a critical role in triggering inflammasome activation by DCA and S1PR2 may represent a new potential therapeutic target for the management of intestinal inflammation in individuals on a high-fat diet.

Inhibition of Rho kinase protects against colitis in mice by attenuating intestinal epithelial barrier dysfunction via MLC and the NF-κB pathway

The aim of the present study was to investigate the role of Rho kinase (also known as ROCK) inhibitor in 2,4,6-trinitrobenzene sulfonic acid induced mouse colitis; and to elucidate the underlying mechanism of ROCK1/ROCK2 inhibition in enhancing intestinal epithelial barrier (IEB) function. A specific inhibitor of ROCK, Y-27632, was used to examine the role of ROCK in mouse colitis models. ROCK1 and ROCK2 were silenced respectively using RNA interference in Caco-2 cells. The expression of tight junction proteins and the downstream molecules of ROCK were assessed. Y-27632 alleviated colonic inflammation and decreased intestinal permeability. ROCK-myosin light chain (MLC) and ROCK-NF-κB pathway were activated in colitis and inhibited by Y-27632. In vitro, ROCK1 RNAi primarily downregulated the phosphorylation of myosin phosphatase-targeting subunit-1 (MYPT-1) and MLC, while ROCK2 RNAi inhibited phosphorylation of nuclear factor-κB (NF-κB). In conclusion, the results suggested that the ROCK inhibitor alleviated colitis and IEB dysfunction. Inhibition of phospho-MYPT-1 and MLC by ROCK1 knockout or inhibition of NF-κB phosphorylation by ROCK2 knockout may be the underlying mechanisms.

The Role of IRE-XBP1 Pathway in Regulation of Retinal Pigment Epithelium Tight Junctions

Purpose

The retinal pigment epithelium (RPE) tight junctions play a pivotal role in maintaining the homeostatic environment of the neural retina. Herein, we investigated the role of X-box binding protein 1 (XBP1), an endoplasmic reticulum (ER) stress-responsive transcription factor, in regulation of RPE tight junctions.

Methods

Human RPE cell line (ARPE-19) and primary primate RPE cells were used for in vitro experiments and RPE-specific XBP1 knockout (KO) mice were used for in vivo study. Endoplasmic reticulum stress was induced by a sublethal dose of thapsigargin or tunicamycin. XBP1 activation was manipulated by IRE inhibitor 4μ8C, which suppresses XBP1 mRNA splicing. The integrity of tight junctions and the involvement of calcium-dependent RhoA/Rho kinase pathway were examined.

Results

Induction of ER stress by thapsigargin, but not tunicamycin, disrupted RPE tight junctions in ARPE-19 cells. Inhibition of XBP1 activation by 4μ8C resulted in a remarkable downregulation of tight junction proteins (ZO-1 and occludin) and defects in tight junction formation in the presence or absence of ER stress inducers. Overexpression of active XBP1 partially reversed 4μ8C-induced anomalies in tight junctions. Mechanistically, XBP1 inhibition resulted in increased intracellular Ca2+ concentration, upregulation of RhoA expression, redistribution of F-actin, and tight junction damage, which was attenuated by Rho kinase inhibitor Y27632. In vivo, deletion of XBP1 in the RPE resulted in defective RPE tight junctions accompanied by increased VEGF expression.

Conclusions

Taken together, these results suggest a protective role of XBP1 in maintaining RPE tight junctions possibly through regulation of calcium-dependent RhoA/Rho kinase signaling and actin cytoskeletal reorganization.

Flavonoid composition of orange peel extract ameliorates alcohol-induced tight junction dysfunction in Caco-2 monolayer

Dry citrus peels, also known as "chenpi", have been traditionally used to treat and relieve intestinal inflammation. Recently we have reported that orange peel extracts (OPE) which contain relatively greater polymethoxylated flavone (PMF) content exhibit superior antioxidant and anti-inflammatory activities in vitro. Moreover, these bioactivities were notably greater than an equivalent flavonoid mixture (FM). The present study compares the effects of different OPE sources with distinct PMF composition on tight junction (TJ) dysfunction induced by ethanol. The OPE obtained from Xinhui, China, contained a 20-fold higher PMF content than extracts derived from the orange peels sourced from Guangxi. Xinhui-OPE treatment of ethanol treated Caco-2 cells corresponded to lower (P < 0.05) lactate dehydrogenase (LDH) leakage and higher (P < 0.05) glutathione reductase activity. Both OPE and the FM prevented ethanol-induced increases in Caco-2 cell paracellular permeability and the dislocation of TJ proteins, including claudin 4, occludin, and zonulin occludin-1 (ZO-1), respectively. Xinhui-OPE increased the expression of claudin 4 and occludin protein, but not mRNA, whereas, Guangxi-OPE and Xinhui-FM had no effect on TJ protein expression. In conclusion, OPE derived from sources that contain higher concentrations of PMF are more effective at preventing intestinal barrier dysfunction of TJ proteins induced by ethanol.

Does Oxidative Stress Induced by Alcohol Consumption Affect Orthodontic Treatment Outcome?

HIGHLIGHTS Ethanol, Periodontal ligament, Extracellular matrix, Orthodontic movement. Alcohol is a legal drug present in several drinks commonly used worldwide (chemically known as ethyl alcohol or ethanol). Alcohol consumption is associated with several disease conditions, ranging from mental disorders to organic alterations. One of the most deleterious effects of ethanol metabolism is related to oxidative stress. This promotes cellular alterations associated with inflammatory processes that eventually lead to cell death or cell cycle arrest, among others. Alcohol intake leads to bone destruction and modifies the expression of interleukins, metalloproteinases and other pro-inflammatory signals involving GSKβ, Rho, and ERK pathways. Orthodontic treatment implicates mechanical forces on teeth. Interestingly, the extra- and intra-cellular responses of periodontal cells to mechanical movement show a suggestive similarity with the effects induced by ethanol metabolism on bone and other cell types. Several clinical traits such as age, presence of systemic diseases or pharmacological treatments, are taken into account when planning orthodontic treatments. However, little is known about the potential role of the oxidative conditions induced by ethanol intake as a possible setback for orthodontic treatment in adults.

The effects of Lactobacillus plantarum on small intestinal barrier function and mucosal gene transcription; a randomized double-blind placebo controlled trial

The aim of this study was to investigate the effects of three Lactobacillus plantarum strains on in-vivo small intestinal barrier function and gut mucosal gene transcription in human subjects. The strains were selected for their differential effects on TLR signalling and tight junction protein rearrangement, which may lead to beneficial effects in a stressed human gut mucosa. Ten healthy volunteers participated in four different intervention periods: 7-day oral intake of either L. plantarum WCFS1, CIP104448, TIFN101 or placebo, proceeded by a 4 weeks wash-out period. Lactulose-rhamnose ratio (an indicator of small intestinal permeability) increased after intake of indomethacin, which was given as an artificial stressor of the gut mucosal barrier (mean ratio 0.06 ± 0.04 to 0.10 ± 0.06, p = 0.001), but was not significantly affected by the bacterial interventions. However, analysis in small intestinal biopsies, obtained by gastroduodenoscopy, demonstrated that particularly L. plantarum TIFN101 modulated gene transcription pathways related to cell-cell adhesion with high turnover of genes involved in tight- and adhesion junction protein synthesis and degradation (e.g. actinin alpha-4, metalloproteinase-2). These effects were less pronounced for L. plantarum WCFS1 and CIP104448. In conclusion, L. plantarum TIFN101 induced the most pronounced probiotic properties with specific gene transcriptional effects on repair processes in the compromised intestine of healthy subjects.

HYDROGEN-RICH MEDIUM AMELIORATES LIPOPOLYSACCHARIDE-INDUCED BARRIER DYSFUNCTION VIA RHOA-MDIA1 SIGNALING IN CACO-2 CELLS

Gastrointestinal barrier dysfunction is associated with the severity and prognosis of sepsis. Hydrogen gas (H2) can ameliorate multiple organ damage in septic animals. Ras homolog gene family member A (RhoA) and mammalian diaphanous-related formin 1 (mDia1) are important to regulate tight junction (TJ) and adherens junction (AJ), both of which determine the integrity of the intestinal barrier. This study was aimed to investigate whether H2 could modulate lipopolysaccharide (LPS)-stimulated dysfunction of the intestinal barrier and whether RhoA-mDia1 signaling is involved. Caco-2 cells were exposed to different concentrations of LPS (1 μg/mL-1 mg/mL). The permeability of the intestinal barrier was evaluated by transepithelial resistance (TER) and fluorescein-isothiocyanate-dextran flux. Expression and distribution of occludin and E-cadherin were analyzed by Western blot and immunofluorescence. RhoA activity was measured by G-Lisa assay, and mDia1 expression was assessed by Western blot. LPS (100 μg/mL) decreased TER and increased fluorescein-isothiocyanate-dextran flux, which were alleviated by H2-rich medium. Also, H2 down-regulated LPS-induced oxidative stress. Moreover, H2 improved the down-regulated expression and redistribution of occludin and E-cadherin caused by LPS. Additionally, H2 alleviated LPS-caused RhoA activation, and the beneficial effects of H2 on barrier were counteracted by RhoA agonist CN03. Rho inhibitor C3 exoenzyme mitigated LPS-induced barrier breakdown. Furthermore, H2-rich medium increased mDia1 expression, and mDia1 knockdown abolished protections of H2 on barrier permeability. mDia1 knockdown eliminated H2-induced benefits for occludin and E-cadherin. These findings suggest that H2 improves LPS-induced hyperpermeability of the intestinal barrier and disruptions of TJ and AJ by moderating RhoA-mDia1 signaling.

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.

Ca2+ -regulated lysosome fusion mediates angiotensin II-induced lipid raft clustering in mesenteric endothelial cells

It has been reported that intracellular Ca2+ is involved in lysosome fusion and membrane repair in skeletal cells. Given that angiotensin II (Ang II) elicits an increase in intracellular Ca2+ and that lysosome fusion is a crucial mediator of lipid raft (LR) clustering, we hypothesized that Ang II induces lysosome fusion and activates LR formation in rat mesenteric endothelial cells (MECs). We found that Ang II acutely increased intracellular Ca2+ content, an effect that was inhibited by the extracellular Ca2+ chelator ethylene glycol tetraacetic acid (EGTA) and the inositol 1,4,5-trisphosphate (IP3)-induced Ca2+ release inhibitor 2-aminoethoxydiphenyl borate (2-APB). Further study showed that EGTA almost completely blocked Ang II-induced lysosome fusion, the translocation of acid sphingomyelinase (ASMase) to LR clusters, ASMase activation and NADPH (nicotinamide adenine dinucleotide phosphate) oxidase activation. In contrast, 2-APB had a slight inhibitory effect. Functionally, both the lysosome inhibitor bafilomycin A1 and the ASMase inhibitor amitriptyline reversed Ang II-induced impairment of vasodilation. We conclude that Ca2+ -regulated lysosome fusion mediates the Ang II-induced regulation of the LR-redox signaling pathway and mesenteric endothelial dysfunction.

Chronic Ethanol Exposure: Pathogenesis of Pulmonary Disease and Dysfunction

Ethanol (EtOH) is the world’s most commonly used drug, and has been widely recognized as a risk factor for developing lung disorders. Chronic EtOH exposure affects all of the organ systems in the body and increases the risk of developing pulmonary diseases such as acute lung injury and pneumonia, while exacerbating the symptoms and resulting in increased mortality in many other lung disorders. EtOH and its metabolites inhibit the immune response of alveolar macrophages (AMs), increase airway leakage, produce damaging reactive oxygen species (ROS), and disrupt the balance of antioxidants/oxidants within the lungs. In this article, we review the role of EtOH exposure in the pathogenesis and progression of pulmonary disease.

Alcohol and the Intestine

Alcohol abuse is a significant contributor to the global burden of disease and can lead to tissue damage and organ dysfunction in a subset of alcoholics. However, a subset of alcoholics without any of these predisposing factors can develop alcohol-mediated organ injury. The gastrointestinal tract (GI) could be an important source of inflammation in alcohol-mediated organ damage. The purpose of review was to evaluate mechanisms of alcohol-induced endotoxemia (including dysbiosis and gut leakiness), and highlight the predisposing factors for alcohol-induced dysbiosis and gut leakiness to endotoxins. Barriers, including immunologic, physical, and biochemical can regulate the passage of toxins into the portal and systemic circulation. In addition, a host of environmental interactions including those influenced by circadian rhythms can impact alcohol-induced organ pathology. There appears to be a role for therapeutic measures to mitigate alcohol-induced organ damage by normalizing intestinal dysbiosis and/or improving intestinal barrier integrity. Ultimately, the inflammatory process that drives progression into organ damage from alcohol appears to be multifactorial. Understanding the role of the intestine in the pathogenesis of alcoholic liver disease can pose further avenues for pathogenic and treatment approaches.

The gut microbiome and the brain

The human gut microbiome impacts human brain health in numerous ways: (1) Structural bacterial components such as lipopolysaccharides provide low-grade tonic stimulation of the innate immune system. Excessive stimulation due to bacterial dysbiosis, small intestinal bacterial overgrowth, or increased intestinal permeability may produce systemic and/or central nervous system inflammation. (2) Bacterial proteins may cross-react with human antigens to stimulate dysfunctional responses of the adaptive immune system. (3) Bacterial enzymes may produce neurotoxic metabolites such as D-lactic acid and ammonia. Even beneficial metabolites such as short-chain fatty acids may exert neurotoxicity. (4) Gut microbes can produce hormones and neurotransmitters that are identical to those produced by humans. Bacterial receptors for these hormones influence microbial growth and virulence. (5) Gut bacteria directly stimulate afferent neurons of the enteric nervous system to send signals to the brain via the vagus nerve. Through these varied mechanisms, gut microbes shape the architecture of sleep and stress reactivity of the hypothalamic-pituitary-adrenal axis. They influence memory, mood, and cognition and are clinically and therapeutically relevant to a range of disorders, including alcoholism, chronic fatigue syndrome, fibromyalgia, and restless legs syndrome. Their role in multiple sclerosis and the neurologic manifestations of celiac disease is being studied. Nutritional tools for altering the gut microbiome therapeutically include changes in diet, probiotics, and prebiotics.

ALDH2 Deficiency Promotes Ethanol-Induced Gut Barrier Dysfunction and Fatty Liver in Mice

BACKGROUND

Acetaldehyde, the toxic ethanol (EtOH) metabolite, disrupts intestinal epithelial barrier function. Aldehyde dehydrogenase (ALDH) detoxifies acetaldehyde into acetate. Subpopulations of Asians and Native Americans show polymorphism with loss-of-function mutations in ALDH2. We evaluated the effect of ALDH2 deficiency on EtOH-induced disruption of intestinal epithelial tight junctions and adherens junctions, gut barrier dysfunction, and liver injury.

METHODS

Wild-type and ALDH2-deficient mice were fed EtOH (1 to 6%) in Lieber-DeCarli diet for 4 weeks. Gut permeability in vivo was measured by plasma-to-luminal flux of FITC-inulin, tight junction and adherens junction integrity was analyzed by confocal microscopy, and liver injury was assessed by the analysis of plasma transaminase activity, histopathology, and liver triglyceride.

RESULTS

EtOH feeding elevated colonic mucosal acetaldehyde, which was significantly greater in ALDH2-deficient mice. ALDH2(-/-) mice showed a drastic reduction in the EtOH diet intake. Therefore, this study was continued only in wild-type and ALDH2(+/-) mice. EtOH feeding elevated mucosal inulin permeability in distal colon, but not in proximal colon, ileum, or jejunum of wild-type mice. In ALDH2(+/-) mice, EtOH-induced inulin permeability in distal colon was not only higher than that in wild-type mice, but inulin permeability was also elevated in the proximal colon, ileum, and jejunum. Greater inulin permeability in distal colon of ALDH2(+/-) mice was associated with a more severe redistribution of tight junction and adherens junction proteins from the intercellular junctions. In ALDH2(+/-) mice, but not in wild-type mice, EtOH feeding caused a loss of junctional distribution of tight junction and adherens junction proteins in the ileum. Histopathology, plasma transaminases, and liver triglyceride analyses showed that EtOH-induced liver damage was significantly greater in ALDH2(+/-) mice compared to wild-type mice.

CONCLUSIONS

These data demonstrate that ALDH2 deficiency enhances EtOH-induced disruption of intestinal epithelial tight junctions, barrier dysfunction, and liver damage.

Dual function of a bacterial protein as an adhesin and extracellular effector of host GTPase signaling

Bacterial pathogens often target conserved cellular mechanisms within their hosts to rewire signaling pathways and facilitate infection. Rho GTPases are important nodes within eukaryotic signaling networks and thus constitute a common target of pathogen-mediated manipulation. A diverse array of microbial mechanisms exists to interfere with Rho GTPase signaling. While targeting of GTPases by secreted bacterial effectors is a well-known strategy bacterial pathogens employ to interfere with the host, we have recently described pathogen adhesion as a novel extracellular stimulus that hijacks host GTPase signaling. The Multivalent Adhesion Molecule MAM7 from Vibrio parahaemolyticus directly binds host cell membrane lipids. The ensuing coalescence of phosphatidic acid ligands in the host membrane leads to downstream activation of RhoA and actin rearrangements. Herein, we discuss mechanistic models of lipid-mediated Rho activation and the implications from the infected host's and the pathogen's perspective.

Pathological implications of cadherin zonation in mouse liver

Both acute and chronic liver diseases are associated with ample re-modeling of the liver parenchyma leading to functional impairment, which is thus obviously the cause or the consequence of the disruption of the epithelial integrity. It was, therefore, the aim of this study to investigate the distribution of the adherens junction components E- and N-cadherin, which are important determinants of tissue cohesion. E-cadherin was expressed in periportal but not in perivenous hepatocytes. In contrast, N-cadherin was more enriched towards the perivenous hepatocytes. In agreement, β-catenin, which links both cadherins via α-catenin to the actin cytoskeleton, was expressed ubiquitously. This zonal expression of cadherins was preserved in acute liver injury after treatment with acetaminophen or partial hepatectomy, but disrupted in chronic liver damage like in non-alcoholic steatohepatitis (NASH) or α1-antitrypsin deficiency. Hepatocyte proliferation during acetaminophen-induced liver damage was predominant at the boundary between the damaged perivenous and the intact periportal parenchyma indicating a minor contribution of periportal hepatocytes to liver regeneration. In NASH livers, an oval cell reaction was observed pointing to massive tissue damage coinciding with the gross impairment of hepatocyte proliferation. In the liver parenchyma, metabolic functions are distributed heterogeneously. For example, the expression of phosphoenolpyruvate carboxykinase and E-cadherin overlapped in periportal hepatocytes. Thus, during liver regeneration after acute damage, the intact periportal parenchyma might sustain essential metabolic support like glucose supply or ammonia detoxification. However, disruption of epithelial integrity during chronic challenges may increase susceptibility to metabolic liver diseases such as NASH or vice versa. This might suggest the regulatory integration of tissue cohesion and metabolic functions in the liver.

Role of defective methylation reactions in ethanol-induced dysregulation of intestinal barrier integrity

Alcoholic liver disease (ALD) is a major healthcare challenge worldwide. Emerging evidence reveals that ethanol administration disrupts the intestinal epithelial tight junction (TJ) complex; this defect allows for the paracellular translocation of gut-derived pathogenic molecules to reach the liver to cause inflammation and progressive liver injury. We have previously demonstrated a causative role of impairments in liver transmethylation reactions in the pathogenesis of ALD. We have further shown that treatment with betaine, a methylation agent that normalizes liver methylation potential, can attenuate ethanol-induced liver injury. Herein, we explored whether alterations in methylation reactions play a causative role in disrupting intestinal mucosal barrier function by employing an intestinal epithelial cell line. Monolayers of Caco-2 cells were exposed to ethanol or a-pan methylation reaction inhibitor, tubercidin, in the presence and absence of betaine. The structural and functional integrity of intestinal epithelial barrier was then examined. We observed that exposure to either ethanol or tubercidin disrupted TJ integrity and function by decreasing the localization of TJ protein occludin-1 to the intracellular junctions, reducing transepithelial electrical resistance and increasing dextran influx. All these detrimental effects of ethanol and tubercidin were attenuated by co-treatment with betaine. We further show that the mechanism of betaine protection was through BHMT-mediated catalysis. Collectively, our data suggest a novel mechanism for alcohol-induced gut leakiness and identifies the importance of normal methylation reactions in maintaining TJ integrity. We also propose betaine as a potential therapeutic option for leaky gut in alcohol-consuming patients who are at the risk of developing ALD.

Protective effect of 1,25-dihydroxyvitamin D3 on ethanol-induced intestinal barrier injury both in vitro and in vivo

Studies have suggested the role of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) in protecting intestinal barrier function from injuries induced by multiple reagents. Vitamin D deficiency was reported to be associated with poor prognosis in patients with alcoholic liver disease (ALD). This study is designed to investigate the effect of 1,25(OH)2D3 on ethanol-induced intestinal barrier dysfunction and the underlying mechanisms utilizing Caco-2 cell monolayers and a mouse model with acute ethanol injury. In Caco-2 monolayers, ethanol significantly increased monolayer permeability, disrupted TJ distribution, increased phosphorylation level of MLC, and induced generation of ROS compared with controls. However, pre-treatment with 1,25(OH)2D3 greatly ameliorated the ethanol-induced barrier dysfunction, TJ disruption, phosphorylation level of MLC, and generation of ROS compared with ethanol-exposed monolayers. Mice fed with vitamin d-sufficient diet had a higher plasma level of 25(OH)D3 and were more resistant to ethanol-induced acute intestinal barrier injury compared with the vitamin d-deficient group. These results suggest that the suppression of generation of ROS and increased phosphorylation level of MLC might be one of the mechanisms underlying the protective effect of 1,25(OH)2D3 on ethanol-induced intestinal barrier injury and provide evidence for the application of vitamin D as therapeutic factors against ethanol-induced gut leakiness.

The intestinal barrier in irritable bowel syndrome: subtype-specific effects of the systemic compartment in an in vitro model

BACKGROUND

Irritable bowel syndrome (IBS) is a disorder with multifactorial pathophysiology. Intestinal barrier may be altered, especially in diarrhea-predominant IBS (IBS-D). Several mediators may contribute to increased intestinal permeability in IBS.

AIM

We aimed to assess effects of tryptase and LPS on in vitro permeability using a 3-dimensional cell model after basolateral cell exposure. Furthermore, we assessed the extent to which these mediators in IBS plasma play a role in intestinal barrier function.

MATERIALS AND METHODS

Caco-2 cells were grown in extracellular matrix to develop into polarized spheroids and were exposed to tryptase (10 - 50 mU), LPS (1 - 50 ng/mL) and two-fold diluted plasma samples of 7 patients with IBS-D, 7 with constipation-predominant IBS (IBS-C) and 7 healthy controls (HC). Barrier function was assessed by the flux of FITC-dextran (FD4) using live cell imaging. Furthermore, plasma tryptase and LPS were determined.

RESULTS

Tryptase (20 and 50 mU) and LPS (6.25 - 50 ng/mL) significantly increased Caco-2 permeability versus control (all P< 0.05). Plasma of IBS-D only showed significantly elevated median tryptase concentrations (7.1 [3.9 - 11.0] vs. 4.2 [2.2 - 7.0] vs. 4.2 [2.5 - 5.9] μg/mL; P<0.05) and LPS concentrations (3.65 [3.00 - 6.10] vs. 3.10 [2.60-3.80] vs. 2.65 [2.40 - 3.40] EU/ml; P< 0.05) vs. IBS-C and HC. Also, plasma of IBS-D increased Caco-2 permeability versus HC (0.14450 ± 0.00472 vs. 0.00021 ± 0.00003; P < 0.001), which was attenuated by selective inhibition of tryptase and LPS (P< 0.05).

CONCLUSION

Basolateral exposure of spheroids to plasma of IBS-D patients resulted in a significantly increased FD4 permeation, which was partially abolished by selective inhibition of tryptase and LPS. These findings point to a role of systemic tryptase and LPS in the epithelial barrier alterations observed in patients with IBS-D.

Effects of compound Ginkgo biloba on intestinal permeability in rats with alcohol-induced liver injury

The mechanism of compound Ginkgo biloba (CGB) to alleviate the liver injury induced by gut-derived endotoxin in alcoholic liver disease.

Abnormal ultrastructure of intestinal epithelial barrier in mice with alcoholic steatohepatitis

Intestinal barrier dysfunction caused by chronic alcohol consumption is closely associated with disruption of the intestinal epithelial apical junction complex. The present study was undertaken to directly display by transmission electron microscopy the abnormal ultrastructure of the intestinal epithelial barrier in mice with alcoholic steatohepatitis. The results showed that chronic alcohol consumption could induce obvious liver injury, with diffuse lipid accumulation and focal inflammatory cell infiltration in the liver, assessed by hematoxylin and eosin staining. The indicators of intestinal barrier dysfunction, d-lactic acid and lipopolysaccharide, were significantly higher in alcohol-fed mice than in control mice. Alcohol exposure obviously caused high permeability in the ileum to fluorescein isothiocyanate-dextran (FD-4; molecular weight 4000). Transmission electron microscopy demonstrated that tight junctions and adherens junctions expanded noticeably in alcohol-fed mice. Although the tight junction (TJ) length of alcohol-fed mice had no significant difference compared with control mice, the adherens junction (AJ) length of alcohol-fed mice significantly decreased compared with control mice. Additionally, the ratios of both TJmax/TJmin and AJmax/AJmin were significantly larger in alcohol-fed mice than in control liquid-fed mice. In conclusion, high intestinal permeability caused by alcohol attributes to the irregular ultrastructure of the intestinal epithelial barrier.