The inflammatory footprints of alcohol-induced oxidative damage in neurovascular components

Mitocytosis Mediated by an Enzyme-Activable Mitochondrion-Disturbing Polymer-Drug Conjugate Enhances Active Penetration in Glioblastoma Therapy

The application of nanomedicines for glioblastoma (GBM) therapy is hampered by the blood-brain barrier (BBB) and the dense glioblastoma tissue. To achieve efficient BBB crossing and deep GBM penetration, this work demonstrates a strategy of active transcellular transport of a mitochondrion-disturbing nanomedicine, pGBEMA22-b-pSSPPT9 (GBEPPT), in the GBM tissue through mitocytosis. GBEPPT is computer-aided designed and prepared by self-assembling a conjugate of an amphiphilic block polymer and a drug podophyllotoxin (PPT). When GBEPPT is delivered to the tumor site, overexpressed γ-glutamyl transpeptidase (GGT) on the brain-blood endothelial cell, or the GBM cell triggered enzymatic hydrolysis of γ-glutamylamide on GBEPPT to reverse its negative charge to positive. Positively charged GBEPPT rapidly enter into the cell and target the mitochondria. These GBEPPT disturb the homeostasis of mitochondria, inducing mitocytosis-mediated extracellular transport of GBEPPT to the neighboring cells via mitosomes. This intracellular-to-intercellular delivery cycle allows GBEPPT to penetrate deeply into the GBM parenchyma, and exert sustainable action of PPT released from GBEPPT on the tumor cells along its penetration path at the tumor site, thus improving the anti-GBM effect. The process of mitocytosis mediated by the mitochondrion-disturbing nanomedicine may offer great potential in enhancing drug penetration through malignant tissues, especially poorly permeable solid tumors.

ICAM-1 Deletion Using CRISPR/Cas9 Protects the Brain from Traumatic Brain Injury-Induced Inflammatory Leukocyte Adhesion and Transmigration Cascades by Attenuating the Paxillin/FAK-Dependent Rho GTPase Pathway

Intercellular adhesion molecule-1 (ICAM-1) is identified as an initiator of neuroinflammatory responses that lead to neurodegeneration and cognitive and sensory-motor deficits in several pathophysiological conditions including traumatic brain injury (TBI). However, the underlying mechanisms of ICAM-1-mediated leukocyte adhesion and transmigration and its link with neuroinflammation and functional deficits following TBI remain elusive. Here, we hypothesize that blocking of ICAM-1 attenuates the transmigration of leukocytes to the brain and promotes functional recovery after TBI. The experimental TBI was induced in vivo by fluid percussion injury (25 psi) in male and female wild-type and ICAM-1-/- mice and in vitro by stretch injury (3 psi) in human brain microvascular endothelial cells (hBMVECs). We treated hBMVECs and animals with ICAM-1 CRISPR/Cas9 and conducted several biochemical analyses and demonstrated that CRISPR/Cas9-mediated ICAM-1 deletion mitigates blood-brain barrier (BBB) damage and leukocyte transmigration to the brain by attenuating the paxillin/focal adhesion kinase (FAK)-dependent Rho GTPase pathway. For analyzing functional outcomes, we used a cohort of behavioral tests that included sensorimotor functions, psychological stress analyses, and spatial memory and learning following TBI. In conclusion, this study could establish the significance of deletion or blocking of ICAM-1 in transforming into a novel preventive approach against the pathophysiology of TBI.

Hemolytic iron regulation in traumatic brain injury and alcohol use

Hemorrhage is a major component of traumatic brain injury (TBI). Red blood cells, accumulated at the hemorrhagic site, undergo hemolysis upon energy depletion and release free iron into the central nervous system. This iron must be managed to prevent iron neurotoxicity and ferroptosis. As prior alcohol consumption is often associated with TBI, we examined iron regulation in a rat model of chronic alcohol feeding subjected to fluid percussion-induced TBI. We found that alcohol consumption prior to TBI altered the expression profiles of the lipocalin 2/heme oxygenase 1/ferritin iron management system. Notably, unlike TBI alone, TBI following chronic alcohol consumption sustained the expression of all three regulatory proteins for 1, 3, and 7 days post-injury. In addition, alcohol significantly affected TBI-induced expression of ferritin light chain at 3 days post-injury. We also found that alcohol exacerbated TBI-induced activation of microglia at 7 days post-injury. Finally, we propose that microglia may also play a role in iron management through red blood cell clearance.

Aggressive-like behaviour and neurocognitive impairment in alcohol herbal mixture-fed mice are associated with increased neuroinflammation and neuronal apoptosis in the prefrontal cortex

Alcohol-induced aggression and related violence is a serious and common social problem globally. Alcohol use is increasingly found in the form of alcoholic herbal mixtures (AHM) with indiscriminate and unregulated alcohol content. This study investigated the effects of AHM on aggressive-like, neurocognitive impairment and brain biochemical alteration in mice. Thirty-two male resident mice were paired housed with female mice for 21 days in four groups (n = 8). Resident mice were treated orally with normal saline, AHM, ethanol and AHM + ethanol daily for 14 days. Aggressive-like behaviour was scored based on the latency and frequency of attacks by the resident mouse on the intruder. Neurocognitive impairment was determined using the Y-maze test (YMT) and novel object recognition test (NORT). Acetylcholinesterase, glutamic acid decarboxylase (GAD), pro-inflammatory and oxidative stress parameters were determined in the prefrontal cortex (PFC). Neuronal morphology, cytochrome c (Cyt-c) and nuclear factor-kappa B (NF-ĸB) expressions were determined. AHM and in combination with ethanol showed an increased index of aggression typified by frequency of attack and reduced latency to attack when compared to normal saline-treated animals. Co-administration of AHM and ethanol significantly reduced cognitive correct alternation (%) and discrimination index in the YMT and NORT, respectively. AHM and ethanol increased acetylcholinesterase, Pro-inflammatory cytokines and oxidative stress parameters while they reduced GAD. There were significantly reduced neuronal counts and increased expression of Cyt-c and NF-ĸB, respectively Alcoholic herbal mixture increased aggressiveness and caused neurocognitive impairment via increased oxido-inflammatory stress in the prefrontal cortex.

Synergistic effect of mild traumatic brain injury and alcohol aggravates neuroinflammation, amyloidogenesis, tau pathology, neurodegeneration, and blood-brain barrier alterations: Impact on psychological stress

After a mild traumatic brain injury (mTBI), victims often experience emotional/psychological stress such as heightened irritability, anxiety, apathy, and depression. Severe mental health complications are common in military populations following a combat-acquired TBI and intensified unhealthy alcohol use. The high prevalence of alcohol abuse among TBI victims underscores how alcohol abuse exacerbates emotional/psychological symptoms such as depression and anxiety. The experimental mTBI was induced in vivo by fluid percussion injury (15 psi) in mice and ethanol diet feeding continued for 28 days. We analyzed different biomarkers of the biochemical mechanisms and pathophysiology of neurological damage, and functional outcome of psychological stress by sucrose preference, and light-dark tests. We demonstrated that the synergistic effect of TBI and alcohol leads to psychological stress such as depression and anxiety. The studies showed that oxidative stress, amyloidogenesis, tau pathology, neuroinflammation, and neurodegeneration markers were elevated, and glial activation and blood-brain barrier (BBB) damage were exacerbated during the synergistic effect of TBI and alcohol. Further, we studied the biochemical mechanisms of psychological stress that showed the significant reduction of 5-HT1AR, neuropeptide-Y, and norepinephrine, and an increase in monoamine oxidase-a in the combined effect of TBI and alcohol. This work suggested that the combined TBI and alcohol-induced effect leads to depression and anxiety, via sequential biochemical changes that cause neuroinflammation, amyloidogenesis, tau pathology, neurodegeneration, and BBB alterations. This clinically relevant study will contribute to developing a comprehensive therapeutic approach for patients suffering from TBI and alcohol-mediated neurological damage and psychological stress.

Innate immune activation: Parallels in alcohol use disorder and Alzheimer’s disease

Alcohol use disorder is associated with systemic inflammation and organ dysfunction especially in the liver and the brain. For more than a decade, studies have highlighted alcohol abuse-mediated impairment of brain function and acceleration of neurodegeneration through inflammatory mechanisms that directly involve innate immune cells. Furthermore, recent studies indicate overlapping genetic risk factors between alcohol use and neurodegenerative disorders, specifically regarding the role of innate immunity in the pathomechanisms of both areas. Considering the pressing need for a better understanding of the relevance of alcohol abuse in dementia progression, here we summarize the molecular mechanisms of neuroinflammation observed in alcohol abuse and Alzheimer’s disease, the most common cause of dementia. In addition, we highlight mechanisms that are already established in the field of Alzheimer’s disease that may be relevant to explore in alcoholism to better understand alcohol mediated neurodegeneration and dementia, including the relevance of the liver-brain axis.

A Multimodal Neuroprosthetic Interface to Record, Modulate and Classify Electrophysiological Biomarkers Relevant to Neuropsychiatric Disorders

Most mental disorders, such as addictive diseases or schizophrenia, are characterized by impaired cognitive function and behavior control originating from disturbances within prefrontal neural networks. Their often chronic reoccurring nature and the lack of efficient therapies necessitate the development of new treatment strategies. Brain-computer interfaces, equipped with multiple sensing and stimulation abilities, offer a new toolbox whose suitability for diagnosis and therapy of mental disorders has not yet been explored. This study, therefore, aimed to develop a biocompatible and multimodal neuroprosthesis to measure and modulate prefrontal neurophysiological features of neuropsychiatric symptoms. We used a 3D-printing technology to rapidly prototype customized bioelectronic implants through robot-controlled deposition of soft silicones and a conductive platinum ink. We implanted the device epidurally above the medial prefrontal cortex of rats and obtained auditory event-related brain potentials in treatment-naïve animals, after alcohol administration and following neuromodulation through implant-driven electrical brain stimulation and cortical delivery of the anti-relapse medication naltrexone. Towards smart neuroprosthetic interfaces, we furthermore developed machine learning algorithms to autonomously classify treatment effects within the neural recordings. The neuroprosthesis successfully captured neural activity patterns reflecting intact stimulus processing and alcohol-induced neural depression. Moreover, implant-driven electrical and pharmacological stimulation enabled successful enhancement of neural activity. A machine learning approach based on stepwise linear discriminant analysis was able to deal with sparsity in the data and distinguished treatments with high accuracy. Our work demonstrates the feasibility of multimodal bioelectronic systems to monitor, modulate and identify healthy and affected brain states with potential use in a personalized and optimized therapy of neuropsychiatric disorders.

Biochemical Mechanisms Associating Alcohol Use Disorders with Cancers

Simple Summary

Of all yearly deaths attributable to alcohol consumption globally, approximately 12% are due to cancers, representing approximately 0.4 million deceased individuals. Ethanol metabolism disturbs cell biochemistry by targeting the structure and function of essential biomolecules (proteins, nucleic acids, and lipids) and by provoking alterations in cell programming that lead to cancer development and cancer malignancy. A better understanding of the metabolic and cell signaling realm affected by ethanol is paramount to designing effective treatments and preventive actions tailored to specific neoplasias.

Abstract

The World Health Organization identifies alcohol as a cause of several neoplasias of the oropharynx cavity, esophagus, gastrointestinal tract, larynx, liver, or female breast. We review ethanol’s nonoxidative and oxidative metabolism and one-carbon metabolism that encompasses both redox and transfer reactions that influence crucial cell proliferation machinery. Ethanol favors the uncontrolled production and action of free radicals, which interfere with the maintenance of essential cellular functions. We focus on the generation of protein, DNA, and lipid adducts that interfere with the cellular processes related to growth and differentiation. Ethanol’s effects on stem cells, which are responsible for building and repairing tissues, are reviewed. Cancer stem cells (CSCs) of different origins suffer disturbances related to the expression of cell surface markers, enzymes, and transcription factors after ethanol exposure with the consequent dysregulation of mechanisms related to cancer metastasis or resistance to treatments. Our analysis aims to underline and discuss potential targets that show more sensitivity to ethanol’s action and identify specific metabolic routes and metabolic realms that may be corrected to recover metabolic homeostasis after pharmacological intervention. Specifically, research should pay attention to re-establishing metabolic fluxes by fine-tuning the functioning of specific pathways related to one-carbon metabolism and antioxidant processes.

Biphasic Effects of Ethanol Exposure on Waste Metabolites Clearance in the CNS

We have shown that the effects of low-dose ethanol promote the clearance of waste metabolites, such as amyloid-beta (Aβ) proteins, from the brain through the perivascular space (PVS). We demonstrated that dilative reactivity of arterial smooth muscle and endothelial cells regulate this clearance. These findings indicate the importance of blood-brain barrier (BBB) transvascular clearance of large size metabolites from the central nervous system (CNS), where the lymphatic clearance system is absent. We next examined the contrasting effects of acute low-dose and chronic moderate ethanol exposure on BBB-associated perivascular clearance. We injected a high molecular weight fluorescent dye into the interstitial space or directly into the cerebrospinal fluid (CSF). Bio-distribution of this tracer was then examined in different brain regions by multiphoton imaging and whole brain tissue section scanning. Ethanol-induced molecular/cellular mechanisms that drive the increase or decrease in movement of the fluorescent tracer were correlated to BBB integrity and arterial vessel reactivity. We found that activation of endothelial nitric oxide synthase (eNOS) under low-dose ethanol conditions with a shift to activation of inducible NOS (iNOS) under chronic high ethanol exposure conditions, which appeared to regulate these contrasting effects. We validated these observations by qualitative and quantitative investigation of eNOS, iNOS, BBB integrity, and perivascular clearance of waste metabolites. We concluded that the effects of low-dose ethanol increased the diffusive movement of waste metabolites via eNOS-derived NO, which increased the arterial endothelial-smooth muscle cell dilative reactivity without affecting BBB integrity, whereas a prolonged induction of iNOS under chronic ethanol exposure conditions caused oxidative damage of the arterial endothelial-smooth muscle layers resulting in cerebral amyloid-like angiopathy. This led to dysfunction of the BBB, dilative reactivity, and impaired waste metabolites movement from the interstitial space or subarachnoid space (SAS) through perivascular clearance.

Alcohol induces programmed death receptor-1 and programmed death-ligand-1 differentially in neuroimmune cells

Engagement of programmed death-1 (PD-1) receptor by its ligands (PD-L1/PD-L2) in activated immune cells is known to be involved in inflammatory neurological disease via a co-inhibitory signal pathway. Interaction of PD-1/PD-L1 is believed to occur only in activated neuroimmune cells because there are undetectable levels of PD-1/PD-L1 in normal physiological conditions. Here, we evaluated whether activation of neuroimmune cells such as human macrophage, brain endothelial cells (hBECs), astrocytes, microglia, and neurons by non-toxic concentrations of ethanol (EtOH) exposure can alter PD-1/PD-L1 expression. Thus, the present study is limited to the screening of PD-1/PD-L1 alterations in neuroimmune cells following ethanol exposure. We found that exposure of human macrophage or microglia to EtOH in primary culture immediately increased the levels of PD-L1 and gradually up-regulated PD-1 levels (beginning at 1-2 h). Similarly, ethanol exposure was able to induce PD-1/PD-L1 levels in hBECs and neuronal culture in a delayed process (occurring at 24 h). Astrocyte culture was the only cell type that showed endogenous levels of PD-1/PD-L1 that was decreased by EtOH exposure time-dependently. We concluded that ethanol (alcohol) mediated the induction of PD-1/PD-L1 differentially in neuroimmune cells. Taken together, our findings suggest that up-regulation of PD-1/PD-L1 by chronic alcohol use may dampen the innate immune response of neuroimmune cells, thereby contributing to neuroinflammation and neurodegeneration.

Alcohol promotes waste clearance in the CNS via brain vascular reactivity

The efficient clearance of the interstitial waste metabolites is essential for the normal maintenance of brain homeostasis. The brain lacks the lymphatic clearance system. Thus, the drainage of waste metabolites in the brain is dependent on a slow flow of cerebrospinal fluid (CSF) system. Glymphatic system claims the direct bulk flow transport of small size water-soluble waste metabolites into to the perivenous space by aquaporin-4 water channels of the astrocyte end-feet, but it did not address the diffusive clearance of large size waste metabolites. Here, we addressed the clearance mechanisms of large size waste metabolites from interstitial fluid to perivascular space as well as from CSF subarachnoid into perivascular space via the paravascular drainage. A low dose ethanol acting as a potent vasodilator promotes the dynamic clearance of waste metabolites through this perivascular-perivenous drainage path. We observed that ethanol-induced increased in vascular endothelial and smooth muscle cell reactivity regulated the enhanced clearance of metabolites. Here, activation of endothelial specific nitric oxide synthase (eNOS) by ethanol and generation of vasodilator nitric oxide mediates the interactive reactivity of endothelial-smooth muscle cells and subsequent diffusion of the CNS waste metabolites towards perivascular space. Detection of tracer dye (waste metabolite) in the perivenous space and in the blood samples further confirmed the improved clearance of waste metabolites through this unraveled interstitial-perivascular-perivenous clearance path. Our results suggest that alcohol intake at low-dose levels may promote clearance of neurological disease associated entangled proteins.

Baccharis trimera protects against ethanol induced hepatotoxicity in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Baccharis trimera has been traditionally used in Brazil to treat liver diseases.

AIM OF THE STUDY

To evaluate the protective effect of Baccharis trimera in an ethanol induced hepatotoxicity model.

MATERIALS AND METHODS

The antioxidant capacity was evaluated in vitro by the ability to scavenged the DPPH radical, by the quantification of ROS, NO and the transcription factor Nrf2. Hepatotoxicity was induced in animals by administration of absolute ethanol for 2 days (acute) or with ethanol diluted for 28 days (chronic). The biochemical parameters of hepatic function (ALT and AST), renal function (urea and creatinine) and lipid profile (total cholesterol, triglycerides and HDL) were evaluated. In addition to antioxidant defense (SOD, catalase, glutathione), oxidative damage markers (TBARS and carbonylated protein), MMP-2 activity and liver histology.

RESULTS

Baccharis trimera promoted a decrease in ROS and NO, and at low concentrations promoted increased transcription of Nrf2. In the acute experiment it promoted increase of HDL, in the activity of SOD and GPx, besides diminishing TBARS and microesteatosis. Already in the chronic experiment B. trimera improved the hepatic and renal profile, decreased triglycerides and MMP-2 activity, in addition to diminishing microesteatosis.

CONCLUSION

We believe that B. trimera action is possibly more associated with direct neutralizing effects or inhibition of reactive species production pathways rather than the modulation of the antioxidant enzymes activity. Thus it is possible to infer that the biological effects triggered by adaptive responses are complex and multifactorial depending on the dose, the time and the compounds used.

Platelet Endothelial Cell Adhesion Molecule-1 and Oligodendrogenesis: Significance in Alcohol Use Disorders

Alcoholism is a chronic relapsing disorder with few therapeutic strategies that address the core pathophysiology. Brain tissue loss and oxidative damage are key components of alcoholism, such that reversal of these phenomena may help break the addictive cycle in alcohol use disorder (AUD). The current review focuses on platelet endothelial cell adhesion molecule 1 (PECAM-1), a key modulator of the cerebral endothelial integrity and neuroinflammation, and a targetable transmembrane protein whose interaction within AUD has not been well explored. The current review will elaborate on the function of PECAM-1 in physiology and pathology and infer its contribution in AUD neuropathology. Recent research reveals that oligodendrocytes, whose primary function is myelination of neurons in the brain, are a key component in new learning and adaptation to environmental challenges. The current review briefly introduces the role of oligodendrocytes in healthy physiology and neuropathology. Importantly, we will highlight the recent evidence of dysregulation of oligodendrocytes in the context of AUD and then discuss their potential interaction with PECAM-1 on the cerebral endothelium.

Hyper-oligodendrogenesis at the vascular niche and reduced blood-brain barrier integrity in the prefrontal cortex during protracted abstinence

Alcoholism is a relapsing disorder with limited treatment options, in part due to our limited understanding of the disease etiology. We have recently shown that increased ethanol-seeking in a behavioral model of relapse in a rat model of alcoholism was associated with increased oligodendrogenesis which was positively correlated with platelet/endothelial cell adhesion molecule (PECAM-1) expression in the medial prefrontal cortex (mPFC). The current study investigated whether newly born oligodendrocytes form close physical associations with endothelial cells expressing PECAM-1 and whether these changes were accompanied by altered blood-brain barrier (BBB) integrity. Colableling and confocal analysis demonstrate that newly born oligodendroglia were always located in close physical proximity to PECAM-1 in the mPFC of rats that were ethanol dependent and demonstrated high propensity for relapse. Notably, the endothelial proximity of new oligodendrocytes was associated with reduced expression of endothelial barrier antigen (SMI-71), a marker for BBB integrity. Furthermore, voluntary wheel running during abstinence enhanced SMI-71 expression in endothelial cells, indicating protection against abstinence-induced reduction in BBB integrity. Taken together, these results suggest that ethanol experience and abstinence disrupts homeostasis in the oligo-vascular niche in the mPFC. Reversing these mechanisms may hold the key to reducing propensity for relapse in individuals with moderate to severe alcohol use disorder.

Increased expression of M1 and M2 phenotypic markers in isolated microglia after four-day binge alcohol exposure in male rats

Microglia activation and neuroinflammation are common features of neurodegenerative conditions, including alcohol use disorders (AUDs). When activated, microglia span a continuum of diverse phenotypes ranging from classically activated, pro-inflammatory (M1) microglia/macrophages to alternatively activated, growth-promoting (M2) microglia/macrophages. Identifying microglia phenotypes is critical for understanding the role of microglia in the pathogenesis of AUDs. Therefore, male rats were gavaged with 25% (w/v) ethanol or isocaloric control diet every 8 h for 4 days and sacrificed at 0, 2, 4, and 7 days after alcohol exposure (e.g., T0, T2, etc.). Microglia were isolated from hippocampus and entorhinal cortices by Percoll density gradient centrifugation. Cells were labeled with microglia surface antigens and analyzed by flow cytometry. Consistent with prior studies, isolated cells yielded a highly enriched population of brain macrophages/microglia (>95% pure), evidenced by staining for the macrophage/microglia antigen CD11b. Polarization states of CD11b⁺CD45^low microglia were evaluated by expression of M1 surface markers, major histocompatibility complex (MHC) II, CD32, CD86, and M2 surface marker, CD206 (mannose receptor). Ethanol-treated animals begin to show increased expression of M1 and M2 markers at T0 (p = n.s.), with significant changes at the T2 time point. At T2, expression of M1 markers, MHC-II, CD86, and CD32 were increased (p < 0.05) in hippocampus and entorhinal cortices, while M2 marker, CD206, was increased significantly only in entorhinal cortices (p < 0.05). All effects resolved to control levels by T4. In summary, four-day binge alcohol exposure produces a transient increase in both M1 (MHC-II, CD32, and CD86) and M2 (CD206) populations of microglia isolated from the entorhinal cortex and hippocampus. Thus, these findings that both pro-inflammatory and potentially beneficial, recovery-promoting microglia phenotypes can be observed after a damaging exposure of alcohol are critically important to our understanding of the role of microglia in the pathogenesis of AUDs.

Activation of NLRP3 inflammasome by cholesterol crystals in alcohol consumption induces atherosclerotic lesions

Epidemiological studies showed a strong association between alcoholism and incidence of stroke, for which the underlying causative mechanisms remain to be understood. Here we found that infiltration of immune cells and deposition of cholesterol at the site of brain artery/capillary injury induced atherosclerosis in chronic alcohol (ethanol) consumption in the presence or absence of high-fat diet. Conversion of cholesterol into sharp edges of cholesterol crystals (CCs) in alcohol intake was key to activation of NLRP3 inflammasome, induction of cerebral atherosclerosis, and development of neuropathy around the atherosclerotic lesions. The presence of alcohol was critical for the formation of CCs and development of the neuropathology. Thus, we observed that alcohol consumption elevated the level of plasma cholesterol, deposition and crystallization of cholesterol, as well as activation of NLRP3 inflammasome. This led to arteriole or capillary walls thickening and increase intracranial blood pressure. Distinct neuropathy around the atherosclerotic lesions indicated vascular inflammation as an initial cause of neuronal degeneration. We demonstrated the molecular mechanisms of NLRP3 activation and downstream signaling cascade event in primary culture of human brain arterial/capillary endothelial cells in the setting of dose-/time-dependent effects of alcohol/CCs using NLRP3 gene silencing technique. We also detected CCs in blood samples from alcohol users, which validated the clinical importance of the findings. Finally, combined therapy of acetyl-l-carnitine and Lipitor® prevented deposition of cholesterol, formation of CCs, activation of NLRP3, thickening of vessel walls, and elevation of intracranial blood pressure. We conclude that alcohol-induced accumulation and crystallization of cholesterol activates NLRP3/caspase-1 in the cerebral vessel that leads to early development of atherosclerosis.

Immune activation and neuroinflammation in alcohol use and HIV infection: evidence for shared mechanisms

BACKGROUND

Emerging research points to innate immune mechanisms in the neuropathological and behavioral consequences of heavy alcohol use. Alcohol use is common among people living with HIV infection (PLWH), a chronic condition that carries its own set of long-term effects on brain and behavior. Notably, neurobiological and cognitive profiles associated with heavy alcohol use and HIV infection share several prominent features. This observation raises questions about interacting biological mechanisms as well as compounded impairment when HIV infection and heavy drinking co-occur.

OBJECTIVE AND METHOD

This narrative overview discusses peer-reviewed research on specific immune mechanisms of alcohol that exhibit apparent potential to compound the neurobiological and psychiatric sequelae of HIV infection. These include microbial translocation, systemic immune activation, blood-brain barrier compromise, microglial activation, and neuroinflammation.

RESULTS

Clinical and preclinical evidence supports overlapping mechanistic actions of HIV and alcohol use on peripheral and neural immune systems. In preclinical studies, innate immune signaling mediates many of the detrimental neurocognitive and behavioral effects of alcohol use. Neuropsychopharmacological research suggests potential for a feed-forward cycle in which heavy drinking induces innate immune signaling, which in turn stimulates subsequent alcohol use behavior.

CONCLUSION

Alcohol-induced immune activation and neuroinflammation are a serious health concern for PLWH. Future research to investigate specific immune effects of alcohol in the context of HIV infection has potential to identify novel targets for therapeutic intervention.

Effects of Ethanol on Brain Extracellular Matrix: Implications for Alcohol Use Disorder

The brain extracellular matrix (ECM) occupies the space between cells and is involved in cell-matrix and cell-cell adhesion. However, in addition to providing structural support to brain tissue, the ECM activates cell signaling and controls synaptic transmission. The expression and activity of brain ECM components are regulated by alcohol exposure. This review will discuss what is currently known about the effects of alcohol on the activity and expression of brain ECM components. An interpretation of how these changes might promote alcohol use disorder (AUD) will be also provided. Ethanol (EtOH) exposure decreases levels of structural proteins involved in the interstitial matrix and basement membrane, with a concomitant increase in proteolytic enzymes that degrade these components. In contrast, EtOH exposure generally increases perineuronal net components. Because the ECM has been shown to regulate both synaptic plasticity and behavioral responses to drugs of abuse, regulation of the brain ECM by alcohol may be relevant to the development of alcoholism. Although investigation of the function of brain ECM in alcohol abuse is still in early stages, a greater understanding of the interplay between ECM and alcohol might lead to novel therapeutic strategies for treating AUD.

Primary blast causes mild, moderate, severe and lethal TBI with increasing blast overpressures: Experimental rat injury model

Injury severity in blast induced Traumatic Brain Injury (bTBI) increases with blast overpressure (BOP) and impulse in dose-dependent manner. Pure primary blast waves were simulated in compressed gas shock-tubes in discrete increments. Present work demonstrates 24 hour survival of rats in 0–450 kPa (0–800 Pa∙s impulse) range at 10 discrete levels (60, 100, 130, 160, 190, 230, 250, 290, 350 and 420 kPa) and determines the mortality rate as a non-linear function of BOP. Using logistic regression model, predicted mortality rate (PMR) function was calculated, and used to establish TBI severities. We determined a BOP of 145 kPa as upper mild TBI threshold (5% PMR). Also we determined 146–220 kPa and 221–290 kPa levels as moderate and severe TBI based on 35%, and 70% PMR, respectively, while BOP above 290 kPa is lethal. Since there are no standards for animal bTBI injury severity, these thresholds need further refinements using histopathology, immunohistochemistry and behavior. Further, we specifically investigated mild TBI range (0–145 kPa) using physiological (heart rate), pathological (lung injury), immuno-histochemical (oxidative/nitrosative and blood-brain barrier markers) as well as blood borne biomarkers. With these additional data, we conclude that mild bTBI occurs in rats when the BOP is in the range of 85–145 kPa.

Role of Matrix Metalloproteinases in the Pathogenesis of Traumatic Brain Injury

Traumatic brain injury (TBI) is a major cause of mortality and morbidity worldwide. Studies revealed that the pathogenesis of TBI involves upregulation of MMPs. MMPs form a large family of closely related zinc-dependent endopeptidases, which are primarily responsible for the dynamic remodulation of the extracellular matrix (ECM). Thus, they are involved in several normal physiological processes like growth, development, and wound healing. During pathophysiological conditions, MMPs proteolytically degrade various components of ECM and tight junction (TJ) proteins of BBB and cause BBB disruption. Impairment of BBB causes leakiness of the blood from circulation to brain parenchyma that leads to microhemorrhage and edema. Further, MMPs dysregulate various normal physiological processes like angiogenesis and neurogenesis, and also they participate in the inflammatory and apoptotic cascades by inducing or regulating the specific mediators and their receptors. In this review, we explore the roles of MMPs in various physiological/pathophysiological processes associated with neurological complications, with special emphasis on TBI.

Alcohol exposure after mild focal traumatic brain injury impairs neurological recovery and exacerbates localized neuroinflammation

Traumatic brain injury (TBI) represents a leading cause of morbidity and mortality among young individuals. Alcohol abuse is a risk factor associated with increased TBI incidence. In addition, up to 26% of TBI patients engage in alcohol consumption after TBI. Limited preclinical studies have examined the impact of post-injury alcohol exposure on TBI recovery. The aim of this study was to determine the isolated and combined effects of TBI and alcohol on cognitive, behavioral, and physical recovery, as well as on associated neuroinflammatory changes. Male Sprague-Dawley rats (∼300g) were subjected to a mild focal TBI by lateral fluid percussion (∼30PSI, ∼25ms) under isoflurane anesthesia. On day 4 after TBI, animals were exposed to either sub-chronic intermittent alcohol vapor (95% ethanol 14h on/10h off; BAL∼200mg/dL) or room air for 10days. TBI induced neurological dysfunction reflected by an increased neurological severity score (NSS) showed progressive improvement in injured animals exposed to room air (TBI/air). In contrast, TBI animals exposed to alcohol vapor (TBI/alcohol) showed impaired NSS recovery throughout the 10-day period of alcohol exposure. Open-field exploration test revealed an increased anxiety-like behavior in TBI/alcohol group compared to TBI/air group. Additionally, alcohol-exposed animals showed decreased locomotion and impaired novel object recognition. Immunofluorescence showed enhanced reactive astrocytes, microglial activation, and HMGB1 expression localized to the injured cortex of TBI/alcohol as compared to TBI/air animals. The expression of neuroinflammatory markers showed significant positive correlation with NSS. These findings indicated a close relationship between accentuated neuroinflammation and impaired neurological recovery from post-TBI alcohol exposure. The clinical implications of long-term consequences in TBI patients exposed to alcohol during recovery warrant further investigation.

Alcohol, phospholipase A2-associated neuroinflammation, and ω3 docosahexaenoic acid protection

Chronic alcohol (ethanol) abuse causes neuroinflammation and brain damage that can give rise to alcoholic dementia. Insightfully, Dr. Albert Sun was an early proponent of oxidative stress as a key factor in alcoholism-related brain deterioration. In fact, oxidative stress has proven to be critical to the hippocampal and temporal cortical neurodamage resulting from repetitive "binge" alcohol exposure in adult rat models. Although the underlying mechanisms are uncertain, our immunoelectrophoretic and related assays in binge alcohol experiments in vivo (adult male rats) and in vitro (rat organotypic hippocampal-entorhinal cortical slice cultures) have implicated phospholipase A(2) (PLA(2))-activated neuroinflammatory pathways, release of pro-oxidative arachidonic acid (20:4 ω6), and elevated oxidative stress adducts (i.e., 4-hydroxynonenal-protein adducts). Also, significantly increased by the binge alcohol treatments was aquaporin-4 (AQP4), a water channel enriched in astrocytes that, when augmented, may trigger brain (esp. cellular) edema and neuroinflammation; of relevance, glial swelling is known to provoke increased PLA(2) activities or levels. Concomitant with PLA(2) activation, the results have further implicated binge alcohol-elevated poly (ADP-ribose) polymerase-1 (PARP-1), an oxidative stress-responsive DNA repair enzyme linked to parthanatos, a necrotic-like neuronal death process. Importantly, supplementation of the brain slice cultures with docosahexaenoic acid (22:6 ω3) exerted potent suppression of the induced changes in PLA(2) isoforms, AQP4, PARP-1 and oxidative stress footprints, and prevention of the binge alcohol neurotoxicity, by as yet unknown mechanisms. These neuroinflammatory findings from our binge alcohol studies and supportive rat binge studies in the literature are reviewed.

Alcohol induces sensitization to gluten in genetically susceptible individuals: a case control study

BACKGROUND

The mechanisms of cerebellar degeneration attributed to prolonged and excessive alcohol intake remain unclear. Additional or even alternative causes of cerebellar degeneration are often overlooked in suspected cases of alcohol-related ataxia. The objectives of this study were two fold: (1) to investigate the prevalence of gluten-related serological markers in patients with alcohol-related ataxia and; (2) to compare the pattern of brain involvement on magnetic resonance imaging between patients with alcohol and gluten ataxias.

MATERIALS & METHODS

Patients diagnosed with alcohol and gluten ataxias were identified from a retrospective review of patients attending a tertiary clinic. HLA genotype and serological markers of gluten-related disorders were recorded. Cerebellar volumetry, MR spectroscopy and voxel-based morphometric analyses were performed on patients and compared with matched control data.

RESULTS

Of 904 registered patients, 104 had alcohol ataxia and 159 had gluten ataxia. 61% of the alcohol ataxia group and 70% of the gluten ataxia group had HLA DQ2/DQ8 genotype compared to 30% in healthy local blood donors. 44% of patients with alcohol ataxia had antigliadin antibodies compared to 12% in the healthy local population and 10% in patients with genetically confirmed ataxias. None of the patients with alcohol ataxia and antigliadin antibodies had celiac disease compared to 40% in patients with gluten ataxia. The pattern of structural brain abnormality in patients with alcohol ataxia who had antigliadin antibodies differed from gluten ataxia and was identical to that of alcohol ataxia.

CONCLUSIONS

Alcohol related cerebellar degeneration may, in genetically susceptible individuals, induce sensitization to gluten. Such sensitization may result from a primary cerebellar insult, but a more systemic effect is also possible. The duration and amount of exposure to alcohol may not be the only factors responsible for the cerebellar insult.

Oxidative stress in aging--matters of the heart and mind

Oxidative damage is considered to be the primary cause of several aging associated disease pathologies. Cumulative oxidative damage tends to be pervasive among cellular macromolecules, impacting proteins, lipids, RNA and DNA of cells. At a systemic level, events subsequent to oxidative damage induce an inflammatory response to sites of oxidative damage, often contributing to additional oxidative stress. At a cellular level, oxidative damage to mitochondria results in acidification of the cytoplasm and release of cytochrome c, causing apoptosis. This review summarizes findings in the literature on oxidative stress and consequent damage on cells and tissues of the cardiovascular system and the central nervous system, with a focus on aging-related diseases that have well-documented evidence of oxidative damage in initiation and/or progression of the disease. The current understanding of the cellular mechanisms with a focus on macromolecular damage, impacted cellular pathways and gross morphological changes associated with oxidative damage is also reviewed. Additionally, the impact of calorific restriction with its profound impact on cardiovascular and neuronal aging is addressed.

Phospholipase A2, oxidative stress, and neurodegeneration in binge ethanol-treated organotypic slice cultures of developing rat brain

BACKGROUND

Brain neurodamage from chronic binge ethanol (EtOH) exposure is linked to neuroinflammation and associated oxidative stress. Using rat organotypic hippocampal-entorhinal cortical (HEC) slice cultures of developing brain age, we reported that binge EtOH promotes release of a neuroinflammatory instigator, arachidonic acid (AA), concomitant with neurodegeneration, and that mepacrine, a global inhibitor of phospholipase A2 (PLA2) enzymes mobilizing AA from phospholipids, is neuroprotective. Here, we sought with binge EtOH-treated HEC cultures to establish that PLA2 activity is responsible in part for significant oxidative stress and to ascertain the PLA2 families responsible for AA release and neurodegeneration.

METHODS

HEC slices, prepared from 1-week-old rats and cultured 2 to 2.5 weeks, were exposed to 100 mM EtOH over 6 successive days, with 4 daytime "withdrawals" (no EtOH). Brain 3-nitrotyrosinated (3-NT)- and 4-hydroxy-2-nonenal (4-HNE)-adducted proteins, oxidative stress footprints, were immunoassayed on days 3 through 6, and mepacrine's effect was determined on day 6. The effects of specific PLA2 inhibitors on neurodegeneration (propidium iodide staining) and AA release (ELISA levels in media) in the cultures were then determined. Also, the effect of JZL184, an inhibitor of monoacylglycerol lipase (MAGL) which is reported to mobilize AA from endocannabinoids during neuroinflammatory insults, was examined.

RESULTS

3-NT- and 4-HNE-adducted proteins were significantly increased by the binge EtOH exposure, consistent with oxidative stress, and mepacrine prevented the increases. The PLA2 inhibitor results implicated secretory PLA2 (group II sPLA2) and to some extent Ca(2+) -independent cytosolic PLA2 (group VI iPLA2) in binge EtOH-induced neurotoxicity and in AA release, but surprisingly, Ca(2+) -dependent cytosolic PLA2 (group IV cPLA2) did not appear important. Furthermore, unlike PLA2 inhibition, MAGL inhibition failed to prevent the neurodegeneration.

CONCLUSIONS

In these developing HEC slice cultures, pro-oxidative signaling via sPLA2 and iPLA2, but not necessarily cPLA2 or MAGL, is involved in EtOH neurotoxicity. This study provides further insights into neuroinflammatory phospholipase signaling and oxidative stress underlying binge EtOH-induced neurodegeneration in developing (adolescent age) brain in vitro.

Induction of oxidative and nitrosative damage leads to cerebrovascular inflammation in an animal model of mild traumatic brain injury induced by primary blast

We investigate the hypothesis that oxidative damage of the cerebral vascular barrier interface (the blood-brain barrier, BBB) causes the development of mild traumatic brain injury (TBI) during a primary blast-wave spectrum. The underlying biochemical and cellular mechanisms of this vascular layer-structure injury are examined in a novel animal model of shock tube. We first established that low-frequency (123kPa) single or repeated shock wave causes BBB/brain injury through biochemical activation by an acute mechanical force that occurs 6-24h after the exposure. This biochemical damage of the cerebral vasculature is initiated by the induction of the free radical-generating enzymes NADPH oxidase 1 and inducible nitric oxide synthase. Induction of these enzymes by shock-wave exposure paralleled the signatures of oxidative and nitrosative damage (4-HNE/3-NT) and reduction of the BBB tight-junction (TJ) proteins occludin, claudin-5, and zonula occluden 1 in the brain microvessels. In parallel with TJ protein disruption, the perivascular unit was significantly diminished by single or repeated shock-wave exposure coinciding with the kinetic profile. Loosening of the vasculature and perivascular unit was mediated by oxidative stress-induced activation of matrix metalloproteinases and fluid channel aquaporin-4, promoting vascular fluid cavitation/edema, enhanced leakiness of the BBB, and progression of neuroinflammation. The BBB leakiness and neuroinflammation were functionally demonstrated in an in vivo model by enhanced permeativity of Evans blue and sodium fluorescein low-molecular-weight tracers and the infiltration of immune cells across the BBB. The detection of brain cell proteins neuron-specific enolase and S100β in the blood samples validated the neuroastroglial injury in shock-wave TBI. Our hypothesis that cerebral vascular injury occurs before the development of neurological disorders in mild TBI was further confirmed by the activation of caspase-3 and cell apoptosis mostly around the perivascular region. Thus, induction of oxidative stress and activation of matrix metalloproteinases by shock wave underlie the mechanisms of cerebral vascular BBB leakage and neuroinflammation.

At low doses ethanol maintains blood-brain barrier (BBB) integrity after hypoxia and reoxygenation: a brain slice study

Post-ischemia ethanol (EtOH) treatments have been shown to exhibit neuroprotective effects in stroke. However, the mechanisms underlying these effects and those on blood-brain barrier (BBB) integrity have yet to be elucidated. In the present study, we determined whether administering differing concentrations of EtOH alter the expressions of BBB integral proteins, including aquaporins-4 and -9 (AQP-4, AQP-9), matrix metallopeptidases-2 and -9 (MMP-2, MMP-9), zonula occludens-1 (ZO-1), and basal lamina (laminin). We employed an organotypic brain slice culture model that utilizes oxygen-glucose deprivation followed by reoxygenation (OGD/R). Brain slices were obtained from 10-day-old Sprague-Dawley rats and divided into the following five groups (n = 8 subjects per group): (1) control, (2) hypoxia (OGD/R), no EtOH, (3) OGD/R and 10 mM EtOH, (4) OGD/R and 30 mM EtOH, and (5) OGD/R and 90 mM EtOH. To assess BBB integrity, levels of AQPs, MMPs, ZO-1, and laminin were determined by Western blot. Compared to control, OGD/R without EtOH significantly increased AQP-4, AQP-9, MMP-2, and MMP-9 levels, while decreasing ZO-1 and laminin levels. All EtOH concentration treatments (groups 3 through 5) significantly reduced the expressions of AQP-4, AQP-9, MMP-2, and MMP-9, compared to the OGD/R, non-alcohol treated slices. Furthermore, compared to the OGD/R without EtOH group, the 30 mM EtOH treatment significantly increased ZO-1 and laminin levels. In contrast, the 90 mM EtOH level neither enhanced the reduction in AQP and MMP levels nor increased ZO-1 or basal lamina expressions observed in the 30 mM treatment. In conclusion, at an optimal dose of 30 mM, EtOH improves the expressions of MMP-2, MMP-9, AQP-4, AQP-9, ZO-1, and basal laminin, previously altered by OGD/R. These effects may indicate a beneficial effect of EtOH on BBB integrity after stroke.

Nutraceutical strategies for ameliorating the toxic effects of alcohol

Rodent studies reveal that oxidative stress, much of it generated via induction/activation of NADPH oxidase, is a key mediator of a number of the pathogenic effects of chronic ethanol overconsumption. The highly reactive ethanol metabolite acetaldehyde is a key driver of this oxidative stress, and doubtless works in other ways to promote alcohol-induced pathology. Effective antioxidant measure may therefore be useful for mitigating the adverse health consequences of alcohol consumption; spirulina may have particular utility in this regard, as its chief phycochemical phycocyanobilin has recently been shown to function as an inhibitor of certain NADPH oxidase complexes, mimicking the physiological role of its chemical relatives biliverdin/bilirubin in this respect. Moreover, certain nutraceuticals, including taurine, pantethine, and lipoic acid, may have the potential to boost the activity of the mitochondrial isoform of aldehyde dehydrogenase, ALDH-2, accelerating conversion of acetaldehyde to acetate (which arguably has protective health effects). Little noticed clinical studies conducted nearly three decades ago reported that pre-ingestion of either taurine or pantethine could blunt the rise in blood acetaldehyde following ethanol consumption. Other evidence suggests that lipoic acid may function within mitochondria to maintain aldehyde dehydrogenase in a reduced active conformation; the impact of this agent on ethanol metabolism has however received little or no study. Studies evaluating the impact of nutracetical strategies on prevention of hangovers - which likely are mediated by acetaldehyde - may represent a quick, low-cost way to identify nutraceutical regimens that merit further attention for their potential impact on alcohol-induced pathology. Measures which boost or preserve ALDH-2 activity may also have important antioxidant potential, as this enzyme functions physiologically to protect cells from toxic aldehydes generated by oxidant stress.

Ethanol transiently suppresses choline-acetyltransferase in basal nucleus of Meynert slices

The cholinergic system plays a major role in learning and cognition and cholinergic neurons appear to be particularly vulnerable to ethanol (EtOH) exposure. There are conflicting results if EtOH directly damages cholinergic neurons. Thus, the aims of the present study were (1) to investigate the effect of different EtOH concentrations on cholinergic neurons in organotypic brain slices of the nucleus basalis of Meynert (nbM) and (2) to study if the most potent cholinotrophic substance nerve growth factor (NGF) or inhibitors of mitogen activated kinase (MAPK) p38- and nitric-oxide synthase (NOS)-pathways may counteract any EtOH effect. Two-week old organotypic rat brain slices of the nbM were exposed to 1–100 mM EtOH for 7 days with or without drugs and the number of choline-acetyltransferase (ChAT)-positive neurons was counted. Our data show that EtOH significantly reduced the number of ChAT-positive neurons with the most potent effect at a concentration of 50 mM EtOH (54 ± 5 neurons per slice, p < 0.001), compared to control slices (120 ± 13 neurons per slice). Inhibition of MAPK p38 (SB 203580, 10 μM) and NOS (L-thiocitrulline, 10 μM) counteracted the EtOH-induced decline of cholinergic neurons and NGF protected cholinergic neurons against the EtOH-induced effect. Withdrawal of EtOH resulted in a reversal of cholinergic neurons to nearly controls. In conclusion, EtOH caused a transient decline of cholinergic neurons, possibly involving MAPK p38- and NOS-pathways suggesting that EtOH does not induce direct cell death, but causes a transient downregulation of the cholinergic key enzyme, possibly reflecting a form of EtOH-associated plasticity.

The mechanisms of cerebral vascular dysfunction and neuroinflammation by MMP-mediated degradation of VEGFR-2 in alcohol ingestion

OBJECTIVE

Blood-brain barrier (BBB) dysfunction caused by activation of matrix metalloproteinases (MMPs) is a pathological feature in vascular/neurological disease. We describe the mechanisms of BBB dysfunction and neuroinflammation as a result of MMP-3/9 activation and disruption of vascular endothelial growth factor (VEGF)-A/VEGFR-2 interaction, impairing effective angiogenesis.

METHODS AND RESULTS

We investigate the hypothesis in human brain endothelial cells and animal model of chronic alcohol ingestion. Proteome array analysis, zymography, immunofluorescence, and Western blotting techniques detected the activation, expression, and levels of MMP-3 and MMP-9. We found that degradation of VEGFR-2 and BBB proteins, for example, occludin, claudin-5, and ZO-1 by MMP-3/9, causes rupture of capillary endothelium and BBB leakiness. Impairment of BBB integrity was demonstrated by increased permeability of dye tracers and Fluo-3/calcein-AM-labeled monocyte adhesion or infiltration and decrease in transendothelial electric resistance. Alcohol-induced degradation of endothelial VEGFR-2 by MMP-3/9 led to a subsequent elevation of cellular/serum VEGF-A level. The decrease in VEGFR-2 with subsequent increase in VEGF-A level led to apoptosis and neuroinflammation via the activation of caspase-1 and IL-1β release. The use of MMPs, VEGFR-2, and caspase-1 inhibitors helped to dissect the underlying mechanisms.

CONCLUSIONS

Alcohol-induced MMPs activation is a key mechanism for dysfunction of BBB via degradation of VEGFR-2 protein and activation of caspase-1 or IL-1β release. Targeting VEGF-induced MMP-3/9 activation can be a novel preventive approach to vascular inflammatory disease in alcohol abuse.

Stabilization of superoxide dismutase by acetyl-l-carnitine in human brain endothelium during alcohol exposure: novel protective approach

Oxidative damage of the endothelium disrupts the integrity of the blood-brain barrier (BBB). We have shown before that alcohol exposure increases the levels of reactive oxygen species (ROS; superoxide and hydroxyl radical) and nitric oxide (NO) in brain endothelial cells by activating NADPH oxidase and inducible nitric oxide synthase. We hypothesize that impairment of antioxidant systems, such as a reduction in catalase and superoxide dismutase (SOD) activity, by ethanol exposure may elevate the levels of ROS/NO in endothelium, resulting in BBB damage. This study examines whether stabilization of antioxidant enzyme activity results in suppression of ROS levels by anti-inflammatory agents. To address this idea, we determined the effects of ethanol on the kinetic profile of SOD and catalase activity and ROS/NO generation in primary human brain endothelial cells (hBECs). We observed an enhanced production of ROS and NO levels due to the metabolism of ethanol in hBECs. Similar increases were found after exposure of hBECs to acetaldehyde, the major metabolite of ethanol. Ethanol simultaneously augmented ROS generation and the activity of antioxidative enzymes. SOD activity was increased for a much longer period of time than catalase activity. A decline in SOD activity and protein levels preceded elevation of oxidant levels. SOD stabilization by the antioxidant and mitochondria-protecting agent acetyl-L-carnitine (ALC) and the anti-inflammatory agent rosiglitazone suppressed ROS levels, with a marginal increase in NO levels. Mitochondrial membrane protein damage and decreased membrane potential after ethanol exposure indicated mitochondrial injury. These changes were prevented by ALC. Our findings suggest the counteracting mechanisms of oxidants and antioxidants during alcohol-induced oxidative stress at the BBB. The presence of enzymatic stabilizers favors the ROS-neutralizing antioxidant redox of the BBB, suggesting an underlying protective mechanism of NO for brain vascular tone and vasodilation.

Neuroinflammatory pathways in binge alcohol-induced neuronal degeneration: oxidative stress cascade involving aquaporin, brain edema, and phospholipase A2 activation

Chronic binge alcohol exposure in adult rat models causes neuronal degeneration in the cortex and hippocampus that is not reduced by excitotoxic receptor antagonists, but is prevented by antioxidants. Neuroinflammatory (glial-neuronal) signaling pathways are believed to underlie the oxidative stress and brain damage. Based on our experimental results as well as increased knowledge about the pro-neuroinflammatory potential of glial water channels, we propose that induction of aquaporin-4 can be a critical initiating factor in alcohol's neurotoxic effects, through the instigation of cellular edema-based neuroinflammatory cascades involving increased phospholipase A2 activities, polyunsaturated fatty acid release/membrane depletion, decreased prosurvival signaling, and oxidative stress. A testable scheme for this pathway is presented that incorporates recent findings in the alcohol-brain literature indicating a role for neuroimmune activation (upregulation of NF-kappaB, proinflammatory cytokines, and toll-like receptors). We present the argument that such neuroimmune activation could be associated with or even dependent on increased aquaporin-4 and glial swelling as well.

Infectious prion protein alters manganese transport and neurotoxicity in a cell culture model of prion disease

Protein misfolding and aggregation are considered key features of many neurodegenerative diseases, but biochemical mechanisms underlying protein misfolding and the propagation of protein aggregates are not well understood. Prion disease is a classical neurodegenerative disorder resulting from the misfolding of endogenously expressed normal cellular prion protein (PrP(C)). Although the exact function of PrP(C) has not been fully elucidated, studies have suggested that it can function as a metal binding protein. Interestingly, increased brain manganese (Mn) levels have been reported in various prion diseases indicating divalent metals also may play a role in the disease process. Recently, we reported that PrP(C) protects against Mn-induced cytotoxicity in a neural cell culture model. To further understand the role of Mn in prion diseases, we examined Mn neurotoxicity in an infectious cell culture model of prion disease. Our results show CAD5 scrapie-infected cells were more resistant to Mn neurotoxicity as compared to uninfected cells (EC(50)=428.8 μM for CAD5 infected cells vs. 211.6 μM for uninfected cells). Additionally, treatment with 300 μM Mn in persistently infected CAD5 cells showed a reduction in mitochondrial impairment, caspase-3 activation, and DNA fragmentation when compared to uninfected cells. Scrapie-infected cells also showed significantly reduced Mn uptake as measured by inductively coupled plasma-mass spectrometry (ICP-MS), and altered expression of metal transporting proteins DMT1 and transferrin. Together, our data indicate that conversion of PrP to the pathogenic isoform enhances its ability to regulate Mn homeostasis, and suggest that understanding the interaction of metals with disease-specific proteins may provide further insight to protein aggregation in neurodegenerative diseases.