Alcohol-Induced Blood-Brain Barrier Impairment: An In Vitro Study

The role of reactive oxygen species in the regulation of the blood-brain barrier

The blood-brain barrier (BBB) regulates the exchange of metabolites and cells between the blood and brain, and maintains central nervous system homeostasis. Various factors affect BBB barrier functions, including reactive oxygen species (ROS). ROS can act as stressors, damaging biological molecules, but they also serve as secondary messengers in intracellular signaling cascades during redox signaling. The impact of ROS on the BBB has been observed in multiple sclerosis, stroke, trauma, and other neurological disorders, making blocking ROS generation a promising therapeutic strategy for BBB dysfunction. However, it is important to consider ROS generation during normal BBB functioning for signaling purposes. This review summarizes data on proteins expressed by BBB cells that can be targets of redox signaling or oxidative stress. It also provides examples of signaling molecules whose impact may cause ROS generation in the BBB, as well as discusses the most common diseases associated with BBB dysfunction and excessive ROS generation, open questions that arise in the study of this problem, and possible ways to overcome them.

Neuroinflammatory Responses and Blood-Brain Barrier Injury in Chronic Alcohol Exposure: Role of Purinergic P2X7 Receptor Signaling

Alcohol consumption leads to neuroinflammation and blood-brain barrier (BBB) damage, resulting in neurological impairment. We previously demonstrated that ethanol-induced disruption of barrier function in human brain endothelial cells was associated with mitochondrial injury, increased ATP and extracellular vesicle (EV) release, and purinergic receptor P2X7R activation. Therefore, we aimed to evaluate the effect of P2X7r blockade on peripheral and neuro-inflammation in EtOH-exposed mice. In a chronic intermittent ethanol (CIE)-exposed mouse model, P2X7R was inhibited by two different methods: Brilliant Blue G (BBG) or gene knockout. We assessed blood ethanol concentration (BEC), plasma P2X7R and P-gp, number of extra-cellular vesicles (EV), serum ATP and EV-ATP levels. Brain microvessel gene expression and EV mtDNA copy numbers were measured by RT2 PCR array and digital PCR, respectively. A RT2 PCR array of brain microvessels revealed significant upregulation of proinflammatory genes involved in apoptosis, vasodilation, and platelet activation in CIE-exposed animals, which were decreased 15-50-fold in BBG-treated CIE-exposed animals. Plasma P-gp levels and serum P2X7R shedding were significantly increased in CIE-exposed animals. Pharmacological or genetic suppression of P2X7R decreased P2X7R shedding to levels equivalent to those in control group. The increase in EV number and EV-ATP content in the CIE-exposed mice was significantly reduced by P2X7R inhibition. CIE mice showed augmented EV-mtDNA copy numbers which were reduced in EVs after P2X7R inhibition or receptor knockout. These observations suggested that P2X7R signaling plays a critical role in ethanol-induced brain injury. Increased eATP, EV-ATP, EV numbers, and EV-mtDNA copy numbers highlight a new mechanism of brain injury during alcohol exposure via P2X7R and biomarkers of such damage. In this study, for the first time, we report the in vivo involvement of P2X7R signaling in CIE-induced brain injury.

Alcohol and stress exposure across the lifespan are key risk factors for Alzheimer's Disease and cognitive decline

Alzheimer's Disease and related dementias (ADRD) are an increasing threat to global health initiatives. Efforts to prevent the development of ADRD require understanding behaviors that increase and decrease risk of neurodegeneration and cognitive decline, in addition to uncovering the underlying biological mechanisms behind these effects. Stress exposure and alcohol consumption have both been associated with increased risk for ADRD in human populations. However, our ability to understand causal mechanisms of ADRD requires substantial preclinical research. In this review, we summarize existing human and animal research investigating the connections between lifetime stress and alcohol exposures and ADRD.

Decreased expression of CD200 on peripheral blood leukocytes in alcohol dependence

Chronic alcohol use induces innate immune genes, which activate the innate immune system. Neuroimmune regulatory proteins [e.g., Cluster of Differentiation 200 (CD200)] are immune response regulators and are involved in balancing the immune response. This study aimed to investigate the expression of CD200 on the surface of peripheral blood leukocytes in patients with alcohol use disorder and compare them with controls. Fifty male patients with alcohol use disorder were included in the study. A baseline assessment was done, and alcohol use history, craving, and withdrawal scores were collected. A 2-mL venous blood sample was collected from cases and controls for immunophenotyping of CD200. The control group consisted of 50 participants with similar socio-economic backgrounds. The cellular expression of CD200 on total leukocytes (median ± IQR) [39.94 (28.85, 50.01)] in cases was significantly lower compared to controls [45.07 (37.70, 51.69)] (U = 896, p = 0.015). Expression of CD200 on lymphocytes in cases was negatively correlated with years of heavy drinking and this was statistically significant (r = -0.321, p = 0.023). The study indicates that cellular expression of CD200 on the surface of peripheral blood leukocytes is reduced in alcohol-dependent patients. This reduction can contribute to exaggerated immune activity, release of pro-inflammatory cytokines, chronic microglial activation, neuroinflammation, and neurodegeneration in alcohol dependence.

Mechanisms of Cadmium Neurotoxicity

Cadmium is a heavy metal that increasingly contaminates food and drink products. Once ingested, cadmium exerts toxic effects that pose a significant threat to human health. The nervous system is particularly vulnerable to prolonged, low-dose cadmium exposure. This review article provides an overview of cadmium's primary mechanisms of neurotoxicity. Cadmium gains entry into the nervous system via zinc and calcium transporters, altering the homeostasis for these metal ions. Once within the nervous system, cadmium disrupts mitochondrial respiration by decreasing ATP synthesis and increasing the production of reactive oxygen species. Cadmium also impairs normal neurotransmission by increasing neurotransmitter release asynchronicity and disrupting neurotransmitter signaling proteins. Cadmium furthermore impairs the blood-brain barrier and alters the regulation of glycogen metabolism. Together, these mechanisms represent multiple sites of biochemical perturbation that result in cumulative nervous system damage which can increase the risk for neurological and neurodegenerative disorders. Understanding the way by which cadmium exerts its effects is critical for developing effective treatment and prevention strategies against cadmium-induced neurotoxic insult.

The blood-brain barrier, a key bridge to treat neurodegenerative diseases

As a highly selective and semi-permeable barrier that separates the circulating blood from the brain and central nervous system (CNS), the blood-brain barrier (BBB) plays a critical role in the onset and treatment of neurodegenerative diseases (NDs). To delay or reverse the NDs progression, the dysfunction of BBB should be improved to protect the brain from harmful substances. Simultaneously, a highly efficient drug delivery across the BBB is indispensable. Here, we summarized several methods to improve BBB dysfunction in NDs, including knocking out risk geneAPOE4, regulating circadian rhythms, restoring the gut microenvironment, and activating the Wnt/β-catenin signaling pathway. Then we discussed the advances in BBB penetration techniques, such as transient BBB opening, carrier-mediated drug delivery, and nasal administration, which facilitates drug delivery across the BBB. Furthermore, various in vivo and in vitro BBB models and research methods related to NDs are reviewed. Based on the current research progress, the treatment of NDs in the long term should prioritize the integrity of the BBB. However, a treatment approach that combines precise control of transient BBB permeability and non-invasive targeted BBB drug delivery holds profound significance in improving treatment effectiveness, safety, and clinical feasibility during drug therapy. This review involves the cross application of biology, materials science, imaging, engineering and other disciplines in the field of BBB, aiming to provide multi-dimensional research directions and clinical ideas for the treating NDs.

Morphological and Functional Effects of Ultrasound on Blood-Brain Barrier Transitory Opening: An In Vitro Study on Rat Brain Endothelial Cells

With the recent advances in medicine, human life expectancy is increasing; however, the extra years of life are not necessarily spent in good health or free from disability, resulting in a significantly higher incidence of age-associated pathologies. Among these disorders, neurodegenerative diseases have a significant impact. To this end, the presence of the protective blood-brain barrier (BBB) represents a formidable obstacle to the delivery of therapeutics. Thus, this makes it imperative to define strategies to bypass the BBB in order to successfully target the brain with the appropriate drugs. It has been demonstrated that targeting the BBB by ultrasound (US) can transiently make this anatomical barrier permeable and in so doing, allow the delivery of therapeutics. Thus, our aim was to carry out an in depth in vitro molecular and morphological study on the effects of US treatment on the BBB. The rat brain endothelial (RBE4) cell line was challenged with exposure to 12 MHz diagnostic US treatment for 10, 20, and 30 min. Cell viability assays, Western blotting analysis on the endoplasmic reticulum (ER), and oxidative stress marker evaluation were then performed, along with cytological and immunofluorescence staining, in order to evaluate the effects of US on the intercellular spaces and tight junction distribution of the brain endothelial cells. We observed that the US treatment exerted no toxic effects on either RBE4 cell viability or the upregulation/dislocation of the ER and oxidative stress marker (GRP78 and cytochrome C, respectively). Further, we observed that the application of US induced an increase in the intercellular spaces, as shown by Papanicolaou staining, mainly due to the altered distribution of the tight junction protein zonula occludens-1 (ZO-1). This latter US-dependent effect was transient and disappeared 20 min after the removal of the stimulus. In conclusion, our results show that US induces a transient alteration of the BBB, without altering the intracellular signaling pathways such as the ER and oxidative stress that could potentially be toxic for endothelial cells. These results suggested that US treatment could represent a potential strategy for improving drug delivery to the brain.

Environmental exposure of the general population to cadmium as a risk factor of the damage to the nervous system: A critical review of current data

Nowadays, more and more attention has been focused on the risk of the neurotoxic action of cadmium (Cd) under environmental exposure. Due to the growing incidence of nervous system diseases, including neurodegenerative changes, and suggested involvement of Cd in their aetiopathogenesis, this review aimed to discuss critically this element neurotoxicity. Attempts have been made to recognize at which concentrations in the blood and urine Cd may increase the risk of damage to the nervous system and compare it to the risk of injury of other organs and systems. The performed overview of the available literature shows that Cd may have an unfavourable impact on the human's nervous system at the concentration >0.8 μg Cd/L in the urine and >0.6 μg Cd/L in the blood. Because such concentrations are currently noted in the general population of industrialized countries, it can be concluded that environmental exposure to this xenobiotic may create a risk of damage to the nervous system and be involved in the aetiopathogenesis of neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease, as well as worsening cognitive and behavioural functions. The potential mechanism of Cd neurotoxicity consists in inducing oxidative stress, disrupting the activity of enzymes essential to the proper functioning of the nervous system and destroying the homoeostasis of bioelements in the brain. Thus, further studies are necessary to recognize accurately both the risk of nervous system damage in the general population due to environmental exposure to Cd and the mechanism of this action.

Effect of drug use in the treatment of acute ischemic stroke: A scoping review

Background:

Drugs of abuse have been associated with ischemic stroke; however, the clinical presentation, outcomes, and treatment data in this population are limited. The overall safety and efficacy of thrombolytic therapy and thrombectomy in these patients remain unclear. This scoping review summarizes published complications and clinical outcomes in patients with recent abuse of cocaine, methamphetamine (MA), cannabis, decongestant, opioids, alcohol, and 3,4-methylenedioxymethamphetamine (MDMA) presenting with acute ischemic stroke.

Methods:

We conducted a scoping review of the primary literature that assessed outcomes data of thrombolytic therapy or thrombectomy in drug users with acute ischemic stroke. We searched PubMed, Ovid Medline, and Web of Science. Demographic and stroke characteristics, treatment, complications, and clinical outcomes at last follow-up were collected and summarized.

Results:

We identified 51 studies in this review. Drugs of abuse of interest were cocaine (14 studies), MDMA (one study), MA (eight studies), cannabis (23 studies), alcohol (two studies), decongestants (one study), and opioids (two studies). Clinical presentation and stroke presentation were most commonly described features. Thrombectomy outcomes were reported for four patients total (two studies), all with history of cocaine use. Thrombolysis treatment and outcomes were reported for 8851 patients (five studies) with history of cocaine, alcohol, or cannabis. Both treatments were pursued in three patients (three studies). Treatment complications included intracerebral hemorrhage, vasospasm, and cerebral edema.

Conclusion:

Evidence for thrombolytic and thrombectomy treatment in drug users remains limited. Controlled studies are needed to examine complication profile and outcomes following thrombolytic and thrombectomy treatment in this population.

The Molecular Mechanisms of Ferroptosis and Its Role in Blood-Brain Barrier Dysfunction

The blood-brain barrier (BBB) is a selective, semi-permeable layer of endothelial cells that protects the central nervous system from harmful substances circulating in blood. It is one of the important barriers of the nervous system. BBB dysfunction is an early pathophysiological change observed in nervous system diseases. There are few treatments for BBB dysfunction, so this motivates the review. Ferroptosis is a novel cell death mode caused by iron-mediated lipid peroxidation accumulation, which has recently attracted more attention due to its possible role in nervous system disorders. Studies have shown that lipid peroxidation and iron accumulation are related to the barrier dysfunction, especially the expression of tight junction proteins. Therefore, examination of the relationship between ferroptosis and BBB dysfunction may reveal new targets for the treatment of brain diseases.

The Protection of Zinc against Acute Cadmium Exposure: A Morphological and Molecular Study on a BBB In Vitro Model

Cadmium (Cd) is a well-known occupational and environmental pollutant worldwide, and its toxicity is widely recognised. Cd is reported to increase the permeability of the blood–brain barrier (BBB) and to penetrate and accumulate in the brain. Although many lines of evidence show that Cd toxicity is induced by different mechanisms, one of the best known is the Cd-dependent production of reactive oxygen species (ROS). Zinc is a trace element known as coenzyme and cofactor for many antioxidant proteins, such as metallothioneins and superoxide dismutase enzymes. To date, very little is known about the role of Zn in preventing Cd-induced blood–brain barrier (BBB) alterations. The goal of this study was to test the Zn antioxidant capacity against Cd-dependent alterations in a rat brain endothelial cell line (RBE4), as an in vitro model for BBB. In order to mimic acute Cd poisoning, RBE4 cells were treated with CdCl₂ 30 µM for 24 h. The protective role of ZnCl₂ (50 µM) was revealed by evaluating the cell viability, reactive oxygen species (ROS) quantification, cytochrome C distribution, and the superoxide dismutase (SOD) protein activity. Additionally, the effectiveness of Zn in counteracting the Cd-induced damage was investigated by evaluating the expression levels of proteins already known to be involved in the Cd signalling pathway, such as GRP78 (an endoplasmic reticulum (ER) stress protein), caspase3 pro- and cleaved forms, and BAX. Finally, we evaluated if Zn was able to attenuate the alterations of zonula occludens-1 (ZO-1), one of the tight-junction (TJ) proteins involved in the formation of the BBB. Our data clearly demonstrate that Zn, by protecting from the SOD activity impairment induced by Cd, is able to prevent the triggering of the Cd-dependent signalling pathway that leads to ZO-1 dislocation and downregulation, and BBB damage.

Alcohol-Induced Alterations in the Vascular Basement Membrane in the Substantia Nigra of the Adult Human Brain

The blood–brain barrier (BBB) represents a highly specialized interface that acts as the first line of defense against toxins. Herein, we investigated the structural and ultrastructural changes in the basement membrane (BM), which is responsible for maintaining the integrity of the BBB, in the context of chronic alcoholism. Human post-mortem tissues from the Substantia Nigra (SN) region were obtained from 44 individuals, then grouped into controls, age-matched alcoholics, and non-age-matched alcoholics and assessed using light and electron microscopy. We found significantly less CD31+ vessels in alcoholic groups compared to controls in both gray and white matter samples. Alcoholics showed increased expression levels of collagen-IV, laminin-111, and fibronectin, which were coupled with a loss of BM integrity in comparison with controls. The BM of the gray matter was found to be more disintegrated than the white matter in alcoholics, as demonstrated by the expression of both collagen-IV and laminin-111, thereby indicating a breakdown in the BM’s structural composition. Furthermore, we observed that the expression of fibronectin was upregulated in the BM of the white matter vasculature in both alcoholic groups compared to controls. Taken together, our findings highlight some sort of aggregation or clumping of BM proteins that occurs in response to chronic alcohol consumption.

Chronic Alcohol Exposure Alters Gene Expression and Neurodegeneration Pathways in the Brain of Adult Mice

BACKGROUND

Chronic alcohol consumption can alter the structure of the central nervous system and disrupt cognitive function. Alcoholics are more likely to develop neurodegenerative disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD). However, the role of alcohol in promoting neurotoxicity and neurodegeneration remains unclear.

OBJECTIVE

In this study, we aimed at estimating the effects of chronic binge alcohol exposure on brain transcriptome and behavior changes in a chronic "Drinking in the Dark" (DID) mouse model.

METHODS

The adult C57BL/6J male mice were exposed to alcohol for 4 weeks. RNA-seq was applied to assess the effects of chronic alcohol exposure on transcriptome in brain. The open field test and novel object recognition test were used to assess the changes of anxiety level, locomotive function, and short-term memory induced by alcohol. RNA-seq analysis revealed that chronic alcohol exposure caused significant change in the brain transcriptome, especially in prefrontal cortex.

RESULTS

The gene dysregulation caused by chronic alcohol exposure includes pathways related to mitochondrial energy metabolism (such as oxidative phosphorylation) and multiple neurodegenerative diseases (such as AD and PD). Furthermore, the pathway and network analyses suggest that the genes involved in mitochondrial energy metabolism, ubiquitin-proteasome system, Wnt signaling pathway, and microtubules may attribute to the neurotoxicity and neurodegeneration caused by chronic alcohol consumption. Additionally, locomotive function was also significantly impaired.

CONCLUSION

This work provides gene transcriptional profile data for future research on alcohol-induced neurodegenerative diseases, especially AD and PD.

Differential effects of alcohol-drinking patterns on the structure and function of the brain and cognitive performance in young adult drinkers: A pilot study

INTRODUCTION

This study was aimed to determine how different patterns of alcohol consumption drive changes to brain structure and function and their correlation with cognitive impairments in young adult alcohol drinkers.

METHODS

In this study, we enrolled five groups participants and defined as: long-term abstinence from alcohol (LA), binge drinking (BD), long-term low dosage alcohol consumption but exceeding the safety drinking dosage (LD), long-term alcohol consumption of damaging dosage (LDD), and long-term heavy drinking (HD). All participants underwent magnetic resonance imaging (MRI) and functional MRI (fMRI) to acquire data on brain structure and function, including gray matter volume (GMV), fractional amplitude of low-frequency fluctuation (fALFF), regional homogeneity (ReHo), functional connectivity (FC), and brain network properties. The cognitive ability was evaluated with the California Verbal Learning Test (CVLT), intelligence quotient (IQ), and short delay free recall (SDFR).

RESULTS

Compared to LA, GMV significantly decreased in the brain regions in VN, SMN, and VAN in the alcohol-drinking groups (BD, LD, LDD, and HD). ReHo was significantly enhanced in the brain regions in VN, SMN, and VAN, while fALFF significantly increased in the brain regions in VN and SMN. The number of intra- and inter-modular connections within networks (VN, SMN, sensory control network [SCN], and VAN) and their connections to other modules were abnormally changed. These changes adversely affected cognition (e.g., IQ, CVLT, SDFR).

CONCLUSION

Despite the small sample size, this study provides new evidence supporting the need for young people to abstain from alcohol to protect their brains. These findings present strong reasoning for updating anti-alcohol slogans and guidelines for young people in the future.

Blood-Spinal Cord Barrier: Its Role in Spinal Disorders and Emerging Therapeutic Strategies

The blood-spinal cord barrier (BSCB) has been long thought of as a functional equivalent to the blood-brain barrier (BBB), restricting blood flow into the spinal cord. The spinal cord is supported by various disc tissues that provide agility and has different local immune responses compared to the brain. Though physiologically, structural components of the BSCB and BBB share many similarities, the clinical landscape significantly differs. Thus, it is crucial to understand the composition of BSCB and also to establish the cause–effect relationship with aberrations and spinal cord dysfunctions. Here, we provide a descriptive analysis of the anatomy, current techniques to assess the impairment of BSCB, associated risk factors and impact of spinal disorders such as spinal cord injury (SCI), amyotrophic lateral sclerosis (ALS), peripheral nerve injury (PNI), ischemia reperfusion injury (IRI), degenerative cervical myelopathy (DCM), multiple sclerosis (MS), spinal cavernous malformations (SCM) and cancer on BSCB dysfunction. Along with diagnostic and mechanistic analyses, we also provide an up-to-date account of available therapeutic options for BSCB repair. We emphasize the need to address BSCB as an individual entity and direct future research towards it.

Antioxidant support to ameliorate the oxaliplatin-dependent microglial alteration: morphological and molecular study

Oxaliplatin is a third-generation chemotherapy drug mainly used for colorectal cancer treatment. However, it is also known to trigger neuropathy whose underlying neurobiological mechanisms are still under investigation and currently available treatments show limited efficacy. It is now established that neurons are not the only cell type involved in chronic pain and that glial cells, mainly astrocytes and microglia, are involved in the initiation and maintenance of neuropathy. Among all the pathogenetic factors involved in neuropathic pain, an oxaliplatin-dependent oxidative stress plays a predominant role. In our study, the antioxidant properties of magnesium (Mg), manganese (Mn) and zinc (Zn) salts were evaluated in order to counteract microglial activation induced by oxaliplatin. The antioxidant efficacy of these metals was evaluated by the means of molecular and morphological assays on the BV-2 microglial cell line. Our data clearly show that Mg, Mn and Zn are able to prevent oxaliplatin-dependent microglial alterations by reducing both oxidative and endoplasmic reticulum stress.