Increased TUNEL positive cells in human alcoholic brains

Disentangling the contributions of alcohol use disorder and alcohol-related liver disease towards dementia: A population-based cohort study

AIMS

The aim of the study was to disentangle the contributions of alcohol and alcohol-related liver disease (ALD) towards dementia by independently measuring the association between alcohol use disorder (AUD) alone and ALD with dementia.

DESIGN

This was a nation-wide cohort study.

SETTING

The study was conducted in Sweden from 1987 to 2020.

PARTICIPANTS

DELIVER (DEcoding the epidemiology of LIVER disease in Sweden) cohort, containing administrative codes on patients with chronic liver disease from the National Patient Register and other registers between 1987 and 2020.

MEASUREMENTS

International Classification of Disease 9th (ICD-9) and 10th (ICD-10) version codes were used to define the presence of AUD, ALD and dementia. The associations of AUD alone and ALD with incident dementia were estimated using Cox regression models adjusting for potential confounders. Cumulative incidences were also calculated accounting for competing risks of death.

FINDINGS

A total of 128 884 individuals with AUD alone, 17 754 with ALD and 2 479 049 controls were identified. During a median follow-up of 8.9 years, 13 395 (10.4%), 2187 (12.3%) and 138 925 (5.6%) dementia cases were identified in these groups, respectively. Dementia rates were increased in AUD alone [adjusted hazard ratio (aHR) = 4.6, 95% confidence interval (CI) = 4.5-4.6] and in ALD (aHR = 8.6, 95% CI = 8.3-9.0) compared with controls. AUD alone was also associated with increased rates of vascular dementia (aHR = 2.3, 95% CI = 2.2-2.5) and Alzheimer's disease (aHR = 1.4, 95% CI = 1.3-1.4), while ALD was only associated with vascular dementia (aHR = 2.7, 95% CI = 2.3-3.2). The median age at dementia diagnosis was 67 years [interquartile range (IQR) = 56-76] in AUD alone and 63 years (IQR = 56-71) in ALD compared with 85 years (IQR = 79-89) in controls.

CONCLUSION

In Sweden, patients with alcohol use disorder (AUD) appear to have increased rates of dementia and diagnosis at a younger age, compared with patients without AUD. Concurrent alcohol-related liver disease appears to increase the diagnosis rate and lower the median age further.

Binge ethanol exposure in advanced age elevates neuroinflammation and early indicators of neurodegeneration and cognitive impairment in female mice

Binge drinking is rising among aged adults (>65 years of age), however the contribution of alcohol misuse to neurodegenerative disease development is not well understood. Both advanced age and repeated binge ethanol exposure increase neuroinflammation, which is an important component of neurodegeneration and cognitive dysfunction. Surprisingly, the distinct effects of binge ethanol exposure on neuroinflammation and associated degeneration in the aged brain have not been well characterized. Here, we establish a model of intermittent binge ethanol exposure in young and aged female mice to investigate the effects of advanced age and binge ethanol on these outcomes. Following intermittent binge ethanol exposure, expression of pro-inflammatory mediators (tnf-α, il-1β, ccl2) was distinctly increased in isolated hippocampal tissue by the combination of advanced age and ethanol. Binge ethanol exposure also increased measures of senescence, the nod like receptor pyrin domain containing 3 (NLRP3) inflammasome, and microglia reactivity in the brains of aged mice compared to young. Binge ethanol exposure also promoted neuropathology in the hippocampus of aged mice, including tau hyperphosphorylation and neuronal death. We further identified advanced age-related deficits in contextual memory that were further negatively impacted by ethanol exposure. These data suggest binge drinking superimposed with advanced age promotes early markers of neurodegenerative disease development and cognitive decline, which may be driven by heightened neuroinflammatory responses to ethanol. Taken together, we propose this novel exposure model of intermittent binge ethanol can be used to identify therapeutic targets to prevent advanced age- and ethanol-related neurodegeneration.

Crossroads of Drug Abuse and HIV Infection: Neurotoxicity and CNS Reservoir

Drug abuse is a common comorbidity in people infected with HIV. HIV-infected individuals who abuse drugs are a key population who frequently experience suboptimal outcomes along the HIV continuum of care. A modest proportion of HIV-infected individuals develop HIV-associated neurocognitive issues, the severity of which further increases with drug abuse. Moreover, the tendency of the virus to go into latency in certain cellular reservoirs again complicates the elimination of HIV and HIV-associated illnesses. Antiretroviral therapy (ART) successfully decreased the overall viral load in infected people, yet it does not effectively eliminate the virus from all latent reservoirs. Although ART increased the life expectancy of infected individuals, it showed inconsistent improvement in CNS functioning, thus decreasing the quality of life. Research efforts have been dedicated to identifying common mechanisms through which HIV and drug abuse lead to neurotoxicity and CNS dysfunction. Therefore, in order to develop an effective treatment regimen to treat neurocognitive and related symptoms in HIV-infected patients, it is crucial to understand the involved mechanisms of neurotoxicity. Eventually, those mechanisms could lead the way to design and develop novel therapeutic strategies addressing both CNS HIV reservoir and illicit drug use by HIV patients.

Autophagy Dynamics and Modulation in a Rat Model of Renal Ischemia-Reperfusion Injury

Renal ischemia-reperfusion (IR) injury leading to cell death is a major cause of acute kidney injury, contributing to morbidity and mortality. Autophagy counteracts cell death by removing damaged macromolecules and organelles, making it an interesting anchor point for treatment strategies. However, autophagy is also suggested to enhance cell death when the ischemic burden is too strong. To investigate whether the role of autophagy depends on the severity of ischemic stress, we analyzed the dynamics of autophagy and apoptosis in an IR rat model with mild (45 min) or severe (60 min) renal ischemia. Following mild IR, renal injury was associated with reduced autophagy, enhanced mammalian target of rapamycin (mTOR) activity, and apoptosis. Severe IR, on the other hand, was associated with a higher autophagic activity, independent of mTOR, and without affecting apoptosis. Autophagy stimulation by trehalose injected 24 and 48 h prior to onset of severe ischemia did not reduce renal injury markers nor function, but reduced apoptosis and restored tubular dilation 7 days post reperfusion. This suggests that trehalose-dependent autophagy stimulation enhances tissue repair following an IR injury. Our data show that autophagy dynamics are strongly dependent on the severity of IR and that trehalose shows the potential to trigger autophagy-dependent repair processes following renal IR injury.

Hydrogen Sulfide Attenuates the Neurotoxicity in the Animal Model of Fetal Alcohol Spectrum Disorders

Fetal alcohol spectrum disorder (FASD), which is caused by prenatal alcohol exposure, can result in cell death in specific brain regions. Alcohol-induced neurocognitive defects offspring's are included with activation of oxidative-inflammatory cascade followed with wide apoptotic neurodegeneration in many brain's regions such as hippocampus. According to the latest studies, H₂S (hydrogen sulfide) can protect neuronal cells via antioxidant, anti-inflammatory, and anti-apoptotic mechanisms in different animal models. Therefore, we aimed to evaluate the protective effects of H₂S on ethanol-induced neuroinflammation and neuronal apoptosis in pup hippocampus with postnatal alcohol exposure. Administration of ethanol (5.27 g/kg) in milk solution (27.8 mL/kg) for each rat pups was performed through intragastric intubation on 2 to 10 postnatal days and NaHS as H₂S donor (1 mg/kg) was injected on similar time, subcutaneously. For examining the antioxidant and anti-inflammatory effects, ELISA assay was performed to determine the levels of TNF-α, IL1β, and antioxidant enzymes. Immunohistochemical staining was performed to evaluate the expression levels of GFAP and caspase-3 also Nissl staining was done for necrotic cell death evaluation. H₂S treatment could significantly increase the activity of total superoxide dismutase, catalase, and glutathione (P < 0.05). It also decreased the levels of TNF-α, IL1β, and malondialdehyde, compared with the ethanol group (P < 0.05). Moreover, the number of hippocampal caspase-3, GFAP-positive cells, and necrotic cells death reduced in the H₂S group (P < 0.01). Based on the findings, H₂S can inhibit apoptotic signaling that is mediated by the oxidative-inflammatory cascade following ethanol exposure of rat pups on postnatal period.

Targeting redox regulation to treat substance use disorder using N‐acetylcysteine

Substance use disorder (SUD) is a chronic relapsing disorder characterized by transitioning from acute drug reward to compulsive drug use. Despite the heavy personal and societal burden of SUDs, current treatments are limited and unsatisfactory. For this reason, a deeper understanding of the mechanisms underlying addiction is required. Altered redox status, primarily due to drug-induced increases in dopamine metabolism, is a unifying feature of abused substances. In recent years, knowledge of the effects of oxidative stress in the nervous system has evolved from strictly neurotoxic to include a more nuanced role in redox-sensitive signaling. More specifically, S-glutathionylation, a redox-sensitive post-translational modification, has been suggested to influence the response to drugs of abuse. In this review we will examine the evidence for redox-mediating drugs as therapeutic tools focusing on N-acetylcysteine as a treatment for cocaine addiction. We will conclude by suggesting future research directions that may further advance this field.

Binge ethanol in adulthood exacerbates negative outcomes following juvenile traumatic brain injury

Traumatic brain injuries (TBI) are a major public health problem with enormous costs in terms of health care dollars, lost productivity, and reduced quality of life. Alcohol is bidirectionally linked to TBI as many TBI patients are intoxicated at the time of their injury and we recently reported that, in accordance with human epidemiological data, animals injured during juvenile development self-administered significantly more alcohol as adults than did sham injured mice. There are also clinical data that drinking after TBI significantly reduces the efficacy of rehabilitation and leads to poorer long-term outcomes. In order to determine whether juvenile traumatic brain injury also increased the vulnerability of the brain to the toxic effects of high dose alcohol, mice were injured at 21days of age and then seven weeks later treated daily with binge-like levels of alcohol 5g/kg (by oral gavage) for ten days. Binge-like alcohol produced a greater degree of neuronal damage and neuroinflammation in mice that sustained a TBI. Further, mice that sustained a juvenile TBI exhibited mild learning and memory impairments in adulthood following binge alcohol and express a significant increase in hippocampal ectopic localization of newborn neurons. Taken together, these data provide strong evidence that a mild brain injury occurring early in life renders the brain highly vulnerable to the consequences of binge-like alcohol consumption.

S-Glutathionylation and Redox Protein Signaling in Drug Addiction

Drug addiction is a chronic relapsing disorder that comes at a high cost to individuals and society. Therefore understanding the mechanisms by which drugs exert their effects is of prime importance. Drugs of abuse increase the production of reactive oxygen and nitrogen species resulting in oxidative stress. This change in redox homeostasis increases the conjugation of glutathione to protein cysteine residues; a process called S-glutathionylation. Although traditionally regarded as a protective mechanism against irreversible protein oxidation, accumulated evidence suggests a more nuanced role for S-glutathionylation, namely as a mediator in redox-sensitive protein signaling. The reversible modification of protein thiols leading to alteration in function under different physiologic/pathologic conditions provides a mechanism whereby change in redox status can be translated into a functional response. As such, S-glutathionylation represents an understudied means of post-translational protein modification that may be important in the mechanisms underlying drug addiction. This review will discuss the evidence for S-glutathionylation as a redox-sensing mechanism and how this may be involved in the response to drug-induced oxidative stress. The function of S-glutathionylated proteins involved in neurotransmission, dendritic spine structure, and drug-induced behavioral outputs will be reviewed with specific reference to alcohol, cocaine, and heroin.

Markers of apoptosis induction and proliferation in the orbitofrontal cortex in alcohol dependence

BACKGROUND

Alcohol-dependent (ALC) subjects exhibit glial and neuronal pathology in the prefrontal cortex (PFC). However, in many patients, neurophysiological disturbances are not associated with catastrophic cell depletion despite prolonged alcohol abuse. It is still unclear how some relevant markers of a cell's propensity to degenerate or proliferate are changed in the PFC of ALC subjects without major neurological disorders.

METHODS

Levels of pro-apoptotic caspase 8 (C8), X-linked inhibitor of apoptosis protein (XIAP), direct IAP binding protein with low pI (DIABLO), proliferating cell nuclear antigen (PCNA), and density of cells immunoreactive for proliferation marker Ki-67 (Ki-67-IR) were measured postmortem in the left orbitofrontal cortex (OFC) of 29 subjects with alcohol dependence and 23 nonpsychiatric comparison subjects.

RESULTS

Alcohol subjects had significantly higher levels of the 14 kDa C8 fragment (C8-14), an indicator of C8 activation. However, there was no change in the levels of DIABLO, XIAP, or in the DIABLO/XIAP ratio. PCNA protein level and density of Ki-67-IR cells were not significantly changed in alcoholics, although PCNA levels were increased in older ALC subjects as compared to controls.

CONCLUSIONS

Significant increase of a C8 activation indicator was found in alcoholism, but without significant changes in XIAP level, DIABLO/XIAP ratio, or Ki-67 labeling. These results would help to explain the absence of catastrophic cell loss in the PFC of many Brigman subjects, while still being consistent with an alcoholism-related vulnerability to slow decline in glial cells and neurons in the OFC of alcoholics.

Females uniquely vulnerable to alcohol-induced neurotoxicity show altered glucocorticoid signaling

Women are more sensitive to the harmful effects of alcohol (EtOH) abuse than men, yet the underlying mechanisms remain poorly understood. Previous gene expression analysis of the medial prefrontal cortex (mPFC) following a chronic intoxication paradigm using continuous 72 h vapor inhalation found that females, but not males, exhibit an inflammatory response at peak withdrawal that is associated with cell damage. Given that glucocorticoids can function as anti-inflammatories, are known to increase with EtOH exposure, and influence neurotoxicity, we hypothesized that males and females may exhibit an altered corticosterone (CORT) response following chronic intoxication. Analysis of serum CORT levels revealed the expected increase during withdrawal with no difference between males and females, while control males but not females exhibited higher CORT concentrations than naive animals. Glucocorticoid signaling characterized using focused qPCR arrays identified a sexually dimorphic response in the mPFC during withdrawal, particularly among astrocyte-enriched genes. These genes include aquaporin-1 (Aqp1), sphingosine kinase 1 (Sphk1) and connective tissue growth factor (Ctgf); genes associated with inflammatory signaling, and tissue damage and repair. Bioinformatic analysis also revealed activation of inflammatory signaling and cell death pathways in females. Confirmation studies showed that female mice exhibited significant neuronal degeneration within the anterior cingulate cortex (ACC). By contrast, EtOH exposure lead to a significant reduction in cell death in males. Thus, distinct glucocorticoid signaling pathways are associated with sexually dimorphic neurotoxicity, suggesting one mechanism by which EtOH-exposed females are particularly vulnerable to the damaging effects of alcohol in the CNS.

Nutrition implications for fetal alcohol spectrum disorder

Prenatal alcohol exposure produces a multitude of detrimental alcohol-induced defects in children collectively known as fetal alcohol spectrum disorder (FASD). Children with FASD often exhibit delayed or abnormal mental, neural, and physical growth. Socioeconomic status, race, genetics, parity, gravidity, age, smoking, and alcohol consumption patterns are all factors that may influence FASD. Optimal maternal nutritional status is of utmost importance for proper fetal development, yet is often altered with alcohol consumption. It is critical to determine a means to resolve and reduce the physical and neurological malformations that develop in the fetus as a result of prenatal alcohol exposure. Because there is a lack of information on the role of nutrients and prenatal nutrition interventions for FASD, the focus of this review is to provide an overview of nutrients (vitamin A, docosahexaenoic acid, folic acid, zinc, choline, vitamin E, and selenium) that may prevent or alleviate the development of FASD. Results from various nutrient supplementation studies in animal models and FASD-related research conducted in humans provide insight into the plausibility of prenatal nutrition interventions for FASD. Further research is necessary to confirm positive results, to determine optimal amounts of nutrients needed in supplementation, and to investigate the collective effects of multiple-nutrient supplementation.

Greater monoamine oxidase a binding in alcohol dependence

BACKGROUND

Alcohol dependence (AD) is a multiorgan disease in which excessive oxidative stress and apoptosis are implicated. Monoamine oxidase A (MAO-A) is an important enzyme on the outer mitochondrial membrane that participates in the cellular response to oxidative stress and mitochondrial toxicity. It is unknown whether MAO-A levels are abnormal in AD. We hypothesized that MAO-A VT, an index of MAO-A level, is elevated in the prefrontal cortex (PFC) during AD, because markers of greater oxidative stress and apoptosis are reported in the brain in AD and a microarray analysis reported greater MAO-A messenger RNA in the PFC of rodents exposed to alcohol vapor.

METHODS

Sixteen participants with alcohol dependence and 16 healthy control subjects underwent [(11)C]-harmine positron emission tomography. All were nonsmoking, medication- and drug-free, and had no other past or present psychiatric or medical illnesses.

RESULTS

MAO-A VT was significantly greater in the PFC (37%, independent samples t test, t₃₀ = 3.93, p < .001), and all brain regions analyzed (mean 32%, multivariate analysis of variance, F₇,₂₄ = 3.67, p = .008). Greater duration of heavy drinking correlated positively with greater MAO-A VT in the PFC (r = .67, p = .005) and all brain regions analyzed (r = .73 to .57, p = .001-.02).

CONCLUSIONS

This finding represents a new pathological marker present in AD that is therapeutically targetable through direct inhibition or by novel treatments toward oxidative/pro-apoptotic processes implicated by MAO-A overexpression.

CNS proteomes in alcohol and drug abuse and dependence

Drugs of abuse, including alcohol, can induce dependency formation and/or brain damage in brain regions important for cognition. 'High-throughput' approaches, such as cDNA microarray and proteomics, allow the analysis of global expression profiles of genes and proteins. These technologies have recently been applied to human brain tissue from patients with psychiatric illnesses, including substance abuse/dependence and appropriate animal models to help understand the causes and secondary effects of these complex disorders. Although these types of studies have been limited in number and by proteomics techniques that are still in their infancy, several interesting hypotheses have been proposed. Focusing on CNS proteomics, we aim to review and update current knowledge in this rapidly advancing area.

Alcoholism and cellular vulnerability in different brain regions

Alcohol-induced damage causes dysfunction of selected brain regions. Multidisciplinary studies have provided an extensive description of changes observed in neurons and glia following alcohol consumption. In this study the authors have elucidated preferential cellular vulnerability in three different brain regions. Autopsy material of the prefrontal cortex, striatum, and substantia nigra obtained from the brain tissue of alcoholic subjects was used in this study. We found that dendritic tree and astroglial damage is irreversible, while neuronal somata and most axons do not display irreversible changes.

Molecular and behavioral aspects of the actions of alcohol on the adult and developing brain

The brain is one of the major target organs of alcohol actions. Alcohol abuse can lead to alterations in brain structure and functions and, in some cases, to neurodegeneration. Cognitive deficits and alcohol dependence are highly damaging consequences of alcohol abuse. Clinical and experimental studies have demonstrated that the developing brain is particularly vulnerable to alcohol, and that drinking during gestation can lead to a range of physical, learning and behavioral defects (fetal alcohol spectrum disorders), with the most dramatic presentation corresponding to fetal alcohol syndrome. Recent findings also indicate that adolescence is a stage of brain maturation and that heavy drinking at this stage can have a negative impact on brain structure and functions causing important short- and long-term cognitive and behavioral consequences. The effects of alcohol on the brain are not uniform; some brain areas or cell populations are more vulnerable than others. The prefrontal cortex, the hippocampus, the cerebellum, the white matter and glial cells are particularly susceptible to the effects of ethanol. The molecular actions of alcohol on the brain are complex and involve numerous mechanisms and signaling pathways. Some of the mechanisms involved are common for the adult brain and for the developing brain, while others depend on the developmental stage. During brain ontogeny, alcohol causes irreversible alterations to the brain structure. It also impairs several molecular, neurochemical and cellular events taking place during normal brain development, including alterations in both gene expression regulation and the molecules involved in cell-cell interactions, interference with the mitogenic and growth factor response, enhancement of free radical formation and derangements of glial cell functions. However, in both adult and adolescent brains, alcohol damages specific brain areas through mechanisms involving excitotoxicity, free radical formation and neuroinflammatory damage resulting from activation of the innate immune system mediated by TLR4 receptors. Alcohol also acts on specific membrane proteins, such as neurotransmitter receptors (e.g. NMDA, GABA-A), ion channels (e.g. L-type Ca²⁺ channels, GIRKs), and signaling pathways (e.g. PKA and PKC signaling). These effects might underlie the wide variety of behavioral effects induced by ethanol drinking. The neuroadaptive changes affecting neurotransmission systems which are more sensitive to the acute effects of alcohol occur after long-term alcohol consumption. Alcohol-induced maladaptations in the dopaminergic mesolimbic system, abnormal plastic changes in the reward-related brain areas and genetic and epigenetic factors may all contribute to alcohol reinforcement and alcohol addiction. This manuscript reviews the mechanisms by which ethanol impacts the adult and the developing brain, and causes both neural impairments and cognitive and behavioral dysfunctions. The identification and the understanding of the cellular and molecular mechanisms involved in ethanol toxicity might contribute to the development of treatments and/or therapeutic agents that could reduce or eliminate the deleterious effects of alcohol on the brain.

Clinical and pathological features of alcohol-related brain damage

One of the sequelae of chronic alcohol abuse is malnutrition. Importantly, a deficiency in thiamine (vitamin B(1)) can result in the acute, potentially reversible neurological disorder Wernicke encephalopathy (WE). When WE is recognized, thiamine treatment can elicit a rapid clinical recovery. If WE is left untreated, however, patients can develop Korsakoff syndrome (KS), a severe neurological disorder characterized by anterograde amnesia. Alcohol-related brain damage (ARBD) describes the effects of chronic alcohol consumption on human brain structure and function in the absence of more discrete and well-characterized neurological concomitants of alcoholism such as WE and KS. Through knowledge of both the well-described changes in brain structure and function that are evident in alcohol-related disorders such as WE and KS and the clinical outcomes associated with these changes, researchers have begun to gain a better understanding of ARBD. This Review examines ARBD from the perspective of WE and KS, exploring the clinical presentations, postmortem brain pathology, in vivo MRI findings and potential molecular mechanisms associated with these conditions. An awareness of the consequences of chronic alcohol consumption on human behavior and brain structure can enable clinicians to improve detection and treatment of ARBD.

Recommended Neuroanatomical Sampling Practices for Comprehensive Brain Evaluation in Nonclinical Safety Studies

Adequate tissue sampling is known to reduce the likelihood that the toxicity of novel biomolecules, chemicals, and drugs might go undetected. Each organ, and often specific structurally and functionally distinct regions within it, must be assessed to detect potential site-specific toxicity. Adequate sampling of the brain requires particular consideration because of the many major substructures and more than 600 subpopulations of generally irreplaceable cells with unique functions and vulnerabilities. All known neurotoxicants affect specific subpopulations (usually neurons) rather than damaging a certain percentage of cells throughout the brain; thus, all populations should be independently assessed for lesions. Historically, the affected neural cell subpopulation has not been predictable, but it is now clear that sampling selected populations (e.g., cerebral cortex, hippocampus, cerebellar folia) cannot forecast the health of other populations. This article reviews the neuroanatomical domains affected by several model neurotoxicants to illustrate the need for more comprehensive neurohistological evaluation during nonclinical development of novel compounds. The article also describes an easily executed, cost-effective method that uses a set number of evenly spaced coronal (cross) sections to accomplish this comprehensive brain assessment during nonclinical safety studies performed in rodents, dogs, and nonhuman primates.

Pivotal role of TLR4 receptors in alcohol-induced neuroinflammation and brain damage

Toll-like receptors play an important role in the innate immune response, although emerging evidence indicates their role in brain injury and neurodegeneration. Alcohol abuse induces brain damage and can sometimes lead to neurodegeneration. We recently found that ethanol can promote TLR4 signaling in glial cells by triggering the induction of inflammatory mediators and causing cell death, suggesting that the TLR4 response could be an important mechanism of ethanol-induced neuroinflammation. This study aims to establish the potential role of TLR4 in both ethanol-induced glial activation and brain damage. Here we report that TLR4 is critical for ethanol-induced inflammatory signaling in glial cells since the knockdown of TLR4, by using both small interfering RNA or cells from TLR4-deficient mice, abolished the activation of microtubule-associated protein kinase and nuclear factor-kappaB pathways and the production of inflammatory mediators by astrocytes. Our results demonstrate, for the first time, that whereas chronic ethanol intake upregulates the immunoreactive levels of CD11b (microglial marker) and glial fibrillary acidic protein (astrocyte marker), and also increases caspase-3 activity and inducible nitric oxide synthase, COX-2, and cytokine levels [interleukin (IL)-1beta, tumor necrosis factor-alpha, IL-6] in the cerebral cortex of female wild-type mice, TLR4 deficiency protects against ethanol-induced glial activation, induction of inflammatory mediators, and apoptosis. Our findings support the critical role of the TLR4 response in the neuroinflammation, brain injury, and possibly in the neurodegeneration induced by chronic ethanol intake.

Infusion of gliotoxins or a gap junction blocker in the prelimbic cortex increases alcohol preference in Wistar rats

Postmortem research has revealed that there is a lower density of glial cells in regions of the prefrontal cortex (PFC) of uncomplicated alcoholics when compared with control subjects. Impairment of astrocyte function in the PFC may contribute to malfunction in circuits involved in emotion- and reward-related subcortical centers, heavily connected with the PFC and directly involved in the pathophysiology of addictive behaviours. The hypothesis was tested that infusion of gliotoxins known to injure astrocytes or of a gap junction blocker into the prelimbic area of the rat PFC results in increased preference for ethanol in rats exposed to free choice between water and 10% ethanol. Fluorocitric acid, L-alpha-aminoadipic acid (AAD) or the gap junction blocker 18-alpha-glycyrrhetinic acid (AGA) were bilaterally infused once into the rat prelimbic cortex and alcohol preference (ratio of 10% ethanol consumed to total liquid ingested) was measured before and after infusion. Infusion of AAD or AGA dissolved in their vehicles, but not of their vehicles alone, resulted in significant transient increase of preference for 10% ethanol. The present data suggest that impaired integrity of glial cells or the gap junctional communication between them in the rat PFC may contribute to changes in ethanol preference.

Dysregulation of cell death machinery in the prefrontal cortex of human alcoholics

In human alcoholics, the cell density is decreased in the prefrontal cortex (PFC) and other brain areas. This may be due to persistent activation of cell death pathways. To address this hypothesis, we examined the status of cell death machinery in the dorsolateral PFC in alcoholics. Protein and mRNA expression levels of several key pro- and anti-apoptotic genes were compared in post-mortem samples of 14 male human alcoholics and 14 male controls. The findings do not support the hypothesis. On the contrary, they show that several components of intrinsic apoptotic pathway are decreased in alcoholics. No differences were evident in the motor cortex, which is less damaged in alcoholics and was analysed for comparison. Thus, cell death mechanisms may be dysregulated by inhibition of intrinsic apoptotic pathway in the PFC in human alcoholics. This inhibition may reflect molecular adaptations that counteract alcohol neurotoxicity in cells that survive after many years of alcohol exposure and withdrawal.

Proteomics approach in the study of the pathophysiology of alcohol-related brain damage

AIMS

Chronic, excessive drinking of alcohol can induce brain damage in the regions important for neurocognitive function. Some of the damage are permanent while some are appearantly reversible. It is our aim to understand the molecular mechanisms underlying alcohol-induced and/or related brain damage, particularly of that observed in 'medically uncomplicated' (without heptatic cirrhosis or Wernicke-Korsakoff Syndrome [WKS]) alcoholics.

METHODS

A high-throughput proteomics technology has been applied to several 'alcohol-sensitive' brain regions from uncomplicated and hepatic cirrhosis-complicated alcoholics to understand the mechanisms of alcohol-related brain damage at the level of protein expression.

RESULTS

It was clearly demonstrated that each brain region reacts in significantly different manner to chronic alcohol ingestion. Appearant abnormalities in vitamin B1 (thiamine)-related biochemical pathways were observed in several brain regions, such as the dorsolateral prefrontal cortex, genu (a frontal part of the corpus callosum) and cerebellar vermis in uncomplicated alcoholics, suggesting that the reduction of this important nutritional component might be associated with brain damage even without the signs of WKS. In addition, in the two different subregions of the corpus callosum (genu and splenium [a posterior part of the corpus callosum]) and the cerebellar vermis, significant differences in protein expression profiles between uncomplicated and complicated alcoholics with hepatic cirrhosis were identified, suggesting that hepatic factors such as ammonia have significant additive influences on brain protein expression, which might lead to the structural changes and/or damage in these brain regions. Furthermore, in the hippocampus, significant change of the level of glutamine synthetase expression was observed, suggesting once again the importance of ammonia as a cause of brain damage in this region.

CONCLUSIONS

Although our data did not show any evidence of "direct" alcohol effects to induce the alteration of protein expression in association with brain damage, high-throughput neuroproteomics approaches are proven to have a potential to dissect the mechanisms of complex brain disorders.

Evidence of DNA damage in Alzheimer disease: phosphorylation of histone H2AX in astrocytes

Phosphorylation of the histone family is not only a response to cell signaling stimuli, but also an important indicator of DNA damage preceding apoptotic changes. While astrocytic degeneration, including DNA damage, has been reported in Alzheimer disease (AD), its pathogenetic significance is somewhat unclear. In an effort to clarify this, we investigated the expression of gamma H2AX as evidence of DNA damage in astrocytes to elucidate the role of these cells in the pathogenesis of AD. In response to the formation of double-stranded breaks in chromosomal DNA, serine 139 on H2AX, a 14-kDa protein that is a member of the H2A histone family and part of the nucleosome structure, becomes rapidly phosphorylated to generate gamma H2AX. Using immunocytochemical techniques, we found significantly increased levels of gamma H2AX in astrocytes in regions know to be vulnerable in AD, i.e., the hippocampal regions and cerebral cortex. These results suggest that astrocytes contain DNA damage, possibly resulting in functional disability, which in turn reduces their support for neurons. These findings further define the role of astrocyte dysfunction in the progression of AD.

Increased tunel positive cells in CA1, CA2, and CA3 subfields of rat hippocampus due to copper and ethanol co-exposure

Copper (Cu) is an essential element for life. However, it is toxic at excessive doses, whereas exposure to ethanol (EtOH) has known to cause morphological changes, degeneration, and neuronal loss in central nervous system. A previous investigation by the authors' group showed that Cu and EtOH co-treatment cause severe hippocampal neuronal loss in CA1, CA2, and CA3 subfields of rat hippocampus. This study was designed to analyze the possible mechanism(s) of action of this effect. In addition, the possible neurogenesis in response to a potent neurodegenerative treatment in rat hippocampus was analyzed. Results demonstrated that Cu and EtOH induced neuronal loss in rat hippocampus was in correlation with the increased cell death analyzed on the basis of TdT-mediated dUTP nick end labeling (TUNEL) assay. On the other hand, neuronal regenerative activity was detectable in analyzed CA1, CA2, and CA3 subfields of the rat hippocampus analyzed on the basis of 5-bromo-2'-deoxy-uridine (BrdU) labeling assay; however, this activity in treated group was not significantly different from that of control group.

Ethanol promotes endoplasmic reticulum stress-induced neuronal death: involvement of oxidative stress

One of the most devastating effects of ethanol exposure during development is the loss of neurons in selected brain areas. The underlying cellular/molecular mechanisms remain unclear. The endoplasmic reticulum (ER) is involved in posttranslational protein processing and transport. The accumulation of unfolded or misfolded proteins in the ER lumen triggers ER stress, which is characterized by translational attenuation, synthesis of ER chaperone proteins such as GRP78, and activation of transcription factors such as ATF4, ATF6, and CHOP. Sustained ER stress ultimately leads to cell death. ER stress response can be induced experimentally by treatment with tunicamycin and thapsigargin. Using SH-SY5Y neuroblastoma cells and primary cerebellar granule neurons as in vitro models, we demonstrated that exposure to ethanol alone had little effect on the expression of markers for ER stress; however, ethanol drastically enhanced the expression of GRP78, CHOP, ATF4, ATF6, and phosphorylated PERK and eIF2 alpha when induced by tunicamycin and thapsigargin. Consistently, ethanol promoted tunicamycin- and thapsigargin-induced cell death. Ethanol rapidly caused oxidative stress in cultured neuronal cells; antioxidants blocked ethanol's potentiation of ER stress and cell death, suggesting that the ethanol-promoted ER stress response is mediated by oxidative stress. CHOP is a proapoptotic transcription factor. We further demonstrated that CHOP played an important role in ethanol-promoted cell death. Thus, the effect of ethanol may be mediated by the interaction between oxidative stress and ER stress.

Effect of postnatal treadmill exercise on c-Fos expression in the hippocampus of rat pups born from the alcohol-intoxicated mothers

Maternal alcohol-intoxication during pregnancy exerts detrimental effects on fetal development and is known to influence learning ability and memory capability by altering neuronal activity in the hippocampus. c-Fos expression represents neuronal activity and plays a crucial role in the brain development. Physical exercise is known to enhance neuronal plasticity and activity. In the present study, we investigated the influence of postnatal treadmill running on the c-Fos expression in the hippocampus of rat pups born from the alcohol-intoxicated mothers. The results obtained show that maternal alcohol-intoxication suppressed c-Fos expression in the hippocampus of rat pups and that postnatal treadmill exercise enhanced c-Fos expression in the hippocampus of these rat pups. The present study suggests that exercise should be considered as a therapeutic means of countering the effects of maternal alcohol-intoxication, and that it may provide a useful strategy for enhancing the neuronal activity of children born from the mothers who abuse alcohol during pregnancy.

Increased MCP-1 and microglia in various regions of the human alcoholic brain

Cytokines and microglia have been implicated in anxiety, depression, neurodegeneration as well as the regulation of alcohol drinking and other consumatory behaviors, all of which are associated with alcoholism. Studies using animal models of alcoholism suggest that microglia and proinflammatory cytokines contribute to alcoholic pathologies [Crews, F.T., Bechara, R., Brown, L.A., Guidot, D.M., Mandrekar, P., Oak, S., Qin, L., Szabo, G., Wheeler, M., Zou, J., (2006) Cytokines and alcohol. Alcohol., Clin. Exp. Res. 30:720-730]. In the current study, human postmortem brains from moderate drinking controls and alcoholics obtained from the New South Wales Tissue Resource Center were used to study the cytokine, monocyte chemoattractant protein 1 (MCP-1,CCL2) and microglia markers in various brain regions. Since MCP-1 is a key proinflammatory cytokine induced by chronic alcohol treatment of mice, and known to regulate drinking behavior in mice, MCP-1 protein levels from human brain homogenate were measured using ELISA, and indicated increased MCP-1 concentration in ventral tegmental area (VTA), substantia nigra (SN), hippocampus and amygdala of alcoholic brains as compared with controls. Immunohistochemistry was further performed to visualize human microglia using ionized calcium binding adaptor protein-1 (Iba-1), and Glucose transporter-5 (GluT5). Alcoholics were found to have brain region-specific increases in microglial markers. In cingulate cortex, both Iba-1 and GluT5 were increased in alcoholic brains relative to controls. Alternatively, no detectable change was found in amygdala nuclei. In VTA and midbrain, only GluT5, but not Iba-1 was increased in alcoholic brains. These data suggest that the enhanced expression of MCP-1 and microglia activities in alcoholic brains could contribute to ethanol-induced pathogenesis.

Differential protein expression profiles in the hippocampus of human alcoholics

Mild to severe cognitive impairments are frequently observed symptoms in chronic alcoholics. Decline of cognitive function significantly affects patients' recovery process and prognosis. The hippocampal region is sensitive to the effects of alcohol and it has been suggested that alcohol-induced hippocampal damage and/or changes in neuronal circuitry play an important role in generating these symptoms. Although various hypotheses have been proposed, molecular mechanisms underlying these alterations in the hippocampus are largely unknown. In the present study, we employed a 2DE-based proteomics approach to compare the protein expression profiles of the hippocampus in human alcoholic and healthy control brains. In the alcoholic hippocampus, 20 protein spots were found to be differentially regulated, 2 increased and 18 decreased. Seventeen proteins were identified using mass spectroscopy and were subcategorized into three energy metabolic proteins, six protein metabolic proteins, four signalling proteins, two oxidative stress-related proteins, one vesicle trafficking protein and one cytoskeletal protein. Some of these proteins have been previously implicated in alcohol-induced brain pathology. Based upon the results, several hypotheses were generated to explain the mechanisms underlying possible functional and/or structural alterations induced by chronic alcohol use in this brain region.

Acute exposure to ethanol potentiates human immunodeficiency virus type 1 Tat-induced Ca(2+) overload and neuronal death in cultured rat cortical neurons

A significant number of human immunodeficiency virus type 1 (HIV-1)-infected patients are alcoholics. Either alcohol or HIV alone induces morphological and functional damage to the nervous system. HIV-1 Tat is a potent transcriptional activator of the viral promoter, with the ability to modulate a number of cellular regulatory circuits including apoptosis and to cause neuronal injury. To further evaluate the involvement of alcohol in neuronal injury, the authors examined the effect of ethanol on Tat-induced calcium responses in rat cerebral cortical neurons, using microfluorimetric calcium determination. HIV Tat protein (10 or 500 nM) elicited two types of calcium responses in cortical neurons: a fast-onset, short-lasting response and a slow-onset, sustained response. The responses were concentration-dependent and diminished in calcium-free saline. A short exposure to ethanol (50 mM) potentiated both types of calcium response, which was markedly decreased when the cells were pretreated with BAPTA-AM (20 microM). In addition, an increase in the neurotoxic effect of Tat, which was assessed by trypan blue exclusion assay, was observed. The result led the authors to conclude that alcohol exposure significantly potentiates Tat-induced calcium overload and neuronal death.

Inhibition of ethanol-induced toxicity by tanshinone IIA in PC12 cells

AIM

To observe the effects of tanshinone IIA (Tan IIA) on the neurotoxicity induced by ethanol in PC12 cells and to explore its protective role.

METHODS

PC12 cell survival was measured by MTT assay. The formation of reactive oxygen species (ROS) and lactate dehydrogenase (LDH) release were detected by 2',7'-dichlorofluorescin (DCF) fluorescence and calorimetric method, respectively. The percentage of cell apoptosis was monitored by flow cytometry. The expression of p53 was detected by immuno-fluorescence and flow cytometry.

RESULTS

Ethanol significantly impaired the survival of PC12 cells as demonstrated by MTT assay. Ethanol also induced significant ROS formation and increased LDH release. Pre-incubation with Tan IIA in the culture medium significantly reversed these changes. Ethanol caused cell apoptosis and the upregulation of p53 protein. The anti-apoptosis effects of Tan IIA on ethanol-induced toxicity were accompanied by the downregulation of pro-apoptotic p53 protein expression.

CONCLUSION

Tan IIA can protect neurons from apoptosis and might serve as a potential therapeutic drug for neurological disorders induced by ethanol.

Ethanol promotes neuronal apoptosis by inhibiting phosphatidylserine accumulation

Prenatal and postnatal ethanol exposure induces abnormal cell death in the nervous system. We have previously reported that docosahexaenoic acid (DHA; 22:6n-3) prevents neuronal apoptosis through promoting phosphatidylserine (PS) accumulation. Previously, we have shown in C6 glioma cells that ethanol inhibits the accumulation of PS caused by DHA supplementation. In this report, we demonstrate that in vitro or in vivo exposure to ethanol inhibits DHA-dependent PS accumulation and neuronal survival. We found that Neuro 2A cells exposed to ethanol accumulated considerably less PS in response to the DHA enrichment and were less effective at phosphorylating Akt and suppressing caspase-3 activity under serum-starved or staurosporine-treated conditions. The in vivo paradigm correlated well with the in vitro findings. We found that the total PS and DHA contents in the fetal hippocampus were slightly but significantly lowered by the prenatal ethanol exposure. Fetal hippocampal cultures obtained at embryonic day 18 from ethanol-treated pregnant rats contained significantly higher apoptotic cells after 7 days in vitro under basal conditions and exhibited particular susceptibility to cell death induced by trophic factor removal in comparison with the pair-fed control group. The reduction of PS and the resulting neuronal cell death inappropriately enhanced during development may contribute to the defects in brain function often observed in fetal alcohol syndrome.

Differential protein expression in the prefrontal white matter of human alcoholics: a proteomics study

Neuroimaging and post-mortem studies indicate that chronic alcohol use induces global changes in brain morphology, such as cortical and subcortical atrophy. Recent studies have shown that frontal lobe structures are specifically susceptible to alcohol-related brain damage and shrinkage in this area is largely due to a loss of white matter. This may explain the high incidence of cognitive dysfunction observed in alcoholics. Using a proteomics-based approach, changes in protein expression in the dorsolateral prefrontal region (BA9) white matter were identified in human alcoholic brains. Protein extracts from the BA9 white matter of 25 human brains (10 controls; eight uncomplicated alcoholics; six alcoholics complicated with hepatic cirrhosis; one reformed alcoholic) were separated using two-dimensional gel electrophoresis. Overall, changes in the relative expression of 60 proteins were identified (P<0.05, ANOVA) in the alcoholic BA9 white matter. In total, 18 protein spots have been identified using MALDI-TOF; including hNP22, alpha-internexin, transketolase, creatine kinase chain B, ubiquitin carboxy-terminal hydrolase L1 and glyceraldehyde-3-phosphate dehydrogenase. Several of these proteins have been previously implicated in alcohol-related disorders and brain damage. By identifying changes in protein expression in this region from alcoholics, hypotheses may draw upon more mechanistic explanations as to how chronic ethanol consumption causes white matter damage.

Lower packing density of glial fibrillary acidic protein-immunoreactive astrocytes in the prelimbic cortex of alcohol-naive and alcohol-drinking alcohol-preferring rats as compared with alcohol-nonpreferring and Wistar rats

BACKGROUND

Low packing density of glial cells, possibly astrocytes, has been described in the prefrontal cortex and hippocampus of "uncomplicated" alcoholics. Astrocytes perform crucial support functions in the processing of neurotransmitters and transfer of energy substrates from blood to cortical neurons. It is still unknown whether attrition in the numbers of astrocytes is only a consequence of prolonged alcohol abuse or also predates the exposure to alcohol in subjects at risk for alcohol dependence.

METHODS

We used alcohol-preferring (P) rats exposed ad libitum for 2 or 6 months to either water only or 10% ethanol and alcohol-nonpreferring (NP) rats and nonselected Wistar rats exposed only to water for 2 months. Sections through the rat frontal cortex were immunostained for glial fibrillary acidic protein (GFAP), a specific marker of astrocytes. The packing density of GFAP-immunoreactive (IR) astrocytes and the area fraction of GFAP immunoreactivity were measured in the prelimbic cortex (PLC) using the dissector probe and analysis of binary images of GFAP immunostaining, respectively.

RESULTS

The packing density of GFAP-IR astrocytes was significantly lower in both alcohol-naive and alcohol-exposed P rats than in NP rats or Wistar rats. The area fraction of GFAP immunoreactivity was significantly lower in the alcohol-exposed P rats than in NP rats, Wistar rats, and alcohol-naive P rats.

CONCLUSION

These results suggest that low density of GFAP-IR astrocytes in the PLC of P rats predates the exposure to alcohol and might be a factor contributing to the increased risk for alcohol dependence. In addition, prolonged free-choice alcohol drinking may reduce the extent of GFAP-IR processes in the PLC of P rats.

Influence of maternal alcohol administration on c-Fos expression in the hippocampus of infant rats

Maternal alcohol consumption during pregnancy is known to have a detrimental effect on the development of the fetus and its central nervous system (CNS) in particular. In the present study, the dose-dependence of the effect of maternal alcohol on hippocampal c-Fos expression, which is a marker of hippocampal neuronal activity and which is induced by a variety of stimuli, was examined in infant rats. In the present study, it was shown that expression of c-Fos in the hippocampus is decreased following treatment with alcohol in a dose-dependent fashion. Based on the results of the present study and the findings of other studies, it can be suggested that suppression of c-Fos expression in the hippocampus of infant rats with maternal alcohol administration mediates the associated developmental retardation and/or anomalies.

Ethanol potentiates HIV-1 gp120-induced apoptosis in human neurons via both the death receptor and NMDA receptor pathways

Neuronal loss is a hallmark of AIDS dementia syndromes. Human immunodeficiency virus type I (HIV-1)-specific proteins may induce neuronal apoptosis, but the signal transduction of HIV-1 gp120-induced, direct neuronal apoptosis remains unclear. Ethanol (EtOH) is considered to be an environmental co-factor in AIDS development. However, whether EtOH abuse in patients with AIDS increases neuronal dysfunction is still uncertain. Using pure, differentiated, and post-mitotic NT2.N-derived human neurons, we investigated the mechanisms of HIV-1 and/or EtOH-related direct neuronal injury and the molecular interactions between HIV-1-specific proteins and EtOH. It was demonstrated that NT2.N neurons were susceptible to HIV-1 Bal (R5-tropic strain) gp120-induced direct cell death. Of importance, EtOH induced cell death in human neurons in a clinically-relevant dose range and EtOH strongly potentiated HIV-1 gp120-induced neuronal injury at low and moderate concentrations. Furthermore, this potentiation of neurotoxicity could be blocked by N-methyl-D-aspartate (NMDA) receptor subunit 2B (NR2B) antagonists. We analyzed human genomic profiles in these human neurons, using Affymetrix genomics technology, to elucidate the apoptotic pathways involved in HIV-1- and EtOH-related neurodegeneration. Our findings indicated significant over-expression of selected apoptosis functional genes. Significant up-regulation of TRAF5 gene expression may play an essential role in triggering potentiation by EtOH of HIV-1 gp120-induced neuronal apoptosis at early stages of interaction. These studies suggested that two primary apoptotic pathways, death receptor (extrinsic) and NMDA receptor (intrinsic)-related programmed cell-death pathways, are both involved in the potentiation by EtOH of HIV-1 gp120-induced direct human neuronal death. Thus, these data suggest rationally-designed, molecular targets for potential anti-HIV-1 neuroprotection.

Selective reduction of chromogranin A-like immunoreactivities in the prefrontal cortex of schizophrenic subjects: a postmortem study

It is suggested that secretogranins/chromogranins play a role in regulating secretion of various proteins and amines, including neurotransmitters from secretory granules. Several studies have implicated the importance of altered synaptic connectivity in schizophrenia. We employed immunohistochemical techniques to determine if the level of chromogranin A (CgA)-immunoreactivity (IR) was altered in the subjects with schizophrenia. Nine subjects with schizophrenia and nine age- and sex-matched control subjects were selected for this study. Immunohistochemistry using specific antibody against CgA was performed on sections of prefrontal cortex and hippocampus. Images of CgA-IR were analyzed by computer-based image analyzing software. CgA-IR was significantly decreased in layers III-V of the prefrontal cortex in schizophrenic subjects compared with control subjects. In the hippocampus, no significant difference was observed between two groups. The results indicate that there may be a decrease in the number of CgA positive large dense-core vesicles per terminal, and/or in the number of CgA positive terminals, suggesting possible functional impairment of prefrontal synaptic contact in schizophrenia.