Moderate ethanol preconditioning of rat brain cultures engenders neuroprotection against dementia-inducing neuroinflammatory proteins: possible signaling mechanisms

Alcohol consumption in relation to cognitive dysfunction and dementia: A systematic review and dose-response meta-analysis of comparative longitudinal studies

BACKGROUND

Alcohol use is associated with a wide spectrum of neurological disorders, including cognitive dysfunction and dementia. Likewise, the high prevalence of cognitive dysfunction and dementia specifies the urgent need to identify modifiable risk factors. Because findings on alcohol and cognitive dysfunction and dementia have been inconsistent, the present dose-response meta-analysis of cohort and case control studies was conducted to evaluate the available evidence.

METHOD AND MATERIALS

A systematic search was conducted on PubMed/MEDLINE, Scopus, Embase, and PsychInfo databases and Google Scholar up to April, 2023. In the dose-response meta-analysis, a restricted cubic spline regression model was conducted to evaluate a possible non-linear relation between alcohol intake and the outcomes. Random-effects model was used to perform the meta-analysis and evaluate heterogeneity. Egger's test and a funnel plot were used to assess small study effects. Subgroup analyses were carried out to explore possible sources of heterogeneity.

RESULTS

Seventeen eligible studies comprising 80,680 total persons with 4929 cases for dementia and 13,530 total persons with 1579 cases for cognitive dysfunction were included for dose-response analysis. When compared to the reference group of 0 g/day of alcohol intake, the dose-response meta-analysis revealed a significant non-linear (J-shaped) association between alcohol intake and the risk of each of cognitive dysfunction, (lower dose range: 1-30.5 g/day, RR: 0.97; 95 % CI 0.95-0.99; higher dose range: >30.5 g/day, RR: 1.07; 95 % CI 1.01-1.15) and dementia (lower dose range: 1-17.5 g/day, RR: 0.92; 95 % CI 0.88-0.96, higher dose range: >17.5 g/day, RR: 1.23; 95 % CI 1.09-1.35). The lowest risk was achieved at approximately 30 g/day of alcohol for cognitive dysfunction and 15 g/day for dementia. The J-shape association remained with subgroups defined by age (≤65; >65 years) or study duration (<10; ≥10 years) for dementia, and within age >65 and duration <10 years for cognitive dysfunction.

CONCLUSION

We observed a J-shape association between alcohol consumption and both cognitive dysfunction and dementia, with light-to-moderate alcohol intake being associated with a reduced risk in adults. Further studies are needed to clarify more specifically the association between alcohol consumption and six domains of cognitive dysfunction based on diagnostic and statistical manual of mental disorders (DSM) criteria.

Association of MAFLD and MASLD with all-cause and cause-specific dementia: a prospective cohort study

BACKGROUND

Liver disease and dementia are both highly prevalent and share common pathological mechanisms. We aimed to investigate the associations between metabolic dysfunction-associated fatty liver disease (MAFLD), metabolic dysfunction-associated steatotic liver disease (MASLD) and the risk of all-cause and cause-specific dementia.

METHODS

We conducted a prospective study with 403,506 participants from the UK Biobank. Outcomes included all-cause dementia, Alzheimer's disease, and vascular dementia. Multivariable Cox proportional hazards models were used for analyses.

RESULTS

155,068 (38.4%) participants had MAFLD, and 111,938 (27.7%) had MASLD at baseline. During a median follow-up of 13.7 years, 5,732 participants developed dementia (2,355 Alzheimer's disease and 1,274 vascular dementia). MAFLD was associated with an increased risk of vascular dementia (HR 1.32 [95% CI 1.18-1.48]) but a reduced risk of Alzheimer's disease (0.92 [0.84-1.0]). Differing risks emerged among MAFLD subtypes, with the diabetes subtype increasing risk of all-cause dementia (1.8 [1.65-1.96]), vascular dementia (2.95 [2.53-3.45]) and Alzheimer's disease (1.46 [1.26-1.69]), the lean metabolic disorder subtype only increasing vascular dementia risk (2.01 [1.25-3.22]), whereas the overweight/obesity subtype decreasing risk of Alzheimer's disease (0.83 [0.75-0.91]) and all-cause dementia (0.9 [0.84-0.95]). MASLD was associated with an increased risk of vascular dementia (1.24 [1.1-1.39]) but not Alzheimer's disease (1.0 [0.91-1.09]). The effect of MAFLD on vascular dementia was consistent regardless of MASLD presence, whereas associations with Alzheimer's disease were only present in those without MASLD (0.78 [0.67-0.91]).

CONCLUSIONS

MAFLD and MASLD are associated with an increased risk of vascular dementia, with subtype-specific variations observed in dementia risks. Further research is needed to refine MAFLD and SLD subtyping and explore the underlying mechanisms contributing to dementia risk.

Bioinformatics and Systems Biology Approaches to Identify the Synergistic Effects of Alcohol Use Disorder on the Progression of Neurological Diseases

Clinical investigations showed that individuals with Alcohol Use Disorder (AUD) have worse Neurological Disease (ND) development, pointing to possible pathogenic relationships between AUD and NDs. It remains difficult to identify risk factors that are predisposing between AUD and NDs. In order to fix these issues, we created the bioinformatics pipeline and network-based approaches for employing unbiased methods to discover genes abnormally stated in both AUD and NDs and to pinpoint some of the common molecular pathways that might underlie AUD and ND interaction. We found 100 differentially expressed genes (DEGs) in both the AUD and ND patient's tissue samples. The most important Gene Ontology (GO) terms and metabolic pathways, including positive control of cytotoxicity caused by T cells, proinflammatory responses, antigen processing and presentation, and platelet-triggered interactions with vascular and circulating cell pathways were then extracted using the overlapped DEGs. Protein-protein interaction analysis was used to identify hub proteins, including CCL2, IL1B, TH, MYCN, HLA-DRB1, SLC17A7, and HNF4A, in the pathways that have been reported as playing a function in these disorders. We determined several TFs (HNF4A, C4A, HLA-B, SNCA, HLA-DMB, SLC17A7, HLA-DRB1, HLA-C, HLA-A, and HLA-DPB1) and potential miRNAs (hsa-mir-34a-5p, hsa-mir-34c-5p, hsa-mir-449a, hsa-mir-155-5p, and hsa-mir-1-3p) were crucial for regulating the expression of AUD and ND which could serve as prospective targets for treatment. Our methodologies discovered unique putative biomarkers that point to the interaction between AUD and various neurological disorders, as well as pathways that could one day be the focus of therapeutic intervention.

Animal models for studies of alcohol effects on the trajectory of age-related cognitive decline

There is growing interest in understanding how ethanol use interacts with advancing age to influence the brain and cognition. Animal models are employed to investigate the cellular and molecular mechanisms of brain aging and age-related neurodegenerative diseases that underlie cognitive decline. However, all too often research on problems and diseases of the elderly are conducted in healthy young animals, providing little clinical relevance. The validity of animal models is discussed, and confounds due to age-related differences in anxiety, sensory-motor function, and procedural learning are highlighted in order to enhance the successful translation of preclinical results into clinical settings. The mechanism of action of ethanol on brain aging will depend on the dose, acute or chronic treatment, or withdrawal from treatment and the age examined. Due to the fact that humans experience alcohol use throughout life, important questions concern the effects of the dose and duration of ethanol treatment on the trajectory of cognitive function. Central to this research will be questions of the specificity of alcohol effects on cognitive functions and related brain regions that decline with age, as well as the interaction of alcohol with mechanisms or biomarkers of brain aging. Alternatively, moderate alcohol use may provide a source of reserve and resilience against brain aging. Longitudinal studies have the advantage of being sensitive to detecting the effects of treatment on the emergence of cognitive impairment in middle age and can minimize effects of stress/anxiety associated with the novelty of alcohol exposure and behavioral testing, which disproportionately influence aged animals. Finally, the effect of alcohol on senescent neurophysiology and biomarkers of brain aging are discussed. In particular, the interaction of age and effects of alcohol on inflammation, oxidative stress, N-methyl-d-aspartate receptor function, and the balance of excitatory and inhibitory synaptic transmission are highlighted.

Changes in Alcohol Consumption and Risk of Dementia in a Nationwide Cohort in South Korea

IMPORTANCE

The impact of serial changes in alcohol consumption on dementia risk has rarely been investigated to date.

OBJECTIVE

To investigate the association of comprehensive patterns of changes in alcohol consumption with the incidence of all-cause dementia, Alzheimer disease (AD), and vascular dementia (VaD).

DESIGN, SETTING, AND PARTICIPANTS

This is a retrospective cohort study. Data were obtained from the Korean National Health Insurance Service database. Adults aged 40 years and older underwent 2 health examinations in 2009 and 2011. The cohort was assessed until December 31, 2018, and statistical analysis was performed in December 2021.

EXPOSURES

Alcohol consumption level was categorized into none (0 g per day), mild (<15 g per day), moderate (15-29.9 g per day), and heavy (≥30 g per day) drinking. On the basis of changes in alcohol consumption level from 2009 to 2011, participants were categorized into the following groups: nondrinker, quitter, reducer, sustainer, and increaser.

MAIN OUTCOMES AND MEASURES

The primary outcome was newly diagnosed AD, VaD, or other dementia.

RESULTS

Among 3 933 382 participants (mean [SD] age, 55.0 [9.6] years; 2 037 948 men [51.8%]), during a mean (SD) follow-up of 6.3 (0.7) years, there were 100 282 cases of all-cause dementia, 79 982 cases of AD, and 11 085 cases of VaD. Compared with sustained nondrinking, sustained mild (adjusted hazard ratio [aHR], 0.79; 95% CI, 0.77-0.81) and moderate (aHR, 0.83; 95% CI, 0.79-0.88) drinking were associated with a decreased risk of all-cause dementia, whereas sustained heavy drinking was associated with an increased risk of all-cause dementia (aHR, 1.08; 95% CI, 1.03-1.12). Compared with sustained levels of drinking, reducing alcohol consumption from a heavy to a moderate level (aHR, 0.92; 95% CI, 0.86-0.99) and the initiation of mild alcohol consumption (aHR, 0.93; 95% CI, 0.90-0.96) were associated with a decreased risk of all-cause dementia. Increasers and quitters exhibited an increased risk of all-cause dementia compared with sustainers. The trends in AD and VaD remained consistent.

CONCLUSIONS AND RELEVANCE

In this cohort study of a Korean population, decreased risk of dementia was associated with maintaining mild to moderate alcohol consumption, reducing alcohol consumption from a heavy to a moderate level, and the initiation of mild alcohol consumption, suggesting that the threshold of alcohol consumption for dementia risk reduction is low.

Identification and Prioritization of PET Neuroimaging Targets for Microglial Phenotypes Associated with Microglial Activity in Alzheimer's Disease

Activation of microglial cells accompanies the progression of many neurodegenerative disorders, including Alzheimer's disease (AD). Development of molecular imaging tools specific to microglia can help elucidate the mechanism through which microglia contribute to the pathogenesis and progression of neurodegenerative disorders. Through analysis of published genetic, transcriptomic, and proteomic data sets, we identified 19 genes with microglia-specific expression that we then ranked based on association with the AD characteristics, change in expression, and potential druggability of the target. We believe that the process we used to identify and rank microglia-specific genes is broadly applicable to the identification and evaluation of targets in other disease areas and for applications beyond molecular imaging.

Moderate Ethanol-Preconditioning Offers Ischemic Tolerance Against Focal Cerebral Ischemic/Reperfusion: Role of Large Conductance Calcium-Activated Potassium Channel

The mechanism underlying moderate ethanol (EtOH)-preconditioning (PC) against ischemic brain injury remains unclear. We evaluated the role of large conductance calcium-sensitive potassium (BK_Ca) channels in EtOH-PC. Almost one hundred and ninety normal adult SD rats (8 to 10 weeks, 320-350 g) were enrolled in this study. Ischemic/reperfusion (I/R) brain injury was induced in rats by middle cerebral artery occlusion for 2 h followed by reperfusion for 24 h. EtOH or the BK_Ca channel opener, NS11021, was administered 24 h before I/R with or without pre-treatment with the BK_Ca channel blocker, paxilline. Infarct volumes were measured by tissue staining and imaging, and neurological functions were assessed by a scoring system. The expression of BK_Ca channel subunit α was detected by Western blotting, and cell apoptosis was assessed using staining. Prior (24 h) administration of ethanol that produced a peak plasma concentration of ~ 45 mg/dl in rats would offer neuroprotection after cerebral I/R. In addition, the expression of BK_Ca channel α-subunit was significantly increased 24 h after EtOH-PC (n = 10; control: 2.00 ± 0.09, EtOH: 1.00 ± 0.06; P < 0.5). Compared to I/R, EtOH-PC enhanced the expression of BK_Ca channel α-subunit both in the penumbra (n = 10; 24 h: I/R: 1.25 ± 0.10, EtOH-PC + I/R: 1.99 ± 0.12; P < 0.01; 4 h: I/R: 1.03 ± 0.03, EtOH-PC + I/R: 1.49 ± 0.05; P < 0.001) and infarct core (n = 10; 4 h: I/R: 1.04 ± 0.04, EtOH-PC + I/R: 1.42 ± 0.05; P < 0.001), improved the neurological function (n = 10; I/R: 14.00 (12.75-15.00), EtOH-PC + I/R: 7.00 (4.75-8.25); P < 0.001), attenuated the apoptosis (n = 10; I/R: 26.80 ± 0.69, EtOH-PC + I/R: 8.46 ± 0.31; P < 0.001), and decreased the infarct volume (n = 10; I/R: 244.00 ± 26.24, EtOH-PC + I/R: 70.09 ± 14.69; P < 0.001) after experimental cerebral I/R. These changes were reversed by paxilline administration. The moderate EtOH-PC protects against I/R-induced brain damage dependent on the upregulation BK_Ca channels.

Perception of the Attributes of Sherry Wine and Its Consumption in Young People in the South of Spain

The wine with the designation of origin “Jerez-Xerez-Sherry” is one of the most produced in Spain and with a greater volume of exports abroad. This study analyzes the preferences of Sherry Wine and its different varieties, based on gender and knowledge and interest in the world of wine. Similarly, the influence of the attributes of Sherry Wine on its choice and consumption is investigated. For this purpose, 1502 participants (1407 wine consumers) were recruited; among the consumers, 58.5% are women, and 74.3% have little knowledge of wine (Mean age 22.6; SD = 3.07; range 18–30). Data collection was done through an online survey. The results reveal that among the types of wines from Sherry, the Fino and the Manzanilla are the most chosen. The young people who have the highest consumption of wine are those who have the most prior knowledge of wine. Also, these young people attribute their choice of wine to intrinsic factors, and even women and connoisseurs are more important in this type of dimension. But the importance of the attributes differs according to the types of wines (Fino/Cream—flavor, Palo Cortado/Pedro Ximénez—color, Amontillado/Manzanilla—price and Oloroso—prizes). These findings will allow establishing measures for their promotion, as well as for the design and specific sales strategies for each type of wine.

Role of Alcohol Drinking in Alzheimer's Disease, Parkinson's Disease, and Amyotrophic Lateral Sclerosis

Neurodegenerative diseases, including Alzheimer’s disease (AD), Parkinson’s disease (PD) and amyotrophic lateral sclerosis (ALS), increase as the population ages around the world. Environmental factors also play an important role in most cases. Alcohol consumption exists extensively and it acts as one of the environmental factors that promotes these neurodegenerative diseases. The brain is a major target for the actions of alcohol, and heavy alcohol consumption has long been associated with brain damage. Chronic alcohol intake leads to elevated glutamate-induced excitotoxicity, oxidative stress and permanent neuronal damage associated with malnutrition. The relationship and contributing mechanisms of alcohol with these three diseases are different. Epidemiological studies have reported a reduction in the prevalence of Alzheimer’s disease in individuals who drink low amounts of alcohol; low or moderate concentrations of ethanol protect against β-amyloid (Aβ) toxicity in hippocampal neurons; and excessive amounts of ethanol increase accumulation of Aβ and Tau phosphorylation. Alcohol has been suggested to be either protective of, or not associated with, PD. However, experimental animal studies indicate that chronic heavy alcohol consumption may have dopamine neurotoxic effects through the induction of Cytochrome P450 2E1 (CYP2E1) and an increase in the amount of α-Synuclein (αSYN) relevant to PD. The findings on the association between alcohol consumption and ALS are inconsistent; a recent population-based study suggests that alcohol drinking seems to not influence the risk of developing ALS. Additional research is needed to clarify the potential etiological involvement of alcohol intake in causing or resulting in major neurodegenerative diseases, which will eventually lead to potential therapeutics against these alcoholic neurodegenerative diseases.

Alcohol protects the CNS by activating HSF1 and inducing the heat shock proteins

Although alcohol abuse and dependence have profound negative health consequences, emerging evidence suggests that exposure to low/moderate concentrations of ethanol protects multiple organs and systems. In the CNS, moderate drinking decreases the risk of dementia and Alzheimer's disease. This neuroprotection correlates with an increased expression of the heat shock proteins (HSPs). Multiple epidemiological studies revealed an inverse association between ethanol intoxication and traumatic brain injury mortality. In this case, ethanol-induced HSPs limit the inflammatory immune response diminishing cell death and improving the neurobehavioural outcome. Ethanol also protects the brain against ischemic injuries via the HSPs. In our laboratory, we demonstrated that ethanol increased the expression of several HSP genes in neurons and astrocytes by activating the transcription factor, heat shock factor 1 (HSF1). HSF1 induces HSPs that target misfolded proteins for refolding or degradation, increasing the survival chances of the cells. These data indicate that ethanol neuroprotection is mediated by the activation HSF1 and the induction of HSPs.

Protective Effects of Donepezil Against Alcohol-Induced Toxicity in Cell Culture: Role of Caspase-3

Ethanol (EtOH) is one of the most frequently abused drugs with heavy health, economic, and societal burdens. Although moderate to low EtOH may have some neuroprotective effects, heavy EtOH consumption associated with high blood alcohol level (BAL) can be quite detrimental. The brain is particularly vulnerable to the damaging effects of high BAL, leading to neuronal loss, cognitive, and behavioral deficits. Although the exact causes of these detriments are not fully elucidated, it is believed that damage to the cholinergic system is at least partially responsible for the cognitive impairment. Thus, high BAL may result in selective apoptotic damage to the cholinergic neurons. Donepezil (DON), a centrally acting, reversible and non-competitive acetylcholinesterase (AChE) inhibitor, approved for use in Alzheimer's disease (AD), may also attenuate EtOH-induced cognitive impairment. Cognitive effects of DON might be due to an anti-apoptotic activity as some AChE inhibitors have been shown to have this property. The aim of this study was to determine whether DON might protect against EtOH-induced toxicity and whether such protection might be apoptotically mediated. We exposed the human neuroblastoma-derived, SH-SY5Y cells to a relatively high concentration of EtOH (500 mM) for 24 h and evaluated the effects of two concentrations of DON (0.1 and 1.0 μM) on alcohol-induced toxicity and caspase-3, an apoptotic marker. We found a dose-dependent protection of DON against EtOH-induced toxicity as well as dose-dependent attenuation of EtOH-induced increases in caspase-3 levels. Thus, DON may inhibit apoptosis as well as alcohol-induced toxicity.

The Association Between Alcohol Use and the Progression of Alzheimer's Disease

OBJECTIVE

To examine the relationship between alcohol, both the amount and type, and cognitive decline in a cohort of Alzheimer's disease (AD) patients.

METHODS

A cohort of 360 patients with early AD in New York, Boston, Baltimore and Paris were followed-up biannually for up to 19.28 years. At each visit, the cognitive profile of the patients was assessed using the modified Mini-Mental State Examination (mMMSE), and patients' alcohol intake, including beverage type, was reported by patients' primary caregivers. General estimating equation analysis was used to determine whether baseline alcohol use was associated with the rate of cognitive decline.

RESULTS

Heavy drinkers (8 or more alcoholic drinks/week) had a faster cognitive decline, deteriorating 1.849 more points on their mMMSE score annually compared to abstainers (P = 0.001), or 2.444 more points compared to mild-moderate drinkers (1-7 alcoholic drinks/week) (P = 0.008). There was no significant difference when comparing mild-moderate drinkers to abstainers. Increasing standard drinks of hard liquor, but not beer or wine, was also associated with a faster rate of cognitive decline (β = -0.117 P = 0.001).

CONCLUSION

Heavy alcohol consumption and more hard liquor are associated with a faster rate of cognitive decline in AD patients, suggesting that they may hasten progression of AD. Our results suggest that alcohol drinking habits might alter the course of AD.

The central role of heat shock factor 1 in synaptic fidelity and memory consolidation

Networks of neuronal synapses are the fundamental basis for making and retaining memory. Reduced synapse number and quality correlates with loss of memory in dementia. Heat shock factor 1 (HSF1), the major transcription factor regulating expression of heat shock genes, plays a central role in proteostasis, in establishing and sustaining synaptic fidelity and function, and in memory consolidation. Support for this thesis is based on these observations: (1) heat shock induces improvements in synapse integrity and memory consolidation; (2) synaptic depolarization activates HSF1; (3) activation of HSF1 alone (independent of the canonical heat shock response) augments formation of essential synaptic elements-neuroligands, vesicle transport, synaptic scaffolding proteins, lipid rafts, synaptic spines, and axodendritic synapses; (4) HSF1 coalesces and activates memory receptors in the post-synaptic dendritic spine; (5) huntingtin or α-synuclein accumulation lowers HSF1 while HSF1 lowers huntingtin and α-synuclein aggregation-a potential vicious cycle; and (6) HSF1 agonists (including physical activity) can improve cognitive function in dementia models. Thus, via direct gene expression of synaptic elements, production of HSPs that assure high protein fidelity, and activation of other neuroprotective signaling pathways, HSF1 agonists could provide breakthrough therapy for dementia-associated disease.

Sub-toxic Ethanol Exposure Modulates Gene Expression and Enzyme Activity of Antioxidant Systems to Provide Neuroprotection in Hippocampal HT22 Cells

Ethanol is known to cause severe systemic damage often explained as secondary to oxidative stress. Brain is particularly vulnerable to ethanol-induced reactive oxygen species (ROS) because the high amounts of lipids, and because nerve cell membranes contain high amounts of peroxidable fatty acids. Usually these effects of ethanol are associated to high and/or chronic exposure to ethanol. However, as we show in this manuscript, a low and acute dose of ethanol trigger a completely different response in hippocampal cells. Thus, we have observed that 0.1% ethanol exposure to HT22 cells, a murine hippocampal-derived cell line, increases the transcriptional expression of different genes belonging to the classical, glutathione/glutaredoxin and thioredoxin/peroxiredoxin antioxidant systems, these including Sod1, Sod2, Gpx1, Gclc, and Txnrd1. Paralleling these changes, enzyme activities of total superoxide dismutase (tSOD), catalase, total glutathione peroxidase (tGPx), glutathione-S-reductase (GSR), and total thioredoxin reductase (tTXNRD), were all increased, while the generation of thiobarbituric acid reactive substances (TBARS), as indicators of lipid peroxidation, and glutathione levels remained unaltered. Ethanol exposure did not affect cell viability or cell growing as assessed by real-time cell culture monitoring, indicating that low ethanol doses are not deleterious for hippocampal cells, but rather prevented glutamate-induced excitotoxicity. In summary, we conclude that sub-toxic exposure to ethanol may well be neuroprotective against oxidative insults in hippocampal cells.

Ethanol-mediated activation of the NLRP3 inflammasome in iPS cells and iPS cells-derived neural progenitor cells

Background

Alcohol abuse produces an enormous impact on health, society, and the economy. Currently, there are very limited therapies available, largely due to the poor understanding of mechanisms underlying alcohol use disorders (AUDs) in humans. Oxidative damage of mitochondria and cellular proteins aggravates the progression of neuroinflammation and neurological disorders initiated by alcohol abuse.

Results

Here we show that ethanol exposure causes neuroinflammation in both human induced pluripotent stem (iPS) cells and human neural progenitor cells (NPCs). Ethanol exposure for 24 hours or 7 days does not affect the proliferation of iPS cells and NPCs, but primes an innate immune-like response by activating the NLR family pyrin domain containing 3 (NLRP3) inflammasome pathway. This leads to an increase of microtubule-associated protein 1A/1B-light chain 3⁺ (LC3B⁺) autophagic puncta and impairment of the mitochondrial and lysosomal distribution. In addition, a decrease of mature neurons derived from differentiating NPCs is evident in ethanol pre-exposed compared to control NPCs. Moreover, a second insult of a pro-inflammatory factor in addition to ethanol preexposure enhances innate cellular inflammation in human iPS cells.

Conclusions

This study provides strong evidence that neuronal inflammation contributes to the pathophysiology of AUDs through the activation of the inflammasome pathway in human cellular models.

Ethanol preconditioning of rat cerebellar cultures targets NMDA receptors to the synapse and enhances peroxiredoxin 2 expression

Epidemiological studies indicate that light-moderate alcohol (ethanol) consumers tend to have reduced risks of cognitive impairment and progression to dementia during aging. Exploring possible mechanisms, we previously found that moderate ethanol preconditioning (MEP, 20-30mM) of rat brain cultures for several days instigated neuroprotection against β-amyloid peptides. Our biochemical evidence implicated the NMDA receptor (NMDAR) as a potential neuroprotective "sensor", specifically via synaptic NMDAR signaling. It remains unclear how ethanol modulates the receptor and its downstream targets to engender neuroprotection. Here we confirm with deconvolution microscopy that MEP of rat mixed cerebellar cultures robustly increases synaptic NMDAR localization. Phospho-activation of the non-receptor tyrosine kinases Src and Pyk2, known to be linked to synaptic NMDAR, is also demonstrated. Additionally, the preconditioning enhances levels of an antioxidant protein, peroxiredoxin 2 (Prx2), reported to be downstream of synaptic NMDAR signaling, and NMDAR antagonism with memantine (earlier found to abrogate MEP neuroprotection) blocks the Prx2 elevations. To further link Prx2 with antioxidant-based neuroprotection, we circumvented the ethanol preconditioning-NMDAR pathway by pharmacologically increasing Prx2 with the naturally-occurring cruciferous compound, 3H-1,2-dithiole-3-thione (D3T). Thus, D3T pretreatment elevated Prx2 expression to a similar extent as MEP, while concomitantly preventing β-amyloid neurotoxicity; D3T also protected the cultures from hydrogen peroxide toxicity. The findings support a mechanism that couples synaptic NMDAR signaling, Prx2 expression and augmented antioxidant defenses in ethanol preconditioning-induced neuroprotection. That this mechanism can be emulated by a cruciferous vegetable constituent suggests that such naturally-occurring "neutraceuticals" may be useful in therapy for oxidative stress-related dementias.

Chronic Voluntary Ethanol Consumption Induces Favorable Ceramide Profiles in Selectively Bred Alcohol-Preferring (P) Rats

Heavy alcohol consumption has detrimental neurologic effects, inducing widespread neuronal loss in both fetuses and adults. One proposed mechanism of ethanol-induced cell loss with sufficient exposure is an elevation in concentrations of bioactive lipids that mediate apoptosis, including the membrane sphingolipid metabolites ceramide and sphingosine. While these naturally-occurring lipids serve as important modulators of normal neuronal development, elevated levels resulting from various extracellular insults have been implicated in pathological apoptosis of neurons and oligodendrocytes in several neuroinflammatory and neurodegenerative disorders. Prior work has shown that acute administration of ethanol to developing mice increases levels of ceramide in multiple brain regions, hypothesized to be a mediator of fetal alcohol-induced neuronal loss. Elevated ceramide levels have also been implicated in ethanol-mediated neurodegeneration in adult animals and humans. Here, we determined the effect of chronic voluntary ethanol consumption on lipid profiles in brain and peripheral tissues from adult alcohol-preferring (P) rats to further examine alterations in lipid composition as a potential contributor to ethanol-induced cellular damage. P rats were exposed for 13 weeks to a 20% ethanol intermittent-access drinking paradigm (45 ethanol sessions total) or were given access only to water (control). Following the final session, tissues were collected for subsequent chromatographic analysis of lipid content and enzymatic gene expression. Contrary to expectations, ethanol-exposed rats displayed substantial reductions in concentrations of ceramides in forebrain and heart relative to non-exposed controls, and modest but significant decreases in liver cholesterol. qRT-PCR analysis showed a reduction in the expression of sphingolipid delta(4)-desaturase (Degs2), an enzyme involved in de novo ceramide synthesis. These findings indicate that ethanol intake levels achieved by alcohol-preferring P rats as a result of chronic voluntary exposure may have favorable vs. detrimental effects on lipid profiles in this genetic line, consistent with data supporting beneficial cardioprotective and neuroprotective effects of moderate ethanol consumption.

Amyloid pore-channel hypothesis: effect of ethanol on aggregation state using frog oocytes for an Alzheimer's disease study

Alzheimer's disease severely compromises cognitive function. One of the mechanisms to explain the pathology of Alzheimer’s disease has been the hypotheses of amyloid-pore/channel formation by complex Aβ-aggregates. Clinical studies suggested the moderate alcohol consumption can reduces probability developing neurodegenerative pathologies. A recent report explored the ability of ethanol to disrupt the generation of complex Aβ in vitro and reduce the toxicity in two cell lines. Molecular dynamics simulations were applied to understand how ethanol blocks the aggregation of amyloid. On the other hand, the in silico modeling showed ethanol effect over the dynamics assembling for complex Aβ-aggregates mediated by break the hydrosaline bridges between Asp 23 and Lys 28, was are key element for amyloid dimerization. The amyloid pore/channel hypothesis has been explored only in neuronal models, however recently experiments suggested the frog oocytes such an excellent model to explore the mechanism of the amyloid pore/channel hypothesis. So, the used of frog oocytes to explored the mechanism of amyloid aggregates is new, mainly for amyloid/pore hypothesis. Therefore, this experimental model is a powerful tool to explore the mechanism implicates in the Alzheimer’s disease pathology and also suggests a model to prevent the Alzheimer’s disease pathology. [BMB Reports 2015; 48(1): 13-18]

Lifestyle and health-related risk factors and risk of cognitive aging among older veterans

Lifestyle and health-related factors are critical components of the risk for cognitive aging among veterans. Because dementia has a prolonged prodromal phase, understanding effects across the life course could help focus the timing and duration of prevention targets. This perspective may be especially relevant for veterans and health behaviors. Military service may promote development and maintenance of healthy lifestyle behaviors, but the period directly after active duty has ended could be an important transition stage and opportunity to address some important risk factors. Targeting multiple pathways in one intervention may maximize efficiency and benefits for veterans. A recent review of modifiable risk factors for Alzheimer's disease estimated that a 25% reduction of a combination of seven modifiable risk factors including diabetes, hypertension, obesity, depression, physical inactivity, smoking, and education/cognitive inactivity could prevent up to 3 million cases worldwide and 492,000 cases in the United States. Lifestyle interventions to address cardiovascular health in veterans may serve as useful models with both physical and cognitive activity components, dietary intervention, and vascular risk factor management. Although the evidence is accumulating for lifestyle and health-related risk factors as well as military risk factors, more studies are needed to characterize these factors in veterans and to examine the potential interactions between them.

The Role of NMDA Receptors in the Development of Brain Resistance through Pre- and Postconditioning

Brain tolerance or resistance can be achieved by interventions before and after injury through potential toxic agents used in low stimulus or dose. For brain diseases, the neuroprotection paradigm desires an attenuation of the resulting motor, cognitive, emotional, or memory deficits following the insult. Preconditioning is a well-established experimental and clinical translational strategy with great beneficial effects, but limited applications. NMDA receptors have been reported as protagonists in the adjacent cellular mechanisms contributing to the development of brain tolerance. Postconditioning has recently emerged as a new neuroprotective strategy, which has shown interesting results when applied immediately, i.e. several hours to days, after a stroke event. Investigations using chemical postconditioning are still incipient, but nevertheless represent an interesting and promising clinical strategy. In the present review pre- and postconditioning are discussed as neuroprotective paradigms and the focus of our attention lies on the participation of NMDA receptors proteins in the processes related to neuroprotection.

Decreased inflammatory responses of human lung epithelial cells after ethanol exposure are mimicked by ethyl pyruvate

Background and Purpose. Leukocyte migration into alveolar space plays a critical role in pulmonary inflammation resulting in lung injury. Acute ethanol (EtOH) exposure exerts anti-inflammatory effects. The clinical use of EtOH is critical due to its side effects. Here, we compared effects of EtOH and ethyl pyruvate (EtP) on neutrophil adhesion and activation of cultured alveolar epithelial cells (A549). Experimental Approach. Time course and dose-dependent release of interleukin- (IL-) 6 and IL-8 from A549 were measured after pretreatment of A549 with EtP (2.5–10 mM), sodium pyruvate (NaP, 10 mM), or EtOH (85–170 mM), and subsequent lipopolysaccharide or IL-1beta stimulation. Neutrophil adhesion to pretreated and stimulated A549 monolayers and CD54 surface expression were determined. Key Results. Treating A549 with EtOH or EtP reduced substantially the cytokine-induced release of IL-8 and IL-6. EtOH and EtP (but not NaP) reduced the adhesion of neutrophils to monolayers in a dose- and time-dependent fashion. CD54 expression on A549 decreased after EtOH or EtP treatment before IL-1beta stimulation. Conclusions and Implications. EtP reduces secretory and adhesive potential of lung epithelial cells under inflammatory conditions. These findings suggest EtP as a potential treatment alternative that mimics the anti-inflammatory effects of EtOH in early inflammatory response in lungs.

Alcohol stress, membranes, and chaperones

Ethanol, which affects all body organs, exerts a number of cytotoxic effects, most of them independent of cell type. Ethanol treatment leads to increased membrane fluidity and to changes in membrane protein composition. It can also interact directly with membrane proteins, causing conformational changes and thereby influencing their function. The cytotoxic action may include an increased level of oxidative stress. Heat shock protein molecular chaperones are ubiquitously expressed evolutionarily conserved proteins which serve as critical regulators of cellular homeostasis. Heat shock proteins can be induced by various forms of stresses such as elevated temperature, alcohol treatment, or ischemia, and they are also upregulated in certain pathological conditions. As heat shock and ethanol stress provoke similar responses, it is likely that heat shock protein activation also has a role in the protection of membranes and other cellular components during alcohol stress.

Preconditioning provides neuroprotection in models of CNS disease: paradigms and clinical significance

Preconditioning is a phenomenon in which brief episodes of a sublethal insult induce robust protection against subsequent lethal injuries. Preconditioning has been observed in multiple organisms and can occur in the brain as well as other tissues. Extensive animal studies suggest that the brain can be preconditioned to resist acute injuries, such as ischemic stroke, neonatal hypoxia/ischemia, surgical brain injury, trauma, and agents that are used in models of neurodegenerative diseases, such as Parkinson's disease and Alzheimer's disease. Effective preconditioning stimuli are numerous and diverse, ranging from transient ischemia, hypoxia, hyperbaric oxygen, hypothermia and hyperthermia, to exposure to neurotoxins and pharmacological agents. The phenomenon of "cross-tolerance," in which a sublethal stress protects against a different type of injury, suggests that different preconditioning stimuli may confer protection against a wide range of injuries. Research conducted over the past few decades indicates that brain preconditioning is complex, involving multiple effectors such as metabolic inhibition, activation of extra- and intracellular defense mechanisms, a shift in the neuronal excitatory/inhibitory balance, and reduction in inflammatory sequelae. An improved understanding of brain preconditioning should help us identify innovative therapeutic strategies that prevent or at least reduce neuronal damage in susceptible patients. In this review, we focus on the experimental evidence of preconditioning in the brain and systematically survey the models used to develop paradigms for neuroprotection, and then discuss the clinical potential of brain preconditioning.

Adaptation and sensitization to proteotoxic stress

Although severe stress can elicit toxicity, mild stress often elicits adaptations. Here we review the literature on stress-induced adaptations versus stress sensitization in models of neurodegenerative diseases. We also describe our recent findings that chronic proteotoxic stress can elicit adaptations if the dose is low but that high-dose proteotoxic stress sensitizes cells to subsequent challenges. In these experiments, long-term, low-dose proteasome inhibition elicited protection in a superoxide dismutase-dependent manner. In contrast, acute, high-dose proteotoxic stress sensitized cells to subsequent proteotoxic challenges by eliciting catastrophic loss of glutathione. However, even in the latter model of synergistic toxicity, several defensive proteins were upregulated by severe proteotoxicity. This led us to wonder whether high-dose proteotoxic stress can elicit protection against subsequent challenges in astrocytes, a cell type well known for their resilience. In support of this new hypothesis, we found that the astrocytes that survived severe proteotoxicity became harder to kill. The adaptive mechanism was glutathione dependent. If these findings can be generalized to the human brain, similar endogenous adaptations may help explain why neurodegenerative diseases are so delayed in appearance and so slow to progress. In contrast, sensitization to severe stress may explain why defenses eventually collapse in vulnerable neurons.

Nonpharmacologic treatment and prevention strategies for dementia

PURPOSE OF REVIEW

Epidemiologic studies can provide critical evidence to inform the timing and duration of nonpharmacologic interventions. Although more studies are needed to further determine long-term efficacy, the evidence supporting modifiable risk factors for prevention is compelling, and prevention strategies that incorporate multidomain nonpharmacologic factors may have the most impact.

RECENT FINDINGS

Epidemiologic studies have identified a number of promising nonpharmacologic factors that have the potential to lower the risk of developing dementia.

SUMMARY

Potential modifiable strategies for dementia prevention include cardiovascular risk factors; lifestyle risk factors such as physical, cognitive, and social activity as well as nutrition, smoking, and alcohol use; and sleep quality. Results of randomized controlled trials for the treatment of cardiovascular risk factors have not been consistent, while interventions that increase physical, cognitive, and social activity have demonstrated protective effects for dementia risk. Trials of single-nutrient dietary supplementation have also been conflicting, but focus on multinutrient supplementation shows promise. Observational data also indicate that sleep quality may be a modifiable risk factor for dementia prevention.

Neuroinflammation, neurodegeneration, and depression

Neurodegeneration and depression are two common co-morbid conditions, particularly within the aging population. Research has linked neuroinflammation as a major contributing factor to both of these diseases. The key to neuroinflammation effects on neurodegeneration and depression appears to lie within the dysregulation of the control and release of pro- and anti-inflammatory cytokines. This can come from an internal or external insult to the system, or from changes in the individual due to aging that culminate in immune dysregulation. The need to reduce neuroinflammation has led to extensive research into neuroprotectants. We discuss the efficacy found with nicotine, alcohol, resveratrol, curcumin, and ketamine. Our main focus will be on what research tells us about the connections between neuroinflammation, neurodegeneration, and depression, and the hope that neuroprotectants research gives people suffering from neurodegeneration and depression stemming from neuroinflammation. We will conclude by making suggestions for future research in this area.

Alcohol consumption in mild cognitive impairment and dementia: harmful or neuroprotective?

OBJECTIVE

In several longitudinal studies, light-to-moderate drinking of alcoholic beverages has been proposed as being protective against the development of age-related changes in cognitive function, predementia syndromes, and cognitive decline of degenerative (Alzheimer's disease, AD) or vascular origin (vascular dementia). However, contrasting findings also exist.

METHOD

The English literature published in this area before September 2011 was evaluated, and information relating to the various factors that may impact upon the relationship between alcohol consumption and dementia or predementia syndromes is presented in the succeeding texts.

RESULTS

Light-to-moderate alcohol consumption may be associated with a reduced risk of incident overall dementia and AD; however, protective benefits afforded to vascular dementia, cognitive decline, and predementia syndromes are less clear. The equivocal findings may relate to many of the studies being limited to cross-sectional designs, restrictions by age or gender, or incomplete ascertainment. Different outcomes, beverages, drinking patterns, and study follow-up periods or possible interactions with other lifestyle-related (e.g., smoking) or genetic factors (e.g., apolipoprotein E gene variation) may all contribute to the variability of findings.

CONCLUSION

Protective effects of moderate alcohol consumption against cognitive decline are suggested to be more likely in the absence of the AD-associated apolipoprotein E ε4 allele and where wine is the beverage. At present, there is no indication that light-to-moderate alcohol drinking would be harmful to cognition and dementia, and attempts to define what might be deemed beneficial levels of alcohol intake in terms of cognitive performance would be highly problematic and contentious.

Rescue from a two hit, high-throughput model of neurodegeneration with N-acetyl cysteine

Postmortem tissue from patients with neurodegeneration exhibits protein-misfolding stress and reduced proteasome activity. This hallmark burden of proteotoxic stress has led to the term "proteinopathies" for neurodegenerative diseases. Proteinopathies may also be exacerbated by previous insults, according to the two hit hypothesis of accelerated neurodegeneration. In order to model the response to two successive insults in a high-throughput fashion, we exposed the neuronal cell line N2a to two hits of the proteasome inhibitor MG132 and performed three unbiased viability assays. MG132 toxicity was synergistically exacerbated following sequential hits provided the first hit was high enough to be toxic. This accelerated viability loss was apparent by (1) a nuclear and cytoplasmic stain (DRAQ5+Sapphire), (2) immunocytochemistry for a cytoskeletal marker (α-tubulin), and (3) ATP levels (Cell Titer Glo). Ubiquitin-conjugated proteins were raised by toxic, but not subtoxic MG132, and were thus correlated with toxicity exacerbation at higher doses. We hypothesized that levels of autophagic and antioxidant defenses would be reduced with toxic, but not subtoxic MG132, explaining their differential impact on a second hit. However, proteins involved in chaperone-mediated autophagy were raised by toxic MG132, not reduced. Furthermore, inhibiting autophagy enhanced the toxicity of both subtoxic and toxic MG132 as well as of dual hits, suggesting that autophagic removal of cellular debris protected against proteasome inhibition. Two toxic hits of MG132 synergistically decreased the antioxidant glutathione. The glutathione precursor N-acetyl cysteine reversed this glutathione loss and prevented the toxic response to dual hits by all three assays. Dietary supplementation with N-acetyl cysteine benefits Alzheimer's patients and is currently undergoing clinical trials in Parkinson's disease. The present report is the first demonstration that this versatile compound is protective against synergistic loss of viability as well as of glutathione following unrelenting, sequential hits of proteotoxic stress as may occur in the diseased brain.

Moderate ethanol ingestion and cardiovascular protection: from epidemiologic associations to cellular mechanisms

While ethanol intake at high levels (3-4 or more drinks), either in acute (occasional binge drinking) or chronic (daily) settings, increases the risk for myocardial infarction and stroke, an inverse relationship between regular consumption of alcoholic beverages at light to moderate levels (1-2 drinks per day) and cardiovascular risk has been consistently noted in a large number of epidemiologic studies. Although initially attributed to polyphenolic antioxidants in red wine, subsequent work has established that the ethanol component contributes to the beneficial effects associated with moderate intake of alcoholic beverages regardless of type (red versus white wine, beer, spirits). Concerns have been raised with regard to interpretation of epidemiologic evidence for this association including heterogeneity of the reference groups examined in many studies, different lifestyles of moderate drinkers versus abstainers, and favorable risk profiles in moderate drinkers. However, better controlled epidemiologic studies and especially work conducted in animal models and cell culture systems have substantiated this association and clearly established a cause and effect relationship between alcohol consumption and reductions in tissue injury induced by ischemia/reperfusion (I/R), respectively. The aims of this review are to summarize the epidemiologic evidence supporting the effectiveness of ethanol ingestion in reducing the likelihood of adverse cardiovascular events such as myocardial infarction and ischemic stroke, even in patients with co-existing risk factors, to discuss the ideal quantities, drinking patterns, and types of alcoholic beverages that confer protective effects in the cardiovascular system, and to review the findings of recent experimental studies directed at uncovering the mechanisms that underlie the cardiovascular protective effects of antecedent ethanol ingestion. Mechanistic interrogation of the signaling pathways invoked by antecedent ethanol ingestion may point the way towards development of new therapeutic approaches that mimic the powerful protective effects of socially relevant alcohol intake to limit I/R injury, but minimize the negative psychosocial impact and pathologic outcomes that also accompany consumption of ethanol.

Positive and negative effects of alcohol and nicotine and their interactions: a mechanistic review

Nicotine and alcohol are two of the most commonly abused legal substances. Heavy use of one drug can often lead to, or is predictive of, heavy use of the other drug in adolescents and adults. Heavy drinking and smoking alone are of significant health hazard. The combination of the two, however, can result in synergistic adverse effects particularly in incidences of various cancers (e.g., esophagus). Although detrimental consequences of smoking are well established, nicotine by itself might possess positive and even therapeutic potential. Similarly, alcohol at low or moderated doses may confer beneficial health effects. These opposing findings have generated considerable interest in how these drugs act. Here we will briefly review the negative impact of drinking-smoking co-morbidity followed by factors that appear to contribute to the high rate of co-use of alcohol and nicotine. Our main focus will be on what research is telling us about the central actions and interactions of these drugs, and what has been elucidated about the mechanisms of their positive and negative effects. We will conclude by making suggestions for future research in this area.

New strategies in neuroprotection and neurorepair

There are currently few clinical strategies in place, which provide effective neuroprotection and repair, despite an intense international effort over the past decades. One possible explanation for this is that a deeper understanding is required of how endogenous mechanisms act to confer neuroprotection. This mini-review reports the proceedings of a recent workshop "Neuroprotection and Neurorepair: New Strategies" (Iguazu Falls, Misiones, Argentina, April 11-13, 2011, Satellite Symposium of the V Neurotoxicity Society Meeting, 2011) in which four areas of active research were identified to have the potential to generate new insights into this field. Topics discussed were (i) metallothionein and other multipotent neuroprotective molecules; (ii) oxidative stress and their signal mediated pathways in neuroregeneration; (iii) neurotoxins in glial cells, and (iv) drugs of abuse with neuroprotective effects.

Moderate alcohol consumption and cognitive risk

We reviewed 143 papers that described the relationship between moderate drinking of alcohol and some aspect of cognition. Two types of papers were found: (1) those that provided ratios of risk between drinkers and nondrinkers (74 papers in total) and (2) those that, although they did not provide such ratios, allowed cognition in drinkers to be rated as "better," "no different," or "worse" than cognition in nondrinkers (69 papers in total). The history of research on moderate drinking and cognition can be divided into two eras: 1977-1997 and 1998-present. Phase I (1977-1997) was the era of neuropsychological evaluation involving mostly young to middle-aged (18-50 years old) subjects. Although initial studies indicated moderate drinking impaired cognition, many later studies failed to confirm this, instead finding no difference in cognition between drinkers and nondrinkers. Phase II (1998-present) was and is the era of mental status exam evaluation involving mostly older (≥55 years old) subjects. These studies overwhelmingly found that moderate drinking either reduced or had no effect on the risk of dementia or cognitive impairment. When all the ratios of risk from all the studies in phase II providing such ratios are entered into a comprehensive meta-analysis, the average ratio of risk for cognitive risk (dementia or cognitive impairment/decline) associated with moderate "social" (not alcoholic) drinking of alcohol is 0.77, with nondrinkers as the reference group. The benefit of moderate drinking applied to all forms of dementia (dementia unspecified, Alzheimer's disease, and vascular dementia) and to cognitive impairment (low test scores), but no significant benefit against cognitive decline (rate of decline in test scores) was found. Both light and moderate drinking provided a similar benefit, but heavy drinking was associated with nonsignificantly higher cognitive risk for dementia and cognitive impairment. Although the meta-analysis also indicated that wine was better than beer or spirits, this was based on a relatively small number of studies because most studies did not distinguish among these different types of alcohol. Furthermore, a number of the studies that did make the distinction reported no difference among the effects of these different types of alcohol. Therefore, at present this question remains unanswered. Analysis also showed that the presence of the apolipoprotein E epsilon 4 allele eliminated the benefit of moderate drinking. However, this was based on a relatively small number of studies and several other studies have found a beneficial effect of the epsilon e4 allele. Further studies are necessary to settle this question. The benefit of moderate alcohol for cognition was seen in both men and women, although the amount and pattern of drinking is very different between the two sexes. Lastly, the finding of unaffected or significantly reduced cognitive risk in light to moderate drinkers was seen in 14/19 countries for which country-specific ratio data were available, with three of the five remaining countries showing nonsignificant reductions as well. Overall, light to moderate drinking does not appear to impair cognition in younger subjects and actually seems to reduce the risk of dementia and cognitive decline in older subjects.

Soluble factors from IL-1β-stimulated astrocytes activate NR1a/NR2B receptors: implications for HIV-1-induced neurodegeneration

Astrocytes play an important role in astrocyte-neuron homeostasis. In HIV-1-infected brain, interleukin 1 beta (IL-1β) activation of astrocytes contributes to neurodegeneration. However, the molecular mechanisms underlying IL-1β-activated-astrocytes-induced neurodegeneration in HIV-1-infected brain are largely unknown. We hypothesize that secretory factors from the activated astrocytes affect N-methyl-d-aspartate (NMDA) receptor, a major pathway implicated in HIV-1-associated neurodegeneration. To test this hypothesis, we studied effects of IL-1β-stimulated astrocyte conditioned medium (ACM+) for its ability to activate NR1a/NR2B receptors expressed on Xenopus oocytes. Astrocytes treated with IL-1β 20ng/ml for 24h induced CXCL8, CCL2, MMP1 and MMP7. Pressure ejection of the ACM(+) produced an inward current in NR1a/NR2B-expressing oocytes. The inward current produced by ACM(+) was blocked by NMDA receptor antagonist, APV but not by non-NMDA receptor antagonist, CNQX. These results suggest that IL-1β stimulated astrocytes activate NR1a/NR2B receptors which may have implications in HIV-1-associated neurodegeneration.