Reversibility of alcohol-related brain damage: clinical and experimental observations

Alcohol and the central nervous system

Ethanol use is common to most cultures but with varying doses and to varying extents. While research has focused on the effects on the liver, alcohol exerts a range of actions on the function and structure of the nervous system. In the central nervous system (CNS) it can provoke or exacerbate neurological and psychiatric disease; its effects on the peripheral nervous system are not included in this review. Sustained alcohol intake can predispose to acute neurochemical changes which, with continued ingestion and incomplete treatment, can lead to chronic structural changes in the CNS: these include generalised cortical and cerebellar atrophy, amnesic syndromes such as Korsakoff's syndrome, and specific white matter disorders such as central pontine myelinolysis and Marchiafava-Bignami syndrome. Alcohol in pregnancy commonly and significantly affects fetal health, though this receives less medical and political attention than other causes of fetal harm. This review looks at the range of disorders that can follow acute or chronic alcohol use, and how these should be managed, and we provide a practical overview on how neurologists might diagnose and manage alcohol addiction.

Alpha-Synuclein in Alcohol Use Disorder, Connections with Parkinson's Disease and Potential Therapeutic Role of 5' Untranslated Region-Directed Small Molecules

Alpha-synuclein (α-Syn) is a 140-amino acid (aa) protein encoded by the Synuclein alpha SNCA gene. It is the synaptic protein associated with Parkinson's disease (PD) and is the most highly expressed protein in the Lewy bodies associated with PD and other alpha synucleopathies, including Lewy body dementia (LBD) and multiple system atrophy (MSA). Iron deposits are present in the core of Lewy bodies, and there are reports suggesting that divalent metal ions including Cu2+ and Fe2+ enhance the aggregation of α-Syn. Differential expression of α-Syn is associated with alcohol use disorder (AUD), and specific genetic variants contribute to the risk for alcoholism, including alcohol craving. Spliced variants of α-Syn, leading to the expression of several shorter forms which are more prone to aggregation, are associated with both PD and AUD, and common transcript variants may be able to predict at-risk populations for some movement disorders or subtypes of PD, including secondary Parkinsonism. Both PD and AUD are associated with liver and brain iron dyshomeostasis. Research over the past decade has shown that α-Syn has iron import functions with an ability to oxidize the Fe3+ form of iron to Fe2+ to facilitate its entry into cells. Our prior research has identified an iron-responsive element (IRE) in the 5' untranslated region (5'UTR) of α-Syn mRNA, and we have used the α-Syn 5'UTR to screen for small molecules that modulate its expression in the H4 neuronal cell line. These screens have led us to identify several interesting small molecules capable of both decreasing and increasing α-Syn expression and that may have the potential, together with the recently described mesenchymal stem cell therapies, to normalize α-Syn expression in different regions of the alcoholic and PD brain.

Protracted abstinence from chronic ethanol exposure alters the structure of neurons and expression of oligodendrocytes and myelin in the medial prefrontal cortex

In rodents, chronic intermittent ethanol vapor exposure (CIE) produces alcohol dependence, alters the structure and activity of pyramidal neurons and decreases the number of oligodendroglial progenitors in the medial prefrontal cortex (mPFC). In this study, adult Wistar rats were exposed to seven weeks of CIE and were withdrawn from CIE for 21 days (protracted abstinence; PA). Tissue enriched in the mPFC was processed for Western blot analysis and Golgi-Cox staining to investigate the long-lasting effects of CIE on the structure of mPFC neurons and the levels of myelin-associated proteins. PA increased dendritic arborization within apical dendrites of pyramidal neurons. These changes occurred concurrently with hypophosphorylation of the N-methyl-d-aspartate (NMDA) receptor 2B (NR2B) at Tyr-1472. PA increased myelin basic protein (MBP) levels which occurred concurrently with hypophosphorylation of the premyelinating oligodendrocyte bHLH transcription factor Olig2 in the mPFC. Given that PA is associated with increased sensitivity to stress and hypothalamic-pituitary-adrenal (HPA) axis dysregulation, and stress alters oligodendrocyte expression as a function of glucocorticoid receptor (GR) activation, the levels of total GR and phosphorylated GR were also evaluated. PA produced hypophosphorylation of the GR at Ser-232 without affecting expression of total protein. These findings demonstrate persistent and compensatory effects of ethanol in the mPFC long after cessation of CIE, including enhanced myelin production and impaired GR function. Collectively, these results suggest a novel relationship between oligodendrocytes and GR in the mPFC, in which stress may alter frontal cortex function in alcohol dependent subjects by promoting hypermyelination, thereby altering the cellular composition and white matter structure in the mPFC.

A novel microassay for measuring blood alcohol concentration using a disposable biosensor strip

A novel disposable amperometric biosensor strip for determination of blood alcohol concentration (BAC) with small volume of sample has been constructed using screen-printed electrodes (SPE), nanocomposite film and alcohol dehydrogenase (ADH). Firstly, the GNPs-MWCNT-Nafion nanocomposite film modified on a working electrode was made of Nafion-117, multi-wall carbon nanotubes (MWCNT) and gold nanoparticles (GNPs). After that Meldola's blue (MB) acted as an electron transfer mediator and the mixed solution of ADH, nicotinamide adenine dinucleotide (NAD(+)) were modified in order on the nanocomposite film. At last, a hydrophilic membrane which had an eyehole in center was placed at the outermost of the working area to make a reaction tank of 5 μL, then the hydrophilic membrane/ADH-NAD(+)/GNPs-MWCNT-MB-Nafion/SPE was prepared. The detection of BAC can be accomplished with 5 μL of blood sample obtained precisely by siphonage. Optimum conditions of the biosensor were experimentally determined by varying several important parameters: working potential, solution pH value, environmental temperature and interferences. Experimental results indicated that the biosensor possessed a good accuracy and stability, the linear response range was 2.0 × 10(-4) to 25 × 10(-3)mol/L and the detection limit of the biosensor was 5.0 × 10(-5)mol/L (S/N=3). In the measurement of blood samples, the proposed biosensor had excellent detection performance for measuring BAC and showed a good correlation with gas chromatography. The prepared biosensor strip can be valid for the analysis of BAC.

Distinct cell proliferation events during abstinence after alcohol dependence: microglia proliferation precedes neurogenesis

Excessive alcohol intake characteristic of Alcohol Use Disorders (AUDs) produces neurodegeneration that may recover with abstinence. The mechanism of regeneration is unclear, however neurogenesis from neural stem/progenitor cells is a feasible mechanism of structural plasticity. Therefore, a timecourse of cell proliferation was examined in a rat model of an AUD and showed a striking burst in cell proliferation at 2 days of abstinence preceding the previously reported neurogenic proliferation at 7 days. New cells at 2 days, assessed by bromo-deoxy-uridine incorporation and endogenous markers, were observed throughout hippocampus and cortex. Although the majority of these new cells did not become neurons, neurogenesis was not altered at this specific time point. These new cells expressed a microglia-specific marker, Iba-1, and survived at least 2 months. This first report of microglia proliferation in a model of an AUD suggests that microgliosis could contribute to volume recovery in non-neurogenic regions during abstinence.

Nicotine self-administration impairs hippocampal plasticity

Nicotine, the neuroactive compound responsible for tobacco addiction, is primarily believed to have beneficial effects on the adult brain. However, in heavy smokers, abstinence from nicotine is accompanied by cognitive impairments that suggest adverse effects of nicotine on brain plasticity. For this reason, we studied changes in plasticity-related processes in the dentate gyrus (DG) of the hippocampal formation of animals trained to self-administer nicotine. The DG was chosen because it undergoes profound plastic rearrangements, many of which have been related to memory and learning performances. In this region, we examined the expression of the polysialylated (PSA) forms of neural cell adhesion molecule (NCAM), PSA-NCAM, neurogenesis, and cell death by measuring the number of pyknotic cells. It was found that nicotine self-administration profoundly decreased, in a dose-dependent manner, the expression of PSA-NCAM in the DG; a significant effect was observed at all the doses tested (0.02, 0.04, and 0.08 mg/kg per infusion). Neurogenesis was also decreased in the DG, but a significant effect was observed only for the two highest doses of nicotine. Finally, the same doses that decreased neurogenesis also increased cell death. These results raise an important additional concern for the health consequences of nicotine abuse and open new insight on the possible neural mechanisms of tobacco addiction.