Effects of long-term moderate ethanol and cholesterol on cognition, cholinergic neurons, inflammation, and vascular impairment in rats

Neurosteroid [3α,5α]3-hydroxypregnan-20-one inhibition of chemokine monocyte chemoattractant protein-1 in alcohol-preferring rat brain neurons, microglia, and astroglia

BACKGROUND

Neuroimmune dysfunction in alcohol use disorder (AUD) is associated with activation of myeloid differentiation primary response 88 (MyD88)-dependent Toll-like receptors (TLR) resulting in overexpression of the chemokine monocyte chemoattractant protein-1 (MCP-1/CCL2). MCP-1 overexpression in the brain is linked to anxiety, higher alcohol intake, neuronal death, and activation of microglia observed in AUD. The neurosteroid [3α,5α][3-hydroxypregnan-20-one (3α,5α-THP) has been reported as an inhibitor of MyD88-dependent TLR activation and MCP-1 overexpression in mouse and human macrophages and the brain of alcohol-preferring (P) rats.

METHODS

We investigated how 3α,5α-THP regulates MCP-1 expression at the cellular level in P rat nucleus accumbens (NAc) and central amygdala (CeA). We focused on neurons, microglia, and astrocytes, examining the individual voxel density of MCP-1, neuronal marker NeuN, microglial marker IBA1, astrocytic marker GFAP, and their shared voxel density, defined as intersection. Ethanol-naïve male and female P rats were perfused 1 h after IP injections of 15 mg/kg of 3α,5α-THP, or vehicle. The NAc and CeA were imaged using confocal microscopy following double-immunofluorescence staining for MCP-1 with NeuN, IBA1, and GFAP, respectively.

RESULTS

MCP-1 intersected with NeuN predominantly and IBA1/GFAP negligibly. 3α,5α-THP reduced MCP-1 expression in NeuN-labeled cells by 38.27 ± 28.09% in male and 56.11 ± 21.46% in female NAc, also 37.99 ± 19.53% in male and 54.96 ± 30.58% in female CeA. In females, 3α,5α-THP reduced the MCP-1 within IBA1 and GFAP-labeled voxels in the NAc and CeA. Conversely, in males, 3α,5α-THP did not significantly alter the MCP-1 within IBA1 in NAc or with GFAP in the CeA. Furthermore, 3α,5α-THP decreased levels of IBA1 in both regions and sexes with no impact on GFAP or NeuN levels. Secondary analysis performed on data normalized to % control values indicated that no significant sex differences were present.

CONCLUSIONS

These data suggest that 3α,5α-THP inhibits neuronal MCP-1 expression and decreases the proliferation of microglia in P rats. These results increase our understanding of potential mechanisms for 3α,5α-THP modulation of ethanol consumption.

Two-Month Voluntary Ethanol Consumption Promotes Mild Neuroinflammation in the Cerebellum but Not in the Prefrontal Cortex, Hippocampus, or Striatum of Mice

Chronic ethanol exposure often triggers neuroinflammation in the brain's reward system, potentially promoting the drive for ethanol consumption. A main marker of neuroinflammation is the microglia-derived monocyte chemoattractant protein 1 (MCP1) in animal models of alcohol use disorder in which ethanol is forcefully given. However, there are conflicting findings on whether MCP1 is elevated when ethanol is taken voluntarily, which challenges its key role in promoting motivation for ethanol consumption. Here, we studied MCP1 mRNA levels in areas implicated in consumption motivation-specifically, the prefrontal cortex, hippocampus, and striatum-as well as in the cerebellum, a brain area highly sensitive to ethanol, of C57BL/6 mice subjected to intermittent and voluntary ethanol consumption for two months. We found a significant increase in MCP1 mRNA levels in the cerebellum of mice that consumed ethanol compared to controls, whereas no significant changes were observed in the prefrontal cortex, hippocampus, or striatum or in microglia isolated from the hippocampus and striatum. To further characterize cerebellar neuroinflammation, we measured the expression changes in other proinflammatory markers and chemokines, revealing a significant increase in the proinflammatory microRNA miR-155. Notably, other classical proinflammatory markers, such as TNFα, IL6, and IL-1β, remained unaltered, suggesting mild neuroinflammation. These results suggest that the onset of neuroinflammation in motivation-related areas is not required for high voluntary consumption in C57BL/6 mice. In addition, cerebellar susceptibility to neuroinflammation may be a trigger to the cerebellar degeneration that occurs after chronic ethanol consumption in humans.

Neuroimmune Activation and Microglia Reactivity in Female Rats Following Alcohol Dependence

The rates of alcohol use disorder among women are growing, yet little is known about how the female brain is affected by alcohol. The neuroimmune system, and specifically microglia, have been implicated in mediating alcohol neurotoxicity, but most preclinical studies have focused on males. Further, few studies have considered changes to the microglial phenotype when examining the effects of ethanol on brain structure and function. Therefore, we quantified microglial reactivity in female rats using a binge model of alcohol dependence, assessed through morphological and phenotypic marker expression, coupled with regional cytokine levels. In a time- and region-dependent manner, alcohol altered the microglial number and morphology, including the soma and process area, and the overall complexity within the corticolimbic regions examined, but no significant increases in the proinflammatory markers MHCII or CD68 were observed. The majority of cytokine and growth factor levels examined were similarly unchanged. However, the expression of the proinflammatory cytokine TNFα was increased, and the anti-inflammatory IL-10, decreased. Thus, female rats showed subtle differences in neuroimmune reactivity compared to past work in males, consistent with reports of enhanced neuroimmune responses in females across the literature. These data suggest that specific neuroimmune reactions in females may impact their susceptibility to alcohol neurotoxicity and other neurodegenerative events with microglial contributions.

Sclerostin, vascular risk factors, and brain atrophy in excessive drinkers

Objective

Heavy alcohol consumption causes several organic complications, including vessel wall calcification. Vascular damage may be involved in the development of brain atrophy and cognitive impairment. Recently, sclerostin (whose levels may be altered in alcoholics) has emerged as a major vascular risk factor. The objective of the present study is to analyze the prevalence of vascular calcifications in alcoholics, and the relationships of these lesions with brain atrophy, as well as the role of sclerostin on these alterations.

Patients and methods

A total of 299 heavy drinkers and 32 controls were included. Patients underwent cranial computed tomography, and several indices related to brain atrophy were calculated. In addition, patients and controls underwent plain radiography and were evaluated for the presence or absence of vascular calcium deposits, cardiovascular risk factors, liver function, alcohol intake, serum sclerostin, and routine laboratory variables.

Results

A total of 145 (48.47%) patients showed vascular calcium deposits, a proportion significantly higher than that observed in controls (χ² = 16.31; p < 0.001). Vascular calcium deposits were associated with age (t = 6.57; p < 0.001), hypertension (t = 5.49; p < 0.001), daily ethanol ingestion (Z = 2.18; p = 0.029), duration of alcohol consumption (Z = 3.03; p = 0.002), obesity (χ² = 4.65; p = 0.031), total cholesterol (Z = 2.04; p = 0.041), triglycerides (Z = 2.05; p = 0.04), and sclerostin levels (Z = 2.64; p = 0.008). Calcium deposits were significantly related to Bifrontal index (Z = 2.20; p = 0.028) and Evans index (Z = 2.25; p = 0.025). Serum sclerostin levels were related to subcortical brain atrophy, assessed by cella media index (Z = 2.43; p = 0.015) and Huckmann index (ρ = 0.204; p = 0.024). Logistic regression analyses disclosed that sclerostin was the only variable independently related to brain atrophy assessed by altered cella media index. Sclerostin was also related to the presence of vascular calcifications, although this relationship was displaced by age if this variable was also included.

Conclusion

Prevalence of vascular calcification in alcoholics is very high. Vascular calcium deposits are related to brain atrophy. Serum sclerostin is strongly related to brain shrinkage and also shows a significant relationship with vascular calcifications, only displaced by advanced age.

Sex differences in stress-induced alcohol intake: a review of preclinical studies focused on amygdala and inflammatory pathways

Clinical studies suggest that women are more likely than men to relapse to alcohol drinking in response to stress; however, the mechanisms underlying this sex difference are not well understood. A number of preclinical behavioral models have been used to study stress-induced alcohol intake. Here, we review paradigms used to study effects of stress on alcohol intake in rodents, focusing on findings relevant to sex differences. To date, studies of sex differences in stress-induced alcohol drinking have been somewhat limited; however, there is evidence that amygdala-centered circuits contribute to effects of stress on alcohol seeking. In addition, we present an overview of inflammatory pathways leading to microglial activation that may contribute to alcohol-dependent behaviors. We propose that sex differences in neuronal function and inflammatory signaling in circuits centered on the amygdala are involved in sex-dependent effects on stress-induced alcohol seeking and suggest that this is an important area for future studies.

Zebrafish models of fetal alcohol spectrum disorders

Fetal alcohol spectrum disorder (FASD) describes a wide range of structural deficits and cognitive impairments. FASD impacts up to 5% of children born in the United States each year, making ethanol one of the most common teratogens. Due to limitations and ethical concerns, studies in humans are limited in their ability to study FASD. Animal models have proven critical in identifying and characterizing the mechanisms underlying FASD. In this review, we will focus on the attributes of zebrafish that make it a strong model in which to study ethanol-induced developmental defects. Zebrafish have several attributes that make it an ideal model in which to study FASD. Zebrafish produced large numbers of externally fertilized, translucent embryos. With a high degree of genetic amenability, zebrafish are at the forefront of identifying and characterizing the gene-ethanol interactions that underlie FASD. Work from multiple labs has shown that embryonic ethanol exposures result in defects in craniofacial, cardiac, ocular, and neural development. In addition to structural defects, ethanol-induced cognitive and behavioral impairments have been studied in zebrafish. Building upon these studies, work has identified ethanol-sensitive loci that underlie the developmental defects. However, analyses show there is still much to be learned of these gene-ethanol interactions. The zebrafish is ideally suited to expand our understanding of gene-ethanol interactions and their impact on FASD. Because of the conservation of gene function between zebrafish and humans, these studies will directly translate to studies of candidate genes in human populations and allow for better diagnosis and treatment of FASD.

Sudden cessation of fluoxetine before alcohol drinking reinstatement alters microglial morphology and TLR4/inflammatory neuroadaptation in the rat brain

Preclinical studies on the effects of abrupt cessation of selective serotonin reuptake inhibitors (SSRIs), a medication often prescribed in alcohol use disorder (AUD) patients with depression, results in alcohol consumption escalation after resuming drinking. However, a potential neuroinflammatory component on this escalation remains unexplored despite the immunomodulatory role of serotonin. Here, we utilized a rat model of 14-daily administration of the SSRI fluoxetine (10 mg/kg/day) along alcohol self-administration deprivation to study the effects of fluoxetine cessation on neuroinflammation after resuming alcohol drinking. Microglial morphology and inflammatory gene expression were analyzed in prelimbic cortex, striatum, basolateral amygdala and dorsal hippocampus. Results indicated that alcohol drinking reinstatement increased microglial IBA1 immunoreactivity and altered morphometric features of activated microglia (fractal dimension, lacunarity, density, roughness, and cell area, perimeter and circularity). Despite alcohol reinstatement, fluoxetine cessation modified microglial morphology in a brain region-specific manner, resulting in hyper-ramified (spatial complexity of branching), reactive (lower heterogeneity and circularity)-like microglia. We also found that microglial cell area correlated with changes in mRNA expression of chemokines (Cx3cl1/fractalkine, Cxcl12/SDF1α, Ccl2/MCP1), cytokines (IL1β, IL6, IL10) and the innate immune toll-like receptor 4 (TLR4) in dorsal hippocampus. Specifically, TLR4 correlated with microglial spatial complexity assessed by fractal dimension in striatum, suggesting a role in process branching. These findings suggest that alcohol drinking reinstatement after fluoxetine treatment cessation disturbs microglial morphology and reactive phenotype associated with a TLR4/inflammatory response to alcohol in a brain region-specific manner, facts that might contribute to alcohol-induced damage through the promotion of escalation of alcohol drinking behavior.

Effects of chronic ethanol consumption on the expression of GLT-1 and neuroplasticity-related proteins in the nucleus accumbens of alcohol-preferring rats

Chronic ethanol exposure induces impairments in CNS excitatory and inhibitory activity. These impairments are associated with glutamatergic dysfunction, including altered neuroplasticity. This study examined the effects of 6-week ethanol (15% and 30% v/v) consumption, by male alcohol-preferring P rats, on protein expression associated with neuroplasticity and glutamate transporter-1 (GLT-1) function. The latter regulates intra- and extra-synaptic glutamate levels. We focused on the shell and core subregions of the nucleus accumbens (Acb); i.e., shell (AcbSh) and core (AcbCo), for these measures. Chronic ethanol exposure increased the expression of BDNF, Arc and phosphorylated (p)-post-synaptic density protein-95 (p-PSD-95) in the AcbSh of P rats. Moreover, the ratio of phospho-neuronal nitric oxide synthase (p-nNOS) to total nNOS was also increased in the AcbSh. These changes in BDNF, Arc and p-nNOS/nNOS ratio were not observed in the AcbCo. Furthermore, chronic ethanol consumption reduced GLT-1 expression in the AcbSh. Alternatively, treatment with ceftriaxone (CEF), a known GLT-1 upregulator, abolished the effect of chronic ethanol consumption on BDNF expression in the AcbSh. Overall, the present findings confirm that chronic ethanol consumption modulates activity-associated synaptic proteins, including BDNF, Arc and nNOS in a subregion-specific (i.e., in the AcbSh but not AcbCo) manner. Thus, alterations in mesocorticolimbic glutamatergic homeostasis and neuroplasticity are possible functional targets for the treatment of alcohol use disorders.

Phenotyping CCL2 Containing Central Amygdala Neurons Controlling Alcohol Withdrawal-Induced Anxiety

Chemokines such as chemokine (C-C motif) ligand 2 (CCL2) play a role in several behaviors, including anxiety-like behavior, but whether neurons are an important source of CCL2 for behavior and how neuronal CCL2 may work to affect behavior are still debated. When a herpes simplex virus (HSV) vector was used to knockdown CCL2 mRNA in neurons of the central nucleus of the amygdala (CeA) in rats experiencing multiple withdrawals from low dose ethanol, anxiety-like behavior appeared in the social interaction task. To examine this finding further Fractalkine (CX3CL1), a chemokine that is often found to have an opposing function to CCL2 was measured in these rats. Both alcohol withdrawal and CCL2 knockdown increased the levels of the anti-inflammatory protein CX3CL1. The combination of alcohol withdrawal and CCL2 knockdown decreased CX3CL1 and may alter pro-inflammatory/anti-inflammatory balance, and thus highlights the potential importance of CCL2 and CCL2/CX3CL1 balance in anxiety. To find a mechanism by which neuronal chemokines like CCL2 could affect behavior, retrograde tracing with fluorescent nanobeads was done in two brain regions associated with anxiety the bed nucleus of the stria terminalis (BNST) and the ventral periaqueductal gray (VPAG). These studies identified CeA projection neurons to these brain regions that contain CCL2. To demonstrate that CCL2 can be transported via axons to downstream brain regions, the axonal transport blocker, colchicine, was given and 24 h later, the accumulation of CCL2 in CeA neuronal cell bodies was found. Finally, CCL2 in CeA neurons was localized to the synapse using confocal microscopy with enhanced resolution following deconvolution and electron microscopy, which along with the other evidence suggests that CCL2 may be transported down axons in CeA neurons and released from nerve terminals perhaps into brain regions like the BNST and VPAG to affect behaviors such as anxiety. These results suggest that neurons are an important target for chemokine research related to behavior.

Tumor Necrosis Factor-Alpha Alters Electrophysiological Properties of Rabbit Hippocampal Neurons

Previous studies have shown tumor necrosis factor-alpha (TNF-α) may impact neurodegeneration in Alzheimer's disease (AD) by regulating amyloid-β and tau pathogenesis. However, it is unclear whether TNF-α has a role in a cholesterol-fed rabbit model of AD or TNF-α affects the electrophysiological properties of rabbit hippocampus. This study was designed to investigate whether long-term feeding of cholesterol diet known to induce AD pathology regulates TNF-α expression in the hippocampus and whether TNF-α would modulate electrophysiological properties of rabbit hippocampal CA1 neurons. TNF-α ELISA showed dietary cholesterol increased hippocampal TNF-α expression in a dose-dependent manner. Whole-cell recordings revealed TNF-α altered the membrane properties of rabbit hippocampal CA1 neurons, which was characterized by a decrease in after-hyperpolarization amplitudes; Field potential recordings showed TNF-α inhibited long-term potentiation but did not influence presynaptic function. Interestingly, TNF-α did not significantly affect the after-hyperpolarization amplitudes of hippocampal CA1 neurons from cholesterol fed rabbits compared to normal chow fed rabbits. In conclusion, dietary cholesterol generated an in vivo model of chronic TNF-α elevation and TNF-α may underlie the learning and memory changes previously seen in the rabbit model of AD by acting as a bridge between dietary cholesterol and brain function and directly modulating the electrophysiological properties of hippocampal CA1 neurons.

Animal models of gene-alcohol interactions

Most birth defects arise from complex interactions between multiple genetic and environmental factors. However, our current understanding of how these interactions and their contributions affect birth defects remains incomplete. Human studies are limited in their ability to identify the fundamental causes of birth defects due to ethical and practical limitations. Animal models provide a great number of resources not available to human studies and they have been critical in advancing our understanding of birth defects and the complex interactions that underlie them. In this review, we discuss the use of animal models in the context of gene-environment interactions that underlie birth defects. We focus on alcohol which is the most common environmental factor associated with birth defects. Prenatal alcohol exposure leads to a wide range of cognitive impairments and structural deficits broadly termed fetal alcohol spectrum disorders (FASD). We discuss the broad impact of prenatal alcohol exposure on the developing embryo and elaborate on the current state of gene-alcohol interactions. Additionally, we discuss how animal models have informed our understanding of the genetics of FASD. Ultimately, these topics will provide insight into the use of animal models in understanding gene-environment interactions and their subsequent impact on birth defects.

Aging with alcohol-related brain damage: Critical brain circuits associated with cognitive dysfunction

Alcoholism is associated with brain damage and impaired cognitive functioning. The relative contributions of different etiological factors, such as alcohol, thiamine deficiency and age vulnerability, to the development of alcohol-related neuropathology and cognitive impairment are still poorly understood. One reason for this quandary is that both alcohol toxicity and thiamine deficiency produce brain damage and cognitive problems that can be modulated by age at exposure, aging following alcohol toxicity or thiamine deficiency, and aging during chronic alcohol exposure. Pre-clinical models of alcohol-related brain damage (ARBD) have elucidated some of the contributions of ethanol toxicity and thiamine deficiency to neuroinflammation, neuronal loss and functional deficits. However, the critical variable of age at the time of exposure or long-term aging with ARBD has been relatively ignored. Acute thiamine deficiency created a massive increase in neuroimmune genes and proteins within the thalamus and significant increases within the hippocampus and frontal cortex. Chronic ethanol treatment throughout adulthood produced very minor fluctuations in neuroimmune genes, regardless of brain region. Intermittent "binge-type" ethanol during the adolescent period established an intermediate neuroinflammatory response in the hippocampus and frontal cortex, that can persist into adulthood. Chronic excessive drinking throughout adulthood, adolescent intermittent ethanol exposure, and thiamine deficiency all led to a loss of the cholinergic neuronal phenotype within the basal forebrain, reduced hippocampal neurogenesis, and alterations in the frontal cortex. Only thiamine deficiency results in gross pathological lesions of the thalamus. The behavioral impairment following these types of treatments is hierarchical: Thiamine deficiency produces the greatest impairment of hippocampal- and prefrontal-dependent behaviors, chronic ethanol drinking ensues mild impairments on both types of tasks and adolescent intermittent ethanol exposure leads to impairments on frontocortical tasks, with sparing on most hippocampal-dependent tasks. However, our preliminary data suggest that as rodents age following adolescent intermittent ethanol exposure, hippocampal functional deficits began to emerge. A necessary requirement for the advancement of understanding the neural consequences of alcoholism is a more comprehensive assessment and understanding of how excessive alcohol drinking at different development periods (adolescence, early adulthood, middle-aged and aged) influences the trajectory of the aging process, including pathological aging and disease.

Neuroinvasion and cognitive impairment in comorbid alcohol dependence and chronic viral infection: An initial investigation

Viruses that invade the central nervous system (CNS) can cause neuropsychiatric impairments. Similarly, chronic alcohol exposure can induce inflammatory responses that alter brain function. However, the effects of a chronic viral infection and comorbid alcohol use on neuroinflammation and behavior are not well-defined. We investigated the role of heavy alcohol intake in regulating inflammatory responses and behavioral signs of cognitive impairments in mice infected with lymphocytic choriomeningitis virus (LCMV) clone 13. LCMV-infected mice exposed to alcohol had increased peripheral inflammation and impaired cognitive function (as indicated by performance on the novel object recognition test). Initial findings suggest that brain region-specific dysregulation of microglial response to viral infection may contribute to cognitive impairments in the context of heavy alcohol use.

Influence of Alcohol Consumption on Body Mass Gain and Liver Antioxidant Defense in Adolescent Growing Male Rats

The World Health Organization (WHO) reported that alcohol consumption is a serious problem in adolescents. The aim of the study was to assess the influence of the time of exposure of various alcoholic beverages on body mass as well as on select parameters of liver antioxidant defense in adolescent Wistar rats. Thirty-day-old animals were divided into 12 groups (six animals in each): control and groups receiving various beverages containing 10% of alcohol (ethanol, red wine, beer), observed for two, four, and six weeks. The body weight gain and energy supply were analyzed for body mass assessment. The catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase, transferase (GST), reductase activities, total antioxidant status, and glutathione level (GSH) were analyzed, for a liver antioxidant defense assessment. Group receiving red wine was characterized by the highest alcohol intake, lowest dietary intake, and highest total energy supply (p < 0.05). However, this did not influence body weight gain (p > 0.05). Reduced diet intake in groups receiving alcohol was counterbalanced by its energy value. Therefore, the energy supply was not lower than for the control (p > 0.05). Alcohol consumption and the experiment duration influenced CAT, SOD, and GST activities and GSH level. Alcohol consumption may influence hepatic antioxidant defense in adolescent male rats, but without influence on body weight gain.

Chronic Alcohol Exposure Induced Neuroapoptosis: Diminishing Effect of Ethyl Acetate Fraction from Aralia elata

An ethyl acetate fraction from Aralia elata (AEEF) was investigated to confirm its neuronal cell protective effect on ethanol-induced cytotoxicity in MC-IXC cells and its ameliorating effect on neurodegeneration in chronic alcohol-induced mice. The neuroprotective effect was examined by methylthiazolyldiphenyl-tetrazolium bromide (MTT) and 2',7'-dichlorodihydrofluorescein diacetate (DCF-DA) assays. As a result, AEEF reduced alcohol-induced cytotoxicity and oxidative stress. To evaluate the improvement of learning, memory ability, and spatial cognition, Y-maze, passive avoidance, and Morris water maze tests were conducted. The AEEF groups showed an alleviation of the decrease in cognitive function in alcohol-treated mice. Then, malondialdehyde (MDA) levels and the superoxide dismutase (SOD) content were measured to evaluate the antioxidant effect of AEEF in the brain tissue. Treatment with AEEF showed a considerable ameliorating effect on biomarkers such as SOD and MDA content in alcohol-induced mice. To assess the cerebral cholinergic system involved in neuronal signaling, acetylcholinesterase (AChE) activity and acetylcholine (ACh) content were measured. The AEEF groups showed increased ACh levels and decreased AChE activities. In addition, AEEF prevented alcohol-induced neuronal apoptosis via improvement of mitochondrial activity, including reactive oxygen species levels, mitochondrial membrane potential, and adenosine triphosphate content. AEEF inhibited apoptotic signals by regulating phosphorylated c-Jun N-terminal kinases (p-JNK), phosphorylated protein kinase B (p-Akt), Bcl-2-associated X protein (BAX), and phosphorylated Tau (p-Tau). Finally, the bioactive compounds of AEEF were identified as caffeoylquinic acid (CQA), 3,5-dicaffeoylquinic acid (3,5-diCQA), and chikusetsusaponin IVa using the UPLC-Q-TOF-MS system.

A Pivotal Role for Thiamine Deficiency in the Expression of Neuroinflammation Markers in Models of Alcohol-Related Brain Damage

BACKGROUND

Alcohol-related brain damage (ARBD) is associated with neurotoxic effects of heavy alcohol use and nutritional deficiency, in particular thiamine deficiency (TD), both of which induce inflammatory responses in brain. Although neuroinflammation is a critical factor in the induction of ARBD, few studies have addressed the specific contribution(s) of ethanol (EtOH) versus TD.

METHODS

Adult rats were randomly divided into 6 conditions: chronic EtOH treatment (CET) where rats consumed a 20% v/v solution of EtOH for 6 months; CET with injections of thiamine (CET + T); severe pyrithiamine-induced TD (PTD); moderate PTD; moderate PTD during CET; and pair-fed controls. After the treatments, the rats were split into 3 recovery phase time points: the last day of treatment (time point 1), acute recovery (time point 2: 24 hours posttreatment), and delayed recovery (time point 3: 3 weeks posttreatment). At these time points, vulnerable brain regions (thalamus, hippocampus, frontal cortex) were collected and changes in neuroimmune markers were assessed using a combination of reverse transcription polymerase chain reaction and protein analysis.

RESULTS

CET led to minor fluctuations in neuroimmune genes, regardless of the structure being examined. In contrast, PTD treatment led to a profound increase in neuroimmune genes and proteins within the thalamus. Cytokine changes in the thalamus ranged in magnitude from moderate (3-fold and 4-fold increase in interleukin-1β [IL-1β] and IκBα) to severe (8-fold and 26-fold increase in tumor necrosis factor-α and IL-6, respectively). Though a similar pattern was observed in the hippocampus and frontal cortex, overall fold increases were moderate relative to the thalamus. Importantly, neuroimmune gene induction varied significantly as a function of severity of TD, and most genes displayed a gradual recovery across time.

CONCLUSIONS

These data suggest an overt brain inflammatory response by TD and a subtle change by CET alone. Also, the prominent role of TD in the immune-related signaling pathways leads to unique regional and temporal profiles of induction of neuroimmune genes.

Imaging with mass spectrometry, the next frontier in sphingolipid research? A discussion on where we stand and the possibilities ahead

In the last ten years, mass spectrometry (MS) has become the favored analytical technique for sphingolipid (SPL) analysis and measurements. Indeed MS has the unique ability to both acquire sensitive and quantitative measurements and to resolve the molecular complexity characteristic of SPL molecules, both across the different SPL families and within the same SPL family. Currently, two complementary MS-based approaches are used for lipid research: analysis of lipid extracts, mainly by infusion electrospray ionization (ESI), and mass spectrometry imaging (MSI) from a sample surface (i.e. intact tissue sections, cells, model membranes, thin layer chromatography plates) (Fig. 1). The first allows for sensitive and quantitative information about total lipid molecular species from a given specimen from which lipids have been extracted and chromatographically separated prior to the analysis; the second, albeit generally less quantitative and less specific in the identification of molecular species due to the complexity of the sample, allows for spatial information of lipid molecules from biological specimens. In the field of SPL research, MS analysis of lipid extracts from biological samples has been commonly utilized to implicate the role of these lipids in specific biological functions. On the other hand, the utilization of MSI in SPL research represents a more recent development that has started to provide interesting descriptive observations regarding the distribution of specific classes of SPLs within tissues. Thus, it is the aim of this review to discuss how MSI technology has been employed to extend the study of SPL metabolism and the type of information that has been obtained from model membranes, single cells and tissues. We envision this discussion as a complementary compendium to the excellent technical reviews recently published about the specifics of MSI technologies, including their application to SPL analysis (Fuchs et al., 2010; Berry et al., 2011; Ellis et al., 2013; Eberlin et al., 2011; Kraft and Klitzing, 2014).

Role of MCP-1 and CCR2 in alcohol neurotoxicity

Alcohol abuse causes profound damage to both the developing brain and the adult brain. Prenatal exposure to alcohol results in a wide range of deficits known as fetal alcohol spectrum disorders (FASD). Alcohol abuse in adults is associated with brain shrinkage, memory and attention deficits, communication disorders and physical disabilities. Monocyte chemoattractant protein-1 (MCP-1/CCL2) is one of the key chemokines that regulate the recruitment and activation of monocytes and microglia. Both MCP-1 and its receptor C-C chemokine receptor type 2 (CCR2) expressed in the brain are involved in various neuroinflammatory disorders, such as multiple sclerosis (MS), Alzheimer's disease (AD) and Parkinson's disease (PD). However, the role of MCP-1/CCR2 in alcohol-induced brain damage is unclear. Recent evidence indicates that alcohol exposure increased the activity of MCP-1/CCR2 in both mature and developing central nervous systems (CNS). MCP-1/CCR2 signaling in the brain was involved in alcohol drinking behavior. MCP-1/CCR2 inhibition alleviated alcohol neurotoxicity by reducing microglia activation/neuroinflammation in the developing brain and spinal cord. In this review, we discussed the role of MCP-1/CCR2 signaling in alcohol-induced neuroinflammation and brain damage. We also discussed the signaling cascades that are involved in the activation of MCP-1/CCR2 in response to alcohol exposure.

Influence of alcoholism and cholesterol on TSPO binding in brain: PET [11C]PBR28 studies in humans and rodents

Neuroinflammation appears to contribute to neurotoxicity observed with heavy alcohol consumption. To assess whether chronic alcohol results in neuroinflammation we used PET and [¹¹C]PBR28, a ligand that binds to the 18-kDa translocator protein (TSPO), to compare participants with an alcohol use disorder (AUD: n = 19) with healthy controls (HC: n = 17), and alcohol-dependent (n = 9) with -nondependent rats (n = 10). Because TSPO is implicated in cholesterol's transport for steroidogenesis, we investigated whether plasma cholesterol levels influenced [¹¹C]PBR28 binding. [¹¹C]PBR28 binding did not differ between AUD and HC. However, when separating by TSPO genotype rs6971, we showed that medium-affinity binders AUD participants showed lower [¹¹C]PBR28 binding than HC in regions of interest (whole brain, gray and white matter, hippocampus, and thalamus), but no group differences were observed in high-affinity binders. Cholesterol levels inversely correlated with brain [¹¹C]PBR28 binding in combined groups, due to a correlation in AUD participants. In rodents, we observed no differences in brain [¹¹C]PBR28 uptake between alcohol-dependent and -nondependent rats. These findings, which are consistent with two previous [¹¹C]PBR28 PET studies, may indicate lower activation of microglia in AUD, whereas failure to observe alcohol effects in the rodent model indicate that species differences do not explain the discrepancy with prior rodent autoradiographic studies reporting increases in TSPO binding with chronic alcohol. However, reduced binding in AUD participants could also reflect competition from endogenous TSPO ligands such as cholesterol; and since the rs6971 polymorphism affects the cholesterol-binding domain of TSPO this could explain why differences were observed only in medium-affinity binders.

Transcriptome analysis of alcohol-treated microglia reveals downregulation of beta amyloid phagocytosis

BACKGROUND

Microglial activation contributes to the neuropathology associated with chronic alcohol exposure and withdrawal, including the expression of inflammatory and anti-inflammatory genes. In the current study, we examined the transcriptome of primary rat microglial cells following incubation with alcohol alone, or alcohol together with a robust inflammatory stimulus.

METHODS

Primary microglia were prepared from mixed rat glial cultures. Cells were incubated with 75 mM ethanol alone or with proinflammatory cytokines ("TII": IL1β, IFNγ, and TNFα). Isolated mRNA was used for RNAseq analysis and qPCR. Effects of alcohol on phagocytosis were determined by uptake of oligomeric amyloid beta.

RESULTS

Alcohol induced nitrite production in control cells and increased nitrite production in cells co-treated with TII. RNAseq analysis of microglia exposed for 24 h to alcohol identified 312 differentially expressed mRNAs ("Alc-DEs"), with changes confirmed by qPCR analysis. Gene ontology analysis identified phagosome as one of the highest-ranking KEGG pathways including transcripts regulating phagocytosis. Alcohol also increased several complement-related mRNAs that have roles in phagocytosis, including C1qa, b, and c; C3; and C3aR1. RNAseq analysis identified over 3000 differentially expressed mRNAs in microglia following overnight incubation with TII; and comparison to the group of Alc-DEs revealed 87 mRNAs modulated by alcohol but not by TII, including C1qa, b, and c. Consistent with observed changes in phagocytosis-related mRNAs, the uptake of amyloid beta1-42, by primary microglia, was reduced by alcohol.

CONCLUSIONS

Our results define alterations that occur to microglial gene expression following alcohol exposure and suggest that alcohol effects on phagocytosis could contribute to the development of Alzheimer's disease.

Altered hippocampal synaptic function in transgenic mice with increased astrocyte expression of CCL2 after withdrawal from chronic alcohol

CNS actions of the chemokine CCL2 are thought to play a role in a variety of conditions that can have detrimental consequences to CNS function, including alcohol use disorders. We used transgenic mice that express elevated levels of CCL2 in the CNS (CCL2-tg) and their non-transgenic (non-tg) littermate control mice to investigate long-term consequences of CCL2/alcohol/withdrawal interactions on hippocampal synaptic function, including excitatory synaptic transmission, somatic excitability, and synaptic plasticity. Two alcohol exposure paradigms were tested, a two-bottle choice alcohol (ethanol) drinking protocol (2BC drinking) and a chronic intermittent alcohol (ethanol) (CIE/2BC) protocol. Electrophysiological measurements of hippocampal function were made ex vivo, starting ∼0.6 months after termination of alcohol exposure. Both alcohol exposure/withdrawal paradigms resulted in CCL2-dependent interactions that altered the effects of alcohol on synaptic function. The synaptic alterations differed for the two alcohol exposure paradigms. The 2BC drinking/withdrawal treatment had no apparent long-term consequences on synaptic responses and long-term potentiation (LTP) in hippocampal slices from non-tg mice, whereas synaptic transmission was reduced but LTP was enhanced in hippocampal slices from CCL2-tg mice. In contrast, the CIE/2BC/withdrawal treatment enhanced synaptic transmission but reduced LTP in the non-tg hippocampus, whereas there were no apparent long-term consequences to synaptic transmission and LTP in hippocampus from CCL2-tg mice, although somatic excitability was enhanced. These results support the idea that alcohol-induced CCL2 production can modulate the effects of alcohol exposure/withdrawal on synaptic function and indicate that CCL2/alcohol interactions can vary depending on the alcohol exposure/withdrawal protocol used.

Transgenic mice with increased astrocyte expression of CCL2 show altered behavioral effects of alcohol

Emerging research provides strong evidence that activation of CNS glial cells occurs in neurological diseases and brain injury and results in elevated production of neuroimmune factors. These factors can contribute to pathophysiological processes that lead to altered CNS function. Recently, studies have also shown that both acute and chronic alcohol consumption can produce activation of CNS glial cells and the production of neuroimmune factors, particularly the chemokine ligand 2 (CCL2). The consequences of alcohol-induced increases in CCL2 levels in the CNS have yet to be fully elucidated. Our studies focus on the hypothesis that increased levels of CCL2 in the CNS produce neuroadaptive changes that modify the actions of alcohol on the CNS. We utilized behavioral testing in transgenic mice that express elevated levels of CCL2 to test this hypothesis. The increased level of CCL2 in the transgenic mice involves increased astrocyte expression. Transgenic mice and their non-transgenic littermate controls were subjected to one of two alcohol exposure paradigms, a two-bottle choice alcohol drinking procedure that does not produce alcohol dependence or a chronic intermittent alcohol procedure that produces alcohol dependence. Several behavioral tests were carried out including the Barnes maze, Y-maze, cued and contextual conditioned fear test, light-dark transfer, and forced swim test. Comparisons between alcohol naïve, non-dependent, and alcohol-dependent CCL2 transgenic and non-transgenic mice show that elevated levels of CCL2 in the CNS interact with alcohol in tests for alcohol drinking, spatial learning, and associative learning.

Neuroprotective effects of phytosterol esters against high cholesterol-induced cognitive deficits in aged rat

Accumulating epidemiological and experimental studies have confirmed that a high-cholesterol diet is detrimental to cognitive performance in animal models.

Dietary high cholesterol and trace metals in the drinking water increase levels of ABCA1 in the rabbit hippocampus and temporal cortex

BACKGROUND

Cholesterol-fed rabbits have been documented to show increased amyloid-β (Aβ) deposits in the brain that can be exacerbated by the quality of drinking water especially if rabbits drink tap water or distilled water containing copper. One mechanism of cholesterol and Aβ clearance may be through the ATP-binding cassette transporter A1 (ABCA1).

OBJECTIVE AND METHODS

Using an ABCA1 antibody, we determined the number of ABCA1-immunopositive neurons in three areas of rabbit brain as a function of feeding 2% cholesterol and providing tap water, distilled water, or distilled water to which aluminum, copper, or zinc was added.

RESULTS

The number of neurons with ABCA1 immunoreactivity was increased significantly as a result of dietary cholesterol in the rabbit hippocampus and inferior and superior temporal cortex. The number of neurons with ABCA1 immunoreactivity was further increased in all three areas as a result of cholesterol-fed rabbits drinking tap water or distilled water with copper. Finally, cholesterol-fed rabbits that drank distilled water with aluminum also showed an increased number of ABCA1-immunopositive neurons in inferior and superior temporal cortex.

CONCLUSIONS

These data suggest that ABCA1 levels increase in parallel with previously documented increases in Aβ levels as a result of high dietary cholesterol and copper in the drinking water. Addition of aluminum to distilled water may have a similar effect in the temporal cortex. ABCA1 has been proposed as a means of clearing Aβ from the brain and manipulations that increase Aβ also result in an increase of clearance machinery.

Cerebral hypoperfusion and glucose hypometabolism: Key pathophysiological modulators promote neurodegeneration, cognitive impairment, and Alzheimer's disease

Aging, hypertension, diabetes, hypoxia/obstructive sleep apnea (OSA), obesity, vitamin B12/folate deficiency, depression, and traumatic brain injury synergistically promote diverse pathological mechanisms including cerebral hypoperfusion and glucose hypometabolism. These risk factors trigger neuroinflammation and oxidative-nitrosative stress that in turn decrease nitric oxide and enhance endothelin, Amyloid-β deposition, cerebral amyloid angiopathy, and blood-brain barrier disruption. Proinflammatory cytokines, endothelin-1, and oxidative-nitrosative stress trigger several pathological feedforward and feedback loops. These upstream factors persist in the brain for decades, upregulating amyloid and tau, before the cognitive decline. These cascades lead to neuronal Ca²⁺ increase, neurodegeneration, cognitive/memory decline, and Alzheimer's disease (AD). However, strategies are available to attenuate cerebral hypoperfusion and glucose hypometabolism and ameliorate cognitive decline. AD is the leading cause of dementia among the elderly. There is significant evidence that pathways involving inflammation and oxidative-nitrosative stress (ONS) play a key pathophysiological role in promoting cognitive dysfunction. Aging and several comorbid conditions mentioned above promote diverse pathologies. These include inflammation, ONS, hypoperfusion, and hypometabolism in the brain. In AD, chronic cerebral hypoperfusion and glucose hypometabolism precede decades before the cognitive decline. These comorbid disease conditions may share and synergistically activate these pathophysiological pathways. Inflammation upregulates cerebrovascular pathology through proinflammatory cytokines, endothelin-1, and nitric oxide (NO). Inflammation-triggered ONS promotes long-term damage involving fatty acids, proteins, DNA, and mitochondria; these amplify and perpetuate several feedforward and feedback pathological loops. The latter includes dysfunctional energy metabolism (compromised mitochondrial ATP production), amyloid-β generation, endothelial dysfunction, and blood-brain-barrier disruption. These lead to decreased cerebral blood flow and chronic cerebral hypoperfusion- that would modulate metabolic dysfunction and neurodegeneration. In essence, hypoperfusion deprives the brain from its two paramount trophic substances, viz., oxygen and nutrients. Consequently, the brain suffers from synaptic dysfunction and neuronal degeneration/loss, leading to both gray and white matter atrophy, cognitive dysfunction, and AD. This Review underscores the importance of treating the above-mentioned comorbid disease conditions to attenuate inflammation and ONS and ameliorate decreased cerebral blood flow and hypometabolism. Additionally, several strategies are described here to control chronic hypoperfusion of the brain and enhance cognition. © 2016 Wiley Periodicals, Inc.

Chronic Drinking During Adolescence Predisposes the Adult Rat for Continued Heavy Drinking: Neurotrophin and Behavioral Adaptation after Long-Term, Continuous Ethanol Exposure

Previous research has found that adolescent ethanol (EtOH) exposure alters drug seeking behaviors, cognition and neuroplasticity. Using male Sprague Dawley rats, differences in spatial working memory, non-spatial discrimination learning and behavioral flexibility were explored as a function of age at the onset (mid-adolescent vs. adult) of chronic EtOH exposure (CET). Concentrations of mature brain-derived neurotrophic factor (mBDNF) and beta-nerve growth factor (β-NGF) in the prefrontal cortex and hippocampus were also assessed at different time-points: during CET, following acute abstinence (48-hrs), and after protracted abstinence (6-8 wks). Our results revealed that an adolescent onset of CET leads to increased EtOH consumption that persisted into adulthood. In both adult and adolescent onset CET groups, there were significant long-term reductions in prefrontal cortical mBDNF and β-NGF levels. However, only adult onset CET rats displayed decreased hippocampal BDNF levels. Spatial memory, assessed by spontaneous alternation and delayed alternation, was not significantly affected by CET as a function of age of drinking onset, but higher blood-EtOH levels were correlated with lower spontaneous alternation scores. Regardless of the age of onset, EtOH exposed rats were impaired on non-spatial discrimination learning and displayed inflexible behavioral patterns upon reversal learning. Our results indicate that adolescent EtOH exposure changes long-term consumption patterns producing behavioral and neural dysfunctions that persist across the lifespan.

Chronic Intracerebroventricular Infusion of Monocyte Chemoattractant Protein-1 Leads to a Persistent Increase in Sweetened Ethanol Consumption During Operant Self-Administration But Does Not Influence Sucrose Consumption in Long-Evans Rats

BACKGROUND

Among the evidence implicating neuroimmune signaling in alcohol use disorders are increased levels of the chemokine monocyte chemoattractant protein-1 (MCP-1) in the brains of human alcoholics and animal models of alcohol abuse. However, it is not known whether neuroimmune signaling can directly increase ethanol (EtOH) consumption, and whether MCP-1 is involved in that mechanism. We designed experiments to determine whether MCP-1 signaling itself is sufficient to accelerate or increase EtOH consumption. Our hypothesis was that increasing MCP-1 signaling by directly infusing it into the brain would increase operant EtOH self-administration.

METHODS

We implanted osmotic minipumps to chronically infuse either one of several doses of MCP-1 or vehicle into the cerebral ventricles (intracerebroventricular) of Long-Evans rats and then tested them in the operant self-administration of a sweetened EtOH solution for 8 weeks.

RESULTS

There was a significant interaction between dose of MCP-1 and sweetened EtOH consumed across the first 4 weeks (while pumps were flowing) and across the 8-week experiment. Animals receiving the highest dose of MCP-1 (2 μg/d) were the highest consumers of EtOH during weeks 3 through 8. MCP-1 did not influence the acquisition of self-administration (measured across the first 5 days), the motivation to consume EtOH (time to lever press or progressive ratio), withdrawal-induced anxiety, or the consumption of sucrose alone.

CONCLUSIONS

We provide novel evidence that neuroimmune signaling can directly increase chronic operant EtOH self-administration, and that this increase persists beyond the administration of the cytokine. These data suggest that EtOH-induced increases in MCP-1, or increases in MCP-1 due to various other neuroimmune mechanisms, may further promote EtOH consumption. Continued research into this mechanism, particularly using models of alcohol dependence, will help determine whether targeting MCP-1 signaling has therapeutic potential in the treatment of alcohol use disorders.

Cholesterol - A putative endogenous contributor towards Parkinson's disease

Elevated levels of cholesterol and its metabolites (oxysterols) have been reported to be associated not only with several metabolic syndromes, but also become a prognostic risk factor of neurodegenerative diseases particularly Alzheimer's disease. The incidence and the prospect of Alzheimer's disease with respect to elevated levels of cholesterol have been studied extensively and reviewed earlier. Recently, several interesting findings have shown the occurrence of equivalent Parkinsonian pathologies in cellular neuronal models, mediated by oxysterols or excess exposure to cholesterol. In this regard, oxysterols are particular in causing alpha-synuclein aggregation and destruction of dopamine containing neurons in in vitro models, which is linked to their direct influence on oxidative stress provoking potency. Inspite of the significant in vitro reports, which suggest the relativeness of cholesterol or oxysterol towards Parkinsonism, several prospective clinical reports provided a negative or no correlation. However, few prospective clinical studies showed a positive correlation between plasma cholesterol and incidence of Parkinson's disease (PD). Also, few significant studies have convincingly demonstrated that high fat diet exacerbates parkinsonian pathologies, including loss of dopaminergic neurons and oxidative stress parameters in animal models of PD. The present review brings together all the neuropathological proceedings mediated by excess cholesterol or its metabolites in brain in the light of their contribution towards the onset of PD. Also we have reviewed the possibilities of cholesterol lowering efficacy of statin therapy, in reducing the occurrence of PD.

Role of microglia in regulation of ethanol neurotoxic action

Exposure to alcohol, during development or adulthood, may result in damage to the nervous system, which underlies neurological and cognitive disruptions observed in patients with alcohol-related disorders, including fetal alcohol spectrum disorders (FASDs) and alcohol-use disorders (AUDs). Both clinical and preclinical evidence suggest microglia, the immune cells of the central nervous system, play a key role in modulating alcohol-induced neurotoxicity. Particularly, microglia are implicated in alcohol-induced neuroinflammation and in alcohol-induced increases in oxidative stress, which can lead to neuronal apoptosis. Recent studies also suggest a regenerative role for microglia in reestablishing homeostasis after alcohol exposure. These studies are summarized and reviewed in this chapter with emphasis on relevance to FASD and AUD.

Chronic ethanol consumption profoundly alters regional brain ceramide and sphingomyelin content in rodents

Ceramides (CER) are involved in alcohol-induced neuroinflammation. In a mouse model of chronic alcohol exposure, 16 CER and 18 sphingomyelin (SM) concentrations from whole brain lipid extracts were measured using electrospray mass spectrometry. All 18 CER concentrations in alcohol exposed adults increased significantly (range: 25–607%); in juveniles, 6 CER decreased (range: −9 to −37%). In contrast, only three SM decreased in adult and one increased significantly in juvenile. Next, regional identification at 50 μm spatial resolution from coronal sections was obtained with matrix implanted laser desorption/ionization mass spectrometry imaging (MILDI-MSI) by implanting silver nanoparticulate matrices followed by focused laser desorption. Most of the CER and SM quantified in whole brain extracts were detected in MILDI images. Coronal sections from three brain levels show qualitative regional changes in CER-SM ion intensities, as a function of group and brain region, in cortex, striatum, accumbens, habenula, and hippocampus. Highly correlated changes in certain white matter CER-SM pairs occur in regions across all groups, including the hippocampus and the lateral (but not medial) cerebellar cortex of adult mice. Our data provide the first microscale MS evidence of regional lipid intensity variations induced by alcohol.

The relationship between cholesterol and cognitive function is homocysteine-dependent

Introduction

Previous studies have identified hyperlipidemia as a potential risk factor for dementia and Alzheimer’s disease. However, studies on cholesterol measured in late-life and cognitive function have been inconsistent. Few studies have explored nonlinear relationships or considered interactions with other biomarker measures.

Methods

A cross-sectional sample of 1,889 participants from four rural counties in the People’s Republic of China was included in this analysis. Serum total cholesterol, high-density lipoprotein, triglycerides, and homocysteine levels were measured in fasting blood samples. A composite cognitive score was derived based on nine standardized cognitive test scores. Analysis of covariance models were used to investigate the association between biomarker measures and the composite cognitive scores.

Results

There was a significant interaction between the homocysteine quartile group and the cholesterol quartile group on cognitive scores (P=0.0478). In participants with normal homocysteine levels, an inverse U-shaped relationship between total cholesterol level and cognitive score was found, indicating that both low and high cholesterol levels were associated with lower cognitive scores. In participants with high homocysteine levels, no significant association between cholesterol and cognition was found.

Conclusion

The relationship between cholesterol levels and cognitive function depends upon homocysteine levels, suggesting an interactive role between cholesterol and homocysteine on cognitive function in the elderly population. Additional research is required to confirm our findings in other populations, and to explore potential mechanisms underlying the lipid–homocysteine interaction.

Gene-ethanol interactions underlying fetal alcohol spectrum disorders

Fetal alcohol spectrum disorders (FASD) is an umbrella term that describes a diverse set of ethanol-induced defects. The phenotypic variation is generated by numerous factors, including timing and dosage of ethanol exposure as well as genetic background. We are beginning to learn about how the concentration, duration, and timing of ethanol exposure mediate variability within ethanol teratogenesis. However, little is known about the genetic susceptibilities in FASD. Studies of FASD animal models are beginning to implicate a number of susceptibility genes that are involved in various pathways. Here we review the current literature that focuses on the genetic predispositions in FASD.

CaV1.2 calcium channel expression in reactive astrocytes is associated with the formation of amyloid-β plaques in an Alzheimer's disease mouse model

Increased activity of L-type Ca2+ channels has been implicated in the pathogenesis of dementia and Alzheimer's disease (AD). Previously we detected CaV1.2 α1-subunit-positive expression in reactive astrocytes surrounding the plaques of 12 month-old transgenic mice overexpressing hAβPP751 with the London (V717I) and Swedish (K670M/N671L) mutations. Here we examined whether increased CaV1.2 α1-subunit expression precedes plaque formation or is specifically associated with the increased amyloid-β (Aβ) load in the plaques. Quantitative RT-PCR expression profiling of all high voltage-gated Ca2+ channel subunits (α1, β, and α2δ) revealed no difference in the hippocampi of 2, 4, and 11 month-old wild type (wt) and transgenic (tg) mice. Immunohistochemistry demonstrated that expression of CaV1.2 α1-subunit, but not of the auxiliary β4 Ca2+ channel subunit, specifically associated with Aβ-positive plaques in brains of 11 month tg mice. No difference in CaV1.2 α1-subunit labeling was found in 2 and 4 month-old wt and tg mice prior to plaque formation. The CaV1.2 α1-subunit-positive cells in 11 month-old tg mice also labeled with GFAP, but not with the microglia marker Iba1. In contrast, GFAP-positive cells induced by injection of quinolinic acid did not reveal any CaV1.2 α1-subunit immunoreactivity. Together these results indicate that the expression of CaV1.2 α1-subunits in reactive astrocytes in the tg AD mouse model is related to the increased amyloid-β load in the plaques rather than caused by effects on gene regulation or mechanisms preceding the manifestation of AD as seen by plaque formation.

Cerebrospinal fluid monocyte chemoattractant protein-1 in alcoholics: support for a neuroinflammatory model of chronic alcoholism

BACKGROUND

Liver inflammation in alcoholism has been hypothesized to influence the development of a neuroinflammatory process in the brain characterized by neurodegeneration and altered cognitive function. Monocyte chemoattractant protein-1/chemokine (C-C motif) ligand 2 (MCP-1/CCL2) elevations have been noted in the alcoholic brain at autopsy and may have a role in this process.

METHODS

We studied cerebrospinal fluid (CSF) levels of MCP-1 as well as interleukin-1β and tumor necrosis factor-α in 13 healthy volunteers and 28 alcoholics during weeks 1 and 4 following detoxification. Serum liver enzymes were obtained as markers of alcohol-related liver inflammation.

RESULTS

Compared to healthy volunteers, MCP-1 levels were significantly higher in alcoholics both on day 4 and day 25 (p < 0.0001). Using multiple regression analysis, we found that MCP-1 concentrations were positively associated with the liver enzymes gamma glutamyltransferase (GGT; p = 0.03) and aspartate aminotransferase/glutamic oxaloacetic transaminase (AST/GOT; p = 0.004).

CONCLUSIONS

These preliminary findings are consistent with the hypothesis that neuroinflammation as indexed by CSF MCP-1 is associated with alcohol-induced liver inflammation, as defined by peripheral concentrations of GGT and AST/GOT.

Ethanol, not detectably metabolized in brain, significantly reduces brain metabolism, probably via action at specific GABA(A) receptors and has measureable metabolic effects at very low concentrations

Ethanol is a known neuromodulatory agent with reported actions at a range of neurotransmitter receptors. Here, we measured the effect of alcohol on metabolism of [3-¹³C]pyruvate in the adult Guinea pig brain cortical tissue slice and compared the outcomes to those from a library of ligands active in the GABAergic system as well as studying the metabolic fate of [1,2-¹³C]ethanol. Analyses of metabolic profile clusters suggest that the significant reductions in metabolism induced by ethanol (10, 30 and 60 mM) are via action at neurotransmitter receptors, particularly α4β3δ receptors, whereas very low concentrations of ethanol may produce metabolic responses owing to release of GABA via GABA transporter 1 (GAT1) and the subsequent interaction of this GABA with local α5- or α1-containing GABA(A)R. There was no measureable metabolism of [1,2-¹³C]ethanol with no significant incorporation of ¹³C from [1,2-¹³C]ethanol into any measured metabolite above natural abundance, although there were measurable effects on total metabolite sizes similar to those seen with unlabelled ethanol.

Short-term ethanol exposure causes imbalanced neurotrophic factor allocation in the basal forebrain cholinergic system: a novel insight into understanding the initial processes of alcohol addiction

Alcohol ingestion affects both motor and cognitive functions. One brain system that is influenced by ethanol is the basal forebrain (BF) cholinergic projection system, which projects to diverse neocortical and limbic areas. The BF is associated with memory and cognitive function. Our primary interest is the examination of how regions that receive BF cholinergic projections are influenced by short-term ethanol exposure through alterations in the mRNA levels of neurotrophic factors [nerve growth factor/TrkA, brain-derived neurotrophic factor/TrkB, and glial-derived neurotrophic factor (GDNF)/GDNF family receptor α1]. Male BALB/C mice were fed a liquid diet containing 5 % (v/v) ethanol. Pair-fed control mice were maintained on an identical liquid diet, except that the ethanol was isocalorically substituted with sucrose. Mice exhibiting signs of ethanol intoxication (stages 1-2) were used for real-time reverse transcription-polymerase chain reaction analyses. Among the BF cholinergic projection regions, decreased levels of GDNF mRNA and increased levels of TrkB mRNA were observed in the basal nucleus, and increased levels of TrkB mRNA were observed in the cerebral cortex. There were no significant alterations in the levels of expression of relevant neurotrophic factors in the septal nucleus and hippocampus. Given that neurotrophic factors function in retrograde/anterograde or autocrine/paracrine mechanisms and that BF cholinergic projection regions are neuroanatomically connected, these findings suggested that an imbalanced allocation of neurotrophic factor ligands and receptors is an initial phenomenon in alcohol addiction. The exact mechanisms underlying this phenomenon in the BF cholinergic system are unknown. However, our results provide a novel notion for the understanding of the initial processes in alcohol addiction.

Microglial activation is not equivalent to neuroinflammation in alcohol-induced neurodegeneration: The importance of microglia phenotype

Excessive alcohol intake, a defining characteristic of an alcohol use disorder (AUD), results in neurodegeneration in the hippocampus and entorhinal cortex that has been linked to a variety of cognitive deficits. Neuroinflammation is thought to be a factor in alcohol-induced neurodegeneration, and microglia activation is a key but not sole component of an inflammatory response. These experiments investigate the effects of ethanol exposure in a well-accepted model of an AUD on both microglial activation and blood brain barrier disruption (BBB) in order to understand their relationship to classical definitions of inflammation and alcohol-induced neurodegeneration. Following a four-day binge ethanol paradigm, rat hippocampal and entorhinal cortex tissue was examined using three distinct approaches to determine microglia phenotype and BBB disruption: immunohistochemistry, autoradiography, and ELISA. After ethanol exposure, there was an increase in [(3)H]-PK-11195 binding and OX-42 immunoreactivity indicative of microglial activation; however, microglia were not fully activated since both OX-6 and ED-1 immunoreactive microglia were absent. This data was supported by functional evidence as there was no increase in the proinflammatory cytokines IL-6 or TNF-α, but a 26% increase in the anti-inflammatory cytokine, IL-10, and a 38% increase in the growth factor, TGF-β, seven days after exposure. Furthermore, there was no evidence of a disruption of the BBB. These data suggest that the four-day binge model of an AUD, which produces neurodegeneration in corticolimbic regions, does not elicit classical neuroinflammation but instead produces partially activated microglia. Partial activation of microglia following binge ethanol exposure suggest that microglia in this model have beneficial or homeostatic roles rather than directly contributing to neurodegeneration and are a consequence of alcohol-induced-damage instead of the source of damage.

Triggers and effectors of oxidative stress at blood-brain barrier level: relevance for brain ageing and neurodegeneration

As fundamental research advances, it is becoming increasingly clear that a clinically expressed disease implies a mixture of intertwining molecular disturbances. Oxidative stress is one of such pathogenic pathways involved in virtually all central nervous system pathologies, infectious, inflammatory, or degenerative in nature. Since brain homeostasis largely depends on integrity of blood-brain barrier (BBB), many studies focused lately on BBB alteration in a wide spectrum of brain diseases. The proper two-way molecular transfer through BBB depends on several factors, including the functional status of its tight junction (TJ) complexes of proteins sealing neighbour endothelial cells. Although there is abundant experimental work showing that oxidative stress associates BBB permeability alteration, less is known about its implications, at molecular level, in TJ protein expression or TJ-related cell signalling. In this paper, oxidative stress is presented as a common pathway for different brain pathogenic mechanisms which lead to BBB dysregulation. We revise here oxidative-induced molecular mechanisms of BBB disruption and TJ protein expression alteration, in relation to ageing and neurodegeneration.

Epigenetic medicine and fetal alcohol spectrum disorders

Epigenetic medicine is still in its infancy. To date, only a handful of diseases have documented epigenetic correlates upstream of gene regulation including cancer, developmental syndromes and late-onset diseases. The finding that epigenetic markers are dynamic and heterogeneous at tissue and cellular levels, combined with recent identification of a new form of functionally distinct DNA methylation has opened a wider window for investigators to pry into the epigenetic world. It is anticipated that many diseases will be elucidated through this epigenetic inquiry. In this review, we discuss the normal course of DNA methylation during development, taking alcohol as a demonstrator of the epigenetic impact of environmental factors in disease etiology, particularly the growth retardation and neurodevelopmental deficits of fetal alcohol spectrum disorders.

Stress-evoked sterile inflammation, danger associated molecular patterns (DAMPs), microbial associated molecular patterns (MAMPs) and the inflammasome

Since the inception of the field of psychoneuroimmunolology research, there has been an appreciation that the physiological response to stressors includes modulation of immune function. Investigators initially focused on the effect of stress on cellular migration and immunosuppression and the resultant decreases in tumor surveillance, anti-viral T cell immunity and antigen-specific antibody responses. More recently, it has become clear that exposure to stressors also potentiate innate immune processes. Stressor exposure, for example, can change the activation status of myeloid lineage cells such as monocytes, macrophages, neutrophils, and microglia, leading to a primed state. In addition, stressor exposure increases the synthesis and release of a vast cadre' of inflammatory proteins both in the blood and within tissues (i.e., spleen, liver, adipose, vasculature and brain). The mechanisms for stress-evoked innate immune 'arousal' remain unknown. The goals of this presidential address are the following: (1) offer a personalized, brief overview of stress and immunity with a focus on 'aroused' innate immunity; (2) describe sterile inflammatory processes and the role of the inflammasome; and (3) suggest that these same processes likely contribute to primed myeloid cells and inflammatory protein responses (systemic and tissue) produced by stress in the absence of pathogens.

Long-term consequences of developmental alcohol exposure on brain structure and function: therapeutic benefits of physical activity

Developmental alcohol exposure both early in life and during adolescence can have a devastating impact on normal brain structure and functioning, leading to behavioral and cognitive impairments that persist throughout the lifespan. This review discusses human work as well as animal models used to investigate the effect of alcohol exposure at various time points during development, as well as specific behavioral and neuroanatomical deficits caused by alcohol exposure. Further, cellular and molecular mediators contributing to these alcohol-induced changes are examined, such as neurotrophic factors and apoptotic markers. Next, this review seeks to support the use of aerobic exercise as a potential therapeutic intervention for alcohol-related impairments. To date, few interventions, behavioral or pharmacological, have been proven effective in mitigating some alcohol-related deficits. Exercise is a simple therapy that can be used across species and also across socioeconomic status. It has a profoundly positive influence on many measures of learning and neuroplasticity; in particular, those measures damaged by alcohol exposure. This review discusses current evidence that exercise may mitigate damage caused by developmental alcohol exposure and is a promising therapeutic target for future research and intervention strategies.

Dietary cholesterol alters memory and synaptic structural plasticity in young rat brain

Cholesterol plays an important role in synaptic plasticity, learning and memory. To better explore how dietary cholesterol contributes to learning and memory and the related changes in synaptic structural plasticity, rats were categorized into a regular diet (RD) group and a cholesterol-enriched diet (CD) group, and were fed with respective diet for 2 months. Dietary cholesterol impacts on learning and memory, hippocampal synaptic ultrastructure, expression levels of postsynaptic density-95 (PSD-95), synaptophysin (SYP) and cannabinoid receptor type 1 (CB1R) were investigated. We found CD rats had better performances in learning and memory using Morris water maze and object recognition test than RD rats. The memory improvement was accompanied with alterations of synaptic ultrastructure in the CA1 area of the hippocampus evaluated by electron microscopy, enhanced immunoreactivity of SYP, a presynaptic marker in hippocampus detected by immunocytochemistry, as well as increased levels of PSD-95, SYP and decreased level of CB1R in brains of CD rats determined by Western blot. Taken together, the results suggest that the improvement of learning and memory abilities of the young adult rats induced by dietary cholesterol may be linked with changes in synaptic structural plasticity in the brain.

Chronic vascular risk factors (cholesterol, homocysteine, ethanol) impair spatial memory, decline cholinergic neurons and induce blood-brain barrier leakage in rats in vivo

Epidemiological studies show that vascular risk factors (e.g. atherosclerosis, diabetes, homocysteine, hypertension or cholesterol) may play a role in the development of Alzheimer's disease. Animal models may help to discover the role of vascular risk factors on cognition. In the present project we treated male Sprague Dawley rats with a diet containing homocysteine (hyperhomocysteinemia) or cholesterol (hypercholesterolemia) for 5 months or exposed the rats to ethanol (20% in drinking water) or a combination of cholesterol + ethanol (mix) for 12 months. Our experiments show that all 3 treatments (homocysteine, cholesterol, ethanol) declined spatial memory in the 8-arm radial maze, reduced the number of cholinergic neurons and induced blood–brain barrier leakage in the cortex. Rats treated with cholesterol also displayed markedly enhanced inflammation in the cortex. Levels of amyloid precursor protein, beta-amyloid_(1–42), as well as tau and phospho-tau 181 were significantly enhanced in the cortex of cholesterol-fed rats. A combination of ethanol and cholesterol did not further potentiate the effects on spatial memory, cholinergic neurons and blood–brain barrier leakage. The data suggest that chronic mild vascular risk factors over months induce small lesions of the brain capillaries in the cortex, which may contribute to the development of vascular dementia or also Alzheimer's disease.

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

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