Corticostriatal BDNF and alcohol addiction

Alcohol use disorder disrupts BDNF maturation via the PAI-1 pathway which could be reversible with abstinence

The plasminogen activator inhibitor-1 (PAI-1)→mature brain-derived neurotrophic factor (mBDNF) pathway plays a pivotal role in the conversion of probrain-BDNF (ProBDNF) to mBDNF, but its clinical relevance in patients with alcohol use disorder (AUD) remains unknown. Enzyme-linked immunosorbent assays were used to examine the relevant protein levels of components of the PAI-1→mBDNF pathway in plasma samples from three groups of subjects, and statistical analysis was performed using analysis of variance (ANOVA) and one-way repeated-measures ANOVA. Our findings revealed significant alterations induced by alcohol. (1) AUD was associated with significant decreases in tissue plasminogen activator (tPA), mBDNF, and tropomyosin receptor kinase B (TrkB); significant increases in PAI-1, ProBDNF, and P75 neurotrophin receptor (P75NTR); and inhibited conversion of ProBDNF to mBDNF. (2) Following abstinence, the levels of tPA, mBDNF, and TrkB in the AUD group significantly increased, whereas the levels of PAI-1, ProBDNF, and P75NTR significantly decreased, promoting the conversion of ProBDNF to mBDNF. These clinical outcomes collectively suggest that AUD inhibits the conversion of ProBDNF to mBDNF and that abstinence reverses this process. The PAI-1→mBDNF cleavage pathway is hypothesized to be associated with AUD and abstinence treatment.

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.

Role of Lactobacillus plantarum-Derived Extracellular Vesicles in Regulating Alcohol Consumption

Alcohol Use Disorder (AUD), characterized by repeated alcohol consumption and withdrawal symptoms, poses a significant public health issue. Alcohol-induced impairment of the intestinal barrier results in alterations in intestinal permeability and the composition of the intestinal microbiota. Such alterations lead to a reduced relative abundance of intestinal lactic acid bacteria. However, the role of gut microbiota in alcohol consumption is not yet fully understood. In this study, we explore the mechanism by which gut microbiota regulates alcohol consumption, specifically using extracellular vesicles derived from Lactobacillus plantarum (L-EVs). L-EVs were administered to Sprague-Dawley rats either through intraperitoneal injection or microinjection into the ventral tegmental area (VTA), resulting in a significant reduction in alcohol consumption 72 hours after withdrawal. The observed reduction was akin to the effect of an intra-VTA microinjection of Brain-Derived Neurotrophic Factor (BDNF). Intriguingly, the microinjection of K252a (a Trk B antagonist) into the VTA blocked the reducing effect of L-EVs on alcohol consumption. The intraperitoneal injection of L-EVs restored the diminished BDNF expression in the VTA of alcohol-dependent rats. Furthermore, L-EVs rescued the low BDNF expression in alcohol-incubated PC12 cells. In conclusion, our study demonstrates that L-EVs attenuated alcohol consumption by enhancing BDNF expression in alcohol-dependent rats, thus suggesting the significant therapeutic potential of L-EVs in preventing excessive alcohol consumption.

Association between a body shape index and cognitive impairment among us older adults from a cross-sectional survey of the NHANES 2011-2014

PURPOSE

This study aimed to assess the relationship between A Body Shape Index (ABSI) and cognitive impairment among older adults in the United States.

METHODS

This cross-sectional study analyzed cognitive function in 2,752 individuals aged 60 and older using data from the 2011-2014 National Health and Nutrition Examination Survey (NHANES). Cognitive assessments were conducted using the Immediate Recall Test (IRT), Delayed Recall Test (DRT), Animal Fluency Test (AFT), and Digit Symbol Substitution Test (DSST). A Body Shape Index (ABSI) was calculated from waist circumference (WC), weight, and height. The relationship between ABSI and cognitive outcomes was examined through multifactorial linear regression, smooth curve fitting, and subgroup and interaction analyses.

RESULTS

With complete data, 2752 persons 60 and older participated in the study. After adjusting for covariables, these results showed statistically significant negative relationships between ABSI, IRT, and DSST scores. The negative correlation between DSST and ABSI is more substantial in males than females. There is less of a negative link between ABSI, AFT, and DSST among drinkers who consume 12 or more drinks annually compared to those who consume less. Furthermore, compared to individuals without high blood pressure(HBP), those who suffered HBP showed a more significant negative connection between ABSI and AFT.

CONCLUSION

Lower cognitive function was linked to higher ABSI.

Neuron enriched extracellular vesicles' MicroRNA expression profiles as a marker of early life alcohol consumption

Alcohol consumption may impact and shape brain development through perturbed biological pathways and impaired molecular functions. We investigated the relationship between alcohol consumption rates and neuron-enriched extracellular vesicles' (EVs') microRNA (miRNA) expression to better understand the impact of alcohol use on early life brain biology. Neuron-enriched EVs' miRNA expression was measured from plasma samples collected from young people using a commercially available microarray platform while alcohol consumption was measured using the Alcohol Use Disorders Identification Test. Linear regression and network analyses were used to identify significantly differentially expressed miRNAs and to characterize the implicated biological pathways, respectively. Compared to alcohol naïve controls, young people reporting high alcohol consumption exhibited significantly higher expression of three neuron-enriched EVs' miRNAs including miR-30a-5p, miR-194-5p, and miR-339-3p, although only miR-30a-5p and miR-194-5p survived multiple test correction. The miRNA-miRNA interaction network inferred by a network inference algorithm did not detect any differentially expressed miRNAs with a high cutoff on edge scores. However, when the cutoff of the algorithm was reduced, five miRNAs were identified as interacting with miR-194-5p and miR-30a-5p. These seven miRNAs were associated with 25 biological functions; miR-194-5p was the most highly connected node and was highly correlated with the other miRNAs in this cluster. Our observed association between neuron-enriched EVs' miRNAs and alcohol consumption concurs with results from experimental animal models of alcohol use and suggests that high rates of alcohol consumption during the adolescent/young adult years may impact brain functioning and development by modulating miRNA expression.

Identifying novel gene dysregulation associated with opioid overdose death: A meta-analysis of differential gene expression in human prefrontal cortex

Only recently have human postmortem brain studies of differential gene expression (DGE) associated with opioid overdose death (OOD) been published; sample sizes from these studies have been modest (N = 40-153). To increase statistical power to identify OOD-associated genes, we leveraged human prefrontal cortex RNAseq data from four independent OOD studies and conducted a transcriptome-wide DGE meta-analysis (N = 285). Using a unified gene expression data processing and analysis framework across studies, we meta-analyzed 20 098 genes and found 335 significant differentially expressed genes (DEGs) by OOD status (false discovery rate < 0.05). Of these, 66 DEGs were among the list of 303 genes reported as OOD-associated in prior prefrontal cortex molecular studies, including genes/gene families (e.g., OPRK1, NPAS4, DUSP, EGR). The remaining 269 DEGs were not previously reported (e.g., NR4A2, SYT1, HCRTR2, BDNF). There was little evidence of genetic drivers for the observed differences in gene expression between opioid addiction cases and controls. Enrichment analyses for the DEGs across molecular pathway and biological process databases highlight an interconnected set of genes and pathways from orexin and tyrosine kinase receptors through MEK/ERK/MAPK signaling to affect neuronal plasticity.

Epigenetic mechanisms of nicotine dependence

Smoking continues to be a leading cause of preventable disease and death worldwide. Nicotine dependence generates a lifelong propensity towards cravings and relapse, presenting an ongoing challenge for the development of treatments. Accumulating evidence supports a role for epigenetics in the development and maintenance of addiction to many drugs of abuse, however, the involvement of epigenetics in nicotine dependence is less clear. Here we review evidence that nicotine interacts with epigenetic mechanisms to enable the maintenance of nicotine-seeking across time. Research across species suggests that nicotine increases permissive histone acetylation, decreases repressive histone methylation, and modulates levels of DNA methylation and noncoding RNA expression throughout the brain. These changes are linked to the promoter regions of genes critical for learning and memory, reward processing and addiction. Pharmacological manipulation of enzymes that catalyze core epigenetic modifications regulate nicotine reward and associative learning, demonstrating a functional role of epigenetic modifications in nicotine dependence. These findings are consistent with nicotine promoting an overall permissive chromatin state at genes important for learning, memory and reward. By exploring these links through next-generation sequencing technologies, epigenetics provides a promising avenue for future interventions to treat nicotine dependence.

Intestinal microbiome dysbiosis in alcohol-dependent patients and its effect on rat behaviors

IMPORTANCE

Intestinal microbiome dysbiosis is associated with psychiatric disease through the "microbiota-gut-brain" axis. Here, we revealed that there was obvious intestinal microbiome (including bacterial and fungal) dysbiosis in alcohol-dependent patients. Alcohol consumption seriously disturbs the gut equilibrium between bacteria and fungi, reduces the interactions among bacterial-fungal trans-kingdom, and increases intestinal permeability. Gut microbiota should be considered as a whole to study the development of alcohol dependence. The gut microbiome of alcohol-dependent patients increased the anxiety- and depression-like behavior in rats. The gut microbiota dysbiosis may promote the development of alcohol dependence by regulating the endogenous cholecystokinin (CCK) and related receptors. Hence, regulating the balance of gut microbiota and the endogenous CCK may be a potential strategy for reducing the risk of relapse in alcohol addiction patients.

Voluntary wheel running during adolescence prevents the increase in ethanol intake induced by social defeat in male mice

RATIONALE

Exposure to social defeat (SD) induces a depressive phenotype, increased ethanol seeking and consumption, accompanied by activation of the neuroinflammatory response. However, a resilient response can be potentiated through physical exercise in the form of voluntary wheel running (VWR) during or after exposure to social stress. Therefore, the aim of this study was to test whether physical exercise during adolescence prior to being exposed to SD can enhance resilience to the increase in ethanol intake.

METHODS

Male mice had access to VWR during adolescence and the effects of social defeat (4 sessions every 72 h) on oral ethanol self-administration (SA) was evaluated. Based on the social interaction test, mice were classified as resilient or susceptible to depressive-like behavior. Two weeks after the last encounter, mice were subjected to the drinking in the dark and oral ethanol SA paradigms. Mice were then sacrificed to measure brain-derived neurotrophic factor (BDNF) levels in the striatum and hippocampus.

RESULTS

As expected, susceptible mice increased ethanol intake in the oral SA protocol. However, susceptible mice in the exercise condition did not increase ethanol intake, showing similar consumption and motivation for ethanol than the control and resilient groups. On the other hand, decreased BDNF levels were observed in susceptible mice in both experimental conditions compared to the control groups after ethanol SA.

CONCLUSIONS

The pre-exposure of VWR prevented the increase in consumption and motivation for ethanol induced by SD in susceptible mice. On the other hand, it appears that VWR did not exhibit any significant long-term effects on BDNF signaling, which is mainly affected in susceptible mice after ethanol intake.

Serum BDNF levels increase during early drug withdrawal in alcohol and crack cocaine addiction

Brain-derived neurotrophic factor (BDNF) is involved in several drug-induced brain neuroadaptations. The impact of withdrawal from substances that have different neurological mechanisms on BDNF levels is unclear. Our goal was to compare serum BDNF levels in inpatients with alcohol or crack cocaine use disorders during the early withdrawal period, and to evaluate the association with substance-related outcomes. We performed a follow-up study with 101 men under detoxification treatment (drug preference: alcohol [n = 37] and crack cocaine [n = 64]). Blood samples were collected on the 1st and 15th days of hospitalization to measure serum BDNF levels. Serum BDNF levels increased during the early stage of withdrawal (28.2 ± 10.0 vs. 32.6 ± 13.3, p < 0.001), similarly in individuals with alcohol and crack cocaine use. In the alcohol group, BDNF levels on the 15th day of hospitalization were negatively correlated with age (r = -0.394, p = 0.023). Delta BDNF levels were also negatively correlated with BDNF on the 1st day of hospitalization (p = 0.011). No significant correlation was found regarding substance-related outcomes. This is the first study to compare BDNF levels in alcohol and crack cocaine users undergoing similar treatment conditions. These findings could be related to clinical improvement after abstinence or even to drug withdrawal itself, decreasing neuronal injury. Furthermore, age may be a crucial factor, hindering the recovery of neuroplasticity in alcohol users.

Interaction of Brain-Derived Neurotrophic Factor with the Effects of Chronic Methamphetamine on Prepulse Inhibition in Mice Is Independent of Dopamine D3 Receptors

The aim of the present study was to gain a better understanding of the role of brain-derived neurotrophic factor (BDNF) and dopamine D3 receptors in the effects of chronic methamphetamine (METH) on prepulse inhibition (PPI), an endophenotype of psychosis. We compared the effect of a three-week adolescent METH treatment protocol on the regulation of PPI in wildtype mice, BDNF heterozygous mice (HET), D3 receptor knockout mice (D3KO), and double-mutant mice (DM) with both BDNF heterozygosity and D3 receptor knockout. Chronic METH induced disruption of PPI regulation in male mice with BDNF haploinsufficiency (HET and DM), independent of D3 receptor knockout. Specifically, these mice showed reduced baseline PPI, as well as attenuated disruption of PPI induced by acute treatment with the dopamine receptor agonist, apomorphine (APO), or the glutamate NMDA receptor antagonist, MK-801. In contrast, there were no effects of BDNF heterozygosity or D3 knockout on PPI regulation in female mice. Chronic METH pretreatment induced the expected locomotor hyperactivity sensitisation, where female HET and DM mice also showed endogenous sensitisation. Differential sex-specific effects of genotype and METH pretreatment were observed on dopamine receptor and dopamine transporter gene expression in the striatum and frontal cortex. Taken together, these results show a significant involvement of BDNF in the long-term effects of METH on PPI, particularly in male mice, but these effects appear independent of D3 receptors. The role of this receptor in psychosis endophenotypes therefore remains unclear.

Neuron Enriched Exosomal MicroRNA Expression Profiles as a Marker of Early Life Alcohol Consumption

Background

Alcohol consumption may impact and shape brain development through perturbed biological pathways and impaired molecular functions. We investigated the relationship between alcohol consumption rates and neuron-enriched exosomal microRNA (miRNA) expression to better understand the impact of alcohol use on early life brain biology.

Methods

Neuron-enriched exosomal miRNA expression was measured from plasma samples collected from young people using a commercially available microarray platform while alcohol consumption was measured using the Alcohol Use Disorders Identification Test. Linear regression and network analyses were used to identify significantly differentially expressed miRNAs and to characterize the implicated biological pathways, respectively.

Results

Compared to alcohol naïve controls, young people reporting high alcohol consumption exhibited significantly higher expression of four neuron-enriched exosomal miRNAs including miR-30a-5p, miR-194-5p, and miR-339-3p, although only miR-30a-5p and miR-194-5p survived multiple test correction. The miRNA-miRNA interaction network inferred by a network inference algorithm did not detect any differentially expressed miRNAs with a high cutoff on edge scores. However, when the cutoff of the algorithm was reduced, five miRNAs were identified as interacting with miR-194-5p and miR-30a-5p. These seven miRNAs were associated with 25 biological functions; miR-194-5p was the most highly connected node and was highly correlated with the other miRNAs in this cluster.

Conclusions

Our observed association between neuron-enriched exosomal miRNAs and alcohol consumption concurs with results from experimental animal models of alcohol use and suggests that high rates of alcohol consumption during the adolescent/young adult years may impact brain functioning and development by modulating miRNA expression.

A Rat Model of the Brain-Derived Neurotrophic Factor Val66Met Polymorphism Shows Attenuated Motivation for Alcohol Self-Administration and Diminished Propensity for Cue-Induced Relapse in Females

Brain-derived neurotrophic factor (BDNF) has been implicated in alcohol use disorder. The Val66Met polymorphism is a common variant of the BDNF gene (rs6265) which reduces activity-dependent BDNF release, and has been suggested as a risk factor for psychiatric disorders and substance use. Using an operant self-administration paradigm, this study aimed to investigate ethanol preference and ethanol seeking in a novel rat model of the BDNF Val66Met polymorphism, Val68Met rats. Male and female BDNF Val68Met rats of three genotypes (Val/Val, Val/Met and Met/Met) were trained to lever press for a 10% ethanol solution. There was no effect of Val68Met genotype on acquisition of stable response to ethanol or its extinction. Met/Met rats of both sexes had a slight, but significantly lower breakpoint during progressive ratio sessions while female rats with the Met/Met genotype demonstrated a lower propensity for reinstatement of responding to cues. There were no effects of Val68Met genotype on anxiety-like behaviour or locomotor activity. In conclusion, Met/Met rats showed lower motivation to continue to press for a reward, and also a decreased propensity to relapse, suggesting a possible protective effect of the Met/Met genotype against alcohol use disorder, at least in females.

Role of BDNF in Neuroplasticity Associated with Alcohol Dependence

Abstract

Chronic alcohol consumption is characterized by disturbances of neuroplasticity. Brain-derived neurotrophic factor (BDNF) is believed to be critically involved in this process. Here we aimed to review actual experimental and clinical data related to BDNF participation in neuroplasticity in the context of alcohol dependence. As has been shown in experiments with rodents, alcohol consumption is accompanied by the brain region-specific changes of BDNF expression and by structural and behavioral impairments. BDNF reverses aberrant neuroplasticity observed during alcohol intoxication. According to the clinical data parameters associated with BDNF demonstrate close correlation with neuroplastic changes accompanying alcohol dependence. In particular, the rs6265 polymorphism within the BDNF gene is associated with macrostructural changes in the brain, while peripheral BDNF concentration may be associated with anxiety, depression, and cognitive impairment. Thus, BDNF is involved in the mechanisms of alcohol-induced changes of neuroplasticity, and polymorphisms within the BDNF gene and peripheral BDNF concentration may serve as biomarkers, diagnostic or prognostic factors in treatment of alcohol abuse.

Chronic Voluntary Alcohol Consumption Alters Promoter Methylation and Expression of Fgf-2 and Fgfr1

Alcohol abuse accounts for 3.3 million deaths annually, rendering it a global health issue. Recently, fibroblast growth factor 2 (FGF-2) and its target, fibroblast growth factor receptor 1 (FGFR1), were discovered to positively regulate alcohol-drinking behaviors in mice. We tested whether alcohol intake and withdrawal alter DNA methylation of Fgf-2 and Fgfr1 and if there is a correlation regarding mRNA expression of these genes. Blood and brain tissues of mice receiving alcohol intermittently over a six-week period were analyzed using direct bisulfite sequencing and qRT-PCR analysis. Assessment of Fgf-2 and Fgfr1 promoter methylation revealed changes in the methylation of cytosines in the alcohol group compared with the control group. Moreover, we showed that the altered cytosines coincided with binding motives of several transcription factors. We also found that Fgf-2 and Fgfr1 gene expression was significantly decreased in alcohol-receiving mice compared with control littermates, and that this effect was specifically detected in the dorsomedial striatum, a brain region involved in the circuitry of the reward system. Overall, our data showed alcohol-induced alterations in both mRNA expression and methylation pattern of Fgf-2 and Fgfr1. Furthermore, these alterations showed a reward system regional specificity, therefore, resembling potential targets for future pharmacological interventions.

Functional roles, regulatory mechanisms and theranostics applications of ncRNAs in alcohol use disorder

Alcohol use disorder (AUD) is one of the most prevalent neuropsychological disorders worldwide, and its pathogenesis is convoluted and poorly understood. There is considerable evidence demonstrating significant associations between multiple heritable factors and the onset and progression of AUD. In recent years, a substantial body of research conducted by emerging biotechnologies has increasingly highlighted the crucial roles of noncoding RNAs (ncRNAs) in the pathophysiology of mental diseases. As in-depth understanding of ncRNAs and their mechanisms of action, they have emerged as prospective diagnostic indicators and preclinical therapeutic targets for a variety of psychiatric illness, including AUD. Of note, dysregulated expression of ncRNAs such as circRNAs, lncRNAs and miRNAs was routinely found in AUD individuals, and besides, exogenous regulation of partial ncRNAs has also been shown to be effective in ameliorating alcohol preference and excessive alcohol consumption. However, the exact molecular mechanism still remains elusive. Herein, we systematically summarized current knowledge regarding alterations in the expression of certain ncRNAs as well as their-mediated regulatory mechanisms in individuals with AUD. And finally, we detailedly reviewed the potential theranostics applications of gene therapy agents targeting ncRNAs in AUD mice. Overall, a deeper comprehension of functional roles and biological mechanisms of ncRNAs may make significant contributions to the accurate diagnosis and effective treatment of AUD.

Increase in serum brain-derived neurotrophic factor levels during early withdrawal in severe alcohol users

INTRODUCTION

Changes in brain-derived neurotrophic factor (BDNF) have been linked to the neuroadaptative consequences of chronic alcohol use and associated with disease severity and prognosis. Few studies have evaluated the influence of drug withdrawal and clinical and sociodemographic data on BDNF levels in severe alcohol users.

OBJECTIVES

Our goals were (1) to evaluate variation in BDNF levels during alcohol withdrawal and, (2) to assess the influence of putative confounding factors on BDNF levels.

METHODS

Our sample consists of 62 men with alcohol use disorder undergoing a detoxification process. Serum BDNF levels were measured using a commercial sandwich-ELISA kit, at two points: before and after the detoxification period.

RESULTS

We found an increase in BDNF levels during alcohol withdrawal (25.4±9.6 at admission vs. 29.8±10.2 ng/ml at discharge; p < 0.001), even after controlling for potential confounders (positive family history, number of days between blood sample collections, and age) (Generalized Estimating Equation: coefficient = -4.37, 95% confidence interval [95%CI] -6.3; -2.4; p < 0.001). Moreover, individuals who had first-degree relative with alcohol dependence had smaller increases in BDNF levels than individuals with no family history (14.8 [95%CI -5.3; 35.6] vs. 35.3 [95%CI 15.4; 74.8]; p = 0.005).

CONCLUSIONS

In summary, variation in BDNF levels seems to be influenced by withdrawal in severe alcohol users. A positive family history of alcohol dependence could also be a factor that influences variation in this biomarker.

From a Cycle to a Period: The Potential Role of BDNF as Plasticity and Phase-Specific Biomarker in Cocaine Use Disorder

Cocaine Use Disorder (CUD) is one of the diseases with the greatest social and health impact, due to the high cost of rehabilitation management and the high risk of dangerous behavior and relapse. This pathology frequently leads to unsuccessful attempts to interrupt the consumption, resulting in relapses and a vicious cycle of binge/intoxication, withdrawal/negative affect, and preoccupation/ anticipation (craving). The alternation of these phases in addiction was well illustrated by Koob and colleagues in the so-called "addictive cycle", which nowadays represents a landmark in the addiction field. Recently, there has been a surge of interest in the worldwide literature for biomarkers that might explain the different stages of addiction, and one of the most studied biomarkers is, without a doubt, Brain-derived Neurotrophic Factor (BDNF). In this perspective article, we discuss the potential role of BDNF as biomarker of the CUD phases described in the "Addictive Cycle", speculating about the close relationship between BDNF fluctuations and the clinical course of CUD. We also discuss BDNF's potential role as "staging" biomarker, predicting the progression of the disease. Finding valuable biomarkers of CUD severity and disease stage could shift clinicians' focus away from behavioral symptomatic treatment and toward a novel brain-based approach, allowing for the development of more effective and targeted therapeutic strategies, thus determining major benefits for CUD patients.

BDNF and its Role in the Alcohol Abuse Initiated During Early Adolescence: Evidence from Preclinical and Clinical Studies

Brain-derived neurotrophic factor (BDNF) is a crucial brain signaling protein that is integral to many signaling pathways. This neurotrophin has shown to be highly involved in brain plastic processes such as neurogenesis, synaptic plasticity, axonal growth, and neurotransmission, among others. In the first part of this review, we revise the role of BDNF in different neuroplastic processes within the central nervous system. On the other hand, its deficiency in key neural circuits is associated with the development of psychiatric disorders, including alcohol abuse disorder. Many people begin to drink alcohol during adolescence, and it seems that changes in BDNF are evident after the adolescent regularly consumes alcohol. Therefore, the second part of this manuscript addresses the involvement of BDNF during adolescent brain maturation and how this process can be negatively affected by alcohol abuse. Finally, we propose different BNDF enhancers, both behavioral and pharmacological, which should be considered in the treatment of problematic alcohol consumption initiated during the adolescence.

Age-related differences in the effect of chronic alcohol on cognition and the brain: a systematic review

Adolescence is an important developmental period associated with increased risk for excessive alcohol use, but also high rates of recovery from alcohol use-related problems, suggesting potential resilience to long-term effects compared to adults. The aim of this systematic review is to evaluate the current evidence for a moderating role of age on the impact of chronic alcohol exposure on the brain and cognition. We searched Medline, PsycInfo, and Cochrane Library databases up to February 3, 2021. All human and animal studies that directly tested whether the relationship between chronic alcohol exposure and neurocognitive outcomes differs between adolescents and adults were included. Study characteristics and results of age-related analyses were extracted into reference tables and results were separately narratively synthesized for each cognitive and brain-related outcome. The evidence strength for age-related differences varies across outcomes. Human evidence is largely missing, but animal research provides limited but consistent evidence of heightened adolescent sensitivity to chronic alcohol's effects on several outcomes, including conditioned aversion, dopaminergic transmission in reward-related regions, neurodegeneration, and neurogenesis. At the same time, there is limited evidence for adolescent resilience to chronic alcohol-induced impairments in the domain of cognitive flexibility, warranting future studies investigating the potential mechanisms underlying adolescent risk and resilience to the effects of alcohol. The available evidence from mostly animal studies indicates adolescents are both more vulnerable and potentially more resilient to chronic alcohol effects on specific brain and cognitive outcomes. More human research directly comparing adolescents and adults is needed despite the methodological constraints. Parallel translational animal models can aid in the causal interpretation of observed effects. To improve their translational value, future animal studies should aim to use voluntary self-administration paradigms and incorporate individual differences and environmental context to better model human drinking behavior.

BDNF-AAV has protective effects on morphine-induced conditioned place preference through BDNF, TrkB, and CREB concentration changes in the VTA and NAc

Brain-derived neurotrophic factor (BDNF) is one of the neurotrophic factors that promotes the survival and protection of neurons in many disorders. The potential protective effect of BDNF and its mechanisms on morphine addiction are unclear. In this study, morphine-induced conditioned place preference (CPP) in mice was used to show the effect of BDNF on rewarding behavior. Western blot assays were used to determine the changes caused by BDNF, for example, changes in total BDNF, tropomyosin-related kinase receptor B (TrkB), and cAMP response element binding protein (CREB) in the ventral tegmental area (VTA) and nucleus accumbens (NAc). The results showed that the BDNF-adeno-associated viral vector (BDNF-AAV) injected in the VTA, attenuated morphine-induced CPP with synergistic changes in BDNF/TrkB/CREB concentrations in the VTA and NAc in the CPP acquisition and recurrence phases; however, the attenuation was lower in the extinction phase, with different changes in molecules downstream of the BDNF.

The impact of heavy alcohol consumption on cognitive impairment in young old and middle old persons

Background

Dementia indicates a significant disease burden worldwide with increased population aging. This study aimed to investigate the impact of alcohol consumption on the risk of cognitive impairment in older adults.

Methods

Participants ≥ 60 years were administered the Digit Symbol Substitution Test (DSST) to evaluate cognitive function in National Health and Nutrition Examination Survey (NHANES) cycles from 1999 to 2002 and 2011 to 2014 for enrollment in the present study. Participants were categorized into non-drinker, drinker, and heavy drinker groups. Logistic regression analyses were performed to explore associations between cognitive impairment and alcohol consumption.

Results

Multivariate analysis showed that older adults, men, people from minority races, persons with lower education or income levels, social difficulties, hypertension, or chronic kidney disease were significantly associated with a higher risk of cognitive impairment (all p < 0.05). In the young old (60–69 years), heavy amount of alcohol drinking was significantly associated with lower risk of cognitive impairment compared with drinkers [adjusted odds ratio (aOR): 0.280, 95% Confidence interval (CI) 0.095–0.826]. But in the middle old persons (≥ 70 years), heavy alcohol drinking was associated with higher risk of cognitive impairment (aOR: 2.929, 95% CI 0.624–13.74).

Conclusions

Our study demonstrated that light to heavy drinking was associated with lower risk of cognitive impairment in participants aged between 60 and 69 years, but caution is needed in the middle old people with heavy alcohol drinking.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03353-3.

Behavioral genetics of alcohol's effects in three zebrafish (Danio rerio) populations

Alcohol abuse is one of the most dangerous and serious problems for patients and society. Interpopulation studies are important in understanding how genetic background contributes to the effects of alcohol. In this study, we applied a chronic alcohol exposure protocol in three zebrafish populations (Danio rerio; both sexes; AB, TU, and outbred fish - OB). We analyzed the behavioral responses and mRNA expression involved in neurotransmitter metabolism - th1, tph1, ache, ada1, gaba1, gad1b, and bdnf. Locomotion patterns were similar between populations (increased speed after acute alcohol and unaltered locomotion after chronic and withdrawal treatments). All populations exhibited increased expression of genes associated with locomotion (th1, gad1b, and gaba1) after acute alcohol exposure. Anxiety-like responses increased in AB and TU fish during withdrawal and decreased in AB fish after acute alcohol exposure. Genes related to anxiety-like behavior (tph1 and ada1) were overexpressed in AB and TU fish after acute and withdrawal treatments, while OB fish exhibited unaltered responses. Bdnf levels decreased during withdrawal in AB and OB fish, while TU showed upregulated levels in both chronic and withdrawal treatments. Our results suggest that zebrafish populations respond differently to alcohol exposure, which may contribute to understanding the mechanisms underlying alcohol use and dependence. Moreover, we found that a more diverse genetic background (OB) was related to higher variability in behavioral and mRNA expression, demonstrating that inbred populations (AB and TU) may be useful tools in identifying alcohol use and abuse mechanisms.

Long-term consequences of alcohol use in early adolescent mice: Focus on neuroadaptations in GR, CRF and BDNF

Our aim was to assess the cognitive and emotional state, as well as related-changes in the glucocorticoid receptor (GR), the corticotropin-releasing factor (CRF) and the brain-derived neurotrophic factor (BDNF) expression of adolescent C57BL/6J male mice after a 5-week two-bottle choice protocol (postnatal day [pd]21 to pd52). Additionally, we wanted to analyse whether the behavioural and neurobiological effects observed in late adolescence (pd62) lasted until adulthood (pd84). Behavioural testing revealed that alcohol during early adolescence increased anxiety-like and compulsive-related behaviours, which was maintained in adulthood. Concerning cognition, working memory was only altered in late adolescent mice, whereas object location test performance was impaired in both ages. In contrast, novel object recognition remained unaltered. Immunohistochemical analysis showed that alcohol during adolescence diminished BDNF+ cells in the cingulate cortex, the hippocampal CA1 layer and the central amygdala. Regarding hypothalamic-pituitary-adrenal axis (HPA) functioning, alcohol abuse increased the GR and CRF expression in the hypothalamic paraventricular nucleus and the central amygdala. Besides this, GR density was also higher in the prelimbic cortex and the basolateral amygdala, regardless of the animals' age. Our findings suggest that adolescent alcohol exposure led to long-term behavioural alterations, along with changes in BDNF, GR and CRF expression in limbic brain areas involved in stress response, emotional regulation and cognition.

FGF2 is an endogenous regulator of alcohol reward and consumption

Alcohol use disorder (AUD) is a chronic, relapsing disorder, characterized by escalating alcohol drinking and loss of control, with very limited available treatments. We recently reported that the expression of fibroblast growth factor 2 (Fgf2) is increased in the striatum of rodents following long-term excessive alcohol drinking and that the systemic or intra-striatal administration of recombinant FGF2 increases alcohol consumption. Here, we set out to determine whether the endogenous FGF2 plays a role in alcohol drinking and reward, by testing the behavioural phenotype of Fgf2 knockout mice. We found that Fgf2 deficiency resulted in decreased alcohol consumption when tested in two-bottle choice procedures with various alcohol concentrations. Importantly, these effects were specific for alcohol, as a natural reward (sucrose) or water consumption was not affected by Fgf2 deficiency. In addition, Fgf2 knockout mice failed to show alcohol-conditioned place preference (CPP) but showed normal fear conditioning, suggesting that deletion of the growth factor reduces alcohol's rewarding properties. Finally, Fgf2 knockout mice took longer to recover from the loss of righting reflex and showed higher blood alcohol concentrations when challenged with an intoxicating alcohol dose, suggesting that their ethanol metabolism might be affected. Together, our results show that the endogenous FGF2 plays a critical role in alcohol drinking and reward and indicate that FGF2 is a positive regulator of alcohol-drinking behaviours. Our findings suggest that FGF2 is a potential biomarker for problem alcohol drinking and is a potential target for pharmacotherapy development for AUD.

Maternal deprivation effect on morphine-induced CPP is related to changes in Opioid receptors in selected rat brain regions (hippocampus, prefrontal cortex, and nucleus accumbens)

Early-life environmental conditions affect offspring's development. Maternal deprivation (MD) can induce persistent changes that give rise to neuropsychiatric diseases including substance abuse disorders. However, long-lasting mechanisms that determine vulnerability to drug addiction remain unknown. We hypothesized that MD could induce changes in Opioid system, HPA (hypothalamic-pituitary-adrenal) axis, and BDNF (brain-derived neurotrophic factor), so may be involved in the drug abuse in later life. Male offspring of Wistar rats (n=8 per group) were subjected to 3h of daily MD during postnatal days 1-14. In adulthood, morphine-induced CPP (conditioned place preference) was investigated using two doses of morphine (3 and 5mg/kg). Serum corticosterone level was measured by ELISA method. The expression level of genes in selected brain regions (hippocampus, prefrontal cortex, and nucleus accumbens) was determined by qPCR (quantitative PCR). A greater morphine-induced CPP was observed in MD rats with 3 and 5mg/kg morphine compared to controls. MD group had a higher corticosterone level. A significant decrease was observed in the expression of BDNF gene (in all of the selected brain regions) and GR (glucocorticoid receptor) gene (in the hippocampus and nucleus accumbens) in MD rats. Also, a significant increase in the expression of μ Opioid receptor (in all of the selected brain regions) and κ Opioid receptor (in the prefrontal cortex and nucleus accumbens) was observed in MD rats. Our results suggest that MD induces alterations in the HPA axis function, BDNF level, and Opioid receptors system that enhance vulnerability to morphine at adulthood.

Non-coding RNA in alcohol use disorder by affecting synaptic plasticity

Alcohol use disorder (AUD) is one of the most serious public health problems worldwide. AUD is a complex disorder, and there is ample evidence that genetic predisposition is critical to its development. Recent studies have shown that genetic predisposition leads to the onset of AUD, and alcohol metabolism can affect epigenetic inheritance, which in turn affects synaptic plasticity, alters brain function, and leads to more severe addictive behaviors. Non-coding RNAs (ncRNAs), especially microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), play an important role in alcohol addiction. This paper reviews the regulatory role of ncRNAs. ncRNAs are involved in enzyme and neurotransmitter reaction systems during alcohol use disorder. Alcohol consumption regulates the expression of ncRNAs that mediate epigenetic modification and synaptic plasticity, which play an important role in the development of chronic AUD. ncRNAs may be used not only as predictors of therapeutic responses but also as therapeutic targets of AUD. Chronic alcoholism is more likely to lead to neuroimmune disorders, including permanent brain dysfunction. AUD induced by long-term alcoholism greatly alters the expression of genes in the human genome, especially the expression of ncRNAs. Alcohol can cause a series of pathological changes by interfering with gene expression, such as through disordered miRNA-mRNA expression networks, epigenetic modifications, disordered metabolism, and even synaptic remodeling. ncRNAs are involved in the transition from moderate drinking to alcohol dependence.

GSK3β Activity in Reward Circuit Functioning and Addiction

Glycogen synthase kinase-3β (GSK3β), primarily described as a regulator of glycogen metabolism, is a molecular hub linking numerous signaling pathways and regulates many cellular processes like cytoskeletal rearrangement, cell migration, apoptosis, and proliferation. In neurons, the kinase is engaged in molecular events related to the strengthening and weakening of synapses, which is a subcellular manifestation of neuroplasticity. Dysregulation of GSK3β activity has been reported in many neuropsychiatric conditions, like schizophrenia, major depressive disorder, bipolar disorder, and Alzheimer’s disease. In this review, we describe the kinase action in reward circuit-related structures in health and disease. The effect of pharmaceuticals used in the treatment of addiction in the context of GSK3β activity is also discussed.

Agomelatine attenuates alcohol craving and withdrawal symptoms by modulating the Notch1 signaling pathway in rats

AIM

Alcohol abuse is a significant causative factor of death worldwide. The Notch1 signaling pathway is involved in alcohol tolerance, withdrawal and dependence. Agomelatine is a known antidepressant acting as a melatonin receptor (MT1/2) agonist and a 5-hydroxytryptamine receptor-2C antagonist. However, its effects on alcohol cravings and alcohol withdrawal symptoms have not been investigated. In this study, we assessed the possibility of using agomelatine for the treatment of these symptoms in a rat model of alcoholism and the possible role of Notch1 signaling.

MAIN METHODS

We induced alcoholism in rats using a free-choice drinking model for 60 days. From day 61, free-choice was continued until day 82 for the craving model, whereas only water was offered in the withdrawal model. Meanwhile, the treated groups for both models received agomelatine (50 mg/kg/day) orally from day 61 to 82, followed by behavioral, histopathological and biochemical assessment.

KEY FINDINGS

Agomelatine treatment caused significant decrease in alcohol consumption with a positive effect on anxiety-like behavior in the open field, memory in the Morris water maze and immobility in the forced swim test. Moreover, agomelatine induced the expression of Notch1 pathway markers, including Notch1, NICD, CREB, CCNE-2, Hes-1, both total and phosphorylated ERK1/2, MMP9, Per2and RGS-2 in the hippocampal formation. By contrast, NMDAR expression was reduced. Furthermore, agomelatine normalized the serum levels of BDNF, cortisol, dopamine and glutamate which were disrupted by alcohol consumption.

SIGNIFICANCE

Based on these findings, agomelatine reversed alcohol cravings and withdrawal symptoms associated with alcohol dependence by modulating the Notch1 signaling pathway.

Trophic factors as potential therapies for treatment of major mental disorders

Notwithstanding major advances in psychotherapeutics, their efficacy and specificity remain limited. The slow onset of beneficial outcomes and numerous adverse effects of widely used medications remain of chief concern, warranting in-depth studies. The majority of frontline therapies are thought to enhance the endogenous monoaminergic drive, to initiate a cascade of molecular events leading to lasting functional and structural plasticity. They also involve alterations in trophic factor signalling, including brain-derived neurotrophic factor (BDNF), VGF (non-acronymic), vascular endothelial growth factor (VEGF), fibroblast growth factor 2 (FGF2), glial cell-derived neurotrophic factor (GDNF), and others. In several major mental disorders, emerging data suggest protective and restorative effects of trophic factors in preclinical models, when applied on their own. Antidepressant outcomes of VGF and FGF2, for instance, were shown in experimental animals, while BDNF and GDNF prove useful in the treatment of addiction, schizophrenia, and autism spectrum disorders. The main challenge with the effective translation of these and other findings in the clinic is the knowledge gap in action mechanisms with potential risks, as well as the lack of effective platforms for validation under clinical settings. Herein, we review the state-of-the-art and advances in the therapeutic use of trophic factors in several major neuropsychiatric disorders.

Genetic inactivation of midkine, not pleiotrophin, facilitates extinction of alcohol-induced conditioned place preference

Pleiotrophin (PTN) and midkine (MK) are growth factors that modulate alcohol consumption and reward. Since both PTN and MK limit the rewarding effects of alcohol, pharmacological potentiation of the PTN and MK signaling pathways has been proposed for the treatment of alcohol use disorders (AUD). Although the use of this therapy in the prevention of alcohol relapse is important, the potential role of these cytokines in extinguishing alcohol-induced seeking behavior is a key question that remains unanswered. To fill this gap, we have now studied the extinction of the conditioned place preference (CPP) induced by different doses of alcohol in Ptn knockout (Ptn^-/-) and Mk knockout (Mk^-/-) mice. The data confirm a higher sensitivity of Ptn^-/- mice to the conditioning effects of a low dose (1 g/kg) and a rewarding dose (2 g/kg) of alcohol, while Mk^-/- mice are only more susceptible to the conditioning effects of the low dose of this drug. More importantly, the percentage of Mk^-/- mice, not Ptn^-/- mice, that efficiently extinguished alcohol-induced CPP was significantly higher than that of Wt mice. Taken together, the data presented here confirm that Ptn and Mk are genetic factors that determine the conditioning effects of alcohol in mice and that Mk is a novel factor that plays an important role in the extinction of alcohol-induced CPP.

Brain-derived neurotrophic factor among patients with alcoholism

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is involved in neurogenesis and in the protection against oxidative damage and neuronal apoptosis. After exercise, there is an increased expression of this myokine, especially in skeletal muscle and brain. Low BDNF levels have been described in neurodegenerative diseases. Alcoholics show both muscle atrophy and brain atrophy. Thus, this study was performed in order to analyze serum BDNF levels among alcoholics and their associations with brain atrophy and muscle strength.

METHODS

Serum BDNF values were determined to 82 male alcoholics and 27 age-matched controls, and compared with handgrip strength, with the presence of brain atrophy, assessed by computed tomography, and with the intensity of alcoholism and liver function derangement.

RESULTS

BDNF levels and handgrip strength were significantly lower among patients. Handgrip strength was correlated with BDNF values, both in the whole population and in alcoholics, especially in patients over 59 years of age. BDNF was poorly related to liver dysfunction but showed no relationship with brain atrophy or age.

CONCLUSION

Chronic alcoholics show decreased BDNF serum levels that are related to muscle function impairment rather than to age, brain atrophy, liver dysfunction, or the amount of ethanol consumed.

Alcohol alters IL-6 Signal Transduction in the CNS of Transgenic Mice with Increased Astrocyte Expression of IL-6

Neuroimmune factors, including the cytokine interleukin-6 (IL-6), are important chemical regulators of central nervous system (CNS) function under both physiological and pathological conditions. Elevated expression of IL-6 occurs in the CNS in a variety of disorders associated with altered CNS function, including excessive alcohol use. Alcohol-induced production of IL-6 has been reported for several CNS regions including the cerebellum. Cerebellar actions of alcohol occur through a variety of mechanisms, but alcohol-induced changes in signal transduction, transcription, and translation are known to play important roles. IL-6 is an activator of signal transduction that regulates gene expression. Thus, alcohol-induced IL-6 production could contribute to cerebellar effects of alcohol by altering gene expression, especially under conditions of chronic alcohol abuse, where IL-6 levels could be habitually elevated. To gain an understanding of the effects of alcohol on IL-6 signal transduction, we studied activation/expression of IL-6 signal transduction partners STAT3 (Signal Transducer and Activator of Transcription), CCAAT-enhancer binding protein (C/EBP) beta, and p42/p44 mitogen-activated protein kinase (MAPK) at the protein level. Cerebella of transgenic mice that express elevated levels of astrocyte produced IL-6 in the CNS were studied. Results show that the both IL-6 and chronic intermittent alcohol exposure/withdrawal affect IL-6 signal transduction partners and that the actions of IL-6 and alcohol interact to alter activation/expression of IL-6 signal transduction partners. The alcohol/IL-6 interactions may contribute to cerebellar actions of alcohol, whereas the effects of IL-6 alone may have relevance to cerebellar changes occurring in CNS disorders associated with elevated levels of IL-6.

Acupuncture Alleviates Anxiety and 22-kHz Ultrasonic Vocalizations in Rats Subjected to Repeated Alcohol Administration by Modulating the Brain-Derived Neurotrophic Factor/Corticotropin-Releasing Hormone Signaling Pathway

The Shenmen point (acupuncture point heart 7: HT7), located in the heart meridian, is frequently used to treat mental disorders, including drug addiction, anxiety, and depression. This study aimed to determine how HT7 regulates anxiety and negative emotions caused by repeated alcohol administration, focusing on the amygdala and paraventricular nucleus (PVN). Repeated administration of alcohol (ETOH; 2 g/kg, i.p. injection, 16% v/v) for 14 days increased the corticosterone (CORT) levels, and HT7 stimulation reduced the plasma CORT levels. HT7 stimulation mitigated anxiety-like behaviors and reduced 22-kHz ultrasonic vocalizations in rats receiving repeated ETOH injections. HT7 stimulation increased the amygdala expression of mature brain-derived neurotropic factor (mBDNF) and phosphorylated tropomyosin receptor kinase B (pTrkB) and decreased the PVN corticotropin-releasing hormone (CRH) expression. Amygdala microinjections of the TrkB antagonist ANA-12 (0.1 pmol/1 μL) reversed the increase in PVN CRH levels. The reduced PVN CRH levels were regulated by CRH-expressing neurons in the amygdala, and the increased amygdala CRH levels were affected by the HT7-stimulation induced increases in mBDNF. HT7 stimulation alleviates increased stress hormone levels and mitigates anxiety and negative emotions caused by repeated ETOH administration. These results provide scientific support for the clinical use of acupuncture to treat various alcoholism-induced diseases.

Pharmacological enhancing agents targeting cognition in patients with alcohol-induced neurocognitive disorders: A systematic review

Debilitating neurocognitive deficits are seen in alcohol use disorders (AUD) and Wernicke-Korsakoff's syndrome (WKS). These shared characteristics suggest a spectrum of alcohol-induced neurocognitive disorders (AIND). Cognitive pharmacological enhancing agents (CPEA) have been examined in the treatment of other psychiatric disorders, but little is known about the effects of these agents on AINDs. Our aim was to synthesize the evidence for the effectiveness of CPEAs on AINDs. Databases were searched for controlled trials examining CPEAs on AUD, WKS, and alcohol-related dementia (ARD). Eligible studies were included in a qualitative synthesis and a quality assessment was conducted. The search identified 23 studies (4 ≤ ns ≤ 98). Evidence suggests that modafinil may improve executive functions in AUD and ARD, but this effect may only be present in patients with severe deficits. The studies were rated as having a moderate risk of bias. Despite the promising effects of modafinil, small samples and inconsistent evidence deem the results preliminary. More research is warranted examining the effects of transdiagnostic CPEAs on deficits across AINDs.

Differential correlation of serum BDNF and microRNA content in rats with rapid or late onset of heavy alcohol use

Heavy alcohol use reduces the levels of the brain-derived neurotrophic factor (BDNF) in the prefrontal cortex of rodents through the upregulation of microRNAs (miRs) targeting BDNF mRNA. In humans, an inverse correlation exists between circulating blood levels of BDNF and the severity of psychiatric disorders including alcohol abuse. Here, we set out to determine whether a history of heavy alcohol use produces comparable alterations in the blood of rats. We used an intermittent access to 20% alcohol using the two-bottle choice paradigm (IA20%2BC) and measured circulating levels of BDNF protein and miRs targeting BDNF in the serum of Long-Evans rats before and after 8 weeks of excessive alcohol intake. We observed that the drinking profile of heavy alcohol users is not unified, whereas 70% of the rats gradually escalate their alcohol intake (late onset), and 30% of alcohol users exhibit a very rapid onset of drinking (rapid onset). We found that serum BDNF levels are negatively correlated with alcohol intake in both rapid onset and late onset rats. In contrast, increased expression of the miRs targeting BDNF, miR30a-5p, miR-195-5p, miR191-5p and miR206-3p, was detected only in the rapid onset rats. Finally, we report that the alcohol-dependent molecular changes are not due to alterations in platelet number. Together, these data suggest that rats exhibit both late and rapid onset of alcohol intake. We further show that heavy alcohol use produces comparable changes in BDNF protein levels in both groups. However, circulating microRNAs are responsive to alcohol only in the rapid onset rats.

Microglia depletion and alcohol: Transcriptome and behavioral profiles

Alcohol abuse induces changes in microglia morphology and immune function, but whether microglia initiate or simply amplify the harmful effects of alcohol exposure is still a matter of debate. Here, we determine microglia function in acute and voluntary drinking behaviors using a colony-stimulating factor 1 receptor inhibitor (PLX5622). We show that microglia depletion does not alter the sedative or hypnotic effects of acute intoxication. Microglia depletion also does not change the escalation or maintenance of chronic voluntary alcohol consumption. Transcriptomic analysis revealed that although many immune genes have been implicated in alcohol abuse, downregulation of microglia genes does not necessitate changes in alcohol intake. Instead, microglia depletion and chronic alcohol result in compensatory upregulation of alcohol-responsive, reactive astrocyte genes, indicating astrocytes may play a role in regulation of these alcohol behaviors. Taken together, our behavioral and transcriptional data indicate that microglia are not the primary effector cell responsible for regulation of acute and voluntary alcohol behaviors. Because microglia depletion did not regulate acute or voluntary alcohol behaviors, we hypothesized that these doses were insufficient to activate microglia and recruit them to an effector phenotype. Therefore, we used a model of repeated immune activation using polyinosinic:polycytidylic acid (poly(I:C)) to activate microglia. Microglia depletion blocked poly(I:C)-induced escalations in alcohol intake, indicating microglia regulate drinking behaviors with sufficient immune activation. By testing the functional role of microglia in alcohol behaviors, we provide insight into when microglia are causal and when they are consequential for the transition from alcohol use to dependence.

Dysregulation of Nociceptin/Orphanin FQ and Dynorphin Systems in the Extended Amygdala of Alcohol Preferring Marchigian Sardinian (msP) Rats

Previous studies have shown that genetically selected Marchigian Sardinian alcohol-preferring (msP) rats consume excessive amounts of ethanol to self-medicate from negative moods and to relieve innate hypersensitivity to stress. This phenotype resembling a subset of alcohol use disorder (AUD) patients, appears to be linked to a dysregulation of the equilibrium between stress and antistress mechanisms in the extended amygdala. Here, comparing water and alcohol exposed msP and Wistar rats we evaluate the transcript expression of the anti-stress opioid-like peptide nociceptin/orphanin FQ (N/OFQ) and its receptor NOP as well as of dynorphin (DYN) and its cognate κ-opioid receptor (KOP). In addition, we measured the transcript levels of corticotropin-releasing factor (CRF), CRF receptor 1 (CRF1R), brain-derived neurotrophic factor (BDNF) and of the tropomyosin receptor kinase B receptor (Trk-B). Results showed an innately up-regulation of the CRFergic system, mediating negative mood and stress responses, as well as an inherent up-regulation of the anti-stress N/OFQ system, both in the amygdala (AMY) and bed nucleus of the stria terminalis (BNST) of msP rats. The up-regulation of this latter system may reflect an attempt to buffer the negative condition elicited by the hyperactivity of pro-stress mechanisms since results showed that voluntary alcohol consumption dampened N/OFQ. Alcohol exposure also reduced the expression of dynorphin and CRF transmissions in the AMY of msP rats. In the BNST, alcohol intake led to a more complex reorganization of these systems increasing receptor transcripts in msP rats, along with an increase of CRF and a decrease of N/OFQ transcripts, respectively. Moreover, mimicking the effects of alcohol in the AMY we observed that the activation of NOP receptor by intracerebroventricular administration of N/OFQ in msP rats caused an increase of BDNF and a decrease of CRF transcripts. Our study indicates that both stress and anti-stress mechanisms are dysregulated in the extended AMY of msP rats. The voluntary alcohol drinking, as well as NOP agonism, have a significant impact on neuropeptidergic systems arrangement, bringing the systems back to normalization.

An in vivo explorative study to observe the protective effects of Puerariae flos extract on chronic ethanol exposure and withdrawal male mice

Protective effects of Puerariae flos extract (PFE) on ethanol (EtOH) exposure have been previously verified. This study attempts to explore the protective effects of PEF on EtOH withdrawal models. Sixty male Kunming mice were involved which were randomly divided into five groups (intact control, EtOH group (35-day EtOH exposure), EtOH withdrawal group (28-day exposure + 7-day withdrawal), EtOH withdrawal group + positive control (Deanxit) group, and EtOH withdrawal group + PFE group). The changes of neuropsychological behaviors; hippocampal BDNF expression and CA1 neuronal density; and plasma corticotropin-releasing hormone (CRH), ACTH, and CORT levels were observed. It was found that depression-like behaviors reduced by EtOH exposure and increased by withdrawal under the 28-day EtOH exposure and 7-day withdrawal conditions. In addition, anxiety-like behaviors worsened by EtOH exposure and unchanged by withdrawal. Deanxit and PEF ameliorated such behaviors (vs. withdrawal group). Hippocampal BDNF expression was significantly downregulated by EtOH exposure and upregulated by withdrawal. Deanxit and PEF significantly upregulated the BDNF expression. The hippocampal CA1 neuronal density significantly decreased by EtOH exposure but unchanged by withdrawal and treatments. The plasma CRH, ACTH, and CORT levels show a significant enhancement by EtOH exposure and reduced by withdrawal. They were further reduced by Deanxit and PEF. The protective effects of PEF on EtOH chronic withdrawal mouse models were verified. The results of this study also indicated a complicated scenario of neuropsychological behaviors, hippocampal BDNF expression, and hypothalamic-pituitary-adrenal axis which are affected by the timing of EtOH exposure and withdrawal.

Brain-Derived neurotrophic factor Val66Met induces female-specific changes in impulsive behaviour and alcohol self-administration in mice

Substance use disorders are a debilitating neuropsychiatric condition, however it remains unclear why some individuals are at greater risk of substance use disorders than others and what genetic factors determine such individual differences. Impulsivity appears a promising candidate endophenotype to bridge the gap between genetic risk and addiction. Brain-derived neurotrophic factor (BDNF), and in particular the BDNF^Val66Met polymorphism, has been suggested to be involved in both impulsivity and substance use disorders, however results so far have been inconsistent. To investigate the role of BDNF, and more specifically the BDNF^Val66Met polymorphism, in both impulsivity and operant alcohol self-administration using the same animal model. Separate cohorts of humanized Val66Met transgenic mice were assessed for either trait impulsivity in the 5-choice serial reaction time (5-CSRT) touchscreen task, or propensity towards obtaining ethanol in an operant paradigm. It was found that female hBDNF^Val/Val mice exhibited both greater impulsivity compared to hBDNF^Met/Met mice of the same sex as shown by a higher number of premature responses at one of three increased inter-trial intervals tested in the 5-CSRT task, and a greater propensity toward stable ethanol self-administration relative to male mice of the same genotype in the operant paradigm. By contrast, male mice showed no difference between genotypes in impulsivity or stable ethanol self-administration. The hBDNF^Met/Met genotype appears to sex-specifically alter aspects of both impulsive behaviour and addiction propensity. These results suggest that impulse behaviour may be a possible predictor of addiction risk.

Microglia Control Escalation of Drinking in Alcohol-Dependent Mice: Genomic and Synaptic Drivers

BACKGROUND

Microglia, the primary immune cells of the brain, are implicated in alcohol use disorder. However, it is not known if microglial activation contributes to the transition from alcohol use to alcohol use disorder or is a consequence of alcohol intake.

METHODS

We investigated the role of microglia in a mouse model of alcohol dependence using a colony stimulating factor 1 receptor inhibitor (PLX5622) to deplete microglia and a chronic intermittent ethanol vapor two-bottle choice drinking procedure. Additionally, we examined anxiety-like behavior during withdrawal. We then analyzed synaptic neuroadaptations in the central nucleus of the amygdala (CeA) and gene expression changes in the medial prefrontal cortex and CeA from the same animals used for behavioral studies.

RESULTS

PLX5622 prevented escalations in voluntary alcohol intake and decreased anxiety-like behavior associated with alcohol dependence. PLX5622 also reversed expression changes in inflammatory-related genes and glutamatergic and GABAergic (gamma-aminobutyric acidergic) genes in the medial prefrontal cortex and CeA. At the cellular level in these animals, microglia depletion reduced inhibitory GABAA and excitatory glutamate receptor-mediated synaptic transmission in the CeA, supporting the hypothesis that microglia regulate dependence-induced changes in neuronal function.

CONCLUSIONS

Our multifaceted approach is the first to link microglia to the molecular, cellular, and behavioral changes associated with the development of alcohol dependence, suggesting that microglia may also be critical for the development and progression of alcohol use disorder.

Growth Factors and Alcohol Use Disorder

Neurotrophic growth factors were originally characterized for their support in neuronal differentiation, outgrowth, and survival during development. However, it has been acknowledged that they also play a vital role in the adult brain. Abnormalities in growth factors have been implicated in a variety of neurological and psychiatric disorders, including alcohol use disorder (AUD). This work focuses on the interaction between alcohol and growth factors. We review literature suggesting that several growth factors play a unique role in the regulation of alcohol consumption, and that breakdown in these growth factor systems is linked to the development of AUD. Specifically, we focus on the brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), fibroblast growth factor 2 (FGF2), and insulin growth factor 1 (IGF-1). We also review the literature on the potential role of midkine (MDK) and pleiotrophin (PTN) and their receptor, anaplastic lymphoma kinase (ALK), in AUD. We show that alcohol alters the expression of these growth factors or their receptors in brain regions previously implicated in addiction, and that manipulations on these growth factors and their downstream signaling can affect alcohol-drinking behaviors in animal models. We conclude that there is a need for translational and clinical research to assess the therapeutic potential of new pharmacotherapies targeting these systems.

Investigating the link between serum concentrations of brain-derived neurotrophic factor and behavioral measures in anxious alcohol-dependent individuals

Brain-derived neurotrophic factor (BDNF) plays a role in different neurophysiological processes, including those involved in alcohol- and anxiety-related behaviors. Preclinical and clinical studies indicate that chronic excessive alcohol use leads to a downregulation of BDNF production in the periphery and in the brain. In addition, a decrease in BDNF concentrations in the blood has been reported to be associated with increased anxiety levels. Non-treatment-seeking alcohol-dependent individuals with high trait anxiety were studied to assess whether serum BDNF concentrations may be linked to self-reported levels of alcohol drinking, anxiety, and other behavioral measures. Participants had a current diagnosis of alcohol dependence, high trait anxiety score, and were not seeking treatment for alcohol dependence or anxiety. A fasting blood sample was collected from each participant and serum BDNF was measured using an enzyme-linked immunosorbent assay (ELISA). Behavioral data were collected on the same day, including measures of alcohol drinking, craving, dependence severity, and anxiety. Bivariate correlations were run between BDNF levels and behavioral measures. Serum BDNF concentrations were negatively correlated with average drinks per drinking days (r = -0.41, p = 0.02) and positively correlated with obsessive-compulsive drinking scale (r = 0.48, p = 0.007) and state-trait anxiety inventory (r = 0.52, p = 0.003) scores. These findings shed light on the possible role of the BDNF system in the neurobiology of alcohol- and anxiety-related behaviors.

BDNF levels and liver stiffness in subjects with alcohol use disorder: Evaluation after alcohol withdrawal

Background: Brain-derived neurotrophic factor (BDNF) plays a key role in the processes of withdrawal and addiction in alcohol use disorder (AUD), and is also involved in liver homeostasis. The role of BDNF in liver damage and its link with liver stiffness are not known. We hypothesize that serum BDNF levels are linked to changes in hepatic elasticity, both of which depend on variations in alcohol consumption.Objectives: We aimed to study the evolution of BDNF levels and changes in the liver stiffness (LS) of AUD subjects, within two months following withdrawal.Methods: We measured LS by FibroScan® (as an indicator of the degree of liver fibrosis), gamma glutamyl transferase (GGT) levels (as a nonspecific but sensitive marker of liver status) and serum BDNF levels of 62 alcohol-dependent subjects without previously identified liver complications. Measures were obtained at the time of withdrawal (M0) and two months later (M2). Results: BDNF levels increased after alcohol withdrawal and small variations of LS were observed. BDNF values increased significantly according to fibrosis stages measured by LS (p = .028 at M0), and were predicted by GGT levels in a regression model (p = .007 at M0 and p = .003 at M2).Conclusion: In AUD, BDNF levels were associated with measured LS when divided into fibrosis risk categories. Changes in LS and BDNF levels after alcohol withdrawal may be related to changes in homeostatic mechanisms, in addition to those of liver status.

Post-stroke BDNF concentration changes following proprioceptive neuromuscular facilitation (PNF) exercises

Background:

Brain-derived neurotrophic factor (BDNF) plays an important role in repairing normal as well as in the injured brain. Physical exercise may have a positive impact on the release of BDNF.

Objective:

PNF is a neurophysiological approach that facilitates the stimulation of central and peripheral nervous systems. In this study, our aim was to assess the levels of BDNF as well as functional recovery before and after the intervention of PNF in patients with acute stroke.

Methods:

A total of 208 patients with first time confirmed stroke were recruited and assessed for stroke severity, type, mini-mental state exam (MMSE), functional independence measure scale, and BDNF levels before and after PNF intervention. BDNF levels were also assessed in healthy individuals for control values.

Results:

A significant decline in levels of BDNF was observed after in stroke. BDNF levels in patients (with different risk factors) with diabetes, hypertension and DM+ HTN, alcohol, and smoking history were 8.8 ± 4.04 ng/mL, 8.86 ± 4.68 ng/mL, 8.65 ± 3.26 ng/mL, 8.51 ± 4.26 ng/mL, and 8.9 ± 3.4 ng/mL, respectively. A decline in BDNF levels was observed in accordance with the severity of stroke in both ischemic and hemorrhagic stroke with the least level being in severe stroke (NIHSS >15 and ICH >3). Despite the type of stroke and the presence of risk factors, a significant improvement in BDNF levels and FIM scale scores was seen in all subjects who received PNF exercises.

Conclusion:

Thus, PNF is efficient in improving functional level in acute stroke irrespective of the type of stroke and risk factors.

Effects and Potential Mechanisms of Alcohol Use Disorder on the Fate Determination of Newly Born Neurons in the Hippocampus

In the adult mammalian brain, new functional neurons are generated throughout life because of sustained proliferation and differentiation of neural stem cells (NSCs). The subventricular zone (SVZ), lining the lateral ventricle, and the subgranular zone (SGZ) in the dentate gyrus (DG) of the hippocampus are the two major neurogenic regions in the adult brain. This process is not fixed but is highly modulated by numerous intrinsic and extrinsic factors. Neurogenesis has become in the focus of interest for its involvement in repairing the damaged brain and this motivates researchers to detect controlling mechanisms of this process. Recent evidence suggests that alcohol usage can directly influence adult hippocampal neurogenesis, but its mechanisms remain a matter for debate. Thus, this review summarizes in vivo/in vitro studies on the role of alcohol in hippocampal neurogenesis during adulthood and clarifies its underlying mechanisms by highlighting neurotransmitters and their receptors.

Brain-derived neurotrophic factor levels in acute stroke and its clinical implications

BACKGROUND:

Brain-derived neurotrophic factor (BDNF) has a very important role in repairing intact and injured brain, also known as neuroplasticity. Risk factors may affect neuroplasticity.

OBJECTIVES:

In this study, our aim was to delineate the levels of BDNF in acute stroke with different etiology and impact of risk factors on its levels.

METHODS:

In this prospective study, 208 patients with first-ever stroke, between 18 and 75 years, were included. All individuals were assessed for severity and type of stroke, risk factors, levels of BDNF in the acute stroke, and its association with outcome of stroke.

RESULTS:

The mean age of the patients in our study was 55.29 ± 11.6 years. Compared to healthy controls, a significant decline in the levels of BDNF was observed after stroke (P < 0.01). Patients with National Institutes of Health Stroke Scale (NIHSS) <6 on the 1^st day of stroke had significantly higher levels of BDNF than those with NIHSS >6 (9.8 ng/ml ± 3.8; P < 0.01). A significant difference in the levels of BDNF was observed on comparing the stroke patients and healthy individuals of age <55 and >55 years (<55 years: 10.4 ng/ml ± 3.2; >55 years: 9.8 ng/ml ± 4.5 and in healthy individuals <55 years: 22.97 ± 3.8, >55 years: 15.4 ± 4.9; P < 0.01). Risk factors have negative impact on levels of BDNF (diabetics, P = 0.001; alcoholics, P = 0.003; both diabetes mellitus + hypertension, P = 0.002; smokers, P = 0.001). The difference was not significant between hypertensives and nonhypertensives (P = 0.06).

CONCLUSION:

BDNF level is significantly reduced in acute stroke. The presence of risk factors further affects its level.

On the interaction between BDNF and serotonin systems: The effects of long-term ethanol consumption in mice

We investigated the effect of chronic (6 weeks) consumption of 10% alcohol on the principal elements of BDNF (BDNF, proBDNF, p75, and TrkB receptors) and 5-HT (5-HT, 5-HIAA, tryptophan hydroxylase-2 [Tph-2], 5-HT transporter [5-HTT], 5-HT_1A, 5-HT_2A, and 5-HT₇ receptors) systems in the brain of C57Bl/6 mice. BDNF mRNA level in the raphe nuclei area and BDNF protein level in the hippocampus were lowered in ethanol-treated mice. The increase in proBDNF protein level in the raphe nuclei area, cortex, and amygdala and the increase of p75 receptor protein levels in the raphe nuclei area were revealed after ethanol exposure. Alcohol intake reduced the protein level and increased the activity of Tph-2, the key enzyme for serotonin biosynthesis in the brain, and increased the main 5-HT metabolite 5-HIAA level and 5-HIAA/5-НТ ratio as well as the 5-HT₇ receptor mRNA level in the raphe nuclei area. In the cortex, 5-HT_2A receptor protein level was reduced, and 5-HIAA/5-HT ratio was increased. These data showed considerable impact of alcoholization on the BDNF system, resulting in proBDNF and p75 receptor expression enhancement. Alcohol-induced changes in BDNF and 5-HT systems were revealed in the raphe nuclei area where the majority of the cell bodies of the 5-HT neurons are localized, as well as in the cortex, hippocampus, and amygdala. Our data suggest that the BDNF/5-HT interaction contributes to the mechanism underlying chronic alcohol-induced neurodegenerative disorders.