Quantitative reduction of type I adenylyl cyclase in human alcoholics

Alcohol-specific transcriptional dynamics of memory reconsolidation and relapse

Relapse, a critical issue in alcohol addiction, can be attenuated by disruption of alcohol-associated memories. Memories are thought to temporarily destabilize upon retrieval during the reconsolidation process. Here, we provide evidence for unique transcriptional dynamics underpinning alcohol memory reconsolidation. Using a mouse place-conditioning procedure, we show that alcohol-memory retrieval increases the mRNA expression of immediate-early genes in the dorsal hippocampus and medial prefrontal cortex, and that alcohol seeking is abolished by post-retrieval non-specific inhibition of gene transcription, or by downregulating ARC expression using antisense-oligodeoxynucleotides. However, since retrieval of memories for a natural reward (sucrose) also increased the same immediate-early gene expression, we explored for alcohol-specific transcriptional changes using RNA-sequencing. We revealed a unique transcriptional fingerprint activated by alcohol memories, as the expression of this set of plasticity-related genes was not altered by sucrose-memory retrieval. Our results suggest that alcohol memories may activate two parallel transcription programs: one is involved in memory reconsolidation in general, and another is specifically activated during alcohol-memory processing.

Cyclic nucleotide phosphodiesterases: potential therapeutic targets for alcohol use disorder

Alcohol use disorder (AUD), which combines the criteria of both alcohol abuse and dependence, contributes as an important causal factor to multiple health and social problems. Given the limitation of current treatments, novel medications for AUD are needed to better control alcohol consumption and maintain abstinence. It has been well established that the intracellular signal transduction mediated by the second messengers cyclic AMP (cAMP) and cyclic GMP (cGMP) crucially underlies the genetic predisposition, rewarding properties, relapsing features, and systemic toxicity of compulsive alcohol consumption. On this basis, the upstream modulators phosphodiesterases (PDEs), which critically control intracellular levels of cyclic nucleotides by catalyzing their degradation, are proposed to play a role in modulating alcohol abuse and dependent process. Here, we highlight existing evidence that correlates cAMP and cGMP signal cascades with the regulation of alcohol-drinking behavior and discuss the possibility that PDEs may become a novel class of therapeutic targets for AUD.

Targeting Phosphodiesterases in Pharmacotherapy for Substance Dependence

Substance dependence is a chronic relapsing brain disorder associated with adaptational changes in synaptic plasticity and neuronal functions. The high levels of substance consumption and relapse rate suggest more reliable medications are in need to better address the underlying causes of this disease. It has been well established that the intracellular second messengers cyclic AMP (cAMP) and cyclic GMP (cGMP) and their signaling systems play an important role in the molecular mechanisms of substance taking behaviors. On this basis, the phosphodiesterase (PDE) superfamily, which crucially controls cyclic nucleotide levels by catalyzing their hydrolysis, has been proposed as a novel class of therapeutic targets for substance use disorders. This chapter reviews the expression patterns of PDEs in the brain with regard to neural structures underlying the dependent process and highlights available evidence for a modulatory role of PDEs in substance dependence.

International Union of Basic and Clinical Pharmacology. CI. Structures and Small Molecule Modulators of Mammalian Adenylyl Cyclases

Adenylyl cyclases (ACs) generate the second messenger cAMP from ATP. Mammalian cells express nine transmembrane AC (mAC) isoforms (AC1-9) and a soluble AC (sAC, also referred to as AC10). This review will largely focus on mACs. mACs are activated by the G-protein Gαs and regulated by multiple mechanisms. mACs are differentially expressed in tissues and regulate numerous and diverse cell functions. mACs localize in distinct membrane compartments and form signaling complexes. sAC is activated by bicarbonate with physiologic roles first described in testis. Crystal structures of the catalytic core of a hybrid mAC and sAC are available. These structures provide detailed insights into the catalytic mechanism and constitute the basis for the development of isoform-selective activators and inhibitors. Although potent competitive and noncompetitive mAC inhibitors are available, it is challenging to obtain compounds with high isoform selectivity due to the conservation of the catalytic core. Accordingly, caution must be exerted with the interpretation of intact-cell studies. The development of isoform-selective activators, the plant diterpene forskolin being the starting compound, has been equally challenging. There is no known endogenous ligand for the forskolin binding site. Recently, development of selective sAC inhibitors was reported. An emerging field is the association of AC gene polymorphisms with human diseases. For example, mutations in the AC5 gene (ADCY5) cause hyperkinetic extrapyramidal motor disorders. Overall, in contrast to the guanylyl cyclase field, our understanding of the (patho)physiology of AC isoforms and the development of clinically useful drugs targeting ACs is still in its infancy.

Chronic alcohol consumption from adolescence-to-adulthood in mice--hypothalamic gene expression changes in the dilated cardiomyopathy signaling pathway

Background

Adolescence is a developmental stage vulnerable to alcohol drinking-related problems and the onset of alcoholism. Hypothalamus is a key brain region for food and water intake regulation, and is one of the alcohol-sensitive brain regions. However, it is not known what would be the alcohol effect on hypothalamus following adolescent alcohol intake, chronically over the adolescent development, at moderate levels.

Results

We employed a paradigm of chronic moderate alcohol intake from adolescence-to-adulthood in mice, and analyzed the alcohol effect on both behavioral and hypothalamic gene expression changes. A total of 751 genes were found and subjected to pathway analysis. The dilated cardiomyopathy (DCM) pathway was identified. The changes of ten genes under this pathway were further verified using RT-PCR. Chronic alcohol consumption during adolescence, even at moderate levels, led to a decrease of motor activity in mice, and also a concerted down regulation of signaling pathway initiating factor (SPIF) genes in the DCM signaling pathway, including β1-adrenergic receptor (Adrb1), Gs protein (Gnas), adenylyl cyclase 1 (Adcy1), and dihydropyridine receptor/L-type calcium channel (Cacna1d).

Conclusions

These findings suggest that adolescent alcohol intake may trigger gene expression changes in the CNS that parallel those found in the dilated cardiomyopathy signaling pathway. If such effects also take place in humans, our findings would serve as a warning against alcohol intake in youth, such as by teens and/or college students.

Consensus paper of the WFSBP task force on biological markers: biological markers for alcoholism

OBJECTIVES

This article presents an overview of the current literature on biological markers for alcoholism, including markers associated with the pharmacological effects of alcohol and markers related to the clinical course and treatment of alcohol-related problems. Many of these studies are well known, while other studies cited are new and still being evaluated.

METHODS

In this paper we first describe known biomarkers of alcohol-related disorders, review their features and the problems involved in their use. We then consider future developments on biomarkers and their possible impact on the field.

RESULTS

More recent findings cited include the work on type 7 adenylcyclase (AC) polymorphism and its lower expression levels in female alcoholics. Neuroimaging studies involving biomarkers have also reported brain volume reductions of gray and white matter, including amygdala and subcortical regions in alcoholic patients, while a high association between the copy number variations (CNVs) in 6q14.1/5q13.2 and alcohol dependence has more recently been identified in genetic studies.

CONCLUSIONS

In addition to their possible importance for diagnosis, biomarkers may have utility for predicting prognosis, progression of the disorder, the development of new treatments, and monitoring treatment effects. Although such findings should be verified in independent studies, the search for new biomarkers is continuing. Several potential candidate biomarkers have been found recently in blood, imaging, and genetic studies with encouraging results.

Loss of dopamine D2 receptors induces atrophy in the temporal and parietal cortices and the caudal thalamus of ethanol-consuming mice

BACKGROUND

The need of an animal model of alcoholism becomes apparent when we consider the genetic diversity of the human populations, an example being dopamine D2 receptor (DRD2) expression levels. Research suggests that low DRD2 availability is associated with alcohol abuse, while higher DRD2 levels may be protective against alcoholism. This study aims to establish whether (i) the ethanol-consuming mouse is a suitable model of alcohol-induced brain atrophy and (ii) DRD2 protect the brain against alcohol toxicity.

METHODS

Adult Drd2+/+ and Drd2-/- mice drank either water or 20% ethanol solution for 6 months. At the end of the treatment period, the mice underwent magnetic resonance (MR) imaging under anesthesia. MR images were registered to a common space, and regions of interest were manually segmented.

RESULTS

We found that chronic ethanol intake induced a decrease in the volume of the temporal and parietal cortices as well as the caudal thalamus in Drd2-/- mice.

CONCLUSIONS

The result suggests that (i) normal DRD2 expression has a protective role against alcohol-induced brain atrophy and (ii) in the absence of Drd2 expression, prolonged ethanol intake reproduces a distinct feature of human brain pathology in alcoholism, the atrophy of the temporal and parietal cortices.

Biological studies on alcohol-induced neuronal damage

Alcohol is a well-known cytotoxic agent which causes various kinds of neuronal damage. In spite of thousands of published studies, the true mechanism of alcohol-induced neuronal damage remains unclear. Neurogenesis is the generation of neurons from neural stem cells (NSCs) and occurs in predominantly two regions of the brain, the subventricular zone and the dentate gyrus of the hippocampus. NSCs are the self-renewing, multipotent precursor cells of neurons, astrocytes, and oligodendrocytes in the central nervous system. Recent studies have begun to illuminate the role of neurogenesis in the biological and cellular basis of psychiatric disorders and several clinical symptoms seen in alcoholism such as depression, cognitive impairment, underlying stress and brain atrophy have been linked to impaired neurogenesis. Heavy alcohol consumption decreases neurogenesis in animals, while in vitro studies have shown decreased generation of new neurons after alcohol exposure. These findings suggest that decreased neurogenesis is important in the pathophysiology of alcoholism. Neurogenesis can be divided into four stages; proliferation, migration, differentiation and survival. Our in vitro studies on NSCs showed that alcohol decreased neuronal differentiation at doses lower than those that affected cell survival and suggested that neuron-restrictive silencer factor, or repressor element-1 silencing transcription factor (NRSF/REST) could be involved in alcohol-induced inhibition of neuronal differentiation. In an animal model of fetal alcohol effects behavioral symptoms improved after NSC transplantation. Neurogenesis could be the target for new strategies to treat alcohol related disorders.

Long-term upregulation of protein kinase A and adenylate cyclase levels in human smokers

Repeated injections of cocaine and morphine in laboratory rats cause a variety of molecular neuroadaptations in the cAMP signaling pathway in nucleus accumbens and ventral tegmental area. Here we report similar neuroadaptations in postmortem tissue from the brains of human smokers and former smokers. Activity levels of two major components of cAMP signaling, cAMP-dependent protein kinase A (PKA) and adenylate cyclase, were abnormally elevated in nucleus accumbens of smokers and in ventral midbrain dopaminergic region of both smokers and former smokers. Protein levels of the catalytic subunit of PKA were correspondingly higher in the ventral midbrain dopaminergic region of both smokers and former smokers. Protein levels of other candidate neuroadaptations, including glutamate receptor subunits, tyrosine hydroxylase, and other protein kinases, were within normal range. These findings extend our understanding of addiction-related neuroadaptations of cAMP signaling to tobacco smoking in human subjects and suggest that smoking-induced brain neuroadaptations can persist for significant periods in former smokers.

Transcriptional changes common to human cocaine, cannabis and phencyclidine abuse

A major goal of drug abuse research is to identify and understand drug-induced changes in brain function that are common to many or all drugs of abuse. As these may underlie drug dependence and addiction, the purpose of the present study was to examine if different drugs of abuse effect changes in gene expression that converge in common molecular pathways. Microarray analysis was employed to assay brain gene expression in postmortem anterior prefrontal cortex (aPFC) from 42 human cocaine, cannabis and/or phencyclidine abuse cases and 30 control cases, which were characterized by toxicology and drug abuse history. Common transcriptional changes were demonstrated for a majority of drug abuse cases (N = 34), representing a number of consistently changed functional classes: Calmodulin-related transcripts (CALM1, CALM2, CAMK2B) were decreased, while transcripts related to cholesterol biosynthesis and trafficking (FDFT1, APOL2, SCARB1), and Golgi/endoplasmic reticulum (ER) functions (SEMA3B, GCC1) were all increased. Quantitative PCR validated decreases in calmodulin 2 (CALM2) mRNA and increases in apolipoprotein L, 2 (APOL2) and semaphorin 3B (SEMA3B) mRNA for individual cases. A comparison between control cases with and without cardiovascular disease and elevated body mass index indicated that these changes were not due to general cellular and metabolic stress, but appeared specific to the use of drugs. Therefore, humans who abused cocaine, cannabis and/or phencyclidine share a decrease in transcription of calmodulin-related genes and increased transcription related to lipid/cholesterol and Golgi/ER function. These changes represent common molecular features of drug abuse, which may underlie changes in synaptic function and plasticity that could have important ramifications for decision-making capabilities in drug abusers.

Chronic ethanol exposure induces an N-type calcium channel splice variant with altered channel kinetics

Chronic ethanol exposure increases the density of N-type calcium channels in brain. We report that ethanol increases levels of mRNA for a splice variant of the N channel specific subunit alpha1 2.2 that lacks exon 31a. Whole cell recordings demonstrated an increase in N-type current with a faster activation rate and a shift in activation to more negative potentials after chronic alcohol exposure, consistent with increased abundance of channels containing this variant. These results identify a novel mechanism whereby chronic ethanol exposure can increase neuronal excitability by altering levels of channel splice variants.

Alcohol and gene expression in the central nervous system

AIMS

To describe recent research focusing on the analysis of gene and protein expression relevant to understanding ethanol consumption, dependence and effects, in order to identify common themes.

METHODS

A selective literature search was used to collate the relevant data.

RESULTS

Over 160 genes have been individually assessed before or after ethanol administration, as well as in genetically selected lines. Techniques for studying gene expression include northern blots, differential display, real time reverse transcriptase-polymerase chain reaction (RT-PCR) and in situ hybridization. More recently, high throughput functional genomic technology, such as DNA microarrays, has been used to examine gene expression. Recent gene expression analyses have dramatically increased the number of candidate genes (nine array papers have illuminated 600 novel gene transcripts that may contribute to alcohol abuse and alcoholism).

CONCLUSIONS

Although functional genomic experiments (transcriptome analysis) have failed to identify a single alcoholism gene, they have illuminated important pathways and gene products that may contribute to the risk of alcohol abuse and alcoholism.

Reduced dopamine D4 receptor mRNA expression in lymphocytes of long-term abstinent alcohol and heroin addicts

AIM

It has been repeatedly suggested that dopamine receptor expression in peripheral blood lymphocytes reflects, to some extent, brain status. The aim of the present study was to investigate dopamine receptor expression in peripheral blood lymphocytes of long-term abstinent alcohol and heroin addicts against the background of the hypothesis, that a persisting dysfunction of the dopaminergic system contributes a biological cause to the chronic character of addiction.

DESIGN

Dopamine D3 and D4 receptor mRNA expression in peripheral blood lymphocytes was measured by real-time polymerase chain reaction (PCR) in 19 alcohol addicts, abstinent for 6.2 +/- 4.7 months (mean +/- SD), and 20 heroin addicts, abstinent for 6.7 +/- 3.7 months (mean +/- SD), and compared to a control group of 29 age- and sex-matched individuals with no life-time history of substance abuse.

FINDINGS

One-way anova showed significant differences in D4 mRNA expression between the groups (P = 0.005): both groups of addicts showed an approximately 50% reduction in D4 receptor mRNA expression in peripheral blood lymphocytes (PBL) compared to controls. No differences were found for D3 mRNA expression between the groups.

CONCLUSION

The results of the present study indicate a withdrawal-persisting dopaminergic imbalance in abstinent addicts as measured by a suggested peripheral marker.

Isoform-specific changes of adenylate cyclase mRNA expression in rat brains following chronic electroconvulsive shock

1. Electroconvulsive shock (ECS) has been reported to regulate the cAMP signaling system at various levels, suggesting that the cAMP system is involved in the therapeutic mechanism. 2. Chronic ECS has been suggested to change the expressions of adenylate cyclase (AC) genes, which constitute at least 9 families. However, little is known about its effect on the expression of AC. Therefore, to understand how chronic ECS alters the expression of AC genes in the brain, the authors analyzed the expression of 9 AC isoforms at the transcriptional level in rat hippocampus and cerebellum by quantitative RT-PCR following chronic ECS treatment. 3. Chronic ECS treatment was found to induce differential changes in the expression of AC isoforms in an isoform- and brain region-specific manner in the rat hippocampus and cerebellum. 4. Thus, it is concluded that chronic ECS induces differential changes in the expression of AC isoform mRNA in an isoform- and brain region-specific manner in the rat hippocampus and cerebellum. This suggests that the differential expression of AC isoforms might be an important mechanism by which chronic ECS treatment regulates the cAMP signaling system in rat brains.

Alteration of annexin IV expression in alcoholics

Western blot analysis was performed by using a specific antibody to measure annexin IV in human postmortem brain samples from alcoholic subjects. The analysis showed a significantly augmented expression in the hippocampus compared with controls, whereas the expression in the frontal cortex was equivalent in both groups. Annexin IV expression in the occipital cortex tended to increase in alcoholics. It was shown further that autoantibodies to annexin IV were increased significantly in alcoholic patients compared with controls. Thus, annexin IV may become a novel biological marker for alcoholics.

Increased levels of calcium-sensitive adenylyl cyclase subtypes in the limbic system of alcoholics: evidence for a specific role of cAMP signaling in the human addictive brain

We examined the amounts of several adenylyl cyclase (AC) isoforms and of cAMP-response element binding protein (CREB) in alcoholic and control brains. Immunoreactivity of type I AC was significantly increased in alcoholic nucleus accumbens and corpus amygdaloideum. Immunoreactivity of type VIII AC was also increased in alcoholic corpus amygdaloideum and hippocampus. CREB immunoreactivities were unchanged. These findings indicate that the brain-region specific increase of Ca(2+)-sensitive AC may contribute to the pathophysiology of alcoholism.

Hippocampal level of neural specific adenylyl cyclase type I is decreased in Alzheimer's disease

Previous studies reported disruption of adenylyl cyclase (AC)-cyclic AMP (cAMP) signal transduction in brain of Alzheimer's disease (AD). We also demonstrated that basal and stimulated AC activities in the presence of calcium and calmodulin (Ca(2+)/CaM) were significantly decreased in AD parietal cortex. In the present study, we examined the amounts of Ca(2+)/CaM-sensitive types I and VIII AC, and Ca(2+)/CaM-insensitive type VII AC in the postmortem hippocampi from AD patients and age-matched controls using immunoblotting. The specificities of the anti-type VII and VIII AC antibodies were confirmed by preabsorption with their specific blocking peptides. We observed a significant decrease in the level of type I AC and a tendency to decrease in the level of type VIII AC in AD hippocampus. On the other hand, the level of type VII AC showed no alteration between AD and controls. A body of evidence from the studies with invertebrates and vertebrates suggests that types I and VIII AC may play an essential role in learning and memory. Our finding thus firstly demonstrated that a specific disruption of the Ca(2+)/CaM-sensitive AC isoforms is likely involved in the pathophysiology in AD hippocampus.