Glutathione S-transferase 8-8 expression is lower in alcohol-preferring than in alcohol-nonpreferring rats

Sex-Specific Impact of Fkbp5 on Hippocampal Response to Acute Alcohol Injection: Involvement in Alterations of Metabolism-Related Pathways

High levels of alcohol intake alter brain gene expression and can produce long-lasting effects. FK506-binding protein 51 (FKBP51) encoded by Fkbp5 is a physical and cellular stress response gene and has been associated with alcohol consumption and withdrawal severity. Fkbp5 has been previously linked to neurite outgrowth and hippocampal morphology, sex differences in stress response, and epigenetic modification. Presently, primary cultured Fkbp5 KO and WT mouse neurons were examined for neurite outgrowth and mitochondrial signal with and without alcohol. We found neurite specification differences between KO and WT; particularly, mesh-like morphology was observed after alcohol treatment and confirmed higher MitoTracker signal in cultured neurons of Fkbp5 KO compared to WT at both naive and alcohol-treated conditions. Brain regions that express FKBP51 protein were identified, and hippocampus was confirmed to possess a high level of expression. RNA-seq profiling was performed using the hippocampus of naïve or alcohol-injected (2 mg EtOH/Kg) male and female Fkbp5 KO and WT mice. Differentially expressed genes (DEGs) were identified between Fkbp5 KO and WT at baseline and following alcohol treatment, with female comparisons possessing a higher number of DEGs than male comparisons. Pathway analysis suggested that genes affecting calcium signaling, lipid metabolism, and axon guidance were differentially expressed at naïve condition between KO and WT. Alcohol treatment significantly affected pathways and enzymes involved in biosynthesis (Keto, serine, and glycine) and signaling (dopamine and insulin receptor), and neuroprotective role. Functions related to cell morphology, cell-to-cell signaling, lipid metabolism, injury response, and post-translational modification were significantly altered due to alcohol. In summary, Fkbp5 plays a critical role in the response to acute alcohol treatment by altering metabolism and signaling-related genes.

Anticataleptic activity of nicotine in rats: involvement of the lateral entorhinal cortex

RATIONALE

Recently, it was found that cyclosomatostatin-induced catalepsy in middle-aged rats is accompanied by neuronal hypoactivation in the lateral entorhinal cortex (LEntCx); this hypoactivation was reversed by systemic administration of nicotine combined with diphenhydramine. These findings suggest the ability of nicotine to regulate catalepsy and the involvement of the LEntCx in this nicotine effect.

OBJECTIVES

The study was aimed to assess whether nicotine alone influences catalepsy when injected into the LEntCx and some other neuroanatomical structures.

METHODS

Experiments were conducted with male Wistar rats of 540-560 days of age. Catalepsy was induced by intracerebroventricular injection of cyclosomatostatin and assessed by the standard bar test. Nicotine was injected into the LEntCx, prelimbic cortex (PrCx), or basolateral amygdala (BLA). The tissue levels of tyrosine hydroxylase, dopamine, and DOPAC in the substantia nigra pars compacta and dorsal striatum were measured with use of HPLC and ELISA.

RESULTS

Injections of nicotine into the LEntCx but not into the PrCx and BLA produced anticataleptic effect; the nicotine effect was significantly reversed by intra-LEntCx administration of NMDA and non-NMDA glutamate receptor antagonists. Nicotine also attenuated cataleptogen-induced changes in nigrostriatal dopamine metabolism.

CONCLUSIONS

This may be the first demonstration of anticataleptic activity of nicotine. The results show that the effect is mediated by nicotine receptors in the LEntCx, via a glutamatergic mechanism. These findings may help advance the development of novel treatments for extrapyramidal disorders, including parkinsonism.

Cyclosomatostatin-induced catalepsy in aged rats: Specific change of brain c-Fos protein expression in the lateral entorhinal cortex

Aging represents the largest risk factor for developing Parkinson's disease (PD); another salient feature of this disorder is a decreased brain levels of somatostatin. Recently, in aged Wistar rats, we simulated the central somatostatinergic deficiency by intracerebroventricular injections of a somatostatin antagonist, cyclosomatostatin (cSST). The treated animals displayed catalepsy, a state that resembles the extrapyramidal signs of Parkinson's disease; young animals were insensitive to cSST. The neuroanatomical substrates responsible for the increased cataleptogenic activity of cSST in aged animals, are currently unknown. To study this issue, we assessed the cSST effect on brain c-Fos-protein expression in aged and young rats; thirty three brain regions were examined. cSST was employed at the dose cataleptogenic for aged animals and non-cataleptogenic for young ones. c-Fos expression patterns in the 'cataleptic' and 'non-cataleptic' animals were very similar, with the only distinction being a decrease in the c-Fos expression in the aged lateral entorhinal cortex (LEntCx). This decrease was not observed when the cSST-induced cataleptic response was inhibited by administration of diphenhydramine and nicotine. Thus, the development of catalepsy in the aged Wistar rats appeared to be associated with a hypoactivation of the LEntCx; possibly, there exists a mechanistic link between the LEntCx hypoactivation and increased susceptibility of aged rats to catalepsy. Apparently, these findings may provide novel insight into the link between mechanisms of parkinsonian motor disorders and aging.

Synergistic anticataleptic effect of imipramine and nicotine in a rotenone-induced rat model

RATIONALE

Some antidepressants have been previously found to produce anti-parkinsonian effect; nicotine was known to mitigate experimental neurotoxic lesions. The anticataleptic efficacy of antidepressant-nicotine co-administration is unstudied.

OBJECTIVES

This work aimed to evaluate anticataleptic action of imipramine-nicotine combination in rotenone model.

METHODS

Catalepsy was measured by the bar test. Concentrations of tyrosine hydroxylase, dopamine, and DOPAC were determined in the substantia nigra and dorsal striatum using ELISA and HPLC techniques; additionally, dopamine/DOPAC ratio was calculated for both areas.

RESULTS

Imipramine and nicotine alone were ineffective; however, co-administration of the drugs significantly (p < 0.01) inhibited rotenone-induced catalepsy and mitigated neurochemical changes in the nigrostriatal system. Anticataleptic effect of the combination exceeded that of levodopa, a standard drug for anti-parkinsonian treatment.

CONCLUSION

The combined use of imipramine and nicotine at relatively low doses inhibits neurotoxin-induced catalepsy and nigrostriatal neurochemical changes. The co-administration of these drugs might be a new approach to the treatment of extrapyramidal dysfunctions.

Estrogen-Dependent Upregulation of Adcyap1r1 Expression in Nucleus Accumbens Is Associated With Genetic Predisposition of Sex-Specific QTL for Alcohol Consumption on Rat Chromosome 4

Humans show sex differences related to alcohol use disorders (AUD). Animal model research has the potential to provide important insight into how sex differences affect alcohol consumption, particularly because female animals frequently drink more than males. In previous work, inbred strains of the selectively bred alcohol-preferring (P) and non-preferring (NP) rat lines revealed a highly significant quantitative trait locus (QTL) on rat chromosome 4, with a logarithm of the odds score of 9.2 for alcohol consumption. Recently, interval-specific congenic strains (ISCS) were developed by backcrossing the congenic P.NP line to inbred P (iP) rats to further refine the chromosome 4 QTL region. Two ISCS sub-strains, ISCS-A and ISCS-B, were obtained with a narrowed QTL, where the smallest region of overlap consisted of 8.9 Mb in ISCS-B. Interestingly, we found that females from both ISCS lines consumed significantly less alcohol than female iP controls (p < 0.05), while no differences in alcohol consumption were observed between male ISCS and iP controls. RNA-sequencing was performed on the nucleus accumbens of alcohol-naïve female ISCS-B and iP rats, which revealed differentially expressed genes (DEG) with greater than 2-fold change and that were functionally relevant to behavior. These DEGs included down-regulation of Oxt, Asb4, Gabre, Gabrq, Chat, Slc5a7, Slc18a8, Slc10a4, and Ngfr, and up-regulation of Ttr, Msln, Mpzl2, Wnt6, Slc17a7, Aldh1a2, and Gstm2. Pathway analysis identified significant alterations in gene networks controlling nervous system development and function, as well as cell signaling, GABA and serotonin receptor signaling and G-protein coupled receptor signaling. In addition, β-estradiol was identified as the most significant upstream regulator. The expression levels of estrogen-responsive genes that mapped to the QTL interval and have been previously associated with alcohol consumption were measured using RT-qPCR. We found that expression of the Adcyap1r1 gene, encoding the pituitary adenylate cyclase-activating polypeptide type 1 (PAC₁) receptor, was upregulated in female ISCS-B compared to female iP controls, while no differences were exhibited in males. In addition, sequence variants in the Adcyap1r1 promoter region showed a differential response to estrogen stimulation in vitro. These findings demonstrate that rat chromosome 4 QTL contains genetic variants that respond to estrogen and are associated with female alcohol consumption.

Glutathione and redox signaling in substance abuse

Throughout the last couple decades, the cause and consequences of substance abuse has expanded to identify the underlying neurobiological signaling mechanisms associated with addictive behavior. Chronic use of drugs, such as cocaine, methamphetamine and alcohol leads to the formation of oxidative or nitrosative stress (ROS/RNS) and changes in glutathione and redox homeostasis. Of importance, redox-sensitive post-translational modifications on cysteine residues, such as S-glutathionylation and S-nitrosylation could impact on the structure and function of addiction related signaling proteins. In this commentary, we evaluate the role of glutathione and redox signaling in cocaine-, methamphetamine- and alcohol addiction and conclude by discussing the possibility of targeting redox pathways for the therapeutic intervention of these substance abuse disorders.

Alcohol-preferring rats show decreased corticotropin-releasing hormone-2 receptor expression and differences in HPA activation compared to alcohol-nonpreferring rats

BACKGROUND

Corticotropin-releasing hormone (CRH) and urocortins (UCNs) bind to corticotropin-releasing hormone type 2 receptor (CRF2 receptor ), a Gs protein-coupled receptor that plays an important role in modulation of anxiety and stress responses. The Crhr2 gene maps to a quantitative trait locus (QTL) for alcohol preference on chromosome 4 previously identified in inbred alcohol-preferring (iP) and-nonpreferring (iNP) F2 rats.

METHODS

Real-time polymerase chain reaction was utilized to screen for differences in Crhr2 mRNA expression in the central nervous system (CNS) of male iP and iNP rats. DNA sequence analysis was then performed to screen for polymorphism in Crhr2 in order to identify genetic variation, and luciferase reporter assays were then applied to test their functional significance. Next, binding assays were used to determine whether this polymorphism affected CRF2 receptor binding affinity as well as CRF2 receptor density in the CNS. Finally, social interaction and corticosterone levels were measured in the P and NP rats before and after 30-minute restraint stress.

RESULTS

Crhr2 mRNA expression studies found lower levels of Crhr2 mRNA in iP rats compared to iNP rats. In addition, DNA sequencing identified polymorphisms in the promoter region, coding region, and 3'-untranslated region between the iP and iNP rats. A 7 bp insertion in the Crhr2 promoter of iP rats altered expression in vitro as measured by reporter assays, and we found that CRF2 receptor density was lower in the amygdala of iP as compared to iNP rats. Male P rats displayed decreased social interaction and significantly higher corticosterone levels directly following 30-minute restraint when compared to male NP rats.

CONCLUSIONS

This study identified Crhr2 as a candidate gene of interest underlying the chromosome 4 QTL for alcohol consumption that was previously identified in the P and NP model. Crhr2 promoter polymorphism is associated with reduced mRNA expression in certain brain regions, particularly the amygdala, and lowered the density of CRF2 receptor in the amygdala of iP compared to iNP rats. Together, these differences between the animals may contribute to the drinking disparity as well as the anxiety differences of the P and NP rats.

Relationship between differential hepatic microRNA expression and decreased hepatic cytochrome P450 3A activity in cirrhosis

Background and Aim

Liver cirrhosis is associated with decreased hepatic cytochrome P4503A (CYP3A) activity but the pathogenesis of this phenomenon is not well elucidated. In this study, we examined if certain microRNAs (miRNA) are associated with decreased hepatic CYP3A activity in cirrhosis.

Methods

Hepatic CYP3A activity and miRNA microarray expression profiles were measured in cirrhotic (n=28) and normal (n=12) liver tissue. Hepatic CYP3A activity was measured via midazolam hydroxylation in human liver microsomes. Additionally, hepatic CYP3A4 protein concentration and the expression of CYP3A4 mRNA were measured. Analyses were conducted to identify miRNAs which were differentially expressed between two groups but also were significantly associated with lower hepatic CYP3A activity.

Results

Hepatic CYP3A activity in cirrhotic livers was 1.7-fold lower than in the normal livers (0.28 ± 0.06 vs. 0.47 ± 0.07mL* min^-1*mg protein^-1 (mean ± SEM), P=0.02). Six microRNAs (miR-155, miR-454, miR-582-5p, let-7f-1*, miR-181d, and miR-500) had >1.2-fold increase in cirrhotic livers and also had significant negative correlation with hepatic CYP3A activity (range of r = -0.44 to -0.52, P <0.05). Notably, miR-155, a known regulator of liver inflammation, had the highest fold increase in cirrhotic livers (2.2-fold, P=4.16E-08) and significantly correlated with hepatic CYP3A activity (r=-0.50, P=0.017). The relative expression (2^-ΔΔCt mean ± SEM) of hepatic CYP3A4 mRNA was significantly higher in cirrhotic livers (21.76 ± 2.65 vs. 5.91 ± 1.29, P=2.04E-07) but their levels did not significantly correlate with hepatic CYP3A activity (r=-0.43, P=0.08).

Conclusion

The strong association between certain miRNAs, notably miR-155, and lower hepatic CYP3A activity suggest that altered miRNA expression may regulate hepatic CYP3A activity.

Gene expression in the ventral tegmental area of 5 pairs of rat lines selectively bred for high or low ethanol consumption

The objective of this study was to determine if there are common innate differences in gene expression or gene pathways in the ventral tegmental area (VTA) among 5 different pairs of rat lines selectively bred for high (HEC) or low (LEC) ethanol consumption: (a) alcohol-preferring (P) vs. alcohol-non-preferring (NP) rats; (b) high-alcohol-drinking (HAD) vs. low-alcohol-drinking (LAD) rats (replicate line pairs 1 and 2); (c) ALKO alcohol (AA) vs. nonalcohol (ANA) rats; and (d) Sardinian alcohol-preferring (sP) vs. alcohol-nonpreferring (sNP) rats. Microarray analysis revealed between 370 and 1340 unique named genes that significantly differed in expression between the individual line-pairs. Analysis using Gene Ontology (GO) and Ingenuity Pathways information indicated significant categories and networks in common for up to 3 line-pairs, but not for all 5 line-pairs; moreover, there were few genes in common in these categories and networks. ANOVA of the combined data for the 5 line-pairs indicated 1295 significant (p<0.01) differences in expression of named genes. Although no individual named gene was significant across all 5 line-pairs, there were 22 genes that overlapped in the same direction in 3 or 4 of the line-pairs. Overall, the findings suggest that (a) some biological categories or networks may be in common for subsets of line-pairs; and (b) regulation of different genes and/or combinations of multiple biological systems (e.g., transcription, synaptic function, intracellular signaling and protection against oxidative stress) within the VTA (possibly involving dopamine and glutamate) may be contributing to the disparate alcohol drinking behaviors of these line-pairs.

Candidate genes for alcohol preference identified by expression profiling in alcohol-preferring and -nonpreferring reciprocal congenic rats

BACKGROUND

Selectively bred alcohol-preferring (P) and alcohol-nonpreferring (NP) rats differ greatly in alcohol preference, in part due to a highly significant quantitative trait locus (QTL) on chromosome 4. Alcohol consumption scores of reciprocal chromosome 4 congenic strains NP.P and P.NP correlated with the introgressed interval. The goal of this study was to identify candidate genes that may influence alcohol consumption by comparing gene expression in five brain regions of alcohol-naïve inbred alcohol-preferring and P.NP congenic rats: amygdala, nucleus accumbens, hippocampus, caudate putamen, and frontal cortex.

RESULTS

Within the QTL region, 104 cis-regulated probe sets were differentially expressed in more than one region, and an additional 53 were differentially expressed in a single region. Fewer trans-regulated probe sets were detected, and most differed in only one region. Analysis of the average expression values across the 5 brain regions yielded 141 differentially expressed cis-regulated probe sets and 206 trans-regulated probe sets. Comparing the present results from inbred alcohol-preferring vs. congenic P.NP rats to earlier results from the reciprocal congenic NP.P vs. inbred alcohol-nonpreferring rats demonstrated that 74 cis-regulated probe sets were differentially expressed in the same direction and with a consistent magnitude of difference in at least one brain region.

CONCLUSIONS

Cis-regulated candidate genes for alcohol consumption that lie within the chromosome 4 QTL were identified and confirmed by consistent results in two independent experiments with reciprocal congenic rats. These genes are strong candidates for affecting alcohol preference in the inbred alcohol-preferring and inbred alcohol-nonpreferring rats.

Identification of candidate genes for alcohol preference by expression profiling of congenic rat strains

BACKGROUND

A highly significant quantitative trait locus (QTL) on chromosome 4 that influenced alcohol preference was identified by analyzing crosses between the iP and iNP rats. Congenic strains in which the iP chromosome 4 QTL interval was transferred to the iNP (NP.P) exhibited the expected increase in alcohol consumption compared with the iNP background strain. This study was undertaken to identify genes in the chromosome 4 QTL interval that might contribute to the differences in alcohol consumption between the alcohol-naïve congenic and background strains.

METHODS

RNA from 5 brain regions from each of 6 NP.P and 6 iNP rats was labeled and analyzed separately on an Affymetrix Rat Genome 230 2.0 microarray to look for both cis-regulated and trans-regulated genes. Expression levels were normalized using robust multi-chip average (RMA). Differential gene expression was validated using quantitative real-time polymerase chain reaction. Five individual brain regions (nucleus accumbens, frontal cortex, amygdala, hippocampus, and striatum) were analyzed to detect differential expression of genes within the introgressed QTL interval, as well as genes outside that region. To increase the power to detect differentially expressed genes, combined analyses (averaging data from the 5 discrete brain regions of each animal) were also carried out.

RESULTS

Analyses within individual brain regions that focused on genes within the QTL interval detected differential expression in all 5 brain regions; a total of 35 genes were detected in at least 1 region, ranging from 6 genes in the nucleus accumbens to 22 in the frontal cortex. Analysis of the whole genome detected very few differentially expressed genes outside the QTL. Combined analysis across brain regions was more powerful. Analysis focused on the genes within the QTL interval confirmed 19 of the genes detected in individual regions and detected 15 additional genes. Whole genome analysis detected 1 differentially expressed gene outside the interval.

CONCLUSIONS

Cis-regulated candidate genes for alcohol consumption were identified using microarray profiling of gene expression differences in congenic animals carrying a QTL for alcohol preference.

Glutathione-S-transferase expression in the brain: possible role in ethanol preference and longevity

Identification of genes that are differentially expressed in rats bidirectionally selected for alcohol preference might reveal biological mechanisms underlying alcoholism or related phenotypes. Microarray analysis from medial prefrontal cortex (mPFC), a key brain region for drug reward, indicated increased expression of glutathione-S-transferases of the alpha (Gsta4) and mu (Gstm1-5) classes in ethanol-preferring AA rats compared with nonpreferring ANA rats. Real-time RT polymerase chain reaction (RT-PCR) analysis demonstrated approximately 2-fold higher Gsta4 transcript levels in several brain regions of ethanol-naive AA compared with ANA rats. Differences in mRNA levels were accompanied by differential levels of GSTA4 protein. We identified a novel haplotype variant in the rat Gsta4 gene, defined here as var3. Allele frequencies of var3 were markedly different between AA and ANA rats, 52% and 100%, respectively. Gsta4 expression was strongly correlated with the gene dose of var3, with approximately 60% of the variance in expression accounted for by genotype at this locus. The contribution of glutathione S-transferase expression to the ethanol-preferring phenotype is presently unclear. It could, however, underlie observed differences in life span between AA and ANA lines, prompting a utility of this animal model in aging research.

The alcohol-preferring AA and alcohol-avoiding ANA rats: neurobiology of the regulation of alcohol drinking

The AA (alko, alcohol) and ANA (alko, non-alcohol) rat lines were among the earliest rodent lines produced by bidirectional selection for ethanol preference. The purpose of this review is to highlight the strategies for understanding the neurobiological factors underlying differential alcohol-drinking behavior in these lines. Most early work evaluated functioning of the major neurotransmitter systems implicated in drug reward in the lines. No consistent line differences were found in the dopaminergic system either under baseline conditions or after ethanol challenges. However, increased opioidergic tone in the ventral striatum and a deficiency in endocannabinoid signaling in the prefrontal cortex of AA rats may comprise mechanisms leading to increased ethanol consumption. Because complex behaviors, such as ethanol drinking, are not likely to be controlled by single factors, system-oriented molecular-profiling strategies have been used recently. Microarray based expression analysis of AA and ANA brains and novel data-mining strategies provide a system biological view that allows us to formulate a hypothesis on the mechanism underlying selection for ethanol preference. Two main factors appear active in the selection: a recruitment of signal transduction networks, including mitogen-activated protein kinases and calcium pathways and involving transcription factors such as Creb, Myc and Max, to mediate ethanol reinforcement and plasticity. The second factor acts on the mitochondrion and most likely provides metabolic flexibility for alternative substrate utilization in the presence of low amounts of ethanol.

Candidate genes and their regulatory elements: alcohol preference and tolerance

QTL analysis of behavioral traits and mouse brain gene expression studies were combined to identify candidate genes involved in the traits of alcohol preference and acute functional alcohol tolerance. The systematic application of normalization and statistical analysis of differential gene expression, behavioral and expression QTL location, and informatics methodologies resulted in identification of 8 candidate genes for the trait of alcohol preference and 22 candidate genes for acute functional tolerance. Pathway analysis, combined with clustering by ontology, indicated the importance of transcriptional regulation and DNA and protein binding elements in the acute functional tolerance trait, and protein kinases and intracellular signal transduction elements in the alcohol preference trait. A rudimentary search for transcription control elements that could indicate coregulation of the panels of candidate genes produced modest results, implicating SMAD-3 in the regulation of four of the eight candidate genes for alcohol preference. However, the realization of the many caveats related to transcription factor binding site analysis, and attempts to correlate between transcription factor binding and function, forestalled any definitive global analysis of transcriptional control of differentially expressed candidate genes.

Toward understanding the genetics of alcohol drinking through transcriptome meta-analysis

Much evidence from studies in humans and animals supports the hypothesis that alcohol addiction is a complex disease with both hereditary and environmental influences. Molecular determinants of excessive alcohol consumption are difficult to study in humans. However, several rodent models show a high or low degree of alcohol preference, which provides a unique opportunity to approach the molecular complexities underlying the genetic predisposition to drink alcohol. Microarray analyses of brain gene expression in three selected lines, and six isogenic strains of mice known to differ markedly in voluntary alcohol consumption provided >4.5 million data points for a meta-analysis. A total of 107 arrays were obtained and arranged into six experimental data sets, allowing the identification of 3,800 unique genes significantly and consistently changed between all models of high or low amounts of alcohol consumption. Several functional groups, including mitogen-activated protein kinase signaling and transcription regulation pathways, were found to be significantly overrepresented and may play an important role in establishing a high level of voluntary alcohol drinking in these mouse models. Data from the general meta-analysis was further filtered by a congenic strain microarray set, from which cis-regulated candidate genes for an alcohol preference quantitative trait locus on chromosome 9 were identified: Arhgef12, Carm1, Cryab, Cox5a, Dlat, Fxyd6, Limd1, Nicn1, Nmnat3, Pknox2, Rbp1, Sc5d, Scn4b, Tcf12, Vps11, and Zfp291 and four ESTs. The present study demonstrates the use of (i) a microarray meta-analysis to analyze a behavioral phenotype (in this case, alcohol preference) and (ii) a congenic strain for identification of cis regulation.

New prospects and strategies for drug target discovery in neurodegenerative disorders

The future of neurodegenerative therapeutics development depends upon effective disease modification strategies centered on carefully investigated targets. Pharmaceutical research endeavors that probe for a much deeper understanding of disease pathogenesis, and explain how adaptive or compensatory mechanisms might be engaged to delay disease onset or progression, will produce the needed breakthroughs. Below, we discuss the prospects for new targets emerging out of the study of brain disease genes and their associated pathogenic pathways. We describe a general experimental paradigm that we are employing across several mouse models of neurodegenerative disease to elucidate molecular determinants of selective neuronal vulnerability. We outline key elements of our target discovery program and provide examples of how we integrate genomic technologies, neuroanatomical methods, and mouse genetics in the search for neurodegenerative disease targets.