A molecular prospective provides new insights into implication of PDYN and OPRK1 genes in alcohol dependence

AddictGene: An integrated knowledge base for differentially expressed genes associated with addictive substance

Addiction, a disorder of maladaptive brain plasticity, is associated with changes in numerous gene expressions. Nowadays, high-throughput sequencing data on addictive substance-induced gene expression have become widely available. A resource for comprehensive annotation of genes that show differential expression in response to commonly abused substances is necessary. So, we developed AddictGene by integrating gene expression, gene-gene interaction, gene-drug interaction and epigenetic regulatory annotation for over 70,156 items of differentially expressed genes associated with 7 commonly abused substances, including alcohol, nicotine, cocaine, morphine, heroin, methamphetamine, and amphetamine, across three species (human, mouse, rat). We also collected 1,141 addiction-related experimentally validated genes by techniques such as RT-PCR, northern blot and in situ hybridization. The easy-to-use web interface of AddictGene (http://159.226.67.237/sun/addictgedb/) allows users to search and browse multidimensional data on DEGs of their interest: 1) detailed gene-specific information extracted from the original studies; 2) basic information about the specific gene extracted from NCBI; 3) SNP associated with substance dependence and other psychiatry disorders; 4) expression alteration of specific gene in other psychiatric disorders; 5) expression patterns of interested gene across 31 primary and 54 secondary human tissues; 6) functional annotation of interested gene; 7) epigenetic regulators involved in the alteration of specific genes, including histone modifications and DNA methylation; 8) protein-protein interaction for functional linkage with interested gene; 9) drug-gene interaction for potential druggability. AddictGene offers a valuable repository for researchers to study the molecular mechanisms underlying addiction, and might provide valuable insights into potential therapies for drug abuse and relapse.

Prodynorphin (PDYN) gene polymorphisms in Turkish patients with methamphetamine use disorder, changes in PDYN serum levels in withdrawal and the relationship between PDYN, temperament and depression

Aim of the study is to compare prodynorphin (PDYN) rs1997794, rs1022563, rs6045819, rs2235749 polymorphisms in individuals with methamphetamine use disorder (MD) to that of healthy controls (HC), and to investigate the differences in serum PDYN levels in methamphetamine withdrawal. It is also aimed to explore the temperament characteristics and depression and their relationship with PDYN polymorphisms and PDYN serum levels in MD group. PDYN gene and serum levels were studied in 134 patients with MD and 97 HC. Patients with MD were administered Beck Depression Inventory (BDI) and Temperament Evaluation of Memphis, Pisa, Paris and San Diego Autoquestionnaire (TEMPS-A). For rs1022563 polymorphism, TT and CT genotype frequency and T allele frequency were significantly higher in the MD group than the frequencies in HC. It was found that rs2235749 polymorphism AA genotype was associated with increased risk of MD. PDYN rs1997794 CT genotypes had significantly higher scores of TEMPS-A irritable than CC genotypes and PDYN rs1022563 CC genotypes had significantly higher scores of TEMPS-A irritable than TT genotypes. PDYN levels among persons with MD were significantly higher than among the HC group when the withdrawal level increased and withdrawal symptoms improved. During the period in which the withdrawal level increased, there was a negative correlation between PDYN level and BDI and a positive relationship between PDYN level and TEMPS-A hyperthymic. It may be beneficial to screen temperament characteristics associated with increased risk of addiction in patients with MD and develop interventions based on temperament characteristics and the effects of PDYN.

Hypermethylation of the κ1 opioid receptor promoter in Chinese heroin and methamphetamine addicts

Heroin and methamphetamine (METH) addiction continues to be a major social, economic and therapeutic problem worldwide. The opioid pathway may mediate the effects of addictive drugs. However, the potential correlation between the κ1 opioid receptor (OPRK1) and drug addiction has not yet been characterized. The aim of the present study was to investigate the potential association between methylation of the OPRK1 promoter and substance abuse. Bisulfite pyrosequencing technology was used to determine the levels of OPRK1 promoter methylation in 60 drug abusers (30 heroin and 30 METH addicts) and 52 controls, observed to exhibit no significant differences in age or gender. The results indicated that levels of OPRK1 promoter methylation were significantly higher in drug addicts when compared with controls (P=2.43×10⁻⁴). Significant correlations between OPRK1 promoter methylation and the length and frequency of drug use were also observed in male heroin addicts (length: r=0.661, P=0.007; frequency: r=−0.684, P=0.005). In addition, a luciferase reporter gene assay indicated that the OPRK1 promoter fragment was able to regulate gene expression (fold change between two groups >32.12, P≤0.0001). In conclusion, results of the present study indicate that methylation of the OPRK1 promoter contributes to the pathophysiology of drug addiction.

Genetic studies of alcohol dependence in the context of the addiction cycle

Family, twin and adoption studies demonstrate clearly that alcohol dependence and alcohol use disorders are phenotypically complex and heritable. The heritability of alcohol use disorders is estimated at approximately 50-60% of the total phenotypic variability. Vulnerability to alcohol use disorders can be due to multiple genetic or environmental factors or their interaction which gives rise to extensive and daunting heterogeneity. This heterogeneity makes it a significant challenge in mapping and identifying the specific genes that influence alcohol use disorders. Genetic linkage and (candidate gene) association studies have been used now for decades to map and characterize genomic loci and genes that underlie the genetic vulnerability to alcohol use disorders. These approaches have been moderately successful in identifying several genes that contribute to the complexity of alcohol use disorders. Recently, genome-wide association studies have become one of the major tools for identifying genes for alcohol use disorders by examining correlations between millions of common single-nucleotide polymorphisms with diagnosis status. Genome-wide association studies are just beginning to uncover novel biology; however, the functional significance of results remains a matter of extensive debate and uncertainty. In this review, we present a select group of genome-wide association studies of alcohol dependence, as one example of a way to generate functional hypotheses, within the addiction cycle framework. This analysis may provide novel directions for validating the functional significance of alcohol dependence candidate genes. This article is part of the Special Issue entitled "Alcoholism".

Kappa opioid receptor signaling in the brain: Circuitry and implications for treatment

Kappa opioid receptors (KORs) in the central nervous system have been known to be important regulators of a variety of psychiatry illnesses, including anxiety and addiction, but their precise involvement in these disorders is complex and has yet to be fully elucidated. Here, we briefly review the pharmacology of KORs in the brain, including KOR's involvement in anxiety, depression, and drug addiction. We also review the known neuronal circuitry impacted by KOR signaling, and interactions with corticotrophin-releasing factor (CRF), another key peptide in anxiety-related illnesses, as well as the role of glucocorticoids. We suggest that KORs are a promising therapeutic target for a host of neuropsychiatric conditions.