preproenkephalin and Heroin-Dependence

The dynorphin/kappa opioid receptor (Dyn/KOR) system is involved in reward processing and dysphoria/anhedonia. Exposure to mu-opioid receptor agonists such as heroin increases expression of the prodynorphin gene (PDYN) in the brain. In this study in a Caucasian cohort, we examined the association of the functional PDYN 68-bp repeat polymorphism with opioid use disorders. In this case-control study, 554 subjects with Caucasian ancestry (142 healthy controls, 153 opioid-exposed, but never opioid dependent, NOD, and 259 with an opioid dependence diagnosis, OD) were examined for association of the PDYN 68-bp repeats with the diagnosis of opioid dependence (DSM-IV criteria), with a dimensional measure of heroin exposure (KMSK scale), and age trajectory parameters of heroin use (age of heroin first use, and age of onset of heaviest use). The PDYN 68-bp repeat genotype (classified as: "short-short" [SS], "long-long" [LL], and "short-long" [SL], based on the number of repeats) was not associated with categorical opioid dependence diagnoses. However, the LL genotype was associated with later age of first heroin use than the SS + SL genotype (19 versus 18 years; p < 0.01). This was also confirmed by a significant positive correlation between the number of repeats and the age of first use of heroin, in volunteers with OD (Spearman r = 0.16; p = 0.01). This suggests that the functional PDYN 68-bp repeat genotype is associated with the age of first use of heroin in Caucasians diagnosed with opioid dependence.

Topics: Adult; Case-Control Studies; Enkephalins; Female; Genetic Association Studies; Genotype; Heroin Dependence; Humans; Male; Middle Aged; Opioid-Related Disorders; Polymorphism, Genetic; Promoter Regions, Genetic; Protein Precursors; White People

Within the core promoter region of prodynorphin (PDYN), a 68-bp sequence was found to occur as a polymorphism element, either singular or as tandemly repeated two, three or four times. We report the sequence of a novel allele (5-repeats). Our study revealed the existence of an ancestral nucleotide (A) at 29th position of the VNTR in human. In total, 442 heroin addicts and 799 controls were included in this study. The present findings revealed a male-limited association between VNTR polymorphism and heroin dependence risk.

Topics: Alleles; Case-Control Studies; Enkephalin, Leucine; Enkephalins; Genetic Predisposition to Disease; Genotype; Heroin Dependence; Humans; Male; Minisatellite Repeats; Polymorphism, Genetic; Promoter Regions, Genetic; Protein Precursors

Negative affect is critical for conferring vulnerability to opiate addiction as reflected by the high comorbidity of opiate abuse with major depressive disorder (MDD). Rodent models implicate amygdala prodynorphin (Pdyn) as a mediator of negative affect; however, evidence of PDYN involvement in human negative affect is limited. Here, we found reduced PDYN mRNA expression in the postmortem human amygdala nucleus of the periamygdaloid cortex (PAC) in both heroin abusers and MDD subjects. Similar to humans, rats that chronically self-administered heroin had reduced Pdyn mRNA expression in the PAC at a time point associated with a negative affective state. Using the in vivo functional imaging technology DREAMM (DREADD-assisted metabolic mapping, where DREADD indicates designer receptors exclusively activated by designer drugs), we found that selective inhibition of Pdyn-expressing neurons in the rat PAC increased metabolic activity in the extended amygdala, which is a key substrate of the extrahypothalamic brain stress system. In parallel, PAC-specific Pdyn inhibition provoked negative affect-related physiological and behavioral changes. Altogether, our translational study supports a functional role for impaired Pdyn in the PAC in opiate abuse through activation of the stress and negative affect neurocircuitry implicated in addiction vulnerability.

Topics: Adult; Amygdala; Animals; Clozapine; Corticosterone; Depressive Disorder, Major; Designer Drugs; Enkephalins; Female; Fluorine Radioisotopes; Fluorodeoxyglucose F18; GTP-Binding Protein alpha Subunits, Gi-Go; Heroin Dependence; Humans; Hungary; Limbic System; Male; Middle Aged; Neuroimaging; Neurons; Positron-Emission Tomography; Protein Precursors; Radiopharmaceuticals; Rats; Rats, Long-Evans; Recombinant Fusion Proteins; RNA, Messenger; United States

The abuse of opioid drugs, both illicit and prescription, is a persistent problem in the United States, accounting for >1.2 million users who require treatment each year. Current treatments rely on suppressing immediate withdrawal symptoms and replacing illicit drug use with long-acting opiate drugs. However, the mechanisms that lead to preventing opiate dependence are still poorly understood. We hypothesized that κ opioid receptor (KOR) activation during chronic opioid intake contributes to negative affective states associated with withdrawal and the motivation to take increasing amounts of heroin. Using a 12 h long-access model of heroin self-administration, rats showed escalation of heroin intake over several weeks. This was prevented by a single high dose (30 mg/kg) of the long-acting KOR antagonist norbinaltorphimine (nor-BNI), paralleled by reduced motivation to respond for heroin on a progressive-ratio schedule of reinforcement, a measure of compulsive-like responding. Systemic nor-BNI also significantly decreased heroin withdrawal-associated anxiety-like behavior. Immunohistochemical analysis showed prodynorphin content increased in the nucleus accumbens core in all heroin-exposed rats, but selectively increased in the nucleus accumbens shell in long-access rats. Local infusion of nor-BNI (4 μg/side) into accumbens core altered the initial intake of heroin but not the rate of escalation, while local injection into accumbens shell selectively suppressed increases in heroin intake over time without altering initial intake. These data suggest that dynorphin activity in the nucleus accumbens mediates the increasing motivation for heroin taking and compulsive-like responding for heroin, suggesting that KOR antagonists may be promising targets for the treatment of opioid addiction.

Topics: Animals; Anxiety; Catheterization; Conditioning, Operant; Enkephalins; Heroin Dependence; Immunohistochemistry; Male; Motivation; Naltrexone; Narcotic Antagonists; Nucleus Accumbens; Protein Precursors; Rats; Rats, Wistar; Receptors, Opioid, kappa; Reinforcement Schedule; Self Administration; Substance Withdrawal Syndrome

Genetic factors are believed to account for 30-50% of the risk for cocaine and heroin addiction. Dynorphin peptides, derived from the prodynorphin (PDYN) precursor, bind to opioid receptors, preferentially the kappa-opioid receptor, and may mediate the aversive effects of drugs of abuse. Dynorphin peptides produce place aversion in animals and produce dysphoria in humans. Cocaine and heroin have both been shown to increase expression of PDYN in brain regions relevant for drug reward and use. Polymorphisms in PDYN are therefore hypothesized to increase risk for addiction to drugs of abuse. In this study, 3 polymorphisms in PDYN (rs1022563, rs910080 and rs1997794) were genotyped in opioid-addicted [248 African Americans (AAs) and 1040 European Americans (EAs)], cocaine-addicted (1248 AAs and 336 EAs) and control individuals (674 AAs and 656 EAs). Sex-specific analyses were also performed as a previous study identified PDYN polymorphisms to be more significantly associated with female opioid addicts. We found rs1022563 to be significantly associated with opioid addiction in EAs [P = 0.03, odds ratio (OR) = 1.31; false discovery rate (FDR) corrected q-value]; however, when we performed female-specific association analyses, the OR increased from 1.31 to 1.51. Increased ORs were observed for rs910080 and rs199774 in female opioid addicts also in EAs. No statistically significant associations were observed with cocaine or opioid addiction in AAs. These data show that polymorphisms in PDYN are associated with opioid addiction in EAs and provide further evidence that these risk variants may be more relevant in females.

Topics: Adolescent; Adult; Alleles; Behavior, Addictive; Black or African American; Cocaine-Related Disorders; Enkephalins; Female; Gene Frequency; Genetic Association Studies; Genetic Predisposition to Disease; Genotype; Heroin Dependence; Humans; Linkage Disequilibrium; Male; Middle Aged; Polymorphism, Single Nucleotide; Protein Precursors; Sex Factors; White People

Dynorphin peptides and k-opioid receptor are important in the rewarding effects of drugs of abuse such as heroin. This study examined potential association between heroin dependence and four single nucleotide polymorphisms (SNPs) of prodynorphin (PDYN) gene (rs35286281 in promoter region and rs1022563, rs2235749, rs910080 in 3'UTR). Participants included 304 heroin-dependent subjects and 300 healthy controls. Genotype, allele frequencies and difference between groups were analyzed by HaploView 4.0 and SPSS 11.5 software. The analysis indicated a significant higher frequency of the PDYN 68bp VNTR (rs35286281) H allele in heroin-dependent subjects than in controls (p=0.002 after Bonferroni correction). Strong linkage disequilibrium was observed between rs1022563, rs2235749 and rs910080 polymorphism (D'>0.9). Significantly more TCT haplotypes were found in heroin-dependent patients than in the controls (p=0.006 after Bonferroni correction). We found significant pointwise correlation of these three variants (rs1022563, rs2235749 and rs910080) with heroin dependence. These findings support the important role of PDYN polymorphism in heroin dependence, and may guide future studies to identify genetic risk factors for heroin dependence.

Topics: Adult; Chi-Square Distribution; Enkephalins; Female; Genetic Predisposition to Disease; Genotype; Heroin Dependence; Humans; Male; Minisatellite Repeats; Polymorphism, Single Nucleotide; Protein Precursors

Prodynorphin (PDYN) binds to kappa-opioid receptors and is known to regulate dopaminergic tone, making this system important for the reinforcing and rewarding properties of drugs of abuse such as opioids. The binding of dynorphins to kappa-opioid receptors also produces aversive states that may affect the development of opioid dependence. Recent animal results have shown that PDYNknockout mice show decreased ethanol consumption; however, this finding was restricted to female mice. We were interested to analyse a possible gender specificity of dynorphin effects in humans and to this end three single-nucleotide polymorphisms (SNPs) in PDYN were genotyped in a Chinese population of 484 opioid dependents and 374 controls. An interaction between sex and genotype was found in female opioid dependents. Chi-squared tests for association revealed that the genotype distributions of SNPs rs1997794 (P = 0.019) and rs1022563 (P = 0.006) in the promoter and 3' region of PDYN, respectively, were found to be associated with opioid dependence. Therefore, SNPs in PDYN are significantly associated with the risk of developing opioid dependence; however, this effect may only be seen in females. These data suggest that PDYN polymorphisms should be studied in additional female opioid-dependent populations with an emphasis on the promoter and 3' regions of the gene.

Topics: 3' Untranslated Regions; Adult; Alleles; China; Enkephalins; Female; Gene Frequency; Genotype; Haplotypes; Heroin Dependence; Humans; Linkage Disequilibrium; Male; Polymorphism, Single Nucleotide; Promoter Regions, Genetic; Protein Precursors; RNA, Messenger; Sex Factors

Prodynorphin, the precursor of the dynorphin opioid peptides, has been shown to play an important role in several aspects of human diseases and complex traits, e.g., drug abuse, epilepsy, and mood disorders. The objective of this study was to identify polymorphisms in the 5' control region of the human prodynorphin gene and to relate these polymorphisms to prodynorphin gene expression. Within the core promoter region, a 68-bp sequence was found to occur as a polymorphic element, either singular or as tandemly repeated element two, three, or four times. This 68-bp repeat element contains an AP-1 transcription factor binding site as demonstrated by electrophoretic mobility shift assay. Reporter gene assays were performed and provided evidence for allele dependent different promoter activity. Dynorphin was found to be involved in many pathophysiological processes so that the described prodynorphin alleles may correlate with the occurrence of several diseases, for example, drug addiction. However, prodynorphin allelic distributions were not significantly different in heroin addicts and control subjects.

Topics: Alleles; Base Sequence; Binding Sites; Cell Line; Chloramphenicol O-Acetyltransferase; DNA; Enkephalins; Gene Expression; Gene Frequency; Genetic Variation; Heroin Dependence; Humans; Polymerase Chain Reaction; Promoter Regions, Genetic; Protein Precursors; Reference Values; Tandem Repeat Sequences; Tetradecanoylphorbol Acetate; Transcription Factor AP-1; Transfection