Alteration of dopamine receptors subtypes in the brain of opioid abusers: A postmortem study in Iran

Parental Exposure to Morphine Before Conception Decreases Morphine and Cocaine-Induced Locomotor Sensitization in Male Offspring

Repeated exposure to abused drugs leads to reorganizing synaptic connections in the brain, playing a pivotal role in the relapse process. Additionally, recent research has highlighted the impact of parental drug exposure before gestation on subsequent generations. This study aimed to explore the influence of parental morphine exposure 10 days prior to pregnancy on drug-induced locomotor sensitization. Adult male and female Wistar rats were categorized into morphine-exposed and control groups. Ten days after their last treatment, they were mated, and their male offspring underwent morphine, methamphetamine, cocaine, and nicotine-induced locomotor sensitization tests. The results indicated increased locomotor activity in both groups after drug exposure, although the changes were attenuated in morphine and cocaine sensitization among the offspring of morphine-exposed parents (MEPs). Western blotting analysis revealed altered levels of D2 dopamine receptors (D2DRs) in the prefrontal cortex and nucleus accumbens of the offspring from MEPs. Remarkably, despite not having direct in utero drug exposure, these offspring exhibited molecular alterations affecting morphine and cocaine-induced sensitization. The diminished sensitization to morphine and cocaine suggested the development of a tolerance phenotype in these offspring. The changes in D2DR levels in the brain might play a role in these adaptations.

End-to-end sequence-structure-function meta-learning predicts genome-wide chemical-protein interactions for dark proteins

Systematically discovering protein-ligand interactions across the entire human and pathogen genomes is critical in chemical genomics, protein function prediction, drug discovery, and many other areas. However, more than 90% of gene families remain "dark"-i.e., their small-molecule ligands are undiscovered due to experimental limitations or human/historical biases. Existing computational approaches typically fail when the dark protein differs from those with known ligands. To address this challenge, we have developed a deep learning framework, called PortalCG, which consists of four novel components: (i) a 3-dimensional ligand binding site enhanced sequence pre-training strategy to encode the evolutionary links between ligand-binding sites across gene families; (ii) an end-to-end pretraining-fine-tuning strategy to reduce the impact of inaccuracy of predicted structures on function predictions by recognizing the sequence-structure-function paradigm; (iii) a new out-of-cluster meta-learning algorithm that extracts and accumulates information learned from predicting ligands of distinct gene families (meta-data) and applies the meta-data to a dark gene family; and (iv) a stress model selection step, using different gene families in the test data from those in the training and development data sets to facilitate model deployment in a real-world scenario. In extensive and rigorous benchmark experiments, PortalCG considerably outperformed state-of-the-art techniques of machine learning and protein-ligand docking when applied to dark gene families, and demonstrated its generalization power for target identifications and compound screenings under out-of-distribution (OOD) scenarios. Furthermore, in an external validation for the multi-target compound screening, the performance of PortalCG surpassed the rational design from medicinal chemists. Our results also suggest that a differentiable sequence-structure-function deep learning framework, where protein structural information serves as an intermediate layer, could be superior to conventional methodology where predicted protein structures were used for the compound screening. We applied PortalCG to two case studies to exemplify its potential in drug discovery: designing selective dual-antagonists of dopamine receptors for the treatment of opioid use disorder (OUD), and illuminating the understudied human genome for target diseases that do not yet have effective and safe therapeutics. Our results suggested that PortalCG is a viable solution to the OOD problem in exploring understudied regions of protein functional space.

Impact of high-access exercise prior to and during early adolescence on later vulnerability to opioid use and relapse in male rats

Middle- and high-school athletes participating in certain team sports are at greater risk of opioid misuse and addiction than those who do not. While this risk is thought to be due to increased access to opioids, in this study we explored the possibility that the sensitizing effects of discontinued high-intensity exercise may also contribute. Specifically, using male rat models with fentanyl, we tested the hypothesis that high-access exercise (24 h/day access to a running wheel) during pre/early adolescence (two weeks, postnatal-day 24-37) would enhance vulnerability to opioid use and relapse during late adolescence/adulthood. Rats with a history of high-access exercise showed stronger fentanyl-associated lever discrimination during acquisition, greater motivation to obtain infusions of fentanyl following acquisition, and had an enhanced sensitivity to the reinstating effects of fentanyl-associated cues following extended (24 h/day), intermittent-access self-administration and protracted abstinence (14 days) compared to sedentary controls. In contrast, sedentary rats had greater overall responding (active- and inactive-lever) during acquisition and greater non-specific (inactive-lever) responding during extended-access self-administration. Molecular markers associated with opioid seeking/relapse were also differentially expressed in the nucleus accumbens core of rats with versus without a history of high-access exercise following relapse testing (e.g., Bdnf-IV and Drd2 expression). Together, these findings demonstrate that high-access exercise prior to and throughout early-adolescence enhances vulnerability to the reinforcing and cue-induced reinstating effects of opioids during later adolescence/adulthood. Thus, it is possible that the discontinuation of high intensity exercise contributes to the enhanced vulnerability observed in middle- and high-school athletes.

Frequency of the Dopamine Receptor D3 (rs6280) vs. Opioid Receptor µ1 (rs1799971) Polymorphic Risk Alleles in Patients with Opioid Use Disorder: A Preponderance of Dopaminergic Mechanisms?

While opioids are a powerful class of drugs that inhibit transmission of pain signals, their use is tarnished by the current epidemic of opioid use disorder (OUD) and overdose deaths. Notwithstanding published reports, there remain gaps in our knowledge of opioid receptor mechanisms and their role in opioid seeking behavior. Thus, novel insights into molecular, neurogenetic and neuropharmacological bases of OUD are needed. We propose that an addictive endophenotype may not be entirely specific to the drug of choice but rather may be generalizable to altered brain reward circuits impacting net mesocorticolimbic dopamine release. We suggest that genetic or epigenetic alterations across dopaminergic reward systems lead to uncontrollable self-administration of opioids and other drugs. For instance, diminished availability via knockout of dopamine D3 receptor (DRD3) increases vulnerability to opioids. Building upon this concept via the use of a sophisticated polymorphic risk analysis in a human cohort of chronic opioid users, we found evidence for a higher frequency of polymorphic DRD3 risk allele (rs6280) than opioid receptor µ1 (rs1799971). In conclusion, while opioidergic mechanisms are involved in OUD, dopamine-related receptors may have primary influence on opioid-seeking behavior in African Americans. These findings suggest OUD-targeted novel and improved neuropharmacological therapies may require focus on DRD3-mediated regulation of dopaminergic homeostasis.

Goofballing of Opioid and Methamphetamine: The Science Behind the Deadly Cocktail

Globally, millions of people suffer from various substance use disorders (SUD), including mono-and polydrug use of opioids and methamphetamine. Brain regions such as the cingulate cortex, infralimbic cortex, dorsal striatum, nucleus accumbens, basolateral and central amygdala have been shown to play important roles in addiction-related behavioral changes. Clinical and pre-clinical studies have characterized these brain regions and their corresponding neurochemical changes in numerous phases of drug dependence such as acute drug use, intoxication, craving, withdrawal, and relapse. At present, many studies have reported the individual effects of opioids and methamphetamine. However, little is known about their combined effects. Co-use of these drugs produces effects greater than either drug alone, where one decreases the side effects of the other, and the combination produces a prolonged intoxication period or a more desirable intoxication effect. An increasing number of studies have associated polydrug abuse with poorer treatment outcomes, drug-related deaths, and more severe psychopathologies. To date, the pharmacological treatment efficacy for polydrug abuse is vague, and still at the experimental stage. This present review discusses the human and animal behavioral, neuroanatomical, and neurochemical changes underlying both morphine and methamphetamine dependence separately, as well as its combination. This narrative review also delineates the recent advances in the pharmacotherapy of mono- and poly drug-use of opioids and methamphetamine at clinical and preclinical stages.

Alteration of orexin-A and PKCα in the postmortem brain of pure-opioid and multi-drug abusers

Finding changes induced by the drug of abuse is one of the most important approaches to design new drugs for the treatment of substance use disorders (SUD). Postmortem study is the most reliable method for detecting alteration in the brain of SUD patients. Recently, the role of orexinergic system in SUD is in consideration. In the current study, we evaluated the level of orexin-A in the CSF and protein kinase Cα (PKCα) in the brain of pure-opioid (POA) and multi-drug abusers (MDA). A total of 56 POA, 45 MDA, and 13 matched control brains were collected from the legal medicine center, Tehran, Iran. The CSF was gathered from the third ventricle immediately after opening the skull and kept at -80 °C. The medial prefrontal cortex (mPFC), lateral prefrontal cortex (lPFC), orbitofrontal cortex (OFC), nucleus accumbens (NAc), and amygdala were dissected from fresh brain, frozen with liquid nitrogen and kept at -80 °C. The level of orexin-A evaluated in the CSF. Using western blotting, the level of PKCα assessed in the brain. Obtained data revealed that the level of orexin-A increased in POA and MDA compared with the control group (p < 0.05). In addition, the level of PKCα increased in the prefrontal cortex and amygdala of the abusers compared with the control group, although we did not detect changes in the level of PKCα in the NAc. Along with animal studies, the current results showed that the level of orexin increased in the CSF of drug abusers, which might be related to increases in the activation of lateral hypothalamic orexinergic neurons faced with the drug of abuse. Enhancement in the level of PKCα in the drug reward circuits might be adaptational changes induced by orexin and drugs of abuse.

Endogenous Opiates and Behavior: 2018

This paper is the forty-first consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2018 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (2), the roles of these opioid peptides and receptors in pain and analgesia in animals (3) and humans (4), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (5), opioid peptide and receptor involvement in tolerance and dependence (6), stress and social status (7), learning and memory (8), eating and drinking (9), drug abuse and alcohol (10), sexual activity and hormones, pregnancy, development and endocrinology (11), mental illness and mood (12), seizures and neurologic disorders (13), electrical-related activity and neurophysiology (14), general activity and locomotion (15), gastrointestinal, renal and hepatic functions (16), cardiovascular responses (17), respiration and thermoregulation (18), and immunological responses (19).

Evaluation of dynorphin and kappa-opioid receptor level in the human blood lymphocytes and plasma: Possible role as a biomarker in severe opioid use disorder

BACKGROUND

The dynorphin (DYN)/kappa opioid receptor (KOR) system plays an important role in the development of addiction, and dysregulation of this system could lead to abnormal activity in the reward pathway. It has been reported that the expression state of the neurotransmitters and their receptors in the brain is reflected in peripheral blood lymphocytes (PBLs).

METHODS

We have evaluated the PBLs and plasma samples of four groups: 1) subjects with severe opioid use disorder (SOD), 2) methadone-maintenance treated (MMT) individuals, 3) long-term abstinent subjects having former SOD, and 4) healthy control subjects (n = 20 in each group). The mRNA expression level of preprodynorphin (pPDYN) and KOR in PBLs has been evaluated by real-time PCR. Peptide expression of PDYN in PBLs has been studied by western blot, and DYN concentration in plasma has been measured by ELISA.

RESULTS

The relative expression level of the pPDYN mRNA and PDYN peptide in PBLs were significantly up-regulated in SOD, MMT, and abstinent groups compared to control subjects. No significant difference was found in the plasma DYN concentration between study groups. The expression level of the KOR mRNA in PBLs was significantly decreased in all three study groups compared to the control subjects.

CONCLUSION

the expression changes in the DYN/KOR system after chronic exposure to opioids, including methadone, seems to be stable and does not return to normal levels even after 12 months abstinence. These long-time and permanent changes in PBLs may serve as a biomarker and footprint of SOD development in the periphery.

Parental morphine exposure affects repetitive grooming actions and marble burying behavior in the offspring: Potential relevance for obsessive-compulsive like behavior

Family, adoption and twin studies have highlighted the significant role of heritable influences on individual differences in opioid addiction. Meanwhile, obsessive-compulsive disorder (OCD) is a disorder wherein the individual experiences recurring thoughts that cause irrational fears and anxiety. In the present study, adult male and female rats received morphine solution for 21 days and were drug-free for 10 days. Offspring were used in 4 distinct groups; (1) paternal morphine-exposed, (2) maternal morphine-exposed, (3) maternal and paternal morphine-exposed, and (4) drug-naïve subjects. We assessed the grooming behavior and marble burying test as an indicator of obsessive-compulsive behavior. To clarify the mechanisms underlying these changes, the mRNA level of BDNF, the phosphorylation level of CREB and the protein level of D2 dopamine receptor (DR) were evaluated in the nucleus accumbens (NAc). The grooming behavior in male offspring with one or two morphine-abstinent parent(s) increased compared with the offspring of drug naïve rats. In addition, the offspring of morphine-exposed parents buried more marbles when compared with the offspring of drug-naïve parents. Also, the BDNF mRNA was down-regulated in the NAC. However, the levels of phospho-CREB and D2 DR were elevated. Previous studies indicated that exposure to morphine in adulthood enhances the risk of psychiatric disorders in offspring. OCD is one the comorbid disorders with addiction and increases the risk of substance abuse disorder in patients. In this survey, we found that morphine exposure in parents before gestation can encourage obsessive-compulsive behavior in offspring.

Molecular Imaging of Opioid and Dopamine Systems: Insights Into the Pharmacogenetics of Opioid Use Disorders

Opioid use in the United States has steadily risen since the 1990s, along with staggering increases in addiction and overdose fatalities. With this surge in prescription and illicit opioid abuse, it is paramount to understand the genetic risk factors and neuropsychological effects of opioid use disorder (OUD). Polymorphisms disrupting the opioid and dopamine systems have been associated with increased risk for developing substance use disorders. Molecular imaging studies have revealed how these polymorphisms impact the brain and contribute to cognitive and behavioral differences across individuals. Here, we review the current molecular imaging literature to assess how genetic variations in the opioid and dopamine systems affect function in the brain's reward, cognition, and stress pathways, potentially resulting in vulnerabilities to OUD. Continued research of the functional consequences of genetic variants and corresponding alterations in neural mechanisms will inform prevention and treatment of OUD.