α2A -Adrenergic receptor polymorphisms and mRNA expression levels are associated with delay discounting in cocaine users

Genotype-by-diagnosis interaction influences self-control in human cocaine addiction

Not everyone who uses drugs loses control over their intake, which is a hallmark of addiction. Although familial risk studies suggest significant addiction heritability, the genetic basis of vulnerability to drug addiction remains largely unknown. In the present study, we investigate the relationship between self-control, cocaine use, and the rs36024 single nucleotide polymorphism of the noradrenaline transporter gene (SLC6A2). We hypothesize that C-allele-carrying adults show impaired self-control, as measured by the stop-signal task and demonstrated previously in adolescents, and further exacerbated by chronic cocaine use. Patients with cocaine use disorder (CUD, n = 79) and healthy unrelated participants with no history of drug abuse (n = 54) completed the stop-signal task. All participants were genotyped for rs36024 allelic variants (CC/TT homozygotes, CT heterozygotes). We measured mean stop-signal reaction time, reflecting the ability to inhibit ongoing motor responses, reaction times to go stimuli, and the proportion of successful stops. CUD patients showed prolonged stop-signal reaction time, however, there was no main effect of rs36024 genotype. Importantly, there was a significant genotype-by-diagnosis interaction such that CUD patients with CC genotype had longer stop-signal reaction time and fewer successful stops compared with CC healthy controls and TT CUD patients. CT CUD patients showed an intermediate performance. Self-control deficits were associated with cocaine use disorder diagnosis, which interacts with the noradrenaline transporter rs36024 polymorphism. Our findings suggest that rs36024 may represent a potential genetic vulnerability marker, which facilitates the transition from first cocaine use to addiction by weakening the inhibitory control over behavior.

Influence of Receptor Polymorphisms on the Response to α-Adrenergic Receptor Blockers in Pheochromocytoma Patients

Background: Presurgical treatment with an α-adrenergic receptor blocker is recommended to antagonize the catecholamine-induced α-adrenergic receptor mediated vasoconstriction in patients with pheochromocytoma or sympathetic paraganglioma (PPGL). There is, however, a considerable interindividual variation in the dose-response relationship regarding the magnitude of blood pressure reduction or the occurrence of side effects. We hypothesized that genetically determined differences in α-adrenergic receptor activity contribute to this variability in dose-response relationship. Methods: Thirty-one single-nucleotide polymorphisms (SNPs) of the α1A, α1B, α1D adrenoreceptor (ADRA1A, ADRA1B, ADRA1D) and α2A, α2B adrenoreceptor (ADRA2A, ADRA2B) genes were genotyped in a group of 116 participants of the PRESCRIPT study. Haplotypes were constructed after determining linkage disequilibrium blocks. Results: The ADRA1B SNP rs10515807 and the ADRA2A SNPs rs553668/rs521674 were associated with higher dosages of α-adrenergic receptor blocker (p < 0.05) and with a higher occurrence of side effects (rs10515807) (p = 0.005). Similar associations were found for haplotype block 6, which is predominantly defined by rs10515807. Conclusions: This study suggests that genetic variability of α-adrenergic receptor genes might be associated with the clinically observed variation in beneficial and adverse therapeutic drug responses to α-adrenergic receptor blockers. Further studies in larger cohorts are needed to confirm our observations.

The Predictive Role of ADRA2A rs1800544 and HTR3B rs3758987 Polymorphisms in Motion Sickness Susceptibility

Motion sickness is a common central nervous system response, the primary sign of which is vomiting. Its susceptibility varies between individuals. To find predictive factors, we investigated the association of ADRA2A rs1800544 and HTR3B rs3758987 with motion sickness susceptibility and examined their mRNA changes during actual voyages. A total of 315 healthy college students were enrolled for SNP genotyping by the PCR-RFLP method. Blood samples were collected from another 42 subjects during two separate voyages to detect their mRNA expression changes at three time points. The frequency of the rs1800544 GG genotype in the susceptibility group was significantly higher (52.26%), and allele G increased the risk of motion sickness (OR = 1.585, 95% CI = 1.136-2.208). In the logistic regression model, the rs3758987 CC+TC genotype and rs1800544 GG genotype increased the risk of motion sickness-induced vomiting (OR = 2.105, 95% CI = 1.112-3.984; OR = 1.992, 95% CI = 1.114-3.571). The ADRA2A mRNA baseline was lower in the GG carriers and the HTR3B mRNA baseline was lower in the TC/CC carriers before sailing, then increased significantly within 24 h and then decreased after a long-term voyage. People carrying the rs1800544 GG genotype seem more susceptible to motion sickness. In combination with the incidence of vomiting during the actual-voyage experiments, our results indicate the involvement of rs1800544 and rs3758987 in motion sickness-induced vomiting.

Psychiatric symptoms and expression of glucocorticoid receptor gene in cocaine users: A longitudinal study

BACKGROUND

Chronic cocaine users (CU) display reduced peripheral expression of the glucocorticoid receptor gene (NR3C1), which is potentially involved in stress-related psychiatric symptoms frequently occurring in CU. However, it is unknown whether psychiatric symptoms and lower NR3C1 expression are related to each other and whether reduction of drug consumption reverse them.

METHOD

At baseline, NR3C1 mRNA expression was measured in 68 recreational CU, 30 dependent CU, and 68 stimulant-naïve controls. Additionally, the Revised Symptom Checklist (SCL-90R) and the Barratt Impulsiveness Scale (BIS) were assessed. At a one-year follow-up, the association between change in NR3C1 expression and psychiatric symptoms was examined in 48 stimulant-naïve controls, 19 CU who increased and 19 CU who decreased their consumption. At both test sessions, cocaine concentrations in hair samples were determined. Mixed-effects models were used to investigate how changes in drug use intensity affect severity of psychiatric symptoms and NR3C1 expression over time.

RESULTS

At baseline, recreational and dependent CU displayed elevated impulsivity and considerable symptom burden across most of the SCL-90R subscales. Time-group interaction effects were found for several impulsivity scores, SCL-90R Global Severity Index, Paranoid Thoughts, and Depression subscales as well as for NR3C1 expression. Pairwise comparisons showed that decreasing CU specifically improved in these SCL-90R subscales, while their NR3C1 expression was adapted. Finally, changes in NR3C1 expression were negatively correlated with changes in impulsivity but not SCL-90R scores.

CONCLUSION

Our findings suggest that NR3C1 expression changes and some psychiatric symptoms are reversible upon reduction of cocaine intake, thus favouring abstinence-oriented treatment approaches.

Doxazosin treatment in cocaine use disorder: pharmacogenetic response based on an alpha-1 adrenoreceptor subtype D genetic variant

Background: The α₁ antagonist doxazosin reduces cocaine use in individuals with cocaine use disorder (CUD) through a functional polymorphism of the α₁ adrenoreceptor. The regulatory role of the α₁ adrenoreceptor subtype D (ADRA1D) gene polymorphism in CUD is uncharacterized.Objectives: To study how the genetic variant of ADRA1D gene (T1848A, rs2236554) may affect the treatment efficacy of doxazosin in reducing cocaine use.Methods: This 12-week pilot trial included 76 participants with CUD with ADRA1D (T1848A, rs2236554) AA (N = 40) or AT/TT genotype (N = 36). Participants were randomized to doxazosin (8 mg/day, N = 47) or placebo (N = 29), and followed with thrice weekly urine toxicology and once weekly cognitive behavioral psychotherapy.Results: The AA and the AT/TT groups had comparable baseline rates of cocaine positive urines at weeks 1-2 (~ 76%). In the placebo group, an increase of cocaine positive urines in the AT/TT group was found as compared to the AA group (24% vs. 9%). In the doxazosin group, a greater decrease in cocaine positive urines was found in the AT/TT group relative to the AA group. The difference between the doxazosin and placebo groups in cocaine negative urines became evident at weeks 5-6 and peaked at weeks 9-10 (~35% difference). The AT/TT group demonstrated a significant medication and time by medication effect (p < .001), whereas the AA group did not.Conclusion: The T-allele carriers showed a greater reduction of cocaine use after treatment with doxazosin in participants with the ADRA1D gene polymorphism (T1848A), suggesting that this SNP may serve as a pharmacogenetic marker in pharmacotherapy of CUD.

Pharmacogenetics of Dopamine β-Hydroxylase in cocaine dependence therapy with doxazosin

The α₁ -adrenergic antagonist, doxazosin, has improved cocaine use disorder (CUD) presumably by blocking norepinephrine (NE) stimulation and reward from cocaine-induced NE increases. If the NE levels for release were lower, then doxazosin might more readily block this NE stimulation and be more effective. The NE available for release can be lower through a genetic polymorphism in dopamine β-hydroxylase (DBH) (C-1021T, rs1611115), which reduces DβH's conversion of dopamine to NE. We hypothesize that doxazosin would be more effective in CUD patients who have these genetically lower DβH levels. This 12-week, double-blind, randomized, placebo-controlled trial included 76 CUD patients: 49 with higher DβH levels from the DBH CC genotype and 27 with lower DβH levels from T-allele carriers (CT or TT). Patients were randomized to doxazosin (8 mg/day, N = 47) or placebo (N = 29) and followed with thrice weekly urine toxicology and once weekly cognitive behavioral psychotherapy. Cocaine use was reduced at a higher rate among patients in the doxazosin than in the placebo arm. We found significantly lower cocaine use rates among patients carrying the T-allele (CT/TT) than the CC genotype. The percentage of cocaine positive urines was reduced by 41 percent from baseline in the CT/TT group with low DβH and NE levels, as compared with no net reduction in the CC genotype group with normal DβH and NE levels. The DBH polymorphism appears play an important role in CUD patients' response to doxazosin treatment, supporting a pharmacogenetic association and potential application for personalized medicine.

Genetic influences on delayed reward discounting: A genome-wide prioritized subset approach

Delayed reward discounting (DRD) is a behavioral economic measure of impulsivity that has been consistently associated with addiction. It has also been identified as a promising addiction endophenotype, linking specific sources of genetic variation to individual risk. A challenge in the studies to date is that levels of DRD are often confounded with prior drug use, and previous studies have also had limited genomic scope. The current investigation sought to address these issues by studying DRD in healthy young adults with low levels of substance use (N = 986; 62% female, 100% European ancestry) and investigating genetic variation genome-wide. The genome-wide approach used a prioritized subset design, organizing the tests into theoretically and empirically informed categories and apportioning power accordingly. Three subsets were used: (a) a priori loci implicated by previous studies; (b) high-value addiction (HVA) markers from the recently developed SmokeScreen array; and (c) an atheoretical genome-wide scan. Among a priori loci, a nominally significant association was present between DRD and rs521674 in ADRA2A. No significant HVA loci were detected. One statistically significant genome-wide association was detected (rs13395777, p = 2.8 × 10-8), albeit in an intergenic region of unknown function. These findings are generally not supportive of the previous candidate gene studies and suggest that DRD has a complex genetic architecture that will require considerably larger samples to identify genetic associations more definitively. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Longitudinal changes in cocaine intake and cognition are linked to cortical thickness adaptations in cocaine users

BACKGROUND

Cocaine use has been consistently associated with decreased gray matter volumes in the prefrontal cortex. However, it is unclear if such neuroanatomical abnormalities depict either pre-existing vulnerability markers or drug-induced consequences. Thus, this longitudinal MRI study investigated neuroplasticity and cognitive changes in relation to altered cocaine intake.

METHODS

Surface-based morphometry, cocaine hair concentration, and cognitive performance were measured in 29 cocaine users (CU) and 38 matched controls at baseline and follow-up. Based on changes in hair cocaine concentration, CU were classified either as Decreasers (n = 15) or Sustained Users (n = 14). Surface-based morphometry measures did not include regional tissue volumes.

RESULTS

At baseline, CU displayed reduced cortical thickness (CT) in lateral frontal regions, and smaller cortical surface area (CSA) in the anterior cingulate cortex, compared to controls. In Decreasers, CT of the lateral frontal cortex increased whereas CT within the same regions tended to further decrease in Sustained Users. In contrast, no changes were found for CSA and subcortical structures. Changes in CT were linked to cognitive performance changes and amount of cocaine consumed over the study period.

CONCLUSIONS

These results suggest that frontal abnormalities in CU are partially drug-induced and can recover with decreased substance use. Moreover, recovery of frontal CT is accompanied by improved cognitive performance confirming that cognitive decline associated with cocaine use is potentially reversible.

Cognitive and neuroanatomical impairments associated with chronic exposure to levamisole-contaminated cocaine

Currently, levamisole is the most common cocaine adulterant worldwide and it is known to induce a variety of adverse side effects. Animal studies and human case reports suggest potential neurotoxicity of the compound but neither neuroanatomical nor cognitive effects of levamisole have been systematically investigated in cocaine users so far. We examined cognitive performance and cortical structural differences between chronic cocaine users with low and high recent exposure to levamisole objectively determined by quantitative toxicological hair analyses. In Study 1, we compared 26 chronic cocaine users with low levamisole exposure (lowLevCU), 49 matched cocaine users with high levamisole exposure (highLevCU), and 78 matched stimulant-naive controls regarding cognitive functioning employing a comprehensive neuropsychological test battery. In Study 2, we investigated cortical thickness by use of T1-weighted MRI in a subgroup of 12 lowLevCU, 17 highLevCU, and 38 stimulant-naive controls. In Study 1, both cocaine user groups showed significant impairments in the cognitive domains of attention and working memory as well as in the global cognitive index. However, highLevCU showed significantly worse executive functions compared to lowLevCU although both groups did not differ in severity of cocaine consumption and other clinical dimensions. Study 2 revealed that highLevCU, displayed reduced cortical thickness specifically in the middle frontal gyrus compared to both controls and lowLevCU. Our results suggest that levamisole exposure during the last months in cocaine users is associated with increased executive function impairments and pronounced thinning of the lateral prefrontal cortex. Consequently, prevention and drug policy-making should aim to reduce levamisole contamination of street cocaine.

Attention-Deficit/Hyperactivity Disorder and Monetary Delay Discounting: A Meta-Analysis of Case-Control Studies

BACKGROUND

A growing number of studies have investigated delay discounting, a behavioral economic index of impulsivity, and its relevance to attention deficit hyperactivity disorder (ADHD), but with mixed findings. The current meta-analysis synthesizes the literature on the relationship between monetary delay discounting and ADHD in studies using case-control designs. Specifically, the objectives were: 1) to characterize the aggregated differences in monetary delay discounting between individuals with ADHD (cases) and controls in studies using categorical case-control designs; 2) to examine potential differences based on sample age (<18 vs. >18), reward outcome (real vs. hypothetical), and prevalence of conduct disorder and oppositional defiant disorder in the sample; and 3) to evaluate potential small-study (publication) bias in the literature.

METHODS

From 567 candidate articles, 21 independent investigations yielded 25 case-control comparisons (total N=3,913). Random effects meta-analysis was conducted using Cohen's d as the common effect size. Publication bias was evaluated using fail-safe N, Begg-Mazumdar and Egger tests, and metaregression of publication year and effect size.

RESULTS

Across studies, a statistically significant difference of medium magnitude effect size was present for the case-control comparisons (d=0.43; p < 10-15). No significant differences based on sample age, reward outcome, or comorbid status was detected. Minimal heterogeneity and evidence of publication bias was present.

CONCLUSIONS

These findings provide robust evidence that delay discounting is significantly elevated among individuals with ADHD compared to controls. Gaps in the literature and the importance of characterizing the neural and genetic bases of this relationship are discussed.