Effects of crack cocaine addiction and stress-related genes on peripheral BDNF levels

Exploring peripheral biomarkers in psychostimulant use: A systematic review on neurotrophins, stress-related hormones, oxidative stress molecules and genetic factors

BACKGROUND

This systematic review aims to comprehensively explore the impact of psychostimulant substances on neurotrophic and inflammatory pathways, including brain-derived neurotrophic factor (BDNF), pro-BDNF, cortisol, dehydroepiandrosterone sulfate (DHEAS), thiobarbituric acid reactive substances (TBARS), interleukins, and the role of genetic factors. The study seeks to address existing gaps in the literature by providing a thorough evaluation of neurotrophic and inflammatory system alterations associated with different stages of psychostimulant dependence for a more nuanced understanding of substance use disorder (SUD) neurobiology.

METHODS

A systematic review was conducted in PubMed, Scopus, and Web of Science databases following the PRISMA guidelines. The research encompasses 50 studies with a participant pool totaling 6792 individuals using psychostimulant substances.

RESULTS

Key findings include diverse impacts of cocaine on BDNF levels, mainly consisting of their significant increase during withdrawal. In contrast, NGF showed an opposite behavior, reducing during withdrawal. Cortisol and DHEAS levels exhibited relevant increases after psychostimulant use, while TBARS showed conflicting results. Genetic investigations predominantly focused on the Val66Met polymorphism of the BDNF gene, revealing associations with susceptibility to stimulant addiction.

CONCLUSIONS

Neurotrophins and inflammatory molecules play a significant role in the pathophysiological mechanisms following psychostimulant use. A better understanding of their complex interplay could aid clinicians in identifying biomarkers of different disease stages. Moreover, clinical interventions designed to interfere with neurotrophic and inflammatory pathways could possibly lead to craving-modulatory strategies and reduce pathological neuronal and systemic consequences of psychostimulant use.

The mediation effect of glucocorticoid receptor gene (NR3C1) methylation between childhood maltreatment and depressive symptoms in Chinese adolescents: A 2-year longitudinal study

This three-wave longitudinal study examined whether methylation alterations in promoter exon 1F of a stress-related gene-NR3C1 (NR3C1-1F)-explained the longitudinal associations between childhood maltreatment and adolescent depressive symptoms. A total of 370 Han Chinese adolescents (Mage  = 16.31 ± 1.28 years; 51.4% girls) recruited from Shandong, China were tracked from 2018 to 2020. The results showed that the severity of childhood maltreatment, especially that of emotional abuse and physical neglect, conferred risk for adolescent depressive symptoms via reducing NR3C1-1F methylation levels. These mediation effects of NR3C1-1F methylation did not vary between adolescent sex or NR3C1 BclI and Tth111I polymorphisms. The findings highlight how childhood maltreatment contributes to psychopathology development at a biological level.

Critical appraisal and systematic review of genes linked with cocaine addiction, depression and anxiety

Recent lifestyle changes have resulted in tremendous peer pressure and mental stress, and increased the incidences of chronic psychological disorders; like addiction, depression and anxiety (ADA). In this context, the stress-tolerance levels vary amongst individuals and genetic factors play prominent roles. Vulnerable individuals may often be drawn towards drug-addiction to combat stress. This systematic review critically appraises the relationship of various genetic factors linked with the incidences of ADA development. For coherence, we focused solely on cocaine as a substance of abuse in this study. Online scholarly databases were used to screen pertinent literature using apt keywords; and the final retrieval included 42 primary-research articles. The major conclusion drawn from this systematic analysis states that there are 51 genes linked with the development of ADA; and 3 (BDNF, PERIOD2 and SLC6A4) of them are common to all the three aspects of ADA. Further, inter-connectivity analyses of the 51 genes further endorsed the central presence of BDNF and SLC6A4 genes in the development of ADA disorders. The conclusions derived from this systematic study pave the way for future studies for the identification of diagnostic biomarkers and drug targets; and for the development of novel and effective therapeutic regimens against ADA.

A three-compartment apparatus alters the brain concentration of cytokines and neurotrophic factors in cocaine-induced CPP in mice

Cocaine-induced neuroinflammation plays an important role in the pathophysiology of drug addiction. Evidence suggests that the immune response contributes for memory consolidation related to place preference behavior underlying cocaine administration in mice. Conditioned place preference (CPP) is a protocol extensively used to study the rewarding and/or aversive motivational effects of drug abuse in rodents, reproducing cocaine-seeking behavior in humans. Besides the variety of apparatus used in the CPP protocol, whether different types of apparatus are able to induce the same conditioned behavior response and neurobiological changes remains to be fully explored. We hypothesize that the immune response is involved in the cocaine-induced CPP and that the type of apparatus might influence this response. Herein, two- and three-compartment apparatuses were tested using the behavioral model of CPP. Cocaine-induced CPP was demonstrated in both apparatuses. However, mice injected with cocaine had decreased levels of IL-1β, IL-6, IL-10, and GDNF in the pre-frontal cortex, and decreased CX3CL1 in the striatum, in the CPP protocol using three compartments compared to controls. While similar levels were seen in the CPP protocol using two compartments. In conclusion, the current study demonstrated that the type of apparatus might influence the investigation of neurobiological mechanisms associated with cocaine-induced CPP. Our data also suggest that the three compartment-apparatus seems to be a more appropriate model to investigate the neuroinflammatory response related to cocaine addiction.

The relationship between occupational stress and job burnout in coal miners: Interactions between GCCR and SLC6A4 gene polymorphisms and the environment

OBJECTIVE

To understand the current situation of job burnout among coal miners in Xinjian. The effects of occupational stress, GCCR and SLC6A4 gene polymorphisms, and gene-environment interactions on job burnout in coal miners were analyzed. This study provides a scientific basis for formulating health strategies to combat job burnout in the future.

METHODS

The job burnout scale and job content questionnaire (JCQ) were used to investigate the general situation of job burnout among coal miners and its influencing factors. The imLDR^TM multiple SNP typing kit was used to type 300 samples (150 samples from the burnout case group and 150 from the control group). The relationship between the occurrence of job burnout, and the GCCR and SLC6A4 genes was analyzed.

RESULTS

There were significant differences in the rate of burnout among miners of different sexes, ages, working years, shifts, working types, and marital status (P < 0.05). The difference in occupational stress between the different job burnout groups was statistically significant (P < 0.05). The GG genotype at rs41423247 increased the risk of burnout (OR=3.224, 95% CI:1.425-7.294). Similarly, compared to the TT genotype at rs11080122, the CC genotype increased the susceptibility of job burnout (OR =2.614, 95% CI:1.047-6.527). The results of gene-environment interaction regression analyses showed that the interaction between rs41423247, rs17209237, and occupational stress increased the risk of job burnout (OR = 5.049, 95% CI = 2.371-10.750).

CONCLUSION

In addition to demographic characteristics, occupational stress was also a risk factor for job burnout. The interaction between rs41423247 and rs17209237 of the GCCR gene and occupational stress increased the risk of job burnout.

The role of glucocorticoid receptor gene in the association between attention deficit-hyperactivity disorder and smaller brain structures

ADHD is associated with smaller subcortical brain volumes and cortical surface area, with greater effects observed in children than adults. It is also associated with dysregulation of the HPA axis. Considering the effects of the glucocorticoid receptor (NR3C1) in neurophysiology, we hypothesize that the blurred relationships between brain structures and ADHD in adults could be partly explained by NR3C1 gene variation. Structural T1-weighted images were acquired on a 3 T scanner (N = 166). Large-scale genotyping was performed, and it was followed by quality control and pruning procedures, which resulted in 48 independent NR3C1 gene variants analyzed. After a stringent Bonferroni correction, two SNPs (rs2398631 and rs72801070) moderated the association between ADHD and accumbens and amygdala volumes in adults. The significant SNPs that interacted with ADHD appear to have a role in gene expression regulation, and they are in linkage disequilibrium with NR3C1 variants that present well-characterized physiological functions. The literature-reported associations of ADHD with accumbens and amygdala were only observed for specific NR3C1 genotypes. Our findings reinforce the influence of the NR3C1 gene on subcortical volumes and ADHD. They suggest a genetic modulation of the effects of a pivotal HPA axis component in the neuroanatomical features of ADHD.

Clustering suicidal phenotypes and genetic associations with brain-derived neurotrophic factor in patients with substance use disorders

Suicide attempts (SA), especially recurrent SA or serious SA, are common in substance use disorders (SUD). However, the genetic component of SA in SUD samples remains unclear. Brain-derived neurotrophic factor (BDNF) alleles and levels have been repeatedly involved in stress-related psychopathology. This investigation uses a within-cases study of BDNF and associated factors in three suicidal phenotypes ('any', 'recurrent', and 'serious') of outpatients seeking treatment for opiate and/or cocaine use disorder. Phenotypic characterization was ascertained using a semi-structured interview. After thorough quality control, 98 SNPs of BDNF and associated factors (the BDNF pathway) were extracted from whole-genome data, leaving 411 patients of Caucasian ancestry, who had reliable data regarding their SA history. Binary and multinomial regression with the three suicidal phenotypes were further performed to adjust for possible confounders, along with hierarchical clustering and compared to controls (N = 2504). Bayesian analyses were conducted to detect pleiotropy across the suicidal phenotypes. Among 154 (37%) ever suicide attempters, 104 (68%) reported at least one serious SA and 96 (57%) two SA or more. The median number of non-tobacco SUDs was three. The BDNF gene remained associated with lifetime SA in SNP-based (rs7934165, rs10835210) and gene-based tests within the clinical sample. rs10835210 clustered with serious SA. Bayesian analysis identified genetic correlation between 'any' and 'serious' SA regarding rs7934165. Despite limitations, 'serious' SA was shown to share both clinical and genetic risk factors of SA-not otherwise specified, suggesting a shared BDNF-related pathophysiology of SA in this population with multiple SUDs.

Sex-specific behavioral and neurogenic responses to cocaine in mice lacking and blocking dopamine D1 or dopamine D2 receptors

Adult neurogenesis in rodents is modulated by dopaminergic signaling and inhibited by cocaine. However, the sex-specific role of dopamine D1 and D2 receptors (D1R, D2R) in the deleterious effect of cocaine on adult neurogenesis has not been described yet. Here, we explored sex differences in (a) cell proliferation (5'-bromo-2'-deoxyuridine [BrdU]), (b) neural precursor (nestin), (c) neuronal phenotype (BrdU/β3-tubulin), and (d) neuronal maturity (NeuN) in the subventricular zone (SVZ) of the lateral ventricles and striatum of mice with genetic deletion (D1^-/- , D2^-/- ) or pharmacological blockage (SCH23390: 0.1 mg/kg/day/5 days; Raclopride: 0.3 mg/kg/day/5 days) of D1R and D2R, and treated (10 mg/kg/day/5 days) and then challenged (5 mg/kg, 48 hr later) with cocaine. Results indicated that hyperactivity responses to cocaine were absent in D1^-/- mice and reduced in SCH23390-treated mice. Activity responses to cocaine were reduced in D2^-/- males, but absent in D2^-/- females and increased in Raclopride-treated females. D1R deletion blocked the deleterious effect of cocaine on SVZ cell proliferation in males. Cocaine-exposed D1^-/- males also had reduced neuronal phenotype of SVZ newborn cells and increased striatal neuronal maturity. D2^-/- mice had lower proliferative and neural precursor responses. Cocaine in D2^-/- females or coadministered with Raclopride in wild-type females improved SVZ cell proliferation, an effect that positively correlated with plasma brain-derived neurotrophic factor (BDNF) concentrations. In conclusion, the sex-specific D1R and D2R signaling on SVZ cell proliferation, neural progenitor and neuronal maturity is differentially perturbed by cocaine, and BDNF may be required to link D2R to neuroplasticity in cocaine addiction in females.

Behavioral and neurobiological alterations induced by chronic use of crack cocaine

Crack cocaine is the crystal form of cocaine and can be smoked, and rapidly absorbed, and, in part for this reason, is potently addictive. It is hypothesized that crack cocaine is able to induce important changes in different tissues and organs, and thus dramatically alter behavior. Nevertheless, which alterations in the central nervous system are related to its frequent use is still a matter of discussion. The present study is a literature review of articles published between the years 2008 and 2018 on the theme 'crack cocaine and brain' available in PUBMED, MEDLINE, EMBASE, and Google scholar databases. The results show that the use of crack cocaine induces important behavioral, neuroanatomical, and biochemical alterations. The main behavioral sequelae include cognitive and emotional changes, such as increased anxiety and depressive symptoms, attention and memory deficits, and hyperactivity. Among the neurobiological alterations are reductions in the activity of the prefrontal, anterior cingulate cortex, and nucleus accumbens. Molecular changes include decreases in neurotrophic factors and increases in oxidative stress and inflammatory cytokines, which may be responsible for the morphological alterations observed. It is also hypothesized that these neurobiological changes might explain the emotional and cognitive dysfunctions experienced by crack cocaine addicts.

Association of CHRNA5 Gene Variants with Crack Cocaine Addiction

Genome-wide studies provide increasing evidence of association of genetic variants with different behaviors. However, there is a growing need for replication and subsequent characterization of specific findings. In this sense, the CHRNA5 gene has been associated with nicotine (with genome-wide significance), alcohol and cocaine addictions. So far, this gene has not been evaluated in smoked (crack) cocaine. We aimed to analyze the influence of CHRNA5 variants in crack addiction susceptibility and severity. The sample includes 300 crack-addicted patients and 769 non-addicted individuals. The CHRNA5 SNPs evaluated were rs588765, rs16969968, and rs514743. Homozygosity for rs16969968 and rs588765 major alleles was nominally associated with a risk to crack addiction (GG, P = 0.032; CC, P = 0.036, respectively). Haplotype analyses reveal significant associations (rs588765|rs16969968|rs514743 p_{global-corrected} = 7.66 × 10^-5) and suggest a substantial role for rs16969968. These findings corroborate previous reports in cocaine addiction-in line with the expected effects of cocaine in the cholinergic system-and in the opposite direction of significant GWAS findings for nicotine addiction susceptibility. These results are strengthened by the first report of an association of rs588765 with crack addiction and by the haplotype findings. In summary, our study highlights the relevance of the α5 subunit on crack cocaine addiction, replicating previous results relating CHRNA5 with the genetics and pathophysiology of addiction of different drugs.

BDNF mRNA Expression in Leukocytes and Frontal Cortex Function in Drug Use Disorder

The brain-derived neurotrophic factor (BDNF) is a neurotrophin recognized to play a major role in neuroplastic modifications associated to drug abuse, being involved in various behavioral changes found in drug use disorders, such as drug sensitization, craving and relapses. These neuroplastic changes were shown to affect the prefrontal cortex functions, which can be briefly measured through cognitive tests such as the Frontal Assessment Battery (FAB). In this study we investigated the BDNF mRNA expression in peripheral blood lymphocytes of crack-cocaine use disorder (CUD) and alcohol use disorder (AUD) patients, after drug detoxification treatment, using a real-time PCR approach and examining its association to FAB performance. BDNF mRNA expression was found to be higher by 2.25-fold in CUD patients and by 2-fold in the AUD patients when normalized to controls, and these values were found to be associated with FAB scores. This preliminary study evaluates, for the first time, BDNF mRNA expression in leukocytes and its relationship to FAB scores in crack-cocaine and alcohol use disorder patients.

Glucocorticoid receptor gene variants and lower expression of NR3C1 are associated with cocaine use

Animal and cross-sectional human studies suggest that chronic cocaine use is associated with altered responsivity of the hypothalamic-pituitary-adrenal axis to stress. Moreover, increased susceptibility to stress has been proposed as an important factor for development, maintenance and relapse of cocaine addiction. As the glucocorticoid receptor gene (NR3C1) mediates genomic effects of the stress hormone cortisol, we investigated NR3C1 expression and the association of NR3C1 genotypes with cocaine use, addiction and comorbid psychiatric symptoms in 126 chronic cocaine users and 98 stimulant-naïve healthy controls. A comprehensive psychiatric assessment was performed including severity of depressive symptoms and current psychological distress. Whole blood NR3C1 mRNA levels were determined and six NR3C1 polymorphisms (rs10482605, rs41423247, rs10052957, rs6189, rs56149945 and rs6198) were genotyped. Compared to controls, cocaine users showed significantly lower NR3C1 expression (P < 0.001), which was not affected by NR3C1 genotypes. In controls, rs41423247 [P < 0.01, false discovery rate (FDR)-corrected], haplotype 2 and haplotype 3 (both P < 0.05, FDR-corrected) were associated with altered NR3C1 gene expression. Haplotype 3 (including minor alleles of rs10052957 and rs41423247) was associated with an increased risk for cocaine addiction (odds ratio = 2.74, P < 0.05, uncorrected). Moreover, addicted cocaine users carrying haplotype 3 showed higher depression scores (P < 0.01, FDR-corrected) than noncarriers. Considering possible confounding effects of alcohol and/or depression, we conclude that chronic cocaine use is associated with lower NR3C1 gene expression suggesting possible direct effects of the drug on the biological adaptation of stress-related genes. Finally, we postulate that haplotype 3 of NR3C1 might serve as a potential risk factor for stimulant addiction and associated psychiatric symptoms.

Interaction Between Stress and Addiction: Contributions From Latin-American Neuroscience

Drug addiction is a chronic neuropsychiatric disorder that escalates from an initial exposure to drugs of abuse, such as cocaine, cannabis, or heroin, to compulsive drug-seeking and intake, reduced ability to inhibit craving-induced behaviors, and repeated cycles of abstinence and relapse. It is well-known that chronic changes in the brain’s reward system play an important role in the neurobiology of addiction. Notably, environmental factors such as acute or chronic stress affect this system, and increase the risk for drug consumption and relapse. Indeed, the HPA axis, the autonomic nervous system, and the extended amygdala, among other brain stress systems, interact with the brain’s reward circuit involved in addictive behaviors. There has been a growing interest in studying the molecular, cellular, and behavioral mechanisms of stress and addiction in Latin-America over the last decade. Nonetheless, these contributions may not be as strongly acknowledged by the broad scientific audience as studies coming from developed countries. In this review, we compile for the first time a series of studies conducted by Latin American-based neuroscientists, who have devoted their careers to studying the interaction between stress and addiction, from a neurobiological and clinical perspective. Specific contributions about this interaction include the study of CRF receptors in the lateral septum, investigations on the neural mechanisms of cross-sensitization for psychostimulants and ethanol, the identification of the Wnt/β-catenin pathway as a critical neural substrate for stress and addiction, and the emergence of the cannabinoid system as a promising therapeutic target. We highlight animal and human studies, including for instance, reports coming from Latin American laboratories on single nucleotide polymorphisms in stress-related genes and potential biomarkers of vulnerability to addiction, that aim to bridge the knowledge from basic science to clinical research.

CRISPR/Cas9, the Powerful New Genome-Editing Tool for Putative Therapeutics in Obesity

The molecular technology known as clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) is revolutionizing the field of medical research and deepening our understanding of numerous biological processes. The attraction of CRISPR/Cas9 lies in its ability to efficiently edit DNA or modulate gene expression in living eukaryotic cells and organisms, a technology that was once considered either too expensive or scientifically risky. CRISPR/Cas9 has been successfully applied in agriculture to develop the next generation of disease-resistant plants. Now, the capability of gene editing has been translated to the biomedical area, focusing on the future of medicine faced with drug-resistant microbes by selectively targeting genes involved in antibiotic resistance, for example, or finding the ultimate strategy for cancer or HIV. In this regard, it was recently demonstrated that an injection of cancer-fighting CRISPR-modified white blood cells in a patient suffering from metastatic lung cancer could lead to promising results. Researchers and bioethicists are debating questions about the regulation of CRISPR/Cas9 that must be addressed. While legal challenges surround the use of this technique for genetically modifying cell lines in humans, we review the basic understanding of CRISPR/Cas9 and discuss how this technology could represent a candidate for treatment of non-communicable diseases in nutrition, such as obesity.

Cross-talk between the epigenome and neural circuits in drug addiction

Drug addiction is a behavioral disorder characterized by dysregulated learning about drugs and associated cues that result in compulsive drug seeking and relapse. Learning about drug rewards and predictive cues is a complex process controlled by a computational network of neural connections interacting with transcriptional and molecular mechanisms within each cell to precisely guide behavior. The interplay between rapid, temporally specific neuronal activation, and longer-term changes in transcription is of critical importance in the expression of appropriate, or in the case of drug addiction, inappropriate behaviors. Thus, these factors and their interactions must be considered together, especially in the context of treatment. Understanding the complex interplay between epigenetic gene regulation and circuit connectivity will allow us to formulate novel therapies to normalize maladaptive reward behaviors, with a goal of modulating addictive behaviors, while leaving natural reward-associated behavior unaffected.