Antidepressive response to sleep deprivation in unipolar depression is not associated with dopamine D3 receptor genotype

Genetics of nonpharmacological treatments of depression

Nonpharmacological antidepressant treatments are effective and well tolerated in selected patients. However, response is heterogeneous and validated biomarkers would be precious to aid treatment choice. We searched Pubmed, Scopus, and Google Scholar until May 2022 for original articles evaluating the association of genetic variables with the efficacy of nonpharmacological treatments for major depressive episodes. Most studies analyzed small sample sizes using the candidate gene approach, leading to poorly replicated findings that need to be interpreted cautiously. The few available methylome-wide and genome-wide association studies (GWASs) considered only electroconvulsive therapy (ECT) and cognitive-behavioral therapy in small samples, providing interesting findings by using polygenic risk scores. A deeper knowledge of the genetic factors implicated in treatment response may lead to a better understanding of the neurobiological mechanisms of nonpharmacological therapies for depression, and depression itself. Future GWAS are going to expand their sample size, thanks to consortia such as the gen-ECT-ic consortium.

Meta-Analysis of Sleep Deprivation Effects on Patients With Depression

Objective: Depression is a common disorder with a high recurrence rate. Since the effect of sleep deprivation on depression in existing studies were inconsistent, the present study aimed to reassess the effects of SD on patients by performing a meta-analysis of updated research. Methods: PubMed, Embase, the Cochrane Library, and Web of Science were searched for articles before January 20th, 2021. Data on participant characteristics, SD characteristics, adjunctive method and tests for depression were extracted. A comprehensive analysis was conducted to assess the effect of SD on depression and subgroup analysis was used to determine the sources of heterogeneity. Results: In total, 8 articles were included. An SD time of <7 days slightly worsened depression levels [0.24 (-0.21, 0.69); I ² = 0%; P = 0.43], a time of 7-14 days had antidepressant effects [-1.52 (-2.07, -0.97); I ² = 19.6%; P = 0.288], and a time of more than 14 days also worsened depression [0.76 (0.12, 1.40); I ² = 43.7%; P = 0.169]. Conclusion: SD may serve as an effective antidepressant measure in humans when the time was 7-14 days, while a time of <7 days and more than 14 days worsened depression.

Pharmacogenetics of the G protein-coupled receptors

Pharmacogenetics investigates the influence of genetic variants on physiological phenotypes related to drug response and disease, while pharmacogenomics takes a genome-wide approach to advancing this knowledge. Both play an important role in identifying responders and nonresponders to medication, avoiding adverse drug reactions, and optimizing drug dose for the individual. G protein-coupled receptors (GPCRs) are the primary target of therapeutic drugs and have been the focus of these studies. With the advance of genomic technologies, there has been a substantial increase in the inventory of naturally occurring rare and common GPCR variants. These variants include single-nucleotide polymorphisms and insertion or deletions that have potential to alter GPCR expression of function. In vivo and in vitro studies have determined functional roles for many GPCR variants, but genetic association studies that define the physiological impact of the majority of these common variants are still limited. Despite the breadth of pharmacogenetic data available, GPCR variants have not been included in drug labeling and are only occasionally considered in optimizing clinical use of GPCR-targeted agents. In this chapter, pharmacogenetic and genomic studies on GPCR variants are reviewed with respect to a subset of GPCR systems, including the adrenergic, calcium sensing, cysteinyl leukotriene, cannabinoid CB1 and CB2 receptors, and the de-orphanized receptors such as GPR55. The nature of the disruption to receptor function is discussed with respect to regulation of gene expression, expression on the cell surface (affected by receptor trafficking, dimerization, desensitization/downregulation), or perturbation of receptor function (altered ligand binding, G protein coupling, constitutive activity). The large body of experimental data generated on structure and function relationships and receptor-ligand interactions are being harnessed for the in silico functional prediction of naturally occurring GPCR variants. We provide information on online resources dedicated to GPCRs and present applications of publically available computational tools for pharmacogenetic studies of GPCRs. As the breadth of GPCR pharmacogenomic data becomes clearer, the opportunity for routine assessment of GPCR variants to predict disease risk, drug response, and potential adverse drug effects will become possible.

Dopamine D₃ receptor gene variation: impact on electroconvulsive therapy response and ventral striatum responsiveness in depression

Dysfunction of dopamine D₃ receptors, particularly in the mesocorticolimbic system, has been linked to the pathogenesis of major depression. Preclinical data show enhanced D₃ receptor binding in the striatum upon antidepressant medication and electroconvulsive therapy (ECT). Thus, the potential impact of dopamine D₃ receptor gene (DRD3) variation on ECT outcome in treatment-resistant major depression was evaluated by applying a combined molecular and imaging genetic approach. Altogether, 10 representative variants covering 95.4% of DRD3 gene variation were investigated for association with response to ECT in a sample of 104 (71 female, 33 male) Caucasian patients with pharmacorefractory major depression. Additionally, ventral striatum responsiveness to happy faces was assessed in two independent samples of depressed patients (total N=54) by means of functional magnetic resonance imaging at 3 T. Significant association of DRD3 rs3732790, rs3773679 and rs9817063 variants with response (uncorrected p=0.02-0.03) and remission (uncorrected p=0.01) after ECT was discerned. Logistic regression analyses revealed association of rs3732790 (uncorrected p=0.009; corrected p=0.045) and rs3773679 (uncorrected p=0.009; corrected p=0.045) with remission when applying a recessive model of inheritance. The rs3732790T allele conferring a more favourable treatment response was furthermore found to be associated with stronger striatal responsiveness to happy facial expressions (sample 1: cluster-corrected p=0.002; sample 2: p=0.023). In summary, the present study suggests some impact of DRD3 gene variation on ECT response, potentially mediated by alteration of striatal engagement during the processing of emotionally rewarding stimuli.

Genetic variation in dopamine pathways differentially associated with smoking progression in adolescence

OBJECTIVE

To clarify the nature of the association between dopamine genes and smoking by examining whether genetic variability in components of the dopamine pathway could explain refined phenotypes in adolescent smoking progression.

METHOD

Data are from an ongoing prospective study of the long-term outcome of early risk factors studied since birth. At age 15 years, 220 participants (108 males, 112 females) completed a self-report questionnaire measuring smoking behavior and were genotyped for five dopamine gene variants.

RESULTS

Smoking initiation was related to allelic variation in the dopamine D4 receptor gene (DRD4), whereas smoking continuation and dependence showed association with the dopamine D2 receptor gene (DRD2). Adolescents with the seven-repeat allele of the common DRD4 exon 3 polymorphism had rates of ever smoking that were significantly higher than in those with other genotypes. Once smoking started, carriers of the T allele of a single nucleotide polymorphism of DRD2 (rs4648317) reported higher rates of current smoking and scored higher on nicotine dependence than their allelic counterparts. Among current smokers, intention to quit was significantly lower in adolescents homozygous for the 10-repeat allele of the common dopamine transporter 3' untranslated region polymorphism.

CONCLUSIONS

Our results provide preliminary evidence of genetic influences on different stages of smoking and suggest the importance of specific dopamine genes in smoking progression in adolescence.

G protein-coupled receptor pharmacogenetics

Common G protein-coupled receptor (GPCR) gene variants that encode receptor proteins with a distinct sequence may alter drug efficacy without always resulting in a disease phenotype. GPCR genetic loci harbor numerous variants, such as DNA insertions or deletions and single-nucleotide polymorphisms that alter GPCR expression and function, thereby contributing to interindividual differences in disease susceptibility/progression and drug responses. In this chapter, these pharmacogenetic phenomena are reviewed with respect to a limited sampling of GPCR systems, including the beta(2)-adrenergic receptors, the cysteinyl leukotriene receptors, and the calcium-sensing receptor. In each example, the nature of the disruption to receptor function that results from each variant is discussed with respect to the regulation of gene expression, expression on cell surface (affected by receptor trafficking, dimerization, desensitization/downregulation), or perturbation of receptor function (by altering ligand binding, G protein coupling, and receptor constitutive activity). Despite the breadth of pharmacogenetic knowledge available, assessment for genetic variants is only occasionally applied to drug development projects involving pharmacogenomics or to optimizing the clinical use of GPCR drugs. The continued effort by the basic science of pharmacogenetics may draw the attention of drug discovery projects and clinicians alike to the utility of personalized pharmacogenomics as a means to optimize novel GPCR drug targets.

Chronotherapeutics in a psychiatric ward

Psychiatric chronotherapeutics is the controlled exposure to environmental stimuli that act on biological rhythms in order to achieve therapeutic effects in the treatment of psychiatric conditions. In recent years some techniques (mainly light therapy and sleep deprivation) have passed the experimental developmental phase and reached the status of powerful and affordable clinical interventions for everyday clinical treatment of depressed patients. These techniques target the same brain neurotransmitter systems and the same brain areas as do antidepressant drugs, and should be administered under careful medical supervision. Their effects are rapid and transient, but can be stabilised by combining techniques among themselves or together with common drug treatments. Antidepressant chronotherapeutics target the broadly defined depressive syndrome, with response and relapse rates similar to those obtained with antidepressant drugs, and good results are obtained even in difficult-to-treat conditions such as bipolar depression. Chronotherapeutics offer a benign alternative to more radical treatments of depression for the treatment of severe depression in psychiatric wards, but with the advantage of rapidity of onset.

The G protein-coupled receptors: pharmacogenetics and disease

Genetic variation in G-protein coupled receptors (GPCRs) is associated with a wide spectrum of disease phenotypes and predispositions that are of special significance because they are the targets of therapeutic agents. Each variant provides an opportunity to understand receptor function that complements a plethora of available in vitro data elucidating the pharmacology of the GPCRs. For example, discrete portions of the proximal tail of the dopamine D1 receptor have been discovered, in vitro, that may be involved in desensitization, recycling and trafficking. Similar in vitro strategies have been used to elucidate naturally occurring GPCR mutations. Inactive, over-active or constitutively active receptors have been identified by changes in ligand binding, G-protein coupling, receptor desensitization and receptor recycling. Selected examples reviewed include those disorders resulting from mutations in rhodopsin, thyrotropin, luteinizing hormone, vasopressin and angiotensin receptors. By comparison, the recurrent pharmacogenetic variants are more likely to result in an altered predisposition to complex disease in the population. These common variants may affect receptor sequence without intrinsic phenotype change or spontaneous induction of disease and yet result in significant alteration in drug efficacy. These pharmacogenetic phenomena will be reviewed with respect to a limited sampling of GPCR systems including the orexin/hypocretin system, the beta2 adrenergic receptors, the cysteinyl leukotriene receptors and the calcium-sensing receptor. These developments will be discussed with respect to strategies for drug discovery that take into account the potential for the development of drugs targeted at mutated and wild-type proteins.

Pharmacogenetics in the treatment of depression: pharmacodynamic studies

The pharmacological treatment of mood disorders has reduced their morbidity and improved mental health for millions of individuals worldwide, favouring a considerable reduction of the direct and indirect costs caused by these common pathologies. Unfortunately, not all individuals benefit, and 30-40% of patients do not show a complete response to treatment. Efficient clinical predictors are not available, although genetic factors are thought to play a substantial (but complex) role in the antidepressant response. Pharmacogenetics, which investigates the influence of genetic features on the pharmacological response, has gained increasing attention and holds great promise for clinical psychiatry. Here, a brief overview is provided on the various pharmacogenetic studies published to date that analyse the commonest treatments for depression: antidepressants, sleep deprivation and lithium salts.

Pharmacogenetics of antidepressants and antipsychotics: the contribution of allelic variations to the phenotype of drug response

Genetic factors contribute to the phenotype of drug response. We systematically analyzed all available pharmacogenetic data from Medline databases (1970-2003) on the impact that genetic polymorphisms have on positive and adverse reactions to antidepressants and antipsychotics. Additionally, dose adjustments that would compensate for genetically caused differences in blood concentrations were calculated. To study pharmacokinetic effects, data for 36 antidepressants were screened. We found that for 20 of those, data on polymorphic CYP2D6 or CYP2C19 were found and that in 14 drugs such genetic variation would require at least doubling of the dose in extensive metabolizers in comparison to poor metabolizers. Data for 38 antipsychotics were examined: for 13 of those CYP2D6 and CYP2C19 genotype was of relevance. To study the effects of genetic variability on pharmacodynamic pathways, we reviewed 80 clinical studies on polymorphisms in candidate genes, but those did not for the most part reveal significant associations between neurotransmitter receptor and transporter genotypes and therapy response or adverse drug reactions. In addition associations found in one study could not be replicated in other studies. For this reason, it is not yet possible to translate pharmacogenetic parameters fully into therapeutic recommendations. At present, antidepressant and antipsychotic drug responses can best be explained as the combinatorial outcome of complex systems that interact at multiple levels. In spite of these limitations, combinations of polymorphisms in pharmacokinetic and pharmacodynamic pathways of relevance might contribute to identify genotypes associated with best and worst responders and they may also identify susceptibility to adverse drug reactions.

No Influence of a functional polymorphism within the serotonin transporter gene on partial sleep deprivation in major depression

Sleep deprivation exerts transient antidepressant efficacy. As a potential mechanism of action an enhancement of serotonergic and dopaminergic neurotransmission within the CNS is discussed. Because genetic variations influencing neurotransmission could have an impact on therapeutic outcome and stability of improvement, we investigated the functional polymorphism of the serotonin transporter (5-HTT) gene, the 5-HTT-linked polymorphic region (5-HTTLPR), to examine the serotonergic pathway. We included 56 patients with major depression (DSM-IV). Psychiatric ratings including the HAM-D21 and HAM-D6 scale were assessed on the day prior to partial sleep deprivation (PSD) and on day 1 and 2 after PSD and related to the different genotypes. The 5-HTTLPR variants were determined following PCR amplification using genomic DNA. 58.1% of the patients were responders to PSD. A significant overall reduction in depression scores could be observed on day 1. Subdivision according 5-HTTLPR gene variants showed no differences in clinical outcome on day 1. As expected the therapeutical effect of PSD was only transient and most patients experienced an exacerbation of depressive symptoms on day 2. 5-HTTLPR variants had no influence on reduction of depressive symptoms on day 2 or relapse on day 3. Thus, the previously reported influence of the serotonin transporter gene on PSD outcome in bipolar depression could not be confirmed in unipolar depressed patients.

Dopamine receptor D2 and D3 gene variants are not associated with the antidepressant effect of total sleep deprivation in bipolar depression

Total sleep deprivation (TSD) is an effective treatment for mood disorders that is thought to act through an enhancement in several neurotransmitter pathways including dopaminergic transmission. Genetic factors are likely to play a major role in determining individual differences in TSD response. The aim of this study is to investigate the influence of dopamine receptor D3 (DRD3) and dopamine receptor D2 (DRD2) variants on TSD antidepressant efficacy in bipolar disorder. One hundred twenty-four depressed inpatients affected by bipolar disorder (DSM-IV) were treated with TSD and were genotyped for DRD3 first exon Gly/Ser variants and DRD2 codon 311 Ser/Cys variants using polymerase chain reaction techniques. DRD3 and DRD2 variants were not associated with TSD outcome. Consideration of possible stratification effects such as gender, age at onset and duration of illness did not reveal any association either. The tested gene variants are not a main factor influencing TSD outcome in bipolar disorder.

Pharmacogenetics in affective disorders

Pharmacogenetics will be of substantial help in the field of affective disorders pharmacotherapy. The possible definition of a genetic liability profile for drug side-effects and efficacy will be of great help in treatments that need weeks to months to be effective. During the last few years, a number of groups have reported possible liability genes. The efficacy and time of onset of selective serotonin reuptake inhibitors have been associated with a polymorphism in the promoter region of the transporter (SERTPR) in many independent studies, while variants at the tryptophan hydroxylase gene, 5-HT2a receptor and G-protein beta3 have been associated with them in pilot studies. Lithium long-term prophylactic efficacy has been associated with SERTPR, TPH and inositol polyphosphate 1-phosphatase variants, though in unreplicated samples. A number of further candidate genes were not associated with these treatments. In conclusion, both acute and long-term treatments appear to be, at least to some extent, under genetic influence and preliminary data have identified possible liability genes.