Pharmacogenetics of antidepressant response: an update

scRank infers drug-responsive cell types from untreated scRNA-seq data using a target-perturbed gene regulatory network

Cells respond divergently to drugs due to the heterogeneity among cell populations. Thus, it is crucial to identify drug-responsive cell populations in order to accurately elucidate the mechanism of drug action, which is still a great challenge. Here, we address this problem with scRank, which employs a target-perturbed gene regulatory network to rank drug-responsive cell populations via in silico drug perturbations using untreated single-cell transcriptomic data. We benchmark scRank on simulated and real datasets, which shows the superior performance of scRank over existing methods. When applied to medulloblastoma and major depressive disorder datasets, scRank identifies drug-responsive cell types that are consistent with the literature. Moreover, scRank accurately uncovers the macrophage subpopulation responsive to tanshinone IIA and its potential targets in myocardial infarction, with experimental validation. In conclusion, scRank enables the inference of drug-responsive cell types using untreated single-cell data, thus providing insights into the cellular-level impacts of therapeutic interventions.

The associations of CNR1 SNPs and haplotypes with vulnerability and treatment response phenotypes in Han Chinese with major depressive disorder: A case-control association study

BACKGROUND

Understanding how genetic polymorphisms are associated with the pathophysiology of major depressive disorder (MDD) may aid in diagnosis and the development of personalized treatment strategies. CNR1 is the gene coding Cannabinoid type 1 receptor which is highly involved in emotional processing and in regulating neurotransmitter releases. We aimed to investigate the associations of CNR1 single-nucleotide polymorphisms (SNPs) with MDD susceptibility and treatment response.

METHODS

The study reported data on 181 Han Chinese with MDD and 80 healthy controls. The associations of CNR1 genetic polymorphisms with MDD susceptibility and treatment response were examined, wherein the MDD patients were subgrouped further by responding to antidepressant treatment, compared with healthy controls separately.

RESULTS

The CNR1 SNPs rs806367 and rs6454674 and haplotype C-T-T-C of rs806366, rs806367, rs806368, and rs806370 were associated with increased susceptibility for MDD and antidepressant treatment resistance, but the association was not detected in other SNPs or the haplotype block of rs806368 and rs806370.

CONCLUSION

The CNR1 is a promising candidate for the genetic association study of MDD. Larger and well-characterized samples are required to confirm the genetic association of CNR1 with MDD because of the limitations such as relatively small sample size and lack of information for correcting confounding factors.

SLC6A4 polymorphisms modulate the efficacy of a tryptophan-enriched diet on age-related depression and social cognition

BACKGROUND & AIMS

In a placebo controlled study we sought to determine if a four-weeks tryptophan-enriched diet is able to improve age-related depression or social cognitive impairment, depending on polymorphisms located in the promoter region of Solute Carrier Family 6 Member 4 (SLC6A4), also known as serotonin transporter (SERT1) gene.

METHODS

91 young volunteers (age: 21 ± 2 yrs) and 127 above 50 years old (58 ± 6 yrs) healthy volunteers completed the study. Participants from the placebo and tryptophan group followed the same protocol. Before starting the study blood samples, to measure serotonin-transporter-linked polymorphic region (5-HTTLPR) and rs25531 polymorphisms, were collected. In addition, before and after completing the study urine samples (to measure 5-hydroxyindolacetic acid (5-HIAA) were taken, while psychological questionnaires (to assess depression and social cognition levels), and a one week dietary record (to calculate the tryptophan (TRP) intake) were assessed.

RESULTS

The triallelic approach of SLC6A4 showed that in S'S´ subjects there was a positive correlation between TRP intake and 5-HIAA levels. Age of participants, SLC6A4 genotype, and experimental condition were important factors contributing to the outcome of depression and social cognition.

CONCLUSIONS

5-HTTLPR and rs25531 polymorphisms play a key role in the response to the TRP- based nutritional intervention, improving only age-related depressive symptoms and empathy in S'S´ subjects who have a higher risk to show signs of depression during their lifetime.

Position statement of the European Psychiatric Association (EPA) on the value of antidepressants in the treatment of unipolar depression

This position statement will address in an evidence-based approach some of the important issues and controversies of current drug treatment of depression such as the efficacy of antidepressants, their effect on suicidality and their place in a complex psychiatric treatment strategy including psychotherapy. The efficacy of antidepressants is clinically relevant. The highest effect size was demonstrated for severe depression. Based on responder rates and based on double-blind placebo-controlled studies, the number needed to treat (NNT) is 5–7 for acute treatment and four for maintenance treatment. Monotherapy with one drug is often not sufficient and has to be followed by other antidepressants or by comedication/augmentation therapy approaches. Generally, antidepressants reduce suicidality, but under special conditions like young age or personality disorder, they can also increase suicidality. However, under the conditions of good clinical practice, the risk–benefit relationship of treatment with antidepressants can be judged as favourable also in this respect. The capacity of psychiatrists to individualise and optimise treatment decisions in terms of ‘the right drug/treatment for the right patient’ is still restricted since currently there are no sufficient powerful clinical or biological predictors which could help to achieve this goal. There is hope that in future pharmacogenetics will contribute significantly to a personalised treatment. With regard to plasma concentration, therapeutic drug monitoring (TDM) is a useful tool to optimize plasma levels therapeutic outcome. The ideal that all steps of clinical decision-making can be based on the strict rules of evidence-based medicine is far away from reality. Clinical experience so far still has a great impact.

Systems Approach to Identify Common Genes and Pathways Associated with Response to Selective Serotonin Reuptake Inhibitors and Major Depression Risk

Despite numerous studies on major depressive disorder (MDD) susceptibility, the precise underlying molecular mechanism has not been elucidated which restricts the development of etiology-based disease-modifying drug. Major depressive disorder treatment is still symptomatic and is the leading cause of (~30%) failure of the current antidepressant therapy. Here we comprehended the probable genes and pathways commonly associated with antidepressant response and MDD. A systematic review was conducted, and candidate genes/pathways associated with antidepressant response and MDD were identified using an integrative genetics approach. Initially, single nucleotide polymorphisms (SNPs)/genes found to be significantly associated with antidepressant response were systematically reviewed and retrieved from the candidate studies and genome-wide association studies (GWAS). Also, significant variations concerning MDD susceptibility were extracted from GWAS only. We found 245 (Set A) and 800 (Set B) significantly associated genes with antidepressant response and MDD, respectively. Further, gene set enrichment analysis revealed the top five co-occurring molecular pathways (p ≤ 0.05) among the two sets of genes: Cushing syndrome, Axon guidance, cAMP signaling pathway, Insulin secretion, and Glutamatergic synapse, wherein all show a very close relation to synaptic plasticity. Integrative analyses of candidate gene and genome-wide association studies would enable us to investigate the putative targets for the development of disease etiology-based antidepressant that might be more promising than current ones.

Effect of Serotonin Transporter 5-HTTLPR Polymorphism on Gastrointestinal Intolerance to Metformin: A GoDARTS Study

OBJECTIVE

The mechanism causing gastrointestinal intolerance to metformin treatment is unknown. We have previously shown that reduced-function alleles of organic cation transporter 1 (OCT1) are associated with increased intolerance to metformin. Considering recent findings that serotonin reuptake transporter (SERT) might also be involved in metformin intestinal absorption, and the role of serotonin in gastrointestinal physiology, in this study we investigated the association between a common polymorphism in the SERT gene and metformin gastrointestinal intolerance.

RESEARCH DESIGN AND METHODS

We explored the effect of composite SERT 5-HTTLPR/rs25531 genotypes, L*L* (LALA), L*S* (LALG, LAS), and S*S* (SS, SLG, LGLG), in 1,356 fully tolerant and 164 extreme metformin-intolerant patients by using a logistic regression model, adjusted for age, sex, weight, OCT1 genotype, and concomitant use of medications known to inhibit OCT1 activity.

RESULTS

The number of low-expressing SERT S* alleles increased the odds of metformin intolerance (odds ratio [OR] 1.31 [95% CI 1.02-1.67], P = 0.031). Moreover, a multiplicative interaction between the OCT1 and SERT genotypes was observed (P = 0.003). In the analyses stratified by SERT genotype, the presence of two deficient OCT1 alleles was associated with more than a ninefold higher odds of metformin intolerance in patients carrying the L*L* genotype (OR 9.25 [95% CI 3.18-27.0], P < 10-4); however, it showed a much smaller effect in L*S* carriers and no effect in S*S* carriers.

CONCLUSIONS

Our results indicate that the interaction between OCT1 and SERT genes might play an important role in metformin intolerance. Further studies are needed to replicate these findings and to substantiate the hypothesis that metformin gastrointestinal side effects could be related to the reduced intestinal serotonin uptake.

Genomewide interaction and enrichment analysis on antidepressant response

BACKGROUND

Genomewide association studies (GWASs) on antidepressant efficacy have yielded modest results. A possible reason is that response is influenced by other factors, which possibly interact with genetic variation. We used a GWAS model to predict antidepressant response, by including predictors previously known to affect response, such as quality of life (QoL). We also evaluated the association between genes, previously implicated in gene-environment (G × E) interactions, and response using an enrichment analysis.

METHOD

We examined a sample of 1426 depressed patients from the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) trial: 774 responders, 652 non-responders and 418,865 single nucleotide polymorphisms (SNPs) were analysed. First, in a GWAS model, we investigated whether genetic variations interact with patients' levels of QoL to predict response, after controlling for demographic characteristics, severity and population stratification. Second, we conducted an enrichment analysis exploring whether candidate genes that have emerged from prior G × E interaction studies on depression are associated with treatment response.

RESULTS

The GWAS model, with QoL as a moderator, yielded one SNP (rs520210) associated with response in the NEDD4L gene (p = 3.64 × 10⁻⁸). In the Caucasian sample only, we observed a drop in significance for this SNP. The enrichment analysis showed that SNPs within serotonergic genes contained more significant markers that predicted response, compared with a random set of genes in the genome.

CONCLUSIONS

Our findings point to possible target genes, which are proposed for further independent replication. Our enrichment analysis provides further support, in a genomewide context, of the role of serotonergic genes in influencing antidepressant response.

Analysis of 34 candidate genes in bupropion and placebo remission

There is considerable variability in the rate of response and remission following treatment with antidepressant drugs or placebo in depression patients. No pharmacogenetic studies of bupropion response have been done. We investigated 532 tagging single nucleotide polymorphisms (SNPs) in 34 candidate genes for association with remission and response to either bupropion (n=319) or placebo (n=257) in patients with major depressive disorder. Analyses were performed using conditional logistic regression. Significant association (gene-wide correction) was observed for remission following treatment with bupropion for a SNP within the serotonin receptor 2A gene (HTR2A rs2770296, p(corrected)=0.02). Response to bupropion treatment was significantly associated with a SNP in the dopamine transporter gene (rs6347, p(corrected)=0.013). Among the patients who received placebo, marginal association for remission was observed between a SNP in HTR2A (rs2296972, p(corrected)=0.055) as well as in the serotonin transporter gene (5-HTT or SLC6A4 rs4251417, p(corrected)=0.050). Placebo response was associated with SNPs in the glucocorticoid receptor gene (NR3C1; rs1048261, p(corrected)=0.040) and monoamine oxidase A gene (MAOA; rs6609257, p corrected=0.046). Although the above observations were significant after gene-wide corrections, none of these would be significant after a more conservative study-wide correction for multiple tests. These results suggest a possible role for HTR2A in remission to bupropion treatment. In accordance with bupropion pharmacology, dopamine transporter may play a role in response. The MAOA gene may be involved in placebo response.

Stress-related depression: neuroendocrine, genetic, and therapeutical aspects

OBJECTIVE

To summarize current concepts on neuroendocrine and genetic principles underlying stress-related depression and to discuss the challenges of personalized treatment in depression.

METHODS

Review of the literature pertaining to genetic and neuroendocrine basis of stress-related depression including aspects of treatment response with a focus on the hypothalamus-pituitary-adrenal (HPA) axis.

RESULTS

There is increasing evidence that genetic polymorphisms and dysregulation of the HPA axis are associated with the pathophysiology of stress-related depression. Individual stress hormone reactivity seems to be determined by a combination of genetic and environmental factors, contributing to both, resilience or vulnerability.

CONCLUSIONS

Although substantial progress has been made, current knowledge is still limited. Further basic and clinical research is needed to identify specific subgroups and to minimize heterogeneity of the depression phenotype. A better characterization is essential to detect genetic and functional predictors of antidepressant treatment response to follow the vision of personalized therapy in psychiatry.

Global gene expression in larval zebrafish (Danio rerio) exposed to selective serotonin reuptake inhibitors (fluoxetine and sertraline) reveals unique expression profiles and potential biomarkers of exposure

Larval zebrafish (Danio rerio) were exposed (96 h) to selective serotonin reuptake inhibitors (SSRIs) fluoxetine and sertraline and changes in transcriptomes analyzed by Affymetrix GeneChip Zebrafish Array were evaluated to enhance understanding of biochemical pathways and differences between these SSRIs. The number of genes differentially expressed after fluoxetine exposure was 288 at 25 μg/L and 131 at 250 μg/L; and after sertraline exposure was 33 at 25 μg/L and 52 at 250 μg/L. Same five genes were differentially regulated in both SSRIs indicating shared molecular pathways. Among these, the gene coding for FK506 binding protein 5, annotated to stress response regulation, was highly down-regulated in all treatments (results confirmed by qRT-PCR). Gene ontology analysis indicated at the gene expression level that regulation of stress response and cholinesterase activities were influenced by these SSRIs, and suggested that changes in transcription of these genes could be used as biomarkers of SSRI exposure.

Clinical and pathogenic aspects of candidate genes for lithium prophylactic efficacy

A number of candidate genes for lithium prophylactic efficacy have been proposed, some of them being also associated with a predisposition to bipolar illness. The aim of the present study was to investigate a possible association between polymorphisms of 14 common genes with the quality of prophylactic lithium response in patients with bipolar mood disorder, in relation to the putative role of these genes in the pathogenesis of this disorder. Some association with lithium prophylactic efficacy was found for the polymorphisms of 5HTT, DRD1, COMT, BDNF and FYN genes, but not for 5HT2A, 5HT2C, DRD2, DRD3, DRD4, GSK-3, NTRK2, GRIN2B and MMP-9. Possible aspects of these genes with regard to the mechanism of lithium activity and pathogenesis of bipolar mood disorder are discussed.

AVPR1A and SLC6A4 polymorphisms in choral singers and non-musicians: a gene association study

Amateur choral singing is a common pastime and worthy of study, possibly conferring benefits to health and social behaviour. Participants might be expected to possess musical ability and share some behavioural characteristics. Polymorphisms in genes concerned with serotonergic neurotransmission are associated with both behaviour and musical aptitude. Those investigated previously include the variable number tandem repeats RS1, RS3 and AVR in the AVPR1A (arginine vasopressin receptor 1a) gene and STin2 in the SLC6A4 (solute carrier family 6 [neurotransmitter transporter, serotonin], member 4) gene, as well as the SLC6A4 promoter region polymorphism, 5-HTTLPR. We conducted a genetic association study on 523 participants to establish whether alleles at these polymorphisms occur more commonly in choral singers than in those not regularly participating in organised musical activity (non-musicians). We also analysed tagging single nucleotide polymorphisms (SNPs) for AVPR1A and SLC6A4 to determine whether other variants in these genes were associated with singer/non-musician status. At the STin2 polymorphism, overall association with singer/non-musician status was evident at P = 0.006. The 9-repeat (P = 0.04) and 12-repeat (P = 0.04) alleles were more common in singers and the 10-repeat allele less so (P = 0.009). Odds ratios were 0.73 (95% CI 0.57–0.94) for the 10-repeat allele and 2.47 (95% CI 0.88–6.94) for the rarer 9-repeat allele. No overall association was detected at P<0.05 between any other polymorphism and singer/non-musician status. Our null findings with respect to RS3, RS1 and AVR, polymorphisms associated with musical ability by other authors, suggest that choir membership may depend partly on factors other than musical ability. In a related musical project involving one participating choir, a new 40-part unaccompanied choral work, “Allele”, was composed and broadcast on national radio. In the piece, each singer's part incorporated their personal RS3 genotype.

Chaperoning steroidal physiology: lessons from mouse genetic models of Hsp90 and its cochaperones

The molecular chaperone Hsp90 is abundant, ubiquitous, and catholic to biological processes in eukaryotes, controlling phosphorylation cascades, protein stability and turnover, client localization and trafficking, and ligand-receptor interactions. Not surprisingly, Hsp90 does not accomplish these activities alone. Instead, an ever-growing number of cochaperones have been identified, leading to an explosion of reports on their molecular and cellular effects on Hsp90 chaperoning of client substrates. Notable among these clients are many members of the steroid receptor family, such as glucocorticoid, androgen, estrogen and progesterone receptors. Cochaperones typically associated with the mature, hormone-competent states of these receptors include p23, the FK506-binding protein 52 (FKBP52), FKBP51, protein phosphatase 5 (PP5) and cyclophilin 40 (Cyp40). The ultimate relevance of these cochaperones to steroid receptor action depends on their physiological effects. In recent years, the first mouse genetic models of these cochaperones have been developed. This work will review the complex and intriguing phenotypes so far obtained in genetically-altered mice and compare them to the known molecular and cellular impacts of cochaperones on steroid receptors. This article is part of a Special Issue entitled: Heat Shock Protein 90 (HSP90).

Sexual dysfunction during treatment with serotonergic and noradrenergic antidepressants: clinical description and the role of the 5-HTTLPR

OBJECTIVES

Sexual dysfunction (SD) is a frequently reported side-effect of antidepressant treatment, particularly of selective serotonin reuptake inhibitors (SSRIs). In the multicentre clinical and pharmacogenetic GENDEP study (Genome-based Therapeutic Drugs for Depression), the effect of the serotonin transporter gene promoter polymorphism 5-HTTLPR on sexual function was investigated during treatment with escitalopram (SSRI) and nortriptyline (tricyclic antidepressant).

METHODS

A total of 494 subjects with an episode of DSM-IV major depression were randomly assigned to treatment with escitalopram or nortriptyline. Over 12 weeks, depressive symptoms and SD were measured weekly with the Montgomery-Asberg Depression Rating Scale, the Antidepressant Side-Effect Checklist, the UKU Side Effect Rating Scale, and the Sexual Functioning Questionnaire.

RESULTS

The incidence of reported SD after 12 weeks of treatment was relatively low, and did not differ significantly between antidepressants (14.9% escitalopram, 19.7% nortriptyline). There was no significant interaction between the 5-HTTLPR and antidepressant on SD. Improvement in depressive symptoms and younger age were both associated with lower SD. The effect of age on SD may have been moderated by the 5-HTTLPR.

CONCLUSIONS

In GENDEP, rates of reported SD during treatment were lower than those described in previous reports. There was no apparent effect of the 5-HTTLPR on the observed decline in SD.

A model to incorporate genetic testing (5-HTTLPR) in pharmacological treatment of major depressive disorders

OBJECTIVE

To evaluate the benefit of pharmacogenetics in antidepressant treatment.

METHODS

In a simulated trial 100,000 subjects in a current episode of major depressive disorder (MDD) received citalopram or bupropion based on the clinician's decision (algorithm A) or following indications from 5-HTTLPR genetic testing (algorithm B), which effect size of was estimated from a meta-analysis of pharmacogenetic trials. A and B were compared in a cost-utility analysis (12 weeks). Costs (international $, 2010) were drawn from official sources. Treatment effects were expressed as quality-adjusted life weeks (QALWs). Outcome was incremental cost-effectiveness ratio (ICER).

RESULTS

Under base-case conditions, genetic test use was associated with increases in antidepressant response (0.062 QALWs) and tolerability (0.016 QALWs) but cost benefit was not acceptable (ICER = $2,890; $1,800-$4,091). However, when the joint effect on antidepressant response and tolerability was analyzed in two recurrent episodes, ICER dropped to $1,392 ($837-$1,982). Cost-effectiveness acceptability curve (CEAC) showed a >80% probability that ICER value fell below the commonly accepted 3 times Gross Domestic Product (GDP) threshold (World Health Organization) and therefore suggesting cost-effectiveness.

CONCLUSION

Notwithstanding some caveats (exclusion of gene-gene and gene-environment interactions; simple 5-HTTLPR architecture), this simulation is favourable to incorporate pharmacogenetic test in antidepressant treatment.

Genome-wide association studies of antidepressant outcome: a brief review

Genome-wide association studies (GWAS) of antidepressant treatment outcome have been at the forefront of psychiatric pharmacogenetics. Such studies may ultimately help match medications with patients, maximizing efficacy while minimizing adverse effects. The hypothesis-free approach of the GWAS has the advantage of interrogating genes that otherwise would have not been considered as candidates due to our limited understanding of their function, and may also uncover important regulatory variation within the large regions of the genome that do not contain protein-coding genes. Three independent samples have so far been studied using a genome-wide approach: The Sequenced Treatment Alternatives to Relieve Depression sample (STAR*D) (n=1953), the Munich Antidepressant Response Signature (MARS) sample (n=339) and the Genome-based Therapeutic Drugs for Depression (GENDEP) sample (n=706). None of the studies reported results that achieved genome-wide significance, suggesting that larger samples and better outcome measures will be needed. This review discusses the published GWAS studies, their strengths, limitations, and possible future directions.

A candidate gene study of serotonergic pathway genes and pain relief during treatment with escitalopram in patients with neuropathic pain shows significant association to serotonin receptor2C (HTR2C)

PURPOSE

Previous studies have shown that a small fraction of patients with peripheral neuropathic pain experiences >50% pain relief during treatment with selective serotonin reuptake inhibitors (SSRIs), whereas most patients have no or only slight relief. The aim of this study was to investigate the association between polymorphisms in genes involved in the serotonergic pathway and the effect of escitalopram on peripheral neuropathic pain.

METHODS

We genotyped 34 participants from a placebo-controlled trial of escitalopram in peripheral neuropathic pain for polymorphisms in five genes: the serotonin receptor 2A (HTR2A) gene, the serotonin receptor 2C (HTR2C) gene, the ABCB1 gene encoding for the P-glycoprotein, the CYP2C19 gene, and the serotonin transporter gene (SLC6A4).

RESULTS

The SNP rs6318 (Cys23Ser) in the HTR2C gene showed significant association with treatment response in men (p = 0.047), with 75% carrying the C allele being responders. The same tendency was seen in women. Similarly, carriership of the C allele at rs6318 was associated with better pain relief during treatment with escitalopram [odds ratio (OR) 15.5, p = 0.014)] Furthermore, there was a tendency of better relief with increasing number of short alleles for the 5-HTTLPR polymorphism of the serotonin transporter (OR 5.7, p = 0.057). None of the other polymorphisms showed a significant association with treatment response to escitalopram.

CONCLUSION

This study indicates that variation in the HTR2C gene is associated to the pain-relieving effect of escitalopram in patients with painful polyneuropathy.

FKBP51-a selective modulator of glucocorticoid and androgen sensitivity

FK506-binding protein 51 (FKBP51) is gaining increased recognition for its essential roles in cell biology. Originally discovered as a component of steroid receptor complexes, it is now known to regulate a diverse set of transcription factors, enzymes and structural proteins. Its cellular properties suggest numerous possible functions for FKBP51 in physiology, and the best clue to its potential importance may be the following: FKBP51 is a glucocorticoid-induced negative regulator of the glucocorticoid receptor. Thus, FKBP51 is intricately involved in regulation of the most pleiotropic hormone known to biology. In contrast to glucocorticoid receptor, FKBP51 is a positive regulator of the androgen receptor, suggesting that it functions as a reciprocal modulator of glucocorticoid-mediated and androgen-mediated physiology. In this work, we evaluate this hypothesis by examining recent cellular and physiological evidence.

PCLO rs2522833 modulates HPA system response to antidepressant treatment in major depressive disorder

Variant rs2522833 of the Piccolo-encoding gene PCLO has recently been found to be associated with major depressive disorder (MDD). PCLO encodes a presynaptic cytomatrix protein which influences monoamine neurotransmitter release. Piccolo could therefore play an important role in treatment response to antidepressant therapy and the improvement of alterations in HPA system reactivity. We investigated the influence of the coding variant rs2522833 in the PCLO gene on treatment response in 205 in-patients with unipolar depression. Treatment response was measured (1) at the level of psychopathology using the Hamilton Depression Rating Scale (HAMD) and (2) with the combined dexamethasone/corticotropin-releasing hormone (Dex/CRH) test, which is a refined tool for showing dysregulation of the hypothalamic-pituitary-adrenocortical (HPA) system, a neurobiological finding in depression. While we did not find an association between variation in PCLO and HAMD scores, HPA dysregulation was less pronounced in carriers of the AA genotype than in carriers of one or two C alleles. HPA activity of individuals with the AA genotype only marginally changed during 4-wk antidepressant treatment, whereas C allele carriers showed a higher hormonal secretion at admission than carriers of the AA genotype but lower responsivity to the Dex/CRH challenge after 4 wk. Our results point to a moderating role of PCLO SNP rs2522833 on HPA regulation during antidepressant treatment, which may represent a neurobiological feature of stability of clinical response.

Pharmacogenetics of antidepressants

Up to 60% of depressed patients do not respond completely to antidepressants (ADs) and up to 30% do not respond at all. Genetic factors contribute for about 50% of the AD response. During the recent years the possible influence of a set of candidate genes as genetic predictors of AD response efficacy was investigated by us and others. They include the cytochrome P450 superfamily, the P-glycoprotein (ABCB1), the tryptophan hydroxylase, the catechol-O-methyltransferase, the monoamine oxidase A, the serotonin transporter (5-HTTLPR), the norepinephrine transporter, the dopamine transporter, variants in the 5-hydroxytryptamine receptors (5-HT1A, 5-HT2A, 5-HT3A, 5-HT3B, and 5-HT6), adrenoreceptor beta-1 and alpha-2, the dopamine receptors (D2), the G protein beta 3 subunit, the corticotropin releasing hormone receptors (CRHR1 and CRHR2), the glucocorticoid receptors, the c-AMP response-element binding, and the brain-derived neurotrophic factor. Marginal associations were reported for angiotensin I converting enzyme, circadian locomotor output cycles kaput protein, glutamatergic system, nitric oxide synthase, and interleukin 1-beta gene. In conclusion, gene variants seem to influence human behavior, liability to disorders and treatment response. Nonetheless, gene × environment interactions have been hypothesized to modulate several of these effects.

Further evidence supporting the influence of brain-derived neurotrophic factor on the outcome of bipolar depression: independent effect of brain-derived neurotrophic factor and harm avoidance

Brain-derived neurotrophic factor is a candidate gene for response to antidepressant treatment. However, response to pharmacological treatments is moderated by both genetic and other factors within individuals. For example, there is evidence of an influence of the temperamental trait of harm avoidance on the outcome of depressive disorders. In the present study we aimed to investigate the effect of the brain-derived neurotrophic factor gene on medium-term outcome in a naturalistic sample of 86 depressed bipolar spectrum patients, taking into account harm avoidance. Both single marker and haplotypes were significantly associated with severity of depression at month 6 after treatment initiation. The haplotype comprising the A-C alleles was associated with a poorer outcome. Harm avoidance maintained a significant effect on depressive outcome in bipolar disorder, independently from brain-derived neurotrophic factor genotypes. However, harm avoidance s influence appeared to be more consistent in patients carrying the protective G-T combination of alleles. Our results indicate brain-derived neurotrophic factor as involved in the outcome of depression in bipolar disorder. Harm avoidance did not interact with brain-derived neurotrophic factor genotypes, though its effect was still significant. Given that many factors may influence response to pharmacological treatments, studies that consider personality and other individual characteristics are warranted also in pharmacogenetic investigations.

The impact of catechol-O-methyltransferase SNPs and haplotypes on treatment response phenotypes in major depressive disorder: a case-control association study

Catechol-O-methyltransferase (COMT) has been suggested to be involved in the pathogenesis and pharmacological treatment of affective disorders. The nonsynonymous single nucleotide polymorphism (SNP) in exon 4 (Val108/158Met; rs4680) influences the COMT enzyme activity. Inconsistent results were found between Val158Met polymorphism (rs4680) and treatment response phenotypes in genetic association studies. However, the haplotype combinations of alleles at the Val108/158Met SNP with the other synonymous SNPs in the COMT gene region have shown association between enzyme activity/amount and COMT-dependent phenotypes. We carried out this study to define the functional impact of COMT genotypes/haplotypes on susceptibility and on treatment response phenotypes of major depressive disorder (MDD). Three hundred and ninety-six patients with MDD diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition [(DSM)-IV] and 295 healthy controls were recruited for this study and genotyped for the seven COMT SNPs (rs2075507, rs737865, rs6269, rs4633, rs4818, rs4680, and rs165599). This is the first study with all these SNPs to investigate for MDD and treatment response phenotypes. Our results show that none of the seven SNPs, including the rs4680, was significantly associated with MDD after permutation correction in single SNP analyses. Although several haplotype combinations showed significance, the combinations of G-T-G-G haplotype for rs6269, rs4633, rs4818 and rs4680 were only present in the MDD group (G-T 4.5%, corrected sim P=0.0001; G-T-G 3.87%, corrected sim P=0.001; G-T-G-G 3.3% corrected sim P=0.0025). In the treatment response phenotypes, the GG genotype of the rs2075507 SNP (located in the promoter region of MB-COMT) was less common in resistant patients in a single SNP analysis with low corrected sim P=0.052 and power=0.086. However, in the haplotype analysis, the haplotypes of exonic SNPs, rs4633, rs4818, and rs4680, were related to the treatment response phenotypes investigated, especially the phenotype of the response to antidepressant treatment. The C-C-A haplotype of these SNPs was overrepresented (almost four-and eight-fold) in the responders compared with the nonresponders and controls, respectively, after Bonferroni correction (corrected sim P=0.048, 0.0001, respectively). Both nonsynonymous and synonymous SNPs within haplotypes may be more relevant than the single SNP in conferring MDD susceptibility and treatment response phenotypes. Despite the limited power of our analysis, this finding suggests that the polymorphic COMT gene that influences catecholaminergic neurotransmission may play a role in the individual response to antidepressants.

Pharmacogenetics and psychoactive drug therapy: ready for the patient?

Psychiatry is one of the most promising areas for bringing pharmacogenomics to the patient. Psychiatric disorders such as depression and schizophrenia contribute significantly to worldwide morbidity and mortality. Forecasts rank depression second only to ischemic heart disease by 2020. In depression and schizophrenia, 30% to 50% of all patients do not respond sufficiently to the initial treatment regime. Genetic variability has been demonstrated to play an important role in the response to pharmacotherapy. Most data are available with regard to polymorphisms in the genes coding for drug-metabolizing enzymes and recommendations for the choice of personalized dosages based on genotyping results are available. Clinical outcome, in particular adverse effects, has been shown to correlate with the results from genotyping. Incorporating pharmacogenomics into clinical practice has, however, been slow and it is still not clear in which clinical situations genotyping should be performed and what the benefit of such procedures could be beyond therapeutic drug monitoring. Additionally, many studies in psychiatry focus on genetic variation in candidate genes of drug targets. However, despite promising reports, no clear recommendation can be given at present to perform such testing in clinical use.

Pharmacological, neurochemical, and behavioral profile of JB-788, a new 5-HT1A agonist

A novel pyridine derivative, 8-{4-[(6-methoxy-2,3-dihydro-[1,4]dioxino[2,3-b]pyridine-3-ylmethyl)-amino]-butyl}-8-aza-spiro[4.5]decane-7,9-dione hydrochloride, termed JB-788, was designed to selectively target 5-HT(1A) receptors. In the present study, the pharmacological profile of JB-788 was characterized in vitro using radioligands binding tests and in vivo using neurochemical and behavioural experiments. JB-788 bound tightly to human 5-HT(1A) receptor expressed in human embryonic kidney 293 (HEK-293) cells with a K(i) value of 0.8 nM. Its binding affinity is in the same range as that observed for the (+/-)8-OH-DPAT, a reference 5HT(1A) agonist compound. Notably, JB-788 only bound weakly to 5-HT(1B) or 5-HT(2A) receptors and moreover the drug displayed only weak or indetectable binding to muscarinic, alpha(2), beta(1) and beta(2) adrenergic receptors, or dopaminergic D(1) receptors. JB-788 was found to display substantial binding affinity for dopaminergic D(2) receptors and, to a lesser extend to alpha(1) adrenoreceptors. JB-788 dose-dependently decreased forskolin-induced cAMP accumulation in HEK cells expressing human 5-HT(1A), thus acting as a potent 5-HT(1A) receptor agonist (E(max.) 75%, EC(50) 3.5 nM). JB-788 did not exhibit any D(2) receptor agonism but progressively inhibited the effects of quinpirole, a D(2) receptor agonist, in the cAMP accumulation test with a K(i) value of 250 nM. JB-788 induced a weak change in cAMP levels in mouse brain but, like some antipsychotics, transiently increased glycogen contents in various brain regions. Behavioral effects were investigated in mice using the elevated plus-maze. JB-788 was found to increase the time duration spent by animals in anxiogenic situations. Locomotor hyperactivity induced by methamphetamine in mouse, a model of antipsychotic activity, was dose-dependently inhibited by JB-788. Altogether, these results suggest that JB-788 displays pharmacological properties, which could be of interest in the area of anxiolytic and antipsychotic drugs.

Pharmacogenetics--genomics and personalized psychiatry

Pharmacogenetic influences on therapeutic response to e.g. antidepressant or neuroleptic treatment are poorly understood and the lack of efficacy in many of the patients together with side effects can both limit therapy and compliance. Thus the aim of pharmacogenetics and pharmacogenomics is to provide predictive tools for the response to psychopharmacologic agents in the therapy of psychiatric disorders and in that ways to provide a real personalized psychiatry. The following review will summarize the current stage of pharmacogenetics and pharmacogenomics and will critically discuss the possibilities of a personalized medicine.

The intersection of pharmacology, imaging, and genetics in the development of personalized medicine

We currently rely on large randomized trials and meta-analyses to make clinical decisions; this places us at a risk of discarding subgroup or individually specific treatment options owing to their failure to prove efficacious across entire populations. There is a new era emerging in personalized medicine that will focus on individual differences that are not evident phenomenologically. Much research is directed towards identifying genes, endophenotypes, and biomarkers of disease that will facilitate diagnosis and predict treatment outcome. We are at the threshold of being able to predict treatment response, primarily through genetics and neuroimaging. In this review we discuss the most promising markers of treatment response and adverse effects emerging from the areas of pharmacogenetics and neuroimaging in depression and schizophrenia.