No Evidence for an Association between Dopamine D2 Receptor Polymorphisms and Tardive Dyskinesia in Korean Schizophrenia Patients

Genetic Factors Associated With Tardive Dyskinesia: From Pre-clinical Models to Clinical Studies

Tardive dyskinesia is a severe motor adverse event of antipsychotic medication, characterized by involuntary athetoid movements of the trunk, limbs, and/or orofacial areas. It affects two to ten patients under long-term administration of antipsychotics that do not subside for years even after the drug is stopped. Dopamine, serotonin, cannabinoid receptors, oxidative stress, plasticity factors, signaling cascades, as well as CYP isoenzymes and transporters have been associated with tardive dyskinesia (TD) occurrence in terms of genetic variability and metabolic capacity. Besides the factors related to the drug and the dose and patients’ clinical characteristics, a very crucial variable of TD development is individual susceptibility and genetic predisposition. This review summarizes the studies in experimental animal models and clinical studies focusing on the impact of genetic variations on TD occurrence. We identified eight genes emerging from preclinical findings that also reached statistical significance in at least one clinical study. The results of clinical studies are often conflicting and non-conclusive enough to support implementation in clinical practice.

Candidate Genes Encoding Dopamine Receptors as Predictors of the Risk of Antipsychotic-Induced Parkinsonism and Tardive Dyskinesia in Schizophrenic Patients

(1) Introduction: Extrapyramidal disorders form the so-called extrapyramidal syndrome (EPS), which is characterized by the occurrence of motor disorders as a result of damage to the basal ganglia and the subcortical-thalamic connections. Often, this syndrome develops while taking medications, in particular antipsychotics (APs). (2) Purpose: To review studies of candidate genes encoding dopamine receptors as genetic predictors of development of AP-induced parkinsonism (AIP) and AP-induced tardive dyskinesia (AITD) in patients with schizophrenia. (3) Materials and Methods: A search was carried out for publications of PubMed, Web of Science, Springer, and e-Library databases by keywords and their combinations over the last 10 years. In addition, the review includes earlier publications of historical interest. Despite extensive searches of these commonly used databases and search terms, it cannot be ruled out that some publications were possibly missed. (4) Results: The review considers candidate genes encoding dopamine receptors involved in pharmacodynamics, including genes DRD1, DRD2, DRD3, and DRD4. We analyzed 18 genome-wide studies examining 37 genetic variations, including single nucleotide variants (SNVs)/polymorphisms of four candidate genes involved in the development of AIP and AITD in patients with schizophrenia. Among such a set of obtained results, only 14 positive associations were revealed: rs1799732 (141CIns/Del), rs1800497 (C/T), rs6275 (C/T), rs6275 (C/T) DRD2; rs167771 (G/A) DRD3 with AIP and rs4532 (A/G) DRD1, rs6277 (C/T), rs6275 (C/T), rs1800497 (C/T), rs1079597 (A/G), rs1799732 (141CIns/Del), rs1045280 (C/G) DRD2, rs6280 (C/T), rs905568 (C/G) DRD3 with AITD. However, at present, it should be recognized that there is no final or unique decision on the leading role of any particular SNVs/polymorphisms in the development of AIP and AITD. (5) Conclusion: Disclosure of genetic predictors of the development of AIP and AITD, as the most common neurological adverse drug reactions (ADRs) in the treatment of patients with psychiatric disorders, may provide a key to the development of a strategy for personalized prevention and treatment of the considered complication of AP therapy for schizophrenia in real clinical practice.

Association between the IL10 rs1800896 Polymorphism and Tardive Dyskinesia in Schizophrenia

OBJECTIVE

Interleukin-10 (IL-10) is a major immunoregulatory cytokine and its gene plays a fundamental role in anti-inflammatory and immunosuppressive activity. This study aimed to examine the association between the IL10 gene promoter -1082G/A polymorphism (rs1800896) and tardive dyskinesia (TD) in schizophrenia.

METHODS

Two hundred and eighty unrelated Korean schizophrenic patients participated in this study (105 TD and 175 non-TD patients). TD was diagnosed using the Research Diagnostic Criteria for TD and Abnormal Involuntary Movement Scale (AIMS). Genotyping was performed by RT-PCR and high-resolution melting curve analysis.

RESULTS

The distributions of genotypic frequencies did not differ between patients with and without TD (χ2=4.33, p=0.115). However, allelic frequencies of the two groups were different (χ2=4.45, p=0.035); the A allele frequency was higher in TD. The total AIMS scores of the three genotypes were not different (F=1.33, p=0.266). However, the total AIMS scores of the A allele carrier and the A allele non-carrier were significantly different (t=5.79, p<0.001). Logistic regression analaysis showed that IL10 -1082G/A genotype significantly predicts presence of TD (p=0.045) after adjusting for covariates such as age and treatment duration.

CONCLUSION

This finding suggests that the A allele of rs1800896 may be associated with TD development following a low IL-10 function.

Genetics of tardive dyskinesia: Promising leads and ways forward

Tardive dyskinesia (TD) is a potentially irreversible and often debilitating movement disorder secondary to chronic use of dopamine receptor blocking medications. Genetic factors have been implicated in the etiology of TD. We therefore have reviewed the most promising genes associated with TD, including DRD2, DRD3, VMAT2, HSPG2, HTR2A, HTR2C, and SOD2. In addition, we present evidence supporting a role for these genes from preclinical models of TD. The current understanding of the etiogenesis of TD is discussed in the light of the recent approvals of valbenazine and deutetrabenazine, VMAT2 inhibitors, for treating TD.

Pharmacogenetics of tardive dyskinesia: an updated review of the literature

Tardive dyskinesia (TD) is a serious and potentially irreversible side effect of long-term exposure to antipsychotic medication characterized by involuntary trunk, limb and orofacial muscle movements. Various mechanisms have been proposed for the etiopathophysiology of antipsychotic-induced TD in schizophrenia patients with genetic factors playing a prominent role. Earlier association studies have focused on polymorphisms in CYP2D6, dopamine-, serotonin-, GABA- and glutamate genes. This review highlights recent advances in the genetic investigation of TD. Recent promising findings were obtained with the HSPG2, DPP6, MTNR1A, SLC18A2, PIP5K2A and CNR1 genes. More research, including collection of well-characterized samples, enhancement of genome-wide strategies, gene–gene interaction and epigenetic analyses, is needed before genetic tests with clinical utility can be made available for TD.

Genetics of Common Antipsychotic-Induced Adverse Effects

The effectiveness of antipsychotic drugs is limited due to accompanying adverse effects which can pose considerable health risks and lead to patient noncompliance. Pharmacogenetics (PGx) offers a means to identify genetic biomarkers that can predict individual susceptibility to antipsychotic-induced adverse effects (AAEs), thereby improving clinical outcomes. We reviewed the literature on the PGx of common AAEs from 2010 to 2015, placing emphasis on findings that have been independently replicated and which have additionally been listed to be of interest by PGx expert panels. Gene-drug associations meeting these criteria primarily pertain to metabolic dysregulation, extrapyramidal symptoms (EPS), and tardive dyskinesia (TD). Regarding metabolic dysregulation, results have reaffirmed HTR2C as a strong candidate with potential clinical utility, while MC4R and OGFR1 gene loci have emerged as new and promising biomarkers for the prediction of weight gain. As for EPS and TD, additional evidence has accumulated in support of an association with CYP2D6 metabolizer status. Furthermore, HSPG2 and DPP6 have been identified as candidate genes with the potential to predict differential susceptibility to TD. Overall, considerable progress has been made within the field of psychiatric PGx, with inroads toward the development of clinical tools that can mitigate AAEs. Going forward, studies placing a greater emphasis on multilocus effects will need to be conducted.

[Pharmacogenetic-based risk assessment of antipsychotic-induced extrapyramidal symptoms]

"Typical" antipsychotics remain the wide-prescribed drugs in modern psychiatry. But these drugs are associated with development of extrapyramidal symptoms (EPS). Preventive methods of EPS are actively developed and they concentrate on personalized approach. The method of taking into account genetic characteristics of patient for prescribing of treatment was proven as effective in cardiology, oncology, HIV-medicine. In this review the modern state of pharmacogenetic research of antipsychotic-induced EPS are considered. There are pharmacokinetic and pharmacodynamic factors which impact on adverse effects. Pharmacokinetic factors are the most well-studied to date, these include genetic polymorphisms of genes of cytochrome P450. However, evidence base while does not allow to do the significant prognosis of development of EPS based on genetic testing of CYP2D6 and CYP7A2 polymorphisms. Genes of pharmacodynamics factors, which realize the EPS during antipsychotic treatment, are the wide field for research. In separate part of review research of such systems as dopaminergic, serotonergic, adrenergic, glutamatergic, GABAergic, BDNF were analyzed. The role of oxidative stress factors in the pathogenesis of antipsychotic-induced EPS was enough detailed considered. The system of those factors may be used for personalized risk assessment of antipsychotics' safety in the future. Although there were numerous studies, the pharmacogenetic-based prevention of EPS before prescribing of antipsychotics was not introduced. However, it is possible to distinguish the most perspectives markers for further research. Furthermore, brief review of new candidate genes provides here, but only preliminary results were published. The main problem of the field is the lack of high- quality studies. Moreover, the several results were not replicated in repeat studies. The pharmacogenetic-based research must be standardized by ethnicity of patients. But there is the ethnical misbalance in world literature. These facts explain why the introduction of pharmacogenetic testing for risk assessment of antipsychotic-induced EPS is so difficult to achieve.

Clinical significance of pharmacogenomic studies in tardive dyskinesia associated with patients with psychiatric disorders

Pharmacogenomics is the study of the effects of genetic polymorphisms on medication pharmacokinetics and pharmacodynamics. It offers advantages in predicting drug efficacy and/or toxicity and has already changed clinical practice in many fields of medicine. Tardive dyskinesia (TD) is a movement disorder that rarely remits and poses significant social stigma and physical discomfort for the patient. Pharmacokinetic studies show an association between cytochrome P450 enzyme-determined poor metabolizer status and elevated serum antipsychotic and metabolite levels. However, few prospective studies have shown this to correlate with the occurrence of TD. Many retrospective, case-control and cross-sectional studies have examined the association of cytochrome P450 enzyme, dopamine (receptor, metabolizer and transporter), serotonin (receptor and transporter), and oxidative stress enzyme gene polymorphisms with the occurrence and severity of TD. These studies have produced conflicting and confusing results secondary to heterogeneous inclusion criteria and other patient characteristics that also act as confounding factors. This paper aims to review and summarize the pharmacogenetic findings in antipsychotic-associated TD and assess its clinical significance for psychiatry patients. In addition, we hope to provide insight into areas that need further research.

Gaba transporter SLC6A11 gene polymorphism associated with tardive dyskinesia

BACKGROUND

Gamma-aminobutyric acid (GABA) insufficiency has been reported to be related to the tardive dyskinesia (TD) susceptibility. Inada et al. (Pharmacogenet Genomics 2008;18:317-23) identified eight genes belonging to GABA receptor signaling pathway that may be involved in TD susceptibility by genome-wide screening and they replicated associations in an independent sample for polymorphisms in SLC6A11 (GABA transporter 3), GABRG3 (c-3 subunit of GABA-A receptor) and GABRB2 (β-2 subunit of GABA-A receptor). In this study, we tried to replicate their finding in a larger Korean sample and find if any of the genes was associated with the susceptibility to TD.

METHODS

We selected three polymorphisms in SLC6A11 (rs4684742), GABRG3 (rs2061051) and GABRB2 (rs918528) from the previous study. We carried out a case-control study (105 TD and 175 non-TD schizophrenic patients) to identify the association between the three candidate polymorphisms and susceptibility to TD and their epistatic interactions by using the multifactor dimensionality reduction (MDR) algorithm.

RESULTS

Among the three variants, SCL6A11 genotypes distribution showed a significant difference between the TD and non-TD patients (P = 0.049). However, GABRG3 and GABRB2 genotype distributions were not associated with TD (P = 0.268 and P = 0.976, respectively). Further, our analyses provided significant evidence for gene-gene interactions (SCL6A11, GABRG3 and GABRB2) in the development of TD. The odds ratio increased to 2.53 (CI = 1.515-4.217, P = 0.0003) when the genetic susceptibility to TD was analyzed with the three genes considered altogether through MDR approach.

CONCLUSION

These results suggest that GABA receptor signaling pathway was associated with the increased susceptibility to TD in Korean schizophrenic patients.

Loss of dopamine neuron terminals in antipsychotic-treated schizophrenia; relation to tardive dyskinesia

The in vivo labeling and brain imaging of dopamine transporters measure the density of dopamine neuron terminals in the human caudate/putamen. A review of such studies shows that the long-term use of antipsychotics had no major effect on the density of the dopamine terminals in individuals who had no tardive dyskinesia, but had reduced the density in those patients with tardive dyskinesia. In addition, the normal loss of dopamine terminals in healthy individuals was approximately 5% per decade. However, this rate of cell loss was apparently increased by approximately three-fold, to about 15% per decade, in schizophrenia patients using antipsychotics on a long-term basis, as measured by the in vivo imaging of the dopamine transporters in the dopamine neuron terminals. While an apparent reduction in dopamine transporters may result from reduced expression of the transporters secondary to antipsychotic treatment, the seemingly increased loss rate is consistent with the accumulation of antipsychotics in the neuromelanin of the substantia nigra, subsequent injury to the dopamine-containing neurons, and the development of extrapyramidal motor disturbances such as tardive dyskinesia or Parkinson's disease.

There is no evidence for an association between the serotonin receptor 3A gene C178T polymorphism and tardive dyskinesia in Korean schizophrenia patients

BACKGROUND

Tardive dyskinesia (TD) is a potential adverse effect of long-term treatment with antipsychotics. Previous studies have suggested a link between brain serotonergic systems and TD vulnerability. A recent report described that a serotonin 3 receptor (5-HTR3) agonist induced rhythmic movements in mice with complete paraplegia. Furthermore, it has been reported that the 5-HTR3 antagonist ondansetron is efficacious in the treatment of Gilles de la Tourette syndrome (GTS).

AIM

The aim of the present study was to determine whether the 5-HTR3A gene C178T polymorphism is associated with antipsychotic-induced TD in Korean schizophrenia patients.

METHODS

We investigated 280 Korean schizophrenia patients. Subjects with TD (n = 105) and without TD (n = 175) were matched for antipsychotic drug exposure and other relevant variables.

RESULTS

The distributions of genotypic (chi-squared = 3.55, p = 0.169) and allelic (chi-squared = 0.40, p = 0.528) frequencies did not differ between patients with and without TD. The total score on the Abnormal Involuntary Movement Scale also did not differ between the two genotype groups (F = 0.94, p = 0.391).

CONCLUSIONS

The findings of the present study do not support the involvement of the 5-HTR3A gene C178T polymorphism in TD in Korean schizophrenia subjects.

No association between PAWR gene polymorphisms and tardive dyskinesia in schizophrenia patients

Tardive dyskinesia (TD) is a hyperkinetic movement disorder associated with the prolonged use of antipsychotic drugs. Since prostate apoptosis response 4 (Par-4) is a key ligand of the dopamine D2 receptor, the Par-4 gene (PAWR) is a good candidate gene to study in the context of TD susceptibility. We examined the association between PAWR gene polymorphisms and TD. Three single nucleotide polymorphisms of PAWR were selected for the analysis: rs7979987, rs4842318, and rs17005769. Two hundred and eighty unrelated Korean schizophrenic patients participated in this study (105 TD and 175 non-TD patients). Genotype/allele-wise and haplotype-wise analyses were performed. There were no significant differences in genotype and allele frequencies between the two groups. Haplotype analysis also did not reveal a difference between the two groups. Within the limitations imposed by the size of the clinical sample, these findings suggest that PAWR gene variants do not significantly contribute to an increased risk of TD.

Genetics of tardive dyskinesia

Tardive dyskinesia (TD) is one of the most serious adverse side effects of antipsychotic drugs and is an important topic of pharmacogenetic studies. Since there is a genetic susceptibility for developing this adverse reaction, and given that it is hard to predict its development prior to or during the early period of medication, the genetic study of TD is a promising research topic that has a direct clinical application. Moreover, such studies would improve our understanding of the genetic mechanism(s) underlying abnormal dyskinetic movement. A substantial number of case-control association studies of TD have been performed, with numbers of studies focusing on the genes involved in antipsychotic drug metabolism, such as those for cytochrome P450 (CYP) and oxidative stress related genes as well as various neurotransmitter related genes. These studies have produced relatively consistent though controversial findings for certain polymorphisms such as CYP2D6*10, DRD2 Taq1A, DRD3 Ser9Gly, HTR2A T102C, and MnSOD Ala9Val. Moreover, the application of the genome-wide association study (GWAS) to the susceptibility of TD has revealed certain associated genes that previously were never considered to be associated with TD, such as the rs7669317 on 4q24, GLI2 gene, GABA pathway genes, and HSPG2 gene. Although a substantial number of genetic studies have investigated TD, many of the positive findings have not been replicated or are inconsistent, which could be due to differences in study design, sample size, and/or subject ethnicity. We expect that more refined research will be performed in the future to resolve these issues, which will then enable the genetic prediction of TD and clinical application thereof.