Oxidative mechanisms and tardive dyskinesia

Unique and overlapping mechanisms of valbenazine, deutetrabenazine, and vitamin E for tardive dyskinesia

In 2017, the Food and Drug Administration (FDA) approved valbenazine and deutetrabenazine, two vesicular monoamine transporter 2 (VMAT2) inhibitors, as treatments for tardive dyskinesia (TD). Additionally, some trials have suggested that vitamin E may benefit TD patients. However, the mechanistic basis for these treatments remains unclear. The objective of this study was to analyze and compare the mechanisms of valbenazine, deutetrabenazine, and vitamin E in TD treatment utilizing network pharmacology and molecular docking approaches. Putative target genes associated with valbenazine, deutetrabenazine, and vitamin E were retrieved from the PharmMapper, CTD, GeneCards, SwissTargetPrediction, and DrugBank databases. TD-related targets were identified using the GeneCards, DisGeNET, OMIM, and TTD databases. A protein-protein interaction (PPI) network was created to identify core targets. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were conducted via DAVID, and Cytoscape was used to build a drug-pathway-target-disease network. Molecular docking evaluated drug-target interactions. A total of 32, 36, and 62 targets relevant to the treatment of TD were identified for valbenazine, deutetrabenazine, and vitamin E, respectively. PPI and KEGG pathway analyses suggested that valbenazine and deutetrabenazine may influence TD through the dopaminergic synapse signaling pathway via common core targets (e.g., Dopamine Receptor D1 (DRD1), DRD2, Monoamine Oxidase B (MAOB), Solute Carrier Family 6 Member 3 (SLC6A3), SLC18A2) and specific targets (DRD3 for valbenazine, MAOA for deutetrabenazine). Vitamin E may affect TD by targeting the PI3K-Akt pathway through AKT Serine/Threonine Kinase 1 (AKT1), Brain-Derived Neurotrophic Factor (BDNF), Insulin (INS), Nitric Oxide Synthase 3 (NOS3), and Toll-Like Receptor 4 (TLR4). This study provides insights into the common and unique molecular mechanisms by which valbenazine, deutetrabenazine, and vitamin E may treat TD. Pharmacological experiments should be conducted to verify and further explore these results. The findings offer a theoretical basis for further pharmacological investigation and a resource for TD drug screening.

Molecular and Behavioral Neuroprotective Effects of Clavulanic Acid and Crocin in Haloperidol-Induced Tardive Dyskinesia in Rats

Clavulanic acid (ClvA), a beta-lactamase inhibitor, is being explored for its significant neuroprotective potential. The effects of ClvA were assessed both individually and in combination with crocin (Cr), an antioxidant derived from saffron, in the context of tardive dyskinesia (TD). In rat haloperidol (Hp)-induced-TD (1 mg/kg, i.p. 21 days), the effects of ClvA (50, 100, 150 mg/kg) and Cr (10, 20, 40 mg/kg) were assessed via vacuous chewing movements (VCM) and tongue protrusion (TP). Striatal malondialdehyde (MDA) and glutathione (GSH) were measured spectrophotometrically. Based on the results, ClvA (100 mg/kg) and Cr (10 mg/kg) were determined with sub-effective doses. Glutamate transporter-subtype1 (GLT1), dopamine active transporter (DAT), vesicular monoamine transporter-type2 (VMAT2), Bax/Bcl2, cleaved Caspase3, phosphorylated AKT/AKT, IL1β, and TNFα levels were quantified using western blotting in sub-effective doses and their combination. The behavioral results of catalepsy and orofacial dyskinesia demonstrated model establishment. Hp decreased GLT1 (p < 0.05), DAT (p < 0.01), VMAT2 (p < 0.001), GSH and pAKT/AKT (p < 0.0001); increased TNFα (p < 0.05), IL1β, cleaved Caspase3 (p < 0.001); MDA and Bax/Bcl2 (p < 0.0001). ClvA 100 mg/kg reversed the decreased GLT1 and VMAT2 (p < 0.01), alongside the increased MDA (p < 0.0001) and VCM (p < 0.05). It also increased AKT phosphorylation (p < 0.05). No effects were noted on DAT, GSH, Bax/Bcl2, or inflammatory factors. However, the combination with Cr at 10 mg/kg influenced ClvA on DAT (p < 0.01) and resulted in a significant increase in GSH (p < 0.0001). Additionally, there was a marked decrease in TNFα (p < 0.0001) and IL1β (p < 0.001), enhancing its effects on reducing MDA and increasing pAKT/AKT (p < 0.0001). The combination adversely affected GLT1. ClvA protects against TD via GLT1 and VMAT2; combined with Cr, it enhances antioxidant effects, improves DAT, and requires dose optimization for GLT1 disruption.

Aqueous and Ethanol Extracts of Acacia sieberiana (Fabaceae) Stem Bark Reverse the Pain-Depression Dyad in Mice Through Modulation of Catecholamines, Proinflammatory Cytokines, and Oxidative Stress

Rationale and Objective: The pain-depression dyad is highly prevalent and has reciprocal psychological and behavioral effects, leading to poor quality of life, increased disability, and challenging therapeutic outcomes. In an attempt to find better substances that can target pain-depression comorbidity, we examined the effect of aqueous (AE) and ethanol (EE) extracts from Acacia sieberiana (A. sieberiana) stem bark on reserpinized mice (female and male Swiss albino mice aged 2-3 months). Methods: The dyad was induced with 3 injections (Days 1-3) of reserpine (1 mg/kg/day, s.c.). Then, animals were treated (Days 4-8) with plant extracts (25, 50 and 100 mg/kg/day, p.o.) or L-tryptophane (100 mg/kg/day, i.p.). Pain-like (tactile and cold allodynia) and depression-like (pole, tail suspension, and force swimming tests) behavioral parameters were evaluated on Days 4 and 8. On Day 9, animals were sacrificed for the quantification of acetylcholinesterase activity, oxidative stress parameters, total catecholamines, dopamine, serotonin, IL-1β, and TNF-α levels in the brain or spinal cord. IL-1β and TNF-α were also assayed in the serum. The acute toxicity and phytochemical analysis of EE were conducted. Results: Reserpine-induced tactile and cold allodynia, depression-like behavior, increased serum IL-1β and TNF-α, brain acetylcholinesterase activity, and decreased catecholamine concentration were all reversed by AE and EE. Plant extracts significantly increased dopamine levels and reduced oxidative stress in the brain and/or spinal cord. No significant effect was observed on brain serotonin and TNF-α. EE elicited the best pharmacological activity and was nontoxic. LC-MS/MS molecular networking phytochemical analysis identified 5 compounds with high certainty including piperine, aurantiamide acetate, and asperphenamate. Conclusion: AE and EE are effective against pain and depression. Their pharmacological activities might be related to the modulation of inflammation, oxidative stress and catecholamine, and the presence of bioactive natural products.

Plasma Metabolic Characteristics and Potential Biomarker Combinations in Schizophrenia Patients With Tardive Dyskinesia

BACKGROUND AND HYPOTHESIS

The pathogenesis of tardive dyskinesia (TD) remains unclear, involving multiple biological pathways. This study aimed to explore biomarkers of TD through untargeted metabolomics for the early identification of TD.

STUDY DESIGN

This study recruited 84 schizophrenia (SZ) patients with TD and 160 SZ patients without TD. TD diagnosis was based on the Schooler-Kane criteria, and the severity of TD and psychiatric symptoms were assessed using the Abnormal Involuntary Movement Scale and the Positive and Negative Syndrome Scale. Fasting blood samples were collected from all patients and subjected to untargeted metabolomics analysis using Ultra-high-performance liquid chromatography-high resolution mass spectrometry, allowing for the quantification and profiling of 699 metabolites. Data were analyzed with orthogonal partial least squares discriminant analysis, and receiver-operating characteristic curves.

STUDY RESULTS

In TD, 57 metabolites exhibited significant changes (variable importance of projection > 1, false discovery rate-adjusted P < .05), primarily involving amino acids and lipids. These changes predominantly affected the phenylalanine, tyrosine, and tryptophan pathway (impact = 0.5, P = .0252), as well as the phenylalanine metabolism pathway (impact = 0.36, P = .0498). N-Acetyl-l-phenylalanine (B = 2.249, t = 4.56, P < .001, 95% CI, 1.302-3.286) and Succinylcarnitine (AcCa(4:0-DC)) (B = 1.009, t = 3.07, P = .002, 95% CI, 0.362-1.656) are negatively related to the total abnormal involuntary movement scale score. Additionally, 5 differential metabolites had area under the curve (AUC) values greater than 0.7 for diagnosing TD, with the combined diagnostic capability exceeding 0.8 (AUC = 0.817, 95% CI, 0.759-0.875).

CONCLUSIONS

In TD, disruptions in amino acid and lipid metabolism were predominantly observed. Amino acids and lipid metabolites may be involved in the development of TD. Additionally, a biomarker panel composed of amino acids and lipids can be used for the differential diagnosis of TD.

Milnacipran and Vanillin Alleviate Fibromyalgia-Associated Depression in Reserpine-Induced Rat Model: Role of Wnt/β-Catenin Signaling

Fibromyalgia (FM) patients are highly susceptible to depression. Wnt/β-catenin signaling has shown a crucial role against depression in several studies. The FDA-approved FM drug, milnacipran (Miln), has shown antinociceptive potential against FM. Yet, no study has investigated its antidepressant potential in FM. Vanillin (Van), a well-known phytochemical often employed as flavoring agent, has been previously reported for its antidepressant and antinociceptive effects in several animal models, but has not been tested so far in FM. This study explored the antidepressant effect of Van and Miln in FM through investigating Wnt/β-catenin signaling. FM was induced in female Wistar rats by injecting reserpine (1 mg/kg/day s.c) for 3 days. Thereafter, animals received either Miln (30 mg/kg/day p.o) or Van (100 mg/kg/day p.o) for the subsequent 14 days. Results showed that both drugs demonstrated antidepressant effect in forced swimming test besides analgesic, and antiallodynic influences observed in Randall-Selitto, hot plate, cold allodynia, Von-Frey, and tail immersion tests. Biochemically, Miln and Van significantly enhanced serotonergic transmission in the hippocampus and upregulated the protein expression of the Wnt/GSK-3β/β-catenin signaling axis, including the downstream proteins, T cell factor, and dicer. This is followed by subsequent upregulation of the resilience micro ribonucleic acids (miRNAs) 124 and 135. Histopathological examinations corroborated the biochemical and molecular findings. Interestingly, these effects of Miln and Van were overturned via administration of the β-catenin inhibitor, XAV939 (0.1 mg/kg, i.p., daily). In conclusion, this study outlined the antidepressant aptitude of Miln and Van through activating Wnt/β-catenin signaling in the hippocampus in reserpine-induced FM.

Associations between Catechol-O-methyltransferase (COMT) polymorphisms and cognitive impairments, psychiatric symptoms and tardive dyskinesia in schizophrenia

INTRODUCTION

Catechol-O-methyltransferase (COMT) is a crucial enzyme involved in dopamine metabolism and has been implicated in the etiology of tardive dyskinesia (TD). We aimed to investigate the associations between COMT gene polymorphisms and the occurrence and severity of TD in a Chinese population, as well as the impact on the psychiatric symptoms and cognitive impairments observed in TD patients.

METHODS

A total of 216 chronic schizophrenia patients, including 59 TD patients and 157 NTD patients, were recruited for this study. Three SNPs of the COMT gene (rs4680, rs165599 and rs4818) were selected and genotyped using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). TD severity, psychopathology and cognitive functioning were assessed using the Abnormal Involuntary Movement Scale (AIMS), the Positive and Negative Syndrome Scale (PANSS) and the Repeated Battery for Assessment of Neuropsychological Status (RBANS), respectively.

RESULTS

In TD patients, total AIMs scores were higher in carriers of the rs4680 AA genotype than in carriers of the AG and GG genotypes (p = 0.01, 0.006), carriers of the rs4818 GC and CC genotypes had higher orofacial scores than in GG genotypes (p = 0.032, 0.002). In male TD patients, carriers of the rs165599 GA genotype scored lower in the extremities and trunk scores than AA genotype carriers (p = 0.015). Moreover, in male TD patients, COMT rs4818 was associated with cognition, since the C allele carriers had significantly higher immediate memory (p = 0.043) and verbal function (p = 0.040) scores than the G allele carriers. In addition, rs165599 genotype interacted with TD diagnosis on depressed factor (p = 0.031).

CONCLUSION

Within the Chinese population, COMT gene polymorphisms could potentially serve as biomarkers for the symptoms and prognosis of TD patients.

Genetic Susceptibility to Tardive Dyskinesia and Cognitive Impairments in Chinese Han Schizophrenia: Role of Oxidative Stress-Related and Adenosine Receptor Genes

Objective

Tardive dyskinesia (TD) is a severe rhythmic movement disorder caused by long-term antipsychotic medication in chronic patients with schizophrenia (SCZ). We aimed to investigate the association between polymorphisms in oxidative stress-related genes (GSTM1, SOD2, NOS1, and NOS3) and adenosine receptor gene (ADORA2A), as well as their interactions, with the occurrence and severity of TD, and cognitive impairments in a Chinese Han population of SCZ patients.

Methods

Two hundred and sixteen SCZ patients were recruited and divided into TD group (n=157) and non-TD group (n=59). DNA extraction was performed by a high-salt method, followed by SNP genotyping using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The severity of TD, psychopathology and cognitive functioning were assessed using the Abnormal Involuntary Movement Scale (AIMS), the Positive and Negative Syndrome Scale (PANSS) and the Repeated Battery for Assessment of Neuropsychological Status (RBANS), respectively.

Results

The combination of GSTM1-rs738491, NOS1-rs738409 and ADORA2A-rs229883 was identified as the best three-point model to predict TD occurrence (p=0.01). Additionally, GSTM-rs738491 CC or NOS3-rs1800779 AG genotypes may be protective factors for psychiatric symptoms in TD patients. TD patients carrying the NOS1-rs738409 AG or ADORA2A-rs229883 TT genotypes exhibited poorer cognitive performance.

Conclusion

Our findings suggest that the interaction of oxidative stress-related genes and adenosine receptor gene may play a role in the susceptibility and severity of TD in Chinese Han SCZ patient. Furthermore, these genes may also affect the psychiatric symptoms and cognitive function of TD patients.

Putative role of immune reactions in the mechanism of tardive dyskinesia

The term extrapyramidal disorders is most often used for conditions such as Parkinson's disease or Huntington's disease, but also refers to a group of extrapyramidal side effects of antipsychotics (EPS), such as tardive dyskinesia (TD). After a brief description of some clinical features of TD, this article summarizes the relatively scarce results of research on a possible link between mainly cytokine levels and TD. This data was found by systematically searching Pubmed and Embase. The limitations of these types of studies are a major obstacle to interpretation. After describing relevant aspects of the neuroinflammatory response and the neuroanatomical backgrounds of EPS, a new hypothesis for the origin of TD is presented with emphasis on dysfunctions in the striosomal compartment of the striatum and the dorsal diencephalic connection system (DDCS). It is postulated that (partly immunologically-induced) increase in oxidative stress and the dopamine-dependent immune response in classic TD proceed primarily via the DDCS, which itself is activated from evolutionarily older parts of the forebrain. Neuroinflammatory responses in the choroid plexus of the third ventricle may contribute due to its proximity to the habenula. It is concluded that direct evidence for a possible role of inflammatory processes in the mechanism of TD is still lacking because research on this is still too much of a niche, but there are indications that warrant further investigation.

Historical developments, hotspots, and trends in tardive dyskinesia research: a scientometric analysis of 54 years of publications

Background

Since being recognized as an important drug-induced clinical entity during the 1960s, tardive dyskinesia (TD) has generated an extensive body of research seeking to understand its clinical characteristics, epidemiology, pathophysiology and management. Modern scientometric approaches allow interactive visualization of large bodies of literature to identify trends and hotspots within knowledge domains. This study thus aimed to provide a comprehensive scientometric review of the TD literature.

Methods

Web of Science was searched for articles, reviews, editorials and letters with the term "tardive dyskinesia" in the title, abstract, or keywords through 12/31/2021. A total of 5,228 publications and 182,052 citations were included. Annual research output, prominent research areas, authors, affiliations and countries were summarized. VOSViewer and CiteSpace were used for bibliometric mapping and co-citation analysis. Structural and temporal metrics were used to identify key publications in the network.

Results

TD-related publications peaked in the 1990s, gradually declined after 2004, and showed a further small increase after 2015. The most prolific authors were Kane JM, Lieberman JA, and Jeste DV overall (1968-2021), and Zhang XY, Correll CU and Remington G in the last decade (2012-2021). The most prolific journal was the Journal of Clinical Psychiatry overall, and the Journal of Psychopharmacology in the last decade. Knowledge clusters in the 1960-1970s dealt with clinical and pharmacological characterization of TD. In the 1980s, epidemiology, clinical TD assessment, cognitive dysfunction and animal models predominated. During the 1990s, research diverged into pathophysiological studies, especially oxidative stress, and clinical trials on atypical antipsychotics, with a focus on clozapine and bipolar disorder. In the 1990-2000s, pharmacogenetics emerged. More recent clusters include serotonergic receptors, dopamine-supersensitivity psychosis, primary motor abnormalities of schizophrenia, epidemiology/meta-analyses, and advances in TD treatment, particularly vesicular monoamine transporter-2 inhibitors since 2017.

Conclusion

This scientometric review visualized the evolution of scientific knowledge on TD over more than five decades. These findings will be useful for researchers to find relevant literature when writing scientific articles, choosing appropriate journals, finding collaborators or mentors for research, and to understand the historical developments and emerging trends in TD research.

Naringenin mitigates reserpine-induced anxiety-like behavior, neurodegeneration, and oxidative stress in male rats

Reserpine (Res) induces anxiety-like behaviors, orofacial dyskinesia, and neurodegeneration in animals, the pathophysiology of which has been related to oxidative stress. The purpose of this study was to investigate whether naringenin (NG) could prevent reserpine-induced anxiety-like behaviors, orofacial dyskinesia, and neurodegeneration in male rats. Twenty-eight male rats were distributed into different groups as follows: Control rats; vehicle rats, which received the vehicles (normal saline, orally; acetic acid, intraperitoneally); Res rats (1 mg/kg/day) every other day for 3 days; and Res + NG rats, which received NG (50 mg/kg, orally, pre-treatment for 7 days), followed by Res. Administration of Res significantly increased chewing frequency compared with the control group (P < 0.01) and NG reversed the effect of Res on this factor (P < 0.05). Res induced an anxiety-like behavior in rats in the plus maze, and pre-treatment with NG improved this behavior. In addition, Res significantly increased the level of oxidative stress markers and degenerated neurons in the striatum; NG was able to ameliorate these damages. The results of this study demonstrated that Res caused behavioral disorders and increased the levels of oxidative stress in male rats; the use of NG was effective in treating these disorders. Therefore, NG should be considered as a preventive agent for reserpine-induced brain damage in male rats.

α-Tocopherol Protects Lipopolysaccharide-Activated BV2 Microglia

Microglia, the resident macrophage-like population in the central nervous system, play a crucial role in the pathogenesis of many neurodegenerative disorders by triggering an inflammatory response that leads to neuronal death. Neuroprotective compounds to treat or prevent neurodegenerative diseases are a new field of study in modern medicine. Microglia are activated in response to inflammatory stimuli. The pathogenesis of various neurodegenerative diseases is closely related to the constant activation of microglia due to their fundamental role as a mediator of inflammation in the brain environment. α-Tocopherol, also known as vitamin E, is reported to possess potent neuroprotective effects. The goal of this study was to investigate the biological effects of vitamin E on BV2 microglial cells, as a possible neuroprotective and anti-inflammatory agent, following stimulation with lipopolysaccharide (LPS). The results showed that the pre-incubation of microglia with α-tocopherol can guarantee neuroprotective effects during microglial activation induced by LPS. α-Tocopherol preserved the branched morphology typical of microglia in a physiological state. It also reduced the migratory capacity; the production of pro-inflammatory and anti-inflammatory cytokines such as TNF-α and IL-10; and the activation of receptors such as TRL4 and CD40, which modulate the PI3K-Akt signaling pathway. The results of this study require further insights and research, but they present new scenarios for the application of vitamin E as an antioxidant for the purpose of greater neuroprotection in vivo for the prevention of possible neurodegenerative diseases.

Analysis of the Influence of IL-6 and the Activation of the Jak/Stat3 Pathway in Fibromyalgia

Background: Fibromyalgia is a medical condition that affects a small percentage of the population, with no known effective treatment. There is evidence to suggest that inflammation is a key factor in the nerve sensitization that characterizes the disorder. Therefore, this paper concentrates on the role of IL-6 in fibromyalgia and the related pain-like symptoms. Methods: This work aimed to evaluate Sprague–Dawley rats, which were injected for three consecutive days with 1 mg/kg of reserpine; IL-6-R Ab was intraperitoneally injected at 1.5 mg/kg seven days after the first reserpine injection. Behavioral analyses were conducted at the beginning of the experiment and at seven and twenty-one days from the first reserpine injection. At this timepoint, the animals were sacrificed, and tissues were collected for molecular and histological analysis. Results: Our data showed the analgesic effect of IL-6-R-Ab administration on mechanical allodynia and thermal hyperalgesia. Additionally, the reserpine + IL-6-R-Ab group showed a reduced expression of the pain-related mediators cFOS and NFG and reduced levels of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) and chemokines (Cxcl5, Cxcl10 and Cx3cl1). From the molecular point of view, the IL-6-R-Ab administration reduced the gp130 phosphorylation and the activation of the Jak/STAT3 pathway. Additionally, the IL-6-R Ab reduced the activation of neuroinflammatory cells. Conclusions: Our study showed that IL-6 plays a crucial role in fibromyalgia by triggering the Jak/STAT3 pathway, leading to an increase in chemokine levels and activating glial cells.

Alpha-lipoic acid-role in improving both reserpine toxicity and paroxetine treatment in the cerebral cortex of albino rats; histological, ultrastructural, immunohistohemical and biochemical studies

Background

Reserpine is a monoamine depletory drug cause oxidative damage and used to induce depression-like features in rodent model. Paroxetine is an antidepressant drug that exerts its effects by inhibiting dopaminergic neurons although it may exert much pathological damage. Alpha-lipoic acid (ALA) is an endogenous antioxidant co-factor of important enzymatic complexes. The present study was aimed to elucidate the possible protective effect of ALA in the improvement of the deleterious cerebral cortex injury after reserpine and paroxetine treatment. Forty adult male albino rats were equally divided into 5 groups. Group I served as control group orally treated with saline solution all the experiment period. Group II animals orally treated with ALA (200 mg/kg/day) for six weeks. The induction of depression-like features occurred when the rest of animals were intraperitoneally treated with 25 mg/kg of reserpine once daily for consecutive 14 day. Then these animals were divided into; Group III (reserpine group) animals in this group were sacrificed on 15th day. Group IV; reserpine-treated animals were treated with paroxetine (20 mg/kg) daily for 6 weeks. Group V, animals in this group were received paroxetine and ALA daily for 6 weeks.

Results

Reserpine-treated rats showed disorganized layers of cerebral cortex with degenerative, apoptotic and necrotic changes. Ultrastructure changes include both pyramidal and granule cells with severe degenerative, necrotic and apoptotic features. The nuclei appeared pyknotic; irregular with chromatin condensation as well as the cytoplasm of these cells contained many degenerated organelles. In addition, a significant increase in total oxidative stress and decrease in total antioxidant capacity, norepinephrine, dopamine and serotonin levels were recorded. The same treatment showed significant decrease in proliferating cell nuclear antigen (PCNA) expression and significant increase in caspase-3 expression in the granule and pyramidal cells. After paroxetine-treatment these parameters were more or less similar to those observed in reserpine-treated ones. While an obvious improvement was appeared when animal treated with both paroxetine and ALA and; all parameters restored its normal features.

Conclusions

This study concluded that; ALA treatment attenuated the cerebral injury induced by reserpine and improved the effects of paroxetine in rats due to its anti-inflammatory, anti-apoptotic and antioxidant activities.

Pathophysiology, prognosis and treatment of tardive dyskinesia

Tardive dyskinesia (TD), a movement disorder associated with antipsychotics, most frequently affects the lower face and jaw muscles, but can also affect walking, breathing and use of the hands and limbs. Knowledge of TD among physicians may be limited, and the pathophysiology of TD is poorly understood. We conducted this review to summarise the current knowledge surrounding the pathophysiology of TD and present recommendations for prevention and treatment based on a literature search and roundtable discussion attended by psychiatrists in Japan. It has been suggested that dopamine hypersensitivity, damaged gamma-aminobutyric acidergic neurons and/or increased production of reactive oxygen species may contribute to development of TD. Symptoms can profoundly affect everyday life; patients who develop TD have poorer prognoses, worse health-related quality of life, greater social withdrawal and higher mortality than patients without TD. Traditional treatment options include dietary supplements, although evidence for their effectiveness is low. Among pharmaceutical interventions, there is moderate evidence that switching to the second-generation antipsychotic clozapine, which has a lower affinity for dopamine D2 receptors than other antipsychotics, may improve symptoms. Vesicular monoamine transporter 2 (VMAT-2) inhibitors, which oppose the increased dopaminergic activity associated with prolonged antipsychotic use by interfering with dopamine uptake and storage, have the strongest evidence for efficacy. VMAT-2 inhibitors are approved in the United States for the treatment of TD, and the first VMAT-2 inhibitor was approved in Japan for this indication in March 2022. Most guidelines recommend treating TD by first reducing the dose of antipsychotics or switching to clozapine or other second-generation antipsychotics, which have a lower association with TD than first-generation antipsychotics. We recommend focusing on prevention and monitoring for TD when prescribing antipsychotics, given that TD is often irreversible. Physicians should treat with antipsychotics only when necessary and at the lowest effective dose, and frequently monitor for TD symptoms.

Plain Language Summary

Plain Language Summary (In Japanese).

Visual Summary

Visual Summary (In Japanese).

Antioxidant Enzymes and Weight Gain in Drug-naive First-episode Schizophrenia Patients Treated with Risperidone for 12 Weeks: A Prospective Longitudinal Study

BACKGROUND

Oxidative stress plays an important role in weight gain induced by antipsychotics in schizophrenia (SCZ). However, little is known about how antioxidant enzymes are involved in weight gain caused by risperidone monotherapy in antipsychotics-naïve first-episode (ANFE) patients with SCZ. Therefore, the main purpose of this study was to investigate the effects of risperidone on several antioxidant enzymes in patients with ANFE SCZ and the relationship between weight gain and changes in antioxidant enzyme activities.

OBJECTIVE

The activities of plasma superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), as well as the levels of malondialdehyde (MDA) were measured in 225 ANFE patients and 125 healthy controls.

METHODS

Patients were treated with risperidone monotherapy for 12 weeks. Clinical symptoms, antioxidant enzyme activities, and MDA levels were measured at baseline and during follow-up.

RESULTS

Compared with healthy controls, the patients showed higher activities of SOD and CAT but lower MDA levels and GPx activity. At baseline, the CAT activity was associated with body weight or BMI. Further, based on a 7% weight increase from baseline to follow-up, we found 75 patients in the weight gain (WG) group and 150 patients in the non-WG group. Comparing SOD, CAT, GPx activities and MDA levels between the WG group and the non-WG group at baseline and during the 12-week follow-up, it was found that after treatment, the SOD activity in the WG group increased while the MDA level decreased in the non-WG group. Moreover, baseline SOD and GPx activities were predictors of weight gain at 12-week follow-up.

CONCLUSION

These results suggest that the antioxidant defense system may have predictive value for the weight gain of ANFE SCZ patients after risperidone treatment.

Association between Changes in Total Antioxidant Levels and Clinical Symptom Improvement in Patients with Antipsychotic-Naïve First-Episode Schizophrenia after 3 Months of Risperidone Monotherapy

Schizophrenia (SCZ) is associated with aberrant redox regulation in the early stages of brain development. There is growing evidence that the antioxidant defense system is closely associated with the therapeutic response to antipsychotics in SCZ patients. The aim of this study was to examine the effect of risperidone monotherapy on total antioxidant status (TAS) and the relationship between symptom improvement and changes in TAS in patients with antipsychotic-naïve first-episode (ANFE) SCZ. Clinical symptoms were evaluated using the Positive and Negative Syndrome Scale (PANSS). Two hundred and forty-six ANFE patients were treated with risperidone for 3 months. PANSS and TAS levels were assessed at baseline and at a 3-month follow-up. Relative to healthy controls, ANFE patients had higher TAS levels, which increased even further during the treatment. Moreover, baseline TAS levels were a predictor of symptom reduction after risperidone treatment. In addition, there was a significant association between increased TAS levels and the decreased cognitive factor. Our findings suggest that antioxidant protection is possibly associated with clinical improvement in ANFE patients after risperidone treatment.

Reserpine-induced altered neuro-behavioral, biochemical and histopathological assessments prevent by enhanced antioxidant defence system of thymoquinone in mice

Thymoquinone (Tq), an active compound of Nigella sativa, has been known for its anti-inflammatory, antioxidant, and neuroprotective characteristics. The present study is aimed to evaluate the effect of Tq on reserpine (Rsp)-induced behavioral (anxiety and/or depression) and, memory deficit; hippocampal inflammatory markers, oxidative markers, antioxidant enzymes, acetylcholinesterase (AChE) activity and histopathology in male mice. Animals were injected with Rsp at a dose of 2 mg/ml/kg and doses of Tq (10 and 20 mg/ml/kg) for 28 days. After the treatment period, behavioral tests [Elevated plus maze (Epm); Light dark box test (Lda); Morris water maze (Mwm); Forced swim test (Fst); Tail suspension test (Tst)] were conducted. After analysis of behaviors, mice were decapitated and brain samples were collected, the hippocampus was removed from the whole-brain sample for biochemical analysis and histology. Administration of Tq at both doses prevent adverse effects of Rsp and increased time spent in open arm and lightbox in Lda and Epm respectively, decreased immobility period in Fst and Tst, decreased latency escape in Mwm, reduced lipid peroxidation (lpo) and inflammatory cytokines, increased defensive enzymes, reduced acetylcholinesterase (AChE) activity and corrected histological lines. It is concluded that Rsp-instigated behavioral and memory deficits were prevented by Tq possibly via its strong antioxidant and anti-inflammatory effects.

Resveratrol prevents haloperidol-induced mitochondria dysfunction through the induction of autophagy in SH-SY5Y cells

BACKGROUND

Haloperidol is a commonly used antipsychotic drug and may increase neuronal oxidative stress associated with the side effects, including tardive dyskinesia and neurite withdraw. Autophagy plays a protective role in response to the accumulated reactive oxygen species (ROS) induced mitochondria damage. Resveratrol is an antioxidant compound having neuroprotective effects; however, it is unknown if resveratrol may stimulate autophagy and decrease mitochondria damage induced by haloperidol.

HYPOTHESIS

We hypothesis that resveratrol stimulates the autophagic process and protects mitochondria lesion induced by haloperidol.

METHODS

MitoSOX™ Red Mitochondrial Superoxide Indicator and MitoTracker™ Green FM staining were used to measure the amount of the mitochondria ROS production and mitochondria mass in human SH-SY5Y cells treated with haloperidol and/or resveratrol. Autophagic related dyes and Western blot were applied to study the autophagic process and related protein expression. Besides, tandem monomeric mRFP-GFP-LC3 was used to investigate the fusion of autophagosome and lysosome. Transmission electron microscopy was used to investigate the mitochondrial and autophagic ultrastructures with or without haloperidol and resveratrol treatment.

RESULTS

Haloperidol administration significantly increased mitochondria ROS and mitochondrial mass, indicating the increase of mitochondria dysfunction. Although haloperidol increased the autophagosomes and lysosome formation, the autophagosome-lysosome fusion and degradation were impaired. This was because we found an increased p62 after haloperidol treatment, an indication of autophagy incompletion. Importantly, resveratrol promoted the degradation of p62, upregulated the formation of autophagolysosome, and reversed haloperidol-induced mitochondria damage.

CONCLUSION

These results collectively suggest that resveratrol may be introduced as a protective compound against haloperidol-induced mitochondria impairment and aberrant autophagy.

Role of Vitamin E and the Orexin System in Neuroprotection

Microglia are the first line of defense at the level of the central nervous system (CNS). Phenotypic change in microglia can be regulated by various factors, including the orexin system. Neuroinflammation is an inflammatory process mediated by cytokines, by the lack of interaction between neurotransmitters and their specific receptors, caused by systemic tissue damage or, more often, associated with direct damage to the CNS. Chronic activation of microglia could lead to long-term neurodegenerative diseases. This review aims to explore how tocopherol (vitamin E) and the orexin system may play a role in the prevention and treatment of microglia inflammation and, consequently, in neurodegenerative diseases thanks to its antioxidant properties. The results of animal and in vitro studies provide evidence to support the use of tocopherol for a reduction in microglia inflammation as well as a greater activation of the orexinergic system. Although there is much in vivo and in vitro evidence of vitamin E antioxidant and protective abilities, there are still conflicting results for its use as a treatment for neurodegenerative diseases that speculate that vitamin E, under certain conditions or genetic predispositions, can be pro-oxidant and harmful.

Altered Antioxidant Defenses in Drug-Naive First Episode Patients with Schizophrenia Are Associated with Poor Treatment Response to Risperidone: 12-Week Results from a Prospective Longitudinal Study

Abnormal redox regulation is thought to contribute to schizophrenia (SCZ). Accumulating studies have shown that the plasma antioxidant enzyme activity is closely associated with the course and outcome in antipsychotics-naïve first-episode (ANFE) patients with SCZ. The main purpose of this study was to investigate the effect of risperidone on oxidative stress markers in ANFE patients and the relationship between risperidone response and changes in oxidative stress markers. Plasma activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) enzyme, total antioxidant status (TAS), and malondialdehyde (MDA) levels were measured in 354 ANFE patients and 152 healthy controls. The clinical symptoms were evaluated by the Positive and Negative Syndrome Scale (PANSS). Patients received risperidone monotherapy for 12 weeks and oxidative stress markers and PANSS were measured at baseline and at follow-up. Compared with healthy controls, the patients exhibited higher activities of SOD, CAT, and TAS levels, but lower MDA levels and GPx activity. A comparison between 168 responders and 50 non-responders at baseline and 12-week follow-up showed that GPx activity decreased in both groups after treatment. Moreover, GPx activity decreased less in responders and was higher in responders than in non-responders at follow-up. These results demonstrate that the redox regulatory system and antioxidant defense enzymes may have predictive value for the response of ANFE patients to risperidone treatment.

A genome-wide association study identifies a gene network associated with paranoid schizophrenia and antipsychotics-induced tardive dyskinesia

In the present study we conducted a genome-wide association study (GWAS) in a cohort of 505 patients with paranoid schizophrenia (SCZ), of which 95 had tardive dyskinesia (TD), and 503 healthy controls. Using data generated by the PsychENCODE Consortium (PEC) and other bioinformatic databases, we revealed a gene network, implicated in neurodevelopment and brain function, associated with both these disorders. Almost all these genes are in gene or isoform co-expression PEC network modules important for the functioning of the brain; the activity of these networks is also altered in SCZ, bipolar disorder and autism spectrum disorders. The associated PEC network modules are enriched for gene ontology terms relevant to the brain development and function (CNS development, neuron development, axon ensheathment, synapse, synaptic vesicle cycle, and signaling receptor activity) and to the immune system (inflammatory response). Results of the present study suggest that orofacial and limbtruncal types of TD seem to share the molecular network with SCZ. Paranoid SCZ and abnormal involuntary movements that indicate the orofacial type of TD are associated with the same genomic loci on chromosomes 3p22.2, 8q21.13, and 13q14.2. The limbtruncal type of TD is associated with a locus on chromosome 3p13 where the best functional candidate is FOXP1, a high-confidence SCZ gene. The results of this study shed light on common pathogenic mechanisms for SCZ and TD, and indicate that the pathogenesis of the orofacial and limbtruncal types of TD might be driven by interacting genes implicated in neurodevelopment.

Tardive syndrome: An update and mini-review from the perspective of phenomenology

Tardive syndrome (TS) is a group of movement disorders caused by the long-term use of dopamine receptor blocking agents. The phenotypic presentation of TS is diverse, ranging from the most well-characterized symptom of tardive dyskinesia to other symptoms, including dystonia, akathisia, myoclonus, parkinsonism, tremor, and tics. These tardive symptoms are distinct not only in their phenomenology but also in their clinical outcomes. However, our knowledge of the pathophysiology and management of TS is almost exclusively based on tardive dyskinesia. First-generation antipsychotics have a higher risk of inducing TS and have largely been replaced by second-generation antipsychotics with a lower risk of TS. However, patients with off-label use of second-generation antipsychotics are still at risk of developing TS. Thus, the management of TS remains a challenging and important issue for physicians. In this review, we update the information on the epidemiology, phenomenology, and treatment of TS from the perspective of the specific form of TS.

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.

Liver enzyme CYP2D6 gene and tardive dyskinesia

Background: Tardive dyskinesia (TD) is an iatrogenic involuntary movement disorder occurring after extended antipsychotic use with unclear pathogenesis. CYP2D6 is a liver enzyme involved in antipsychotic metabolism and a well-studied gene candidate for TD. Materials & methods: We tested predicted CYP2D6 metabolizer phenotype with TD occurrence and severity in our two samples of European chronic schizophrenia patients (total n = 198, of which 82 had TD). Results: TD occurrence were associated with extreme metabolizer phenotype, controlling for age and sex (p = 0.012). In other words, individuals with either increased and no CYP2D6 activity were at higher risk of having TD. Conclusion: Unlike most previous findings, TD occurrence may be associated with both extremes of CYP2D6 metabolic activity rather than solely for poor metabolizers.

Putative role of pharmacogenetics to elucidate the mechanism of tardive dyskinesia in schizophrenia

Identifying biomarkers which can be used as a diagnostic tool is a major objective of pharmacogenetic studies. Most mental and many neurological disorders have a compiled multifaceted nature, which may be the reason why this endeavor has hitherto not been very successful. This is also true for tardive dyskinesia (TD), an involuntary movement complication of long-term treatment with antipsychotic drugs. The observed associations of specific gene variants with the prevalence and severity of a disorder can also be applied to try to elucidate the pathogenesis of the condition. In this paper, this strategy is used by combining pharmacogenetic knowledge with theories on the possible role of a dysfunction of specific cellular elements of neostriatal parts of the (dorsal) extrapyramidal circuits: various glutamatergic terminals, medium spiny neurons, striatal interneurons and ascending monoaminergic fibers. A peculiar finding is that genetic variants which would be expected to increase the neostriatal dopamine concentration are not associated with the prevalence and severity of TD. Moreover, modifying the sensitivity to glutamatergic long-term potentiation (and excitotoxicity) shows a relationship with levodopa-induced dyskinesia, but not with TD. Contrasting this, TD is associated with genetic variants that modify vulnerability to oxidative stress. Reducing the oxidative stress burden of medium spiny neurons may also be the mechanism behind the protective influence of 5-HT2 receptor antagonists. It is probably worthwhile to discriminate between neostriatal matrix and striosomal compartments when studying the mechanism of TD and between orofacial and limb-truncal components in epidemiological studies.

Plasma total antioxidant status and cognitive impairments in first-episode drug-naïve patients with schizophrenia

Accumulating evidence suggest that excessive reactive oxygen species-induced oxidative damage may underlie neurodegeneration and cognitive impairment in several disorders including schizophrenia. In this study we examined the association of oxidative stress with cognitive deficits in first-episode drug-naïve (FEDN) patients with schizophrenia. We recruited 54 FEDN patients and 50 age- and sex-matched healthy controls and examined the Measurement and Treatment Research to Improve Cognition in Schizophrenia Consensus cognitive Battery (MCCB) and plasma total antioxidant status (TAS). Psychopathological symptoms were assessed using the Positive and Negative Syndrome Scale. The results showed that plasma TAS levels were significantly lower in the patients than those in the healthy subjects (94.7 ± 25.0 U/ml vs 156.6 ± 46.7 U/ml, p < 0.0001). The patients scored lower than healthy controls on the MCCB total score, speed of processing, attention/vigilance and managing emotion test index and STROOP test. For the patients, TAS was associated with some domains of cognitive deficits in schizophrenia, such as speed of processing, attention/vigilance and emotion managing. Our results suggested that oxidative stress may be involved in the pathophysiology of schizophrenia at the early of stage and its cognitive impairment.

No evidence so far of a major role of AKT1 and GSK3B in the pathogenesis of antipsychotic-induced tardive dyskinesia

OBJECTIVE

AKT1 and GSK3B take part in one of the intracellular cascades activated by the D2 dopamine receptor (DRD2). This receptor is antagonized by antipsychotics and plays a role in the pathogenesis of antipsychotic-induced tardive dyskinesia (TD). The present study investigated association of several polymorphisms in the two candidate genes, AKT1 and GSK3B, with TD in antipsychotic-treated patients with schizophrenia.

METHODS

DNA samples from 449 patients from several Siberian regions (Russia) were genotyped, and the results were analyzed using chi-squared tests and analyses of variance.

RESULTS

Antipsychotic-induced TD was not associated with either of the tested functional polymorphisms (rs334558, rs1130214, and rs3730358).

CONCLUSIONS

Despite regulation of AKT1 and GSK3B by DRD2, we found no evidence that these two kinases play a major role in the pathogenesis of antipsychotic-induced TD. These results agree with previously published data and necessitate further exploration of other pathogenic mechanisms, such as neurotoxicity due to excessive dopamine metabolism.

Cannabidiol prevents haloperidol-induced vacuos chewing movements and inflammatory changes in mice via PPARγ receptors

The chronic use of drugs that reduce the dopaminergic neurotransmission can cause a hyperkinetic movement disorder called tardive dyskinesia (TD). The pathophysiology of this disorder is not entirely understood but could involve oxidative and neuroinflammatory mechanisms. Cannabidiol (CBD), the major non-psychotomimetic compound present in Cannabis sativa plant, could be a possible therapeutic alternative for TD. This phytocannabinoid shows antioxidant, anti-inflammatory and antipsychotic properties and decreases the acute motor effects of classical antipsychotics. The present study investigated if CBD would attenuate orofacial dyskinesia, oxidative stress and inflammatory changes induced by chronic administration of haloperidol in mice. Furthermore, we verified in vivo and in vitro (in primary microglial culture) whether these effects would be mediated by PPARγ receptors. The results showed that the male Swiss mice treated daily for 21 days with haloperidol develop orofacial dyskinesia. Daily CBD administration before each haloperidol injection prevented this effect. Mice treated with haloperidol showed an increase in microglial activation and inflammatory mediators in the striatum. These changes were also reduced by CBD. On the other hand, the levels of the anti-inflammatory cytokine IL-10 increased in the striatum of animals that received CBD and haloperidol. Regarding oxidative stress, haloperidol induced lipid peroxidation and reduced catalase activity. This latter effect was attenuated by CBD. The combination of CBD and haloperidol also increased PGC-1α mRNA expression, a co-activator of PPARγ receptors. Pretreatment with the PPARγ antagonist, GW9662, blocked the behavioural effect of CBD in our TD model. CBD also prevented LPS-stimulated microglial activation, an effect that was also antagonized by GW9662. In conclusion, our results suggest that CBD could prevent haloperidol-induced orofacial dyskinesia by activating PPARγ receptors and attenuating neuroinflammatory changes in the striatum.

What is the evidence on cholinergic medication for tardive dyskinesia?

Antipsychotic drugs are associated with movement disorders, especially with long-term use. Tardive dyskinesia, a condition characterised by repetitive involuntary muscle activity, is considered to be the most chronic, distressing and disabling of antipsychotic-associated movement disorders. There is theoretical justification for the use of cholinergic drugs in tardive dyskinesia, and they are used in clinical practice. A Cochrane systematic review synthesised randomised controlled trial data evaluating the effectiveness of cholinergic drugs for tardive dyskinesia, and for a range of secondary outcomes, including quality of life. In line with the authors of the review, this Commentary concludes that much higher-quality evidence on the use of cholinergic drugs in tardive dyskinesia is necessary, and that a patient with tardive dyskinesia should be offered the opportunity to try a newer cholinergic drug, ideally in the context of a well-conducted and reported clinical trial. At the same time, given uncertainty regarding clinical effectiveness, and in view of their accepted adverse effects, it would be understandable if a person with tardive dyskinesia decided to avoid cholinergic drugs.

DECLARATION OF INTEREST

None.

What is the risk-benefit ratio of long-term antipsychotic treatment in people with schizophrenia?

The long-term benefit-to-risk ratio of sustained antipsychotic treatment for schizophrenia has recently been questioned. In this paper, we critically examine the literature on the long-term efficacy and effectiveness of this treatment. We also review the evidence on the undesired effects, the impact on physical morbidity and mortality, as well as the neurobiological correlates of chronic exposure to antipsychotics. Finally, we summarize factors that affect the risk-benefit ratio. There is consistent evidence supporting the efficacy of antipsychotics in the short term and mid term following stabilization of acute psychotic symptoms. There is insufficient evidence supporting the notion that this effect changes in the long term. Most, but not all, of the long-term cohort studies find a decrease in efficacy during chronic treatment with antipsychotics. However, these results are inconclusive, given the extensive risk of bias, including increasing non-adherence. On the other hand, long-term studies based on national registries, which have lower risk of bias, find an advantage in terms of effectiveness during sustained antipsychotic treatment. Sustained antipsychotic treatment has been also consistently associated with lower mortality in people with schizophrenia compared to no antipsychotic treatment. Nevertheless, chronic antipsychotic use is associated with metabolic disturbance and tardive dyskinesia. The latter is the clearest undesired clinical consequence of brain functioning as a potential result of chronic antipsychotic exposure, likely from dopaminergic hypersensitivity, without otherwise clear evidence of other irreversible neurobiological changes. Adjunctive psychosocial interventions seem critical for achieving recovery. However, overall, the current literature does not support the safe reduction of antipsychotic dosages by 50% or more in stabilized individuals receiving adjunctive psychosocial interventions. In conclusion, the critical appraisal of the literature indicates that, although chronic antipsychotic use can be associated with undesirable neurologic and metabolic side effects, the evidence supporting its long-term efficacy and effectiveness, including impact on life expectancy, outweighs the evidence against this practice, overall indicating a favorable benefit-to-risk ratio. However, the finding that a minority of individuals diagnosed initially with schizophrenia appear to be relapse free for long periods, despite absence of sustained antipsychotic treatment, calls for further research on patient-level predictors of positive outcomes in people with an initial psychotic presentation.

New findings in pharmacogenetics of schizophrenia

PURPOSE OF REVIEW

This review highlights recent advances in the investigation of genetic factors for antipsychotic response and side effects.

RECENT FINDINGS

Antipsychotics prescribed to treat psychotic symptoms are variable in efficacy and propensity for causing side effects. The major side effects include tardive dyskinesia, antipsychotic-induced weight gain (AIWG), and clozapine-induced agranulocytosis (CIA). Several promising associations of polymorphisms in genes including HSPG2, CNR1, and DPP6 with tardive dyskinesia have been reported. In particular, a functional genetic polymorphism in SLC18A2, which is a target of recently approved tardive dyskinesia medication valbenazine, was associated with tardive dyskinesia. Similarly, several consistent findings primarily from genes modulating energy homeostasis have also been reported (e.g. MC4R, HTR2C). CIA has been consistently associated with polymorphisms in the HLA genes (HLA-DQB1 and HLA-B). The association findings between glutamate system genes and antipsychotic response require additional replications.

SUMMARY

The findings to date are promising and provide us a better understanding of the development of side effects and response to antipsychotics. However, more comprehensive investigations in large, well characterized samples will bring us closer to clinically actionable findings.

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.

Future directions in tardive dyskinesia research

Tardive dyskinesia (TD) research is at a crossroads because of renewed interest in this syndrome following the successful development and regulatory approval of two novel vesicular monoamine transport 2 (VMAT2) inhibitors. Despite these clinical advances, significant lacunae exist in the knowledge base of TD pathophysiology, prognosis, and epidemiology. Moreover, conflicting definitions of TD as either a syndrome that encompasses a broad array of related phenomena or as a specific subset of tardive syndromes are an impediment to both clinical and basic science research, and to educational efforts targeting nonspecialist clinicians. A unique opportunity is thus presented by the enhanced focus on TD to resolve fundamental issues with regards to nomenclature and clinical criteria, thereby facilitating more sophisticated surveillance and genetic and epidemiological research into tardive movement disorders related to dopamine receptor blocking agents. The widespread use of newer antipsychotics portends that TD will remain a persistent public health issue. This article will present one view of research avenues to be explored for this neuropsychiatric condition, including those that may yield immediate therapeutic benefits by extending expert knowledge into routine clinical care situations.

Effect of psychotropic drug treatment on sterol metabolism

Cholesterol metabolism is vital for brain function. Previous work in cultured cells has shown that a number of psychotropic drugs inhibit the activity of 7-dehydrocholesterol reductase (DHCR7), an enzyme that catalyzes the final steps in cholesterol biosynthesis. This leads to the accumulation of 7-dehydrocholesterol (7DHC), a molecule that gives rise to oxysterols, vitamin D, and atypical neurosteroids. We examined levels of cholesterol and the cholesterol precursors desmosterol, lanosterol, 7DHC and its isomer 8-dehydrocholesterol (8DHC), in blood samples of 123 psychiatric patients on various antipsychotic and antidepressant drugs, and 85 healthy controls, to see if the observations in cell lines hold true for patients as well. Three drugs, aripiprazole, haloperidol and trazodone increased circulating 7DHC and 8DHC levels, while five other drugs, clozapine, escitalopram/citalopram, lamotrigine, olanzapine, and risperidone, did not. Studies in rat brain verified that haloperidol dose-dependently increased 7DHC and 8DHC levels, while clozapine had no effect. We conclude that further studies should investigate the role of 7DHC and 8DHC metabolites, such as oxysterols, vitamin D, and atypical neurosteroids, in the deleterious and therapeutic effects of psychotropic drugs. Finally, we recommend that drugs that increase 7DHC levels should not be prescribed during pregnancy, as children born with DHCR7 deficiency have multiple congenital malformations.

Association between DBH 19bp insertion/deletion polymorphism and cognition in schizophrenia with and without tardive dyskinesia

Long-term antipsychotic treatment for schizophrenia is associated with the development of tardive dyskinesia (TD), which is involved in increased cognitive impairment. Dopamine beta-hydroxylase (DBH) gene associated with dopamine and norepinephrine systems influences cognition. Schizophrenia with TD have higher DBH activity than those without TD. This study examined whether DBH5'-insertion/deletion (-Ins/Del) polymorphism could influence cognitive function in schizophrenia with and without TD. The presence of DBH5'-Ins/Del polymorphism was determined in 345 schizophrenia with TD and 397 schizophrenia without TD. The Abnormal Involuntary Movement Scale and Repeatable Battery for Assessment of Neuropsychological Status (RBANS) were used to assess TD severity and cognition. The allele and genotype frequencies of DBH5'-Ins/Del polymorphism did not differ between patients with and without TD (both p>0.05). RBANS total score and subscales did not differ by DBH5'-Ins/Del genotype groups in patients with TD (all p>0.05). However, attention score significantly differed by DBH5'-Ins/Del genotype groups in those without TD (p<0.05). Patients without TD who were Del homozygous had significantly lower attention score than those without TD who were Ins alleles (p<0.05). Immediate memory and attention scores were lower in patients with TD than without TD (both p<0.05). This study indicated that DBH5'-Ins/Del polymorphism may not play a role in the susceptibility to TD and cognitive deficits in schizophrenia with TD, but it may influence cognitive function in schizophrenia with non-TD. Moreover, schizophrenia with TD experienced greater cognitive deficits than those with non-TD, especially in immediate memory and attention.

Level of serum thioredoxin and correlation with neurocognitive functions in patients with schizophrenia using clozapine and other atypical antipsychotics

Thioredoxin is a serum antioxidant that has been investigated in the etiology of schizophrenia. The aim of this study is investigating the relationship between serum thioredoxin levels and cognitive functions in acute psychotic episode and remission state patients with schizophrenia; and examining whether there were differences between patients using clozapine and other atypical antipsychotics; including risperidone, olanzapine and amisulpride. This research was performed in schizophrenia patients hospitalized with acute psychotic episode (n=57), reevaluated patients after the initiation of treatment (mean 16 weeks) (n=46), and healthy controls (n=41). Positive and Negative Syndrome Scale, Clinic Global Impressions Scale, Neuropsychologic test battery to assess cognitive performance, and serum thioredoxin levels measured by ELISA were used in this research. Serum thioredoxin levels were highest in acute psychotic episode, lower in the remission state and the lowest in healthy controls. Significant correlation has been established between serum thioredoxin levels and Trail Making Test-A performance in remission state patients. In conclusion, serum thioredoxin levels were increased in acute psychotic episode and decreased in remission state, and its relationship with attention is worth to consider in schizophrenia patients.

Ginkgo biloba leaf extract and alpha-tocopherol attenuate haloperidol-induced orofacial dyskinesia in rats: Possible implication of antiapoptotic mechanisms by preventing Bcl-2 decrease and Bax elevation

BACKGROUND

Tardive dyskinesia (TD) is a serious side effect of long-term administration of typical neuroleptics, such as haloperidol. The pathophysiology of TD remains unclear, but the experimental evidence suggests that free radical-induced neuronal apoptosis in the basal ganglia may play an important role.

PURPOSE

This study was to investigate changes in Bax and Bcl-2 expression levels in TD-associated brain regions and the effects of the antioxidant EGb761 on Bax and Bcl-2 levels in an animal model of TD.

METHODS

Thirty-two rats were randomly divided into four study groups: saline control (saline), haloperidol-alone (haloperidol), EGb761-haloperidol (EGb), and alpha-tocopherol-haloperidol (vitamin E). Rats were treated with daily intraperitoneal haloperidol injections (2 mg/kg/day) for 5 weeks. EGb761 (50 mg/kg/day) and alpha-tocopherol (20 mg/kg/day) were then administered for another 5 weeks during the withdrawal period. Behavioral assessments were performed, and Bax and Bcl-2 protein expression levels were immunohistochemically analyzed in four brain regions, including the prefrontal cortex, striatum, substantia nigra, and globus pallidum.

RESULTS

We found that increased vacuous chewing movements (VCMs) were associated with increased proapoptotic Bax protein expression, decreased antiapoptotic Bcl-2 protein expression, and an increased Bax/Bcl-2 ratio. EGb761 and alpha-tocopherol treatment reversed the increase in VCMs, decreased Bax expression, increased Bcl-2 expression, and decreased the Bax/Bcl-2 ratio.

CONCLUSIONS

These results demonstrate that long-term haloperidol administration may affect Bcl-2 protein family expression and promote neuronal apoptosis in the basal ganglia. In combination with their antioxidant capacity, EGb761 and alpha-tocopherol's antiapoptotic effects through Bcl-2 might account for the symptom improvement observed in haloperidol-induced TD rats.

Forgotten but not gone: new developments in the understanding and treatment of tardive dyskinesia

The broad use of atypical antipsychotics was expected to dramatically reduce the prevalence and incidence of tardive dyskinesia (TD), but data show that TD remains an important challenge due the persistent nature of its symptoms and resistance to numerous treatment modalities, including antipsychotic discontinuation. Recent insights on genetic risk factors and new concepts surrounding pathophysiology have spurred interest in the possibility of targeted treatment for TD. As will be reviewed in this article, the number of evidence-based strategies for TD treatment is small: only clonazepam, amantadine, ginkgo biloba extract, and the vesicular monoamine transporter 2 (VMAT2) inhibitor tetrabenazine have compelling data. Using new insights into the metabolism of tetrabenazine and the properties of its active metabolites, 2 modifications of tetrabenazine have been synthesized to improve the kinetic profile, and are currently involved in double-blind placebo controlled studies aimed at U.S. Food and Drug Administration (FDA) regulatory approval. The possible availability of these new agents, deuterated tetrabenazine and valbenazine, significantly widens the range of treatment choices for patients with TD. For clinicians with patients at risk for TD due to dopamine antagonist exposure, experience has shown that the problem of TD will be an ongoing issue in modern psychiatry, and that an appreciation of new developments in the pathophysiology of, risk factors for, and treatment of TD is crucial to managing this condition.

Influence of magnesium supplementation on movement side effects related to typical antipsychotic treatment in rats

Chronic use of typical antipsychotic haloperidolis related to movement disturbances such as parkinsonism, akathisia and tardive dyskinesia which have been related to excitotoxicity in extrapyramidal brain areas, requiring their prevention and treatment. In the current study we evaluated the influence of the magnesium on prevention (for 28days before-), reversion (for 12days after-) and concomitant supplementation on haloperidol-induced movement disorders in rats. Sub-chronic haloperidol was related to orofacial dyskinesia (OD) and catalepsy development, increased generation of reactive species (RS) and levels of protein carbonyl (PC) in cortex, striatum and substantia nigra (SN) in all experimental protocols. When provided preventatively, Mg reduced the increase of OD and catalepsy time 14 and 7days after haloperidol administration, respectively. When supplemented after haloperidol-induced OD establishment, Mg reversed this behavior after 12days, while catalepsy was reversed after 6days of Mg supplementation.When Mg was concomitantly supplemented with haloperidol administration, OD and catalepsy were prevented. Moreover, Mg supplementation was able to prevent the RS generation in both cortex and SN, reducing PC levels in all brain areas evaluated. When supplemented after haloperidol, Mg reversed RS generation in cortex and striatum, decreasing PC levels in SN and striatum.The co-administration of haloperidol and Mg supplementation prevented RS generation in cortex, striatum and SN, and PC levels in the SN.These outcomes indicate that Mg supplementation may be a useful alternative to prevent movement disturbances resulting of classic antipsychotic pharmacotherapy as haloperidol.