Monoamine Transporter Research Articles

Real-World Effectiveness and Safety of Deutetrabenazine in Combination with Antipsychotic Drugs in Patients With Chorea Associated With Huntington Disease (P2-11.010)

<h3>Objective:</h3> To describe the effectiveness and safety of vesicular monoamine transporter 2 inhibitor deutetrabenazine (DTBZ) combined with antipsychotic agents (APs) in patients with Huntington disease (HD)-related chorea in a real-world setting. <h3>Background:</h3> DTBZ effectiveness and safety for HD-related chorea have been well documented in clinical trials; however, patients receiving APs were not included. Safety and effectiveness data for DTBZ+AP are needed to inform real-world practice. <h3>Design/Methods:</h3> Data were collected from charts of patients with HD-associated chorea who received DTBZ+AP at Vanderbilt University Medical Center from April 3, 2017, until data collection (May–November 2021). Effectiveness was assessed by Total Maximal Chorea (TMC) scores over time. Safety was assessed via adverse drug reactions (ADRs) based on a predefined list of known DTBZ ADRs. <h3>Results:</h3> Among 57 patients treated with DTBZ+AP, 13 started APs first and had TMC scores available within 1 month before and any time after DTBZ addition, and 8 had TMC scores available within 1 month before AP initiation. After initiating APs and before adding DTBZ, TMC scores improved for 2/8 (25%) patients and worsened for 6 (75%). After adding DTBZ, TMC scores further improved for 8/13 (62%) patients, did not change for 1 (8%), and worsened for 4 (31%). In patients with history of tetrabenazine use, TMC scores improved after adding DTBZ for 4/8 (50%), versus 4/5 (80%) patients without history. Among all 57 patients treated with DTBZ+AP, 25 (44%) patients had ≥1 new/continuing ADR, with agitation, akathisia (both n=7; 12%), and somnolence (n=4; 7%) being most frequent; 2 (4%) patients discontinued DTBZ because of ADRs/tolerability issues while receiving combination treatment. <h3>Conclusions:</h3> In this retrospective chart review, adding DTBZ to APs improved motor signs and had a favorable benefit-risk profile. However, prospective, controlled trials investigating the efficacy and safety of DTBZ+AP in patients with HD-related chorea are needed. <b>Disclosure:</b> Dr. Claassen has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Teva Neuroscience. Dr. Claassen has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Spark . The institution of Dr. Claassen has received personal compensation in the range of $50,000-$99,999 for serving as a Consultant for Alterity. Dr. Claassen has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Teva Neuroscience. Dr. Claassen has received personal compensation in the range of $500-$4,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for HD Insights. The institution of Dr. Claassen has received research support from NIH. The institution of Dr. Claassen has received research support from CHDI. The institution of Dr. Claassen has received research support from HDSA. The institution of Dr. Claassen has received research support from Department of Defense. The institution of Dr. Claassen has received research support from Griffin Family Foundation. The institution of Dr. Claassen has received research support from Neurocrine. The institution of Dr. Claassen has received research support from Vaccinex. The institution of Dr. Claassen has received research support from AbbVie. The institution of Dr. Claassen has received research support from CHDI. The institution of Dr. Claassen has received research support from Genentech/ Roche. The institution of Dr. Claassen has received research support from Prilenia. The institution of Dr. Claassen has received research support from Neurocrine/ HSG. Dr. Romdhani has nothing to disclose. Rajeev Ayyagari, PhD has received personal compensation for serving as an employee of Analysis Group, Inc. . Debbie Goldschmidt has received personal compensation for serving as an employee of Analysis Group. Ms. Moroz has nothing to disclose. Ms. Hernandez has nothing to disclose. Nayla Chaijale has received personal compensation for serving as an employee of Teva Pharmaceuticals. Dr. Leo has received personal compensation for serving as an employee of Teva Pharmaceutical Industries.

Baseline Characteristics and Treatment Patterns of a Global Huntington Disease Population Stratified by Chorea Severity (P2-11.011)

<h3>Objective:</h3> To describe baseline characteristics and treatment patterns in Huntington Disease-associated chorea by chorea severity. <h3>Background:</h3> Though multiple treatment options exist for HD-associated chorea, there are little real-world data on treatment patterns, especially across disease trajectory and variation by severity of chorea. <h3>Design/Methods:</h3> Participants were adults from “Enroll-HD”, a global observational registry for patients with HD and their families (data cut 2013 – 31 October, 2020). Data on age, sex, Total Maximal Chorea (TMC) score, vesicular monoamine transporter 2 (VMAT2) inhibitors, and antipsychotic agents (APs; typical, atypical, and other [lithium]) were collected at the baseline visit. Participants were grouped by chorea severity (TMC score categories) recorded at baseline (0–7, 8–14, 15–21, 22–28). <h3>Results:</h3> There were 10,903 participants (TMC 0–7, n=5055; TMC 8–14, n=4374; TMC 15–21, n=1310; TMC 22–28, n=164). 51% were female (51.2%, 51.5%, 51.4%, and 53.1%, respectively) and the mean age at baseline was 53.0 years (50.8, 54.5, 55.9, 54.4, respectively). Overall, VMAT2i use at baseline was 14.9% and increased with chorea severity (10.8%, 16.4%, 23.9%, 29.3%, respectively). The proportion of patients using APs at baseline was 34.5% overall and increased with chorea severity (29.9%, 35.1%, 47.8%, 57.3%, respectively). Overall, 5.8% of patients used VMAT2 inhibitors combined with APs, and combined use increased with chorea severity (3.9%, 5.8%, 11.5%, 15.9%, respectively). <h3>Conclusions:</h3> Use of medications to treat chorea was low across the spectrum of chorea severities but increased incrementally in patients with greater chorea severity. Use of a combination of VMAT2 inhibitors and APs at baseline was low but increased as chorea severity increased. These data suggest that HD-associated chorea may be under treated globally. More data are needed to understand chorea treatment considerations and the utility of VMAT2 inhibitors and APs for treating HD-associated chorea and comorbidities. <b>Disclosure:</b> Dr. Sung has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Teva Neuroscience. Dr. Sung has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Genentech. Dr. Furr-Stimming has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Teva Pharmaceuticals. Dr. Furr-Stimming has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Michael J. Fox Foundation. Dr. Furr-Stimming has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Teva Pharmaceuticals. The institution of Dr. Furr-Stimming has received research support from Cures within Reach. The institution of Dr. Furr-Stimming has received research support from Huntington’s Disease Society of America. The institution of Dr. Furr-Stimming has received research support from Roche/Genetech. The institution of Dr. Furr-Stimming has received research support from Uniqure. The institution of Dr. Furr-Stimming has received research support from CHDI. The institution of Dr. Furr-Stimming has received research support from Huntington Study Group/Neurocrine. The institution of Dr. Furr-Stimming has received research support from NIH/University of Iowa. The institution of Dr. Furr-Stimming has received research support from Sage Therapeutics. Dr. Furr-Stimming has received publishing royalties from a publication relating to health care. Dr. Reshef has received personal compensation for serving as an employee of Teva. Ms. Willock has received personal compensation for serving as an employee of HCD Economics. Rinat Ribalov has received personal compensation for serving as an employee of TEVA. Miss Brighton has nothing to disclose. Dr. Leo has received personal compensation for serving as an employee of Teva Pharmaceutical Industries.

The Seventh Prevention of Syncope Trial (POST VII)—A randomized clinical trial of atomoxetine for the prevention of vasovagal syncope: Rationale and study design

Vasovagal syncope (VVS) is common, recurs, and is associated with markedly reduced quality of life, anxiety, and frequent injuries. The few pharmacological therapies for VVS proven to have a moderate benefit in reducing recurrences are limited to patients without coexisting conditions such as hypertension or heart failure. Although there is some data to suggest Atomoxetine, a norepinephrine reuptake transport inhibitor (NET), may be a promising treatment option, an adequately powered randomized placebo-controlled trial is needed. POST VII is a multicenter, randomized, double-blind, placebo-controlled, crossover study that will randomize 180 patients with VVS and at least 2 syncopal spells in the preceding year to a target daily dose of atomoxetine 80 mg daily or to a matching placebo, with an observation period of 6 months in each phase and with a 1-week washout period between phases. The primary end point will be the proportion of patients with at least one syncope recurrence in each arm analyzed with an intention-to-treat approach. The secondary end points include total syncope burden, quality of life, cost, and cost-effectiveness. Assuming a 33% relative risk reduction in syncope recurrence with atomoxetine, and a dropout rate of 16%, the enrollment of 180 patients will give an 85% power of reaching a positive conclusion about atomoxetine, with P=.05. This will be the first adequately powered trial to determine whether atomoxetine is effective in preventing VVS. If proven effective, atomoxetine might become the first-line pharmacological treatment for recurrent VVS.

Robust aversive effects of trace amine-associated receptor 1 activation in mice.

Drugs that stimulate the trace amine-associated receptor 1 (TAAR1) are under clinical investigation as treatments for several neuropsychiatric disorders. Previous studies in a genetic mouse model of voluntary methamphetamine intake identified TAAR1, expressed by the Taar1 gene, as a critical mediator of aversive methamphetamine effects. Methamphetamine is a TAAR1 agonist, but also has actions at monoamine transporters. Whether exclusive activation of TAAR1 has aversive effects was not known at the time we conducted our studies. Mice were tested for aversive effects of the selective TAAR1 agonist, RO5256390, using taste and place conditioning procedures. Hypothermic and locomotor effects were also examined, based on prior evidence of TAAR1 mediation. Male and female mice of several genetic models were used, including lines selectively bred for high and low methamphetamine drinking, a knock-in line in which a mutant form of Taar1 that codes for a non-functional TAAR1 was replaced by the reference Taar1 allele that codes for functional TAAR1, and their matched control line. RO5256390 had robust aversive, hypothermic and locomotor suppressing effects that were found only in mice with functional TAAR1. Knock-in of the reference Taar1 allele rescued these phenotypes in a genetic model that normally lacks TAAR1 function. Our study provides important data on TAAR1 function in aversive, locomotor, and thermoregulatory effects that are important to consider when developing TAAR1 agonists as therapeutic drugs. Because other drugs can have similar consequences, potential additive effects should be carefully considered as these treatment agents are being developed.

Biological-Activity-Based Prioritization of Antidepressants in Wastewater in England and Japan.

Antidepressants are one of the most commonly prescribed pharmaceuticals. Although they have been frequently detected in aquatic environments around the globe, little is known regarding their adverse effects on humans and aquatic organisms. Recently, an in vitro monoamine transporter inhibition assay was developed to detect transporter-inhibitory activities of antidepressants in wastewater in Japan. However, it was unclear which antidepressants were responsible for transporter-inhibitory activities in wastewater. Herein, the per capita consumption of 32 antidepressants, their excretion of unchanged parent compounds, per capita water consumption, removal rate during wastewater treatment processes, and potency values from the monoamine transporter inhibition assay were used to prioritize antidepressants of concern in effluent wastewater in England and Japan. In both countries, sertraline and O-desmethylvenlafaxine had the highest contribution to inhibitory activities against the human serotonin transporter (hSERT) and zebrafish SERT (zSERT), respectively. It was found that the antidepressants inhibited the zSERT more strongly than the hSERT. The inhibitory activities found against the zSERT in wastewater in England and Japan were higher than thresholds for abnormal behavior in fish. The antidepressants prioritized in this study provide insight into launching environmental monitoring and ecotoxicological studies of antidepressants.

Preclinical Pharmacology of Solriamfetol: Potential Mechanisms for Wake Promotion

AbstractIntroductionSolriamfetol is a wake-promoting agent (WPA) approved for the treatment of excessive daytime sleepiness associated with narcolepsy and obstructive sleep apnea. The wake-promoting mechanism of solriamfetol may result from dopamine and norepinephrine reuptake inhibition. Preclinical pharmacology studies were conducted to further elucidate the molecular targets activated by solriamfetol and compare them to that of known WPAs and traditional stimulants.MethodsIn vitro binding and functional studies were conducted in a panel of cell lines or membrane preparations expressing transmembrane receptors and monoamine transporters to measure the activity of solriamfetol, comparator WPAs, and traditional stimulants. Electrophysiology studies were conducted in slice preparations from mouse ventral tegmental area (VTA). Studies to measure locomotor activity and wake-promoting effects were conducted in mice.ResultsIn vitro functional studies showed agonist activity of solriamfetol at human, mouse, and rat TAAR1 receptors. hTAAR1 EC50 values (10–16 μM) were within the clinically observed therapeutic solriamfetol plasma concentration range and overlapped with the observed DAT/NET inhibitory potencies of solriamfetol in vitro. TAAR1 agonist activity was unique to solriamfetol; neither the WPA modafinil nor the DAT/NET inhibitor bupropion had TAAR1 agonist activity. Solriamfetol (1–10 μM) dose-dependently inhibited the firing frequency of dopaminergic VTA neurons in mouse brain slices, similar to known TAAR1 agonists; however, these effects were inhibited by a D2 antagonist, suggesting a DAT-mediated effect. Unlike traditional stimulants, solriamfetol did not increase locomotor activity in naive mice, but inhibited the increase in locomotor activity in DAT knockout mice.ConclusionsPreclinical studies have identified agonist activity at the TAAR1 receptor and, possibly, lower potency agonist activity at 5-HT1A receptors as potential pharmacological targets for solriamfetol, in addition to its activity as a DAT/NET inhibitor. Given the current understanding of TAAR1 agonists as modulators of monoamine transmission with potential wake-promoting effects in multiple preclinical species, agonist activity at the hTAAR1 receptor may represent an additional pharmacological target underlying the wake-promoting effects for solriamfetol, in addition to its DNRI activity.FundingAxsome Therapeutics, Jazz Pharmaceuticals

Anticholinergics Should Not Be Used to Treat Tardive Dyskinesia: Insights From an Expert Panel of Psychiatry and Neurology Healthcare Professionals

AbstractIntroductionTardive dyskinesia (TD) is a persistent and often disabling hyperkinetic movement disorder associated with prolonged exposure to dopamine receptor blocking agents (e.g., antipsychotics, antiemetics). The use of anticholinergics for the treatment of movement disorders including TD is a common practice, despite a lack of supportive evidence and the potential to worsen TD. Moreover, there are now FDA-approved medications specifically indicated for TD. Two virtual meetings were held with movement disorder experts from neurology and psychiatry to better understand the real-world use of anticholinergics for TD.MethodsIn November 2020, a panel of eight experts was convened to gather insights on the challenges of differentiating TD from other drug-induced movement disorders (DIMDs) and to discuss appropriate treatments for TD and other DIMDs. A follow-up meeting was held in June 2021 to consolidate these insights. Key recommendations based on the panel discussions are presented.ResultsThe panel emphasized that while anticholinergics can help with managing some DIMDs, current evidence indicates that they are not effective in TD and may even worsen symptoms. Therefore, FDA-approved vesicular monoamine transporter 2 (VMAT2) inhibitors like valbenazine were recommended by the panel as first-line TD therapies. The panel noted that TD is often grouped under the term “extrapyramidal symptoms,” which leads to difficulty in differentiating TD from other DIMDs and the inappropriate treatment of TD with anticholinergics. The panel agreed that prophylaxis with anticholinergics is only appropriate in patients at high risk of acute dystonia. However, chronic anticholinergic use should be avoided whenever possible due to potentially serious adverse effects (e.g., cognitive difficulties) and anticholinergic burden, particularly in older patients. The potential for abuse, addiction, and diversion should also be considered when prescribing anticholinergics. Abrupt anticholinergic discontinuation can result in cholinergic rebound, which is characterized by sleep disturbances, gastrointestinal problems, urinary urgency, and manifestations of DIMDs. Thus, when used appropriately (e.g., for acute dystonia), anticholinergics should be prescribed at minimally effective doses and slowly tapered for successful discontinuation.ConclusionsThese findings align with the current TD treatment guidelines, including the lack of evidence for anticholinergic use and recommended first-line treatment with approved VMAT2 inhibitors. Conclusions from this panel highlight educational needs across HCPs on the phenomenology of DIMDs, the inappropriate use of anticholinergics for TD, TD risks and assessment, and treatment strategies for TD.FundingNeurocrine Biosciences, Inc.

Treatment Success and Psychiatric Stability in Adults With Tardive Dyskinesia: Post Hoc Analyses of Two Long-Term Valbenazine Studies

AbstractIntroductionTardive dyskinesia (TD) is a persistent and potentially disabling movement disorder associated with exposure to antipsychotics and other dopamine receptor blocking agents. Effective and comprehensive treatment of TD requires reducing patients’ abnormal involuntary movements without disrupting their psychiatric stability. This can be especially challenging when patients have complex psychiatric conditions (e.g., &gt;1 psychiatric diagnosis) and are taking multiple medications. Valbenazine, a highly potent and selective vesicular monoamine transporter 2 (VMAT2) inhibitor, is approved for the once-daily treatment of TD. This post hoc analysis of two long-term studies (KINECT 3, KINECT 4) was conducted to evaluate changes in psychiatric status and clinician- and patient-reported treatment success in study participants who received valbenazine (40 or 80 mg) for 48 weeks.MethodsData from KINECT 3 and KINECT 4 were pooled and analyzed in participants categorized by their primary psychiatric diagnosis: schizophrenia/schizoaffective disorder (“SCHZ”) or mood disorder (“MD”). Concomitant medications needed for managing these and other psychiatric or medical conditions were allowed. Treatment success was defined as achieving a rating of “much improved” or “very much improved” at Week 48, as assessed using the Clinical Global Impression of Change-Tardive Dyskinesia (CGI-TD) and Patient Global Impression of Change (PGIC). Psychiatric stability was monitored using the following scales: Positive and Negative Syndrome Scale (PANSS) and Calgary Depression Scale for Schizophrenia (CDSS) in the SCHZ subgroup; Young Mania Rating Scale (YMRS) and Montgomery-Åsberg Depression Rating Scale (MADRS) in the MD subgroup. Suicidal ideation/behavior was monitored using the Columbia-Suicide Severity Rating Scale.ResultsMore than 75% of study participants in the SCHZ subgroup achieved treatment success with valbenazine, based on clinician assessment (CGI-TD, 79.7%) and patient self-report (PGIC, 78.0%). Mean changes from baseline to Week 48 for PANSS scores (positive symptoms [-0.7], negative symptoms [‑0.6], general psychopathology [-1.9], total [-3.2]) and CDSS total score (-0.5) indicated maintenance of psychiatric stability in the SCHZ subgroup. Similar treatment success rates were found in the MD subgroup for both CGI-TD (77.6%) and PGIC (84.5%), with mean changes from baseline in YMRS total score (-1.0) and MADRS total score (+0.3) indicating psychiatric stability was maintained. No emergence of suicidal ideation/behavior was observed during the studies.ConclusionsPooled analyses from two 48-week studies indicate that long-term treatment of TD with once-daily valbenazine resulted in substantial clinician- and patient-reported global improvements in TD, while psychiatric stability was maintained regardless of primary psychiatric condition.FundingNeurocrine Biosciences, Inc.

368 Development of Interactome Network to Understand Adverse Drug Reactions for Antidepressant Medications

OBJECTIVES/GOALS: Patient adherence with antidepressant therapy is a critical aspect of clinical management. Drug molecules often interact with other off-target proteins resulting in adverse events. We utilized an interactome model for predicting the likelihood of adverse drug reactions in order to accurately prescribe antidepressant medications to a patient. METHODS/STUDY POPULATION: We utilized an interactome model to study physical interactions between proteins and biological functions disrupted by major depression to understand how changes in genes alter patient-specific drug efficacy and cause adverse drug-reactions. To study how drugs and diseases propagate through the proteins and biological functions, we harnessed diffusion profiles to represent nodes in the graphical model and used a biased random walks model to illustrate how signals propagate in a heterogeneous biological network. The edge weights were defined for the drug, disease, protein, and biological function node types. The interactions studied included drug-protein, disease-protein, protein-protein, protein-biological function, biological function-biological function. RESULTS/ANTICIPATED RESULTS: Based on previous studies, we anticipate that the genetic variants modulating antidepressant response include 5-HTT, STin2, HTR1A, HTR2A, TPH1 and BDNF. Additionally, genetic variants such as SLC6A4 as well as the HPA pathway may play an important role in antidepressant therapeutic response. With regards to medication drug response, the genes, SLC6A4 and HTR2A, have been known for encoding proteins that affect the synaptic cleft of serotonergic neurons. Also, the gene SLC6A4 has been shown to encode for the serotonin reuptake transporter, which is the main pharmacological target of SSRIs. In female patients with major depression, the polymorphism associated with MAOA gene may be involved in the pharmacological response. DISCUSSION/SIGNIFICANCE: The key to successful depression treatment is early adherence but nearly 60% of patients discontinue antidepressants within three months. By developing a strong understanding of the genes that alter treatment efficacy, we can provide patients with more awareness regarding the most effective treatment plan to minimize adverse events.

Viloxazine Increases Cortical Serotonin Without Inhibiting Serotonin Reuptake at Doses Used to Treat ADHD

AbstractBackgroundMost FDA-approved ADHD treatments increase norepinephrine (NE) and dopamine (DA); however, our prior preclinical studies of the non-stimulant ADHD treatment viloxazine ER (Qelbree®) demonstrated that viloxazine also increases serotonin (5-HT). A prior microdialysis study showed increases in NE, DA, and 5-HT in the rat prefrontal cortex (PFC); however, the 50 mg/kg dose resulted in supratherapeutic plasma concentrations. Viloxazine is a moderate affinity selective NE reuptake inhibitor, structurally different than traditional SSRI antidepressants. Viloxazine has negligible activity at the serotonin reuptake transporter (SERT), suggesting viloxazine has a different mechanism of 5-HT PFC elevation than SSRIs. The current microdialysis study was undertaken to further characterize if viloxazine affects 5-HT and its 5-HIAA metabolite at therapeutically relevant plasma concentrations. Results are compared to similar microdialysis studies of SSRIs.MethodsRats were implanted with I-shaped microdialysis probes connected to a microperfusion pump, delivering artificial cerebrospinal fluid, in the PFC. After a 2-hour baseline period, viloxazine (1, 3, 10, or 30 mg/kg) was administered (ip). Dialysate samples were collected from the interstitial fluid (ISF) of the PFC before and after dosing. LC-MS/MS was used to determine the dialysate concentrations of viloxazine and viloxazine-induced changes in NE, 5-HT, and their respective metabolites, DHPG and 5-HIAA. Viloxazine plasma concentrations were also measured.Animal research was approved by the Institutional Animal Care and Use Committee and conducted in accordance with the National Research Council’s Guide for the Care and Use of Laboratory Animals.ResultsViloxazine administration resulted in significant dose-dependent increases in ISF NE levels and corresponding decreases in DHPG (NE metabolite) at all doses tested, reflecting viloxazine’s activity as a NET inhibitor. Viloxazine treatment also resulted in a dose-dependent elevation of ISF 5-HT levels in the PFC. Of the doses tested, 30 mg/kg was found to be clinically relevant as it induced ISF concentrations approximating unbound plasma concentrations in pediatric ADHD patients. At this dose, 5-HT levels were significantly increased over baseline and higher than vehicle levels. Coincident changes in 5-HIAA concentrations were not observed, reaffirming viloxazine’s lack of activity as a SERT inhibitor.ConclusionViloxazine induced dose-dependent increases in NE and 5-HT in the PFC, a critical target region for ADHD therapies. At clinically relevant viloxazine plasma concentrations, 5-HT was increased in the PFC. Unlike SSRIs, which correspondingly decrease the 5-HT metabolite in the PFC (indicating serotonin reuptake inhibition), viloxazine did not affect 5-HIAA levels. Thus, viloxazine increases cortical 5-HT levels by a different mechanism than SSRIs. Whether 5-HT effects aid in viloxazine therapeutic efficacy in ADHD is yet unknown.FundingSupernus Pharmaceuticals, Inc.

Resveratrol prevents hearing loss and a subregion specific- reduction of serotonin reuptake transporter induced by noise exposure in the central auditory system.

Prolonged or excessive exposure to noise can lead to hearing loss, tinnitus and hypersensitivity to sound. The effects of noise exposure on main excitatory and inhibitory neurotransmitter systems in auditory pathway have been extensively investigated. However, little is known about aberrant changes in neuromodulator systems caused by noise exposure. In the current study, we exposed 2-month-old mice to a narrow band noise at 116 dB SPL for 6 h or sham exposure, assessed auditory brainstem responses as well as examined the expression of serotonin reuptake transporter (SERT) in the cochlear nucleus (CN), inferior colliculus (IC), and primary auditory cortex (Au1) using immunohistochemistry. We found that noise exposure resulted in a significant increase in hearing thresholds at 4, 8, 16, 24, and 32 kHz, as well as led to a significant reduction of SERT in dorsal cochlear nucleus (DCN), dorsal IC (ICd), external IC (ICe), and Au1 layers I-IV. This reduction of SERT in these subregions of central auditory system was partially recovered 15 or 30 days after noise exposure. Furthermore, we examined efficacy of resveratrol (RSV) on hearing loss and loss of SERT induced by noise exposure. The results demonstrated that RSV treatment significantly attenuated threshold shifts of auditory brainstem responses and loss of SERT in DCN, ICd, ICe, and Au1 layers I-IV. These findings show that noise exposure can cause hearing loss and subregion-specific loss of SERT in the central auditory system, and RSV treatment could attenuate noise exposure-induced hearing loss and loss of SERT in central auditory system.

Components of the sympathetic nervous system as targets to modulate inflammation – rheumatoid arthritis synovial fibroblasts as neuron-like cells?

BackgroundCatecholamines are major neurotransmitters of the sympathetic nervous system (SNS) and they are of pivotal importance in regulating numerous physiological and pathological processes. Rheumatoid arthritis (RA) is influenced by the activity of the SNS and its neurotransmitters norepinephrine (NE) and dopamine (DA) and early sympathectomy alleviates experimental arthritis in mice. In contrast, late sympathectomy aggravates RA, since this procedure eliminates anti-inflammatory, tyrosine hydroxylase (TH) positive cells that appear in the course of RA. While it has been shown that B cells can take up, degrade and synthesize catecholamines it is still unclear whether this also applies to synovial fibroblasts, a mesenchymal cell that is actively engaged in propagating inflammation and cartilage destruction in RA. Therefore, this study aims to present a detailed description of the catecholamine pathway and its influence on human RA synovial fibroblasts (RASFs).ResultsRASFs express all catecholamine-related targets including the synthesizing enzymes TH, DOPA decarboxylase, dopamine beta-hydroxylase, and phenylethanolamine N-methyltransferase. Furthermore, vesicular monoamine transporters 1/2 (VMAT1/2), dopamine transporter (DAT) and norepinephrine transporter (NET) were detected. RASFs are also able to degrade catecholamines as they express monoaminoxidase A and B (MAO-A/MAO-B) and catechol-O-methyltransferase (COMT). TNF upregulated VMAT2, MAO-B and NET levels in RASFs. DA, NE and epinephrine (EPI) were produced by RASFs and extracellular levels were augmented by either MAO, COMT, VMAT or DAT/NET inhibition but also by tumor necrosis factor (TNF) stimulation. While exogenous DA decreased interleukin-6 (IL-6) production and cell viability at the highest concentration (100 μM), NE above 1 μM increased IL-6 levels with a concomitant decrease in cell viability. MAO-A and MAO-B inhibition had differential effects on unstimulated and TNF treated RASFs. The MAO-A inhibitor clorgyline fostered IL-6 production in unstimulated but not TNF stimulated RASFs (10 nM-1 μM) while reducing IL-6 at 100 μM with a dose-dependent decrease in cell viability in both groups. The MAO-B inhibitor lazabemide hydrochloride did only modestly decrease cell viability at 100 μM while enhancing IL-6 production in unstimulated RASFs and decreasing IL-6 in TNF stimulated cells.ConclusionsRASFs possess a complete and functional catecholamine machinery whose function is altered under inflammatory conditions. Results from this study shed further light on the involvement of sympathetic neurotransmitters in RA pathology and might open therapeutic avenues to counteract inflammation with the MAO enzymes being key candidates.

Discontinuation of methylphenidate after long-term exposure in nonhuman primates

Attention-deficit hyperactivity disorder (ADHD) is a common human neurobehavioral disorder that usually begins in early childhood. Methylphenidate (MPH) has been used extensively as a first-line medicine for the treatment of ADHD. Since ADHD is often diagnosed in early childhood and can persist for the entire lifespan, individuals may take MPH for many years. Given that in the course of one's lifetime a person may stop taking MPH for periods of time, or may implement lifestyle changes that may reduce the need for MPH entirely, it is important to understand how cessation of MPH affects the adult brain following long-term use of MPH. The blockage of the dopamine transporter (DAT) and the norepinephrine transporter (NET) by MPH may help with ADHD symptoms by boosting monoamine levels in the synapse. In the present study, microPET/CT was used to investigate possible neurochemical alterations in the cerebral dopamine system after cessation of long-term MPH administration in nonhuman primates. MicroPET/CT images were collected from adult male rhesus monkeys 6 months after they stopped receiving vehicle or MPH following 12 years of chronic treatment. The neurochemical status of brain dopaminergic systems was evaluated using the vesicular monoamine transporter 2 (VMAT2) ligand [18F]-AV-133 and a tracer for imaging dopamine subtype 2 (D2) and serotonin subfamily 2 (5HT2) receptors, [18F]-FESP. Each tracer was injected intravenously and ten minutes later microPET/CT images were obtained over 120 min. The binding potential (BP) of each tracer in the striatum was obtained using the Logan reference tissue model with the cerebellar cortex time activity curve (TAC) as an input function. Brain metabolism was also evaluated using microPET/CT images of [18F]-FDG. [18F]-FDG was injected intravenously, and ten minutes later, microPET/CT images were obtained over 120 min. Radiolabeled tracer accumulation in regions of interest (ROIs) in the prefrontal cortex, temporal cortex, striatum, and cerebellum were converted into standard uptake values (SUVs). Compared to the vehicle control group, the BPs of [18F] AV-133 and [18F]-FESP in the striatum were not significantly altered in MPH treated groups. Additionally, no significant differences were detected in the SUVs of [18F]-FDG in the MPH treated group compared with control. This study demonstrates that 6 months after cessation of long-term, chronic MPH treatment, there are no significant neurochemical or neural metabolic changes in the central nervous system (CNS) of non-human primates (NHPs) and suggests that microPET imaging is helpful in assessing the status of biomarkers of neurochemical processes linked to chronic CNS drug exposure. (Supported by NCTR).

Ectopic expression of MmSERT, a mouse serotonin transporter gene, regulates salt tolerance and ABA sensitivity in apple and Arabidopsis

5-hydroxytryptamine (5-HT) is ubiquitously present in animals and plants, playing a vital regulatory role. SERT, a conserved serotonin reuptake transporter in animals, regulates intracellular and extracellular concentrations of 5-HT. Few studies have reported 5-HT transporters in plants. Hence, we cloned MmSERT, a serotonin reuptake transporter, from Mus musculus. Ectopic expression of MmSERT into apple calli, apple roots and Arabidopsis. Because 5-HT plays a momentous role in plant stress tolerance, we used MmSERT transgenic materials for stress treatment. We found that MmSERT transgenic materials, including apple calli, apple roots and Arabidopsis, exhibited a stronger salt tolerance phenotype. The reactive oxygen species (ROS) produced were significantly lower in MmSERT transgenic materials compared with controls under salt stress. Meanwhile, MmSERT induced the expression of SOS1, SOS3, NHX1, LEA5 and LTP1 in response to salt stress. 5-HT is the precursor of melatonin, which regulates plant growth under adversity and effectively scavenges ROS. Detection of MmSERT transgenic apple calli and Arabidopsis revealed higher melatonin levels than controls. Besides, MmSERT decreased the sensitivity of apple calli and Arabidopsis to abscisic acid (ABA). In summary, these results demonstrated that MmSERT plays a vital role in plant stress resistances, which perhaps serves as a reference for the application of transgenic technology to improve crops in the future.

The Relationship between Rem Sleep Behaviour Disorder and Parkinson’s Disease Revisited – Are They One and the Same?

This paper reviews the relationship between RBD and PD and the pathophysiology. Most RBD patients develop PD within 14 years. PD pathophysiology is α-synucleinopathy with dopamine degeneration in nigrostriatal pathways. RBD pathology is poorly understood. Anomalies suggest RBD and PD are different, evidenced by smoking. RBD and PD are associated with glucocerebrosidase gene mutations (GBA gene), suggesting RDB with GBA gene mutation predicts PD. PET imaging, assessing vesicular monoamine transporter 2 (VMAT2), indexing nigrostriatal dopamine innervation, is lower in PD and RBD, in the putamen, ventral striatum and globus pallidus but not substantia nigra or subthalamus, compared with controls. VMAT2 may not contribute to pathophysiology of RBD in PD. Treatments for RBD and PD differ. PD with RBD had more depression, compared to PD without RBD. Only PD with RBD had statistically significant increased depression, compared with controls, and non-significant lowered cognition. PD patients, with and without RBD, had decreased ligand binding, compared to healthy controls, indicating no difference in VMAT2 within the caudate and putamen. Research showed differences in cholinergic levels, noradrenaline and glucose metabolism for PD with and without RBD. RBD with PD, is multi-systematic, affecting regions beyond dopaminergic pathways. Treatment of RBD does not affects PD neurodegeneration. Researchers continue to search for neuro-protective intervention. There is a relationship between PD and RBD but it is not absolute. PD nigrostriatal degeneration is independent of RBD. Pathophysiological differences may explain why treatment of RBD does not alter its natural history.

Computational models of dopamine release measured by fast scan cyclic voltammetry in vivo.

Dopamine neurotransmission in the striatum is central to many normal and disease functions. Ventral midbrain dopamine neurons exhibit ongoing tonic firing that produces low extrasynaptic levels of dopamine below the detection of conventional extrasynaptic cyclic voltammetry (∼10-20 nanomolar), with superimposed bursts that can saturate the dopamine uptake transporter and produce transient micromolar concentrations. The bursts are known to lead to marked presynaptic plasticity via multiple mechanisms, but analysis methods for these kinetic parameters are limited. To provide a deeper understanding of the mechanics of the modulation of dopamine neurotransmission by physiological, genetic, and pharmacological means, we present three computational models of dopamine release with different levels of spatiotemporal complexity to analyze in vivo fast-scan cyclic voltammetry recordings from the dorsal striatum of mice. The models accurately fit to cyclic voltammetry data and provide estimates of presynaptic dopamine facilitation/depression kinetics and dopamine transporter reuptake kinetics, and we used the models to analyze the role of synuclein proteins in neurotransmission. The models' results support recent findings linking the presynaptic protein α-synuclein to the short-term facilitation and long-term depression of dopamine release, as well as reveal a new role for β-synuclein and/or γ-synuclein in the long-term regulation of dopamine reuptake.

Integrated regulation of dopaminergic and epigenetic effectors of neuroprotection in Parkinson’s disease models

Whole-exome sequencing of Parkinson's disease (PD) patient DNA identified single-nucleotide polymorphisms (SNPs) in the tyrosine nonreceptor kinase-2 (TNK2) gene. Although this kinase had a previously demonstrated activity in preventing the endocytosis of the dopamine reuptake transporter (DAT), a causal role for TNK2-associated dysfunction in PD remains unresolved. We postulated the dopaminergic neurodegeneration resulting from patient-associated variants in TNK2 were a consequence of aberrant or prolonged TNK2 overactivity, the latter being a failure in TNK2 degradation by an E3 ubiquitin ligase, neuronal precursor cell-expressed developmentally down-regulated-4 (NEDD4). Interestingly, systemic RNA interference protein-3 (SID-3) is the sole TNK2 ortholog in the nematode Caenorhabditis elegans, where it is an established effector of epigenetic gene silencing mediated through the dsRNA-transporter, SID-1. We hypothesized that TNK2/SID-3 represents a node of integrated dopaminergic and epigenetic signaling essential to neuronal homeostasis. Use of a TNK2 inhibitor (AIM-100) or a NEDD4 activator [N-aryl benzimidazole 2 (NAB2)] in bioassays for either dopamine- or dsRNA-uptake into worm dopaminergic neurons revealed that sid-3 mutants displayed robust neuroprotection from 6-hydroxydopamine (6-OHDA) exposures, as did AIM-100 or NAB2-treated wild-type animals. Furthermore, NEDD4 activation by NAB2 in rat primary neurons correlated to a reduction in TNK2 levels and the attenuation of 6-OHDA neurotoxicity. CRISPR-edited nematodes engineered to endogenously express SID-3 variants analogous to TNK2 PD-associated SNPs exhibited enhanced susceptibility to dopaminergic neurodegeneration and circumvented the RNAi resistance characteristic of SID-3 dysfunction. This research exemplifies a molecular etiology for PD whereby dopaminergic and epigenetic signaling are coordinately regulated to confer susceptibility or resilience to neurodegeneration.

Structural basis of GABA reuptake inhibition.

γ-Aminobutyric acid (GABA) transporter 1 (GAT1), a member of the neurotransmitter sodium symporter (NSS) family, regulates neuronal excitation by clearing the synaptic cleft of the main inhibitory neurotransmitter GABA upon its release from synaptic vesicles. Elevating GABA levels in the synaptic cleft, by inhibiting GABA reuptake transporters, is an established strategy to treat neurological disorders, such as epilepsy. Here we present the cryo-electron microscopy structure of full-length, wild-type human GAT1 in complex with its clinically used inhibitor, the anticonvulsant tiagabine. Our structure reveals that tiagabine locks GAT1 in the inward-open conformation, by blocking the intracellular gate of the GABA release pathway, and thus suppresses neurotransmitter uptake. Our results provide insights into the mixed-type inhibition of GAT1 by tiagabine. Tiagabine's pharmacodynamic profile, confirmed by our experimental data, suggests initial binding to the substrate-binding site in the outward-open conformation, whereas our structure presents the drug stalling the transporter in the inward-open conformation, consistent with a two-step induced-fit mechanism of inhibition. The presented structure of GAT1 gives crucial insights into the biology and pharmacology of this important neurotransmitter transporter and provides blueprints for the rational design of neuromodulators.

In vivo reduction of age-dependent neuromelanin accumulation mitigates features of Parkinson's disease.

Humans accumulate with age the dark-brown pigment neuromelanin inside specific neuronal groups. Neurons with the highest neuromelanin levels are particularly susceptible to degeneration in Parkinson's disease, especially dopaminergic neurons of the substantia nigra, the loss of which leads to characteristic motor Parkinson's disease symptoms. In contrast to humans, neuromelanin does not appear spontaneously in most animals, including rodents, and Parkinson's disease is an exclusively human condition. Using humanized neuromelanin-producing rodents, we recently found that neuromelanin can trigger Parkinson's disease pathology when accumulated above a specific pathogenic threshold. Here, by taking advantage of this newly developed animal model, we assessed whether the intracellular build-up of neuromelanin that occurs with age can be slowed down in vivo to prevent or attenuate Parkinson's disease. Because neuromelanin derives from the oxidation of free cytosolic dopamine, we enhanced dopamine vesicular encapsulation in the substantia nigra of neuromelanin-producing rats by viral vector-mediated overexpression of vesicular monoamine transporter 2 (VMAT2). This strategy reduced the formation of potentially toxic oxidized dopamine species that can convert into neuromelanin and maintained intracellular neuromelanin levels below their pathogenic threshold. Decreased neuromelanin production was associated with an attenuation of Lewy body-like inclusion formation and a long-term preservation of dopamine homeostasis, nigrostriatal neuronal integrity and motor function in these animals. Our results demonstrate the feasibility and therapeutic potential of modulating age-dependent intracellular neuromelanin production in vivo, thereby opening an unexplored path for the treatment of Parkinson's disease and, in a broader sense, brain ageing.

Perfused rat term placenta as a preclinical model to investigate placental dopamine and norepinephrine transport.

The placenta represents a non-neuronal organ capable of transporting and metabolizing monoamines. Since these bioactive molecules participate in numerous processes essential for placental and fetal physiology, any imbalance in their levels during pregnancy may affect brain development, projecting a higher risk of behavioral disorders in childhood or adulthood. Notably, the monoamine system in the placenta is a target of various psychoactive drugs and can be disrupted in several pregnancy pathologies. As research in pregnant women poses significant ethical restrictions, animal models are widely employed to study monoamine homeostasis as a mechanism involved in fetal programming. However, detailed knowledge of monoamine transport in the rat placenta is still lacking. Moreover, relatability to the human placental monoamine system is not examined. The present study provides insights into the transplacental monoamine dynamics between maternal and fetal circulation. We show that norepinephrine maternal-to-fetal transport is <4% due to high metabolism within the trophoblast. In contrast, dopamine maternal-to-fetal transport exceeds 25%, likely through passive transport across the membrane. In addition, we show high clearance of norepinephrine and dopamine from the fetal circulation mediated by the organic cation transporter 3 (OCT3). Altogether, we present transcriptional and functional evidence that the in situ rat placenta perfusion represents a suitable model for (patho)physiological investigation of dopamine and norepinephrine homeostasis in the fetoplacental unit. With the rapid advancements in drug discovery and environmental toxicity, the use of rat placenta as a preclinical model could facilitate screening of possible xenobiotic effects on monoamine homeostasis in the placenta.