Synaptic Vesicle Protein 2A Research Articles

Comprehensive mapping of synaptic vesicle protein 2A (SV2A) in health and neurodegenerative diseases: a comparative analysis with synaptophysin and ground truth for PET-imaging interpretation.

Synaptic dysfunction and loss are central to neurodegenerative diseases and correlate with cognitive decline. Synaptic Vesicle Protein 2A (SV2A) is a promising PET-imaging target for assessing synaptic density in vivo, but comprehensive mapping in the human brain is needed to validate its biomarker potential. This study used quantitative immunohistochemistry and Western blotting to map SV2A and synaptophysin (SYP) densities across six cortical regions in healthy controls and patients with early-onset Alzheimer's disease (EOAD), late-onset Alzheimer's disease (LOAD), progressive supranuclear palsy (PSP), and frontotemporal lobar degeneration with TDP-43 inclusions (FTLD-GRN). We identified region in SV2A density among controls and observed disease- and region-specific reductions, with the most severe in FTLD-GRN (up to 59.5%) and EOAD. EOAD showed a 49% reduction in the middle frontal gyrus (MFG), while LOAD had over 30% declines in the inferior frontal gyrus (IFG) and hippocampus (CA1). In PSP, smaller but significant reductions were noted in the hippocampal formation, with the inferior temporal gyrus (ITG) relatively unaffected. A strong positive correlation between SV2A and SYP densities confirmed SV2A's reliability as a synaptic integrity marker. This study supports the use of SV2A PET imaging for early diagnosis and monitoring of neurodegenerative diseases, providing essential data for interpreting in vivo PET results. Further research should explore SV2A as a therapeutic target and validate these findings in larger, longitudinal studies.

Ru-Catalyzed Asymmetric Hydrogenation of α,β-Unsaturated γ-Lactams.

A highly efficient Ru-catalyzed asymmetric hydrogenation of α,β-unsaturated γ-lactams has been developed by using a C2-symmetric ruthenocenyl phosphine-oxazoline as the chiral ligand. This method achieves the enantioselective synthesis of chiral β-substituted γ-lactams in high yields and with excellent enantioselectivities (up to 99% yield with 99% ee). Mechanistic studies based on detailed control experiments and computational investigation revealed that the cationic Ru-complex acts as the active catalytic species; the protonation process of the oxa-π-allyl-Ru complex, which is formed by the migratory insertion of the C=C double bond to the Ru-H bond (the stereocontrolling step) followed by an isomerization process, is the rate-determining step, and the existence of PPh3 is crucial for the highly efficient catalytic behavior. The protocol provides a straightforward and practical pathway for the synthesis of key intermediates for several chiral drugs and bioactive compounds, particularly for the 150 kg-scale industrial production of Brivaracetam, an antiepileptic drug that shows 13-fold more potent binding to the synaptic vesicle protein 2A compared with the well-known Levetiracetam.

SV2A controls the surface nanoclustering and endocytic recruitment of Syt1 during synaptic vesicle recycling.

Following exocytosis, the recapture of plasma membrane-stranded vesicular proteins into recycling synaptic vesicles (SVs) is essential for sustaining neurotransmission. Surface clustering of vesicular proteins has been proposed to act as a 'pre-assembly' mechanism for endocytosis that ensures high-fidelity retrieval of SV cargo. Here, we used single-molecule imaging to examine the nanoclustering of synaptotagmin-1 (Syt1) and synaptic vesicle protein 2A (SV2A) in hippocampal neurons. Syt1 forms surface nanoclusters through the interaction of its C2B domain with SV2A, which are sensitive to mutations in this domain (Syt1K326A/K328A) and SV2A knockdown. SV2A co-clustering with Syt1 is reduced by blocking SV2A's cognate interaction with Syt1 (SV2AT84A). Surprisingly, impairing SV2A-Syt1 nanoclustering enhanced the plasma membrane recruitment of key endocytic protein dynamin-1, causing accelerated Syt1 endocytosis, altered intracellular sorting and decreased trafficking of Syt1 to Rab5-positive endocytic compartments. Therefore, SV2A and Syt1 are segregated from the endocytic machinery in surface nanoclusters, limiting dynamin recruitment and negatively regulating Syt1 entry into recycling SVs.

Levetiracetam-induced Rhabdomyolysis - A Rare Complication

Background: Levetiracetam is an anti-epileptic drug that works by modulation of synaptic neurotransmitter release through binding to the synaptic vesicle protein 2A. Levetiracetam is generally well tolerated. Common side effects of levetiracetam include lethargy, drowsiness, headaches, and mood changes. Rhabdomyolysis and an increase in Creatine Kinase (CK) levels are one of the rarely reported effects of levetiracetam. Case presentation: We present a case of a 20-year-old patient with previously known epilepsy (non-compliant with medicine) who presented with a seizure. The patient was given 1 gram of levetiracetam in the emergency department and was kept at a maintenance dose of 500 mg twice a day. The workup revealed acute kidney injury and raised levels of creatinine kinase that peaked at 19,757 IU/L 72 hours after levetiracetam was started. Levetiracetam was later switched to lamotrigine and aggressive intravenous hydration was done. Gradual improvement of CK level was noted accompanied by improvement in renal function. Conclusion: Only a few cases of levetiracetam-induced rhabdomyolysis have been reported worldwide. Our case report highlights the importance of monitoring creatinine and CK levels while treating patients with levetiracetam as rhabdomyolysis can be asymptomatic with a rise in CK levels only.

Structures of synaptic vesicle protein 2A and 2B bound to anticonvulsants.

Epilepsy is a common neurological disorder characterized by abnormal activity of neuronal networks, leading to seizures. The racetam class of anti-seizure medications bind specifically to a membrane protein found in the synaptic vesicles of neurons called synaptic vesicle protein 2 (SV2) A (SV2A). SV2A belongs to an orphan subfamily of the solute carrier 22 organic ion transporter family that also includes SV2B and SV2C. The molecular basis for how anti-seizure medications act on SV2s remains unknown. Here we report cryo-electron microscopy structures of SV2A and SV2B captured in a luminal-occluded conformation complexed with anticonvulsant ligands. The conformation bound by anticonvulsants resembles an inhibited transporter with closed luminal and intracellular gates. Anticonvulsants bind to a highly conserved central site in SV2s. These structures provide blueprints for future drug design and will facilitate future investigations into the biological function of SV2s.

Evaluation of [11C]UCB-A positron emission tomography in human brains

BackgroundIn preclinical studies, the positron emission tomography (PET) imaging with [11C]UCB-A provided promising results for imaging synaptic vesicle protein 2A (SV2A) as a proxy for synaptic density. This paper reports the first-in-human [11C]UCB-A PET study to characterise its kinetics in healthy subjects and further evaluate SV2A-specific binding.ResultsTwelve healthy subjects underwent 90-min baseline [11C]UCB-A scans with PET/MRI, with two subjects participating in an additional blocking scan with the same scanning procedure after a single dose of levetiracetam (1500 mg). Our results indicated abundant [11C]UCB-A brain uptake across all cortical regions, with slow elimination. Kinetic modelling of [11C]UCB-A PET using various compartment models suggested that the irreversible two-tissue compartment model best describes the kinetics of the radioactive tracer. Accordingly, the Patlak graphical analysis was used to simplify the analysis. The estimated SV2A occupancy determined by the Lassen plot was around 66%. Significant specific binding at baseline and comparable binding reduction as grey matter precludes the use of centrum semiovale as reference tissue.Conclusions[11C]UCB-A PET imaging enables quantifying SV2A in vivo. However, its slow kinetics require a long scan duration, which is impractical with the short half-life of carbon-11. Consequently, the slow kinetics and complicated quantification methods may restrict its use in humans.

Narrative Review of Brivaracetam: Preclinical Profile and Clinical Benefits in the Treatment of Patients with Epilepsy.

One third of patients with epilepsy will continue to have uncontrolled seizures despite treatment with antiseizure medications (ASMs). There is therefore a need to develop novel ASMs. Brivaracetam (BRV) is an ASM that was developed in a major drug discovery program aimed at identifying selective, high-affinity synaptic vesicle protein 2A (SV2A) ligands, the target molecule of levetiracetam. BRV binds to SV2A with 15- to 30-fold higher affinity and greater selectivity than levetiracetam. BRV has broad-spectrum antiseizure activity in animal models of epilepsy, a favorable pharmacokinetic profile, few clinically relevant drug-drug interactions, and rapid brain penetration. BRV is available in oral and intravenous formulations and can be initiated at target dose without titration. Efficacy and safety of adjunctive BRV (50-200mg/day) treatment of focal-onset seizures was demonstrated in three pivotal phase III trials (NCT00490035/NCT00464269/NCT01261325), including in patients who had previously failed levetiracetam. Efficacy and safety of adjunctive BRV were also demonstrated in adult Asian patients with focal-onset seizures (NCT03083665). In several open-label trials (NCT00150800/NCT00175916/NCT01339559), long-term safety and tolerability of adjunctive BRV was established, with efficacy maintained for up to 14years, with high retention rates. Evidence from daily clinical practice highlights BRV effectiveness and tolerability in specific epilepsy patient populations with high unmet needs: the elderly (≥ 65years of age), children (< 16years of age), patients with cognitive impairment, patients with psychiatric comorbid conditions, and patients with acquired epilepsy of specific etiologies (post-stroke epilepsy/brain tumor related epilepsy/traumatic brain injury-related epilepsy). Here, we review the preclinical profile and clinical benefits of BRV from pivotal trials and recently published evidence from daily clinical practice.

Synaptic vesicle protein 2A mitigates parthanatos via apoptosis-inducing factor in a rat model of pharmacoresistant epilepsy.

Synaptic vesicle protein 2A (SV2A) is a unique therapeutic target for pharmacoresistant epilepsy (PRE). As seizure-induced neuronal programmed death, parthanatos was rarely reported in PRE. Apoptosis-inducing factor (AIF), which has been implicated in parthanatos, shares a common cytoprotective function with SV2A. We aimed to investigate whether parthanatos participates in PRE and is mitigated by SV2A via AIF. An intraperitoneal injection of lithium chloride-pilocarpine was used to establish an epileptic rat model, and phenytoin and phenobarbital sodium were utilized to select PRE and pharmacosensitive rats. The expression of SV2A was manipulated via lentivirus delivery into the hippocampus. Video surveillance was used to assess epileptic ethology. Biochemical tests were employed to test hippocampal tissues following a successful SV2A infection. Molecular dynamic calculations were used to simulate the interaction between SV2A and AIF. Parthanatos core index, PARP1, PAR, nuclear AIF and MIF, γ-H2AX, and TUNEL staining were all increased in PRE. SV2A is bound to AIF to form a stable complex, successfully inhibiting AIF and MIF nuclear translocation and parthanatos and consequently mitigating spontaneous recurrent seizures in PRE. Moreover, parthanatos deteriorated after the SV2A reduction. SV2A protected hippocampal neurons and mitigated epileptic seizures by inhibiting parthanatos via binding to AIF in PRE.

Synaptic density patterns in early Alzheimer's disease assessed by independent component analysis.

Synaptic loss is a primary pathology in Alzheimer's disease and correlates best with cognitive impairment as found in post-mortem studies. Previously, we observed in vivo reductions of synaptic density with [11C]UCB-J PET (radiotracer for synaptic vesicle protein 2A) throughout the neocortex and medial temporal brain regions in early Alzheimer's disease. In this study, we applied independent component analysis to synaptic vesicle protein 2A-PET data to identify brain networks associated with cognitive deficits in Alzheimer's disease in a blinded data-driven manner. [11C]UCB-J binding to synaptic vesicle protein 2A was measured in 38 Alzheimer's disease (24 mild Alzheimer's disease dementia and 14 mild cognitive impairment) and 19 cognitively normal participants. [11C]UCB-J distribution volume ratio values were calculated with a whole cerebellum reference region. Principal components analysis was first used to extract 18 independent components to which independent component analysis was then applied. Subject loading weights per pattern were compared between groups using Kruskal-Wallis tests. Spearman's rank correlations were used to assess relationships between loading weights and measures of cognitive and functional performance: Logical Memory II, Rey Auditory Verbal Learning Test-long delay, Clinical Dementia Rating sum of boxes and Mini-Mental State Examination. We observed significant differences in loading weights among cognitively normal, mild cognitive impairment and mild Alzheimer's disease dementia groups in 5 of the 18 independent components, as determined by Kruskal-Wallis tests. Only Patterns 1 and 2 demonstrated significant differences in group loading weights after correction for multiple comparisons. Excluding the cognitively normal group, we observed significant correlations between the loading weights for Pattern 1 (left temporal cortex and the cingulate gyrus) and Clinical Dementia Rating sum of boxes (r = -0.54, P = 0.0019), Mini-Mental State Examination (r = 0.48, P = 0.0055) and Logical Memory II score (r = 0.44, P = 0.013). For Pattern 2 (temporal cortices), significant associations were demonstrated between its loading weights and Logical Memory II score (r = 0.34, P = 0.0384). Following false discovery rate correction, only the relationship between the Pattern 1 loading weights with Clinical Dementia Rating sum of boxes (r = -0.54, P = 0.0019) and Mini-Mental State Examination (r = 0.48, P = 0.0055) remained statistically significant. We demonstrated that independent component analysis could define coherent spatial patterns of synaptic density. Furthermore, commonly used measures of cognitive performance correlated significantly with loading weights for two patterns within only the mild cognitive impairment/mild Alzheimer's disease dementia group. This study leverages data-centric approaches to augment the conventional region-of-interest-based methods, revealing distinct patterns that differentiate between mild cognitive impairment and mild Alzheimer's disease dementia, marking a significant advancement in the field.

In vivo PET of synaptic density as potential diagnostic marker for cognitive disorders: prospective comparison with current imaging markers for neuronal dysfunction and relation to symptomatology - study protocol

Background18F-FDG brain PET is clinically used for differential diagnosis in cognitive dysfunction of unclear etiology and for exclusion of a neurodegenerative cause in patients with cognitive impairment in late-life psychiatric disorders. 18F-FDG PET measures regional glucose metabolism, which represents a combination of neuronal/synaptic activity but also astrocytic activity and neuroinflammation. Recently, imaging of synaptic vesicle protein 2 A (SV2A) has become available and was shown to be a proxy of synaptic density. This prospective study will investigate the use of 18F-SynVesT-1 for imaging SV2A and its discriminative power for differential diagnosis in cognitive disorders in a head-to-head comparison to 18F-FDG PET. In addition, simultaneous PET/MR allows an evaluation of contributing factors and the additional value of advanced MRI imaging to FDG/SV2A PET imaging will be investigated. In this work, the study design and protocol are depicted.MethodsIn this prospective, multimodal imaging study, 110 patients with uncertain diagnosis of cognitive impairment who are referred for 18F-FDG PET brain imaging in their diagnostic work-up in a tertiary memory clinic will be recruited. In addition, 40 healthy volunteers (HV) between 18 and 85 years (M/F) will be included. All study participants will undergo simultaneous 18F-SynVesT-1 PET/MR and an extensive neuropsychological evaluation. Amyloid status will be measured by PET using 18FNAV4694, in HV above 50 years of age. Structural T1-weighted and T2-weighted fluid-attenuated inversion recovery MR images, triple-tagging arterial spin labeling (ASL) and resting-state functional MRI (rs-fMRI) will be obtained. The study has been registered on ClinicalTrials.gov (NCT05384353) and is approved by the local Research Ethics Committee.DiscussionThe main endpoint of the study will be the comparison of the diagnostic accuracy between 18F-SynVesT-1 and 18F-FDG PET in cognitive disorders with uncertain etiology and in exclusion of a neurodegenerative cause in patients with cognitive impairment in late-life psychiatric disorders. The strength of the relationship between cognition and imaging data will be assessed, as well as the potential incremental diagnostic value of including MR volumetry, ASL perfusion and rs-fMRI.

SV2A PET imaging in human neurodegenerative diseases.

This manuscript presents a thorough review of synaptic vesicle glycoprotein 2A (SV2A) as a biomarker for synaptic integrity using Positron Emission Tomography (PET) in neurodegenerative diseases. Synaptic pathology, characterized by synaptic loss, has been linked to various brain diseases. Therefore, there is a need for a minimally invasive approach to measuring synaptic density in living human patients. Several radiotracers targeting synaptic vesicle protein 2A (SV2A) have been created and effectively adapted for use in human subjects through PET scans. SV2A is an integral glycoprotein found in the membranes of synaptic vesicles in all synaptic terminals and is widely distributed throughout the brain. The review delves into the development of SV2A-specific PET radiotracers, highlighting their advancements and limitations in neurodegenerative diseases. Among these tracers, 11C-UCB-J is the most used so far. We summarize and discuss an increasing body of research that compares measurements of synaptic density using SV2A PET with other established indicators of neurodegenerative diseases, including cognitive performance and radiological findings, thus providing a comprehensive analysis of SV2A's effectiveness and reliability as a diagnostic tool in contrast to traditional markers. Although the literature overall suggests the promise of SV2A as a diagnostic and therapeutic monitoring tool, uncertainties persist regarding the superiority of SV2A as a biomarker compared to other available markers. The review also underscores the paucity of studies characterizing SV2A distribution and loss in human brain tissue from patients with neurodegenerative diseases, emphasizing the need to generate quantitative neuropathological maps of SV2A density in cases with neurodegenerative diseases to fully harness the potential of SV2A PET imaging in clinical settings. We conclude by outlining future research directions, stressing the importance of integrating SV2A PET imaging with other biomarkers and clinical assessments and the need for longitudinal studies to track SV2A changes throughout neurodegenerative disease progression, which could lead to breakthroughs in early diagnosis and the evaluation of new treatments.

Efficacy and Safety of Brivaracetam in Persons With Epilepsy in a Real-World Setting: A Prospective, Non-Interventional Study.

Epilepsy stands out as one of the most prevalent neurological conditions. Brivaracetam (BRV) is a noteworthy antiseizure medication (ASM) distinguished by its pronounced and selective interaction with the synaptic vesicle protein 2A (SV2A) within the brain. Prior investigations, including regulatory trials, post-marketing assessments, and comparative meta-analyses, have consistently underscored BRV's equivalency in efficacy and superior tolerability when pitted against other antiseizure drugs. This study aimed to evaluate the effectiveness, safety, and acceptability of BRV in treating epileptic patients in the Pakistani population. This prospective observational study, conducted in Pakistan from February to December 2022, employed a non-probability consecutive sampling technique. This study included 368 adult patients diagnosed with epilepsy, with a focus on those aged 18 and above experiencing focal seizures. Demographic data, clinical history, seizure types, and epilepsy profiles were recorded. Patients were administered BRV (Brivera; manufactured by Helix Pharma Pvt Ltd., Sindh, Pakistan) monotherapy therapy under physician guidance and followed up for three months. The study assessed changes in seizure frequency, side effects, and drug resistance at baseline, 14th day, and 90th day. Safety aspects were monitored, including documenting any adverse effects associated with BRV therapy. A total of 368 epileptic patients were included in this study, of which 287 (61.3%) were males and 181 (38.7%) were females. The mean age was 32.91±17.11 years. The mean number of seizures at the baseline visit was 5.74±6.21, at 14 days was 2.89±3.84 and at 90 days was 1.73±5.01 (p<0.001). Overall, a more than 50% reduction in seizure episodes was achieved in 178 (56.3%) patients at day 90, and less than 50% reduction in seizure episodes was achieved by 95 (26.8%) patients on Day 14, with a highly significant association between them (p<0.001). Among 316 patients, only 41 (4.4%) of all BRV-treated patients experienced adverse events; Of these 41 patients, 17 (41.7%) reported dizziness and 14(34.2%) reported behavioral issues. Epileptic patients receiving BRV demonstrated a substantial reduction of greater than 50% seizure episodes at the end of follow-up visits. Moreover, BRV exhibited fewer adverse effects in individuals with epilepsy.

Mapping changes in synaptic vesicle protein 2A (SV2A) in neurodegenerative diseases

AbstractBackgroundSynaptic loss is an early feature of neurodegenerative diseases and the best correlate of clinical decline. Synaptophysin is a pre‐synaptic protein used as a marker of synaptic integrity. Although no biomarker is available to measure synaptic integrity in the clinical setting, various potential PET‐scan tracers are under development. Tracers to detect synaptic vesicle protein 2A (SV2A), an integral glycoprotein in the membrane of synaptic vesicles, are among the most promising among those in development. However, the topographical distribution of SV2A in the human brain and the degree of regional changes in different neurodegenerative conditions are unclear, making it challenging to establish the utility of SV2A tracers in clinical practice. To close this gap, we mapped the density of SV2A in five areas vulnerable to age‐related neuropathology in postmortem brain tissue of subjects with four different types of neurodegenerative disease and healthy controls. Furthermore, we compared SV2A maps to synaptophysin maps obtained from adjacent slides.MethodTable 1 details the subjects' features. The regions of interest include middle and inferior frontal gyri, inferior temporal gyrus, angular gyrus, and CA1 sector/entorhinal cortex. 8 µm thick FFPE adjacent slides underwent immunohistochemistry for SV2A (1:150, Atlas Antibodies, rabbit polyclonal) or synaptophysin (1:75, Atlas Antibodies, rabbit polyclonal). All slides were scanned using a calibrated Zeiss Axioscan and quantified using the Zen software. Density was measured in 40 cortical ROIs (20 white &amp; 20 gray matter) per area/case, randomly distributed. Values were normalized for white matter intensity.ResultSVA2 loss was present in all disease conditions. The pattern of change was region and disease‐specific (Fig 1). Interestingly, the correlation between SV2A and synaptophysin density was poor to moderate (Fig 2).ConclusionReduced SV2A expression/level in all diseases indicates that SV2A is a potential marker to detect neurodegeneration. However, the lack of correlation between synaptophysin and SV2A level changes suggests that these markers signal different pathways. Additional research is needed to investigate the relationship between regional loss of SV2A and its potential significance as a marker for neurodegenerative disorders. We are performing Western blotting and autoradiography in the same samples to confirm the immunohistochemistry findings.

Understanding synaptic loss in PSP brains with UCB‐J

AbstractBackgroundProgressive supranuclear palsy (PSP) is a 4R‐tauopathy causing problems with balance, movement, vision, speech, and swallowing. There is a lack of biomarkers for PSP, which often leads to misdiagnosis, prescription of incorrect pharmacological treatments and likely underdiagnosis. Synaptic vesicle protein 2A (SV2A) PET‐tracer UCB‐J has shown great promise in imaging synaptic loss in many neurodegenerative diseases in vivo including PSP. UCB‐J‐PET imaging holds great potential for the early and accurate diagnosis of PSP, however, there is a substantial gap in knowledge around the extent of synaptic loss in PSP. Hence, it is of utmost importance to investigate synaptic changes in PSP brains with UCB‐J and to establish its correlation with other synaptic and neuropathological markers to gain a deeper understanding of underlying mechanisms for future biomarker validation.MethodWe performed specialized postmortem brain imaging (small and large frozen brain autoradiography) and radioligand binding assays (saturation, competition, and regional distribution), alongside immunohistochemistry and biochemical analyses in PSP and control (CN) brains.ResultSaturation studies in brain homogenates (BH) from the frontal cortex (FC) showed lower specific binding of 3H‐UCB‐J in PSP (Bmax: 348‐409 fmol/mg, Kd∼2.7nM) as compared to CN brains (Bmax:0.4‐0.5 pmol/mg, Kd∼3.5nM), indicating a loss in SV2A. Importantly, PSP brains showed much higher 3H‐UCB‐J specific binding in nuclear membrane P1‐fractions (Bmax 18.7‐22.1 pmol/mg, Kd ∼3.0nM) and synaptosomal‐membrane P2‐fractions (Bmax: 10.3‐12.3 pmol/mg, Kd∼2.4nM) as compared to BH (see above). Small section autoradiography showed lower 3H‐UCB‐J specific binding in PSP FC, but unexpectedly higher average specific binding in globus pallidus as compared to CN, suggesting regional differences and potential interaction with other brain tissue components/proteins.ConclusionOur findings clearly demonstrate that there are region‐specific changes in UCB‐J binding in PSP brains compared to CN and further reflect the need for its in‐depth validation in postmortem brains and correlation with other synaptic and neuropathological markers. Moreover, P2 fraction is most optimal for reflecting synaptic loss with UCB‐J. The ongoing regional distribution, biochemical and immunostaining studies will help elucidate changes in synaptic integrity in PSP.

Inflammatory and synaptic PET imaging in behavioural variant frontotemporal dementia caused by a repeat expansion in C9orf72 (C9orf72‐FTD)

AbstractBackgroundPathophysiological mechanisms associated with neurodegeneration include chronic neuroinflammation and synaptic dysfunction/loss. Radiotracer [11C]PBR28 is a marker of inflammation which binds to a translocator protein expressed by activated microglia. [11C]UCB‐J is a marker of synaptic density which binds to synaptic vesicle protein 2A. We evaluated both tracers as biomarkers of C9orf72‐FTD.MethodThree individuals with C9orf72‐FTD (mean age 62.7 years) underwent two PET scans between 3 and 13 months apart using [11C]PBR28 and [11C]UCB‐J. Dynamic PET data were acquired for 90 minutes following injection of each tracer. Arterial plasma input functions were generated from arterial blood samples. Participants also had volumetric MRI scans for each PET scan. Age‐matched controls from different cohorts underwent the same procedures (n = 5 for [11C]PBR28; n = 17 for [11C]UCB‐J).Regions of interest (ROIs) were defined on co‐registered T1‐weighted MR images using the CIC anatomical atlas. [11C]PBR28 BPND values were generated using a simplified reference tissue model with a cerebellar reference region. [11C]UCB‐J DVR‐1 values were generated using regional VT normalised to the VT in the centrum semiovale. ROI volumes were expressed as a percentage of total intracranial volume. W‐scores computed from each control cohort, using age and gender as covariates, illustrated the magnitude of differences between cases and controls. W‐scores &gt;1.65 were considered abnormal for [11C]PBR28 and ←1.65 for [11C]UCB‐J and MRI.Result[11C]PBR28 w‐scores indicated significant neuroinflammation in FTD but varied between cases. Differences in BPND were greater than in volume in frontal/temporal/cingulate cortices in the individual with the longest disease duration (DD) (16‐17 years). Inversely, in the individual with the shortest DD (1‐2 years), there were greater differences in volume than BPND in most ROIs.[11C]UCB‐J w‐scores indicated significant synaptic dysfunction/loss and were lower than w‐scores of volume in all cortical ROIs. In the individual with the longest DD, differences in [11C]PBR28 were greater than in [11C]UCB‐J in most ROIs. An inverse pattern again observed in the individual with the shortest DD suggests synaptic dysfunction/loss may precede significant neuroinflammation.ConclusionInflammatory and synaptic PET may provide more sensitive biomarkers of C9orf72‐FTD than MRI. Variability in PET signal within this genotype may be explained by DD.

Development of SV2A Ligands for Epilepsy Treatment: A Review of Levetiracetam, Brivaracetam, and Padsevonil.

Epilepsy is a common neurological disorder that is primarily treated with antiseizure medications (ASMs). Although dozens of ASMs are available in the clinic, approximately 30% of epileptic patients have medically refractory seizures; other limitations in most traditional ASMs include poor tolerability and drug-drug interactions. Therefore, there is an urgent need to develop alternative ASMs. Levetiracetam (LEV) is a first-line ASM that is well tolerated, has promising efficacy, and has little drug-drug interaction. Although it is widely accepted that LEV acts through a unique therapeutic target synaptic vesicle protein (SV) 2A, the molecular basis of its action remains unknown. Even so, the next-generation SV2A ligands against epilepsy based on the structure of LEV have achieved clinical success. This review highlights the research and development (R&D) process of LEV and its analogs, brivaracetam and padsevonil, to provide ideas and experience for the R&D of novel ASMs.

Modulating Hyperpolarization-Activated Cation Currents through Small Molecule Perturbations: Magnitude and Gating Control.

The hyperpolarization-activated cation current (Ih) exhibits a slowly activating time course of the current (Ih) when the cell membrane is hyperpolarized for an extended duration. It is involved in generating electrical activity in various excitable cells. Numerous structurally distinct compounds or herbal drugs have the potential to impact both the magnitude and gating kinetics of this current. Brivaracetam, a chemical analog of levetiracetam known to be a ligand for synaptic vesicle protein 2A, could directly suppress the Ih magnitude. Carisbamate, an anticonvulsant agent, not only inhibited the Ih amplitude but also reduced the strength of voltage-dependent hysteresis (Hys(V)) associated with Ih. Cilobradine, similar to ivabradine, inhibited the amplitude of Ih; however, it also suppressed the amplitude of delayed-rectifier K+ currents. Dexmedetomidine, an agonist of α2-adrenergic receptor, exerted a depressant action on Ih in a concentration-dependent fashion. Suppression of Ih amplitude was observed when GAL-021, a breathing control modulator, was present at a concentration exceeding 30 μM. Lutein, one of the few xanthophyll carotenoids, was able to suppress the Ih amplitude as well as to depress Hys(V)'s strength of Ih. Pirfenidone, a pyridine derivative known to be an anti-fibrotic agent, depressed the Ih magnitude in a concentration- and voltage-dependent fashion. Tramadol, a synthetic centrally active analgesic, was shown to reduce the Ih magnitude, independent of its interaction with opioid receptors. Various herbal drugs, including ent-kaurane-type diterpenoids from Croton tonkinensis, Ganoderma triterpenoids, honokiol, and pterostilbene, demonstrated efficacy in reducing the magnitude of Ih. Conversely, oxaliplatin, a platinum-based chemotherapeutic compound, was observed to effectively increase the Ih amplitude. Collectively, the regulatory effects of these compounds or herbal drugs on cellular function can be partly attributed to their perturbations on Ih.

Longitudinal Imaging of Regional Brain Volumes, SV2A, and Glucose Metabolism In Huntington's Disease.

Development of disease-modifying treatments for Huntington's disease (HD) could be aided by the use of imaging biomarkers of disease progression. Positron emission tomography (PET) with 11 C-UCB-J, a radioligand for the brain-wide presynaptic marker synaptic vesicle protein 2A (SV2A), detects more widespread brain changes in early HD than volumetric magnetic resonance imaging (MRI) and 18 F-fludeoxyglucose (18 F-FDG) PET, but longitudinal 11 C-UCB-J PET data have not been reported. The aim of this study was to compare the sensitivity of 11 C-UCB-J PET, 18 F-FDG PET, and volumetric MRI for detection of longitudinal changes in early HD. Seventeen HD mutation carriers (six premanifest and 11 early manifest) and 13 healthy controls underwent 11 C-UCB-J PET, 18 F-FDG PET, and volumetric MRI at baseline (BL) and after 21.4 ± 2.7 months (Y2). Within-group and between-group longitudinal clinical and imaging changes were assessed. The HD group showed significant 2-year worsening of Unified Huntington's Disease Rating Scale motor scores. There was significant longitudinal volume loss within the HD group in caudate (-4.5% ± 3.8%), putamen (-3.6% ± 3.5%), pallidum (-3.0% ± 2.7%), and frontal cortex (-2.0% ± 2.1%) (all P < 0.001). Within the HD group there was longitudinal loss of putaminal SV2A binding (6.4% ± 8.8%, P = 0.01) and putaminal glucose metabolism (-2.8% ± 4.4%, P = 0.008), but these changes were not significant after correction for multiple comparisons. Premanifest subjects at BL only had significantly lower SV2A binding than controls in basal ganglia structures, but at Y2 additionally had significant SV2A loss in frontal and parietal cortex, indicating spread of SV2A loss from subcortical to cortical regions. Volumetric MRI may be more sensitive than 11 C-UCB-J PET and 18 F-FDG PET for detection of 2-year brain changes in early HD. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Loss of SV2A promotes human neural stem cell apoptosis via p53 signaling

This study investigated the role of synaptic vesicle protein 2A (SV2A) in the regulation of human induced pluripotent stem cell-derived neural stem cells (NSCs). SV2A was highly expressed in NSCs. SV2A knockdown promotes apoptosis, which was associated with an upregulation of genes involved in p53 signaling as determined by transcriptome analysis. Treatment with the small molecule p53 inhibitor pifithrin-α reversed the promotion of NSC apoptosis induced by loss of SV2A. These results demonstrate that SV2A plays an important role in regulating NSC survival via the p53 signaling pathway.

A review of cognitive and behavioral outcomes of Brivaracetam.

Anti-seizure medications (ASMs) can cause cognitive or behavioral adverse drug reactions, which is an important consideration when selecting an appropriate ASM. Brivaracetam (BRV) is a newer synaptic vesicle protein 2A ligand, which is expected to result in fewer neuropsychiatric adverse effects due to its mechanism of action. To understand the impact of BRV on cognition and behavior compared with other ASMs, we conducted a review of the literature using the Cochrane Library, PubMed/MEDLINE, and Embase. After the screening process, a total of two animal studies, one randomized controlled trial, one pooled analysis of clinical trials, one controlled study, and nine observational studies were included. The animal studies showed that BRV did not worsen cognitive or behavioral performance in rodents. The human studies showed that BRV was associated with fewer cognitive adverse events compared with other second- or third-generation ASMs. In addition, BRV was less associated with behavioral disturbance than levetiracetam. In summary, this review revealed that BRV has a limited impact on cognition and behavior. For patients who are intolerant to levetiracetam and have levetiracetam-related behavioral side effects, switching to BRV could be beneficial. However, heterogeneity between studies resulted in low-quality of evidence, and further trials are needed to confirm the findings.