A Mitochondrial Role of SV2a Protein in Aging and Alzheimer's Disease: Studies with Levetiracetam

Two Cases of Levetiracetam-Induced Rhabdomyolysis With Low Levetiracetam Blood Concentrations

Levetiracetam is an antiepileptic drug used to treat tonic-clonic convulsions and partial seizures. In general, levetiracetam is well tolerated; however, rhabdomyolysis has been reported as a rare side effect. The underlying mechanism is unclear. This case report describes two cases of rhabdomyolysis during levetiracetam treatment for convulsive status epilepticus, both of whom developed rhabdomyolysis a few days after starting levetiracetam. When levetiracetam was replaced with lacosamide, creatinine kinase decreased to the normal range within approximately 10 days. Furthermore, blood levels of levetiracetam were measured at the onset of rhabdomyolysis, and the results suggest that its adverse effects may not be correlated with its levels in the blood. Monitoring creatinine kinase is important for early detection of levetiracetam-induced rhabdomyolysis.

Post mortem validation and mechanistic study of UCB-J in progressive supranuclear palsy patients' brains

INTRODUCTION

Progressive supranuclear palsy (PSP) is a devastating 4R tauopathy affecting motor functions and is often misdiagnosed/underdiagnosed due to a lack of specific biomarkers. Synaptic loss is an eminent feature of tauopathies including PSP. Novel synaptic positron emission tomography tracer UCB-J holds great potential for early diagnosis; however, there is a substantial knowledge gap in terms of the mechanism and the extent and nature of synaptic loss in PSP.

METHODS

Here, we report an in-depth post mortem validation and mechanistic study of UCB-J in PSP and control brains using radioligand/autoradiography binding studies, alongside biochemical correlation analyses of synaptic markers.

RESULTS AND DISCUSSION

3H-UCB-J targeted synaptic vesicle protein 2A protein with high specificity and demonstrated a distinct interrelation with synaptic markers in PSP patients' brain regions. The loss of UCB-J binding in the early and severely affected globus pallidus of PSP patients' brains revealed deficits of glutamate/GABAergic synaptic terminals. Cortical and subcortical 4R tau load differentially impacted synaptic marker profiles across PSP patients, warranting further investigation.

HIGHLIGHTS

UCB-J targeted synaptic vesicle protein 2A with high specificity in progressive supranuclear palsy (PSP) brains and demonstrated a conserved single nM binding site across different brain regions. UCB-J depicted prominent synaptic loss at the synaptosome levels and revealed deficits of glutamate/GABAergic synaptic terminals in the early affected globus pallidus of PSP brains as compared to the control. Cortical and subcortical 4R tau load distinctly influenced synaptic markers profile across PSP patients and highlighted that presynaptic "ubiquitous" markers individually might not be able to represent the complete state of synaptic deficits/loss in PSP brains.

Oligoprotective Activity of Levetiracetam against Glutamate Toxicity: An In vitro Study

INTRODUCTION

The role of glutamate in the development of some brain pathological conditions, such as multiple sclerosis, has been well described. Levetiracetam (LEV), a new broad-spectrum antiseizure medicine, is widely used to control certain types of seizures. Apart from its anti-seizure activity, LEV exerts neuroprotection via anti-inflammatory, antioxidant, and antiapoptotic effects. The current study was designed to evaluate the protective potential of LEV against glutamate-induced injury in OLN-93 oligodendrocytes.

METHODS

At first, the potential negative impact of LEV on OLN-93 viability was evaluated. After that, the cells were concurrently treated with LEV (0-100 μM) and glutamate (8 mM) for 24 h. The viability, redox status, and the rate of apoptosis of OLN-93 cells were then assessed using 3-[4,5-dimethylthiazol- 2-yl]-2,5-diphenyl-2H-tetrazolium bromide (MTT), 2',7' dichlorodihydrofluorescein diacetate (H2DCFDA), 2-thiobarbituric acid reactive substances (TBARS) and annexin V/propidium iodide (PI) assays, respectively. Moreover, caspase-3 expression, as a marker of cell apoptosis, was evaluated by Western blotting.

RESULTS

LEV at 1-800 μM did not have any negative effect on cell survival. Treatment with LEV (50 and 100 μM) substantially enhanced the cell viability following glutamate insult. The cytoprotective activity of LEV (50 and 100 μM) against glutamate toxicity was accompanied by reduced reactive oxygen species (ROS) accumulation and malondialdehyde (MDA) level. Moreover, 100 μM of LEV inhibited apoptosis and decreased the expression level of cleaved caspase-3 following glutamate exposure.

CONCLUSION

Taken together, the results suggested that LEV has protective effects against glutamate-mediated cytotoxicity in OLN-93 cells. The oligoprotective action of LEV was shown to be exerted via inhibition of oxidative stress and cellular apoptosis.

Evaluating the Efficacy of Levetiracetam on Non-Cognitive Symptoms and Pathology in a Tau Mouse Model

Background/Objectives: Alzheimer's disease (AD) is marked by amyloid-β plaques and hyperphosphorylated tau neurofibrillary tangles (NFTs), leading to cognitive decline and debilitating non-cognitive symptoms. This study aimed to evaluate compounds from four different classes in a short-term (7-day) study using transgenic tau mice to assess their ability to reduce non-cognitive symptoms. The best candidate was then evaluated for longer exposure to assess non-cognitive symptoms, cognition, and pathology. Methods: Tg4510 mice, expressing mutated human tau (P301L), were administered with levetiracetam, methylphenidate, diazepam, and quetiapine for 7 days at 6 months old, when pathology and cognitive deficits are established. Drugs were given in the diet, and non-cognitive symptoms were evaluated using metabolic cages. Levetiracetam was chosen for longer exposure (3 months) in 3-month-old Tg4510 mice and non-transgenic controls to assess behavior and pathology. Results: After 3 months of diet, levetiracetam mildly reduced tau pathology in the hippocampus but did not improve cognition in Tg4510 mice. Interestingly, it influenced appetite, body weight, anxiety-like behavior, and contextual fear memory in non-transgenic animals but not in Tg4510 mice. Conclusions: While levetiracetam has shown benefits in amyloid deposition models, it had limited effects on tau pathology and behavior in an animal model of tau deposition, which is crucial for AD context. The differential effects on non-transgenic versus Tg4510 mice warrant further investigation.

Synaptic changes in psychiatric and neurological disorders: state-of-the art of in vivo imaging

Synapses are implicated in many neuropsychiatric illnesses. Here, we provide an overview of in vivo techniques to index synaptic markers in patients. Several positron emission tomography (PET) tracers for synaptic vesicle glycoprotein 2 A (SV2A) show good reliability and selectivity. We review over 50 clinical studies including over 1700 participants, and compare findings in healthy ageing and across disorders, including addiction, schizophrenia, depression, posttraumatic stress disorder, and neurodegenerative disorders, including tauopathies, Huntington's disease and α-synucleinopathies. These show lower SV2A measures in cortical brain regions across most of these disorders relative to healthy volunteers, with the most well-replicated findings in tauopathies, whilst changes in Huntington's chorea, Parkinson's disease, corticobasal degeneration and progressive supranuclear palsy are predominantly subcortical. SV2A PET measures are correlated with functional connectivity across brain networks, and a number of other measures of brain function, including glucose metabolism. However, the majority of studies found no relationship between grey matter volume measured with magnetic resonance imaging and SV2A PET measures. Cognitive dysfunction, in domains including working memory and executive function, show replicated inverse relationships with SV2A measures across diagnoses, and initial findings also suggest transdiagnostic relationships with mood and anxiety symptoms. This suggests that synaptic abnormalities could be a common pathophysiological substrate underlying cognitive and, potentially, affective symptoms. We consider limitations of evidence and future directions; highlighting the need to develop postsynaptic imaging markers and for longitudinal studies to test causal mechanisms.

Identification of non-model mammal species using the MinION DNA sequencer from Oxford Nanopore

Background

The Neotropics harbors the largest species richness of the planet; however, even in well-studied groups, there are potentially hundreds of species that lack a formal description, and likewise, many already described taxa are difficult to identify using morphology. Specifically in small mammals, complex morphological diagnoses have been facilitated by the use of molecular data, particularly from mitochondrial sequences, to obtain accurate species identifications. Obtaining mitochondrial markers implies the use of PCR and specific primers, which are largely absent for non-model organisms. Oxford Nanopore Technologies (ONT) is a new alternative for sequencing the entire mitochondrial genome without the need for specific primers. Only a limited number of studies have employed exclusively ONT long-reads to assemble mitochondrial genomes, and few studies have yet evaluated the usefulness of such reads in multiple non-model organisms.

Methods

We implemented fieldwork to collect small mammals, including rodents, bats, and marsupials, in five localities in the northern extreme of the Cordillera Central of Colombia. DNA samples were sequenced using the MinION device and Flongle flow cells. Shotgun-sequenced data was used to reconstruct the mitochondrial genome of all the samples. In parallel, using a customized computational pipeline, species-level identifications were obtained based on sequencing raw reads (Whole Genome Sequencing). ONT-based identifications were corroborated using traditional morphological characters and phylogenetic analyses.

Results

A total of 24 individuals from 18 species were collected, morphologically identified, and deposited in the biological collection of Universidad EAFIT. Our different computational pipelines were able to reconstruct mitochondrial genomes from exclusively ONT reads. We obtained three new mitochondrial genomes and eight new molecular mitochondrial sequences for six species. Our species identification pipeline was able to obtain accurate species identifications for up to 75% of the individuals in as little as 5 s. Finally, our phylogenetic analyses corroborated the identifications from our automated species identification pipeline and revealed important contributions to the knowledge of the diversity of Neotropical small mammals.

Discussion

This study was able to evaluate different pipelines to reconstruct mitochondrial genomes from non-model organisms, using exclusively ONT reads, benchmarking these protocols on a multi-species dataset. The proposed methodology can be applied by non-expert taxonomists and has the potential to be implemented in real-time, without the need to euthanize the organisms and under field conditions. Therefore, it stands as a relevant tool to help increase the available data for non-model organisms, and the rate at which researchers can characterize life specially in highly biodiverse places as the Neotropics.

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

AIMS

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.

METHODS

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.

RESULTS

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.

SIGNIFICANCE

SV2A protected hippocampal neurons and mitigated epileptic seizures by inhibiting parthanatos via binding to AIF in PRE.

A review of the pharmacology and clinical applications of levetiracetam in dogs and cats

OBJECTIVE

To review and summarize the pharmacology of the antiepileptic drug (AED), levetiracetam (LEV), and to discuss its clinical utility in dogs and cats.

DATA SOURCES

Veterinary and human peer-reviewed medical literature and the authors' clinical experience.

SUMMARY

LEV is an AED with mechanisms of action distinct from those of other AEDs. In people and small animals, LEV exhibits linear kinetics, excellent oral bioavailability, and minimal drug-drug interactions. Serious side effects are rarely reported in any species. LEV use is gaining favor for treating epilepsy in small animals and may have wider clinical applications in patients with portosystemic shunts, neuroglycopenia, and traumatic brain injury. In people, LEV may improve cognitive function in patients with dementia.

CONCLUSION

LEV is a well-tolerated AED with well-documented efficacy in human patients. Although its use is becoming more common in veterinary medicine, its role as a first-line monotherapy in small animal epileptics remains to be determined. This review of the human and animal literature regarding LEV describes its role in epileptic people and animals as well as in other disease states and provides recommendations for clinical usage.

An Alzheimer's disease risk variant in TTC3 modifies the actin cytoskeleton organization and the PI3K-Akt signaling pathway in iPSC-derived forebrain neurons

A missense variant in the tetratricopeptide repeat domain 3 (TTC3) gene (rs377155188, p.S1038C, NM_003316.4:c 0.3113C>G) was found to segregate with disease in a multigenerational family with late-onset Alzheimer's disease. This variant was introduced into induced pluripotent stem cells (iPSCs) derived from a cognitively intact individual using CRISPR genome editing, and the resulting isogenic pair of iPSC lines was differentiated into cortical neurons. Transcriptome analysis showed an enrichment for genes involved in axon guidance, regulation of actin cytoskeleton, and GABAergic synapse. Functional analysis showed that the TTC3 p.S1038C iPSC-derived neuronal progenitor cells had altered 3-dimensional morphology and increased migration, while the corresponding neurons had longer neurites, increased branch points, and altered expression levels of synaptic proteins. Pharmacological treatment with small molecules that target the actin cytoskeleton could revert many of these cellular phenotypes, suggesting a central role for actin in mediating the cellular phenotypes associated with the TTC3 p.S1038C variant.

Correlation of SV2C rs1423099 single nucleotide polymorphism with sporadic Parkinson's disease in Han population in Southern China

BACKGROUND

The synaptic vesicle glycoprotein 2 (SV2) has been implicated in synaptic function throughout the brain. Accumulating evidence investigated that SV2C contributed to dopamine release and the disrupted expression of SV2C was considered to be a unique feature of PD that may facilitate dopaminergic neuron dysfunction.

OBJECTIVE

This study aimed to examine the relationship between the SV2C rs1423099 single nucleotide polymorphism and sporadic Parkinson's disease (PD) in the Chinese Han population.

MATERIALS AND METHODS

This study enrolled 351 patients with sporadic PD and 240 normal controls in Chinese Han population. Peripheral blood DNA was extracted by DNA extraction kits and the rs1423099 genotype was analyzed by Agena MassARRAY DNA mass spectrometry. The differences in genotype and allele distribution frequencies between PD patients and control groups were compared using chi-squared tests or Fisher's exact tests.

RESULTS

No statistical difference was revealed in age and sex distribution between the cases and control groups, and the distribution of genotype and allele frequencies was consistent with the Hardy-Weinberg equilibrium test. In SV2C rs1423099 dominant model, the frequency of the CC/CT genotype was significantly higher in the PD group compared to the control group (OR = 4.065,95% CI: 2.801-10.870, p = 0.002). Nevertheless, in the recessive model, CC or CT/TT genotypes have no statistical difference in the two groups (p = 0.09). Additionally, in allelic analysis, the C allele was investigated to increase the risk of PD (OR = 1.346, 95% CI: 1.036-1.745, p = 0.026); Furthermore, subgroup analysis suggested that those carrying the C allele in the male subgroup were at a higher risk to afflicted with PD (OR = 1.637, 95% CI: 1.147-2.336, p = 0.006).

CONCLUSION

SV2C rs1423099 single nucleotide polymorphism was associated with sporadic Parkinson's disease in the Chinese Han population, particularly in males.

An Alzheimer's disease risk variant in TTC3 modifies the actin cytoskeleton organization and the PI3K-Akt signaling pathway in iPSC-derived forebrain neurons

A missense variant in the tetratricopeptide repeat domain 3 ( TTC3 ) gene (rs377155188, p.S1038C, NM_003316.4:c.3113C>G) was found to segregate with disease in a multigenerational family with late onset Alzheimer's disease. This variant was introduced into induced pluripotent stem cells (iPSCs) derived from a cognitively intact individual using CRISPR genome editing and the resulting isogenic pair of iPSC lines were differentiated into cortical neurons. Transcriptome analysis showed an enrichment for genes involved in axon guidance, regulation of actin cytoskeleton, and GABAergic synapse. Functional analysis showed that the TTC3 p.S1038C iPSC-derived neuronal progenitor cells had altered 3D morphology and increased migration, while the corresponding neurons had longer neurites, increased branch points, and altered expression levels of synaptic proteins. Pharmacological treatment with small molecules that target the actin cytoskeleton could revert many of these cellular phenotypes, suggesting a central role for actin in mediating the cellular phenotypes associated with the TTC3 p.S1038C variant.

Highlights

The AD risk variant TTC3 p.S1038C reduces the expression levels of TTC3 The variant modifies the expression of AD specific genes BACE1 , INPP5F , and UNC5C Neurons with the variant are enriched for genes in the PI3K-Akt pathwayiPSC-derived neurons with the alteration have increased neurite length and branchingThe variant interferes with actin cytoskeleton and is ameliorated by Cytochalasin D.

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.

Synaptic Vesicle Glycoprotein 2A: Features and Functions

In recent years, the field of neuroimaging dramatically moved forward by means of the expeditious development of specific radioligands of novel targets. Among these targets, the synaptic vesicle glycoprotein 2A (SV2A) is a transmembrane protein of synaptic vesicles, present in all synaptic terminals, irrespective of neurotransmitter content. It is involved in key functions of neurons, focused on the regulation of neurotransmitter release. The ubiquitous expression in gray matter regions of the brain is the basis of its candidacy as a marker of synaptic density. Following the development of molecules derived from the structure of the anti-epileptic drug levetiracetam, which selectively binds to SV2A, several radiolabeled markers have been synthetized to allow the study of SV2A distribution with positron emission tomography (PET). These radioligands permit the evaluation of in vivo changes of SV2A distribution held to be a potential measure of synaptic density in physiological and pathological conditions. The use of SV2A as a biomarker of synaptic density raises important questions. Despite numerous studies over the last decades, the biological function and the expressional properties of SV2A remain poorly understood. Some functions of SV2A were claimed, but have not been fully elucidated. While the expression of SV2A is ubiquitous, stronger associations between SV2A and Υ amino butyric acid (GABA)-ergic rather than glutamatergic synapses were observed in some brain structures. A further issue is the unclear interaction between SV2A and its tracers, which reflects a need to clarify what really is detected with neuroimaging tools. Here, we summarize the current knowledge of the SV2A protein and we discuss uncertain aspects of SV2A biology and physiology. As SV2A expression is ubiquitous, but likely more strongly related to a certain type of neurotransmission in particular circumstances, a more extensive knowledge of the protein would greatly facilitate the analysis and interpretation of neuroimaging results by allowing the evaluation not only of an increase or decrease of the protein level, but also of the type of neurotransmission involved.

Mechanisms Involved in Epileptogenesis in Alzheimer's Disease and Their Therapeutic Implications

Epilepsy and Alzheimer's disease (AD) incidence increases with age. There are reciprocal relationships between epilepsy and AD. Epilepsy is a risk factor for AD and, in turn, AD is an independent risk factor for developing epilepsy in old age, and abnormal AD biomarkers in PET and/or CSF are frequently found in late-onset epilepsies of unknown etiology. Accordingly, epilepsy and AD share pathophysiological processes, including neuronal hyperexcitability and an early excitatory-inhibitory dysregulation, leading to dysfunction in the inhibitory GABAergic and excitatory glutamatergic systems. Moreover, both β-amyloid and tau protein aggregates, the anatomopathological hallmarks of AD, have proepileptic effects. Finally, these aggregates have been found in the resection material of refractory temporal lobe epilepsies, suggesting that epilepsy leads to amyloid and tau aggregates. Some epileptic syndromes, such as medial temporal lobe epilepsy, share structural and functional neuroimaging findings with AD, leading to overlapping symptomatology, such as episodic memory deficits and toxic synergistic effects. In this respect, the existence of epileptiform activity and electroclinical seizures in AD appears to accelerate the progression of cognitive decline, and the presence of cognitive decline is much more prevalent in epileptic patients than in elderly patients without epilepsy. Notwithstanding their clinical significance, the diagnosis of clinical seizures in AD is a challenge. Most are focal and manifest with an altered level of consciousness without motor symptoms, and are often interpreted as cognitive fluctuations. Finally, despite the frequent association of epilepsy and AD dementia, there is a lack of clinical trials to guide the use of antiseizure medications (ASMs). There is also a potential role for ASMs to be used as disease-modifying drugs in AD.

Imaging Synaptic Density: The Next Holy Grail of Neuroscience?

The brain is the central and most complex organ in the nervous system, comprising billions of neurons that constantly communicate through trillions of connections called synapses. Despite being formed mainly during prenatal and early postnatal development, synapses are continually refined and eliminated throughout life via complicated and hitherto incompletely understood mechanisms. Failure to correctly regulate the numbers and distribution of synapses has been associated with many neurological and psychiatric disorders, including autism, epilepsy, Alzheimer’s disease, and schizophrenia. Therefore, measurements of brain synaptic density, as well as early detection of synaptic dysfunction, are essential for understanding normal and abnormal brain development. To date, multiple synaptic density markers have been proposed and investigated in experimental models of brain disorders. The majority of the gold standard methodologies (e.g., electron microscopy or immunohistochemistry) visualize synapses or measure changes in pre- and postsynaptic proteins ex vivo. However, the invasive nature of these classic methodologies precludes their use in living organisms. The recent development of positron emission tomography (PET) tracers [such as (¹⁸F)UCB-H or (¹¹C)UCB-J] that bind to a putative synaptic density marker, the synaptic vesicle 2A (SV2A) protein, is heralding a likely paradigm shift in detecting synaptic alterations in patients. Despite their limited specificity, novel, non-invasive magnetic resonance (MR)-based methods also show promise in inferring synaptic information by linking to glutamate neurotransmission. Although promising, all these methods entail various advantages and limitations that must be addressed before becoming part of routine clinical practice. In this review, we summarize and discuss current ex vivo and in vivo methods of quantifying synaptic density, including an evaluation of their reliability and experimental utility. We conclude with a critical assessment of challenges that need to be overcome before successfully employing synaptic density biomarkers as diagnostic and/or prognostic tools in the study of neurological and neuropsychiatric disorders.

Past, present and future of therapeutic strategies against amyloid-β peptides in Alzheimer's disease: a systematic review

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease in ageing, affecting around 46 million people worldwide but few treatments are currently available. The etiology of AD is still puzzling, and new drugs development and clinical trials have high failure rates. Urgent outline of an integral (multi-target) and effective treatment of AD is needed. Accumulation of amyloid-β (Aβ) peptides is considered one of the fundamental neuropathological pillars of the disease, and its dyshomeostasis has shown a crucial role in AD onset. Therefore, many amyloid-targeted therapies have been investigated. Here, we will systematically review recent (from 2014) investigational, follow-up and review studies focused on anti-amyloid strategies to summarize and analyze their current clinical potential. Combination of anti-Aβ therapies with new developing early detection biomarkers and other therapeutic agents acting on early functional AD changes will be highlighted in this review. Near-term approval seems likely for several drugs acting against Aβ, with recent FDA approval of a monoclonal anti-Aβ oligomers antibody -aducanumab- raising hopes and controversies. We conclude that, development of oligomer-epitope specific Aβ treatment and implementation of multiple improved biomarkers and risk prediction methods allowing early detection, together with therapies acting on other factors such as hyperexcitability in early AD, could be the key to slowing this global pandemic.

Positron Emission Computed Tomography Imaging of Synaptic Vesicle Glycoprotein 2A in Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder seen in age-dependent dementia. There is currently no effective treatment for AD, which may be attributed in part to lack of a clear underlying mechanism. Early diagnosis of AD is of great significance to control the development of the disease. Synaptic loss is an important pathology in the early stage of AD, therefore the measurement of synaptic density using molecular imaging technology may be an effective way to early diagnosis of AD. Synaptic vesicle glycoprotein 2A (SV2A) is located in the presynaptic vesicle membrane of virtually all synapses. SV2A Positron Emission Computed Tomography (PET) could provide a way to measure synaptic density quantitatively in living humans and to track changes in synaptic density in AD. In view of the fact that synaptic loss is the pathology of both epilepsy and AD, this review summarizes the potential role of SV2A in the pathogenesis of AD, and suggests that SV2A should be used as an important target molecule of PET imaging agent for the early diagnosis of AD.

The Synaptic Vesicle Protein 2A Interacts With Key Pathogenic Factors in Alzheimer's Disease: Implications for Treatment

Alzheimer’s disease (AD), a serious neurodegenerative disease, is pathologically characterized by synaptic loss and dysfunction. Synaptic vesicle protein 2A (SV2A) is an indispensable vesicular protein specifically expressed in synapses and can be used as a biomarker for synaptic density. We found that the expression of SV2A was down-regulated in the hippocampus of AD patients, yet the relation of SV2A to other hallmarks of AD pathology such as amyloid precursor protein (APP), β-amyloid (Aβ), and Tau protein is not thoroughly clear. In addition, SV2A colocalized with APP and was down-regulated at Aβ deposition. Moreover, we found that SV2A deficiency leads to a simultaneous increase in Aβ and Tau hyperphosphorylation, while SV2A overexpression was associated with downregulation of β-site APP cleaving enzyme 1 and apolipoprotein E genes. In addition, evidence gained in the study points to the phosphatidylinositol 3-kinase signaling pathway as a possible mediator in SV2A regulation influencing the incidence and development of AD. With limited effective diagnostic methods for AD, a close interplay between SV2A and AD-related proteins demonstrated in our study may provide novel and innovative diagnostic and therapeutic opportunities.

Berberine Improves Behavioral and Cognitive Deficits in a Mouse Model of Alzheimer's Disease via Regulation of β-Amyloid Production and Endoplasmic Reticulum Stress

Alzheimer's disease (AD) is a neurodegenerative disease characterized by β-amyloid (Aβ), neurofibrillary tangles, and neuronal cell death. Aggressive Aβ accumulation accelerates senile plaque formation and perturbs endoplasmic reticulum (ER) function. Aβ accumulation-induced changes stimulate the unfolded protein response (UPR), which can trigger neuronal apoptosis. Protein kinase RNA-like endoplasmic reticulum kinase (PERK), whose activation is stress-dependent, increases the phosphorylation of eukaryotic translation initiation factor-2α (eIF2α). eIF2α promotes the synthesis of β-site APP cleavage enzyme 1 (BACE1), which in turn facilitates Aβ generation and subsequent neuronal apoptosis. In this study, we investigated whether berberine could improve cognitive deficits in the triple-transgenic mouse model of Alzheimer's disease (3 × Tg AD) mice. Our results revealed that berberine treatment may inhibit PERK/eIF2α signaling-mediated BACE1 translation, thus reducing Aβ production and resultant neuronal apoptosis. Further, berberine may have neuroprotective effects, via attenuation of ER stress and oxidative stress. In sum, our study demonstrates the therapeutic potential of berberine for treating AD.

Temporal Lobe Epilepsy and Alzheimer's Disease: From Preclinical to Clinical Evidence of a Strong Association

Increasing evidence coming from both experimental and humans' studies strongly suggest the existence of a link between epilepsy, in particular temporal lobe epilepsy (TLE), and Alzheimer's disease (AD). Patients with mild cognitive impairment and AD are more prone to have seizures, and seizures seem to facilitate amyloid-β and tau deposits, thus promoting neurodegenerative processes. Consistent with this view, long-lasting drug-resistant TLE and AD have been shown to share several pathological and neuroimaging features. Even if studies addressing prevalence of interictal and subclinical epileptiform activity in these patients are not yet conclusive, their findings raise the possibility that epileptiform activity might negatively impact memory and hasten cognitive decline, either directly or by association with unrecognized silent seizures. In addition, data about detrimental effect of network hyperexcitability in temporal regions in the premorbid and early stages ofADopen up newtherapeutic opportunities for antiseizure medications and/or antiepileptic strategies that might complement or enhance existing therapies, and potentially modify disease progression. Here we provide a review of evidence linking epileptiform activity, network hyperexcitability, and AD, and their role promoting and accelerating neurodegenerative process. Finally, the effects of antiseizure medications on cognition and their optimal administration in patients with AD are summarized.

Operation Brain Trauma Therapy: An Exploratory Study of Levetiracetam Treatment Following Mild Traumatic Brain Injury in the Micro Pig

Operation brain trauma therapy (OBTT) is a drug- and biomarker-screening consortium intended to improve the quality of preclinical studies and provide a rigorous framework to increase the translational potential of experimental traumatic brain injury (TBI) treatments. Levetiracetam (LEV) is an antiepileptic agent that was the fifth drug tested by OBTT in three independent rodent models of moderate to severe TBI. To date, LEV has been the most promising drug tested by OBTT and was therefore advanced to testing in the pig. Adult male micro pigs were subjected to a mild central fluid percussion brain injury followed by a post-injury intravenous infusion of either 170 mg/kg LEV or vehicle. Systemic physiology was assessed throughout the post-injury period. Serial serum samples were obtained pre-injury as well as at 1 min, 30 min, 1 h, 3 h, and 6 h post-injury for a detailed analysis of the astroglial biomarker glial fibrillary acidic protein (GFAP) and ubiquitin carboxy-terminal hydrolase L1. Tissue was collected 6 h following injury for histological assessment of diffuse axonal injury using antibodies against the amyloid precursor protein (APP). The animals showed significant increases in circulating GFAP levels from baseline to 6 h post-injury; however, LEV treatment was associated with greater GFAP increases compared to the vehicle. There were no differences in the numbers of APP+ axonal swellings within the pig thalamus with LEV treatment; however, significant alterations in the morphological properties of the APP+ axonal swellings, including reduced swelling area and increased swelling roundness, were observed. Additionally, expression of the neurite outgrowth marker, growth-associated protein 43, was reduced in axonal swellings following LEV treatment, suggesting potential effects on axonal outgrowth that warrant further investigation.

Deep Brain Stimulation for Alzheimer's Disease: Tackling Circuit Dysfunction

OBJECTIVES

Treatments for Alzheimer's disease are urgently needed given its enormous human and economic costs and disappointing results of clinical trials targeting the primary amyloid and tau pathology. On the other hand, deep brain stimulation (DBS) has demonstrated success in other neurological and psychiatric disorders leading to great interest in DBS as a treatment for Alzheimer's disease.

MATERIALS AND METHODS

We review the literature on 1) circuit dysfunction in Alzheimer's disease and 2) DBS for Alzheimer's disease. Human and animal studies are reviewed individually.

RESULTS

There is accumulating evidence of neural circuit dysfunction at the structural, functional, electrophysiological, and neurotransmitter level. Recent evidence from humans and animals indicate that DBS has the potential to restore circuit dysfunction in Alzheimer's disease, similarly to other movement and psychiatric disorders, and may even slow or reverse the underlying disease pathophysiology.

CONCLUSIONS

DBS is an intriguing potential treatment for Alzheimer's disease, targeting circuit dysfunction as a novel therapeutic target. However, further exploration of the basic disease pathology and underlying mechanisms of DBS is necessary to better understand how circuit dysfunction can be restored. Additionally, robust clinical data in the form of ongoing phase III clinical trials are needed to validate the efficacy of DBS as a viable treatment.

Assessment of a white matter reference region for 11C-UCB-J PET quantification

¹¹C-UCB-J is a positron emission tomography (PET) radioligand that has been used in humans for synaptic vesicle glycoprotein 2A (SV2A) imaging and as a potential synaptic density marker. The centrum semiovale (CS) is a proposed reference region for noninvasive quantification of ¹¹C-UCB-J, due to negligible concentrations of SV2A in this region in baboon brain assessed by in vitro methods. However, in displacement scans with SV2A-specific drug levetiracetam in humans, a decrease in ¹¹C-UCB-J concentration was observed in the CS, consistent with some degree of specific binding. The current study aims to validate the CS as a reference region by (1) optimizing CS region of interest (ROI) to minimize spill-in from gray matter with high radioactivity concentrations; (2) investigating convergence of CS ROI values using ordered subset expectation maximization (OS-EM) reconstruction, and (3) comparing baseline CS volume of distribution (V_T) to nondisplaceable uptake in gray matter, V_ND. Improving ROI definition and increasing OS-EM iterations during reconstruction decreased the difference between CS V_T and V_ND. However, even with these corrections, CS V_T overestimated V_ND by ∼35-40%. These measures showed significant correlation, suggesting that, though biased, the CS may be a useful estimate of nondisplaceable uptake, allowing for noninvasive quantification for SV2A PET.

Mitochondrial abnormalities in neurodegenerative models and possible interventions: Focus on Alzheimer's disease, Parkinson's disease, Huntington's disease

Mitochondrial abnormalities in the brain are considered early pathological changes in neurogenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease (HD). The mitochondrial dysfunction in the brain can be induced by toxic proteins, including amyloid-beta (Aβ), phosphorylated tau, alpha-synuclein (α-syn) and mutant huntingtin (mtHTT). These proteins cause mitochondrial genome damage, increased oxidative stress, decreased mitochondrial membrane permeability, and diminished ATP production. Consequently, synaptic dysfunction, synaptic loss, neuronal apoptosis, and ultimately cognitive impairment are exhibited. Therefore, the restoration of mitochondrial abnormalities in the brain is an alternative intervention to delay the progression of neurodegenerative diseases in addition to reducing the level of toxic proteins, especially Aβ, and restored synaptic dysfunction by interventions. Here we comprehensively review mitochondrial alterations in the brain of neurodegenerative models, specifically AD, PD and HD, from both in vitro and in vivo studies. Additionally, the correlation between mitochondrial changes, cognitive function, and disease progression from in vivo studies is described. This review also summarizes interventions that possibly attenuate mitochondrial abnormalities in AD, PD and HD models from both in vitro and in vivo studies. This may lead to the introduction of novel therapies that target on brain mitochondria to delay the progression of AD, PD and HD.

Development and In Vivo Preclinical Imaging of Fluorine-18-Labeled Synaptic Vesicle Protein 2A (SV2A) PET Tracers

PURPOSE

Synaptic vesicle protein 2A (SV2A) serves as a biomarker of synaptic density and positron emission tomography (PET) imaging of SV2A could provide a tool to assess progression of neurodegenerative diseases. Two tracers have primarily been reported and characterized in vivo: [¹¹C]UCB-J and [¹⁸F]UCB-H. In early human studies, [¹¹C]UCB-J showed promising results, while its F-18-labeled analogue [¹⁸F]UCB-H showed suboptimal specific signal in comparison to [¹¹C]UCB-J. Considering the limited use of [¹¹C]UCB-J to facilities with a cyclotron, having a F-18 variant would facilitate large, multicenter imaging trials. We have screened several F-18 derivatives of UCB-J in non-human primates and identified a promising F-18 PET candidate, [¹⁸F]MNI-1126, with additional investigations of the racemate [¹⁸F]MNI-1038, affording a signal comparable to [¹¹C]UCB-J.

PROCEDURES

F-18 derivatives of UCB-J and UCB-H were synthesized and administered to non-human primates for microPET imaging. Following screenings, [¹⁸F]MNI-1038 (racemate) and [¹⁸F]MNI-1126 (R-enantiomer) were identified with the highest signal and favorable kinetics and were selected for further imaging. Kinetic modeling with one- and two-tissue compartmental models, and linear methods were applied to PET data using metabolite-corrected arterial input function. Pre-block scans with levetiracetam (LEV, 10, 30 mg/kg, iv) were performed to determine the tracers' in vivo specificity for SV2A. Two whole-body PET studies were performed with [¹⁸F]MNI-1038 in one male and one female rhesus, and radiation absorbed dose estimates and effective dose (ED, ICRP-103) were estimated with OLINDA/EXM 2.0.

RESULTS

All compounds screened displayed very good brain penetration, with a plasma-free fraction of ~ 40 %. [¹⁸F]MNI-1126 and [¹⁸F]MNI-1038 showed uptake and distribution the most consistent with UCB-J, while the other derivatives showed suboptimal results, with similar or lower uptake than [¹⁸F]UCB-H. V_T of [¹⁸F]MNI-1126 and [¹⁸F]MNI-1038 was high in all gray matter regions (within animal averages ~ 30 ml/cm³) and highly correlated with [¹¹C]UCB-J (r > 0.99). Pre-blocking of [¹⁸F]MNI-1126 or [¹⁸F]MNI-1038 with LEV showed robust occupancy across all gray matter regions, similar to that reported with [¹¹C]UCB-J (~ 85 % at 30 mg/kg, ~ 65 % at 10 mg/kg). Using the centrum semiovale as a reference region, BP_ND of [¹⁸F]MNI-1126 reached values of up to ~ 30 to 40 % higher than those reported for [¹¹C]UCB-J. From whole-body imaging average ED of [¹⁸F]MNI-1038 was estimated to be 22.3 μSv/MBq, with tracer being eliminated via both urinary and hepatobiliary pathways.

CONCLUSIONS

We have identified a F-18-labeled tracer ([¹⁸F]MNI-1126) that exhibits comparable in vivo characteristics and specificity for SV2A to [¹¹C]UCB-J in non-human primates, which makes [¹⁸F]MNI-1126 a promising PET radiotracer for imaging SV2A in human trials.

Rapid mitochondrial genome sequencing based on Oxford Nanopore Sequencing and a proxy for vertebrate species identification

Molecular information is crucial for species identification when facing challenging morphology-based specimen identifications. The use of DNA barcodes partially solves this problem, but in some cases when PCR is not an option (i.e., primers are not available, problems in reaction standardization), amplification-free approaches could be an optimal alternative. Recent advances in DNA sequencing, like the MinION device from Oxford Nanopore Technologies (ONT), allow to obtain genomic data with low laboratory and technical requirements, and at a relatively low cost. In this study, we explore ONT sequencing for molecular species identification from a total DNA sample obtained from a neotropical rodent and we also test the technology for complete mitochondrial genome reconstruction via genome skimming. We were able to obtain "de novo" the complete mitogenome of a specimen from the genus Melanomys (Cricetidae: Sigmodontinae) with average depth coverage of 78X using ONT-only data and by combining multiple assembly routines. Our pipeline for an automated species identification was able to identify the sample using unassembled sequence data (raw) in a reasonable computing time, which was substantially reduced when a priori information related to the organism identity was known. Our findings suggest ONT sequencing as a suitable candidate to solve species identification problems in metazoan nonmodel organisms and generate complete mtDNA datasets.

Synthesis and Preclinical Evaluation of an 18F-Labeled Synaptic Vesicle Glycoprotein 2A PET Imaging Probe: [18F]SynVesT-2

Synaptic vesicle glycoprotein 2A (SV2A) is a 12-pass transmembrane glycoprotein ubiquitously expressed in presynaptic vesicles. In vivo imaging of SV2A using PET has potential applications in the diagnosis and prognosis of a variety of neuropsychiatric diseases, e.g., Alzheimer's disease, Parkinson's disease, schizophrenia, multiple sclerosis, autism, epilepsy, stroke, traumatic brain injury, post-traumatic stress disorder, depression, etc. Herein, we report the synthesis and evaluation of a new ¹⁸F-labeled SV2A PET imaging probe, [¹⁸F]SynVesT-2, which possesses fast in vivo binding kinetics and high specific binding signals in non-human primate brain.

Levetiracetam inhibits THP-1 monocyte chemotaxis and adhesion via the synaptic vesicle 2A

Long-term therapy with older antiepileptic drugs (AEDs), but not levetiracetam (LEV), may increase the risk of atherosclerosis (AS), suggesting that LEV may have a potential anti-AS effect. The synaptic vesicle 2A (SV2A) is known to the specific binding site of LEV. Numerous studies have documented that SV2A is a membrane protein specifically expressed in nervous system. Interestingly, our previous research showed that SV2A also existed in human CD8+ T lymphocytes. Therefore, we hypothesized that LEV was associated with decreased risk of AS by regulating monocytes chemotaxis and adhesion. We showed that SV2A protein were detected in THP-1 human monocytic leukemia cells. LEV (300 μM) inhibited the chemotaxis and adhesion of THP-1 cells after transfection with plasmids expressing SV2AWT, but not SV2AR383Q which was a known functional mutation site of human SV2A. Furthermore, RT-PCR and western blot analysis demonstrated that LEV (300 μM) decreased the expression level of chemokine-related receptors (CX3CL1, CCR1, CCR2, and CCR5),and reduced levels of phosphorylated AKT (p-AKT) in THP-1 cells with SV2AWT expressing plasmids. Taken together, these findings indicated that LEV has an inhibitory effect on THP-1 monocyte adhesion and chemotaxis, suggesting that SV2A may serve as a novel therapeutic target to prevent AS.

Increased Inflammation and Unchanged Density of Synaptic Vesicle Glycoprotein 2A (SV2A) in the Postmortem Frontal Cortex of Alzheimer's Disease Patients

Sections from the middle frontal gyrus (Brodmann area 46) of autopsy-confirmed Alzheimer's disease (AD) patients and non-demented subjects were examined for the prevalence of hallmark AD pathology, including amyloid-β (Aβ) plaques, phosphorylated tau (pTau) tangles, neuroinflammation and synaptic loss (n = 7 subjects/group). Dense-core deposits of Aβ were present in all AD patients (7/7) and some non-demented subjects (3/7), as evidenced by 6E10 immunohistochemistry. Levels of Aβ immunoreactivity were higher in AD vs. non-AD cases. For pTau, AT8-positive neurofibrillary tangles and threads were exclusively observed in AD patient tissue. Levels of [³H]PK11195 binding to the translocator protein (TSPO), a marker of inflammatory processes, were elevated in the gray matter of AD patients compared to non-demented subjects. Levels of [³H]UCB-J binding to synaptic vesicle glycoprotein 2A (SV2A), a marker of synaptic density, were not different between groups. In AD patients, pTau immunoreactivity was positively correlated with [³H]PK11195, and negatively correlated with [³H]UCB-J binding levels. No correlation was observed between Aβ immunoreactivity and markers of neuroinflammation or synaptic density. These data demonstrate a close interplay between tau pathology, inflammation and SV2A density in AD, and provide useful information on the ability of neuroimaging biomarkers to diagnose AD dementia.

The Synaptic Vesicle Glycoprotein 2: Structure, Function, and Disease Relevance

The synaptic vesicle glycoprotein 2 (SV2) family is comprised of three paralogues: SV2A, SV2B, and SV2C. In vertebrates, SV2s are 12-transmembrane proteins present on every secretory vesicle, including synaptic vesicles, and are critical to neurotransmission. Structural and functional studies suggest that SV2 proteins may play several roles to promote proper vesicular function. Among these roles are their potential to stabilize the transmitter content of vesicles, to maintain and orient the releasable pool of vesicles, and to regulate vesicular calcium sensitivity to ensure efficient, coordinated release of the transmitter. The SV2 family is highly relevant to human health in a number of ways. First, SV2A plays a role in neuronal excitability and as such is the specific target for the antiepileptic drug levetiracetam. SV2 proteins also act as the target by which potent neurotoxins, particularly botulinum, gain access to neurons and exert their toxicity. Both SV2B and SV2C are increasingly implicated in diseases such as Alzheimer's disease and Parkinson's disease. Interestingly, despite decades of intensive research, their exact function remains elusive. Thus, SV2 proteins are intriguing in their potentially diverse roles within the presynaptic terminal, and several recent developments have enhanced our understanding and appreciation of the protein family. Here, we review the structure and function of SV2 proteins as well as their relevance to disease and therapeutic development.

Levetiracetam administration is correlated with lower mortality in patients with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes: a retrospective study

Background:

Studies on the relationship between antiepileptic drug (AED) administration and clinical outcomes in patients with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) remain scarce. Levetiracetam (LEV) is an AED that is neuroprotective in various neurologic disorders. This study aimed to determine the impact of LEV on the outcome of MELAS.

Methods:

A retrospective, single-center study was performed based on a large cohort of patients with MELAS with a history of seizures (n = 102). Decisions on antiepileptic therapies were made empirically. Patients were followed up for 1 to 8 years (median, 4 years) and divided into 2 groups based on whether LEV was administered (LEV or non-LEV). The modified Rankin scale (mRS) scores and mortality risks were analyzed in all patients.

Results:

LEV, carbamazepine, benzodiazepines, topiramate, oxcarbazepine, valproate, and lamotrigine were administered in 48, 37, 18, 13, 11, 9, and 9 patients, singly or in combination, respectively. The mean mRS score of the LEV group (n = 48) was lower than that of the non-LEV group (n = 54; mean ± standard deviation, 2.79 ± 1.47 vs. 3.83 ± 1.93, P = 0.006) up to the end of the study. Nevertheless, there was no difference in the proportion of subjects without disability (mRS ranging 0–1) between the groups (P = 0.37). The multivariate regressions revealed that LEV treatment was associated with lower mRS scores (odds ratio 0.32, 95% confidence interval [CI] 0.15–0.68, P = 0.003) and mortality rates (hazard ratio 0.24, 95% CI 0.08–0.74, P = 0.013). There was a significant difference in the Kaplan-Meier survival curves between the groups (χ² = 4.29, P = 0.04).

Conclusions:

The LEV administration is associated with lower mortality in patients with MELAS in this retrospective study. Further laboratory research and prospective cohort studies are needed to confirm whether LEV has neuroprotective effects on patients with mitochondrial diseases.

Temporal Lobe Cavernous Malformation Caused Epileptic Amnesic Episodes and Mild Cognitive Impairment

Neuropathological features in Alzheimer's disease (AD) are amyloid β (Aβ) deposits and neurofibrillary changes. AD is characterized by memory impairment and cognitive dysfunction, with some reports associating these impairments with hyperexcitability caused by Aβ in the medial temporal lobe. Epileptic seizures are known to be common in AD. We encountered a 65-year-old patient with cavernous malformation (CM) in the right temporal lobe who exhibited epileptic amnesia (EA) and AD-like symptoms. Scalp electroencephalography (EEG), including long-term video-EEG, showed no interictal discharges, but intraoperative subdural electrode (SE) recording from the right parahippocampal area showed frequent epileptiform discharges. Neuropathologically, senile plaques were found in the surrounding normal cortex of the CM. Postoperatively, the patient has remained free of EA and AD-like symptoms since total removal of the CM. This is the first surgical case report to confirm temporal lobe hyperexcitability associated with EA and AD-like symptoms.

Mitochondrial Function, Dynamics, and Permeability Transition: A Complex Love Triangle as A Possible Target for the Treatment of Brain Aging and Alzheimer's Disease

Because of the failure of all amyloid-β directed treatment strategies for Alzheimer's disease (AD), the concept of mitochondrial dysfunction as a major pathomechanism of the cognitive decline in aging and AD has received substantial support. Accordingly, improving mitochondrial function as an alternative strategy for new drug development became of increasing interest and many different compounds have been identified which improve mitochondrial function in preclinical in vitro and in vivo experiments. However, very few if any have been investigated in clinical trials, representing a major drawback of the mitochondria directed drug development. To overcome these problems, we used a top-down approach by investigating several older antidementia drugs with clinical evidence of therapeutic efficacy. These include EGb761® (standardized ginkgo biloba extract), piracetam, and Dimebon. All improve experimentally many aspects of mitochondrial dysfunction including mitochondrial dynamics and also improve cognition and impaired neuronal plasticity, the functionally most relevant consequences of mitochondrial dysfunction. All partially inhibit opening events of the mitochondrial permeability transition pore (mPTP) which previously has mainly been discussed as a mechanism relevant for the induction of apoptosis. However, as more recent work suggests the mPTP as a master regulator of many mitochondrial functions, our data suggest the mPTP as a possible relevant drug target within the love triangle between mPTP regulation, mitochondrial dynamics, and mitochondrial function including regulation of neuronal plasticity. Drugs interfering with mPTP function will improve not only mitochondrial impairment in aging and AD but also will have beneficial effects on impaired neuronal plasticity, the pathomechanism which correlates best with functional deficits (cognition, behavior) in aging and AD.

Synthesis and in vivo evaluation of [18F]UCB-J for PET imaging of synaptic vesicle glycoprotein 2A (SV2A)

PURPOSE

Synaptic abnormalities have been implicated in a variety of neuropsychiatric disorders, including epilepsy, Alzheimer's disease, and schizophrenia. Hence, PET imaging of the synaptic vesicle glycoprotein 2A (SV2A) may be a valuable in vivo biomarker for neurologic and psychiatric diseases. We previously developed [¹¹C]UCB-J, a PET radiotracer with high affinity and selectivity toward SV2A; however, the short radioactive half-life (20 min for ¹¹C) places some limitations on its broader application. Herein, we report the first synthesis of the longer-lived ¹⁸F-labeled counterpart (half-life: 110 min), [¹⁸F]UCB-J, and its evaluation in nonhuman primates.

METHODS

[¹⁸F]UCB-J was synthesized from the iodonium precursors. PET imaging experiments with [¹⁸F]UCB-J were conducted in rhesus monkeys to assess the pharmacokinetic and in vivo binding properties. Arterial samples were taken for analysis of radioactive metabolites and generation of input functions. Regional time-activity curves were analyzed using the one-tissue compartment model to derive regional distribution volumes and binding potentials for comparison with [¹¹C]UCB-J.

RESULTS

[¹⁸F]UCB-J was prepared in high radiochemical and enantiomeric purity, but low radiochemical yield. Evaluation in nonhuman primates indicated that the radiotracer displayed pharmacokinetic and imaging characteristics similar to those of [¹¹C]UCB-J, with moderate metabolism rate, high brain uptake, fast and reversible binding kinetics, and high specific binding signals.

CONCLUSION

We have accomplished the first synthesis of the novel SV2A radiotracer [¹⁸F]UCB-J. [¹⁸F]UCB-J is demonstrated to be an excellent imaging agent and may prove to be useful for imaging and quantification of SV2A expression, and synaptic density, in humans.

The Protective Effects of Levetiracetam on a Human iPSCs-Derived Spinal Muscular Atrophy Model

Spinal muscular atrophy (SMA) is an inherited disease characterized by progressive motor neuron death and subsequent muscle weakness and is caused by deletion or mutation of survival motor neuron (SMN) 1 gene. Protecting spinal motor neuron is an effective clinical strategy for SMA. The purpose of this study was to investigate the potential effect of an anti-epileptic drug levetiracetam on SMA. In the present study, we used differentiated spinal motor neurons (MNs) from SMA patient-derived induced pluripotent stem cells (SMA-iPSCs) to investigate the effect of levetiracetam. Levetiracetam promoted neurite elongation in SMA-iPSCs-MNs. TUNEL-positive spinal motor neurons were significantly reduced by levetiracetam in SMA-iPSCs-MNs. In addition, the expression level of cleaved-caspase 3 was decreased by levetiracetam in SMA-iPSCs-MNs. Furthermore, levetiracetam improved impaired mitochondrial function in SMA-iPSCs-MNs. On the other hand, levetiracetam did not affect the expression level of SMN protein in SMA-iPSCs-MNs. These findings indicate that levetiracetam has a neuroprotective effect for SMA.

Canine Cognitive Dysfunction: Pathophysiology, Diagnosis, and Treatment

Canine cognitive dysfunction (CCD) is the canine analog of human Alzheimer disease (AD). The pathophysiology of CCD/AD is multifaceted. CCD is common in aged (>8 years) dogs, affecting between 14% and 35% of the pet dog population. Apparent confusion, anxiety, disturbance of the sleep/wake cycle, and decreased interaction with owners are all common clinical signs of CCD. Although there is no cure for CCD, several proven effective therapeutic approaches are available for improving cognitive ability and maintaining a good quality of life; instituting such therapies early in the disease course is likely to have the greatest positive clinical effect.

Association between stroke-like episodes and neuronal hyperexcitability in MELAS with m.3243A>G: A case report

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The pathophysiology of the stroke-like episodes of MELAS has not completely been elucidated.

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Here we report a case of stroke-like episodes, successfully treated with levetiracetam.

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Neuronal hyperexcitability can be the underlying mechanism of stroke-like episodes in MELAS.

Mitochondrial Pharmacology of Dimebon (Latrepirdine) Calls for a New Look at its Possible Therapeutic Potential in Alzheimer's Disease

Dimebon (latrepirdine), an old antihistaminic drug, showed divergent results in two large clinical trials in Alzheimer disease (AD), which according to our review might be related to the specific pharmacological properties of the drug and the different patient populations included in both studies. Out of the many pharmacological effects of Dimebon, improvement of impaired mitochondrial function seeems to be most relevant for the substantial effects on cognition and behaviour reported in one of the studies, as these effects are already present at the low concentrations of dimebon measured in plasma and tissues of patients and experimental animals. Since impaired mitochondrial function seems to be the major driving force for the progression of the clinical symptoms and since most of the clinical benefits of dimebon originate from an effect on the symptomatic deterioration, mitochondrial improvement can also explain the lack of efficacy of this drug in another clinical trial where symptoms of the patiets remained stable for the time of the study. Accordingly, it seems worthwhile to reevaluate the clinical data to proof that clinical response is correlated with high levels of Neuropsychiatric Symptoms as these show a good relationship to the individual speed of symptomatic decline in AD patients related to mitochondrial dysfunction.

Immunochemical analysis of the expression of SV2C in mouse, macaque and human brain

The synaptic vesicle glycoprotein 2C (SV2C) is an undercharacterized protein with enriched expression in phylogenetically old brain regions. Its precise role within the brain is unclear, though various lines of evidence suggest that SV2C is involved in the function of synaptic vesicles through the regulation of vesicular trafficking, calcium-induced exocytosis, or synaptotagmin function. SV2C has been linked to multiple neurological disorders, including Parkinson's disease and psychiatric conditions. SV2C is expressed in various cell types-primarily dopaminergic, GABAergic, and cholinergic cells. In mice, it is most highly expressed in nuclei within the basal ganglia, though it is unknown if this pattern of expression is consistent across species. Here, we use a custom SV2C-specific antiserum to describe localization within the brain of mouse, nonhuman primate, and human, including cell-type localization. We found that the immunoreactivity with this antiserum is consistent with previously-published antibodies, and confirmed localization of SV2C in the basal ganglia of rodent, rhesus macaque, and human. We observed strongest expression of SV2C in the substantia nigra, ventral tegmental area, dorsal striatum, pallidum, and nucleus accumbens of each species. Further, we demonstrate colocalization between SV2C and markers of dopaminergic, GABAergic, and cholinergic neurons within these brain regions. SV2C has been increasingly linked to dopamine and basal ganglia function. These antisera will be an important resource moving forward in our understanding of the role of SV2C in vesicle dynamics and neurological disease.

Targeting Neural Hyperactivity as a Treatment to Stem Progression of Late-Onset Alzheimer's Disease

Sporadic late-onset Alzheimer's disease (LOAD), the most common form of dementia in the elderly, causes progressive and severe loss of cognitive abilities. With greater numbers of people living to advanced ages, LOAD will increasingly burden both the healthcare system and society. There are currently no available disease-modifying therapies, and the failure of several recent pathology-based strategies has highlighted the urgent need for effective therapeutic targets. With aging as the greatest risk factor for LOAD, targeting mechanisms by which aging contributes to disease could prove an effective strategy to delay progression to clinical dementia by intervention in elderly individuals in an early prodromal stage of disease. Excess neural activity in the hippocampus, a recently described phenomenon associated with age-dependent memory loss, was first identified in animal models of aging and subsequently translated to clinical conditions of aging and early-stage LOAD. Critically, elevated activity was similarly localized to specific circuits within the hippocampal formation in aged animals and humans. Here we review evidence for hippocampal hyperactivity as a significant contributor to age-dependent cognitive decline and the progressive accumulation of pathology in LOAD. We also describe studies demonstrating the efficacy of reducing hyperactivity with an initial test therapy, levetiracetam (Keppra), an atypical antiepileptic. By targeting excess neural activity, levetiracetam may improve cognition and attenuate the accumulation of pathology contributing to progression to the dementia phase of LOAD.

Puzzling Out Synaptic Vesicle 2 Family Members Functions

Synaptic vesicle proteins 2 (SV2) were discovered in the early 80s, but the clear demonstration that SV2A is the target of efficacious anti-epileptic drugs from the racetam family stimulated efforts to improve understanding of its role in the brain. Many functions have been suggested for SV2 proteins including ions or neurotransmitters transport or priming of SVs. Moreover, several recent studies highlighted the link between SV2 and different neuronal disorders such as epilepsy, Schizophrenia (SCZ), Alzheimer's or Parkinson's disease. In this review article, we will summarize our present knowledge on SV2A function(s) and its potential role(s) in the pathophysiology of various brain disorders.

Synaptic Vesicle Glycoprotein 2A Ligands in the Treatment of Epilepsy and Beyond

The synaptic vesicle glycoprotein SV2A belongs to the major facilitator superfamily (MFS) of transporters and is an integral constituent of synaptic vesicle membranes. SV2A has been demonstrated to be involved in vesicle trafficking and exocytosis, processes crucial for neurotransmission. The anti-seizure drug levetiracetam was the first ligand to target SV2A and displays a broad spectrum of anti-seizure activity in various preclinical models. Several lines of preclinical and clinical evidence, including genetics and protein expression changes, support an important role of SV2A in epilepsy pathophysiology. While the functional consequences of SV2A ligand binding are not fully elucidated, studies suggest that subsequent SV2A conformational changes may contribute to seizure protection. Conversely, the recently discovered negative SV2A modulators, such as UCB0255, counteract the anti-seizure effect of levetiracetam and display procognitive properties in preclinical models. More broadly, dysfunction of SV2A may also be involved in Alzheimer's disease and other types of cognitive impairment, suggesting potential novel therapies for levetiracetam and its congeners. Furthermore, emerging data indicate that there may be important roles for two other SV2 isoforms (SV2B and SV2C) in the pathogenesis of epilepsy, as well as other neurodegenerative diseases. Utilization of recently developed SV2A positron emission tomography ligands will strengthen and reinforce the pharmacological evidence that SV2A is a druggable target, and will provide a better understanding of its role in epilepsy and other neurological diseases, aiding in further defining the full therapeutic potential of SV2A modulation.

Enhanced Neuroplasticity by the Metabolic Enhancer Piracetam Associated with Improved Mitochondrial Dynamics and Altered Permeability Transition Pore Function

The mitochondrial cascade hypothesis of dementia assumes mitochondrial dysfunction leading to reduced energy supply, impaired neuroplasticity, and finally cell death as one major pathomechanism underlying the continuum from brain aging over mild cognitive impairment to initial and advanced late onset Alzheimer's disease. Accordingly, improving mitochondrial function has become an important strategy to treat the early stages of this continuum. The metabolic enhancer piracetam has been proposed as possible prototype for those compounds by increasing impaired mitochondrial function and related aspects like mechanisms of neuroplasticity. We here report that piracetam at therapeutically relevant concentrations improves neuritogenesis in the human cell line SH-SY5Y over conditions mirroring the whole spectrum of age-associated cognitive decline. These effects go parallel with improvement of impaired mitochondrial dynamics shifting back fission and fusion balance to the energetically more favorable fusion site. Impaired fission and fusion balance can also be induced by a reduction of the mitochondrial permeability transition pore (mPTP) function as atractyloside which indicates the mPTP has similar effects on mitochondrial dynamics. These changes are also reduced by piracetam. These findings suggest the mPTP as an important target for the beneficial effects of piracetam on mitochondrial function.

Enabling Efficient Positron Emission Tomography (PET) Imaging of Synaptic Vesicle Glycoprotein 2A (SV2A) with a Robust and One-Step Radiosynthesis of a Highly Potent 18F-Labeled Ligand ([18F]UCB-H)

We herein describe the straightforward synthesis of a stable pyridyl(4-methoxyphenyl)iodonium salt and its [¹⁸F] radiolabeling within a one-step, fully automated and cGMP compliant radiosynthesis of [¹⁸F]UCB-H ([¹⁸F]7), a PET tracer for the imaging of synaptic vesicle glycoprotein 2A (SV2A). Over the course of 1 year, 50 automated productions provided 34 ± 2% of injectable [¹⁸F]7 from up to 285 GBq (7.7 Ci) of [¹⁸F]fluoride in 50 min (uncorrected radiochemical yield, specific activity of 815 ± 185 GBq/μmol). The successful implementation of our synthetic strategy within routine, high-activity, and cGMP productions attests to its practicality and reliability for the production of large doses of [¹⁸F]7. In addition to enabling efficient and cost-effective clinical research on a range of neurological pathologies through the imaging of SV2A, this work further demonstrates the real value of iodonium salts for the cGMP ¹⁸F-PET tracer manufacturing industry, and their ability to fulfill practical and regulatory requirements in that field.

Linking mitochondrial dysfunction, metabolic syndrome and stress signaling in Neurodegeneration

Mounting evidence suggests a link between metabolic syndrome (MetS) such as diabetes, obesity, non-alcoholic fatty liver disease in the progression of Alzheimer's disease (AD), Parkinson's disease (PD) and other neurodegenerative diseases (NDDs). For instance, accumulated Aβ oligomer is enhancing neuronal Ca²⁺ release and neural NO where increased NO level in the brain through post translational modification is modulating the level of insulin production. It has been further confirmed that irrespective of origin; brain insulin resistance triggers a cascade of the neurodegeneration phenomenon which can be aggravated by free reactive oxygen species burden, ER stress, metabolic dysfunction, neuorinflammation, reduced cell survival and altered lipid metabolism. Moreover, several studies confirmed that MetS and diabetic sharing common mechanisms in the progression of AD and NDDs where mitochondrial dynamics playing a critical role. Any mutation in mitochondrial DNA, exposure of environmental toxin, high-calorie intake, homeostasis imbalance, glucolipotoxicity is causative factors for mitochondrial dysfunction. These cumulative pleiotropic burdens in mitochondria leads to insulin resistance, increased ROS production; enhanced stress-related enzymes that is directly linked MetS and diabetes in neurodegeneration. Since, the linkup mechanism between mitochondrial dysfunction and disease phenomenon of both MetS and NDDs is quite intriguing, therefore, it is pertinent for the researchers to identify and implement the therapeutic interventions for targeting MetS and NDDs. Herein, we elucidated the pertinent role of MetS induced mitochondrial dysfunction in neurons and their consequences in NDDs. Further, therapeutic potential of well-known biomolecules and chaperones to target altered mitochondria has been comprehensively documented. This article is part of a Special Issue entitled: Oxidative Stress and Mitochondrial Quality in Diabetes/Obesity and Critical Illness Spectrum of Diseases - edited by P. Hemachandra Reddy.