Synaptic Vesicle Protein SV2A Research Articles

LPC-DHA/EPA-Enriched Diets Increase Brain DHA and Modulate Behavior in Mice That Express Human APOE4.

Compared with APOE3, APOE4 is associated with greater age-related cognitive decline and higher risk of neurodegenerative disorders. Therefore, development of supplements that target APOE genotype-modulated processes could provide a great benefit for the aging population. Evidence suggests a link between APOE genotype and docosahexaenoic acid (DHA); however, clinical studies with current DHA supplements have produced negative results in dementia. The lack of beneficial effects with current DHA supplements may be related to limited bioavailability, as the optimal form of DHA for brain uptake is lysophosphatidylcholine (LPC)-DHA. We previously developed a method to enrich the LPC-DHA content of krill oil through lipase treatment (LT-krill oil), which resulted in fivefold higher enrichment in brain DHA levels in wild-type mice compared with untreated krill oil. Here, we evaluated the effect of a control diet, diet containing krill oil, or a diet containing LT-krill oil in APOE3- and APOE4-targeted replacement mice (APOE-TR mice; treated from 4 to 12 months of age). We found that DHA levels in the plasma and hippocampus are lower in APOE4-TR mice and that LT-krill oil increased DHA levels in the plasma and hippocampus of both APOE3- and APOE4-TR mice. In APOE4-TR mice, LT-krill oil treatment resulted in higher levels of the synaptic vesicle protein SV2A and improved performance on the novel object recognition test. In conclusion, our data demonstrate that LPC-DHA/EPA-enriched krill oil can increase brain DHA and improve memory-relevant behavior in mice that express APOE4. Therefore, long-term use of LT-krill oil supplements may on some level protect against age-related neurodegeneration.

Levetiracetam treatment leads to functional recovery after thoracic or cervical injuries of the spinal cord

Spinal cord injury (SCI) leads to dramatic impairments of motor, sensory, and autonomic functions of affected individuals. Following the primary injury, there is an increased release of glutamate that leads to excitotoxicity and further neuronal death. Therefore, modulating glutamate excitotoxicity seems to be a promising target to promote neuroprotection during the acute phase of the injury. In this study, we evaluated the therapeutic effect of a FDA approved antiepileptic drug (levetiracetam-LEV), known for binding to the synaptic vesicle protein SV2A in the brain and spinal cord. LEV therapy was tested in two models of SCI—one affecting the cervical and other the thoracic level of the spinal cord. The treatment was effective on both SCI models. Treated animals presented significant improvements on gross and fine motor functions. The histological assessment revealed a significant decrease of cavity size, as well as higher neuronal and oligodendrocyte survival on treated animals. Molecular analysis revealed that LEV acts by stabilizing the astrocytes allowing an effective uptake of the excess glutamate from the extracellular space. Overall, our results demonstrate that Levetiracetam may be a promising drug for acute management of SCI.

Levetiracetam treatment ameliorates LRRK2 pathological mutant phenotype.

Mutations in leucine‐rich repeat kinase 2 (LRRK2) are the most common genetic cause of Parkinson's disease (PD). The LRRK2 physiological and pathological function is still debated. However, different experimental evidence based on LRRK2 cellular localization and LRRK2 protein interactors suggests that LRRK2 may be part and regulate a protein network modulating vesicle dynamics/trafficking. Interestingly, the synaptic vesicle protein SV2A is part of this protein complex. Importantly, SV2A is the binding site of the levetiracetam (LEV), a compound largely used in human therapy for epilepsy treatment. The binding of LEV to SV2A reduces the neuronal firing by the modulation of vesicle trafficking although by an unclear molecular mechanism. In this short communication, we have analysed the interaction between the LRRK2 and SV2A pathways by LEV treatment. Interestingly, LEV significantly counteracts the effect of LRRK2 G2019S pathological mutant expression in three different cellular experimental models. Our data strongly suggest that LEV treatment may have a neuroprotective effect on LRRK2 pathological mutant toxicity and that LEV repositioning could be a viable compound for PD treatment.

Levetiracetam – a drug that can be used not only in the treatment of epilepsy

Levetiracetam, which belongs to the new generation of antiepileptic drugs, has a unique and not well-known mechanism of action. The drug affects the release of neurotransmitters through the binding to the synaptic vesicle protein SV2A. Moreover, it acts on calcium channels, inhibits glutamatergic neurotransmission and affects GABA-ergic neurotransmission through e.g. the Zn²⁺-induced suppression of GABAA-mediated presynaptic inhibition and the modulation of the action of GABAA antagonists. Levetiracetam has also neuroprotective activity which is associated with the influence on transcription processes, neurotransmission, antioxidant and anti-inflammatory activity. The results of recent research indicate that this complex action creates the prospect of using it in the alleviation of epileptogenesis, poststroke seizuires, seizure prophylaxis in brain injured patients and diabetic neuropathy. Furthermore, the drug may also have a beneficial effect in the treatment of Alzheimer patients with epileptic seizures and levodopa-induced dyskinesias in Parkinson’s disease.

Preparation of 99mTc-levetiracetam intranasal microemulsion as the first radiotracer for SPECT imaging of the Synaptic Vesicle Protein SV2A

Selective receptors imaging using gamma emitting radiopharmaceuticals allows accurate diagnosis and follow up of many brain related disorders. Levetiracetam, a selective SV2A receptor antiepileptic, was successfully radiolabeled using 99mTc. Different conditions affecting the labelling process were studied and optimum radiochemical yield of 89.8% was obtained. 99mTc-levetiracetam was effectively formulated and characterized as microemulsion with particle size of 16.34 ± 5.58 nm and polydispersity index of 0.382 ± 0.05. Parallel biodistribution studies were performed comparing brain targeting efficiency of I.V 99mTc-levetiracetam solution, I.N 99mTc-levetiracetam solution and I.N 99mTc-levetiracetam microemulsion. Brain radioactivity uptake and brain/blood uptake ratio for I.N 99mTc-levetiracetam microemulsion were higher than the other two routes at all time intervals. Such results present intranasal 99mTc-levetiracetam microemulsion as the first SPECT tracer for imaging SV2A receptor.

Syndesi launches as spin-off from UCB

Syndesi Therapeutics has launched with about $21 million in funding from investors including UCB and Johnson & Johnson. Based at J&J’s JLINX incubator in Beerse, Belgium, Syndesi will develop small molecules licensed from UCB that modulate the synaptic vesicle protein SV2A. UCB markets the SV2A modulator levetiracetam as an epilepsy treatment. The compounds that went to Syndesi are not antiepileptic but have what Syndesi calls procognitive properties that could treat neurological disorders such as Alzheimer’s disease.

Seletracetam enhances short term depression in vitro

Seletracetam (SEL), an analog of the antiepileptic drug levetiracetam (LEV), decreases seizure activity in a number of epilepsy models and binds to the synaptic vesicle protein SV2A with a higher affinity than LEV. Experiments were performed to determine if SEL, like LEV, reduces the later EPSPs in long trains of stimuli in a manner dependent upon access to the interior of synaptic vesicles and SV2A binding. When hippocampal slices were incubated in 3–30μM SEL for 3h, but not 30min, the relative amplitude of the CA1 field excitatory synaptic potentials decreased over the course of a train of high frequency stimuli more than for control slices. This short term depression was frequency and dose dependent and largely disappeared when the spontaneous activity during the loading period was removed by cutting the Schaffer collaterals. The SEL effect was also observed in slices loaded during prolonged stimulation at 1Hz, but not 10Hz. Hippocampal slices loaded with both SEL and FM1-43 to visualize synaptic boutons released the FM1-43 in response to prolonged stimulation much more slowly than control slices during prolonged stimulation. Like LEV, SEL produced a frequency-dependent decrement of synaptic transmission that was dependent upon the drug entering recycling synaptic vesicles and compatible with SV2A binding. Previous observations of SV2A binding affinity correlated with the current effect of SEL and the previously reported effect of LEV on synaptic transmission validate SV2A as an extremely attractive target for future antiepileptic drug development.

Levetiracetam – epilepsy treatment, pharmacokinetics, mechanism of action, interaction and toxicity

Kozlowski Piotr, Czepinska-Cwik Wioleta, Kozlowska Magdalena, Kozlowska Karolina. Levetiracetam – epilepsy treatment, pharmacokinetics, mechanism of action, interaction and toxicity. Journal of Education, Health and Sport. 2015;5(4):143-150. ISSN 2391-8306. DOI: 10.5281/zenodo.16694 http://ojs.ukw.edu.pl/index.php/johs/article/view/2015%3B5%284%29%3A143-150 https://pbn.nauka.gov.pl/works/553762 http://dx.doi.org/10.5281/zenodo.16694 Formerly Journal of Health Sciences. ISSN 1429-9623 / 2300-665X. Archives 2011 – 2014 http://journal.rsw.edu.pl/index.php/JHS/issue/archive Deklaracja. Specyfika i zawartośc merytoryczna czasopisma nie ulega zmianie. Zgodnie z informacją MNiSW z dnia 2 czerwca 2014 r., ze w roku 2014 nie bedzie przeprowadzana ocena czasopism naukowych; czasopismo o zmienionym tytule otrzymuje tyle samo punktow co na wykazie czasopism naukowych z dnia 31 grudnia 2014 r. The journal has had 5 points in Ministry of Science and Higher Education of Poland parametric evaluation. Part B item 1089. (31.12.2014). © The Author (s) 2015; This article is published with open access at Licensee Open Journal Systems of Kazimierz Wielki University in Bydgoszcz, Poland and Radom University in Radom, Poland Open Access. This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. This is an open access article licensed under the terms of the Creative Commons Attribution Non Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non commercial use, distribution and reproduction in any medium, provided the work is properly cited. This is an open access article licensed under the terms of the Creative Commons Attribution Non Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non commercial use, distribution and reproduction in any medium, provided the work is properly cited. The authors declare that there is no conflict of interests regarding the publication of this paper. Received: 20.01.2015. Revised 27.03.2015. Accepted: 27.03.2015. LEVETIRACETAM – EPILEPSY TREATMENT, PHARMACOKINETICS, MECHANISM OF ACTION, INTERACTION AND TOXICITY Piotr Kozlowski 1 , Wioleta Czepinska-Cwik 2 , Magdalena Kozlowska 3 , Karolina Kozlowska 4 1 Katedra i Zaklad Anatomii Prawidlowej Czlowieka, UM w Lublinie 2 Klinika Chorob Wewnetrznych, 1 Wojskowy Szpital Kliniczny z Polikliniką w Lublinie 3 Katedra i Zaklad Farmakologii doświadczalnej i Klinicznej, UM w Lublinie 4 Instytut Filologii Angielskiej, KUL Uniwersytet Medyczny w Lublinie ul. W. Chodźki 1, 20-093 Lublin e-mail: piotr7176@gmail.com Abstract Epilepsy is a common chronic neurological disorder that requires a long-term antiepileptic drug therapy. Epilepsy affects approximately 1% of the world’s population, so about 50 million people worldwide have epilepsy. It more likely occurs among children and people over the age of 65. This chronic condition is characterized by recurrent, unprovoked epileptic seizures. Although there are many innovative methods of seizure control, such as neurosurgery, vagal nerve stimulations (VNS) and ketogenic diet, pharmacology is most forceful method of epilepsy treatment. Unfortunately, anticonvulsant drugs are not always effective; the number of non-responding patients is higher than 30% [2,25,29,31]. Levetiracetam (LEV) is one of the newest AEDs, marketed worldwide only since 2000 [29]. This novel antiepileptic drug has a unique and non-standard mechanism of action. The structure of LEV is similar to the prototypical nootropic drug piracetam. Its novel mechanism of action is connected with the synaptic vesicle protein SV2A in the brain. The elimination plasma half-live of LEV is approximately from 6 to 8 hours among adults. About 66% of the drug is excreted unchanged and 27% as inactive hydrolysis product [12]. LEV is mainly removed by the kidneys so that elimination parallels kidney function (renal clearance: 0,6 ml/min/kg) [3,12,32]. LEV was found to be well tolerated and effective in all types of seizures in adults and children [18]. It can be also used in combinations with other AEDs. The drug may also be useful in treatment of Lennox-Gastaut syndrome [9]. This article reviews available published data on LEV in the treatment of adults and children, including information about LEV`s pharmacokinetics, chemistry, mechanism of action, interactions and toxicity. Key words: levetiracetam, antiepileptic drugs, seizures, epilepsy.

Photoactivatable glycopolymers for the proteome-wide identification of fucose-α(1-2)-galactose binding proteins.

Although fucose-α(1-2)-galactose (Fucα(1-2)Gal)-containing glycans have been implicated in cognitive processes such as learning and memory, their precise molecular mechanisms are poorly understood. Here we employed the use of multivalent glycopolymers to enable the first proteome-wide identification of weak affinity, low abundance Fucα(1-2)Gal glycan-binding proteins (GBPs). Biotin-terminated glycopolymers containing photoactivatable cross-linking groups were designed to capture and enrich GBPs from rat brain lysates. Candidate proteins were tested for their ability to bind Fucα(1-2)Gal, and the functional significance of the interaction was investigated for the synaptic vesicle protein SV2a using a knockout mouse system. The results suggest a role for SV2a-Fucα(1-2)Gal interactions in SV2a trafficking and synaptic vesicle recycling. More broadly, our studies outline a general chemical approach for the systems-level discovery of novel GBPs.

Levetiracetam resistance: Synaptic signatures & corresponding promoter SNPs in epileptic hippocampi

Pharmacoresistance to antiepileptic drugs (AEDs) is a major clinical problem in patients with mesial temporal lobe epilepsy (mTLE). Levetiracetam (LEV) represents a unique type of AED as its high-affinity binding site, the synaptic vesicle protein SV2A, is a component of the presynaptic release machinery. LEV often leads to full seizure control even in previously refractory patients. However, approximately 30% of LEV-treated mTLE patients do not show a significant response to LEV from the beginning of the pharmacotherapy and are therefore classified as a priori non-responders. This unexpected phenomenon prompted genetic studies, which failed to characterize responsible SV2A sequence alterations.Here, we followed a different approach to study the mechanisms of LEV pharmacoresistance by screening for mRNA signatures specifically expressed in LEV a priori non-responders in epileptic brain tissue and subsequent promoter analyses of highly altered transcripts. To this end, we have used our unique access to analyze hippocampal tissue from pharmacoresistant TLE patients who underwent epilepsy surgery for seizure control (n=53) stratified according to a priori LEV responders versus patients with impaired LEV-response. Transcriptome (Illumina platform) and subsequent multimodal cluster analyses uncovered strikingly abundant synapse-associated molecule mRNA signatures in LEV a priori non-responders. Subsequent promoter characterization revealed accumulation of the single nucleotide polymorphism (SNP) rs9305614 G-allele in a priori non-responders to correlate to abundant mRNAs of phosphatidylinositol N-acetylglucosaminyltransferase (PIGP), i.e. a key component of the Wnt-signaling pathway. By luciferase assays, we observed significantly stronger activation by the LBP-1 transcription factor of the rs9305614 G-allele PIGP promoter. The present data suggest an abundance of transcripts encoding for key synaptic components in the hippocampi of LEV a priori non-responder mTLE patients, which for PIGP as proof of concept can be explained by a particular promoter variant. Our data argue for epigenetic factors predisposing for a priori LEV pharmacoresistance by transcriptional ‘overexposure of targets’.

Levetiracetam: A Review of its use in the treatment of epilepsy

Background: Levetiracetam is a novel antiepileptic drug. It is marketed worldwide since 2000. Aim: The paper reviewed the mechanism of action, pharmacokinetics, adverse drug reactions, contraindications and uses of levetiracetam in the treatment of various types of epileptic seizures. Methods: Literature searches were done to identify relevant studies. Results: Levetiracetam acts by binding to the synaptic vesicle protein SV2A, thereby modulation of one or more of its actions and ultimately affecting neural excitability. It has less protein binding and lacks hepatic metabolism. In contrast to traditional therapy, it has a wide safety margin and does not require serum drug monitoring. It does not interact with other anti-epileptics. Conclusion: The above-mentioned favourable pharmacological benefits of LEV make it an important first-line or adjunctive therapy for epileptic seizures.

Prospects of Levetiracetam as a Neuroprotective Drug Against Status Epilepticus, Traumatic Brain Injury, and Stroke

Levetiracetam (LEV) is an anti-epileptic drug commonly used for the treatment of partial onset and generalized seizures. In addition to its neuromodulatory and neuroinhibitory effects via its binding to the synaptic vesicle protein SV2A, multiple studies have suggested neuroprotective properties for LEV in both epileptic and non-epileptic conditions. The purpose of this review is to discuss the extent of LEV-mediated protection seen in different neurological conditions, the potential of LEV for easing epileptogenesis, and the possible mechanisms that underlie the protective properties of LEV. LEV has been found to be particularly beneficial for restraining seizures in animal models of spontaneous epilepsy, acute seizures, and status epilepticus (SE). However, its ability for easing epileptogenesis and cognitive dysfunction following SE remains controversial with some studies implying favorable outcomes and others reporting no beneficial effects. Efficacy of LEV as a neuroprotective drug against traumatic brain injury (TBI) has received much attention. While animal studies in TBI models have showed significant neuroprotection and improvements in motor and memory performance with LEV treatment, clinical studies suggest that LEV has similar efficacy as phenytoin in terms of its ability to prevent post-traumatic epilepsy. LEV treatment for TBI is also reported to have fewer adverse effects and monitoring considerations but electroencephalographic recordings suggest the presence of increased seizure tendency. Studies on stroke imply that LEV is a useful alternative to carbamazepine for preventing post-stroke seizures in terms of efficacy and safety. Thus, LEV treatment has promise for restraining SE-, TBI-, or stroke-induced chronic epilepsy. Nevertheless, additional studies are needed to ascertain the most apt dose, timing of intervention, and duration of treatment after the initial precipitating injury and the mechanisms underlying LEV-mediated beneficial effects.

Commentary: Neurotransmitter Secretion and Cell Signaling

Many proteins involved in neurotransmitter release have been identified, but how these molecules interact and function together to mediate neurotransmission is not completely known. Chromaffin cells have been one of the favorite models for the study of the molecular mechanism of exocytosis and regulation of the differential release of catecholamine and peptides co-stored in the chromaffin granules. Several talks were presented at this meeting, describing the function of different molecules in regulating neurotransmitter secretion and synaptic transmission. Corey Smith (USA) reported that by using various frequencies to mimic basal and acute sympathetic activity to stimulate chromaffin cells, he was able to demonstrate that differential release of neurotransmitters is regulated by the opening of the fusion pore mediated by an interaction between syndapin and dynamin. Xuelin Lou (USA) presented new data on the role of dynamin isoforms in synaptic transmission by showing that presynaptic dynamin 3 function synergizes with dynamin 1. Significantly, neurons lacking both dynamins develop, differentiate, and establish synapses in vitro. But most strikingly, nerve terminals can recycle synaptic vesicles in the absence of both dynamins, implying that dynamin 2 alone and/or dynamin independent mechanisms are sufficient to support basic synaptic function. These results collectively demonstrate that neither dynamin 1 nor 3 are essential for regenerating synaptic vesicles, but rather contribute to the efficiency of this process. Chen Zhang (China) discussed the role of presenilin, a molecule implicated in the pathogenesis of Alzheimer’s disease, in neurotransmitter secretion. He used genetic approaches to conditionally inactivate the protein in presynaptic and postsynaptic neurons in the hippocampus. His results showed that only presynaptic, but not postsynaptic inactivation of presenilin impaired synaptic activity and this impairment was induced by modulation of Ca release from the endoplasmic reticulumCa stores.Kathrin Engisch (USA) used the isolated mouse chromaffin cells to study the effects of levetiracetam, an anticonvulsant that binds to the synaptic vesicle protein SV2A on neurotransmitter release. She showed that levetiracetam decreases the high activity-induced Ca currents and secretion but had no effect on the resting cells. The results may shed some light on the pharmacology of the drug on neurotransmission. The effects of some molecules on catecholamine secretion were also presented. Damien Keating (Australia) discussed interesting results on the molecular mechanism of exocytosis regulated by HAP1, Huntingtin-associated protein 1. Kevin Curie (USA) reported the paracrine effects of PGE2 on the secretion, possibly mediated by EP3 receptor. Daniel O’Connor (USA) reported a systematic study of the polymorphism found in the enzymes involved in catecholamine biosynthesis. G-protein coupled receptors (GPCR) and glutamate receptors play major roles in cell signaling. Duk-Su Koh (USA) presented studies on glutaminergic signaling in pancreatic islets. Extending his presentation at the meeting, he has provided a comprehensive review (below) on how islet hormones such as insulin and glucagon act as paracrine or autocrine modulators of neighboring cells in the pancreatic islets to regulate glucose levels. In addition, he has described a role of excitatory glutamate and inhibitory γ-amino butyric L.-S. Kao Department of Life Sciences and Institute of Genome Sciences, Brain Research Center, National Yang-Ming University, Taipei, Taiwan e-mail: lskao@ym.edu.tw

Levetiracetam Reverses Synaptic Deficits Produced by Overexpression of SV2A

Levetiracetam is an FDA-approved drug used to treat epilepsy and other disorders of the nervous system. Although it is known that levetiracetam binds the synaptic vesicle protein SV2A, how drug binding affects synaptic functioning remains unknown. Here we report that levetiracetam reverses the effects of excess SV2A in autaptic hippocampal neurons. Expression of an SV2A-EGFP fusion protein produced a ∼1.5-fold increase in synaptic levels of SV2, and resulted in reduced synaptic release probability. The overexpression phenotype parallels that seen in neurons from SV2 knockout mice, which experience severe seizures. Overexpression of SV2A also increased synaptic levels of the calcium-sensor protein synaptotagmin, an SV2-binding protein whose stability and trafficking are regulated by SV2. Treatment with levetiracetam rescued normal neurotransmission and restored normal levels of SV2 and synaptotagmin at the synapse. These results indicate that changes in SV2 expression in either direction impact neurotransmission, and suggest that levetiracetam may modulate SV2 protein interactions.

Levetiracetam Extended Release as Adjuvant Therapy for the Control of Partial-onset Seizures

Extended release (XR) formulation of levetiracetam (LEV) is approved by the Food and Drug Administration as an add-on to other antiepileptic drugs (AEDs) for adults with partial onset seizures. This is based on class-I evidence demonstrating significant seizure reduction in once daily dosing. Keppra-XR is marketed with the brand name of Keppra XR since 2008 (UCB Pharma). Its original immediate release (IR) formulation has been in the market since 2000. LEV has a unique molecular structure which is chemically unrelated to existing AEDs. The precise mechanism of action is unknown. Animal studies showed binding to synaptic vesicle protein SV2A, thought to be involved in modulating synaptic neurotransmitter release. LEV-IR is proven effective as adjunctive therapy for partial-onset seizures, primary generalized tonic-clonic seizures and myoclonic seizures. It was shown to be equivalent to carbamazepine as first-line treatment for partial-onset seizures. The extended release formulation added advantages such as better tolerance and increased compliance.

Retrograde influence of muscle fibers on their innervation revealed by a novel marker for slow motoneurons

Mammalian limb and trunk skeletal muscles are composed of muscle fibers that differ in contractile and molecular properties. They are commonly divided into four categories according to the myosin heavy chain that they express: I, IIA, IIX and IIB, ranging from slowest to fastest. Individual motor axons innervate tens of muscle fibers, nearly all of which are of the same type. The mechanisms accounting for this striking specificity, termed motor unit homogeneity, remain incompletely understood, in part because there have been no markers for motoneuron types. Here we show in mice that the synaptic vesicle protein SV2A is selectively localized in motor nerve terminals on slow (type I and small type IIA) muscle fibers; its close relatives, SV2B and SV2C, are present in all motor nerve terminals. SV2A is broadly expressed at birth; fast motoneurons downregulate its expression during the first postnatal week. An inducible transgene incorporating regulatory elements from the Sv2a gene permits selective labeling of slow motor units and reveals their composition. Overexpression of the transcriptional co-regulator PGC1α in muscle fibers, which converts them to a slow phenotype, leads to an increased frequency of SV2A-positive motor nerve terminals, indicating a fiber type-specific retrograde influence of muscle fibers on their innervation. This retrograde influence must be integrated with known anterograde influences in order to understand how motor units become homogeneous.

Assessment of levetiracetam bioavailability from targeted sites in the human intestine using remotely activated capsules and gamma scintigraphy: Open-label, single-dose, randomized, four-way crossover study in healthy male volunteers

Background: Levetiracetam is a broad-spectrum antiepileptic drug that binds to synaptic vesicle protein SV2A. Levetiracetam is indicated in the adjunctive treatment of partial-onset seizures, myoclonic seizures, and generalized tonic-clonic seizures. It is also approved in Europe as monotherapy for newly diagnosed partial-onset seizures. A Phase I clinical pharmacology trial was conducted during preregistration clinical development to better understand the regional gastrointestinal (GI) absorption of levetiracetam. Objective: This study evaluated the relative bioavailability of levetiracetam in various regions of the GI tract using a noninvasive, remote-controlled capsule device providing targeted drug delivery, relative to that after oral administration, and explored the drug's absorption characteristics in healthy volunteers. Methods: Pharmacokinetic data were obtained from healthy men aged 18 to 65 years in an open-label, single-dose, randomized, 4-way crossover study. Treatments included levetiracetam 250 mg administered as an immediate-release tablet and capsule delivery of 250 mg drug substance (levetiracetam powder without excipients) to the proximal small bowel, distal small bowel, and ascending colon. The location of the capsule in the GI tract was monitored using γ-scintigraphic imaging. Blood samples for plasma levetiracetam concentration were collected before dosing; at 10, 20, 30, and 45 minutes; and at 1, 1.5, 2, 3, 6, 9, 12, 16, 20, and 24 hours after tablet intake or after capsule activation. Pharmacokinetic parameters C max, T max, AUC 0−last, AUC 0−∞ and t ½ were calculated using noncompartmental methods. Tolerability was determined using clinical assessment, monitoring of vital signs, laboratory analysis, and interviews with the volunteers regarding adverse events. Results: Nine healthy men, 7 whites and 2 Asians, were enrolled (mean [SD] age, 31 [14] years; weight, 77 [5] kg; height, 176 [6] cm). Six volunteers completed all 4 treatments. Seven adverse events (headache [3], lethargy [2], tachycardia [1], and contusion [1]) were reported in 5 volunteers, but only 2 (headache and lethargy) were judged by the investigator to be possibly drug related. The geometric mean (%CV) AUC 0−last values of levetiracetam delivered in the proximal small bowel, distal small bowel, ascending colon, and stomach (oral tablet) were 58.2 (9.3%), 59.6 (8.9%), 51.5 (12.0%), and 59.0 (7.4%) μg · h/mL, respectively. Values for bioavailability in the proximal small bowel, distal small bowel, and ascending colon relative to the tablet were 98.5% (95% CI, 89.7%–108.2%), 100.8% (95% CI, 91.4%–111.1%), and 87.1% (95% CI, 77.9%–97.5%). Conclusion: After delivery in the proximal small bowel, distal small bowel, or ascending colon, the systemic bioavailability of levetiracetam (AUC), but not C max and T max, appeared comparable to that after oral administration and thus appeared site independent in this small group of healthy fasting men.

Brivaracetam (ucb 34714) inhibits Na + current in rat cortical neurons in culture

Brivaracetam (ucb 34714; BRV), a new antiepileptic drug (AED) candidate, is a pyrrolidone derivative displaying a markedly higher affinity than levetiracetam (LEV; Keppra) to the synaptic vesicle protein SV2A, shown to be the brain-specific binding site of LEV. The higher affinity for SV2A correlates significant antiepileptic activity in animal epilepsy models in vitro and in vivo. Since many AEDs act upon inhibiting neuronal Na(+) currents, this study explored putative activity of BRV on the properties of these currents. Voltage-activated Na(+) currents were recorded by whole-cell patch-clamp on neuronal somas of rat neocortical neurons, grown in dissociated cell culture for up to 12 days. BRV, dissolved at the desired final concentration (between 0.2microM and 1mM) was applied by a multi-barrel pipette system near the soma of the recorded neuron. BRV produced a concentration-dependent inhibition of voltage-dependent Na(+) currents with IC(50) values of 41microM at the holding potential of -100mV, and of 6.5microM at the holding potential of -60mV. The voltage-dependence of activation and the kinetics of fast inactivation were not modified in the presence of BRV (30microM). Conversely, the recovery from fast inactivation was significantly slower and the voltage of half-maximal inactivation was shifted toward hyperpolarized value after BRV perfusion in a concentration-dependent manner. Furthermore, BRV (30microM) induced a significant use-dependent block at 50Hz stimulation frequency. These results indicate that BRV is able to modulate the voltage-activated Na(+) inflow in cortical neurons, which conceivably might contribute to the antiepileptic activity of this drug.

Glycosylated SV2A and SV2B Mediate the Entry of Botulinum Neurotoxin E into Neurons

Botulinum neurotoxin E (BoNT/E) can cause paralysis in humans and animals by blocking neurotransmitter release from presynaptic nerve terminals. How this toxin targets and enters neurons is not known. Here we identified two isoforms of the synaptic vesicle protein SV2, SV2A and SV2B, as the protein receptors for BoNT/E. BoNT/E failed to enter neurons cultured from SV2A/B knockout mice; entry was restored by expressing SV2A or SV2B, but not SV2C. Mice lacking SV2B displayed reduced sensitivity to BoNT/E. The fourth luminal domain of SV2A or SV2B alone, expressed in chimeric receptors by replacing the extracellular domain of the low-density lipoprotein receptor, can restore the binding and entry of BoNT/E into neurons lacking SV2A/B. Furthermore, we found disruption of a N-glycosylation site (N573Q) within the fourth luminal domain of SV2A rendered the mutant unable to mediate the entry of BoNT/E and also reduced the entry of BoNT/A. Finally, we demonstrate that BoNT/E failed to bind and enter ganglioside-deficient neurons; entry was rescued by loading exogenous gangliosides into neuronal membranes. Together, the data reported here demonstrate that glycosylated SV2A and SV2B act in conjunction with gangliosides to mediate the entry of BoNT/E into neurons.

Levetiracetam in the treatment of epilepsy

Epilepsy is a common chronic disorder that requires long-term antiepileptic drug therapy. Approximately one half of patients fail the initial antiepileptic drug and about 35% are refractory to medical therapy, highlighting the continued need for more effective and better tolerated drugs. Levetiracetam is an antiepileptic drug marketed since 2000. Its novel mechanism of action is modulation of synaptic neurotransmitter release through binding to the synaptic vesicle protein SV2A in the brain. Its pharmacokinetic advantages include rapid and almost complete absorption, minimal insignificant binding to plasma protein, absence of enzyme induction, absence of interactions with other drugs, and partial metabolism outside the liver. The availability of an intravenous preparation is yet another advantage. It has been demonstrated effective as adjunctive therapy for refractory partial-onset seizures, primary generalized tonic-clonic seizures, and myoclonic seizures of juvenile myoclonic epilepsy. In addition, it was found equivalent to controlled release carbamazepine as first-line therapy for partial-onset seizures, both in efficacy and tolerability. Its main adverse effects in randomized adjunctive trials in adults have been somnolence, asthenia, infection, and dizziness. In children, the behavioral adverse effects of hostility and nervousness were also noted. Levetiracetam is an important addition to the treatment of epilepsy.