Protein SV2A Research Articles

Evidence for a Differential Interaction of Brivaracetam and Levetiracetam with the SV2A Protein (P5.246)

Evidence for a Differential Interaction of Brivaracetam and Levetiracetam with the SV2A Protein (P5.246)

Brivaracetam for the treatment of epilepsy

ABSTRACTIntroduction: Approximately one third of patients with epilepsy fail to respond to existing medications. Levetiracetam is an effective antiepileptic drug (AED) postulated to act by binding to synaptic vesicle protein 2A. Brivaracetam is a novel high affinity SV2A ligand with approximately 20-fold higher affinity for SV2A protein than levetiracetam. It is at an advanced stage of clinical development for treatment of epilepsy.Areas covered: This article reviews animal data, pharmacokinetics, and phase 1-3 data of Brivaracetam treatment of epilepsy. Brivaracetam has broad-spectrum anticonvulsant activity in animal models.Expert Opinion: Phase 1 studies indicated that single oral doses of 5-800 mg and repeated oral doses of up to 600 mg were well tolerated and showed favorable pharmacokinetic profile. Phase 2 studies indicated good safety and tolerability of brivaracetam in the dose range of 5-150 mg/day and provided proof of concept for efficacy in treating refractory partial onset seizures. Efficacy and safety have been evaluated in 4 phase 3 studies with dose range of 5-200 mg which have demonstrated efficacy in the range of 100-200 mg/day dose and, in most studies, also with 50 mg/day dose, and good safety and tolerability profile across 5-200 mg doses in adjunctive treatment of refractory partial onset seizures.

Study of the SV2A protein role in Epilepsy

Study of the SV2A protein role in Epilepsy

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.

Amyloid precursor protein knockout diminishes synaptic vesicle proteins at the presynaptic active zone in mouse brain.

The amyloid precursor protein (APP) has previously been allocated to an organellar pool residing in the Golgi apparatus and in endosomal compartments, and in its mature form to a presynaptic active zone-localized pool. By analyzing homozygous APP knockout mice we evaluated the impact of APP on synaptic vesicle protein abundance at synaptic release sites. Following immunopurification of synaptic vesicles and the attached presynaptic plasma membrane, individual proteins were subjected to quantitative Western blot analysis. We demonstrate that APP deletion in knockout animals reduces the abundance of the synaptic vesicle proteins synaptophysin, synaptotagmin-1, and SV2A at the presynaptic active zone. Conversely, deletion of the additional APP family members, APLP1 and APLP2 resulted in an increase in synaptophysin, synaptogamin-1, and SV2A abundance. When transmembrane APP is lacking in APPsα-KI/APLP2-KO mice synaptic vesicle protein abundance corresponds to that in APP -KO mice. Deletion of the synaptic vesicle protein 2 (SV2) A and B had no effect on APP and synaptophysin abundance but decreased synaptotagmin-1. Our data suggest that APP controls the abundance of synaptic vesicle proteins at the presynaptic release sites and thus impacts synaptic transmission.

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

Rare protein sequence variation in SV2A gene does not affect response to levetiracetam

Levetiracetam, a broad spectrum antiepileptic drug, binds to membrane protein SV2A. The protein coding region of SV2A was sequenced in 158 patients with focal or generalized epilepsies divided into three groups based on their response to levetiracetam: responders (>75% decrease), exacerbators (50% increase) and non-responders. Nonsynonymous coding variation within SV2A was extremely rare, suggesting that rare variation is not likely to account for the individual differences in response to levetiracetam.

Levetiracetam has an activity‐dependent effect on inhibitory transmission

Previous work has shown that levetiracetam (LEV) binds the vesicular protein SV2A and reduces excitatory neurotransmitter release during trains of high-frequency activity, most likely by accessing its binding site through vesicular endocytosis into excitatory synaptic terminals. Because there are differences in excitatory and inhibitory transmitter release mechanisms, and there are suggestions that neurons differ in their SV2A expression, we were curious whether LEV also reduces inhibitory transmission. We used patch-clamp recording from CA1 neurons in rat brain slices to quantify the effects of LEV on inhibitory postsynaptic currents (IPSCs). We were able to elicit pure IPSCs by stimulating inhibitory terminals close to neuronal soma and blocking excitatory postsynaptic currents with specific antagonists. We found that LEV reduces inhibitory currents in a frequency-dependent manner, with the largest relative effect on the later IPSCs in the highest frequency trains. However, in contrast to excitatory postsynaptic currents (EPSCs), LEV reduced IPSC trains after a briefer, 30 min incubation. When spontaneous activity during incubation was blocked with antagonists of excitatory transmission, LEV no longer reduced IPSCs. If slices were returned to LEV-free artificial cerebrospinal fluid (ACSF) after LEV incubation, but prior to recording, the IPSC reduction failed to appear. However, if synaptic activity was limited by treating with excitatory transmitter antagonists, after the initial LEV exposure, LEV still diminished trains of IPSC. The concentration required to diminish IPSC trains was lower than for EPSCs. LEV exerts a qualitatively similar, frequency-dependent effect on both IPSCs and EPSCs. The much shorter latency for IPSC reduction is consistent with the greater levels of spontaneous inhibition in brain slices, supporting the hypothesis that vesicular uptake is necessary for the entry of LEVs into terminals. The vesicular entry of LEV resembles the cell entry pathways for tetanus and botulinum neurotoxins, but is unique for small, neuroactive drugs. Although the reduction of IPSC trains by LEV initially seems counterintuitive for an antiepileptic drug, there are multiple reasons that disruption of γ-aminobutyric acid (GABA) release could ultimately attenuate pathologic discharges.

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.

A randomized, placebo‐controlled trial of levetiracetam in central pain in multiple sclerosis

Levetiracetam is an anticonvulsant which is assumed to act by modulating neurotransmitter release via binding to the vesicle protein SV2A. This could have an impact on signalling in the pain pathway. The aim of this study was to test the analgesic effect of levetiracetam in central pain in multiple sclerosis. This was a randomized, double-blind, placebo-controlled, cross-over trial with levetiracetam 3000 mg/day versus placebo (6-week treatment periods). Patients with multiple sclerosis, symptoms and signs complying with central neuropathic pain and pain symptoms for more than 6 months, as well as pain intensity of more than 4 on a 0 to 10-point numeric rating scale were included in the study. The primary outcome measure was pain relief at the end of each treatment period as measured on a 6-point verbal scale. Eighty-nine patients were screened for participation and 30 patients entered the study. Twenty-seven patients were included in the data analysis. There were no differences in the ratings of pain relief (levetiracetam 2.4 vs. placebo 2.1, p = 0.169), total pain intensity (levetiracetam 5.3 vs. placebo 5.7, p = 0.147) or any of the other outcome measures (p = 0.086-0.715) in the total sample of patients. However, there was significant reduction of pain, increased pain relief and/or more favourable pain relief with levetiracetam than with placebo in patients with lancinating or without touch-evoked pain (p = 0.025-0.046). This study found no effect of the anticonvulsant levetiracetam in non-selected patients with central pain in multiple sclerosis, but an effect in subgroups with specific pain symptoms was indicated.

Increased levels of SV2A botulinum neurotoxin receptor in clinical sensory disorders and functional effects of botulinum toxins A and E in cultured human sensory neurons

BackgroundThere is increasing evidence that botulinum neurotoxin A may affect sensory nociceptor fibers, but the expression of its receptors in clinical pain states, and its effects in human sensory neurons, are largely unknown.MethodsWe studied synaptic vesicle protein subtype SV2A, a receptor for botulinum neurotoxin A, by immunostaining in a range of clinical tissues, including human dorsal root ganglion sensory neurons, peripheral nerves, the urinary bladder, and the colon. We also determined the effects of botulinum neurotoxins A and E on localization of the capsaicin receptor, TRPV1, and functional sensitivity to capsaicin stimuli in cultured human dorsal root ganglion neurons.ResultsImage analysis showed that SV2A immunoreactive nerve fibers were increased in injured nerves proximal to the injury (P = 0.002), and in painful neuromas (P = 0.0027); the ratio of percentage area SV2A to neurofilaments (a structural marker) was increased proximal to injury (P = 0.0022) and in neuromas (P = 0.0001), indicating increased SV2A levels in injured nerve fibers. In the urinary bladder, SV2A nerve fibers were found in detrusor muscle and associated with blood vessels, with a significant increase in idiopathic detrusor over-activity (P = 0.002) and painful bladder syndrome (P = 0.0087). Colon biopsies showed numerous SV2A-positive nerve fibers, which were increased in quiescent inflammatory bowel disease with abdominal pain (P = 0.023), but not in inflammatory bowel disease without abdominal pain (P = 0.77) or in irritable bowel syndrome (P = 0.13). In vitro studies of botulinum neurotoxin A-treated and botulinum neurotoxin E-treated cultured human sensory neurons showed accumulation of cytoplasmic vesicles, neurite loss, and reduced immunofluorescence for the heat and capsaicin receptor, TRPV1. Functional effects included dose-related inhibition of capsaicin responses on calcium imaging after acute treatment with botulinum neurotoxins A and E.ConclusionDifferential levels of SV2A protein expression in clinical disorders may identify potential new targets for botulinum neurotoxin therapy. In vitro studies indicate that treatment with botulinum neurotoxins A and E may affect receptor expression and nociceptor function in sensory neurons.

MicroRNA regulation of homeostatic synaptic plasticity

Homeostatic mechanisms are required to control formation and maintenance of synaptic connections to maintain the general level of neural impulse activity within normal limits. How genes controlling these processes are co-coordinately regulated during homeostatic synaptic plasticity is unknown. MicroRNAs (miRNAs) exert regulatory control over mRNA stability and translation and may contribute to local and activity-dependent posttranscriptional control of synapse-associated mRNAs. However, identifying miRNAs that function through posttranscriptional gene silencing at synapses has remained elusive. Using a bioinformatics screen to identify sequence motifs enriched in the 3'UTR of rapidly destabilized mRNAs, we identified a developmentally and activity-regulated miRNA (miR-485) that controls dendritic spine number and synapse formation in an activity-dependent homeostatic manner. We find that many plasticity-associated genes contain predicted miR-485 binding sites and further identify the presynaptic protein SV2A as a target of miR-485. miR-485 negatively regulated dendritic spine density, postsynaptic density 95 (PSD-95) clustering, and surface expression of GluR2. Furthermore, miR-485 overexpression reduced spontaneous synaptic responses and transmitter release, as measured by miniature excitatory postsynaptic current (EPSC) analysis and FM 1-43 staining. SV2A knockdown mimicked the effects of miR-485, and these effects were reversed by SV2A overexpression. Moreover, 5 d of increased synaptic activity induced homeostatic changes in synaptic specializations that were blocked by a miR-485 inhibitor. Our findings reveal a role for this previously uncharacterized miRNA and the presynaptic protein SV2A in homeostatic plasticity and nervous system development, with possible implications in neurological disorders (e.g., Huntington and Alzheimer's disease), where miR-485 has been found to be dysregulated.

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.

The anticonvulsant levetiracetam for the treatment of pain in polyneuropathy: A randomized, placebo-controlled, cross-over trial

Levetiracetam is an anticonvulsant which is assumed to act by modulating neurotransmitter release via binding to the vesicle protein SV2A. This could have an impact on signaling in the nociceptive system, and a pilot study indicated relief of neuropathic pain with levetiracetam. Objectives The aim of this study was to test the analgesic effect of levetiracetam in painful polyneuropathy. Methods This was a randomized, double-blind, placebo-controlled, cross-over trial with levetiracetam 3000 mg/day versus placebo (6-week treatment periods). Patients with diagnosed polyneuropathy and symptoms for more than 6 months, age between 20 and 80 years, pain intensity of more than 4 on a 0–10-point numeric rating scale, and pain at least 4 days a week were included in the study. The primary outcome measure was pain relief at the end of each treatment period as measured on a 6-point verbal scale. Results Ninety-three patients were screened for participation and 39 patients entered the study. Thirty-five patients were included in the data analysis. There were no differences in the ratings of pain relief (levetiracetam 2.29 versus placebo 2.28, p = 0.979), total pain intensity (levetiracetam 5.5 versus placebo 5.3, p = 0.293) or any of the other outcome measures ( p = 0.147–1.00). Conclusion This study indicates that the anticonvulsant levetiracetam has no clinically relevant effect on painful polyneuropathy.

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.