Hydrogen adsorption on nitrogen and boron doped graphene

Hydrogen adsorption on boron and nitrogen doped graphene is investigated in detail by means of first-principles calculations. A comprehensive study is performed of the structural, electronic, and magnetic properties of chemisorbed hydrogen atoms and atom pairs near the dopant sites. The main effect of the substitutional atoms is charge doping which is found to greatly affect the adsorption process by increasing the binding energy at the sites closest to the substitutional species. It is also found that doping does not induce magnetism despite the odd number of electrons per atom introduced by the foreign species, and that it quenches the paramagnetic response of chemisorbed H atoms on graphene. Overall, the effects are similar for B and N doping, with only minor differences in the adsorption energetics due to different sizes of the dopant atoms and the accompanying lattice distortions

Drug repurposing for Dravet syndrome in scn1Lab(-/-) mutant zebrafish

Dravet syndrome (DS) is a severe genetic epileptic encephalopathy with onset during the first year of life. Zebrafish models recapitulating human diseases are often used as drug discovery platforms, but also for drug repurposing testing. It was recently shown that pharmacological modulation of three serotonergic (5-HT) receptors (5-HT1D , 5-HT2C , 5-HT2A ) exerts antiseizure effects in a zebrafish scn1Lab-/- mutant model of DS. Using the zebrafish DS model, our aim was to examine the possibility of repurposing efavirenz (EFA), lisuride (LIS), and rizatriptan (RIZA), marketed medicines with a 5-HT on- or off-target profile, as antiepileptic drugs for DS. To examine whether these compounds have a broader antiseizure profile, they were tested in pentylenetetrazol and ethyl ketopentenoate (EKP) zebrafish models. Pharmacological effects were assessed by locomotor behavior, local field potential brain recordings, and bioluminescence. EFA was active in all models, whereas LIS was selectively active in the zebrafish DS model. Mainly, a poor response was observed to RIZA. Taken together, our preclinical results show that LIS could be a potential candidate for DS treatment. EFA was also active in the EKP model, characterized by a high level of treatment resistance, and hence these data are potentially important for future treatment of drug-resistant epilepsy.status: publishe

Zebrafish-Based Screening of Antiseizure Plants Used in Traditional Chinese Medicine: Magnolia officinalis Extract and Its Constituents Magnolol and Honokiol Exhibit Potent Anticonvulsant Activity in a Therapy-Resistant Epilepsy Model

With the aim to discover interesting lead compounds that could be further developed into compounds active against pharmacoresistant epilepsies, we first collected 14 medicinal plants used in traditional Chinese medicine (TCM) against epilepsy. Of the six extracts that tested positive in a pentylenetetrazole (PTZ) behavioral zebrafish model, only the ethanol and acetone extracts from Magnolia officinalis (M. officinalis) also showed effective antiseizure activity in the ethylketopentenoate (EKP) zebrafish model. The EKP model is regarded as an interesting discovery platform to find mechanistically novel antiseizure drugs, as it responds poorly to a large number of marketed anti-epileptics. We then demonstrated that magnolol and honokiol, two major constituents of M. officinalis, displayed an effective behavioral and electrophysiological antiseizure activity in both the PTZ and the EKP models. Out of six structural analogues tested, only 4-O-methylhonokiol was active and to a lesser extent tetrahydromagnolol, whereas the other analogues (3,3'-dimethylbiphenyl, 2,2'-biphenol, 2-phenylphenol, and 3,3',5,5'-tetra-tert-butyl-[1,1'-biphenyl]-2,2'-diol) were not consistently active in the aforementioned assays. Finally, magnolol was also active in the 6 Hz psychomotor mouse model, an acute therapy-resistant rodent model, thereby confirming the translation of the findings from zebrafish larvae to mice in the field of epilepsy. We also developed a fast and automated power spectral density (PSD) analysis of local field potential (LFP) recordings. The PSD results are in agreement with the visual analysis of LFP recordings using Clampfit software and manually counting the epileptiform events. Taken together, screening extracts of single plants employed in TCM, using a combination of zebrafish- and mouse-based assays, allowed us to identify allyl biphenol as a chemical scaffold for the future development of compounds with potential activity against therapy-resistant epilepsies.status: publishe

Connectivity mapping using a novel sv2a loss-of-function zebrafish epilepsy model as a powerful strategy for anti-epileptic drug discovery

Synaptic vesicle glycoprotein 2A (SV2A) regulates action potential-dependent neurotransmitter release and is commonly known as the primary binding site of an approved anti-epileptic drug, levetiracetam. Although several rodent knockout models have demonstrated the importance of SV2A for functional neurotransmission, its precise physiological function and role in epilepsy pathophysiology remains to be elucidated. Here, we present a novel sv2a knockout model in zebrafish, a vertebrate with complementary advantages to rodents. We demonstrated that 6 days post fertilization homozygous sv2a(–/–) mutant zebrafish larvae, but not sv2a(+/–) and sv2a(+/+) larvae, displayed locomotor hyperactivity and spontaneous epileptiform discharges, however, no major brain malformations could be observed. A partial rescue of this epileptiform brain activity could be observed after treatment with two commonly used anti-epileptic drugs, valproic acid and, surprisingly, levetiracetam. This observation indicated that additional targets, besides Sv2a, maybe are involved in the protective effects of levetiracetam against epileptic seizures. Furthermore, a transcriptome analysis provided insights into the neuropathological processes underlying the observed epileptic phenotype. While gene expression profiling revealed only one differentially expressed gene (DEG) between wildtype and sv2a(+/–) larvae, there were 4386 and 3535 DEGs between wildtype and sv2a(–/–), and sv2a(+/–) and sv2a(–/–) larvae, respectively. Pathway and gene ontology (GO) enrichment analysis between wildtype and sv2a(–/–) larvae revealed several pathways and GO terms enriched amongst up- and down-regulated genes, including MAPK signaling, synaptic vesicle cycle, and extracellular matrix organization, all known to be involved in epileptogenesis and epilepsy. Importantly, we used the Connectivity map database to identify compounds with opposing gene signatures compared to the one observed in sv2a(–/–) larvae, to finally rescue the epileptic phenotype. Two out of three selected compounds rescued electrographic discharges in sv2a(–/–) larvae, while negative controls did not. Taken together, our results demonstrate that sv2a deficiency leads to increased seizure vulnerability and provide valuable insight into the functional importance of sv2a in the brain in general. Furthermore, we provided evidence that the concept of connectivity mapping represents an attractive and powerful approach in the discovery of novel compounds against epilepsy

Zebrafish-Based Discovery of Antiseizure Compounds from the North Sea: Isoquinoline Alkaloids TMC-120A and TMC-120B

There is a high need for the development of new and improved antiseizure drugs (ASDs) to treat epilepsy. Despite the potential of marine natural products (MNPs), the EU marine biodiscovery consortium PharmaSea has made the only effort to date to perform ASD discovery based on large-scale screening of MNPs. To this end, the embryonic zebrafish photomotor response assay and the larval zebrafish pentylenetetrazole (PTZ) model were used to screen MNP extracts for neuroactivity and antiseizure activity, respectively. Here we report the identification of the two known isoquinoline alkaloids TMC-120A and TMC-120B as novel antiseizure compounds, which were isolated by bioactivity-guided purification from the marine-derived fungus Aspergillus insuetus. TMC-120A and TMC-120B were observed to significantly lower PTZ-induced seizures and epileptiform brain activity in the larval zebrafish PTZ seizure model. In addition, their structural analogues TMC-120C, penicisochroman G, and ustusorane B were isolated and also significantly lowered PTZ-induced seizures. Finally, TMC-120A and TMC-120B were investigated in a mouse model of drug-resistant focal seizures. Compound treatment significantly shortened the seizure duration, thereby confirming their antiseizure activity. These data underscore the possibility to translate findings in zebrafish to mice in the field of epilepsy and the potential of the marine environment for ASD discovery.status: publishe

Biallelic VARS variants cause developmental encephalopathy with microcephaly that is recapitulated in vars knockout zebrafish

Aminoacyl tRNA synthetases (ARSs) link specific amino acids with their cognate transfer RNAs in a critical early step of protein translation. Mutations in ARSs have emerged as a cause of recessive, often complex neurological disease traits. Here we report an allelic series consisting of seven novel and two previously reported biallelic variants in valyl-tRNA synthetase (VARS) in ten patients with a developmental encephalopathy with microcephaly, often associated with early-onset epilepsy. In silico, in vitro, and yeast complementation assays demonstrate that the underlying pathomechanism of these mutations is most likely a loss of protein function. Zebrafish modeling accurately recapitulated some of the key neurological disease traits. These results provide both genetic and biological insights into neurodevelopmental disease and pave the way for further in-depth research on ARS related recessive disorders and precision therapies

Biallelic VARS variants cause developmental encephalopathy with microcephaly that is recapitulated in vars knockout zebrafish

Aminoacyl tRNA synthetases (ARSs) link specific amino acids with their cognate transfer RNAs in a critical early step of protein translation. Mutations in ARSs have emerged as a cause of recessive, often complex neurological disease traits. Here we report an allelic series consisting of seven novel and two previously reported biallelic variants in valyl-tRNA synthetase (VARS) in ten patients with a developmental encephalopathy with microcephaly, often associated with early-onset epilepsy. In silico, in vitro, and yeast complementation assays demonstrate that the underlying pathomechanism of these mutations is most likely a loss of protein function. Zebrafish modeling accurately recapitulated some of the key neurological disease traits. These results provide both genetic and biological insights into neurodevelopmental disease and pave the way for further in-depth research on ARS related recessive disorders and precision therapies.status: publishe