Publications by authors named "Véronique André"

66 Publications

Development of a Rat Model for Glioma-Related Epilepsy.

Int J Mol Sci 2020 Sep 23;21(19). Epub 2020 Sep 23.

4Brain, Department of Head and Skin, Ghent University, 9000 Ghent, East Flanders, Belgium.

Seizures are common in patients with high-grade gliomas (30-60%) and approximately 15-30% of glioblastoma (GB) patients develop drug-resistant epilepsy. Reliable animal models are needed to develop adequate treatments for glioma-related epilepsy. Therefore, fifteen rats were inoculated with F98 GB cells (GB group) and four rats with vehicle only (control group) in the right entorhinal cortex. MRI was performed to visualize tumor presence. A subset of seven GB and two control rats were implanted with recording electrodes to determine the occurrence of epileptic seizures with video-EEG recording over multiple days. In a subset of rats, tumor size and expression of tumor markers were investigated with histology or mRNA in situ hybridization. Tumors were visible on MRI six days post-inoculation. Time-dependent changes in tumor morphology and size were visible on MRI. Epileptic seizures were detected in all GB rats monitored with video-EEG. Twenty-one days after inoculation, rats were euthanized based on signs of discomfort and pain. This study describes, for the first time, reproducible tumor growth and spontaneous seizures upon inoculation of F98 cells in the rat entorhinal cortex. The development of this new model of GB-related epilepsy may be valuable to design new therapies against tumor growth and associated epileptic seizures.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijms21196999DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7582710PMC
September 2020

Comparative Toxigenicity and Associated Mutagenicity of and Group Isolates Collected from the Agricultural Environment.

Toxins (Basel) 2020 07 17;12(7). Epub 2020 Jul 17.

Faculty of Health, Normandie University, UNICAEN, Centre F. Baclesse, UR ABTE EA4651, 14000 Caen, France.

The mutagenic patterns of and extracts were evaluated. These strains of toxigenic were collected from the agricultural environment. The Ames test was performed on strains TA98, TA100 and TA102, without and with S9mix (exogenous metabolic activation system). These data were compared with the mutagenicity of the corresponding pure mycotoxins tested alone or in reconstituted mixtures with equivalent concentrations, in order to investigate the potential interactions between these molecules and/or other natural metabolites. At least 3 mechanisms are involved in the mutagenic response of these aflatoxins: firstly, the formation of AFB-8,9-epoxide upon addition of S9mix, secondly the likely formation of oxidative damage as indicated by significant responses in TA102, and thirdly, a direct mutagenicity observed for higher doses of some extracts or associated mycotoxins, which does not therefore involve exogenously activated intermediates. Besides the identified mycotoxins (AFB, AFB and AFM), additional "natural" compounds contribute to the global mutagenicity of the extracts. On the other hand, AFB and AFM modulate negatively the mutagenicity of AFB when mixed in binary or tertiary mixtures. Thus, the evaluation of the mutagenicity of "natural" mixtures is an integrated parameter that better reflects the potential impact of exposure to toxigenic Aspergilli.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/toxins12070458DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7404940PMC
July 2020

Unraveling the mechanism and the risk behind seizure liability of lead compounds in a neuroscience project.

J Pharmacol Toxicol Methods 2020 Jul - Aug;104:106874. Epub 2020 May 22.

UCB Biopharma SRL, chemin du Foriest, Braine-l'Alleud, Belgium.

Introduction: Several compounds from a neuroscience project induced convulsions in animals, at low exposure levels via a hypothetical off-target mechanism. A set of in vitro and in vivo experiments were conducted in order to 1) identify the mechanism behind convulsions; 2) characterize the convulsions, 3) detect premonitory signs that could be monitored clinically, and 4) assess the development of tolerance after repeat dosing.

Methods: Patch clamp assays were conducted on 12 different ion channels (e.g. sodium, potassium, calcium, AMPA, NMDA, GABA and purinergic receptors) known to be associated with seizures, to identify the off-target culprit. A multiphase study was conducted with UCB-A and UCB-B in Beagle dogs telemetered for video EEG/EMG monitoring to further characterize the convulsive pattern. First, both compounds were administered by intravenous constant infusion (dose: 5 mg/kg/h) over 2 h. Thereafter, the same dogs received a daily oral administration of UCB-A (8 mg/kg/day) for 7 days.

Results: Compounds inducing convulsions showed strong inhibitory activity on GABA channels (IC values <10 μM), whereas compounds with partial or no inhibitory effect on these channels did not induce seizures. In EEG experiments, convulsions were preceded by premonitory clinical signs (e.g. tremors, myoclonic jerks) and morphological EEG abnormalities (e.g. sharp waves, spike and wave patterns), confirming their CNS origin. No attenuation of the seizurogenic effects was observed over the 7-day treatment period.

Discussion: A well-designed set of experiments including electrophysiological assays on seizure-related ion channels and EEG/EMG assessment in telemetered dogs allowed a proper seizure liability risk assessment, leading to a rapid no go decision for the two most advanced leads.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.vascn.2020.106874DOI Listing
May 2021

Discovery of a small molecule modulator of the Kv1.1/Kvβ1 channel complex that reduces neuronal excitability and in vitro epileptiform activity.

CNS Neurosci Ther 2019 04 21;25(4):442-451. Epub 2018 Sep 21.

Department of Neuroscience Research, UCB Pharma, Braine l'Alleud, Belgium.

Aims: Kv1.1 (KCNA1) channels contribute to the control of neuronal excitability and have been associated with epilepsy. Kv1.1 channels can associate with the cytoplasmic Kvβ1 subunit resulting in rapid inactivating A-type currents. We hypothesized that removal of channel inactivation, by modulating Kv1.1/Kvβ1 interaction with a small molecule, would lead to decreased neuronal excitability and anticonvulsant activity.

Methods: We applied high-throughput screening to identify ligands able to modulate the Kv1.1-T1 domain/Kvβ1 protein complex. We then selected a compound that was characterized on recombinant Kv1.1/Kvβ1 channels by electrophysiology and further evaluated on sustained neuronal firing and on in vitro epileptiform activity using a high K -low Ca model in hippocampal slices.

Results: We identified a novel compound able to modulate the interaction of the Kv1.1/Kvβ1 complex and that produced a functional inhibition of Kv1.1/Kvβ1 channel inactivation. We demonstrated that this compound reduced the sustained repetitive firing in hippocampal neurons and was able to abolish the development of in vitro epileptiform activity.

Conclusions: This study describes a rational drug discovery approach for the identification of novel ligands that inhibit Kv1.1 channel inactivation and provides pharmacological evidence that such a mechanism translates into physiological effects by reducing in vitro epileptiform activity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/cns.13060DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6488918PMC
April 2019

Chemical characterization of fine and ultrafine PM, direct and indirect genotoxicity of PM and their organic extracts on pulmonary cells.

J Environ Sci (China) 2018 Sep 27;71:168-178. Epub 2018 Apr 27.

University of the Littoral Opal Coast, Unit of Environmental Chmistry and Interactions with Living Organisms, UCEIV EA4492, SFR Condorcet FR CNRS 3417, Dunkerque, France.

Particulate matter in ambient air constitutes a complex mixture of fine and ultrafine particles composed of various chemical compounds including metals, ions, and organics. A multidisciplinary approach was developed by studying physico-chemical characteristics and mechanisms involved in the toxicity of particulate atmospheric pollution. PM and PM including ultrafine particles were sampled in Dunkerque, a French industrialized seaside city. PM samples were characterized from a chemical and toxicological point of view. Physico-chemical characterization evidenced that PM comes from several sources: natural ones, such as soil resuspension and marine sea-salt emissions, as well as anthropogenic ones, such as shipping traffic, road traffic, and industrial activities. Human BEAS-2B lung cells were exposed to PM, or to the Extractable Organic Matter (EOM) of PM and PM. These exposures induced several mechanisms of action implied in the genotoxicity, such as oxidative DNA adducts and DNA Damage Response. The toxicity of PM-EOM was higher for the sample including the ultrafine fraction (PM) containing also higher concentrations of polycyclic aromatic hydrocarbons. These results evidenced the major role of organic compounds in the toxicity of PM.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jes.2018.04.022DOI Listing
September 2018

Chaga ( Inonotus obliquus), a Future Potential Medicinal Fungus in Oncology? A Chemical Study and a Comparison of the Cytotoxicity Against Human Lung Adenocarcinoma Cells (A549) and Human Bronchial Epithelial Cells (BEAS-2B).

Integr Cancer Ther 2018 09 27;17(3):832-843. Epub 2018 Feb 27.

1 Normandie University, UNICAEN, Centre F. Baclesse, Caen, France.

Background: Inonotus obliquus, also known as Chaga, is a parasitic fungus growing on birches and used in traditional medicine (especially by Khanty people) to treat various health problems. In this study, we aimed to quantify the 3 metabolites frequently cited in literature, that is, betulin, betulinic acid, and inotodiol in the Chaga recently discovered in forests located in Normandy (France), and to compare their concentrations with Ukrainian and Canadian Chaga. This study also explores the cytotoxicity of the French Chaga against cancer-derived cells and transformed cells.

Methods: A quantification method by HPLC-MS-MS (high-performance liquid chromatography-tandem mass spectrometry) of betulin, betulinic acid, and inotodiol was developed to study the French Chaga and compare the concentration of these metabolites with extracts provided from Chaga growing in Canada and Ukraine. This method was also used to identify and quantify those 3 compounds in other traditional preparations of Chaga (aqueous extract, infusion, and decoction). Among these preparations, the aqueous extract that contains betulin, betulinic acid, and inotodiol was chosen to evaluate and compare its cytotoxic activity toward human lung adenocarcinoma cells (A549 line) and human bronchial epithelial cells (BEAS-2B line).

Results: French Chaga contains betulin and betulinic acid at higher levels than in other Chaga, whereas the concentration of inotodiol is greater in the Canadian Chaga. Moreover, the results highlighted a cytotoxic activity of the Chaga's aqueous extract after 48 and 72 hours of exposure with a higher effect on cancer-derived cells A549 than on normal transformed cells BEAS-2B ( P = 0.025 after 48 hours of exposure and P = 0.004 after 72 hours of exposure).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1177/1534735418757912DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6142110PMC
September 2018

Comparative study of diesel and biodiesel exhausts on lung oxidative stress and genotoxicity in rats.

Environ Pollut 2018 Apr 8;235:514-524. Epub 2018 Jan 8.

Normandie Univ, UNICAEN, UNIROUEN, ABTE, 14000 Caen et 76000, Rouen, France; Centre François Baclesse, Caen, France. Electronic address:

The contribution of diesel exhaust to atmospheric pollution is a major concern for public health, especially in terms of occurrence of lung cancers. The present study aimed at addressing the toxic effects of a repeated exposure to these emissions in an animal study performed under strictly controlled conditions. Rats were repeatedly exposed to the exhaust of diesel engine. Parameters such as the presence of a particle filter or the use of gasoil containing rapeseed methyl ester were investigated. Various biological parameters were monitored in the lungs to assess the toxic and genotoxic effects of the exposure. First, a transcriptomic analysis showed that some pathways related to DNA repair and cell cycle were affected to a limited extent by diesel but even less by biodiesel. In agreement with occurrence of a limited genotoxic stress in the lungs of diesel-exposed animals, small induction of γ-H2AX and acrolein adducts was observed but not of bulky adducts and 8-oxodGuo. Unexpected results were obtained in the study of the effect of the particle filter. Indeed, exhausts collected downstream of the particle filter led to a slightly higher induction of a series of genes than those collected upstream. This result was in agreement with the formation of acrolein adducts and γH2AX. On the contrary, induction of oxidative stress remained very limited since only SOD was found to be induced and only when rats were exposed to biodiesel exhaust collected upstream of the particle filter. Parameters related to telomeres were identical in all groups. In summary, our results point to a limited accumulation of damage in lungs following repeated exposure to diesel exhausts when modern engines and relevant fuels are used. Yet, a few significant effects are still observed, mostly after the particle filter, suggesting a remaining toxicity associated with the gaseous or nano-particular phases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.envpol.2017.12.077DOI Listing
April 2018

GRIN2B gain of function mutations are sensitive to radiprodil, a negative allosteric modulator of GluN2B-containing NMDA receptors.

Neuropharmacology 2017 Sep 19;123:322-331. Epub 2017 May 19.

UCB BioPharma Sprl, Neurosciences Therapeutic Area, Chemin du Foriest, B-1420 Braine l'Alleud, Belgium. Electronic address:

De novo gain of function mutations in GRIN2B encoding the GluN2B subunit of the N-methyl-d-aspartate (NMDA) receptor have been linked with epileptic encephalopathies, including infantile spasms. We investigated the effects of radiprodil, a selective GluN2B negative allosteric modulator and other non-selective NMDA receptor inhibitors on glutamate currents mediated by NMDA receptors containing mutated GluN2B subunits. The experiments were performed in Xenopus oocytes co-injected with the following human mRNAs: GRIN1/GRIN2B, GRIN1/GRIN2B-R540H, GRIN1/GRIN2B-N615I and GRIN1/GRIN2B-V618G. Glutamate displayed slightly increased potency in the R540H variant, but not in N615I and V618G variants. However, the inhibition by Mg was completely abolished in N615I and V618G variants. In fact, Mg enhanced glutamate responses in those variants. The potency of radiprodil to block glutamate-evoked currents was not affected in any of the variants, while the effects by non-selective NMDA inhibitors were greatly reduced in some of the variants. Additionally, in the Mg insensitive variants, radiprodil blocked glutamate-activated currents with the same potency as in the absence of Mg. The gain of function observed in the reported GRIN2B variants could be a key pathophysiological factor leading to neuronal hyper-excitability in epileptic encephalopathies. The GluN2B-selective inhibitor radiprodil fully retained its pharmacological profile under these conditions, while other non-selective NMDA receptor antagonists lost their potency. Consequently, our data suggest that radiprodil may be a valuable therapeutic option for treatment of pediatric epileptic encephalopathies associated with GRIN2B mutations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuropharm.2017.05.017DOI Listing
September 2017

Assessment of multi-contaminant exposure in a cancer treatment center: a 2-year monitoring of molds, mycotoxins, endotoxins, and glucans in bioaerosols.

Environ Monit Assess 2017 Jan 23;189(1):31. Epub 2016 Dec 23.

ABTE EA 4651, Normandie Université, UNICAEN, UNIROUEN, 14000, Caen, France.

Indoor air quality in health care facilities is a major public health concern, particularly for immunocompromised patients who may be exposed to microbiological contaminants such as molds, mycotoxins, endotoxins, and (1,3)-ß-D-glucans. Over 2 years, bioaerosols were collected on a monthly basis in a cancer treatment center (Centre F. Baclesse, Normandy, France), characterized from areas where there was no any particular air treatment. Results showed the complexity of mycoflora in bioaerosols with more than 100 fungal species identified. A list of major strains in hospital environments could be put forward due to the frequency, the concentration level, and/or the capacity to produce mycotoxins in vitro: Aspergillus fumigatus, Aspergillus melleus, Aspergillus niger, Aspergillus versicolor, Cladosporium herbarum, Purpureocillium lilacinum, and Penicillium brevicompactum. The mean levels of viable airborne fungal particles were less than 30.530 CFU per m of air and were correlated to the total number of 0.30 to 20 μm particles. Seasonal variations were observed with fungal particle peaks during the summer and autumn. Statistical analysis showed that airborne fungal particle levels depended on the relative humidity level which could be a useful indicator of fungal contamination. Finally, the exposure to airborne mycotoxins was very low (only 3 positive samples), and no mutagenic activity was found in bioaerosols. Nevertheless, some fungal strains such as Aspergillus versicolor or Penicillium brevicompactum showed toxigenic potential in vitro.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10661-016-5751-zDOI Listing
January 2017

Fine and ultrafine atmospheric particulate matter at a multi-influenced urban site: Physicochemical characterization, mutagenicity and cytotoxicity.

Environ Pollut 2017 Feb 30;221:130-140. Epub 2016 Nov 30.

Univ. Littoral Côte d'Opale, EA 4492 - UCEIV - Unité de Chimie Environnementale et Interactions sur le Vivant, F-59140, Dunkerque, France.

Particulate Matter (PM) air pollution is one of the major concerns for environment and health. Understanding the heterogeneity and complexity of fine and ultrafine PM is a fundamental issue notably for the assessment of PM toxicological effects. The aim of this study was to evaluate mutagenicity and cytotoxicity of a multi-influenced urban site PM, with or without the ultrafine fraction. For this purpose, PM (PM with aerodynamic diameter ranging from 0.3 to 2.5 μm) and PM were collected in Dunkerque, a French coastal industrial city and were extensively characterized for their physico-chemical properties, including inorganic and organic species. In order to identify the possible sources of atmospheric pollution, specific criteria like Carbon Preference Index (CPI) and PAH characteristic ratios were investigated. Mutagenicity assays using Ames test with TA98, TA102 and YG1041 Salmonella strains with or without S9 activation were performed on native PM sample and PM organic extracts and water-soluble fractions. BEAS-2B cell viability and cell proliferation were evaluated measuring lactate dehydrogenase release and mitochondrial dehydrogenase activity after exposure to PM and their extracts. Several contributing sources were identified in PM: soil resuspension, marine emissions including sea-salt or shipping, road traffic and industrial activities, mainly related to steelmaking or petro-chemistry. Mutagenicity of PM was evidenced, especially for PM, including ultrafine fraction, in relation to PAHs content and possibly nitro-aromatics compounds. PM induced cytotoxic effects at relatively high doses, while alteration of proliferation with low PM doses could be related to underlying mechanisms such as genotoxicity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.envpol.2016.11.054DOI Listing
February 2017

In Vitro and In Vivo Identification of Novel Positive Allosteric Modulators of the Human Dopamine D2 and D3 Receptor.

Mol Pharmacol 2016 Feb 11;89(2):303-12. Epub 2015 Dec 11.

UCB Biopharma SPRL, Chemin du Foriest, B-1420, Braine-l'Alleud, Belgium.

Agonists at dopamine D2 and D3 receptors are important therapeutic agents in the treatment of Parkinson's disease. Compared with the use of agonists, allosteric potentiators offer potential advantages such as temporal, regional, and phasic potentiation of natural signaling, and that of receptor subtype selectivity. We report the identification of a stereoselective interaction of a benzothiazol racemic compound that acts as a positive allosteric modulator (PAM) of the rat and human dopamine D2 and D3 receptors. The R isomer did not directly stimulate the dopamine D2 receptor but potentiated the effects of dopamine. In contrast the S isomer attenuated the effects of the PAM and the effects of dopamine. In radioligand binding studies, these compounds do not compete for binding of orthosteric ligands, but indeed the R isomer increased the number of high-affinity sites for [(3)H]-dopamine without affecting K(d). We went on to identify a more potent PAM for use in native receptor systems. This compound potentiated the effects of D2/D3 signaling in vitro in electrophysiologic studies on dissociated striatal neurons and in vivo on the effects of L-dopa in the 6OHDA (6-hydroxydopamine) contralateral turning model. These PAMs lacked activity at a wide variety of receptors, lacked PAM activity at related Gi-coupled G protein-coupled receptors, and lacked activity at D1 receptors. However, the PAMs did potentiate [(3)H]-dopamine binding at both D2 and D3 receptors. Together, these studies show that we have identified PAMs of the D2 and D3 receptors both in vitro and in vivo. Such compounds may have utility in the treatment of hypodopaminergic function.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1124/mol.115.100172DOI Listing
February 2016

Diagnostic methods and treatment options for focal cortical dysplasia.

Epilepsia 2015 Nov 5;56(11):1669-86. Epub 2015 Oct 5.

Department of Neuropathology, University Hospital Erlangen, Erlangen, Germany.

Our inability to adequately treat many patients with refractory epilepsy caused by focal cortical dysplasia (FCD), surgical inaccessibility and failures are significant clinical drawbacks. The targeting of physiologic features of epileptogenesis in FCD and colocalizing functionality has enhanced completeness of surgical resection, the main determinant of outcome. Electroencephalography (EEG)-functional magnetic resonance imaging (fMRI) and magnetoencephalography are helpful in guiding electrode implantation and surgical treatment, and high-frequency oscillations help defining the extent of the epileptogenic dysplasia. Ultra high-field MRI has a role in understanding the laminar organization of the cortex, and fluorodeoxyglucose-positron emission tomography (FDG-PET) is highly sensitive for detecting FCD in MRI-negative cases. Multimodal imaging is clinically valuable, either by improving the rate of postoperative seizure freedom or by reducing postoperative deficits. However, there is no level 1 evidence that it improves outcomes. Proof for a specific effect of antiepileptic drugs (AEDs) in FCD is lacking. Pathogenic mutations recently described in mammalian target of rapamycin (mTOR) genes in FCD have yielded important insights into novel treatment options with mTOR inhibitors, which might represent an example of personalized treatment of epilepsy based on the known mechanisms of disease. The ketogenic diet (KD) has been demonstrated to be particularly effective in children with epilepsy caused by structural abnormalities, especially FCD. It attenuates epigenetic chromatin modifications, a master regulator for gene expression and functional adaptation of the cell, thereby modifying disease progression. This could imply lasting benefit of dietary manipulation. Neurostimulation techniques have produced variable clinical outcomes in FCD. In widespread dysplasias, vagus nerve stimulation (VNS) has achieved responder rates >50%; however, the efficacy of noninvasive cranial nerve stimulation modalities such as transcutaneous VNS (tVNS) and noninvasive (nVNS) requires further study. Although review of current strategies underscores the serious shortcomings of treatment-resistant cases, initial evidence from novel approaches suggests that future success is possible.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/epi.13200DOI Listing
November 2015

Brivaracetam differentially affects voltage-gated sodium currents without impairing sustained repetitive firing in neurons.

CNS Neurosci Ther 2015 Mar 1;21(3):241-51. Epub 2014 Dec 1.

UCB Pharma SA, Neurosciences Therapeutic Area, Braine l'Alleud, Belgium.

Aims: Brivaracetam (BRV) is an antiepileptic drug in Phase III clinical development. BRV binds to synaptic vesicle 2A (SV2A) protein and is also suggested to inhibit voltage-gated sodium channels (VGSCs). To evaluate whether the effect of BRV on VGSCs represents a relevant mechanism participating in its antiepileptic properties, we explored the pharmacology of BRV on VGSCs in different cell systems and tested its efficacy at reducing the sustained repetitive firing (SRF).

Methods: Brivaracetam investigations on the voltage-gated sodium current (I(Na)) were performed in N1E-155 neuroblastoma cells, cultured rat cortical neurons, and adult mouse CA1 neurons. SRF was measured in cultured cortical neurons and in CA1 neurons. All BRV (100-300 μM) experiments were performed in comparison with 100 μM carbamazepine (CBZ).

Results: Brivaracetam and CBZ reduced IN a in N1E-115 cells (30% and 40%, respectively) and primary cortical neurons (21% and 47%, respectively) by modulating the fast-inactivated state of VGSCs. BRV, in contrast to CBZ, did not affect I(Na) in CA1 neurons and SRF in cortical and CA1 neurons. CBZ consistently inhibited neuronal SRF by 75-93%.

Conclusions: The lack of effect of BRV on SRF in neurons suggests that the reported inhibition of BRV on VGSC currents does not contribute to its antiepileptic properties.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/cns.12347DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4359682PMC
March 2015

Differential Synaptic and Extrasynaptic Glutamate-Receptor Alterations in Striatal Medium-Sized Spiny Neurons of Aged YAC128 Huntington's Disease Mice.

PLoS Curr 2014 May;6

Intellectual and Developmental Disabilities Research Center, David Geffen School of Medicine, University of California Los Angeles, California, USA.

Huntington's disease (HD) is a late-onset, slowly progressing neurodegenerative disorder caused by an expansion of glutamine repeats. The YAC128 mouse model has been widely used to study the progression of HD symptoms, but little is known about synaptic alterations in very old animals. The present experiments examined synaptic properties of striatal medium-sized spiny neurons (MSNs) in 16 month-old YAC128 mice. These mice were crossed with mice expressing enhanced green fluorescent protein (EGFP) under the control of either D1 or D2 dopamine receptor promoters to identify MSNs originating the direct and indirect pathways, respectively. The input-output curves of evoked excitatory postsynaptic currents mediated by activation of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) or N-methyl-D-aspartate (NMDA) receptors were reduced in MSNs in both pathways. In the presence of DL-threo-β-Benzyloxyaspartic acid (DL-TBOA), a glutamate transporter blocker used to increase activation of extrasynaptic receptors, NMDA receptor-mediated currents displayed altered amplitudes, longer decay times, and greater charge (response areas) in both direct and indirect pathway MSNs in YAC128 mice compared to wildtype controls. Amplitudes were significantly increased, primarily in direct pathway MSNs while normalized areas were significantly increased only in indirect pathway MSNs, suggesting that the two types of MSNs are affected in different ways. It may be that indirect pathway neurons are more susceptible to changes in glutamate transport. Taken together, the present findings demonstrate differential alterations in synaptic versus extrasynaptic NMDA receptors in both direct and indirect pathway MSNs in late HD, which may contribute to the dysfunction and degeneration in both pathways.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1371/currents.hd.34957c4f8bd7cb1f5ec47381dfc811c3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4032384PMC
May 2014

Assessment of the genotoxic and carcinogenic potentials of 3-aminothiophene derivatives using in vitro and in silico methodologies.

J Appl Toxicol 2014 Jul 11;34(7):775-86. Epub 2013 Oct 11.

Normandie Univ, France; UNICAEN, CERMN (Centre d'Etudes et de Recherche sur le Médicament de Normandie, FR CNRS INC3M - SF ICORE, Université de Caen Basse - Normandie, U.F.R. des Sciences Pharmaceutiques), F-14032, Caen, France.

Thiophene derivatives, a class of compounds widely used in products such as pharmaceuticals, agrochemicals or dyestuffs, represent chemicals of concern. Indeed, the thiophene ring is often considered as a structural moiety that may be involved in toxic effects in humans. We primarily focus on the genotoxic/mutagenic and carcinogenic potentials of the methyl 3-amino-4-methylthiophene-2-carboxylate (1), a precursor of the articaine local anesthetic (4) which falls within the scope of the European REACH (Registration, Evaluation, Authorisation and restriction of CHemicals) legislation. To discern some structure-toxicity relationships, we also studied two related compounds, namely the 3-amino 4-methylthiophene (2) and the 2-acetyl 4-chlorothiophene (3). Techniques employed to assess mutagenic and DNA-damaging effects involved the Salmonella mutagenicity assay (or Ames test) and the single-cell gel electrophoresis assay (or Comet assay). In the range of tested doses, none of these derivatives led to a positive response in the Ames tests and DNA damage was only observed in the Comet assay after high concentration exposure of 2. The study of their carcinogenic potential using the in vitro SHE (Syrian Hamster Embryo) cell transformation assay (CTA) highlighted the activity of compound 2. A combination of experimental data with in silico predictions of the reactivity of thiophene derivatives towards cytochrome P450 (CYP450), enabled us to hypothesize possible pathways leading to these toxicological profiles.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jat.2938DOI Listing
July 2014

Xenobiotic metabolism induction and bulky DNA adducts generated by particulate matter pollution in BEAS-2B cell line: geographical and seasonal influence.

J Appl Toxicol 2014 Jun 30;34(6):703-13. Epub 2013 Sep 30.

Université Lille Nord de France, France; ULCO, UCEIV EA4492, F-59140, Dunkerque, France.

Airborne particulate matter (PM) toxicity is of growing interest as diesel exhaust particles have been classified as carcinogenic to humans. However, PM is a mixture of chemicals, and respective contribution of organic and inorganic fractions to PM toxicity remains unclear. Thus, we analysed the link between chemical composition of PM samples and bulky DNA adduct formation supported by CYP1A1 and 1B1 genes induction and catalytic activities. We used six native PM samples, collected in industrial, rural or urban areas, either during the summer or winter, and carried out our experiments on the human bronchial epithelial cell line BEAS-2B. Cell exposure to PM resulted in CYP1A1 and CYP1B1 genes induction. This was followed by an increase in EROD activity, leading to bulky DNA adduct formation in exposed cells. Bulky DNA adduct intensity was associated to global EROD activity, but this activity was poorly correlated with CYPs mRNA levels. However, EROD activity was correlated with both metal and polycyclic aromatic hydrocarbon (PAH) content. Finally, principal components analysis revealed three clusters for PM chemicals, and suggested synergistic effects of metals and PAHs on bulky DNA adduct levels. This study showed the ability of PM samples from various origins to generate bulky DNA adducts in BEAS-2B cells. This formation was promoted by increased expression and activity of CYPs involved in PAHs activation into reactive metabolites. However, our data highlight that bulky DNA adduct formation is only partly explained by PM content in PAHs, and suggest that inorganic compounds, such as iron, may promote bulky DNA adduct formation by supporting CYP activity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jat.2931DOI Listing
June 2014

Multiple sources of striatal inhibition are differentially affected in Huntington's disease mouse models.

J Neurosci 2013 Apr;33(17):7393-406

Intellectual and Developmental Disabilities Research Center, Brain Research Institute, Semel Institute for Neuroscience, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California 90095, USA.

In Huntington's disease (HD) mouse models, spontaneous inhibitory synaptic activity is enhanced in a subpopulation of medium-sized spiny neurons (MSNs), which could dampen striatal output. We examined the potential source(s) of increased inhibition using electrophysiological and optogenetic methods to assess feedback and feedforward inhibition in two transgenic mouse models of HD. Single whole-cell patch-clamp recordings demonstrated that increased GABA synaptic activity impinges principally on indirect pathway MSNs. Dual patch recordings between MSNs demonstrated reduced connectivity between MSNs in HD mice. However, while connectivity was strictly unidirectional in controls, in HD mice bidirectional connectivity occurred. Other sources of increased GABA activity in MSNs also were identified. Dual patch recordings from fast spiking (FS) interneuron-MSN pairs demonstrated greater but variable amplitude responses in MSNs. In agreement, selective optogenetic stimulation of parvalbumin-expressing, FS interneurons induced significantly larger amplitude MSN responses in HD compared with control mice. While there were no differences in responses of MSNs evoked by activating single persistent low-threshold spiking (PLTS) interneurons in recorded pairs, these interneurons fired more action potentials in both HD models, providing another source for increased frequency of spontaneous GABA synaptic activity in MSNs. Selective optogenetic stimulation of somatostatin-expressing, PLTS interneurons did not reveal any significant differences in responses of MSNs in HD mice. These findings provide strong evidence that both feedforward and to a lesser extent feedback inhibition to MSNs in HD can potentially be sources for the increased GABA synaptic activity of indirect pathway MSNs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1523/JNEUROSCI.2137-12.2013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3686572PMC
April 2013

Recurrence of Stachybotrys chartarum during mycological and toxicological study of bioaerosols collected in a dairy cattle shed.

Ann Agric Environ Med 2012 ;19(1):61-7

Universite de Caen Basse Normandie, Caen, France.

Agricultural occupations associated with animal breeding and the processing of animal materials in confinement systems could potentially lead to bioaerosol exposures. Moulds and mycotoxins could be constituents of bioaerosols and should be studied because of their possible involvement in respiratory diseases and cancers. In order to characterize the fungal contamination of the indoor air in a dairy barn, bioaerosols were collected during 20 days in a cattle farm located in Normandy (France). Mycobiota, mycotoxins and the mutagenicity of bioaerosols were studied. The toxigenic ability of Aspergillus flavus group and Aspergillus fumigatus isolates was also evaluated in vitro. The prevalent airborne moulds were from the following potentially toxigenic species: Aspergillus flavus group, Aspergillus fumigatus, Penicillium chrysogenum, Stachybotrys chartarum, and the allergenic species Ulocladium chartarum, Cladosporium cladosporioides. In comparison with harvesting, grain handling or broiler breeding, the concentrations of viable moulds were lower in the cattle shed. Seasonal variations in levels of several species were also observed. This study revealed that aflatoxins were detected in bioaerosols and, for the first time, showed that farmers are possibly exposed to Stachybotrys chartarum during routine barn work. Moreover, the finding of mutagenicity from bioaerosols needs further investigations on bioaerosol composition.
View Article and Find Full Text PDF

Download full-text PDF

Source
July 2012

Benzo[a]pyrene, aflatoxine B₁ and acetaldehyde mutational patterns in TP53 gene using a functional assay: relevance to human cancer aetiology.

PLoS One 2012 3;7(2):e30921. Epub 2012 Feb 3.

Groupe Régional d'Etudes sur le Cancer-EA 1772, Université de Caen Basse-Normandie, Caen, France.

Mutations in the TP53 gene are the most common alterations in human tumours. TP53 mutational patterns have sometimes been linked to carcinogen exposure. In hepatocellular carcinoma, a specific G>T transversion on codon 249 is classically described as a fingerprint of aflatoxin B(1) exposure. Likewise G>T transversions in codons 157 and 158 have been related to tobacco exposure in human lung cancers. However, controversies remain about the interpretation of TP53 mutational pattern in tumours as the fingerprint of genotoxin exposure. By using a functional assay, the Functional Analysis of Separated Alleles in Yeast (FASAY), the present study depicts the mutational pattern of TP53 in normal human fibroblasts after in vitro exposure to well-known carcinogens: benzo[a]pyrene, aflatoxin B(1) and acetaldehyde. These in vitro patterns of mutations were then compared to those found in human tumours by using the IARC database of TP53 mutations. The results show that the TP53 mutational patterns found in human tumours can be only partly ascribed to genotoxin exposure. A complex interplay between the functional impact of the mutations on p53 phenotype and the cancer natural history may affect these patterns. However, our results strongly support that genotoxins exposure plays a major role in the aetiology of the considered cancers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0030921PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3272023PMC
September 2012

Functional Differences Between Direct and Indirect Striatal Output Pathways in Huntington's Disease.

J Huntingtons Dis 2012 ;1(1):17-25

Intellectual and Developmental Disabilities Research Center, Semel Institute for Neuroscience and Human Behavior and the Brain Research Institute, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA.

There is morphological evidence for differential alterations in striatal medium-sized spiny neurons (MSNs) giving rise to the direct and indirect output pathways in Huntington's disease (HD). MSNs of the indirect pathway appear to be particularly vulnerable and markers for these neurons are lost early in postmortem brains and in genetic mouse models. In contrast, MSNs of the direct pathway appear to be relatively spared in the early stages. Because of the great morphological and electrophysiological similarities between MSNs of these pathways, until recently it was difficult to tease apart their functional alterations in HD models. The recent use of the enhanced green fluorescent protein gene as a reporter to identify dopamine D1 (direct pathway) and D2 (indirect pathway) receptor-expressing MSNs has made it possible to examine synaptic function in each pathway. The outcomes of such studies demonstrate significant time-dependent changes in the balance of excitatory and inhibitory inputs to both direct and indirect pathway MSNs in HD and emphasize early increases in both excitatory and inhibitory inputs to direct pathway MSNs. There also is a strong influence of alterations in dopamine modulation that possibly cause some of the changes in excitatory and inhibitory synaptic transmission in the HD models. These changes will markedly alter the output structures, the GPi and the SNr. In the future, the use of combined optogenetics with identified neurons in each pathway will help unravel the next set of questions about how the output nuclei are affected in HD.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3233/JHD-2012-120009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4116084PMC
May 2016

A critical window of CAG repeat-length correlates with phenotype severity in the R6/2 mouse model of Huntington's disease.

J Neurophysiol 2012 Jan 9;107(2):677-91. Epub 2011 Nov 9.

Intellectual and Developmental Disabilities Research Center, Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles, California 90095, USA.

The R6/2 mouse is the most frequently used model for experimental and preclinical drug trials in Huntington's disease (HD). When the R6/2 mouse was first developed, it carried exon 1 of the huntingtin gene with ~150 cytosine-adenine-guanine (CAG) repeats. The model presented with a rapid and aggressive phenotype that shared many features with the human condition and was particularly similar to juvenile HD. However, instability in the CAG repeat length due to different breeding practices has led to both decreases and increases in average CAG repeat lengths among colonies. Given the inverse relationship in human HD between CAG repeat length and age at onset and to a degree, the direct relationship with severity of disease, we have investigated the effect of altered CAG repeat length. Four lines, carrying ~110, ~160, ~210, and ~310 CAG repeats, were examined using a battery of tests designed to assess the basic R6/2 phenotype. These included electrophysiological properties of striatal medium-sized spiny neurons, motor activity, inclusion formation, and protein expression. The results showed an unpredicted, inverted "U-shaped" relationship between CAG repeat length and phenotype; increasing the CAG repeat length from 110 to 160 exacerbated the R6/2 phenotype, whereas further increases to 210 and 310 CAG repeats greatly ameliorated the phenotype. These findings demonstrate that the expected relationship between CAG repeat length and disease severity observed in humans is lost in the R6/2 mouse model and highlight the importance of CAG repeat-length determination in preclinical drug trials that use this model.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/jn.00762.2011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3349621PMC
January 2012

Polycyclic aromatic hydrocarbons within airborne particulate matter (PM(2.5)) produced DNA bulky stable adducts in a human lung cell coculture model.

J Appl Toxicol 2013 Feb 13;33(2):109-19. Epub 2011 Sep 13.

Université Lille Nord de France, Lille, France.

To extend current knowledge on the underlying mechanisms of air pollution particulate matter (PM(2.5))-induced human lung toxicity, the metabolic activation of polycyclic aromatic hydrocarbons (PAH) within PM(2.5) and PAH-DNA bulky stable adduct patterns in human alveolar macrophage (AM) and/or human lung epithelial L132 cells in mono- and cocultures were studied. In the coculture system, only human AM were exposed to air pollution PM(2.5), unlike L132 cells. Particles, inorganic fraction and positive controls [i.e. TiO(2), thermally desorbed PM (dPM) and benzo[a]pyrene, B[a]P, respectively] were included in the experimental design. Cytochrome P450 (CYP) 1A1 gene expression, CYP1A1 catalytic activity and PAH-DNA bulky stable adducts were studied after 24, 48 and/or 72 h. Relatively low doses of PAH within PM(2.5) induced CYP1A1 gene expression and CYP1A1 catalytic activity in human AM and, thereafter, PAH-DNA bulky stable adduct formation. Adduct spots in PM(2.5) -exposed human AM were higher than those in dPM-exposed ones, thereby showing the incomplete removal of PAH by thermal desorption. PAH within air pollution PM(2.5) induced CYP1A1 gene expression but not CYP1A1 catalytic activity in L132 cells. However, despite the absence of PAH-DNA bulky stable adduct in L132 cells from human AM/L132 cell cocultures exposed to dPM(2.5) or PM(2.5), reliable quantifiable PAH-DNA bulky stable adducts were observed in L132 cells from human AM/L132 cell coculture exposed to B[a]P. Taken together, these results support the exertion of genotoxicity of highly reactive B[a]P-derived metabolites produced within human AM not only in primary target human AM, but also in secondary target L132 cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jat.1722DOI Listing
February 2013

Enhanced GABAergic network and receptor function in pediatric cortical dysplasia Type IIB compared with Tuberous Sclerosis Complex.

Neurobiol Dis 2012 Jan 23;45(1):310-21. Epub 2011 Aug 23.

Intellectual and Developmental Disabilities Research Center, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90024, USA.

Tuberous Sclerosis Complex (TSC) and cortical dysplasia Type IIB (CDIIB) share histopathologic features that suggest similar epileptogenic mechanisms. This study compared the morphological and electrophysiological properties of cortical cells in tissue from pediatric TSC (n=20) and CDIIB (n=20) patients using whole-cell patch clamp recordings and biocytin staining. Cell types were normal-appearing and dysmorphic-cytomegalic pyramidal neurons, interneurons, and giant/balloon cells, including intermediate neuronal-glial cells. In the cortical mantle, giant/balloon cells occurred more frequently in TSC than in CDIIB cases, whereas cytomegalic pyramidal neurons were found more frequently in CDIIB. Cell morphology and membrane properties were similar in TSC and CDIIB cases. Except for giant/balloon and intermediate cells, all neuronal cell types fired action potentials and displayed spontaneous postsynaptic currents. However, the frequency of spontaneous glutamatergic postsynaptic currents in normal pyramidal neurons and interneurons was significantly lower in CDIIB compared with TSC cases and the GABAergic activity was higher in all neuronal cell types in CDIIB. Further, acutely dissociated pyramidal neurons displayed higher sensitivity to exogenous application of GABA in CDIIB compared with TSC cases. These results indicate that, in spite of similar histopathologic features and basic cell membrane properties, TSC and CDIIB display differences in the topography of abnormal cells, excitatory and inhibitory synaptic network properties, and GABA(A) receptor sensitivity. These differences support the notion that the mechanisms of epileptogenesis could differ in patients with TSC and CDIIB. Consequently, pharmacologic therapies should take these findings into consideration.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.nbd.2011.08.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3225687PMC
January 2012

DNA adduct variations in non-smoking crop farmers: potential relationship with occupational exposure to pesticides?

Environ Toxicol Pharmacol 2011 Jul 18;32(1):1-9. Epub 2011 Jan 18.

Laboratoire Départemental Franck Duncombe (LDFD14), Conseil Général du Calvados, 1, route de Rosel, 14053, Caen Cedex 4, France.

Genotoxic impact of the occupational exposure was measured in farmers from Normandy, France. White blood cell DNA-adduct levels were measured for 116 non-smoking French crop farmers, using the (32)P-postlabelling method. A single blood sample was collected per farmer, at a randomised period of the year. Significantly higher bulky DNA-adduct levels were observed for samples collected from April to July, compared with samples collected during the other months. Agricultural practices were not significantly different between these two groups of farmers, but interestingly, the mean and the median duration without exposure to pesticides were significantly shorter for farmers sampled between April and July. These data, obtained in a homogeneous population of farmers, indicate a genotoxic impact for a sub-group, with a potential association with the use of pesticides. From the rest of the group, this study also gives for the first time additional information on the background fluctuations of this biomarker over the year.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.etap.2010.12.005DOI Listing
July 2011

Altered Balance of Activity in the Striatal Direct and Indirect Pathways in Mouse Models of Huntington's Disease.

Front Syst Neurosci 2011 16;5:46. Epub 2011 Jun 16.

Intellectual and Developmental Disabilities Research Center, Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, Semel Institute, University of California at Los Angeles Los Angeles, CA, USA.

Imbalance in the activity of striatal direct and indirect pathway neurons contributes to motor disturbances in several neurodegenerative diseases. In Huntington's disease (HD), indirect pathway [dopamine (DA) D2 receptor-expressing] medium-sized spiny neurons (MSNs) are believed to show earlier vulnerability than direct pathway MSNs. We examined synaptic activity and DA modulation in MSNs forming the direct and indirect pathways in YAC128 and BACHD mouse models of HD. To visualize the two types of MSNs, we used mice expressing enhanced green fluorescent protein under the control of the promoter for the DA D1 or D2 receptor. Experiments were performed in early symptomatic (1.5 months) and symptomatic (12 months) mice. Behaviorally, early symptomatic mice showed increased stereotypies while symptomatic mice showed decreased motor activity. Electrophysiologically, at the early stage, excitatory and inhibitory transmission onto D1-YAC128 and D1-BACHD MSNs were increased, while there was no change in D2 MSNs. DA modulation of spontaneous excitatory postsynaptic currents (sEPSCs) in slices was absent in YAC128 cells at the early stage, but was restored by treating the slices with the DA depleter tetrabenazine (TBZ). In BACHD mice TBZ restored paired-pulse ratios and a D1 receptor antagonist induced a larger decrease of sEPSCs than in D1-WT cells, suggesting increased DA tone. Finally, TBZ decreased stereotypies in BACHD mice. These results indicate that by reducing DA or antagonizing D1 receptors, increases in inhibitory and excitatory transmission in early phenotypic direct pathway neurons can be normalized. In symptomatic YAC128 mice, excitatory synaptic transmission onto D1 MSNs was decreased, while inhibitory transmission was increased in D2 MSNs. These studies provide evidence for differential and complex imbalances in glutamate and GABA transmission, as well as in DA modulation, in direct and indirect pathway MSNs during HD progression.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fnsys.2011.00046DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3118454PMC
July 2011

Dissecting the contribution of individual receptor subunits to the enhancement of N-methyl-d-aspartate currents by dopamine D1 receptor activation in striatum.

Front Syst Neurosci 2011 11;5:28. Epub 2011 May 11.

Intellectual and Developmental Disabilities Research Center, Semel Institute, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA.

Dopamine, via activation of D1 receptors, enhances N-methyl-d-aspartate (NMDA) receptor-mediated responses in striatal medium-sized spiny neurons. However, the role of specific NMDA receptor subunits in this enhancement remains unknown. Here we used genetic and pharmacological tools to dissect the contribution of NR1 and NR2A/B subunits to NMDA responses and their modulation by dopamine receptors. We demonstrate that D1 enhancement of NMDA responses does not occur or is significantly reduced in mice with genetic knock-down of NR1 subunits, indicating a critical role of these subunits. Interestingly, spontaneous and evoked α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid (AMPA) receptor-mediated responses were significantly enhanced in NR1 knock-down animals, probably as a compensatory mechanism for the marked reduction in NMDA receptor function. The NMDA receptor subunits NR2A and NR2B played differential roles in D1 modulation. Whereas genetic deletion or pharmacological blockade of NR2A subunits enhanced D1 potentiation of NMDA responses, blockade of NR2B subunits reduced this potentiation, suggesting that these regulatory subunits of the NMDA receptor counterbalance their respective functions. In addition, using D1 and D2 receptor EGFP-expressing mice, we demonstrate that NR2A subunits contribute more to NMDA responses in D1-MSSNs, whereas NR2B subunits contribute more to NMDA responses in D2 cells. The differential contribution of discrete receptor subunits to NMDA responses and dopamine modulation in the striatum has important implications for synaptic plasticity and selective neuronal vulnerability in disease states.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fnsys.2011.00028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3095815PMC
June 2011

Forebrain striatal-specific expression of mutant huntingtin protein in vivo induces cell-autonomous age-dependent alterations in sensitivity to excitotoxicity and mitochondrial function.

ASN Neuro 2011 Jun 7;3(3):e00060. Epub 2011 Jun 7.

Department of Neurology, Mount Sinai School of Medicine, New York, NY, U.S.A.

HD (Huntington's disease) is characterized by dysfunction and death of striatal MSNs (medium-sized spiny neurons). Excitotoxicity, transcriptional dysregulation and mitochondrial abnormalities are among the mechanisms that are proposed to play roles in HD pathogenesis. To determine the extent of cell-autonomous effects of mhtt (mutant huntingtin) protein on vulnerability to excitotoxic insult in MSNs in vivo, we measured the number of degenerating neurons in response to intrastriatal injection of QA (quinolinic acid) in presymptomatic and symptomatic transgenic (D9-N171-98Q, also known as DE5) mice that express mhtt in MSNs but not in cortex. After QA, the number of degenerating neurons in presymptomatic DE5 mice was not significantly different from the number in WT (wild-type) controls, suggesting the early, increased vulnerability to excitotoxicity demonstrated in other HD mouse models has a largely non-cell-autonomous component. Conversely, symptomatic DE5 mice showed significantly fewer degenerating neurons relative to WT, implying the resistance to excitotoxicity observed at later ages has a primarily cell-autonomous origin. Interestingly, mitochondrial complex II respiration was enhanced in striatum of symptomatic mice, whereas it was reduced in presymptomatic mice, both relative to their age-matched controls. Consistent with the QA data, MSNs from symptomatic mice showed decreased NMDA (N-methyl-d-aspartate) currents compared with age-matched controls, suggesting that in addition to aging, cell-autonomous mechanisms mitigate susceptibility to excitotoxicity in the symptomatic stage. Also, symptomatic DE5 mice did not display some of the electrophysiological alterations present in other HD models, suggesting that blocking the expression of mhtt in cortical neurons may restore corticostriatal function in HD.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1042/AN20110009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3155197PMC
June 2011

Differential electrophysiological changes in striatal output neurons in Huntington's disease.

J Neurosci 2011 Jan;31(4):1170-82

Department of Psychiatry and Biobehavioral Sciences, University of California, LA, CA 90095, USA.

There is considerable evidence that alterations in striatal medium-sized spiny neurons (MSSNs) giving rise to the direct (D1 receptor-expressing) and indirect (D2 receptor-expressing) pathways differentially contribute to the phenotype of Huntington's disease (HD). To determine how each subpopulation of MSSN is functionally affected, we examined spontaneous excitatory postsynaptic currents (sEPSCs) and dopamine (DA) modulation in two HD mouse models, the YAC128 and the BACHD (a bacterial-artificial chromosome). These mice also expressed enhanced green fluorescent protein (EGFP) under the control of the promoter for either DA D1 or D2 receptors to identify neurons. In early symptomatic YAC128 and BACHD mice, glutamate transmission was increased in both D1 and D2 MSSNs, but in different ways. D1 cells displayed increased sEPSC frequencies and decreased paired-pulse ratios (PPRs) while D2 cells displayed larger evoked glutamate currents but no change in sEPSC frequencies or PPRs. D1 receptor modulation of sEPSCs was absent in D1-YAC128 cells at the early symptomatic stage but was restored by treating the slices with tetrabenazine. In contrast, in fully symptomatic YAC128 mice, glutamate transmission was decreased specifically in D1 cells, and D1 receptor modulation was normal in D1-YAC128 cells. Behaviorally, early symptomatic mice showed increased stereotypies that were decreased by tetrabenazine treatment. Together, these studies support differential imbalances in glutamate and DA transmission in direct and indirect pathway MSSNs. Stereotypic behavior at an early stage could be explained by increased glutamate activity and DA tone in direct pathway neurons, whereas hypokinesia at later stages could result from reduced input onto these neurons.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1523/JNEUROSCI.3539-10.2011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3071260PMC
January 2011

Interneurons, GABAA currents, and subunit composition of the GABAA receptor in type I and type II cortical dysplasia.

Epilepsia 2010 Jul;51 Suppl 3:166-70

Intellectual and Developmental Disabilities Research Center, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California 90095, USA.

Interneurons, gamma-aminobutyric acid (GABA)(A) receptor density, and subunit composition determine inhibitory function in pyramidal neurons and control excitability in cortex. Abnormalities in GABAergic cells or GABA(A) receptors could contribute to seizures in malformations of cortical development. Herein we review data obtained in resected cortex from pediatric epilepsy surgery patients with type I and type II cortical dysplasia (CD) and non-CD pathologies. Our studies found fewer interneurons immunolabeled for glutamic acid decarboxylase (GAD) in type II CD, whereas there were no changes in tissue from type I CD. GAD-labeled neurons had larger somata, and GABA transporter (VGAT and GAT1) staining showed a dense plexus surrounding cytomegalic neurons in type II CD. Functionally, neurons from type I CD tissue showed GABA currents with increased half maximal effective concentration compared to cells from the other groups. In type II CD, cytomegalic pyramidal neurons showed alterations in GABA currents, decreased sensitivity to zolpidem and zinc, and increased sensitivity to bretazenil. In addition, pyramidal neurons from type II CD displayed higher frequency of spontaneous inhibitory post synaptic currents. The GABAergic system is therefore, altered differently in cortex from type I and type II CD patients. Alterations in zolpidem, zinc, and bretazenil sensitivity and spontaneous inhibitory postsynaptic currents (IPSCs) suggest that type II CD neurons have altered GABA(A) receptor subunit composition and receive dense GABA inputs. These findings support the hypothesis that patients with type I and type II CD will respond differently to GABA receptor-mediated antiepileptic drugs and that cytomegalic neurons have features similar to immature neurons.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1528-1167.2010.02634.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2909022PMC
July 2010