scholarly journals Astrocytic Connexin43 Channels as Candidate Targets in Epilepsy Treatment

Biomolecules ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1578 ◽  
Author(s):  
Laura Walrave ◽  
Mathieu Vinken ◽  
Luc Leybaert ◽  
Ilse Smolders
Keyword(s):  
Transmembrane Protein ◽  
Epileptiform Activity ◽  
Brain Slices ◽  
High Energy ◽  
Experimental Models ◽  
Functional Coupling ◽  
Seizure Outcome ◽  
Mrna Levels

In epilepsy research, emphasis is put on exploring non-neuronal targets such as astrocytic proteins, since many patients remain pharmacoresistant to current treatments, which almost all target neuronal mechanisms. This paper reviews available data on astrocytic connexin43 (Cx43) signaling in seizures and epilepsy. Cx43 is a widely expressed transmembrane protein and the constituent of gap junctions (GJs) and hemichannels (HCs), allowing intercellular and extracellular communication, respectively. A plethora of research papers show altered Cx43 mRNA levels, protein expression, phosphorylation state, distribution and/or functional coupling in human epileptic tissue and experimental models. Human Cx43 mutations are linked to seizures as well, as 30% of patients with oculodentodigital dysplasia (ODDD), a rare genetic condition caused by mutations in the GJA1 gene coding for Cx43 protein, exhibit neurological symptoms including seizures. Cx30/Cx43 double knock-out mice show increased susceptibility to evoked epileptiform events in brain slices due to impaired GJ-mediated redistribution of K+ and glutamate and display a higher frequency of spontaneous generalized chronic seizures in an epilepsy model. Contradictory, Cx30/Cx43 GJs can traffic nutrients to high-energy demanding neurons and initiate astrocytic Ca2+ waves and hyper synchronization, thereby supporting proconvulsant effects. The general connexin channel blocker carbenoxolone and blockers from the fenamate family diminish epileptiform activity in vitro and improve seizure outcome in vivo. In addition, interventions with more selective peptide inhibitors of HCs display anticonvulsant actions. To conclude, further studies aiming to disentangle distinct roles of HCs and GJs are necessary and tools specifically targeting Cx43 HCs may facilitate the search for novel epilepsy treatments.

scholarly journals Epileptiform Discharges With In-Vivo-Like Features in Slices of Rat Piriform Cortex With Longitudinal Association Fibers

2001 ◽  
Vol 86 (5) ◽  
pp. 2445-2460 ◽  
Author(s):  
Rezan Demir ◽  
Lewis B. Haberly ◽  
Meyer B. Jackson
Keyword(s):  
Seizure Activity ◽  
Epileptiform Activity ◽  
Piriform Cortex ◽  
Brain Slices ◽  
Epileptiform Discharges ◽  
Local Circuitry ◽  
Association Fibers ◽  
Discharge Propagation

Brain slices serve as useful models for the investigation of epilepsy. However, the preparation of brain slices disrupts circuitry and severs axons, thus complicating efforts to relate epileptiform activity in vitro to seizure activity in vivo. This issue is relevant to studies in transverse slices of the piriform cortex (PC), the preparation of which disrupts extensive rostrocaudal fiber systems. In these slices, epileptiform discharges propagate slowly and in a wavelike manner, whereas such discharges in vivo propagate more rapidly and jump abruptly between layers. The objective of the present study was to identify fiber systems responsible for these differences. PC slices were prepared by cutting along three different nearly orthogonal planes (transverse, parasagittal, and longitudinal), and epileptiform discharges were imaged with a voltage-sensitive fluorescent dye. Interictal-like epileptiform activity was enabled by either a kindling-like induction process or disinhibition with bicuculline. The pattern of discharge onset was very similar in slices cut in different planes. As described previously in transverse PC slices, discharges were initiated in the endopiriform nucleus (En) and adjoining regions in a two-stage process, starting with low-amplitude “plateau activity” at one site and leading to an accelerating depolarization and discharge onset at another nearby site. The similar pattern of onset in slices of various orientations indicates that the local circuitry and neuronal properties in and around the En, rather than long-range fibers, assume dominant roles in the initiation of epileptiform activity. Subtle variations in the onset site indicate that interneurons can fine tune the site of discharge onset. In contrast to the mode of onset, discharge propagation showed striking variations. In longitudinal slices, where rostrocaudal association fibers are best preserved, discharge propagation resembled in vivo seizure activity in the following respects: propagation was as rapid as in vivo and about two to three times faster than in other slices; discharges jumped abruptly between the En and PC; and discharges had large amplitudes in superficial layers of the PC. Cuts in longitudinal slices that partially separated the PC from the En eliminated these unique features. These results help clarify why epileptiform activity differs between in vitro and in vivo experiments and suggest that rostrocaudal pyramidal cell association fibers play a major role in the propagation of discharges in the intact brain. The longitudinal PC slice, which best preserves these fibers, is ideally suited for the study their role.

Silencing of sodium/hydrogen exchanger in the heart by direct injection of naked siRNA

2011 ◽  
Vol 111 (2) ◽  
pp. 566-572 ◽  
Author(s):  
Patricio E. Morgan ◽  
María V. Correa ◽  
Irene L. Ennis ◽  
Ariel A. Diez ◽  
Néstor G. Pérez ◽  
...  
Keyword(s):  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Direct Injection ◽  
Experimental Models ◽  
Left Ventricular ◽  
Maximal Velocity ◽  
Mrna Levels ◽  
Small Interference Rna

Cardiac Na+/H+ exchanger (NHE1) hyperactivity is a central factor in cardiac remodeling following hypertension, myocardial infarction, ischemia-reperfusion injury, and heart failure. Treatment of these pathologies by inhibiting NHE1 is challenging because specific drugs that have been beneficial in experimental models were associated with undesired side effects in clinical practice. In the present work, small interference RNA (siRNA) produced in vitro to specifically silence NHE1 (siRNANHE1) was injected once in vivo into the apex of the left ventricular wall of mouse myocardium. After 48 h, left ventricular NHE1 protein expression was reduced in siRNANHE1-injected mice compared with scrambled siRNA by 33.2 ± 3.4% ( n = 5; P < 0.05). Similarly, NHE1 mRNA levels were reduced by 20 ± 2.0% ( n = 4). At 72 h, siRNANHE1 spreading was evident from the decrease in NHE1 expression in three portions of the myocardium (apex, medium, base). NHE1 function was assessed based on maximal velocity of intracellular pH (pHi) recovery (dpHi/d t) after an ammonium prepulse-induced acidic load. Maximal dpHi/d t was reduced to 14% in siRNANHE1-isolated left ventricular papillary muscles compared with scrambled siRNA. In conclusion, only one injection of naked siRNANHE1 successfully reduced NHE1 expression and activity in the left ventricle. As has been previously suggested, extensive NHE1 expression reduction may indicate myocardial spread of siRNA molecules from the injection site through gap junctions, providing a valid technique not only for further research into NHE1 function, but also for consideration as a potential therapeutic strategy.

scholarly journals Characterizing concentration-dependent neural dynamics of 4-aminopyridine-induced epileptiform activity

2018 ◽  
Author(s):  
Timothy L Myers ◽  
Oscar C González ◽  
Jacob B Stein ◽  
Maxim Bazhenov
Keyword(s):  
Epileptiform Activity ◽  
Brain Slices ◽  
Population Level ◽  
Frequency Component ◽  
Pharmacological Agents ◽  
Spatio Temporal ◽  
Dose Dependent ◽  
Array Recordings

AbstractEpilepsy remains one of the most common neurological disorders. In patients, it is characterized by unprovoked, spontaneous, and recurring seizures or ictal events. Typically, inter-ictal events or large bouts of population level activity can be measured between seizures and are generally asymptomatic. Decades of research has focused on understanding the mechanisms leading to the development of seizure-like activity using various proconvulsive pharmacological agents, including 4-aimnopyridine (4AP). However, the lack of consistency in the concentrations used for studying 4AP-induced epileptiform activity in animal models may give rise to differences in the results and interpretation thereof. Indeed, the range of 4AP concentration in both in vivo and in vitro studies varies from 3μM to 40mM. Here, we explored the effects of various 4AP concentrations on the development and characteristics of hippocampal epileptiform activity in acute mouse brain slices of either sex. Using multielectrode array recordings, we show that 4AP induces hippocampal epileptiform activity for broad range of concentrations. The frequency component and the spatio-temporal patterns of the epileptiform activity revealed a dose-dependent response. Finally, in the presence of 4AP, reduction of KCC2 co-transporter activity by KCC2 antagonist VU0240551 prevented the manifestation of the frequency component differences between different concentrations of 4AP. Overall, the study predicts that different concentrations of 4AP can result in the different mechanisms behind hippocampal epileptiform activity, of which some are dependent on the KCC2 co-transporter function.

scholarly journals Chemicogenetic recruitment of specific interneurons suppresses seizure activity

2018 ◽  
Author(s):  
Alexandru Călin ◽  
Mihai Stancu ◽  
Ana-Maria Zagrean ◽  
John G. Jefferys ◽  
Andrei S. Ilie ◽  
...  
Keyword(s):  
Mouse Model ◽  
Seizure Activity ◽  
Epileptiform Activity ◽  
Experimental Models ◽  
Inhibitory Neurons ◽  
Synaptic Inhibition ◽  
Inhibitory Mechanisms ◽  
Hippocampal Seizures

AbstractEnhancing the brain’s endogenous inhibitory mechanisms represents an important strategy for suppressing epileptic discharges. Indeed, drugs that boost synaptic inhibition can disrupt epileptic seizure activity, although these drugs generate complex effects due to the broad nature of their action. Recently developed chemicogenetic techniques provide the opportunity to pharmacologically enhance endogenous inhibitory mechanisms in a more selective manner. Here we use chemicogenetics to assess the anti-epileptic potential of enhancing the synaptic output from three major interneuron populations in the hippocampus: parvalbumin (PV), somatostatin (SST) and vasoactive intestinal peptide (VIP) expressing interneurons. Targeted pre- and post-synaptic whole cell recordings in an in vitro hippocampal mouse model revealed that all three interneuron types increase their firing rate and synaptic output following chemicogenetic activation. However, the interneuron populations exhibited different anti-epileptic effects. Recruiting VIP interneurons resulted in a mixture of pro-epileptic and anti-epileptic effects. In contrast, recruiting SST or PV interneurons produced robust suppression of epileptiform activity. PV interneurons exhibited the strongest effect per cell, eliciting at least a five-fold greater reduction in epileptiform activity than the other cell types. Consistent with this, we found that chemicogenetic recruitment of PV interneurons was effective in an in vivo mouse model of hippocampal seizures. Following efficient delivery of the chemicogenetic tool, pharmacological enhancement of the PV interneuron population suppressed a range of seizure-related behaviours and prevented generalized seizures. Our findings therefore support the idea that selective chemicogenetic enhancement of synaptic inhibitory pathways offers potential as an anti-epileptic strategy.Significance statementDrugs that enhance synaptic inhibition can be effective anticonvulsants but often cause complex effects due to their widespread action. Here we examined the anti-epileptic potential of recently developed chemicogenetic techniques, which offer a way to selectively enhance the synaptic output of distinct types of inhibitory neurons. A combination of in vitro and in vivo experimental models were used to investigate seizure activity in the mouse hippocampus. We find that chemicogenetically recruiting the parvalbumin-expressing population of inhibitory neurons produces the strongest anti-epileptic effect per cell, and that recruiting this cell population can suppress a range of epileptic behaviours in vivo. The data therefore support the idea that targeted chemicogenetic enhancement of synaptic inhibition offers promise for developing new treatments.

Low-Calcium Epileptiform Activity in the Hippocampus In Vivo

2003 ◽  
Vol 90 (4) ◽  
pp. 2253-2260 ◽  
Author(s):  
Zhouyan Feng ◽  
Dominique M. Durand
Keyword(s):  
Synaptic Transmission ◽  
Epileptiform Activity ◽  
Brain Slices ◽  
Early Period ◽  
Epileptic Activity ◽  
Slow Waves ◽  
Stratum Radiatum ◽  
Low Calcium

It has been clearly established that nonsynaptic interactions are sufficient for generating epileptiform activity in brain slices. However, it is not known whether this type of epilepsy model can be generated in vivo. In this paper we investigate low-calcium nonsynaptic epileptiform activity in an intact hippocampus. The calcium chelator EGTA was used to lower [Ca2+]o in the hippocampus of urethane anesthetized rats. Spontaneous and evoked field potentials in CA1 pyramidal stratum and in CA1 stratum radiatum were recorded using four-channel silicon recording probes. Three different types of epileptic activity were observed while synaptic transmission was gradually blocked by a decline in hippocampal [Ca2+]o. A short latency burst, named early-burst, occurred during the early period of EGTA application. Periodic slow-waves and a long latency high-frequency burst, named late-burst, were seen after synaptic transmission was mostly blocked. Therefore these activities appear to be associated with nonsynaptic mechanisms. Moreover, the slow-waves were similar in appearance to the depolarization potential shifts in vitro with low calcium. In addition, excitatory postsynaptic amino acid antagonists could not eliminate the development of slow-waves and late-bursts. The slow-waves and late-bursts were morphologically similar to electrographic seizure activity seen in patients with temporal lobe epilepsy. These results clearly show that epileptic activity can be generated in vivo in the absence of synaptic transmission. This type of low-calcium nonsynaptic epilepsy model in an intact hippocampus could play an important role in revealing additional mechanisms of epilepsy disorders and in developing novel anti-convulsant drugs.

Layer I Ectopias and Increased Excitability in Murine Neocortex

2002 ◽  
Vol 87 (5) ◽  
pp. 2471-2479 ◽  
Author(s):  
Lisa A. Gabel ◽  
Joseph J. LoTurco
Keyword(s):  
Animal Models ◽  
Cognitive Impairments ◽  
Epileptiform Activity ◽  
Brain Slices ◽  
Inbred Lines ◽  
Seizure Susceptibility ◽  
Cortical Dysplasias ◽  
Layer I

Cortical dysplasias are associated with both epilepsy and cognitive impairments in humans. Similarly, several animal models of cortical dysplasia show that dysplasia causes increased seizure susceptibility and behavioral deficits in vivo and increased levels of excitability in vitro. As most current animal models involve either global disruptions in cortical architecture or the induction of lesions, it is not yet clear whether small spontaneous neocortical malformations are also associated with increased excitability or seizure susceptibility. Small groups of displaced neurons in layer I of the neocortex, ectopias, have been identified in patients with cognitive impairments, and similar malformations occur sporadically in some inbred lines of mice where they are associated with behavioral and sensory-processing deficits. In a previous study, we characterized the physiology of cells within neocortical ectopias, in one of the inbred lines (NXSM-D/Ei) and showed that the presence of multiple ectopias is associated with the generation of spontaneous epileptiform activity in slices. In this study, we use extracellular recordings from brain slices to show that even single-layer I ectopias are associated with higher excitability. Specifically, slices that contain single ectopias display epileptiform activity at significantly lower concentrations of the GABAA receptor antagonist bicuculline than do slices without ectopias (either from opposite hemispheres or animals without ectopias). Moreover, because removal of ectopias from slices does not restore normal excitability, enhanced excitability is not generated within the ectopia. Finally, we show that in vivo, mice with ectopias are more sensitive to the convulsant pentylenetetrazole than are mice without ectopias. Together these results suggest that alterations in cortical hemispheres containing focal layer I malformations increase cortical excitability and that even moderately small spontaneous cortical dysplasias are associated with increased excitability in vitro and in vivo.

scholarly journals Delayed Puberty in Spontaneously Hypertensive Rats Involves a Primary Ovarian Failure Independent of the Hypothalamic KiSS-1/GPR54/GnRH System

Endocrinology ◽  
2009 ◽  
Vol 150 (6) ◽  
pp. 2889-2897 ◽  
Author(s):  
L. Pinilla ◽  
J. M. Castellano ◽  
M. Romero ◽  
M. Tena-Sempere ◽  
F. Gaytán ◽  
...  
Keyword(s):  
Ovarian Function ◽  
Follicular Development ◽  
Experimental Models ◽  
Gnrh Receptor ◽  
Delayed Puberty ◽  
Mrna Levels ◽  
Spontaneously Hypertensive ◽  
And Function

Spontaneously hypertensive (SH) rats, extensively used as experimental models of essential human hypertension, display important alterations in the neuroendocrine reproductive axis, which manifest as markedly delayed puberty onset in females but whose basis remains largely unknown. We analyze herein in female SH rats: 1) possible alterations in the expression and function of KiSS-1/GPR54 and GnRH/GnRH-receptor systems, 2) the integrity of feedback mechanisms governing the hypothalamic-pituitary-ovarian axis, and 3) the control of ovarian function by gonadotropins. Our data demonstrate that, despite overtly delayed puberty, no significant decrease in hypothalamic KiSS-1, GPR54, or GnRH mRNA levels was detected in this strain. Likewise, in vivo gonadotropin responses to ovariectomy and systemic kisspeptin-10 or GnRH administration, as well as in vitro gonadotropin responses to GnRH, were fully preserved in SH rats. Moreover, circulating LH levels were grossly conserved during prepubertal maturation, whereas FSH levels were even enhanced from d 20 postpartum onwards. In striking contrast, ovarian weight and hormone (progesterone and testosterone) responses to human chorionic gonadotropin (CG) in vitro were profoundly decreased in SH rats, with impaired follicular development and delayed ovulation at puberty. Such reduced hormonal responses to human CG could not be attributed to changes in LH/CG or FSH-receptor mRNA expression but might be linked to blunted P450scc, 3β-hydroxy steroid dehydrogenase, and aromatase mRNA levels in ovaries from SH rats. In conclusion, our results indicate that the expression and function of KiSS-1/GPR54 and GnRH/GnRH-receptor systems is normal in SH rats, whereas ovarian development, steroidogenesis, and responsiveness to gonadotropins are strongly compromised.

scholarly journals Resistin Regulates Pituitary Lipid Metabolism and InflammationIn VivoandIn Vitro

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
F. Rodriguez-Pacheco ◽  
M. G. Novelle ◽  
M. J. Vazquez ◽  
E. Garcia-Escobar ◽  
F. Soriguer ◽  
...  
Keyword(s):  
Lipid Metabolism ◽  
Pituitary Gland ◽  
Primary Source ◽  
Chronic Administration ◽  
Metabolic Enzymes ◽  
Experimental Models ◽  
Regulatory Role ◽  
Mrna Levels

The adipokine resistin is an insulin-antagonizing factor that also plays a regulatory role in inflammation, immunity, food intake, and gonadal function and also regulates growth hormone (GH) secretion in rat adenopituitary cells cultures with the adipokine. Although adipose tissue is the primary source of resistin, it is also expressed in other tissues, including the pituitary. The aim of this study is to investigate the possible action of resistin on the lipid metabolism in the pituitary glandin vivo(rats in two different nutritional status, fed and fast, treated with resistin on acute and a chronic way) andin vitro(adenopituitary cell cultures treated with the adipokine). Here, by a combination ofin vivoandin vitroexperimental models, we demonstrated that central acute and chronic administration of resistin enhance mRNA levels of the lipid metabolic enzymes which participated on lipolysis and moreover inhibiting mRNA levels of the lipid metabolic enzymes involved in lipogenesis. Taken together, our results demonstrate for the first time that resistin has a regulatory role on lipid metabolism in the pituitary gland providing a novel insight in relation to the mechanism by which this adipokine can participate in the integrated control of lipid metabolism.

Neutralization of a Low Molecular Weight Heparin (LHN-1) and Conventional Heparin by Protamine Sulfate in Rats

1986 ◽  
Vol 56 (03) ◽  
pp. 318-322 ◽  
Author(s):  
V Diness ◽  
P B Østergaard
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Thrombus Formation ◽  
Experimental Models ◽  
Protamine Sulfate ◽  
Low Molecular Weight ◽  
Antithrombotic Effect ◽  
Higher Doses

SummaryThe neutralization of a low molecular weight heparin (LHN-1) and conventional heparin (CH) by protamine sulfate has been studied in vitro and in vivo. In vitro, the APTT activity of CH was completely neutralized in parallel with the anti-Xa activity. The APTT activity of LHN-1 was almost completely neutralized in a way similar to the APTT activity of CH, whereas the anti-Xa activity of LHN-1 was only partially neutralized.In vivo, CH 3 mg/kg and LHN-1 7.2 mg/kg was given intravenously in rats. The APTT and anti-Xa activities, after neutralization by protamine sulfate in vivo, were similar to the results in vitro. In CH treated rats no haemorrhagic effect in the rat tail bleeding test and no antithrombotic effect in the rat stasis model was found at a protamine sulfate to heparin ratio of about 1, which neutralized APTT and anti-Xa activities. In LHN-1 treated rats the haemorrhagic effect was neutralized when APTT was close to normal whereas higher doses of protamine sulfate were required for neutralization of the antithrombotic effect. This probably reflects the fact that in most experimental models higher doses of heparin are needed to induce bleeding than to prevent thrombus formation. Our results demonstrate that even if complete neutralization of APTT and anti-Xa activities were not seen in LHN-1 treated rats, the in vivo effects of LHN-1 could be neutralized as efficiently as those of conventional heparin. The large fall in blood pressure caused by high doses of protamine sulfate alone was prevented by the prior injection of LHN-1.

Antimicrobial peptides for the treatment of pulmonary tuberculosis, allies or foes?

2018 ◽  
Vol 24 (10) ◽  
pp. 1138-1147
Author(s):  
Bruno Rivas-Santiago ◽  
Flor Torres-Juarez
Keyword(s):  
Pulmonary Tuberculosis ◽  
Antimicrobial Peptides ◽  
Experimental Models ◽  
New Drugs ◽  
World Health ◽  
Public Health Issue ◽  
Health Organization ◽  
Drug Resistant Strains

Tuberculosis is an ancient disease that has become a serious public health issue in recent years, although increasing incidence has been controlled, deaths caused by Mycobacterium tuberculosis have been accentuated due to the emerging of multi-drug resistant strains and the comorbidity with diabetes mellitus and HIV. This situation is threatening the goals of World Health Organization (WHO) to eradicate tuberculosis in 2035. WHO has called for the creation of new drugs as an alternative for the treatment of pulmonary tuberculosis, among the plausible molecules that can be used are the Antimicrobial Peptides (AMPs). These peptides have demonstrated remarkable efficacy to kill mycobacteria in vitro and in vivo in experimental models, nevertheless, these peptides not only have antimicrobial activity but also have a wide variety of functions such as angiogenesis, wound healing, immunomodulation and other well-described roles into the human physiology. Therapeutic strategies for tuberculosis using AMPs must be well thought prior to their clinical use; evaluating comorbidities, family history and risk factors to other diseases, since the wide function of AMPs, they could lead to collateral undesirable effects.

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