KCC2 overexpression prevents the paradoxical seizure-promoting action of somatic inhibition

Magloire, Vincent; Cornford, Jonathan; Lieb, Andreas; Kullmann, Dimitri M.; Pavlov, Ivan

doi:10.1101/279539

Cited by 27 publications

(51 citation statements)

References 57 publications

(59 reference statements)

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“…However, due to the transient and widespread collapse of the postsynaptic Clgradient in pyramidal neurons, GABAergic interneurons are ineffective at curtailing epileptiform discharges, and in fact drive the generation of these events during SE-like activity. Our data complements recent in vitro and in vivo results, which suggest that various GABAergic interneuronal subtypes may promote the extension of seizures when activated once epileptiform activity has become established (Ellender et al, 2014;Sato et al, 2017;Magloire et al, 2018).…”

Section: Discussionsupporting

confidence: 88%

“…Furthermore, significant Claccumulation and a temporary excitatory shift in GABAergic signalling has been shown to accompany single seizure-like events in both in vitro (Lamsa and Kaila, 1997;Isomura et al, 2003;Fujiwara-Tsukamoto et al, 2010;Ilie et al, 2012;Ellender et al, 2014) and in vivo (Sato et al, 2017) models. The breakdown of the Clgradient serves to explain the surprising excitatory effects of GABAergic interneuronal subtypes recently observed during in vitro and in vivo seizure events (Ellender et al, 2014;Khoshkhoo et al, 2017;Magloire et al, 2018). This suggests that in circuits where seizures have caused sufficient Clloading, GABAAR mediated synaptic signalling can serve to exacerbate rather than control hyperexcitablity, which has direct relevance for the inhibitory efficacy of benzodiazepines.…”

Section: Introductionmentioning

confidence: 98%

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Excitatory GABAergic signalling is associated with acquired benzodiazepine resistance in status epilepticus

Burman

Călin

Codadu

et al. 2018

Preprint

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Status epilepticus (SE) is defined as a state of unrelenting seizure activity. It is associated with a rapidly rising mortality rate, and thus constitutes a medical emergency. Benzodiazepines, which act as positive modulators of chloride (Cl -) permeable GABAA receptors, are indicated as the first line of treatment, but this is ineffective in many cases. We found that 48% of children presenting with SE were unresponsive to benzodiazepine treatment, and critically, that the duration of SE at the time of treatment is an important predictor of non-responsiveness. We therefore investigated the cellular mechanisms that underlie acquired benzodiazepine resistance, using rodent organotypic brain slices. Removing Mg 2+ ions leads to an evolving pattern of epileptiform activity, and eventually to a persistent state of repetitive discharges that strongly resembles clinical EEG recordings of SE. We show that the persistent SE-like activity is associated with a reduction in GABAA receptor conductance and Clextrusion capability. We explored the effect on intraneuronal Clusing both gramicidin, perforated-patch clamp recordings and Climaging. This showed that during SE-like activity, reduced Clextrusion capacity was further exacerbated by activity-dependent Clloading, resulting in a persistently high intraneuronal Cl -. Consistent with these results, we found that optogenetic stimulation of GABAergic interneurons in the SE-like state, actually enhanced epileptiform activity in a GABAAR dependent manner. Together our findings describe a novel potential mechanism underlying benzodiazepine-resistant SE, with relevance to how this life-threatening condition should be managed in the clinic.

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Section: Discussionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 98%

Excitatory GABAergic signalling is associated with acquired benzodiazepine resistance in status epilepticus

Burman

Călin

Codadu

et al. 2018

Preprint

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“…CI, confidence interval. activation to an excitatory one (Magloire et al, 2019), consistent with the previous demonstration in organotypic cultures (Ellender et al, 2014). They further showed that this GABAergic switch could be prevented by over-expressing KCC2 artificially (introduced by viral vectors), providing strong support for the hypothesized role of short-term ionic plasticity in ictogenesis (Magloire et al, 2019).…”

Section: Discussionsupporting

confidence: 86%

Divergent paths to seizure‐like events

et al. 2019

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Much debate exists about how the brain transitions into an epileptic seizure. One source of confusion is that there are likely to be critical differences between experimental seizure models. To address this, we have compared the evolving activity patterns in two widely used in vitro models of epileptic discharges. Brain slices from young adult mice were prepared in the same way and bathed either in 0 Mg2+ or 100 µmol/L 4AP artificial cerebrospinal fluid. We have found that while local field potential recordings of epileptiform discharges in the two models appear broadly similar, patch‐clamp analysis reveals an important difference in the relative degree of glutamatergic involvement. 4AP affects parvalbumin‐expressing interneurons more than other cortical populations, destabilizing their resting state and inducing spontaneous bursting behavior. Consequently, the most prominent pattern of transient discharge (“interictal event”) in this model is almost purely GABAergic, although the transition to seizure‐like events (SLEs) involves pyramidal recruitment. In contrast, interictal discharges in 0 Mg2+ are only maintained by a very large glutamatergic component that also involves transient discharges of the interneurons. Seizure‐like events in 0 Mg2+ have significantly higher power in the high gamma frequency band (60–120Hz) than these events do in 4AP, and are greatly delayed in onset by diazepam, unlike 4AP events. We, therefore, conclude that the 0 Mg2+ and 4AP models display fundamentally different levels of glutamatergic drive, demonstrating how ostensibly similar pathological discharges can arise from different sources. We contend that similar interpretative issues will also be relevant to clinical practice.

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“…A cannula (Bilaney Consultants Ltd., UK) was implanted in the same location as the recording electrode for sequential pilocarpine injections. Animals were allowed to recover for 2 weeks before induction of acute seizures by pilocarpine (3.5M in saline) (Magloire et al, 2019) injected 0.5mm below the cannula using a microinjection pump (WPI Ltd., USA), a 5 µl…”

Section: Rnamentioning

confidence: 99%

“…We complemented the chronic epilepsy study by looking at the effect of Kcna1-dCas9A treatment on acute seizures evoked by a different mechanism, focal pilocarpine injection in the visual cortex before and after doxycycline administration (Lieb et al, 2018;Magloire et al, 2019). We did not observe robust differences in EEG coastline and power in different frequency bands recorded for 1 hour after pilocarpine in either group, although there was a non-significant trend for Kcna1-dCas9 animals to show an attenuation in seizure severity ( Supplementary Figure 8).…”

Section: Kcna1-dcas9a Decreases Seizure Frequency In a Mouse Model Ofmentioning

confidence: 99%

In vivo CRISPRa decreases seizures and rescues cognitive deficits in a rodent model of epilepsy

Colasante

Qiu

Massimino

et al. 2018

Preprint

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Epilepsy is a major health burden, calling for new mechanistic and therapeutic insights.CRISPR-mediated gene editing shows promise to cure genetic pathologies, although hitherto it has mostly been applied ex-vivo. Its translational potential for treating non-genetic pathologies is still unexplored. Furthermore, neurological diseases represent an important challenge for the application of CRISPR, because of the need in many cases to manipulate gene function of neurons in situ. A variant of CRISPR, CRISPRa, offers the possibility to modulate the expression of endogenous genes by directly targeting their promoters. We asked if this strategy can effectively treat acquired focal epilepsy, focusing on ion channels because their manipulation is known be effective in changing network hyperactivity and hypersynchronisation. We applied a doxycycline-inducible CRISPRa technology to increase the expression of the potassium channel gene Kcna1 (encoding Kv1.1) in mouse hippocampal excitatory neurons. CRISPRa-mediated Kv1.1 upregulation led to a substantial decrease in neuronal excitability. Continuous video-EEG telemetry showed that AAV9-mediated delivery of CRISPRa, upon doxycycline administration, decreased spontaneous generalized tonicclonic seizures in a model of temporal lobe epilepsy, and rescued cognitive impairment and transcriptomic alterations associated with chronic epilepsy. The focal treatment minimizes concerns about off-target effects in other organs and brain areas. This study provides the proof of principle for a translational CRISPR-based approach to treat neurological diseases characterized by abnormal circuit excitability.

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KCC2 overexpression prevents the paradoxical seizure-promoting action of somatic inhibition

Cited by 27 publications

References 57 publications

Excitatory GABAergic signalling is associated with acquired benzodiazepine resistance in status epilepticus

Excitatory GABAergic signalling is associated with acquired benzodiazepine resistance in status epilepticus

Divergent paths to seizure‐like events

In vivo CRISPRa decreases seizures and rescues cognitive deficits in a rodent model of epilepsy

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