Optogenetic stimulation suppresses ictal activity in a 4-aminopyridine model of epileptic activity in vitro
- Authors: Zaitsev A.V.1, Proskurina E.Y.1, Trofimova A.M.1, Postnikova T.Y.1, Ergina Y.L.1, Amahin D.V.1, Kim K.K.1, Tiselko V.S.1, Chizhov A.V.1
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Affiliations:
- Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences
- Issue: Vol 18, No 4 (2023)
- Pages: 786-788
- Section: Conference proceedings
- URL: https://genescells.ru/2313-1829/article/view/623343
- DOI: https://doi.org/10.17816/gc623343
- ID: 623343
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Abstract
The WHO estimates that nearly 1% of the population suffers from epilepsy. Despite advances in the development of new antiepileptic drugs, seizures cannot be completely eliminated in nearly one-third of patients.
One promising approach to the treatment of epilepsy may be gene therapy. Because epileptic activity is caused by an imbalance between excitation and inhibition, researchers have focused primarily on regulating neuronal excitability. Initially, the main approaches were based on the hyperexpression of inhibitory peptides such as galanin or NPY, or the suppression of neuronal excitability by the hyperexpression of potassium channels in neurons. However, these effects should be well calculated and strictly dosed, as it is difficult to correct the expression later. If the expression is too low, the anticonvulsant effect will not be achieved, and if the expression is too high, the neuronal networks will be impaired due to strong inhibition.
For this reason, methodological approaches to treatment in which the effect on the neuronal excitability in the epileptic focus can be controlled are of great interest. Optogenetic methods offer such an advantage. Optogenetics uses light to alter the excitability of specific neuronal populations and can also be used in a biofeedback paradigm in which the light source is activated only at the risk of generating seizure activity. A number of optogenetic tools have now been developed, including light-activated cationic (e.g., ChR2) and anion channels (ACR), metabotropic receptors, pumps (NpHR, Arch), and enzymes. However, the optogenetic approach has a number of technical difficulties in delivering the light source and the risk of developing an immune response to the expression of rhodopsins.
This report reviews the experience of practical application of optogenetic tools in the use of 4-aminopyridine in vitro model of epileptiform activity in experiencing slices of the entorhinal cortex. We tested the efficacy of suppressing ictal activity using several variants of optogenetic stimulation: (1) activation of excitatory and inhibitory neurons (in Thy1-ChR2-YFP mice), (2) activation of inhibitory interneurons only (in PV-Cre mice after virus injection with the channelodopsin-2 gene), hyperpolarization of excitatory neurons after expression of (3) archaeodopsin or (4) a light-dependent sodium pump. We found that ictal activity was successfully suppressed when low-frequency optogenetic stimulation induced regular interictal activity. Usually, interictal activity was induced by rhythmic synchronous activation of the principal neurons of the entorhinal cortex. In other cases, the ictal activity was preserved, although its characteristics may have changed. We determined the parameters of optogenetic stimulation that were most effective in suppressing ictal activity.
The availability of a wide range of gene therapy approaches for epilepsy that have demonstrated efficacy in preclinical studies suggests that clinical trials of some of these approaches will begin in the next few years.
Full Text
The World Health Organization estimates that around 1% of the population experiences epilepsy. Despite the progress made in creating new antiepileptic medications, seizures continue to persist in almost one-third of patients.
One promising approach to treating epilepsy is gene therapy. Since epileptic activity stems from an imbalance between excitation and inhibition, researchers prioritize regulating neuronal excitability. Initially, they focused on hyperexpressing inhibitory peptides like galanin or NPY or suppressing neuronal excitability through potassium channel hyperexpression in neurons. However, it is imperative to carefully calculate and strictly regulate these effects since correcting the expression at a later stage can be arduous. If the expression is insufficient, the anticonvulsant effect won’t be attained, and if it is excessive, the neuronal networks will be impaired due to excessive inhibition.
Therefore, approaches to treat epilepsy by controlling neuronal excitability in the epileptic focus are of great interest. Optogenetic methods provide such an advantage by altering the excitability of specific neuronal populations using light. In addition, optogenetics can be used in a biofeedback paradigm in which the light source is activated only when there is a risk of generating seizure activity. Several optogenetic tools exist, such as light-activated cationic (e.g. ChR2) and anion channels (ACR), metabotropic receptors, pumps (NpHR, Arch), and enzymes. However, the optogenetic approach encounters technical challenges in delivering the light source and the risk of an immune response to the expression of rhodopsins.
This report presents a review of the practical application experience using optogenetic tools in conjunction with the 4-aminopyridine in vitro model to observe epileptiform activity in slices of the entorhinal cortex. We evaluated the effectiveness of various optogenetic stimulation techniques in inhibiting ictal activity. These techniques included activating both excitatory and inhibitory neurons (in Thy1-ChR2-YFP mice), activating only inhibitory interneurons (in PV-Cre mice with channelodopsin-2 gene virus injection), hyperpolarizing excitatory neurons after expressing archaeodopsin, and hyperpolarizing excitatory neurons through a light-sensitive sodium pump. Ictal activity was effectively suppressed through low-frequency optogenetic stimulation, inducing regular interictal activity. The entorhinal cortex’s principal neurons were typically rhythmically activated, creating interictal activity. However, in some cases, the ictal activity persisted, albeit with changed characteristics. We identified the most successful optogenetic stimulation parameters for suppressing ictal activity.
The wide range of gene therapy approaches available for epilepsy, with demonstrated efficacy in preclinical studies, indicate that clinical trials for some of these approaches will commence in the coming years.
ADDITIONAL INFORMATION
Authors’ contribution. All authors made a substantial contribution to the conception of the work, acquisition, analysis, interpretation of data for the work, drafting and revising the work, final approval of the version to be published and agree to be accountable for all aspects of the work.
Funding sources. The study was supported by the Russian Science Foundation (project No. 21-15-00430).
Competing interests. The authors declare that they have no competing interests.
About the authors
A. V. Zaitsev
Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences
Author for correspondence.
Email: aleksey_zaitsev@mail.ru
Russian Federation, Saint Petersburg
E. Yu. Proskurina
Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences
Email: aleksey_zaitsev@mail.ru
Russian Federation, Saint Petersburg
A. M. Trofimova
Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences
Email: aleksey_zaitsev@mail.ru
Russian Federation, Saint Petersburg
T. Yu. Postnikova
Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences
Email: aleksey_zaitsev@mail.ru
Russian Federation, Saint Petersburg
Yu. L. Ergina
Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences
Email: aleksey_zaitsev@mail.ru
Russian Federation, Saint Petersburg
D. V. Amahin
Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences
Email: aleksey_zaitsev@mail.ru
Russian Federation, Saint Petersburg
K. Kh. Kim
Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences
Email: aleksey_zaitsev@mail.ru
Russian Federation, Saint Petersburg
V. S. Tiselko
Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences
Email: aleksey_zaitsev@mail.ru
Russian Federation, Saint Petersburg
A. V. Chizhov
Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences
Email: aleksey_zaitsev@mail.ru
Russian Federation, Saint Petersburg
References
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