Long term chemogenetic suppression of spontaneous seizures in a mouse model for temporal lobe epilepsy
Jana
Desloovere1*,
Paul
Boon1,
Lars
E.
Larsen1, 2,
Caroline
Merckx1, 3,
Marie-Gabrielle
Goossens1,
Chirs
Van Den Haute4, 5,
Veerle
Baekelandt4,
Evelien
Carrette1,
Jean
Delbeke1,
Alfred
Meurs1,
Kristl
Vonck1,
Wytse
Wadman1 and
Robrecht
Raedt1
-
1
4 Brain, Department of Head and Skin, Ghent University, Belgium, Belgium
-
2
Medical Imaging and Signal Processing, Ghent University, Belgium
-
3
Laboratory for Neuropathology, Department of Neurology, Ghent University, Belgium, Belgium
-
4
Laboratory for Neurobiology and Gene Therapy, Department of Neurosciences, KU Leuven, Belgium
-
5
Leuven Viral Vector Core, Centre for Molecular Medicine and Leuven Brain Institute, KU Leuven, Belgium, Belgium
AIM
More than one third of patients with epilepsy continue to have seizures despite treatment with anti-epileptic drugs. In this study we evaluate whether selective silencing of excitatory hippocampal neurons using the inhibitory Designer Receptor Exclusively Activated by Designer Drugs (DREADD) hM4Di leads to suppression of spontaneous hippocampal seizures in the intrahippocampal kainic acid (IHKA) mouse model for TLE.
METHODS
Mice (n=60) were injected with kainic acid in the right hippocampus (200ng/50nl, AP -2mm ML +1.5mm DV -1.8mm relative to bregma). Three weeks later, animals were injected in the KA-lesioned hippocampus with 500nl adeno-associated-viral vector carrying genes encoding hM4Di-mCherry fusion protein (2.7E+13 GC/ml, DREADD group, n = 43) or mCherry only (2.1E+13 GC/ml, non-DREADD group, n=13) under transcriptional control of CamKIIalpha promotor, specific for excitatory neurons. Subsequently a bipolar recording electrode was implanted at the injection site. Mice with most frequent hippocampal seizures were selected for further treatment. DREADD animals were treated with three subclinical single doses of clozapine (0.01, 0.03 and 0.1mg/kg ; n=8, 9 and 10) and with repeated doses (every 8 hours for 3 days , n=5, 4 and 5). Non-DREADD animals (n=4) received a single 0.1mg/kg clozapine injection. The fraction of time an animal spent in seizures (FTS) was used as a measure for epileptic activity.
RESULTS
Administration of 0.1mg/kg clozapine resulted in a strong inhibition of epileptic activity only in DREADD-expressing animals (baseline (BL) FTS values of 16 ± 2 % and 21 ± 4 %, post treatment FTS values of 6 ± 1 % and 20 ± 2 % in DREADD and non-DREADD animals respectively). Both groups were statistically different from each other for at least 18 hours after treatment. Acute administration of 0.1mg/kg lead to a stronger seizure suppression in comparison to 0.03 and 0.01mg/kg injection (BL FTS values of 15 ± 2 % and 18 ± 3 % reduced to 10 ± 1 % and 11 ± 1 % post treatment with 0.03 and 0.01mg/kg respectively). Similarly, sustained treatment for three consecutive days resulted into a dose-dependent suppression of epileptic activity (0.1mg/kg resulted in a more potent suppression than 0.03 and 0.01mg/kg; 0.03 mg/kg resulted in a more potent suppression than 0.01mg/kg, BL FTS values of 15 ± 2 %, 21 ± 2 % and 25 ± 2% reduced to 3 ± 2%, 6 ± 2% and 11 ± 2% during chronic treatment with 0.1, 0.03 and 0.01mg/kg respectively).
CONCLUSION
This study shows the potency of chemogenetics to robustly and chronically suppress spontaneous epileptic seizures. Moreover, this indicates that excitatory hippocampal neurons are essential in the seizure generation process in the IHKA mouse model. Additionally we show that different subclinical doses of clozapine can be used to activate DREADDs and that 0.1mg/kg clozapine is the most potent dose to suppress spontaneous seizures. This could lead to epilepsy therapy where a systemically administered drug very selectively modulates specific neurons of the seizure network, resulting in a very potent seizure suppression.
Acknowledgements
Funding: J.D. and MG.G. are PhD fellows of te Research foundation Flanders (1S74519N, 1S30017N)
Keywords:
Epilepsy,
chemogenetics,
Gene Therapy,
Hippocampus,
Temporal Lobe Epilepsy (TLE),
IHKA mouse model,
DREADD receptors,
hM4Di receptors
Conference:
13th National Congress of the Belgian Society for Neuroscience , Brussels, Belgium, 24 May - 24 May, 2019.
Presentation Type:
Poster presentation
Topic:
Behavioral/Systems Neuroscience
Citation:
Desloovere
J,
Boon
P,
Larsen
LE,
Merckx
C,
Goossens
M,
Van Den Haute
C,
Baekelandt
V,
Carrette
E,
Delbeke
J,
Meurs
A,
Vonck
K,
Wadman
W and
Raedt
R
(2019). Long term chemogenetic suppression of spontaneous seizures in a mouse model for temporal lobe epilepsy.
Front. Neurosci.
Conference Abstract:
13th National Congress of the Belgian Society for Neuroscience .
doi: 10.3389/conf.fnins.2019.96.00011
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Received:
30 Apr 2019;
Published Online:
27 Sep 2019.
*
Correspondence:
Ms. Jana Desloovere, 4 Brain, Department of Head and Skin, Ghent University, Belgium, Ghent, Belgium, jana.desloovere@ugent.be