Selective Neuronal Knockout of STAT3 Function Inhibits Epilepsy Progression, Improves Cognition, and Restores Dysregulated Gene Networks in a Temporal Lobe Epilepsy Model

Abstract

Objective Temporal lobe epilepsy (TLE) is a progressive disorder mediated by pathological changes in molecular cascades and hippocampal neural circuit remodeling that results in spontaneous seizures and cognitive dysfunction. Targeting these cascades may provide disease‐modifying treatments for TLE patients. Janus Kinase/Signal Transducer and Activator of Transcription (JAK/STAT) inhibitors have emerged as potential disease‐modifying therapies; a more detailed understanding of JAK/STAT participation in epileptogenic responses is required, however, to increase the therapeutic efficacy and reduce adverse effects associated with global inhibition. Methods We developed a mouse line in which tamoxifen treatment conditionally abolishes STAT3 signaling from forebrain excitatory neurons (nSTAT3KO). Seizure frequency (continuous in vivo electroencephalography) and memory (contextual fear conditioning and motor learning) were analyzed in wild‐type and nSTAT3KO mice after intrahippocampal kainate (IHKA) injection as a model of TLE. Hippocampal RNA was obtained 24 h after IHKA and subjected to deep sequencing. Results Selective STAT3 knock‐out in excitatory neurons reduced seizure progression and hippocampal memory deficits without reducing the extent of cell death or mossy fiber sprouting induced by IHKA injection. Gene expression was rescued in major networks associated with response to brain injury, neuronal plasticity, and learning and memory. We also provide the first evidence that neuronal STAT3 may directly influence brain inflammation. Interpretation Inhibiting neuronal STAT3 signaling improved outcomes in an animal model of TLE, prevented progression of seizures and cognitive co‐morbidities while rescuing pathogenic changes in gene expression of major networks associated with epileptogenesis. Specifically targeting neuronal STAT3 may be an effective disease‐modifying strategy for TLE. ANN NEUROL 2023;94:106–122

Disease modification upon brief exposure to tofacitinib during chronic epilepsy

“…Network analysis placed STAT3 in the center of the Black GRN and immunofluorescence confirmed induction of STAT3 in neurons post SE. While activation of the JAK/STAT pathway in non-neuronal cells post-SE is well-characterized 26,47,61,62 , the role of STAT3 in neurons, especially in epilepsy has been less studied 45 . The mechanisms of neurogenic inflammation post-SE are not clear.…”

“…Cytokines released from glial cells following seizures increase neuronal excitability 66 , and type I IFNs increase excitability in neocortical pyramidal neurons via PKC 67 . Others have reported that seizure-induced activation of the JAK/STAT pathway reduces the number of gamma-aminobutyric acid (GABA) type A alpha1 receptors expressed in neurons following seizures, influencing GABA(A)R-dependent inhibition 27 ; this group has also utilized pharmacological inhibition of STAT3 32 and genetic ablation of the STAT3 SH2 domain 45 to reduce spontaneous seizure frequency in rodent models of epilepsy. In summary, activation of neuroinflammatory pathways, including the JAK/STAT pathway, has been shown to modulate neuronal excitability, and herein we identify EZH2 as a key negative regulator of the JAK/STAT pathway in epileptogenesis.…”

“…The ontology network highlights the innate immune response (NFkB, Interferon Gamma), microglial processes (Complement) and inflammation (IL6 Jak Stat3) amongst others. The term 'IL6 Jak Stat3' was of particular interest given that our previous work highlighted STAT3 as a driver of gene activation across models of epilepsy 23 , and others have identified a role for the JAK/STAT pathway in epileptogenesis 27,32,[45][46][47][48] . To determine which transcription factors and cofactors (hereafter together referred to as 'Factors') control expression of Black cluster genes, we used MAGIC 21 .…”

Epileptic Neurons Know JAK/STAT3

“…1,2 There is growing evidence suggesting that increased JAK/STAT activity also plays a role in epilepsy in both human and experimental settings (animal and cell/ organotypic culture models). [3][4][5][6] However, the precise contribution of this activity to epileptogenesis is still being established. The study by Tipton et al investigated the specific role of neuronal JAK/STAT3 function in epileptogenic processes, unprovoked seizure progression, and cognitive comorbidities in a mouse model of acquired temporal lobe epilepsy (TLE) generated by administration of intrahippocampal kainic acid (IHKA).…”

“…The study by Tipton et al investigated the specific role of neuronal JAK/STAT3 function in epileptogenic processes, unprovoked seizure progression, and cognitive comorbidities in a mouse model of acquired temporal lobe epilepsy (TLE) generated by administration of intrahippocampal kainic acid (IHKA). 3 Brain injury linked to events of traumatic brain injury, ischemia, and status epilepticus (SE) can trigger hyperactivation of the JAK/STAT pathway. 4,6,7 In a pilocarpine rat model of SE and acquired TLE, this group previously reported that suppression of the JAK/STAT signaling cascade with WP1066, a small molecule inhibitor of STAT3 signaling, given at the onset of SE resulted in a long-lasting reduction of spontaneous recurrent seizures (SRS).…”