Abstracts

Rationale: Antiepileptogenic therapies remain limited, even in preclinical models. Thus, identifying targets to prevent the development of epilepsy (i.e., epileptogenesis) is a large unmet need. In animal models, a common epileptogenic insult is prolonged seizure activity (status epilepticus [SE]) which leads to significant pathological changes. These changes include neuronal apoptosis, DNA damage, oxidative stress, and inflammation are thought to contribute to the emergence of spontaneous recurrent seizures [SRS] in the days-weeks following SE. These resemble the hallmarks of cellular senescence, a conserved program which halts cell proliferation and triggers an inflammatory senescence associated secretory phenotype (SASP) in response to damaging stimuli. Senescent Cells (SCs) canonically upregulate cell-cycle inhibition genes such as p16. Cellular senescence is of growing interest in neurodegeneration. Ablating SCs rescues disease associated impairments. Senescence has not been examined in the context of epilepsy.

Methods: To test the hypothesis that senescent cells play a role in epileptogenesis, we induced SE in mice, and histologically and examined the senescence phenotype, which was predominantly in microglia. To better understand the physiological impact of senescent microglia, we examined the microglial process convergence in response to stimuli (ATP) and spontaneous motility in live slices of a senescence (p16) and microglia reporter line following SE. In a separate cohort of mice, we ablated SCs immediately following SE and until euthanasia. Senescent cells were ablated genetically in a genetic model of p16+ SC ablation, INK-ATTAC, and pharmacologically using a senolytic cocktail of dasatinib and quercetin (DQ), and were compared to their respective vehicle-treated mice. SC ablated mice and their vehicle-treated (SC remaining) counterparts were monitored for seizure burden with EEG and behavioral analysis to assess spatial, recognition, and anxiety-like behaviors.

Results: Our data suggest that p16+ SC accumulate in hippocampi as early as two weeks following SE and continue to accumulate as time progresses following epileptogenesis. Interestingly, of the p16+ SCs, approximately 85% colocalize with microglia at all time points. Further, microglial process motility is increased in the SE p16+ microglia compared to SE p16- microglia. With senolytic treatment there is a significant reduction in seizure duration, number, and cumulative seizure duration over a 2 week seizure monitoring period. Lastly, spatial memory assessed through Barnes Maze and context-recognition memory were significantly improved with genetic SC ablation. However anxiety-like behavior or recognition memory were not significantly changed when compared to vehicle treated animals.

Conclusions: These findings suggest that cellular senescence is induced, predominantly in microglia, following epileptogenesis. Senescent cell ablation reduces seizure burden and improves spatial and context-recognition memory.

Funding: This research is supported by 1R21NS125552 and 5T32NS041218.