Purpose: Early-life seizures increase vulnerability to subsequent neurologic insult. We tested the hypothesis that early-life seizures increase susceptibility to later neurologic injury by causing chronic glial activation. To determine the mechanisms by which glial activation may modulate neurologic injury, we examined both acute changes in proinflammatory cytokines and long-term changes in astrocyte and microglial activation and astrocyte glutamate transporters in a "two-hit" model of kainic acid (KA)-induced seizures.
Methods: Postnatal day (P) 15 male rats were administered KA or phosphate buffered saline (PBS). On P45 animals either received a second treatment of KA or PBS. On P55, control (PBS-PBS), early-life seizure (KA-PBS), adult seizure (PBS-KA), and "two-hit" (KA-KA) groups were examined for astrocyte and microglial activation, alteration in glutamate transporters, and expression of the glial protein, clusterin.
Results: P15 seizures resulted in an acute increase in hippocampal levels of IL-1beta and S100B, followed by behavioral impairment and long-term increases in GFAP and S100B. Animals in the "two-hit" group showed greater microglial activation, neurologic injury, and susceptibility to seizures compared to the adult seizure group. Glutamate transporters increased following seizures but did not differ between these two groups. Treatment with Minozac, a small molecule inhibitor of proinflammatory cytokine upregulation, following early-life seizures prevented both the long-term increase in activated glia and the associated behavioral impairment.
Conclusions: These data suggest that glial activation following early-life seizures results in increased susceptibility to seizures in adulthood, in part through priming microglia and enhanced microglial activation. Glial activation may be a novel therapeutic target in pediatric epilepsy.