Transcriptome profiling of hippocampal CA1 after early-life seizure-induced preconditioning may elucidate new genetic therapies for epilepsy

Injury of the CA1 subregion induced by a single injection of kainic acid (1 x KA) in juvenile animals (P20) is attenuated in animals with two prior sustained neonatal seizures on P6 and P9. To identify gene candidates involved in the spatially protective effects produced by early-life conditioning seizures we profiled and compared the transcriptomes of CA1 subregions from control, 1 x KA- and 3 x KA-treated animals. More genes were regulated following 3 x KA (9.6%) than after 1 x KA (7.1%). Following 1 x KA, genes supporting oxidative stress, growth, development, inflammation and neurotransmission were upregulated (e. g. Cacng1, Nadsyn1, Kcng1, Aven, S100a4, GFAP, Vim, Hrsp12 and Grik1). After 3 x KA, protective genes were differentially over-expressed [e. g. Cat, Gpx7, Gad1, Hspa12A, Foxn1, adenosine A1 receptor, Ca2+ adaptor and homeostasis proteins, Cacnb4, Atp2b2, anti-apoptotic Bcl-2 gene members, intracellular trafficking protein, Grasp and suppressor of cytokine signaling (Socs3)]. Distinct anti-inflammatory interleukins (ILs) not observed in adult tissues [e. g. IL-6 transducer, IL-23 and IL-33 or their receptors (IL-F2)] were also over-expressed. Several transcripts were validated by real-time polymerase chain reaction (QPCR) and immunohistochemistry. QPCR showed that casp 6 was increased after 1 x KA but reduced after 3 x KA; the pro-inflammatory gene Cox1 was either upregulated or unchanged after 1 x KA but reduced by similar to 70% after 3 x KA. Enhanced GFAP immunostaining following 1 x KA was selectively attenuated in the CA1 subregion after 3 x KA. The observed differential transcriptional responses may contribute to early-life seizure-induced pre-conditioning and neuroprotection by reducing glutamate receptor-mediated Ca2+ permeability of the hippocampus and redirecting inflammatory and apoptotic pathways. These changes could lead to new genetic therapies for epilepsy.