Decreased expression of Ras-GRF1 in the brain tissue of the intractable epilepsy patients and experimental rats

Ras-guanine nucleotide-releasing factor 1 (Ras-GRF1) is present mainly at synaptosome and its expression after birth increases in parallel with the development of neuronal circuitry. Evidences suggested that Ras-GRF1 could mediate forms of synaptic plasticity and might participate in the regulation of neuronal excitability and neurite outgrowth though various signal transduction pathway. The aim of this study was to measure Ras-GRF1 expression in brain tissue of patients with drug-refractory temporal lobe epilepsy (TLE) and lithium chloride-pilocarprine kindled rats using double-label immunofluorescence, immunohistochemistry and Western blotting and to discuss the possible role of Ras-GRF1 in TLE. We randomly selected 30 temporal neocortices tissues from patients with TLE and 9 histologically normal temporal neocortices samples from controls. Meanwhile, we investigated the distribution and level of Ras-GRF1 protein expression during the different phases (the acute period, the latent period and the chronic phase) in the epileptic and control rats. Ras-GRF1 was mainly expressed in the plasma membrane and dendrite of neurons, but it was not co-expressed with GFAP-positive astrocytes in the brain tissue of patients and epileptic rats. Compared with controls, Ras-GRF1 expression was significantly decreased in TLE patients. Ras-GRF1 expression in epileptic rats was already reduced at 1 day post-seizures, then gradually decreased during the latent period and reached a minimum level during the chronic phase. These results demonstrated that the decreased expression of Ras-GRF1 could be involved in the pathogenesis of human TLE.

► We examined the expression of Ras-GRF1 in brain tissue of patients and experimental epilepsy.
► Down-regulation of Ras-GRF1 was observed in the temporal neocortex of patients.
► Ras-GRF1 expression was also decreased in the rat brain during the epileptic process.
► These results suggested that Ras-GRF1 may be involved in the pathophysiology of epilepsy.