Pharmacological inhibition of S6K1 rescues synaptic deficits and attenuates seizures and depression in chronic epileptic rats.

Abstract

Recent studies have shown that mTOR signaling plays an important role in synaptic plasticity. However, the function of S6K1, the mechanistic target of rapamycin kinase complex 1 (mTORC1) substrate, in epilepsy remains unknown. Our present study aimed to explore the mechanism by which S6K1 is involved in chronic epilepsy. First, immunostaining was used to measure neurite length and complexity in kainic acid (KA)-treated primary cultured neurons treated with PF-4708671, a highly selective S6K1 inhibitor. We obtained evidence for the role of S6K1 in protecting and promoting neuronal growth and development in vitro. Next, to explore the function and mechanism of the S6K1 inhibitor in epilepsy, a pilocarpine-induced chronic epileptic rat model was established. In vivo electrophysiology (including local field potentiation in CA1 and long-term potentiation), depression/anxiety-like behavior tests, and Golgi staining were performed to assess seizure behavior, power spectral density, depression/anxiety-like behavior, and synaptic plasticity. Furthermore, western blotting was applied to explore the potential molecular mechanisms. We found that inhibition of S6K1 expression significantly decreased seizures and depression-like behavior and restored power at low frequencies (1-80 Hz), especially in the delta, theta, and alpha bands, in chronic epileptic rats. In addition, PF-4708671 reversed the LTP defect in hippocampal CA3-CA1 and corrected spine loss and dendritic pathology. In conclusion, our data suggest that inhibition of S6K1 attenuates seizures and depression in chronic epileptic rats via the rescue of synaptic structural and functional deficits. Given the wide range of physiological functions of mTOR, inhibition of its effective but relatively simple functional downstream molecules is a promising target for the development of drugs for epilepsy.