The Dephosphorylation of p70S6 (Thr389) Kinase as a Marker of L-Glutamate-Induced Excitotoxicity Related to Diabetes Disturbances-an Unconventional In Vitro Model.

Excitotoxicity is a modern clinical condition included in the pathogenesis of Alzheimer's disease. It is connected with diabetic disturbance, and it is still being analyzed in the context of the participation of the PI3K/mTOR pathway. A very important protein belonging to this pathway is p70S6K, whose activation promotes the pathogenesis of type 2 diabetes by the induction of insulin resistance. The study model was based on a PC12 cell line, derived from the pheochromocytoma of a rat adrenal medulla, cultured in RPMI 1640. The three reagents were used in different concentrations to create the model of excitotoxicity related to diabetes disturbances: L-glutamate (2.5 mM; 10 mM), glucose (150 mM; 200 mM), and insulin (0.093 mM; 0.371 mM). The aim of our study was to examine and evaluate the levels of phosphorylation of proteins involved in signal transduction controlled by MAPK, PI3K/Akt, and mTOR signaling pathways in L-glutamate-induced excitotoxicity with comorbid hyperglycemia and hyperinsulinemia imitating diabetic disturbances in in vitro conditions on PC12 cells. The results we obtained demonstrated the increased phosphorylation of p70S6K in Thr389 residue in almost all combinations of reagents, except for those including the highest concentration of L-glutamate, in which dephosphorylation was confirmed. This confirms the inhibition of mTOR kinase and suggests that p70S6K (Thr389) plays a functional role in the regulation of the signaling pathway in excitotoxicity related to diabetic disturbances.