Neuroprotective Effects of the Small-Molecule Enhancer of Rapamycin in the Cellular Model of Parkinson’s Disease

Abstract

Parkinson’s disease (PD) is one of the most frequent neurodegenerative diseases. We investigated the protective effects of the small-molecule enhancer of rapamycin SMER28 in the SH-SY5Y cellular model of PD induced by 6-hydroxydopamine (6-OHDA). The cell viability and apoptosis estimations were performed using MTT and annexin V-FITC assays, respectively. The levels of intracellular reactive oxygen species (ROSs) and mitochondrial membrane potential were determined by the respective fluorescence detection. ELISA assays were performed to detect the levels of dopamine and α-synuclein. Additionally, mTOR signaling and the expression levels of autophagy-related proteins, including Beclin-1, p62, and LC3, were analyzed by Western blot. SMER28 increased the cell viability and mitochondrial membrane potential but decreased ɑ-synuclein and intracellular ROSs. SMER28 also reversed the decreased dopamine level and increased α-synuclein expression induced by 6-OHDA. The latter (100 μM) induced intense apoptosis, but 50 μM SMER28 prevented the latter via autophagy induction. We also noticed that SMER28 triggered autophagy and enhanced Beclin-1 expression, and LC3-I to LC3-II conversion, as well as decreased p62 expression and mTOR signaling activation in SH-SY5Y cells. Blocking of autophagy by a selective inhibitor, 3-methyladenosine, decreased the autophagy ratio in SMER28-treated SH-SY5Y cells, suggesting a considerable neuroprotective role of SMER28-induced autophagy. Taken together, it can be concluded that SMER28 exerts a protective effect against cellular damage induced by 6-OHDA via autophagy induction. Therefore, SMER28 may serve as a promising potential adjuvant therapy for PD treatment.