Knockdown of NogoA prevents MPP+-induced neurotoxicity in PC12 cells via the mTOR/STAT3 signaling pathway

NogoA is a myelin-associated protein, which is important in the inhibition of axonal fiber growth and in regeneration following injury of the mammalian central nervous system. A previous study suggested that NogoA may be key in the process of Parkinson's disease (PD), which is the second most common chronic neurodegenerative disorder worldwide. The regulatory mechanism underlying the effect of NogoA on the process of PD remains to be fully elucidated. The present study aimed to investigate the effect and underlying mechanism of NogoA on cellular viability, apoptosis and autophagy induced by 1-methyl-4-phenylpyridinium (MPP+) in PC12 cells, a commonly used in vitro PD model. PC12 cells were treated with 1 mM MPP+ for 24 h and the cells were harvested for western blotting. The results demonstrated that the protien expression levels of NogoA were increased in the PC12 cells treated with MPP+. Subsequently, NogoA small interfering RNA was synthesized and transfected into PC12 cells to silence the expression of NogoA. NogoA knockdown significantly reduced the MPP+-induced decrease in cell viability and apoptosis, detected using a cell counting kit-8 and flow cytometric analysis, respectively. Interference in the expression of NogoA increased the MPP+-induced decrease in mitochondrial membrane potential, determined quantitatively by flow cytometry using JC-1 dye, and the protein levels of Beclin-1. In addition, MPP+ treatment activated the mammalian target of rapamycin (mTOR)/signal transducer and activator of transcription 3 (STAT3) signaling pathway. Knockdown of NogoA significantly inhibited the expression levels of mTOR and STAT3. Furthermore, overexpression of NogoA had similar neurotoxic effects on the PC12 cells as MPP+ treatment. Treatment with rapamycin, an inhibitor of the mTOR/STAT3 signaling pathway had a similar effect to that of NogoA knockdown in the MPP+-treated PC12 cells. Taken together, the results from the present study demonstrated that NogoA may regulate MPP+-induced neurotoxicity in PC12 cells via the mTOR/STAT3 signaling pathway and provided an explanation regarding the regulatory mechanism of NogoA on the process of PD.