Tingzi Yin, Xiaolu Cao, Wan Xiao, Ying Zhang, Shuqi Zhao and Xiamin Hu
Nebracetam has been recently proposed to have a neuroprotective action and cognitive enhancing effect being characteristic of a nootropic drug, while the mechanisms remained ambiguity. In this study, we investigated the protective effects of nebracetam on hippocampus neurons injury-induced by β-amyloid protein(Aβ25-35)and its mechanisms. Hippocampus neurons were treated with nebracetam (0.05 mM, 0.2 mM or 0.8 mM) or Aβ25-35 (20 uM/L). We found that Nebracetam significantly reduced apoptotic induced by Aβ25-35 and increase in the total number of dendritic spines and dendritic spine density in a dose-dependent manner. RT-PCR assay and Western blotting analysis revealed that nebracetam increased the expressions of myeloid cell leukemia-1 (Mcl-1), B-cell lymphoma-2 (Bcl-2) and activity regulated cytoskeleton associated protein (Arc) in Aβ25-35-treated hippocampus neurons. Cotreatment nebracetam with MRTF-A (Myocardin-related transcription factor-A) siRNA reversed Mcl-1, Bcl-2 and Arc mRNA and protein levels. What’s more, the luciferase assays indicated that the transcriptional activities of Mcl-1, Bcl-2 and Arc genes were significantly abolished by MRTF-A siRNA while it showed no changes on activities of mut Mcl- 1-promoter-luc, mut Bcl-2-promoter-luc and mut Arc-promoter-luc. Additionally, the up-regulation of Mcl-1, Bcl-2 and Arc protein expressions in nebracetam-treated group was inhibited by extracellular signal regulated protein kinase 1/2 (ERK1/2) inhibitor PH98059. These results demonstrated that nebracetam inhibited Aβ25-35-induced hippocampus neurons injury by enhancing the transactivity of Mcl-1, Bcl-2 and Arc, which may actively based in MRTF-A-CArGdependent manner by thwarting the ERK1/2 pathway.
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