MiR-299-5p regulates apoptosis through autophagy in neurons and ameliorates cognitive capacity in APPswe/PS1dE9 mice.

Yueqi Zhang,Hong Ping,Chengeng Liu,Peichang Wang,Jinling Wang,Qiliang Li,Shichao Gao

doi:10.1038/srep24566

Yueqi Zhang, Hong Ping + Show 5 more

Open Access

https://doi.org/10.1038/srep24566

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Abstract

Abnormalities of autophagy can result in neurodegenerative disorders such as Alzheimer’s disease (AD). Nevertheless, the regulatory mechanisms of autophagy in AD are not well understood. Here, we describe our findings that microRNA (miR)-299-5p functions as an autophagy inhibitor by suppressing Atg5 and antagonizing caspase-dependent apoptosis. We observed decreased levels of miR-299-5p both in primary neurons under conditions of starvation and in hippocampi of APPswe/PS1dE9 mice. Additionally, low levels of miR-299-5p were observed in cerebrospinal fluid of AD patients. MiR-299-5p treatment resulted in attenuation of Atg5 and autophagy in primary neurons from APPswe/PS1dE9 mice, N2a cells and SH-SY5Y cells, whereas antagomiR-299-5p enhanced autophagy. Atg5 was verified as a direct target of miR-299-5p by dual luciferase reporter assays. Furthermore, transfection of miR-299-5p into primary hippocampal neurons caused the attenuation of caspase-mediated apoptosis, which was reversed upon starvation-induced autophagy. Inhibition of autophagy by shRNA knockdown of LC3β reduced apoptotic neuron death induced by antagomiR-299-5p. Injection of agomiR-299-5p into the cerebral ventricles of AD mice inhibited both autophagy and apoptosis and also improved the cognitive performance of mice. Overall, our results suggest that miR-299-5p modulates neuron survival programs by regulating autophagy. Thus, miR-299-5p serves as a potential neuroprotective factor in AD.

Highlights

3 miRs were considered as potential regulators both in autophagy and in Alzheimer’s disease (AD). (b) The 3 miRs or scrambled miRs (Scr-miR) were transfected into primary neurons for 24 h, and autophagy related proteins were analyzed by western blotting (n = 3). β -actin was used as a loading control. (c) RT-PCR confirmed that mmu-miR-299-5p levels were lower in 9-month-old APPswe/PS1dE9 mice (Tg) than C57 mice (n = 4 per group)
We demonstrate that miR-299-5p inhibits autophagy by downregulating Atg[5], and that autophagy modulated by miR-299-5p is closely associated with caspase-mediated apoptosis in neurons
(e) The percentage of positive cells was calculated as the apoptosis rate

Summary

Introduction

3 miRs were considered as potential regulators both in autophagy and in AD. Increasing evidence has shown that miRs are strongly associated with AD12. We identified specific miRs that can be used as biomarkers to diagnose AD16–18, and using microarray analysis, we showed that the expression of multiple miRs is significantly changed in the hippocampi of 9-months-old APP/PS1 double transgenic mice[16]. We show that miR-299-5p regulates both neuron autophagy and apoptosis in vitro. Exogenous expression of pharmacologic miR-299-5p by agomiR injection effectively reduces the apoptosis of hippocampi neurons and improves the cognitive capability of transgenic mice, demonstrating a possible therapeutic approach for AD

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