miR-384-5p promotes spinal cord injury recovery in rats through suppressing of autophagy and endoplasmic reticulum stress

Abstract

Background: Spinal cord injury (SCI) is one of the most serious neurological disorders and is characterized by high morbidity and disability. Unfortunately, there is a lack of effective treatment. Recently, the micro RNA, miR-384-5p, was reported to play a significant role in cell survival in response to different insults.

Methods: In vitro model of traumatic neuronal injury was induced by application of a sharp sterile blade to generate cuts in PC12 cells, and in vivo SCI was produced by applying vascular clips (force of 15 g) to the dura via T9-T10 laminectomy, and then, the role of miR-384-5p in the development of SCI was investigated.

Results: Dual-luciferase reporter assays confirmed that miR-384-5p regulates the gene expression of Beclin-1, an important promoter of autophagy. Quantitative polymerase chain reaction and western blot analyses revealed that treatment with miR-384-5p decreased mRNA and protein expression of Beclin-1 in the mechanically injured PC12 cells. In rats with spinal cord compression injuries, miR-384-5p expression was significantly decreased. Treatment with miR-384-5p increased spinal cord neuron survival and promoted locomotor function recovery in rats. Further study revealed that miR-384-5p administration decreased immunofluorescent labeling of Beclin-1 in spinal cord tissues and reduced autophagosome formation in neurons, as shown by transmission electron microscopy. These results indicated that miR-384-5p promotes recovery of rats with SCI by suppressing autophagy via direct targeting of Beclin-1. Moreover, miR-384-5p also inhibited the activation of endoplasmic reticulum (ER) stress by decreasing GRP78 expression in both in vitro and in vivo models.

Conclusions: This study for the first time demonstrates that the protective role of miR-384-5p in the process of SCI is associated with simultaneous suppression of autophagy and ER stress and miR-384-5p could be a promising candidate for SCI therapeutics.

Keywords: Autophagy; Beclin-1; Endoplasmic reticulum stress; Spinal cord injury; miR-384-5p.