MiR-365 targets β-arrestin 2 to reverse morphine tolerance in rats.

Jian Wang,Zongbin Song,Yu Zou,Wei Xu,Wangyuan Zou,Zhuofeng Ding,Qulian Guo,Xinzhong Dong,Tao Zhong

doi:10.1038/srep38285

Abstract

Morphine tolerance is a challenging clinical problem that limits its clinical application in pain treatment. Non-coding microRNAs (miRNAs) modulate gene expression in a post transcriptional manner, and their dysregulation causes various diseases. However, the significance of miRNAs in morphine tolerance is still poorly understood. In the present study, we hypothesized that microRNA-365 (miR-365) is a key functional small RNA that reverses morphine tolerance through regulation of β-arrestin 2 in rats. Here, microarray analysis and quantitative real-time PCR showed that miR-365 was robustly decreased in the spinal cord after chronic morphine administration. In situ hybridization and immunochemistry double staining showed that miR-365 was expressed in neurons of the spinal cord. We identified β-arrestin 2 as the target gene of miR-365 by bioinformatics analysis and luciferase reporter assay. The data showed that overexpression of miR-365 prevented and reversed established morphine tolerance, and increased expression of miR-365 caused a decrease in expression of β-arrestin 2 protein. miR-365 downregulation is involved in the development and maintenance of morphine tolerance through regulation of β-arrestin 2, and miR-365 upregulation provides a promising and novel approach for treatment of morphine tolerance.

Highlights

Morphine tolerance is a challenging clinical problem that limits its clinical application in pain treatment
Compared with the normal saline (NS) group (Fig. 1B), we found a broad range of miRNA expression changes in the morphine treated (MT) spinal cord. miR-365 was one of the most robustly reduced of these miRNAs, and the expression levels of miR-365 were confirmed by qPCR (Fig. 1C). miR-365 expression was not altered on day 3 after morphine injection, on day 5 it began to decline (Fig. 1D), and these changes were consistent with development of morphine tolerance
Downregulation of miR-365 is involved in development of morphine tolerance, and exogenous overexpression of miR-365 alleviated morphine tolerance by targeting β-arrestin 2, a key component in MOR desensitization and endocytosis

Summary

Introduction

Morphine tolerance is a challenging clinical problem that limits its clinical application in pain treatment. Studies have reported that miRNAs are highly expressed in the CNS where opioid activity occurs,[23,24,25,26] and some are involved in morphine tolerance, such as fentanyl increased NeuroD protein level was mediated by miR1908. He et al.[10] have shown that the μopioid receptor (MOR) mRNA 3′-UTR has a binding site for let-7 and that let-7 could repress MOR expression in mice. Based on miRNA microarray profiling, miR-365 was robustly down-regulated in the spinal cord after chronic administration of morphine

Methods

Results

Conclusion