Perioperative stress prolong post-surgical pain via miR-339-5p targeting oprm1 in the amygdala

Background: The decreased expression of mu-opioid receptors (MOR) in the amygdala may be a key molecular in chronic post-surgical pain (CPSP). It is known that miR-339-5p expression in the amygdala of a stressed rat model was increased. Analyzed by RNAhybrid, miR-339-5p could target opioid receptor mu 1 (oprm1) which codes MOR directly. So, the authors hypothesized that miR-339-5p could regulate the expression of MOR via targeting oprm1 and cause the effects to CPSP. Methods: To simulate perioperative short-term stress, a perioperative stress prolongs incision-induced pain hypersensitivity without changing basal pain perception rat model was built. A pmiR-RB-REPORT (TM) dual luciferase assay was taken to verify whether miR-339-5p could act on oprm1 as a target. The serum glucocorticoid level of rats was test. Differential expressions of MOR, GFAP, and pERK1/2 in each group of the rats' amygdala were tested, and the expressions of miR-339-5p in each group of rats' amygdalas were also measured. Results: Perioperative stress prolonged the recovery time of incision pain. The expression of MOR was down-regulated in the amygdala of rats in stress + incision (S + IN) group significantly compared with other groups (P < 0.050). miR-339-5p was up-regulated in the amygdala of rats in group S + IN significantly compared with other groups (P < 0.050). miR-339-5p acts on oprm1 3'UTR and take MOR mRNA as a target. Conclusions: Perioperative stress could increase the expression of miR-339-5p, and miR-339-5p could cause the expression of MOR to decrease via targeting oprm1. This regulatory pathway maybe an important molecular mechanism of CPSP.

Automated summary

This study investigated the effects of perioperative stress on MOR and its mechanism, and found that miR-339-5p down-regulated MOR expression by targeting oprm1. This finding is of great significance for understanding the molecular mechanism of chronic postoperative pain.