Objectives: Neuropathic pain (NP) is one of the main challenges towards NP syndrome treatment. miR-340-5p exhibit different expression levels in NP models. Its effects on NP remained unclear. The objective of this study was to explore the potential regulation mechanisms of miR-340-5p in NP.
Methods: Rat model of chronic constriction injury (CCI) was established to induce NP in vivo. NP levels were assessed using mechanical withdrawal threshold (MWT). The inflammation response in CCI rats were determined by HE staining and ELISA assay. The target genes of miR-340-5p were verified by luciferase report assays.
Results: In CCI rats, level of miR-340-5p was down-regulated both in spinal cord tissues and isolated microglial cells. Paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) were decreased in CCI rats, which were restored upon miR-340-5p overexpression. miR-340-5p overexpression also decreased inflammation as well as expression levels of COX-2, IL-1β, TNF-α and IL-6 in CCI rats. Luciferase report assays revealed Rap1A was a target gene of miR-340-5p in the experimental model. Elevated miR-340-5p decreased Rap1A expression level in vitro and in vivo. Overexpression of Rap1A protein restored expression levels of COX-2, IL-1β, TNF-α and IL-6, reduced the PWT and PWL and increased inflammation response in CCI rats.
Conclusion: miR-340-5p alleviated CCI-induced NP by targeting Rap1A. miR-340-5p and Rap1A may be the potential treatment targets for NP therapeutics.
Keywords: Chronic constriction injury; MiR-340-5p, Rap1A; Neuropathic pain.