ABSTRACT
OBJECTIVE: The aim of this study was to investigate the effects of miR-92b-5p inhibitor and interleukin-18-binding protein (IL-18BP) on interleukin-18 (IL-18)-mediated inflammatory response after spinal cord injury (SCI). MATERIALS AND METHODS: In this work, microglia was isolated from the newborn C57/B6J mice spinal cord to in vitro culture. The expression of IL-18BP and IL-18 was measured by the quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) after transfection of miR-92b-5p into activated microglia. The expression of IL-18BP and IL-18 was determined following miR-92b-5p inhibitor treatment. In addition, the spinal cord injury model was established in mice. The expressions of miR-92b-5p, IL-18BP, and IL-18 were measured by qRT-PCR, and the expressions of inducible nitric oxide synthase (iNOS), tumor necrosis factor (TNF-α) and interleukin-1 ß (IL-1 ß) were determined by Western blot. After intrathecal injection of miR-92b-5p inhibitor, the mRNA expression of miR-92b-5p, IL-18BP, and IL-18 and the expression of iNOS, TNF-α, and IL-1 ß in the injured area of the spinal cord of mice were measured. Basso Mouse Scale (BMS) was used to determine the recovery of locomotor function after spinal cord injury and miR-92b-5p inhibition. RESULTS: After miR-92b-5p transfection, the expression of IL-18BP was significantly decreased compared with that of untransfected microglia cells, whereas the level of IL-18 mRNA was significantly increased. However, the level of IL-18BP elevated significantly and the level of IL-18 reduced markedly after treatment with corresponding inhibitors. In addition, compared with the sham operation group (Sham), the RNA level of miR-92b-5p in the SCI group was significantly higher than that in the Sham, but the expression of IL-18BP was evidently declined and the expression of IL-18 was significantly increased in the SCI group. Meanwhile, the expression of miR-92b-5p in miR-92b-5p inhibitor intrathecal injection mice was remarkably lower than that in SCI group, the expression level of IL-18BP was significantly increased, and the RNA expression of IL-18 was weakened accordingly. Moreover, the protein expression of iNOS, TNF-α, and IL-1 ß in miR-92b-5p inhibitor-treated mice was significantly lower than that in the SCI group. The locomotor evaluation of miR-92b-5p inhibitor group was dramatically higher than that of the SCI group. CONCLUSIONS: Suppressing the expression of miR-92b-5p after SCI can effectively intensify the level of IL-18BP, reduce the expanded inflammatory effect of IL-18, decline the release of iNOS, TNF-α, and IL-1 ß, thus alleviate the neuronal injury and improve the locomotor function after SCI.
Subject(s)
Intercellular Signaling Peptides and Proteins/metabolism , Interleukin-18/metabolism , MicroRNAs/genetics , Microglia/immunology , Spinal Cord Injuries/immunology , Spinal Cord/immunology , Animals , Cells, Cultured , Disease Models, Animal , Intercellular Signaling Peptides and Proteins/genetics , Interleukin-18/genetics , Male , Mice, Inbred C57BL , MicroRNAs/antagonists & inhibitors , Microglia/metabolism , Motor Activity/genetics , Primary Cell Culture , Spinal Cord/metabolism , Spinal Cord Injuries/genetics , Spinal Cord Injuries/metabolism , TransfectionABSTRACT
OBJECTIVE: The aim of this study was to explore the specific role of miR-219-5p in spinal cord injury (SCI), and to investigate its underlying mechanism. MATERIALS AND METHODS: The SCI model was first constructed in mice, and the motor function of each mouse was evaluated by the Basso Beattie Bresnahan (BBB) method. The protein and mRNA expression levels of miR-219-5p and NEUROD2 in SCI mice were detected by Western blot and quantitative Real Time-Polymerase Chain Reaction (qRT-PCR), respectively. Subsequently, all mice were assigned into 3 groups, including the sham operation group, the SCI group and the SCI+miR-219-5p group. The levels of inflammatory factors (TNF-α, IL-1ß and IL-6) were detected by Western blot and qRT-PCR. Meanwhile, reactive oxygen species (ROS) were detected by flow cytometry. Target genes of miR-219-5p were predicted by TargetScan and verified by Luciferase reporter gene assay. For in vitro experiments, the possible molecule mechanism of miR-219-5p in regulating NEUROD2 was detected by Western blot. RESULTS: MiR-219-5p was significantly downregulated after SCI. The expression level of miR-219-5p was decreased in the SCI group than that of the sham operation group in a time-dependent manner, which reached the lowest level on the 7th day. Besides, the mRNA and protein levels of NEUROD2 in the SCI group were both remarkably increased in a time-dependent manner, which reached a peak on the 7th day. The levels of inflammatory factors (TNF-α, IL-1ß and IL-6) and ROS were significantly higher in the SCI group, which could be reversed by miR-219-5p mimics transfection in SCI mice. Meanwhile, the BBB score in the SCI group was remarkably lower than that of the SCI + miR-219-5p group from the 4th day after SCI. TargetScan predicted that NEUROD2 was the target gene of miRNA-219-5p. In addition, Western blot results indicated that miR-219-5p could regulate NEUROD2, eventually promoting the recovery of SCI. CONCLUSIONS: Overexpressed miR-219-5p promotes SCI recovery and motor function elevation via alleviating NEUROD2-regulated inflammation and oxidative stress.