Abstract
BackgroundIschemia-reperfusion (IR) affects microRNA (miR) expression and causes substantial inflammation. Multiple roles of the tumor suppressor miR-129-5p in cerebral IR have recently been reported, but its functions in the spinal cord are unclear. Here, we investigated the role of miR-129-5p after spinal cord IR, particularly in regulating high-mobility group box-1 (HMGB1) and the Toll-like receptor (TLR)-3 pathway.MethodsIschemia was induced via 5-min occlusion of the aortic arch. The relationship between miR-129-5p and HMGB1 was elucidated via RT-PCR, western blotting, and luciferase assays. The cellular distribution of HMGB1 was determined via double immunofluorescence. The effect of miR-129-5p on the expression of HMGB1, TLR3, and downstream cytokines was evaluated using synthetic miRs, rHMGB1, and the TLR3 agonist Poly(I:C). Blood-spinal cord barrier (BSCB) permeability was examined by measuring Evans blue (EB) dye extravasation and the water content.ResultsThe temporal miR-129-5p and HMGB1 expression profiles and luciferase assay results indicated that miR-129-5p targeted HMGB1. Compared with the Sham group, the IR group had higher HMGB1 immunoreactivity, which was primarily distributed in neurons and microglia. Intrathecal injection of the miR-129-5p mimic significantly decreased the HMGB1, TLR3, interleukin (IL)-1β and tumor necrosis factor (TNF)-α levels and the double-labeled cell count 48 h post-surgery, whereas rHMGB1 and Poly(I:C) reversed these effects. Injection of miR-129-5p mimic preserved motor function and prevented BSCB leakage based on increased Basso Mouse Scale scores and decreased EB extravasation and water content, whereas injection rHMGB1 and Poly(I:C) aggravated these injuries.ConclusionsIncreasing miR-129-5p levels protect against IR by ameliorating inflammation-induced neuronal and BCSB damage by inhibiting HMGB1 and TLR3-associated cytokines.
Highlights
Ischemia-reperfusion (IR) affects microRNA expression and causes substantial inflammation
We have demonstrated that activation of the TLR4-mediated nuclear factor-kappa B (NF-κB)/interleukin (IL)-1β positive feedback loop promotes substantial inflammatory damage to neurons and the blood-spinal cord barrier (BSCB) after spinal cord IR [5]
Temporal expression of miR-129-5p and high-mobility group box-1 (HMGB1) after IR The IR-induced changes in the miR-129-5p and HMGB1 expression levels were examined at 12-h intervals for 48 h post-surgery. miR-129-5p expression was obviously downregulated with time and reached its lowest levels at both 12 and 48 h after IR compared with the levels in the sham surgery group (Fig. 2a, P < 0.05)
Summary
Ischemia-reperfusion (IR) affects microRNA (miR) expression and causes substantial inflammation. Multiple roles of the tumor suppressor miR-129-5p in cerebral IR have recently been reported, but its functions in the spinal cord are unclear. We investigated the role of miR-129-5p after spinal cord IR, in regulating high-mobility group box-1 (HMGB1) and the Toll-like receptor (TLR)-3 pathway. Spinal cord ischemia-reperfusion (IR) injury is a severe but unpredictable and unpreventable complication that commonly occurs during thoracoabdominal aortic surgery. Previous studies have shown that increases in microglia and upregulation of Toll-like receptors (TLRs) are associated with proinflammatory cytokine release through recognition of damage-associated molecular pattern molecules (DAMPs) during spinal cord ischemia [4, 5]. Treatments that regulate the interactions between TLRs and HMGB1 may be used as novel therapeutic approaches for spinal cord IR injury
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