Targeting miR-499-5p for neuroprotection in spinal cord injury: Implications for inflammation and ROS-induced neuronal damage.

Abstract

Spinal cord injury (SCI) leads to a cascade of secondary damage responses, including inflammation, apoptosis, and oxidative stress. These processes are crucial in determining the extent of tissue damage and recovery. It is well-established that various molecular mechanisms, such as the regulation of gene expression by non-coding RNAs, contribute significantly to the pathophysiology of SCI. However, the processes behind miRNA-regulated secondary damage are not entirely understood. The SCI mouse model and the cellular model were developed to investigate the effects of miRNAs during SCI. The GEO miRNA expression profile (GSE158195) was retrieved, and the differentially expressed miRNAs were examined using bioinformatics tools. Quantitative real-time polymerase chain reaction (qRT-PCR) was employed to assess the expression levels of miRNA and programmed cell death protein 4 (PDCD4). The Basso, Beattie, and Bresnahan (BBB) scoring system was used to assess neurological function. The concentrations of inflammatory cytokines were quantified via ELISA, whereas the production of reactive oxygen species (ROS) was assessed utilizing commercial kits. Our findings revealed a significant down-regulation of miR-499-5p in the spinal cord tissue of SCI mice. According to the functional study, agomir-miR-499 treatment significantly improved locomotor recovery, reduced tissue damage and edema, and suppressed neuronal death. Agomir-miR-499 also reduced SCI-induced ROS and inflammatory responses in mice. In SCI mice and cell models, miR-499 was discovered to target programmed cell death 4 and regulated its expression at protein and mRNA levels. Furthermore, increasing PDCD4 reversed agomir-miR-499's suppressive effects on the inflammatory response, ROS, and cell death. Agomir-miR-499, meanwhile, has the ability to suppress PDCD4 expression and stimulate the PI3K/AKT signaling pathway in SCI mice. Overall, our research shows that miR-499, a potential therapeutic target for SCI, reduces ROS-induced neuronal death and inflammation through PI3K/Akt signaling in SCI mice.