The Ischemic Stroke-Induced Neuronal Apoptosis is Mediated by RGMa and NKIRAS2 via Inflammatory Activation of Microglia

Background: The repulsive guidance molecule-a (RGMa) is associated with neuronal death after stroke. The nuclear factor kappa-B (NF-kappa B) inhibitor-interacting Ras-like protein 2 (NKIRAS2) is involved in regulating the NF-kappa B signaling pathway. Nonetheless, the effects of RGMa and NKIRAS2 on the progression of ischemic stroke are still unknown. Therefore, this study aims to explore the mechanism of action of RGMa and NKIRAS2 on ischemic stroke through in vivo and in vitro experiments. Methods: Highly aggressively proliferating immortalized (HAPI) microglia were stimulated with lipopolysaccharide (LPS) and oxygen-glucose deprivation/reperfusion (OGD/R) induced primary rat neurons. Small interfering RNA (siRNA)-RGMa and siRNA-NKIRAS2 were transfected to observe the effects of RGMa and NKIRAS2 on neuronal cell damage in vitro. Additionally, a rat model of middle cerebral artery occlusion and reperfusion (MCAO/R) was constructed and injected with short hairpin RNA (shRNA)-RGMa and sh-NKIRAS2 after reperfusion. Hematoxylin-eosin (H&E) staining was used to detect pathological changes in brain tissue, 2, 3, 5-triphenyltetrazolium chloride staining was used to evaluate cerebral infarction, and enzyme-linked immunosorbent assay was used to detect the level of inflammatory factors. Quantitative real-time polymerase chain reaction (qRT-PCR) and western blot were used to detect mRNA and protein levels, flow cytometry was used to detect apoptosis, and immunofluorescence was used to identify primary rat neurons. Finally, a cell counting kit-8 (CCK-8) reagent was used to determine primary rat neuron cell viability. Results: Cell experiments showed that siRNA-RGMa decreased the expression level of NF-kappa B pathway-related proteins and the secretion of inflammatory factors in HAPI microglia (p < 0.05). After OGD/R treatment, the conditioned medium supplemented with LPS and siRNA-RGMa stimulated HAPI microglia, significantly improving the activity of neuronal cells and inhibiting the apoptosis level and inflammatory response of neuronal cells (p < 0.05). These effects were eliminated by siRNA-NKIRAS2 (p < 0.05). The animal experiments showed that adenovirus (Ad)-sh-RGMa alleviated the damage of nerve function in MCAO/R rats, significantly improving neuronal injury, cerebral infarction size, inhibiting the secretion of inflammatory cytokines, microglia p65 nuclear ectopic, apoptosis gene and protein levels in brain tissue (p < 0.05). These effects can be reversed by Ad-sh-NKIRAS2 (p < 0.05). Conclusions: The development of ischemic stroke could be alleviated by silencing RGMa and elevating NKIRAS2, indicating that both RGMa and NKIRAS2 could be potential therapeutic targets for ischemic stroke.