The Study Of Restoring Spinal Cord Injury By Inhibiting MAPK/ERK Signaling Pathway With U0126

Purpose Spinal cord injury(SCI) is an injury that the axons of the nerve cells has been disrupted with either temporary or permanent, devastating neurological outcomes in the cord's normal motor, sensory, or autonomic function. And most research were aimed at reducing the devastated effects of injury and promoting regrowth of functional nerve fibers. The Ras/Raf/ERK1/2 signaling pathway play important roles in central and peripheral neurons such as dendritic arborization, neuronal polarity and axon assembly. Emerging evidence also points to that up-regulation of this signaling pathway may lead to the development of spinal cord injury. Hence,we sought to clarify the role of the Ras/Raf/ERK1/2 signaling pathway in spine cord injury by establish spine cord injury mouse model and the spine cord injury cell model to investigate how the Ras/Raf/ERK1/2 inhibitor U0126 restoring the spinal cord injury neurons in vivo and in vitro.Method First,SCI neurons were come from the SCI model C57BL/6J mouse one week later which was developed with NYU Impactor-?machine with 10g×5mm weight drop and Sham-operated neurons(Sham neurons) were come from one day old C57BL/6J mouse.Electron microscope and immunofluorescence were used to identify our cell model, western blotting, cell adhesion assay and cell migration assay as well as Di L labeling were employed to investigate the effective of inhibit the Ras/Raf/ERK1/2 pathways in SCI neurons.Then, four weeks C57BL/6J mouse were prepared, SCI mouse model was developed with NYU Impactor- ? machine, then grouped them: Sham operation group(simple laminectomy, DMSO injection,A group) and control group(spinal cord injury group, DMSO injection, B group) and experimental group(spinal cord injury group U0126 injection, C group). BMS was used to score the mouse hind limb function recovery after spinal cord injury were evaluated and the expression of neuronal cell specific markers of NF200 and astrocyte specific marker GFAP were assayed using immunohistochemistry staining method.Result In this study, the electron microscope results of the motoneurons morphology and immunofluorescence results of the synapses formation was indicated that our spinal cord injured neurons was established. The immunofluorescence staining showed that Synaptophsin, VGLUT1 and VGAT staining were significantly reduced in the SCI neurons than those in the Sham neurons(P < 0.05), the difference was statistically significant. The western blot results identified that the phosphorylation of Erk in SCI neurons was up-regulated and U0126 could inhibit the phosphorylation of Erk, which is the downstream kinases of Ras/Raf signaling. Cell migration assay showed that the migration ability of cells was significantly increased in the SCI group(P < 0.05), while the cell adhesion ability was decreased(P < 0.05). While after inhibition the Ras/Raf/ERK1/2 signaling, the cell migration and adhesion ability was also significantly increased in SCI neurons(P < 0.05). The Di L labeling results also showed that after spinal cord injury, the dendritic spine density was significantly decreased(P < 0.05), and the formation of mature spines was significantly increased after inhibition the Ras/Raf/ERK1/2 signaling(P < 0.05), the difference was statistically significant.Our BMS score result showed that 7 day after the spinal cord injury with Mek inhibitor U0216 injection group,the BMS score was higher than the control group(P<0.05).Immunohistochemical staining results showed that a large number of NF-200 positive staining cells expressed around the center of the spinal cord injury site, the NF-200 positive cells staining IOD number was higher in C group than B group, the difference is statistically insignificant(P=0.041). A large number of GFAP positive staining cells expressed around the center of the spinal cord injury site,GFAP positive staining in C group and A group has significantly differences(P=0.030).Conclusion The results showed that inhibiting the Ras/Raf/ERK1/2 pathway by U0216 could restore the spinal cord injury by promoting the neuron cell migration and adhesion capacity as well as increasing the density of the neuronal dendritic spine. And the activation of Ras/Raf/ERK1/2 signaling pathway involved in the process of spinal cord injury and the scar formation after injury. U0126 could reduce the apoptosis of spinal cord injury neurons and reduce the formation of glial scar. These results indicated that the Ras/Raf/ERK1/2 signaling pathways may be an effective target for restoring SCI.