The present study focuses on the function of cpg15, a neurotrophic factor, in ischemic neuronal recovery using transient global cerebral ischemic (TGI) mouse model and oxygen-glucose deprivation (OGD)-treated primary cultured cells. The results showed that expression of cpg15 proteins in astrocytes, predominantly the soluble form, was significantly increased in mouse hippocampus after TGI and in the cultured astrocytes after OGD. Addition of the medium from the cpg15-overexpressed astrocytic culture into the OGD-treated hippocampal neuronal cultures reduces the neuronal injury, while the recovery of neurite outgrowths of OGD-injured neurons was prevented when cpg15 in the OGD-treated astrocytes was knocked down, or the OGD treated-astrocytic medium was immunoabsorbed by cpg15 antibody. Furthermore, lentivirus-delivered knocking down of cpg15 expression in mouse hippocampal astrocytes diminishes the dendritic branches and exacerbates injury of neurons in CA1 region after TGI. In addition, treatment with inhibitors of MEK1/2, PI3K, and TrkA decreases, while overexpression of p-CREB, but not dp-CREB, increases the expression of cpg15 in U118 or primary cultured astrocytes. Also, it is observed that the Flag-tagged soluble cpg15 from the astrocytes transfected with Flag-tagged cpg15-expressing plasmids adheres to the surface of neuronal bodies and the neurites. In conclusion, our results suggest that the soluble cpg15 from astrocytes induced by ischemia could ameliorate the recovery of the ischemic-injured hippocampal neurons via adhering to the surface of neurons. The up-regulated expression of cpg15 in astrocytes may be activated via MAPK and PI3K signal pathways, and regulation of CREB phosphorylation.
Any Conflict of Interest: None
We thank Ke Qiao from Key Laboratory of Medical Molecular Virology, Ministry of Education and Public Health, Shanghai Medical School, Fudan University for her excellent technique in the confocal microscopy. We thank Prof. Bing-Qiao Zhao, Professor Ping Zheng, PhD students Ping Yang, Jiao-Jiao Song, Da Shao and Jia-Lin Mo for their kind helps in the techniques of mouse brain ischemia and mouse stereotaxic injection. This work was supported by grants from the National Foundation of Natural Sciences of China (No.31571037, 30971464, 31370788), and the Shanghai Leading Academic Discipline Project (No. B111).