1 Department of Biochemistry, School of Basic Courses, Guangdong Pharmaceutical University, Guangzhou 510006, China
2 Department of Obstetrics and Gynaecology, Wu Jing Zong Dui Hospital of Guangdong Province, Guangzhou 510507, China
3 Department of Pathology, Wu Jing Zong Dui Hospital of Guangdong Province, Guangzhou 510507, China
4 Department of Neurosurgery, Guangdong General Hospital, Guangzhou 510000, China
5 Institute of Cardiovascular Sciences, Peking University Health Science Center, Peking University, Beijing 100191, China

Abstract 

Objective 
To observe the change of the neuropeptide pro-protein processing system in the ischemic retina ganglion cell-5 (RGC-5) cells, pro-protein convertase-2 (PC2), carboxypeptidase-E (CPE) and preproneuropeptide Y (preproNPY) protein levels in the ischemic RGC-5 cells and conditioned medium were analyzed. 
Methods 
The RGC-5 cell was differentiated in 0.1 μmol/L staurosporine for 24 h and then stressed by different doses of oxygen and glucose deprivation (OGD). The acute or chronic OGD-induced cell death rates were obtained by using PI or TUNEL staining. The protein expression levels were determined by using the Western blot method and PC2 activity analysis. 
Results 
The ischemia caused substantial cell death in an OGD dose-dependent manner. In the cells, proPC2 and preproNPY protein levels gradually increased whereas proCPE gradually decreased. After OGD, PC2 activity was decreased. In the conditioned medium, proPC2 and PC2 proteins gradually decreased whereas proCPE, CPE, and preproNPY proteins gradually increased. 
Conclusion 
These Results demonstrated that OGD inhibited the neuropeptide pro-protein processing system by reducing PC2 activity and the maturation of proPC2. The aggregation of the pro-proteins and the increase of the active CPE excision adversely exacerbated the cell injury. The pro-protein processing system might play a critical role in the ischemic stress of RGC-5 cells.

Keywords

neuropeptide pro-protein processing system; retina ganglion cell-5; in vitro; oxygen and glucose deprivation; pro-protein convertase-2; carboxypeptidase-E; preproneuropeptide-Y

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