The Role And Mechanism Of Nogo-A/RhoA/ROCK In The Regulation Of Angiogenesis In PDMCI Mice

Objective: The incidence of mild cognitive impairment in Parkinson’s disease(PDMCI)is as high as 18%-55%.However,the pathological mechanism of PDMCI is not yet clear.Previous research showed that microvascular pathology and chronic cerebral hypoperfusion(CHH)synergistically participated in the occurrence and development of PD-MCI.It has proved that Nogo-A could be used as a negative regulator to participate in the regeneration of microvascular in the central nervous system.Therefore,we speculated that Nogo-A might be involved in the negative regulation of PDMCI angiogenesis.The aim of this study was to test whether Nogo-A participates in the regulation of microvascular injury and angiogenesis in PDMCI mice and the related mechanisms of the regulation of cognitive function of PDMCI.This study aims to clarify the regulatory role and mechanism of Nogo-A in the microvascular injury of PDMCI mice,so as to provide reliable evidence for the prevention and treatment of PDMCI.Methods: In this study,C57BL/6J mice were injected with shRNA-Nogo-A into the lateral ventricle and were then intraperitoneally injected with a combination of1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP)and probenecid.Subjects were classified into the following seven groups based on the Morris water maze(MWM)test: control,CON+shRNA-GFP,CON+shRNA-Nogo-A,cognitive normal in Parkinson’s disease(PDCN),PDMCI,PDCN+shRNA-Nogo-A,and PDMCI+shRNA-Nogo-A.Further,Evens blue(EB)permeability,fluorescein isothiocyanate(FITC)-conjugated dextran,transmission electron microscopy,immunofluorescence and Western blot(WB)analyses were performed.Results:(1)The result of Morris water maze test showed that,compared with the Control group,the PDCN and PDMCI groups had significant impairment of spatial cognition and memory(P<0.05).In addition,with the low expression of Nogo-A,the cognitive impairment of PDMCI+shRNA-Nogo-A was less severe than that of the PDMCI group,which was manifested in shorter escape latency,longer duration of target quadrant and more frequence crossing the platform(P<0.05).(2)The results of the leakage of EB,FITC-dextran staining and transmission electron microscopy showed that in the PDCN and PDMCI groups,there were significant decreases in microvascular density and obvious impairment in vascular endothelial and blood-brain barrier,and the damage was more serious in the PDMCI group(P<0.05 vs Control).PDCN+shRNA-Nogo-A group had less damage than PDCN group,and PDMCI+shRNA-Nogo-A group had also less damage than PDMCI group(P<0.05).(3)The results of immunofluorescence and WB of CD34 and VEGF showed that compared with the Control group,the expressions in the PDMCI and PDCN groups were significantly decreased(P<0.05).(4)The expressions of Nogo-A,S1PR2,RhoA,ROCK proteins in the PDCN,PDMCI groups were significantly increased than that in the Control group(P<0.05).With the downregulation of Nogo-A,the expressions of S1PR2,RhoA and ROCK proteins significantly decreased in the PDCN+shRNA-Nogo-A group than that in the PDCN group,and they were also lower in the PDMCI+shRNA-Nogo-A group than that the PDMCI group(P<0.05).Conclusion: The injection of MPTP leaded to the impairment of cognition and microvascular.The combination of Nogo-A and S1PR2 can subsequently activate RhoA/ROCK signaling pathways,eventually leading to the inhibition of microvascular remodeling in PDMCI mice.This study indicated that down-regulation of Nogo-A could improve the cognition of PDMCI,decrease the damage of BBB and microvascular,and mediate microvascular angiogenesis,which provided a new opportunity for understanding the pathogenesis of PDMCI.