Effects Of Chronic Hypoxic Environment On Brain Aging At High Altitude

Objective:To investigate the effects of chronic hypoxic environment exposure at high altitude on brain aging in mice and the changes of related aging proteins and genes.Methods:Thirty SPF C57BL/6 male mice(about 6-8 weeks old)were randomly divided into high altitude group(4300m altitude,in Qinghai province maduo county and plain group(450m altitude,in Shaanxi province Xi’an City),each group had 15 mice.After feeding for 6 months,the rat brains were processed to make brain sections,and Nissl staining was performed to observe the morphological changes of mouse neurons,TUNEL staining was used to determine whether there was apoptosis in mouse neurons;transmission electron microscopy was used to observe the ultrastructure of mouse brain cells;RT-PCR and Western-blot were used to detect the expression changes of Caspase-3,Klotho,P16,P21,and P53 in mouse brain tissues at the gene and protein levels.Results:Compared with the plain group,the number of neuronal Nissl bodies in the hippocampus and cortex of mice in the high altitude group was significantly reduced(P<0.05).TUNEL staining showed that no apoptosis was found in the hippocampus of the plain group and the hippocampus of the cortex and high altitude groups,and apoptosis was only observed in the cortex of the high altitude area.Compared with the plain group,although neuronal apoptosis was observed in the hippocampus and cortex of mice in the high altitude group under electron microscope,there was no statistically significant difference.RT-PCR showed that compared with the plain group,Caspase-3 m RNA expression was distinctly increased(P<0.05),Klotho m RNA expression was significantly decreased(P<0.05),P16 m RNA,P21 m RNA,P53 m RNA expression was distinctly increased(P<0.05),in the cortical tissue of the high high altitude group;Caspase-3 m RNA expression was distinctly increased(P<0.05),P21 m RNA expression was distinctly increased(P<0.05),and P53 m RNA expression was significantly increased(P <0.05)in the hippocampal tissue.Western-blot revealed that Caspase-3 protein expression was distinctly increased(P<0.01),Klotho protein expression was significantly decreased(P<0.05),and P-P53 protein expression was significantly increased(P<0.01)in the hippocampus of the high altitude group compared with the plain group;Caspase3 protein expression was significantly increased(P<0.01);Klotho protein expression was significantly decreased(P<0.05);P16 protein expression was distinctly increased(P<0.05);and P-P53 protein expression was significantly increased(P<0.01).Conclusions:Chronic hypoxic environment at high altitude may accelerate the process of brain aging in mice.