Effects Of "Physical-mental Exercise" On Spatial Cognition And Mitophagy-related Protein In Aging Mice

Obj ective:To investigate the effect of "physical-mental exercise" on the spatial memory,histological structure of hippocampus and morphology of mitochondria,and the mechanism of improving aging by regulating the mitophagy-related proteinMethods:48 female 18-month-old C57BL/6 mice are divided into old control group(OC),old physical exercise group(PE),mental exercise group(ME)and physical-mental exercise group(PME)by the random number table(n=12).12 female 3-month-old C57BL/6 mice are settled as young control group(YC).Y C and OC were fed in standard environment.PE,ME and PME were given corresponding treadmill training,enriched environment intervention or treadmill training combined with enriched environment intervention five times a week for eight weeks.Morris water maze is used to test the spatial memory of mice.HE staining is used to observe the pathological changes of hippocampal CA1 region in mice.Transmission electron microscope(TEM)is used to observe changes of cell ultrastructure and mitochondrial morphology in hippocampal C A1 region of mice Western Blot is used to detect the expression of Parkin,LC3 and p62 proteins in hippocampus of miceResults:1.Spatial memory of mice in each group(1)Place Navigation Test:the escape latency of each group is gradually shortened with different range.Compared with YC,the latency of OC is prolonged(P<0.05).Compared with OC,the escape latency of PE,ME and PME is shorter(P<0.05)(2)Spatial Probe Test:percentage of time in third quadrant of OC is shortened(P<0.05).Compared with OC,percentage of time in third quadrant of PE,ME and PME increased(P<0.05),and percentage of time in third quadrant of PME is longer than PE or ME(P<0.05)2.Histological structure of hippocampal CA1 region of mice in each group:the hippocampal CA1 area of YC is rich in neurons,with a large number,neat arrangement,compact structure and obvious staining.Compared with the YC,the number of neurons in OC has significantly reduced,with loose structure and disordered arrangement,abnormal cell morphology,shrinking nucleus with deepening staining,light and uneven staining of cellular stroma;Compared with the OC,the pathological manifestations of hippocampal C A1 region in PME is significantly improved.The number of neurons is obviously increased,the arrangement is more orderly,the cell structure is more complete,the boundary is clearer,and the phenomenon of nuclear shrink is reduced.The pathological manifestations of hippocampal CA1 region in PE has improved,with complete cell morphology,normal structure,neat arrangement and reduced neuron loss.The pathological changes in ME is slightly improved,but the effect is not obvious.The number and volume of neurons have decreased,the cell interval has increased,and the arrangement is looser3.Ultrastructure and mitochondrial structure of neurons in hippocampus C A1 region of mice in each group:neurons in hippocampal CA1 region of YC are normal in morphology and intact in structure.Nucleolus,nuclear membrane and chromatin can be observed with uniform distribution.Mitochondrial structure is complete.Most nerve cells in hippocampal CA1 region of OC mice are damaged,with incomplete structure,nuclear morphological changes and incomplete nuclear membrane.Mitochondria has decreased,contents are lost,mitochondrial cristae are fractured,and mitochondria are densely stained.Most cells in hippocampal CA1 region of PME have complete structure,better mitochondrial state and complete mitochondrial cristae.Mitochondria in some cells showed membrane damage.Mitochondria in some neurons in CA1 region of hippocampus of PE mice are damaged and dissolved,the contents are lost,and a small number of mitochondria is densely stained.In the ME,the neuronal structure in hippocampal CA1 region of mice is destroyed to varying degrees,the mitochondrial content of some cells has lost,and the mitochondrial cristae are broken4.Expression of Parkin,LC3 and p62 proteins in mice of each group:the expression of Parkin,LC3-Ⅱ,LC3-Ⅱ/Ⅰ and p62 proteins in Y C are basic level.Compared with the YC,the Parkin in OC decreased while the LC3-Ⅱ,LC3-Ⅱ/Ⅰ and p62 increased(P<0.05)Compared with the OC,the expressions of Parkin in PE,ME and PME are up-regulated and the expressions of LC3-Ⅱ,LC3-Ⅱ/Ⅰ and p62 are down-regulated(P<0.05).Compared with the PE and ME,the expression of Parkin in PME increased(P<0.05),and the expressions of LC3-Ⅱ,LC3-Ⅱ/Ⅰ and p62 decreased(P<0.05)Conclusions:1.The intervention of "physical-mental exercise" can improve the spatial memory ability of aging mice and improve the tissue structure as well as mitochondrial morphology of hippocampal CA1 region of mice.And the effect is better than only physical exercise or mental exercise2.The intervention of "physical-mental exercise" may moderately restore mitophagy function and improve mitochondrial ultrastructure by up-regulating the expression of Parkin and down-regulating the expression of LC3-Ⅱ,LC3-Ⅱ/Ⅰ and p62 and play the role of delaying aging.