Mechanisms Of Mitochondrial And Mitochondria-associated Endoplasmic Reticulum Membrane Structure And Function In Cognitive Dysfunction In Aging Rats

OBJECTIVE: To observe the effects of sevoflurane anesthesia on the structure and function of mitochondria and mitochondria-associated endoplasmic reticulum membranes(MAMs)in the hippocampal neurons of aged rats by establishing a model of cognitive dysfunction in aged SD rats,and to investigate the possible mechanisms of mitochondria and MAM structure and function abnormalities in cognitive dysfunction.To investigate the possible mechanisms of structural and functional abnormalities in cognitive dysfunction.METHODS: Thirty 18-month-old SPF SD rats were randomly divided into two groups:the model group(M group)and the blank control group(C group),15 rats in each group.The Morris water maze experiment was performed in each group of SD rats 6 d before and 1 d after modeling,and the evasion latency,swimming distance,the number of times crossing the platform within 60 s,and the distance and time of activity in the quadrant where the platform was located(quadrant 3)were recorded in each group.The total distance and average speed of the rats in the box were recorded in the open-field experiments on the 1st,3rd and 7th days after modeling.The activity of mitochondrial respiratory chain complexes(MRCC)I-IV was measured,and the amount of reactive oxygen species(ROS)produced by mitochondria was measured by immunofluorescence.monophosphate(AMP),phosphocreatine(PCr),and mitochondria and MAMs of aging brain hippocampal neuronal cells were observed by transmission electron microscopy.Results: 1.Animal behavioral test results:(1)Water maze experiment: 1d and 3d escape latency(El)and total swimming path(Sp)were prolonged in group M compared with group C after modeling(P<0.05);1d,3d and 7d quadrant activity path(Ap),time(Dwell time,Dt)and number of crossing platforms(Cn)were reduced in group M compared with group C after modeling(P<0.05).(Dwell time,Dt)and the number of crossing platforms(Cn)were reduced in group M compared with group C(P<0.05).The difference between the two groups decreased 7 d after modeling.(2)Open field experiment: the total distance and mean speed were reduced in group M compared with group C(P<0.05).2.MRCC test results showed that the vitality of MRCC Ⅰ-Ⅳdecreased in group M compared with group C at 1d,3d,and 7d after modeling.3.The results of immunofluorescence detection of ROS production: compared with group C,group M showed an increase in ROS production in hippocampal area cells after modeling.4.The results of high performance liquid chromatography showed that there was no statistical difference between group C and group M in PCr content 1d,3d and7 d after modeling(P>0.05),but group M showed an increasing trend in PCr content 1d and 3d after modeling.5.Transmission electron microscopy results showed that:(1)1day after modeling: organelles were abundant in group C cells,mitochondria were abundant and clear structure could be observed,most of the mitochondrial cristae were neatly arranged,no swelling and no vacuole generation;the structure of the rough endoplasmic reticulum was clear and more numerous,mitochondria were tightly connected to the endoplasmic reticulum,and the structure of MAMs was clear.Golgi apparatus and lysosomes could be seen.Compared with group C,the number of intracellular organelles in group M was reduced,and swollen and vacuolated mitochondria with reduced number were seen;the endoplasmic reticulum was enlarged and scattered,and the structure of MAMs was blurred.(2)3 days after modeling:Organelles were abundant in group C cells,mitochondria were abundant and clear structure could be observed,most of mitochondrial cristae were neatly arranged,no swelling,no vacuole generation,endoplasmic reticulum structure was clear and more numerous,MAMs structure was normal,Golgi apparatus,lysosomes and centrosomes were visible.The mitochondria were deformed and mildly swollen,and the mitochondrial cristae were partially broken and shortened.The rough endoplasmic reticulum was mildly dilated,the MAMs were blurred,and the Golgi vesicle membrane was slightly dilated.(The mitochondrial matrix was more uniform,and the mitochondrial cristae were mostly neat and a little shortened,with occasional mitochondrial vacuolization.Compared with group C,the organelles in the field of view of group M became confused and changed in shape,and it was difficult to distinguish organelle types.Some organelle fragments could be observed,mitochondria were enlarged and vacuolated,and mitochondrial cristae were broken,reduced,or even disappeared.The endoplasmic reticulum was mildly dilated and the number of ribosomal degranules on the endoplasmic reticulum was reduced.the structure of MAMs was disrupted,mitochondria were decoupled from the endoplasmic reticulum,a few lysosomes were visible,and the Golgi vesicle membrane was significantly dilated.CONCLUSIONS: Neuronal cells in the hippocampal region of aged rats with cognitive dysfunction showed impaired mitochondrial functional activity and energy metabolism,resulting in abnormal structural morphology of mitochondria and mitochondria-associated endoplasmic reticulum membranes,which are jointly involved in the development of cognitive dysfunction.