Study On The Relationship Among Oxidative Stress,mitochondrial DNA Mutation And The Development Of Alzheimer's Disease

Recently, more and more attentions were paid on the theory of oxidative damages in developments of neurodegenerative diseases such as Alzheimer's disease (AD). The mitochondria is the mainly place which produce oxygen free radicals in cells. There are about 90% oxygen consumed in the mitochondria in body. Therefore, the oxidative attacks in AD might be related to the damages of mitochondria. Lots of changes of mitochondrial enzymes and mitochondrial DNA were found in the patients with AD and other neurodegenerative diseases. However, controversies concerned with the relationship between the mitochondrial oxidative damages and the development of AD are still continued. In order to explore the relationship among the mitochondrial DNA,oxidative stress and the development of AD, we undertake corresponding experiments as followed: (l)The bioinformatics analysis of mitochondrial DNA which encode cytochrome C oxidase subunit II (CO2) were made in 16 primates.(2)The pholymorphic fragment and the sequencing of CO2 gene were analyzed in the patients with AD.(3)The antimycin A,which can improve the productions of free radicals in mitochondria,and the neurotoxic A P (1-42) piptides were used to deal with the PC 12 cells.The cells were analyzed in many aspect, including mitochondrial membrane potential assay.MTT analysis,enzyme activity determination and the expression analysis of some genes concerned about mitochondria. (4)The representational difference analysis(RDA) method was used to seek new DNA fragments that are sensitive to the extraneous free radicals.The result as followed: (l)There was accompanying the decline of oxidative stress during the course of the evolution in primates. (2) Compared with the normals, the amount of the mitochondrial DNA were decreased universally in the patients with AD. There also exist many different kinds of mutations (include point mutations, deletions and rearrangements) in the patients with AD.(3) The more production of reactive oxyge^ species wouldcause the changes of mitochondrial membrane potential and lead to the apoptosis of cells.(4) The antimycin A could affect the activity of cytochrome C oxidase by inducing the production of reactive oxygen species in mitochondria.(5) A P (1-42) might stimulate the production of reactive oxygen species in mitochondria indirectly.lt also can alter the activity of various antioxidantive enemzy and their mRNA levels. (6) A 3 (1-42) might increase the production of intrinsic free radical and decrease the expression of APP770.(7) Compared with the mitochondrial DNA,some DNA fragment on genome may be more sensitive to the oxidative damages induced byHA.We also have gained some new findings during our experiments: (l):Two new mutations were found in a patient with AD firstly. The natural and mutational CO2 genes coexist in a patient with AD. (2): A new rejoint fragment of deletional CO2 gene was found in a patient with AD firstly. (3): Three new genome DNA fragments were discovered and logged on Genbank.We also found a new genome DNA fragment, which named POX,is sensitive to extrinsic oxidative stress. The POX contains a new SnoRNA gene .The POX is sensitive to the A ?(1-42) and a -TNF.