Effects Of Antibodies And Natural Medicines On The Adhesion Of Target Cells On Extracellular Abeta42Matrix

Alzheimer’s disease (AD) is a kind of degenerative diseases of the centralnervous system based on cognitive dysfunction and memory impairment as the mainclinical features. Senile plaques (SPs) formed in the brain of patients by beta-amyloidprotein (Abeta) aggregate are believed to be the most important pathological features.More researches indicate that Abeta42tend to assmble each other to differentaggregates when it reaches a certain concentration in vivo. Abeta42monomer andother three Abeta42aggregates play a key role in the pathogenesis of AD. Accordingto the current study, the most neurotoxic form among Abeta42aggregates is Abeta42oligomers. However, the way of Abeta42aggregation, and the neurotoxicity mechanismof Abeta42has been unknown to date. Abeta42results from amyloid precursor protein(APP) by beta-secretase and gamma-secretases in vivo, thus the occurrence anddevelopment of AD must be a close relationship with APP. APP is a kind of type Itransmembrane protein with a membrane receptor-like structure. The currentresearches indicated that interactions can occur between the APP molecules to formdimers, also Abeta42is able to interact with APP to promote the accumulation of APP,but the specific binding sites for the interaction is unclear.First, in this thesis, Abeta42monomer and other three Abeta42aggregates wereprepared and confirmed by electron microscopy to verify their accuracy. In order toverify whether there is an interaction between APP and the Abeta42monomer andother three Abeta42aggregate, these Abeta42were coated as the matrix onto highbinding96-well plates. The African green monkey kidney cells COS7was used as themodel cell in this thesis. After added the cells expressing APP on the surface into the96-well plates already coated with Abeta42matrix, the number of adherent cells wasdetected by MTT. The results showed that the number of the adherent cells onAbeta42matrix in the transfected group was significantly higher than that in thenon-transfected group, which indicated that there are interactions between APP and Abeta42, the adhesion of the target cells on Abeta42matrix is mediated through theseinteractions, and the strength of the interaction between APP and Abeta42waspositively correlated with the concentrations of Abeta42.Second, the effects of our thirteen anti-Abeta42antibodies on the adhesion of thetarget cells on Abeta42matrix were analyzed. On the whole, all of the thirteenanti-Abeta42antibodies could inhibit the adhesion of target cells Abeta42matrix,which meant that these thirteen antibodies could inhibit the interactions between APPand Abeta42. Also different antibody had a different inhibitory effect on thisinteraction. Our researches showed that the inhibitory effects of these antibodies onthe interaction between APP and Abeta42not only through blocking the interactionregion of APP, but also through blocking some other molecules.Finally, we detected the influences of two kinds of natural medicine compoundsMH and MN (called A and B as followed) on the aggregation of Abeta42and theinteractions between APP and Abeta42. The results of the electron microscopyshowed that both the compounds A and B could inhibit the aggregation of the fourAbeta42forms and make Abeta42fibers depolymerization. Also, the compound Bcould inhibit the adhesion of transfected COS7cells on four matrix of Abeta42, but onthe Abeta42monomer, the compound A could do that only at higher concentration. Onthe other hand, the inhibitory effect of the compound A on the interaction betweenAPP and Abeta42oligomers was more powerful at the same concentration ofcompound A. In addition, the inhibitory effects of the compound B on interactionsbetween APP and four matrix of Abeta42seemed to be similar.The results in this thesis laid the foundation for the study of the interactionbetween APP and Abeta42, and provided a basis for the study of the pathogenesis ofAbeta42. In the AD treatment by immune therapy and natural medicine, analysis ofthe adhesion of the target cells on the extracellular matrix might be a convenient andeffective way to detect the effectiveness of antibodies and drugs.