The Role of Lipoproteins/Cholesterol in Genomic Instability and Chromosome Mis-segregation in Alzheimer's and Cardiovascular Disease

Several lines of evidence link Alzheimer’s disease (AD) to atherosclerosis (CVD), including that elevated low density lipoprotein (LDL)-cholesterol is a common risk factor. Development of genomic instability could also link the two diseases. Previous fluorescence in situ hybridization (FISH) analyses revealed a clonal expansion of aneuploid smooth muscle cells underlying atherosclerotic plaques. Likewise, cellular and mouse models of AD revealed tau-dependent mitotic defects and subsequent aneuploidy partly resulting from amyloid-beta (Aβ) interference with microtubule (MT) stability, and specific MT motors function. Moreover, AD patients develop aneuploid/hyperploid cells in brain and peripheral tissues, implicating similar mechanism that may lead to apoptosis and neurodegeneration.;This dissertation tested the hypothesis that elevated lipoproteins and cholesterol may contribute to genomic instability in AD and CVD and showed that: (1) treatment with oxidized LDL (OX-LDL), LDL and water soluble cholesterol, but not high density lipoprotein (HDL), induced chromosome mis-segregation, including trisomy and tetrasomy 12, 21, and 7 in human epithelial cells (h-TERT-HME1), primary aortic smooth muscle cells, fibroblasts, mouse splenocytes and neural precursors; (2) LDL-induced aneuploidy may depend on a functional LDL receptor (LDLR), but not amyloid precursor protein (APP) gene; (3) fibroblasts and brain cells of patient with the mutation in the Niemann-Pick C1 gene (NPC1) characterized by impaired intracellular cholesterol trafficking and changed intracellular cholesterol distribution harbored trisomy 21 cells; (4) young wild-type mice fed high and low cholesterol diets developed aneuploidy in spleen but not in brain cells within 12 weeks; (5) like with the studies on Aβ-induced aneuploidy, calcium (Ca2+) chelation reduced OX-LDL and LDL-mediated chromosomal instability; and (6) altering plasma membrane fluidity with ethanol attenuated OX-LDL and LDL-induced aneuploidy.;These results suggest a novel biological mechanism by which disrupted cholesterol homeostasis may promote both atherosclerosis and AD by inducing chromosome mis-segregation and development of aneuploid cells. Understanding the cause and consequence of chromosomal instability as a common pathological trait in AD and CVD may be beneficial to designing therapies relevant for both diseases.