Repair of oxidative DNA damage, cell-cycle regulation and neuronal death may influence the clinical manifestation of Alzheimer's disease

Alzheimer's disease (AD) is characterized by progressive cognitive decline associated with a featured neuropathology (neuritic plaques and neurofibrillary tangles). Several studies have implicated oxidative damage to DNA, DNA repair, and altered cell-cycle regulation in addition to cell death in AD post-mitotic neurons. However, there is a lack of studies that systematically assess those biological processes in patients with AD neuropathology but with no evidence of cognitive impairment. We evaluated markers of oxidative DNA damage (8-OHdG, H2AX), DNA repair (p53, BRCA1, PTEN), and cell-cycle (Cdk1, Cdk4, Cdk5, Cyclin B1, Cyclin D1, p27Kip1, phospho-Rb and E2F1) through immunohistochemistry and cell death through TUNEL in autopsy hippocampal tissue samples arrayed in a tissue microarray (TMA) composed of three groups: I) "clinical-pathological AD" (CP-AD)--subjects with neuropathological AD (Braak ≥ IV and CERAD = B or C) and clinical dementia (CDR ≥ 2, IQCODE>3.8); II) "pathological AD" (P-AD)--subjects with neuropathological AD (Braak ≥ IV and CERAD = B or C) and without cognitive impairment (CDR 0, IQCODE