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

PLoS One. 2014 Jun 17;9(6):e99897. doi: 10.1371/journal.pone.0099897. eCollection 2014.

Abstract

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<3.2); and III) "normal aging" (N)--subjects without neuropathological AD (Braak ≤ II and CERAD 0 or A) and with normal cognitive function (CDR 0, IQCODE<3.2). Our results show that high levels of oxidative DNA damage are present in all groups. However, significant reductions in DNA repair and cell-cycle inhibition markers and increases in cell-cycle progression and cell death markers in subjects with CP-AD were detected when compared to both P-AD and N groups, whereas there were no significant differences in the studied markers between P-AD individuals and N subjects. This study indicates that, even in the setting of pathological AD, healthy cognition may be associated with a preserved repair to DNA damage, cell-cycle regulation, and cell death in post-mitotic neurons.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged, 80 and over
  • Alzheimer Disease / metabolism
  • Alzheimer Disease / pathology*
  • Apoptosis*
  • Cell Cycle
  • DNA Damage*
  • DNA Repair*
  • Female
  • Hippocampus / metabolism
  • Hippocampus / pathology
  • Humans
  • Male
  • Neurons / physiology*
  • Oxidative Stress
  • Tissue Array Analysis
  • Transcriptome

Grants and funding

This research is supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP - www.fapesp.br) grants 2011/01652-6, 2009/02030-9, 2009/01527-7. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.