Oxidative damage, protein synthesis, and protein degradation in Alzheimer's disease.

A large number of studies has firmly established that increases in oxidative damage occurs in Alzheimer's disease (AD). Such studies have demonstrated that increased in oxidative damage selectively occurs within the brain regions involved in regulating cognitive performance. Studies from our laboratory and others have provided experimental evidence that increased levels of oxidative damage occur in subjects with Mild Cognitive Impairment (MCI), which is believed to be one of the earliest stages of AD, and is a condition which is devoid of dementia or the extensive neurofibrillary pathology and neuritic plaque deposition observed in AD. Together, these data support a role for the accrual of oxidative damage potentially serving as an early event that then initiates the development of cognitive disturbances and pathological features observed in AD. Recent studies from our laboratory have demonstrated that a decline in protein synthesis capabilities occurs in the same brain regions which exhibit increased levels of oxidative damage in MCI and AD subjects. The focus of this review is to describe the large number of studies which suggest protein synthesis may be one of the earliest cellular processes disrupted by oxidative damage in AD. Taken together, these findings have important implications for understanding the molecular and cellular basis of AD, understanding the basis for oxidative stress in AD, and may have important implications for studies involving proteomics and proteolysis in AD.