Vitamin E paradox in Alzheimer's disease: it does not prevent loss of cognition and may even be detrimental.

There is controversy as to whether vitamin E is beneficial in Alzheimer's disease (AD). In this study, we tested if vitamin E prevents oxidative stress and loss of cognition in AD. Fifty-seven AD patients were recruited and divided in two groups: placebo or treated with 800 IU of vitamin E per day for six months. Of these 57 patients, only 33 finished the study. We measured blood oxidized glutathione (GSSG) and used the following cognitive tests: Mini-Mental State Examination, Blessed-Dementia Scale, and Clock Drawing Test. Of those patients treated with vitamin E, we found two groups. In the first group, "respondents" to vitamin E, GSSG levels were lower after the treatment and scores on the cognitive tests were maintained. The second group, "non-respondents", consisted of patients in which vitamin E was not effective in preventing oxidative stress. In these patients, cognition decreased sharply, to levels even lower than those of patients taking placebo. Based on our findings, it appears that vitamin E lowers oxidative stress in some AD patients and maintains cognitive status, however, in those in which vitamin E does not prevent oxidative stress, it is detrimental in terms of cognition. Therefore, supplementation of AD patients with vitamin E cannot be recommended without determination of its antioxidant effect in each patient.

Gender and age-dependent differences in the mitochondrial apoptogenic pathway in Alzheimer's disease.

Age-related mitochondrial oxidative stress is highly gender dependent. The aim of this study was to determine the role of gender in the mitochondrial contribution to neuronal apoptosis in Alzheimer's disease (AD). We used mitochondria isolated from brains of Wistar rats to study the toxicity of ss-amyloid peptide (Ass), and found that it increases mitochondrial peroxide production, nitration and oxidation of proteins, and release of cytochrome c. The toxic effects occurred in young males and in old females but not in young females, indicating their resistance to Ass. This resistance was abolished with age. These toxic effects of Ass were prevented by heme. Our findings provide a molecular mechanism for the contribution of Abeta to the mitochondrial dysfunction and oxidative stress seen in AD, as well as for the mitochondria-dependent pathway of apoptosis in AD. Gender and age-related differences seen in the development of AD can also be partially explained.

The depletion of nuclear glutathione impairs cell proliferation in 3t3 fibroblasts.

BACKGROUND: Glutathione is considered essential for survival in mammalian cells and yeast but not in prokaryotic cells. The presence of a nuclear pool of glutathione has been demonstrated but its role in cellular proliferation and differentiation is still a matter of debate. PRINCIPAL FINDINGS: We have studied proliferation of 3T3 fibroblasts for a period of 5 days. Cells were treated with two well known depleting agents, diethyl maleate (DEM) and buthionine sulfoximine (BSO), and the cellular and nuclear glutathione levels were assessed by analytical and confocal microscopic techniques, respectively. Both agents decreased total cellular glutathione although depletion by BSO was more sustained. However, the nuclear glutathione pool resisted depletion by BSO but not with DEM. Interestingly, cell proliferation was impaired by DEM, but not by BSO. Treating the cells simultaneously with DEM and with glutathione ethyl ester to restore intracellular GSH levels completely prevented the effects of DEM on cell proliferation. CONCLUSIONS: Our results demonstrate the importance of nuclear glutathione in the control of cell proliferation in 3T3 fibroblasts and suggest that a reduced nuclear environment is necessary for cells to progress in the cell cycle.