Estrogen receptor-mediated neuroprotection: The role of the Alzheimer's disease-related gene seladin-1.

Experimental evidence supports a protective role of estrogen in the brain. According to the fact that Alzheimer's disease (AD) is more common in postmenopausal women, estrogen treatment has been proposed. However, there is no general consensus on the beneficial effect of estrogen or selective estrogen receptor modulators in preventing or treating AD. It has to be said that several factors may markedly affect the efficacy of the treatment. A few years ago, the seladin-1 gene (for selective Alzheimer's disease indicator-1) has been isolated and found to be down-regulated in brain regions affected by AD. Seladin-1 has been found to be identical to the gene encoding the enzyme 3-beta-hydroxysterol delta-24-reductase, involved in the cholesterol biosynthetic pathway, which confers protection against beta-amyloid-mediated toxicity and from oxidative stress, and is an effective inhibitor of caspase-3 activity, a key mediator of apoptosis. Interestingly, we found earlier that the expression of this gene is up-regulated by estrogen. Furthermore, our very recent data support the hypothesis that seladin-1 is a mediator of the neuroprotective effects of estrogen. This review will summarize the current knowledge regarding the neuroprotective effects of seladin-1 and the relationship between this protein and estrogen.