Statins have been reported to lower the risk of developing Alzheimer's disease; however, the mechanism of this potentially important neuroprotective action is not understood. Lowering cholesterol levels does not appear to be the primary mechanism. Statins have pleiotropic effects in addition to lowering cholesterol, and statins may act on several different pathways involving distinct gene expression patterns that would be difficult to determine by focusing on a few genes or their products in a single study. In addition, gene expression patterns may be specific to a particular statin. To understand the molecular targets of statins in brain, DNA microarrays were used to identify gene expression patterns in the cerebral cortex of mice chronically treated with lovastatin, pravastatin, and simvastatin. Furthermore, brain statin levels were determined using liquid chromatography/tandem mass spectrometry. These studies revealed 15 genes involved in cell growth and signaling and trafficking that were similarly changed by all three statins. Overall, simvastatin had the greatest influence on expression as demonstrated by its ability to modify the expression of 23 genes in addition to those changed by all three drugs. Of particular interest was the expression of genes associated with apoptotic pathways that were altered by simvastatin. Reverse transcription-polymerase chain reaction experiments confirmed the microarray findings. All three drugs were detected in the cerebral cortex, and acute experiments revealed that statins are relatively rapidly removed from the brain. These results provide new insight into possible mechanisms for the potential efficacy of statins in reducing the risk of Alzheimer's disease and lay the foundation for future studies.

Statins are most commonly prescribed to reduce hypercholesterolemia; however, recent studies have shown that statins have additional benefits, including neuroprotection. Until now, the mechanism underlying statin-induced neuroprotection has been poorly understood. Recent in vivo studies from our lab reported the novel finding that simvastatin increased expression levels of a gene encoding for a major cell survival protein, bcl-2 [Johnson-Anuna et al., J. Pharmacol. Exp. Ther. 312 (2005) 786]. The purpose of the present experiments was to determine if simvastatin could protect neurons from excitotoxicity by altering Bcl-2 levels. Neurons were pre-treated with simvastatin and challenged with a compound known to reduce Bcl-2 levels and induce cell death. Simvastatin pre-treatment resulted in a significant reduction in cytotoxicity (lactate dehydrogenase release and caspase 3 activation) following challenge compared with unchallenged neurons. In addition, chronic simvastatin treatment significantly increased Bcl-2 mRNA and protein levels while challenge resulted in a significant reduction in Bcl-2 protein abundance. G3139, an antisense oligonucleotide directed against Bcl-2, abolished the protective effects of simvastatin and eliminated simvastatininduced up-regulation of Bcl-2 protein. These findings suggest that neuroprotection by simvastatin is dependent on the drug's previously unexplored and important effect of up-regulating Bcl-2.

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