Environmental enrichment stimulates neurogenesis in apolipoprotein E3 and neuronal apoptosis in apolipoprotein E4 transgenic mice
Article first published online: 21 AUG 2006
Journal of Neurochemistry
Volume 100, Issue 1, pages 202–210, January 2007
How to Cite
Levi, O. and Michaelson, D. M. (2007), Environmental enrichment stimulates neurogenesis in apolipoprotein E3 and neuronal apoptosis in apolipoprotein E4 transgenic mice. Journal of Neurochemistry, 100: 202–210. doi: 10.1111/j.1471-4159.2006.04189.x
- Issue published online: 21 AUG 2006
- Article first published online: 21 AUG 2006
- Received May 24, 2006; revised manuscript received July 26, 2006; accepted August 7, 2006.
- apolipoprotein E4;
- caspase 3;
- environmental stimulation;
Neurodegeneration in Alzheimer's disease (AD) is associated with the activation of neurogenesis. The mechanisms underlying this crosstalk between neuronal death and birth and the extent to which it is affected by genetic risk factors of AD are not known. We employed transgenic mice expressing human apolipoprotein E4 (apoE4), the most prevalent genetic risk factor for AD, or expressing human apoE3 (an AD-benign allele), in order to examine the hypothesis that apoE4 tilts the balance between neurogenesis and neuronal cell death in favor of the latter. The results showed an isoform-specific increase in neurogenesis in the hippocampal dentate gyrus (DG) under standard conditions in apoE4-transgenic mice. Environmental stimulation, which increases neurogenesis in the DG of apoE3-transgenic and wild-type mice, had the opposite effect on the apoE4 mice, where it triggered apoptosis while decreasing hippocampal neurogenesis. These effects were specific to the DG and were not observed in the subventricular zone, where neurogenesis was unaffected by either the apoE genotype or the environmental conditions. These in vivo findings demonstrate a linkage between neuronal apoptosis and the impaired neuronal plasticity and cognition of apoE4-transgenic mice, and suggest that similar interactions between apoE4 and environmental factors might occur in AD.