Using APPNLh/APPNLh x PS-1P246L/PS-1P246L human double knock-in (APP/PS-1) mice, we examined whether phosphatidylserine (PtdSer) asymmetry is significantly altered in brain of this familial Alzheimer disease mouse model in an age-dependent manner as a result of oxidative stress, toxic Aβ(1-42) oligomer production, and/or apoptosis. Annexin V (AV) and NBD-PS fluorescence in synaptosomes of wild-type (WT) and APP/PS-1 mice were used to determine PtdSer exposure with age, while Mg2+ ATPase activity was determined to correlate PtdSer asymmetry changes with PtdSer translocase, flippase, activity. AV and NBD-PS results demonstrated significant PtdSer exposure beginning at 9 months compared to 1-month-old WT controls for both assays, a trend that was exacerbated in synaptosomes of APP/PS-1 mice. Decreasing Mg2+ ATPase activity confirms that the age-related loss of PtdSer asymmetry is likely due to loss of flippase activity, more prominent in APP/PS-1 brain. Two-site sandwich ELISA on SDS- and FA-soluble APP/PS-1 brain fractions were conducted to correlate Aβ(1-40) and Aβ(1-42) levels with age-related trends determined from the AV, NBD-PS, and Mg2+ ATPase assays. ELISA revealed a significant increase in both SDS- and FA-soluble Aβ(1-40) and Aβ(1-42) with age, consistent with PtdSer and flippase assay trends. Lastly, because PtdSer exposure is affected by pro-apoptotic caspase-3, levels of both latent and active forms were measured. Western blotting results demonstrated an increase in both active fragments of caspase-3 with age, while levels of pro-caspase-3 decrease. These results are discussed with relevance to loss of lipid asymmetry and consequent neurotoxicity in brain of subjects with Alzheimer disease.
|Number of pages||12|
|Journal||Neurobiology of Disease|
|State||Published - Apr 2010|
Bibliographical noteFunding Information:
This research was supported in part by NIH grants to D.A.B [ AG-029839 ; AG-05119 , AG-10836 ], to W.R.M. [ AG-05119 ], and to M.P.M. [ AG-005119 ; NS-058382 ]. C.M.S. is a fellow of the Myositosis Association. We thank Cephalon, Inc., Frazer, PA, for the donation of the animals used in this study.
- Amyloid precursor protein (APP)
- Familial Alzheimer disease (FAD)
- Lipid peroxidation
- Oxidative stress
- Phosphatidylserine (PtdSer)
- Phospholipid asymmetry
- Presenilin-1 (PS-1)
- Toxic Aβ(1-42) oligomers
ASJC Scopus subject areas