Selective modulation of amyloid-β peptide degradation by flurbiprofen, fenofibrate, and related compounds regulates Aβ levels
2009
Abdul-Hay, Samer O. | Edirisinghe, Praneeth | Thatcher, Gregory R.J.
Gamma-secretase modulators (GSMs) include selected non-steroidal anti-inflammatory drugs such as flurbiprofen that selectively lowers the neurotoxic amyloid-β peptide Aβ₁₋₄₂. GSMs are attractive targets for Alzheimer's disease, in contrast to 'inverse GSMs,' such as fenofibrate, which selectively increase the level of Aβ₁₋₄₂. A methodology for screening of Aβ modulating drugs was developed utilizing an Aβ-producing neuroblastoma cell line stably transfected with mutant human amyloid precursor protein, immunoprecipitation of Aβ peptides, and mass spectroscopic quantitation of Aβ₁₋₃₇/Aβ₁₋₃₈/Aβ₁₋₄₀/Aβ₁₋₄₂ using an Aβ internal standard. The unexpected conclusion of this work was that in this system, drug effects are independent of γ-secretase. The methodology recapitulated reported results for modulation of Aβ by GSMs. However, control experiments in which exogenous Aβ₁₋₄₀/Aβ₁₋₄₂ was added (i) to drug-treated wild-type cells or (ii) to conditioned media from these wild-type cells, gave comparable patterns of Aβ modulation. These results, suggesting that drugs modulate the ability of cell-derived factors to degrade Aβ, was interrogated by adding protease inhibitors and performing molecular weight cut-off fractionation. The results confirmed that modulation of Aβ₁₋₄₀/Aβ₁₋₄₂ was mediated by selective proteolysis. Treatment of N2a cells with flurbiprofen or fenofibric acid selectively enhanced Aβ₁₋₄₂ clearance by extracellular proteolysis; treatment with HCT-1026 or fenofibrate (esters of flurbiprofen and fenobric acid) inhibited clearance of Aβ₁₋₄₀ and Aβ₁₋₄₂.
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