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β‐Amyloid inhibits NOS activity by subtracting NADPH availability
Author(s) -
Venturini Giorgio,
Colasanti Marco,
Persichini Tiziana,
Fioravanti Emanuela,
Ascenzi Paolo,
Palomba Letizia,
Cantoni Orazio,
Musci Giovanni
Publication year - 2002
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.02-0186fje
Subject(s) - internalization , nitric oxide , chemistry , nitric oxide synthase , cell culture , cell , biochemistry , pharmacology , microbiology and biotechnology , biophysics , biology , genetics , organic chemistry
The amyloid peptides Aβ1–42 and Aβ25–35 strongly inhibited the activity of constitutive neuronal and endothelial nitric oxide synthases (i.e., NOS‐I and NOS‐III, respectively) in cell‐free assays. The molecular mechanism of NOS inhibition by Aβ fragments was studied in detail with Aβ25–35. The inhibitory ability was mostly NADPH‐dependent and specific for the soluble form of Aβ25–35. Optical, fluorescence, and NMR spectroscopy showed that the soluble, but not aggregated, Aβ25–35 interacted with NADPH, thus suggesting that a direct recruitment of NADPH may result in diminished availability of the redox cofactor for NOS functioning. To assess the physiological relevance of our findings, rat neuronal‐like PC12 and glioma C6 cell lines were used as cellular models. After Aβ25–35 internalization into cells was verified, the activity of constitutive NOS was measured using the DAF‐2DA detection system and found to be severely impaired upon Aβ25–35 uptake. Consistent with previous results on the molecular cross‐talk between NOS isoforms, repression of constitutive NOS by Aβ25–35 resulted in enhanced expression of inducible NOS (NOS‐II) mRNA in C6 cells. Our results represent the first evidence that amyloid fragments impair constitutive NOS activity in cell‐free and cellular systems, providing a possible molecular mechanism for the onset and/or maintenance of Alzheimer's disease.