title: Nitric oxide-mediated regulation of β-amyloid clearance via alterations of MMP-9/TIMP-1.
abstract: Fibrillar amyloid plaques are largely composed of amyloid-beta (Aβ) peptides that are metabolized into products, including Aβ1-16, by proteases including matrix metalloproteinase 9 (MMP-9). The balance between production and degradation of Aβ proteins is critical to amyloid accumulation and resulting disease. Regulation of MMP-9 and its endogenous inhibitor tissue inhibitor of metalloproteinase (TIMP)-1 by nitric oxide (NO) has been shown. We hypothesize that nitric oxide synthase (NOS2) protects against Alzheimer's disease pathology by increasing amyloid clearance through NO regulation of MMP-9/TIMP-1 balance. We show NO-mediated increased MMP-9/TIMP-1 ratios enhanced the degradation of fibrillar Aβ in vitro, which was abolished when silenced for MMP-9 protein translation. The in vivo relationship between MMP-9, NO and Aβ degradation was examined by comparing an Alzheimer's disease mouse model that expresses NOS2 with a model lacking NOS2. To quantitate MMP-9 mediated changes, we generated an antibody recognizing the Aβ1-16 fragment, and used mass spectrometry multi-reaction monitoring assay for detection of immunoprecipitated Aβ1-16 peptides. Aβ1-16 levels decreased in brain lysates lacking NOS2 when compared with strains that express human amyloid precursor protein on the NOS2 background. TIMP-1 increased in the APPSwDI/NOS2(-/-)  mice with decreased MMP activity and increased amyloid burden, thereby supporting roles for NO in the regulation of MMP/TIMP balance and plaque clearance.
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA.
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Ridnour
authors.forename: Sneha
authors.initials: S
authors.lastname: Dhanapal
authors.forename: Michael
authors.initials: M
authors.lastname: Hoos
authors.forename: Joan
authors.initials: J
authors.lastname: Wilson
authors.forename: Jennifer
authors.initials: J
authors.lastname: Lee
authors.forename: Robert Y S
authors.initials: RY
authors.lastname: Cheng
authors.forename: Ernst E
authors.initials: EE
authors.lastname: Brueggemann
authors.forename: Harry B
authors.initials: HB
authors.lastname: Hines
authors.forename: Donna M
authors.initials: DM
authors.lastname: Wilcock
authors.forename: Michael P
authors.initials: MP
authors.lastname: Vitek
authors.forename: David A
authors.initials: DA
authors.lastname: Wink
authors.forename: Carol A
authors.initials: CA
authors.lastname: Colton
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D001921:Brain / Q000378:metabolism; D002853:Chromatography, Liquid; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D047468:Immunoprecipitation; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D009569:Nitric Oxide / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053719:Tandem Mass Spectrometry; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism*
chemical_list: D016229:Amyloid beta-Peptides; D019715:Tissue Inhibitor of Metalloproteinase-1; D009569:Nitric Oxide; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9