title: Somatostatin receptor subtype-4 agonist NNC 26-9100 decreases extracellular and intracellular Aβ₁₋₄₂ trimers.
abstract: Soluble amyloid β-protein (Aβ) oligomers are primary mediators of synaptic dysfunction associated with the progression of Alzheimer's disease. Such Aβ oligomers exist dependent on their rates of aggregation and metabolism. Use of selective somatostatin receptor-subtype agonists have been identified as a potential means to mitigate Aβ accumulation in the brain, via regulation of the enzyme neprilysin. Herein, we first evaluated the impact of the somatostatin receptor subtype-4 agonist 1-[3-[N-(5-Bromopyridin-2-yl)-N-(3,4-dichlorobenzyl)amino]propyl]-3-[3-(1H-imidazol-4-yl)propyl]thiourea (NNC 26-9100) on learning and memory in 12-month SAMP8 mice (i.c.v. injection). NNC 26-9100 (0.2 μg-dose) was shown to enhance both learning (T-maze) and memory (object recognition) compared to vehicle controls. Cortical and hippocampal tissues were evaluated subsequent to NNC 26-9100 (0.2 μg) or vehicle administration for changes in neprilysin activity, along with protein expression of amyloid-precursor protein (APP), neprilysin, and Aβ₁₋₄₂ oligomers within respective cellular fractions (extracellular, intracellular and membrane). NNC 26-9100 increased neprilysin activity in cortical tissue, with an associated protein expression increase in the extracellular fraction and decreased in the intracellular fraction. A decrease in intracellular APP expression was found with treatment in both cortical and hippocampal tissues. NNC 26-9100 also significantly decreased expression of Aβ₁₋₄₂ trimers within both the extracellular and intracellular cortical fractions. No expression changes were found in membrane fractions for any protein. These finding suggest the potential use of selective SSTR4 agonists to mitigate toxic oligomeric forms of Aβ₁₋₄₂ in critical regions of the brain identified with learning and memory decline.
authors.affiliation: Pharmaceutical Sciences, School of Pharmacy, Southern Illinois University Edwardsville, 200 University Park Drive, Edwardsville, IL, United States.
authors.forename: Karin E
authors.initials: KE
authors.lastname: Sandoval
authors.forename: Susan A
authors.initials: SA
authors.lastname: Farr
authors.forename: William A
authors.initials: WA
authors.lastname: Banks
authors.forename: Albert M
authors.initials: AM
authors.lastname: Crider
authors.forename: John E
authors.initials: JE
authors.lastname: Morley
authors.forename: Ken A
authors.initials: KA
authors.lastname: Witt
mesh_terms: D000631:Aminopyridines / Q000008:administration & dosage / Q000494:pharmacology*; D016229:Amyloid beta-Peptides / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism; D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects*; D045604:Extracellular Fluid / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D006624:Hippocampus / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D007276:Injections, Intraventricular; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D008568:Memory / Q000187:drug effects; D051379:Mice; D008815:Mice, Inbred Strains; D008970:Molecular Weight; D015260:Neprilysin / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000819:agonists / Q000737:chemistry / Q000378:metabolism; D009474:Neurons / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D018697:Nootropic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D010446:Peptide Fragments / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D017481:Receptors, Somatostatin / Q000819:agonists*; D012995:Solubility; D013890:Thiourea / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D000631:Aminopyridines; D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; C115929:NNC 26-9100; D009419:Nerve Tissue Proteins; D018697:Nootropic Agents; D010446:Peptide Fragments; D017481:Receptors, Somatostatin; C075222:amyloid beta-protein (1-42); C098681:somatostatin receptor subtype-4; D015260:Neprilysin; D013890:Thiourea