n-(n-(3-5-difluorophenacetyl)alanyl)phenylglycine-tert-butyl-ester and Nervous-System-Diseases

Perioperative discontinuation of aspirin is often considered due to bleeding concern. We determined whether this discontinuation affected neurological outcome after brain ischemia.. Adult male Sprague-Dawley rats were subjected to a 90-minute right middle cerebral arterial occlusion (MCAO). They received 30 mg/kg/day aspirin via gastric gavage: 1) for 2 days at 5 days before MCAO; 2) for 2 days at 5 days before MCAO and for 3 days after MCAO; 3) for 7 days before MCAO; or 4) for 7 days before MCAO and for 3 days after MCAO. Neurological outcome was evaluated 3 days after the MCAO. Ischemic penumbral cortex was harvested 1 or 3 days after MCAO for determining Notch intracellular domain (NICD), IL-6 and IL-1β levels.. Aspirin given by regimen 2 and 3 but not by regimen 1 improved neurological outcome. Neuroprotection was achieved by N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT), a Notch activation inhibitor. DAPT and aspirin given only by regimen 2 and 3 reduced NICD, IL-6 and IL-1β in the ischemic penumbral cortex. NICD was found in microglial nuclei. Microglial activation in the ischemic tissues was inhibited by aspirin.. Aspirin use during the perioperative period provides neuroprotection. Inhibition of Notch activation and neuroinflammation may contribute to the neuroprotection of aspirin.

Topics: Analysis of Variance; Animals; Anti-Inflammatory Agents, Non-Steroidal; Aspirin; Brain Infarction; Dipeptides; Disease Models, Animal; Enzyme Inhibitors; Enzyme-Linked Immunosorbent Assay; Infarction, Middle Cerebral Artery; Interleukin-1beta; Interleukin-6; Male; Nervous System Diseases; Psychomotor Performance; Rats, Sprague-Dawley; Time Factors

Prenatal exposure to mercury causes neurodevelopmental disorders and neurological pathologies in infants, such as microcephaly and mental retardation. Despite critical importance, the molecular interactions leading to mercury toxicity are yet to be elucidated. We first used a cell-free assay to investigate mercury effects on purified γ-secretase activity. Next, we treated adult Drosophila melanogaster with mercury and collected control and mercury-treated embryos, which were subjected to mild hypotonic protein extraction, or immunostained to reveal nervous system morphology. Embryos left to develop into adults were examined for wing phenotypes. Relative to control metals, we found that mercury strongly inhibits in vitro γ-secretase processing of both amyloid-β precursor protein (APP) and Notch. Mercury inhibited APP and Notch cleavage in a dose-dependent manner, with IC(50) values of 50-125 nM, and is therefore comparable in potency to benchmark γ-secretase inhibitors. Immunoblot analysis of embryonic protein extracts showed that mercury inhibits Notch cleavage by γ-secretase in vivo. This is accompanied by severe neurodevelopmental abnormalities in embryos and adult wing-notching phenotypes. Our findings provide first evidence that mercury is a direct and potent γ-secretase inhibitor and suggest that inhibition of γ-secretase and disruption of the Notch developmental pathway potentially contribute to mercury-induced toxicity in the nervous system.

Topics: Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Animals; Blotting, Western; Dipeptides; Dose-Response Relationship, Drug; Drosophila melanogaster; Drosophila Proteins; Embryo, Nonmammalian; Female; Immunohistochemistry; Male; Mercury; Methylmercury Compounds; Nervous System Diseases; Receptors, Notch; Wings, Animal