ABSTRACT
Current therapies for Alzheimer's disease (AD) offer partial symptomatic relief and do not modify disease progression. There is substantial evidence indicating a disease onset years before clinical diagnosis, at which point no effective therapy has been found. In this study, we investigated the efficacy of a new multi-target drug, M30, at relatively early stages of the AD-like amyloid pathology in a robust rat transgenic model. McGill-R-Thy1-APP transgenic rats develop the full AD-like amyloid pathology in a progressive fashion, and have a minimal genetic burden. McGill rats were given 5âmg/kg M30 or vehicle per os, every 2 days for 4 months, starting at a stage where the transgenic animals suffer detectable cognitive impairments. At the completion of the treatment, cognitive functions were assessed with Novel Object Location and Novel Object Recognition tests. The brains were then analyzed to assess amyloid-ß (Aß) burden and the levels of key inflammatory markers. Long-term treatment with M30 was associated with both the prevention and the reversal of transgene-related cognitive decline. The effects on cognition were accompanied by a shift of the Aß-immunoreactive material toward an amyloid plaque aggregated molecular form, diminished molecular signs of CNS inflammation and a change in microglia morphology toward a surveying phenotype. This study is the first to demonstrate the therapeutic potential of M30 in a rat model of the AD amyloid pathology. It provides a rationale for further investigations with M30 and with potential multi-target approaches to delay, prevent or reverse the progression the AD pathology at early disease-stages.
Subject(s)
Alzheimer Disease/drug therapy , Anti-Inflammatory Agents/pharmacology , Brain/drug effects , Cognition/drug effects , Hydroxyquinolines/pharmacology , Nootropic Agents/pharmacology , Alzheimer Disease/immunology , Amyloid beta-Peptides/metabolism , Animals , Brain/immunology , Cognition/physiology , Disease Models, Animal , Female , Lipid Peroxidation/drug effects , Lipid Peroxidation/physiology , Male , Microglia/drug effects , Microglia/metabolism , Microglia/pathology , Neuroprotective Agents/pharmacology , Rats, Transgenic , Recognition, Psychology/drug effectsABSTRACT
Chronic brain inflammation is associated with Alzheimer's disease (AD) and is classically attributed to amyloid plaque deposition. However, whether the amyloid pathology can trigger early inflammatory processes before plaque deposition remains a matter of debate. To address the possibility that a pre-plaque inflammatory process occurs, we investigated the status of neuronal, astrocytic, and microglial markers in pre- and post-amyloid plaque stages in a novel transgenic rat model of an AD-like amyloid pathology (McGill-R-Thy1-APP). In this model, we found a marked upregulation of several classical inflammatory markers such as COX-2, IL-1ß, TNF-α, and fractalkine (CX3CL1) in the cerebral cortex and hippocampus. Interestingly, many of these markers were highly expressed in amyloid beta-burdened neurons. Activated astrocytes and microglia were associated with these Aß-burdened neurons. These findings confirm the occurrence of a proinflammatory process preceding amyloid plaque deposition and suggest that Aß-burdened neurons play a crucial role in initiating inflammation in AD.
Subject(s)
Alzheimer Disease/metabolism , Alzheimer Disease/pathology , Amyloid beta-Peptides/metabolism , Disease Models, Animal , Neurons/metabolism , Neurons/pathology , Plaque, Amyloid/metabolism , Plaque, Amyloid/pathology , Animals , Astrocytes/metabolism , Astrocytes/pathology , Brain/metabolism , Brain/pathology , Female , Inflammation , Male , Microglia/metabolism , Microglia/pathology , Rats, TransgenicABSTRACT
LASSBio-767 [(-)-3-O-acetyl-spectaline] and LASSBio-822 [(-)-3-O-tert-Boc-spectaline] were recently described as cholinesterase inhibitors derived from the natural piperidine alkaloid (-)-spectaline, obtained from the flowers of Senna spectabilis (Fabaceae). We investigated their mechanism of inhibition of acetylcholinesterase and their efficacy in reversing scopolamine-induced amnesia. Competition assays with the substrate acetylthiocholine showed a concentration-dependent reduction in rat brain cholinesterase Vmax without changes in apparent Km. The kinetic data for LASSBio-767 and LASSBio-822 were best fit by a model of simple linear noncompetitive inhibition with Ki of 6.1 microM and 7.5 microM, respectively. A dilution assay showed a fast and complete reversal of inhibition, independent of incubation time. Simulated docking of the compounds into the catalytic gorge of Torpedo acetylcholinesterase showed interactions with the peripheral anionic site, but not with the catalytic triad. Anti-amnestic effects in mice were assessed in a step-down passive avoidance test and in the Morris water maze 30 min after injection of scopolamine (1 mg/kg i.p.). Saline, LASSBio-767, or LASSBio-822 was administered 15 min before scopolamine. Both compounds reversed the scopolamine-induced reduction in step-down latency at 0.1 mg/kg i.p. LASSBio-767 reversed scopolamine-induced changes in water maze escape latency at 1 mg/kg i.p. or p.o., while its cholinergic side effects were absent or mild up to 30 mg/kg i.p. (LD50 above 100 mg/kg i.p.). Thus, the (-)-spectaline derivatives are potent cholinergic agents in vivo, with a unique profile combining noncompetitive cholinesterase inhibition and CNS selectivity, with few peripheral side effects.
Subject(s)
Alkaloids/pharmacology , Cholinesterase Inhibitors/pharmacology , Piperidines/pharmacology , Acetylcholinesterase/metabolism , Administration, Oral , Alkaloids/chemistry , Alkaloids/isolation & purification , Amnesia/chemically induced , Amnesia/drug therapy , Amnesia/physiopathology , Animals , Behavior, Animal/drug effects , Brain/enzymology , Catalysis/drug effects , Cholinesterase Inhibitors/administration & dosage , Cholinesterase Inhibitors/chemistry , Dose-Response Relationship, Drug , Drugs, Investigational/administration & dosage , Drugs, Investigational/chemistry , Drugs, Investigational/pharmacology , Injections, Intraperitoneal , Kinetics , Maze Learning/drug effects , Mice , Models, Molecular , Molecular Structure , Piperidines/administration & dosage , Piperidines/chemistry , Rats , Rats, Wistar , Scopolamine/toxicity , Space Perception/drug effects , StereoisomerismABSTRACT
Five new piperidine alkaloids were designed from natural (-)-3-O-acetyl-spectaline and (-)-spectaline that were obtained from the flowers of Senna spectabilis (sin. Cassia spectabilis, Leguminosae). Two semi-synthetic analogues (7 and 9) inhibited rat brain acetylcholinesterase, showing IC50 of 7.32 and 15.1 microM, and were 21 and 9.5 times less potent against rat brain butyrylcholinesterase, respectively. Compound 9 (1mg/kg, i.p.) was fully efficacious in reverting scopolamine-induced amnesia in mice. The two active compounds (7 and 9) did not show overt toxic effects at the doses tested in vivo.
