ABSTRACT
Lithium is first-line therapy for bipolar affective disorder and has recently been shown to have protective effects in populations at risk for Alzheimer's disease (AD). However, the mechanism underlying this protection is poorly understood and consequently limits its possible therapeutic application in AD. Moreover, conventional lithium formulations have a narrow therapeutic window and are associated with a severe side effect profile. Here we evaluated a novel microdose formulation of lithium, coded NP03, in a well-characterized rat model of progressive AD-like amyloid pathology. This formulation allows microdose lithium delivery to the brain in the absence of negative side effects. We found that NP03 rescued key initiating components of AD pathology, including inactivating GSK-3ß, reducing BACE1 expression and activity, and reducing amyloid levels. Notably, NP03 rescued memory loss, impaired CRTC1 promoter binding of synaptic plasticity genes and hippocampal neurogenesis. These results raise the possibility that NP03 be of therapeutic value in the early or preclinical stages of AD.
Subject(s)
Amyloid Precursor Protein Secretases/antagonists & inhibitors , Aspartic Acid Endopeptidases/antagonists & inhibitors , Hippocampus/drug effects , Lithium/administration & dosage , Memory Disorders/drug therapy , Memory/drug effects , Neuroprotective Agents/administration & dosage , Alzheimer Disease/drug therapy , Alzheimer Disease/metabolism , Alzheimer Disease/pathology , Amyloid beta-Peptides/metabolism , Animals , Female , Hippocampus/metabolism , Hippocampus/pathology , Lithium/therapeutic use , Male , Memory Disorders/metabolism , Memory Disorders/pathology , Neurogenesis/drug effects , Neuroprotective Agents/therapeutic use , Rats , Rats, TransgenicABSTRACT
BACKGROUND: Alzheimer's disease (AD) neuropathology likely begins decades before clinical symptoms are manifested. Investigations on the early stages of the amyloid pathology are crucial for the discovery of diagnostic biomarkers or new therapeutic targets. Our transgenic (tg) animal models are most suitable to study early AD pathological events, as the pathology evolves in a well-staged manner, starting with intracellular Aß accumulation and ending with plaque deposition. OBJECTIVE: To determine the occurrence of key inflammatory markers and to look for signs of nerve growth factor (NGF) dysmetabolism at preplaque and postplaque stages in tg models of AD-like amyloid pathology and in human AD brains. METHODS: We used our own tg lines (mice and rat), high-quality human brain material and applied neurochemical and immunohistochemical experimental approaches. RESULTS: In both tg models, we observed an intracellular accumulation of oligomeric Aß in cortical and hippocampal pyramidal neurons. This coincided with an upregulation of key inflammatory markers (iNOS, MHCII, COX-2) and a recruitment of microglia towards Aß-burdened neurons. Using human AD brains, we showed alterations in the NGF metabolic pathway, which were mirrored in our tg rat model at early and late stages of amyloid plaque generation. CONCLUSION: A proinflammatory process and, consequently, the deregulation of the NGF metabolic pathway could be amongst the earliest pathological events in the progression of AD.
Subject(s)
Alzheimer Disease/pathology , Central Nervous System/metabolism , Inflammation/chemically induced , Alzheimer Disease/genetics , Amyloid beta-Protein Precursor/genetics , Animals , Animals, Genetically Modified , Cyclooxygenase 2/metabolism , Disease Models, Animal , Gene Expression Regulation/genetics , Humans , Matrix Metalloproteinase 9/metabolism , Mice , Mutation/genetics , Nerve Growth Factor/metabolism , Nitric Oxide Synthase Type II/metabolism , Protein Precursors/metabolism , RatsABSTRACT
BACKGROUND: Intracellular accumulation of beta-amyloid (Abeta) is one of the early features in the neuropathology of Alzheimer's disease (AD) and Down's syndrome. This can be reproduced in cell and transgenic animal models of the AD-like amyloid pathology. In a transgenic rat model, our lab has previously shown that the intracellular accumulation of Abeta is sufficient to provoke cognitive impairments and biochemical alterations in the cerebral cortex and hippocampus in the absence of amyloid plaques. OBJECTIVE: To investigate an early, pre-plaque inflammatory process in AD-like transgenic models and establish whether the neurotoxic effects of Abeta oligomers and proinflammatory responses can be arrested with minocycline. METHODS: For these studies, we used naïve mice and transgenic animal models of the AD-like amyloid pathology and applied neurochemical, immunohistochemical and behavioral experimental approaches. RESULTS: In the early stages of the AD-like amyloid pathology, intracellular Abeta oligomers accumulate within neurons of the cerebral cortex and hippocampus. Coincidental with this, behavioral impairments occur prior to the appearance of amyloid plaques, together with an upregulation of MHC-II, i-NOS and COX-2, well-known proinflammatory markers. Treatment with minocycline corrected behavioral impairments, lowered inflammatory markers and levels of Abeta trimers. CONCLUSION: A pharmacological approach targeting the early neuroinflammatory effects of Abeta might be a promising strategy to prevent or delay the onset of AD.
