ABSTRACT
The accumulation of beta amyloid (Aß) can cause synaptic impairments, but the characteristics and mechanisms of the synaptic impairment induced by the accumulation of Aß in Alzheimer's disease (AD) remain unclear. In identified single neurons in a newly developed Drosophila AD model, in which Aß accumulates intraneuronally, we found an age-dependent reduction in the synaptic vesicle release probability that was associated with a decrease in the density of presynaptic calcium channel clusters and an increase in the presynaptic and postsynaptic contact length. Moreover, these alterations occurred in the absence of presynaptic bouton loss. In addition, we found that Aß expression also produced an age-dependent decrease in the amount of Bruchpilot (Brp), which plays an important role in controlling Ca(2+) channel clustering and synaptic vesicle release in the presynaptic active zone. Our study indicates that the chronic accumulation of intraneuronal Aß can induce functional and structural changes in the presynaptic active zone prior to a loss of presynaptic buttons in the same neuron.
Subject(s)
Aging/pathology , Alzheimer Disease/pathology , Amyloid beta-Peptides/adverse effects , Synapses/ultrastructure , Aging/physiology , Alzheimer Disease/metabolism , Alzheimer Disease/physiopathology , Amyloid beta-Peptides/metabolism , Animals , Blotting, Western , Disease Models, Animal , Drosophila melanogaster , Microscopy, Confocal , Microscopy, Electron, Transmission , Patch-Clamp Techniques , Presynaptic Terminals/metabolism , Presynaptic Terminals/ultrastructure , Synaptic Transmission/physiology , Synaptic Vesicles/ultrastructureABSTRACT
Shear stress, especially low shear stress (LowSS), plays an important role in vascular remodeling during atherosclerosis. Endothelial cells (ECs), which are directly exposed to shear stress, convert mechanical stimuli into intracellular signals and interact with the underlying vascular smooth muscle cells (VSMCs). The interactions between ECs and VSMCs modulate the LowSS-induced vascular remodeling. With the use of proteomic analysis, the protein profiles of rat aorta cultured under LowSS (5 dyn/cm(2)) and normal shear stress (15 dyn/cm(2)) were compared. By using Ingenuity Pathway Analysis to identify protein-protein association, a network was disclosed that involves two secretary molecules, PDGF-BB and TGF-ß1, and three other linked proteins, lamin A, lysyl oxidase, and ERK 1/2. The roles of this network in cellular communication, migration, and proliferation were further studied in vitro by a cocultured parallel-plate flow chamber system. LowSS up-regulated migration and proliferation of ECs and VSMCs, increased productions of PDGF-BB and TGF-ß1, enhanced expressions of lysyl oxidase and phospho-ERK1/2, and decreased Lamin A in ECs and VSMCs. These changes induced by LowSS were confirmed by using PDGF-BB recombinant protein, siRNA, and neutralizing antibody. TGF-ß1 had similar influences on ECs as PDGF-BB, but not on VSMCs. Our results suggest that ECs convert the LowSS stimuli into up-regulations of PDGF-BB and TGF-ß1, but these two factors play different roles in LowSS-induced vascular remodeling. PDGF-BB is involved in the paracrine control of VSMCs by ECs, whereas TGF-ß1 participates in the feedback control from VSMCs to ECs.
