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Microglial VEGF receptor response is an integral chemotactic component in Alzheimer's disease pathology
Jae K Ryu1, Taesup Cho, Hyun B Choi
1Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
Abstract:
We hypothesize that microglial chemotactic responses to amyloid-beta peptide (Abeta(1-42)) serve as an early and integral component of inflammatory response in Alzheimer's disease (AD) brain. This study reports a receptor for vascular endothelial growth factor (VEGF), termed VEGF-1 (Flt-1), subserves microglial chemotactic responses induced by Abeta(1-42) stimulation, in vivo and in vitro. Expression of Flt-1 was significantly increased in tissue obtained from AD patients [compared with tissue from nondemented (ND) individuals], in Abeta(1-42)-injected rat hippocampus, and in peptide-stimulated human microglia. Single and double immunohistochemical staining demonstrated marked immunoreactivity, for both Flt-1 and its ligand VEGF, in association with microglia and Abeta deposits in AD, but not ND, brain tissue. Functionally, treatment with anti-Flt-1 antibody was highly effective in inhibiting microglial mobility and chemotactic responses measured in vitro using a transwell migration assay. In vivo, transplanted enhanced green fluorescent protein (EGFP)-labeled microglia exhibited Flt-1-dependent chemotaxis induced by peptide injection with anti-Flt-1 effective in blocking migration of cells. Importantly, anti-Flt-1 reduction of microglial mobility was neuroprotective in peptide-injected hippocampus and associated with a significant increase in numbers of viable hippocampal neurons. The results of this study suggest critical functional roles for Flt-1 in mediating microglial chemotactic inflammatory responses which contribute to pathological conditions in AD brain.
Insights
Vascular Endothelial Growth Factor-1 (Flt-1) mediates microglial cell movement towards amyloid-beta in Alzheimer's disease (AD) brains. Blocking Flt-1 reduces inflammation and protects neurons, offering a potential therapeutic target for AD.
Area of Science:
- Neuroscience
- Immunology
- Pathology
Background:
- Alzheimer's disease (AD) involves neuroinflammation driven by microglial responses to amyloid-beta (Abeta).
- Understanding the molecular mechanisms of microglial chemotaxis in AD is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the role of vascular endothelial growth factor receptor-1 (VEGF-1 or Flt-1) in mediating microglial chemotaxis induced by amyloid-beta (Abeta(1-42)).
- To assess the therapeutic potential of targeting Flt-1 in Alzheimer's disease models.
Main Methods:
- In vivo and in vitro experiments using human microglia and rat hippocampus models.
- Immunohistochemistry to detect Flt-1 and VEGF expression in AD and non-demented (ND) brain tissue.
- Transwell migration assays to measure microglial chemotaxis.
- Administration of anti-Flt-1 antibodies to block Flt-1 function.
- Neuroprotection assessment by counting viable hippocampal neurons.
Main Results:
- Flt-1 expression was significantly upregulated in AD patient tissues, Abeta(1-42)-injected rat hippocampi, and stimulated human microglia.
- Flt-1 and VEGF showed co-localization with microglia and Abeta deposits in AD brains.
- Anti-Flt-1 antibody treatment effectively inhibited microglial migration in vitro and in vivo.
- Blocking Flt-1-mediated microglial migration demonstrated neuroprotective effects, increasing hippocampal neuron survival.
Conclusions:
- Flt-1 plays a critical role in mediating Abeta-induced microglial chemotaxis and neuroinflammation in Alzheimer's disease.
- Targeting Flt-1 represents a promising therapeutic strategy for mitigating AD pathology and neurodegeneration.
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