Reduced Alzheimer's disease progression and neutrophil adhesion via competition using neutrophil-derived or engineered nanoparticles

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PROJECT SUMMARY Many Alzheimer’s disease (AD) drugs under development target aggregated amyloid beta (Aβ) peptide, but this approach is controversial due to disappointing clinical outcomes. Thus, the need to develop new therapeutic strategies for AD persists. Blood flow in the brain of Alzheimer disease patients is substantially decreased as compared to age-matched healthy controls. Recently, intravital imaging with two-photon microscopy showed that blood flow in AD mouse models is reduced because neutrophils plug up capillaries resulting in a small, but impactful number of stalled capillaries. Removing these stalls by interfering with neutrophil adhesion improves blood flow in minutes and also improves performance on tasks involving short term or episodic memory within hours. Although this approach is promising because it targets blood flow and inflammation, key features of AD unaddressed by amyloid-targeting drugs, it is currently limited to experimental treatments with limited possibility for clinical translation. Existing experimental approaches interfere with a protein not found in humans, Ly6G, or would cause severe compromise of the immune system. This proposal aims to develop a novel strategy based on highly biocompatible neutrophil-derived extracellular vesicles or nanoparticles that specifically target and block neutrophil adhesion sites in the brain to reduce capillary stalls and the associated blood flow deficits. These novel agents are encapsulated in neutrophil membranes that preserve many of the neutrophil functions so possess the same targeting capacity as neutrophils. When injected systemically, these engineered particles compete with neutrophils for binding sites on the brain capillaries, acting to reduce neutrophil arrest. Importantly, the particles are only <1% of the size of neutrophils and do not cause capillary stalls. The proposed work will engineer and characterize a novel AD therapy with the following Specific Aims: 1) Investigate the targeting of naturally- derived neutrophil EVs (nEVs) that are generated from congenic mouse donors. This aim will follow up on preliminary data that suggests these nEVs bind to capillaries in AD, but not wild type controls, and appear to decrease capillary stall frequency while increasing cerebral blood flow. 2) Explore the therapeutic potential of nEVs. Previous experimental capillary stall reduction strategies resulted in rapid recovery of memory function, so it is expected that the novel nEVs would have a similar effect as assayed by working and spatial memory tests. 3) Engineer neutrophil membrane-coated nanoparticles (NMPs) with cargo- carrying capabilities. This aim will develop a second-generation engineered particle based on the same neutrophil-membrane encapsulation as nEVs that could be loaded with drugs. This would provide the ability to target therapies specifically to stall-prone capillaries in the brain. The proposed work combines expertise in nanomaterials, extracellular vesicle biology, neurodegeneration, and in vivo multiphoton imaging to develop a novel treatment for AD.