Engineering theranostic nanovehicles capable of targeting cerebrovascular amyloid deposits.

Cerebral amyloid angiopathy (CAA) is characterized by the deposition of amyloid beta (Aß) proteins within the walls of the cerebral vasculature with subsequent aggressive vascular inflammation leading to recurrent hemorrhagic strokes. The objective of the study was to develop theranostic nanovehicles (TNVs) capable of a) targeting cerebrovascular amyloid; b) providing magnetic resonance imaging (MRI) contrast for the early detection of CAA; and c) treating cerebrovascular inflammation resulting from CAA. The TNVs comprised of a polymeric nanocore made from Magnevist (MRI contrast agent) conjugated chitosan. The nanocore was also loaded with cyclophosphamide (CYC), an immunosuppressant shown to reduce the cerebrovascular inflammation in CAA. Putrescine modified F(ab')2 fragment of anti-amyloid antibody, IgG4.1 (pF(ab')24.1) was conjugated to the surface of the nanocore to target cerebrovascular amyloid. The average size of the control chitosan nanoparticles (conjugated with albumin and are devoid of Magnevist, CYC, and pF(ab')24.1) was 164±1.2 nm and that of the TNVs was 239±4.1 nm. The zeta potential values of the CCNs and TNVs were 21.6±1.7 mV and 11.9±0.5 mV, respectively. The leakage of Magnevist from the TNVs was a modest 0.2% over 4 days, and the CYC release from the TNVs followed Higuchi's model that describes sustained drug release from polymeric matrices. The studies conducted in polarized human microvascular endothelial cell monolayers (hCMEC/D3) in vitro as well as in mice in vivo have demonstrated the ability of TNVs to target cerebrovascular amyloid. In addition, the TNVs provided contrast for imaging cerebrovascular amyloid using MRI and single photon emission computed tomography. Moreover, the TNVs were shown to reduce pro-inflammatory cytokine production by the Aß challenged blood brain barrier (BBB) endothelium more effectively than the cyclophosphamide alone.

Traffic jam at the blood-brain barrier promotes greater accumulation of Alzheimer's disease amyloid-ß proteins in the cerebral vasculature.

Amyloid-ß (Aß) deposition in the brain vasculature results in cerebral amyloid angiopathy (CAA), which occurs in about 80% of Alzheimer's disease (AD) patients. While Aß42 predominates parenchymal amyloid plaques in AD brain, Aß40 is prevalent in the cerebrovascular amyloid. Dutch mutation of Aß40 (E22Q) promotes aggressive cerebrovascular accumulation and leads to severe CAA in the mutation carriers; knowledge of how DutchAß40 drives this process more efficiently than Aß40 could reveal various pathophysiological events that promote CAA. In this study we have demonstrated that DutchAß40 shows preferential accumulation in the blood-brain-barrier (BBB) endothelial cells due to its inefficient blood-to-brain transcytosis. Consequently, DutchAß40 establishes a permeation barrier in the BBB endothelium, prevents its own clearance from the brain, and promotes the formation of amyloid deposits in the cerebral microvessels. The BBB endothelial accumulation of native Aß40 is not robust enough to exercise such a significant impact on its brain clearance. Hence, the cerebrovascular accumulation of Aß40 is slow and may require other copathologies to precipitate into CAA. In conclusion, the magnitude of Aß accumulation in the BBB endothelial cells is a critical factor that promotes CAA; hence, clearing vascular endothelium of Aß proteins may halt or even reverse CAA.

Development of a smart nano-vehicle to target cerebrovascular amyloid deposits and brain parenchymal plaques observed in Alzheimer's disease and cerebral amyloid angiopathy.

PURPOSE: To design a smart nano-vehicle (SNV) capable of permeating the blood-brain barrier (BBB) to target cerebrovascular amyloid formed in both Alzheimer's disease (AD) and cerebrovascular amyloid angiopathy (CAA). METHODS: SNV consists of a chitosan polymeric core prepared through ionic gelation with tripolyphosphate. A polyamine modified F(ab') portion of IgG4.1, an anti-amyloid antibody, was coated as a biosensor on the SNV surface. A similar polymeric core coated with bovine serum albumin (BSA) served as a control nano-vehicle (CNV). The BBB uptake of (125)I-SNVs and (125)I-CNVs was evaluated in mice. The uptake and transcytosis of SNVs and CNVs across bovine brain microvascular endothelial cells (BBMECs) was evaluated using flow cytometry and confocal microscopy. RESULTS: Plasma clearance of (125)I-SNVs was nine times higher than that of the (125)I-CNVs. However, the uptake of (125)I-SNVs in various brain regions was about 8 to 11 times higher than that of (125)I-CNVs. The uptake of FITC-BSA loaded SNVs in BBMECs was twice the uptake of FITC-BSA loaded CNVs. Confocal micrographs demonstrated the uptake and transcytosis of Alexa Fluor 647 labeled SNVs, but not CNVs, across the BBMEC monolayer. CONCLUSIONS: SNVs are capable of carrying a payload of model protein across the BBB to target cerebral amyloid.