Class A scavenger receptor-1/2 facilitates the uptake of bovine milk exosomes in murine bone marrow-derived macrophages and C57BL/6J mice

Bovine milk exosomes (BMEs) are being explored in drug delivery despite their rapid elimination by macrophages. We aimed at identifying the BME transporter in murine bone marrow-derived macrophages (BMDMs). Fluorophore-labeled BMEs were used in transport studies in BMDMs from C57BL/6J and class A scavenger receptor type 1/2 (CASR-1/2) knockout mice and tissue accumulation in macrophage-depleted C57BL/6J mice. Parametric and non-parametric statistics tests for pairwise and multiple comparisons were used. Chemical inhibitors of phagocytosis by cytochalasin D led to a 69 ± 18% decrease in BME uptake compared to controls (P ˂ 0.05), whereas inhibitors of endocytic pathways other than phagocytosis had a modest effect on uptake (P > 0.05). Inhibitors of class A scavenger receptors (CASRs) including CASR-1/2 caused a 70% decrease in BME uptake (P ˂ 0.05). The uptake of BMEs by BMDMs from CASR-1/2 knockout mice was smaller by 58 ± 23% compared to wild-type controls (P ˂ 0.05). Macrophage depletion by clodronate caused a more than 44% decrease in BME uptake in the spleen and lungs (P ˂ 0.05) whereas the decrease observed in liver was not statistically significant. In conclusion, CASR-1/2 facilitates the uptake of BMEs in BMDMs and C57BL/6J mice.

Class A Scavenger Receptor-Mediated Phagocytosis of Bovine Milk Exosomes in Murine Bone Marrow-Derived Macrophages

Objectives Bovine milk exosomes (BMEs) are promising candidates for delivering drugs to brain tumors because they are scalable, bioavailable after oral administration, and cross the blood-brain barrier. The use of BMEs in drug delivery is limited by their rapid elimination by macrophages. The objectives of this study were to identify the BME transporter and assess BME transport kinetics in murine bone marrow-derived macrophages (BMDMs) as a first step toward developing strategies that decrease the elimination of drug-loaded BMEs. Methods BMEs were isolated by differential centrifugation from skim milk. For transport studies, proteins and lipids on the BME surface were labeled with HiLyte™ Fluor 750 hydrazide and PKH26, respectively, and RNAs in BMEs were labeled with Exo-Red; unlabeled BMEs were used to assess background noise. Bone marrow cells were isolated from the femur and tibia of both C57BL/6J and scavenger receptor A-I/II knockout mice and differentiated ex vivo into BMDMs for use in transport studies. ANOVA, Dunnett's and Kruskal-Wallis test, Dunn's post-hoc test, unpaired t-test, and two-tailed Mann–Whitney U tests were used for statistical analysis; P < 0.05 was considered statistically significant. Results The uptake of BME was not saturated at the highest concentration used (4.3 × 1011 BMEs/mL) and the longest incubation time (53 h) tested. Chemical inhibition of phagocytosis by cytochalasin D led to a 69 ± 18% decrease in BME uptake compared to solvent controls (P ˂ 0.05), whereas inhibition of macropinocytosis, caveolar-dependent endocytosis, and endocytosis of clathrin-coated vesicles had no significant effect on BME uptake (11%-33% decrease compared to controls; P > 0.05). Treatment with inhibitors of class A scavenger receptor (CASR), fucoidan and dextran sulfate caused a 70 ± 8.1% and 70 ± 18% decrease (P ˂ 0.05), respectively, in BME uptake. The role of CASR in BME uptake was confirmed by using a genetics approach: the uptake of BMEs by BMDMs from scavenger receptor A-I/II knockout mice decreased by 58 ± 23% compared to BMDMs from wild-type mice (P ˂ 0.05). Conclusions BME uptake is facilitated by CASR in BMDMs and uptake cannot be saturated under physiological conditions. Funding Sources NIH 1P20GM104320, and NIFA 2016–67,001-25,301 and 2020–67,017-30,834, USDA Hatch-1,011,996, and USDA W4002 (all to J.Z.). J.Z is a consultant for PureTech Health, Inc.

Superparamagnetic iron oxide nanoparticles conjugated with Aβ oligomer-specific scFv antibody and class A scavenger receptor activator show therapeutic potentials for Alzheimer’s Disease

Background Alzheimer’s disease (AD) is a progressive neurodegenerative disorder. No disease-modifying strategy to prevent or delay AD progression currently exists. Aβ oligomers (AβOs), rather than monomers or fibrils, are considered as the primary neurotoxic species. Therapeutic approaches that direct against AβOs and promote Aβ clearance may have great value for AD treatment. Results We here reported a multifunctional superparamagnetic iron oxide nanoparticle conjugated with Aβ oligomer-specific scFv antibody W20 and class A scavenger receptor activator XD4 (W20/XD4-SPIONs). Besides the diagnostic value, W20/XD4-SPIONs retained the anti-Aβ properties of W20 and XD4 by inhibiting Aβ aggregation, attenuating AβO-induced cytotoxicity and increasing microglial phagocytosis of Aβ. When applied to APP/PS1 mice, W20/XD4-SPIONs significantly rescued cognitive deficits and alleviated neuropathology of AD mice. Conclusion These results suggest that W20/XD4-SPIONs show therapeutic benefits for AD. In combination with the early diagnostic property, W20/XD4-SPIONs present as a promising agent for early-stage AD diagnosis and intervention.

Superparamagnetic iron oxide nanoparticles conjugated with Aβ oligomer-specific scFv antibody and class A scavenger receptor activator show therapeutic potentials for Alzheimer’s Disease

Background: Alzheimer’s disease (AD) is a progressive neurodegenerative disorder. No disease-modifying strategy to prevent or delay AD progression currently exists. Aβ oligomers (AβOs), rather than monomers or fibrils, are considered as the primary neurotoxic species. Therapeutic approaches that direct against AβOs and promote Aβ clearance may have great value for AD treatment. Results: We here reported a multifunctional superparamagnetic iron oxide nanoparticle conjugated with oligomer-specific scFv antibody W20 and class A scavenger receptor activator XD4 (W20/XD4-SPIONs). Besides the diagnostic value, W20/XD4-SPIONs retained the anti-Aβ properties of W20 and XD4 by inhibiting Aβ aggregation, attenuating AβO-induced cytotoxicity and increasing microglial phagocytosis of Aβ. When applied to APP/PS1 mice, W20/XD4-SPIONs significantly rescued cognitive deficits and alleviated neuropathology of AD mice. Conclusion: These results suggest that W20/XD4-SPIONs show therapeutic benefits for AD. In combination with the early diagnostic property, W20/XD4-SPIONs present as a promising agent for early-stage AD diagnosis and intervention.

Superparamagnetic Iron Oxide Nanoparticles Conjugated with Aβ Oligomer-Specific scFv Antibody and Class A Scavenger Receptor Activator Show Therapeutic Potentials for Alzheimer’s Disease

Background: Alzheimer’s disease (AD) is an incurable and progressive neurodegenerative disorder. Disease-modifying strategies to prevent or delay AD progression are urgently needed. Aβ oligomers (AβOs), rather than monomers or fibrils, are considered as the most neurotoxic species. Therapeutic approaches that direct against these oligomers and promote Aβ clearance may have great value for AD intervention. Results: We here reported the novel multifunctional nanoparticle W20/XD4-SPIONs, which were constructed by conjugating oligomer-specific scFv antibody W20 and class A scavenger receptor activator XD4 onto superparamagnetic iron oxide nanoparticles (SPIONs). Besides the diagnostic value, W20/XD4-SPIONs retained the properties of W20 and XD4 by inhibiting Aβ aggregation, attenuating AβOs-induced cytotoxicity and increasing microglial phagocytosis of Aβ. When applied to AD transgenic mouse model, W20/XD4-SPIONs significantly rescued cognitive deficits and alleviated neuropathology of AD transgenic mice. Conclusion: These results suggest that W20/XD4-SPIONs are a promising therapeutic agent for AD. As a molecular probe, W20/XD4-SPIONs also specifically and sensitively bind to the AβOs in AD brains to provide an MRI signal, demonstrating that W20/XD4-SPIONs are a promising agent for early-stage AD.