Michael Graner

Alzheimer’s disease (AD) is the fifth leading cause of death among adults aged 65 and older, yet the onset and progression of the disease is poorly understood. What is known is that the presence of amyloid, particularly polymerized Aβ42, defines when people are on the AD continuum. Interestingly, as AD progresses, less Aβ42 is detectable in the plasma, a phenomenon thought to result from Aβ becoming more aggregated in the brain and less Aβ42 and Aβ40 being transported from the brain to the plasma via the CSF. We propose that extracellular vesicles (EVs) play a role in this transport. EVs are found in bodily fluids such as blood, urine, and cerebrospinal fluid and carry diverse “cargos” of bioactive molecules (e.g., proteins, nucleic acids, lipids, metabolites) that dynamically reflect changes in the cells from which they are secreted. While Aβ42 and Aβ40 have been reported to be present in EVs, it is not known whether this interaction is specific for these peptides and thus whether amyloid-carrying EVs play a role in AD and/or serve as brain-specific biomarkers of the AD process. To determine if there is a specific interaction between Aβ and EVs, we used isothermal titration calorimetry (ITC) and discovered that Aβ42 and Aβ40 bind to EVs in a manner that is sequence specific, saturable, and endothermic. In addition, Aβ incubation with EVs overnight yielded larger amounts of bound Aβ peptide that was fibrillar in structure. These findings point to a specific amyloid–EV interaction, a potential role for EVs in the transport of amyloid from the brain to the blood, and a role for this amyloid pool in the AD process.

Glioblastomas (GBM) are a devastating disease with extremely poor clinical outcomes. Resident (microglia) and infiltrating macrophages are a substantial component of the tumor environment. In GBM and other cancers, tumor-derived extracellular vesicles (EVs) suppress macrophage inflammatory responses, impairing their ability to identify and phagocytose cancerous tissues. Furthermore, these macrophages then begin to produce EVs that support tumor growth and migration. This cross-talk between macrophages/microglia and gliomas is a significant contributor to GBM pathophysiology. Here, we review the mechanisms through which GBM-derived EVs impair macrophage function, how subsequent macrophage-derived EVs support tumor growth, and the current therapeutic approaches to target GBM/macrophage EV crosstalk.