Exosomes from eosinophils autoregulate and promote eosinophil functions

Abstract

Eosinophils are able to secrete exosomes that have an undefined role in asthma pathogenesis. We hypothesized that exosomes released by eosinophils autoregulate and promote eosinophil function. Eosinophils of patients with asthma ( = 58) and healthy volunteers ( = 16) were purified from peripheral blood, and exosomes were isolated and quantified from eosinophils of the asthmatic and healthy populations. Apoptosis, adhesion, adhesion molecules expression, and migration assays were performed with eosinophils in the presence or absence of exosomes from healthy and asthmatic individuals. Reactive oxygen species (ROS) were evaluated by flow cytometry with an intracellular fluorescent probe and nitric oxide (NO) and a colorimetric kit. In addition, exosomal proteins were analyzed by mass spectrometry. Eosinophil-derived exosomes induced an increase in NO and ROS production on eosinophils. Moreover, exosomes could act as a chemotactic factor on eosinophils, and they produced an increase in cell adhesion, giving rise to a specific augmentation of adhesion molecules, such as ICAM-1 and integrin α2. Protein content between exosomes from healthy and asthmatic individuals seems to be similar in both groups. In conclusion, we found that exosomes from the eosinophils of patients with asthma could modify several specific eosinophil functions related to asthma pathogenesis and that they could contribute fundamentally to the development and maintenance of asthma.

Recent advances in understanding eosinophil biology

“…As expected, eosinophil exosomes express CD63 and CD9 on their surface and contain a variety of eosinophil proteins, including eosinophil cationic protein and eosinophil peroxidase 84 . Eosinophil production of exosomes was increased in patients with asthma and in response to in vitro stimulation with CCL11, TNFα, or interferon gamma 82, 83 .…”

“…Eosinophil production of exosomes was increased in patients with asthma and in response to in vitro stimulation with CCL11, TNFα, or interferon gamma 82, 83 . Moreover, eosinophil-derived exosomes induced an increase in reactive oxygen intermediates by eosinophils and could induce eosinophil adhesion and chemotaxis in vitro 84 . Since the composition of eosinophil exosomes appears to be similar between asthmatic patients and normal controls, these data suggest that selective packaging of mediators into exosomes may play an important role in modulating the outcomes of eosinophil activation in different settings.…”

Novel Modulators of Asthma and Allergy: Exosomes and MicroRNAs

“…To date, there are only two published studies by our group that have characterized eosinophil exosomes and their implications for the pathogenesis of asthma (8, 69). Eosinophils secrete nanovesicles that are consistent in size (162 nm diameter, by NanoSight measurement), shape (cup-shape morphology), and composition (presence of CD63, CD9, and ALIX) with exosomes.…”

“…Also, these exosomes increase the migratory capacity in eosinophils, as well as, their adhesion and adhesion molecule expression, which are important processes in asthma. By contrast, eosinophil-derived exosomes from healthy patients do not affect to asthmatic eosinophil functionality (69). Also, we have described the exosome uptake mechanism of eosinophils which involves direct internalization of the whole vesicle, corresponding with one of the two previously described uptake mechanisms (70).…”

Exosomes from Thymic Stromal Lymphopoietin-Activated Dendritic Cells Promote Th2 Differentiation through the OX40 Ligand

“…For example, mast cell-derived exosomes induce DCs to have an antigen-presenting capacity for T cells and modulate the activation of T lymphocytes to secrete cytokines such as IL-6, IL-12, and IFN-γ [23, 24]. Exosomes are also released by eosinophils and increased in asthmatic patients; they contain the main eosinophilic proteins and may play a role in driving the progression of asthma via eosinophils by increasing the production of chemokines, reactive oxygen species (ROS), and nitric oxide (NO) [25, 26]. B-cell-derived exosomes can specifically present antigens to T cells and induce T-cell responses [27].…”