Cytokines Stimulate the Release of Microvesicles from Myeloid Cells Independently from the P2X7 Receptor/Acid Sphingomyelinase Pathway

Abstract

Microvesicles (MVs) are membrane particles of 200–500 nm released by all cell types constitutively. MVs of myeloid origin are found increased in the cerebrospinal fluid (CSF) of patients suffering from neuroinflammatory disorders, although the factors triggering their production have never been defined. Here, we report that both pro- and anti-inflammatory cytokines, specifically interferon-γ and interleukin-4, are equally able to stimulate the production of MVs from microglia cells and monocytes. Additionally, we found this process to be independent from the best characterized molecular pathway so far described for membrane shedding, which is centered on the purinergic receptor P2X7, whose activation by high concentrations of extracellular ATP (exATP) results in membrane blebbing operated by the secreted enzyme acid sphingomyelinase (ASMase). Moreover, a potent inhibitor of ASMase, injected in a mouse model of multiple sclerosis, failed to reduce the number of MVs in their CSF. This suggests that cytokines, rather than exATP, may exert a long-term control of MV production in the context of chronic inflammation, where both pro- and anti-inflammatory factors play coordinated roles.

Role of sphingolipids in the biogenesis and biological activity of extracellular vesicles

“…Intriguingly, both constitutive release of MVs and cytokine-induced MV release were efficiently blocked by a sub-toxic concentration of actinomycin D, a strong inhibitor of transcription. While ruling out a role for a-SMase in constitutive release of MVs, this study suggests that cytokines may strengthen constitutive MV production through modulation of the transcriptional activity in myeloid cells (97).…”

Extracellular Vesicles Containing IL-4 Modulate Neuroinflammation in a Mouse Model of Multiple Sclerosis

“…EVs were purified from the cell media using a standardized protocol 35 with slight modifications: conditioned cell supernatants were collected and centrifuged for 10 min at 300 Â g to remove floating cells and debris. The resulting supernatants were further cleared through a 0.45-mm syringe filter (Millex, Millipore), then ultra-centrifuged at 100,000 Â g for 1 hr to pellet EVs.…”

NeuroEVs: Characterizing Extracellular Vesicles Generated in the Neural Domain

“…More recently, EVs have also been shown to prevent antibody-mediated neutralization of encapsulated viral particles, thereby allowing for the propagation of viral infection (Bello-Morales et al, 2018). Additionally, during an activated neuroimmune response, both microglia and astrocytes release EVs that contain the cytokine interleukin-1␤ (IL-1␤), which further contributes to immune signaling (Bianco et al, 2005(Bianco et al, , 2009Colombo et al, 2018). EVs released from microglia also contain other signaling factors related to the immune response, including major histocompatibility Class II receptors, CD13, TNF, caspase 1, metalloproteinases, tetraspanins, and chaperones (Potolicchio et al, 2005;Robbins and Morelli, 2014;Budnik et al, 2016).…”