Acid sphingomyelinase activity triggers microparticle release from glial cells

CNR Institute of Neuroscience and Department of Medical Pharmacology, University of Milano, Milano, Italy.
The EMBO Journal (Impact Factor: 10.75). 04/2009; 28(8):1043-54. DOI: 10.1038/emboj.2009.45
Source: PubMed

ABSTRACT We have earlier shown that microglia, the immune cells of the CNS, release microparticles from cell plasma membrane after ATP stimulation. These vesicles contain and release IL-1beta, a crucial cytokine in CNS inflammatory events. In this study, we show that microparticles are also released by astrocytes and we get insights into the mechanism of their shedding. We show that, on activation of the ATP receptor P2X7, microparticle shedding is associated with rapid activation of acid sphingomyelinase, which moves to plasma membrane outer leaflet. ATP-induced shedding and IL-1beta release are markedly reduced by the inhibition of acid sphingomyelinase, and completely blocked in glial cultures from acid sphingomyelinase knockout mice. We also show that p38 MAPK cascade is relevant for the whole process, as specific kinase inhibitors strongly reduce acid sphingomyelinase activation, microparticle shedding and IL-1beta release. Our results represent the first demonstration that activation of acid sphingomyelinase is necessary and sufficient for microparticle release from glial cells and define key molecular effectors of microparticle formation and IL-1beta release, thus, opening new strategies for the treatment of neuroinflammatory diseases.

Download full-text


Available from: Roberto Furlan, Aug 18, 2015
1 Follower
  • Source
    • "Microparticles containing ␤-actin are released from vascular endothelial cells stimulated by inflammatory mediators [29] [30] [31] [32]. However, reported released vesicles and microparticles are generally much smaller in size than the cofilin rods seen here in AD brain [29] [30]. Nevertheless, these mechanisms could point to cofilin rods/aggregates as potential markers of microglial activation and/or inflammation. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Background: Imaging of human brain as well as cellular and animal models has highlighted a role for the actin cytoskeleton in the development of cell pathology in Alzheimer's disease (AD). Rods and aggregates of the actin-associated protein cofilin are abundant in grey matter of postmortem AD brain and rods are found inside neurites in animal and cell models of AD. Objective: We sought further understanding of the significance of cofilin rods/aggregates to the disease process: Do rods/aggregates correlate with AD progression and the development of hallmark neurofibrillary tangles and neuropil threads? Are cofilin rods/aggregates found in the same neurites as hyperphosphorylated tau? Methods: The specificity of rods/aggregates to AD compared with general aging and their spatial relationship to tau protein was examined in postmortem human hippocampus, inferior temporal cortex, and anterior cingulate cortex. Results: The presence of cofilin rods/aggregates correlated with the extent of tau pathology independent of patient age. Densities of rods/aggregates were fourfold greater in AD compared with aged-matched control brains and rods/aggregates were significantly larger in AD brain. We did not find evidence for our hypothesis that intracellular cofilin rods are localized to tau-positive neuropil threads. Instead, data suggest the involvement of microglia in the clearance of cofilin rods/aggregates and/or in their synthesis in and around amyloid plaques and surrounding neuropil. Conclusion: Cofilin rods and aggregates signify events initiated early in the pathological cascade. Further definition of the mechanisms leading to their formation in the human brain will provide insights into the cellular causes of AD.
    Journal of Alzheimer's disease: JAD 07/2014; 42(4). DOI:10.3233/JAD-140393 · 4.15 Impact Factor
  • Source
    • "It has been suggested that these micMP may be a rapid and specific way for the brain to relay its immune status to not only its own resident microglial population, but also to the systemic circulation (Bianco et al., 2009). MicMP and astrocytic MP are frequently found to contain IL-1b and have been shown to release it upon stimulation by ATP (Bianco et al., 2009). Since ATP is often associated with neuroinflammation , it is therefore reasonable to assume that the release of ATP from damaged neurons may be a way of rapidly activating microglia and opening MP pores for swift dissemination of IL-1b and other proinflammatory cytokines. "
  • Source
    • "EVs were obtained by ultracentrifugation as described earlier [9] [14] [33] [34]. Briefly, culture supernatants were centrifuged for 10 min at 400 g, followed by 2 h at 100,000 g to pellet EVs, which were washed extensively in phosphate buffered saline (PBS). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Transitions of the cancer cell phenotype between epithelial and mesenchymal states is likely to alter the patterns of intercellular communication. In this regard we have previously documented that EMT-like changes trigger quantitative changes in exosomal vesicle emission in A431 cancer cells driven by oncogenic epidermal growth factor receptor (EGFR). Here we report that extracellular vesicles (EVs) produced by these cancer cells in their epithelial and mesenchymal states exhibit profound qualitative differences in their proteome. Thus, induction of the EMT-like state through blockade of E-cadherin and EGFR stimulation resulted in mesenchymal shift in cellular morphology and enrichment in the CD44-high/CD24-low immunophenotype, often linked to cellular stemness. This change also resulted in reprogramming of the EV-related proteome (distinct from that of corresponding cells), which contained 30 unique protein signals, and revealed enrichment in pathways related to cellular growth, cell-to-cell signalling, and cell movement. Some of the most prominent EV-related proteins were validated, including integrin ∀2 and tetraspanin CD9. We propose that changes in cellular differentiation status translate into unique qualitative rearrangements in the cargo of EVs, a process that may have implications for intercellular communication and could serve as source of new biomarkers of EMT-like changes in cancer.
    Experimental Cell Research 08/2013; 319(17). DOI:10.1016/j.yexcr.2013.08.003 · 3.37 Impact Factor
Show more