The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles (“MISEV”) guidelines for the field in 2014. We now update these “MISEV2014” guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points.
The activation of Toll-like receptors (TLRs) is central to innate and adaptive immunity. All TLRs use the adaptor MyD88 for signalling, but the mechanisms underlying the MyD88-mediated gene induction programme are as yet not fully understood. Here, we demonstrate that the transcription factor IRF-5 is generally involved downstream of the TLR-MyD88 signalling pathway for gene induction of proinflammatory cytokines, such as interleukin-6 (IL-6), IL-12 and tumour-necrosis factor-alpha. In haematopoietic cells from mice deficient in the Irf5 gene (Irf5-/- mice), the induction of these cytokines by various TLR ligands is severely impaired, whereas interferon-alpha induction is normal. We also provide evidence that IRF-5 interacts with and is activated by MyD88 and TRAF6, and that TLR activation results in the nuclear translocation of IRF-5 to activate cytokine gene transcription. Consistently, Irf5-/- mice show resistance to lethal shock induced by either unmethylated DNA or lipopolysaccharide, which correlates with a marked decrease in the serum levels of proinflammatory cytokines. Thus, our study identifies IRF-5 as a new, principal downstream regulator of the TLR-MyD88 signalling pathway and a potential target of therapeutic intervention to control harmful immune responses.
Environmental stressors during childhood and adolescence influence postnatal brain maturation and human behavioral patterns in adulthood. Accordingly, excess stressors result in adult-onset neuropsychiatric disorders. We describe an underlying mechanism in which glucocorticoids link adolescent stressors to epigenetic controls in neurons. In a mouse model of this phenomenon, a mild isolation stress affects the mesocortical projection of dopaminergic neurons in which DNA hypermethylation of the tyrosine hydroxylase gene is elicited, but only when combined with a relevant genetic risk for neuropsychiatric disorders. These molecular changes are associated with several neurochemical and behavioral deficits that occur in this mouse model, all of which are blocked by a glucocorticoid receptor antagonist. The biology and phenotypes of the mouse models resemble those of psychotic depression, a common and debilitating psychiatric disease.
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