TNF-α promotes extracellular vesicle release in mouse astrocytes through glutaminase

Abstract

BackgroundExtracellular vesicles (EVs) are membrane-contained vesicles shed from cells. EVs contain proteins, lipids, and nucleotides, all of which play important roles in intercellular communication. The release of EVs is known to increase during neuroinflammation. Glutaminase, a mitochondrial enzyme that converts glutamine to glutamate, has been implicated in the biogenesis of EVs. We have previously demonstrated that TNF-α promotes glutaminase expression in neurons. However, the expression and the functionality of glutaminase in astrocytes during neuroinflammation remain unknown. We posit that TNF-α can promote the release of EVs in astrocytes through upregulation of glutaminase expression.ResultsRelease of EVs, which was demonstrated by electron microscopy, nanoparticle tracking analysis (NTA), and Western Blot, increased in mouse astrocytes when treated with TNF-α. Furthermore, TNF-α treatment significantly upregulated protein levels of glutaminase and increased the production of glutamate, suggesting that glutaminase activity is increased after TNF-α treatment. Interestingly, pretreatment with a glutaminase inhibitor blocked TNF-α-mediated generation of reactive oxygen species in astrocytes, which indicates that glutaminase activity contributes to stress in astrocytes during neuroinflammation. TNF-α-mediated increased release of EVs can be blocked by either the glutaminase inhibitor, antioxidant N-acetyl-l-cysteine, or genetic knockout of glutaminase, suggesting that glutaminase plays an important role in astrocyte EV release during neuroinflammation.ConclusionsThese findings suggest that glutaminase is an important metabolic factor controlling EV release from astrocytes during neuroinflammation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-017-0853-2) contains supplementary material, which is available to authorized users.

Propofol reduces microglia activation and neurotoxicity through inhibition of extracellular vesicle release

“…EVs can be found in interstitial fluid, cerebrospinal fluid (Vella et al, 2008), circulating blood (Suetsugu et al, 2013), and primarily assert biological function through delivering cytokines, nucleic acids, lipids, and proteins to nearby or distant cells, suggesting that they play an important role in cell-to-cell communication (Thery et al, 2006). EV secretion is increased during neuroinflammation; our previous studies, along with others', have suggested that EVs fuel pathogenic processes in the brain during neuroinflammation (Gupta and Pulliam, 2014;Huang et al, 2018;Wang et al, 2017;Wu et al, 2015;Wu et al, 2018).…”

Glutaminase 1 Regulates Neuroinflammation After Cerebral Ischemia Through Enhancing Microglial Activation and Pro-Inflammatory Exosome Release

“…Because our previous findings indicate that GLS1 is a key enzyme in exosomes release of glial cells including microglia and astrocytes in vitro (16,17), we examined whether or not the alteration of exosome release in focal cerebral ischemic brains is mediated by GLS1. NTA demonstrated that GLS1 inhibition by CB839 administration significantly reduced the concentration of exosome in ischemic rat brains vs. the DMSO-treated ischemia group (Figure 5A).…”

The Role and Impact of Extracellular Vesicles in the Modulation and Delivery of Cytokines during Autoimmunity

“…TNF-α is implicated across a range of autoimmune conditions and diseases and has received great attention as a therapeutic target [ 23 ]. Organ-specific increases in TNF-α have been shown to induce innate immune cell infiltration and activation, tissue resident cell activation, and pro-inflammatory cytokine secretion [ 24 , 25 , 26 ]. In particular, the blockade of TNF-α has been shown to ameliorate the inflammatory symptoms of RA and attenuate the extent of joint and cartilage erosion [ 27 ].…”