Extracellular microvesicles promote microglia‐mediated pro‐inflammatory responses to ethanol

• Published in: Journal of neuroscience research Vol. 99; no. 8; pp. 1940 - 1956
• Main Authors: Crews, Fulton T., Zou, Jian, Coleman, Leon G.
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.08.2021; John Wiley and Sons Inc
• Subjects: 1-Phosphatidylinositol 3-kinase; Abuse; Alcohol abuse; Alcohol use; alcohol use disorder; Animals; Brain - metabolism; Brain slice preparation; Cell culture; Class I Phosphatidylinositol 3-Kinases - metabolism; CX3C Chemokine Receptor 1 - metabolism; CX3CR1 protein; Depletion; Drug abuse; Ethanol; Ethanol - pharmacology; Extracellular vesicles; Extracellular Vesicles - drug effects; Extracellular Vesicles - metabolism; Female; Fractalkine; Gene Expression; Glycyrrhizin; Hippocampus - metabolism; HMGB1 protein; HMGB1 Protein - metabolism; Imipramine; inflammation; Interleukin-1beta - metabolism; Kinases; Male; Membrane Glycoproteins; Microglia; Microglia - drug effects; Microglia - metabolism; neuroimmune; Neuroinflammatory Diseases - metabolism; Phagocytes; Phosphatidylinositol 3-Kinases - metabolism; Primary Cell Culture; Rats; Rats, Sprague-Dawley; Receptors; Receptors, Immunologic; Receptors, Purinergic P2Y12 - metabolism; Reduction; Signaling; Therapeutic targets; Tumor necrosis factor; Tumor Necrosis Factor-alpha - metabolism; alcohol use disorder; neuroimmune; extracellular vesicles; inflammation; microglia
• ISSN: 0360-4012; 1097-4547
• DOI: 10.1002/jnr.24813

Alcohol use disorder (AUD) pathology features pro‐inflammatory gene induction and microglial activation. The underlying cellular processes that promote this activation remain unclear. Previously considered cellular debris, extracellular vesicles (EVs) have emerged as mediators of inflammatory signaling in several disease states. We investigated the role of microvesicles (MVs, 50 nm–100 µm diameter EVs) in pro‐inflammatory and microglial functional gene expression using primary organotypic brain slice culture (OBSC). Ethanol caused a unique immune gene signature that featured: temporal induction of pro‐inflammatory TNF‐α and IL‐1β, reduction of homeostatic microglia state gene Tmem119, progressive increases in purinergic receptor P2RY12 and the microglial inhibitory fractalkine receptor CX3CR1, an increase in the microglial presynaptic gene C1q, and a reduction in the phagocytic gene TREM2. MV signaling was implicated in this response as reduction of MV secretion by imipramine blocked pro‐inflammatory TNF‐α and IL‐1β induction by ethanol, and ethanol‐conditioned MVs (EtOH‐MVs) reproduced the ethanol‐associated immune gene signature in naïve OBSC slices. Depletion of microglia prior to ethanol treatment prevented pro‐inflammatory activity of EtOH‐MVs, as did incubation of EtOH‐MVs with the HMGB1 inhibitor glycyrrhizin. Ethanol caused HMGB1 secretion from cultured BV2 microglia in MVs through activation of PI3 kinase. In summary, these studies find MVs modulate pro‐inflammatory gene induction and microglial activation changes associated with ethanol. Thus, MVs may represent a novel therapeutic target to reduce neuroinflammation in the setting of alcohol abuse or other diseases that feature a neuroimmune component. [Correction added on 5 April 2021, after first online publication: The copyright line was changed.] Ethanol causes the secretion of pro‐inflammatory microvesicles (MVs) from brain tissue. Ethanol‐induced MVs reproduce the pro‐inflammatory gene induction and microglial activation seen with ethanol alone, and inhibition of their secretion blocks ethanol‐induced neuroinflammation. Microglia are required for the generation of pro‐inflammatory MVs, with MV secretion involving activation of microglial PI3K.