Plasma derived extracellular vesicle biomarkers of microglia activation in an experimental stroke model.

Chronic microglia activation post-stroke is associated with worse neurological and cognitive outcomes. However, measurement of microglia activation in vivo is currently limited. Plasma derived extracellular vesicles (EVs) are cell-specific indicators that may allow for non-invasive measurement of microglia phenotype. The aim of this study was to identify activation-state specific microglia EVs (MEVs) in vitro followed by validation in an experimental stroke model. Following pro-inflammatory activation, MEVs contain the microglia protein TMEM119 alongside increased expression of the Toll-like receptor 4 co-receptor CD14. Immunoprecipitation followed by fluorescent nanoparticle tracking analysis (ONI Nanoimager) was used to confirm the isolation of TMEM119+/CD14+ EVs from rat plasma. Electron microscopy confirmed that TMEM119 and CD14 localize to the MEV membrane. To model ischemia, plasma was collected from 3-month wildtype Fischer344 rats prior to, 7 and 28 days after endothelin-1 or saline injection into the dorsal right striatum. Fluorescently labelled MEVs were directly measured in the plasma using nanoflow cytometry (Apogee A60 Microplus). We report a significant increase in circulating TMEM119+/CD14+ EVs 28-days post-stroke in comparison to baseline levels and saline-injected rats, which correlated weakly with stroke volume. TMEM119+/MHC-II+ EVs were also increased post-stroke in comparison to baseline and saline-injected animals. This study is the first to describe an EV biomarker of activated microglia detected directly in plasma following stroke and represents a future tool for the measurement of microglia activity in vivo.

Fibrinogen primes the microglial NLRP3 inflammasome and propagates pro-inflammatory signaling via extracellular vesicles: Implications for blood-brain barrier dysfunction.

The brain's response to acute injury is characterized by increased permeability of the blood-brain barrier (BBB) and pro-inflammatory microglia signaling, both of which have been linked to poor cognitive outcomes and neurological disease. The damaged BBB has increased leakiness, allowing serum proteins like fibrinogen into the brain, which interacts with local cells in a deleterious manner. At the same time, in response to injury, microglia demonstrate increased NLRP3 inflammasome activity and heightened release of pro-inflammatory cytokines. The relationship between increased fibrinogen uptake and microglial inflammasome signaling in the injured brain has not been well described. In this work, we investigate fibrinogen mediated NLRP3 inflammasome priming of BV-2 cells and primary adult microglia and propose a role for extracellular vesicles (EVs) as propagators of this interaction. Following exposure to fibrinogen microglia significantly upregulate transcription of IL-1ß, IL-6, NLRP3 and other pro-inflammatory cytokines which was sustained by repeated fibrinogen exposure. Inhibition of fibrinogen mediated NLRP3 signaling was achieved at the transcriptional and assembly level using cannabidiol (CBD) and the NLRP3 inhibitor MCC950, respectively. EVs released following NLRP3 priming carry IL-1ß, IL-18 mRNA and fibrinogen, propagate inflammatory signaling and can be detected in the circulation following BBB disruption in a preclinical stroke model. In conclusion, the interplay between fibrinogen extravasation, microglial NLRP3 signaling, and EV release can perpetuate chronic pro-inflammatory signaling and represents a novel method of inflammatory propagation.

Ambroxol as a novel disease-modifying treatment for Parkinson's disease dementia: protocol for a single-centre, randomized, double-blind, placebo-controlled trial.

BACKGROUND: Currently there are no disease-modifying treatments for Parkinson's disease dementia (PDD), a condition linked to aggregation of the protein α-synuclein in subcortical and cortical brain areas. One of the leading genetic risk factors for Parkinson's disease is being a carrier in the gene for ß-Glucocerebrosidase (GCase; gene name GBA1). Studies in cell culture and animal models have shown that raising the levels of GCase can decrease levels of α-synuclein. Ambroxol is a pharmacological chaperone for GCase and is able to raise the levels of GCase and could therefore be a disease-modifying treatment for PDD. The aims of this trial are to determine if Ambroxol is safe and well-tolerated by individuals with PDD and if Ambroxol affects cognitive, biochemical, and neuroimaging measures. METHODS: This is a phase II, single-centre, double-blind, randomized placebo-controlled trial involving 75 individuals with mild to moderate PDD. Participants will be randomized into Ambroxol high-dose (1050 mg/day), low-dose (525 mg/day), or placebo treatment arms. Assessments will be undertaken at baseline, 6-months, and 12-months follow up times. Primary outcome measures will be the Alzheimer's disease Assessment Scale-cognitive subscale (ADAS-Cog) and the ADCS Clinician's Global Impression of Change (CGIC). Secondary measures will include the Parkinson's disease Cognitive Rating Scale, Clinical Dementia Rating, Trail Making Test, Stroop Test, Unified Parkinson's disease Rating Scale, Purdue Pegboard, Timed Up and Go, and gait kinematics. Markers of neurodegeneration will include MRI and CSF measures. Pharmacokinetics and pharmacodynamics of Ambroxol will be examined through plasma levels during dose titration phase and evaluation of GCase activity in lymphocytes. DISCUSSION: If found effective and safe, Ambroxol will be one of the first disease-modifying treatments for PDD. TRIAL REGISTRATION: ClinicalTrials.gov NCT02914366, 26 Sep 2016/retrospectively registered.

Ataxia in prion protein (PrP)-deficient mice is associated with upregulation of the novel PrP-like protein doppel.

The novel locus Prnd is 16 kb downstream of the mouse prion protein (PrP) gene Prnp and encodes a 179 residue PrP-like protein designated doppel (Dpl). Prnd generates major transcripts of 1.7 and 2.7 kb as well as some unusual chimeric transcripts generated by intergenic splicing with Prnp. Like PrP, Dpl mRNA is expressed during embryogenesis but, in contrast to PrP, it is expressed minimally in the CNS. Unexpectedly, Dpl is upregulated in the CNS of two PrP-deficient (Prnp(0/0)) lines of mice, both of which develop late-onset ataxia, suggesting that Dpl may provoke neurodegeneration. Dpl is the first PrP-like protein to be described in mammals, and since Dpl seems to cause neurodegeneration similar to PrP, the linked expression of the Prnp and Prnd genes may play a previously unrecognized role in the pathogenesis of prion diseases or other illnesses.