Periodic Reporting for period 1 - ENTRAIN (ENdoThelial macRophage Alliance In Neuroinflammation) Reporting period: 2019-05-01 to 2021-04-30 Summary of the context and overall objectives of the project Neurological diseases cause enormous suffering and a great economic burden. Almost 20 million Europeans are affected by the most frequently occurring and disabling disease entities, such as stroke, Alzheimer’s disease (AD), or multiple sclerosis (MS), and these numbers do not include the large group of rare diseases that affect the CNS. Overall, the annual costs for patient care amount to 400 billion Euros. Common features of many neurological diseases are a vascular pathology with impaired blood-brain barrier function or with reduced blood flow and inflammatory changes. As the two are often associated, disentangling their intricate and mutual relationship is a major task for translational neuroscience that could improve the treatment of many neurological diseases. At the cellular level, key players are brain endothelial cells as the building blocks of cerebral vessels and macrophages as the main inflammatory cells of the brain. Recent discoveries indicate that endothelial cells and brain macrophages are in intimate contact and closely interact. However, there is a huge gap of knowledge regarding the specific mode and the consequences of these interactions. Therefore, in-depth analyses of the molecular mechanisms involved are essential to identify and understand key features of macrophage-endothelial cross-talk, and exploitation of this information for the development of treatments of neurological diseases. ENTRAIN undertakes this task, using novel and emerging technologies, such as cutting-edge chemoproteomics, unique genetic and viral tools for targeting of defined cell populations, and high resolution intravital imaging. By characterising the pas de deux of endothelial cells and macrophages at the functional and morphological level, we aim to lay the foundation for better therapies for neurological diseases. The results may impact on the understanding of neuroinflammation, but also on the rarefaction of vessels. Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far In ENTRAIN thirteen partners from the academic and private sector with complementary scientific background have joined forces. Partners have experience in investigating the blood-brain barrier and/or brain macrophages. They have acquired a large number of tools and methods to explore the biology of brain endothelial cells and macrophages. Investigating key aspects of endothelial-macrophage interaction, they train 14 Early Stage Researchers (ESRs) in experimental and translational research. Work is structured according to the direction of the interaction. WP1 focuses on effects of endothelial cells on macrophages. WP2 takes a reverse perspective and looks at macrophage effects on the blood-brain. Finally, WP3 aims for pharmacological tools to modulate the mutual interaction. In a very fruitful kick-off meeting in Barcelona in October 2019 we have reinforced our close collaborations and coordinated the first steps for implementing the project. Due to the corona pandemic, the 2nd network meeting took place as an online meeting in May 2020. To compensate for restricted traveling we have established a monthly online seminar consisting of project report and journal club as well as an introductory lecture by one of the PIs. Starting on May 1st 2019, ENTRAIN runs for four years. After the first 24 months, preliminary results have been obtained. In WP1 “Endothelial checkpoints of macrophage function”, Kristina Berve, UNIBERN, has established a mouse model to investigate the effects of angiopoietin-2 on CNS-resident macrophages and inflammatory myeloid cells. Sai Kiran Samawar Reddy, WWU, investigates how the basement membrane proteins laminin α4 and α5 impact on the immigration of myeloid cells into the inflamed CNS. Lais Sousa da Silva Ferreira, UKLFR, has performed the first steps to manipulate lysine-specific demethylation in glial cells of the CNS. To explore the apicobasal polarisation of brain endothelial cells when orchestrating the immigration of immune cells into the CNS, Jacqueline Hammer, ETHZ, has set up proteomics tools and cell culture models of the blood-brain barrier. The cell biology work has been performed in close cooperation with VUMC. In WP2 “Modulation of endothelial function by macrophages”, Cathrin Hansen, VUMC, has adapted lipidomics to characterize the production and secretion of bioactive lipids that are involved in the resolution of inflammation. Ana Rita Bras, IEM HAS, is characterizing anatomical contacts between endothelial cells and brain macrophages by employing high-end imaging techniques. Tibzit Bogale, UNIBS, explores the role of α-synuclein in shaping the interaction between endothelial cells and brain macrophages. Martina Glavan, INSERM, employs advanced imaging techniques to analyse the role of perivascular macrophages in the pathogenesis of aneurysms. Joe Kelk, IRFMN, focuses on the role of perivascular macrophages in models of ischemic stroke and characterizes morphological aspects of these cells. Ümit Özorhan, UZL, investigates whether microglia and perivascular macrophages determine vessel density in a model of small vessel disease. In WP3 “Endothelial-macrophage interaction as a therapeutic target”, Arya Lekshmi Nair, MIM, has established a human neurovascular unit on-a-chip model to promote pharmacological studies. In a parallel endeavour, Ying-Chieh Wu is reconstituting in vitro blood-brain barrier models with cells derived from patient iPSCs. Dimitrios Spyropoulos, UZL, is studying the role of G protein signalling as a target of potential drugs that restore the blood-brain barrier. Last but not least, Sara Figuerola, CSIC, explores the interaction between perivascular macrophages and brain endothelial cells as a drug target focusing on exosomes. Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far) Continuing along these lines, we expect that the consortium will refine current concepts on the interaction between macrophages and endothelial cells in the CNS. The scientific progress we aim for may provide the basis for drug development in the future. Up to now the first scientific results of the consortium have been published in 12 papers –and counting. Second and equally important, the consortium takes pride in training 14 talented ESRs that show a high degree of team spirit despite the difficulties caused by the pandemic. We are very confident that the ESRs will make important contributions to the European scientific community and to translational research. For further information please visit the ENTRAIN website: https://itn-entrain.eu or contact the coordinator Markus Schwaninger, Institute for Pharmacology and Toxicology, Ratzeburger Allee 160, 23562 Lübeck, Germany, Tel: +49-451-3101-7200, E-Mail: markus.schwaninger@uni-luebeck.de. Microglia in close contact with vessels and string vessel. Iba-1 labeled microglia distributed along
