ACKR1 favors transcellular over paracellular T-cell diapedesis across the blood-brain barrier during neuroinflammation

The migration of CD4+ effector/memory T cells across the blood-brain barrier (BBB) is a critical step in multiple sclerosis or its animal model, experimental autoimmune encephalomyelitis (EAE). T-cell diapedesis across the BBB can occur paracellular, via the complex BBB tight junctions or transcellular via a pore through the brain endothelial cell body. Making use of primary mouse brain microvascular endothelial cells (pMBMECs) as in vitro model of the BBB we here directly compared the transcriptome profile of pMBMECs favoring transcellular or paracellular T-cell diapedesis by RNA sequencing (RNA-seq). We identified the atypical chemokine receptor 1 (Ackr1) as one of the main candidate genes upregulated in pMBMECs favoring transcellular T-cell diapedesis. We confirmed upregulation of ACKR1 protein in pMBMECs favoring transcellular T-cell diapedesis and in venular endothelial cells in the CNS during EAE. Lack of endothelial ACKR1 reduced transcellular T-cell diapedesis across pMBMECs under physiological flow in vitro. Combining our previous observation that endothelial ACKR1 contributes to EAE pathogenesis by shuttling chemokines across the BBB, the present data supports that ACKR1 mediated chemokine shuttling across the BBB enhances transcellular T-cell diapedesis during autoimmune neuroinflammation. Non-stimulated, TNFalpha or IL1beta-stimulated pMBMECs were sequenced using Illumina Hiseq 2500 and differential expression was assesed between the 3 groups using DESeq2