Postarrest stalling rather than crawling favors CD8<sup>+</sup> over CD4<sup>+</sup> T‐cell migration across the blood–brain barrier under flow in vitro

Leukocyte adhesion to brain endothelial cells, the blood-brain barrier main component, is a critical step in the pathogenesis of neuroinflammatory diseases such as multiple sclerosis (MS). Leukocyte adhesion is mediated mainly by selectins, cell adhesion molecules and chemokines induced by pro-inflammatory cytokines such as TNFα and IFNγ, but the regulation of this process is not fully clear. This study investigated the regulation of firm leukocyte adhesion to human brain endothelium by two different brain endothelial microRNAs (miRs), miR-126 and miR-126*, that are downregulated by TNFα and IFNγ in a human brain endothelial cell line, hCMEC/D3. Using a leukocyte adhesion in vitro assay under shear forces mimicking blood flow, we observed that reduction of endothelial miR-126 and miR-126* enhanced firm monocyte and T cell adhesion to hCMEC/D3 cells, whereas their increased expression partially prevented THP1, Jurkat and primary MS patient-derived PBMC firm adhesion. Furthermore, we observed that miR-126* and miR-126 downregulation increased E-selectin and VCAM1, respectively, while miR-126 overexpression reduced VCAM1 and CCL2 expression by hCMEC/D3 cells, suggesting that these miRs regulate leukocyte adhesion by modulating the expression of adhesion-associated endothelial mRNA targets. Hence, human brain endothelial miR-126 and miR-126* could be used as a therapeutic tool to reduce leukocyte adhesion and thus reduce neuroinflammation.

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“…3G and most of them were CD8+ T cells (Supplemental Fig. S1) as previously reported36, and, recently confirmed37.…”

Section: Resultssupporting

confidence: 87%

MiR-126 and miR-126* regulate shear-resistant firm leukocyte adhesion to human brain endothelium

Cerutti

Edwards

Vries

et al. 2017

Sci Rep

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“…Blocking these immunocheckpoints has become critical in cancer cell immunotherapy in recent years. The CNS has long been considered as an immune‐privileged tissue because of its unique blood‐brain barrier (BBB) structure 36,37 . With the progression of CNS tumor or inflammation, the BBB becomes freely permeable to larger molecules, thus allowing peripheral immune cells to pass through the BBB 36,37 .…”

Section: Discussionmentioning

confidence: 99%

“…The CNS has long been considered as an immune‐privileged tissue because of its unique blood‐brain barrier (BBB) structure 36,37 . With the progression of CNS tumor or inflammation, the BBB becomes freely permeable to larger molecules, thus allowing peripheral immune cells to pass through the BBB 36,37 . As several studies have shown that high level of PD‐L1 expression is associated with poor prognosis in patients with GBM, 38‐40 the therapeutic blockade of PD‐L1/PD‐1 may become an important immunotherapy direction in patients with GBM.…”

Section: Discussionmentioning

confidence: 99%

EGFR‐ERK pathway regulates CSN6 to contribute to PD‐L1 expression in glioblastoma

Guo

Lou

et al. 2020

Molecular Carcinogenesis

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Glioblastoma (GBM) is the most common and malignant brain tumor in adults. Recently, programmed death‐1/programmed death‐ligand 1 (PD‐1/PD‐L1) checkpoint blockades have been applied for GBM treatment. However, the mechanism of PD‐L1 upregulation in GBM is still unclear. COP9 signalosome 6 (CSN6) is crucial for maintaining the protein stabilization in cancer cells. In this study, we applied human GBM specimens and cell lines to investigate whether the EGFR‐ERK pathway regulates CSN6 for PD‐L1 upregulation. Data from The Cancer Genome Atlas dataset showed that high expression of EGFR, CSN6, and PD‐L1 in patients with glioma was associated with poor prognosis. In 47 human GBM specimens, high expression of PD‐L1 was associated with low amount of CD8+ T cell infiltration as well as the poor prognosis of patients. CSN6 was positively correlated with EGFR and PD‐L1 expression in human GBM specimens. We treated two GBM cell lines (U87 and U251) with epidermal growth factor (EGF) in vitro, and found EGF‐upregulated p‐EGFR, p‐ERK, CSN6, and PD‐L1 expression in GBM cells. PD98059, the ERK blocker, inhibited upregulations of CSN6 and PD‐L1 in EGF‐treated cells. Inhibition of CSN6 by small interfering RNA decreased PD‐L1 expression but also increased CHIP expression in GBM cells. When the cells were treated with EGF and cycloheximide (CHX), a protein synthesis inhibitor, EGF‐reduced CHX‐induced CSN6 and PD‐L1 turnover in GBM cells. Furthermore, CSN6‐mediated downregulation of PD‐L1 was inhibited by MG132, a proteasome inhibitor in U87 cells. Thus, these results suggest that the EGFR‐ERK pathway may upregulate CSN6, which may inhibit PD‐L1 degradation and subsequently maintain PD‐L1 stability in GBM.

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“…Tissue inflammation drives the mobilization of monocytes from the bone marrow and from splenic secondary reservoir into the bloodstream 15,51 , from which these cells can potentially access the CNS at the level of the BBB, the BCSFB, or at the subarachnoid vasculature within the leptomeninges 6 indicating that neuroinflammatory conditions can increase the extravasation of monocytederived cells as shown for other immune cells 44,52,53 . While in vitro inflammatory conditions decreased pMBMEC TEER implying impaired junctional barrier properties, immune staining did not reveal any significant changes in junctional continuity, in line with the notion that BBB physical disruption is not strictly needed for cell extravasation 54 .…”

Section: Studying the Migration Of Immune Cells Through Distinct Cns mentioning

confidence: 99%

Monocyte recruitment to the inflamed central nervous system: migration pathways and distinct functional polarization

Ivan

Walthert

Locatelli

2020

Preprint

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The central nervous system (CNS) parenchyma is enclosed by anatomical interfaces including multilayered meninges, the blood-brain barrier (BBB), the choroid plexuses within ventricles and the glia limitans. These border areas hold distinct functional specializations which control the trafficking of monocyte-derived cells toward the CNS parenchyma, altogether maintaining CNS homeostasis. By crossing activated endothelial, epithelial and glial borders, circulating leukocytes gain however access to the CNS parenchyma in several inflammatory diseases including multiple sclerosis.Studies in animal models of neuroinflammation have helped describing the phenotypic specifications of these invading monocyte-derived cells, able to exert detrimental or beneficial functions depending on the local environment. In this context, in vivo visualization of iNOS + pro-inflammatory and arginase-1 + anti-inflammatory macrophages has recently revealed that these distinct cell phenotypes are highly compartmentalized by CNS borders. While arginase-1 + macrophages densely populate the leptomeninges, iNOS + macrophages rather accumulate in perivascular spaces and at the pia mater-CNS parenchymal interface.How and where these macrophages acquire their functional commitment, and whether differentially-activated monocyte-derived cells infiltrate the CNS through distinct gateways, remains however unclear.In this study, we have investigated the interaction of monocyte-derived macrophages with endothelial (BBB) and epithelial (choroid plexus) barriers of the CNS, both in vitro and in vivo. By using primary mouse brain microvascular endothelial cells as in vitro model of the BBB, we observed that, compared to unpolarized primary macrophages, adhesion of functionally-committed macrophages to endothelial cells was drastically reduced, literally abrogating their diapedesis across the BBB. Conversely, when interacting with an activated choroid plexus epithelium, both pro-and anti-inflammatory macrophages displayed substantial adhesive and migratory properties. Accordingly, in vivo analysis of choroid plexuses revealed increased macrophage trafficking and a scattered presence of polarized cells upon induction of anti-CNS inflammation.Altogether, we show that acquisition of distinct macrophage polarizations significantly alters the adhesive and migratory properties of these cells in a barrier-specific fashion. While monocytes trafficking at the level of the BBB seem to acquire their signature phenotype only following diapedesis, other anatomical interfaces can be the entry site for functionally activated monocyte-derived cells. Our study highlights the choroid plexus as a key access gateway for macrophages during neuroinflammation, and its stroma as a potential priming site for their functional polarization.3

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Postarrest stalling rather than crawling favors CD8⁺ over CD4⁺ T‐cell migration across the blood–brain barrier under flow in vitro

Cited by 45 publications

References 65 publications

MiR-126 and miR-126* regulate shear-resistant firm leukocyte adhesion to human brain endothelium

MiR-126 and miR-126* regulate shear-resistant firm leukocyte adhesion to human brain endothelium

EGFR‐ERK pathway regulates CSN6 to contribute to PD‐L1 expression in glioblastoma

Monocyte recruitment to the inflamed central nervous system: migration pathways and distinct functional polarization

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Postarrest stalling rather than crawling favors CD8+ over CD4+ T‐cell migration across the blood–brain barrier under flow in vitro

Cited by 45 publications

References 65 publications

MiR-126 and miR-126* regulate shear-resistant firm leukocyte adhesion to human brain endothelium

MiR-126 and miR-126* regulate shear-resistant firm leukocyte adhesion to human brain endothelium

EGFR‐ERK pathway regulates CSN6 to contribute to PD‐L1 expression in glioblastoma

Monocyte recruitment to the inflamed central nervous system: migration pathways and distinct functional polarization

Contact Info

Product

Resources

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Postarrest stalling rather than crawling favors CD8⁺ over CD4⁺ T‐cell migration across the blood–brain barrier under flow in vitro