Neutrophils Mediate Blood–Spinal Cord Barrier Disruption in Demyelinating Neuroinflammatory Diseases

Abstract

Disruption of the blood–brain and blood–spinal cord barriers (BBB and BSCB, respectively) and immune cell infiltration are early pathophysiological hallmarks of multiple sclerosis (MS), its animal model experimental autoimmune encephalomyelitis (EAE), and neuromyelitis optica (NMO). However, their contribution to disease initiation and development remains unclear. In this study, we induced EAE in lys-eGFP-ki mice and performed single, nonterminal intravital imaging to investigate BSCB permeability simultaneously with the kinetics of GFP+ myeloid cell infiltration. We observed a loss in BSCB integrity within a day of disease onset, which paralleled the infiltration of GFP+ cells into the CNS and lasted for ∼4 d. Neutrophils accounted for a significant proportion of the circulating and CNS-infiltrating myeloid cells during the preclinical phase of EAE, and their depletion delayed the onset and reduced the severity of EAE while maintaining BSCB integrity. We also show that neutrophils collected from the blood or bone marrow of EAE mice transmigrate more efficiently than do neutrophils of naive animals in a BBB cell culture model. Moreover, using intravital videomicroscopy, we demonstrate that the IL-1R type 1 governs the firm adhesion of neutrophils to the inflamed spinal cord vasculature. Finally, immunostaining of postmortem CNS material obtained from an acutely ill multiple sclerosis patient and two neuromyelitis optica patients revealed instances of infiltrated neutrophils associated with regions of BBB or BSCB leakage. Taken together, our data provide evidence that neutrophils are involved in the initial events that take place during EAE and that they are intimately linked with the status of the BBB/BSCB.

Selective Blockade of CD28-Mediated T Cell Costimulation Protects Rhesus Monkeys against Acute Fatal Experimental Autoimmune Encephalomyelitis

“…CD63 mRNA was also elevated in ALN, although only trending toward significance, but not in the spleen. Neutrophils play a role in certain rodent EAE models as well (42)(43)(44) but their role in MS has not yet been thoroughly investigated.…”

Kruppel-like factor 4 regulates neutrophil activation

“…9 Accumulating clinical and experimental evidence implicates neutrophils in the pathogenesis of MS and EAE. [11][12][13]26,27 Upon immunization, Cre mice developed EAE with disease onset at ;7 to 14 days and peak at ;21 to 28 days ( Figure 2D). In contrast, K4-cKO mice showed a delayed onset and significant reduction in severity of EAE despite 100% disease incidence ( Figure 2D; supplemental 7A).…”

“…12 It has been reported that neutrophils may play a role in mediating blood-brain barrier breakdown. 13 In addition, neutrophils isolated from the CNS at onset of EAE produce tumor necrosis factor a (TNF-a), interleukin-6 (IL-6), IL-12, IL-1b, and interferon g, cytokines important to the maturation of antigenpresenting cells and activation of adaptive immune system. 12 Therefore, neutrophils may influence MS and EAE at multiple levels.…”

Endothelial Wnt/β-catenin signaling reduces immune cell infiltration in multiple sclerosis

“…Structural and functional BBB degradation precedes lesion development in both MS and EAE (5)(6)(7)(8)(9), and focal BBB abnormalities correlate with clinical exacerbations in the relapsing-remitting form of MS (10). Moreover, BBB leakage precedes the entry of T cells and monocytes into the brain parenchyma (7,11) and coincides with early infiltration of neutrophils before the onset of EAE (12). Although the severity of barrier leakage decreases over time for most relapsing-remitting MS lesions, as assessed by gadoliniumenhancing magnetic resonance imaging (7,(13)(14)(15), whether BBB recovery is an active process and, if so, which pathways mediate its repair, remain unclear.…”