Junctional adhesion molecule-A deficient mice are protected from severe experimental autoimmune encephalomyelitis.

In multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE), early pathological features include immune cell infiltration into the central nervous system (CNS) and blood-brain barrier (BBB) disruption. We investigated the role of junctional adhesion molecule-A (JAM-A), a tight junction protein, in active EAE (aEAE) pathogenesis. Our study confirms JAM-A expression at the blood-brain barrier and its luminal redistribution during aEAE. JAM-A deficient (JAM-A-/-) C57BL/6J mice exhibited milder aEAE, unrelated to myelin oligodendrocyte glycoprotein-specific CD4+ T-cell priming. While JAM-A absence influenced macrophage behavior on primary mouse brain microvascular endothelial cells (pMBMECs) under flow in vitro, it did not impact T-cell extravasation across primary mouse brain microvascular endothelial cells. At aEAE onset, we observed reduced lymphocyte and CCR2+ macrophage infiltration into the spinal cord of JAM-A-/- mice compared to control littermates. This correlated with increased CD3+ T-cell accumulation in spinal cord perivascular spaces and brain leptomeninges, suggesting JAM-A absence leads to T-cell trapping in central nervous system border compartments. In summary, JAM-A plays a role in immune cell infiltration and clinical disease progression in aEAE.

Pharmacological Inhibition of Acid Sphingomyelinase Ameliorates Experimental Autoimmune Encephalomyelitis.

BACKGROUND/AIMS: Multiple sclerosis (MS) is one of the most common autoimmune disorders of the central nervous system (CNS) and the leading cause of neurological disability among young adults in the Western world. We have previously shown that the acid sphingomyelinase plays an important role in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. METHODS: We induced adoptively transferred EAE in wildtype and acid sphingomyelinase-deficient mice. In addition, we immunized mice with MOGaa35-55 to induce active EAE and treated the mice with amitriptyline, a functional inhibitor of the acid sphingomyelinase. We investigated symptoms of EAE, blood-brain barrier integrity and neuroinflammation. RESULTS: In the model of adoptively transferred EAE we demonstrate that expression of acid sphingomyelinase in the recipients rather than on transferred encephalitogenic T cells contributes to the clinical development of EAE symptoms. To test if pharmacological targeting of acid sphingomyelinase can be explored for the development of novel therapies for MS, we inhibited acid sphingomyelinase with amitriptyline in mice in which EAE was induced by active immunization. We demonstrate that pharmacological inhibition of acid sphingomyelinase using amitriptyline protects against the development of EAE and markedly attenuates the characteristic detrimental neuroinflammatory response. CONCLUSION: The studies identify the acid sphingomyelinase as a novel therapeutic target for treating MS patients.

Postarrest stalling rather than crawling favors CD8(+) over CD4(+) T-cell migration across the blood-brain barrier under flow in vitro.

Although CD8(+) T cells have been implied in the pathogenesis of multiple sclerosis (MS), the molecular mechanisms mediating CD8(+) T-cell migration across the blood-brain barrier (BBB) into the central nervous system (CNS) are ill defined. Using in vitro live cell imaging, we directly compared the multistep extravasation of activated CD4(+) and CD8(+) T cells across primary mouse brain microvascular endothelial cells (pMBMECs) as a model for the BBB under physiological flow. Significantly higher numbers of CD8(+) than CD4(+) T cells arrested on pMBMECs under noninflammatory and inflammatory conditions. While CD4(+) T cells polarized and crawled prior to their diapedesis, the majority of CD8(+) T cells stalled and readily crossed the pMBMEC monolayer preferentially via a transcellular route. T-cell arrest and crawling were independent of G-protein-coupled receptor signaling. Rather, absence of endothelial ICAM-1 and ICAM-2 abolished increased arrest of CD8(+) over CD4(+) T cells and abrogated T-cell crawling, leading to the efficient reduction of CD4(+) , but to a lesser degree of CD8(+) , T-cell diapedesis across ICAM-1(null) /ICAM-2(-/-) pMBMECs. Thus, cellular and molecular mechanisms mediating the multistep extravasation of activated CD8(+) T cells across the BBB are distinguishable from those involved for CD4(+) T cells.

Migration of encephalitogenic CD8 T cells into the central nervous system is dependent on the α4ß1-integrin.

Although CD8 T cells are key players in neuroinflammation, little is known about their trafficking cues into the central nervous system (CNS). We used a murine model of CNS autoimmunity to define the molecules involved in cytotoxic CD8 T-cell migration into the CNS. Using a panel of mAbs, we here show that the α4ß1-integrin is essential for CD8 T-cell interaction with CNS endothelium. We also investigated which α4ß1-integrin ligands expressed by endothelial cells are implicated. The blockade of VCAM-1 did not protect against autoimmune encephalomyelitis, and only partly decreased the CD8(+) T-cell infiltration into the CNS. In addition, inhibition of junctional adhesion molecule-B expressed by CNS endothelial cells also decreases CD8 T-cell infiltration. CD8 T cells may use additional and possibly unidentified adhesion molecules to gain access to the CNS.

T Cell-Mediated Transport of Polymer Nanoparticles across the Blood-Brain Barrier.

Delivery of therapeutics to the central nervous system (CNS) is challenging due to the presence of the blood-brain barrier (BBB). Amongst various approaches that have been explored to facilitate drug delivery to the CNS, the use of cells that have the intrinsic ability to cross the BBB is relatively unexplored, yet very attractive. This paper presents a first proof-of-concept that demonstrates the feasibility of activated effector/memory CD4+ helper T cells (CD4+ TEM cells) as carriers for the delivery of polymer nanoparticles across the BBB. This study shows that CD4+ TEM cells can be decorated with poly(ethylene glycol)-modified polystyrene nanoparticles using thiol-maleimide coupling chemistry, resulting in the immobilization of ≈105 nanoparticles per cell as determined by confocal microscopy. The ability of these cells to serve as carriers to transport nanoparticles across the BBB is established in vitro and in vivo. Using in vitro BBB models, CD4+ TEM cells are found to be able to transport nanoparticles across the BBB both under static conditions as well as under physiological flow. Finally, upon systemic administration, nanoparticle-modified T cells are shown to enter the brain parenchyma of mice, demonstrating the brain delivery potential of this T cell subset in allogeneic hosts.

Impaired T-cell migration to the CNS under fingolimod and dimethyl fumarate.

OBJECTIVE: To evaluate the long-term effects of treatments used in MS on the T-cell trafficking profile. METHODS: We enrolled 83 patients with MS under fingolimod (FTY), natalizumab (NTZ), dimethyl fumarate (DMF), or other disease-modifying treatments (DMTs). Blood was drawn before treatment onset and up to 36-48 months. The ex vivo expression of CNS-related integrins (α4ß1 and αL subunit of LFA-1) and the gut-related integrin (α4ß7) was assessed using flow cytometry on CD4+ and CD8+ T cells. The adhesion profiles of CD3+ T cells to specific integrin ligands (vascular cell adhesion molecule-1 [VCAM-1], intercellular adhesion molecule-1 [ICAM-1], and mucosal vascular addressin cell adhesion molecule-1 [MAdCAM-1]) were measured in vitro before and after 12 and 36-48 months. RESULTS: NTZ decreased the frequency of α4ß1+ and α4ß7+ integrin expressing T cells and the binding of these cells to VCAM-1 and MAdCAM-1, respectively. After 12 months, DMF induced a decreased frequency of αLhighCD4+ T cells combined with reduced binding to ICAM-1. By contrast, with FTY, there was a doubling of the frequency of α4ß1+ and αLhigh, but a decreased frequency of α4ß7+ T cells. Strikingly, the binding of α4ß1+, α4ß7+, and to a lesser extent of αLhigh T cells to VCAM-1, MAdCAM-1, and ICAM-1, respectively, was decreased at month 12 under FTY treatment. The presence of manganese partially restored the binding of these T cells to VCAM-1 in vitro, suggesting that FTY interferes with integrin activation. CONCLUSIONS: In addition to NTZ, DMF and FTY but not other tested DMTs may also decrease T-cell-mediated immune surveillance of the CNS. Whether this mechanism may contribute to the onset of CNS opportunistic infections remains to be shown.

A novel classification of quiescent and transit amplifying adult neural stem cells by surface and metabolic markers permits a defined simultaneous isolation.

Adult neural stem and progenitor cells (NSPCs) are usually defined retrospectively by their ability to proliferate in vivo (bromodeoxyuridine uptake) or to form neurospheres and to differentiate into neurons, astrocytes and oligodendrocytes in vitro. Additional strategies to identify and to isolate NSPCs are of great importance for the investigation of cell differentiation and fate specification. Using the cell surface molecules Prominin-1 and Lewis X and a metabolic marker, the aldehyde dehydrogenase activity, we isolated and characterized five main populations of NSPCs in the neurogenic subventricular zone (SVZ) and the non-neurogenic spinal cord (SC). We used clonal analysis to assess neurosphere formation and multipotency, BrdU retention to investigate in vivo proliferation activity and quantified the expression of NSPC associated genes. Surprisingly, we found many similarities in NSPC subpopulations derived from the SVZ and SC suggesting that subtypes with similar intrinsic potential exist in both regions. The marker defined classification of NSPCs will help to distinguish subpopulations of NSPCs and allows their prospective isolation using fluorescence activated cell sorting.