[Show abstract][Hide abstract] ABSTRACT: The ability of the Blood Brain Barrier (BBB) to maintain proper barrier functions, keeping an optimal environment for central nervous system (CNS) activity and regulating leukocytes' access, can be affected in CNS diseases. Endothelial cells and astrocytes are the principal BBB cellular constituents and their interaction is essential to maintain its function. Both endothelial cells and astrocytes express the receptors for the bioactive sphingolipid S1P. Fingolimod, an immune modulatory drug whose structure is similar to S1P, has been approved for treatment in multiple sclerosis (MS): fingolimod reduces the rate of MS relapses by preventing leukocyte egress from the lymph nodes. Here, we examined the ability of S1P and fingolimod to act on the BBB, using an in vitro co-culture model that allowed us to investigate the effects of S1P on endothelial cells, astrocytes, and interactions between the two. Acting selectively on endothelial cells, S1P receptor signaling reduced cell death induced by inflammatory cytokines. When acting on astrocytes, fingolimod treatment induced the release of a factor, granulocyte macrophage colony-stimulating factor (GM-CSF) that reduced the effects of cytokines on endothelium. In an in vitro BBB model incorporating shear stress, S1P receptor modulation reduced leukocyte migration across the endothelial barrier, indicating a novel mechanism that might contribute to fingolimod efficacy in MS treatment.
PLoS ONE 08/2015; 10(7). DOI:10.1371/journal.pone.0133392 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The blood-brain barrier (BBB) is a brain-specific capillary barrier critical for preventing entry of toxic substances into the central nervous system. In contrast to vessels of peripheral organs, the BBB limits the exchange of inflammatory cells and mediators under physiological and pathological conditions. Clarifying these regulation of the BBB would provide new insights into neuroprotective strategies in neuroinflammatory diseases. However, the physiology of the BBB and the pathogenesis of BBB disruption remain incompletely understood. A major limiting factor is the lack of reliable models of the human BBB. Several different in vitro models suggest that there is no perfect model system, with different models advantageous in specific situations. In this review, we summarize the current knowledge on BBB cellular components and in vitro BBB models with a particular focus on novel and recent findings.
Brain and nerve = Shinkei kenkyū no shinpo 08/2015; 67(8):1035-1042. DOI:10.11477/mf.1416200250
[Show abstract][Hide abstract] ABSTRACT: The blood–brain barrier (BBB), an anatomically and functionally unique structure, maintains the homeostasis of the central nervous system (CNS) by maintaining the optimal ionic environment for neuronal function and transporting trophins or nutrients, as well as restricting access of toxic substances, inflammatory cells, circulating antibodies, and pathogens under physiological and pathological conditions. Brain microvascular endothelial cells directly mediate BBB function. Along with a battery of efflux transporters, the tight junctions of brain microvascular endothelial cells form the anatomical and functional basis of the barrier function of the BBB. Access to the CNS by inflammatory cells is restricted, but not prohibited. Transendothelial migration through the BBB is characterized by tightly controlled multi-step processes. BBB dysfunction in neurological autoimmune diseases is associated with autoreactive and inflammatory cells and autoantibodies that invade the CNS and induce neuroinflammation. It is still incompletely understood how these neuro-invaders affect the BBB and gain entry into the CNS across the BBB. In the present review, we introduce current knowledge of BBB cellular components and the multistep process of inflammatory cells crossing the BBB in physiological conditions, and summarize their biological mechanisms to cross the BBB in pathological conditions in representative neurological autoimmune diseases (multiple sclerosis, neuromyelitis optica and systemic lupus erythematosus) with a particular focus on new and recent findings.
Clinical and Experimental Neuroimmunology 07/2015; DOI:10.1111/cen3.12229
[Show abstract][Hide abstract] ABSTRACT: Objective:
Severe damage to the blood-brain barrier (BBB) allows anti-aquaporin 4 (AQP4) antibodies to access the astrocytic endfeet in neuromyelitis optica (NMO). In the current study, we identified the pathogenic cytokines/chemokines that are responsible for the BBB malfunction induced by NMO sera.
We measured the levels of 27 cytokines/chemokines in human brain microvascular endothelial cells (BMECs) after exposure to sera obtained from patients with the acute and stable phases of anti-AQP4 antibody-positive NMO spectrum disorder (NMOSD), multiple sclerosis (MS) patients and healthy controls (HC) using a multiplexed fluorescent bead-based immunoassay system.
The induced protein (IP)-10 level in the cells was markedly increased following exposure to acute phase NMOSD sera. Other cytokines/chemokines including interleukin (IL)-6 and monocyte chemotactic protein (MCP)-1 were also significantly increased in the acute NMOSD group compared to both the MS and HC groups. The up-regulation of the IP-10 levels in the cells after exposure to the acute-phase NMOSD sera was also observed using another specified ELISA, and this effect was significantly decreased during the remission phase in the individual NMOSD patients. Furthermore, the increase in the level of IP-10 after exposure to the sera was significantly correlated with the cerebrospinal fluid/serum albumin ratio.
Sera from the acute phase of NMO markedly increased the autocrine secretion of IP-10 by BMECs. The over-production of IP-10 in BMECs may play an important role in the pathogenesis of NMO and may therefore help to mediate the trafficking of T cells expressing its receptor across the BBB.
PLoS ONE 03/2015; 10(3):e0122000. DOI:10.1371/journal.pone.0122000 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Effect of fingolimod in multiple sclerosis (MS) is thought to involve the prevention of lymphocyte egress from lymphoid tissues, thereby reducing autoaggressive lymphocyte infiltration into the central nervous system across blood-brain barrier (BBB). However, brain microvascular endothelial cells (BMECs) represent a possible additional target for fingolimod in MS patients by directly repairing the function of BBB, as S1P receptors are also expressed by BMECs. In this study, we evaluated the effects of fingolimod on BMECs and clarified whether fingolimod-phosphate restores the BBB function after exposure to MS sera.
Changes in tight junction proteins, adhesion molecules and transendothelial electrical resistance (TEER) in BMECs were evaluated following incubation in conditioned medium with or without fingolimod/fingolimod-phosphate. In addition, the effects of sera derived from MS patients, including those in the relapse phase of relapse-remitting (RR) MS, stable phase of RRMS and secondary progressive MS (SPMS), on the function of BBB in the presence of fingolimod-phosphate were assessed.
Incubation with fingolimod-phosphate increased the claudin-5 protein levels and TEER values in BMECs, although it did not change the amount of occludin, ICAM-1 or MelCAM proteins. Pretreatment with fingolimod-phosphate restored the changes in the claudin-5 and VCAM-1 protein/mRNA levels and TEER values in BMECs after exposure to MS sera.
Pretreatment with fingolimod-phosphate prevents BBB disruption caused by both RRMS and SPMS sera via the upregulation of claudin-5 and downregulation of VCAM-1 in BMECs, suggesting that fingolimod-phosphate is capable of directly modifying the BBB. BMECs represent a possible therapeutic target for fingolimod in MS patients.
PLoS ONE 03/2015; 10(3):e0121488. DOI:10.1371/journal.pone.0121488 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background: In vitro blood-brain barrier (BBB) models can be useful for understanding leukocyte-endothelial interactions at this unique vascular-tissue interface. Desirable features of such a model include shear stress, non-transformed cells and co-cultures of brain microvascular endothelial cells with astrocytes. Recovery of transmigrated leukocytes for further analysis is also appealing. New methods: We report an in vitro BBB model for leukocyte transmigration incorporating shear stress with co-culture of conditionally immortalized human endothelial cell line (hBMVEC) and human astrocyte cell line (hAST). Transmigrated leukocytes can be recovered for comparison with input and non-transmigrated cells. Result: hBMVEC and hAST exhibited physiological and morphological BBB properties when cocultured back-to-back on membranes. In particular, astrocyte processes protruded through 3. μm membrane pores, terminating in close proximity to the hBMVEC with a morphology reminiscent of end-feet. Co-culture with hAST also decreased the permeability of hBMVEC. In our model, astrocytes promoted transendothelial leukocyte transmigration. Comparison with existing methods: This model offers the opportunity to evaluate whether BBB properties and leukocyte transmigration across cytokine-activated hBMVEC are influenced by human astrocytes. Conclusions: We present a BBB model for leukocyte transmigration incorporating shear stress with co-culture of hBMVEC and hAST. We demonstrate that hAST promoted leukocyte transmigration and also increased certain barrier functions of hBMVEC. This model provides reproducible assays for leukocyte transmigration with robust results, which will enable further defining the relationships among leukocytes and the cellular elements of the BBB.
[Show abstract][Hide abstract] ABSTRACT: The blood-brain barrier (BBB) is the brain-specific capillary barrier that is critical for preventing toxic substances from entering the central nervous system (CNS). In contrast to vessels of peripheral organs, the BBB limits the exchange of inflammatory cells and mediators under physiological and pathological conditions. Clarifying these limitations and the role of chemokines in regulating the BBB would provide new insights into neuroprotective strategies in neuroinflammatory diseases. Because there is a paucity of in vitro BBB models, however, some mechanistic aspects of transmigration across the BBB still remain largely unknown. In this review, we summarize current knowledge of BBB cellular components, the multistep process of inflammatory cells crossing the BBB, functions of CNS-derived chemokines, and in vitro BBB models for transmigration, with a particular focus on new and recent findings.
[Show abstract][Hide abstract] ABSTRACT: The accumulation of inflammatory cells in the brain parenchyma is a critical step in the pathogenesis of neuroinflammatory diseases such as multiple sclerosis (MS). Chemokines and adhesion molecules orchestrate leukocyte transmigration across the blood-brain barrier (BBB), but the dynamics of chemokine receptor expression during leukocyte transmigration are unclear. We describe an in vitro BBB model system using human brain microvascular endothelial cells that incorporates shear forces mimicking blood flow to elucidate how chemokine receptor expression is modulated during leukocyte transmigration. In the presence of the chemokine CXCL12, we examined modulation of its receptor CXCR4 on human T cells, B cells, and monocytes transmigrating across the BBB under flow conditions. CXCL12 stimulated transmigration of CD4(+) and CD8(+) T cells, CD19(+) B cells, and CD14(+) monocytes. Transmigration was blocked by CXCR4-neutralizing antibodies. Unexpectedly, CXCL12 selectively down-regulated CXCR4 on transmigrating monocytes, but not T cells. Monocytes underwent preferential CXCL12-mediated adhesion to the BBB in vitro compared with lymphocytes. These findings provide new insights into leukocyte-endothelial interactions at the BBB under conditions mimicking blood flow and suggest that in vitro BBB models may be useful for identifying chemokine receptors that could be modulated therapeutically to reduce neuroinflammation in diseases such as MS.
Science translational medicine 02/2012; 4(119):119ra14. DOI:10.1126/scitranslmed.3003197 · 15.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A 46-year-old man experienced numbness and muscle weakness in the distal portions of both hands, which progressed over following three months. Neurological examination showed mild muscle weakness only in distal arms, hypoflexia or areflexia, and hypesthesia in glove and stocking distribution. Motor conduction study revealed markedly prolonged distal latency and abnormal temporal dispersion. Sensory nerve potentials were reduced or could not be recorded. Histopathlogical findings of the sural nerve showed several nerve fibers with thinning myelin sheath and mild reduction of myelinated fibers. These results suggested the diagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP). Two weeks after intravenous immunoglobulin therapy, neurological deficits rapidly improved and electrophysiological abnormalities were also ameliorated. Thereafter, there was no clinical deterioration for two years without further treatment. Our patient suggested that immunomodulating treatment is needed for stopping the initial progression of neurological deficits, but maintenance therapy is not always necessary for keeping the remitting state in distal variant of CIDP.