In inflammatory central nervous system conditions such as multiple sclerosis, breakdown of the blood-brain barrier is a key event in lesion pathogenesis, predisposing to oedema, excitotoxicity, and ...ingress of plasma proteins and inflammatory cells. Recently, we showed that reactive astrocytes drive blood-brain barrier opening, via production of vascular endothelial growth factor A (VEGFA). Here, we now identify thymidine phosphorylase (TYMP; previously known as endothelial cell growth factor 1, ECGF1) as a second key astrocyte-derived permeability factor, which interacts with VEGFA to induce blood-brain barrier disruption. The two are co-induced NFκB1-dependently in human astrocytes by the cytokine interleukin 1 beta (IL1B), and inactivation of Vegfa in vivo potentiates TYMP induction. In human central nervous system microvascular endothelial cells, VEGFA and the TYMP product 2-deoxy-d-ribose cooperatively repress tight junction proteins, driving permeability. Notably, this response represents part of a wider pattern of endothelial plasticity: 2-deoxy-d-ribose and VEGFA produce transcriptional programs encompassing angiogenic and permeability genes, and together regulate a third unique cohort. Functionally, each promotes proliferation and viability, and they cooperatively drive motility and angiogenesis. Importantly, introduction of either into mouse cortex promotes blood-brain barrier breakdown, and together they induce severe barrier disruption. In the multiple sclerosis model experimental autoimmune encephalitis, TYMP and VEGFA co-localize to reactive astrocytes, and correlate with blood-brain barrier permeability. Critically, blockade of either reduces neurologic deficit, blood-brain barrier disruption and pathology, and inhibiting both in combination enhances tissue preservation. Suggesting importance in human disease, TYMP and VEGFA both localize to reactive astrocytes in multiple sclerosis lesion samples. Collectively, these data identify TYMP as an astrocyte-derived permeability factor, and suggest TYMP and VEGFA together promote blood-brain barrier breakdown.
Lesions and neurologic disability in inflammatory CNS diseases such as multiple sclerosis (MS) result from the translocation of leukocytes and humoral factors from the vasculature, first across the ...endothelial blood-brain barrier (BBB) and then across the astrocytic glia limitans (GL). Factors secreted by reactive astrocytes open the BBB by disrupting endothelial tight junctions (TJs), but the mechanisms that control access across the GL are unknown. Here, we report that in inflammatory lesions, a second barrier composed of reactive astrocyte TJs of claudin 1 (CLDN1), CLDN4, and junctional adhesion molecule A (JAM-A) subunits is induced at the GL. In a human coculture model, CLDN4-deficient astrocytes were unable to control lymphocyte segregation. In models of CNS inflammation and MS, mice with astrocyte-specific Cldn4 deletion displayed exacerbated leukocyte and humoral infiltration, neuropathology, motor disability, and mortality. These findings identify a second inducible barrier to CNS entry at the GL. This barrier may be therapeutically targetable in inflammatory CNS disease.
Breakdown of the blood-brain barrier (BBB) is an early and significant event in CNS inflammation. Astrocyte-derived VEGF-A has been implicated in this response, but the underlying mechanisms remain ...unresolved. Here, we identify the endothelial transmembrane tight junction proteins claudin-5 (CLN-5) and occludin (OCLN) as targets of VEGF-A action. Down-regulation of CLN-5 and OCLN accompanied up-regulation of VEGF-A and correlated with BBB breakdown in experimental autoimmune encephalomyelitis, an animal model of CNS inflammatory disease. In cultures of brain microvascular endothelial cells, VEGF-A specifically down-regulated CLN-5 and OCLN protein and mRNA. In mouse cerebral cortex, microinjection of VEGF-A disrupted CLN-5 and OCLN and induced loss of barrier function. Importantly, functional studies revealed that expression of recombinant CLN-5 protected brain microvascular endothelial cell cultures from a VEGF-induced increase in paracellular permeability, whereas recombinant OCLN expressed under the same promoter was not protective. Previous studies have shown CLN-5 to be a key determinant of trans-endothelial resistance at the BBB. Our findings suggest that its down-regulation by VEGF-A constitutes a significant mechanism in BBB breakdown.
Background. Leprosy is characterized by a spectrum of clinical manifestations that depend on the type of immune response against the pathogen. Patients may undergo immunological changes known as ...“reactional states” (reversal reaction and erythema nodosum leprosum) that result in major clinical deterioration. The goal of the present study was to assess the effect of Toll-like receptor 2 (TLR2) polymorphisms on susceptibility to and clinical presentation of leprosy. Methods. Three polymorphisms in TLR2 (597C→T, 1350T→C, and a microsatellite marker) were analyzed in 431 Ethiopian patients with leprosy and 187 control subjects. The polymorphism-associated risk of developing leprosy, lepromatous (vs. tuberculoid) leprosy, and leprosy reactions was assessed by multivariate logistic regression models. Results. The microsatellite and the 597C→T polymorphisms both influenced susceptibility to reversal reaction. Although the 597T allele had a protective effect (odds ratio OR, 0.34 95% confidence interval {CI}, 0.17–0.68; P = .002 under the dominant model), homozygosity for the 280-bp allelic length of the microsatellite strongly increased the risk of reversal reaction (OR, 5.83 95% CI, 1.98–17.15; P = .001 under the recessive model). These associations were consistent among 3 different ethnic groups. Conclusions. These data suggest a significant role for TLR-2 in the occurrence of leprosy reversal reaction and provide new insights into the immunogenetics of the disease.
Abstract Multiple sclerosis (MS) is a chronic neuroinflammatory disease characterized by immune cell infiltration of CNS, blood–brain barrier (BBB) breakdown, localized myelin destruction, and ...progressive neuronal degeneration. There exists a significant need to identify novel therapeutic targets and strategies that effectively and safely disrupt and even reverse disease pathophysiology. Signaling cascades initiated by semaphorin 4D (SEMA4D) induce glial activation, neuronal process collapse, inhibit migration and differentiation of oligodendrocyte precursor cells (OPCs), and disrupt endothelial tight junctions forming the BBB. To target SEMA4D, we generated a monoclonal antibody that recognizes mouse, rat, monkey and human SEMA4D with high affinity and blocks interaction between SEMA4D and its cognate receptors. In vitro, anti-SEMA4D reverses the inhibitory effects of recombinant SEMA4D on OPC survival and differentiation. In vivo, anti-SEMA4D significantly attenuates experimental autoimmune encephalomyelitis in multiple rodent models by preserving BBB integrity and axonal myelination and can be shown to promote migration of OPC to the site of lesions and improve myelin status following chemically-induced demyelination. Our study underscores SEMA4D as a key factor in CNS disease and supports the further development of antibody-based inhibition of SEMA4D as a novel therapeutic strategy for MS and other neurologic diseases with evidence of demyelination and/or compromise to the neurovascular unit.
In the developing CNS, Notch1 and its ligand, Jagged1, regulate oligodendrocyte differentiation and myelin formation, but their role in repair of demyelinating lesions in diseases such as multiple ...sclerosis remains unresolved. To address this question, we generated a mouse model in which we targeted Notch1 inactivation to oligodendrocyte progenitor cells (OPCs) using Olig1Cre and a floxed Notch1 allele, Notch1¹²f. During CNS development, OPC differentiation was potentiated in Olig1Cre:Notch1¹²f/¹²f mice. Importantly, in adults, remyelination of demyelinating lesions was also accelerated, at the expense of proliferation within the progenitor population. Experiments in vitro confirmed that Notch1 signaling was permissive for OPC expansion but inhibited differentiation and myelin formation. These studies also revealed that astrocytes exposed to TGF-β1 restricted OPC maturation via Jagged1-Notch1 signaling. These data suggest that Notch1 signaling is one of the mechanisms regulating OPC differentiation during CNS remyelination. Thus, Notch1 may represent a potential therapeutical avenue for lesion repair in demyelinating disease.
IL-11 Regulates Autoimmune Demyelination Gurfein, Blake T; Zhang, Yueting; Lopez, Carolina B ...
The Journal of immunology (1950),
10/2009, Letnik:
183, Številka:
7
Journal Article
Recenzirano
Odprti dostop
Current therapies for the autoimmune demyelinating disease multiple sclerosis (MS) target inflammation, but do not directly address neuroprotection or lesion repair. Cytokines of the gp130 family ...regulate survival and differentiation of both neural and immune cells, and we recently identified expression of the family member IL-11 in active MS plaques. In this study, we show that IL-11 regulates the clinical course and neuropathology of experimental autoimmune encephalomyelitis, a demyelinating model that mimics many of the clinical and pathologic features of MS. Importantly, the effects of IL-11 are achieved via a combination of immunoregulation and direct neuroprotection. IL-11R-alpha-null (IL-11Ralpha(-/-)) mice displayed a significant increase in clinical severity and neuropathology of experimental autoimmune encephalomyelitis compared with wild-type littermates. Inflammation, demyelination, and oligodendrocyte and neuronal loss were all exacerbated in IL-11Ra(-/-) animals. Conversely, wild-type mice treated with IL-11 displayed milder clinical signs and neuropathology than vehicle-treated controls. In cocultures of murine myelin oligodendrocyte glycoprotein(35-55)-specific CD4+ T lymphocytes and CD11c+ APCs, IL-11 treatment resulted in a significant decrease in T cell-derived effector cytokine production. This effect was generated via modulation of CD11c+ APC-mediated lymphocyte activation, and was associated with a decrease in the size of the CD11c+ cell population. Conversely, IL-11 strongly reduced apoptosis and potentiated mitosis in primary cultures of mouse oligodendrocyte progenitors. Collectively, these data reveal that IL-11 regulates inflammatory demyelination via a unique combination of immunoregulation and neuroprotection. IL-11 signaling may represent a therapeutic avenue to restrict CNS inflammation and potentiate oligodendrocyte survival in autoimmune demyelinating disease.
In inflammatory CNS conditions such as multiple sclerosis (MS), current options to treat clinical relapse are limited, and more selective agents are needed. Disruption of the blood-brain barrier ...(BBB) is an early feature of lesion formation that correlates with clinical exacerbation, leading to edema, excitotoxicity, and entry of serum proteins and inflammatory cells. Here, we identify astrocytic expression of VEGF-A as a key driver of BBB permeability in mice. Inactivation of astrocytic Vegfa expression reduced BBB breakdown, decreased lymphocyte infiltration and neuropathology in inflammatory and demyelinating lesions, and reduced paralysis in a mouse model of MS. Knockdown studies in CNS endothelium indicated activation of the downstream effector eNOS as the principal mechanism underlying the effects of VEGF-A on the BBB. Systemic administration of the selective eNOS inhibitor cavtratin in mice abrogated VEGF-A-induced BBB disruption and pathology and protected against neurologic deficit in the MS model system. Collectively, these data identify blockade of VEGF-A signaling as a protective strategy to treat inflammatory CNS disease.
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