Interferon-γ safeguards blood-brain barrier during experimental autoimmune encephalomyelitis

IFN-γ-responsiveness of lymphatic endothelial cells inhibits melanoma lymphatic dissemination via AMPK-mediated metabolic control

The integrity of the lymphatic system is critical for preventing the dissemination of tumor cells, such as melanoma, to distant parts of the body. IFN-γ is well studied as a negative regulator for lymphangiogenesis, which is strongly associated with cancer metastasis. However, the exact mechanisms underlying this process remain unclear. In the present study, we investigated whether IFN-γ signaling in lymphatic endothelial cells (LECs) affects tumor cell dissemination by regulating the barrier function of tumor-associated lymphatic vessels. Using LEC-specific IFN-γ receptor (IFN-γR) knockout mice, we found that the loss of IFN-γR in LECs increased the dissemination of melanoma cells into the draining lymph nodes. Notably, IFN-γ signaling in LECs inhibited trans-lymphatic endothelial cell migration of melanoma cells, indicating its regulation of lymphatic barrier function. Further investigations revealed that IFN-γ upregulated the expression of the tight junction protein Claudin-3 in LECs, while knockdown of Claudin-3 in LECs abolished IFN-γ-induced inhibition of trans-lymphatic endothelial migration activity. Mechanistically, IFN-γ inhibits AMPK signaling activation, which is involved in the regulation of fatty acid metabolism. Modulating fatty acid metabolism and AMPK activation in LECs also affected the lymphatic dissemination of melanoma cells, further confirming that this process is involved in IFN-γ-induced regulation of lymphatic barrier function. These results provide novel insights into how IFN-γ modulates tight junctions in LECs, inhibiting the dissemination of melanoma cells via the lymphatic vessels.

T lymphocyte-derived IFN-γ facilitates breast cancer cells to pass the blood-brain barrier: An in vitro study corroborating translational data

The appearance of brain metastasis is the most serious complication of breast cancer with mostly fatal outcomes. To reach the brain, tumor cells need to pass the blood-brain barrier (BBB). The molecular mechanisms underlying penetration of the BBB are largely unknown. Previously we found that tumor-infiltrating T lymphocytes enhance the development of brain metastasis of estrogen receptor-negative (ER-) breast cancer. In the current study, we investigate the contribution of T lymphocytes and the IFN-γ pathway in enabling breast cancer cells to pass the in vitro BBB. CD8+ cells display the strongest stimulatory effect on breast cancer cell passage. We show that inhibition of the IFN-γ receptor in MDA-MB-231 breast cancer cells, or neutralization of soluble IFN-γ, impairs the in vitro trespassing of breast cancer cells. Importantly, we validated our findings using gene expression data of breast cancer patients. The CXCL-9,-10,-11/CXCR3 axis, dependent on IFN-γ signaling activity, was overexpressed in primary breast cancer samples of patients who developed brain metastasis. The data support a role for T-lymphocytes and the IFN-γ pathway in the formation of brain metastasis of ER-breast cancer, and offer targets to design future therapies for preventing breast cancer cells to cross the BBB.

The Basic Requirement of Tight Junction Proteins in Blood-Brain Barrier Function and Their Role in Pathologies

This review addresses the role of tight junction proteins at the blood-brain barrier (BBB). Their expression is described, and their role in physiological and pathological processes at the BBB is discussed. Based on this, new approaches are depicted for paracellular drug delivery and diagnostics in the treatment of cerebral diseases. Recent data provide convincing evidence that, in addition to its impairment in the course of diseases, the BBB could be involved in the aetiology of CNS disorders. Further progress will be expected based on new insights in tight junction protein structure and in their involvement in signalling pathways.

A single nuclear transcriptomic characterisation of mechanisms responsible for impaired angiogenesis and blood-brain barrier function in Alzheimer's disease

Brain perfusion and blood-brain barrier (BBB) integrity are reduced early in Alzheimer's disease (AD). We performed single nucleus RNA sequencing of vascular cells isolated from AD and non-diseased control brains to characterise pathological transcriptional signatures responsible for this. We show that endothelial cells (EC) are enriched for expression of genes associated with susceptibility to AD. Increased β-amyloid is associated with BBB impairment and a dysfunctional angiogenic response related to a failure of increased pro-angiogenic HIF1A to increased VEGFA signalling to EC. This is associated with vascular inflammatory activation, EC senescence and apoptosis. Our genomic dissection of vascular cell risk gene enrichment provides evidence for a role of EC pathology in AD and suggests that reducing vascular inflammatory activation and restoring effective angiogenesis could reduce vascular dysfunction contributing to the genesis or progression of early AD.

Berberine: A natural modulator of immune cells in multiple sclerosis

Berberine is a benzylisoquinoline alkaloid found in such plants as Berberis vulgaris, Berberis aristata, and others, revealing a variety of pharmacological properties as a result of interacting with different cellular and molecular targets. Recent studies have shown the immunomodulatory effects of Berberine which result from its impacts on immune cells and immune response mediators such as diverse T lymphocyte subsets, dendritic cells (DCs), and different inflammatory cytokines. Multiple sclerosis (MS) is a chronic disabling and neurodegenerative disease of the central nervous system (CNS) characterized by the recruitment of autoreactive T cells into the CNS causing demyelination, axonal damage, and oligodendrocyte loss. There have been considerable changes discovered in MS regards to the function and frequency of T cell subsets such as Th1 cells, Th17 cells, Th2 cells, Treg cells, and DCs. In the current research, we reviewed the outcomes of in vitro, experimental, and clinical investigations concerning the modulatory effects that Berberine provides on the function and numbers of T cell subsets and DCs, as well as important cytokines that are involved in MS.

Inhibiting the NLRP3 Inflammasome with MCC950 Alleviates Neurological Impairment in the Brain of EAE Mice

Multiple sclerosis (MS) is a chronic disease that is characterized by demyelination and neuronal damage. Experimental autoimmune encephalomyelitis (EAE) mice are used to model the disease progression of MS and mirror MS-like pathology. Previous researches have confirmed that inhibition of NLRP3 inflammasome significantly alleviated the severity of EAE mice and the demyelination of spinal cord, but its effect on neuronal damage and oligodendrocyte loss in the brain remains unclear. In this study, female C57BL/6 mice were immunized with MOG35-55 and PTX to establish experimental autoimmune encephalomyelitis (EAE) model. MCC950, a selective NLRP3 inflammasome inhibitor, was used to investigate the effect of NLRP3 inflammasome on the pathological changes and glial cell activation in the brain of EAE mice by immunohistochemistry. Our results demonstrated that MCC950 ameliorated the neuronal damage, demyelination, and oligodendrocyte loss in the brain of EAE mice. This protective effect of MCC950 may be attributed to its ability to suppress the activation of glial cells and prevents microglia polarization to M1 phenotype. Our work indicates that inhibition of NLRP3 inflammasome has the therapeutic effects of neuroprotection through immunomodulation and is a promising therapeutic strategy for MS.

The Cellular Dysfunction of the Brain-Blood Barrier from Endothelial Cells to Astrocytes: The Pathway towards Neurotransmitter Impairment in Schizophrenia

Schizophrenia (SCZ) is an articulated psychiatric syndrome characterized by a combination of genetic, epigenetic, and environmental factors. Our intention is to present a pathogenetic model combining SCZ alterations and the main cellular actors of the blood-brain barrier (BBB): endothelial cells (ECs), pericytes, and astrocytes. The homeostasis of the BBB is preserved by the neurovascular unit which is constituted by ECs, astrocytes and microglia, neurons, and the extracellular matrix. The role of the BBB is strictly linked to its ability to preserve the biochemical integrity of brain parenchyma integrity. In SCZ, there is an increased BBB permeability, demonstrated by elevated levels of albumin and immunoglobulins in the cerebrospinal fluid, and this is the result of an intrinsic endothelial impairment. Increased BBB permeability would lead to enhanced concentrations of neurotoxic and neuroactive molecules in the brain. The pathogenetic involvement of astrocytes in SCZ reverberates its consequences on BBB, together with the impact on its permeability and selectivity represented by the EC and pericyte damage occurring in the psychotic picture. Understanding the strict interaction between ECs and astrocytes, and its consequent impact on cognition, is diriment not only for comprehension of neurotransmitter dyshomeostasis in SCZ, but also for focusing on other potential therapeutic targets.

Development and Optimization of a Target Engagement Model of Brain IDO Inhibition for Alzheimer's Disease

BACKGROUND

Indoleamine 2,3-dioxygenase (IDO1) inhibition is a promising target as an Alzheimer's disease (AD) Disease-modifying therapy capable of downregulating immunopathic neuroinflammatory processes.

METHODS

To aid in the development of IDO inhibitors as potential AD therapeutics, we optimized a lipopolysaccharide (LPS) based mouse model of brain IDO1 inhibition by examining the dosedependent and time-course of the brain kynurenine:tryptophan (K:T) ratio to LPS via intraperitoneal dosing.

RESULTS

We determined the optimal LPS dose to increase IDO1 activity in the brain, and the ideal time point to quantify the brain K:T ratio after LPS administration. We then used a brain penetrant tool compound, EOS200271, to validate the model, determine the optimal dosing profile and found that a complete rescue of the K:T ratio was possible with the tool compound.

CONCLUSION

This LPS-based model of IDO1 target engagement is a useful tool that can be used in the development of brain penetrant IDO1 inhibitors for AD. A limitation of the present study is the lack of quantification of potential clinically relevant biomarkers in this model, which could be addressed in future studies.

The interplay between T helper cells and brain barriers in the pathogenesis of multiple sclerosis

The blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB) represent two complex structures protecting the central nervous system (CNS) against potentially harmful agents and circulating immune cells. The immunosurveillance of the CNS is governed by immune cells that constantly patrol the BCSFB, whereas during neuroinflammatory disorders, both BBB and BCSFB undergo morphological and functional alterations, promoting leukocyte intravascular adhesion and transmigration from the blood circulation into the CNS. Multiple sclerosis (MS) is the prototype of neuroinflammatory disorders in which peripheral T helper (Th) lymphocytes, particularly Th1 and Th17 cells, infiltrate the CNS and contribute to demyelination and neurodegeneration. Th1 and Th17 cells are considered key players in the pathogenesis of MS and its animal model, experimental autoimmune encephalomyelitis. They can actively interact with CNS borders by complex adhesion mechanisms and secretion of a variety of molecules contributing to barrier dysfunction. In this review, we describe the molecular basis involved in the interactions between Th cells and CNS barriers and discuss the emerging roles of dura mater and arachnoid layer as neuroimmune interfaces contributing to the development of CNS inflammatory diseases.

Claudin-12 deficiency inhibits tumor growth by impairing transendothelial migration of myeloid-derived suppressor cells

Migration of myeloid-derived suppressor cells (MDSCs) out of the circulation, across vascular walls, and into tumor is crucial for their immunosuppressive activity. A deeper understanding of critical junctional molecules and the regulatory mechanisms that mediate the extravasation of MDSCs could identify approaches to overcome cancer immunosuppression. In this study we used mice deficient in tight-junction protein Claudin-12 (Cldn12) compared to wild-type mice and found that loss of host Cldn12 inhibited the growth of transplanted tumors, reduced intratumoral accumulation of MDSCs, increased anti-tumor immune responses, and decreased tumor vescular density. Further studies revealed that Cldn12 expression on the cell surface of both MDSCs and endothelial cells is required for MDSCs transit across tumor vascular endothelial cells (ECs). Importantly, expression of Cldn12 in MDSCs was modulated by granulocyte-macrophage colony-stimulating factor (GM-CSF) in an AKT-dependent manner. Therefore, our results indicate that Cldn12 could serve as a promising target for restoring the anti-tumor response by interfering with MDSCs transendothelial migration.

Transcryptomic Analysis of Human Brain -Microvascular Endothelial Cell Driven Changes in -Vascular Pericytes

Many pathological conditions of the brain are associated with structural abnormalities within the neurovascular system and linked to pericyte (PC) loss and/or dysfunction. Since crosstalk between endothelial cells (ECs) and PCs greatly impacts the function of the blood–brain barrier (BBB), effects of PCs on endothelial integrity and function have been investigated extensively. However, the impact of ECs on the function and activity of PCs remains largely unknown. Hence, using co-cultures of human brain vascular PCs with human cerebral microvascular ECs on opposite sides of porous Transwell inserts which facilitates direct EC–PC contact and improves EC barrier function, we analyzed EC-driven transcriptomic changes in PCs using microarrays and changes in cytokines/chemokines using proteome arrays. Gene expression analysis (GEA) in PCs co-cultured with ECs versus PCs cultured alone showed significant upregulation of 1′334 genes and downregulation of 964 genes. GEA in co-cultured PCs revealed increased expression of five prominent PC markers as well as soluble factors, such as transforming growth factor beta, fibroblast growth factor, angiopoietin 1, brain-derived neurotrophic factor, all of which are involved in EC–PC crosstalk and BBB induction. Pathway enrichment analysis of modulated genes showed a strong impact on many inflammatory and extracellular matrix (ECM) pathways including interferon and interleukin signaling, TGF-β and interleukin-1 regulation of ECM, as well as on the mRNA processing pathway. Interestingly, while co-culture induced the mRNA expression of many chemokines and cytokines, including several CCL- and CXC-motif ligands and interleukins, we observed a decreased expression of the same inflammatory mediators on the protein level. Importantly, in PCs, ECs significantly induced interferon associated proteins (IFIT1, IFI44L, IF127, IFIT3, IFI6, IFI44) with anti-viral actions; downregulated prostaglandin E receptor 2 (prevent COX-2 mediated BBB damage); upregulated fibulin-3 and connective tissue growth factor essential for BBB integrity; and multiple ECMs (collagens and integrins) that inhibit cell migration. Our findings suggest that via direct contact, ECs prime PCs to induce molecules to promote BBB integrity and cell survival during infection and inflammatory insult. Taken together, we provide first evidence that interaction with ECs though porous membranes induces major changes in the transcriptomic and proteomic profile of PCs. ECs influence genes involved in diverse aspects of PC function including PC maturation, cell survival, anti-viral defense, blood flow regulation, immuno-modulation and ECM deposition.

T cell transgressions: Tales of T cell form and function in diverse disease states

Insights into T cell form, function, and dysfunction are rapidly evolving. T cells have remarkably varied effector functions including protecting the host from infection, activating cells of the innate immune system, releasing cytokines and chemokines, and heavily contributing to immunological memory. Under healthy conditions, T cells orchestrate a finely tuned attack on invading pathogens while minimizing damage to the host. The dark side of T cells is that they also exhibit autoreactivity and inflict harm to host cells, creating autoimmunity. The mechanisms of T cell autoreactivity are complex and dynamic. Emerging research is elucidating the mechanisms leading T cells to become autoreactive and how such responses cause or contribute to diverse disease states, both peripherally and within the central nervous system. This review provides foundational information on T cell development, differentiation, and functions. Key T cell subtypes, cytokines that create their effector roles, and sex differences are highlighted. Pathological T cell contributions to diverse peripheral and central disease states, arising from errors in reactivity, are highlighted, with a focus on multiple sclerosis, rheumatoid arthritis, osteoarthritis, neuropathic pain, and type 1 diabetes.

Learning-dependent dendritic spine plasticity is impaired in spontaneous autoimmune encephalomyelitis

Cognitive impairment is often observed in multiple sclerosis and its animal models, experimental autoimmune encephalomyelitis (EAE). Using mice with immunization-induced EAE, we have previously shown that the stability of cortical synapses is markedly decreased before the clinical onset of EAE. In this study, we examined learning-dependent structural synaptic plasticity in a spontaneous EAE model. Transgenic mice expressing myelin basic protein-specific T cell receptor genes develop EAE spontaneously at around 8 weeks of age. Using in vivo two-photon microscopy, we found that the elimination and formation rates of postsynaptic dendritic spines in somatosensory and motor cortices increased weeks before detectable signs of EAE and remained to be high during the disease onset. Despite the elevated basal spine turnover, motor learning-induced spine formation was reduced in presymptomatic EAE mice, in line with their impaired ability to retain learned motor skills. Additionally, we found a substantial elevation of IFN-γ mRNA in the brain of 4-week-old presymptomatic mice, and treatment of anti-IFN-γ antibody reduced dendritic spine elimination in the cortex. Together, these findings reveal synaptic instability and failure to form new synapses after learning as early brain pathology of EAE, which may contribute to cognitive and behavioral deficits seen in autoimmune diseases.

Cytokines in CAR T Cell-Associated Neurotoxicity

Chimeric antigen receptor (CAR) T cells provide new therapeutic options for patients with relapsed/refractory hematologic malignancies. However, neurotoxicity is a frequent, and potentially fatal, complication. The spectrum of manifestations ranges from delirium and language dysfunction to seizures, coma, and fatal cerebral edema. This novel syndrome has been designated immune effector cell-associated neurotoxicity syndrome (ICANS). In this review, we draw an arc from our current understanding of how systemic and potentially local cytokine release act on the CNS, toward possible preventive and therapeutic approaches. We systematically review reported correlations of secreted inflammatory mediators in the serum/plasma and cerebrospinal fluid with the risk of ICANS in patients receiving CAR T cell therapy. Possible pathophysiologic impacts on the CNS are covered in detail for the most promising candidate cytokines, including IL-1, IL-6, IL-15, and GM-CSF. To provide insight into possible final common pathways of CNS inflammation, we place ICANS into the context of other systemic inflammatory conditions that are associated with neurologic dysfunction, including sepsis-associated encephalopathy, cerebral malaria, thrombotic microangiopathy, CNS infections, and hepatic encephalopathy. We then review in detail what is known about systemic cytokine interaction with components of the neurovascular unit, including endothelial cells, pericytes, and astrocytes, and how microglia and neurons respond to systemic inflammatory challenges. Current therapeutic approaches, including corticosteroids and blockade of IL-1 and IL-6 signaling, are reviewed in the context of what is known about the role of cytokines in ICANS. Throughout, we point out gaps in knowledge and possible new approaches for the investigation of the mechanism, prevention, and treatment of ICANS.

Occludin regulation of blood-brain barrier and potential therapeutic target in ischemic stroke

Occludin is a key structural component of the blood–brain barrier (BBB) that has recently become an important focus of research in BBB damages. Many studies have demonstrated that occludin could regulate the integrity and permeability of the BBB. The function of BBB depends on the level of occludin protein expression in brain endothelial cells. Moreover, occludin may serve as a potential biomarker for hemorrhage transformation after acute ischemic stroke. In this review, we summarize the role of occludin in BBB integrity and the regulatory mechanisms of occludin in the permeability of BBB after ischemic stroke. Multiple factors have been found to regulate occludin protein functions in maintaining BBB permeability, such as Matrix metalloproteinas-mediated cleavage, phosphorylation, ubiquitination, and related inflammatory factors. In addition, various signaling pathways participate in regulating the occludin expression, including nuclear factor-kappa B, mitogen-activated protein kinase, protein kinase c, RhoK, and ERK1/2. Emerging therapeutic interventions for ischemic stroke targeting occludin are described, including normobaric hyperoxia, Chinese medicine, chemical drugs, genes, steroid hormones, small molecular peptides, and other therapies. Since occludin has been shown to play a critical role in regulating BBB integrity, further preclinical studies will help evaluate and validate occludin as a viable therapeutic target for ischemic stroke.

Interferon-γ potentiates GABAA receptor-mediated inhibitory currents in rat hippocampal CA1 pyramidal neurons

The neural transmission and plasticity can be differentially modulated by various elements of the immune system. Interferon-γ (IFN-γ) is a "pro-inflammatory" cytokine mainly produced by T lymphocytes, activates its corresponding receptor and plays important roles under both homeostatic and inflammatory conditions. However, the impact of IFN-γ on the γ-aminobutyric acid (GABA)-mediated currents in the hippocampus, a major brain region involved in the cognitive function, has not been investigated. Here we detected abundant expression of both IFN-γ receptor subunit gene transcripts (Ifngr1 and Ifngr2) in the rat hippocampus by quantitative PCR. In addition, we pre-incubated rat hippocampal slices with IFN-γ (100 ng/ml) and recorded GABA-activated spontaneous and miniature postsynaptic inhibitory currents (sIPSCs and mIPSCs) and tonic currents in hippocampal CA1 pyramidal neurons by the whole-cell patch-clamp method. The pre-incubation with IFN-γ increased the frequency but not the mean amplitude, rise time or decay time of both sIPSCs and mIPSCs in hippocampal CA1 pyramidal neurons, suggesting a presynaptic effect of IFN-γ. Moreover, the GABA-activated tonic currents were enhanced by IFN-γ. In conclusion, the potentiation of GABAergic currents in hippocampal neurons by IFN-γ may contribute to the disturbed neuronal excitability and cognitive dysfunction during neuroinflammation.

Microglia in Memory Decline from Zika Virus and West Nile Virus Infection

Neurotropic viral infection can result in complications underscored by persistent T cell presence in the brain linked with cognitive decline. A recent study by Garber et al. showed that sustained T cell production of interferon (IFN)-γ mediating microglia activation triggers cognitive decline during recovery from Zika virus (ZIKV) or West Nile virus (WNV) infection.

Evaluation of multiplexed biomarkers in assessment of CSF infiltration in pediatric acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is a very common pediatric malignancy with high survival rates. The course of treatment is modified according to the occurrence of central nervous system (CNS) disease. Aim: To relate serum and cerebrospinal fluid levels of five biomarkers (matrix metalloprotienase 9, CCL-2, sVCAM-1, IFN-γ and inducible protein 10) at diagnosis to the development of CNS infiltration. Methods: The present study was carried on 64 children with ALL and 20 controls. Multiplexed cytokines were measured by Luminex technology (Matrix metalloprotienase 9, CCL-2, sVCAM-1, IFN-γ and inducible protein 10). Results: Significantly higher sMMP-9 and lower sCCL2 were found in patients who developed CNS leukemia. Conclusion: Serum multiplexed parameters at diagnosis of childhood ALL may predict of development of CNS leukemia.

Mesenchymal stem cells decrease blood-brain barrier permeability in rats with severe acute pancreatitis

Background

Impairment of the blood–brain barrier (BBB) could result in secondary cerebral edema and life-threatening pancreatic encephalopathy in patients with severe acute pancreatitis (SAP). Mesenchymal stem cells (MSCs) have been widely adopted in clinical research because of their pleiotropic functions. The aim of this study was to investigate the impact of MSCs on BBB permeability in SAP and the potential mechanisms driving these effects.

Methods

Sprague-Dawley rats were randomly assigned to the control, SAP and SAP+MSCs groups. Pancreatic impairment was assessed. The serum levels of amylase, TNF-α and IL-10, expression levels of claudin-5, Bax, Bcl-2 and MMP-9, and the BBB permeability were measured. Endothelial cell apoptosis was evaluated.

Results

SAP rats showed BBB impairment with increased permeability and secondary cerebral edema, which was confirmed using the Evans blue assay and the calculation of the brain dry/wet ratio. Treatment with MSCs decreased the serum levels of amylase and TNF-α, increased the serum levels of IL-10, attenuated the apoptosis of brain microvascular endothelial cells, upregulated claudin-5 expression and downregulated MMP-9 expression. This treatment attenuated the increased BBB permeability in SAP rats.

Conclusions

MSCs attenuated the impairment of the BBB and decreased its permeability, producing protective effects in SAP rats.

Electronic supplementary material

The online version of this article (10.1186/s11658-019-0167-8) contains supplementary material, which is available to authorized users.

IFNγ inhibits fibroblast-leading tumor cell invasion through downregulating N-cadherin

Tumor metastasis accounts for most tumor-associated mortality and is closely related with stromal fibroblasts in the tumor microenvironment. It was reported that fibroblasts promoted tumor metastasis through directly leading tumor cell invasion; however, inflammatory microenvironment in the growing tumor may influence the outcome. Here, we found that the cytokine IFNγ, a key immune mediator secreted by T cells, could alter mouse lung tumor associated fibroblast-leading LLC tumor cell invasion in Matrigel. The motility of fibroblasts and adhesion with tumor cells were dramatically impaired upon IFNγ stimulation. We further found that IFNγ reduced the expression of N-cadherin on the surface of fibroblasts through upregulating SMAD7 and suppressing the downstream SMAD2 phosphorylation. N-cadherin was essential for fibroblast motility and adhesions with tumor cells. Moreover, fibroblasts could promote tumor progression and the deficiency of IFNγR signaling in fibroblasts reduced liver metastasis of LLC tumor in vivo. Collectively, our results demonstrate that IFNγ inhibits fibroblast-leading tumor cell invasion by inhibiting the motility of fibroblasts and their adhesion with tumor cells. The findings indicate that inflammatory cytokines in the tumor microenvironment may regulate the fibroblast-associated tumor metastasis.

Claudin-5: gatekeeper of neurological function

Tight junction proteins of the blood–brain barrier are vital for maintaining integrity of endothelial cells lining brain blood vessels. The presence of these protein complexes in the space between endothelial cells creates a dynamic, highly regulated and restrictive microenvironment that is vital for neural homeostasis. By limiting paracellular diffusion of material between blood and brain, tight junction proteins provide a protective barrier preventing the passage of unwanted and potentially damaging material. Simultaneously, this protective barrier hinders the therapeutic effectiveness of central nervous system acting drugs with over 95% of small molecule therapeutics unable to bypass the blood–brain barrier. At the blood–brain barrier, claudin-5 is the most enriched tight junction protein and its dysfunction has been implicated in neurodegenerative disorders such as Alzheimer’s disease, neuroinflammatory disorders such as multiple sclerosis as well as psychiatric disorders including depression and schizophrenia. By regulating levels of claudin-5, it is possible to abrogate disease symptoms in many of these disorders. This review will give an overview of the blood–brain barrier and the role of tight junction complexes in maintaining blood–brain barrier integrity before focusing on the role of claudin-5 and its regulation in homeostatic and pathological conditions. We will also summarise therapeutic strategies to restore integrity of cerebral vessels by targeting tight junction protein complexes.

Increased vessel perfusion predicts the efficacy of immune checkpoint blockade

Immune checkpoint blockade (ICB) has demonstrated curative potential in several types of cancer, but only for a small number of patients. Thus, the identification of reliable and noninvasive biomarkers for predicting ICB responsiveness is an urgent unmet need. Here, we show that ICB increased tumor vessel perfusion in treatment-sensitive EO771 and MMTV-PyVT breast tumor as well as CT26 and MCA38 colon tumor models, but not in treatment-resistant MCaP0008 and 4T1 breast tumor models. In the sensitive tumor models, the ability of anti-cytotoxic T lymphocyte-associated protein 4 or anti-programmed cell death 1 therapy to increase vessel perfusion strongly correlated with its antitumor efficacy. Moreover, globally enhanced tumor vessel perfusion could be detected by Doppler ultrasonography before changes in tumor size, which predicted final therapeutic efficacy with more than 90% sensitivity and specificity. Mechanistically, CD8+ T cell depletion, IFN-γ neutralization, or implantation of tumors in IFN-γ receptor knockout mice abrogated the vessel perfusion enhancement and antitumor effects of ICB. These results demonstrated that ICB increased vessel perfusion by promoting CD8+ T cell accumulation and IFN-γ production, indicating that increased vessel perfusion reflects the successful activation of antitumor T cell immunity by ICB. Our findings suggest that vessel perfusion can be used as a novel noninvasive indicator for predicting ICB responsiveness.

Effector T Cells in Multiple Sclerosis

Multiple sclerosis (MS) has long been considered a CD4 T-cell disease, primarily because of the findings that the strongest genetic risk for MS is the major histocompatibility complex (MHC) class II locus, and that T cells play a central role in directing the immune response. The importance that the T helper (Th)1 cytokine, interferon γ (IFN-γ), and the Th17 cytokine, interleukin (IL)-17, play in MS pathogenesis is indicated by recent clinical trial data by the enhanced presence of Th1/Th17 cells in central nervous system (CNS) tissue, cerebrospinal fluid (CSF), and blood, and by research on animal models of MS, such as experimental autoimmune encephalomyelitis (EAE). Although the majority of research on MS pathogenesis has centered on the role of effector CD4 T cells, accumulating data suggests that CD8 T cells may play a significant role in the human disease. In fact, in contrast to most animal models, the primary T cell found in the CNS in patients with MS, is the CD8 T cell. As patient-derived effector T cells are also resistant to mechanisms of dominant tolerance such as that induced by interaction with regulatory T cells (Tregs), their reduced response to regulation may also contribute to the unchecked effector T-cell activity in patients with MS. These concepts will be discussed below.

Interleukin-10 attenuates impairment of the blood-brain barrier in a severe acute pancreatitis rat model

Background

Impairment of the blood-brain barrier (BBB) in severe acute pancreatitis (SAP) could result in life-threatening pancreatic encephalopathy. Interleukin-10 (IL-10) is a classical cytokine that is well-known for its strong immunoregulatory and anti-inflammatory abilities. However, whether and how IL-10 protects the BBB in SAP are still unclear.

Methods

This study includes in vivo experiments using a SAP rat model and in vitro experiments using an in vitro BBB model consisting of a monolayer of brain microvascular endothelial cells (BMECs). The study groups are divided into the control, SAP (in vivo)/TNF-α (in vitro), IL-10 treatment, IL-10 + signal transducer and activator of transcription 3 (STAT3) inhibitor S3I-201 treatment groups. Pancreatic pathological scores, serum amylase, serum TNF-α levels and BBB permeability by Evan’s blue assay in SAP rat models were evaluated. BMEC apoptosis in SAP rats or induced by TNF-αin vitro was detected by terminal-deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) and flow cytometry, separately. Expression levels of claudin-5 and proteins involved in the STAT3 signaling pathway were measured by Western blotting. Location and changes of junctional structure of claudin-5 on BMECs were assessed by immunohistochemistry and immunofluorescence.

Results

In vivo, IL-10 alleviated the severity of inflammation, attenuated the increased BBB permeability in SAP rat models by reducing BMEC apoptosis via the STAT3 pathway and ameliorated the down-regulation of claudin-5 expression in BMECs; in vitro, IL-10 improved BBB integrity against TNF-α by attenuating BMEC apoptosis via the STAT3 pathway, the impairment of tight junction structure and the down-regulation of claudin-5 expression in BMECs.

Conclusions

IL-10 improves BBB properties in SAP by attenuating the down-regulation of claudin-5 expression and the impairment of tight junctions and by STAT3 pathway-mediated anti-apoptotic effects on BMECs.

Accelerated tumour metastasis due to interferon-γ receptor-mediated dissociation of perivascular cells from blood vessels

Angiostasis mediated by interferon (IFN)-γ is a key mechanism of anti-tumour immunity; however, the effect of IFN-γ on host vascular endothelial growth factor A (VEGFA)-expressing cells during tumour progression is still elusive. Here, we developed transgenic mice with IFN-γ receptor (IFNγR) expression under control of the Vegfa promoter (V-γR). In these mice, the IFN-γ responsiveness of VEGFA-expressing cells led to dramatic growth suppression of transplanted lung carcinoma cells. Surprisingly, increased mortality and tumour metastasis were observed in the tumour-bearing V-γR mice, in comparison with the control wild-type and IFNγR-deficient mice. Further study showed that perivascular cells were VEGFA-expressing cells and potential IFN-γ targets. In vivo, tumour vascular perfusion and pericyte association with blood vessels were massively disrupted in V-γR mice. In vitro, IFN-γ inhibited transforming growth factor-β signalling by upregulating SMAD7, and therefore downregulated N-cadherin expression in pericytes. Importantly, IFN-γ neutralization in vivo with a monoclonal antibody reduced tumour metastasis. Together, the results suggest that IFNγR-mediated dissociation of perivascular cells from blood vessels contributes to the acceleration of tumour metastasis. Thus, the inhibition of tumour growth via IFN-γ-induced angiostasis might also accelerate tumour metastasis. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Kv1.3 channel blocker (ImKTx88) maintains blood-brain barrier in experimental autoimmune encephalomyelitis

BACKGROUND

Disruption of blood-brain barrier (BBB) and subsequent infiltration of auto-reactive T lymphocytes are major characteristics of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). Kv1.3 channel blockers are demonstrated potential therapeutic effects on MS patients and EAE models, maybe via reducing activation of T cells. However, it remains to be explored whether Kv1.3 channel blockers maintain integrity of BBB in MS model.

RESULTS

In this study, ImKTx88, a highly selective Kv1.3 channel blocker, was used to determine the role of Kv1.3 channel in the pathogenesis of EAE, particularly in the maintenance of BBB. ImKTx88 ameliorated pathological severity in the EAE rats, and reduced extravasation into CNS. ImKTx88 also ameliorated the severity of loss or redistribution of tight junction proteins, and inhibited over-expression of ICAM-1 and VCAM-1 in the brain from EAE rats. Furthermore ImKTx88 protection was associated with activation of Ang-1/Tie-2 axis, and might be due to decreased IL-17 production.

CONCLUSIONS

ImKTx88 may be a novel therapeutic agent for MS treatment by stabilizing the BBB.

Barrier function in the peripheral and central nervous system-a review

The peripheral (PNS) and central nervous system (CNS) are delicate structures, highly sensitive to homeostatic changes-and crucial for basic vital functions. Thus, a selection of barriers ensures the protection of the nervous system from noxious blood-borne or surrounding stimuli. In this chapter, anatomy and functioning of the blood-nerve (BNB), the blood-brain (BBB), and the blood-spinal cord barriers (BSCB) are presented and the key tight junction (TJ) proteins described: claudin-1, claudin-3, claudin-5, claudin-11, claudin-12, claudin-19, occludin, Zona occludens-1 (ZO-1), and tricellulin are by now identified as relevant for nerval barriers. Different diseases can lead to or be accompanied by neural barrier disruption, and impairment of these barriers worsens pathology. Peripheral nerve injury and inflammatory polyneuropathy cause an increased permeability of BNB as well as BSCB, while, e.g., diseases of the CNS such as amyotrophic lateral sclerosis, multiple sclerosis, spinal cord injury, or Alzheimer's disease can progress and worsen through barrier dysfunction. Moreover, the complex role and regulation of the BBB after ischemic stroke is described. On the other side, PNS and CNS barriers hamper the delivery of drugs in diseases when the barrier is intact, e.g., in certain neurodegenerative diseases or inflammatory pain. Understanding of the barrier - regulating processes has already lead to the discovery of new molecules as drug enhancers. In summary, the knowledge of all of these mechanisms might ultimately lead to the invention of drugs to control barrier function to help ameliorating or curing neurological diseases.

Cytokine networks in neuroinflammation

Cytokines provide cells with the ability to communicate with one another and orchestrate complex multicellular behaviour. There is an emerging understanding of the role that cytokines play in normal homeostatic tissue function and how dysregulation of these cytokine networks is associated with pathological conditions. The central nervous system (CNS), where few blood-borne immune cells circulate, seems to be particularly vulnerable to dysregulated cytokine networks. In degenerative diseases, such as proteopathies, CNS-resident cells are the predominant producers of pro-inflammatory cytokines. By contrast, in classical neuroinflammatory diseases, such as multiple sclerosis and encephalitides, pro-inflammatory cytokines are mainly produced by tissue-invading leukocytes. Whereas the effect of dysregulated cytokine networks in proteopathies is controversial, cytokines delivered to the CNS by invading immune cells are in general detrimental to the tissue. Here, we summarize recent observations on the impact of dysregulated cytokine networks in neuroinflammation.

Opposing Roles of Interferon-Gamma on Cells of the Central Nervous System in Autoimmune Neuroinflammation

Multiple sclerosis (MS) is the principal cause of autoimmune neuroinflammation in humans, and its animal model, experimental autoimmune encephalomyelitis (EAE), is widely used to gain insight about their immunopathological mechanisms for and the development of novel therapies for MS. Most studies on the role of interferon (IFN)-γ in the pathogenesis and progression of EAE have focused on peripheral immune cells, while its action on central nervous system (CNS)-resident cells has been less explored. In addition to the well-known proinflammatory and damaging effects of IFN-γ in the CNS, evidence has also endowed this cytokine both a protective and regulatory role in autoimmune neuroinflammation. Recent investigations performed in this research field have exposed the complex role of IFN-γ in the CNS uncovering unexpected mechanisms of action that underlie these opposing activities on different CNS-resident cell types. The mechanisms behind these two-faced effects of IFN-γ depend on dose, disease phase, and cell development stage. Here, we will review and discuss the dual role of IFN-γ on CNS-resident cells in EAE highlighting its protective functions and the mechanisms proposed.

Antibodies as Mediators of Brain Pathology

The brain is normally sequestered from antibody exposure by the blood brain barrier. However, antibodies can access the brain during fetal development before the barrier achieves full integrity, and in disease states when barrier integrity is compromised. Recent studies suggest that antibodies contribute to brain pathology associated with autoimmune diseases such as systemic lupus erythematosus and neuromyelitis optica, and can lead to transient or permanent behavioral or cognitive abnormalities. We review these findings here and examine the circumstances associated with antibody entry into the brain, the routes of access and the mechanisms that then effect pathology. Understanding these processes and the nature and specificity of neuronal autoantibodies may reveal therapeutic strategies toward alleviating or preventing the neurological pathologies and behavioral abnormalities associated with autoimmune disease.

Specific binding of Clostridium perfringens enterotoxin fragment to Claudin-b and modulation of zebrafish epidermal barrier

Claudins (Cldn) are the major components of tight junctions (TJs) sealing the paracellular cleft in tissue barriers of various organs. Zebrafish Cldnb, the homolog of mammalian Cldn4, is expressed at epithelial cell-cell contacts and is important for regulating epidermal permeability. The bacterial toxin Clostridium perfringens enterotoxin (CPE) has been shown to bind to a subset of mammalian Cldns. In this study, we used the Cldn-binding C-terminal domain of CPE (194-319 amino acids, cCPE 194-319 ) to investigate its functional role in modulating zebrafish larval epidermal barriers. In vitro analyses show that cCPE 194-319 removed Cldn4 from epithelial cells and disrupted the monolayer tightness, which could be rescued by the removal of cCPE 194-319. Incubation of zebrafish larvae with cCPE 194-319 removed Cldnb specifically from the epidermal cell membrane. Dye diffusion analysis with 4-kDa fluorescent dextran indicated that the permeability of the epidermal barrier increased due to cCPE 194-319 incubation. Electron microscopic investigation revealed reversible loss of TJ integrity by Cldnb removal. Collectively, these results suggest that cCPE 194-319 could be used as a Cldnb modulator to transiently open the epidermal barrier in zebrafish. In addition, zebrafish might be used as an in vivo system to investigate the capability of cCPE to enhance drug delivery across tissue barriers.