Capture, crawl, cross: the T cell code to breach the blood–brain barriers

Huang-Lian-Jie-Du decoction inhibits CD4+ T cell infiltration into CNS in MCAO rats by regulating BBB

BACKGROUND

Stroke, especially ischemic stroke (IS), represents a major global health challenge due to its high incidence, disability, mortality, recurrence, and economic impact. The limited therapeutic window for thrombolysis underscores the need for new treatments. The blood-brain barrier (BBB), which protects the brain, becomes compromised following ischemia-reperfusion injury, allowing peripheral immune cell infiltration and subsequent neuroinflammation. Huang-Lian-Jie-Du Decoction (HLJDT), a traditional formula with significant neuroprotective effects demonstrated in preliminary studies and literature reviews, has not yet been fully explored for its potential to inhibit peripheral immune cell infiltration through BBB protection.

PURPOSE

This study aims to: (1) Evaluate the efficacy of HLJDT in treating MCAO. (2) Observe the regulatory effect of HLJDT on the infiltration of CD4+ T cells into the central nervous system. (3) Investigate the effect of HLJDT on the Wnt/β-Catenin Signaling Pathway.

METHODS

A focal MCAO reperfusion model will be used to evaluate HLJDT's effects on neurological function (Zea Longa and Garcia scores), infarction volume (TTC staining), and pathological changes (HE and NISSL staining). Immune-inflammatory responses will be assessed using ELISA for cytokines, flow cytometry for T lymphocyte distribution, and immunofluorescence staining for CD4+ T cell infiltration. The interaction of T cell antigens (LFA-1) and endothelial adhesion molecules (ICAM-1) will be studied with ELISA and immunofluorescence. BBB protection will be evaluated with Evans blue staining and transmission electron microscopy. Mechanisms of T cell infiltration will be examined using transmission electron microscopy and Western blotting (WB) for key proteins. Additionally, the impact of HLJDT on the Wnt/β-catenin pathway will be assessed with WB.

RESULTS

HLJDT significantly improves neurological scores, reduces infarction volume, and mitigates pathological damage. It balances CD4+ T cell responses by inhibiting pro-inflammatory cytokines and enhancing anti-inflammatory ones, reducing CD4+ T cell CNS infiltration. HLJDT inhibits LFA-1/ICAM-1 interactions. It can also inhibit CD4+ T cell infiltration by repairing paracellular and transcellular structures of the BBB, with the Wnt/β-catenin signaling pathway playing a key role in this process.

CONCLUSION

We have innovatively demonstrated for the first time that HLJDT can regulate the balance between peripheral and central immune inflammation. It inhibits LFA-1/ICAM-1-mediated cell adhesion and, by modulating the Wnt/β-catenin pathway, improves the paracellular and transcellular structures of the blood-brain barrier, thereby suppressing CD4+ T cell infiltration and providing multifaceted protective effects for MCAO rats.

Non-neuronal brain biology and its relevance to animal welfare

Non-neuronal cells constitute a significant portion of brain tissue and are seen as having key roles in brain homeostasis and responses to challenges. This review illustrates how non-neuronal biology can bring new perspectives to animal welfare through understanding mechanisms that determine welfare outcomes and highlighting interventions to improve welfare. Most obvious in this respect is the largely unrecognised relevance of neuroinflammation to animal welfare which is increasingly found to have roles in determining how animals respond to challenges. We start by introducing non-neuronal cells and review their involvement in affective states and cognition often seen as core psychological elements of animal welfare. We find that the evidence for a causal involvement of glia in cognition is currently more advanced than the corresponding evidence for affective states. We propose that translational research on affective disorders could usefully apply welfare science derived approaches for assessing affective states. Using evidence from translational research, we illustrate the involvement of non-neuronal cells and neuroinflammatory processes as mechanisms modulating resilience to welfare challenges including disease, pain, and social stress. We review research on impoverished environments and environmental enrichment which suggests that environmental conditions which improve animal welfare also improve resilience to challenges through balancing pro- and anti-inflammatory non-neuronal processes. We speculate that non-neuronal biology has relevance to animal welfare beyond neuro-inflammation including facilitating positive affective states. We acknowledge the relevance of neuronal biology to animal welfare whilst proposing that non-neuronal biology provides additional and relevant insights to improve animals' lives.

Border-associated macrophages as gatekeepers of brain homeostasis and immunity

The brain's border tissues serve as essential hubs for neuroimmune regulation and the trafficking of biomaterials to and from the brain. These complex tissues-including the meninges, perivascular spaces, choroid plexus, and circumventricular organs-balance the brain's need for immune privilege with immune surveillance and blood-brain communication. Macrophages are integral components of these tissues, taking up key strategic positions within the brain's circulatory system. These border-associated macrophages, or "BAMs," are therefore emerging as pivotal for brain homeostasis and disease. BAMs perform trophic functions that help to support border homeostasis but also act as immune sentinels essential for border defense. In this review, we integrate recent findings on BAM origins, cell states, and functions, aiming to provide global insights and perspectives on the complex relationship between these macrophages and their border niche.

IQGAP2 regulates blood-brain barrier immune dynamics

Brain endothelial cells (BECs) play an important role in maintaining central nervous system (CNS) homeostasis through blood-brain barrier (BBB) functions. BECs express low baseline levels of adhesion receptors, which limits entry of leukocytes. However, the molecular mediators governing this phenotype remain mostly unclear. Here, we explored how infiltration of immune cells across the BBB is influenced by the scaffold protein IQ motif containing GTPase-activating protein 2 (IQGAP2). In mice and zebrafish, we demonstrate that loss of Iqgap2 increases infiltration of peripheral leukocytes into the CNS under homeostatic and inflammatory conditions. Using single-cell RNA sequencing and immunohistology, we further show that BECs from mice lacking Iqgap2 exhibit a profound inflammatory signature, including extensive upregulation of adhesion receptors and antigen-processing machinery. Human tissue analyses also reveal that Alzheimer's disease is associated with reduced hippocampal IQGAP2. Overall, our results implicate IQGAP2 as an essential regulator of BBB immune privilege and immune cell entry into the CNS.

A New Perspective on Mechanisms of Neurodegeneration in Experimental Autoimmune Encephalomyelitis and Multiple Sclerosis: the Early and Critical Role of Platelets in Neuro/Axonal Loss

Multiple sclerosis (MS) is a central nervous system (CNS) autoimmune disorder, with limited treatment options. This disease is characterized by differential pathophysiology between grey matter (GM) and white matter (WM). The predominant WM hallmark is the perivascular plaque, associated with blood brain barrier (BBB) loss of function, lymphocytic infiltration, microglial reactivity, demyelination and axonal injury and is adequately addressed with immunomodulatory drugs. By contrast, mechanisms underlying GM damage remain obscure, with consequences for neuroprotective strategies. Cortical GM pathology is already significant in early MS and characterized by reduced BBB disruption and lymphocytic infiltration relative to WM, but a highly inflammatory environment, microglial reactivity, demyelination and neuro/axonal loss. There is no satisfactory explanation for the occurrence of neurodegeneration without large-scale inflammatory cell influx in cortical GM. A candidate mechanism suggests that it results from soluble factors originating from meningeal inflammatory cell aggregates, which diffuse into the underlying cortical tissue and trigger microglial activation. However, the recent literature highlights the central role of platelets in inflammation, together with the relationship between coagulation factors, particularly fibrinogen, and tissue damage in MS. Using the experimental autoimmune encephalomyelitis (EAE) model, we identified platelets as drivers of neuroinflammation and platelet-neuron associations from the pre-symptomatic stage. We propose that fibrinogen leakage across the BBB is a signal for platelet infiltration and that platelets represent a major and early participant in neurodegeneration. This concept is compatible with the new appreciation of platelets as immune cells and of neuronal damage driven by inflammatory cells sequestered in the meninges.

Inhibition of IFITM3 in cerebrovascular endothelium alleviates Alzheimer's-related phenotypes

INTRODUCTION

Interferon-induced transmembrane protein 3 (IFITM3) modulates γ-secretase in Alzheimer's Disease (AD). Although IFITM3 knockout reduces amyloid β protein (Aβ) production, its cell-specific effect on AD remains unclear.

METHODS

Single nucleus RNA sequencing (snRNA-seq) was used to assess IFITM3 expression. Adeno-associated virus-BI30 (AAV-BI30) was injected to reduce IFITM3 expression in the cerebrovascular endothelial cells (CVECs). The effects on AD phenotypes in cells and AD mice were examined through behavioral tests, two-photon imaging, flow cytometry, Western blot, immunohistochemistry, and quantitative polymerase chain reaction assay (qPCR).

RESULTS

IFITM3 expression was increased in the CVECs of patients with AD. Overexpression of IFITM3 in primary endothelial cells enhanced Aβ generation through regulating beta-site APP cleaving enzyme 1 (BACE1) and γ-secretase. Aβ further increased IFITM3 expression, creating a vicious cycle. Knockdown of IFITM3 in CVECs decreased Aβ accumulation within cerebrovascular walls, reduced Alzheimer's-related pathology, and improved cognitive performance in AD transgenic mice.

DISCUSSION

Knockdown of IFITM3 in CVECs alleviates AD pathology and cognitive impairment. Targeting cerebrovascular endothelial IFITM3 holds promise for AD treatment.

HIGHLIGHTS

Interferon-induced transmembrane protein 3 (IFITM3) expression was increased in the cerebrovascular endothelial cells (CVECs) of patients with Alzheimer's Disease (AD). Cerebrovascular endothelial IFITM3 regulates amyloid β protein (Aβ) generation through regulating beta-site APP cleaving enzyme 1 (BACE1) and γ-secretase. Knockdown of IFITM3 in CVECs reduces Aβ deposits and improves cognitive impairments in AD transgenic mice. Cerebrovascular endothelial IFITM3 could be a potential target for the treatment of AD.

The role of CXCL12/CXCR4/CXCR7 axis in cognitive impairment associated with neurodegenerative diseases

Neurodegenerative diseases, including Alzheimer's Disease (AD), Parkinson's Disease (PD), Multiple Sclerosis (MS), and Amyotrophic Lateral Sclerosis (ALS), are characterized by progressive neuronal loss and cognitive impairment (CI). The: Cysteine-X-cysteine chemokine ligand 12(CXCL12)/CXC chemokine receptor type 4 (CXCR4)/CXC chemokine receptor type 7 (CXCR7) axis has emerged as a critical molecular pathway in the development of CI in these disorders. This review explores the role of this axis in the pathogenesis of CI across these neurodegenerative diseases, synthesizing current evidence and its implications for targeted therapies. In AD, dysregulation of this axis contributes to amyloid-β accumulation and tau hyperphosphorylation, leading to synaptic dysfunction and cognitive decline. PD studies reveal that CXCL12/CXCR4 signaling influences dopaminergic neuron survival and microglial activation, affecting cognitive function. In MS, the axis modulates neuroinflammation and demyelination processes, impacting cognitive performance. ALS research indicates that the CXCL12/CXCR4/CXCR7 pathway is involved in motor neuron degeneration and associated cognitive deficits. Across these diseases, the axis influences neuroinflammation, synaptic plasticity, and neuronal survival through various signaling cascades, including PI3K/AKT, MAPK, and JAK/STAT pathways. Emerging evidence suggests that modulating this axis could provide neuroprotective effects and potentially alleviate cognitive symptoms. This review highlights the potential of the CXCL12/CXCR4/CXCR7 axis as a therapeutic target for addressing CI in neurodegenerative diseases. It also underscores the need for further research to fully elucidate its role and develop effective interventions, potentially leading to improved clinical management strategies for these devastating disorders.

Activation of Wnt/β-catenin in neural progenitor cells regulates blood-brain barrier development and promotes neuroinflammation

The central nervous system (CNS) requires specialized blood vessels to support neural function within specific microenvironments. During neurovascular development, endothelial Wnt/β-catenin signaling is required for BBB development within the brain parenchyma, whereas fenestrated blood vessels that lack BBB properties do not require Wnt/β-catenin signaling. Here, we used zebrafish to further characterize this phenotypic heterogeneity of the CNS vasculature. Using transgenic reporters of Wnt/β-catenin transcriptional activity, we found an inverse correlation between activated Wnt/β-catenin signaling in endothelial cells (ECs) versus non-ECs within these distinct microenvironments. Our results indicated that the level of Wnt/β-catenin signaling in non-ECs may regulate Wnt/β-catenin activity in adjacent ECs. To further test this concept, we generated a transgenic Tet-On inducible system to drive constitutively active β-catenin expression in neural progenitor cells (NPCs). We found that dose-dependent activation of Wnt/β-catenin in NPCs caused severe deficiency in CNS angiogenesis and BBB development. Additionally, we discovered a significant increase in the proliferation of microglia and infiltration of peripheral neutrophils indicative of a stereotypical neuroinflammatory response. In conclusion, our results demonstrate the importance of proper Wnt/β-catenin signaling within specific CNS microenvironments and highlights the potentially deleterious consequences of aberrant Wnt activation.

Intranasal delivery of mesenchymal stem cell-derived exosomes ameliorates experimental autoimmune encephalomyelitis

BACKGROUND

Exosomes derived from bone marrow mesenchymal stem cells (BMSCs-Exos) have shown therapeutic potential in experimental autoimmune encephalomyelitis (EAE). As a non-invasive method of drug administration, intranasal delivery is anticipated to emerge as a novel option for the treatment of central nervous system (CNS) disorders. Therefore, this study aims to treat EAE by nasal exosomes and explore its specific mechanism, especially its impact on the blood-brain barrier (BBB).

METHODS

BMSCs-Exos were isolated and characterized. An EAE model was then established, and these exosomes were administered intranasally to the mice. Changes in body weight and clinical scores were monitored following treatment to assess the efficacy. Additionally, inflammatory infiltrates and demyelination in the CNS were evaluated, alongside the quantification of expression levels of BBB-related adhesion molecules and tight junction (TJ) proteins.

RESULTS

Intranasal delivery of BMSCs-Exos ameliorates the severity of EAE disease, reducing inflammatory infiltration in the CNS and demyelination in the spinal cord. This treatment did not influence the differentiation of T cells in the spleen. Furthermore, the nasal delivery of BMSCs-Exos enhances the integrity of TJs in the cerebral cortex and spinal cord, as well as inhibiting the expression of adhesion molecules. These exosomes promote the expression of TJ-related markers in bEnd3 cells, including ZO-1, Occludin, and Claudin 5. At the same time, they suppress the expression of adhesion molecule-related markers, such as ICAM1 and VCAM1.

CONCLUSIONS

Our study suggests that intranasal administration of BMSCs-Exos significantly reduces inflammatory infiltration and demyelination in the CNS of EAE mice. Furthermore, this treatment does not influence the differentiation of T cells in the spleen. Additionally, nasal reinfusion of BMSCs-Exos can improve the integrity of the BBB in EAE mice.

Intrathecal Immunoglobulin A Synthesis in Multiple Sclerosis: From Biological Aspects to Clinical Relevance

Intrathecal immunoglobulin A (IgA) synthesis in multiple sclerosis (MS) has long earned little attention, despite a potential significance in disease pathogenesis and prognosis. The presence of IgA-positive plasma cells in MS lesions and along damaged axons suggests a role in disease pathogenesis. Available clinical evidence about a potential positive or negative prognostic role is scarce and inconclusive. Recent observations, however, highlight the migration of immune regulatory IgA-producing plasma cells from the gut to the central nervous system (CNS) in experimental autoimmune encephalitis models. A connection between intrathecal IgA synthesis and the gut-brain axis in MS was further corroborated by the discovery of gut microbiota-specific IgA+ B cells in human CNS during relapse. In this review, we summarize current evidence on the occurrence and immunopathology of intrathecal IgA synthesis in MS, explore its biological implications, and address methodological challenges regarding the detection of IgA as a major limitation and possible source of inconsistencies in clinical studies. By synthesizing these diverse lines of evidence, we highlight the importance of further research and the need for standardized detection methods to clarify the role of IgA in MS pathogenesis, disease progression, and as potential biomarker.

Targeting Oligodendrocyte Dynamics and Remyelination: Emerging Therapies and Personalized Approaches in Multiple Sclerosis Management

Multiple sclerosis (MS) is a progressive autoimmune condition that primarily affects young people and is characterized by demyelination and neurodegeneration of the central nervous system (CNS). This in-depth review explores the complex involvement of oligodendrocytes, the primary myelin- producing cells in the CNS, in the pathophysiology of MS. It discusses the biochemical processes and signalling pathways required for oligodendrocytes to function and remain alive, as well as how they might fail and cause demyelination to occur. We investigate developing therapeutic options that target remyelination, a fundamental component of MS treatment. Remyelination approaches promote the survival and differentiation of oligodendrocyte precursor cells (OPCs), restoring myelin sheaths. This improves nerve fibre function and may prevent MS from worsening. We examine crucial parameters influencing remyelination success, such as OPC density, ageing, and signalling pathway regulation (e.g., Retinoid X receptor, LINGO-1, Notch). The review also examines existing neuroprotective and antiinflammatory medications being studied to see if they can assist oligodendrocytes in surviving and reducing the severity of MS symptoms. The review focuses on medicines that target the myelin metabolism in oligodendrocytes. Altering oligodendrocyte metabolism has been linked to reversing demyelination and improving MS patient outcomes through various mechanisms. We also explore potential breakthroughs, including innovative antisense technologies, deep brain stimulation, and the impact of gut health and exercise on MS development. The article discusses the possibility of personalized medicine in MS therapy, emphasizing the importance of specific medicines based on individual molecular profiles. The study emphasizes the need for reliable biomarkers and improved imaging tools for monitoring disease progression and therapy response. Finally, this review focuses on the importance of oligodendrocytes in MS and the potential for remyelination therapy. It also underlines the importance of continued research to develop more effective treatment regimens, taking into account the complexities of MS pathology and the different factors that influence disease progression and treatment.

Basement membranes' role in immune cell recruitment to the central nervous system

Basement membranes form part of the extracellular matrix (ECM), which is the structural basis for all tissue. Basement membranes are cell-adherent sheets found between cells and vascular endothelia, including those of the central nervous system (CNS). There is exceptional regional specialisation of these structures, both in tissue organisation and regulation of tissue-specific cellular processes. Due to their location, basement membranes perform a key role in immune cell trafficking and therefore are important in inflammatory processes causing or resulting from CNS disease and injury. This review will describe basement membranes in detail, with special focus on the brain. We will cover how genetic changes drive brain pathology, describe basement membranes' role in immune cell recruitment and how they respond to various brain diseases. Understanding how basement membranes form the junction between the immune and central nervous systems will be a major advance in understanding brain disease.

Isolation method of brain microvessels from small frozen human brain tissue for blood-brain barrier protein expression analysis

BACKGROUND

Protein expression analysis of isolated brain microvessels provides valuable insights into the function of the blood-brain barrier (BBB). However, isolation of brain microvessels from human brain tissue, particularly in small quantities, poses significant challenges. This study presents a method for isolating brain microvessels from a small amount of frozen human brain tissue, adapting techniques from an established mouse brain capillary isolation method.

METHODS

Brain microvessel fractions were obtained from approximately 0.3 g of frozen human brain tissue (frontal cortex) using a bead homogenizer for homogenization, followed by purification with a combination of cell strainers and glass beads. Protein expression in the isolated human microvessel fractions and whole-brain lysates was analyzed by western blot and proteomic analysis.

RESULTS

Microscopic imaging confirmed the successful isolation of brain microvessels from frozen human brain tissue. Protein quantification assays demonstrated that the microvessel fraction yielded sufficient protein for detailed expression analysis. Western blot analysis revealed an enrichment of BBB-selective proteins including multidrug resistance 1 (MDR1)/ATP-binding cassette sub-family B member 1 (ABCB1), glucose transporter protein type 1 (GLUT1)/solute carrier family 2 member 1 (SLC2A1), and claudin 5 (CLDN5), in the brain microvessel fraction compared to whole-brain lysates. Multiple reaction monitoring quantification of six BBB-selective proteins-MDR1, breast cancer resistance protein (BCRP)/ATP binding cassette subfamily G member 2 (ABCG2), GLUT1, monocarboxylate transporter 1 (MCT1)/solute carrier family 16 member 1 (SLC16A1), transferrin receptor, and CLDN5-revealed expression levels consistent with those observed in larger human brain samples. Sequential Window Acquisition of all Theoretical Mass Spectra (SWATH-MS)-based quantitative proteomics further demonstrated significant enrichment of human microvascular endothelial cells in the isolated fraction, corroborating the findings from mouse models.

CONCLUSIONS

We successfully developed a method for isolation of brain microvessels from a small amount of frozen human brain tissue, facilitating detailed study of BBB proteome in aging or pathological conditions. This technique provides valuable insights into BBB dysfunction in central nervous system disorders and holds potential for improving brain-targeted drug delivery strategies.

Tension at the gate: sensing mechanical forces at the blood-brain barrier in health and disease

Microvascular brain endothelial cells tightly limit the entry of blood components and peripheral cells into the brain by forming the blood-brain barrier (BBB). The BBB is regulated by a cascade of mechanical and chemical signals including shear stress and elasticity of the adjacent endothelial basement membrane (BM). During physiological aging, but especially in neurological diseases including multiple sclerosis (MS), stroke, small vessel disease, and Alzheimer's disease (AD), the BBB is exposed to inflammation, rigidity changes of the BM, and disturbed cerebral blood flow (CBF). These altered forces lead to increased vascular permeability, reduced endothelial reactivity to vasoactive mediators, and promote leukocyte transmigration. Whereas the molecular players involved in leukocyte infiltration have been described in detail, the importance of mechanical signalling throughout this process has only recently been recognized. Here, we review relevant features of mechanical forces acting on the BBB under healthy and pathological conditions, as well as the endothelial mechanosensory elements detecting and responding to altered forces. We demonstrate the underlying complexity by focussing on the family of transient receptor potential (TRP) ion channels. A better understanding of these processes will provide insights into the pathogenesis of several neurological disorders and new potential leads for treatment.

Pre-operative stereotactic radiosurgery and peri-operative dexamethasone for resectable brain metastases: a two-arm pilot study evaluating clinical outcomes and immunological correlates

Enhancing the efficacy of immunotherapy in brain metastases (BrM) requires an improved understanding of the immune composition of BrM and how this is affected by radiation and dexamethasone. Our two-arm pilot study (NCT04895592) allocated 26 patients with BrM to either low (Arm A) or high (Arm B) dose peri-operative dexamethasone followed by pre-operative stereotactic radiosurgery (pSRS) and resection (n= 13 per arm). The primary endpoint, a safety analysis at 4 months, was met. The secondary clinical endpoints of overall survival, distant brain failure, leptomeningeal disease and local recurrence at 12-months were 66%, 37.3%, 6%, and 0% respectively and were not significantly different between arms (p= 0.7739, p= 0.3884, p= 0.3469). Immunological data from two large retrospective BrM datasets and confirmed by correlates from both arms of this pSRS prospective trial revealed that BrM CD8 T cells were composed of predominantly PD1+ TCF1+ stem-like and PD1+ TCF1-TIM3+ effector-like cells. Clustering of TCF1+ CD8 T cells with antigen presenting cells in immune niches was prognostic for local control, even without pSRS. Following pSRS, CD8 T cell and immune niche density were transiently reduced compared to untreated BrM, followed by a rebound 6+ days post pSRS with an increased frequency of TCF1- effector-like cells. In sum, pSRS is safe and therapeutically beneficial, and these data provide a framework for how pSRS may be leveraged to maximize intracranial CD8 T cell responses.

Astrocytic DLL4-NOTCH1 signaling pathway promotes neuroinflammation via the IL-6-STAT3 axis

Under neuroinflammatory conditions, astrocytes acquire a reactive phenotype that drives acute inflammatory injury as well as chronic neurodegeneration. We hypothesized that astrocytic Delta-like 4 (DLL4) may interact with its receptor NOTCH1 on neighboring astrocytes to regulate astrocyte reactivity via downstream juxtacrine signaling pathways. Here we investigated the role of astrocytic DLL4 on neurovascular unit homeostasis under neuroinflammatory conditions. We probed for downstream effectors of the DLL4-NOTCH1 axis and targeted these for therapy in two models of CNS inflammatory disease. We first demonstrated that astrocytic DLL4 is upregulated during neuroinflammation, both in mice and humans, driving astrocyte reactivity and subsequent blood-brain barrier permeability and inflammatory infiltration. We then showed that the DLL4-mediated NOTCH1 signaling in astrocytes directly drives IL-6 levels, induces STAT3 phosphorylation promoting upregulation of astrocyte reactivity markers, pro-permeability factor secretion and consequent blood-brain barrier destabilization. Finally we revealed that blocking DLL4 with antibodies improves experimental autoimmune encephalomyelitis symptoms in mice, identifying a potential novel therapeutic strategy for CNS autoimmune demyelinating disease. As a general conclusion, this study demonstrates that DLL4-NOTCH1 signaling is not only a key pathway in vascular development and angiogenesis, but also in the control of astrocyte reactivity during neuroinflammation.

Barriers to T Cell Functionality in the Glioblastoma Microenvironment

Glioblastoma (GBM) is an aggressive primary brain tumor depicted by a cold tumor microenvironment, low immunogenicity, and limited effective therapeutic interventions. Its location in the brain, a highly immune-selective organ, acts as a barrier, limiting immune access and promoting GBM dissemination, despite therapeutic interventions. Currently, chemotherapy and radiation combined with surgical resection are the standard of care for GBM treatment. Although immune checkpoint blockade has revolutionized the treatment of solid tumors, its observed success in extracranial tumors has not translated into a significant survival benefit for GBM patients. To develop effective immunotherapies for GBM, it is vital to tailor treatments to overcome the numerous immunosuppressive barriers that inhibit T cell responses to these tumors. In this review, we address the unique physical and immunological barriers that make GBM challenging to treat. Additionally, we explore potential therapeutic mechanisms, studied in central nervous system (CNS) and non-CNS cancers, that may overcome these barriers. Furthermore, we examine current and promising immunotherapy clinical trials and immunotherapeutic interventions for GBM. By highlighting the array of challenges T cell-based therapies face in GBM, we hope this review can guide investigators as they develop future immunotherapies for this highly aggressive malignancy.

Ultrasound frequency-controlled microbubble dynamics in brain vessels regulate the enrichment of inflammatory pathways in the blood-brain barrier

Microbubble-enhanced ultrasound provides a noninvasive physical method to locally overcome major obstacles to the accumulation of blood-borne therapeutics in the brain, posed by the blood-brain barrier (BBB). However, due to the highly nonlinear and coupled behavior of microbubble dynamics in brain vessels, the impact of microbubble resonant effects on BBB signaling and function remains undefined. Here, combined theoretical and prospective experimental investigations reveal that microbubble resonant effects in brain capillaries can control the enrichment of inflammatory pathways that are sensitive to wall shear stress and promote differential expression of a range of transcripts in the BBB, supporting the notion that microbubble dynamics exerted mechanical stress can be used to establish molecular, in addition to spatial, therapeutic windows to target brain diseases. Consistent with these findings, a robust increase in cytotoxic T-cell accumulation in brain tumors was observed, demonstrating the functional relevance and potential clinical significance of the observed immuno-mechano-biological responses.

Establishment of a novel amyotrophic lateral sclerosis patient (TARDBP N345K/+)-derived brain microvascular endothelial cell model reveals defective Wnt/β-catenin signaling: investigating diffusion barrier dysfunction and immune cell interaction

Amyotrophic lateral sclerosis (ALS) is a major neurodegenerative disease for which there is currently no curative treatment. The blood-brain barrier (BBB), multiple physiological functions formed by mainly specialized brain microvascular endothelial cells (BMECs), serves as a gatekeeper to protect the central nervous system (CNS) from harmful molecules in the blood and aberrant immune cell infiltration. The accumulation of evidence indicating that alterations in the peripheral milieu can contribute to neurodegeneration within the CNS suggests that the BBB may be a previously overlooked factor in the pathogenesis of ALS. Animal models suggest BBB breakdown may precede neurodegeneration and link BBB alteration to the disease progression or even onset. However, the lack of a useful patient-derived model hampers understanding the pathomechanisms of BBB dysfunction and the development of BBB-targeted therapies. In this study, we differentiated BMEC-like cells from human induced pluripotent stem cells (hiPSCs) derived from ALS patients to investigate BMEC functions in ALS patients. TARDBP N345K/+ carrying patient-derived BMEC-like cells exhibited increased permeability to small molecules due to loss of tight junction in the absence of neurodegeneration or neuroinflammation, highlighting that BMEC abnormalities in ALS are not merely secondary consequences of disease progression. Furthermore, they exhibited increased expression of cell surface adhesion molecules like ICAM-1 and VCAM-1, leading to enhanced immune cell adhesion. BMEC-like cells derived from hiPSCs with other types of TARDBP gene mutations (TARDBP K263E/K263E and TARDBP G295S/G295S) introduced by genome editing technology did not show such BMEC dysfunction compared to the isogenic control. Interestingly, transactive response DNA-binding protein 43 (TDP-43) was mislocalized to cytoplasm in TARDBP N345K/+ carrying model. Wnt/β-catenin signaling was downregulated in the ALS patient (TARDBP N345K/+)-derived BMEC-like cells and its activation rescued the leaky barrier phenotype and settled down VCAM-1 expressions. These results indicate that TARDBP N345K/+ carrying model recapitulated BMEC abnormalities reported in brain samples of ALS patients. This novel patient-derived BMEC-like cell is useful for the further analysis of the involvement of vascular barrier dysfunctions in the pathogenesis of ALS and for promoting therapeutic drug discovery targeting BMEC.

Unveiling the hidden connection: the blood-brain barrier's role in epilepsy

Epilepsy is characterized by abnormal synchronous electrical activity of neurons in the brain. The blood-brain barrier, which is mainly composed of endothelial cells, pericytes, astrocytes and other cell types and is formed by connections between a variety of cells, is the key physiological structure connecting the blood and brain tissue and is critical for maintaining the microenvironment in the brain. Physiologically, the blood-brain barrier controls the microenvironment in the brain mainly by regulating the passage of various substances. Disruption of the blood-brain barrier and increased leakage of specific substances, which ultimately leading to weakened cell junctions and abnormal regulation of ion concentrations, have been observed during the development and progression of epilepsy in both clinical studies and animal models. In addition, disruption of the blood-brain barrier increases drug resistance through interference with drug trafficking mechanisms. The changes in the blood-brain barrier in epilepsy mainly affect molecular pathways associated with angiogenesis, inflammation, and oxidative stress. Further research on biomarkers is a promising direction for the development of new therapeutic strategies.

Effects of HTLV-1 on leukocyte trafficking and migration in ACs compared to healthy individuals

Human T-lymphotropic virus type 1 (HTLV-1) is a RNA virus belonging to Retroviridae family and is associated with the development of various diseases, including adult T-cell leukemia/lymphoma (ATLL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Aside from HAM/TSP, HTLV-1 has been implicated in the development of several disorders that mimic auto-inflammation. T-cell migration is important topic in the context of HTLV-1 associated diseases progression. The primary objective of this case-control study was to assess the relationship between increased mRNA expression in virus migration following HTLV-1 infection. PBMCs from 20 asymptomatic patients and 20 healthy subjects were analyzed using real-time PCR to measure mRNA expression of LFA1, MLCK, RAC1, RAPL, ROCK1, VAV1 and CXCR4. Also, mRNA expression of Tax and HBZ were evaluated. Mean expression of Tax and HBZ in ACs (asymptomatic carriers) was 0.7218 and 0.6517 respectively. The results revealed a noteworthy upregulation of these genes involved in T-cell migration among ACs patients in comparison to healthy individuals. Considering the pivotal role of gene expression alterations associated with the progression into two major diseases (ATLL or HAM/TSP), analyzing the expression of these genes in the ACs group can offer probable potential diagnostic markers and aid in monitoring the condition of ACs.

Mitophagy and cGAS-STING crosstalk in neuroinflammation

Mitophagy, essential for mitochondrial health, selectively degrades damaged mitochondria. It is intricately linked to the cGAS-STING pathway, which is crucial for innate immunity. This pathway responds to mitochondrial DNA and is associated with cellular stress response. Our review explores the molecular details and regulatory mechanisms of mitophagy and the cGAS-STING pathway. We critically evaluate the literature demonstrating how dysfunctional mitophagy leads to neuroinflammatory conditions, primarily through the accumulation of damaged mitochondria, which activates the cGAS-STING pathway. This activation prompts the production of pro-inflammatory cytokines, exacerbating neuroinflammation. This review emphasizes the interaction between mitophagy and the cGAS-STING pathways. Effective mitophagy may suppress the cGAS-STING pathway, offering protection against neuroinflammation. Conversely, impaired mitophagy may activate the cGAS-STING pathway, leading to chronic neuroinflammation. Additionally, we explored how this interaction influences neurodegenerative disorders, suggesting a common mechanism underlying these diseases. In conclusion, there is a need for additional targeted research to unravel the complexities of mitophagy-cGAS-STING interactions and their role in neurodegeneration. This review highlights potential therapies targeting these pathways, potentially leading to new treatments for neuroinflammatory and neurodegenerative conditions. This synthesis enhances our understanding of the cellular and molecular foundations of neuroinflammation and opens new therapeutic avenues for neurodegenerative disease research.

Blood-brain barrier alterations and their impact on Parkinson's disease pathogenesis and therapy

There is increasing evidence for blood-brain barrier (BBB) alterations in Parkinson's disease (PD), the second most common neurodegenerative disorder with rapidly rising prevalence. Altered tight junction and transporter protein levels, accumulation of α-synuclein and increase in inflammatory processes lead to extravasation of blood molecules and vessel degeneration. This could result in a self-perpetuating pathophysiology of inflammation and BBB alteration, which contribute to neurodegeneration. Toxin exposure or α-synuclein over-expression in animal models has been shown to initiate similar pathologies, providing a platform to study underlying mechanisms and therapeutic interventions. Here we provide a comprehensive review of the current knowledge on BBB alterations in PD patients and how rodent models that replicate some of these changes can be used to study disease mechanisms. Specific challenges in assessing the BBB in patients and in healthy controls are discussed. Finally, a potential role of BBB alterations in disease pathogenesis and possible implications for therapy are explored. The interference of BBB alterations with current and novel therapeutic strategies requires more attention. Brain region-specific BBB alterations could also open up novel opportunities to target specifically vulnerable neuronal subpopulations.

Macrophages and HLA-Class II Alleles in Multiple Sclerosis: Insights in Therapeutic Dynamics

Antigen presentation is a crucial mechanism that drives the T cell-mediated immune response and the development of Multiple Sclerosis (MS). Genetic alterations within the highly variable Major Histocompatibility Complex Class II (MHC II) have been proven to result in significant changes in the molecular basis of antigen presentation and the clinical course of patients with both Adult-Onset MS (AOMS) and Pediatric-Onset MS (POMS). Among the numerous polymorphisms of the Human Leucocyte Antigens (HLA), within MHC II complex, HLA-DRB1*15:01 has been labeled, in Caucasian ethnic groups, as a high-risk allele for MS due to the ability of its structure to increase affinity to Myelin Basic Protein (MBP) epitopes. This characteristic, among others, in the context of the trimolecular complex or immunological synapsis, provides the foundation for autoimmunity triggered by environmental or endogenous factors. As with all professional antigen presenting cells, macrophages are characterized by the expression of MHC II and are often implicated in the formation of MS lesions. Increased presence of M1 macrophages in MS patients has been associated both with progression and onset of the disease, each involving separate but similar mechanisms. In this critical narrative review, we focus on macrophages, discussing how HLA genetic alterations can promote dysregulation of this population's homeostasis in the periphery and the Central Nervous System (CNS). We also explore the potential interconnection in observed pathological macrophage mechanisms and the function of the diverse structure of HLA alleles in neurodegenerative CNS, seen in MS, by comparing available clinical with molecular data through the prism of HLA-immunogenetics. Finally, we discuss available and experimental pharmacological approaches for MS targeting the trimolecular complex that are based on cell phenotype modulation and HLA genotype involvement and try to reveal fertile ground for the potential development of novel drugs.

Hypoxia within the glioblastoma tumor microenvironment: a master saboteur of novel treatments

Glioblastoma (GBM) tumors are the most aggressive primary brain tumors in adults that, despite maximum treatment, carry a dismal prognosis. GBM tumors exhibit tissue hypoxia, which promotes tumor aggressiveness and maintenance of glioma stem cells and creates an overall immunosuppressive landscape. This article reviews how hypoxic conditions overlap with inflammatory responses, favoring the proliferation of immunosuppressive cells and inhibiting cytotoxic T cell development. Immunotherapies, including vaccines, immune checkpoint inhibitors, and CAR-T cell therapy, represent promising avenues for GBM treatment. However, challenges such as tumor heterogeneity, immunosuppressive TME, and BBB restrictiveness hinder their effectiveness. Strategies to address these challenges, including combination therapies and targeting hypoxia, are actively being explored to improve outcomes for GBM patients. Targeting hypoxia in combination with immunotherapy represents a potential strategy to enhance treatment efficacy.

Peripheral endotoxin exposure in mice activates crosstalk between phagocytes in the brain and periphery

Background

Inflammation is a central process of many neurological diseases, and a growing number of studies suggest that non-brain-resident immune cells may contribute to this neuroinflammation. However, the unique contributions of specific immune cell subsets to neuroinflammation are presently unknown, and it is unclear how communication between brain-resident and non-resident immune cells underlies peripheral immune cell involvement in neuroinflammation.

Methods

In this study, we employed the well-established model of lipopolysaccharide (LPS)-induced neuroinflammation and captured brain-resident and non-resident immune cells from the brain and its vasculature by magnetically enriching cell suspensions from the non-perfused brain for CD45 + cells. Then, we identified immune subtype-specific neuroinflammatory processes using single-cell genomics and predicted the crosstalk between immune cell subtypes by analyzing the simultaneous expression of ligands and receptors.

Results

We observed a greater abundance of peripheral phagocytes associated with the brain in this model of neuroinflammation, and report that these professional phagocytes activated similar transcriptional profiles to microglia during LPS-induced neuroinflammation. And, we observed that the probable crosstalk between microglia and peripheral phagocytes was activated in this model while homotypic microglial communication was likely to be decreased.

Conclusions

Our novel findings reveal that microglia signaling to non-brain-resident peripheral phagocytes is preferentially triggered by peripheral inflammation, which is associated with brain infiltration of peripheral cells. Overall, our study supports the involvement of peripheral immune cells in neuroinflammation and suggests several possible molecular signaling pathways between microglia and peripheral cells that may facilitate central-peripheral crosstalk during inflammation. Examining these molecular mediators in human disease and other rodent models may reveal novel targets that modify brain health, especially in comorbidities characterized by peripheral inflammation.

IL-1β disrupts the initiation of blood-brain barrier development by inhibiting endothelial Wnt/β-catenin signaling

During neuroinflammation, the proinflammatory cytokine interleukin-1β (IL-1β) impacts blood-brain barrier (BBB) function by disrupting brain endothelial tight junctions, promoting vascular permeability, and increasing transmigration of immune cells. Here, we examined the effects of Il-1β on the in vivo initiation of BBB development. We generated doxycycline-inducible transgenic zebrafish to secrete Il-1β in the CNS. To validate the utility of our model, we showed Il-1β dose-dependent mortality, recruitment of neutrophils, and expansion of microglia. Using live imaging, we discovered that Il-1β causes a significant reduction in CNS angiogenesis and barriergenesis. To demonstrate specificity, we rescued the Il-1β induced phenotypes by targeting the zebrafish il1r1 gene using CRISPR-Cas9. Mechanistically, we determined that Il-1β disrupts the initiation of BBB development by decreasing Wnt/β-catenin transcriptional activation in brain endothelial cells. Given that several neurodevelopmental disorders are associated with inflammation, our findings support further investigation into the connections between proinflammatory cytokines, neuroinflammation, and neurovascular development.

Blood-Brain Barrier-Targeting Nanoparticles: Biomaterial Properties and Biomedical Applications in Translational Neuroscience

Overcoming the blood-brain barrier (BBB) remains a significant hurdle in effective drug delivery to the brain. While the BBB serves as a crucial protective barrier, it poses challenges in delivering therapeutic agents to their intended targets within the brain parenchyma. To enhance drug delivery for the treatment of neurological diseases, several delivery technologies to circumvent the BBB have been developed in the last few years. Among them, nanoparticles (NPs) are one of the most versatile and promising tools. Here, we summarize the characteristics of NPs that facilitate BBB penetration, including their size, shape, chemical composition, surface charge, and importantly, their conjugation with various biological or synthetic molecules such as glucose, transferrin, insulin, polyethylene glycol, peptides, and aptamers. Additionally, we discuss the coating of NPs with surfactants. A comprehensive overview of the common in vitro and in vivo models of the BBB for NP penetration studies is also provided. The discussion extends to discussing BBB impairment under pathological conditions and leveraging BBB alterations under pathological conditions to enhance drug delivery. Emphasizing the need for future studies to uncover the inherent therapeutic properties of NPs, the review advocates for their role beyond delivery systems and calls for efforts translating NPs to the clinic as therapeutics. Overall, NPs stand out as a highly promising therapeutic strategy for precise BBB targeting and drug delivery in neurological disorders.

Targeted Therapy of Multiple Sclerosis: A Case for Antigen-Specific Tregs

Multiple sclerosis is an autoinflammatory condition that results in damage to myelinated neurons in affected patients. While disease-modifying treatments have been successful in slowing the progression of relapsing-remitting disease, most patients still progress to secondary progressive disease that is largely unresponsive to disease-modifying treatments. Similarly, there is currently no effective treatment for patients with primary progressive MS. Innate and adaptive immune cells in the CNS play a critical role in initiating an autoimmune attack and in maintaining the chronic inflammation that drives disease progression. In this review, we will focus on recent insights into the role of T cells with regulatory function in suppressing the progression of MS, and, more importantly, in promoting the remyelination and repair of MS lesions in the CNS. We will discuss the exciting potential to genetically reprogram regulatory T cells to achieve immune suppression and enhance repair locally at sites of tissue damage, while retaining a fully competent immune system outside the CNS. In the future, reprogramed regulatory T cells with defined specificity and function may provide life medicines that can persist in patients and achieve lasting disease suppression after one cycle of treatment.

M-MDSCs mediated trans-BBB drug delivery for suppression of glioblastoma recurrence post-standard treatment

We found that immunosuppressive monocytic-myeloid-derived suppressor cells (M-MDSCs) were more likely to be recruited by glioblastoma (GBM) through adhesion molecules on GBM-associated endothelial cells upregulated post-chemoradiotherapy. These cells are continuously generated during tumor progression, entering tumors and expressing PD-L1 at a high level, allowing GBM to exhaust T cells and evade attack from the immune system, thereby facilitating GBM relapse. αLy-6C-LAMP is composed of (i) drug cores with slightly negative charges condensed by cationic protamine and plasmids encoding PD-L1 trap protein, (ii) pre-formulated cationic liposomes targeted to Ly-6C for encapsulating the drug cores, and (iii) a layer of red blood cell membrane on the surface for effectuating long-circulation. αLy-6C-LAMP persistently targets peripheral, especially splenic, M-MDSCs and delivers secretory PD-L1 trap plasmids, leveraging M-MDSCs to transport the plasmids crossing the blood-brain barrier (BBB), thus expressing PD-L1 trap protein in tumors to inhibit PD-1/PD-L1 pathway. Our proposed drug delivery strategy involving intermediaries presents an efficient cross-BBB drug delivery concept that incorporates live-cell targeting and long-circulating nanotechnology to address GBM recurrence.

CNS Viral Infections-What to Consider for Improving Drug Treatment: A Plea for Using Mathematical Modeling Approaches

Neurotropic viruses may cause meningitis, myelitis, encephalitis, or meningoencephalitis. These inflammatory conditions of the central nervous system (CNS) may have serious and devastating consequences if not treated adequately. In this review, we first summarize how neurotropic viruses can enter the CNS by (1) crossing the blood-brain barrier or blood-cerebrospinal fluid barrier; (2) invading the nose via the olfactory route; or (3) invading the peripheral nervous system. Neurotropic viruses may then enter the intracellular space of brain cells via endocytosis and/or membrane fusion. Antiviral drugs are currently used for different viral CNS infections, even though their use and dosing regimens within the CNS, with the exception of acyclovir, are minimally supported by clinical evidence. We therefore provide considerations to optimize drug treatment(s) for these neurotropic viruses. Antiviral drugs should cross the blood-brain barrier/blood cerebrospinal fluid barrier and pass the brain cellular membrane to inhibit these viruses inside the brain cells. Some antiviral drugs may also require intracellular conversion into their active metabolite(s). This illustrates the need to better understand these mechanisms because these processes dictate drug exposure within the CNS that ultimately determine the success of antiviral drugs for CNS infections. Finally, we discuss mathematical model-based approaches for optimizing antiviral treatments. Thereby emphasizing the potential of CNS physiologically based pharmacokinetic models because direct measurement of brain intracellular exposure in living humans faces ethical restrictions. Existing physiologically based pharmacokinetic models combined with in vitro pharmacokinetic/pharmacodynamic information can be used to predict drug exposure and evaluate efficacy of antiviral drugs within the CNS, to ultimately optimize the treatments of CNS viral infections.

Blood-brain barrier biomarkers

The blood-brain barrier (BBB) is a dynamic interface that regulates the exchange of molecules and cells between the brain parenchyma and the peripheral blood. The BBB is mainly composed of endothelial cells, astrocytes and pericytes. The integrity of this structure is essential for maintaining brain and spinal cord homeostasis and protection from injury or disease. However, in various neurological disorders, such as traumatic brain injury, Alzheimer's disease, and multiple sclerosis, the BBB can become compromised thus allowing passage of molecules and cells in and out of the central nervous system parenchyma. These agents, however, can serve as biomarkers of BBB permeability and neuronal damage, and provide valuable information for diagnosis, prognosis and treatment. Herein, we provide an overview of the BBB and changes due to aging, and summarize current knowledge on biomarkers of BBB disruption and neurodegeneration, including permeability, cellular, molecular and imaging biomarkers. We also discuss the challenges and opportunities for developing a biomarker toolkit that can reliably assess the BBB in physiologic and pathophysiologic states.

IQGAP2 regulates blood-brain barrier immune dynamics

Brain endothelial cells (BECs) play an important role in maintaining central nervous system (CNS) homeostasis through blood-brain barrier (BBB) functions. BECs express low baseline levels of adhesion receptors, which limits entry of leukocytes. However, the molecular mediators governing this phenotype remain mostly unclear. Here, we explored how infiltration of immune cells across the BBB is influenced by the scaffold protein IQ motif containing GTPase activating protein 2 (IQGAP2). In mice and zebrafish, we demonstrate that loss of Iqgap2 increases infiltration of peripheral leukocytes into the CNS under homeostatic and inflammatory conditions. Using single-cell RNA sequencing and immunohistology, we further show that BECs from mice lacking Iqgap2 exhibit a profound inflammatory signature, including extensive upregulation of adhesion receptors and antigen-processing machinery. Human tissue analyses also reveal that Alzheimer's disease is associated with reduced hippocampal IQGAP2. Overall, our results implicate IQGAP2 as an essential regulator of BBB immune privilege and immune cell entry into the CNS.

Progress in the Treatment of Central Nervous System Diseases Based on Nanosized Traditional Chinese Medicine

Traditional Chinese Medicine (TCM) is widely used in clinical practice to treat diseases related to central nervous system (CNS) damage. However, the blood-brain barrier (BBB) constitutes a significant impediment to the effective delivery of TCM, thus substantially diminishing its efficacy. Advances in nanotechnology and its applications in TCM (also known as nano-TCM) can deliver active ingredients or components of TCM across the BBB to the targeted brain region. This review provides an overview of the physiological and pathological mechanisms of the BBB and systematically classifies the common TCM used to treat CNS diseases and types of nanocarriers that effectively deliver TCM to the brain. Additionally, drug delivery strategies for nano-TCMs that utilize in vivo physiological properties or in vitro devices to bypass or cross the BBB are discussed. This review further focuses on the application of nano-TCMs in the treatment of various CNS diseases. Finally, this article anticipates a design strategy for nano-TCMs with higher delivery efficiency and probes their application potential in treating a wider range of CNS diseases.

Regulation of autoimmune-mediated neuroinflammation by endothelial cells

The CNS has traditionally been considered an immune-privileged organ, but recent studies have identified a plethora of immune cells in the choroid plexus, meninges, perivascular spaces, and cribriform plate. Although those immune cells are crucial for the maintenance of CNS homeostasis and for neural protection against infections, they can lead to neuroinflammation in some circumstances. The blood and the lymphatic vasculatures exhibit distinct structural and molecular features depending on their location in the CNS, greatly influencing the compartmentalization and the nature of CNS immune responses. In this review, we discuss how endothelial cells regulate the migration and the functions of T cells in the CNS both at steady-state and in murine models of neuroinflammation, with a special focus on the anatomical, cellular, and molecular mechanisms implicated in EAE.

T cell infiltration mediates neurodegeneration and cognitive decline in Alzheimer's disease

Alzheimer's disease (AD) is a prevalent neurodegenerative disorder with pathological features of β-amyloid (Aβ) and hyperphosphorylated tau protein accumulation in the brain, often accompanied by cognitive decline. So far, our understanding of the extent and role of adaptive immune responses in AD has been quite limited. T cells, as essential members of the adaptive immune system, exhibit quantitative and functional abnormalities in the brains of AD patients. Dysfunction of the blood-brain barrier (BBB) in AD is considered one of the factors leading to T cell infiltration. Moreover, the degree of neuronal loss in AD is correlated with the quantity of T cells. We first describe the differentiation and subset functions of peripheral T cells in AD patients and provide an overview of the key findings related to BBB dysfunction and how T cells infiltrate the brain parenchyma through the BBB. Furthermore, we emphasize the risk factors associated with AD, including Aβ, Tau protein, microglial cells, apolipoprotein E (ApoE), and neuroinflammation. We discuss their regulation of T cell activation and proliferation, as well as the connection between T cells, neurodegeneration, and cognitive decline. Understanding the innate immune response is crucial for providing comprehensive personalized therapeutic strategies for AD.

Inflammation-induced TRPV4 channels exacerbate blood-brain barrier dysfunction in multiple sclerosis

BACKGROUND

Blood-brain barrier (BBB) dysfunction and immune cell migration into the central nervous system (CNS) are pathogenic drivers of multiple sclerosis (MS). Ways to reinstate BBB function and subsequently limit neuroinflammation present promising strategies to restrict disease progression. However, to date, the molecular players directing BBB impairment in MS remain poorly understood. One suggested candidate to impact BBB function is the transient receptor potential vanilloid-type 4 ion channel (TRPV4), but its specific role in MS pathogenesis remains unclear. Here, we investigated the role of TRPV4 in BBB dysfunction in MS.

MAIN TEXT

In human post-mortem MS brain tissue, we observed a region-specific increase in endothelial TRPV4 expression around mixed active/inactive lesions, which coincided with perivascular microglia enrichment in the same area. Using in vitro models, we identified that microglia-derived tumor necrosis factor-α (TNFα) induced brain endothelial TRPV4 expression. Also, we found that TRPV4 levels influenced brain endothelial barrier formation via expression of the brain endothelial tight junction molecule claudin-5. In contrast, during an inflammatory insult, TRPV4 promoted a pathological endothelial molecular signature, as evidenced by enhanced expression of inflammatory mediators and cell adhesion molecules. Moreover, TRPV4 activity mediated T cell extravasation across the brain endothelium.

CONCLUSION

Collectively, our findings suggest a novel role for endothelial TRPV4 in MS, in which enhanced expression contributes to MS pathogenesis by driving BBB dysfunction and immune cell migration.

[Blood-brain barrier breakdown and autoimmune cerebellar ataxia]

Autoimmune cerebellar ataxia is a disease entity that affects the cerebellum and is induced by autoimmune mechanisms. The disease is classified into several etiologies, including gluten ataxia, anti-glutamate decarboxylase (GAD) ataxia, paraneoplastic cerebellar degeneration, primary autoimmune cerebellar ataxia and postinfectious cerebellar ataxia. The autoimmune response in the periphery cross-reacts with similar antigens in the cerebellum due to molecular mimicry. Breakdown of the blood‒brain barrier (BBB) could potentially explain the vulnerability of the cerebellum during the development of autoimmune cerebellar ataxia, as it gives rise to the entry of pathogenic autoantibodies or lymphocytes into the cerebellum. In this review, the maintenance of the BBB under normal conditions and the molecular basis of BBB disruption under pathological conditions are highlighted. Next, the pathomechanism of BBB breakdown in each subtype of autoimmune cerebellar ataxia is discussed. We recently identified glucose-regulated protein (GRP) 78 antibodies in paraneoplastic cerebellar degeneration and Lambert-Eaton myasthenic syndrome, and GRP78 antibodies induced by cross-reactivity with tumors can disrupt the BBB and penetrate anti-P/Q type voltage-gated calcium channel (VGCC) antibodies into the cerebellum, thus leading to cerebellar ataxia in this disease.

Current Role of Surgery in the Treatment of Neurocysticercosis

Neurocysticercosis (NCC) is a common parasitic disease of the central nervous system (CNS) in low- and middle-income countries. The infection is pleomorphic, caused by the larval form of the cestode, Taenia solium, and part of the heterogeneity of its clinical presentations is associated with the localization of the parasite within the CNS. Changes in the current epidemiological trends of NCC indicate that extra-parenchymal NCC is proportionally becoming more frequent. Extraparenchymal NCC is commonly accompanied by raised intracranial hypertension due to hydrocephalus, which is an emergency requiring cyst extirpation by surgical intervention to relieve the symptoms. Although less frequent, parenchymal cysts may also reach giant sizes requiring urgent surgical treatment. Finally, there is an advancement in the comprehension of the association between NCC and epilepsy-and patients with drug-resistant seizures are candidates for surgical treatment. In this narrative review, we summarize the present state of knowledge to update the current trends in the role of surgery in the treatment of NCC.

IL-1β disrupts blood-brain barrier development by inhibiting endothelial Wnt/β-catenin signaling

During neuroinflammation, the proinflammatory cytokine Interleukin-1β (IL-1β) impacts blood-brain barrier (BBB) function by disrupting brain endothelial tight junctions, promoting vascular permeability, and increasing transmigration of immune cells. Here, we examined the effects of Il-1β on the in vivo development of the BBB. We generated a doxycycline-inducible transgenic zebrafish model that drives secretion of Il-1β in the CNS. To validate the utility of our model, we showed Il-1β dose-dependent mortality, recruitment of neutrophils, and expansion of microglia. Using live imaging, we discovered that Il-1β causes a significant reduction in CNS angiogenesis and barriergenesis. To demonstrate specificity, we rescued the Il-1β induced phenotypes by targeting the zebrafish il1r1 gene using CRISPR/Cas9. Mechanistically, we determined that Il-1β disrupts BBB development by decreasing Wnt/β-catenin transcriptional activation in brain endothelial cells. Given that several neurodevelopmental disorders are associated with inflammation, our findings support further investigation into the connections between proinflammatory cytokines, neuroinflammation, and neurovascular development.

Th1 cells contribute to retinal ganglion cell loss in glaucoma in a VCAM-1-dependent manner

Glaucoma is a complex neurodegenerative disorder characterized by the progressive loss of retinal ganglion cells (RGC) and optic nerve axons, leading to irreversible visual impairment. Despite its clinical significance, the underlying mechanisms of glaucoma pathogenesis remain poorly understood. In this study, we aimed to unravel the multifaceted nature of glaucoma by investigating the interaction between T cells and retinas. By utilizing clinical samples, murine glaucoma models, and T cell transfer models, we made several key findings. Firstly, we observed that CD4+ T cells from glaucoma patients displayed enhanced activation and a bias towards T helper (Th) 1 responses, which correlated with visual impairment. Secondly, we identified the infiltration of Th1 cells into the retina, where they targeted RGC and integrated into the pro-inflammatory glial network, contributing to progressive RGC loss. Thirdly, we discovered that circulating Th1 cells upregulated vascular cell adhesion protein 1 (VCAM-1) on retinal microvessels, facilitating their entry into the neural retina. Lastly, we found that Th1 cells underwent functional reprogramming before reaching the retina, acquiring a phenotype associated with lymphocyte migration and neurodegenerative diseases. Our study provides novel insights into the role of peripheral CD4+ T cells in glaucoma pathogenesis, shedding light on the mechanisms underlying their infiltration into the retina and offering potential avenues for innovative therapeutic interventions in this sight-threatening disease.

Increased perivascular space volume in white matter and basal ganglia is associated with cognition in Parkinson's Disease

Perivascular spaces (PVS), fluid-filled compartments surrounding brain vasculature, are an essential component of the glymphatic system responsible for transport of waste and nutrients. Glymphatic system impairment may underlie cognitive deficits in Parkinson's disease (PD). Studies have focused on the role of basal ganglia PVS with cognition in PD, but the role of white matter PVS is unknown. This study examined the relationship of white matter and basal ganglia PVS with domain-specific and global cognition in individuals with PD. Fifty individuals with PD underwent 3T T1w magnetic resonance imaging (MRI) to determine PVS volume fraction, defined as PVS volume normalized to total regional volume, within (i) centrum semiovale, (ii) prefrontal white matter (medial orbitofrontal, rostral middle frontal, superior frontal), and (iii) basal ganglia. A neuropsychological battery included assessment of global cognitive function (Montreal Cognitive Assessment, and global cognitive composite score), and cognitive-specific domains (executive function, memory, visuospatial function, attention, and language). Higher white matter rostral middle frontal PVS was associated with lower scores in both global cognitive and visuospatial function. In the basal ganglia higher PVS was associated with lower scores for memory with a trend towards lower global cognitive composite score. While previous reports have shown that greater amount of PVS in the basal ganglia is associated with decline in global cognition in PD, our findings suggest that increased white matter PVS volume may also underlie changes in cognition.

The Dance Between Tumor Molecular Biology and Antitumor Immune Response

When the cyclin kinase 4/6 inhibitor abemaciclib was sequenced with PD-1 blockade in mostly immunologically "cold" murine models, enhanced immune-mediated antitumor effects-including increased lifespan, recruitment of CD8 cells to tumor, reduction of regulatory T-cell and immunosuppressive cytokines in tumor, increased tumor antigen presentation, and broadening of the T-cell receptor repertoire-were achieved in both cutaneous and brain metastases. See related article by Nayyar et al., p. 420.

Microglia and Systemic Immunity

Microglia are specialized immune cells that reside in the central nervous system (CNS) and play a crucial role in maintaining the homeostasis of the brain microenvironment. While traditionally regarded as a part of the innate immune system, recent research has highlighted their role in adaptive immunity. The CNS is no longer considered an immune-privileged organ, and increasing evidence suggests bidirectional communication between the immune system and the CNS. Microglia are sensitive to systemic immune signals and can respond to systemic inflammation by producing various inflammatory cytokines and chemokines. This response is mediated by activating pattern recognition receptors (PRRs), which recognize pathogen- and danger-associated molecular patterns in the systemic circulation. The microglial response to systemic inflammation has been implicated in several neurological conditions, including depression, anxiety, and cognitive impairment. Understanding the complex interplay between microglia and systemic immunity is crucial for developing therapeutic interventions to modulate immune responses in the CNS.

Immunotherapy for Pediatric Gliomas: CAR-T Cells Against B7H3: A Review of the Literature

BACKGROUND

B7H3 is a co-stimulatory molecule for immune reactions found on the surface of tumor cells in a wide variety of tumors. Preclinical and clinical studies have reported it as a tumor target towards which various immunotherapy modalities could be directed. So far, good results have been obtained in hematological neoplasms; however, a contrasting situation is evident in solid tumors, including those of the CNS, which show high refractoriness to current treatments. The appearance of cellular immunotherapies has transformed oncology due to the reinforcement of the immune response that is compromised in people with cancer.

OBJECTIVE

This article aims to review the literature to describe the advancement in knowledge on B7H3 as a target of CAR-T cells in pediatric gliomas to consider them as an alternative in the treatment of these patients.

RESULTS

Although B7H3 is considered a suitable candidate as a target agent for various immunotherapy techniques, there are still limitations in using CAR-T cells to achieve the desired success.

CONCLUSION

Results obtained with CAR-T cells can be further improved by the suggested proposals; therefore, more clinical trials are needed to study this new therapy in children with gliomas.

A20 regulates lymphocyte adhesion in murine neuroinflammation by restricting endothelial ICOSL expression in the CNS

A20 is a ubiquitin-modifying protein that negatively regulates NF-κB signaling. Mutations in A20/TNFAIP3 are associated with a variety of autoimmune diseases, including multiple sclerosis (MS). We found that deletion of A20 in central nervous system (CNS) endothelial cells (ECs) enhances experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. A20ΔCNS-EC mice showed increased numbers of CNS-infiltrating immune cells during neuroinflammation and in the steady state. While the integrity of the blood-brain barrier (BBB) was not impaired, we observed a strong activation of CNS-ECs in these mice, with dramatically increased levels of the adhesion molecules ICAM-1 and VCAM-1. We discovered ICOSL to be expressed by A20-deficient CNS-ECs, which we found to function as adhesion molecules. Silencing of ICOSL in CNS microvascular ECs partly reversed the phenotype of A20ΔCNS-EC mice without reaching statistical significance and delayed the onset of EAE symptoms in WT mice. In addition, blocking of ICOSL on primary mouse brain microvascular ECs impaired the adhesion of T cells in vitro. Taken together, we propose that CNS EC-ICOSL contributes to the firm adhesion of T cells to the BBB, promoting their entry into the CNS and eventually driving neuroinflammation.

Microfluidic models of the neurovascular unit: a translational view

The vasculature of the brain consists of specialized endothelial cells that form a blood-brain barrier (BBB). This barrier, in conjunction with supporting cell types, forms the neurovascular unit (NVU). The NVU restricts the passage of certain substances from the bloodstream while selectively permitting essential nutrients and molecules to enter the brain. This protective role is crucial for optimal brain function, but presents a significant obstacle in treating neurological conditions, necessitating chemical modifications or advanced drug delivery methods for most drugs to cross the NVU. A deeper understanding of NVU in health and disease will aid in the identification of new therapeutic targets and drug delivery strategies for improved treatment of neurological disorders.To achieve this goal, we need models that reflect the human BBB and NVU in health and disease. Although animal models of the brain's vasculature have proven valuable, they are often of limited translational relevance due to interspecies differences or inability to faithfully mimic human disease conditions. For this reason, human in vitro models are essential to improve our understanding of the brain's vasculature under healthy and diseased conditions. This review delves into the advancements in in vitro modeling of the BBB and NVU, with a particular focus on microfluidic models. After providing a historical overview of the field, we shift our focus to recent developments, offering insights into the latest achievements and their associated constraints. We briefly examine the importance of chip materials and methods to facilitate fluid flow, emphasizing their critical roles in achieving the necessary throughput for the integration of microfluidic models into routine experimentation. Subsequently, we highlight the recent strides made in enhancing the biological complexity of microfluidic NVU models and propose recommendations for elevating the biological relevance of future iterations.Importantly, the NVU is an intricate structure and it is improbable that any model will fully encompass all its aspects. Fit-for-purpose models offer a valuable compromise between physiological relevance and ease-of-use and hold the future of NVU modeling: as simple as possible, as complex as needed.

Neuroinflammation, memory, and depression: new approaches to hippocampal neurogenesis

As one of most common and severe mental disorders, major depressive disorder (MDD) significantly increases the risks of premature death and other medical conditions for patients. Neuroinflammation is the abnormal immune response in the brain, and its correlation with MDD is receiving increasing attention. Neuroinflammation has been reported to be involved in MDD through distinct neurobiological mechanisms, among which the dysregulation of neurogenesis in the dentate gyrus (DG) of the hippocampus (HPC) is receiving increasing attention. The DG of the hippocampus is one of two niches for neurogenesis in the adult mammalian brain, and neurotrophic factors are fundamental regulators of this neurogenesis process. The reported cell types involved in mediating neuroinflammation include microglia, astrocytes, oligodendrocytes, meningeal leukocytes, and peripheral immune cells which selectively penetrate the blood-brain barrier and infiltrate into inflammatory regions. This review summarizes the functions of the hippocampus affected by neuroinflammation during MDD progression and the corresponding influences on the memory of MDD patients and model animals.

RGS5 maintaining vascular homeostasis is altered by the tumor microenvironment

BACKGROUND

Regulator of G protein signaling 5 (RGS5), as a negative regulator of G protein-coupled receptor (GPCR) signaling, is highly expressed in arterial VSMCs and pericytes, which is involved in VSMC phenotypic heterogeneity and vascular remodeling in tumors. However, its role in normal and tumor vascular remodeling is controversial.

METHODS

RGS5 knockout (Rgs5-KO) mice and RGS5 overexpression or knockdown in VSMCs in vivo by adeno-associated virus type 9 (AAV) carrying RGS5 cDNA or small hairpin RNA (shRNA) targeting RGS5 were used to determine the functional significance of RGS5 in vascular inflammation. RGS5 expression in the triple-negative (TNBCs) and non-triple-negative breast cancers (Non-TNBCs) was determined by immunofluorescent and immunohistochemical staining. The effect of breast cancer cell-conditioned media (BC-CM) on the pro-inflammatory phenotype of VSMCs was measured by phagocytic activity assays, adhesion assay and Western blot.

RESULTS

We identified that knockout and VSMC-specific knockdown of RGS5 exacerbated accumulation and pyroptosis of pro-inflammatory VSMCs, resulting in vascular remodeling, which was negated by VSMC-specific RGS5 overexpression. In contrast, in the context of breast cancer tissues, the role of RGS5 was completely disrupted. RGS5 expression was increased in the triple-negative breast cancer (TNBC) tissues and in the tumor blood vessels, accompanied with an extensive vascular network. VSMCs treated with BC-CM displayed enhanced pro-inflammatory phenotype and higher adherent with macrophages. Furthermore, tumor-derived RGS5 could be transferred into VSMCs.

CONCLUSIONS

These findings suggest that tumor microenvironment shifts the function of RGS5 from anti-inflammation to pro-inflammation and induces the pro-inflammatory phenotype of VSMCs that is favorable for tumor metastasis.

Learning CNS immunopathology from therapeutic interventions

Modulation of immune cell trafficking across the blood-brain barrier has not only introduced a therapeutic avenue for multiple sclerosis (MS) but also represents an example of reverse translational medicine. Data from clinical trials of drugs such as natalizumab and fingolimod have revealed the involvement of different compartments in relapsing versus non-relapsing MS immune biology, contributed to our understanding of central nervous system (CNS) immune surveillance, and stimulated new fields of research. Here, we discuss the results of these trials, as well as patient biomaterial-based scientific projects, and how both have informed our understanding of CNS immunopathology.