The ins and outs of T-lymphocyte trafficking to the CNS: anatomical sites and molecular mechanisms

Meningeal lymphatic vessel crosstalk with central nervous system immune cells in aging and neurodegenerative diseases

Meningeal lymphatic vessels form a relationship between the nervous system and periphery, which is relevant in both health and disease. Meningeal lymphatic vessels not only play a key role in the drainage of brain metabolites but also contribute to antigen delivery and immune cell activation. The advent of novel genomic technologies has enabled rapid progress in the characterization of myeloid and lymphoid cells and their interactions with meningeal lymphatic vessels within the central nervous system. In this review, we provide an overview of the multifaceted roles of meningeal lymphatic vessels within the context of the central nervous system immune network, highlighting recent discoveries on the immunological niche provided by meningeal lymphatic vessels. Furthermore, we delve into the mechanisms of crosstalk between meningeal lymphatic vessels and immune cells in the central nervous system under both homeostatic conditions and neurodegenerative diseases, discussing how these interactions shape the pathological outcomes. Regulation of meningeal lymphatic vessel function and structure can influence lymphatic drainage, cerebrospinal fluid-borne immune modulators, and immune cell populations in aging and neurodegenerative disorders, thereby playing a key role in shaping meningeal and brain parenchyma immunity.

Inflammation-Triggered Enlargement of Choroid Plexus in Subacute COVID-19 Patients with Neurological Symptoms

OBJECTIVE

To investigate whether choroid plexus volumes in subacute coronavirus disease 2019 (COVID-19) patients with neurological symptoms could indicate inflammatory activation or barrier dysfunction and assess their association with clinical data.

METHODS

Choroid plexus volumes were measured in 28 subacute COVID-19 patients via cerebral magnetic resonance imaging (MRI), compared with those in infection-triggered non-COVID-19 encephalopathy patients (n = 25), asymptomatic individuals after COVID-19 (n = 21), and healthy controls (n = 21). Associations with inflammatory serum markers (peak counts of leukocytes, C-reactive protein [CRP], interleukin 6), an MRI-based marker of barrier dysfunction (CSF volume fraction [V-CSF]), and clinical parameters like olfactory performance and cognitive scores (Montreal Cognitive Assessment) were investigated.

RESULTS

COVID-19 patients showed significantly larger choroid plexus volumes than control groups (p < 0.001, η2 = 0.172). These volumes correlated significantly with peak leukocyte levels (p = 0.001, Pearson's r = 0.621) and V-CSF (p = 0.009, Spearman's rho = 0.534), but neither with CRP nor interleukin 6. No significant correlations were found with clinical parameters.

INTERPRETATION

In patients with subacute COVID-19, choroid plexus volume is a marker of central nervous system inflammation and barrier dysfunction in the presence of neurologic symptoms. The absence of plexus enlargement in infection-triggered non-COVID-19 encephalopathy suggests a specific severe acute respiratory syndrome coronavirus 2 effect. This study also documents an increase in choroid plexus volume for the first time as a parainfectious event. ANN NEUROL 2024;96:715-725.

MicroRNA (miRNA) as a biomarker for diagnosis, prognosis, and therapeutics molecules in neurodegenerative disease

Neurodegenerative diseases that include Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), Huntington's disease (HD), and multiple sclerosis (MS) that arise due to numerous causes like protein accumulation and autoimmunity characterized by neurologic depletion which lead to incapacity in normal physiological function such as thinking and movement in these patients. Glial cells perform an important role in protective neuronal function; in the case of neuroinflammation, glial cell dysfunction can promote the development of neurodegenerative diseases. miRNA that participates in gene regulation and plays a vital role in many biological processes in the body; in the central nervous system (CNS), it can play an essential part in neural maturation and differentiation. In neurodegenerative diseases, miRNA dysregulation occurs, enhancing the development of these diseases. In this review, we discuss neurodegenerative disease (Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS)) and how miRNA is preserved as a diagnostic biomarker or therapeutic agent in these disorders. Finally, we highlight miRNA as therapy.

Characterisation of choroid plexus-infiltrating T cells reveals novel therapeutic targets in murine neuropsychiatric lupus

OBJECTIVE

Diffuse central nervous system manifestations, referred to as neuropsychiatric lupus (NPSLE), are observed in 20-40% of lupus patients and involve complex mechanisms that have not yet been adequately elucidated. In murine NPSLE models, choroid plexus (ChP)-infiltrating T cells have not been fully evaluated as drivers of neuropsychiatric disease.

METHOD

Droplet-based single-cell transcriptomic analysis (single-cell RNA sequencing) and immune T-cell receptor profiling were performed on ChP tissue from MRL/lpr mice, an NPSLE mouse model, at an 'early' and 'late' disease state, to investigate the infiltrating immune cells that accumulate with NPSLE disease progression.

RESULTS

We found 19 unique clusters of stromal and infiltrating cells present in the ChP of NPSLE mice. Higher resolution of the T-cell clusters uncovered multiple T-cell subsets, with increased exhaustion and hypoxia expression profiles. Clonal analysis revealed that the clonal CD8+T cell CDR3 sequence, ASGDALGGYEQY, matched that of a published T-cell receptor sequence with specificity for myelin basic protein. Stromal fibroblasts are likely drivers of T-cell recruitment by upregulating the VCAM signalling pathway. Systemic blockade of VLA-4, the cognate ligand of VCAM, resulted in significant resolution of the ChP immune cell infiltration and attenuation of the depressive phenotype.

CONCLUSION

Our analysis details the dynamic transcriptomic changes associated with murine NPSLE disease progression, and highlights its potential use in identifying prospective lupus brain therapeutic targets.

CD4+ T-cell subsets are associated with chronic stress effects in newly diagnosed anxiety disorders

Aim

Prior research has indicated a connection between CD4+ T cells and the development of anxiety, but the specific CD4+ T cell subsets linked to anxiety disorders remain uncertain. Our study seeks to investigate the relationship between distinct CD4+ T cell subsets and anxiety, as well as to explore whether CD4+ T cell subsets mediate the effect of chronic psychological stress on anxiety.

Methods

56 eligible matched participants were recruited in Peking Union Medical College Hospital. The diagnosis was made based on DSM-5 diagnostic criteria. The severity of anxiety and depression symptoms was assessed using the Hamilton Anxiety Rating Scale and Hamilton Depression Rating Scale, respectively. The Life Events Scale (LES) evaluated the chronic stress level. CD4+ T cell subsets were characterized using multiparametric flow cytometry. To assess the impact of CD4+ T cells on the effect of chronic psychological stress on anxiety, Partial Least Squares Structural Equation Modeling (PLS-SEM) analysis was employed.

Results

We discovered fifteen notably distinct CD4+ T-cell subsets in anxiety disorder patients compared to healthy controls. Multiple linear regression analysis unveiled an association between anxiety severity and CD27+CD45RA- Th cells, CD27+CD28+ Tregs, and the total Life Events Scale (LES) score. The PLS-SEM analysis demonstrated that CD4+ T cell subsets and LES could explain 80.2% of the variance in anxiety. Furthermore, it was observed that CD27+CD28+ Th/Treg cells acted as inverse mediators of the effects of LES on anxiety (P = 0.031).

Conclusions

Drug naïve anxiety disorder patients exhibited significant alterations in numerous CD4+ T-cell subsets. Specifically, the memory subset of CD27+CD45RA- Th cells and the naïve subset of CD27+CD28+ Treg cells were found to be independent factors associated with the severity of anxiety. Additionally, the CD27+CD28+ Th and Treg cell subsets played a significant mediating role in the influence of long-term psychological stress on anxiety.

The potential protective role of peripheral immunophenotypes in Alzheimer's disease: a Mendelian randomization study

Introduction

Alzheimer's disease (AD) is the most widespread neurodegenerative disease in the world. Previous studies have shown that peripheral immune dysregulation plays a paramount role in AD, but whether there is a protective causal relationship between peripheral immunophenotypes and AD risk remains ambiguous.

Methods

Two-sample Mendelian randomization (MR) was performed using large genome-wide association study (GWAS) genetic data to assess causal effects between peripheral immunophenotypes and AD risk. Utilizing the genetic associations of 731 immune cell traits as exposures. We adopted the inverse variance weighted method as the primary approach. The Weighted median and MR-Egger regression methods were employed as supplements. Various sensitivity analyses were performed to assess the robustness of the outcomes.

Results

Based on the IVW method, we identified 14 immune cell traits that significantly reduced the risk of AD, of which six demonstrated statistical significance in both IVW and Weighted median methods. Among the seven immune traits, four were related to regulatory T (Treg) cells : (1) CD25++ CD45RA- CD4 not regulatory T cell % T cell (odds ratio (OR) [95% confidence interval (CI)] = 0.96 [0.95, 0.98], adjusted P = 1.17E-02), (2) CD25++ CD45RA- CD4 not regulatory T cell % CD4+ T cell (OR [95% CI] = 0.97 [0.96, 0.99], adjusted P = 3.77E-02), (3) Secreting CD4 regulatory T cell % CD4 regulatory T cell (OR [95% CI] = 0.98 [0.97, 0.99], adjusted P = 7.10E-03), (4) Activated & secreting CD4 regulatory T cell % CD4 regulatory T cell(OR [95% CI] = 0.98 [0.97, 0.99], adjusted P = 7.10E-03). In addition, HLA DR++ monocyte % monocyte (OR [95% CI] = 0.93 [0.89, 0.98], adjusted P = 4.87E-02) was associated with monocytes, and HLA DR on myeloid Dendritic Cell (OR [95% CI] = 0.93 [0.89, 0.97], adjusted P = 1.17E-02) was related to dendritic cells (DCs).

Conclusion

These findings enhance the comprehension of the protective role of peripheral immunity in AD and provide further support for Treg and monocyte as potential targets for immunotherapy in AD.

The Emerging Role of Microglial Hv1 as a Target for Immunomodulation in Myelin Repair

In the central nervous system (CNS), the myelin sheath ensures efficient interconnection between neurons and contributes to the regulation of the proper function of neuronal networks. The maintenance of myelin and the well-organized subtle process of myelin plasticity requires cooperation among myelin-forming cells, glial cells, and neural networks. The process of cooperation is fragile, and the balance is highly susceptible to disruption by microenvironment influences. Reactive microglia play a critical and complicated role in the demyelination and remyelination process. Recent studies have shown that the voltage-gated proton channel Hv1 is selectively expressed in microglia in CNS, which regulates intracellular pH and is involved in the production of reactive oxygen species, underlying multifaceted roles in maintaining microglia function. This paper begins by examining the molecular mechanisms of demyelination and emphasizes the crucial role of the microenvironment in demyelination. It focuses specifically on the role of Hv1 in myelin repair and its therapeutic potential in CNS demyelinating diseases.

Traumatic Brain Injury: A Comprehensive Review of Biomechanics and Molecular Pathophysiology

Traumatic brain injury (TBI) is a critical public health concern with profound consequences for affected individuals. This comprehensive literature review delves into TBI intricacies, encompassing primary injury biomechanics and the molecular pathophysiology of the secondary injury cascade. Primary TBI involves a complex interplay of forces, including impact loading, blast overpressure, and impulsive loading, leading to diverse injury patterns. These forces can be categorized into inertial (e.g., rotational acceleration causing focal and diffuse injuries) and contact forces (primarily causing focal injuries like skull fractures). Understanding their interactions is crucial for effective injury management. The secondary injury cascade in TBI comprises multifaceted molecular and cellular responses, including altered ion concentrations, dysfunctional neurotransmitter networks, oxidative stress, and cellular energy disturbances. These disruptions impair synaptic function, neurotransmission, and neuroplasticity, resulting in cognitive and behavioral deficits. Moreover, neuroinflammatory responses play a pivotal role in exacerbating damage. As we endeavor to bridge the knowledge gap between biomechanics and molecular pathophysiology, further research is imperative to unravel the nuanced interplay between mechanical forces and their consequences at the molecular and cellular levels, ultimately guiding the development of targeted therapeutic strategies to mitigate the debilitating effects of TBI. In this study, we aim to provide a concise review of the bridge between biomechanical processes causing primary injury and the ensuing molecular pathophysiology of secondary injury, while detailing the subsequent clinical course for this patient population. This knowledge is crucial for advancing our understanding of TBI and developing effective interventions to improve outcomes for those affected.

Targeting brain-peripheral immune responses for secondary brain injury after ischemic and hemorrhagic stroke

The notion that the central nervous system is an immunologically immune-exempt organ has changed over the past two decades, with increasing evidence of strong links and interactions between the central nervous system and the peripheral immune system, both in the healthy state and after ischemic and hemorrhagic stroke. Although primary injury after stroke is certainly important, the limited therapeutic efficacy, poor neurological prognosis and high mortality have led researchers to realize that secondary injury and damage may also play important roles in influencing long-term neurological prognosis and mortality and that the neuroinflammatory process in secondary injury is one of the most important influences on disease progression. Here, we summarize the interactions of the central nervous system with the peripheral immune system after ischemic and hemorrhagic stroke, in particular, how the central nervous system activates and recruits peripheral immune components, and we review recent advances in corresponding therapeutic approaches and clinical studies, emphasizing the importance of the role of the peripheral immune system in ischemic and hemorrhagic stroke.

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.

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.

Blood and CSF findings of cellular immunity in anti-NMDAR encephalitis

OBJECTIVES

To investigate the immunopathogenic mechanisms of anti-N-methyl-D-aspartate receptor encephalitis (NMDAR-E) by characterizing the changes of immune cells in both peripheral blood (PB) and cerebrospinal fluid (CSF) of patients with NMDAR-E.

METHODS

Cytology and flow cytometry were used to explore and compare different immunological parameters in PB and CSF of patients with NMDAR-E, viral encephalitis (VE) and healthy volunteers. Moreover, different models were established to assess the possibility of identifying NMDAR-E patients based on PB and CSF parameters.

RESULTS

The neutrophil counts and monocyte-to-lymphocyte ratios (MLR) in PB are higher in NMDAR-E patients than in both VEs and controls (P < 0.001, respectively), while the percentages of CD3 + T, CD4 + T lymphocytes, and the leukocytes count in CSF were lower in NMDAR-Es than in VEs (P < 0.01, respectively). The higher percentages of CD8 + T cells in blood and CSF were both correlated with more severe NMDAR-E (P < 0.05, respectively). The poor neurological status group had significantly higher PB leukocytes but lower CSF leukocyte count (P < 0.05). Longitudinal observations in patients with NMDAR-E showed a decreasing trend of leukocyte count, neutrophils count, neutrophil-to-monocyte ratios (NMR), and neutrophil-to-lymphocyte ratios (NLR) with the gradual recovery of neurological function.

CONCLUSIONS

The expression patterns of T lymphocyte subsets were different in patients with NMDAR-E and viral encephalitis. The changing trends of leukocyte and lymphocyte populations in peripheral blood and cerebrospinal fluid may provide clues for the diagnosis of different types of encephalitides, including NMDARE, and can be used as immunological markers to assess and predict the prognosis.

Immune cells: potential carriers or agents for drug delivery to the central nervous system

Drug delivery systems (DDS) have recently emerged as a promising approach for the unique advantages of drug protection and targeted delivery. However, the access of nanoparticles/drugs to the central nervous system (CNS) remains a challenge mainly due to the obstruction from brain barriers. Immune cells infiltrating the CNS in the pathological state have inspired the development of strategies for CNS foundation drug delivery. Herein, we outline the three major brain barriers in the CNS and the mechanisms by which immune cells migrate across the blood-brain barrier. We subsequently review biomimetic strategies utilizing immune cell-based nanoparticles for the delivery of nanoparticles/drugs to the CNS, as well as recent progress in rationally engineering immune cell-based DDS for CNS diseases. Finally, we discuss the challenges and opportunities of immune cell-based DDS in CNS diseases to promote their clinical development.

Targeting Vascular Impairment, Neuroinflammation, and Oxidative Stress Dynamics with Whole-Body Cryotherapy in Multiple Sclerosis Treatment

Multiple sclerosis (MS), traditionally perceived as a neurodegenerative disease, exhibits significant vascular alternations, including blood-brain barrier (BBB) disruption, which may predispose patients to increased cardiovascular risks. This vascular dysfunction is intricately linked with the infiltration of immune cells into the central nervous system (CNS), which plays a significant role in perpetuating neuroinflammation. Additionally, oxidative stress serves not only as a byproduct of inflammatory processes but also as an active contributor to neural damage. The synthesis of these multifaceted aspects highlights the importance of understanding their cumulative impact on MS progression. This review reveals that the triad of vascular damage, chronic inflammation, and oxidative imbalance may be considered interdependent processes that exacerbate each other, underscoring the need for holistic and multi-targeted therapeutic approaches in MS management. There is a necessity for reevaluating MS treatment strategies to encompass these overlapping pathologies, offering insights for future research and potential therapeutic interventions. Whole-body cryotherapy (WBCT) emerges as one of the potential avenues for holistic MS management approaches which may alleviate the triad of MS progression factors in multiple ways.

CD4+ CD11b+ T cells infiltrate and aggravate the traumatic brain injury depending on brain-to-cervical lymph node signaling

AIM

We aim to identify the specific CD4+ T-cell subtype influenced by brain-to-CLN signaling and explore their role during the acute phase of traumatic brain injury (TBI).

METHOD

Cervical lymphadenectomy or cervical afferent lymphatic ligation was performed before TBI. Cytokine array and western blot were used to detect cytokines, while the motor function was assessed using mNss and rotarod test. CD4+ T-cell subtypes in blood, brain, and CLNs were analyzed with Cytometry by time-of-flight analysis (CyTOF) or fluorescence-activated cell sorting (FACS). Brain edema and volume changes were measured by 9.4T MRI. Neuronal apoptosis was evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining.

RESULTS

Cervical lymphadenectomy and ligation of cervical lymphatic vessels resulted in a decreased infiltration of CD4+ T cells, specifically CD11b-positive CD4+ T cells, within the affected region. The population of CD4+ CD11b+ T cells increased in ligated CLNs, accompanied by a decrease in the average fluorescence intensity of sphingosine-1-phosphate receptor-1 (S1PR1) on these cells. Administration of CD4+ CD11b+ T cells sorted from CLNs into the lateral ventricle reversed the attenuated neurologic deficits, brain edema, and lesion volume following cervical lymphadenectomy.

CONCLUSION

The infiltration of CD4+ CD11b+ T cells exacerbates secondary brain damage in TBI, and this process is modulated by brain-to-CLN signaling.

Understanding immune microenvironment alterations in the brain to improve the diagnosis and treatment of diverse brain diseases

Abnormal inflammatory states in the brain are associated with a variety of brain diseases. The dynamic changes in the number and function of immune cells in cerebrospinal fluid (CSF) are advantageous for the early prediction and diagnosis of immune diseases affecting the brain. The aggregated factors and cells in inflamed CSF may represent candidate targets for therapy. The physiological barriers in the brain, such as the blood‒brain barrier (BBB), establish a stable environment for the distribution of resident immune cells. However, the underlying mechanism by which peripheral immune cells migrate into the brain and their role in maintaining immune homeostasis in CSF are still unclear. To advance our understanding of the causal link between brain diseases and immune cell status, we investigated the characteristics of immune cell changes in CSF and the molecular mechanisms involved in common brain diseases. Furthermore, we summarized the diagnostic and treatment methods for brain diseases in which immune cells and related cytokines in CSF are used as targets. Further investigations of the new immune cell subtypes and their contributions to the development of brain diseases are needed to improve diagnostic specificity and therapy.

Emerging role of mesenchymal stem cells-derived extracellular vesicles in vascular dementia

Vascular dementia (VD) is a prevalent cognitive disorder among the elderly. Its pathological mechanism encompasses neuronal damage, synaptic dysfunction, vascular abnormalities, neuroinflammation, and oxidative stress, among others. In recent years, extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) have garnered significant attention as an emerging therapeutic strategy. Current research indicates that MSC-derived extracellular vesicles (MSC-EVs) play a pivotal role in both the diagnosis and treatment of VD. Thus, this article delves into the recent advancements of MSC-EVs in VD, discussing the mechanisms by which EVs influence the pathophysiological processes of VD. These mechanisms form the theoretical foundation for their neuroprotective effect in VD treatment. Additionally, the article highlights the potential applications of EVs in VD diagnosis. In conclusion, MSC-EVs present a promising innovative treatment strategy for VD. With rigorous research and ongoing innovation, this concept can transition into practical clinical treatment, providing more effective options for VD patients.

Discrete class I molecules on brain endothelium differentially regulate neuropathology in experimental cerebral malaria

Cerebral malaria is the deadliest complication that can arise from Plasmodium infection. CD8 T-cell engagement of brain vasculature is a putative mechanism of neuropathology in cerebral malaria. To define contributions of brain endothelial cell major histocompatibility complex (MHC) class I antigen-presentation to CD8 T cells in establishing cerebral malaria pathology, we developed novel H-2Kb LoxP and H-2Db LoxP mice crossed with Cdh5-Cre mice to achieve targeted deletion of discrete class I molecules, specifically from brain endothelium. This strategy allowed us to avoid off-target effects on iron homeostasis and class I-like molecules, which are known to perturb Plasmodium infection. This is the first endothelial-specific ablation of individual class-I molecules enabling us to interrogate these molecular interactions. In these studies, we interrogated human and mouse transcriptomics data to compare antigen presentation capacity during cerebral malaria. Using the Plasmodium berghei ANKA model of experimental cerebral malaria (ECM), we observed that H-2Kb and H-2Db class I molecules regulate distinct patterns of disease onset, CD8 T-cell infiltration, targeted cell death and regional blood-brain barrier disruption. Strikingly, ablation of either molecule from brain endothelial cells resulted in reduced CD8 T-cell activation, attenuated T-cell interaction with brain vasculature, lessened targeted cell death, preserved blood-brain barrier integrity and prevention of ECM and the death of the animal. We were able to show that these events were brain-specific through the use of parabiosis and created the novel technique of dual small animal MRI to simultaneously scan conjoined parabionts during infection. These data demonstrate that interactions of CD8 T cells with discrete MHC class I molecules on brain endothelium differentially regulate development of ECM neuropathology. Therefore, targeting MHC class I interactions therapeutically may hold potential for treatment of cases of severe malaria.

The brain cytokine orchestra in multiple sclerosis: from neuroinflammation to synaptopathology

The central nervous system (CNS) is finely protected by the blood-brain barrier (BBB). Immune soluble factors such as cytokines (CKs) are normally produced in the CNS, contributing to physiological immunosurveillance and homeostatic synaptic scaling. CKs are peptide, pleiotropic molecules involved in a broad range of cellular functions, with a pivotal role in resolving the inflammation and promoting tissue healing. However, pro-inflammatory CKs can exert a detrimental effect in pathological conditions, spreading the damage. In the inflamed CNS, CKs recruit immune cells, stimulate the local production of other inflammatory mediators, and promote synaptic dysfunction. Our understanding of neuroinflammation in humans owes much to the study of multiple sclerosis (MS), the most common autoimmune and demyelinating disease, in which autoreactive T cells migrate from the periphery to the CNS after the encounter with a still unknown antigen. CNS-infiltrating T cells produce pro-inflammatory CKs that aggravate local demyelination and neurodegeneration. This review aims to recapitulate the state of the art about CKs role in the healthy and inflamed CNS, with focus on recent advances bridging the study of adaptive immune system and neurophysiology.

Stem Cell Interventions in Neurology: From Bench to Bedside

Stem cell therapies are progressively redefining the treatment landscape for a spectrum of neurological and age-related disorders. This review discusses the molecular and functional attributes of stem cells, emphasizing the roles of neural stem cells and mesenchymal stem cells in the context of neurological diseases such as stroke, multiple sclerosis, amyotrophic lateral sclerosis, traumatic brain injury, Parkinson's disease, and Alzheimer's disease. The review also explores the potential of stem cells in addressing the aging process. The paper analyzes stem cells' intrinsic properties of self-renewal, differentiation, and paracrine effects, alongside the importance of laboratory-modified stem cells like induced pluripotent stem cells and transgenic stem cells. Insights into disease-specific stem cell treatments are offered, reviewing both successes and challenges in the field. This includes the translational difficulties from rodent studies to human trials. The review concludes by acknowledging the uncharted territories that warrant further investigation, emphasizing the potential roles of stem cell-derived exosomes and indole-related molecules, and aiming at providing a basic understanding of stem cell therapies.

Interplay of G-proteins and Serotonin in the Neuroimmunoinflammatory Model of Chronic Stress and Depression: A Narrative Review

INTRODUCTION

This narrative review addresses the clinical challenges in stress-related disorders such as depression, focusing on the interplay between neuron-specific and pro-inflammatory mechanisms at the cellular, cerebral, and systemic levels.

OBJECTIVE

We aim to elucidate the molecular mechanisms linking chronic psychological stress with low-grade neuroinflammation in key brain regions, particularly focusing on the roles of G proteins and serotonin (5-HT) receptors.

METHODS

This comprehensive review of the literature employs systematic, narrative, and scoping review methodologies, combined with systemic approaches to general pathology. It synthesizes current research on shared signaling pathways involved in stress responses and neuroinflammation, including calcium-dependent mechanisms, mitogen-activated protein kinases, and key transcription factors like NF-κB and p53. The review also focuses on the role of G protein-coupled neurotransmitter receptors (GPCRs) in immune and pro-inflammatory responses, with a detailed analysis of how 13 of 14 types of human 5-HT receptors contribute to depression and neuroinflammation.

RESULTS

The review reveals a complex interaction between neurotransmitter signals and immunoinflammatory responses in stress-related pathologies. It highlights the role of GPCRs and canonical inflammatory mediators in influencing both pathological and physiological processes in nervous tissue.

CONCLUSION

The proposed Neuroimmunoinflammatory Stress Model (NIIS Model) suggests that proinflammatory signaling pathways, mediated by metabotropic and ionotropic neurotransmitter receptors, are crucial for maintaining neuronal homeostasis. Chronic mental stress can disrupt this balance, leading to increased pro-inflammatory states in the brain and contributing to neuropsychiatric and psychosomatic disorders, including depression. This model integrates traditional theories on depression pathogenesis, offering a comprehensive understanding of the multifaceted nature of the condition.

Regulatory T cells: A suppressor arm in post-stroke immune homeostasis

The activation of the immune system and the onset of pro- and anti-inflammatory responses play crucial roles in the pathophysiological processes of ischaemic stroke (IS). CD4+ regulatory T (Treg) cells is the main immunosuppressive cell population that is studied in the context of peripheral tolerance, autoimmunity, and the development of chronic inflammatory diseases. In recent years, more studies have focused on immune modulation after IS, and Treg cells have been demonstrated to be essential in the remission of inflammation, nerve regeneration, and behavioural recovery. However, the exact effects of Treg cells in the context of IS remain controversial, with some studies suggesting a negative correlation with stroke outcomes. In this review, we aim to provide a comprehensive overview of the current understanding of Treg cell involvement in post-stroke homeostasis. We summarized the literature focusing on the temporal changes in Treg cell populations after IS, the mechanisms of Treg cell-mediated immunomodulation in the brain, and the potential of Treg cell-based therapies for treatment. The purposes of the current article are to address the importance of Treg cells and inspire more studies to help physicians, as well as scientists, understand the whole map of immune responses during IS.

Paediatric obesity and metabolic syndrome associations with cognition and the brain in youth: Current evidence and future directions

Obesity and components of the metabolic syndrome (MetS) are associated with differences in brain structure and function and in general and food-related cognition in adults. Here, we review evidence for similar phenomena in children and adolescents, with a focus on the implications of extant research for possible underlying mechanisms and potential interventions for obesity and MetS in youth. Current evidence is limited by a relative reliance on small cross-sectional studies. However, we find that youth with obesity and MetS or MetS components show differences in brain structure, including alterations in grey matter volume and cortical thickness across brain regions subserving reward, cognitive control and other functions, as well as in white matter integrity and volume. Children with obesity and MetS components also show some evidence for hyperresponsivity of food reward regions and hyporesponsivity of cognitive control circuits during food-related tasks, altered brain responses to food tastes, and altered resting-state connectivity including between cognitive control and reward processing networks. Potential mechanisms for these findings include neuroinflammation, impaired vascular reactivity, and effects of diet and obesity on myelination and dopamine function. Future observational research using longitudinal measures, improved sampling strategies and study designs, and rigorous statistical methods, promises to further illuminate dynamic relationships and causal mechanisms. Intervention studies targeted at modifiable biological and behavioural factors associated with paediatric obesity and MetS can further inform mechanisms, as well as test whether brain and behaviour can be altered for beneficial outcomes.

Microglial crosstalk with astrocytes and immune cells in amyotrophic lateral sclerosis

In recent years, biomedical research efforts aimed to unravel the mechanisms involved in motor neuron death that occurs in amyotrophic lateral sclerosis (ALS). While the main causes of disease progression were first sought in the motor neurons, more recent studies highlight the gliocentric theory demonstrating the pivotal role of microglia and astrocyte, but also of infiltrating immune cells, in the pathological processes that take place in the central nervous system microenvironment. From this point of view, microglia-astrocytes-lymphocytes crosstalk is fundamental to shape the microenvironment toward a pro-inflammatory one, enhancing neuronal damage. In this review, we dissect the current state-of-the-art knowledge of the microglial dialogue with other cell populations as one of the principal hallmarks of ALS progression. Particularly, we deeply investigate the microglia crosstalk with astrocytes and immune cells reporting in vitro and in vivo studies related to ALS mouse models and human patients. At last, we highlight the current experimental therapeutic approaches that aim to modulate microglial phenotype to revert the microenvironment, thus counteracting ALS progression.

Skin Wound following Irradiation Aggravates Radiation-Induced Brain Injury in a Mouse Model

Radiation injury- and radiation combined with skin injury-induced inflammatory responses in the mouse brain were evaluated in this study. Female B6D2F1/J mice were subjected to a sham, a skin wound (SW), 9.5 Gy ⁶⁰Co total-body gamma irradiation (RI), or 9.5 Gy RI combined with a skin puncture wound (RCI). Survival, body weight, and wound healing were tracked for 30 days, and mouse brain samples were collected on day 30 after SW, RI, RCI, and the sham control. Our results showed that RCI caused more severe animal death and body weight loss compared with RI, and skin wound healing was significantly delayed by RCI compared to SW. RCI and RI increased the chemokines Eotaxin, IP-10, MIG, 6Ckine/Exodus2, MCP-5, and TIMP-1 in the brain compared to SW and the sham control mice, and the Western blot results showed that IP-10 and p21 were significantly upregulated in brain cells post-RI or -RCI. RI and RCI activated both astrocytes and endothelial cells in the mouse brain, subsequently inducing blood-brain barrier (BBB) leakage, as shown by the increased ICAM1 and GFAP proteins in the brain and GFAP in the serum. The Doublecortin (DCX) protein, the "gold standard" for measuring neurogenesis, was significantly downregulated by RI and RCI compared with the sham group. Furthermore, RI and RCI decreased the expression of the neural stem cell marker E-cadherin, the intermediate progenitor marker MASH1, the immature neuron cell marker NeuroD1, and the mature neuron cell marker NeuN, indicating neural cell damage in all development stages after RI and RCI. Immunohistochemistry (IHC) staining further confirmed the significant loss of neural cells in RCI. Our data demonstrated that RI and RCI induced brain injury through inflammatory pathways, and RCI exacerbated neural cell damage more than RI.

Astrocytic engagement of the corticostriatal synaptic cleft is disrupted in a mouse model of Huntington's disease

Astroglial dysfunction contributes to the pathogenesis of Huntington's disease (HD), and glial replacement can ameliorate the disease course. To establish the topographic relationship of diseased astrocytes to medium spiny neuron (MSN) synapses in HD, we used 2-photon imaging to map the relationship of turboRFP-tagged striatal astrocytes and rabies-traced, EGFP-tagged coupled neuronal pairs in R6/2 HD and wild-type (WT) mice. The tagged, prospectively identified corticostriatal synapses were then studied by correlated light electron microscopy followed by serial block-face scanning EM, allowing nanometer-scale assessment of synaptic structure in 3D. By this means, we compared the astrocytic engagement of single striatal synapses in HD and WT brains. R6/2 HD astrocytes exhibited constricted domains, with significantly less coverage of mature dendritic spines than WT astrocytes, despite enhanced engagement of immature, thin spines. These data suggest that disease-dependent changes in the astroglial engagement and sequestration of MSN synapses enable the high synaptic and extrasynaptic levels of glutamate and K+ that underlie striatal hyperexcitability in HD. As such, these data suggest that astrocytic structural pathology may causally contribute to the synaptic dysfunction and disease phenotype of those neurodegenerative disorders characterized by network overexcitation.

Remyelination in multiple sclerosis from the miRNA perspective

Remyelination relies on the repair of damaged myelin sheaths, involving microglia cells, oligodendrocyte precursor cells (OPCs), and mature oligodendrocytes. This process drives the pathophysiology of autoimmune chronic disease of the central nervous system (CNS), multiple sclerosis (MS), leading to nerve cell damage and progressive neurodegeneration. Stimulating the reconstruction of damaged myelin sheaths is one of the goals in terms of delaying the progression of MS symptoms and preventing neuronal damage. Short, noncoding RNA molecules, microRNAs (miRNAs), responsible for regulating gene expression, are believed to play a crucial role in the remyelination process. For example, studies showed that miR-223 promotes efficient activation and phagocytosis of myelin debris by microglia, which is necessary for the initiation of remyelination. Meanwhile, miR-124 promotes the return of activated microglia to the quiescent state, while miR-204 and miR-219 promote the differentiation of mature oligodendrocytes. Furthermore, miR-138, miR-145, and miR-338 have been shown to be involved in the synthesis and assembly of myelin proteins. Various delivery systems, including extracellular vesicles, hold promise as an efficient and non-invasive way for providing miRNAs to stimulate remyelination. This article summarizes the biology of remyelination as well as current challenges and strategies for miRNA molecules in potential diagnostic and therapeutic applications.

Microglia and the Blood-Brain Barrier: An External Player in Acute and Chronic Neuroinflammatory Conditions

Microglia are the resident immune cells of the central nervous system that guarantee immune surveillance and exert also a modulating role on neuronal synaptic development and function. Upon injury, microglia get activated and modify their morphology acquiring an ameboid phenotype and pro- or anti-inflammatory features. The active role of microglia in blood-brain barrier (BBB) function and their interaction with different cellular components of the BBB-endothelial cells, astrocytes and pericytes-are described. Here, we report the specific crosstalk of microglia with all the BBB cell types focusing in particular on the involvement of microglia in the modulation of BBB function in neuroinflammatory conditions that occur in conjunction with an acute event, such as a stroke, or in a slow neurodegenerative disease, such as Alzheimer's disease. The potential of microglia to exert a dual role, either protective or detrimental, depending on disease stages and environmental conditioning factors is also discussed.

Blockade of VEGFR3 signaling leads to functional impairment of dural lymphatic vessels without affecting autoimmune neuroinflammation

The recent discovery of lymphatic vessels (LVs) in the dura mater, the outermost layer of meninges around the central nervous system (CNS), has opened a possibility for the development of alternative therapeutics for CNS disorders. The vascular endothelial growth factor C (VEGF-C)/VEGF receptor 3 (VEGFR3) signaling pathway is essential for the development and maintenance of dural LVs. However, its significance in mediating dural lymphatic function in CNS autoimmunity is unclear. We show that inhibition of the VEGF-C/VEGFR3 signaling pathway using a monoclonal VEGFR3-blocking antibody, a soluble VEGF-C/D trap, or deletion of the Vegfr3 gene in adult lymphatic endothelium causes notable regression and functional impairment of dural LVs but has no effect on the development of CNS autoimmunity in mice. During autoimmune neuroinflammation, the dura mater was only minimally affected, and neuroinflammation-induced helper T (T_H) cell recruitment, activation, and polarization were significantly less pronounced in the dura mater than in the CNS. In support of this notion, during autoimmune neuroinflammation, blood vascular endothelial cells in the cranial and spinal dura expressed lower levels of cell adhesion molecules and chemokines, and antigen-presenting cells (i.e., macrophages and dendritic cells) had lower expression of chemokines, MHC class II-associated molecules, and costimulatory molecules than their counterparts in the brain and spinal cord, respectively. The significantly weaker T_H cell responses in the dura mater may explain why dural LVs do not contribute directly to CNS autoimmunity.

Bacillus Calmette-Guérin Tokyo-172 vaccine provides age-related neuroprotection in actively induced and spontaneous experimental autoimmune encephalomyelitis models

Multiple sclerosis is the most common immune-mediated disorder affecting the central nervous system in young adults but still has no cure. Bacillus Calmette-Guérin (BCG) vaccine is reported to have non-specific anti-inflammatory effects and therapeutic benefits in autoimmune disorders including multiple sclerosis. However, the precise mechanism of action of BCG and the host immune response to it remain unclear. In this study, we aimed to investigate the efficacy of the BCG Tokyo-172 vaccine in suppressing experimental autoimmune encephalomyelitis (EAE). Groups of young and mature adult female C57BL/6J mice were BCG-vaccinated 1 month prior or 6 days after active EAE induction using myelin oligodendrocyte glycoprotein (MOG)35-55 peptide. Another group of 2D2 TCRMOG transgenic female mice was BCG-vaccinated before and after the onset of spontaneous EAE. BCG had an age-associated protective effect against active EAE only in wild-type mice vaccinated 1 month before EAE induction. Furthermore, the incidence of spontaneous EAE was significantly lower in BCG vaccinated 2D2 mice than in non-vaccinated controls. Protection against EAE was associated with reduced splenic T-cell proliferation in response to MOG35-55 peptide together with high frequency of CD8+ interleukin-10-secreting T cells in the spleen. In addition, microglia and astrocytes isolated from BCG-vaccinated mice showed polarization to anti-inflammatory M2 and A2 phenotypes, respectively. Our data provide new insights into the cell-mediated and humoral immune mechanisms underlying BCG vaccine-induced neuroprotection, potentially useful for developing better strategies for the treatment of MS.

Long-lived autoreactive memory CD4+ T cells mediate the sustained retinopathy in chronic autoimmune uveitis

Chronic uveitis comprises heterogeneous clinical entities characterized by sustained and recurrent intraocular inflammation that is believed to be driven by autoimmune responses. The management of chronic uveitis is challenging with the limited availability of efficacious treatments, and the underlying mechanisms mediating disease chronicity remain poorly understood as the majority of experimental data are derived from the acute phase of the disease (the first 2-3 weeks post-induction). Herein, we investigated the key cellular mechanisms underlying chronic intraocular inflammation using our recently established murine model of chronic autoimmune uveitis. We demonstrate unique long-lived CD44hi IL-7R+ IL-15R+ CD4+ memory T cells in both retina and secondary lymphoid organs after 3 months postinduction of autoimmune uveitis. These memory T cells functionally exhibit antigen-specific proliferation and activation in response to retinal peptide stimulation in vitro. Critically, these effector-memory T cells are capable of effectively trafficking to the retina and accumulating in the local tissues secreting both IL-17 and IFN-γ upon adoptively transferred, leading to retinal structural and functional damage. Thus, our data reveal the critical uveitogenic functions of memory CD4+ T cells in sustaining chronic intraocular inflammation, suggesting that memory T cells can be a novel and promising therapeutic target for treating chronic uveitis in future translational studies.

The adaptation model of immunity: A new insight into aetiology and treatment of multiple sclerosis

Current research and drug development for multiple sclerosis (MS) is fully influenced by the self-nonself (SNS) model of immunity, suggesting that breakage of immunological tolerance towards self-antigens expressed in the central nervous system (CNS) is responsible for pathogenesis of MS; thus, immune suppressive drugs are recommended for the management of the disease. However, this model provides incomplete understanding of the causes and pathways involved in the onset and progression of MS and limits our ability to effectively treat this neurological disease. Some pre-clinical and clinical reports have been misunderstood; some others have been underappreciated because of the lack of a theoretical model that can explain them. Also, current immunotherapies are guided according to the models that are not designed to explain the functional outcomes of an immune response. The adaptation model of immunity is proposed to offer a new understanding of the existing data and galvanize a new direction for the treatment of MS. According to this model, the immune system continuously communicates with the CNS through the adaptation receptors (AdRs) and adaptation ligands (AdLs) or co-receptors, signal IV, to support cell growth and neuroplasticity. Alterations in the expression of the neuronal AdRs results in MS by shifting the cerebral inflammatory immune responses from remyelination to demyelination. Therefore, novel therapeutics for MS should be focused on the discovery and targeting of the AdR/AdL axis in the CNS rather than carrying on with immune suppressive interventions.

Senescent cells in the brain and where to find them

Cellular senescence is a process in which cells change their characteristic phenotype in response to stress and enter a state of prolonged cell cycle arrest accompanied by a distinct secretory phenotype. Cellular senescence has both beneficial and detrimental outcomes. With age, senescent cells progressively accumulate in tissues and might be the bridge connecting ageing to many age-related pathologies. In recent years, evidence emerged supporting the accumulation of brain senescent cells during neurological disorders and ageing. Here, we will discuss the different brain cell populations that exhibit a senescent phenotype. Subsequently, we will explore several senolytic strategies which have been developed to eliminate senescent cells. Finally, we will examine their potential to directly eliminate these senescent brain cells.

Adenosine A2A receptor controls the gateway of the choroid plexus

The choroid plexus (CP) is one of the key gateways regulating the entry of peripheral immune cells into the CNS. However, the neuromodulatory mechanisms of maintaining its gateway activity are not fully understood. Here, we identified adenosine A_2A receptor (A_2AR) activity as a regulatory signal for the activity of CP gateway under physiological conditions. In association with a tightly closed CP gateway, we found that A_2AR was present at low density in the CP. The RNA-seq analysis revealed that the A_2AR antagonist KW6002 affected the expression of the cell adhesion molecules' (CAMs) pathway and cell response to IFN-γ in the CP. Furthermore, blocking or activating A_2AR signaling in the CP resulted in a decreased and an increased, respectively, expression of lymphocyte trafficking determinants and disruption of the tight junctions (TJs). Furthermore, A_2AR signaling regulates the CP permeability. Thus, A_2AR activity in the CP may serve as a therapeutic target for remodeling the immune homeostasis in the CNS with implications for the treatment of neuroimmunological disorders.

Role of Nanomedicine-Based Therapeutics in the Treatment of CNS Disorders

Central nervous system disorders, especially neurodegenerative diseases, are a public health priority and demand a strong scientific response. Various therapy procedures have been used in the past, but their therapeutic value has been insufficient. The blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier is two of the barriers that protect the central nervous system (CNS), but are the main barriers to medicine delivery into the CNS for treating CNS disorders, such as brain tumors, Parkinson's disease, Alzheimer's disease, and Huntington's disease. Nanotechnology-based medicinal approaches deliver valuable cargos targeting molecular and cellular processes with greater safety, efficacy, and specificity than traditional approaches. CNS diseases include a wide range of brain ailments connected to short- and long-term disability. They affect millions of people worldwide and are anticipated to become more common in the coming years. Nanotechnology-based brain therapy could solve the BBB problem. This review analyzes nanomedicine's role in medication delivery; immunotherapy, chemotherapy, and gene therapy are combined with nanomedicines to treat CNS disorders. We also evaluated nanotechnology-based approaches for CNS disease amelioration, with the intention of stimulating the immune system by delivering medications across the BBB.

Acquired immunity and Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disease characterized by progressive cognitive defects. The role of the central immune system dominated by microglia in the progression of AD has been extensively investigated. However, little is known about the peripheral immune system in AD pathogenesis. Recently, with the discovery of the meningeal lymphatic vessels and glymphatic system, the roles of the acquired immunity in the maintenance of central homeostasis and neurodegenerative diseases have attracted an increasing attention. The T cells not only regulate the function of neurons, astrocytes, microglia, oligodendrocytes and brain microvascular endothelial cells, but also participate in the clearance of β-amyloid (Aβ) plaques. Apart from producing antibodies to bind Aβ peptides, the B cells affect Aβ-related cascades via a variety of antibody-independent mechanisms. This review systemically summarizes the recent progress in understanding pathophysiological roles of the T cells and B cells in AD.

CNS and CNS diseases in relation to their immune system

The central nervous system is the most important nervous system in vertebrates, which is responsible for transmitting information to the peripheral nervous system and controlling the body's activities. It mainly consists of the brain and spinal cord, which contains rich of neurons, the precision of the neural structures susceptible to damage from the outside world and from the internal factors of inflammation infection, leading to a series of central nervous system diseases, such as traumatic brain injury, nerve inflammation, etc., these diseases may cause irreversible damage on the central nervous or lead to subsequent chronic lesions. After disease or injury, the immune system of the central nervous system will play a role, releasing cytokines to recruit immune cells to enter, and the immune cells will differentiate according to the location and degree of the lesion, and become specific immune cells with different functions, recognize and phagocytose inflammatory factors, and repair the damaged neural structure. However, if the response of these immune cells is not suppressed, the overexpression of some genes can cause further damage to the central nervous system. There is a need to understand the molecular mechanisms by which these immune cells work, and this information may lead to immunotherapies that target certain diseases and avoid over-activation of immune cells. In this review, we summarized several immune cells that mainly play a role in the central nervous system and their roles, and also explained the response process of the immune system in the process of some common neurological diseases, which may provide new insights into the central nervous system.

Alzheimer's Disease: From Immune Homeostasis to Neuroinflammatory Condition

Alzheimer's Disease is the most common cause in the world of progressive cognitive decline. Although many modifiable and non-modifiable risk factors have been proposed, in recent years, neuroinflammation has been hypothesized to be an important contributing factor of Alzheimer's Disease pathogenesis. Neuroinflammation can occur through the combined action of the Central Nervous System resident immune cells and adaptive peripheral immune system. In the past years, immunotherapies for neurodegenerative diseases have focused wrongly on targeting protein aggregates Aβ plaques and NFT treatment. The role of both innate and adaptive immune cells has not been fully clarified, but several data suggest that immune system dysregulation plays a key role in neuroinflammation. Recent studies have focused especially on the role of the adaptive immune system and have shown that inflammatory markers are characterized by increased CD4+ Teff cells' activities and reduced circulating CD4+ Treg cells. In this review, we discuss the key role of both innate and adaptive immune systems in the degeneration and regeneration mechanisms in the pathogenesis of Alzheimer's Disease, with a focus on how the crosstalk between these two systems is able to sustain brain homeostasis or shift it to a neurodegenerative condition.

Autoimmunity and SARS-CoV-2 infection: Unraveling the link in neurological disorders

According to the World Health Organization, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has already infected more than 400 million people and caused over 5 million deaths globally. The infection is associated with a wide spectrum of clinical manifestations, ranging from no signs of illness to severe pathological complications that go beyond the typical respiratory symptoms. On this note, new-onset neurological and neuropsychiatric syndromes have been increasingly reported in a large fraction of COVID-19 patients, thus potentially representing a significant public health threat. Although the underlying pathophysiological mechanisms remain elusive, a growing body of evidence suggests that SARS-CoV-2 infection may trigger an autoimmune response, which could potentially contribute to the establishment and/or exacerbation of neurological disorders in COVID-19 patients. Shedding light on this aspect is urgently needed for the development of effective therapeutic intervention. This review highlights the current knowledge of the immune responses occurring in Neuro-COVID patients and discusses potential immune-mediated mechanisms by which SARS-CoV-2 infection may trigger neurological complications.

Unique aspects of IFN-γ/STAT1 signaling in neurons

The IFN-γ/STAT1 immune signaling pathway impacts many homeostatic and pathological aspects of neurons, beyond its canonical role in controlling intracellular pathogens. Well known for its potent pro-inflammatory and anti-viral functions in the periphery, the IFN-γ/STAT1 pathway is rapidly activated then deactivated to prevent excessive inflammation; however, neurons utilize unique IFN-γ/STAT1 activation patterns, which may contribute to the non-canonical neuron-specific downstream effects. Though it is now well-established that the immune system interacts and supports the CNS in health and disease, many aspects regarding IFN-γ production in the CNS and how neurons respond to IFN-γ are unclear. Additionally, it is not well understood how the diversity of the IFN-γ/STAT1 pathway is regulated in neurons to control homeostatic functions, support immune surveillance, and prevent pathologies. In this review, we discuss the neuron-specific mechanisms and kinetics of IFN-γ/STAT1 activation, the potential sources and entry sites of IFN-γ in the CNS, and the diverse set of homeostatic and pathological effects IFN-γ/STAT1 signaling in neurons has on CNS health and disease. We will also highlight the different contexts and conditions under which IFN-γ-induced STAT1 activation has been studied in neurons, and how various factors might contribute to the vast array of downstream effects observed.

The role of neutrophils in the dysfunction of central nervous system barriers

Leukocyte migration into the central nervous system (CNS) represents a central process in the development of neurological diseases with a detrimental inflammatory component. Infiltrating neutrophils have been detected inside the brain of patients with several neuroinflammatory disorders, including stroke, multiple sclerosis and Alzheimer’s disease. During inflammatory responses, these highly reactive innate immune cells can rapidly extravasate and release a plethora of pro-inflammatory and cytotoxic factors, potentially inducing significant collateral tissue damage. Indeed, several studies have shown that neutrophils promote blood-brain barrier damage and increased vascular permeability during neuroinflammatory diseases. Recent studies have shown that neutrophils migrate into the meninges and choroid plexus, suggesting these cells can also damage the blood-cerebrospinal fluid barrier (BCSFB). In this review, we discuss the emerging role of neutrophils in the dysfunction of brain barriers across different neuroinflammatory conditions and describe the molecular basis and cellular interplays involved in neutrophil-mediated injury of the CNS borders.

An optimized ionizable cationic lipid for brain tumor-targeted siRNA delivery and glioblastoma immunotherapy

Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor with a high mortality rate. Immunotherapy has achieved promising clinical results in multiple cancers, but shows unsatisfactory outcome in GBM patients, and poor drug delivery across the blood-brain barrier (BBB) is believed to be one of the main limitations that hinder the therapeutic efficacy of drugs. Herein, a new cationic lipid nanoparticle (LNP) that can efficiently deliver siRNA across BBB and target mouse brain is prepared for modulating the tumor microenvironment for GBM immunotherapy. By designing and screening cationic LNPs with different ionizable amine headgroups, a lipid (named as BAMPA-O16B) is identified with an optimal acid dissociation constant (pKa) that significantly enhances the cellular uptake and endosomal escape of siRNA lipoplex in mouse GBM cells. Importantly, BAMPA-O16B/siRNA lipoplex is highly effective to deliver siRNA against CD47 and PD-L1 across the BBB into cranial GBM in mice, and downregulate target gene expression in the tumor, resulting in synergistically activating a T cell-dependent antitumor immunity in orthotopic GBM. Collectively, this study offers an effective strategy for brain targeted siRNA delivery and gene silencing by optimizing the physicochemical property of LNPs. The effectiveness of modulating immune environment of GBM could further be expanded for potential treatment of other brain tumors.

Ameliorating potential of curcumin and its analogue in central nervous system disorders and related conditions: A review of molecular pathways

Curcumin, isolated from turmeric (Curcuma longa L.) is one of the broadly studied phytomolecule owing to its strong antioxidant and anti-inflammatory potential and has been considered a promising therapeutic candidate in a wide range of disorders. Considering, its low bioavailability, different curcumin analogs have been developed to afford desired pharmacokinetic profile and therapeutic outcome in varied pathological states. Several preclinical and clinical studies have indicated that curcumin ameliorates mitochondrial dysfunction, inflammation, oxidative stress apoptosis-mediated neural cell degeneration and could effectively be utilized in the treatment of different neurodegenerative diseases. Hence, in this review, we have summarized key findings of experimental and clinical studies conducted on curcumin and its analogues with special emphasis on molecular pathways, viz. NF-kB, Nrf2-ARE, glial activation, apoptosis, angiogenesis, SOCS/JAK/STAT, PI3K/Akt, ERK1/2 /MyD88 /p38 MAPK, JNK, iNOS/NO, and MMP pathways involved in imparting ameliorative effects in the therapy of neurodegenerative disorders and associated conditions.

Study of BBB Dysregulation in Neuropathogenicity Using Integrative Human Model of Blood-Brain Barrier

The blood-brain barrier (BBB) is a cellular and physical barrier with a crucial role in homeostasis of the brain extracellular environment. It controls the imports of nutrients to the brain and exports toxins and pathogens. Dysregulation of the blood-brain barrier increases permeability and contributes to pathologies, including Alzheimer's disease, epilepsy, and ischemia. It remains unclear how a dysregulated BBB contributes to these different syndromes. Initial studies on the role of the BBB in neurological disorders and also techniques to permit the entry of therapeutic molecules were made in animals. This review examines progress in the use of human models of the BBB, more relevant to human neurological disorders. In recent years, the functionality and complexity of in vitro BBB models have increased. Initial efforts consisted of static transwell cultures of brain endothelial cells. Human cell models based on microfluidics or organoids derived from human-derived induced pluripotent stem cells have become more realistic and perform better. We consider the architecture of different model generations as well as the cell types used in their fabrication. Finally, we discuss optimal models to study neurodegenerative diseases, brain glioma, epilepsies, transmigration of peripheral immune cells, and brain entry of neurotrophic viruses and metastatic cancer cells.

Pathogenic mechanisms and therapeutic promise of phytochemicals and nanocarriers based drug delivery against radiotherapy-induced neurotoxic manifestations

Radiotherapy is one of the extensively used therapeutic modalities in glioblastoma and other types of cancers. Radiotherapy is either used as a first-line approach or combined with pharmacotherapy or surgery to manage and treat cancer. Although the use of radiotherapy significantly increased the survival time of patients, but its use has been reported with marked neuroinflammation and cognitive dysfunction that eventually reduced the quality of life of patients. Based on the preclinical and clinical investigations, the profound role of increased oxidative stress, nuclear translocation of NF-kB, production of proinflammatory cytokines such as TNF-α, IL-6, IL-β, increased level of MMPs, increased apoptosis, reduced angiogenesis, neurogenesis, and histological aberrations in CA1, CA2, CA3 and DG region of the hippocampus have been reported. Various pharmacotherapeutic drugs are being used as an adjuvant to counteract this neurotoxic manifestation. Still, most of these drugs suffer from systemic adverse effect, causes interference to ongoing chemotherapy, and exhibit pharmacokinetic limitations in crossing the blood-brain barrier. Therefore, various phytoconstituents, their nano carrier-based drug delivery systems and miRNAs have been explored to overcome the aforementioned limitations. The present review is focused on the mechanism and evidence of radiotherapy-induced neuroinflammation and cognitive dysfunction, pathological and molecular changes in the brain homeostasis, available adjuvants, their limitations. Additionally, the potential role and mechanism of neuroprotection of various nanocarrier based natural products and miRNAs have been discussed.

Neutrophil Count Predicts Malignant Cerebellar Edema and Poor Outcome in Acute Basilar Artery Occlusion Receiving Endovascular Treatment: A Nationwide Registry-Based Study

Background

Acute basilar artery occlusion (ABAO) is known to have a poor outcome with a high rate of morbidity and mortality despite endovascular treatment (EVT), highlighting the necessities of exploring factors to limit the efficacy of EVT in these patients. Cerebellar infarctions in ABAO might progress to malignant cerebellar edema (MCE), a life-threatening complication after reperfusion, posing a secondary injury to the brainstem by mass effects. Therefore, the present research aimed to explore the impacts of MCE on a long-term outcome and investigate the prognostic factors for MCE among ABAO after EVT.

Methods

In the national BASILAR registry, a total of 329 ABO patients with cerebellar infarctions treated by EVT met the inclusion criteria. The presence of MCE defined by the Jauss scale ≥4 points, was evaluated on the computed tomography performed 72 h after EVT. The adjusted odds ratio and 95% CI were obtained by logistic regression models. A favorable outcome was defined as a 90-day modified Rankin Scale score of 0-3.

Results

MCE was statistically associated with the decreased incidence of a favorable outcome [adjusted odds ratio, 0.35(95% CI, 0.18-0.68), P=0.002]. The baseline National Institutes of Health Stroke Scale score, collateral circulation, neutrophil count at admission, and recanalization status were predictors for MCE and a favorable functional status at 90 days (all P<0.05). Among all inflammatory factors, the neutrophil count achieved the highest accuracy, sensitivity, and specificity for MCE. Adding the neutrophil count status into the baseline model obviously enhanced its prediction ability for MCE and favorable outcome by increasing the area under curve and achieving both net reclassification and integrated discrimination improvement (all P<0.05). Mediation analysis indicated that MCE mediated the association between the increased neutrophil count and worse functional outcome (P=0.026).

Discussion

MCE acted essential roles in worsening prognosis for ABAO after EVT. A high neutrophil count at admission was linked to MCE and a poor outcome among ABAO patients, which could be further incorporated into the clinical decision-making system and guide immunomodulation therapy.

The Role of Immunity in Alzheimer's Disease

With the increase in the aging population, age-related conditions such as dementia and Alzheimer's disease will become ever more prevalent in society. As there is no cure for dementia and extremely limited therapeutic options, researchers are examining the mechanisms that contribute to the progression of cognitive decline in hopes of developing better therapies and even an effective, long-lasting treatment for this devastating condition. This review will provide an updated perspective on the role of immunity in triggering the changes that lead to the development of dementia. It will detail the latest findings on Aβ- and tau-induced microglial activation, including the role of the inflammasome. The contribution of the adaptive immune system, specifically T cells, will be discussed. Finally, whether the innate and adaptive immune system can be modulated to protect against dementia will be examined, along with an assessment of the prospective candidates for these that are currently in clinical trials.

The intrinsic and microenvironmental features of diffuse midline glioma; implications for the development of effective immunotherapeutic treatment strategies

Diffuse midline glioma (DMG), including those of the brainstem (diffuse intrinsic pontine glioma), are pediatric tumors of the central nervous system (CNS). Recognized as the most lethal of all childhood cancers, palliative radiotherapy remains the only proven treatment option, however, even for those that respond, survival is only temporarily extended. DMG harbor an immunologically “cold” tumor microenvironment (TME) with few infiltrating immune cells. The mechanisms underpinning the cold TME are not well understood. Low expression levels of immune checkpoint proteins, including PD-1, PD-L1, and CTLA-4, are recurring features of DMG and likely contribute to the lack of response to immune checkpoint inhibitors (ICIs). The unique epigenetic signatures (including stem cell-like methylation patterns), a low tumor mutational burden, and recurring somatic mutations (H3K27M, TP53, ACVR1, MYC, and PIK3CA), possibly play a role in the reduced efficacy of traditional immunotherapies. Therefore, to circumvent the lack of efficacy thus far seen for the use of ICIs, adoptive cell transfer (including chimeric antigen receptor T cells) and the use of oncolytic viruses, are currently being evaluated for the treatment of DMG. It remains an absolute imperative that we improve our understanding of DMG’s intrinsic and TME features if patients are to realize the potential benefits offered by these sophisticated treatments. Herein, we summarize the limitations of immunotherapeutic approaches, highlight the emerging safety and clinical efficacy shown for sophisticated cell-based therapies, as well as the evolving knowledge underpinning the DMG-immune axis, to guide the development of immunotherapies that we hope will improve outcomes.

A Breakdown of Immune Tolerance in the Cerebellum

Cerebellar dysfunction can be associated with ataxia, dysarthria, dysmetria, nystagmus and cognitive deficits. While cerebellar dysfunction can be caused by vascular, traumatic, metabolic, genetic, inflammatory, infectious, and neoplastic events, the cerebellum is also a frequent target of autoimmune attacks. The underlying cause for this vulnerability is unclear, but it may be a result of region-specific differences in blood–brain barrier permeability, the high concentration of neurons in the cerebellum and the presence of autoantigens on Purkinje cells. An autoimmune response targeting the cerebellum—or any structure in the CNS—is typically accompanied by an influx of peripheral immune cells to the brain. Under healthy conditions, the brain is protected from the periphery by the blood–brain barrier, blood–CSF barrier, and blood–leptomeningeal barrier. Entry of immune cells to the brain for immune surveillance occurs only at the blood-CSF barrier and is strictly controlled. A breakdown in the barrier permeability allows peripheral immune cells uncontrolled access to the CNS. Often—particularly in infectious diseases—the autoimmune response develops because of molecular mimicry between the trigger and a host protein. In this review, we discuss the immune surveillance of the CNS in health and disease and also discuss specific examples of autoimmunity affecting the cerebellum.