APOE from patient-derived astrocytic extracellular vesicles alleviates neuromyelitis optica spectrum disorder in a mouse model.

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune astrocytopathy of the central nervous system, mediated by antibodies against aquaporin-4 water channel protein (AQP4-Abs), resulting in damage of astrocytes with subsequent demyelination and axonal damage. Extracellular communication through astrocyte-derived extracellular vesicles (ADEVs) has received growing interest in association with astrocytopathies. However, to what extent ADEVs contribute to NMOSD pathogenesis remains unclear. Here, through proteomic screening of patient-derived ADEVs, we observed an increase in apolipoprotein E (APOE)-rich ADEVs in patients with AQP4-Abs-positive NMOSD. Intracerebral injection of the APOE-mimetic peptide APOE130-149 attenuated microglial reactivity, neuroinflammation, and brain lesions in a mouse model of NMOSD. The protective effect of APOE in NMOSD pathogenesis was further established by the exacerbated lesion volume in APOE-deficient mice, which could be rescued by exogenous APOE administration. Genetic knockdown of the APOE receptor lipoprotein receptor-related protein 1 (LRP1) could block the restorative effects of APOE130-149 administration. The transfusion ADEVs derived from patients with NMOSD and healthy controls also alleviated astrocyte loss, reactive microgliosis, and demyelination in NMOSD mice. The slightly larger beneficial effect of patient-derived ADEVs as compared to ADEVs from healthy controls was further augmented in APOE-/- mice. These results indicate that APOE from astrocyte-derived extracellular vesicles could mediate disease-modifying astrocyte-microglia cross-talk in NMOSD.

Autonomic dysfunction and treatment strategies in intracerebral hemorrhage.

AIMS: Autonomic dysfunction with central autonomic network (CAN) damage occurs frequently after intracerebral hemorrhage (ICH) and contributes to a series of adverse outcomes. This review aims to provide insight and convenience for future clinical practice and research on autonomic dysfunction in ICH patients. DISCUSSION: We summarize the autonomic dysfunction in ICH from the aspects of potential mechanisms, clinical significance, assessment, and treatment strategies. The CAN structures mainly include insular cortex, anterior cingulate cortex, amygdala, hypothalamus, nucleus of the solitary tract, ventrolateral medulla, dorsal motor nucleus of the vagus, nucleus ambiguus, parabrachial nucleus, and periaqueductal gray. Autonomic dysfunction after ICH is closely associated with neurological functional outcomes, cardiac complications, blood pressure fluctuation, immunosuppression and infection, thermoregulatory dysfunction, hyperglycemia, digestive dysfunction, and urogenital disturbances. Heart rate variability, baroreflex sensitivity, skin sympathetic nerve activity, sympathetic skin response, and plasma catecholamine concentration can be used to assess the autonomic functional activities after ICH. Risk stratification of patients according to autonomic functional activities, and development of intervention approaches based on the restoration of sympathetic-parasympathetic balance, would potentially improve clinical outcomes in ICH patients. CONCLUSION: The review systematically summarizes the evidence of autonomic dysfunction and its association with clinical outcomes in ICH patients, proposing that targeting autonomic dysfunction could be potentially investigated to improve the clinical outcomes.

Efficacy and safety of low- and ultralow-dose rituximab in neuromyelitis optica spectrum disorder.

BACKGROUND: Rituximab effectively targets B cells and reduces relapses in neuromyelitis optica spectrum disorder (NMOSD). But the ideal dosage and treatment intervals remain unanswered. We aimed to assess the efficacy and safety of low and ultralow-dose rituximab in NMOSD. METHODS: We conducted a retrospective analysis of NMOSD patients treated with rituximab at two Chinese tertiary hospitals. Patients received either a low-dose regimen (500 mg reinfusion every 6 months) or an ultralow-dose regimen: 100 to 300 mg rituximab based on CD19+B cells (100 mg for 1-1.5% of peripheral blood mononuclear cells, 200 mg for 1.5-5%, and 300 mg for over 5%). RESULTS: We analyzed data from 136 patients (41 in the low-dose group, 95 in the ultralow-dose group) with median follow-up durations of 43 and 34.2 months, respectively. Both groups exhibited similar sex distribution, age at disease onset, annual relapse rate, and baseline disease duration. Survival analysis showed that ultralow-dose rituximab was noninferior to low-dose rituximab in preventing relapses. Infusion reactions occurred in 20 of 173 (11.6%) low-dose treatments and 9 of 533 (1.7%) ultralow-dose treatments. B-cell re-emergence was observed in 137 of 236 (58.1%) monitors in the low-dose group and 367 of 1136 (32.3%) monitors in the ultralow-dose group. CONCLUSION: Ultralow dose rituximab was noninferior to low-dose rituximab in preventing NMOSD relapses. A randomized controlled trial is essential to validate these findings.

Neurovascular Inflammation and Complications of Thrombolysis Therapy in Stroke.

Intravenous thrombolysis via tPA (tissue-type plasminogen activator) is the only approved pharmacological treatment for acute ischemic stroke, but its benefits are limited by hemorrhagic transformation. Emerging evidence reveals that tPA swiftly mobilizes immune cells which extravasate into the brain parenchyma via the cerebral vasculature, augmenting neurovascular inflammation, and tissue injury. In this review, we summarize the pronounced alterations of immune cells induced by tPA in patients with stroke and experimental stroke models. We argue that neuroinflammation, triggered by ischemia-induced cell death and exacerbated by tPA, compromises neurovascular integrity and the microcirculation, leading to hemorrhagic transformation. Finally, we discuss current and future approaches to attenuate thrombolysis-associated hemorrhagic transformation via uncoupling immune cells from the neurovascular unit.

White matter disease derived from vascular and demyelinating origins.

Damage or microstructural alterations of the white matter can cause dysfunction of the intrinsic neural networks in a condition termed as white matter disease (WMD). Frequently detected on brain computed tomography and magnetic resonance imaging scans, WMD is commonly presented in inflammatory demyelinating diseases like multiple sclerosis (MS) and vascular diseases such as cerebral small vessel disease (CSVD). Prevention of MS and CSVD progression requires early treatments with drastically different medications and approaches, as such, early and accurate diagnosis of WMD, derived from vascular or demyelinating etiologies, is of paramount importance. However, the clinical and imaging similarities between MS, especially during the early stage, and CSVD, pose a significant dilemma in differentiating these two conditions. In this review, we attempt to summarize and contrast the distinguishing features of MS and CSVD for aiding accurate diagnosis to ensure timely corresponding management in the early stages of MS and CSVD.

CD4+ T cells aggravate hemorrhagic brain injury.

Leukocyte infiltration accelerates brain injury following intracerebral hemorrhage (ICH). Yet, the involvement of T lymphocytes in this process has not been fully elucidated. Here, we report that CD4+ T cells accumulate in the perihematomal regions in the brains of patients with ICH and ICH mouse models. T cells activation in the ICH brain is concurrent with the course of perihematomal edema (PHE) development, and depletion of CD4+ T cells reduced PHE volumes and improved neurological deficits in ICH mice. Single-cell transcriptomic analysis revealed that brain-infiltrating T cells exhibited enhanced proinflammatory and proapoptotic signatures. Consequently, CD4+ T cells disrupt the blood-brain barrier integrity and promote PHE progression through interleukin-17 release; furthermore, the TRAIL-expressing CD4+ T cells engage DR5 to trigger endothelial death. Recognition of T cell contribution to ICH-induced neural injury is instrumental for designing immunomodulatory therapies for this dreadful disease.

Plasma Neurofilament Light Chain Predicts Mortality and Long-Term Neurological Outcomes in Patients with Intracerebral Hemorrhage.

Patients with intracerebral hemorrhage (ICH) often suffer from heterogeneous long-term neurological deficits, such as cognitive decline. Our ability to measure secondary brain injury to predict the long-term outcomes of these patients is limited. We investigated whether the blood neurofilament light chain (NfL) can monitor brain injury and predict long-term outcomes in patients with ICH. We enrolled 300 patients with first-episode ICH within 24 h recruited in the Chinese Cerebral Hemorrhage Mechanisms and Intervention study cohort from January 2019 to June 2020. Patients were prospectively followed up for 12 months. Blood samples were collected from 153 healthy participants. Plasma NfL levels determined using a single-molecule array revealed a biphasic increase in plasma NfL in ICH patients compared to healthy controls, with the first peak at around 24 h and a second elevation from day 7 through day 14 post-ICH. Plasma NfL levels were positively correlated with hemorrhage volume, National Institute of Health Stroke Scale, and Glasgow Coma Scale scores of ICH patients. Higher NfL concentration within 72 h after ictus was independently associated with 6- and 12-month worsened functional outcomes (modified Rankin Scale ≥ 3) and higher all-cause mortality. Magnetic resonance imaging and cognitive function evaluation were available for 26 patients at 6 months post-ICH, and NfL levels measured 7 days post-ictus correlated with decreased white matter fiber integrity and poor cognitive function at 6 months after stroke. These findings suggest that blood NfL is a sensitive marker for monitoring axonal injury post-ICH and can predict long-term functional ability and survival.

Targeting CCL5 signaling attenuates neuroinflammation after seizure.

BACKGROUND: Epilepsy is a neurological condition that causes unprovoked, recurrent seizures. Accumulating evidence from clinical and experimental studies indicates that neuroinflammation exacerbates seizure activity. METHODS: We investigated the transcriptional changes occurring in specific brain domains of a seizure mouse model, using 10× Genomics spatial transcriptomics. Differential gene expression and pathway analysis were applied to investigate potential signaling targets for seizure, including CCL5/CCR5 pathway. Maraviroc, an FDA-approved C-C chemokine receptor 5 (CCR5) antagonist, was used to verify the impact of CCL5/CCR5 signaling in seizure mice. RESULTS: We found distinguished regional transcriptome features in the hippocampus of seizure mice. The hippocampus exhibited unique inflammatory gene signatures, including glia activation, apoptosis, and immune response in seizure mice. Especially, we observed notable expression of C-C chemokine ligand 5 (CCL5) throughout the entire seizure hippocampus. Blockade of CCL5/CCR5 signaling via maraviroc prevented microglia activation and neuron degeneration in seizure mice. CONCLUSIONS: This study supports the potential of CCL5/CCR5 signaling for targeting neuroinflammation after seizure.

Brain-derived programmed death-ligand 1 mediates immunosuppression post intracerebral hemorrhage.

Immunosuppression commonly occurs after a stroke, which is believed to be associated with the increased risk of infectious comorbidities of stroke patients, while the mechanisms underlying post-stroke immunosuppression is yet to be elucidated. In the brains of intracerebral hemorrhage (ICH) patients and murine ICH models, we identified that neuron-derived programmed death-ligand 1 (PD-L1) is reduced in the perihematomal area, associating increased soluble PD-L1 level in the peripheral blood. ICH induced a significant decrease of T and natural killer (NK) cell numbers in the periphery with an upregulation of programed death-1 (PD-1) in these cells. Blocking PD-1 pathway with an anti-PD1 monoclonal antibody prevented the T and NK cell compartment contraction and spleen atrophy post-ICH, with reduced pulmonary bacterial burden and improved neurological outcome. Thus, we here identified that brain-derived PD-L1 as a new mechanism driving post-stroke immunosuppression, and anti-PD1 treatment could be potentially developed to reducing the risk of post-stroke infections.

Bone marrow hematopoiesis drives multiple sclerosis progression.

Multiple sclerosis (MS) is a T cell-mediated autoimmune disease of the central nervous system (CNS). Bone marrow hematopoietic stem and progenitor cells (HSPCs) rapidly sense immune activation, yet their potential interplay with autoreactive T cells in MS is unknown. Here, we report that bone marrow HSPCs are skewed toward myeloid lineage concomitant with the clonal expansion of T cells in MS patients. Lineage tracing in experimental autoimmune encephalomyelitis, a mouse model of MS, reveals remarkable bone marrow myelopoiesis with an augmented output of neutrophils and Ly6Chigh monocytes that invade the CNS. We found that myelin-reactive T cells preferentially migrate into the bone marrow compartment in a CXCR4-dependent manner. This aberrant bone marrow myelopoiesis involves the CCL5-CCR5 axis and augments CNS inflammation and demyelination. Our study suggests that targeting the bone marrow niche presents an avenue to treat MS and other autoimmune disorders.

Endothelial BACE1 Impairs Cerebral Small Vessels via Tight Junctions and eNOS.

BACKGROUND: Cerebral small vessel injury, including loss of endothelial tight junctions, endothelial dysfunction, and blood-brain barrier breakdown, is an early and typical pathology for Alzheimer's disease, cerebral amyloid angiopathy, and hypertension-related cerebral small vessel disease. Whether there is a common mechanism contributing to these cerebrovascular alterations remains unclear. Studies have shown an elevation of BACE1 (ß-site amyloid precursor protein cleaving enzyme 1) in cerebral vessels from cerebral amyloid angiopathy or Alzheimer's disease patients, suggesting that vascular BACE1 may involve in cerebral small vessel injury. METHODS: To understand the contribution of vascular BACE1 to cerebrovascular impairments, we combined cellular and molecular techniques, mass spectrometry, immunostaining approaches, and functional testing to elucidate the potential pathological mechanisms. RESULTS: We observe a 3.71-fold increase in BACE1 expression in the cerebral microvessels from patients with hypertension. Importantly, we discover that an endothelial tight junction protein, occludin, is a completely new substrate for endothelial BACE1. BACE1 cleaves occludin with full-length occludin reductions and occludin fragment productions. An excessive cleavage by elevated BACE1 induces membranal accumulation of caveolin-1 and subsequent caveolin-1-mediated endocytosis, resulting in lysosomal degradation of other tight junction proteins. Meanwhile, membranal caveolin-1 increases the binding to eNOS (endothelial nitric oxide synthase), together with raised circulating Aß (ß-amyloid peptides) produced by elevated BACE1, leading to an attenuation of eNOS activity and resultant endothelial dysfunction. Furthermore, the initial endothelial damage provokes chronic reduction of cerebral blood flow, blood-brain barrier leakage, microbleeds, tau hyperphosphorylation, synaptic loss, and cognitive impairment in endothelial-specific BACE1 transgenic mice. Conversely, inhibition of aberrant BACE1 activity ameliorates tight junction loss, endothelial dysfunction, and memory deficits. CONCLUSIONS: Our findings establish a novel and direct relationship between endothelial BACE1 and cerebral small vessel damage, indicating that abnormal elevation of endothelial BACE1 is a new mechanism for cerebral small vessel disease pathogenesis.

O-GlcNAcase inhibitor has protective effects in intracerebral hemorrhage by suppressing the inflammatory response.

BACKGROUND: Intracerebral hemorrhage (ICH) is aggravated by immune cells that participate in the inflammatory response from the blood-brain barrier (BBB). O-Glycosylation has been reported to regulate the inflammatory response in the central nervous system but its cerebral protective effects remain unknown. Therefore, this study was carried out to investigate the protective effects of O-GlcNAcylation in a murine model of ICH and the possible mechanisms involved. METHODS: The effects of O-GlcNAcylation on hematoma and edema formation were tested using pathological and dry/wet weight methods, whereas its effects on neural function were determined using neurologic tests. The effect of O-GlcNAcylation on BBB integrity was determined by Evans blue dye extrusion. Flow cytometry was used to quantify the immune cells in the central nervous system. Immunofluorescence was used to detect the protective effect of O-GlcNAcylation in ICH. RESULTS: The hematoma volume was significantly lower in the prevention and treatment groups than in the control group after ICH induction, indicating that O-GlcNAcylation had reduced the formation of cerebral hematoma in ICH. In the prevention and treatment groups, the modified neurological severity score, corner turn test and rotating rod test results were improved and the BBB integrity was better than that in the control group. O-GlcNAcylation also regulated the microglia, neutrophils and other central nervous system immune cells after ICH, effectively reducing the inflammatory response. CONCLUSIONS: O-GlcNAcylation played an important role in suppressing the inflammatory response, enhancing the BBB integrity and reducing edema after ICH.

Brain injury instructs bone marrow cellular lineage destination to reduce neuroinflammation.

Acute brain injury mobilizes circulating leukocytes to transmigrate into the perivascular space and brain parenchyma. This process amplifies neural injury. Bone marrow hematopoiesis replenishes the exhausted peripheral leukocyte pools. However, it is not known whether brain injury influences the development of bone marrow lineages and how altered hematopoietic cell lineages affect neurological outcome. Here, we showed that bone marrow hematopoietic stem cells (HSCs) can be swiftly skewed toward the myeloid lineage in patients with intracerebral hemorrhage (ICH) and experimental ICH models. Lineage tracing revealed a predominantly augmented hematopoiesis of Ly6Clow monocytes infiltrating the ICH brain, where they generated alternatively activated macrophages and suppressed neuroinflammation and brain injury. The ICH brain uses ß3-adrenergic innervation that involves cell division cycle 42 to promote bone marrow hematopoiesis of Ly6Clow monocytes, which could be further potentiated by the U.S. Food and Drug Administration-approved ß3-adrenergic agonist mirabegron. Our results suggest that brain injury modulates HSC lineage development to curb distal brain inflammation, implicating the bone marrow as a unique niche for self-protective neuroimmune interaction that might be exploited to obtain therapeutic effects.

Low-dose rituximab treatment for new-onset generalized myasthenia gravis.

The aim of this retrospective case series study was to evaluate the response and durability of rituximab in patients with new-onset acetylcholine receptor positive (AChR +) generalized myasthenia gravis (MG). Patients were initiated with low-dose rituximab treatment within 3.5 months of onset without concomitant oral immunosuppressants. Seventeen patients (89%) remained relapse-free with a mean follow-up of 51.3 months. Clinical improvement was observed in parallel with the maintenance of low-dose corticosteroids or the complete discontinuation of corticosteroids. Long-term depletion of B cells with low-dose rituximab treatment has shown favorable efficacy and tolerance in reducing disease activity for AChR+ generalized MG.

tPA Mobilizes Immune Cells That Exacerbate Hemorrhagic Transformation in Stroke.

RATIONALE: Hemorrhagic complications represent a major limitation of intravenous thrombolysis using tPA (tissue-type plasminogen activator) in patients with ischemic stroke. The expression of tPA receptors on immune cells raises the question of what effects tPA exerts on these cells and whether these effects contribute to thrombolysis-related hemorrhagic transformation. OBJECTIVE: We aim to determine the impact of tPA on immune cells and investigate the association between observed immune alteration with hemorrhagic transformation in ischemic stroke patients and in a rat model of embolic stroke. METHODS AND RESULTS: Paired blood samples were collected before and 1 hour after tPA infusion from 71 patients with ischemic stroke. Control blood samples were collected from 27 ischemic stroke patients without tPA treatment. A rat embolic middle cerebral artery occlusion model was adopted to investigate the underlying mechanisms of hemorrhagic transformation. We report that tPA induces a swift surge of circulating neutrophils and T cells with profoundly altered molecular features in ischemic stroke patients and a rat model of focal embolic stroke. tPA exacerbates endothelial injury, increases adhesion and migration of neutrophils and T cells, which are associated with brain hemorrhage in rats subjected to embolic stroke. Genetic ablation of annexin A2 in neutrophils and T cells diminishes the effect of tPA on these cells. Decoupling the interaction between mobilized neutrophils/T cells and the neurovascular unit, achieved via a S1PR (sphingosine-1-phosphate receptor) 1 modulator RP101075 and a CCL2 (C-C motif chemokine ligand 2) synthesis inhibitor bindarit, which block lymphocyte egress and myeloid cell recruitment, respectively, attenuates hemorrhagic transformation and improves neurological function after tPA thrombolysis. CONCLUSIONS: Our findings suggest that immune invasion of the neurovascular unit represents a previously unrecognized mechanism underlying tPA-mediated brain hemorrhage, which can be overcome by precise immune modulation during thrombolytic therapy.

Neuroblast senescence in the aged brain augments natural killer cell cytotoxicity leading to impaired neurogenesis and cognition.

Normal aging is accompanied by escalating systemic inflammation. Yet the potential impact of immune homeostasis on neurogenesis and cognitive decline during brain aging have not been previously addressed. Here we report that natural killer (NK) cells of the innate immune system reside in the dentate gyrus neurogenic niche of aged brains in humans and mice. In situ expansion of these cells contributes to their abundance, which dramatically exceeds that of other immune subsets. Neuroblasts within the aged dentate gyrus display a senescence-associated secretory phenotype and reinforce NK cell activities and surveillance functions, which result in NK cell elimination of aged neuroblasts. Genetic or antibody-mediated depletion of NK cells leads to sustained improvements in neurogenesis and cognitive function during normal aging. These results demonstrate that NK cell accumulation in the aging brain impairs neurogenesis, which may serve as a therapeutic target to improve cognition in the aged population.

Cortical Thinning and Ventricle Enlargement in Neuromyelitis Optica Spectrum Disorders.

Background: In neuromyelitis optica spectrum disorders (NMOSDs), inflammation is not the sole driver of accumulation of disability; neurodegeneration is another important pathological process. We aim to explore different patterns of cortical atrophy and ventricular enlargement in NMOSD. Methods: We retrospectively analyzed a cohort of 230 subjects, comprising 55 healthy controls (HCs), 85 multiple sclerosis (MS), and 90 NMOSD patients from Tianjin Medical University General Hospital and Beijing Tiantan Hospital. Different compartments of the brain (total gray, cortex, subcortex gray, and ventricle volume) were evaluated with the FreeSurfer. Multiple linear regressions were adopted to explore associations between cortex volume and predict factors. Results: Compared with HCs, NMOSD, and MS displayed an enlarged lateral and third ventricle (p < 0.001), whereas expansion of the fourth ventricle was observed in MS rather than NMOSD (p = 0.321). MS and NMOSD patients exhibited cortical thinning in comparison with HCs. However, pronounced cortical atrophy were only significant in pre-cuneus, parahippocampal, and lateral occipital lobe between MS and NMOSD. Patients with NMOSD had decreased local gyrification index in orbitofrontal and pre-cuneus lobe, and reduced pial surface area. Linear regression analysis revealed cortex volume were predicated by advanced age (standardized ß = -0.404, p = 0.001) as well as prolonged disease history (standardized ß = -0.311, p = 0.006). Conclusion: NMOSD exhibited global cortex atrophy with enlarged lateral and third ventricles. Moreover, cortex volume is associated with age and disease duration.