High-salt diet downregulates TREM2 expression and blunts efferocytosis of macrophages after acute ischemic stroke.

BACKGROUND: A high-salt diet (HSD) is one of the major risk factors for acute ischemic stroke (AIS). As a potential mechanism, surplus salt intake primes macrophages towards a proinflammatory phenotype. In this study, whether HSD could blunt the efferocytic capability of macrophages after ischemic stroke, thus exacerbating post-stroke neural inflammation, was investigated. METHODS: Wild-type male C57BL/6 mice were fed with fodder containing 8% sodium chloride for 4 weeks and subjected to transient middle cerebral occlusion (tMCAO). Disease severity, macrophage polarization as well as efferocytic capability were evaluated. Bone marrow-derived macrophages were cultured in vitro, and the impact of high salinity on their efferocytic activity, as well as their expression of phagocytic molecules, were analyzed. The relationships among sodium concentration, macrophage phenotype, and disease severity in AIS patients were explored. RESULTS: HSD-fed mice displayed increased infarct volume and aggravated neurological deficiency. Mice fed with HSD suffered exacerbated neural inflammation as shown by higher inflammatory mediator expression and immune cell infiltration levels. Infiltrated macrophages within stroke lesions in HSD-fed mice exhibited a shift towards proinflammatory phenotype and impaired efferocytic capability. As assessed with a PCR array, the expression of triggering receptor expressed on myeloid cells 2 (TREM2), a receptor relevant to phagocytosis, was downregulated in high-salt-treated bone marrow-derived macrophages. Enhancement of TREM2 signaling restored the efferocytic capacity and cellular inflammation resolution of macrophages in a high salinity environment in vitro and in vivo. A high concentration of urine sodium in AIS patients was found to be correlated with lower TREM2 expression and detrimental stroke outcomes. CONCLUSIONS: HSD inhibited the efferocytic capacity of macrophages by downregulating TREM2 expression, thus impeding inflammation resolution after ischemic stroke. Enhancing TREM2 signaling in monocytes/macrophages could be a promising therapeutic strategy to enhance efferocytosis and promote post-stroke inflammation resolution.

Myelin oligodendrocyte glycoprotein-associated disorders are associated with HLA subtypes in a Chinese paediatric-onset cohort.

OBJECTIVE: Myelin oligodendrocyte glycoprotein-associated disorders (MOGADs) are a rare new neurological autoimmune disease with unclear pathogenesis. Since a linkage of the disease to the human leucocyte antigen (HLA) has not been shown, we here investigated whether MOGAD is associated with the HLA locus. METHODS: HLA genotypes of 95 patients with MOGADs, assessed between 2016 and 2018 from three academic centres, were compared with 481 healthy Chinese Han individuals. Patients with MOGADs included 51 paediatric-onset and 44 adult-onset cases. All patients were seropositive for IgG targeting the myelin oligodendrocyte glycoprotein (MOG). RESULTS: Paediatric-onset MOGAD was associated with the DQB1*05:02-DRB1*16:02 alleles (OR=2.43; OR=3.28) or haplotype (OR=2.84) of HLA class II genes. The prevalence of these genotypes in patients with paediatric-onset MOGAD was significantly higher than healthy controls (padj=0.0154; padj=0.0221; padj=0.0331). By contrast, adult-onset MOGAD was not associated with any HLA genotype. Clinically, patients with the DQB1*05:02-DRB1*16:02 haplotype exhibited significantly higher expanded disability status scale scores at onset (p=0.004) and were more likely to undergo a disease relapse (p=0.030). HLA-peptide binding prediction algorithms and computational docking analysis provided supporting evidence for the close relationship between the MOG peptide subunit and DQB1*05:02 allele. In vitro results indicated that site-specific mutations of the predicted target sequence reduced the antigen-antibody binding, especially in the paediatric-onset group with DQB1*05:02 allele. CONCLUSIONS: This study demonstrates a possible association between specific HLA class II alleles and paediatric-onset MOGAD, providing evidence for the conjecture that different aetiology and pathogenesis likely underlie paediatric-onset and adult-onset cases of MOGAD.

Chloride channel-3 mediates multidrug resistance of cancer by upregulating P-glycoprotein expression.

Chloride channel-3 (ClC-3), a member of the ClC family of voltage-gated Cl- channels, is involved in the resistance of tumor cells to chemotherapeutic drugs. Here, we report a new mechanism for ClC-3 in mediating multidrug resistance (MDR). ClC-3 was highly expressed in the P-glycoprotein (P-gp)-dependent human lung adenocarcinoma cell line (A549)/paclitaxel (PTX) and the human breast carcinoma cell line (MCF-7)/doxorubicin (DOX) resistant cells. Changes in the ClC-3 expression resulted in the development of drug resistance in formerly drug-sensitive A549 or MCF-7 cells, and drug sensitivity in formerly drug-resistant A549/Taxol and MCF-7/DOX cells. Double transgenic MMTV-PyMT/CLCN3 mice with spontaneous mammary cancer and ClC-3 overexpression demonstrated drug resistance to PTX and DOX. ClC-3 expression upregulated the expression of MDR1 messenger RNA and P-gp by activating the nuclear factor-κB (NF-κB)-signaling pathway. These data suggest that ClC-3 expression in cancer cells induces MDR by upregulating NF-κB-signaling-dependent P-gp expression involving another new mechanism for ClC-3 in the development of drug resistance of cancers.

Chronic Stress Exacerbates Cerebral Amyloid Angiopathy Through Promoting Neutrophil Extracellular Traps Formation.

Cerebral amyloid angiopathy (CAA) is the leading cause of vascular dementia among the elderly. Neuropsychiatric symptoms are commonly manifested in cerebral amyloid angiopathy patients but are usually considered as consequences of cerebral amyloid angiopathy pathology. Here, it is reported that chronic stress promotes cerebral amyloid angiopathy progression, which enhances deposition of amyloid protein beta (Aß) in brain blood vessels and exacerbates subsequent brain injury. Mechanistically, neutrophil is implicated in cerebral amyloid angiopathy development. Aß that accumulates in brain vasculature induces neutrophil extracellular traps (NETs) by activating STAT6 signaling, which inhibits neutrophil apoptosis and switches the programmed cell death toward NETosis. During chronic stress, circulatory Norepinephrine (NE) strengthens STAT6 activation in neutrophil and promotes NET formation, thus exacerbates the NET-dependent angiopathy. It is demonstrated that inhibiting neutrophil chemotaxis towards brain or suppressing NET formation both ameliorate cerebral amyloid angiopathy severity in the context of chronic stress. Therefore, it is proposed that stress-associated psychological disorders and NETs are promising therapeutic targets in cerebral amyloid angiopathy.

Bone marrow-derived mesenchymal stem cell ameliorates post-stroke enterobacterial translocation through liver-gut axis.

BACKGROUND: Enterobacterial translocation is a leading contributor to fatal infection among patients with acute ischaemic stroke (AIS). Accumulative evidence suggests that mesenchymal stem cell (MSC) effectively ameliorates stroke outcomes. Whether MSC could inhibit post-stroke enterobacterial translocation remains elusive. METHODS: Patients with AIS and healthy individuals were enrolled in the study. Mice subjected to transient middle cerebral artery occlusion were treated with bone marrow-derived MSC (BM-MSC) right after reperfusion. Enterobacterial translocation was evaluated with Stroke Dysbiosis Index and circulating endotoxin. Thickness of mucus was assessed with Alcian blue staining. Hepatic glucocorticoid (GC) metabolism was analysed with expression of HSD11B2, HSD11B1 and SRD5A1. RESULTS: We report that the gut mucus layer was attenuated after the stroke leading to pronounced enterobacterial translocation. The attenuation of the gut mucus was attributed to diminished mucin production by goblet cells in response to the elevated systemic GC after cerebral ischaemia. Transferred-BM-MSC restored the mucus thickness, thus preserving gut microbiota homeostasis and preventing enterobacterial invasion. Mechanistically, the transferred-BM-MSC stationed in the liver and enhanced peroxisome proliferator-activated receptor γ signalling in hepatocytes. Consequently, expression of HSD11B2 and SRD5A1 was increased while HSD11B1 expression was downregulated which promoted GC catabolism and subsequently restored mucin production. CONCLUSIONS: Our findings reveal that MSC transfer improves post-stroke gut barrier integrity and inhibits enterobacterial translocation by enhancing the hepatic GC metabolism thus representing a protective modulator of the liver-gut-brain axis in AIS.

Myelin endocytosis by brain endothelial cells causes endothelial iron overload and oligodendroglial iron hunger in hypoperfusion-induced white matter injury.

AIMS: Hypoperfusion induces significant white matter injury in cerebral vascular disorders, including arteriosclerotic cerebral small vessel disease (aCSVD), which is prevalent among the elderly. Iron transport by blood vessel endothelial cells (BVECs) from the periphery supports oligodendrocyte maturation and white matter repair. This study aims to elucidate the association between iron homeostasis changes and white matter injury severity, and explore the crosstalk between BVECs and oligodendroglial lineage cells. METHODS: In vivo: C57BL/6 mice were subjected to unilateral common carotid artery occlusion (UCCAO). In vitro: BVECs with myelin pretreatment were co-cultured with oligodendrocyte progenitor cells (OPCs) or organotypic cerebellar slices subjected to oxygen and glucose deprivation. RESULTS: Circulatory iron tends to be stored in aCSVD patients with white matter injury. Myelin debris endocytosis by BVECs impairs iron transport, trapping iron in the blood and away from the brain, worsening oligodendrocyte iron deficiency in hypoperfusion-induced white matter injury. Iron accumulation in BVECs triggers ferroptosis, suppressing iron transport and hindering white matter regeneration. Intranasal holo-transferrin (hTF) administration bypassing the BBB alleviates oligodendrocyte iron deficiency and promotes myelin regeneration in hypoperfusion-induced white matter injury. CONCLUSION: The iron imbalance between BVECs and oligodendroglial lineage cells is a potential therapeutic target in hypoperfusion-induced white matter injury.

Agomelatine promotes differentiation of oligodendrocyte precursor cells and preserves white matter integrity after cerebral ischemic stroke.

White matter injury contributes to neurological disorders after acute ischemic stroke (AIS). The repair of white matter injury is dependent on the re-myelination by oligodendrocytes. Both melatonin and serotonin antagonist have been proved to protect against post-stroke white matter injury. Agomelatine (AGM) is a multi-functional treatment which is both a melatonin receptor agonist and selective serotonin receptor antagonist. Whether AGM protects against white matter injury after stroke and the underlying mechanisms remain elusive. Here, using the transient middle cerebral artery occlusion (tMCAO) model, we evaluated the therapeutic effects of AGM in stroke mice. Sensorimotor and cognitive functions, white matter integrity, oligodendroglial regeneration and re-myelination in stroke hemisphere after AGM treatment were analyzed. We found that AGM efficiently preserved white matter integrity, reduced brain tissue loss, attenuated long-term sensorimotor and cognitive deficits in tMCAO models. AGM treatment promoted OPC differentiation and enhanced re-myelination both in vitro, ex vivo and in vivo, although OPC proliferation was unaffected. Mechanistically, AGM activated low density lipoprotein receptor related protein 1 (LRP1), peroxisome proliferator-activated receptor γ (PPARγ) signaling thus promoted OPC differentiation and re-myelination after stroke. Inhibition of PPARγ or knock-down of LRP1 in OPCs reversed the beneficial effects of AGM. Altogether, our data indicate that AGM represents a novel therapy against white matter injury after cerebral ischemia.

Melatonin Offers Dual-Phase Protection to Brain Vessel Endothelial Cells in Prolonged Cerebral Ischemia-Recanalization Through Ameliorating ER Stress and Resolving Refractory Stress Granule.

Ischemic-reperfusion injury limits the time window of recanalization therapy in cerebral acute ischemic stroke (AIS). Brain vessel endothelial cells (BVECs) form the first layer of the blood-brain barrier (BBB) and are thus the first sufferer of ischemic-reperfusion disorder. The current study demonstrates that melatonin can reduce infarct volume, alleviate brain edema, ameliorate neurological deficits, and protect BBB integrity in prolonged-stroke mice. Here, we demonstrate that endoplasmic reticulum (ER)-associated injury contributes to BVEC death in the dural phase of reperfusion after prolonged ischemia. When encountering ischemia, ER stress arises, specifically activating PERK-EIF2α signaling and the subsequent programmed cell death. Prolonged ischemia leads stress granules (SGs) to be refractory, which remain unresolved and accumulate in ER during recanalization. During reperfusion, refractory SGs activate PKR-EIF2α and further exacerbate BVEC injury. We report that melatonin treatment downregulates ER stress in the ischemic period and enhances dissociation of the refractory SGs during reperfusion, thus offering dual-phase protection to BVECs in prolonged cerebral stroke. Mechanistically, melatonin enhances autophagy in BVECs, which preserves ER function and resolves refractory SGs. We, therefore, propose that melatonin is a potential treatment to extend the time window of delayed recanalization therapy in AIS.

Identification of fecal microbiome signatures associated with familial longevity and candidate metabolites for healthy aging.

Gut microbiota associated with longevity plays an important role in the adaptation to damaging stimuli accumulated during the aging process. The mechanism by which the longevity-associated microbiota protects the senescent host remains unclear, while the metabolites of the gut bacteria are of particular interest. Here, an integrated analysis of untargeted metabolomics and 16S rRNA gene sequencing was used to characterize the metabolite and microbiota profiles of long-lived individuals (aged ≥90 years) in comparison to old-elderly (aged 75-89 years), young-elderly (aged 60-74 years), and young to middle-aged (aged ≤59 years) individuals. This novel study constructed both metabolite and microbiota trajectories across aging in populations from Jiaoling county (the seventh longevity town of the world) in China. We found that the long-lived group exhibited remarkably differential metabolomic signatures, highlighting the existence of metabolic heterogeneity with aging. Importantly, we also discovered that long-lived individuals from the familial longevity cohort harbored a microbiome distinguished from that of the general population. Specifically, we identified that the levels of a candidate metabolite, pinane thromboxane A2 (PTA2), which is positively associated with aging, were consistently higher in individuals with familial longevity and their younger descendants than in those of the general population. Furtherly, functional analysis revealed that PTA2 potentiated the efficiency of microglial phagocytosis of ß-amyloid 40 and enhanced an anti-inflammatory phenotype, indicating a protective role of PTA2 toward host health. Collectively, our results improve the understanding of the role of the gut microbiome in longevity and may facilitate the development of strategies for healthy aging.

A novel rare variant of CNPY3 from familial NMOSD impairs the TLR-mediated immune response.

Toll-like receptors (TLRs) are a class of proteins that play essential roles in innate and adaptive immune responses. Recently, accumulating evidence has demonstrated that impairments in the TLR signalling pathway contribute to the development and progression of neuroimmune diseases, such as neuromyelitis optica spectrum disorder (NMOSD). However, the cellular and molecular mechanisms are still largely unknown. In this study, we report a novel variant, C52Y, of canopy FGF signalling regulator 3 (CNPY3) from patients with familial NMOSD and demonstrate that this variant shows a stronger interaction with GP96 and TLRs than with wild-type CNPY3. We find that C52Y has dominant negative effects on TLR4 surface expression. Importantly, the TLR4 surface expression level is decreased in RAW264.7 cells infected with the C52Y virus upon LPS stimulation. We further demonstrate that bone marrow-derived macrophages (BMDMs) from CNPY3C52Y/+ transgenic mice secrete less tumour necrosis factor (TNF) and interleukin (IL)-6 than BMDMs from wild-type mice upon stimulation with LPS. These data suggest that impairment of TLR trafficking may contribute to the development of neuroimmune disorders.

Bone Marrow Mesenchymal Stem Cell-Derived Dermcidin-Containing Migrasomes enhance LC3-Associated Phagocytosis of Pulmonary Macrophages and Protect against Post-Stroke Pneumonia.

Pneumonia is one of the leading causes of death in patients with acute ischemic stroke (AIS). Antibiotics fail to improve prognosis of patients with post-stroke pneumonia, albeit suppressing infection, due to adverse impacts on the immune system. The current study reports that bone marrow mesenchymal stem cells (BM-MSC) downregulate bacterial load in the lungs of stroke mice models. RNA-sequencing of the lung from BM-MSC-treated stroke models indicates that BM-MSC modulates pulmonary macrophage activities after cerebral ischemia. Mechanistically, BM-MSC promotes the bacterial phagocytosis of pulmonary macrophages through releasing migrasomes, which are migration-dependent extracellular vesicles. With liquid chromatography-tandem mass spectrometry (LC-MS/MS), the result shows that BM-MSC are found to load the antibacterial peptide dermcidin (DCD) in migrasomes upon bacterial stimulation. Besides the antibiotic effect, DCD enhances LC3-associated phagocytosis (LAP) of macrophages, facilitating their bacterial clearance. The data demonstrate that BM-MSC is a promising therapeutic candidate against post-stroke pneumonia, with dual functions of anti-infection and immunol modulation, which is more than a match for antibiotics treatment.

Macrophage lineage cells-derived migrasomes activate complement-dependent blood-brain barrier damage in cerebral amyloid angiopathy mouse model.

Accumulation of amyloid beta protein (Aß) in brain vessels damages blood brain barrier (BBB) integrity in cerebral amyloid angiopathy (CAA). Macrophage lineage cells scavenge Aß and produce disease-modifying mediators. Herein, we report that Aß40-induced macrophage-derived migrasomes are sticky to blood vessels in skin biopsy samples from CAA patients and brain tissue from CAA mouse models (Tg-SwDI/B and 5xFAD mice). We show that CD5L is packed in migrasomes and docked to blood vessels, and that enrichment of CD5L impairs the resistance to complement activation. Increased migrasome-producing capacity of macrophages and membrane attack complex (MAC) in blood are associated with disease severity in both patients and Tg-SwDI/B mice. Of note, complement inhibitory treatment protects against migrasomes-mediated blood-brain barrier injury in Tg-SwDI/B mice. We thus propose that macrophage-derived migrasomes and the consequent complement activation are potential biomarkers and therapeutic targets in CAA.

Identification of Medium-Length Antineurofilament Autoantibodies in Patients with Anti-N-Methyl-D-Aspartate Receptor Encephalitis.

BACKGROUND AND PURPOSE: Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is a severe central nervous system disorder mediated by NMDAR antibodies that damages neurons. We investigated the correlation between cytoskeletal autoantibodies and the clinical severity in patients with anti-NMDAR encephalitis. METHODS: Non-NMDAR autoantibodies were identified by screening matched cerebrospinal fluid (CSF) and the serum samples of 45 consecutive patients with anti-NMDAR encephalitis and 60 healthy individuals against N-methyl-D-aspartate receptor 1-transfected and nontransfected human embryonic kidney 293T cells. Immunocytochemistry was performed to assess antibody binding in rat brain sections and primary cortical neurons. Cell-based assays and Western blotting were applied to identify autoantibodies targeting medium neurofilaments (NFMs). We compared clinical characteristics between patients with NMDAR encephalitis who were positive and negative for anti-NFM-autoantibodies. RESULTS: Anti-NFM autoantibodies were detected in both the serum and CSF in one patient (2%) and in the serum only in six patients (13%). No antibodies were detected in the serum of healthy controls (7/45 vs. 0/60, p=0.0016). Four of the seven patients with anti-NFM autoantibodies in serum were children (57%), and three (43%) had abnormalities in brain magnetic resonance imaging. These patients responded well to immunotherapy, and either no significant or only mild disability was observed at the last follow-up. Anti-NMDAR encephalitis did not differ with the presence of anti-NFM autoantibodies. CONCLUSIONS: Anti-NFM autoantibodies may be present in patients with anti-NMDAR encephalitis, indicating underlying neuronal damage. A large cohort study is warranted to investigate the clinical differences between patients with NMDAR encephalitis according to their anti-NFM antibody status.

Myelin Oligodendrocyte Glycoprotein-IgG Contributes to Oligodendrocytopathy in the Presence of Complement, Distinct from Astrocytopathy Induced by AQP4-IgG.

Immunoglobulin G against myelin oligodendrocyte glycoprotein (MOG-IgG) is detectable in neuromyelitis optica spectrum disorder (NMOSD) without aquaporin-4 IgG (AQP4-IgG), but its pathogenicity remains unclear. In this study, we explored the pathogenic mechanisms of MOG-IgG in vitro and in vivo and compared them with those of AQP4-IgG. MOG-IgG-positive serum induced complement activation and cell death in human embryonic kidney (HEK)-293T cells transfected with human MOG. In C57BL/6 mice and Sprague-Dawley rats, MOG-IgG only caused lesions in the presence of complement. Interestingly, AQP4-IgG induced astroglial damage, while MOG-IgG mainly caused myelin loss. MOG-IgG also induced astrocyte damage in mouse brains in the presence of complement. Importantly, we also observed ultrastructural changes induced by MOG-IgG and AQP4-IgG. These findings suggest that MOG-IgG directly mediates cell death by activating complement in vitro and producing NMOSD-like lesions in vivo. AQP4-IgG directly targets astrocytes, while MOG-IgG mainly damages oligodendrocytes.

Brain histopathological study and prognosis in MOG antibody-associated demyelinating pseudotumor.

Our objective was to examine the brain biopsies by histopathology and investigate the prognosis of patients with myelin oligodendrocyte glycoprotein antibody-associated demyelinating pseudotumor. The clinical, MRI, and histological features of two patients with myelin oligodendrocyte glycoprotein antibody-associated demyelinating pseudotumor were reviewed. Both patients were treated with steroid plus rituximab and followed up. The brain biopsies of both cases revealed T cells, macrophages, and complement-mediated demyelination, which was in accord with multiple sclerosis-like pathology. Moreover, both cases showed favorable response to steroid plus rituximab therapy. Our cases add a new variant to the myelin oligodendrocyte glycoprotein-encephalomyelitis spectrum, which favorably responds to immunotherapy.