Astrocytic neogenin/netrin-1 pathway promotes blood vessel homeostasis and function in mouse cortex

Netrin-1-engineered endothelial cell exosomes induce the formation of pre-regenerative niche to accelerate peripheral nerve repair

The formation of vascular niche is pivotal during the early stage of peripheral nerve regeneration. Nevertheless, the mechanisms of vascular niche in the regulation of peripheral nerve repair remain unclear. Netrin-1 (NTN1) was found up-regulated in nerve stump after peripheral nerve injury (PNI). Herein, we demonstrated that NTN1-high endothelial cells (NTN1+ECs) were the critical component of vascular niche, fostering angiogenesis, axon regeneration, and repair-related phenotypes. We also found that NTN1+EC-derived exosomes (NTN1 EC-EXO) were involved in the formation of vascular niche as a critical role. Multi-omics analysis further verified that NTN1 EC-EXO carried a low-level expression of let7a-5p and activated key pathways associated with niche formation including focal adhesion, axon guidance, phosphatidylinositol 3-kinase-AKT, and mammalian target of rapamycin signaling pathway. Together, our study suggested that the construction of a pre-regenerative niche induced by NTN1 EC-EXO could establish a beneficial microenvironment for nerve repair and facilitate functional recovery after PNI.

Kdm6a-CNN1 axis orchestrates epigenetic control of trauma-induced spinal cord microvascular endothelial cell senescence to balance neuroinflammation for improved neurological repair

Cellular senescence assumes pivotal roles in various diseases through the secretion of proinflammatory factors. Despite extensive investigations into vascular senescence associated with aging and degenerative diseases, the molecular mechanisms governing microvascular endothelial cell senescence induced by traumatic stress, particularly its involvement in senescence-induced inflammation, remain insufficiently elucidated. In this study, we present a comprehensive demonstration and characterization of microvascular endothelial cell senescence induced by spinal cord injury (SCI). Lysine demethylase 6A (Kdm6a), commonly known as UTX, emerges as a crucial regulator of cell senescence in injured spinal cord microvascular endothelial cells (SCMECs). Upregulation of UTX induces senescence in SCMECs, leading to an amplified release of proinflammatory factors, specifically the senescence-associated secretory phenotype (SASP) components, thereby modulating the inflammatory microenvironment. Conversely, the deletion of UTX in endothelial cells shields SCMECs against senescence, mitigates the release of proinflammatory SASP factors, and promotes neurological functional recovery after SCI. UTX forms an epigenetic regulatory axis by binding to calponin 1 (CNN1), orchestrating trauma-induced SCMECs senescence and SASP secretion, thereby influencing neuroinflammation and neurological functional repair. Furthermore, local delivery of a senolytic drug reduces senescent SCMECs and suppresses proinflammatory SASP secretion, reinstating a local regenerative microenvironment and enhancing functional repair after SCI. In conclusion, targeting the UTX-CNN1 epigenetic axis to prevent trauma-induced SCMECs senescence holds the potential to inhibit SASP secretion, alleviate neuroinflammation, and provide a novel treatment strategy for SCI repair.

Lactate Metabolism, Signaling, and Function in Brain Development, Synaptic Plasticity, Angiogenesis, and Neurodegenerative Diseases

Neural tissue requires a great metabolic demand despite negligible intrinsic energy stores. As a result, the central nervous system (CNS) depends upon a continuous influx of metabolic substrates from the blood. Disruption of this process can lead to impairment of neurological functions, loss of consciousness, and coma within minutes. Intricate neurovascular networks permit both spatially and temporally appropriate metabolic substrate delivery. Lactate is the end product of anaerobic or aerobic glycolysis, converted from pyruvate by lactate dehydrogenase-5 (LDH-5). Although abundant in the brain, it was traditionally considered a byproduct or waste of glycolysis. However, recent evidence indicates lactate may be an important energy source as well as a metabolic signaling molecule for the brain and astrocytes-the most abundant glial cell-playing a crucial role in energy delivery, storage, production, and utilization. The astrocyte-neuron lactate-shuttle hypothesis states that lactate, once released into the extracellular space by astrocytes, can be up-taken and metabolized by neurons. This review focuses on this hypothesis, highlighting lactate's emerging role in the brain, with particular emphasis on its role during development, synaptic plasticity, angiogenesis, and disease.

Attenuation of Alzheimer's brain pathology in 5XFAD mice by PTH1-34, a peptide of parathyroid hormone

BACKGROUND

Alzheimer's disease (AD) and osteoporosis are two distinct diseases but often occur in the same patient. Their relationship remains poorly understood. Studies using Tg2576 AD animal model demonstrate bone deficits, which precede the brain phenotypes by several months, arguing for the independence of bone deficits on brain degeneration and raising a question if the bone deficits contribute to the AD development. To address this question, we investigated the effects of PTH_1-34, a peptide of parathyroid hormone analog and a well-recognized effective anabolic therapy drug for patients with osteoporosis, on 5XFAD animal model.

METHODS

5XFAD mice, an early onset β-amyloid (Aβ)-based AD mouse model, were treated with PTH_1-34 intermittently [once daily injection of hPTH_1-34 (50 μg/Kg), 5 days/week, starting at 2-month old (MO) for 2-3 month]. Wild type mice (C57BL/6) were used as control. The bone phenotypes were examined by microCT and evaluated by measuring serum bone formation and resorption markers. The AD relevant brain pathology (e.g., Aβ and glial activation) and behaviors were assessed by a combination of immunohistochemical staining analysis, western blots, and behavior tests. Additionally, systemic and brain inflammation were evaluated by serum cytokine array, real-time PCR (qPCR), and RNAscope.

RESULTS

A reduced trabecular, but not cortical, bone mass, accompanied with a decrease in bone formation and an increase in bone resorption, was detected in 5XFAD mice at age of 5/6-month old (MO). Upon PTH_1-34 treatments, not only these bone deficits but also Aβ-associated brain pathologies, including Aβ and Aβ deposition levels, dystrophic neurites, glial cell activation, and brain inflammatory cytokines, were all diminished; and the cognitive function was improved. Further studies suggest that PTH_1-34 acts on not only osteoblasts in the bone but also astrocytes in the brain, suppressing astrocyte senescence and expression of inflammatory cytokines in 5XFAD mice.

CONCLUSIONS

These results suggest that PTH_1-34 may act as a senolytic-like drug, reducing systemic and brain inflammation and improving cognitive function, and implicate PTH_1-34's therapeutic potential for patients with not only osteoporosis but also AD.

Netrin-1 binding to Unc5B regulates Blood-Retina Barrier integrity

Background

The blood brain barrier (BBB) preserves neuronal function in the central nervous system (CNS) by tightly controlling metabolite exchanges with the blood. In the eye, the retina is likewise protected by the blood-retina barrier (BRB) to maintain phototransduction. We showed that the secreted guidance cue Netrin-1 regulated BBB integrity, by binding to endothelial Unc5B and regulating canonical β-catenin dependent expression of BBB gene expression.

Objective

Here, we investigated if Netrin-1-binding to endothelial Unc5B also controlled BRB integrity, and if this process involved Norrin/β-catenin signaling, which is the major known driver of BRB development and maintenance.

Methods

We analyzed Tamoxifen-inducible loss- and gain- of-function alleles of Unc5B, Ntn1 and Ctnnb1 in conjunction with tracer injections and biochemical signaling studies.

Results

Inducible endothelial Unc5B deletion, and inducible global Ntn1 deletion in postnatal mice reduced phosphorylation of the Norrin receptor LRP5, leading to reduced β-catenin and LEF1 expression, conversion of retina endothelial cells from a barrier-competent Claudin-5+/PLVAP- state to a Claudin-5-/PLVAP+ leaky phenotype, and extravasation of injected low molecular weight tracers. Inducible Ctnnb1 gain of function rescued vascular leak in Unc5B mutants, and Ntn1 overexpression induced BRB tightening. Unc5B expression in pericytes contributed to BRB permeability, via regulation of endothelial Unc5B. Mechanistically, Netrin-1-Unc5B signaling promoted β-catenin dependent BRB signaling by enhancing phosphorylation of the Norrin receptor LRP5 via the Discs large homologue 1 (Dlg1) intracellular scaffolding protein.

Conclusions

The data identify Netrin1-Unc5B as novel regulators of BRB integrity, with implications for diseases associated with BRB disruption.

Placental Therapeutic Targets and Nanodelivery Systems

Pregnancy complications affect millions of women each year. Some of these diseases have high morbidity and mortality such as preeclampsia. At present, there is no safe and effective treatment for pregnancy complications, so it is still a difficult clinical problem. As many pregnancy complications are closely related to placental dysplasia, placenta-specific therapy, as an important method, is expected to be a safe, effective, and specific therapeutic strategy. This review explains in detail the placenta physiological structure, characteristics, and action mechanism of some biomolecules and signaling pathways that play roles in normal development and disorders of the development of the placenta, and how to use these biomolecules as therapeutic targets when the placenta disorder causes disease, combining the latest progress in the field of nanodelivery systems, so as to lay a foundation for the development of placenta-specific therapy of pregnancy complications.

Diverse roles for axon guidance pathways in adult tissue architecture and function

Classical axon guidance ligands and their neuronal receptors were first identified due to their fundamental roles in regulating connectivity in the developing nervous system. Since their initial discovery, it has become clear that these signaling molecules play important roles in the development of a broad array of tissue and organ systems across phylogeny. In addition to these diverse developmental roles, there is a growing appreciation that guidance signaling pathways have important functions in adult organisms, including the regulation of tissue integrity and homeostasis. These roles in adult organisms include both tissue-intrinsic activities of guidance molecules, as well as systemic effects on tissue maintenance and function mediated by the nervous and vascular systems. While many of these adult functions depend on mechanisms that mirror developmental activities, such as regulating adhesion and cell motility, there are also examples of adult roles that may reflect signaling activities that are distinct from known developmental mechanisms, including the contributions of guidance signaling pathways to lineage commitment in the intestinal epithelium and bone remodeling in vertebrates. In this review, we highlight studies of guidance receptors and their ligands in adult tissues outside of the nervous system, focusing on in vivo experimental contexts. Together, these studies lay the groundwork for future investigation into the conserved and tissue-specific mechanisms of guidance receptor signaling in adult tissues.

Leptin Promotes Angiogenesis via Pericyte STAT3 Pathway upon Intracerebral Hemorrhage

Angiogenesis is a vital endogenous brain self-repair processes for neurological recovery after intracerebral hemorrhage (ICH). Increasing evidence suggests that leptin potentiates angiogenesis and plays a beneficial role in stroke. However, the proangiogenic effect of leptin on ICH has not been adequately explored. Moreover, leptin triggers post-ICH angiogenesis through pericyte, an important component of forming new blood vessels, which remains unclear. Here, we reported that exogenous leptin infusion dose-dependent promoted vascular endothelial cells survival and proliferation at chronic stage of ICH mice. Additionally, leptin robustly ameliorated pericytes loss, enhanced pericytes proliferation and migration in ICH mice in vivo, and in ICH human brain microvascular pericytes (HBVPC) in vitro. Notably, we showed that pericytes-derived pro-angiogenic factors were responsible for enhancing the survival, proliferation and tube formation followed leptin treatment in human brain microvascular endothelial cells (HCMEC/D3)/HBVPC co-culture models. Importantly, considerable improvements in neurobehavioral function and hostile microenvironment were observed in leptin treatment ICH mice, indicating that better vascular functionality post ICH improves outcome. Mechanistically, this study unveiled that leptin boost post-ICH angiogenesis potentially through modulation of leptin receptor (leptinR)/Signal Transducer and Activator of Transcription 3 (STAT3) signaling pathway in pericyte. Thus, leptin may be a lucrative option for the treatment of ICH.

Historical and current perspectives on blood endothelial cell heterogeneity in the brain

Dynamic brain activity requires timely communications between the brain parenchyma and circulating blood. Brain-blood communication is facilitated by intricate networks of brain vasculature, which display striking heterogeneity in structure and function. This vascular cell heterogeneity in the brain is fundamental to mediating diverse brain functions and has long been recognized. However, the molecular basis of this biological phenomenon has only recently begun to be elucidated. Over the past century, various animal species and in vitro systems have contributed to the accumulation of our fundamental and phylogenetic knowledge about brain vasculature, collectively advancing this research field. Historically, dye tracer and microscopic observations have provided valuable insights into the anatomical and functional properties of vasculature across the brain, and these techniques remain an important approach. Additionally, recent advances in molecular genetics and omics technologies have revealed significant molecular heterogeneity within brain endothelial and perivascular cell types. The combination of these conventional and modern approaches has enabled us to identify phenotypic differences between healthy and abnormal conditions at the single-cell level. Accordingly, our understanding of brain vascular cell states during physiological, pathological, and aging processes has rapidly expanded. In this review, we summarize major historical advances and current knowledge on blood endothelial cell heterogeneity in the brain, and discuss important unsolved questions in the field.

Diprotin A TFA Exerts Neurovascular Protection in Ischemic Cerebral Stroke

Background

It has been established that the dipeptidyl peptidase-4 (DPP-4) inhibitor Diprotin A TFA can reduce vascular endothelial (VE)-cadherin disruption by inhibiting the increase in cleaved β-catenin in response to hypoxia, thereby protecting the vascular barrier of human umbilical vein endothelial cells. In this study, we sought to investigate the possible effect of Diprotin A TFA on the VE barrier after cerebral ischemic stroke in mice.

Methods

C57BL/6J mice were divided into five groups, namely, (1) sham, (2) stroke, (3) stroke + dimethyl sulfoxide (DMSO), (4) stroke + Diprotin A TFA, and (5) stroke + Diprotin A TFA + XAV-939. First, the cerebral ischemia model was established by photothrombotic ischemia, followed by intraperitoneal injection with Diprotin A TFA and XAV-939 at doses of 70 μg/kg and 40 mg/kg 30 min once in the morning and once in the evening for 3 days. Immunofluorescence staining and Western blot methods were used to analyze the expression of vascular and blood-brain barrier (BBB)-associated molecular markers in the peri-infarct area.

Results

Compared with the vehicle control group, we found that mice injected with Diprotin A TFA exhibited reduced cerebral infarction volume, increased vascular area and length around the brain injury, increased pericyte and basement membrane coverage, upregulated expression of BBB tight junction proteins, and improved their BBB permeability, whereas the group injected with both drug and inhibitor exhibited significantly aggravated vascular injury and BBB permeability.

Conclusion

Diprotin A TFA can reduce VE-cadherin disruption by inhibiting ischemia-hypoxia-induced β-catenin cleavage to protect blood vessels.

A novel spinal neuron connection for heat sensation

Heat perception enables acute avoidance responses to prevent tissue damage and maintain body thermal homeostasis. Unlike other modalities, how heat signals are processed in the spinal cord remains unclear. By single-cell gene profiling, we identified ErbB4, a transmembrane tyrosine kinase, as a novel marker of heat-sensitive spinal neurons in mice. Ablating spinal ErbB4+ neurons attenuates heat sensation. These neurons receive monosynaptic inputs from TRPV1+ nociceptors and form excitatory synapses onto target neurons. Activation of ErbB4+ neurons enhances the heat response, while inhibition reduces the heat response. We showed that heat sensation is regulated by NRG1, an activator of ErbB4, and it involves dynamic activity of the tyrosine kinase that promotes glutamatergic transmission. Evidence indicates that the NRG1-ErbB4 signaling is also engaged in hypersensitivity of pathological pain. Together, these results identify a spinal neuron connection consisting of ErbB4+ neurons for heat sensation and reveal a regulatory mechanism by the NRG1-ErbB4 signaling.

Endothelial Unc5B controls blood-brain barrier integrity

Blood-brain barrier (BBB) integrity is critical for proper function of the central nervous system (CNS). Here, we show that the endothelial Unc5B receptor controls BBB integrity by maintaining Wnt/β-catenin signaling. Inducible endothelial-specific deletion of Unc5B in adult mice leads to BBB leak from brain capillaries that convert to a barrier-incompetent state with reduced Claudin-5 and increased PLVAP expression. Loss of Unc5B decreases BBB Wnt/β-catenin signaling, and β-catenin overexpression rescues Unc5B mutant BBB defects. Mechanistically, the Unc5B ligand Netrin-1 enhances Unc5B interaction with the Wnt co-receptor LRP6, induces its phosphorylation and activates Wnt/β-catenin downstream signaling. Intravenous delivery of antibodies blocking Netrin-1 binding to Unc5B causes a transient BBB breakdown and disruption of Wnt signaling, followed by neurovascular barrier resealing. These data identify Netrin-1-Unc5B signaling as a ligand-receptor pathway that regulates BBB integrity, with implications for CNS diseases.

The authors show that Netrin-1-Unc5B signaling controls blood-brain barrier integrity by maintaining Wnt/b-catenin signaling and that delivery of antibodies blocking Netrin-1 binding to Unc5B causes transient and size-selective BBB breakdown.

Upregulation of Neogenin-1 by a CREB1-BAF47 Complex in Vascular Endothelial Cells is Implicated in Atherogenesis

Atherosclerosis is generally considered a human pathology of chronic inflammation, to which endothelial dysfunction plays an important role. Here we investigated the role of neogenin 1 (Neo-1) in oxidized low-density lipoprotein (oxLDL) induced endothelial dysfunction focusing on its transcriptional regulation. We report that Neo-1 expression was upregulated by oxLDL in both immortalized vascular endothelial cells and primary aortic endothelial cells. Neo-1 knockdown attenuated whereas Neo-1 over-expression enhanced oxLDL-induced leukocyte adhesion to endothelial cells. Neo-1 regulated endothelial-leukocyte interaction by modulating nuclear factor kappa B (NF-κB) activity to alter the expression of adhesion molecules. Neo-1 blockade with a blocking antibody ameliorated atherogenesis in Apoe^−/− mice fed a Western diet. Ingenuity pathway analysis combined with validation assays confirmed that cAMP response element binding protein 1 (CREB1) and Brg1-associated factor 47 (BAF47) mediated oxLDL induced Neo-1 upregulation. CREB1 interacted with BAF47 and recruited BAF47 to the proximal Neo-1 promoter leading to Neo-1 trans-activation. In conclusion, our data delineate a novel transcriptional mechanism underlying Neo-1 activation in vascular endothelial cells that might contribute to endothelial dysfunction and atherosclerosis.

De novo Lipogenesis in Astrocytes Promotes the Repair of Blood-Brain Barrier after Transient Cerebral Ischemia Through Interleukin-33

Astrocytes experience significant metabolic shifts in the "sensitive period" of neurological function recovery following cerebral ischemia. However, the changes in astrocyte lipid metabolism and their implications for neurological recovery remain unknown. In the present study, we employed a mouse middle cerebral artery occlusion model to investigate the changes in de novo lipogenesis and interleukin-33 (IL-33) production in astrocytes and elucidate their role in blood-brain barrier (BBB) repair in the subacute phase of cerebral ischemia. Neurological behavior evaluation was used to assess functional changes in mice. Pharmacological inhibition and astrocyte-specific downregulation of fatty acid synthase (FASN) were used to evaluate the role of de novo lipogenesis in brain injury. Intracerebroventricular administration of recombinant IL-33 was performed to study the contribution of IL-33 to BBB disruption. Extravasation of Evans blue dye, dextran and IgG were used to assess BBB integrity. Western blotting of tight junction proteins ZO-1, Occludin, and Claudin-5 were performed at defined time points to evaluate changes in BBB. It was found that de novo lipogenesis was activated, and IL-33 production increased in astrocytes at the subacute stage of cerebral ischemia injury. Inhibition of lipogenesis in astrocytes decreased IL-33 production in the peri-infarct area, deteriorated BBB damage and interfered with neurological recovery. In addition, supplementation of IL-33 alleviated BBB destruction and improved neurological recovery worsened by lipogenesis inhibition. These findings indicate that astrocyte lipogenesis increases the production of IL-33 in the peri-infarct area, which promotes BBB repair in the subacute phase of cerebral ischemia injury and improves long-term functional recovery.

Astrocytes in the Traumatic Brain Injury: the Good and the Bad

Astrocytes control many processes of the nervous system in health and disease, and respond to injury quickly. Astrocytes produce neuroprotective factors in the injured brain to clear cellular debris and to orchestrate neurorestorative processes that are beneficial for neurological recovery after traumatic brain injury (TBI). However, astrocytes also become dysregulated and produce cytotoxic mediators that hinder CNS repair by induction of neuronal dysfunction and cell death. Hence, we discuss the potential role of astrocytes in neuropathological processes such as neuroinflammation, neurogenesis, synaptogenesis and blood-brain barrier repair after TBI. Thus, an improved understanding of the dual role of astrocytes may advance our knowledge of post-brain injury recovery, and provide opportunities for the development of novel therapeutic strategies for TBI.

CD146 mediates the anti-apoptotic role of Netrin-1 in endothelial progenitor cells under hypoxic conditions

Modulating the biological status of endothelial progenitor cells (EPCs), such as function and survival, is essential for therapeutic angiogenesis in ischemic vascular disease environments. This study aimed to explore the role and molecular mechanisms underlying Netrin-1 in the viability and angiogenic function of EPCs. EPCs were isolated from the bone barrow of adult C57/BL6 mice. The apoptosis and various functions of EPCs were analyzed in vitro by manipulating the expression of Netrin-1. The TUNEL assay was performed to detect apoptotic EPCs. Cell migration and tube formation assays were performed to detect EPC function. Trypan blue staining was performed to detect cell viability. Western blot analysis was performed to detect the protein expression levels of Netrin-1, CD146 and apoptotic factors. Quantitative PCR analysis was performed to detect the expression levels of Netrin-1 receptors. The results demonstrated that treatment with exogenous Netrin-1 promoted EPC migration and tube formation, whereas transfection with small interfering (si)RNA targeting Netrin-1 exhibited the opposite effects. Exogenous Netrin-1 protected EPCs from hypoxia-induced apoptosis, whereas the interruption of endogenous Netrin-1 enhancement under hypoxia by Netrin-1-siRNA exacerbated the apoptosis of EPCs. Furthermore, CD146, one of the immunoglobulin receptors activated by Netrin-1, was screened for in the present study. Results demonstrated that CD146 did not participate in Netrin-1-promoted EPC function, but mediated the anti-apoptotic effects of Netrin-1 in EPCs. In conclusion, Netrin-1 enhanced the angiogenic function of EPCs and alleviated hypoxia-induced apoptosis, which was mediated by CD146. This biological function of Netrin-1 may provide a potential therapeutic option to promote EPCs for the treatment of ischemic vascular diseases.

Megalencephalic leukoencephalopathy with subcortical cysts is a developmental disorder of the gliovascular unit

Absence of the astrocyte-specific membrane protein MLC1 is responsible for megalencephalic leukoencephalopathy with subcortical cysts (MLC), a rare type of leukodystrophy characterized by early-onset macrocephaly and progressive white matter vacuolation that lead to ataxia, spasticity, and cognitive decline. During postnatal development (from P5 to P15 in the mouse), MLC1 forms a membrane complex with GlialCAM (another astrocytic transmembrane protein) at the junctions between perivascular astrocytic processes. Perivascular astrocytic processes along with blood vessels form the gliovascular unit. It was not previously known how MLC1 influences the physiology of the gliovascular unit. Here, using the Mlc1 knock-out mouse model of MLC, we demonstrated that MLC1 controls the postnatal development and organization of perivascular astrocytic processes, vascular smooth muscle cell contractility, neurovascular coupling, and intraparenchymal interstitial fluid clearance. Our data suggest that MLC is a developmental disorder of the gliovascular unit, and perivascular astrocytic processes and vascular smooth muscle cell maturation defects are primary events in the pathogenesis of MLC and therapeutic targets for this disease.

Unfractionated Heparin Attenuated Histone-Induced Pulmonary Syndecan-1 Degradation in Mice: a Preliminary Study on the Roles of Heparinase Pathway

Endothelial glycocalyx degradation is thought to facilitate the development of sepsis. Histone is a significant mediator in sepsis. Unfractionated heparin (UFH) possessed beneficial effects on sepsis. Thereby, this study aims to figure out whether histone can disrupt glycocalyx and to investigate the protective effect and mechanism of UFH. Male mice (C57BL/6, 8-10 weeks old, weighing 20-25 g) were randomly divided into five groups including control group, histone group, histone + UFH group, histone + heparinase (HPA) inhibitor group, and histone + UFH + HPA inhibitor group. The mice were treated with histone (50 mg/kg) via tail vein immediately after HPA (20 mg/kg) injection. UFH (400 U/kg) was injected 1h after histone administration. The other groups were injected with equal volume of sterile saline accordingly. UFH alleviated histone-induced lung injury and pulmonary edema. UFH inhibited histone-induced lung coagulation activation and inflammatory response. UFH treatment markedly inhibited pulmonary glycocalyx degradation by reducing the histone-induced decrease in the levels of lung syndecan-1 mRNA and protein. UFH downregulated histone-induced expression of HPA mRNA and protein, and thus alleviated glycocalyx degradation. UFH protects against histone-induced pulmonary glycocalyx injury partly by heparinase pathway.

Elevated RGMA Expression Predicts Poor Prognosis in Patients with Glioblastoma

Background

Glioblastoma (GBM) is the most aggressive type of human brain tumor with a poor prognosis and a low survival rate. Secreted proteins from tumors are recently considered as important modulators to promote tumorigenesis by communicating with microenvironments. Repulsive guidance molecule A (RGMA) was initially characterized as an axon guidance molecule after secretion in the brain during embryogenesis but has not been studied in GBM. In this study, we investigated secreted gene expression patterns and the correlation between RGMA expression and prognosis in GBM using in silico analysis.

Methods

RGMA mRNA levels in normal human astrocyte (NHA), human glioma cells, and GBM patient-derived glioma stem cells (GSCs) were assessed by qRT‐PCR. Patient survival analysis was performed with the Kaplan–Meier curve and univariate and multivariate analyses using publicly available datasets. The predictive roles of RGMA in progressive malignancy were evaluated using Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA).

Results

RGMA mRNA expression was elevated in glioma cells and GSCs compared with NHA and correlated with unfavorable prognosis in glioma patients. Thus, RGMA could serve as an independent predictive factor for GBM. Furthermore, the increased levels of RGMA expression and its putative receptor, neogenin (NEO1), were associated with poor patient survival rates in GBM.

Conclusion

We identified RGMA as an independent prognostic biomarker for progressive malignancy in glioblastoma and address the possibilities to develop novel therapeutic strategies against glioblastoma.

Netrin-1 as a Multitarget Barrier Stabilizer in the Peripheral Nerve after Injury

The blood–nerve barrier and myelin barrier normally shield peripheral nerves from potentially harmful insults. They are broken down during nerve injury, which contributes to neuronal damage. Netrin-1 is a neuronal guidance protein with various established functions in the peripheral and central nervous systems; however, its role in regulating barrier integrity and pain processing after nerve injury is poorly understood. Here, we show that chronic constriction injury (CCI) in Wistar rats reduced netrin-1 protein and the netrin-1 receptor neogenin-1 (Neo1) in the sciatic nerve. Replacement of netrin-1 via systemic or local administration of the recombinant protein rescued injury-induced nociceptive hypersensitivity. This was prevented by siRNA-mediated knockdown of Neo1 in the sciatic nerve. Mechanistically, netrin-1 restored endothelial and myelin, but not perineural, barrier function as measured by fluorescent dye or fibrinogen penetration. Netrin-1 also reversed the decline in the tight junction proteins claudin-5 and claudin-19 in the sciatic nerve caused by CCI. Our findings emphasize the role of the endothelial and myelin barriers in pain processing after nerve damage and reveal that exogenous netrin-1 restores their function to mitigate CCI-induced hypersensitivity via Neo1. The netrin-1-neogenin-1 signaling pathway may thus represent a multi-target barrier protector for the treatment of neuropathic pain.

An Insight into the microRNAs Associated with Arteriovenous and Cavernous Malformations of the Brain

Background: Brain arteriovenous malformations (BAVMs) and cerebral cavernous malformations (CCMs) are rare developmental anomalies of the intracranial vasculature, with an irregular tendency to rupture, and as of yet incompletely deciphered pathophysiology. Because of their variety in location, morphology, and size, as well as unpredictable natural history, they represent a management challenge. MicroRNAs (miRNAs) are strands of non-coding RNA of around 20 nucleotides that are able to modulate the expression of target genes by binding completely or partially to their respective complementary sequences. Recent breakthroughs have been made on elucidating their contribution to BAVM and CCM occurrence, growth, and evolution; however, there are still countless gaps in our understanding of the mechanisms involved. Methods: We have searched the Medline (PubMed; PubMed Central) database for pertinent articles on miRNAs and their putative implications in BAVMs and CCMs. To this purpose, we employed various permutations of the terms and idioms: ‘arteriovenous malformation’, ‘AVM’, and ‘BAVM’, or ‘cavernous malformation’, ‘cavernoma’, and ‘cavernous angioma’ on the one hand; and ‘microRNA’, ‘miRNA’, and ‘miR’ on the other. Using cross-reference search; we then investigated additional articles concerning the individual miRNAs identified in other cerebral diseases. Results: Seven miRNAs were discovered to play a role in BAVMs, three of which were downregulated (miR-18a, miR-137, and miR-195*) and four upregulated (miR-7-5p, miR-199a-5p, miR-200b-3p, and let-7b-3p). Similarly, eight miRNAs were identified in CCM in humans and experimental animal models, two being upregulated (miR-27a and mmu-miR-3472a), and six downregulated (miR-125a, miR-361-5p, miR-370-3p, miR-181a-2-3p, miR-95-3p, and let-7b-3p). Conclusions: The following literature review endeavored to address the recent discoveries related to the various implications of miRNAs in the formation and growth of BAVMs and CCMs. Additionally, by presenting other cerebral pathologies correlated with these miRNAs, it aimed to emphasize the potential directions of upcoming research and biological therapies.

Hippocampal astrocytic neogenin regulating glutamate uptake, a critical pathway for preventing epileptic response

Epilepsy, a common neurological disorder, is featured with recurrent seizures. Its underlying pathological mechanisms remain elusive. Here, we provide evidence for loss of neogenin (NEO1), a coreceptor for multiple ligands, including netrins and bone morphological proteins, in the development of epilepsy. NEO1 is reduced in hippocampi from patients with epilepsy based on transcriptome and proteomic analyses. Neo1 knocking out (KO) in mouse brains displays elevated epileptiform spikes and seizure susceptibility. These phenotypes were undetectable in mice, with selectively depleted NEO1 in excitatory (NeuroD6-Cre⁺) or inhibitory (parvalbumin⁺) neurons, but present in mice with specific hippocampal astrocytic Neo1 KO. Additionally, neurons in hippocampal dentate gyrus, a vulnerable region in epilepsy, in mice with astrocyte-specific Neo1 KO show reductions in inhibitory synaptic vesicles and the frequency of miniature inhibitory postsynaptic current(mIPSC), but increase of the duration of miniature excitatory postsynaptic current and tonic NMDA receptor currents, suggesting impairments in both GABAergic transmission and extracellular glutamate clearance. Further proteomic and cell biological analyses of cell-surface proteins identified GLAST, a glutamate-aspartate transporter that is marked reduced in Neo1 KO astrocytes and the hippocampus. NEO1 interacts with GLAST and promotes GLAST surface distribution in astrocytes. Expressing NEO1 or GLAST in Neo1 KO astrocytes in the hippocampus abolishes the epileptic phenotype. Taken together, these results uncover an unrecognized pathway of NEO1-GLAST in hippocampal GFAP⁺ astrocytes, which is critical for GLAST surface distribution and function, and GABAergic transmission, unveiling NEO1 as a valuable therapeutic target to protect the brain from epilepsy.

Linking cortical astrocytic neogenin deficiency to the development of Moyamoya disease-like vasculopathy

Moyamoya-like vasculopathy, the "puff of smoke"-like small vessels in the brain, is initially identified in patients with Moyamoya disease (MMD), a rare cerebrovascular disease, and later found in patients with various types of neurological conditions, including Down syndrome, Stroke, and vascular dementia. It is thus of interest to understand how this vasculopathy is developed. Here, we provided evidence for cortical astrocytic neogenin (NEO1) deficiency to be a risk factor for its development. NEO1, a member of deleted in colorectal cancer (DCC) family netrin receptors, was reduced in brain samples of patients with MMD. Astrocytic Neo1-loss resulted in an increase of small blood vessels (BVs) selectively in the cortex. These BVs were dysfunctional, with leaky blood-brain barrier (BBB), thin arteries, and accelerated hyperplasia in veins and capillaries, resembled to the features of moyamoya-like vasculopathy. Additionally, we found that both MMD patient and Neo1 mutant mice exhibited altered gene expression in their cortex in proteins critical for not only angiogenesis [e.g., an increase in vascular endothelial growth factor (VEGFa)], but also axon guidance (e.g., netrin family proteins) and inflammation. In aggregates, these results suggest a critical role of astrocytic NEO1-loss in the development of Moyamoya-like vasculopathy, providing a mouse model for investigating mechanisms of Moyamoya-like vasculopathy.