Astrocytic Aquaporin-4 Research Articles

Orchestrating aquaporin-4 and connexin-43 expression in brain: Differential roles of α1- and β1-syntrophin

Aquaporin-4 (AQP4) water channels and gap junction proteins (connexins) are two classes of astrocytic membrane proteins critically involved in brain water and ion homeostasis. AQP4 channels are anchored by α1-syntrophin to the perivascular astrocytic endfoot membrane domains where they control water flux at the blood-brain interface while connexins cluster at the lateral aspects of the astrocytic endfeet forming gap junctions that allow water and ions to dissipate through the astrocyte syncytium. Recent studies have pointed to an interdependence between astrocytic AQP4 and astrocytic gap junctions but the underlying mechanism remains to be explored. Here we use a novel transgenic mouse line to unravel whether β1-syntrophin (coexpressed with α1-syntrophin in astrocytic plasma membranes) is implicated in the expression of AQP4 isoforms and formation of gap junctions in brain. Our results show that while the effect of β1-syntrophin deletion is rather limited, double knockout of α1- and β1-syntrophin causes a downregulation of the novel AQP4 isoform AQP4ex and an increase in the number of astrocytic gap junctions. The present study highlight the importance of syntrophins in orchestrating specialized functional domains of brain astrocytes.

Acute systemic LPS-exposure impairs perivascular CSF distribution in mice

BackgroundThe exchange of cerebrospinal (CSF) and interstitial fluid is believed to be vital for waste clearance in the brain. The sleep-dependent glymphatic system, which is comprised of perivascular flow of CSF and is largely dependent on arterial pulsatility and astrocytic aquaporin-4 (AQP4) expression, facilitates much of this brain clearance. During the last decade, several observations have indicated that impaired glymphatic function goes hand in hand with neurodegenerative diseases. Since pathologies of the brain carry inflammatory components, we wanted to know how acute inflammation, e.g., with lipopolysaccharide (LPS) injections, would affect the glymphatic system. In this study, we aim to measure the effect of LPS on perivascular CSF distribution as a measure of glymphatic function.MethodsThree hours after injection of LPS (1 mg/kg i.p.), C57bl/6 mice were (1) imaged for two CSF tracers, injected into cisterna magna, (2) transcardially perfused with buffer, or (3) used for physiological readouts. Tracer flow was imaged using a low magnification microscope on fixed brains, as well as using vibratome-cut slices for measuring tracer penetration in the brain. Cytokines, glial, and BBB-permeability markers were measured with ELISAs, Western blots, and immunohistochemistry. Cerebral blood flow was approximated using laser Doppler flowmetry, respiration and heart rate with a surgical monitor, and AQP4-polarization was quantified using confocal microscopy of immunolabeled brain sections.ResultsLPS-injections significantly lowered perivascular CSF tracer flow and penetration into the parenchyma. No differences in AQP4 polarization, cytokines, astroglial and BBB markers, cerebral blood flow, or respiration were detected in LPS-injected mice, although LPS did elevate cortical Iba1+ area and heart rate.ConclusionsThis study reports another physiological response after acute exposure to the bacterial endotoxin LPS, namely the statistically significant decrease in perivascular distribution of CSF. These observations may benefit our understanding of the role of systemic inflammation in brain clearance.

Neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein IgG associated disorder: A comprehensive neuro-ophthalmic review.

Neuromyelitis optica spectrum disorder (NMOSD) is an antibody-mediated inflammatory disease of the central nervous system that involves the optic nerves, spinal cord, and often other specific brain regions such as area postrema of the medulla. NMOSD was formerly classified as a variant of multiple sclerosis (MS), given the similar symptomatology and relapsing course but is now considered to have distinct clinical, paraclinical, immunological and prognostic features. The discovery of aquaporin 4 (AQP4) immunoglobulin G (IgG) has improved the ability to diagnose NMOSD. AQP4-IgG targets the astrocytic AQP4 water channel leading to complement activation and increased blood-brain barrier permeability. Accurate and early diagnosis is crucial as timely treatment may result in mitigation of long-term disability. Myelin oligodendrocyte glycoprotein (MOG)-IgG associated disorder (MOGAD) is a distinct nosologic entity, which has been more recently described. Its clinical spectrum partly overlaps that of seronegative NMOSD and MS. Although it is considered to have fewer relapses and better prognosis than NMOSD, the clinical course and outcome of MOGAD has not been fully characterized.

Comprehensive gene expression profiling of human astrocytes treated with a hepatic encephalopathy-inducible factor, alpha 1-antichymotripsin

Astrocytes are major glial cells that play a critical role in brain homeostasis. Abnormalities in astrocytic function, such as hepatic encephalopathy (HE) during acute liver failure, can result in brain death following brain edema and the associated astrocyte swelling. Recently, we have identified alpha 1-antichymotripsin (ACT) to be a biomarker candidate for HE. ACT induces astrocyte swelling by upregulating aquaporin 4 (AQP4); however, the causal connection between these proteins is not clear yet. In this study, we utilized a microarray profile to screen the differentially expressed genes (DEGs) in astrocytes treated with ACT. We then performed Gene Ontology, REACTOME, and the comprehensive resource of mammalian protein complexes (CORUM) enrichment analyses of the identified DEGs. The results of these analyses indicated that the DEGs were enriched in pathways activating adenylate cyclase (AC)-coupled G protein-coupled receptors (GPCRs) and therefore were involved in the cyclic adenosine monophosphate (cAMP) signaling. These results indicate that ACT may act as a ligand of Gs-GPCRs and subsequently upregulate cAMP. As cAMP is known to upregulate AQP4 in astrocytes, these results suggest that ACT may upregulate AQP4 by activating AC GPCRs and therefore serve as a therapeutic target for acute HE.

Activated microglia-derived macrophage-like cells exacerbate brain edema after ischemic stroke correlate with astrocytic expression of aquaporin-4 and interleukin-1 alpha release

Brain edema following brain infarction affects mobility and mortality. The mechanisms underlying this process remain to be elucidated. Animal studies have shown that aquaporin-4 (AQP4) expression in astrocytes increases after stroke, and its deletion significantly reduces brain swelling. Recently, two kinds of cells, resident microglia-derived macrophage-like cells (MG-MΦ) and bone marrow-derived macrophages (BM-MΦ), have been reported to accumulate in the ischemic core and stimulate adjacent astrocytes. Therefore, we hypothesized that these cells play crucial roles in the expression of AQP4 and ultimately lead to exacerbated brain edema. To verify this hypothesis, we investigated the role of MG- or BM-MΦ in brain edema using a rat model of transient middle cerebral artery occlusion and rat astrocyte primary cultures. AQP4 expression significantly increased in the peri-infarct tissue at 3–7 days post-reperfusion (dpr) and in the core tissue at 5 and 7 dpr, which synchronized with the expression of Iba1, Il1a, Tnf, and C1qa mRNA. Interleukin (IL)-1α treatment or coculture with MG- and BM-MΦ increased AQP4 expression in astrocytes, while an IL-1 receptor type I antagonist reduced these effects. Furthermore, aggravated animals exhibited high expression of Aqp4 and Il1a mRNA in the ischemic core at 7 dpr, which led to the exacerbation of brain edema. MG-MΦ signature genes were highly expressed in the ischemic core in aggravated rats, while BM-MΦ signature genes were weakly expressed. These findings suggest that IL-1α produced by MG-MΦ induces astrocytic AQP4 expression in the peri-infarct and ischemic core tissues, thereby exacerbating brain edema. Therefore, the regulation of MG-MΦ may prevent the exacerbation of brain edema.

Effect of NMO-IgG on the interleukin-6 cascade in astrocytes via activation of the JAK/STAT3 signaling pathway

AimsAstrocytes expressing the aquaporin-4 (AQP4) water channel are pathogenic, disease specific immunoglobulins (IgG) found in neuromyelitis optica spectrum disorder (NMOSD), referred to as NMO-IgG, which targets astrocytic AQP4. The interleukin-6 (IL-6) signaling when astrocytes were exposed to NMO-IgG present in the serum of NMOSD patients was evaluated. Main methodsSerum or human-IgG from NMOSD or healthy controls were exposed to astrocytes. The selectivity and immuno-pathological consequences of Ig binding to surface epitopes were measured by confocal microscopy. Astrocytes were exposed to medium, IL-6, soluble IL-6 receptor (sIL-6R), IL-6 + sIL-6R (IL-6/R), NMO-IgG or control-IgG, NMO-IgG + IL-6/R. The expression of key proteins in IL-6 signaling pathway, IL-6 cytokine and mRNA levels were evaluated by western blotting, enzyme-linked immunosorbent assay and quantitative polymerase chain reaction, respectively. Key findingsSerum or NMO-IgG from NMOSD patients both induced the rapid downregulation of AQP4 expression on the surface of astrocytes. Stimulation of astrocytes with NMO-IgG, IL-6/R, and NMO-IgG + IL-6/R resulted in the enhancement of IL-6 mRNA expression. Meanwhile, the exogenous addition of NMO-IgG elicited an inflammatory transcriptional response that involved signaling through the Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) pathway. Inhibition of the IL-6/JAK/STAT3 pathway with the JAK1/2 specific inhibitor, AZD1480, reversed the associated increase of IL-6. SignificanceOur findings suggest that NMO-IgG can stimulate the astrocytic JAK1/2/STAT3-dependent inflammatory response, which represents one of the important events in NMO pathogenesis. Inhibition of the JAK1/2 signaling pathway may be a novel promising therapy for NMOSD.

Monoclonal Antibody-Based Treatments for Neuromyelitis Optica Spectrum Disorders: From Bench to Bedside.

Neuromyelitis optica (NMO)/NMO spectrum disorder (NMOSD) is a chronic, recurrent, antibody-mediated, inflammatory demyelinating disease of the central nervous system, characterized by optic neuritis and transverse myelitis. The binding of NMO-IgG with astrocytic aquaporin-4 (AQP4) functions directly in the pathogenesis of >60% of NMOSD patients, and causes astrocyte loss, secondary inflammatory infiltration, demyelination, and neuron death, potentially leading to paralysis and blindness. Current treatment options, including immunosuppressive agents, plasma exchange, and B-cell depletion, are based on small retrospective case series and open-label studies. It is noteworthy that monoclonal antibody (mAb) therapy is a better option for autoimmune diseases due to its high efficacy and tolerability. Although the pathophysiological mechanisms of NMOSD remain unknown, increasingly, therapeutic studies have focused on mAbs, which target B cell depletion, complement and inflammation cascade inactivation, blood-brain-barrier protection, and blockade of NMO-IgG-AQP4 binding. Here, we review the targets, characteristics, mechanisms of action, development, and potential efficacy of mAb trials in NMOSD, including preclinical and experimental investigations.

Haplotype of the astrocytic water channel AQP4 is associated with slow wave energy regulation in human NREM sleep.

Cerebrospinal fluid (CSF) flow through the brain parenchyma is facilitated by the astrocytic water channel aquaporin 4 (AQP4). Homeostatically regulated electroencephalographic (EEG) slow waves are a hallmark of deep non-rapid eye movement (NREM) sleep and have been implicated in the regulation of parenchymal CSF flow and brain clearance. The human AQP4 gene harbors several single nucleotide polymorphisms (SNPs) associated with AQP4 expression, brain-water homeostasis, and neurodegenerative diseases. To date, their role in sleep-wake regulation is unknown. To investigate whether functional variants in AQP4 modulate human sleep, nocturnal EEG recordings and cognitive performance were investigated in 123 healthy participants genotyped for a common eight-SNP AQP4-haplotype. We show that this AQP4-haplotype is associated with distinct modulations of NREM slow wave energy, strongest in early sleep and mirrored by changes in sleepiness and reaction times during extended wakefulness. The study provides the first human evidence for a link between AQP4, deep NREM sleep, and cognitive consequences of prolonged wakefulness.

The Pattern of AQP4 Expression in the Ageing Human Brain and in Cerebral Amyloid Angiopathy.

In the absence of lymphatics, fluid and solutes such as amyloid-β (Aβ) are eliminated from the brain along basement membranes in the walls of cerebral capillaries and arteries—the Intramural Peri-Arterial Drainage (IPAD) pathway. IPAD fails with age and insoluble Aβ is deposited as plaques in the brain and in IPAD pathways as cerebral amyloid angiopathy (CAA); fluid accumulates in the white matter as reflected by hyperintensities (WMH) on MRI. Within the brain, fluid uptake by astrocytes is regulated by aquaporin 4 (AQP4). We test the hypothesis that expression of astrocytic AQP4 increases in grey matter and decreases in white matter with onset of CAA. AQP4 expression was quantitated by immunocytochemistry and confocal microscopy in post-mortem occipital grey and white matter from young and old non-demented human brains, in CAA and in WMH. Results: AQP4 expression tended to increase with normal ageing but AQP4 expression in severe CAA was significantly reduced when compared to moderate CAA (p = 0.018). AQP4 expression tended to decline in the white matter with CAA and WMH, both of which are associated with impaired IPAD. Adjusting the level of AQP4 activity may be a valid therapeutic target for restoring homoeostasis in the brain as IPAD fails with age and CAA.

Amyloid-ß peptides inhibit the expression of AQP4 and glutamate transporter EAAC1 in insulin-treated C6 glioma cells

Astrocytic aquaporin 4 (AQP4) facilitates glutamate clearance via regulation of the glutamate transporter function, involved in the modulation of brain plasticity and cognitive function to prevent neurodegenerative disorders such as Alzheimer’s disease (AD). In in vitro studies, the C6 rat glioma cell line is a widely applied aging model system to investigate changes in glial cells associated with aging or AD. However, the neurotoxicity mechanism whether AQP4 mediate glutamate uptake in Aβ-stimulated C6 cell remain uncertain. In this study, we examined the effects of Aβ on the expression of AQP4, Glu transporters, Glu uptake, and cell viability in insulin-treated C6 cells. Our results showed that the expression of AQP4 mRNA and protein was significantly enhanced by insulin in older cultures (passage 45), and the expression was inhibited by Aβ at 10 μM. In addition, the cell viability and glutamate uptake in Aβ-treated C6 cells were decreased in dose-dependent manners. GFAP showed similar changes in gene and protein expression patterns as AQP4, but no significant alterations were seen in GLAST expression. In C6 cells, the glutamate transport was found to be EAAC1, not GLT-1. EAAC1 expression was decreased by the treatment of Aβ. Taken together, our findings suggest that C6 cells may have astrocytic characteristics, and the astrocytic cytotoxicity induced by Aβ was mediated by reduction of glutamate uptake through AQP4/EAAC1 pathway in C6 cells. This indicates that C6 glioma cells could be used to study the roles of AQP4 on astrocyte function in AD.

Affinity-matured ‘aquaporumab’ anti-aquaporin-4 antibody for therapy of seropositive neuromyelitis optica spectrum disorders

Pathogenesis in seropositive neuromyelitis optica spectrum disorders (herein called NMO) involves binding of IgG1 autoantibodies to aquaporin-4 (AQP4) on astrocytes in the central nervous system, which initiates complement and cellular injury. We previously developed an antibody blocking approach for potential therapy of NMO in which an engineered, monoclonal, anti-AQP4 antibody lacking cytotoxicity effector functions (called aquaporumab) blocked binding of NMO autoantibodies to astrocyte AQP4 (Tradtrantip et al. Ann. Neurol. 71, 314–322, 2012). Here, a high-affinity aquaporumab, which was generated by affinity maturation using saturation mutagenesis, was shown to block cellular injury caused by NMO patient sera. Anti-AQP4 antibody rAb-53, a fully human antibody with effector function neutralizing Fc mutations L234A/L235A and affinity-enhancing Fab mutations Y50R/S56R, called AQmabAM, bound to AQP4 in cell cultures with Kd ~ 18 ng/ml (~0.12 nM), ~8-fold greater affinity than the original antibody. AQmabAM, but without L234A/L235A Fc mutations, produced complement-dependent cytotoxicity (CDC) with EC50 ~ 82 ng/ml. AQmabAM prevented CDC produced by sera from eight NMO patients with IC50 ranging from 40 to 80 ng/ml, and similarly prevented antibody-dependent cellular cytotoxicity (ADCC). Mechanistic studies demonstrated that AQmabAM blocked binding of serum NMO autoantibodies to AQP4. AQmabAM offers a targeted, non-immunosuppressive approach for therapy of seropositive NMO. Autoantibody blocking may be a useful therapeutic strategy for other autoimmune diseases as well.

Review: Recent advances in the understanding of the pathophysiology of neuromyelitis optica spectrum disorder.

Neuromyelitis optica is an autoimmune inflammatory disorder of the central nervous system that preferentially targets the spinal cord and optic nerve. Following the discovery of circulating antibodies against the astrocytic aquaporin 4 (AQP4) water channel protein, recent studies have expanded our knowledge of the unique complexities of the pathogenesis of neuromyelitis optica and its relationship with the immune response. This review describes and summarizes the recent advances in our understanding of the molecular mechanisms underlying neuromyelitis optica disease pathology and examines their potential as therapeutic targets. Additionally, we update the most recent research by proposing major unanswered questions regarding how peripheral AQP4 antibodies are produced and their entry into the central nervous system, the causes of AQP4-IgG-seronegative disease, why peripheral AQP4-expressing organs are spared from damage, and the impact of this disease on pregnancy.

Dystroglycan is involved in the activation of ERK pathway inducing the change of AQP4 expression in scratch-injured astrocytes

We previously reported that aquaporin 4 (AQP4) played a critical role in formation of brain edema and the altered expression of dystroglycan (DG) could relate with AQP4 expression after traumatic brain injury (TBI). However the mechanisms of this process remain unclear. DG was showed could act as a scaffold involved in adhesion-mediated signaling in ERK/MAPK pathway. We hypothesize that after scratch, extracellular α-DG and transmembrane β-DG may act as the scaffold in scratch mechanical force activating ERK pathway which may regulate the expression of AQP4. Use ERK inhibitor and activator to confirm whether the expression of AQP4 is regulated by the activation of ERK pathway in scratched astrocytes. Use DG siRNA to confirm whether DG takes part in the process that the extracellular signal transduces into cell and activates the ERK pathway. The significant increase of AQP4 and DG expression induced by scratch could be abolished by blocking ERK signaling and enhanced by activating ERK signaling. Blockade of DG by siRNA led to no obvious effect of scratched-injury on the ERK signaling pathway. It demonstrated that DG may act as the scaffold in scratch mechanical force activating ERK pathway which can regulate the expression of AQP4 in astrocytes after scratch.

Visual discrimination impairment after experimental stroke is associated with disturbances in the polarization of the astrocytic aquaporin-4 and increased accumulation of neurotoxic proteins

Numerous clinical studies have documented the high incidence of cognitive impairment after stroke. However, there is only limited knowledge about the underlying mechanisms. Interestingly, there is emerging evidence suggesting that cognitive function after stroke may be affected due to reduced waste clearance and subsequent accumulation of neurotoxic proteins. To further explore this potential association, we utilised a model of experimental stroke in mice. Specifically, a photothrombotic vascular occlusion targeting motor and sensory parts of the cerebral cortex was induced in young adult mice, and changes in cognition were assessed using a touchscreen platform for pairwise visual discrimination. The results showed that the execution of the visual discrimination task was impaired in mice 10 to 14 days post-stroke compared to sham. Stroke also induced significant neuronal loss within the peri-infarct, thalamus and the CA1 sub-region of the hippocampus. Further, immunohistochemical and protein analyses of the selected brain regions revealed an increased accumulation and aggregation of both amyloid-β and α-synuclein. These alterations were associated with significant disturbances in the aquaporin-4 protein expression and polarization at the astrocytic end-feet. The results suggest a link between the increased accumulation of neurotoxic proteins and the stroke-induced cognitive impairment. Given that the neurotoxic protein accumulation appeared alongside changes in astrocytic aquaporin-4 distribution, we suggest that the function of the waste clearance pathways in the brain post-stroke may represent a therapeutic target to improve brain recovery.

Role of Glutamatergic Excitotoxicity in Neuromyelitis Optica Spectrum Disorders.

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory disorder mediated by immune-humoral responses directed against central nervous system (CNS) antigens. Most patients are positive for specific immunoglobulin G (IgG) auto-antibodies for aquaporin-4 (AQP4), a water channel present in astrocytes. Antigen-antibody binding promotes complement system cascade activation, immune system cell infiltration, IgG deposition, loss of AQP4 and excitatory amino acid transporter 2 (EAAT2) expression on the astrocytic plasma membrane, triggering necrotic destruction of spinal cord tissue and optic nerves. Astrocytes are very important cells in the CNS and, in addition to supporting other nerve cells, they also regulate cerebral homeostasis and control glutamatergic synapses by modulating neurotransmission in the cleft through the high-affinity glutamate transporters present in their cell membrane. Specific IgG binding to AQP4 in astrocytes blocks protein functions and reduces EAAT2 activity. Once compromised, EAAT2 cannot take up free glutamate from the extracellular space, triggering excitotoxicity in the cells, which is characterized by overactivation of glutamate receptors in postsynaptic neurons. Therefore, the longitudinally extensive myelitis and optic neuritis lesions observed in patients with NMOSD may be the result of primary astrocytic damage triggered by IgG binding to AQP4, which can activate the immune-system cascade and, in addition, downregulate EAAT2. All these processes may explain the destructive lesions in NMOSD secondary to neuroinflammation and glutamatergic excitotoxicity. New or repurposed existing drugs capable of controlling glutamatergic excitotoxicity may provide new therapeutic options to reduce tissue damage and permanent disability after NMOSD attacks.

The role of astrocytes on the effects of exercise on episodic memory function.

This review discusses the potential role that glial cells may play in influencing the relationship between exercise and episodic memory function. A narrative review methodology is employed. Herein, the different types of glial cells, their implications in subserving episodic memory function, and how exercise can modulate glial cell activity, particularly astrocyte functionality, are discussed. Although additional experimental work is needed, astrocytes appear to play an important role in the exercise-memory interaction. Exercise may increase astrocytic size, attenuate astrogliodegeneration, improve astrocytic aquaporin-4 expression, and increase astrocytic transporter levels. These effects, in turn, may help to increase the number of synapses that neurons form, increase the number of synaptic structures, and increase presynaptic function and postsynaptic receptor localization. Ultimately, these effects may help influence long-term potentiation and episodic memory function.

Persistent Malfunction of Glymphatic and Meningeal Lymphatic Drainage in a Mouse Model of Subarachnoid Hemorrhage.

Subarachnoid hemorrhage (SAH) is a devastating cerebrovascular event that often is followed by permanent brain impairments. It is necessary to explore the pathogenesis of secondary pathological damages in order to find effective interventions for improving the prognosis of SAH. Blockage of brain lymphatic drainage has been shown to worsen cerebral ischemia and edema after acute SAH. However, whether or not there is persistent dysfunction of cerebral lymphatic drainage following SAH remains unclear. In this study, autologous blood was injected into the cisterna magna of mice to establish SAH model. One week after surgery, SAH mice showed decreases in fluorescent tracer drainage to the deep cervical lymph nodes (dcLNs) and influx into the brain parenchyma after injection into the cisterna magna. Moreover, SAH impaired polarization of astrocyte aquaporin-4 (AQP4) that is a functional marker of glymphatic clearance and resulted in accumulations of Tau proteins as well as CD3+, CD4+, and CD8+ cells in the brain. In addition, pathological changes, including microvascular spasm, activation of glial cells, neuroinflammation, and neuronal apoptosis were observed in the hippocampus of SAH mice. Present results demonstrate persistent malfunction of glymphatic and meningeal lymphatic drainage and related neuropathological damages after SAH. Targeting improvement of brain lymphatic clearance potentially serves as a new strategy for the treatment of SAH.

Ethyl pyruvate reduces spinal cord edema after spinal cord injury and attenuates spinal cord astrocyte swelling and aquaporin-4 expression after oxygen-glucose deprivation and reoxygenation in vitro by inhibiting high mobility group box-1 in rats

Objective To study the roles of ethyl pyruvate (EP) in spinal cord edema after spinal cord injury (SCI) and in spinal cord astrocytic swelling after oxygen-glucose deprivation and reoxygenation (OGD/R) in vitro in rats. Methods After SCI models were established in adult Sprague-Dawley (SD) rats, an intraperitoneal injection of EP was conducted to inhibit high mobility group box-1 (HMGB1). Effects of EP on spinal cord edema, HMGB1 expression and astrocyte activation (glial fibrillary acidic protein (GFAP) expression) in SCI rats were analyzed. Spinal cord astrocytes were cultured in post-natal SD rats and incubated under OGD/R procedure. Effects of EP on cell swelling, expression of HMGB1, aquaporin-4 (AQP4) and toll-like receptor 4 (TLR4), and nuclear expression of nuclear factor-kappa B (NF-κB) in spinal cord astrocytes were observed. Results The water content in the spinal cord was increased significantly more at 1 d after SCI than at 12 h and 3 d (P<0.05). Intraperitoneal injection of EP at 50 mg/kg reduced spinal cord water content, HMGB1 expression and astrocyte activation (GFAP expression) in SCI rats significantly more than that at 25 mg/kg or 100 mg/kg (P<0.05). The volume of spinal cord astrocytes cultured in vitro after OGD 6 h/R 24 h was significantly greater than that after OGD 6 h/R 6 h or OGD 6 h/R 12 h (P<0.05). EP at 12 μmol/L reduced cell swelling, decreased expression of HMGB1, AQP4 and TLR4, and downgraded nuclear expression of NF-κB in spinal cord astrocytes after OGD/R significantly more than EP at 6 μmol/L(P<0.05). Conclusion EP may reduce early spinal cord edema after SCI, attenuate spinal cord astrocyte swelling and decrease AQP4 expression after OGD/R in vitro by inhibiting HMGB1 in rats. Key words: Spinal cord injury; Astrocyte; Ethyl pyruvate; High mobility group box-1; Aquaporin-4

Inhibiting High Mobility Group Box-1 Reduces Early Spinal Cord Edema and Attenuates Astrocyte Activation and Aquaporin-4 Expression after Spinal Cord Injury in Rats.

High mobility group box-1 (HMGB1) could function as an early trigger for pro-inflammatory activation after spinal cord injury (SCI). Spinal cord edema contributes to inflammatory response mechanisms and a poor clinical prognosis after SCI, for which efficient therapies targeting the specific molecules involved remain limited. This study was designed to evaluate the roles of HMGB1 on the regulation of early spinal cord edema, astrocyte activation, and aquaporin-4 (AQP4) expression in a rat SCI model. Adult female Sprague-Dawley rats underwent laminectomy at T10, and the SCI model was induced by a heavy falling object. After SCI, rats received ethyl pyruvate (EP) or glycyrrhizin (GL) via an intraperitoneal injection to inhibit HMGB1. The effects of HMGB1 inhibition on the early spinal cord edema, astrocyte activation (glial fibrillary acidic protein [GFAP] expression), and AQP4 expression after SCI (12 h-3 days) were analyzed. The results showed that EP or GL effectively inhibited HMGB1 expression in the spinal cord and HMGB1 levels in the serum of SCI rats. HMGB1 inhibition improved motor function, reduced spinal cord water content, and attenuated spinal cord edema in SCI rats. HMGB1 inhibition decreased SCI-associated GFAP and AQP4 overexpression in the spinal cord. Further, HMGB1 inhibition also repressed the activation of the toll-like receptor 4/myeloid differentiation primary response gene 88/nuclear factor-kappa B signaling pathway. These results implicate that HMGB1 inhibition improved locomotor function and reduced early spinal cord edema, which was associated with a downregulation of astrocyte activation (GFAP expression) and AQP4 expression in SCI rats.

Diagnosis of multiple sclerosis: revision of the McDonald criteria 2017

Multiple sclerosis (MS) is the most common chronic autoimmune disorder of the central nervous system (CNS) largely affecting young adults. The diagnosis of MS is based on two pillars: 1)detection of the spatial and temporal dissemination of focal neurological deficits and 2)exclusion of important differential diagnoses. The current revision of the diagnostic criteria (McDonald 2017) also follows these principles, takes new data on magnetic resonance imaging (MRI) into account and reintroduces the role of cerebrospinal fluid (CSF) diagnostics for relapsing-remitting forms. The main priority is areliable diagnosis as early as possible with the aim of atimely initiation of course-adapted treatment. Some of the concrete innovations are the consideration of cortical MRI lesions (equivalent to juxtacortical foci), the elimination of adistinction between asymptomatic and symptomatic MRI lesions and consideration of characteristic CSF findings for the criterion of temporal dissemination. Relapsing MS can be diagnosed at the time of the first attack by the detection of CSF-specific oligoclonal bands and the MRI detection of atypical local lesion distribution (even without simultaneous detection of a contrast-enhancing lesion). For the primary progressive course, for which afirst treatment option has recently been approved, the known definition remains unaltered. With respect to the differential diagnosis there is aclear demarcation from Devic's syndrome, now known as neuromyelitis optica spectrum disorders (NMOSD), as recent insights indicate aseparate disease entity caused by an autoimmune response against the astrocytic aquaporin4 (AQP4) water channel. Finally, future studies will have to provide adefinition for secondary progressive MS courses and clarify how to handle diseases characterized by antibodies against myelin oligodendrocyte glycoprotein (MOG) or patients with radiologically isolated syndrome (RIS), i. e. incidental MRI-based detection of CNS lesions in the absence of any clinical event. In summary, McDonald 2017 is within the conceptual structure of its predecessor and simplifies an early diagnosis, thus paving the way to early treatment of MS.