Water Channel Protein Aquaporin-4 Research Articles

Evaluation of the anti-aging potential of acetyl tripeptide-30 citrulline in cosmetics

Acetyl tripeptide-30 citrulline, a commercialized bio-active peptide, is widely used in anti-wrinkle formulations. Volunteer-based tests have demonstrated that topical application of products containing acetyl tripeptide-30 citrulline significantly reduces the visibility of stretch marks. However, there is still a lack of research dedicated to systematically and holistically evaluating its cosmetic properties and elucidating its mechanisms of action. In this study, we assessed the cosmetic potential of acetyl tripeptide-30 citrulline using human immortalized keratinocytes (HaCaT) and mouse embryonic fibroblasts (3T3). Our findings reveal that acetyl tripeptide-30 citrulline exhibits anti-inflammatory and antioxidant activities in skin cells, particularly effective against the inflammatory markers cyclooxygenase-2 (COX2), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6), and the extent of inhibition of reactive oxygen species (ROS) production ranged from 95 % to 340 %. Moreover, acetyl tripeptide-30 citrulline specifically up-regulates Collagen IV and down-regulates matrix metalloproteinase-9 (MMP9), enhances the expression of skin barrier proteins transglutaminase 1 (TGM1) and filaggrin (FLG), thereby demonstrating its reparative capabilities. Additionally, acetyl tripeptide-30 citrulline increases the expression of the water channel protein aquaporin 3 (AQP3), thus improving skin hydration function. These results substantiate the previously proclaimed cosmetic attributes of acetyl tripeptide-30 citrulline and support its efficacy as an anti-aging agent in dermatological applications.

Actin cytoskeleton aggregation involves the water channel protein aquaporin 1-mediated human chondrocyte degeneration.

Water metabolism and actin cytoskeleton remoulding act as essential characters in the process of osteoarthritis (OA). However, the relation between water channel protein aquaporin 1 (AQP1) and actin filament during chondrocytes (CHs) degeneration is not evident. Therefore, the present study aimed to evaluate the role of actin remoulding in the AQP1 mediated CHs degeneration. Primary CHs were collected from human hip cartilage and were degenerated from long-time monolayer culture or IL-1β stimulation. Besides, the CHs were transfected with AQP1‑specific siRNA or vectors to mediate the AQP1 gene expression. The potent inhibitor of actin polymerization Cytochalasin D was also supplemented during culture. RT-PCR was performed to determine the relative gene expression. AQP1 and F-actin fluorescence staining were performed to determine the AQP1 and F-actin organization. Moreover, the cell area and viability were also analyzed. AQP1 and F-actin organization were both increased during seven days' CHs culture or three days' IL-1β stimulation. Silencing of AQP1 prevented the cell area spreading and degenerated phenotype of CHs with suppression of F-actin aggregation in both natural or IL-1β-caused inflammatory-related degeneration. Besides, upregulating the AQP1 in the CHs via gene editing promoted the cell area spreading, and F-actin accumulation, and accelerated the CHs degeneration, which can be alleviated by Cytochalasin D treatment. These findings suggested that AQP1-mediated human CHs degeneration is related to F-actin aggregation.

Severe disease reactivation in seropositive neuromyelitis optica spectrum disorders patients after stopping eculizumab treatment.

Neuromyelitis optica spectrum disorders (NMOSD) is an autoimmune, inflammatory disease of the central nervous system affecting the optic nerves and spinal cord. Most NMOSD patients have autoantibodies against the astrocyte water channel protein aquaporin-4 (AQP4). Eculizumab treatment is used effectively and safely in AQP4-IgG+ NMOSD. Our study evaluated the prognosis and outcomes of all clinical trial (PREVENT) patients from Turkey who received eculizumab treatment for AQP4-IgG+ NMOSD. Clinical and demographic data of all patients enrolled in the PREVENT and OLE clinical trial in Turkey were analyzed during the study period and after the study ended. Clinical follow-up results were recorded in detail in patients who had to discontinue eculizumab treatment. The study included 10 patients who participated in PREVENT and OLE. Seven patients completed the studies, three patients did not continue the study and were switched to other treatments. Only one of the seven patients was able to continue treatment after eculizumab was approved in AQP4-IgG+NMOSD. The other six patients could not continue treatment due to reimbursement conditions. Four of the six patients who could not continue eculizumab treatment experienced early relapse (within the first three months after stopping the drug). All of these patients had high disease activity before eculizumab and had never relapsed under eculizumab treatment over the long term. Eculizumab was used effectively and safely in Turkish AQP4-IgG+NMOSD patients with high disease activity. Disease reactivation and relapse may occur after discontinuation of eculizumab treatment in patients with a long-term stable course. In these cases, close monitoring for disease reactivation is recommended.

B cells Regulation by Interferon-gamma in a Neuromyelitis Optica Spectrum Disorder animal model

Abstract Neuromyelitis Optica Spectrum Disorder (NMOSD) is an autoimmune disease of the central nervous system (CNS) mediated by Th17 and auto-antibody response against the water channel protein Aquaporin-4 (AQP4). In NMOSD, B cells plays a central role regulating autoreactive T and antibody secreting cells, and the use of anti-B cells therapy is a common practice for patients. Despite this, the mechanisms of B cells response against AQP4 are poorly understood. We have demonstrated that the immune tolerance against the immunodominant AQP4 201–220peptide in mice is maintained by IFN-g, controlling disease incidence, severity, and chronicity. Actively immunization of C57BL/6 (WT) treated with neutralizing anti-IFN-g antibodies, IFN-g knockout (IFNGKO) and IFN-g receptor KO (IFNRKO) mice was induced using the AQP4 201–220peptide, showing an ascendant paralysis starting from the tail to complete hind limb paralysis. CNS histological analysis showed an increased presence of T and B cells, and the complement system in lesion sites, associated with CNS damage. CNS Th17 profile was also observed in the anti-IFN-g treated group. Conversely, IFN-g treatment in IFNGKO mice decrease disease severity with a reduction of CNS CD4 +and B cells. Remarkably, IFN-g regulates the IL-6 expression by B cells in an antigen specific fashion. B-cell depletion significantly reduced the disease incidence, T cells CNS infiltration and anti-AQP4 201–220serum antibodies. Finally, using anti-IL-6R treatment, we showed that IL-6 signaling is necessary for the B cell activation and their induction of Th17 cells. In conclusion, AQP4 201–220tolerance is strictly regulated by IFN-g and its signaling, restraining B cells pathogenicity through IL-6 signaling modulation. This work was supported by National Institutes of Health grants R21AI151438 and R01 NS099334

188 CD44 functions as a novel interacting partner of Aquaporin 5 in keratinocytes

Dominant missense mutations in AQP5, encoding the water channel protein Aquaporin 5, underlie diffuse non-epidermolytic palmoplantar keratoderma (NEPPK), a rare skin condition characterized by thickening of the epidermis in palms and soles. Prior to this, AQP5 was only known to be expressed in sweat gland cells in the skin and the role of this water channel in the epidermis remains unclear. To study the role of AQP5 in skin, we have characterized two patient-derived keratinocyte cell lines expressing mutant AQP5Ile45Ser.

Alternate-Day Fasting Ameliorates Newly Established Sjögren's Syndrome-like Sialadenitis in Non-Obese Diabetic Mice.

Intermittent fasting confers protections to various diseases including autoimmune disorders, but the specific effects of intermittent fasting on Sjögren's syndrome (SS) remains inconclusive. The present study was undertaken to determine the specific impact of alternate-day fasting (ADF) on newly established SS-like sialadenitis using non-obese diabetic (NOD) mice. Female NOD mice were deprived of food every other day from 10 to 13 weeks of age, the early stage of established SS, and then analyzed for the disease characteristics. Mice in the ADF group had higher salivary flow rate and attenuated submandibular gland (SMG) inflammation, compared to the control mice fed with standard chow ad libitum. The improvements were accompanied with a decrease in the total leukocytes, T and B lymphocytes and activated CD4 and CD8 T cells, and a down-regulation of pro-inflammatory cytokines IFN-γ and IL-17, chemokine receptor CXCR3 and its ligands CXCL9 and CXCL11 in the SMGs. ADF also led to elevated mRNA levels of water channel protein aquaporin 5 and tight junction protein claudin-1, two factors crucial for normal salivary secretion in the SMGs. In addition, ADF reduced the proportion of IFN-γ- and IL-17- expressing CD4 T cells and diminished mRNA levels of IFN-γ, TNF-α, and IL-17 in the total submandibular draining lymph node cells. Taken together, ADF is effective in ameliorating newly established SS-associated salivary gland exocrinopathy in NOD mice.

Dental Pulp Stem Cell-Derived Conditioned Medium Alleviates Subarachnoid Hemorrhage-Induced Microcirculation Impairment by Promoting M2 Microglia Polarization and Reducing Astrocyte Swelling.

Aneurysmal subarachnoid hemorrhage (SAH) can cause severe neurological deficits and high mortality. Early brain edema following SAH contributes to the initiation of microcirculation impairment and may further lead to delayed ischemic neurologic deficit (DIND). This study aimed to investigate whether dental pulp stem cell conditioned medium (DPSC-CM) ameliorates SAH-induced microcirculation impairment and the underlying mechanisms. SAH was induced via intrathecal injection of fresh autologous blood in Wistar male adult rat. DPSC-CM or DPSC-CM + insulin growth factor-1 (IGF-1) antibody was randomly administered by intrathecal route 5min after SAH induction. To evaluate the underlying mechanisms of DPSC-CM in the treatment of SAH, primary rat astrocyte and microglia co-cultures were challenged with hemolysate or SAH-patient CSF in the presence or absence of DPSC-CM. The results showed that in vivo, DPSC-CM treatment decreased the brain water content, improved microcirculation impairment and enhanced functional recovery at 24h post-SAH. DPSC-CM treatment also alleviated the expressions of water channel protein aquaporin-4 (AQP4) and pro-inflammatory cytokines, and enhanced the expressions of anti-inflammatory factors in the cortical region. However, all the beneficial effects of DPSC-CM were abrogated after treatment with IGF-1 neutralizing antibody. The in vitro results further showed that DPSC-CM treatment reduced hemolysate/SAH-patient CSF-induced astrocyte swelling and promoted M2 microglia polarization, partially through IGF-1/AKT signaling. The data suggested that DPSC-CM significantly reduced brain edema and rescued microcirculation impairment with concomitant anti-inflammatory benefits after SAH, and may potentially be developed into a novel therapeutic strategy for SAH.

Neuromyelitis Optica Spectrum Disorder: From Basic Research to Clinical Perspectives.

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory disease of the central nervous system characterized by relapses and autoimmunity caused by antibodies against the astrocyte water channel protein aquaporin-4. Over the past decade, there have been significant advances in the biologic knowledge of NMOSD, which resulted in the IDENTIFICATION of variable disease phenotypes, biomarkers, and complex inflammatory cascades involved in disease pathogenesis. Ongoing clinical trials are looking at new treatments targeting NMOSD relapses. This review aims to provide an update on recent studies regarding issues related to NMOSD, including the pathophysiology of the disease, the potential use of serum and cerebrospinal fluid cytokines as disease biomarkers, the clinical utilization of ocular coherence tomography, and the comparison of different animal models of NMOSD.

Midbody-Localized Aquaporin Mediates Intercellular Lumen Expansion During Early Cleavage of an Invasive Freshwater Bivalve.

Intercellular lumen formation is a crucial aspect of animal development and physiology that involves a complex interplay between the molecular and physical properties of the constituent cells. Embryos of the invasive freshwater mussel Dreissena rostriformis are ideal models for studying this process due to the large intercellular cavities that readily form during blastomere cleavage. Using this system, we show that recruitment of the transmembrane water channel protein aquaporin exclusively to the midbody of intercellular cytokinetic bridges is critical for lumenogenesis. The positioning of aquaporin-positive midbodies thereby influences the direction of cleavage cavity expansion. Notably, disrupting cytokinetic bridge microtubules impairs not only lumenogenesis but also cellular osmoregulation. Our findings reveal a simple mechanism that provides tight spatial and temporal control over the formation of luminal structures and likely plays an important role in water homeostasis during early cleavage stages of a freshwater invertebrate species.

Immuno-pathogenesis of neuromyelitis optica and emerging therapies.

Neuromyelitis optica (NMO) is an inflammatory disease that resembles MS in the relapsing clinical course of optic neuritis and myelitis. Two decades of studies have revealed that autoantibodies, reactive to the water channel protein aquaporin 4 (AQP4)are detected in the core group of patients. These autoantibodies play a crucial role in the inflammatory pathology of NMO, involving proinflammatory cytokines, chemokines, and various inflammatory cells such as Th17 cells. Anti-AQP4 antibody-positive NMO differs fundamentally from MS, particularly in the responsiveness to therapies and the neuropathology accompanying destruction of astrocytes. Research into the immunological mechanism has led to the identification of possible targets of therapy, including complement pathway and interleukin-6 (IL-6) receptor signaling. Recent randomized controlled clinical trials have shown the remarkable efficacy of antibodies specific for complement C5, IL-6 receptor, and CD19+ B cells in prevention of NMO spectrum disorder relapses, although no such effects were found in anti-AQP4 antibody-negative patients. These results imply that anti-AQP4 antibody is a biomarker predicting the efficacy of therapies, and indicate the future direction towards "precision medicine."

Interferon-gamma controls pathogenic T-helper 17 and B cells in a new Aquaporin-4 induced experimental autoimmune encephalomyelitis

Abstract Background Neuromyelitis Optica (NMO) is an autoimmune disease of the Central Nervous System (CNS) mediated by Th17 cells and antibody response to the water channel protein Aquaporin 4 (AQP4), leading to chronic damage of the optic nerves and spinal cord. NMO animal models are substandard inducing disease inconsistently and weakly. Objectives Characterize a new NMO mouse model, which best represents the human disease in terms of incidence and chronicity of the disease, severity of symptoms and underlying molecular mechanisms. Methods C57BL/6 (WT) and IFN-γ receptor knockout (R-KO) mice were immunized subcutaneously with the AQP4201–220 peptide in Complete Freund Adjuvant and treated with pertussis toxin at day 0 and +2. WT were treated weakly with neutralizing anti-IFN-γ antibodies. mRNA expression and flow cytometry analysis of infiltrating CNS cells were performed. CNS histopathology was determined by immunofluorescence. In vivo B-cell depletion was made using anti-CD20 antibodies. Results WT mice treated with anti-IFN-γ and RKO mice showed ascendant paralysis starting from the tail to complete hind limb paralysis. Mice showed increased disease incidence and symptoms were more severe and chronic. CNS IL-17 expressing T cells and Th17 associated genes were upregulated in the absence of IFN-γ. CSN histological analysis showed an increased presence of T and B cells in lesion sites, associated with astrocytes and myelin loss. B-cell depletion in AQP4 primed RKO mice, diminished the incidence and severity of the disease confirming B cell pathogenicity. Conclusions AQP4 mouse model is strictly regulated by IFN-γ and its signaling, which control the disease progression and severity, by restraining pathogenic Th17 and B cells. Supported by grant from NIH (R21 Grant 12878760)

Aquaporin (AQP) channels in the spiny dogfish, Squalus acanthias II: Localization of AQP3, AQP4 and AQP15 in the kidney.

Three aquaporin water channel proteins, AQP3, AQP4 and AQP15 were localized to cells within the kidney of the spiny dogfish, Squalus acanthias, using an immunohistochemical approach. Dogfish kidney has two zones, the bundle zone (including five nephron segment bundles) and the sinus zone (with two major loops). In order to discriminate between the two loops, the cilia occurring in the first proximal/intermediate loop were labeled with two antibodies including an anti-acetylated tubulin antibody. The second late distal tubule loop (LDT) was identified, as the nephron in that region has no luminal cilia. Strong staining of the rabbit anti-dogfish AQP3, AQP4 (AQP4/2) or AQP15 polyclonal antibodies localized to LDT tubules. These antibodies were further co-stained with a mouse anti-Na+,K+-ATPase a5 monoclonal antibody, as Na+,K+-ATPase has previously been suggested to localize to the early distal tubule (EDT) and LDT and a mouse anti-NKCC T4 antibody, as NKCC2 was previously suggested to be located in the EDT and the second half of the LDT. In the LDT, strong AQP4/2 and AQP15 antibody staining localized together with the strong Na+,K+-ATPase antibody staining, whereas strong AQP3 antibody staining was largely separate but with an overlapping distribution. Very low levels of AQP4/2 antibody basal membrane staining was also detected in the first proximal /intermediate loop of the sinus zone. There was no mouse anti-NKCC T4 antibody staining apparent in the LDT. In the convoluted part of the bundle zone, the AQP4/2 and Na+,K+-ATPase but not the AQP3 or AQP15 antibodies stained tubule segments, with both AQP4/2 and Na+,K+-ATPase staining the EDT, and with low-level AQP4/2 staining of two other tubules of the bundle, which were most likely to be the proximal 1a (PIa) and intermediate II (IS II) tubules. The AQP4/2 antibody also stained the EDT in the straight bundle zone. The mouse anti-NKCC T4 antibody stained the apical region of EDT tubules in the convoluted bundle zone, suggesting that the antibody was binding to the NKCC2 cotransporter. The AQP15 antibody appeared to bind to the peritubular sheath surrounding bundles in the bundle zone. Due to the AQP4/2 antibody staining in the EDT that immediately proceeds and continues into the LDT, this suggested that the strong AQP4/2, AQP15 and Na+,K+-ATPase antibody staining was located at the beginning of the LDT and therefore the strong AQP3 was located at the end of the LDT. The staining of all three AQP antibodies was blocked by the peptide-antigen used to make each one, suggesting that all the staining is specific to each antibody.

Pathobiology, Diagnosis, and Current Biomarkers in Neuromyelitis Optica Spectrum Disorders.

Neuromyelitis optica spectrum disorder (NMOSD) is characterized by chronic inflammation of the central nervous system (CNS), particularly the optic nerves and spinal cord. Although it displays some clinical features similar to multiple sclerosis (MS), the etiology and treatment are distinct, and therefore accurate diagnosis is essential. Autoantibodies targeting the water channel protein aquaporin-4 (AQP4) and the myelin sheath protein myelin oligodendrocyte glycoprotein are the major antigen-specific serological biomarkers known to date, with destruction of astrocytes as the primary mode of CNS damage in AQP4-positive disease. This mini-review summarizes the pathobiology, clinical features, and current methods of serological testing used to assess NMOSD and differentiate this disorder from MS. A brief summary of emerging therapies is also presented. NMOSD can be distinguished from MS through a combination of clinical findings, imaging investigations, and serological analysis. Seronegative cases are particularly difficult to diagnose and can pose a challenge to clinicians. As knowledge deepens, new therapies and biomarkers are expected to improve treatment of this rare debilitating disease.

Treatment of Neuromyelitis Optica Spectrum Disorders.

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune central nervous system (CNS) inflammatory disorder that can lead to serious disability and mortality. Females are predominantly affected, including those within the reproductive age. Most patients develop relapsing attacks of optic neuritis; longitudinally extensive transverse myelitis; and encephalitis, especially brainstem encephalitis. The majority of NMOSD patients are seropositive for IgG autoantibodies against the water channel protein aquaporin-4 (AQP4-IgG), reflecting underlying aquaporin-4 autoimmunity. Histological findings of the affected CNS tissues of patients from in-vitro and in-vivo studies support that AQP4-IgG is directly pathogenic in NMOSD. It is believed that the binding of AQP4-IgG to CNS aquaporin-4 (abundantly expressed at the endfoot processes of astrocytes) triggers astrocytopathy and neuroinflammation, resulting in acute attacks. These attacks of neuroinflammation can lead to pathologies, including aquaporin-4 loss, astrocytic activation, injury and loss, glutamate excitotoxicity, microglial activation, neuroinflammation, demyelination, and neuronal injury, via both complement-dependent and complement-independent pathophysiological mechanisms. With the increased understanding of these mechanisms underlying this serious autoimmune astrocytopathy, effective treatments for both active attacks and long-term immunosuppression to prevent relapses in NMOSD are increasingly available based on the evidence from retrospective observational data and prospective clinical trials. Knowledge on the indications and potential side effects of these medications are essential for a clear evaluation of the potential benefits and risks to NMOSD patients in a personalized manner. Special issues such as pregnancy and the coexistence of other autoimmune diseases require additional concern and meticulous care. Future directions include the identification of clinically useful biomarkers for the prediction of relapse and monitoring of the therapeutic response, as well as the development of effective medications with minimal side effects, especially opportunistic infections complicated by long-term immunosuppression.

Activation of Aquaporin 5 by carcinogenic Helicobacter pylori infection promotes epithelial-mesenchymal transition via the MEK/ERK pathway.

Helicobacter pylori (H.pylori) is a major risk factor for gastric cancer. The water channel protein Aquaporin 5 (AQP5) is involved in the tumorigenesis and progression of various cancers. In this study, we aimed to explore the role of AQP5 in H.pylori-induced gastric carcinogenesis. We collected 160 samples which inculded CNAG, IM, Dys and gastric cancer from patients who underwent endoscopy and detected the expression of AQP5. In vivo and vitro H.pylori infection models, we explored the relationship between AQP5 and H.pylori. Plasmid, siRNA and inhibitors were used to investigated the relationship between AQP5 and EMT and the role of AQP5 in H.pylori-induced gastric carcinogenesis. AQP5 expression was gradually increased in human gastric tissues with the progression of chronic nonatrophic gastritis to gastric cancer and associated with the H.pylori infection status. In vivo and in vitro studies showed that H.pylori infection induced AQP5 expression in gastric epithelial cells in a CagA-dependent manner. Knockdown of AQP5 reversed H.pylori-induced cell proliferation and invasion, and -suppressed cell apoptosis. Additionally, knockdown of AQP5 suppressed H.pylori-induced Epithelial-mesenchymal transition (EMT) phenotypes by regulating transcriptional factors, mesenchymal markers, and epithelial markers. We explored the underlying mechanism and our results indicated that knockdown of AQP5 significantly suppressed H.pylori infection-induced phosphorylation of ERK1/2, MEK and the expression levels of downstream genes. Treatment with an ERK inhibitor suppressed the EMT induced by H.pylori infection. Taken together, this study suggest that pathogenic H.pylori infection promotes AQP5 expression to induce the EMT via the MEK/ERK signaling pathway.

Deletion of beaded filament proteins or the C-terminal end of Aquaporin 0 causes analogous abnormal distortion aberrations in mouse lens

Lens-specific beaded filament (BF) proteins CP49 and filensin interact with the C-terminus of the water channel protein Aquaporin 0 (AQP0). Previously we have reported that a C-terminally end-deleted AQP0-expressing transgenic mouse model AQP0ΔC/ΔC developed abnormal optical aberrations in the lens. This investigation was undertaken to find out whether the total loss of the BF structural proteins alter the optical properties of the lens and cause optical aberrations similar to those in AQP0ΔC/ΔC lenses; also, to map the changes in the optical quality as a function of age in the single or double BF protein knockouts as well as to assess whether there is any significant change in the water channel function of AQP0 in these knockouts. A double knockout mouse (2xKO) model for CP49 and filensin was developed by crossing CP49-KO and filensin-KO mice. Wild type, CP49-KO, filensin-KO, and 2xKO lenses at different ages, and AQP0ΔC/ΔC lenses at postnatal day-17 were imaged through the optical axis and compared for optical quality and focusing property. All three knockout models showed loss of transparency, and development of abnormal optical distortion aberration similar to that in AQP0ΔC/ΔC. Copper grid focusing by the lenses at 6, 9 and 12 months of age showed an increase in aberrations as age advanced. With progression in age, the grid images produced by the lenses of all KO models showed a transition from a positive barrel distortion aberration to a pincushion distortion aberration with the formation of three distinct aberration zones similar to those produced by AQP0ΔC/ΔC lenses. Water permeability of fiber cell membrane vesicles prepared from CP49-KO, filensin-KO and 2xKO models, measured using the osmotic shrinking method, remained similar to that of the wild type without any statistically significant alteration (P > 0.05). Western blotting and quantification revealed the expression of comparable quantities of AQP0 in all three BF protein KOs. Our study reveals that loss of single or both beaded filament proteins significantly affect lens refractive index gradient, transparency and focusing ability in an age-dependent manner and the interaction of BF proteins with AQP0 is critical for the proper functioning of the lens. The presence of BF proteins is necessary to prevent abnormal optical aberrations and maintain homeostasis in the aging lens.

Glymphatic Dysfunction: A Bridge Between Sleep Disturbance and Mood Disorders.

Mounting evidence demonstrates a close relationship between sleep disturbance and mood disorders, including major depression disorder (MDD) and bipolar disorder (BD). According to the classical two-process model of sleep regulation, circadian rhythms driven by the light–dark cycle, and sleep homeostasis modulated by the sleep–wake cycle are disrupted in mood disorders. However, the exact mechanism of interaction between sleep and mood disorders remains unclear. Recent discovery of the glymphatic system and its dynamic fluctuation with sleep provide a plausible explanation. The diurnal variation of the glymphatic circulation is dependent on the astrocytic activity and polarization of water channel protein aquaporin-4 (AQP4). Both animal and human studies have reported suppressed glymphatic transport, abnormal astrocytes, and depolarized AQP4 in mood disorders. In this study, the “glymphatic dysfunction” hypothesis which suggests that the dysfunctional glymphatic pathway serves as a bridge between sleep disturbance and mood disorders is proposed.

Unbe‐leaf‐able! Aquaporin‐4's Connection to Neuromyelitis Optica

Neuromyelitis optica (NMO) is an incurable disease with debilitating symptoms that occurs when autoantibodies attack and destroy the water channel protein Aquaporin-4 (AQP4), located in the endfeet of astrocytes in the optic nerve, spinal cord, and brain. Our research on AQP4's role in NMO focused on the AQP-M23 isoform. The autoantibody Immunoglobulin G (IgG) can bind to epitopes on AQP4; this interaction is linked to neuroautoimmune disorders, specifically NMO. We hypothesized that structural similarities between certain plant AQPs and human AQP4 could be a trigger for neurological disorders. Individuals may develop an antigenic reaction to AQP by consuming plants high in AQP; the dietary antibodies produced could mistake human AQP4 for a particular plant AQP and attack it by crossing a compromised blood-brain barrier, leading to a neuroautoimmune response. It is essential to understand the relationship between AQP4's structure and IgG to better understand the cause for NMO and other neuroautoimmune disorders so that we can find more effective forms of treatment and propose potential cures. Additionally, it is important to know if there is a link between the consumption of plants high in AQP and the development of neuroautimmune disorders; if so, at-risk individuals with a damaged blood-brain barrier can avoid consuming AQP-rich foods. To identify possible binding sites between AQP4 and IgG, we examined the properties of extracellular loops A, C, and E in AQP4, focusing on amino acid residues 207-232 located on loop E. This segment of AQP4 has portions of its sequence that are identical to the corresponding portions on spinach, corn, soybean, and tomato AQP. We hypothesized that there might be a possible epitope for IgG binding within these residues on loop E. We used our research to then identify other possible locations for epitopes on AQP4 by analyzing the hydrophobicity and size of potential binding residues. To do this, we used the human AQP4 Protein Data Bank file, 3GD8, and Jmol molecular modeling software to highlight possible epitope locations and examine the structural changes that will occur when IgG binds to AQP4. We also highlighted variations between human AQP4 and plant AQP, specifically spinach AQP, which is the most commonly reactive. The Mahtomedi MSOE Center for BioMolecular Modeling MAPS Team used 3-D modeling and printing technology to examine the structure-function relationships of AQP4 in autoantibody binding. The visual model was a valuable tool in developing our story.

Could Galectin-3 be a key player in the etiology of neuromyelitis optica spectrum disorder?

Neuromyelitis Optica Spectrum Disorder (NMOSD) is a chronic, inflammatory, demyelinating disorder of the central nervous system (CNS) characterized primarily by transverse myelitis (TM) and optic neuritis (ON). Serum antibodies of the IgG class to the water channel protein aquaporin-4 (AQP4) are associated with NMOSD in most cases. These antibodies are thought to cause functional abnormality or changed expressional pattern of AQP4 channel proteins in the CNS lesions.Activation of microglia is one of the chief antibody-mediated effects in NMOSD and it has opposing detrimental and protective effects in NMOSD. On the one hand, it promotes neuroinflammation, demyelination and BBB breakdown. On the other, it aids in remyelination. What controls the switch between these effects is unknown.Recently, Galectin- 3, a lectin, has been identified as a key player in several neurodegenerative diseases. In transient focal brain ischemia, alzheimer’s disease (AD), huntington disease (HD), and experimental autoimmune encephalitis (EAE), Galectin-3 promotes microglia-mediated inflammation.Conversely, in amyotrophic lateral sclerosis (ALS), Galectin-3 reduces inflammation. It also suppresses Th17 cytokines, which play a crucial role in NMOSD pathogenesis. Being devoid of a leader signal, Gal-3 localizes in different cellular compartments and is subject to various post-translational modifications. These reasons explain why Galectin-3 expression has opposing effects under different physiological conditions. Microglia-mediated inflammation in NMOSD has not been extensively studied. The factors that regulate microglia-mediated inflammation in NMOSD are unknown. Here, I hypothesize that Galectin-3 might be an etiological factor in NMOSD that regulates microglia-mediated inflammation. Analysing the role of Gal-3 in NMOSD could help in the development of novel therapies to treat NMOSD.

Aquaporin-4 Expression during Toxic and Autoimmune Demyelination.

The water channel protein aquaporin-4 (AQP4) is required for a normal rate of water exchange across the blood–brain interface. Following the discovery that AQP4 is a possible autoantigen in neuromyelitis optica, the function of AQP4 in health and disease has become a research focus. While several studies have addressed the expression and function of AQP4 during inflammatory demyelination, relatively little is known about its expression during non-autoimmune-mediated myelin damage. In this study, we used the toxin-induced demyelination model cuprizone as well as a combination of metabolic and autoimmune myelin injury (i.e., Cup/EAE) to investigate AQP4 pathology. We show that during toxin-induced demyelination, diffuse AQP4 expression increases, while polarized AQP4 expression at the astrocyte endfeet decreases. The diffuse increased expression of AQP4 was verified in chronic-active multiple sclerosis lesions. Around inflammatory brain lesions, AQP4 expression dramatically decreased, especially at sites where peripheral immune cells penetrate the brain parenchyma. Humoral immune responses appear not to be involved in this process since no anti-AQP4 antibodies were detected in the serum of the experimental mice. We provide strong evidence that the diffuse increase in anti-AQP4 staining intensity is due to a metabolic injury to the brain, whereas the focal, perivascular loss of anti-AQP4 immunoreactivity is mediated by peripheral immune cells.