scholarly journals Aquaporin-4 dependent glymphatic solute transport in rodent brain

2017 ◽  
Author(s):  
Humberto Mestre ◽  
Benjamin T. Kress ◽  
Wenyan Zou ◽  
Tinglin Pu ◽  
Giridhar Murlidharan ◽  
...  
Keyword(s):  
Solute Transport ◽  
Healthy Aging ◽  
Fluid Transport ◽  
Water Channel ◽  
Amyloid Β ◽  
Aquaporin 4 ◽  
Tau Proteins ◽  
Glymphatic System ◽  
Aqp4 Expression ◽  
Transgenic Lines

AbstractThe glymphatic system is a brain-wide metabolite clearance pathway, impairment of which in post-traumatic and ischemic brain or healthy aging is proposed to contribute to intracerebral accumulation of amyloid-β and tau proteins. Glymphatic perivascular influx of cerebrospinal fluid (CSF) depends upon the expression and perivascular localization of the astroglial water channel aquaporin-4 (AQP4). Prompted by a recent publication that failed to find an effect of Aqp4 knockout on perivascular CSF tracer influx and interstitial fluid (ISF) tracer dispersion, four independent research groups have herein re-examined the importance of Aqp4 in glymphatic fluid transport. We concur in finding that CSF tracer influx, as well as fluorescently-tagged amyloid-β efflux, are significantly faster in wild-type mice than in three different transgenic lines featuring disruption of the Aqp4 gene and one line in which AQP4 expression lacks the critical perivascular localization (Snta1 knockout). These data validate the role of AQP4 in supporting fluid and solute transport and efflux in brain in accordance with the glymphatic system model.

scholarly journals Protective Effects of Aquaporin-4 Deficiency on Longer-Term Neurological Outcomes in a Mouse Model of Traumatic Brain Injury

2020 ◽  
Author(s):  
Xiaosong Liu ◽  
Yingxin Xie ◽  
Xiangdong Wan ◽  
Jianliang Wu ◽  
Zhenzeng Fan ◽  
...  
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Mouse Model ◽  
Water Channel ◽  
Amyloid Β ◽  
Aquaporin 4 ◽  
Protective Effects ◽  
Fluid Exchange ◽  
Glymphatic System ◽  
Neurological Outcomes

Abstract Background: Traumatic brain injury (TBI) has been a crucial health problem, with more than 50 million patients worldwide each year. Glymphatic system is a fluid exchange system that relies on the polarized water channel aquaporin-4 (AQP4) at the astrocytes, accounting for the clearance of abnormal proteins and metabolites from brain tissues. However, the dysfunction of glymphatic system and alteration of AQP4 polarization during the progression of TBI remain unclear.Methods: AQP4−/− and Wild Type (WT) mice were used to establish the TBI mouse model respectively. Morris water maze (MWM) was used to establish the cognitive functions of AQP4−/− and WT mice post TBI. Western-blot and qRT-PCR assays were performed to demonstrate protective effects of AQP4 deficiency to blood-brain barrier (BBB) integrity and amyloid-β clearance. The inflammation of cerebral tissues post TBI was estimated by ELISA assay.Results: AQP4 deficiency alleviated the brain edema and neurological deficit in TBI mice. AQP4-knockout led to improved cognitive outcomes in mice post TBI. The BBB integrity and cerebral amyloid-β clearance were protected by AQP4 deficiency in TBI mice. AQP4 deficiency ameliorated the TBI-induced inflammation.Conclusion: AQP4 deficiency improved longer-term neurological outcomes in a mouse model of TBI.

scholarly journals Aquaporin-4 Expression during Toxic and Autoimmune Demyelination

Cells ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 2187
Author(s):  
Sven Olaf Rohr ◽  
Theresa Greiner ◽  
Sarah Joost ◽  
Sandra Amor ◽  
Paul van der Valk ◽  
...  
Keyword(s):  
Immune Cells ◽  
Water Channel ◽  
Staining Intensity ◽  
Brain Parenchyma ◽  
Aquaporin 4 ◽  
Aqp4 Expression ◽  
Humoral Immune ◽  
Autoimmune Demyelination ◽  
Peripheral Immune Cells ◽  
The Brain

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.

scholarly journals Immunohistochemical localization of aquaporin 4 (AQP4) in the porcine gastrointestinal tract

2015 ◽  
Vol 84 (4) ◽  
pp. 321-326 ◽  
Author(s):  
Marcin Bartłomiej Arciszewski ◽  
Małgorzata Matysek ◽  
Waldemar Sienkiewicz
Keyword(s):  
Gastrointestinal Tract ◽  
Epithelial Cells ◽  
Colonic Mucosa ◽  
Water Channel ◽  
Immunohistochemical Localization ◽  
Aquaporin 4 ◽  
Enteric Neurons ◽  
Aqp4 Expression ◽  
Enteric Ganglia ◽  
Strong Immunoreactivity

The water channel aquaporin-4 (AQP4) is a protein widely expressed on plasma membrane of a variety of epithelial cells. In this study we investigated the expression of AQP4 in the gastrointestinal tract of the pig using immunohistochemical staining. We found no presence of AQP4 in the different regions of the pig stomach. In the porcine small intestine moderate immunoreactivity to AQP4 was detected in enterocytes (along the villi and in the bottom of the crypts), duodenal Brunner’s glands and in enteric ganglia in cells lying in close vicinity to myenteric as well as submucous neurons. In superficial epithelial cells of the colonic mucosa as well as of caecal and colonic glands a very strong immunoreactivity to AQP4 was found. Both in the myenteric and submucous ganglia of the large intestine AQP4-positive cells surrounding enteric neurons were observed. We concluded that AQP4 expression in the porcine gastrointestinal tract showed some species-dependent differences in relation to other species. Based on the presented distribution pattern of AQP4, it is likely that the aquaporin plays a role in mucous (but not acid) secretion and intestinal absorptive processes in the pig.

scholarly journals Aquaporin-4-dependent glymphatic solute transport in the rodent brain

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Humberto Mestre ◽  
Lauren M Hablitz ◽  
Anna LR Xavier ◽  
Weixi Feng ◽  
Wenyan Zou ◽  
...  
Keyword(s):  
Interstitial Fluid ◽  
Meta Analysis ◽  
Water Channel ◽  
Amyloid Β ◽  
Aquaporin 4 ◽  
Tracer Transport ◽  
Wild Type ◽  
Knock Out ◽  
Rodent Brain

The glymphatic system is a brain-wide clearance pathway; its impairment contributes to the accumulation of amyloid-β. Influx of cerebrospinal fluid (CSF) depends upon the expression and perivascular localization of the astroglial water channel aquaporin-4 (AQP4). Prompted by a recent failure to find an effect of Aqp4 knock-out (KO) on CSF and interstitial fluid (ISF) tracer transport, five groups re-examined the importance of AQP4 in glymphatic transport. We concur that CSF influx is higher in wild-type mice than in four different Aqp4 KO lines and in one line that lacks perivascular AQP4 (Snta1 KO). Meta-analysis of all studies demonstrated a significant decrease in tracer transport in KO mice and rats compared to controls. Meta-regression indicated that anesthesia, age, and tracer delivery explain the opposing results. We also report that intrastriatal injections suppress glymphatic function. This validates the role of AQP4 and shows that glymphatic studies must avoid the use of invasive procedures.

scholarly journals Protective Role of Early Aquaporin 4 Induction against Postischemic Edema Formation

2008 ◽  
Vol 29 (2) ◽  
pp. 423-433 ◽  
Author(s):  
Lorenz Hirt ◽  
Béatrice Ternon ◽  
Melanie Price ◽  
Nabil Mastour ◽  
Jean-François Brunet ◽  
...  
Keyword(s):  
Water Channel ◽  
Protective Role ◽  
Aquaporin 4 ◽  
Late Time ◽  
Protective Mechanisms ◽  
Edema Formation ◽  
Aqp4 Expression ◽  
Blood Brain Barrier Disruption ◽  
Brain Barrier Disruption

Aquaporin 4 (AQP4) is a water channel involved in water movements across the cell membrane and is spatially organized on the cell surface in orthogonal array particles (OAPs). Its role in edema formation or resolution after stroke onset has been studied mainly at late time points. We have shown recently that its expression is rapidly induced after ischemia coinciding in time with an early swelling of the ischemic hemisphere. There are two isoforms of AQP4: AQP4-M1 and AQP4-M23. The ratio of these isoforms influences the size of the OAPs but the functional impact is not known. The role of the early induction of AQP4 is not yet known. Thrombin preconditioning in mice provides a useful model to study endogenous protective mechanisms. Using this model, we provide evidence for the first time that the early induction of AQP4 may contribute to limit the formation of edema and that the AQP4-M1 isoform is predominantly induced in the ischemic tissue at this time point. Although it prevents edema formation, the early induction of the AQP4 expression does not prevent the blood—brain barrier disruption, suggesting an effect limited to the prevention of edema formation possibly by removing of water from the tissue.

Effect of C-type natriuretic peptide (CNP) on water channel aquaporin-4 (AQP4) expression in cultured astrocytes

2004 ◽  
Vol 122 (2) ◽  
pp. 109-115 ◽  
Author(s):  
Masakazu Miyajima ◽  
Hajime Arai ◽  
Osamu Okuda ◽  
Makoto Hishii ◽  
Hajime Nakanishi ◽  
...  
Keyword(s):  
Natriuretic Peptide ◽  
Water Channel ◽  
Aquaporin 4 ◽  
Aqp4 Expression ◽  
Cultured Astrocytes

Distribution of aquaporin-4 water channel expression within rat kidney

1995 ◽  
Vol 269 (6) ◽  
pp. F775-F785 ◽  
Author(s):  
J. Terris ◽  
C. A. Ecelbarger ◽  
D. Marples ◽  
M. A. Knepper ◽  
S. Nielsen
Keyword(s):  
Collecting Duct ◽  
Rat Kidney ◽  
Basolateral Membrane ◽  
Regional Distribution ◽  
Water Channel ◽  
Aquaporin 4 ◽  
Molecular Water ◽  
Water Restriction ◽  
Aqp4 Expression ◽  
Aquaporin 2

The aquaporins are a family of transmembrane proteins that function as molecular water channels. Recently, a mercurial-insensitive water channel [MIWC or aquaporin-4 (AQP4)] has been cloned, and its mRNA was found to be expressed strongly in kidney inner medulla and several nonrenal tissues. We prepared affinity-purified polyclonal antipeptide antibodies to AQP4 to define the regional distribution and cellular location of this water channel within the kidney. Immunoblotting of membrane fractions from different regions of the kidney revealed strongest expression in the base of the renal inner medulla, with detectable levels also in the inner medullary tip, but little or no expression in the outer medulla or cortex. Immunocytochemistry (light microscopy) revealed renal AQP4 labeling exclusively in the collecting duct principal cells, chiefly in the proximal two-thirds of the inner medullary collecting duct (IMCD). Little or no expression was seen in the outer medullary and cortical collecting ducts. Immunoelectron microscopy demonstrated AQP4 labeling of the basolateral membrane of IMCD cells, with relatively little labeling of intracellular vesicles. Differential centrifugation of inner medullary homogenates also revealed a lack of distribution to the vesicle-enriched fraction, which contains the vasopressin-regulated water channel, aquaporin-2. In contrast to aquaporin-2 and aquaporin-3, water restriction of rats did not increase the level of AQP4 expression. These results suggest a possible role for AQP4 in the basolateral exit of water from the IMCD.

scholarly journals Aquaporin-4 Mediates Permanent Brain Alterations in a Mouse Model of Hypoxia-Aged Hydrocephalus

2021 ◽  
Vol 22 (18) ◽  
pp. 9745
Author(s):  
José Luis Trillo-Contreras ◽  
Juan José Toledo-Aral ◽  
Javier Villadiego ◽  
Miriam Echevarría
Keyword(s):  
Cognitive Deficits ◽  
Water Channel ◽  
Aquaporin 4 ◽  
Ependymal Cells ◽  
Cerebral Tissue ◽  
Principal Characteristics ◽  
Aqp4 Expression ◽  
Aged Mice ◽  
The Brain ◽  
Ventricular Distensibility

Aquaporin-4 (AQP4) is the principal water channel in the brain being expressed in astrocytes and ependymal cells. AQP4 plays an important role in cerebrospinal fluid (CSF) homeostasis, and alterations in its expression have been associated with hydrocephalus. AQP4 contributes to the development of hydrocephalus by hypoxia in aged mice, reproducing such principal characteristics of the disease. Here, we explore whether these alterations associated with the hydrocephalic state are permanent or can be reverted by reexposure to normoxia. Alterations such as ventriculomegaly, elevated intracranial pressure, and cognitive deficits were reversed, whereas deficits in CSF outflow and ventricular distensibility were not recovered, remaining impaired even one month after reestablishment of normoxia. Interestingly, in AQP4−/− mice, the impairment in CSF drainage and ventricular distensibility was completely reverted by re-normoxia, indicating that AQP4 has a structural role in the chronification of those alterations. Finally, we show that aged mice subjected to two hypoxic episodes experience permanent ventriculomegaly. These data reveal that repetitive hypoxic events in aged cerebral tissue promote the permanent alterations involved in hydrocephalic pathophysiology, which are dependent on AQP4 expression.

scholarly journals Assessment of Amyloid Forming Tendency of Peptide Sequences from Amyloid Beta and Tau Proteins Using Force-Field, Semi-Empirical, and Density Functional Theory Calculations

2021 ◽  
Vol 22 (6) ◽  
pp. 3244
Author(s):  
Charuvaka Muvva ◽  
Natarajan Arul Murugan ◽  
Venkatesan Subramanian
Keyword(s):  
Force Field ◽  
Density Functional ◽  
Amyloid Β ◽  
Density Functional Theory Calculations ◽  
Tau Proteins ◽  
Functional Theory ◽  
Energy Profiles ◽  
Α Helix ◽  
Semi Empirical ◽  
Β Sheet

A wide variety of neurodegenerative diseases are characterized by the accumulation of protein aggregates in intraneuronal or extraneuronal brain regions. In Alzheimer’s disease (AD), the extracellular aggregates originate from amyloid-β proteins, while the intracellular aggregates are formed from microtubule-binding tau proteins. The amyloid forming peptide sequences in the amyloid-β peptides and tau proteins are responsible for aggregate formation. Experimental studies have until the date reported many of such amyloid forming peptide sequences in different proteins, however, there is still limited molecular level understanding about their tendency to form aggregates. In this study, we employed umbrella sampling simulations and subsequent electronic structure theory calculations in order to estimate the energy profiles for interconversion of the helix to β-sheet like secondary structures of sequences from amyloid-β protein (KLVFFA) and tau protein (QVEVKSEKLD and VQIVYKPVD). The study also included a poly-alanine sequence as a reference system. The calculated force-field based free energy profiles predicted a flat minimum for monomers of sequences from amyloid and tau proteins corresponding to an α-helix like secondary structure. For the parallel and anti-parallel dimer of KLVFFA, double well potentials were obtained with the minima corresponding to α-helix and β-sheet like secondary structures. A similar double well-like potential has been found for dimeric forms for the sequences from tau fibril. Complementary semi-empirical and density functional theory calculations displayed similar trends, validating the force-field based free energy profiles obtained for these systems.

Age-Dependency of Total Tau in the Cerebrospinal Fluid Is Corrected by Amyloid-β 1–40: A Correlational Study in Healthy Adults

2021 ◽  
pp. 1-8
Author(s):  
Paul Theo Zebhauser ◽  
Achim Berthele ◽  
Marie-Sophie Franz ◽  
Oliver Goldhardt ◽  
Janine Diehl-Schmid ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
Amyloid Β ◽  
Healthy Adults ◽  
Tau Proteins ◽  
Clinical Settings ◽  
Inclusion Criteria ◽  
Total Tau ◽  
Potential Marker ◽  
Wide Range ◽  
The Relationship

Background: Tau proteins are established biomarkers of neuroaxonal damage in a wide range of neurodegenerative conditions. Although measurement of total-Tau in the cerebrospinal fluid is widely used in research and clinical settings, the relationship between age and total-Tau in the cerebrospinal fluid is yet to be fully understood. While past studies reported a correlation between age and total-Tau in the cerebrospinal fluid of healthy adults, in clinical practice the same cut-off value is used independently of patient’s age. Objective: To further explore the relationship between age and total-Tau and to disentangle neurodegenerative from drainage-dependent effects. Methods: We analyzed cerebrospinal fluid samples of 76 carefully selected cognitively healthy adults and included amyloid-β 1–40 as a potential marker of drainage from the brain’s interstitial system. Results: We found a significant correlation of total-Tau and age, which was no longer present when correcting total-Tau for amyloid-β 1–40 concentrations. These findings were replicated under varied inclusion criteria. Conclusion: Results call into question the association of age and total-Tau in the cerebrospinal fluid. Furthermore, they suggest diagnostic utility of amyloid-β 1–40 as a possible proxy for drainage-mechanisms into the cerebrospinal fluid when interpreting biomarker concentrations for neurodegenerative diseases.

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