scholarly journals Reply to ‘Aquaporin 4 and glymphatic flow have central roles in brain fluid homeostasis’

Author(s):  
Nanna MacAulay
Author(s):  
Mootaz M. Salman ◽  
Philip Kitchen ◽  
Jeffrey J. Iliff ◽  
Roslyn M. Bill

2021 ◽  
Vol 12 ◽  
Author(s):  
Jacek Szczygielski ◽  
Marta Kopańska ◽  
Anna Wysocka ◽  
Joachim Oertel

In the past, water homeostasis of the brain was understood as a certain quantitative equilibrium of water content between intravascular, interstitial, and intracellular spaces governed mostly by hydrostatic effects i.e., strictly by physical laws. The recent achievements in molecular bioscience have led to substantial changes in this regard. Some new concepts elaborate the idea that all compartments involved in cerebral fluid homeostasis create a functional continuum with an active and precise regulation of fluid exchange between them rather than only serving as separate fluid receptacles with mere passive diffusion mechanisms, based on hydrostatic pressure. According to these concepts, aquaporin-4 (AQP4) plays the central role in cerebral fluid homeostasis, acting as a water channel protein. The AQP4 not only enables water permeability through the blood-brain barrier but also regulates water exchange between perivascular spaces and the rest of the glymphatic system, described as pan-cerebral fluid pathway interlacing macroscopic cerebrospinal fluid (CSF) spaces with the interstitial fluid of brain tissue. With regards to this, AQP4 makes water shift strongly dependent on active processes including changes in cerebral microcirculation and autoregulation of brain vessels capacity. In this paper, the role of the AQP4 as the gatekeeper, regulating the water exchange between intracellular space, glymphatic system (including the so-called neurovascular units), and intravascular compartment is reviewed. In addition, the new concepts of brain edema as a misbalance in water homeostasis are critically appraised based on the newly described role of AQP4 for fluid permeation. Finally, the relevance of these hypotheses for clinical conditions (including brain trauma and stroke) and for both new and old therapy concepts are analyzed.


Author(s):  
Yu-Long Lan ◽  
Jian-Jiao Chen ◽  
Gang Hu ◽  
Jun Xu ◽  
Ming Xiao ◽  
...  

2018 ◽  
Vol 17 (4) ◽  
pp. 299-308 ◽  
Author(s):  
Bogdan Catalin ◽  
Otilia-Constantina Rogoveanu ◽  
Ionica Pirici ◽  
Tudor Adrian Balseanu ◽  
Adina Stan ◽  
...  

Background: Edema represents one of the earliest negative markers of survival and consecutive neurological deficit following stroke. The mixture of cellular and vasogenic edema makes treating this condition complicated, and to date, there is no pathogenically oriented drug treatment for edema, which leaves parenteral administration of a hypertonic solution as the only non-surgical alternative. Objective: New insights into water metabolism in the brain have opened the way for molecular targeted treatment, with aquaporin 4 channels (AQP4) taking center stage. We aimed here to assess the effect of inhibiting AQP4 together with the administration of a neurotropic factor (Cerebrolysin) in ischemic stroke. Methods: Using a permanent medial cerebral artery occlusion rat model, we administrated a single dose of the AQP4 inhibitor TGN-020 (100 mg/kg) at 15 minutes after ischemia followed by daily Cerebrolysin dosing (5ml/kg) for seven days. Rotarod motor testing and neuropathology examinations were next performed. Results: We showed first that the combination treatment animals have a better motor function preservation at seven days after permanent ischemia. We have also identified distinct cellular contributions that represent the bases of behavior testing, such as less astrocyte scarring and a larger neuronalsurvival phenotype rate in animals treated with both compounds than in animals treated with Cerebrolysin alone or untreated animals. Conclusion: Our data show that water diffusion inhibition and Cerebrolysin administration after focal ischemic stroke reduces infarct size, leading to a higher neuronal survival in the peri-core glial scar region.


Author(s):  
Junyuan Wu ◽  
Zhiwei Li ◽  
Wei Yuan ◽  
Qiang Zhang ◽  
Yong Liang ◽  
...  

BACKGROUND: Shenfu injection (SFI) is a traditional Chinese herbal medicine which has been clinically used for treatment of septic shock and cardiac shock. The aim of this study was to clarify effects of SFI on cerebral microcirculation and brain injury after hemorrhagic shock (HS). METHODS: Twenty-one domestic male Beijing Landrace pigs were randomly divided into three groups: SFI group (SFI, n = 8), saline group (SA, n = 8) or sham operation group (SO, n = 5). In the SFI group, animals were induced to HS by rapid bleeding to a mean arterial pressure of 40 mmHg within 10 minutes and maintained at 40±3 mmHg for 60 minutes. Volume resuscitation (shed blood and crystalloid) and SFI were given after 1 hour of HS. In the SA group, animals received the same dose of saline instead of SFI. In the SO group, the same surgical procedure was performed but without inducing HS and volume resuscitation. The cerebral microvascular flow index (MFI), nitric oxide synthase (NOS) expression, aquaporin-4 expression, interleukin-6, tumor necrosis factor-α (TNF-α) and ultrastructural of microvascular endothelia were measured. RESULTS: Compared with the SA group, SFI significantly improved cerebral MFI after HS. SFI up regulated cerebral endothelial NOS expression, but down regulated interleukin-6, TNF-α, inducible NOS and aquaporin-4 expression compared with the SA group. The cerebral microvascular endothelial injury and interstitial edema in the SFI group were lighter than those in the SA group. CONCLUSIONS: Combined application of SFI with volume resuscitation after HS can improve cerebral microcirculation and reduce brain injury.


2021 ◽  
Vol 11 (16) ◽  
pp. 7187
Author(s):  
Peter V. Hauser ◽  
Hsiao-Min Chang ◽  
Norimoto Yanagawa ◽  
Morgan Hamon

The kidneys are vital organs performing several essential functions. Their primary function is the filtration of blood and the removal of metabolic waste products as well as fluid homeostasis. Renal filtration is the main pathway for drug removal, highlighting the importance of this organ to the growing field of nanomedicine. The kidneys (i) have a key role in the transport and clearance of nanoparticles (NPs), (ii) are exposed to potential NPs’ toxicity, and (iii) are the targets of diseases that nanomedicine can study, detect, and treat. In this review, we aim to summarize the latest research on kidney-nanoparticle interaction. We first give a brief overview of the kidney’s anatomy and renal filtration, describe how nanoparticle characteristics influence their renal clearance, and the approaches taken to image and treat the kidney, including drug delivery and tissue engineering. Finally, we discuss the future and some of the challenges faced by nanomedicine.


2021 ◽  
Vol 17 (1) ◽  
Author(s):  
Patricia Álvarez ◽  
Ester Blasco ◽  
Martí Pumarola ◽  
Annette Wessmann

Abstract Background Aquaporin-4 (AQP4) is in growing recognition as potential marker for cancer progression, differentiation and therapeutic intervention. No information is available about AQP4 expression in the normal canine brain. The aim of this histopathological study is to confirm the presence of AQP4 by immunohistochemistry technique in a group of non-pathological canine brains and to describe its expression and distribution across the brain. Results Twelve non-pathological canine brains of various ages (ranging from 21 days to 17 years) and breeds were included in the study. Immunohistochemical expression of AQP4 was analyzed using formalin-fixed paraffin-embedded brain tissue sections. The findings were correlated between AQP4 expressing cells and astrocytes using glial fibrillary acidic protein (GFAP). AQP4 expression was more marked in the astrocyte foot processes of subpial, perivascular and periventricular surfaces in all specimens. The majority of the canine brain sections (9/12) presented with an AQP4 predilection for white matter tracts. Interestingly, the two youngest dogs (21 days and 3 months old) were characterized by diffuse AQP4 labelling in both grey and white matter tracts. This result may suggest that brain development and ageing may play a role in the AQP4 distribution throughout the canine brain. Conclusions This is the first study to describe immunohistochemical distribution of AQP4 in normal canine brains. The AQP4 expression and distribution in non-pathological canine brains was comparable to other species. Larger studies are needed to substantiate the influence of breed and ageing on AQP4 expression in the normal canine brain.


2020 ◽  
Vol 237 (11) ◽  
pp. 1290-1305
Author(s):  
Brigitte Wildemann ◽  
Solveig Horstmann ◽  
Mirjam Korporal-Kuhnke ◽  
Andrea Viehöver ◽  
Sven Jarius

ZusammenfassungDie Optikusneuritis (ON) ist vielfach die erste Manifestation einer AQP4-Antikörper-vermittelten NMOSD (AQP4: Aquaporin-4, NMOSD: Neuromyelitis-optica-Spektrum-Erkrankung, Engl.: neuromyelitis optica spectrum disorders) oder einer Myelin-Oligodendrozyten-Glykoprotein-Antikörper-assoziierten Enzephalomyelitis (MOG-EM; auch MOG antibody associated disorders, MOGAD). Für beide Erkrankungen wurden in den vergangenen Jahren internationale Diagnosekriterien und Empfehlungen zu Indikation und Methodik der serologischen Testung vorgelegt. Seit Kurzem liegen zudem Ergebnisse aus 4 großen, internationalen Phase-III-Studien zur Behandlung der NMOSD vor. Mit dem den Komplementfaktor C5 blockierenden monoklonalen Antikörper Eculizumab wurde 2019 erstmalig ein Medikament zur Langzeitbehandlung der NMOSD, die bislang vornehmlich Off-Label mit Rituximab, Azathioprin und anderen Immunsuppressiva erfolgt, auf dem europäischen Markt zugelassen. Für die erst vor wenigen Jahren erstbeschriebene MOG-EM stehen inzwischen Daten aus mehreren retrospektiven Studien zur Verfügung, die eine Wirksamkeit von Rituximab und anderen Immunsuppressiva in der Schubprophylaxe auch in dieser Indikation nahelegen. Viele der zur Therapie der MS zugelassenen Medikamente sind entweder unwirksam oder können, wie z. B. Interferon-β, eine Verschlechterung des Krankheitsverlaufes bewirken. Beide Erkrankungen werden im Akutstadium mit hochdosierten Glukokortikoiden und Plasmapherese oder Immunadsorption behandelt. Diese Behandlung sollte möglichst rasch nach Symptombeginn eingeleitet werden. Insbesondere die MOG-EM ist durch eine oft ausgeprägte Steroidabhängigkeit gekennzeichnet, die ein langsames Ausschleichen der Steroidtherapie erfordert, und schließt viele Fälle der bislang meist als „idiopathisch“ klassifizierten „chronic relapsing inflammatory optic neuropathy“ (CRION) ein. Unbehandelt kann sowohl die NMOSD- als auch die MOG-EM-assoziierte ON zu schweren, persistierenden und oft bilateralen Visuseinschränkungen bis hin zur Erblindung führen. Beide Erkrankungen verlaufen meist relapsierend. Neben den Sehnerven sind häufig das Myelon sowie der Hirnstamm und, vor allem bei NMO-Patienten, das Dienzephalon betroffen; supratentorielle Hirnläsionen im kranialen MRT sind, anders als früher gedacht, kein Ausschlusskriterium, sondern häufig. In der vorliegenden Arbeit geben wir einen Überblick über Klinik, Diagnostik und Therapie dieser beiden wichtigen Differenzialdiagnosen der MS-assoziierten und idiopathischen ON.


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