Aquaporins in Brain Edema and Neuropathological Conditions

Roles of mechanosensitive ion channel PIEZO1 in the pathogenesis of brain injury after experimental intracerebral hemorrhage

Secondary brain injury after intracerebral hemorrhage (ICH) is the main cause of poor prognosis in ICH patients, but the underlying mechanisms remain less known. The involvement of Piezo1 in brain injury after ICH was studied in a mouse model of ICH. ICH was established by injecting autologous arterial blood into the basal ganglia in mice. After vehicle, Piezo1 blocker, GsMTx4, Piezo1 activator, Yoda-1, or together with mannitol (tail vein injection) was injected into the left lateral ventricle of mouse brain, Piezo1 level and the roles of Piezo1 in neuronal injury, brain edema, and neurological dysfunctions after ICH were determined by the various indicated methods. Piezo1 protein level in neurons was significantly upregulated 24 h after ICH in vivo (human and mice). Piezo1 protein level was also dramatically upregulated in HT22 cells (a murine neuron cell line) cultured in vitro 24 h after hemin treatment as an in vitro ICH model. GsMTx4 treatment or together with mannitol significantly downregulated Piezo1 and AQP4 levels, markedly increased Bcl2 level, maintained more neurons alive, considerably restored brain blood flow, remarkably relieved brain edema, substantially decreased serum IL-6 level, and almost fully reversed the neurological dysfunctions at ICH 24 h group mice. In contrast, Yoda-1 treatment achieved the opposite effects. In conclusion, Piezo1 plays a crucial role in the pathogenesis of brain injury after ICH and may be a target for clinical treatment of ICH.

A disease similarity approach identifies short-lived Niemann-Pick type C disease mice with accelerated brain aging as a novel mouse model for Alzheimer's disease and aging research

Since its first description in 1906 by Dr. Alois Alzheimer, Alzheimer's disease (AD) has been the most common type of dementia. Initially thought to be caused by age-associated accumulation of plaques, in recent years, research has increasingly associated AD with lysosomal storage and metabolic disorders, and the explanation of its pathogenesis has shifted from amyloid and tau accumulation to oxidative stress and impaired lipid and glucose metabolism aggravated by hypoxic conditions. However, the underlying mechanisms linking those cellular processes and conditions to disease progression have yet to be defined. Here, we applied a disease similarity approach to identify unknown molecular targets of AD by using transcriptomic data from congenital diseases known to increase AD risk, namely Down Syndrome, Niemann Pick Disease Type C (NPC), and Mucopolysaccharidoses I. We uncovered common pathways, hub genes, and miRNAs across in vitro and in vivo models of these diseases as potential molecular targets for neuroprotection and amelioration of AD pathology, many of which have never been associated with AD. We then investigated common molecular alterations in brain samples from an NPC disease mouse model by juxtaposing them with brain samples of both human and mouse models of AD. Detailed phenotypic and molecular analyses revealed that the NPC mut mouse model can serve as a potential short-lived in vivo model for AD research and for understanding molecular factors affecting brain aging. This research represents the first comprehensive approach to congenital disease association with neurodegeneration and a new perspective on AD research while highlighting shortcomings and lack of correlation in diverse in vitro models. Considering the lack of an AD mouse model that recapitulates the physiological hallmarks of brain aging, the characterization of a short-lived NPC mouse model will further accelerate the research in these fields and offer a unique model for understanding the molecular mechanisms of AD from a perspective of accelerated brain aging.

Inhibition of aquaporin-4 and its subcellular localization attenuates below-level central neuropathic pain by regulating astrocyte activation in a rat spinal cord injury model

The mechanisms of central neuropathic pain (CNP) caused by spinal cord injury have not been sufficiently studied. We have found that the upregulation of astrocytic aquaporin-4 (AQP4) aggravated peripheral neuropathic pain after spinal nerve ligation in rats. Using a T13 spinal cord hemisection model, we showed that spinal AQP4 was markedly upregulated after SCI and mainly expressed in astrocytes in the spinal dorsal horn (SDH). Inhibition of AQP4 with TGN020 suppressed astrocyte activation, attenuated the development and maintenance of below-level CNP and promoted motor function recovery in vivo. In primary astrocyte cultures, TGN020 also changed cell morphology, diminished cell proliferation and suppressed astrocyte activation. Moreover, T13 spinal cord hemisection induced cell-surface abundance of the AQP4 channel and perivascular localization in the SDH. Targeted inhibition of AQP4 subcellular localization with trifluoperazine effectively diminished astrocyte activation in vitro and further ablated astrocyte activation, attenuated the development and maintenance of below-level CNP, and accelerated functional recovery in vivo. Together, these results provide mechanistic insights into the roles of AQP4 in the development and maintenance of below-level CNP. Intervening with AQP4, including targeting AQP4 subcellular localization, might emerge as a promising agent to prevent chronic CNP after SCI.

Norepinephrine-Activated p38 MAPK Pathway Mediates Stress-Induced Cytotoxic Edema of Basolateral Amygdala Astrocytes

The amygdala is a core region in the limbic system that is highly sensitive to stress. Astrocytes are key players in stress disorders such as anxiety and depression. However, the effects of stress on the morphology and function of amygdala astrocytes and its potential mechanisms remain largely unknown. Hence, we performed in vivo and in vitro experiments using a restraint stress (RS) rat model and stress-induced astrocyte culture, respectively. Our data show that norepinephrine (NE) content increased, cytotoxic edema occurred, and aquaporin-4 (AQP4) expression was up-regulated in the basolateral amygdala (BLA) obtained from RS rats. Additionally, the p38 mitogen-activated protein kinase (MAPK) pathway was also observed to be significantly activated in the BLA of rats subjected to RS. The administration of NE to in vitro astrocytes increased the AQP4 level and induced cell edema. Furthermore, p38 MAPK signaling was activated. The NE inhibitor alpha-methyl-p-tyrosine (AMPT) alleviated cytotoxic edema in astrocytes, inhibited AQP4 expression, and inactivated the p38 MAPK pathway in RS rats. Meanwhile, in the in vitro experiment, the p38 MAPK signaling inhibitor SB203580 reversed NE-induced cytotoxic edema and down-regulated the expression of AQP4 in astrocytes. Briefly, NE-induced activation of the p38 MAPK pathway mediated cytotoxic edema in BLA astrocytes from RS rats. Thus, our data provide novel evidence that NE-induced p38 MAPK pathway activation may be one of the mechanisms leading to cytotoxic edema in BLA under stress conditions, which also could enable the development of an effective therapeutic strategy against cytotoxic edema in BLA under stress and provide new ideas for the treatment of neuropsychiatric diseases.

Aquaporin 1 overexpression may enhance glioma tumorigenesis by interacting with the transcriptional regulation networks of Foxo4, Maz, and E2F families

BACKGROUND

The glioblastoma has served as a valuable experimental model system for investigating the growth and invasive properties of glioblastoma. Aquaporin-1 (AQP1) in facilitating cell migration and potentially contributing to tumor progression. In this study, we analyzed the role of AQP1 overexpression in glioblastoma and elucidated the main mechanisms involved.

METHODS

AQP1 overexpression recombinant vector was introduced into C6 rat glioma cells to construct an AQP1 overexpression C6 cell line, and its effect on cell viability and migration ability was detected by MTT and Transwell. RNA was extracted by Trizol method for gene sequencing and transcriptomics analysis, and the differentially expressed genes (DEGs) were enriched for up- and downregulated genes by Principal component analysis (PCA), and the molecular mechanism of AQP1 overexpression was analyzed in comparison with the control group using the NCBI GEO database. Statistical analysis was performed using Mann-Whitney paired two tailed t test.

RESULTS

The cell viability of AQP1-transfected cell lines increased by 23% and the mean distance traveled increased by 67% compared with the control group. Quantitative analysis of gene expression showed that there were 12,121 genes with an average transcripts per million (TPM) value greater than 1. DEGs accounted for 13% of the genes expressed, with the highest correlation with upregulated genes being FOXO4 and MAZ, and the highest with downregulated genes being E2F TFs.

CONCLUSIONS

AQP1 may be implicated in glioma formation by interacting with the transcriptional regulation networks involving the FOXO4, MAZ, and E2F1/2. These findings shed light on the potential significance of AQP1 in glioma pathogenesis and warrant further investigations to unravel the underlying molecular mechanisms.

Brain water content in sudden unexpected infant death

The extensive and rapid development of the human brain during the first years of life complicates the postmortem diagnosis of brain edema in infancy. The aim of this study was to describe brain water content, the brain weight/body weight ratio, and the brain weight/head circumference ratio throughout the first years of life. Furthermore, we examined the relationship between these parameters and rs2075575 in the AQP4 gene. Our hypothesis was that dysregulated water homeostasis might be a risk factor for sudden infant death syndrome (SIDS), which may be reflected by increased water content in the brain. The study included 90 subjects with sudden unexpected death < 4 years of age: 22 cases of sudden infant death syndrome, 11 cases of sudden unexplained death in childhood, 47 cases of death due to disease, and 10 cases of accident/violent death. Brain water content, brain weight/body weight ratio, and brain weight/head circumference ratio were investigated according to corrected age, diagnosis group, attempt to resuscitate, and presence of brain edema. We found that brain water content and brain weight/body weight ratio were significantly reduced with increasing age, while brain weight/head circumference were increased. Brain weight/head circumference was correlated with brain water content. Cases with brain edema had a significantly higher brain weight/head circumference than the non-edematous cases. No differences were found between the diagnosis groups for any of the investigated parameters. In summary, the findings contribute to the current body of knowledge regarding brain growth during the first months of life.

Ion Channels and Ionotropic Receptors in Astrocytes: Physiological Functions and Alterations in Alzheimer's Disease and Glioblastoma

The human brain is composed of nearly one hundred billion neurons and an equal number of glial cells, including macroglia, i.e., astrocytes and oligodendrocytes, and microglia, the resident immune cells of the brain. In the last few decades, compelling evidence has revealed that glial cells are far more active and complex than previously thought. In particular, astrocytes, the most abundant glial cell population, not only take part in brain development, metabolism, and defense against pathogens and insults, but they also affect sensory, motor, and cognitive functions by constantly modulating synaptic activity. Not surprisingly, astrocytes are actively involved in neurodegenerative diseases (NDs) and other neurological disorders like brain tumors, in which they rapidly become reactive and mediate neuroinflammation. Reactive astrocytes acquire or lose specific functions that differently modulate disease progression and symptoms, including cognitive impairments. Astrocytes express several types of ion channels, including K+, Na+, and Ca2+ channels, transient receptor potential channels (TRP), aquaporins, mechanoreceptors, and anion channels, whose properties and functions are only partially understood, particularly in small processes that contact synapses. In addition, astrocytes express ionotropic receptors for several neurotransmitters. Here, we provide an extensive and up-to-date review of the roles of ion channels and ionotropic receptors in astrocyte physiology and pathology. As examples of two different brain pathologies, we focus on Alzheimer's disease (AD), one of the most diffuse neurodegenerative disorders, and glioblastoma (GBM), the most common brain tumor. Understanding how ion channels and ionotropic receptors in astrocytes participate in NDs and tumors is necessary for developing new therapeutic tools for these increasingly common neurological conditions.

From Homeostasis to Pathology: Decoding the Multifaceted Impact of Aquaporins in the Central Nervous System

Aquaporins (AQPs), integral membrane proteins facilitating selective water and solute transport across cell membranes, have been the focus of extensive research over the past few decades. Particularly noteworthy is their role in maintaining cellular homeostasis and fluid balance in neural compartments, as dysregulated AQP expression is implicated in various degenerative and acute brain pathologies. This article provides an exhaustive review on the evolutionary history, molecular classification, and physiological relevance of aquaporins, emphasizing their significance in the central nervous system (CNS). The paper journeys through the early studies of water transport to the groundbreaking discovery of Aquaporin 1, charting the molecular intricacies that make AQPs unique. It delves into AQP distribution in mammalian systems, detailing their selective permeability through permeability assays. The article provides an in-depth exploration of AQP4 and AQP1 in the brain, examining their contribution to fluid homeostasis. Furthermore, it elucidates the interplay between AQPs and the glymphatic system, a critical framework for waste clearance and fluid balance in the brain. The dysregulation of AQP-mediated processes in this system hints at a strong association with neurodegenerative disorders such as Parkinson's Disease, idiopathic normal pressure hydrocephalus, and Alzheimer's Disease. This relationship is further explored in the context of acute cerebral events such as stroke and autoimmune conditions such as neuromyelitis optica (NMO). Moreover, the article scrutinizes AQPs at the intersection of oncology and neurology, exploring their role in tumorigenesis, cell migration, invasiveness, and angiogenesis. Lastly, the article outlines emerging aquaporin-targeted therapies, offering a glimpse into future directions in combatting CNS malignancies and neurodegenerative diseases.

Potential Role of Antibodies against Aquaporin-1 in Patients with Central Nervous System Demyelination

Aquaporins (AQPs; AQP0-AQP12) are water channels expressed in many and diverse cell types, participating in various functions of cells, tissues, and systems, including the central nervous system (CNS). AQP dysfunction and autoimmunity to AQPs are implicated in several diseases. The best-known example of autoimmunity against AQPs concerns the antibodies to AQP4 which are involved in the pathogenesis of neuromyelitis optica spectrum disorder (NMOSD), an autoimmune astrocytopathy, causing also CNS demyelination. The present review focuses on the discovery and the potential role of antibodies against AQP1 in the CNS, and their potential involvement in the pathophysiology of NMOSD. We describe (a) the several techniques developed for the detection of the AQP1-antibodies, with emphasis on methods that specifically identify antibodies targeting the extracellular domain of AQP1, i.e., those of potential pathogenic role, and (b) the available evidence supporting the pathogenic relevance of AQP1-antibodies in the NMOSD phenotype.

Cellular and Molecular Pathophysiology of Traumatic Brain Injury: What Have We Learned So Far?

Traumatic brain injury (TBI) is one of the leading causes of long-lasting morbidity and mortality worldwide, being a devastating condition related to the impairment of the nervous system after an external traumatic event resulting in transitory or permanent functional disability, with a significant burden to the healthcare system. Harmful events underlying TBI can be classified into two sequential stages, primary and secondary, which are both associated with breakdown of the tissue homeostasis due to impairment of the blood-brain barrier, osmotic imbalance, inflammatory processes, oxidative stress, excitotoxicity, and apoptotic cell death, ultimately resulting in a loss of tissue functionality. The present study provides an updated review concerning the roles of brain edema, inflammation, excitotoxicity, and oxidative stress on brain changes resulting from a TBI. The proper characterization of the phenomena resulting from TBI can contribute to the improvement of care, rehabilitation and quality of life of the affected people.

The Role of Aquaporins in Epileptogenesis-A Systematic Review

Aquaporins (AQPs) are a family of membrane proteins involved in the transport of water and ions across cell membranes. AQPs have been shown to be implicated in various physiological and pathological processes in the brain, including water homeostasis, cell migration, and inflammation, among others. Epileptogenesis is a complex and multifactorial process that involves alterations in the structure and function of neuronal networks. Recent evidence suggests that AQPs may also play a role in the pathogenesis of epilepsy. In animal models of epilepsy, AQPs have been shown to be upregulated in regions of the brain that are involved in seizure generation, suggesting that they may contribute to the hyperexcitability of neuronal networks. Moreover, genetic studies have identified mutations in AQP genes associated with an increased risk of developing epilepsy. Our review aims to investigate the role of AQPs in epilepsy and seizure onset from a pathophysiological point of view, pointing out the potential molecular mechanism and their clinical implications.

Ferroptosis and PPAR-gamma in the limelight of brain tumors and edema

Human malignant brain tumors such as gliomas are devastating due to the induction of cerebral edema and neurodegeneration. A major contributor to glioma-induced neurodegeneration has been identified as glutamate. Glutamate promotes cell growth and proliferation in variety of tumor types. Intriguently, glutamate is also an excitatory neurotransmitter and evokes neuronal cell death at high concentrations. Even though glutamate signaling at the receptor and its downstream effectors has been extensively investigated at the molecular level, there has been little insight into how glutamate enters the tumor microenvironment and impacts on metabolic equilibration until recently. Surprisingly, the 12 transmembrane spanning tranporter xCT (SLC7A11) appeared to be a major player in this process, mediating glutamate secretion and ferroptosis. Also, PPARγ is associated with ferroptosis in neurodegeneration, thereby destroying neurons and causing brain swelling. Although these data are intriguing, tumor-associated edema has so far been quoted as of vasogenic origin. Hence, glutamate and PPARγ biology in the process of glioma-induced brain swelling is conceptually challenging. By inhibiting xCT transporter or AMPA receptors in vivo, brain swelling and peritumoral alterations can be mitigated. This review sheds light on the role of glutamate in brain tumors presenting the conceptual challenge that xCT disruption causes ferroptosis activation in malignant brain tumors. Thus, interfering with glutamate takes center stage in forming the basis of a metabolic equilibration approach.

Effects of different dietary protein levels on intestinal aquaporins in weaned piglets

This study was conducted to investigate the relationship between changes in intestinal aquaporins (AQPs) in piglets fed diets with different protein levels and nutritional diarrhoea in piglets. Briefly, 96 weaned piglets were randomly divided into four groups fed diets with crude protein (CP) levels of 18%, 20%, 22% and 24%. The small intestines and colons of the weaned piglets were collected, and several experiments were conducted. In the small intestine, AQP4 protein expression was higher in weaned piglets fed the higher-CP diets (22% and 24% CP) than in those fed the 20% CP diet except at 72 h (p < 0.01). At 72 h, the AQP4 protein expression in the small intestine was lower in the 18% group than in the other three groups (p < 0.01). Under 20% CP feeding, AQP2, AQP4 and AQP9 protein expression in the colons of piglets peaked at certain time points. The AQP2 and AQP4 mRNA levels in the colon and the AQP4 and AQP4 mRNA levels in the distal colon were approximately consistent with the protein expression levels. However, the AQP9 mRNA content in the colon was highest in the 18% group, and the AQP2 mRNA content in the distal colon was significantly higher in the 24% group than in the 20% group. AQP2 and AQP4 were expressed mainly around columnar cells in the upper part of the smooth colonic intestinal villi, and AQP9 was expressed mainly on columnar cells and goblet cells in the colonic mucosa. In conclusion, 20% CP is beneficial to the normal expression of AQP4 in the small intestine, AQP2, AQP4 and AQP9 in the colon of weaned piglets, which in turn maintains the balance of intestinal water absorption and secretion in piglets.

Sulfatide Deficiency, an Early Alzheimer's Lipidomic Signature, Causes Brain Ventricular Enlargement in the Absence of Classical Neuropathological Hallmarks

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive memory loss and a decline in activities of daily life. Ventricular enlargement has been associated with worse performance on global cognitive tests and AD. Our previous studies demonstrated that brain sulfatides, myelin-enriched lipids, are dramatically reduced in subjects at the earliest clinically recognizable AD stages via an apolipoprotein E (APOE)-dependent and isoform-specific process. Herein, we provided pre-clinical evidence that sulfatide deficiency is causally associated with brain ventricular enlargement. Specifically, taking advantage of genetic mouse models of global and adult-onset sulfatide deficiency, we demonstrated that sulfatide losses cause ventricular enlargement without significantly affecting hippocampal or whole brain volumes using histological and magnetic resonance imaging approaches. Mild decreases in sulfatide content and mild increases in ventricular areas were also observed in human APOE4 compared to APOE2 knock-in mice. Finally, we provided Western blot and immunofluorescence evidence that aquaporin-4, the most prevalent aquaporin channel in the central nervous system (CNS) that provides fast water transportation and regulates cerebrospinal fluid in the ventricles, is significantly increased under sulfatide-deficient conditions, while other major brain aquaporins (e.g., aquaporin-1) are not altered. In short, we unraveled a novel and causal association between sulfatide deficiency and ventricular enlargement. Finally, we propose putative mechanisms by which sulfatide deficiency may induce ventricular enlargement.

Heterogeneity evaluation of multi-high b-value apparent diffusion coefficient on cerebral ischemia in MCAO rat

Purpose

To assess brain damage in a rat model of cerebral ischemia based on apparent diffusion coefficient (ADC) data obtained from multi-high b-values and evaluate the relationship between Aquaporin 4 (AQP4) expression and ADC.

Methods

Thirty eight male Sprague-Dawley rats were randomized into two groups: (1) sham controls (n = 6) and (2) cerebral ischemia (successful model, n = 19). All rats underwent diffusion-weighted imaging (DWI) with both standard b-values and multi-high b-values (2,500-4,500 s/mm²) using a 3.0-T device. Standard ADC (ADC_st) maps and multi-high b-value ADCs (ADC_mh) were calculated, respectively. Aquaporin 4 expression was quantified using Western blot. Relative values of ADC_st and ADC_mh, AQP4 expression were compared between the sham group and the ischemia group. Correlations between ADC values and AQP4 expression were evaluated.

Results

At 0.5 h after suture insertion, the value of ADC_mh on the lesion was obviously decreased, and there was no difference in lesion volume when compared with ADC_st. After reperfusion, besides similar regions where ADC_st values decreased, we also found additional large values on ADC_mh within the cortex of the ipsilateral side or surrounding the lesion. The lesion evolution of the large value on ADC_mh was quite different from other indicators. But the total ADC_mh values were still significantly associated with ADC_st. The AQP4 protein expression level was appreciably increased after middle cerebral artery occlusion (MCAO), but there was no correlation between AQP4 expression either with ADC_mh or ADC_st.

Conclusion

We found the large values on ADC_mh during the progression of cerebral infarction is varied, but there was no correlation between ADC_mh values and AQP4 expression. ADC_mh may indicate the heterogeneity of ischemia lesions, but the underlying pathological basis should be further explored.

Photodynamic Opening of the Blood-Brain Barrier and the Meningeal Lymphatic System: The New Niche in Immunotherapy for Brain Tumors

Photodynamic therapy (PDT) is a promising add-on therapy to the current standard of care for patients with glioblastoma (GBM). The traditional explanation of the anti-cancer PDT effects involves the PDT-induced generation of a singlet oxygen in the GBM cells, which causes tumor cell death and microvasculature collapse. Recently, new vascular mechanisms of PDT associated with opening of the blood-brain barrier (OBBB) and the activation of functions of the meningeal lymphatic vessels have been discovered. In this review, we highlight the emerging trends and future promises of immunotherapy for brain tumors and discuss PDT-OBBB as a new niche and an important informative platform for the development of innovative pharmacological strategies for the modulation of brain tumor immunity and the improvement of immunotherapy for GBM.

Characterization of aquaporin-1ab (Aqp1ab) mRNA in mud loach (Misgurnus mizolepis) exposed to heavy metal and immunostimulant stimuli

Aquaporins (AQPs) are key proteins that regulate fluid homeostasis in cells via modulating osmotic water transport. In the present study, we identified three variants of Aqp1ab transcript (mmAQP1ab x1, mmAQP1ab x2, and mmAQP1ab x3) in mud loaches (Misgurnus mizolepis), and their expression patterns were examined in response to heavy metal and immunostimulant exposure. Mud loach Aqp1ab gene has a somewhat different organizational structure (i.e. five exons interrupted by four introns) compared to most other teleostean Aqp1ab orthologues, which have four exons. The 5'-flanking regulatory region of Aqp gene showed diverse transcription factor binding motifs, particularly those associated with stress/immune responses. Developmental expression patterns indicated that Aqp1ab mRNA was maternally inherited, presumably important for fine-tuning gene expression during embryonic and early larval developments. Expression of mud loach Aqp1ab mRNA was significantly and differentially modulated in several tissues (intestine, kidneys, spleen, and liver) in response to various heavy metal treatments. In addition, Aqp1ab gene expression was highly induced in response to immune challenge (LPS and polyI:C injections). Collectively, our results suggested that AQPs are multifunctional effectors playing diverse roles in cellular pathways relevant to immune and/or stress adaptation responses, in addition to their involvement in osmoregulation.

A Focal Impact Model of Traumatic Brain Injury in Xenopus Tadpoles Reveals Behavioral Alterations, Neuroinflammation, and an Astroglial Response

Traumatic Brain Injury (TBI) is a global driver of disability, and we currently lack effective therapies to promote neural repair and recovery. TBI is characterized by an initial insult, followed by a secondary injury cascade, including inflammation, excitotoxicity, and glial cellular response. This cascade incorporates molecular mechanisms that represent potential targets of therapeutic intervention. In this study, we investigate the response to focal impact injury to the optic tectum of Xenopus laevis tadpoles. This injury disrupts the blood-brain barrier, causing edema, and produces deficits in visually-driven behaviors which are resolved within one week. Within 3 h, injured brains show a dramatic transcriptional activation of inflammatory cytokines, upregulation of genes associated with inflammation, and recruitment of microglia to the injury site and surrounding tissue. Shortly afterward, astrocytes undergo morphological alterations and accumulate near the injury site, and these changes persist for at least 48 h following injury. Genes associated with astrocyte reactivity and neuroprotective functions also show elevated levels of expression following injury. Since our results demonstrate that the response to focal impact injury in Xenopus resembles the cellular alterations observed in rodents and other mammalian models, the Xenopus tadpole offers a new, scalable vertebrate model for TBI.

AQP2 Promotes Astrocyte Activation by Modulating the TLR4/NFκB-p65 Pathway Following Intracerebral Hemorrhage

Microglial and astrocyte activation and related cytokine secretion play key roles in secondary brain injury following intracerebral hemorrhage (ICH). We assessed the role of aquaporin (AQP)2 in immune response after ICH. We prospectively collected data from 33 patients with ICH and analyzed the serum AQP2 levels in these patients and age-matched healthy controls. A correlation analysis was also performed between patient serum AQP2 levels and clinical factors. In the rat ICH model, double-fluorescence staining for glial fibrillary acidic protein (GFAP) and AQP2 was performed to investigate the relationship between astrocytes and AQP2. Relative mRNA expression levels of GFAP and AQP2 were also measured. In the rat astrocyte cell line CTX-TNA2, toll-like receptor (TLR)4/nuclear factor kappa B (NFκB)-p65 pathway activation and GFAP levels were measured. The indirect influence of AQP2 on microglial polarization was assessed following exposure to the medium of astrocytes treated with AQP2-overexpression plasmid or silencing RNA. We found that the serum AQP2 expression was lower in patients with ICH. Sex and blood neutrophil count influenced serum AQP2 concentrations in patients with ICH on admission. Lower serum AQP2 levels were inversely correlated with 90-day Modified Rankin Scale scores after ICH, but were not correlated with National Institute of Health stroke scale (NIHSS) scores on admission. AQP2 overexpression and localization in GFAP-labeled astrocytes were observed in rats. AQP2 overexpression induced astrocyte activation with GFAP upregulation via TLR/NFκB-p65 signaling pathway activation in the rat astrocyte cell line CTX-TNA2. Astrocyte activation promoted interleukin-1β secretion. The medium of AQP2-overexpression astrocytes promoted the pro-inflammatory M1 phenotype in the immortal rat (HAPI) microglial cell line. Therefore, serum AQP2 is negatively correlated with post-ICH prognosis and may be a marker of inflammation in early-stage ICH. AQP2 overexpression promotes astrocyte activation and pro-inflammatory secretion, affects astrocyte-microglia crosstalk, and indirectly induces microglial polarization, which may augment inflammation after ICH.

Mini Review: Forensic Value of Aquaporines

Forensic pathologists are routinely confronted with unclear causes of death or findings. In some scenarios, it can be difficult to answer the specific questions posed by criminal investigators or prosecutors. Such scenarios may include questions about wound vitality or causes of death when typical or landmark findings are difficult to find. In addition to the usual subsequent examinations to clarify unclear causes of death or special questions, immunohistochemical analysis has become increasingly important since its establishment in the early 40s of the 20th century. Since then, numerous studies have been conducted to determine the usefulness and significance of immunohistochemical investigations on various structures and proteins. These proteins include, for example, aquaporins, which belong to the family of water channels. They enable the transport of water and of small molecules, such as glycerol, through biological channels and so far, 13 classes of aquaporins could have been identified in vertebrates. The classic aquaporin channels 1, 2, 4 and 5 are only permeable to water. The aquaporin channels 3, 7, 9, and 10 are also called aquaglycerolporins since they can also transport glycerol. This mini review discusses the immunohistochemical research on aquaporins, their range of applications, and respective forensic importance, their current limitations, and possible further implementations in the future.

Effects of lactate and carbon monoxide interactions on neuroprotection and neuropreservation

Lactate, historically considered a waste product of anerobic metabolism, is a metabolite in whole-body metabolism needed for normal central nervous system (CNS) functions and a potent signaling molecule and hormone in the CNS. Neuronal activity signals normally induce its formation primarily in astrocytes and production is dependent on anerobic and aerobic metabolisms. Functions are dependent on normal dynamic, expansive, and evolving CNS functions. Levels can change under normal physiologic conditions and with CNS pathology. A readily combusted fuel that is sshuttled throughout the body, lactate is used as an energy source and is needed for CNS hemostasis, plasticity, memory, and excitability. Diffusion beyond the neuron active zone impacts activity of neurons and astrocytes in other areas of the brain. Barriergenesis, function of the blood-brain barrier, and buffering between oxidative metabolism and glycolysis and brain metabolism are affected by lactate. Important to neuroprotection, presence or absence is associated with L-lactate and heme oxygenase/carbon monoxide (a gasotransmitter) neuroprotective systems. Effects of carbon monoxide on L-lactate affect neuroprotection - interactions of the gasotransmitter with L-lactate are important to CNS stability, which will be reviewed in this article.

The impact of hypoxia on blood-brain, blood-CSF, and CSF-brain barriers

The blood-brain barrier (BBB), blood-cerebrospinal fluid (CSF) barrier (BCSFB), and CSF-brain barriers (CSFBB) are highly regulated barriers in the central nervous system comprising complex multicellular structures that separate nerves and glia from blood and CSF, respectively. Barrier damage has been implicated in the pathophysiology of diverse hypoxia-related neurological conditions, including stroke, multiple sclerosis, hydrocephalus, and high-altitude cerebral edema. Much is known about the damage to the BBB in response to hypoxia, but much less is known about the BCSFB and CSFBB. Yet, it is known that these other barriers are implicated in damage after hypoxia or inflammation. In the 1950s, it was shown that the rate of radionucleated human serum albumin passage from plasma to CSF was five times higher during hypoxic than normoxic conditions in dogs, due to BCSFB disruption. Severe hypoxia due to administration of the bacterial toxin lipopolysaccharide is associated with disruption of the CSFBB. This review discusses the anatomy of the BBB, BCSFB, and CSFBB and the impact of hypoxia and associated inflammation on the regulation of those barriers.

Novel therapeutics for hydrocephalus: Insights from animal models

Hydrocephalus is a cerebrospinal fluid physiological disorder that causes ventricular dilation with normal or high intracranial pressure. The current regular treatment for hydrocephalus is cerebrospinal fluid shunting, which is frequently related to failure and complications. Meanwhile, considering that the current nonsurgical treatments of hydrocephalus can only relieve the symptoms but cannot eliminate this complication caused by primary brain injuries, the exploration of more effective therapies has become the focus for many researchers. In this article, the current research status and progress of nonsurgical treatment in animal models of hydrocephalus are reviewed to provide new orientations for animal research and clinical practice.

Human Aquaporins: Functional Diversity and Potential Roles in Infectious and Non-infectious Diseases

Aquaporins (AQPs) are integral membrane proteins and found in all living organisms from bacteria to human. AQPs mainly involved in the transmembrane diffusion of water as well as various small solutes in a bidirectional manner are widely distributed in various human tissues. Human contains 13 AQPs (AQP0-AQP12) which are divided into three sub-classes namely orthodox aquaporin (AQP0, 1, 2, 4, 5, 6, and 8), aquaglyceroporin (AQP3, 7, 9, and 10) and super or unorthodox aquaporin (AQP11 and 12) based on their pore selectivity. Human AQPs are functionally diverse, which are involved in wide variety of non-infectious diseases including cancer, renal dysfunction, neurological disorder, epilepsy, skin disease, metabolic syndrome, and even cardiac diseases. However, the association of AQPs with infectious diseases has not been fully evaluated. Several studies have unveiled that AQPs can be regulated by microbial and parasitic infections that suggest their involvement in microbial pathogenesis, inflammation-associated responses and AQP-mediated cell water homeostasis. This review mainly aims to shed light on the involvement of AQPs in infectious and non-infectious diseases and potential AQPs-target modulators. Furthermore, AQP structures, tissue-specific distributions and their physiological relevance, functional diversity and regulations have been discussed. Altogether, this review would be useful for further investigation of AQPs as a potential therapeutic target for treatment of infectious as well as non-infectious diseases.

Evaluation of AQP4/TRPV4 Channel Co-expression, Microvessel Density, and its Association with Peritumoral Brain Edema in Intracranial Meningiomas

Apart from VEGF-A pathway activation, the existence of peritumoral edema (PTBE) in meningiomas has been correlated with the expression levels of water transporter aquaporin 4 (AQP4). A novel cooperation of AQP4 with the transient receptor potential isoform 4 (TRPV4), a polymodal swelling-sensitive cation channel, has been proposed for regulating cell volume in glial cells. We investigated AQP4/TRPV4 channel co-expression in meningiomas along with the neovascularization of tumors and associate with PTBE. Immunohistochemical staining for AQP4 and TRPV4 expression was quantitatively analyzed in semi-serial sections of archival tissue from 174 patients. Microvessel density was expressed as microvessel count (MVC). PTBE was measured and edema index (EI) was assessed in 23 patients, based on magnetic resonance images (MRI) whereas mRNA levels of AQP4 and TRPV4 were evaluated in these patients using quantitative real-time PCR. High AQP4 was associated with lower-tumor grade (p < 0.05). AQP4 and TRPV4 were correlated in benign (WHO, grade I) (p < 0.0001) but not in high-grade (WHO, grades II and III) meningiomas (p > 0.05). AQP4/TRPV4 levels were independent of EI and MVC (p > 0.05). In contrast, EI was correlated to MVC (p = 0.02). AQP4/TRPV4 co-expression was detected in both edematous and non-edematous meningiomas. However, most of tumors with larger edema (EI ≥ 2) demonstrated increased levels of AQP4 and TRPV4. Importantly, peri-meningioma tissue of edematous meningiomas demonstrated significantly increased expression for AQP4 (p = 0.007) but not for TRPV4 (p > 0.05) compared with the main tumor. AQP4 and TRPV4 expression is rather associated with a response to vasogenic edema of meningiomas than with edema formation.

Hydrogen sulfide attenuates hyperhomocysteinemia-induced blood-brain barrier permeability by inhibiting MMP-9

Backgroud: Hyperhomocysteinemia (HHcy) is implicated in various neurovascular disorders including vascular dementia, subarachnoid hemorrhage and stroke. Elevated homocysteine (Hcy) levels are associated with increased oxidative stress and compromised blood-brain barrier (BBB) integrity. Hydrogen sulfide (H₂S) has recently emerged as potent neuroprotective molecule in various neurological conditions including those associated with HHcy. The present study evaluates the protective effect of sodium hydrogen sulfide (NaHS; a source of H₂S) on HHcy-induced BBB dysfunction and underpin molecular mechanisms.Materials and methods: Supplementation of NaHS restored the increased BBB permeability in the cortex and hippocampus of HHcy animals assessed in terms of diffused sodium fluorescein and Evans blue tracer dyes in the brain. Activity of matrix metalloproteinases (MMPs) assessed by gelatinase activity and in situ gelatinase assay was restored to the normal in the cortex and hippocampus of HHcy animals supplemented with NaHS.Results: Application of gelatin zymography revealed that specifically MMP-9 activity was increased in the cortex and hippocampus of HHcy animals, which was inhibited by NaHS supplementation. Real-time RT-PCR analysis showed that NaHS administration also decreased mRNA expression of MMP-9 in the hippocampus of HHcy animals. NaHS supplementation was further observed to reduce water retention in the brain regions of Hcy treated animals.Conclusion: Taken together, these findings suggest that NaHS supplementation ameliorates HHcy-induced BBB permeability and brain edema by inhibiting the mRNA expression and activity of MMP-9. Therefore, H₂S and H₂S releasing drugs may be used as a novel therapeutic approach to treat HHcy-associated neurovascular disorders.

Aquaporin-1 and aquaporin-9 gene variations in sudden infant death syndrome

Several studies have indicated that a vulnerability in the development and regulation of brain function is involved in sudden infant death syndrome (SIDS). The aim of this study was to investigate the genes encoding the brain aquaporins (AQPs) AQP1 and AQP9 in SIDS. The hypothesis was that specific variants of these genes are part of the genetic vulnerability predisposing infants to sudden unexpected death. The study included 168 SIDS cases with a median age of 15.5 (range 2–52) weeks and 372 adolescent/adult deceased controls with a median age of 44 (range 11–91) years. In the AQP1 gene, the rs17159702 CC/CT genotypes were found to be associated with SIDS (p = 0.02). In the AQP9 gene, the combination of a TT genotype of rs8042354, rs2292711 and rs13329178 was more frequent in SIDS cases than in controls (p = 0.03). In the SIDS group, an association was found between genetic variations in the AQP1 gene and maternal smoking and between the 3xTT combination in the AQP9 gene and being found lifeless in a prone position. In conclusion, this study adds further evidence to the involvement of brain aquaporins in SIDS, suggesting that specific variants of AQP genes constitute a genetic predisposition, making the infant vulnerable to sudden death together with external risk factors and probably other genetic factors.

Astrocytes, HIV and the Glymphatic System: A Disease of Disrupted Waste Management?

The discovery of the glial-lymphatic or glymphatic fluid clearance pathway in the rodent brain led researchers to search for a parallel system in humans and to question the implications of this pathway in neurodegenerative diseases. Magnetic resonance imaging studies revealed that several features of the glymphatic system may be present in humans. In both rodents and humans, this pathway promotes the exchange of interstitial fluid (ISF) and cerebrospinal fluid (CSF) through the arterial perivascular spaces into the brain parenchyma. This process is facilitated in part by aquaporin-4 (AQP4) water channels located primarily on astrocytic end feet that abut cerebral endothelial cells of the blood brain barrier. Decreased expression or mislocalization of AQP4 from astrocytic end feet results in decreased interstitial flow, thereby, promoting accumulation of extracellular waste products like hyperphosphorylated Tau (pTau). Accumulation of pTau is a neuropathological hallmark in Alzheimer's disease (AD) and is accompanied by mislocalization of APQ4 from astrocyte end feet to the cell body. HIV infection shares many neuropathological characteristics with AD. Similar to AD, HIV infection of the CNS contributes to abnormal aging with altered AQP4 localization, accumulation of pTau and chronic neuroinflammation. Up to 30% of people with HIV (PWH) suffer from HIV-associated neurocognitive disorders (HAND), and changes in AQP4 may be clinically important as a contributor to cognitive disturbances. In this review, we provide an overview and discussion of the potential contributions of NeuroHIV to glymphatic system functions by focusing on astrocytes and AQP4. Although HAND encompasses a wide range of neurocognitive impairments and levels of neuroinflammation vary among and within PWH, the potential contribution of disruption in AQP4 may be clinically important in some cases. In this review we discuss implications for possible AQP4 disruption on NeuroHIV disease trajectory and how HIV may influence AQP4 function.

Genetic underpinnings of cerebral edema in acute brain injury: an opportunity for pathway discovery

Cerebral edema constitutes an important contributor to secondary injury in acute brain injury. The quantification of cerebral edema in neuroimaging, a well-established biomarker of secondary brain injury, represents a useful intermediate phenotype to study edema formation. Population genetics provides powerful tools to identify novel susceptibility genes, biological pathways and therapeutic targets related to brain edema formation. Here, we provide an overview of the pathogenesis of cerebral edema, introduce relevant genetic methods to study this process, and discuss the ongoing research on the genetic underpinnings of edema formation in acute brain injury. The epsilon 2 and 4 variants within the Apolipoprotein E (APOE) gene are associated with worse outcome after traumatic brain injury and intracerebral hemorrhage, and recent studies link these polymorphisms to inflammatory processes that lead to blood-brain barrier disruption and vasogenic edema. For the Haptoglobin gene (HP), the Hp 2-2 genotype associates with worse outcome after acute brain injury, whereas the haptoglobin Hp 1-1 genotype correlates with increased edema in the early phases of intracerebral hemorrhage. Another important protein in cerebral edema is aquaporin 4, coded by the AQP4 gene. AQP4 mutations contribute to the formation of cytotoxic edema, and further genetic research is necessary to help elucidate the mediating mechanism. Findings supporting the target genes outlined above require replication in larger samples and evaluation in non-white populations. These next steps will be significantly facilitated by the rapid changes observed in the field of population genetics, including large international collaborations, open access to genetic data, and significant reductions in the cost of genotyping technologies.

Bloodletting Puncture at Hand Twelve Jing-Well Points Improves Neurological Recovery by Ameliorating Acute Traumatic Brain Injury-Induced Coagulopathy in Mice

Traumatic brain injury (TBI) contributes to hypocoagulopathy associated with prolonged bleeding and hemorrhagic progression. Bloodletting puncture therapy at hand twelve Jing-well points (BL-HTWP) has been applied as a first aid measure in various emergent neurological diseases, but the detailed mechanisms of the modulation between the central nervous system and systemic circulation after acute TBI in rodents remain unclear. To investigate whether BL-HTWP stimulation modulates hypocoagulable state and exerts neuroprotective effect, experimental TBI model of mice was produced by the controlled cortical impactor (CCI), and treatment with BL-HTWP was immediately made after CCI. Then, the effects of BL-HTWP on the neurological function, cerebral perfusion state, coagulable state, and cerebrovascular histopathology post-acute TBI were determined, respectively. Results showed that BL-HTWP treatment attenuated cerebral hypoperfusion and improve neurological recovery post-acute TBI. Furthermore, BL-HTWP stimulation reversed acute TBI-induced hypocoagulable state, reduced vasogenic edema and cytotoxic edema by regulating multiple hallmarks of coagulopathy in TBI. Therefore, we conclude for the first time that hypocoagulopathic state occurs after acute experimental TBI, and the neuroprotective effect of BL-HTWP relies on, at least in part, the modulation of hypocoagulable state. BL-HTWP therapy may be a promising strategy for acute severe TBI in the future.

The petrosal vein mutilation affects the SOD activity, MDA levels and AQP4 level in cerebellum and brain stem in rabbit

Cerebral edema after brain surgery remains a life-threatening complication in the clinic. For a better operating field view, superior petrosal vein (SPV) can be easily damaged during neurosurgery. SPV sacrifice may sometimes be inevitable in clinic. However, the safety of SPV sacrifice is still a controversial question. Whether petrosal vein injury has an effect on cerebral edema after brain surgery is still unknown. In this study, rabbits were divided into two groups. The rabbits in the surgery group underwent petrosal vein sacrifice. The control group was subjected to sham surgery. Cerebellum and brain stem tissues were collected at 4 h, 8 h, 12 h, 24 h, 48 h and 72 h post-surgery. The superoxidase dismutase (SOD) activity and expression of malondialdehyde (MDA) were tested in the collected samples. Quantitiative real time polymerase chain reaction and immunohistochemistry were used to detect the mRNA and protein levels, respectively, of aquaporin 4 (AQP4) in the tissue samples. Compared to the control sham group, the activity of SOD and MDA expression in cerebellum was decreased and increased, respectively, at 4 h, 8 h, 12 h and 24 h post-, surgery The SOD activity and expression of MDA in brain stem was decreased and increased, respectively, only in 4 h after surgery, compared with control group. The mRNA and protein levels of AQP4 were increased in cerebellum at 4 h, 8 h, 12 h and 24 h after surgery, but in the brain stem, the levels were increased only at 4 h after surgery compared with sham group. Our results thus show that SPV sacrifice influences oxidative stress and the expression of AQP4 in cerebellum and brain stem of rabbits; highlighting the importance of protecting the petrosal vein during neurosurgery.

[MicroRNA and their potential role in the pathogenesis of hemorrhagic stroke]

Spontaneous (non-traumatic) intracerebral hemorrhage (ICH), or hemorrhagic stroke, is a common and serious disease with high morbidity and mortality. Current methods of treating hemorrhagic stroke, from conservative to surgical, are insufficient, which justifies the continuation of the study of this condition, including cellular and molecular changes that occur during a stroke. MicroRNAs (miRNAs) are a class of small non-coding RNAs that play an important role in post-transcriptional regulation of gene expression. MicroRNAs are involved in almost all biological processes, including cell proliferation, apoptosis and cell differentiation, and are also key substances in pathophysiological processes in many diseases, and therefore they can be both potential biomarkers and new therapeutic targets in cancer, degenerative and cardiovascular disease. In recent years, a number of studies have been aimed at studying the role of microRNAs in pathophysiological processes in hemorrhagic stroke, such as apoptosis, inflammation, oxidative stress, violation of the blood-brain barrier (BBB) and cerebral edema. The results of the studies demonstrated that changes in miRNA expression may be associated with the prognosis of ICH. In this article, we consider studies related to miRNAs and hemorrhagic stroke, and clarify the complex relationship between them.

The Medical Management of Cerebral Edema: Past, Present, and Future Therapies

Cerebral edema is commonly associated with cerebral pathology, and the clinical manifestation is largely related to the underlying lesioned tissue. Brain edema usually amplifies the dysfunction of the lesioned tissue and the burden of cerebral edema correlates with increased morbidity and mortality across diseases. Our modern-day approach to the medical management of cerebral edema has largely revolved around, an increasingly artificial distinction between cytotoxic and vasogenic cerebral edema. These nontargeted interventions such as hyperosmolar agents and sedation have been the mainstay in clinical practice and offer noneloquent solutions to a dire problem. Our current understanding of the underlying molecular mechanisms driving cerebral edema is becoming much more advanced, with differences being identified across diseases and populations. As our understanding of the underlying molecular mechanisms in neuronal injury continues to expand, so too is the list of targeted therapies in the pipeline. Here we present a brief review of the molecular mechanisms driving cerebral edema and a current overview of our understanding of the molecular targets being investigated.

Glibenclamide and Therapeutic Hypothermia Have Comparable Effect on Attenuating Global Cerebral Edema Following Experimental Cardiac Arrest

BACKGROUND

Cerebral edema is one of the major causes of mortality following cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). A subunit of the sulfonylurea receptor 1-transient receptor potential M4 (Sur1-TRPM4) channel has been implicated in the pathogenesis of ischemia-evoked cerebral edema. In this study, we examined whether glibenclamide (GBC), a Sur1-TRPM4 channel inhibitor, attenuates cerebral edema following CA/CPR and further examined the efficacy of GBC combined with therapeutic hypothermia.

METHODS

Isoflurane-anesthetized adult male wild-type C57Bl/6 mice subjected to 7-min CA/CPR were randomized into five groups: sham operation, control with normothermia, GBC with normothermia, control with hypothermia, and GBC with hypothermia. The primary outcome was to evaluate regional brain water content; the secondary outcome was to measure blood glucose level, Sur1-TRPM4 expression, and pro-inflammatory factor expression.

RESULTS

Compared with normothermia, GBC treatment or hypothermia significantly attenuated brain water content in mice subjected to CA/CPR. GBC combined with hypothermia had no additional effects on attenuating cerebral edema. Pro-inflammatory factor messenger RNA expression (TNF-α and IL-6), NFκβ activation, and SUR1-TRPM4 levels were upregulated after CA/CPR. Compared with normothermia, hypothermia, but not GBC, partly suppressed these factors' expression.

CONCLUSIONS

GBC attenuated cerebral edema following CA/CPR by blocking Sur1-TRPM4 channels upregulated by CA insult. The effect of GBC was comparable with that of therapeutic hypothermia alone. These results suggest that GBC is an alternative approach for treating CA-evoked cerebral edema.

Aquaporin Channels in the Heart-Physiology and Pathophysiology

Mammalian aquaporins (AQPs) are transmembrane channels expressed in a large variety of cells and tissues throughout the body. They are known as water channels, but they also facilitate the transport of small solutes, gasses, and monovalent cations. To date, 13 different AQPs, encoded by the genes AQP0–AQP12, have been identified in mammals, which regulate various important biological functions in kidney, brain, lung, digestive system, eye, and skin. Consequently, dysfunction of AQPs is involved in a wide variety of disorders. AQPs are also present in the heart, even with a specific distribution pattern in cardiomyocytes, but whether their presence is essential for proper (electro)physiological cardiac function has not intensively been studied. This review summarizes recent findings and highlights the involvement of AQPs in normal and pathological cardiac function. We conclude that AQPs are at least implicated in proper cardiac water homeostasis and energy balance as well as heart failure and arsenic cardiotoxicity. However, this review also demonstrates that many effects of cardiac AQPs, especially on excitation-contraction coupling processes, are virtually unexplored.

Age differences in photodynamic therapy-mediated opening of the blood-brain barrier through the optical clearing skull window in mice

BACKGROUND

Photodynamic therapy (PDT), a minimally invasive therapeutic tool, has been an important option for post-surgical treatment of malignant gliomas (MGs) in both adult and young patients. Recent studies have shown that PDT can also open the blood-brain barrier (BBB). However, there are no optimized parameters of PDT for patients at different ages. To determine whether there are age differences in PDT effects on the BBB, we studied PDT-related BBB opening through the optical clearing skull window in healthy 4- and 8-week-old mice.

METHODS

In this work, we realized BBB opening by combining PDT with the optical clearing skull window by using different radiant exposures (635 nm, 10-20-30-40 J/cm² ) and 5-aminole-vulinic acid (5-ALA, 20 mg/kg). Then, we evaluated BBB permeability by: (i) spectrofluorimetric measuring of Evans Blue dye (EBd) leakage; (ii) confocal imaging of 70 kDa FITC-dextran extravasation and the BBB integrity; and (iii) histological analysis of brain tissues.

RESULTS

Using the skull optical clearing method, we demonstrated PDT-induced BBB opening to EBd and FITC-dextran in a radiant exposure manner. The histological analysis revealed the different severities of vasogenic edema corresponding to radiant exposures. Besides, the PDT-related increase in the BBB permeability to high weight molecules (EBd and FITC-dextran) and solutes (vasogenic edema) was more pronounced in 4-week-old mice than in 8-week-old mice.

CONCLUSIONS

The more pronounced PDT-induced BBB disruption in juvenile mice compared with adult mice suggests age differences in PDT-related BBB opening. This might be an important informative platform for a new application of PDT as a method for brain drug delivery, especially for post-surgical treatment of MGs. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Expression of matrix Metalloproteinases-2 and aquaporin-1 in corneoscleral junction after angle-closure in rabbits

Background

To investigate the expression of Matrix Metalloproteinases 2 and aquaporin-1 in corneoscleral junction and explore the mechanism of trabecular damageafter angle-closure.

Methods

Thirty New Zealand white rabbits were randomly assigned into 2 groups, theexperimental group (Group 1) including twenty five rabbits and the control group (Group 2) including 5 rabbits. The rabbits in the experimental group were used to establish angle-closure models, and the rabbits in the control group were not subjected to any operation. All the rabbits were followed by slit lamp microscopy, Tonopen tonometer, and anterior segment optical coherent tomography (AS-OCT). The expressions of metalloproteinase MMP-2, aquaporin-1, and tissue inhibitors of metalloproteinase-2 in corneoscleral junctionwere evaluatedin both groups byimmunofluorescence, quantitative reverse-transcription polymerase chain reaction (qRT-PCR), and enzyme-linked immunosorbent assay (ELISA).

Results

Slit-lamp examination showed that angle-closure model was successfully established in twenty rabbits. The extent of angle-closure was about 2 to 4 clock hours in all the rabbit models, but the intraocular pressure (IOP) of the rabbits distributed from 8.57 to 15.25 mmHg and no significant high IOP was found in the follow-up period. The AQP-1-positive cells mainly located in Schlemm’s canal, the inner surface of trabecular meshwork (TM), and the surface of iris, which began to decline on 1 month after angle-closure. MMP2 staining was diffuse in trabecular meshwork and iris. Immunofluorescence signal of MMP2 was strong within 1 month after angle-closure, and subsequently became weak. qRT-PCR and ELISA showed that the expression of MMP-2 and TIMP-2 increased within 1 month after angle-closure and then declined gradually. The AQP-1 levels showed slightly declined on 1 month after angle-closure.

Conclusions

Altered levels of MMPs, TIMPs, and AQP-1 were found in the area of angle-closure, which may be involved in the damage of TM and Schlemm’s canal after angle-closure.

Immunohistochemical Evaluation of Aquaporin-4 and its Correlation with CD68, IBA-1, HIF-1α, GFAP, and CD15 Expressions in Fatal Traumatic Brain Injury

Traumatic brain injury (TBI) is one of the leading causes of death and disability worldwide. Our understanding of its pathobiology has substantially increased. Following TBI, the following occur, edema formation, brain swelling, increased intracranial pressure, changes in cerebral blood flow, hypoxia, neuroinflammation, oxidative stress, excitotoxicity, and apoptosis. Experimental animal models have been developed. However, the difficulty in mimicking human TBI explains why few neuroprotective strategies, drawn up on the basis of experimental studies, have translated into improved therapeutic strategies for TBI patients. In this study, we retrospectively examined brain samples in 145 cases of death after different survival times following TBI, to investigate aquaporin-4 (AQP4) expression and correlation with hypoxia, and neuroinflammation in human TBI. Antibodies anti-glial fibrillary acid protein (GFAP), aquaporin-4 (AQP4), hypoxia induced factor-1α (HIF-1α), macrophage/phagocytic activation (CD68), ionized calcium-binding adapter molecule-1 (IBA-1), and neutrophils (CD15) were used. AQP4 showed a significant, progressive increase between the control group and groups 2 (one-day survival) and 3 (three-day survival). There were further increases in AQP4 immunopositivity in groups 4 (seven-day survival), 5 (14-dayssurvival), and 6 (30-day survival), suggesting an upregulation of AQP4 at 7 to 30 days compared to group 1. GFAP showed its highest expression in non-acute cases at the astrocytic level compared with the acute TBI group. Data emerging from the HIF-1α reaction showed a progressive, significant increase. Immunohistochemistry with IBA-1 revealed activated microglia starting three days after trauma and progressively increasing in the next 15 to 20 days after the initial trauma. CD68 expression demonstrated basal macrophage and phagocytic activation mostly around blood vessels. Starting from one to three days of survival after TBI, an increase in the number of CD68 cells was progressively observed; at 15 and 30 days of survival, CD68 showed the most abundant immunopositivity inside or around the areas of necrosis. These findings need to be developed further to gain insight into the mechanisms through which brain AQP4 is upregulated. This could be of the utmost clinicopathological importance.

A Precision Medicine Approach to Cerebral Edema and Intracranial Hypertension after Severe Traumatic Brain Injury: Quo Vadis?

PURPOSE OF REVIEW

Standard clinical protocols for treating cerebral edema and intracranial hypertension after severe TBI have remained remarkably similar over decades. Cerebral edema and intracranial hypertension are treated interchangeably when in fact intracranial pressure (ICP) is a proxy for cerebral edema but also other processes such as extent of mass lesions, hydrocephalus, or cerebral blood volume. A complex interplay of multiple molecular mechanisms results in cerebral edema after severe TBI, and these are not measured or targeted by current clinically available tools. Addressing these underpinnings may be key to preventing or treating cerebral edema and improving outcome after severe TBI.

RECENT FINDINGS

This review begins by outlining basic principles underlying the relationship between edema and ICP including the Monro-Kellie doctrine and concepts of intracranial compliance/elastance. There is a subsequent brief discussion of current guidelines for ICP monitoring/management. We then focus most of the review on an evolving precision medicine approach towards cerebral edema and intracranial hypertension after TBI. Personalization of invasive neuromonitoring parameters including ICP waveform analysis, pulse amplitude, pressure reactivity, and longitudinal trajectories are presented. This is followed by a discussion of cerebral edema subtypes (continuum of ionic/cytotoxic/vasogenic edema and progressive secondary hemorrhage). Mechanisms of potential molecular contributors to cerebral edema after TBI are reviewed. For each target, we present findings from preclinical models, and evaluate their clinical utility as biomarkers and therapeutic targets for cerebral edema reduction. This selection represents promising candidates with evidence from different research groups, overlap/inter-relatedness with other pathways, and clinical/translational potential. We outline an evolving precision medicine and translational approach towards cerebral edema and intracranial hypertension after severe TBI.

Pathophysiology and treatment of cerebral edema in traumatic brain injury

Cerebral edema (CE) and resultant intracranial hypertension are associated with unfavorable prognosis in traumatic brain injury (TBI). CE is a leading cause of in-hospital mortality, occurring in >60% of patients with mass lesions, and ∼15% of those with normal initial computed tomography scans. After treatment of mass lesions in severe TBI, an important focus of acute neurocritical care is evaluating and managing the secondary injury process of CE and resultant intracranial hypertension. This review focuses on a contemporary understanding of various pathophysiologic pathways contributing to CE, with a subsequent description of potential targeted therapies. There is a discussion of identified cellular/cytotoxic contributors to CE, as well as mechanisms that influence blood-brain-barrier (BBB) disruption/vasogenic edema, with the caveat that this distinction may be somewhat artificial since molecular processes contributing to these pathways are interrelated. While an exhaustive discussion of all pathways with putative contributions to CE is beyond the scope of this review, the roles of some key contributors are highlighted, and references are provided for further details. Potential future molecular targets for treating CE are presented based on pathophysiologic mechanisms. We thus aim to provide a translational synopsis of present and future strategies targeting CE after TBI in the context of a paradigm shift towards precision medicine. This article is part of the Special Issue entitled "Novel Treatments for Traumatic Brain Injury".

Expression of AQP3 and AQP5 as a prognostic marker in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a common type of breast malignancy with high a propensity for metastasis and locoregional recurrence. The aim of the present study was to investigate the expression of aquaporin (AQP) 3 and AQP5, analyze their association with clinicopathological parameters and explore their clinical significance in tissue samples from patients with TNBC. Immunohistochemistry was performed to detect the expression patterns of AQP3 and AQP5 in 96 patients with TNBC who underwent surgery between 2007 and 2012. AQP3 and AQP5 were expressed primarily in the membrane and cytoplasm of tumor cells within TNBC tissues. AQP3 and AQP5 expression was notably stronger in carcinoma tissue compared with adjacent normal tissue. Overexpression of AQP3 and AQP5 was significantly associated with tumor size, lymph node status and local relapse/distant metastasis. In addition, aberrant overexpression of AQP5 was observed more frequently in TNBC tissues with higher Ki-67 expression than in those with lower Ki-67 expression. In univariate analysis, patients with TNBC with high AQP3 and AQP5 expression demonstrated poorer 5-year disease-free survival and overall survival compared with patients with low AQP3 and AQP5 expression. In multivariate analysis, the combined expression of AQP3 and AQP5 was an independent prognostic marker in patients with TNBC. The results of the present study suggest that the overexpression of AQP3 and AQP5 may serve as a novel therapeutic marker in patients with TNBC.

Aquaporin-4 deletion ameliorates hypoglycemia-induced BBB permeability by inhibiting inflammatory responses

Background

Severe hypoglycemia induces brain edema by upregulating aquaporin-4 (AQP4) expression and by degrading tight junctions. Acute severe hypoglycemia induces a proinflammatory environment that may contribute to a disruption in the epithelial barrier by decreasing tight junction protein expression. Interestingly, the altered AQP4 expression has been considered to play a critical role in neuroinflammation during acute brain injury. It has been shown that AQP4 deletion reduces brain inflammation in AQP4-null mice after intracerebral LPS injection. However, the effect of AQP4 deletion regarding protection against hypoglycemia-induced blood-brain barrier (BBB) breakdown is unknown.

Methods

An acute severe hypoglycemic stress model was established via injection of 4 unit/kg body weight of insulin. Evans blue (EB) staining and water measurement were used to assess BBB permeability. Western blot, reverse transcription polymerase chain reaction, and immunofluorescence were used to detect the expression of related proteins. The production of cytokines was assessed via enzyme-linked immunosorbent assay.

Results

Hypoglycemia-induced brain edema and BBB leakage were reduced in AQP4^−/− mice. AQP4 deletion upregulated PPAR-γ and inhibited proinflammatory responses. Moreover, knockdown of aquaporin-4 by small interfering RNA in astrocytes co-cultured with endothelial cells effectively reduced transendothelial permeability and degradation of tight junctions. Treatment with PPAR-γ inhibitors showed that upregulation of PPAR-γ was responsible for the protective effect of AQP4 deletion under hypoglycemic conditions.

Conclusions

Our data suggest that AQP4 deletion protects BBB integrity by reducing inflammatory responses due to the upregulation of PPAR-γ expression and attenuation of proinflammatory cytokine release. Reduction in AQP4 may be protective in acute severe hypoglycemia.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1203-8) contains supplementary material, which is available to authorized users.