Targeting Aquaporin-4 Subcellular Localization to Treat Central Nervous System Edema.

Swelling of the brain or spinal cord (CNS edema) affects millions of people every year. All potential pharmacological interventions have failed in clinical trials, meaning that symptom management is the only treatment option. The water channel protein aquaporin-4 (AQP4) is expressed in astrocytes and mediates water flux across the blood-brain and blood-spinal cord barriers. Here we show that AQP4 cell-surface abundance increases in response to hypoxia-induced cell swelling in a calmodulin-dependent manner. Calmodulin directly binds the AQP4 carboxyl terminus, causing a specific conformational change and driving AQP4 cell-surface localization. Inhibition of calmodulin in a rat spinal cord injury model with the licensed drug trifluoperazine inhibited AQP4 localization to the blood-spinal cord barrier, ablated CNS edema, and led to accelerated functional recovery compared with untreated animals. We propose that targeting the mechanism of calmodulin-mediated cell-surface localization of AQP4 is a viable strategy for development of CNS edema therapies.

Mechanisms of aquaporin-4 vesicular trafficking in mammalian cells.

The aquaporin-4 (AQP4) water channel is abundantly expressed in the glial cells of the central nervous system and facilitates brain swelling following diverse insults, such as traumatic injury or stroke. Lack of specific and therapeutic AQP4 inhibitors highlights the need to explore alternative routes to control the water permeability of glial cell membranes. The cell surface abundance of AQP4 in mammalian cells fluctuates rapidly in response to changes in oxygen levels and tonicity, suggesting a role for vesicular trafficking in its translocation to and from the cell surface. However, the molecular mechanisms of AQP4 trafficking are not fully elucidated. In this work, early and recycling endosomes were investigated as likely candidates of rapid AQP4 translocation together with changes in cytoskeletal dynamics. In transiently transfected HEK293 cells a significant amount of AQP-eGFP colocalised with mCherry-Rab5-positive early endosomes and mCherry-Rab11-positive recycling endosomes. When exposed to hypotonic conditions, AQP4-eGFP rapidly translocated from intracellular vesicles to the cell surface. Co-expression of dominant negative forms of the mCherry-Rab5 and -Rab11 with AQP4-eGFP prevented hypotonicity-induced AQP4-eGFP trafficking and led to concentration at the cell surface or intracellular vesicles respectively. Use of endocytosis inhibiting drugs indicated that AQP4 internalisation was dynamin-dependent. Cytoskeleton dynamics-modifying drugs also affected AQP4 translocation to and from the cell surface. AQP4 trafficking mechanisms were validated in primary human astrocytes, which express high levels of endogenous AQP4. The results highlight the role of early and recycling endosomes and cytoskeletal dynamics in AQP4 translocation in response to hypotonic and hypoxic stress and suggest continuous cycling of AQP4 between intracellular vesicles and the cell surface under physiological conditions.

Long noncoding RNA ANRIL alleviates hypoxia-induced pulmonary microvascular endothelial cell damage.

BACKGROUND: High-altitude pulmonary oedema (HAPE) is a form of noncardiogenic pulmonary oedema. Studies have found that long noncoding RNA (lncRNA) plays an important role in HAPE. ANRIL is significant in pulmonary illnesses, which implies that alterations in ANRIL expression levels may be involved in the beginning and development of HAPE. However, the specific mechanism is indistinct. The present study is meant to explore the effect and mechanism of ANRIL on hypoxic-induced injury of pulmonary microvascular endothelial cells (PMEVCs). METHODS: In the hypoxic model of PMVECs, overexpression of ANRIL or knockdown of miR-181c-5p was performed to assess cell proliferation, apoptosis, and migration. Furthermore, the levels of apoptosis-related proteins, inflammatory factors, and vascular active factors were also measured. RESULTS: The results showed that, after 24 h of hypoxia, PMVECs proliferation and migration were suppressed in comparison to the control group, along with an increase in apoptosis, a decrease in the expression of ANRIL, and an increase in the expression of miR-181c-5p (all p < .05). The damage caused by hypoxia in PMVECs can be lessened by overexpressing ANRIL, which also inhibits the production of TNF-α, iNOS, and VEGF as well as BAX and cleaved caspase-3 (all p < .05). Further experimental results showed that overexpression of ANRIL and knockdown of miR-181c-5p had the same protection against hypoxic injury in PMVECs (all p < .05). CONCLUSIONS: Our study suggests that ANRIL may prevent hypoxia injury to PMVECs in HAPE through the negative regulation of miR-181c-5p.

Acetazolamide-induced pulmonary oedema: A disproportionality analysis from the EudraVigilance database.

To our knowledge, no prior study has analysed a possible association between acetazolamide and pulmonary oedema. The aim of this study was to use data from the EudraVigilance to detect a safety signal for acetazolamide-induced pulmonary oedema. We performed a disproportionality analysis (case-noncase method), calculating reporting odds ratios (RORs) up to 22 February 2024. Among 11 684 208 spontaneous cases of adverse reactions registered in EudraVigilance, 38 275 were pulmonary oedemas. Acetazolamide was involved in 31 cases. In more than half of those cases, the patients received a single dose of acetazolamide after undergoing cataract surgery: latency was 10-90 min. Remarkably, there were five cases of positive rechallenge and six cases resulted in death. The ROR for acetazolamide was 3.63 (95% CI 2.55-5.17). Disproportionality was also observed in VigiBase®: ROR 4.44 (95% CI 3.34-5.90). Our study confirms a signal that suggests a risk of serious pulmonary oedema associated with acetazolamide.

Perihaematomal Oedema Evolution over 2 Weeks after Spontaneous Intracerebral Haemorrhage and Association with Outcome: A Prospective Cohort Study.

INTRODUCTION: We know little about the evolution of perihaematomal oedema (PHO) >24 h after ICH onset. We aimed to determine the trajectory of PHO after ICH onset and its association with outcome. METHODS: We did a prospective cohort study using a pre-specified scanning protocol in adults with first-ever spontaneous ICH and measured absolute PHO volumes on CT head scans at ICH diagnosis and 3 ± 2, 7 ± 2, and 14 ± 2 days after ICH onset. We used the largest ICH if ICHs were multiple. The primary outcomes were (a) the trajectory of PHO after ICH onset and (b) the association between PHO (absolute volume at the time when most repeat CT head scans were obtained, and change in PHO volume at this time compared with the first CT head scan) and poor functional outcome (modified Rankin scale 3-6 at 90 days). We pre-specified multivariable logistic regression models of this association adjusting analyses for potential confounders: age, GCS, infratentorial ICH location, and intraventricular extension. RESULTS: In 106 participants of whom 49 (46%) were female, with a median ICH volume 7 mL (interquartile range [IQR] 2-22 mL), the trajectory of median PHO volume increased from 14 mL (IQR: 7-26 mL) at diagnosis to 18 mL (IQR: 8-40 mL) at 3 ± 2 days (n = 87), 20 mL (IQR: 8-48 mL) at 7 ± 2 days (n = 93) and 21 mL (IQR: 10-54 mL) at 14 ± 2 days (n = 78) (p = <0.001). PHO volume at each time point was collinear with ICH volume at diagnosis (│r│ >0.7), but the change in PHO volume between diagnosis and each time point was not. Given collinearity, we used total lesion (i.e., ICH + PHO) volume instead of PHO volume in a logistic regression model of its association at each time point with outcome. Increasing total lesion (ICH + PHO) volume at day 7 ± 2 was associated with poor functional outcome (adjusted OR per mL 1.02, 95% CI: 1.00-1.03; p = 0.036), but the increase in PHO volume between diagnosis and day 7 ± 2 was not associated with poor functional outcome (adjusted OR per mL 1.03, 95% CI: 0.99-1.07; p = 0.132). CONCLUSION: PHO volume increases throughout the first 2 weeks after onset of mild to moderate ICH. Total lesion (ICH + PHO) volume at day 7 ± 2 was associated with poor functional outcome, but the change in PHO volume between diagnosis and day 7 ± 2 was not. Prospective cohort studies with larger sample sizes are needed to investigate these associations and their modifiers.

Benefits of an Adjustable Compression Garment System for the Reduction of Chronic Leg Oedema (ACROE Study).

OBJECTIVE: This study aimed to assess whether a specific adjustable compression garment (ACG) system (Coolflex Standard Calf and Coolflex Standard Foot; Sigvaris Inc.) promotes self-care in patients with chronic leg oedema. Secondary aims were to assess the effectiveness of this ACG in reducing oedema, improving patient reported outcomes, and determining the patients' degree of satisfaction with the handling of the wrap. METHODS: This was a multicentre prospective observational study. The study included 99 adult patients aged 18 - 90 years presenting with chronic oedema of the lower extremity, which encompasses conditions such as lymphoedema, venous oedema, and phlebolymphoedema. At baseline, all patients received an ACG. After two to three days and after six weeks, their overall satisfaction with the therapy was assessed. Leg volume was determined in a contactless manner during the baseline and follow up visits. All patients completed the cross cultural adaptation of the Lymphoedema Functioning, Disability and Health Questionnaire for Patients with Lymphoedema of the Lower Extremity in Germany (Lymph-ICF-UG). RESULTS: A total of 86 patients completed the study and were followed up for six weeks. At the final six week follow up, 82 (95.3%) of the 86 subjects indicated that they were able to put on the wrap independently or with a little help from relatives. The overall satisfaction rate was 88.0% (95% confidence interval [CI], 79.64 - 93.9%). The mean leg volume reduction from baseline to six weeks was -4.7% (95% CI -6.3 - -3.0%; p < .001). Lymph-ICF-UG scores and scores in all domains improved significantly from baseline to the final follow up. CONCLUSION: The ACG used in this study was found to promote self-care in a high proportion of patients with chronic leg oedema. A significant reduction in oedema was observed.

Aquaporin-4 and GPRC5B: old and new players in controlling brain oedema.

Brain oedema is a life-threatening complication of various neurological conditions. Understanding molecular mechanisms of brain volume regulation is critical for therapy development. Unique insight comes from monogenic diseases characterized by chronic brain oedema, of which megalencephalic leukoencephalopathy with subcortical cysts (MLC) is the prototype. Variants in MLC1 or GLIALCAM, encoding proteins involved in astrocyte volume regulation, are the main causes of MLC. In some patients, the genetic cause remains unknown. We performed genetic studies to identify novel gene variants in MLC patients, diagnosed by clinical and MRI features, without MLC1 or GLIALCAM variants. We determined subcellular localization of the related novel proteins in cells and in human brain tissue. We investigated functional consequences of the newly identified variants on volume regulation pathways using cell volume measurements, biochemical analysis and electrophysiology. We identified a novel homozygous variant in AQP4, encoding the water channel aquaporin-4, in two siblings, and two de novo heterozygous variants in GPRC5B, encoding the orphan G protein-coupled receptor GPRC5B, in three unrelated patients. The AQP4 variant disrupts membrane localization and thereby channel function. GPRC5B, like MLC1, GlialCAM and aquaporin-4, is expressed in astrocyte endfeet in human brain. Cell volume regulation is disrupted in GPRC5B patient-derived lymphoblasts. GPRC5B functionally interacts with ion channels involved in astrocyte volume regulation. In conclusion, we identify aquaporin-4 and GPRC5B as old and new players in genetic brain oedema. Our findings shed light on the protein complex involved in astrocyte volume regulation and identify GPRC5B as novel potentially druggable target for treating brain oedema.

Vascular leak in sepsis: physiological basis and potential therapeutic advances.

Sepsis is a life-threatening condition characterised by endothelial barrier dysfunction and impairment of normal microcirculatory function, resulting in a state of hypoperfusion and tissue oedema. No specific pharmacological therapies are currently used to attenuate microvascular injury. Given the prominent role of endothelial breakdown and microcirculatory dysfunction in sepsis, there is a need for effective strategies to protect the endothelium. In this review we will discuss key mechanisms and putative therapeutic agents relevant to endothelial barrier function.

Visualising myocardial injury after noncardiac surgery: a case series using postoperative cardiovascular MRI.

Myocardial injury after noncardiac surgery (MINS) and perioperative myocardial injury are associated with increased morbidity and mortality. Both are diagnosed by a perioperative increase in troponin, yet there is controversy if MINS is a genuine myocardial insult. We applied postoperative cardiovascular magnetic resonance T2 mapping techniques to visualise acute myocardial injury (i.e. oedema) in six patients with multiple cardiovascular risk factors who underwent aortic surgery. The burden of myocardial oedema was substantially higher in four patients with elevated troponin qualifying for MINS, compared with patients without MINS. The data and images suggest that MINS represents genuine myocardial injury.

Interpretation of SD-OCT imaging data in real-life conditions versus standardized reading centre analysis in eyes with diabetic macular oedema or macular oedema secondary to retinal vein occlusion: 24-month follow-up of the ORCA study.

PURPOSE: As part of the prospective, non-interventional OCEAN study, the ORCA module evaluated physicians' spectral domain optical coherence tomography (SD-OCT) image interpretations in the treatment of diabetic macular oedema (DME) or macular oedema (ME) secondary to retinal vein occlusion (RVO). METHODS: Presence of intraretinal fluid (IRF) and/or subretinal fluid (SRF) was evaluated independently by physicians and reading centres (RCs) on 1612 SD-OCT scans of 133 patients diagnosed with either DME or ME secondary to RVO. Agreement between physicians and RCs was calculated for both cohorts individually and as a combined ME cohort. Physicians' treatment decisions were analysed related to the results of the OCT-evaluations. RESULTS: For the combined ME cohort, presence of IRF/SRF was recorded by RCs in 792/1612 (49.1%) visits and by physicians in 852/1612 (52.9%) visits, with an agreement regarding presence or absence of foveal fluid in 70.4% of cases. In 64.4% (510/792) of visits with RC-detected foveal IRF and/or SRF no injection was given. In 30.3% of these visits with foveal fluid no reason was identified for a 'watch and wait' approach indicating possible undertreatment. BCVA deterioration was seen in a quarter of these eyes at the following visit. CONCLUSION: Despite good agreement between physicians and RCs to recognize SRF and IRF, our data indicate that omitting injections despite foveal involvement of fluid is frequent in routine clinical practice. This may put patients at risk of undertreatment, which may negatively impact real-life BCVA outcomes. TRIAL REGISTRATION: www. CLINICALTRIALS: gov , identifier NCT02194803.