AQP4 tag SNPs in patients with intracerebral hemorrhage in Greek and Polish population

Exploring Aquaporins in Human Studies: Mechanisms and Therapeutic Potential in Critical Illness

Aquaporins (AQPs) are membrane proteins facilitating water and other small solutes to be transported across cell membranes. They are crucial in maintaining cellular homeostasis by regulating water permeability in various tissues. Moreover, they regulate cell migration, signaling pathways, inflammation, tumor growth, and metastasis. In critically ill patients, such as trauma, sepsis, and patients with acute respiratory distress syndrome (ARDS), which are frequently encountered in intensive care units (ICUs), water transport regulation is crucial for maintaining homeostasis, as dysregulation can lead to edema or dehydration, with the latter also implicating hemodynamic compromise. Indeed, AQPs are involved in fluid transport in various organs, including the lungs, kidneys, and brain, where their dysfunction can exacerbate conditions like ARDS, acute kidney injury (AKI), or cerebral edema. In this review, we discuss the implication of AQPs in the clinical entities frequently encountered in ICUs, such as systemic inflammation and sepsis, ARDS, AKI, and brain edema due to different types of primary brain injury from a clinical perspective. Current and possible future therapeutic implications are also considered.

Aquaporin-4 Polymorphisms Are Associated With Cognitive Performance in Parkinson’s Disease

Objective

Aquaporin-4 (AQP4) facilitates a sleep-enhanced interstitial brain waste clearance system. This study was conducted to determine the clinical implication of AQP4 polymorphisms in Parkinson’s disease (PD).

Methods

Three-hundred and eighty-two patients with PD and 180 healthy controls with a mean follow-up time of 66.1 months from the Parkinson’s Progression Marker Initiative study were analyzed. We examined whether AQP4 SNPs were associated with an altered rate of motor or cognitive decline using linear mixed model and Cox regression. We then investigated whether AQP4 SNPs were associated with Aβ burden as measured by 18F Florbetapir standard uptake values. Furthermore, we examined if AQP4 SNPs moderated the association between REM sleep behavior disorder (RBD) and CSF biomarkers.

Results

In patients with PD, AQP4 rs162009 (AA/AG vs. GG) was associated with slower dementia conversion, better performance in letter-number sequencing and symbol digit modalities, lower Aβ deposition in the putamen, anterior cingulum, and frontotemporal areas. In the subgroup of high RBD screening questionnaire score, rs162009 AA/AG had a higher CSF Aβ42 level. rs162009 AA/AG also had better performance in semantic fluency in healthy controls. Besides, rs68006382 (GG/GA vs. AA) was associated with faster progression to mild cognitive impairment, worse performance in letter-number sequencing, semantic fluency, and symbol digit modalities in patients with PD.

Interpretation

Genetic variations of AQP4 and subsequent alterations of glymphatic efficacy might contribute to an altered rate of cognitive decline in PD. AQP4 rs162009 is likely a novel genetic prognostic marker of glymphatic function and cognitive decline in PD.

Profiling of Blood-Brain Barrier Disruption in Mouse Intracerebral Hemorrhage Models: Collagenase Injection vs. Autologous Arterial Whole Blood Infusion

Disruption of the blood-brain barrier (BBB) and the subsequent formation of brain edema is the most severe consequence of intracerebral hemorrhage (ICH), leading to drastic neuroinflammatory responses and neuronal cell death. A better understanding of ICH pathophysiology to develop effective therapy relies on selecting appropriate animal models. The collagenase injection ICH model and the autologous arterial whole blood infusion ICH model have been developed to investigate the pathophysiology of ICH. However, it remains unclear whether the temporal progression and the underlying mechanism of BBB breakdown are similar between these two ICH models. In this study, we aimed to determine the progression and the mechanism of BBB disruption via the two commonly used murine ICH models: the collagenase-induced ICH model (c-ICH) and the double autologous whole blood ICH model (b-ICH). Intrastriatal injection of 0.05 U collagenase or 20 μL autologous blood was used for a comparable hematoma volume in these two ICH models. Then we analyzed BBB permeability using Evan’s blue and IgG extravasation, evaluated tight junction (TJ) damage by transmission electron microscope (TEM) and Western blotting, and assessed matrix metalloproteinase-9 (MMP-9) activity and aquaporin 4 (AQP4) mRNA expression by Gelatin gel zymography and RT-PCR, respectively. The results showed that the BBB leakage was associated with a decrease in TJ protein expression and an increase in MMP-9 activity and AQP4 expression on day 3 in the c-ICH model compared with that on day 5 in the b-ICH model. Additionally, using TEM, we found that the TJ was markedly damaged on day 3 in the c-ICH model compared with that on day 5 in the b-ICH model. In conclusion, the BBB was disrupted in the two ICH models; compared to the b-ICH model, the c-ICH model presented with a more pronounced disruption of BBB at earlier time points, suggesting that the c-ICH model might be a more suitable model for studying early BBB damage and protection after ICH.

Circulating AQP4 Levels in Patients with Cerebral Amyloid Angiopathy-Associated Intracerebral Hemorrhage

Cerebral amyloid angiopathy (CAA) is a major cause of lobar intracerebral hemorrhage (ICH) in elderly patients. Growing evidence suggests a potential role of aquaporin 4 (AQP4) in amyloid-beta-associated diseases, including CAA pathology. Our aim was to investigate the circulating levels of AQP4 in a cohort of patients who had suffered a lobar ICH with a clinical diagnosis of CAA. AQP4 levels were analyzed in the serum of 60 CAA-related ICH patients and 19 non-stroke subjects by enzyme-linked immunosorbent assay (ELISA). The CAA–ICH cohort was divided according to the time point of the functional outcome evaluation: mid-term (12 ± 18.6 months) and long-term (38.5 ± 32.9 months) after the last ICH. Although no differences were found in AQP4 serum levels between cases and controls, lower levels were found in CAA patients presenting specific hemorrhagic features such as ≥2 lobar ICHs and ≥5 lobar microbleeds detected by magnetic resonance imaging (MRI). In addition, CAA-related ICH patients who presented a long-term good functional outcome had higher circulating AQP4 levels than subjects with a poor outcome or controls. Our data suggest that AQP4 could potentially predict a long-term functional outcome and may play a protective role after a lobar ICH.

The physiopathology of spontaneous hemorrhagic stroke: a systematic review

Hemorrhagic stroke (HS) is a major cause of death and disability worldwide, despite being less common, it presents more aggressively and leads to more severe sequelae than ischemic stroke. There are two types of HS: Intracerebral Hemorrhage (ICH) and Subarachnoid Hemorrhage (SAH), differing not only in the site of bleeding, but also in the mechanisms responsible for acute and subacute symptoms. This is a systematic review of databases in search of works of the last five years relating to the comprehension of both kinds of HS. Sixty two articles composed the direct findings of the recent literature and were further characterized to construct the pathophysiology in the order of events. The road to the understanding of the spontaneous HS pathophysiology is far from complete. Our findings show specific and individual results relating to the natural history of the disease of ICH and SAH, presenting common and different risk factors, distinct and similar clinical manifestations at onset or later days to weeks, and possible complications for both.

Potential therapeutic targets for intracerebral hemorrhage-associated inflammation: An update

Intracerebral hemorrhage (ICH) is a subtype of stroke with high mortality and disability but no specific or effective treatment. In the last two decades, much has been learned about the pathologic mechanisms of ICH. It is now known that after ICH onset, immune and inflammatory responses contribute to blood-brain barrier disruption, edema development, and cell death processes, jointly resulting in secondary brain injury. However, the translation of potential therapies from preclinical to clinical success has been disappointing. With the development of new laboratory technology, recent progress has been made in the understanding of ICH pathomechanisms, and promising therapeutic targets have been identified. This review provides an update of recent progress on ICH and describes the prospects for further preclinical studies in this field. Our goal is to discuss new therapeutic targets and directions for the treatment of ICH and promote the effective transformation from preclinical to clinical trials.

Haplotype of the astrocytic water channel AQP4 is associated with slow wave energy regulation in human NREM sleep

Cerebrospinal fluid (CSF) flow through the brain parenchyma is facilitated by the astrocytic water channel aquaporin 4 (AQP4). Homeostatically regulated electroencephalographic (EEG) slow waves are a hallmark of deep non-rapid eye movement (NREM) sleep and have been implicated in the regulation of parenchymal CSF flow and brain clearance. The human AQP4 gene harbors several single nucleotide polymorphisms (SNPs) associated with AQP4 expression, brain-water homeostasis, and neurodegenerative diseases. To date, their role in sleep-wake regulation is unknown. To investigate whether functional variants in AQP4 modulate human sleep, nocturnal EEG recordings and cognitive performance were investigated in 123 healthy participants genotyped for a common eight-SNP AQP4-haplotype. We show that this AQP4-haplotype is associated with distinct modulations of NREM slow wave energy, strongest in early sleep and mirrored by changes in sleepiness and reaction times during extended wakefulness. The study provides the first human evidence for a link between AQP4, deep NREM sleep, and cognitive consequences of prolonged wakefulness.

ERCC6L2 rs591486 polymorphism and risk for amyotrophic lateral sclerosis in Greek population

BACKGROUND

Α number of genetic variants have been associated with amyotrophic lateral sclerosis (ALS). A recent study supports that rs591486 across the ERCC6L2 gene and exposure to pesticides seem to have a joint effect on the development of Parkinson's disease, a disease which shares a few common characteristics with ALS.

OBJECTIVE

To detect a possible contribution of rs591486 ERCC6L2 to ALS.

METHODS

A total of 155 patients with ALS and 155 healthy controls were included in the study and genotyped for rs591486. Using logistic regression analyses (crude and adjusted for age and sex), rs591486 was tested for association with ALS risk. Subgroup analysis based on ALS site of onset was also performed. Cox regression analysis was applied in order for the effect of ERCC6L2 rs591486 on ALS age of onset to be tested.

RESULTS

Adjusted analysis showed that ERCC6L2 rs591486 was associated with an increased risk of ALS development, in dominant [odds ratio, OR (95% confidence interval, CI) 2.15 (1.04-4.46), p = 0.037] and over-dominant [OR (95%CI) = 1.91 (1.01-3.60), p = 0.043], modes. Subgroup analysis based on ALS site of onset revealed an association between ERCC6L2 rs591486 and ALS with limb onset. Results for Cox regression analysis indicated that G/A carriers had a lower age of ALS limb onset when compared to G/G carriers.

CONCLUSIONS

The current study provides preliminary indication for an implication of ERCC6L2 rs591486 in ALS development, as a possible genetic risk factor. These results possibly suggest that oxidative stress may be the main contributor in the pathophysiology of ALS.