Variants of WNT7A and GPR124 are associated with hemorrhagic transformation following intravenous thrombolysis in ischemic stroke

Compromised endothelial Wnt/β-catenin signaling mediates the blood-brain barrier disruption and leads to neuroinflammation in endotoxemia

The blood-brain barrier (BBB) is a critical interface that maintains the central nervous system homeostasis by controlling the exchange of substances between the blood and the brain. Disruption of the BBB plays a vital role in the development of neuroinflammation and neurological dysfunction in sepsis, but the mechanisms by which the BBB becomes disrupted during sepsis are not well understood. Here, we induced endotoxemia, a major type of sepsis, in mice by intraperitoneal injection of lipopolysaccharide (LPS). LPS acutely increased BBB permeability, activated microglia, and heightened inflammatory responses in brain endothelium and parenchyma. Concurrently, LPS or proinflammatory cytokines activated the NF-κB pathway, inhibiting Wnt/β-catenin signaling in brain endothelial cells in vitro and in vivo. Cell culture study revealed that NF-κB p65 directly interacted with β-catenin to suppress Wnt/β-catenin signaling. Pharmacological NF-κB pathway inhibition restored brain endothelial Wnt/β-catenin signaling activity and mitigated BBB disruption and neuroinflammation in septic mice. Furthermore, genetic or pharmacological activation of brain endothelial Wnt/β-catenin signaling substantially alleviated LPS-induced BBB leakage and neuroinflammation, while endothelial conditional ablation of the Wnt7a/7b co-receptor Gpr124 exacerbated the BBB leakage caused by LPS. Mechanistically, Wnt/β-catenin signaling activation rectified the reduced expression levels of tight junction protein ZO-1 and transcytosis suppressor Mfsd2a in brain endothelial cells of mice with endotoxemia, inhibiting both paracellular and transcellular permeability of the BBB. Our findings demonstrate that endotoxemia-associated systemic inflammation decreases endothelial Wnt/β-catenin signaling through activating NF-κB pathway, resulting in acute BBB disruption and neuroinflammation. Targeting the endothelial Wnt/β-catenin signaling may offer a promising therapeutic strategy for preserving BBB integrity and treating neurological dysfunction in sepsis.

Role of Gpr124 in the Migration and Proliferation of Retinal Microvascular Endothelial Cells and Microangiopathies in Diabetic Retinopathy

Retinal microangiopathies, such as neovascularization and preretinal and vitreous hemorrhages, are the primary pathological features of diabetic retinopathy (DR). These conditions can worsen visual impairment and may result in blindness. Furthermore, multiple metabolic pathways are associated with microangiopathy in DR. However, the specific underlying pathological mechanisms remain unclear. Several studies have demonstrated the important role of G protein-coupled receptor 124 (Gpr124) in cerebral vascular endothelial cells, but its effect on the retinal endothelium has not been elucidated. In this study, we found that Gpr124 is expressed in both pathological retinal fibrous vascular membranes of DR patients and retinal blood vessels of mice, with elevated protein expression specifically observed in the retinas of DR model mice. Furthermore, Gpr124 expression was elevated after high-glucose treatment of human retinal microvascular endothelial cells (HRMECs). Inhibition of Gpr124 expression affected the high glucose-induced proliferation, migration, and tube-forming ability of HRMECs. We concluded that Gpr124 expression was upregulated in DR and promoted HRMECs angiogenesis in a high-glucose environment. This finding may help to elucidate the pathogenesis of DR and provide a critical research basis for identifying effective treatments.

Association of IL-6 rs1800795, but not TNF-α rs1800629, and IL-1β rs16944 polymorphisms' genotypes with recovery of ischemic stroke patients following thrombolysis

OBJECTIVES

Inflammatory cytokines like tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 can cause brain injury, slow recovery, and adverse effects (ADEs) in ischemic stroke (IS) patients treated with recombinant tissue plasminogen activator (rtPA). We explored the relationship between selected polymorphisms within TNF-α, IL-1β and IL-6 genes, and post-IS outcome and ADEs in patients treated with rtPA.

METHODS

One hundred and sixty-six patients with IS treated with rtPA were included in this study. The modified Rankin Scale (mRS) was used to assess functional recovery 3 months after IS likewise thrombolytic therapy efficacy. Patients were classified into groups with favorable (0-1) or poor recovery based on their mRS score at the ninetieth day post-IS. During hospitalization, ADEs following rtPA were monitored. TNF-α-308 G/A (rs1800629), IL-1β-511 G/A (rs16944), and IL-6-174 G/C (rs1800795) polymorphisms were genotyped using Real-Time PCR. SPSS software version 22.0 was used for statistical analyses.

RESULTS

Patients with the TNF-α-308 G/A GG genotype had a higher mean NIHSS value at admission (12.75 ± 5.176) than those carrying A-allele (10.56 ± 3.979;p = 0.016). Individuals with the CC genotype of the IL-6-174 G/C polymorphism had significantly lower NIHSS scores (8.79 ± 5.053) than those with G-allele (12.06 ± 6.562) 24 hours after rtPA (p = 0.050). Patients with the GG genotype of the IL-6-174 G/C polymorphism had a significantly poorer outcome (p = 0.024; OR = 2.339; 95%CI 1.121-4.880), while patients who were G-allele carriers of the Il-6-174 G/C polymorphism and had the AA genotype of the IL-1β-511 G/A polymorphism were statistically significantly more likely to experience hemorrhagic transformation (p = 0.046; OR = 2.7273; 95%CI 1.0414-7.1426).

CONCLUSION

GG genotype of the IL-6-174 G/C polymorphism is associated with poor recovery after IS treated with rtPA therapy.

Ischemia-reperfusion injury: molecular mechanisms and therapeutic targets

Ischemia-reperfusion (I/R) injury paradoxically occurs during reperfusion following ischemia, exacerbating the initial tissue damage. The limited understanding of the intricate mechanisms underlying I/R injury hinders the development of effective therapeutic interventions. The Wnt signaling pathway exhibits extensive crosstalk with various other pathways, forming a network system of signaling pathways involved in I/R injury. This review article elucidates the underlying mechanisms involved in Wnt signaling, as well as the complex interplay between Wnt and other pathways, including Notch, phosphatidylinositol 3-kinase/protein kinase B, transforming growth factor-β, nuclear factor kappa, bone morphogenetic protein, N-methyl-D-aspartic acid receptor-Ca2+-Activin A, Hippo-Yes-associated protein, toll-like receptor 4/toll-interleukine-1 receptor domain-containing adapter-inducing interferon-β, and hepatocyte growth factor/mesenchymal-epithelial transition factor. In particular, we delve into their respective contributions to key pathological processes, including apoptosis, the inflammatory response, oxidative stress, extracellular matrix remodeling, angiogenesis, cell hypertrophy, fibrosis, ferroptosis, neurogenesis, and blood-brain barrier damage during I/R injury. Our comprehensive analysis of the mechanisms involved in Wnt signaling during I/R reveals that activation of the canonical Wnt pathway promotes organ recovery, while activation of the non-canonical Wnt pathways exacerbates injury. Moreover, we explore novel therapeutic approaches based on these mechanistic findings, incorporating evidence from animal experiments, current standards, and clinical trials. The objective of this review is to provide deeper insights into the roles of Wnt and its crosstalk signaling pathways in I/R-mediated processes and organ dysfunction, to facilitate the development of innovative therapeutic agents for I/R injury.

Shaping the brain vasculature in development and disease in the single-cell era

The CNS critically relies on the formation and proper function of its vasculature during development, adult homeostasis and disease. Angiogenesis - the formation of new blood vessels - is highly active during brain development, enters almost complete quiescence in the healthy adult brain and is reactivated in vascular-dependent brain pathologies such as brain vascular malformations and brain tumours. Despite major advances in the understanding of the cellular and molecular mechanisms driving angiogenesis in peripheral tissues, developmental signalling pathways orchestrating angiogenic processes in the healthy and the diseased CNS remain incompletely understood. Molecular signalling pathways of the 'neurovascular link' defining common mechanisms of nerve and vessel wiring have emerged as crucial regulators of peripheral vascular growth, but their relevance for angiogenesis in brain development and disease remains largely unexplored. Here we review the current knowledge of general and CNS-specific mechanisms of angiogenesis during brain development and in brain vascular malformations and brain tumours, including how key molecular signalling pathways are reactivated in vascular-dependent diseases. We also discuss how these topics can be studied in the single-cell multi-omics era.

Efficacy and safety of spot heating and ultrasound irradiation on in vitro and in vivo thrombolysis models

The feasibility of transcranial sonothrombolysis has been demonstrated, although little is known about the relationships between thermal or mechanical mechanisms and thrombolytic outcomes. Therefore, the present study aims to reveal the effect and safety of temperature and ultrasound through in vitro and in vivo thrombolysis models. Artificial clots in microtubes were heated in a water bath or sonicated by ultrasound irradiation, and then clots weight decrease with rising temperature and sonication time was confirmed. In the in vitro thrombotic occlusion model, based on spot heating, clot volume was reduced and clots moved to the distal side, followed by recanalization of the occlusion. In the in vivo study, the common carotid artery of rats was exposed to a spot heater or to sonication. No brain infarct or brain blood barrier disruption was shown, but endothelial junctional dysintegrity and an inflammatory response in the carotid artery were detected. The present spot heating and ultrasound irradiation models seem to be effective for disintegrating clots in vitro, but the safety of the in vivo model was not fully supported by the data. However, the data indicates that a shorter time exposure could be less invasive than a longer exposure.

Lithium attenuates blood-brain barrier damage and brain edema following intracerebral hemorrhage via an endothelial Wnt/β-catenin signaling-dependent mechanism in mice

Background

Vasogenic cerebral edema resulting from blood–brain barrier (BBB) damage aggravates the devastating consequences of intracerebral hemorrhage (ICH). Although augmentation of endothelial Wnt/β‐catenin signaling substantially alleviates BBB breakdown in animals, no agents based on this mechanism are clinically available. Lithium is a medication used to treat bipolar mood disorders and can upregulate Wnt/β‐catenin signaling.

Methods

We evaluated the protective effect of lithium on the BBB in a mouse model of collagenase IV‐induced ICH. Furthermore, we assessed the effect and dependency of lithium on Wnt/β‐catenin signaling in mice with endothelial deletion of the Wnt7 coactivator Gpr124.

Results

Lithium treatment (3 mmol/kg) significantly decreased the hematoma volume (11.15 ± 3.89 mm³ vs. 19.97 ± 3.20 mm³ in vehicle controls, p = 0.0016) and improved the neurological outcomes of mice following ICH. Importantly, lithium significantly increased the BBB integrity, as evidenced by reductions in the levels of brain edema (p = 0.0312), Evans blue leakage (p = 0.0261), and blood IgG extravasation (p = 0.0009) into brain tissue around the hematoma. Mechanistically, lithium upregulated the activity of endothelial Wnt/β‐catenin signaling in mice and increased the levels of tight junction proteins (occludin, claudin‐5 and ZO‐1). Furthermore, the protective effect of lithium on cerebral damage and BBB integrity was abolished in endothelial Gpr124 knockout mice, suggesting that its protective effect on BBB function was mainly dependent on Gpr124‐mediated endothelial Wnt/β‐catenin signaling.

Conclusion

Our findings indicate that lithium may serve as a therapeutic candidate for treating BBB breakdown and brain edema following ICH.

Activation of Wnt/Beta-Catenin Signaling Pathway as a Promising Therapeutic Candidate for Cerebral Ischemia/Reperfusion Injury

Stroke is one of the leading causes of mortality, and survivors experience serious neurological and motor behavioral deficiencies. Following a cerebral ischemic event, substantial alterations in both cellular and molecular activities occur because of ischemia/reperfusion injury. Wnt signaling is an evolutionarily conserved signaling pathway that has been manifested to play a key role in embryo development and function maintenance in adults. Overactivation of Wnt signaling has previously been investigated in cancer-based research studies. Recently, abnormal Wnt signaling activity has been observed in ischemic stroke, which is accompanied by massive blood–brain barrier (BBB) disruption, neuronal apoptosis, and neuroinflammation within the central nervous system (CNS). Significant therapeutic effects were observed after reactivating the adynamic signaling activity of canonical Wnt signaling in different cell types. To better understand the therapeutic potential of Wnt as a novel target for stroke, we reviewed the role of Wnt signaling in the pathogenesis of stroke in different cell types, including endothelial cells, neurons, oligodendrocytes, and microglia. A comprehensive understanding of Wnt signaling among different cells may help to evaluate its potential value for the development of novel therapeutic strategies based on Wnt activation that can ameliorate complications and improve functional rehabilitation after ischemic stroke.

Endothelial β-Catenin Deficiency Causes Blood-Brain Barrier Breakdown via Enhancing the Paracellular and Transcellular Permeability

Disruption of the blood-brain barrier (BBB) causes or contributes to neuronal dysfunction and several central nervous system (CNS) disorders. Wnt/β-catenin signaling is essential for maintaining the integrity of the adult BBB in physiological and pathological conditions, including stroke. However, how the impairment of the endothelial Wnt/β-catenin signaling results in BBB breakdown remains unclear. Furthermore, the individual contributions of different BBB permeability-inducing mechanisms, including intercellular junction damage, endothelial transcytosis, and fenestration, remains unexplored. Here, we induced β-catenin endothelial-specific conditional knockout (ECKO) in adult mice and determined its impact on BBB permeability and the underlying mechanism. β-catenin ECKO reduced the levels of active β-catenin and the mRNA levels of Wnt target genes in mice, indicating downregulation of endothelial Wnt/β-catenin signaling. β-catenin ECKO mice displayed severe and widespread leakage of plasma IgG and albumin into the cerebral cortex, which was absent in wild-type controls. Mechanistically, both the paracellular and transcellular transport routes were disrupted in β-catenin ECKO mice. First, β-catenin ECKO reduced the tight junction protein levels and disrupted the intercellular junction ultrastructure in the brain endothelium. Second, β-catenin ECKO substantially increased the number of endothelial vesicles and caveolae-mediated transcytosis through downregulating Mfsd2a and upregulating caveolin-1 expression. Interestingly, fenestration and upregulated expression of the fenestration marker Plvap were not observed in β-catenin ECKO mice. Overall, our study reveals that endothelial Wnt/β-catenin signaling maintains adult BBB integrity via regulating the paracellular as well as transcellular permeability. These findings may have broad applications in understanding and treatment of CNS disorders involving BBB disruption.

GAS6/Axl Signaling Modulates Blood-Brain Barrier Function Following Intravenous Thrombolysis in Acute Ischemic Stroke

Background and Purpose

Recent studies have shown that several proteins, including Axl, are related to hemorrhagic transformation (HT) following intravenous thrombolysis by affecting blood-brain barrier (BBB) function. However, the effects of these proteins on BBB function have been studied primarily in animal models. In this study, we aimed to identify serum protein markers that predict HT following intravenous thrombolysis in patients with acute ischemic stroke (AIS) and verify whether these serum proteins regulate BBB function and HT in animal stroke models.

Methods

First, 118 AIS patients were enrolled in this study, including 52 HT patients and 66 non-HT patients. In Step 1, baseline serum levels of Axl, angiopoietin-like 4, C-reactive protein, ferritin, hypoxia-inducible factor-1 alpha, HTRA2, Lipocalin2, matrix metallopeptidase 9, platelet-derived growth factor-BB, and tumor necrosis factor alpha were measured using a quantitative cytokine chip. Next, sequence mutations and variations in genes encoding the differentially expressed proteins identified in Step 1 and subsequent function-related proteins were detected. Finally, we verified whether manipulation of differentially expressed proteins affected BBB function and HT in a hyperglycemia-induced rat stroke model.

Results

Serum Axl levels were significantly lower in the HT group than in the non-HT group; none of the other protein markers differed significantly between the two groups. Genetic testing revealed that sequence variations of GAS6 (the gene encoding the Axl ligand)-derived long non-coding RNA, GAS6-AS1, were significantly correlated with an increased risk of HT after intravenous thrombolysis. In animal studies, administration of recombinant GAS6 significantly reduced brain infarction and neurological deficits and attenuated BBB disruption and HT.

Conclusions

Lower serum Axl levels, which may result from sequence variations in GAS6-AS1, are correlated with an increased risk of HT after intravenous thrombolysis in stroke patients. Activation of the Axl signaling pathway by the GAS6 protein may serve as a therapeutic strategy to reduce HT in AIS patients.

Contribution of WNT2B Genetic Variants to Ischemic Stroke Occurrence in a Chinese Han Population

ABSTRACT

Wnt signaling pathway-related WNT2B gene was upregulated in ischemic brain damage. We aimed to assess the contribution of WNT2B genetic variant to ischemic stroke (IS) susceptibility in the Chinese Han population. Five polymorphisms including rs3790606, rs351364, rs3790608, rs12037987, and rs10776752 in WNT2B were genotyped using Agena MassARRAY platform in 476 healthy controls and 501 patients with IS. Odds ratio (OR) and 95% confidence interval (CI) adjusted for age and gender were estimated by logistic regression analysis. Analysis of variance was used to evaluate the association between genotypes of WNT2B variants and blood lipid parameters. Rs12037987 (OR = 1.82, 95% CI: 1.18-2.82, P = 0.007) and rs10776752 (OR = 1.74, 95% CI: 1.13-2.68, P = 0.012) were related to the increased IS susceptibility. Interestingly, rs12037987 (OR = 2.01, P = 0.028) and rs10776752 (OR = 2.02, P = 0.028) had the higher IS risk in the subjects younger than or equal to 65 years. Rs12037987 (OR = 2.70, P = 0.013), rs10776752 (OR = 2.71, P = 0.012), and rs3790606 (OR = 1.89, P = 0.036) manifested an increasing-risk association with IS occurrence in women. Moreover, rs3790606 genotype was related to serum levels of triglyceride (P = 0.008) and total cholesterol (P = 0.001). Our study reported that rs12037987 and rs10776752 were associated with the increased risk for IS in the Chinese Han population. Our findings may be useful for insight into the contribution of WNT2B variants to the complex pathogenesis of IS.

Zebrafish as a Model for In-Depth Mechanistic Study for Stroke

Stroke is one of the world's leading causes of death and disability, posing enormous burden to the society. However, the pathogenesis and mechanisms that underlie brain injury and brain repair remain largely unknown. There's an unmet need of in-depth mechanistic research in this field. Zebrafish (Danio rerio) is a powerful tool in brain science research mainly due to its small size and transparent body, high genome synteny with human, and similar nervous system structures. It can be used to establish both hemorrhagic and ischemic stroke models easily and effectively through different ways. After the establishment of stroke model, research methods including behavioral test, in vivo imaging, and drug screening are available to explore mechanisms that underlie the brain injury and brain repair after stroke. This review focuses on the advantages and the feasibility of zebrafish stroke model, and will also introduce the key methods available for stroke studies in zebrafish, which may drive future mechanistic studies in the pursuit of discovering novel therapeutic targets for stroke patients.

Single-Nucleotide Polymorphisms in Oxidative Stress-Related Genes and the Risk of a Stroke in a Polish Population-A Preliminary Study

The present preliminary case-control study was undertaken to detect the potential association of six single nucleotide polymorphisms (SNPs) in oxidative stress-related genes: SOD2 (c.47T > C; rs4880), CAT (c.-89A > T; rs7943316), GPX4 (c.660T > A; rs713041), NOS1 (g.117803515C > T; rs1879417) and NOS2 (c.1823C > T; rs2297518 and c.-227G > C; rs10459953) and the occurrence of a stroke. The SNPs were determined using the TaqMan^® Allelic Discrimination Assay in 107 patients with strokes and 107 age- and sex-matched individuals who had not experienced cerebrovascular accidents. The T alleles of the rs4880 were positively correlated with a stroke (bootstrap OR 1.31; 1.07-1.59 95% CI). In the case of the rs713041, an association with the T allele was found (bootstrap OR 1.36; 1.12-1.67). In addition, the occurrence of a stroke was associated with the presence of the C allele of the rs1879417 (bootstrap OR 1.32; 1.09-1.61). We also found that the C/C genotype and C allele of the rs2297518 increased the risk of a stroke (bootstrap ORs 7.00; 4.34-11.29 and 4.96; 3.88-6.34, respectively). Moreover, the C allele of the rs10459953 was associated with an increased occurrence of this disease (bootstrap OR 1.31; 1.08-1.60). These results indicated that genetics variants in the SOD2, GPX4, NOS1 and NOS2 might be associated with susceptibility to strokes in the Polish population.