Background: Apelin-13 has been found to have protective effects on many neurological diseases, including cerebral ischemia. However, whether Apelin-13 acts on blood-brain barrier (BBB) disruption following cerebral ischemia is largely unknown. Aquaporin-4 (AQP4) has a close link with BBB due to the high concentration in astrocyte foot processes and regulation of astrocytes function. Here, we aimed to test Apelin-13′s effects on ischemic BBB injury and examine whether the effects were dependent on AQP4. Methods: We detected the expression of AQP4 induced by Apelin-13 injection at 1, 3, and 7 days after middle cerebral artery occlusion. Meanwhile, we examined the effects of Apelin-13 on neurological function, infarct volume, and BBB disruption owing to cerebral ischemia in wild type mice, and tested whether such effects were AQP4 dependent by using AQP4 knock-out mice. Furthermore, we assessed the possible signal transduction pathways activated by Apelin-13 to regulate AQP4 expression via astrocyte cultures. Results: It was found that Apelin-13 highly increased AQP4 expression as well as reduced neurological scores and infarct volume. Importantly, Apelin-13 played a role of BBB protection in both types of mice by reducing BBB permeability, increased vascular endothelial growth factor, upregulated endothelial nitric oxide synthase, and downregulated inducible NOS. In morphology, we demonstrated Apelin-13 suppressed tight junction opening and endothelial cell swelling via electron microscopy detection. Meanwhile, Apelin-13 also alleviated apoptosis of astrocytes and promoted angiogenesis. Interestingly, effects of AQP4 on neurological function and infarct volume varied with time course, while AQP4 elicited protective effects on BBB at all time points. Statistical analysis of 2-way analysis of variance with replication indicated that AQP4 was required for these effects. In addition, Apelin-13 upregulated phosphorylation of extracellular signal-regulated kinase (ERK) and Akt as well as AQP4 protein in cultured astrocytes. The latter was inhibited by ERK and phosphatidylinositol 3′-kinase (PI3K) inhibitors. Conclusion: Our data suggest that Apelin-13 protects BBB from disruption after cerebral ischemia both morphologically and functionally, which is highly associated with the increased levels of AQP4, possibly through the activation of ERK and PI3K/Akt pathways. This study provides double targets to protection of ischemic BBB damage, which can present new insights to drugs development.

Background: This study aimed to develop a prediction score named inflammatory score based on proper integration of several inflammatory markers and investigate whether it was associated with hematoma expansion and poor outcomes in patients with intracerebral hemorrhage (ICH). Methods: This study involved a consecutive series of spontaneous ICH patients of two cohorts admitted within 24 hours after symptom onset. Inflammatory score (0–9) was developed with the combination of neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, monocyte-to-lymphocyte ratio, systemic immune-inflammation index, lactate dehydrogenase, and C-reactive protein. The authors investigated the association between inflammatory score and hematoma expansion and poor outcomes by using univariate and multivariate logistic regression analyses. The optimal cutoff point of inflammatory score was determined by receiver operating characteristic analysis in the development cohort and then validated. Results: A total of 301 and 154 ICH patients were enrolled in the development and validation cohorts. Inflammatory score was significantly higher in patients with hematoma expansion and poor outcomes. The multivariate logistic regression analysis revealed inflammatory score was independently associated with hematoma expansion, secondary neurological deterioration within 48 hours, 30-day mortality, and 3-month poor modified Rankin scale (4–6). The diagnostic accuracy of inflammatory score exhibited by area under the curve showed numerically or statistically higher than most of the individual indicators. Moreover, inflammatory score greater than or equal to 5 was selected as the optimal cutoff point, which was further prospectively validated with high diagnostic accuracy. Conclusions: The inflammatory score is a reliable predictor for early hematoma expansion and short-term and long-term poor outcomes with good diagnostic accuracies in ICH patients.

Cerebrovascular diseases are conditions caused by problems with brain vasculature, which have a high morbidity and mortality. Aquaporin-4 (AQP4) is the most abundant water channel in the brain and crucial for the formation and resolution of brain edema. Considering brain edema is an important pathophysiological change after stoke, AQP4 is destined to have close relation with cerebrovascular diseases. However, this relation is not limited to brain edema due to other biological effects elicited by AQP4. Till now, multiple studies have investigated roles of AQP4 in cerebrovascular diseases. This review focuses on expression of AQP4 and the effects of AQP4 on brain edema and neural cells injuries in cerebrovascular diseases including cerebral ischemia, intracerebral hemorrhage and subarachnoid hemorrhage. In the current review, we pay more attention to the studies of recent years directly from cerebrovascular diseases animal models or patients, especially those using AQP4 gene knockout mice. This review also elucidates the potential of AQP4as an excellent therapeutic target.

Aquaporin-4 (AQP4) is the most abundantly expressed aquaporin in the central nervous system (CNS) and is an integral part of the glymphatic system that cannot be ignored. The CNS has the glymphatic system instead of the conventional lymphatic system. The glymphatic system plays an essential role in the pathophysiological processes of many cognitive disorders. AQP4 shows noteworthy changes in various cognitive disorders and is part of the pathogenesis of these diseases. For this reason, AQP4 has attracted attention as a potential and promising target for regulating and even reversing cognitive dysfunction. This review will summarize the role of AQP4 in the pathophysiological processes of several cognitive disorders as reported in recent studies.

We previously reported that aquaporin-4 deletion (AQP4-/-) in mice increased edema and altered blood-brain barrier integrity following intracerebral hemorrhage (ICH). To date, little is known about the role of AQP4 in apoptosis after ICH. The purpose of this study was to examine the role of AQP4 in apoptosis and its mechanisms after ICH using AQP4-/- mice. We compared the survival rate and neurological deficits in wild-type (AQP4+/+) mice with those in AQP4-/- mice following ICH. Histological changes were detected with terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining and Hoechst staining. The cell types involved were determined by immunocytochemical studies. We also measured activated caspase-3, caspase-9, caspase-8, Bax, and Bcl-2 with Western blotting at 1, 3, and 7 days after ICH. A cytokine protein assay was used to detect cytokines in AQP4+/+ and AQP4-/- mice following ICH, and the results were verified by ELISA. We found more apoptotic cells in AQP4-/- mice following ICH; the cell types involved were predominantly neurons and astrocytes. Western blotting showed that the expression of activated caspase-3 and caspase-8 was significantly increased (P <0.05). Moreover, we demonstrated a greater enhancement in the release of TNF-Α and IL-1Β, as well as their receptors, in AQP4-/- mice following ICH than in AQP4+/+ mice by cytokine protein assay and Western blotting (P <0.05). The inhibitors of TNF-Α and IL-1Β reduced apoptotic cells after ICH in AQP4-/- mice compared with wild-type mice (P <0.05). AQP4 deletion increases apoptosis following ICH, and the underlying mechanism may be through cytokines, especially TNF-Α and IL-1Β, initiating the apoptotic cascade, as well as activation of caspase-3 and caspase-8.