Neutralization of interleukin‐9 ameliorates experimental stroke by repairing the blood–brain barrierviadown‐regulation of astrocyte‐derived vascular endothelial growth factor‐A

Abstract

Astrocytes mediate the destruction of the blood–brain barrier (BBB) during ischemic stroke (IS). IL‐9 is a pleiotropic cytokine that we previously found to be highly expressed in peripheral blood mononuclear cells from patients with IS, and the presence of IL‐9 receptors on astrocytes has been reported in the literature. Here, we detected the effect of IL‐9 on astrocytes using an anti–IL‐9‐neutralizing antibody to treat rats with experimental stroke. Supernatants from astrocytes treated with or without oxygen–glucose deprivation and/or IL‐9 were incubated with bEnd.3 cell monolayers after blocking the IL‐9 receptor on the endothelium. Immunofluorescence staining and Western blot analyses were conducted to observe the change in tight junction proteins (TJPs) in bEnd.3 cells as well as the level of VEGF‐A and possible signal pathways in astrocytes. We also applied middle cerebral artery occlusion (MCAO) models to determine the effect of anti–IL‐9‐neutralizing antibodies on IS. As a result, astrocyte‐conditioned medium treated with IL‐9 aggravated the disruption of the BBB accomplished by the degradation of TJPs in endothelial cells. In addition, IL‐9 increased the level of VEGF‐A in astrocytes, and blocking the effect of VEGF‐A reversed the breakdown of the BBB. In the MCAO model, anti–IL‐9‐neutralizing antibody reduced the infarct volume and BBB destruction. Mechanistically, the anti–IL‐9‐neutralizing antibody repaired the damaged TJPs (zonula occludens 1, occludin, and claudin‐5) and induced a decrease in VEGF‐A expression in ischemic lateral brain tissue. In contrast, a local injection of recombinant murine IL‐9 to the brain resulted in a marked up‐regulation of VEGF‐A in the striatum. In conclusion, anti–IL‐9‐neutralizing antibody can reduce the severity of IS partially by alleviating the destruction of the BBB via down‐regulation of astrocyte‐derived VEGF‐A. This finding suggests that targeting IL‐9 or VEGF‐A could provide a new direction for the treatment of IS.—Tan, S., Shan, Y., Lin, Y., Liao, S., Zhang, B., Zeng, Q., Wang, Y., Deng, Z., Chen, C, Hu, X., Peng, L., Qiu, W., Lu, Z. Neutralization of IL‐9 ameliorates experimental stroke by repairing the blood–brain barrier via down‐regulation of astrocyte‐derived vascular endothelial growth factor‐A. FASEB J. 33, 4376–4387 (2019). http://www.fasebj.org

Principal component analysis, a useful tool to study cyclin-dependent kinase-inhibitor’s effect on cerebral ischaemia

“…Reactive astrocytes, characterized by proliferation and astrogliosis [defined by GFAP upregulation ( Zamanian et al , 2012 ; Hol and Pekny, 2015 )], promote infarct progression ( Yao et al , 2015 ), exacerbate inflammation ( Colombo and Farina, 2016 ), compromise BBB function ( Tan et al , 2019 ) and aggravate cytotoxic oedema ( Manley et al , 2000 ; Liu and Chopp, 2016 ). No GFAP signal was detected in the lesion area itself probably because of astrocyte necrosis in the core of ischaemia.…”

Peripheral inflammation and blood–brain barrier disruption: effects and mechanisms

“…Lots of bacterial and viral infections cause degradation or disorganization of TJs indirectly through diverse pathways 71‐73 . For example, cytokines including IL‐1β, IL‐6, IL‐9, IL‐17, IFN‐γ, TNF‐α, and CCL2, can lead to reduced TJ expression or false TJ allocation 74‐79 . Claudin‐5 among others is the most important TJ protein responsible for selective permeability of the BBB, and inflammation leads to its downregulation and BBB disruption 80 .…”

“…It has been reported that during inflammation astrocytes altered claudin‐5 expression likely by upregulating the immune‐related GTPase family M‐1 protein (IRGM‐1) in the EAE mouse model 99 . In middle cerebral artery occlusion (MCAO) model, researchers found high IL‐9 expression in peripheral blood and IL‐9 receptors on astrocytes, and further study revealed that IL‐9 enhances the permeability of the BBB by promoting the secretion of VEGF‐A from astrocytes 76 . Peripheral inflammation induced by LPS can cause proliferation and activation of astrocytes, changes in the end‐feet structure and altered expression of other related gene, which collectively and indirectly lead to destruction of the BBB 100,101 …”

This was the year that was: brain barriers and brain fluid research in 2019

“…Recently, Bonsack et al [29] demonstrated the importance of astrocyte-derived pentraxin-3 in regulating BBB permeability. Tan et al [30] have also shown that leukocytes can cause BBB disruption in stroke via effects on astrocytes. Leukocytes release interleukin-9 that causes astrocytes to release vascular endothelial growth factor-A which, in turn, causes BBB hyperpermeability.…”