Interleukin (IL)-9 exerts a variety of functions in autoimmune diseases. However, its role in ischemic brain injury remains unknown. The present study explored the biological effects of IL-9 in ischemic stroke (IS). We recruited 42 patients newly diagnosed with IS and 22 age- and sex-matched healthy controls. The expression levels of IL-9 and percentages of IL-9-producing T cells, including CD3+CD4+IL-9+ and CD3+CD8+IL-9+ cells, were determined in peripheral blood mononuclear cells (PBMCs) obtained from patients and control individuals. We also investigated the effects of IL-9 on the blood–brain barrier (BBB) following oxygen–glucose deprivation (OGD) and the potential downstream signaling pathways. We found that patients with IS had higher IL-9 expression levels and increased percentages of IL-9-producing T cells in their PBMCs. The percentages of CD3+CD4+IL-9+ and CD3+CD8+IL-9+ T cells were positively correlated with the severity of illness. In in vitro experiments using bEnd.3 cells, exogenously administered IL-9 exacerbated the loss of tight junction proteins (TJPs) in cells subjected to OGD plus reoxygenation (RO). This effect was mediated via activation of IL-9 receptors, which increased the level of endothelial nitric oxide synthase (eNOS), as well as through up-regulated phosphorylation of signal transducer and activator of transcription 1 and 3 and down-regulated phosphorylated protein kinase B/phosphorylated phosphatidylinositol 3-kinase signaling. These results indicate that IL-9 has a destructive effect on the BBB following OGD, at least in part by inducing eNOS production, and raise the possibility of targetting IL-9 for therapeutic intervention in IS.
Exacerbation of oxygen–glucose deprivation-induced blood–brain barrier disruption: potential pathogenic role of interleukin-9 in ischemic stroke
Sha Tan, Yilong Shan, Yuge Wang, Yinyao Lin, Siyuan Liao, Zhezhi Deng, Li Zhou, Wei Cai, Qin Zeng, Lei Zhang, Bingjun Zhang, Xuejiao Men, Haiyan Li, Xueqiang Hu, Changyou Wu, Lisheng Peng, Zhengqi Lu; Exacerbation of oxygen–glucose deprivation-induced blood–brain barrier disruption: potential pathogenic role of interleukin-9 in ischemic stroke. Clin Sci (Lond) 1 July 2017; 131 (13): 1499–1513. doi: https://doi.org/10.1042/CS20170984
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