细胞内胆固醇代谢受 SREBP-2 和 LXR 信号通路调节。炎症对这些分子机制的影响仍知之甚少，特别是在血脑屏障（BBB）水平上。肿瘤坏死因子 α (TNFα) 是一种与 BBB 功能障碍相关的促炎细胞因子。因此，我们研究的目的是研究 TNFα 对 BBB 胆固醇代谢的影响，重点关注其潜在的信号通路。使用由人脑样内皮细胞 (hBLEC) 和脑周细胞 (HBP) 组成的体外 BBB 模型，我们观察到 TNFα 通过降解紧密连接蛋白 CLAUDIN-5 并激活两种细胞类型中的应激信号通路来增加 BBB 通透性。 TNFα还促进胆固醇释放并减少胆固醇积累和APOE分泌。在 hBLEC 中，SREBP-2 靶标（LDLR 和 HMGCR）的表达增加，而 ABCA1 表达减少。在 HBP 中，仅 LDLR 和 ABCA1 表达增加。 TNFα 治疗还会诱导 25-羟基胆固醇 (25-HC) 的产生，这是一种参与免疫反应和细胞内胆固醇代谢的胆固醇代谢物。 25-HC 预处理可减弱 TNFα 诱导的 BBB 渗漏，并部分减轻 TNFα 对 ABCA1、LDLR 和 HMGCR 表达的影响。总体而言，我们的结果表明 TNFα 通过 BBB 上的 LXR/ABCA1 独立机制促进胆固醇流出，同时激活 SREBP-2 途径。 25-HC 治疗部分逆转了 TNFα 对 LXR/SREBP-2 通路的影响。我们的研究为更好地理解与神经炎症性疾病中 BBB 功能障碍和胆固醇代谢相关的脑血管信号传导事件提供了新的视角。版权所有 © 2024。由 Elsevier B.V. 出版。

Intracellular cholesterol metabolism is regulated by the SREBP-2 and LXR signaling pathways. The effects of inflammation on these molecular mechanisms remain poorly studied, especially at the blood-brain barrier (BBB) level. Tumor necrosis factor α (TNFα) is a proinflammatory cytokine associated with BBB dysfunction. Therefore, the aim of our study was to investigate the effects of TNFα on BBB cholesterol metabolism, focusing on its underlying signaling pathways. Using a human in vitro BBB model composed of human brain-like endothelial cells (hBLECs) and brain pericytes (HBPs), we observed that TNFα increases BBB permeability by degrading the tight junction protein CLAUDIN-5 and activating stress signaling pathways in both cell types. TNFα also promotes cholesterol release and decreases cholesterol accumulation and APOE secretion. In hBLECs, the expression of SREBP-2 targets (LDLR and HMGCR) is increased, while ABCA1 expression is decreased. In HBPs, only LDLR and ABCA1 expression is increased. TNFα treatment also induces 25-hydroxycholesterol (25-HC) production, a cholesterol metabolite involved in the immune response and intracellular cholesterol metabolism. 25-HC pretreatment attenuates TNFα-induced BBB leakage and partially alleviates the effects of TNFα on ABCA1, LDLR, and HMGCR expression. Overall, our results suggest that TNFα favors cholesterol efflux via an LXR/ABCA1-independent mechanism at the BBB, while it activates the SREBP-2 pathway. Treatment with 25-HC partially reversed the effect of TNFα on the LXR/SREBP-2 pathways. Our study provides novel perspectives for better understanding cerebrovascular signaling events linked to BBB dysfunction and cholesterol metabolism in neuroinflammatory diseases.Copyright © 2024. Published by Elsevier B.V.