目的:炎症性肠病(IBD)患者血浆高密度脂蛋白(HDL)胆固醇水平经常降低。因此,因为高密度脂蛋白具有抗炎活性,我们研究了HDL及其主要蛋白质成分载脂蛋白A-I(apoA-I)是否在体内和体外调节粘膜炎症反应。
方法:以人肠上皮细胞系T84作为体外模型,检测HDL对肿瘤坏死因子(TNF)表达和分泌的影响,白细胞介素-8(IL-8),和细胞内粘附分子(ICAM)。核因子-κB(NF-κB)应答启动子活性通过双荧光素酶报告基因测定进行研究。在apoA-I转基因(Tg)和apoA-I敲除(KO)和野生型(WT)小鼠中,通过结肠镜检查和组织学对葡聚糖硫酸钠(DSS)和2,4,6-三硝基苯磺酸(TNBS)诱导的结肠炎的粘膜损伤进行评分。在肠组织样品中测定髓过氧化物酶(MPO)活性以及TNF和ICAM表达。通过Westernblot分析研究自噬,免疫荧光,和电子显微镜。
结果:HDL和apoA-I下调TNF诱导的TNFmRNA表达,IL-8和ICAM,以及TNF诱导的NF-κB应答启动子活性。DSS/TNBS处理的apoA-IKO小鼠在结肠镜检查和组织学上表现出增加的粘膜损伤,与WT和apoA-ITg小鼠相比,肠道MPO活性和TNF和ICAM的mRNA表达增加。相比之下,apoA-ITg小鼠在DSS和TNBS结肠炎模型中通过结肠镜检查和MPO活性监测显示不太严重的症状。此外,HDL诱导的自噬,导致磷酸化IκB激酶募集到自噬小室,从而阻止NF-κB活化和细胞因子表达的诱导。
结论:综合来看,体外和体内研究结果表明,HDL和apoA-I通过自噬抑制肠道炎症,是IBD治疗的潜在治疗靶点.
OBJECTIVE: Plasma levels of high-density lipoprotein (HDL) cholesterol are frequently found decreased in patients with inflammatory bowel disease (IBD). Therefore, and because HDL exerts anti-inflammatory activities, we investigated whether HDL and its major protein component apolipoprotein A-I (apoA-I) modulate mucosal inflammatory responses in vitro and in vivo.
METHODS: The human intestinal epithelial cell line T84 was used as the in vitro model for measuring the effects of HDL on the expression and secretion of tumor necrosis factor (TNF), interleukin-8 (IL-8), and intracellular adhesion molecule (ICAM). Nuclear factor-κB (NF-κB)-responsive promoter activity was studied by dual luciferase reporter assays. Mucosal damage from colitis induced by dextran sodium sulphate (DSS) and 2,4,6-trinitrobenzenesulfonic acid (TNBS) was scored by colonoscopy and histology in apoA-I transgenic (Tg) and apoA-I knockout (KO) and wild-type (WT) mice. Myeloperoxidase (MPO) activity and TNF and ICAM expression were determined in intestinal tissue samples. Autophagy was studied by Western blot analysis, immunofluorescence, and electron microscopy.
RESULTS: HDL and apoA-I down-regulated TNF-induced mRNA expression of TNF, IL-8, and ICAM, as well as TNF-induced NF-κB-responsive promoter activity. DSS/TNBS-treated apoA-I KO mice displayed increased mucosal damage upon both colonoscopy and histology, increased intestinal MPO activity and mRNA expression of TNF and ICAM as compared with WT and apoA-I Tg mice. In contrast, apoA-I Tg mice showed less severe symptoms monitored by colonoscopy and MPO activity in both the DSS and TNBS colitis models. In addition, HDL induced autophagy, leading to recruitment of phosphorylated IκB kinase to the autophagosome compartment, thereby preventing NF-κB activation and induction of cytokine expression.
CONCLUSIONS: Taken together, the in vitro and in vivo findings suggest that HDL and apoA-I suppress intestinal inflammation via autophagy and are potential therapeutic targets for the treatment of IBD.