Schofield L, Novakovic S, Gerold P, Schwarz R T, McConville M J, Tachado S D
Immunoparasitology Unit, Royal Melbourne Hospital, Victoria, Australia.
J Immunol. 1996 Mar 1;156(5):1886-96.
In this study we demonstrate that glycosylphosphatidylinositol (GPI) of malaria parasite origin directly increases cell adhesion molecule expression in purified HUVECs in a dose- and time-dependent manner, resulting in a marked increase in parasite and leukocyte cytoadherence to these target cells. The structurally related glycolipids dipalmitoyl-phosphatidylinositol and iM4 glycoinositolphospholipid of Leishmania mexicana had no such activity. Malarial GPI exerts this effect by activation of an endogenous GPI-based signal transduction pathway in endothelial cells. GPI induces rapid onset tyrosine phosphorylation of multiple intracellular substrates within 1 min of addition to cells in a dose-dependent manner. This activity can be blocked by the protein tyrosine kinase-specific antagonist herbimycin A, genistein, and tyrphostin. These tyrosine kinase antagonists also inhibit GPI-mediated up-regulation of adhesion expression and parasite cytoadherence. GPI-induced up-regulation of adhesion expression and parasite cytoadherence can also be blocked by the NF kappa B/c-rel antagonist pyrrolidine-dithiocarbamate, suggesting the involvement of this family of transcription factors in GPI-induced adhesin expression. The direct activation of endothelial cells by GPI does not require the participation of TNF or IL-1. However, GPI is also responsible for the indirect pathway of increased adhesin expression mediated by TNF and IL-1 output from monocytes/macrophages. Total parasite extracts also up-regulate adhesin expression and parasite cytoadherence in HUVECs, and this activity is blocked by a neutralizing mAb to malaria GPI, suggesting that GPI is the dominant agent of parasite origin responsible for this activity. Thus, a parasite-derived GPI toxin activates vascular endothelial cells by tyrosine kinase-mediated signal transduction, leading to NF kappa B/c-rel activation and downstream expression of adhesins, events that may play a central role in the etiology of cerebral malaria.
在本研究中，我们证明源自疟原虫的糖基磷脂酰肌醇（GPI）以剂量和时间依赖性方式直接增加纯化的人脐静脉内皮细胞（HUVECs）中细胞粘附分子的表达，导致寄生虫和白细胞对这些靶细胞的细胞粘附显著增加。墨西哥利什曼原虫的结构相关糖脂二棕榈酰磷脂酰肌醇和iM4糖肌醇磷脂没有这种活性。疟疾GPI通过激活内皮细胞内基于GPI的内源性信号转导途径发挥这种作用。GPI在添加到细胞后1分钟内以剂量依赖性方式诱导多种细胞内底物快速发生酪氨酸磷酸化。这种活性可被蛋白酪氨酸激酶特异性拮抗剂赫伯霉素A、染料木黄酮和 tyrphostin阻断。这些酪氨酸激酶拮抗剂也抑制GPI介导的粘附表达上调和寄生虫细胞粘附。GPI诱导的粘附表达上调和寄生虫细胞粘附也可被NF-κB/c-rel拮抗剂吡咯烷二硫代氨基甲酸盐阻断，表明该转录因子家族参与GPI诱导的粘附素表达。GPI对内皮细胞的直接激活不需要TNF或IL-1的参与。然而，GPI也负责由单核细胞/巨噬细胞输出的TNF和IL-1介导的粘附素表达增加的间接途径。总寄生虫提取物也上调HUVECs中的粘附素表达和寄生虫细胞粘附，并且这种活性被针对疟疾GPI的中和单克隆抗体阻断，表明GPI是负责这种活性的寄生虫来源的主要因子。因此，一种源自寄生虫的GPI毒素通过酪氨酸激酶介导的信号转导激活血管内皮细胞，导致NF-κB/c-rel激活和粘附素的下游表达，这些事件可能在脑型疟疾的病因学中起核心作用。
