杀菌通透性增加蛋白体外抑制革兰阴性细菌脂多糖激活血小板的作用

本研究旨在探索杀菌通透性增加蛋白(bactericidal permeability-increasing protein,BPI)能否抑制G-细菌脂多糖(LPS)激活血小板的作用。取10例健康体检者全血制备富含血小板血浆(PRP,1×108/ml)。实验分为4组:正常血小板组:不作任何处理;LPS组:LPS(10μg/ml)刺激6 h;BPI组:BPI(100μg/ml)处理1 h;BPI+LPS组:BPI(100μg/ml)预孵育1 h后,再接受LPS(10μg/ml)刺激6 h。应用流式细胞术(FCM)检测各组血小板膜Toll样受体-4(TLR-4)的表达,酶联免疫吸附测定法(ELISA)测定PRP上清中细胞因子释放水平,包括肿瘤坏死因子-α(TNF-α)和白介素-6(IL-6)。结果表明,与正常血小板组相比,LPS刺激血小板后血小板膜TLR-4表达及上清中TNF-α和IL-6浓度均明显增高(P<0.001)。在接受BPI预处理后,LPS刺激血小板表达TLR-4及TNF-α和IL-6的作用明显下降,但仍高于正常血小板组。BPI单独刺激血小板不引起血小板TLR-4表达增高及细胞因子水平改变。结论:BPI能够抑制LPS诱导的血小板活化。

Bactericidal permeability increasing protein inhibits lipopolysaccharide-mediated platelet activation in vitro

This study was purposed to investigate the inhibitory effect of bactericidal permeability-increasing protein (BPI) on lipopolysaccharide (LPS)-mediated activation of platelets. Venous blood samples were obtained from 10 healthy volunteers and were prepared into platelet-rich plasma (PRP, 1 × 10(8)/ml). Experiments were divided into four groups: normal platelet group (untreated group); LPS group, BPI group and BPI+LPS group. PRP were stimulated by LPS (10 μg/ml) in the presence and absence of BPI (100 μg/ml) or BPI alone. Then platelets were harvested and determined for Toll-like receptor-4 (TLR-4) with flow cytometry (FCM), the supernatant was used for detection of cytokines including tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) with enzyme-linked immunosorbent assay (ELISA). The results showed that as compared with normal platelet group, TLR-4 expression on platelets was significantly increased under LPS stimulation (P < 0.001); the levels of TNF-α and IL-6 in the supernatant were also remarkably elevated (P < 0.001). However, either TLR-4 expression or the cytokine levels significantly decreased in the presence of BPI when platelets underwent LPS-challenge (P < 0.05), but still were higher than that in normal platelet group. Stimulating the platelets with BPI alone could not enhance the TLR-4 expression and cytokine levels. It is concluded that BPI has the ability to inhibit the LPS-induced platelet activation.