Montrucchio Giuseppe, Bosco Ornella, Del Sorbo Lorenzo, Fascio Pecetto Paolo, Lupia Enrico, Goffi Alberto, Omedè Paola, Emanuelli Giorgio, Camussi Giovanni
Department of Clinical Pathophysiology, University of Turin, Italy.
Thromb Haemost. 2003 Nov;90(5):872-81. doi: 10.1160/TH03-02-0085.
Several studies focused on the ability of bacterial lipopolysac-charides (LPS) in triggering platelet and/or leukocyte activation. The aim of this study was to investigate the molecular mechanisms involved in the aggregation of platelets and in their interaction with leukocytes in whole blood after stimulation with low doses of LPS. LPS did not directly induce platelet aggregation in whole blood, but they primed the aggregation of platelets induced by epinephrine, adenosine diphosphate and arachidonic acid. As shown by cytofluorimetry, platelets neither bind FITC-LPS, nor express the LPS-receptors CD14 and toll-like receptor 4 (TLR4). On the contrary, LPS primed monocytes and to a lesser extent polymorphonuclear neutrophils to adhere to platelets. Both platelet-leukocyte interaction and platelet aggregation in whole blood were inhibited by blockade of CD14 and TLR4. Moreover, the interaction between platelets and leukocytes was inhibited by P-selectin, and by blockade of PAF and reactive oxygen species, suggesting a role of P-selectin and of leukocyte-derived mediators. In conclusion, these results elucidate the mechanisms leading to platelet activation and interaction with leukocytes triggered by LPS. They suggest that the activation of platelets by LPS is mainly dependent on leukocytes and especially monocytes as a result of CD14 and TLR4 engagement. Moreover, we found that leukocyte-platelet interaction was triggered by the synthesis of PAF and the generation of oxygen radicals that induced upregulation of surface expression of P-selectin.
多项研究聚焦于细菌脂多糖（LPS）引发血小板和/或白细胞激活的能力。本研究的目的是探究低剂量LPS刺激后全血中血小板聚集及其与白细胞相互作用所涉及的分子机制。LPS在全血中并不直接诱导血小板聚集，但能使肾上腺素、二磷酸腺苷和花生四烯酸诱导的血小板聚集致敏。细胞荧光分析显示，血小板既不结合异硫氰酸荧光素标记的LPS，也不表达LPS受体CD14和Toll样受体4（TLR4）。相反，LPS使单核细胞致敏，并在较小程度上使多形核中性粒细胞致敏，使其黏附于血小板。全血中的血小板 - 白细胞相互作用和血小板聚集均受到CD14和TLR4阻断的抑制。此外，血小板与白细胞之间的相互作用受到P - 选择素以及PAF和活性氧阻断的抑制，提示P - 选择素和白细胞衍生介质发挥了作用。总之，这些结果阐明了LPS引发血小板激活及其与白细胞相互作用的机制。结果表明，LPS对血小板的激活主要依赖于白细胞，尤其是单核细胞，这是CD14和TLR4参与的结果。此外，我们发现白细胞 - 血小板相互作用是由PAF的合成和氧自由基的产生触发的，它们诱导了P - 选择素表面表达的上调。
