Arachidonate 15-Lipoxygenase Enzyme Products Increase Platelet Aggregation and Thrombin Generation

Atherosclerotic cardiovascular diseases are the leading causes of morbidity and mortality worldwide. We have previously shown that arachidonate 15-lipoxygenase B (ALOX15B) is highly expressed in atherosclerotic carotid plaques, and elucidation of mechanisms downstream of activated lipoxygenases may be relevant to our understanding of the genesis of atherosclerotic diseases. We examined 120 carotid plaques from patients with symptomatic carotid artery stenosis and showed that the extent of ALOX15B staining was significantly increased in carotid plaques with thrombosis. Impedance aggregometry analyses showed that the ALOX15B enzyme products 15-HETE and 15-HPETE increased platelet aggregation. By using a calibrated automatic thrombin assay, we showed that the ALOX15B products also increased both peak levels of thrombin and the total endogenous thrombin potential. Moreover, platelet aggregation was increased by addition of cell lysates from ischemic human macrophages, whereas platelet aggregation was reduced after knockdown of ALOX15B in human macrophages. Our data show that ALOX15B expression in human carotid plaques is associated with thrombus formation and that enzyme products of ALOX15B increase platelet aggregation and thrombin generation. We therefore propose that activated ALOX15B in macrophages may play a role in the induction of atherothrombotic events by increasing platelet aggregation and thrombin generation.

动脉粥样硬化性心血管疾病（Atherosclerotic cardiovascular diseases）是全球范围内首要的致死致残病因。我们此前的研究已证实，花生四烯酸15-脂氧合酶B（arachidonate 15-lipoxygenase B，ALOX15B）在动脉粥样硬化性颈动脉斑块中呈高表达状态；阐明激活型脂氧合酶的下游调控机制，或有助于理解动脉粥样硬化性疾病的发病进程。本研究纳入120例有症状颈动脉狭窄患者的颈动脉斑块样本，分析发现伴血栓形成的颈动脉斑块中，ALOX15B的染色强度显著升高。阻抗聚集分析法结果显示，ALOX15B的酶促产物15-HETE与15-HPETE可增强血小板聚集能力。通过校准后的自动凝血酶检测实验，我们证实ALOX15B的产物不仅可提升凝血酶峰值水平，还能增加总内源性凝血酶潜能。此外，缺血性人类巨噬细胞的细胞裂解液可增强血小板聚集，而在人巨噬细胞中敲低ALOX15B的表达则会降低血小板聚集水平。本研究数据表明，人颈动脉斑块中的ALOX15B表达与血栓形成密切相关，且ALOX15B的酶促产物可增强血小板聚集与凝血酶生成过程。据此我们推测，巨噬细胞中激活的ALOX15B可能通过增强血小板聚集与凝血酶生成，参与动脉粥样硬化血栓事件的诱发过程。