Södergren Anna L, Svensson Holm Ann-Charlotte B, Ramström Sofia, Lindström Eva G, Grenegård Magnus, Öllinger Karin
a Department of Clinical and Experimental Medicine, Faculty of Health Sciences , Linköping University , Linköping , Sweden .
b Department of Medical and Health Sciences, Faculty of Health Sciences , Linköping University , Linköping , Sweden , and.
Platelets. 2016;27(1):86-92. doi: 10.3109/09537104.2015.1042446. Epub 2015 May 13.
Exocytosis of lysosomal contents from platelets has been speculated to participate in clearance of thrombi and vessel wall remodelling. The mechanisms that regulate lysosomal exocytosis in platelets are, however, still unclear. The aim of this study was to identify the pathways underlying platelet lysosomal secretion and elucidate how this process is controlled by platelet inhibitors. We found that high concentrations of thrombin induced partial lysosomal exocytosis as assessed by analysis of the activity of released N-acetyl-β-glucosaminidase (NAG) and by identifying the fraction of platelets exposing the lysosomal-associated membrane protein (LAMP)-1 on the cell surface by flow cytometry. Stimulation of thrombin receptors PAR1 or PAR4 with specific peptides was equally effective in inducing LAMP-1 surface expression. Notably, lysosomal exocytosis in response to thrombin was significantly reduced if the secondary activation by ADP was inhibited by the P2Y12 antagonist cangrelor, while inhibition of thromboxane A2 formation by treatment with acetylsalicylic acid was of minor importance in this regard. Moreover, the NO-releasing drug S-nitroso-N-acetyl penicillamine (SNAP) or the cyclic AMP-elevating eicosanoid prostaglandin I2 (PGI2) significantly suppressed lysosomal exocytosis. We conclude that platelet inhibitors that mimic functional endothelium such as PGI2 or NO efficiently counteract lysosomal exocytosis. Furthermore, we suggest that secondary release of ADP and concomitant signaling via PAR1/4- and P2Y12 receptors is important for efficient platelet lysosomal exocytosis by thrombin.
血小板溶酶体内容物的胞吐作用被推测参与血栓清除和血管壁重塑。然而，调节血小板溶酶体胞吐作用的机制仍不清楚。本研究的目的是确定血小板溶酶体分泌的潜在途径，并阐明该过程是如何由血小板抑制剂控制的。我们发现，通过分析释放的N-乙酰-β-氨基葡萄糖苷酶（NAG）的活性以及通过流式细胞术鉴定细胞表面暴露溶酶体相关膜蛋白（LAMP）-1的血小板比例来评估，高浓度凝血酶可诱导部分溶酶体胞吐作用。用特异性肽刺激凝血酶受体PAR1或PAR4在诱导LAMP-1表面表达方面同样有效。值得注意的是，如果P2Y12拮抗剂坎格雷洛抑制ADP的二次激活，凝血酶诱导的溶酶体胞吐作用会显著降低，而在这方面，用乙酰水杨酸处理抑制血栓素A2的形成则不太重要。此外，释放NO的药物S-亚硝基-N-乙酰青霉胺（SNAP）或升高环磷酸腺苷的类花生酸前列环素I2（PGI2）可显著抑制溶酶体胞吐作用。我们得出结论，模拟功能性内皮的血小板抑制剂，如PGI2或NO，可有效对抗溶酶体胞吐作用。此外，我们认为ADP的二次释放以及通过PAR1/4和P2Y12受体的伴随信号传导对于凝血酶有效诱导血小板溶酶体胞吐作用很重要。
