Gritters Mareille, Borgdorff Piet, Grooteman Muriel P C, Schoorl Marianne, Schoorl Margreet, Bartels Piet C M, Tangelder Geert-Jan, Nubé Menso J
Department of Nephrology, VU University Medical Centre, PO Box 7075, 1007 MB Amsterdam, The Netherlands.
Nephrol Dial Transplant. 2008 Sep;23(9):2911-7. doi: 10.1093/ndt/gfn137. Epub 2008 Mar 25.
The sum of undesirable side effects, occurring during haemodialysis (HD), is called bio-incompatibility. Concerning platelets, both an increase in the expression of the cell surface marker P-selectin (CD62p) and release of the intracellular granule product platelet factor 4 (PF4) have been described. However, as PF4 is also abundantly present on endothelium-bound proteoglycans, it is questionable whether the HD-induced increase is exclusively attributable to release from platelets. With respect to the cause of HD-induced bio-incompatibility, interest has been focused mainly on the extracorporeal circuit (ECC), especially the dialyser, whereas only little attention has been paid to other parts of the ECC and the mode of anticoagulation applied. To address the cause and origin of platelet activation and PF4 release during clinical HD, two complementary clinical studies were performed.
In study I, the relative influence of the various parts of the ECC was evaluated by measuring the expression of CD62p, platelet aggregation and levels of PF4 and serotonin at various sampling points. In study II, low-molecular-weight heparin (LMWH) was administered 10 min before the actual start of HD, in order to separate the effects from LMWH and the ECC on platelet activation.
In study I, CD62p expression increased across the entire length of the ECC, including the roller pump and dialyser (median at t(5) from 26% to 43%, P = 0.008; median at t(30) from 28% to 48%, P = 0.007). Increments in PF4 and aggregation of platelets were relatively modest. Platelet serotonin content, which was below reference values in healthy controls, and plasma serotonin concentration, which was above reference values, did not change. In study II, PF4 levels increased markedly after the injection of LMWH (from 12 IU/ml at t(-10) to 75 IU/ml at t(0), P = 0.018), whereas CD62p expression remained stable until the start of HD.
Platelet activation, as measured by the up-regulation of CD62p, is an early process, occurring not only within the dialyser, but across the entire length of the ECC. As CD62p remained unaltered after the administration of LMWH 10 min before the actual start of HD, this kind of activation is independent of LMWH. Considering PF4 however, a sharp increment was observed after the administration of LMWH and before the start of HD. This finding suggests that the PF4 release observed early in clinical HD is largely independent from the ECC, and is probably the result of LMWH-induced detachment from the endothelium. As the platelet serotonin content was relatively reduced and the plasma serotonin levels were elevated, platelets from chronic HD patients might be depleted due to chronic repetitive activation. Based on these data, it appears first, that PF4 is an inferior marker of platelet activation in clinical HD and second, that LMWH is a major contributor to HD-induced bio-incompatibility.
血液透析（HD）过程中出现的不良副作用总和称为生物不相容性。关于血小板，已描述了细胞表面标志物P-选择素（CD62p）表达增加以及细胞内颗粒产物血小板因子4（PF4）释放。然而，由于PF4在内皮结合蛋白聚糖上也大量存在，HD诱导的增加是否完全归因于血小板释放尚存在疑问。关于HD诱导的生物不相容性的原因，人们的兴趣主要集中在体外循环（ECC），尤其是透析器，而对ECC的其他部分和所应用的抗凝方式关注较少。为了探讨临床HD期间血小板活化和PF4释放的原因及来源，进行了两项互补的临床研究。
在研究I中，通过在不同采样点测量CD62p的表达、血小板聚集以及PF4和5-羟色胺水平，评估了ECC各部分的相对影响。在研究II中，在实际HD开始前10分钟给予低分子量肝素（LMWH），以区分LMWH和ECC对血小板活化的影响。
在研究I中，ECC全长包括滚压泵和透析器，CD62p表达均增加（t(5)时中位数从26%增至43%，P = 0.008；t(30)时中位数从28%增至48%，P = 0.007）。PF4增加和血小板聚集相对较小。血小板5-羟色胺含量低于健康对照参考值，而血浆5-羟色胺浓度高于参考值，两者均未改变。在研究II中，注射LMWH后PF4水平显著升高（从t(-10)时的12 IU/ml升至t(0)时的75 IU/ml，P = 0.018），而CD62p表达在HD开始前保持稳定。
通过CD62p上调测量的血小板活化是一个早期过程，不仅发生在透析器内，而且发生在ECC全长。由于在实际HD开始前10分钟给予LMWH后CD62p未改变，这种活化与LMWH无关。然而，考虑到PF4，在给予LMWH后且HD开始前观察到急剧增加。这一发现表明临床HD早期观察到的PF4释放很大程度上与ECC无关，可能是LMWH诱导其从内皮脱落的结果。由于慢性HD患者的血小板5-羟色胺含量相对降低而血浆5-羟色胺水平升高，慢性HD患者的血小板可能因慢性重复活化而耗竭。基于这些数据，首先，PF4在临床HD中是血小板活化的较差标志物；其次，LMWH是HD诱导的生物不相容性的主要促成因素。
