Comparison of activation process of platelets and neutrophils after coronary stent implantation versus balloon angioplasty for stable angina pectoris.

The pathophysiologic features of stent-induced cellular responses of platelets and leukocytes have not been established. This study was designed to clinically investigate the activation of platelets and neutrophils after coronary stenting and to identify its effects on the long-term results of coronary stents. Forty-eight consecutive patients with left anterior descending coronary artery disease indicating coronary intervention were randomly assigned to either a balloon angioplasty group or a coronary stent group. Flow cytometric analysis demonstrated that the transcardiac gradient (the value of coronary sinus blood minus the value of peripheral blood) of platelet surface expression of CD62P (p < 0.001) and CD63 (p < 0.01) increased immediately after coronary stenting, but increased less significantly immediately after balloon angioplasty (CD62P, p < 0.01; CD63, p < 0.05). These increases were persistently observed after coronary stenting but transiently after balloon angioplasty alone during a 48-hour observation period after the procedures. The gradient for neutrophil surface expression of CD11b increased, and that of CD62 L decreased 48 hours after coronary stenting (CD11b, p < 0.001; CD62 L, p < 0.05), but these changes showed less significance 48 hours after balloon angioplasty alone (CD11b, p < 0.05; CD62 L, p = NS). The gradients 48 hours after the procedures for both CD62P (r = 0.39, p < 0.05) and CD11b (r = 0.44, p < 0.01) were independently correlated with the late loss in the stent group, whereas the correlation was seen only for CD11b (r = 0.38, p < 0.05) in the balloon angioplasty group. Both platelet and neutrophil activation was greater after coronary stenting than after balloon angioplasty. Cellular interactions between platelets and neutrophils may be related to the progression of neointimal proliferation leading to restenosis after coronary stent implantation.

Cilostazol inhibits the expression of activation-dependent membrane surface glycoprotein on the surface of platelets stimulated in vitro.

Cilostazol is a newly developed antiplatelet drug that has been widely applied for clinical use. Its antiplatelet action appears to be mainly related to inhibition of intracellular phosphodiesterase activity. Our study was designed to investigate inhibitory effects of cilostazol on the expression of activation-dependent platelet membrane surface glycoproteins. We performed flow cytometric analysis using monoclonal antibodies, PAC-1 (antibody against activation dependent epitope of GPIIb/IIIa), anti-CD62P (P-selectin), and anti-CD63. In vitro ADP stimulation of platelets taken from seven healthy volunteers produced significant increases in the mean channel fluorescence intensities (MFI) for PAC-1 (148% increase) and CD62P (43% increase) but did not increase in that for CD63. The enhanced MFI for CD62P was suppressed to the control level by pretreatment with 1 microM (88% suppression), 3 microM (94% suppression), and 10 microM (95% suppression) of cilostazol. However, that of PAC-1 was suppressed to a lesser degree (12, 16, and 21% suppressions, respectively). Cilostazol may inhibit P-selectin release from alpha-granule, rather than activation-dependent conformational change of GPIIb/IIIa in platelets. Cilostazol inhibits cellular interaction among platelets, leukocytes, and vascular endothelial cells mediated by P-selectin.

Detection of platelets activated during acetylcholine-induced coronary vasospasm.

Although platelet activation may play a role in coronary artery spasm, platelets activated following coronary vasospasm have not been clinically detected. We performed flow cytometric analysis of activation-dependent granular proteins, CD62P (P-selectin), CD63, PAC-1 (activated glycoprotein [GP] IIb/IIIa) and thrombospondin on the platelet plasma membrane in patients who exhibited acetylcholine-induced coronary vasospasm and compared findings with those in control patients without vasospasm. We simultaneously investigated the plasma levels of thrombin anti-thrombin III complex (TAT), plasmin alpha2-plasmin inhibitor complex (PIC), and thrombomodulin. In patients with vasospasm, the expression of CD62P, CD63 and PAC-1 on the platelet membrane surface increased in coronary sinus blood samples following coronary vasospasm, although the expression in aortic samples did not change. The TAT level also increased in the coronary sinus after vasospasm. Platelets might be activated by coronary vasospasm within the coronary circulation. The platelet activation process may be modulated by thrombin generation.

Early detection of platelet activation after coronary angioplasty.

BACKGROUND: Although platelet activation has been considered an important reaction after percutaneous transluminal coronary angioplasty (PTCA), it is still difficult to detect the activated platelets in vivo directly. METHODS: To detect platelets activated at an early stage after PTCA, blood samples were take from the coronary sinus and the aorta in 22 patients with coronary artery disease, who underwent PTCA for a lesion of the left anterior descending artery. Ten patients with coronary artery disease, who underwent diagnostic coronary angiography only, were compared with them. The expression of activation-dependent granular protein, CD62P (P-selectin) and CD63, on the platelet membrane surface was analysed using flow cytometry. The plasma thrombomodulin level was also measured. RESULTS: The percentage of platelets positive for CD62P (0.53 +/- 0.04 to 0.80 +/- 0.11%, P < 0.01) and CD63 (16.0 +/- 1.4 to 19.8 +/- 2.0%, P < 0.05) increased after PTCA in the coronary sinus, although it did not change in the aorta. The plasma thrombomodulin level also increased after PTCA in the coronary sinus (16.7 +/- 1.0 to 20.4 +/- 2.0 mu/ml, P < 0.05). However, these parameters did not change after coronary angiography only. After PTCA, the plasma thrombomodulin level was correlated with the percentage of platelets positive for CD62P (r = 0.88, P < 0.001) and with that for CD63 (r = 0.69, P < 0.001) in the coronary sinus. CONCLUSIONS: PTCA produced activation of circulatory platelets, which might have been caused by balloon-induced vascular endothelial injury. One should take care to avoid needless vascular injury during the PTCA procedure to inhibit the platelet activation.