Guanylate cyclase-cyclic GMP signaling pathway in platelet disaggregation associated with dissociation of PAF-receptor complex

PAF分子与其受体的持续结合对于人和兔血小板的长期聚集是必需的。另一方面，PAF完全聚集的人和兔血小板经历缓慢的解聚，但被PAF受体拮抗剂WEB-2086和Y-24180迅速解聚。加入Y-24180后，PAF与受体迅速解离，血小板鸟苷酸环化酶（GC）活性和细胞内cGMP水平升高，血小板解聚，细胞表面P-选择素消失，[Ca^2+]i无变化。此外，GC激活剂YC-1（1 × 104 μ <-5>M）和cGMP磷酸二酯酶抑制剂潘生丁（3 × 104 <-6>μ M）抑制PAF（2 × 104 μ <-10>M）诱导的兔血小板聚集，并通过增加细胞内cGMP水平使PAF聚集的血小板解聚。CPT-cGMP（0.2 mM）而不是CPT-cAMP（0.2 mM）也解聚PAF（2 × 10 μ <-10>M）聚集的血小板。而NO-d ...更多信息 可溶性GC抑制剂ODQ（1 × 10 ~（-1）<-5>M）抑制硝普钠诱导的血小板cGMP生成，但对Y-24180解聚PAF聚集的血小板cGMP生成无影响。PAF能使PAF受体阳性/阳性小鼠的血小板聚集，PAF受体拮抗剂能阻断血小板聚集，而PAF受体阴性/阴性小鼠的血小板不被PAF聚集。PAF拮抗剂Y24180和Rho激酶抑制剂Y27632协同解聚PAF刺激的血小板。这些结果表明，血小板PAF受体与中性粒细胞相同，但通过血小板PAF受体的信号转导途径是独特的，这些观察结果表明，除了NO依赖的sGC外，GC在血小板解聚与PAF受体复合物解离相关的信号转导机制中起重要作用。少

Continuous binding of the PAF molecule to its receptor is necessary for the long-term aggregation of human and rabbit platelets. On the other hand, human and rabbit platelets fully aggragated by PAF underwent slow disaggregation but were rapidly disaggregated by the PAF receptor antagonists WEB-2086 and Y-24180. PAF dissociated promptly from its receptor when Y-24180 was added, in parallel with elevation in platelet guanylate cyclase (GC) activity and intracellular cGMP level, followed by platelet disaggregation and disappearance of P-selectin on the cell surface, but no alteration in [Ca^<2+>]i. In addition, GC activator YC-1 (1 x 10^<-5> M) and cGMP phosphodiesterase inhibitor dipyridamole (3 x 10^<-6> M) suppressed PAF (2 x 10^<-10> M)-induced rabbit platelet aggregation, and moreover disaggregated the PAF-aggregated platelets by increasing intracellular cGMP level. CPT-cGMP (0.2 mM) but not CPT-cAMP (0.2 mM) also disaggregated PAF (2 x 10^<-10> M)-aggregated platelets. Whereas NO-d … More ependent soluble GC inhibitor ODQ (1 x 10^<-5> M) inhibited sodium nitroprusside-induced cGMP production in the platelets, ODQ did not affect the cGMP production when Y-24180 disaggregated PAF-aggregated platelets.We succeded in isolating a cDNA encoding PAF receptor from a human megakaryocytic cell line MEG01 and CMKII-5 cDNA, that is the same as neutrophile PAF receptor. Whereas platelets from PAF receptor+/+ mice were aggregated by PAF and the aggregation was blocked by PAF receptor antagonists, platelets from PAF receptor-/- mice were not aggregated by PAF. PAF antagonist Y24180 and Rho kinase inhibitor Y27632 synergistically disaggregated PAF-stimulted platelets. These results indicate that platelet PAF receptor is the same as that of neutrophile, but the signalling pathway through platelet PAF receptor is characteristic.In conclusion, these observations indicate that GC beside NO-dependent sGC plays an important role in signal transduction mechanism in platelet disaggregation associated with dissociation of PAF-receptor complex. Less