15-hydroxy-11-alpha-9-alpha-(epoxymethano)prosta-5-13-dienoic-acid and 3-(5--hydroxymethyl-2--furyl)-1-benzylindazole

1. Our previous study demonstrated that YC-1, a derivative of benzylindazole, is a novel activator of soluble guanylate cyclase (sGC) in rabbit platelets. This work investigated whether the antiplatelet effect of YC-1 was mediated by a nitric oxide (NO)/sGC/cyclic GMP pathway in human platelets. 2. In human washed platelets, YC-1 inhibited platelet aggregation and ATP released induced by U46619 (2 microM), collagen (10 micro ml(-1)) and thrombin (0.1 u ml(-1)) in a concentration-dependent manner with IC50 values of (microM) 2.1 +/- 0.03, 11.7 +/- 2.1 and 59.3 +/- 7.1, respectively. 3. In a 30,000 g supernatant fraction from human platelet homogenate, YC-1 (5-100 microM) increased sGC activity in a concentration-dependent manner. At the same concentration-range, YC-1 elevated cyclic GMP levels markedly, but only slightly elevated cyclic AMP levels in the intact platelets. 4. MY-5445, a selective inhibitor of cyclic GMP phosphodiesterase, potentiated the increases in cyclic GMP caused by YC-1, and shifted the concentration-anti-aggregation curve of YC-1 to the left. In contrast, HL-725, a selective inhibitor of cyclic AMP phosphodiesterase, did not affect either the increases in cyclic nucleotides or the anti-aggregatory effect caused by YC-1. 5. Methylene blue, an inhibitor of sGC, blocked the increases of cyclic GMP caused by YC-1, and attenuated markedly the anti-aggregatory effect of YC-1. The adenylate cyclase inhibitor, 2',5'-dideoxyadenosine (DDA) did not affect YC-1-induced inhibition of platelet aggregation. 6. Haemoglobin, which binds NO, prevented the activation of sGC and anti-aggregatory effect caused by sodium nitroprusside, but did not affect YC-1 response. 7. These results would suggest that YC-1 activates sGC of human platelets by a NO-dependent mechanism, and exerts its antiplatelet effects through the sGC/cyclic GMP pathway.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adenosine Triphosphate; Blood Platelets; Collagen; Cyclic AMP; Cyclic GMP; Dideoxyadenosine; Dose-Response Relationship, Drug; Enzyme Activation; Furans; Guanylate Cyclase; Hemoglobins; Humans; Indazoles; Nitric Oxide; Phosphodiesterase Inhibitors; Phthalazines; Platelet Aggregation Inhibitors; Prostaglandin Endoperoxides, Synthetic; Solubility; Thrombin; Thromboxane A2; Vasoconstrictor Agents