| pA2 online © Copyright 2004 The British Pharmacological Society |
021P
University of Newcastle Winter Meeting December 2004 |
C-type natriuretic peptide (CNP) inhibits thrombin-induced platelet aggregation 1Amrita Ahluwalia, 1Marc Cohen, 2Ramona Scotland & 2Adrian Hobbs. 1Clinical Pharmacology, William Harvey Research Institute, Barts and The London & 2Wolfson Institute for Biomedical Research, University College London. |
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Print abstractC-type natriuretic peptide (CNP) has been recently identified as an endothelium-derived hyperpolarizing factor (EDHF) in the mesenteric and coronary vasculature and shown to activate a novel signalling pathway involving natriuretic peptide receptor C (NPR-C; Chauhan et al., 2003; Hobbs et al., 2004). Recent evidence also indicates that CNP, via the activation of this newly described NPR-C-dependent pathway, is protective against ischaemia-reperfusion injury and inhibits leukocyte-endothelial cell interactions (Hobbs et al., 2004; Scotland et al., 2004). In this study, we tested the hypothesis that the vasoprotective nature of CNP/NPR-C signaling also extends to the regulation of platelet reactivity.
Human blood was collected from individuals who had not taken non-steroidal anti-inflammatory drugs for the previous 14 days and prostacyclin (PGI2)-washed platelet suspensions (WP) were prepared as described previously (Radomski & Moncada, 1983). Platelet aggregation was measured in a Chronolog whole blood ionised calcium lumi-aggregometer. Following determination of collagen (0.1-10μg/ml) and thrombin (0.1-1U/ml) concentration response curves (in the absence and presence of the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester, L-NAME; 300μM), CNP (0.1-10 μM) was incubated with the WP (2.5x108 platelets/ml) for 5 mins prior to addition of EC30-EC70 concentrations of collagen or thrombin and platelet aggregation monitored for 10 mins. This study was performed with local ethical approval.
Thrombin (0.1-1U/ml) elicited a concentration-dependent aggregation of platelets that was significantly enhanced in the presence of L-NAME (n>5; P<0.05, ANOVA). CNP (0.1-1μM) inhibited platelet aggregation in response to 0.3U/ml thrombin in a concentration-dependent manner (assessed using a students t-test). Collagen (0.1-10μg/ml) also produced a concentration-dependent aggregation of platelets. However, the aggregatory effect of collagen was unchanged in the presence of L-NAME (n>5; P>0.05) or CNP (0.1-1μM) (assessed using ANOVA).
In conclusion, these data demonstrate that CNP exerts an anti-thrombotic activity via inhibition of thrombin-induced platelet aggregation. This phenomenon further expands the physiological roles of endothelium-derived CNP and extends its potential anti-atherogenic activity.
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