Key result
Native dipyridamole, but not its oxidized form, exhibits antioxidant properties, inhibits platelet adhesion, enhances VASP phosphorylation, and suppresses inflammatory NF kappa B signaling.
The beneficial antioxidant and anti-inflammatory effects of dipyridamole, including platelet inhibition, are critically dependent on its native redox state.
Redox dependence of dipyridamole effects in animals leaves open translation to human antiplatelet or anti-inflammatory use.
Dipyridamole, a well-known inhibitor of cGMP-dependent phosphodiesterase and the adenosine transporter, reportedly possesses antioxidant properties and attenuates reactive oxygen species (ROS) formation in platelet and endothelial cells. The relevance of the redox status of this compound or the mechanism for its redox-dependent effects is unknown. Oxidation of dipyridamole by horseradish peroxidase and hydrogen peroxide diminished its fluorescence and attenuated dipyridamole-mediated DPPH and ferric ferrozine reduction. Oxidation also led to elimination of dipyridamole's redox-sensitive properties, including inhibiting Cu (II)-induced LDL oxidation and ROS generation. Attenuation of activation- induced platelet release of soluble CD40 ligand (sCD40L) was diminished after dipyridamole oxidation. Dipyridamole but not oxidized dipyridamole effectively inhibited platelet adhesion to collagen-coated slides under flow conditions. By Western blot analysis, dipyridamole enhanced stimulation-induced platelet VASP phosphorylation, whereas oxidized dipyridamole caused attenuation. Using luciferase assays and nuclear translocation studies with confocal microscopy and Western blot analysis, native dipyridamole diminished TNF alpha or thrombin-induced NF kappa B activation and I kappa B alpha phosphorylation. Oxidized dipyridamole had no effect on TNFalpha-mediated NF kappa B activation. These results indicate: (1) the redox state of dipyridamole regulates its antioxidant properties; (2) dipyridamole's platelet inhibitory effects are manifested by enhanced VASP phosphorylation and platelet adhesion on collagen; and (3) dipyridamole's antioxidant effects in vascular cells are at least partially mediated via suppression of inflammatory NF kappa B signaling.
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Chakrabarti et al. (2007) studied this question. Dipyridamole vs. Oxidized dipyridamole was evaluated on Antioxidant properties, platelet inhibitory effects, and NF kappa B signaling. Native dipyridamole, but not its oxidized form, exhibits antioxidant properties, inhibits platelet adhesion, enhances VASP phosphorylation, and suppresses inflammatory NF kappa B signaling.
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