In vitro and in vivo experimental models have demonstrated that vascular endothelial function is significantly impaired as a result of oxidative stress, mediated by the generation of
oxygen-derived
free radicals in response to chronic or acute
inflammation. In particular, super-
oxide () at specific concentrations leads to the impairment of
nitric oxide (NO) bioactivity, and it is known that NO plays a fundamental role in the maintenance of vascular homeostasis. The relationship between
reactive oxygen species (ROS) and NO release in
thrombosis-related endothelial damage in the peripheral microvasculature remains unclear, however. The purpose of the present study was to investigate the effect of the
free-radical scavenger,
edaravone, on NO synthesis and thrombotic potential in arterioles after exposure to
laser irradiation. Highly sensitive electrochemical NO microsensors were positioned in femoral arterioles of mice, and the kinetics of NO release were recorded in response to standardized
laser irradiation in vivo. In addition, images of NO release from damaged vascular cells were investigated in a similar rat model using the NO-sensitive
dye 4,5-diaminofluorescein diacetate (DAF-2DA). Thrombogenesis was assessed in carotid arterioles by continuous video microscopy using image analysis software.
Laser irradiation led to NO release from perturbed endothelial cells and from platelet-rich thrombi.
Edaravone had no significant effect on NO release in non-
laser treated, intact endothelium compared with placebo. In contrast,
edaravone demonstrated a dose-dependent effect on NO release and thrombogenicity. At a concentration of 10.5 mg/kg per h,
edaravone promoted a 5-fold increase in NO and a reduction in platelet-rich
thrombus volume to 58% of the placebo values. Our data provide direct evidence to confirm that acute endothelial damage in peripheral microvessels initially induces NO release and that the
free-radical scavenger,
edaravone, augments NO synthesis leading to suppression of platelet
thrombus formation.