Summary
There is a growing body of evidence to suggest that reactive oxidant species (ROS)
including O2
−, OH− or H2O2 act as second messengers to activate platelets via 1) calcium mobilisation, 2) nitric
oxide (NO) inac-tivation, and 3) interaction with arachidonic to give formation of
isoprostanes. Among the enzymes generating ROS formation NOX2, the catalytic core
of NADPH oxidase (NOX), plays a prominent role as shown by the almost absent ROS production
by platelets taken from patients with hereditary deficiency of NOX2. Experimental
and clinical studies provided evidence that NOX2 is implicated in platelet activation.
Thus, impaired platelet activation has been detected in patients with NOX2 hereditary
deficiency. Similarly, normal platelets added with NOX2 specific inhibitors disclosed
impaired platelet activation along with ROS down-regulation. Accordingly, animals
prone to atherosclerosis treated with apocynin, a NOX inhibitor, showed reduced platelet
adhesion and atherosclerotic plaque. Furthermore, a significant association between
NOX2 up-regulation and platelet activation has been detected in patients at athero-thrombotic
risk, but a cause-effect relationship needs to be established. These findings may
represent a rationale to plan interventional trials with NOX inhibitors to establish
if blocking NOX2 or other NOX isoforms may represent a novel anti-platelet approach.
Keywords
Platelets - oxidative stress - NOX - reactive oxygen species