Summary
Chronic platelet activation may be involved in thromboembolic complications, a leading
cause of morbidity and mortality in β-thalassemia. Oxidative stress, with the generation
of reactive oxygen species (ROS), is suspected to play a role in the pathophysiology
of thalassemia and cardiovascular disorders. In the present study, we adapted flow
cytometric techniques to measure oxidative state markers, ROS generation and reduced
glutathione (GSH) content in platelets. Our results show that platelets obtained from
β-thalassemic patients contain higher ROS and lower GSH levels than do platelets from
normal donors, indicating a state of oxidative stress. In the absence of any known
inherent abnormality in thalassemia platelets, this may be attributed to continuous
exposure to oxidative insults from extra-platelet sources. We found that exposure
of platelets to oxidants such as hydrogen peroxide and tertbutylhydroperoxide or to
the platelet activators thrombin, calcium ionophore or phorbol myristate acetate stimulated
the platelets’ oxidative stress.This was also increased by plasma of thalassemia patients,
and decreased following treatment of the plasma with the iron-chelator Desferoxamin.
Iron and hemin, the levels of which are augmented in plasma of thalassemia patients,
stimulated the platelets’ oxidative stress.The oxidative status of the platelets was
also affected by red blood cells (RBC); it was higher in normal platelets incubated
with thalassemic RBC than with normal RBC. Normal RBC stimulated with hydrogen peroxide
had a greater effect on platelets than did unstimulated RBC.The platelets’ oxidative
stress was ameliorated by antioxidants such as N-acetyl-L-cysteine and vitamin C.
Our findings indicate that in thalassemia, platelets undergo a state of oxidative
stress, leading to their activation and potentially to thromboembolic consequences,
and suggest that this hypercoagulable state might be treated with antioxidants.
Keywords
Thalassemia - platelets - free radicals - glutathione - flow cytometry
