Summary
Retinal vein occlusion (RVO) is the most common retinal vascular disorder second to
diabetic retinopathy. The main risk factors in patients with RVO are hypertension,
diabetes, hyperlipidemia, increased blood viscosity and glaucoma. The pathogenesis
of RVO has not yet been clarified. In these events platelets could play a very important
role. In the present study the platelet response to collagen was deeply investigated.
Experiments were carried out on a selected group of RVO patients, which were compared
to a group of healthy subjects matched for age, sex, clinical and metabolic characteristics.
In resting and activated platelets of both groups of subjects p72syk phosphorylation,
phospholipase Cγ 2 phosphorylation, protein kinase C activation, intracellular calcium
levels and nitric oxide formation were measured. Results show that platelets of patients
were more responsive to collagen or ADP than healthy subjects and that the response
was significantly different (p < 0.0005) at low concentrations of these agonists.
In platelets of patients stimulated with collagen increased phosphorylation of p72syk
and phospholipase C γ 2 was found. Also protein kinase C was more activated in patients.
In addition intracellular calcium rise induced by collagen was significantly higher
in patients than in healthy subjects. RVO patients showed a lower basal level of nitric
oxide both in resting and stimulated platelets compared to healthy subjects. Altogether
these results suggest that the platelet hyperaggregability described in patients might
be an important factor in the development of RVO contributing to the thrombogenic
effects.
Keywords
Collagen - human platelets - retinal vein occlusion