Abstract:
Background: β-thalassemia/Hb E patients suffer from many systemic complications due to ineffective erythrocytosis, chronic hemolysis and iron overload. Vascular complications are essential, and previous studies proposed that impaired nitric oxide bioavailability is one of mechanisms. The alteration of nitric oxide may contribute to endothelial dysfunction. There are limited studies to determine an association between nitric oxide depletion and endothelial dysfunction in this particular population. Methods: Forty three β-thalassemia/HbE patients without clinically documented vascular symptoms from hematology clinic and 43 age-sex matched healthy controls were enrolled. The endothelial function was measured using the flow-mediated dilatation (FMD) test of the brachial artery before and after nitroglycerine (NTG) administration which were defined as endothelium-dependent and independent, respectively. Plasma nitric oxide metabolites (nitrite/nitrate; NOx), prostaglandin E2 (PGE2) and soluble thrombomodulin (sTM) levels were measured. Results: The mean age of thalassemia and control group were 34.6+/-9.7 and 36.7+/-8.6 years old, respectively. Males and females were equal. The mean of baseline diameters of brachial artery in thalassemia was smaller than the control group (32.3+/-5.1 mm. vs. 37.1+/-5.8 mm, p<0.01). The mean of percent changes in diameter of FMD test before NTG administration in thalassemia group was significantly less than control subjects (5.0+/-5.9% vs. 9.0+/-4.0%, p <0.01) but no significant changes between both groups after NTG administration (18.4+/-8.3% vs. 17.8+/-6.3%, p=0.71). NOx and PGE2 levels were significantly decreased in thalassemia patients compared to healthy controls (117.2+/-27.3 vs. 135.8+/-11.3 µmol/L, p<0.01) and (701.9+/-676.0 vs. 1,374.7+/-716.5 pg/ml, p<0.01), respectively, while a significant elevation in sTM levels (3,587.7+/-1,310.0 vs. 3,093.9 +/-583.8 pg/ml, p =0.028) in thalassemia group. NOx and PGE2 levels were significantly correlated with endothelial dysfunction (r =0.28, p=0.038) and (r=0.38, p=0.001), respectively, whereas no significant correlation between sTM and endothelial dysfunction was observed. Conclusion: This is the first study that has demonstrated the association of endothelial dysfunction and nitric oxide as well as PGE2 depletion in patients with β-thalassemia/HbE without vascular symptoms. Further studies to define the mechanisms of nitric oxide and PGE2 depletion-related endothelial dysfunction are warranted.