Hemin: A possible cause of oxidative stress in blood circulation of β-thalassemia/hemoglobin E disease

Abstract

A correlation between endogenous hemin and pro-oxidant activity was revealed in serum of β-thalassemia/hemoglobin E disease (Β-thal/Hb E), which is the most common prevalent type of thalassemia in Thailand. The technique of low temperature electron spin resonance spectroscopy was used for characterization and quantification of high spin ferric heme, which had been identified as hemin (iron (III)-protoporphyrin IX). Hemin was present at levels ranging from 50 to 280 μM in serum of β-thal/Hb E but not detectable in serum of non-thalassemia. Pro-oxidant activity in serum of β-thal/Hb E was demonstrated by luminol-mediated chemiluminescence, a sensitive method for screening of free radical generation in vitro. In the presence of H2O2, the chemiluminescence intensity (CL) was about 20 fold enhanced in serum of β-thal/Hb E, indicating its extensive pro-oxidant activity. The CL showed a good correlation with serum hemin, r = 0.778 (p < 0.001), while the correlations with total serum iron and serum ferritin were 0.260 (p = 0.259) and 0.519 (p = 0.004), respectively Our finding suggested that serum hemin readily catalyzed free radical reactions and it may contribute a major pro-oxidant in blood circulation of β-thal/Hb E.