Iron and iron proteins found in the genetic disease, hereditary spherocytosis

Abstract

Hereditary spherocytosis (HS) is a disorder of the red blood cell (RBC) membrane, characterized by abnormally fragile and spherical RBCs. It is the predominant cause of haemolytic anaemia in people of northern European descent. Owing to the increased rate of RBC synthesis that is characteristic of the condition, it may result in an increase in absorption of iron from the diet by the affected individual. Ultimately, pathological iron overload may develop. Fortunately, the condition responds well to surgical removal of the spleen (splenectomy). In this project, iron studies were performed on a set of spleen tissue samples obtained following routine splenectomy for HS. Cell architecture and level of deposition of haemosiderin, the distinctive form of iron found in iron-loaded tissues, were assessed. The tissue iron content was determined by AAS and ICP (mean value=2276±507 μg g−1 dry tissue, values reported for normal spleens range from 972±60 to 1345±190 μg g−1). Ion exchange chromatography was employed to separate the protein content of the tissue into four chromatographic bands, notionally transferrin, ferritin, haemprotein and haemosiderin, and these proteins quantified. Mössbauer spectroscopy identified the iron as Fe(III), predominantly in ferrihydrite (5Fe2O3·9H2O) and haem environments within the tissue. Typical spectral parameters, recorded at 300 K, were: isomer shift and quadrupole splitting of 0.36 and 0.62 mm s−1, respectively, (ferrihydrite) and 0.14 and 1.97 mm s−1 (haem). The results indicate a condition corresponding to mild iron overload.