Lipid membrane peroxidation in beta-thalassemia major.

The composition of membrane lipids was studied in 17 splenectomized and eight unsplenectomized patients with beta-thalassemia major and compared to normal controls. The results showed a nearly twofold increase in total cell lipids; a reduction in the percentage, but not the absolute amount of phosphatidylethanolamine, and a corresponding increase in phosphatidylcholine in the lipids; a considerable increase in the percentage of the saturated fatty acid, palmitic acid, and a reciprocal decrease in the polyunsaturated fatty acid, arachidonic acid; a twofold increase in the amount of malonyldialdehyde (MDA) generated after peroxide threat to the RBC when calculated either per gram hemoglobin or per cell; no change in the amount of MDA generated when calculated per microgram of membrane phosphorus at risk per cell; and a considerable decrease in serum alpha-tocopherol (vitamin E) levels. Thalassemic erythrocytes contain more lipid per cell which is susceptible to peroxidation. In addition, the distribution of fatty acids in these cells suggests that autooxidation of that lipid may have occurred. Autooxidation may be initiated by free radicals, which are constantly formed in the normal red cell, and may be especially prevalent when unstable hemoglobins are present. The low MCHC or some other intracellular defect of thalassemic cells may allow such potent oxidants to find their way to the cell membrane. Vitamin E, a biologic antioxidant is decreased in these patients, and clinical supplementation may be indicated to prevent some of the membrane damage in thalassemia.