Effects of Thimerosal on Lipid Bilayers and Human Erythrocytes: An In Vitro Study

Thimerosal (THI, ethyl-mercury thiosalicylate) is added to vaccines as a preservative; as a consequence, infants may have been exposed to bolus doses of Hg that collectively added up to nominally 200 µg Hg during the first 6 months of life. While several studies report an association between THI-containing vaccines and neurological disorders, other studies do not support the causal relation between THI and autism. With the purpose to understand the molecular mechanisms of the toxic effect of THI it was assayed on human red cells and in bilayers built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE), classes of phospholipids found in the outer and inner monolayers of the human erythrocyte membrane, respectively. The capacity of THI to interact with DMPC and DMPE was determined by X-ray diffraction and differential scanning calorimetry, whereas intact human erythrocytes were observed by optical, defocusing and scanning electron microscopy. The experimental findings of this study demonstrated that THI interacted in a concentration-dependent manner with DMPC and DMPE bilayers, and in vitro interacted with erythrocytes inducing morphological changes. However, concentrations were considerable higher than those present in vaccines.