Consequences of thimerosal on human erythrocyte hemoglobin: Assessing functional and structural protein changes induced by an organic mercury compound

• Published in: Journal of trace elements in medicine and biology 2022-05, Vol.71, p.126928, Article 126928
• Main Authors: Sales, Marcos V.S., da Silva Filho, Reginaldo C., Silva, Marina M., Rocha, Jeanynne L., Freire, Ricardo O., de L. Tanabe, Eloiza Lopes, Silva, Elaine C.O., Fonseca, Eduardo Jorge S., Figueiredo, Isis M., Rocha, Ueslen, Santos, Josué Carinhanha C., Leite, Ana Catarina R.
• Format: Article
• Language: English
• Subjects: Functional alterations; Organic mercury compound; Protein structural changes
• ISSN: 0946-672X; 1878-3252
• DOI: 10.1016/j.jtemb.2022.126928

[Display omitted] •Thimerosal damages the structure of hemoglobin inducing the loss of its main function as O2 transporter.•Raman indicates that thimerosal causes a distortion in the hemoglobin heme ring.•Ethylmercury decreases the amount of thiol groups free from hemoglobin.•Atomic Force Microscopy shows morphological changes caused by thimerosal.•Thimerosal crosses the erythrocyte membrane without causing osmotic fragility. Thimerosal (TM) is an organic mercury compound used as a preservative in many pharmacological inputs. Mercury toxicity is related to structural and functional changes in macromolecules such as hemoglobin (Hb) in erythrocytes (Ery). Human Hb and Ery were used to evaluate O2 uptake based on the TM concentration, incubation time, and temperature. The influence of TM on the sulfhydryl content, production of reactive oxygen species (ROS), and membrane fragility was also evaluated. Raman spectra and atomic force microscopy (AFM) profiles for Ery in the presence and absence of TM were calculated, and docking studies were performed. At 37 °C, with 2.50 μM TM (higher concentration) and after 5 min of incubation in Hb and Ery, we observed a reduction in O2 uptake of up to 50 %, while HgCl2, which was used as a positive control, showed a reduction of at least 62 %. Total thiol assays in the presence of NEM (thiol blocker) quantified the preservation of almost 60 % of free SH in Ery. Based on the Raman spectrum profile from Ery-TM, structural differences in the porphyrinic ring and the membrane lipid content were confirmed. Finally, studies using AFM showed changes in the morphology and biomechanical properties of Ery. Theoretical studies confirmed these experimental results and showed that the cysteine (Cys) residues present in Hb are involved in the binding of TM. Our results show that TM binds to human Hb via free Cys residues, causing conformation changes and leading to harmful effects associated with O2 transport.