Cytoprotective effects of imidazole-based [S1] and [S2]-donor ligands against mercury toxicity: a bioinorganic approach

3,3'-Diselenodipropionic acid (DSePA) forms 1:1 complex with Hg (II) and prevents oxidative stress in cultured cells and mice model

Mercury is one of the most toxic heavy metal for mammals particularly in inorganic form. In present study, 3,3'-diselenodipropionic acid (DSePA), a well-known pharmacological diselenide was evaluated for its interaction with HgCl₂ and ability to prevent HgCl₂-induced toxicity in experimental cellular and mice models. UV-visible, stopped flow, Fourier-transform infrared spectroscopy and ¹H nuclear magnetic resonance spectroscopy studies confirmed that DSePA sequestered Hg (II) ions with stoichiometry of 1:1 and binding constant of ~10⁴ M^-1. X-ray photoelectron spectroscopy and X-ray powder diffraction analysis suggested that diselenide group of DSePA was involved in the complexation with Hg (II) ions. Further, Hg-DSePA complex degraded within 10 days to form excretable HgSe. The binding constant of DSePA and Hg (II) was comparable with that of dihydrolipoic acid, a standard disulfide compound used in heavy metal detoxification. Corroborating these observations, pre-treatment of DSePA (10 μM) significantly prevented the HgCl₂ (50 μM)-induced glutathione oxidation (GSH/GSSG), decrease of thioredoxin reductase (TrxR) and glutathione peroxidase (GPx) activities and cell death in Chinese Hamster Ovary (CHO) cells. Similarly, intraperitoneal administration of DSePA at a dosage of 2 mg/kg for 5 consecutive days prior to exposure of HgCl₂ (1 mg/kg) significantly suppressed oxidative stress in renal and hepatic tissues of C57BL/6 mice. In conclusion, the protective effect of DSePA against Hg induced oxidative stress is attributed to its ability to rescue the activities of GPx, TrxR and GSH by sequestering Hg (II) ions. DSePA being a relatively safer selenium-compound for in vivo administration can be explored for mercury detoxification.