Amelioration of cadmium cytotoxicity to human cells by nutrient cation contents and the building of a biotic ligand model

Abstract

A variety of important major and trace elements may competitively inhibit cadmium (Cd) absorption in human cells and reduce Cd toxicity. However, the impact of essential elements on the cytotoxicity of metals can be difficult to quantify and anticipate. Cd acute toxicity to Caco-2 cell viability was studied in culture solutions and modeled by a biotic ligand model (BLM). The individual effects of the cations potassium (K+), calcium (Ca2+), magnesium (Mg2+), ferrous ion(Fe2+), zinc (Zn2+) and manganese (Mn2+) on Cd toxicity were also investigated. The results indicated that the toxicity of Cd in culture solutions to cell viability declined with increasing concentrations of Zn2+ and Mn2+ in the solutions, while K+, Ca2 +, Mg2 + and Fe2+ had no significant effect. Using the BLM, the stability constants for the binding of Cd2 +, Zn2+, and Mn2+ to biotic ligands were determined to be logKCdBL = 5.76, logKZnBL = 4.39 and logKMnBL = 5.31, respectively. Moreover, it was calculated that 51% occupancy of the biotic ligand sites for Cd by Cd was required to cause a 50% reduction in Caco-2 cell viability. A BLM was successfully established using the estimated constants to predict the Cd cytotoxicity to Caco-2 cell viability as a function of solution characteristics, so that the effective concentrations that reduced cell viability by 50% (EC50) could be predicted by the BLM within 1.6 fold changes of the observed EC50. The application's viability and precision for foretelling Cd toxicity in Caco-2 cells are discussed.