Hormetic Effect of Low Doses of Cadmium,Mercury Alone or in Combination on Human Embryo Liver Cells

Objective To understand the hormetic effects of low dose of cadmium,mercury alone or in combination on LO2 cells and the mechanism.Methods Human embryo liver LO2 cells were exposed to different concentration of cadmium(II),mercury(II) alone or in combination for 24 hours.The survival rate of LO2 cells was measured by Vi-CELLTM XR Viability Analyzer;the activity of SOD and GSH-Px were measured by corresponding testing cassette;the level of ROS was measured according to Parvinder Kaur's methods;the heavy metal uptake was measured by atomic absorption spectroscopy and atomic fluorescence spectroscopy.Results After exposure to low doses of mercury(0.01,0.05 and 0.25 μmol/L),cadmium(0.01,0.05,0.25 μmol/L) and cadmium+mercury(0.01,0.05 μmol/L) for 24 hours,the growth of LO2 cells was significantly stimulated.The results got from Finney model showed that the joint toxicity was simple additive effect when LO2 cells exposed to cadmium+mercury.The activity of GSH-Px and SOD were increased when exposed to low dose of cadmium and mercury alone or in combination,but it was inhibited when the concentration came up to 25.6 μmol/L.The level of intracellular ROS and heavy metal uptake were increased with the increasing of heavy metal.Conclusion Exposed to low concentration of cadmium,mercury alone or in combination may significantly stimulate the growth of LO2 cells,the possible mechanisms may be that low concentrations of cadmium and mercury can enhance the activity of GSH-Px and SOD to scavenge free radicals and protect cells from oxidative damage.