Quercetin protects human thyroid cells against cadmium toxicity

Various natural compounds have been successfully tested for preventing or counteracting the toxic effects of exposure to heavy metals. In this study, we analyzed the effects of cadmium chloride (CdCl2) on immortalized, non\u2010tumorigenic thyroid cells Nthy\u2010ori\u20103\u20101. We investigated the molecular mechanism underlying its toxic action as well as the potential protective effect of quercetin against CdCl2\u2010induced damage. CdCl2 suppressed cell growth in a dose\u2010 and time\u2010dependent manner (IC50 value ~10 \u3bcM) associated with a decrease in levels of phospho\u2010ERK. In addition, CdCl2 elicited an increase in reactive oxygen species (ROS) production and lipid peroxidation. A significant increase in GRP78, an endoplasmic reticulum (ER) stress\u2010related protein, was also observed. Supplementation of quercetin counteracted the growth\u2010inhibiting action of CdCl2 by recovering ERK protein phosphorylation levels, attenuating ROS overproduction, decreasing MDA content and reducing the expression of GRP78 in cells exposed to CdCl2. Thus, in addition to revealing the molecular effects involved in cadmium\u2010induced toxicity, the present study demonstrated, for the first time, a protective effect of quercetin against cadmium\u2010induced damages to normal thyroid cells