Selenium Stimulates Cadmium Detoxification in <i>Caenorhabditis elegans</i> through Thiols-Mediated Nanoparticles Formation and Secretion

Antagonism between heavy metal and selenium (Se) could significantly affect their biotoxicity, but little is known about the mechanisms underlying such microbial-mediated antagonistic processes as well as the formed products. In this work, we examined the cadmium (Cd)–Se interactions and their fates in <i>Caenorhabditis elegans</i> through in vivo and in vitro analysis and elucidated the machinery of Se-stimulated Cd detoxification. Although the Se introduction induced up to 3-fold higher bioaccumulation of Cd in <i>C. elegans</i> than the Cd-only group, the nematode viability remained at a similar level to the Cd-only group. The relatively lower level of reactive oxygen species in the Se & Cd group confirms a significantly enhanced Cd detoxification by Se. The Cd–Se interaction, mediated by multiple thiols, including glutathione and phytochelatin, resulted in the formation of less toxic cadmium selenide (CdSe)/cadmium sulfide (CdS) nanoparticles. The CdSe/CdS nanoparticles were mainly distributed in the pharynx and intestine of the nematodes, and continuously excreted from the body, which also benefitted the <i>C. elegans</i> survival. Our findings shed new light on the microbial-mediated Cd–Se interactions and may facilitate an improved understanding and control of Cd biotoxicity in complicated coexposure environments.