Mitochondrial iron deficiency mediated inhibition of ecdysone synthesis underlies lead (Pb) induced developmental toxicity in Drosophila melanogaster

Abstract

Lead (Pb) is a pervasive heavy metal possessing developmental toxicity, at least in part, by disrupting iron homeostasis. In this study, we aimed to elucidate the underlying mechanism of iron deficiency mediated developmental defects in Pb exposed Drosophila melanogaster, mainly focusing on iron-dependent synthesis of ecdysone signaling, which plays a key role in the development of insects. Herein, we found Pb exposure resulted in iron deficiency in mitochondria by inhibiting expression of mitoferrin (evidenced by qPCR assay), the mitochondrial iron importer. Further study demonstrated that biosynthesis of ecdysone, a hormone synthesized with the help of iron-containing cytochrome P450s in mitochondria, was inhibited following Pb exposure. Ecdysone supplementation, to some extent, rescued Pb induced developmental delay and reproductive defects in Drosophila melanogaster. Furthermore, we found that disruption of mitoferrin and ecdysone synthesis was restored by NAC (N-Acetylcysteine, a well-known ROS scavenger), suggesting that oxidative stress plays a key role in Pb mediated mitochondrial iron dys-homeostasis and developmental toxicity. This study therefore revealed that mitochondrial iron deficiency mediated inhibition of ecdysone synthesis is a key event associated with iron dys-homeostasis mediated developmental defects caused by Pb exposure. Meanwhile, our study indicated that mitochondria may act as an important target of Pb, thus providing potential protective strategies against Pb toxicity.