Cadmium Disrupts Vestibular Function by Interfering with Otolith Formation

Abstract

Cadmium (Cd2+) is a transition metal found ubiquitously in the earths crust and is extracted in the production of other metals such as copper, lead, and zinc1,2. Human exposure to Cd2+ occurs through food consumption, cigarette smoking, and the combustion of fossil fuels. Cd2+ has been shown to be nephrotoxic, neurotoxic, and osteotoxic, and is a known carcinogen. Animal studies and epidemiological studies have linked prenatal Cd2+ exposure to hyperactivity and balance disorders although the mechanisms remain unknown. In this study we show that zebrafish developmentally exposed to Cd2+ exhibit abnormal otolith development and show an increased tendency to swim in circles, observations that are consistent with an otolith-mediated vestibular defect, in addition to being hyperactive. We also demonstrate that the addition of calcium rescues otolith malformation and reduces circling behavior but has no ameliorating effect on hyperactivity, suggesting that hyperactivity and balance disorders in human populations exposed to Cd are manifestations of separate underlying molecular pathways.