Copper exposure induced developmental toxicity and cardiotoxicity in zebrafish

Copper (Cu) is a global environmental pollutant that poses a serious threat to humans and ecosystems. Cu is cardiotoxic in rodents, but the exact mechanism has not been elucidated. In the present study, zebrafish embryos were exposed to 0, 10, 20, and 40 μg/L Cu²⁺ until 72-h post-fertilization (hpf) to assess cardiotoxicity of Cu. The results showed that the mortality of zebrafish embryos was increased, while the hatching rate, heart rate and body length were decreased after Cu²⁺ exposure. The pericardial area and atrial ventricular spacing were increased, while the cardiac development genes in zebrafish were downregulated, including Tbx2b, Tbx5, Nkx2.5, Bmp4, Gata4, Nppa, and Myh6. Mechanistically, Cu²⁺ exposure increased reactive oxygen species (ROS), decreased antioxidant enzyme activities (SOD, CAT, GSH), and elevated malondialdehyde (MDA). Exposure to Cu²⁺ caused significant cell apoptosis in larvae, accompanied by increased expression levels of apoptosis-related genes. In addition, Cu²⁺ also inhibited the Wnt signaling pathway. Treatment with the Wnt activator BML-284 and the antioxidant NAC protected zebrafish embryos from the cardiotoxic effects of Cu²⁺, indicating that oxidative stress and inhibition of Wnt signaling pathway are the mechanistic basis of Cu-induced developmental toxicity and cardiotoxicity in zebrafish. Overall, the study might deepen the understanding of cardiotoxicity mechanism of environmental Cu exposure.