Acute waterborne cadmium exposure induces liver ferroptosis in Channa argus

The impact of cadmium (Cd) toxicity on fish liver injury has received much attention in recent years. Currently, autophagy, apoptosis and endoplasmic reticulum stress were reported in Cd exposed fish liver, and if there are other mechanisms (such as ferroptosis) and relevant signaling pathways involved in fish remains unknown. An experiment was conducted to investigate Cd toxicity in Channa argus (Cantor, 1842) exposed to 0, 1.0, and 2.0 mg Cd/L of water for 96 h. Cd disrupted the structure of mitochondria in the liver. Besides, Cd induced ferroptosis by significantly increasing the level of Fe²⁺, ROS, MDA and significantly decreasing the level of Ferritin, GSH, GSH-Px, GPX4, GST and SOD (p < 0.05 in all cases). In addition, the mRNA expression of ferroptosis related genes, gpx4 and slc7a11, were significantly downregulated by Cd. Moreover, Cd exposure significantly inhibited the Nrf2/Keap1 signaling pathway, one of the pathways involved in ferroptosis, by upregulating the mRNA levels of keap1a and keap1b, and downregulating the mRNA levels of nrf2 and its target genes (ho-1, nqo1 and cat). Cd exposure also caused extensive accumulation of vacuoles and lipid droplets in liver, as well as an increase in triglyceride content. Cd significantly affected lipid metabolism related enzyme activity and gene expression, which were also regulated by Nrf2/Keap1 signaling pathway. In summary, these results indicate that ferroptosis is a mechanism in waterborne Cd exposed fish liver injury via the Nrf2/Keap1 signaling pathway and the Cd induced hepatic steatosis is also modulated by Nrf2/Keap1 pathway at the whole-body level in fish. These findings provide new insights into the fish liver injury and molecular basis of Cd toxicity.