Cadmium Through Disturbing MTF1-Mediated Metal Response Induced Cerebellar Injury

Abstract

Cadmium (Cd) is a toxic environmental contaminant, which bio-accumulate in animals through the food chain. Cerebellum is one of the primary target organs for Cd exposure. In this study, we established a chronic Cd exposure model; 60 chickens were treated with Cd (0 mg/kg, 35 mg/kg, 70 mg/kg) for 90 days. Clinical manifestations indicated that the chicken was depressed and has unstable gait under Cd exposure. Histopathological results indicated that Cd induced neuronal shrunken and indistinct nucleoli, and the number of Purkinje cells decreased significantly. Cerebellar metal contents were analyzed by ICP-MS. We found that Cd caused Cd and Cu accumulation and decreased the content of Se, Fe, and Zn, suggesting that Cd disturbed metal homeostasis. Besides, Cd treatment group also showed high levels of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) content and inhibited selenoprotein transcriptome, suggesting that Cd exposure resulted in oxidative stress. Notably, low-dose Cd exposure activated MTF1 mRNA and protein expression and its target metal-responsive genes, including MT1, MT2, DMT1, ZIP8, ZIP10, TF, and ATP7B which indicate cellular adaptive response against Cd-induced damage. On the other hand, 70 mg/kg Cd downregulated MTF1-mediated metal response, which was involved in Cd-induced cerebellar injury in chicken. In conclusion, our data demonstrated that molecular mechanisms are associated with Cd-induced cerebellar injury due to disturbing MTF1-mediated metal response. This study indicated that the cerebellum is one of the target organs of Cd-induced toxicity. Additionally, Cd exposure induced metal dyshomeostasis in chicken's cerebellum, whereas this study found that lower level of Cd dose triggered the activation of the cytoprotective mechanism through activating the expression of MTF1 which regulate MT1, MT2, DMT1, ZIP8, ZIP10, TF, and ATP7B expressions in cerebellum. However, MTF1-mediated metal response was inhibited under the exposure of high dose of Cd, which ultimately caused cerebellar injury. The present study provides a new insight that Cd through disturbed MTF1-mediated metal response disrupts metal homeostasis that induced cerebellar injury.

Keywords: Cadmium; Cerebellar injury; Chicken; MTF1-mediated metal response; Selenoprotein transcriptome.