Mechanism of vitamin C alleviating the immunotoxicity of 17α-methyltestosterone in Carassius auratus.

Background: In recent years, the use of endocrine-disrupting chemicals (EDCs) has become increasingly common, leading to severe environmental pollution and harm to aquatic organisms. 17α-Methyltestosterone (MT) is a synthetic androgen that can cause immunotoxicity in aquaculture, affecting fish health. To address this issue, this study aimed to investigate the effect of Vitamin C (VC) on MT-induced immunotoxicity and determine the optimal VC supplementation.

Results: Carassius auratus was exposed to 50 ng/L MT and treated with 25, 50, and 150 mg/kg VC for 7, 14, and 21 d. Morphological indicators, histological characteristics, hepatic antioxidant capacity, and immune-related gene expression were analyzed. Additionally, RNA-seq was performed on the liver tissues of the control, MT, and MT + 25 mg/kg VC groups after 21 d. Results showed that, MT treatment significantly increased liver malondialdehyde content and inhibited immune-related gene expression (TNF-α, IL-8, INF-γ, IL-10, Caspase-9, and IGF-I), causing oxidative stress and immunotoxicity, leading to hepatic steatosis. However, supplementation with 25-50 mg/kg VC effectively alleviated the MT-induced damage to the hepatic structure and immune system. RNA-seq revealed significant enrichment of differentially expressed genes in multiple signaling pathways, including the mTOR, MAPK, and Wnt pathways.

Conclusions: In summary, 25-50 mg/kg VC alleviated inhibitory effect of MT on immune-related genes in C. auratus liver, reducing MT-induced tissue damage. VC not only alleviated inflammation, oxidative stress, and immunotoxicity induced by MT through the regulation of the mTOR, MAPK, and Wnt signaling pathways, but also indirectly enhanced cellular antioxidant defense mechanisms by regulating the NRF2 pathway. This provides a theoretical basis for VC application in aquaculture, improving fish health and increasing efficiency.