Astragaloside IV improved antioxidative stress capacity and related gene expression of the Keap1‐Nrf2 pathway in grass carp ( Ctenopharyngodon idella ) hepatocytes under heat stress

This study aims to investigate the protective effects of astragaloside IV (AS-IV) on the hepatocytes of grass carp (Ctenopharyngodon idella) upon heat stress. Cultured cells were treated with AS-IV (0, 50, 100, and 200 μg/mL) at 28°C for 24 h and then exposed to heat stress by increasing the culturing temperature (32 ± 0.5°C) for 6 h. The increased temperatures significantly reduced cell viability and superoxide dismutase (SOD) activity, and increased malondialdehyde (MDA) levels in the 0 μg/mL AS-IV treatment group at 32°C; however, the grass carp hepatocytes treated with 100 and 200 μg/mL AS-IV had a significantly increased cell viability and SOD activity and decreased MDA levels. The mRNA levels of keap1a, keap1b, nrf2, gsh-px, cat, cu-zn sod, mgst1, and il-6 were significantly lower in the 0 μg/mL AS-IV treatment group at 32°C, while those of keap1a, nrf2, gsh-px, cat, cu-zn sod, gstp1, ho-1, and il-6 were significantly higher in cells treated with 100 or 200 μg/mL AS-IV. Our findings indicate that AS-IV could enhance the anti-oxidative stress capacity of grass carp hepatocytes under heat stress, and its mechanism may be associated with the activation of the Keap1-Nrf2 pathway. Thus, these results provide new insights into how to alleviate heat stress in grass carp. This article is protected by copyright. All rights reserved.