Quercetin and taxifolin enhance immunity in Chinese sucker (Myxocyprinus asiaticus) and increase its resistance to Aeromonas hydrophila.

This study investigated the effects of short-term exposure to flavonoids, specifically quercetin and taxifolin, on the transcriptomic responses of Chinese sucker (Myxocyprinus asiaticus) to validate their influence on gene expression related to immunity, antioxidant activity, and metabolism. Using transcriptomic data, we also analyzed their influence on relevant immune genes and examined the Chinese suckers' resistance to A. hydrophila. Oxidative stress, immune defense, and glucose metabolism of Chinese suckers were tested to assess potential enhancements. Significant alterations were observed in multiple immune-related Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways in the liver of Chinese suckers, notably the complement and coagulation cascades, degradation of aromatic compounds, and xenobiotic metabolism by cytochrome P450. The key immune markers such as UGT, MPO, C3, and C4 were highlighted in these pathways, underlining their importance in fish immunity. Additionally, oxidative stress related KEGG pathways were notably influenced after exposure to quercetin and taxifolin, displaying markers such as CYP3A, superoxide dismutase, GST, malondialdehyde, and catalase. Quercetin particularly affected the enzymatic activity of glucose oxidase, hexokinase, phosphofructokinase, and ATPase, which are enzymes related to stress responses in fish. Antimicrobial tests revealed that both flavonoids enhanced Chinese suckers' defense against A. hydrophila by bolstering oxidative stress resistance and immunity. These results provided valuable insights for using flavonoids to enhance fish immunity.