Hepcidin agonists grape seed proanthocyanidins and berberine hydrochloride improve immunity and prevention against bacterial infection in grass carp (Ctenopharyngodon idella)

Hepcidin is an antimicrobial peptide and iron-regulating factor that has been shown to play a crucial role in combating bacterial diseases, making it a viable alternative to antibiotics. However, its widespread application is limited due to its susceptibility to degradation in vivo and high production costs. Certain extracts from traditional Chinese medicinal plants exhibit significant potential in treating iron overload conditions. This study aims to identify an effective and practical herbal agent as a hepcidin agonist. The results indicated that grape seed proanthocyanidins (GSP) and berberine hydrochloride (BBR) significantly upregulate the expression levels of hepcidin and ferritin genes in L8824 cells. Additionally, both compounds exhibited excellent in vitro antibacterial activity. Interestingly, the combined application of these two substances yields unexpectedly favorable results. Oral administration of GSP + BBR effectively promoted growth in grass carp, enhanced survival rates, and significantly increased serum innate immunity indicators. Furthermore, it reduced bacterial loads in the head kidney, spleen, hepatopancreas, and intestinal of grass carp following infection. Additionally, it elevated the expression levels of immune genes IL-1β, IL-6, and TNF-α in the head kidney after infection, and markedly alleviated pathological damage in intestinal tissues. These results demonstrated that GSP and BBR act as hepcidin agonists to enhance the expression of endogenous hepcidin, providing a novel approach for the prevention of bacterial infections in aquaculture.