Dietary <i>Acanthopanax senticosus</i> extracts modulated the inflammatory and apoptotic responses of yellow catfish to protect against <i>Edwardsiella ictaluri</i> infection
Zixi Song, Congrui Jiao, Baoyang Chen, Wenyu Xu, Mengya Wang, Jiahong Zou, Weiqi Xu, Zhen Xu, Qingchao Wang
Abstract
Herbal extracts interfere with bacterial adhesion and support apoptosis-dependent exfoliation to protect mammals against bacterial infection. In this study, juvenile yellow catfish were fed with control diet or Acanthopanax senticosus extracts (AS)-supplemented diet. After 60 days, AS (180 ml/kg feed) significantly elevated fish growth and feed utilization, with higher weight gain and feed efficiency. After challenged with Edwardsiella ictaluri, survival rate of AS-supplemented fish (65%) was significantly higher than control fish (30%). Control fish exhibited obvious skin lesions since 1 day post-infection (dpi) and decreased thickness of epidermis with prolonged days, while AS-supplemented fish skin structure showed better integrity. Moreover, length of secondary branchial filaments of AS-supplemented fish was higher than control fish that showed obvious occlusion between adjacent lamellae. Unlike its pro-inflammatory role in spleen, AS significantly inhibited gill inflammation at 4 dpi via regulating TLRs-NFκB pathway. Moreover, haematoxylin–eosin staining exhibited that AS delayed the liver vasculitis and necrotic hepatitis of yellow catfish. Further study by TUNEL assay, caspase-3 activity and mRNA expression indicated that AS significantly promoted hepatic apoptosis at 1 dpi to prevent further necrosis, which process was regulated by JAK/STAT pathway. All results demonstrated AS modulated inflammation and apoptosis to protect yellow catfish against Edwardsiella ictaluri infection.