The antioxidant status, apoptosis, intercellular integrity and immune function of grass carp (Ctenopharyngodon idella) head kidney and spleen fed different levels of pyridoxine

This study was carried out to investigate the effects of dietary pyridoxine (PN) on the antioxidant status, apoptosis, intercellular integrity and immune function of head kidney and spleen in young grass carp (Ctenopharyngodon idella). Results showed that compared with the optimal PN level, (a) PN deficiency decreased antioxidant enzyme activities and down-regulated the mRNA levels of antioxidant enzymes, NF-E2-related factor 2 (Nrf2), myeloid cell leukaemia-1 (Mcl-1) and tight junction proteins, whereas it increased the contents of reactive oxygen species (ROS), malondialdehyde (MDA) and protein carbonyl (PC), and up-regulated the mRNA levels of cysteinyl aspartic acid-protease (caspase), Fas ligand (FasL), p38 mitogen-activated protein kinase (p38MAPK) and myosin light chain kinase (MLCK) in the head kidney and spleen of fish (p < .05). (b) PN deficiency decreased lysozyme (LZ) and acid phosphatase (ACP) activities, and complement contents, and down-regulated the mRNA levels of antibacterial peptides, anti-inflammatory cytokines, inhibitor of kappa B alpha (I kappa B alpha) and target of rapamycin (TOR), whereas it up-regulated the mRNA levels of pro-inflammatory cytokines and nuclear factor kappa B p65 (NF-kappa Bp65) in the head kidney and spleen of fish (p < .05). (c) Dietary PN requirements of grass carp based on the malondialdehyde content and lysozyme activity were estimated as 4.97 and 4.99 mg/kg diet, respectively.