Effects Of Dietary Zearalenone(ZEA) On The Growth Performance,Structure Integrity And Immune Function Of Immune Organs As Well As The Mechainsms In Juvenile Grass Carp(Ctenopharyngodon Idella)

The present study was designed to determine the effects of zearalenone(ZEA)on growth,structure intergrity and immune function of immune organs(head kidney and spleen)as well as the potential mechainsms in juvenile grass carp(Ctenopharyngodon idella).A total of 1440 juvenile grass carp(15.34 ± 0.06g)were randomly distributed into six groups of each three replicates,fed six diets containin graded levels of ZEA at 0,535,1041,1548,2002 and 2507 ?g/kg diet for 10 weeks.After the feeding trial,challenge tests were conducted by injection fish with Aeromonas hydrophila to study the effect of ZEA on the disease resistance of juvenile grass carp.The result of growth trial found that compared with control group,1041 ?g/kg or higher levels ZEA in diet decrease percent weight gain(PWG)and specific growth rate(P < 0.05),indicating that ZEA inhibited the growth of juvenile grass carp.Fish growth is associated with its health status,which is effected by structural integrity and function of immune organs(head kidney and spleen).The present study revealed that the level of ZEA ? 1041 ?g/kg increase the contents of ROS,MDA and PC in head kidney and spleen of juvenile grass carp,indicating that ZEA caused the oxidative damage,meanwhile,ZEA decreased MnSOD,CAT,GPx(rather than GPx4 b in spleen),GST and GR activities and mRNA levels,down-regulated Nrf2 mRNA levels and up-regulated Keap1 a [rather than Keap1b(except for spleen)] mRNA levels,declined the ability of antioxidative damage,damaged the structure integrity of immune organ;the level of ZEA ? 1548 ?g/kg up-regulated p38 MAPK and JNK mRNA levels,apoptosis executor caspase-3(except for head kidney)and caspase-7,apoptosis promoters caspase-2,caspase-8 and caspase-9 and pro-apoptotic protein apoptotic protease Apaf-1 as well as Bax mRNA levels,and down-regulated the anti-apoptotic protein Bcl-2,IAP and Mcl-1 mRNA level in head kidney and spleen of juvenile grass carp,aggravated the cell apoptosis of the head kidney and spleen;the level of ZEA ? 1041 ?g/kg down-regulated the tight junction barrier proteins occludin,ZO-1,ZO-2b,claudin-b,-c(except for spleen),-3c,-7a,-7b and-11 in immune organs,up-regulated claudin-12 and claudin-15b(rather than claudin-15a),destructed intercellular structural integrity.Further study found that ZEA decreased the immune function of head kidney and spleen.(1)the level of ZEA ? 1041 ?g/kg declined the activities of lysozyme(LZ)and ACP,the contents of C3,C4 and immunoglobulin M,down-regulated the mRNA levels of ?-defensin-1,LEAP-2A,LEAP-2B and Mucin-2 to suppress immune function of immune organs in juvenile grass carp;(2)the level of ZEA ? 1041 ?g/kg up-regulated the pro-inflammatory cytokines TNF-?(rather than head kidney),IFN-?2,IL-6,IL-8,IL-15,IL-17 D and IL-12p35(rather than IL-12p40)mRNA levels,and up-regulated anti-inflammatory cytokines IL-11,TGF-?1,TGF-?2,IL-4/13 A and IL-4/13 B mRNA levels,up-regulated pro-inflammatory signaling molecules IKK?,IKK?,NF-?B p65,NF-?B p52 and c-Rel mRNA levels,while down-regulated I?B? mRNA levles to exacerbate the inflammatory response and decreased the grass carp immune function of immune organ.In conclusion,ZEA decreased growth performance of juvenile grass carp,disrupted the structural integrity of immune organs(the head kidney and spleen)and decreased the immune function.The decrease of the immune function is closely related to the increase of the inflammatory response of the immune organs.Based on growth performance(PWG),oxidative damage(MDA in head kidney and PC in spleen)and immune related index(LZ in spleen),the maximum permissible levels of ZEA for juvenile grass carp(15.34-115.40g)are estimated to be 496.22,401.25,397.23 and 273.73 ?g/kg diet,respectively.