The Investigation On Cadmium Content In Chicken And The Effect Of Polysaccharides On Cadmium-induced Damage Of Central Immune Organs In Chicks

As a kind of widespread heavy metal,cadmium(Cd)can accumulate in tissues and organs of animals,long-term exposure to low levels of Cd can induce the accumulation of free radicals and change content of cytokines.Plant polysaccharides are widely used in immune regulation,and can eliminate reactive oxygen free radicals,thereby reducing the damage of the body.In this study,the Cd content in chicks of Harbin city was investigated,and the effects of plant polysaccharides(Agaricus blazei polysaccharide and Ganoderma lucidum polysaccharides)on the immune organs and cell damage of Cd poisoning chickens were investigated from the perspective of pattern recognition and oxidative stress.Mass spectrometry was used to detect the Cd content in 60 samples of chicken liver and muscle in supermarkets of Harbin city.The results showed that Cd was detected in all the tested samples,but the content was lower than the limit of pollutants in food standard for Cd in the national standard of the People's Republic of China(GB 2762-2012).In vivo trial,the 7-day-old Hyline white chickens were divided into control(C)group,Cd(G)group,Agaricus blazei polysaccharides(ABPs)+Cd(TG)group and Ganoderma lucidum polysaccharides(GLPs)+Cd(LG)group.The Hyline white chickens were fed with Cd,ABPs and GLPs for 20 days,40 days and 60 days,then take the central immune organs(thymus,bursa).The expression of TLR4,cytokine content and oxidative-antioxidant indexes in thymus,bursa of Fabricius were detected by mass spectrometry,Western Blot,ELISA and biochemical methods.The results showed that the Cd content in thymus and bursa of Cd group was significantly higher than that in the control group(P<0.01).The Cd content in treatment group with two kinds of polysaccharides was significantly lower than that in Cd group(P<0.01).The expression of TLR4 in the thymus and bursa of G,TC,LG group was lower than that in C group at 20 days,while the expression of TLR4 in G group was higher than that in C,TG,LG group on the 40th day and the 60th day.The expression of TLR4 in TG,LG group was lower than that in G group(P<0.01).The content of IL-1?,IL-6,TNF-a and IFN-? in thymus and bursa in G group were significantly higher than those in C group(P<0.01),the content of TNF-a,IFN-? in treatment group with two kinds of polysaccharides was between the C group and G group;the activity of SOD and GSH-Px in thymus and bursa in G group was significantly lower than that in C group(P<0.01),the content of MDA was significantly higher than that in C group(P<0.01),SOD,GSH-Px activity in TG,LG group was significantly higher than that in G group(P<0.01),the content of MDA was significantly lower than that in G group(P<0.01).The results showed that ABPs and GLPs could decrease the content of Cd,expression of TLR4,cytokines(IL-1?,IL-6,TNF-a,IFN-?)content and MDA content in thymus and bursa of Cd poisoned chickens,increased SOD,GSH-Px activity to reduce the damage of Cd on central immune organs of chickens.In vitro trial,the peripheral blood lymphocytes of healthy chicks were divided into control(C)group,Cd(G)group,GLPs(L)group,lipopolysaccharide(LPS)group,TLR4 inhibitor(TAK-242)group,GLPs+Cd(LG)group,LPS+Cd(LPSG)group,TAK-242+Cd group(TAKG).The expression of TLR4 and its signaling molecules NF-?B,IRF3 and cytokines of IL-1? and IL-6 mRNA in peripheral blood lymphocytes were detected by quantitative polymerase chain reaction(RT-PCR).The results showed that the relative expression levels of TLR4,NF-?B and IRF3 mRNA in LPSG group were the highest,but the expression of TLR4 was not affected by LPS and Cd alone,in TAK-242 group,the relative expression of TLR4,NF-?B,IRF3 mRNA was the lowest;the expression of TLR4 mRNA in LG group was lower than that in G group,the expression of NF-?B,IRF3 mRNA in LG group was higher than that in G group,but the expression of TAKG group was similar to the LG group.Compared with group C,the expression of IL-1,IL-6,TNF-a mRNA in G group were significantly increased(P<0.01 or P<0.05),but the effects of polysaccharide treatment on the expression of IL-1,IL-6,TNF-a mRNA were different.The results showed that Cd could induce the damage of the body by activating TLR4 signaling pathway,and GLPs could reduce the damage caused by Cd through inhibiting the TLR4 signaling pathway.This study showed that the protective effect of ABPs and GLPs on the immune organs and peripheral blood lymphocytes in Cd poisoned chickens was associated with TLR4 signaling and oxidative stress.This study provides a scientific basis for the further study of Cd damage and alleviation of Cd damage mechanism.