| China's feed industry has developed rapidly which has become the world's largest feed producer in the 2013.The quality of feed is closely related to the health of livestock and poultry and the safety of its products.Cadmium(Cd)is one of the important pollutants in feed.The discharge of industrial wastes,such as waste gas,waste water and waste residue,will contaminate feed materials.Cd accumulates in the body after ingestion and produces many toxic effects.Selenium(Se)is the essential trace element which has the various functions,such as anti-oxidation,anti-aging,strengthening immunity and anticancer.In addtion,Se can also alleviate the toxicity of a variety of heavy metals.In order to evaluate the situation of Cd pollution in a chicken feed in Heilongjiang province,the Cd content of chicken feed was detected by inductively coupled plasma mass spectrometry(ICP-MS).In order to investigate the effect of dietary Cd on the apoptosis of chicken spleen tissue and the antagonism effect of Se,the model of apoptosis induced by the interaction of Se and Cd in chicken spleen was reproduced.Forty-eight 28-day-old Isa Brown male chickens were divided randomly into four groups.The control group was fed a basal diet;the Se content was 0.2 mg/kg.The Se group was fed the basic diet supplemented with Na2 Se O3;the total Se content was 2 mg/kg.The Se+Cd group was fed the basic diet supplemented with Na2 Se O3(the total Se content was 2 mg/kg)and 150 mg/kg Cd Cl2.The Cd group was fed the basic diet supplemented with 150 mg/kg Cd Cl2.The duration of experiment was 90 days and the 10 chickens in each group were selected randomly for detection of experimental indexes.The ultrastructure of chicken spleen,the apoptosis rate,and the expression of immune-related genes(Il-1?,IL-2,TNF-? and IFN-?),apoptosis-related genes(Bax,Bak,Bcl-2,Cyt-C,p53,Caspase3 and Caspase9),mitochondrial dynamics-related genes(Drp1,Mff,Mfn1,Mfn2 and OPA1)and energy metabolism-related genes(LDHA,LDHB,HK1,HK2,PK,SDHB,PFK and ACO2)were detected,in order to elucidate the mechanism of the antagonism effect of Se on Cd-induced immune dysfunction and apoptosis.Results were as follows:(1)The overall exceeding rate of Cd content was 7.1%,and the maximum value was 0.57 mg/kg.(2)Compared with control group,the m RNA expression of IL-1?,TNF-?,IL-2 and IFN-? were no significant difference in chicken spleen in Se group(P > 0.05);Compared with control group,the m RNA expression of Il-1? and TNF-? markedely increased and that of IL-2 and IFN-? decreased in chicken spleen in Cd group(P < 0.05).However,Se could alleviate the abnormol expression of immune-related genes.The results showed that Cd cloud induce immune dysfunction by changing the expression of cytokines in chicken spleen,and Se could alleviate the toxicity of Cd.(3)In Cd group,the ultrastructure of the chicken spleen with characteristic morphological changes of apoptosis was observed,such as chromosome condensed,mitochondria swelling,fragmentation,mitochondrial ridge degeneration and disappearance.Cd can also increase the number of apoptotic cells.The expression of Drp1 and Mff significantly increased(P < 0.05),the expression of Mfn1,Mfn2 and Opa1 significantly decreased(P < 0.05);The expression of LDHA,LDHB,HK1,HK2,PK,SDHB,PFK and ACO2 significantly decreased;The expressions of the pro-apoptosis gene(Bax,Bak,Cyt-C,p53,Caspase3 and Caspase9)increased significantly(P < 0.05),and the expression of anti-apoptotic gene(Bcl-2)decreased(P < 0.05).Compared with Cd group,the spleen ultrastructure of chicken in Se+Cd group was completed,the number of apoptotic cells significantly decreased,the expression of mitochondrial dynamics,energy metabolism and apoptosis-related gene expression were partly recovered.Above results showed that Cd cloud induce apoptosis via disrupting the mitochondrial dynamic balance and inhibiting the energy metabolism and Se could antagonism Cd toxicity in chicken spleen.In conclusion,we found that the Cd content of chicken feed exceeds the standard in certain city.Animal experiments showed that Cd could induce the apoptosis of chicken spleen by destroying the equilibrium of mitochondrial dynamics and inhibiting energy metabolism,thus reducing the immune function.Se supplementation could restore the equilibrium of mitochondrial dynamics,improve energy metabolism function,antagonist Cd-induced apoptosis of chicken spleen,and restore immune function.The mechanism of Se antagonism Cd-induced apoptosis and immune dysfunction in chickens was expounded for the first time from the perspective of mitochondrial dynamic and energy metabolism,which provides a theoretical basis for the addition of Se as a Cd attenuated substance in chicken feed. |
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