Research On The Mechanism Of Selenium Deficiency-Induced Immunosuppression In Chicken

As an essential trace element of animal body, selenium, the scavenger of free radicals, co-constituted the antioxidant defense system with other antioxidants in order to maintain the dynamic balance of the free radicals. There were many selenium-deficiency areas in different countries all over the world, and China was one of them. Selenium deficiency was a worldwide disease that harmed various animals. Some reserches showed that it could cause diseases such as exudative diathesis, pancreatic fibrosis and white myopathy in chickens, mulberry heart disease and liver necrosis in pigs, muscular dystrophy in cattles and sheep, which made enomous economic losses to the farming industry. Most studies localized on clinical symptoms, autopsy changes, epidemiology, pathogenic factors and pathogenesis, but few studies on the mechanism of selenium deficiency induced immuno-suppression in chicken. In this study, the selenium deficiency animal model was replicated through feeding 0.032 mg/kg Se in basal diet. Samples were collected at 30, 45, 60 and 75 d. The study preliminaryly revealed the mechanism of selenium deficiency on the immunosuppression through observing of pathology and detecting the metabolism of NO and antioxidant function in immune organs and serum, cytokine levels in serum, cell cycle and DNA damage of lumphocyte inimmune organs as well as the detection on the mRNA expression levels of the immune organs'apoptotic related genes(Fas, Caspase-3). The results show that:1. Selenium deficiency could cause microstructure and ultrastructure to change in apoptosis degeneration, and necrosis of chicken immune organ by pathological observation and TUNEL assay, which was morphology foundation of selenium deficiency induced immunosuppression.2. The content of IL-1βand IL-2 decreased, TNF content increased in serum of selenium deficiency groups through detection with radio-immunity, which indicated that selenium deficiency could cause immune function increase.3. The detection of antioxidative ability and NO metabolism confirmed that selenium deficiency could cause GSH-Px,SOD activity and T-AOC to decrease, content of MDA and NO, NOS activity increase. It revealed that the effects of selenium deficiency on oxidative stress may be one of important mechanisms of lymphocytic apoptosis.4. The damage effects of the selenium deficiency on lymphocytes'DNA in chick's immune organs were detected with Alkaline SCGE and DNA Ladder assay. The results indicated that the selenium deficiency could cause DNA damage on lymphocytes, which indicated that selenium deficiency could cause immunosuppression by DNA damage of lymphocyte.5. Selenium deficiency could increase the expression levels of Fas mRNA and Caspase-3 mRNA, and the number of apoptosis cells, which indicated that selenium deficiency could induce apoptosis by Fas path.In this study, we preliminarily reveals the immunosuppressive mechanisms of Selenium deficiency on chicken through observing aspects about the changes in morphologic structure of immune organs, oxidative stress, DNA damage, cytokine, apoptosis and the expression apoptotic related genes(Fas, Caspase-3). The results preliminaryly revealed the mechanism of selenium deficiency on immunosuppressive, and provided the scientific rationale for diagnose and treatment of selenium deficiency illness and mirror for comparative medicine.