| Aflatoxin B1 (AFB1) severely influences the health of human and animal, such as acute toxicity, nutrition disorders, immunosuppression and carcinogenesis. Besides, AFB1 causes the huge losses of economy in poultry industry. Up to now, people have paid attention to the studies on the protective roles of selenium against the toxicity of AFB1, and researches on these branches have made certain progress. However, there were rarely reports concerning the protective roles of selenium against the cell proliferation and apoptosis of broiler’s digestive tract especially the jejunum induced by AFB,.The effects of AFB1 exposure and sodium selenite supplementation on the cell proliferation and apoptosis of jejunal mucosa in broilers were studied by histopathology, immunohistochemistry, flow cytometry and Quantitative real time-polymerase chain reaction (qRT-PCR) methods.240 one-day-old AA broilers were divided into four groups of 60 each, fed with control diet (containing 0.332mg/kg Se), AFB1 diet (0.3 mg/kg AFB1),+Se group diet (sodium selenite containing 0.4mg/kg Se was supplemented in the control diet, total 0.732mg/kg Se), AFB1+Se group diet (sodium selenite containing 0.4mg/kg Se was supplemented in the AFB1 diet, total 0.732mg/kg Se) for 21 days, respectively. Results were as follow:Histological observation of jejunum showed that the villus height at 7,14 and 21 days of age and villus/crypt ratio at 7 and 14 days decreased in the AFB1 group, but the crypt depth in the AFB1 group increased at 7 and 14 day, when compared with those in the control group. Meanwhile, the epithelial cells in the apical region of villi were shedding in the AFB1 group at 7 and 14 days. The immunohistochemical tests revealed that the proliferation cell nuclear antigen (PCNA)-positive cells in the AFB1 group were significantly lower than those in the control group at 7 and 14 days of age. However, the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay (TUNEL)-positive cells in the AFB1 group were significantly higher than those in the control group at 7,14 and 21 days of age. The flow cytometry assay demonstrated that the percentage of cells in G0/G1 phase was significantly lower in the AFB1 group than that in the control group on day 7 and 14, and the percentage of cells in G2/M phase in the AFB1 group were significantly higher than those in the control group at 7 and 14 days of age. The qRT-PCR assay showed that the expression levels of Caspase-3 and Bax mRNA were increased; while the expression levels of Bcl-2 mRNA and the ratio of Bcl-2/Bax were decreased in the AFB1 group at 7,14 and 21 days of age, when compared with the control group.Compared with the control group, there were no significant changes in the histology of jejunum, the number of PCNA-positive cells and TUNEL-positive cells, the percentage of cell cycle, the expression levels of Caspase-3, Bax, Bcl-2 mRNA and the ratio of Bcl-2/Bax in the+Se group, with the exception of villus height increased on day 14, the percentage of cells in G0/G1 phase reduced on 7 day, the expression levels of Bax decreased on 7 and 14 day, and the expression levels of Bcl-2 increased on day 7.No significant changes were observed in the histology and the number of PCNA-positive cells in the AFB1+Se group during the experiment when compared with the control group, but the number of TUNEL-positive cells (7,14 and 21 days), the percentage of cells in S phase (7 and 14 days) and the expression levels of Caspase-3 mRNA (7,14 and 21 days) in the AFB1+Se group were significantly higher than those in the AFB1 group. However, the percentage of cells in G0/G1 phase (7 days), the expression levels of Bcl-2 mRNA (7,14 and 21 days) and the ratio of Bcl-2/Bax (7,14 and 21 days) were significantly lower than those in the AFB1 group. Compared with the AFB1 group, the number of PCNA-positive cells, the percentage of cells in G0/G1 phase, the expression levels of Bcl-2 mRNA and the ratio of Bcl-2/Bax were increased in the AFB1+Se group at the age of 7 and 14, and the number of TUNEL-positive cells, the percentage of cells in G2/M phase and the expression levels of Caspase-3 mRNA were decreased in AFB1+Se group at the age of 7 and 14.In conclusion,0.3 mg/kg AFB1 in the broiler’s diet caused the damages of jejunal histology, the decrease on cell proliferation and increase on cell apoptosis. However, supplementation of dietary sodium selenite (total 0.732mg/kg Se) could counteract these toxic effects caused by AFB1. The mechanisms for these might attribute to the protective roles of Se by up-regulation of Bcl-2 mRNA expression and down-regulation of Bax and Caspase-3 mRNA expression and by improving the arrest of G2/M and increasing the expression of PCNA. |
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