Effect Of High Dietary Fluorine On The Cecal Tonsil In Broilers

Long-term excessive fluoride intake is known to be toxic and can lead to fluorosis and bone pathologies. However, the cellular mechanisms underlying sodium fluoride-induced cytotoxicity in the cecal tonsil lymphocytes are not well understood. The aims of this study were to investigate the effect of high dietary fluorine on the cecal tonsil in broilers by methods of ELLISA, flow cytometry (FCM) and immunohistochemical labeling of HRP-streptavidin detection. Avian broilers which were280one-day-old were randomly divided into four groups, and observed in feeding them a control diet containing22.6mg F/kg and three high F diets containing400,800, and1200mg F/kg for high F groups Ⅰ, Ⅱ and Ⅲ throughout a42-day experimental periodResults as follows:①The results showed that malondialdehyde (MDA) content was significantly higher (p<0.01)in high F groups II and III than in the control group. In contrast, the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px), glutathione (GSH) contents, and ability to inhibit hydroxyl radical were significantly decreased (p<0.01) in high fluorine groups Ⅱ and Ⅲ. In conclusion, dietary F, in the range of800-1200mg/kg, could induce oxidative damage and impair the antioxidation and immune function of the cecal tonsil in broilers.②Histopathologically, the population of lymphocytes was decreased in high fluorine groups Ⅱ and Ⅲ. The apoptotic cecal tonsil T lymphocytes population was significantly increased in the high fluorine groups Ⅱ and Ⅲ when compared with those in the control group. Meanwhile, immunohistochemical tests showed the bcl-2protein expression was decreased, and the bax and caspase-3protein expression were increased in the high fluorine groups Ⅱ and Ⅲ. In conclusion, dietary fluorine in the range of800-1200mg/kg increased lymphocyte apoptosis in cecal tonsil, suggesting that fluorine-induced cecal tonsil lymphocyte apoptosis was mediated by direct effects of fluoride on the expression of bcl-2, bax and caspase-3.③The percentages of CD3+, CD3+CD4+, and CD3+CD8+T-cells in the cecal tonsil were significantly decreased (p<0.05or p<0.01) in high fluorine groups Ⅱ and Ⅲ; however, the CD4+/CD8+ratio was not significantly changed. In conclusion, dietary F in the range of800-1200mg/kg reduced the percentages of cecal tonsil T-cell subsets and IL-2contents, implying that the local mucosal immune function can be adversely impacted by high F in broilers.④The changes in the cecal tonsil content of the cytokine proteins interleukin-2(IL-2), interleukin-4(IL-4), in terleukin-6(IL-6), tumour necrosis factor alpha (TNF-a), and interferon gamma (IFN-y) were detected by enzyme-linked immunosorbent assay (ELISA). The results showed that the content of these cytokines in the cecal tonsil was significantly lower (p<0.05or p<0.01) in the high fluorine groups II and III than in the control group. Lower cytokine levels in the cecal tonsil can impact the local immune function of intestines by affecting pathways that decrease the lymphocyte numbers and/or lymphocyte activation.⑤Immunohistochemistry detection showed that the quantities of IgA+B cells were lower (p<0.05or p<0.01) and the IgA, IgG, and IgM contents were decreased (p<0.05or p<0.01) in high fluorine groups Ⅱ and Ⅲ. In conclusion, dietary F, in the range of800-1200mg/kg, could reduce the numbers of the IgA+B cells and immunoglobulin contents in the cecal tonsil, implying the local mucosal immune function was finally impacted in broilers.Conclusion①Dietary fluorine, in the range of800-1200mg/kg, could induce oxidative damage and impair the antioxidation and immune function of the cecal tonsil in broilers.②Dietary fluorine in the range of800-1200mg/kg increased lymphocyte apoptosis in the cecal tonsil, suggesting that fluorine-induced cecal tonsil lymphocyte apoptosis was mediated by direct effects of fluoride on the expression of bcl-2, bax and caspase-3. ③Dietary fluorine in the range of800～1200mg/kg reduced the percentages of cecal tonsil T-cell subsets, implying that the local mucosal immune function can be adversely impacted by high fluorine in broilers.④Lower cytokine levels in the cecal tonsil can impact the local immune function of intestines by affecting pathways that decrease the lymphocyte numbers and/or lymphocyte activation.⑤It was concluded that dietary fluorine, in the range of800-1200mg/kg, could reduce the numbers of the IgA+B cells and immunoglobulin contents in the cecal tonsil, implying the local mucosal immune function was finally impacted in broilers.