Analysis of the roles of dietary protein and calcium in fluoride‐induced changes in T‐lymphocyte subsets in rat

The roles of dietary protein (Pr) and calcium (Ca) levels on the changes in T-lymphocyte subsets induced by excessive fluoride (F) intake were assessed using rats that were malnourished for 120 days as a model. The CD4+ and CD8+ T-lymphocytes in the spleen tissue were determined by flow cytometry and immunofluorescence assay. The percentages of CD3+ , CD4+ , and CD8+ T-lymphocytes were reduced in the spleen of rats exposed to excessive F, and malnutrition aggravated these changes in the T-lymphocytes. In addition, the mRNA expression levels of IL-1β, IL-2, IL-6, TNF-α, and IFN-γ in the spleen were downregulated significantly. We also reported herein the increased apoptosis ratio following caspase-9 and caspase-3 upregulation in the spleen of rats exposed to excessive amount of F. Light and transmisison electron microscopy revealed the irregularly arranged lymphocytes, few lymph nodules and the apoptotic characteristic of lymphocytes, which are caused by the increased expression of caspase. In addition, Pr and Ca supplementation reversed the morphologic and T-lymphocytic changes in spleen under malnutrition. Taken together, our results revealed an endogenous caspase-mediated mechanism of regulating the apoptosis of the T-lymphocyte subsets, as well as the immune-related cytokine secretion, which reduces the immune function in F-induced rats. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1587-1595, 2017.