The Immune Regulatory Effect of Boron on Ostrich Chick Splenic Lymphocytes

Boron is a trace element which plays important roles in immune response. The relationship between boron and splenic lymphocyte proliferation, apoptosis, secretion of cytokines, and genes potentially related to immune response in ostrich chicks were investigated in the present study. Different concentrations of boron (0, 0.01, 0.1, 0.5, 1, 5, 10, 25, 50, and 100 mmol/L) were applied to splenic lymphocytes of African ostrich, respectively. The effect of boron on lymphocyte proliferation was checked by the CCK-8 method. Flow cytometry was used to detect the effect of boron on apoptosis. The secretion levels of IL-6 and IFN-α were determined by ELISA. Splenic lymphocyte gene expression profiles of ostrich chicks treated with boron (0, 0.1, 100 mmol/L) were studied using RNA-seq technology. The results showed that cell proliferation increased with 0.01–10 mmol/L boron, when it was 25–100 mmol/L, the cell proliferation gradually decreased as the boron concentration increased. Apoptosis ratio in ostrich splenic lymphocytes was closely related to boron concentrations. 0.01- and 0.1-mmol/L boron inhibited apoptosis in splenic lymphocytes, whereas 1, 10, 50, and 100-mmol/L boron promoted apoptosis. As the concentration of boron increased, the secretion of IL-6 gradually decreased; IFN-α was initially increased and then decreased with boron concentrations increased, reaching the maximum level with 1 mmol/L boron. In terms of the RNA-Seq data, there was no differentially expressed gene between the 0- and 0.1-mmol/L boron-treated samples; 21 differentially expressed genes were found between the 0- and 100-mmol/L boron-treated samples; 43 differentially expressed genes were found between the 0.1- and 100-mmol/L boron-treated samples. Functional analysis of the differentially expressed genes by Gene Ontology verified multiple functions associated with immune response. Pathway analysis showed that systemic lupus erythematosus, alcoholism, viral carcinogenesis, and necroptosis pathway were the major enriched pathways, and BIRC2-3, FTH1, and IL-1β genes showed differential expression in necroptosis pathway. These results demonstrated that low concentrations (0.01–0.1 mmol/L) of boron may promote the proliferation and the secretion of cytokines, inhibit cell apoptosis of ostrich splenic lymphocytes by enhancing the function of the cell membrane and the activity of intracellular catalytic enzymes, whereas high-concentration (25–100 mmol/L) boron had opposite effects on cells. The necroptosis pathway might play a pivotal role in regulating the immune response of boron-treated splenic lymphocytes in ostrich chicks.