Relationships between in vitro selenium supply, glutathione peroxidase activity, and phagocytic function in the HL-60...

Utilizing the HL-60 human promyelocytic leukemia cell line cultured in defined medium, we examined the quantitative and temporal relationships between Se supply and the activity of the selenoenzyme glutathione peroxidase, as well as the effects of selenium deficiency on phagocytic function. Glutathione peroxidase activity depended on the medium Se concentration up to 2.6 X 10(-8) M (sodium selenate, 5 ng/ml), above which a plateau occurred. HL-60 cells grown in medium without Se supplementation became GSH peroxidase deficient, with activity 1-3% that of Se-replete cells. Replenishment of the medium with sodium selenate returned enzyme activity to 23% that of replete cells by 24 h and to 85% by 7 days, a process blocked by cycloheximide. Se-deficient HL-60 cells induced to granulocytic differentiation by dimethylformamide showed decreased hexose monophosphate shunt activity in response to phorbol myristate acetate and to an exogenous enzymatic H2O2-generating system. However, Se-deficient and -replete cells showed equal responses to methylene blue, which stimulates the shunt independently from the glutathione cycle. Se-deficient mature HL-60 cells stimulated with phorbol myristate acetate released 2.3-fold more H2O2 than Se-replete cells and only slightly (not significantly) less O2. Se-deficient and -replete differentiated HL-60 cells did not differ significantly in their capacities for cell motility or for ingestion of serum-opsonized bacteria. Differences between the findings of the present study and previous in vivo rat studies may reflect both the defined in vitro environment of the cell line and the inverse ratios of catalase and glutathione peroxidase activities in human and rat granulocytes.