Identification by differential display PCR of the selenoprotein thioredoxin reductase as a 1α,25(OH)2-vitamin D3-responsive gene in human osteoblasts - regulation by selenite

1 alpha,25(OH)(2) vitamin D-3 (1,25(OH)(2)D-3) is a potent hormone, stimulating bone cell growth and differentiation. In order to detect novel targets for 1,25(OH)(2)D-3 action, we applied differential display PCR (ddPCR) to human fetal osteoblasts (FOB cells). By ddPCR analysis, we identified the selenoprotein thioredoxin reductase (TRR) as a 1,25(OH)(2)D-3-responsive gene. In FOB cells, the response of TRR mRNA steady state levels to 1,25(OH)(2)D-3 was fast and transient. Maximal stimulation was observed after one hour of 1,25(OH)(2)D-3 treatment, thereafter TRR steady state mRNA levels declined to control levels. This transient response of TRR mRNA was not reflected at the TRR enzyme activity level upon treatment with 1,25(OH)(2)D-3 for up to 48 h. Sodium selenite added to differentiated FOB cells increased TRR enzyme activity 2.6-fold, whereas no selenite effect on TRR mRNA steady state levels was measurable. Our data might provide a link between the induction of a differentiation program by 1,25(OH)(2)D-3 and the expression of the selenium responsive TRR system in human osteoblasts.