Figure 1.

The effect of vitamin D derivatives on the proliferation of human melanoma A375 cells treated with H₂O₂. The cells were treated with serial dilutions (10⁻¹²-10⁻⁶ M) of (A) 1,25(OH)₂D3, (B) 20(OH)D3, (C) 21(OH)pD or (D) calcipotriol. ^*P<0.05, ^**P<0.005 and ^***P<0.0005 versus control using one-way analysis of variance. The cells were treated with serial dilutions of H₂O₂ (0.0039-0.25 mM) alone or in combination with (E) 10 nM 1,25(OH)₂D3, (F) 20(OH)D3, (G) 21(OH)pD or (H) calcipotriol for 24 h. The results presented are representative of three experiments (n=6). ^*P<0.05, ^**P<0.01 and ^***P<0.001 between the two treatments at each H₂O₂ concentration, using one-way analysis of variance followed by Tukey’s multiple comparison test. The same control data is plotted in each graph. In order to investigate the effect of secosteroid pre-treatment on mitochondrial transmembrane potential, human melanoma A375 cells were treated with (I) 100 nM 1,25(OH)₂D3 or calcipotriol for 24 h, and subsequently exposed to 7.5 µM H₂O₂ for 1 or 3 h, then stained with JC-1 and analyzed by flow cytometry. The data are presented as mean ± standard deviation of 3 independent experiments. ^***P<0.001 versus untreated control or between the two groups indicated by the bracket using one-way analysis of variance followed by Tukey’s multiple comparison test. The positive control was exposed to CCCP for 5 min prior to staining with JC-1. IC50, half maximal inhibitory concentration; 1α,25(OH)₂D3, 1α, 25-dihydroxyvitamin D3; 20(OH)D3, 20S-hydroxyvitamin D3; 21(OH)pD, 21-hydroxypregnacalciferol; H₂O₂, hydrogen peroxide; CCCP, carbonyl cyanide 3-chlorophenylhydrazone.