Cellular redox state and activating protein-1 are involved in ascorbate effect on calcitriol-induced differentiation

Ascorbate has been related to the differentiation of several mesenchymal ce lls including haematopoietic cells. We have previously demonstrated that as corbate enhances the activity of 1 alpha ,25-dihydroxyvitamin D-3 (1 alpha ,25(OH)(2)D-3)on monocytic differentiation of HL-60 cells. Here, we show th at ascorbate-mediated modification of cellular redox state and AP-1 (activa ting protein-1) DNA binding during early phases are related to the enhancin g effect of ascorbate on differentiation. Ascorbate, but not its fully oxid ized form, dehydroascorbate, or an ascorbate analogue with a low rate of ox idation, ascorbate-2-phosphate, enhanced the differentiation induced by la, 25(OH)2D3, modified cytosolic reactive oxygen species levels and mitochondr ial redox potential (Delta psi (m)), and modulated AP-1 DNA binding in HL-6 0 cells. Ascorbate itself increased AP-1 binding to DNA in noninduced cells , whereas it inhibited AP-1 binding in 1 alpha ,25(OH)(2)D-3-induced cells. However, ascorbate increased the mRNA levels of c-jun, junB, and c-fos in 1 alpha ,25(OH)(2)D-3-induced cells. Taken together, these results suggest that the enhancing effect of ascorbate on HL-60 differentiation induced by 1 alpha ,25(OH)(2)D-3 is related to its effect on the cellular redox state and the modulation of AP-1 activity.