Hydroxyl Radical-Mediated Commitment of HL-60 Cells to Differentiation Modulation of Differentiation Process by Phosphodiesterase Inhibitors

Hydroxyl Radical-Mediated Commitment of HL-60 Cells to Differentiation Modulation of Differentiation Process by Phosphodiesterase Inhibitors

<P> This report shows that hydroxyl radical, generated by a Fenton reaction involving adenosine 5 -diphosphate/Fe<SUP>2+</SUP> complex (5-15 &#12557;M) and H<SUB>2</SUB>O<SUB>2</SUB> (2 &#12557;M), induced differentiation of HL-60 cells in a dose- and time-dependent manner. This is evidenced by the increases in 12-O-tetradecanoylphorbol 13-acetate- and fMLP-stimulated superoxide production capability. The cells exposed to hydroxyl radical for defined periods (24∼96 hr) continued to differentiate even after the hydroxyl radical generating system had been removed. The differentiated cells displayed fMLP-stimulated calcium mobilization and increased expression of myeloid-specific antigen CD11b and CD14. The extent of the differentiation was markedly reduced by desferrioxamine (100 &#12557;M), dimethylthiourea (5 mM), <I>N,N </I>-diphenyl-1,4-phenylenediamine (2 &#12557;M), and N-acetyl-L-cysteine (5 mM). The induction of differentiation by hydroxyl radical was enhanced by 3-isobutyl-1-methylxanthine (200 &#12557;M) and Ro-20-1724 (8 &#12557;M), and inhibited by dipyridamole (2 &#12557;M). <P>These results suggest that hydroxyl radicals may induce commitment of HL-60 cells to differentiate into more mature cells of myelomonocytic lineage through specific signal-transduction pathway that is modulated by phosphodiesterase inhibitors.