Appearance of the arachidonic acid metabolic pathway in human promyelocytic leukemia (HL-60) cells during monocytic differentiation: enhancement of thromboxane synthesis by 1α,25-dihydroxy vitamin D-3

Abstract

The appearance of the arachidonic acid metabolic pathway in human promyelocytic leukemia (HL-60) cells was investigated during 1α,25-dihydroxy vitamin D-3-induced monocytic differentiation. 1α,25-Dihydroxy-vitamin D-3-treated HL-60 cells acquired the ability to convert [1- 14C] arachidonic acid to thromboxane B 2 and prostaglandin E 2 during monocytic differentiation. The major cyclooxygenase product synthesized by the HL-60 cells after 3–4 days exposure to 1α,25-dihydroxyvitamin D-3 (48 nM) was thromboxane B 2 and its production was about 19–25-times higher than that of untreated HL-60 cells. The percent conversion of thromboxane B 2 from [1- 14C]arachidonic acid in the 1α,25-dihydroxyvitamin D-3 (48 nM, 3 day exposure) -treated HL-60 cells was about 4.4% as compared to that (about 0.3%) of the untreated cells, whereas the percent conversion of thromboxane B 2 from [1- 14C]prostaglandin H 2 in the 1α,25-dihydroxy vitamin D-3-treated cell homogenate was about 22.4% as compared to that (about 13.6%) of the untreated cell homogenate. The stimulatory effect of 1α,25-dihydroxy vitamin D-3 on thromboxane B 2 production from [1- 14C]arachidonic acid and from [1- 14C]prostaglandin H 2 in HL-60 cells was inhibited by the addition of cycloheximide (1 μg/ml). However, 1α,25-dihydroxy vitamin D-3 (48 nM) did not significantly stimulate the arachidonic acid release either in HL-60 cells or in 1α,25-dihydroxyvitamin D-3-induced cells. These results suggest that the stimulatory effect of α,25-dihydroxyvitamin D-3 on the thromboxane production in HL-60 cells was not due to the activation of phospholipase A 2 but due to the induction of fatty acid cyclooxygenase and thromboxane synthetase activities. Thromboxane A 2 actively produced during the monocytic differentiation of HL-60 cells could influence the cell adhesiveness of the monocyte-macrophage-differentiated cells.