Arachidonic acid metabolism by a vitamin D3-differentiated human leukemic cell line.

HL-60 is a human promyelocytic cell line that differentiates along the granulocytic pathway when incubated with dimethylsulfoxide and along the monocytic pathway when incubated with 1,25-(OH)2D3. We compared arachidonic acid metabolism in undifferentiated, DMSO-differentiated, and 1,25-(OH)2D3-differentiated cells. DMSO- and 1,25-(OH)2D3-differentiated cells metabolized exogenous arachidonic acid to both cyclo-oxygenase products (predominantly thromboxane B2 and prostaglandin E2) and 5-lipoxygenase products, including leukotriene B4. Undifferentiated cells produce these metabolites in much smaller amounts. DMSO-differentiated cells released a large percentage of phospholipid-bound arachidonic acid in response to stimulation with the ionophore A23187, zymosan, or formylmethionylleucylphenylalanine (FMLP). DMSO-differentiated cells stimulated with A23187 converted released arachidonate to LTB4 and TxB2. In contrast, 1,25-(OH)2D3-differentiated cells released a smaller percentage of phospholipid-bound arachidonate in response to stimuli, and undifferentiated cells released none at all. The three cell types (undifferentiated, DMSO-differentiated, and 1,25-(OH)2D3-differentiated) were homogenized and the 10,000 X g supernatant incubated with [14C]arachidonic acid. The supernatants from the homogenates of the DMSO- and 1,25-(OH)2D3-differentiated cells metabolized [14C]arachidonic acid to cyclooxygenase and lipoxygenase products, but the supernatant from the homogenate of undifferentiated cells did not. These data indicate that differentiation of HL-60 cells with DMSO or 1,25-(OH)2D3 induces cyclooxygenase and 5-lipoxygenase and induces mechanisms for the release of arachidonate from phospholipids by soluble and particulate stimuli.