thromboxane-b2 and Leukemia--Promyelocytic--Acute

We studied the conversion of arachidonic acid or prostaglandin H2 into eicosanoids in promyelocytic leukemia cells (HL-60) that were differentiating into macrophages or neutrophils. Our results indicate that several enzymes of eicosanoid synthesis are coordinately and differentially upregulated early in the neutrophil and macrophage differentiation pathways. They also provide evidence for a preferential upregulation of thromboxane synthase in the macrophage differentiation pathway that contrasts with a preferential upregulation of enzymes of the 5-lipoxygenase pathway during neutrophil differentiation. Nicotine at 100 nM selectively inhibited the formation of thromboxane in HL-60 cells induced to differentiate into macrophages. Nicotine therefore alters the pattern of activity of the eicosanoid-synthesizing enzymes in HL-60 cells undergoing macrophage differentiation.

Topics: Arachidonic Acid; Arachidonic Acids; Cell Line; Dinoprostone; Epoprostenol; Humans; Leukemia, Promyelocytic, Acute; Macrophages; Thromboxane B2; Thromboxane-A Synthase

Arachidonic acid (AA) metabolism in nuclei of human pro-myelocytic leukemia (HL-60) cells was investigated during retinoic acid (RA)-induced granulocytic differentiation and 1 alpha, 25 dihydroxy-vitamin D3-induced monocytic differentiation. The whole control HL-60 cells and their nuclei hardly converted [1-14C]-AA to any metabolites comigrating with authentic prostaglandins (PGs). On the other hand, RA-treated HL-60 cells acquired the ability to convert [1-14C]-AA to PGE2 predominantly and thromboxane B2 (TXB2) to a small degree, whereas the nuclei of the differentiated cells acquired the ability to convert predominantly to TXB2. In contrast, 1 alpha, 25-dihydroxy-vitamin D3-treated HL-60 cells acquired the ability to convert [1-14C]-AA to PGE2, PGF2 alpha, TXB2 and 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT), whereas the nuclei of the differentiated cells acquired the ability to convert to PGF2 alpha, TXB2 and HHT. The significance of the acquisition of cyclooxygenase and TX synthetase by the nucleus is unclear, but there may be a specific relationship between the specific PGs formed by the nuclear membrane and nuclear events during HL-60 cell differentiation.

Topics: Arachidonic Acid; Calcitriol; Cell Differentiation; Cell Nucleus; Dinoprost; Dinoprostone; Fatty Acids, Unsaturated; Granulocytes; Humans; Leukemia, Promyelocytic, Acute; Monocytes; Thromboxane B2; Tretinoin; Tumor Cells, Cultured

Using new steroidal side-chain-lengthened 26,27-dialkyl analogues of 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25-(OH)2D3], we manipulated the synthesis of thromboxane and thromboxane-producing enzymes, cyclo-oxygenase and thromboxane synthase, in human promyelocytic leukemia (HL-60) cells in serum-free culture. The order of potency of the analogues for stimulating thromboxane B2 synthetic activity from arachidonic acid (reflecting combined cyclo-oxygenase activity and thromboxane synthase activity) and from prostaglandin H2 (thromboxane synthase activity only) as well as for cyclo-oxygenase induction was 1 alpha,25-(OH)2D3 > or = 1 alpha,25-(OH)2-26,27-CH3)2D3 > 1 alpha,25-(OH)2-26,27-(C2H5)2D3 >> 1 alpha,25-(OH)2-26,27-(C3H7)2D3. These results suggest that there are functional and structural limits to the chain length of C-26 and C-27 dialkyl groups flanking the C-25-OH group in the 1 alpha,25-(OH)2D3 molecule for expressing thromboxane synthetic activity in HL-60 cells. Removal of the C-1 alpha-OH group from 1 alpha,25-(OH)2D3 led to markedly decreased thromboxane synthetic activity in HL-60 cells. These structure-activity relationships indicate that both the C-25-OH and C-1 alpha-OH groups in the 1 alpha,25-(OH)2D3 molecule are essential for expressing thromboxane synthesis in HL-60 cells. Also, the rank order for stimulating thromboxane synthesis correlated well with the binding affinity of these dialkyl analogues for the 1 alpha,25-(OH)2D3 receptor of HL-60 cells, suggesting a 1 alpha,25-(OH)2D3 receptor-mediated induction mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Calcitriol; Cell Differentiation; Electrophoresis, Polyacrylamide Gel; Enzyme Induction; Humans; Leukemia, Promyelocytic, Acute; Precipitin Tests; Prostaglandin-Endoperoxide Synthases; Receptors, Calcitriol; Receptors, Steroid; Structure-Activity Relationship; Thromboxane B2; Thromboxane-A Synthase; Tumor Cells, Cultured