title: Manipulation of thromboxane synthesis by novel 26,27-dialkyl analogues of 1 alpha,25-dihydroxyvitamin D3 in human promyelocytic leukemia (HL-60) cells.
abstract: 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)
authors.affiliation: Department of Biochemistry, Tokyo College of Pharmacy, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Honda
authors.forename: Y
authors.initials: Y
authors.lastname: Mori
authors.forename: N
authors.initials: N
authors.lastname: Ikekawa
authors.forename: A
authors.initials: A
authors.lastname: Raz
mesh_terms: D002117:Calcitriol / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D004591:Electrophoresis, Polyacrylamide Gel; D004790:Enzyme Induction; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000378:metabolism*; D011233:Precipitin Tests; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis*; D018167:Receptors, Calcitriol; D011987:Receptors, Steroid / Q000378:metabolism; D013329:Structure-Activity Relationship; D013929:Thromboxane B2 / Q000096:biosynthesis*; D013930:Thromboxane-A Synthase / Q000096:biosynthesis*; D014407:Tumor Cells, Cultured
chemical_list: D018167:Receptors, Calcitriol; D011987:Receptors, Steroid; D013929:Thromboxane B2; D011451:Prostaglandin-Endoperoxide Synthases; D013930:Thromboxane-A Synthase; D002117:Calcitriol