tretinoin and 4-bromophenacyl-bromide

The role of phospholipase A2 (PLA2) and its metabolite arachidonic acid (AA) in the proliferation and differentiation of HL-60 cells was investigated. Addition of either 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) or retinoic acid (RA) to HL-60 cells for 2 h inhibited PMA-stimulated PLA2 activity measured by [3H]AA release. The inhibitor of PLA2 activity, p-bromophenacyl bromide (BPB), significantly inhibited the proliferation of HL-60 cells and of fibroblast L929 and Swiss 3T3 cells in a dose-dependent manner. The effect of BPB on proliferation is probably through its inhibitory effect on PLA2 activity, since the same doses of BPB which inhibited proliferation also inhibited PLA2 activity determined by [3H]AA release. The importance of PLA2 activity for cell growth was further supported by the effect of two other PLA2 inhibitors, AACOCF3 and scalaradial, which inhibited HL-60 proliferation in a dose-dependent manner. BPB, AACOCF3 and scalaradial significantly increased the doubling time to 32.4 h, 34.0 h and 31.8 h, respectively, compared with 24.6 h in the control. The inhibitory effect of BPB on HL-60 proliferation was reversed by addition of exogenous free AA to HL-60 cells, indicating the importance of this metabolite for the proliferation process. This reversible effect is specific for AA since it was not achieved by other fatty acids like linolenic acid (LA) or oleic acid (OA). Addition of free AA to HL-60 cells did not induce differentiation, as expected. Although BPB, AACOCF3, or scalaradial inhibited proliferation, they did not induce differentiation nor affect the differentiation induced by 1,25(OH)2D3 or RA. These results implicate that PLA2 activity has no regulatory role in differentiation of HL-60 cells. The differential effect of PLA2 inhibitors on proliferation and differentiation of HL-60 cells suggests that these two processes function under different regulatory mechanisms.

Topics: 3T3 Cells; Acetophenones; Animals; Anti-Inflammatory Agents; Arachidonic Acid; Arachidonic Acids; Blotting, Northern; Calcitriol; Cell Differentiation; Cell Division; Enzyme Inhibitors; Granulocytes; HL-60 Cells; Homosteroids; Humans; Mice; Phospholipases A; Phospholipases A2; Sesterterpenes; Terpenes; Tetradecanoylphorbol Acetate; Tretinoin

To determine whether low mol. wt phospholipase A2 (PLA2) is involved in the mechanism of arachidonic acid mobilization induced by zymosan in mouse peritoneal macrophages, we developed an immunoblot analysis and ELISA assay using the polyclonal antibodies anti-PLA2 type I and type II previously characterized. We also measured the effect of low mol. wt PLA2 inhibitors such as p-bromophenacyl bromide, aristolochic acid, nordihydroguaiaretic acid, all trans-retinal and all trans-retinoic acid on the action of these enzymes. The antibodies antitype I PLA2 bound to mouse platelet protein fraction, while the antibodies antitype I or antitype II did not recognize components of the macrophages. Furthermore, low mol. wt PLA2 inhibitors did not inhibit arachidonic acid release produced during the phagocytosis of zymosan. This suggests that low mol. wt PLA2 are not present in cells such as macrophages. These results are consistent with a role for high mol. wt PLA2 in arachidonic acid mobilization.

Topics: Acetophenones; Animals; Arachidonic Acid; Aristolochic Acids; Blotting, Western; Cross Reactions; Crotalid Venoms; Crotalus; Elapid Venoms; Electrophoresis, Polyacrylamide Gel; Enzyme-Linked Immunosorbent Assay; Immune Sera; Macrophages, Peritoneal; Male; Masoprocol; Mice; Molecular Weight; Pancreas; Phagocytosis; Phenanthrenes; Phospholipases A; Phospholipases A2; Rats; Rats, Sprague-Dawley; Swine; Tretinoin; Zymosan

Two polyacetates, aplysiatoxin and debromoaplysiatoxin, as well as 12-O-tetradecanoylphorbol-13-acetate (TPA), mezerein and teleocidin enhance nitroblue tetrazolium (NBT) reduction in mouse peritoneal macrophages in vitro. The ED50 values for NBT reduction of these 5 TPA-type tumor promoters were 4.2 ng/ml for TPA, 36 ng/ml for mezerein, 0.53 ng/ml for teleocidin, 1.5 ng/ml for aplysiatoxin and 108 ng/ml for debromoaplysiatoxin. The NBT reduction induced by the 5 tumor promoters is inhibited by 2 inhibitors of tumor promotion, retinoic acid and dibromoacetophenone. The possibility that tumor promotion by TPA-type tumor promoters involves similar mechanisms such as superoxide anion radicals release in cell membranes is discussed.

Topics: Acetophenones; Animals; Carcinogens; Cells, Cultured; Diterpenes; Female; Free Radicals; Lyngbya Toxins; Macrophages; Mice; Mice, Inbred Strains; Nitroblue Tetrazolium; Superoxides; Terpenes; Tetradecanoylphorbol Acetate; Tetrazolium Salts; Tretinoin