Search PubMed⌕ Search

Biomedical subjects

H Fujiki

Publications and source records attributed to H Fujiki.

At least 181 records · Page 10Linked to original sources
PubMed1988

Lysis of human immunodeficiency virus infected cells by TPA-type and non-TPA type tumor promoters.

We reported previously that TPA facilitates the replication of human immunodeficiency virus (HIV) and has a selective lethal effect on HIV-infected cells by a cytopathic effect induced by HIV. We have now studied the cytopathic effects of TPA-type tumor promoters (teleocidin, aplysiatoxin, and TPA) and the non-TPA type tumor promoters (palytoxin and thapsigargin) on MOLT-4/HIVHTLV-IIIB cells. All TPA-type and non-TPA type tumor promoters tested except palytoxin stimulated in HIV production three- to sevenfold, and caused more lysis of MOLT-4/HIVHTLV-IIIB cells than of the parental MOLT-4 cells. Fifty percent of the MOLT-4/HIVHTLV-IIIB cells were killed by teleocidin, aplysiatoxin, TPA and thapsigargin at concentrations of 2.0, 2.0, 1.0 and 10 ng/ml respectively, and by palytoxin at the very low concentration of 2.0 pg/ml. Moreover, combinations of one TPA-type tumor promoter and one non-TPA type tumor promoter--but not the combination of two TPA-type tumor promoters--had additive lethal effects, supporting the idea that TPA-type and non-TPA type tumor promoters exert their cytolytic effects by different mechanisms. These latter effects may be due to production of prostaglandin E2, which is commonly induced by both types of tumor promoters.

Carcinogens↗
PubMed1988

Effects of palytoxin or ouabain on growth and squamous differentiation of human bronchial epithelial cells in vitro.

The effects of the non-12-O-tetradecanoylphorbol-13-acetate type tumor promoter palytoxin on human bronchial epithelial cells was studied in an in vitro serum-free culture system. Unlike the results of previous studies with another tumor promoter, 12-O-tetradecanoylphorbol-13-acetate, palytoxin did not induce squamous differentiation of normal bronchial epithelial cells and was equally cytotoxic for normal human bronchial epithelial cells, a human lung tumor cell line, and human bronchial epithelial cells immortalized by infection with adenovirus 12-SV40 hybrid virus (BEAS-2B cells). Palytoxin did not induce a change in free cytosolic Ca2+ concentration of BEAS-2B cells. The effect of palytoxin on the c-myc mRNA steady state level in BEAS-2B cells was studied: 1 pM palytoxin increased the steady-state level at 12 and 18 h. Furthermore, the induction was accompanied by an increase in [3H]thymidine uptake. Because palytoxin binds to (Na+ + K+)ATPase, the effects of ouabain were compared to the effects of palytoxin. A ouabain-resistant cell line was as sensitive to the growth inhibitory effect of palytoxin as the parent ouabain-sensitive cell line, suggesting different binding sites to the (Na+ + K+)-ATPase for palytoxin and ouabain. Ouabain also increased the steady-state level of c-myc gene expression, but earlier than palytoxin, and the increase in the level of c-myc mRNA was accompanied by a drop in DNA synthesis. These results suggest that palytoxin does not act by growth stimulation, differential cytotoxicity or terminal differentiation of normal versus neoplastic cells which are proposed mechanisms of tumor promotion.

Acrylamides↗
PubMed1988

A radioimmunoassay for the teleocidins using 26 (2'-aminoethylthio)-tetrahydroteleocidin A-2 as hapten.

A teleocidin A-2 derivative, 26 (2'-aminoethylthio)-tetrahydroteleocidin A-2, induced ornithine decarboxylase in mouse skin and inhibited the specific binding of [3H]12-O-tetradecanoyl-phorbol-13-acetate to a mouse skin particulate fraction with a potency that was weaker than that of teleocidin A-2 and stronger than that of (-)-indolactam-V. To obtain antibodies, 26 (2'-aminoethylthio)-tetrahydroteleocidin A-2 was covalently linked to bovine albumin with a carbodiimide and the resulting conjugate used for immunization of rabbits. Antibodies directed toward teleocidin were produced as measured by neutralization of teleocidin's capacity to stimulate arachidonic acid metabolism in rat liver cells (the C-9 cell line). An 125I-labeled ligand was prepared by reaction of the same derivative with radiolabeled Bolton-Hunter reagent. The antibodies bound this radiolabeled hapten, and the binding increased progressively with repeated immunizations. After absorption of the rabbit IgG with a goat anti-rabbit IgG, binding was reduced greater than 95%. The binding of the 125I-labeled ligand to the antibodies of one rabbit had an apparent average association constant of 2.84 x 10(9) M-1 at 0 degrees C. The serologic specificity of the antiserum was characterized by measuring the inhibition of binding by several teleocidins of varying structure as well as by other tumor promoters and toxins. The rank order of inhibitory activity expressed as concentration required for 50% inhibition (IC50) was for 26 (2'-aminoethylthio)-tetrahydroteleocidin A-2'(0.56 pmol) greater than teleocidin A-1 (6.5 pmol) greater than or equal to teleocidin A-2 (7.3 pmol) greater than (-)-indolactam-V (3.7 nmol) greater than teleocidin B-4 (13 nmol). Maitotoxin, aplysiatoxin, palytoxin, mezerein, okadaic acid and 12-O-tetradecanoylphorbol-13-acetate did not inhibit at the levels tested.

Animals↗
PubMed1988

Diarrhetic shellfish toxin, dinophysistoxin-1, is a potent tumor promoter on mouse skin.

Dinophysistoxin-1, 35-methylokadaic acid, is a causative agent of diarrhetic shellfish poisoning. The biological activities and tumor-promoting activity of dinophysistoxin-1 were studied together with those of okadaic acid and 7-O-palmitoyl okadaic acid. Dinophysistoxin-1 is a skin irritant and induces ornithine decarboxylase in mouse skin with the same potency as okadaic acid. 7-O-Palmitoyl okadaic acid induced a lower activity than the other compounds. Dinophysistoxin-1 inhibited the specific [3H]okadaic acid binding to a particulate fraction of mouse epidermis. The binding affinities of dinophysistoxin-1 and okadaic acid to a particulate fraction were almost the same. Dinophysistoxin-1 showed a tumor-promoting activity as strong as that of okadaic acid in a two-stage carcinogenesis experiment on mouse skin. The percentages of tumor-bearing mice in the groups treated with 100 micrograms of 7,12-dimethylbenz[a]anthracene (DMBA) followed by 5 micrograms of dinophysistoxin-1, twice a week, and with DMBA followed by 5 micrograms of okadaic acid twice a week were 86.7% and 80.0% in week 30, respectively. The average number of tumors per mouse was 4.6 in the former group and 3.9 in the latter. Dinophysistoxin-1 and okadaic acid act on cells through different pathways from the 12-O-tetradecanoylphorbol-13-acetate-type tumor promoters.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1988

Analysis of the stimulative effect of thapsigargin, a non-TPA-type tumour promoter, on arachidonic acid metabolism in rat peritoneal macrophages.

1. At concentrations above 10 ng ml-1, the tumour promoter thapsigargin stimulates the release of radioactivity from [3H]-arachidonic acid-labelled macrophages harvested from rat peritoneal cavity. 2. The release of radioactivity from prelabelled macrophages was augmented more than additively when the cells were incubated in the medium containing both thapsigargin (10 ng ml-1) and other tumour promoters (10 ng ml-1), such as 12-O-tetradecanoylphorbol-13-acetate (TPA), teleocidin and aplysiatoxin. 3. Thapsigargin required extracellular Ca2+ for the stimulation of arachidonic acid release, while TPA did not. 4. Cytoplasmic free calcium level was increased by thapsigargin treatment but not by TPA treatment. 5. An inhibitor of protein kinases, H-7 inhibited the effect of TPA dose-dependently, whereas H-7 did not inhibit that of thapsigargin. 6. These results suggest that thapsigargin stimulates arachidonic acid release by a mechanism different from that of TPA, viz by acting as a selective Ca2+ mobilizer, but not by activating protein kinase C as TPA does.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1987

Heterologous regulation of the epidermal growth factor receptor by palytoxin, a non-12-O-tetradecanoylphorbol-13-acetate-type tumor promoter.

Previous results have established that 12-O-tetradecanoylphorbol-13-acetate (TPA)-type tumor promoters can alter the properties of the epidermal growth factor (EGF) receptor through activation of protein kinase C. In order to determine whether other, non-TPA-type tumor promoters might similarly influence growth-mediating receptors, we investigated the effect of palytoxin on EGF binding in Swiss 3T3 fibroblasts and human epidermal carcinoma (A431) cells. In both cell types, pretreatment with a low dose of palytoxin (1-11 pM) at 37 degrees C causes a decrease in EGF binding. In Swiss 3T3 cells the inhibitory effect is temperature dependent and does not occur at 4 degrees C, indicating that palytoxin is not directly competing with EGF for binding. As assessed by effects on DNA synthesis, palytoxin is not toxic at these concentrations and does not appear to be mitogenic for these cells. Although palytoxin, like phorbol esters, alters EGF binding, its action in Swiss 3T3 cells differs from that of TPA-type tumor promoters in at least 4 respects: (a) the kinetics and dose dependence differ significantly from that of phorbol dibutyrate; (b) the effect is not readily reversible; (c) there is loss of low-affinity as well as high-affinity binding sites; (d) the effect is independent of cellular protein kinase C levels. These results indicate that palytoxin is capable of heterologous regulation of the EGF receptor through a novel mechanism and suggest that certain non-TPA-type tumor promoters as well as TPA-type tumor promoters may act in part through modulation of growth regulatory pathways.

Acrylamides↗
PubMed1987

Analysis of tumor-promoter-induced inflammation in rats: participation of histamine and prostaglandin E2.

Inflammatory reactions induced by TPA (12-O-tetradecanoylphorbol 13-acetate)-type tumor promoters, including TPA, teleocidin and aplysiatoxin, and chemical mediators responsible for such inflammatory reactions were analyzed. The tumor promoter dissolved in a 0.8% sodium carboxymethyl cellulose solution was injected into a subcutaneous air pouch preformed on the dorsum of rats. Within 30 min after the injection, vascular permeability as measured by the leakage of labeled albumin into the pouch fluid was increased, with a concomitant increase in histamine level. This increase in vascular permeability was inhibited by a histamine antagonist, pyrilamine, and a serotonin antagonist, methysergide. Vascular permeability at 4 h was not inhibited by pyrilamine or methysergide but was inhibited by a cyclooxygenase inhibitor, indomethacin, with a parallel decrease in the prostaglandin E2 level in the pouch fluid. These results suggest that the TPA-type tumor promoters induce inflammation by the mechanism of mast cell degranulation within a short period, this being followed by the stimulation of arachidonic acid metabolism. The mechanism of the in vivo effect of the TPA-type tumor promoters is discussed and compared with in vitro effects that we have previously reported.

Animals↗
PubMed1987

Stimulation of superoxide anion formation by the non-TPA type tumor promoters palytoxin and thapsigargin in porcine and human neutrophils.

The non-12-O-tetradecanoylphorbol-13-acetate (TPA) type tumor promoters palytoxin and thapsigargin provoked a respiratory burst in porcine and human neutrophils. The amounts of oxygen consumed and superoxide anion (O2-) produced were found to be stoichiometric. Concentrations of 6.5 X 10(-8) M palytoxin and 1.2 X 10(-6) M thapsigargin were required for half-maximal stimulation to 3 X 10(6) porcine cells/ml in Hanks' solution. Combinations of palytoxin and thapsigargin, and of one non-TPA type and one TPA-type tumor promoter, had synergistic effects in stimulating O2- formation in neutrophils, suggesting that these compounds activate the cells by different signal transduction mechanisms.

Acrylamides↗
PubMed1987

Tumor promoting activity of teleocidin in skin and forestomach of mice initiated transplacentally with 7,12-dimethylbenz(a)anthracene.

Experiments on the effect of transplacental initiation with 7,12-dimethylbenz(a)anthracene (DMBA) and postnatal promotion with teleocidin were carried out in mice. The percentage of tumor-bearing mice among females treated with DMBA transplacentally on day 17 of gestation and postnatally by topical application of teleocidin to the skin of the back was 73.3% in week 30, whereas that among females treated with DMBA on day 10 of gestation and postnatally by topical application of teleocidin was 20.0%. This indicates that teleocidin shows potent tumor promoting activity on mouse skin in a transplacental initiation and postnatal promotion protocol. Furthermore, in the males treated with DMBA transplacentally on day 17 of gestation and given diet containing 0.01% teleocidin postnatally five tumors of the forestomach were found in 5 of 19 effective mice (26.3%) in week 52. One of these five tumors was a squamous cell carcinoma, and the others were papillomas. This indicates that teleocidin also has tumor promoting activity in the forestomach of mice.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1987

Stimulation of arachidonic acid metabolism in rat peritoneal macrophages by thapsigargin, a non-(12-O-tetradecanoylphorbol-13-acetate) (TPA)-type tumor promoter.

The effects of thapsigargin, which is a histamine secretagogue and has recently been found to be a non-(12-O-tetradecanoylphorbol-13-acetate) (TPA)-type tumor promoter in two-stage carcinogenesis using mouse skin, on arachidonic acid metabolism in rat peritoneal macrophages were examined. The release of radioactivity from 3H arachidonic acid-labeled macrophages was increased at doses more than 10 ng/ml. Prostaglandin E2 production was also increased dose-dependently without inducing prominent changes in cell morphology. The potency to stimulate prostaglandin E2 production by thapsigargin was stronger than that by TPA at a dose of 10 ng/ml when measured 6 h after the incubation. HPLC analysis revealed that thapsigargin stimulated the production of lipoxygenase products such as leukotriene B4 and 12-hydroxyeicosatetraenoic acid as well as cyclooxygenase products such as prostaglandin E2 and 6-keto prostaglandin F 1 alpha. Thapsigargin, an analogue of thapsigargin, also stimulated prostaglandin E2 production. The mechanism of the action of thapsigargin was discussed. It was confirmed that the tumor promoters are associated with the activity to stimulate arachidonic acid metabolism irrespective of their type, TPA-type or non-TPA-type.

Animals↗
PubMed1987

Production of antibodies to palytoxin: neutralization of several biological properties of palytoxin.

Palytoxin stimulated arachidonic acid metabolism (in bovine aorta endothelial and smooth muscle cells, rat keratinocytes, porcine aorta endothelial cells and rat liver cells), hemolyzed rat erythrocytes and was lethal to mice when administered intraperitoneally. Serum from rabbits immunized with a conjugate in which palytoxin was covalently bound to bovine albumin through its free amino group neutralized these biologic activities of palytoxin. Ninety-nine per cent of the neutralizing activity of the immunized rabbit serum was removed after precipitation of the rabbit IgG with a goat anti-rabbit IgG.

Acrylamides↗
PubMed1987

Effects of various tumor promoters on expression of cartilage phenotypes in rabbit costal chondrocytes in culture.

12-O-Tetradecanoylphorbol-13-acetate (TPA), a skin tumor-promoting phorbol ester, and teleocidin and aplysiatoxin, which are potent tumor promoters in mouse skin but are chemically unrelated to phorbol esters, induced change of cultured rabbit costal chondrocytes from a polygonal to a fibroblastic shape and inhibited glycosaminoglycan (GAG) synthesis and metachromatic matrix formation in these cells. The potencies of teleocidin and aplysiatoxin to inhibit GAG synthesis were almost the same as that of TPA. On the other hand, Tween 60 and cantharidin, weak mouse skin tumor promoters, phenobarbital, a liver tumor promoter, and saccharin, a bladder tumor promoter, had no effect on the morphology or GAG synthesis of cultured chondrocytes. Like TPA, teleocidin and aplysiatoxin increased DNA and RNA syntheses of chondrocytes. Parathyroid hormone (PTH) and dibutyryl cyclic AMP reversed the morphological and histochemical changes caused by a 4-day treatment with teleocidin or aplysiatoxin as well as with TPA, reversal being apparent after 2 days. PTH increased intracellular cyclic AMP after 2 min in chondrocytes pretreated with teleocidin or aplysiatoxin as well as with TPA. PTH also increased ornithine decarboxylase [ODC; EC 4.1.1.17] activity in these chondrocytes after 4 h. These results show that retention of responsiveness to PTH is a typical characteristic of chondrocytes dedifferentiated by treatment with TPA-type tumor promoters such as TPA, teleocidin and aplysiatoxin. The results also suggest that ODC induction mediated by elevation of cyclic AMP plays an important role in re-differentiation of teleocidin- and aplysiatoxin-treated chondrocytes.

Animals↗
PubMed1987

Resistance of human bronchial epithelial cells to teleocidin in a two-stage carcinogenesis experiment.

The tumor-promoting activity of teleocidin in two-stage carcinogenesis was tested using human bronchi grafted into athymic nude mice. On treatment with 7,12-dimethylbenz(a) anthracene (DMBA) plus teleocidin, no bronchial carcinomas were produced in 44 grafted human bronchi, but 8 spindle cell sarcomas developed in mouse tissues. Application of DMBA to grafted human bronchi produced only 3 spindle cell sarcomas in the tissues of 30 mice. Application of teleocidin did not produce any tumors in 24 grafts of bronchi obtained from heavy smokers. Thus, teleocidin had an effect on mouse tissues, but seemed to have no effect on human bronchial cells, although it is uncertain whether the grafted human bronchi were initiated by DMBA.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1987

Palytoxin: an extraordinarily potent stimulator of prostaglandin production and bone resorption in cultured mouse calvariae.

Palytoxin, a nonphorbol ester-type tumor promoter, stimulated the production of prostaglandin E2 (PGE2) and bone resorption in neonatal mouse calvariae in organ culture. The action of palytoxin on bone resorption occurred at extraordinarily low concentrations; enhanced resorption was regularly observed at 0.5 pg/ml, and the ED50 was 1-2 pg/ml (approximately 3 X 10(-13) M). Palytoxin-induced formation of PGE2 and bone resorption were inhibited completely by indomethacin (200 ng/ml). Concentrations of palytoxin above 10 pg/ml led to progressively decreasing enhancement of bone resorption; by 100-250 pg/ml no stimulation of resorption was observed despite continued high production of PGE2. Treatment with high concentrations of palytoxin (100 or 250 pg/ml) for 24-72 h inhibited cAMP accumulation stimulated by exogenous PGE2 or PTH and inhibited bone resorption induced by PGE2, PTH, or an analog of cAMP. Thus, palytoxin exhibited a biphasic dose-response curve for enhanced bone resorption, with stimulation at low concentrations (0.5-10 pg/ml) and toxic inhibition at high concentrations (greater than 50 pg/ml). Palytoxin is one of the most potent stimulators of bone resorption yet identified.

1-Methyl-3-isobutylxanthine↗
PubMed1987

Presence of tumor promoters in the seed oil of Jatropha curcas L. from Thailand.

The seed oil of Jatropha curcas L. was shown to contain skin tumor promoters in a two-stage mouse carcinogenesis experiment. By using the irritant test on mouse ear to monitor activity, the "irritant fraction" was partially purified from the methanol extract of the seed oil by column chromatographies on Florisil and Sephadex LH-20. The irritant fraction obtained induced ornithine decarboxylase in mouse skin and inhibited the specific binding of 3H-12-O-tetradecanoylphorbol-13-acetate to a particulate fraction of mouse skin. After initiation with 7,12-dimethylbenz[a]anthracene (DMBA), this "irritant fraction" induced tumors in the skin of 36% of the mice tested in 30 weeks. Tumor incidences in the groups treated with DMBA alone and "irritant fraction" alone were 7% and 13% in week 30, respectively. Since the skin of Thai people comes into direct contact with this seed oil, an epidemiological study on human skin cancer in Thailand is indicated.

9,10-Dimethyl-1,2-benzanthracene↗