phorbol-12-13-didecanoate and mezerein

In this paper, recent studies on the role of cell communication in cancer induction, particularly in two-stage carcinogenesis, were reviewed. Cell communication has been proposed to play an important role in cell growth and differentiation since its discovery. The recent finding that tumor promoters inhibit cell communication supports this possibility. The inhibition of cell communication by phorbol ester tumor promoters was also shown to correlate with enhancement of in vitro carcinogenesis in Balb/c 3T3 cells. This strongly suggests that the blocked cell communication may play a crucial causative role in the process of carcinogenesis. Accumulated evidence indicates that phorbol ester may induce blockage of cell communication through binding to its membrane receptor which is presumably Ca2+/phospholipid-dependent kinase. cAMP enhances cell communication and protects its inhibition by phorbol ester, presumably through activating cAMP-dependent kinase. This indicates the possibility that the two kinases may be key elements for physiological regulation of cell communication. It is proposed that the disturbance of the kinase systems by endogenous and exogenous factors may be responsible for the promotion phase of cancer induction. However, the true physiological role of cell communication in carcinogenesis remains to be demonstrated more directly. Especially, what kinds of molecules can pass through the gap junction and regulate cell functions in a cell community must be challenged in future. Some such molecules were speculatively described in this review.

Topics: Animals; Antigens, Surface; Calcium; Carcinogens; Carrier Proteins; Cell Adhesion Molecules; Cell Communication; Cell Division; Cell Line; Cell Transformation, Neoplastic; Cyclic AMP; Diterpenes; Humans; Intercellular Junctions; Mice; Mice, Inbred BALB C; Permeability; Phorbol Esters; Phospholipids; Protein Kinases; Sodium-Hydrogen Exchangers; Sodium-Potassium-Exchanging ATPase; Terpenes; Tetradecanoylphorbol Acetate

Recently, new daphnane, tigliane, and jatrophane diterpenoids have been isolated from various Euphorbiaceae species, of which some have been shown to be potent inhibitors of chikungunya virus (CHIKV) replication. To further explore this type of compound, the antiviral activity of a series of 29 commercially available natural diterpenoids was evaluated. Phorbol-12,13-didecanoate (11) proved to be the most potent inhibitor, with an EC50 value of 6.0 ± 0.9 nM and a selectivity index (SI) of 686, which is in line with the previously reported anti-CHIKV potency for the structurally related 12-O-tetradecanoylphorbol-13-acetate (13). Most of the other compounds exhibited low to moderate activity, including an ingenane-type diterpene ester, compound 28, with an EC50 value of 1.2 ± 0.1 μM and SI = 6.4. Diterpene compounds are known also to inhibit HIV replication, so the antiviral activities of compounds 1-29 were evaluated also against HIV-1 and HIV-2. Tigliane- (4β-hydroxyphorbol analogues 10, 11, 13, 15, 16, and 18) and ingenane-type (27 and 28) diterpene esters were shown to inhibit HIV replication in vitro at the nanomolar level. A Pearson analysis performed with the anti-CHIKV and anti-HIV data sets demonstrated a linear relationship, which supported the hypothesis made that PKC may be an important target in CHIKV replication.

Topics: Anti-HIV Agents; Antiviral Agents; Chikungunya virus; Diterpenes; DNA Replication; Esters; Euphorbiaceae; HIV Infections; HIV-1; HIV-2; Molecular Structure; Phorbol Esters; Tetradecanoylphorbol Acetate; Virus Replication

Tumor-promoting phorbol esters have been shown previously to either induce or repress the expression of numerous cellular genes, and this property is likely to be important for the in vitro and in vivo biological effects of these compounds. In this report, we demonstrate that phorbol 12-myristate 13-acetate induces the accumulation of basic fibroblast growth factor mRNA and protein in human dermal fibroblasts. In contrast, acidic fibroblast growth factor expression was unaffected by this compound. The enhancement of basic fibroblast growth factor gene expression by phorbol 12-myristate 13-acetate was blocked by the isoquinolinesulfonamide derivative H7, a potent inhibitor of protein kinase C. Two additional tumor promoters that bind to and activate protein kinase C, phorbol 12,13-didecanoate and mezerein, also increased basic fibroblast growth factor mRNA levels. Basic fibroblast growth factor is a mitogen for many cell types and can stimulate angiogenesis; thus, some tumor promoter-induced cellular responses may be mediated by this polypeptide.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Carcinogens; Cell Line; Diterpenes; Fibroblast Growth Factor 1; Fibroblast Growth Factor 2; Fibroblasts; Gene Expression; Isoquinolines; Phorbol Esters; Piperazines; RNA, Messenger; Skin; Sulfonamides; Terpenes; Tetradecanoylphorbol Acetate

Catecholamine secretions during continuous receptor stimulations by histamine, muscarine and bradykinin in the rat adrenal medulla commonly consisted of two phases, a transient initial secretion followed by a sustained secretion. On activating protein kinase C (PKC) by phorbol dibutyrate (PDBu), both phases of histamine-evoked secretion were inhibited whereas the initial phase alone was inhibited with muscarine. In contrast, bradykinin-evoked secretion as a whole was potentiated. Similar modes of modulations were exhibited when the secretions with these agonists were elicited in muscarine- or bradykinin-pretreated medullae in which PKC had been activated by endogenous processes. It is suggested that PKC may selectively affect the receptors or/and GTP-binding proteins to cause the differential effects on the secretory response in the rat adrenal medulla.

Topics: Adrenal Medulla; Animals; Bradykinin; Catecholamines; Diterpenes; Enzyme Activation; GTP-Binding Proteins; Histamine; In Vitro Techniques; Male; Muscarine; Phorbol 12,13-Dibutyrate; Phorbol Esters; Phosphatidylinositols; Protein Kinase C; Rats; Rats, Inbred Strains; Receptors, Cell Surface; Terpenes

Interleukin-1 (IL-1) stimulates proteoglycan degradation and prostaglandin E2 (PGE2) release and inhibits proteoglycan synthesis by cartilage in organ culture. Addition of the protein kinase C (PKC) activator, mezerein, resulted in the concentration-dependent inhibition of IL-1 activity on proteoglycan metabolism. Similar effects were seen with other compounds which stimulated PKC, such as teleocidin B4 and phorbol dibutyrate (PDBu), but not with a phorbol analog that is inactive in stimulating PKC. Simultaneous addition of the PKC antagonist, staurosporine, blocked the mezerein-induced inhibition of IL-1 activity on both proteoglycan degradation and synthesis in a concentration-related manner. In contrast to its inhibition of the effect of IL-1 on proteoglycan metabolism, mezerein did not block the release of PGE2 by cartilage in response to IL-1 but caused a synergistic stimulation of PGE2 release. Importantly, in cultures made deficient in PKC by prolonged incubation with PDBu, the effects of this PKC agonist on proteoglycan breakdown and PGE2 were blocked, while stimulation by IL-1 persisted. These data indicate that the effects of IL-1 on proteoglycan metabolism and prostaglandin production are mediated by an intracellular signal distinct from PKC and suggest that activation of PKC in chondrocytes may play a role in modulating the action of IL-1 on proteoglycan metabolism.

Topics: Alkaloids; Animals; Carcinogens; Cartilage; Cattle; Dinoprostone; Diterpenes; Down-Regulation; Enzyme Activation; Interleukin-1; Organ Culture Techniques; Phorbol 12,13-Dibutyrate; Phorbol Esters; Protein Kinase C; Proteoglycans; Staurosporine; Terpenes

The microfilament inhibitors cytochalasins B and D have been traditionally used to indirectly evaluate the requirement for actin in the uptake of invasive bacterial pathogens by nonprofessional phagocytes. Through their effects on microfilaments, both cytochalasins also impart profound alterations in cellular morphology and surface topology, which likely interfere with adherence. Alterations affecting adherence would complicate interpretation of the effect of cytochalasins on entry alone. As an alternative to cytochalasins, the effect of the tumor promoter phorbol myristate acetate (PMA) was examined for its effects on uptake of several invasive bacterial pathogens by HeLa 229 cells. In this communication, PMA was shown to induce a similar change in HeLa cell actin distribution, but, in contrast to cytochalasins B and D, PMA had no significant effect on gross cell morphology. The modified actin distribution was shown to reduce internalization of Bordetella pertussis, Yersinia pseudotuberculosis, Shigella flexneri, and Salmonella hadar in a dose-dependent manner at concentrations ranging from 1 to 1,000 ng/ml. The magnitude of reduction at a PMA concentration of 1,000 ng/ml was greater than the reduction elicited by cytochalasin B at 2.5 micrograms/ml but was less than that elicited by cytochalasin D at 2.5 micrograms/ml. Mezerein, a functional analog of PMA, caused a similar dose-dependent reduction in uptake of B. pertussis, whereas an inactive analog of PMA, alpha-4-phorbol-12,13-didecanoate was without effect on invasion. Binding studies further reveal that pretreatment of HeLa cells with PMA or mezerein did not significantly impair the ability of B. pertussis to adhere, in contrast to cytochalasins B and D, which caused a marked reduction in adherence.

Topics: Actins; Bacteria; Bacterial Adhesion; Bordetella pertussis; Cytochalasin B; Cytochalasin D; Cytoskeletal Proteins; Diterpenes; Fluorescent Dyes; HeLa Cells; Humans; Phorbol Esters; Terpenes; Tetradecanoylphorbol Acetate; Vinculin

Pulmonary endothelial extraction (E) of serotonin (5-HT) is decreased after exposure to phorbol myristate acetate (PMA) in intact (D. Riggs, A. M. Havill, B. R. Pitt, and C. N. Gillis. J. Appl. Physiol. 64: 2508-2516, 1988.) or perfused (C. L. Myers and B. R. Pitt. J. Appl. Physiol. 65: 377-384, 1988.) lungs. Although the mechanism underlying this change is unclear, we hypothesized, based on studies in cultured pulmonary arterial endothelial cells [C. L. Myers, J. S. Lazo, and B. R. Pitt. Am. J. Physiol. 258 (Lung Cell. Mol. Physiol. 1): L253-L258, 1989] that activation of protein kinase C (PKC) by PMA inhibits this uptake process. Accordingly, we studied the ability of staurosporine, a potent inhibitor of PKC, to block the acute effect of PMA on E(5-HT) by rat lungs perfused at 10 ml/min with Krebs-bicarbonate with 3% albumin. Pulmonary E(5-HT) was measured by indicator-dilution techniques using 5-[3H]HT and [14C]dextran. Both PMA and mezerein (nonphorbol PKC activator) caused dose-dependent decreases in E(5-HT) and increases in perfusion pressure (Ppa). Staurosporine, alone, did not significantly affect either E(5-HT) or Ppa; however, staurosporine (100 nM) completely inhibited the effects of PMA (100 nM) on the above parameters. Papaverine, a nonspecific vasodilator, was able to partially inhibit the pressor response to PMA while not affecting the inhibition of E(5-HT) by PMA, suggesting that the effect on E(5-HT) was not secondary to vasoconstriction (and derecruitment). These data support the hypothesis that activation of PKC leads to prominent pulmonary vascular effects including vasoconstriction and inhibition of endothelial cell 5-HT uptake.

Topics: Alkaloids; Animals; Carcinogens; Diterpenes; Enzyme Activation; Kinetics; Lung; Male; Papaverine; Perfusion; Phorbol Esters; Protein Kinase C; Pulmonary Circulation; Rats; Rats, Inbred Strains; Serotonin; Staurosporine; Terpenes; Tetradecanoylphorbol Acetate

The effects of TPA, PDD, PDB, PDA, or MEZ on epithelial and mesenchymal skin tumors induced by a s.c. injection of MCA were studied histologically. Group-I mice received only MCA. At 6 weeks after MCA injection, mice in groups II to VII received acetone, 1.8 nmol TPA, PDD, PDB, PDA, or 6.1 nmol MEZ respectively in 0.1 ml acetone twice weekly until tumor development. Alterations in skin tumor induction patterns were also studied in animals that had been exposed to TPA or acetone for 10 weeks prior to s.c. injection of MCA. Exposure of mouse skin to TPA before or after carcinogen administration increased 2- to 3.5-fold, the incidence of carcinoma and mixed tumors of epithelial and mesenchymal histogenesis. The average time of tumor induction decreased in mice treated with MCA + TPA and 100% of the test animals in the TPA + MCA group developed tumors. In contrast, TPA-related phorbol esters inhibited skin tumor development, particularly trichoepithelioma and fibrosarcoma and increased the average time of tumor induction.

Topics: Animals; Carcinoma; Diterpenes; Female; Mesenchymoma; Methylcholanthrene; Mice; Mice, Inbred Strains; Phorbol Esters; Skin Neoplasms; Terpenes; Tetradecanoylphorbol Acetate

Tumor promoters are known to induce reorganization of actin, morphological changes and enhancement of proliferation of epidermal cells in vivo. In this study, we have examined the effects of tumor promoters on these events to clarify the role played by the organization of actin filaments in the regulation of the shape and growth of colonies of epithelial cells in culture. Treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) caused a change in the shape of colonies of FL and Madin-Darby canine kidney (MDCK) cells within 6 hr. Changes in the shape of colonies were consistent with the morphological change of individual cells and the dissociation of groups of cells in the colonies. Addition of TPA also caused reorganization of actin filaments after 2 hr, and it caused enhancement of proliferation of FL and MDCK cells after 48 hr but did not cause any such changes in KB cells. However, the binding affinities of 4 beta-phorbol 12,13-dibutyrate (PDBu) to FL and MDCK cells were similar to that of PDBu to KB cells. Related tumor promoters such as phorbol 12,13 didecanoate (PDD) and mezerein caused effects similar to those caused by TPA. In contrast, nontumor promoting phorbol esters, such as 4 alpha-PDD and phorbol, had no effect. Cyclic AMP blocked the TPA-induced changes in FL and MDCK cells. These results suggest that TPA-induced reorganization of actin filaments which can be inhibited by cyclic AMP results in changes in the shape of colonies and enhancement of proliferation.

Topics: Actins; Animals; Cell Division; Cyclic AMP; Diterpenes; Dogs; Epithelial Cells; Epithelium; Kidney; Microscopy, Fluorescence; Phorbol 12,13-Dibutyrate; Phorbol Esters; Terpenes; Tetradecanoylphorbol Acetate; Time Factors

The tumor promoters mezerein and phorbol myristate acetate, and the phorbol diesters phorbol diacetate, phorbol dibenzoate, and phorbol didecanoate synergistically enhanced the production of lymphotoxin (LT) by phytohemagglutinin-stimulated human peripheral blood or tonsil and adenoid lymphocytes. LT production was elevated 2-20-fold, depending on such parameters as the nature of the promoter and dose, the lectin dose, and the lymphocyte source. The increased LT levels were primarily due to enhanced production of the alpha-light (alpha L) class of LT. The alpha L-class obtained from supernatants from promoter-synergized, lectin-stimulated lymphocyte cultures was compared with the alpha L from lectin-stimulated cultures. They were indistinguishable by molecular sieving on Ultrogel AcA44, were both composed primarily of the alpha 2-subclass as determined by ion-exchange chromatography on DEAE-Sepharose, and were immunologically cross-reactive. Lectin-affinity chromatography on concanavalin A-Sepharose and on lentil-lectin--Sepharose revealed that both alpha L preparations were dominated by components with affinity for these matrices. Affinity chromatography on alkyl sorbents also indicated very similar hydrophobicities. Chromatofocusing of the alpha L preparations demonstrated a comparable pattern of isoelectric points. Thus, the use of these drugs in lectin-stimulated human lymphocyte cultures provides an effective means for significantly increasing the yield of alpha L-LT suitable for biochemical purification and analysis, and biological testing in vitro.

Topics: Carcinogens; Chromatography, Affinity; Chromatography, Ion Exchange; Diterpenes; Humans; In Vitro Techniques; Lymphocytes; Lymphotoxin-alpha; Phorbol Esters; Phorbols; Phytohemagglutinins; Terpenes; Tetradecanoylphorbol Acetate

A tumour promoter, 12-O-tetradecanoyl phorbol-13-acetate (TPA), reversibly inhibits the onset and maintenance of cell-cell communication measured by electrophysiological method. We have now studied the mechanism by which TPA inhibits communication of human cells (FL) in culture. Using [3H]phorbol-12,13-dibutyrate [( 3H]PDBu), we found a class of specific, high-affinity, saturable binding sites in intact FL cells; they have a dissociation constant of 15.4 nM, and at saturation about 3 X 10(5) PDBu molecules were bound to each cell. The binding of [3H]PDBu to FL cells was inhibited by TPA, phorbol-12-13-didecanoate and mezerein, whereas phorbol and 4 alpha-phorbol-12-13-didecanoate had no effect. There is a close correlation between the ability of the former compounds to inhibit [3H]PDBu binding and their capacity to inhibit cell-cell communication. When FL cells are dispersed with EDTA and plated onto a culture dish, they start to couple electrically within 2 h; such cell coupling was not affected by the presence of cycloheximide or actinomycin D. TPA inhibits the formation of electrical cell coupling as well as its maintenance, even in the presence of cycloheximide; the recovery of cell-cell communication after the removal of TPA was not significantly affected by the addition of cycloheximide or actinomycin D. Taken together, these results suggest that TPA-mediated reversible inhibition of intercellular communication is mediated by specific binding of TPA to cellular receptors and that macromolecular synthesis is not necessary.

Topics: Binding Sites; Cell Communication; Cell Line; Cycloheximide; Dactinomycin; Diterpenes; Electrophysiology; Humans; Phorbol 12,13-Dibutyrate; Phorbol Esters; Phorbols; Protein Biosynthesis; RNA; Terpenes; Tetradecanoylphorbol Acetate