bryostatin-2 and bryostatin-1

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus showing a recent resurgence and rapid spread worldwide. While vaccines are under development, there are currently no therapies to treat this disease, except for over-the-counter (OTC) analgesics, which alleviate the devastating arthritic and arthralgic symptoms. To identify novel inhibitors of the virus, analogues of the natural product bryostatin 1, a clinical lead for the treatment of cancer, Alzheimer's disease, and HIV eradication, were investigated for in vitro antiviral activity and were found to be among the most potent inhibitors of CHIKV replication reported to date. Bryostatin-based therapeutic efforts and even recent anti-CHIKV strategies have centered on modulation of protein kinase C (PKC). Intriguingly, while the C ring of bryostatin primarily drives interactions with PKC, A- and B-ring functionality in these analogues has a significant effect on the observed cell-protective activity. Significantly, bryostatin 1 itself, a potent pan-PKC modulator, is inactive in these assays. These new findings indicate that the observed anti-CHIKV activity is not solely mediated by PKC modulation, suggesting possible as yet unidentified targets for CHIKV therapeutic intervention. The high potency and low toxicity of these bryologs make them promising new leads for the development of a CHIKV treatment.

Topics: Analgesics; Animals; Antiviral Agents; Bryostatins; Cell Death; Cell Line; Chikungunya Fever; Chikungunya virus; Chlorocebus aethiops; Cyclic AMP-Dependent Protein Kinases; Humans; Molecular Structure; Nonprescription Drugs; Structure-Activity Relationship; Virus Replication

An atom economic, selective, and highly practical two-metal one-pot synthesis of heterocycles has been developed that efficiently affords enantio- and diastereopure N- and O-heterocyclic products. Furthermore, use of a chiral catalyst in the two-metal procedure allows formation of all possible diastereomers, even those that are traditionally difficult to access via cyclization routes due to thermodynamics. Interestingly, the nature of the enantiodiscriminating event differs between the use of amine versus alcohol nucleophiles. The method also affords heterocyclic products that are synthetically useful intermediates. Through the Z-vinylsilane a variety of stereodefined trisubstituted olefin products can be accessed including several all-carbon motifs. Finally, the utility of these heterocyclic products in total synthesis is demonstrated through concise syntheses of a kainoid intermediate, a constituent of oil of rose, and the ring B portion of bryostatin, a potent chemotherapeutic.

Topics: Alkynes; Bryostatins; Catalysis; Cyclization; Furans; Heterocyclic Compounds; Macrolides; Palladium; Piperidines; Pyrans; Ruthenium; Stereoisomerism

Bryostatins, macrocyclic lactones from the marine bryozoan Bugula neritina, are potent antineoplastic agents and multi-potential stimulators of immune cells. We have examined the effects of bryostatins on mediator release from human basophilic leukocytes and human tissue mast cells. Bryostatins 1, 2, and 5 (10 to 3,000 nmol/L) induced histamine secretion from purified and unpurified peripheral blood basophils, whereas they caused no release of peptide-leukotriene C4 from these cells. The rate of histamine release caused by bryostatin 1 was slower than that caused by anti-IgE (t1/2 +/- SEM = 38.2 +/- 4.7 minutes v 8.9 +/- 0.2 minutes; P < .01), whereas the temperature dependence was similar (optimum release at 37 degrees C, approximately 30% less at 30 degrees C, and no release at 22 degrees C or 4 degrees C). The addition of increasing concentrations of extracellular Ca2+ to the medium caused histamine release in the presence of bryostatins. Subeffective concentrations of bryostatins and anti-IgE produced a synergistic effect on histamine release from basophils. Staurosporine, chelerythrine, and calphostin C (0.1 to 10 nmol/L), which are protein kinase C inhibitors, inhibited the histamine secretion activated by bryostatin 1 and tetradecanoylphorbol-acetate (TPA). Preincubation with granulocyte-monocyte colony-stimulating factor (GM-CSF; 1 and 5 nmol/L) and interleukin-3 (IL-3; 10 ng/mL) potentiated the activation of human basophils induced by bryostatin 1. Neither bryostatin 1 nor bryostatin 2 induced the release of histamine from mast cells isolated from human lung or skin tissues. However, brief (10 minutes) preincubation with bryostatin 1 (3 to 300 nmol/L) potently inhibited the histamine secretion induced by anti-IgE from skin or lung mast cells. Bryostatin 1 was a more potent (by approximately 30 times) inhibitor of IgE-mediated histamine release than was TPA. The heterogeneous effects exerted by bryostatins on human basophils and mast cells can be of interest for those designing therapeutic trials using these agents.

Topics: Antibodies, Anti-Idiotypic; Basophils; Bryostatins; Granulocyte-Macrophage Colony-Stimulating Factor; Histamine Release; Interleukin-3; Interleukin-5; Lactones; Leukotriene C4; Lung; Macrolides; Mast Cells; Protein Kinase C; Skin; Tetradecanoylphorbol Acetate

The phorbol ester tumor promoter, 12-O-tetradecanoylphorbol-13-acetate [TPA) or phorbol 12-myristate 13-acetate), directly activates the calcium- and phospholipid-dependent protein kinase C (protein kinase C), which, in turn, generates a number of cellular responses. The bryostatins, a family of macrocyclic lactones isolated from marine bryozoans, also bind to and active protein kinase C. However, they differ from TPA in the selectivity of their responses in that they behave either as agonists or antagonists of protein kinase C actions. We used several bryostatins and TPA to examine the role of protein kinase C in the regulation of GH4C1 rat pituitary tumor cell proliferation. TPA inhibited [3H]thymidine incorporation in GH4 cells in a stereoselective and concentration-dependent manner. Examination of cell cycle distribution by flow cytometry revealed that TPA decreased the percentage of cells in S-phase and proportionally increased the percentage of G1-phase cells. Bryostatin 1 alone did not affect cell proliferation, but prevented the TPA inhibition of cell proliferation. Bryostatin 1 treatment from 30 min to 6 h after TPA treatment also prevented the growth-inhibitory action of TPA, suggesting that prolonged stimulation of protein kinase C is necessary for growth inhibition. Both bryostatin 1 and TPA down-regulated protein kinase C, indicating that down regulation of the enzyme cannot account for the growth inhibitory action of TPA. Bryostatin 2, which differs from bryostatin 1 by a hydroxyl substitution for the acetyl group at the C-7 carbon of the macrocyclic lactone ring (R1), inhibited cell proliferation and did not reduce the growth-inhibitory action of TPA. Bryostatins 3 and 8 (each of which has an ester group in the R1 position, yet contains other structural modifications) are antagonists for TPA inhibition of GH4 cell proliferation like bryostatin 1. We next examined the effect of bryostatins 3 and 8 on cell-substratum adhesion, a cellular response observed after GH4 cells are treated with growth-inhibitory agents. Bryostatin 8 (like bryostatin 1) did not enhance cell-substratum adhesion and blocked the action of TPA. In contrast, bryostatin 3 enhanced cell-substratum adhesion. Because bryostatin 3 blocked TPA inhibition of cell proliferation, yet did not block TPA-enhanced cell-substratum adhesion, these responses are not interdependent. We next examined the effect of bryostatin on other growth-inhibitory agents for GH4 cells. Bryostatin 8 blo

Topics: Animals; Antineoplastic Agents; Bryostatins; Cell Adhesion; Cell Cycle; Cell Division; Cell Line; DNA Replication; Epidermal Growth Factor; Kinetics; Lactones; Macrolides; Pituitary Neoplasms; Protein Kinase C; Rats; Structure-Activity Relationship; Tetradecanoylphorbol Acetate; Thymidine; Thyrotropin-Releasing Hormone

SH-SY5Y human neuroblastoma cells can be induced to differentiate to mature ganglion cells when treated with the phorbol ester tetradecanoylphorbol acetate (TPA). Bryostatins are a new class of protein kinase C activators that are structurally unrelated to phorbol esters. This paper describes the effects of bryostatins 1 and 2 on morphological and functional differentiation of SH-SY5Y cells. Both bryostatins induced a rapid translocation of protein kinase C from the cytosol to the membrane fraction. Within 24 h, the bryostatins had caused a nearly complete down-regulation of the enzyme. Bryostatin 1 competed for [3H]phorbol-12,13-dibutyrate binding in intact cells with potency equal to that of TPA, in contrast to bryostatin 2, which exhibited a Ki value 1 order of magnitude higher than those of the two other agents. Bryostatins induced morphological changes similar to those induced by TPA. These changes were, however, only transient, occurring during the first 6 h of incubation in the presence of these compounds. By 72 h, the cells had acquired a morphology typical of untreated cells and, although a wide range of bryostatin concentrations were used, morphological changes characteristic of differentiated SH-SY5Y cells were not detected at 72 h. Bryostatin 1 at 5 nM and bryostatin 2 at 100 nM inhibited DNA synthesis, as measured by incorporation of [3H]thymidine by SH-SY5Y cells, although to a significantly lesser degree than TPA. In spite of the fact that bryostatins failed to induce morphological differentiation in SH-SY5Y cells, these compounds down-regulated c-myc mRNA expression. Bryostatins were significantly weaker in stimulating noradrenaline synthesis, compared with TPA, and high concentrations of these agents blocked the effect of the phorbol ester when they were included together with TPA. When SH-SY5Y cells were incubated in the presence of high concentrations of bryostatins, a decreased sensitivity of cells to muscarinic agonist-induced increases in cytosolic free Ca2+ was observed. The results suggest that down-regulation of protein kinase C activity and c-myc mRNA expression do not necessarily correlate with the morphological differentiation of SH-SY5Y cells.

Topics: Antineoplastic Agents; Bryostatins; DNA, Neoplasm; Down-Regulation; Enzyme Induction; Humans; Lactones; Macrolides; Neuroblastoma; Norepinephrine; Oncogenes; Phorbol 12,13-Dibutyrate; Protein Kinase C; Receptors, Muscarinic; RNA, Messenger; RNA, Neoplasm; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured

This study examines the action of phorbol 12-myristate 13-acetate (PMA) on the synthesis of cholesterol sulfate in cultured normal and transformed human epidermal keratinocytes and assesses the antagonistic effects by retinoids and bryostatins on PMA action in relation to the multistep program of squamous differentiation. Treatment of normal human epidermal keratinocytes (NHEK) with PMA induces terminal cell division (irreversible growth-arrest) and causes a time- and dose-dependent increase in the incorporation of Na2(35)SO4 into cholesterol sulfate, a marker for squamous cell differentiation. This stimulation in sulfate incorporation appears specific for cholesterol sulfate and is due to increased levels of cholesterol sulfotransferase activity. The increase in cholesterol sulfate accumulation parallels the increase in transglutaminase type I, another marker for squamous differentiation. Several transformed NHEK cell lines do not exhibit increased levels of cholesterol sulfate and transglutaminase type I activity after PMA treatment, indicating that they acquired defects in the regulation of squamous differentiation. Bryostatins 1 and 2, and several diacylglycerol analogues neither inhibit cell proliferation nor increase cholesterol sulfate synthesis or transglutaminase activity, indicating that these agents do not induce terminal differentiation. In contrast, the bryostatins block the increase in cholesterol sulfate and transglutaminase activity as well as the commitment to terminal cell division by PMA. Bryostatin 1 inhibits the commitment to terminal cell division and the accumulation of cholesterol sulfate significantly even when added 8 h after PMA administration. Retinoids inhibit cholesterol sulfate accumulation and the increase in transglutaminase activity by PMA but do not affect the commitment to terminal cell division. In summary, phorbol esters induce in NHEK cells a program of squamous differentiation. This process of differentiation consists of the commitment to terminal cell division and expression of a squamous phenotype. Expression of this phenotype is accompanied by an accumulation of cholesterol sulfate and increased cholesterol sulfotransferase activity. Bryostatins 1 and 2 and retinoic acid affect this differentiation process at different stages.

Topics: Bryostatins; Cell Differentiation; Cell Line, Transformed; Cholesterol Esters; Diglycerides; Epidermal Cells; Humans; Keratins; Lactones; Macrolides; Tetradecanoylphorbol Acetate; Tretinoin

Previous studies have shown that normal human tracheobronchial epithelial (HBE) cells undergo squamous differentiation upon treatment with phorbol 12-myristate 13-acetate (PMA). In this study, we report that induction of this differentiation program is accompanied by an increase in the accumulation of cholesterol sulfate and in transglutaminase type I activity, two markers of squamous differentiation. Several carcinoma cell lines did not exhibit an increase in these differentiation markers after PMA-treatment and appear to have acquired a defect in the mechanism that triggers differentiation. The diacylglycerol analogue, didecanoylglycerol (diC10), was also able to induce squamous differentiation. Bryostatin 1, another activator of protein kinase C, did not induce terminal cell division or increase cholesterol sulfate accumulation or transglutaminase type I activity. Bryostatin 1 not only failed to inhibit cell proliferation and to induce differentiation but antagonized the PMA- and diC10-induced commitment to terminal differentiation. The bryostatin blocked both the PMA-induced terminal cell division as well as the expression of the two differentiation markers. Retinoids were found not to affect the PMA-induced commitment to terminal cell division but did inhibit the expression of the differentiated phenotype. Our results indicate that the bryostatins and retinoids affect the multistep process of squamous differentiation in tracheobronchial epithelial cells at two different stages.

Topics: Antineoplastic Agents; Bronchi; Bryostatins; Cell Differentiation; Cells, Cultured; Diglycerides; Epithelial Cells; Epithelium; Glycerides; Humans; Kinetics; Lactones; Macrolides; Organ Culture Techniques; Sulfates; Tetradecanoylphorbol Acetate; Trachea; Transglutaminases; Tretinoin

Activators of protein kinase C (PKC), such as 12-O-tetradecanoylphorbol-13-acetate (TPA) and bryostatins 1 and 2, inhibit the growth of A549 cells. At high concentrations the bryostatins do not affect cell growth. Here the hypothesis has been tested that modulation of A549 cell growth is the consequence of agent-induced changes in location or extent of cellular PKC activity. PKC activity was measured after semi-purification with nondenaturing polyacrylamide gel electrophoresis in the cytosol and the particulate fraction of A549 cells. When cells were exposed to TPA or mezerein, PKC activity underwent rapid and concentration-dependent translocation from the cytosol to the membrane. TPA at 0.1 microM or mezerein at 1 microM caused almost complete translocation within 30 min. Incubation with bryostatins 1 or 2 also led to enzyme translocation, which was, however, much weaker than that observed with the tumor promoters. Neither 4 alpha-phorboldidecanoate nor the synthetic diacylglycerols 1,2-sn-dioctanoylglycerol or 1-oleoyl-2-acetyl-sn-glycerol mimicked TPA in this way. Exposure of cells to TPA or the bryostatins for longer than 30 min caused the gradual disappearance of total cellular PKC activity. PKC downregulation was concentration dependent and complete after 24 h. A549 cells which had acquired temporary resistance toward the growth-arresting potential of TPA were completely devoid of any measurable PKC activity. The bryostatins were potent inhibitors of the binding of [3H]phorbol-12,13-dibutyrate to its receptors in intact cells, and the inhibition was dependent on bryostatin concentration. The results support the contention that PKC is involved in the mediation of growth inhibition caused by TPA or the bryostatins. However, the relationship between growth arrest and PKC translocation or downregulation seems to be a complex one.

Topics: Antineoplastic Agents; Bryostatins; Cell Line; Cytosol; Humans; Kinetics; Lactones; Lung Neoplasms; Macrolides; Membranes; Protein Kinase C; Tetradecanoylphorbol Acetate

Phorbol esters such as 12-O-tetradecanoylphorbol-13-acetate (TPA) inhibit the growth of A549 human lung carcinoma cells at non-toxic concentrations, whereas 1-oleoyl-2-acetylglycerol and 1,2-dioctanoylglycerol, synthetic analogues of the physiological ligands of protein kinase C (PKC), do not. Experiments were conducted to test the hypothesis that other activators of PKC are capable of interfering with A549 cell growth. The non-phorboid tumour promotor mezerein mimicked the growth-inhibitory effect of TPA in that it arrested growth for 5 days, after which cells proliferated again in the continued presence of the agent. TPA was 20 times more potent as a growth inhibitor than was mezerein. Bryostatin 1 at 10 nM and bryostatin 2 at 100 nM also arrested A549 cell growth and inhibited DNA replication as measured by incorporation of [methyl-3H]-thymidine into cells. Inhibition of DNA synthesis to between 90 and 75% of control values developed during the first hour of incubation of the cells with TPA, mezerein or the bryostatins. The extent of inhibition changed little during the subsequent 5 hr of incubation, after which it increased further to reach maximal values within 12 hr. At concentrations above those which caused maximal growth inhibition, the bryostatins abolished both their own inhibition of DNA synthesis and the anti-replicative effect of TPA and mezerein. The results show that activators of PKC other than phorbol esters are capable of inhibiting the growth of A549 cells. The bryostatins not only interfere with A549 cell growth but can also counter the growth-inhibitory effect of PKC activators, presumably via interaction with a target separate from the phorbol ester receptor site.

Topics: Animals; Bryostatins; Cell Division; Diterpenes; DNA Replication; Enzyme Activation; Lactones; Lung Neoplasms; Macrolides; Protein Kinase C; Terpenes; Tetradecanoylphorbol Acetate; Time Factors

The bryostatins, a group of macrocyclic lactones isolated on the basis of their antineoplastic activity, protein kinase C in vitro and block phorbol ester binding to this enzyme. In some cellular systems, bryostatins mimic phorbol ester action. In other systems, however, the bryostatins display only marginal agonistic action and, instead, inhibit phorbol ester-induced responses. At least in primary mouse epidermal cells, a transient duration of action of bryostatin 1 could rationalize these differences. To determine whether this model of transient activation could explain the dual actions of bryostatin 1 in other cell systems, we have examined the effects of bryostatin 1 on short-term responses in C3H 10T1/2 mouse fibroblasts. Even at very short exposures (30 min), bryostatin 1 blocked phorbol ester-induced arachidonic acid metabolite release and induced only minimal release when assayed alone. In contrast, epidermal growth factor binding was markedly and rapidly decreased in bryostatin 1-treated C3H 10T1/2 cells, and this decrease showed only limited reversal 16 h after initial exposure. Bryostatins 2, 3, 4, 10, and several of their derivatives caused variable arachidonic acid metabolite release (10 to 60% of phorbol ester control) and correspondingly variable inhibition of phorbol ester action. Our findings on arachidonic acid metabolite release argue against transient activation of the protein kinase C pathway as the sole explanation of bryostatin 1 action. They indicate, moreover, differences in the structure-activity relations of the bryostatins for the phorbol ester-mimetic and phorbol ester-inhibitory actions.

Topics: Animals; Arachidonic Acids; Bryostatins; Calcimycin; Calcium; Cell Line; Epidermal Growth Factor; ErbB Receptors; Lactones; Macrolides; Mice; Phorbol Esters; Protein Kinase C; Structure-Activity Relationship; Time Factors

Low concentrations of the protein kinase C activators, bryostatins 1 and 2 synergized with recombinant B cell stimulatory factor-1 in triggering differentiation (granule enzyme expression) and cytotoxic T lymphocyte (CTL) development in naive, resting lymph node T cells. Bryostatin greatly enhances efficiency of recombinant interleukin-2 in triggering development of in vivo primed CTL during in vitro incubation, thereby providing experimental evidence for the efficacious use of lower concentrations of recombinant interleukin-2 for in vivo tumor rejection studies. Both bryostatins 1 and 2 were able to trigger cytotoxicity of CTL clones against antigen-nonbearing target cells and inhibited CTL cytotoxicity against Ag-specific target cells. Bryostatin 1 and 2 synergize with Ca2+ ionophores in triggering the exocytosis of cytolytic granules from CTL at very low concentrations. In view of the lack of tumor promoting activity of the bryostatins, the possible use of these agents in vivo is discussed.

Topics: Adjuvants, Immunologic; Animals; Bryostatins; Cytotoxicity, Immunologic; Enzyme Activation; Immunosuppressive Agents; Lactones; Macrolides; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Inbred DBA; Protein Kinase C; Spleen; T-Lymphocytes, Cytotoxic