cAMP phosphodiesterase activity evaluation in human carcinoma of salivary glands

The aim of this study was to evaluate differences of cAMP-PDE activity in human salivary glands, between a control group and some different benign tumours groups and, where present, with 2 malignant tumors groups. The value of the enzymatic activity in the groups analysed was 50% lower than control samples. The differences between the control group (82 +/- 7.9 nmols/mg of protein) and the 3 pathologic groups (Benign A: 44 +/- 6.2; Malignant A: 40 +/- 16; Benign B: 40 +/- 14.2; Malign A: 9.1; Benign C: 22 nmols/mg of protein) are statistically significant.     

Effect of cold exposure on liver and muscle cAMP content and cAMP phosphodiesterase activity

Adenosine 3',5'-cyclic monophosphate (cAMP) concentration and 3',5'-cyclic-nucleotide phosphodiesterase (PDE) activity were measured in skeletal muscle, heart, and liver of rats exposed to 1, 3, 5, and 7 days of cold. Cyclic nucleotide concentration increased in fast-twitch red muscle at the same time that PDE activity was decreasing. Nucleotide concentration and enzyme activity of slow-twitch red muscle were not altered by the cold exposure. The PDE activity of fast-twitch white muscle was elevated approximately 50% above control after 1 and 3 days of cold exposure. By the 5th day in the cold, white muscle PDE activity had returned to control levels and remained there through the 7th day of experimentation. cAMP concentration in hearts of cold-exposed rats was significantly (P less than 0.01) elevated above control at all time points measured. Myocardial PDE activity was elevated above control (P less than 0.05) at 1 and 3 days of cold exposure but returned to control levels by the 5th day in the cold. Hepatic cAMP and PDE activity were elevated above control at all time points analyzed. These data suggest that changes in cyclic nucleotide metabolism play a role in attaining homeostasis during acute cold exposure.     

Effect of interferons on the activity of human tumor degeneration factor (TDF)

KB cells were cultivated in the well with tumor-degenerating factor (TDF) and the natural and recombinant interferons. TDF alone induced the degenerative changes of the KB cells and formed the cell-free area, but the interferons alone did not induce the changes and did not form the cell-free area. When KB cells were cultivated with TDF and natural interferons (HuIFN-alpha, -beta and -gamma), the cell-free area was enlarged. Particularly, HuIFN-gamma enhanced the TDF activity most strongly. The recombinant interferons (HuIFN-alpha, -beta and -gamma) also augmented in the same ways as the natural interferons.     

Effect of a highly dispersed zinc powder on the cAMP phosphodiesterase activity in mouse thymocytes

The inhibition of cAMP phosphodiesterase activity by high dispersed zinc powder and zinc ions has been found in vitro experiments. The enzyme activity dependence on concentration of inhibitors is characterized by sigmoidal curve with Hill coefficients 1,8-2,1 and 1,2-1,3 correspondingly that may indicate the presence of positive cooperativity on inhibitor in enzyme. Magnesium ions influence the inhibited effect of zinc ions and the preparation of high dispersed zinc powder.     

The effect of oncomodulin on cAMP phosphodiesterase activity

Oncomodulin was purified from Morris rat hepatoma according to the procedure of Durkin, J.P., Brewer, L.M. and MacManus, J.P. (1983) Cancer Res. 43, 5390-5394. The preparation, in general, had the properties and amino acid composition of the material which they described. However, we were unable to confirm the reported stimulation of cyclic nucleotide phosphodiesterase under conditions where calmodulin gave the usual stimulation.     

Phosphorylation results in activation of a cAMP phosphodiesterase in human platelets

Agents such as prostaglandins E1 and I2 which elevate cAMP levels in platelets also increase cAMP phosphodiesterase activity. Since much of the cAMP phosphodiesterase activity in human platelets is due to the cGMP-inhibited isozyme (Macphee, C. H., Harrison, S. A., and Beavo, J. A. (1986) Proc. Natl. Acad. Sci. U. S. A. 83, 6600-6663), we examined the regulation of this isozyme by prostaglandins E1 and I2 in intact platelets. Because this isozyme is a minor component of platelet protein, normally requiring several thousand-fold purification to achieve homogeneity, a specific monoclonal antibody (CGI-5) was utilized to identify and isolate the cGMP-inhibited phosphodiesterase activity. Treatment of intact platelets with the prostaglandins promoted an increase in the phosphorylation state of the cGMP-inhibited phosphodiesterase and a corresponding increase in phosphodiesterase activity. The effect on activity and phosphorylation of the cGMP-inhibited phosphodiesterase was observed within 2 min after intact platelets were exposed to the prostaglandins. The half-maximal effective dose for prostaglandin I2 (10 nM) was approximately 10-fold lower than that for prostaglandin E1. The phosphorylated, cGMP-inhibited isozyme migrated as a 110-kDa peptide following sodium dodecyl sulfate gel electrophoresis. Direct in vitro phosphorylation of the platelet cGMP-inhibited phosphodiesterase by the catalytic subunit of cAMP-dependent protein kinase caused a similar increase in phosphodiesterase activity. Treatment with PKI peptide, a specific inhibitor of cAMP-dependent protein kinase, blocked the phosphorylation and the effect on activity. Taken together, the data strongly suggest that the effects of prostaglandins E1 and I2 on platelet phosphodiesterase activity are mediated by a direct cAMP-dependent protein kinase-catalyzed phosphorylation of the cGMP-inhibited phosphodiesterase isozyme.     

Changes in cAMP phosphodiesterase activity and cAMP concentration during mouse preimplantation development.

Cyclic nucleotide phosphodiesterase (PDE) activity and cAMP amounts were measured in mouse preimplantation embryos at the 1-cell, 2-cell, 8-cell/morula, and mid-blastocyst stages. PDE activity remained constant between the 1-cell and 2-cell stages. It decreased by the 8-cell stage and continued to decrease by the mid blastocyst stage to about 14% of the 1- and 2-cell values. By contrast, cAMP amounts remained essentially constant at 0.05 fmole/embryo (0.3 microM) from the 1-cell to the blastocyst stage and increased to 0.175 fmole in the fully expanded blastocyst that was close to hatching. Measurements of embryo volume indicated that intracellular volume remained essentially constant up to the blastocyst stage. The morphological changes in cell shape that accompany differentiation of the trophectoderm and that are coupled with blastocoel expansion decreased the intracellular volume. This decrease resulted in an increase in the cAMP concentration to about 0.4 microM by the mid-blastocyst stage. Previous studies indicate that either cAMP or TGF-alpha/EGF can stimulate the rate of blastocoel expansion. Although TGF-alpha/EGF can elevate cAMP levels in other cell types, TGF-alpha, at a concentration that maximally stimulates the rate of blastocoel expansion, did not elevate cAMP in blastocysts. Thus, it was unlikely that elevation of cAMP is the mechanism by which TGF-alpha stimulates the rate of blastocoel expansion.     

Effect of streptozotocin-induced diabetes on phosphodiesterase activity in rat luteal cells

The present studies were carried out to characterize the cAMP-phosphodiesterase enzyme (PDE) in luteal cells recovered from pseudopregnant rats with streptozotocin-induced diabetes. A significant increase in the specific activity of the enzyme was detected in luteal cells from diabetic rats (Group D) with respect to control rats (Group C). This increase could not be prevented by insulin therapy (Group I). Luteal cells from Groups C and D rats responded in vitro to insulin by increasing their PDE activity (% of stimulus of specific activity: C = 75%, D = 110%). However, in cells isolated from Group I, the hormone caused an inhibition of PDE activity (% of inhibition of specific activity: 48%). When cytosolic fractions from Groups C, D, and I were submitted to ion exchange chromatography, two PDE activity peaks could be observed and the activity of the different fractions was increased in the presence of Ca²⁺ and calmodulin. Nevertheless, the Ca²⁺—calmodulin effect was much lower in the extracts from Groups D and I than for controls. Kinetic studies of luteal PDE showed nonlinear Lineweaver-Burk graphs with two apparent ATP hydrolysis sites. Similar K_m values were found for PDE from groups C, D, and I, whereas the V_max2 for the enzyme was higher in Groups D and I. The endogenous concentration of cAMP, measured by RIA, showed no significant differences among Groups C, D, and I. On the basis of these results, we conclude that the specific activity of PDE is significantly increased in luteal cells from streptozotocin-induced diabetic animals, which could explain the previously described reduction in LH-stimulated progesterone production by luteal cells in diabetic rats. © 1996 Wiley-Liss, Inc.     

Cyclase and phosphodiesterase activity on pre-T lymphoid human cells, treated with dimethyl sulfoxide (DMSO)

Our aim is to estimate the role of the DMSO on pre-T lymphoid human cells, we have searched the cyclase and phosphodiesterase activity. We have studied the GTPspecific cyclase (G-Case) and have observed an analogous course to that one of the cAMP-PDE, where, in both cases, the differences ratio is approximately 5. For the cyclase activity values it has been found that cAMP neo formed is undeterminable in these cells, for the controls and the treated samples.     

Calcium-independent growth of human ovarian carcinoma cells

Evidence in the literature suggests that cancer cell growth in vitro is generally not sensitive to external calcium. A human ovarian carcinoma cell line (SKOV3) retained 60% of its normal growth in Dulbecco modified Eagle's medium (DME) when the calcium concentration was reduced from 3 mM to 10 microM. Chinese hamster ovary cells (CHO) were growth-arrested in media containing less than 500 microM calcium. In low-calcium (10 microM) DME, 10 microM of a calmodulin antagonist W7 inhibited the growth of SKOV3 cells by more than 90%, while 100 microM of its inactive analog W5 was mildly inhibitory (20%). The growth inhibition by W7 was antagonized by increasing calcium concentrations in the culture media, while the inhibition by W5 was calcium-independent. The phorbol ester TPA was also effective in antagonizing W7's growth inhibition in low-calcium DME, suggesting that the W7 effect is mediated via protein kinase C inhibition. SKOV3 total cellular protein kinase C activity was 1.6 times higher than CHO cells when incubated in normal DME. When incubated in low-calcium DME, a large drop in protein kinase C activity in the CHO cells was observed while the enzyme activity was unchanged in the SKOV3 cells. Our data suggest that these human ovarian tumor cells have altered cellular calcium regulatory processes associated with the defective down-regulation of protein kinase C. This defect may confer these cells the ability to proliferate independently of the external calcium concentration. Targeting the cellular signal transduction components may be useful in cancer chemotherapy.     

Evolution of cAMP phosphodiesterase activity in cultured myometrial cells: Effects of steroids and of successive subcultures

Cyclic AMP phosphodiesterase (PDE) activity was characterized in culture of ewe myometrial cells and its sensitivity to steroid hormones was tested. Cultured myometrial cells were maintained from the first to the 20th subculture in the presence of 2% of serum in a medium supplemented with 1 μM of insulin. It was found that myometrial cells possess a PDE activity with atypical kinetics. The nonlinear responses in Lineweaver-Burke plots suggest the presence of high- and low-affinity PDE activities. In cell culture, apparent Km values were similar to those obtained from the original myometrium. Vmax values increased with successive subcultures, revealing an increase in the capacity of the cells to degrade cAMP; in parallel, the growth rate decreased. The PDE specific activity in cultured myometrial cells was inhibited by estra-diol or progesterone. When added together, no synergistic effect was obtained. The rate of inhibition for both steroids was constant during successive passages for both low- and high-affinity conditions. Results obtained in myometrial cell long-term culture were compatible with reports in other species in vivo. Considering the role of cAMP in the regulation of uterine functions, subcultured myometrial cells provided us a useful experimental system with which to study the cAMP metabolism process.     

Effect of water activity on the growth and the production of cAMP phosphodiesterase inhibitor with Bacillus subtilis

Summary Bacillus subtilis C-756, a producer of cyclic adenosine 3,5-monophosphate (cAMP) phosphodiesterase inhibitor, was cultured in media adjusted to various water activity (a_w) levels by addition of three different solutes, sodium chloride, ethylene glycol and polyethylene glycol 1540 (PEG). B. subtilis C-756 can grow, however weakly, at a_w levels of 0.94 and 0.93.The presence of all three solutes in the medium inhibited growth, cell mass as well as inhibitor production. PEG was found to be most inhibitory, but the effect can not be explained in terms of a decreased water activity in the medium. It is rather the increased viscosity of the medium, which results in a decreased oxygen transfer rate.Comparing ethylene glycol and sodium chloride, the presence of ethylene glycol appears to favour inhibitor production, whereas sodium chloride favours cell mass production.     

Effect of dicarboxylic (C6 and C9) acids on a human squamous carcinoma cell line in culture

In tissue culture, azelaic acid (C9) has been shown to have an anti-proliferative and cytotoxic effect on human and murine malignant melanocytes, with inhibition of mitochondrial oxido-reductase enzymes and DNA synthesis, and damage to mitochondria. Recent reports of effects on differentiation of normal keratocytes have led to the present study of its effects on a squamous carcinoma cell line. Cells were exposed to single doses of disodium salts of azelaic (C9(2)Na) and adipic (C6(2)Na) acids at concentrations of 10(-2)M and 5 x 10(-2)M for 48 hrs. Only C9(2)Na at 5 x 10(-2) M for 4 hrs., and longer, significantly affected proliferation, and the cells exhibited massive swelling of mitochondria with loss of cristae. The results further confirm the probable value of azelaic acid as a general anti-tumoral agent rather than a specifically melanocytotoxic one. They could justify clinical studies on the effect of topical azelaic acid therapy on squamous cell carcinoma in vivo.     

Modulation of the antigenic phenotype of human breast carcinoma cells by modifiers of protein kinase C activity and recombinant human interferons

Summary In the present study we have analyzed the effect of a synthetic protein kinase C (PKC) activator 3-(N-acetylamino)-5-(N-decyl-N-methylamino)-benzyl alcohol (ADMB) and the natural PKC-activating tumor-promoting agents 12-O-tetradecanoylphorbol 13-acetate (TPA) and mezerein on the antigenic phenotype of T47D human breast carcinoma cells. All three agents increased the surface expression of the tumor-associated antigen BCA 225 and various cellular antigens, including HLA class II antigens, intercellular adhesion molecule 1 (ICAM-1) and c-erbB-2. Expression of the same antigens was also upregulated to various extents in T47D cells by recombinant fibroblast (IFN) and immune (IFN) interferon. Shedding of BCA 225 from T47D cells was induced by TPA, mezerein, IFN and IFN, whereas ADMB did not display this activity. The ability of ADMB, TPA and mezerein to modulate the antigenic phenotype of T47D cells appears to involve a PKC-mediated pathway, since the PKC inhibitor, H-7, eliminates antigenic modulation. In contrast, the ability of IFN and IFN to enhance the synthesis, expression and shedding of BCA 225, as well as to enhance HLA class II antigens, c-erbB-2 and ICAM-1 expression, was either unchanged or modestly reduced by simultaneous exposure to H-7. Analysis of steady-state mRNA levels for HLA class I antigens, HLA class II-DR antigen, ICAM-1 and c-erbB-2 indicated that the ability of H-7 to inhibit expression of these antigens in TPA-, mezerein- and ADMB-treated cells was not a consequence of a reduction in the steady-state levels of mRNAs for these antigens. The results of the present investigation indicate that the biochemical pathways mediating enhanced antigenic expression in T47D cells induced by TPA, mezerein and the synthetic PKC activator ADMB are different from those induced by recombinant interferons. Furthermore, up-regulation of antigenic expression in T47D cells can occur by a PKC-dependent or a PKC-independent pathway.     

Sensitivity of influenza a viruses to human interferons in human diploid cells

Abstract The sensitivity of influenza virus to the action of natural human interferon (IFN)-α+β and -γ, and to the action of highly purified recombinant HuIFN-αB, -αD, and -αF, has been investigated. A plaque assay for the fowl-plague strain of influenza A virus has been established using human embryonic foreskin (HEF) cells. The sensitivity of influenza virus to all IFNs tested in this assay was comparable to that shown by vesicular stomatitis virus (VSV) which was taken as the reference standard. The high sensitivity to IFN action found for the fowl-plague strain was confirmed for the WSN strain of human origin in a yield reduction assay.     

Altered sphingolipid metabolism in N-(4-hydroxyphenyl)-retinamide-resistant A2780 human ovarian carcinoma cells

In the present work, we studied the effects of fenretinide (N-(4-hydroxyphenyl)retinamide (HPR)), a hydroxyphenyl derivative of all-trans-retinoic acid, on sphingolipid metabolism and expression in human ovarian carcinoma A2780 cells. A2780 cells, which are sensitive to a pharmacologically achievable HPR concentration, become 10-fold more resistant after exposure to increasing HPR concentrations. Our results showed that HPR was able to induce a dose- and time-dependent increase in cellular ceramide levels in sensitive but not in resistant cells. This form of resistance in A2780 cells was not accompanied by the overexpression of multidrug resistance-specific proteins MDR1 P-glycoprotein and multidrug resistance-associated protein, whose mRNA levels did not differ in sensitive and resistant A2780 cells. HPR-resistant cells were characterized by an overall altered sphingolipid metabolism. The overall content in glycosphingolipids was similar in both cell types, but the expression of specific glycosphingolipids was different. Specifically, our findings indicated that glucosylceramide levels were similar in sensitive and resistant cells, but resistant cells were characterized by a 6-fold lower expression of lactosylceramide levels and by a 6-fold higher expression of ganglioside levels than sensitive cells. The main gangliosides from resistant A2780 cells were identified as GM3 and GM2. The possible metabolic mechanisms leading to this difference were investigated. Interestingly, the mRNA levels of glucosylceramide and lactosylceramide synthases were similar in sensitive and resistant cells, whereas GM3 synthase mRNA level and GM3 synthase activity were remarkably higher in resistant cells.     

Primary culture and mRNA analysis of human ovarian cells

Established cell lines are invaluable for studying cell and molecular biological questions. A variety of human ovarian cancer (OC) cell lines exist, however, most have acquired significant genetic alterations from their cells of origin, including deletion of important cell cycle regulatory genes. In order to analyze signaling events related to cell cycle control in human OC, we have modified existing protocols for isolating and culturing OC cells from patient ascites fluid and normal ovarian surface epithelial (OSE) cells from benign ovarian tissue sections. These cells maintain an epithelial phenotype and can be manipulated experimentally for several passages before cellular senescence. An example using TGF1 treatment of OC cells to examine signaling and target gene activation is presented. This work is supported in part by the National Cancer Institute of Canada with funds from the Canadian Cancer Society (#13631), the Nova Scotia Health Research Foundation, and by Cancer Research and Education (CaRE) Nova Scotia with funding from the Faculty of Medicine, Dalhousie University. L.D.D. is supported by the Rossetti Studentship for Cancer Research with funds from the Dalhousie Medical Research Foundation, T.G.S. is supported by a CaRE Fellowship with funding from the Canadian Cancer Society, and M.W.N is a Canadian Institutes of Health Research Scholar. Published: October 28, 2002.