Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.1.4.1 (phosphodiesterase)
18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Macrophage cell lines were used in these studies as a model system to dissect the biochemical and functional mosaic of the macrophage activation process. In particular, the requirements for the induction of tumoricidal and bactericidal activity in the RAW 264.7 and WEHI-3 cell lines by interferon-gamma (IFN-gamma) and bacterial lipopolysaccharide (LPS) were determined. Changes in expression of a series of macrophage markers traditionally associated with macrophage activation were monitored during stimulation of the cells in order to determine whether a detectable pattern of activation-associated changes is associated with the development of a particular functional activity. These markers included changes in the cell surface expression of major histocompatibility complex-encoded Class I and Class II antigens and antigens in the Mac-1/LFA-1 family, alterations in the levels of membrane enzymes (5' nucleotidase and alkaline phosphodiesterase), and production of secretory products including hydrogen peroxide and the monokines interleukin-1, interferons-alpha/beta, and tumor necrosis factor-alpha. Our results demonstrate that a given homogeneous macrophage population expresses a distinct subset of functional activities in response to single, defined activating signals such as IFN-gamma and LPS. The display of a variety of macrophage surface antigens, enzymes, and secreted products is activated simultaneously by such treatment; however, the particular pattern of such activation-associated markers cannot reproducibly be used to predict the ability of an activated cell to perform a particular function. The results also suggest that macrophage cell lines expressing differential response patterns following IFN-gamma stimulation provide a valuable system for dissection of the molecular and cell biology of macrophage activation.
...
PMID:Differential induction of activation markers in macrophage cell lines by interferon-gamma. 254 31

It was possible to define the effects of trehalose dimycolate (TDM), a glycolipid extracted from Mycobacterium tuberculosis, on mouse peritoneal macrophages more precisely using endotoxin-free culture conditions. TDM-elicited macrophages, when assayed in vitro in the absence of endotoxin, were unable to limit tumor growth; however, after a short treatment (4 h) with low doses of lipopolysaccharide (LPS; 1-10 ng/ml), they exhibited a strong cytostatic capacity against P815 mastocytoma cells. Thus, TDM injected in vivo did not activate macrophages fully but it primed them to respond in vitro to low doses of LPS, which provided the final stimulus for activation to antitumor competence. Macrophages elicited by an injection of killed group C Streptococci were also in a primed state; in contrast, thioglycollate-elicited macrophages were in a nonreceptive state. Besides LPS, concanavalin A (5 micrograms/ml), MDP (0.2-1 microgram/ml) and the ionophore A23187 (5 microM) can deliver the activation signal to TDM-primed macrophages. Primed macrophages were found to express several biochemical markers previously described as specific for activated macrophages (low levels of alkaline phosphodiesterase and beta-galactosidase, for example) and, although they were not cytotoxic for tumor cells, they had the capacity to release large amounts of H2O2. However, when pulsed by LPS or MDP, primed macrophages responded by further modifications in their metabolism: the rate of glucose consumption and the labeling of glycoproteins by D-[2-3H]mannose were greatly increased and the secretion of a polypeptide of 22 kDa was enhanced. The activation-associated biochemical markers are thus acquired in two steps. The ability to produce activated oxygen species is expressed earlier than the antitumoral activity.
...
PMID:Macrophage activation by trehalose dimycolate requirement for an expression signal in vitro for antitumoral activity; biochemical markers distinguishing primed and fully activated macrophages. 300 1

A protein resembling calmodulin was isolated from non-parenchymal and parenchymal cells of rat liver by affinity chromatography. The biological activity of the purified protein was assessed by the bovine brain cAMP phosphodiesterase assay. A highly sensitive radioimmunoassay as well as the cAMP phosphodiesterase method were employed to determine the calmodulin content of crude extracts from monolayer cultures of rat Kupffer cells and hepatocytes. An ATP-dependent, calmodulin-enhanced calcium transport was demonstrated in a membrane fraction of the non-parenchymal cells. Phospholipase A2 activity specific for 2-arachidonoyl phosphatide and with a pH optimum of 8.1 was measured in homogenized Kupffer cells; it was stimulated by agents previously shown to enhance prostaglandin synthesis in Kupffer cells, e.g. zymosan particles and lipopolysaccharide isolated from Salmonella minnesota. The increase in activity was completely prevented by pretreatment with or simultaneous addition of R 24571, a known calmodulin antagonist. However, if this inhibitor or calmodulin was added to the cell-free extract phospholipase A2 activity was not influenced. Phospholipase A1 activity could be detected at pH 5 only, showing a slight decrease in the homogenate of stimulated macrophages. Acyltransferase activity was high but independent of treatment of the Kupffer cells.
...
PMID:Calmodulin content and activity of Ca2+-ATPase and phospholipase A2 in rat Kupffer cells. 623 Nov 83

We assessed the role of cyclic nucleotides in modulating lipopolysaccharide (LPS)-induced tumor necrosis factor-alpha (TNF-alpha) generation in human peripheral blood monocytes. Exposure of monocytes to LPS (3 ng/ml) evoked a delayed, time-dependent generation of TNF-alpha that reached a maximum level 5-6 hr after LPS challenge and remained constant for up to 24 hr. This effect was concentration dependent and resulted in a 20-40-fold increase in the release of TNF-alpha that was sensitive to actinomycin D and cycloheximide. Treatment of monocytes with agents reputed to activate the cAMP/cAMP-dependent protein kinase (PKA) cascade in general inhibited LPS-induced TNF-alpha generation. Thus, the beta 2-adrenoceptor agonists albuterol and procaterol partially (approximately 40%) suppressed TNF-alpha generation in a propranolol-sensitive manner. Furthermore, 8-bromo-cAMP, cholera toxin, prostaglandin E2, and a number of drugs (i.e., rolipram (ZK 62711), denbufylline (BRL 30892), Ro 20-1724, benafentrine (AH 21-132), that inhibit the phosphodiesterase (PDE) 4 isoenzyme family abolished cytokine generation. In contrast, forskolin, inhibitors of PDE3 and PDE5, and activators of soluble and particulate guanylyl cyclase were essentially inactive. Interestingly, rolipram failed to potentiate the inhibitory effect of albuterol on LPS-induced TNF-alpha biosynthesis but, paradoxically, synergized with albuterol in the generation of cAMP and in the activation of PKA. When PGE2 was used to activate adenylyl cyclase, however, rolipram potentiated cAMP accumulation, PKA activation, and inhibition of TNF-alpha generation. In contrast, forskolin did not increase the cAMP content of monocytes in the absence or presence of rolipram. Collectively, these data suggest that LPS-induced TNF-alpha generation by human peripheral blood monocytes is due to increased transcription and subsequent translation of the TNF-alpha gene and that these effects are suppressed by a range of agents that activate the cAMP/PKA cascade. However, the failure of rolipram to potentiate the inhibitory effect of albuterol and procaterol on TNF-alpha generation suggests that beta 2-adrenoceptor agonists may affect gene expression and/or post-transcriptional regulatory processes by, at least in part, a cAMP-independent mechanism(s).
...
PMID:Suppression of lipopolysaccharide-induced tumor necrosis factor-alpha generation from human peripheral blood monocytes by inhibitors of phosphodiesterase 4: interaction with stimulants of adenylyl cyclase. 747 3

Exposure of human monocytes (HM) to E. coli lipopolysaccharide (LPS) results in measurable production of both IL-1 beta and TNF alpha in culture supernatants. It has previously been reported that the elevation of cAMP levels in HM selectively suppresses the LPS-induced TNF alpha but not IL-1 beta production. In this study we investigated whether the novel anti-inflammatory drug, SK&F 86002 [5-4(-pyridyl)-6(4-fluorophenyl)-2,3-dihydroimidazole(2,1-b)thi azol] and related analogs of the pyridinyl imidazole class, inhibit IL-1 and TNF production via a cAMP-dependent mechanism. These compounds, when added together with LPS result in inhibition of IL-1 and TNF production with equal-rank-order potency. Although the pyridinyl imidazole compounds were found to be generally weak phosphodiesterase inhibitors, they did not affect cAMP levels in HM, alone or in the presence of LPS. In contrast, PGE2, which significantly elevated intracellular cAMP levels, inhibited TNF but not IL-1 production at the transcriptional level. Taken together, these results suggest that the pyridinyl imidazoles inhibit the production of IL-1 beta and TNF alpha through pathways independent of cAMP elevating mechanisms.
...
PMID:Inhibition of interleukin-1 (IL-1) and tumor necrosis factor (TNF) production by pyridinyl imidazole compounds is independent of cAMP elevating mechanisms. 750 4

Previous studies have shown that prostacyclin analogs can inhibit the expression of tissue factor (TF) procoagulant activity by human monocytes. The present studies have investigated this phenomenon further, by using a plasma coagulation assay to measure cellular TF activity, an immunoassay to measure TF antigen and reverse transcription/polymerase chain reaction with appropriate oligomer primers to measure TF mRNA. Iloprost and cicaprost inhibited lipopolysaccharide-induced increases in TF activity, antigen and mRNA (50% inhibition, 2-8 nM), with no apparent effect on TF mRNA stability. These agents therefore act at or before the level of transcription of the TF gene. The analogs were more potent inhibitors of tumor necrosis factor-alpha synthesis (50% inhibition at 334 +/- 40 pM cicaprost or 846 +/- 182 pM iloprost) and extraordinarily potent when combined with a phosphodiesterase inhibitor (50% inhibition at 101 +/- 31 pM iloprost in the presence of 20 microM isobutylmethylxanthine). Iloprost and cicaprost were less potent in inhibiting the synthesis of interleukin-1 beta (50% inhibition, 50-100 nM). Cicaprost inhibited lipopolysaccharide-induced increases in mRNA levels for TF, tumor necrosis factor-alpha and interleukin-1 beta; differential potency was again observed. We conclude that these three important monocyte functions can be down-regulated by prostacyclin analogs, and with differential sensitivity. Furthermore, the extreme sensitivity of tumor necrosis factor-alpha synthesis to inhibition suggests that such inhibition may be a major physiological function of prostacyclin itself.
...
PMID:Effects of prostacyclin analogs on the synthesis of tissue factor, tumor necrosis factor-alpha and interleukin-1 beta in human monocytic THP-1 cells. 752 28

The aim of the present study was to determine whether two classical macrophage activators, bacterial lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) could affect the accumulation of the second messenger cAMP in cultured rat microglia and astrocytes. Purified microglia and astrocyte secondary cultures obtained from the neonatal rat were grown for 3 days in basal medium Eagle (BME) + 10% fetal calf serum (FCS). Exposure of microglia to LPS resulted into a dose- and time-dependent decrease in the accumulation of cAMP induced by receptor-mediated (isoproterenol or prostaglandin E2) or direct (forskolin) activation of adenylate cyclase. The inhibitory effect of LPS was rapid (a 10 min preincubation was sufficient to approach a maximal effect), occurred at low doses (IC50 = 1.2 ng/ml), and was not abrogated by pertussis toxin. A selective inhibitor of type IV phosphodiesterase (rolipram, 100 nM) prevented the effect of LPS on cAMP accumulation, while inhibitors of other forms of phosphodiesterase were unable to do so. IFN-gamma (100 u/ml) also caused a depression of the evoked cAMP accumulation in microglia after a 10 min preincubation, and its effect was prevented by rolipram, as in the case of LPS. Astrocytes differed from microglia in that LPS (1-100 ng/ml) did not inhibit the accumulation of cAMP induced by either isoproterenol or forskolin; on the other hand, IFN-gamma did have an inhibitory effect (though less pronounced than in microglia) that could be prevented by rolipram.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Interferon-gamma and lipopolysaccharide reduce cAMP responses in cultured glial cells: reversal by a type IV phosphodiesterase inhibitor. 755 45

The marine natural products manoalide and scalaradial are potent anti-inflammatory agents that inactivate the enzyme phospholipase A2 (PLA2) in vitro. To study the mechanism of inhibition of prostaglandin E2 (PGE2) production in human monocytes by manoalide and scalaradial, lipopolysaccharide (LPS)-induced prostaglandin biosynthesis and induction of prostaglandin H synthase (PGHS) were evaluated. LPS (10 ng/mL) and interleukin-1 beta (IL-1 beta, 50-1000 ng/mL) but not tumor necrosis factor alpha (TNF alpha, 300 ng/mL) induced the expression of the PGHS-2 isoform as determined by immunoblot analysis with a specific polyclonal antibody for PGHS-2. Manoalide and scalaradial (1-10 microM) inhibited LPS-induced endogeneous PGE2 production, reduced the LPS-induced PGHS activity, and reduced the expression of PGHS-2. Indomethacin [a PGHS inhibitor (0.01 to 0.1 microM)], zileuton [a 5-lipoxygenase inhibitor (3-10 microM)], and WEB-2806 [a platelet-activating factor (PAF) antagonist (30 microM)] did not affect the LPS-induced expression of PGHS-2 in human monocytes. These results suggest that modulation of lipid mediator production by manoalide or scalaradial may not be involved in the observed effects on the expression of PGHS-2. Manoalide and scalaradial also inhibited the release of IL-1 beta and TNF alpha from LPS-stimulated monocytes. Expression of PGHS-2 induced by either LPS or IL-1 beta was blocked by the IL-1 receptor antagonist (IL-1ra, 2 micrograms/mL) but not by rolipram, a phosphodiesterase IV inhibitor that inhibits TNF alpha but not IL-1 beta release. Similar to LPS, IL-1 beta-induced PGHS-2 expression was apparently not regulated by lipid mediators such as prostaglandins, leukotrienes or PAF as determined with specific inhibitors and antagonists. Scalaradial and to some extent manoalide were capable of blocking the IL-1 beta-induced expression of PHGS-2. These results indicate that IL-1 beta is the predominant cytokine responsible for the induction of PGHS-2 in the human monocyte. Furthermore, marine natural products such as scalaradial have novel effects on the IL-1 beta-mediated induction of PGHS-2 in human monocytes, which appears to be independent of effects on lipid mediator production.
...
PMID:Regulation of prostaglandin H synthase 2 expression in human monocytes by the marine natural products manoalide and scalaradial. Novel effects independent of inhibition of lipid mediator production. 757 73

Many functions of the immune and inflammatory responses are inhibited by agents that increase intracellular levels of cAMP. Recent investigations have revealed that cAMP levels in inflammatory cells are regulated by cyclic nucleotide phosphodiesterases (PDEs) belonging to the PDE4 family (cAMP-specific PDEs). At least four different genes are known to encode PDE4 isozymes, which are characterized by their selectivity for cAMP over cGMP and their sensitivity to the antidepressant drug rolipram. The aim of our studies was to investigate whether monocytic cells could regulate PDE4 activity and whether certain PDE4 isozymes were expressed preferentially over others. Our results showed that treatment of peripheral blood monocytes or closely related Mono Mac 6 cells with dibutyryl-cAMP or other cAMP-elevating agents transiently increased rolipram-sensitive PDE4 activity 2-3-fold, without concomitant increases in cGMP-inhibited PDE (PDE3) activity. PDE4 activity was predominantly cytosolic, whereas PDE3 activity was localized to the particulate fraction. Our Northern and Western blot studies with reagents recognizing three distinct PDE4 gene products (PDE4A, PDE4B, and PDE4D) revealed that their expression is transcriptionally regulated in monocytic cells. Although none of the three isozymes was detectable under normal culture conditions, all of these were up-regulated when Mono Mac 6 cells were exposed to dibutyryl-cAMP. Distinct differences were observed in their temporal patterns of expression. Endotoxin lipopolysaccharide, a potent monocyte stimulus, also enhanced PDE4 activity in monocytic cells. These data indicate that monocytic cells may express different PDE4 isozymes, depending on their state of activation or differentiation. These isozymes could thus regulate intracellular cAMP levels at various stages of monocyte activation and could thereby be important in limiting the inflammatory response.
...
PMID:Regulation of distinct cyclic AMP-specific phosphodiesterase (phosphodiesterase type 4) isozymes in human monocytic cells. 760 56

Three inhibitors of calcium-dependent cyclic adenosine 3'5'-monophosphate (cAMP) dependent phosphodiesterase IV (PDE IV) were evaluated for their effects on lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF) production in vitro and in vivo and for their ability to protect mice from LPS-induced lethality in D-galactosamine (D-gal) sensitized mice. In vitro, on LPS-stimulated murine peritoneal macrophages (PEM), BRL 61063 (1,3-di(cyclopropylmethyl)-8-aminoxanthine) and rolipram (4-(3-cyclopentyloxy-4-methoxyphenyl)-2-pyrrolidone) had similar TNF inhibitory activity with an IC50 ranging from 0.1 to 0.5 microM. Pentoxifylline (PTX), (3,7-dimethyl-1-(5-oxohexyl)xanthine) was less potent with an IC50 = 100 microM. In vivo, there was a rank order potency on serum TNF levels in LPS challenged D-gal sensitized mice. BRL 61063 inhibited TNF production with an ID50 of 0.1 mg/kg, rolipram at 1 mg/kg, and PTX at 200 mg/kg. Thus, BRL 61063 is 2,000 times more potent than PTX in reducing TNF serum levels in this model. Interestingly, TNF is implicated as having a central pathogenic role in the LPS/D-gal model, since survival of animals correlated directly with reduction of serum TNF levels for all three compounds tested. It is proposed that potent inhibitors of TNF may have therapeutic activity in disease states where TNF appears to play a role in the pathogenesis of the disease.
...
PMID:Beneficial effects of the phosphodiesterase inhibitors BRL 61063, pentoxifylline, and rolipram in a murine model of endotoxin shock. 762 60


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---