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

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

Normal rat liver cells (BRL-1) that respond to isoproterenol (beta+2), prostaglandin E1 (PGE+1) and adenosine (Ado+) with a rise in adenosine 3':5'-monophosphate (cAMP) content have been hybridized with rat hepatoma cells (H35) which do not respond to any of these agonists (beta-2, PGE-1 and Ado-). Both the initial hybrid line (BF5) and a subclone (BF5-1-1) expressed a beta+2, PGE+1, Ado- phenotype. However, full expression of the responsive phenotype in the BF5 line was apparent only if phosphodiesterase activity was blocked, for example, by methylisobutylxanthine (MIX). Direct measurements showed the rate of degradation of cAMP to be 7 times greater in intact BF5 cells than in the BRL-1 parent. In contrast to BF5 cells, the BF5-1-1 cells did not express maximal responsiveness to any of the agonists even in the presence of MIX. The differential accumulation of intracellular cAMP observed with BRL-1, BF5 and BF5-1-1 cells in response to isoproterenol was shown not to be as a result of differential rates of excretion of cAMP. Furthermore, no differences in the apparent affinities of the beta 2-catecholamine receptors for isoproterenol were observed. It is suggested that the increased degradative capacity of BF5 cells accounts for the difference in cAMP accumulation in these cells compared with the BRL-1 parent. The reduced responsiveness of BF5-1-1 cells, however, does not appear to be solely due to increased phosphodiesterase activity. It appears that the beta 2- phenotype may not always be dominant in hybrid crosses of this type as has been reported previously.
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PMID:Expression of the regulation of cAMP metabolism in somatic cell hybrids. 9 76

The ability of isoproterenol, glucagon, PGE1 and cholera toxin to stimulate the synthesis of cAMP and protein kinase activity in line of liver cells (BRL) and a line of rat hepatoma cells (H35) has been determined. The concentration of cAMP in BRL cells (approximately 10 pmoles/mg protein) is in the range reported for other cultured cell lines but H35 cells contain extraordinarily low amounts of this cyclic nucleotide (approximately 0.05 pmoles/mg protein). Isoproterenol and PGE1 caused an increase in cAMP content, and protein kinase activation in BRL cells, although glucagon was ineffective. H35 cells, in contrast, were completely insensitive to all hormonal agonists. Despite this fact, cholera toxin was able to produce a marked increase in cAMP content, adenylate cyclase activity and protein kinase activation in H35 cells. binding studies with [125 I]-iodohydroxybenzylpindolol, a specific beta-adrenergic receptor antagonist, revealed that each H35 cell possesses fewer than 10 beta-adrenergic receptors whereas BRL cells contain 2-5,000 receptors per cell. The low level of cAMP in H35 cells appears to result from a combination of totally unstimulated adenylate cyclase and apparently elevated phosphodiesterase activities.
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PMID:Studies of cAMP metabolism in cultured hepatoma cells: presence of functional adenylate cyclase despite low cAMP content and lack of hormonal responsiveness. 20 52

1. The pharmacological profile of the inhibitory 5-hydroxytryptamine (5-HT) receptor in rat oesophageal smooth muscle has been characterized by means of a series of agonists active at 5-HT1-, 5-HT2-, 5-HT3- and 5-HT4-receptor sites, and a broad range of antagonists. The possible involvement of cyclic nucleotides in the 5-HT response was also examined. 2. Under conditions of tone induced by muscarinic receptor activation, the upper two-thirds (proximal segment) of the oesophageal smooth muscle tunic was more sensitive to the inhibitory effects of 5-HT receptor agonists when compared with the distal region. 3. The inhibitory response to 5-HT was blocked by MDL 72222 (5-HT3 antagonist) and ICS 205-930 (5-HT3/5-HT4 antagonist) but not by antagonists active at 5-HT1- or 5-HT2-receptors. 4. The phosphodiesterase inhibitor, 3-isobutyl-methyl-xanthine (IBMX) enhanced oesophageal smooth muscle inhibitory response to 5-HT, isoprenaline and forskolin, but not that elicited by the potassium channel opener, BRL 34915. 5. 5-HT increased tissue cyclic AMP content over basal levels in proximal and distal segments of oesophageal smooth muscle. However, 5-HT had no significant effect on basal cyclic GMP levels in both segments. 6. We conclude that the inhibitory 5-HT receptor in rat oesophageal smooth muscle may represent a high affinity subtype which is sensitive to 5-HT3/5-HT4 antagonists and is coupled to the cyclic AMP pathway.
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PMID:Pharmacological profile of the 5-hydroxytryptamine receptor that mediates relaxation of rat oesophageal smooth muscle. 132 46

Airway smooth muscle plasma membranes are rich in K+ channels of various types. Charybdotoxin (ChTX) is a potent blocker of the high-conductance Ca(++)-activated K+ channel in smooth muscle and produces a concentration-dependent contraction of guinea pig trachea. In the present study, pharmacologic experiments were performed on carbachol-contracted (0.34 microM) guinea-pig trachea contracted further with ChTX in order to determine if Ca(++)-activated K+ channels play a role in the responses to cAMP-dependent and cAMP-independent bronchodilators. Relaxation concentration response curves to the beta-agonists, isoproterenol and salbutamol; the phosphodiesterase inhibitor, aminophylline; the cAMP mimic, N6-2'-O-adenosine 3':5'-cyclic monophosphate the guanylate cyclase activator, sodium nitroprusside; and the K+ channel agonists, BRL-34915 and pinacidil, were obtained in the absence and presence of ChTX. The concentration response curves to isoproterenol and salbutamol were shifted to the right (approximately 27-fold and greater than 40-fold, respectively) by 180 nM ChTX, whereas concentration response curves to N6-2'-O-adenosine 3':5'-cyclic monophosphate and aminophylline were affected significantly less (shifted approximately 7.5-fold). Concentration response curves to the cGMP-dependent relaxant sodium nitroprusside were also altered by ChTX (17-fold rightward shift at 180 nM). In the presence of 60 nM ChTX, the concentration response curves to the above relaxants were shifted only 3- to 5-fold. In contrast, ChTX (60 and 180 nM) failed to produce a significant rightward shift in the concentration response curves to BRL-34915 or pinacidil. Relaxation to BRL-34915 was however, blocked by glybenclamide, suggesting differences in the mechanism of relaxation. Contraction of tissues with depolarizing concentrations of KCl (20-80 mM) inhibited responses to all bronchodilators. These results suggest that hyperpolarization of tracheal smooth muscle as a result of opening various types of K+ channels can lead to relaxation of carbachol-contracted tracheal smooth muscle.
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PMID:Selective inhibition of relaxation of guinea-pig trachea by charybdotoxin, a potent Ca(++)-activated K+ channel inhibitor. 170 Aug 17

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).
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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

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.
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PMID:Beneficial effects of the phosphodiesterase inhibitors BRL 61063, pentoxifylline, and rolipram in a murine model of endotoxin shock. 762 60

BRL 61063 is a novel xanthine phosphodiesterase (PDE) type IV inhibitor with selective inhibitory activity for tumor necrosis factor (TNF) alpha production. This compound inhibits TNF alpha production by activated human blood monocytes in vitro and in animal models of endotoxemia and influenza infection. Inhibition of TNF alpha may be beneficial in many diseases; however, little is known about potential adverse effects of such inhibition on host defense. In an ex vivo study, we examined the effect of BRL 61,063 on the microbicidal and tumoricidal activity of pulmonary lavage cells during a local inflammatory response in rats challenged with Poly I:C. Pentoxifylline, a PDE inhibitor which also blocks TNF alpha production, was used for comparison. Treatment with BRL 61063 or pentoxifylline did not block the inflammatory response to Poly I:C or the activation of bronchoalveolar lavage (BAL) cells but reduced the level of tumoricidal activity attained. At the dosages used, pentoxifylline was more inhibitory than BRL 61063. Drug treatment did not prevent further stimulation of tumoricidal activity by LPS in vitro. LPS-stimulated cells from BRL 61063-treated rats reached a level of activation similar to the control group while the LPS-stimulated activity of BAL cells from pentoxifylline treated rats remained lower than control. Although pentoxifylline was more inhibitory for tumoricidal activity than BRL 61063, the latter was a more potent inhibitor of TNF alpha release as measured in vivo in LPS-challenged rats. This finding indicates that TNF alpha is not the main mediator involved in the activation of pulmonary macrophage tumoricidal function. Treatment with either BRL 61063 or pentoxifylline had little or no effect on the Poly I:C-induced candidacidal activity of BAL cells indicating that these compounds are unlikely to compromise non-specific host defense against infection.
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PMID:Effect of TNF alpha production inhibitors BRL 61063 and pentoxifylline on the response of rats to poly I:C. 782 85

To investigate a possible physiological desensitization process for beta 3-adrenergic responses, the effect of cold acclimation of hamsters on adrenergically stimulated oxygen consumption of isolated brown fat cells was investigated. Cells were prepared from control and from cold-acclimated hamsters. In agreement with earlier findings, cells isolated from cold-acclimated hamsters responded to norepinephrine addition with a decreased sensitivity (approximately 10 times higher 50% effective concentration) and a decreased maximal rate of oxygen consumption compared with cells from control hamsters. When cells were stimulated with the general beta-adrenergic agonist isoprenaline or with the beta 3-selective agonists BRL-37344 or CGP-12177, a similarly desensitized response was observed, demonstrating that it was indeed a beta 3-adrenergic response that was functionally desensitized. However, when the mitochondria within the cells were directly stimulated with exogenous free fatty acids (palmitate or octanoate), no difference between cells from control and cold-acclimated animals was seen, indicating that a mediatory step must be desensitized. When the cells were stimulated with forskolin (to activate adenylyl cyclase) or with 8-bromoadenosine 3',5'-cyclic monophosphate, the desensitized response was still observed. At post-adenosine 3',5'-cyclic monophosphate levels, a desensitization was not evident. Cyclic nucleotide phosphodiesterase activity was increased in cells from cold-acclimated animals. It is therefore suggested that this increased activity of phosphodiesterase could be (at least partly) responsible for the physiologically induced desensitized responses observed here.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Physiological desensitization of beta 3-adrenergic responses in brown fat cells: involvement of a postreceptor process. 790 9

Alkylation of the selective type IV phosphodiesterase inhibitor, 8-amino-1,3-bis(cyclopropylmethyl)-xanthine (1, BRL 61063), led exclusively to the N-7 substituted derivatives 2-9, which showed varying selectivities for the PDE type IV isoenzyme relative to PDE Va. The 4-methoxybenzyl derivative 6 in particular was a highly potent PDE Va inhibitor (IC50 0.14 microM) and showed a 24-fold selectivity for this isoenzyme relative to PDE IV. Sulfonation of 1 was more complex, with the product profile being highly dependent on the reaction conditions. As with alkylation, sulfonation at N-7 generally increased potency against PDE Va, especially in the aryl-containing moieties lacking strongly electron-withdrawing substituents (12, 15-17, 19). Bis-arylsulfonation at the exocyclic amino group generally reduced inhibitory potency against both PDE IV and Va. An 8-amidino compound 33, formed by the unusual reaction of 1 with N-methylpyrrolidinone in the presence of benzenesulfonyl chloride, had an IC50 value of 0.05 microM against PDE Va and is believed to be the most potent inhibitor of this isoenzyme reported. No correlation of PDE IV inhibition with displacement of [3H]rolipram from its high-affinity binding site was demonstrated. This suggests that either the catalytic site and the rolipram binding site are not the same or that PDE IV can exist in two conformations, only one of which binds to rolipram with high affinity, and that the compounds described vary in their selectivity for this isoform.
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PMID:Inhibition of cyclic nucleotide phosphodiesterase by derivatives of 1,3-bis(cyclopropylmethyl)xanthine. 812 Aug 66

The role of the phosphodiesterase type IV isozyme (PDE IV) in the regulation of cerebrovascular tone was investigated in the canine basilar artery in vitro and in vivo. The PDE isozymes extracted from the canine basilar artery were isolated by diethylaminoethanol (DEAE)-Sepharose affinity chromatography and identified based on sensitivity to isozyme-selective PDE inhibitors. [3H]cAMP hydrolysis was observed in one major and one minor peak of activity. The predominant peak was inhibited by the addition of cGMP (25%), siguazodan (26%), rolipram (39%), and the combination of siguazodan and rolipram (95%). Selective PDE IV inhibitors BRL 61063, rolipram, and denbufylline were equieffective inhibitors of [3H]-ccAMP hydrolysis mediated by PDE IV isolated from the canine basilar artery [concentrations producing 50% inhibition (IC50S) = 0.21 +/- 0.05 microM, 0.67 +/- 0.23 microM, and 0.73 +/- 0.16 microM, respectively]. In precontracted isolated ring segments of the canine basilar artery, selective PDE IV inhibitors produced potent and complete relaxation (IC50S < 150 nM). In contrast, zaprinast (a selective PDE V inhibitor) and siguazodan (a selective PDE III inhibitor) produced only weak relaxation of the basilar artery (IC50S = 4.5 microM and > 10 microM, respectively). Vasorelaxation produced by PDE IV inhibitors was not altered by removing the endothelium, 1-NAME, or adenosine receptor antagonism. In a canine model of acute cerebral vasospasm, all three selective PDE IV inhibitors reversed basilar artery spasm produced by autologous blood without altering mean arterial blood pressure. In contrast, prolonged treatment with BRL 61063 failed to alter the development of basilar spasm in the two hemorrhage canine models of chronic cerebral vasospasm. Denbufylline-induced relaxation in vitro was also significantly impaired in basilar arteries obtained from the model of chronic vasospasm. In conclusion, PDE IV appears to be the predominant isozyme regulating vascular tone mediated by cAMP hydrolysis in cerebral vessels. In addition, vasorelaxation modulated by PDE IV is compromised in chronic cerebral vasospasm associated with subarachnoid hemorrhage.
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PMID:Identification, characterization, and functional role of phosphodiesterase type IV in cerebral vessels: effects of selective phosphodiesterase inhibitors. 904 May 1


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