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)

Ever since xanthines were introduced into asthma therapy, more than 125 years ago, their therapeutic effectiveness has been explained as being due to extrapulmonary rather than, or in addition to, pulmonary drug actions. This article emphasizes that theophylline may have several potentially important effects in the lung. Theophylline relaxes the smooth muscle of large and small airways in humans and animals. Its relaxant effect is relatively independent of the type of mediator that constricts the airway. This suggests that functional antagonism, rather than specific pharmacologic mediator antagonism (e.g., adenosine antagonism), explains its bronchodilator effect. The consistent relaxant property of such xanthines as theophylline distinguishes these compounds from many other classes of established and experimental bronchodilator agents. Furthermore, many anti-inflammatory effects have been noted, suggesting that xanthines might be considered as prophylactic agents. Theophylline may not only attenuate the activity of stationary and blood-borne pulmonary inflammatory cells; it may also exert an anti-inflammatory action by directly affecting targets such as the epithelial lining (increasing the mucociliary transport rate) and the microvasculature (possibly reducing plasma exudation). The experimental anti-inflammatory pharmacology of theophylline is compatible with the observation that theophylline inhibits late pulmonary reactions in patients with atopic asthma and in sensitized animals challenged with allergen. The mechanism(s) of action behind the pulmonary actions of theophylline has not been assessed (neither phosphodiesterase inhibition nor adenosine antagonism may be involved). Central nervous system, gastroesophageal, renal, and metabolic actions of theophylline are briefly reviewed. Headache, nausea, and the relaxation of the lower esophageal sphincter can perhaps be classified as nonexcitatory and inhibitory effects in which the mechanism(s) of action is unknown.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Overview of effects of theophylline. 287 16

Alveolar macrophages are the most numerous cells within human airways. They release inflammatory mediators following immunological challenge and have been implicated in the pathogenesis of asthma. beta-agonists and phosphodiesterase inhibitors are frequently used in the treatment of asthma and are potent inhibitors of human mast cells. We have examined the role of the beta-agonist, isoprenaline, the phosphodiesterase inhibitor Ro-20 1724, and the adenylate cyclase stimulator forskolin on the activation of human alveolar macrophages. This was assessed by monitoring the release of thromboxane B2 (TXB2), leukotriene B4, N-acetyl-beta-D-glucosaminidase (NAG), and superoxide (SO) following stimulation of the cells by opsonised zymosan or IgE/anti IgE complexes. Neither isoprenaline (1nM-10 microM) nor Ro-20 1724 (0.5-50 microM) alone or in combination had any inhibitory effect on release of these mediators. However, forskolin (0.1-100 microM) significantly inhibited release of both TXB2 and SO but not NAG. This result shows that human alveolar macrophages do not possess functional beta-receptors, although stimulation of adenylate cyclase with forskolin, inhibits some of the elements of macrophage activation.
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PMID:Human alveolar macrophage activation: inhibition by forskolin but not beta-adrenoceptor stimulation or phosphodiesterase inhibition. 290 87

Atopic dermatitis (AD) is a familial inflammatory skin disorder which is characterized by extreme pruritus, the typical morphology and distribution, the chronic or chronically relapsing time course and the personal or family history of atopy (asthma, allergic rhinitis, atopic dermatitis). However, there exists a variety of additional features which are either less specific or relatively rare. Although this disease has been well-known since the beginning of the century, the pathogenesis is not clearly understood at present. This review summarizes the reported deviations of the immune system as well as the alterations of the mediators of inflammation and the abnormalities of cyclic nucleotide regulation. These findings will be correlated with clinical symptoms. In particular the following topics were taken into consideration: association with HLA-antigens, elevation of serum IgE and generation of IgE immune complexes, numerical and functional deficiencies of T-suppressor cells, involvement of granulocytes, alterations of mediators of inflammation and especially the observations on the cyclic adenosine monophosphate (cAMP)-phosphodiesterase. These extremely complex findings based on the interaction between disregulation of the autonomous nervous system and alterations of the immune system may provide a better understanding of the pathogenesis of atopic dermatitis.
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PMID:[Pathogenesis of atopic dermatitis]. 299 74

Methylxanthines have been used for the treatment of asthma for more than 60 years, but their mechanism of action is poorly understood. Their ability to inhibit cyclic adenosine monophosphate phosphodiesterase has attracted much attention. However, this is clearly demonstrable only in high doses and is more likely to be related to toxicity. An alternative mechanism is antagonism of adenosine receptors in the lung. Adenosine has been shown to be released in asthma and cause bronchoconstriction in patients with asthma. Its effects are selectively inhibited by concentrations of theophylline that do not block histamine-induced bronchoconstriction. Neither phosphodiesterase inhibition nor adenosine receptor antagonism explains the action of enprofylline in asthma. Consequently, additional actions of methylxanthines are likely to contribute to their beneficial effects. They may include adrenaline release from the adrenal medulla, an effect on cell calcium distribution, inhibition of the generation of contractile prostaglandins, and an improvement of diaphragmatic contractility.
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PMID:Relationships between adenosine, cyclic nucleotides, and xanthines in asthma. 302 33

Activation of white cells, including the neutrophil, eosinophil, basophil, and mast cell, has long been known to be suppressed by high, nonphysiological levels of E-prostaglandins (PGE). In contrast, PGE at levels consistent with an interaction with the PGE receptor (5 X 10(-9) M) have recently been shown to suppress leukotriene (LT) and prostaglandin (PG) production by neutrophils and eosinophils. This occurs by cyclic AMP-dependent inhibition of release of substrate arachidonic acid (AA) from phospholipid pools. The additional observation that indomethacin (10(-9) M) enhances release of eicosanoids by suppressing endogenous PGE2 acting to increase cAMP levels in these cells. Theophylline and other phosphodiesterase inhibitors precisely duplicate the action of PGE2, and the combined effects of such phosphodiesterase inhibitors and adenylate cyclase stimulators are synergistic. The mechanism of action of theophylline in asthma is not know, although it is generally agreed that its effect is a direct one on the bronchial smooth muscle. The findings described in this report now permit the bronchial smooth muscle, but is primarily one of suppressing mediator release from relevant white cells by inhibition of cAMP phosphodiesterase, an action that is enhanced by the presence of inflammatory prostaglandins in the lung.
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PMID:Cyclic AMP-dependent regulation of lipid mediators in white cells. A unifying concept for explaining the efficacy of theophylline in asthma. 303 56

The beta-adrenoceptor agonists have become the cornerstone of bronchodilator therapy. These agents are "functional" or "physiologic" antagonists that actively relax airway smooth muscle through a cyclic-AMP (cAMP)-mediated decrease in myoplasmic Ca2+ content. Hence, unlike specific receptor antagonists, the sympathomimetics should reverse bronchoconstriction regardless of the mediator(s) involved. Indeed, one of the primary beneficial attributes of beta-adrenoceptor agonists is their inhibitory activity against a wide range of bronchoconstrictors. As successful as the sympathomimetic bronchodilators have been, they are not without liabilities. These liabilities include: 1) cardiovascular and skeletal muscle side effects, 2) an inherent subsensitivity of the patient population to beta-adrenoceptor agonists, 3) the development of tolerance, and 4) loss of efficacy during severe asthmatic episodes. These limitations are not specific for individual agents but are shared by all beta-adrenoceptor agonists. A significant improvement in the pharmacotherapy of asthma would be obtained by identifying novel bronchodilators devoid of one or more of the aforementioned liabilities. The development of isozyme-selective phosphodiesterase (PDE) inhibitors is one promising approach toward this goal. Interest in PDE inhibition as a therapeutic target has been renewed by the realization that PDEs exist in multiple isoforms and that the distribution of these isoforms varies significantly among tissues. This information, coupled with the recent synthesis of PDE inhibitors selective for several of the isozymes, raises the possibility of breeding organ-selectivity into this class of compounds. Results from preliminary experiments with isozyme-selective PDE inhibitors have helped to identify appropriate drug targets in airway smooth muscle. These early studies suggest that the synthesis of novel isozyme-selective PDE inhibitors not only may provide tools with which to understand the biologic function of various PDE isozymes, but may also lead to the development of improved therapeutic agents.
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PMID:Action of mediators on airway smooth muscle: functional antagonism as a mechanism for bronchodilator drugs. 305 35

In the majority of patients one of the primary features of bronchial asthma is the occurrence of nocturnal symptoms. There are significant bioperiodicities for hormonal, neural, cellular and humoral factors and for mediators, which are all in favour of reducing bronchial patency during the night. In the morning hours between 2 and 6 a.m. the histamine concentration shows a peak, the adrenaline and cyclic AMP have their minimum, while the cortisol secretion with its delayed onset of action is already ascending. The kallikrein kinin system is activated by histamine. Circadian variations have also been found for the receptor density of beta-receptors, cAMP, adenylcyclase and phosphodiesterase. While circadian rhythms are not known for the platelet activating factor (PAF) at the present time, the known nocturnal peak of thromboxane A2 may influence PAF-liberation as well. The bronchodilating metabolite of the cyclooxygenase pathway, PGE2, was found to have depressed levels during the night. Total plasma, total protein as well as IgA, IgM, IgG and IgE have a minimum during the night, cellular elements like T11-, T4-, B-lymphocytes and Leu8 have a maximum. Slow release theophylline is today the most important drug for nocturnal asthma. Theophylline is known to interfere with histamine release from mast cells, mediator release of arachidonic acid metabolites, the cyclic AMP concentration and suppressor cell activity. Important work remains to be done to clarify the therapeutic and immunological role of theophylline in nocturnal asthma and to identify the subgroups of patients having the greatest benefit of theophylline treatment.
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PMID:Biochemical and cellular basis for circadian rhythms in obstructive lung disease and implications for theophylline therapy. 305 28

The heterogeneity in the aetiology and the precipitating factors, as well as the pathology of asthma makes the response to the conventional treatment also variable. Ketotifen is a derivative of the cyclohepatotifen which has shown to have an antianaphylactic effect which inhibits chemical mediator release in mast cells and basophils. This effect is similar to that of the methylxanthines inhibiting phosphodiesterase propitiating the increase of CAMP and favouring bronchodilatation. It also exerts a blocking action on the H receptors of histamine and possesses a calcium antagonist effect in the depolarized smooth muscle; for this reason it is probable that ketotifen does not have a direct effect on the contraction of smooth fibres provoked by diverse stimuli. The present work is a prospective study with placebo group and double blind method to evaluate the effectivity and tolerance of ketotifen as a prophylaxis for extrinsic bronchial asthma in 60 children. This is to observe if there exists or not a reduction in the frequency, intensity and duration of signs and symptoms. Among the most interesting conclusions observed are the following: The general characteristics of both the ketotifen group as well as the placebo group did not show any significative statistical differences which were susceptible of comparison among them. The ketotifen proved itself as very efficient, obtaining a reduction which was highly significative of the asthmatic symptomatology (p less than 0.001). In the placebo group some highlights were obtained which can be attributed to the fact that both groups received desensitizing immunotherapy to diverse allergens. Nevertheless, in general terms, the symptomatology did not diminish in this group in a significative way.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Ketotifen in the prophylaxis of infantile asthma. Controlled clinical trials]. 389 Apr 97

Theophylline has emerged as a major prophylactic agent for controlling the symptoms of chronic asthma, but it provides little if any relief of pulmonary symptoms caused by irreversible chronic airways obstruction. Although in vitro it inhibits phosphodiesterase and antagonizes adenosine receptors, theophylline's mechanism of action in asthma is unknown. Often, 10 to 20 micrograms/ml is used as the range of serum concentrations where there is the greatest likelihood of obtaining maximal benefit safely. Slow-release products have the potential to provide more stable serum concentrations with longer dosing intervals. However, clinically important differences in rate and sometimes extent of absorption exist between the 15 formulations sold under 29 brand names in this country. In patients with more rapid elimination, few products have sufficiently slow absorption to allow twice-daily use. Often these formulations must be administered every eight hours to prevent breakthrough in asthmatic symptoms despite promotional claims to the contrary. In patients with slower elimination, differences among products are unlikely to be clinically important with 12-hour dosing intervals. Current products approved for "once-a-day" dosing are clinically inadequate because of erratic absorption or excessive serum concentration fluctuations. Moreover, food induces dose dumping of potentially toxic amounts of theophylline from Theo-24, greatly increases the extent of absorption of theophylline from Uniphyl, decreases extent of absorption from Theo-dur-Sprinkle capsules, but has no clinically important effect on Theo-Dur tablets, Theobid, Slo-Bid, or Somophyllin-CRT. The effects of food or other factors that alter gastrointestinal physiology on theophylline absorption are unknown for most other products.
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PMID:Update on the pharmacodynamics and pharmacokinetics of theophylline. 389 22

LY171883, 1-less than2-hydroxy-3-propyl-4-less than 4-(h-tetrazol-5-yl)butoxy greater than phenyl greater than ethanone, proved to be a potent antagonist of leukotriene (LT) D4 in guinea-pig ileum, trachea and lung parenchyma. The compound had little or no effect on contractions of isolated tissues to LTB4, prostaglandin F2 alpha, serotonin, histamine, bradykinin or carbamycholine. Responses of trachea to U46619, a thromboxane A2 mimetic, were antagonized by LY171883, but the doses required were approximately 10-fold higher than those necessary to produce the same degree of antagonism against LTD4. U46619 produced weak ileal contractions that were not blocked by LY171883. LY171883 antagonized both LTD4- and antigen-induced increases in total pulmonary resistance in anesthetized guinea pigs. LTD4 given intradermally to guinea pigs caused vascular leakage which was suppressed by prior administration of LY171883. LTC4-induced contractions of isolated ilea were only minimally antagonized by LY171883 whereas this agent reduced LTC4-evoked increases in total pulmonary resistance. Trachea contracted by LTD4 were relaxed by LY171883. Likewise, trachea contracted by either histamine or carbamylcholine were relaxed by LY171883 suggesting that this compound has airway smooth muscle relaxing properties. In vivo experiments supported these observations. In concert with these findings, biochemical studies showed LY171883 to be a potent inhibitor of phosphodiesterase obtained from human polymorphonuclear leukocytes and various guinea-pig tissues. This pharmacologic analysis indicates that LY171883, or a congener, may be of therapeutic value in asthma and in disease states characterized by an overproduction of LTD4.
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PMID:LY171883, 1-less than 2-hydroxy-3-propyl-4-less than 4-(1H-tetrazol-5-yl) butoxy greater than phenyl greater than ethanone, an orally active leukotriene D4 antagonist. 398 52


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