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)

Numerous investigations have described cutaneous and systemic physiological and pharmacological aberrations in atopic dermatitis and the atopic diathesis. Some of these studies set the stage for a focus upon cyclic nucleotide abnormalities. Elevated leukocyte cyclic AMP-phosphodiesterase accounts for low intracellular cyclic AMP levels in atopic dermatitis. The resultant permissive effect correlates with abnormal functional parameters such as increased basophil histamine release and in vitro IgE synthesis. In vitro and clinical use of phosphodiesterase inhibitors corrects abnormal parameters and may indicate future therapeutic directions.
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PMID:Pharmacological abnormalities in atopic dermatitis. 247 82

Significantly elevated activity of peripheral blood mononuclear cell cAMP specific phosphodiesterase (PDE) activity has been previously reported in adults with atopic dermatitis and in the cord blood of children born to atopic parents. We have been unable to confirm such a significant elevation in children with atopic dermatitis, and we have not found any correlation with dermatitis severity, age or total serum IgE.
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PMID:Peripheral blood mononuclear leukocyte cyclic adenosine monophosphate specific phosphodiesterase activity in childhood atopic dermatitis. 254 17

Binding of polyvalent antigens to IgE present in Fc epsilon receptors on the surface of mast cells and the RBL-2H3 cell line triggers the exocytotic release of allergic mediators. Preincubation of RBL-2H3 cells with cholera toxin (CT) was found to potentiate greater than or equal to 2- to 3-fold the rate and final amount of antigen-induced secretion of [3H]serotonin and N-acetyl beta-D-glucosaminidase. This was accompanied by a more variable increase in the initial rate of antigen-triggered formation of inositol phosphates. The holotoxin was required for potentiation, as neither the A nor the B subunit was effective when added separately. Four observations indicate that cAMP was not the primary effector of the augmentation of secretion caused by CT: (i) culture conditions were found in which CT caused large increases in secretion but very modest (or no) increases in cAMP; (ii) under other conditions, progressive increase in [CT] caused a maximum 2.5- to 3-fold increase in cAMP followed by a return to basal levels, whereas the secretory response saturated and remained stable; (iii) permeant cAMP analogs consistently enhanced secretion at low doses and inhibited at higher doses, but the peak enhancement was always much less than that achieved by an optimal dose of CT; (iv) the selective phosphodiesterase inhibitor Ro 20-1724 exhibited similar biphasic dose-response curves, the maximum enhancement again being small compared to that caused by CT itself. Both in vitro and in vivo, CT catalyzed transfer of ADP-ribose from NAD to two membrane proteins that comigrated on NaDodSO4/polyacrylamide gel electrophoresis with two CT substrates in other cell types, and these were identified by immunoblotting as Gs alpha. These results suggest that ADP-ribosylation of a cholera toxin substrate potentiates IgE-mediated secretion from RBL-2H3 cells by a largely cAMP-independent route.
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PMID:Cholera toxin potentiates IgE-coupled inositol phospholipid hydrolysis and mediator secretion by RBL-2H3 cells. 284 4

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

Atopic dermatitis is clearly characterized by altered cutaneous physiologic responses. There is a tendency to acral vasoconstriction. Rubbing causes skin pallor and white dermographism. Vascular instability is demonstrated by responses to cholinergic agents, histamine, and nicotinates. Psychophysiologic studies demonstrate exaggerated vasodilator responses to emotional stress with consequent pruritus and scratching. The itch threshold is low, duration is prolonged, and nighttime scratching movements may be frequent or almost continuous. Regardless of the inciting trigger factors, the scratching causes the damage and the severe dermatitis. Thermal as well as emotional stimuli to sweating cause severe itching in AD, yet the concept of a miliaria-type, poral occlusion mechanism remains unproven. Some studies suggest actually increased sweating along with erythema and pruritus during acute flares of AD. The concept of sweat-borne allergens causing skin reactions during sweating is interesting but has never been proven. Studies of sweat responses to pharmacologic agents have produced conflicting data, and attempts to link these responses to Szentivanyi's beta-adrenergic blockade theory are not convincing. The numerous variables of climate, season, sex, age, and habitus affect sweating greatly. Future studies must carefully control for each of these factors before pharmacologically induced sweat responses can be interpreted clearly. A number of lines of evidence suggest involvement of histamine and other mediators in the evolution of erythema, pruritus, and scratching in AD. Flares of the condition have been reproducibly evoked by only two incitants: experimental emotional stress interviews and specific food challenge in selected sensitive individuals. In the latter, increased plasma histamine has been demonstrated, presumably generated by antigen/IgE stimulated degranulation of mast cells in the gut and/or skin. The demonstrated increased histamine releasability of basophils from atopic individuals may be the result of defective cellular regulatory mechanisms. Recent studies have demonstrated increased cyclic AMP-phosphodiesterase activity in leukocytes from atopic individuals. The resultant decreased intracellular cyclic AMP removes an inhibitory factor, which in turn causes net cellular hyperresponsiveness. This effect has been shown to account, at least in part, for increased histamine release from leukocytes of patients with AD. These and other studies focused upon cell functional regulation are providing better understanding of basic biochemical abnormalities and may lead to improved diagnostic and therapeutic approaches in managing atopic disease.
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PMID:Pharmacophysiology of atopic dermatitis. 300 74

Leukocytes of patients with atopic eczema exhibit a variety of biochemical abnormalities, particularly an alteration in cyclic nucleotide metabolism. The basic defect is an elevation of phosphodiesterase activity in these cells, which leads to a diminished modulation of cellular immune function by cAMP. This, in turn, leads to an elevation of IgE synthesis and enhanced release of inflammatory mediators from mast cells and basophils. The phosphodiesterase defect offers new approaches to the treatment of atopic eczema.
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PMID:[Changed phosphodiesterase activity of leukocytes in atopic eczema]. 303 85

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

Peripheral blood mononuclear leukocytes (MNL) from patients with atopic dermatitis spontaneously produce large amounts of IgE in vitro. These cells also show markedly elevated levels of cAMP phosphodiesterase (PDE) which may be responsible for the observed abnormal cAMP responsiveness. Treatment of atopic dermatitis MNL with varying concentrations of the cAMP PDE inhibitor Ro 20-1724 resulted in progressively decreasing amounts of IgE synthesis, statistically significant at the 10(-4) M and 10(-5) M concentrations. There was a close correlation between PDE inhibition and inhibition of IgE synthesis, r = 0.93, p less than 0.05. To define the cellular target of the drug, we used monoclonal antibodies directed toward MNL subsets (Lyt 3, OKT8, OKT4, monocyte-myeloid) in a modified "panning" method to perform experiments with purified subsets. With untreated subsets, removal of OKT4-positive cells significantly reduced IgE synthesis; readdition of OKT4-positive cells enhanced IgE synthesis. OKT8 cells and monocytes did not affect IgE synthesis. Pretreatment of T cell-depleted MNL with Ro 20-1724 resulted in significantly more inhibition of IgE synthesis than did pretreatment of T enriched cells prior to recombination with the reciprocal untreated subset and subsequent culture. Similarly, pretreatment of monocyte-depleted cells resulted in significantly more inhibition of IgE synthesis than pretreatment of monocyte-enriched cells prior to recombination and culture. The majority of the effect appeared to be mediated by a direct effect on the B cells. However, some inhibition of IgE synthesis was also achieved through pretreatment of T enriched cells. Since pretreatment of isolated suppressor/cytotoxic or helper/inducer T-cell subsets did not give the same degree of inhibition as with unfractionated T cells, a T-T interaction may be involved in this aspect. The imidazolidinone derivative, Ro 20-1724, significantly and consistently inhibited both the elevated cAMP phosphodiesterase activity and the elevated spontaneous IgE synthesis of MNL from patients with atopic dermatitis. These findings demonstrate a previously undescribed link between cAMP PDE levels and in vitro IgE synthesis.
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PMID:Phosphodiesterase inhibition by Ro 20-1724 reduces hyper-IgE synthesis by atopic dermatitis cells in vitro. 399 94

The history of atopic dermatitis is replete with many disparate theories. The most enduring is the allergic causation theory but definitive, convincing evidence remains elusive. Elevated IgE synthesis is well established and reflects abnormal immune regulation. The basic mechanism for the regulatory defect remains conjectural. Cellular immune functions, including delayed cutaneous hypersensitivity, in vitro lymphocyte transformation and chemotaxis are reduced in atopic dermatitis. However, these abnormalities fluctuate with the clinical condition and may be secondary phenomena. A number of physiologic and pharmacologic abnormalities in atopic dermatitis are not clearly understood. Recent studies of patients leukocytes have shown that the diminished cyclic AMP responses are a consequence of increased catabolism by elevated cyclic AMP-specific phosphodiesterase. This high enzyme activity correlates well with elevated IgE synthesis and histamine release by cultured leukocytes. Both of these functions can be reduced by phosphodiesterase inhibitors in vitro. These new investigations provide fresh insight into the pathogenesis of atopic dermatitis and offer possible new therapeutic approaches. Basic studies of biochemical abnormalities may help define the defective molecular site that accounts for the many immune and physiologic abnormalities that have been described in atopic dermatitis and the other atopic conditions.
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PMID:Basic and clinical aspects of atopic dermatitis. 614 76


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