Characterization of guinea-pig eosinophil phosphodiesterase activity

1 This study aimed to evaluate the effects of phosphodiesterase (PDE) inhibitors and currently prescribed anti-asthma drugs for their ability to inhibit inflammatory cell activation in vitro. 2 Alveolar macrophages and eosinophils were isolated from the bronchoalveolar lavage (BAL) fluid of ovalbumin (Ovalb)-sensitized guinea-pigs. Opsonized zymosan (OZ) and PAF stimulated leukotriene B4 (LTB4) release from eosinophils was measured by radioimmunoassay. Ovalb-induced superoxide generation was measured by reduction of cytochrome C. 3 Monocytes were separated from human peripheral venous blood and mast cells were dispersed from human lung fragments. Lipopolysaccharide (LPS)-induced tumour necrosis factor-a (TNF-a) release from monocytes was measured by ELISA and anti-IgE stimulated histamine release from mast cells was measured by a radioenzymatic method. 4 The fl2 agonist, salbutamol inhibited TNF-a release from monocytes and histamine release from mast cells whilst having no effect on eosinophil-derived LTB4 release or macrophage superoxide generation. 5 The PDE 3 inhibitor, milrinone produced a concentration-related inhibition of TNF-a release from monocytes which achieved statistical significance at 10-5 M but inhibited LTB4 release from eosinophils and superoxide generation from macrophages only at the highest concentration (10-3 M) examined. Milrinone had no effect on histamine release from mast cells. 6 The selective PDE 4 inhibitors, denbufylline and rolipram and the corticosteroid, beclomethasone produced a concentration-related inhibition of LTB4 release from eosinophils, TNF-ax release from monocytes and superoxide generation from alveolar macrophages whilst having no effect on histamine release from mast cells. 7 The mixed PDE 3/4 inhibitor, benzafentrine produced a concentration-related inhibition of LTB4 release from eosinophils, TNF-a release from monocytes, superoxide generation from alveolar macrophages and histamine release from mast cells. 8 In conclusion these data clearly show that both established anti-asthma medication as well as PDE inhibitors have the potential to inhibit inflammatory cell activation in vitro but that the anti-secretory actions of fl2 agonists, corticosteroids and PDE inhibitors are distinct.

Section: Discussionsupporting

confidence: 72%

The effect of selective phosphodiesterase 3 and 4 isoenzyme inhibitors and established anti‐asthma drugs on inflammatory cell activation

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Moriggi

Ros

et al. 1996

“…Surprisingly, none of the selective PDE inhibitors tested substantially inhibited ECP/EDN secretion or the chemiluminescence response, although all of these compounds were much more potent PDE IV inhibitors than theophylline or even IBMX in the cell-free system. These results are in contrast to guinea-pig peritoneal eosinophils, the 02-formation of which has been demonstrated to be sensitive to inhibition by selective PDE IV inhibitors both in resting cells (Souness et al, 1991) and in opsonized zymosanstimulated cells (Dent et al, 1991). Whether this difference represents species-specific effects or is due to differences in the experimental conditions remains unexplained at the moment.…”

Section: Discussioncontrasting

confidence: 47%

“…These results indicate that the handling of the cells prior to and during disruption is a critical determinant of PDE IV localization at least in human eosinophils. Differences in the experimental procedure for the preparation of subcellular fractions may therefore account for the membrane localization of PDE IV reported by others in human (Giembycz & Barnes, 1993) as well as guinea-pig (Souness et al, 1991;Dent et al, 1991) eosinophils. In addition, the localization of PDE IV in eosinophils may be speciesdependent.…”

Section: Discussionmentioning

confidence: 97%

Differential effects of non‐selective and selective phosphodiesterase inhibitors on human eosinophil functions

Hatzelmann

Tenor

Schudt

1995

1 The effect of non-selective (3-isobutyl-l-methylxanthine, IBMX; theophylline) and type IV-or tolafentrine also inhibited both cell responses in the presence of salbutamol, the potency of these two compounds in inhibiting eosinophil function in intact cells was at least two orders of magnitude lower than would have been expected from the inhibition of PDE IV activity in the cell-free system. 5 These results indicate that (i) C0a-stimulated human eosinophils are sensitive to inhibition by the non-selective PDE inhibitors theophylline and IBMX, (ii) the inhibitory effect of these non-selective PDE inhibitors cannot be mimicked by selective PDE IV or PDE III/IV inhibitors although human eosinophils almost exclusively contain PDE IV; (iii) the selective PDE inhibitors need an additional cyclic AMP trigger like a P2-adrenoceptor agonist to be effective; but (iv) under the latter conditions inhibition of cell responses in intact cells does not correspond to inhibition of PDE IV activity in the cell-free system. 6 We conclude that the non-selective PDE-inhibiting xanthines may inhibit C5a-stimulated human eosinophil responses by other action(s) in addition to PDE IV inhibition, and that inhibition of PDE IV activity in the cell-free system by the selective inhibitors may not generally represent the potency of the compounds in intact cells.

“…The type 4 PDE isoenzyme appears to be the main PDE isoenzyme present in inflammatory cells and has been characterized in T-lymphocytes, eosinophils, neutrophils, monocytes, basophils, mast cells and endothelial cells (Souness et al, 1991;Giembycz, 1992), although the type 3 PDE isoenzyme has also been identified in human peripheral blood lymphocytes (Thompson et al, 1976;Robicsek et al, 1991).…”

Section: Discussionmentioning

confidence: 99%

Differential effect of phosphodiesterase 4 inhibitors on the proliferation of human peripheral blood mononuclear cells from normals and subjects with atopic dermatitis

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Roberts

Page

1995