1 In the present study, for the ®rst time, PDE4 subtypes were identi®ed and semi-quanti®ed in both CD4 and CD8 lymphocytes from healthy and asthmatic individuals. 2 CD4 and CD8 lymphocytes from healthy and mild asymptomatic asthmatic subjects (receiving bagonist therapy only) were isolated from peripheral venous blood using appropriate antibody coated paramagnetic beads. PDE4 subtypes and b-actin were identi®ed by digoxigenin (DIG)-labelling reverse transcriptase-polymerase chain reaction and semi-quanti®ed by DIG-detection enzyme-linked immunosorbance assay. 3 In CD4 and CD8 lymphocytes PDE4A, PDE4B and PDE4D were detected, with no signi®cant di erences observed between healthy and asthmatic groups. In CD8 lymphocytes, enzyme subtype expression was lower and showed more intersubject variability. 4 In functional studies investigating the e ects of various PDE inhibitors on PHA-induced proliferation of mononuclear cells from healthy and asthmatic subjects, CDP840 (0.03 ± 10 mM), rolipram (0.1 ± 10 mM) and theophylline (10 mM ± 1 mM) inhibited PHA-induced proliferation of mononuclear cells from healthy and asthmatic subjects in a concentration-dependent manner, although no signi®cant di erence was observed between the groups investigated. 5 In additional studies, total monocyte cyclic AMP PDE activity was investigated in cells isolated from asthmatic subjects both prior to and 24 h after allergen challenge. Total monocyte cyclic AMP PDE activity remained una ected following challenge of asthmatic subjects with either house dust mite or cat dander and was inhibited in a concentration-dependent manner by rolipram (0.01 ± 100 mM) both before and after allergen challenge.

1 For a subpopulation of asthmatics, symptoms persist even with high doses of glucocorticoids. Glucocorticoids reduce the levels of the proinflammatory and fibrogenic cytokine, granulocytemacrophage colony-stimulating factor (GM-CSF) produced by human cultured airway smooth muscle (ASM). We have contrasted the effects of a synthetic glucocorticoid, dexamethasone, on thrombin-and IL-1a-stimulated GM-CSF production in human ASM cells. 2 Although IL-1a stimulated three-fold higher levels of GM-CSF mRNA and protein compared to thrombin, dexamethasone concentration-dependently reduced IL-1a-stimulated GM-CSF more potently and to a greater extent than the response to thrombin. This pattern of glucocorticoid regulation was also observed at the GM-CSF mRNA level and was reproduced with other glucocorticoids such as fluticasone propionate. 3 IL-1a and thrombin stimulated NF-kB-dependent luciferase expression equally. Dexamethasone treatment reduced luciferase expression stimulated by both IL-1a and thrombin. 4 The GM-CSF mRNA half life was markedly prolonged by IL-1a compared to thrombin. This IL-1a-induced GM-CSF mRNA stability was prevented by either dexamethasone or the p38 MAPK inhibitor, SB203580, neither of which influenced GM-CSF mRNA stability in thrombin-treated cells. Dexamethasone inhibited p38 MAPK phosphorylation in IL-1a-stimulated ASM, whereas thrombin does not stimulate p38 MAPK phosphorylation. 5 These data suggest that the mechanism underlying the greater potency and efficacy of glucocorticoids in reducing GM-CSF synthesis stimulated by IL-1a depends on inhibition of the involvement of p38 MAPK -induced increases in GM-CSF message stability.

No abstract

No abstract