Identification and quantification of phosphodiesterase 4 subtypes in CD4 and CD8 lymphocytes from healthy and asthmatic subjects

1 In the present study, for the first time, PDE4 subtypes were identified a nd semi-quantified ill both CD4 and CD8 lymphocytes from healthy and asthma tic individuals. 2 CD4 and CD8 lymphocytes from healthy and mild asymptomatic asthmatic subj ects (receiving beta -agonist therapy only) were isolated from peripheral v enous blood using appropriate antibody coated paramagnetic beads. PDE4 subt ypes and beta -actin were identified by digoxigenin (DIG)-labelling reverse transcriptase-polymerase chain reaction and semi-quantified by DIG-detecti on enzyme-linked immunosorbance assay. 3 In CD4 and CD8 lymphocytes PDE4A, PDE4B and PDE4D were detected, with no significant differences observed between healthy and asthmatic groups. In C D8 lymphocytes, enzyme subtype expression was lower and showed more intersu bject variability. 4 In functional studies investigating the effects of various PDE inhibitors on PHA-induced proliferation of mononuclear cells from healthy and asthmat ic subjects, CDP840 (0.03-10 muM), rolipram (0.1-10 muM) and theophylline ( 10 muM-1 mM) inhibited PHA-induced proliferation of mononuclear cells from healthy and asthmatic subjects in a concentration-dependent manner, althoug h no significant difference was observed between the groups investigated. 5 In additional studies, total monocyte cyclic AMP PDE activity was investi gated in cells isolated from asthmatic subjects both prior to and 24 h afte r allergen challenge. Total monocyte cyclic AMP PDE activity remained unaff ected following challenge of asthmatic subjects with either house dust mite or cat dander and was inhibited in a concentration-dependent manner by rol ipram (0.01-100 muM) both before and after allergen challenge.