beta-Adrenoceptor stimulation up-regulates phosphodiesterase 4 activity and reduces prostaglandin E-2-inhibitory effects in human neutrophils

Human neutrophils were treated for 4 h with a combination of salbutamol (1 mu M), a beta(2)-adrenoceptor agonist, and rolipram (30 mu M), a selective phosphodiesterase 4 inhibitor, to investigate whether this treatment produc es up-regulation of phosphodiesterase activity with functional consequences . Anion-exchange chromatography coupled with the use of selective activator s and inhibitors demonstrated that a phosphodiesterase activity with charac teristics of the isoenzyme type 4 was increased in drug-treated cells. Kine tic analysis showed a similar to 1.5-fold increase in V-max without alterat ion of K-m values. The augmented phosphodiesterase activity in drug-treated cells was abolished by actinomycin D. Cyclic AMP content in drug-treated c ells was higher than resting values (27.28+/-2.79 pmol/10(6) cells vs. 0.34 +/-0.03 pmol/10(6) cells). Reverse transcriptase-polymerase chain reaction showed increased expression of mRNA transcripts for PDE4B and PDE4A in drug -treated cells. Functionally, up-regulation of phosphodiesterase 4 reduced the inhibition by prostaglandin E-2 of zymosan-induced superoxide generatio n.