Human bronchial cyclic nucleotide phosphodiesterase isoenzymes: biochemical and pharmacological analysis using selective inhibitors

Abstract

1 The aims of the present study were to characterize the cyclic nucleotide phosphodiesterase (PDE) isoenzyme activities present in human bronchi and to examine the ability of selective isoenzyme inhibitors to relax histamine and methacholine precontracted preparations of human bronchi. 2 Three separations of pooled human bronchial tissue samples were performed. Ion-exchange chromatography showed that the soluble fraction of human bronchial preparations contains PDE I, II, III, IV and V isoenzyme activities. Multiple forms of PDE I and PDE IV were observed and PDE IV was the main cyclic AMP hydrolytic activity. 3 3-Isobutyl-l-methylxanthine (IBMX) non-selectively inhibited all separated isoenzyme activities. Zaprinast selectively inhibited PDE V, but also effectively inhibited one of the two PDE I isoforms identified. The PDE IV selective inhibitors rolipram and RO-201724, inhibited the PDE IV activities as did the dual PDE III/IV inhibitor, Org 30029. Org 9935, a PDE III selective inhibitor, potently attenuated part of the PDE IV activity peak in one of three separations performed, indicating that some PDE III activity may co-elute with PDE IV under the experimental conditions employed. 4 PDE IV-selective (rolipram), PDE III-selective (Org 9935) and dual PDE III/IV (Org 30029) inhibitors were effective relaxants of human bronchial smooth muscle. The PDE V/PDE I inhibitor, zaprinast was relatively ineffective. 5 The present study demonstrates in human bronchi, as in animal airways smooth muscle, that inhibitors of PDE III, PDEIV and dual PDE III/IV have potentially useful bronchodilator activity and are worthy of further consideration as anti-asthma drugs.

Effect of the Mixed Phosphodiesterase 3/4 Inhibitor RPL554 on Human Isolated Bronchial Smooth Muscle Tone

“…Inhibition of PDE3/4 has previously been reported to induce relaxation of canine airways, guinea pig trachea, and human ASM preparations (de Boer et al, 1992;Naline et al, 1996;Torphy, 1998;Boswell-Smith et al, 2006b). We have demonstrated that the selective inhibition of PDE3/4 by RPL554 elicited relaxation of bronchial tone in human isolated airways, which extends and supports observations previously reported in guinea pig isolated trachea with this drug Fig.…”

Effects of rolipram and siguazodan on the human isolated bronchus and their interaction with isoprenaline and sodium nitroprusside

“…under conditions similar to those described by Tomkinson et al (1993) on the airways of guinea-pig, cow, pig and mousetend to support previous observations and suggest that there may be a similar relationship between P2-adrenoceptors and PDE type IV in the human bronchus since rolipram seems to be as potent (or slightly more potent) than isoprenaline and salbutamol, and about 10 fold more potent than siguazodan. Since both rolipram and the selective PDE III inhibitor Org 9935 were potently active at concentrations required for selectivity (de Boer et al, 1992), both PDE III and IV may be important in regulating contractility. Indeed de Boer et al (1992) demonstrated that equally potent inhibition of methacholine-induced contractions was seen with selective type IV and type III cyclic AMP PDE inhibitors.…”

“…Since both rolipram and the selective PDE III inhibitor Org 9935 were potently active at concentrations required for selectivity (de Boer et al, 1992), both PDE III and IV may be important in regulating contractility. Indeed de Boer et al (1992) demonstrated that equally potent inhibition of methacholine-induced contractions was seen with selective type IV and type III cyclic AMP PDE inhibitors. This was not the case in our study where rolipram was 10 fold more potent than siguazodan.…”

The Pharmacology of Two Novel Long-Acting Phosphodiesterase 3/4 Inhibitors, RPL554 [9,10-Dimethoxy-2(2,4,6-trimethylphenylimino)-3-(N-carbamoyl-2-aminoethyl)-3,4,6,7-tetrahydro-2H-pyrimido[6,1-a]isoquinolin-4-one] and RPL565 [6,7-Dihydro-2-(2,6-diisopropylphenoxy)-9,10-dimethoxy-4H-pyrimido[6,1-a]isoquinolin-4-one]

“…Airway smooth muscle relaxation is observed following inhibition of PDE3 or PDE4 in canine (Torphy et al, 1988;Torphy and Undem, 1991), guinea pig trachea (Raeburn et al, 1993;Spina et al, 1995), and human airway preparations (de Boer et al, 1992;Rabe et al, 1995), which is primarily thought to be mediated by PDE3 (Cortijo et al, 1993). RPL554 and RPL565 both caused a concentration-and timedependent inhibition of contractile responses elicited by EFS.…”