Role of Phosphodiesterases in Adult-Onset Pulmonary Arterial Hypertension - Phosphodiesterases as Drug Targets - page 284

a b

500

400
300
150

100

50

0

c

Fig. 1 Multiple PDE isoforms are expressed in PASMCs and upregulated with PAH. (a) Real-
time PCR shows that mRNA of multiple PDEs are expressed in PASMCs, Ct normalized to
PDE11. (b) PDE1A, 1C, 3B, 5A, and 7A are upregulated in PAH-PASMCs vs. control-PASMCs.
(c) The relative contribution of PDE1 and PDE3 to total cAMP-PDE activity is increased with
PAH. PDE activity was determined using 1 m M cAMP as substrate through a two-step radioassay
procedure (Keravis et al. 2005 ; Thompson et al. 1974 ). To identify the contribution of activity
of specific PDEs, assays were performed in the presence of specific PDE inhibitors [PDE1, 30 m M
vinpocetine, 30 m M 8-methoxy-methyl-3-isobutyl-1-methylxanthine (8-MM-IBMX); PDE2,
10 m M erythro-9-(2-hydroxy-3-nonyl)-adenine (EHNA) in the presence of excess cGMP; PDE3,
10 m M milrinone; and PDE4, 10 m M rolipram] and with or without Ca 2+ /calmodulin in the
presence of EGTA. PASMCs used in these experiments were between passage 4 and 6. n ¼ 5,

* P 0.05 vs. control

<

support the role of PDEs in their vasodilator capacity in PAH and other aspects
of the disease for which targeting of PDEs may be beneficial.

3.1 Targeting PDEs in Pulmonary Artery Vasoconstriction
and Remodeling

3.1.1 Role of PDE5 in Pulmonary Vasculature

PDE5, the main cGMP-PDE in the lung, is thought to contribute to ~80% of cGMP
hydrolysis in PASMCs and therefore is important for the regulation of normal
pulmonary vascular tone (Ahn et al. 1991 ; Corbin et al. 2005 ; Fink et al. 1999 ;