Expression and function of phosphodiesterases in nitrofen-induced congenital diaphragmatic hernia in rats.
BACKGROUND
Congenital diaphragmatic hernia (CDH) is an anomaly associated with pulmonary hypoplasia and pulmonary hypertension (PH). The limited efficacy of current approaches to treat PH in CDH, including inhaled nitric oxide (NO), drives the search for other therapies. Phosphodiesterases (PDEs) degrade cyclic nucleotide second messenger cAMP and cGMP downstream of NO thereby limiting the vasodilatory response to NO.


OBJECTIVE
To identify therapeutic targets by cataloguing the expression and function of PDE isoforms in the pulmonary vasculature in nitrofen-induced CDH in fetal rats.


RESULTS
Quantitative RT-PCR revealed PDE1-5 and PDE9 mRNA expression in pulmonary arteries (PAs) of control and nitrofen-induced CDH term fetal rats. In this order of potency, the PDE inhibitors Sildenafil (PDE5) > EHNA (PDE2) > Rolipram (PDE4) > Cilostamide (PDE3) all dilated isolated third generation PA after pre-constriction with the thromboxane analog U46619. Hyperoxic pre-incubation of PAs significantly attenuated vasodilatation induced by the PDE5 inhibitor Sildenafil (65% vs. 33%, P < 0.004). CDH PAs dilated significantly less to PDE2 inhibitor EHNA compared to control (51% vs. 72%, P < 0.05). Subsequently PDE2 protein expression was higher in PAs of CDH animals.


CONCLUSIONS
Most PDE isoforms exist in the PAs of fetal rats and their inhibition causes pulmonary vasodilatation. PDE5 inhibition was the most potent vasodilator, however, there were no differences between groups. PDE5-induced vasodilatation was attenuated by hyperoxic pre-incubation. PDE inhibitors might be considered therapeutic targets in combination with iNO in neonates with CDH.
van der Horst
Irene W J M
IW
Department of Pediatrics and Physiology, Division of Neonatology, Women and Children Health Research Institute, University of Alberta, Edmonton, Alberta, Canada.
Morgan
Beverly
B
Eaton
Farah
F
Reiss
Irwin
I
Tibboel
Dick
D
Thébaud
Bernard
B
D000818:Animals; D004195:Disease Models, Animal; D006548:Hernia, Diaphragmatic / Q000139:chemically induced / Q000201:enzymology*; D065630:Hernias, Diaphragmatic, Congenital; D018496:Hyperoxia / Q000201:enzymology; D010647:Phenyl Ethers; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D011651:Pulmonary Artery / Q000201:enzymology; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D014664:Vasodilation
D010647:Phenyl Ethers; D010727:Phosphoric Diester Hydrolases; C007350:nitrofen