0027: NGF contributes to medial and intimal remodelling of pulmonary arteries in pulmonary hypertension: receptors and signalling pathways involved in smooth muscle and endothelial cell proliferation

Abstract

We have previously identified critical roles for the nerve growth factor NGF in pathophysiology of pulmonary hypertension (PH). We have here evaluated whether NGF may contribute to medial and intimal remodelling of pulmonary arteries in vivo in PH rat models. We have also investigated the NGF receptors and signalling pathways involved in vitro in NGF-induced proliferation of human pulmonary arterial smooth muscle (hPASMC) and endothelial cells (hPAEC). Experimental PH in the rat was induced either by a single injection of monocrotaline (MCT, 60mg/kg), or after 28 days of chronic hypoxia (CH, 0.5atm). Anti-NGF blocking antibodies (10μg/kg ip) were administered as a preventive or a curative treatment. Pulmonary arterial pressure was assessed after 28 days. Medial and intimal remodelling of pulmonary arteries were then evaluated on lung sections after hematoxylin/eosin or Van Gieson stainings. hPASMC or hPAEC proliferation was assessed by the BrdU technique, and involvement of the NGF receptors TrkA and p75 NTR was studied by both pharmalogical and SiRNA approaches. In vivo , NGF inhibition with anti-NGF blocking antibodies both prevented and reversed medial and intimal remodelling of pulmonary arteries in MCT and CH rats. In vitro , NGF-induced hPASMC proliferation occurred at low concentrations and only involved TrkA/PI3-kinase dependent signalling pathways. NGF-induced hPAEC proliferation occurred at higher concentrations and involved both TrkA and p75 NTR receptors activating PI3-kinase independent/ NF?B-dependent signalling pathways. We show here that NGF contributes to medial and intimal remodelling of pulmonary arteries in vivo in PH rat models. This may occur through stimulation of both hPASMC and hPAEC proliferation, but through distinct receptors and signalling pathways in these two different cell types, thus suggesting that blocking both NGF receptors may be of therapeutical interest in PH.