Late Breaking Abstract - NGF induces pulmonary arterial hyperreactivity through increased connexin-43 expression: potential role in pulmonary hypertension

Introduction: We previously showed a pivotal role of the nerve growth factor NGF in pulmonary hypertension (PH). We and others also showed a role of connexin-based GAP junctions in PH. We have here studied whether NGF may affect connexin-43 (Cx43) pulmonary arterial expression to contribute to PH pathophysiology. Methods: Control human pulmonary arterial endothelial (hPAEC) or smooth muscle cells (hPASMC) and control rat pulmonary arteries (PA) were treated in vitro/ex vivo with NGF (0‑100ng/ml, 24h). In vivo, rats were exposed to chronic hypoxia (CH, 0.5atm, 28 days) to induce experimental PH, and were concomitantly treated with anti-NGF blocking antibodies (10µg/kg ip). Cx43 expression in human cells and rat PA was assessed by Western blotting. Contractions of control rat PA were induced ex vivo by phenylephrine (PHE, 10-10-10-4M) in absence or presence of NGF (100ng/ml, 24h). Results: NGF significantly increased Cx43 expression in human cells and rat PA. This increase was abolished after treatment with K252a (TrkA kinase inhibitor) or in cells transfected with a TrkA siRNA. Wortmannin (PI3K inhibitor) and PD98059 (ERK pathway inhibitor) also totally blocked this increase. In vivo, anti-NGF blocking antibodies prevented Cx43 increased expression in PA from CH rats. Ex vivo, NGF significantly increased rat PA reactivity to PHE. K252a, wortmannin, PD98059 and 43Gap26 (Cx43 blocking peptide) abolished this effect. Conclusions: Our results show that NGF increases Cx43 expression in human and rat PA through a TrkA/PI3K/ERK-dependent signalling pathway. This mechanism contributes to NGF‑induced PA hyperreactivity and may thus participate in PH pathophysiology.