Pulmonary Arterial Hypertension (PAH) is characterized by progressive pulmonary arteries (PAs) obstruction leading to heart failure and death. PA smooth muscle cells (PASMCs) from PAH patients display a ?cancer-like? phenotype contributing to PA remodeling. Eukaryotic translation initiation factor 5A (eIF5A) provides cancer cells with a competitive advantage by increasing translation of mRNAs with oncogenic proprieties. eIF5A is the only protein containing the unique spermidine-derived amino acid hypusine required for its function. Hypusine formation is catalyzed by the sequential action of DHPS and DOHH. We hypothesized that hypusine signaling is increased in PAH and contributes to pulmonary vascular remodeling.

As assessed by LC-MSMS and WB, expression levels of DHPS, DOHH and both total and hypusinated forms of eIF5A were found increased in PAs and PASMCs from PAH patients and animal models. In vitro, both molecular and pharmacological inhibition of DHPS and DOHH significantly attenuates PAH-PASMCs survival (WB Survivin; Annexin V) and proliferation (WB MCM2, PLK1; Ki67 labelling and EdU incorporation). These effects were associated with a decrease in mitochondrial oxidative phosphorylation (LC-MSMS, WB, Seahorse). In vivo, smooth muscle cells-targeted inactivation of one allele of Dhps conferred partial protection against the development of Sugen/Hypoxia (Su/Hx)-induced PAH in mice. Pharmacological inhibition of DHPS using GC7 improved hemodynamics (RVSP, mPAP, CO) and vascular remodeling (EVG) in monocrotaline and Su/Hx rats with established PAH.

In conclusion, we showed for the first time that hypusine signaling is implicated in PAH development and represents a new promising therapeutic target.