Trifluoperazine (TFP), an antipsychotic drug approved by the Food and Drug Administration, has been show to exhibit anti-cancer effects. Pulmonary arterial hypertension (PAH) is a devastating disease characterized by a progressive obliteration of small pulmonary arteries (PAs) due to exaggerated proliferation and resistance to apoptosis of PA smooth muscle cells (PASMCs). However, the therapeutic potential of TFP for correcting the cancer-like phenotype of PAH-PASMCs and improving PAH in animal models remains unknown. PASMCs isolated from PAH patients were exposed to different concentrations of TFP before assessments of cell proliferation and apoptosis. The in vivo therapeutic potential of TFP was tested in two preclinical models with established PAH, namely the monocrotaline and sugen/hypoxia-induced rat models. Assessments of hemodynamics by right heart catheterization and histopathology were conducted. TFP showed strong anti-survival and anti-proliferative effects on cultured PAH-PASMCs. Exposure to TFP was associated with downregulation of AKT activity and nuclear translocation of forkhead box protein O3 (FOXO3). In both preclinical models, TFP significantly lowered the right ventricular systolic pressure and total pulmonary resistance and improved cardiac function. Consistently, TFP reduced the medial wall thickness of distal PAs. Overall, our data indicate that TFP could have beneficial effects in PAH and support the view that seeking new uses for old drugs may represent a fruitful approach.

Pulmonary arterial hypertension is a debilitating chronic disorder marked by the progressive obliteration of the pre-capillary arterioles. This imposes a pressure overload on the right ventricle (RV) pushing the latter to undergo structural and mechanical adaptations that inexorably culminate in RV failure and death. Thanks to the advances in molecular biology, it has been proposed that some aspects of the RV and pulmonary vascular remodeling processes are orchestrated by a subversion of developmental regulatory mechanisms with an upregulation of a suite of genes responsible for the embryo’s early growth and normally repressed in adults. In this review, we present relevant background regarding the close relationship between overactivation of fetal genes and cardiopulmonary remodeling, exploring whether the reawakening of developmental factors plays a causative role or constitutes a protective mechanism in the setting of PAH.

Pulmonary arterial hypertension (PAH) is characterized by the narrowing of pulmonary arteries (PAs), causing right ventricular (RV) failure and premature death. Pulmonary artery smooth muscle cells (PASMCs) from PAH patients exhibit increased proliferation and resistance to apoptosis in response to extracellular matrix remodeling. Integrins are known to be involved in all these processes. Our hypothesis is that integrin signaling promotes PASMCs proliferation and apoptosis resistance, leading to PA remodeling, RV maladaptive hypertrophy and fibrosis, resulting in RV failure in PAH. Using NanoString, we identified members of the fibronectin-binding integrins (FnBIs) family as the most abundantly expressed in PAH-PASMCs. We confirmed the changes in FnBIs expression levels by Western blot (WB) in distal PAs, PASMCs and decompensated RVs from PAH patients compared to controls. Pharmacological inhibition of FnBIs decreased PAH-PASMCs proliferation (WB PLK1; Ki67), resistance to apoptosis (WB Survivin; Annexin V) and was associated with a decreased activation of FnBIs downstream signaling pathways FAK and ILK. In adult rat cardiomyocytes and human RV fibroblasts (RVFbs), FnBIs inhibition decreased phenylephrine-induced hypertrophy (f-actin labelling) and TGFβ1-induced RVFbs activation (WB αSMA, COL1). In both monocrotaline and sugen/hypoxia rats, pharmacological inhibition of FnBIs alone or in combination with macitentan and tadalafil improved RV function (mPAP, CO, TAPSE) and vascular remodeling (EVG). In the PA banding rat model, inhibition of FnBIs attenuated RV failure (CO, TAPSE, RVEDP). In conclusion, FnBIs signaling promotes maladaptive remodeling of the pulmonary vasculature and RV in PAH.

Right ventricular (RV) function critically influences outcomes in pulmonary arterial hypertension (PAH), yet the mechanisms behind RV dysfunction are unclear. Epicardial adipose tissue (EAT), uniquely located near the heart, differs significantly in its transcriptome and secretome from other fat depots. EAT can either support the myocardium by providing energy or harm it by releasing pro-inflammatory and profibrotic cytokines. Increased EAT volume is associated with worse PAH outcomes and RV dysfunction, highlighting the need to understand EAT's role better. Our study analyzed EAT from 8 PAH patients and 8 age-matched controls, identifying 1595 upregulated and 2099 downregulated genes (fold change ≥2, adjusted p-value <0.0001) in PAH. Principal component analysis showed unsupervised PAH-control clustering by EAT transcriptome. Gene ontology analysis indicated that downregulated genes were linked to oxidative metabolism and mitochondrial function, while upregulated genes were associated with inflammation. We also found increased levels of IL-1β, IL-6, TNFα, MCP-1, Leptin, and Resistin in PAH EAT. Targeting transcripts for secreted proteins revealed 240 primarily related to fibrosis and inflammation. Validation in 60 PAH patients showed those with decompensated RV had higher blood levels of 23 proteins from these transcripts compared to patients with normal RV function. In conclusion, our study highlights EAT dysfunction in PAH, suggesting its significant impact on RV dysfunction and potential as a therapeutic target.

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.

Pulmonary arterial hypertension (PAH) is characterized by progressive narrowing of distal pulmonary arteries (PAs), leading to right ventricular (RV) failure and premature death. Despite a cytotoxic inflammatory environment inducing DNA damage, PA smooth muscle cells (PASMCs) adapt and continue to proliferate. Persistent activation of the DNA damage response (DDR) drives this abnormal phenotype. Among DDR proteins, poly (ADP-ribose) polymerase (PARP) promotes aberrant DNA repair, survival, and proliferation. PARP can be inhibited by Olaparib, an orally available drug approved for ovarian cancer. PARP inhibition also improves RV function in preclinical PAH models. This study aimed to evaluate Olaparib efficacy in PAH using in vitro and ex vivo models and a Phase 1b clinical trial. In PASMCs and PA endothelial cells from PAH patients, Olaparib reduced proliferation (MCM2, Ki67) and apoptosis resistance (Survivin, Annexin V). PAH-PASMCs with high baseline expression of DDR-associated proteins (RAD51, CHK2, BRCA1) showed reduced responsiveness to Olaparib compared to PAH-PASMCs with low expression of these proteins. Olaparib improved established vascular remodeling in human PCLS from PAH patients. In a Phase 1b clinical trial (OPTION, NCT03782818) involving 17 patients with severe PAH, Olaparib improved hemodynamics in 6 patients, stabilized hemodynamics in 3 patients. Post-baseline hemodynamics worsened in 3 patients and were unavailable in 5 patients due to premature discontinuation (mostly due to unrelated disease worsening). Olaparib exerts anti-remodeling effects in PAH models influenced by baseline DDR activation. In patients, response was heterogeneous. Ongoing studies aim to determine whether baseline DDR activity and additional biomarkers predict hemodynamic response.