Author Correction: Deficiency of Axl aggravates pulmonary arterial hypertension via BMPR2.

Abstract: Pulmonary arterial hypertension (PAH), is a fatal disease characterized by a pseudo-malignant phenotype. We investigated the expression and the role of the receptor tyrosine kinase Axl in experimental (i.e., monocrotaline and Su5416/hypoxia treated rats) and clinical PAH. In vitro Axl inhibition by R428 and Axl knock-down inhibited growth factor-driven proliferation and migration of non-PAH and PAH PASMCs. Conversely, Axl overexpression conferred a growth advantage. Axl declined in PAECs of PAH patients. Axl blockage inhibited BMP9 signaling and increased PAEC apoptosis, while BMP9 induced Axl phosphorylation. Gas6 induced SMAD1/5/8 phosphorylation and ID1/ID2 increase were blunted by BMP signaling obstruction. Axl association with BMPR2 was facilitated by Gas6/BMP9 stimulation and diminished by R428. In vivo R428 aggravated right ventricular hypertrophy and dysfunction, abrogated BMPR2 signaling, elevated pulmonary endothelial cell apoptosis and loss. Together, Axl is a key regulator of endothelial BMPR2 signaling and potential determinant of PAH

Response by Mendes-Ferreira et al to Letter Regarding Article, “Bmpr2 Mutant Rats Develop Pulmonary and Cardiac Characteristics of Pulmonary Arterial Hypertension”

Comment onBmpr2 Mutant Rats Develop Pulmonary and Cardiac Characteristics of Pulmonary Arterial Hypertension. [Circulation. 2019]Letter by Nadeau et al Regarding Article, "Bmpr2 Mutant Rats Develop Pulmonary and Cardiac Characteristics of Pulmonary Arterial Hypertension". [Circulation. 2019]International audienceno abstrac

Familial pulmonary arterial hypertension by KDR heterozygous loss of function

Comment inVanishing vessels aboding pulmonary disease: a role for VEGFR2. [Eur Respir J. 2020]International audienceBeyond the major gene BMPR2, several new genes predisposing to PAH have been identified during the last decade. Recently, preliminary evidence of the involvement of the KDR gene was found in a large genetic association study.We prospectively analysed the KDR gene by targeted panel sequencing in a series of 311 PAH patients referred to a clinical molecular laboratory for genetic diagnosis of PAH.Two index cases with severe PAH from two different families were found to carry a loss-of-function mutation in the KDR gene. These two index cases were clinically characterised by low diffusing capacity for carbon monoxide adjusted for haemoglobin (D LCOc) and interstitial lung disease. In one family, segregation analysis revealed that variant carriers are either presenting with PAH associated with low D LCOc, or have only decreased D LCOc, whereas non-carrier relatives have normal D LCOc. In the second family, a single affected carrier was alive. His carrier mother was unaffected with normal D LCOc.We provided genetic evidence for considering KDR as a newly identified PAH-causing gene by describing the segregation of KDR mutations with PAH in two families. In our study, KDR mutations are associated with a particular form of PAH characterised by low D LCOc and radiological evidence of parenchymal lung disease including interstitial lung disease and emphysema

Smooth Muscle Phenotype in Idiopathic Pulmonary Hypertension: Hyper-Proliferative but not Cancerous

International audienceIdiopathic pulmonary arterial hypertension (IPAH) is a complex disease associated with vascular remodeling and a proliferative disorder in pulmonary artery smooth muscle cells (PASMCs) that has been variably described as having neoplastic features. To decode the phenotype of PASMCs in IPAH, PASMCs from explanted lungs of patients with IPAH (IPAH-PASMCs) and from controls (C-PASMCs) were cultured. The IPAH-PASMCs grew faster than the controls; however, both growth curves plateaued, suggesting contact inhibition in IPAH cells. No proliferation was seen without stimulation with exogenous growth factors, suggesting that IPAH cells are incapable of self-sufficient growth. IPAH-PASMCs were more resistant to apoptosis than C-PASMCs, consistent with the increase in the Bcl2/Bax ratio. As cell replication is governed by telomere length, these parameters were assessed jointly. Compared to C-PASMCs, IPAH-PASMCs had longer telomeres, but a limited replicative capacity. Additionally, it was noted that IPAH-PASMCs had a shift in energy production from mitochondrial oxidative phosphorylation to aerobic glycolysis. As DNA damage and genomic instability are strongly implicated in IPAH development a comparative genomic hybridization was performed on genomic DNA from PASMCs which showed multiple break-points unaffected by IPAH severity. Activation of DNA damage/repair factors (γH2AX, p53, and GADD45) in response to cisplatin was measured. All proteins showed lower phosphorylation in IPAH samples than in controls, suggesting that the cells were resistant to DNA damage. Despite the cancer-like processes that are associated with end-stage IPAH-PASMCs, we identified no evidence of self-sufficient proliferation in these cells-the defining feature of neoplasia

Bmpr2 Mutant Rats Develop Pulmonary and Cardiac Characteristics of Pulmonary Arterial Hypertension

International audienceBACKGROUND: Monoallelic mutations in the gene encoding bone morphogenetic protein receptor 2 (Bmpr2) are the main genetic risk factor for heritable pulmonary arterial hypertension (PAH) with incomplete penetrance. Several Bmpr2 transgenic mice have been reported to develop mild spontaneous PAH. In this study, we examined whether rats with the Bmpr2 mutation were susceptible to developing more severe PAH

Association between Leflunomide and Pulmonary Hypertension

International audienceRationale: Pulmonary hypertension (PH) has been described in patients treated with leflunomide. Objectives: To assess the association between leflunomide and PH. Methods: We identified incident cases of PH in patients treated with leflunomide from the French PH Registry and through the pharmacoVIGIlAnce in Pulmonary ArTerial Hypertension (VIGIAPATH) program between September 1999 to December 2019. PH etiology, clinical, functional, radiologic, and hemodynamic characteristics were reviewed at baseline and follow-up. A pharmacovigilance disproportionality analysis using the World Health Organization's global database was conducted. We then investigated the effect of leflunomide on human pulmonary endothelial cells. Data are expressed as median (min-max). Results: Twenty-eight patients treated with leflunomide before PH diagnosis was identified. A total of 21 (75%) had another risk factor for PH and 2 had two risk factors. The median time between leflunomide initiation and PH diagnosis was 32 months (1-120). Right heart catheterization confirmed precapillary PH with a cardiac index of 2.37 L⋅min-1 ⋅m-2 (1.19-3.1) and elevated pulmonary vascular resistance at 9.63 Wood Units (3.6-22.1) without nitric oxide reversibility. Five patients (17.9%) had no other risk factor for PH besides exposure to leflunomide. No significant hemodynamic improvement was observed after leflunomide withdrawal. The pharmacovigilance disproportionality analysis using the World Health Organization's database revealed a significant overrepresentation of leflunomide among reported pulmonary arterial hypertension-adverse drug reactions. In vitro studies showed the dose-dependent toxicity of leflunomide on human pulmonary endothelial cells. Conclusions: PH associated with leflunomide is rare and usually associated with other risk factors. The pharmacovigilance analysis suggests an association reinforced by experimental data

Comparison of Human and Experimental Pulmonary Veno-Occlusive Disease

International audiencePulmonary veno-occlusive disease (PVOD) occurs in humans either as heritable form (hPVOD) due to biallelic inactivating mutations of EIF2AK4 (encoding GCN2), or as a sporadic form at older age (sPVOD). The chemotherapeutic agent Mitomycin C is a potent inducer of PVOD in humans and in rats (MMC-PVOD). Here we compared human hPVOD and sPVOD, and MMC-PVOD pathophysiology at the histological, cellular and molecular levels to unravel common altered pathomechanisms. MMC-exposure in rats was primarily associated with arterial and microvessels remodeling and secondarily followed by venous remodeling, when PVOD became symptomatic. In all forms of PVOD tested, there were convergent GCN2-dependent but eIF2α-independent pulmonary protein overexpression of heme oxygenase 1 (HO-1) and CCAAT-enhancer-binding protein (C/EBP) homologous protein (CHOP), two downstream effectors of GCN2 signaling and endoplasmic reticulum (ER) stress. In human PVOD samples, CHOP immunohistochemical staining mainly labeled endothelial cells in remodeled veins and arteries. Strong HO-1 staining was observed only within capillary hemangiomatosis foci, where intense microvascular proliferation occurs. HO-1 and CHOP stainings were not observed in control and pulmonary arterial hypertension lung tissues, supporting the specificity for CHOP and HO-1 involvement in PVOD pathobiology. In vivo loss of GCN2 (EIF2AK4 mutations carriers and Eif2ak4-/- rats) or in vitro GCN2 inhibition in cultured pulmonary artery endothelial cells (PAECs) using pharmacological and siRNA approaches demonstrated that GCN2 loss-of-function negatively regulates BMP-dependent SMAD1/5/9 signaling. Exogenous BMP9 was still able to reverse GCN2 inhibition-induced PAECs proliferation. In conclusion, we identified CHOP and HO-1 inhibition, and BMP9 as potential therapeutic options for PVOD