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Given the increasing popularity of electronic cigarettes (e-cigs), it is imperative to evaluate the potential health risks of e-cigs, especially in users with preexisting health concerns such as pulmonary arterial hypertension (PAH). The aim of the present study was to investigate whether differential susceptibility exists between healthy and patients with PAH to e-cig exposure and the molecular mechanisms contributing to it. Patient-specific induced pluripotent stem cell-derived endothelial cells (iPSC-ECs) from healthy individuals and patients with PAH were used to investigate whether e-cig contributes to the pathophysiology of PAH and affects EC homeostasis in PAH. Our results showed that PAH iPSC-ECs showed a greater amount of damage than healthy iPSC-ECs upon e-cig exposure. Transcriptomic analyses revealed that differential expression of Akt3 may be responsible for increased autophagic flux impairment in PAH iPSC-ECs, which underlies increased susceptibility upon e-cig exposure. Moreover, knockdown of Akt3 in healthy iPSC-ECs significantly induced autophagic flux impairment and endothelial dysfunction, which further increased with e-cig treatment, thus mimicking the PAH cell phenotype after e-cig exposure. In addition, functional disruption of mTORC2 by knocking down Rictor in PAH iPSC-ECs caused autophagic flux impairment, which was mediated by downregulation of Akt3. Finally, pharmacological induction of autophagy via direct inhibition of mTORC1 and indirect activation of mTORC2 with rapamycin reverses e-cig-induced decreased Akt3 expression, endothelial dysfunction, autophagic flux impairment, and decreased cell viability, and migration in PAH iPSC-ECs. Taken together, these data suggest a potential link between autophagy and Akt3-mediated increased susceptibility to e-cig in PAH., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Background: Nitrative stress is a characteristic feature of the pathology of human pulmonary arterial hypertension. However, the role of nitrative stress in the pathogenesis of obliterative vascular remodelling and severe pulmonary arterial hypertension remains largely unclear., Method: Our recently identified novel mouse model ( Egln1 Tie2Cre , Egln1 encoding prolyl hydroxylase 2 (PHD2)) has obliterative vascular remodelling and right heart failure, making it an excellent model to use in this study to examine the role of nitrative stress in obliterative vascular remodelling., Results: Nitrative stress was markedly elevated whereas endothelial caveolin-1 (Cav1) expression was suppressed in the lungs of Egln1 Tie2Cre mice. Treatment with a superoxide dismutase mimetic, manganese (III) tetrakis (1-methyl-4-pyridyl) porphyrin pentachloride or endothelial Nos3 knockdown using endothelial cell-targeted nanoparticle delivery of CRISPR-Cas9/guide RNA plasmid DNA inhibited obliterative pulmonary vascular remodelling and attenuated severe pulmonary hypertension in Egln1 Tie2Cre mice. Genetic restoration of Cav1 expression in Egln1 Tie2Cre mice normalised nitrative stress, reduced pulmonary hypertension and improved right heart function., Conclusion: These data suggest that suppression of Cav1 expression secondary to PHD2 deficiency augments nitrative stress through endothelial nitric oxide synthase activation, which contributes to obliterative vascular remodelling and severe pulmonary hypertension. Thus, a reactive oxygen/nitrogen species scavenger might have therapeutic potential for the inhibition of obliterative vascular remodelling and severe pulmonary arterial hypertension., Competing Interests: Conflict of interest: Y-Y. Zhao is the founder and chief scientific officer of MountView Therapeutics LLC. This project utilises technologies subject to the following pending patents entitled “PLGA-PEG nanoparticles and methods of uses” and “Cationic polymer-formulated nanoparticles and methods of use” to Y-Y. Zhao. The other authors declare no conflicts of interest., (Copyright ©The authors 2022.)

Pulmonary arterial hypertension (PAH) is a devastating disease that involves pulmonary vasoconstriction, small vessel obliteration, large vessel thickening and obstruction, and development of plexiform lesions. PAH vasculopathy leads to progressive increases in pulmonary vascular resistance, right heart failure and, ultimately, premature death. Besides other cell types that are known to be involved in PAH pathogenesis ( e.g. smooth muscle cells, fibroblasts and leukocytes), recent studies have demonstrated that endothelial cells (ECs) have a crucial role in the initiation and progression of PAH. The EC-specific role in PAH is multi-faceted and affects numerous pathophysiological processes, including vasoconstriction, inflammation, coagulation, metabolism and oxidative/nitrative stress, as well as cell viability, growth and differentiation. In this review, we describe how EC dysfunction and cell signalling regulate the pathogenesis of PAH. We also highlight areas of research that warrant attention in future studies, and discuss potential molecular signalling pathways in ECs that could be targeted therapeutically in the prevention and treatment of PAH., Competing Interests: Conflict of interest: N.D. Cober reports grants from Canadian Institute of Health Research and Canadian Vascular Network, during the conduct of the study. Conflict of interest: Z. Dai reports grants from National Institutes of Health, American Heart Association and American Thoracic Society, during the conduct of the study. Conflict of interest: D.J. Stewart reports other (founding member, equity stake) from Northern Therapeutics, outside the submitted work. Conflict of interest: Y-Y. Zhao reports grants from National Institutes of Health/National Heart, Lung, and Blood Institute (R01HL123957, R01HL133951, R01HL140409 and R01HL148810), during the conduct of the study. Conflict of interest: C.E. Evans reports grants (Career Development Award, 19CDA34500000) from American Heart Association, during the conduct of the study., (Copyright ©The authors 2021. For reproduction rights and permissions contact permissions@ersnet.org.)

Endothelial autocrine signaling is essential to maintain vascular homeostasis. There is limited information about the role of endothelial autocrine signaling in regulating severe pulmonary vascular remodeling during the onset of pulmonary arterial hypertension (PAH). In this study, we employed the first severe pulmonary hypertension (PH) mouse model, Egln1 Tie2Cre ( Tie2Cre -mediated disruption of Egln1 ) mice, to identify the novel autocrine signaling mediating the pulmonary vascular endothelial cell (PVEC) proliferation and the pathogenesis of PAH. PVECs isolated from Egln1 Tie2Cre lung expressed upregulation of many growth factors or angiocrine factors such as CXCL12, and exhibited pro-proliferative phenotype coincident with the upregulation of proliferation-specific transcriptional factor FoxM1. Treatment of CXCL12 on PVECs increased FoxM1 expression, which was blocked by CXCL12 receptor CXCR4 antagonist AMD3100 in cultured human PVECs. The endothelial specific deletion of Cxcl12 (Egln1/Cxcl12 Tie2Cre ) or AMD3100 treatment in Egln1 Tie2Cre mice downregulated FoxM1 expression in vivo. We then generated and characterized a novel mouse model with endothelial specific FoxM1 deletion in Egln1 Tie2Cre mice ( Egln1/Foxm1 Tie2Cre ), and found that endothelial FoxM1 deletion reduced pulmonary vascular remodeling and right ventricular systolic pressure. Together, our study identified a novel mechanism of endothelial autocrine signaling in regulating PVEC proliferation and pulmonary vascular remodeling in PAH.

BMP signaling deficiency is evident in the lungs of patients with pulmonary arterial hypertension. We demonstrated that PHD2 deficiency suppresses BMP signaling in the lung endothelial cells, suggesting the novel mechanisms of dysregulated BMP signaling in the development of pulmonary arterial hypertension. [ABSTRACT FROM AUTHOR]

Rationale: Pulmonary arterial hypertension (PAH) is a devastating disease characterized by progressive vasoconstriction and obliterative vascular remodeling that leads to right heart failure (RHF) and death. Current therapies do not target vascular remodeling and RHF, and result in only modest improvement of morbidity and mortality.Objectives: To determine whether targeting HIF-2α (hypoxia-inducible factor-2α) with a HIF-2α-selective inhibitor could reverse PAH and RHF in various rodent PAH models.Methods: HIF-2α and its downstream genes were evaluated in lung samples and pulmonary arterial endothelial cells and smooth muscle cells from patients with idiopathic PAH as well as various rodent PAH models. A HIF-2α-selective inhibitor was used in human lung microvascular endothelial cells and in Egln1Tie2Cre mice, and in Sugen 5416/hypoxia- or monocrotaline-exposed rats.Measurements and Main Results: Upregulation of HIF-2α and its target genes was observed in lung tissues and isolated pulmonary arterial endothelial cells from patients with idiopathic PAH and three distinct rodent PAH models. Pharmacological inhibition of HIF-2α by the HIF-2α translation inhibitor C76 (compound 76) reduced right ventricular systolic pressure and right ventricular hypertrophy and inhibited RHF and fibrosis as well as obliterative pulmonary vascular remodeling in Egln1Tie2Cre mice and Sugen 5416/hypoxia PAH rats. Treatment of monocrotaline-exposed PAH rats with C76 also reversed right ventricular systolic pressure, right ventricular hypertrophy, and pulmonary vascular remodeling; prevented RHF; and promoted survival.Conclusions: These findings demonstrate that pharmacological inhibition of HIF-2α is a promising novel therapeutic strategy for the treatment of severe vascular remodeling and right heart failure in patients with PAH. [ABSTRACT FROM AUTHOR]