Reduced FOXF1 links unrepaired DNA damage to pulmonary arterial hypertension

High Shear Stress Reduces ERG Causing Endothelial-Mesenchymal Transition and Pulmonary Arterial Hypertension

BACKGROUND

Computational modeling indicated that pathological high shear stress (HSS; 100 dyn/cm2) is generated in pulmonary arteries (PAs; 100-500 µm) in congenital heart defects causing PA hypertension (PAH) and in idiopathic PAH with occlusive vascular remodeling. Endothelial-to-mesenchymal transition (EndMT) is a feature of PAH. We hypothesize that HSS induces EndMT, contributing to the initiation and progression of PAH.

METHODS

We used the Ibidi perfusion system to determine whether HSS applied to human PA endothelial cells (ECs) induces EndMT when compared with physiological laminar shear stress (15 dyn/cm2). The mechanism was investigated and targeted to prevent PAH in a mouse with HSS induced by an aortocaval shunt.

RESULTS

EndMT, a feature of PAH not previously attributed to HSS, was observed. HSS did not alter the induction of transcription factors KLF (Krüppel-like factor) 2/4, but an ERG (ETS-family transcription factor) was reduced, as were histone H3 lysine 27 acetylation enhancer-promoter peaks containing ERG motifs. Consequently, there was reduced interaction between ERG and KLF2/4, a feature important in tethering KLF and the chromatin remodeling complex to DNA. In PA ECs under laminar shear stress, reducing ERG by siRNA caused EndMT associated with decreased BMPR2 (bone morphogenetic protein receptor 2), CDH5 (cadherin 5), and PECAM1 (platelet and EC adhesion molecule 1) and increased SNAI1/2 (Snail/Slug) and ACTA2 (smooth muscle α2 actin). In PA ECs under HSS, transfection of ERG prevented EndMT. HSS was then induced in mice by an aortocaval shunt, causing progressive PAH over 8 weeks. An adeno-associated viral vector (AAV2-ESGHGYF) was used to replenish ERG selectively in PA ECs. Elevated PA pressure, EndMT, and vascular remodeling (muscularization of peripheral arteries) in the aortocaval shunt mice were markedly reduced by ERG delivery.

CONCLUSIONS

Pathological HSS reduced lung EC ERG, resulting in EndMT and PAH. Agents that upregulate ERG could reverse HSS-mediated PAH and occlusive vascular remodeling resulting from high flow or narrowed PAs.

Decoding the enigmatic estrogen paradox in pulmonary hypertension: delving into estrogen metabolites and metabolic enzymes

Pulmonary hypertension (PH) presents a puzzling sex bias, being more prevalent in women yet often less severe than in men, and the underlying reasons remain unclear. Studies using animal models, and limited clinical data have revealed a protective influence of exogenous estrogens, known as the estrogen paradox. Research suggests that beyond its receptor-mediated effects, estrogen acts through metabolites such as 2-ME2, 4-OHE2, and 16-OHE2, which are capable of exhibiting protective or detrimental effects in PH, prompting the need to explore their roles in PH to untangle sex differences and the estrogen paradox. Hypoxia disrupts the balance of estrogen metabolites by affecting the enzymes responsible for estrogen metabolism. Delving into the role of these metabolic enzymes not only illuminates the sex difference in PH but also provides a potential rationale for the estrogen paradox. This review delves into the intricate interplay between estrogen metabolites, metabolic enzymes, and PH, offering a deeper understanding of sex-specific differences and the perplexing estrogen paradox in the context of this condition.

Przewaquinone A inhibits Angiotensin II-induced endothelial diastolic dysfunction activation of AMPK

BACKGROUND

Endothelial dysfunction (ED), characterized by markedly reduced nitric oxide (NO) bioavailability, vasoconstriction, and a shift toward a proinflammatory and prothrombotic state, is an important contributor to hypertension, atherosclerosis, and other cardiovascular diseases. Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) is widely involved in cardiovascular development. Przewaquinone A (PA), a lipophilic diterpene quinone extracted from Salvia przewalskii Maxim, inhibits vascular contraction.

PURPOSE

Herein, the goal was to explore the protective effect of PA on ED in vivo and in vitro, as well as the underlying mechanisms.

METHODS

A human umbilical vein endothelial cell (HUVEC) model of ED induced by angiotensin II (AngII) was used for in vitro observations. Levels of AMPK, endothelial nitric oxide synthase (eNOS), vascular cell adhesion molecule-1 (VCAM-1), nitric oxide (NO), and endothelin-1 (ET-1) were detected by western blotting and ELISA. A mouse model of hypertension was established by continuous infusion of AngII (1000 ng/kg/min) for 4 weeks using osmotic pumps. Following PA and/or valsartan administration, NO and ET-1 levels were measured. The levels of AMPK signaling-related proteins in the thoracic aorta were evaluated by immunohistochemistry. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) were measured using the tail cuff method. Isolated aortic vascular tone measurements were used to evaluate the vasodilatory function in mice. Molecular docking, molecular dynamics, and surface plasmon resonance imaging (SPRi) were used to confirm AMPK and PA interactions.

RESULTS

PA inhibited AngII-induced vasoconstriction and vascular adhesion as well as activated AMPK signaling in a dose-dependent manner. Moreover, PA markedly suppressed blood pressure, activated vasodilation in mice following AngII stimulation, and promoted the activation of AMPK signaling. Furthermore, molecular simulations and SPRi revealed that PA directly targeted AMPK. AMPK inhibition partly abolished the protective effects of PA against endothelial dysfunction.

CONCLUSION

PA activates AMPK and ameliorates endothelial dysfunction during hypertension.

Pathology and pathobiology of pulmonary hypertension: current insights and future directions

In recent years, major advances have been made in the understanding of the cellular and molecular mechanisms driving pulmonary vascular remodelling in various forms of pulmonary hypertension, including pulmonary arterial hypertension, pulmonary hypertension associated with left heart disease, pulmonary hypertension associated with chronic lung disease and hypoxia, and chronic thromboembolic pulmonary hypertension. However, the survival rates for these different forms of pulmonary hypertension remain unsatisfactory, underscoring the crucial need to more effectively translate innovative scientific knowledge into healthcare interventions. In these proceedings of the 7th World Symposium on Pulmonary Hypertension, we delve into recent developments in the field of pathology and pathophysiology, prioritising them while questioning their relevance to different subsets of pulmonary hypertension. In addition, we explore how the latest omics and other technological advances can help us better and more rapidly understand the myriad basic mechanisms contributing to the initiation and progression of pulmonary vascular remodelling. Finally, we discuss strategies aimed at improving patient care, optimising drug development, and providing essential support to advance research in this field.

Role of Forkhead box F1 in the Pathobiology of Pulmonary Arterial Hypertension

Rationale

Approximately 80% of patients with non-familial pulmonary arterial hypertension (PAH) lack identifiable pathogenic genetic variants. While most genetic studies of PAH have focused on predicted loss-of-function variants, recent approaches have identified ultra-rare missense variants associated with the disease. FOXF1 encodes a highly conserved transcription factor, essential for angiogenesis and vasculogenesis in human and mouse lungs.

Objectives

We identified a rare FOXF1 missense coding variant in two unrelated probands with PAH. FOXF1 is an evolutionarily conserved transcription factor required for lung vascular development and vascular integrity. Our aims were to determine the frequency of FOXF1 variants in larger PAH cohorts compared to the general population, study FOXF1 expression in explanted lung tissue from PAH patients versus control (failed-donor) lungs, and define potential downstream targets linked to PAH development.

Methods

Three independent, international, multicenter cohorts were analyzed to evaluate the frequency of FOXF1 rare variants. Various composite prediction models assessed the deleteriousness of individual variants. Bulk RNA sequencing datasets from human explanted lung tissues were compared to failed-donor controls to determine FOXF1 expression. Bioinformatic tools identified putative FOXF1 binding targets, which were orthogonally validated using mouse ChIP-seq datasets.

Measurements and Main Results

Seven novel or ultra-rare missense coding variants were identified across three patient cohorts in different regions of the FOXF1 gene, including the DNA binding domain. FOXF1 expression was dysregulated in PAH lungs, correlating with disease severity. Histological analysis showed heterogeneous FOXF1 expression, with the lowest levels in phenotypically abnormal endothelial cells within complex vascular lesions in PAH samples. A hybrid bioinformatic approach identified FOXF1 downstream targets potentially involved in PAH pathogenesis, including BMPR2 .

Conclusions

Large genomic and transcriptomic datasets suggest that decreased FOXF1 expression or predicted dysfunction is associated with PAH.

TGF-β2-induced alterations of m6A methylation in hTERT RPE-1 cells

N6-methyladenosine (m6A) is a major type of RNA modification implicated in various pathophysiological processes. Transforming growth factor β2 (TGF-β2) induces epithelial-mesenchymal transition (EMT) in retinal pigmental epithelial (RPE) cells and promotes the progression of proliferative vitreoretinopathy (PVR). However, the role of m6A methylation in the EMT of human telomerase reverse transcriptase (hTERT) retinal pigmental epithelium (RPE)-1 cells has not been clarified. Here, we extracted RNA from RPE cells subjected to 0 or 20 ng/mL TGF-β2 for 72 h and identified differentially methylated genes (DMGs) by m6A-Seq and differentially expressed genes (DEGs) by RNA-Seq. We selected the genes related to EMT by conjoint m6A-Seq/RNA-Seq analysis and verified them by qRT-PCR. We then confirmed the function of m6A methylation in the EMT of RPE cells by knocking down the methyltransferase METTL3 and the m6A reading protein YTHDF1. Sequencing yielded 5814 DMGs and 1607 DEGs. Conjoint analysis selected 467 genes altered at the m6A and RNA levels that are closely associated with the EMT-related TGF-β, AGE-RAGE, PI3K-Akt, P53, and Wnt signaling pathways. We also identified ten core EMT genes ACTG2, BMP6, CDH2, LOXL2, SNAIL1, SPARC, BMP4, EMP3, FOXM1, and MYC. Their RNA levels were evaluated by qRT-PCR and were consistent with the sequencing results. We observed that METTL3 knockdown enhanced RPE cell migration and significantly upregulated the EMT markers N-cadherin (encoded by CDH2), fibronectin (FN), Snail family transcription repressor (SLUG), and vimentin. However, YTHDF1 knockdown had the opposite effects and decreased both cell migration and the N-cadherin, FN, and SLUG expression levels. The present study clarified TGF-β2-induced m6A- and RNA-level differences in RPE cells, indicated that m6A methylation might regulate EMT marker expression, and showed that m6A could regulate TGF-β2-induced EMT.

High Shear Stress Reduces ERG Causing Endothelial-Mesenchymal Transition and Pulmonary Arterial Hypertension

Pathological high shear stress (HSS, 100 dyn/cm 2 ) is generated in distal pulmonary arteries (PA) (100-500 μm) in congenital heart defects and in progressive PA hypertension (PAH) with inward remodeling and luminal narrowing. Human PA endothelial cells (PAEC) were subjected to HSS versus physiologic laminar shear stress (LSS, 15 dyn/cm 2 ). Endothelial-mesenchymal transition (EndMT), a feature of PAH not previously attributed to HSS, was observed. H3K27ac peaks containing motifs for an ETS-family transcription factor (ERG) were reduced, as was ERG-Krüppel-like factors (KLF)2/4 interaction and ERG expression. Reducing ERG by siRNA in PAEC during LSS caused EndMT; transfection of ERG in PAEC under HSS prevented EndMT. An aorto-caval shunt was preformed in mice to induce HSS and progressive PAH. Elevated PA pressure, EndMT and vascular remodeling were reduced by an adeno-associated vector that selectively replenished ERG in PAEC. Agents maintaining ERG in PAEC should overcome the adverse effect of HSS on progressive PAH.