Endothelial PHD2 deficiency induces nitrative stress via suppression of caveolin-1 in pulmonary hypertension

Inhibition of CAV1 attenuates diabetic cardiomyopathy through reducing ferroptosis via activating NRF2/GCLC signaling pathway

Background: Diabetic cardiomyopathy (DCM), a prevalent complication of diabetes, is a major cause of heart failure and death among patients with diabetes. However, the pathological mechanisms underlying the development of DCM remain unclear. This study aims to investigate the role and underlying mechanisms of caveolin-1 (CAV1) in DCM. Methods: DCM model was established in vivo through intraperitoneal injection of streptozotocin in mice and in vitro through high-glucose (HG) treatment in neonatal rat ventricular myocytes (NRVMs). CAV1-knockout (CAV1-KO) and overexpression (by injecting adeno-associated virus 9 (AAV9) encoding CAV1) mice were utilized to explore the role of CAV1 in DCM. Nuclear factor erythroid 2-related factor 2 (NRF2)-KO and AAV9-NRF2 mice and ML385 (an NRF2 inhibitor) were used to investigate the effect of NRF2 on DCM. Results: CAV1 expression was significantly increased in the cardiac tissues of diabetic mice and HG-treated NRVMs. CAV1 deficiency significantly alleviated diabetes-induced myocardial hypertrophy, fibrosis, abnormal mitochondria, excessive reactive oxygen species production, and ferroptosis. Conversely, cardiac-specific overexpression of CAV1 exacerbated cardiac dysfunction and myocardial histological abnormalities caused by diabetes. Mechanistically, CAV1 directly bound to NRF2 and inhibited its nuclear translocation, reducing the transcription of glutamate cysteine ligase catalytic subunit (GCLC), accumulating excess peroxide, and inducing ferroptosis and myocardial injury. Conclusion: CAV1 exacerbates the progression of DCM by suppressing the NRF2/GCLC pathway, suggesting that targeting CAV1 is a potential therapeutic approach for DCM.

High-altitude pulmonary hypertension: a comprehensive review of mechanisms and management

High-altitude pulmonary hypertension (HAPH) is characterized by an increase in pulmonary artery pressure due to prolonged exposure to hypoxic environment at high altitudes. The development of HAPH involves various factors such as pressure changes, inflammation, oxidative stress, gene regulation, and signal transduction. The pathophysiological mechanisms of this condition operate at molecular, cellular, and genetic levels. Diagnosis of HAPH often relies on echocardiography, cardiac catheterization, and other methods to assess pulmonary artery pressure and its impact on cardiac function. Treatment options for HAPH encompass both nondrug and drug therapies. While advancements have been made in understanding the pathological mechanisms through research on animal models and clinical trials, there are still limitations to be addressed. Future research should focus on exploring molecular targets, personalized medicine, long-term management strategies, and interdisciplinary approaches. By leveraging advanced technologies like systems biology, omics technology, big data, and artificial intelligence, a comprehensive analysis of HAPH pathogenesis can lead to the identification of new treatment targets and strategies, ultimately enhancing patient quality of life and prognosis. Furthermore, research on health monitoring and preventive measures for populations living at high altitudes should be intensified to reduce the incidence and mortality of HAPH.

Mendelian randomization study of serum uric acid levels and urate-lowering drugs on pulmonary arterial hypertension outcomes

This study aims to explore the causal relationships between serum uric acid level and pulmonary arterial hypertension (PAH) using the Mendelian randomization (MR) approach, and to assess the therapeutic impacts of urate-lowering drugs on PAH. Utilizing published genome-wide association study (GWAS) data, we applied MR and colocalization analysis to assess the link between serum uric acid levesl and PAH across four GWAS datasets from two distinct European populations. The validity and reliability of these findings were confirmed through multiple statistical methods, along with an MR analysis of urate-lowering drug targets to investigate their potential effects on PAH treatment. MR analysis revealed a significant positive correlation between serum uric acid levels and PAH (odds ratio (OR) 1.106, 95% confidence intervals (CI) 1.021-1.200, P = 0.014), corroborated by a replication MR analysis (OR 1.859, 95% CI 1.130-3.057, P = 0.015). No significant heterogeneity or horizontal pleiotropy was found in the sensitivity analyses. However, urate-lowering drugs did not demonstrate a significant direct therapeutic effect on PAH. This study establishes a genetic basis for a causal link between serum uric acid levels and PAH. However, urate-lowering drugs do not appear to have a direct causal effect on improving PAH. These findings provide a novel reference point for developing future therapeutic strategies for PAH.

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.

Inhibition of DYRK1A attenuates vascular remodeling in pulmonary arterial hypertension via suppressing STAT3/Pim-1/NFAT pathway

Pulmonary arterial hypertension (PAH) is characterized by progressive vascular remodeling caused by the excessive proliferation and survival of pulmonary artery smooth muscle cells (PASMCs). Dual-specificity tyrosine regulated kinase 1A (DYRK1A) is a pleiotropic kinase involved in the regulation of multiple biological functions, including cell proliferation and survival. However, the role and underlying mechanisms of DYRK1A in PAH pathogenesis remain unclear. We found that DYRK1A was upregulated in PASMCs in response to hypoxia, both in vivo and in vitro. Inhibition of DYRK1A by harmine significantly attenuated hypoxia-induced pulmonary hypertension and pulmonary artery remodeling. Mechanistically, we found that DYRK1A promoted pulmonary arterial remodeling by enhancing the proliferation and survival of PASMCs through activating the STAT3/Pim-1/NFAT pathway, because STAT3 gain-of-function via adeno-associated virus serotype 2 (AAV2) carrying the constitutively active form of STAT3 (STAT3C) nearly abolished the protective effect of harmine on PAH. Collectively, our results reveal a significant role for DYRK1A in pulmonary arterial remodeling and suggest it as a drug target with translational potential for the treatment of PAH.

Pulmonary artery smooth muscle cell pyroptosis promotes the proliferation of PASMCs by paracrine IL‑1β and IL‑18 in monocrotaline‑induced pulmonary arterial hypertensive rats

Pulmonary arterial hypertension (PAH) is a common vascular disease, and pulmonary vascular remodeling is a pivotal pathophysiological mechanism of PAH. Major pathological changes of pulmonary arterial remodeling, including proliferation, hypertrophy and enhanced secretory activity, can occur in pulmonary artery smooth muscle cells (PASMCs). Multiple active factors and cytokines play important roles in PAH. However, the regulatory mechanisms of the active factors and cytokines in PAH remain unclear. The present study aimed to reveal the crucial role of PASMC pyroptosis in PAH and to elucidate the intrinsic mechanisms. To establish the PAH rat models, Sprague-Dawley rats were injected intraperitoneally with monocrotaline (MCT) at a dose of 60 mg/kg. The expression of proteins and interleukins were detected by western blotting and ELISA assay. The results indicated that the pyroptosis of PASMCs is significantly increased in MCT-induced PAH rats. Notably, pyroptotic PASMCs can secret IL-1β and IL-18 to promote the proliferation of PASMCs. On this basis, inhibiting the secretion of IL-1β and IL-18 can markedly inhibit PASMC proliferation. Collectively, the findings of the present study indicate a critical role for PASMC pyroptosis in MCT-induced PAH rats, prompting a new preventive and therapeutic strategy for PAH.

Endothelial Cell-Specific Prolyl Hydroxylase-2 Deficiency Augments Angiotensin II-Induced Arterial Stiffness and Cardiac Pericyte Recruitment in Mice

BACKGROUND

Endothelial prolyl hydroxylase-2 (PHD2) is essential for pulmonary remodeling and hypertension. In the present study, we investigated the role of endothelial PHD2 in angiotensin II-mediated arterial stiffness, pericyte recruitment, and cardiac fibrosis.

METHODS AND RESULTS

Chondroitin sulfate proteoglycan 4 tracing reporter chondroitin sulfate proteoglycan 4- red fluorescent protein (DsRed) transgenic mice were crossed with PHD2flox/flox (PHD2f/f) mice and endothelial-specific knockout of PHD2 (PHD2ECKO) mice. Transgenic PHD2f/f (TgPHD2f/f) mice and TgPHD2ECKO mice were infused with angiotensin II for 4 weeks. Arterial thickness, stiffness, and histological and immunofluorescence of pericytes and fibrosis were measured. Infusion of TgPHD2f/f mice with angiotensin II resulted in a time-dependent increase in pulse-wave velocity. Angiotensin II-induced pulse-wave velocity was further elevated in the TgPHD2ECKO mice. TgPHD2ECKO also reduced coronary flow reserve compared with TgPHD2f/f mice infused with angiotensin II. Mechanistically, knockout of endothelial PHD2 promoted aortic arginase activity and angiotensin II-induced aortic thickness together with increased transforming growth factor-β1 and ICAM-1/VCAM-1 expression in coronary arteries. TgPHD2f/f mice infused with angiotensin II for 4 weeks exhibited a significant increase in cardiac fibrosis and hypertrophy, which was further developed in the TgPHD2ECKO mice. Chondroitin sulfate proteoglycan 4 pericyte was traced by DsRed+ staining and angiotensin II infusion displayed a significant increase of DsRed+ pericytes in the heart, as well as a deficiency of endothelial PHD2, which further promoted angiotensin II-induced pericyte increase. DsRed+ pericytes were costained with fibroblast-specific protein 1 and α-smooth muscle actin for measuring pericyte-myofibroblast cell transition. The knockout of endothelial PHD2 increased the amount of DsRed+/fibroblast-specific protein 1+ and DsRed+/α-smooth muscle actin+ cells induced by angiotensin II infusion.

CONCLUSIONS

Knockout of endothelial PHD2 enhanced angiotensin II-induced cardiac fibrosis by mechanisms involving increasing arterial stiffness and pericyte-myofibroblast cell transitions.

A Novel Animal Model for Pulmonary Hypertension: Lung Endothelial-Specific Deletion of Egln1 in Mice

Pulmonary arterial hypertension (PAH) is a devastating disease characterized by high blood pressure in the pulmonary arteries, which can potentially lead to heart failure over time. Previously, our lab found that endothelia-specific knockout of Egln1, encoding prolyl 4-hydroxylase-2 (PHD2), induced spontaneous pulmonary hypertension (PH). Recently, we elucidated that Tmem100 is a lung-specific endothelial gene using Tmem100-CreERT2 mice. We hypothesize that lung endothelial-specific deletion of Egln1 could lead to the development of PH without affecting Egln1 gene expression in other organs. Tmem100-CreERT2 mice were crossed with Egln1 flox/flox mice to generate Egln1 f/f ;Tmem100-CreERT2 (LiCKO) mice. Western blot and immunofluorescent staining were performed to verify the knockout efficacy of Egln1 in multiple organs of LiCKO mice. PH phenotypes, including hemodynamics, right heart size and function, pulmonary vascular remodeling, were evaluated by right heart catheterization and echocardiography measurements. Tamoxifen treatment induced Egln1 deletion in the lung endothelial cells (ECs) but not in other organs of adult LiCKO mice. LiCKO mice exhibited an increase in right ventricular systolic pressure (RVSP, ~35 mmHg) and right heart hypertrophy. Echocardiography measurements showed right heart hypertrophy, as well as cardiac and pulmonary arterial dysfunction. Pulmonary vascular remodeling, including increased pulmonary wall thickness and muscularization of distal pulmonary arterials, was enhanced in LiCKO mice compared to wild-type mice. Tmem100 promoter-mediated lung endothelial knockout of Egln1 in mice leads to development of spontaneous PH. LiCKO mice could serve as a novel mouse model for PH to study lung and other organ crosstalk.

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.

Pulmonary hypertension

Pulmonary hypertension encompasses a range of conditions directly or indirectly leading to elevated pressures within the pulmonary arteries. Five main groups of pulmonary hypertension are recognized, all defined by a mean pulmonary artery pressure of >20 mmHg: pulmonary arterial hypertension (rare), pulmonary hypertension associated with left-sided heart disease (very common), pulmonary hypertension associated with lung disease (common), pulmonary hypertension associated with pulmonary artery obstructions, usually related to thromboembolic disease (rare), and pulmonary hypertension with unclear and/or multifactorial mechanisms (rare). At least 1% of the world's population is affected, with a greater burden more likely in low-income and middle-income countries. Across all its forms, pulmonary hypertension is associated with adverse vascular remodelling with obstruction, stiffening and vasoconstriction of the pulmonary vasculature. Without proactive management this leads to hypertrophy and ultimately failure of the right ventricle, the main cause of death. In older individuals, dyspnoea is the most common symptom. Stepwise investigation precedes definitive diagnosis with right heart catheterization. Medical and surgical treatments are approved for pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension. There are emerging treatments for other forms of pulmonary hypertension; but current therapy primarily targets the underlying cause. There are still major gaps in basic, clinical and translational knowledge; thus, further research, with a focus on vulnerable populations, is needed to better characterize, detect and effectively treat all forms of pulmonary hypertension.

Study on Potential Differentially Expressed Genes in Idiopathic Pulmonary Fibrosis by Bioinformatics and Next-Generation Sequencing Data Analysis

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive lung disease with reduced quality of life and earlier mortality, but its pathogenesis and key genes are still unclear. In this investigation, bioinformatics was used to deeply analyze the pathogenesis of IPF and related key genes, so as to investigate the potential molecular pathogenesis of IPF and provide guidance for clinical treatment. Next-generation sequencing dataset GSE213001 was obtained from Gene Expression Omnibus (GEO), and the differentially expressed genes (DEGs) were identified between IPF and normal control group. The DEGs between IPF and normal control group were screened with the DESeq2 package of R language. The Gene Ontology (GO) and REACTOME pathway enrichment analyses of the DEGs were performed. Using the g:Profiler, the function and pathway enrichment analyses of DEGs were performed. Then, a protein-protein interaction (PPI) network was constructed via the Integrated Interactions Database (IID) database. Cytoscape with Network Analyzer was used to identify the hub genes. miRNet and NetworkAnalyst databaseswereused to construct the targeted microRNAs (miRNAs), transcription factors (TFs), and small drug molecules. Finally, receiver operating characteristic (ROC) curve analysis was used to validate the hub genes. A total of 958 DEGs were screened out in this study, including 479 up regulated genes and 479 down regulated genes. Most of the DEGs were significantly enriched in response to stimulus, GPCR ligand binding, microtubule-based process, and defective GALNT3 causes HFTC. In combination with the results of the PPI network, miRNA-hub gene regulatory network and TF-hub gene regulatory network, hub genes including LRRK2, BMI1, EBP, MNDA, KBTBD7, KRT15, OTX1, TEKT4, SPAG8, and EFHC2 were selected. Cyclothiazide and rotigotinethe are predicted small drug molecules for IPF treatment. Our findings will contribute to identification of potential biomarkers and novel strategies for the treatment of IPF, and provide a novel strategy for clinical therapy.

E2F1 Mediates SOX17 Deficiency-Induced Pulmonary Hypertension

BACKGROUND

Rare genetic variants and genetic variation at loci in an enhancer in SOX17 (SRY-box transcription factor 17) are identified in patients with idiopathic pulmonary arterial hypertension (PAH) and PAH with congenital heart disease. However, the exact role of genetic variants or mutations in SOX17 in PAH pathogenesis has not been reported.

METHODS

SOX17 expression was evaluated in the lungs and pulmonary endothelial cells (ECs) of patients with idiopathic PAH. Mice with Tie2Cre-mediated Sox17 knockdown and EC-specific Sox17 deletion were generated to determine the role of SOX17 deficiency in the pathogenesis of PAH. Human pulmonary ECs were cultured to understand the role of SOX17 deficiency. Single-cell RNA sequencing, RNA-sequencing analysis, and luciferase assay were performed to understand the underlying molecular mechanisms of SOX17 deficiency-induced PAH. E2F1 (E2F transcription factor 1) inhibitor HLM006474 was used in EC-specific Sox17 mice.

RESULTS

SOX17 expression was downregulated in the lung and pulmonary ECs from patients with idiopathic PAH. Mice with Tie2Cre-mediated Sox17 knockdown and EC-specific Sox17 deletion induced spontaneously mild pulmonary hypertension. Loss of endothelial Sox17 in EC exacerbated hypoxia-induced pulmonary hypertension in mice. Loss of SOX17 in lung ECs induced endothelial dysfunctions including upregulation of cell cycle programming, proliferative and antiapoptotic phenotypes, augmentation of paracrine effect on pulmonary arterial smooth muscle cells, impaired cellular junction, and BMP (bone morphogenetic protein) signaling. E2F1 signaling was shown to mediate the SOX17 deficiency-induced EC dysfunction. Pharmacological inhibition of E2F1 in Sox17 EC-deficient mice attenuated pulmonary hypertension development.

CONCLUSIONS

Our study demonstrated that endothelial SOX17 deficiency induces pulmonary hypertension through E2F1. Thus, targeting E2F1 signaling represents a promising approach in patients with PAH.

The Role of a Lung Vascular Endothelium Enriched Gene TMEM100

Transmembrane protein 100 (TMEM100) is a crucial factor in the development and maintenance of the vascular system. The protein is involved in several processes such as angiogenesis, vascular morphogenesis, and integrity. Furthermore, TMEM100 is a downstream target of the BMP9/10 and BMPR2/ALK1 signaling pathways, which are key regulators of vascular development. Our recent studies have shown that TMEM100 is a lung endothelium enriched gene and plays a significant role in lung vascular repair and regeneration. The importance of TMEM100 in endothelial cells' regeneration was demonstrated when Tmem100 was specifically deleted in endothelial cells, causing an impairment in their regenerative ability. However, the role of TMEM100 in various conditions and diseases is still largely unknown, making it an interesting area of research. This review summarizes the current knowledge of TMEM100, including its expression pattern, function, molecular signaling, and clinical implications, which could be valuable in the development of novel therapies for the treatment of cardiovascular and pulmonary diseases.

Egln1Tie2Cre Mice Exhibit Similar Therapeutic Responses to Sildenafil, Ambrisentan, and Treprostinil as Pulmonary Arterial Hypertension (PAH) Patients, Supporting Egln1Tie2Cre Mice as a Useful PAH Model

Pulmonary arterial hypertension (PAH) is a progressive and inevitably fatal disease characterized by the progressive increase of pulmonary vascular resistance and obliterative pulmonary vascular remodeling, which lead to right-sided heart failure and premature death. Many of the genetically modified mouse models do not develop severe PH and occlusive vascular remodeling. Egln1^Tie2Cre mice with Tie2Cre-mediated deletion of Egln1, which encodes hypoxia-inducible factor (HIF) prolyl hydroxylase 2 (PHD2), is the only mouse model with severe PAH, progressive occlusive pulmonary vascular remodeling, and right-sided heart failure leading to 50-80% mortality from the age of 3-6 months, indicating that the Egln1^Tie2Cre mice model is a long-sought-after murine PAH model. However, it is unknown if Egln1^Tie2Cre mice respond to FDA-approved PAH drugs in a way similar to PAH patients. Here, we tested the therapeutic effects of the three vasodilators: sildenafil (targeting nitric oxide signaling), ambrisentan (endothelin receptor antagonist), and treprostinil (prostacyclin analog) on Egln1^Tie2Cre mice. All of them attenuated right ventricular systolic pressure (RVSP) in Egln1^Tie2Cre mice consistent with their role as vasodilators. However, these drugs have no beneficial effects on pulmonary arterial function. Cardiac output was also markedly improved in Egln1^Tie2Cre mice by any of the drug treatments. They only partially improved RV function and reduced RV hypertrophy and pulmonary vascular remodeling as well as improving short-term survival in a drug-dependent manner. These data demonstrate that Egln1^Tie2Cre mice exhibit similar responses to these drugs as PAH patients seen in clinical trials. Thus, our study provides further evidence that the Egln1^Tie2Cre mouse model of severe PAH is an ideal model of PAH and is potentially useful for enabling identification of drug targets and preclinical testing of novel PAH drug candidates.

Fatty Acid Metabolism in Endothelial Cell

The endothelium is a monolayer of cells lining the inner blood vessels. Endothelial cells (ECs) play indispensable roles in angiogenesis, homeostasis, and immune response under normal physiological conditions, and their dysfunction is closely associated with pathologies such as cardiovascular diseases. Abnormal EC metabolism, especially dysfunctional fatty acid (FA) metabolism, contributes to the development of many diseases including pulmonary hypertension (PH). In this review, we focus on discussing the latest advances in FA metabolism in ECs under normal and pathological conditions with an emphasis on PH. We also highlight areas of research that warrant further investigation.