Pathobiology of pulmonary arterial hypertension and right ventricular failure

Sex-dependent Pathophysiology and Therapeutic Considerations in Right Heart Disease

Right ventricular (RV) adaptation to the increased afterload in the setting of pulmonary hypertension (PH) and other cardiac and pulmonary vascular conditions is a major determinant of survival. Although the RV remains understudied and less well understood than the left ventricle, recent advances have been made in understanding the function and biology of the RV in health and in disease, particularly in PH. RV adaptation in PH exhibits significant sexual dimorphisms in pathophysiology, adaptation, and outcomes. Despite a higher incidence of PH, women consistently demonstrate better RV adaptation and survival rates in the setting of increased RV afterload compared with men. Sexual dimorphisms extend to therapy responsiveness, with women benefiting more from certain pulmonary vasodilators and exhibiting superior RV recovery. In this review we discuss the current literature on sexual dimorphisms in RV structure, function, and molecular pathways in health and disease, as well as in RV-specific clinical manifestations, treatments, and outcomes in PH. Sex steroid-mediated effects as well as emerging studies on sex steroid-independent effects are reviewed. In general, sex steroids such as 17β-estradiol and dehydroepiandrosterone exert RV-protective effects. In contrast, testosterone negatively impacts RV structure and function. Emerging evidence highlights the influence of nonhormonal genetic determinants, such as BMPR1A and DMRT2 loci, which are associated with better RV function in women. A better understanding of the interplay between sex hormones, genetic factors, and RV biology is crucial for advancing and developing RV-directed therapies for patients of either sex.

Enhanced lung endothelial glycolysis is implicated in the development of severe pulmonary hypertension in type 2 diabetes

Metabolic abnormalities in pulmonary endothelial cells are implicated in pulmonary hypertension (PH) while increasing evidence shows the influence of diabetes on progressing PH. In this study, we examined the effect of type 2 diabetes on hypoxia-induced PH and investigated its molecular mechanisms using hypoxia-induced diabetic male mice. Chronic hypoxia led to a more severe PH in type 2 diabetic mice than in control mice. Next, we compared gene expression patterns in isolated pulmonary endothelial cells (MPECs) from control mice in normoxia (CN), diabetic mice in normoxia (DN), control mice exposed to hypoxia (CH), and diabetic mice exposed to hypoxia (DH). The results showed that expression levels of 27 mRNAs, out of 92 mRNAs, were significantly different among the four groups. Two glycolysis-related proteins, GAPDH and HK2, were increased in MPECs of DH mice compared with those in DN or CH mice. In addition, the levels of pyruvate and lactate (glycolysis end products) were significantly increased in MPECs of DH mice, but not in CH mice, compared with MPECs of CN mice. Augmentation of glycolysis by terazosin exacerbated hypoxia-induced PH in CH mice but not in DH mice. On the contrary, inhibiting GAPDH (a key enzyme of the glycolytic pathway) by koningic acid ameliorated hypoxia-induced PH in DH mice but had no effect in CH mice. These data suggest that enhanced glycolysis in diabetic mice is involved in severe hypoxia-induced PH, and glycolysis inhibition is a potential target to reduce the severe progression of PH in patients with diabetes.NEW & NOTEWORTHY Increasing evidence shows that diabetes exacerbates the progression of pulmonary hypertension; however, its molecular mechanisms are understudied. In this study, we revealed that augmented glycolysis in diabetic pulmonary endothelial cells is involved in the development of severe PH in diabetes. Inhibition of glycolysis could be a therapeutic strategy for treating pulmonary hypertension in patients with diabetes.

Smooth Muscle Cell-Specific LKB1 Protects Against Sugen 5416/Hypoxia-induced Pulmonary Hypertension through Inhibition of BMP4

Pulmonary hypertension (PH) is a life-threatening syndrome associated with hyperproliferation of pulmonary artery smooth muscle cells (PASMCs), which exhibit features similar to those of cancer cells. Currently, there is no curative treatment for PH. LKB1 is known as a tumor suppressor gene with an antiproliferative effect on cancer cells. However, its role and mechanism in the development of PH remain unclear. Gain- and loss-of-function strategies were used to elucidate the mechanisms of LKB1 in regulating the occurrence and progression of PH. Sugen 5416/hypoxia (SuHx) PH model was utilized for in vivo study. We observed a decreased expression of LKB1 not only in the lung vessels of the SuHx mouse model but also in human PASMCs (HPASMCs) exposed to hypoxia. Smooth muscle-specific LKB1 knockout significantly aggravated SuHx-induced PH in mice. RNA-sequencing analysis revealed a substantial increase in bone morphogenetic protein 4 (BMP4) in the aortas of LKB1SMKO mice compared with controls, identifying BMP4 as a novel target of LKB1. LKB1 knockdown in HPASMCs cultured under hypoxic conditions increased BMP4 protein level and HPASMC proliferation and migration. The coimmunoprecipitation analysis revealed that LKB1 directly modulates BMP4 protein degradation through phosphorylation. Therapeutically, suppressing BMP4 expression in smooth muscle cells alleviates PH in LKB1SMKO mice. Our findings demonstrate that LKB1 attenuates PH by enhancing the lysosomal degradation of BMP4, thus suppressing the proliferation and migration of HPASMCs. Modulating the LKB1-BMP4 axis in smooth muscle cells could be a promising therapeutic strategy of PH.

Glycoprotein 130 Antagonism Counteracts Metabolic and Inflammatory Alterations to Enhance Right Ventricle Function in Pulmonary Artery Banded Pigs

Background

Right ventricular dysfunction (RVD) is a risk factor for death in multiple cardiovascular diseases, but RV-enhancing therapies are lacking. Inhibition of glycoprotein-130 (GP130) signaling with the small molecule SC144 improves RV function in rodent RVD via anti-inflammatory and metabolic mechanisms. However, SC144's efficacy and molecular effects in a translational large animal model of RVD are unknown.

Methods

4-week-old castrated male pigs underwent pulmonary artery banding (PAB). After 3 weeks, PAB pigs were randomized into 2 groups (daily injections of SC144 [2.2 mg/kg, PAB-SC144, n=5] or vehicle [PAB-Veh, n=5] for 3 weeks). Five age-matched pigs served as controls. Cardiac MRI quantified RV size/function. Right heart catheterization evaluated hemodynamics. Single-nucleus RNA sequencing delineated cell-type specific changes between experimental groups. Electron microscopy evaluated RV mitochondrial morphology. Phosphoproteomics identified dysregulated RV kinases. Lipidomics and metabolomics quantified lipid species and metabolites in RV tissue. Quantitative proteomics examined RV mitochondrial protein regulation.

Results

SC144 significantly improved RV ejection fraction (Control: 60±4%, PAB-Veh: 22±10%, PAB-SC144: 37±6%) despite similar RV afterload. Single-nucleus RNA sequencing demonstrated PAB-Veh pigs had lower cardiomyocyte and higher macrophage/lymphocyte/pericyte/endothelial cell abundances as compared to control, and many of these changes were blunted by SC144. SC144 combatted the downregulation of cardiomyocyte metabolic genes induced by PAB. Kinome enrichment analysis suggested SC144 counteracted RV mTORC1 activation. Correspondingly, SC144 rebalanced RV autophagy pathway proteins and improved mitochondrial morphology. Integrated lipidomics, metabolomics, and proteomics analyses revealed SC144 restored fatty acid metabolism. Finally, CellChat analysis revealed SC144 restored pericyte-endothelial cell cross-talk.

Conclusion

GP130 antagonism blunts elevated immune cell abundance, reduces pro-inflammatory gene transcription in macrophages and lymphocytes, rebalances autophagy and preserves fatty acid metabolism in cardiomyocytes, and restores endothelial cell and pericyte communication to improve RV function.

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.

Pulmonary Hypertension Associated with Connective Tissue Disease

Pulmonary hypertension (PH), a syndrome characterized by elevated pulmonary pressures, commonly complicates connective tissue disease (CTD) and is associated with increased morbidity and mortality. The incidence of PH varies widely between CTDs; patients with systemic sclerosis are most likely to develop PH. Several different types of PH can present in CTD, including PH related to left heart disease and respiratory disease. Importantly, CTD patients are at risk for developing pulmonary arterial hypertension, a rare form of PH that is associated with high morbidity and mortality. Future therapies targeting pulmonary vascular remodeling may improve outcomes for patients with this devastating disease.

Leukotriene B4 levels in CHD-associated paediatric pulmonary hypertension

BACKGROUND

The aim of this study is to evaluate the role of leukotriene B4, an inflammatory mediator, in the development of pulmonary hypertension in paediatric patients with CHD with left-right shunt.

METHODS

The study included forty patients with CHD with left-right shunts. Based on haemodynamic data obtained from cardiac diagnostic catheterisation, 25 patients who met the criteria for pulmonary arterial hypertension were included in the patient group. The control group comprised 15 patients who did not meet the criteria. The standard cardiac haemodynamic study was conducted. Leukotriene B4 levels were assessed in blood samples taken from both pulmonary arteries and peripheral veins.

RESULTS

The median age of patients with pulmonary arterial hypertension was 10 months (range: 3-168), while the median age of the control group was 50 months (range: 3-194). In the pulmonary hypertension group, the median pulmonary artery systolic/diastolic/mean pressures were 38/18/24 mmHg, compared to 26/10/18 mmHg in the control group. Leukotriene B4 levels in pulmonary artery blood samples were significantly higher in the pulmonary arterial hypertension group compared to the controls (p < 0.05). Peripheral leukotriene B4 levels were also elevated in the pulmonary arterial hypertension group in comparison to the control group, though the difference was not statistically significant.

CONCLUSION

The discovery of elevated leukotriene B4 levels in pulmonary artery samples from paediatric patients with pulmonary arterial hypertension secondary to CHD with left-to-right shunt suggests that local inflammation may have a pathological role in the development of pulmonary arterial hypertension.

Novel insights into the potential applications of stem cells in pulmonary hypertension therapy

Pulmonary hypertension (PH) refers to a group of deadly lung diseases characterized by vascular lesions in the microvasculature and a progressive increase in pulmonary vascular resistance. The prevalence of PH has increased over time. Currently, the treatment options available for PH patients have limited efficacy, and none of them can fundamentally reverse pulmonary vascular remodeling. Stem cells represent an ideal seed with proven efficacy in clinical studies focusing on liver, cardiovascular, and nerve diseases. Since the potential therapeutic effect of mesenchymal stem cells (MSCs) on PH was first reported in 2006, many studies have demonstrated the efficacy of stem cells in PH animal models and suggested that stem cells can help slow the deterioration of lung tissue. Existing PH treatment studies basically focus on the paracrine action of stem cells, including protein regulation, exosome pathway, and cell signaling; however, the specific mechanisms have not yet been clarified. Apoptotic and afunctional pulmonary microvascular endothelial cells (PMVECs) and alveolar epithelial cells (AECs) are two fundamental promoters of PH although they have not been extensively studied by researchers. This review mainly focuses on the supportive communication and interaction between PMVECs and AECs as well as the potential restorative effect of stem cells on their injury. In the future, more studies are needed to prove these effects and explore more radical cures for PH.

A peripheral system disease-Pulmonary hypertension

Pulmonary hypertension (PH) is a cardiovascular disorder characterized by substantial morbidity and mortality rates. It is a chronic condition characterized by intricate pathogenesis and uncontrollable factors. We summarized the pathological effects of estrogen, genetics, neuroinflammation, intestinal microbiota, metabolic reorganization, and histone modification on PH. PH is not only a pulmonary vascular disease, but also a systemic disease. The findings emphasize that the onset of PH is not exclusively confined to the pulmonary vasculature, consequently necessitating treatment approaches that extend beyond targeting pulmonary blood vessels. Hence, the research on the pathological mechanism of PH is not limited to target organs such as pulmonary vessels, but also focuses on exploring other fields (such as estrogen, genetics, neuroinflammation, intestinal microbiota, metabolic reorganization, and histone modification).

Pulmonary arterial hypertension: Sex matters

Pulmonary arterial hypertension (PAH) is a complex disease of multifactorial origin. While registries have demonstrated that women are more susceptible to the disease, females with PAH have superior right ventricle (RV) function and a better prognosis than their male counterparts, a phenomenon referred to as the 'estrogen paradox'. Numerous pre-clinical studies have investigated the involvement of sex hormones in PAH pathobiology, often with conflicting results. However, recent advances suggest that abnormal estrogen synthesis, metabolism and signalling underpin the sexual dimorphism of this disease. Other sex hormones, such as progesterone, testosterone and dehydroepiandrosterone may also play a role. Several non-hormonal factor including sex chromosomes and epigenetics have also been implicated. Though the underlying pathophysiological mechanisms are complex, several compounds that modulate sex hormones levels and signalling are under investigation in PAH patients. Further elucidation of the estrogen paradox will set the stage for the identification of additional therapeutic targets for this disease.

Vitamin C deficiency can lead to pulmonary hypertension: a systematic review of case reports

BACKGROUND

In the early literature, unintentional vitamin C deficiency in humans was associated with heart failure. Experimental vitamin C deficiency in guinea pigs caused enlargement of the heart. The purpose of this study was to collect and analyze case reports on vitamin C and pulmonary hypertension.

METHODS

We searched Pubmed and Scopus for case studies in which vitamin C deficiency was considered to be the cause of pulmonary hypertension. We selected reports in which pulmonary hypertension was diagnosed by echocardiography or catheterization, for any age, sex, or dosage of vitamin C. We extracted quantitative data for our analysis. We used the mean pulmonary artery pressure (mPAP) as the outcome of primary interest.

RESULTS

We identified 32 case reports, 21 of which were published in the last 5 years. Dyspnea was reported in 69%, edema in 53% and fatigue in 28% of the patients. Vitamin C plasma levels, measured in 27 cases, were undetectable in 24 and very low in 3 cases. Diet was poor in 30 cases and 17 cases had neuropsychiatric disorders. Right ventricular enlargement was reported in 24 cases. During periods of vitamin C deficiency, the median mPAP was 48 mmHg (range 29-77 mmHg; N = 28). After the start of vitamin C administration, the median mPAP was 20 mmHg (range 12-33 mmHg; N = 18). For the latter 18 cases, mPAP was 2.4-fold (median) higher during vitamin C deficiency. Pulmonary vascular resistance (PVR) during vitamin C deficiency was reported for 9 cases, ranging from 4.1 to 41 Wood units. PVR was 9-fold (median; N = 5) higher during vitamin C deficiency than during vitamin C administration. In 8 cases, there was direct evidence that the cases were pulmonary artery hypertension (PAH). Probably the majority of the remaining cases were also PAH.

CONCLUSIONS

The cases analyzed in our study indicate that pulmonary hypertension can be one explanation for the reported heart failure of scurvy patients in the early literature. It would seem sensible to measure plasma vitamin C levels of patients with PH and examine the effects of vitamin C administration.

A computational study of right ventricular mechanics in a rat model of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) presents a significant challenge to right ventricular (RV) function due to progressive pressure overload, necessitating adaptive remodeling in the form of increased wall thickness, enhanced myocardial contractility and stiffness to maintain cardiac performance. However, the impact of these remodeling mechanisms on RV mechanics in not clearly understood. In addition, there is a lack of quantitative understanding of how each mechanism individually influences RV mechanics. Utilizing experimental data from a rat model of PAH at three distinct time points, we developed biventricular finite element models to investigate how RV stress and strain evolved with PAH progression. The finite element models were fitted to hemodynamic and morphological data to represent different disease stages and used to analyze the impact of RV remodeling as well as the altered RV pressure. Furthermore, we performed a number of theoretical simulation studies with different combinations of morphological and physiological remodeling, to assess and quantify their individual impact on overall RV load and function. Our findings revealed a substantial 4-fold increase in RV stiffness and a transient 2-fold rise in contractility, which returned to baseline by week 12. These changes in RV material properties in addition to the 2-fold increase in wall thickness significantly mitigated the increase in wall stress and strain caused by the progressive increase in RV afterload. Despite the PAH-induced cases showing increased wall stress and strain at end-diastole and end-systole compared to the control, our simulations suggest that without the observed remodeling mechanisms, the increase in stress and strain would have been much more pronounced. Our model analysis also indicated that while changes in the RV's material properties-particularly increased RV stiffness - have a notable effect on its mechanics, the primary compensatory factor limiting the stress and strain increase in the early stages of PAH was the significant increase in wall thickness. These findings underscore the importance of RV remodeling in managing the mechanical burden on the right ventricle due to pressure overload.

Multi-omic and multispecies analysis of right ventricular dysfunction

BACKGROUND

Right ventricular failure (RVF) is a leading cause of morbidity and mortality in multiple cardiovascular diseases, but there are no treatments for RVF as therapeutic targets are not clearly defined. Contemporary transcriptomic/proteomic evaluations of RVF are predominately conducted in small animal studies, and data from large animal models are sparse. Moreover, a comparison of the molecular mediators of RVF across species is lacking.

METHODS

Transcriptomics and proteomics analyses defined the pathways associated with cardiac magnetic resonance imaging (MRI)-derived values of RV hypertrophy, dilation, and dysfunction in control and pulmonary artery banded (PAB) pigs. Publicly available data from rat monocrotaline-induced RVF and pulmonary arterial hypertension patients with preserved or impaired RV function were used to compare molecular responses across species.

RESULTS

PAB pigs displayed significant right ventricle/ventricular (RV) hypertrophy, dilation, and dysfunction as quantified by cardiac magnetic resonance imaging. Transcriptomic and proteomic analyses identified pathways associated with RV dysfunction and remodeling in PAB pigs. Surprisingly, disruptions in fatty acid oxidation (FAO) and electron transport chain (ETC) proteins were different across the 3 species. FAO and ETC proteins and transcripts were mostly downregulated in rats but were predominately upregulated in PAB pigs, which more closely matched the human response. All species exhibited similar dysregulation of the dilated cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy pathways.

CONCLUSIONS

The porcine metabolic molecular signature was more similar to human RVF than rodents. These data suggest there may be divergent molecular responses of RVF across species, and pigs may more accurately recapitulate metabolic aspects of human RVF.

Proteomic and Phosphoproteomic Analysis of Right Ventricular Hypertrophy in the Pulmonary Hypertension Rat Model

Pulmonary arterial hypertension (PAH) is a progressive disease that affects both the lungs and heart. Right ventricle (RV) hypertrophy is a primary pathological feature of PAH; however, its underlying molecular mechanisms remain insufficiently studied. In this study, we employed tandem mass tag (TMT)-based quantitative proteomics for the integrative analysis of the proteome and phosphoproteome of the RV derived from monocrotaline-induced PAH model rats. Compared with control samples, 564 significantly upregulated proteins, 616 downregulated proteins, 622 downregulated phosphopeptides, and 683 upregulated phosphopeptides were identified (P < 0.05, abs (log2 (fold change)) > log2 1.2) in the MCT samples. The quantitative real-time polymerase chain reaction (qRT-PCR) validated the expression levels of top 20 significantly altered proteins, including Nppa (natriuretic peptides A), latent TGF-β binding protein 2 (Ltbp2), periostin, connective tissue growth factor 2 (Ccn2), Ncam1 (neural cell adhesion molecule), quinone reductase 2 (Nqo2), and tropomodulin 4 (Tmod4). Western blotting confirmed the upregulation of Ncam1 and downregulation of Nqo2 and Tmod4 in both MCT-induced and hypoxia-induced PH rat models. Pathway enrichment analyses indicated that the altered proteins are associated with pathways, such as vesicle-mediated transport, actin cytoskeleton organization, TCA cycle, and respiratory electron transport. These significantly changed phosphoproteins were enriched in pathways such as diabetic cardiomyopathy, hypertrophic cardiomyopathy, glycolysis/gluconeogenesis, and cardiac muscle contraction. In summary, this study provides an initial analysis of the RV proteome and phosphoproteome in the progression of PAH, highlighting several RV dysfunction-associated proteins and pathways.

A pneumonectomy model to study flow-induced pulmonary hypertension and compensatory lung growth

In newborns, developmental disorders such as congenital diaphragmatic hernia (CDH) and specific types of congenital heart disease (CHD) can lead to defective alveolarization, pulmonary hypoplasia, and pulmonary arterial hypertension (PAH). Therapeutic options for these patients are limited, emphasizing the need for new animal models representative of disease conditions. In most adult mammals, compensatory lung growth (CLG) occurs after pneumonectomy; however, the underlying relationship between CLG and flow-induced pulmonary hypertension (PH) is not fully understood. We propose a murine model that involves the simultaneous removal of the left lung and right caval lobe (extended pneumonectomy), which results in reduced CLG and exacerbated reproducible PH. Extended pneumonectomy in mice is a promising animal model to study the cellular response and molecular mechanisms contributing to flow-induced PH, with the potential to identify new treatments for patients with CDH or PAH-CHD.

RGS5 as a Biomarker of Pericytes, Involvement in Vascular Remodeling and Pulmonary Arterial Hypertension

Introduction

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by a sustained rise in mean pulmonary artery pressure. Pulmonary vascular remodeling serves an important role in PAH. Identifying a key driver gene to regulate vascular remodeling of the pulmonary microvasculature is critical for PAH management.

Methods

Differentially expressed genes were identified using the Gene Expression Omnibus (GEO) GSE117261, GSE48149, GSE113439, GSE53408 and GSE16947 datasets. A co-expression network was constructed using weighted gene co-expression network analysis. Novel and key signatures of PAH were screened using four algorithms, including weighted gene co-expression network analysis, GEO2R analysis, support vector machines recursive feature elimination and robust rank aggregation rank analysis. Regulator of G-protein signaling 5 (RGS5), a pro-apoptotic/anti-proliferative protein, which regulate arterial tone and blood pressure in vascular smooth muscle cells. The expression of RGS5 was determined using reverse transcription-quantitative PCR (RT-qPCR) in PAH and normal mice. The location of RGS5 and pericytes was detected using immunofluorescence.

Results

Compared with that in the normal group, RGS5 expression was upregulated in the PAH group based on GEO and RT-qPCR analyses. RGS5 expression in single cells was enriched in pericytes in single-cell RNA sequencing analysis. RGS5 co-localization with pericytes was detected in the pulmonary microvasculature of PAH.

Conclusion

RGS5 regulates vascular remodeling of the pulmonary microvasculature and the occurrence of PAH through pericytes, which has provided novel ideas and strategies regarding the occurrence and innovative treatment of PAH.

Emerging biologics for the treatment of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare pulmonary vascular disorder, wherein mean systemic arterial pressure (mPAP) becomes abnormally high because of aberrant changes in various proliferative and inflammatory signalling pathways of pulmonary arterial cells. Currently used anti-PAH drugs chiefly target the vasodilatory and vasoconstrictive pathways. However, an imbalance between bone morphogenetic protein receptor type II (BMPRII) and transforming growth factor beta (TGF-β) pathways is also implicated in PAH predisposition and pathogenesis. Compared to currently used PAH drugs, various biologics have shown promise as PAH therapeutics that elicit their therapeutic actions akin to endogenous proteins. Biologics that have thus far been explored as PAH therapeutics include monoclonal antibodies, recombinant proteins, engineered cells, and nucleic acids. Because of their similarity with naturally occurring proteins and high binding affinity, biologics are more potent and effective and produce fewer side effects when compared with small molecule drugs. However, biologics also suffer from the limitations of producing immunogenic adverse effects. This review describes various emerging and promising biologics targeting the proliferative/apoptotic and vasodilatory pathways involved in PAH pathogenesis. Here, we have discussed sotatercept, a TGF-β ligand trap, which is reported to reverse vascular remodelling and reduce PVR with an improved 6-minute walk distance (6-MWDT). We also elaborated on other biologics including BMP9 ligand and anti-gremlin1 antibody, anti-OPG antibody, and getagozumab monoclonal antibody and cell-based therapies. Overall, recent literature suggests that biologics hold excellent promise as a safe and effective alternative to currently used PAH therapeutics.

Jiedu Quyu Decoction mitigates monocrotaline-induced right-sided heart failure associated with pulmonary artery hypertension by inhibiting NLRP3 inflammasome in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Right-side heart failure could accelerate mortality in patients of pulmonary hypertension, Jiedu Quyu Decoction (JDQYF) was used to manage pulmonary hypertension, but its right-sided heart protective effect associated with pulmonary artery hypertension is still unclear.

AIM OF THE STUDY

Here, we evaluated the therapeutic effect of JDQYF on monocrotaline-induced right-sided heart failure associated with pulmonary arterial hypertension in Sprague-Dawley (SD) rats and investigated the potential mechanism of action.

MATERIALS AND METHODS

The main chemical components of JDQYF were detected and analyzed using ultra-high-performance liquid chromatography quadrupole time-of-flight mass spectrometry. The effects of JDQYF were investigated using a rat model of monocrotaline-induced right-sided heart failure associated with pulmonary arterial hypertension. We assessed the morphology of cardiac tissue using histopathology and the structure and function of the right heart using echocardiography. The biomarkers of heart failure, atrial natriuretic peptide and B-type natriuretic peptide, as well as serum pro-inflammatory markers, interleukin (IL)-1β, and IL-18, were measured by enzyme-linked immunosorbent assay (ELISA). Furthermore, the mRNA and protein expression levels of NLRP3 (NOD-, LRR-, and pyrin domain-containing 3), capase-1, IL-1β, and IL-18 in the right heart tissue were examined by real-time quantitative reverse transcription PCR and western blotting.

RESULTS

JDQYF improved ventricular function, alleviated pathological lesions in the right cardiac tissue, reduced the expression levels of biomarkers of heart failure and serum pro-inflammatory factors (IL-1β and IL-18), and downregulated the mRNA and protein expression levels of NLRP3, caspase-1, IL-1β, and IL-18 in the right cardiac tissue.

CONCLUSIONS

JDQYF possesses cardioprotective effect against right heart failure induced by pulmonary arterial hypertension, possibly owing to reduction of cardiac inflammation through the inhibition of NLRP3 inflammasome activation.

Inhibition of YTHDF1 prevents hypoxia-induced pulmonary artery smooth muscle cell proliferation by regulating Foxm1 translation in an m6A-dependent manner

Pulmonary arterial hypertension (PAH) is a chronic disease characterized by pulmonary vascular remodeling. It refers to the abnormal proliferation of pulmonary artery smooth muscle cells (PASMCs), and hypoxia is an important risk factor for this progression. The present study aims to investigate the role of YTHDF1 in the regulation of hypoxic PASMC proliferation and the underlying mechanism. Human PASMCs were transfected with si-YTHDF1/2/3 followed by treatment of hypoxia, and the PASMC proliferation and Foxm1 expression were detected. Through RNA pull-down, RNA immunoprecipitation, and protein synthesis assay, the mechanism of YTHDF1 regulating Foxm1 was explored. Next, Foxm1 was inhibited by thiostrepton, and cell proliferation was detected. In vivo, mice received a tail vein injection of adenovirus containing si-YTHDF1 and were exposed to hypoxia treatment. Pulmonary vascular changes, right ventricular systolic pressure (RVSP), and genes involving proliferation were analyzed. YTHDF1 silencing reduced more hypoxic PASMC proliferation and Foxm1 protein level than YTHDF2/3 silencing. Mechanical results showed that YTHDF1 interacted with Foxm1 mRNA and up-regulated Foxm1 protein level by enhancing the translation efficiency in an m6A-dependent manner. Furthermore, YTHDF1 facilitated hypoxic PASMC proliferation and proliferation marker expressions through up-regulation of Foxm1 in an m6A-dependent manner. In vivo, the YTHDF1 silencing alleviated pulmonary vascular changes and fibrosis, reduced RVSP, inhibited the interaction of YTHDF1 and Foxm1, and reduced proliferation marker levels, as compared to the PAH group. In conclusion, YTHDF1 silencing inhibits hypoxic PASMC proliferation by regulating Foxm1 translation in an m6A-dependent manner.

A Multi-omic and Multi-Species Analysis of Right Ventricular Failure

Right ventricular failure (RVF) is a leading cause of morbidity and mortality in multiple cardiovascular diseases, but there are no approved treatments for RVF as therapeutic targets are not clearly defined. Contemporary transcriptomic/proteomic evaluations of RVF are predominately conducted in small animal studies, and data from large animal models are sparse. Moreover, a comparison of the molecular mediators of RVF across species is lacking. Here, we used transcriptomics and proteomics analyses to define the molecular pathways associated with cardiac MRI-derived values of RV hypertrophy, dilation, and dysfunction in pulmonary artery banded (PAB) piglets. Publicly available data from rat monocrotaline-induced RVF and pulmonary arterial hypertension patients with preserved or impaired RV function were used to compare the three species. Transcriptomic and proteomic analyses identified multiple pathways that were associated with RV dysfunction and remodeling in PAB pigs. Surprisingly, disruptions in fatty acid oxidation (FAO) and electron transport chain (ETC) proteins were different across the three species. FAO and ETC proteins and transcripts were mostly downregulated in rats, but were predominately upregulated in PAB pigs, which more closely matched the human data. Thus, the pig PAB metabolic molecular signature was more similar to human RVF than rodents. These data suggest there may be divergent molecular responses of RVF across species, and that pigs more accurately recapitulate the metabolic aspects of human RVF.

Pathophysiology and new advances in pulmonary hypertension

Pulmonary hypertension is a progressive and often fatal cardiopulmonary condition characterised by increased pulmonary arterial pressure, structural changes in the pulmonary circulation, and the formation of vaso-occlusive lesions. These changes lead to increased right ventricular afterload, which often progresses to maladaptive right ventricular remodelling and eventually death. Pulmonary arterial hypertension represents one of the most severe and best studied types of pulmonary hypertension and is consistently targeted by drug treatments. The underlying molecular pathogenesis of pulmonary hypertension is a complex and multifactorial process, but can be characterised by several hallmarks: inflammation, impaired angiogenesis, metabolic alterations, genetic or epigenetic abnormalities, influence of sex and sex hormones, and abnormalities in the right ventricle. Current treatments for pulmonary arterial hypertension and some other types of pulmonary hypertension target pathways involved in the control of pulmonary vascular tone and proliferation; however, these treatments have limited efficacy on patient outcomes. This review describes key features of pulmonary hypertension, discusses current and emerging therapeutic interventions, and points to future directions for research and patient care. Because most progress in the specialty has been made in pulmonary arterial hypertension, this review focuses on this type of pulmonary hypertension. The review highlights key pathophysiological concepts and emerging therapeutic directions, targeting inflammation, cellular metabolism, genetics and epigenetics, sex hormone signalling, bone morphogenetic protein signalling, and inhibition of tyrosine kinase receptors.

Hypoxia-induced pulmonary hypertension upregulates eNOS and TGF-β contributing to sex-linked differences in BMPR2 +/R899X mutant mice

Dysfunctional bone morphogenetic protein receptor 2 (BMPR2) and endothelial nitric oxide synthase (eNOS) have been largely implicated in the pathogenesis of pulmonary arterial hypertension (PAH); a life-threatening cardiopulmonary disease. Although the incident of PAH is about three times higher in females, males with PAH usually have a worse prognosis, which seems to be dependent on estrogen-associated cardiac and vascular protection. Here, we evaluated whether hypoxia-induced pulmonary hypertension (PH) in humanized BMPR2+/R899X loss-of-function mutant mice contributes to sex-associated differences observed in PAH by altering eNOS expression and inducing expansion of hyperactivated TGF-β-producing pulmonary myofibroblasts. To test this hypothesis, male and female wild-type (WT) and BMPR2+/R899X mutant mice were kept under hypoxic or normoxic conditions for 4 weeks, and then right ventricular systolic pressure (RVSP) and right ventricular hypertrophy (RVH) were measured. Chronic hypoxia exposure elevated RVSP, inducing RVH in both groups, with a greater effect in BMPR2+/R899X female mice. Lung histology revealed no differences in vessel thickness/area between sexes, suggesting RVSP differences in this model are unlikely to be in response to sex-dependent vascular narrowing. On the other hand, hypoxia exposure increased vascular collagen deposition, the number of TGF-β-associated α-SMA-positive microvessels, and eNOS expression, whereas it also reduced caveolin-1 expression in the lungs of BMPR2+/R899X females compared to males. Taken together, this brief report reveals elevated myofibroblast-derived TGF-β and eNOS-derived oxidants contribute to pulmonary microvascular muscularization and sex-linked differences in incidence, severity, and outcome of PAH.

Single-Cell RNA-Sequencing Reveals the Active Involvement of Macrophage Polarizations in Pulmonary Hypertension

Background. Sustained hypoxia can trigger a progressive rise in pulmonary artery pressure and cause serious pulmonary diseases. Macrophages play important roles along the progression of pulmonary hypertension. However, the state of macrophage polarization during the early stage of pulmonary hypertension is unclear. Methods. Unlike traditional sequencing method, single-cell sequencing can accurately distinguish among cell types and better understand cell-to-cell relationships. In this study, we investigated the polarization of macrophages in pulmonary hypertension via single-cell RNA-sequencing in a mice hypoxia model, which was then validated in patients with pulmonary hypertension. Results. We identified that the intermittent exposure to hypoxic conditions could lead to the production of more M2-type macrophages than M1-type macrophages in a mouse model. Further validation analysis was performed by analyzing lung tissue of patients with pulmonary hypertension, revealing that the number of disease-associated M2 macrophages was substantially increased. Conclusions. In this study, the active anti-inflammatory response of macrophage involved in pulmonary hypertension has been identified, suggesting that intervention against the polarization of macrophages to the M2 type may be a potential way to reduce chronic pulmonary inflammation, pulmonary vascular remodeling, and artery pressure. Thus, investigation of macrophage polarization associated with hypoxia could help us better understand disease mechanism and craft effective prevention strategies and approaches.

Metabolic reprogramming: A novel metabolic model for pulmonary hypertension

Pulmonary arterial hypertension, or PAH, is a condition that is characterized by pulmonary artery pressures above 20 mmHg (at rest). In the treatment of PAH, the pulmonary vascular system is regulated to ensure a diastolic and contraction balance; nevertheless, this treatment does not prevent or reverse pulmonary vascular remodeling and still causes pulmonary hypertension to progress. According to Warburg, the link between metabolism and proliferation in PAH is similar to that of cancer, with a common aerobic glycolytic phenotype. By activating HIF, aerobic glycolysis is enhanced and cell proliferation is triggered. Aside from glutamine metabolism, the Randle cycle is also present in PAH. Enhanced glutamine metabolism replenishes carbon intermediates used by glycolysis and provides energy to over-proliferating and anti-apoptotic pulmonary vascular cells. By activating the Randle cycle, aerobic oxidation is enhanced, ATP is increased, and myocardial injury is reduced. PAH is predisposed by epigenetic dysregulation of DNA methylation, histone acetylation, and microRNA. This article discusses the abnormal metabolism of PAH and how metabolic therapy can be used to combat remodeling.

Pyrroloquinoline quinone (PQQ) improves pulmonary hypertension by regulating mitochondrial and metabolic functions

Excessive proliferation of pulmonary artery smooth muscle cells (PASMCs) and endothelial cells (PAECs), inflammation, as well as mitochondrial and metabolic dysregulation, contributes to the development of pulmonary hypertension (PH). Pyrroloquinoline quinone (PQQ), a potent natural antioxidant with anti-diabetic, neuroprotective, and cardioprotective properties, is known to promote mitochondrial biogenesis. However, its effect on cellular proliferation, apoptosis resistance, mitochondrial and metabolic alterations associated with PH remains unexplored. The current study was designed to investigate the effect of PQQ in the treatment of PH. Human pulmonary artery smooth muscle cells (HPASMCs), endothelial cells (PAECs), and primary cultured cardiomyocytes were subjected to hypoxia to induce PH-like phenotype. Furthermore, Sprague Dawley (SD) rats injected with monocrotaline (MCT) (60 mg/kg, SC, once) progressively developed pulmonary hypertension. PQQ treatment (2 mg/kg, PO, for 35 days) attenuated cellular proliferation and promoted apoptosis via a mitochondrial-dependent pathway. Furthermore, PQQ treatment in HPASMCs prevented mitochondrial and metabolic dysfunctions, improved mitochondrial bioenergetics while preserving respiratory complexes, and reduced insulin resistance. In addition, PQQ treatment (preventive and curative) significantly attenuated the increase in right ventricle pressure and hypertrophy as well as reduced endothelial dysfunction and pulmonary artery remodeling in MCT-treated rats. PQQ also prevented cardiac fibrosis and improved cardiac functions as well as reduced inflammation in MCT-treated rats. Altogether, the above findings demonstrate that PQQ can attenuate mitochondrial as well as metabolic abnormalities in PASMCs and also prevent the development of PH in MCT treated rats; hence PQQ may act as a potential therapeutic agent for the treatment of PH.

Computational models of ventricular mechanics and adaptation in response to right-ventricular pressure overload

Pulmonary arterial hypertension (PAH) is associated with substantial remodeling of the right ventricle (RV), which may at first be compensatory but at a later stage becomes detrimental to RV function and patient survival. Unlike the left ventricle (LV), the RV remains understudied, and with its thin-walled crescent shape, it is often modeled simply as an appendage of the LV. Furthermore, PAH diagnosis is challenging because it often leaves the LV and systemic circulation largely unaffected. Several treatment strategies such as atrial septostomy, right ventricular assist devices (RVADs) or RV resynchronization therapy have been shown to improve RV function and the quality of life in patients with PAH. However, evidence of their long-term efficacy is limited and lung transplantation is still the most effective and curative treatment option. As such, the clinical need for improved diagnosis and treatment of PAH drives a strong need for increased understanding of drivers and mechanisms of RV growth and remodeling (G&R), and more generally for targeted research into RV mechanics pathology. Computational models stand out as a valuable supplement to experimental research, offering detailed analysis of the drivers and consequences of G&R, as well as a virtual test bench for exploring and refining hypotheses of growth mechanisms. In this review we summarize the current efforts towards understanding RV G&R processes using computational approaches such as reduced-order models, three dimensional (3D) finite element (FE) models, and G&R models. In addition to an overview of the relevant literature of RV computational models, we discuss how the models have contributed to increased scientific understanding and to potential clinical treatment of PAH patients.

IL-13 alleviates idiopathic pulmonary hypertension by inhibiting the proliferation of pulmonary artery smooth muscle cells and regulating macrophage infiltration

BACKGROUND

Idiopathic pulmonary arterial hypertension (IPAH) is characterized by medial hypertrophy due to pulmonary artery smooth muscle cell (PASMC) hyperplasia. In the present study, we conducted bioinformatic analyses and cellular experiments to assess the involvement of the interleukin-13 (IL-13) in IPAH.

METHODS

The differentially expressed genes (DEGs) in IPAH and DEGs in IPAH caused by IL-13 treatment were screened using the GEO database. PPI networks were used to analyze the hub genes. Hypoxia-induced PASMCs were treated with IL-13 for in vitro assays. CCK8 and EdU staining were used to observe proliferation of PASMCs, and RT-qPCR was applied to detect the expression of hub genes. The conserved binding sites of microRNAs (miRNAs) in the 3'UTR of hub genes were investigated, and the regulatory relationships of the relevant miRNAs on their targets were verified by RT-qPCR and dual-luciferase assays. The GO and KEGG analyses were performed to study the downstream pathways. The effect of hub genes on immune cell infiltration in IPAH was investigated.

RESULTS

IL-13 altered gene expression in IPAH. IL-13 inhibited the proliferation and the expression of hub genes in PASMCs. The 3'UTR sites between HNRNPA2B1, HNRNPH1, SRSF1, HNRNPU and HNRNPA3 in the hub genes and candidate regulatory miRNAs were well conserved in humans. IL-13-mediated hub genes regulated multiple pathways and influenced immune cell infiltration. Hypoxia-induced PASMCs promoted the M2 polarization of macrophages, whereas IL-13-treated PASMCs skewed the macrophages toward M1 polarization.

CONCLUSIONS

IL-13-mediated alterations in hub genes inhibit PASMC proliferation and promote M1 macrophage infiltration in IPAH.

Insights on the Gut-Mesentery-Lung Axis in Pulmonary Arterial Hypertension: A Poorly Investigated Crossroad

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by the hyperproliferation of vascular cells, including smooth muscle and endothelial cells. Hyperproliferative cells eventually obstruct the lung vasculature, leading to irreversible lesions that collectively drive pulmonary pressure to life-threatening levels. Although the primary cause of PAH is not fully understood, several studies have indicated it results from chronic pulmonary inflammation, such as observed in response to pathogens' infection. Curiously, infection by the intravascular parasite Schistosoma mansoni recapitulates several aspects of the widespread pulmonary inflammation that leads to development of chronic PAH. Globally, >200 million people are currently infected by Schistosoma spp., with about 5% developing PAH (Sch-PAH) in response to the parasite egg-induced obliteration and remodeling of the lung vasculature. Before their settling into the lungs, Schistosoma eggs are released inside the mesenteric veins, where they either cross the intestinal wall and disturb the gut microbiome or migrate to other organs, including the lungs and liver, increasing pressure. Spontaneous or surgical liver bypass via collateral circulation alleviates the pressure in the portal system; however, it also allows the translocation of pathogens, toxins, and antigens into the lungs, ultimately causing PAH. This brief review provides an overview of the gut-mesentery-lung axis during PAH, with a particular focus on Sch-PAH, and attempts to delineate the mechanism by which pathogen translocation might contribute to the onset of chronic pulmonary vascular diseases.

The Glycobiology of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive pulmonary vascular disease of complex etiology. Cases of PAH that do not receive therapy after diagnosis have a low survival rate. Multiple reports have shown that idiopathic PAH, or IPAH, is associated with metabolic dysregulation including altered bioavailability of nitric oxide (NO) and dysregulated glucose metabolism. Multiple processes such as increased proliferation of pulmonary vascular cells, angiogenesis, apoptotic resistance, and vasoconstriction may be regulated by the metabolic changes demonstrated in PAH. Recent reports have underscored similarities between metabolic abnormalities in cancer and IPAH. In particular, increased glucose uptake and altered glucose utilization have been documented and have been linked to the aforementioned processes. We were the first to report a link between altered glucose metabolism and changes in glycosylation. Subsequent reports have highlighted similar findings, including a potential role for altered metabolism and aberrant glycosylation in IPAH pathogenesis. This review will detail research findings that demonstrate metabolic dysregulation in PAH with an emphasis on glycobiology. Furthermore, this report will illustrate the similarities in the pathobiology of PAH and cancer and highlight the novel findings that researchers have explored in the field.

Treating Inflammation Associated with Pulmonary Hypertension: An Overview of the Literature

Pulmonary hypertension (PH) comprises five groups of serious clinical entities characterized by pulmonary artery vasoconstriction and vascular remodeling leading to right heart failure and death. In addition to vascular remodeling, recruitment and exaggerated accumulation of several perivascular inflammatory cells is also observed, including macrophages, monocytes, T and B-lymphocytes, dendritic cells and mast cells distributed in pulmonary perivascular spaces and around remodeling pulmonary vessels. Current pulmonary arterial hypertension (PAH)-targeted therapies aim to improve functional capacity, pulmonary hemodynamic conditions, and delay disease progression. Nevertheless, PAH remains incurable, with a poor prognosis and is often refractory to drug therapy, highlighting the need for further research. In the last three decades, the best pathophysiological understanding of PAH has allowed for progression from a disease of little-known pathogenesis, without specific and effective therapy to expanding the arsenal of drugs on a cellular, genetic and molecular basis. This article provides an overview on current knowledge and progress in recent advances in pharmacological therapy in PAH.

Recent Developments in Nanomaterials-Based Drug Delivery and Upgrading Treatment of Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading causes of morbidity and mortality worldwide. However, despite the recent developments in the management of CVDs, the early and long outcomes vary considerably in patients, especially with the current challenges facing the detection and treatment of CVDs. This disparity is due to a lack of advanced diagnostic tools and targeted therapies, requiring innovative and alternative methods. Nanotechnology offers the opportunity to use nanomaterials in improving health and controlling diseases. Notably, nanotechnologies have recognized potential applicability in managing chronic diseases in the past few years, especially cancer and CVDs. Of particular interest is the use of nanoparticles as drug carriers to increase the pharmaco-efficacy and safety of conventional therapies. Different strategies have been proposed to use nanoparticles as drug carriers in CVDs; however, controversies regarding the selection of nanomaterials and nanoformulation are slowing their clinical translation. Therefore, this review focuses on nanotechnology for drug delivery and the application of nanomedicine in CVDs.

Research Progress on the Natural Product Aloperine and Its Derivatives

In this review, an effort towards presenting an all-around account of the recent progress on the natural product, aloperine, is made, and the antivirus structure-activity relationship of its derivatives is also summarized comprehensively. In addition, the principal pharmacological effects and corresponding molecular mechanisms of aloperine are discussed. Some new structural modifications of aloperine are also given, which might provide brief guidance for further investigations on the natural product aloperine.

Cell-to-Cell Crosstalk: A New Insight into Pulmonary Hypertension

Pulmonary hypertension (PH) is a disease with high pulmonary arterial pressure, pulmonary vasoconstriction, pulmonary vascular remodeling, and microthrombosis in complex plexiform lesions, but it has been unclear of the exact mechanism of PH. A new understanding of the pathogenesis of PH is occurred and focused on the role of crosstalk between the cells on pulmonary vessels and pulmonary alveoli. It was found that the crosstalks among the endothelial cells, smooth muscle cells, fibroblasts, pericytes, alveolar epithelial cells, and macrophages play important roles in cell proliferation, migration, inflammation, and so on. Therefore, the heterogeneity of multiple pulmonary blood vessels and alveolar cells and tracking the transmitters of cell communication could be conducive to the further insights into the pathogenesis of PH to discover the potential therapeutic targets for PH.

The effect of transglutaminase-2 inhibitor on pulmonary vascular remodeling in rats with pulmonary arterial hypertension

To investigate the relationship between transglutaminase type 2 (TG2) and pulmonary vascular remodeling in the formation of pulmonary arterial hypertension (PAH), and to investigate the effect of the inhibitor cystamine dihydrochloride on pulmonary vascular remodeling in rats with PAH.

Thirty healthy male Sprague Dawley rats were randomly divided into a control group, a PAH model group, and an intervention group. The mean pulmonary artery pressure (mPAP), the right ventricular hypertrophy index (RVHI), the percentage wall thickness of the pulmonary artery (WT%), and the degree of neointimal proliferation were measured, and the pathological changes in the pulmonary tissues were observed.Messenger ribonucleic acid (mRNA) and protein expressions of TG2, 5-hydroxytryptamine transporter (5-HTT), and Rho-associated protein kinase 2 (ROCK2) in the pulmonary tissues of the three groups of rats were detected.

Compared with the control group, the mPAP, RVHI, and WT% were significantly higher in the model group, the degree of neointimal proliferation was significantly increased, and the mRNA and protein expressions of TG2, 5-HTT, and ROCK2 in the pulmonary tissue were significantly increased. Compared with the model group, the mPAP, RVHI, WT%, and the degree of neointimal proliferation were significantly lower in the intervention group, as were the mRNA and protein expressions of TG2, 5-HTT, and ROCK2 in the pulmonary tissue.

The TG2 inhibitor cystamine dihydrochloride can prevent the formation of PAH to some extent. This might be due to the inhibition of the TG2 activity, 5-HTT expression, and possibly the inhibition of RhoA/ROCK signaling pathway activation.

Combination Therapy With Rapamycin and Low Dose Imatinib in Pulmonary Hypertension

Rationale: Enhanced proliferation and distal migration of human pulmonary arterial smooth muscle cells (hPASMCs) both contribute to the progressive increases in pulmonary vascular remodeling and resistance in pulmonary arterial hypertension (PAH). Our previous studies revealed that Rictor deletion, to disrupt mTOR Complex 2 (mTORC2), over longer periods result in a paradoxical rise in platelet-derived growth factor receptor (PDGFR) expression in PASMCs. Thus, the purpose of this study was to evaluate the role of combination therapy targeting both mTOR signaling with PDGFR inhibition to attenuate the development and progression of PAH.

Methods and Results: Immunoblotting analyses revealed that short-term exposure to rapamycin (6h) significantly reduced phosphorylation of p70S6K (mTORC1-specific) in hPASMCs but had no effect on the phosphorylation of AKT (p-AKT S473, considered mTORC2-specific). In contrast, longer rapamycin exposure (>24 h), resulted in differential AKT (T308) and AKT (S473) phosphorylation with increases in phosphorylation of AKT at T308 and decreased phosphorylation at S473. Phosphorylation of both PDGFRα and PDGFRβ was increased in hPASMCs after treatment with rapamycin for 48 and 72 h. Based on co-immunoprecipitation studies, longer exposure to rapamycin (24–72 h) significantly inhibited the binding of mTOR to Rictor, mechanistically suggesting mTORC2 inhibition by rapamycin. Combined exposure of rapamycin with the PDGFR inhibitor, imatinib significantly reduced the proliferation and migration of hPASMCs compared to either agent alone. Pre-clinical studies validated increased therapeutic efficacy of rapamycin combined with imatinib in attenuating PAH over either drug alone. Specifically, combination therapy further attenuated the development of monocrotaline (MCT)- or Hypoxia/Sugen-induced pulmonary hypertension (PH) in rats as demonstrated by further reductions in the Fulton index, right ventricular systolic pressure (RVSP), pulmonary vascular wall thickness and vessel muscularization, and decreased proliferating cell nuclear antigen (PCNA) staining in PASMCs.

Conclusion: Prolonged rapamycin treatment activates PDGFR signaling, in part, via mTORC2 inhibition. Combination therapy with rapamycin and imatinib may be a more effective strategy for the treatment of PAH.

Endothelial upregulation of mechanosensitive channel Piezo1 in pulmonary hypertension

Piezo is a mechanosensitive cation channel responsible for stretch-mediated Ca2+ and Na+ influx in multiple types of cells. Little is known about the functional role of Piezo1 in the lung vasculature and its potential pathogenic role in pulmonary arterial hypertension (PAH). Pulmonary arterial endothelial cells (PAECs) are constantly under mechanic stretch and shear stress that are sufficient to activate Piezo channels. Here, we report that Piezo1 is significantly upregulated in PAECs from patients with idiopathic PAH and animals with experimental pulmonary hypertension (PH) compared with normal controls. Membrane stretch by decreasing extracellular osmotic pressure or by cyclic stretch (18% CS) increases Ca2+-dependent phosphorylation (p) of AKT and ERK, and subsequently upregulates expression of Notch ligands, Jagged1/2 (Jag-1 and Jag-2), and Delta like-4 (DLL4) in PAECs. siRNA-mediated downregulation of Piezo1 significantly inhibited the stretch-mediated pAKT increase and Jag-1 upregulation, whereas downregulation of AKT by siRNA markedly attenuated the stretch-mediated Jag-1 upregulation in human PAECs. Furthermore, the mRNA and protein expression level of Piezo1 in the isolated pulmonary artery, which mainly contains pulmonary arterial smooth muscle cells (PASMCs), from animals with severe PH was also significantly higher than that from control animals. Intraperitoneal injection of a Piezo1 channel blocker, GsMTx4, ameliorated experimental PH in mice. Taken together, our study suggests that membrane stretch-mediated Ca2+ influx through Piezo1 is an important trigger for pAKT-mediated upregulation of Jag-1 in PAECs. Upregulation of the mechanosensitive channel Piezo1 and the resultant increase in the Notch ligands (Jag-1/2 and DLL4) in PAECs may play a critical pathogenic role in the development of pulmonary vascular remodeling in PAH and PH.

Xinmai 'an extract enhances the efficacy of sildenafil in the treatment of pulmonary arterial hypertension via inhibiting MAPK signalling pathway

CONTEXT

Xinmai 'an tablet has been used to improve myocardial blood supply. Recently, some compounds from its formula have shown that they can treat pulmonary arterial hypertension (PAH).

OBJECTIVE

This study investigates the effects of Xinmai 'an extract (XMA) on PAH and further tests the co-therapeutic enhancement with sildenafil (SIL).

MATERIALS AND METHODS

Pulmonary artery smooth muscle cells were subjected to stimulation with SIL (12.5 μM) and XMA (250 μg/mL) for 48 h. Sprague-Dawley rats were randomly grouped into eight groups (n = 8 per group): (I) control group received saline; (II) MCT group received MCT (60 mg/kg); (III) SIL-Low group received MCT + SIL at 10 mg/kg/day; (IV) SIL-high group received MCT + SIL at 30 mg/kg/day; (V) XMA-High group received MCT + XMA at 251.6 mg/kg/day; (VI) SIL (Low)+XMA (Low) group received SIL (10 mg/kg) + XMA at 62.9 mg/kg/day; (VII) SIL (Low)+XMA (Medium) group received SIL (10 mg/kg) + XMA at 125.8 mg/kg/day; (VIII) SIL (Low)+XMA (High) group received SIL (10 mg/kg) + XMA at 251.6 mg/kg/day. Both XMA and SIL were given by gavage and were maintained daily for 2 weeks.

RESULTS

XMA could improve SIL's efficacy in the treatment of PAH by decreasing cell viability more effectively at non-cytotoxic concentrations (250 μg/mL) and reducing Right Ventricular Systolic Pressure (RVSP) in PAH rat. Potential mechanisms might at least in part be through activating the MAPK signalling pathway.

DISCUSSION AND CONCLUSIONS

The combination of XMA and SIL can improve the efficacy of pulmonary hypertension and reduce the dosage of SIL.

Pulmonary Hypertension Associated with Connective Tissue Disease

Pulmonary hypertension (PH), a syndrome characterized by elevated pulmonary pressures, commonly complicates connective tissue disease (CTD) and is associated with increased morbidity and mortality. The incidence of PH varies widely between CTDs; patients with systemic sclerosis are most likely to develop PH. Several different types of PH can present in CTD, including PH related to left heart disease and respiratory disease. Importantly, CTD patients are at risk for developing pulmonary arterial hypertension, a rare form of PH that is associated with high morbidity and mortality. Future therapies targeting pulmonary vascular remodeling may improve outcomes for patients with this devastating disease.

Dapagliflozin has No Protective Effect on Experimental Pulmonary Arterial Hypertension and Pulmonary Trunk Banding Rat Models

Sodium-glucose cotransporter-2 (SGLT2) inhibitors, a novel class of hypoglycemic drugs, show excellent cardiovascular benefits, and have further improved heart failure outcomes, significantly reducing cardiovascular and all-cause mortality irrespective of diabetes status. However, the efficacy of SGLT2 inhibitors in pulmonary arterial hypertension (PAH) and right ventricular (RV) dysfunction remains unknown. This study aimed to evaluate the effects of dapagliflozin in rats with PAH and RV dysfunction. PAH was induced in rats by monocrotaline (MCT) subcutaneous injection (60 mg/kg). Isolated RV dysfunction was induced in another group of rats by pulmonary trunk banding (PTB). Dapagliflozin (1.5 mg/kg) was administered daily via oral gavage one day (prevention groups) or two weeks (reversal groups) after modeling. Echocardiography and hemodynamic assessments were used to observe pulmonary vascular resistance and RV function. Histological staining was used to observe pulmonary vascular and RV remodeling. As compared with MCT group, dapagliflozin treatment did not significantly improve the survival of rats. Pulmonary arterial media wall thickness in MCT group was significantly increased, but dapagliflozin did not significantly improved vascular remodeling both in the prevention group and reversal group. In MCT group, RV hypertrophy index, RV area, the fibrosis of RV increased significantly, and RV function decreased significantly. Consistently, dapagliflozin did not show protective effect on the RV remodeling and function. In the PTB model, we also did not find the direct effect of dapagliflozin on the RV. This is a negative therapeutic experiment, suggesting human trials with dapagliflozin for PAH or RV failure should be cautious.

The Role of Regulatory T Cells in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a chronic, incurable condition characterized by pulmonary vascular remodeling, perivascular inflammation, and right heart failure. Regulatory T cells (Tregs) stave off autoimmunity, and there is increasing evidence for their compromised activity in the inflammatory milieu of PAH. Abnormal Treg function is strongly correlated with a predisposition to PAH in animals and patients. Athymic Treg-depleted rats treated with SU5416, an agent causing pulmonary vascular injury, develop PAH, which is prevented by infusing missing CD4+CD25highFOXP3+ Tregs. Abnormal Treg activity may also explain why PAH disproportionately affects women more than men. This mini review focuses on the role of Tregs in PAH with a special view to sexual dimorphism and the future promise of Treg therapy.

Inhibition of the prolyl isomerase Pin1 improves endothelial function and attenuates vascular remodelling in pulmonary hypertension by inhibiting TGF-β signalling

Pulmonary arterial hypertension (PAH) is a devastating disease, characterized by obstructive pulmonary vascular remodelling ultimately leading to right ventricular (RV) failure and death. Disturbed transforming growth factor-β (TGF-β)/bone morphogenetic protein (BMP) signalling, endothelial cell dysfunction, increased proliferation of smooth muscle cells and fibroblasts, and inflammation contribute to this abnormal remodelling. Peptidyl-prolyl isomerase Pin1 has been identified as a critical driver of proliferation and inflammation in vascular cells, but its role in the disturbed TGF-β/BMP signalling, endothelial cell dysfunction, and vascular remodelling in PAH is unknown. Here, we report that Pin1 expression is increased in cultured pulmonary microvascular endothelial cells (MVECs) and lung tissue of PAH patients. Pin1 inhibitor, juglone significantly decreased TGF-β signalling, increased BMP signalling, normalized their hyper-proliferative, and inflammatory phenotype. Juglone treatment reversed vascular remodelling through reducing TGF-β signalling in monocrotaline + shunt-PAH rat model. Juglone treatment decreased Fulton index, but did not affect or harm cardiac function and remodelling in rats with RV pressure load induced by pulmonary artery banding. Our study demonstrates that inhibition of Pin1 reversed the PAH phenotype in PAH MVECs in vitro and in PAH rats in vivo, potentially through modulation of TGF-β/BMP signalling pathways. Selective inhibition of Pin1 could be a novel therapeutic option for the treatment of PAH.

DUSP5-mediated inhibition of smooth muscle cell proliferation suppresses pulmonary hypertension and right ventricular hypertrophy

Pulmonary hypertension (PH) is associated with structural remodeling of pulmonary arteries (PAs) because of excessive proliferation of fibroblasts, endothelial cells, and smooth muscle cells (SMCs). The peptide hormone angiotensin II (ANG II) contributes to pulmonary vascular remodeling, in part, through its ability to trigger extracellular signal-regulated kinase (ERK1/2) activation. Here, we demonstrate that the ERK1/2 phosphatase, dual-specificity phosphatase 5 (DUSP5), functions as a negative regulator of ANG II-mediated SMC proliferation and PH. In contrast to wild-type controls, Dusp5 null mice infused with ANG II developed PH and right ventricular (RV) hypertrophy. PH in Dusp5 null mice was associated with thickening of the medial layer of small PAs, suggesting an in vivo role for DUSP5 as a negative regulator of ANG II-dependent SMC proliferation. Consistent with this, overexpression of DUSP5 blocked ANG II-mediated proliferation of cultured human pulmonary artery SMCs (hPASMCs) derived from patients with idiopathic PH or from failed donor controls. Collectively, the data support a role for DUSP5 as a feedback inhibitor of ANG II-mediated ERK signaling and PASMC proliferation and suggest that disruption of this circuit leads to adverse cardiopulmonary remodeling.NEW & NOTEWORTHY Dual-specificity phosphatases (DUSPs) serve critical roles in the regulation of mitogen-activated protein kinases, but their functions in the cardiovascular system remain poorly defined. Here, we provide evidence that DUSP5, which resides in the nucleus and specifically dephosphorylates extracellular signal-regulated kinase (ERK1/2), blocks pulmonary vascular smooth muscle cell proliferation. In response to angiotensin II infusion, mice lacking DUSP5 develop pulmonary hypertension and right ventricular cardiac hypertrophy. These findings illustrate DUSP5-mediated suppression of ERK signaling in the lungs as a protective mechanism.

NAADP-induced intracellular calcium ion is mediated by the TPCs (two-pore channels) in hypoxia-induced pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a form of obstructive vascular disease. Chronic hypoxic exposure leads to excessive proliferation of pulmonary arterial smooth muscle cells and pulmonary arterial endothelial cells. This condition can potentially be aggravated by [Ca²⁺] _i mobilization. In the present study, hypoxia exposure of rat's model was established. Two‐pore segment channels (TPCs) silencing was achieved in rats' models by injecting Lsh‐TPC1 or Lsh‐TPC2. The effects of TPC1/2 silencing on PAH were evaluated by H&E staining detecting pulmonary artery wall thickness and ELISA assay kit detecting NAADP concentrations in lung tissues. TPC1/2 silencing was achieved in PASMCs and PAECs, and cell proliferation was detected by MTT and BrdU incorporation assays. As the results shown, NAADP‐activated [Ca²⁺]_i shows to be mediated via two‐pore segment channels (TPCs) in PASMCs, with TPC1 being the dominant subtype. NAADP generation and TPC1/2 mRNA and protein levels were elevated in the hypoxia‐induced rat PAH model; NAADP was positively correlated with TPC1 and TPC2 expression, respectively. In vivo, Lsh‐TPC1 or Lsh‐TPC2 infection significantly improved the mean pulmonary artery pressure and PAH morphology. In vitro, TPC1 silencing inhibited NAADP‐AM‐induced PASMC proliferation and [Ca²⁺]_i in PASMCs, whereas TPC2 silencing had minor effects during this process; TPC2 silencing attenuated NAADP‐AM‐ induced [Ca²⁺]_i and ECM in endothelial cells, whereas TPC1 silencing barely ensued any physiological changes. In conclusion, TPC1/2 might provide a unifying mechanism within pulmonary arterial hypertension, which can potentially be regarded as a therapeutic target.

Lung Pericytes in Pulmonary Vascular Physiology and Pathophysiology

Pericytes are mesenchymal-derived mural cells localized within the basement membrane of pulmonary and systemic capillaries. Besides structural support, pericytes control vascular tone, produce extracellular matrix components, and cytokines responsible for promoting vascular homeostasis and angiogenesis. However, pericytes can also contribute to vascular pathology through the production of pro-inflammatory and pro-fibrotic cytokines, differentiation into myofibroblast-like cells, destruction of the extracellular matrix, and dissociation from the vessel wall. In the lung, pericytes are responsible for maintaining the integrity of the alveolar-capillary membrane and coordinating vascular repair in response to injury. Loss of pericyte communication with alveolar capillaries and a switch to a pro-inflammatory/pro-fibrotic phenotype are common features of lung disorders associated with vascular remodeling, inflammation, and fibrosis. In this article, we will address how to differentiate pericytes from other cells, discuss the molecular mechanisms that regulate the interactions of pericytes and endothelial cells in the pulmonary circulation, and the experimental tools currently used to study pericyte biology both in vivo and in vitro. We will also discuss evidence that links pericytes to the pathogenesis of clinically relevant lung disorders such as pulmonary hypertension, idiopathic lung fibrosis, sepsis, and SARS-COVID. Future studies dissecting the complex interactions of pericytes with other pulmonary cell populations will likely reveal critical insights into the origin of pulmonary diseases and offer opportunities to develop novel therapeutics to treat patients afflicted with these devastating disorders. © 2021 American Physiological Society. Compr Physiol 11:2227-2247, 2021.

Osthole improves pulmonary artery hypertension by inducing apoptosis in pulmonary artery smooth muscle cells

OBJECTIVES

The objectives of this study were to explore the effect of Osthole (Ost) on apoptosis in pulmonary artery smooth muscle cells (PASMCs) and investigate the potential mechanism of this effect.

METHODS

Rats were injected subcutaneously with monocrotaline (MCT) to establish a PAH model, and Ost were intragastrically administrated from day 1 to day 35. After 35 days administration, the mean pulmonary artery pressure and lung weight index were measured. HE and TUNEL staining were used to observe the morphology of pulmonary artery and the apoptosis of PASMCs. In addition, the apoptosis of PASMCs were detected by flow cytometry in cultured PASMCs. The proteins of Bax and Bcl-2, and the levels of p-ASK1 and cleaved caspase 3 were measured by Western blot.

KEY FINDINGS

Ost decreased the mean pulmonary artery pressure and lung weight index in MCT-induced rats, and promoted apoptosis in PASMCs in MCT-induced rats and PDGF-BB stimulated PASMCs. Ost increased the ratio of Bax/Bcl-2 and the levels of p-ASK1, cleaved caspase 3 in MCT-induced rats and PDGF-BB stimulated PASMCs.

CONCLUSION

Ost promoted apoptosis in PASMCs in vivo and in vitro, and the mechanism may be associated with upregulation of ASK1 and the Bax/Bcl-2-caspase 3 signalling pathway.

Inhibition of the Proliferation of Human Lung Fibroblasts by Prostacyclin Receptor Agonists is Linked to a Sustained cAMP Signal in the Nucleus

Idiopathic pulmonary fibrosis is a chronic and progressive fibrotic lung disease, and current treatments are limited by their side effects. Proliferation of human lung fibroblasts in the pulmonary interstitial tissue is a hallmark of this disease and is driven by prolonged ERK signalling in the nucleus in response to growth factors such as platelet-derived growth factor (PDGF). Agents that increase cAMP have been suggested as alternative therapies, as this second messenger can inhibit the ERK cascade. We previously examined a panel of eight Gα_s-cAMP-coupled G protein-coupled receptors (GPCRs) endogenously expressed in human lung fibroblasts. Although the cAMP response was important for the anti-fibrotic effects of GPCR agonists, the magnitude of the acute cAMP response was not predictive of anti-fibrotic efficacy. Here we examined the reason for this apparent disconnect by stimulating the Gα_s-coupled prostacyclin receptor and measuring downstream signalling at a sub-cellular level. MRE-269 and treprostinil caused sustained cAMP signalling in the nucleus and complete inhibition of PDGF-induced nuclear ERK and fibroblast proliferation. In contrast, iloprost caused a transient increase in nuclear cAMP, there was no effect of iloprost on PDGF-induced ERK in the nucleus, and this agonist was much less effective at reversing PDGF-induced proliferation. This suggests that sustained elevation of cAMP in the nucleus is necessary for efficient inhibition of PDGF-induced nuclear ERK and fibroblast proliferation. This is an important first step towards understanding of the signalling events that drive GPCR inhibition of fibrosis.

Glutaminolysis: A Driver of Vascular and Cardiac Remodeling in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a decimating ailment described by chronic precapillary pulmonary hypertension, an elevated mean pulmonary arterial pressure with a normal pulmonary capillary wedge pressure, and a raised pulmonary vascular resistance resulting in increased right ventricular afterload culminating in heart failure and death. Current PAH treatments regulate the vasodilatory/vasoconstrictory balance of pulmonary vessels. However, these treatment options are unable to stop the progression of, or reverse, an already established disease. Recent studies have advanced a metabolic dysregulation, featuring increased glutamine metabolism, as a mechanism driving PAH progression. Metabolic dysregulation in PAH leads to increased glutaminolysis to produce substrate to meet the high-energy requirement by hyperproliferative and apoptosis-resistant pulmonary vascular cells. This article explores the role of glutamate metabolism in PAH and how it could be targeted as an anti-remodeling therapeutic strategy.

Resistin-Like Molecule α Dysregulates Cardiac Bioenergetics in Neonatal Rat Cardiomyocytes

Heart (right) failure is the most frequent cause of death in patients with pulmonary arterial hypertension. Although historically, increased right ventricular afterload has been considered the main contributor to right heart failure in such patients, recent evidence has suggested a potential role of load-independent factors. Here, we tested the hypothesis that resistin-like molecule α (RELMα), which has been implicated in the pathogenesis of vascular remodeling in pulmonary artery hypertension, also contributes to cardiac metabolic remodeling, leading to heart failure. Recombinant RELMα (rRELMα) was generated via a Tet-On expression system in the T-REx 293 cell line. Cultured neonatal rat cardiomyocytes were treated with purified rRELMα for 24 h at a dose of 50 nM. Treated cardiomyocytes exhibited decreased mRNA and protein expression of peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α) and transcription factors PPARα and ERRα, which regulate mitochondrial fatty acid metabolism, whereas genes that encode for glycolysis-related proteins were significantly upregulated. Cardiomyocytes treated with rRELMα also exhibited a decreased basal respiration, maximal respiration, spare respiratory capacity, ATP-linked OCR, and increased glycolysis, as assessed with a microplate-based cellular respirometry apparatus. Transmission electron microscopy revealed abnormal mitochondrial ultrastructure in cardiomyocytes treated with rRELMα. Our data indicate that RELMα affects cardiac energy metabolism and mitochondrial structure, biogenesis, and function by downregulating the expression of the PGC-1α/PPARα/ERRα axis.