Cellular and molecular basis of pulmonary arterial hypertension

SP1/ADAM10/DRP1 axis links intercellular communication between smooth muscle cells and endothelial cells under hypoxia pulmonary hypertension

BACKGROUND

Crosstalk between endothelial cells (ECs) and smooth muscle cells (SMCs) contributes to the progression of hypoxia pulmonary hypertension (HPH).

OBJECTIVE

In this study, we investigated whether the SP1/ADAM10/DRP1 and ADAM10-PI3K-AKT-mTOR axis mediate the crosstalk between ECs and SMCs.

METHODS AND RESULTS

The expression of ADAM10 increased in hypoxia-treated rats and ECs. Furthermore, the knockdown of ADAM10 alleviated HPH in rats and the malignant phenotype of hypoxia ECs. ADAM10 expression upregulated in the conditioned medium of hypoxia ECs. Conditioned medium was separated and added to the SMC culture system. Adding SMCs to a conditioned medium containing hypoxia-induced ECs promoted proliferation and decreased the apoptosis of SMCs. When SMCs were treated with a conditioned medium from ECs in which ADAM10 expression was knocked down, we found that the effects of the conditioned medium on the proliferation and apoptosis of SMCs were reduced. The protein levels of DRP1, PI3K, AKT, and mTOR decreased in SMCs treated with a conditioned medium of ECs in which ADAM10 was knocked down. After overexpressing ADAM10 in ECs, the medium was collected and added into the SMC culture system containing Mdivi-1 (DRP1 inhibitor) or LY294002 (PI3K inhibitor), and the SMCs showed reduced proliferation and increased apoptosis. SP1 was predicted based on the promoter regions of ADAM10 using the JASPAR database. The downregulation of SP1 decreases ADAM10 expression.

CONCLUSION

SP1 increases the secretion and levels of ADAM10 in hypoxia ECs. ADAM10 released by ECs regulates the hypoxia-induced malignant phenotype of SMCs via the DRP1 and PI3K/AKT/mTOR signaling pathways.

ASH2L Deficiency in Smooth Muscle Drives Pulmonary Vascular Remodeling

BACKGROUND

Histone H3 lysine 4 methylation is one of the most abundant epigenetic modifications, which has been recently linked to vascular remodeling in pulmonary hypertension (PH). SET1/MLL methyltransferase complexes comprise the main enzymes responsible for methylating H3 lysine 4, yet their roles in vascular remodeling and PH are not fully understood. We aim to assess the contribution of ASH2L, a core SET1/MLL family member, to the pathogenesis of PH.

METHODS

Human pulmonary artery specimens and primary vascular cells, smooth muscle cell (SMC)-specific ASH2L-deficient mice, rats with SMC-specific ASH2L overexpression, mass spectrometry, immunoprecipitation, and chromatin immunoprecipitation were used to define the role of ASH2L in PH.

RESULTS

Analysis of bulk RNA-sequencing data sets from human lung vessels identified ASH2L as the only differentially expressed SET1/MLL family member in PH compared with healthy controls. Decreased ASH2L expression in human pulmonary arteries correlated with the clinical severity of PH, which contrasted with elevated H3 lysine 4 methylation and was primarily localized to SMCs. Depletion of ASH2L promoted whereas its restoration ameliorated SMC proliferation and vascular remodeling in PH. Mechanistically, we revealed that ASH2L functioned independently of the canonical H3 lysine 4 trimethylation-based transcriptional activation, while it formed a protein complex with KLF5 and FBXW7, thereby accelerating the ubiquitin-proteasomal degradation of KLF5. NOTCH3 was discovered as a new downstream target of KLF5, and the loss of ASH2L promoted the recruitment of KLF5 to the NOTCH3 promoter, thus enhancing NOTCH3 expression. Pharmacological blockage of KLF5 attenuated PH in chronic hypoxia-exposed SMC-specific ASH2L-deficient mice and sugen/hypoxia-challenged rats.

CONCLUSIONS

This study demonstrated that ASH2L deficiency causatively affects SMC proliferation and lung vascular remodeling that is partially mediated through KLF5-dependent NOTCH3 transcription. Activating ASH2L or targeting KLF5 might represent potential therapeutic strategies for PH.

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.

Exercise improves systemic metabolism in a monocrotaline model of pulmonary hypertension

Exercise training in pulmonary arterial hypertension (PAH) has been gaining popularity with guidelines now recommending it as an important adjunct to medical therapy. Despite improvements in function and quality of life, an understanding of metabolic changes and their mechanisms remain unexplored. The objective of this study was therefore to understand the metabolic basis of exercise in a monocrotaline model of PAH. 24 male Wistar rats (age: 8-12 weeks and mean body weight: [262.16 ​± ​24.49] gms) were assigned to one of the four groups (i.e., Control, PAH, Exercise and PAH ​+ ​Exercise). The exercise groups participated in treadmill running at 13.3 ​m/min, five days a week for five weeks. Demographic and clinical characteristics were monitored regularly. Following the intervention, LC-MS based metabolomics were performed on blood samples from all groups at the end of five weeks. Metabolite profiling, peak identification, alignment and isotope annotation were also performed. Statistical inference was carried out using dimensionality reducing techniques and analysis of variance. Partial-least-squares discrimination analysis and variable importance in the projection scores showed that the model was reliable, and not over lifting. The analysis demonstrated significant perturbations to lipid and amino acid metabolism, arginine and homocysteine pathways, sphingolipid (p ​< ​0.05), glycerophospholipid (p ​< ​0.05) and nucleotide metabolism in PAH. Exercise, however, was seen to restore arginine (p ​< ​0.05) and homocysteine(p ​< ​0.000 1) levels which were independent effects, irrespective of PAH. Dysregulated arginine and homocysteine pathways are seen in PAH. Exercise restores these dysregulated pathways and could potentially impact severity and outcome in PAH.

GATA2 participates in protection against hypoxia-induced pulmonary vascular remodeling

The vascular endothelium is vital for cardio-pulmonary homeostasis and, thus, plays a crucial role in preventing life-threatening lung diseases. The transcription factor GATA2 is essential for hematopoiesis and maintaining vascular integrity. Heterozygous mutations in GATA2 can lead to a primary immunodeficiency syndrome with pulmonary manifestations. Some GATA2 haploinsufficient patients develop pulmonary hypertension (PH), characterized by vascular remodeling and occlusion of small pulmonary arteries. However, the mechanism underlying pulmonary vascular remodeling in GATA2 haploinsufficient patients remain unclear. To understand how GATA2 deficiency affects pulmonary artery homeostasis, we applied a chronic hypoxia-mediated PH model using inducible systemic Gata2 conditionally deficient (G2-CKO) mice. The G2-CKO mice exhibited augmented pulmonary vascular remodeling, with enhanced α-smooth muscle actin accumulation and increased apoptotic cells in the vascular wall upon chronic hypoxia. Transcript analysis and chromatin immunoprecipitation assays using mouse pulmonary vascular endothelial cells revealed that GATA2 directly regulates the expression of G6pdx (a crucial cytoprotective enzyme) and Bmp4 (a growth factor that mediates vascular homeostasis). These results suggest that GATA2-deficient lungs are vulnerable to the hypoxic stress due to a diminished cellular protective response, making G2-CKO mice more prone to vascular remodeling upon chronic hypoxia. These findings provide insights into the mechanisms underlying GATA2-haploinsufficiency-related pulmonary hypertension.

Structural and functional determination of peptide versus small molecule ligand binding at the apelin receptor

We describe a structural and functional study of the G protein-coupled apelin receptor, which binds two endogenous peptide ligands, apelin and Elabela/Toddler (ELA), to regulate cardiovascular development and function. Characterisation of naturally occurring apelin receptor variants from the UK Genomics England 100,000 Genomes Project, and AlphaFold2 modelling, identifies T892.64 as important in the ELA binding site, and R1684.64 as forming extensive interactions with the C-termini of both peptides. Base editing to introduce an R/H1684.64 variant into human stem cell-derived cardiomyocytes demonstrates that this residue is critical for receptor binding and function. Additionally, we present an apelin receptor crystal structure bound to the G protein-biased, small molecule agonist, CMF-019, which reveals a deeper binding mode versus the endogenous peptides at lipophilic pockets between transmembrane helices associated with GPCR activation. Overall, the data provide proof-of-principle for using genetic variation to identify key sites regulating receptor-ligand engagement.

Cathepsin L Promotes Pulmonary Hypertension via BMPR2/GSDME-Mediated Pyroptosis

BACKGROUND

Pulmonary hypertension (PH) is a fatal progressive disease characterized by pulmonary endothelial injury and occlusive pulmonary vascular remodeling. Lysosomal protease cathepsin L degrades essential molecules to participate in the human pathophysiological process. BMPR2 (bone morphogenetic protein type II receptor) deficiency, an important cause of PH, results from mutational inactivation or excessive lysosomal degradation and induces caspase-3-mediated cell death. Given recent evidence that pyroptosis, as a new form of programmed cell death, is induced by caspase-3-dependent GSDME (gasdermin E) cleavage, we hypothesized that cathepsin L might promote PH through BMPR2/caspase-3/GSDME axis-mediated pyroptosis.

METHODS

Cathepsin L expression was evaluated in the lungs and plasma of patients with pulmonary arterial hypertension. The role of cathepsin L in the progression of PH and vascular remodeling was assessed in vivo. Small interfering RNA, specific inhibitors, and lentiviruses were used to explore the mechanisms of cathepsin L on human pulmonary arterial endothelial cell dysfunction.

RESULTS

Cathepsin L expression is elevated in pulmonary artery endothelium from patients with idiopathic pulmonary arterial hypertension and experimental PH models. Genetic ablation of cathepsin L in PH rats relieved right ventricular systolic pressure, pulmonary vascular remodeling, and right ventricular hypertrophy, also restoring endothelial integrity. Mechanistically, cathepsin L promotes caspase-3/GSDME-mediated endothelial cell pyroptosis and represses BMPR2 signaling activity. Cathepsin L degrades BMPR2 via the lysosomal pathway, and restoring BMPR2 signaling prevents the pro-pyroptotic role of cathepsin L in PAECs and experimental PH models.

CONCLUSIONS

These results show for the first time that cathepsin L promotes the development of PH by degrading BMPR2 to induce caspase-3/GSDME-mediated endothelial pyroptosis.

LncRNA MYOSLID contributes to PH via targeting BMPR2 signaling in pulmonary artery smooth muscle cell

BACKGROUND/OBJECTIVE

The pathogenesis and vascular remodeling during pulmonary hypertension (PH) have been associated with dysregulation of bone morphogenetic protein receptor type 2 (BMPR2) and transforming growth factor-β (TGF-β) signaling in pulmonary artery smooth muscle cells (PASMCs). Evidence suggests that the human-specific lncRNA MYOSLID is a transcriptional target of the TGF-β/SMAD pathway. In this study, we investigated the involvement of MYOSLID in the pathogenesis of PH.

METHODS

Lung tissues from PH patients and rat PH models were analyzed to assess clinical relevance. RNA-Seq was performed to identify target genes. Pulmonary artery smooth muscle cells (PASMCs) were used to evaluate function and underlying mechanisms.

RESULTS

RNA-Seq analysis of PASMCs stimulated by TGF-β1 revealed significantly dysregulated lncRNAs. MYOSLID expression was markedly elevated in lung tissues from PH patients and in PASMCs stimulated with TGF-β1. Mechanistically, loss of MYOSLID inhibited the TGF-β pathway by reducing SMAD2/3 PHosphorylation and activated the BMPR2 pathway by enhancing SMAD1/5/9 phosphorylation and increasing ID genes expression in PASMCs. DAZAP2, a target gene of MYOSLID, functions as an inhibitor of BMPR2 signaling. Moreover, DAZAP2 expression was significantly elevated in lung tissues from PH patients and rat PH models. Functionally, knockdown of MYOSLID and DAZAP2 reduced proliferation, migration, and apoptosis resistance in PASMCs.

CONCLUSION

The activation of the MYOSLID-DAZAP2-BMPR2 axis contributes to pulmonary vascular remodeling, and targeting MYOSLID and DAZAP2 may represent novel therapeutic strategies for PH treatment.

Pulmonary arterial hypertension: Navigating the pathways of progress in diagnosis, treatment, and patient care

Pulmonary arterial hypertension (PAH) is a form of precapillary pulmonary hypertension caused by a complex process of endothelial dysfunction and vascular remodeling. If left untreated, this progressive disease presents with symptoms of incapacitating fatigue causing marked loss of quality of life, eventually culminating in right ventricular failure and death. Patient management is complex and based on accurate diagnosis, risk stratification, and treatment initiation, with close monitoring of response and disease progression. Understanding the underlying pathophysiology has enabled the development of multiple drugs directed at different targets in the pathological chain. Vasodilator therapy has been the mainstay approach for the last few years, significantly improving quality of life, functional status, and survival. Recent advances in therapies targeting dysfunctional pathways beyond endothelial dysfunction may address the fundamental processes underlying the disease, raising the prospect of increasingly effective options for this high-risk group of patients with a historically poor prognosis.

Panorama of artery endothelial cell dysfunction in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a fatal lung disease characterized by progressive pulmonary vascular remodeling. The initial cause of pulmonary vascular remodeling is the dysfunction of pulmonary arterial endothelial cells (PAECs), manifested by changes in the categorization of cell subtypes, endothelial programmed cell death, such as apoptosis, necroptosis, pyroptosis, ferroptosis, et al., overproliferation, senescence, metabolic reprogramming, endothelial-to-mesenchymal transition, mechanosensitivity, and regulation ability of peripheral cells. Therefore, it is essential to explore the mechanism of endothelial dysfunction in the context of PAH. This review aims to provide a comprehensive understanding of the molecular mechanisms underlying endothelial dysfunction in PAH. We highlight the developmental process of PAECs and changes in PAH and summarise the latest classification of endothelial dysfunction. Our review could offer valuable insights into potential novel EC-specific targets for preventing and treating PAH.

Super-Enhancer-Driven Syndecan-4 Regulates Intercellular Communication in Hypoxic Pulmonary Hypertension

BACKGROUND

Unveiling pro-proliferation genes involved in crosstalk between pulmonary artery endothelial cells and pulmonary artery smooth muscle cells (PASMCs) are important to improving the therapeutic outcome of pulmonary hypertension (PH). Although growing studies have shown that super-enhancers (SEs) play a pivotal role in pathological and physiological processes, the SE-associated genes in PH and their impact on PASMC proliferation remain largely unexplored.

METHODS AND RESULTS

We used serotype 5 adenovirus-associated virus to interfere with syndecan-4 and constructed an SU5416 combined with hypoxia-PH model. Chromatin immunoprecipitation sequencing analysis, chromatin immunoprecipitation quantitative polymerase chain reaction, and bioinformatics were used to confirm early growth response 1 was involved in regulating syndecan-4-associated SE in PASMCs. The effects of syndecan-4 and its underlying mechanisms were subsequently elucidated using Western blot, coimmunoprecipitation, and cell coculture assays. Herein, we identified a novel SE-associated gene, syndecan-4, in hypoxia-exposed PASMCs. Syndecan-4 was transcriptionally driven by early growth response 1 via an SE and was significantly overexpressed in hypoxic PASMCs and plasma from patients with PH. Mechanism studies revealed that syndecan-4 induces PASMC proliferation by interacting and regulating protein kinase C α ubiquitination. In addition, syndecan-4 was enriched in exosomes secreted from hypoxic PASMCs, which subsequently transported and led to pulmonary artery endothelial cell dysfunction. Syndecan-4 inhibition in hypoxia by serotype 5 adenovirus-associated virus treatment attenuated the pulmonary artery remodeling and development of PH in vivo.

CONCLUSIONS

Taken together, our results demonstrate that an SE-driven syndecan-4 modulates crosstalk of PASMCs and pulmonary artery endothelial cells and promotes vascular remodeling via the protein kinase C α and exosome pathway, thus providing potential targets for the early diagnosis and treatment of hypoxic PH.

Mechanistic investigation of wogonin in delaying the progression of endothelial mesenchymal transition by targeting the TGF-β1 pathway in pulmonary hypertension

Pulmonary hypertension (PH) is characterized by pulmonary vascular remodeling, which endothelial-to-mesenchymal transition (EndMT) being its main progressive phase. Wogonin, a flavonoid extracted from the root of Scutellaria baicalensis Georgi, hinders the abnormal proliferation of cells and has been employed in the treatment of several cardiopulmonary diseases. This study was designed to investigate how wogonin affected EndMT during PH. Monocrotaline (MCT) was used to induce PH in rats. Binding capacity of TGF-β1 receptor to wogonin detected by molecular docking and molecular dynamics. EndMT model was established in pulmonary microvascular endothelial cells (PMVECs) by transforming growth factor beta-1 (TGF-β1). The result demonstrated that wogonin (20 mg/kg/day) attenuated right ventricular systolic pressure (RVSP), right ventricular hypertrophy and pulmonary vascular thickness in PH rats. EndMT in the pulmonary vascular was inhibited after wogonin treatment as evidenced by the restored expression of CD31 and decreased expression of α-SMA. Wogonin has strong affinity for both TGFBRI and TGFBRII, and has a better binding stability for TGFBRI. In TGF-β1-treated PMVECs, wogonin (0.3, 1, and 3 μM) exhibited significant inhibitory effects on this transformation process via down-regulating the expression of p-Smad2 and Snail, while up-regulating the expression of p-Smad1/5. Additionally, results of Western blot and fluorescence shown that the expression of α-SMA were decrease with increasing level of CD31 in PMVECs. In conclusion, our research showed that wogonin suppressed EndMT via the TGF-β1/Smad pathway which may lead to its alleviated effect on PH. Wogonin may be a promising drug against PH.

Unraveling the Complex Relationship-Atrial Fibrillation and Pulmonary Hypertension

PURPOSE OF REVIEW

In this article, we underscore the importance of identifying risk factors and monitoring pulmonary hypertension patients for signs of arrhythmias, as this proactive approach can reduce morbidity and mortality.

RECENT FINDINGS

Atrial fibrillation is the most prevalent among cardiac arrhythmias and is associated with an increased risk of stroke, morbidity, and mortality. Smoking, obesity, hypertension, a sedentary lifestyle, and diabetes mellitus are some of the modifiable risk factors for atrial fibrillation. Recent studies show that the risk of atrial fibrillation is rising in patients with parenchymal and vascular lung disease. Stretching in the atria and pulmonary veins may lead to the onset of atrial fibrillation in cardiac conditions like hypertension, heart failure, and valvular disease. Atrial fibrillation in patients with pulmonary hypertension (PH) denotes a more advanced disease. Patients with PH are more susceptible to hemodynamic stress caused by tachycardia and an uncoordinated atrioventricular contraction. Therefore, atrial arrhythmias need to be treated because inadequate control of cardiac arrhythmias may result in poor clinical outcomes and lead to disease progression in PH patients. Aside from being a sign of severe disease, AF can also speed up and exacerbate the condition.

Ginsenoside Rg1 alleviates vascular remodeling in hypoxia-induced pulmonary hypertension mice through the calpain-1/STAT3 signaling pathway

Background

Hypoxic pulmonary hypertension (HPH) is the main pathological change in vascular remodeling, a complex cardiopulmonary disease caused by hypoxia. Some research results have shown that ginsenoside Rg1 (Rg1) can improve vascular remodeling, but the effect and mechanism of Rg1 on hypoxia-induced pulmonary hypertension are not clear. The purpose of this study was to discuss the potential mechanism of action of Rg1 on HPH.

Methods

C57BL/6 mice, calpain-1 knockout mice and Pulmonary artery smooth muscle cells (PASMCs) were exposed to a low oxygen environment with or without different treatments. The effect of Rg1 and calpain-1 silencing on inflammation, fibrosis, proliferation and the protein expression levels of calpain-1, STAT3 and p-STAT3 were determined at the animal and cellular levels.

Results

At the mouse and cellular levels, hypoxia promotes inflammation, fibrosis, and cell proliferation, and the expression of calpain-1 and p-STAT3 is also increased. Ginsenoside Rg1 administration and calpain-1 knockdown, MDL-28170, and HY-13818 treatment showed protective effects on hypoxia-induced inflammation, fibrosis, and cell proliferation, which may be associated with the downregulation of calpain-1 and p-STAT3 expression in mice and cells. In addition, overexpression of calpain 1 increased p-STAT3 expression, accelerating the onset of inflammation, fibrosis and cell proliferation in hypoxic PASMCs.

Conclusion

Ginsenoside Rg1 may ameliorate hypoxia-induced pulmonary vascular remodeling by suppressing the calpain-1/STAT3 signaling pathway.

Corosolic acid attenuates platelet-derived growth factor signaling in macrophages and smooth muscle cells of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive and life-threatening disease that is characterized by vascular remodeling of the pulmonary artery. Pulmonary vascular remodeling is primarily caused by the excessive proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs), which are facilitated by perivascular inflammatory cells including macrophages. Corosolic acid (CRA) is a natural pentacyclic triterpenoid that exerts anti-inflammatory effects. In the present study, the effects of CRA on the viability of macrophages were examined using monocrotaline (MCT)-induced PAH rats and human monocyte-derived macrophages. Although we previously reported that CRA inhibited signal transducer and activator of transcription 3 (STAT3) signaling and ameliorated pulmonary vascular remodeling in PAH, the inhibitory mechanism remains unclear. Therefore, the underlying mechanisms were investigated using PASMCs from idiopathic PAH (IPAH) patients. In MCT-PAH rats, CRA inhibited the accumulation of macrophages around remodeled pulmonary arteries. CRA reduced the viability of human monocyte-derived macrophages. In IPAH-PASMCs, CRA attenuated cell proliferation and migration facilitated by platelet-derived growth factor (PDGF)-BB released from macrophages and PASMCs. CRA also downregulated the expression of PDGF receptor β and its signaling pathways, STAT3 and nuclear factor-κB (NF-κB). In addition, CRA attenuated the phosphorylation of PDGF receptor β and STAT3 following the PDGF-BB simulation. The expression and phosphorylation levels of PDGF receptor β after the PDGF-BB stimulation were reduced by the small interfering RNA knockdown of NF-κB, but not STAT3, in IPAH-PASMCs. In conclusion, CRA attenuated the PDGF-PDGF receptor β-STAT3 and PDGF-PDGF receptor β-NF-κB signaling axis in macrophages and PASMCs, and thus, ameliorated pulmonary vascular remodeling in PAH.

HMGB2 Release Promotes Pulmonary Hypertension and Predicts Severity and Mortality of Patients With Pulmonary Arterial Hypertension

BACKGROUND

Pulmonary hypertension (PH) is a progressive and life-threatening disease characterized by pulmonary vascular remodeling, which involves aberrant proliferation and apoptosis resistance of the pulmonary arterial smooth muscle cells (PASMCs), resembling the hallmark characteristics of cancer. In cancer, the HMGB2 (high-mobility group box 2) protein promotes the pro-proliferative/antiapoptotic phenotype. However, the function of HMGB2 in PH remains uninvestigated.

METHODS

Smooth muscle cell (SMC)-specific HMGB2 knockout or HMGB2-OE (HMGB2 overexpression) mice and HMGB2 silenced rats were used to establish hypoxia+Su5416 (HySu)-induced PH mouse and monocrotaline-induced PH rat models, respectively. The effects of HMGB2 and its underlying mechanisms were subsequently elucidated using RNA-sequencing and cellular and molecular biology analyses. Serum HMGB2 levels were measured in the controls and patients with pulmonary arterial (PA) hypertension.

RESULTS

HMGB2 expression was markedly increased in the PAs of patients with PA hypertension and PH rodent models and was predominantly localized in PASMCs. SMC-specific HMGB2 deficiency or silencing attenuated PH development and pulmonary vascular remodeling in hypoxia+Su5416-induced mice and monocrotaline-treated rats. SMC-specific HMGB2 overexpression aggravated hypoxia+Su5416-induced PH. HMGB2 knockdown inhibited PASMC proliferation in vitro in response to PDGF-BB (platelet-derived growth factor-BB). In contrast, HMGB2 protein stimulation caused the hyperproliferation of PASMCs. In addition, HMGB2 promoted PASMC proliferation and the development of PH by RAGE (receptor for advanced glycation end products)/FAK (focal adhesion kinase)-mediated Hippo/YAP (yes-associated protein) signaling suppression. Serum HMGB2 levels were significantly increased in patients with PA hypertension, and they correlated with disease severity, predicting worse survival.

CONCLUSIONS

Our findings indicate that targeting HMGB2 might be a novel therapeutic strategy for treating PH. Serum HMGB2 levels could serve as a novel biomarker for diagnosing PA hypertension and determining its prognosis.

The Intersection of HIV and Pulmonary Vascular Health: From HIV Evolution to Vascular Cell Types to Disease Mechanisms

People living with HIV (PLWH) face a growing burden of chronic diseases, owing to the combinations of aging, environmental triggers, lifestyle choices, and virus-induced chronic inflammation. The rising incidence of pulmonary vascular diseases represents a major concern for PLWH. The study of HIV-associated pulmonary vascular complications ideally requires a strong understanding of pulmonary vascular cell biology and HIV pathogenesis at the molecular level for effective applications in infectious diseases and vascular medicine. Active HIV infection and/or HIV proteins disturb the delicate balance between vascular tone and constriction, which is pivotal for maintaining pulmonary vascular health. One of the defining features of HIV is its high genetic diversity owing to several factors including its high mutation rate, recombination between viral strains, immune selective pressures, or even geographical factors. The intrinsic HIV genetic diversity has several important implications for pathogenic outcomes of infection and the overall battle to combat HIV. Challenges in the field present themselves from two sides of the same coin: those imposed by the virus itself and those stemming from the host. The field may be advanced by further developing in vivo and in vitro models that are well described for both pulmonary vascular diseases and HIV for mechanistic studies. In essence, the study of HIV-associated pulmonary vascular complications requires a multidisciplinary approach, drawing upon insights from both infectious diseases and vascular medicine. In this review article, we discuss the fundamentals of HIV virology and their impact on pulmonary disease, aiming to enhance the understanding of either area or both simultaneously. Bridging the gap between preclinical research findings and clinical practice is essential for improving patient care. Addressing these knowledge gaps requires interdisciplinary collaborations, innovative research approaches, and dedicated efforts to prioritize HIV-related pulmonary complications on the global research agenda.

RNA m6A methylation and regulatory proteins in pulmonary arterial hypertension

m6A (N6‑methyladenosine) is the most common and abundant apparent modification in mRNA of eukaryotes. The modification of m6A is regulated dynamically and reversibly by methyltransferase (writer), demethylase (eraser), and binding protein (reader). It plays a significant role in various processes of mRNA metabolism, including regulation of transcription, maturation, translation, degradation, and stability. Pulmonary arterial hypertension (PAH) is a malignant cardiopulmonary vascular disease characterized by abnormal proliferation of pulmonary artery smooth muscle cells. Despite the existence of several effective and targeted therapies, there is currently no cure for PAH and the prognosis remains poor. Recent studies have highlighted the crucial role of m6A modification in cardiovascular diseases. Investigating the role of RNA m6A methylation in PAH could provide valuable insights for drug development. This review aims to explore the mechanism and function of m6A in the pathogenesis of PAH and discuss the potential targeting of RNA m6A methylation modification as a treatment for PAH.

The role of transcription factors in the pathogenesis and therapeutic targeting of vascular diseases

Transcription factors (TFs) constitute an essential component of epigenetic regulation. They contribute to the progression of vascular diseases by regulating epigenetic gene expression in several vascular diseases. Recently, numerous regulatory mechanisms related to vascular pathology, ranging from general TFs that are continuously activated to histiocyte-specific TFs that are activated under specific circumstances, have been studied. TFs participate in the progression of vascular-related diseases by epigenetically regulating vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs). The Krüppel-like family (KLF) TF family is widely recognized as the foremost regulator of vascular diseases. KLF11 prevents aneurysm progression by inhibiting the apoptosis of VSMCs and enhancing their contractile function. The presence of KLF4, another crucial member, suppresses the progression of atherosclerosis (AS) and pulmonary hypertension by attenuating the formation of VSMCs-derived foam cells, ameliorating endothelial dysfunction, and inducing vasodilatory effects. However, the mechanism underlying the regulation of the progression of vascular-related diseases by TFs has remained elusive. The present study categorized the TFs involved in vascular diseases and their regulatory mechanisms to shed light on the potential pathogenesis of vascular diseases, and provide novel insights into their diagnosis and treatment.

Lactylation Modification in Cardiometabolic Disorders: Function and Mechanism

Cardiovascular disease (CVD) is recognized as the primary cause of mortality and morbidity on a global scale, and developing a clear treatment is an important tool for improving it. Cardiometabolic disorder (CMD) is a syndrome resulting from the combination of cardiovascular, endocrine, pro-thrombotic, and inflammatory health hazards. Due to their complex pathological mechanisms, there is a lack of effective diagnostic and treatment methods for cardiac metabolic disorders. Lactylation is a type of post-translational modification (PTM) that plays a regulatory role in various cellular physiological processes by inducing changes in the spatial conformation of proteins. Numerous studies have reported that lactylation modification plays a crucial role in post-translational modifications and is closely related to cardiac metabolic diseases. This article discusses the molecular biology of lactylation modifications and outlines the roles and mechanisms of lactylation modifications in cardiometabolic disorders, offering valuable insights for the diagnosis and treatment of such conditions.

The biased apelin receptor agonist, MM07, reverses Sugen/hypoxia-induced pulmonary arterial hypertension as effectively as the endothelin antagonist macitentan

Introduction: Pulmonary arterial hypertension (PAH) is characterised by endothelial dysfunction and pathological vascular remodelling, resulting in the occlusion of pulmonary arteries and arterioles, right ventricular hypertrophy, and eventually fatal heart failure. Targeting the apelin receptor with the novel, G protein-biased peptide agonist, MM07, is hypothesised to reverse the developed symptoms of elevated right ventricular systolic pressure and right ventricular hypertrophy. Here, the effects of MM07 were compared with the clinical standard-of-care endothelin receptor antagonist macitentan. Methods: Male Sprague-Dawley rats were randomised and treated with either normoxia/saline, or Sugen/hypoxia (SuHx) to induce an established model of PAH, before subsequent treatment with either saline, macitentan (30 mg/kg), or MM07 (10 mg/kg). Rats were then anaesthetised and catheterised for haemodynamic measurements, and tissues collected for histopathological assessment. Results: The SuHx/saline group presented with significant increases in right ventricular hypertrophy, right ventricular systolic pressure, and muscularization of pulmonary arteries compared to normoxic/saline controls. Critically, MM07 was as at least as effective as macitentan in significantly reversing detrimental structural and haemodynamic changes after 4 weeks of treatment. Discussion: These results support the development of G protein-biased apelin receptor agonists with improved pharmacokinetic profiles for use in human disease.

Targeting cellular senescence: A promising approach in respiratory diseases

Cellular senescence serves as a significant tumor suppression mechanism in mammals. Cellular senescence is induced in response to various stressors and acts as a safeguard against the uncontrolled proliferation of damaged cells that could lead to malignant transformation. Senescent cells also exhibit a distinctive feature known as the senescence-associated secretory phenotype (SASP), wherein they secrete a range of bioactive molecules, including pro-inflammatory cytokines, growth factors, and proteases. These SASP components have both local and systemic effects, influencing the surrounding microenvironment and distant tissues, and have been implicated in the processes of tissue aging and the development of chronic diseases. Recent studies utilizing senolysis models have shed light on the potential therapeutic implications of targeting senescent cells. The targeting of senescent cell may alleviate the detrimental effects associated with cellular senescence and its SASP components. Senolytics have shown promise in preclinical studies for treating age-related pathologies and chronic diseases, including cancer, cardiovascular disorders, and neurodegenerative conditions. Respiratory diseases have emerged as a significant global health concern, responsible for a considerable number of deaths worldwide. Extensive research conducted in both human subjects and animal models has demonstrated the involvement of cellular senescence in the pathogenesis of respiratory diseases. Chronic pulmonary conditions such as chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis have been linked to the accumulation of senescent cells. This review aims to present the findings from research on respiratory diseases that have utilized systems targeting senescent cells and to identify potential therapeutic strategies for the clinical management of these conditions. Geriatr Gerontol Int 2024; 24: 60-66.

The effect of peroxisome proliferator-activated receptor gamma (PPARγ) as a mediator of dietary fatty acids and thiazolidinedione in pulmonary arterial hypertension induced by cold stress of broilers

The objective of this experiment was to evaluate the effects of dietary fish oil and pioglitazone as peroxisome proliferators-activated receptor gamma (PPARγ) activating ligands on the reduction of cold-induced ascites in broiler chickens. A total of 480 one-day-old (Ross 308) male chicks were randomly allocated to four treatment groups with eight replicates of 15 birds each. The following treatments were used: 1) ambient temperature (negative control), with basal diet; 2) cold-induced ascites (positive control), with basal diet; 3) cold-induced ascites, with basal diet +10 mg/kg/day pioglitazone and 4) cold-induced ascites, with basal diet +1% of fish oil. When compared with the positive control, body weight gain was higher (P ≤ 0.05) for broilers fed diets containing fish oil and pioglitazone at 28, 42, and 0-42 d. Broilers under cold-induced ascites had the highest blood pressure at 21 and 42 d, while fish oil and pioglitazone treatment reduced the blood pressure (P ≤ 0.05). Red blood cells, white blood cells, hematocrit, erythrocyte osmotic fragility, bursa of Fabricius and spleen weights were improved (P ≤ 0.05) for chickens fed fish oil diets and pioglitazone compared to the cold-induced ascites (positive control). Exposure to cold temperature resulted in an increase in plasma T3 and T3/T4 ratio and decline in plasma T4 (P ≤ 0.05). In conclusion, PPARγ agonist pioglitazone and fish oil as source of omega-3 polyunsaturated fatty acid could be used as a strategy to reduce the negative effects of pulmonary arterial hypertension and ascites in broiler chickens.

Calcium sensing receptor: A promising therapeutic target in pulmonary hypertension

Pulmonary hypertension (PH) is characterized by elevation of pulmonary arterial pressure and pulmonary vascular resistance. The increased pulmonary arterial pressure and pulmonary vascular resistance due to sustained pulmonary vasoconstriction and pulmonary vascular remodeling can lead to right heart failure and eventual death. A rise in intracellular Ca2+ concentration ([Ca2+]i) and enhanced pulmonary arterial smooth muscle cells (PASMCs) proliferation contribute to pulmonary vasoconstriction and pulmonary vascular remodeling. Recent studies demonstrated that extracellular calcium sensing receptor (CaSR) as a G-protein coupled receptor participates in [Ca2+]i increase induced by hypoxia in the experimental animals of PH and in PH patients. Pharmacological blockade or gene knockout of CaSR significantly attenuates the development of PH. This review will aim to discuss and update the pathogenicity of CaSR attributed to onset and progression in PH.

FAK mediates hypoxia-induced pulmonary artery smooth muscle cell proliferation by modulating mitochondrial transcription termination factor 1/cyclin D1

This study aimed to investigate the mechanism of FAK-dependent hypoxia-induced proliferation on human pulmonary artery smooth muscle cells (HPASMCs). Primary HPASMCs were isolated and cultured in vitro under normal and hypoxia conditions to assess cell proliferation with cell counting kit-8. FAK and mitochondrial transcription termination factor 1 (mTERF1) were silenced with siRNA, mRNA, and protein levels of FAK, mTERF1, and cyclin D1 were determined. HPASMC proliferation increased under hypoxia compared to normal conditions. Knocking down FAK or mTERF1 with siRNA led to decreased cell proliferation under both normal and hypoxia conditions. FAK knockdown led to the reduction of both mTERF1 and cyclin D1 expressions under the hypoxia conditions, whereas mTERF1 knockdown led to the downregulation of cyclin D1 expression but not FAK expression under the same condition. However, under normal conditions, knocking down either FAK or mTERF1 had no impact on cyclin D1 expression. These results suggested that FAK may regulate the mTERF1/cyclin D1 signaling pathway to modulate cell proliferation in hypoxia.

Atorvastatin rescues pulmonary artery hypertension by inhibiting the AKT/ERK-dependent PDGF-BB/HIF-1α axis

BACKGROUND

The aim of this study is to explore the role of atorvastatin in rescuing pulmonary artery hypertension (PAH) by inhibiting the AKT/ERK-dependent PDGF-BB/HIF-1α axis.

METHODS

PAH model in rats was established by MCT induction, followed by Atorvastatin intervention. Pulmonary hemodynamic measurement and pulmonary morphological evaluation in rats were conducted. Human pulmonary artery smooth muscle cells (hPASMCs) were subjected to hypoxic exposure or PDGF-BB treatment, followed by atorvastatin induction. Relative levels of HIF-1α, p-ERK and p-Akt were detected. Viability and apoptosis were respectively determined by cell counting kit-8 (CCK-8) assay and flow cytometry.

RESULTS

Atorvastatin protected PAH-induced increases in RVSP and Fulton's index in rats. Meanwhile, it inhibited vascular remodeling following PAH by downregulating HIF-1α and PDGF-BB. Hypoxia or PDGF-BB treatment in hPASMCs resulted in upregulation of p-ERK and p-Akt, and viability increase, which were partially abolished by Atorvastatin intervention. In addition, atorvastatin triggered apoptosis in hypoxia or PDGF-BB-induced hPASMCs.

CONCLUSIONS

Atorvastatin inhibits the activation of HIF-1α and proliferative ability, and triggers apoptosis in hPASMCs exposed to hypoxia or PDGF-BB treatment through inactivating the AKT/ERK pathway.

Reversal of Pulmonary Hypertension in a Human-Like Model: Therapeutic Targeting of Endothelial DHFR

BACKGROUND

Pulmonary hypertension (PH) is a progressive disorder characterized by remodeling of the pulmonary vasculature and elevated mean pulmonary arterial pressure, resulting in right heart failure.

METHODS

Here, we show that direct targeting of the endothelium to uncouple eNOS (endothelial nitric oxide synthase) with DAHP (2,4-diamino 6-hydroxypyrimidine; an inhibitor of GTP cyclohydrolase 1, the rate-limiting synthetic enzyme for the critical eNOS cofactor tetrahydrobiopterin) induces human-like, time-dependent progression of PH phenotypes in mice.

RESULTS

Critical phenotypic features include progressive elevation in mean pulmonary arterial pressure, right ventricular systolic blood pressure, and right ventricle (RV)/left ventricle plus septum (LV+S) weight ratio; extensive vascular remodeling of pulmonary arterioles with increased medial thickness/perivascular collagen deposition and increased expression of PCNA (proliferative cell nuclear antigen) and alpha-actin; markedly increased total and mitochondrial superoxide production, substantially reduced tetrahydrobiopterin and nitric oxide bioavailabilities; and formation of an array of human-like vascular lesions. Intriguingly, novel in-house generated endothelial-specific dihydrofolate reductase (DHFR) transgenic mice (tg-EC-DHFR) were completely protected from the pathophysiological and molecular features of PH upon DAHP treatment or hypoxia exposure. Furthermore, DHFR overexpression with a pCMV-DHFR plasmid transfection in mice after initiation of DAHP treatment completely reversed PH phenotypes. DHFR knockout mice spontaneously developed PH at baseline and had no additional deterioration in response to hypoxia, indicating an intrinsic role of DHFR deficiency in causing PH. RNA-sequencing experiments indicated great similarity in gene regulation profiles between the DAHP model and human patients with PH.

CONCLUSIONS

Taken together, these results establish a novel human-like murine model of PH that has long been lacking in the field, which can be broadly used for future mechanistic and translational studies. These data also indicate that targeting endothelial DHFR deficiency represents a novel and robust therapeutic strategy for the treatment of PH.

Up-regulated expression of two-pore domain K+ channels, KCNK1 and KCNK2, is involved in the proliferation and migration of pulmonary arterial smooth muscle cells in pulmonary arterial hypertension

Background

Pulmonary arterial hypertension (PAH) is a severe and rare disease in the cardiopulmonary system. Its pathogenesis involves vascular remodeling of the pulmonary artery, which results in progressive increases in pulmonary arterial pressure. Chronically increased pulmonary arterial pressure causes right ventricular hypertrophy and subsequent right heart failure. Pulmonary vascular remodeling is attributed to the excessive proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs), which are induced by enhanced Ca2+ signaling following the up-/down-regulation of ion channel expression.

Objectives

In the present study, the functional expression of two-pore domain potassium KCNK channels was investigated in PASMCs from idiopathic PAH (IPAH) patients and experimental pulmonary hypertensive (PH) animals.

Results

In IPAH-PASMCs, the expression of KCNK1/TWIK1 and KCNK2/TREK1 channels was up-regulated, whereas that of KCNK3/TASK1 and KCNK6/TWIK2 channels was down-regulated. The similar up-regulated expression of KCNK1 and KCNK2 channels was observed in the pulmonary arterial smooth muscles of monocrotaline-induced PH rats, Sugen 5416/hypoxia-induced PH rats, and hypoxia-induced PH mice. The facilitated proliferation of IPAH-PASMCs was suppressed by the KCNK channel blockers, quinine and tetrapentylammonium. The migration of IPAH-PASMCs was also suppressed by these channel blockers. Furthermore, increases in the proliferation and migration were inhibited by the siRNA knockdown of KCNK1 or KCNK2 channels. The siRNA knockdown also caused membrane depolarization and subsequent decrease in cytosolic [Ca2+]. The phosphorylated level of c-Jun N-terminal kinase (JNK) was elevated in IPAH-PASMCs compared to normal-PASMCs. The increased phosphorylation was significantly reduced by the siRNA knockdown of KCNK1 or KCNK2 channels.

Conclusion

Collectively, these findings indicate that the up-regulated expression of KCNK1 and KCNK2 channels facilitates the proliferation and migration of PASMCs via enhanced Ca2+ signaling and JNK signaling pathway, which is associated with vascular remodeling in PAH.

Role of Exercise in Pulmonary Hypertension: Evidence from Bench to Bedside

Background

Pulmonary hypertension (PH) is a debilitating condition characterized by elevated pulmonary arterial pressure and progressive vascular remodelling, leading to exercise intolerance. The progression of PAH is regulated at a cellular and molecular level which influences various physiological processes. Exercise plays an important role in improving function in PH. Although the signalling pathways that regulate cardio-protection through exercise have not been fully understood, the positive impact of exercise on the various physiological systems is well established.

Summary

Exercise has emerged as a potential adjunctive therapy for PH, with growing evidence supporting its beneficial effects on various aspects of the disease pathophysiology. This review highlights the contributions of cellular and molecular pathways and physiological processes to exercise intolerance. Preclinical studies have provided insight into the mechanisms underlying exercise-induced improvements in PH which are modulated through improvements in endothelial function, inflammation, oxidative stress, and mitochondrial function. Along with preclinical studies, various clinical studies have demonstrated that exercise training can lead to significant improvements in exercise capacity, haemodynamics, quality of life, and functional status. Moreover, exercise interventions have been shown to improve skeletal muscle function and enhance pulmonary vascular remodelling, contributing to overall disease management. Further research efforts aimed at better understanding the role of exercise in PH pathophysiology, and refining exercise interventions are warranted to realize its full potential in the management of this complex disease.

Key Messages

Despite the promising benefits of exercise in PH, several challenges remain, including the optimal intensity, duration, and type of exercise training, as well as patient selection criteria and long-term adherence. Additionally, the mechanisms underlying the observed improvements require further elucidation to optimize exercise protocols and personalize treatment strategies. Nonetheless, exercise represents a promising therapeutic approach that can complement existing pharmacological therapies and improve outcomes in PH patients.

HTNpedia: A Knowledge Base for Hypertension Research

BACKGROUND

Hypertension is notably a serious public health concern due to its high prevalence and strong association with cardiovascular disease and renal failure. It is reported to be the fourth leading disease that leads to death worldwide.

OBJECTIVES

Currently, there is no active operational knowledge base or database for hypertension or cardiovascular illness.

METHODS

The primary data source was retrieved from the research outputs obtained from our laboratory team working on hypertension research. We have presented a preliminary dataset and external links to the public repository for detailed analysis to readers.

RESULTS

As a result, HTNpedia was created to provide information regarding hypertension-related proteins and genes.

CONCLUSION

The complete webpage is accessible via www.mkarthikeyan.bioinfoau.org/HTNpedia.

Global and endothelial G-protein coupled receptor 75 (GPR75) knockout relaxes pulmonary artery and mitigates hypoxia-induced pulmonary hypertension

RATIONALE

Pulmonary hypertension (PH) is a multifactorial disease with a poor prognosis and inadequate treatment options. We found two-fold higher expression of the orphan G-Protein Coupled Receptor 75 (GPR75) in leukocytes and pulmonary arterial smooth muscle cells from idiopathic PH patients and from lungs of C57BL/6 mice exposed to hypoxia. We therefore postulated that GPR75 signaling is critical to the pathogenesis of PH.

METHODS

To test this hypothesis, we exposed global (Gpr75-/-) and endothelial cell (EC) GPR75 knockout (EC-Gpr75-/-) mice and wild-type (control) mice to hypoxia (10% oxygen) or normal atmospheric oxygen for 5 weeks. We then recorded echocardiograms and performed right heart catheterizations.

RESULTS

Chronic hypoxia increased right ventricular systolic and diastolic pressures in wild-type mice but not Gpr75-/- or EC-Gpr75-/- mice. In situ hybridization and qPCR results revealed that Gpr75 expression was increased in the alveoli, airways and pulmonary arteries of mice exposed to hypoxia. In addition, levels of chemokine (CC motif) ligand 5 (CCL5), a low affinity ligand of GPR75, were increased in the lungs of wild-type, but not Gpr75-/-, mice exposed to hypoxia, and CCL5 enhanced hypoxia-induced contraction of intra-lobar pulmonary arteries in a GPR75-dependent manner. Gpr75 knockout also increased pulmonary cAMP levels and decreased contraction of intra-lobar pulmonary arteries evoked by endothelin-1 or U46619 in cAMP-protein kinase A-dependent manner.

CONCLUSION

These results suggest GPR75 has a significant role in the development of hypoxia-induced PH.

The Emerging Therapeutic Role of Prostaglandin E2 Signaling in Pulmonary Hypertension

Mild-to-moderate pulmonary hypertension (PH) is a common complication of chronic obstructive pulmonary disease (COPD). It is characterized by narrowing and thickening of the pulmonary arteries, resulting in increased pulmonary vascular resistance (PVR) and ultimately leading to right ventricular dysfunction. Pulmonary vascular remodeling in COPD is the main reason for the increase of pulmonary artery pressure (PAP). The pathogenesis of PH in COPD is complex and multifactorial, involving chronic inflammation, hypoxia, and oxidative stress. To date, prostacyclin and its analogues are widely used to prevent PH progression in clinical. These drugs have potent anti-proliferative, anti-inflammatory, and stimulating endothelial regeneration properties, bringing therapeutic benefits to the slowing, stabilization, and even some reversal of vascular remodeling. As another well-known and extensively researched prostaglandins, prostaglandin E2 (PGE2) and its downstream signaling have been found to play an important role in various biological processes. Emerging evidence has revealed that PGE2 and its receptors (i.e., EP1-4) are involved in the regulation of pulmonary vascular homeostasis and remodeling. This review focuses on the research progress of the PGE2 signaling pathway in PH and discusses the possibility of treating PH based on the PGE2 signaling pathway.

Therapeutic potential of apelin and Elabela in cardiovascular disease

Apelin and Elabela (Ela) are peptides encoded by APLN and APELA, respectively, which act on their receptor APJ and play crucial roles in the body. Recent research has shown that they not only have important effects on the endocrine system, but also promote vascular development and maintain the homeostasis of myocardial cells. From a molecular biology perspective, we explored the roles of Ela and apelin in the cardiovascular system and summarized the mechanisms of apelin-APJ signaling in the progression of myocardial infarction, ischemia-reperfusion injury, atherosclerosis, pulmonary arterial hypertension, preeclampsia, and congenital heart disease. Evidences indicated that apelin and Ela play important roles in cardiovascular diseases, and there are many studies focused on developing apelin, Ela, and their analogues for clinical treatments. However, the literature on the therapeutic potential of apelin, Ela and their analogues and other APJ agonists in the cardiovascular system is still limited. This review summarized the regulatory pathways of apelin/ELA-APJ axis in cardiovascular function and cardiovascular-related diseases, and the therapeutic effects of their analogues in cardiovascular diseases were also included.

Peroxisome proliferator-activated receptor gamma (PPARγ) activation: a potential treatment for ascites syndrome in broiler chickens

Ascites (serous fluid accumulation in the abdominal cavity) has been observed worldwide in fast growing broilers. Pulmonary vascular remodeling is an important pathological feature of broiler ascites syndrome. Peroxisome proliferators-activated receptor gamma (PPARγ) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) are expressed in pulmonary vascular endothelial cells and vascular smooth muscle cells (VSMC) where they participate in the regulation of normal pulmonary vascular function. The objective of the present study was to investigate the effects of omega-3 fatty acids (found in fish oil) and pioglitazone (PIO) as natural and synthetic PPARγ ligands supplementation on PPARγ and PGC-1α expression in the prevention of pulmonary arterial hypertension (PAH) syndrome in broiler chickens. The experiment was conducted with 4 treatment groups: 1) negative control, normal temperature conditions with basal diet; 2) positive control, low-temperature conditions with basal diet; 3) positive control + 10 mg PIO/kg of weight/d and 4) positive control + 1% FO. Each treatment had 5 replicates. Ascites heart index (RV/TV) was significantly (P < 0.05) reduced in chickens receiving FO (0.20) and PIO (0.21) compared to the positive control group (0.26). The addition of PIO in broilers under cold-induced ascites significantly increased the expression of PPARγ (9.44) and PGC-1α (5.81) genes in lung tissue compared to the negative control group (1.03, P < 0.05). Proliferative indexes of VSMC in pulmonary arteries such as PMT, PIT, and percentage wall thickness were significantly elevated in positive control group, indicating that pulmonary vascular remodeling occurred following VSMC proliferation in ascites. The vessel internal diameter was increased in FO and PIO groups. Based on these results, activation and expression of PPARγ and PGC-1α genes as a critical regulator of pulmonary artery smooth muscle cell using ligands, especially PIO, can be effective in reducing the incidence of PAH in broiler chickens.

Case report: Progressive pulmonary artery hypertension in a case of megalencephaly-capillary malformation syndrome

Megalencephaly-capillary malformation syndrome (MCAP, OMIM # 602501) is caused by hyperactivity of the thephosphoinositide-3-kinase (PI3K)-Vakt murine thymoma viral oncogene homolog (AKT)-mammalian target of rapamycin (mTOR) pathway, which results in megalencephaly, capillary malformations, asymmetrical overgrowth, and connective tissue dysplasia. Herein, we report the case of a 7-month-old girl with MCAP due to a PIK3CA somatic mosaic variant who presented with atrial tachycardia, finally diagnosed as pulmonary arterial hypertension (PAH). Oxygen therapy and sildenafil decreased pulmonary blood pressure and improved atrial tachycardia. Previous studies reported an association between the PI3K/AKT/mTOR pathway and abnormal pulmonary arterial smooth muscle cell proliferation, which may be associated with PAH. PAH should be considered a potentially lethal complication in MCAP patients, even when no structural cardiac abnormalities are identified in the neonatal period.

Frequency of acute vasodilator response (AVR) in incident and prevalent patients with pulmonary arterial hypertension: Results from the pulmonary vascular disease phenomics study

The prevalence of acute vasodilator response (AVR) to inhaled nitric oxide (iNO) during right heart catheterization (RHC) is 12% in idiopathic pulmonary arterial hypertension (IPAH). AVR, however, is reportedly lower in other disease-associated pulmonary arterial hypertension (PAH), such as connective tissue disease (CTD). The prevalence of AVR in patients on PAH therapy (prevalent cases) is unknown. We sought to determine AVR prevalence in Group 1 PH in the PVDOMICS cohort of incident and prevalent patients undergoing RHC. AVR was measured in response to 100% O2 and O2 plus iNO, with positivity defined as (1) decrease in mean pulmonary artery pressure (mPAP) by ≥10 mmHg to a value ≤40 mmHg, with no change or an increase in cardiac output (definition 1); or (2) decrease in mPAP by ≥12% and pulmonary vascular resistance by ≥30% (definition 2). AVR rates and cumulative survival were compared between incident and prevalent patients. In 338 mainly prevalent (86%) patients, positive AVR to O2-only was <2%, and 5.1% to 16.9%, based on definition 1 and 2 criteria, respectively; following O2 + iNO. IPAH AVR prevalence (4.1%-18.7%) was similar to prior reports. AVR positivity was 7.7% to 15.4% in mostly CTD-PAH prevalent cases, and 2.6% to 11.8% in other PAH groups. Survival was 89% in AVR responders versus 77% in nonresponders from PAH diagnosis, and 91% versus 86% from PVDOMICS enrollment (log-rank test p = 0.04 and p = 0.05, respectively). In conclusion, AVR in IPAH patients is similar to prior studies. AVR in non-IPAH patients was higher than previously reported. The relationship between PAH therapy, AVR response, and survival warrants further investigation.

Pathophysiology and pathogenic mechanisms of pulmonary hypertension: role of membrane receptors, ion channels, and Ca2+ signaling

The pulmonary circulation is a low-resistance, low-pressure, and high-compliance system that allows the lungs to receive the entire cardiac output. Pulmonary arterial pressure is a function of cardiac output and pulmonary vascular resistance, and pulmonary vascular resistance is inversely proportional to the fourth power of the intraluminal radius of the pulmonary artery. Therefore, a very small decrease of the pulmonary vascular lumen diameter results in a significant increase in pulmonary vascular resistance and pulmonary arterial pressure. Pulmonary arterial hypertension is a fatal and progressive disease with poor prognosis. Regardless of the initial pathogenic triggers, sustained pulmonary vasoconstriction, concentric vascular remodeling, occlusive intimal lesions, in situ thrombosis, and vascular wall stiffening are the major and direct causes for elevated pulmonary vascular resistance in patients with pulmonary arterial hypertension and other forms of precapillary pulmonary hypertension. In this review, we aim to discuss the basic principles and physiological mechanisms involved in the regulation of lung vascular hemodynamics and pulmonary vascular function, the changes in the pulmonary vasculature that contribute to the increased vascular resistance and arterial pressure, and the pathogenic mechanisms involved in the development and progression of pulmonary hypertension. We focus on reviewing the pathogenic roles of membrane receptors, ion channels, and intracellular Ca2+ signaling in pulmonary vascular smooth muscle cells in the development and progression of pulmonary hypertension.

Cavin-2 loss exacerbates hypoxia-induced pulmonary hypertension with excessive eNOS phosphorylation and protein nitration

Pulmonary hypertension (PH) is associated with a poor prognosis even in recent years. Caveolin-1 (CAV1), a caveolae-associated protein, is a causal gene in PH. Cavin-2, one of the other caveolae-associated proteins, forms protein complexes with CAV1 and influences each other's functions. However, the role of Cavin-2 in PH has not been thoroughly investigated. To clarify the role of Cavin-2 in PH, we exposed Cavin-2-deficient (Cavin-2 KO) mice to hypoxia. A part of the analyses was confirmed in human pulmonary endothelial cells (HPAECs). After 4-week 10% O₂ hypoxic exposure, we performed physiological, histological, and immunoblotting analyses. Right ventricular (RV) systolic pressure elevation and RV hypertrophy were exacerbated in Cavin-2 KO mice with hypoxia-induced PH (Cavin-2 KO PH mice). The vascular wall thickness of pulmonary arterioles was aggravated in Cavin-2 KO PH mice. Cavin-2 loss reduced CAV1 and induced sustained endothelial nitric oxide synthase (eNOS) hyperphosphorylation in the Cavin-2 KO PH lungs and HPAECs. NOx production associated with eNOS phosphorylation was also increased in the Cavin-2 KO PH lung and HPAECs. Furthermore, the nitration of proteins, including protein kinase G (PKG), was raised in the Cavin-2 KO PH lungs. In conclusion, we revealed that Cavin-2 loss exacerbated hypoxia-induced PH. Our results suggest that Cavin-2 loss leads to sustained eNOS hyperphosphorylation in pulmonary artery endothelial cells via CAV1 reduction, resulting in Nox overproduction-mediated nitration of proteins, including PKG, in smooth muscle cells.

SOX17 is a Critical Factor in Maintaining Endothelial Function in Pulmonary Hypertension by an Exosome-Mediated Autocrine Manner

Endothelial dysfunction is considered a predominant driver for pulmonary vascular remodeling in pulmonary hypertension (PH). SOX17, a key regulator of vascular homoeostasis, has been found to harbor mutations in PH patients, which are associated with PH susceptibility. Here, this study explores whether SOX17 mediates the autocrine activity of pulmonary artery ECs to maintain endothelial function and vascular homeostasis in PH and its underlying mechanism. It is found that SOX17 expression is downregulated in the endothelium of remodeled pulmonary arteries in IPH patients and SU5416/hypoxia (Su/hypo)-induced PH mice as well as dysfunctional HPAECs. Endothelial knockdown of SOX17 accelerates the progression of Su/hypo-induced PH in mice. SOX17 overexpression in the pulmonary endothelium of mice attenuates Su/hypo-induced PH. SOX17-associated exosomes block the proliferation, apoptosis, and inflammation of HPAECs, preventing pulmonary arterial remodeling and Su/hypo-induced PH. Mechanistic analyses demonstrates that overexpressing SOX17 promotes the exosome-mediated release of miR-224-5p and miR-361-3p, which are internalized by injured HPAECs in an autocrine manner, ultimately repressing the upregulation of NR4A3 and PCSK9 genes and improving endothelial function. These results suggest that SOX17 is a key gene in maintaining endothelial function and vascular homeostasis in PH through regulating exosomal miRNAs in an autocrine manner.

GATA6 coordinates cross-talk between BMP10 and oxidative stress axis in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a life-threatening condition characterized by a progressive increase in pulmonary vascular resistance leading to right ventricular failure and often death. Here we report that deficiency of transcription factor GATA6 is a shared pathological feature of PA endothelial (PAEC) and smooth muscle cells (PASMC) in human PAH and experimental PH, which is responsible for maintenance of hyper-proliferative cellular phenotypes, pulmonary vascular remodeling and pulmonary hypertension. We further show that GATA6 acts as a transcription factor and direct positive regulator of anti-oxidant enzymes, and its deficiency in PAH/PH pulmonary vascular cells induces oxidative stress and mitochondrial dysfunction. We demonstrate that GATA6 is regulated by the BMP10/BMP receptors axis and its loss in PAECs and PASMC in PAH supports BMPR deficiency. In addition, we have established that GATA6-deficient PAEC, acting in a paracrine manner, increase proliferation and induce other pathological changes in PASMC, supporting the importance of GATA6 in pulmonary vascular cell communication. Treatment with dimethyl fumarate resolved oxidative stress and BMPR deficiency, reversed hemodynamic changes caused by endothelial Gata6 loss in mice, and inhibited proliferation and induced apoptosis in human PAH PASMC, strongly suggesting that targeting GATA6 deficiency may provide a therapeutic advance for patients with PAH.

Early Growth Response-1: Friend or Foe in the Heart?

Cardiovascular disease is a major cause of mortality and morbidity worldwide. Early growth response-1 (Egr-1) plays a critical regulatory role in a range of experimental models of cardiovascular diseases. Egr-1 is an immediate-early gene and is upregulated by various stimuli including shear stress, oxygen deprivation, oxidative stress and nutrient deprivation. However, recent research suggests a new, underexplored cardioprotective side of Egr-1. The main purpose of this review is to explore and summarise the dual nature of Egr-1 in cardiovascular pathobiology.

The emerging role of the piRNA/PIWI complex in respiratory tract diseases

PIWI-interacting RNA (piRNA) is a class of recently discovered small non-coding RNA molecules with a length of 18-33 nt that interacts with the PIWI protein to form the piRNA/PIWI complex. The PIWI family is a subfamily of Argonaute (AGO) proteins that also contain the AGO family which bind to microRNA (miRNA). Recently studies indicate that piRNAs are not specific to in the mammalian germline, they are also expressed in a tissue-specific manner in a variety of human tissues and participated in various of diseases, such as cardiovascular, neurological, and urinary tract diseases, and are especially prevalent in malignant tumors in these systems. However, the functions and abnormal expression of piRNAs in respiratory tract diseases and their underlying mechanisms remain incompletely understood. In this review, we discuss current studies summarizing the biogenetic processes, functions, and emerging roles of piRNAs in respiratory tract diseases, providing a reference value for future piRNA research.

Molecular Mechanisms and Therapeutic Implications of Endothelial Dysfunction in Patients with Heart Failure

Heart failure is a complex medical syndrome that is attributed to a number of risk factors; nevertheless, its clinical presentation is quite similar among the different etiologies. Heart failure displays a rapidly increasing prevalence due to the aging of the population and the success of medical treatment and devices. The pathophysiology of heart failure comprises several mechanisms, such as activation of neurohormonal systems, oxidative stress, dysfunctional calcium handling, impaired energy utilization, mitochondrial dysfunction, and inflammation, which are also implicated in the development of endothelial dysfunction. Heart failure with reduced ejection fraction is usually the result of myocardial loss, which progressively ends in myocardial remodeling. On the other hand, heart failure with preserved ejection fraction is common in patients with comorbidities such as diabetes mellitus, obesity, and hypertension, which trigger the creation of a micro-environment of chronic, ongoing inflammation. Interestingly, endothelial dysfunction of both peripheral vessels and coronary epicardial vessels and microcirculation is a common characteristic of both categories of heart failure and has been associated with worse cardiovascular outcomes. Indeed, exercise training and several heart failure drug categories display favorable effects against endothelial dysfunction apart from their established direct myocardial benefit.

Eliminating Senescent Cells Can Promote Pulmonary Hypertension Development and Progression

BACKGROUND

Senescent cells (SCs) are involved in proliferative disorders, but their role in pulmonary hypertension remains undefined. We investigated SCs in patients with pulmonary arterial hypertension and the role of SCs in animal pulmonary hypertension models.

METHODS

We investigated senescence (p16, p21) and DNA damage (γ-H2AX, 53BP1) markers in patients with pulmonary arterial hypertension and murine models. We monitored p16 activation by luminescence imaging in p16-luciferase (p16^LUC/+) knock-in mice. SC clearance was obtained by a suicide gene (p16 promoter-driven killer gene construct in p16-ATTAC mice), senolytic drugs (ABT263 and cell-permeable FOXO4-p53 interfering peptide [FOXO4-DRI]), and p16 inactivation in p16^LUC/LUC mice. We investigated pulmonary hypertension in mice exposed to normoxia, chronic hypoxia, or hypoxia+Sugen, mice overexpressing the serotonin transporter (SM22-5-HTT⁺), and rats given monocrotaline.

RESULTS

Patients with pulmonary arterial hypertension compared with controls exhibited high lung p16, p21, and γ-H2AX protein levels, with abundant vascular cells costained for p16, γ-H2AX, and 53BP1. Hypoxia increased thoracic bioluminescence in p16^LUC/+ mice. In wild-type mice, hypoxia increased lung levels of senescence and DNA-damage markers, senescence-associated secretory phenotype components, and p16 staining of pulmonary endothelial cells (P-ECs, 30% of lung SCs in normoxia), and pulmonary artery smooth muscle cells. SC elimination by suicide gene or ABT263 increased the right ventricular systolic pressure and hypertrophy index, increased vessel remodeling (higher dividing proliferating cell nuclear antigen-stained vascular cell counts during both normoxia and hypoxia), and markedly decreased lung P-ECs. Pulmonary hemodynamic alterations and lung P-EC loss occurred in older p16^LUC/LUC mice, wild-type mice exposed to Sugen or hypoxia+Sugen, and SM22-5-HTT⁺ mice given either ABT263 or FOXO4-DRI, compared with relevant controls. The severity of monocrotaline-induced pulmonary hypertension in rats was decreased slightly by ABT263 for 1 week but was aggravated at 3 weeks, with loss of P-ECs.

CONCLUSIONS

Elimination of senescent P-ECs by senolytic interventions may worsen pulmonary hemodynamics. These results invite consideration of the potential impact on pulmonary vessels of strategies aimed at controlling cell senescence in various contexts.

Mitochondrial Dysfunction in Pulmonary Hypertension

Pulmonary hypertension (PH) is a multi-etiological condition with a similar hemodynamic clinical sign and end result of right heart failure. Although its causes vary, a similar link across all the classifications is the presence of mitochondrial dysfunction. Mitochondria, as the powerhouse of the cells, hold a number of vital roles in maintaining normal cellular homeostasis, including the pulmonary vascular cells. As such, any disturbance in the normal functions of mitochondria could lead to major pathological consequences. The Warburg effect has been established as a major finding in PH conditions, but other mitochondria-related metabolic and oxidative stress factors have also been reported, making important contributions to the progression of pulmonary vascular remodeling that is commonly found in PH pathophysiology. In this review, we will discuss the role of the mitochondria in maintaining a normal vasculature, how it could be altered during pulmonary vascular remodeling, and the therapeutic options available that can treat its dysfunction.

Corosolic acid ameliorates vascular remodeling in pulmonary arterial hypertension via the downregulation of STAT3 signaling

Pulmonary arterial hypertension (PAH) is a progressive and fatal disease that is characterized by vascular remodeling of the pulmonary artery. PAH remodeling is primarily caused by the excessive proliferation of pulmonary arterial smooth muscle cells (PASMCs). Therefore, an inhibitory mechanism is expected as a target for the treatment of PAH. Corosolic acid (CRA) is a pentacyclic triterpenoid extracted from the leaves of Banaba (Lagerstroemia speciosa) that exerts anti-diabetic, anti-inflammatory, and anti-tumor effects. In the present study, the effects of CRA on PAH remodeling were examined using PASMCs from idiopathic pulmonary arterial hypertension (IPAH) patients and monocrotaline (MCT)-induced pulmonary hypertensive (PH) rats. CRA inhibited the excessive proliferation of IPAH-PASMCs in a concentration-dependent manner (IC₅₀ = 14.1 μM). It also reduced the migration of IPAH-PASMCs. The CRA treatment downregulated the expression of signal transducer and activator of transcription 3 (STAT3) in IPAH-PASMCs. In MCT-PH rats, the administration of CRA (1 mg/kg/day) attenuated increases in right ventricular systolic pressure, pulmonary vascular remodeling, and right ventricular hypertrophy. CRA also decreased the expression of STAT3 in pulmonary arterial smooth muscles from MCT-PH rats. In conclusion, the anti-proliferative and anti-migratory effects of CRA in PASMCs ameliorated PAH remodeling by downregulating STAT3 signaling pathways.

lncRNA-TCONS_00008552 expression in patients with pulmonary arterial hypertension due to congenital heart disease

Long noncoding RNAs (lncRNAs) are potential regulators of a variety of cardiovascular diseases. Therefore, there is a series of differentially expressed lncRNAs in pulmonary arterial hypertension (PAH) that may be used as markers to diagnose PAH and even predict the prognosis. However, their specific mechanisms remain largely unknown. Therefore, we investigated the biological role of lncRNAs in patients with PAH. First, we screened patients with PAH secondary to ventricular septal defect (VSD) and those with VSD without PAH to assess differences in lncRNA and mRNA expression between the two groups. Our results revealed the significant upregulation of 813 lncRNAs and 527 mRNAs and significant downregulation of 541 lncRNAs and 268 mRNAs in patients with PAH. Then, we identified 10 hub genes in a constructed protein-protein interaction network. Next, we performed bioinformatics analyses, including Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis and subsequently constructed coding-noncoding co-expression networks. We screened lncRNA-TCONS_00008552 and lncRNA-ENST00000433673 as candidate genes and verified the expression levels of the lncRNAs using quantitative reverse-transcription PCR. Although expression levels of lncRNA-TCONS_00008552 in the plasma from the PAH groups were significantly increased compared with the control groups, there was no significant difference in the expression of lncRNA-ENST00000433673 between the two groups. This study bolsters our understanding of the role of lncRNA in PAH occurrence and development and indicates that lncRNA-TCONS_00008552 is a novel potential molecular marker for PAH.

Expanding the apelin receptor pharmacological toolbox using novel fluorescent ligands

INTRODUCTION

The apelin receptor binds two distinct endogenous peptides, apelin and ELA, which act in an autocrine/paracrine manner to regulate the human cardiovascular system. As a class A GPCR, targeting the apelin receptor is an attractive therapeutic strategy. With improvements in imaging techniques, and the stability and brightness of dyes, fluorescent ligands are becoming increasingly useful in studying protein targets. Here, we describe the design and validation of four novel fluorescent ligands; two based on [Pyr1]apelin-13 (apelin488 and apelin647), and two based on ELA-14 (ELA488 and ELA647).

METHODS

Fluorescent ligands were pharmacologically assessed using radioligand and functional in vitro assays. Apelin647 was validated in high content imaging and internalisation studies, and in a clinically relevant human embryonic stem cell-derived cardiomyocyte model. Apelin488 and ELA488 were used to visualise apelin receptor binding in human renal tissue.

RESULTS

All four fluorescent ligands retained the ability to bind and activate the apelin receptor and, crucially, triggered receptor internalisation. In high content imaging studies, apelin647 bound specifically to CHO-K1 cells stably expressing apelin receptor, providing proof-of-principle for a platform that could screen novel hits targeting this GPCR. The ligand also bound specifically to endogenous apelin receptor in stem cell-derived cardiomyocytes. Apelin488 and ELA488 bound specifically to apelin receptor, localising to blood vessels and tubules of the renal cortex.

DISCUSSION

Our data indicate that the described novel fluorescent ligands expand the pharmacological toolbox for studying the apelin receptor across multiple platforms to facilitate drug discovery.

Promoting angiogenesis and diabetic wound healing through delivery of protein transduction domain-BMP2 formulated nanoparticles with hydrogel

Decreased angiogenesis contributes to delayed wound healing in diabetic patients. Recombinant human bone morphogenetic protein-2 (rhBMP2) has also been demonstrated to promote angiogenesis. However, the short half-lives of soluble growth factors, including rhBMP2, limit their use in wound-healing applications. To address this limitation, we propose a novel delivery model using a protein transduction domain (PTD) formulated in a lipid nanoparticle (LNP). We aimed to determine whether a gelatin hydrogel dressing loaded with LNP-formulated PTD-BMP2 (LNP-PTD-BMP2) could enhance the angiogenic function of BMP2 and improve diabetic wound healing. In vitro, compared to the control and rhBMP2, LNP-PTD-BMP2 induced greater tube formation in human umbilical vein endothelial cells and increased the cell recruitment capacity of HaCaT cells. We inflicted large, full-thickness back skin wounds on streptozotocin-induced diabetic mice and applied gelatin hydrogel (GH) cross-linked by microbial transglutaminase containing rhBMP2, LNP-PTD-BMP2, or a control to these wounds. Wounds treated with LNP-PTD-BMP2-loaded GH exhibited enhanced wound closure, increased re-epithelialization rates, and higher collagen deposition than those with other treatments. Moreover, LNP-PTD-BMP2-loaded GH treatment resulted in more CD31- and α-SMA-positive cells, indicating greater neovascularization capacity than rhBMP2-loaded GH or GH treatments alone. Furthermore, in vivo near-infrared fluorescence revealed that LNP-PTD-BMP2 has a longer half-life than rhBMP2 and that BMP2 localizes around wounds. In conclusion, LNP-PTD-BMP2-loaded GH is a viable treatment option for diabetic wounds.