Pulmonary Smooth Muscle Cells Research Articles

Impact of sodium-glucose cotransporter-2 inhibitors on pulmonary vascular cell function and arterial remodeling.

Sodium-glucose cotransporter-2 (SGLT-2) inhibitors represent a cutting-edge class of oral antidiabetic therapeutics that operate through selective inhibition of glucose reabsorption in proximal renal tubules, consequently augmenting urinary glucose excretion and attenuating blood glucose levels. Extensive clinical investigations have demonstrated their profound cardiovascular efficacy. Parallel basic science research has elucidated the mechanistic pathways through which diverse SGLT-2 inhibitors beneficially modulate pulmonary vascular cells and arterial remodeling. Specifically, these inhibitors exhibit promising potential in enhancing pulmonary vascular endothelial cell function, suppressing pulmonary smooth muscle cell proliferation and migration, reversing pulmonary arterial remodeling, and maintaining hemodynamic equilibrium. This comprehensive review synthesizes current literature to delineate the mechanisms by which SGLT-2 inhibitors enhance pulmonary vascular cell function and reverse pulmonary remodeling, thereby offering novel therapeutic perspectives for pulmonary vascular diseases.

Chronic hypoxia promotes pulmonary venous smooth muscle cell proliferation through the CaSR-TRPC6/ROCE pathway

The mechanism underlying chronic hypoxia (CH)-induced pulmonary venous remodeling remains unclear. Cell proliferation is key in vascular remodeling, and the calcium-sensing receptor (CaSR) protein contributes to CH-induced pulmonary venous smooth muscle cell (PVSMC) proliferation. In pulmonary arterial smooth muscle cells, CaSR and transient receptor potential canonical (TRPC) proteins interact, contributing to CH-induced cell proliferation via CaSR-TRPC1/6 signaling. We investigated whether a similar pathway exists in PVSMCs. Rat PVSMCs were isolated and subjected to CH. Cell proliferation was assessed by cell counting, CCK-8, and BrdU incorporation assays. Expression of CaSR and TRPC was analyzed by qPCR and western blotting, while interactions between CaSR and TRPC were detected by co-immunoprecipitation assay. Extracellular Ca2+ restoration was evaluated, to assess store- and receptor-operated Ca2+ entry (SOCE and ROCE, respectively). CH enhanced PVSMC numbers, viability, and DNA synthesis, and upregulated CaSR and TRPC6 expression. Further, CaSR and TRPC6 interacted with one another. CaSR inhibitors (NPS2143, NPS2390) reduced, whereas activators (spermine, R568) enhanced, CH-induced increases in PVSMC numbers, viability, DNA synthesis, and TRPC6 expression. CaSR knockdown using siRNA inhibited CH-induced TRPC6 upregulation and attenuated CH-induced increases in PVSMC numbers, viability, and DNA synthesis. TRPC6 knockdown had no significant effect on CH-induced CaSR upregulation, but significantly attenuated CH-induced increases in PVSMC number, viability, and DNA synthesis. CaSR knockdown reduced ROCE, but not SOCE, enhancement. Overall, CH promotes PVSMC proliferation through the CaSR-TRPC6/ROCE pathway.

Death-associated protein kinase 1 prevents hypoxia-induced metabolic shift and pulmonary arterial smooth muscle cell proliferation in PAH

Pulmonary hypertension (pH) is a general term used to describe high blood pressure in the lungs from any cause. Pulmonary arterial hypertension (PAH) is a progressive, and fatal disease that causes the walls of the pulmonary arteries to tighten and stiffen. One of the major characteristics of PAH is the hyperproliferation and resistance to apoptosis of vascular cells, which trigger excessive pulmonary vascular remodeling and vasoconstriction. The death-associated protein DAP-kinase (DAPK) is a tumor suppressor and Ser/Thr protein kinase, which was previously shown to regulate the hypoxia inducible factor (HIF)-1α. Against this background, we now show that DAPK1 regulates human pulmonary smooth muscle cell (hPASMC) proliferation and energy metabolism in a HIF-dependent manner. DAPK1 expression is downregulated in pulmonary vessels and PASMCs of human and experimental PH lungs. Reduced expression of DAPK1 in hypoxia and non-hypoxia PAH-PASMCs correlates with increased expression of HIF-1/2α. RNA interference-mediated depletion of DAPK1 leads to fundamental metabolic changes, including a significantly decreased rate of oxidative phosphorylation associated with enhanced expression of both HIF-1α and HIF-2α and glycolytic enzymes, as hexokinase 2 (HK2), lactate dehydrogenase A (LDHA), and an integrator between the glycolysis and citric acid cycle, pyruvate dehydrogenase kinase 1 (PDK1). DAPK1 ablation in healthy donor hPASMCs leads to an increase in proliferation, while its overexpression provides the opposite effects. Together our data indicate that DAPK1 serves as a new inhibitor of the pro-proliferative and glycolytic phenotype of PH in PASMCs acting via HIF-signaling pathway.

Perspectives on Sotatercept in Pulmonary Arterial Hypertension.

Sotatercept acts as a type IIA-Fc activin receptor, thereby scavenging free activin from its physiological membrane receptor. Through this type of action, sotaterpect leads to a rebalancing of the proliferation and antiproliferation pathways of pulmonary smooth muscle cells in response to bone morphogenic protein (BMP). Although sotatercept has been approved as the fourth pillar of therapy for group 1 pulmonary arterial hypertension (PAH) in the United States and Europe, several studies are ongoing to broaden the application of the drug to non-Group 1 PAH. We provide an overview of the clinical and preclinical evidence of targeting the activation pathway by sotatercept in the treatment of PAH. We also discuss other potential applications of sotatercept in the context of pulmonary hypertension other than PAH group 1.

Quercetin regulates pulmonary vascular remodeling in pulmonary hypertension by downregulating TGF-β1-Smad2/3 pathway

BackgroundPulmonary arterial hypertension (PAH) is a worldwide challenging disease characterized by progressive elevation of pulmonary artery pressure. The proliferation, migration and phenotypic transformation of pulmonary smooth muscle cells are the key steps of pulmonary vascular remodeling. Quercetin (3,3', 4', 5, 6-pentahydroxyflavone, Que) is a natural flavonol compound that has antioxidant, anti-inflammatory, anti-tumor and other biological activities. Studies have shown that Que has therapeutic effects on PAH. However, the effect of quercetin on pulmonary vascular remodeling in PAH and its mechanism remain unclear.Methods and resultsIn vivo, PAH rats were constructed by intraperitoneal injection of monocrotaline (MCT) at 60 mg/kg. Human pulmonary artery smooth muscle cells (HPASMCs) were treated with platelet-derived growth factor BB (PDGF-BB) 20 ng/mL to construct PAH cell model in vitro. The results showed that in vivo studies, MCT could induce right ventricular wall hyperplasia, narrow the small and medium pulmonary artery cavity, up-regulate the expression of proliferating and migration-related proteins proliferating cell nuclear antigen (PCNA) and osteopontin (OPN), and down-regulate the expression of alpha-smooth muscle actin (α-SMA). Que reversed the MCT-induced results. This process works by down-regulating the transforming growth factor-β1 (TGF-β1)/ Smad2/3 signaling pathway. In vitro studies, Que had the same effect on PDGF-BB-induced proliferation and migration cell models.ConclusionsQue inhibits the proliferation, migration and phenotypic transformation of HPASMCs by down-regulating TGF-β1/Smad2/Smad3 pathway, thereby reducing right ventricular hyperplasia (RVH) and pulmonary vascular remodeling, providing potential pharmacological and molecular explanations for the treatment of PAH.

Novel Role of Calcium-Sensitive Receptors in Chronic Hypoxia-Induced Proliferation of Pulmonary Vein Smooth Muscle Cells

Novel Role of Calcium-Sensitive Receptors in Chronic Hypoxia-Induced Proliferation of Pulmonary Vein Smooth Muscle Cells

Neutrophil extracellular traps promote proliferation of pulmonary smooth muscle cells mediated by CCDC25 in pulmonary arterial hypertension

BackgroundPrevious studies have indicated that neutrophil extracellular traps (NETs) play a pivotal role in pathogenesis of pulmonary arterial hypertension (PAH). However, the specific mechanism underlying the impact of NETs on pulmonary artery smooth muscle cells (PASMCs) has not been determined. The objective of this study was to elucidate underlying mechanisms through which NETs contribute to progression of PAH.MethodsBioinformatics analysis was employed in this study to screen for potential molecules and mechanisms associated with occurrence and development of PAH. These findings were subsequently validated in human samples, coiled-coil domain containing 25 (CCDC25) knockdown PASMCs, as well as monocrotaline-induced PAH rat model.ResultsNETs promoted proliferation of PASMCs, thereby facilitating pathogenesis of PAH. This phenomenon was mediated by the activation of transmembrane receptor CCDC25 on PASMCs, which subsequently activated ILK/β-parvin/RAC1 pathway. Consequently, cytoskeletal remodeling and phenotypic transformation occur in PASMCs. Furthermore, the level of NETs could serve as an indicator of PAH severity and as potential therapeutic target for alleviating PAH.ConclusionThis study elucidated the involvement of NETs in pathogenesis of PAH through their influence on the function of PASMCs, thereby highlighting their potential as promising targets for the evaluation and treatment of PAH.

(18)F-fluorodeoxyglucose uptake by positron emission tomography in patients with IPAH and CTEPH.

Pulmonary arterial hypertension (PAH) is driven by pathologies associated with increased metabolism such as pulmonary revascularization, vasoconstriction and smooth muscle cell proliferation in pulmonary artery wall. 18-fluorodeoxyglucose positron emission tomography (18FDG-PET) is an imaging technique sensitive to glucose metabolism and might be considered as a non-invasive method for diagnosis due to significant role of inflammation in idiopathic pulmonary artery hypertension (IPAH) and chronic thromboembolic pulmonary hypertension (CTEPH). The present study aimed to investigate the role of PET/CT imaging of patients with IPAH and CTEPH as an alternative diagnosis method. Demographic characteristics, FDG uptake in lungs, pulmonary artery and right ventricle (RV) of 17 patients (10 IPAH, 7 CTEPH), and 30 controls were evaluated. PET scanning, 6-min walk test, pro-BNP level, right heart catheterization of patients were performed both at the onsert and after 6-month PAH specific treatment. IPAH and CTEPH patients had significantly higher left lung FDG (p = 0.006), right lung FDG (p = 0.004), right atrial (RA) FDG (p < 0.001) and RV FDG (p < 0.001) uptakes than controls. Positive correlation was detected between the RV FDG uptake and the mean pulmonary artery pressure (mPAP) (r = 0.7, p = 0.012) and between the RA FDG uptake and the right atrial pressure (RAP) (r = 0.5, p = 0.02). Increased RV FDG and RA FDG uptakes predicts the presence of pulmonary hypertension and correlates with mPAP and RAP, respectively, which are important indicators in the prognosis of PAH. Further studies are required whether FDG PET imaging can be used to diagnose or predict the prognosis of pulmonary hypertension.

Identification of the shared gene signatures between pulmonary fibrosis and pulmonary hypertension using bioinformatics analysis.

Pulmonary fibrosis (PF) and pulmonary hypertension (PH) have common pathophysiological features, such as the significant remodeling of pulmonary parenchyma and vascular wall. There is no effective specific drug in clinical treatment for these two diseases, resulting in a worse prognosis and higher mortality. This study aimed to screen the common key genes and immune characteristics of PF and PH by means of bioinformatics to find new common therapeutic targets. Expression profiles are downloaded from the Gene Expression Database. Weighted gene co-expression network analysis is used to identify the co-expression modules related to PF and PH. We used the ClueGO software to enrich and analyze the common genes in PF and PH and obtained the protein-protein interaction (PPI) network. Then, the differential genes were screened out in another cohort of PF and PH, and the shared genes were crossed. Finally, RT-PCR verification and immune infiltration analysis were performed on the intersection genes. In the result, the positive correlation module with the highest correlation between PF and PH was determined, and it was found that lymphocyte activation is a common feature of the pathophysiology of PF and PH. Eight common characteristic genes (ACTR2, COL5A2, COL6A3, CYSLTR1, IGF1, RSPO3, SCARNA17 and SEL1L) were gained. Immune infiltration showed that compared with the control group, resting CD4 memory T cells were upregulated in PF and PH. Combining the results of crossing characteristic genes in ImmPort database and RT-PCR, the important gene IGF1 was obtained. Knocking down IGF1 could significantly reduce the proliferation and apoptosis resistance in pulmonary microvascular endothelial cells, pulmonary smooth muscle cells, and fibroblasts induced by hypoxia, platelet-derived growth factor-BB (PDGF-BB), and transforming growth factor-β1 (TGF-β1), respectively. Our work identified the common biomarkers of PF and PH and provided a new candidate gene for the potential therapeutic targets of PF and PH in the future.

Human pulmonary microvascular endothelial cell DDAH1-mediated nitric oxide production promotes pulmonary smooth muscle cell apoptosis in co-culture.

Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease in preterm infants, and pulmonary hypertension (PH) develops in 25%-40% of patients with BPD, increasing morbidity and mortality. BPD-PH is characterized by vasoconstriction and vascular remodeling. Nitric oxide (NO) is a pulmonary vasodilator and apoptotic mediator made in the pulmonary endothelium by NO synthase (eNOS). Asymmetric dimethylarginine (ADMA) is an endogenous eNOS inhibitor, primarily metabolized by dimethylarginine dimethylaminohydrolase-1 (DDAH1). Our hypothesis is that DDAH1 knockdown in human pulmonary microvascular endothelial cells (hPMVEC) will result in lower NO production, decreased apoptosis, and greater proliferation of human pulmonary arterial smooth muscle cells (hPASMC), whereas DDAH1 overexpression will have the opposite effect. hPMVECs were transfected with small interfering RNA targeting DDAH1 (siDDAH1)/scramble or adenoviral vector containing DDAH1 (AdDDAH1)/AdGFP for 24 h and co-cultured for 24 h with hPASMC. Analyses included Western blot for cleaved and total caspase-3, caspase-8, caspase-9, β-actin; trypan blue exclusion for viable cell numbers; terminal deoxynucleotide transferase dUTP nick end labeling (TUNEL); and BrdU incorporation. Small interfering RNA targeting DDAH1 (siDDAH1) transfected into hPMVEC resulted in lower media nitrites, cleaved caspase-3 and caspase-8 protein expression, and TUNEL staining; and greater viable cell numbers and BrdU incorporation in co-cultured hPASMC. Adenoviral-mediated transfection of the DDAH1 gene (AdDDAH1) into hPMVEC resulted in greater cleaved caspase-3 and caspase-8 protein expression and lower viable cell numbers in co-cultured hPASMC. Partial recovery of hPASMC viable cell numbers after AdDDAH1-hPMVEC transfection was observed when media were treated with hemoglobin to sequester NO. In conclusion, hPMVEC-DDAH1-mediated NO production positively regulates hPASMC apoptosis, which may prevent/attenuate aberrant pulmonary vascular proliferation/remodeling in BPD-PH.NEW & NOTEWORTHY BPD-PH is characterized by vascular remodeling. NO is an apoptotic mediator made in the pulmonary endothelium by eNOS. ADMA is an endogenous eNOS inhibitor metabolized by DDAH1. EC-DDAH1 overexpression resulted in greater cleaved caspase-3 and caspase-8 protein expression and lower viable cell numbers in co-cultured SMC. After NO sequestration, SMC viable cell numbers partially recovered despite EC-DDAH1 overexpression. EC-DDAH1-mediated NO production positively regulates SMC apoptosis, which may prevent/attenuate aberrant pulmonary vascular proliferation/remodeling in BPD-PH.

The novel KV7 channel activator URO-K10 exerts enhanced pulmonary vascular effects independent of the KCNE4 regulatory subunit

KV7 channels exert a pivotal role regulating vascular tone in several vascular beds. In this context, KV7 channel agonists represent an attractive strategy for the treatment of pulmonary arterial hypertension (PAH). Therefore, in this study, we have explored the pulmonary vascular effects of the novel KV7 channel agonist URO-K10. Consequently, the vasodilator and electrophysiological effects of URO-K10 were tested in rat and human pulmonary arteries (PA) and PA smooth muscle cells (PASMC) using myography and patch-clamp techniques. Protein expression was also determined by Western blot. Morpholino-induced knockdown of KCNE4 was assessed in isolated PA. PASMC proliferation was measured by BrdU incorporation assay. In summary, our data show that URO-K10 is a more effective relaxant of PA than the classical KV7 activators retigabine and flupirtine. URO-K10 enhanced KV currents in PASMC and its electrophysiological and relaxant effects were inhibited by the KV7 channel blocker XE991. The effects of URO-K10 were confirmed in human PA. URO-K10 also exhibited antiproliferative effects in human PASMC. Unlike retigabine and flupirtine, URO-K10-induced pulmonary vasodilation was not affected by morpholino-induced knockdown of the KCNE4 regulatory subunit. Noteworthy, the pulmonary vasodilator efficacy of this compound was considerably increased under conditions mimicking the ionic remodelling (as an in vitro model of PAH) and in PA from monocrotaline-induced pulmonary hypertensive rats. Taking all together, URO-K10 behaves as a KCNE4-independent KV7 channel activator with much increased pulmonary vascular effects compared to classical KV7 channel activators. Our study identifies a promising new drug in the context of PAH.

Biomimetic Nanoparticle-Mediated Target Delivery of Hypoxia-Responsive Plasmid of Angiotensin-Converting Enzyme 2 to Reverse Hypoxic Pulmonary Hypertension.

Hypoxic pulmonary hypertension (HPH) is characterized by pulmonary vascular sustained constriction and progressive remodeling, which are initiated by hypoxia then with hypoxia-induced additive factors including pulmonary vascular endothelium injury, intrapulmonary angiotension system imbalance, and inflammation. Now HPH is still an intractable disease lacking effective treatments. Gene therapy has a massive potential for HPH but is hindered by a lack of efficient targeted delivery and hypoxia-responsive regulation systems for transgenes. Herein, we constructed the hypoxia-responsive plasmid of angiotensin-converting enzyme 2 (ACE2) with endothelial-specific promoter Tie2 and a hypoxia response element and next prepared its biomimetic nanoparticle delivery system, named ACE2-CS-PRT@PM, by encapsulating the plasmid of ACE2 with protamine and chondroitin sulfate as the core then coated it with a platelet membrane as a shell for targeting the injured pulmonary vascular endothelium. ACE2-CS-PRT@PM has a 194.3 nm diameter with a platelet membrane-coating core-shell structure and a negatively charged surface, and it exhibits higher delivery efficiency targeting to pulmonary vascular endothelium and hypoxia-responsive overexpression of ACE2 in endothelial cells in a hypoxia environment. In vitro, ACE2-CS-PRT@PM significantly inhibited the hypoxia-induced proliferation of pulmonary smooth muscle cells. In vivo, ACE2-CS-PRT@PM potently ameliorated the hemodynamic dysfunction and morphological abnormality and largely reversed HPH via inhibiting the hypoxic proliferation of pulmonary artery smooth muscle cells, reducing pulmonary vascular remodeling, restoring balance to the intrapulmonary angiotension system, and improving the inflammatory microenvironment without any detectable toxicity. Therefore, ACE2-CS-PRT@PM is promising for the targeted gene therapy of HPH.

A modified primary culture method of rat pulmonary vein smooth muscle cells

BackgroundAlthough the pressure of pulmonary vein increases before pulmonary artery in pulmonary hypertension due to left heart disease (PH-LHD), only a few studies have assessed pulmonary vein smooth muscle cells (PVSMCs) because of the lack of a simple and feasible isolation method.MethodsIn this study, we introduced a simple method to obtain PVSMCs. Primary pulmonary veins were removed by puncture needle cannula guidance. Then, PVSMCs were cultured by the tissue explant method and purified by the differential adhesion method. The cells were characterized by hematoxylin-eosin (HE) staining, immunohistochemistry, western blotting, and immunofluorescence to observe the morphology and verify the expression of alpha-smooth muscle actin (α-SMA).ResultsThe HE staining results showed that the pulmonary vein media was thinner than the pulmonary artery, the intima and adventitia of the pulmonary vein were removed by this method, and the obtained cells with good activity exhibited morphological characteristics of smooth muscle cells. In addition, higher α-SMA expression was observed in the cells obtained by our isolation method than in the traditional method.ConclusionThis study established a simple and feasible method to isolate and culture PVSMCs that might facilitate the cytological experiments for PH-LHD.

Krüppel-like Factor 7 inhibits proliferation and migration of pulmonary smooth muscle cells via p21 activation

The aberrant proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs) are critical contributors to the pulmonary vascular remodeling that occurs during the development of Pulmonary arterial hypertension (PAH). Krüppel-like Factor 7 (KLF7) has been reported to be involved in the development of certain cardiovascular diseases. However, the role of KLF7 in PAH remains unknown. Here, we aimed to explore whether KLF7 mediates the proliferation and migration of PASMCs and its underlying mechanism. In this study, Sprague Dawley rats were exposed to 60 mg/kg monocrotaline (MCT) for 3 weeks to induce PAH and human PASMCs were stimulated with 20 ng/ml platelet-derived growth factor-BB (PDGF-BB) for 24 h to induce proliferation and migration. The mRNA and protein expression of KLF7 were significantly down-regulated in MCT-induced PAH rats and PDGF-BB-treated PASMCs. Under normal conditions, KLF7 knockdown obviously promoted PASMCs proliferation and migration, whereas KLF7 overexpression exhibited the opposite effects. Furthermore, PDGF-BB promoted the PASMCs proliferation and migration, increased the cell proportion in S phase, which was significantly attenuated by overexpression of KLF7. Mechanistic investigation indicated that KLF7 through activation its target protein, the cell cycle inhibitor p21, which finally leading to the inhibition of PASMCs growth. Consistently, UC2288, a specific inhibitor of p21, partially reversed the PASMCs proliferation inhibited by KLF7 overexpression. Taken collectively, the data suggested that KLF7 inhibits PASMCs proliferation and migration via p21 pathway and it may be used as a new therapeutic target for the PAH.

Abstract P1075: Elucidate The Mechanism Driving The Imbalance Between BMPs And Activin/Gdfs Signaling In Pulmonary Arterial Hypertension

Transforming Growth Factor-beta (TGF-β) family signaling is involved in Pulmonary Arterial Hypertension (PAH) in humans. PAH is a rare, highly morbid disorder characterized by dysregulated pulmonary vascular remodeling, elevated pulmonary vascular resistance, and the progressive obliteration of the pulmonary arteriolar circulation. The progression of PAH is largely influenced by the proliferation and migration of the pulmonary smooth muscle cells (PASMCs) and pulmonary endothelial cells (PAECs). While the exact mechanism is not understood, there is evidence that germline mutations in the BMPRII gene, one of the TGF-β family type II receptors, is present in PAH patients. Due to the functional similarity of BMPRII and type II Activin receptors ACVR2A and ACVR2B, they interact with overlapping TGF-β family ligands to activate either the SMAD 1/5/8 or SMAD 2/3 signaling. In the pulmonary vasculature, the BMP-9 ligand regulates cell proliferation by binding to type I receptors, ALK-1 and BMPRII, to activate SMAD 1/5/8 signaling. In PAH, there is a decrease in SMAD 1/5/8 signaling and an increase in SMAD 2/3 signaling. However, what causes the signaling switch is still unknown. In our lab, we found out that BMPRII and ACVR2A bind TGF-β ligands with nearly identical geometry based on our crystal structures. Both of the receptors contain a conserved hydrophobic hot spot within the ligand binding pocket. We found that the BMPRII ligand binding domain may exhibit greater flexibility than ACVR2A. We also investigated eight soluble BMPRII extracellular domain mutants and expressed them as BMPRII-Fc fusion proteins (BMPRII-Fc variants). Using surface plasmon resonance, we observed four of the BMPRII-Fc variants bind to high affinity ligands, such as BMP9, BMP10, Activin B and Activin A. In reporter gene assays, we found these BMPRII-Fc variants act as a ligand trap and attenuate BMP9 and BMP10-mediated SMAD1/5/8 signaling in HEK293 cells. Interestingly, they did not inhibit Activin B-mediated SMAD2/3 signaling. In conclusion, our findings show gain of function of specific BMPRII mutations and suggest that imbalances between SMAD1/5/8 and SMAD2/3 signaling may lead to PAH progression.

Synemin promotes pulmonary artery smooth muscle cell phenotypic switch in shunt-induced pulmonary arterial hypertension.

Although considerable progress has been made in the diagnosis and treatment of congenital heart disease-associated pulmonary heart hypertension (CHD-PAH), the clinical prognosis and overall survival of patients with CHD-PAH remain poor. Therefore, the molecular pathogenesis of CHD-PAH requires further investigation. The intermediate filament protein synemin (SYN) is reported to modulate phenotypic alterations and varicose vein development, but there is little understanding of its exact functions in CHD-PAH. SYN expression in the pulmonary arterioles of CHD-PAH patients and shunt-induced PAH rat models was evaluated using immunohistochemistry and western blot. Cell counts and Transwell migration assays were used to assess the effect of SYN on the proliferation and migration capability of human pulmonary smooth muscle cells (hPASMCs). Adeno-associated viruses (AAVs) have been used to suppress SYN expression in the pulmonary arterioles of rats. Such rats were further used to construct a shunt-induced PAH animal model to investigate the function of SYN in PAH and pulmonary vascular remodelling. Compared with the normal control group, SYN expression was found to be clearly up-regulated in the remodelled pulmonary arterioles of CHD-PAH and shunt-induced PAH rat models. In addition, SYN suppression increased the expression of hPASMC contractile-phenotype markers and decreased the expression of synthetic phenotype markers, in contrast to the control group. SYN suppression also dramatically attenuated the proliferation and migration capability of hPASMCs. Conversely, SYN overexpression promoted phenotypic switch, proliferation, and migration of hPASMCs, whereas these effects were notably alleviated by the protein kinase B (AKT) inhibitor MK-2206. Furthermore, we confirmed that SYN suppression mitigated PAH and pulmonary vascular remodelling induced by high blood flow in vivo. Our findings indicated that SYN may represent a promising therapeutic target in the treatment of CHD-PAH.

Cysteine and glycine-rich protein 2 promotes hypoxic pulmonary vascular smooth muscle cell proliferation through the Wnt3α-β-catenin/lymphoid enhancer-binding factor 1pathway.

Pulmonary hypertension (PH) is mainly characterized by abnormal pulmonary vascular hyperplasia and vascular remodeling, but its mechanism is complicated and currently unclear. Cysteine and glycine-rich protein 2 (Csrp2) has been reported to promote cell proliferation and migration, and affect cell cycle progression. As a new invasive actin-binding factor, Csrp2 increased the invasion and even metastasis of some cancer cells. It was associated with tumor recurrence and chemotherapy resistance. However, the role of Csrp2 in PH remains unknown. We found that Csrp2 expression was increased both in pulmonary arteries (PAs) and smooth muscle cells (PASMCs) in PH. Csrp2 enhanced PASMC proliferation and phenotypic transition. The Wnt3α-β-catenin/lymphoid enhancer-binding factor 1 (LEF1) pathway is involved in cell proliferation and phenotypic transition regulated by Csrp2 expression. These results suggest that hypoxia downregulates YinYang-1 (YY1) and then increases Csrp2 expression. Increased Csrp2 promotes PASMC proliferation and phenotypic transition by activating the Wnt3α-β-catenin/LEF1 pathways, which leads to pulmonary vascular remodeling and even provides a new theoretical basis for studying the pathogenesis and therapeutic targets of PH.

The Platelet-Derived Growth Factor Pathway in Pulmonary Arterial Hypertension: Still an Interesting Target?

The lack of curative options for pulmonary arterial hypertension drives important research to understand the mechanisms underlying this devastating disease. Among the main identified pathways, the platelet-derived growth factor (PDGF) pathway was established to control vascular remodeling and anti-PDGF receptor (PDGFR) drugs were shown to reverse the disease in experimental models. Four different isoforms of PDGF are produced by various cell types in the lung. PDGFs control vascular cells migration, proliferation and survival through binding to their receptors PDGFRα and β. They elicit multiple intracellular signaling pathways which have been particularly studied in pulmonary smooth muscle cells. Activation of the PDGF pathway has been demonstrated both in patients and in pulmonary hypertension (PH) experimental models. Tyrosine kinase inhibitors (TKI) are numerous but without real specificity and Imatinib, one of the most specific, resulted in beneficial effects. However, adverse events and treatment discontinuation discouraged to pursue this therapy. Novel therapeutic strategies are currently under experimental evaluation. For TKI, they include intratracheal drug administration, low dosage or nanoparticles delivery. Specific anti-PDGF and anti-PDGFR molecules can also be designed such as new TKI, soluble receptors, aptamers or oligonucleotides.

Circulating Blood-Based Biomarkers in Pulmonary Hypertension.

Pulmonary hypertension (PH) is a serious hemodynamic condition, characterized by increased pulmonary vascular resistance (PVR), leading to right heart failure (HF) and death when not properly treated. The prognosis of PH depends on etiology, hemodynamic and biochemical parameters, as well as on response to specific treatment. Biomarkers appear to be useful noninvasive tools, providing information about the disease severity, treatment response, and prognosis. However, given the complexity of PH, it is impossible for a single biomarker to be adequate for the broad assessment of patients with different types of PH. The search for novel emerging biomarkers is still ongoing, resulting in a few potential biomarkers mirroring numerous pathophysiological courses. In this review, markers related to HF, myocardial remodeling, inflammation, hypoxia and tissue damage, and endothelial and pulmonary smooth muscle cell dysfunction are discussed in terms of diagnosis and prognosis. Extracellular vesicles and other markers with complex backgrounds are also reviewed. In conclusion, although many promising biomarkers have been identified and studied in recent years, there are still insufficient data on the application of multimarker strategies for monitoring and risk stratification in PH patients.

Glucose-6-phosphate dehydrogenase and MEG3 controls hypoxia-induced expression of serum response factor (SRF) and SRF-dependent genes in pulmonary smooth muscle cell.

Although hypoxia induces aberrant gene expression and dedifferentiation of smooth muscle cells (SMCs), mechanisms that alter dedifferentiation gene expression by hypoxia remain unclear. Therefore, we aimed to gain insight into the hypoxia-controlled gene expression in SMCs. We conducted studies using SMCs cultured in 3% oxygen (hypoxia) and the lungs of mice exposed to 10% oxygen (hypoxia). Our results suggest hypoxia upregulated expression of transcription factor CP2-like protein1, krüppel-like factor 4, and E2f transcription factor 1 enriched genes including basonuclin 2 (Bcn2), serum response factor (Srf), polycomb 3 (Cbx8), homeobox D9 (Hoxd9), lysine demethylase 1A (Kdm1a), etc. Additionally, we found that silencing glucose-6-phosphate dehydrogenase (G6PD) expression and inhibiting G6PD activity downregulated Srf transcript and hypomethylation of SMC genes (Myocd, Myh11, and Cnn1) and concomitantly increased their expression in the lungs of hypoxic mice. Furthermore, G6PD inhibition hypomethylated MEG3, a long non-coding RNA, gene and upregulated MEG3 expression in the lungs of hypoxic mice and in hypoxic SMCs. Silencing MEG3 expression in SMC mitigated the hypoxia-induced transcription of SRF. These findings collectively demonstrate that MEG3 and G6PD codependently regulate Srf expression in hypoxic SMCs. Moreover, G6PD inhibition upregulated SRF-MYOCD-driven gene expression, determinant of a differentiated SMC phenotype.