Human Pulmonary Artery Endothelial Cells Research Articles

Increased Prolylcarboxypeptidase Expression Can Serve as a Biomarker of Senescence in Culture

Prolylcarboxypeptidase (PRCP, PCP, Lysosomal Pro-X-carboxypeptidase, Angiotensinase C) controls angiotensin- and kinin-induced cell signaling. Elevation of PRCP appears to be activated in chronic inflammatory diseases [cardiovascular disease (CVD), diabetes] in proportion to severity. Vascular endothelial cell senescence and mitochondrial dysfunction have consistently been shown in models of CVD in aging. Cellular senescence, a driver of age-related dysfunction, can differentially alter the expression of lysosomal enzymes due to lysosomal membrane permeability. There is a lack of data demonstrating the effect of age-related dysfunction on the expression and function of PRCP. To explore the changes in PRCP, the PRCP-dependent prekallikrein (PK) pathway was characterized in early- and late-passage human pulmonary artery endothelial cells (HPAECs). Detailed kinetic analysis of cells treated with high molecular weight kininogen (HK), a precursor of bradykinin (BK), and PK revealed a mechanism by which senescent HPAECs activate the generation of kallikrein upon the assembly of the HK–PK complex on HPAECs in parallel with an upregulation of PRCP and endothelial nitric oxide (NO) synthase (eNOS) and NO formation. The NO production and expression of both PRCP and eNOS increased in early-passage HPAECs and decreased in late-passage HPAECs. Low activity of PRCP in late-passage HPAECs was associated with rapid decreased telomerase reverse transcriptase mRNA levels. We also found that, with an increase in the passage number of HPAECs, reduced PRCP altered the respiration rate. These results indicated that aging dysregulates PRCP protein expression, and further studies will shed light into the complexity of the PRCP-dependent signaling pathway in aging.

Identification of Prostaglandin I2 Synthase Rare Variants in Patients With Williams Syndrome and Severe Peripheral Pulmonary Stenosis.

Peripheral pulmonary stenosis (PPS) is a condition characterized by the narrowing of the pulmonary arteries, which impairs blood flow to the lung. The mechanisms underlying PPS pathogenesis remain unclear. Thus, the aim of this study was to investigate the genetic background of patients with severe PPS to elucidate the pathogenesis of this condition. We performed genetic testing and functional analyses on a pediatric patient with PPS and Williams syndrome (WS), followed by genetic testing on 12 patients with WS and mild-to-severe PPS, 50 patients with WS but not PPS, and 21 patients with severe PPS but not WS. Whole-exome sequencing identified a rare PTGIS nonsense variant (p.E314X) in a patient with WS and severe PPS. Prostaglandin I2 synthase (PTGIS) expression was significantly downregulated and cell proliferation and migration rates were significantly increased in cells transfected with the PTGIS p.E314X variant-encoding construct when compared with that in cells transfected with the wild-type PTGIS-encoding construct. p.E314X reduced the tube formation ability in human pulmonary artery endothelial cells and caspase 3/7 activity in both human pulmonary artery endothelial cells and human pulmonary artery smooth muscle cells. Compared with healthy controls, patients with PPS exhibited downregulated pulmonary artery endothelial prostaglandin I2 synthase levels and urinary prostaglandin I metabolite levels. We identified another PTGIS rare splice-site variant (c.1358+2T>C) in another pediatric patient with WS and severe PPS. In total, 2 rare nonsense/splice-site PTGIS variants were identified in 2 pediatric patients with WS and severe PPS. PTGIS variants may be involved in PPS pathogenesis, and PTGIS represents an effective therapeutic target.

Deficiency of the Deubiquitinase UCHL1 Attenuates Pulmonary Arterial Hypertension.

The ubiquitin-proteasome system regulates protein degradation and the development of pulmonary arterial hypertension (PAH), but knowledge about the role of deubiquitinating enzymes in this process is limited. UCHL1 (ubiquitin carboxyl-terminal hydrolase 1), a deubiquitinase, has been shown to reduce AKT1 (AKT serine/threonine kinase 1) degradation, resulting in higher levels. Given that AKT1 is pathological in pulmonary hypertension, we hypothesized that UCHL1 deficiency attenuates PAH development by means of reductions in AKT1. Tissues from animal pulmonary hypertension models as well as human pulmonary artery endothelial cells from patients with PAH exhibited increased vascular UCHL1 staining and protein expression. Exposure to LDN57444, a UCHL1-specific inhibitor, reduced human pulmonary artery endothelial cell and smooth muscle cell proliferation. Across 3 preclinical PAH models, LDN57444-exposed animals, Uchl1 knockout rats (Uchl1-/-), and conditional Uchl1 knockout mice (Tie2Cre-Uchl1fl/fl) demonstrated reduced right ventricular hypertrophy, right ventricular systolic pressures, and obliterative vascular remodeling. Lungs and pulmonary artery endothelial cells isolated from Uchl1-/- animals exhibited reduced total and activated Akt with increased ubiquitinated Akt levels. UCHL1-silenced human pulmonary artery endothelial cells displayed reduced lysine(K)63-linked and increased K48-linked AKT1 levels. Supporting experimental data, we found that rs9321, a variant in a GC-enriched region of the UCHL1 gene, is associated with reduced methylation (n=5133), increased UCHL1 gene expression in lungs (n=815), and reduced cardiac index in patients (n=796). In addition, Gadd45α (an established demethylating gene) knockout mice (Gadd45α-/-) exhibited reduced lung vascular UCHL1 and AKT1 expression along with attenuated hypoxic pulmonary hypertension. Our findings suggest that UCHL1 deficiency results in PAH attenuation by means of reduced AKT1, highlighting a novel therapeutic pathway in PAH.

Human Pulmonary Artery Endothelial Cells Increased Glycolysis and Decreased Nitric Oxide Synthase O-GlcNAcylation in Pulmonary Arterial Hypertension

Human Pulmonary Artery Endothelial Cells Increased Glycolysis and Decreased Nitric Oxide Synthase O-GlcNAcylation in Pulmonary Arterial Hypertension

ErbB3 Governs Endothelial Dysfunction in Hypoxia-Induced Pulmonary Hypertension.

Pulmonary hypertension, characterized by vascular remodeling, currently lacks curative therapeutic options. The dysfunction of pulmonary artery endothelial cells plays a pivotal role in the initiation and progression of pulmonary hypertension (PH). ErbB3 (human epidermal growth factor receptor 3), also recognized as HER3, is a member of the ErbB family of receptor tyrosine kinases. Microarray, immunofluorescence, and Western blotting analyses were conducted to investigate the pathological role of ErbB3. Blood samples were collected for biomarker examination from healthy donors or patients with hypoxic PH. The pathological functions of ErbB3 were further validated in rodents subjected to chronic hypoxia- and Sugen-induced PH, with or without adeno-associated virus-mediated ErbB3 overexpression, systemic deletion, or endothelial cell-specific ErbB3 knockdown. Primary human pulmonary artery endothelial cells and pulmonary artery smooth muscle cells were used to elucidate the underlying mechanisms. ErbB3 exhibited significant upregulation in the serum, lungs, distal pulmonary arteries, and pulmonary artery endothelial cells isolated from patients with PH compared with those from healthy donors. ErbB3 overexpression stimulated hypoxia-induced endothelial cell proliferation, exacerbated pulmonary artery remodeling, elevated systolic pressure in the right ventricle, and promoted right ventricular hypertrophy in murine models of PH. Conversely, systemic deletion or endothelial cell-specific knockout of ErbB3 yielded opposite effects. Coimmunoprecipitation and proteomic analysis identified YB-1 (Y-box binding protein 1) as a downstream target of ErbB3. ErbB3 induced nuclear translocation of YB-1 and subsequently promoted hypoxia-inducible factor 1/2α transcription. A positive loop involving ErbB3-periostin-hypoxia-inducible factor 1/2α was identified to mediate the progressive development of this disease. MM-121, a human anti-ErbB3 monoclonal antibody, exhibited both preventive and therapeutic effects against hypoxia-induced PH. Our study reveals, for the first time, that ErbB3 serves as a novel biomarker and a promising target for the treatment of PH.

Blood DNA methylation profiling identifies cathepsin Z dysregulation in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterised by pulmonary vascular remodelling causing premature death from right heart failure. Established DNA variants influence PAH risk, but susceptibility from epigenetic changes is unknown. We addressed this through epigenome-wide association study (EWAS), testing 865,848 CpG sites for association with PAH in 429 individuals with PAH and 1226 controls. Three loci, at Cathepsin Z (CTSZ, cg04917472), Conserved oligomeric Golgi complex 6 (COG6, cg27396197), and Zinc Finger Protein 678 (ZNF678, cg03144189), reached epigenome-wide significance (p < 10−7) and are hypermethylated in PAH, including in individuals with PAH at 1-year follow-up. Of 16 established PAH genes, only cg10976975 in BMP10 shows hypermethylation in PAH. Hypermethylation at CTSZ is associated with decreased blood cathepsin Z mRNA levels. Knockdown of CTSZ expression in human pulmonary artery endothelial cells increases caspase-3/7 activity (p < 10−4). DNA methylation profiles are altered in PAH, exemplified by the pulmonary endothelial function modifier CTSZ, encoding protease cathepsin Z.

In Vitro Experimental Approach for Studying Human Pulmonary Artery Smooth Muscle Cells and Endothelial Cells Proliferation and Migration.

Pulmonary arterial hypertension (PAH) is a severe vascular disease characterized by persistent precapillary pulmonary hypertension, leading to right heart failure and death. Despite intense research in the last decades, PAH remains an incurable disease with high morbidity and mortality. New directions and therapies to improve understanding and treatment of PAH are desperately needed. The pathological mechanisms leading to this fatal disorder remain mostly undetermined, although structural remodeling of the pulmonary vessels is known to be an early feature of PAH. Pulmonary vascular remodeling includes proliferation and migration of pulmonary artery smooth muscle cells (PASMCs) and pulmonary artery endothelial cells (PAECs). The use of in vitro approaches is useful to delineate the mechanisms involved in the pathogenesis of PAH and to identify new therapeutic strategies for PAH. In this chapter, we describe protocols for culturing and assessing proliferation and migration of human PASMCs and PAECs.

The Protective Role of Mitochondria-Associated Endoplasmic Reticulum Membrane (MAM) Protein Sigma-1 Receptor in Regulating Endothelial Inflammation and Permeability Associated with Acute Lung Injury.

Earlier studies from our lab identified endoplasmic reticulum (ER) chaperone BiP/GRP78, an important component of MAM, to be a novel determinant of endothelial cell (EC) dysfunction associated with acute lung injury (ALI). Sigma1R (Sig1R) is another unique ER receptor chaperone that has been identified to associate with BiP/GRP78 at the MAM and is known to be a pluripotent modulator of cellular homeostasis. However, it is unclear if Sig1R also plays a role in regulating the EC inflammation and permeability associated with ALI. Our data using human pulmonary artery endothelial cells (HPAECs) showed that siRNA-mediated knockdown of Sig1R potentiated LPS-induced the expression of proinflammatory molecules ICAM-1, VCAM-1 and IL-8. Consistent with this, Sig1R agonist, PRE-084, known to activate Sig1R by inducing its dissociation from BiP/GRP78, blunted the above response. Notably, PRE-084 failed to blunt LPS-induced inflammatory responses in Sig1R-depleted cells, confirming that the effect of PRE-084 is driven by Sig1R. Furthermore, Sig1R antagonist, NE-100, known to inactivate Sig1R by blocking its dissociation from BiP/GRP78, failed to block LPS-induced inflammatory responses, establishing that dissociation from BiP/GRP78 is required for Sig1R to exert its anti-inflammatory action. Unlike Sig1R, the siRNA-mediated knockdown or Subtilase AB-mediated inactivation of BiP/GRP78 protected against LPS-induced EC inflammation. Interestingly, the protective effect of BiP/GRP78 knockdown or inactivation was abolished in cells that were depleted of Sig1R, confirming that BiP/GRP78 knockdown/inactivation-mediated suppression of EC inflammation is mediated via Sig1R. In view of these findings, we determined the in vivo relevance of Sig1R in a mouse model of sepsis-induced ALI. The intraperitoneal injection of PRE-084 mitigated sepsis-induced ALI, as evidenced by a decrease in ICAM-1, IL-6 levels, lung PMN infiltration, and lung vascular leakage. Together, these data evidence a protective role of Sig1R against endothelial dysfunction associated with ALI and identify it as a viable target in terms of controlling ALI in sepsis.

Inhibition of Hsp110-STAT3 interaction in endothelial cells alleviates vascular remodeling in hypoxic pulmonary arterial Hypertension model

BackgroundPulmonary arterial hypertension (PAH) is a progressive and devastating disease characterized by pulmonary vascular remodeling which is associated with the malignant phenotypes of pulmonary vascular cells. Recently, the effects of heat shock protein 110 (Hsp110) in human arterial smooth muscle cells were reported. However, the underlying roles and mechanisms of Hsp110 in human pulmonary arterial endothelial cells (HPAECs) that was disordered firstly at the early stage of PAH remain unknown.MethodsIn this research, the expression of Hsp110 in PAH human patients and rat models was investigated, and the Hsp110 localization was determined both in vivo and in vitro. The roles and mechanism of elevated Hsp110 in excessive cell proliferation and migration of HPAECs were assessed respectively exposed to hypoxia. Small molecule inhibitors targeting Hsp110-STAT3 interaction were screened via fluorescence polarization, anti-aggregation and western blot assays. Moreover, the effects of compound 6 on HPAECs abnormal phenotypes in vitro and pulmonary vascular remodeling of hypoxia-indued PAH rats in vivo by interrupting Hsp110-STAT3 interaction were evaluated.ResultsOur studies demonstrated that Hsp110 expression was increased in the serum of patients with PAH, as well as in the lungs and pulmonary arteries of PAH rats, when compared to their respective healthy subjects. Moreover, Hsp110 levels were significantly elevated in HPAECs under hypoxia and mediated its aberrant phenotypes. Furthermore, boosted Hsp110-STAT3 interaction resulted in abnormal proliferation and migration via elevating p-STAT3 and c-Myc in HPAECs. Notably, we successfully identified compound 6 as potent Hsp110-STAT3 interaction inhibitor, which effectively inhibited HPAECs proliferation and migration, and significantly ameliorated right heart hypertrophy and vascular remodeling of rats with PAH.ConclusionsOur studies suggest that elevated Hsp110 plays a vital role in HPAECs and inhibition of the Hsp110-STAT3 interaction is a novel strategy for improving vascular remodeling. In addition, compound 6 could serve as a promising lead compound for developing first-in-class drugs against PAH.

Cyclin D-CDK4 Disulfide Bond Attenuates Pulmonary Vascular Cell Proliferation.

Pulmonary hypertension (PH) is a chronic vascular disease characterized, among other abnormalities, by hyperproliferative smooth muscle cells and a perturbed cellular redox and metabolic balance. Oxidants induce cell cycle arrest to halt proliferation; however, little is known about the redox-regulated effector proteins that mediate these processes. Here, we report a novel kinase-inhibitory disulfide bond in cyclin D-CDK4 (cyclin-dependent kinase 4) and investigate its role in cell proliferation and PH. Oxidative modifications of cyclin D-CDK4 were detected in human pulmonary arterial smooth muscle cells and human pulmonary arterial endothelial cells. Site-directed mutagenesis, tandem mass-spectrometry, cell-based experiments, in vitro kinase activity assays, in silico structural modeling, and a novel redox-dead constitutive knock-in mouse were utilized to investigate the nature and definitively establish the importance of CDK4 cysteine modification in pulmonary vascular cell proliferation. Furthermore, the cyclin D-CDK4 oxidation was assessed in vivo in the pulmonary arteries and isolated human pulmonary arterial smooth muscle cells of patients with pulmonary arterial hypertension and in 3 preclinical models of PH. Cyclin D-CDK4 forms a reversible oxidant-induced heterodimeric disulfide dimer between C7/8 and C135, respectively, in cells in vitro and in pulmonary arteries in vivo to inhibit cyclin D-CDK4 kinase activity, decrease Rb (retinoblastoma) protein phosphorylation, and induce cell cycle arrest. Mutation of CDK4 C135 causes a kinase-impaired phenotype, which decreases cell proliferation rate and alleviates disease phenotype in an experimental mouse PH model, suggesting this cysteine is indispensable for cyclin D-CDK4 kinase activity. Pulmonary arteries and human pulmonary arterial smooth muscle cells from patients with pulmonary arterial hypertension display a decreased level of CDK4 disulfide, consistent with CDK4 being hyperactive in human pulmonary arterial hypertension. Furthermore, auranofin treatment, which induces the cyclin D-CDK4 disulfide, attenuates disease severity in experimental PH models by mitigating pulmonary vascular remodeling. A novel disulfide bond in cyclin D-CDK4 acts as a rapid switch to inhibit kinase activity and halt cell proliferation. This oxidative modification forms at a critical cysteine residue, which is unique to CDK4, offering the potential for the design of a selective covalent inhibitor predicted to be beneficial in PH.

Abstract 12953: Targeting NEDD9 and SMAD3 in the Pathogenesis of Chronic Thromboembolic Pulmonary Hypertension

Background: Chronic thromboembolic pulmonary hypertension (CTEPH) is characterized by unresolved pulmonary thrombi due, in part, to impaired fibrinolysis. We showed previously that oxidation of the Cas protein NEDD9 at cysteine-18 (Cys 18 ) inhibits complex formation between NEDD9 and the anti-fibrinolytic transcription factor SMAD3 in human pulmonary artery endothelial cells (HPAECs). However, the effect of NEDD9-Cys 18 oxidation on SMAD3 bioactivity in HPAECs is not known. Hypothesis: NEDD9-Cys 18 oxidation increases bioavailable SMAD3, which upregulates SERPINE1 that encodes plasminogen activator inhibitor (PAI)-1 to inhibit fibrinolysis pathways in HPAECs. Methods/Results: To assess the effect of SMAD3 on SERPINE1 transcription, HPAECs were transfected with cDNA-SMAD3 (1 μg/μl) for 72 hr to induce SMAD3 overexpression. Compared to vehicle (V) control, cDNA-SMAD3 increased PAI-1 and SERPINE1 expression by 35% (P=0.004) by immunoblot and 70% (P=0.003) by real-time PCR, respectively (N=3). To determine the effect of NEDD9 inhibition on SMAD3 activation, we analyzed the ratio of P-SMAD-Ser423/425:SMAD3 by immunoblot. Compared to scrambled RNA (scRNA), transfection with siRNA against NEDD9 (siNEDD9) for 48 hr increased the relative quantity of activated SMAD3 by 1.4-fold (P=0.006) and upregulated PAI-1 (P=0.004) expression by 1.7-fold in HPAECs (N=4). Next, we monitored the effect of oxidant stress on SMAD3 bioactivity. Compared to V-control, the expression of NEDD9, total SMAD3, and P-SMAD3 was increased by 66% (P=0.04), 81% (P=0.03), and 29% (P=0.04), respectively, in HPAECs treated with hydrogen peroxide (H 2 O 2 ) (500 μM) for 20 min. Next, the effect of NEDD9 silencing on H 2 O 2 accumulation in HPAECs was measured by Amplex Red assay. HPAECs were transfected with scRNA or siNEDD9 for 48 hr followed by measurement of H 2 O 2 production. Compared to scRNA, NEDD9 silencing significantly decreased H 2 O 2 concentration by 56% (N=4, P=0.02). Conclusion: These data demonstrate that oxidant stress increases SMAD3 activity and SMAD3-dependent upregulation of PAI-1 through a mechanism involving redox regulation of NEDD9. Identifying prothrombotic control of SMAD3 by NEDD9 may have important therapeutic implications for CTEPH.

Abstract 18284: Inhibition of Sulfatase-1 Prevents Pulmonary Arterial Hypertension in Animal Models of Disease

Introduction: Sulfatase-1 (Sulf1) is an extracellular enzyme that removes 6-O-sulfate groups from heparan sulfate and is implicated in cardiovascular disease. In human pulmonary artery endothelial cells (HPAECs), Sulf1 mRNA and protein levels are regulated by the fibroproliferative protein NEDD9 involved in PAH. Hypothesis: Sulf1 regulates migration and profibrotic potential of HPAECs and its downregulation prevents the development of PAH. Methods: HPAECs were transfected with Sulf1 siRNA or adenovirus expressing Sulf1 and cell migration was analyzed by scratch assay. In a PAH disease prevention treatment protocol, rats received intratracheal injection of Sulf1 siRNA (si-Sulf1) (1mg/kg of body weight, once a week for 3 weeks) beginning one day following the administration of monocrotaline (MCT). In a disease reversal protocol, injection of si-Sulf1 (1mg/kg of body weight, once every 5 days for a total of 3 doses) began 14 days following initiation of SU-5416/Hypoxia (SU/Hypox) PAH model. Results: Overexpression of Sulf1 in HPAECs resulted in a significant reduction in migration compared to empty vector (wound size 506 ± 39 vs 353 ± 19 μm, P&lt;0.01), whereas transfection with si-Sulf1 increased migration significantly compared to si-Scrambled control (wound size 212 ± 30 vs 295 ± 31 μm, P&lt;0.01). Overexpression of Sulf1 also increased extracellular collagen III deposition in cultured HPAECs compared to empty vector (15.4 ± 5 vs. 7 ± 1 arb. units, P&lt;0.01). Immunostaining of HPAECs for Sulf1 showed strong expression at focal adhesions. In both in vivo PAH models, si-Sulf1 treatment significantly decreased right ventricular (RV) systolic pressure compared to si-Scrambled control (MCT: 41 ± 5 vs 58 ± 6 mm Hg, P&lt;0.05; SU/Hypox: 40 ± 5 vs 75 ± 15 mm Hg, P&lt;0.05) and RV mass measured by Fulton index (MCT: 0.33 ± 0.06 vs 0.56 ± 0.06, P&lt;0.01; SU/Hypox: 0.32 ± 0.02 vs 0.41 ± 0.02, P&lt;0.05). Conclusions: These data demonstrate that pulmonary endothelial expression of Sulf1 is increased at focal adhesions and regulates cellular migration. Inhibition of Sulf1 significantly reduced the severity of PAH in vivo, which, taken together, identifies Sulf1 as a potential therapeutic target by which to improve proliferative vascular remodeling and pulmonary hypertension in PAH.

Abstract 18631: Mechanistic Insight on the Protective Role of Microbiome-Derived Butyrate in Pulmonary Hypertension

Introduction: Endothelial cell (EC) dysfunction is increasingly recognized as a precipitating event in Pulmonary hypertension (PH), a progressive, severe disease characterized by high blood pressure in the pulmonary circulation and excessive pulmonary vascular remodeling and inflammation. Microbiome-derived metabolites are altered in PH but their role in this disease remains poorly understood. Butyrate, a microbiome-derived short-chain fatty acid (SCFA) with biological activity, has been associated with benefit in cardiovascular diseases such as atherosclerosis. We aimed to test whether and how butyrate plays a protective role in PH. Results: PH-related inflammatory cytokine IL1β (10 ng/ml) increased expression of mesenchymal markers fibronectin, N-cadherin and transgelin (SM22) in human pulmonary arterial EC (HPAEC), consistent with induction of endothelial-to-mesenchymal transdifferentiation (EndMT). Butyrate (given as sodium butyrate, NaB; 2mM) attenuated this IL1β -induced upregulation (p&lt;0.01, p&lt;0.001, p&lt;0.001 for each gene, respectively). Likewise, butyrate inhibited IL1β-induced upregulation of b-catenin (p&lt;0.001), an important mediator of EndoMT. We previously showed that butyrate reversed IL1 β-induced downregulation of the PDZ protein EBP50, which we showed as a critical modulator of EndMT. In vivo, butyrate (NaB, 150mM) reversed PH phenotypes in wildtype mice (WT) following hypoxia exposure. In contrast, this reversal was attenuated in EBP50 heterozygous mice (Het, 50% EBP50 expression vs. WT) under hypoxia supplemented with butyrate. Similarly, butyrate reduced the number of circulating monocytes in hypoxia exposed WT but not Het mice. Conclusions: Collectively our results demonstrate that butyrate attenuates PH potentially via protecting against pulmonary vascular endothelial reprogramming and myeloid cell induction, through a mechanism that involves EBP50. These findings support the possible therapeutic benefits of butyrate in PH and shed mechanistic insight on the underlying cellular pathways propagating butyrate protection.

Abstract 14597: Beyond Sex Bias: The Uncharted Role of Rage Signaling in Pulmonary Arterial Hypertension

Background: Pulmonary arterial hypertension (PAH) is a life-threatening disease that initiates in response to pulmonary artery endothelial cells (PAEC) damage followed by inadequate repair. The Receptor for Advanced Glycation Endproducts (RAGE) triggered upon the damage, plays a crucial role in vascular regeneration. However, its specific impact on PAH remains incompletely explored. Hypothesis: In this study, we investigated the sex-specific outcome of RAGE deletion on PAEC homeostasis. Methods: The effect of the global RAGE knockout (KO) on pulmonary hemodynamics, cardiac and endothelial function was studied disaggregated by sex in WT and RAGE KO rats. Endothelial integrity was evaluated via the expression of endothelial junction proteins, the activity of barrier disruptive signaling pathways, and in vivo pulmonary vascular permeability assay. To understand the significance of diminished RAGE signaling in male PAH, we measured membrane RAGE levels in untreated and Sugen/Hypoxia treated rats of both sexes and examined the publicly available single-cell transcriptomic profiles of human PAECs. Results: Male but not female RAGE KO rats developed a spontaneous PAH characterized by a significant increase in the right ventricle (RV) systolic pressure and RV hypertrophy. The PAH phenotype in males corresponded with a male-specific decrease in the expression of CD31 (WT vs. RAGE KO: 1.0 ± 0.07 vs. 0.1 ± 0.02, p &lt;0001, N=6), activation of p38/RhoA signaling axis (p-p38 in WT vs. RAGE KO: 1.0 ± 0.2 vs. 3.2 ± 0.6, p=0.01, N=4), significant PAEC cytoskeletal rearrangement, and increased FITC-dextran extravasation, while female RAGE KOs remained unaffected. We also discovered that Sugen/Hypoxia treatment induced a substantial loss of membrane RAGE, specifically in males. Additionally, human PAEC transcriptomic data revealed that RAGE is expressed primarily in young females but not in males or older females. Conclusions: We conclude that the male sex associates with a reduced RAGE expression and signaling in PAEC, which is further diminished in PAH. The disruption in RAGE signaling, in turn, impairs the pulmonary endothelial barrier, instigates spontaneous PAH, and may contribute to the more severe phenotype observed in male PAH patients.

Impact of reduced apolipoprotein A-I levels on pulmonary arterial hypertension

ObjectiveThe significance of apolipoprotein A-I (ApoA-I) is the anti-inflammatory functional component of high-density lipoprotein, which needs to be further studied in relation to pulmonary arterial hypertension (PAH). This study aimed to identify the predictive value of ApoA-1 on the risk and prognosis of PAH, as well as the underlying anti-inflammatory mechanism. MethodsProteomic analysis was conducted on lung tissue from 6 PAH patients and 4 lung donors. Prediction of risk and mortality risk factors associated with PAH in 343 patients used logistic analysis and Cox regression analysis, respectively. The protective function of ApoA-I was assessed in human pulmonary arterial endothelial cells (HPAEC), while its anti-inflammatory function was evaluated in THP-1 macrophages. ResultsIn the lung tissues of patients with PAH, 168 differentially expressed proteins were associated with lipid metabolism according to GO and KEGG enrichment analysis. A protein-protein interaction network identified ApoA-I as a key protein associated with PAH. Lower ApoA-I levels were independent risk factors for PAH and displayed a stronger predictive value for PAH mortality. Plasma interleukin 6 (IL-6) levels were positively correlated with risk stratification and were higher in PAH patients with lower ApoA-I levels. ApoA-I was downregulated in the lung tissues of monocrotaline (MCT) -induced rats. ApoA-I could reduce the IL-6-induced pro-proliferative and pro-migratory abilities of HPAEC and inhibit the secretion of IL-6 from macrophages, which is compromised under hypoxic conditions. ConclusionOur study identified the significance of ApoA-I as a biomarker for predicting the survival outcome of PAH patients, which might relate to its altered anti-inflammatory properties.

Changes in hemoglobin oxidation and band 3 during blood storage impact oxygen sensing and mitochondrial bioenergetic pathways in the human pulmonary arterial endothelial cell model.

Red blood cells (RBCs) undergo metabolic, oxidative, and physiological changes during storage, collectively described as the "storage lesion." The impact of storage on oxygen homeostasis, following transfusion, is not fully understood. We show that RBC storage induces changes in oxygen binding that were linked to changes in oxygen sensing (hypoxia-inducible factor, HIF-1α) mechanisms and mitochondrial respiration in human pulmonary arterial endothelial cells (HPAECs). A decrease in oxygen affinity (P50) to approximately 20 from 30mmHg was seen at the first week but remained unchanged for up to 42 days. This led to the suppression of HIF-1α in the first 3weeks due to limited oxygen supplies by RBCs. Furthermore, membrane oxidative damage, band 3 alterations, and subsequent microparticle (MP) formation were also noted. Mass spectrometric analysis revealed the upregulation of transitional endoplasmic reticulum ATPase, essential for clearing ROS-damaged membrane proteins and the protein DDI1 homolog, a proteasomal shuttle chaperone. Band 3 complex proteins and superoxide dismutase were among the downregulated proteins. Mitochondrial oxygen consumption rates measured in HPAECs incubated with RBC-derived MPs (14-day and 42-day) showed a rise in maximal respiration. Intervention strategies that target intracellular hemoglobin (Hb)'s redox transitions and membrane changes may lead to the reestablishment of oxygen homeostasis in old RBCs.

Culin5 aggravates hypoxic pulmonary hypertension by activating TRAF6/NF-κB/HIF-1α/VEGF

Hypoxic pulmonary hypertension (HPH) lacks effective pharmacologic treatments. Microarray-based gene expression indicates the crucial role of Cullin 5 (Cul 5) in HPH. This study showed that Cul 5 was upregulated in HPH patients and a murine model of HPH. Invitro, Cul 5 promoted the angiogenesis and adhesion capacity of human pulmonary artery endothelial cells (PAECs), which could be mitigated by Cul 5 inactivation mediated by pevonedistat or NEDD8 silence. Invivo, silencing of Cul 5 in the endothelium and Cul 5 inactivation by pevonedistat could also alleviate hypoxic vascular remodeling. Mechanistic research showed that Cul 5 participated in HPH pathogenesis via the TRAF6/NF-κB/HIF-1α/VEGF pathway. Inhibition of the TRAF6/NF-κB/HIF-1α/VEGF pathway could reverse Cul 5-induced human PAEC dysfunction. These findings demonstrate that Cul 5 is an important mediator of HPH via the TRAF6/NF-κB/HIF-1α/VEGF pathway firstly, and could be considered as a potential therapeutic target in the clinical treatment of HPH.

NDRG1 promotes endothelial dysfunction and hypoxia-induced pulmonary hypertension by targeting TAF15.

Pulmonary hypertension (PH) represents a threatening pathophysiologic state that can be induced by chronic hypoxia and is characterized by extensive vascular remodeling. However, the mechanism underlying hypoxia-induced vascular remodeling is not fully elucidated. By using quantitative polymerase chain reactions, western blotting, and immunohistochemistry, we demonstrate that the expression of N-myc downstream regulated gene-1 (NDRG1) is markedly increased in hypoxia-stimulated endothelial cells in a time-dependent manner as well as in human and rat endothelium lesions. To determine the role of NDRG1 in endothelial dysfunction, we performed loss-of-function studies using NDRG1 short hairpin RNAs and NDRG1 over-expression plasmids. In vitro, silencing NDRG1 attenuated proliferation, migration, and tube formation of human pulmonary artery endothelial cells (HPAECs) under hypoxia, while NDRG1 over-expression promoted these behaviors of HPAECs. Mechanistically, NDRG1 can directly interact with TATA-box binding protein associated factor 15 (TAF15) and promote its nuclear localization. Knockdown of TAF15 abrogated the effect of NDRG1 on the proliferation, migration and tube formation capacity of HPAECs. Bioinformatics studies found that TAF15 was involved in regulating PI3K-Akt, p53, and hypoxia-inducible factor 1 (HIF-1) signaling pathways, which have been proved to be PH-related pathways. In addition, vascular remodeling and right ventricular hypertrophy induced by hypoxia were markedly alleviated in NDRG1 knock-down rats compared with their wild-type littermates. Taken together, our results indicate that hypoxia-induced upregulation of NDRG1 contributes to endothelial dysfunction through targeting TAF15, which ultimately contributes to the development of hypoxia-induced PH.

Abstract P321: &lt;RKER-012, A Novel Activin Receptor Type Ilb (actrllb) Ligand Trap, Inhibited Mediators Of Dysregulated Vascular Remodeling In Pulmonary Arterial Endothelial And Smooth Muscle Cells&gt;

Rationale: Imbalance in TGF-β signaling molecules SMAD2/3 and SMAD1/5/9 is a key driver of vascular dysfunction and pulmonary arterial hypertension (PAH) pathophysiology. KER-012, a novel ActRIIB ligand trap, designed to bind activin (Act) A and ActB to inhibit SMAD2/3: thereby permitting bone morphogenic protein (BMP) ligand signaling via SMAD1/5/9 to potentially rebalance TGF-β signaling and restore vascular homeostasis in PAH and associated disorders. Methods: Using hypoxia (1% O2) to mimic the pulmonary cell environment of PAH, we evaluated the effect of KER-012 or RKER -012 (a research form of KER-012) on TGF-β signaling in human pulmonary arterial endothelial cells (HPAECs) and smooth muscle cells (HPASMCs), two key cell types involved in the vascular remodeling in PAH. Gene expression of hypoxia/normoxia cultured cells was assessed by qPCR, phosphorylation of SMAD2 (pSMAD2) by alphaLISA, and ActA protein levels by ELISA. Results: HPAECs and HPASMCs both responded to TGF-β ligands implicated in PAH. ActA and Growth Differentiation Factor (GDF)11 increased SMAD2 phosphorylation and BMP9 increased SMAD1 phosphorylation (pSMAD1), confirming activation of the respective signaling pathways. KER-012 inhibited ActA and GDF11 induced pSMAD2, but not BMP9 induced pSMAD1. In hypoxic HPAECs, ActA gene expression increased &gt;3-fold and BMPR2 expression decreased &gt;2-fold relative to normoxia. ActA protein levels from hypoxic HPAEC supernatant also increased 10-fold, which was associated with an observed increase in pSMAD2 activation. While RKER-012 did not affect ActA gene expression, it did reduce ActA protein levels in supernatant to normoxic levels. This reduction in ActA may represent the fraction not bound to RKER-012, and potentially demonstrates a reduction in ActA availability for SMAD2/3 activation. Conclusions: ActA inhibition by RKER-012 restored homeostatic SMAD2 signaling in HPAECs and HPASMCs in an in vitr o PAH hypoxia model. RKER012 has also shown not to effect BMP signaling in these cells. These studies suggest that RKER-012 can potentially correct imbalanced SMAD signaling in PAH, partially via binding and inhibition of ActA protein.

Persistent Hypoxia with Intermittent Aggravation Causes Imbalance in Smad3/Myocardin-Related Transcription Factor Signaling with Consequent Endothelial Senescence and Pulmonary Arterial Remodeling.

Loss of Smad3 and the consequent activation of myocardin-related transcription factor (MRTF) are associated with vascular pathologies. This study aimed to examine the impact of persistent hypoxia with intermittent aggravation (PI hypoxia) on cellular senescence and pulmonary arterial remodeling mediated by the Smad3/MRTF imbalance. We examined the effects of PI hypoxia on the Smad3/MRTF pathway and cellular senescence using human pulmonary artery endothelial cells (HPAECs) and in vivo studies in rats. The senescent degree was evaluated using β-galactosidase staining, p16 quantitation and the measurement of senescence-associated secretory phenotype. Structural data in the pathological analysis of pulmonary artery remodeling were collected. Compared to the control, HPAECs and pulmonary tissue from rats exposed to PI hypoxia showed a significantly higher senescent degree, lower expression of Smad3, and higher MRTF levels. The overexpression of Smad3 significantly mitigated HPAECs senescence in vitro. Further, treatment with CCG-203971, which inhibits MRTF, increased Smad3 levels and reduced β-galactosidase positive cells in rat lung tissue. This intervention also alleviated PI hypoxia-induced pathological changes, including remodeling indices of pulmonary arterial thickening, muscularization, and collagen formation. In conclusion, imbalanced Smad3/MRTF signaling is linked to PI hypoxia-induced senescence and pulmonary arterial remodeling, making it a potential therapeutic target for patients with sleep apnea and chronic obstructive pulmonary disease.