Pathogenesis Of Pulmonary Hypertension Research Articles

Characteristics of circular RNA expression in lung tissues from mice with hypoxia‑induced pulmonary hypertension.

Pulmonary hypertension (PH) is a life-threatening lung disease, characterized by an increase in pulmonary arterial pressure caused by vasoconstriction and vascular remodeling. The pathogenesis of PH is not fully understood, and there is a lack of potential biomarkers for the diagnosis and treatment of patients with PH. Non-coding RNAs with a characteristic covalently closed loop structure, termed circular RNAs (circRNAs), are present in a number of pulmonary diseases. To the best of our knowledge, the present study is the first to use microarray analysis to determine the expression profile of circRNAs in lung tissues from mice with hypoxia-induced PH. In total, 23 significantly upregulated and 41 significantly down-regulated circRNAs were identified. Of these, 12 differentially expressed circRNAs were selected for further validation using reverse transcription-quantitative polymerase chain reaction. Putative microRNAs (miRNAs) that bind to the dysregulated circRNAs were predicted. Subsequently, bioinformatics tools were used to construct circRNA-miRNA-mRNA networks for the two most promising circRNAs, namely mmu_circRNA_004592 and mmu_circRNA_018351. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses of target genes of the dysregulated circRNAs revealed that these dysregulated circRNAs may serve an important role in the pathogenesis of hypoxia-induced PH. Therefore, these dysregulated circRNAs are candidate diagnostic biomarkers and potential therapeutic targets for PH.

PAI-1 is a novel component of the miR-17~92 signaling that regulates pulmonary artery smooth muscle cell phenotypes.

We have previously reported that miR-17~92 is critically involved in the pathogenesis of pulmonary hypertension (PH). We also identified two novel mR-17/20a direct targets, PDZ and LIM domain protein 5 (PDLIM5) and prolyl hydroxylase 2 (PHD2), and elucidated the signaling pathways by which PDLIM5 and PHD2 regulate functions of pulmonary artery smooth muscle cells (PASMCs). In addition, we have shown that plasminogen activator inhibitor-1 (PAI-1) is also downregulated in PASMCs that overexpress miR-17~92. However, it is unclear whether PAI-1 is a direct target of miR-17~92 and whether it plays a role in regulating the PASMC phenotype. In this study, we have identified PAI-1 as a novel target of miR-19a/b, two members of the miR-17~92 cluster. We found that the 3'-untranslated region (UTR) of PAI-1 contains a miR-19a/b binding site and that miR-19a/b can target this site to suppress PAI-1 protein expression. MiR-17/20a, two other members of miR-17~92, may also indirectly suppress PAI-1 expression through PDLIM5. PAI-1 is a negative regulator of miR-17~92-mediated PASMC proliferation. Silencing of PAI-1 induces Smad2/calponin signaling in PASMCs, suggesting that PAI-1 is a negative regulator of the PASMC contractile phenotype. We also found that PAI-1 is essential for the metabolic gene expression in PASMCs. Furthermore, although there is no significant change in PAI-1 levels in PASMCs isolated from idiopathic pulmonary arterial hypertension and associated pulmonary arterial hypertension patients, PAI-1 is downregulated in hypoxia/Sugen-induced hypertensive rat lungs. These results suggest that miR-17~92 regulates the PASMC contractile phenotype and proliferation coordinately and synergistically by direct and indirect targeting of PAI-1.

The Long Non‐Coding RNA XIST Is Decreased in Lungs and Plasma Exosomes of Sickle Cell Mice and in Hemin‐Treated Human Pulmonary Artery Endothelial Cells

RationalePulmonaryhypertension (PH), a serious complication of sicklecell disease (SCD), causes significant morbidity andmortality. The release ofhemoglobin and free heme during hemolysis triggers endothelial dysfunction andcontributes to PH pathogenesis. Emerging evidence indicates that longnon‐coding RNAs (lncRNAs) play a pivotal role in cellular proliferation,differentiation, and apoptosis. Circulating exosomes, which are nano‐sized extracellular vesicles, contain lncRNAs and play an important role in intercellular communication. However, the role of lncRNAs released from lungs and plasmaexosomes in SCD‐PH pathogenesis has not been defined. We hypothesized that lncRNAs are differentially expressed in SSmouse lungs and plasma exosomes and in hemin‐treated human pulmonary artery endothelialcells (HPAECs).Methods and ResultslncRNAs were isolated from lungs and plasma exosomes of sicklecell (SS) mice and littermate control (AA) mice at age 15–17 weeks. Isolated plasma exosomes were characterized forlevels of exosomal markers (CD9, CD45, and CD63), following which exosomes andlung samples were subjected to determine theexpression profiles of 90 lncRNAs using the LncProfiler™ lncRNA qPCR array(System Bioscienes). 5 lncRNAs were increased and10 lncRNAs were decreased in the lungs and plasma exosomes of SS mice compared to AA mice. One of thelncRNAs found to be decreased in SS samples was X‐inactivespecific transcript (XIST). To further examinewhether hemin reduces lncRNA XIST expression, HPAECs were treated with DMSO or hemin (5 uM) for 72 hours. XIST expression was decreased in hemin‐treatedHPAECs. Hemin also stimulated dose (0–10 μM)− and time (0–72hours)‐dependent increases in HPAEC monocyteadhesion and proliferation (BrdU assays). Because PPAR gamma (PPARg) levels were reduced in the lungs of SS mice,and pharmacological PPARg activation attenuated SCD‐PH, we examined the impactof PPARg activation on XIST levels in SS mouse lungs and found that PPARgactivation attenuates reductions in XIST expression.ConclusionsTheseresults suggest that sickle cell disease can impact lncRNAs and these effectsmay be reversed by treatment with PPARg agonists. Therefore, characterizationof lncRNAs are impacted in SCD may provide new insights into SCD pulmonaryvascular dysfunction and PH pathogenesis and identify novel targets fortherapeutic intervention.Support or Funding InformationSupported by NIH HL102167 (RLS and CMH) and NIH HL133053‐01A1 (BYK).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Hemodynamic Mechanisms of Exercise-Induced Pulmonary Hypertension in Patients with Lymphangioleiomyomatosis: The Role of Exercise Stress Echocardiography

The pathogenesis of pulmonary hypertension (PH) in lymphangioleiomyomatosis (LAM) has not yet been completely clarified. The aim of this study was to conduct a noninvasive evaluation of the main hemodynamic mechanisms of exercise-induced PH in patients with LAM, assessed using exercise stress echocardiography. Fifteen patients with LAM (mean age, 47±13years; all women) without resting PH were enrolled in a prospective single-center study and compared with 15 healthy female control subjects (mean age, 45.2±8years; P=.65). A complete echocardiographic study with Doppler tissue imaging was performed at baseline and during semisupine symptom-limited exercise testing to evaluate (1) left ventricular systolic and diastolic function, (2) right ventricular contractile function, (3) estimated pulmonary capillary wedge pressure, (4) estimated systolic and mean pulmonary artery pressure, and (5) estimated pulmonary vascular resistance. Compared with healthy control subjects, patients with LAM during exercise showed echocardiographic signs of right ventricular overload and right ventricular systolic dysfunction and significant increases in mean pulmonary artery pressure (14.4±6.5 vs 4.2±3.1mm Hg, P<.0001), pulmonary vascular resistance(+68.3±42.1 vs -0.1±18.3 dyne-sec/cm5, P<.0001), and, unexpectedly, pulmonary capillary wedge pressure (+8.3±5.3 vs -0.5±1.3mm Hg, P<.0001). Exercise-induced PH in patients with LAM could be related not only to hypoxic pulmonary vascular vasoconstriction during exercise (precapillary PH) but also to a significant exercise-induced increase in estimated pulmonary capillary wedge pressure, probably secondary to diastolic dysfunction (postcapillary PH).

Hypoxia induces endothelial‑mesenchymal transition in pulmonary vascular remodeling.

It is well established that hypoxia induces epithelial-mesenchymal transition in vitro and in vivo. However, the role of hypoxia in endothelial-mesenchymal transition (EndMT), an important process in the pathogenesis of pulmonary hypertension, is not well-characterized. The present study demonstrated a significant downregulation of the endothelial marker CD31 and its co-localization with a mesenchymal marker, α-smooth muscle actin (α-SMA), in the intimal layer of small pulmonary arteries of rats exposed to chronic hypoxia. These results suggest a possible role of hypoxia in inducing EndMT in vivo. Consistent with these observations, pulmonary microvascular endothelial cells (PMVECs) cultured under hypoxic conditions exhibited a significant decrease in CD31 expression, alongside a marked increase in the expression of α-SMA and two other mesenchymal markers, collagen (Col) 1A1 and Col3A1. In addition, hypoxia promoted the proliferation and migration of α-SMA-expressing mesenchymal-like cells, but not of PMVECs. Of note, knockdown of hypoxia-inducible factor 1α (HIF-1α) effectively inhibited hypoxic induction of α-SMA, Col1A1 and the transcription factor Twist1, while rescuing hypoxic suppression of CD31; these results suggest that HIF-1α is essential for hypoxia-induced EndMT and that it serves as an upstream regulator of Twist1. Mechanistically, HIF-1α was identified to bind to the promoter of the Twist1 gene, thus activating Twist1 transcription and regulating EndMT. Collectively, the present results indicate that the HIF-1α/Twist1 pathway has a critical role in mediating the effect of hypoxia-induced EndMT in pulmonary arterial remodeling.

Renin angiotensin system and pulmonary hemodynamics in chronic obstructive pulmonary disease

Background: Pulmonary hypertension in chronic obstructive pulmonary disease (COPD) due to chronic alveolar hypoxia is probably the main contributor to the pathogenesis of pulmonary hypertension in COPD. Angiotensin II is a potent vasoconstrictor in renin angiotensin aldosterone system (RAAS), it has been shown to promote growth response in vascular smooth muscle cell contributing towards pulmonary hypertension. So, the Echocardiographicaliy measured MPAP and its correlation with RAAS in patients of COPD was evaluated.Methods: A prospective observational study was done in 32 patients with COPD and 10 age matched healthy, non-smoker subject included as controls. Stable patients requiring no change in their medication in the previous four weeks and not having had an acute exacerbation in that period were included. MPAP was calculated. Measurement of Ang II and aldosterone was done.Results: Thirty-two cases of COPD, meeting inclusion criteria were enrolled comprising of 32 males and the mean age of patients ±2sd was (55.6 ±16.8), while mean age of controls ± 2sd was 49.60 ±5.56. Arterial blood gas analysis, PaO2 was ranged from (mean±2sd 75.44±12.1), PaCo2 ranged from (mean ±2sd 41.36±3.79) and SpO2 ranged from (mean±2sd 94.03 2±.74). Mean ±2sd of plasma Ang II in COPD cases was (4.9±3.8) ng/dl, significantly higher in comparison with controls (p &lt; 0.001). Mean ±2sd of plasma ACE activity was (51.12±26.9) in COPD. Mean ±2sd of plasma aldosterone was (182.35±364.2) in COPD cases with significant (p&lt;0.01). The MPAP in COPD cases was (mean±2sd 34.53±7.70).Conclusions: Use of Doppler has the advantage of being noninvasive and has been shown to be extremely reproducible in evaluation of MPAP and CO. The increased level of Ang II with increase MPAP in the present study would suggest that this may be a suitable model for investigating effects of novel vasodilator drugs for the treatment of pulmonary hypertension developed due to COPD.

Pulmonary Hypertension in Predialysis Chronic Kidney Disease: Frequency and Potential Mechanisms

AbstractBackground: Pulmonary arterial hypertension (PH) and Chronic Kidney Disease (CKD) both profoundly affect patient outcomes, whether as primary disease states or as comorbid conditions. PH is a common comorbidity in CKD and vice versa. PH is an independent predictor of mortality in such patients. In a recent review, the prevalence of PHT in ESRD patients was reported to be around 40-50% however, the epidemiological data for this disorder in earlier stages of Chronic Kidney Disease (CKD) and the risk factors associated with its presence are scarce.Aim: To evaluate the frequency of pulmonary hypertension among chronic kidney disease nondialysis dependent patients and to compare clinical and metabolic variables among those patients with the control group to search for possible mecha-nisms.Subjects and Methods: 40 CKD patients (55% men, 45% women; mean age, 42.9±15.13 years) with. According to the magnitude of Glomerular Filtration Rate (GFR) decrease, the CKD patients have divided into 3 groups: (1) 2 patients with a GFR of 89-60ml/min; (2) 6 with a GFR of 59-45ml/min; (3) 32 with a GFR of 44-15ml/min. A control group consisted of 40 individuals with preserved kidney function (a GFR of >90 ml/min). Physical examination and echocardiography were performed in all the patients. The serum concentrations of homocysteine and serum PTH were determined.Results: PH was detected in 20 (50%) of the 40 patients with CKD. As CKD progressed, the frequency of pulmonary hypertension in Groups 1, 2, and 3 increased, amounting to 18.2%, 24.2%, and 35%, respectively.Conclusion: This study demonstrated a high frequency of pulmonary hypertension among patients with CKD without dialysis.The frequency was highest among patients especially those with older age higher, serum creatinine phosphorus c-reactive protein parathyroid hormone and homocysteine; lower hemoglobin, lower EF% which all positively correlated with PASP and may be involved in the pathogenesis of pulmonary hypertension. Early detection of pulmonary hypertension is important in order to avoid the serious consequences of the disease, also managing these potential mechanisms will result in areduction in the occurrence of pulmonary hypertension and thus reducing the incidence of the cardiovascular compli-cations which are considered as one of the most important causes of death in the group of patients.

Serotonin 2A receptor inhibition protects against the development of pulmonary hypertension and pulmonary vascular remodeling in neonatal mice.

Pulmonary hypertension (PH) complicating bronchopulmonary dysplasia (BPD) worsens clinical outcomes in former preterm infants. Increased serotonin (5-hydroxytryptamine, 5-HT) signaling plays a prominent role in PH pathogenesis and progression in adults. We hypothesized that increased 5-HT signaling contributes to the pathogenesis of neonatal PH, complicating BPD and neonatal lung injury. Thus, we investigated 5-HT signaling in neonatal mice exposed to bleomycin, previously demonstrated to induce PH and alveolar simplification. Newborn wild-type mice received intraperitoneal PBS, ketanserin (1 mg/kg), bleomycin (3 U/kg) or bleomycin (3 U/kg) plus ketanserin (1 mg/kg) three times weekly for 3 wk. Following treatment with bleomycin, pulmonary expression of the rate-limiting enzyme of 5-HT synthesis, tryptophan hydroxylase-1 (Tph1), was significantly increased. Bleomycin did not affect pulmonary 5-HT 2A receptor (R) expression, but did increase pulmonary gene expression of the 5-HT 2BR and serotonin transporter. Treatment with ketanserin attenuated bleomycin-induced PH (increased RVSP and RVH) and pulmonary vascular remodeling (decreased vessel density and increased muscularization of small vessels). In addition, we found that treatment with ketanserin activated pulmonary MAPK and Akt signaling in mice exposed to bleomycin. We conclude that 5-HT signaling is increased in a murine model of neonatal PH and pharmacological inhibition of the 5-HT 2AR protects against the development of PH in neonatal lung injury. We speculate this occurs through restoration of MAPK signaling and increased Akt signaling.

Mitochondrial dysfunction and pulmonary hypertension: cause, effect, or both.

Pulmonary hypertension describes a heterogeneous disease defined by increased pulmonary artery pressures, and progressive increase in pulmonary vascular resistance due to pathologic remodeling of the pulmonary vasculature involving pulmonary endothelial cells, pericytes, and smooth muscle cells. This process occurs under various conditions, and although these populations vary, the clinical manifestations are the same: progressive dyspnea, increases in right ventricular (RV) afterload and dysfunction, RV-pulmonary artery uncoupling, and right-sided heart failure with systemic circulatory collapse. The overall estimated 5-yr survival rate is 72% in highly functioning patients, and as low as 28% for those presenting with advanced symptoms. Metabolic theories have been suggested as underlying the pathogenesis of pulmonary hypertension with growing evidence of the role of mitochondrial dysfunction involving the major proteins of the electron transport chain, redox-related enzymes, regulators of the proton gradient and calcium homeostasis, regulators of apoptosis, and mitophagy. There remain more studies needed to characterize mitochondrial dysfunction leading to impaired vascular relaxation, increase proliferation, and failure of regulatory mechanisms. The effects on endothelial cells and resulting interactions with their microenvironment remain uncharted territory for future discovery. Additionally, on the basis of observations that the "plexigenic lesions" of pulmonary hypertension resemble the unregulated proliferation of tumor cells, similarities between cancer pathobiology and pulmonary hypertension have been drawn, suggesting interactions between mitochondria and angiogenesis. Recently, mitochondria targeting has become feasible, which may yield new therapeutic strategies. We present a state-of-the-art review of the role of mitochondria in both the pathobiology of pulmonary hypertension and potential therapeutic targets in pulmonary vascular processes.

NLRC3: A Novel Noninvasive Biomarker for Pulmonary Hypertension Diagnosis.

The nucleotide-oligomerization domain (NOD)-like receptor subfamily C3 (NLRC3) is a newly discovered and incompletely characterized member of the NLR family which negatively regulates inflammatory responses. Inflammation is considered a critical pathogenesis in pulmonary hypertension (PH). This is the first study to hypothesize that NLRC3 is closely correlated with PH. Total of 43 PH patients who were diagnosed by right heart catheterization (RHC) and 20 age-matched healthy control subjects were included. Echocardiographic variables and blood biochemical parameters were tested. Results of World Health Organization functional class (WHOFC), Borg dyspnea score and 6-minute walk tests (6MWT) were recorded. Mean pulmonary arterial pressure (mPAP) and pulmonary vascular resistance (PVR) were measured from RHC. Serum NLRC3 concentrations were detected by ELISA. ROC curve analysis was used to evaluate the diagnostic value of NLRC3 concentrations in PH. We found that serum NLRC3 concentration was significantly decreased in PH compared to the healthy control group. Serum NLRC3 concentration correlated negatively with mPAP and PVR. In addition, a negative correlation between serum NLRC3 concentration and WHOFC were detected. We proposed a cut-off value of 2.897ng/mL for serum NLRC3 concentration which was able to predict PH with 88% sensitivity and 85% specificity. In conclusion, NLRC3 concentrations in PH were significantly decreased, suggesting that NLRC3 may potentially be a diagnosis index and represent a prognostic factor for PH patients.

Predictive value of pulmonary function testing in the evaluation of pulmonary hypertension in sarcoidosis.

Background: In sarcoidosis patients, pulmonary hypertension (PH) is associated with significant morbidity and mortality. Early identification of sarcoidosis-associated pulmonary hypertension (SAPH) has substantial clinical implications. While a number of pulmonary function testing (PFT) variables have been associated with SAPH, the optimal use of PFT’s in screening for SAPH is unknown. Objectives: To examine the predictive value of PFT’s for echocardiographic PH in a cohort of sarcoidosis patients. Methods: We conducted a retrospective cohort study of patients with sarcoidosis from a single center over a period of five years. All consecutive adult patients with a diagnosis of biopsy-proven sarcoidosis (determined by review of the medical chart) who underwent PFT and echocardiographic testing were included. Echocardiographic risk of PH (either intermediate or high) was determined by the presence of echocardiographic PH signs and tricuspid regurgitant jet velocity. Data analysis was performed using multivariate logistic regression analysis with least absolute shrinkage and selection operator. Results: Of the 156 patients included in the study, 42 (27%) met the criteria for echocardiographic PH. Roughly equal proportions met the criteria for intermediate risk (45%) as did for high risk of PH (55%). The percent predicted of diffusion capacity for carbon monoxide (%DLCO) and forced vital capacity (%FVC) were predictive of echocardiographic PH. No other PFT variables outperformed these two markers, and the incorporation of additional PFT variables failed to significantly enhance the model. Conclusions: The %FVC and %DLCO emerged as being predictive of echocardiographic PH in this cohort of biopsy-proven sarcoidosis patients. Potentially reflecting the multifactorial pathogenesis of PH in sarcoidosis, incorporation of other PFT variables failed to enhance screening for PH in this population. (Sarcoidosis Vasc Diffuse Lung Dis 2018; 35: 308-316)

Effect of asiaticoside on endothelial cells in hypoxia‑induced pulmonary hypertension.

Pulmonary hypertension (PH) is a chronic progressive disease with limited treatment options. The exact etiology and pathogenesis of PH remain to be elucidated, however there is novel evidence that implicates abnormal endothelial cells (ECs) apoptosis and dysfunction of ECs to be involved in the initiation of PH. Asiaticoside (AS) is a saponin monomer extracted from a medicinal plant called Centella asiatica, which had a preventing effect of hypoxia-induced pulmonary hypertension (hypoxic PH) by blocking transforming growth factor-β1/SMAD family member 2/3 signaling in our previous study. The present study demonstrated that AS can prevent the development of hypoxic PH and reverse the established hypoxic PH. AS may activate the nitric oxide (NO)-mediated signals by enhancing the phosphorylation of serine/threonine-specific protein kinase/eNOS, thus promoting NO production, and prevent ECs from hypoxia-induced apoptosis. All these findings imply that AS may be a potential therapeutic option for hypoxic PH patients due to its effect on the vitality and function of endothelial cells.

PPARγ Regulates Mitochondrial Structure and Function and Human Pulmonary Artery Smooth Muscle Cell Proliferation.

Pulmonary hypertension (PH) is a progressive disorder that causes significant morbidity and mortality despite existing therapies. PH pathogenesis is characterized by metabolic derangements that increase pulmonary artery smooth muscle cell (PASMC) proliferation and vascular remodeling. PH-associated decreases in peroxisome proliferator-activated receptor γ (PPARγ) stimulate PASMC proliferation, and PPARγ in coordination with PPARγ coactivator 1α (PGC1α) regulates mitochondrial gene expression and biogenesis. To further examine the impact of decreases in PPARγ expression on human PASMC (HPASMC) mitochondrial function, we hypothesized that depletion of either PPARγ or PGC1α perturbs mitochondrial structure and function to stimulate PASMC proliferation. To test this hypothesis, HPASMCs were exposed to hypoxia and treated pharmacologically with the PPARγ antagonist GW9662 or with siRNA against PPARγ or PGC1α for 72 hours. HPASMC proliferation (cell counting), target mRNA levels (qRT-PCR), target protein levels (Western blotting), mitochondria-derived H2O2 (confocal immunofluorescence), mitochondrial mass and fragmentation, and mitochondrial bioenergetic profiling were determined. Hypoxia or knockdown of either PPARγ or PGC1α increased HPASMC proliferation, enhanced mitochondria-derived H2O2, decreased mitochondrial mass, stimulated mitochondrial fragmentation, and impaired mitochondrial bioenergetics. Taken together, these findings provide novel evidence that loss of PPARγ diminishes PGC1α and stimulates derangements in mitochondrial structure and function that cause PASMC proliferation. Overexpression of PGC1α reversed hypoxia-induced HPASMC derangements. This study identifies additional mechanistic underpinnings of PH, and provides support for the notion of activating PPARγ as a novel therapeutic strategy in PH.

Micro-RNA-1 is decreased by hypoxia and contributes to the development of pulmonary vascular remodeling via regulation of sphingosine kinase 1.

Sphingosine kinase 1 (SphK1) upregulation is associated with pathologic pulmonary vascular remodeling in pulmonary arterial hypertension (PAH), but the mechanisms controlling its expression are undefined. In this study, we sought to characterize the regulation of SphK1 expression by micro-RNAs (miRs). In silico analysis of the SphK1 3'-untranslated region identified several putative miR binding sites, with miR-1-3p (miR-1) being the most highly predicted target. Therefore we further investigated the role of miR-1 in modulating SphK1 expression and characterized its effects on the phenotype of pulmonary artery smooth muscle cells (PASMCs) and the development of experimental pulmonary hypertension in vivo. Our results demonstrate that miR-1 is downregulated by hypoxia in PASMCs and can directly inhibit SphK1 expression. Overexpression of miR-1 in human PASMCs inhibits basal and hypoxia-induced proliferation and migration. Human PASMCs isolated from PAH patients exhibit reduced miR-1 expression. We also demonstrate that miR-1 is downregulated in mouse lung tissues during experimental hypoxia-mediated pulmonary hypertension (HPH), consistent with upregulation of SphK1. Furthermore, administration of miR-1 mimics in vivo prevented the development of HPH in mice and attenuated induction of SphK1 in PASMCs. These data reveal the importance of miR-1 in regulating SphK1 expression during hypoxia in PASMCs. A pivotal role is played by miR-1 in pulmonary vascular remodeling, including PASMC proliferation and migration, and its overexpression protects from the development of HPH in vivo. These studies improve our understanding of the molecular mechanisms underlying the pathogenesis of pulmonary hypertension.

Role of cigarette smoke in the pathogenesis of pulmonary hypertension

Role of cigarette smoke in the pathogenesis of pulmonary hypertension

Gender disparities in pulmonary hypertension at a tertiary centre in Cameroon.

Pulmonary hypertension (PH) is a potent cause of heart failure and has been little investigated in the African setting. To investigate the effects of gender on the clinical presentation, echocardiographic features and outcomes of patients with PH in Douala, Cameroon. A prospective cohort study was conducted from March 2012 to December 2013 as part of the Pan African Pulmonary Hypertension Cohort study. PH was diagnosed by echocardiography and defined as a right ventricular systolic pressure >35 mmHg in the absence of acute right heart failure. Patients were followed up for a maximum of 12 months for primary endpoint mortality. In total, 130 patients with PH were recruited; 71 (54.6%) were women. The median age was 59.2 years for men and 58.3 years for women (p=0.76). Active smoking and alcohol use were more frequent in men than women (both p<0.001), but women had greater exposure to indoor cooking fumes than men (p<0.001). Previous tuberculosis infection (11.3% v. 1.7%) and S3 gallop rhythm (30.9% v. 11.9%) were more common in women (both p<0.03). Women had a significantly higher mean systolic blood pressure (134 mmHg v. 125 mmHg; p=0.04) and pulse pressure (53.8 mmHg v. 44.9 mmHg; p=0.01) and a lower mean haemoglobin concentration (10.4 g/dL v. 12.4 g/dL; p<0.05) compared with men. Echocardiographic left ventricular (LV) systolic dysfunction was more frequent in men: mean LV ejection fraction 42.6% v. 51.5% (p=0.01) and mean fractional shortening 21.4% v. 28.6% (p=0.01). The overall mortality rate was 20.3%, and rates were similar in the two groups (Kaplan-Meier log rank 1.1; p=0.30). Despite differences in baseline characteristics including cardiovascular risk factors, mortality rates on follow-up were similar in men and women in this study. However, these different baseline characteristics probably suggest differences in the pathogenesis of PH in men and women in our setting that need further investigation.

Twist1 in Hypoxia-induced Pulmonary Hypertension through Transforming Growth Factor-β-Smad Signaling.

Pulmonary hypertension (PH) is a devastating pulmonary vascular disease characterized by aberrant muscularization of the normally nonmuscularized distal pulmonary arterioles. The expression of the transcription factor, Twist1, increases in the lungs of patients with pulmonary arterial hypertension. However, the mechanisms by which Twist1 controls the pathogenesis of PH remain unclear. It is becoming clear that endothelial-to-mesenchymal transition (EndMT) contributes to various vascular pathologies, including PH; Twist1 is known to mediate EndMT. In this report, we demonstrate that Twist1 overexpression increases transforming growth factor (TGF) β receptor2 (TGF-βR2) expression and Smad2 phosphorylation, and induces EndMT in cultured human pulmonary arterial endothelial (HPAE) cells, whereas a mutant construct of Twist1 at the serine 42 residue (Twist1S42A) fails to induce EndMT. We also implanted fibrin gel supplemented with HPAE cells on the mouse lung, and found that these HPAE cells form vascular structures and that Twist1-overexpressing HPAE cells undergo EndMT in the gel, whereas Twist1S42A-overexpressing cells do not. Furthermore, hypoxia-induced EndMT is inhibited in endothelial cells overexpressing Twist1S42A mutant construct in vitro. Hypoxia-induced accumulation of α-smooth muscle actin-positive cells in the pulmonary arterioles is attenuated in Tie2-specific Twist1 conditional knockout mice in vivo. These findings suggest that Twist1 serine 42 phosphorylation plays a key role in EndMT through TGF-β signaling and that modulation of Twist1 phosphorylation could be an effective strategy for managing PH.

MicroRNA-424(322) as a new marker of disease progression in pulmonary arterial hypertension and its role in right ventricular hypertrophy by targeting SMURF1.

MicroRNAs (miRNAs) have been implicated in the pathogenesis of pulmonary hypertension (PH), a multifactorial and progressive condition associated with an increased afterload of the right ventricle leading to heart failure and death. The main aim of this study was to correlate the levels of miR-424(322) with the severity and prognosis of PH and with right ventricle hypertrophy progression. Additionally, we intended to evaluate the mechanisms and signalling pathways whereby miR-424(322) secreted by pulmonary arterial endothelial cells (PAECs) impacts cardiomyocytes. Using quantitative real-time PCR, we showed that the levels of circulating miR-424(322) are higher in PH patients when compared with healthy subjects. Moreover, we found that miR-424(322) levels correlated with more severe symptoms and haemodynamics. In the subgroup of Eisenmenger syndrome patients, miR-424(322) displayed independent prognostic value. Furthermore, we demonstrated that miR-424(322) targets SMURF1, through which it sustains bone morphogenetic protein receptor 2 signalling. Moreover, we showed that hypoxia induces the secretion of miR-424(322) by PAECs, which after being taken up by cardiomyocytes leads to down-regulation of SMURF1. In the monocrotaline rat model of PH, we found an association between circulating miR-424(322) levels and the stage of right ventricle hypertrophy, as well as an inverse correlation between miR-424(322) and SMURF1 levels in the hypertrophied right ventricle. This study shows that miR-424(322) has diagnostic and prognostic value in PH patients, correlating with markers of disease severity. Additionally, miR-424(322) can target proteins with a direct effect on heart function, suggesting that this miRNA can act as a messenger linking pulmonary vascular disease and right ventricle hypertrophy.

Endothelial to haematopoietic transition contributes to pulmonary arterial hypertension.

The pathogenic mechanisms of pulmonary arterial hypertension (PAH) remain unclear, but involve dysfunctional endothelial cells (ECs), dysregulated immunity and inflammation in the lung. We hypothesize that a developmental process called endothelial to haematopoietic transition (EHT) contributes to the pathogenesis of pulmonary hypertension (PH). We sought to determine the role of EHT in mouse models of PH, to characterize specific cell types involved in this process, and to identify potential therapeutic targets to prevent disease progression. When transgenic mice with fluorescence protein ZsGreen-labelled ECs were treated with Sugen/hypoxia (Su/Hx) combination to induce PH, the percentage of ZsGreen+ haematopoietic cells in the peripheral blood, primarily of myeloid lineage, significantly increased. This occurrence coincided with the depletion of bone marrow (BM) ZsGreen+ c-kit+ CD45- endothelial progenitor cells (EPCs), which could be detected accumulating in the lung upon PH-induction. Quantitative RT-PCR based gene array analysis showed that key transcription factors driving haematopoiesis were expressed in these EPCs. When transplanted into lethally irradiated recipient mice, the BM-derived EPCs exhibited long-term engraftment and haematopoietic differentiation capability, indicating these EPCs are haemogenic in nature. Specific inhibition of the critical haematopoietic transcription factor Runx1 blocked the EHT process in vivo, prevented egress of the BM EPCs and ultimately attenuated PH progression in Su/Hx- as well as in monocrotaline-induced PH in mice. Thus, myeloid-skewed EHT promotes the development of PH and inhibition of this process prevents disease progression in mouse models of PH. Furthermore, high levels of Runx1 expression were found in circulating CD34+ CD133+ EPCs isolated from peripheral blood of patients with PH, supporting the clinical relevance of our proposed mechanism of EHT. EHT contributes to the pathogenesis of PAH. The transcription factor Runx1 may be a novel therapeutic target for the treatment of PAH.

Myeloid-derived Suppressor Cells Are Necessary for Development of Pulmonary Hypertension.

Pulmonary hypertension (PH) complicates the care of patients with chronic lung disease, such as idiopathic pulmonary fibrosis (IPF), resulting in a significant increase in morbidity and mortality. Disease pathogenesis is orchestrated by unidentified myeloid-derived cells. We used murine models of PH and pulmonary fibrosis to study the role of circulating myeloid cells in disease pathogenesis and prevention. We administered clodronate liposomes to bleomycin-treated wild-type mice to induce pulmonary fibrosis and PH with a resulting increase in circulating bone marrow-derived cells. We discovered that a population of C-X-C motif chemokine receptor (CXCR) 2+ myeloid-derived suppressor cells (MDSCs), granulocytic subset (G-MDSC), is associated with severe PH in mice. Pulmonary pressures worsened despite improvement in bleomycin-induced pulmonary fibrosis. PH was attenuated by CXCR2 inhibition, with antagonist SB 225002, through decreasing G-MDSC recruitment to the lung. Molecular and cellular analysis of clinical patient samples confirmed a role for elevated MDSCs in IPF and IPF with PH. These data show that MDSCs play a key role in PH pathogenesis and that G-MDSC trafficking to the lung, through chemokine receptor CXCR2, increases development of PH in multiple murine models. Furthermore, we demonstrate pathology similar to the preclinical models in IPF with lung and blood samples from patients with PH, suggesting a potential role for CXCR2 inhibitor use in this patient population. These findings are significant, as there are currently no approved disease-specific therapies for patients with PH complicating IPF.