Antiproliferative effect of selexipag active metabolite MRE-269 on pulmonary arterial smooth muscle cells from patients with chronic thromboembolic pulmonary hypertension.

Chronic thromboembolic pulmonary hypertension (CTEPH) is a group 4 pulmonary hypertension (PH) characterized by nonresolving thromboembolism in the central pulmonary artery and vascular occlusion in the proximal and distal pulmonary artery. Medical therapy is chosen for patients who are ineligible for pulmonary endarterectomy or balloon pulmonary angioplasty or who have symptomatic residual PH after surgery or intervention. Selexipag, an oral prostacyclin receptor agonist and potent vasodilator, was approved for CTEPH in Japan in 2021. To evaluate the pharmacological effect of selexipag on vascular occlusion in CTEPH, we examined how its active metabolite MRE-269 affects platelet-derived growth factor-stimulated pulmonary arterial smooth muscle cells (PASMCs) from CTEPH patients. MRE-269 showed a more potent antiproliferative effect on PASMCs from CTEPH patients than on those from normal subjects. DNA-binding protein inhibitor (ID) genes ID1 and ID3 were found by RNA sequencing and real-time quantitative polymerase chain reaction to be expressed at lower levels in PASMCs from CTEPH patients than in those from normal subjects and were upregulated by MRE-269 treatment. ID1 and ID3 upregulation by MRE-269 was blocked by co-incubation with a prostacyclin receptor antagonist, and ID1 knockdown by small interfering RNA transfection attenuated the antiproliferative effect of MRE-269. ID signaling may be involved in the antiproliferative effect of MRE-269 on PASMCs. This is the first study to demonstrate the pharmacological effects on PASMCs from CTEPH patients of a drug approved for the treatment of CTEPH. Both the vasodilatory and the antiproliferative effect of MRE-269 may contribute to the efficacy of selexipag in CTEPH.

Chronic thromboembolic pulmonary hypertension in Austria and Japan.

OBJECTIVE: Chronic thromboembolic pulmonary hypertension (CTEPH) is characterized by one or more of the following features: intraluminal thrombus organization, fibrous stenosis, and complete obliteration of major pulmonary arteries, amenable to significant improvement by pulmonary endarterectomy (PEA) or balloon pulmonary angioplasty, and medical treatments with vasodilators. Because treatment practices and outcomes differ in Europe versus Japan, we hypothesized that population-based characteristics of pulmonary vascular phenotypes may exist in Austria compared with Japan. The objectives of this study were to analyze clinical characteristics, hemodynamics, and PEA specimens in consecutive patients with CTEPH undergoing PEA in Austria and Japan. METHODS: Clinical features, hemodynamics, and PEA specimens were collected and analyzed in patients with CTEPH undergoing PEA, and clinical features and hemodynamics were collected and analyzed in patients with not-operated CTEPH and in patients with nonthromboembolic pulmonary arterial hypertension. RESULTS: Apart from key differences between Austrian and Japanese patients regarding body size, lung function vital capacity, cardiac output, and serum high-density lipoprotein levels, Austrian patients were more likely to be obese, have greater hematocrits and greater white blood cells counts, greater C-reactive protein levels, and significantly elevated serum myeloperoxidase levels compared with Japanese patients with CTEPH. Analysis of PEA specimens demonstrated more proximal thrombus and more fresh red thrombus components in Austrian patients. CONCLUSIONS: This study documents an inflammatory thrombotic phenotype in Austrian compared with Japanese patients with CTEPH that may be a determinant of differential treatment outcomes.

Use of vasodilators for the treatment of pulmonary veno-occlusive disease and pulmonary capillary hemangiomatosis: A systematic review.

BACKGROUND: There are several medications available to treat pulmonary arterial hypertension (PAH): PAH-targeted drugs. However, in patients with pulmonary veno-occlusive disease and pulmonary capillary hemangiomatosis (PVOD/PCH), rare diseases that cause pulmonary hypertension, the effectiveness and safety of vasodilators, including PAH-targeted drugs, are unclear. METHODS: We searched English-language publications listed in three electronic databases (PubMed, Cochrane Library, and the Japan Medical Abstracts Society). Reports with efficacy outcomes (survival, improvement in 6-minute walk distance, and pulmonary vascular resistance) and data on development of pulmonary edema after administration of vasodilators to patients with PVOD/PCH were selected (1966 to August 2015). RESULTS: We identified 20 reports that met our criteria. No randomized controlled or prospective controlled studies were reported. The survival time ranged from 71 minutes to 4 years or more after initiation of vasodilators. Most of the reported cases showed an improvement in the 6-minute walk distance and pulmonary vascular resistance. Pulmonary edema was reported in 15 articles, some cases of which were lethal. CONCLUSIONS: The present study demonstrates the potential efficacy and difficulties in the use of vasodilators in patients with PVOD/PCH; however, drawing a firm conclusion was difficult because of the lack of randomized controlled trials. Further research is needed to ascertain if vasodilator use is beneficial and safe in patients with PVOD/PCH.

Vascular Injury Is a Major Cause of Lung Injury After Balloon Pulmonary Angioplasty in Patients With Chronic Thromboembolic Pulmonary Hypertension.

BACKGROUND: Balloon pulmonary angioplasty (BPA) has become an alternative treatment for inoperable patients with chronic thromboembolic pulmonary hypertension. Lung injury (LI) is a major complication of BPA and may attenuate the benefits of BPA. Therefore, we conducted a retrospective study to evaluate the association between patient and procedural characteristics and LI in patients with chronic thromboembolic pulmonary hypertension. METHODS AND RESULTS: We reviewed 76 patients with chronic thromboembolic pulmonary hypertension who underwent BPA and multidetector computed tomography scanning pre- and post-BPA procedures. We performed BPA on 1247 vessels during 297 BPA procedures and reviewed 594 multidetector computed tomography scans. By comparing pre- and post-BPA multidetector computed tomography images, we diagnosed LI as follows: newly appeared ground-glass opacity, consolidation, and pleural effusion. LI was detected using multidetector computed tomography scans during 138 procedures (47%), and mechanical ventilation was required during 40 procedures (13%). Angiographic findings of extravasation with or without simultaneous clinical symptoms (BPA-related vascular injury) occurred during 50 procedures (17%). In mixed-effect logistic regression models, the BPA-related vascular injury was an independent predictor of LI after BPA, odds ratio, 20.1 (6.43-63.1). High mean pulmonary artery pressure before BPA procedure and BPA-related vascular injury were independent predictors of mechanical ventilation after BPA, odds ratio, 1.13 (1.03-1.24) and 10.8 (3.77-30.9), respectively. CONCLUSIONS: Vascular injury during BPA could be a triggering factor of LI after BPA, and its severity could be exacerbated by a high pulmonary artery pressure.

Clinical prediction score for identifying patients with pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis.

BACKGROUND: Pulmonary veno-occlusive disease (PVOD) and pulmonary capillary hemangiomatosis (PCH) are rare causes of pulmonary hypertension. Although diagnosis is based on pathological findings, an early diagnosis is crucial because of poor prognosis compared to other types of pulmonary hypertension. Furthermore, vasodilators may cause fatal pulmonary edema in patients with PVOD/PCH. This study aimed to identify specific characteristics for patients with PVOD/PCH to clinically diagnose PVOD/PCH. METHODS: Clinical data were obtained at baseline and were compared between 19 patients with PVOD/PCH and 55 patients with idiopathic/heritable pulmonary arterial hypertension. Receiver operating characteristic analyses were used to determine characteristics specific for patients with PVOD/PCH and a scoring system to diagnose PVOD/PCH was developed. RESULTS: Patients with PVOD/PCH had a smoking history and were predominantly male. Six-minute walk distance was significantly lower and oxygen desaturation was severe during the walk. Diffusion capacity of carbon monoxide was significantly low. Radiological findings included ground glass opacity on chest high-resolution computed tomography (CT) in all patients with PVOD/PCH, and thickened septal lines in 90% of the patients. Lung perfusion scintigraphy showed defect in >70% of the patients. Pulmonary edema after initiation of vasodilation therapy was frequently observed in PVOD/PCH patients. Based on these results, we identified nine important clinical characteristics and a novel scoring system was designed to clinically diagnose PVOD/PCH: male sex, smoking history, 6-minute walk distance<285m, minimum SpO2<92% during the 6-minute walk test, %DLco<34%, ground glass opacity and thickening of the interlobular septa in high-resolution CT, defects in the perfusion lung scan, and pulmonary edema due to vasodilators. Score≥5 points had 95% sensitivity and 98% specificity to predict PVOD/PCH (area under the curve: 0.991; 95% CI: 0.976-1.000). CONCLUSIONS: Our novel prediction rule for diagnosing PVOD/PCH may offer an early clinical diagnosis of these diseases.

Balloon Pulmonary Angioplasty for Chronic Thromboembolic Pulmonary Hypertension: Results of a Multicenter Registry.

BACKGROUND: Balloon pulmonary angioplasty (BPA) is an alternative therapy for patients with chronic thromboembolic pulmonary hypertension who are ineligible for pulmonary endarterectomy-the standard therapy. Currently, most reported results of BPA are from relatively small cohorts treated at single centers. The present study evaluated the safety and efficacy of BPA for chronic thromboembolic pulmonary hypertension based on a multicenter registry. METHODS AND RESULTS: A total of 308 patients (62 men and 246 women; mean age, 61 years) underwent 1408 procedures at 7 institutions in Japan. Data were retrospectively reviewed to evaluate clinical outcome and complications. Hemodynamics were significantly improved in 249 patients in whom BPA was terminated, most often because of improvement in mean pulmonary arterial pressure or symptomatic improvement after 1154 procedures. In 196 patients who underwent follow-up right heart catheterization, improvement of hemodynamic parameters was maintained. Mean pulmonary arterial pressure decreased from 43.2±11.0 to 24.3±6.4 mm Hg after final BPA and 22.5±5.4 mm Hg at follow-up, with significant reduction of concomitant use of pulmonary hypertension-targeted therapy and oxygen supplementation. Complications occurred in 511 (36.3%), including pulmonary injury (17.8%), hemoptysis (14.0%), and pulmonary artery perforation (2.9%). Twelve patients (3.9%) died during follow-up, including 8 patients who died within 30 days after BPA. The leading causes of death were right heart failure, multiorgan failure, and sepsis. Overall survival was 96.8% (95% confidence interval, 93.7%-98.4%) at 1 and 2 years and 94.5% (95% confidence interval, 89.3%-97.3%) at 3 years, respectively, after the initial BPA procedure for all 308 patients. CONCLUSIONS: This multicenter registry suggested improved hemodynamic results after BPA. Complication rates were high, but overall survival was comparable with pulmonary endarterectomy. BPA may be an important therapeutic option in patients with chronic thromboembolic pulmonary hypertension.

Efficacy and safety of long-term imatinib therapy for patients with pulmonary veno-occlusive disease and pulmonary capillary hemangiomatosis.

BACKGROUND: Pulmonary veno-occlusive disease (PVOD) and pulmonary capillary hemangiomatosis (PCH) are categorized as Group 1' in the clinical classification of pulmonary hypertension. No medical therapy has been proven to be effective in patients with PVOD/PCH. Imatinib is a molecular targeted drug and was expected to be effective in patients with pulmonary arterial hypertension. We evaluated its efficacy and safety in patients with PVOD/PCH. METHODS: In the present observational study, 9 patients with PVOD/PCH received imatinib. Clinical data including exercise capacity and hemodynamics at baseline and at follow-up were compared. Survival rate of patients treated with imatinib was compared to those of 7 patients who did not treated with imatinib. RESULTS: Imatinib was prescribed at doses of 100-400 mg/day and was well-tolerated. At follow-up, World Health Organization functional class and brain natriuretic peptide levels significantly improved. Mean pulmonary arterial pressure was significantly reduced (from 56.8 ± 8.3 to 43.7 ± 9.0 mmHg) with preserved cardiac index. Patients were treated with imatinib for 797.2 ± 487.0 days. Seven patients (77.8%) died and 2 patients (22.2%) underwent lung transplantation. Mean survival time in patients treated with imatinib therapy was 1493.7 ± 196.3 days (95% confidence interval, 1108.9-1878.5 days), significantly longer than those without imatinib treatment (713.0 ± 258.1 days, log-rank test, P = 0.04). CONCLUSIONS: Imatinib improved exercise capacity, hemodynamics and survival in patients with PVOD/PCH. In patients with PVOD/PCH, who have no effective medical therapy available, imatinib might function as a bridge to lung transplantation, and may become a potential therapeutic option to improve their survival.

Fluidic Culture and Analysis of Pulmonary Artery Smooth Muscle Cells for the Study of Pulmonary Hypertension.

There is an urgent need to develop novel in-vitro models to mimic the disease conditions in pulmonary hypertension (PH). We developed a microfluidic cell culture device for PH studies that withstood high shear stress. Techniques were also developed for cell recovery from the microchannel and mRNA isolation from the collected cells. Using this device, we found that shear stress caused a 7.5-fold increase in the transcription levels of a PH-related molecule, Cyclin D1.

Epoprostenol Therapy for Pulmonary Arterial Hypertension.

Pulmonary arterial hypertension (PAH) is characterized by elevation of pulmonary artery pressure caused by pulmonary vasoconstriction and vascular remodeling, which leads to right heart failure and death. Epoprostenol (prostaglandin I2) has a potent short-acting vasodilator property, and intravenous continuous epoprostenol is therefore used for treatment of PAH. Here we review evidence for the usefulness of intravenous continuous epoprostenol therapy in patients with PAH. Epoprostenol therapy is effective in idiopathic PAH patients and in patients with PAH associated with connective tissue disease, portal hypertension or congenital heart diseases, but it is not effective in patients with pulmonary veno-occlusive disease or pulmonary capillary hemangiomatosis. High-dose epoprostenol therapy markedly improved hemodynamics in some patients with PAH, possibly due to reverse remodeling of pulmonary arteries. This therapy has several side effects and complications such as headache, hypotension and catheter-related infections. Intravenous continuous epoprostenol is an effective treatment, but there are still some problems to be resolved.

Pulmonary microvascular remodeling after balloon pulmonary angioplasty in a patient with chronic thromboembolic pulmonary hypertension.

We herein report a case of peripheral type chronic thromboembolic pulmonary hypertension treated with medical therapy and subsequent balloon pulmonary angioplasty (BPA). After a series of BPA procedures, the patient's hemodynamics almost completely normalized. The patient was later diagnosed with lung carcinoma, and the vasculature of the resected lung demonstrated intimal thickening and luminal stenosis in the pulmonary arteries in both the areas where BPA was performed and not performed, in spite of a marked reduction in pulmonary arterial pressure. The present case is the first report on the histology of the pulmonary vasculature following BPA.

Imatinib is partially effective for the treatment of pulmonary capillary hemangiomatosis.

A 43-year-old man presented with dyspnea on exertion. Right heart catheterization demonstrated pulmonary arterial hypertension (PAH). He was treated with bosentan, sildenafil and intravenous epoprostenol. Despite the administration of such intensive therapy, the patient's condition deteriorated to a World Health Organization functional class (WHO-FC) of IV. He participated in a clinical trial of imatinib for PAH. After three months of treatment with imatinib, the chest X-ray and echocardiography findings improved, and the WHO-FC class was III. One year after, however, the PAH worsened again, and the patient died 2.6 years after the first diagnosis. At autopsy, patchy capillary proliferation was observed in the lungs. The definitive diagnosis was pulmonary capillary hemangiomatosis.

Pulmonary tumor thrombotic microangiopathy with circulatory failure treated with imatinib.

Pulmonary tumor thrombotic microangiopathy is a lethal, yet difficult to diagnose, complication of gastrointestinal carcinoma. Even if properly diagnosed, there is no treatment, especially after a circulatory collapse. We herein report a case of pulmonary tumor thrombotic microangiopathy with circulatory failure due to pulmonary hypertension. The patient was temporarily successfully treated with imatinib, an inhibitor of the platelet-derived growth factor receptor. Pulmonary hypertension was dramatically ameliorated and the patient was able to be weaned from percutaneous cardiopulmonary support within 20 days of treatment. Imatinib may be effective for ameliorating pulmonary hypertension that is caused by pulmonary tumor thrombotic microangiopathy.

Different sizes of centrilobular ground-glass opacities in chest high-resolution computed tomography of patients with pulmonary veno-occlusive disease and patients with pulmonary capillary hemangiomatosis.

BACKGROUND: Centrilobular ground-glass opacity (GGO) is one of the characteristic findings in chest high-resolution computed tomography (HRCT) of patients with pulmonary veno-occlusive disease (PVOD) and patients with pulmonary capillary hemangiomatosis (PCH). However, clinical differential diagnosis of these two diseases is difficult and has not been established. In order to clarify their differences, we compared the sizes of GGOs in chest HRCT and the sizes of capillary assemblies in pulmonary vascular casts between patients diagnosed pathologically with PVOD and PCH. METHODS: We evaluated chest HRCT images for four patients with idiopathic pulmonary arterial hypertension (IPAH), three patients with PVOD and three patients with PCH, and we evaluated pulmonary vascular casts of lung tissues obtained from those patients at lung transplantation or autopsy. RESULTS: Centrilobular GGOs in chest HRCT were observed in patients with PVOD and patients with PCH but not in patients with IPAH. We measured the longest diameter of the GGOs. The size of centrilobular GGOs was significantly larger in patients with PCH than in patients with PVOD (5.60±1.43 mm versus 2.51±0.79 mm, P<.01). We succeeded in visualization of the 3-dimensional structures of pulmonary capillary vessels obtained from the same patients with PVOD and PCH undergoing lung transplantation or autopsy and measured the diameters of capillary assemblies. The longest diameter of capillary assemblies was also significantly larger in patients with PCH than in patients with PVOD (5.44±1.71 mm versus 3.07±1.07 mm, P<.01). CONCLUSION: Measurement of the sizes of centrilobular GGOs in HRCT is a simple and useful method for clinical differential diagnosis of PVOD and PCH.

Prostaglandin I2 induces apoptosis via upregulation of Fas ligand in pulmonary artery smooth muscle cells from patients with idiopathic pulmonary arterial hypertension.

BACKGROUND: Pulmonary vascular remodeling with idiopathic pulmonary arterial hypertension (IPAH) is associated with impaired apoptosis of pulmonary artery smooth muscle cells (PASMCs). We have reported that high-dose prostaglandin I2 (PGI2) therapy markedly improved hemodynamics in IPAH patients. The therapy is thought to reverse vascular remodeling, though the mechanism is unclear. The aim of this study is to assess proapoptotic effects of PGI2 on PASMCs obtained from IPAH patients. METHODS: We investigated proapoptotic effects of PGI2 in PAH-PASMCs by TUNEL assays, caspase-3,-7 assays and transmission electron microscopy. We examined the expression of Fas ligand (FasL), an apoptosis-inducing member of the TNF cytokine family, in PAH-PASMCs. We measured the serum FasL levels in IPAH patients treated with PGI2. RESULTS: TUNEL-positive, caspase-3, 7-active cells and fragmentation of the nucleus were detected in PAH-PASMCs treated with PGI2. The percentage of apoptotic cells induced by PGI2 at a high concentration was higher than that induced by PGI2 at a low concentration. PCR-array analysis revealed that PGI2 upregulated the FasL gene in PAH-PASMCs, and we measured the FasL expression by quantitative RT-PCR and Western blotting. PGI2 significantly increased the mRNA level of FasL by 3.98 fold and the protein level of FasL by 1.70 fold. An IP receptor antagonist inhibited the induction of apoptosis, elevation of cyclic AMP and upregulation of FasL by PGI2. Serum FasL level had a significant positive correlation with PGI2 dose in IPAH patients treated with PGI2. CONCLUSIONS: PGI2 has proapoptotic effects on PAH-PASMCs via the IP receptor and upregulation of FasL.

Safety and efficacy of epoprostenol therapy in pulmonary veno-occlusive disease and pulmonary capillary hemangiomatosis.

BACKGROUND: Pulmonary veno-occlusive disease (PVOD) and pulmonary capillary hemangiomatosis (PCH) are rare causes of pulmonary hypertension. There is no proven medical therapy to treat these diseases, and lung transplantation is thought to be the only cure. Administration of vasodilators including epoprostenol sometimes causes massive pulmonary edema and could be fatal in these patients. METHODS AND RESULTS: Eight patients were treated with epoprostenol for 387.3±116.3 days (range, 102-1,063 days), who were finally diagnosed with PVOD or PCH by pathological examination. The maximum dose of epoprostenol given was 55.3±10.7 ng·kg(-1)·min(-1) (range, 21.0-110.5 ng·kg(-1)·min(-1)). With careful management, epoprostenol therapy significantly improved the 6-min walk distance (97.5±39.2 to 329.4±34.6 m, P<0.001) and plasma brain natriuretic peptide levels (381.3±136.8 to 55.2±14.4 pg/ml, P<0.05). The cardiac index significantly increased from 2.1±0.1 to 2.9±0.3 L·min(-1)·m(-2) (P<0.05). However, pulmonary artery pressure and pulmonary vascular resistance were not significantly reduced. For 4 patients, epoprostenol therapy acted as a bridge to lung transplantation. For the other patients who had no chance to undergo lung transplantation, epoprostenol therapy was applied for 528.0±216.6 days and the maximum dose was 63.9±19.0 ng·kg(-1)·min(-1). CONCLUSIONS: This study data suggest that cautious application of epoprostenol can be considered as a therapeutic option in patients with PVOD and PCH.

Pro-apoptotic effects of imatinib on PDGF-stimulated pulmonary artery smooth muscle cells from patients with idiopathic pulmonary arterial hypertension.

BACKGROUND: Remodeling of the pulmonary artery by an inappropriate increase of pulmonary artery smooth muscle cells (PASMCs) is problematic in the treatment of idiopathic pulmonary arterial hypertension (IPAH). Effective treatment that achieves reverse remodeling is required. The aim of this study was to assess the pro-apoptotic effects of imatinib, a platelet-derived growth factor (PDGF)-receptor tyrosine kinase inhibitor, on PASMCs obtained from patients with IPAH. METHODS: PASMCs were obtained from 8 patients with IPAH undergoing lung transplantation. Cellular proliferation was assessed by (3)H-thymidine incorporation. Pro-apoptotic effects of imatinib were examined using TUNEL and caspase-3,7 assays and using transmission electron microscopy. RESULTS: Treatment with imatinib (0.1 to 10 µg/mL) significantly inhibited PDGF-BB (10 ng/mL)-induced proliferation of PASMCs from IPAH patients. Imatinib (1 µg/mL) did not induce apoptosis in quiescent IPAH-PASMCs, but it had a pro-apoptotic effect on IPAH-PASMCs stimulated with PDGF-BB. Imatinib did not induce apoptosis in normal control PASMCs with or without PDGF-BB stimulation. PDGF-BB induced phosphorylation of Akt at 15 min, and Akt phosphorylation was inhibited by imatinib in IPAH-PASMCs. Akt-I-1/2 (1 µmol/L), an Akt inhibitor, in the presence of PDGF-BB significantly increased apoptotic cells compared with the control condition. Thus, Akt-I-1/2 could mimic the effects of imatinib on PASMCs. CONCLUSION: Imatinib has anti-proliferative and pro-apoptotic effects on IPAH-PASMCs stimulated with PDGF. The inhibitory effect of imatinib on Akt phosphorylation induced by PDGF plays an important role in the pro-apoptotic effect.

PDGF enhances store-operated Ca2+ entry by upregulating STIM1/Orai1 via activation of Akt/mTOR in human pulmonary arterial smooth muscle cells.

Platelet-derived growth factor (PDGF) and its receptor are known to be substantially elevated in lung tissues and pulmonary arterial smooth muscle cells (PASMC) isolated from patients and animals with pulmonary arterial hypertension. PDGF has been shown to phosphorylate and activate Akt and mammalian target of rapamycin (mTOR) in PASMC. In this study, we investigated the role of PDGF-mediated activation of Akt signaling in the regulation of cytosolic Ca(2+) concentration and cell proliferation. PDGF activated the Akt/mTOR pathway and, subsequently, enhanced store-operated Ca(2+) entry (SOCE) and cell proliferation in human PASMC. Inhibition of Akt attenuated the increase in cytosolic Ca(2+) concentration due to both SOCE and PASMC proliferation. This effect correlated with a significant downregulation of stromal interacting molecule (STIM) and Orai, proposed molecular correlates for SOCE in many cell types. The data from this study present a novel pathway for the regulation of Ca(2+) signaling and PASMC proliferation involving activation of Akt in response to upregulated expression of PDGF. Targeting this pathway may lead to the development of a novel therapeutic option for the treatment of pulmonary arterial hypertension.