Prevention of progression of pulmonary hypertension by the Nur77 agonist 6-mercaptopurine: role of BMP signalling.

Pulmonary arterial hypertension (PAH) is a progressive fatal disease characterised by abnormal remodelling of pulmonary vessels, leading to increased vascular resistance and right ventricle failure. This abnormal vascular remodelling is associated with endothelial cell dysfunction, increased proliferation of smooth muscle cells, inflammation and impaired bone morphogenetic protein (BMP) signalling. Orphan nuclear receptor Nur77 is a key regulator of proliferation and inflammation in vascular cells, but its role in impaired BMP signalling and vascular remodelling in PAH is unknown.We hypothesised that activation of Nur77 by 6-mercaptopurine (6-MP) would improve PAH by inhibiting endothelial cell dysfunction and vascular remodelling.Nur77 expression is decreased in cultured pulmonary microvascular endothelial cells (MVECs) and lungs of PAH patients. Nur77 significantly increased BMP signalling and strongly decreased proliferation and inflammation in MVECs. In addition, conditioned medium from PAH MVECs overexpressing Nur77 inhibited the growth of healthy smooth muscle cells. Pharmacological activation of Nur77 by 6-MP markedly restored MVEC function by normalising proliferation, inflammation and BMP signalling. Finally, 6-MP prevented and reversed abnormal vascular remodelling and right ventricle hypertrophy in the Sugen/hypoxia rat model of severe angioproliferative PAH.Our data demonstrate that Nur77 is a critical modulator in PAH by inhibiting vascular remodelling and increasing BMP signalling, and activation of Nur77 could be a promising option for the treatment of PAH.

TGF-ß and BMPR2 Signaling in PAH: Two Black Sheep in One Family.

Knowledge pertaining to the involvement of transforming growth factor ß (TGF-ß) and bone morphogenetic protein (BMP) signaling in pulmonary arterial hypertension (PAH) is continuously increasing. There is a growing understanding of the function of individual components involved in the pathway, but a clear synthesis of how these interact in PAH is currently lacking. Most of the focus has been on signaling downstream of BMPR2, but it is imperative to include the role of TGF-ß signaling in PAH. This review gives a state of the art overview of disturbed signaling through the receptors of the TGF-ß family with respect to vascular remodeling and cardiac effects as observed in PAH. Recent (pre)-clinical studies in which these two pathways were targeted will be discussed with an extended view on cardiovascular research fields outside of PAH, indicating novel future perspectives.

p38 MAPK Inhibition Improves Heart Function in Pressure-Loaded Right Ventricular Hypertrophy.

Although p38 mitogen-activated protein kinase (MAPK) is known to have a role in ischemic heart disease and many other diseases, its contribution to the pathobiology of right ventricular (RV) hypertrophy and failure is unclear. Therefore, we sought to investigate the role of p38 MAPK in the pathophysiology of pressure overload-induced RV hypertrophy and failure. The effects of the p38 MAPK inhibitor PH797804 were investigated in mice with RV hypertrophy/failure caused by exposure to hypoxia or pulmonary artery banding. In addition, the effects of p38 MAPK inhibition or depletion (by small interfering RNA) were studied in isolated mouse RV fibroblasts. Echocardiography, invasive hemodynamic measurements, immunohistochemistry, collagen assays, immunofluorescence staining, and Western blotting were performed. Expression of phosphorylated p38 MAPK was markedly increased in mouse and human hypertrophied/failed RVs. In mice, PH797804 improved RV function and inhibited cardiac fibrosis compared with placebo. In isolated RV fibroblasts, p38 MAPK inhibition reduced transforming growth factor (TGF)-ß-induced collagen production as well as stress fiber formation. Moreover, p38 MAPK inhibition/depletion suppressed TGF-ß-induced SMAD2/3 phosphorylation and myocardin-related transcription factor A (MRTF-A) nuclear translocation, and prevented TGF-ß-induced cardiac fibroblast transdifferentiation. Moreover, p38 MAPK inhibition in mice exposed to pulmonary artery banding led to diminished nuclear levels of MRTF-A and phosphorylated SMAD3 in RV fibroblasts. Together, our data indicate that p38 MAPK inhibition significantly improves RV function and inhibits RV fibrosis. Inhibition of p38 MAPK in RV cardiac fibroblasts, resulting in coordinated attenuation of MRTF-A cytoplasmic-nuclear translocation and SMAD3 deactivation, indicates that p38 MAPK signaling contributes to distinct disease-causing mechanisms.

Bone Morphogenetic Protein Receptor Type 2 Mutation in Pulmonary Arterial Hypertension: A View on the Right Ventricle.

BACKGROUND: The effect of a mutation in the bone morphogenetic protein receptor 2 (BMPR2) gene on right ventricular (RV) pressure overload in patients with pulmonary arterial hypertension is unknown. Therefore, we investigated RV function in patients who have pulmonary arterial hypertension with and without the BMPR2 mutation by combining in vivo measurements with molecular and histological analysis of human RV and left ventricular tissue. METHODS AND RESULTS: In total, 95 patients with idiopathic or familial pulmonary arterial hypertension were genetically screened for the presence of a BMPR2 mutation: 28 patients had a BMPR2 mutation, and 67 patients did not have a BMPR2 mutation. In vivo measurements were assessed using right heart catheterization and cardiac MRI. Despite a similar mean pulmonary artery pressure (noncarriers 54±15 versus mutation carriers 55±9 mm Hg) and pulmonary vascular resistance (755 [483-1043] versus 931 [624-1311] dynes·s(-1)·cm(-5)), mutation carriers presented with a more severely compromised RV function (RV ejection fraction: 37.6±12.8% versus 29.0±9%: P<0.05; cardiac index 2.7±0.9 versus 2.2±0.4 L·min(-1)·m(-2)). Differences continued to exist after treatment. To investigate the role of transforming growth factor ß and bone morphogenetic protein receptor II signaling, human RV and left ventricular tissue were studied in controls (n=6), mutation carriers (n=5), and noncarriers (n=11). However, transforming growth factor ß and bone morphogenetic protein receptor II signaling, and hypertrophy, apoptosis, fibrosis, capillary density, inflammation, and cardiac metabolism, as well, were similar between mutation carriers and noncarriers. CONCLUSIONS: Despite a similar afterload, RV function is more severely affected in mutation carriers than in noncarriers. However, these differences cannot be explained by a differential transforming growth factor ß, bone morphogenetic protein receptor II signaling, or cardiac adaptation.

Levosimendan Prevents and Reverts Right Ventricular Failure in Experimental Pulmonary Arterial Hypertension.

BACKGROUND: We investigated whether chronic levosimendan treatment can prevent and revert right ventricular (RV) failure and attenuate pulmonary vascular remodeling in a rat model of pulmonary arterial hypertension (PAH). METHODS AND RESULTS: PAH was induced in rats by exposure to SU5416 and hypoxia (SuHx). The rats were randomized to levosimendan (3 mg·kg·d) initiated before SuHx (n = 10, PREV), levosimendan started 6 weeks after SuHx (n = 12, REV), or vehicle treatment (n = 10, VEH). Healthy control rats received vehicle (n = 10, CONT). Ten weeks after SuHx, RV function was evaluated by echocardiography, magnetic resonance imaging, invasive pressure-volume measurements, histology, and biochemistry. Levosimendan treatment improved cardiac output (VEH vs. PREV 77 ± 7 vs. 137 ± 6 mL/min; P < 0.0001; VEH vs. REV 77 ± 7 vs. 117 ± 10 mL/min; P < 0.01) and decreased RV afterload compared with VEH (VEH vs. PREV 219 ± 33 vs. 132 ± 20 mm Hg/mL; P < 0.05; VEH vs. REV 219 ± 33 vs. 130 ± 11 mm Hg/mL; P < 0.01). In the PREV group, levosimendan restored right ventriculoarterial coupling (VEH vs. PREV 0.9 ± 0.1 vs. 1.8 ± 0.3; P < 0.05) and prevented the development of pulmonary arterial occlusive lesions (VEH vs. PREV 37 ± 7 vs. 15 ± 6% fully occluded lesions; P < 0.05). CONCLUSION: Chronic treatment with levosimendan prevents and reverts the development of RV failure and attenuates pulmonary vascular remodeling in a rat model of PAH.

Delayed Microvascular Shear Adaptation in Pulmonary Arterial Hypertension. Role of Platelet Endothelial Cell Adhesion Molecule-1 Cleavage.

RATIONALE: Altered pulmonary hemodynamics and fluid flow-induced high shear stress (HSS) are characteristic hallmarks in the pathogenesis of pulmonary arterial hypertension (PAH). However, the contribution of HSS to cellular and vascular alterations in PAH is unclear. OBJECTIVES: We hypothesize that failing shear adaptation is an essential part of the endothelial dysfunction in all forms of PAH and tested whether microvascular endothelial cells (MVECs) or pulmonary arterial endothelial cells (PAECs) from lungs of patients with PAH adapt to HSS and if the shear defect partakes in vascular remodeling in vivo. METHODS: PAH MVEC (n = 7) and PAH PAEC (n = 3) morphology, function, protein, and gene expressions were compared with control MVEC (n = 8) under static culture conditions and after 24, 72, and 120 hours of HSS. MEASUREMENTS AND MAIN RESULTS: PAH MVEC showed a significantly delayed morphological shear adaptation (P = 0.03) and evidence of cell injury at sites of nonuniform shear profiles that are critical loci for vascular remodeling in PAH. In clear contrast, PAEC isolated from the same PAH lungs showed no impairments. PAH MVEC gene expression and transcriptional shear activation were not altered but showed significant decreased protein levels (P = 0.02) and disturbed interendothelial localization of the shear sensor platelet endothelial cell adhesion molecule-1 (PECAM-1). The decreased PECAM-1 levels were caused by caspase-mediated cytoplasmic cleavage but not increased cell apoptosis. Caspase blockade stabilized PECAM-1 levels, restored endothelial shear responsiveness in vitro, and attenuated occlusive vascular remodeling in chronically hypoxic Sugen5416-treated rats modeling severe PAH. CONCLUSIONS: Delayed shear adaptation, which promotes shear-induced endothelial injury, is a newly identified dysfunction specific to the microvascular endothelium in PAH. The shear response is normalized on stabilization of PECAM-1, which reverses intimal remodeling in vivo.

Left ventricular outflow tract gradient is associated with reduced capillary density in hypertrophic cardiomyopathy irrespective of genotype.

BACKGROUND: Coronary microvascular dysfunction (CMD) is an important feature of hypertrophic cardiomyopathy (HCM), which contributes negatively to symptoms and long-term outcome. Previous in vivo imaging studies in HCM suggest that left ventricular outflow tract (LVOT) gradient and genetic status are important contributors to CMD. CMD may be caused by reduced capillary density. Here, we investigated whether a reduction in capillary density is related to genetic status or LVOT gradient severity in an in vitro study of HCM cardiac samples. METHODS: Using immunofluorescence microscopy, we analysed capillaries (Cap) and cardiomyocytes (CM) in myectomy specimens from 18 HCM patients with maximum left ventricular (LV) wall thickness ≥15 mm. All subjects exhibited significant LVOT obstruction, necessitating septal myectomy. In addition, control myocardium from the LV septal wall was collected at autopsy of 6 individuals that suffered a noncardiac death. RESULTS: CM area was higher in patients with HCM compared to controls. Capillary density was significantly lower in patients with HCM compared with controls (1425 ± 262 vs. 2543 ± 509 Cap/mm(2) , P < 0·001), as was the number of Cap per CM corrected for CM area (2·2 ± 0·5 vs. 4·2 ± 0·9 Cap/CM area, P < 0·001). Capillary density did not differ between genotype-negative and genotype-positive HCM patients at similar resting LVOT gradients. A significant correlation was present between resting LVOT gradient and CM area (r = 0·73, P < 0·001), capillary density (r = -0·74, P < 0·001) and the number of Cap per CM corrected for CM area (r = -0·82, P < 0·001). CONCLUSIONS: Our data indicate that LVOT gradient, rather than genetic status, is associated with reduced capillary density in HCM.

SuHx rat model: partly reversible pulmonary hypertension and progressive intima obstruction.

The SU5416 combined with hypoxia (SuHx) rat model features angio-obliterative pulmonary hypertension resembling human pulmonary arterial hypertension. Despite increasing use of this model, a comprehensive haemodynamic characterisation in conscious rats has not been reported. We used telemetry to characterise haemodynamic responses in SuHx rats and associated these with serial histology. Right ventricular systolic pressure (RVSP) increased to a mean±sd of 106±7 mmHg in response to SuHx and decreased but remained elevated at 72±8 mmHg upon return to normoxia. Hypoxia-only exposed rats showed a similar initial increase in RVSP, a lower maximum RVSP and near-normalisation of RVSP during subsequent normoxia. Progressive vascular remodelling consisted of a four-fold increase in intima thickness, while only minimal changes in media thickness were found. The circadian range in RVSP provided an accurate longitudinal estimate of vascular remodelling. In conclusion, in SuHx rats, re-exposure to normoxia leads to a partial decrease in pulmonary artery pressure, with persisting hypertension and pulmonary vascular remodelling characterised by progressive intima obstruction.

Imaging the TGFß type I receptor in pulmonary arterial hypertension.

Transforming growth factor ß (TGFß) activity is perturbed in remodelled pulmonary vasculature of patients with pulmonary arterial hypertension (PAH), cancer, vascular diseases and developmental disorders. Inhibition of TGFß, which signals via activin receptor-like kinase 5 (ALK5), prevents progression and development of experimental PAH. The purpose of this study was to assess two ALK5 targeting positron emission tomography (PET) tracers ([11C]LR111 and [18F]EW-7197) for imaging ALK5 in monocrotaline (MCT)- and Sugen/hypoxia (SuHx)-induced PAH. Both tracers were subjected to extensive in vitro and in vivo studies. [11C]LR111 showed the highest metabolic stability, as 46 ± 2% of intact tracer was still present in rat blood plasma after 60 min. In autoradiography experiments, [11C]LR111 showed high ALK5 binding in vitro compared with controls, 3.2 and 1.5 times higher in SuHx and MCT, respectively. In addition, its binding could be blocked by SB431542, an adenosine triphosphate competitive ALK5 kinase inhibitor. However, [18F]EW-7197 showed the best in vivo results. 15 min after injection, uptake was 2.5 and 1.4 times higher in the SuHx and MCT lungs, compared with controls. Therefore, [18F]EW-7197 is a promising PET tracer for ALK5 imaging in PAH.

Altered TGFß/SMAD Signaling in Human and Rat Models of Pulmonary Hypertension: An Old Target Needs Attention.

Recent translational studies highlighted the inhibition of transforming growth factor (TGF)-ß signaling as a promising target to treat pulmonary arterial hypertension (PAH). However, it remains unclear whether alterations in TGF-ß signaling are consistent between PAH patients and animal models. Therefore, we compared TGF-ß signaling in the lungs of PAH patients and rats with experimental PAH induced by monocrotaline (MCT) or SU5416+hypoxia (SuHx). In hereditary PAH (hPAH) patients, there was a moderate increase in both TGFßR2 and pSMAD2/3 protein levels, while these were unaltered in idiopathic PAH (iPAH) patients. Protein levels of TGFßR2 and pSMAD2/3 were locally increased in the pulmonary vasculature of PAH rats under both experimental conditions. Conversely, the protein levels of TGFßR2 and pSMAD2/3 were reduced in SuHx while slightly increased in MCT. mRNA levels of plasminogen activator inhibitor (PAI)-1 were increased only in MCT animals and such an increase was not observed in SuHx rats or in iPAH and hPAH patients. In conclusion, our data demonstrate considerable discrepancies in TGFß-SMAD signaling between iPAH and hPAH patients, as well as between patients and rats with experimental PAH.

Imatinib in patients with severe COVID-19: a randomised, double-blind, placebo-controlled, clinical trial.

BACKGROUND: The major complication of COVID-19 is hypoxaemic respiratory failure from capillary leak and alveolar oedema. Experimental and early clinical data suggest that the tyrosine-kinase inhibitor imatinib reverses pulmonary capillary leak. METHODS: This randomised, double-blind, placebo-controlled, clinical trial was done at 13 academic and non-academic teaching hospitals in the Netherlands. Hospitalised patients (aged ≥18 years) with COVID-19, as confirmed by an RT-PCR test for SARS-CoV-2, requiring supplemental oxygen to maintain a peripheral oxygen saturation of greater than 94% were eligible. Patients were excluded if they had severe pre-existing pulmonary disease, had pre-existing heart failure, had undergone active treatment of a haematological or non-haematological malignancy in the previous 12 months, had cytopenia, or were receiving concomitant treatment with medication known to strongly interact with imatinib. Patients were randomly assigned (1:1) to receive either oral imatinib, given as a loading dose of 800 mg on day 0 followed by 400 mg daily on days 1-9, or placebo. Randomisation was done with a computer-based clinical data management platform with variable block sizes (containing two, four, or six patients), stratified by study site. The primary outcome was time to discontinuation of mechanical ventilation and supplemental oxygen for more than 48 consecutive hours, while being alive during a 28-day period. Secondary outcomes included safety, mortality at 28 days, and the need for invasive mechanical ventilation. All efficacy and safety analyses were done in all randomised patients who had received at least one dose of study medication (modified intention-to-treat population). This study is registered with the EU Clinical Trials Register (EudraCT 2020-001236-10). FINDINGS: Between March 31, 2020, and Jan 4, 2021, 805 patients were screened, of whom 400 were eligible and randomly assigned to the imatinib group (n=204) or the placebo group (n=196). A total of 385 (96%) patients (median age 64 years [IQR 56-73]) received at least one dose of study medication and were included in the modified intention-to-treat population. Time to discontinuation of ventilation and supplemental oxygen for more than 48 h was not significantly different between the two groups (unadjusted hazard ratio [HR] 0·95 [95% CI 0·76-1·20]). At day 28, 15 (8%) of 197 patients had died in the imatinib group compared with 27 (14%) of 188 patients in the placebo group (unadjusted HR 0·51 [0·27-0·95]). After adjusting for baseline imbalances between the two groups (sex, obesity, diabetes, and cardiovascular disease) the HR for mortality was 0·52 (95% CI 0·26-1·05). The HR for mechanical ventilation in the imatinib group compared with the placebo group was 1·07 (0·63-1·80; p=0·81). The median duration of invasive mechanical ventilation was 7 days (IQR 3-13) in the imatinib group compared with 12 days (6-20) in the placebo group (p=0·0080). 91 (46%) of 197 patients in the imatinib group and 82 (44%) of 188 patients in the placebo group had at least one grade 3 or higher adverse event. The safety evaluation revealed no imatinib-associated adverse events. INTERPRETATION: The study failed to meet its primary outcome, as imatinib did not reduce the time to discontinuation of ventilation and supplemental oxygen for more than 48 consecutive hours in patients with COVID-19 requiring supplemental oxygen. The observed effects on survival (although attenuated after adjustment for baseline imbalances) and duration of mechanical ventilation suggest that imatinib might confer clinical benefit in hospitalised patients with COVID-19, but further studies are required to validate these findings. FUNDING: Amsterdam Medical Center Foundation, Nederlandse Organisatie voor Wetenschappelijk Onderzoek/ZonMW, and the European Union Innovative Medicines Initiative 2.

The BMP Receptor 2 in Pulmonary Arterial Hypertension: When and Where the Animal Model Matches the Patient.

Background: Mutations in bone morphogenetic protein receptor type II (BMPR2) are leading to the development of hereditary pulmonary arterial hypertension (PAH). In non-hereditary forms of PAH, perturbations in the transforming growth factor-ß (TGF-ß)/BMP-axis are believed to cause deficient BMPR2 signaling by changes in receptor expression, the activity of the receptor and/or downstream signaling. To date, BMPR2 expression and its activity in the lungs of patients with non-hereditary PAH is poorly characterized. In recent decades, different animal models have been used to understand the role of BMPR2 signaling in PAH pathophysiology. Specifically, the monocrotaline (MCT) and Sugen-Hypoxia (SuHx) models are extensively used in interventional studies to examine if restoring BMPR2 signaling results in PAH disease reversal. While PAH is assumed to develop in patients over months or years, pulmonary hypertension in experimental animal models develops in days or weeks. It is therefore likely that modifications in BMP and TGF-ß signaling in these models do not fully recapitulate those in patients. In order to determine the translational potential of the MCT and SuHx models, we analyzed the BMPR2 expression and activity in the lungs of rats with experimentally induced PAH and compared this to the BMPR2 expression and activity in the lungs of PAH patients. Methods: the BMPR2 expression was analyzed by Western blot analysis and immunofluorescence (IF) microscopy to determine the quantity and localization of the receptor in the lung tissue from normal control subjects and patients with hereditary or idiopathic PAH, as well as in the lungs of control rats and rats with MCT or SuHx-induced PAH. The activation of the BMP pathway was analyzed by determining the level and localization of phosphorylated Smad1/5/8 (pSmad 1/5/8), a downstream mediator of canonical BMPR2 signaling. Results: While BMPR2 and pSmad 1/5/8 expression levels were unaltered in whole lung lysates/homogenates from patients with hereditary and idiopathic PAH, IF analysis showed that BMPR2 and pSmad 1/5/8 levels were markedly decreased in the pulmonary vessels of both PAH patient groups. Whole lung BMPR2 expression was variable in the two PAH rat models, while in both experimental models the expression of BMPR2 in the lung vasculature was increased. However, in the human PAH lungs, the expression of pSmad 1/5/8 was downregulated in the lung vasculature of both experimental models. Conclusion: BMPR2 receptor expression and downstream signaling is reduced in the lung vasculature of patients with idiopathic and hereditary PAH, which cannot be appreciated when using human whole lung lysates. Despite increased BMPR2 expression in the lung vasculature, the MCT and SuHx rat models did develop PAH and impaired downstream BMPR2-Smad signaling similar to our findings in the human lung.

Nintedanib improves cardiac fibrosis but leaves pulmonary vascular remodelling unaltered in experimental pulmonary hypertension.

Aims: Pulmonary arterial hypertension (PAH) is associated with increased levels of circulating growth factors and corresponding receptors such as platelet derived growth factor, fibroblast growth factor and vascular endothelial growth factor. Nintedanib, a tyrosine kinase inhibitor targeting primarily these receptors, is approved for the treatment of patients with idiopathic pulmonary fibrosis. Our objective was to examine the effect of nintedanib on proliferation of human pulmonary microvascular endothelial cells (MVEC) and assess its effects in rats with advanced experimental pulmonary hypertension (PH). Methods and results: Proliferation was assessed in control and PAH MVEC exposed to nintedanib. PH was induced in rats by subcutaneous injection of Sugen (SU5416) and subsequent exposure to 10% hypoxia for 4 weeks (SuHx model). Four weeks after re-exposure to normoxia, nintedanib was administered once daily for 3 weeks. Effects of the treatment were assessed with echocardiography, right heart catheterization, and histological analysis of the heart and lungs. Changes in extracellular matrix production was assessed in human cardiac fibroblasts stimulated with nintedanib. Decreased proliferation with nintedanib was observed in control MVEC, but not in PAH patient derived MVEC. Nintedanib treatment did not affect right ventricular (RV) systolic pressure or total pulmonary resistance index in SuHx rats and had no effects on pulmonary vascular remodelling. However, despite unaltered pressure overload, the right ventricle showed less dilatation and decreased fibrosis, hypertrophy, and collagen type III with nintedanib treatment. This could be explained by less fibronectin production by cardiac fibroblasts exposed to nintedanib. Conclusion: Nintedanib inhibits proliferation of pulmonary MVECs from controls, but not from PAH patients. While in rats with experimental PH nintedanib has no effects on the pulmonary vascular pathology, it has favourable effects on RV remodelling.

Renal Denervation Reduces Pulmonary Vascular Remodeling and Right Ventricular Diastolic Stiffness in Experimental Pulmonary Hypertension.

Neurohormonal overactivation plays an important role in pulmonary hypertension (PH). In this context, renal denervation, which aims to inhibit the neurohormonal systems, may be a promising adjunct therapy in PH. In this proof-of-concept study, we have demonstrated in 2 experimental models of PH that renal denervation delayed disease progression, reduced pulmonary vascular remodeling, lowered right ventricular afterload, and decreased right ventricular diastolic stiffness, most likely by suppression of the renin-angiotensin-aldosterone system.

Intravenous iron therapy in patients with idiopathic pulmonary arterial hypertension and iron deficiency.

UNLABELLED: In patients with idiopathic pulmonary arterial hypertension (iPAH), iron deficiency is common and has been associated with reduced exercise capacity and worse survival. Previous studies have shown beneficial effects of intravenous iron administration. In this study, we investigated the use of intravenous iron therapy in iron-deficient iPAH patients in terms of safety and effects on exercise capacity, and we studied whether altered exercise capacity resulted from changes in right ventricular (RV) function and skeletal muscle oxygen handling. Fifteen patients with iPAH and iron deficiency were included. Patients underwent a 6-minute walk test, cardiopulmonary exercise tests, cardiac magnetic resonance imaging, and a quadriceps muscle biopsy and completed a quality-of-life questionnaire before and 12 weeks after receiving a high dose of intravenous iron. The primary end point, 6-minute walk distance, was not significantly changed after 12 weeks (409 ± 110 m before vs. 428 ± 94 m after; P = 0.07). Secondary end points showed that intravenous iron administration was well tolerated and increased body iron stores in all patients. In addition, exercise endurance time (P < 0.001) and aerobic capacity (P < 0.001) increased significantly after iron therapy. This coincided with improved oxygen handling in quadriceps muscle cells, although cardiac function at rest and maximal [Formula: see text] were unchanged. Furthermore, iron treatment was associated with improved quality of life (P < 0.05). In conclusion, intravenous iron therapy in iron-deficient iPAH patients improves exercise endurance capacity. This could not be explained by improved RV function; however, increased quadriceps muscle oxygen handling may play a role. ( TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT01288651).

Nebivolol for improving endothelial dysfunction, pulmonary vascular remodeling, and right heart function in pulmonary hypertension.

BACKGROUND: Endothelial cell (EC) dysfunction plays a central role in the pathogenesis of pulmonary arterial hypertension (PAH), promoting vasoconstriction, smooth muscle proliferation, and inflammation. OBJECTIVES: This study sought to test the hypothesis that nebivolol, a ß1-antagonist and ß2,3-agonist, may improve PAH and reverse the PAH-related phenotype of pulmonary ECs (P-EC). METHODS: We compared the effects of nebivolol with metoprolol, a first-generation ß1-selective ß-blocker, on human cultured PAH and control P-EC proliferation, vasoactive and proinflammatory factor production, and crosstalk with PA smooth muscle cells. We assessed the effects of both ß-blockers in precontracted PA rings. We also compared the effects of both ß-blockers in experimental PAH. RESULTS: PAH P-ECs overexpressed the proinflammatory mediators interleukin-6 and monocyte chemoattractant protein-1, fibroblast growth factor-2, and the potent vasoconstrictive agent endothelin-1 as compared with control cells. This pathological phenotype was corrected by nebivolol but not metoprolol in a dose-dependent fashion. We confirmed that PAH P-EC proliferate more than control cells and stimulate more PA smooth muscle cell mitosis, a growth abnormality that was normalized by nebivolol but not by metoprolol. Nebivolol but not metoprolol induced endothelium-dependent and nitric oxide-dependent relaxation of PA. Nebivolol was more potent than metoprolol in improving cardiac function, pulmonary vascular remodeling, and inflammation of rats with monocrotaline-induced pulmonary hypertension. CONCLUSIONS: Nebivolol could be a promising option for the management of PAH, improving endothelial dysfunction, pulmonary vascular remodeling, and right heart function. Until clinical studies are undertaken, however, routine use of ß-blockers in PAH cannot be recommended.

Histone deacetylase inhibition with trichostatin A does not reverse severe angioproliferative pulmonary hypertension in rats (2013 Grover Conference series).

Pulmonary arterial hypertension (PAH) is a rapidly progressive and devastating disease characterized by remodeling of lung vessels, increased pulmonary vascular resistance, and eventually right ventricular hypertrophy and failure. Because histone deacetylase (HDAC) inhibitors are agents hampering tumor growth and cardiac hypertrophy, they have been attributed a therapeutic potential for patients with PAH. Outcomes of studies evaluating the use of HDAC inhibitors in models of PAH and right ventricular pressure overload have been equivocal, however. Here we describe the levels of HDAC activity in the lungs and hearts of rats with pulmonary hypertension and right heart hypertrophy or failure, experimentally induced by monocrotaline (MCT), the combined exposure to the VEGF-R inhibitor SU5416 and hypoxia (SuHx), and pulmonary artery banding (PAB). We show that HDAC activity levels are reduced in the lungs of rat with experimentally induced hypertension, whereas activity levels are increased in the hypertrophic hearts. In contrast to what was previously found in the MCT model, the HDAC inhibitor trichostatin A had no effect on pulmonary vascular remodeling in the SuHx model. When our results and those in the published literature are taken together, it is suggested that the effects of HDAC inhibitors in humans with PAH and associated RV failure are, at best, unpredictable. Significant progress can perhaps be made by using more specific HDAC inhibitors, but before clinical tests in human PAH can be undertaken, careful preclinical studies are required to determine potential cardiotoxicity.