Profiling nitric oxide metabolites in patients with idiopathic pulmonary arterial hypertension

Impact of BMPR2 mutation on the severity of pulmonary arterial hypertension: a systematic review and meta-analysis

OBJECTIVE

To evaluate the association between PAH severity in patients with and without BMPR2 mutation. Additionally, subgroup analyses were also performed to investigate whether differences existed among different ethnicities.

METHODS

A literature search of the PubMed-MEDLINE, EMBASE, Web of Science, Scopus, and Cochrane Central Register of Controlled Trials databases was conducted from inception through June, 2024, to identify eligible studies. Analyses were performed using Stata.

RESULTS

Seventeen nonrandomized studies comprising a total of 2,190 patients were included in the analysis. Among the hemodynamic variables, the mPAP (WMD = 6.41, 95% CI: 5.07 ~ 7.76, P = 0.000), PVR (WMD = 3.66, 95% CI: 2.79 ~ 4.53, P = 0.000), CI (WMD=-0.38, 95% CI: -0.45 ~ -0.32, P = 0.000), and CO (WMD=-0.60, 95% CI: -0.99 ~ -0.21, P = 0.003) were significantly different at diagnosis between patients with and without BMPR2 mutations. No significant differences were found in RAP and PAWP. Furthermore, subgroup analysis was conducted on data showing significant differences, revealing no significant differences in mPAP and PVR between Asian and Caucasian patients with BMPR2 mutations. However, significant differences in CI and CO were observed between these two ethnic groups, with CI and CO in Caucasians being more affected by BMPR2 mutations and decreasing more than in Asians.

CONCLUSION

There is a statistically significant difference in the hemodynamic variables of PAH between BMPR2 mutation carriers and non-carriers, highlighting the mutation's impact on PAH severity. This influence is not associated with ethnicity in mPAP and PVR; however, it is associated with ethnicity in CI and CO, with Caucasians being more affected by BMPR2 mutations than Asians. This suggests that Caucasians may be more sensitive to BMPR2 mutations. These findings underscore the necessity of genetic testing for PAH patients, particularly among the Caucasian population. Given the poorer clinical phenotype and prognosis of BMPR2 mutation carriers, closer follow-up may be required.

Circulating biomarkers in pulmonary arterial hypertension: State-of-the-art review and future directions

Pulmonary arterial hypertension is a complex and heterogeneous condition, associated with a considerable diagnostic delay, diminished exercise capacity, and poor outcomes. In pulmonary arterial hypertension, biomarker research has become a subject of intense inquiry, and novel circulating biomarkers acknowledged in a multitude of mechanistic pathways are emerging. Beyond the widely used natriuretic peptides, novel biomarkers may provide deeper pathophysiological understanding, support clinical decision-making, and prompt the incorporation of precision medicine by enabling a more precise individual phenotyping. In this state-of-the-art review, the recent advances in circulating biomarkers in pulmonary arterial hypertension from a clinical perspective are discussed, with particular emphasis on the current state of knowledge, gaps in evidence, and future perspectives.

Magnesium Sulfate, Rosuvastatin, Sildenafil and Their Combination in Chronic Hypoxia-Induced Pulmonary Hypertension in Male Rats

Previous experimental findings have led to considerable interest in the beneficial effects on pulmonary hypertension (PH) produced by sildenafil and in the pleiotropic effects of rosuvastatin and their positive role in the process of pulmonary angiogenesis. However, magnesium sulfate, the most abundant intracellular cation, is essential in vascular endothelial functionality due to its anti-inflammatory and vasodilatory effects. Therefore, the present study aims to assess these treatment regimens and how they could potentially provide some additional benefits in PH therapy. Fourteen days after chronic-hypoxia PH was induced, rosuvastatin, sildenafil and magnesium sulfate were administered for an additional fourteen days to male Wistar rats. The Fulton Index, right ventricle (RV) anterior wall thickness, RV internal diameter and pulmonary arterial (PA) acceleration time/ejection time were evaluated, and another four biochemical parameters were calculated: brain natriuretic peptide, vascular endothelial growth factor, nitric oxide metabolites and endothelin 1. The present study demonstrates that sildenafil and rosuvastatin have modest effects in reducing RV hypertrophy and RV systolic pressure. The drug combination of sildenafil + rosuvastatin + magnesium sulfate recorded statistically very highly significant results on all parameters; through their positive synergistic effects on vascular endothelial function, oxidative stress and pathological RV remodeling, they attenuated PH in the chronic hypoxia pulmonary hypertension (CHPH) rat model.

Idiopathic and connective tissue disease-associated pulmonary arterial hypertension (PAH): Similarities, differences and the role of autoimmunity

Pre-capillary pulmonary arterial hypertension (PAH) is hemodynamically characterized by a mean pulmonary arterial pressure (mPAP) ≥ 20 mmHg, pulmonary capillary wedge pressure (PAWP) ≤15 mmHg and pulmonary vascular resistance (PVR) > 2. PAH is classified in six clinical subgroups, including idiopathic PAH (IPAH) and PAH associated to connective tissue diseases (CTD-PAH), that will be the main object of this review. The aim is to compare these two PAH subgroups in terms of epidemiology, histological and pathogenic findings in an attempt to define disease-specific features, including autoimmunity, that may explain the heterogeneity of response to therapy between IPAH and CTD-PAH.

Hemoglobin resident in the lung epithelium is protective for smooth muscle soluble guanylate cyclase function

Hemoglobin (Hb) present in the lung epithelium is of unknown significance. However Hb being an nitric oxide (NO) scavenger can bind to NO and reduce its deleterious effects. Hence we postulated an NO scavenging role for this lung Hb. Doing transwell co-culture with bronchial epithelial cells, A549/16-HBE (apical) and human airway smooth muscle cells (HASMCs as basal), we found that Hb can protect the smooth muscle soluble guanylyl cyclase (sGC) from excess NO. Inducing the apical A549/16-HBE cells with cytokines to trigger iNOS expression and NO generation caused a time dependent increase in SNO-sGC and this was accompanied with a concomitant drop in sGC-α1β1 heterodimerization. Silencing Hbαβ in the apical cells further increased the SNO on sGC with a faster drop in the sGC heterodimer and these effects were additive along with further silencing of thioredoxin 1 (Trx1). Since heme of Hb is critical for NO scavenging we determined the Hb heme in a mouse model of allergic asthma (OVA) and found that Hb in the inflammed OVA lungs was low in heme or heme-free relative to those of naïve lungs. Further we established a direct correlation between the status of the sGC heterodimer and the Hb heme from lung samples of human asthma, iPAH, COPD and cystic fibrosis. These findings present a new mechanism of protection of lung sGC by the epithelial Hb, and suggests that this protection maybe lost in asthma or COPD where lung Hb is unable to scavenge the NO due to it being heme-deprived.

Plasma biomarkers of endothelial function, inflammation and oxidative stress in individuals with non-freezing cold injury

NEW FINDINGS

What is the central question of this study? Are biomarkers of endothelial function, oxidative stress and inflammation altered by non-freezing cold injury (NFCI)? What is the main finding and its importance? Baseline plasma [interleukin-10] and [syndecan-1] were elevated in individuals with NFCI and cold-exposed control participants. Increased [endothelin-1] following thermal challenges might explain, in part, the increased pain/discomfort experienced with NFCI. Mild to moderate chronic NFCI does not appear to be associated with either oxidative stress or a pro-inflammatory state. Baseline [interleukin-10] and [syndecan-1] and post-heating [endothelin-1] are the most promising candidates for diagnosis of NFCI.

ABSTRACT

Plasma biomarkers of inflammation, oxidative stress, endothelial function and damage were examined in 16 individuals with chronic NFCI (NFCI) and matched control participants with (COLD, n = 17) or without (CON, n = 14) previous cold exposure. Venous blood samples were collected at baseline to assess plasma biomarkers of endothelial function (nitrate, nitrite and endothelin-1), inflammation [interleukin-6 (IL-6), interleukin-10 (IL-10), tumour necrosis factor alpha and E-selectin], oxidative stress [protein carbonyl, 4-hydroxy-2-nonenal (4-HNE), superoxide dismutase and nitrotyrosine) and endothelial damage [von Willebrand factor, syndecan-1 and tissue type plasminogen activator (TTPA)]. Immediately after whole-body heating and separately, foot cooling, blood samples were taken for measurement of plasma [nitrate], [nitrite], [endothelin-1], [IL-6], [4-HNE] and [TTPA]. At baseline, [IL-10] and [syndecan-1] were increased in NFCI (P < 0.001 and P = 0.015, respectively) and COLD (P = 0.033 and P = 0.030, respectively) compared with CON participants. The [4-HNE] was elevated in CON compared with both NFCI (P = 0.002) and COLD (P < 0.001). [Endothelin-1] was elevated in NFCI compared with COLD (P < 0.001) post-heating. The [4-HNE] was lower in NFCI compared with CON post-heating (P = 0.032) and lower than both COLD (P = 0.02) and CON (P = 0.015) post-cooling. No between-group differences were seen for the other biomarkers. Mild to moderate chronic NFCI does not appear to be associated with a pro-inflammatory state or oxidative stress. Baseline [IL-10] and [syndecan-1] and post-heating [endothelin-1] are the most promising candidates for diagnosing NFCI, but it is likely that a combination of tests will be required.

Cyclic GMP modulating drugs in cardiovascular diseases: mechanism-based network pharmacology

Mechanism-based therapy centred on the molecular understanding of disease-causing pathways in a given patient is still the exception rather than the rule in medicine, even in cardiology. However, recent successful drug developments centred around the second messenger cyclic guanosine-3'-5'-monophosphate (cGMP), which is regulating a number of cardiovascular disease modulating pathways, are about to provide novel targets for such a personalized cardiovascular therapy. Whether cGMP breakdown is inhibited or cGMP synthesis is stimulated via guanylyl cyclases or their upstream regulators in different cardiovascular disease phenotypes, the outcomes seem to be so far uniformly protective. Thus, a network of cGMP-modulating drugs has evolved that act in a mechanism-based, possibly causal manner in a number of cardiac conditions. What remains a challenge is the detection of cGMPopathy endotypes amongst cardiovascular disease phenotypes. Here, we review the growing clinical relevance of cGMP and provide a glimpse into the future on how drugs interfering with this pathway may change how we treat and diagnose cardiovascular diseases altogether.

AAV-mediated gene transfer of inducible nitric oxide synthase (iNOS) to an animal model of pulmonary hypertension

Pulmonary hypertension (PH) is characterized by progressive obstruction of pulmonary arteries due to inflammatory processes, cellular proliferation, and extracellular matrix deposition and vasoconstriction. As treatment options are limited, we studied gene transfer of an inducible nitric oxide synthase (iNOS) using adeno-associated virus (AAV) vectors specifically targeted to endothelial cells of pulmonary vessels in a murine model of PH. Adult mice were intravenously injected with AAV vectors expressing iNOS. Mice were subjected to hypoxia for three weeks and sacrificed afterwards. We found elevated levels of iNOS both in lung tissue and pulmonary endothelial cells in hypoxic controls which could be further increased by AAV-mediated iNOS gene transfer. This additional increase in iNOS was associated with decreased wall thickness of pulmonary vessels, less macrophage infiltration, and reduced molecular markers of fibrosis. Taken together, using a tissue-targeted approach, we show that AAV-mediated iNOS overexpression in endothelial cells of the pulmonary vasculature significantly decreases vascular remodeling in a murine model of PH, suggesting upregulation of iNOS as promising target for treatment of PH.

Therapy for Pulmonary Arterial Hypertension: Glance on Nitric Oxide Pathway

Pulmonary arterial hypertension (PAH) is a severe disease with a resultant increase of the mean pulmonary arterial pressure, right ventricular hypertrophy and eventual death. Research in recent years has produced various therapeutic options for its clinical management but the high mortality even under treatment remains a big challenge attributed to the complex pathophysiology. Studies from clinical and non-clinical experiments have revealed that the nitric oxide (NO) pathway is one of the key pathways underlying the pathophysiology of PAH. Many of the essential drugs used in the management of PAH act on this pathway highlighting its significant role in PAH. Meanwhile, several novel compounds targeting on NO pathway exhibits great potential to become future therapy medications. Furthermore, the NO pathway is found to interact with other crucial pathways. Understanding such interactions could be helpful in the discovery of new drug that provide better clinical outcomes.

Thioredoxin system activation is associated with the progression of experimental pulmonary arterial hypertension

In addition to being an antioxidant, thioredoxin (Trx) is known to stimulate signaling pathways involved in cell proliferation and to inhibit apoptosis. The aim of this study was to explore the role of Trx in some of these pathways along the progression of monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH). Male rats were first divided into two groups: monocrotaline (MCT - 60 mg/kg i.p.) and control (received saline), that were further divided into three groups: 1, 2, and 3 weeks. Animals were submitted to echocardiographic analysis. Right and left ventricles were used for the measurement of hypertrophy, through morphometric and histological analysis. The lung was prepared for biochemical and molecular analysis. One week after MCT injection, there was an increase in thioredoxin reductase (TrxR) activity, a reduction in glutathione reductase (GR) activity, and an increase in Trx-1 and vitamin D3 up-regulated protein-1 (VDUP-1) expression. Two weeks after MCT injection, there was an increase in VDUP-1, Akt and cleaved caspase-3 activation, and a decrease in Trx-1 and Nrf2 expression. PAH-induced by MCT promoted a reduction in Nrf2 and Trx-1 expression as well as an increase in Akt and VDUP-1 expression after three weeks. The increase in pulmonary vascular resistance was accompanied by increased TrxR activity, suggesting an association between the Trx system and functional changes in the progression of PAH. It seems that Trx-1 activation was an adaptive response to MCT administration to cope with pulmonary remodeling and disease progression, suggesting a potential new target for PAH therapeutics.

Impact of dietary nitrate supplementation on exercise capacity and cardiovascular parameters in chronic respiratory disease: a systematic review and meta-analysis

Background

Dietary nitrate supplementation, usually in the form of beetroot juice, may improve exercise performance and endothelial function. We undertook a systematic review and meta-analysis to establish whether this approach has beneficial effects in people with respiratory disease.

Methods

A systematic search of records up to March 2021 was performed on PubMed, CINAHL, MEDLINE (Ovid), Cochrane and Embase to retrieve clinical trials that evaluated the efficacy of dietary nitrate supplementation on cardiovascular parameters and exercise capacity in chronic respiratory conditions. Two authors independently screened titles, abstracts and full texts of potential studies and performed the data extraction.

Results

After full-text review of 67 papers, eleven (two randomised controlled trials and nine crossover trials) involving 282 participants met the inclusion criteria. Three were single dose; seven short term; and one, the largest (n=122), done in the context of pulmonary rehabilitation. Pooled analysis showed that dietary nitrate supplementation reduced systolic blood pressure (BP), diastolic BP and mean arterial pressure (mean difference (95% CI), −3.39 mm Hg (−6.79 to 0.01); p=0.05 and –2.20 mm Hg (−4.36 to −0.03); p=0.05 and −4.40 mm Hg (−7.49 to −1.30); p=0.005, respectively). It was associated with increased walk distance in the context of pulmonary rehabilitation (standardised mean difference (95% CI), 0.47 (0.11 to 0.83), p=0.01), but no effect was identified in short-term studies (0.08 (−0.32 to 0.49).

Conclusion

Dietary nitrate supplementation may have a beneficial effect on BP and augment the effect of pulmonary rehabilitation on exercise capacity. Short-term studies do not suggest a consistent benefit on exercise capacity.

PROSPERO registration number

CRD42019130123.

Dual-Functional MN-08 Attenuated Pulmonary Arterial Hypertension Through Vasodilation and Inhibition of Pulmonary Arterial Remodeling

[Figure: see text].

Profile of new vascular damage biomarkers in middle-aged men with arterial hypertension

PURPOSE

Normal endothelial function is important for the homeostasis of the cardiovascular (CV) system. The aim of the present study was to determine the profile of key parameters of endothelial dysfunction in middle-aged men that play a significant role in the functioning of endothelial vessels, which seems to be crucial for the early diagnosis of cardiovascular disorders.

MATERIALS AND METHODS

The study included 53 men, 20 with hypertension (HTN), 18 with HTN and related diseases, 15 healthy controls Apart from general testing (BMI, biochemical analysis, SBP, DBP), we used the Griess reaction to assess the total amount of nitric oxide (NO), and used ELISA to verify the concentrations of malondialdehyde (MDA), nitrotyrosine (NT), asymmetric dimethylarginine (ADMA), tumor necrosis factor-alpha (TNF-α), monocyte chemotactic protein 1 (MCP-1), and myeloperoxidase (MPO). Furthermore, we assessed the concentration of circulating free DNA (cfDNA) using the fluorescence method.

RESULTS

The values of MDA, ADMA, cfDNA, and MPO observed in samples from men with HTN were determined to be higher compared to those from men without HTN. In the group of men with HTN and other concomitant cardiovascular disorders, we observed low concentrations of NO, MDA, and ADMA with high concentrations of cfDNA.

CONCLUSIONS

The results obtained for parameters selected for the study, should be considered by cardiologists as a prompt to include in the diagnostic profile the assessment of NO and cfDNA concentrations for risk evaluation and/or diagnosis of endothelial dysfunction in patients suffering from HTN or related complications.

The Nitric Oxide Pathway in Pulmonary Arterial Hypertension: Pathomechanism, Biomarkers and Drug Targets

The altered Nitric Oxide (NO) pathway in the pulmonary endothelium leads to increased vascular smooth muscle tone and vascular remodelling, and thus contributes to the development and progression of pulmonary arterial hypertension (PAH). The pulmonary NO signalling is abrogated by the decreased expression and dysfunction of the endothelial NO synthase (eNOS) and the accumulation of factors blocking eNOS functionality. The NO deficiency of the pulmonary vasculature can be assessed by detecting nitric oxide in the exhaled breath or measuring the degradation products of NO (nitrite, nitrate, S-nitrosothiol) in blood or urine. These non-invasive biomarkers might show the potential to correlate with changes in pulmonary haemodynamics and predict response to therapies. Current pharmacological therapies aim to stimulate pulmonary NO signalling by suppressing the degradation of NO (phosphodiesterase- 5 inhibitors) or increasing the formation of the endothelial cyclic guanosine monophosphate, which mediates the downstream effects of the pathway (soluble guanylate cyclase sensitizers). Recent data support that nitrite compounds and dietary supplements rich in nitrate might increase pulmonary NO availability and lessen vascular resistance. This review summarizes current knowledge on the involvement of the NO pathway in the pathomechanism of PAH, explores novel and easy-to-detect biomarkers of the pulmonary NO.

Alteration of Extracellular Superoxide Dismutase in Idiopathic Pulmonary Arterial Hypertension

Background: Superoxide dismutases (SODs) are an important family of antioxidant enzymes that modulate reactive oxygen species levels. It is largely unknown which SOD isoform(s) change in vivo in idiopathic pulmonary arterial hypertension (IPAH) patients.

Methods: A total of 133 consecutive adult IPAH patients who underwent bone morphogenetic protein receptor type 2 (BMPR2) genetic counseling were enrolled in this prospective study. The plasma activities of three subtypes of SOD [copper–zinc (Cu/Zn-SOD), manganese (Mn-SOD), and extracellular SOD (Ec-SOD)] were examined.

Results: The activities of SODs were significantly lower in IPAH patients than in healthy subjects. However, only Ec-SOD activity in BMPR2 mutation patients was significantly decreased compared to those in patients without a mutation. The reduced Ec-SOD activity was markedly associated with mean pulmonary arterial pressure, pulmonary vascular resistance (PVR), and 6-min walking distance (6MWD). The reduction of Mn-SOD activity was only associated with 6MWD. There was no association between Cu/Zn-SOD and hemodynamics. Patients with a lower Ec-SOD level had a worse survival compared to those with a higher baseline. The reduced Ec-SOD activity and the raised PVR increased the mortality risk.

Conclusions: Ec-SOD was correlated with BMPR2 mutation, hemodynamic dysfunction, and poor outcomes. Circulating Ec-SOD could be a potentially vital antioxidant enzyme in the pathogenesis of IPAH.

BRG1 Activates PR65A Transcription to Regulate NO Bioavailability in Vascular Endothelial Cells

Vascular endothelial cells contribute to the pathogenesis of cardiovascular diseases by producing and disseminating angiocrine factors. Nitric oxide (NO), catalyzed by endothelial NO synthase (eNOS), is one of the prototypical angiocrine factors. eNOS activity is modulated by site-specific phosphorylation. We have previously shown that endothelial-specific knockdown of BRG1 in Apoe^–/– mice attenuates the development of atherosclerosis, in which eNOS-dependent NO catalysis plays an antagonizing role. Here we report that attenuation of atherogenesis in mice by BRG1 knockdown was accompanied by partial restoration of NO biosynthesis by 44% in the arteries and a simultaneous up-regulation of eNOS serine 1177 phosphorylation by 59%. Indeed, BRG1 depletion or inhibition ameliorated oxLDL-induced loss of NO bioavailability and eNOS phosphorylation in cultured endothelial cells. Further analysis revealed that BRG1 regulated eNOS phosphorylation and NO synthesis by activating the transcription of protein phosphatase 2A (PP2A) structural subunit a (encoded by PR65A). BRG1 interacted with ETS1, was recruited by ETS1 to the PR65A promoter, and cooperated with ETS1 to activate PR65A transcription. Finally, depletion of ETS1, similar to BRG1, repressed PR65A induction, normalized eNOS phosphorylation, and rescued NO biosynthesis in endothelial cells treated with oxLDL. In conclusion, our data characterize a novel transcriptional cascade that regulates NO bioavailability in vascular endothelial cells.

An update on the diagnosis and treatment of pediatric pulmonary hypertension

INTRODUCTION

Pulmonary hypertension (PH) is a heterogeneous disease that mainly affects the pulmonary arterioles, leading to significant morbidity and mortality. Pulmonary hypertension in children from birth to adolescence presents important differences from that of adults. The majority of pediatric pulmonary arterial hypertension (PAH) cases are idiopathic or associated with congenital heart disease. However, the management of pediatric PAH mainly depends on the results of evidence-based adult studies and the clinical experiences of pediatric experts.

AREAS COVERED

This article briefly reviews the recent updates on the definition, classification, and diagnostic evaluation of pediatric PAH and their impact on treatment strategies. The main purpose of this review is to discuss the current pediatric therapies, as well as the prospective therapies, in terms of therapeutic targets, actions, side effects, and dosages.

EXPERT OPINION

Although there is no cure for PAH, recent advances in the form of new treatment options have improved the quality of life and survival rates of PAH patients. PAH-targeted drugs and treatment strategies for adult PAH have not been sufficiently studied in children. However, the growing scientific activity in that field will surely change the treatment option recommendations in pediatric PH from experience-based to evidence-based in the near future.

Protective Role of Myelocytic Nitric Oxide Synthases against Hypoxic Pulmonary Hypertension in Mice

RATIONALE

Nitric oxide (NO), synthesized by NOSs (NO synthases), plays a role in the development of pulmonary hypertension (PH). However, the role of NO/NOSs in bone marrow (BM) cells in PH remains elusive.

OBJECTIVES

To determine the role of NOSs in BM cells in PH.

METHODS

Experiments were performed on 36 patients with idiopathic pulmonary fibrosis and on wild-type (WT), nNOS (neuronal NOS)^-/-, iNOS (inducible NOS)^-/-, eNOS (endothelial NOS)^-/-, and n/i/eNOSs^-/- mice.

MEASUREMENTS AND MAIN RESULTS

In the patients, there was a significant correlation between higher pulmonary artery systolic pressure and lower nitrite plus nitrate levels in the BAL fluid. In the mice, hypoxia-induced PH deteriorated significantly in the n/i/eNOSs^-/- genotype and, to a lesser extent, in the eNOS^-/- genotype as compared with the WT genotype. In the n/i/eNOSs^-/- genotype exposed to hypoxia, the number of circulating BM-derived vascular smooth muscle progenitor cells was significantly larger, and transplantation of green fluorescent protein-transgenic BM cells revealed the contribution of BM cells to pulmonary vascular remodeling. Importantly, n/i/eNOSs^-/--BM transplantation significantly aggravated hypoxia-induced PH in the WT genotype, and WT-BM transplantation significantly ameliorated hypoxia-induced PH in the n/i/eNOSs^-/- genotype. A total of 69 and 49 mRNAs related to immunity and inflammation, respectively, were significantly upregulated in the lungs of WT genotype mice transplanted with n/i/eNOSs^-/--BM compared with those with WT-BM, suggesting the involvement of immune and inflammatory mechanisms in the exacerbation of hypoxia-induced PH caused by n/i/eNOSs^-/--BM transplantation.

CONCLUSIONS

These results demonstrate that myelocytic n/i/eNOSs play an important protective role in the pathogenesis of PH.

Effects of Oral Supplementation With Nitrate-Rich Beetroot Juice in Patients With Pulmonary Arterial Hypertension-Results From BEET-PAH, an Exploratory Randomized, Double-Blind, Placebo-Controlled, Crossover Study

BACKGROUND

The nitrate-nitrite-nitric oxide (NO) pathway may represent a potential therapeutic target in patients with pulmonary arterial hypertension (PAH). We explored the effects of dietary nitrate supplementation, with the use of nitrate-rich beetroot juice (BRJ), in patients with PAH.

METHODS AND RESULTS

We prospectively studied 15 patients with PAH in an exploratory randomized, double-blind, placebo-controlled, crossover trial. The patients received nitrate-rich beetroot juice (∼16 mmol nitrate per day) and placebo in 2 treatment periods of 7 days each. The assessments included; exhaled NO and NO flow-independent parameters (alveolar NO and bronchial NO flux), plasma and salivary nitrate and nitrite, biomarkers and metabolites of the NO-system, N-terminal pro-B-type natriuretic peptide, echocardiography, ergospirometry, diffusing capacity of the lung for carbon monoxide, and the 6-minute walk test. Compared with placebo ingestion of BRJ resulted in increases in; fractional exhaled NO at all flow-rates, alveolar NO concentrations and bronchial NO flux, and plasma and salivary levels of nitrate and nitrite. Plasma ornithine levels decreased and indices of relative arginine availability increased after BRJ compared to placebo. A decrease in breathing frequency was observed during ergospirometry after BRJ. A tendency for an improvement in right ventricular function was observed after ingestion of BRJ. In addition a tendency for an increase in the peak power output to peak oxygen consumption ratio (W peak/VO₂ peak) was observed, which became significant in patients reaching an increase of plasma nitrite >30% (responders).

CONCLUSIONS

BRJ administered for 1 week increases pulmonary NO production and the relative arginine bioavailability in patients with PAH, compared with placebo. An increase in the W peak/VO₂ peak ratio was observed after BRJ ingestion in plasma nitrite responders. These findings indicate that supplementation with inorganic nitrate increase NO synthase-independent NO production from the nitrate-nitrite-NO pathway.

Sex differences in pulmonary vascular control: focus on the nitric oxide pathway

Although the incidence of pulmonary hypertension is higher in females, the severity and prognosis of pulmonary vascular disease in both neonates and adults have been shown to be worse in male subjects. Studies of sex differences in pulmonary hypertension have mainly focused on the role of sex hormones. However, the contribution of sex differences in terms of vascular signaling pathways regulating pulmonary vascular function remains incompletely understood. Consequently, we investigated pulmonary vascular function of male and female swine in vivo, both at rest and during exercise, and in isolated small pulmonary arteries in vitro, with a particular focus on the NO‐cGMP‐PDE5 pathway. Pulmonary hemodynamics at rest and during exercise were virtually identical in male and female swine. Moreover, NO synthase inhibition resulted in a similar degree of pulmonary vasoconstriction in male and female swine. However, NO synthase inhibition blunted bradykinin‐induced vasodilation in pulmonary small arteries to a greater extent in male than in female swine. PDE5 inhibition resulted in a similar degree of vasodilation in male and female swine at rest, while during exercise there was a trend towards a larger effect in male swine. In small pulmonary arteries, PDE5 inhibition failed to augment bradykinin‐induced vasodilation in either sex. Finally, in the presence of NO synthase inhibition, the pulmonary vasodilator effect of PDE5 inhibition was significantly larger in female swine both in vivo and in vitro. In conclusion, the present study demonstrated significant sex differences in the regulation of pulmonary vascular tone, which may contribute to understanding sex differences in incidence, treatment response, and prognosis of pulmonary vascular disease.

miR-190a-5p participates in the regulation of hypoxia-induced pulmonary hypertension by targeting KLF15 and can serve as a biomarker of diagnosis and prognosis in chronic obstructive pulmonary disease complicated with pulmonary hypertension

PURPOSE

miR-190a-5p expression alters dynamically in response to hypoxia. However, the role of miR-190a-5p expression in hypoxia-induced pulmonary hypertension (PH) remains unclear. We sought to correlate the miR-190a-5p expression levels with the severity, diagnosis, and prognosis of PH in relation to chronic obstructive pulmonary disease (COPD-PH). Additionally, we evaluated the effect of miR-190a-5p through in vitro experiments on human pulmonary endothelial cells (HPECs) that were exposed to hypoxia and in vivo experiments using an animal model of hypoxia-induced PH.

METHODS

Circulating miR-190a-5p levels were measured from 73 patients with PH and 32 healthy controls through quantitative real-time PCR. The levels of miR-190a-5p and the expression of Krüppel-like factor 15 (KLF15) were analyzed in HPECs that were exposed to hypoxia, and the effects of antagomir-190a-5p in mice with chronic hypoxia-induced PH were tested. Target gene analysis was performed by Western blot and luciferase assay.

RESULTS

The miR-190a-5p level was significantly higher in patients with COPD-PH than in the healthy controls. Higher miR-190a-5p levels were associated with a greater severity of COPD-PH. In vitro experiments on HPECs showed that exposure to hypoxia increased the miR-190a-5p levels significantly. KLF15 was validated as a target of miR-190a-5p. Transfection with miR-190a-5p mimicked inhibition of KLF15 expression in HPECs. In the mouse model of PH, antagomir-190a-5p reduced right ventricular systolic pressure and enhanced the KLF15 expression levels in lung tissue.

CONCLUSION

miR-190a-5p regulates hypoxia-induced PH by targeting KLF15. The circulating levels of miR-190a-5p correlate with the severity of COPD-PH, thereby confirming the diagnostic and prognostic value of this parameter in COPD-PH.