Right ventricular adaptation and failure in pulmonary arterial hypertension

Stem cell therapy targeting the right ventricle in pulmonary arterial hypertension: is it a potential avenue of therapy?

Pulmonary arterial hypertension (PAH) is an incurable disease characterized by an increase in pulmonary arterial pressure due to pathological changes to the pulmonary vascular bed. As a result, the right ventricle (RV) is subject to an increased afterload and undergoes multiple changes, including a decrease in capillary density. All of these dysfunctions lead to RV failure. A number of studies have shown that RV function is one of the main prognostic factors for PAH patients. Many stem cell therapies targeting the left ventricle are currently undergoing development. The promising results observed in animal models have led to clinical trials that have shown an improvement of cardiac function. In contrast to left heart disease, stem cell therapy applied to the RV has remained poorly studied, even though it too may provide a therapeutic benefit. In this review, we discuss stem cell therapy as a treatment for RV failure in PAH. We provide an overview of the results of preclinical and clinical studies for RV cell therapies. Although a large number of studies have targeted the pulmonary circulation rather than the RV directly, there are nonetheless encouraging results in the literature that indicate that cell therapies may have a direct beneficial effect on RV function. This cell therapy strategy may therefore hold great promise and warrants further studies in PAH patients.

Evaluation of the effects of RP5063, a novel, multimodal, serotonin receptor modulator, as single-agent therapy and co-administrated with sildenafil, bosentan, and treprostinil in a monocrotaline-induced pulmonary arterial hypertension rat model

Pulmonary arterial hypertension (PAH), a condition that is defined by pulmonary vasculature constriction and remodeling, involves dysfunctional signaling of the serotonin (5-HT) receptors, 5-HT_2A/2B/7. In a rat model of monocrotaline (MCT)-induced PAH, the effectiveness of RP5063 (RP), a dopamine and 5-HT receptor modulator, was evaluated as monotherapy and as an adjunct to standard PAH treatments. After a single 60 mg/kg dose of MCT, rats received vehicle (MCT+Veh; gavage twice-daily [b.i.d.]), RP (10 mg/kg; gavage b.i.d.), bosentan (B; 100 mg/kg; gavage BID), sildenafil (S; 50 mg/kg; gavage, BID), treprostinil (T; 100 ng/kg/min over 24 h intravenous), RP+B, RP+S, and RP+T for 28 days. Single-agent RP limited the functional and structural effects of PAH seen in the MCT+Veh group, with significant improvements in pulmonary hemodynamics, right ventricular (RV) hypertrophy, SO₂, and pulmonary blood vessel structural changes. These effects appeared comparable with those associated with B, S, and T. Adjunctive RP treatment resulted in significantly lower mean pulmonary arterial pressures, RV systolic pressure. It also improved SO₂ measurements, as compared with MCT+Veh (P < 0.05), and diastolic pulmonary artery pressure (P < 0.05), as compared with single-agent B and S therapy (Bonferroni method adjusting for multiplicity). RP+S appeared to show the most consistent and extensive effects on pulmonary hemodynamics, respiratory parameters, and histopathologic changes. These results corroborate earlier preclinical findings supporting the efficacy of single-agent RP in PAH. RP, as mono and adjunctive therapy compared with induced-control, mitigated the functional and structural effects of MCT-induced PAH.

Stage‑dependent changes of β2‑adrenergic receptor signaling in right ventricular remodeling in monocrotaline‑induced pulmonary arterial hypertension

Right ventricular (RV) remodeling coupled with extensive apoptosis in response to unrestrained biomechanical stress may lead to RV failure (RVF), which is the immediate cause of death in the majority of patients with pulmonary arterial hypertension (PAH). Overexpression of β₂-adrenergic receptor (β₂-AR) signaling has been reported to induce myocardiotoxicity in patients with left heart failure. However, the role of β₂-AR signaling in the pathophysiology of PAH development has remained elusive. To address this issue, the present study investigated the changes in cardiopulmonary function and structure, as well as the expression of regulators of fibrosis and apoptosis in RVF following monocrotaline (MCT; 60 mg/kg, i.p.)-induced PAH in rats. Cardiopulmonary function and structure, remodeling and apoptosis, as well as G protein-coupled receptor (GPCR) and β₂-AR signaling, were documented over a period of 6 weeks. In the early stages, elevated pulmonary arterial pressure, pulmonary lesions, RV hypertrophy, evidence of left ventricular (LV) hyperfunction and accelerated heart rate were observed in animals with MCT-induced PAH. The levels of angiotensin II receptor type 1b (Agtr1b), Agtr2 and Agt were markedly upregulated and the expression of β₂-AR phospho-Ser(355,356) steadily decreased in the right heart. As the disease progressed, LV dysfunction was observed, as evidenced by decreased LV systolic pressure and increased LV end-diastolic pressure, which was accompanied by a sustained increase in circulating brain natriuretic peptide levels. Of note, increased levels of cardiomyocyte apoptosis and concomitant RV remodeling, including hypertrophy, dilatation, inflammation and fibrosis, were observed, despite the enhanced RV contractility. Furthermore, alterations in GPCR signaling and activation in β₂-AR-G_s-protein kinase A/Ca²⁺/calmodulin-dependent kinase II signaling were observed in the late stages of PAH. These results suggested that treatment with MCT results in adaptive and maladaptive RV remodeling and apoptosis during the progression of PAH, which is accompanied by distinct changes in the β₂-AR signaling. Therefore, these results enable researchers to better understand of pathophysiology of MCT-induced PAH, as well as to determine the effects of novel therapies.

Cardiovascular Supportive Therapies for Neonates With Asphyxia - A Literature Review of Pre-clinical and Clinical Studies

Asphyxiated neonates often have hypotension, shock, and poor tissue perfusion. Various "inotropic" medications are used to provide cardiovascular support to improve the blood pressure and to treat shock. However, there is incomplete literature on the examination of hemodynamic effects of these medications in asphyxiated neonates, especially in the realm of clinical studies (mostly in late preterm or term populations). Although the extrapolation of findings from animal studies and other clinical populations such as children and adults require caution, it seems appropriate that findings from carefully conducted pre-clinical studies are important in answering some of the fundamental knowledge gaps. Based on a literature search, this review discusses the current available information, from both clinical studies and animal models of neonatal asphyxia, on common medications used to provide hemodynamic support including dopamine, dobutamine, epinephrine, milrinone, norepinephrine, vasopressin, levosimendan, and hydrocortisone.

Current and Emerging Biomarkers for Pulmonary Hypertension

“A biological molecule found in blood, other body fluids, or tissues that is a sign of a normal or abnormal process, or of a condition or disease. A biomarker may be used to see how well the body responds to a treatment for a disease or condition. Also called molecular marker or signature molecule” – Biomarker definition, National Institutes of Health, National Cancer Institute, Dictionary of Cancer Terms

Although this definition pertains to the field of cancer and cancer biology, it applies to many disciplines, including the field of pulmonary vascular disease. In the world of pulmonary hypertension (PH), biomarkers hold a special place. In the diagnosis of PH subtype, we are limited by the risk of lung biopsy1 and, further, in patients with pulmonary arterial hypertension (PAH) we are limited by the inability to frequently obtain our strongest predictors of mortality: invasive pulmonary hemodynamic assessment. Thus, biomarkers hold much promise for the field of PH. We are searching for markers of PH subtypes and endophenotypes. We are looking for predictors of mortality in all forms of PH and, critically, we are hoping to find peripheral blood markers that will help us discover which drugs are likely to benefit a particular patient. Although we have made inroads in all 3 areas, there are substantial opportunities for refinement of our current biomarkers and discovery of novel markers to improve the care of PH patients. This review will cover the state of current biomarkers in PH and discuss challenges and future directions.

Pharmacological Inhibition of mTOR Kinase Reverses Right Ventricle Remodeling and Improves Right Ventricle Structure and Function in Rats

Pulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling, increased pulmonary artery (PA) pressure, right-heart afterload and death. Mechanistic target of rapamycin (mTOR) promotes smooth muscle cell proliferation, survival, and pulmonary vascular remodeling via two functionally distinct mTOR complexes (mTORCs)-1 (supports cell growth) and -2 (promotes cell survival), and dual mTORC1/mTORC2 inhibition selectively induces pulmonary arterial hypertension PA vascular smooth muscle cell apoptosis and reverses pulmonary vascular remodeling. The consequences of mTOR inhibition on right ventricle (RV) morphology and function are not known. Using SU5416/hypoxia rat model of pulmonary hypertension (PH), we report that, in contrast to activation of both mTORC1 and mTORC2 pathways in small remodeled PAs, RV tissues had predominant up-regulation of mTORC1 signaling accompanied by cardiomyocyte and RV hypertrophy, increased RV wall thickness, RV/left ventricle end-diastolic area ratio, RV contractility and afterload (arterial elastance), and shorter RV acceleration time compared with controls. Treatment with mTOR kinase inhibitor, PP242, at Weeks 6-8 after PH induction suppressed both mTORC1 and mTORC2 in small PAs, but only mTORC1 signaling in RV, preserving basal mTORC2-Akt levels. Vehicle-treated rats showed further PH and RV worsening and profound RV fibrosis. PP242 reversed pulmonary vascular remodeling and prevented neointimal occlusion of small PAs, significantly reduced PA pressure and pulmonary vascular resistance, reversed cardiomyocyte hypertrophy and RV remodeling, improved max RV contractility, arterial elastance, and RV acceleration time, and prevented development of RV fibrosis. Collectively, these data show a predominant role of mTORC1 versus mTORC2 in RV pathology, and suggest potential attractiveness of mTOR inhibition to simultaneously target pulmonary vascular remodeling and RV dysfunction in established PH.

Plasma Growth Differentiation Factor-15 is a Potential Biomarker for Pediatric Pulmonary Arterial Hypertension Associated with Congenital Heart Disease

We aimed to investigate plasma growth differentiation factor-15 (GDF-15) levels in pediatric pulmonary arterial hypertension secondary to congenital heart disease (PAH-CHD), and assess the association with hemodynamic parameters. Plasma GDF-15 levels were measured in children with PAH-CHD (n = 46) and compared to children with CHD without PAH (n = 39). Normal individuals (n = 30) served as health control group. Plasma GDF-15 levels were significantly elevated in patients with PAH-CHD compared with those with CHD without PAH (median 1415 ng/L, interquartile range [IQR] 926.7-2111.7 ng/L vs. 890.6 ng/L, IQR 394.7-1094.3 ng/L, p < 0.01). Elevated plasma GDF-15 levels were positively related to Functional Class, uric acid, N-terminal pro-B-type natriuretic peptide (NT-proBNP), pulmonary artery systolic pressure, mean pulmonary artery pressure, pulmonary blood flow/systemic blood flow and pulmonary vascular resistance, and a lower mixed venous oxygen saturation (Sv_o2). The area under the curve (AUC) for adding GDF-15 to NT-proBNP was not superior to the AUC of NT-pro BNP alone (AUC difference 0.0295, p = 0.324) (NT-proBNP, AUC 0.823, 95% CI 0.725-0.897; GDF-15 plus NT-proBNP, AUC 0.852, 95% CI 0.759-0.92), whereas it revealed a slightly greater specificity and positive predictive value. The diagnostic power of NT-pro BNP was not inferior to GDF-15 (AUC difference 0.0443, p = 0.43). Plasma GDF-15 levels might be a surrogate marker for pediatric PAH-CHD.

PPARγ Alleviates Right Ventricular Failure Secondary to Pulmonary Arterial Hypertension in Rats

Pulmonary arterial hypertension (PAH) is characterized by pulmonary vascular remodeling leading to right ventricular hypertrophy (RVH) and failure. Peroxisome proliferator-activated receptor γ (PPARγ), a member of nuclear receptors, has been proved to ameliorate PAH. However, its effect on PAH-induced right ventricular failure (RVF) remains unknown. Therefore, we investigated the therapeutic potential of PPARγ in preventing monocrotaline (MCT)-induced RV dysfunction. The PAH model was induced by MCT administration. Male rats were administered with MCT to develop PAH and RVF formed by approximately day 30. Significant increase in RV area, RVAW resulted in an ascending RV index. However, the LV function including EF, FS, and LVID did not change significantly. PPARγ agonist prevented PAH-induced RVF by preserving RV index and preventing RVH. PPARγ's beneficial effects seem to result from various factors, including anti-apoptosis, preservation RV index, reversal of inflammation, improvement of glucolipid metabolism, reduction of ROS. In a word, PPARγ agonist prevents the development of RVF.

Management of the Critically Ill Adult With Congenital Heart Disease

Survival of adults with congenital heart disease (CHD) has improved significantly over the last 2 decades, leading to an increase in hospital and intensive care unit (ICU) admissions of these patients. Whereas most of the ICU admissions in the past were related to perioperative management, the incidence of medical emergencies from long-term sequelae of palliative or corrective surgical treatment of these patients is rising. Intensivists now are confronted with patients who not only have complex anatomy after congenital cardiac surgery, but also complex pathophysiology due to decades of living with abnormal cardiac anatomy and diseases of advanced age. Comorbidities affect all organ systems, including cognitive function, pulmonary and cardiovascular systems, liver, and kidneys. Critical care management requires an in-depth understanding of underlying anatomy and pathophysiology in order to apply contemporary concepts of adult ICU care to this population and optimize patient outcomes. In this review, the main CHD lesions and their common surgical management approaches are described, and the sequelae of CHD physiology are discussed. In addition, the effects of chronic comorbidities on the management of critically ill adults are explored, and the adjustments of current ICU management modalities and pharmacology to optimize care are discussed.

Design of a right ventricular mock circulation loop as a test bench for right ventricular assist devices

Right heart failure (RHF), e.g. due to pulmonary hypertension (PH), is a serious health issue with growing occurrence and high mortality rate. Limited efficacy of medication in advanced stages of the disease constitutes the need for mechanical circulatory support of the right ventricle (RV). An essential contribution to the process of developing right ventricular assist devices (RVADs) is the in vitro test bench, which simulates the hemodynamic behavior of the native circulatory system. To model healthy and diseased arterial-pulmonary hemodynamics in adults (mild and severe PH and RHF), a right heart mock circulation loop (MCL) was developed. Incorporating an anatomically shaped silicone RV and a silicone atrium, it not only enables investigations of hemodynamic values but also suction events or the handling of minimal invasive RVADs in an anatomical test environment. Ventricular pressure-volume loops of all simulated conditions as well as pressure and volume waveforms were recorded and compared to literature data. In an exemplary test, an RVAD was connected to the apex to further test the feasibility of studying such devices with the developed MCL. In conclusion, the hemodynamic behavior of the native system was well reproduced by the developed MCL, which is a useful basis for future RVAD tests.

Trimedazidine alleviates pulmonary artery banding-induced acute right heart dysfunction and activates PRAS40 in rats

The molecular mechanism underlying acute right heart failure (RHF) is poorly understood. We used pulmonary artery banding (PAB) to induce acute RHF characterized by a rapid rise of right ventricular pressure, and then a decrease in right ventricular pressure along with a decrease in blood pressure right after banding. We found higher brain natriuretic peptide (BNP) and beta-myosin heavy chain (βMHC) levels and lower alpha-myosin heavy chain (αMHC) levels in RHF rats than sham-operated rats. Hemodynamic indexes in rats with acute RHF were slightly improved by trimedazidine TMZ, a key inhibitor of fatty acid (FA) oxidation. TMZ also reversed downregulation of peroxisome proliferator-activated receptor gamma coactivator 1-beta (PGC-1β) and peroxisome proliferator-activated receptor alpha (PPARα) by PAB and up-regulates peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), peroxisome proliferator-activated receptor delta (PPARδ) and pyruvate dehydrogenase kinase isoform 4 (PDK4). In addition, TMZ reversed upregulation of phosphorylated Akt by PAB and increased phosphorylated proline-rich Akt-substrate 40 (PRAS40). Autophagy and apoptosis were not modified by PAB or TMZ. An acute RHF model was established in rats through 70% constriction of the pulmonary artery. TMZ treatment alleviated PAB-induced acute RHF by activating PRAS40 and upregulatingPGC-1α, PGC-1β, PPARα, PPARδ, and PDK4.

Right Heart End-Systolic Remodeling Index Strongly Predicts Outcomes in Pulmonary Arterial Hypertension: Comparison With Validated Models

BACKGROUND

Right ventricular (RV) end-systolic dimensions provide information on both size and function. We investigated whether an internally scaled index of end-systolic dimension is incremental to well-validated prognostic scores in pulmonary arterial hypertension.

METHODS AND RESULTS

From 2005 to 2014, 228 patients with pulmonary arterial hypertension were prospectively enrolled. RV end-systolic remodeling index (RVESRI) was defined by lateral length divided by septal height. The incremental values of RV free wall longitudinal strain and RVESRI to risk scores were determined. Mean age was 49±14 years, 78% were female, 33% had connective tissue disease, 52% were in New York Heart Association class ≥III, and mean pulmonary vascular resistance was 11.2±6.4 WU. RVESRI and right atrial area were strongly connected to the other right heart metrics. Three zones of adaptation (adapted, maladapted, and severely maladapted) were identified based on the RVESRI to RV systolic pressure relationship. During a mean follow-up of 3.9±2.4 years, the primary end point of death, transplant, or admission for heart failure was reached in 88 patients. RVESRI was incremental to risk prediction scores in pulmonary arterial hypertension, including the Registry to Evaluate Early and Long-Term PAH Disease Management score, the Pulmonary Hypertension Connection equation, and the Mayo Clinic model. Using multivariable analysis, New York Heart Association class III/IV, RVESRI, and log NT-proBNP (N-Terminal Pro-B-Type Natriuretic Peptide) were retained (χ², 62.2; P<0.0001). Changes in RVESRI at 1 year (n=203) were predictive of outcome; patients initiated on prostanoid therapy showed the greatest improvement in RVESRI. Among right heart metrics, RVESRI demonstrated the best test-retest characteristics.

CONCLUSIONS

RVESRI is a simple reproducible prognostic marker in patients with pulmonary arterial hypertension.

Colchicine Depolymerizes Microtubules, Increases Junctophilin-2, and Improves Right Ventricular Function in Experimental Pulmonary Arterial Hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a lethal disease characterized by obstructive pulmonary vascular remodeling and right ventricular (RV) dysfunction. Although RV function predicts outcomes in PAH, mechanisms of RV dysfunction are poorly understood, and RV-targeted therapies are lacking. We hypothesized that in PAH, abnormal microtubular structure in RV cardiomyocytes impairs RV function by reducing junctophilin-2 (JPH2) expression, resulting in t-tubule derangements. Conversely, we assessed whether colchicine, a microtubule-depolymerizing agent, could increase JPH2 expression and enhance RV function in monocrotaline-induced PAH.

METHODS AND RESULTS

Immunoblots, confocal microscopy, echocardiography, cardiac catheterization, and treadmill testing were used to examine colchicine's (0.5 mg/kg 3 times/week) effects on pulmonary hemodynamics, RV function, and functional capacity. Rats were treated with saline (n=28) or colchicine (n=24) for 3 weeks, beginning 1 week after monocrotaline (60 mg/kg, subcutaneous). In the monocrotaline RV, but not the left ventricle, microtubule density is increased, and JPH2 expression is reduced, with loss of t-tubule localization and t-tubule disarray. Colchicine reduces microtubule density, increases JPH2 expression, and improves t-tubule morphology in RV cardiomyocytes. Colchicine therapy diminishes RV hypertrophy, improves RV function, and enhances RV-pulmonary artery coupling. Colchicine reduces small pulmonary arteriolar thickness and improves pulmonary hemodynamics. Finally, colchicine increases exercise capacity.

CONCLUSIONS

Monocrotaline-induced PAH causes RV-specific derangement of microtubules marked by reduction in JPH2 and t-tubule disarray. Colchicine reduces microtubule density, increases JPH2 expression, and improves both t-tubule architecture and RV function. Colchicine also reduces adverse pulmonary vascular remodeling. These results provide biological plausibility for a clinical trial to repurpose colchicine as a RV-directed therapy for PAH.

Assessment of right ventricular longitudinal strain by 2D speckle tracking imaging compared with RV function and hemodynamics in pulmonary hypertension

The right ventricular longitudinal strain (RVLS) of pulmonary hypertension (PH) patients and its relationship with RV function parameters measured by echocardiography and hemodynamic parameters measured by right heart catheterization was investigated. According to the WHO functional class (FC), 66 PH patients were divided into FC I/II (group 1) and III/IV (group 2). RV function parameters were measured by echocardiographic examinations. Hemodynamic parameters were obtained by right heart catheterization. Patients in group 2 had higher systolic pulmonary artery pressure (sPAP; P < 0.05) than patients in group (1) significant between-group differences were observed in global RVLS (RVLS_global), free wall RVLS (RVLS_FW; P < 0.01), and RV conventional function parameters (all P < 0.05). Moreover, mPAP and PVR increased remarkably and CI decreased significantly in group (2) RVLS_global had a positive correlation with 6-min walking distance (6MWD; r = 0.492, P < 0.001) and N-terminal pro-brain natriuretic peptide (NT-proBNP; r = 0.632, P < 0.001), while RVLS_FW had a positive correlation with 6MWD (r = 0.483, P < 0.001) and NT-proBNP (r = 0.627, P < 0.001). Hemodynamics analysis revealed that RVLS_global had a positive correlation with mPAP (r = 0.594, P < 0.001), PVR (r = 0.573, P < 0.001) and CI (r = 0.366, P = 0.003), while RVLS_FW had a positive correlation with mPAP (r = 0.597, P < 0.001), PVR (r = 0.577, P < 0.001) and CI (r = 0.369, P = 0.002). According to receiver operating characteristic curves, the optimal cut-off values of RVLS_global (-15.0%) and RVLS_FW (-15.3%) for prognosis detection with good sensitivity and specificity. Evidence has shown that RVLS measurement can provide the much-needed and reliable information on RV function and hemodynamics. Therefore, this qualifies as a patient-friendly approach for the clinical management of PH patients.

Altered mTOR and Beclin-1 mediated autophagic activation during right ventricular remodeling in monocrotaline-induced pulmonary hypertension

Background

Right ventricular structure and function is a major predictor of outcomes in pulmonary hypertension (PH), yet the underlying mechanisms remain poorly understood. Growing evidence suggests the importance of autophagy in cardiac remodeling; however, its dynamics in the process of right ventricle(RV) remodeling in PH has not been fully explored. We sought to study the time course of cardiomyocyte autophagy in the RV in PH and determine whether mammalian target of rapamycin (mTOR) and Beclin-1 hypoxia-related pro-autophagic pathways are underlying mechanisms.

Methods

Rats were studied at 2, 4, and 6 weeks after subcutaneous injection of 60 mg/kg monocrotaline (MCT) (MCT-2 W, 4 W, 6 W) or vehicle (CON-2 W, 4 W, 6 W). Cardiac hemodynamics and RV function were assessed in rats. Autophagy structures and markers were assessed using transmission electron microscope, RT-qPCR, immunohistochemistry staining, and western blot analyses. Western blot was also used to quantify the expression of mTOR and Beclin-1 mediated pro-autophagy signalings in the RV.

Results

Two weeks after MCT injection, pulmonary artery systolic pressure increased and mild RV hypertrophy without RV dilation was observed. RV enlargement presented at 4 weeks with moderately decreased function, whereas typical characteristics of RV decompensation and failure occurred at 6 weeks thus demonstrating the progression of RV remodeling in the MCT model. A higher LC3 (microtubule- associated protein light chain 3) II/I ratio, upregulated LC3 mRNA and protein levels, as well as accumulation of autophagosomes in RV of MCT rats indicated autophagy induction. Autophagy activation was coincident with increased pulmonary artery systolic pressure. Pro-autophagy signaling pathways were activated in a RV remodeling stage-dependent manner since phospho-AMPK (adenosine monophosphate-activated protein kinase)-α were primarily upregulated and phospho-mTOR suppressed in the RV at 2 and 4 weeks post-MCT injection, whearas, BNIP3 (Bcl2-interacting protein 3) and beclin-1 expression were relatively low during these stages, they were significantly upregulated after 6 weeks in this model.

Conclusions

Our findings provide evidence of sustained activation of autophagy in RV remodeling of MCT induced PH model, while pro-autophagic signaling pathways varied depending on the phase.

World Health Organization Group I Pulmonary Hypertension: Epidemiology and Pathophysiology

Pulmonary arterial hypertension (PAH) is a debilitating disease characterized by pathologic remodeling of the resistance pulmonary arteries, ultimately leading to right ventricular (RV) failure and death. In this article we discuss the definition of PAH, the initial epidemiology based on the National Institutes of Health Registry, and the updated epidemiology gleaned from contemporary registries, pathogenesis of pulmonary vascular dysfunction and proliferation, and RV failure in PAH.

Capsaicin pretreatment reversed pulmonary arterial hypertension by alleviating inflammation via p38MAPK pathway

Purpose/Aim: Pulmonary arterial hypertension (PAH) is a lethal disease associated with pulmonary vascular remodeling as well as inflammation. As a kind of tachykinin secreted by nerves and inflammatory cells, substance P (SP) has been proved to be involved in the progression of PAH. Capsaicin can deplete substance P and provide benefits in PAH. However, the mechanism is still unclear. In this article, we aim to illustrate the possible mechanism involved in the process of capsaicin alleviating PAH.

MATERIALS AND METHODS

A single injection of monocrotaline (MCT) to male Sprague-Dawley (SD) rats was conducted to induce PAH. Capsaicin pretreatment was administered three days before MCT injection to deplete substance P. P38mitogen-activated protein kinase (p38MAPK) activator or inhibitor was given intraperitoneally after MCT injection. After 28 days, hemodynamic studies were carried out, and right ventricular systolic pressure (RVSP), right ventricular (RV)/left ventricle plus septum (LV+S), RV/body weight (BW), and lung weight (LW)/BW were recorded and calculated. In addition, the pulmonary vascular remodeling (pulmonary arterial medial wall thickness, area, perivascualr fibrosis), pro-inflammatory cytokines, the common signal pathways, such as peroxisome proliferator-activated receptor gamma (PPARγ), extracellular signal-regulated kinases (Erk), protein kinase B (Akt), and p38MAPK were also detected.

RESULTS

Capsaicin pretreatment reversed PAH, including decreasing RVSP, RV/(LV+S), RV/BW, and LW/BW, and alleviating inflammation. Phosphorylated-p38 (p-p38) MAPK was up-regulated, which was partially reversed by capsaicin pretreatment. Interestingly, expression of Akt, Erk, and PPARγ was not altered by capsaicin pretreatment. Inhibition of p38MAPK provided the same benefits with capsaicin pretreatment, whereas it failed to provide additional improvement in the presence of capsaicin. Besides, p38MAPK activator abolished the effects of capsaicin pretreatment on PAH, suggesting a key role of p38MPAK pathway in the effects of capsaicin reversing PAH.

CONCLUSIONS

Capsaicin pretreatment reversed PAH by alleviating inflammation via p38MAPK pathway.

NADPH oxidase: its potential role in promotion of pulmonary arterial hypertension

NADPH oxidases (NOXs) are a group of enzymes for superoxide anion (O₂^·- ) generation through transferring electrons from NADPH to molecular oxygen, which is rapidly converted into hydrogen peroxide (H₂O₂). There are seven members in NOX family, including NOX1 to NOX5, dual oxidase1, and dual oxidase 2. Recent studies have demonstrated that NOX subtypes may have different functions in different types of pulmonary arterial hypertension (PAH). The NOX-derived reactive oxygen species (ROS) are key factors that are involved in promoting the processes of pulmonary vascular remodeling, such as endothelial dysfunction, proliferation of pulmonary arterial smooth muscle cells (PASMCs), and cellular trans-differentiation, which are the basic pathologic characteristics of PAH. Inhibition of NOX shows beneficial effect on prevention of PAH development. Thus, NOX might be a potential target for PAH therapy. The main purpose of this review is to summarize recent findings on the role of NOX, particularly the NOX subtypes, in promotion of PAH development and to list recent progress regarding the NOX-based intervention for PAH.

The effects of pulmonary vasodilating agents on right ventricular parameters in severe group 3 pulmonary hypertension: a pilot study

Pulmonary arterial hypertension (PAH)-approved vasodilators improve right ventricular (RV) function in patients with PAH. However, whether PAH-approved drugs ameliorate RV morphology and function in lung disease-associated pulmonary hypertension (lung-PH) remains unclear. We aimed to prospectively evaluate the changes in RV volume and ejection fraction (RVEF) in 14 consecutive severe lung-PH patients treated with PAH-approved vasodilators. Severe lung-PH was defined as a mean pulmonary arterial pressure (MPAP) of ≥35 mmHg or an MPAP of ≥25 mmHg with a cardiac index (L/min/m²) of <2. Right heart catheterization and cardiac magnetic resonance (CMR) imaging were performed at baseline and at 3 months after starting sildenafil with or without other PAH-approved drugs. Follow-up was conducted at 3 months in 11 participants; compared with baseline values, MPAP and pulmonary vascular resistance (PVR) decreased by 18% and 37%, respectively. Baseline CMR imaging revealed an elevated RV end-diastolic volume index (RVEDVI; mL/m²) of 117.5 ± 35.9 and a below-average RVEF of 25.2% ± 7.2%; after 3 months, RVEDVI decreased by 23.7% (P = 0.0061) and RVEF increased by 32.9% (P = 0.0165). Among the 11 patients, 3 were thought to be a stable and homogenous subset in terms of background lung disease and medical management administered. These 3 patients exhibited similar ameliorations in PVR and RVEF, compared with the other 8 patients. PAH-approved drug treatment may improve RV dilatation and systolic function among patients with severe lung-PH. This study was approved by University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR) on September 1, 2013 (UMIN000011541).

Effect of early administration of lower dose versus high dose of fresh mitochondria on reducing monocrotaline-induced pulmonary artery hypertension in rat

OBJECTIVE

This study aim to investigate whether early mitochondrial administration would be effective and whether high-dose mitochondria (15000 μg/rat) would be more effective than low-dose mitochondria (1500 μg/rat) for attenuating the monocrotaline (MCT/65 mg/kg/rat)-induced pulmonary artery hypertension (PAH) in rat.

METHOD AND RESULTS

Male-adult SD rats (n = 32) were randomized categorized into groups 1 (sham-control), 2 (PAH), 3 (PAH + low-dose mitochondria), and 4 (PAH + high-dose mitochondria). Mitochondria were admitted at day 5 and rats were sacrificed at day 35 post-MCT treatment. By day 35, oxygen saturation (saO₂) was highest in group 1 and lowest in group 2, and significantly higher in group 3 than in group 4 (P<0.001). Conversely, right ventricular systolic blood pressure showed an opposite pattern compared with saO₂ among all groups (P<0.001). Histological integrity of alveolar sacs exhibited a pattern identical to saO₂, whereas lung crowding score and number of muscularized artery displayed an opposite pattern (all P<0.001). The protein expression of indices of inflammation (MMP-9, TNF-α, NF-κB), oxidative stress (oxidized protein, NO-1, NOX-2, NOX-4), apoptosis (Bax, cleaved caspase-3 and PARP), fibrosis (p-Smad3, TGF-β), mitochondrial-damage (cytosolic cytochrome-C), and hypoxia-smooth muscle proliferative factors (HIF-α, connexin43, TRPCs) showed an opposite pattern compared, whereas anti-fibrosis (p-Smad1/5, BMP-2) and mitochondrial integrity (mitochondrial cytochrome-C) exhibited an identical pattern to saO₂ in all groups (all P<0.001).

CONCLUSION

Low dose is superior to high dose of mitochondria for protecting against MCT-induced PAH. The paradoxical beneficial effect may imply therapy with 15000 μg/rat mitochondria is overdose in this situation.

Right ventricular relative wall thickness as a predictor of outcomes and of right ventricular reverse remodeling for patients with pulmonary hypertension

Mid-term right ventricular (RV) reverse remodeling after treatment in patients with pulmonary hypertension (PH) is associated with long-term outcome as well as baseline RV remodeling. However, baseline factors influencing mid-term RV reverse remodeling after treatment and its prognostic capability remain unclear. We studied 54 PH patients. Mid-term RV remodeling was assessed in terms of the RV area, which was traced planimetrically at the end-systole (RVESA). RV reverse remodeling was defined as a relative decrease in the RVESA of at least 15% at 10.2 ± 9.4 months after treatment. Long-term follow-up was 5 years. Adverse events occurred in ten patients (19%) and mid-term RV reverse remodeling after treatment was observed in 37 (69%). Patients with mid-term RV reverse remodeling had more favorable long-term outcomes than those without (log-rank: p = 0.01). Multivariate logistic regression analysis showed that RV relative wall thickness (RV-RWT), as calculated as RV free-wall thickness/RV basal linear dimension at end-diastole, was an independent predictor of mid-term RV reverse remodeling (OR 1.334; 95% CI, 1.039-1.713; p = 0.03). Moreover, patients with RV-RWT ≥0.21 showed better long-term outcomes than did those without (log-rank p = 0.03), while those with RV-RWT ≥0.21 and mid-term RV reverse remodeling had the best long-term outcomes. Patients with RV-RWT <0.21 and without mid-term RV reverse remodeling, on the other hand, had worse long-term outcomes than other sub-groups. In conclusions, RV-RWT could predict mid-term RV reverse remodeling after treatment in PH patients, and was associated with long-term outcomes. Our finding may have clinical implications for better management of PH patients.

Gender-related differences in pulmonary arterial hypertension targeted drugs administration

During the last 15 years, a real "paradigm-shift" occurred, due to the development of PAH-targeted drugs, leading to crucial improvements in symptoms, exercise capacity, hemodynamics and outcome of PAH patients. In order to describe differences regarding epidemiology and therapy in PAH according to gender, we performed a review of the available literature in "PubMed" and "Web of Science" databases. In order to find relevant articles, we combined each of the following the keywords "pulmonary arterial hypertension", "gender", "sex", "men", "woman", "male", "female", "phosphodiesterase inhibitors", "endothelin receptor antagonists", "prostanoids". While there is a substantial agreement among epidemiological studies in reporting an increased prevalence of pulmonary arterial hypertension (PAH) among women, male PAH patients are affected by a higher impairment of the right ventricular function and consequently experience poorer outcomes. With regards to PAH-targeted drug administration, endothelin receptor antagonists (ERAs) and prostacyclin analogues (PC) show better treatment results in female PAH patients, while phosphodiesterase-5 inhibitors (PD5-I) seem to exert a more beneficial effect on male patients. However, to date no clear consensus could be formed by the available literature, which is constituted mainly by retrospective studies. Females with PAH are more prone to develop PAH, while males experience poorer outcomes. Females PAH might benefit more from ERAs and PC, while males seem to have more beneficial effects from PD5-I administration. However, more research is warranted in order to assess the most effective treatment for PAH patients according to gender.

The emerging role of epigenetics in pulmonary arterial hypertension: an important avenue for clinical trials (2015 Grover Conference Series)

Epigenetics is an emerging field of research and clinical trials in cancer therapy that also has applications for pulmonary arterial hypertension (PAH), as there is evidence that epigenetic control of gene expression plays a significant role in PAH. The three types of epigenetic modification include DNA methylation, histone modification, and RNA interference. All three have been shown to be involved in the development of PAH. Currently, the enzymes that perform these modifications are the primary targets of neoplastic therapy. These targets are starting to be explored for therapies in PAH, mostly in animal models. In this review we summarize the basics of each type of epigenetic modification and the known sites and molecules involved in PAH, as well as current targets and prospects for clinical trials.

Role of Biomarkers in the Diagnosis, Risk Assessment, and Management of Pulmonary Hypertension

Pulmonary hypertension is a severe and debilitating disease with no definite cure, and the domain of targeted therapies is a promising field for better management of this severe condition. The disease comprises pulmonary arterial remodeling, hypoxia, endothelial dysfunction, and inflammation, with subsequent organ damage including right heart and liver dysfunction. Biomarkers have a valuable role at different levels of the disease, from diagnosis to risk assessment and management, in order to decrease the burden of the disease in terms of both morbidity and mortality.

Hemodynamic instability in the critically ill neonate: An approach to cardiovascular support based on disease pathophysiology

Hemodynamic disturbance in the sick neonate is common, highly diverse in underlying pathophysiology and dynamic. Dysregulated systemic and cerebral blood flow is hypothesized to have a negative impact on neurodevelopmental outcome and survival. An understanding of the physiology of the normal neonate, disease pathophysiology, and the properties of vasoactive medications may improve the quality of care and lead to an improvement in survival free from disability. In this review we present a modern approach to cardiovascular therapy in the sick neonate based on a more thoughtful approach to clinical assessment and actual pathophysiology. Targeted neonatal echocardiography offers a more detailed insight into disease processes and offers longitudinal assessment, particularly response to therapeutic intervention. The pathophysiology of common neonatal conditions and the properties of cardiovascular agents are described. In addition, we outline separate treatment algorithms for various hemodynamic disturbances that are tailored to clinical features, disease characteristics and echocardiographic findings.

Metabolic Changes Precede the Development of Pulmonary Hypertension in the Monocrotaline Exposed Rat Lung

There is increasing interest in the potential for metabolic profiling to evaluate the progression of pulmonary hypertension (PH). However, a detailed analysis of the metabolic changes in lungs at the early stage of PH, characterized by increased pulmonary artery pressure but prior to the development of right ventricle hypertrophy and failure, is lacking in a preclinical animal model of PH. Thus, we undertook a study using rats 14 days after exposure to monocrotaline (MCT), to determine whether we could identify early stage metabolic changes prior to the manifestation of developed PH. We observed changes in multiple pathways associated with the development of PH, including activated glycolysis, increased markers of proliferation, disruptions in carnitine homeostasis, increased inflammatory and fibrosis biomarkers, and a reduction in glutathione biosynthesis. Further, our global metabolic profile data compare favorably with prior work carried out in humans with PH. We conclude that despite the MCT-model not recapitulating all the structural changes associated with humans with advanced PH, including endothelial cell proliferation and the formation of plexiform lesions, it is very similar at a metabolic level. Thus, we suggest that despite its limitations it can still serve as a useful preclinical model for the study of PH.

Changes in Caspase-3, B Cell Leukemia/Lymphoma-2, Interleukin-6, Tumor Necrosis Factor-α and Vascular Endothelial Growth Factor Gene Expression after Human Umbilical Cord Blood Derived Mesenchymal Stem Cells Transfusion in Pulmonary Hypertension Rat Models

Background and Objectives

Failure of vascular smooth muscle apoptosis and inflammatory response in pulmonary arterial hypertension (PAH) is a current research focus. The goals of this study were to determine changes in select gene expressions in monocrotaline (MCT)-induced PAH rat models after human umbilical cord blood derived mesenchymal stem cells (hUCB-MSCs) transfusion.

Materials and Methods

The rats were separated into 3 groups i.e., control group (C group), M group (MCT 60 mg/kg), and U group (hUCB-MSCs transfusion) a week after MCT injection.

Results

TUNEL assay showed that the U group had significantly lowered positive apoptotic cells in the lung tissues, as compared with the M group. mRNA of caspase-3, B cell leukemia/lymphoma (Bcl)-2, interleukin (IL)-6, tumor necrosis factor (TNF)-α and vascular endothelial growth factor (VEGF) in the lung tissues were greatly reduced at week 4 in the U group. Immunohistochemical staining of the lung tissues also demonstrated a similar pattern, with the exception of IL-6. The protein expression of caspase-3, Bcl-2 VEGF, IL-6, TNF-α and brain natriuretic peptide in the heart tissues were significantly lower in the U group, as compared with the M group at week 2. Furthermore, the protein expression of VEGF, IL-6 and BNP in the heart tissues were significantly lower in the U group at week 4. Collagen content in the heart tissues was significantly lower in the U group, as compared with M group at weeks 2 and 4, respectively.

Conclusion

hUCB-MSCs could prevent inflammation, apoptosis and remodeling in MCT-induced PAH rat models.

Longitudinal Assessment of Left and Right Myocardial Function in Preterm Infants Using Strain and Strain Rate Imaging

BACKGROUND

There is a paucity of longitudinal data on left ventricular (LV) and right ventricular (RV) function in preterm infants of less than 29 weeks' gestation.

OBJECTIVE

The aim of this study was to describe changes in tissue Doppler-derived basal longitudinal strain (BLS) and systolic (SRs), early (SRe) and late (SRa) diastolic strain rates in extremely premature infants from birth to 36 weeks postmenstrual age (PMA).

METHODS

Echocardiographic assessments were carried out on days 1, 2, 5-7 and at 36 weeks PMA. We assessed the following associations: correlation with systemic vascular resistance (SVR) on day 1, influence of a patent ductus arteriosus (PDA) during days 5-7, and the effect of chronic lung disease (CLD).

RESULTS

In total, 105 infants with a median gestation of 27.1 weeks (IQR 26.0-28.1) and a birthweight of 965 g (IQR 785-1,153) were included. There was an increase in most of the measurements across the four time points. On day 1, there was a weak negative correlation between SVR and LV BLS (r = -0.3, p = 0.01), SVR and septal BLS (r = -0.4, p < 0.001) and SVR and LV SRe (r = -0.4, p = 0.005). On days 5-7, infants with a PDA >1.5 mm had higher LV BLS [-13.0 (2.4) vs. -11.9 (1.9)%, p = 0.03]. At 36 weeks, infants with CLD (n = 28/47) had lower RV BLS [-26.4 (5.0) vs. -30.7 (5.5)%, p = 0.01] and lower RV SRa [4.2 (1.3) vs. 5.3 (1.9) s-1, p = 0.04].

CONCLUSION

Myocardial function undergoes important longitudinal changes in preterm infants. Left heart strain measurements appear to be weakly influenced by changes in preload and afterload. CLD appears to leave a negative impact on RV function.

Different Predictors of Right and Left Ventricular Metabolism in Healthy Middle-Aged Men

Dysfunction of the right ventricle (RV) plays a crucial role in the outcome of various cardiovascular diseases. Previous studies on RV metabolism are sparse although evidence implies it may differ from left ventricular (LV) metabolism. Therefore, the aims of this study were (1) to determine predictors of RV glucose uptake (GU) and free fatty acid uptake (FFAU) and (2) to compare them to predictors of LV metabolism in healthy middle-aged men. Altogether 28 healthy, sedentary, middle-aged (40-55 years) men were studied. Insulin-stimulated GU and fasting FFAU were measured by positron emission tomography and RV and LV structural and functional parameters by cardiac magnetic resonance. Several parameters related to whole-body health were also measured. Predictors of RV and LV metabolism were determined by pairwise correlation analysis, lasso regression models, and variable clustering using heatmap. RVGU was most strongly predicted by age and moderately by RV ejection fraction (EF). The strongest determinants of RVFFAU were exercise capacity (peak oxygen uptake), resting heart rate, LVEF, and whole-body insulin-stimulated glucose uptake rate. When considering LV metabolism, age and RVEF were associated also with LVGU. In addition, LVGU was strongly, and negatively, influenced by whole-body insulin-stimulated glucose uptake rate. LVFFAU was predicted only by LVEF. This study shows that while RV and LV metabolism have shared characteristics, they also have unique properties. Age of the subject should be taken into account when measuring myocardial glucose utilization. Ejection fraction is related to myocardial metabolism, and even so that RVEF may be more closely related to GU of both ventricles and LVEF to FFAU of both ventricles, a finding supporting the ventricular interdependence. However, only RV fatty acid utilization associates with exercise capacity so that better physical fitness in a relatively sedentary population is related with decreased RV fat metabolism. To conclude, this study highlights the need for further study designed specifically on less-known RV, as the results on LV metabolism and physiology may not be directly applicable to the RV.

Right ventricle dysfunction in pulmonary hypertension: mechanisms and modes of detection

PURPOSE OF REVIEW

This review highlights the right ventricular (RV) involvement in pulmonary hypertension from pathophysiologic changes to current imaging tools used to screen, diagnose and follow up RV function in patients with pulmonary hypertension.

RECENT FINDINGS

Although right heart catheterization is the gold standard for the diagnosis of pulmonary hypertension, other diagnostic methods such as echocardiography, magnetic resonance and nuclear imaging are of great utility in the assessment of the RV in pulmonary hypertension. Apart from its conventional use as a screening tool for pulmonary hypertension, echocardiography allows assessment of RV size and function and has prognostic value. Among the novel applications of echocardiography, exercise echocardiography and measurements of RV strain might help unveil subclinical pulmonary hypertension, whereas three-dimensional echocardiography allows more accurate measures of RV morphology and function. Cardiac magnetic resonance imaging is currently the gold standard noninvasive imaging method to assess RV volume, mass and function and has prognostic value in the assessment of pulmonary hypertension. Finally, positron emission tomography is a promising tool in the metabolic assessment of the RV and pulmonary circulation.

SUMMARY

RV assessment is essential in the overall evaluation of pulmonary hypertension. Despite the availability of several methods and measurements for this assessment, there is, however, no standard approach or broad consensus on their application.

Molecular switches under TGFβ signalling during progression from cardiac hypertrophy to heart failure

Cardiac hypertrophy is a mechanism to compensate for increased cardiac work load, that is, after myocardial infarction or upon pressure overload. However, in the long run cardiac hypertrophy is a prevailing risk factor for the development of heart failure. During pathological remodelling processes leading to heart failure, decompensated hypertrophy, death of cardiomyocytes by apoptosis or necroptosis and fibrosis as well as a progressive dysfunction of cardiomyocytes are apparent. Interestingly, the induction of hypertrophy, cell death or fibrosis is mediated by similar signalling pathways. Therefore, tiny changes in the signalling cascade are able to switch physiological cardiac remodelling to the development of heart failure. In the present review, we will describe examples of these molecular switches that change compensated hypertrophy to the development of heart failure and will focus on the importance of the signalling cascades of the TGFβ superfamily in this process. In this context, potential therapeutic targets for pharmacological interventions that could attenuate the progression of heart failure will be discussed.

Downregulation of MicroRNA-126 Contributes to the Failing Right Ventricle in Pulmonary Arterial Hypertension

BACKGROUND

Right ventricular (RV) failure is the most important factor of both morbidity and mortality in pulmonary arterial hypertension (PAH). However, the underlying mechanisms resulting in the failed RV in PAH remain unknown. There is growing evidence that angiogenesis and microRNAs are involved in PAH-associated RV failure. We hypothesized that microRNA-126 (miR-126) downregulation decreases microvessel density and promotes the transition from a compensated to a decompensated RV in PAH.

METHODS AND RESULTS

We studied RV free wall tissues from humans with normal RV (n=17), those with compensated RV hypertrophy (n=8), and patients with PAH with decompensated RV failure (n=14). Compared with RV tissues from patients with compensated RV hypertrophy, patients with decompensated RV failure had decreased miR-126 expression (quantitative reverse transcription-polymerase chain reaction; P<0.01) and capillary density (CD31(+) immunofluorescence; P<0.001), whereas left ventricular tissues were not affected. miR-126 downregulation was associated with increased Sprouty-related EVH1 domain-containing protein 1 (SPRED-1), leading to decreased activation of RAF (phosphorylated RAF/RAF) and mitogen-activated protein kinase (MAPK); (phosphorylated MAPK/MAPK), thus inhibiting the vascular endothelial growth factor pathway. In vitro, Matrigel assay showed that miR-126 upregulation increased angiogenesis of primary cultured endothelial cells from patients with decompensated RV failure. Furthermore, in vivo miR-126 upregulation (mimic intravenous injection) improved cardiac vascular density and function of monocrotaline-induced PAH animals.

CONCLUSIONS

RV failure in PAH is associated with a specific molecular signature within the RV, contributing to a decrease in RV vascular density and promoting the progression to RV failure. More importantly, miR-126 upregulation in the RV improves microvessel density and RV function in experimental PAH.