Longitudinal in vivo SPECT/CT imaging reveals morphological changes and cardiopulmonary apoptosis in a rodent model of pulmonary arterial hypertension

Dose-related Effects of Resveratrol in Different Models of Pulmonary Arterial Hypertension: A Systematic Review

BACKGROUND

Pulmonary Arterial Hypertension (PAH) is a severe and progressive disease of pulmonary arterioles. This pathology is characterized by elevation of the pulmonary vascular resistance and pulmonary arterial pressure, leading to right heart failure and death. Studies have demonstrated that resveratrol possesses a protective effect on the mechanisms related to the genesis of the PAH-induced by different models.

OBJECTIVE

This study aimed to investigate the dose-related effects of resveratrol in different models of pulmonary arterial hypertension.

METHODS

To identify eligible papers, we performed a systematic literature search on Scielo, Pub- Med, and Scholar Google. The research was limited to articles written in English in the last 10 years. We used the following descriptors to search: Pulmonary Arterial Hypertension and Resveratrol, OR Resveratrol, and Animal models of Pulmonary Arterial Hypertension, OR Resveratrol, and in vitro models of Pulmonary Arterial Hypertension.

RESULTS

1724 studies were identified through the descriptors used, fifty-five studies with different models of pulmonary arterial hypertension were selected for the full review, forty-four were excluded after application of exclusion and inclusion criteria, totalizing eleven studies included in this systematic review.

CONCLUSION

The results showed that resveratrol, at low and high doses, protects in a dosedependent manner against the development of PAH induced through monocrotaline, normoxia and hypoxia models. In addition to having chemopreventive, anti-inflammatory, antioxidant and antiproliferative properties. In the case of PAH-related myocardial injury, resveratrol protects cells from apoptosis, thus working as an antiapoptotic agent.

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.

Evidence of apoptosis in right ventricular dysfunction in rheumatic mitral valve stenosis

Background & objectives:

Right ventricular (RV) dysfunction is one of the causes of morbidity and mortality in valvular heart disease. The phenomenon of apoptosis, though rare in cardiac muscle may contribute to loss of its function. Role of apoptosis in RV in patients with rheumatic valvular heart disease is investigated in this study.

Methods:

Patients with rheumatic mitral valve stenosis formed two groups based on RV systolic pressure (RVSP) as RVSP <40 mmHg (group I, n=9) and RVSP ≥40 mmHg (group II, n=30). Patients having atrial septal defect (ASD) with RVSP <40 mmHg served as control (group III, n=15). Myocardial performance index was assessed for RV function. Real-time polymerase chain reaction was performed on muscle biopsy procured from RV to assess expression of pro-apoptotic genes (Bax, cytochrome c, caspase 3 and Fas) and anti-apoptotic genes (Bcl-2). Apoptosis was confirmed by histopathology and terminal deoxynucleotide-transferase-mediated dUTP nick end labelling.

Results:

Group II had significant RV dysfunction compared to group I (P=0.05) while caspase 3 (P=0.01) and cytochrome c (P=0.03) were expressed excessively in group I. When group I was compared to group III (control), though there was no difference in RV function, a highly significant expression of pro-apoptotic genes was observed in group I (Bax, P=0.02, cytochrome c=0.001 and caspase 3=0.01). There was a positive correlation between pro-apoptotic genes. Nuclear degeneration was present conforming to apoptosis in valve disease patients (groups I and II) while it was absent in patients with ASD.

Interpretation & conclusion:

Our findings showed evidence of apoptosis in RV of patients with valvular heart disease. Apoptosis was set early in the course of rheumatic valve disease even with lower RVSP, followed by RV dysfunction; however, expression of pro-apoptotic genes regressed.

Right heart imaging in patients with heart failure: a tale of two ventricles

PURPOSE OF REVIEW

The purpose is to describe the recent advances made in imaging of the right heart, including deformation imaging, tissue, and flow characterization by MRI, and molecular imaging.

RECENT FINDINGS

Recent developments have been made in the field of deformation imaging of the right heart, which may improve risk stratification of patients with heart failure and pulmonary hypertension. In addition, more attention has been given to load adaptability metrics of the right heart; these simplified indices, however, still face challenges from a conceptual point of view. The emergence of novel MRI sequences, such as native T1 mapping, allows better detection and quantification of myocardial fibrosis and could allow better prediction of postsurgical recovery of the right heart. Other advances in MRI include four-dimensional flow imaging, which may be particularly useful in congenital heart disease or for the detection of early stages of pulmonary vascular disease.

SUMMARY

The review will place the recent developments in right heart imaging in the context of clinical care and research.

Hypoxia-induced pulmonary arterial hypertension augments lung injury and airway reactivity caused by ozone exposure

Ozone (O3)-related cardiorespiratory effects are a growing public health concern. Ground level O3 can exacerbate pre-existing respiratory conditions; however, research regarding therapeutic interventions to reduce O3-induced lung injury is limited. In patients with chronic obstructive pulmonary disease, hypoxia-associated pulmonary hypertension (HPH) is a frequent comorbidity that is difficult to treat clinically, yet associated with increased mortality and frequency of exacerbations. In this study, we hypothesized that established HPH would confer vulnerability to acute O3 pulmonary toxicity. Additionally, we tested whether improvement of pulmonary endothelial barrier integrity via rho-kinase inhibition could mitigate pulmonary inflammation and injury. To determine if O3 exacerbated HPH, male C57BL/6 mice were subject to either 3 weeks continuous normoxia (20.9% O2) or hypoxia (10.0% O2), followed by a 4-h exposure to either 1ppm O3 or filtered air (FA). As an additional experimental intervention fasudil (20mg/kg) was administered intraperitoneally prior to and after O3 exposures. As expected, hypoxia significantly increased right ventricular pressure and hypertrophy. O3 exposure in normoxic mice caused lung inflammation but not injury, as indicated by increased cellularity and edema in the lung. However, in hypoxic mice, O3 exposure led to increased inflammation and edema, along with a profound increase in airway hyperresponsiveness to methacholine. Fasudil administration resulted in reduced O3-induced lung injury via the enhancement of pulmonary endothelial barrier integrity. These results indicate that increased pulmonary vascular pressure may enhance lung injury, inflammation and edema when exposed to pollutants, and that enhancement of pulmonary endothelial barrier integrity may alleviate such vulnerability.

Microarray analysis after umbilical cord blood derived mesenchymal stem cells injection in monocrotaline-induced pulmonary artery hypertension rats

Pulmonary arterial hypertension (PAH) is associated with structural alterations of lung vasculature. PAH is still a devastating disease needing an aggressive therapeutic approach. Despite the therapeutic potential of human umbilical cord mesenchymal stem cells (MSCs), the molecular parameters to define the stemness remain largely unknown. Using high-density oligonucleotide microarrays, the differential gene expression profiles between a fraction of mononuclear cells of human umbilical cord blood (UCB) and its MSC subpopulation were obtained. Of particular interest was a subset of 46 genes preferentially expressed at 7-fold or higher in the group treated with human UCB-MSCs. This subset contained numerous genes involved in the inflammatory response, immune response, lipid metabolism, cell adhesion, cell migration, cell differentiation, apoptosis, cell growth, transport, cell proliferation, transcription, and signal transduction. Our results provide a foundation for a more reproducible and reliable quality control using genotypic analysis for the definition of human UCB-MSCs. Therefore, our results will provide a basis for studies on molecular mechanisms controlling the core properties of human MSCs.

Molecular imaging of the pulmonary circulation in health and disease

The pulmonary circulation, at the unique crossroads between the left and the right heart, is submitted to large physiologic hemodynamic variations and possesses numerous important metabolic functions mediated through its vast endothelial surface. There are many pathologic conditions that can directly or indirectly affect the pulmonary vasculature and modify its physiology and functions. Pulmonary hypertension, the end result of many of these affections, is unfortunately diagnosed too late in the disease process, meaning that there is a crying need for earlier diagnosis and surrogate markers of disease progression and regression. By targeting endothelial, medial and adventitial targets of the pulmonary vasculature, novel molecular imaging agents could provide early detection of physiologic and biologic perturbation in the pulmonary circulation. This review provides the rationale for the development of molecular imaging agents for the diagnosis and follow-up of disorders of the pulmonary circulation and discusses promising targets for SPECT and positron emission tomographic imaging.

Muscle RING finger-1 promotes a maladaptive phenotype in chronic hypoxia-induced right ventricular remodeling

Exposure to chronic hypoxia (CH) induces elevated pulmonary artery pressure/resistance, leading to an eventual maladaptive right ventricular hypertrophy (RVH). Muscle RING finger-1 (MuRF1) is a muscle-specific ubiquitin ligase that mediates myocyte atrophy and has been shown to play a role in left ventricular hypertrophy and altered cardiac bioenergetics in pressure overloaded hearts. However, little is known about the contribution of MuRF1 impacting RVH in the setting of CH. Therefore, we hypothesized that MuRF1 deletion would enhance RVH compared to their wild-type littermates, while cardiac-specific overexpression would reduce hypertrophy following CH-induced pulmonary hypertension. We assessed right ventricular systolic pressure (RVSP), right ventricle to left ventricle plus septal weight ratio (RV/LV+S) and hematocrit (Hct) following a 3-wk isobaric CH exposure. Additionally, we conducted dual-isotope SPECT/CT imaging with cardiac function agent ²⁰¹Tl-chloride and cell death agent ^99mTc-annexin V. Predictably, CH induced pulmonary hypertension, measured by increased RVSP, RV/LV+S and Hct in WT mice compared to normoxic WT mice. Normoxic WT and MuRF1-null mice exhibited no significant differences in RVSP, RV/LV+S or Hct. CH-induced increases in RVSP were also similar between WT and MuRF1-null mice; however, RV/LV+S and Hct were significantly elevated in CH-exposed MuRF1-null mice compared to WT. In cardiac-specific MuRF1 overexpressing mice, RV/LV+S increased significantly due to CH exposure, even greater than in WT mice. This remodeling appeared eccentric, maladaptive and led to reduced systemic perfusion. In conclusion, these results are consistent with an atrophic role for MuRF1 regulating the magnitude of right ventricular hypertrophy following CH-induction of pulmonary hypertension.

Resveratrol and clinical trials: the crossroad from in vitro studies to human evidence

Resveratrol (3,5,4’-trihydroxy-trans-stilbene) is a non-flavonoid polyphenol that may be present in a limited number of food-stuffs such as grapes and red wine. Resveratrol has been reported to exert a plethora of health benefits through many different mechanisms of action. This versatility and presence in the human diet have drawn the worldwide attention of many research groups over the past twenty years, which has resulted in a huge output of in vitro and animal (preclinical) studies. In line with this expectation, many resveratrol-based nutraceuticals are consumed all over the world with questionable clinical/scientific support. In fact, the confirmation of these benefits in humans through randomized clinical trials is still very limited. The vast majority of preclinical studies have been performed using assay conditions with a questionable extrapolation to humans, i.e. too high concentrations with potential safety concerns (adverse effects and drug interactions), short-term exposures, in vitro tests carried out with non-physiological metabolites and/or concentrations, etc. Unfortunately, all these hypothesis-generating studies have contributed to increased the number of ‘potential’ benefits and mechanisms of resveratrol but confirmation in humans is very limited. Therefore, there are many issues that should be addressed to avoid an apparent endless loop in resveratrol research. The so-called ‘Resveratrol Paradox’, i.e., low bioavailability but high bioactivity, is a conundrum not yet solved in which the final responsible actor (if any) for the exerted effects has not yet been unequivocally identified. It is becoming evident that resveratrol exerts cardioprotective benefits through the improvement of inflammatory markers, atherogenic profile, glucose metabolism and endothelial function. However, safety concerns remain unsolved regarding chronic consumption of high RES doses, specially in medicated people. This review will focus on the currently available evidence regarding resveratrol’s effects on humans obtained from randomized clinical trials. In addition, we will provide a critical outlook for further research on this molecule that is evolving from a minor dietary compound to a possible multi-target therapeutic drug.

Biomarkers for pediatric pulmonary arterial hypertension - a call to collaborate

Therapeutic approaches in pediatric pulmonary arterial hypertension (PAH) are based primarily on clinician experience, in contrast to the evidence-based approach in adults with pulmonary hypertension. There is a clear and present need for non-invasive and objective biomarkers to guide the accurate diagnosis, treatment, and prognosis of this disease in children. The multifaceted spectrum of disease, clinical presentation, and association with other diseases makes this a formidable challenge. However, as more progress is being made in the understanding and management of adult PAH, the potential to apply this knowledge to children has never been greater. This review explores the state of the art with regard to non-invasive biomarkers in PAH, with an eye toward those adult PAH biomarkers potentially suitable for application in pediatric PAH.