Oxidative stress contributes to pulmonary hypertension in the transgenic (mRen2)27 rat

Combined physical training protects the left ventricle from structural and functional damages in experimental pulmonary arterial hypertension

BACKGROUND

Under the adverse remodeling of the right ventricle and interventricular septum in pulmonary arterial hypertension (PAH) the left ventricle (LV) dynamics is impaired. Despite the benefits of combined aerobic and resistance physical trainings to individuals with PAH, its impact on the LV is not fully understood.

OBJECTIVE

To test whether moderate-intensity combined physical training performed during the development of PAH induced by MCT in rats is beneficial to the LV's structure and function.

METHODS

Male Wistar rats were divided into two groups: Sedentary Hypertensive Survival (SHS, n = 7); and Exercise Hypertensive Survival (EHS, n = 7) to test survival. To investigate the effects of combined physical training, another group of rats were divided into three groups: Sedentary Control (SC, n = 7); Sedentary Hypertensive (SH, n = 7); and Exercise Hypertensive (EH, n = 7). PAH was induced through an intraperitoneal injection of MCT (60 mg/kg). Echocardiographic evaluations were conducted on the 22nd day after MCT administration. Animals in the EHS and EH groups participated in a combined physical training program, alternating aerobic (treadmill running: 50 min, 60% maximum running speed) and resistance (ladder climbing: 15 climbs with 1 min interval, 60% maximum carrying load) exercises, one session/day, 5 days/week for approximately 4 weeks.

RESULTS

The physical training increased survival and tolerance to aerobic (i.e., maximum running speed) and resistance (i.e., maximum carrying load) exertions and prevented reductions in ejection fraction and fractional shortening. In addition, the physical training mitigated oxidative stress (i.e., CAT, SOD and MDA) and inhibited adverse LV remodeling (i.e., Collagen, extracellular matrix, and cell dimensions). Moreover, the physical training preserved the amplitude and velocity of contraction and hindered the reductions in the amplitude and velocity of the intracellular Ca2+ transient in LV single myocytes.

CONCLUSION

Moderate-intensity combined physical training performed during the development of MCT-induced PAH in rats protects their LV from damages to its structure and function and hence increases their tolerance to physical exertion and prolongs their survival.

Ageing and endothelium-mediated vascular dysfunction: the role of the NADPH oxidases

The present study aimed to determine the isoform-specific role of the NADPH oxidases (NOX) in the endothelium-mediated vascular dysfunction associated with ageing. Endothelium-dependent [intraluminal flow- and acetylcholine (ACh)-induced] vasodilatation in human skeletal muscle feed arteries (SMFAs) of young (24 ± 1 years, n = 16), middle aged (45 ± 1 years, n = 18) and old (76 ± 2 years, n = 21) subjects was assessed in vitro with and without the inhibition of NOX1 (ML090), NOX2 (gp91) and NOX4 (plumbagin). To identify the role of nitric oxide (NO) bioavailability in these responses, NO synthase blockade (l-NG -monomethyl arginine citrate) was utilized. SMFA NOX1, NOX2 and NOX4 protein expression was determined by western blotting. Age related endothelium-dependent vasodilatory dysfunction was evident in response to flow (young: 69 ± 3; middle aged: 51 ± 3; old: 27 ± 3%, P < 0.05) and ACh (young: 89 ± 2; middle aged: 72 ± 3; old: 45 ± 4%, P < 0.05). NOX1 inhibition had no effect on SMFA vasodilatation, whereas NOX2 inhibition restored flow- and ACh-induced vasodilatation in the middle aged and the old SMFAs (middle aged + gp91: 69 ± 3; 86 ± 3, old + gp91: 65 ± 5; 83 ± 2%, P < 0.05) and NOX4 inhibition tended to restore these vasodilatory responses in these two groups, but neither achieved statistical significance (P ≈ 0.06). l-NG -monomethyl arginine citrate negated the restorative effects of NOX2 and NOX4 blockade. Only NOX2 and NOX4 protein expression was significantly greater in the two older groups and inversely related to vascular function (r = 0.48 to 0.93, P < 0.05). NOX2 and, to a lesser extent, NOX4 appear to play an important, probably NO-mediated, role in age-related endothelial dysfunction. KEY POINTS: The present study aimed to determine the isoform-specific role of the NADPH oxidases (NOX) in the endothelium-mediated vascular dysfunction associated with ageing. Age related endothelium-dependent vasodilatory dysfunction was evident in skeletal muscle feed arteries in response to both flow and acetylcholine. NOX2 inhibition (gp91) restored endothelium-dependent vasodilatation in the middle aged and the old skeletal muscle feed arteries, and NOX4 inhibition (plumbagin) tended to restore these vasodilatory responses in these two groups. Nitric oxide synthase inhibition negated the restorative effects of NOX2 and NOX4 blockade. NOX2 and NOX4 protein expression was significantly greater in the two older groups and inversely related to vascular function. NOX2 and, to a lesser extent, NOX4 appear to play an important, probably nitric oxide-mediated, role in age-related endothelial dysfunction and could be important therapeutic targets to maintain vascular health with ageing.

Pulmonary hypertension associated with cardiopulmonary bypass and cardiac surgery

BACKGROUND AND AIM

Pulmonary hypertension (PH) is frequently associated with cardiovascular surgery and is a common complication that has been observed after surgery utilizing cardiopulmonary bypass (CPB). The purpose of this review is to explain the characteristics of PH, the mechanisms of PH induced by cardiac surgery and CPB, treatments for postoperative PH, and future directions in treating PH induced by cardiac surgery and CPB using up-to-date findings.

METHODS

The PubMed database was utilized to find published articles.

RESULTS

There are many mechanisms that contribute to PH after cardiac surgery and CPB which involve pulmonary vasomotor dysfunction, cyclooxygenase, the thromboxane A2 and prostacyclin pathway, the nitric oxide pathway, inflammation, and oxidative stress. Furthermore, there are several effective treatments for postoperative PH within different types of cardiac surgery.

CONCLUSIONS

By possessing a deep understanding of the mechanisms that contribute to PH after cardiac surgery and CPB, researchers can develop treatments for clinicians to use which target the mechanisms of PH and ultimately reduce and/or eliminate postoperative PH. Additionally, learning about the most up-to-date studies regarding treatments can allow clinicians to choose the best treatments for patients who are undergoing cardiac surgery and CPB.

Pathogenesis of Congenital Malformations: Possible Role of Oxidative Stress

OBJECTIVE

Congenital anomalies are important causes of morbidity and mortality in children. Oxidative stress (OS) is involved in the physiopathology of pregnancy-related congenital malformations. This review summarizes the role of OS in the pathogenesis of congenital malformations; in particular, its purpose is to describe how OS influences the development of heart congenital malformations, oesophageal atresia, biliary atresia, diaphragmatic hernia, and autosomal dominant polycystic kidney disease.

STUDY DESIGN

Systematic review of previous studies about the role of OS in pregnancy and its possible effects in developing of congenital malformations. One electronic database (PubMed) was searched and reference lists were checked.

RESULTS

An imbalance between the production of reactive oxygen species (ROS) and antioxidant defense can occur early in pregnancy and continue in the postnatal life, producing OS. It may destroy the signaling pathways needed for a correct embryogenesis leading to birth defects. In fact, cell functions, especially during embryogenesis, needs specific signaling pathways to regulate the development. These pathways are sensitive to both endogenous and exogenous factors; therefore, they can produce structural alterations of the developing fetus.

CONCLUSION

Because OS plays a significant role in pathogenesis of congenital malformations, studies should be developed in order to better define their OS mechanisms and the beneficial effects of supplemental therapeutic strategies.

KEY POINTS

· Oxidative stress is involved in the pathogenesis of congenital malformations.. · Heart malformations, oesophageal atresia, biliary atresia, diaphragmatic hernia, and autosomal dominant polycystic kidney are analyzed.. · A knowledge of pathomechanism of OS-related congenital malformations could be useful to prevent them..

Therapeutic Challenges and Emerging Treatment Targets for Pulmonary Hypertension in Left Heart Disease

Pulmonary hypertension (PH) attributable to left heart disease (LHD) is believed to be the most common form of PH and is strongly associated with increased mortality and morbidity in this patient population. Specific therapies for PH‐LHD have not yet been identified and the use of pulmonary artery hypertension‐targeted therapies in PH‐LHD are not recommended. Endothelin receptor antagonists, phosphodiesterase‐5 inhibitors, guanylate cyclase stimulators, and prostacyclins have all been studied in PH‐LHD with conflicting results. Understanding the mechanisms underlying PH‐LHD could potentially provide novel therapeutic targets. Fibrosis, oxidative stress, and metabolic syndrome have been proposed as pathophysiological components of PH‐LHD. Genetic associations have also been identified, offering additional mechanisms with biological plausibility. This review summarizes the evidence and challenges for treatment of PH‐LHD and focuses on underlying mechanisms on the horizon that could develop into potential therapeutic targets for this disease.

Inflammation as the Common Biological Link Between Depression and Cardiovascular Diseases: Can Carnosine Exert a Protective Role?

Several epidemiological studies have clearly shown the high co-morbidity between depression and Cardiovascular Diseases (CVD). Different studies have been conducted to identify the common pathophysiological events of these diseases such as the overactivation of the hypothalamic- pituitary-adrenal axis and, most importantly, the dysregulation of immune system which causes a chronic pro-inflammatory status. The biological link between depression, inflammation, and CVD can be related to high levels of pro-inflammatory cytokines, such as IL-1β, TNF-α, and IL-6, released by macrophages which play a central role in the pathophysiology of both depression and CVD. Pro-inflammatory cytokines interfere with many of the pathophysiological mechanisms relevant to depression by upregulating the rate-limiting enzymes in the metabolic pathway of tryptophan and altering serotonin metabolism. These cytokines also increase the risk to develop CVD, because activation of macrophages under this pro-inflammatory status is closely associated with endothelial dysfunction and oxidative stress, a preamble to atherosclerosis and atherothrombosis. Carnosine (β-alanyl-L-histidine) is an endogenous dipeptide which exerts a strong antiinflammatory activity on macrophages by suppressing reactive species and pro-inflammatory cytokines production and altering pro-inflammatory/anti-inflammatory macrophage polarization. This dipeptide exhibits antioxidant properties scavenging reactive species and preventing oxidative stress-induced pathologies such as CVD. In the present review we will discuss the role of oxidative stress and chronic inflammation as common pathophysiological events both in depression and CVD and the preclinical and clinical evidence on the protective effect of carnosine in both diseases as well as the therapeutic potential of this dipeptide in depressed patients with a high co-morbidity of cardiovascular diseases.

Prognostic Value of Oxidative Stress Markers in Patients with Pulmonary Arterial or Chronic Thromboembolic Pulmonary Hypertension

Oxidative stress is regarded to play a crucial role in the pathophysiology of pulmonary arterial hypertension (PAH) and inoperable chronic thromboembolic pulmonary hypertension (CTEPH). This study evaluated the prognostic value of serum oxidative stress markers (malondialdehyde (MDA), total antioxidant capacity (TAC), catalase activity (CAT), and superoxide activity (SOD)) in patients with PAH and CTEPH (n = 45). During 13 months of follow-up (median 9 months), clinical deterioration occurred in 14 patients (including 2 deaths). On the Cox regression analysis, MDA, TAC, and CAT were associated with clinical deterioration (p = 0.0068, HR = 1.42, 95% CI: 1.10-1.82; p = 0.0038, HR = 0.033, 95% CI: 0.0032-0.33; and p = 0.046, HR = 0.20, 95% CI: 0.04-0.98, respectively). There was no significant difference in SOD (p = 0.53, HR = 0.97, 95% CI: 0.87-1.08). The cut-off value derived from ROC curve analysis was 3.79 μM (p = 0.0048, AUC = 0.76, 95% CI: 0.62-0.91) for MDA, 0.49 mM (p = 0.027, AUC = 0.71, 95% CI: 0.18-0.47) for TAC, and 1.34 U/L (p = 0.029, AUC = 0.71, 95% CI: 0.55-0.86) for CAT. MDA in the group with deterioration was higher (p = 0.0041), while TAC as well as CAT were lower (p = 0.027 and p = 0.028, respectively) when compared to stable patients. Survival without clinical deterioration was significantly longer in patients with lower MDA (p = 0.037, HR = 0.37, 95% CI: 0.12-1.14, log-rank), higher TAC (p = 0.0018, HR = 0.19, 95% CI: 0.06-0.60, log-rank), and higher CAT (p = 0.044, HR = 0.31 95% CI: 0.11-0.88, log-rank). Markers of oxidative stress such as MDA, TAC, and CAT were associated with adverse clinical outcomes in patients with PAH and inoperable or residual CTEPH.

Toxicity effects in zebrafish embryos (Danio rerio) induced by prothioconazole

Triazole fungicides are widely used in agriculture production and have adverse impacts on aquatic organisms. As one of the triazole fungicides, prothioconazole has been reported to cause many toxicological effects, but its risks to aquatic organisms are unknown. In this study, we systematically explored the toxicity effects of prothioconazole exposure on zebrafish embryos (Danio rerio) involving in developmental toxicity, oxidative damage and metabolism disorders. The results showed that prothioconazole exposure to zebrafish embryos produced a series of toxic symptoms, including hatching inhibition, shortening of body length, pericardial cyst and yolk cyst. In addition, prothioconazole exposure caused significant lipid peroxidation and oxidative damage. Particularly, we also found that metabolites and genes involved in lipid metabolism also showed significant changes. This study may provide theoretical basis for systematically assessing the potential risks of zebrafish embryos with prothioconazole exposure.

Blueberry extract decreases oxidative stress and improves functional parameters in lungs from rats with pulmonary arterial hypertension

OBJECTIVES

Pulmonary arterial hypertension (PAH) is a condition characterized by an increased resistance of pulmonary vasculature, culminating in an increase in pulmonary pressure. This process involves disturbances in lung redox homeostasis, causing progressive right heart failure. In this context, the use of natural antioxidants, such as those found in blueberries, may represent a therapeutic approach. The aim of this study was to evaluate the effect of blueberry extract (BB) on functional parameters and oxidative stress levels in rat lungs with induced PAH.

METHODS

Forty-eight male Wistar rats (weighing 200 ± 20 g) were randomized into five groups: control, monocrotaline, monocrotaline + BB 50, monocrotaline + BB 100, and monocrotaline + BB 200. PAH was induced by the administration of monocrotaline (60 mg/kg, intraperitoneal). Rats were treated with BB at doses of 50, 100, and 200 mg/kg via gavage for 5 wk (2 wk before monocrotaline and 3 wk after monocrotaline injection). At day 35, rats were submitted to echocardiography and catheterization. They were then sacrificed and lungs were harvested for biochemical analyses.

RESULTS

BB increased the E/A ratio of blood flow across the tricuspid valve and tricuspid annular phase systolic excursion, as wells as decreased the mean pulmonary artery pressure of animals compared with the PAH group. Moreover, BB decreased total reactive species concentration and lipid oxidation, reduced activity of nicotinamide adenine dinucleotide phosphate oxidase and expression of xanthine oxidase, increased the activity of superoxide dismutase and restored sulfhydryl content in the animal lungs compared with those in the PAH group. Additionally, BB restored expression of the antioxidant transcriptional factor Nrf2 in the lungs of the animal subjects. Finally, BB normalized the endothelin receptor (ETA/ETB) expression ratio in the animal lungs, which were increased in the PAH group.

CONCLUSION

Intervention with BB mitigated functional PAH outcomes through improvement of the pulmonary redox state. Our results provide a basis for future research on natural antioxidant interventions as a novel treatment strategy in PAH.

Macrolides induce severe cardiotoxicity and developmental toxicity in zebrafish embryos

Macrolide antibiotics (MALs) are widely used for both human and animal health. Most MALs and their metabolites transfer into aquatic organisms and environment resulting in violent consequences. Previous studies show that MALs cause cardiotoxicity in humans and mammals. However, the potential risk of these chemicals in aquatic organisms remains unclear. Here, we used zebrafish embryos as a model to evaluate the toxicity of MALs. Zebrafish embryos were exposed to four typical MALs including azithromycin (AZM), clarithromycin (CLR), tilmicosin (TMS) and tylosin (TYL) to study their cardiotoxicity. The heart rate of zebrafish embryos showed similar biphasic distribution in the presence of four MALs at 2 days post-fertilization (dpf). The heart rate increased significantly at low levels of MALs while decreased obviously at high levels. Subsequently, TMS was chose to study its acute toxicity and developmental toxicity, which caused pericardial edema and spinal curvature in zebrafish embryos at 4 dpf. Furthermore, we found that TMS triggered oxidative stress, with decreased SOD activities and increased MDA contents. Lastly, apoptosis was observed in zebrafish embryos under TMS treatment, with up-regulation of apoptosis associated genes such as p53, bcl 2, bax, caspase 3 and caspase 9, confirmed by increased protein expression based on Western blot analysis. Taken together, these data indicate that MALs can cause serious toxicity in the development of zebrafish. Great caution should be taken due to the huge consumption of MALs for food animal production and treatments with TMS for infections in aquaculture.

The Role of Oxidative Stress in the Pathomechanism of Congenital Malformations

Congenital anomalies are significant causes of mortality and morbidity in infancy and childhood. Embryogenesis requires specific signaling pathways to regulate cell proliferation and differentiation. These signaling pathways are sensitive to endogenous and exogenous agents able to produce several structural changes of the developing fetus. Oxidative stress, due to an imbalance between the production of reactive oxygen species and antioxidant defenses, disrupts signaling pathways with a causative role in birth defects. This review provides a basis for understanding the role of oxidative stress in the pathomechanism of congenital malformations, discussing the mechanisms related to some congenital malformations. New insights in the knowledge of pathomechanism of oxidative stress-related congenital malformations, according to experimental and human studies, represent the basis of possible clinical applications in screening, prevention, and therapies.

Review on Chamber-Specific Differences in Right and Left Heart Reactive Oxygen Species Handling

Reactive oxygen species (ROS) exert signaling character (redox signaling), or damaging character (oxidative stress) on cardiac tissue depending on their concentration and/or reactivity. The steady state of ROS concentration is determined by the interplay between its production (mitochondrial, cytosolic, and sarcolemmal enzymes) and ROS defense enzymes (mitochondria, cytosol). Recent studies suggest that ROS regulation is different in the left and right ventricle of the heart, specifically by a different activity of superoxide dismutase (SOD). Mitochondrial ROS defense seems to be lower in right ventricular tissue compared to left ventricular tissue. In this review we summarize the current evidence for heart chamber specific differences in ROS regulation that may play a major role in an observed inability of the right ventricle to compensate for cardiac stress such as pulmonary hypertension. Based on the current knowledge regimes to increase ROS defense in right ventricular tissue should be in the focus for the development of future therapies concerning right heart failure.

Central role of T helper 17 cells in chronic hypoxia-induced pulmonary hypertension

Inflammation is a prominent pathological feature in pulmonary arterial hypertension, as demonstrated by pulmonary vascular infiltration of inflammatory cells, including T and B lymphocytes. However, the contribution of the adaptive immune system is not well characterized in pulmonary hypertension caused by chronic hypoxia. CD4⁺ T cells are required for initiating and maintaining inflammation, suggesting that these cells could play an important role in the pathogenesis of hypoxic pulmonary hypertension. Our objective was to test the hypothesis that CD4⁺ T cells, specifically the T helper 17 subset, contribute to chronic hypoxia-induced pulmonary hypertension. We compared indices of pulmonary hypertension resulting from chronic hypoxia (3 wk) in wild-type mice and recombination-activating gene 1 knockout mice (RAG1^-/-, lacking mature T and B cells). Separate sets of mice were adoptively transferred with CD4⁺, CD8⁺, or T helper 17 cells before normoxic or chronic hypoxic exposure to evaluate the involvement of specific T cell subsets. RAG1^-/- mice had diminished right ventricular systolic pressure and arterial remodeling compared with wild-type mice exposed to chronic hypoxia. Adoptive transfer of CD4⁺ but not CD8⁺ T cells restored the hypertensive phenotype in RAG1^-/- mice. Interestingly, RAG1^-/- mice receiving T helper 17 cells displayed evidence of pulmonary hypertension independent of chronic hypoxia. Supporting our hypothesis, depletion of CD4⁺ cells or treatment with SR1001, an inhibitor of T helper 17 cell development, prevented increased pressure and remodeling responses to chronic hypoxia. We conclude that T helper 17 cells play a key role in the development of chronic hypoxia-induced pulmonary hypertension.

Possible role of increased oxidative stress in pulmonary hypertension in experimental diaphragmatic hernia

PURPOSE

Congenital diaphragmatic hernia (CDH) is one of the causes of respiratory failure in newborns due to lung hypoplasia and pulmonary abnormalities leading to pulmonary hypertension (PH). NAD(P)H oxidase (Nox) is a family of isoenzymes that generate reactive oxygen species (ROS) which can contribute to PH-induced vascular dysfunction. On the other hand, superoxide dismutase (SOD) 1-2 and catalase are the antioxidant enzymes that eliminate the excess of ROS in pulmonary vascular cells. Our aim is to examine whether PH-associated with CDH is due to a dysregulation of ROS production in lungs from CDH fetuses.

METHODS

Pregnant rats received either 100 mg nitrofen or vehicle on E9.5. Fetuses were recovered on E21. (1) Nox activity, (2) H2O2 production and (3) mRNA levels of Nox1, Nox2, Nox4, SOD1, SOD2 and catalase were analyzed in fetal lungs.

RESULTS

Nox activity and Nox1 and Nox2 mRNA levels were increased in the lungs of fetuses with CDH. However, there were no changes in H2O2 production and Nox4 mRNA levels. SOD1, SOD2 and catalase were decreased.

CONCLUSIONS

The raised oxidative stress due to increase in ROS generation by Nox isoenzymes and dysfunction of antioxidant enzymes seems to be a potential mechanism responsible on PH-associated with CDH.

Oxidative stress and nitric oxide signaling related biomarkers in patients with pulmonary hypertension: a case control study

BACKGROUND

Oxidative stress (OS) and reduced nitric oxide (NO) bioavailability contribute to the pathogenesis of pulmonary hypertension (PH). Whether there are associations between OS and NO signaling biomarkers and whether these biomarkers are associated with the severity of PH remain unclear.

METHODS

Blood samples were collected from 35 healthy controls and 35 patients with pulmonary arterial hypertension (PAH, n = 12) or chronic thromboembolic pulmonary hypertension (CTEPH, n = 23). The mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance index (PVRI) were measured by right heart catheterization. We measured the derivative of reactive oxygen molecules (d-ROMs), biological antioxidant potential (BAP) and superoxide dismutase (SOD) by automatic biochemical analyzer, malondialdehyde (MDA) and asymmetric dimethylarginine (ADMA) by enzyme-linked immunosorbent assay. The relationship between oxidative-antioxidative biomarkers and ADMA, as well as their association with pulmonary hemodynamics, were analyzed.

RESULTS

Compared with age- and gender-matched controls, there was no significant difference of d-ROMs in PAH and CTEPH patients; MDA was increased in CTEPH patients (P = 0.034); BAP and SOD were decreased in PAH (P = 0.014, P < 0.001) and CTEPH patients (P = 0.015, P < 0.001); ADMA level was significantly higher in PAH (P = 0.007) and CTEPH patients (P < 0.001). No association between oxidative-antioxidative biomarkers and ADMA was found. Serum ADMA concentration was correlated with mPAP (r = 0.762, P = 0.006) and PVRI (r = 0.603, P = 0.038) in PAH patients.

CONCLUSIONS

The antioxidative potential and NO signaling are impaired in PAH and CTEPH. Increased serum ADMA level is associated with unfavorable pulmonary hemodynamics in PAH patients. Thus, ADMA may be useful in the severity evaluation and risk stratification of PAH.

Protein disulfide isomerase expression increases in resistance arteries during hypertension development. Effects on Nox1 NADPH oxidase signaling

NADPH oxidases derived reactive oxygen species (ROS) play an important role in vascular function and remodeling in hypertension through redox signaling processes. Previous studies demonstrated that protein disulfide isomerase (PDI) regulates Nox1 expression and ROS generation in cultured vascular smooth muscle cells. However, the role of PDI in conductance and resistance arteries during hypertension development remains unknown. The aim of the present study was to investigate PDI expression and NADPH oxidase dependent ROS generation during hypertension development. Mesenteric resistance arteries (MRA) and thoracic aorta were isolated from 6, 8, and 12 week-old spontaneously hypertensive (SHR) and Wistar rats. ROS production (dihydroethidium fluorescence), PDI (WB, imunofluorescence), Nox1 and NOX4 (RT-PCR) expression were evaluated. Results show a progressive increase in ROS generation in MRA and aorta from 8 to 12 week-old SHR. This effect was associated with a concomitant increase in PDI and Nox1 expression only in MRA. Therefore, suggesting a positive correlation between PDI and Nox1 expression during the development of hypertension in MRA. In order to investigate if this effect was due to an increase in arterial blood pressure, pre hypertensive SHR were treated with losartan (20 mg/kg/day for 30 days), an AT1 receptor antagonist. Losartan decreased blood pressure and ROS generation in both vascular beds. However, only in SHR MRA losartan treatment lowered PDI and Nox1 expression to control levels. In MRA PDI inhibition (bacitracin, 0.5 mM) decreased Ang II redox signaling (p-ERK 1/2). Altogether, our results suggest that PDI plays a role in triggering oxidative stress and vascular dysfunction in resistance but not in conductance arteries, increasing Nox1 expression and activity. Therefore, PDI could be a new player in oxidative stress and functional alterations in resistance arteries during the establishment of hypertension.

Neutrophil/Lymphocyte Ratio Can Predict Postoperative Mortality in Patients with Chronic Thromboembolic Pulmonary Hypertension

OBJECTIVE

The aim of our study was to investigate clinical importance of neutrophil/ lymphocyte ratio in patients with Chronic thromboembolic pulmonary hypertension.

METHODS

125 consecutive patients with a diagnosis of Chronic thromboembolic pulmonary hypertension were operated pulmonary thromboendarterectomy in our center between February 2011 and August 2013. 106 patients included into the study due to limitations. The patients were classified into two groups as patients discharged alive (Group 1) and those dying in the hospital (Group 2). Baseline neutrophil/lymphocyte ratio level was measured by dividing neutrophil count to lymphocyte count.

RESULTS

84 patients (79%) were in Group 1, 22 patients (21%) were in Group 2. Patients with higher neutrophil/lymphocyte ratio in admission have a significantly higher mortality rate and postoperative pulmonary vascular resistance was found statistically significant variable to predict the mortality. Receiver operator characteristic (ROC) analysis revealed that using a cut-off point of 2.54, admission neutrophil/lymphocyte ratio predicts mortality. Also, correlation analysis showed a significant correlation between preoperative pulmonary vascular resistance and neutrophil/lymphocyte ratio.

CONCLUSION

The neutrophil/lymphocyte ratio level may be a useful and noninvasive biomarker for operative risk stratification for mortality after pulmonary thromboendarterectomy.

Intrapulmonary Activation of the Angiotensin-Converting Enzyme Type 2/Angiotensin 1-7/G-Protein-Coupled Mas Receptor Axis Attenuates Pulmonary Hypertension in Ren-2 Transgenic Rats Exposed to Chronic Hypoxia

The present study was performed to evaluate the role of intrapulmonary activity of the two axes of the renin-angiotensin system (RAS): vasoconstrictor angiotensin-converting enzyme (ACE)/angiotensin II (ANG II)/ANG II type 1 receptor (AT1) axis, and vasodilator ACE type 2 (ACE2)/angiotensin 1-7 (ANG 1-7)/Mas receptor axis, in the development of hypoxic pulmonary hypertension in Ren-2 transgenic rats (TGR). Transgene-negative Hannover Sprague-Dawley (HanSD) rats served as controls. Both TGR and HanSD rats responded to two weeks´ exposure to hypoxia with a significant increase in mean pulmonary arterial pressure (MPAP), however, the increase was much less pronounced in the former. The attenuation of hypoxic pulmonary hypertension in TGR as compared to HanSD rats was associated with inhibition of ACE gene expression and activity, inhibition of AT1 receptor gene expression and suppression of ANG II levels in lung tissue. Simultaneously, there was an increase in lung ACE2 gene expression and activity and, in particular, ANG 1-7 concentrations and Mas receptor gene expression. We propose that a combination of suppression of ACE/ANG II/AT1 receptor axis and activation of ACE2/ANG 1-7/Mas receptor axis of the RAS in the lung tissue is the main mechanism explaining attenuation of hypoxic pulmonary hypertension in TGR as compared with HanSD rats.

Inhibition of NOX/VPO1 pathway and inflammatory reaction by trimethoxystilbene in prevention of cardiovascular remodeling in hypoxia-induced pulmonary hypertensive rats

Recent studies show that resveratrol exerts beneficial effects on prevention of pulmonary hypertension. This study is performed to explore the effects of trimethoxystilbene, a novel resveratrol analog, on rat pulmonary vascular remodeling and right ventricular hypertrophy in hypoxia-induced pulmonary arterial hypertension (PAH) and the underlying mechanisms. Sprague-Dawley rats were placed in a chamber and exposed to 10% O(2) continuously for 4 weeks to induce PAH. The effects of trimethoxystilbene (5 or 10 mg/kg per day, intragastric [i.g.]) and resveratrol (as a positive control, 25 mg/kg per day, i.g.) on hypoxia-induced PAH vascular remodeling and right ventricle hypertrophy were evaluated. At the end of experiments, the index for pulmonary vascular remodeling and right ventricle hypertrophy, inflammatory cell infiltration in lung tissue, the plasma levels and lung tissue contents of hydrogen peroxide (H(2)O(2)), the mRNA and protein levels for NADPH oxidases (NOX2, NOX4) and vascular peroxidase 1 (VPO1) in pulmonary artery or right ventricle were measured. The results showed that trimethoxystilbene treatment significantly attenuated hypoxia-induced pulmonary vascular remodeling (such as decrease in the ratio of wall thickness to vessel external diameter) and right ventricle hypertrophy (such as decrease in the ratio of right ventricle weight to the length of the tibia), accompanied by downregulation of NOX2, NOX4, and VPO1 expression in pulmonary artery or right ventricle, decrease in H(2)O(2) production and inflammatory cell infiltration in lung tissue. Trimethoxystilbene is able to prevent pulmonary vascular remodeling and right ventricle hypertrophy in hypoxia-induced rat model of PAH, which is related to inhibition of the NOX/VPO1 pathway-mediated oxidative stress and the inflammatory reaction.

Novel approach to reactive oxygen species in nontransfusion-dependent thalassemia

The term Nontransfusion dependent thalassaemia (NTDT) was suggested to describe patients who had clinical manifestations that are too severe to be termed minor yet too mild to be termed major. Those patients are not entirely dependent on transfusions for survival. If left untreated, three main factors are responsible for the clinical sequelae of NTDT: ineffective erythropoiesis, chronic hemolytic anemia, and iron overload. Reactive oxygen species (ROS) generation in NTDT patients is caused by 2 major mechanisms. The first one is chronic hypoxia resulting from chronic anemia and ineffective erythropoiesis leading to mitochondrial damage and the second is iron overload also due to chronic anemia and tissue hypoxia leading to increase intestinal iron absorption in thalassemic patients. Oxidative damage by reactive oxygen species (generated by free globin chains and labile plasma iron) is believed to be one of the main contributors to cell injury, tissue damage, and hypercoagulability in patients with thalassemia. Independently increased ROS has been linked to a myriad of pathological outcomes such as leg ulcers, decreased wound healing, pulmonary hypertension, silent brain infarcts, and increased thrombosis to count a few. Interestingly many of those complications overlap with those found in NTDT patients.

Fasudil reversed MCT-induced and chronic hypoxia-induced pulmonary hypertension by attenuating oxidative stress and inhibiting the expression of Trx1 and HIF-1α

Antioxidant therapy attenuates pulmonary hypertension (PH). In the present study, we tested the antioxidant effects of fasudil against PH in rats. Monocrotaline (MCT)-induced and chronic hypoxia-induced PH models of rats were established, and the haemodynamic and pathomorphologic results of three different doses of fasudil (10 mg/kg, 30 mg/kg, and 75 mg/kg per day) were subsequently compared with those of bosentan (30 mg/kg per day). Additionally, the protein expressions of thioredoxin-1 (Trx1) and hypoxia inducible factor-1α (HIF-1α), the content of superoxide dismutase (SOD), and the levels of hydrogen peroxide (H2O2), malonyldialdehyde (MDA), and hydroxy radical (·OH) were investigated. Fasudil effectively reduced the right ventricular systolic pressure (RVSP) and alleviated right ventricle (RV) hypertrophy, as well as the histological changes in the pulmonary arterioles. Moreover, fasudil markedly lessened the expression of Trx1 and HIF-1α, up-regulated the concentration of SOD, and lowered the levels of H2O2, MDA, and ·OH. In conclusion, fasudil is a notably attractive potential therapy for PH.

N-acetylcysteine improves established monocrotaline-induced pulmonary hypertension in rats

Background

The outcome of patients suffering from pulmonary arterial hypertension (PAH) are predominantly determined by the response of the right ventricle to the increase afterload secondary to high vascular pulmonary resistance. However, little is known about the effects of the current available or experimental PAH treatments on the heart. Recently, inflammation has been implicated in the pathophysiology of PAH. N-acetylcysteine (NAC), a well-known safe anti-oxidant drug, has immuno-modulatory and cardioprotective properties. We therefore hypothesized that NAC could reduce the severity of pulmonary hypertension (PH) in rats exposed to monocrotaline (MCT), lowering inflammation and preserving pulmonary vascular system and right heart function.

Methods

Saline-treated control, MCT-exposed, MCT-exposed and NAC treated rats (day 14–28) were evaluated at day 28 following MCT for hemodynamic parameters (right ventricular systolic pressure, mean pulmonary arterial pressure and cardiac output), right ventricular hypertrophy, pulmonary vascular morphometry, lung inflammatory cells immunohistochemistry (monocyte/macrophages and dendritic cells), IL-6 expression, cardiomyocyte hypertrophy and cardiac fibrosis.

Results

The treatment with NAC significantly decreased pulmonary vascular remodeling, lung inflammation, and improved total pulmonary resistance (from 0.71 ± 0.05 for MCT group to 0.50 ± 0.06 for MCT + NAC group, p < 0.05). Right ventricular function was also improved with NAC treatment associated with a significant decrease in cardiomyocyte hypertrophy (625 ± 69 vs. 439 ± 21 μm² for MCT and MCT + NAC group respectively, p < 0.001) and heart fibrosis (14.1 ± 0.8 vs. 8.8 ± 0.1% for MCT and MCT + NAC group respectively, p < 0.001).

Conclusions

Through its immuno-modulatory and cardioprotective properties, NAC has beneficial effect on pulmonary vascular and right heart function in experimental PH.

Oxidative stress is associated with increased pulmonary artery systolic pressure in humans

Oxidative stress contributes to the development of pulmonary hypertension in experimental models, but this association in humans is unknown. We investigated the relationship between pulmonary artery systolic pressure measured by echocardiography and plasma aminothiol oxidative stress markers, with the hypothesis that oxidative stress will be higher in those with pulmonary hypertension. A group of 347 patients aged 65±12 years from the Emory Cardiovascular Biobank underwent echocardiographic assessment of left ventricular ejection fraction and pulmonary artery systolic pressure. Plasma aminothiols, cysteine, its oxidized form, cystine, glutathione, and its oxidized disulphide were measured and the redox potentials (Eh) of cysteine/cystine and glutathione/oxidized glutathione couples were calculated. Non-normally distributed variables were log transformed (Ln). Univariate predictors of pulmonary artery systolic pressure included age (P<0.001), sex (P=0.002), mitral regurgitation (P<0.001), left ventricular ejection fraction (P<0.001), left atrial size (P<0.001), diabetes mellitus (P=0.03), plasma Ln cystine (β=9.53; P<0.001), Ln glutathione (β=-5.4; P=0.002), and Eh glutathione (β=0.21; P=0.001). A multivariate linear regression model adjusting for all confounding variables demonstrated that Ln cystine (β=6.56; P=0.007), mitral regurgitation (β=4.52; P<0.001), statin use (β=-3.39; P=0.03), left ventricular ejection fraction (β=-0.26; P=0.003), and age (β=0.17; P=0.003) were independent predictors of pulmonary artery systolic pressure. For each 1% increase in plasma cystine, pulmonary artery systolic pressure increased by 16%. This association persisted in the subgroup with preserved left ventricular ejection fraction (≥50%) and no significant mitral regurgitation. Whether treatment of oxidative stress will improve pulmonary hypertension requires further study.

Salt loading exacerbates diastolic dysfunction and cardiac remodeling in young female Ren2 rats

OBJECTIVE

Recent data would suggest pre-menopausal insulin resistant women are more prone to diastolic dysfunction than men, yet it is unclear why. We and others have reported that transgenic (mRen2)27 (Ren2) rats overexpressing the murine renin transgene are insulin resistant due to oxidative stress in insulin sensitive tissues. As increased salt intake promotes inflammation and oxidative stress, we hypothesized that excess dietary salt would promote diastolic dysfunction in transgenic females under conditions of excess tissue Ang II and circulating aldosterone levels.

MATERIALS/METHODS

For this purpose we evaluated cardiac function in young female Ren2 rats or age-matched Sprague-Dawley (SD) littermates exposed to a high (4%) salt or normal rat chow intake for three weeks.

RESULTS

Compared to SD littermates, at 10weeks of age, female Ren2 rats fed normal chow showed elevations in left ventricular (LV) systolic pressures, LV and cardiomyocyte hypertrophy, and displayed reductions in LV initial filling rate accompanied by increases in 3-nitrotyrosine content as a marker of oxidant stress. Following 3weeks of a salt diet, female Ren2 rats exhibited no further changes in LV systolic pressure, insulin resistance, or markers of hypertrophy but exaggerated increases in type 1 collagen, 3-nitrotryosine content, and diastolic dysfunction. These findings occurred in parallel with ultrastructural findings of pericapillary fibrosis, increased LV remodeling, and mitochondrial biogenesis.

CONCLUSION

These data suggest that a diet high in salt in hypertensive female Ren2 rats promotes greater oxidative stress, maladaptive LV remodeling, fibrosis, and associated diastolic dysfunction without further changes in LV systolic pressure or hypertrophy.

AKIP1 expression modulates mitochondrial function in rat neonatal cardiomyocytes

A kinase interacting protein 1 (AKIP1) is a molecular regulator of protein kinase A and nuclear factor kappa B signalling. Recent evidence suggests AKIP1 is increased in response to cardiac stress, modulates acute ischemic stress response, and is localized to mitochondria in cardiomyocytes. The mitochondrial function of AKIP1 is, however, still elusive. Here, we investigated the mitochondrial function of AKIP1 in a neonatal cardiomyocyte model of phenylephrine (PE)-induced hypertrophy. Using a seahorse flux analyzer we show that PE stimulated the mitochondrial oxygen consumption rate (OCR) in cardiomyocytes. This was partially dependent on PE mediated AKIP1 induction, since silencing of AKIP1 attenuated the increase in OCR. Interestingly, AKIP1 overexpression alone was sufficient to stimulate mitochondrial OCR and in particular ATP-linked OCR. This was also true when pyruvate was used as a substrate, indicating that it was independent of glycolytic flux. The increase in OCR was independent of mitochondrial biogenesis, changes in ETC density or altered mitochondrial membrane potential. In fact, the respiratory flux was elevated per amount of ETC, possibly through enhanced ETC coupling. Furthermore, overexpression of AKIP1 reduced and silencing of AKIP1 increased mitochondrial superoxide production, suggesting that AKIP1 modulates the efficiency of electron flux through the ETC. Together, this suggests that AKIP1 overexpression improves mitochondrial function to enhance respiration without excess superoxide generation, thereby implicating a role for AKIP1 in mitochondrial stress adaptation. Upregulation of AKIP1 during different forms of cardiac stress may therefore be an adaptive mechanism to protect the heart.

Oxidative stress augments pulmonary hypertension in chronically hypoxic mice overexpressing the oxidized LDL receptor

Chronic hypoxia is one of the main causes of pulmonary hypertension (PH) associated with ROS production. Lectin-like oxidized low-density lipoprotein receptor (LOX)-1 is known to be an endothelial receptor of oxidized low-density lipoprotein, which is assumed to play a role in the initiation of ROS generation. We investigated the role of LOX-1 and ROS generation in PH and vascular remodeling in LOX-1 transgenic (TG) mice. We maintained 8- to 10-wk-old male LOX-1 TG mice and wild-type (WT) mice in normoxia (room air) or hypoxia (10% O2 chambers) for 3 wk. Right ventricular (RV) systolic pressure (RVSP) was comparable between the two groups under normoxic conditions; however, chronic hypoxia significantly increased RVSP and RV hypertrophy in LOX-1 TG mice compared with WT mice. Medial wall thickness of the pulmonary arteries was significantly greater in LOX-1 TG mice than in WT mice. Furthermore, hypoxia enhanced ROS production and nitrotyrosine expression in LOX-1 TG mice, supporting the observed pathological changes. Administration of the NADPH oxidase inhibitor apocynin caused a significant reduction in PH and vascular remodeling in LOX-1 TG mice. Our results suggest that LOX-1-ROS generation induces the development and progression of PH.

NFAT is required for spontaneous pulmonary hypertension in superoxide dismutase 1 knockout mice

Elevated reactive oxygen species are implicated in pulmonary hypertension (PH). Superoxide dismutase (SOD) limits superoxide bioavailability, and decreased SOD activity is associated with PH. A decrease in SOD activity is expected to increase superoxide and reduce hydrogen peroxide levels. Such an imbalance of superoxide/hydrogen peroxide has been implicated as a mediator of nuclear factor of activated T cells (NFAT) activation in epidermal cells. We have shown that NFATc3 is required for chronic hypoxia-induced PH. However, it is unknown whether NFATc3 is activated in the pulmonary circulation in a mouse model of decreased SOD1 activity and whether this leads to PH. Therefore, we hypothesized that an elevated pulmonary arterial superoxide/hydrogen peroxide ratio activates NFATc3, leading to PH. We found that SOD1 knockout (KO) mice have elevated pulmonary arterial wall superoxide and decreased hydrogen peroxide levels compared with wild-type (WT) littermates. Right ventricular systolic pressure (RVSP) was elevated in SOD1 KO and was associated with pulmonary arterial remodeling. Vasoreactivity to endothelin-1 was also greater in SOD1 KO vs. WT mice. NFAT activity and NFATc3 nuclear localization were increased in pulmonary arteries from SOD1 KO vs. WT mice. Administration of A-285222 (selective NFAT inhibitor) decreased RVSP, arterial wall thickness, vasoreactivity, and NFAT activity in SOD1 KO mice to WT levels. The SOD mimetic, tempol, also reduced NFAT activity, NFATc3 nuclear localization, and RVSP to WT levels. These findings suggest that an elevated superoxide/hydrogen peroxide ratio activates NFAT in pulmonary arteries, which induces vascular remodeling and increases vascular reactivity leading to PH.

Suicidal erythrocyte death, eryptosis, as a novel mechanism in heart failure-associated anaemia

AIMS

Suicidal death of erythrocytes (eryptosis) is characterized by cell shrinkage and exposure of phosphatidylserine (PS) residues at the cell surface. Excessive eryptosis may lead to anaemia. We aimed to study the role of eryptosis in heart failure (HF)-associated anaemia.

METHODS AND RESULTS

We measured eryptosis in rodent models of HF. Typical measures of eryptosis including PS-exposure, increased intracellular Ca(2+) levels, and decreased cell volume were determined by flow cytometry. Transgenic REN2 rats displayed mild anaemia which was associated with a two-fold increase in erythrocyte PS-exposure when compared with Sprague Dawley (SD) control rats (P < 0.01). Upon stimulation with eryptotic triggers such as oxidative stress, hyperosmotic shock and energy depletion, eryptosis was more prominent in REN2 as shown by increased PS-exposure, cytosolic Ca(2+) influx, and cell shrinkage (P < 0.05 vs. SD). Increasing cytosolic Ca(2+) levels resulted in a stronger increase in PS-exposure in REN2 erythrocytes (P < 0.01 vs. SD). Accordingly, inhibition of Ca(2+) entry blunted the increased PS-exposure upon oxidative stress. The REN2 rats had significantly higher reticulocytes (REN2: 10.6 ± 2.3%; SD: 5.4 ± 0.1%; P < 0.05) and erythrocyte turnover was increased, indicated by increased clearance of eryptotic erythrocytes. Eryptosis was also increased in a rat model of hypertensive cardiac remodelling (uninephrectomized rats implanted with deoxycorticosterone acetate pellets), in mice after transverse aortic constriction, as well as in a small proof-of-concept study in human HF patients.

CONCLUSION

Eryptosis is increased during HF development and could contribute to HF-associated anaemia. Eryptosis may therefore become a novel target for therapy in HF-associated anaemia.

Obesity-related alterations in cardiac lipid profile and nondipping blood pressure pattern during transition to diastolic dysfunction in male db/db mice

Obesity and a nondipping circadian blood pressure (BP) pattern are associated with diastolic dysfunction. Ectopic lipid accumulation is increasingly recognized as an important metabolic abnormality contributing to diastolic dysfunction. However, little is known about the contribution of different lipids and the composition of lipid analytes to diastolic dysfunction. We have performed functional and structural studies and analyzed cardiac lipid profile at two time points during progression to diastolic dysfunction in a genetic model of obesity. Serial cardiac magnetic resonance imaging and telemetric measures of BP between 12 and 15 wk of age in obese male db/db mice indicated a nondipping circadian BP pattern and normal diastolic function at 12 wk that progressed to a deteriorating nondipping pattern and onset of diastolic dysfunction at 15 wk of age. Lipidomic analysis demonstrated elevated fatty acids and ceramides in db/db at 12 wk, but their levels were decreased at 15 wk, and this was accompanied by persistent mitochondrial ultrastructural abnormalities in concert with evidence of increased fatty acid oxidation and enhanced production of reactive oxygen species. Triacylglyceride and diacylglyceride levels were elevated at both 12 and 15 wk, but their composition changed to consist of more saturated and less unsaturated fatty acyl at 15 wk. An increase in the lipid droplets was apparent at both time points, and this was associated with increases in phosphatidycholine. In conclusion, a distinct pattern of myocardial lipid remodeling, accompanied by oxidative stress, is associated with the onset of diastolic dysfunction in obese, insulin-resistant db/db mice.

Living-donor liver transplantation for moderate or severe porto-pulmonary hypertension accompanied by pulmonary arterial hypertension: a single-centre experience over 2 decades in Japan

BACKGROUND

Candidates for orthotopic liver transplantation (OLT) often have porto-pulmonary hypertension (PPHTN) with pulmonary arterial hypertension (PAH). Poor outcomes of PPHTN contraindicate OLT. There are no guidelines for living-donor liver transplantation (LDLT) in PPHTN patients.

METHODS

We present our experiences of LDLT in six patients with moderate or severe PPHTN, along with our institutional guidelines. Three had liver cirrhosis and three were non-cirrhotic. Catheterization studies were undertaken before, during and after LDLT, and the mean pulmonary arterial pressure (mPAP), cardiac output (CO), pulmonary vascular resistance and total peripheral resistance (TPR) were monitored.

RESULTS

The results showed significant differences in CO and TPR between cirrhotic and non-cirrhotic patients before, during and after LDLT. Cirrhotic patients showed systemic hyperdynamic state. Two cirrhotic patients showed poor responses to pre-transplant treatment, and continued to have increased PAH and poor clinical courses after LDLT. LDLT has an advantage of flexible timing of LT. Currently in our institution, PPHTN patients with mPAP <40 mmHg are registered for LDLT after treatment and catheterization. However, LDLT is performed when mPAP is ≤35 mmHg, leading to improved outcomes.

CONCLUSION

PPHTN patients with well-controlled PAH, or secondary PAH resulting from porto-systemic shunts, may be appropriate candidates for LDLT after careful considerations.

The potential of biomarkers in pulmonary arterial hypertension

Effective management of patients with pulmonary arterial hypertension (PAH) requires comprehensive prognostic evaluation in order to determine optimal management strategies. Although a number of clinical and hemodynamic parameters linked to PAH prognosis have been identified, some are associated with significant limitations (eg, invasive techniques, subjective measures). There is a need for noninvasive and objective measures to be established that function as biomarkers for the diagnosis and assessment of disease prognosis, and that determine response to therapy in patients with PAH. Reflecting the highly complex etiology of the disease, a large number of potential biomarkers have been, and continue to be, investigated in PAH, including those reflecting right heart function, endothelial dysfunction, and markers of inflammation and second organ failure. However, it has become clear that scientifically interesting biomarkers may not necessarily be clinically useful. Of the range of biomarkers investigated in PAH to date, only brain natriuretic peptide and its N-terminal cleavage product have been included as prognostic parameters in treatment guidelines. It is unlikely that any single biomarker will provide all the relevant information required for an individual patient, and the potential for combining markers is currently of considerable interest. Future studies are required to determine the optimal combination of existing and emerging biomarkers in the clinical setting.

Today's and tomorrow's imaging and circulating biomarkers for pulmonary arterial hypertension

The pathobiology of pulmonary arterial hypertension (PAH) involves a remodeling process in distal pulmonary arteries, as well as vasoconstriction and in situ thrombosis, leading to an increase in pulmonary vascular resistance, right heart failure and death. Its etiology may be idiopathic, but PAH is also frequently associated with underlying conditions such as connective tissue diseases. During the past decade, more than welcome novel therapies have been developed and are in development, including those increasingly targeting the remodeling process. These therapeutic options modestly increase the patients' long-term survival, now approaching 60% at 5 years. However, non-invasive tools for confirming PAH diagnosis, and assessing disease severity and response to therapy, are tragically lacking and would help to select the best treatment. After exclusion of other causes of pulmonary hypertension, a final diagnosis still relies on right heart catheterization, an invasive technique which cannot be repeated as often as an optimal follow-up might require. Similarly, other techniques and biomarkers used for assessing disease severity and response to treatment generally lack specificity and have significant limitations. In this review, imaging as well as current and future circulating biomarkers for diagnosis, prognosis, and follow-up are discussed.

Reactive oxygen and nitrogen species in pulmonary hypertension

Pulmonary vascular disease can be defined as either a disease affecting the pulmonary capillaries and pulmonary arterioles, termed pulmonary arterial hypertension, or a disease affecting the left ventricle, called pulmonary venous hypertension. Pulmonary arterial hypertension (PAH) is a disorder of the pulmonary circulation characterized by endothelial dysfunction, as well as intimal and smooth muscle proliferation. Progressive increases in pulmonary vascular resistance and pressure impair the performance of the right ventricle, resulting in declining cardiac output, reduced exercise capacity, right-heart failure, and ultimately death. While the primary and heritable forms of the disease are thought to affect over 5000 patients in the United States, the disease can occur secondary to congenital heart disease, most advanced lung diseases, and many systemic diseases. Multiple studies implicate oxidative stress in the development of PAH. Further, this oxidative stress has been shown to be associated with alterations in reactive oxygen species (ROS), reactive nitrogen species (RNS), and nitric oxide (NO) signaling pathways, whereby bioavailable NO is decreased and ROS and RNS production are increased. Many canonical ROS and NO signaling pathways are simultaneously disrupted in PAH, with increased expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases and xanthine oxidoreductase, uncoupling of endothelial NO synthase (eNOS), and reduction in mitochondrial number, as well as impaired mitochondrial function. Upstream dysregulation of ROS/NO redox homeostasis impairs vascular tone and contributes to the pathological activation of antiapoptotic and mitogenic pathways, leading to cell proliferation and obliteration of the vasculature. This paper will review the available data regarding the role of oxidative and nitrosative stress and endothelial dysfunction in the pathophysiology of pulmonary hypertension, and provide a description of targeted therapies for this disease.

Ultrastructure Study of Transgenic Ren2 Rat Aorta - Part 1: Endothelium and Intima

BACKGROUND: The renin-angiotensin-aldosterone system plays an important role in the development and progression of hypertension and accelerated atherosclerosis (atheroscleropathy) associated with the cardiorenal metabolic syndrome and type 2 diabetes mellitus. Additionally, the renin-angiotensin-aldosterone system plays an important role in vascular-endothelial-intimal cellular and extracellular remodeling. METHODS: Thoracic aortas of young male transgenic heterozygous (mRen2)27 (Ren2) rats were utilized for this ultrastructural study. This lean model of hypertension, insulin resistance and oxidative stress harbors the mouse renin gene with increased local tissue (aortic) levels of angiotensin II and angiotensin type 1 receptors and elevated plasma aldosterone levels. RESULTS: The ultrastructural observations included marked endothelial cell retraction, separation, terminal nuclear lifting, adjacent duplication, apoptosis and a suggestion of endothelial progenitor cell attachment. The endothelium demonstrated increased caveolae, microparticles, depletion of Weibel-Palade bodies, loss of cell-cell and basal adhesion hemidesmosome-like structures, platelet adhesion and genesis of subendothelial neointima. CONCLUSION: These observational ultrastructural studies of the transgenic Ren2 vasculature provide an in-depth evaluation of early abnormal remodeling changes within conduit-elastic arteries under conditions of increased local levels of angiotensin II, oxidative stress, insulin resistance and hypertension.

Loss of receptor activity-modifying protein 3 exacerbates cardiac hypertrophy and transition to heart failure in a sex-dependent manner

Sex differences exist in the hypertrophic response, cardiac remodeling, and transition to heart failure of hypertensive patients, and while some of these differences are likely influenced by estrogen, the genetic pathways downstream of estrogen that impact on cardioprotection have yet to be fully elucidated. We have previously shown that the cardioprotective effects of adrenomedullin (AM), an emerging clinical biomarker for cardiovascular disease severity, vary with sex in mouse models. AM signaling during cardiovascular stress is strongly modulated by receptor activity-modifying protein 3 (RAMP3) via its interaction with the G protein-coupled receptor calcitonin receptor-like receptor (CLR). Like AM, RAMP3 expression is potently regulated by estrogen, and so we sought to determine the consequences of genetic Ramp3 loss on cardiac adaptation to chronic hypertension, with a particular focus on characterizing potential sex differences. We generated and bred RAMP3(-/-) mice to RenTgMK mice that consistently display severe angiotensin II-mediated CV disease and compared CV disease progression in RenTgMK to that of RenTgMK:RAMP3(-/-) offspring. As expected, RAMP3 gene expression was higher in cardiovascular tissues of RenTgMK mice and more strongly up-regulated in female RenTgMK mice relative to wildtype controls. RAMP3 loss did not affect the development of hypertension or the presence and severity of perivascular and interstitial fibrosis in the left ventricle (LV). However, echocardiography revealed that while RenTgMK mice developed concentric cardiac hypertrophy with sustained systolic function, male RenTgMK:RAMP3(-/-) mice showed evidence of LV chamber dilatation and depressed systolic function, suggestive of cardiac decompensation. Consistent with these measures of heart failure, male RenTgMK:RAMP3(-/-) mice had increased cardiac apoptosis and elevated activation of Akt. These phenotypes were not present in female RenTgMK:RAMP3(-/-) mice. Collectively, these data demonstrate a sex-dependant, cardioprotective role of RAMP3 in the setting of chronic hypertension.

Cross talk between mitochondria and NADPH oxidases

Reactive oxygen species (ROS) play an important role in physiological and pathological processes. In recent years, a feed-forward regulation of the ROS sources has been reported. The interactions between the main cellular sources of ROS, such as mitochondria and NADPH oxidases, however, remain obscure. This work summarizes the latest findings on the role of cross talk between mitochondria and NADPH oxidases in pathophysiological processes. Mitochondria have the highest levels of antioxidants in the cell and play an important role in the maintenance of cellular redox status, thereby acting as an ROS and redox sink and limiting NADPH oxidase activity. Mitochondria, however, are not only a target for ROS produced by NADPH oxidase but also a significant source of ROS, which under certain conditions may stimulate NADPH oxidases. This cross talk between mitochondria and NADPH oxidases, therefore, may represent a feed-forward vicious cycle of ROS production, which can be pharmacologically targeted under conditions of oxidative stress. It has been demonstrated that mitochondria-targeted antioxidants break this vicious cycle, inhibiting ROS production by mitochondria and reducing NADPH oxidase activity. This may provide a novel strategy for treatment of many pathological conditions including aging, atherosclerosis, diabetes, hypertension, and degenerative neurological disorders in which mitochondrial oxidative stress seems to play a role. It is conceivable that the use of mitochondria-targeted treatments would be effective in these conditions.

Aldosterone stimulates superoxide production in macula densa cells

Two major factors which regulate tubuloglomerular feedback (TGF)-mediated constriction of the afferent arteriole are release of superoxide (O(2)(-)) and nitric oxide (NO) by macula densa (MD) cells. MD O(2)(-) inactivates NO; however, among the factors that increase MD O(2)(-) release, the role of aldosterone is unclear. We hypothesize that aldosterone activates the mineralocorticoid receptor (MR) on MD cells, resulting in increased O(2)(-) production due to upregulation of cyclooxygenase-1 (COX-2) and NOX-2, and NOX-4, isoforms of NAD(P)H oxidase. Studies were performed on MMDD1 cells, a renal epithelial cell line with properties of MD cells. RT-PCR and Western blotting confirmed the expression of MR. Aldosterone (10(-8) mol/l for 30 min) doubled MMDD1 cell O(2)(-) production, and this was completely blocked by MR inhibition with 10(-5) mol/l eplerenone. RT-PCR, real-time PCR, and Western blotting demonstrated aldosterone-induced increases in COX-2, NOX-2, and NOX-4 expression. Inhibition of COX-2 (NS398), NADPH oxidase (apocynin), or a combination blocked aldosterone-induced O(2)(-) production to the same degree. These data suggest that aldosterone-stimulated MD O(2)(-) production is mediated by COX-2 and NADPH oxidase. Next, COX-2 small-interfering RNA (siRNA) specifically decreased COX-2 mRNA without affecting NOX-2 or NOX-4 mRNAs. In the presence of the COX-2 siRNA, the aldosterone-induced increases in COX-2, NOX-2, and NOX-4 mRNAs and O(2)(-) production were completely blocked, suggesting that COX-2 causes increased expression of NOX-2 and NOX-4. In conclusion 1) MD cells express MR; 2) aldosterone increases O(2)(-) production by activating MR; and 3) aldosterone stimulates COX-2, which further activates NOX-2 and NOX-4 and generates O(2)(-). The resulting balance between O(2)(-) and NO in the MD is important in modulating TGF.

Tempol, a superoxide dismutase mimetic, prevents cerebral vessel remodeling in hypertensive rats

Increased reactive oxygen species (ROS) production is involved in the pathogenesis of hypertension and stroke. The effects of ROS on cerebral vessels from hypertensive rats have not been studied. We hypothesized that tempol, a superoxide dismutase mimetic, would prevent middle cerebral artery (MCA) remodeling in stroke-prone spontaneously hypertensive rats (SHRSP). Six-week-old male SHRSP were treated with tempol (1mM) for 6weeks. The MCA was then removed and mounted in a pressure myograph to study tone generation, vessel reactivity, and passive vessel structure. Data are shown as mean±SEM, tempol vs. control. Plasma thiobarbituric acid reactive substances (TBARS) were decreased by tempol treatment (14.15±1.46 vs. 20.55±1.25nM of malondialdehyde [MDA]/ml, p=0.008). Maximum serotonin-induced constriction was increased by tempol treatment, without changes in dilation to adenosine diphosphate or tone generation. At an intralumenal pressure of 80mmHg, tempol caused a dramatic increase in the MCA lumen diameter (246±5 vs. 207±3μm, p<0.001), outer diameter (281±5 vs. 241±3μm, p<0.001), lumen cross-sectional area, and vessel cross-sectional area. Collagen IV mRNA expressions were increased by 2.4-fold after tempol treatment. These results suggest that ROS are involved in the remodeling of the cerebral vasculature of SHRSP and that ROS scavenging can attenuate this process.

Comparative analysis of telmisartan and olmesartan on cardiac function in the transgenic (mRen2)27 rat

Telmisartan, an angiotensin receptor blocker, may have unique benefits as it possesses partial peroxisome proliferator-activated receptor (PPAR)-γ agonist activity in addition to antihypertensive effects. In this study, we test whether treatment with telmisartan ameliorates cardiovascular abnormalities to a greater extent than olmesartan, which has little PPAR-γ activity. The hypertensive rodent model of tissue renin-angiotensin system activation, transgenic (mRen2)27 (Ren2) rats and their littermate Sprague-Dawley controls were used. Rats were treated with telmisartan (2 mg · kg(-1) · day(-1)), olmesartan (2.5 mg · kg(-1) · day(-1)), or vehicle via drinking water for 3 wk; these doses achieved similar blood pressure control, as measured by telemetry. Ren2 rats displayed impaired diastolic and systolic function using left ventricular (LV) pressure-volume (P-V) analysis. Load-independent diastolic indexes, including the time constant of isovolumic relaxation and the slope of the end-diastolic P-V relationship, as well as systolic indexes, including preload recruitable stroke work, the dP/dt(max)-end-diastolic volume (EDV) relationship, and the P-V area-EDV relationship, were elevated in Ren2 rats compared with Sprague-Dawley controls (P < 0.05). The Ren2 myocardium exhibited parallel increases in the oxidant markers NADPH oxidase and 3-nitrotyrosine. The increase in the prohypertrophic protein Jak2 in Ren2 rats was associated with cardiac structural abnormalities using light microscopic and ultrastructural analysis, which included interstitial fibrosis, cardiomyocyte and LV hypertrophy, and mitochondrial derangements. Both angiotensin receptor blockers attenuate these abnormalities to a similar extent. Our data suggest that the beneficial effect of telmisartan and olmesartan on cardiac structure and function may be predominantly pressor-related or angiotensin type 1 receptor dependent in this model of renin-angiotensin system activation.

Contribution of oxidative stress to pulmonary arterial hypertension

Recent data implicate oxidative stress as a mediator of pulmonary hypertension (PH) and of the associated pathological changes to the pulmonary vasculature and right ventricle (RV). Increases in reactive oxygen species (ROS), altered redox state, and elevated oxidant stress have been demonstrated in the lungs and RV of several animal models of PH, including chronic hypoxia, monocrotaline toxicity, caveolin-1 knock-out mouse, and the transgenic Ren2 rat which overexpresses the mouse renin gene. Generation of ROS in these models is derived mostly from the activities of the nicotinamide adenine dinucleotide phosphate oxidases, xanthine oxidase, and uncoupled endothelial nitric oxide synthase. As disease progresses circulating monocytes and bone marrow-derived monocytic progenitor cells are attracted to and accumulate in the pulmonary vasculature. Once established, these inflammatory cells generate ROS and secrete mitogenic and fibrogenic cytokines that induce cell proliferation and fibrosis in the vascular wall resulting in progressive vascular remodeling. Deficiencies in antioxidant enzymes also contribute to pulmonary hypertensive states. Current therapies were developed to improve endothelial function, reduce pulmonary artery pressure, and slow the progression of vascular remodeling in the pulmonary vasculature by targeting deficiencies in either NO (PDE-type 5 inhibition) or PGI(2) (prostacyclin analogs), or excessive synthesis of ET-1 (ET receptor blockers) with the intent to improve patient clinical status and survival. New therapies may slow disease progression to some extent, but long term management has not been achieved and mortality is still high. Although little is known concerning the effects of current pulmonary arterial hypertension treatments on RV structure and function, interest in this area is increasing. Development of therapeutic strategies that simultaneously target pathology in the pulmonary vasculature and RV may be beneficial in reducing mortality associated with RV failure.