Pulmonary Arterial Medial Thickness Research Articles

Early Alteration of Right Ventricle-Pulmonary Artery Coupling in Experimental Heart Failure With Preserved Ejection Fraction.

Pulmonary hypertension and right ventricular (RV) dysfunction are major prognostic determinants in patients with heart failure with preserved ejection fraction (HFpEF). The underlying pathomechanisms remain unknown. In this context, we sought to study the pathogenesis of pulmonary hypertension and RV dysfunction in a rat model of obesity-associated HFpEF. HFpEF was induced in obesity-prone rats fed a high-fat diet (n=13) and compared with obesity-resistant rats fed with standard chow (n=9). After 12 months, the animals underwent echocardiographic and hemodynamic evaluation followed by tissue sampling for pathobiological assessment. HFpEF rats presented mild RV pressure overload (with increased RV systolic pressure and pulmonary vascular resistance). No changes in pulmonary artery medial thickness and exvivo vasoreactivity (to acetylcholine and endothelin-1) were observed and RNA sequencing analysis failed to identify gene clustering in HFpEF lungs. However, released nitric oxide levels were decreased in HFpEF pulmonary artery, while lung expression of preproendothelin-1 was increased. In HFpEF rats, RV structure and function were altered, with RV enlargement, decreased RV fractional area change and free wall longitudinal fractional shortening, together with altered right ventricle-pulmonary artery coupling (estimated by tricuspid annular plane systolic excursion/systolic pulmonary artery pressure). Hypertrophy and apoptosis (evaluated by transferase biotin- dUTP nick-end labeling staining) were increased in right and left ventricles of HFpEF rats. There was an inverse correlation between tricuspid annular plane systolic excursion/systolic pulmonary artery pressure and RV apoptotic rate. Plasma levels of soluble suppression of tumorigenicity-2, interleukin-1β, -6 and -17A were increased in HFpEF rats. Obesity-associated HFpEF in rats spontaneously evolves to pulmonary hypertension-HFpEF associated with impaired right ventricle-pulmonary artery coupling that appears disproportionate to a slight increase in RV afterload.

Ameliorative Effects of Beetroot Juice Supplementation on Monocrotaline-Induced Pulmonary Hypertension in Rats

Beetroot is a nitrate-rich vegetable with cardiovascular benefits. This study examined whether ingestion of beetroot juice (BRJ) protects against pulmonary hypertension (PH). Rats were injected subcutaneously with 60 mg/kg monocrotaline (MCT) and randomized to receive either drinking water, low-dose BRJ (BRJ-L, nitrate content: 1.4 mmol/L), or high-dose BRJ (BRJ-H, nitrate content: 3.5 mmol/L), which was started 1 week after MCT injection and continued until the end of the experiment. Four weeks after MCT injection, right ventricle (RV) hypertrophy, right ventricular systolic pressure (RVSP) elevation, and pulmonary vascular remodeling were observed. These PH symptoms were less severe in rats supplemented with BRJ-L (Fulton index, p = 0.07; RVSP, p = 0.09, pulmonary arterial medial thickening, p < 0.05), and the beneficial effects were more pronounced than those of BRJ-H supplementation. Plasma and RV nitrite and nitrate levels did not change significantly, even when BRJ-L and BRJ-H were administered. There were no differences in plasma thiobarbituric acid reactive substances (TBARS), a biomarker of oxidative stress, among the groups. BRJ-L supplementation significantly decreased RV TBARS levels compared to MCT alone (p < 0.05), whereas BRJ-H supplementation did not. These findings suggest that starting BRJ supplementation from an early stage of PH ameliorates disease severity, at least partly through the inhibition of local oxidative stress. Habitual ingestion of BRJ may be useful for the management of PH.

Abstract 10715: Therapeutic Efficacy of Drpitor1a, a Novel Dynamin-Related Protein 1 (DRP1) Inhibitor, in Preclinical Pulmonary Arterial Hypertension

Introduction: Dynamin-related protein 1 (DRP1) is a large GTPase that mediates mitotic fission (the division of mitochondria which is coordinated with mitosis, ensuring equitable distribution of mitochondria to daughter cells). In pulmonary arterial hypertension (PAH) pulmonary artery smooth muscle cells (PASMC), mitotic fission, and DRP1 activity are increased, contributing to its hyperproliferative phenotype. We investigated the therapeutic efficacy of Drpitor1a, a novel, small molecule, Drp1 GTPase inhibitor, in a rat PAH model. Methods: A single dose of monocrotaline (MCT, 60mg/kg, SC) or PBS was injected to female Sprague-Dawley rats on day 0 (n=20 for MCT and n=15 for PBS). On day 14, the development of PAH was confirmed by echocardiography and the rats were randomized for treatments. An indwelling catheter was implanted through the left jugular vein on day 15. Drpitor1a (1mg/kg) or normal saline (NS) was administered by IV every 48 hours from day 17 to day 27. Right ventricular (RV) structure and function were assessed on day 28 with echocardiography. Pulmonary hemodynamics was evaluated on day 29 using right heart catheterization (RHC). Results: MCT rats developed PAH with RV dysfunction on day 14. There was no statistical difference between the Drpitor1a and NS groups at randomization. At the endpoint, MCT+Drpitor1a rats, vs. MCT+NS rats, had a significantly reduced severity of pulmonary hypertension evident as longer pulmonary artery acceleration time (PAAT) and lower pulmonary vascular resistance index. Drpitor1a also improved RV function, evident as greater RV free wall thickening (RVFWT%), increased tricuspid annular plane systolic excursion (TAPSE), and increased cardiac index (CI). Drpitor1a regressed pulmonary artery medial thickening and inhibited RV hypertrophy without hepatological, renal or hepatic toxicities. Conclusion: Drpitor1a is a safe and effective treatment for preclinical PAH.

Elastin Insufficiency Confers Proximal and Distal Pulmonary Vasculopathy in Mice, Partially Remedied by the KATP Channel Opener Minoxidil: Considerations and Cautions for the Treatment of People With Williams-Beuren Syndrome.

BackgroundWilliams Beuren syndrome (WBS) is a recurrent microdeletion disorder that removes one copy of elastin (ELN), resulting in large artery vasculopathy. Early stenosis of the pulmonary vascular tree is common, but few data are available on longer-term implications of the condition.MethodsComputed tomography (CT) angiogram (n = 11) and echocardiogram (n = 20) were performed in children with WBS aged 3.4–17.8 years. Controls (n = 11, aged 4.4–16.8 years) also underwent echocardiogram. Eln+/− mice were analyzed by invasive catheter, echocardiogram, micro-CT (μCT), histology, and pressure myography. We subsequently tested whether minoxidil resulted in improved pulmonary vascular endpoints.ResultsWBS participants with a history of main or branch pulmonary artery (PA) stenosis requiring intervention continued to exhibit increased right ventricular systolic pressure (RVSP, echocardiogram) relative to their peers without intervention (p < 0.01), with no clear difference in PA size. Untreated Eln+/− mice also show elevated RVSP by invasive catheterization (p < 0.0001), increased normalized right heart mass (p < 0.01) and reduced caliber branch PAs by pressure myography (p < 0.0001). Eln+/− main PA medias are thickened histologically relative to Eln+/+ (p < 0.0001). Most Eln+/− phenotypes are shared by both sexes, but PA medial thickness is substantially greater in Eln+/− males (p < 0.001). Eln+/− mice showed more acute proximal branching angles (p < 0.0001) and longer vascular segment lengths (p < 0.0001) (μCT), with genotype differences emerging by P7. Diminished PA acceleration time (p < 0.001) and systolic notching (p < 0.0001) were also observed in Eln+/− echocardiography. Vascular casting plus μCT revealed longer generation-specific PA arcade length (p < 0.0001), with increased PA branching detectable by P90 (p < 0.0001). Post-weaning minoxidil decreased RVSP (p < 0.01) and normalized PA caliber (p < 0.0001) but not early-onset proximal branching angle or segment length, nor later-developing peripheral branch number.ConclusionsVascular deficiencies beyond arterial caliber persist in individuals with WBS who have undergone PA stenosis intervention. Evaluation of Eln+/− mice reveals complex vascular changes that affect the proximal and distal vasculatures. Minoxidil, given post-weaning, decreases RVSP and improves lumen diameter, but does not alter other earlier-onset vascular patterns. Our data suggest additional therapies including minoxidil could be a useful adjunct to surgical therapy, and future trials should be considered.

Abstract 12114: Endothelial Extracellular Signal-Regulated Kinase 2 Contributed to the Development of Pulmonary Arterial Hypertension in Mice Through the Impairment of Endothelial Nitric Oxide Synthase Function

Introduction: Pulmonary arterial hypertension (PAH) is a progressive disease, characterized by abnormal muscularization and endothelial dysfunction in pulmonary artery (PA). Previous study showed that endothelial extracellular signal-regulated kinase 2 (eERK2) released vasoconstrictive factors and decreased NO bioactivity resulting in obese-induced hypertension and endothelial dysfunction. However, the role of eERK2 in the pathogenesis of PAH remains to be elucidated. Hypothesis: We hypothesized eERK2 impaired eNOS function and progressed the pathogenesis of PAH. Methods and Results: We generated eERK2 knock out mice (EE2KO) crossing Tie2-Cre mice and ERK2 flox mice and induced PAH by exposing mice to chronic hypoxia (10%) for 4 weeks. The littermate ERK2 flox mice without Cre expression were used as Control (Ctr). Immuno-histochemical staining showed the deficiency of eERK2 expression in the PA of EE2KO. We assessed the medial thickness of pulmonary arteries (MTPA) and measured right ventricular systolic pressure (RVSP). Although Ctr exhibited the progression of PA muscularization with an increase in MTPA, EE2KO revealed the significantly attenuated MTPA under hypoxic condition. Moreover, we found the lower RVSPs in EE2KO than those in Ctr under hypoxia in spite of similar RVSPs in normoxia. In RT-PCR, lung endothelin1 (ET1) gene expression was significantly lower in EE2KO than Ctr under hypoxia. Interestingly, hypoxia increased eNOS protein expression both in Ctr and EE2KO with Western blot analysis. The phosphorylation of AMPKα and eNOS were up-regulated in the lungs of EE2KO relative to Ctr under hypoxia. In addition, eNOS dimer/monomer ratios with non redusing SDS-PAGE was significantly increased in EE2KO compared to the Ctr under hypoxia (1.29±0.10 vs. 0.87±0.02, P=0.02, dimer / monomer ratios), suggesting improved eNOS uncoupling. Conclusions: These findings suggest that hypoxia increased eNOS expression and function, and that eERK2 impaired eNOS function by decreasing the phosphorylation of AMPKα and eNOS, and inducing eNOS uncoupling. In addition, ET1 synthesis through eERK2 might contribute to these pathogenesis of PAH with hypoxia.

Abstract 13094: Pharmacokinetics and Therapeutic Efficacy of Drpitor1a, a Novel Dynamin-Related Protein 1 Inhibitor, in a Preclinical Model of Pulmonary Arterial Hypertension

Introduction: Increased dynamin-related protein 1 (Drp1)-mediated mitochondrial fission contributes to the pathogenesis of pulmonary arterial hypertension (PAH). We investigated the pharmacokinetic characteristics of Drpitor1a, a novel, small molecule, ellipticine Drp1 inhibitor (prepared in-house), and tested its therapeutic efficacy in a pilot study using the rat monocrotaline (MCT)-PAH model. Methods: A single dose of Drpitor1a (5mg/kg) was administered IV or PO to male and female rats (n=3/sex). Blood was collected at 0, 5 and 30 minutes, and at 1, 2, 4, 6, 8 and 24 hours post drug administration. Plasma, lung and right ventricle (RV) were collected and tissue concentration of Drpitor1a was measured using HPLC coupled with mass spectrometry. The effects of Drpitor1a on mitochondrial fission and cell proliferation were assessed in human PAH pulmonary artery smooth muscle cells (PASMC). In an MCT-PAH model, a catheter was implanted in the left jugular vein on day 14 post-MCT injection. Drpitor1a (1mg/kg) was administered by IV every 48 hours from day 17 to day 27. On day 28, RV function and pulmonary hemodynamics were assessed. Results: Drpitor1a’s half-life varies by sex (9.9±5.3 hours and 24.3±21.4 hours in male and female rats respectively). Oral bioavailability of Drpitor1a was similar in males (21.1%) and females (19.7%). Lung concentration of Drpitor1a was similar between males and females (0.441±0.015 nM/mg and 0.444±0.581 nM/mg, respectively). In the RV, Drpitor1a level was higher in females (0.102±0.053 nM/mg) than males (0.055±0.015 nM/mg). Drpitor1a inhibited mitochondrial fission and cell proliferation in human PAH PASMC. In addition, Drpitor1a regressed pulmonary artery medial thickening (25.5% vs 34.9%), inhibited RV hypertrophy (Fulton index: 0.33 vs 0.39) and improved RV function (TAPSE: 2.2mm vs 1.8mm) in female MCT-PAH rats. Conclusion: Drpitor1a is a potential therapeutic agent for preclinical PAH and may be more effective in females.

Preventive effects of nitrate-rich beetroot juice supplementation on monocrotaline-induced pulmonary hypertension in rats.

Beetroot (Beta vulgaris L.) has a high level of nitrate; therefore, its dietary intake could increase nitric oxide (NO) level in the body, possibly preventing the development of pulmonary hypertension (PH). In this study, we examined the effects of beetroot juice (BJ) supplementation on PH and the contribution of nitrate to such effects using a rat model of monocrotaline (MCT, 60 mg/kg s.c.)-induced PH. Rats were injected subcutaneously with saline or 60 mg/kg MCT and were sacrificed 28 days after the injection. In some rats injected with MCT, BJ was supplemented from the day of MCT injection to the day of sacrifice. First, MCT-induced right ventricular systolic pressure elevation, pulmonary arterial medial thickening and muscularization, and right ventricular hypertrophy were suppressed by supplementation with low-dose BJ (nitrate: 1.3 mmol/L) but not high-dose BJ (nitrate: 4.3 mmol/L). Of the plasma nitrite, nitrate, and their sum (NOx) levels, only the nitrate levels were found to be increased by the high-dose BJ supplementation. Second, in order to clarify the possible involvement of nitrate in the preventive effects of BJ on PH symptoms, the effects of nitrate-rich BJ (nitrate: 0.9 mmol/L) supplementation were compared with those of the nitrate-depleted BJ. While the former exerted preventive effects on PH symptoms, such effects were not observed in rats supplemented with nitrate-depleted BJ. Neither supplementation with nitrate-rich nor nitrate-depleted BJ affected plasma nitrite, nitrate, and NOx levels. These findings suggest that a suitable amount of BJ ingestion, which does not affect systemic NO levels, can prevent the development of PH in a nitrate-dependent manner. Therefore, BJ could be highly useful as a therapy in patients with PH.

Discovery of Novel Pyrazolo[3,4-b] Pyridine Derivatives with Dual Activities of Vascular Remodeling Inhibition and Vasodilation for the Treatment of Pulmonary Arterial Hypertension.

Current pulmonary arterial hypertension (PAH) therapeutic strategies mainly focus on vascular relaxation with less emphasis on vascular remodeling, which results in poor prognosis. Hence, dual pathway regulators with vasodilation effect via soluble guanylate cyclase (sGC) stimulation and vascular remodeling regulation effect by AMP-activated protein kinase (AMPK) inhibition provide more advantages and potentialities. Herein, we designed and synthesized a series of novel pyrazolo[3,4-b] pyridine derivatives based on sGC stimulator and AMPK inhibitor scaffolds. In vitro, 2 exhibited moderate vasodilation activity and higher proliferation and migration suppressive effects compared to riociguat. In vivo, 2 significantly decreased right ventricular systolic pressure (RVSP), attenuated pulmonary artery medial thickness (PAMT), and right ventricular hypertrophy (RVH) in hypoxia-induced PAH rat models (i.g.). Given the unique advantages of significant vascular remodeling inhibition and moderate vascular relaxation based on the dual pathway regulation, we proposed 2 as a promising lead for anti-PAH drug discovery.

Fasudil dichloroacetate (FDCA), an orally available agent with potent therapeutic efficiency on monocrotaline-induced pulmonary arterial hypertension rats.

Given the therapeutic efficacy of fasudil hydrochloride (F) and dichloroacetate (DCA) on pulmonary arterial hypertension (PAH), a new salt fasudil dichloroacetate (FDCA) was designed, synthesized and biologically evaluated. FDCA exhibited comparable ROCK II inhibitory activity relative to fasudil hydrochloride, and suppressed the expression of TNF-α and IL-6 in both PDGF-BB and hypoxia-treated pulmonary arterial smooth muscle cells (PASMCs) and endothelial cells (PAECs). Significantly, FDCA lowered mean pulmonary artery pressure (mPAP) and right ventricular systolic pressure (RVSP), and decreased right ventricular hypertrophy (RVH) in monocrotaline (MCT)-induced PAH rats. Meanwhile, FDCA remarkably decreased pulmonary artery medial thickness (PAMT) and hyperplasia, restoring the elasticity of elastic fiber, reduced cardiac hypertrophy, and attenuated fibrosis of heart and lung. Collectively, FDCA exhibited triple activities of pulmonary vasodilation, vascular remodeling inhibition and RVH inhibition, suggesting that it may be a promising agent for PAH intervention.

Elevated pulmonary arterial pressure in Zucker diabetic fatty rats.

Diabetes is a very strong predictor of chronic systemic vascular diseases and acute cardiovascular events. Recently, associations between metabolic disorders and pulmonary hypertension have also been reported in both humans and animal models. In order to get some further insight into the relationship of pulmonary hypertension with obesity, insulin resistance and hyperglycemia, herein we have used the Zucker diabetic fatty rats (ZDF/clr-lepr fa) at 20 weeks fed a standard diet and compared to their lean Zucker littermates (ZL). ZDF rats were obese, had elevated plasma glucose levels and insulin resistance, i.e. a clinically relevant model of type 2 diabetes. They presented elevated systolic, diastolic and mean pulmonary arterial pressures and a parallel increase in the Fulton index. Systemic arterial pressures were also increased but the left ventricle plus septum weight was similar in both groups and the heart rate was reduced. Wall media thickening was observed in the small pulmonary arteries from the ZDF rats. Isolated pulmonary arteries mounted in a wire myograph showed similar vasoconstrictor responses to phenylephrine and 5-HT and similar responses to the endothelium-dependent vasodilator acetylcholine. However, the iNOS inhibitor 1400W enhanced the vasoconstrictor responses in ZDF but not in ZL rats. The protein expression of eNOS and iNOS was not significantly different in the lungs of the two groups. The lung expression of Bmpr2 mRNA was downregulated. However, the mRNA expression of Kcna5, Kcnk3, Kcnq1, Kcnq4 or Kcnq5, which encode for the potassium channels Kv1.5, TASK-1, Kv7.1, Kv7.4 and Kv7.5, respectively, was similar in ZL and ZDF rats. In conclusion, ZDF rats show increased pulmonary arterial pressure, right ventricular hypertrophy, pulmonary arterial medial thickening and downregulated lung Bmpr2 despite leptin resistance. These changes were mild but are consistent with the view that diabetes is a risk factor for pulmonary hypertension.

Stimulation of nitric oxide-sensitive soluble guanylate cyclase in monocrotaline-induced pulmonary hypertensive rats

AimsIn this study, we examined whether a disruption in the balance between nitric oxide (NO)-sensitive and -insensitive soluble guanylate cyclase (sGC) is observed in pulmonary hypertension (PH) and whether treatment with NO-enhancing drugs can halt disease progression. Main methodsRats were injected subcutaneously with saline or 60 mg/kg monocrotaline (MCT). At 14 days after injection, the vascular reactivity of isolated extralobar pulmonary arteries was assessed by organ chamber technique. In a separate experiment, isosorbide mononitrate (0.3 or 1 g/L) or sodium nitrite (30 or 300 mg/L) was administered in drinking water for the last 14 days (from day 15 to day 28), and their therapeutic potential was evaluated. Key findingsThe NO-sensitive sGC stimulant BAY 41-2272 and the NO-insensitive sGC stimulant BAY 60-2770 both relaxed the pulmonary arteries, which was comparable between saline- and MCT-injected rats. Treatment with isosorbide mononitrate suppressed the MCT-induced right ventricular systolic pressure (RVSP) elevation and pulmonary arterial medial thickening but not right ventricular hypertrophy. However, the beneficial effects on RVSP and pulmonary vascular remodeling were not observed when a high dose was administered. The same results were obtained following the sodium nitrite treatment. Interestingly, NO-enhancing drugs did not increase plasma nitrite plus nitrate levels at a dose that provided the greatest therapeutic advantage. SignificanceThese findings suggest that the balance between NO-sensitive and -insensitive sGC is not disrupted in the early stage of MCT-induced PH. Furthermore, supplementation with an adequate amount of NO may be a useful therapy to prevent the progression of PH.

Identification of a Novel Hybridization from Isosorbide 5-Mononitrate and Bardoxolone Methyl with Dual Activities of Pulmonary Vasodilation and Vascular Remodeling Inhibition on Pulmonary Arterial Hypertension Rats.

Given the clinical therapeutic efficacy of oral-dosed bardoxolone methyl (1) and the selective vasodilatory effect caused by inhalation of nitric oxide (NO) on pulmonary arterial hypertension (PAH) patients, a new hybrid (CDDO-NO, 2) from 1 and NO donor isosorbide 5-mononitrate (3) was designed and synthesized. This hybrid could liberate 1 and NO in the lungs of rats after trachea injection. Significantly, 2 lowered mean pulmonary artery pressure (mPAP) and right ventricular systolic pressure (RVSP), decreased right ventricular hypertrophy (RVH), and attenuated pulmonary artery medial thickness (PAMT) and vascular muscularization in monocrotaline (MCT)-induced PAH rats. Meanwhile, 2 inhibited overproliferation of perivascular cells and diminished macrophage infiltration and oxidative stress by inactivation of NOX4. In addition, 2 markedly reduced cardiac hypertrophy and fibrosis in the PAH rats. Overall, 2 exhibited potent dual activities of pulmonary vasodilation and vascular remodeling inhibition, suggesting that it may be a promising agent for PAH intervention.

Morphological characterization of pulmonary microvascular disease in bronchopulmonary dysplasia caused by hyperoxia in newborn mice.

Pulmonary microvascular injury is associated with the pathogenesis of bronchopulmonary dysplasia (BPD). To characterize the mechanisms of pulmonary vascular disease resulting from BPD, we studied the ultrastructural changes affecting pulmonary microvasculature. Newborn ICR mice were exposed to 85% hyperoxia or normoxia for 14days, and then normal air replacement conditions for the following 7days. At postnatal day (P)14 and P21, lungs were harvested for ultrastructural examination and assessment of pulmonary hypertension. The ultrastructure of pulmonary microvasculature in the hyperoxia-exposed lungs revealed a collapsed capillary lumen. This was due to the abnormal morphology of endothelial cells (ECs) characterized by heterogeneously thick cytoplasm. Compared to normal air controls, the specimens displayed also remarkably thick blood-air barriers (BABs), most of which were occupied by EC layer components. Structural changes were accompanied by increased pulmonary artery medial thickness and right ventricular hypertrophy (RVH). Moreover, abnormalities in ECs persisted even after exposure to 7days of normal air replacement conditions. Results were confirmed by morphometric quantification. Our results suggest that the abnormal morphology of capillary ECs and thick BABs correlates with pulmonary artery remodeling and RVH. These ultrastructural changes might represent possible mechanisms of secondary pulmonary hypertension in BPD.

Evidence of Pulmonary Vascular Reverse Remodeling After Pulmonary Artery Banding Performed in Early Infancy in Patients With Congenital Heart Defects.

Histomorphometric evidence of the effect of pulmonary artery banding (PAB) in infancy on pulmonary vascular reverse remodeling has not been fully described.Methods and Results:We retrospectively reviewed 34 patients who underwent serial lung biopsies before and after PAB.Index of pulmonary vascular disease (IPVD) as a measure of the degree of progression of pulmonary arteriopathy significantly decreased after PAB (1.22±0.25 at 1st and 1.13±0.21 at 2nd biopsy, P=0.04). Additionally,DR=100 µmas an indicator of medial thickness of pulmonary arteries significantly decreased after PAB (15.6±3.7 at 1st and 11.4±2.6 at 2nd biopsy, P<0.0001). Patients were divided into 3 groups by age at PAB: <3 months (Group 1), between 3 and 6 months (Group 2), and >6 months (Group 3). The average secondDR=100 µmof groups 1 and 2 was significantly lower than that of group 3 (11.1±2.2 and 9.8±2.0 vs. 14.9±2.8, respectively; P<0.0001). Additionally, the second IPVD was also significantly lower in groups 1 and 2 than in group 3 (1.1±0.2 and 1.1±0.2 vs. 1.3±0.4, respectively; P=0.02). Histomorphometric evidence of post-PAB pulmonary vascular reverse remodeling is robust. The magnitude of vascular reversibility is pronounced when PAB is performed before 6 months of age.

Exendin-4 improves cardiovascular function and survival in flow-induced pulmonary hypertension

ObjectivesSystemic left-to-right shunting causes pulmonary arteriopathy, leading to progressive cardiopulmonary failure and a poor prognosis. In this study, we examined the extraglycemic effect of a synthetic glucagon-like peptide, exendin-4, on pulmonary arteriopathy regression and cardiopulmonary function in nondiabetic rats. MethodsPulmonary hypertension (PH) was induced by monocrotaline (60 mg/kg, subcutaneous) injection followed by the creation of an aortocaval fistula. After 4 weeks, exendin-4 (1 μg/kg/day) was administered intraperitoneally for 3 consecutive weeks, followed by an assessment of cardiopulmonary function, pulmonary artery vasoreactivity, tissue and blood biochemistry, and lung histology. ResultsExendin-4 significantly reduced right ventricle mass and pulmonary artery pressure, which improved right ventricle function and the survival rate in rats with PH. Tissue and blood interleukin-1β levels decreased, whereas pulmonary artery cyclic adenosine monophosphate levels were restored by exendin-4. Smooth muscle-myosin heavy chain-II and α-smooth muscle actin protein levels increased in the pulmonary arteries of exendin-4-treated rats. Histology showed that exendin-4 decreased the main and intra-acinar pulmonary artery medial thickness. ConclusionsExendin-4 treatment improved pulmonary artery function in flow-induced PH via its direct vasoactive properties, anti-inflammatory effects, and vascular smooth muscle cell phenotypic modulation. Mitigation of pulmonary arteriopathy further potentiated right ventricle performance and reduced overall mortality. These responses were associated with suppressed expression and activity of interleukin-1β and its downstream signaling molecules. Glucagon-like peptide analogs may possess pleiotropic therapeutic potential in flow-induced PH.

Reversal of experimental severe pulmonary hypertension by NGF inhibition

Introduction NGF expression is significantly increased in a new rat model of severe pulmonary hypertension (SPH) combining injection of monocrotaline (MCT) and chronic hypoxia (CH). Administration of anti-NGF blocking antibodies in vivo in this SPH model prevented, at least partially, increase in pulmonary arterial pressure (PAP), pulmonary arterial inflammation, remodelling, and hyperreactivity. In the present work, we studied whether anti-NGF blocking antibodies also displayed curative effects in this SPH model. Methods SPH was induced in rats by a single injection of MCT [day (D)1, 60 mg/kg] followed by chronic hypoxia (CH, 0.5 atm, D3 to D28). Anti-NGF blocking antibodies (10 μg/kg IP) were administered curatively at D15-19-22-26. Mean pulmonary arterial pressure (mPAP) and Fulton index (index of cardiac remodelling) were assessed at D28. Secretion of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) from rat pulmonary arteries were evaluated by Elisa. Pulmonary arterial reactivity to phenylephrine (PHE) or prostaglandin F2α (PGF2α) was evaluated ex vivo. Pulmonary arterial remodelling was assessed by measuring medial thickness and luminal occlusion (eosin-hematoxylin or van Gieson stainings). Results In the SPH model, mPAP and Fulton index were significantly increased compared to controls. Increased secretions of IL-1β and TNF-α were observed, as well as pulmonary arterial remodelling and hyperreactivity to both PHE and PGF2α. The curative treatment with anti-NGF blocking antibodies totally reversed TNF-α increased secretion, pulmonary arterial medial thickness, luminal occlusion and hyperreactivity to PHE. This curative protocol also partially reduced increased mPAP, IL-1β increased secretion, hyperreactivity to PGF2α and cardiac remodelling. Conclusions We show that inhibition of NGF in vivo in a new rat model of severe PH partially reversed increased mPAP and cardiac remodelling. Moreover, our results show that NGF plays a role in various pathophysiological aspects of severe PH, and may therefore be of therapeutical interest in this disease.

Pulmonary vasoreactivity in spontaneously hypertensive rats - Effects of endothelin-1 and leptin

BackgroundSystemic hypertension may be associated with an increased pulmonary vascular resistance, which we hypothesized could be, at least in part, mediated by increased leptin.MethodsVascular reactivity to phenylephrine (1 μmol/L), endothelin-1 (10 nmol/L) and leptin (0.001–100 nmol/L) was evaluated in endothelium-intact and -denuded isolated thoracic aorta and pulmonary arteries from spontaneously hypertensive versus control Wistar rats. Arteries were sampled for pathobiological evaluation and lung tissue for morphometric evaluation.ResultsIn control rats, endothelin-1 induced a higher level of contraction in the pulmonary artery than in the aorta. After phenylephrine or endothelin-1 precontraction, leptin relaxed intact pulmonary artery and aortic rings, while no response was observed in denuded arteries. Spontaneously hypertensive rats presented with increased reactivity to phenylephrine and endothelin-1 in endothelium-intact pulmonary arteries. After endothelin-1 precontraction, endothelium-dependent relaxation to leptin was impaired in pulmonary arteries from hypertensive rats. In both strains of rats, aortic segments were more responsive to leptin than pulmonary artery. In hypertensive rats, pulmonary arteries exhibited increased pulmonary artery medial thickness, associated with increased expressions of preproendothelin-1, endothelin-1 receptors type A and B, inducible nitric oxide synthase and decreased endothelial nitric oxide synthase, together with decreased leptin receptor and increased suppressor of cytokine signaling 3 expressions.ConclusionsAltered pulmonary vascular reactivity in hypertension may be related to a loss of endothelial buffering of vasoconstriction and decreased leptin-induced vasodilation in conditions of increased endothelin-1.

Increased Pericyte Coverage Mediated by Endothelial-Derived Fibroblast Growth Factor-2 and Interleukin-6 Is a Source of Smooth Muscle–Like Cells in Pulmonary Hypertension

Pericytes and their crosstalk with endothelial cells are critical for the development of a functional microvasculature and vascular remodeling. It is also known that pulmonary endothelial dysfunction is intertwined with the initiation and progression of pulmonary arterial hypertension (PAH). We hypothesized that pulmonary endothelial dysfunction, characterized by abnormal fibroblast growth factor-2 and interleukin-6 signaling, leads to abnormal microvascular pericyte coverage causing pulmonary arterial medial thickening. In human lung tissues, numbers of pericytes are substantially increased (up to 2-fold) in distal PAH pulmonary arteries compared with controls. Interestingly, human pulmonary pericytes exhibit, in vitro, an accentuated proliferative and migratory response to conditioned media from human idiopathic PAH endothelial cells compared with conditioned media from control cells. Importantly, by using an anti-fibroblast growth factor-2 neutralizing antibody, we attenuated these proliferative and migratory responses, whereas by using an anti-interleukin-6 neutralizing antibody, we decreased the migratory response without affecting the proliferative response. Furthermore, in our murine retinal angiogenesis model, both fibroblast growth factor-2 and interleukin-6 administration increased pericyte coverage. Finally, using idiopathic PAH human and NG2DsRedBAC mouse lung tissues, we demonstrated that this increased pericyte coverage contributes to pulmonary vascular remodeling as a source of smooth muscle-like cells. Furthermore, we found that transforming growth factor-β, in contrast to fibroblast growth factor-2 and interleukin-6, promotes human pulmonary pericyte differentiation into contractile smooth muscle-like cells. To the best of our knowledge, this is the first report of excessive pericyte coverage in distal pulmonary arteries in human PAH. We also show that this phenomenon is directly linked with pulmonary endothelial dysfunction.

Platelet-derived growth factor (PDGF) induces pulmonary vascular remodeling through 15-LO/15-HETE pathway under hypoxic condition

15-lipoxygenase (15-LO) is known to play an important role in chronic pulmonary hypertension. Accumulating evidence for its down-stream participants in the vasoconstriction and remodeling processes of pulmonary arteries, while how hypoxia regulates 15-LO/15-hydroxyeicosatetraenoic acid (15-HETE) to mediate hypoxic pulmonary hypertension is still unknown. Platelet-derived growth factor (PDGF) is an important vascular regulator whose concentration increases under hypoxic condition in the lungs of both humans and mice with pulmonary hypertension. The present study was carried out to determine whether hypoxia advances the pulmonary vascular remodeling through the PDGF/15-LO/15-HETE pathway. We found that pulmonary arterial medial thickening caused by hypoxia was alleviated after a treatment of the hypoxic rats with imatinib, which was associated with down-regulations of 15-LO-2 expression and 15-HETE production. Moreover, the increases in cell proliferation and endogenous 15-HETE content by hypoxia were attenuated by the inhibitors of PDGF-β receptor in pulmonary artery smooth muscle cells (PASMCs). The effects of PDGF-BB on cell proliferation and survival were weakened after the administration of 15-LO inhibitors or 15-LO RNA interference. These results suggest that hypoxia promotes PASMCs proliferation and survival, contributing to pulmonary vascular medial hypertrophy, which is likely to be mediated via the PDGF-BB/15-LO-2/15-HETE pathway.

Beneficial effects of γ-aminobutyric acid on right ventricular pressure and pulmonary vascular remodeling in experimental pulmonary hypertension

AimsIt has been reported that activation of the sympathetic nervous system and increase in plasma norepinephrine (NE) levels are observed in patients with pulmonary hypertension (PH). γ-Aminobutyric acid (GABA) is one of the major inhibitory neurotransmitters in the central nervous system and suppresses peripheral sympathetic neurotransmission. This study investigated whether chronic treatment with GABA prevents the development of monocrotaline (MCT)-induced PH. To elucidate the relationship between the development of PH and sympathetic nerve activity, hemodynamic parameters, cardiac functions, and plasma NE concentrations as well as cardiac endothelin-1 (ET-1) contents of MCT-induced PH rats were evaluated with or without GABA treatment. Main methodsRats were injected with MCT (60mg/kg) or saline subcutaneously and these rats were randomly divided into GABA (500mg/kg/day for 4weeks)- or vehicle-treated groups, respectively. Key findingMCT-treated rats had higher right ventricular systolic pressures, right ventricle-to-left ventricle plus septum weight ratios, pulmonary arterial medial thickening, and plasma NE levels than those of saline-injected rats. MCT-induced alternations were significantly attenuated by treatment with GABA. In MCT-induced PH rats with or without GABA treatment, plasma NE levels were positively correlated with right ventricular systolic pressure. Right ventricular endothelin-1 (ET-1) contents were increased by MCT injection, but these increments were not affected by treatment with GABA. SignificanceThese results suggest that plasma NE levels play an important role in the development of MCT-induced PH in rats and that GABA exerts a preventive effect against MCT-induced PH by suppressing the sympathetic nervous system but not the cardiac ET-1 system.