The Effect of ACE Inhibition on the Pulmonary Vasculature in Combined Models of Chronic Hypoxia and Pulmonary Arterial Banding in Sprague Dawley Rats

Microfocal CT was used to image the pulmonary arterial (PA) tree in rodent models of pulmonary hypertension (PH). CT images were used to measure the arterial tree diameter along the main arterial trunk at several hydrostatic intravascular pressures and calculate distensibility. High-resolution planar angiographic imaging was also used to examine distal PA microstructure. Data on pulmonary artery tree morphology improves our understanding of vascular remodeling and response to treatments. Angiotensin II (ATII) has been identified as a mediator of vasoconstriction and proliferative mitotic function. ATII has been shown to promote vascular smooth muscle cell hypertrophy and hyperplasia as well as stimulate synthesis of extracellular matrix proteins. Available ATII is targeted through angiotensin converting enzyme inhibitors (ACEIs), a method that has been used in animal models of PH to attenuate vascular remodeling and decrease pulmonary vascular resistance. In this study, we used rat models of chronic hypoxia to induce PH combined with partial left pulmonary artery occlusion (arterial banding, PLPAO) to evaluate effects of the ACEI, captopril, on pulmonary vascular hemodynamic and morphology. Male Sprague Dawley rats were placed in hypoxia (FiO2 0.1), with one group having underwent PLPAO three days prior to the chronic hypoxia. After the twenty-first day of hypoxia exposure, treatment was started with captopril (20 mg/kg/day) for an additional twenty-one days. At the endpoint, lungs were excised and isolated to examine: pulmonary vascular resistance, ACE activity, pulmonary vessel morphology and biomechanics. Hematocrit and RV/LV+septum ratio was also measured. CT planar images showed less vessel dropout in rats treated with captopril versus the non-treatment lungs. Distensibility data shows no change in rats treated with captopril in both chronic hypoxia (CH) and CH with PLPAO (CH+PLPAO) models. Hemodynamic measurements also show no change in the pulmonary vascular resistance with captopril treatment in both CH and CH+PLPAO

Dynamical Measurements of Black Hole Masses in Four Brightest Cluster Galaxies at 100 Mpc

We present stellar kinematics and orbit superposition models for the central regions of four Brightest Cluster Galaxies (BCGs), based upon integral-field spectroscopy at Gemini, Keck, and McDonald Observatories. Our integral-field data span radii from < 100 pc to tens of kpc. We report black hole masses, M_BH, of 2.1 +/- 1.6 x 10^10 M_Sun for NGC 4889, 9.7 + 3.0 - 2.6 x 10^9 M_Sun for NGC 3842, and 1.3 + 0.5 - 0.4 x 10^9 M_Sun for NGC 7768. For NGC 2832 we report an upper limit of M_BH < 9 x 10^9 M_Sun. Stellar orbits near the center of each galaxy are tangentially biased, on comparable spatial scales to the galaxies' photometric cores. We find possible photometric and kinematic evidence for an eccentric torus of stars in NGC 4889, with a radius of nearly 1 kpc. We compare our measurements of M_BH to the predicted black hole masses from various fits to the relations between M_BH and stellar velocity dispersion, luminosity, or stellar mass. The black holes in NGC 4889 and NGC 3842 are significantly more massive than all dispersion-based predictions and most luminosity-based predictions. The black hole in NGC 7768 is consistent with a broader range of predictions.Comment: 24 pages, 18 figures. Accepted for publication in Ap

Arterial Morphology Responds Differently to Captopril then N-Acetylcysteine in a Monocrotaline Rat Model of Pulmonary Hypertension

Pulmonary hypertension (PH) is an incurable condition inevitably resulting in death because of increased right heart workload and eventual failure. PH causes pulmonary vascular remodeling, including muscularization of the arteries, and a reduction in the typically large vascular compliance of the pulmonary circulation. We used a rat model of monocrotaline (MCT) induced PH to evaluated and compared Captopril (an angiotensin converting enzyme inhibitor with antioxidant capacity) and N-acetylcysteine (NAC, a mucolytic with a large antioxidant capacity) as possible treatments. Twenty-eight days aftcr MCT injection, the rats were sacrificed and heart, blood, and lungs were studied to measure indices such as right ventricular hypertrophy (RVH), hematocrit, pulmonary vascular resistance (PVR). vessel morphology and biomechanics. We implemented microfocal X-ray computed tomography to image the pulmonary arterial tree at intravascular pressures of 30, 21,12, and 6 mmHg and then used automated vessel detection and measurement algorithms to perform morphological analysis and estimate the distensibility of the arterial tree. The vessel detection and measurement algorithms quickly and effectively mapped and measured the vascular trees at each intravascular pressure. Monocrotaline treatment, and the ensuing PH, resulted in a significantly decreased arterial distensibility, increased PVR, and tended to decrease the length of the main pulmonary trunk. In rats with PH induced by monocrotaline, Captopril treatment significantly increased arterial distensibility and decrease PVR. NAC treatment did not result in an improvement, it did not significantly increase distensibility and resulted in further increase in PVR. Interestingly, NAC tended to increase peripheral vascular density. The results suggest that arterial distensibility may be more important than distal collateral pathways in maintaining PVR at normally low values

Abstract 17098: Cardiac overexpression of GTP cyclohydrolase 1 attenuates cardiac remodeling after myocardial infarction by a neuronal nitric oxide synthase-mediated mechanism

Introduction: Cardiac remodeling after myocardial infarction is associated with dysregulation of nitric oxide synthase and sarcoplasmic reticulum Ca2+ handling proteins. Emerging evidence suggests that GTP cyclohydrolase 1 (GCH1) regulates the function and expression of nitric oxide synthase and sarcoplasmic reticulum Ca2+ handling proteins. Hypothesis: We hypothesized that cardiac overexpression of GCH1 will benefit postinfarct cardiac remodeling. Methods: Myocardial infarction was produced in transgenic mice with cardiomyocyte-specific overexpression of human GCH1 and in control C57BL/6 mice by ligating the left coronary artery. Sham control mice underwent the same procedures except coronary artery ligation. The left ventricular geometry and function were measured with echocardiography, in Masson’s trichrome-stained heart sections, or in isolated Langendorff-perfused hearts. The expression of GCH1, dimeric and monomeric nitric oxide synthases, sarcoplasmic reticulum Ca2+ handling proteins were determined by Western blot analyses. Results: Compared with sham-operated mice, C57BL/6 mice undergoing coronary artery ligation showed significant decreases in cardiac GCH1 proteins (GCH1/GAPDH: 0.14±0.04 in infarction vs 0.50±0.08 in sham, n=6 mice/group, P\u3c0.05), anterior wall thickness at end-diastole (0.67±0.04 mm vs. 0.92±0.07 mm, n=8-12 mice/group, P\u3c0.05) and at end-systole, fractional shortening, +dP/dt, and the ratios of dimers/monomers of neuronal nitric oxide synthase, ryanodine receptors/GAPDH, and sarcoplasmic reticulum Ca2+ ATPase/GAPDH; and significant increases in infarct size, left ventricular internal diameters, and interstitial fibrosis 4 weeks after surgery. These adverse changes in the left ventricle were significantly attenuated in GCH1 overexpressing mice. Treatment of GCH1 overexpressing mice with 7-nitroindazole (an inhibitor for neuronal nitric oxide synthase) for 4 weeks blocked the beneficial effects of GCH1 overexpression on the heart after myocardial infarction. Conclusions: Cardiac overexpression of GCH1 ameliorates postinfarct cardiac remodeling by elevating the dimerization of neuronal nitric oxide synthase and expression of sarcoplasmic reticulum Ca2+ handling proteins

Transgenic overexpression of GTP cyclohydrolase 1 in cardiomyocytes ameliorates post-infarction cardiac remodeling

GTP cyclohydrolase 1 (GCH1) and its product tetrahydrobiopterin play crucial roles in cardiovascular health and disease, yet the exact regulation and role of GCH1 in adverse cardiac remodeling after myocardial infarction are still enigmatic. Here we report that cardiac GCH1 is degraded in remodeled hearts after myocardial infarction, concomitant with increases in the thickness of interventricular septum, interstitial fibrosis, and phosphorylated p38 mitogen-activated protein kinase and decreases in left ventricular anterior wall thickness, cardiac contractility, tetrahydrobiopterin, the dimers of nitric oxide synthase, sarcoplasmic reticulum Ca(2+) release, and the expression of sarcoplasmic reticulum Ca(2+) handling proteins. Intriguingly, transgenic overexpression of GCH1 in cardiomyocytes reduces the thickness of interventricular septum and interstitial fibrosis and increases anterior wall thickness and cardiac contractility after infarction. Moreover, we show that GCH1 overexpression decreases phosphorylated p38 mitogen-activated protein kinase and elevates tetrahydrobiopterin levels, the dimerization and phosphorylation of neuronal nitric oxide synthase, sarcoplasmic reticulum Ca(2+) release, and sarcoplasmic reticulum Ca(2+) handling proteins in post-infarction remodeled hearts. Our results indicate that the pivotal role of GCH1 overexpression in post-infarction cardiac remodeling is attributable to preservation of neuronal nitric oxide synthase and sarcoplasmic reticulum Ca(2+) handling proteins, and identify a new therapeutic target for cardiac remodeling after infarction

Cardiomyocyte GTP Cyclohydrolase 1 Protects the Heart Against Diabetic Cardiomyopathy.

Diabetic cardiomyopathy increases the risk of heart failure and death. At present, there are no effective approaches to preventing its development in the clinic. Here we report that reduction of cardiac GTP cyclohydrolase 1 (GCH1) degradation by genetic and pharmacological approaches protects the heart against diabetic cardiomyopathy. Diabetic cardiomyopathy was induced in C57BL/6 wild-type mice and transgenic mice with cardiomyocyte-specific overexpression of GCH1 with streptozotocin, and control animals were given citrate buffer. We found that diabetes-induced degradation of cardiac GCH1 proteins contributed to adverse cardiac remodeling and dysfunction in C57BL/6 mice, concomitant with decreases in tetrahydrobiopterin, dimeric and phosphorylated neuronal nitric oxide synthase, sarcoplasmic reticulum Ca(2+) handling proteins, intracellular [Ca(2+)]i, and sarcoplasmic reticulum Ca(2+) content and increases in phosphorylated p-38 mitogen-activated protein kinase and superoxide production. Interestingly, GCH-1 overexpression abrogated these detrimental effects of diabetes. Furthermore, we found that MG 132, an inhibitor for 26S proteasome, preserved cardiac GCH1 proteins and ameliorated cardiac remodeling and dysfunction during diabetes. This study deepens our understanding of impaired cardiac function in diabetes, identifies GCH1 as a modulator of cardiac remodeling and function, and reveals a new therapeutic target for diabetic cardiomyopathy

Genetic evidence for NAD(P)H:quinone oxidoreductase 1-catalyzed quinone reduction on passage through the mouse pulmonary circulation

The quinones duroquinone (DQ) and coenzyme Q1 (CoQ1) and quinone reductase inhibitors have been used to identify reductases involved in quinone reduction on passage through the pulmonary circulation. In perfused rat lung, NAD(P)H:quinone oxidoreductase 1 (NQO1) was identified as the predominant DQ reductase and NQO1 and mitochondrial complex I as the CoQ1 reductases. Since inhibitors have nonspecific effects, the goal was to use Nqo1-null (NQO1−/−) mice to evaluate DQ as an NQO1 probe in the lung. Lung homogenate cytosol NQO1 activities were 97 ± 11, 54 ± 6, and 5 ± 1 (SE) nmol dichlorophenolindophenol reduced·min−1·mg protein−1 for NQO1+/+, NQO1+/−, and NQO1−/− lungs, respectively. Intact lung quinone reduction was evaluated by infusion of DQ (50 μM) or CoQ1 (60 μM) into the pulmonary arterial inflow of the isolated perfused lung and measurement of pulmonary venous effluent hydroquinone (DQH2 or CoQ1H2). DQH2 efflux rates for NQO1+/+, NQO1+/−, and NQO1−/− lungs were 0.65 ± 0.08, 0.45 ± 0.04, and 0.13 ± 0.05 (SE) μmol·min−1·g dry lung−1, respectively. DQ reduction in NQO1+/+ lungs was inhibited by 90 ± 4% with dicumarol; there was no inhibition in NQO1−/− lungs. There was no significant difference in CoQ1H2 efflux rates for NQO1+/+ and NQO1−/− lungs. Differences in DQ reduction were not due to differences in lung dry weights, wet-to-dry weight ratios, perfusion pressures, perfused surface areas, or total DQ recoveries. The data provide genetic evidence implicating DQ as a specific NQO1 probe in the perfused rodent lung