Eosinophils are necessary for pulmonary arterial remodeling in a mouse model of eosinophilic inflammation-induced pulmonary hypertension.

There is increasing evidence that inflammation plays a pivotal role in the pathogenesis of some forms of pulmonary hypertension (PH). We recently demonstrated that deficiency of adiponectin (APN) in a mouse model of PH induced by eosinophilic inflammation increases pulmonary arterial remodeling, pulmonary pressures, and the accumulation of eosinophils in the lung. Based on these data, we hypothesized that APN deficiency exacerbates PH indirectly by increasing eosinophil recruitment. Herein, we examined the role of eosinophils in the development of inflammation-induced PH. Elimination of eosinophils in APN-deficient mice by treatment with anti-interleukin-5 antibody attenuated pulmonary arterial muscularization and PH. In addition, we observed that transgenic mice that are devoid of eosinophils also do not develop pulmonary arterial muscularization in eosinophilic inflammation-induced PH. To investigate the mechanism by which APN deficiency increased eosinophil accumulation in response to an allergic inflammatory stimulus, we measured expression levels of the eosinophil-specific chemokines in alveolar macrophages isolated from the lungs of mice with eosinophilic inflammation-induced PH. In these experiments, the levels of CCL11 and CCL24 were higher in macrophages isolated from APN-deficient mice than in macrophages from wild-type mice. Finally, we demonstrate that the extracts of eosinophil granules promoted the proliferation of pulmonary arterial smooth muscle cells in vitro. These data suggest that APN deficiency may exacerbate PH, in part, by increasing eosinophil recruitment into the lung and that eosinophils could play an important role in the pathogenesis of inflammation-induced PH. These results may have implications for the pathogenesis and treatment of PH caused by vascular inflammation.

Phosphodiesterase 3A expression is modulated by nitric oxide in rat pulmonary artery smooth muscle cells.

Phosphodiesterases (PDEs) limit vasodilation in response to a variety of signaling cascades by metabolizing the cyclic nucleotides cAMP and cGMP. The objective of this study was to test the hypothesis that NO regulates expression of PDE3A, a cGMP-inhibited PDE. Incubation of rat pulmonary artery smooth muscle cells (rPaSMCs) with the NO-donor compound S-nitroso-glutathione (GSNO) increased PDE3A gene expression in a dose- and time-dependent manner. NO-donors increased PDE3A protein levels. Total and milrinone inhibitable cAMP PDE activity were increased 2.8 ± 0.1- and 2.0 ± 0.1-fold respectively in extracts of rPaSMCs exposed to GSNO. The effects of GSNO on PDE3A gene expression were mimicked by the soluble guanylate cyclase (sGC) activators YC-1 and BAY 41-2272 and blocked by the sGC inhibitor ODQ. Incubation of rPaSMC with interleukin-1ß and tumor necrosis factor-α induced PDE3A gene expression, an effect which was inhibited by L-NIL, an antagonist of NO synthase 2, or ODQ. Actinomycin D, an inhibitor of RNA polymerase, blocked the GSNO-induced increase of PDE3A mRNA levels, whereas cycloheximide, an inhibitor of protein translation, did not. These observations suggest that NO modulates PDE3A gene expression via mechanisms dependent upon cGMP synthesis and gene transcription. Prolonged exposure to NO may alter the sensitivity of vascular smooth muscle to cGMP- or cAMP-dependent vasodilators, as well as PDE isoform-selective inhibitors.

Stromal inactivation of BMPRII leads to colorectal epithelial overgrowth and polyp formation.

Stromal-epithelial interactions play a central role in development and tumorigenesis. Bone morphogenetic protein (BMP) signaling in the intestine is involved in both of these processes. Inactivation of BMP pathway genes in the epithelium is known to cause intestinal polyposis. However, the role of the intestinal stroma in polyp initiation is incompletely understood. We observed that conditional inactivation of the BMP type II receptor (BMPRII) in the stroma leads to epithelial hyperplasia throughout the colon with increased epithelial cell proliferation. Mutant mice developed rectal bleeding and hamartomatous polyps in the colorectum. The polyps demonstrated increased proliferation of epithelial and mesenchymal cells in the mucosa with an expansion of the myofibroblast cell population. These results demonstrate that genetic mutations altering the BMP signaling pathway in the stromal microenvironment can lead to epithelial tumors in the colon.

Endothelial nitric oxide synthase limits left ventricular remodeling after myocardial infarction in mice.

Background- To investigate the role of endothelial nitric oxide synthase (NOS3) in left ventricular (LV) remodeling after myocardial infarction (MI), the impact of left anterior descending coronary artery ligation on LV size and function was compared in 2- to 4-month-old wild-type (WT) and NOS3-deficient mice (NOS3(-/-)). Methods and Results- Two days after MI, both strains of mice had a similar LV size, fractional shortening, and ejection fraction by echocardiography. Twenty-eight days after MI, both strains had dilated LVs with decreased fractional shortening and lower ejection fractions. Although the infarcted fraction of the LV was similar in both strains, LV end-diastolic internal diameter, end-diastolic volume, and mass were greater, but fractional shortening, ejection fraction, and the maximum rate of developed LV pressure (dP/dt(max)) were lower in NOS3(-/-) than in WT mice. Impairment of diastolic function, as measured by the time constant of isovolumic relaxation (tau) and the maximum rate of LV pressure decay (dP/dt(min)), was more marked in NOS3(-/-) than in WT mice. Mortality after MI was greater in NOS3(-/-) than in WT mice. Long-term administration of hydralazine normalized blood pressure in NOS3(-/-) mice, but it did not prevent the LV dilatation, impaired systolic and diastolic function, and increased LV mass that followed MI. In WT mice, capillary density and myocyte width in the nonischemic portion of the LV did not differ before and 28 days after MI, whereas in NOS3(-/-) mice, capillary density decreased and myocyte width increased after MI, whether or not hydralazine was administered. Conclusions- These results suggest that the presence of NOS3 limits LV dysfunction and remodeling in a murine model of MI by an afterload-independent mechanism, in part by decreasing myocyte hypertrophy in the remote myocardium.

Cessation of platelet-mediated cyclic canine coronary occlusion after thrombolysis by combining nitric oxide inhalation with phosphodiesterase-5 inhibition.

OBJECTIVES: We sought to evaluate the ability of type 5 phosphodiesterase (PDE5) inhibitors to augment the antithrombotic effects of inhaled nitric oxide (NO) in a canine model of platelet-mediated coronary thrombosis after thrombolysis. BACKGROUND: Type 5 phosphodiesterase inhibitors potentiate the ability of NO to inhibit platelet aggregation in vitro by preventing platelet cyclic guanosine monophosphate catabolism. We previously reported that breathing low concentrations of NO gas attenuated, but did not prevent, cyclic flow reductions (CFRs) in a canine model of coronary thrombosis after thrombolysis. METHODS: Cyclic flow reductions were induced after creation of a left anterior descending coronary artery stenosis, endothelial injury, thrombus formation and thrombolysis. Dogs were either untreated or treated with inhaled NO (20 ppm by volume), intravenous zaprinast, intravenous dipyridamole or the combination of inhaled NO with either PDE5 inhibitor (n = 4 per group). RESULTS: Cyclic flow reductions ceased, and complete coronary patency was achieved in all dogs after they breathed NO combined with zaprinast (by 12.0+/-4.7 min [mean +/- SEM]) or dipyridamole (by 9.8+/-4.7 min). The frequency of CFRs was unaffected by NO, dipyridamole or zaprinast alone. Systemic arterial blood pressure and bleeding time were unchanged with any treatment. Ex vivo thrombin-induced platelet aggregation in dogs breathing NO and receiving dipyridamole was reduced by 75+/-7% (p < 0.05). CONCLUSIONS: The PDE5 inhibitors potentiated the antithrombotic properties of inhaled NO in a canine model of platelet-mediated coronary artery thrombosis after thrombolysis, without prolonging the bleeding time or causing systemic hypotension.

Nebulized sildenafil is a selective pulmonary vasodilator in lambs with acute pulmonary hypertension.

OBJECTIVE: To determine whether inhalation of aerosolized sildenafil with and without inhaled nitric oxide (NO) causes selective pulmonary vasodilation in a sheep model of pulmonary hypertension. DESIGN: A controlled laboratory study in instrumented, awake, spontaneously breathing lambs. SETTING: Animal research laboratory affiliated with a university hospital. SUBJECT: Twenty Suffolk lambs. INTERVENTIONS: Lambs were instrumented with a carotid artery catheter, a pulmonary artery catheter, and a tracheostomy tube and studied awake. After baseline measurements, pulmonary hypertension was induced by the continuous infusion of U46619, a thromboxane A2 analog. After breathing three concentrations of inhaled NO (2, 5, and 20 ppm), lambs were divided into two groups. Group 1 (n = 7) breathed aerosols containing 1, 10, and 30 mg of sildenafil alone, and group 2 (n = 4) simultaneously breathed NO (2 and 5 ppm) and aerosols containing 10 mg of sildenafil. Hemodynamic measurements were obtained before and at the end of each drug administration. Venous admixture was calculated, and plasma cyclic guanosine monophosphate and sildenafil concentrations were measured. MEASUREMENTS AND MAIN RESULTS: Aerosols containing 10 mg and 30 mg of sildenafil selectively decreased the pulmonary artery pressure by 21% +/- 3% and 26% +/- 3%, respectively (p < .05 vs. baseline pulmonary hypertension). When 10 mg of sildenafil was inhaled while simultaneously breathing 2 ppm and 5 ppm NO, the pulmonary artery pressure decreased by 35% +/- 3% and 43% +/- 2% (p < .05 vs. baseline pulmonary hypertension). Inhaled sildenafil did not impair systemic oxygenation, increase right-to-left intrapulmonary shunting, or impair the ability of inhaled NO to reduce right-to-left shunting. CONCLUSIONS: Nebulized sildenafil is a selective pulmonary vasodilator that can potentiate the pulmonary vasodilating effects of inhaled NO.

Attenuation of hypoxic pulmonary vasoconstriction by endotoxemia requires 5-lipoxygenase in mice.

Sepsis and endotoxemia impair hypoxic pulmonary vasoconstriction (HPV), thereby reducing systemic oxygenation. To assess the role of leukotrienes (LTs) in the attenuation of HPV during endotoxemia, the increase in left lung pulmonary vascular resistance (LPVR) before and during left mainstem bronchus occlusion (LMBO) was measured in mice with and without a deletion of the gene encoding 5-lipoxygenase (5-LO). LMBO increased the LPVR equally in saline-challenged wild-type and 5-LO-deficient mice (96+/-20% and 94+/-19%, respectively). Twenty-two hours after challenge with Escherichia coli endotoxin, the ability of LMBO to increase LPVR was markedly impaired in wild-type mice (27+/-7%; P<0.05) but not in 5-LO-deficient mice (72+/-9%) or in wild-type mice pretreated with MK886, an inhibitor of 5-LO activity (76+/-10%). Compared with wild-type mice, endotoxin-induced disruption of lung structures and inflammatory cell influx in the lung were markedly attenuated in 5-LO-deficient mice. Administration of MK571, a selective cysteinyl LT(1) receptor antagonist, 1 hour before endotoxin challenge preserved HPV and attenuated pulmonary injury in wild-type mice but did not prevent the endotoxin-induced increase in pulmonary myeloperoxidase activity. Taken together, these findings demonstrate that a 5-LO product, most likely a cysteinyl LT, contributes to the attenuation of HPV and to pulmonary injury after challenge with endotoxin.

Inhibition of lung phosphodiesterase improves responsiveness to inhaled nitric oxide in isolated-perfused lungs from rats challenged with endotoxin.

OBJECTIVES: To investigate the ability of phosphodiesterase (PDE) selective inhibitors to improve responsiveness to inhaled nitric oxide (NO) in isolated-perfused lungs of rats pretreated with endotoxin/lipopolysaccharide (LPS). DESIGN AND SETTING: Prospective, controlled animal study in the animal research facility of a university hospital. INTERVENTIONS: Sixteen hours after adult Sprague-Dawley rats were injected intraperitoneally with 0.4 mg/ kg E. coli 0111:B4 LPS administration, lungs were isolated and perfused, and the thromboxane mimetic U46619 was employed to increase the mean pulmonary artery pressure by 5-7 mmHg. The lungs were then ventilated with or without 0.4 ppm NO, and erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA; PDE type 2 inhibitor), milrinone (PDE type 3 inhibitor), or zaprinast (inhibitor of PDE types 5 and 9) were added to the perfusate. MEASUREMENTS AND RESULTS: In the presence of EHNA (12.5, 25, 50 microM) the vasodilator response to inhaled NO was not greater than in its absence (0.25 +/- 0.25, 0.5 +/- 0.25, 0.75 +/- 0.25 mmHg vs. 0.25 +/- 0.25, 0.5 +/- 0.25, 0.75 +/- 0.25 mmHg, respectively). In the presence of milrinone (125, 250, 500 nM), the vasodilator response to inhaled NO was also not improved. In contrast, zaprinast (3.7, 7.4, 14.8 microM) augmented the pulmonary vasodilatory effect of inhaled NO in lungs from LPS-pretreated rats from 0.25 +/- 0.25, 0.5 +/- 0.25, 0.75 +/- 0.25 mmHg to 0.75 +/- 0.25, 1.5 +/- 0.5, 1.75 +/- 0.75 mmHg, respectively (p < 0.05). CONCLUSIONS: Our results demonstrate that inhibition of pulmonary PDE enzyme activity with zaprinast increases vasodilator responsiveness to inhaled NO in lungs obtained from rats 16 h after LPS challenge.

Cytokines decrease sGC in pulmonary artery smooth muscle cells via NO-dependent and NO-independent mechanisms.

Exposure of rat pulmonary artery smooth muscle cells (rPASMC) to cytokines leads to nitric oxide (NO) production by NO synthase 2 (NOS2). NO stimulates cGMP synthesis by soluble guanylate cyclase (sGC), a heterodimer composed of alpha(1)- and beta(1)-subunits. Prolonged exposure of rPASMC to NO decreases sGC subunit mRNA and protein levels. The objective of this study was to determine whether levels of NO produced endogenously by NOS2 are sufficient to decrease sGC expression in rPASMC. Interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) increased NOS2 mRNA levels and decreased sGC subunit mRNA levels. Exposure of rPASMC to IL-1beta and TNF-alpha for 24 h decreased sGC subunit protein levels and NO-stimulated sGC enzyme activity. L-N(6)-(1-iminoethyl)lysine (NOS2 inhibitor) or 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (sGC inhibitor) partially prevented the cytokine-mediated decrease in sGC subunit mRNA levels. However, cytokines also decreased sGC subunit mRNA levels in PASMC derived from NOS2-deficient mice. These results demonstrate that levels of NO and cGMP produced in cytokine-exposed PASMC are sufficient to decrease sGC subunit mRNA levels. In addition, cytokines can decrease sGC subunit mRNA levels via NO-independent mechanisms.

Soluble guanylate cyclase alpha(1) and beta(1) gene transfer increases NO responsiveness and reduces neointima formation after balloon injury in rats via antiproliferative and antimigratory effects.

In vascular smooth muscle cells, NO stimulates the synthesis of cGMP by soluble guanylate cyclase (sGC), a heterodimer composed of alpha(1) and beta(1) subunits. NO/cGMP signal transduction affects multiple cell functions that contribute to neointima formation after vascular injury. Balloon-induced vascular injury was found to decrease sGC subunit expression and enzyme activity in rat carotid arteries. The effect of restoring sGC enzyme activity on neointima formation was investigated using recombinant adenoviruses specifying sGC alpha(1) and beta(1) subunits (Adalpha1 and Adbeta1). Coinfection of cultured rat aortic smooth muscle cells with Adalpha1 and Adbeta1 increased NO-stimulated intracellular cGMP levels 60-fold and decreased DNA synthesis and migration by 16% and 48%, respectively. Immunoreactivity for alpha(1) and beta(1) subunits colocalized in carotid arteries infected with Adalpha1 and Adbeta1. Molsidomine-stimulated carotid tissue cGMP levels were greater after coinfection with Adalpha1 and Adbeta1 than after infection with a control virus, AdRR5 (0.53+/-0.09 pmol/mg protein, mean+/-SEM, versus 0.23+/-0.09, P<0.05). Mean intima/media ratio, 2 weeks after balloon injury and twice-daily administration of 5 mg/kg molsidomine, was less in rats coinfected with Adalpha1 and Adss1 than in rats infected with AdRR5 or in uninfected rats (0.36+/-0.11 versus 0. 81+/-0.13 and 0.75+/-0.25, respectively, P<0.05). Thus, Adalpha1 and Adbeta1 gene transfer to balloon-injured rat carotid arteries increases NO responsiveness and attenuates neointima formation via a direct antiproliferative and antimigratory effect on vascular smooth muscle cells.

Digestion of DNA with restriction endonucleases.

Restriction endonucleases recognize short DNA sequences and cleave double-stranded DNA at specific sites within or adjacent to the recognition sequences. Restriction endonuclease cleavage of DNA into discrete fragments is one of the most basic procedures in molecular biology. This appendix describes restriction endonucleases and their properties.

Digestion of DNA with restriction endonucleases.

Restriction endonucleases recognize short DNA sequences and cleave double-stranded DNA at specific sites within or adjacent to the recognition sequences. Restriction endonuclease cleavage of DNA into discrete fragments is one of the most basic procedures in molecular biology. This appendix describes restriction endonucleases and their properties.

Digestion of DNA with restriction endonucleases.

Restriction endonucleases recognize short DNA sequences and cleave double-stranded DNA at specific sites within or adjacent to the recognition sequences. Restriction endonuclease cleavage of DNA into discrete fragments is one of the most basic procedures in molecular biology. The first method presented in this unit is the cleavage of a single DNA sample with a single restriction endonuclease. A number of common applications of this technique are also described. These include digesting a given DNA sample with more than one endonuclease, digesting multiple DNA samples with the same endonuclease, and partially digesting DNA such that cleavage only occurs at a subset of the restriction sites. A protocol for methylating specific DNA sequences and protecting them from restriction endonuclease cleavage is also presented. A collection of tables describing restriction endonucleases and their properties (including information about recognition sequences, types of termini produced, buffer conditions, and conditions for thermal inactivation) is given at the end of the unit.

Mapping by multiple endonuclease digestions.

In this unit, a protocol is provided in which the DNA of interest is cleaved with a variety of restriction endonucleases, either individually or in combination, and the resulting products are separated by agarose or acrylamide gel electrophoresis. By determining the sizes of DNA fragments produced by endonuclease cleavage, the restriction map is deduced progressively from simple situations where enzymes cleave the DNA once or twice to more complex situations where cleavage occurs more frequently.

Mapping by partial endonuclease digestions.

In the procedure described in this unit, a DNA fragment radiolabeled at one of its two ends is purified by gel electrophoresis and subjected to partial cleavage by a restriction endonuclease. Analysis of the resulting products by polyacrylamide (or agarose) gel electrophoresis enables one to define the distance of restriction sites from the labeled end.

Congenital deficiency of nitric oxide synthase 2 protects against endotoxin-induced myocardial dysfunction in mice.

BACKGROUND: Sepsis can be complicated by severe myocardial dysfunction and is associated with increased nitric oxide (NO) production by inducible NO synthase (NOS2). To investigate the role of NOS2 in endotoxin-induced myocardial dysfunction in vivo, we studied wild-type and NOS2-deficient mice. METHODS AND RESULTS: Serial echocardiographic parameters of myocardial function were measured before and at 4, 7, 16, and 24 hours after an endotoxin challenge. Seven hours after challenge with either endotoxin or saline, systemic and left ventricular pressures were measured, and the first derivative of left ventricular developed pressure (dP/dt), slope of the end-systolic pressure-dimension relationship (Slope(LVESPD)), and time constant of isovolumic relaxation (tau) were calculated. Endotoxin challenge in wild-type mice decreased left ventricular fractional shortening, velocity of circumferential shortening, dP/dt(max), Slope(LVESPD), and dP/dt(min) and increased time constant tau. Endotoxin-induced myocardial dysfunction was associated with increased ventricular NOS2 gene expression and cGMP concentrations. Seven hours after endotoxin challenge, NOS2-deficient mice had greater fractional shortening, dP/dt(max), and Slope(LVESPD) than did endotoxin-challenged wild-type mice. Measures of diastolic function, dP/dt(min) and time constant tau, were preserved in endotoxin-challenged NOS2-deficient mice. After endotoxin challenge in wild-type mice, early (3-hour) inhibition of NOS2 with L-N:(6)-(1-iminoethyl)lysine hydrochloride prevented, whereas later (7-hour) inhibition could not reverse, endotoxin-induced myocardial dysfunction. CONCLUSIONS: These results suggest that NOS2 is required for the development of systolic and diastolic dysfunction in murine sepsis.

Nitric oxide inhalation decreases pulmonary artery remodeling in the injured lungs of rat pups.

Vascular injury causes the muscularization of peripheral pulmonary arteries, which is more pronounced in the infant than in the adult lung. Although inhaled NO gas attenuates pulmonary artery remodeling in hypoxic rats, whether or not it protects the lung by mitigating vasoconstriction is unknown. This investigation tested whether inhaled NO decreases the muscularization of injured pulmonary arteries in rat pups by modulating vascular tone. One week after monocrotaline administration, the percentage of muscularized rat pup lung arteries was increased by >3-fold. Nevertheless, monocrotaline exposure did not cause right ventricular hypertrophy, pulmonary hypertension, or vasoconstriction. In addition, it did not increase the expression of markers of inflammation (interleukin-1beta, intercellular adhesion molecule-1, and E-selectin) or of platelet-mediated thrombosis (GPIbalpha). Continuous inhalation of 20 ppm NO gas prevented the neomuscularization of the pulmonary arteries in pups with lung injury. Moreover, a 3-fold increase in cell proliferation and 30% decrease in cell numbers in pulmonary arteries caused by monocrotaline exposure was prevented by NO inhalation. These data indicate that inhaled NO protects infants against pulmonary remodeling induced by lung injury by mechanisms that are independent of pulmonary tone, inflammation, or thrombosis.

Sp110 localizes to the PML-Sp100 nuclear body and may function as a nuclear hormone receptor transcriptional coactivator.

The nuclear body is a multiprotein complex that may have a role in the regulation of gene transcription. This structure is disrupted in a variety of human disorders including acute promyelocytic leukemia and viral infections, suggesting that alterations in the nuclear body may have an important role in the pathogenesis of these diseases. In this study, we identified a cDNA encoding a leukocyte-specific nuclear body component designated Sp110. The N-terminal portion of Sp110 was homologous to two previously characterized components of the nuclear body (Sp100 and Sp140). The C-terminal region of Sp110 was homologous to the transcription intermediary factor 1 (TIF1) family of proteins. High levels of Sp110 mRNA were detected in human peripheral blood leukocytes and spleen but not in other tissues. The levels of Sp110 mRNA and protein in the human promyelocytic leukemia cell line NB4 increased following treatment with all-trans retinoic acid (ATRA), and Sp110 localized to PML-Sp100 nuclear bodies in ATRA-treated NB4 cells. Because of the structural similarities between Sp110 and TIF1 proteins, the effect of Sp110 on gene transcription was examined. An Sp110 DNA-binding domain fusion protein activated transcription of a reporter gene in transfected mammalian cells. In addition, Sp110 produced a marked increase in ATRA-mediated expression of a reporter gene containing a retinoic acid response element. Taken together, the results of this study demonstrate that Sp110 is a member of the Sp100/Sp140 family of nuclear body components and that Sp110 may function as a nuclear hormone receptor transcriptional coactivator. The predominant expression of Sp110 in leukocytes and the enhanced expression of Sp110 in NB4 cells treated with ATRA raise the possibility that Sp110 has a role in inducing differentiation of myeloid cells.

Sildenafil is a pulmonary vasodilator in awake lambs with acute pulmonary hypertension.

BACKGROUND: Phosphodiesterase type 5 (PDE5) hydrolyzes cyclic guanosine monophosphate in the lung, thereby modulating nitric oxide (NO)/cyclic guanosine monophosphate-mediated pulmonary vasodilation. Inhibitors of PDE5 have been proposed for the treatment of pulmonary hypertension. In this study, we examined the pulmonary and systemic vasodilator properties of sildenafil, a novel selective PDE5 inhibitor, which has been approved for the treatment of erectile dysfunction. METHODS: In an awake lamb model of acute pulmonary hypertension induced by an intravenous infusion of the thromboxane analog U46619, we measured the effects of 12.5, 25, and 50 mg sildenafil administered via a nasogastric tube on pulmonary and systemic hemodynamics (n = 5). We also compared the effects of sildenafil (n = 7) and zaprinast (n = 5), a second PDE5 inhibitor, on the pulmonary vasodilator effects of 2.5, 10, and 40 parts per million inhaled NO. Finally, we examined the effect of infusing intravenous l-NAME (an inhibitor of endogenous NO production) on pulmonary vasodilation induced by 50 mg sildenafil (n = 6). RESULTS: Cumulative doses of sildenafil (12.5, 25, and 50 mg) decreased the pulmonary artery pressure 21%, 28%, and 42%, respectively, and the pulmonary vascular resistance 19%, 23%, and 45%, respectively. Systemic arterial pressure decreased 12% only after the maximum cumulative sildenafil dose. Neither sildenafil nor zaprinast augmented the ability of inhaled NO to dilate the pulmonary vasculature. Zaprinast, but not sildenafil, markedly prolonged the duration of pulmonary vasodilation after NO inhalation was discontinued. Infusion of l-NAME abolished sildenafil-induced pulmonary vasodilation. CONCLUSIONS: Sildenafil is a selective pulmonary vasodilator in an ovine model of acute pulmonary hypertension. Sildenafil induces pulmonary vasodilation via a NO-dependent mechanism. In contrast to zaprinast, sildenafil did not prolong the pulmonary vasodilator action of inhaled NO.

Aerosol gene transfer with inducible nitric oxide synthase reduces hypoxic pulmonary hypertension and pulmonary vascular remodeling in rats.

BACKGROUND: Nitric oxide (NO) is a potent vasodilator with an important role in the regulation of pulmonary vascular tone. The effects of NO synthase (NOS) gene transfer on pulmonary vascular remodeling associated with hypoxic pulmonary hypertension are unknown. METHODS AND RESULTS: We aerosolized 3 x 10(9) pfu of an adenoviral vector containing inducible NOS gene (AdNOS2), constitutive NOS3 gene (AdNOS3), or no transgene (AdRR5) into rat lungs. Exhaled NO levels, monitored with chemiluminescence, were higher in AdNOS2-infected rats than in AdNOS3- and AdRR5-infected rats (at 3 days, 33+/-6 ppb, n=9, versus 17+/-4, n=9, and 6+/-2 ppb, n=3, P:<0.05 for both). Exposure to FIO(2) 0.10 for 7 days increased pulmonary artery pressure from 19+/-4 mm Hg (baseline) to 27+/-1 and 26+/-2 mm Hg in AdNOS3- and AdRR5-infected rats, respectively, but only to 21+/-1 mm Hg in AdNOS2-infected animals (P:<0.05). After 7 days of hypoxia, total pulmonary resistance in AdRR5- and AdNOS3-infected rats was significantly higher than in AdNOS2-infected animals (0.41+/-0.05 and 0.39+/-0.07 versus 0.35+/-0. 03 mm Hg. mL(-)(1). min(-)(1), respectively, P:<0.05). Right ventricular hypertrophy was reduced in AdNOS2-infected rats [right ventricular/(left ventricular+septal) weight, 0.19+/-0.10 versus 0. 28+/-0.10 and 0.32+/-0.10 in AdRR5- and AdNOS3-infected rats, respectively, P:<0.05]. The percentage of muscularized precapillary pulmonary resistance vessels was also significantly decreased (18+/-4% versus 25+/-8% and 30+/-5% in AdRR5- and AdNOS3-infected rats, P:<0.05). CONCLUSIONS: Aerosol NOS2 gene transfer increases pulmonary NO production and significantly reduces hypoxic pulmonary hypertension and pulmonary vascular remodeling. Aerosol NOS2 gene transfer may be a promising strategy to target pulmonary vascular disorders.