Role of aldosterone on lung structural remodelling and right ventricular function in congestive heart failure.

BACKGROUND: The mechanisms of benefit of mineralocorticoid receptors antagonists in congestive heart failure (CHF) are still debated. We hypothesized that aldosterone contributes to pulmonary remodelling and right ventricular (RV) dysfunction associated with CHF by stimulation of lung myofibroblasts (MYFs) proliferation. METHODS: Rats with moderate to large myocardial infarcts (MI) and CHF were studied. Two weeks after MI, spironolactone 100 mg/kg/day (n = 21) or no treatment (n = 24) were given for 3 weeks and compared to sham (n = 8). RESULTS: Infarct size was similar by ultrasound and pathologic measures in both MI groups.The MI-untreated group developed important lung remodelling with nearly doubling of dry lung weight (p < 0.01), reduced left ventricular (LV) fractional shortening (16 ± 2% vs. 53 ± 1%; mean ± SEM, p < 0.0001), pulmonary hypertension (RV systolic pressure: 40 ± 3 mmHg vs. 27 ± 1 mmHg, p < 0.01) and RV hypertrophy (RV/(LV + septum): 38 ± 3% vs. 24 ± 1%, p < 0.05). Spironolactone had no effect on these parameters and did not improve LV or RV performance (tricuspid annular plane systolic excursion and RV myocardial performance index) measured by echocardiography. CHF induced a restrictive respiratory syndrome with histological lung fibrosis: this was also unaffected by spironolactone. Finally, isolated lung MYFs did not proliferate after exposure to aldosterone. CONCLUSION: Aldosterone does not significantly contribute to pulmonary remodelling and RV dysfunction associated with CHF. Other mechanisms are responsible for the beneficial effects of spironolactone in CHF.

Single measurement of troponin T for early prediction of infarct size, congestive heart failure, and pulmonary hypertension in an animal model of myocardial infarction.

BACKGROUND: Early prediction of infarct size and of the subsequent development of congestive heart failure (CHF) and pulmonary hypertension (PH) would be useful in therapeutic trials using the rat myocardial infarction (MI) model. METHODS: A total of 194 rats were subjected to MI or sham surgery, and plasma cardiac troponin T (cTnT) was measured 24 h after surgery in rats. Echocardiography was performed after 2 and 5 weeks. Hemodynamic and morphometric parameters were evaluated 5 weeks after MI. RESULTS: cTnT had strong positive correlations with left ventricular (LV) wall motion abnormalities at 2 and 5 weeks (R=.85 and .89; P<.0001), and with histological infarct size (R=.87, P<.0001). cTnT ≥5.1 µg/l predicted LV wall motion abnormalities ≥ 30% with a sensitivity of 90.9% and specificity of 84.0%. Rats with cTnT≥5.1 µg/l developed PH [right ventricular (RV) systolic pressure 37 ± 3 vs. 23 ± 0.6 mmHg], RV hypertrophy (RV/LV+septum weight 42 ± 4% vs. 24 ± 0.5%), and lung structural remodeling (all P<.01). CONCLUSION: Early single cTnT measurement correlates with infarct size in rats, and a cutoff value of 5.1 µg/l provides good sensitivity and specificity to predict CHF with secondary PH. cTnT could be used for treatment allocations in therapeutic trials of secondary pulmonary hypertension using this model.

Beneficial effects of atorvastatin on lung structural remodeling and function in ischemic heart failure.

BACKGROUND: Studies have suggested some benefit of 3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors in congestive heart failure (CHF), although the mechanisms remain uncertain. We hypothesized that statins could improve pulmonary hypertension and right ventricular function in ischemic CHF by reducing lung remodeling. METHODS AND RESULTS: Two weeks after myocardial infarct, rats received atorvastatin (n = 23) or no treatment (n = 23) for 3 weeks and were compared with a sham group (n = 16). Infarct size was similar by echocardiography and pathologic evaluations. Atorvastatin greatly reduced pulmonary hypertension and right ventricular hypertrophy: right ventricular systolic pressure 42 +/- 5 vs. 28 +/- 2 mm Hg (P < .01). Atorvastatin did not reduce left ventricular fibrosis and had minimal effects on left ventricular function. Right ventricular myocardial performance index was markedly improved by therapy (P < .01). CHF caused a restrictive lung syndrome with a downward shift of the respiratory pressure-volume loop, increased dry lung weight, and interstitial fibrosis that were greatly improved by atorvastatin. Reduced lung nitric oxide synthase expression was normalized by treatment. Atorvastatin also reduced isolated lung myofibroblasts proliferation after transforming growth factor-beta stimulation (-36 +/- 6%, P < 0.01). CONCLUSIONS: 3-hydroxy-3-methyl-glutaryl-CoA reductase inhibition reduces lung remodeling and dysfunction associated with heart failure with prevention of right ventricular hypertrophy and pulmonary hypertension.

Atrial natriuretic peptide gene transfection with a novel envelope vector system ameliorates pulmonary hypertension in rats.

OBJECTIVES: A novel hemagglutinating virus of Japan (HVJ, a murine parainfluenza virus) envelope vector system, in which DNA is incorporated into an inactivated viral particle deprived of its genome, was recently developed as a ready-to-use vector for gene therapy. We therefore investigated whether intratracheal gene transfer using this vector can induce transgene expression in the lung and whether atrial natriuretic peptide gene transfer ameliorates pulmonary hypertension in rats. METHODS: Rats transfected intratracheally with beta-galactosidase vector, atrial natriuretic peptide vector, or mock vector were investigated for the evaluation of beta-galactosidase expression, atrial natriuretic peptide mRNA expression, and inflammatory cell infiltration. Rats were divided into 5 treatment groups (n = 73): normoxic rats treated intratracheally with mock vector or atrial natriuretic peptide gene and chronic hypoxic rats treated similarly with mock vector, atrial natriuretic peptide, or a reporter gene, beta-galactosidase. Pulmonary hypertension and transfected gene expression were evaluated. RESULTS: Beta-galactosidase gene transfer induced its intense enzymatic activity in bronchial and alveolar epithelial cells but not in other organs in normoxic rats. Transfected lungs were not associated with inflammatory cell infiltration. Atrial natriuretic peptide gene transfection inhibited pulmonary hypertension, which is associated with its mRNA expression in the lungs. Indices of right ventricular hypertrophy and pulmonary vascular diseases induced by chronic hypoxia were significantly but incompletely ameliorated. CONCLUSIONS: HVJ-envelope vector is an efficient, relatively safe, and ready-to-use gene delivery system for pulmonary vascular diseases. Atrial natriuretic peptide gene transfer to lungs by using this vector could be a promising therapeutic approach against pulmonary hypertension.

A nuclear factor-kappaB inhibitor pyrrolidine dithiocarbamate ameliorates pulmonary hypertension in rats.

BACKGROUND: Pulmonary hypertension (PH) is a fatal disorder that is associated with structural changes and inflammatory responses in the pulmonary vasculature. Nuclear factor (NF)-kappaB is a key transcription factor that is involved in the tissue remodeling mediated by inflammatory and fibroproliferative responses. However, the contribution of NF-kappaB-mediated inflammatory pathways to the development of PH is unknown. METHODS: We therefore investigated whether NF-kappaB activation and the expression of a downstream product vascular cell adhesion molecule (VCAM)-1 is associated with pulmonary vascular diseases in rats that have been injected with the toxin monocrotaline (MCT), and whether a NF-kappaB inhibitor, pyrrolidine dithiocarbamate (PDTC), ameliorates such diseases in rats. RESULTS: VCAM-1 expression and the nuclear localization of the p65 subunit of NF-kappaB, as analyzed immunohistochemically, was significantly up-regulated in the endothelium of diseased vessels on the days 8 to 22 (p < 0.05). Next, 39 rats were divided into three groups (rats injected with MCT and treated with saline solution or PDTC, and controls similarly treated with saline solution). Compared to controls, MCT treatment increased the mean (+/- SE) pulmonary artery pressure (31.2 +/- 1.4 mm Hg [p < 0.05] vs 22.8 +/- 0.9 mm Hg, respectively), which was reduced by PDTC treatment (24.3 +/- 1.2 mm Hg; p < 0.05). Indexes of right ventricular hypertrophy and pulmonary vascular diseases induced by MCT were similarly inhibited (p < 0.05), which was associated with the suppression of VCAM-1 expression and macrophage infiltration. CONCLUSIONS: We concluded that the NF-kappaB nuclear localization and VCAM-1 expression is temporally and spatially associated with the development of MCT-induced PH in rats, which was ameliorated by administering a NF-kappaB inhibitor, PDTC.

A novel inhibitor of inducible nitric oxide synthase, ONO-1714, does not ameliorate hypoxia-induced pulmonary hypertension in rats.

A recent study showed that long-term administration of the inducible nitric oxide synthase (iNOS) inhibitor L-NIL reduced the development of pulmonary hypertension. The purpose of the present study was to identify the effect of an another iNOS inhibitor, ONO-1714, on the development of pulmonary hypertensive vascular changes in chronic hypoxic pulmonary hypertension in rats. ONO-1714 was administered to rats exposed to hypobaric hypoxia (air at 380 mmHg) for 10 days. Muscularization of normally nonmuscular peripheral arteries and medial hypertrophy of normally muscular arteries were assessed by light microscopy. iNOS mRNA and protein levels of the lung were assessed in normal and hypoxic rats. Chronic hypoxia induced pulmonary hypertension, right ventricular hypertrophy, and hypertensive pulmonary vascular changes. Although an acute single injection of ONO-1714 induced a significant increase in mean pulmonary artery pressure in chronic hypoxic pulmonary hypertensive rats, the increase was slight and transient. There were no significant differences among rats with and without long-term administration of ONO-1714 in pulmonary artery pressure, right ventricular hypertrophy, medial wall thickness of muscular arteries, and the percentage of muscularized arteries at the alveolar wall and duct levels. Although there was a significantly increased expression of iNOS as assessed with the reverse-transcription polymerase chain reaction in rats that were exposed to 10 days of hypobaric hypoxia, we could not detect a significant level of iNOS protein by Western blotting. ONO-1714 does not have a therapeutic role in preventing the development of chronic hypoxic pulmonary hypertension.

Acute vasodilator effect of fasudil, a Rho-kinase inhibitor, in monocrotaline-induced pulmonary hypertension in rats.

Pulmonary arterial hypertension is a progressive and fatal disease for which Rho-kinase may be substantially involved. In this study, we examined the acute vasodilator effects of fasudil, a Rho-kinase inhibitor, in monocrotaline (MCT)-induced pulmonary hypertension (PH) in rats. Three weeks after a single subcutaneous injection of MCT (60 mg/kg), hemodynamic variables were measured under conscious and free-moving conditions before and after oral administration of fasudil. MCT caused a significant elevation of mean pulmonary arterial pressure (mPAP). Although a low dose of fasudil (3 mg/kg) had no effect on mPAP, a middle dose (10 mg/kg) caused a significant reduction in mPAP without change in mean systemic arterial pressure (mSAP), and a high dose (30 mg/kg) significantly reduced both mPAP and mSAP. Rho-kinase activity was significantly increased by MCT injection in pulmonary arteries but not in the aorta. Fasudil (10 mg/kg) inhibited only the Rho-kinase activity in pulmonary arteries without any effect in the aorta. Plasma concentration of hydroxyfasudil, a metabolite of fasudil, was within its clinical range in humans. These results demonstrate that fasudil exerts effective and selective vasodilatation of pulmonary arteries in rats with MCT-induced PH at a given dose, suggesting its usefulness for the treatment of the fatal disorder.

Prolonged nitric oxide inhalation during recovery from chronic hypoxia does not decrease nitric oxide-dependent relaxation in pulmonary arteries.

STUDY OBJECTIVE: To investigate the effects of long-term nitric oxide (NO) inhalation on the recovery process of right ventricular hypertrophy (RVH) and functional alterations in the NO-cyclic guanosine monophosphate (cGMP) relaxation pathway in rat conduit pulmonary arteries (PAs) in established chronic hypoxic pulmonary hypertension. MATERIALS AND METHODS: A total of 35 rats were exposed to chronic hypobaric hypoxia (380 mm Hg, 10% oxygen), and 39 rats were exposed to air for 10 days. Both groups were then exposed to 3 or 10 days of NO 10 ppm, NO 40 ppm, or air (control groups for each NO concentration), resulting in a total of 16 groups. Acetylcholine- and sodium nitroprusside (SNP)-induced relaxation were evaluated in precontracted PA rings. RVH was assessed by heart weight ratio of right ventricle to left ventricle plus septum. RESULTS: NO inhalation had no effect on either the regression of RVH or the recovery process of impaired relaxation induced by acetylcholine or SNP in a endothelium-intact hypertensive conduit extrapulmonary artery or intrapulmonary artery (IPA). In a normal endothelium-intact conduit IPA, 40 ppm NO inhalation for 10 days partially augmented SNP-induced relaxation, but not that induced by acetylcholine. CONCLUSION: Continuous NO inhalation did not affect the regression process of either established RVH or the impaired endogenous NO-cGMP relaxation cascade in a conduit PA in rats during the recovery period after chronic hypoxia.

Prolonged nitric oxide inhalation fails to regress hypoxic vascular remodeling in rat lung.

STUDY OBJECTIVE: The purpose of present study was to investigate whether long-term nitric oxide (NO) inhalation during the recovery in air might improve the regression of chronic hypoxic pulmonary hypertension (PH) and vascular changes. MATERIALS AND METHODS: The rats were exposed to 10 ppm of NO in air for 10 days (n = 12) and 30 days (n = 4), or 40 ppm of NO in air for 10 days (n = 6) and 30 days (n = 12) following 10 days of hypobaric hypoxia (380 mm Hg, 10% oxygen). For each NO group, air control rats following hypoxic exposure were studied at the same time (n = 13, 11, 9, and 11, respectively). Normal air rats (n = 6) without hypoxic exposure and rats (n = 7) following 10 days of hypoxic exposure were used as normal and chronic hypoxic control groups, respectively. Muscularization of normally nonmuscular peripheral arteries and medial hypertrophy of normally muscular arteries were assessed by light microscopy. An additional 16 rats were used to investigate the recovery of pulmonary artery pressure with (n = 8) and without NO inhalation (n = 8) after 10 days of hypobaric hypoxia. RESULTS: Long-term hypoxia-induced PH, right ventricular hypertrophy (RVH), and hypertensive pulmonary vascular changes, each of which regressed partly after recovery in room air. There were no differences among rats with and without NO during each recovery period in RVH, medial wall thickness of muscular artery, and the percentages of muscularized arteries at the alveolar wall and duct levels. Continuous inhaled 40 ppm NO decreased pulmonary artery pressure from 40.1 +/- 1.1 to 29.9 +/- 3.8 mm Hg (mean +/- SE) [n = 8], which was not different in the rats without NO inhalation (n = 8). Urine nitrate level was higher in rats that had inhaled NO. CONCLUSION: Continuous NO inhalation showed no effect on regression of pulmonary vascular remodeling in chronic hypoxic PH after returning to room air.