dinoprost and Hypertrophy--Right-Ventricular

Colforsin, a water-soluble forskolin derivative, directly activates adenylate cyclase and thereby increases the 3',5'-cyclic adenosine monophosphate (cAMP) level in vascular smooth muscle cells. In this study, we investigated the vasodilatory action of colforsin on structurally remodeled pulmonary arteries from rats with pulmonary hypertension (PH).. A total of 32 rats were subjected to hypobaric hypoxia (380 mmHg, 10% oxygen) for 10 days to induce chronic hypoxic PH, while 39 rats were kept in room air. Changes in isometric force were recorded in endothelium-intact (+E) and -denuded (-E) pulmonary arteries from the PH and control (non-PH) rats.. Colforsin-induced vasodilation was impaired in both +E and -E arteries from PH rats compared with their respective controls. Endothelial removal did not influence colforsin-induced vasodilation in the arteries from control rats, but attenuated it in arteries from PH rats. The inhibition of nitric oxide (NO) synthase did not influence colforsin-induced vasodilation in +E arteries from controls, but attenuated it in +E arteries from PH rats, shifting its concentration-response curve closer to that of -E arteries from PH rats. Vasodilation induced by 8-bromo-cAMP (a cell-permeable cAMP analog) was also impaired in -E arteries from PH rats, but not in +E arteries from PH rats, compared with their respective controls.. cAMP-mediated vasodilatory responses without beta-adrenergic receptor activation are impaired in structurally remodeled pulmonary arteries from PH rats. In these arteries, endothelial cells presumably play a compensatory role against the impaired cAMP-mediated vasodilatory response by releasing NO (and thereby attenuating the impairment). The results suggest that colforsin could be effective in the treatment of PH.

Topics: 8-Bromo Cyclic Adenosine Monophosphate; Animals; Chronic Disease; Colforsin; Dinoprost; Drug Synergism; Fluorescent Dyes; Fura-2; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; In Vitro Techniques; Isometric Contraction; Male; Muscle Contraction; Potassium Chloride; Pulmonary Artery; Rats; Rats, Wistar; Vasodilation; Vasodilator Agents

Xanthine oxidase (XO)-derived reactive oxygen species (ROS) formation contributes to experimental chronic hypoxic pulmonary hypertension in adults, but its role in neonatal pulmonary hypertension has received little attention. In rats chronically exposed to hypoxia (13% O(2)) for 14 days from birth, we examined the effects of ROS scavengers (U74389G 10 mg.kg(-1).day(-1) or Tempol 100 mg.kg(-1).day(-1) ip) or a XO inhibitor, Allopurinol (50 mg.kg(-1).day(-1) ip). Both ROS scavengers limited oxidative stress in the lung and attenuated hypoxia-induced vascular remodeling, confirming a critical role for ROS in this model. However, both interventions also significantly inhibited somatic growth and normal cellular proliferation in distal air spaces. Hypoxia-exposed pups had evidence of increased serum and lung XO activity, increased vascular XO-derived superoxide production, and vascular nitrotyrosine formation. These changes were all prevented by treatment with Allopurinol, which also attenuated hypoxia-induced vascular remodeling and partially reversed inhibited endothelium-dependent arterial relaxation, without affecting normal growth and proliferation. Collectively, our findings suggest that XO-derived superoxide induces endothelial dysfunction, thus impairing pulmonary arterial relaxation, and contributes to vascular remodeling in hypoxia-exposed neonatal rats. Due to the potential for adverse effects on normal growth, targeting XO may represent a superior "antioxidant" strategy to ROS scavengers for neonates with pulmonary hypertension.

Topics: Acetylcholine; Allopurinol; Animals; Animals, Newborn; Cell Proliferation; Chronic Disease; Cyclic N-Oxides; Dinoprost; Free Radical Scavengers; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; In Vitro Techniques; Lung; Nitric Oxide Synthase Type III; Organ Size; Oxidative Stress; Pregnatrienes; Pulmonary Artery; Rats; Reactive Oxygen Species; Spin Labels; Superoxides; Time Factors; Xanthine Oxidase

In this paper, we studied the relationship between the prostaglandin F(2alpha) (PGF(2alpha))-induced cardiac hypertrophy and calcineurin (CaN) signal transduction pathway in vivo and in vitro. Male Sprague-Dawley rats were given a single i.p. injection with monocrotaline (MCT) (60 mg/kg) and then given orally with celecoxib (20 mg/kg) or vehicle once a day for 14 d before (from d 1 to d 14) or after (from d 15 to d 28) right ventricular hypertrophy (RVH) was formed. Body weight (BW), right ventricular weight (RV), left ventricular with septum weight (LV), as well as lung weight were determined. RVH index (RVHI=RV/LV), RV/BW, and lung weight/BW were calculated and histological changes were observed with transmission electron microscope. PGF(2alpha) level, atrial natriuretic peptide (ANP) and CaN mRNA expressions, expression of CaN and its downstream effectors, NFAT(3) and GATA(4) protein were assayed by EIA kit, RT-PCR, and Western blotting, respectively. The cardiomyocyte hypertrophy in primary culture induced by PGF(2alpha) (0.1 micromol/L) was evaluated by measuring the cell diameter, protein content, and ANP mRNA as well as CaN mRNA expressions. It was found that 14 d or 28 d after MCT was given, the RVHI, RV/BW, and lung weight/BW were significantly increased by 47%, 53% and 118%, and by 64%, 94% and 156%, respectively; at the same time PGF(2alpha) levels in RV tissue were increased by 44% and by 51% with increasing RVHI, and elevated expressions of ANP and CaN mRNA, as well as CaN, NFAT(3) and GATA(4) proteins in a positive correlation manner. Furthermore, some histological injuries were found in RV tissue. Celecoxib, a cyclooxygenase inhibitor, obviously blunted the elevation of RVHI, RV/BW, and lung weight/BW no matter it was given before or after RVH. In vitro experiments showed that 0.1 micromol/L PGF(2alpha) significantly increased the cardiomyocyte diameter and protein content, and promoted ANP and CaN mRNA expressions, which was blocked by cyclosporin A, a CaN inhibitor. Our results indicate that PGF(2alpha) may be involved in cardiac hypertrophy induced by MCT in rats through CaN signal transduction pathway.

Topics: Animals; Calcineurin; Cells, Cultured; Dinoprost; Hypertrophy, Right Ventricular; Male; Monocrotaline; Myocytes, Cardiac; Rats; Rats, Sprague-Dawley; RNA, Messenger; Signal Transduction

Endothelin-1 (ET-1) mediates the development of pulmonary hypertension (PHT) in newborn rats exposed to 60% O(2) for 14 days, a model for human chronic neonatal lung injury. ET-1 production by d-14 rat pulmonary artery smooth muscle cells in vitro was markedly increased by thromboxane (TX) A(2) receptor agonists and inhibited by a competitive antagonist. We hypothesized that stimulation of the TX A(2) receptor contributed to O(2)-mediated PHT in vivo. Newborn rat pups received daily intraperitoneal injections of L670596, a competitive TX A(2) receptor antagonist, or 5,5-dimethyl-3-(3-fluorophenyl)4-(4-methylsulfonyl)phenyl-2(5H)-furanone (DFU), a cyclooxygenase-2 inhibitor, during 14 days of 60% O(2) or air exposure. L670596, but not DFU, prevented 60% O(2)-mediated right ventricular and small pulmonary vessel smooth muscle hypertrophy. Lung ET-1 content was significantly reduced by L670596 in 60% O(2)-exposed animals. We conclude that TX A(2) receptor activation, though not by TX A(2), caused upregulation of ET-1 and PHT in this model. A likely mediator is the stable lipid peroxidation product, 8-iso-prostane, which acts as an incidental ligand of the TX A(2) receptor and is a potent inducer of ET-1 production by cultured d-14 rat pulmonary artery smooth muscle cells in vitro.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Animals, Newborn; Blotting, Western; Carbazoles; Cells, Cultured; Cyclooxygenase Inhibitors; Dinoprost; Endothelin-1; F2-Isoprostanes; Furans; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Immunohistochemistry; Lung; Muscle, Smooth, Vascular; Oxygen; Prostaglandin Antagonists; Prostaglandin-Endoperoxide Synthases; Pulmonary Artery; Rats; Receptors, Thromboxane; Thromboxane B2; Up-Regulation; Vasoconstrictor Agents

Newborn rats exposed to 60% O(2) for 14 d demonstrated a bronchopulmonary dysplasia-like lung morphology and pulmonary hypertension. A 21-aminosteroid antioxidant, U74389G, attenuated both pulmonary hypertension and macrophage accumulation in the O(2)-exposed lungs. To determine whether macrophage accumulation played an essential role in the development of pulmonary hypertension in this model, pups were treated with gadolinium chloride (GdCl(3)) to reduce lung macrophage content. Treatment of 60% O(2)-exposed animals with GdCl(3) prevented right ventricular hypertrophy (p < 0.05) and smooth muscle hyperplasia around pulmonary vessels, but had no effect on morphologic changes in the lung parenchyma. In addition, GdCl(3) inhibited 60% O(2)-mediated increases in endothelin-1, 8-isoprostane, and nitrotyrosine residues. Organotypic cultures of fetal rat distal lung cells were subjected to cyclical mechanical strain to assess the potential role of GdCl(3)-induced blockade of stretch-mediated cation channels in these effects. Mechanical strain caused a moderate increase of endothelin-1 (p < 0.05), which was unaffected by GdCl(3), but had no effect on 8-isoprostane or nitric oxide synthesis. A critical role for endothelin-1 in O(2)-mediated pulmonary hypertension was confirmed using the combined endothelin receptor antagonist SB217242. We concluded that pulmonary macrophage accumulation, in response to 60% O(2), mediated pulmonary hypertension through up-regulation of endothelin-1.

Topics: Animals; Animals, Newborn; Bronchopulmonary Dysplasia; Cell Movement; Cells, Cultured; Dinoprost; Endothelin-1; F2-Isoprostanes; Gadolinium; Humans; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Infant, Newborn; Macrophages, Alveolar; Oxygen; Rats; Rats, Sprague-Dawley; Tyrosine

To study the changes of endothelium-dependent and -independent relaxation in structurally remodeled pulmonary arteries with hypoxic pulmonary hypertension and their reversibility during recovery in room air, rats were exposed to hypobaric hypoxia (air at 380 mmHg) for 10 days and then allowed to recover in room air for 3, 14, 28, or 56 days. Relaxation by acetylcholine, sodium nitroprusside (SNP), and isoproterenol was depressed in large- and small-conduit pulmonary arterial rings from rats exposed to 10 days of hypoxia. The relaxant response to isoproterenol and SNP was normalized completely after 3 and 28 days of recovery, respectively. The relaxation by acetylcholine was still impaired at high concentrations after 56 days. A cyclooxygenase inhibitor, indomethacin, enhanced relaxation by acetylcholine of rings from experimental rats but not from control rats. Endothelium-denuded rings showed no difference in the response to acetylcholine between control and experimental rats. In conclusion, the impaired response to acetylcholine may be related to acetylcholine-induced, cyclooxygenase-dependent production of a vasoconstrictor by endothelial cells and to depressed smooth muscle response to nitric oxide (NO). During recovery, the NO-induced guanosine 3',5'-cyclic monophosphate-dependent dilation returned to normal. However, the release of cyclooxygenase-dependent production of a vasoconstrictor may persist even after 56 days of recovery.

Topics: Animals; Body Weight; Dinoprost; Endothelium, Vascular; Hypertension; Hypertrophy, Right Ventricular; Hypoxia; Male; Nitric Oxide; Potassium Chloride; Pulmonary Artery; Rats; Rats, Wistar; Vasodilator Agents