Yoshiteru Morio

Endothelin-1 and serotonin are involved in activation of RhoA/Rho kinase signaling in the chronically hypoxic hypertensive rat pulmonary circulation.

We have previously reported that vasoconstrictor sensitivity to KCl (a receptor-independent and voltage-gated Ca2+ influx-mediated vasoconstrictor) is augmented in the chronically hypoxic hypertensive rat pulmonary circulation probably through increased Rho kinase-mediated Ca2+ sensitization. However, the upstream mechanism by which the RhoA/Rho kinase signaling pathway is activated is unknown. This study examined if endogenous endothelin-1 (ET-1) and serotonin (5-HT) play roles in the Rho kinase-mediated augmented vasoconstrictor response to KCl and the activation of RhoA in chronically hypoxic hypertensive rat pulmonary arteries. The augmented KCl vasoconstriction in hypertensive lungs was reduced by the ETA receptor antagonist BQ123, while a dual ETA/B antagonist had no further effects. A combination of BQ123 and a 5-HT1B/1D receptor antagonist, GR127935, was more effective than either agent alone. The combined antagonists also reduced augmented contractile sensitivity to KCl in hypertensive intrapulmonary arteries. Membrane-to-cytosol ratio of RhoA expression in hypertensive arteries was greater than that in normotensive arteries and was reduced by BQ123 and GR127935. These results suggest that stimulation of ETA and 5-HT1B/1D receptors by endogenous ET-1 and 5-HT, respectively, is involved in RhoA/Rho kinase-mediated increased Ca2+ sensitization in the chronically hypoxic hypertensive rat pulmonary circulation.

Chronic hypoxia augments endothelin-B receptor-mediated vasodilation in isolated perfused rat lungs

To investigate whether chronic hypoxia affects endothelin-B (ETB) receptor-mediated pulmonary vasodilation, we compared the vasodilator responses to IRL-1620, a selective ETB-receptor agonist, in isolated perfused lungs from normoxic and chronically hypoxic adult male rats. IRL-1620 caused a dose-dependent vasodilation that was greater in the hypertensive lungs than in the normotensive lungs. In normotensive lungs, a nitric oxide (NO) synthase inhibitor, N ω-nitro-l-arginine (l-NNA; 300 μM), and an ATP-sensitive potassium (KATP)-channel inhibitor, glibenclamide (Glib; 10 μM), each reduced the vasodilator response to IRL-1620 (1 nM), but the combination ofl-NNA and Glib inhibited it more effectively than either drug alone. In contrast,l-NNA alone, but not Glib alone, completely blocked IRL-1620-induced vasodilation in hypertensive lungs. The vasodilator response to a KATP-channel opener, NIP-121 (1 μM), but not the response to sodium nitroprusside (1 μM), was enhanced in hypertensive lungs. We also found increased expression of mRNA for the ETB receptor in lung tissue after hypoxic exposure. In addition, semiquantitative immunohistochemistry demonstrated higher expression levels of ETB receptors in the endothelium of distal segments of the pulmonary artery in hypoxic than in normoxic rats. These results suggest that ETB receptor-mediated pulmonary vasodilation is augmented after chronic hypoxic exposure and that release of NO may be the sole mechanism of this vasodilation in hypertensive lungs, whereas both release of NO and activation of KATP channels are involved in normotensive lungs. We speculate that the underlying mechanism responsible for this augmentation may partly be related to upregulation of ETB receptors in the endothelium of pulmonary resistance arteries in hypertensive lungs.To investigate whether chronic hypoxia affects endothelin-B (ETB) receptor-mediated pulmonary vasodilation, we compared the vasodilator responses to IRL-1620, a selective ETB-receptor agonist, in isolated perfused lungs from normoxic and chronically hypoxic adult male rats. IRL-1620 caused a dose-dependent vasodilation that was greater in the hypertensive lungs than in the normotensive lungs. In normotensive lungs, a nitric oxide (NO) synthase inhibitor, Nomega-nitro-L-arginine (L-NNA; 300 microM), and an ATP-sensitive potassium (KATP)-channel inhibitor, glibenclamide (Glib; 10 microM), each reduced the vasodilator response to IRL-1620 (1 nM), but the combination of L-NNA and Glib inhibited it more effectively than either drug alone. In contrast, L-NNA alone, but not Glib alone, completely blocked IRL-1620-induced vasodilation in hypertensive lungs. The vasodilator response to a KATP-channel opener, NIP-121 (1 microM), but not the response to sodium nitroprusside (1 microM), was enhanced in hypertensive lungs. We also found increased expression of mRNA for the ETB receptor in lung tissue after hypoxic exposure. In addition, semiquantitative immunohistochemistry demonstrated higher expression levels of ETB receptors in the endothelium of distal segments of the pulmonary artery in hypoxic than in normoxic rats. These results suggest that ETB receptor-mediated pulmonary vasodilation is augmented after chronic hypoxic exposure and that release of NO may be the sole mechanism of this vasodilation in hypertensive lungs, whereas both release of NO and activation of KATP channels are involved in normotensive lungs. We speculate that the underlying mechanism responsible for this augmentation may partly be related to upregulation of ETB receptors in the endothelium of pulmonary resistance arteries in hypertensive lungs.

Genistein, a Phytoestrogen, Attenuates Monocrotaline-Induced Pulmonary Hypertension

Background: Pulmonary hypertension is characterized by high pulmonary blood pressure, vascular remodeling, and right ventricular hypertrophy. Although recent studies suggest that an imbalance between endothelial mediators on pulmonary vasculature may contribute to the development of pulmonary hypertension, the pathogenesis is not fully understood and the treatment of pulmonary hypertension is still unresolved. Objective: The purpose of this study was to investigate whether genistein, a phytoestrogen derived from soybean, would prevent the development of monocrotaline (MCT)-induced pulmonary hypertension in rats. Hemodynamic parameters of catheterized rats and morphological feature of lungs were evaluated among MCT-treated rats receiving or not receiving genistein. Furthermore, examination of expression in endothelial nitric oxide synthase and endothelin-1 peptide level was performed. Methods: Daily supplementation with either genistein (0.2 mg/kg) or vehicle was started 2 days prior to a single-dose injection of MCT (60 mg/kg). On day 28, rats underwent catheterization, and right ventricular hypertrophy and morphological features were assessed. Furthermore, endothelial nitric oxide synthase and endothelin-1 were examined by Western blot analysis and radioimmunoassay, respectively, in homogenated lungs. Results: In rats that received daily supplementation of genistein, mean pulmonary arterial pressure was significantly reduced, whereas mean systemic arterial pressure and heart rate were unaltered compared with MCT control rats on day 28 after MCT injection. Right ventricular hypertrophy, medial wall thickness of pulmonary arteries corresponding to the terminal bronchioles, and the degree of neomuscularization of more distal arteries were less severe in genistein-treated rats. Genistein supplementation improved MCT-induced downregulation of expression of endothelial nitric oxide synthase in the lungs. However, endothelin-1 peptide levels did not differ among all groups of lungs. Conclusions: We conclude that daily supplementation of genistein potently attenuates MCT-induced pulmonary hypertension, right ventricular hypertrophy, and pulmonary vascular remodeling in rats. The underlying mechanism responsible for this effect may be partly related to the restoration of a decreased expression of endothelial nitric oxide synthase.

Downregulation of Angiopoietin-1 and Tie2 in Chronic Hypoxic Pulmonary Hypertension

Background: Angiopoietins, newly discovered vascular-specific growth factors, and vascular endothelial growth factors (VEGF) play distinct and complementary roles in angiogenesis and vascular maturation. However, the exact roles of angiogenic factors in the adult pulmonary vasculature remain unclear. Objective: To elucidate possible roles of angiopoietins and VEGF in the development of hypoxic pulmonary hypertension (PH), changes in the expression of angiogenic factors were examined. Methods: The cellular distribution and expression of angiopoietins and their receptor Tie2 and VEGF were investigated by RT-PCR, immunoblot, and immunohistochemical methods in rat lung under normal and hypoxic conditions. Results: During the development of PH with vascular remodeling characterized by a decrease in vessel density of intrapulmonary arteries, protein expression of angiopoietin-1 (Ang-1), Tie2, and VEGF significantly decreased in the pulmonary arteries, and Tie2 receptor was inactivated in the lung. The expression of angiopoietin-3 (Ang-3), an endogenous antagonist of Ang-1, significantly increased in the intima under hypoxic conditions. Conclusions: Since both Ang-1/Tie2 and VEGF promote angiogenesis and vascular survival, and play protective roles in the adaptation of microvascular changes during the onset of PH, the downregulation of both Ang-1/Tie2 and VEGF and upregulation of Ang-3 appear to be associated with vascular rarefaction and the development of hypoxic PH.

Pulmonary sarcoidosis and antiphospholipid syndrome.

Abstract:  Various autoimmune diseases have been reported to occur in patients with sarcoidosis. However, coexistence of sarcoidosis and antiphospholipid syndrome (APS) is extremely rare. We describe a 59‐year‐old female patient with pulmonary sarcoidosis who had preceding APS. Her previous medical history consisted of a miscarriage and ischemic colitis. She was diagnosed as APS during the onset of a brainstem infarction with positive reaction to β2‐glycoprotein I‐dependent anticardiolipin antibody. Two years later, chest CT revealed enlargement of the hilar and mediastinal lymph nodes and small nodules in the lung fields. Transbronchial lung biopsy demonstrated non‐caseating epithelioid cell granuloma leading to the diagnosis of definite pulmonary sarcoidosis. This is the first APS case where pulmonary involvement with sarcoidosis has been confirmed through lung biopsy. Our case report suggests that APS should be recognized as an accompanying disorder of sarcoidosis.

Activity of Endothelium-Derived Hyperpolarizing Factor Is Augmented in Monocrotaline-Induced Pulmonary Hypertension of Rat Lungs

The mechanism of endothelium-dependent vasodilator signaling involves three components such as nitric oxide, prostacyclin, and endothelium-derived hyperpolarizing factor (EDHF). Although EDHF is distinct from nitric oxide and prostacyclin, it requires activation of Ca2+-sensitive K+ channels (KCa) and cytochrome P450 metabolites. However, the physiological role of EDHF in the pulmonary circulation is unclear. Thus, we tested if EDHF would regulate vascular tone in rat lungs of control and monocrotaline (MCT)-induced pulmonary hypertension. Inhibition of EDHF with a combination of KCa blockers, charybdotoxin (50 nM) plus apamin (50 nM), increased baseline vascular tone in MCT-induced hypertensive lungs. Thapsigargin (TG; 100 nM), an inhibitor of Ca-ATPase, caused greater EDHF-mediated vasodilation in MCT-induced hypertensive lungs. TG-induced vasodilation was abolished with the charybdotoxin-apamin combination. Sulfaphenazole (10 µM), a cytochrome P450 inhibitor, reduced the TG-induced vasodilation in MCT-induced hypertensive lungs. RT-PCR analysis exhibited an increase in KCa mRNA in MCT-treated lungs. These results indicate the augmentation of tonic EDHF activity, at least in part, through the alteration in cytochrome P450 metabolites and the upregulation of KCa expression in MCT-induced pulmonary hypertension.

Successful resection of dermatomyositis associated with thymic carcinoma: Report of a case

We report a case of thymic carcinoma associated with dermatomyositis (DM) in a 53-year-old man. The patient presented with the characteristic features of a skin rash with Gottron’s papules, proximal muscle weakness, and increased serum levels of the muscle-associated enzymes. Comprehensive clinical examinations revealed an anterior mediastinal tumor. We resected the tumor and histological examination confirmed squamous cell carcinoma of the thymus. Thereafter, his clinical symptoms improved dramatically and his serum levels of muscleassociated enzymes dropped, indicating that the DM was a paraneoplastic phenomenon. Our search of the literature found only one other case report of DM accompanied by thymic carcinoma, and to our knowledge, this is the fi rst documented case of dramatic improvement of DM after resection of thymic carcinoma. We propose that thymic carcinoma should be added to the list of malignancies that can complicate DM as a paraneoplastic disease.

Distal Airspace Enlargement in the Fawn-Hooded Rat: Influences of Aging and Alveolar Wall Destruction

Background: A recent study has revealed that the peripheral airspace in the lungs of the fawn-hooded rat (FHR) is enlarged. However, morphological and functional factors of the FHR lung have not been fully investigated. Objective: The purpose of our study was to examine the structural and functional changes in the FHR lung and to investigate the influence of aging on this process. Furthermore, morphological and functional measurements of the lungs of FHRs (4–48 weeks of age) were performed and the results compared with those of age-matched Wistar control rats (WCRs). Methods: All animals were studied under controlled conditions, and morphological and functional changes of the lungs were examined. Measurements of body and lung weights were recorded, and the lungs were subjected to morphological evaluation. Morphological measurements: mean linear intercept (MLI) and destructive index were determined. Functional evaluation of the lungs: total lung capacity, pressure-volume curve, and exponential constant (K) which describes the shape of the curve were analyzed. In addition, right ventricular hypertrophy measurements were performed to assess the severity of pulmonary hypertension. Statistical analysis was performed using the unpaired t test, analysis of variance, and the Fisher post hoc test (p < 0.05). Results: Morphological analysis revealed a significant increase in airspace size (MLI) in all FHRs as compared with the WCRs which was evident from an early age (4 weeks). The increase in MLI did not progress age dependently in the FHR, whereas a tendency for an age-dependent increase in MLI was observed in the WCR. The destructive index measurements revealed that the increase in MLI of FHR was not accompanied by alveolar wall destruction. Concerning the functional examination, a leftward and upward shift of the pressure-volume curve was observed in the FHRs as compared with the WCRs at all ages. As compared with the WCRs, a higher K value was observed in all FHRs which was evident from an early age (4 weeks). Age-dependent changes similar to those in MLI were observed in the K in both rat strains. Conclusions: The results of our study suggest that FHRs manifest characteristics of distal airspace enlargement accompanied by increased lung distensibility without alveolar wall destruction at an early age and that the changes do not progress age dependently. Neither an accelerated aging process nor destruction of the alveolar walls appears to be the mechanism responsible for the enlarged airspace in this rat strain.

Involvement of Rho kinase in the pathogenesis of acute pulmonary embolism-induced polystyrene microspheres in rats

Acute pulmonary embolism (PE) is a life-threatening disease, and several vasoconstrictors, including endothelin-1 (ET-1), play a key role in vasoconstriction and hypoxemia during the development of PE. Rho kinase is activated by various vasoconstrictors resulting in vascular contraction and remodeling. Recent evidence has revealed an important role of Rho kinase in the pathogenesis of systemic and pulmonary vascular diseases. However, contribution of Rho kinase in PE remains unclear. We thus investigated the role of Rho kinase in the PE rat model induced by intrajugular administration of polystyrene microspheres (mean diameter, 26 microm). At 6 h following the administration of microspheres (1.5 ml/kg), right ventricular systolic pressure (RVSP) was higher in the PE than in the control rats (15.8 +/- 1.6 vs. 32.9 +/- 7.5 mmHg). Arterial oxygen tension was lower (92.3 +/- 12.5 vs. 66.0 +/- 17.7 Torr), and alveolar-arterial difference in oxygen partial pressure was higher (3.9 +/- 3.8 vs. 36.5 +/- 26.9 Torr) in the PE rats. Western blotting analysis revealed upregulation and downregulation in expression of vascular cell adhesion molecule-1 and endothelial nitric oxide synthase in lungs from the PE rats, respectively, and radioimmunoassay demonstrated an increase in plasma ET-1 levels. Lung Rho kinase alpha expression was greater in the PE rats. At 5 h following administration of microspheres (0.75 ml/kg), intravenous Rho kinase inhibitors HA1077 and Y27632 (3 mg/kg each) attenuated elevation of RVSP (22.0 +/- 3.7, 17.1 +/- 3.2, 14.3 +/- 2.6 mmHg, PE, PE+HA1077, PE+Y27632) and the severity of hypoxemia (66.3 +/- 16.2, 94.9 +/- 23.0, 89.1 +/- 8.5 Torr, PE, PE+HA1077, PE+Y27632) in the PE rats. These results suggest that pulmonary endothelial dysfunction and activation of Rho kinase may contribute to the potentiation of vasoconstriction and hypoxemia in the PE rats.

Isolated congenital spleen agenesis: a rare cause of chronic thromboembolic pulmonary hypertension in an adult.

Abstract:  This report describes a case of isolated congenital spleen agenesis complicated by chronic thromboembolic pulmonary hypertension (CTPH) in a 44‐year‐old female patient. The patient had increasing exertional dyspnoea and thrombocytosis. An echocardiogram showed severe pulmonary hypertension and right ventricular hypertrophy, and contrast‐enhanced chest CT revealed multiple thromboemboli within both pulmonary arteries. A perfusion lung scan demonstrated multiple segmental defects and no spleen was detected by abdominal CT, ultrasonography or scintigraphy. Comprehensive clinical examinations disclosed no evidence of a thrombus elsewhere or of an associated malformation such as a cardiac anomaly. Anticoagulation therapy was started, and a perfusion lung scan revealed partial improvement of the hypoperfusion in the right lower lobe. However, repeat echocardiography showed the pulmonary hypertension persisting for 1 year. The multiple segmental defects in the perfusion lung scans were also persistent. Collectively, a diagnosis of CTPH with isolated congenital spleen agenesis was established. This is the first documented case of CTPH in an adult with isolated congenital asplenia. Although congenital spleen agenesis is a rare condition, this case report suggests that this possibility should be considered when a diagnosis of CTPH and thrombocytosis is made.