scholarly journals Heme biosynthesis modulation via δ-aminolevulinic acid administration attenuates chronic hypoxia-induced pulmonary hypertension

2015 ◽  
Vol 308 (7) ◽  
pp. L719-L728 ◽  
Author(s):  
Raed Alhawaj ◽  
Dhara Patel ◽  
Melissa R. Kelly ◽  
Dong Sun ◽  
Michael S. Wolin
Keyword(s):  
Pulmonary Hypertension ◽  
Right Ventricular ◽  
Chronic Hypoxia ◽  
Aminolevulinic Acid ◽  
Pulmonary Arteries ◽  
Protoporphyrin Ix ◽  
Heme Biosynthesis ◽  
Mitochondrial Superoxide ◽  
Stat3 Phosphorylation ◽  
Biosynthesis Modulation

This study examines how heme biosynthesis modulation with δ-aminolevulinic acid (ALA) potentially functions to prevent 21-day hypoxia (10% oxygen)-induced pulmonary hypertension in mice and the effects of 24-h organoid culture with bovine pulmonary arteries (BPA) with the hypoxia and pulmonary hypertension mediator endothelin-1 (ET-1), with a focus on changes in superoxide and regulation of micro-RNA 204 (miR204) expression by src kinase phosphorylation of signal transducer and activator of transcription-3 (STAT3). The treatment of mice with ALA attenuated pulmonary hypertension (assessed through echo Doppler flow of the pulmonary valve, and direct measurements of right ventricular systolic pressure and right ventricular hypertrophy), increases in pulmonary arterial superoxide (detected by lucigenin), and decreases in lung miR204 and mitochondrial superoxide dismutase (SOD2) expression. ALA treatment of BPA attenuated ET-1-induced increases in mitochondrial superoxide (detected by MitoSox), STAT3 phosphorylation, and decreases in miR204 and SOD2 expression. Because ALA increases BPA protoporphyrin IX (a stimulator of guanylate cyclase) and cGMP-mediated protein kinase G (PKG) activity, the effects of the PKG activator 8-bromo-cGMP were examined and found to also attenuate the ET-1-induced increase in superoxide. ET-1 increased superoxide production and the detection of protoporphyrin IX fluorescence, suggesting oxidant conditions might impair heme biosynthesis by ferrochelatase. However, chronic hypoxia actually increased ferrochelatase activity in mouse pulmonary arteries. Thus, a reversal of factors increasing mitochondrial superoxide and oxidant effects that potentially influence remodeling signaling related to miR204 expression and perhaps iron availability needed for the biosynthesis of heme by the ferrochelatase reaction could be factors in the beneficial actions of ALA in pulmonary hypertension.

scholarly journals Exposure of mice to chronic hypoxia attenuates pulmonary arterial contractile responses to acute hypoxia by increases in extracellular hydrogen peroxide

2014 ◽  
Vol 307 (4) ◽  
pp. R426-R433 ◽  
Author(s):  
Dhara Patel ◽  
Raed Alhawaj ◽  
Michael S. Wolin
Keyword(s):  
Hydrogen Peroxide ◽  
Pulmonary Hypertension ◽  
Chronic Hypoxia ◽  
Soluble Guanylate Cyclase ◽  
Aminolevulinic Acid ◽  
Acute Hypoxia ◽  
Pulmonary Arteries ◽  
Protoporphyrin Ix

Exposing mice to a chronic hypoxic treatment (10% oxygen, 21 days) that promotes pulmonary hypertension was observed to attenuate the pulmonary vasoconstriction response to acute hypoxia (HPV) both in vivo and in isolated pulmonary arteries. Since catalase restored the HPV response in isolated arteries, it appeared to be attenuated by extracellular hydrogen peroxide. Chronic hypoxia promoted the detection of elevated lung superoxide, extracellular peroxide, extracellular SOD expression, and protein kinase G (PKG) activation [based on PKG dimerization and vasodilator-stimulated phosphoprotein (VASP) phosphorylation], suggesting increased generation of extracellular peroxide and PKG activation may contribute to the suppression of HPV. Aorta from mice exposed to 21 days of hypoxia also showed evidence for extracellular hydrogen peroxide, suppressing the relaxation response to acute hypoxia. Peroxide appeared to partially suppress contractions to phenylephrine used in the study of in vitro hypoxic responses. Treatment of mice with the heme precursor δ-aminolevulinic acid (ALA; 50 mg·kg−1·day−1) during exposure to chronic hypoxia was examined as a pulmonary hypertension therapy because it could potentially activate beneficial cGMP-mediated effects through promoting a prolonged protoporphyrin IX (PpIX)-elicited activation of soluble guanylate cyclase. ALA attenuated pulmonary hypertension, increases in both superoxide and peroxide, and the suppression of in vitro and in vivo HPV responses. ALA generated prolonged detectible increases in PpIX and PKG-associated phosphorylation of VASP, suggesting PKG activation may contribute to suppression of pulmonary hypertension and prevention of alterations in extracellular peroxide that appear to be attenuating HPV responses caused by chronic hypoxia.

scholarly journals Role of ASIC1 in the development of chronic hypoxia-induced pulmonary hypertension

2014 ◽  
Vol 306 (1) ◽  
pp. H41-H52 ◽  
Author(s):  
Carlos H. Nitta ◽  
David A. Osmond ◽  
Lindsay M. Herbert ◽  
Britta F. Beasley ◽  
Thomas C. Resta ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Right Ventricular ◽  
Chronic Hypoxia ◽  
Hypoxic Pulmonary Vasoconstriction ◽  
Acute Hypoxia ◽  
Pulmonary Arteries ◽  
Systolic Pressure ◽  
Arterial Remodeling ◽  
Ventricular Systolic Pressure ◽  
Intracellular Ca

Chronic hypoxia (CH) associated with respiratory disease results in elevated pulmonary vascular intracellular Ca2+ concentration, which elicits enhanced vasoconstriction and promotes vascular arterial remodeling and thus has important implications in the development of pulmonary hypertension (PH). Store-operated Ca2+ entry (SOCE) contributes to this elevated intracellular Ca2+ concentration and has also been linked to acute hypoxic pulmonary vasoconstriction (HPV). Since our laboratory has recently demonstrated an important role for acid-sensing ion channel 1 (ASIC1) in mediating SOCE, we hypothesized that ASIC1 contributes to both HPV and the development of CH-induced PH. To test this hypothesis, we examined responses to acute hypoxia in isolated lungs and assessed the effects of CH on indexes of PH, arterial remodeling, and vasoconstrictor reactivity in wild-type (ASIC1+/+) and ASIC1 knockout (ASIC1−/−) mice. Restoration of ASIC1 expression in pulmonary arterial smooth muscle cells from ASIC1−/− mice rescued SOCE, confirming the requirement for ASIC1 in this response. HPV responses were blunted in lungs from ASIC1−/− mice. Both SOCE and receptor-mediated Ca2+ entry, along with agonist-dependent vasoconstrictor responses, were diminished in small pulmonary arteries from control ASIC−/− mice compared with ASIC+/+ mice. The effects of CH to augment receptor-mediated vasoconstrictor and SOCE responses in vessels from ASIC1+/+ mice were not observed after CH in ASIC1−/− mice. In addition, ASIC1−/− mice exhibited diminished right ventricular systolic pressure, right ventricular hypertrophy, and arterial remodeling in response to CH compared with ASIC1+/+ mice. Taken together, these data demonstrate an important role for ASIC1 in both HPV and the development of CH-induced PH.

scholarly journals The Role of Collagen Synthesis in Ventricular and Vascular Adaptation to Hypoxic Pulmonary Hypertension

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
David Schreier ◽  
Timothy Hacker ◽  
Gouqing Song ◽  
Naomi Chesler
Keyword(s):  
Pulmonary Hypertension ◽  
Pulmonary Artery ◽  
Right Ventricular ◽  
Collagen Synthesis ◽  
Chronic Hypoxia ◽  
Coupling Efficiency ◽  
Pulmonary Arteries ◽  
Collagen Accumulation ◽  
The Impact ◽  
Rv Function

Pulmonary arterial hypertension (PAH) is a rapidly fatal disease in which mortality is typically due to right ventricular (RV) failure. An excellent predictor of mortality in PAH is proximal pulmonary artery stiffening, which is mediated by collagen accumulation in hypoxia-induced pulmonary hypertension (HPH) in mice. We sought to investigate the impact of limiting vascular and ventricular collagen accumulation on RV function and the hemodynamic coupling efficiency between the RV and pulmonary vasculature. Inbred mice were exposed to chronic hypoxia for 10 days with either no treatment (HPH) or with treatment with a proline analog that impairs collagen synthesis (CHOP-PEG; HPH + CP). Both groups were compared to control mice (CTL) exposed only to normoxia (no treatment). An admittance catheter was used to measure pressure-volume loops at baseline and during vena cava occlusion, with mice ventilated with either room air or 8% oxygen, from which pulmonary hemodynamics, RV function, and ventricular-vascular coupling efficiency (ηvvc) were calculated. Proline analog treatment limited increases in RV afterload (neither effective arterial elastance Ea nor total pulmonary vascular resistance significantly increased compared to CTL with CHOP-PEG), limited the development of pulmonary hypertension (CHOP-PEG reduced right ventricular systolic pressure by 10% compared to HPH, p < 0.05), and limited RV hypertrophy (CHOP-PEG reduced RV mass by 18% compared to HPH, p < 0.005). In an acutely hypoxic state, treatment improved RV function (CHOP-PEG increased end-systolic elastance Ees by 43%, p < 0.05) and maintained ηvvc at control, room air levels. CHOP-PEG also decreased lung collagen content by 12% measured biochemically compared to HPH (p < 0.01), with differences evident in large and small pulmonary arteries by histology. Our results demonstrate that preventing new collagen synthesis limits pulmonary hypertension development by reducing collagen accumulation in the pulmonary arteries that affect RV afterload. In particular, the proline analog limited structural and functional changes in distal pulmonary arteries in this model of early and somewhat mild pulmonary hypertension. We conclude that collagen plays an important role in small pulmonary artery remodeling and, thereby, affects RV structure and function changes induced by chronic hypoxia.

scholarly journals CREB depletion in smooth muscle cells promotes medial thickening, adventitial fibrosis and elicits pulmonary hypertension

2020 ◽  
Vol 10 (2) ◽  
pp. 204589401989837 ◽  
Author(s):  
Chrystelle V. Garat ◽  
Susan M. Majka ◽  
Timothy M. Sullivan ◽  
Joseph T. Crossno ◽  
Jane E.B. Reusch ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Smooth Muscle ◽  
Pulmonary Artery ◽  
Smooth Muscle Cells ◽  
Right Ventricular ◽  
Chronic Hypoxia ◽  
Pulmonary Arteries ◽  
Systolic Pressure ◽  
Muscle Cells

Levels of the cAMP-responsive transcription factor, CREB, are reduced in medial smooth muscle cells in remodeled pulmonary arteries from hypertensive calves and rats with chronic hypoxia-induced pulmonary hypertension. Here, we show that chronic hypoxia fails to promote CREB depletion in pulmonary artery smooth muscle cells or elicit significant remodeling of the pulmonary arteries in mice, suggesting that sustained CREB expression prevents hypoxia-induced pulmonary artery remodeling. This hypothesis was tested by generating mice, in which CREB was ablated in smooth muscle cells. Loss of CREB in smooth muscle cells stimulated pulmonary artery thickening, right ventricular hypertrophy, profound adventitial collagen deposition, recruitment of myeloid cells to the adventitia, and elevated right ventricular systolic pressure without exposure to chronic hypoxia. Isolated murine CREB-null smooth muscle cells exhibited serum-independent proliferation and hypertrophy in vitro and medium conditioned by CREB-null smooth muscle cells stimulated proliferation and expression of extracellular matrix proteins by adventitial fibroblasts. We conclude that CREB governs the pathologic switch from homeostatic, quiescent smooth muscle cells to proliferative, synthetic cells that drive arterial remodeling contributing to the development or pulmonary hypertension.

Abstract 12873: Clonal Hematopoiesis With JAK2V617F Promotes Pulmonary Hypertension Through ALK1

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Yusuke KIMISHIMA ◽  
Tomofumi Misaka ◽  
Tetsuro Yokokawa ◽  
Kento Wada ◽  
Koki Ueda ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Pulmonary Hypertension ◽  
Right Ventricular ◽  
Chronic Hypoxia ◽  
Myeloproliferative Neoplasms ◽  
Clonal Hematopoiesis ◽  
Stat3 Phosphorylation ◽  
Clinical Scenarios ◽  
Pulmonary Arterial ◽  
The Impact

Rationale: Pulmonary hypertension (PH) is associated with hematological disorders by unclear multifactorial mechanisms. JAK2 V617F is the most frequent driver mutation among the myeloproliferative neoplasms and is recently identified in clonal hematopoiesis. However, the impact of clonal hematopoiesis on PH remains unknown. Objectives: To elucidate the mechanistic relevance of hematopoietic JAK2V617F in the development of PH. Methods: We applied experimental mouse models, mimicking hematological clinical scenarios using Jak2 V617F-transgenic (JAK2 V617F ) mice and recipient mice transplanted with JAK2 V617F bone marrow cells (JAK2 V617F recipients), exposed to chronic hypoxia to induce PH. The presence of JAK2 V617F was also examined prospectively in PH patients. Measurements and Main Results: Increases in right ventricular systolic pressure and right ventricular hypertrophy accompanied by pulmonary arterial structural remodeling after exposure to chronic hypoxia were significantly exacerbated in both JAK2 V617F mice which showed a myeloproliferative neoplasm-phenotype and JAK2 V617F recipients which modeled clonal hematopoiesis compared to corresponding controls. JAK2V617F-expressing neutrophils were specifically accumulated in pulmonary arterial regions, accompanied by increases in neutrophil-derived elastase activity and chemokines. RNA sequencing identified progressive upregulation of Acvrl1 (encoding ALK1) during the differentiation from bone marrow stem/progenitor cells peripherally into mature neutrophils of pulmonary arterial regions in the enrichment of JAK-STAT-related molecules by JAK2V617F. JAK2V617F-mediated STAT3 phosphorylation upregulated ALK1-Smad1/5/8 signaling. Strikingly, ALK1 inhibition completely rescued the development of PH in JAK2 V617F mice. Furthermore, clonal hematopoiesis with JAK2 V617F was significantly more common in PH patients than in healthy subjects. Conclusions: Our study reveals clonal hematopoiesis with JAK2V617F as a crucial factor that causally leads to PH through ALK1.

Protoporphyrin IX generation from δ-aminolevulinic acid elicits pulmonary artery relaxation and soluble guanylate cyclase activation

2006 ◽  
Vol 291 (3) ◽  
pp. L337-L344 ◽  
Author(s):  
Christopher J. Mingone ◽  
Sachin A. Gupte ◽  
Joseph L. Chow ◽  
Mansoor Ahmad ◽  
Nader G. Abraham ◽  
...  
Keyword(s):  
Guanylate Cyclase ◽  
Vascular Function ◽  
Soluble Guanylate Cyclase ◽  
Aminolevulinic Acid ◽  
Pulmonary Arteries ◽  
Protoporphyrin Ix ◽  
Physiological Mechanism ◽  
No Donor ◽  
Vasp Phosphorylation ◽  
Guanylate Cyclase Activation

Protoporphyrin IX is an activator of soluble guanylate cyclase (sGC), but its role as an endogenous regulator of vascular function through cGMP has not been previously reported. In this study we examined whether the heme precursor δ-aminolevulinic acid (ALA) could regulate vascular force through promoting protoporphyrin IX-elicited activation of sGC. Exposure of endothelium-denuded bovine pulmonary arteries (BPA) in organoid culture to increasing concentrations of the heme precursor ALA caused a concentration-dependent increase in BPA epifluorescence, consistent with increased tissue protoporphyrin IX levels, associated with decreased force generation to increasing concentrations of serotonin. The force-depressing actions of 0.1 mM ALA were associated with increased cGMP-associated vasodilator-stimulated phosphoprotein (VASP) phosphorylation and increased sGC activity in homogenates of BPA cultured with ALA. Increasing iron availability with 0.1 mM FeSO4 inhibited the decrease in contraction to serotonin and increase in sGC activity caused by ALA, associated with decreased protoporphyrin IX and increased heme. Chelating endogenous iron with 0.1 mM deferoxamine increased the detection of protoporphyrin IX and force depressing activity of 10 μM ALA. The inhibition of sGC activation with the heme oxidant 10 μM 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) attenuated the force depressing actions of an NO donor without altering the actions of ALA. Thus control of endogenous formation of protoporphyrin IX from ALA by the availability of iron is potentially a novel physiological mechanism of controlling vascular function through regulating the activity of sGC.

The distribution of the obstruction in the pulmonary arteries modifies pulsatile right ventricular afterload in pulmonary hypertension

2015 ◽  
Vol 181 ◽  
pp. 232-234 ◽  
Author(s):  
Maria J. Ruiz-Cano ◽  
J.C. Grignola ◽  
Joan A. Barberá ◽  
S. Garcia Garcia ◽  
M. Lázaro Salvador ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Right Ventricular ◽  
Pulmonary Arteries ◽  
Right Ventricular Afterload ◽  
Ventricular Afterload

Abstract 15303: Dimethylarginine Dimethylaminohydrolase-1 is Not Involved in Chronic Hypoxic Pulmonary Hypertension and Right Ventricular Hypertrophy in Mice

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Juliane Hannemann ◽  
Antonia Glatzel ◽  
Jonas Hillig ◽  
Julia Zummack ◽  
Rainer H Boeger
Keyword(s):  
Pulmonary Hypertension ◽  
Right Ventricular ◽  
Ventricular Hypertrophy ◽  
Chronic Hypoxia ◽  
Right Ventricular Hypertrophy ◽  
Cardiomyocyte Hypertrophy ◽  
No Production ◽  
Knock Out ◽  
Knock Out Mice ◽  
Adma Concentration

Introduction: Chronic hypoxia causes persistent pulmonary vasoconstriction and leads to pulmonary hypertension and right ventricular hypertrophy. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of NO synthesis; its level increases in hypoxia concomitantly with reduced activity of dimethylarginine dimethylaminohydrolases (DDAH-1 and DDAH-2), the enzymes metabolizing ADMA. DDAH knockout models may therefore help to understand the pathophysiological roles of this enzyme and its substrate, ADMA, in the development of hypoxia-associated pulmonary hypertension. Hypothesis: We hypothesized that DDAH1 knock-out mice have an attenuated hypoxia-induced elevation of ADMA and reduced right ventricular hypertrophy. Methods: DDAH1 knock-out mice (KO) and their wild-type littermates (WT) were subjected to normoxia (NX) or hypoxia (HX) during 21 days. We measured ADMA concentration in plasma, DDAH1 and DDAH2 expression in the lung, right ventricular hypertrophy by the Fulton index, cardiomyocyte hypertrophy by dystrophin staining of heart tissues, and muscularization of pulmonary arterioles by CD31 and α-actin staining of lung sections. Results: DDAH1 KO mice had higher ADMA concentration than WT under NX (2.31±0.33 μmol/l vs. 1.20±0.17 μmol/l; p < 0.05). ADMA significantly increased in WT-HX (to 1.74±0.86 μmol/l; p < 0.05 vs. normoxia), whilst it did not further increase in KO-HX (2.58±0.58 μmol/l; p = n.s.). This was paralleled by a 38±13% reduction in DDAH1 mRNA but not DDAH2 mRNA expression, and reduced DDAH protein expression. We observed right ventricular hypertrophy under hypoxia in both, WT and KO mice, with no significant differences between both genotypes. Further, cardiomyocyte hypertrophy and pulmonary arteriolar muscularization were significantly increased by hypoxia, but not significantly different between WT and KO mice. Conclusions: We conclude that chronic hypoxia causes an elevation of ADMA, which impairs NO production and leads to endothelial dysfunction and vasoconstriction. Downregulation of DDAH expression and activity may be involved in this; however, knockout of DDAH1 does not modify the pathophysiological changes in remodeling of the pulmonary vasculature and the right ventricle.

scholarly journals Chronic Hypoxia Decreases Endothelial Connexin 40, Attenuates Endothelium‐Dependent Hyperpolarization–Mediated Relaxation in Small Distal Pulmonary Arteries, and Leads to Pulmonary Hypertension

2020 ◽  
Vol 9 (24) ◽  
Author(s):  
Rui Si ◽  
Qian Zhang ◽  
Jody Tori O. Cabrera ◽  
Qiuyu Zheng ◽  
Atsumi Tsuji‐Hosokawa ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Pulmonary Hypertension ◽  
Right Ventricular ◽  
Knockout Mice ◽  
Chronic Hypoxia ◽  
Systolic Pressure ◽  
Right Ventricular Systolic Pressure ◽  
Ventricular Systolic Pressure ◽  
Pulmonary Endothelial Cells ◽  
Endothelium Dependent Relaxation

Background Abnormal endothelial function in the lungs is implicated in the development of pulmonary hypertension; however, there is little information about the difference of endothelial function between small distal pulmonary artery (PA) and large proximal PA and their contribution to the development of pulmonary hypertension. Herein, we investigate endothelium‐dependent relaxation in different orders of PAs and examine the molecular mechanisms by which chronic hypoxia attenuates endothelium‐dependent pulmonary vasodilation, leading to pulmonary hypertension. Methods and Results Endothelium‐dependent relaxation in large proximal PAs (second order) was primarily caused by releasing NO from the endothelium, whereas endothelium‐dependent hyperpolarization (EDH)–mediated vasodilation was prominent in small distal PAs (fourth–fifth order). Chronic hypoxia abolished EDH‐mediated relaxation in small distal PAs without affecting smooth muscle–dependent relaxation. RNA‐sequencing data revealed that, among genes related to EDH, the levels of Cx37 , Cx40 , Cx43 , and IK were altered in mouse pulmonary endothelial cells isolated from chronically hypoxic mice in comparison to mouse pulmonary endothelial cells from normoxic control mice. The protein levels were significantly lower for connexin 40 (Cx40) and higher for connexin 37 in mouse pulmonary endothelial cells from hypoxic mice than normoxic mice. Cx40 knockout mice exhibited significant attenuation of EDH‐mediated relaxation and marked increase in right ventricular systolic pressure. Interestingly, chronic hypoxia led to a further increase in right ventricular systolic pressure in Cx40 knockout mice without altering EDH‐mediated relaxation. Furthermore, overexpression of Cx40 significantly decreased right ventricular systolic pressure in chronically hypoxic mice. Conclusions These data suggest that chronic hypoxia‐induced downregulation of endothelial Cx40 results in impaired EDH‐mediated relaxation in small distal PAs and contributes to the development of pulmonary hypertension.

scholarly journals Exogenous Ghrelin Attenuates the Progression of Chronic Hypoxia-Induced Pulmonary Hypertension in Conscious Rats

Endocrinology ◽  
2007 ◽  
Vol 149 (1) ◽  
pp. 237-244 ◽  
Author(s):  
Daryl O. Schwenke ◽  
Takeshi Tokudome ◽  
Mikiyasu Shirai ◽  
Hiroshi Hosoda ◽  
Takeshi Horio ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Pulmonary Hypertension ◽  
Right Ventricular ◽  
Endothelial Nitric Oxide Synthase ◽  
Ventricular Hypertrophy ◽  
Chronic Hypoxia ◽  
Right Ventricular Hypertrophy ◽  
Pulmonary Arterial ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide

Chronic exposure to hypoxia, a common adverse consequence of most pulmonary disorders, can lead to a sustained increase in pulmonary arterial pressure (PAP), right ventricular hypertrophy, and is, therefore, closely associated with heart failure and increased mortality. Ghrelin, originally identified as an endogenous GH secretagogue, has recently been shown to possess potent vasodilator properties, likely involving modulation of the vascular endothelium and its associated vasoactive peptides. In this study we hypothesized that ghrelin would impede the pathogenesis of pulmonary arterial hypertension during chronic hypoxia (CH). PAP was continuously measured using radiotelemetry, in conscious male Sprague Dawley rats, in normoxia and during 2-wk CH (10% O2). During this hypoxic period, rats received a daily sc injection of either saline or ghrelin (150 μg/kg). Subsequently, heart and lung samples were collected for morphological, histological, and molecular analyses. CH significantly elevated PAP in saline-treated rats, increased wall thickness of peripheral pulmonary arteries, and, consequently, induced right ventricular hypertrophy. In these rats, CH also led to the overexpression of endothelial nitric oxide synthase mRNA and protein, as well as endothelin-1 mRNA within the lung. Exogenous ghrelin administration attenuated the CH-induced overexpression of endothelial nitric oxide synthase mRNA and protein, as well as endothelin-1 mRNA. Consequently, ghrelin significantly attenuated the development of pulmonary arterial hypertension, pulmonary vascular remodeling, and right ventricular hypertrophy. These results demonstrate the therapeutic benefits of ghrelin for impeding the pathogenesis of pulmonary hypertension and right ventricular hypertrophy, particularly in subjects prone to CH (e.g. pulmonary disorders).

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