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The PPAR? ligand rosiglitazone attenuates hypoxia-induced endothelin signaling in vitro and in vivo.

ABSTRACT: Peroxisome proliferator-activated receptor (PPAR) ? activation attenuates hypoxia-induced pulmonary hypertension (PH) in mice. The current study examined the hypothesis that PPAR? attenuates hypoxia-induced endothelin-1 (ET-1) signaling to mediate these therapeutic effects. To test this hypothesis, human pulmonary artery endothelial cells (HPAECs) were exposed to normoxia or hypoxia (1% O(2)) for 72 h and treated with or without the PPAR? ligand rosiglitazone (RSG, 10 ?M) during the final 24 h of exposure. HPAEC proliferation was measured with MTT assays or cell counting, and mRNA and protein levels of ET-1 signaling components were determined. To explore the role of hypoxia-activated transcription factors, selected HPAECs were treated with inhibitors of hypoxia-inducible factor (HIF)-1? (chetomin) or nuclear factor (NF)-?B (caffeic acid phenethyl ester, CAPE). In parallel studies, male C57BL/6 mice were exposed to normoxia (21% O(2)) or hypoxia (10% O(2)) for 3 wk with or without gavage with RSG (10 mg·kg(-1)·day(-1)) for the final 10 days of exposure. Hypoxia increased ET-1, endothelin-converting enzyme-1, and endothelin receptor A and B levels in mouse lung and in HPAECs and increased HPAEC proliferation. Treatment with RSG attenuated hypoxia-induced activation of HIF-1?, NF-?B activation, and ET-1 signaling pathway components. Similarly, treatment with chetomin or CAPE prevented hypoxia-induced increases in HPAEC ET-1 mRNA and protein levels. These findings indicate that PPAR? activation attenuates a program of hypoxia-induced ET-1 signaling by inhibiting activation of hypoxia-responsive transcription factors. Targeting PPAR? represents a novel therapeutic strategy to inhibit enhanced ET-1 signaling in PH pathogenesis.

SUBMITTER: Kang BY

PROVIDER: S-EPMC3233829 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature

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The PPARγ ligand rosiglitazone attenuates hypoxia-induced endothelin signaling in vitro and in vivo.

Kang Bum-Yong BY Kleinhenz Jennifer M JM Murphy Tamara C TC Hart C Michael CM

American journal of physiology. Lung cellular and molecular physiology 20110916 6

Peroxisome proliferator-activated receptor (PPAR) γ activation attenuates hypoxia-induced pulmonary hypertension (PH) in mice. The current study examined the hypothesis that PPARγ attenuates hypoxia-induced endothelin-1 (ET-1) signaling to mediate these therapeutic effects. To test this hypothesis, human pulmonary artery endothelial cells (HPAECs) were exposed to normoxia or hypoxia (1% O(2)) for 72 h and treated with or without the PPARγ ligand rosiglitazone (RSG, 10 μM) during the final 24 h o ...[more]

PMID: 21926265

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Project description:The Notch signaling pathway participates in pulmonary artery smooth muscle cell (PASMC) proliferation and apoptosis. Astragaloside IV (AS‑IV) is an effective antiproliferative treatment for vascular diseases. The present study aimed to investigate the protective effects and mechanisms underlying AS‑IV on hypoxia‑induced PASMC proliferation and pulmonary vascular remodeling in pulmonary arterial hypertension (PAH) model rats. Rats were divided into the following four groups: i) normoxia; ii) hypoxia (10% O2); iii) treatment, hypoxia + intragastrical administration of AS‑IV (2 mg/kg) daily for 28 days; and iv) DAPT, hypoxia + AS‑IV treatment + subcutaneous administration of DAPT (10 mg/kg) three times daily. The effects of AS‑IV treatment on the development of hypoxia‑induced PAH, right ventricle (RV) hypertrophy and pulmonary vascular remodeling were examined. Furthermore, PASMCs were treated with 20 µmol/l AS‑IV under hypoxic conditions for 48 h. To determine the effect of Notch signaling in vascular remodeling and the potential mechanisms underlying AS‑IV treatment, 5 mmol/l γ‑secretase inhibitor [N‑[N‑(3,5‑difluorophenacetyl)‑L‑alanyl]‑S‑phenylglycine t‑butyl ester (DAPT)] was used. Cell viability and apoptosis were determined by performing the MTT assay and flow cytometry, respectively. Immunohistochemistry was conducted to detect the expression of proliferating cell nuclear antigen (PCNA). Moreover, the mRNA and protein expression levels of Notch‑3, Jagged‑1, hes family bHLH transcription factor 5 (Hes‑5) and PCNA were measured via reverse transcription‑quantitative PCR and western blotting, respectively. Compared with the normoxic group, hypoxia‑induced PAH model rats displayed characteristics of PAH and RV hypertrophy, whereas AS‑IV treatment alleviated PAH and prevented RV hypertrophy. AS‑IV also inhibited hypoxia‑induced pulmonary vascular remodeling, as indicated by reduced wall thickness and increased lumen diameter of pulmonary arterioles, and decreased muscularization of distal pulmonary vasculature in hypoxia‑induced PAH model rats. Compared with normoxia, hypoxia promoted PASMC proliferation in vitro, whereas AS‑IV treatment inhibited hypoxia‑induced PASMC proliferation by downregulating PCNA expression in vitro and in vivo. In hypoxia‑treated PAH model rats and cultured PASMCs, AS‑IV treatment reduced the expression levels of Jagged‑1, Notch‑3 and Hes‑5. Furthermore, Notch signaling inhibition via DAPT significantly inhibited the pulmonary vascular remodeling effect of AS‑IV in vitro and in vivo. Collectively, the results indicated that AS‑IV effectively reversed hypoxia‑induced pulmonary vascular remodeling and PASMC proliferation via the Notch signaling pathway. Therefore, the present study provided novel insights into the mechanism underlying the use of AS‑IV for treatment of vascular diseases, such as PAH.

Project description:BackgroundPulmonary edema is one of the pathological characteristics of acute respiratory distress syndrome (ARDS). The epithelial sodium channel (ENaC) is thought to be the rate-limiting factor for alveolar fluid clearance (AFC) during pulmonary edema. The peroxisome proliferator-activated receptor γ (PPARγ) agonist rosiglitazone was shown to stimulate ENaC-mediated salt absorption in the kidney. However, its role in the lung remains unclear. Here, we investigated the role of the PPARγ agonist in the lung to find out whether it can regulate AFC during acute lung injury (ALI). We also attempted to elucidate the mechanism for this.MethodsOur ALI model was established through intratracheal instillation of lipopolysaccharide (LPS) in C57BL/6 J mice. The mice were randomly divided into 4 groups of 10. The control group underwent a sham operation and received an equal quantity of saline. The three experimental groups underwent intratracheal instillation of 5 mg/kg LPS, followed by intraperitoneal injection of 4 mg/kg rosiglitazone, 4 mg/kg rosiglitazone plus 1 mg/kg GW9662, or only equal quantity of saline. The histological morphology of the lung, the levels of TNF-α and IL-1β in the bronchoalveolar lavage fluid (BALF), the level of AFC, and the expressions of αENaC and serum and glucocorticoid-induced kinase-1 (SGK1) were determined. Type 2 alveolar (AT II) cells were incubated with rosiglitazone (15 μM) with or without GW9662 (10 μM). The expressions of αENaC and SGK1 were determined 24 h later.ResultsA mouse model of ALI was successfully established. Rosiglitazone significantly ameliorated the lung injury, decreasing the TNF-α and IL-1β levels in the BALF, enhancing AFC, and promoting the expressions of αENaC and SGK1 in ALI mice, which were abolished by the specific PPARγ blocker GW9662. In vitro, rosiglitazone increased the expressions of αENaC and SGK1. This increase was prevented by GW9662.ConclusionsRosiglitazone ameliorated the lung injury and promoted ENaC-mediated AFC via a PPARγ/SGK1-dependent signaling pathway, alleviating pulmonary edema in a mouse model of ALI.

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The PPAR? ligand rosiglitazone attenuates hypoxia-induced endothelin signaling in vitro and in vivo.

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The PPARγ ligand rosiglitazone attenuates hypoxia-induced endothelin signaling in vitro and in vivo.

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