Adiponectin decreases pulmonary arterial remodeling in murine models of pulmonary hypertension - PubMed (original) (raw)

Adiponectin decreases pulmonary arterial remodeling in murine models of pulmonary hypertension

Meiqian Weng et al. Am J Respir Cell Mol Biol. 2011 Aug.

Abstract

Remodeling of the pulmonary arteries is a common feature among the heterogeneous disorders that cause pulmonary hypertension. In these disorders, the remodeled pulmonary arteries often demonstrate inflammation and an accumulation of pulmonary artery smooth muscle cells (PASMCs) within the vessels. Adipose tissue secretes multiple bioactive mediators (adipokines) that can influence both inflammation and remodeling, suggesting that adipokines may contribute to the development of pulmonary hypertension. We recently reported on a model of pulmonary hypertension induced by vascular inflammation, in which a deficiency of the adipokine adiponectin (APN) was associated with the extensive proliferation of PASMCs and increased pulmonary artery pressures. Based on these data, we hypothesize that APN can suppress pulmonary hypertension by directly inhibiting the proliferation of PASMCs. Here, we tested the effects of APN overexpression on pulmonary arterial remodeling by using APN-overexpressing mice in a model of pulmonary hypertension induced by inflammation. Consistent with our hypothesis, mice that overexpressed APN manfiested reduced pulmonary hypertension and remodeling compared with wild-type mice, despite developing similar levels of pulmonary vascular inflammation in the model. The overexpression of APN was also protective in a hypoxic model of pulmonary hypertension. Furthermore, APN suppressed the proliferation of PASMCs, and reduced the activity of the serum response factor-serum response element pathway, which is a critical signaling pathway for smooth muscle cell proliferation. Overall, these data suggest that APN can regulate pulmonary hypertension and pulmonary arterial remodeling through its direct effects on PASMCs. Hence, the activation of APN-like activity in the pulmonary vasculature may be beneficial in pulmonary hypertension.

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Figures

Figure 1.

Overexpression of adiponectin (APN) reduces pulmonary vascular remodeling. (A) Representative hematoxylin and eosin–stained lung sections from wild-type mice (i, ×40 magnification; iii, ×200 magnification) and ΔGly-APN mice (ii, ×40 magnification; iv, ×200 magnification) after ovalbumin (OVA) immunization and challenge (n = 7–8 mice per group). Arrows indicate pulmonary arteries. Bars, 100 μm. (B) Representative α-smooth muscle cell actin staining of a lung section from a wild-type mouse (i, ×200 magnification) and ΔGly-APN mouse (ii, ×400 magnification) after OVA immunization and challenge. Arrows indicate pulmonary arteries. Bars, 100 μm. (C) Vessel medial wall thickness (percentage of total) in medium and small pre-acinar blood vessels in lung sections from wild-type (circles) and ΔGly-APN (squares) mice after OVA immunization and challenge (n = 7–8 mice per group).

Figure 2.

APN overexpression inhibits the development of pulmonary hypertension. (A) Right ventricular systolic pressure (RVSP) in wild-type and ΔGly-APN mice measured after OVA immunization and OVA or PBS challenges. Circles, squares, triangles and inverse triangles indicate data from wild-type PBS, wild-type OVA, ΔGly-APN PBS, and ΔGly-APN OVA mice, respectively (n = 4–10 mice per group). (B) RVSP in wild-type and ΔGly-APN mice measured after 3 weeks of hypoxia. Squares and triangles indicate data from wild-type hypoxia mice and ΔGly-APN hypoxia mice, respectively (n = 8 mice per group).

Figure 3.

APN overexpression does not affect inflammation. (A and B) Percentage and number of mononuclear cells (Mono), neutrophils (PMN), and eosinophils (Eos) in bronchoalveolar lavage (BAL) fluid of wild-type and ΔGly-APN mice after OVA immunization and challenge (n = 8 mice per group). (C and D) Percentage and number of lymphocyte subsets in BAL fluid of wild-type and ΔGly-APN mice after OVA immunization and challenge (n = 8 mice per group). Chemokine (E) and growth factor (F) RNA expression in lungs of wild-type and ΔGly-APN mice after OVA immunization and challenge, expressed as copy number of indicated transcripts, divided by number of copies of the housekeeping gene β2-microglobulin (n = 8 mice per group). CCL, chemokine (C-C motif) ligand; PDGF-A, platelet-derived growth factor isoform A; PDGF-B, platelet-derived growth factor isoform B; PAI-I, plasminogen activator inhibitor 1; CTGF, connective tissue growth factor; TGFβ, transforming growth factor beta; EGF, vascular endothelial growth factor.

Figure 4.

APN reduces the proliferation of pulmonary artery smooth muscle cells (PASMCs). (A) Western blot of protein isolated from PASMCs after incubation with APN or PBS and staining with the indicated antibodies. Data shown are from one of three independent experiments. (B) Proliferation of PASMCs after 72 hours of stimulation under the indicated conditions, as measured by a fluorescent assay. Each condition was performed in triplicate. PASMCs were prepared from three wild-type mice (*P < 0.05). (C) Western blot of lung protein extracts prepared from OVA-challenged wild-type, ΔGly-APN, and APN-deficient (APN−/−) mice, and stained with the indicated antibodies. The experiment was repeated three times. (D) Adiponectin protein concentrations in the lungs of OVA-challenged wild-type and ΔGly-APN mice were assayed by densitometry of Western blots (expressed as density ratio between APN band and α-actin band) and protein ELISA (n = 3–4 samples per group). (E) Proliferation of PASMCs after 72 hours of stimulation with lung protein extracts from OVA-challenged wild-type and ΔGly-APN mice, as measured by a fluorescent assay. Each condition was performed in triplicate, using four mice per group for lung samples. PASMCs were prepared from three wild-type mice (*P < 0.05).

Figure 5.

APN suppresses activity of serum response element (SRE) in PASMCs. (A) Relative luciferase activity (ratio of SRE–luciferase to Renilla–luciferase in each condition, compared with activity in PASMCs in serum-free conditions) in PASMCs after cotransfection with SRE–luciferase and Renilla–luciferase constructs and 6 hours of stimulation under the indicated conditions. Each condition was performed in duplicate, and the experiment was repeated three times. PASMCs were prepared from six wild-type mice. (B) Relative luciferase activity of PASMCs after cotransfection with SRE–luciferase and Renilla–luciferase constructs and 6 hours of stimulation with lung protein extracts from OVA-challenged wild-type and ΔGly-APN mice. Each condition was performed in duplicate, and the experiment was repeated three times. PASMCs were prepared from six wild-type mice.

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Adiponectin decreases pulmonary arterial remodeling in murine models of pulmonary hypertension - PubMed (original) (raw)