Dexin Zhang

Heme oxygenase‐1/p21WAF1 mediates peroxisome proliferator‐activated receptor‐γ signaling inhibition of proliferation of rat pulmonary artery smooth muscle cells

Activation of peroxisome proliferator‐activated receptor (PPAR)‐γ suppresses proliferation of rat pulmonary artery smooth muscle cells (PASMCs), and therefore ameliorates the development of pulmonary hypertension in animal models. However, the molecular mechanisms underlying this effect remain largely unknown. This study addressed this issue. The PPARγ agonist rosiglitazone dose‐dependently stimulated heme oxygenase (HO)‐1 expression in PASMCs, 5 μm rosiglitazone inducing a 12.1‐fold increase in the HO‐1 protein level. Cells pre‐exposed to rosiglitazone showed a dose‐dependent reduction in proliferation in response to serotonin; this was abolished by pretransfection of cells with sequence‐specific small interfering RNA against HO‐1. In addition, rosiglitazone stimulated p21WAF1 expression in PASMCs, a 2.34‐fold increase in the p21WAF1 protein level being achieved with 5 μm rosiglitazone; again, this effect was blocked by knockdown of HO‐1. Like loss of HO‐1, loss of p21WAF1 through siRNA transfection also reversed the inhibitory effect of rosiglitazone on PASMC proliferation triggered by serotonin. Taken together, our findings suggest that activation of PPARγ induces HO‐1 expression, and that this in turn stimulates p21WAF1 expression to suppress PASMC proliferation. Our study also indicates that rosiglitazone, a medicine widely used in the treatment of type 2 diabetes mellitus, has potential benefits for patients with pulmonary hypertension.

Activation of PPAR-γ ameliorates pulmonary arterial hypertension via inducing heme oxygenase-1 and p21WAF1: An in vivo study in rats

AIMS Our previous study has indicated that activation of PPAR-γ inhibits the proliferation of rat pulmonary artery smooth muscle cells (PASMCs) in vitro through inducing the expression of heme oxygenase-1 (HO-1), which in turn up-regulates the p21(WAF1) expression. In the present study, we intended to determine whether similar mechanisms have been involved in activation of PPAR-γ inhibition of development of rat PAH model. MATERIAL AND METHODS Rat pulmonary arterial hypertension (PAH) model was established by subcutaneous injection of monocrotaline (MCT). Rosiglitazone was administered to activate PPAR-γ. Zinc protoporphyria IX (ZnPP-IX), was used to confirm the role of HO-1 in mediating PPAR-γ function. Parameters including the right ventricle systolic pressure (RVSP), the right ventricular hypertrophy (RVH) and the percentage of medial wall thickness were used to evaluate the development of PAH. Immunoblotting was used to determine the expression of HO-1 and p21(WAF1). KEY FINDINGS Rosiglitazone significantly decreased the RVSP and inhibited the RVH in MCT-induced rat PAH model, and partially inhibited the pulmonary vascular remodeling. These effects were coupled with the sequential increase of HO-1 and p21(WAF1) expressions by rosiglitazone. SIGNIFICANCE Activation of PPAR-γ benefits PAH by inhibiting proliferation of PASMCs and reducing pulmonary vascular remodeling. The present study suggests that enhancing PPAR-γ activity might have potential value in clinical treatment of PAH.

Statins inhibit pulmonary artery smooth muscle cell proliferation by upregulation of HO-1 and p21WAF1

Simvastatin is a 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor, which has been shown to ameliorate the development of pulmonary hypertension in animal model by suppression of pulmonary artery smooth muscle cells (PASMCs) proliferation, yet its underlying molecular mechanisms are not completely understood. In this study, we show that simvastatin dose-dependently inhibited serotonin-stimulated PASMCs proliferation. This was accompanied with the parallel induction of heme oxyganase-1 (HO-1) and upregulation of p21WAF1. More importantly, we found that Tin-protoporphyrin (SnPP), a selective inhibitor of HO-1, could block the effect of simvastatin on inhibition of cell proliferation in response to serotonin and abolish simvastatin-induced p21WAF1 expression. The inhibitive effect of simvastatin on cell proliferation was also significantly suppressed by silencing p21WAF1 with siRNA transfection. The extent of effect of SnPP on inhibition of cell proliferation was similar to that of lack of p21WAF1 by siRNA transfection. Taken together, our study suggests that simvastatin inhibits PASMCs proliferation by sequential upregulation of HO-1 and p21WAF1 to benefit pulmonary hypertension.

The PPARγ agonist, rosiglitazone, attenuates airway inflammation and remodeling via heme oxygenase-1 in murine model of asthma

Aim:Rosiglitazone is one of the specific PPARγ agonists showing potential therapeutic effects in asthma. Though PPARγ activation was considered protective in inhibiting airway inflammation and remodeling in asthma, the specific mechanisms are still unclear. This study was aimed to investigate whether heme oxygenase-1 (HO-1) related pathways were involved in rosiglitazone-activated PPARγ signaling in asthma treatment.Methods:Asthma was induced in mice by multiple exposures to ovalbumin (OVA) in 8 weeks. Prior to every OVA challenge, the mice received rosiglitazone (5 mg/kg, po). After the mice were sacrificed, the bronchoalveolar lavage fluid (BALF), blood samples and lungs were collected for analyses. The activities of HO-1, MMP-2 and MMP-9 in airway tissue were assessed, and the expression of PPARγ, HO-1 and p21 proteins was also examined.Results:Rosiglitazone administration significantly attenuated airway inflammation and remodeling in mice with OVA-induced asthma, which were evidenced by decreased counts of total cells, eosinophils and neutrophils, and decreased levels of IL-5 and IL-13 in BALF, and by decreased airway smooth muscle layer thickness and reduced airway collagen deposition. Furthermore, rosiglitazone administration significantly increased PPARγ, HO-1 and p21 expression and HO-1 activity, decreased MMP-2 and MMP-9 activities in airway tissue. All the therapeutic effects of rosiglitazone were significantly impaired by co-administration of the HO-1 inhibitor ZnPP.Conclusion:Rosiglitazone effectively attenuates airway inflammation and remodeling in OVA- induced asthma of mice by activating PPARγ/HO-1 signaling pathway.

MiR-21 modulates human airway smooth muscle cell proliferation and migration in asthma through regulation of PTEN expression.

ABSTRACT Background: Asthma is characterized by airway remodeling arising from an increase in airway smooth muscle (ASM) mass. This increase is regulated in part by ASM cell proliferation and migration. MicroRNA (miR)-21 also plays a role in asthma, but the molecular mechanisms underlying its effects are not completely understood. This study investigated the effects and mechanism of miR-21 on the human ASM (HASM) cell proliferation and migration. Materials and Methods: HASM cells were transduced with a miR-21 vector, and the expression of miR-21 was determined by quantitative real-time polymerase chain reaction (qRT-PCR). The effect of the miR-21 on HASM cell proliferation and migration was analyzed by CCK8 and transwell assay. The expression level of PTEN (phosphatase and tensin homolog deleted on chromosome 10) in HASM cells was assessed by qRT-PCR and Western blot analysis. Meanwhile, the activity of PTEN was measured by PTEN malachite green assay kit. Results: Lentivirus-mediated miR-21 overexpression markedly enhanced the proliferation and migration of HASM cells (P < .05), and ablation of miR-21 by anti-miR-21 inhibitor markedly reduced cell proliferation and migration. We demonstrated that miR-21 overexpression significantly reduced the expression of PTEN (P < .05), while PTEN knock-down markedly increased HASM cell proliferation and migration. Furthermore, we found that overexpression of PTEN led to a decrease of HASM cell proliferation and migration. MiR-21 mediated HASM cell proliferation and migration through activation of the phosphoinositide 3-kinase pathway. Conclusions: This study provides the first in vitro evidence that overexpression of miR-21 in HASM cells can trigger cell proliferation and migration, and the effects of miR-21 depend on the level of PTEN.

Benefits of adding fluticasone propionate/salmeterol to tiotropium in COPD: a meta-analysis.

OBJECTIVE This meta-analysis was performed to evaluate the efficacy and safety of adding fluticasone propionate/salmeterol (FSC) to tiotropium (Tio) in COPD patients. METHODS A systematic search was made of MEDLINE, Cochrane, ISI Web of Science and SCOPUS databases, and a hand search of leading respiratory journals. Randomized clinical trials on treatment of stable COPD with the addition of FSC, compared with tiotropium alone, were reviewed. Studies were pooled to odds ratio (OR) and weighted mean differences (WMD), with 95% confidence interval (CI). RESULTS Six trials met the inclusion criteria. Compared with tiotropium, addition of FSC presented significant effects on trough forced expiratory volume in 1s (FEV1) (WMD 54.64 mL; 95% CI 51.76 to 57.52 mL; P<0.001), COPD exacerbations (OR 0.73; 95% CI 0.55 to 0.96; p=0.03), and health-related quality of life (WMD 4.63; 95% CI 4.26 to 5.01; P<0.001). No significant increase was noticed in adverse events in the Tio+FSC group (OR 1.24; 95% CI 0.98 to 1.57; p=0.07). CONCLUSIONS The addition of FSC to subjects with COPD treated with tiotropium significantly improves lung function, quality of life and COPD exacerbations without increasing the risk of adverse events.

Sildenafil inhibits calcineurin/NFATc2-mediated cyclin A expression in pulmonary artery smooth muscle cells.

AIMS To examine whether calcineurin/NFAT signaling pathway leads to proliferation of pulmonary artery smooth muscle cells (PASMCs) by regulating cell cycle proteins and whether the phosphodiesterase-5 (PDE5) inhibitor sildenafil affects calcineurin/NFAT-induced cell proliferation. MAIN METHODS A [(3)H]thymidine incorporation assay was used to examine DNA synthesis (cell proliferation); cyclin A and NFATc2 expressions were determined by Western blot. Cyclin-dependent kinase 2 (CDK2) activity was measured with an in vitro kinase activity assay, and calcineurin and NFAT activity were evaluated using a calcineurin assay kit and a luciferase activity assay, respectively. A chemical inhibitor or siRNA transfection was used to inhibit calcineurin/NFAT signaling pathway. KEY FINDINGS Serotonin dose-dependently stimulated cyclin A expression in PASMCs. This effect was accompanied by dose-dependent increases in CDK2 activity and the rate of DNA synthesis. At the same time, PASMCs treated with serotonin showed dose-dependent activation of calcineurin/NFAT signaling pathway. Inhibition of calcineurin activity by cyclosporine A or loss of NFATc2 protein by siRNA transfection abolished serotonin-induced cyclin A expression and consequent CDK2 activation and DNA synthesis. We further found that pretreatment of cells with sildenafil suppressed serotonin-triggered activation of calcineurin/NFATc2 signaling pathway and resultant cyclin A expression, CDK2 activation and cell proliferation, while the presence of DT-3 [a specific protein kinase G (PKG) peptide inhibitor] reversed the effects of sildenafil on PASMCs. SIGNIFICANCE Our study suggests that enhanced PKG activity suppresses calcineurin/NFATc2 cascade-mediated cyclin A expression, CDK2 activation and PASMC proliferation to contribute to the overall effects of sildenafil in the treatment of pulmonary hypertension.

PPAR-γ inhibits IL-13-induced collagen production in mouse airway fibroblasts

Interleukin-13 (IL-13) plays an important role in extracellular matrix production of airway remodeling in asthma. Activation of PPAR-γ has been shown to inhibit the occurrence of airway fibrosis in asthma, yet it remains unknown whether the effect of PPAR-γ on suppression of airway fibrosis is associated with the inhibition of IL-13 signaling. In the present study, primary cultured airway fibroblasts were stimulated with IL-13, and JAK inhibitor, PDGF receptor blocker and MEK inhibitor were applied to investigate the involvement of these pathways in IL-13-induced collagen production. Our results demonstrate that IL-13 dose- and time-dependently induced collagen production in primary cultured mouse airway fibroblasts; this effect was blocked by inhibition of JAK/STAT6 signal pathway. IL-13 also stimulated JAK/STAT6-dependent PDGF production, elevation of PDGF in turn activated ERK1/2 MAPK and caused collagen production. Activation of PPAR-γ by rosiglitazone reduced IL-13-induced collagen expression by suppression of STAT6-driven PDGF production. Our results indicate that activation of JAK/STAT6 signal and subsequent PDGF generation and ERK1/2 MAPK activation mediate IL-13-induced collagen production in airway fibroblasts. This study suggests that activation of PPAR-γ might be a novel strategy for the treatment of asthma partially by inhibition of airway fibrosis.