Yanting Zhu

LKB1/AMPK/mTOR signaling pathway in non-small-cell lung cancer.

Links between cancer and metabolism have been suggested for a long time but compelling evidence for this hypothesis came from the recent molecular characterization of the LKB1/AMPK signaling pathway as a tumor suppressor axis. Besides the discovery of somatic mutations in the LKB1 gene in certain type of cancers, a critical emerging point was that the LKB1/AMPK axis remains generally functional and could be stimulated by pharmacological molecules such as metformin in cancer cells. In addition, AMPK plays a central role in the control of cell growth, proliferation and autophagy through the regulation of mTOR activity, which is consistently deregulated in cancer cells. Targeting of AMPK/mTOR is thus an attractive strategy in the development of therapeutic agents against non-small-cell lung cancer (NSCLC). In this review, the LKB1/AMPK/mTOR signaling pathway is described, highlighting its protective role, and opportunities for therapeutic intervention, and clinical trials in NSCLC.

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.

Activation of AMPK inhibits PDGF-induced pulmonary arterial smooth muscle cells proliferation and its potential mechanisms

The aims of the present study were to examine signaling mechanisms for PDGF-induced pulmonary arterial smooth muscle cells (PASMC) proliferation and to determine the effect of AMPK activation on PDGF-induced PASMC proliferation and its underlying mechanisms. PDGF activated PI3K/Akt/mTOR signaling pathway, and this in turn up-regulated Skp2 and consequently reduced p27 leading to PASMC proliferation. Prior incubation of PASMC with metformin induced a dramatic AMPK activation and significantly blocked PDGF-induced cell proliferation. PASMC lacking AMPKα2 were resistant to the inhibitory effect of metformin on PDGF-induced cell proliferation. Metformin did not affect Akt activation but blocked mTOR phosphorylation in response to PDGF; these were accompanied by the reversion of Skp2 up-regulation and p27 reduction. Our study suggests that the activation of AMPK negatively regulates mTOR activity to suppress PASMC proliferation and therefore has a potential value in the prevention and treatment of pulmonary hypertension by negatively modulating pulmonary vascular remodeling.

Association between rhinovirus wheezing illness and the development of childhood asthma: a meta-analysis

Objective The relation between early-life rhinovirus (RV) wheezing illness and later onset of wheezing/asthma remains a subject of debate. Therefore, we conducted this meta-analysis to evaluate the association between RV wheezing illness in the first 3 years of life and the subsequent development of wheezing/asthma. Design Systematic review and meta-analysis. Methods The PubMed, EMBASE, Web of Science, Chinese National Knowledge Infrastructure (CNKI) and Wanfang databases were systematically searched for studies published between 1988 and February 2017, and additional studies were found by searching reference lists of relevant articles. 2 reviewers independently extracted data and assessed the quality of each study. Results were pooled using fixed-effect models or random-effects models as appropriate. Results The meta-analysis included 15 original articles which met the criteria, while 10 articles reported the results of 4 longitudinal cohort studies with different follow-up periods. RV wheezing illness in the first 3 years of life was associated with an increased risk of wheezing/asthma in later life (relative risk (RR)=2.00, 95% CI 1.62 to 2.49, p<0.001). In subgroup analysis by age at follow-up, the association still remained significant in <10 years (RR=2.02, 95% CI 1.70 to 2.39, p<0.001) and ≥10 years (RR=1.92, 95% CI 1.36 to 2.72, p<0.001). Conclusions The meta-analysis suggests an association between RV-induced wheezing in the first 3 years of life and the subsequent development of wheezing/asthma. Large-scale and well-designed studies that adequately address concerns for potential confounding factors are required to validate the risk identified in the current meta-analysis.

Platelet-derived growth factor mediates interleukin-13-induced collagen I production in mouse airway fibroblasts

Interleukin-13 (IL-13) is associated with the production of collagen in airway remodelling of asthma. Yet, the molecular mechanisms underlying IL-13 induction of collagen remain unclear; the aim of this study is to address this issue. IL-13 dose- and time-dependently-induced collagen I production in primary cultured airway fibroblasts; this was accompanied with the STAT6 phosphorylation, and pre-treatment of cells with JAK inhibitor suppressed IL-13-induced collagen I production. Further study indicated that IL-13 stimulated JAK/STAT6-dependent PDGF production and subsequent ERK1/2 MAPK activation in airway fibroblasts, and the presence of either PDGF receptor blocker or MEK inhibitor partially suppressed IL-13-induced collagen I production. Taken together, our study suggests that activation of JAK/STAT6 signal pathway and subsequent PDGF generation and resultant ERK1/2 MAPK activation mediated IL-13-induced collagen I production in airway fibroblasts.

Activation of Notch3 promotes pulmonary arterial smooth muscle cells proliferation via Hes1/p27Kip1 signaling pathway.

Activation of the Notch3 cascade is involved in the development of pulmonary arterial hypertension by stimulating the proliferation of vascular smooth muscle cells. However, the detailed molecular mechanisms underlying this effect are still unclear. The present study aims to address this issue. We demonstrated that over‐expression of intracellular domain of the Notch3 receptor (NICD3) by adenovirus transfection dramatically induced proliferation of primary cultured pulmonary artery smooth muscle cells. This was accompanied with up‐regulation of Hes1 protein and down‐regulation of p27Kip1 protein. More importantly, we observed that prior silencing of Hes1 with siRNA blocked NICD3 over‐expression‐induced p27Kip1 reduction and cell proliferation. The present study suggests that Hes1 lies downstream of NICD3 and particularly mediates Notch3 signaling‐induced proliferation of pulmonary arterial smooth muscle cells by down‐regulation of p27Kip1 expression.

Inhibition of Notch3 prevents monocrotaline-induced pulmonary arterial hypertension

ABSTRACT It has been shown that activation of Notch3 signaling is involved in the development of pulmonary arterial hypertension (PAH) by stimulating pulmonary arteries remodeling, while the molecular mechanisms underlying this are still largely unknown. The aims of this study are to address these issues. Monocrotaline dramatically increased right ventricle systolic pressure to 39.0 ± 2.6 mmHg and right ventricle hypertrophy index to 53.4 ± 5.3% (P < 0.05 versus control) in rats, these were accompanied with significantly increased proliferation and reduced apoptosis of pulmonary vascular cells as well as pulmonary arteries remodeling. Treatment of PAH model with specific Notch inhibitor DAPT significantly reduced right ventricle systolic pressure to 26.6 ± 1.3 mmHg and right ventricle hypertrophy index to 33.5 ± 2.6% (P < 0.05 versus PAH), suppressed proliferation and enhanced apoptosis of pulmonary vascular cells as well as inhibited pulmonary arteries remodeling. Our results further indicated that level of Notch3 protein and NICD3 were increased in MCT-induced model of PAH, this was accompanied with elevation of Skp2 and Hes1 protein level and reduction of P27Kip1. Administration of rats with DAPT-prevented MCT induced these changes. Our results suggest that Notch3 signaling activation stimulated pulmonary vascular cells proliferation by Skp2-and Hes1-mediated P27Kip1 reduction, and Notch3 might be a new target to treat PAH.

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.

Activation of AMPK Prevents Monocrotaline-Induced Extracellular Matrix Remodeling of Pulmonary Artery

Background The current study was performed to investigate the effect of adenosine monophosphate (AMP) – activated protein kinase (AMPK) activation on the extracellular matrix (ECM) remodeling of pulmonary arteries in pulmonary arterial hypertension (PAH) and to address its potential mechanisms. Material/Methods PAH was induced by a single intraperitoneal injection of monocrotaline (MCT) into Sprague-Dawley rats. Metformin (MET) was administered to activate AMPK. Immunoblotting was used to determine the phosphorylation and expression of AMPK and expression of tissue inhibitor of metalloproteinase-1 (TIMP-1). Gelatin zymography was performed to determine the activity of matrix metalloproteinase-2 (MMP-2) and MMP-9. Results Activation of AMPK by MET significantly reduced the right ventricle systolic pressure and the right ventricular hypertrophy in MCT-induced rat PAH model, and partially inhibited the ECM remodeling of pulmonary arteries. These effects were coupled with the decrease of MMP-2/9 activity and TIMP-1 expression. Conclusions This study suggests that activation of AMPK benefits PAH by inhibiting ECM remodeling of pulmonary arteries. Enhancing AMPK activity might have potential value in clinical treatment of PAH.

Knockdown of AMPKα2 Promotes Pulmonary Arterial Smooth Muscle Cells Proliferation via mTOR/Skp2/p27Kip1 Signaling Pathway

It has been shown that activation of adenosine monophosphate-activated protein kinase (AMPK) suppresses proliferation of a variety of tumor cells as well as nonmalignant cells. In this study, we used post-transcriptional gene silencing with small interfering RNA (siRNA) to specifically examine the effect of AMPK on pulmonary arterial smooth muscle cells (PASMCs) proliferation and to further elucidate its underlying molecular mechanisms. Our results showed that knockdown of AMPKα2 promoted primary cultured PASMCs proliferation; this was accompanied with the elevation of phosphorylation of mammalian target of rapamycin (mTOR) and S-phase kinase-associated protein 2 (Skp2) protein level and reduction of p27Kip1. Importantly, prior silencing of mTOR with siRNA abolished AMPKα2 knockdown-induced Skp2 upregulation, p27Kip1 reduction as well as PASMCs proliferation. Furthermore, pre-depletion of Skp2 by siRNA also eliminated p27Kip1 downregulation and PASMCs proliferation caused by AMPKα2 knockdown. Taken together, our study indicates that AMPKα2 isoform plays an important role in regulation of PASMCs proliferation by modulating mTOR/Skp2/p27Kip1 axis, and suggests that activation of AMPKα2 might have potential value in the prevention and treatment of pulmonary arterial hypertension.