Acute inflammation induces insulin-like growth factor-1 to mediate Bcl-2 and Muc5ac expression in airway epithelial cells

The Role of Proprotein Convertases in Upper Airway Remodeling

Chronic rhinosinusitis (CRS) is a multifactorial, heterogeneous disease characterized by persistent inflammation of the sinonasal mucosa and tissue remodeling, which can include basal/progenitor cell hyperplasia, goblet cell hyperplasia, squamous cell metaplasia, loss or dysfunction of ciliated cells, and increased matrix deposition. Repeated injuries can stimulate airway epithelial cells to produce inflammatory mediators that activate epithelial cells, immune cells, or the epithelial-mesenchymal trophic unit. This persistent inflammation can consequently induce aberrant tissue remodeling. However, the molecular mechanisms driving disease within the different molecular CRS subtypes remain inadequately characterized. Numerous secreted and cell surface proteins relevant to airway inflammation and remodeling are initially synthesized as inactive precursor proteins, including growth/differentiation factors and their associated receptors, enzymes, adhesion molecules, neuropeptides, and peptide hormones. Therefore, these precursor proteins require post-translational cleavage by proprotein convertases (PCs) to become fully functional. In this review, we summarize the roles of PCs in CRS-associated tissue remodeling and discuss the therapeutic potential of targeting PCs for CRS treatment.

Effects of Wood Smoke Constituents on Mucin Gene Expression in Mice and Human Airway Epithelial Cells and on Nasal Epithelia of Subjects with a Susceptibility Gene Variant in Tp53

BACKGROUND

Exposure to wood smoke (WS) increases the risk for chronic bronchitis more than exposure to cigarette smoke (CS), but the underlying mechanisms are unclear.

OBJECTIVE

The effect of WS and CS on mucous cell hyperplasia in mice and in human primary airway epithelial cells (AECs) was compared with replicate the findings in human cohorts. Responsible WS constituents were identified to better delineate the pathway involved, and the role of a tumor protein p53 (Tp53) gene polymorphism was investigated.

METHODS

Mice and primary human AECs were exposed to WS or CS and the signaling receptor and pathway were identified using short hairpin structures, small molecule inhibitors, and Western analyses. Mass spectrometric analysis was used to identify active WS constituents. The role of a gene variant in Tp53 that modifies proline to arginine was examined using nasal brushings from study participants in the Lovelace Smokers Cohort, primary human AECs, and mice with a modified Tp53 gene.

RESULTS

WS at 25-fold lower concentration than CS increased mucin expression more efficiently in mice and in human AECs in a p53 pathway-dependent manner. Study participants who were homozygous for p53 arginine compared with the proline variant showed higher mucin 5AC (MUC5AC) mRNA levels in nasal brushings if they reported WS exposure. The WS constituent, oxalate, increased MUC5AC levels similar to the whole WS extract, especially in primary human AECs homozygous for p53 arginine, and in mice with a modified Tp53 gene. Further, the anion exchange protein, SLC26A9, when reduced, enhanced WS- and oxalate-induced mucin expression.

DISCUSSION

The potency of WS compared with CS in inducing mucin expression may explain the increased risk for chronic bronchitis in participants exposed to WS. Identification of the responsible compounds could help estimate the risk of pollutants in causing chronic bronchitis in susceptible individuals and provide strategies to improve management of lung diseases. https://doi.org/10.1289/EHP9446.

A comparison of three mucus-secreting airway cell lines (Calu-3, SPOC1 and UNCN3T) for use as biopharmaceutical models of the nose and lung

The aim of this work was to compare three existing mucus-secreting airway cell lines for use as models of the airways to study drug transport in the presence of mucus. Each cell line secreted mature, glycosylated mucins, evidenced by the enzyme-linked lectin assay. The secretagogue, adenylyl-imidodiphosphate, increased mucin secretion in SPOC1 (3.5-fold) and UNCN3T (1.5-fold) cells but not in Calu-3 cells. In a novel mucus-depleted (MD) model the amount of mucus in the non-depleted wells was 3-, 8- and 4-fold higher than in the mucus-depleted wells of the Calu-3, SPOC1 and UNCN3T cells respectively. The permeability of 'high mucus' cells to testosterone was significantly less in SPOC1 and UNCN3T cells (P < 0.05) but not Calu-3 cells. Mucin secretion and cytokine release were investigated as indicators of drug irritancy in the SPOC1 and UNCN3T cell lines. A number of inhaled drugs significantly increased mucin secretion at high concentrations and the release of IL-6 and IL-8 from SPOC1 or UNCN3T cells (P < 0.05). SPOC1 and UNCN3T cell lines are better able to model the effect of mucus on drug absorption than the Calu-3 cell line and are proposed for use in assessing drug-mucus interactions in inhaled drug and formulation development.

Epithelial Cells and Inflammation in Pulmonary Wound Repair

Respiratory diseases are frequently characterised by epithelial injury, airway inflammation, defective tissue repair, and airway remodelling. This may occur in a subacute or chronic context, such as asthma and chronic obstructive pulmonary disease, or occur acutely as in pathogen challenge and acute respiratory distress syndrome (ARDS). Despite the frequent challenge of lung homeostasis, not all pulmonary insults lead to disease. Traditionally thought of as a quiescent organ, emerging evidence highlights that the lung has significant capacity to respond to injury by repairing and replacing damaged cells. This occurs with the appropriate and timely resolution of inflammation and concurrent initiation of tissue repair programmes. Airway epithelial cells are key effectors in lung homeostasis and host defence; continual exposure to pathogens, toxins, and particulate matter challenge homeostasis, requiring robust defence and repair mechanisms. As such, the epithelium is critically involved in the return to homeostasis, orchestrating the resolution of inflammation and initiating tissue repair. This review examines the pivotal role of pulmonary airway epithelial cells in initiating and moderating tissue repair and restitution. We discuss emerging evidence of the interactions between airway epithelial cells and candidate stem or progenitor cells to initiate tissue repair as well as with cells of the innate and adaptive immune systems in driving successful tissue regeneration. Understanding the mechanisms of intercellular communication is rapidly increasing, and a major focus of this review includes the various mediators involved, including growth factors, extracellular vesicles, soluble lipid mediators, cytokines, and chemokines. Understanding these areas will ultimately identify potential cells, mediators, and interactions for therapeutic targeting.

[Menthol enhances interleukin-13-induced synthesis and secretion of mucin 5AC in human bronchial epithelial cells]

OBJECTIVE

To investigate the effect of interleukin (IL) -13 combined with cold stimulation on synthesis and secretion of mucin (MUC) 5AC in human bronchial epithelial cell line 16HBE and explore the role of transient receptor potential 8 (TRPM8) and anti-apoptotic factor B-cell lymphoblast-2 (Bcl-2) in this process.

METHODS

16HBE cells were stimulated with 10 ng/mL IL-13, 1 mmol/L menthol, or both (1 mmol/L menthol was added after 6 days of IL-13 stimulation), and the changes in the expression of MUC5AC, intracellular Ca²⁺ concentration and Bcl-2 expression were evaluated. The effects of ABT-263 (a Bcl-2 inhibitor) and BCTC (a TRPM8 ion channel inhibitor), alone or in combination, on MUC5AC expression in the cells were tested, and the changes in intracellular Ca²⁺ and Bcl-2 expression following BCTC treatment were observed. The cell viability was assessed using CCK-8 assay, the mRNA expressions of MUC5AC and Bcl-2 were detected with real-time quantitative PCR, the level of MUC5AC in the culture medium was measured with ELISA, and the intracellular Ca²⁺ fluorescence intensity was determined with flow cytometry.

RESULTS

The mRNA and protein expressions of MUC5AC increased significantly in 16HBE cells following stimulation with IL-13, menthol, and both (P < 0.05), and were the highest in the combined treatment group with its peak level occurred at 24 h (P < 0.01). The intracellular Ca²⁺ fluorescence intensity and Bcl-2 mRNA expression were also increased in 16HBE cells after the stimulations (P < 0.05), and the increments were the most obvious in the combined treatment group (P < 0.01). Treatment with BCTC significantly lowered intracellular Ca²⁺ fluorescence intensity and the expressions of Bcl-2 and MUC5AC mRNA and protein in the cells stimulated with menthol or with both IL-13 and menthol (P < 0.05), but caused no significant changes in IL-13-stimulated cells (P > 0.05). Treatment with ABT-263 significantly lowered the mRNA and protein expressions of MUC5AC in the cells stimulated with IL-13 and menthol either alone or in combination (P < 0.05).

CONCLUSIONS

Menthol combined with IL-13 produces a synergistic effect to promote the synthesis and secretion of MUC5AC in 16HBE cells possibly by activating TRPM8 receptor to upregulate the expression of Bcl-2.

A Small Molecule BH3-mimetic Suppresses Cigarette Smoke-Induced Mucous Expression in Airway Epithelial Cells

Cigarette smoke (CS) exposure is one of the primary risk factors associated with the chronic mucous hypersecretion (CMH). The antiapoptotic protein, Bcl-2 sustains hyperplastic mucous cells, and the airway epithelium of ex-smokers with CMH as well as mice exposed to chronic CS showed increased Bcl-2 expression. Therefore, we investigated whether Bcl-2 plays a role in CS-induced mucous expression. Primary airway epithelial cells (AECs) of murine and human origin were treated with CS extract (CSE), and there was a concentration- and time-dependent increase in secretory mucin (MUC5AC), mucous regulator (SPDEF) and Bcl-2 expression. Using differentiated human AECs cultured on air-liquid interface, EGFR and ERK1/2 pathways were interrogated. Bcl-2 activity was blocked using a small molecule BH3 mimetic ABT-263 that disrupts the Bcl-2 interaction with pro-apoptotic proteins. The ABT-263 treatment resulted in the downregulation of CSE-induced mucus expression and disrupted the EGFR-signaling while inducing the apoptosis and the pro-apoptotic protein, Bik expression. This strategy significantly suppressed the mainstream CS-induced mucous phenotype in a 3-D human airway epithelium model. Therefore, the present study suggests that CS induces Bcl-2 expression to help promote mucous cell survival; and small molecule BH3 mimetics targeting Bcl-2 could be useful in suppressing the CS-induced mucous response.

The first line of defence: insights into mechanisms and relevance of phagocytosis in epithelial cells

Epithelial tissues cover most of the external and internal surfaces of the body and its organs. Inevitably, these tissues serve as first line of defence against inorganic, organic, and microbial intruders. Epithelial cells are the main cell type of these tissues. Besides their function as cellular barrier, there is growing evidence that epithelial cells are of particular relevance as initial sensors of danger and also as executers of adequate defence responses. These cells feature various essential functions to maintain tissue integrity in health and disease. In this review, we survey some of the different innate immune functions of epithelial cells in mucosal tissues being constantly exposed to a plethora of harmless contaminants but also of pathogens. We discuss how epithelial cells avoid inadequate immune responses in such conditions. In particular, we will focus on the diverse types and mechanisms of phagocytosis used by epithelial cells to not only maintain homeostasis but to also harness the host response against invading pathogens.

Pro-apoptotic effects of micro-ribonucleic acid-365 on retinal neurons by targeting insulin-like growth factor-1 in diabetic rats: An in vivo and in vitro study

AIMS/OBJECTIVE

The present study aimed to explore the effects of micro-ribonucleic acid-365 (miR-365) on apoptosis of retinal neurons by targeting insulin-like growth factor-1 (IGF-1) in diabetes mellitus rats.

MATERIALS AND METHODS

High glucose-induced retinal neurons were assigned into the blank (with no plasmid transfection), negative control (with plasmid transfection), anti-miR-365 (transfected miR-365 antagomir), transfected IGF-1 short hairpin RNA plasmid (sh-IGF-1) and transfected miR-365 antagomir and IGF-1 shRNA plasmid (anti-miR-365 + sh-IGF-1) groups. Proliferation and apoptosis of retinal neurons were detected by 5-ethynyl-2'-deoxyuridine assay and Hoechst 33342 staining, respectively. Expressions of miR-365, IGF-1, Bcl-2-associated X protein (Bax) and Bcl-2 were determined by reverse transcription quantitative polymerase chain reaction and western blotting. A control group contained 10 healthy rats. Terminal deoxynucleotidyl transferase dUTP nick-end labeling staining was used to evaluate apoptosis of retinal neurons in rats.

RESULTS

In the anti-miR-365 group, the apoptosis rate and Bax expression were reduced in comparison with the negative control and blank groups, whereas the sh-IGF-1 and anti-miR-365 + sh-IGF-1 groups presented an opposite trend. Compared with the normal group, expressions of miR-365 and Bax were increased, and expressions of IGF-1 and Bcl-2 were decreased, with more apoptotic cells in diabetes mellitus rat models. The sh-IGF-1 group had lower Bax expression, and higher expressions of IGF-1 and Bcl-2 with fewer apoptotic cells. Additionally, Bax expression was upregulated, expressions of IGF-1 and Bcl-2 were downregulated, and apoptotic cells were higher in the anti-miR-365 + sh-IGF-1 groups than the anti-miR-365 group.

CONCLUSION

The results of the present study suggest that suppressed miR-365 increases the IGF-1 expression, leading to anti-apoptotic effects on retinal neurons in diabetic rats.

Insulin-Like Growth Factor-1 Signaling in Lung Development and Inflammatory Lung Diseases

Insulin-like growth factor-1 (IGF-1) was firstly identified as a hormone that mediates the biological effects of growth hormone. Accumulating data have indicated the role of IGF-1 signaling pathway in lung development and diseases such as congenital disorders, cancers, inflammation, and fibrosis. IGF-1 signaling modulates the development and differentiation of many types of lung cells, including airway basal cells, club cells, alveolar epithelial cells, and fibroblasts. IGF-1 signaling deficiency results in alveolar hyperplasia in humans and disrupted lung architecture in animal models. The components of IGF-1 signaling pathways are potentiated as biomarkers as they are dysregulated locally or systemically in lung diseases, whereas data may be inconsistent or even paradoxical among different studies. The usage of IGF-1-based therapeutic agents urges for more researches in developmental disorders and inflammatory lung diseases, as the majority of current data are collected from limited number of animal experiments and are generally less exuberant than those in lung cancer. Elucidation of these questions by further bench-to-bedside researches may provide us with rational clinical diagnostic approaches and agents concerning IGF-1 signaling in lung diseases.

Inhibition of insulin-like growth factor receptor-1 reduces necroptosis-related markers and attenuates LPS-induced lung injury in mice

Insulin-like growth factor-1 (IGF-1) levels are known to increase in the bronchoalveolar lavage fluid (BALF) of patients with acute respiratory distress syndrome. Herein, we investigated the role of IGF-1 in lipopolysaccharide (LPS)-induced lung injury. In LPS-treated cells, expressions of receptor-interacting protein 3 (RIP3) and phosphorylated mixed lineage kinase domain-like protein (MLKL) were decreased in IGF-1 receptor small interfering RNA (siRNA)-treated cells compared to control cells. The levels of pro-inflammatory cytokines including interleukin (IL)-1β, IL-6, IL-10, tumour necrosis factor-α, and macrophage inflammatory protein 2/C-X-C motif chemokine ligand 2 in the supernatant were significantly reduced in IGF-1 receptor siRNA-treated cells compared to control cells. In LPS-induced murine lung injury model, total cell counts, polymorphonuclear leukocytes counts, and pro-inflammatory cytokine levels in the BALF were significantly lower and histologically detected lung injury was less common in the group treated with IGF-1 receptor monoclonal antibody compared to the non-treated group. On western blotting, RIP3 and phosphorylated MLKL expressions were relatively decreased in the IGF-1 receptor monoclonal antibody group compared to the non-treated group. IGF-1 may be associated with RIP3-mediated necroptosis in vitro, while blocking of the IGF-1 pathway may reduce LPS-induced lung injuries in vivo.

IL-13 in LPS-Induced Inflammation Causes Bcl-2 Expression to Sustain Hyperplastic Mucous cells

Exposure to lipopolysaccharides (LPS) causes extensive neutrophilic inflammation in the airways followed by mucous cell hyperplasia (MCH) that is sustained by the anti-apoptotic protein, Bcl-2. To identify inflammatory factor(s) that are responsible for Bcl-2 expression, we established an organ culture system consisting of airway epithelial tissue from the rat nasal midseptum. The highest Muc5AC and Bcl-2 expression was observed when organ cultures were treated with brochoalveolar lavage (BAL) fluid harvested from rats 10 h post LPS instillation. Further, because BAL harvested from rats depleted of polymorphonuclear cells compared to controls showed increased Bcl-2 expression, analyses of cytokine levels in lavages identified IL-13 as an inducer of Bcl-2 expression. Ectopic IL-13 treatment of differentiated airway epithelial cells increased Bcl-2 and MUC5AC expression in the basal and apical regions of the cells, respectively. When Bcl-2 was blocked using shRNA or a small molecule inhibitor, ABT-263, mucous cell numbers were reduced due to increased apoptosis that disrupted the interaction of Bcl-2 with the pro-apoptotic protein, Bik. Furthermore, intranasal instillation of ABT-263 reduced the LPS-induced MCH in bik^+/+ but not bik^−/− mice, suggesting that Bik mediated apoptosis in hyperplastic mucous cells. Therefore, blocking Bcl-2 function could be useful in reducing IL-13 induced mucous hypersecretion.

Klotho Regulates Cigarette Smoke-Induced Autophagy: Implication in Pathogenesis of COPD

INTRODUCTION

Chronic obstructive pulmonary disease is a progressive lung disease characterized by abnormal cellular responses to cigarette smoke, resulting in tissue destruction and airflow limitation. Autophagy is a fundamental cellular process that eliminates long-lived proteins and damaged organelles through lysosomal degradation pathway, though its role in human diseases remains unclear. We hypothesized that an anti-aging protein, Klotho plays an important role in regulating autophagy in response to cigarette smoke (CS).

METHODS

Autophagy was measured by detecting LC3-I and LC3-II expressions. The regulation of autophagy expression by cigarette smoke extract (CSE) was studied in vitro, and small-interfering RNA (siRNA) and recombinant Klotho were employed to investigate the role of Klotho on CSE-induced autophagy. Protein levels and phosphorylation were measured by Western blot assay.

RESULTS

CS exposure resulted in induction of autophagy in alveolar macrophages. Pretreatment of cells with Klotho attenuated CS-induced autophagy whereas knockdown of Klotho augmented CS-induced autophagy. Klotho inhibited phosphorylation of ERK, Akt, and IGF-1 in CSE-stimulated cells.

CONCLUSIONS

These data suggest that Klotho plays a critical role in the regulation of CS-induced autophagy and have important implications in understanding the mechanisms of CS-induced cell death and senescence.

Proprotein convertase inhibition promotes ciliated cell differentiation - a potential mechanism for the inhibition of Notch1 signalling by decanoyl-RVKR-chloromethylketone

Chronic repetitive rounds of injury and repair in the airway lead to airway remodelling, including ciliated cell loss and mucous cell hyperplasia. Airway remodelling is mediated by many growth and differentiation factors including Notch1, which are proteolytically processed by proprotein convertases (PCs). The present study evaluated a novel approach for controlling basal cell‐type determination based on the inhibition of PCs. It was found that decanoyl‐RVKR‐chloromethylketone (CMK), a PC inhibitor, promotes ciliated cell differentiation and has no effect on the ciliary beat frequency in air–liquid interface (ALI) cultures of human nasal epithelial cells (HNECs). Comparative microarray analysis revealed that CMK considerably increases ciliogenesis‐related gene expression. Use of cell‐permeable and cell‐impermeable PC inhibitors suggests that intracellular PCs regulate basal cell‐type determination in ALI culture. Furthermore, CMK effect on ciliated cell differentiation was reversed by a Notch inhibitor N‐[N‐(3,5‐difluorophenacetyl)‐l‐alanyl]‐S‐phenylglycine t‐butyl ester (DAPT). CMK inhibited the processing of Notch1, a key regulator of basal cell differentiation toward secretory cell lineages in the airway epithelium, and down‐regulated the expression of Notch1 target genes together with furin, a PC. Specific lentiviral shRNA‐mediated knockdown of furin resulted in reduced Notch1 processing and increased numbers of ciliated cells in HNECs. Moreover, CMK inhibited Notch1 processing and promoted regeneration and ciliogenesis of the mouse nasal respiratory epithelium after ZnSO₄ injury. These observations suggest that PC inhibition promotes airway ciliated cell differentiation, possibly through suppression of furin‐mediated Notch1 processing. © 2016 The Authors Journal of Tissue Engineering and Regenerative Medicine Published by John Wiley & Sons Ltd

Involvement of Igf1r in Bronchiolar Epithelial Regeneration: Role during Repair Kinetics after Selective Club Cell Ablation

Regeneration of lung epithelium is vital for maintaining airway function and integrity. An imbalance between epithelial damage and repair is at the basis of numerous chronic lung diseases such as asthma, COPD, pulmonary fibrosis and lung cancer. IGF (Insulin-like Growth Factors) signaling has been associated with most of these respiratory pathologies, although their mechanisms of action in this tissue remain poorly understood. Expression profiles analyses of IGF system genes performed in mouse lung support their functional implication in pulmonary ontogeny. Immuno-localization revealed high expression levels of Igf1r (Insulin-like Growth Factor 1 Receptor) in lung epithelial cells, alveolar macrophages and smooth muscle. To further understand the role of Igf1r in pulmonary homeostasis, two distinct lung epithelial-specific Igf1r mutant mice were generated and studied. The lack of Igf1r disturbed airway epithelial differentiation in adult mice, and revealed enhanced proliferation and altered morphology in distal airway club cells. During recovery after naphthalene-induced club cell injury, the kinetics of terminal bronchiolar epithelium regeneration was hindered in Igf1r mutants, revealing increased proliferation and delayed differentiation of club and ciliated cells. Amid airway restoration, lungs of Igf1r deficient mice showed increased levels of Igf1, Insr, Igfbp3 and epithelial precursor markers, reduced amounts of Scgb1a1 protein, and alterations in IGF signaling mediators. These results support the role of Igf1r in controlling the kinetics of cell proliferation and differentiation during pulmonary airway epithelial regeneration after injury.

T cells suppress memory-dependent rapid mucous cell metaplasia in mouse airways

Background

Airway epithelial cells (AECs) are crucial for mucosal and adaptive immunity but whether these cells respond in a memory-dependent manner is poorly studied. Previously, we have reported that LPS intratracheal instillation in rodents causes extensive neutrophilic inflammation and airway epithelial cell hyperplasia accompanied by mucous cell metaplasia (MCM). And the resolution process required a period of 40 d for the inflammation to subside and the lung epithelia to resemble the non-exposed condition. Therefore, the present study investigated the memory-dependent response of airway epithelial cells to a secondary LPS challenge after the initial inflammation was resolved.

Methods

Airway epithelial and mucous cells were assessed in response to a secondary LPS challenge in F344/N rats, and in C57BL/6 wild-type (Foxn1^WT) and T cell-deficient athymic (Foxn1^nu) mice that were instilled with LPS or saline 40 d earlier. Epithelial expression of TLR4, EGFR, and phosphorylated-ERK1/2 (pERK) were also analyzed.

Results

LPS-pretreated F344/N rats responded with elevated numbers of AECs after saline challenge and with 3-4-fold increased MCM following the LPS challenge in LPS- compared with saline-pretreated rats. LPS-pretreated rats showed 5-fold higher number of AECs expressing TLR4 apically than saline-pretreated rats. Also, the expression of EGFR was increased in LPS-pretreated rats along with the number of AECs with active or nuclear pERK, and the levels were further increased upon LPS challenge. LPS-pretreated Foxn1^nu compared with Foxn1^WT mice showed increased MCM and elevated levels of TLR4, EGFR, and nuclear pERK at 40 d after LPS instillation. LPS challenge further augmented MCM rapidly in Foxn1^nu compared with Foxn1^WT mice.

Conclusion

Together, these data suggest that AECs preserve an ‘innate memory’ that drives a rapid mucous phenotype via spatiotemporal regulation of TLR4 and EGFR. Further, T cells may suppress the sustained elevated expression of TLR4 and EGFR and thereby the hyperactive epithelial response.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-016-0446-0) contains supplementary material, which is available to authorized users.

Associations of Insulin and IGFBP-3 with Lung Cancer Susceptibility in Current Smokers

BACKGROUND

The epidermal growth factor receptor (EGFR) signaling network is involved in lung carcinogenesis. This study examined whether ligands that activate or suppress the EGFR signaling network were associated with lung cancer risk in ever smokers.

METHODS

A nested case-control study within the Women's Health Initiative assessed baseline plasma levels of insulin, insulin-like growth factor (IGF)-1, insulin-like growth factor binding protein (IGFBP)-3, interleukin (IL)-6, hepatocyte growth factor (HGF), and nerve growth factor (NGF) in 1143 ever-smoking lung cancer cases and 1143 controls. Leptin was measured as an adiposity biomarker. Conditional logistic regression was used in data analyses.

RESULTS

Leptin was inversely associated with lung cancer risk (odds ratio [ORcontinuous] per Ln [pg/mL] = 0.85, 95% confidence interval [CI] = 0.74 to 0.98). After adjusting for adiposity and other risk factors, null associations were found for IL-6, HGF, and NGF. In current smokers, but not former smokers, high insulin levels were associated with increased lung cancer risk (OR for 4th quartile vs others [ORq4] = 2.06, 95% CI = 1.30 to 3.26) whereas IGFBP-3 had a linear inverse association (ORcontinuous per μg/mL = 0.64, 95% CI = 0.41 to 0.98). The insulin association was consistent across subgroups defined by body mass index and histological type, but the IGFBP-3 association was specific to small cell lung cancer. There was a modest positive association between IGF-1 and lung cancer risk in current smokers (ORq4 = 1.44, 95% CI = 0.90 to 2.29).

CONCLUSIONS

Independent of obesity, high insulin levels but reduced levels of IGFBP-3 were associated with increased lung cancer risk in current smokers.

Is insulin-like growth factor 1 (IGF-1) system an attractive target inflammatory bowel diseases? Benefits and limitation of potential therapy

Inflammatory bowel diseases (IBD) are chronic gastrointestinal disorders with unknown etiology, whose incidence dramatically increased over the past 50 years. Currently available strategies for IBD treatment, such as biological therapies, corticosteroids, and immunosuppressive agents are effective, but their side effects and economic costs cannot be ignored. Better understanding of IBD etiology and new therapeutics are thus needed. The aim of this paper is to briefly discuss IGF-1 dependent functions, with particular focus on IGF-1 use in IBD therapy. Data collection was based on records found in medical literature. Data analysis included records published between 1984 and 2014. The IGF-1 system is involved in major physiological functions, such as cell proliferation and metabolism, and growth promotion. Most importantly IGF-1 has anti-inflammatory properties and its use in IBD treatment can be recommended. However, potential IGF-1 therapy has some limitations, which include aggravation of fibrosis in Crohn's patients and facilitated transformation to malignancy. Taken into consideration their possible side effects, IGF-1 analogs and recombinants are nonetheless a promising target for IBD therapy for a specific group of patients. Further studies, at the clinical level are thus recommended.

A genetic variant of p53 restricts the mucous secretory phenotype by regulating SPDEF and Bcl-2 expression

Despite implications for carcinogenesis and other chronic diseases, basic mechanisms of p53 and its variants in suppressing Bcl-2 levels are poorly understood. Bcl-2 sustains mucous cell metaplasia, whereas p53(-/-) mice display chronically increased mucous cells. Here we show that p53 decreases bcl-2 mRNA half-life by interacting with the 5' untranslated region (UTR). The p53-bcl-2 mRNA interaction is modified by the substitution of proline by arginine within the p53 proline-rich domain (PRD). Accordingly, more mucous cells are present in primary human airway cultures with p53(Arg) compared with p53(Pro). Also, the p53(Arg) compared with p53(Pro) displays higher affinity to and activates the promoter region of SAM-pointed domain-containing Ets-like factor (SPDEF), a driver of mucous differentiation. On two genetic backgrounds, mice with targeted replacement of prolines in p53 PRD show enhanced expression of SPDEF and Bcl-2 and mucous cell metaplasia. Together, these studies define the PRD of p53 as a determinant for chronic mucous hypersecretion.

Molecular processes that drive cigarette smoke-induced epithelial cell fate of the lung

Cigarette smoke contains numerous chemical compounds, including abundant reactive oxygen/nitrogen species and aldehydes, and many other carcinogens. Long-term cigarette smoking significantly increases the risk of various lung diseases, including chronic obstructive pulmonary disease and lung cancer, and contributes to premature death. Many in vitro and in vivo studies have elucidated mechanisms involved in cigarette smoke-induced inflammation, DNA damage, and autophagy, and the subsequent cell fates, including cell death, cellular senescence, and transformation. In this Translational Review, we summarize the known pathways underlying these processes in airway epithelial cells to help reveal future challenges and describe possible directions of research that could lead to better management and treatment of these diseases.

Autophagy induction by SIRT6 through attenuation of insulin-like growth factor signaling is involved in the regulation of human bronchial epithelial cell senescence

Cigarette smoke (CS)-induced cellular senescence has been implicated in the pathogenesis of chronic obstructive pulmonary disease, and SIRT6, a histone deacetylase, antagonizes this senescence, presumably through the attenuation of insulin-like growth factor (IGF)-Akt signaling. Autophagy controls cellular senescence by eliminating damaged cellular components and is negatively regulated by IGF-Akt signaling through the mammalian target of rapamycin (mTOR). SIRT1, a representative sirtuin family, has been demonstrated to activate autophagy, but a role for SIRT6 in autophagy activation has not been shown. Therefore, we sought to investigate the regulatory role for SIRT6 in autophagy activation during CS-induced cellular senescence. SIRT6 expression levels were modulated by cDNA and small interfering RNA transfection in human bronchial epithelial cells (HBECs). Senescence-associated β-galactosidase staining and Western blotting of p21 were performed to evaluate senescence. We demonstrated that SIRT6 expression levels were decreased in lung homogenates from chronic obstructive pulmonary disease patients, and SIRT6 expression levels correlated significantly with the percentage of forced expiratory volume in 1 s/forced vital capacity. CS extract (CSE) suppressed SIRT6 expression in HBECs. CSE-induced HBEC senescence was inhibited by SIRT6 overexpression, whereas SIRT6 knockdown and mutant SIRT6 (H133Y) without histone deacetylase activity enhanced HBEC senescence. SIRT6 overexpression induced autophagy via attenuation of IGF-Akt-mTOR signaling. Conversely, SIRT6 knockdown and overexpression of a mutant SIRT6 (H133Y) inhibited autophagy. Autophagy inhibition by knockdown of ATG5 and LC3B attenuated the antisenescent effect of SIRT6 overexpression. These results suggest that SIRT6 is involved in CSE-induced HBEC senescence via autophagy regulation, which can be attributed to attenuation of IGF-Akt-mTOR signaling.

Increased methylation of lung cancer-associated genes in sputum DNA of former smokers with chronic mucous hypersecretion

Background

Chronic mucous hypersecretion (CMH) contributes to COPD exacerbations and increased risk for lung cancer. Because methylation of gene promoters in sputum has been shown to be associated with lung cancer risk, we tested whether such methylation was more common in persons with CMH.

Methods

Eleven genes commonly silenced by promoter methylation in lung cancer and associated with cancer risk were selected. Methylation specific PCR (MSP) was used to profile the sputum of 900 individuals in the Lovelace Smokers Cohort (LSC). Replication was performed in 490 individuals from the Pittsburgh Lung Screening Study (PLuSS).

Results

CMH was significantly associated with an overall increased number of methylated genes, with SULF2 methylation demonstrating the most consistent association. The association between SULF2 methylation and CMH was significantly increased in males but not in females both in the LSC and PLuSS (OR = 2.72, 95% CI = 1.51-4.91, p = 0.001 and OR = 2.97, 95% CI = 1.48-5.95, p = 0.002, respectively). Further, the association between methylation and CMH was more pronounced among 139 male former smokers with persistent CMH compared to current smokers (SULF2; OR = 3.65, 95% CI = 1.59-8.37, p = 0.002).

Conclusions

These findings demonstrate that especially male former smokers with persistent CMH have markedly increased promoter methylation of lung cancer risk genes and potentially could be at increased risk for lung cancer.

LPS stimulates MUC5AC expression in human biliary epithelial cells: whether there exists a possible pathway of PKC/NADPH/ROS?

Previous studies have shown that lipopolysaccharide (LPS) can upregulate MUC5AC in airway epithelial cells. However, the relationship and mechanism between bacterial infection and altered mucus secretion in the biliary tract remains unclear. Human biliary epithelial cells were induced by LPS, H2O2 production in the cell supernatants were detected by specific kit and expression of MUC5AC were detected by real-time PCR, Western blot, and immunohistochemistry. H2O2 production increased in a dose-dependent manner, LPS upregulate MUC5AC expression in both mRNA and protein level while specific inhibitors can reduce this high expression. Reactive oxygen species participates in the process of LPS by upregulating MUC5AC secretion. Moreover, PKC and NADPH oxidase regulate MUC5AC production in LPS-challenged human biliary epithelial cells.

LPS induces MUC5AC expression in human biliary epithelial cells

AIM: To examine whether lipopolysaccharide (LPS) stimulates MUC5AC expression in human biliary epithelial cells.

METHODS: Human biliary epithelial cells were treated with LPS, and MUC5AC mRNA and protein expression was detected by real time-PCR, Western blot and immunohistochemistry 12 and 24 h after LPS treatment.

RESULTS: LPS stimulation significantly increased MUC5AC mRNA expression (3.67 ± 0.22 vs 1.00 ± 0.05, P < 0.05). MUC5AC protein expression was also increased after LPS treatment (0.26 vs 0.59, P < 0.05).

CONCLUSION: LPS can induce MUC5AC expression in human biliary epithelial cells.