LPS-stimulated MUC5AC production involves Rac1-dependent MMP-9 secretion and activation in NCI-H292 cells

Lixisenatide ameliorated lipopolysaccharide (LPS)-induced expression of mucin and inflammation in bronchial epithelial cells

Chronic obstructive pulmonary disease (COPD) induces serious social and economic burdens due to its high disability and mortality, the pathogenesis of which is highly involved with inflammation, oxidative stress (OS), and mechanism of mucin 5AC (MUC5AC) secretion. Lixisenatide is a selective glucagon-like peptide 1 receptor agonist recently reported to have anti-inflammatory properties. Our study will focus on the potential impact of lixisenatide on lipopolysaccharide (LPS)-induced mucin secretion and inflammation in 16 human bronchial epithelial (16HBE) cells to check its potential function in COPD. 16HBE cells were treated with LPS, with or without lixisenatide (10 and 20 nM) for 1 day. Remarkably declined cell viability, enhanced lactate dehydrogenase release, activated OS, and elevated release of inflammatory cytokines were observed in LPS-treated 16HBE cells, accompanied by the activation of nuclear factor-κB signaling, all of which were signally reversed by lixisenatide. Moreover, elevated expression and release of MUC5AC were observed in LPS-treated 16HBE cells but were markedly repressed by lixisenatide. Furthermore, the repressed nuclear factor erythroid 2-related factor 2 (Nrf2) level in LPS-treated 16HBE cells was notably rescued by lixisenatide. Lastly, following the knockdown of Nrf2, the protective function of lixisenatide on LPS-triggered MUC5AC release in 16HBE cells was significantly abrogated. Collectively, lixisenatide ameliorated LPS-induced expression of mucin and inflammation in bronchial epithelial cells by regulating Nrf2.

PI3K signalling in chronic obstructive pulmonary disease and opportunities for therapy

Chronic obstructive pulmonary disease (COPD) is a chronic lung disease characterised by airway inflammation and progressive obstruction of the lung airflow. Current pharmacological treatments include bronchodilators, alone or in combination with steroids, or other anti-inflammatory agents, which have only partially contributed to the inhibition of disease progression and mortality. Therefore, further research unravelling the underlying mechanisms is necessary to develop new anti-COPD drugs with both lower toxicity and higher efficacy. Extrinsic signalling pathways play crucial roles in COPD development and exacerbations. In particular, phosphoinositide 3-kinase (PI3K) signalling has recently been shown to be a major driver of the COPD phenotype. Therefore, several small-molecule inhibitors have been identified to block the hyperactivation of this signalling pathway in COPD patients, many of them showing promising outcomes in both preclinical animal models of COPD and human clinical trials. In this review, we discuss the critically important roles played by hyperactivated PI3K signalling in the pathogenesis of COPD. We also critically review current therapeutics based on PI3K inhibition, and provide suggestions focusing on PI3K signalling for the further improvement of the COPD phenotype. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Novel computational analysis of large transcriptome datasets identifies sets of genes distinguishing chronic obstructive pulmonary disease from healthy lung samples

Chronic obstructive pulmonary disease (COPD) kills over three million people worldwide every year. Despite its high global impact, the knowledge about the underlying molecular mechanisms is still limited. In this study, we aimed to extend the available knowledge by identifying a small set of COPD-associated genes. We analysed different publicly available gene expression datasets containing whole lung tissue (WLT) and airway epithelium (AE) samples from over 400 human subjects for differentially expressed genes (DEGs). We reduced the resulting sets of 436 and 663 DEGs using a novel computational approach that utilises a random depth-first search to identify genes which improve the distinction between COPD patients and controls along the first principle component of the data. Our method identified small sets of 10 and 15 genes in the WLT and AE, respectively. These sets of genes significantly (p < 10^–20) distinguish COPD patients from controls with high fidelity. The final sets revealed novel genes like cysteine rich protein 1 (CRIP1) or secretoglobin family 3A member 2 (SCGB3A2) that may underlie fundamental molecular mechanisms of COPD in these tissues.

A novel macrolide, solithromycin suppresses mucin overexpression induced by Pseudomonas aeruginosa LPS in airway epithelial cells

Some macrolides such as 14- and 15-membered macrolides have immunomodulatory effects such as suppression of mucin overproduction. Because a novel macrolide, solithromycin, was developed, we examined whether it suppresses the overexpression of mucin in vitro. A human airway epithelial cell line NCI-H292 was stimulated by Pseudomonas aeruginosa lipopolysaccharides to induce the overproduction of a major mucin, MUC5AC. Treatment with 10 μg/mL of solithromycin significantly inhibited LPS-induced MUC5AC in both mRNA and protein levels as well as a 15-membered macrolide, azithromycin. These findings support that solithromycin has a potential immunomodulatory effect.

Epidermal growth factor upregulates expression of MUC5AC via TMEM16A, in chronic rhinosinusitis with nasal polyps

Background

Mucus hypersecretion and goblet cell upregulation are common features of chronic rhinosinusitis with nasal polyps (CRSwNP). Although epidermal growth factor (EGF) has been reported to stimulate the expression of MUC5AC, the major macro-molecular constituent of airway mucus, the precise mechanisms underlying the regulation of MUC5AC expression are still not fully understood. The aim of this study therefore was to investigate the role of EGF in regulation of mucin MUC5AC expression and define the involvement of transmembrane protein 16A (TMEM16A) in mediating the EGF-induced mucus overexpression.

Methods

Human nasal epithelial cells (HNECs) derived from tissue of patients with CRSwNP and control subjects were established as air-liquid interface (ALI) cultures. Differentiated cultures were treated with different concentrations of EGF for 4-24 h, and assessed for the expression of TMEM16A and MUC5AC by real-time RT-PCR, Western blotting, ELISA and immunofluorescence. Cultures pretreated for 30 min with T16Ainh-A01 (a specific TMEM16A inhibitor) or LY294002 (a phosphoinositide 3-kinase (PI3K) inhibitor) were also assessed similarly following EGF treatment.

Results

EGF treatment (10-100 ng/ml for 4-24 h) significantly increased the expression of both TMEM16A and MUC5AC mRNA and protein, as well as the percentage of TMEM16A-positive cells, MUC5AC-positive cells and cells coexpressing TMEM16A and MUC5AC in HNECs compared to control non-EGF-treated HNECs. Pretreatment of the HNECs with T16Ainh-A01 and LY294002 attenuated these EGF-induced effects.

Conclusions

This study demonstrated that EGF upregulates the expression of MUC5AC in HNECs from CRSwNP patients. Furthermore, the EGF-mediated regulation of MUC5AC expression is likely to involve a PI3K-TMEM16A signalling pathway in CRSwNP.

Crocin protects against cerebral- ischemia-induced damage in aged rats through maintaining the integrity of blood-brain barrier

BACKGROUND

A clear relationship exists between oxidative stress and disruption of blood-brain barrier (BBB) during cerebral ischemia, in which aging may exacerbate the extent of leakage. Here, we aim to examine the potential role of a water-soluble carotenoid-based antioxidant crocin on BBB damage in aged rats following cerebral ischemia.

METHODS

A two months oral administration of crocin was applied to 24-month-old rats followed by an induction of brain ischemia by middle cerebral artery occlusion (MCAO). Brain infarction volume, water content, and neurological behavior assessments were measured in these animals at 24 hours after MCAO as compared to vehicle-treated controls. Evans blue dye extravasation assay was used to evaluate the BBB integrity. The levels of tight junction proteins, oxidative stress, and MMP (matrix metalloproteinases) activities were also determined in the ipsilateral brains of the MCAO-treated rats.

RESULTS

MCAO-induced brain injury was alleviated by the pretreatment of crocin. Crocin-treated animals also showed the preserved BBB function in the presence of ischemic injury. The loss of tight junction proteins and enhanced NADPH oxidase in the ipsilateral brains of the MCAO-treated rats were both reduced by crocin. Finally, the induction of MMP-2 and MMP-9 by cerebral ischemia was partially blocked by crocin in aged rats.

CONCLUSION

These findings indicate that crocin or related antioxidants may protect against cerebral ischemia of elderly patients by maintaining the integrity of BBB in aged rats, an effect likely through repressing the activation of matrix metalloproteinase pathway.

Role of LPS-elicited signaling in triggering gastric mucosal inflammatory responses to H. pylori: modulatory effect of ghrelin

Infection with Helicobacter pylori is a primary culprit in the etiology of gastric disease, and its cell-wall lipopolysaccharide (LPS) is recognized as a potent endotoxin responsible for triggering a pattern of the mucosal inflammatory responses. The engagement by the LPS of gastric mucosal Toll-like receptor 4 (TLR4) leads to initiation of signal transduction events characterized by the activation of mitogen-activated protein kinase (MAPK) cascade, induction of phosphoinositide-specific phospholipase C (PLC)/protein kinase C (PKC)/phosphatidylinositol 3-kinase (PI3K) pathway, and up-regulation in Src/Akt. These signaling events in turn exert their influence over H. pylori-elicited excessive generation of NO and PGE2 caused by the disturbances in nitric oxide synthase and cyclooxygenase isozyme systems, increase in epidermal growth factor receptor transactivation, and the induction in matrix metalloproteinase-9 (MMP-9) release. Interestingly, the extent of gastric mucosal inflammatory response to H. pylori is influenced by a peptide hormone, ghrelin, the action of which relays on the growth hormone secretagogue receptor type 1a (GHS-R1a)-mediated mobilization of G-protein dependent transduction pathways. Yet, the signals triggered by TLR-4 activation as well as those arising through GHS-R1a stimulation converge at MAPK and PLC/PKC/PI3K pathways that form a key integration node for proinflammatory signals generated by H. pylori LPS as well as for those involved in modulation of inflammation by ghrelin. Hence, therapeutic targeting these signals' convergence and integration node could provide a novel and attractive opportunities for developing more effective treatments of H. pylori-related gastric disease.

Neutrophil elastase stimulates MUC5AC expression in human biliary epithelial cells: a possible pathway of PKC/Nox/ROS

INTRODUCTION

Bacterial infection and bile flow retardation form a vicious cycle which promotes stone formation and recurrence, and it seems that mucin overexpression plays an important role in this process. However, the mechanism of increased mucus secretion in the biliary tract by bacterial infection and its treatment remain unclear.

MATERIAL AND METHODS

Human biliary epithelial cells were induced by neutrophil elastase (NE), and H₂O₂ production in the cell supernatants was detected by a specific kit, and then cells were pretreated with a H₂O₂ inhibitor, and expression of MUC5AC was detected by real-time polymerase chain reaction (PCR), Western blot, and immunohistochemistry. Moreover, selective PKC and Nox inhibitors, apocynin and bisindolylmaleimide I, were used to pretreat cells and detect H₂O₂, MUC5AC mRNA and protein expression. Then, we pretreated cells with selective inhibitors or NE, and detected transforming growth factor α (TGF-α) using an ELISA kit.

RESULTS

H₂O₂ production increased in an NE dose-dependent manner (p < 0.001), and NE upregulated MUC5AC expression at both mRNA and protein levels, while DMTU, could reduce this high expression (p < 0.01 at mRNA level, p < 0.001 at grey analysis for western blot and p < 0.01 at mean density for immunohistochemical staining at protein level). Moreover, apocynin and bisindolylmaleimide I could reduce the H₂O₂ production stimulated by NE (p < 0.05), and reduce MUC5AC high expression (p < 0.01 at mRNA level, p < 0.001 at both grey analysis for western blot and mean density for immunohistochemical staining at protein level). In addition, NE induced TGF-α production, and any of the three selective inhibitors could reduce it (p < 0.05).

CONCLUSIONS

NE-induced reactive oxygen species participated in the upregulation of MUC5AC production. Moreover, protein kinase C and NADPH oxidase (Nox) regulate MUC5AC production in NE-challenged human biliary epithelial cells.

The activation of EGFR promotes myocardial tumor necrosis factor-α production and cardiac failure in endotoxemia

To study the effect of EGFR activation on the generation of TNF-α and the occurrence of cardiac dysfuncetion during sepsis, PD168393 and erlotinib (both are EGFR inhibitors) were applied to decreased the production of TNF-α and phosphrylation of ERK1/2 and p38 induced by LPS in cardiomyocytes. These results were further proved by specifically knocked down the expression of EGFR in vitro. Both TAPI-1, a TNF-α converting enzyme (TACE) inhibitor, and TGF-α neutralizing antibody could inhibit the activation of EGFR and the generation of TNF-α mRNA after LPS treatment. The increase of TGF-α in response to LPS could also be suppressed by TAPI-1. On the other hand, exogenous TGF-α increased the expression of TNF-α mRNA and partially reversed the inhibitory effect of TAPI-1 on expression of TNF-α mRNA in response to LPS indicating that the transactivation of EGFR by LPS in cardiomyocytes needs the help of TACE and TGF-α. In endotoxemic mice, inhibition the activation of EGFR not only decreased TNF-α production in the myocardium but also improved left ventricular pump function and ameliorated cardiac dysfunction and ultimately improved survival rate. All these results provided a new insight of how EGFR regulation the production of TNF-α in cardiomyocytes and a potential new target for the treatment of cardiac dysfunction in sepsis.

Helicobacter pylori-elicited induction in gastric mucosal matrix metalloproteinase-9 (MMP-9) release involves ERK-dependent cPLA2 activation and its recruitment to the membrane-localized Rac1/p38 complex

Matrix metalloproteinases (MMPs) are a family of endopeptidases implicated in a wide rage of degenerative and inflammatory diseases, including Helicobacter pylori-associated gastritis, and gastric and duodenal ulcer. As gastric mucosal inflammatory responses to H. pylori are characterized by the rise in MMP-9 production, as well as the induction in mitogen-activated protein kinase (MAPK) and Rac1 activation, we investigated the role of Rac1/MAPK in the processes associated with the release of MMP-9. We show that H. pylori LPS-elicited induction in gastric mucosal MMP-9 release is associated with MAPK, ERK and p38 activation, and occurs with the involvement of Rac1 and cytosolic phospholipase A2 (cPLA2). Further, we demonstrate that the LPS-induced MMP-9 release requires ERK-mediated phosphorylation of cPLA2 on Ser(505) that is essential for its membrane localization with Rac1, and that this process necessitates p38 participation. Moreover, we reveal that the activation and membrane translocation of p38 to the Rac1-GTP complex plays a pivotal role in cPLA2-dependent enhancement in MMP-9 release. Hence, our findings provide a strong evidence for the role of ERK/cPLA2 and Rac1/p38/cPLA2 cascade in H. pylori LPS-induced up-regulation in gastric mucosal MMP-9 release.

Effect of inhaled endotoxin on mucociliary clearance and airway inflammation in mild smokers and nonsmokers

BACKGROUND

In healthy nonsmokers, inhaled endotoxin [lipopolysaccharide (LPS)] challenge induces airway neutrophilia and modifies innate immune responses, but the effect on mucociliary clearance (MCC), a key host defense response, is unknown. Although smokers are chronically exposed to LPS through inhaled tobacco smoke, the acute effect of inhaled LPS on both MCC and airway inflammation is also unknown. The purpose of this study was to determine the effect of inhaled LPS on MCC in nonsmokers and mild smokers with normal pulmonary function.

METHODS

We performed an open-label inhalational challenge with 20,000 endotoxin units in healthy adult nonsmokers (n=18) and young adult, mild smokers (n=12). At 4 hr post LPS challenge, we measured MCC over a period of 2 hr, followed by sputum induction to assess markers of airway inflammation.

RESULTS

No significant changes in spirometry occurred in either group following LPS challenge. Following LPS, MCC was significantly (p<0.05) slowed in nonsmokers, but not in smokers [MCC=10±9% (challenge) vs. 15±8% (baseline), MCC=14±9% (challenge) vs. 16±10% (baseline), respectively]. Both groups showed a significant (p<0.05) increase in sputum neutrophils 6 hr post LPS challenge versus baseline. Although there was no correlation between the increased neutrophilia and depressed MCC post LPS in the nonsmokers, baseline neutrophil concentration predicted the LPS-induced decrease in MCC in the nonsmokers, i.e., lower baseline neutrophil concentration was associated with greater depression in MCC with LPS challenge (p<0.05).

CONCLUSIONS

These data show that a mild exposure to endotoxin acutely slows MCC in healthy nonsmokers. MCC in mild smokers is unaffected by mild endotoxin challenge, likely due to preexisting effects of cigarette smoke on their airway epithelium.

Omega-3 PUFA docosahexaenoic acid decreases LPS-stimulated MUC5AC production by altering EGFR-related signaling in NCI-H292 cells

Chronic obstructive pulmonary disease (COPD) is an inflammatory process characterized by airway mucus hypersecretion. Lipopolysaccharides (LPS) are known to stimulate the production of mucin 5AC (MUC5AC) via epidermal growth factor receptor (EGFR) in human airway cells. Noteworthy, we have previously demonstrated that EGFR/Rac1/reactive oxygen species (ROS)/matrix metalloproteinase 9 (MMP-9) is a key signaling cascade regulating MUC5AC production in airway cells challenged with LPS. Various reports have shown an inverse association between the intake of polyunsaturated fatty acids (PUFA) of the n-3 (omega-3) family or fish consumption and COPD. In the present study, we investigated the influence of docosahexaenoic acid (DHA), one of the most important omega-3 PUFA contained in fish oil, on the production of MUC5AC in LPS-challenged human airway cells NCI--H292. Our results indicate that DHA is capable of counteracting MUC5AC overproduction in LPS-stimulated cells by abrogating both EGFR phosphorylation and its downstream signaling pathway. This signaling pathway not only includes Rac1, ROS and MMP-9, but also NF-κB, since we have found that ROS require NF-κB activity to induce MMP-9 secretion and activation.

Caveolin-1 aggravates cigarette smoke extract-induced MUC5AC secretion in human airway epithelial cells

Airway mucus hypersecretion is a major pathological characteristic of chronic obstructive pulmonary disease (COPD), and cigarette smoke is highly implicated in mucus secretion and the development of COPD. Cigarette smoke reportedly induces mucin overproduction through the epidermal growth factor receptor (EGFR) in the airway epithelium; however, the underlying mechanisms responsible for the activation of EGFR remain unknown. Caveolin-1, a component protein in the cytomembrane, reportedly regulates airway inflammation and lung injury. In this study, we aimed to determine whether caveolin-1 modulates mucin hyperproduction induced by cigarette smoke. Our results revealed that cigarette smoke extract (CSE) significantly increased MUC5AC production, as well as the levels of phosphorylated EGFR (p-EGFR) and phosphorylated Akt (p-Akt) in human bronchial epithelial cells (16HBE cells), as shown by ELISA, RT-PCR and western blot analysis. These effects were prevented by treatment with EGFR inhibitor (AG1478) and phosphatidylinostol-3-kinase (PI3K) inhibitor (LY294002). We also found that the overexpression of caveolin-1 enhanced the expression of MUC5AC, p-EGFR and p-Akt induced by CSE. Conversely, the downregulation of caveolin-1 by siRNA against caveolin-1 inhibited the expression of MUC5AC, p-EGFR and p-Akt. Taken together, our data suggest that caveolin-1 enhances CSE-induced MUC5AC hypersecretion through the EGFR/PI3K/Akt signaling pathway.

Regulation of high glucose-mediated mucin expression by matrix metalloproteinase-9 in human airway epithelial cells

Mucus hypersecretion is the key manifestation in patients with chronic inflammatory airway diseases and mucin 5AC (MUC5AC) is a major component of airway mucus. Matrix metalloproteinases (MMP)-9, have been found to be involved in the pathogenesis of inflammatory airway diseases. Hyperglycemia has been shown to be an independent risk factor for respiratory infections. We hypothesize that high glucose (HG)-regulates MMP-9 production and MMP-9 activity through nicotinamide adenine dinucleotide phosphate (NADPH)/reactive oxygen species (ROS) cascades pathways, leading to mucin production in human airway epithelial cells (16HBE). We show that HG increases MMP-9 production, MMP-9 activity and MUC5AC expression. These effects are prevented by small interfering RNA (siRNA) for MMP-9, indicating that HG-induced mucin production is MMP-9-dependent. HG activates MMP-9 production, MMP-9 activity and MUC5AC overproduction, which is inhibited by nPG, DMSO and DPI (inhibitors of ROS and NADPH), suggesting that HG-activated mucin synthesis is mediated by NADPH/ROS in 16HBE cells. These observations demonstrate an important role for MMP-9 activated by NADPH/ROS signaling pathways in regulating HG-induced MUC5AC expression. These findings may bring new insights into the molecular pathogenesis of the infections related to diabetes mellitus and lead to novel therapeutic intervention for mucin overproduction in chronic inflammatory airway diseases.

Supplementation with γ-tocopherol attenuates endotoxin-induced airway neutrophil and mucous cell responses in rats

Neutrophil-mediated tissue injury is a shared pathogenesis of both chronic pulmonary diseases and acute responses to pathogens, allergens, and airborne pollutants. Interventions to minimize toxic effects of neutrophil-derived oxidants and proteases are usually limited to corticosteroids, which can have adverse side effects. We used a rodent model of endotoxin-induced lung injury to test the hypothesis that the dietary supplement γ-tocopherol (γT), a natural form of vitamin E with antioxidant and novel anti-inflammatory properties, will protect from adverse nasal and pulmonary inflammatory responses induced by endotoxin (lipopolysaccharide; LPS). Male Fisher F344 rats were intranasally (i.n.) instilled with LPS for 2 consecutive days. Beginning 2 days before i.n. LPS, the rats were gavaged daily with 30mg/kg γT. Twenty-four hours after the last i.n. LPS, bronchoalveolar lavage fluid (BALF) was collected, and pulmonary and nasal tissues were analyzed for gene expression and morphometric analyses of neutrophils and intraepithelial mucosubstances (IM). LPS caused increased BALF total cells (70% increase), neutrophils (300%), protein (35%), PGE2 (500%), and secreted mucins (75%). Robust increases in neutrophils and IM were detected in conducting airways. Pulmonary expression of MUC5AC, MIP-2, CINC-1, and MCP-1 was elevated three- to eightfold by LPS. Treatment with γT inhibited LPS-induced increases in BALF total cells, neutrophils, protein, PGE2, and secreted mucins, as well as IM and tissue neutrophil influx. Furthermore γT induced the expression of the regulatory cytokines IL-10 and IFN-γ while decreasing MUC5AC, MIP-2, CINC-1, and MCP-1. These data demonstrate novel therapeutic effects of the dietary vitamin E γT promoting anti-inflammatory pathways to protect from neutrophil-mediated lung injury.

Interleukin-13-induced MUC5AC expression is regulated by a PI3K-NFAT3 pathway in mouse tracheal epithelial cells

Interleukin-13 (IL-13) plays a critical role in asthma mucus overproduction, while the mechanisms underlying this process are not fully elucidated. Previous studies showed that nuclear factor of activated T cells (NFAT) is involved in the pathogenesis of asthma, but whether it can directly regulate IL-13-induced mucus (particularly MUC5AC) production is still not clear. Here we showed that IL-13 specifically induced NFAT3 activation through promoting its dephosphorylation in air-liquid interface (ALI) cultures of mouse tracheal epithelial cells (mTECs). Furthermore, both Cyclosporin A (CsA, a specific NFAT inhibitor) and LY294002 (a Phosphoinositide 3-kinase (PI3K) inhibitor) significantly blocked IL-13-induced MUC5AC mRNA and protein production through the inhibition of NFAT3 activity. We also confirmed that CsA could not influence the forkhead Box A2 (Foxa2) and mouse calcium dependent chloride channel 3 (mClca3) expression in IL-13-induced MUC5AC production, which both are known to be important in IL-13-stimulated mucus expression. Our study is the first to demonstrate that the PI3K-NFAT3 pathway is positively involved in IL-13-induced mucus production, and provided novel insights into the molecular mechanism of asthma mucus hypersecretion.

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 increases MUC5AC by TACE/TGF-α/EGFR pathway in human intrahepatic biliary epithelial cell

BACKGROUND

Mucin 5AC (MUC5AC) overproduction plays important roles in stone formation and recurrence of hepatolithiasis. We aim to investigate the involved mechanism and the potential target to block this process.

METHODS

42 bile duct samples from hepatolithiasis and 15 normal bile duct samples from hemangioma patients were collected for detecting MUC5AC expression by immunohistochemistry. MUC5AC and phosphoepidermal growth factor receptor (pEGFR) expressions in human intrahepatic biliary epithelial cells (HIBECs) cultured with or without lipopolysaccharide (LPS) were detected by real-time PCR and western blot analysis. Transforming growth factor-α (TGF-α) secretion in HIBECs was detected by ELISA.

RESULTS

MUC5AC was overexpressed in bile ducts of hepatolithiasis samples compared with bile ducts from hemangioma samples. LPS upregulated MUC5AC expression in HIBECs. LPS promoted EGFR activation, and inhibiting EGFR activation by AG1478 significantly decreased LPS-induced MUC5AC overexpression in HIBECs. Moreover, LPS increased TGF-α secretion, and inhibiting tumor necrosis factor-α converting enzyme (TACE), which has been implicated in ectodomain cleavage of TGF-α, significantly inhibited LPS-induced EGFR activation and subsequent MUC5AC overexpression in HIBECs.

CONCLUSION

Our results suggested that LPS increases MUC5AC expression through the TACE/TGF-α/EGFR pathway in HIBECs. This new finding might give light to the prevention of stone formation and recurrence of hepatolithiasis.

A new isoflavone glycitein 7-O-beta-D-glucoside 4''-O-methylate, isolated from Cordyceps militaris grown on germinated soybeans extract, inhibits EGF-induced mucus hypersecretion in the human lung mucoepidermoid cells

A new isoflavone glycitein 7-O-beta-d-glucoside 4''-O-methylate (CGLM) has been isolated recently from Cordyceps militaris grown on germinated soybean extract and has antioxidant activity. In the present study, CGLM was investigated for its suppression of airway mucous hyper-secretion in epidermal growth factor (EGF)-treated human lung mucoepidermoid cells. NCI-H292 cells were treated with CGLM for 1 h, followed by EGF treatment for 24 h. The decrease in cyclooxygenase-2 (COX-2) production was correlated with reduced levels of protein and mRNA of inducible matrix metalloproteinase 9 (MMP-9) and also MUC5AC gene expression. CGLM directly inhibited down-regulated NF-κB activity, and significantly inhibited the phosphorylation of p38 and ERK1/2 (p42/p44) in NCI-H292 cells. These results suggest that CGLM protects NCI-H292 cells from EGF-induced damage by down-regulation of COX-2, MMP-9 and MUC5AC gene expression, mediated via blocking the NF-kappa-B and p38/ERK MAPK pathways.

Aberrantly activated EGFR contributes to enhanced IL-8 expression in COPD airways epithelial cells via regulation of nuclear FoxO3A

BACKGROUND

Decreased activity of forkhead transcription factor class O (FoxO)3A, a negative regulator of NF-κB-mediated chemokine expression, is implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). Previously, we showed that quercetin reduces lung inflammation in a murine model of COPD. Here, we examined the mechanisms underlying decreased FoxO3A activation and its modulation by quercetin in COPD human airway epithelial cells and in a COPD mouse model.

METHODS

Primary COPD and normal human airway epithelial cells were treated with quercetin, LY294002 or erlotinib for 2 weeks. IL-8 was measured by ELISA. FoxO3A, Akt, and epidermal growth factor (EGF) receptor (EGFR) phosphorylation and nuclear FoxO3A levels were determined by Western blot analysis. Effects of quercetin on lung chemokine expression, nuclear FoxO3A levels and phosphorylation of EGFR and Akt were determined in COPD mouse model.

RESULTS

Compared with normal, COPD cells showed significantly increased IL-8, which negatively correlated with nuclear FoxO3A levels. COPD bronchial biopsies also showed reduced nuclear FoxO3A. Decreased FoxO3A in COPD cells was associated with increased phosphorylation of EGFR, Akt and FoxO3A and treatment with quercetin, LY294002 or erlotinib increased nuclear FoxO3A and decreased IL-8 and phosphorylation of Akt, EGFR and FoxO3A, Compared with control, elastase/LPS-exposed mice showed decreased nuclear FoxO3A, increased chemokines and phosphorylation of EGFR and Akt. Treatment with quercetin partially reversed these changes.

CONCLUSIONS

In COPD airways, aberrant EGFR activity increases PI 3-kinase/Akt-mediated phosphorylation of FoxO3A, thereby decreasing nuclear FoxO3A and increasing chemokine expression. Quercetin restores nuclear FoxO3A and reduces chemokine expression partly by modulating EGFR/PI 3-kinase/Akt activity.

Isoorientin induces apoptosis through mitochondrial dysfunction and inhibition of PI3K/Akt signaling pathway in HepG2 cancer cells

Isoorientin (ISO) is a flavonoid compound that can be extracted from several plant species, such as Phyllostachys pubescens, Patrinia, and Drosophyllum lusitanicum; however, its biological activity remains poorly understood. The present study investigated the effects and putative mechanism of apoptosis induced by ISO in human hepatoblastoma cancer (HepG2) cells. The results showed that ISO induced cell death in a dose-dependent manner in HepG2 cells, but no toxicity in human liver cells (HL-7702) and buffalo rat liver cells (BRL-3A) treated with ISO at the indicated concentrations. ISO-induced cell death included apoptosis which characterized by the appearance of nuclear shrinkage, the cleavage of poly (ADP-ribose) polymerase (PARP) and DNA fragmentation. ISO significantly (p<0.01) increased the Bax/Bcl-2 ratio, disrupted the mitochondrial membrane potential (MMP), increased the release of cytochrome c, activated caspase-3, and enhanced intracellular levels of reactive oxygen species (ROS) and nitric oxide (NO). In addition, ISO effectively inhibited the phosphorylation of Akt and increased FoxO4 expression. The PI3K/Akt inhibitor LY294002 enhanced the apoptosis-inducing effect of ISO. However, LY294002 markedly quenched ROS and NO generation and diminished the protein expression of heme peroxidase enzyme (HO-1) and inducible nitric oxide synthase (iNOS). Furthermore, the addition of a ROS inhibitor (N-acetyl cysteine, NAC) or iNOS inhibitor (N-[3-(aminomethyl) benzyl] acetamidine, dihydrochloride, 1400W) significantly diminished the apoptosis induced by ISO and also blocked the phosphorylation of Akt. These results demonstrated for the first time that ISO induces apoptosis in HepG2 cells and indicate that this apoptosis might be mediated through mitochondrial dysfunction and PI3K/Akt signaling pathway, and has no toxicity in normal liver cells, suggesting that ISO may have good potential as a therapeutic and chemopreventive agent for liver cancer.

Mucins and toll-like receptors: kith and kin in infection and cancer

Inflammation is underlying biological phenomenon common in infection and cancer. Mucins are glycoproteins which establish a physical barrier for undesirable entry of foreign materials through epithelial surfaces. A deregulated expression and an anomalous glycosylation pattern of mucins are known in large number of cancers. TLRs are class of receptors which recognize the molecular patterns of invading pathogens and activate complex inflammatory pathways to clear them. Aberrant expression of TLRs is observed in many cancers. A highly orchestrated action of mucins and TLRs is well evolved host defence mechanism; however, a link between the two in other non-infectious conditions has received less attention. Here we present an overview as to how mucins and TLRs give protection to the host and are deregulated during carcinogenesis. Further, we propose the possible mechanisms of cross-regulation between them in pathogenesis of cancer. As both mucins and TLRs are therapeutically important class of molecules, an understanding of the underlying molecular mechanisms connecting the two will open new avenues for the therapeutic targeting of cancer.

Scutellarin Attenuates Human-Neutrophil-Elastase-Induced Mucus Production by Inhibiting the PKC-ERK Signaling Pathway in Vitro and in Vivo

The aim of this study was to investigate the influence of scutellarin on mucus production induced by human neutrophil elastase (HNE) and the possible in vitro and in vivo mechanisms. To this purpose, cells were incubated with saline, scutellarin or gefitinib for 60 min and exposed to 0.1 μM HNE for 24 h. After being pretreated respectively with saline, scutellarin or gefitinib, rats were challenged intratracheally with HNE by means of nebulization for 30 days. The expression of mucin (MUC) 5AC, protein kinase C (PKC), and extracellular signal-regulated kinase 1/2 (ERK1/2) was assessed by ELISA, RT-PCR or Western blotting. The results showed that scutellarin inhibited MUC5AC mRNA and protein expressions induced by HNE in a concentration-dependent manner in vitro. In the in vivo model, scutellarin significantly attenuated MUC5AC mRNA expression and goblet cell hyperplasia in rats treated with HNE for 30 days, as well as decreased the phosporylation of PKC and ERK1/2 compared to the HNE control group. Therefore, our study showed that scutellarin could prevent mucus hypersecretion by inhibiting the PKC-ERK signaling pathway. Inhalation scutellarin may be valuable in the treatment of chronic inflammatory lung disease.

The liquid Panax ginseng inhibits epidermal growth factor-induced metalloproteinase 9 and cyclooxygenase 2 expressions via inhibition of inhibitor factor kappa-B-alpha and extracellular signal-regulated kinase in NCI-H292 human airway epithelial cells

BACKGROUND

Ginseng (Panax ginseng C.A. Meyer) has been used in Asian countries for the treatment of various diseases. However, the mechanisms of liquid Panax ginseng (LG) on allergic inflammatory response in epidermal growth factor (EGF)-stimulated human airway epithelial cells remain largely unclear.

METHODS

MUC5AC, cyclooxygenase (COX) 2, and matrix metalloproteinase (MMP) 9 expressions were measured using reverse transcription-polymerase chain reaction, Western blotting, and gelatin zymogram analyses in NCI-H292 cells. Extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (MAPK) protein levels were analyzed by Western blotting.

RESULTS

To gain insight into the antiallergy effects of LG, we examined its influence on epidermal growth factor (EGF)-induced MMP-9 and COX-2 productions in NCI-H292 cells. LG was treated for 1 hour and then followed by EGF treatment for 24 hours into NCI-H292 cells. The decrease of COX-2 production was correlated with the reduced levels of proteins and mRNAs of inducible MMP-9 and MUC5AC. LG blocked upstream signaling of NF-kappa-B activation via inhibition of phosphorylations of inhibitor factor-kappa- B-alpha (I-kappa-B-alpha) and ERK. These results suggest that LG protects NCI-H292 cells from EGF-induced damage by down-regulation of COX-2, MMP-9, and MUC5AC gene expressions by blocking NF-kappa-B and ERK.

CONCLUSION

LG modulates allergic inflammatory response in EGF-stimulated NCI-H292 human airway epithelial cells via inhibition of I-kappa-B-alpha and ERK.

The extracellular signal-regulated kinase mitogen-activated protein kinase/ribosomal S6 protein kinase 1 cascade phosphorylates cAMP response element-binding protein to induce MUC5B gene expression via D-prostanoid receptor signaling

Mucus hypersecretion is a prominent feature of respiratory diseases, and MUC5B is a major airway mucin. Mucin gene expression can be affected by inflammatory mediators, including prostaglandin (PG) D(2,) an inflammatory mediator synthesized by hematopoietic PGD synthase (H-PGDS). PGD(2) binds to either D-prostanoid receptor (DP1) or chemoattractant receptor homologous molecule expressed on T-helper type 2 cells (CRTH2). We investigated the mechanisms by which PGD(2) induces MUC5B gene expression in airway epithelial cells. Western blot analysis showed that H-PGDS was highly expressed in nasal polyps. Similar results were obtained for PGD(2) expression. In addition, we could clearly detect the expressions of both H-PGDS and DP1 in nasal epithelial cells but not CRTH2. We demonstrated that PGD(2) increased MUC5B gene expression in normal human nasal epithelial cells as well as in NCI-H292 cells in vitro. S5751, a DP1 antagonist, inhibited PGD(2)-induced MUC5B expression, whereas a CRTH2 antagonist (OC0459) did not. These data suggest that PGD(2) induced MUC5B expression via DP1. Pretreatment with extracellular signal-regulated kinase (ERK) inhibitor (PD98059) blocked both PGD(2)-induced ERK mitogen-activated protein kinase (MAPK) activation and MUC5B expression. Proximity ligation assays showed direct interaction between RSK1 and cAMP response element-binding protein (CREB). Stimulation with PGD(2) caused an increase in intracellular cAMP levels, whereas intracellular Ca(2+) did not have such an effect. PGD(2)-induced MUC5B mRNA levels were regulated by CREB via direct interaction with two cAMP-response element sites (-921/-914 and -900/-893). Finally, we demonstrated that PGD(2) can induce MUC5B overproduction via ERK MAPK/RSK1/CREB signaling and that DP1 receptor may have suppressive effects in controlling MUC5B overproduction in the airway.

Inhibition of Rac activity alleviates lipopolysaccharide-induced acute pulmonary injury in mice

BACKGROUND

Rac small GTPases play important roles in cytoskeleton and many cell functions including cell cycle, cell growth, cell adhesion and gene transcription. Here, we investigated the roles of Rac including Rac1 and Rac2 in lipopolysaccharide (LPS)-induced pulmonary injury.

METHODS

After LPS was intratracheally instilled to lungs in mice, Rac, CDC42 and RhoA activation assay by pull-down and West blot, inflammatory cell infiltration assay by counting cell numbers and lung histological examination, pro-inflammatory mediator mRNA expression assay by quantitative RT-PCR, measurement of myeloperoxidase (MPO) activity, Evans Blue and albumin accumulation by spectrophotometry were performed to evaluate the roles of Rac in pulmonary injury by using its specific inhibitor, NSC23766.

RESULTS

LPS challenge led to increases of both Rac1 and Rac2, but not CDC42 or RhoA activities in lungs, and intraperitoneal administration with NSC23766 inhibited both Rac1 and Rac2, but not CDC42 or RhoA activities. Treatment with NSC23766 at 1 or 3mg/kg not only reduced the inflammatory cells infiltration and MPO activities, but also inhibited pro-inflammatory mediators, tumor necrosis factor-α and interleukin-1β, mRNA expression. Moreover, in vitro neutrophil migration assay and in vivo microvascular permeability assay indicated that NSC23766 not only inhibited neutrophil transwell migration toward a chemoattractant, fMLP, but also reduced Evans Blue and albumin accumulation in LPS-challenged lungs. LPS activated both Rac1 and Rac2, but not CDC42 or RhoA activities in lungs, and specific inhibition of Rac activities by NSC23766 effectively alleviated LPS-induced injury.

GENERAL SIGNIFICANCE

Rac could be a potential target for therapeutic intervention of pulmonary inflammation.

Role of hyaluronan and CD44 in reactive oxygen species-induced mucus hypersecretion

Mucus hypersecretion is an important manifestation in patients with chronic inflammatory airway diseases. Mucin 5AC (MUC5AC) is a major component of airway mucus. MUC5AC expression is regulated by epidermal growth factor receptor (EGFR) which can be activated by reactive oxygen species (ROS). Hyaluronan (HA), a linear glycosaminoglycan with molecular weights ranging from 2 × 10(5) to 1 × 10(7), is expressed in airway epithelium and can be depolymerized by ROS into hyaluronan fragments. The mechanisms through which fragmented HA exerts its biologic functions have been elucidated by interactions with its receptor CD44. The aim of our study was to examine the role of HA and CD44 in ROS-induced EGFR activation and MUC5AC expression. We exposed NCI-H292 cells to ROS generated by xanthine/xanthine oxidase (X/XO). ROS-induced EGFR phosphorylation, which was activated by tissue kallekrein (TK) activation and EGF release. We found ROS promoted CD44 co-immunoprecipitation with EGFR and MUC5AC up-regulation. These effects were mimicked by hyaluronan fragments. All the effects were inhibited by blocking CD44 or EGFR, suggesting that CD44 plays a critical role in ROS-induced MUC5AC up-regulation. These results show that ROS depolymerizes hyaluronan into fragments, and these fragments bind their receptor CD44 to induce TK activation, which cleaves EGF precursors into mature EGF to activate its receptor EGFR. Furthermore, we provide evidence that hyaluronan fragments are sufficient to induce CD44/EGFR interaction and EGFR signaling which lead to MUC5AC expression. The results indicate that the regulation of ROS-induced MUC5AC expression by hyaluronan and CD44 may provide important insights in the mechanism of mucus hypersecretion.

Rac1-mediated mitochondrial H2O2 generation regulates MMP-9 gene expression in macrophages via inhibition of SP-1 and AP-1

Aberrant matrix deposition is a hallmark of pulmonary fibrosis and is characterized by an imbalance between matrix deposition and degradation. We have previously shown that mice harboring a conditional deletion of the GTP-binding protein, Rac1, in macrophages are protected from asbestos-induced pulmonary fibrosis. To investigate the contribution of aberrant matrix degradation, we addressed the role of Rac1 in regulating expression of macrophage-specific MMP-9 (matrix metalloproteinase-9). We found that MMP-9 gene transcription was significantly greater in Rac1 null macrophages. Deletion and mutational analysis of the MMP-9 promoter revealed that both SP-1 and AP-1 are essential for MMP-9 transcription. Overexpression of constitutive active Rac1 (V12) revealed that H(2)O(2) was derived from the mitochondria. Rac1-induced H(2)O(2) generation down-regulated MMP-9 gene transcription, whereas catalase overexpression in WT cells enhanced MMP-9 expression. SP-1 interacted directly with both c-Jun and c-Fos, and H(2)O(2) decreased this binding, suggesting that SP-1 and AP-1 function cooperatively to regulate MMP-9 transcription. Rac1-mediated H(2)O(2) inhibited the ERK MAPK, which was essential for activation of SP-1 and AP-1. ERK activation and MMP-9 expression were recovered by overexpressing catalase or transfecting siRNA for the mitochondrial iron-sulfur protein, Rieske. These observations were recapitulated in vivo. MMP-9 mRNA was higher in alveolar macrophages isolated from Rac1 null mice and wild type mice given catalase. Rac1 regulates MMP-9 transcription via mitochondrial H(2)O(2) generation, providing a potential mechanism by which Rac1 null mice fail to develop pulmonary fibrosis.