Epithelium-fibroblast interactions in response to airway inflammation

Understanding fibroblast-immune cell interactions via co-culture models and their role in asthma pathogenesis

Asthma is a chronic lung disease involving airway inflammation and fibrosis. Fibroblasts are the main effector cells important for lung tissue production which becomes abnormal in asthmatics and is one of the main contributors to airway fibrosis. Although fibroblasts were traditionally viewed solely as structural cells, they have been discovered to be highly active, and involved in lung inflammatory and fibrotic processes in asthma. In line with this, using 2D and 3D in vitro co-culture models, a complex interaction between lung fibroblasts and various immune cells important for the pathogenesis of asthma have been recently uncovered. Hence, in this review, we provide the first-ever summary of various studies that used 2D and 3D in vitro co-culture models to assess the nature of aberrant immune cell-fibroblast interactions and their contributions to chronic inflammation and fibrotic mechanisms in asthma pathogenesis.

Innate Immunity, Epithelial Plasticity, and Remodeling in Asthma

Innate immune responses (IIR) of the epithelium play a critical role in the initiation and progression of asthma. The core of the IIR is an intracellular signaling pathway activated by pattern recognition receptors (PRRs) to limit the spread of infectious organisms. This chapter will focus on the epithelium as the major innate sentinel cell and its role in acute exacerbations (AEs). Although the pathways of how the IIR activates the NFκB transcription factor, triggering cytokine secretion, dendritic cell activation, and Th2 polarization are well-described, recent exciting work has developed mechanistic insights into how chronic activation of the IIR is linked to mucosal adaptive responses. These adaptations include changes in cell state, now called epithelial-mesenchymal plasticity (EMP). EMP is a coordinated, genomic response to airway injury disrupting epithelial barrier function, expanding the basal lamina, and producing airway remodeling. EMP is driven by activation of the unfolded protein response (UPR), a transcriptional response producing metabolic shunting of glucose through the hexosamine biosynthetic pathway (HBP) to protein N-glycosylation. NFκB signaling and UPR activation pathways potentiate each other in remodeling the basement membrane. Understanding of injury-repair process of epithelium provides new therapeutic targets for precision approaches to the treatment of asthma exacerbations and their sequelae.

The anti-asthmatic potential of Rho-kinase inhibitor hydroxyfasudil in the model of experimentally induced allergic airway inflammation

OBJECTIVE

This experimental study evaluated the anti-asthmatic potential of the Rho-kinase inhibitor hydroxyfasudil in the settings of allergen-induced allergen-induced experimental asthma.

METHODS

Chronic allergic airway inflammation was caused by 28 days-sensitisation of guinea pigs with ovalbumin (OVA). Hydroxyfasudil was administered intraperitoneally in two doses for the last two weeks (1 mg/kg b.w.; 10 mg/kg b.w.). The degree of allergic inflammation was determined based on concentrations of inflammatory Th2 cytokines (IL-4, IL-13), Th1 cytokines (TNF-α and IFN-γ) in the lung homogenate and leukocyte count in the bronchoalveolar lavage fluid (BALF). The markers of remodelling and fibrosis, the growth factors (TGF-β1, EGF), EGF receptor, collagen type III and V were estimated in lung homogenate. The changes in specific airway resistance (sRaw) were used as an in vivo bronchial hyperreactivity parameter.

RESULTS

Hydroxyfasudil administration at both doses significantly reduced sRaw after a week of therapy. We observed a decline of IL-13, TNF-α and IFN-γ in lung homogenate and a lower presence of lymphocytes in BALF after 14 days of hydroxyfasudil administration at both tested doses. Hydroxyfasudil 14 days-treatment at both doses effectively reduced the concentrations of TGF-β1, EGF receptors, collagen type III and V in BALF and modulated EGF levels.

CONCLUSIONS

These findings indicate that RhoA/Rho-kinase is involved in the pathophysiology of allergic airway inflammation and suggest that Rho-kinase inhibitor hydroxyfasudil has therapeutic potential for asthma management.

The Hexosamine Biosynthetic Pathway Links Innate Inflammation With Epithelial-Mesenchymal Plasticity in Airway Remodeling

Disruption of the lower airway epithelial barrier plays a major role in the initiation and progression of chronic lung disease. Here, repetitive environmental insults produced by viral and allergens triggers metabolic adaptations, epithelial-mesenchymal plasticity (EMP) and airway remodeling. Epithelial plasticity disrupts epithelial barrier function, stimulates release of fibroblastic growth factors, and remodels the extracellular matrix (ECM). This review will focus on recent work demonstrating how the hexosamine biosynthetic pathway (HBP) links innate inflammation to airway remodeling. The HBP is a core metabolic pathway of the unfolded protein response (UPR) responsible for protein N-glycosylation, relief of proteotoxic stress and secretion of ECM modifiers. We will overview findings that the IκB kinase (IKK)-NFκB pathway directly activates expression of the SNAI-ZEB1 mesenchymal transcription factor module through regulation of the Bromodomain Containing Protein 4 (BRD4) chromatin modifier. BRD4 mediates transcriptional elongation of SNAI1-ZEB as well as enhancing chromatin accessibility and transcription of fibroblast growth factors, ECM and matrix metalloproteinases (MMPs). In addition, recent exciting findings that IKK cross-talks with the UPR by controlling phosphorylation and nuclear translocation of the autoregulatory XBP1s transcription factor are presented. HBP is required for N glycosylation and secretion of ECM components that play an important signaling role in airway remodeling. This interplay between innate inflammation, metabolic reprogramming and lower airway plasticity expands a population of subepithelial myofibroblasts by secreting fibroblastic growth factors, producing changes in ECM tensile strength, and fibroblast stimulation by MMP binding. Through these actions on myofibroblasts, EMP in lower airway cells produces expansion of the lamina reticularis and promotes airway remodeling. In this manner, metabolic reprogramming by the HBP mediates environmental insult-induced inflammation with remodeling in chronic airway diseases.

Responsiveness of human bronchial fibroblasts and epithelial cells from asthmatic and non-asthmatic donors to the transforming growth factor-β1 in epithelial-mesenchymal trophic unit model

BACKGROUND

The asthma-related airway wall remodeling is associated i.a. with a damage of bronchial epithelium and subepithelial fibrosis. Functional interactions between human bronchial epithelial cells and human bronchial fibroblasts are known as the epithelial-mesenchymal trophic unit (EMTU) and are necessary for a proper functioning of lung tissue. However, a high concentration of the transforming growth factor-β₁ (TGF-β₁) in the asthmatic bronchi drives the structural disintegrity of epithelium with the epithelial-to-mesenchymal transition (EMT) of the bronchial epithelial cells, and of subepithelial fibrosis with the fibroblast-to-myofibroblast transition (FMT) of the bronchial fibroblasts. Since previous reports indicate different intrinsic properties of the human bronchial epithelial cells and human bronchial fibroblasts which affect their EMT/FMT potential beetween cells derived from asthmatic and non-asthmatic patients, cultured separatelly in vitro, we were interested to see whether corresponding effects could be obtained in a co-culture of the bronchial epithelial cells and bronchial fibroblasts. In this study, we investigate the effects of the TGF-β₁ on the EMT markers of the bronchial epithelial cells cultured in the air-liquid-interface and effectiveness of FMT in the bronchial fibroblast populations in the EMTU models.

RESULTS

Our results show that the asthmatic co-cultures are more sensitive to the TGF-β₁ than the non-asthmatic ones, which is associated with a higher potential of the asthmatic bronchial cells for a profibrotic response, analogously to be observed in '2D' cultures. They also indicate a noticeable impact of human bronchial epithelial cells on the TGF-β₁-induced FMT, stronger in the asthmatic bronchial fibroblast populations in comparison to the non-asthmatic ones. Moreover, our results suggest the protective effects of fibroblasts on the structure of the TGF-β₁-exposed mucociliary differentiated bronchial epithelial cells and their EMT potential.

CONCLUSIONS

Our data are the first to demonstrate a protective effect of the human bronchial fibroblasts on the properties of the human bronchial epithelial cells, which suggests that intrinsic properties of not only epithelium but also subepithelial fibroblasts affect a proper condition and function of the EMTU in both normal and asthmatic individuals.

Pathophysiology of Lung Disease and Wound Repair in Cystic Fibrosis

Cystic fibrosis (CF) is an autosomal recessive, life-threatening condition affecting many organs and tissues, the lung disease being the chief cause of morbidity and mortality. Mutations affecting the CF Transmembrane Conductance Regulator (CFTR) gene determine the expression of a dysfunctional protein that, in turn, triggers a pathophysiological cascade, leading to airway epithelium injury and remodeling. In vitro and in vivo studies point to a dysregulated regeneration and wound repair in CF airways, to be traced back to epithelial CFTR lack/dysfunction. Subsequent altered ion/fluid fluxes and/or signaling result in reduced cell migration and proliferation. Furthermore, the epithelial-mesenchymal transition appears to be partially triggered in CF, contributing to wound closure alteration. Finally, we pose our attention to diverse approaches to tackle this defect, discussing the therapeutic role of protease inhibitors, CFTR modulators and mesenchymal stem cells. Although the pathophysiology of wound repair in CF has been disclosed in some mechanisms, further studies are warranted to understand the cellular and molecular events in more details and to better address therapeutic interventions.

The SWI/SNF-Related, Matrix Associated, Actin-Dependent Regulator of Chromatin A4 Core Complex Represses Respiratory Syncytial Virus-Induced Syncytia Formation and Subepithelial Myofibroblast Transition

Epigenetics plays an important role in the priming the dynamic response of airway epithelial cells to infectious and environmental stressors. Here, we examine the epigenetic role of the SWI/SNF Related, Matrix Associated, Actin Dependent Regulator of Chromatin A4 (SMARCA4) in the epithelial response to RSV infection. Depletion of SMARCA4 destabilized the abundance of the SMARCE1/ARID1A SWI/SNF subunits, disrupting the innate response and triggering a hybrid epithelial/mesenchymal (E/M) state. Assaying SMARCA4 complex-regulated open chromatin domains by transposase cleavage -next generation sequencing (ATAC-Seq), we observed that the majority of cleavage sites in uninfected cells have reduced chromatin accessibility. Paradoxically, SMARCA4 complex-depleted cells showed enhanced RSV-inducible chromatin opening and gene expression in the EMT pathway genes, MMP9, SNAI1/2, VIM, and CDH2. Focusing on the key MMP9, we observed that SMARCA4 complex depletion reduced basal BRD4 and RNA Polymerase II binding, but enhanced BRD4/Pol II binding in response to RSV infection. In addition, we observed that MMP9 secretion in SMARCA4 complex deficient cells contributes to mesenchymal transition, cellular fusion (syncytia) and subepithelial myofibroblast transition. We conclude the SMARCA4 complex is a transcriptional repressor of epithelial plasticity, whose depletion triggers a hybrid E/M state that affects the dynamic response of the small airway epithelial cell in mucosal remodeling via paracrine MMP9 activity.

Interleukin-26 in host defense and inflammatory disorders of the airways

The dimeric cytokine interleukin (IL)-26 belongs to the IL-10 family. Whereas it was originally perceived as a T-helper (Th)17 cytokine, subsequent studies have shown that IL-26 is produced by several populations of leukocytes and structural cells. This cytokine binds to a heterodimeric receptor complex including IL-10R2 and -20R1 (IL-26R) and signals through STAT 1 and 3 to induce the release of chemokines and growth factors. Remarkably, IL-26 directly kills bacteria and inhibits viral replication. The most recent studies on human airways confirm multiple cellular sources in this critical interphase of host defense and demonstrate that stimulation of toll-like receptors (TLR) trigger the release of IL-26. Once released, it exerts a dualistic effect on cytokine production and up-regulates gene expression of IL-26R. It also potentiates chemotaxis and inhibits chemokinesis for neutrophils, thereby facilitating the accumulation of innate effector cells at the site of bacterial stimulation. The high levels of IL-26 in human airways are altered in inflammatory airway disorders such as asthma and chronic obstructive pulmonary disease. Thus, IL-26 emerges as an important mediator, providing direct and indirect actions on microbes, actions that are essential for host defense and inflammation and bears potential as a biomarker of disease.

The Differential Effect of Carbon Dots on Gene Expression and DNA Methylation of Human Embryonic Lung Fibroblasts as a Function of Surface Charge and Dose

This study presents a toxicological evaluation of two types of carbon dots (CD), similar in size (<10 nm) but differing in surface charge. Whole-genome mRNA and miRNA expression (RNAseq), as well as gene-specific DNA methylation changes, were analyzed in human embryonic lung fibroblasts (HEL 12469) after 4 h and 24 h exposure to concentrations of 10 and 50 µg/mL (for positive charged CD; pCD) or 10 and 100 µg/mL (for negative charged CD, nCD). The results showed a distinct response for the tested nanomaterials (NMs). The exposure to pCD induced the expression of a substantially lower number of mRNAs than those to nCD, with few commonly differentially expressed genes between the two CDs. For both CDs, the number of deregulated mRNAs increased with the dose and exposure time. The pathway analysis revealed a deregulation of processes associated with immune response, tumorigenesis and cell cycle regulation, after exposure to pCD. For nCD treatment, pathways relating to cell proliferation, apoptosis, oxidative stress, gene expression, and cycle regulation were detected. The expression of miRNAs followed a similar pattern: more pronounced changes after nCD exposure and few commonly differentially expressed miRNAs between the two CDs. For both CDs the pathway analysis based on miRNA-mRNA interactions, showed a deregulation of cancer-related pathways, immune processes and processes involved in extracellular matrix interactions. DNA methylation was not affected by exposure to any of the two CDs. In summary, although the tested CDs induced distinct responses on the level of mRNA and miRNA expression, pathway analyses revealed a potential common biological impact of both NMs independent of their surface charge.

Serum periostin and TNF-α levels in patients with obstructive sleep apnea-hypopnea syndrome

PURPOSE

Obstructive sleep apnea-hypopnea syndrome (OSAHS) may cause pulmonary diseases, and periostin plays an important role on the development of pulmonary diseases. In addition, periostin and pro-inflammatory cytokine TNF-α can regulate each other in vivo. This study aimed to observe the changes of serum periostin and TNF-α levels in patients with OSAHS compared with healthy volunteers and to investigate their correlation.

METHODS

A convenience sample of 67 patients with OSAHS in our hospital from December 2018 to December 2019 was selected and categorized into mild, moderate, and severe groups according to apnea-hypopnea index by polysomnography. In addition, 21 healthy volunteers were selected as the control group. Serum levels of periostin and TNF-α were determined by enzyme-linked immunosorbent assay (ELISA). Results were analyzed using the SPSS software.

RESULTS

Both serum periostin and TNF-α levels in all the three OSAHS groups were higher than those of the control group and increased with severity of OSAHS. The severe group had significantly higher serum periostin and TNF-α levels than the mild and moderate groups (p < 0.05). For patients with OSAHS, serum periostin and TNF-α levels positively correlated with the apnea-hypopnea index (AHI) (p < 0.01) and negatively correlated with the lowest saturation oxygen (LSaO₂) and mean saturation oxygen (MSaO₂) (both p < 0.01). In addition, there was a positive correlation between serum periostin and TNF-α levels in patients with OSAHS (p < 0.001).

CONCLUSIONS

Serum periostin and TNF-α levels were significantly increased in patients with OSAHS and may serve as a potential biomarker for severity of OSAHS. These findings suggest that it may be fruitful to study the role of periostin and TNF-α in OSAHS-induced pulmonary diseases.

Cell-Specific DNA Methylation Signatures in Asthma

Asthma is a complex trait, often associated with atopy. The genetic contribution has been evidenced by familial occurrence. Genome-wide association studies allowed for associating numerous genes with asthma, as well as identifying new loci that have a minor contribution to its phenotype. Considering the role of environmental exposure on asthma development, an increasing amount of literature has been published on epigenetic modifications associated with this pathology and especially on DNA methylation, in an attempt to better understand its missing heritability. These studies have been conducted in different tissues, but mainly in blood or its peripheral mononuclear cells. However, there is growing evidence that epigenetic changes that occur in one cell type cannot be directly translated into another one. In this review, we compare alterations in DNA methylation from different cells of the immune system and of the respiratory tract. The cell types in which data are obtained influences the global status of alteration of DNA methylation in asthmatic individuals compared to control (an increased or a decreased DNA methylation). Given that several genes were cell-type-specific, there is a great need for comparative studies on DNA methylation from different cells, but from the same individuals in order to better understand the role of epigenetics in asthma pathophysiology.

Pharmacological Modulation of Endotoxin-Induced Release of IL-26 in Human Primary Lung Fibroblasts

Background: Interleukin (IL)-26 is a neutrophil-mobilizing and bactericidal cytokine that is enhanced in human airways in vivo in response to endotoxin from Gram-negative bacteria. This cytokine is also enhanced in the airways during exacerbations of chronic obstructive pulmonary disease (COPD). Here, we investigated whether human primary lung fibroblasts (HLF) release IL-26 constitutively and in response to TLR4 stimulation by endotoxin and characterized the effects of bronchodilatory and anti-inflammatory drugs utilized in COPD.

Methods: The HLF were stimulated with different concentrations of endotoxin. Cells were also treated with different concentrations of bronchodilatory and anti-inflammatory drugs, with and without endotoxin stimulation. Cytokine protein concentrations were quantified in the cell-free conditioned media [enzyme-linked immunosorbent assay (ELISA)], and the phosphorylation levels of intracellular signaling molecules were determined (phosphoELISA).

Results: Whereas HLF displayed constitutive release of IL-26 into the conditioned medium, endotoxin markedly enhanced this release, as well as that of IL-6 and IL-8. This cytokine release was paralleled by increased phosphorylation of the intracellular signaling molecules NF-κB, c-Jun N-terminal kinase (JNK) 1-3, p38, and extracellular signal-regulated kinase (ERK) 1/2. The glucocorticoid hydrocortisone caused substantial inhibition of the endotoxin-induced release of IL-26, IL-6, and IL-8, an effect paralleled by a decrease of the phosphorylation of NF-κB, p38, and ERK1/2. The muscarinic receptor antagonist (MRA) tiotropium, but not aclidinium, caused minor inhibition of the endotoxin-induced release of IL-26 and IL-8, paralleled by a decreased phosphorylation of NF-κB. The β2-adrenoceptor agonist salbutamol caused modest inhibition of the endotoxin-induced release of IL-26 and IL-8, paralleled by a decreased phosphorylation of NF-κB, JNK1-3, and p38. Similar pharmacological effects were observed for the constitutive release of IL-26.

Conclusions: The HLF constitute an abundant source of IL-26 that may contribute to local host defense against Gram-negative bacteria. Among the tested drugs, the glucocorticoid displayed the most powerful inhibitory effect, affecting the NF-κB, p38, and ERK1/2 signaling pathways. Whether or not this inhibition of IL-26 contributes to an increased risk for local infections in COPD requires further evaluation.

Efficacy of Novel Highly Specific Bromodomain-Containing Protein 4 Inhibitors in Innate Inflammation-Driven Airway Remodeling

NF-κB/RelA triggers innate inflammation by binding to bromodomain-containing protein 4 (BRD4), an atypical histone acetyltransferase (HAT). Although RelA·BRD4 HAT mediates acute neutrophilic inflammation, its role in chronic and functional airway remodeling is not known. We observed that BRD4 is required for Toll-like receptor 3 (TLR3)-mediated mesenchymal transition, a cell-state change that is characteristic of remodeling. We therefore tested two novel highly selective BRD4 inhibitors, ZL0420 and ZL0454, for their effects on chronic airway remodeling produced by repetitive TLR3 agonist challenges, and compared their efficacy with that of two nonselective bromodomain and extraterminal (BET) protein inhibitors, JQ1 and RVX208. We observed that ZL0420 and ZL0454 more potently reduced polyinosinic:polycytidylic acid-induced weight loss and fibrosis as assessed by microcomputed tomography and second harmonic generation microscopy. These measures correlated with the collagen deposition observed in histopathology. Importantly, the ZL inhibitors were more effective than the nonselective BET inhibitors at equivalent doses. The ZL inhibitors had significant effects on lung physiology, reversing TLR3-associated airway hyperresponsiveness and increasing lung compliance in vivo. At the molecular level, ZL inhibitors reduced elaboration of the transforming growth factor-β-induced growth program, thereby preventing mucosal mesenchymal transition and disrupting BRD4 HAT activity and complex formation with RelA. We also observed that ZL0454 treatment blocked polyinosinic:polycytidylic acid-associated expansion of the α-SMA1⁺/COL1A⁺ myofibroblast population and prevented myofibroblast transition in a coculture system. We conclude that 1) BRD4 is a central effector of the mesenchymal transition that results in paracrine activation of myofibroblasts, mechanistically linking innate inflammation to airway hyperresponsiveness and fibrosis, and 2) highly selective BRD4 inhibitors may be effective in reversing the effects of repetitive airway viral infections on innate inflammation-mediated remodeling.

Radiation-induced lung injury: impact on macrophage dysregulation and lipid alteration - a review

Lung cancer continues to be the leading cause of cancer deaths and more than one million lung cancer patients will die every year worldwide. Radiotherapy (RT) plays an important role in lung cancer treatment, but the side effects of RT are pneumonitis and pulmonary fibrosis. RT-induced lung injury causes damage to alveolar-epithelial cells and vascular endothelial cells. Macrophages play an important role in the development of pulmonary fibrosis despite its role in immune response. These injury activated macrophages develop into classically activated M1 macrophage or alternative activated M2 macrophage. It secretes cytokines, interleukins, interferons, and nitric oxide. Several pro-inflammatory lipids and pro-apoptotic proteins cause lipotoxicity such as LDL, FC, DAG, and FFA. The overall findings in this review conclude the importance of macrophages in inducing toxic/inflammatory effects during RT of lung cancer, which is clinically vital to treat the radiation-induced fibrosis.

Nasal polyp fibroblasts modulate epithelial characteristics via Wnt signaling

BACKGROUND

While essential to the normal differentiation of ciliated airway epithelial cells, upregulated Wnt signaling in chronic rhinosinusitis with nasal polyps (CRSwNP) has been proposed to result in abnormal epithelial morphology and dysfunctional mucociliary clearance. The mechanism of epithelial Wnt signaling dysregulation in CRSwNP is unknown, and importantly cellular sources of Wnt ligands in CRSwNP have not yet been investigated.

METHODS

Human sinonasal epithelial cells (hSNECs) and human sinonasal fibroblasts (hSNFs) were collected from 34 human subjects (25 control and 9 CRSwNP) and differentiated as primary air-liquid interface (ALI) and organoid co-cultures. hSNECs were isolated to the apical compartment of the transwell and hSNFs were isolated to the basolateral compartment. After 21 days of ALI culture, ciliary expression and sinonasal epithelial morphology were examined by immunohistochemistry (IHC) and quantitative real-time polymerase chain reaction (qRT-PCR). An organoid model was used to evaluate proliferation of basal cells in presence of hSNFs.

RESULTS

Epithelial cells co-cultured with CRSwNP-hSNFs revealed significantly decreased ciliated cells, altered epithelial cell morphology, and increased colony forming efficiency compared to epithelial cells co-cultured with control-hSNFs. CRSwNP-hSNFs showed significantly higher messenger RNA (mRNA) expression of canonical WNT3A. A Wnt agonist, CHIR99021, replicated CRSwNP-hSNF co-cultures, and treatment with the Wnt inhibitor IWP2 prevented abnormal morphologies.

CONCLUSION

These results suggest that abnormal interactions between epithelial cells and fibroblasts may contribute to CRSwNP pathogenesis and supports the concept that dysregulated Wnt signaling contributes impairment to epithelial function in CRSwNP.

Cigarette smoke upregulates SPRR3 by favoring c-Jun/Fra1 heterodimerization in human bronchial epithelial cells

AIM

The airway epithelium of smokers exhibits upregulated SPRR3, an indicator of pathogenic keratinization. The mechanisms underlying this phenomenon require investigation.

PATIENTS & METHODS

Human bronchial epithelial (HBE) SPRR3 expression was analyzed by smoking status. Primary HBE cells were exposed to cigarette smoke (CS). SPRR3 expression, SPRR3 promoter activity, AP-1 factor binding and AP-1 factors' effects were analyzed.

RESULTS

Current smokers display SPRR3 upregulation relative to never smokers. CS upregulates SPRR3 transcription in an exposure-dependent manner. CS promotes c-Jun and Fra1 binding to the SPRR3-AP-1/TRE site. Wild-type c-Jun and Fra1 upregulate, whereas c-Jun and Fra1, dominant-negative mutants, suppress SPRR3 promoter activity.

CONCLUSION

CS induces SPRR3 upregulation in HBE cells by promoting aberrant c-Jun/Fra1 dimerization.

Biochemical and histological alterations induced by the smoke of allethrin based mosquito coil on mice model

BACKGROUND

Mosquito coil (MC) emits insecticide upon burning which provides limited protection against lethal mosquito borne diseases. However, apart from killing the insect, toxicities associated with the inhalation of these insecticides poses severe health hazards. However, the use of MC is increasing day by day in third world countries in particular but, yet to receive enough attention of both policy maker and general public. The current study was aimed to assess the MC smoke induced damage of pulmonary and hepatic tissues along with observing the alterations of several blood biochemical parameters in mice model.

METHODS

A total of twenty four Swiss albino mice were allowed to inhale the smoke of allethrin based MC at different duration per day for 120 days. By the end of treatment period, blood sample was drawn from each mouse and blood biochemical parameters including alanine transaminase (ALT), aspartate transaminase (AST), blood urea nitrogen(BUN), serum total protein, cholesterol, low density lipoprotein (LDL) and triglyceride (TG) were analyzed. Intact lung and liver were collected for histological analysis using standard protocol.

RESULTS

Biochemical study indicates elevated activity of two hepatic enzymes: ALT (89%), AST (85%), in comparison with the respective control. Increased level of some parameters of lipid profile including cholesterol (36%), LDL (48%) and triglyceride (30%) in smoke inhaled mice is the new finding of this study. On the contrary, the activity of serum total protein and BUN was decreased by 20% and 24%, respectively in inhaled mice. Pulmonary tissue of treated mice shows severe forms of emphysema and hyperplasia, especially in the peripheral region of lung, which is the hallmark of chronic obstructive pulmonary disease (COPD). Histological study of hepatic tissue shows apoptosis mediated damage of hepatocytes along with severe form of necrosis. Infiltration of Inflammatory cells was also observed in both of the organs.

CONCLUSION

Results from the present studies suggest that chronic exposure of allethrin based MC is responsible factor for severe health complications such as COPD due to the alterations of the key biochemical parameters of blood and histo-organization of lung and liver.

Chemopreventive Strategies for Inflammation-Related Carcinogenesis: Current Status and Future Direction

A sustained and chronically-inflamed environment is characterized by the presence of heterogeneous inflammatory cellular components, including neutrophils, macrophages, lymphocytes and fibroblasts. These infiltrated cells produce growth stimulating mediators (inflammatory cytokines and growth factors), chemotactic factors (chemokines) and genotoxic substances (reactive oxygen species and nitrogen oxide) and induce DNA damage and methylation. Therefore, chronic inflammation serves as an intrinsic niche for carcinogenesis and tumor progression. In this article, we summarize the up-to-date findings regarding definitive/possible causes and mechanisms of inflammation-related carcinogenesis derived from experimental and clinical studies. We also propose 10 strategies, as well as candidate agents for the prevention of inflammation-related carcinogenesis.

Modelling oviduct fluid formation in vitro

Oviduct fluid is the microenvironment that supports early reproductive processes including fertilisation, embryo cleavage, and genome activation. However, the composition and regulation of this critical environment remains rather poorly defined. This study uses an in vitro preparation of the bovine oviduct epithelium, to investigate the formation and composition of in vitro derived oviduct fluid (ivDOF) within a controlled environment. We confirm the presence of oviduct specific glycoprotein 1 in ivDOF and show that the amino acid and carbohydrate content resembles that of previously reported in vivo data. In parallel, using a different culture system, a panel of oviduct epithelial solute carrier genes, and the corresponding flux of amino acids within ivDOF in response to steroid hormones were investigated. We next incorporated fibroblasts directly beneath the epithelium. This dual culture arrangement represents more faithfully the in vivo environment and impacts on ivDOF composition. Lastly, physiological and pathophysiological endocrine states were modelled and their impact on the in vitro oviduct preparation evaluated. These experiments help clarify the dynamic function of the oviduct in vitro and suggest a number of future research avenues, such as investigating epithelial-fibroblast interactions, probing the molecular aetiologies of subfertility, and optimising embryo culture media.

Comparative assessment of HIF-1α and Akt responses in human lung and skin cells exposed to benzo[α]pyrene: Effect of conditioned medium from pre-exposed primary fibroblasts

Exposure to atmospheric pollutants has been accused for many adverse health effects. Benzo[α]pyrene (Β[α]Ρ) in particular, the most extensively studied member of pollutants, is implicated in both cancer initiation and promotion. In the present study, we compared the effects of noncytotoxic doses of Β[α]Ρ, between human skin and lung epithelial cells A431 and A549, respectively, focusing on Akt kinase and HIF-1α, as it is well known that these proteins are upregulated in various human cancers promoting survival, angiogenesis and metastasis of tumor cells. Also, taking into consideration that fibroblasts are involved in cancer progression, we tested the possible modulation of epithelial cell response by paracrine factors secreted by Β[α]Ρ-treated fibroblasts. Low doses of Β[α]Ρ were found to enhance epithelial cell proliferation and upregulate both Akt kinase and HIF-1α, with A549 cells exhibiting a more sustained profile of upregulation. It is to notice that, the response of HIF-1α was remarkably early, acting as a sensitive marker in response to airborne pollutants. Also, HIF-1α was induced by Β[α]Ρ in both lung and skin fibroblasts indicating that this effect may be conserved throughout different cell types and tissues. Interestingly however, the response of both proteins was differentially modified upon treatment with conditioned medium from Β[α]Ρ-exposed fibroblasts. This is particularly evident in A459 cells and confirms the critical role of intercellular and paracrine factors in the modulation of the final response to an extracellular signal. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1103-1112, 2016.

A pro-inflammatory role for the Frizzled-8 receptor in chronic bronchitis

RATIONALE

We have previously shown increased expression of the Frizzled-8 receptor of the Wingless/integrase-1 (WNT) signalling pathway in COPD. Here, we investigated if the Frizzled-8 receptor has a functional role in airway inflammation associated with chronic bronchitis.

METHODS

Acute cigarette-smoke-induced airway inflammation was studied in wild-type and Frizzled-8-deficient mice. Genetic association studies and lung expression quantitative trait loci (eQTL) analyses for Frizzled-8 were performed to evaluate polymorphisms in FZD8 and their relationship to tissue expression in chronic bronchitis. Primary human lung fibroblasts and primary human airway epithelial cells were used for in vitro studies.

RESULTS

Cigarette-smoke-exposure induced airway inflammation in wild-type mice, which was prevented in Frizzled-8-deficient mice, suggesting a crucial role for Frizzled-8 in airway inflammation. Furthermore, we found a significant genetic association (p=0.009) between single nucleotide polymorphism (SNP) rs663700 in the FZD8 region and chronic mucus hypersecretion, a characteristic of chronic bronchitis, in a large cohort of smoking individuals. We found SNP rs663700 to be a cis-eQTL regulating Frizzled-8 expression in lung tissue. Functional data link mesenchymal Frizzled-8 expression to inflammation as its expression in COPD-derived lung fibroblasts was regulated by pro-inflammatory cytokines in a genotype-dependent manner. Moreover, Frizzled-8 regulates inflammatory cytokine secretion from human lung fibroblasts, which in turn promoted MUC5AC expression by differentiated human airway epithelium.

CONCLUSIONS

These findings indicate an important pro-inflammatory role for Frizzled-8 and suggest that its expression is related to chronic bronchitis. Furthermore, our findings indicate an unexpected role for fibroblasts in regulating airway inflammation in COPD.

PDGF-BB induces PRMT1 expression through ERK1/2 dependent STAT1 activation and regulates remodeling in primary human lung fibroblasts

Tissue remodeling of sub-epithelial mesenchymal cells is a major pathology occurring in chronic obstructive pulmonary disease (COPD) and asthma. Fibroblasts, as a major source of interstitial connective tissue extracellular matrix, contribute to the fibrotic and inflammatory changes in these airways diseases. Previously, we described that protein arginine methyltransferase-1 (PRMT1) participates in airway remodeling in a rat model of pulmonary inflammation. In this study we investigated the mechanism by which PDGF-BB regulates PRMT1 in primary lung fibroblasts, isolated from human lung biopsies. Fibroblasts were stimulated with PDGF-BB for up-to 48h and the regulatory and activation of signaling pathways controlling PRMT1 expression were determined. PRMT1 was localized by immuno-histochemistry in human lung tissue sections and by immunofluorescence in isolated fibroblasts. PRMT1 activity was suppressed by the pan-PRMT inhibitor AMI1. ERK1/2 mitogen activated protein kinase (MAPK) was blocked by PD98059, p38 MAPK by SB203580, and STAT1 by small interference (si) RNA treatment. The results showed that PDGF-BB significantly increased PRMT1 expression after 1h lasting over 48h, through ERK1/2 MAPK and STAT1 signaling. The inhibition of ERK1/2 MAPK or of PRMT1 activity decreased PDGF-BB induced fibroblast proliferation, COX2 production, collagen-1A1 secretion, and fibronectin production. These findings suggest that PRMT1 is a central regulator of tissue remodeling and that the signaling sequence controlling its expression in primary human lung fibroblast is PDGF-ERK-STAT1. Therefore, PRMT1 presents a novel therapeutic and diagnostic target for the control of airway wall remodeling in chronic lung diseases.

A biologically inspired lung-on-a-chip device for the study of protein-induced lung inflammation

This study reports a biomimetic microsystem that reconstitutes the lung microenvironment for monitoring the role of eosinophil cationic protein (ECP) in lung inflammation. ECP induces the airway epithelial cell expression of CXCL-12, which in turn stimulates the migration of fibrocytes towards the epithelium. This two-layered microfluidic system provides a feasible platform for perfusion culture, and was used in this study to reveal that the CXCL12-CXCR4 axis mediates ECP induced fibrocyte extravasation in lung inflammation. This 'lung-on-a-chip' microdevice serves as a dynamic transwell system by introducing a flow that can reconstitute the blood vessel-tissue interface for in vitro assays, enhancing pre-clinical studies. We made an attempt to develop a new microfluidic model which could not only simulate the transwell for studying cell migration, but could also study the migration in the presence of a flow mimicking the physiological conditions in the body. As blood vessels are the integral part of our body, this model gives an opportunity to study more realistic in vitro models of organs where the blood vessel i.e. flow based migration is involved.

Activation of protease-activated receptors (PARs)-1 and -2 promotes alpha-smooth muscle actin expression and release of cytokines from human lung fibroblasts

Previous studies have shown that protease-activated receptors (PARs) play an important role in various physiological processes. In the present investigation, we determined the expression of PARs on human lung fibroblasts (HLF-1) and whether they were involved in cellular differentiation and pro-inflammatory cytokine and prostaglandin (PGE₂) secretion. PAR-1, PAR-2, PAR-3, and PAR-4 were detected in fibroblasts using RT-PCR, immunocytochemistry, and flow cytometry. Increased expression of PAR-4, but not other PARs, was observed in fibroblasts stimulated with phorbol myristate acetate. The archetypical activators of PARs, namely, thrombin and trypsin, as well as PAR-1 and PAR-2 agonist peptides, stimulated transient increases in intracellular Ca²⁺, and promoted increased α-smooth muscle actin expression. The proteolytic and peptidic PAR activators also stimulated the release of IL-6 and IL-8, as well as PGE₂, with a rank order of potency of PAR-1 > PAR-2. The combined stimulation of PAR-1 and PAR-2 resulted in an additive release of both IL-6 and IL-8. In contrast, PAR-3 and PAR-4 agonist peptides, as well as all the PAR control peptides examined, were inactive. These results suggest an important role for PARs associated with fibroblasts in the modulation of inflammation and remodeling in the airway.

Pericytes contribute to airway remodeling in a mouse model of chronic allergic asthma

Myofibroblast accumulation, subepithelial fibrosis, and vascular remodeling are complicating features of chronic asthma, but the mechanisms are not clear. Platelet-derived growth factors (PDGFs) regulate the fate and function of various mesenchymal cells and have been implicated as mediators of lung fibrosis. However, it is not known whether PDGF-BB signaling via PDGFRβ, which is critical for the recruitment of pericytes to blood vessels, plays a role in airway remodeling in chronic asthma. In the present study, we used a selective PDGFRβ inhibitor (CP-673451) to investigate the role of PDGFRβ signaling in the development of airway remodeling and lung dysfunction in an established mouse model of house dust mite-induced chronic allergic asthma. Unexpectedly, we found that pharmacological inhibition of PDGFRβ signaling in the context of chronic aeroallergen exposure led to exacerbated lung dysfunction and airway smooth muscle thickening. Further studies revealed that the inflammatory response to aeroallergen challenge in mice was associated with decreased PDGF-BB expression and the loss of pericytes from the airway microvasculature. In parallel, cells positive for pericyte markers accumulated in the subepithelial region of chronically inflamed airways. This process was exacerbated in animals treated with CP-673451. The results indicate that perturbed PDGF-BB/PDGFRβ signaling and pericyte accumulation in the airway wall may contribute to airway remodeling in chronic allergic asthma.

Developing accurate models of the human airways

Objectives

Particle delivery to the airways is an attractive prospect for many potential therapeutics, including vaccines. Developing strategies for inhalation of particles provides a targeted, controlled and non-invasive delivery route but, as with all novel therapeutics, in vitro and in vivo testing are needed prior to clinical use. Whilst advanced vaccine testing demands the use of animal models to address safety issues, the production of robust in vitro cellular models would take account of the ethical framework known as the 3Rs (Replacement, Reduction and Refinement of animal use), by permitting initial screening of potential candidates prior to animal use. There is thus a need for relevant, realistic in vitro models of the human airways.

Key findings

Our laboratory has designed and characterised a multi-cellular model of human airways that takes account of the conditions in the airways and recapitulates many salient features, including the epithelial barrier and mucus secretion.

Summary

Our human pulmonary models recreate many of the obstacles to successful pulmonary delivery of particles and therefore represent a valid test platform for screening compounds and delivery systems.

The response of human nasal and bronchial organotypic tissue cultures to repeated whole cigarette smoke exposure

Exposure to cigarette smoke (CS) is linked to the development of respiratory diseases, and there is a need to understand the mechanisms whereby CS causes damage. Although animal models have provided valuable insights into smoking-related respiratory tract damage, modern toxicity testing calls for reliable in vitro models as alternatives for animal experimentation. We report on a repeated whole mainstream CS exposure of nasal and bronchial organotypic tissue cultures that mimic the morphological, physiological, and molecular attributes of the human respiratory tract. Despite the similar cellular staining and cytokine secretion in both tissue types, the transcriptomic analyses in the context of biological network models identified similar and diverse biological processes that were impacted by CS-exposed nasal and bronchial cultures. Our results demonstrate that nasal and bronchial tissue cultures are appropriate in vitro models for the assessment of CS-induced adverse effects in the respiratory system and promising alternative to animal experimentation.

A novel electrospun biphasic scaffold provides optimal three-dimensional topography for in vitro co-culture of airway epithelial and fibroblast cells

Conventional airway in vitro models focus upon the function of individual structural cells cultured in a two-dimensional monolayer, with limited three-dimensional (3D) models of the bronchial mucosa. Electrospinning offers an attractive method to produce defined, porous 3D matrices for cell culture. To investigate the effects of fibre diameter on airway epithelial and fibroblast cell growth and functionality, we manipulated the concentration and deposition rate of the non-degradable polymer polyethylene terephthalate to create fibres with diameters ranging from nanometre to micrometre. The nanofibre scaffold closely resembles the basement membrane of the bronchiole mucosal layer, and epithelial cells cultured at the air-liquid interface on this scaffold showed polarized differentiation. The microfibre scaffold mimics the porous sub-mucosal layer of the airway into which lung fibroblast cells showed good penetration. Using these defined electrospinning parameters we created a biphasic scaffold with 3D topography tailored for optimal growth of both cell types. Epithelial and fibroblast cells were co-cultured onto the apical nanofibre phase and the basal microfibre phase respectively, with enhanced epithelial barrier formation observed upon co-culture. This biphasic scaffold provides a novel 3D in vitro platform optimized to mimic the different microenvironments the cells encounter in vivo on which to investigate key airway structural cell interactions in airway diseases such as asthma.

Biological Effects of Clinically Relevant CoCr Nanoparticles in the Dura Mater: An Organ Culture Study

Medical interventions for the treatment of spinal disc degeneration include total disc replacement and fusion devices. There are, however, concerns regarding the generation of wear particles by these devices, the majority of which are in the nanometre sized range with the potential to cause adverse biological effects in the surrounding tissues. The aims of this study were to develop an organ culture model of the porcine dura mater and to investigate the biological effects of CoCr nanoparticles in this model. A range of histological techniques were used to analyse the structure of the tissue in the organ culture. The biological effects of the CoCr wear particles and the subsequent structural changes were assessed using tissue viability assays, cytokine assays, histology, immunohistochemistry, and TEM imaging. The physiological structure of the dura mater remained unchanged during the seven days of in vitro culture. There was no significant loss of cell viability. After exposure of the organ culture to CoCr nanoparticles, there was significant loosening of the epithelial layer, as well as the underlying collagen matrix. TEM imaging confirmed these structural alterations. These structural alterations were attributed to the production of MMP-1, -3, -9, -13, and TIMP-1. ELISA analysis revealed that there was significant release of cytokines including IL-8, IL-6, TNF-α, ECP and also the matrix protein, tenascin-C. This study suggested that CoCr nanoparticles did not cause cytotoxicity in the dura mater but they caused significant alterations to its structural integrity that could lead to significant secondary effects due to nanoparticle penetration, such as inflammation to the local neural tissue.

Immunocompetent 3D model of human upper airway for disease modeling and in vitro drug evaluation

The development of more complex in vitro models for the assessment of novel drugs and chemicals is needed because of the limited biological relevance of animal models to humans as well as ethical considerations. Although some human-cell-based assays exist, they are usually 2D, consist of single cell type, and have limited cellular and functional representation of the native tissue. In this study, we have used biomimetic porous electrospun scaffolds to develop an immunocompetent 3D model of the human respiratory tract comprised of three key cell types present in upper airway epithelium. The three cell types, namely, epithelial cells (providing a physical barrier), fibroblasts (extracellular matrix production), and dendritic cells (immune sensing), were initially grown on individual scaffolds and then assembled into the 3D multicell tissue model. The epithelial layer was cultured at the air-liquid interface for up to four weeks, leading to formation of a functional barrier as evidenced by an increase in transepithelial electrical resistance (TEER) and tight junction formation. The response of epithelial cells to allergen exposure was monitored by quantifying changes in TEER readings and by assessment of cellular tight junctions using immunostaining. It was found that epithelial cells cocultured with fibroblasts formed a functional epithelial barrier at a quicker rate than single cultures of epithelial cells and that the recovery from allergen exposure was also more rapid. Also, our data show that dendritic cells within this model remain viable and responsive to external stimulation as evidenced by their migration within the 3D construct in response to allergen challenge. This model provides an easy to assemble and physiologically relevant 3D model of human airway epithelium that can be used for studies aiming at better understanding lung biology, the cross-talk between immune cells, and airborne allergens and pathogens as well as drug delivery.

Sustained release of prostaglandin E₂ in fibroblasts expressing ectopically cyclooxygenase 2 impairs P2Y-dependent Ca²⁺-mobilization

The nucleotide uridine trisphosphate (UTP) released to the extracellular milieu acts as a signaling molecule via activation of specific pyrimidine receptors (P2Y). P2Y receptors are G protein-coupled receptors expressed in many cell types. These receptors mediate several cell responses and they are involved in intracellular calcium mobilization. We investigated the role of the prostanoid PGE2 in P2Y signaling in mouse embryonic fibroblasts (MEFs), since these cells are involved in different ontogenic and physiopathological processes, among them is tissue repair following proinflammatory activation. Interestingly, Ca(2+)-mobilization induced by UTP-dependent P2Y activation was reduced by PGE2 when this prostanoid was produced by MEFs transfected with COX-2 or when PGE2 was added exogenously to the culture medium. This Ca(2+)-mobilization was important for the activation of different metabolic pathways in fibroblasts. Moreover, inhibition of COX-2 with selective coxibs prevented UTP-dependent P2Y activation in these cells. The inhibition of P2Y responses by PGE2 involves the activation of PKCs and PKD, a response that can be suppressed after pharmacological inhibition of these protein kinases. In addition to this, PGE2 reduces the fibroblast migration induced by P2Y-agonists such as UTP. Taken together, these data demonstrate that PGE2 is involved in the regulation of P2Y signaling in these cells.

In vitro construction of scaffold-free bilayered tissue-engineered skin containing capillary networks

Many types of skin substitutes have been constructed using exogenous materials. Angiogenesis is an important factor for tissue-engineered skin constructs. In this study, we constructed a scaffold-free bilayered tissue-engineered skin containing a capillary network. First, we cocultured dermal fibroblasts with dermal microvascular endothelial cells at a ratio of 2 : 1. A fibrous sheet was formed by the interactions between the fibroblasts and the endothelial cells, and capillary-like structures were observed after 20 days of coculture. Epithelial cells were then seeded on the fibrous sheet to assemble the bilayered tissue. HE staining showed that tissue-engineered skin exhibited a stratified epidermis after 7 days. Immunostaining showed that the epithelium promoted the formation of capillary-like structures. Transmission electron microscopy (TEM) analysis showed that the capillary-like structures were typical microblood vessels. ELISA demonstrated that vascularization was promoted by significant upregulation of vascularization associated growth factors due to interactions among the 3 types of cells in the bilayer, as compared to cocultures of fibroblast and endothelial cells and monocultures.

The transcription of the alarmin cytokine interleukin-1 alpha is controlled by hypoxia inducible factors 1 and 2 alpha in hypoxic cells

During hypoxia, cells undergo transcriptional changes to adjust to metabolic stress, to promote cell survival, and to induce pro-angiogenic factors. Hypoxia-induced factors (HIFs) regulate these transcriptional alterations. Failure to restore oxygen levels results in cell death by necrosis. IL-1α is one of the most important mediators of sterile inflammation following hypoxia-mediated necrosis. During hypoxia, IL-1α is up-regulated and released from necrotic cells, promoting the initiation of sterile inflammation. This study examined the role of IL-1α transcription in initiation of hypoxic stress and the correlation between IL-1α transcription and HIFα factors. In an epithelial cell line cultured under hypoxic conditions, IL-1α transcription was up-regulated in a process mediated and promoted by HIFα factors. IL-1α transcription was also up-regulated in hypoxia in a fibroblast cell line, however, in these cells, HIFα factors inhibited the elevation of transcription. These data suggest that HIFα factors play a significant role in initiating sterile inflammation by controlling IL-1α transcription during hypoxia in a differential manner, depending on the cell type.

Lung epithelial healing: a modified seed and soil concept

Airway epithelial healing is defined as restoration of health or soundness; to cure. Our research indicates that two types of progenitor cells participate in this process: the tissue-specific stem cell (TSC) and the facultative basal progenitor (FBP). The TSC restores the epithelium to its normal structure and function. Thus, the TSC regenerates the epithelium. In contrast, the FBP-derived epithelium is characterized by regions of cellular hyperplasia and hypoplasia. Since the FBP-derived epithelium deviates from normal, we term the FBP-mediated process repair. Our work indicates that the TSC responds to signals from other epithelial cells, including the FBP. These signals instruct the TSC to proliferate or to select one of several differentiation pathways. We interpret these data in the context of Stephen Padget's "seed and soil" paradigm. Therein, Padget explained that metastasis of a tumor, the seed, to a specific site, the soil, was determined by the growth and differentiation requirements of the tumor cell. By extending the seed and soil paradigm to airway epithelial healing, we suggest that proliferation and differentiation of the TSC, the seed, is determined by its interactions with other cell types, the soil. Based on this concept, we provide a set of suggestions for development of cell-based therapies that are directed toward chronic airways disease.

Intratracheal bleomycin causes airway remodeling and airflow obstruction in mice

In addition to parenchymal fibrosis, fibrotic remodeling of the distal airways has been reported in interstitial lung diseases. Mechanisms of airway wall remodeling, which occurs in a variety of chronic lung diseases, are not well defined and current animal models are limited. The authors quantified airway remodeling in lung sections from subjects with idiopathic pulmonary fibrosis (IPF) and controls. To investigate intratracheal bleomycin as a potential animal model for fibrotic airway remodeling, the authors evaluated lungs from C57BL/6 mice after bleomycin treatment by histologic scoring for fibrosis and peribronchial inflammation, morphometric evaluation of subepithelial connective tissue volume density, TUNEL (terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling) assay, and immunohistochemistry for transforming growth factor β1 (TGFβ1), TGFβ2, and the fibroblast marker S100A4. Lung mechanics were determined at 3 weeks post bleomycin. IPF lungs had small airway remodeling with increased bronchial wall thickness compared to controls. Similarly, bleomycin-treated mice developed dose-dependent airway wall inflammation and fibrosis and greater airflow resistance after high-dose bleomycin. Increased TUNEL(+) bronchial epithelial cells and peribronchial inflammation were noted by 1 week, and expression of TGFβ1 and TGFβ2 and accumulation of S100A4(+) fibroblasts correlated with airway remodeling in a bleomycin dose-dependent fashion. IPF is characterized by small airway remodeling in addition to parenchymal fibrosis, a pattern also seen with intratracheal bleomycin. Bronchial remodeling from intratracheal bleomycin follows a cascade of events including epithelial cell injury, airway inflammation, profibrotic cytokine expression, fibroblast accumulation, and peribronchial fibrosis. Thus, this model can be utilized to investigate mechanisms of airway remodeling.

Effects of the histone deacetylase inhibitor, trichostatin A, in a chronic allergic airways disease model in mice

There is a need for new asthma therapies that can concurrently address airway remodeling, airway hyperresponsiveness and progressive irreversible loss of lung function, in addition to inhibiting inflammation. Histone deacetylase inhibitors (HDACi) alter gene expression by interfering with the removal of acetyl groups from histones. The HDACi trichostatin A (TSA) has pleiotropic effects targeting key pathological processes in asthma including inflammation, proliferation, angiogenesis and fibrosis. The aim was to evaluate the effects of TSA treatment in a mouse model of chronic allergic airways disease (AAD). Wild-type BALB/c mice with AAD were treated intraperitoneally with 5 mg/kg TSA or vehicle control. Airway inflammation was assessed by bronchoalveolar lavage fluid (BALF) cell counts and histological examination of lung tissue sections. Remodeling was assessed by morphometric analysis and airway hyperresponsiveness was assessed by invasive plethysmography. TSA-treated mice had a reduced number of total inflammatory cells and eosinophils within the BALF as compared to vehicle-treated mice (both p < 0.05). Furthermore, airway remodeling changes were significantly reduced with TSA compared to vehicle-treated mice, with fewer goblet cells (p < 0.05), less subepithelial collagen deposition (p < 0.05) and attenuated airway hyperresponsiveness at the highest methacholine dose. These findings demonstrate that treatment with an HDACi can concurrently reduce structural airway remodeling changes and airway hyperresponsiveness, in addition to attenuating airway inflammation in a chronic AAD model. This has important implications for the development of novel treatments for severe asthma.

Is there a regulatory role of immunoglobulins on tissue forming cells relevant in chronic inflammatory lung diseases?

Epithelial cells, fibroblasts and smooth muscle cells together form and give structure to the airway wall. These three tissue forming cell types are structure giving elements and participate in the immune response to inhaled particles including allergens and dust. All three cell types actively contribute to the pathogenesis of chronic inflammatory lung diseases such as asthma and chronic obstructive pulmonary disease (COPD). Tissue forming cells respond directly to allergens through activated immunoglobulins which then bind to their corresponding cell surface receptors. It was only recently reported that allergens and particles traffic through epithelial cells without modification and bind to the immunoglobulin receptors on the surface of sub-epithelial mesenchymal cells. In consequence, these cells secrete pro-inflammatory cytokines, thereby extending the local inflammation. Furthermore, activation of the immunoglobulin receptors can induce proliferation and tissue remodeling of the tissue forming cells. New studies using anti-IgE antibody therapy indicate that the inhibition of immunoglobulins reduces the response of tissue forming cells. The unmeasured questions are: (i) why do tissue forming cells express immunoglobulin receptors and (ii) do tissue forming cells process immunoglobulin receptor bound particles? The focus of this review is to provide an overview of the expression and function of various immunoglobulin receptors.

Trefoil factor 2 regulates airway remodeling in animal models of asthma

BACKGROUND

Epithelial denudation and metaplasia are important in the pathogenesis of airway remodeling and asthma. Trefoil factor 2 (TFF2) is a member of a family of peptides involved in protection and healing of the gastrointestinal epithelium but which are also secreted in the airway mucosa.

METHODS

We investigated the role of TFF2 in airway remodeling by histological and morphometric analysis of lung tissue from TFF2-deficient mice subjected to two relevant animal models of asthma: an ovalbumin model of allergic airways disease and an Aspergillus fumigatus antigen sensitization model.

RESULTS

In the ovalbumin model TFF2-deficient mice had increased goblet cell hyperplasia, but not epithelial thickening compared to wild-type (WT) counterparts. In the Aspergillus model TFF2-deficient mice also had increased goblet cell hyperplasia, and epithelial thickness was also increased in the Aspergillus-sensitized mice compared to WT controls. TFF2 deficiency was also associated with increased subepithelial collagen layer thickness.

DISCUSSION

The current study demonstrates a role of TFF2 in airway remodeling in mouse models of airway disease. Further studies into the mechanisms of action of TFF2 and its role in asthma are warranted.

Toward managing chronic rejection after lung transplant: the fate and effects of inhaled cyclosporine in a complex environment

The fate and effects of inhaled cyclosporine A (CsA) are considered after deposition on the lung surface. Special emphasis is given to a post-lung transplant environment and to the potential effects of the drug on the various cell types it is expected to encounter. The known stability, metabolism, pharmacokinetics and pharmacodynamics of the drug have been reviewed and discussed in the context of the lung microenvironment. Arguments support the contention that the immuno-inhibitory and anti-inflammatory effects of CsA are not restricted to T-cells. It is likely that pharmacologically effective concentrations of CsA can be sustained in the lungs but due to the complexity of uptake and action, the elucidation of effective posology must ultimately rely on clinical evidence.

Airway branching morphogenesis in three dimensional culture

Background

Lungs develop from the fetal digestive tract where epithelium invades the vascular rich stroma in a process called branching morphogenesis. In organogenesis, endothelial cells have been shown to be important for morphogenesis and the maintenance of organ structure. The aim of this study was to recapitulate human lung morphogenesis in vitro by establishing a three dimensional (3D) co-culture model where lung epithelial cells were cultured in endothelial-rich stroma.

Methods

We used a human bronchial epithelial cell line (VA10) recently developed in our laboratory. This cell line cell line maintains a predominant basal cell phenotype, expressing p63 and other basal markers such as cytokeratin-5 and -14. Here, we cultured VA10 with human umbilical vein endothelial cells (HUVECs), to mimic the close interaction between these cell types during lung development. Morphogenesis and differentiation was monitored by phase contrast microscopy, immunostainings and confocal imaging.

Results

We found that in co-culture with endothelial cells, the VA10 cells generated bronchioalveolar like structures, suggesting that lung epithelial branching is facilitated by the presence of endothelial cells. The VA10 derived epithelial structures display various complex patterns of branching and show partial alveolar type-II differentiation with pro-Surfactant-C expression. The epithelial origin of the branching VA10 colonies was confirmed by immunostaining. These bronchioalveolar-like structures were polarized with respect to integrin expression at the cell-matrix interface. The endothelial-induced branching was mediated by soluble factors. Furthermore, fibroblast growth factor receptor-2 (FGFR-2) and sprouty-2 were expressed at the growing tips of the branching structures and the branching was inhibited by the FGFR-small molecule inhibitor SU5402.

Discussion

In this study we show that a human lung epithelial cell line can be induced by endothelial cells to form branching bronchioalveolar-like structures in 3-D culture. This novel model of human airway morphogenesis can be used to study critical events in human lung development and suggests a supportive role for the endothelium in promoting branching of airway epithelium.

Differentiation of embryonic stem cells into fibroblast-like cells in three-dimensional type I collagen gel cultures

Fibroblasts are heterogeneous mesenchymal cells that play important roles in the production and maintenance of extracellular matrix. Although their heterogeneity is recognized, progenitor progeny relationships among fibroblasts and the factors that control fibroblast differentiation are poorly defined. The current study was designed to develop a reliable method that would permit in vitro differentiation of fibroblast-like cells from human and murine embryonic stem cells (ESCs). Undifferentiated ESCs were differentiated into embryoid bodies (EBs) with differentiation media. EBs were then cast into type I collagen gels and cultured for 21 d with basal media. The spindle-shaped cells that subsequently grew from the EBs were released from the gels and subsequently cultured as monolayers in basal media supplemented with serum. Differentiated cells showed a characteristic spindle-shaped morphology and had ultrastructural features consistent with fibroblasts. Immunocytochemistry showed positive staining for vimentin and alpha-smooth muscle actin but was negative for stage-specific embryonic antigens and cytokeratins. Assays of fibroblast function, including proliferation, chemotaxis, and contraction of collagen gels demonstrated that the differentiated cells, derived from both human and murine ESCs, responded to transforming growth factor-β1 and prostaglandin E(2) as would be expected of fibroblasts, functions not expected of endothelial or epithelial cells. The current study demonstrates that cells with the morphologic and functional features of fibroblasts can be reliably derived from human and murine ESCs. This methodology provides a means to investigate and define the mechanisms that regulate fibroblast differentiation.

Regulation and function of the IL-1 family cytokine IL-1F9 in human bronchial epithelial cells

The IL-1 family of cytokines, which now includes 11 members, is well known to participate in inflammation. Although the most recently recognized IL-1 family cytokines (IL-1F5-11) have been shown to be expressed in airway epithelial cells, the regulation of their expression and function in the epithelium has not been extensively studied. We investigated the regulation of IL-1F5-11 in primary normal human bronchial epithelial cells. Messenger (m)RNAs for IL-1F6 and IL-1F9, but not IL-1F5, IL-1F8 or IL-1F10, were significantly up-regulated by TNF, IL-1β, IL-17 and the Toll-like receptor (TLR)3 ligand double-stranded (ds)RNA. mRNAs for IL-1F7 and IL-1F11 (IL-33) were weakly up-regulated by some of the cytokines tested. Notably, mRNAs for IL-1F6 and IL-1F9 were synergistically enhanced by the combination of TNF/IL-17 or dsRNA/IL-17. IL-1F9 protein was detected in the supernatant following stimulation with dsRNA or a combination of dsRNA and IL-17. IL-1F6 protein was detected in the cell lysate but was not detected in the supernatant. We screened for the receptor for IL-1F9 and found that lung fibroblasts expressed this receptor. We found that IL-1F9 activated mitogen-activated protein kinases and the transcription factor NF-κB in primary normal human lung fibroblasts. IL-1F9 also stimulated the expression of the neutrophil chemokines IL-8 and CXCL3 and the Th17 chemokine CCL20 in lung fibroblasts. These results suggest that epithelial activation by TLR3 (e.g., by respiratory viral infection) and exposure to cytokines from Th17 cells (IL-17) and inflammatory cells (TNF) may amplify neutrophilic inflammation in the airway via induction of IL-1F9 and activation of fibroblasts.

Remodeling in asthma and COPD--differences and similarities

BACKGROUND

Asthma and chronic obstructive pulmonary disease (COPD) are both inflammatory disorders. Diagnosis of these diseases is based upon limitation of expiratory airflow. The pathophysiological correlates to this impaired lung function are complex but they are associated with the development of structural changes in the airways and lung parenchyma. These remodeling processes differ between the two diseases. In asthma, airways obstruction is predominately located in the large airways, although recent studies indicate that inflammation and structural changes also is present in other compartments of the lungs. In COPD, remodeling of the small airways and lung parenchyma are the main correlates to the limitation of expiratory airflow. However, both asthma and COPD are heterogeneous disorders including various phenotypes and there is a considerable overlap between the two diseases.

METHODS AND RESULTS

In the present review, airway remodeling in asthma and COPD will be discussed in three different compartments of the airways: large airways, small airways and lung parenchyma. Different inflammatory cells will be mentioned, as well as markers of remodeling.

CONCLUSION

In COPD and severe asthma, current anti-inflammatory pharmacotherapy does not restore lung function impairment fully. It is therefore recognized that research aiming to explore mechanisms of airway remodeling should be encouraged.

Mesenchymal cell survival in airway and interstitial pulmonary fibrosis

Fibrotic reactions in the airways of the lung or the pulmonary interstitium are a common pathologic outcome after exposure to a wide variety of toxic agents, including metals, particles or fibers. The survival of mesenchymal cells (fibroblasts and myofibroblasts) is a key factor in determining whether a fibroproliferative response that occurs after toxic injury to the lung will ultimately resolve or progress to a pathologic state. Several polypeptide growth factors, including members of the platelet-derived growth factor (PDGF) family and the epidermal growth factor (EGF) family, are prosurvival factors that stimulate a replicative and migratory mesenchymal cell phenotype during the early stages of lung fibrogenesis. This replicative phenotype can progress to a matrix synthetic phenotype in the presence of transforming growth factor-β1 (TGF-β1). The resolution of a fibrotic response requires growth arrest and apoptosis of mesenchymal cells, whereas progressive chronic fibrosis has been associated with mesenchymal cell resistance to apoptosis. Mesenchymal cell survival or apoptosis is further influenced by cytokines secreted during Th1 inflammation (e.g., IFN-γ) or Th2 inflammation (e.g., IL-13) that modulate the expression of growth factor activity through the STAT family of transcription factors. Understanding the mechanisms that regulate the survival or death of mesenchymal cells is central to ultimately developing therapeutic strategies for lung fibrosis.

Roles of epithelial cell-derived periostin in TGF-beta activation, collagen production, and collagen gel elasticity in asthma

Periostin is considered to be a matricellular protein with expression typically confined to cells of mesenchymal origin. Here, by using in situ hybridization, we show that periostin is specifically up-regulated in bronchial epithelial cells of asthmatic subjects, and in vitro, we show that periostin protein is basally secreted by airway epithelial cells in response to IL-13 to influence epithelial cell function, epithelial-mesenchymal interactions, and extracellular matrix organization. In primary human bronchial epithelial cells stimulated with periostin and epithelial cells overexpressing periostin, we reveal a function for periostin in stimulating the TGF-beta signaling pathway in a mechanism involving matrix metalloproteinases 2 and 9. Furthermore, conditioned medium from the epithelial cells overexpressing periostin caused TGF-beta-dependent secretion of type 1 collagen by airway fibroblasts. In addition, mixing recombinant periostin with type 1 collagen in solution caused a dramatic increase in the elastic modulus of the collagen gel, indicating that periostin alters collagen fibrillogenesis or cross-linking and leads to stiffening of the matrix. Epithelial cell-derived periostin in asthma has roles in TGF-beta activation and collagen gel elasticity in asthma.

INFLAMMATORY CELL RECRUITMENT FOLLOWING THORACIC IRRADIATION

Ionizing radiation leads to a progressive injury in which a monocyte/macrophage-rich pneumonitis is followed by a chronic progressive fibrosis. In the present study, the role of macrophage/monocyte recruitment in the genesis of radiation-induced pulmonary fibrosis was examined. The objectives were threefold: (i) characterize the inflammatory cells recruited into the lung during the development of radiation-induced fibrosis; (ii) investigate changes in lung response following depletion of resident alveolar macrophages in vivo prior to radiation treatment; (iii) assess if inhalation of low levels of endotoxin would potentiate the radiation-initiated injury. One group of fibrosis-sensitive C57BL/6 mice was irradiated with a single dose of 15 Gy to the thorax. In a second group, resident inflammatory cells were depleted using clodronate, encapsulated into liposomes, 48 hours prior to irradiation with a single dose of 15 Gy to the thorax. Control animals were sham irradiated. All groups of animals then were examined 8, 16, or 24 weeks post irradiation. No difference in total cell numbers or cell differentials was observed between irradiated mice or those that were both liposome treated and irradiated at any time point. At 16 weeks, mice that received radiation showed a 5- to 6-fold increase in lymphocytes regardless of treatment as compared to control animals. At 24 weeks post irradiation, select groups were exposed to lipopolysaccharide (LPS) and examined 24 hours post inhalation. Lavageable protein was increased several fold in mice that received both radiation and LPS exposure as compared to 15 Gy or LPS exposure alone. These results demonstrate: (i) macrophages and lymphocytes are the predominately recruited cell types through 24 weeks post irradiation; (ii) recovery of inflammatory cells, regardless of prior macrophage depletion, were similar, suggesting that early responses are primarily driven by parenchymal cell injury; (iii) thoracic irradiation-induced injury can cause sensitization to a secondary stimulus that may result in injuries/responses not predicted by evaluating exposures individually.

Role of relaxin in regulation of fibrosis in the lung

Airway remodeling changes are a key pathological feature of asthma. They are associated with airway hyperresponsiveness and fixed airway obstruction. Aged, relaxin-deficient mice display structural changes resembling airway remodeling in asthma, including thickening of the bronchial epithelium and extracellular matrix (ECM) deposition in the subepithelial region. Relaxin-deficient mice also have exaggerated airway remodeling in models of allergic airway disease compared to wild-type controls. Both in vitro and in vivo studies have suggested that airway fibrosis may drive other changes of airway remodeling, including epithelial changes. A suggested paradigm is that subepithelial fibrosis (deposition of ECM in the basement membrane region) may lead to increased epithelial cell proliferation and transforming growth factor-beta1 production, which in turn may lead to further fibrosis. Relaxin may therefore prevent or reverse activation of the epithelial and fibroblast remodeling in asthma. Control of epithelial remodeling and ECM production in the airway wall may play an important role in maintaining normal lung function. Understanding how relaxin protects against airway remodeling changes may have important implications in developing new therapies to treat airway remodeling in asthma.