Histamine induces human lung fibroblast-mediated collagen gel contraction via histamine H1 receptor

A role for age-associated alterations in esophageal epithelium in eosinophilic esophagitis-associated fibrosis

Subepithelial fibrosis occurs in a subset of eosinophilic esophagitis (EoE) patients and is associated with esophageal stricture. While mechanisms driving EoE fibrosis remain incompletely understood, findings from experimental systems support roles for epithelial-fibroblast crosstalk in this type of tissue remodeling. The current paradigm presents EoE as a progressive fibrostenotic disease in which aged patients develop fibrosis as a function of disease chronicity. In the current study we provide evidence that altered epithelial biology in the aging esophagus may also contribute to EoE-associated fibrosis. We find that induction of EoE inflammation in young and aged mice using the MC903/Ovalbumin protocol for the same time period results in increased lamina propria thickness uniquely in aged animals. Additionally, epithelial cells from aged mice less efficiently limit fibroblast contractility in collagen plug contraction assays compared to those from their young counterparts. Finally, to identify potential mechanisms through which aged esophageal epithelial cells may stimulate fibrotic remodeling, we perform cytokine array experiments in young and aged mice. These studies are significant as identification of age-associated factors that contribute to fibrotic remodeling may aid in the design of strategies toward early detection, prevention, and therapy of fibrostenotic EoE.

Histamine activates an intracellular Ca2+ signal in normal human lung fibroblast WI-38 cells

Histamine is an inflammatory mediator that can be released from mast cells to induce airway remodeling and cause persistent airflow limitation in asthma. In addition to stimulating airway smooth muscle cell constriction and hyperplasia, histamine promotes pulmonary remodeling by inducing fibroblast proliferation, contraction, and migration. It has long been known that histamine receptor 1 (H1R) mediates the effects of histamine on human pulmonary fibroblasts through an increase in intracellular Ca2+ concentration ([Ca2+]i), but the underlying signaling mechanisms are still unknown. Herein, we exploited single-cell Ca2+ imaging to assess the signal transduction pathways whereby histamine generates intracellular Ca2+ signals in the human fetal lung fibroblast cell line, WI-38. WI-38 fibroblasts were loaded with the Ca2+-sensitive fluorophore, FURA-2/AM, and challenged with histamine in the absence and presence of specific pharmacological inhibitors to dissect the Ca2+ release/entry pathways responsible for the onset of the Ca2+ response. Histamine elicited complex intracellular Ca2+ signatures in WI-38 fibroblasts throughout a concentration range spanning between 1 µM and 1 mM. In accord, the Ca2+ response to histamine adopted four main temporal patterns, which were, respectively, termed peak, peak-oscillations, peak-plateau-oscillations, and peak-plateau. Histamine-evoked intracellular Ca2+ signals were abolished by pyrilamine, which selectively blocks H1R, and significantly reduced by ranitidine, which selectively inhibits H2R. Conversely, the pharmacological blockade of H3R and H4R did not affect the complex increase in [Ca2+]i evoked by histamine in WI-38 fibroblasts. In agreement with these findings, histamine-induced intracellular Ca2+ signals were initiated by intracellular Ca2+ release from the endoplasmic reticulum through inositol-1,4,5-trisphosphate (InsP3) receptors (InsP3R) and sustained by store-operated Ca2+ channels (SOCs). Conversely, L-type voltage-operated Ca2+ channels did not support histamine-induced extracellular Ca2+ entry. A preliminary transcriptomic analysis confirmed that WI-38 human lung fibroblasts express all the three InsP3R isoforms as well as STIM2 and Orai3, which represent the molecular components of SOCs. The pharmacological blockade of InsP3 and SOC, therefore, could represent an alternative strategy to prevent the pernicious effects of histamine on lung fibroblasts in asthmatic patients.

Soft Polymer-Based Technique for Cellular Force Sensing

Soft polymers have emerged as a vital type of material adopted in biomedical engineering to perform various biomechanical characterisations such as sensing cellular forces. Distinct advantages of these materials used in cellular force sensing include maintaining normal functions of cells, resembling in vivo mechanical characteristics, and adapting to the customised functionality demanded in individual applications. A wide range of techniques has been developed with various designs and fabrication processes for the desired soft polymeric structures, as well as measurement methodologies in sensing cellular forces. This review highlights the merits and demerits of these soft polymer-based techniques for measuring cellular contraction force with emphasis on their quantitativeness and cell-friendliness. Moreover, how the viscoelastic properties of soft polymers influence the force measurement is addressed. More importantly, the future trends and advancements of soft polymer-based techniques, such as new designs and fabrication processes for cellular force sensing, are also addressed in this review.

Non-targeted metabolomics of multiple human cells revealing differential toxic effects of perfluorooctanoic acid

Differences in toxic effects of contaminants among human cells are essential for evaluating their health risks to humans. In this study, non-targeted metabolomics of multiple human cell lines (A549 (lung), DLD-1 (intestine) and L-02 (liver) cells) was used to address the differential toxicity of perfluorooctanoic acid (PFOA). The number of differential metabolites (DMs) identified in the PFOA-treated A549 cells (67) was highest, followed by DLD-1 (12) and L-02 cells (10). The categorization of DMs was almost uniquely specific to each of cell lines. PFOA significantly promoted linoleic acid metabolism in L-02 cells whereas this metabolism was inhibited in the PFOA-treated A549 cells. The levels of interleukin (IL)-1β, IL-6, IL-8 and IL-13 were about 1.5 times higher in the PFOA-treated A549 and L-02 cells than in the controls. PFOA stimulated the biosynthesis of arginine and the metabolism of vitamin B6 in A549 cells. Arginine and vitamin B6 supplemented into cell culture effectively decreased the levels of IL-6 and IL-8. The inhibition of purine metabolism by PFOA resulted in the arrestation of DLD-1 cells at the G₀/G₁-phase. Our results suggest that the differential toxicity of PFOA related to exposure pathways could be elucidated by metabolic profiles specific to various human cells.

Histamine augments collagen content via H1 receptor stimulation in cultures of myofibroblasts taken from wound granulation tissue

The inflammatory reaction influences the deposition of collagen within wound granulation tissue. The aim of the present study is to determine whether histamine acting directly on myofibroblasts derived from wound granulation tissue may influence collagen deposition. It also identifies the histamine receptor involved in this process. The experiments were carried out on cells isolated from the granulation tissue of a wound model (a polypropylene net inserted subcutaneously to rats) or intact rat skin. Collagen content was measured following the addition of different concentrations of histamine and treatment with histamine receptor antagonists (ketotifen - H1 inhibitor, ranitidine - H2 inhibitor) and a histamine receptor H1 agonist (2-pyridylethylamine dihydrochloride).The cells were identified as myofibroblasts: alpha-smooth muscle actin, vimentin, and desmin positive in all experimental conditions. Histamine increased the collagen level within both cell cultures, i.e., those isolated from granulation tissue or intact skin. It did not, however, influence the expression of either the collagen type I or III genes within the cultured myofibroblasts. Histamine activity was reduced by ketotifen (the H1 receptor inhibitor) and increased by the H1 receptor agonist, as demonstrated by changes in the levels of collagen in the myofibroblast culture. Histamine increased collagen content within the cultures, acting directly on myofibroblasts via H1 receptor stimulation.

FOXL1 Regulates Lung Fibroblast Function via Multiple Mechanisms

Fibroblasts provide a structural framework for multiple organs and are essential for wound repair and fibrotic processes. Here, we demonstrate functional roles of FOXL1 (forkhead box L1), a transcription factor that characterizes the pulmonary origin of lung fibroblasts. We detected high FOXL1 transcripts associated with DNA hypomethylation and super-enhancer formation in lung fibroblasts, which is in contrast with fibroblasts derived from other organs. RNA in situ hybridization and immunohistochemistry in normal lung tissue indicated that FOXL1 mRNA and protein are expressed in submucosal interstitial cells together with airway epithelial cells. Transcriptome analysis revealed that FOXL1 could control a broad array of genes that potentiate fibroblast function, including TAZ (transcriptional coactivator with PDZ-binding motif)/YAP (Yes-associated protein) signature genes and PDGFRα (platelet-derived growth factor receptor-α). FOXL1 silencing in lung fibroblasts attenuated cell growth and collagen gel contraction capacity, underscoring the functional importance of FOXL1 in fibroproliferative reactions. Of clinical importance, increased FOXL1 mRNA expression was found in fibroblasts of idiopathic pulmonary fibrosis lung tissue. Our observations suggest that FOXL1 regulates multiple functional aspects of lung fibroblasts as a key transcription factor and is involved in idiopathic pulmonary fibrosis pathogenesis.

Current Approaches Targeting the Wound Healing Phases to Attenuate Fibrosis and Scarring

Cutaneous fibrosis results from suboptimal wound healing following significant tissue injury such as severe burns, trauma, and major surgeries. Pathologic skin fibrosis results in scars that are disfiguring, limit normal movement, and prevent patient recovery and reintegration into society. While various therapeutic strategies have been used to accelerate wound healing and decrease the incidence of scarring, recent studies have targeted the molecular regulators of each phase of wound healing, including the inflammatory, proliferative, and remodeling phases. Here, we reviewed the most recent literature elucidating molecular pathways that can be targeted to reduce fibrosis with a particular focus on post-burn scarring. Current research targeting inflammatory mediators, the epithelial to mesenchymal transition, and regulators of myofibroblast differentiation shows promising results. However, a multimodal approach addressing all three phases of wound healing may provide the best therapeutic outcome.

CISH is a negative regulator of IL-13-induced CCL26 production in lung fibroblasts

BACKGROUND

Bronchial asthma is a chronic airway disease characterized by eosinophilic airway inflammation. Lung fibroblasts activated by IL-13 serve as important sources of chemokines, such as eotaxins, contributing to persistent eosinophilic inflammation. Src-homology 2-containing protein (CISH), belonging to the suppressor of cytokine signaling (SOCS) family, acts as a negative regulator of cytokine induction. The aim of this study was to elucidate the role of CISH in the production of eosinophil chemotactic chemokines in human lung fibroblasts.

METHODS

Normal human lung fibroblasts were stimulated by IL-13, and global gene expression profile was assessed by cDNA microarray. Expression changes and downstream of IL-13 signaling were evaluated by quantitative RT-PCR, ELISA or western blotting. Loss- and gain-of-function analyses of CISH were performed by small interfering RNA and vector overexpression, respectively.

RESULTS

Ingenuity pathway analysis revealed that IL-13 induced chemokine signaling, including the eotaxin family, while significantly suppressing IFN-α/β signaling. Among eight SOCS family members, CISH was most strongly induced by IL-13 via phosphorylation of signal transducer and activator of transcription 6 (STAT6). Loss- and gain-of-function studies demonstrated that CISH negatively regulated the expression of CCL26.

CONCLUSIONS

These findings suggest that CISH plays a key role in the eosinophilic inflammation associated with bronchial asthma by regulating IL-13-induced CCL26 production. Augmentation of CISH function could be a novel approach for treating eosinophilic inflammation in severe asthma.

Membrane-bound ICAM-1 contributes to the onset of proinvasive tumor stroma by controlling acto-myosin contractility in carcinoma-associated fibroblasts

Acto-myosin contractility in carcinoma-associated fibroblasts leads to assembly of the tumor extracellular matrix. The pro-inflammatory cytokine LIF governs fibroblast activation in cancer by regulating the myosin light chain 2 activity. So far, however, how LIF mediates cytoskeleton contractility remains unknown. Using phenotypic screening assays based on knock-down of LIF-dependent genes in fibroblasts, we identified the glycoprotein ICAM-1 as a crucial regulator of stroma fibroblast proinvasive matrix remodeling. We demonstrate that the membrane-bound ICAM-1 isoform is necessary and sufficient to promote inflammation-dependent extracellular matrix contraction, which favors cancer cell invasion. Indeed, ICAM-1 mediates generation of acto-myosin contractility downstream of the Src kinases in stromal fibroblasts. Moreover, acto-myosin contractility regulates ICAM-1 expression by establishing a positive feedback signaling. Thus, targeting stromal ICAM-1 might constitute a possible therapeutic mean to counteract tumor cell invasion and dissemination.

An impedance-based cell contraction assay using human primary smooth muscle cells and fibroblasts

INTRODUCTION

Many cell types (including muscle cells and fibroblasts) can contract at physiological conditions and their contractility may change during tissue injury and repair or other diseases such as allergy and asthma. The conventional gel contraction assay is commonly used to monitor the cellular contractility. It is a manual assay and the experiment usually takes hours even days to complete. As its readout is not always accurate and reliable, the gel contraction assay is often used to qualitatively (but not quantitatively) characterize cellular contractility under various conditions.

METHOD

To overcome the limits of the gel contraction assay, we developed an impedance-based contraction assay using the xCELLigence RTCA MP system. This technology utilizes special 96-well E-plates with gold microelectrode arrays printed in individual wells to monitor cellular adhesion by recording the electrical impedance in real time. The impedance change (percentage vs. control) can be used as the readout for cellular contraction.

RESULTS

We demonstrated that the impedance-based contraction assay can be performed within 2h. Using this new method, we quantitatively characterized the effects of several contractile stimulators and inhibitors on human primary bronchial smooth muscle cells and primary lung fibroblasts.

DISCUSSION

The impedance-based contraction assay can be applied to both basic research and drug discovery for characterizing cellular contraction quantitatively. Because it has high throughput capacity and high reproducibility, the impedance-based contraction assay is useful for high throughput functional screening in drug industry.

TBX4 is involved in the super-enhancer-driven transcriptional programs underlying features specific to lung fibroblasts

Lung fibroblasts participate in the pathogenesis of respiratory diseases, including lung cancer and pulmonary fibrosis. Although fibroblasts are ubiquitous constituents of various organs, their cellular diversity among different organs has been poorly characterized. Here, we aimed to investigate the distinct gene signature of lung fibroblasts that represents its pulmonary origin and the underlying gene regulatory networks. Promoter-level differential expression analysis by cap analysis of gene expression (CAGE) sequencing revealed distinct gene expression patterns of fibroblasts derived from different anatomical sites and identified 88 coding genes with higher expression in lung fibroblasts relative to other fibroblasts. Multiple key transcription factors important for lung mesenchyme development, including the T-box transcription factors TBX2, TBX4, and TBX5 were enriched in this lung-specific signature and were associated with super-enhancers. TBX4 showed highly specific expression in lung fibroblasts and was required for cell proliferation and collagen gel contraction capacity. Transcriptome analysis revealed that TBX4 could broadly regulate fibroblast-related pathways and partly contribute to super-enhancer-mediated transcriptional programs. Of pathological importance, lung fibroblast-specific genes were globally downregulated in lung cancer-associated fibroblasts (CAFs). Notably, TBX2, TBX4, and TBX5 were downregulated and hypermethylated in lung CAFs, suggesting an association between epigenetic silencing of these factors and phenotypic alteration of lung fibroblasts in cancer. Our study highlights the importance of T-box transcription factors, especially TBX4, and super-enhancers in the roles of lung fibroblasts in pulmonary physiology and pathogenesis.

Development of an In Vitro Assay to Evaluate Contractile Function of Mesenchymal Cells that Underwent Epithelial-Mesenchymal Transition

Fibrosis is often involved in the pathogenesis of various chronic progressive diseases such as interstitial pulmonary disease. Pathological hallmark is the formation of fibroblastic foci, which is associated with the disease severity. Mesenchymal cells consisting of the fibroblastic foci are proposed to be derived from several cell sources, including originally resident intrapulmonary fibroblasts and circulating fibrocytes from bone marrow. Recently, mesenchymal cells that underwent epithelial-mesenchymal transition (EMT) have been also supposed to contribute to the pathogenesis of fibrosis. In addition, EMT can be induced by transforming growth factor β, and EMT can be enhanced by pro-inflammatory cytokines like tumor necrosis factor α. The gel contraction assay is an ideal in vitro model for the evaluation of contractility, which is one of the characteristic functions of fibroblasts and contributes to wound repair and fibrosis. Here, the development of a gel contraction assay is demonstrated for evaluating contractile ability of mesenchymal cells that underwent EMT.

Histamine induces NF-κB controlled cytokine secretion by orbital fibroblasts via histamine receptor type-1

Mast cells and their products are likely to be involved in regulating orbital fibroblast activity in Graves' Ophthalmopathy (GO). Histamine is abundantly present in granules of mast cells and is released upon mast cell activation. However, the effect of histamine on orbital fibroblasts has not been examined so far. Orbital tissues from GO patients and controls were analyzed for the presence of mast cells using toluidine blue staining and immunohistochemical detection of CD117 (stem cell factor receptor). Orbital fibroblasts were cultured from GO patients and healthy controls, stimulated with histamine and cytokines (IL-6, IL-8, CCL2, CCL5, CCL7, CXCL10 and CXCL11) were measured in culture supernatants. Also hyaluronan levels were measured in culture supernatants and hyaluronan synthase (HAS) and hyaluronidase (HYAL) gene expression levels were determined. In addition, histamine receptor subtype gene expression levels were examined as well as the effect of the histamine receptor-1 (HRH1) antagonist loratadine and NF-κB inhibitor SC-514 on histamine-induced cytokine production. Mast cell numbers were increased in GO orbital tissues. Histamine stimulated the production of IL-6, IL-8 and CCL2 by orbital fibroblasts, while it had no effect on the production of CCL5, CCL7, CXCL10, CXCL11 and hyaluronan. Orbital fibroblasts expressed HRH1 and loratadine and SC-514 both blocked histamine-induced IL-6, IL-8 and CCL2 production by orbital fibroblasts. In conclusion, this study demonstrates that histamine can induce the production of NF-κB controlled-cytokines by orbital fibroblasts, which supports a role for mast cells in GO.

A novel collagen gel-based measurement technique for quantitation of cell contraction force

Cell contraction force plays an important role in wound healing, inflammation,angiogenesis and metastasis. This study describes a novel method to quantify single cell contraction force in vitro using human aortic adventitial fibroblasts embedded in a collagen gel. The technique is based on a depth sensing nano-indentation tester to measure the thickness and elasticity of collagen gels containing stimulated fibroblasts and a microscopy imaging system to estimate the gel area. In parallel, a simple theoretical model has been developed to calculate cell contraction force based on the measured parameters. Histamine (100 mM) was used to stimulate fibroblast contraction while the myosin light chain kinase inhibitor ML-7 (25 mM) was used to inhibit cell contraction. The collagen matrix used in the model provides a physiological environment for fibroblast contraction studies. Measurement of changes in collagen gel elasticity and thickness arising from histamine treatments provides a novel convenient technique to measure cell contraction force within a collagen matrix. This study demonstrates that histamine can elicit a significant increase in contraction force of fibroblasts embedded in collagen,while the Young's modulus of the gel decreases due to the gel degradation.

Three-dimensional Co-culture model for tumor-stromal interaction

Cancer progression (initiation, growth, invasion and metastasis) occurs through interactions between malignant cells and the surrounding tumor stromal cells. The tumor microenvironment is comprised of a variety of cell types, such as fibroblasts, immune cells, vascular endothelial cells, pericytes and bone-marrow-derived cells, embedded in the extracellular matrix (ECM). Cancer-associated fibroblasts (CAFs) have a pro-tumorigenic role through the secretion of soluble factors, angiogenesis and ECM remodeling. The experimental models for cancer cell survival, proliferation, migration, and invasion have mostly relied on two-dimensional monocellular and monolayer tissue cultures or Boyden chamber assays. However, these experiments do not precisely reflect the physiological or pathological conditions in a diseased organ. To gain a better understanding of tumor stromal or tumor matrix interactions, multicellular and three-dimensional cultures provide more powerful tools for investigating intercellular communication and ECM-dependent modulation of cancer cell behavior. As a platform for this type of study, we present an experimental model in which cancer cells are cultured on collagen gels embedded with primary cultures of CAFs.