Epigen is induced during the interleukin-13-stimulated cell proliferation in murine primary airway epithelial cells

Increased expression of ORMDL3 in allergic asthma: a case control and in vitro study

BACKGROUND

Asthma is the most frequent chronic disease in children. One of the most replicated genetic findings in childhood asthma is the ORMDL3 gene confirmed in several GWA studies in several pediatric populations.

OBJECTIVES

The purpose of this study was to analyze ORMDL3 variants and expression in childhood asthma in the Polish population.

METHODS

In the study we included 416 subject, 223 asthmatic children and 193 healthy control subjects. The analysis of two SNPs (rs3744246 and rs8076131) was performed using genotyping with TaqMan probes. The methylation of the ORMDL3 promoter was examined with Methylation Sensitive HRM (MS-HRM), covering 9 CpG sites. The expression of ORMDL3 was analyzed in PBMCs from pediatric patients diagnosed with allergic asthma and primary human bronchial epithelial cells derived from healthy subjects treated with IL-13, IL-4, or co-treatment with both cytokines to model allergic airway inflammation.

RESULTS

We found that ORMDL3 expression was increased in allergic asthma both in PBMCs from asthmatic patients as well as in human bronchial epithelial cells stimulated with the current cytokines. We did not observe significant differences between cases and controls either in the genotype distribution of analyzed SNPs (rs3744246 and rs8076131) nor in the level of promoter methylation.

CONCLUSIONS

Increased ORMDL3 expression is associated with pediatric allergic asthma and upregulated in the airways upon Th2-cytokines stimulation, but further functional studies are required to fully understand its role in this disease.

Development of Adaptive Immunity and Its Role in Lung Remodeling

Asthma is characterized by airflow limitations resulting from bronchial closure, which can be either reversible or fixed due to changes in airway tissue composition and structure, also known as remodeling. Airway remodeling is defined as increased presence of mucins-producing epithelial cells, increased thickness of airway smooth muscle cells, angiogenesis, increased number and activation state of fibroblasts, and extracellular matrix (ECM) deposition. Airway inflammation is believed to be the main cause of the development of airway remodeling in asthma. In this chapter, we will review the development of the adaptive immune response and the impact of its mediators and cells on the elements defining airway remodeling in asthma.

Effect of Skeletal Paracrine Signals on the Proliferation of Interzone Cells

OBJECTIVE

Articular cartilage in mammals has limited intrinsic capacity to repair structural defects, a fact that contributes to the chronic and progressive nature of osteoarthritis. In contrast, Mexican axolotl salamanders have demonstrated the remarkable ability to spontaneously and completely repair large joint cartilage lesions, a healing process that involves interzone cells in the intraarticular space. Furthermore, interzone tissue transplanted into skeletal defects in the axolotl salamander demonstrates a multi-differentiation potential. Cellular and molecular mechanisms of this repair process remain unclear. The objective of this study was to examine whether paracrine mitogenic signals are an important variable in the interaction between interzone cells and the skeletal microenvironment.

DESIGN

The paracrine regulation of the proliferation of equine interzone cells was evaluated in an in vitro co-culture system. Cell viability and proliferation were measured in equine fetal interzone cells after exposure to conditioned medium from skeletal and nonskeletal primary cell lines. Steady-state expression was determined for genes encoding 37 putative mitogens secreted by cells that generated the conditioned medium.

RESULTS

All experimental groups of conditioned media elicited a mitogenic response in interzone cells. Fetal anlage chondrocytes (P < 0.0001) and dermal fibroblasts (P < 0.0001) conditioned medium showed a significantly higher mitogenic potential compared with interzone cells. Conditioned medium from bone marrow-derived cells elicited a significantly higher proliferative response relative to that from young adult articular chondrocytes (P < 0.0001) or dermal fibroblasts (P < 0.0001). Sixteen genes had expression patterns consistent with the functional proliferation assays.

CONCLUSIONS

The results indicate a mitogenic effect of skeletal paracrine signals on interzone cells.

Mesenchymal Stem Cells Increase Alveolar Differentiation in Lung Progenitor Organoid Cultures

Lung epithelial cell damage and dysfunctional repair play a role in the development of lung disease. Effective repair likely requires the normal functioning of alveolar stem/progenitor cells. For example, we have shown in a mouse model of bronchopulmonary dysplasia (BPD) that mesenchymal stem cells (MSC) protect against hyperoxic lung injury at least in part by increasing the number of Epcam⁺ Sca-1⁺ distal lung epithelial cells. These cells are capable of differentiating into both small airway (CCSP⁺) and alveolar (SPC⁺) epithelial cells in three-dimensional (3D) organoid cultures. To further understand the interactions between MSC and distal lung epithelial cells, we added MSC to lung progenitor 3D cultures. MSC stimulated Epcam⁺ Sca-1⁺ derived organoid formation, increased alveolar differentiation and decreased self-renewal. MSC-conditioned media was sufficient to promote alveolar organoid formation, demonstrating that soluble factors secreted by MSC are likely responsible for the response. This work provides strong evidence of a direct effect of MSC-secreted factors on lung progenitor cell differentiation.

Effects of Epithelial IL-13Rα2 Expression in Inflammatory Bowel Disease

Background: Mucosal IL-13 Receptor alpha 2 (IL13RA2) mRNA expression is one of the best predictive markers for primary non-responsiveness to infliximab therapy in patients with inflammatory bowel disease (IBD). The objective of this study was to understand how IL-13Rα2, a negative regulator of IL-13 signaling, can contribute to IBD pathology. Methods:IL13RA2 knockout (KO) and wild type (WT) mice were exposed to dextran sodium sulfate (DSS) in drinking water to induce colitis. Furthermore, mucosal biopsies and resection specimen of healthy individuals and IBD patients before the start of anti-tumor necrosis factor (anti-TNF) therapy were obtained for immunohistochemistry and gene expression analysis. Results: After induction of DSS colitis, IL13RA2 KO mice had similar disease severity, but recovered more rapidly than WT animals. Goblet cell numbers and mucosal architecture were also more rapidly restored in IL13RA2 KO mice. In mucosal biopsies of active IBD patients, immunohistochemistry revealed that IL-13Rα2 protein was highly expressed in epithelial cells, while expression was restricted to goblet cells in healthy controls. Mucosal IL13RA2 mRNA negatively correlated with mRNA of several goblet cell-specific and barrier genes, and with goblet cell numbers. Conclusions: The data suggest that IL-13Rα2 on epithelial cells contributes to IBD pathology by negatively influencing goblet cell recovery, goblet cell function and epithelial restoration after injury. Therefore, blocking IL-13Rα2 could be a promising target for restoration of the epithelial barrier in IBD.

Gene expression analysis of Atlantic salmon gills reveals mucin 5 and interleukin 4/13 as key molecules during amoebic gill disease

Amoebic gill disease (AGD) is one of the main diseases affecting Atlantic salmon (Salmo salar L.) mariculture. Hallmarks of AGD are hyperplasia of the lamellar epithelium and increased production of gill mucus. This study investigated the expression of genes involved in mucus secretion, cell cycle regulation, immunity and oxidative stress in gills using a targeted 21-gene PCR array. Gill samples were obtained from experimental and natural Neoparamoeba perurans infections, and sampling points included progressive infection stages and post-freshwater treatment. Up-regulation of genes related to mucin secretion and cell proliferation, and down-regulation of pro-inflammatory and pro-apoptotic genes were associated with AGD severity, while partial restoration of the gill homeostasis was detected post-treatment. Mucins and Th2 cytokines accoun ted for most of the variability observed between groups highlighting their key role in AGD. Two mucins (muc5, muc18) showed differential regulation upon disease. Substantial up-regulation of the secreted muc5 was detected in clinical AGD, and the membrane bound muc18 showed an opposite pattern. Th2 cytokines, il4/13a and il4/13b2, were significantly up-regulated from 2 days post-infection onwards, and changes were lesion-specific. Despite the differences between experimental and natural infections, both yielded comparable results that underline the importance of the studied genes in the respiratory organs of fish, and during AGD progression.

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

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

The route to pathologies in chronic inflammatory diseases characterized by T helper type 2 immune cells

T helper type 2 (Th2)-characterized inflammatory responses are highly dynamic processes initiated by epithelial cell damage resulting in remodelling of the tissue architecture to prevent further harm caused by a dysfunctional epithelial barrier or migrating parasites. This process is a temporal and spatial response which requires communication between immobile cells such as epithelial, endothelial, fibroblast and muscle cells and the highly mobile cells of the innate and adaptive immunity. It is further characterized by a high cellular plasticity that enables the cells to adapt to a specific inflammatory milieu. Incipiently, this milieu is shaped by cytokines released from epithelial cells, which stimulate Th2, innate lymphoid and invariant natural killer (NK) T cells to secrete Th2 cytokines and to activate dendritic cells which results in the further differentiation of Th2 cells. This milieu promotes wound-healing processes which are beneficial in parasitic infections or toxin exposure but account for increasingly dysfunctional vital organs, such as the lung in the case of asthma and the colon in ulcerative colitis. A better understanding of the dynamics underlying relapses and remissions might lead ultimately to improved therapeutics for chronic inflammatory diseases adapted to individual needs and to different phases of the inflammation.

Structure and function of epigen, the last EGFR ligand

Epigen is the latest addition to the mammalian family of EGFR ligands. Epigen was initially identified as a novel expressed sequence tag with homology to the EGF family by high throughput sequencing of a mouse keratinocyte complementary DNA library, and received its name for its ability to act as an epithelial mitogen. In vitro studies attributed to epigen several unique features, such as persistent and potent biological actions involving low affinity receptor binding, as well as sub-maximal receptor activation and inactivation. Similarly to the other EGFR ligands, the expression of epigen is up-regulated by hormones and in certain cancer types. While the biological functions of epigen remain to be uncovered, it appears to play a role in epidermal structures, such as the mammary gland and the sebaceous gland. The latter organ, in particular, was greatly enlarged in transgenic mice overexpressing epigen. Interestingly, mice lacking epigen develop and grow normally, probably due to functional compensation by other EGFR ligands. Future studies are likely to reveal the biological roles of the unique receptor binding properties of epigen, as well as its potential harnessing during disease.

Increased activation of the epidermal growth factor receptor in transgenic mice overexpressing epigen causes peripheral neuropathy

In the mammalian nervous system, axons are commonly surrounded by myelin, a lipid-rich sheath that is essential for precise and rapid conduction of nerve impulses. In the peripheral nervous system (PNS), myelin sheaths are formed by Schwann cells which wrap around individual axons. While the tyrosine kinase receptors ERBB2 and ERBB3 are established mediators of peripheral myelination, less is known about the functions of the related epidermal growth factor receptor (EGFR) in the regulation of PNS myelination. Here, we report a peripheral neurodegenerative disease caused by increased EGFR activation. Specifically, we characterize a symmetric and distally pronounced, late-onset muscular atrophy in transgenic mice overexpressing the EGFR ligand epigen. Histological examination revealed a demyelinating neuropathy and axon degeneration, and molecular analysis of signaling pathways showed reduced protein kinase B (PKB, AKT) activation in the nerves of Epigen-tg mice, indicating that the muscular phenotype is secondary to PNS demyelination and axon degeneration. Crossing of Epigen-tg mice into an EGFR-deficient background revealed the pathology to be completely EGFR-dependent. This mouse line provides a new model for studying molecular events associated with early stages of peripheral neuropathies, an essential prerequisite for the development of successful therapeutic interventions.

Genetic deletion of the EGFR ligand epigen does not affect mouse embryonic development and tissue homeostasis

The epidermal growth factor receptor (EGFR) is a tyrosine kinase receptor with manifold functions during development, tissue homeostasis and disease. EGFR activation, the formation of homodimers or heterodimers (with the related ERBB2-4 receptors) and downstream signaling is initiated by the binding of a family of structurally related growth factors, the EGFR ligands. Genetic deletion experiments clarified the biological function of all family members except for the last characterized ligand, epigen. We employed gene targeting in mouse embryonic stem cells to generate mice lacking epigen expression. Loss of epigen did not affect mouse development, fertility, or organ physiology. Quantitative RT-PCR analysis revealed increased expression of betacellulin and EGF in a few organs of epigen-deficient mice, suggesting a functional compensation by these ligands. In conclusion, we completed the genetic analysis of EGFR ligands and show that epigen has non-essential functions or functions that can be compensated by other EGFR ligands during growth and tissue homeostasis.