Modulation of pulmonary fibrosis by IL-13Rα2

Research on the potential mechanism of Deapioplatycodin D against pulmonary fibrosis based on bioinformatics and experimental verification

BACKGROUND

Pulmonary fibrosis (PF) is a group of respiratory diseases that are extremely complex and challenging to treat. Due to its high mortality rate and short survival, it's often referred to as a "tumor-like disease" that poses a serious threat to human health.

OBJECTIVE

We aimed validate the potential of Deapioplatycodin D (DPD) to against PF and clarify the underlying mechanism of action of DPD for the treatment of PF based on bioinformatics and experimental verification. This finding provides a basis for the development of safe and effective therapeutic PF drugs based on DPD.

METHODS

We used LPS-induced early PF rats as a PF model to test the overall efficacy of DPD in vivo. Then, A variety of bioinformatics methods, such as WGCNA, LASSO algorithm and immune cell infiltration (ICI), were applied to analyze the gene microarray related to PF obtained from Gene Expression Omnibus (GEO) to obtained key targets of PF. Finally, an in vitro PF model was constructed based on BEAS-2B cells while incorporating rat lung tissues to validate the regulatory effects of DPD on critical genes.

RESULTS

DPD can effectively alleviate inflammatory and fibrotic markers in rat lungs. WGCNA analysis resulted in a total of six expression modules, with the brown module having the highest correlation with PF. Subsequently, seven genes were acquired by intersecting the genes in the brown module with DEGs. Five key genes were identified as potential biomarkers of PF by LASSO algorithm and validation dataset verification analysis. In the ICI analysis, infiltration of activated B cell, immature B cell and natural killer cells were found to be more crucial in PF. Ultimately, it was observed that DPD could modulate key genes to achieve anti-PF effects.

CONCLUSION

In short, these comprehensive analysis methods were employed to identify critical biomarkers closely related to PF, which helps to elucidate the pathogenesis and potential immunotherapy targets of PF. It also provides essential support for the potential of DPD against PF.

IL13Rα2 as a crucial receptor for Chi3l1 in osteoclast differentiation and bone resorption through the MAPK/AKT pathway

BACKGROUND

Previous research has revealed that the 18 glycoside hydrolase gene family (GH18) member Chitinase 3-like 1 (Chi3l1) can regulate osteoclast differentiation and bone resorption. However, its downstream receptors and molecular mechanisms during osteoclastogenesis have yet to be elucidated.

METHODS

Initially, we conducted a comprehensive investigation to evaluate the effects of recombinant Chi3l1 protein or Chi3l1 siRNA on osteoclast differentiation and the RANKL-induced MAPK/AKT signaling pathways. Moreover, we used immunofluorescence and immunoprecipitation assays to identify IL13Rα2 as the downstream receptor of Chi3l1. Subsequently, we investigated the impact of IL13Rα2 recombinant protein or IL13Rα2-siRNA on osteoclast differentiation and the associated signaling pathways. Finally, we performed in vivo experiments to examine the effect of recombinant IL13Rα2 protein in an LPS-induced mouse model of cranial osteolysis.

RESULTS

Our findings highlight that the administration of recombinant Chi3l1 protein increased the formation of osteoclasts and bolstered the expression of several osteoclast-specific genes (TRAP, NFATC1, CTR, CTSK, V-ATPase d2, and Dc-STAMP). Additionally, Chi3l1 significantly promoted the RANKL-induced MAPK (ERK/P38/JNK) and AKT pathway activation, whereas Chi3l1 silencing inhibited this process. Next, using immunofluorescence and co-immunoprecipitation assays, we identified IL13Rα2 as the binding partner of Chi3l1 during osteoclastogenesis. IL13Rα2 recombinant protein or IL13Rα2-siRNA also inhibited osteoclast differentiation, and IL13Rα2-siRNA attenuated the RANKL-induced activation of the MAPK (ERK/P38/JNK) and AKT pathways, similar to the effects observed upon silencing of Chi3l1. Moreover, the promoting effect of recombinant Chi3l1 protein on osteoclastogenesis and the activation of the MAPK and AKT pathways was reversed by IL13Rα2 siRNA. Finally, recombinant LI13Rα2 protein significantly attenuated the LPS-induced cranial osteolysis and the number of osteoclasts in vivo.

CONCLUSIONS

Our findings suggested that IL13Rα2 served as a crucial receptor for Chi3l1, enhancing RANKL-induced MAPK and AKT activation to promote osteoclast differentiation. These findings provide valuable insights into the molecular mechanisms of Chi3l1 in osteoclastogenesis, with potential therapeutic implications for osteoclast-related diseases. Video Abstract.

The mechanism of IL-13 targeting IL-13Rα2 in regulating oral mucosal FBs through PI3K/AKT/mTOR

OBJECTIVE

The objective of this investigation was to examine the presence of interleukin (IL)-13 and its receptor IL-13Rα2 in the tissues of oral submucous fibrosis (OSF), investigate their biological functions, and explore the underlying mechanisms involved in the development of OSF.

MATERIALS AND METHODS

The expression of IL-13 and IL-13Rα2 in the oral mucosa of patients with OSF and normal individuals was determined through immunohistochemistry and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Primary fibroblasts (FBs) were extracted through enzymatic digestion and then cultured. Immunofluorescence was employed to identify the FB cultures and the location of IL-13Rα2. The effects of IL-13/IL-13Rα2/PI3K/AKT/mTOR on the migration, proliferation, and secretion of fiber-related proteins of FBs were explored via the wound healing assay, CCK-8 assay, EDU assay, and RT-qPCR. The impact of IL-13Rα2 silencing and PI3K/AKT inhibition on the effect of IL-13 on FBs was analyzed by RT-qPCR and Western blotting.

RESULTS

IL-13 and IL-13Rα2 were highly expressed in OSF. Primary FBs were successfully extracted and cultured. IL-13Rα2 was found to be localized in myofibroblasts. IL-13 promoted the proliferation, migration, and secretion of fibril-associated proteins in FBs. The proliferation, migration, and secretion of fibril-associated proteins of FBs were decreased following IL-13Rα2 silencing and inhibition of the PI3K/AKT/mTOR pathway.

CONCLUSION

IL-13 may promote the proliferation, migration, and secretion of fiber-related proteins of FBs through the PI3K/AKT/mTOR pathway by targeting IL-13Rα2.

Injectable, Drug-Eluting Nanocrystals Prevent Fibrosis and Stricture Formation In Vivo

BACKGROUND & AIMS

Tissue fibrosis results from uncontrolled healing responses leading to excessive mesenchymal cell activation and collagen and other extracellular matrix deposition. In the gastrointestinal tract, fibrosis leads to narrowing of the lumen and stricture formation. A drug treatment to prevent fibrosis and strictures in the gastrointestinal tract would be transformational for patient care. We aimed to develop a stricture treatment with the following characteristics and components: a small molecule with strong antifibrotic effects that is delivered locally at the site of the stricture to ensure correct lesional targeting while protecting the systemic circulation, and that is formulated with sustained-release properties to act throughout the wound healing processes.

METHODS

A high-throughput drug screening was performed to identify small molecules with antifibrotic properties. Next, we formulated an antifibrotic small molecule for sustained release and tested its antifibrotic potential in 3 animal models of fibrosis.

RESULTS

Sulconazole, a US Food and Drug Administration-approved drug for fungal infections, was found to have strong antifibrotic properties. Sulconazole was formulated as sulconazole nanocrystals for sustained release. We found that sulconazole nanocrystals provided superior or equivalent fibrosis prevention with less frequent dosing in mouse models of skin and intestinal tissue fibrosis. In a patient-like swine model of bowel stricture, a single injection of sulconazole nanocrystals prevented stricture formation.

CONCLUSIONS

The current data lay the foundation for further studies to improve the management of a range of diseases and conditions characterized by tissue fibrosis.

Targeting of the Interleukin-13 Receptor (IL-13R)α2 Expressing Prostate Cancer by a Novel Hybrid Lytic Peptide

The IL-13Rα2 cell surface receptor is highly expressed in tumours such as prostate cancer. In this report, we evaluated the hypothesis that prostate cancer cells with enhanced IL-13Rα2 expression are a suitable target for the hybrid lytic peptide (Pep-1-Phor21) peptide, which is generated by fusing the IL-13Rα2 specific ligand (Pep-1) and a cell membrane disrupting lytic peptide (Phor21). The expression of IL-13Rα2 mRNA and protein in prostate cancer tissues and cell lines was assessed via real-time PCR (RT-PCR) and immunoblotting. The effect of Pep-1-Phor21 on the viability of prostate cancer cells grown in monolayers (2D) and microtissue spheroids (3D) was assessed via CellTox green cytotoxic assay. IL-13Rα2 expression and Pep-1-Phor21-mediated killing were also determined in the cells treated with epigenetic regulators (Trichostatin A (TSA) and 5-aza-2 deoxycytidine (5-Aza-dC)). The hybrid lytic peptide cytotoxic activity correlated with the expression of IL-13Rα2 in prostate cancer cell lines cultured as monolayers (2D) or 3D spheroids. In addition, TSA or 5-Aza-dC treatment of prostate cancer cells, particularly those with low expression of IL-13Rα2, enhanced the cells' sensitivity to the lytic peptide by increasing IL-13Rα2 expression. These results demonstrate that the Pep-1-Phor21 hybrid lytic peptide has potent and selective anticancer properties against IL-13Rα2-expressing prostate cancer cells.

Artificial neural network identified the significant genes to distinguish Idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease that causes irreversible damage to lung tissue characterized by excessive deposition of extracellular matrix (ECM) and remodeling of lung parenchyma. The current diagnosis of IPF is complex and usually completed by a multidisciplinary team including clinicians, radiologists and pathologists they work together and make decision for an effective treatment, it is imperative to introduce novel practical methods for IPF diagnosis. This study provided a new diagnostic model of idiopathic pulmonary fibrosis based on machine learning. Six genes including CDH3, DIO2, ADAMTS14, HS6ST2, IL13RA2, and IGFL2 were identified based on the differentially expressed genes in IPF patients compare to healthy subjects through a random forest classifier with the existing gene expression databases. An artificial neural network model was constructed for IPF diagnosis based these genes, and this model was validated by the distinctive public datasets with a satisfactory diagnostic accuracy. These six genes identified were significant correlated with lung function, and among them, CDH3 and DIO2 were further determined to be significantly associated with the survival. Putting together, artificial neural network model identified the significant genes to distinguish idiopathic pulmonary fibrosis from healthy people and it is potential for molecular diagnosis of IPF.

A potential three-gene-based diagnostic signature for idiopathic pulmonary fibrosis

Background: Idiopathic pulmonary fibrosis (IPF) is a life-threatening disease whose etiology remains unknown. This study aims to explore diagnostic biomarkers and pathways involved in IPF using bioinformatics analysis. Methods: IPF-related gene expression datasets were retrieved and downloaded from the NCBI Gene Expression Omnibus database. Differentially expressed genes (DEGs) were screened, and weighted correlation network analysis (WGCNA) was performed to identify key module and genes. Functional enrichment analysis was performed on genes in the clinically significant module. Then least absolute shrinkage and selection operator (LASSO) logistic regression and support vector machine-recursive feature elimination (SVM-RFE) algorithms were run to screen candidate biomarkers. The expression and diagnostic value of the biomarkers in IPF were further validated in external test datasets (GSE110147). Results: 292 samples and 1,163 DEGs were screened to construct WGCNA. In WGCNA, the blue module was identified as the key module, and 59 genes in this module correlated highly with IPF. Functional enrichment analysis of blue module genes revealed the importance of extracellular matrix-associated pathways in IPF. IL13RA2, CDH3, and COMP were identified as diagnostic markers of IPF via LASSO and SVM-RFE. These genes showed good diagnostic value for IPF and were significantly upregulated in IPF. Conclusion: This study indicates that IL13RA2, CDH3, and COMP could serve as diagnostic signature for IPF and might offer new insights in the underlying diagnosis of IPF.

Relaxin in fibrotic ligament diseases: Its regulatory role and mechanism

Fibrotic ligament diseases (FLDs) are diseases caused by the pathological accumulation of periarticular fibrotic tissue, leading to functional disability around joint and poor life quality. Relaxin (RLX) has been reported to be involved in the development of fibrotic lung and liver diseases. Previous studies have shown that RLX can block pro-fibrotic process by reducing the excess extracellular matrix (ECM) formation and accelerating collagen degradation in vitro and in vivo. Recent studies have shown that RLX can attenuate connective tissue fibrosis by suppressing TGF-β/Smads signaling pathways to inhibit the activation of myofibroblasts. However, the specific roles and mechanisms of RLX in FLDs remain unclear. Therefore, in this review, we confirmed the protective effect of RLX in FLDs and summarized its mechanism including cells, key cytokines and signaling pathways involved. In this article, we outline the potential therapeutic role of RLX and look forward to the application of RLX in the clinical translation of FLDs.

A novel iridoid glycoside leonuride (ajugol) attenuates airway inflammation and remodeling through inhibiting type-2 high cytokine/chemokine activity in OVA-induced asthmatic mice

BACKGROUND

Asthma is a chronic airway disorder with a hallmark feature of airflow obstruction that associated with the remodeling and inflammation in the airway wall. Effective therapy for controlling both remodeling and inflammation is still urgently needed. Leonuride is the main pharmacological component identified from Bu-Shen-Yi-Qi-Tang (BSYQT) which has been traditionally used in treatment of lung diseases. However, no pharmacological effects of leonuride in asthma were reported.

PURPOSE

Here we aimed to investigated whether leonuride provided a therapeutic efficacy in reversing asthma airway remodeling and inflammation and uncover the underlying mechanisms.

STUDY DESIGN AND METHODS

Mouse models of chronic asthma were developed with ovalbumin (OVA) exposure for 8 weeks. Respiratory mechanics, lung histopathology and asthma-related cytokines were examined. Lung tissues were analyzed using RNA sequencing to reveal the transcriptional profiling changes.

RESULTS

After oral administration with leonuride (15 mg/kg or 30 mg/kg), mice exhibited a lower airway hyperresponsiveness in comparison to asthmatic mice. Leonuride suppressed airway inflammation evidenced by the significant reductions in accumulation of inflammatory cells around bronchi and vessels, leukocyte population counts and the abundance of type 2 inflammatory mediators (OVA specific IgE, IL-4, IL-5 and IL-13) in bronchoalveolar lavage fluid (BALF). On the other hand, leonuride slowed down the process of active remodeling as demonstrated by weaker goblet cell metaplasia and subepithelial fibrosis in lung histopathology and lower transforming growth factor (TGF)-β1 levels in serum and BALF in comparison to mice treated with OVA only. Furthermore, we uncovered transcriptional profiling alternations in lung tissue of mice after OVA exposure and leonuride treatment. Gene sets belonging to type-2 cytokine/chemokine activity stood out in leonuride target transcripts. Those upregulated (Bmp10, Ccl12, Ccl22, Ccl8, Ccl9, Cxcl15, Il13, Il33, Tnfrsf9, Il31ra, Il5ra, Il13ra2 and Ccl24) or downregulated (Acvr1c and Il18) genes in asthmatic mice, were all reversely regulated by leonuride treatment.

CONCLUSIONS

Our results revealed the therapeutic efficacy of leonuride in experimental chronic asthma for the first time, and implied that its anti-inflammatory and antifibrotic properties might be mediated by regulation of type-2 high cytokine/chemokines responses.

Human Cytomegalovirus and Human Herpesvirus 6 Coinfection of Dermal Fibroblasts Enhances the Pro-Inflammatory Pathway Predisposing to Fibrosis: The Possible Impact on Systemic Sclerosis

Systemic sclerosis (SSc) is a severe autoimmune disease likely triggered by genetic and environmental factors, including viral infections. Human cytomegalovirus (HCMV) and human herpesvirus 6A species (HHV-6A) have been associated with SSc, based on in vivo and in vitro evidence, but the data are still inconclusive. Furthermore, despite both viruses being highly prevalent in humans and able to exacerbate each other’s effects, no data are available on their joint effects. Hence, we aimed to study their simultaneous impact on the expression of cell factors correlated with fibrosis and apoptosis in in vitro coinfected fibroblasts, representing the main target cell type in SSc. The results, obtained by a microarray detecting 84 fibrosis/apoptosis-associated factors, indicated that coinfected cells underwent higher and more sustained expression of fibrosis-associated parameters compared with single-infected cells. Thus, the data, for the first time, suggest that HCMV and HHV-6A may cooperate in inducing alterations potentially leading to cell fibrosis, thus further supporting their joint role in SSc. However, further work is required to definitively answer whether β-herpesviruses are causally linked to the disease and to enable the possible use of targeted antiviral treatments to improve clinical outcomes.

99mTc-labeled peptide targeting interleukin 13 receptor α 2 for tumor imaging in a cervical cancer mouse model

OBJECTIVE

Pep-1 (CGEMGWVRC) can potently bind to interleukin 13 receptor α 2 (IL-13Rα2), a tumor-restricted receptor found to be expressed in various malignancies. In this study, we intended to prepare a ^99mTc-labeled probe and evaluate its in vivo tumor accumulation properties in a cervical cancer xenograft model.

METHODS

The Pep-1 was designed and radiolabeled with ^99mTc by conjugation with mercaptoacetyl-triglycine (MAG₃). The labeling yield, radiochemical purity and stability were characterized in vitro. Cell uptake assays and fluorescence imaging were conducted for qualitative and quantitative evaluation of the specificity and affinity of Pep-1. Flow cytometry and tissue immunofluorescence were used to confirm the IL-13Rα2 expression in cervical cancer. Biodistribution and in vivo imaging were performed periodically to evaluate the imaging value of ^99mTc-MAG₃-Pep-1 in cervical cancer xenograft model.

RESULTS

^99mTc-MAG₃-Pep-1 was successfully prepared with a high labeling yield and radiochemical purity (> 95%). Specific cell uptake was demonstrated by scramble control and unlabeled MAG₃-Pep-1 blockade. Flow cytometry and tissue immunofluorescence also confirmed the mild IL-13Rα2 expression of HeLa. In the gamma imaging study and biodistribution, the tumors were imaged clearly at 2-6 h after injection of ^99mTc-MAG₃-Pep-1 and the accumulation of ^99mTc-MAG₃-Pep-1 in tumor was significantly higher than that in the blocking and scramble controls, demonstrating ligand-receptor binding specificity.

CONCLUSIONS

This work demonstrated that ^99mTc-MAG₃-Pep-1 can bind to cervical cancer with high affinity and specificity. MAG₃-Pep-1 may be a prospective precursor for IL-13Rα2-expressing cancer therapy.

Evaluation of Pirfenidone and Nintedanib in a Human Lung Model of Fibrogenesis

Introduction: Idiopathic pulmonary fibrosis (IPF) is a progressive, fatal lung disease with a poor prognosis and increasing incidence. Pirfenidone and nintedanib are the only approved treatments for IPF but have limited efficacy and their mechanisms of action are poorly understood. Here we have examined the effects of pirfenidone and nintedanib in a human model of lung fibrogenesis, and compared these with the putative anti-fibrotic compounds Lipoxin A4 (LXA4), and senicapoc, a K_Ca3.1 ion channel blocker. Methods: Early fibrosis was induced in cultured human lung parenchyma using TGFβ1 for 7 days, ± pirfenidone, nintedanib, or LXA4. Pro-fibrotic responses were examined by RT-PCR, immunohistochemistry and soluble collagen secretion. Results: Thirty six out of eighty four IPF and fibrosis-associated genes tested were significantly upregulated by TGFβ1 in human lung parenchyma with a ≥0.5 log2FC (n = 32). Nintedanib (n = 13) reduced the mRNA expression of 14 fibrosis-associated genes including MMPs (MMP1,-4,-13,-14), integrin α2, CXCR4 and PDGFB, but upregulated α-smooth muscle actin (αSMA). Pirfenidone only reduced mRNA expression for MMP3 and -13. Senicapoc (n = 11) previously attenuated the expression of 28 fibrosis-associated genes, including αSMA, several growth factors, collagen type III, and αV/β6 integrins. Pirfenidone and nintedanib significantly inhibited TGFβ1-induced fibroblast proliferation within the tissue, but unlike senicapoc, neither pirfenidone nor nintedanib prevented increases in tissue αSMA expression. LXA4 was ineffective. Conclusions: Pirfenidone and nintedanib demonstrate modest anti-fibrotic effects and provide a benchmark for anti-fibrotic activity of new drugs in human lung tissue. Based on these data, we predict that the K_Ca3.1 blocker senicapoc will show greater benefit than either of these licensed drugs in IPF.

Therapeutic targeting of the IL-13 pathway in skin inflammation

Introduction: Atopic dermatitis (AD) is a heterogeneous, chronic, inflammatory skin disease with a non-negligible prevalence at present. Its pathogenesis is complex, but mainly characterized by constitutive T helper type 2 (Th2)-cell activation. Systemic therapies for moderate-to-severe AD can be associated with adverse events that encumber their satisfactory long-term use. Several drugs targeting relevant molecules in the immunopathogenesis of AD have been approved or are under clinical development for the treatment of moderate to severe AD. To elaborate this review, literature searches were performed in PubMed on 29 August 2020.Areas covered: This narrative literature review is focused on the pivotal role of IL-13 in the immunopathogenesis of AD and other skin diseases.Expert opinion: Dupilumab has demonstrated the central role of IL-13 and IL-4 in the pathogenesis of AD, asthma, and other diseases in the atopic spectrum. In addition, phase III randomized clinical trials (RCTs) evaluating specific blockade of IL-13 with tralokinumab for treatment of AD also demonstrated favorable results, and phase III RCT evaluating lebrikizumab are ongoing. The role of IL-13 in other skin diseases should be further investigated.

Regulation of Skin Barrier Function via Competition between AHR Axis versus IL-13/IL-4‒JAK‒STAT6/STAT3 Axis: Pathogenic and Therapeutic Implications in Atopic Dermatitis

Atopic dermatitis (AD) is characterized by skin inflammation, barrier dysfunction, and chronic pruritus. As the anti-interleukin-4 (IL-4) receptor α antibody dupilumab improves all three cardinal features of AD, the type 2 cytokines IL-4 and especially IL-13 have been indicated to have pathogenic significance in AD. Accumulating evidence has shown that the skin barrier function is regulated via competition between the aryl hydrocarbon receptor (AHR) axis (up-regulation of barrier) and the IL-13/IL-4‒JAK‒STAT6/STAT3 axis (down-regulation of barrier). This latter axis also induces oxidative stress, which exacerbates inflammation. Conventional and recently developed agents for treating AD such as steroid, calcineurin inhibitors, cyclosporine, dupilumab, and JAK inhibitors inhibit the IL-13/IL-4‒JAK‒STAT6/STAT3 axis, while older remedies such as coal tar and glyteer are antioxidative AHR agonists. In this article, I summarize the pathogenic and therapeutic implications of the IL-13/IL-4‒JAK‒STAT6/STAT3 axis and the AHR axis in AD.

CXCR3A promotes the secretion of the antifibrotic decoy receptor sIL-13Rα2 by pulmonary fibroblasts

CXC chemokine receptor 3 (CXCR3) A and its IFN-inducible ligands CXCL9 and CXCL10 regulate vascular remodeling and fibroblast motility. IL-13 is a profibrotic cytokine implicated in the pathogenesis of inflammatory and fibroproliferative conditions. Previous work from our laboratory has shown that CXCR3A is negatively regulated by IL-13 and is necessary for the basal regulation of the IL-13 receptor subunit IL-13Rα2. This study investigates the regulation of fibroblast phenotype, function, and downstream IL-13 signaling by CXCR3A in vitro. CXCR3A was overexpressed via transient transfection. CXCR3A^-/- lung fibroblasts were isolated for functional analysis. Additionally, the contribution of CXCR3A to tissue remodeling following acute lung injury was assessed in vivo with wild-type (WT) and CXCR3^-/- mice challenged with IL-13. CXCR3 and IL-13Rα2 displayed a reciprocal relationship after stimulation with either IL-13 or CXCR3 ligands. CXCR3A reduced expression of fibroblast activation makers, soluble collagen production, and proliferation. CXCR3A enhanced the basal expression of pERK1/2 while inducing IL-13-mediated downregulation of NF-κB-p65. CXCR3A^-/- pulmonary fibroblasts were increasingly proliferative and displayed reduced contractility and α-smooth muscle actin expression. IL-13 challenge regulated expression of the CXCR3 ligands and soluble IL-13Rα2 levels in lungs and bronchoalveolar lavage fluid (BALF) of WT mice; this response was absent in CXCR3^-/- mice. Alveolar macrophage accumulation and expression of genes involved in lung remodeling was increased in CXCR3^-/- mice. We conclude that CXCR3A is a central antifibrotic factor in pulmonary fibroblasts, limiting fibroblast activation and reducing extracellular matrix (ECM) production. Therefore, targeting of CXCR3A may be a novel approach to regulating fibroblast activity in lung fibrosis and remodeling.

Fibrosis Mediators in the Colonic Mucosa of Acute and Healed Ulcerative Colitis

OBJECTIVES

A healed intestinal mucosa is the aim of therapy in acute ulcerative colitis (UC). Disruption of mucosal wound healing may lead to severe complications including intestinal fibrosis. This study examined mucosal gene expression in the healing process of acute UC with a special focus on known mediators of fibrosis.

METHODS

Endoscopic biopsies from patients with acute, moderate to severe UC were analyzed with a quantitative polymerase chain reaction array for 84 genes involved in fibrosis pathways. All patients were treated with infliximab (anti- tumor necrosis factor). Biopsies were taken before therapy and when disease remission was reached, defined as a Mayo score of ≤2, with an endoscopic subscore of 0 or 1. A healthy control group was included. Immunostaining of matrix metallopeptidase 9 and smooth muscle actin was performed.

RESULTS

Mucosal biopsies from acute UC (n = 28), remission UC (n = 28), and healthy controls (n = 13) were analyzed. Fibrosis and extracellular matrix-associated genes were upregulated in the endoscopically healed UC mucosa vs controls, with collagen type III alpha 1 chain, actin alpha 2, lysyl oxidase, TIMP metallopeptidase inhibitor 3, and caveolin 1 uniquely showing no overlap with acute disease. Pro- and antifibrotic mediators (interleukin [IL]13 receptor subunit alpha 2, IL1B, IL10, tumor necrosis factor, snail family transcriptional repressor 1, and C-C motif chemokine ligand 2) were upregulated in both acute and healed UC compared with controls. An attenuated pattern of the canonical transforming growth factor beta (TGFB) pathway was observed in acute UC and to a lesser extent in the healed mucosa, except for TGFB2, which was enhanced.

DISCUSSION

The endoscopically healed mucosa of UC showed a persisting dysregulation of fibrosis-associated mediators compared with controls, including extracellular matrix remodeling, profibrotic cytokines, and TGFB signaling pathways.

Impact of Human Cytomegalovirus and Human Herpesvirus 6 Infection on the Expression of Factors Associated with Cell Fibrosis and Apoptosis: Clues for Implication in Systemic Sclerosis Development

Systemic sclerosis (SSc) is a severe autoimmune disorder characterized by vasculopathy and multi-organ fibrosis; its etiology and pathogenesis are still largely unknown. Herpesvirus infections, particularly by human cytomegalovirus (HCMV) and human herpesvirus 6 (HHV-6), have been suggested among triggers of the disease based on virological and immunological observations. However, the direct impact of HCMV and/or HHV-6 infection on cell fibrosis and apoptosis at the cell microenvironment level has not yet been clarified. Thus, this study aimed to investigate the effects of HCMV and HHV-6 infection on the induction of pro-fibrosis or pro-apoptosis conditions in primary human dermal fibroblasts, one of the relevant SSc target cells. The analysis, performed by microarray in in vitro HCMV- or HHV-6-infected vs. uninfected cells, using specific panels for the detection of the main cellular factors associated with fibrosis or apoptosis, showed that both viruses significantly modified the expression of at least 30 pro-fibrotic and 20 pro-apoptotic factors. Notably, several recognized pro-fibrotic factors were highly induced, and most of them were reported to be involved in vivo in the multifactorial and multistep pathogenic process of SSc, thus suggesting a potential role of both HCMV and HHV-6.

Transcriptomics Study to Determine the Molecular Mechanism by which sIL-13Rα2-Fc Inhibits Caudal Intervertebral Disc Degeneration in Rats

Background

Intervertebral disc degeneration is related to tissue fibrosis. ADAMTS can degrade the important components of the ECM during the process of intervertebral disc degeneration, ultimately resulting in the loss of intervertebral disc function. sIL-13Rα2-Fc can inhibit fibrosis and slow down the degeneration process, but the mechanism involved remains unclear.

Objective

To determine the mechanism by which sIL-13Rα2-Fc inhibits ECM degradation and reduces intervertebral disc tissue fibrosis using a transcriptomics analysis.

Methods

A rat model of caudal intervertebral disc degeneration was established, and Sirius red staining was used to observe the pathological changes in the caudal intervertebral disc. Transcriptome sequencing was employed to assess the gene expression profiles of the intervertebral disc tissues in the model group and the sIL-13Rα2-Fc-treated group. Differentially expressed genes were identified and analyzed using GO annotation and KEGG pathway analyses. Real-time fluorescence quantitative PCR was used to verify the expression levels of candidate genes. The levels of GAG and HA were quantitatively assessed by ELISA, and the levels of collagen I and collagen II were analyzed by western blotting.

Results

Sirius red staining showed that in the model group, the annulus fibrosus was disordered, the number of breaks increased, and the type I collagen protein levels increased, whereas in the sIL-13Rα2-Fc group, the annulus fibrosus was ordered, the number of breaks decreased, and the type II collagen protein levels increased. In comparison with the model group, we identified 58 differentially expressed genes in the sIL-13Rα2-Fc group, and these were involved in 35 signaling pathways. Compared with those in the model group, the mRNA expression levels of Rnux1, Sod2, and Tnfaip6 in the IL-13Rα2-Fc group were upregulated, and the mRNA expression levels of Aldh3a1, Galnt3, Fgf1, Celsr1, and Adamts8 were downregulated; these results were verified by real-time fluorescence quantitative PCR. TIMP-1 (an ADAMTS inhibitor) and TIMP-1 combined with the sIL-13Rα2-Fc intervention increased the levels of GAG and HA, inhibited the expression of type I collagen, and promoted the expression of type II collagen.

Conclusion

Adamts8 may participate in the degradation of ECM components such as GAG and HA and lead to an imbalance in the ECM of the intervertebral disc, resulting in intervertebral disc degeneration. sIL-13Rα2-Fc promoted anabolism of the ECM and increased the levels of ECM components by inhibiting the expression of Adamts8, thus maintaining the dynamic equilibrium of the ECM and ultimately delaying intervertebral disc degeneration.

Implications of IL-13Rα2 in atopic skin inflammation

Atopic dermatitis (AD) is a common eczematous skin disorder characterized by skin inflammation, barrier disruption, chronic pruritus and marked scratching. Th2 cytokines, especially IL-13, play a pathogenic role in AD. IL-13 signals via a heterodimeric receptor composed of IL-4Rα and IL-13 Rα1. A second receptor, IL-13 Rα2, binds to IL-13 with high affinity, but it works as a decoy receptor. IL-13 Rα2 is overexpressed in the lesional skin of AD. Notably, mechanical scratching, as well as IL-13 itself, also upregulates IL-13 Rα2 expression. The scratch-induced IL-13 Rα2 upregulation may attenuate the IL-13-mediated epidermal barrier dysfunction and dermal fibrosis. Recent studies stress an importance of another IL-13 Rα2 ligand, chitinase 3-like 1 or YKL-40 in Th2 differentiation. However, the implications of increased IL-13 Rα2 levels remain elusive in AD. In this review, we summarize the recent topics on IL-13 Rα2 in atopic skin inflammation.

Oxidative Stress in Pulmonary Fibrosis

Oxidative stress has been linked to various disease states as well as physiological aging. The lungs are uniquely exposed to a highly oxidizing environment and have evolved several mechanisms to attenuate oxidative stress. Idiopathic pulmonary fibrosis (IPF) is a progressive age-related disorder that leads to architectural remodeling, impaired gas exchange, respiratory failure, and death. In this article, we discuss cellular sources of oxidant production, and antioxidant defenses, both enzymatic and nonenzymatic. We outline the current understanding of the pathogenesis of IPF and how oxidative stress contributes to fibrosis. Further, we link oxidative stress to the biology of aging that involves DNA damage responses, loss of proteostasis, and mitochondrial dysfunction. We discuss the recent findings on the role of reactive oxygen species (ROS) in specific fibrotic processes such as macrophage polarization and immunosenescence, alveolar epithelial cell apoptosis and senescence, myofibroblast differentiation and senescence, and alterations in the acellular extracellular matrix. Finally, we provide an overview of the current preclinical studies and clinical trials targeting oxidative stress in fibrosis and potential new strategies for future therapeutic interventions. © 2020 American Physiological Society. Compr Physiol 10:509-547, 2020.

Transcriptional regulation of the IL-13Rα2 gene in human lung fibroblasts

Interleukin (IL)-13 is a type 2 cytokine with important roles in allergic diseases, asthma, and tissue fibrosis. Its receptor (R) α1 is primarily responsible for the biological actions of this cytokine, while Rα2 possesses a decoy function which can block IL-13 signaling. Although the expression of Rα2 is known to be subject to modulation, information about its transcriptional regulation is limited. In this study, we sought to expand the understanding of transcriptional control of Rα2 in lung fibroblasts. We confirmed previous reports that IL-13 elicited modest induction of Rα2 in normal adult human lung fibroblasts, but found that prostaglandin E2 (PGE2) and fibroblast growth factor 2 (FGF-2) -mediators known to influence fibroblast activation in tissue fibrosis but not previously investigated in this regard - led to a much greater magnitude of Rα2 induction. Although both PGE2 (via protein kinase A) and FGF-2 (via protein kinase B, also known as AKT) depended on activation of cAMP-responsive element-binding protein (CREB) for induction of Rα2 expression, they nevertheless demonstrated synergy in doing so, likely attributable to their differential utilization of distinct transcriptional start sites on the Rα2 promoter. Our data identify CREB activation via PGE2 and FGF-2 as a previously unrecognized molecular controller of Rα2 gene induction and provide potential new insights into strategies for therapeutic manipulation of this endogenous brake on IL-13 signaling.

Effect of sIL-13Rα2-Fc on the progression of rat tail intervertebral disc degeneration

BACKGROUND

The incidence of degenerative disc disease caused by intervertebral disc injury is increasing annually, seriously affecting the quality of life of patients and increasing the disease burden on society. The mechanisms of intervertebral disc degeneration include changes in extracellular matrix (ECM) deposition and tissue fibrosis. sIL-13Rα2-Fc potently inhibits interleukin (IL)-13, as well as blocks related cell signaling pathways and inhibits fibrosis in certain tissues. However, it is unknown whether sIL-13Rα2-Fc inhibits fibrosis in injured intervertebral discs and slows the process of degeneration. We hypothesized that sIL-13Rα2-Fc delays the progression of intervertebral disc degeneration by inhibiting intervertebral disc fibrosis and improving ECM deposition.

METHODS

A rat tail intervertebral disc degeneration model was established. Pathological changes in rat intervertebral disc tissue were observed by hematoxylin and eosin staining and Masson staining. Glycosaminoglycan (GAG), chondroitin sulfate (CS), keratan sulfate (KS), and hyaluronic acid (HA) contents were quantitatively analyzed by enzyme-linked immunosorbent assay. Type I and type II collagen expression levels were analyzed by reverse transcription-PCR and western blotting.

RESULTS

Hematoxylin and eosin staining and Masson staining revealed annulus fibrosus rupture, disordered arrangement, decreased nucleus pulposus tissue, and decreased collagen fiber in the rat intervertebral disc tissue. Following treatment with sIL-13Rα2-Fc, pathological changes in the rat intervertebral disc were reduced. Rat intervertebral disc tissue showed decreased GAG, CS-KS, and (HA) contents, increased type I collagen levels, and decreased type II collagen levels in degenerated intervertebral discs. sIL-13Rα2-Fc intervention increased the contents of GAG, CS, KS, and HA; inhibited the expression of type I collagen; and promoted the expression of type II collagen.

CONCLUSION

These results demonstrate that intervertebral disc degeneration is associated with tissue fibrosis. sIL-13Rα2-Fc can regulate type I and type II collagen expression levels by increasing GAG, CS, KS, and HA contents, thereby slowing the progression of intervertebral disc degeneration.

Akt1 regulates pulmonary fibrosis via modulating IL-13 expression in macrophages

Idiopathic pulmonary fibrosis is a progressive interstitial pneumonia characterised by fibroblast accumulation, collagen deposition and extracellular matrix (ECM) remodelling. It was reported that Akt1 mediated idiopathic pulmonary fibrosis progression through regulating the apoptosis of alveolar macrophage, while its effect on macrophage-produced cytokines remains largely unknown. In the present study, we first examined the phosphorylation of Akt1 in lung sections from idiopathic pulmonary fibrosis patients by immunohistochemistry before applying a bleomycin-induced idiopathic pulmonary fibrosis model using Akt1−/− mice and Akt1+/+ littermates. The results showed that Akt1 was remarkably up-regulated in idiopathic pulmonary fibrosis patients, while in vivo studies revealed that Akt1-deficient mice had well-preserved alveolar structure and fewer collagens, secreted fewer matrix components, including alpha smooth-muscle actin and fibronectin and survived significantly longer than Akt1+/+ littermates. Additionally, the pro-fibrogenic cytokine IL-13 was down-regulated at least twofold in Akt1−/−mice compared to the Akt1+/+group on d 3 and 7 after bleomycin treatment. Furthermore, it was found that Akt1–/– macrophages displayed down-regulation of IL-13 compared to Akt1+/+ macrophages in which Akt1 was phosphorylated in response to IL-33 stimulation. These findings indicate that Akt1 modulates pulmonary fibrosis through inducing IL-13 production by macrophages, suggesting that targeting Akt1 may simultaneously block the fibrogenic processes of idiopathic pulmonary fibrosis.

Scratching Counteracts IL-13 Signaling by Upregulating the Decoy Receptor IL-13Rα2 in Keratinocytes

The vicious itch–scratch cycle is a cardinal feature of atopic dermatitis (AD), in which IL-13 signaling plays a dominant role. Keratinocytes express two receptors: The heterodimeric IL-4Rα/IL-13Rα1 and IL-13Rα2. The former one transduces a functional IL-13 signal, whereas the latter IL-13Rα2 works as a nonfunctional decoy receptor. To examine whether scratch injury affects the expression of IL-4Rα, IL-13Rα1, and IL-13Rα2, we scratched confluent keratinocyte sheets and examined the expression of three IL-13 receptors using quantitative real-time PCR (qRT-PCR) and immunofluorescence techniques. Scratch injuries significantly upregulated the expression of IL13RA2 in a scratch line number-dependent manner. Scratch-induced IL13RA2 upregulation was synergistically enhanced in the simultaneous presence of IL-13. In contrast, scratch injuries did not alter the expression of IL4R and IL13RA1, even in the presence of IL-13. Scratch-induced IL13RA2 expression was dependent on ERK1/2 and p38 MAPK signals. The expression of IL-13Rα2 protein was indeed augmented in the scratch edge area and was also overexpressed in lichenified lesional AD skin. IL-13 inhibited the expression of involucrin, an important epidermal terminal differentiation molecule. IL-13-mediated downregulation of involucrin was attenuated in IL-13Rα2-overexpressed keratinocytes, confirming the decoy function of IL-13Rα2. Our findings indicate that scratching upregulates the expression of the IL-13 decoy receptor IL-13Rα2 and counteracts IL-13 signaling.

Role of Macrophages in Acute Lung Injury and Chronic Fibrosis Induced by Pulmonary Toxicants

A diverse group of toxicants has been identified that cause injury to the lung including gases (eg, ozone, chlorine), particulates/aerosols (eg, diesel exhaust, fly ash, other combustion products, mustards, nanomaterials, silica, asbestos), chemotherapeutics (eg, bleomycin), and radiation. The pathologic response to these toxicants depends on the dose and duration of exposure and their physical/chemical properties. A common response to pulmonary toxicant exposure is an accumulation of proinflammatory/cytotoxic M1 macrophages at sites of tissue injury, followed by the appearance of anti-inflammatory/wound repair M2 macrophages. It is thought that the outcome of the pathogenic responses to toxicants depends on the balance in the activity of these macrophage subpopulations. Overactivation of either M1 or M2 macrophages leads to injury and disease pathogenesis. Thus, the very same macrophage-derived mediators, released in controlled amounts to destroy injurious materials and pathogens (eg, reactive oxygen species, reactive nitrogen species, proteases, tumor necrosis factor α) and initiate wound repair (eg, transforming growth factor β, connective tissue growth factor, vascular endothelial growth factor), can exacerbate acute lung injury and/or induce chronic disease such as fibrosis, chronic obstructive pulmonary disease, and asthma, when released in excess. This review focuses on the role of macrophage subsets in acute lung injury and chronic fibrosis. Understanding how these pathologies develop following exposure to toxicants, and the contribution of resident and inflammatory macrophages to disease pathogenesis may lead to the development of novel approaches for treating lung diseases.

Matrix remodeling in chronic lung diseases

Multicellular organisms synthesize and renew components of their subcellular and scaffolding proteins, collectively known as the extracellular matrix molecules (ECMs). In the lung, ECMs maintain tensile strength, elasticity, and dictate the specialized function of multiple cell lineages. These functions are critical in lung homeostatic processes including cellular migration and proliferation during morphogenesis or in response to repair. Alterations in lung ECMs that expose cells to new cryptic fragments, generated in response to endogenous proteinases or exogenous toxins, are associated with the development of several common respiratory diseases. How lung ECMs provide or relay vital signals to epithelial and mesenchymal cells has shed new light on development and progression of several common chronic respiratory diseases. This review will consider how ECMs regulate lung homeostasis and their reorganization under pathological conditions that can modulate the inflammatory diseases asthma, chronic obstructive pulmonary disease (COPD), and idiopathic pulmonary fibrosis (IPF). Better understanding of changes in the distribution of lung ECM could provide novel therapeutic approaches to treat chronic lung diseases.

Potential Risks Related to Modulating Interleukin-13 and Interleukin-4 Signalling: A Systematic Review

Introduction

Interleukin-13 and interleukin-4 are type-II cytokines signalling through the shared type II interleukin-4 receptor. As a result of their structural similarity, interleukin-13 and interleukin-4 have overlapping functions in the mediation of type-II-driven diseases and are, therefore, promising targets of biologic drugs currently in development for the treatment of such diseases, including asthma and atopic dermatitis.

Objective

This systematic review was conducted to assess preclinical evidence of potential safety concerns related to blockade of interleukin-13 alone or interleukin-13 and interleukin-4 in combination.

Methods

We specifically examined risks related to infection, malignancy and the cardiovascular system. We systematically searched the BIOSIS, MEDLINE and EMBASE databases to identify preclinical studies published between January 2006 and October 2016 that addressed the effects of interleukin-13/interleukin-4 blockade and modulation on the risk of infection, malignancy and cardiovascular events. To provide a clinical context, we also performed a search for clinical trials targeting the interleukin-13/interleukin-4 pathways. Relevant data from preclinical and clinical trials were abstracted and presented descriptively.

Results

Aside from expected evidence that inhibition of interleukin-13 and interleukin-4 impaired host responses to helminth infections, we did not identify other preclinical evidence suggesting safety risks relating to infection, malignancy or cardiovascular events. We found no evidence in clinical trials suggesting serious safety concerns, i.e. increased risk for infections, malignancy or cardiovascular events from therapeutic modulation of the interleukin-13 pathway alone or the combined interleukin-13/interleukin-4 pathways.

Conclusions

Although our findings are reassuring, long-term safety assessments of biologics that target the interleukin-13/interleukin-4 pathways currently in clinical development are needed.

Electronic supplementary material

The online version of this article (10.1007/s40264-017-0636-9) contains supplementary material, which is available to authorized users.

Novel differences in gene expression and functional capabilities of myofibroblast populations in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF), a chronic progressive interstitial pneumonia, is characterized by excessive fibroproliferation. Key effector cells in IPF are myofibroblasts that are recruited from three potential sources: resident fibroblasts, fibrocytes, and epithelial cells. We hypothesized that IPF myofibroblasts from different sources display unique gene expression differences and distinct functional characteristics. Primary human pulmonary fibroblasts (normal and IPF), fibrocytes, and epithelial cells were activated using the profibrotic factors TGF-β and TNF-α. The resulting myofibroblasts were characterized using cell proliferation, soluble collagen, and contractility assays, ELISA, and human fibrosis PCR arrays. Genes of significance in human whole lung were validated by immunohistochemistry on human lung sections. Fibroblast-derived myofibroblasts exhibited the greatest increase in expression of profibrotic genes and genes involved in extracellular matrix remodeling and signal transduction. Functional studies demonstrated that myofibroblasts derived from fibrocytes expressed mostly soluble collagen and chemokine (C-C) motif ligand (CCL) 18 but were the least proliferative of the myofibroblast progeny. Activated IPF fibroblasts displayed the highest levels of contractility and CCL2 production. This study identified novel differences in gene expression and functional characteristics of different myofibroblast populations. Further investigation into the myofibroblast phenotype may lead to potential therapeutic targets in future IPF research.

Serum level of interleukin-13 receptor alpha 2 in infants with biliary atresia - is it of value?

Aim of the study

We aimed to assess the utility of serum level IL-13Rα2 receptors as a non-invasive marker for early diagnosis of biliary atresia (BA) and selection of BA patients indicated for Kasai portoenterostomy.

Material and methods

The study included 60 infants with neonatal cholestasis in three groups; early BA group (n = 20), delayed BA group (n = 20) and non-BA cholestasis group (n = 20). A fourth group of 20 healthy neonates (n = 20) served as controls. IL-13Rα2 was measured by enzyme-linked immunosorbent assay in all patients and controls.

Results

The mean value of IL-13Rα2 was significantly higher in delayed BA group (11.05 ± 10.9 ng/ml) compared to early BA (0.34 ± 0.37 ng/ml), non-BA (0.54 ± 0.85 ng/ml) and control (0.24-0.2 ng/ml) groups. The levels of serum IL-13Rα2 increase with the severity of the degree of fibrosis. IL-13Rα2 at a cutoff level > 0.782 ng/ml could predict late fibrosis with accuracy of 77.55% (p < 0.0001). IL-13Rα2 could differentiate between preserved and disturbed liver architecture at a cut off value of more than 0.42 ng/ml with an accuracy of 81.6%.

Conclusions

Serum IL-13Rα2 not a diagnostic marker for BA however it could be used as a noninvasive marker for detection of advanced liver fibrosis and presence of disturbed liver architecture that helps in patient selection for undergoing Kasai operation. Serum IL-13Rα2 could be a future therapeutic target for management of BA patients and any fibrotic liver disease.

Association of IL-13 rs20541 and rs1295686 variants with symptomatic asthma in a Saudi Arabian population

OBJECTIVE

Interleukin 13 (IL-13) plays a critical pro-inflammatory role in asthma. Several single nucleotide polymorphisms (SNPs) are associated with asthma susceptibility in specific populations; however, further replicative studies in other ethnic groups are mandatory.

METHODS

The association between IL-13 SNPs rs762534, rs20541, rs1295686, and rs1800925 (risk alleles A, A, T, and A, respectively) and asthma predisposition in a Saudi Arabian cohort was examined via a case-control cross-sectional study.

RESULTS

The frequencies of alleles between asthmatics and control populations were significantly different for rs20541 and rs1295686 SNPs (p < 0.001), whereas the frequencies of genotypes between asthmatics and controls were significantly different only for rs20541. The association of the risk (minor) alleles with asthma was examined using the dominant genetic model. Individuals with at least one copy of the risk alleles A (for rs20541) and T (for rs1295686) had significantly greater odds of being asthmatic (OR = 2.13, 95% CI = 1.39-3.26, p < 0.0001; OR = 1.69, 95% CI = 1.12-2.54, p = 0.008) relative to their most common homozygous genotypes. On the other hand, the minor A alleles for rs762534 and rs1800925 were not significantly associated with asthma risk. Regarding haplotype association analysis, individuals with at least one copy of the minor "risk" allele for both rs20541 and rs1295686 (CATG and CATA, respectively) had greater odds of being asthmatic relative to CGCG haplotype; however, this trend was not statistically significant (p > 0.3).

CONCLUSIONS

IL-13 minor T and A alleles for rs1295686 and rs20541, respectively, were associated with significantly higher risk of asthma in the Saudi Arabian population.

Targeted Therapy for Idiopathic Pulmonary Fibrosis: Where To Now?

Idiopathic pulmonary fibrosis (IPF) is an aging-associated, recalcitrant lung disease with historically limited therapeutic options. The recent approval of two drugs, pirfenidone and nintedanib, by the US Food and Drug Administration in 2014 has heralded a new era in its management. Both drugs have demonstrated efficacy in phase III clinical trials by retarding the rate of progression of IPF; neither drug appears to be able to completely arrest disease progression. Advances in the understanding of IPF pathobiology have led to an unprecedented expansion in the number of potential therapeutic targets. Drugs targeting several of these are under investigation in various stages of clinical development. Here, we provide a brief overview of the drugs that are currently approved and others in phase II clinical trials. Future therapeutic opportunities that target novel pathways, including some that are associated with the biology of aging, are examined. A multi-targeted approach, potentially with combination therapies, and identification of individual patients (or subsets of patients) who may respond more favourably to specific agents are likely to be more effective.

IL-4 and IL-13 signaling in allergic airway disease

Aberrant production of the prototypical type 2 cytokines, interleukin (IL)-4 and IL-13 has long been associated with the pathogenesis of allergic disorders. Despite tremendous scientific inquiry, the similarities in their structure, and receptor usage have made it difficult to ascertain the distinct role that these two look-alike cytokines play in the onset and perpetuation of allergic inflammation. However, recent discoveries of differences in receptor distribution, utilization/assembly and affinity between IL-4 and IL-13, along with the discovery of unique innate lymphoid 2 cells (ILC2) which preferentially produce IL-13, not IL-4, are beginning to shed light on these mysteries. The purpose of this chapter is to review our current understanding of the distinct roles that IL-4 and IL-13 play in allergic inflammatory states and the utility of their modulation as potential therapeutic strategies for the treatment of allergic disorders.