Modulation of pulmonary fibrosis by IL-13Rα2.

Pulmonary fibrosis is a progressive and fatal disease that involves the remodeling of the distal airspace and the lung parenchyma, which results in compromised gas exchange. The median survival time once diagnosed is less than three years. Interleukin (IL)-13 has been shown to play a role in a number of inflammatory and fibrotic diseases. IL-13 modulates its effector functions via a complex receptor system that includes the IL-4 receptor (R) α, IL-13Rα1, and the IL-13Rα2. IL-13Rα1 binds IL-13 with low affinity, yet, when it forms a complex with IL-4α, it binds with much higher affinity, inducing the effector functions of IL-13. IL-13Rα2 binds IL-13 with high affinity but has a short cytoplasmic tail and has been shown to act as a nonsignaling decoy receptor. Transfection of fibroblasts and epithelial cells with IL-13Rα2 inhibited the IL-13 induction of soluble collagen, TGF-ß, and CCL17. Adenoviral overexpression of IL-13Rα2 in the lung reduced bleomycin-induced fibrosis. Our work shows that overexpression of IL-13Rα2 inhibits the IL-13 induction of fibrotic markers in vitro and inhibits bleomycin-induced pulmonary fibrosis. In summary our study highlights the antifibrotic nature of IL-13Ra2.

IL-13 receptor α2-arginase 2 pathway mediates IL-13-induced pulmonary hypertension.

Although previous literature suggests that interleukin (IL)-13, a T-helper type 2 cell effector cytokine, might be involved in the pathogenesis of pulmonary hypertension (PH), direct proof is lacking. Furthermore, a potential mechanism underlying IL-13-induced PH has never been explored. This study's goal was to investigate the role and mechanism of IL-13 in the pathogenesis of PH. Lung-specific IL-13-overexpressing transgenic (Tg) mice were examined for hemodynamic changes and pulmonary vascular remodeling. IL-13 Tg mice spontaneously developed PH phenotype by the age of 2 mo with increased expression and activity of arginase 2 (Arg2). The role of Arg2 in the development of IL-13-stimulated PH was further investigated using Arg2 and IL-13 receptor α2 (Rα2) null mutant mice and the small-interfering RNA (siRNA)-silencing approach in vivo and in vitro, respectively. IL-13-stimulated medial thickening of pulmonary arteries and right ventricle systolic pressure were significantly decreased in the IL-13 Tg mice with Arg2 null mutation. On the other hand, the production of nitric oxide was further increased in the lungs of these mice. In our in vitro evaluations, the recombinant IL-13 treatment significantly enhanced the proliferation of human pulmonary artery smooth muscle cells in an Arg2-dependent manner. The IL-13-stimulated cellular proliferation and the expression of Arg2 in hpaSMC were markedly decreased with IL-13Rα2 siRNA silencing. Our studies demonstrate that IL-13 contributes to the development of PH via an IL-13Rα2-Arg2-dependent pathway. The intervention of this pathway could be a potential therapeutic target in pulmonary arterial hypertension.

IL-13 in asthma and allergic disease: asthma phenotypes and targeted therapies.

Decades of research in animal models have provided abundant evidence to show that IL-13 is a key T(H)2 cytokine that directs many of the important features of airway inflammation and remodeling in patients with allergic asthma. Several promising focused therapies for asthma that target the IL-13/IL-4/signal transducer and activator of transcription 6 pathway are in development, including anti-IL-13 mAbs and IL-4 receptor antagonists. The efficacy of these new potential asthma therapies depends on the responsiveness of patients. However, an understanding of how IL-13-directed therapies might benefit asthmatic patients is confounded by the complex heterogeneity of the disease. Recent efforts to classify subphenotypes of asthma have focused on sputum cellular inflammation profiles, as well as cluster analyses of clinical variables and molecular and genetic signatures. Researchers and clinicians can now evaluate biomarkers of T(H)2-driven airway inflammation in asthmatic patients, such as serum IgE levels, sputum eosinophil counts, fraction of exhaled nitric oxide levels, and serum periostin levels, to aid decision making in clinical trials and drug development and to identify subsets of patients who might benefit from therapies. Although it is unlikely that these therapies will benefit all asthmatic patients with this heterogeneous disease, advances in understanding asthma subphenotypes in relation to clinical variables and T(H)2 cytokine responses offer the opportunity to improve the efficacy and safety of proposed therapies for asthma.

High expression of IL-13 receptor α2 in colorectal cancer is associated with invasion, liver metastasis, and poor prognosis.

Autocrine secretion of cytokines by metastatic colorectal cancer cells and their role during invasion and liver homing has been poorly characterized. In this study, we used cytokine arrays to analyze the secretomes of poorly and highly metastatic colorectal cancer cells. Compared with poorly metastatic cancer cells, highly metastatic cells expressed increased levels of the immunosuppressive cytokines interleukin (IL)-4 and IL-13 in addition to increased surface expression of the high affinity IL-13 receptor IL-13Rα2, suggesting that IL-13Rα2 mediates IL-13 effects in colorectal cancer cells. Silencing of IL-13Rα2 in highly metastatic cells led to a decrease in adhesion capacity in vitro and a reduction in liver homing and increased survival in vivo, revealing a role for this receptor in cell adhesion, migration, invasion, and metastatic colonization. In support of this, IL-13 signaling activated the oncogenic signaling molecules phosphoinositide 3-kinase, AKT, and SRC in highly metastatic cells. Clinically, high expression of IL-13Rα2 was associated with later stages of disease progression and poor outcome in patients with colorectal cancer. Our findings therefore support a critical role for IL-13Rα2 expression in colon cancer invasion and metastasis.

Accelerated and progressive and lethal liver fibrosis in mice that lack interleukin (IL)-10, IL-12p40, and IL-13Rα2.

BACKGROUND & AIMS: Progressive fibrosis contributes to the morbidity of several chronic diseases; it typically develops slowly, so the mechanisms that control its progression and resolution have been difficult to model. The proteins interleukin (IL)-10, IL-12p40, and IL-13Rα2 regulate hepatic fibrosis following infection with the helminth parasite Schistosoma mansoni. We examined whether these mediators interact to slow the progression of hepatic fibrosis in mice with schistosomiasis. METHODS: IL-10(-/-), IL-12/23(p40)(-/-), and IL-13Rα2(-/-) mice were crossed to generate triple knockout (TKO) mice. We studied these mice to determine whether the simultaneous deletion of these 3 negative regulators of the immune response accelerated mortality from liver fibrosis following infection with S mansoni. RESULTS: Induction of inflammation by S mansoni, liver fibrosis, and mortality increased greatly in TKO mice compared with wild-type mice; 100% of the TKO mice died by 10 weeks after infection. Morbidity and mortality were associated with the development of portal hypertension, hepatosplenomegaly, gastrointestinal bleeding, ascites, thrombocytopenia, esophageal and gastric varices, anemia, and increased levels of liver enzymes, all features of advanced liver disease. IL-10, IL-12p40, and IL-13Rα2 reduced the production and activity of the profibrotic cytokine IL-13. A neutralizing antibody against IL-13 reduced the morbidity and mortality of the TKO mice following S mansoni infection. CONCLUSIONS: IL-10, IL-12p40, and IL-13Rα2 act cooperatively to suppress liver fibrosis in mice following infection with S mansoni. This model rapidly reproduces many of the complications observed in patients with advanced cirrhosis, so it might be used to evaluate the efficacy of antifibrotic reagents being developed for schistosomiasis or other fibrotic diseases associated with a T-helper 2 cell-mediated immune response.

IL-13Rα2 has a protective role in a mouse model of cutaneous inflammation.

IL-13 is expressed in lesions of atopic dermatitis (AD) and has been associated with increased disease severity. IL-13 has two cognate receptors: IL-13Rα1 and IL-13Rα2. Although IL-13Rα2 expression is known to be induced in response to IL-13 in keratinocytes, its function in AD has never been evaluated. We characterized the loss of skin barrier function and the development of cutaneous inflammation in IL-13Rα2-null versus wild-type BALB/c mice following an epicutaneous allergen-sensitization/challenge model that shares similarities with human AD. Mice lacking IL-13Rα2 had significantly increased transepidermal water loss, cutaneous inflammation, peripheral eosinophilia, and IgG1 and IgE levels compared with wild-type mice. The rate of resolution of the cutaneous inflammation was not significantly altered in the IL-13Rα2-null mice. IL-13 induced expression of IL-13Rα2 in keratinocyte cell lines and primary human keratinocytes. Depletion of IL-13Rα2 in a keratinocyte cell line resulted in increased STAT6 signaling in response to IL-13. In conclusion, IL-13Rα2 serves a protective role in the pathogenesis of allergic inflammation and loss of skin barrier function in a mouse model of AD, suggesting that it may be an important endogenous regulator of IL-13-induced cutaneous inflammation in humans.

IL-13 induces esophageal remodeling and gene expression by an eosinophil-independent, IL-13R alpha 2-inhibited pathway.

Eosinophilic esophagitis (EE) is an emerging disease associated with both food and respiratory allergy characterized by extensive esophageal tissue remodeling and abnormal esophageal gene expression, including increased IL-13. We investigated the ability of increased airway IL-13 to induce EE-like changes. Mice with pulmonary (but not esophageal) overexpression of IL-13 evidenced esophageal IL-13 accumulation and developed prominent esophageal remodeling with epithelial hyperplasia, angiogenesis, collagen deposition, and increased circumference. IL-13 induced notable changes in esophageal transcripts that overlapped with the human EE esophageal transcriptome. IL-13-induced esophageal eosinophilia was dependent on eotaxin-1 (but not eotaxin-2). However, remodeling occurred independent of eosinophils as demonstrated by eosinophil lineage-deficient, IL-13 transgenic mice. IL-13-induced remodeling was significantly enhanced by IL-13Ralpha2 deletion, indicating an inhibitory effect of IL-13Ralpha2. In the murine system, there was partial overlap between IL-13-induced genes in the lung and esophagus, yet the transcriptomes were divergent at the tissue level. In human esophagus, IL-13 levels correlated with the magnitude of the EE transcriptome. In conclusion, inducible airway expression of IL-13 results in a pattern of esophageal gene expression and extensive tissue remodeling that resembles human EE. Notably, we identified a pathway that induces EE-like changes and is IL-13-driven, eosinophil-independent, and suppressed by IL-13Ralpha2.

Interleukin 13 mediates signal transduction through interleukin 13 receptor alpha2 in pancreatic ductal adenocarcinoma: role of IL-13 Pseudomonas exotoxin in pancreatic cancer therapy.

PURPOSE: Interleukin-13 receptor alpha2 (IL-13Ralpha2) is a tumor antigen that is overexpressed in certain human tumors. However, its significance and expression in pancreatic cancer is not known. It is also not known whether IL-13 can signal through IL-13Ralpha2 in cancer. EXPERIMENTAL DESIGN: The expression of IL-13Ralpha2 was assessed in pancreatic cancer samples by immunohistochemistry and in cell lines by flow cytometry and reverse transcription-PCR. The role of IL-13Ralpha2 was examined by IL-13-induced signaling in pancreatic cancer cell lines. IL-13Ralpha2-positive tumors were targeted by IL-13PE cytotoxin in vitro and in vivo in an orthotopic murine model of human pancreatic cancer. RESULTS: Of the pancreatic tumor samples 71% overexpressed moderate to high-density IL-13Ralpha2 chain compared with normal pancreatic samples. IL-13 induced transforming growth factor-beta1 promoter activity in IL-13Ralpha2-positive tumor cells and in cells engineered to express IL-13Ralpha2 but not in IL-13Ralpha2-negative or RNA interference knockdown cells. c-Jun and c-Fos of the AP-1 family of nuclear factors were activated by IL-13 only in IL-13Ralpha2-positive cells. In the orthotopic mouse model, IL13-PE significantly decreased tumor growth when assessed by whole-body imaging and prolonged the mean survival time. Similar results were observed in mice xenografted with a surgically resected human pancreatic tumor sample. CONCLUSIONS: These results indicate that IL-13Ralpha2 is a functional receptor as IL-13 mediates signaling in human pancreatic cancer cell lines. IL-13 causes transforming growth factor-beta activation via AP-1 pathway, which may cause tumor induced immunosuppression in the host. In addition, IL13-PE cytotoxin may be an effective therapeutic agent for the treatment of pancreatic cancer.

Overexpression of interleukin-13 receptor-alpha2 in neuroendocrine malignant pheochromocytoma: a novel target for receptor directed anti-cancer therapy.

CONTEXT: Pheochromocytomas and paragangliomas are rare catecholamine-secreting neuroendocrine tumors arising from the adrenal medulla and sympathetic tissues. When complete surgical resection is not an option, the treatment of pheochromocytoma is limited. OBJECTIVE: The objective of the study was to identify and characterize overexpression of IL-13 receptor-alpha2 (IL-13Ralpha2) gene expression in human and murine tumors and verify xenograft mouse pheochromocytoma cell (MPC)-derived tumor's response to a selective cytotoxin. DESIGN/SETTING/PATIENTS: Expression of IL-13Ralpha2 was evaluated in a panel of 25 human pheochromocytoma clinical samples by RT-PCR and eight MPC tumors by indirect immunofluorescence assay and RT-PCR. INTERVENTION: The function of IL-13Ralpha2 in these tumor cells was examined by evaluating tumor sensitivity to a recombinant IL-13-Pseudomonas exotoxin (IL-13PE). Subcutaneous small and large MPC tumors in athymic nude mice (n = 10) were treated intratumorally with IL-13PE (100 m icrog/kg). MAIN OUTCOME MEASURES: IC(50) and tumor size were measured. RESULTS: IL-13PE immunotoxin was highly cytotoxic to IL-13Ralpha2-overexpressing MPC cells (IC(50) <2.5 ng/ml) in vitro. Furthermore, IL-13PE was highly cytotoxic to sc tumors. Our results showed a statistically significant decrease in tumor size as early as 3 d after initial treatment and further suppressed growth of MPC tumors. All tumors displayed a histological evidence of necrosis in response to IL-13 immunotoxin without any adverse effects in host at this dose. CONCLUSIONS: Human and murine neuroendocrine pheochromocytoma overexpress the IL-13Ralpha2 chain, and an IL-13PE-based receptor-directed anticancer approach may prove useful in treatment for metastatic pheochromocytoma patients.

[Roles of serum and urinary interleukins 13Ralpha2 and other cytokines in pediatric Henoch-Schonlein purpura].

OBJECTIVE: To study the roles of serum and urinary interleukins (IL)-13Ralpha2, IL-4, IL-6, IL-8 and tumor necrosis factor-alpha(TNF-alpha) in pediatric Henoch-Schonlein purpura (HSP). METHODS: Serum and urinary levels of IL-13Ralpha2, IL-4, IL-6, IL-8 and TNF-alpha were examined using ELISA in 52 children with HSP and 45 healthy children. The results were compared between the two groups. RESULTS: Serum levels of IL-13Ralpha2, IL-4, IL-6, IL-8 and TNF-alpha in HSP patients with or without renal lesions were higher than those in the control group (p<0.01 or 0.05). Urinary levels of IL-6 and TNF-alpha in HSP patients without renal lesions were higher than those in the control group (p<0.05). Except for urinary levels of IL-6 and TNF-alpha, urinary IL-13Ralpha2 levels in HSP patients with renal lesions (HSPN) were higher than those in the control group (p<0.05). CONCLUSIONS: Cytokines IL-13Ralpha2, IL-4, IL-6, IL-8 and TNF-alpha may play roles in the pathogenesis of pediatric HSP/HSPN.

Novel role of IL-13 in fibrosis induced by nonalcoholic steatohepatitis and its amelioration by IL-13R-directed cytotoxin in a rat model.

Nonalcoholic steatohepatitis (NASH), the most common cause of chronic liver fibrosis, progresses to cirrhosis in up to 20% of patients. We report that hepatic stellate cells (HSC) in sinusoidal lesions of liver of patients with NASH express high levels of high-affinity IL-13R (IL-13Ralpha2), which is colocalized with smooth muscle actin, whereas fatty liver and normal liver specimens do not express IL-13Ralpha2. HSCs engineered to overexpress IL-13Ralpha2 respond to IL-13 and induce TGFB1 promoter activity and TGF-beta1 production. We also developed NASH in rats by feeding a choline-deficient l-amino acid diet. These rats developed liver fibrosis as assessed by H&E staining, Masson's trichrome and Sirius red staining, and hydroxyproline assays. Treatment of these rats with IL-13R-directed cytotoxin caused a substantial decline in fibrosis and liver enzymes without organ toxicity. These studies demonstrate that functional IL-13Ralpha2 are overexpressed in activated HSCs involved in NASH and that IL-13 cytotoxin ameliorates pathological features of NASH in rat liver, indicating a novel role of this cytotoxin in potential therapy.

Identification of a human leukocyte antigen-A24-restricted T-cell epitope derived from interleukin-13 receptor alpha2 chain, a glioma-associated antigen.

OBJECT: The human leukocyte antigen-A24 (HLA-A24) allele is highly expressed in Asians. This allele is expressed in 60% of the Japanese population and in a significant number of people of other ethnicities. The interleukin-13 type alpha2 receptor (IL-13Ralpha2) has been shown to be a glioma-specific antigen, and is abundantly expressed in a majority of high-grade astrocytomas. In this study, the authors first investigated the suitability of IL-13Ralpha2 as a target antigen of malignant glioma cells, and then identified a potential HLA-A24-restricted peptide derived from IL-13Ralpha2. METHODS: The expression of IL-13Ralpha2 in glioma tissues was examined by reverse transcription-polymerase chain reaction analysis. To identify the desired epitope, the authors selected 5 candidate peptides from IL-13Ralpha2 that were predicted to bind to HLA-A24. The lytic activity of cytotoxic T lymphocytes (CTLs) induced by peptide-pulsed dendritic cells was analyzed against various glioma cell lines and freshly isolated human glioma cells. RESULTS: In a series of glioma tissues obtained in 29 patients, the authors found that > 50% of high-grade gliomas expressed IL-13Ralpha2. Of the 5 peptides tested, P174 (WYEGLDHAL) was found to be the most useful for the induction of HLA-A24-restricted and IL-13Ralpha2-specific CTLs. A CTL line induced by P174 also showed antigen-specific cytotoxicity to surgically removed glioma cells depending on their level of expression of IL-13Ralpha2 and HLA-A24. CONCLUSIONS: Interleukin-13Ralpha2 is a glioma-specific antigen, and the immunogenic peptide P174 may contribute to a peptide-based immunotherapy against malignant glioma cells expressing HLA-A24.

IL-13 receptor alpha2 selectively inhibits IL-13-induced responses in the murine lung.

IL-13 is a critical cytokine at sites of Th2 inflammation. In these locations it mediates its effects via a receptor complex, which contains IL-4Ralpha and IL-13Ralpha1. A third, high-affinity IL-13 receptor, IL-13Ralpha2, also exists. Although it was initially felt to be a decoy receptor, this has not been formally demonstrated and the role(s) of this receptor has recently become controversial. To define the role(s) of IL-13Ralpha2 in IL-13-induced pulmonary inflammation and remodeling, we compared the effects of lung-targeted transgenic IL-13 in mice with wild-type and null IL-13Ralpha2 loci. We also investigated the effect of IL-13Ralpha2 deficiency on the OVA-induced inflammatory response. In this study, we show that in the absence of IL-13Ralpha2, IL-13-induced pulmonary inflammation, mucus metaplasia, subepithelial fibrosis, and airway remodeling are significantly augmented. These changes were accompanied by increased expression and production of chemokines, proteases, mucin genes, and TGF-beta1. Similarly, an enhanced inflammatory response was observed in an OVA-induced phenotype. In contrast, disruption of IL-13Ralpha2 had no effect on the tissue effects of lung-targeted transgenic IL-4. Thus, IL-13Ralpha2 is a selective and powerful inhibitor of IL-13-induced inflammatory, remodeling, and physiologic responses in the murine lung.

IL-13Ralpha2 and IL-10 coordinately suppress airway inflammation, airway-hyperreactivity, and fibrosis in mice.

Development of persistent Th2 responses in asthma and chronic helminth infections are a major health concern. IL-10 has been identified as a critical regulator of Th2 immunity, but mechanisms for controlling Th2 effector function remain unclear. IL-10 also has paradoxical effects on Th2-associated pathology, with IL-10 deficiency resulting in increased Th2-driven inflammation but also reduced airway hyperreactivity (AHR), mucus hypersecretion, and fibrosis. We demonstrate that increased IL-13 receptor alpha 2 (IL-13Ralpha2) expression is responsible for the reduced AHR, mucus production, and fibrosis in BALB/c IL-10(-/-) mice. Using models of allergic asthma and chronic helminth infection, we demonstrate that IL-10 and IL-13Ralpha2 coordinately suppress Th2-mediated inflammation and pathology, respectively. Although IL-10 was identified as the dominant antiinflammatory mediator, studies with double IL-10/IL-13Ralpha2-deficient mice illustrate an indispensable role for IL-13Ralpha2 in the suppression of AHR, mucus production, and fibrosis. Thus, IL-10 and IL-13Ralpha2 are both required to control chronic Th2-driven pathological responses.