An updated meta-analysis of transforming growth factor-β1 gene: Three well-characterized polymorphisms with asthma

Unveiling the TGF- β1 paradox: Significant implication of TGF- β1 promoter variants and its mRNA and protein expression in atopic dermatitis

BACKGROUND

Atopic Dermatitis (AD) is a chronic inflammatory skin disorder with evidence of lichenification in later stages. There is mounting evidence supporting the role of TGF- β1 in mediating inflammation as well as subsequent tissue remodeling, often resulting in fibrosis. Given the role of genetic variants in the differential expression of TGF-β1 in various diseases, this study seeks to ascertain the role of TGF-β1 promoter variants (rs1800469 and rs1800468) in AD susceptibility, as well as their association with TGF- β1 mRNA expression, TGF- β1 serum levels and skin prick test positivity in Atopic Dermatitis patients.

METHODS

An aggregate of 246 subjects including 134 AD cases and 112 matched healthy controls were genotyped for TGF-β1 promoter polymorphisms by PCR-RFLP. TGF- β1 mRNA was quantified by quantitative Real-Time PCR (qRT-PCR), Vitamin-D levels by chemiluminescence, and serum TGF- β1, and total IgE levels were determined by ELISA. In-vivo allergy testing was performed for the evaluation of allergic reactions to house dust mites and food allergens.

RESULTS

A higher frequency of TT genotypes of rs1800469 (OR = 7.7, p = 0.0001) and GA+AA genotypes of rs1800468 (OR-4.4, p < 0.0001) were observed in AD cases than those in controls. Haplotype analysis demonstrated that TG haplotype carriers had an increased risk of AD (p = 0.013). Quantitative analysis revealed a significant upregulation of both mRNA (p = 0.0002) and serum levels (p < 0.0001) of TGF- β1 with a substantial positive correlation between them (Correlation coefficient=0.504; p = 0.01). Moreover, serum TGF-β1 levels were associated with quality of life (p = 0.03), the severity of the disease (p = 0.03), and House dust mite allergy (p = 0.01) whereas TGF-β1 mRNA levels positively correlated with disease severity(p = 0.02). Stratification analysis revealed that the TT genotype of rs1800469 was associated with higher IgE levels (p = 0.01) and eosinophil percentage(p = 0.007) whereas the AA genotype of rs1800468 correlated with elevated serum IgE levels (p = 0.01). Besides, no significant association of genotypes with mRNA and serum expression of TGF-β1 was observed.

CONCLUSION

Our study indicates that TGF-β1 promoter SNPs bear a significant risk of AD development. Moreover, upregulation of TGF-β1 mRNA and serum levels and their association with disease severity, quality of life, and HDM allergy suggests its role as a diagnostic/prognostic biomarker that could help in the development of new therapeutic and prevention strategies.

An integrated approach to identify environmental modulators of genetic risk factors for complex traits

Complex traits and diseases can be influenced by both genetics and environment. However, given the large number of environmental stimuli and power challenges for gene-by-environment testing, it remains a critical challenge to identify and prioritize specific disease-relevant environmental exposures. We propose a framework for leveraging signals from transcriptional responses to environmental perturbations to identify disease-relevant perturbations that can modulate genetic risk for complex traits and inform the functions of genetic variants associated with complex traits. We perturbed human skeletal-muscle-, fat-, and liver-relevant cell lines with 21 perturbations affecting insulin resistance, glucose homeostasis, and metabolic regulation in humans and identified thousands of environmentally responsive genes. By combining these data with GWASs from 31 distinct polygenic traits, we show that the heritability of multiple traits is enriched in regions surrounding genes responsive to specific perturbations and, further, that environmentally responsive genes are enriched for associations with specific diseases and phenotypes from the GWAS Catalog. Overall, we demonstrate the advantages of large-scale characterization of transcriptional changes in diversely stimulated and pathologically relevant cells to identify disease-relevant perturbations.

Enhanced asthma-related fibroblast to myofibroblast transition is the result of profibrotic TGF-β/Smad2/3 pathway intensification and antifibrotic TGF-β/Smad1/5/(8)9 pathway impairment

Airway remodelling with subepithelial fibrosis, which abolishes the physiological functions of the bronchial wall, is a major issue in bronchial asthma. Human bronchial fibroblasts (HBFs) derived from patients diagnosed with asthma display in vitro predestination towards TGF-β₁-induced fibroblast-to-myofibroblast transition (FMT), a key event in subepithelial fibrosis. As commonly used anti-asthmatic drugs do not reverse the structural changes of the airways, and the molecular mechanism of enhanced asthma-related TGF-β₁-induced FMT is poorly understood, we investigated the balance between the profibrotic TGF-β/Smad2/3 and the antifibrotic TGF-β/Smad1/5/9 signalling pathways and its role in the myofibroblast formation of HBF populations derived from asthmatic and non-asthmatic donors. Our findings showed for the first time that TGF-β-induced activation of the profibrotic Smad2/3 signalling pathway was enhanced, but the activation of the antifibrotic Smad1/5/(8)9 pathway by TGF-β₁ was significantly diminished in fibroblasts from asthmatic donors compared to those from their healthy counterparts. The impairment of the antifibrotic TGF-β/Smad1/5/(8)9 pathway in HBFs derived from asthmatic donors was correlated with enhanced FMT. Furthermore, we showed that Smad1 silencing in HBFs from non-asthmatic donors increased the FMT potential in these cells. Additionally, we demonstrated that activation of antifibrotic Smad signalling via BMP7 or isoliquiritigenin [a small-molecule activator of the TGF-β/Smad1/5/(8)9 pathway] administration prevents FMT in HBFs from asthmatic donors through downregulation of profibrotic genes, e.g., α-SMA and fibronectin. Our data suggest that influencing the balance between the antifibrotic and profibrotic TGF-β/Smad signalling pathways using BMP7-mimetic compounds presents an unprecedented opportunity to inhibit subepithelial fibrosis during airway remodelling in asthma.

Tumor Suppressors-HTRA Proteases and Interleukin-12-in Pediatric Asthma and Allergic Rhinitis Patients

Background and objective: Allergy belongs to a group of mast cell-related disorders and is one of the most common diseases of childhood. It was shown that asthma and allergic rhinitis diminish the risk of various cancers, including colon cancer and acute lymphoblastic leukemia. On the other hand, asthma augments the risk of lung cancer and an increased risk of breast cancer in patients with allergy has been observed. Thus, the relation between allergy and cancer is not straightforward and furthermore, its biological mechanism is unknown. The HTRA (high temperature requirement A) proteases promote apoptosis, may function as tumor suppressors and HTRA1 is known to be released by mast cells. Interleukin-12 (Il-12) is an important cytokine that induces antitumor immune responses and is produced mainly by dendritic cells that co-localize with mast cells in superficial organs. Material and methods: In the present study we have assessed with ELISA plasma levels of the HTRA proteins, Il-12, and of the anti-HTRA autoantibodies in children with allergy (40) and in age matched controls (39). Children are a special population, since they usually do not have comorbidities and take not many drugs the processes we want to observe are not influenced by many other factors. Results: We have found a significant increase of HTRA1, 2 and 3, and of the Il-12 levels in the children with atopy (asthma and allergic rhinitis) compared to controls. Conclusion: Our results suggest that the HTRA1-3 and Il-12 levels might be useful in analyzing the pro- and antioncogenic potential in young atopic patients.

Polymorphism -509C/T in TGFB1 Promoter Is Associated With Increased Risk and Severity of Persistent Allergic Rhinitis in a Chinese Population

BACKGROUND

Polymorphism -509C/T in the promoter of transforming growth factor beta1 (TGFB1) gene is implicated in the pathogenesis of asthma. This polymorphism might also act to regulate the development of allergic rhinitis (AR).

OBJECTIVES

To investigate whether -509C/T is associated with AR susceptibility and severity in a Han Chinese population.

METHODS

The study enrolled 263 patients with persistent AR and 249 healthy controls. AR patients were classified as mild or moderate/severe AR groups according to the Allergic Rhinitis and its Impact on Asthma classification. TGFB1 gene polymorphism -509C/T was genotyped with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Serum total Immunoglobulin E (IgE) and specific IgE levels were determined using an ImmunoCAP.

RESULTS

Significant difference was found in the allele frequency of TGFB1 -509C/T between AR patients and healthy controls (P = .027) but not in the genotype frequency (P =.051). However, the genotype frequency of TGFB1 -509C/T showed significant difference between the mild AR group, the moderate/severe AR group, and the control group (P = .012); between the moderate/severe AR group and the control group (P =.036); between the mild AR group and the moderate/severe AR group (P = .038); but not between the mild AR group and the control group (P =.075).

CONCLUSION

TGFB1 promoter polymorphism -509C/T may be associated with the susceptibility and the severity of persistent AR of Han Chinese, but the functional relationship still needs clarification.

TGF-β Signaling in Lung Health and Disease

Transforming growth factor (TGF)-β is an evolutionarily conserved pleiotropic factor that regulates a myriad of biological processes including development, tissue regeneration, immune responses, and tumorigenesis. TGF-β is necessary for lung organogenesis and homeostasis as evidenced by genetically engineered mouse models. TGF-β is crucial for epithelial-mesenchymal interactions during lung branching morphogenesis and alveolarization. Expression and activation of the three TGF-β ligand isoforms in the lungs are temporally and spatially regulated by multiple mechanisms. The lungs are structurally exposed to extrinsic stimuli and pathogens, and are susceptible to inflammation, allergic reactions, and carcinogenesis. Upregulation of TGF-β ligands is observed in major pulmonary diseases, including pulmonary fibrosis, emphysema, bronchial asthma, and lung cancer. TGF-β regulates multiple cellular processes such as growth suppression of epithelial cells, alveolar epithelial cell differentiation, fibroblast activation, and extracellular matrix organization. These effects are closely associated with tissue remodeling in pulmonary fibrosis and emphysema. TGF-β is also central to T cell homeostasis and is deeply involved in asthmatic airway inflammation. TGF-β is the most potent inducer of epithelial-mesenchymal transition in non-small cell lung cancer cells and is pivotal to the development of tumor-promoting microenvironment in the lung cancer tissue. This review summarizes and integrates the current knowledge of TGF-β signaling relevant to lung health and disease.

Association Between TGF-β1 Polymorphisms and Asthma Susceptibility Among the Chinese: A Meta-Analysis

OBJECTIVE

Asthma is the most common chronic pulmonary disease in China and is characterized by airway inflammation and episodic airflow obstruction. The aim of this meta-analysis was to evaluate the relation of two transforming growth factor-β1 (TGF-β1) polymorphisms with asthma risk in Chinese population.

METHODS

PubMed, Springer, EMBASE, MEDLINE, CNKI (China National Knowledge Infrastructure), and Wanfang databases were used to search and retrieve relevant eligible case-control studies published through December 2017. The odds ratios (OR) and 95% confidence intervals (CI) were used to evaluate the effect.

RESULTS

A total of 2040 asthma patients and 1952 controls from 12 studies were analyzed. Two polymorphic sites of TGF-β1 gene were identified: -509C/T and +869T/C. We found that the -509C/T polymorphism was associated with increased asthma risk under the heterozygous model (CT vs. CC: OR = 1.40, 95% CI = 1.03-1.90, p = 0.03) and the dominant model (TT+CT vs. CC: OR = 1.41, 95% CI = 1.05-1.90, p = 0.02). Subgroup analyses by age suggested that -509C/T variant was associated with childhood asthma. Analysis of disease severity indicated that this variant was associated with both mild-to-moderate asthma and severe asthma. However, the +869T/C polymorphism was not associated with asthma susceptibility in subgroup analysis by age or disease severity.

CONCLUSIONS

This study demonstrated that the -509C/T polymorphism of the TGF-β1 gene might be a risk factor for asthma in the Chinese population, especially in Chinese children. Further large-scale case-control studies are still required.

Phenotypic and genetic aspects of epithelial barrier function in asthmatic patients

The bronchial epithelium is continuously exposed to a multitude of noxious challenges in inhaled air. Cellular contact with most damaging agents is reduced by the action of the mucociliary apparatus and by formation of a physical barrier that controls passage of ions and macromolecules. In conjunction with these defensive barrier functions, immunomodulatory cross-talk between the bronchial epithelium and tissue-resident immune cells controls the tissue microenvironment and barrier homeostasis. This is achieved by expression of an array of sensors that detect a wide variety of viral, bacterial, and nonmicrobial (toxins and irritants) agents, resulting in production of many different soluble and cell-surface molecules that signal to cells of the immune system. The ability of the bronchial epithelium to control the balance of inhibitory and activating signals is essential for orchestrating appropriate inflammatory and immune responses and for temporally modulating these responses to limit tissue injury and control the resolution of inflammation during tissue repair. In asthmatic patients abnormalities in many aspects of epithelial barrier function have been identified. We postulate that such abnormalities play a causal role in immune dysregulation in the airways by translating gene-environment interactions that underpin disease pathogenesis and exacerbation.