ABSTRACT
Thymic stromal lymphopoietin (TSLP) triggers dendritic cell--mediated T helper (Th) 2 inflammatory responses. A single-nucleotide polymorphism (SNP), rs3806933, in the promoter region of the TSLP gene creates a binding site for the transcription factor activating protein (AP)-1. The variant enhances AP-1 binding to the regulatory element, and increases the promoter--reporter activity of TSLP in response to polyinosinic-polycytidylic acid (poly[I:C]) stimulation in normal human bronchial epithelium (NHBE). We investigated whether polymorphisms including the SNP rs3806933 could affect the susceptibility to and clinical phenotypes of bronchial asthma. We selected three representative (i.e., Tag) SNPs and conducted association studies of the TSLP gene, using two independent populations (639 patients with childhood atopic asthma and 838 control subjects, and 641 patients with adult asthma and 376 control subjects, respectively). We further examined the effects of corticosteroids and a long-acting ß(2)-agonist (salmeterol) on the expression levels of the TSLP gene in response to poly(I:C) in NHBE. We found that the promoter polymorphisms rs3806933 and rs2289276 were significantly associated with disease susceptibility in both childhood atopic and adult asthma. The functional SNP rs3806933 was associated with asthma (meta-analysis, P = 0.000056; odds ratio, 1.29; 95% confidence interval, 1.14-1.47). A genotype of rs2289278 was correlated with pulmonary function. Moreover, the induction of TSLP mRNA and protein expression induced by poly(I:C) in NHBE was synergistically impaired by a corticosteroid and salmeterol. TSLP variants are significantly associated with bronchial asthma and pulmonary function. Thus, TSLP may serve as a therapeutic target molecule for combination therapy.
Subject(s)
Asthma/genetics , Cytokines/genetics , Genetic Predisposition to Disease , Polymorphism, Single Nucleotide , Promoter Regions, Genetic , Adolescent , Adult , Aged , Albuterol/analogs & derivatives , Albuterol/pharmacology , Binding Sites , Bronchodilator Agents/pharmacology , Case-Control Studies , Child , Child, Preschool , Cytokines/physiology , Female , Humans , Male , Middle Aged , Salmeterol Xinafoate , Thymic Stromal LymphopoietinABSTRACT
Thymic stromal lymphopoietin (TSLP) is an IL-7-like cytokine that triggers dendritic cell-mediated T helper (Th)2 inflammatory responses, and is implicated in the pathogenesis of allergic diseases in humans. Two TSLP splice variants have been reported. To find functional genetic variants that might contribute to disease, we conducted analyses of single nucleotide polymorphisms (SNPs) of the TSLP gene in human bronchial epithelial cells. We surveyed SNPs on the TSLP gene by sequencing genomic DNA from 36 subjects, and characterized the linkage disequilibrium of the gene. We examined whether the SNPs have functional effects on mRNA expression or protein production using real-time PCR, reporter gene analysis, and enzyme-linked immunosorbent assay. We identified a total of 23 polymorphisms in the TSLP gene. The long form of TSLP, which is associated with allergic inflammation, was highly induced by poly(I:C) (double-stranded RNA) stimulation in normal human bronchial epithelial cells (NHBE) (P = 0.0060). The SNP rs3806933 (-847C > T) in the promoter region of long-form TSLP was found to create a binding site for the transcription factor activating protein (AP)-1, and in vitro functional analyses demonstrated that the SNP enhanced AP-1 binding to the regulatory element. The functional variant increased promoter-reporter activity of long-form TSLP in response to poly(I:C) stimulation in NHBE. Functional genetic polymorphism of the TSLP gene appears to contribute to Th2-polarized immunity through higher TSLP production by bronchial epithelial cells in response to viral respiratory infections.
