ABSTRACT
BACKGROUND: Asthma is the most common chronic disease in children. Underlying immunologic mechanisms-in particular of different phenotypes-are still just partly understood. The objective of the study was the identification of distinct cellular pathways in allergic asthmatics (AA) and nonallergic asthmatics (NA) vs healthy controls (HC). METHODS: Peripheral blood mononuclear cells (PBMCs) of steroid-naïve children (n(AA/NA/HC) = 35/13/34)) from the CLARA study (n = 275) were stimulated (anti-CD3/CD28, LpA) or kept unstimulated. Gene expression was investigated by transcriptomics and quantitative RT-PCR. Differentially regulated pathways between phenotypes were assessed after adjustment for sex and age (KEGG pathways). Networks based on correlations of gene expression were built using force-directed graph drawing. RESULTS: Allergic asthmatics vs NA and asthmatics overall vs HC showed significantly different expression of Ca2+ and innate immunity-associated pathways. PCR analysis confirmed significantly increased Ca2+ -associated gene regulation (ORMDL3 and ATP2A3) in asthmatics vs HC, most prominent in AA. Innate immunity receptors (LY75, TLR7), relevant for virus infection, were also upregulated in AA and NA compared to HC. AA and NA could be differentiated by increased ATP2A3 and FPR2 in AA, decreased CLEC4E in AA, and increased IFIH1 expression in NA following anti-CD3/28 stimulation vs unstimulated (fold change). CONCLUSIONS: Ca2+ regulation and innate immunity response pattern to viruses were activated in PBMCs of asthmatics. Asthma phenotypes were differentially characterized by distinct regulation of ATP2A3 and expression of innate immune receptors (FPR2, CLEC4E, IFIH1). These genes may present promising targets for future in-depth investigation with the long-term goal of more phenotype-specific therapeutic interventions in asthmatics.
Subject(s)
Asthma/metabolism , Calcium/metabolism , Immunity, Innate/genetics , Leukocytes, Mononuclear/metabolism , Adolescent , Asthma/immunology , Cell Culture Techniques , Child , Child, Preschool , Cytokines/metabolism , Female , Gene Expression Profiling/methods , Gene Expression Regulation , Humans , Male , Microarray Analysis/methods , Phenotype , Real-Time Polymerase Chain Reaction/methods , Signal TransductionABSTRACT
BACKGROUND: Allergic and non-allergic childhood asthma has been characterized by distinct immune mechanisms. While interferon regulating factor 1 (IRF-1) polymorphisms (SNPs) influence atopy risk, the effect of SNPs on asthma phenotype-specific immune mechanisms is unclear. We assessed whether IRF-1 SNPs modify distinct immune-regulatory pathways in allergic and non-allergic childhood asthma (AA/NA). METHODS: In the CLARA study, asthma was characterized by doctor's diagnosis and AA vs NA by positive or negative specific IgE. Children were genotyped for four tagging SNPs within IRF-1 (n = 172). mRNA expression was measured with qRT-PCR. Gene expression was analyzed depending on genetic variants within IRF-1 and phenotype including haplotype estimation and an allelic risk score. RESULTS: Carrying the risk alleles of IRF-1 in rs10035166, rs2706384, or rs2070721 was associated with increased risk for AA. Carrying the non-risk allele in rs17622656 was associated with lower risk for AA but not NA. In AA carrying the risk alleles, an increased pro-inflammatory expression of ICAM3, IRF-8, XBP-1, IFN-γ, RGS13, RORC, and TSC2 was observed. NOD2 expression was decreased in AA with risk alleles in rs2706384 and rs10035166 and with risk haplotype. Further, AA with risk haplotype showed increased IL-13 secretion. NA with risk allele in rs2070721 compared to non-risk allele in rs17622656 showed significantly upregulated calcium, innate, mTOR, neutrophil, and inflammatory-associated genes. CONCLUSION: IRF-1 polymorphisms influence the risk for childhood allergic asthma being associated with increased pro-inflammatory gene regulation. Thus, it is critical to implement IRF-1 genetics in immune assessment for childhood asthma phenotypes.
