Title: A genetic effect of IL-5 receptor α polymorphism in patients with aspirin-exacerbated respiratory disease
Abstract: Persistent eosinophil activation in both the upper and lower airway mucosa is a central feature of aspirin-exacerbated respiratory disease (AERD). Eosinophil activation and survival are profoundly influenced by interleukin 5 (IL-5) and its receptor, IL-5R. In patients susceptible to allergic disorders, IL-5 receptor α (IL5RA) polymorphisms have been reported; however, an association with AERD remains unclear. We hypothesize that IL5RA polymorphisms may contribute to eosinophil activation in AERD patients. We recruited 139 AERD patients, 171 aspirin-tolerant asthma patients and 160 normal controls. IL5RA polymorphisms (−5993G>A, −5567C>G and −5091G>A) were genotyped and functional activity of polymorphism was assessed by luciferase reporter assay and electrophoretic mobility shift assay (EMSA). There was no significant difference in the genotype frequency of the three polymorphisms among the three groups. AERD patients carrying the AA genotype at −5993G>A had a significantly higher presence of serum-specific immunoglobulin E (IgE) to staphylococcal enterotoxin A (P=0.008) than those with the GG/GA genotype. In vitro, the −5993A allele had a higher promoter activity compared with the −5993G allele in human mast cell (HMC-1; P=0.030) and human promyelocytic leukemia (HL-60; P=0.013) cells. In EMSA, a −5993A probe produced a specific shifted band than the −5993G had. These findings suggest that a functional polymorphism in IL5RA may contribute to eosinophil and mast cell activation along with specific IgE responses to staphylococcal enterotoxin A in AERD patients. A mutation in an immune-associated gene may help drive aspirin-exacerbated respiratory disease (AERD), as evidenced by an activated immune system in people with the disease who harbor this DNA variant. AERD is a chronic medical condition characterized by asthma, recurrent sinus disease and a sensitivity to aspirin and other non-steroidal anti-inflammatory drugs. Hae-Sim Park and her colleagues at the Ajou University School of Medicine, Korea, studied polymorphisms in the gene encoding the interleukin 5 receptor alpha (IL5RA) subunit, a cytokine receptor involved in white blood cell development. They found that AERD patients with the IL5RA mutation known as 5993G>A had elevated levels of inflammatory molecules that respond to a pathogenic toxin, a hallmark of the disease. The mutation also made the IL5RA gene more active.