title: The IL6R variation Asp(358)Ala is a potential modifier of lung function in subjects with asthma.
abstract: BACKGROUND
  The IL6R single nucleotide polymorphism (SNP) rs4129267 has recently been identified as an asthma susceptibility locus in subjects of European ancestry but has not been characterized with respect to asthma severity. The SNP rs4129267 is in linkage disequilibrium (r(2) = 1) with the IL6R coding SNP rs2228145 (Asp(358)Ala). This IL6R coding change increases IL-6 receptor (IL-6R) shedding and promotes IL-6 transsignaling.
  
  
  OBJECTIVE
  We sought to evaluate the IL6R SNP rs2228145 with respect to asthma severity phenotypes.
  
  
  METHODS
  The IL6R SNP rs2228145 was evaluated in subjects of European ancestry with asthma from the Severe Asthma Research Program (SARP). Lung function associations were replicated in the Collaborative Study on the Genetics of Asthma (CSGA) cohort. Serum soluble IL-6R levels were measured in subjects from SARP. Immunohistochemistry was used to qualitatively evaluate IL-6R protein expression in bronchoalveolar lavage cells and endobronchial biopsies.
  
  
  RESULTS
  The minor C allele of IL6R SNP rs2228145 was associated with a lower percent predicted FEV(1) in the SARP cohort (P= .005), the CSGA cohort (P= .008), and in a combined cohort analysis (P= .003). Additional associations with percent predicted forced vital capacity (FVC), FEV(1)/FVC ratio, and PC(20) were observed. The rs2228145 C allele (Ala(358)) was more frequent in severe asthma phenotypic clusters. Elevated serum soluble IL-6R levels were associated with lower percent predicted FEV(1) (P= .02) and lower percent predicted FVC (P= .008) (n= 146). IL-6R protein expression was observed in bronchoalveolar lavage macrophages, airway epithelium, vascular endothelium, and airway smooth muscle.
  
  
  CONCLUSIONS
  The IL6R coding SNP rs2228145 (Asp(358)Ala) is a potential modifier of lung function in subjects with asthma and might identify subjects at risk for more severe asthma. IL-6 transsignaling might have a pathogenic role in the lung.
authors.affiliation: Center for Genomics and Personalized Medicine Research, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA. ghawkins@wakehealth.edu
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Hawkins
authors.forename: Mac B
authors.initials: MB
authors.lastname: Robinson
authors.forename: Annette T
authors.initials: AT
authors.lastname: Hastie
authors.forename: Xingnan
authors.initials: X
authors.lastname: Li
authors.forename: Huashi
authors.initials: H
authors.lastname: Li
authors.forename: Wendy C
authors.initials: WC
authors.lastname: Moore
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Howard
authors.forename: William W
authors.initials: WW
authors.lastname: Busse
authors.forename: Serpil C
authors.initials: SC
authors.lastname: Erzurum
authors.forename: Sally E
authors.initials: SE
authors.lastname: Wenzel
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Peters
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Meyers
authors.forename: Eugene R
authors.initials: ER
authors.lastname: Bleecker
mesh_terms: D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000235:genetics* / Q000276:immunology / Q000503:physiopathology; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D002648:Child; D015331:Cohort Studies; D005260:Female; D005541:Forced Expiratory Volume / Q000235:genetics; D015870:Gene Expression / Q000276:immunology*; D005838:Genotype; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D015810:Linkage Disequilibrium; D008168:Lung / Q000276:immunology / Q000473:pathology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide / Q000235:genetics* / Q000276:immunology; D019947:Receptors, Interleukin-6 / Q000235:genetics* / Q000378:metabolism; D012720:Severity of Illness Index; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D014797:Vital Capacity / Q000235:genetics; D044465:White People / Q000235:genetics*
chemical_list: C508600:IL6 protein, human; C508603:IL6R protein, human; D015850:Interleukin-6; D019947:Receptors, Interleukin-6