Influence of glucocorticoid receptor gene NR3C1 646 C>G polymorphism on glucocorticoid resistance in asthmatics: a preliminary study

BACKGROUND Glucocorticoid receptor gene polymorphism (NR3C1 646 C>G) may play an important role in the development of severe bronchial asthma and resistance to glucocorticoids (GCs). OBJECTIVE The aim of the present study was to determine the relation between the 646 C>G polymorphism of the glucocorticoid receptor gene (NR3C1) and resistance to GCs with development of severe bronchial asthma. MATERIAL AND METHODS This case-control study included 40 patients with severe bronchial asthma and 20 apparently healthy controls. Atopic status was determined by skin prick test reaction to the most common locally-encountered allergens. GCs reversibility test was performed to differentiate between GCs sensitive and GCs resistant asthma. For all subjects, analysis of the glucocorticoid receptor gene polymorphism (NR3C1 646 C>G) was done using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). RESULTS The frequencies of NR3C1 646 C>G genotypes and alleles differed significantly between asthmatic patients and controls. The frequencies of the CC genotype and C allele carriers were significantly higher among asthmatics than among controls, and also among GCs sensitive asthmatics than among GCs resistant asthmatics. However, NR3C1 646 C>G genotypes and alleles frequencies did not differ significantly according to the atopic status in asthmatics. CONCLUSIONS The too small sized of the investigated groups is a shortcoming of this study. Nevertheless, the observed variations demonstrate a marked association of NR3C1 646 C>G CC genotype with the development of bronchial asthma and a higher frequency of the C allele among GCs sensitive asthmatics. Large-scale studies are required to investigate the association between polymorphisms of the NR3C1 gene and GCs resistance among asthmatic patients.