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.