Aim: To evaluate the link between promotional polymorphism -930A > G of the cytochrome b gene (CYBA) and onset of bronchial asthma; to examine effects of this locus on the risk of the disease development depending on the pro- and antioxidant action of environmental factors.
Material and methods: We studied samples of DNA obtained from 214 healthy individuals and 215 patients with bronchial asthma treated in Regional Kursk Hospital. We used polymerase chain reaction and analysed polymorphism of restriction fragments lengths for genotyping of -930A > G polymorphism of CYBA gene.
Results: Incidence of a variant allele -930G of CYBA gene among men with nonallergic bronchial asthma (nBA) was higher than in healthy men (OR 1.95; CI 1.02-3.73; p = 0.04). The homozygous variant genotype -930G/G was associated with a high risk of nBA in males (OR 2.66; CI 1.14-6.20; p = 0.02). In healthy individuals polymorphisms -930A > G and 640A > G were in negative linkage equilibrium (D = -0.057; p < 0.001) while in patients such associations were not registered. Male smokers with genotype -930G/G had the highest risk of nBA (OR 2.86; CI 1.06-7.77; p = 0.04) while non-smokers with this genotype had no risk of the disease (OR 1.50; CI 0.11-19.64; p = 0.70). Males with -930G/G on low or no vegetable diet had the highest risk of nBA (OR 3.11; CI 1.01-9.63; p = 0.04) while regular vegetable eaters had no risk to develop nBA (OR 0.73; CI 0.30-1.82; p = 0.50).
Conclusion: We were the first to find relations between -930A > G polymorphism of CYBA gene and predisposition to nBA. This association exists in males and depends on the smoking status and vegetable diet.