Associations of IL-18 and IL-9 expressions and gene polymorphisms with asthma

OBJECTIVE: To explore the associations of interleukin-18 (IL-18) and IL-9 gene polymorphisms with susceptibility to asthma, and to study the associations between IL-18 and IL-9 expression levels and polymorphisms. PATIENTS AND METHODS: A total of 200 asthma patients in our hospital were collected as disease group, while 200 healthy people were taken as control group. The deoxyribonucleic acid (DNA) was extracted from peripheral blood and sent to the company for the detection of IL-18 and IL-9 gene polymorphisms via sequencing. The levels of serum IL-18 and IL-9 were determined using enzyme-linked immunosorbent assay (ELISA), and arterial blood gas analysis was performed for patients. RESULTS: The allele distributions at IL-18 gene loci rs189667 and rs360715 had no differences between control group and disease group. The allele distributions at IL-9 gene loci rs1859430 and rs2066758 were different between the two groups (p=0.001, p=0.022), among which the G allele frequency was the highest in disease group [245 (0.613)]. and the T allele frequency was also the highest in disease group [240 (0.600)]. There was a difference in the genotype distribution at IL-9 gene locus rs1859430 between the two groups, and the GG genotype frequency in disease group [82 (0.410)] was significantly higher than that in control group (p=0.005). The CC genotype frequency at rs2066758 was significantly lower in disease group [27 (0.135), p=0.044]. In disease group, the frequency of heterozygous model CT (p=0.047) at IL-18 gene locus rs360715, and recessive model GA+AA (p=0.021) and heterozygous model GA (p=0.031) at IL-19 gene locus rs1859430 was significantly lower than that in control group. In disease group, the AC haplotype frequency at IL-18 gene loci rs189667 and rs360715 was evidently lower than that in control group (p=0.048). Disease group had evidently lower AT haplotype frequency (p=0.006) and evidently higher GT haplotype frequency (p=0.000) at IL-9 gene loci rs1859430 and rs2066758. Moreover, the level of serum IL-18 in patients with TT genotype at IL-18 gene locus rs360715 was higher than that in those with other genotypes in disease group (p<0.05), and the level of serum IL-9 in patients with AG genotype at IL-9 gene locus rs1859430 was also higher than that in those with other genotypes in disease group (p<0.05). There was a remarkable association between CT genotype at IL-18 gene locus rs360715 and partial pressure of oxygen (PaO2) (p=0.035), and between CC genotype at IL-9 gene locus rs2066758 and partial pressure of carbon dioxide (PaCO2) (p=0.041). CONCLUSIONS: The expression levels of serum IL-18 and IL-9 and their gene polymorphisms are significantly associated with asthma.