Genotype and allele frequencies of IL-10 gene promoter polymorphisms
In this study, according to the results of clinical examination performed by the ophthalmologist on patients and controls, 114 PEX, 118 PEXG, 114 POAG and 126 healthy subjects were selected. The genotype and allele frequencies of IL-10 gene promoter SNPs -592C/A, -819C/T and -1082A/G in control subjects and PEX, PEXG and POAG affected patients are shown in Table 1. With respect to genotype frequencies (AA vs. AC and CC), at position -592C/A, significant difference was observed for the frequency of AA genotype in PEX patients (but not in PEXG and POAG patients) compared to controls (14 % vs. 3.2 %). At position -819C/T (TT vs. TC and CC), frequencies of TT genotype (14%, 8.5% and 10.5% for PEX, PEXG and POAG patients, respectively vs. 1.6% in controls) demonstrated significant differences between patients and healthy controls. Similar results were obtained for -1082A/G polymorphism, so that comparison of AA genotype frequency in PEX, PEXG and POAG patients (19.3 %, 20.3 % and 21.3 %, respectively) exhibited a significant difference compared to controls (1.6 %) (Table 1). Totally, among the studied genotypes, TT and AA genotypes of -819C/T and -1082A/G SNPs, respectively, were much more frequent in PEX, PEXG and POAG patients in comparison with healthy controls. However, at position -592C/A, higher frequency of AA genotype was observed in just PEX affected patients compared to controls.
Haplotype analysis of IL-10 gene promoter polymorphisms
Based on the obtained results, five different haplotypes including GCC (reference haplotype), ACC, GTA, ATA and GCA were investigated in studied population. Constituents of the haplotypes were written in the order of -1082A/G, -819C/T and -592C/A of the IL-10 gene promoter. The frequencies of these haplotypes for PEX, PEXG and POAG affected patients and control subjects are summarized in Table 2. According to this table, the frequency of ACC haplotype in PEX (14 %), PEXG (18.6 %) and POAG (19.3 %) patients are much higher than healthy controls (3.2 %). However, no significant differences were observed between the other studied haplotypes in both groups.
Association of studied polymorphisms/haplotypes with susceptibility to PEX, PEXG and POAG eye disorders
Associations between three studied promoter polymorphisms of IL-10 gene with susceptibility to PEX, PEXG and POAG eye disorders were evaluated. With regard to -592C/A polymorphism, the AA genotype significantly increased the susceptibility to PEX disorder (P = 0.04, OR = 4.97, 95 % CI = 4.45-21.08) compared to the wild-type genotypes. However, no association was found between this genotype and susceptibility to PEXG and POAG disorders (Table 1). In regards to -819C/T promoter position, significant association was observed between TT genotype with susceptibility to PEX (P = 0.004, OR = 10.12, 95 % CI = 13.29-71.61), PEXG (P = 0.03, OR = 5.74, 95 % CI = 7.98-43.34) and POAG (P = 0.01, OR = 7.29, 95 % CI = 9.89-53.53). Similarly, the AA genotype of -1082A/G promoter SNP was significantly associated with susceptibility to PEX (P = 0.02, OR = 7.29, 95 % CI = 6.37-29.69), PEXG (P = 0.002, OR = 7.79, 95 % CI = 6.76-31.39) and POAG (P = 0.005, OR = 8.13, 95 % CI = 7.06-32.82) (Table 1).
At the haplotype level, the ACC haplotype was significantly associated with susceptibility to PEX (P = 0.02, OR = 5.76, 95 % CI = 5.17-24.49), PEXG (P = 0.006, OR = 7.54, 95 % CI = 6.62-30.76) and POAG (P = 0.003, OR = 8.11, 95 % CI = 7.13-33.15). However, no statistically significant association was found between ATG, ATA and ACG haplotypes with PEX, PEXG and POAG (Table 2). Using logistic multivariate regression analysis, association of ACC haplotype with susceptibility to PEX (P = 0.002, OR = 5.76, 95 % CI = 1.86-17.84), PEXG (P = 0.001, OR = 7.55, 95 % CI = 2.51-22.69) and POAG (P = 0.001, OR = 8.11, 95 % CI = 2.69-24.43) was observed. Similar association was obtained between GTA haplotype and susceptibility to PEX (P = 0.012, OR = 7.19, 95 % CI = 1.53-33.70), PEXG (P = 0.034, OR = 5.49, 95 % CI = 1.14-26.49) and POAG (P = 0.011, OR = 7.37, 95 % CI = 1.57-34.56). However, no statistically significant association was found between ATA and ACG haplotypes and the risk of PEX, PEXG and POAG disorders (Table 3).