Vascular endothelial growth factor (VEGF) and Interleukin-6 (IL-6) polymorphisms in ankylosing spondylitis

Aim: In this study, we aimed to investigate the roles of polymorphisms of vascular endothelial growth factor (VEGF) and interleukin-6 (IL-6) in susceptibility to ankylosing spondylitis (AS), and assess the relationships with clinical, laboratory and radiological findings.Patients and methods: Adult AS patients diagnosed according to the modified New York criteria were included in the study. Patients with systemic illness or another inflammatory romatologic disease were excluded. Healthy volunteers constituted the control group. The demographic and clinical assessments of the subjects were recorded. DNA?s were isolated from peripheral bloods. Desired locations with specific primers were duplicated with polymerase chain reaction (PCR). Enzyme cuts were carried out to PCR products with NIa III (IL-6) and BsmFI (VEGF). They were executed in 3% gel and monitorized under ultraviolet light. IL-6 -174 G/C and VEGF +405 G/C polymorphisms were determined in the patient and control groups. Statistical analysis were performed by SPSS 15.0. IL-6 and VEGF polymorphisms were determined with chi-square test in the patient and control groups. All physical examination and assessment scales were compared by Mann-Whitney U test with Pearson correlation method. The comparisons of gene polymorphisms with physical examination and functional assessment scales were done with Kruskal-Wallis test. Data were considered as statistically significant at p<0.05.Results: 71 AS patients and 74 healthy volunteers were included in the study. The mean ages were 37,6 (SD: 10.6) for the patient group (61 men, 10 women) and 40.3 ( SD: 9.9) for the controls (49 men, 25 women). Age and sex differences were not significant between the groups (p>0.05).IL-6 polymorphisms were analyzed in all patients and controls. However; owing to technical failures, VEGF polymorphisms were analyzed in 63 AS patients and 64 controls. In 71 AS patients, IL-6 genotypes were GG in 19 (26.8%), GC in 38 (53.5%), and CC in 14 (19.7%). In the control group consisting of 74 healthy volunteers, IL-6 genotypes were GG in 41 (55.4%), GC in 31 (41.9%) and CC in 2 (2.7%). In 64 AS patients, VEGF gene polymorphisms were GG in 14 (21.9%), GC in 38 (59.4%) and CC in 12 (18.8%). In the control group of 63 healthy volunteers, genotypes were GG in 23 (36.5%), GC in 34 (54%) and CC in 6 (9.5%). Genotype distributions did not show significant differences among the patient and control groups. Additionally, no significant relationship was found between the genotype distributions and clinical, laboratory and radiological parameters.In this study, no significant relationship was determined between AS and IL -6 -174 G/C and VEGF +405 G/C polymorphisms. Nevertheless, IL-6 GC genotype was more than 50% in the patient group with respect to the controls and 60% with family history. BASRI score revealing the severity of radiologic damage was 7.9 and was higher with family history and GC genotypeConclusions: IL-6 GC genotype was more frequent in the patient group with respect to controls and additionally this frequency was more dense in the patients with family history. These findings reveal that this genotype may influence the susceptibility to the disease. Higher BASRI scores in this genotype also make us consider a possible role in foreseeing the severity of the Disease. Further studies with wider patient populations are needed for more powerful evidences in order to determine the roles of IL-6 -174 G/C and VEGF +405 G/C polymorphisms in ankylosing spondylitis.Key words: Vascular endothelial growth factor, interleukin-6, ankylosing spondylitis, polymorphism