Ankylosing spondylitis is a chronic inflammatory disease characterized by a range of symptoms, including persistent back pain and stiffness, which can significantly impair mobility and overall quality of life. The disease primarily affects the axial skeleton but can also involve peripheral joints and other organs. Ankylosing spondylitis is a disease with various symptoms and requires multidisciplinary treatment coordinated by a specialized physician [21]. The main goal of treatment is to control symptoms and inflammation, prevent progressive structural damage and maximize health-related quality of life in the long term [22].
GCRs play a significant role in pathophysiology of many diseases such as cardiovascular diseases [23], autoimmune diseases [24, 25], cancer [26] and neurodegenerative and cerebrovascular diseases [27]. These receptors found the largest family of membrane receptors constitute on the cell surface and are encoded by approximately one-thousand genes [28–30]. GPCRs share a conserved structure characterized by seven transmembrane (7TM) helices, which are connected by three intracellular and three extracellular loops. This structural configuration allows GPCRs to transduce extracellular signals into intracellular responses, influencing various physiological processes, including inflammation and immune response, which are central to the pathogenesis of ankylosing spondylitis [31]. Some studies showed that rs4676410 polymorphism in GPR35 is susceptibility with inflammatory bowel diseases [32, 33]. Another study has shown that rs4676410 and rs2531875 have been identified as genetic markers associated with the risk of AS in the Han Chinese population [17]. In this study, we first analyzed the association between the rs4676410 polymorphism in the GPR35 gene and the risk of AS in a Turkish population, and the second evaluated and compared the correlations between disease activity scores and biochemical parameters and the association of genotype and allele frequencies with disease risk.
Our results showed a significant association between the rs4676410 polymorphism and AS, particularly highlighting the increased prevalence of the AA genotype in the patient group compared to the healthy group. This suggests that individuals carrying the AA genotype may have a higher susceptibility to AS, whereas those with the GG and GA genotypes may have a lower risk. These results are consistent with previous studies that have identified certain SNPs within or near the GPR35 gene as being associated with various inflammatory conditions, such as inflammatory bowel disease and primary sclerosing cholangitis [17, 32–34]. When we analyzed the genotype and allele frequencies, we found that the A allele was more common in the patient group, while the G allele was more common in the healthy group. This finding is also correlated with the literature [17]. The role of the GPR35 gene in modulating immune responses may support its involvement in AS pathogenesis. Moreover, our study found important links between disease activity scores (BASFI, BASDAI, ASDAS-CRP) and higher levels of inflammatory markers (CRP and ESR), underscoring the pivotal role of inflammation in AS progression. The significant difference in ASDAS-CRP scores among different genotypes further supports the hypothesis that genetic factors can not only affect the risk of developing AS but also affect the severity of the disease [35]. The biochemical analyses showed that patients with AS had much greater levels of CRP, ESR, WBC, PLT, NEUT%, and other inflammatory markers compared to the healthy group, alongside lower levels of RBC, HGB, and HCT. These alterations in hematological parameters suggest an enhanced inflammatory response in AS patients, which is a direct consequence of the disease's chronic inflammatory nature.
In conclusion, our study provides the first evidence of an association between the rs4676410 polymorphism in the GPR35 gene and AS risk in a Turkish population. The presence of the AA genotype and A allele appears to be linked with an increased or susceptibility risk of AS. Furthermore, the correlation between genetic variants and disease activity scores highlights the potential of using genetic markers to predict disease severity and alter treatment strategies. Further research with larger sample sizes and diverse populations is necessary to validate these findings and to explore the underlying mechanisms by which the GPR35 gene influences AS pathogenesis.