Association of Interleukin-6 and Tumor Necrosis Factor-alpha Gene Polymorphisms with Gnetic Susceptibility of Psoriatic Arthritis in Kuwaiti Arab Patients

Background: Psoriatic arthritis (PsA) is an inflammatory arthritic disease in which joint inflammation occurs with psoriasis. It results from a complex interplay between genetic, immunological and environmental factors. In PsA, the activation of T cells is considered as a crucial step in the disease process. The T-lymphocytes affect the proliferation of epidermal skin cells and result in abnormal differentiation. Altered cytokine networks have been shown to play a central role in the pathogenesis of PsA. Psoriasis is characterized by Th-1 type cytokine pattern in which there is a marked variation in the secretion of interleukin-6 (IL6), interleukin-13 (IL13) and Tumor necrosis factor-alpha (TNF-alpha). This study investigated the association of IL6 , IL13 and TNF - alpha gene polymorphisms with genetic susceptibility of PsA in Kuwaiti patients. Methods: The genotypes of IL6 gene (-174G/C; rs1800795), IL13 gene (R130Q; rs20541) and TNF-alpha gene (-308A/G’ rs1800629) polymorphisms were detected in 113 Kuwaiti PsA patients and were compared to that in 104 healthy controls. The PsA patients were diagnosed on the basis of the presence of inflammatory arthritis with psoriasis with no rheumatoid factor in the serum. The genotypes for IL6 , IL13 and TNF-alpha gene polymorphisms were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods and were confirmed by DNA sequencing. Results: The frequency of IL6 gene (-174G/C; rs1800795) and TNF-alpha gene (-308A/G’ rs1800629) polymorphisms manifested a statistically significant difference between Kuwaiti PsA patients and controls. However, the frequency of IL13 gene (R130Q; rs20541) polymorphism did not show a significant difference between Kuwaiti PsA patients and the controls. Conclusion: Our data show an association of two cytokine gene polymorphisms in IL6 gene (-174G/C; rs1800795) and TNF-alpha gene (-308A/G’ rs1800629) with PsA in Kuwaiti patients highlighting their significant contribution to genetic susceptibility of this chronic disease possibly along with other factors.