Association between forkhead box P3 expression level and gender of Iranian juvenile idiopathic arthritis patients

Juvenile idiopathic arthritis (JIA) is a childhood autoimmune rheumatoid disease. Past studies have confirmed that JIA is a complex disease, which means that genes and environmental factors affect the aetiology of the disease. In this study, we analysed the expression of interleukin 32, forkhead box P3 (FOXP3), methyl-CpG binding domain protein 1 (MBD1), and methyl-CpG-binding protein 2 (MECP2) in peripheral blood mononuclear cells of children with JIA in comparison with the expression of those in healthy children. Interleukin 32 is an inflammatory factor, FOXP3 is a transcription factor, and MBD1 and MECP2 are binding proteins that bind to the methylated deoxyribonucleic acid (DNA).

We collected blood from JIA patients who had been diagnosed and classified into clinical subtypes by a rheumatologist from the division of paediatric rheumatology. Healthy children, whose clinical and preclinical analysis confirmed they had no disease and just came to the hospital for a check-up or minor surgical procedures were considered as a control group. Age and gender were matched in patients and the control group. Total ribonucleic acid was extracted from blood, and cDNA was synthesized. Eventually, the transcript levels were analysed by quantitative polymerase chain reaction, and statistical analysis was carried out.

Statistical analysis of gene expressions in young females affected by JIA demonstrated that MECP2 and FOXP3 were increased significantly (p-value = 0.002 and 0.05, respectively). Interleukin 32 gene expression was also increased (p-value = 0.14), whereas MBD1 gene expression was decreased (p-value = 0.06); however, these changes in the expression of all 4 genes were not significant in young males.

Different expression levels of the mentioned genes between affected young females and males result from hormones in both gender and also methotrexate (MTX) drug. Also, the reason affected young females are more prone to JIA than males can be the lower level of FOXP3 expression in healthy females than healthy males.