Expression of c-FLIP in peripheral blood mononuclear cells of patients with rheumatoid arthritis and its relation with extrinsic apoptotic pathway

Abstract

To investigate the expression of apoptosis related protein cellular Fas associated death domain like interleukin 1 converting enzyme inhibitory protein (c-FLIP) in peripheral blood mononuclear cells (PBMCs) of patients with rheumatoid arthritis and its relation with extrinsic apoptotic pathway. Sixty patients with rheumatoid arthritis were collected from Zhangzhou Affiliated Hospital of Fujian Medical University during January 2014 and June 2015, including 22 patients with low activities (DAS28<3.2), 20 patients with middle activities (3.2 ≤ DAS28 ≤ 5.1), and 18 patients with high activities (DAS28>5.1). And 25 healthy controls were also collected. The mRNA and protein expression levels of c-FLIP and the extrinsic apoptotic pathway related proteins Fas-associated protein with death domain (FADD), caspase-8 in PBMCs were detected by real-time RT-PCR and Western blot, respectively. Correlations between c-FLIP and FADD, caspase-8 in PBMCs were analyzed by pearson test. mRNA expression levels of c-FLIP, FADD and caspase-8 in PBMCs of patients with rheumatoid arthritis were all higher than those of healthy controls (all P<0.05). mRNA expression levels of FADD and caspase-8 in patients with middle activities were significantly higher than those in patients with low activities (all P<0.05), but the mRNA expression level of c-FLIP was not significantly higher than that in patients with low activities. mRNA expression level of c-FLIP in patients with high activities was higher than those in patients with middle or low activities (all P<0.05), while the mRNA expression level of caspase-8 was lower than those in patients with middle or low activities (all P<0.05). mRNA expression level of FADD in patients with high activities was higher than those in patients with low activities (P<0.05). Pearson analysis showed that there was a positive correlation between c-FLIP and FADD mRNA expression (r=0.323, P<0.05), and negative correlation between c-FLIP and caspase-8 mRNA expression (r=-1.104, P<0.05). The protein expression levels of c-FLIP and FADD in patients with middle activities were significantly higher than those in control group and patients with low or high activities (P<0.05 or 0.01). The protein expression levels of caspase-8 in patients with middle and high activities were significantly higher than those in control group and patients with low activities (P<0.05 or P<0.01), and the protein expression level of caspase-8 in patients with high activities was higher than that in patients with middle activities (P<0.05). c-FLIP may be involved in the extrinsic apoptotic pathway in rheumatoid arthritis, and can provide reference for the evaluation of disease activities.