To investigate the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-27, and 5-hydroxytryptamine (5-HT) in collagen-induced arthritis (CIA) comorbid with depression.

A rat model of rheumatoid arthritis (RA) comorbid with depression was established by subjecting type II CIA rats to chronic unpredictable mild stress (CUMS). Thirty-two female Wistar rats were randomly divided into four groups: normal group (four rats per cage, normal feeding), RA group (four rats per cage, normal feeding after modeling), depression group (one rat per cage, CUMS was given to rats), and RA comorbid with depression group (one rat in each cage, CUMS was given one week after the arthritis model was established). Serum TNF-α, IL-27, and 5-HT levels were analyzed by enzyme-linked immunosorbent assay. One-way ANOVA and LSD-t test were used for the overall comparison between groups.

The levels of TNF-α and IL-27 in the model group were significantly higher than those in the control group [(297.97±34.23) ng/L vs (142.31±13.24) ng/L, t=3.41, P=0.021; (297.97±34.73) ng/L vs (212.43±14.52) ng/L, t=4.78, P=0.029]. The levels of 5-HT in the model group was significantly lower than that in the control group [(108.54±11.51) ng/L vs (241.23±13.48) ng/L, t=7.821, P=0.017].

The increase of TNF-α and IL-27 levels and the decrease of 5-HT levels in rats with RA comorbid with depression suggest that TNF- α, IL-27, and 5-HT might be involved in the pathogenesis of RA comorbid with depression. They can be used as important reference indexes to judge the progression of the disease and the therapeutic effect.