Impact of TRAIL gene knockout on regulatory T cells in mice with dextran sodium sulphate-induced experimental colitis

Abstract

Objective To investigate the impact of knocking out tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) gene (TRAIL-/-) on colonic inflammation and regulatory T cells (Treg) in mice with dextran sulfate sodium (DSS)-induced experimental colitis. Methods C57BL/6 mice were randomly assigned into four groups with 10 in each group: wild-type (WT) control, WT colitis, TRAIL-/- control and TRAIL-/- colitis. The mouse model of colitis was induced by oral administration of 3.5% DSS and the severity of colonic inflammation was assessed. Peripheral blood mononuclear cells (PBMCs) and mesenteric lymph nodes (MLNs) were collected. The ratios of Treg cells to CD4+ T cells in PBMCs were detected by flow cytometry. Expression of Treg cell-associated transcription factor (Foxp3) and cytokine (IL-10) at mRNA level was measured by real-time fluorescent quantitative polymerase chain reaction. Western blot and enzyme-linked immunosorbent assay (ELISA) were used to detect the expression of Foxp3 and IL-10 at protein level, respectively. Results Compared with the WT control group, the WT colitis group showed significantly decreased proportions of Treg cells in PBMCs [(1.85±0.38)% vs (3.12±0.69)%, P<0.05], but increased proportions in MLNs [(11.79±1.18)% vs (6.24±1.04)%, P<0.05]. Compared with the WT mice with colitis, the TRAIL-/- mice with colitis had more severe colonic inflammation and significantly increased proportions of Treg cells in PBMCs [(3.15±0.64)% vs (1.85±0.38)%, P<0.05], but decreased Treg cells in MLNs [(9.80±0.50)% vs (11.79±1.18)%, P<0.05]. Expression of Foxp3 and IL-10 at mRNA and protein levels in PBMCs of the WT mice with colitis was significantly lower than that in the WT control mice [Foxp3 mRNA: 0.48±0.21 vs 1.06±0.31, IL-10 mRNA: 0.23±0.07 vs 1.22±0.38; Foxp3 protein: 0.68±0.12 vs 1, IL-10 protein: (4.91± 0.72) pg/ml vs (21.86±2.40) pg/ml; all P<0.05], while in MLNs, the expression of Foxp3 and IL-10 at mRNA and protein levels was significantly higher than that of the WT control group [Foxp3 mRNA: 3.71±0.49 vs 1.03±0.15, IL-10 mRNA: 11.98±6.10 vs 1.01±0.31; Foxp3 protein: 1.60±0.03 vs 1, IL-10 protein: (1 260.00±18.02) pg/ml vs (1 184.00±38.62) pg/ml; all P<0.05]. Compared with the WT mice with colitis, the TRAIL-/- mice with colitis showed significantly increased expression of Foxp3 and IL-10 at mRNA and protein levels [Foxp3 mRNA: 1.80±0.49 vs 0.48±0.21, IL-10 mRNA: 1.67±0.99 vs 0.23±0.07; Foxp3 protein: 1.10±0.01 vs 0.68±0.12, IL-10 protein: (31.33± 25.02) pg/ml vs (4.58±3.73) pg/ml; all P<0.05], while decreased expression in MLNs [Foxp3 mRNA: 0.49±0.21 vs 3.71±0.49, IL-10 mRNA: 2.80±1.82 vs 11.98±6.10; Foxp3 protein: 1.21±0.12 vs 1.60±0.03, IL-10 protein: (1 158.00±26.48) pg/ml vs (1 190.00±37.19) pg/ml; all P<0.05]. Conclusions Knocking out the expression of TRAIL might affect the ratios of Treg cells in peripheral blood and MLNs, thereby aggravating the colitis in mice. Key words: Tumour necrosis factor-related apoptosis-inducing ligand; Regulatory T cell; Dextran sodium sulphate; Colitis