To explore the mechanism of theaflavin improving the inflammatory response of intestinal epithelial cells in ulcerative colitis (UC) through regulating NOD-like receptor thermal protein domain associated protein 3 (NLRP3) / Caspase-1 signaling pathway mediated by astrocyte elevated gene 1 (AEG-1).

NCM460 cells were divided into control group (conventional culture of NCM460 cells without any intervention treatment, model group (treated with 1 mg·L^-1 lipopolysaccharide in NCM460 cells for 24 hours), experimental group (treated with 64 μmol·L^-1 theaflavin and 1 mg·L^-1 lipopolysaccharide in NCM460 cells for 24 h), pcDNA3.1-NC group (after NCM460 cells were transfected with the pcDNA3.1-NC plasmid, treated with 64 μmol·L^-1 theaflavin and 1 mg·L^-1 lipopolysaccharide for 24 h) and pcDNA3.1-AEG-1 group (after NCM460 cells were transfected with the pcDNA3.1-AEG-1 plasmid, treated with 64 μmol·L^-1 theaflavin and 1 mg·L^-1 lipopolysaccharide for 24 h). Cell viability was detected by cell counting kit-8 method, cell invasion ability was detected by Transwell assay, cell migration ability was detected by cell scratch assay, and mRNA levels of AEG-1 and barrier damage-related proteins were detected by real-time fluorescence quantitative reverse transcription polymerase chain reaction. Western blotting was used to detect the expressions of AEG-1, apoptosis, barrier injury and NLRP3/Caspase-1 signaling pathway-related proteins and enzyme-linked immunosorbent assay was used to detect the contents of inflammatory factors.

The cell migration rate of the control group, model group, experimental group were (78.85±13.47)%, (19.32±3.15)% and (54.97±9.03)%, respectively. The levels of interleukin-6 (IL-6) in the control group, model group, experimental group, pcDNA3.1-NC group and pcDNA3.1-AEG-1 group were (0.49±0.07), (1.36±0.21), (0.64±0.09), (0.68±0.10) and (1.21±0.18) pg·L^-1, respectively; the apoptosis rates were (8.26±1.47)%, (27.09±4.62)%, (14.51±2.18)%, (16.75±2.83)% and (22.68±3.56)%, respectively; the relative expression levels of B-cell lymphoma-2 (Bcl-2) protein were 1.00±0.16, 0.39±0.07, 0.71±0.12, 0.67±0.09 and 0.54±0.08, respectively; the relative expression levels of Bcl-2-associated X (Bax) protein were 1.00±0.19, 6.45±1.12, 3.90±0.64, 3.79±0.58 and 6.07±0.96, respectively; the mRNA levels of AEG-1 were 1.00±0.13, 4.35±0.76, 1.92±0.33, 2.08±0.32 and 3.26±0.57, respectively; the relative expression levels of AEG-1 protein were 1.00±0.17, 4.82±0.79, 2.07±0.34, 2.25±0.36 and 3.94±0.71, respectively; the mRNA levels of Zonula Occludens-1 (ZO-1) were 1.00±0.15, 0.37±0.06, 0.76±0.13, 0.79±0.14 and 0.51±0.09, respectively, while the mRNA levels of Occludin were 1.00±0.16, 0.29±0.05, 0.58±0.10, 0.52±0.09 and 0.37±0.06, respectively; the relative protein expression levels of NLRP3 were 1.00±0.19, 6.58±1.06, 2.71±0.43, 2.59±0.42 and 5.16±0.94, respectively; the relative protein expression levels of cleaved caspase-1 were 1.00±0.16, 5.26±0.93, 3.42±0.59, 3.65±0.64 and 5.09±0.87, respectively. When comparing the model group with the control group and the experimental group, and the pcDNA3.1-NC group with the pcDNA3.1-AEG-1 group, the differences in the above indicators were all statistically significant (P<0.01, P<0.001).

Theaflavin can improve the inflammatory response of LPS-induced UC intestinal epithelial cells and inhibit cell apoptosis, and has a protective effect on epithelial barrier function. The mechanism may be related to the down-regulation of AEG-1 expression and the inhibition of the NLRP3/Caspase-1 signaling pathway.