STAT3 pathway is involved in interleukin-22 promoting expression of tight junction protein in human colorectal cancer cell line HT29

Objective To investigate the effect of interleukin-22(IL-22) on intestinal epithelial barrier tight junction and its mechanism. Methods Human colon cancer HT29 cells were divided into control group, IL-22 group(100 ng/mL), FLLL32 group(pretreatment with FLLL32 before IL-22 intervention) and colivelin group(pretreatment with colivelin before IL-22 intervention). The transfection treatment groups included: shNC group, shNC+ IL-22 group(infection with negative control virus before IL-22 intervention), shSTAT3 group(infection with LV-STAT3-RNAi virus), and shSTAT3+ IL-22 group(LV-STAT3-RNAi virus infection before IL-22 intervention). Western blot and real-time PCR were used to detect the protein and mRNA expression of STAT3, p-STAT3 tight junction protein ZO-1, occludin, claudin-1 and claudin-2 in HT29 cells. Transmission electron microscopy(TEM) was used to observe the changes in the structure of tight junctions of HT29 cells. Results The protein and mRNA expression level of STAT3, p-STAT3, ZO-1, occludin, claudin-1 and claudin-2 in IL-22 group were significantly higher than those in the control group(P＜0.05) with more compact, tight junction. Compared with IL-22 group, protein and mRNA expression level of the above indexes in FLLL32 group were significantly decreased(P＜0.05), the tight junction was poor, the expression of colivelin group was up-regulated(P＜0.05), the tight junction was intact. The shNC+ IL-22 group significantly increased the expression of all tightly bound proteins and mRNA compared with the shNC group(P＜0.05), the tight junction structure was more dense, while the shSTAT3+ IL-22 group showed no significant difference in protein and mRNA expression level when compared with theose of shSTAT3 group. Conclusions STAT3 signaling pathway is involved in IL-22 to promote the expression of tight junction proteins ZO-1, occludin, claudin-1 and claudin-2 in HT29 cells.