Regulatory Mechanism of Mesalazine on Let-7i-5p/TLR4/MyD88 Signaling Pathway in a Mouse Model of Ulcerative Colitis
Objective:To investigate the regulatory mechanism of mesalazine(MSLZ)on Let-7i-5p and TLR4/MyD88 signaling pathway in a mouse model of 2,4,6-trinitrobenzene sulfonic acid(TNBS)-in-duced ulcerative colitis(UC).Methods:A UC model was established using the TNBS/ethanol method.Forty-four male mice were randomly divided into four groups:control group,model group,MSLZ group,and Let-7i-5p inhibitor group,with 11 mice in each group.Mice were gavaged or intraperitoneally injected with corre-sponding drugs or saline for 14 consecutive days.The expression levels of Let-7i-5p in colon tissues and ser-um of mice were detected by real-time quantitative polymerase chain reaction(qRT-PCR).The pathological changes of colon tissues were observed by hematoxylin and eosin(HE)staining under a microscope.The mR-NA and protein levels of TLR4/MyD88 signaling pathway-related genes in colon tissues of mice were detected by qRT-PCR,Western blot,and immunohistochemistry,respectively.The expression levels of TNF-α and IL-1β in mouse serum were detected by ELISA.Results:According to the disease activity index(DAI),co-lon damage score,and pathological lesion score,the mouse UC model was successfully established.The ex-pression levels of Let-7i-5p in colon tissues and serum of mice in the model group were significantly higher than those in the control group(P<0.0001).Compared with the model group,both MSLZ and Let-7i-5p in-hibitor treatment could significantly inhibit the expression of Let-7i-5p(P<0.0001).Compared with the control group,the mRNA and protein levels of TLR4/MyD88 signaling pathway-related genes(including TLR4,MyD88,TRAF-6,and NF-κB)in colon tissues of mice in the model group were significantly upregu-lated.MSLZ and Let-7i-5p inhibitor treatment could significantly inhibit the expression of these genes,and the inhibitory effect of MSLZ was slightly stronger than that of Let-7i-5p inhibitor.Compared with the control group,the mRNA levels of IL-1β and TNF-α in colon tissues and the protein levels in serum of mice in the model group were significantly upregulated.MSLZ and Let-7i-5p inhibitor treatment could inhibit the expres-sion levels of IL-1β and TNF-α.Conclusion:In the TNBS/ethanol-induced UC mouse model,MSLZ can inhibit the expression of Let-7i-5p in colon tissues and serum.In addition,MSLZ can also inhibit the release of inflammatory factors by inhibiting the TLR4/MyD88-dependent pathway in UC mice.
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