Objective To investigate the mechanism of in alleviating colonic mucosal inflammation in ten-eleven translocation (TET) protein 2 gene knockout (TET2-/-) mice with ulcerative colitis (UC) by regulating DNA methyltransferase (DNMT) and DNA hydroxymethylase.
Methods Male specific pathogen-free (SPF) grade C57BL/6J wild-type (WT) mice (n = 8) and TET2-/- mice (n = 20) were used to establish UC models by freely drinking 3% dextran sulfate sodium solution for 7 d. After UC model validation through histopathological examination in two mice from each type, the remaining mice were divided into four groups (n = 6 in each group): WT model (WT + UC), TET2-/- model (TET2-/- + UC), TET2-/- mild moxibustion (TET2-/- + MM), and TET2-/- electroacupuncture (TET2-/- + EA) groups. TET2-/- + MM group received mild moxibustion on Tianshu (ST25) and Qihai (CV6) for 10 min daily for 7 d. The TET2-/- + EA group also applied electroacupuncture (1 mA, 2/100 Hz) at the same acupoints for 10 min daily for 7 d. The disease activity index (DAI) scores of each group of mice were accessed daily. The colon lengths of mice in groups were measured following intervention. The pathological changes in the colon tissues were observed with hematoxylin and eosin (HE) staining. The concentrations of interleukin (IL)-6, C-C motif chemokine 17 (CCL17), and C-X-C motif chemokine ligand 10 (CXCL10) in serum were detected by enzyme-linked immunosorbent assay (ELISA). The expression of DNMT proteins (DNMT1, DNMT3A, and DNMT3B) in the colon tissues was detected by immunohistochemistry. The expression of 5-methylcytosine (5-mC), 5-hydroxymethylcytosine (5-hmC), histone deacetylase 2 (HDAC2), and DNA hydroxymethylase family proteins (TET 1 and TET3) was detected using immunofluorescence, which also determined the co-localization of TET1 and IL-6 protein.
Results Compared with WT + UC group, TET2-/- + UC group exhibited significantly higher DAI scores and shorter colon lengths (P < 0.01). Both mild moxibustion and electroacupuncture significantly decreased DAI scores and ameliorated colon shortening in TET2-/- mice (P < 0.001). Histopathological scores of TET2-/- + UC mice were significantly higher than those of WT + UC group (P < 0.001) and were significantly reduced after both mild moxibustion and electroacupuncture interventions (P < 0.001). Serum levels of IL-6, CCL17, and CXCL10 were significantly elevated in TET2-/- + UC group compared with WT + UC group (P < 0.001). Mild moxibustion significantly reduced IL-6, CCL17, and CXCL10 levels (P < 0.001, P < 0.001, and P < 0.01, respectively), while electroacupuncture also significantly reduced IL-6, CCL17, and CXCL10 levels (P < 0.05, P < 0.01, and P < 0.01, respectively). TET2-/- + UC mice showed increased expression levels of DNMT1, DNMT3A , DNMT3B, and 5-mC (P < 0.05, P < 0.01 and P < 0.001, respectively), with decreased expression levels of TET1, TET3, 5-hmC, and HDAC2 (P < 0.001). Mild moxibustion significantly reduced DNMT1, DNMT3B, and 5-mC levels (P < 0.05, P < 0.01, and P < 0.001, respectively), while increasing expression levels of TET1, TET3, 5-hmC, and HDAC2 (P < 0.001, P < 0.001, P < 0.05, and P < 0.001, respectively). Electroacupuncture significantly decreased 5-mC and DNMT3B levels (P < 0.001 and P < 0.01, respectively) and increased 5-hmC and HDAC2 levels (P < 0.05 and P < 0.001, respectively), but did not significantly affect TET1 and TET3 expression (P > 0.05). Compared with TET2-/- + MM group, TET2-/- + EA group showed significantly higher 5-mC expression (P < 0.001). TET2-/- + UC group exhibited markedly increased IL-6 expression and higher co-localization of TET1 and IL-6 in mucosal epithelium, whereas minimal IL-6 expression was observed in the other groups.
Conclusion Mild moxibustion and electroacupuncture significantly ameliorate colonic inflammation exacerbated by TET2 deficiency in UC mice via epigenetic modulation. Distinct mechanisms exist between the two interventions: mild moxibustion regulates both DNMT and hydroxymethylase, whereas electroacupuncture primarily affects DNMT.
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