Periodontitis-induced oral microbiome alterations provide clues on how periodontitis exacerbates colitis.

AIM: To evaluate whether and how microbiota-derived metabolites associated with periodontitis aggravate colitis in mice. MATERIALS AND METHODS: A mouse model of periodontitis and colitis was constructed. Unbiased transcriptomic analyses of the colon were performed to explore important pathways through which periodontitis exacerbated colitis. Oral and gut bacteria were analysed using 16S rRNA sequencing. Gas chromatography-mass spectrometry was used to observe the alterations of oral and gut metabolites. Isolated intestinal lamina propria lymphocytes were analysed by flow cytometry. Inflammasome pathway was detected using qRT-PCR, Western blotting or ELISA. RESULTS: Periodontitis activated the colonic inflammasome pathway and altered the gut microbial composition and metabolite profiles in mice with colitis. Notably, periodontitis induced increase of the faecal metabolite isoleucine (Ile) which was synthesized by microbiota and plants. Moreover, periodontitis upregulated the Ile levels in saliva, but not in serum, indicating that Ile might be an oral pathobiont-synthesizing metabolite that transited from the oral cavity to the gut. Ile triggered the inflammasome pathway, upregulated the number of inflammatory IL-1ßhigh MHCIIhigh Ly6Chigh monocytes in colonic lamina propria, and exacerbated colitis. Further studies found that the Ile metabolite acetyl-coenzyme A positively regulated NLRP3 inflammasome by KAT5-mediated acetylation of NLRP3. CONCLUSIONS: Our study revealed that alteration in periodontitis-induced microbial metabolites deteriorated colitis in a mouse model and that this was associated with Ile production.

TET1 Knockdown Inhibits Porphyromonas gingivalis LPS/IFN-γ-Induced M1 Macrophage Polarization through the NF-κB Pathway in THP-1 Cells.

Tet-eleven translocation 1 (TET1) is a dioxygenase that plays an important role in decreasing the abundance of DNA methylation and changing the expression levels of specific genes related to inflammation. Porphyromonas gingivalis (Pg.) lipopolysaccharide (LPS) can induce periodontal diseases that present with severe bone loss and collagen fiber destruction accompanied by a high number of M1 macrophages. M1-polarized macrophages are pivotal immune cells that promote the progression of the periodontal inflammatory response, but the function of TET1 during M1 macrophage activation is still unknown. Our results showed that the mRNA and protein expression levels of TET1 decreased in THP-1 cells during M1 macrophage differentiation. TET1 knockdown resulted in a significant decrease in the production of proinflammatory markers such as IL-6, TNF-α, CCL2, and HLA-DR in Pg. LPS/IFN-γ- and Escherichia coli (E. coli) LPS/IFN-γ-induced M1 macrophages. Mechanistically, TET1 knockdown downregulated the activity of the NF-κB signaling pathway. After treatment with the NF-κB inhibitor BAY 11-7082, M1 marker expression showed no significant difference between the TET1 knockdown group and the control group. Taken together, these results suggest that TET1 depletion inhibited Pg. LPS/IFN-γ-induced M1 macrophage polarization through the NF-κB pathway in THP-1 cells.