3.6 TBⅡ reduces NLRP3 expression by suppressing NF-κB signaling
One of the pivotal steps for the activation of NLRP3 inflammasomes is priming step (signal 1), which is transcriptionally regulated the expression of NLRP3 by NF-κB, a master transcriptional factor of pro-inflammatory genes. We and other had evidenced that The NLRP3 promoter region has two critical binding sites for NF-κB, and thus for transcriptional regulation of its expression (Chen et al., 2020; Song et al., 2022). Given the fact that TBⅡ reduces LPS+ATP-induced NLRP3 gene expression, hinting a possibility that TBⅡ-mediated NLRP3 inhibition may be associated with the regulation of NF-κB. To confirm the mechanism involved, we determined the expression of NF-κB signaling in the inflamed colon tissues of colitis mice, and the LPS+ATP-treated HCoEpiC epithelial cells and BMDM macrophages. As expected, the protein levels of phosphorylated NF-κB (p-NF-κB) and IκBα (p-IκBα) were dramatically elevated in DSS-induced colitis mice or LPS+ATP induced HCoEpiC cells and BMDMs, respectively (Figure 7A-C). However, TBⅡ treatment markedly reversed this effect in a dose-dependent manner (Figure 7A-C). To corroborate the mechanism of TBⅡ involved in the NF-κB-mediated NLRP3 inhibition, NF-κB inhibitor BAY11-7082 was used. Co-treatment TBⅡ with BAY11-7082 partially impaired TBⅡ-mediated NLRP3 inhibition, and thereby affecting the IL-1β mature and secretion (IL-1β-p17) (Figure 7D). Collectively, these results suggested that TBⅡ-mediated NLRP3 inhibition may be partly associated with the suppression of NF-κB.