An epithelial Nfkb2 pathway exacerbates intestinal inflammation by supplementing latent RelA complexes to the canonical NF-kB module

The canonical NF-kB module induces nuclear translocation of RelA heterodimers from the latent cytoplasmic complexes. RelA directs inflammatory immune responses against microbial entities. However, aberrant RelA activity also triggers destructive inflammation, including those associated with inflammatory bowel disease (IBD). What provokes this pathological RelA activity remains unclear. As such, the noncanonical NF-kB pathway activates RelB heterodimers and mediates immune organogenesis. Because NF-kB-activating pathways are interlinked, we asked if noncanonical NF-kB signaling exacerbated intestinal inflammation. Our investigation revealed recurrent engagement of the noncanonical pathway in human IBD. In a mouse model of chemical colitis, the noncanonical NF-kB signaling gene Nfkb2 aggravated inflammation by amplifying the RelA activity induced in intestinal epithelial cells. Our mechanistic studies clarified that noncanonical signaling augmented the abundance of latent RelA complexes leading to hyperactive canonical NF-kB response in the colitogenic gut. In sum, latent dimer homeostasis appears to link noncanonical NF-kB signaling to RelA-driven inflammatory pathologies. IECs were obtained from WT and Nfkb2-/- mice, either left untreated or treated with DSS for 48h. mRNA levels in all four samples with 3 biological replicates were generated via next generation sequencing.