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Crohn’s disease is a chronic inflammatory disease of the intestinal tract that results from a loss of tolerance to the enteric microbiota. Previous studies have established that interleukin (IL)-10 is an important anti-inflammatory cytokine driving intestinal macrophage (IM) tolerance. Within a cell, transcriptional responses are governed by transcription factors binding of accessible, nucleosome-free regions of DNA. Previously published studies have shown that marked changes in chromatin accessibility occur in IMs isolated from colitis-prone Il10-/- mice. Interestingly, addition of ectopic IL-10 to Il10-/- mice did not recover chromatin accessibility changes in 95% of the regions identified, suggesting that these chromatin accessibility changes were stable. We hypothesized that the stable chromatin landscape of Il10-/- macrophages may be altered using small molecule inhibitors of chromatin modifying proteins resulting in the restitution of IM tolerance to the enteric microbiota. A high-throughput screen with a chromatin accessibility readout was used to test small molecule inhibitors of chromatin modifying enzymes in Il10-/- macrophages. Changes in chromatin accessibility were assessed using a relative chromatin inhibition (RCI) score which compares accessibility changes at two regions that are only accessible in Il10-/- macrophages and two control regions. This screen identified several bromodomain inhibitors, including (+)-JQ1, that have the ability to decrease relative chromatin accessibility. Subsequent testing using (+)-JQ1 revealed that (+)-JQ1 attenuates mRNA levels of inflammatory Il6 and Il12ß in lipopolysaccharide (LPS)-stimulated Il10-/- macrophages. We conclude that bromodomain inhibitors decrease chromatin accessibility and attenuate the production of inflammatory cytokines in Il10-/- macrophages. |
