| dc.description.abstract | A major feature of intestinal macrophages in the normal gut is inflammatory anergy,
a state of tolerance essential for intestinal homeostasis, changes in which lead to
inflammatory bowel disease (IBD).
Intestinal macrophages undergo a specific process of differentiation. Under
homeostatic conditions, cytokines in the local environment drive functional
differentiation of newly recruited monocytes into noninflammatory intestinal
macrophage. This process is associated with downregulation of proinflammatory
cytokines.
Growing evidence supports the idea that epigenetic changes contribute to
macrophage reprogramming, and lead to tailored gene expression in response to gut
environmental factors. However, current knowledge on how chromatin modification
drives genes expression in human intestinal macrophages is still limited.
This project aimed to define the relationship between chromatin modification
(histone methylation) and the repression of inflammatory genes in intestinal
macrophages isolated from mucosa of control subjects and IBD patients. It was of
particular interest to understand if the anergic state of macrophages in normal gut is
associated with repressive marks. Also in IBD, if there are any differences in
epigenetic modifications between resident and infiltrating macrophages. Finally, if
by blocking histone methylation, it is possible to prevent/reduce TNFα production
by macrophages from IBD mucosa.
TNF-α is an inflammatory cytokine that plays a critical role in innate and adaptive
immune responses and its dysregulation has been implicated in the pathology of
IBD. Considering its central role in IBD pathology, the TNFA gene was selected and
different repressive and permissive histone modifications were investigated.
Silencing marks H3K27me3, H3K9me3 and H3K9me1, as well as activating marks
H3K4me3, H3K4me1 and also RNAPII were selected and analysed using chromatin
immunoprecipitation (ChIP) assays.
Based on data collected, it was speculated that a break of anergic phenotype in IBD
macrophages might be associated with changes in level of silencing marks.
Macrophages isolated from mucosa of CD patients showed decreased enrichment of
H3K27me3 and H3K9me3, with H3K27me3 having the greatest reduction.
Additional analysis of peripheral blood monocytes suggested that in healthy gut, the
differentiation of blood monocytes into resident intestinal macrophages is associated
with deposition of H3K27me3 and H3K9me3 silencing marks at the TNFA TSS, and
that this process fails in IBD environment. | en_US |
