Interleukin-10 Deficiency Impacts on TNF-Induced NFκB Regulated Responses In Vivo

SIMPLE SUMMARY: Chronic inflammation of the gut is a multifactorial, incurable condition that involves interactions between our immune cells and the cells that line the surface layer of gut, known as the epithelium. Interleukin-10, a protein well known to be released by our immune cells, has a protective role in countering inflammation, partly due to the fact that it can block the NFκB pathway, a signalling pathway within cells that promotes genes involved in inflammatory responses. However, we recently showed that laboratory cultures of gut epithelial cells can also synthesise interleukin-10, which acts as a positive regulator of the NFκB pathway to support gut health. In this study here, we investigated further the impact of the role of interleukin-10 on the NFκB pathway and its targets within the gut using a whole animal approach, and confirmed that NFκB activation is indeed positively regulated by interleukin-10, affecting the expression of downstream target genes and their encoded proteins. This strengthens the importance of the interleukin-10/NFκB signalling pathway axis in maintenance of gut health and response to damage, inflammation, and infection. Understanding cell-specific biological roles of interleukin-10 and its interactions with NFκB could prove useful for future therapeutic intervention for interleukin-10 regulated inflammatory conditions. ABSTRACT: Interleukin-10 (IL-10) is an anti-inflammatory cytokine that has a major protective role against intestinal inflammation. We recently revealed that intestinal epithelial cells in vitro regulate NFκB-driven transcriptional responses to TNF via an autocrine mechanism dependent on IL-10 secretion. Here in this study, we investigated the impact of IL-10 deficiency on the NFκB pathway and its downstream targets in the small intestinal mucosa in vivo. We observed dysregulation of TNF, IκBα, and A20 gene and protein expression in the small intestine of steady-state or TNF-injected Il10(−/−) mice, compared to wild-type C57BL6/J counterparts. Upon TNF injection, tissue from the small intestine showed upregulation of NFκB p65[RelA] activity, which was totally diminished in Il10(−/−) mice and correlated with reduced levels of TNF, IκBα, and A20 expression. In serum, whilst IgA levels were noted to be markedly downregulated in IL-10-deficient(-) mice, normal levels of mucosal IgA were seen in intestine mucosa. Importantly, dysregulated cytokine/chemokine levels were observed in both serum and intestinal tissue lysates from naïve, as well as TNF-injected Il10(−/−) mice. These data further support the importance of the IL-10-canonical NFκB signaling pathway axis in regulating intestinal mucosa homeostasis and response to inflammatory triggers in vivo.