Akt isoforms and TLR5 in intestinal barrier function and inflammatory bowel disease

Laburpena

The leakiness of the intestinal epithelial barrier plays a major role in the development of inflammatory bowel disease (IBD). We show that either Akt1 overexpression or Akt2 chemical inhibition have similar effects on intestinal epithelial cells, enhancing the permeability of the epithelial barrier and the expression and intracellular localization of the tight junctions’ proteins (TJP) whereas Akt1 inhibition or Akt2 overexpression show the opposite results. Akt1 overexpression or Akt2 inhibition also promotes activation of βCatenin. Moreover, mouse intestinal organoids treated ex vivo with Akt1 inhibitors present dissembled and disorganized structures that mimic IBD histological features. Importantly, in mice with IBD induced by DSS, Akt2 inhibition strongly ameliorates disease, with animals presenting healthy-like crypts, having tightened colon epithelial cells expressing TJP, and presenting an anti-inflammatory M2 macrophage phenotype. In contrast, treatment with Akt1 inhibitors enhances histological damage, TJP disorganization and promotes a more proinflammatory milieu further favoring the development of the disease. Those results suggest that a balance between Akt1 and Akt2 regulates the functionality of the intestinal epithelial barrier and inflammation and that Akt2 inhibition can be considered as a new therapy for IBD. TLR5 is also relevant on intestinal homeostasis and mice with deletion of this receptor develop spontaneous colitis. In the study we demonstrate that FliC, agonist for TLR5 receptor, increases activation of Akt1 and increase the major TJP, ZO1, contrary to other TLRs ligands, being those effects prevented. by a TLR5 antagonist. Moreover, FliC increases anti-inflammatory mediator IL10. We studied un vivo the stimulation of TLR5 as a possible treatment against IBD development and we found that FliC increases in vivo M2 response, decreases the tissue damage and also increases LGR5 expression the main intestinal stem cell marker