6533b834fe1ef96bd129d763

RESEARCH PRODUCT

Hypoxic macrophages impair autophagy in epithelial cells through Wnt1: relevance in IBD.

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A defective induction of epithelial autophagy may have a role in the pathogenesis of inflammatory bowel diseases. This process is regulated mainly by extracellular factors such as nutrients and growth factors and is highly induced by diverse situations of stress. We hypothesized that epithelial autophagy is regulated by the immune response that in turn is modulated by local hypoxia and inflammatory signals present in the inflamed mucosa. Our results reveal that HIF-1 alpha and Wnt1 were co-localized with CD68 in cells of the mucosa of IBD patients. We have observed increased protein levels of beta-catenin, phosphorylated mTOR, and p62 and decreased expression of LC3II in colonic epithelial crypts from damaged mucosa in which beta-catenin positively correlated with phosphorylated mTOR and negatively correlated with autophagic protein markers. In cultured macrophages, HIF-1 mediated the increase in Wnt1 expression induced by hypoxia, which enhanced protein levels of beta-catenin, activated mTOR, and decreased autophagy in epithelial cells in co-culture. Our results demonstrate a HIF-1-dependent induction of Wnt1 in hypoxic macrophages that undermines autophagy in epithelial cells and suggest a role for Wnt signaling and mTOR pathways in the impaired epithelial autophagy observed in the mucosa of IBD patients.