CD14 and ALPK1 Affect Expression of Tight Junction Components and Proinflammatory Mediators upon Bacterial Stimulation in a Colonic 3D Organoid Model.

and both encode pathogen recognition receptors and are known candidate genes for affecting severity in inflammatory bowel diseases. CD14 acts as a coreceptor for bacterial lipopolysaccharide (LPS), while ALPK1 senses ADP-D-glycero-beta-D-manno-heptose, a metabolic intermediate of LPS biosynthesis. Intestinal barrier integrity can be influenced by CD14, whereas to date, the role of ALPK1 in maintaining barrier function remains unknown. We used colon-derived 3D organoids, first characterised for growth, proliferation, stem cell markers, and expression of tight junction (TJ) components using qPCR and immunohistochemistry. They showed characteristic crypt stem cells, apical shedding of dead cells, and TJ formation. Afterwards, organoids of different genotypes (WT, , , and ) were then stimulated with either LPS or Nissle 1917 (N). Gene expression and protein levels of cytokines and TJ components were analysed. WT organoids increased expression of and tight junction components. organoids expressed significantly less and after LPS stimulation than WT organoids but reacted similarly to WT organoids after N stimulation. In contrast, compared to WT, organoids showed decreased expression of different TJ and cytokine genes in response to N but not LPS. However, Western blotting revealed an effect of ALPK1 on TJ protein levels. These findings demonstrate that , but not , alters the response to LPS stimulation in colonic epithelial cells, whereas is involved in the response upon bacterial challenge.