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Superoxide output and expression of NADPH oxidase 1 in human colonic epithelial cells
Critical Care volume 5, Article number: P069 (2001)
Translocation of microorganisms from the gut lumen may contribute to morbidity in sepsis. Conservation of normal barrier function should, therefore, be a goal in critical illness, but its components is only partly defined. Beyond mechanical contribution, the colonic epithelium may possess antimicrobial activity via yet undefined mediators . Superoxide (O2-), generated by membrane-bound NADPH oxidase (Nox), is a key antimicrobial agent of phagocytes, but output from human colonic epithelial cells has not been demonstrated.
To measure O2- output and expression of the non-phagocytic NADPH oxidase, Nox1, in short term cultures of primary epithelial cells from normal human colon and in Caco-2 colonic epithelial cell line.
Colonic epithelial cells were isolated from biopsies of subjects with uninflamed bowel and Caco-2 cells were grown in 24-well plates . Output of O2- was measured by the cytochrome c assay or luminol-enhanced luminescence and localised by the nitrobluetetrazolium (NBT) assay .Effects of 1 mM NADPH, oxidoreductase inhibition by 10 µM diphenylene iodonium (DPI) and protein kinase C-activation by 0.5 µg/ml phorbol myristate ester (PMA) were assessed. mRNA expression of Nox1 was analysed by RT-PCR.
Identical results were obtained in primary epithelial cells (see Figs) and Caco-2 cells. NBT-reduction was observed at the outer cell membrane and Nox1 mRNA was detected in all cell cultures. NADPH increased output of O2- within seconds although cell membranes are impermeable to NADPH.
These results show that cultures of human colonic epithelial cells produce extracellular O2- possibly through membrane-bound Nox1, which appears to independent of protein kinase C activation. O2- from epithelial cells may possess antimicrobial activity and contribute to colonic barrier function.
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Perner, A., Andresen, L., Pedersen, G. et al. Superoxide output and expression of NADPH oxidase 1 in human colonic epithelial cells. Crit Care 5, P069 (2001). https://doi.org/10.1186/cc1136
- NADPH Oxidase
- Colonic Epithelial Cell
- Short Term Culture
- Outer Cell Membrane