Bacterial Particle Endocytosis by Epithelial Cells Is Selective and Enhanced by Tumor Necrosis Factor Receptor Ligands

Abstract

Bacterial pathogens use virulence strategies to invade epithelial barriers, but active processes of epithelial cells may also contribute to the endocytosis of microbial particles. To focus on the latter, we studied the uptake of fixed and fluorescently labeled bacterial particles in intestinal and bronchoepithelial cell cultures and found it to be enhanced in Caco-2BBe and NCI-H292 cells after treatment with tumor necrosis factor alpha and an agonist antibody against the lymphotoxin beta receptor. Confocal fluorescence microscopy, flow cytometry, and transmission electron microscopy revealed that Staphylococcus aureus and Yersinia enterocolitica were readily endocytosed, although there was scant uptake of Shigella sonnei, Salmonella enterica serovar Typhimurium, and Klebsiella pneumoniae particles. Endocytosed Staphylococcus was often associated with cytoplasmic claudin-4 vesicles; this was not found for Yersinia, suggesting that cytokine treatment upregulated two distinct endocytosis pathways. Interestingly, when Staphylococcus and Yersinia were coincubated with epithelial monolayers, the cells were unlikely to take up Yersinia unless they had also endocytosed large numbers of Staphylococcus particles, although the two bacteria were apparently processed in distinct compartments. Cytokine treatment induced an upregulation and redistribution of ␤1 integrin to the apical surface of NCI-H292 cells; consistent with this effect, treatment with anti-␤1 integrin antibody blocked uptake of both Yersinia and Staphylococcus in NCI-H292 and Caco-2BBe cells. Our results suggest that capture of bacterial particles by mucosal epithelial cells is selective and that different endocytic mechanisms are enhanced by proinflammatory cytokines.

TNFR and LTβR agonists induce follicle-associated epithelium and M cell specific genes in rat and human intestinal epithelial cells

“…These changes were also associated with a functional increase in the endocytosis of bacterial particles, as shown by the Staphylococcus aureus endocytosed by the cytokine-treated Caco-2BBe cells (Figure 4b). This effect has also been described in more quantitative studies [42]. …”

“…We recently reported that the same cytokine treatment of airway and intestinal epithelial cells also increased their capacity to endocytose bacterial particles [42], and in some cases Claudin-4 was associated with the endocytosis vesicles.…”

“…Caco-2BBe cell cultures were given Staphylococcus aureus particles for 12 hours prior to fixation as described in reference [42]. Scale bar: 2 microns.…”

CD137 Is Required for M Cell Functional Maturation but Not Lineage Commitment

“…The cytoplasmic vesicles with CD137 did not co-localize with the tight junction protein Claudin 4, a protein that we previously reported to be associated with particle endocytosis in cytokinetreated cells. 17,31 However, we did find that most of the cytoplasmic CD137 co-localized with the extracellular matrix protein fibronectin (Figure 1), though it was not associated with fibronectin at the surface of the cells. The cytoplasmic associations may also account for the apparent decrease in cell-associated fibronectin in the cytokine treated cells; this pattern suggests that fibronectin synthesized by the epithelial cells was endocytosed in association with CD137 either during synthesis or soon after both proteins appeared at the surface of the cells.…”

GROWTH AND DEVELOPMENT SYMPOSIUM: Endotoxin, inflammation, and intestinal function in livestock1,2

“…The gut is the first line of defense against endotoxin and, if cornpromised via nutrition, stress or rnetabolic state, endotoxin transport can increase (Suganuma et al, 2002;Clark et al, 2009;Liu et al, 2009). A greater understanding of gut endotoxin transport ( Figure 2) will allow for the development of nutritional and pharmacological mitigation strategies to avert the negative effects of endotoxin and improve production efficiencies in livestock.…”