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Vectorial secretion of interleukin-8 mediates autocrine signalling in intestinal epithelial cells via apically located CXCR1.

Rossi O, Karczewski J, Stolte EH, Brummer RJ, van Nieuwenhoven MA, Meijerink M, van Neerven JR, van Ijzendoorn SC, van Baarlen P, Wells JM - BMC Res Notes (2013)

Bottom Line: In the intestinal mucosa, several adaptations of TLR signalling have evolved to avoid chronic inflammatory responses to the presence of commensal microbes.In the Caco-2 BBE model of polarized villus-like epithelium, apical stimulation with TLR2 and TLR5 ligands resulted in the apical secretion of IL-8.Transcriptome analyses revealed that Caco-2 BBE cells respond to stimulation with IL-8 supporting the hypothesis that IL-8 induces G protein-coupled receptor signalling.

View Article: PubMed Central - HTML - PubMed

Affiliation: Host-Microbe Interactomics Group, ASG, University of Wageningen, Wageningen, The Netherlands. jerry.wells@wur.nl.

ABSTRACT

Background: In the intestinal mucosa, several adaptations of TLR signalling have evolved to avoid chronic inflammatory responses to the presence of commensal microbes. Here we investigated whether polarized monolayers of intestinal epithelial cells might regulate inflammatory responses by secreting IL-8 in a vectorial fashion (i.e. apical versus basolateral) depending on the location of the TLR stimulus.

Results: In the Caco-2 BBE model of polarized villus-like epithelium, apical stimulation with TLR2 and TLR5 ligands resulted in the apical secretion of IL-8. The CXCR1 receptor for IL-8 was expressed only on the apical membrane of Caco-2 BBE cells and differentiated epithelial cells in the human small intestine and colon. Transcriptome analyses revealed that Caco-2 BBE cells respond to stimulation with IL-8 supporting the hypothesis that IL-8 induces G protein-coupled receptor signalling.

Conclusions: These results show that IL-8 induces autocrine signalling via an apical CXCR1 in Caco-2 BBE intestinal epithelial cells and that this receptor is also expressed on the apical surface of differentiated human intestinal epithelial cells in vivo, suggesting an autocrine function for IL-8 secreted in the lumen.

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Caco-2 BBE monolayers express CXCR1 on the apical surface. The cellular localization of CXCR1 in Caco-2 BBE polarized monolayers visualized by immunofluorescent detection and confocal microscopy; anti-occludin (red), DRAQ5 (blue) and anti-CXCR1 (green). CXCR1 was expressed on the apical side of Caco-2 BBE monolayers. (x-y (a) and x-z (b) sections).
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Figure 2: Caco-2 BBE monolayers express CXCR1 on the apical surface. The cellular localization of CXCR1 in Caco-2 BBE polarized monolayers visualized by immunofluorescent detection and confocal microscopy; anti-occludin (red), DRAQ5 (blue) and anti-CXCR1 (green). CXCR1 was expressed on the apical side of Caco-2 BBE monolayers. (x-y (a) and x-z (b) sections).

Mentions: CXCR1 was localized to the apical pole of polarized Caco-2 BBE cells by confocal microscopy (Figure 2a and b). The speckled or ‘patchy’ staining for CXCR1 is suggestive of its localization in (macro)-domains, possibly microvilli. Other GPCRs and their effector proteins have shown patchy staining in cytoplasmic membrane domains of epithelial cells [12,13]. No CXCR1 staining was observed using an isotope control of the primary antibody at the same concentration as the anti-CXCR1 antibody or the secondary antibody alone as a control, indicating that fluorescence was not due to non-specific antibody binding (not shown).


Vectorial secretion of interleukin-8 mediates autocrine signalling in intestinal epithelial cells via apically located CXCR1.

Rossi O, Karczewski J, Stolte EH, Brummer RJ, van Nieuwenhoven MA, Meijerink M, van Neerven JR, van Ijzendoorn SC, van Baarlen P, Wells JM - BMC Res Notes (2013)

Caco-2 BBE monolayers express CXCR1 on the apical surface. The cellular localization of CXCR1 in Caco-2 BBE polarized monolayers visualized by immunofluorescent detection and confocal microscopy; anti-occludin (red), DRAQ5 (blue) and anti-CXCR1 (green). CXCR1 was expressed on the apical side of Caco-2 BBE monolayers. (x-y (a) and x-z (b) sections).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231470&req=5

Figure 2: Caco-2 BBE monolayers express CXCR1 on the apical surface. The cellular localization of CXCR1 in Caco-2 BBE polarized monolayers visualized by immunofluorescent detection and confocal microscopy; anti-occludin (red), DRAQ5 (blue) and anti-CXCR1 (green). CXCR1 was expressed on the apical side of Caco-2 BBE monolayers. (x-y (a) and x-z (b) sections).
Mentions: CXCR1 was localized to the apical pole of polarized Caco-2 BBE cells by confocal microscopy (Figure 2a and b). The speckled or ‘patchy’ staining for CXCR1 is suggestive of its localization in (macro)-domains, possibly microvilli. Other GPCRs and their effector proteins have shown patchy staining in cytoplasmic membrane domains of epithelial cells [12,13]. No CXCR1 staining was observed using an isotope control of the primary antibody at the same concentration as the anti-CXCR1 antibody or the secondary antibody alone as a control, indicating that fluorescence was not due to non-specific antibody binding (not shown).

Bottom Line: In the intestinal mucosa, several adaptations of TLR signalling have evolved to avoid chronic inflammatory responses to the presence of commensal microbes.In the Caco-2 BBE model of polarized villus-like epithelium, apical stimulation with TLR2 and TLR5 ligands resulted in the apical secretion of IL-8.Transcriptome analyses revealed that Caco-2 BBE cells respond to stimulation with IL-8 supporting the hypothesis that IL-8 induces G protein-coupled receptor signalling.

View Article: PubMed Central - HTML - PubMed

Affiliation: Host-Microbe Interactomics Group, ASG, University of Wageningen, Wageningen, The Netherlands. jerry.wells@wur.nl.

ABSTRACT

Background: In the intestinal mucosa, several adaptations of TLR signalling have evolved to avoid chronic inflammatory responses to the presence of commensal microbes. Here we investigated whether polarized monolayers of intestinal epithelial cells might regulate inflammatory responses by secreting IL-8 in a vectorial fashion (i.e. apical versus basolateral) depending on the location of the TLR stimulus.

Results: In the Caco-2 BBE model of polarized villus-like epithelium, apical stimulation with TLR2 and TLR5 ligands resulted in the apical secretion of IL-8. The CXCR1 receptor for IL-8 was expressed only on the apical membrane of Caco-2 BBE cells and differentiated epithelial cells in the human small intestine and colon. Transcriptome analyses revealed that Caco-2 BBE cells respond to stimulation with IL-8 supporting the hypothesis that IL-8 induces G protein-coupled receptor signalling.

Conclusions: These results show that IL-8 induces autocrine signalling via an apical CXCR1 in Caco-2 BBE intestinal epithelial cells and that this receptor is also expressed on the apical surface of differentiated human intestinal epithelial cells in vivo, suggesting an autocrine function for IL-8 secreted in the lumen.

Show MeSH
Related in: MedlinePlus