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IL-6 stimulates intestinal epithelial proliferation and repair after injury.

Kuhn KA, Manieri NA, Liu TC, Stappenbeck TS - PLoS ONE (2014)

Bottom Line: IL-6 is a pleiotropic cytokine often associated with inflammation.Inhibition of this pathway has led to successful treatment of rheumatoid arthritis, but one unforeseen potential complication of anti-IL-6 therapy is bowel perforation.Inhibition of IL-6 resulted in impaired wound healing due to decreased epithelial proliferation.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, United States of America; Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America.

ABSTRACT
IL-6 is a pleiotropic cytokine often associated with inflammation. Inhibition of this pathway has led to successful treatment of rheumatoid arthritis, but one unforeseen potential complication of anti-IL-6 therapy is bowel perforation. Within the intestine, IL-6 has been shown to prevent epithelial apoptosis during prolonged inflammation. The role of IL-6 in the intestine during an initial inflammatory insult is unknown. Here, we evaluate the role of IL-6 at the onset of an inflammatory injury. Using two murine models of bowel injury - wound by biopsy and bacterial triggered colitis - we demonstrated that IL-6 is induced soon after injury by multiple cell types including intraepithelial lymphocytes. Inhibition of IL-6 resulted in impaired wound healing due to decreased epithelial proliferation. Using intestinal tissue obtained from patients who underwent surgical resection of the colon due to traumatic perforation, we observed cells with detectable IL-6 within the area of perforation and not at distant sites. Our data demonstrate the important role of IL-6 produced in part by intraepithelial lymphocytes at the onset of an inflammatory injury for epithelial proliferation and wound repair.

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Intraepithelial lymphocytes were a source of IL-6 early after injury.(A) Biopsy of the colon mucosa was performed in WT mice to create small wounds. IL-6 expression in the wound bed and adjacent tissue was evaluated by in situ hybridization one day after biopsy. Representative images were shown. Bars = 200 µm. Colored bars above wound images indicate areas of the wound bed as depicted in Figure 4B. (B) Co-localization by immunofluorescence was performed for IL-6 (red), CD3ε (green), and bis-benzimide (blue) on colon tissue from dnKO mice at day 6 after co-housing. Representative staining was shown at 63X. Bar = 200 µm. (C) Epithelial cells were harvested from dnKO mice on day 6 after co-housing, stained for T cell markers and IL-6, and assessed by flow cytometry. Representative dot plots were shown. (D, E) CD3+ CD4- CD8- IELs were harvested from WT mice and stimulated ex vivo with 10 ng/ml PMA and 1 µg/ml ionamycin for 5 hours. (D) RNA was collected and evaluated by qRT-PCR for IL-6 expression. (E) Culture supernatants were harvested and evaluated for secreted IL-6 by electrochemilluminescence. Data were shown as the average IL-6 expression or protein ± SEM. A paired student's t-test was used to determine significance; *, P<0.05.
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pone-0114195-g005: Intraepithelial lymphocytes were a source of IL-6 early after injury.(A) Biopsy of the colon mucosa was performed in WT mice to create small wounds. IL-6 expression in the wound bed and adjacent tissue was evaluated by in situ hybridization one day after biopsy. Representative images were shown. Bars = 200 µm. Colored bars above wound images indicate areas of the wound bed as depicted in Figure 4B. (B) Co-localization by immunofluorescence was performed for IL-6 (red), CD3ε (green), and bis-benzimide (blue) on colon tissue from dnKO mice at day 6 after co-housing. Representative staining was shown at 63X. Bar = 200 µm. (C) Epithelial cells were harvested from dnKO mice on day 6 after co-housing, stained for T cell markers and IL-6, and assessed by flow cytometry. Representative dot plots were shown. (D, E) CD3+ CD4- CD8- IELs were harvested from WT mice and stimulated ex vivo with 10 ng/ml PMA and 1 µg/ml ionamycin for 5 hours. (D) RNA was collected and evaluated by qRT-PCR for IL-6 expression. (E) Culture supernatants were harvested and evaluated for secreted IL-6 by electrochemilluminescence. Data were shown as the average IL-6 expression or protein ± SEM. A paired student's t-test was used to determine significance; *, P<0.05.

Mentions: Previous studies using dextran sodium sulfate and T cell transfer models of colitis suggested monocytes and T cells are the source of IL-6 during these injuries [22], [23]. However, the data in our models demonstrated that IL-6 expression occurred quickly after injury, before monocytes and T cells have time to migrate into the injured tissue. Therefore, we sought to identify the initial source of IL-6 using in situ hybridization. In the endoscopic-guided biopsy injury model, in situ hybridization of IL-6 at 24 hours post-injury showed abundant IL-6 expressing cells located within highly proliferative crypts/wound channels that are located adjacent/within the wound bed (Figure 5A). Many of these cells were morphologically consistent with IELs based on size and position. These IL-6 expressing cells were not present in areas distant from the wound (Figure 5A). Similarly, by in situ hybridization in triggered dnKO mice, the majority of IL-6 positive cells at day six post-induction also appeared to be IELs (Figure 1A).


IL-6 stimulates intestinal epithelial proliferation and repair after injury.

Kuhn KA, Manieri NA, Liu TC, Stappenbeck TS - PLoS ONE (2014)

Intraepithelial lymphocytes were a source of IL-6 early after injury.(A) Biopsy of the colon mucosa was performed in WT mice to create small wounds. IL-6 expression in the wound bed and adjacent tissue was evaluated by in situ hybridization one day after biopsy. Representative images were shown. Bars = 200 µm. Colored bars above wound images indicate areas of the wound bed as depicted in Figure 4B. (B) Co-localization by immunofluorescence was performed for IL-6 (red), CD3ε (green), and bis-benzimide (blue) on colon tissue from dnKO mice at day 6 after co-housing. Representative staining was shown at 63X. Bar = 200 µm. (C) Epithelial cells were harvested from dnKO mice on day 6 after co-housing, stained for T cell markers and IL-6, and assessed by flow cytometry. Representative dot plots were shown. (D, E) CD3+ CD4- CD8- IELs were harvested from WT mice and stimulated ex vivo with 10 ng/ml PMA and 1 µg/ml ionamycin for 5 hours. (D) RNA was collected and evaluated by qRT-PCR for IL-6 expression. (E) Culture supernatants were harvested and evaluated for secreted IL-6 by electrochemilluminescence. Data were shown as the average IL-6 expression or protein ± SEM. A paired student's t-test was used to determine significance; *, P<0.05.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4257684&req=5

pone-0114195-g005: Intraepithelial lymphocytes were a source of IL-6 early after injury.(A) Biopsy of the colon mucosa was performed in WT mice to create small wounds. IL-6 expression in the wound bed and adjacent tissue was evaluated by in situ hybridization one day after biopsy. Representative images were shown. Bars = 200 µm. Colored bars above wound images indicate areas of the wound bed as depicted in Figure 4B. (B) Co-localization by immunofluorescence was performed for IL-6 (red), CD3ε (green), and bis-benzimide (blue) on colon tissue from dnKO mice at day 6 after co-housing. Representative staining was shown at 63X. Bar = 200 µm. (C) Epithelial cells were harvested from dnKO mice on day 6 after co-housing, stained for T cell markers and IL-6, and assessed by flow cytometry. Representative dot plots were shown. (D, E) CD3+ CD4- CD8- IELs were harvested from WT mice and stimulated ex vivo with 10 ng/ml PMA and 1 µg/ml ionamycin for 5 hours. (D) RNA was collected and evaluated by qRT-PCR for IL-6 expression. (E) Culture supernatants were harvested and evaluated for secreted IL-6 by electrochemilluminescence. Data were shown as the average IL-6 expression or protein ± SEM. A paired student's t-test was used to determine significance; *, P<0.05.
Mentions: Previous studies using dextran sodium sulfate and T cell transfer models of colitis suggested monocytes and T cells are the source of IL-6 during these injuries [22], [23]. However, the data in our models demonstrated that IL-6 expression occurred quickly after injury, before monocytes and T cells have time to migrate into the injured tissue. Therefore, we sought to identify the initial source of IL-6 using in situ hybridization. In the endoscopic-guided biopsy injury model, in situ hybridization of IL-6 at 24 hours post-injury showed abundant IL-6 expressing cells located within highly proliferative crypts/wound channels that are located adjacent/within the wound bed (Figure 5A). Many of these cells were morphologically consistent with IELs based on size and position. These IL-6 expressing cells were not present in areas distant from the wound (Figure 5A). Similarly, by in situ hybridization in triggered dnKO mice, the majority of IL-6 positive cells at day six post-induction also appeared to be IELs (Figure 1A).

Bottom Line: IL-6 is a pleiotropic cytokine often associated with inflammation.Inhibition of this pathway has led to successful treatment of rheumatoid arthritis, but one unforeseen potential complication of anti-IL-6 therapy is bowel perforation.Inhibition of IL-6 resulted in impaired wound healing due to decreased epithelial proliferation.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, United States of America; Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America.

ABSTRACT
IL-6 is a pleiotropic cytokine often associated with inflammation. Inhibition of this pathway has led to successful treatment of rheumatoid arthritis, but one unforeseen potential complication of anti-IL-6 therapy is bowel perforation. Within the intestine, IL-6 has been shown to prevent epithelial apoptosis during prolonged inflammation. The role of IL-6 in the intestine during an initial inflammatory insult is unknown. Here, we evaluate the role of IL-6 at the onset of an inflammatory injury. Using two murine models of bowel injury - wound by biopsy and bacterial triggered colitis - we demonstrated that IL-6 is induced soon after injury by multiple cell types including intraepithelial lymphocytes. Inhibition of IL-6 resulted in impaired wound healing due to decreased epithelial proliferation. Using intestinal tissue obtained from patients who underwent surgical resection of the colon due to traumatic perforation, we observed cells with detectable IL-6 within the area of perforation and not at distant sites. Our data demonstrate the important role of IL-6 produced in part by intraepithelial lymphocytes at the onset of an inflammatory injury for epithelial proliferation and wound repair.

Show MeSH
Related in: MedlinePlus