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Interleukin 34: a new modulator of human and experimental inflammatory bowel disease.

Zwicker S, Martinez GL, Bosma M, Gerling M, Clark R, Majster M, Söderman J, Almer S, Boström EA - Clin. Sci. (2015)

Bottom Line: We found distinct expression patterns of IL34 and CSF1 in ileum and colon, with higher IL34 in ileum and, in contrast, higher CSF1 in colon.In humans, infiltrating cells of the lamina propria and intestinal epithelial cells expressed IL-34, and TNF-α (tumour necrosis factor α) regulated IL-34 expression in intestinal epithelial cells through the NF-κB (nuclear factor κB) pathway.These data demonstrate the expression pattern of IL-34 in ileum and colon and suggest IL-34 as a new modulator of inflammation in IBD.

View Article: PubMed Central - PubMed

Affiliation: *Department of Dental Medicine, Division of Periodontology, Karolinska Institutet, Alfred Nobels Allé 8, SE-141 52, Huddinge, Sweden.

ABSTRACT
IBD (inflammatory bowel disease), where CD (Crohn's disease) and UC (ulcerative colitis) represent the two main forms, are chronic inflammatory conditions of the intestine. Macrophages play a central role in IBD pathogenesis and are regulated by major differentiation factors such as CSF-1 (colony-stimulating factor 1) in homoeostasis and inflammation. IL (interleukin)-34 has recently been discovered as a second ligand for CSF-1R (CSF-1 receptor). However, expression and involvement of IL-34 in IBD remain unknown. In the present paper, we investigated the expression of IL34, CSF1 and their shared receptor CSF1R in normal human ileum and colon, in inflamed and non-inflamed tissues of CD and UC patients, and in a mouse model of experimental colitis. We found distinct expression patterns of IL34 and CSF1 in ileum and colon, with higher IL34 in ileum and, in contrast, higher CSF1 in colon. Furthermore, IL34 and CSF1 expression was increased with inflammation in IBD patients and in experimental colitis. In humans, infiltrating cells of the lamina propria and intestinal epithelial cells expressed IL-34, and TNF-α (tumour necrosis factor α) regulated IL-34 expression in intestinal epithelial cells through the NF-κB (nuclear factor κB) pathway. These data demonstrate the expression pattern of IL-34 in ileum and colon and suggest IL-34 as a new modulator of inflammation in IBD.

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Presence of IL-34 in gut epithelium, and NF-κB-dependent regulation of TNF-α-induced IL34 and CSF1 expression in colon epithelial cells(A) Immunohistochemical staining of human colon showing the presence of IL-34 and isotype control. (B) TNF-α (1–100 ng/ml) up-regulates IL34 gene expression at 6 h. (C) Blocking NF-κB with celastrol down-regulates IL34 expression in colon epithelial cells. (D) The presence of IL-34 shown by immunofluorescent staining of intestinal epithelial cells following TNF-α stimulation. Comparisons were calculated by ordinary one-way ANOVA. Results are means±S.E.M. for two to four individual experiments. *P≤0.05; **P≤0.01; ***P≤0.001.
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Figure 3: Presence of IL-34 in gut epithelium, and NF-κB-dependent regulation of TNF-α-induced IL34 and CSF1 expression in colon epithelial cells(A) Immunohistochemical staining of human colon showing the presence of IL-34 and isotype control. (B) TNF-α (1–100 ng/ml) up-regulates IL34 gene expression at 6 h. (C) Blocking NF-κB with celastrol down-regulates IL34 expression in colon epithelial cells. (D) The presence of IL-34 shown by immunofluorescent staining of intestinal epithelial cells following TNF-α stimulation. Comparisons were calculated by ordinary one-way ANOVA. Results are means±S.E.M. for two to four individual experiments. *P≤0.05; **P≤0.01; ***P≤0.001.

Mentions: Given the finding of IL34 expression in the gut, we next investigated the localization of IL-34 in colon tissue using immunohistochemistry. A positive signal of IL-34 was detected in the epithelial layer; additionally, IL-34-expressing cells were detected in the connective tissue suspected to be infiltrating immune cells (Figure 3A). TNF-α induces the IL-34 expression in fibroblasts and anti-TNF-α inhibits its expression in vivo [19,22]. We therefore assessed whether intestinal epithelial cells (Caco-2 cells) express IL34 and CSF1 and whether the expression was regulated by TNF-α. For IL34, a dose-dependent increase was detected following TNF-α stimulation with the highest expression observed at 100 ng/ml. Also, CSF1 expression was dose-dependently increased (Figure 3B). The expression of IL-34 was also detected at the protein level by immunofluorescent staining of intestinal epithelial cells; the higher magnification suggests IL-34 expression around the nucleus (Figure 3D). To determine the intracellular signalling involved in TNF-α-induced IL34 and CSF1 expression in intestinal epithelial cells, we next used pharmacological inhibitors of NF-κB, a transcription factor downstream of the TNF-α receptor. Treatment with celastrol, an inhibitor of NF-κB, resulted in 80% inhibition of TNF-α-induced IL34, and treatment with the inhibitor of the downstream IKKβ [IκB (inhibitor of NF-κB) kinase β] resulted in 25% inhibition of TNF-α-induced IL34, which did not reach statistical significance. We found no significant differences in the expression of CSF1 after blocking NF-κB by the NF-κB inhibitor or the IKKβ inhibitor (Figure 3C).


Interleukin 34: a new modulator of human and experimental inflammatory bowel disease.

Zwicker S, Martinez GL, Bosma M, Gerling M, Clark R, Majster M, Söderman J, Almer S, Boström EA - Clin. Sci. (2015)

Presence of IL-34 in gut epithelium, and NF-κB-dependent regulation of TNF-α-induced IL34 and CSF1 expression in colon epithelial cells(A) Immunohistochemical staining of human colon showing the presence of IL-34 and isotype control. (B) TNF-α (1–100 ng/ml) up-regulates IL34 gene expression at 6 h. (C) Blocking NF-κB with celastrol down-regulates IL34 expression in colon epithelial cells. (D) The presence of IL-34 shown by immunofluorescent staining of intestinal epithelial cells following TNF-α stimulation. Comparisons were calculated by ordinary one-way ANOVA. Results are means±S.E.M. for two to four individual experiments. *P≤0.05; **P≤0.01; ***P≤0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4557398&req=5

Figure 3: Presence of IL-34 in gut epithelium, and NF-κB-dependent regulation of TNF-α-induced IL34 and CSF1 expression in colon epithelial cells(A) Immunohistochemical staining of human colon showing the presence of IL-34 and isotype control. (B) TNF-α (1–100 ng/ml) up-regulates IL34 gene expression at 6 h. (C) Blocking NF-κB with celastrol down-regulates IL34 expression in colon epithelial cells. (D) The presence of IL-34 shown by immunofluorescent staining of intestinal epithelial cells following TNF-α stimulation. Comparisons were calculated by ordinary one-way ANOVA. Results are means±S.E.M. for two to four individual experiments. *P≤0.05; **P≤0.01; ***P≤0.001.
Mentions: Given the finding of IL34 expression in the gut, we next investigated the localization of IL-34 in colon tissue using immunohistochemistry. A positive signal of IL-34 was detected in the epithelial layer; additionally, IL-34-expressing cells were detected in the connective tissue suspected to be infiltrating immune cells (Figure 3A). TNF-α induces the IL-34 expression in fibroblasts and anti-TNF-α inhibits its expression in vivo [19,22]. We therefore assessed whether intestinal epithelial cells (Caco-2 cells) express IL34 and CSF1 and whether the expression was regulated by TNF-α. For IL34, a dose-dependent increase was detected following TNF-α stimulation with the highest expression observed at 100 ng/ml. Also, CSF1 expression was dose-dependently increased (Figure 3B). The expression of IL-34 was also detected at the protein level by immunofluorescent staining of intestinal epithelial cells; the higher magnification suggests IL-34 expression around the nucleus (Figure 3D). To determine the intracellular signalling involved in TNF-α-induced IL34 and CSF1 expression in intestinal epithelial cells, we next used pharmacological inhibitors of NF-κB, a transcription factor downstream of the TNF-α receptor. Treatment with celastrol, an inhibitor of NF-κB, resulted in 80% inhibition of TNF-α-induced IL34, and treatment with the inhibitor of the downstream IKKβ [IκB (inhibitor of NF-κB) kinase β] resulted in 25% inhibition of TNF-α-induced IL34, which did not reach statistical significance. We found no significant differences in the expression of CSF1 after blocking NF-κB by the NF-κB inhibitor or the IKKβ inhibitor (Figure 3C).

Bottom Line: We found distinct expression patterns of IL34 and CSF1 in ileum and colon, with higher IL34 in ileum and, in contrast, higher CSF1 in colon.In humans, infiltrating cells of the lamina propria and intestinal epithelial cells expressed IL-34, and TNF-α (tumour necrosis factor α) regulated IL-34 expression in intestinal epithelial cells through the NF-κB (nuclear factor κB) pathway.These data demonstrate the expression pattern of IL-34 in ileum and colon and suggest IL-34 as a new modulator of inflammation in IBD.

View Article: PubMed Central - PubMed

Affiliation: *Department of Dental Medicine, Division of Periodontology, Karolinska Institutet, Alfred Nobels Allé 8, SE-141 52, Huddinge, Sweden.

ABSTRACT
IBD (inflammatory bowel disease), where CD (Crohn's disease) and UC (ulcerative colitis) represent the two main forms, are chronic inflammatory conditions of the intestine. Macrophages play a central role in IBD pathogenesis and are regulated by major differentiation factors such as CSF-1 (colony-stimulating factor 1) in homoeostasis and inflammation. IL (interleukin)-34 has recently been discovered as a second ligand for CSF-1R (CSF-1 receptor). However, expression and involvement of IL-34 in IBD remain unknown. In the present paper, we investigated the expression of IL34, CSF1 and their shared receptor CSF1R in normal human ileum and colon, in inflamed and non-inflamed tissues of CD and UC patients, and in a mouse model of experimental colitis. We found distinct expression patterns of IL34 and CSF1 in ileum and colon, with higher IL34 in ileum and, in contrast, higher CSF1 in colon. Furthermore, IL34 and CSF1 expression was increased with inflammation in IBD patients and in experimental colitis. In humans, infiltrating cells of the lamina propria and intestinal epithelial cells expressed IL-34, and TNF-α (tumour necrosis factor α) regulated IL-34 expression in intestinal epithelial cells through the NF-κB (nuclear factor κB) pathway. These data demonstrate the expression pattern of IL-34 in ileum and colon and suggest IL-34 as a new modulator of inflammation in IBD.

Show MeSH
Related in: MedlinePlus