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A novel crosstalk between TLR4- and NOD2-mediated signaling in the regulation of intestinal inflammation.

Kim H, Zhao Q, Zheng H, Li X, Zhang T, Ma X - Sci Rep (2015)

Bottom Line: Specifically, NOD2 is able to sense the intensity of TLR4-mediated signaling, resulting in either synergistic stimulation of Interluekin-12 (IL-12) production when the TLR signaling intensity is low; or in the inhibition of IL-12 synthesis and maintenance of intestinal mucosal homeostasis when the TLR signaling intensifies.Additionally, in contrast to the dogma, we find that the major Crohn's disease-associated NOD2 mutations could cause a primarily immunodeficient phenotype by selectively impairing TLR4-mediated IL-12 production and host defense.To restore the impaired homeostasis would be a way forward to developing novel therapeutic strategies for inflammatory bowel diseases.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Microbial Metabolism, Sheng Yushou Center of Cell Biology and Immunology and School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, China 200240.

ABSTRACT
Although Toll-like receptor 4 (TLR4)- and nucleotide-binding oligomerization domain 2 (NOD2)-mediated signaling mechanisms have been extensively studied individually, the crosstalk between them in the regulation of intestinal mucosal defense and tissue homeostasis has been underappreciated. Here, we uncover some novel activities of NOD2 by gene expression profiling revealing the global nature of the cross-regulation between TLR4- and NOD2-mediated signaling. Specifically, NOD2 is able to sense the intensity of TLR4-mediated signaling, resulting in either synergistic stimulation of Interluekin-12 (IL-12) production when the TLR signaling intensity is low; or in the inhibition of IL-12 synthesis and maintenance of intestinal mucosal homeostasis when the TLR signaling intensifies. This balancing act is mediated through receptor-interacting serine/threonine kinase 2, and the transcriptional regulator CCAAT/enhancer-binding protein α (C/EBPα) via its serine 248 phosphorylation by Protein Kinase C. Mice deficient in C/EBPα in the hematopoietic compartment are highly susceptible to chemically induced experimental colitis in an IL-12-dependent manner. Additionally, in contrast to the dogma, we find that the major Crohn's disease-associated NOD2 mutations could cause a primarily immunodeficient phenotype by selectively impairing TLR4-mediated IL-12 production and host defense. To restore the impaired homeostasis would be a way forward to developing novel therapeutic strategies for inflammatory bowel diseases.

No MeSH data available.


Related in: MedlinePlus

RIP2 and c-Rel in NOD2-mediated regulation of IL-12p35 and p40 expression.Thioglycolate-elicited peritoneal macrophages from wild-type (WT), Rip2−/− and Crel−/− mice were stimulated for 6 h with LPS (500 ng/ml) with or without MDP (5 μg/ml). RNA analyses were carried out by real time RT-PCR for (a) IL-12p35 (upper), p40 (middle), and TNF-α (lower). (b) Cytokines were measured from culture supernatant by ELISA for IL-12 (upper) and IL-23 (lower). (c) THP-1 cells were stimulated with LPS for 6 h with a low dose of Bay11–7082 (0.5 μM). Levels of p35 mRNA were analyzed by real-time RT-PCR. Numbers within the bars (22% and 21%, respectively) in MDP-treated cells indicate the percentages of remaining mRNA levels in the presence of Bay11–7082 compared to controls.
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f4: RIP2 and c-Rel in NOD2-mediated regulation of IL-12p35 and p40 expression.Thioglycolate-elicited peritoneal macrophages from wild-type (WT), Rip2−/− and Crel−/− mice were stimulated for 6 h with LPS (500 ng/ml) with or without MDP (5 μg/ml). RNA analyses were carried out by real time RT-PCR for (a) IL-12p35 (upper), p40 (middle), and TNF-α (lower). (b) Cytokines were measured from culture supernatant by ELISA for IL-12 (upper) and IL-23 (lower). (c) THP-1 cells were stimulated with LPS for 6 h with a low dose of Bay11–7082 (0.5 μM). Levels of p35 mRNA were analyzed by real-time RT-PCR. Numbers within the bars (22% and 21%, respectively) in MDP-treated cells indicate the percentages of remaining mRNA levels in the presence of Bay11–7082 compared to controls.

Mentions: To further delineate the molecular mechanisms underlying NOD2-mediated selective inhibition of IL-12p35 gene transcription, we analyzed macrophages derived from mice deficient in receptor interacting protein 2 (RIP2)24, the protein kinase downstream of NOD2. We observed that in mice genetically deficient in RIP2, the inhibition of IL-12p35 mRNA expression by MDP in LPS-activated, highly inflammatory peritoneal macrophages was completely lost (Fig. 4a, upper panel, white bars), in comparison to the lack of responses of the p40 (mid-panel) and TNF-α (lower panel) genes in the same cells. The RIP2 dependency is consistent with the previous observation by Biswas et al. that RIP2- and NOD2-deficient mice share the same susceptibility to Helicobacter hepaticus-induced granulomatous inflammation of the ileum, characterized by an increased expression of Th1-related genes and inflammatory cytokines25.


A novel crosstalk between TLR4- and NOD2-mediated signaling in the regulation of intestinal inflammation.

Kim H, Zhao Q, Zheng H, Li X, Zhang T, Ma X - Sci Rep (2015)

RIP2 and c-Rel in NOD2-mediated regulation of IL-12p35 and p40 expression.Thioglycolate-elicited peritoneal macrophages from wild-type (WT), Rip2−/− and Crel−/− mice were stimulated for 6 h with LPS (500 ng/ml) with or without MDP (5 μg/ml). RNA analyses were carried out by real time RT-PCR for (a) IL-12p35 (upper), p40 (middle), and TNF-α (lower). (b) Cytokines were measured from culture supernatant by ELISA for IL-12 (upper) and IL-23 (lower). (c) THP-1 cells were stimulated with LPS for 6 h with a low dose of Bay11–7082 (0.5 μM). Levels of p35 mRNA were analyzed by real-time RT-PCR. Numbers within the bars (22% and 21%, respectively) in MDP-treated cells indicate the percentages of remaining mRNA levels in the presence of Bay11–7082 compared to controls.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4495563&req=5

f4: RIP2 and c-Rel in NOD2-mediated regulation of IL-12p35 and p40 expression.Thioglycolate-elicited peritoneal macrophages from wild-type (WT), Rip2−/− and Crel−/− mice were stimulated for 6 h with LPS (500 ng/ml) with or without MDP (5 μg/ml). RNA analyses were carried out by real time RT-PCR for (a) IL-12p35 (upper), p40 (middle), and TNF-α (lower). (b) Cytokines were measured from culture supernatant by ELISA for IL-12 (upper) and IL-23 (lower). (c) THP-1 cells were stimulated with LPS for 6 h with a low dose of Bay11–7082 (0.5 μM). Levels of p35 mRNA were analyzed by real-time RT-PCR. Numbers within the bars (22% and 21%, respectively) in MDP-treated cells indicate the percentages of remaining mRNA levels in the presence of Bay11–7082 compared to controls.
Mentions: To further delineate the molecular mechanisms underlying NOD2-mediated selective inhibition of IL-12p35 gene transcription, we analyzed macrophages derived from mice deficient in receptor interacting protein 2 (RIP2)24, the protein kinase downstream of NOD2. We observed that in mice genetically deficient in RIP2, the inhibition of IL-12p35 mRNA expression by MDP in LPS-activated, highly inflammatory peritoneal macrophages was completely lost (Fig. 4a, upper panel, white bars), in comparison to the lack of responses of the p40 (mid-panel) and TNF-α (lower panel) genes in the same cells. The RIP2 dependency is consistent with the previous observation by Biswas et al. that RIP2- and NOD2-deficient mice share the same susceptibility to Helicobacter hepaticus-induced granulomatous inflammation of the ileum, characterized by an increased expression of Th1-related genes and inflammatory cytokines25.

Bottom Line: Specifically, NOD2 is able to sense the intensity of TLR4-mediated signaling, resulting in either synergistic stimulation of Interluekin-12 (IL-12) production when the TLR signaling intensity is low; or in the inhibition of IL-12 synthesis and maintenance of intestinal mucosal homeostasis when the TLR signaling intensifies.Additionally, in contrast to the dogma, we find that the major Crohn's disease-associated NOD2 mutations could cause a primarily immunodeficient phenotype by selectively impairing TLR4-mediated IL-12 production and host defense.To restore the impaired homeostasis would be a way forward to developing novel therapeutic strategies for inflammatory bowel diseases.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Microbial Metabolism, Sheng Yushou Center of Cell Biology and Immunology and School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, China 200240.

ABSTRACT
Although Toll-like receptor 4 (TLR4)- and nucleotide-binding oligomerization domain 2 (NOD2)-mediated signaling mechanisms have been extensively studied individually, the crosstalk between them in the regulation of intestinal mucosal defense and tissue homeostasis has been underappreciated. Here, we uncover some novel activities of NOD2 by gene expression profiling revealing the global nature of the cross-regulation between TLR4- and NOD2-mediated signaling. Specifically, NOD2 is able to sense the intensity of TLR4-mediated signaling, resulting in either synergistic stimulation of Interluekin-12 (IL-12) production when the TLR signaling intensity is low; or in the inhibition of IL-12 synthesis and maintenance of intestinal mucosal homeostasis when the TLR signaling intensifies. This balancing act is mediated through receptor-interacting serine/threonine kinase 2, and the transcriptional regulator CCAAT/enhancer-binding protein α (C/EBPα) via its serine 248 phosphorylation by Protein Kinase C. Mice deficient in C/EBPα in the hematopoietic compartment are highly susceptible to chemically induced experimental colitis in an IL-12-dependent manner. Additionally, in contrast to the dogma, we find that the major Crohn's disease-associated NOD2 mutations could cause a primarily immunodeficient phenotype by selectively impairing TLR4-mediated IL-12 production and host defense. To restore the impaired homeostasis would be a way forward to developing novel therapeutic strategies for inflammatory bowel diseases.

No MeSH data available.


Related in: MedlinePlus