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An NK Cell Perforin Response Elicited via IL-18 Controls Mucosal Inflammation Kinetics during Salmonella Gut Infection.

Müller AA, Dolowschiak T, Sellin ME, Felmy B, Verbree C, Gadient S, Westermann AJ, Vogel J, LeibundGut-Landmann S, Hardt WD - PLoS Pathog. (2016)

Bottom Line: IL-18 boosted NK cell chemoattractants and enhanced the NK cells' migratory capacity, thus promoting mucosal accumulation of mature, activated NK cells.NK cell depletion and Prf-/- ablation (but not granulocyte-depletion or T-cell deficiency) delayed tissue inflammation.This may have broad relevance for mucosal defense against microbial pathogens.

View Article: PubMed Central - PubMed

Affiliation: Institute of Microbiology, ETH Zürich, Zürich, Switzerland.

ABSTRACT
Salmonella Typhimurium (S.Tm) is a common cause of self-limiting diarrhea. The mucosal inflammation is thought to arise from a standoff between the pathogen's virulence factors and the host's mucosal innate immune defenses, particularly the mucosal NAIP/NLRC4 inflammasome. However, it had remained unclear how this switches the gut from homeostasis to inflammation. This was studied using the streptomycin mouse model. S.Tm infections in knockout mice, cytokine inhibition and -injection experiments revealed that caspase-1 (not -11) dependent IL-18 is pivotal for inducing acute inflammation. IL-18 boosted NK cell chemoattractants and enhanced the NK cells' migratory capacity, thus promoting mucosal accumulation of mature, activated NK cells. NK cell depletion and Prf-/- ablation (but not granulocyte-depletion or T-cell deficiency) delayed tissue inflammation. Our data suggest an NK cell perforin response as one limiting factor in mounting gut mucosal inflammation. Thus, IL-18-elicited NK cell perforin responses seem to be critical for coordinating mucosal inflammation during early infection, when S.Tm strongly relies on virulence factors detectable by the inflammasome. This may have broad relevance for mucosal defense against microbial pathogens.

No MeSH data available.


Related in: MedlinePlus

Neutrophil recruitment into the infected mucosa is decreased in absence of IL-18 but neutrophil depletion does not seem to be a main driver during the initiation of mucosal inflammation.(a) Il18-/- mice and littermate controls were Sm-pretreated, infected orally with 5x107 CFU S.Tm for 12h (n = 3–4 per group). RNA-Seq was performed on RNA extracted from complete cecum tissue. RNA-Seq analysis: The Volcano plot shows the induction (log2 fold change) versus the -log10 p-value for all chemokines. Chemokines able to induce neutrophil recruitment are highlighted in green. (b) C57BL/6 WT mice and Il18-/- mice and littermates were Sm-pretreated and either uninfected (WT) or infected orally with 5x107 CFU S.Tm for 12h (n = 4–5 per group). Cxcl1 and Cxcl2 mRNA levels in whole cecum tissue were measured by RT-qPCR. Results are presented relative to the expression of Actb. (c and d) Flow cytometric analysis of isolated cecal LP cells from Sm-pretreated C57BL/6 WT mice, either uninfected or infected with 5x107 CFU S.Tm (n = 6 per group). Single live cells were gated on CD45+CD3-CD19-CD11b+ cells. (c) Representative dot plots and (d) quantification of Ly-6G+ cells. (e and f) Flow cytometric analysis of isolated cecal LP cells from Il18-/- mice and littermates, Sm-pretreated and orally infected with 5x107 CFU S.Tm for 12h (n = 8 per group). Single live cells were gated on CD45+CD3-CD19-CD11b+ cells. (e) Representative dot plots and (f) quantification of Ly-6G+ cells. (g and h) C57BL/6 WT mice were injected intraperitoneally with anti-G-CSF (0.4mg/kg; two consecutive days) and anti-Ly-6G (6mg/kg; two days prior to infection) or PBS. Mice were Sm-pretreated and infected orally with 5x107 CFU S.Tm for 12h (n = 6 per group). (g) Pathological score and (h) representative HE-stained cryosection. Data represent the mean ± SD and statistical analysis was performed using the Mann-Whitney-U test (ns = not significant, *: p<0.05; **: p<0.01).
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ppat.1005723.g002: Neutrophil recruitment into the infected mucosa is decreased in absence of IL-18 but neutrophil depletion does not seem to be a main driver during the initiation of mucosal inflammation.(a) Il18-/- mice and littermate controls were Sm-pretreated, infected orally with 5x107 CFU S.Tm for 12h (n = 3–4 per group). RNA-Seq was performed on RNA extracted from complete cecum tissue. RNA-Seq analysis: The Volcano plot shows the induction (log2 fold change) versus the -log10 p-value for all chemokines. Chemokines able to induce neutrophil recruitment are highlighted in green. (b) C57BL/6 WT mice and Il18-/- mice and littermates were Sm-pretreated and either uninfected (WT) or infected orally with 5x107 CFU S.Tm for 12h (n = 4–5 per group). Cxcl1 and Cxcl2 mRNA levels in whole cecum tissue were measured by RT-qPCR. Results are presented relative to the expression of Actb. (c and d) Flow cytometric analysis of isolated cecal LP cells from Sm-pretreated C57BL/6 WT mice, either uninfected or infected with 5x107 CFU S.Tm (n = 6 per group). Single live cells were gated on CD45+CD3-CD19-CD11b+ cells. (c) Representative dot plots and (d) quantification of Ly-6G+ cells. (e and f) Flow cytometric analysis of isolated cecal LP cells from Il18-/- mice and littermates, Sm-pretreated and orally infected with 5x107 CFU S.Tm for 12h (n = 8 per group). Single live cells were gated on CD45+CD3-CD19-CD11b+ cells. (e) Representative dot plots and (f) quantification of Ly-6G+ cells. (g and h) C57BL/6 WT mice were injected intraperitoneally with anti-G-CSF (0.4mg/kg; two consecutive days) and anti-Ly-6G (6mg/kg; two days prior to infection) or PBS. Mice were Sm-pretreated and infected orally with 5x107 CFU S.Tm for 12h (n = 6 per group). (g) Pathological score and (h) representative HE-stained cryosection. Data represent the mean ± SD and statistical analysis was performed using the Mann-Whitney-U test (ns = not significant, *: p<0.05; **: p<0.01).

Mentions: Cytokine and chemokine response patterns can provide cues about underlying immunological processes. To elucidate how IL-18 affects the mounting of gut inflammation, we therefore collected infected cecum tissue samples from IL-18-deficient mice and littermate controls (12h p.i., 5x107 CFU S.Tm) and performed transcriptional profiling by RNA-Seq. In total, mRNA levels for more than 200 genes were reduced in IL-18-deficient mice compared to the littermate controls (for a complete list of significantly regulated genes, see S1 Table). Many of those differentially expressed genes belonged to pathways involved in general pro-inflammatory responses, immunity to infection as well as chemokine and cytokine signaling. One group of these IL-18 dependent chemokines is known to coordinate the recruitment of neutrophils to sites of infection (Fig 2a, depicted in green). The accumulation of neutrophils in the infected mucosa is a hallmark of S.Tm-induced tissue inflammation [16, 33] and represents a key line of pathogen defense in the cecum lumen, the cecum tissue as well as at systemic sites at later stages of the infection [34–39]. However, their function in eliciting mucosal inflammation had remained unclear. We speculated that reduced neutrophil recruitment in IL-18-deficient mice could explain their delayed onset of mucosal pathology.


An NK Cell Perforin Response Elicited via IL-18 Controls Mucosal Inflammation Kinetics during Salmonella Gut Infection.

Müller AA, Dolowschiak T, Sellin ME, Felmy B, Verbree C, Gadient S, Westermann AJ, Vogel J, LeibundGut-Landmann S, Hardt WD - PLoS Pathog. (2016)

Neutrophil recruitment into the infected mucosa is decreased in absence of IL-18 but neutrophil depletion does not seem to be a main driver during the initiation of mucosal inflammation.(a) Il18-/- mice and littermate controls were Sm-pretreated, infected orally with 5x107 CFU S.Tm for 12h (n = 3–4 per group). RNA-Seq was performed on RNA extracted from complete cecum tissue. RNA-Seq analysis: The Volcano plot shows the induction (log2 fold change) versus the -log10 p-value for all chemokines. Chemokines able to induce neutrophil recruitment are highlighted in green. (b) C57BL/6 WT mice and Il18-/- mice and littermates were Sm-pretreated and either uninfected (WT) or infected orally with 5x107 CFU S.Tm for 12h (n = 4–5 per group). Cxcl1 and Cxcl2 mRNA levels in whole cecum tissue were measured by RT-qPCR. Results are presented relative to the expression of Actb. (c and d) Flow cytometric analysis of isolated cecal LP cells from Sm-pretreated C57BL/6 WT mice, either uninfected or infected with 5x107 CFU S.Tm (n = 6 per group). Single live cells were gated on CD45+CD3-CD19-CD11b+ cells. (c) Representative dot plots and (d) quantification of Ly-6G+ cells. (e and f) Flow cytometric analysis of isolated cecal LP cells from Il18-/- mice and littermates, Sm-pretreated and orally infected with 5x107 CFU S.Tm for 12h (n = 8 per group). Single live cells were gated on CD45+CD3-CD19-CD11b+ cells. (e) Representative dot plots and (f) quantification of Ly-6G+ cells. (g and h) C57BL/6 WT mice were injected intraperitoneally with anti-G-CSF (0.4mg/kg; two consecutive days) and anti-Ly-6G (6mg/kg; two days prior to infection) or PBS. Mice were Sm-pretreated and infected orally with 5x107 CFU S.Tm for 12h (n = 6 per group). (g) Pathological score and (h) representative HE-stained cryosection. Data represent the mean ± SD and statistical analysis was performed using the Mann-Whitney-U test (ns = not significant, *: p<0.05; **: p<0.01).
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ppat.1005723.g002: Neutrophil recruitment into the infected mucosa is decreased in absence of IL-18 but neutrophil depletion does not seem to be a main driver during the initiation of mucosal inflammation.(a) Il18-/- mice and littermate controls were Sm-pretreated, infected orally with 5x107 CFU S.Tm for 12h (n = 3–4 per group). RNA-Seq was performed on RNA extracted from complete cecum tissue. RNA-Seq analysis: The Volcano plot shows the induction (log2 fold change) versus the -log10 p-value for all chemokines. Chemokines able to induce neutrophil recruitment are highlighted in green. (b) C57BL/6 WT mice and Il18-/- mice and littermates were Sm-pretreated and either uninfected (WT) or infected orally with 5x107 CFU S.Tm for 12h (n = 4–5 per group). Cxcl1 and Cxcl2 mRNA levels in whole cecum tissue were measured by RT-qPCR. Results are presented relative to the expression of Actb. (c and d) Flow cytometric analysis of isolated cecal LP cells from Sm-pretreated C57BL/6 WT mice, either uninfected or infected with 5x107 CFU S.Tm (n = 6 per group). Single live cells were gated on CD45+CD3-CD19-CD11b+ cells. (c) Representative dot plots and (d) quantification of Ly-6G+ cells. (e and f) Flow cytometric analysis of isolated cecal LP cells from Il18-/- mice and littermates, Sm-pretreated and orally infected with 5x107 CFU S.Tm for 12h (n = 8 per group). Single live cells were gated on CD45+CD3-CD19-CD11b+ cells. (e) Representative dot plots and (f) quantification of Ly-6G+ cells. (g and h) C57BL/6 WT mice were injected intraperitoneally with anti-G-CSF (0.4mg/kg; two consecutive days) and anti-Ly-6G (6mg/kg; two days prior to infection) or PBS. Mice were Sm-pretreated and infected orally with 5x107 CFU S.Tm for 12h (n = 6 per group). (g) Pathological score and (h) representative HE-stained cryosection. Data represent the mean ± SD and statistical analysis was performed using the Mann-Whitney-U test (ns = not significant, *: p<0.05; **: p<0.01).
Mentions: Cytokine and chemokine response patterns can provide cues about underlying immunological processes. To elucidate how IL-18 affects the mounting of gut inflammation, we therefore collected infected cecum tissue samples from IL-18-deficient mice and littermate controls (12h p.i., 5x107 CFU S.Tm) and performed transcriptional profiling by RNA-Seq. In total, mRNA levels for more than 200 genes were reduced in IL-18-deficient mice compared to the littermate controls (for a complete list of significantly regulated genes, see S1 Table). Many of those differentially expressed genes belonged to pathways involved in general pro-inflammatory responses, immunity to infection as well as chemokine and cytokine signaling. One group of these IL-18 dependent chemokines is known to coordinate the recruitment of neutrophils to sites of infection (Fig 2a, depicted in green). The accumulation of neutrophils in the infected mucosa is a hallmark of S.Tm-induced tissue inflammation [16, 33] and represents a key line of pathogen defense in the cecum lumen, the cecum tissue as well as at systemic sites at later stages of the infection [34–39]. However, their function in eliciting mucosal inflammation had remained unclear. We speculated that reduced neutrophil recruitment in IL-18-deficient mice could explain their delayed onset of mucosal pathology.

Bottom Line: IL-18 boosted NK cell chemoattractants and enhanced the NK cells' migratory capacity, thus promoting mucosal accumulation of mature, activated NK cells.NK cell depletion and Prf-/- ablation (but not granulocyte-depletion or T-cell deficiency) delayed tissue inflammation.This may have broad relevance for mucosal defense against microbial pathogens.

View Article: PubMed Central - PubMed

Affiliation: Institute of Microbiology, ETH Zürich, Zürich, Switzerland.

ABSTRACT
Salmonella Typhimurium (S.Tm) is a common cause of self-limiting diarrhea. The mucosal inflammation is thought to arise from a standoff between the pathogen's virulence factors and the host's mucosal innate immune defenses, particularly the mucosal NAIP/NLRC4 inflammasome. However, it had remained unclear how this switches the gut from homeostasis to inflammation. This was studied using the streptomycin mouse model. S.Tm infections in knockout mice, cytokine inhibition and -injection experiments revealed that caspase-1 (not -11) dependent IL-18 is pivotal for inducing acute inflammation. IL-18 boosted NK cell chemoattractants and enhanced the NK cells' migratory capacity, thus promoting mucosal accumulation of mature, activated NK cells. NK cell depletion and Prf-/- ablation (but not granulocyte-depletion or T-cell deficiency) delayed tissue inflammation. Our data suggest an NK cell perforin response as one limiting factor in mounting gut mucosal inflammation. Thus, IL-18-elicited NK cell perforin responses seem to be critical for coordinating mucosal inflammation during early infection, when S.Tm strongly relies on virulence factors detectable by the inflammasome. This may have broad relevance for mucosal defense against microbial pathogens.

No MeSH data available.


Related in: MedlinePlus