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Matrikines are key regulators in modulating the amplitude of lung inflammation in acute pulmonary infection.

Akthar S, Patel DF, Beale RC, Peiró T, Xu X, Gaggar A, Jackson PL, Blalock JE, Lloyd CM, Snelgrove RJ - Nat Commun (2015)

Bottom Line: The physiological significance of this secondary anti-inflammatory activity remains unknown.Here we show, using readily resolving pulmonary inflammation models, that loss of this secondary activity leads to more pronounced and sustained inflammation and illness owing to PGP accumulation.This highlights a critical role for the secondary anti-inflammatory activity of LTA4H and thus has consequences for the generation of global LTA4H inhibitors currently being developed.

View Article: PubMed Central - PubMed

Affiliation: Leukocyte Biology Section, National Heart and Lung Institute, Imperial College London, London SW7 2AZ, UK.

ABSTRACT
Bioactive matrix fragments (matrikines) have been identified in a myriad of disorders, but their impact on the evolution of airway inflammation has not been demonstrated. We recently described a pathway where the matrikine and neutrophil chemoattractant proline-glycine-proline (PGP) could be degraded by the enzyme leukotriene A4 hydrolase (LTA4H). LTA4H classically functions in the generation of pro-inflammatory leukotriene B4, thus LTA4H exhibits opposing pro- and anti-inflammatory activities. The physiological significance of this secondary anti-inflammatory activity remains unknown. Here we show, using readily resolving pulmonary inflammation models, that loss of this secondary activity leads to more pronounced and sustained inflammation and illness owing to PGP accumulation. PGP elicits an exacerbated neutrophilic inflammation and protease imbalance that further degrades the extracellular matrix, generating fragments that perpetuate inflammation. This highlights a critical role for the secondary anti-inflammatory activity of LTA4H and thus has consequences for the generation of global LTA4H inhibitors currently being developed.

No MeSH data available.


Related in: MedlinePlus

Failure to degrade PGP drives an exacerbated neutrophilic inflammation in response to Hib infection.Lta4h−/− mice and littermate controls were infected intranasally with 1 × 107 Hib and the concentration of LTB4 (a), KC (b), MIP-2 (c), TNF-α (d) and IL-6 (e) in the BALF was determined. The concentration of PGP in BALF was determined by ESI–LC/MS/MS (f). BALF from different time points post Hib infection was incubated with PGP and degradation was assessed after 2 h by mass spectrometry (g) or release of free proline (h). Mice were infected intranasally with 1 × 107 Hib and 2 h later treated intranasally with AcPGP or control peptide, AcPGG, and at 24 h post infection the number of neutrophils recruited into airways was determined by flow cytometry (i) and the bacterial burden in the BALF was assessed by performing serial dilutions on Brain Heart Infusion (BHI) agar plates (j). Lta4h−/− mice and littermate controls infected intranasally with 1 × 107 Hib were administered vehicle or RTR peptide, and the concentration of PGP in BALF was determined by ESI–LC/MS/MS (k). Total cell numbers in the airways (l) and lung tissue (m) enumerated at 24 h post infection. Bacterial burden at this time point was assessed by performing serial dilutions of lung homogenate (n) on BHI agar plates. The number of neutrophils recruited into the airways (o) and lung tissue (p) of Hib-infected mice was determined by flow cytometry. The concentration of TNF-α (q) and IL-6 (r) in the BALF was determined by ELISA. Data (mean±s.e.m.) are combined from two separate experiments with 4–5 mice per group and are representative of 3–4 experiments (a–h) or are representative of at least two experiments with 5–6 mice per group (i–r). *P<0.05; **P<0.01 using the Mann–Whitney test.
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f4: Failure to degrade PGP drives an exacerbated neutrophilic inflammation in response to Hib infection.Lta4h−/− mice and littermate controls were infected intranasally with 1 × 107 Hib and the concentration of LTB4 (a), KC (b), MIP-2 (c), TNF-α (d) and IL-6 (e) in the BALF was determined. The concentration of PGP in BALF was determined by ESI–LC/MS/MS (f). BALF from different time points post Hib infection was incubated with PGP and degradation was assessed after 2 h by mass spectrometry (g) or release of free proline (h). Mice were infected intranasally with 1 × 107 Hib and 2 h later treated intranasally with AcPGP or control peptide, AcPGG, and at 24 h post infection the number of neutrophils recruited into airways was determined by flow cytometry (i) and the bacterial burden in the BALF was assessed by performing serial dilutions on Brain Heart Infusion (BHI) agar plates (j). Lta4h−/− mice and littermate controls infected intranasally with 1 × 107 Hib were administered vehicle or RTR peptide, and the concentration of PGP in BALF was determined by ESI–LC/MS/MS (k). Total cell numbers in the airways (l) and lung tissue (m) enumerated at 24 h post infection. Bacterial burden at this time point was assessed by performing serial dilutions of lung homogenate (n) on BHI agar plates. The number of neutrophils recruited into the airways (o) and lung tissue (p) of Hib-infected mice was determined by flow cytometry. The concentration of TNF-α (q) and IL-6 (r) in the BALF was determined by ELISA. Data (mean±s.e.m.) are combined from two separate experiments with 4–5 mice per group and are representative of 3–4 experiments (a–h) or are representative of at least two experiments with 5–6 mice per group (i–r). *P<0.05; **P<0.01 using the Mann–Whitney test.

Mentions: The augmented neutrophilic inflammation observed in Hib-infected lta4h−/− mice, despite the absence of LTB4 (Fig. 4a), was not attributable to an elevation in KC and MIP-2 since levels in BALF (Fig. 4b,c) were comparable between WT and lta4h−/− mice. Other neutrophil chemoattractants C5a, lungkine/CXCL15 and ENA-78/CXCL5 were also comparable between WT and lta4h−/− mice (Supplementary Fig. 4A–C). Levels of pro-inflammatory cytokines tumour-necrosis factor (TNF)-α (Fig. 4d) and IL-6 (Fig. 4e), which can regulate neutrophil recruitment, were elevated at 24 h in Hib-infected lta4h−/− mice, but seemed insufficient alone to drive the observed phenotype. However, while no PGP was detectable in the BALF of Hib-infected WT mice, significant quantities were present in lta4h−/− animals (Fig. 4f). Accordingly, the capacity of BALF to degrade PGP was absent in Hib-infected lta4h−/− mice (Fig. 4g,h). PGP administration to Hib-infected WT mice augmented airway neutrophilia (Fig. 4i) and promoted bacterial clearance (Fig. 4j), supporting the notion that the phenotype of the lta4h−/− animals could be attributable to PGP accumulation.


Matrikines are key regulators in modulating the amplitude of lung inflammation in acute pulmonary infection.

Akthar S, Patel DF, Beale RC, Peiró T, Xu X, Gaggar A, Jackson PL, Blalock JE, Lloyd CM, Snelgrove RJ - Nat Commun (2015)

Failure to degrade PGP drives an exacerbated neutrophilic inflammation in response to Hib infection.Lta4h−/− mice and littermate controls were infected intranasally with 1 × 107 Hib and the concentration of LTB4 (a), KC (b), MIP-2 (c), TNF-α (d) and IL-6 (e) in the BALF was determined. The concentration of PGP in BALF was determined by ESI–LC/MS/MS (f). BALF from different time points post Hib infection was incubated with PGP and degradation was assessed after 2 h by mass spectrometry (g) or release of free proline (h). Mice were infected intranasally with 1 × 107 Hib and 2 h later treated intranasally with AcPGP or control peptide, AcPGG, and at 24 h post infection the number of neutrophils recruited into airways was determined by flow cytometry (i) and the bacterial burden in the BALF was assessed by performing serial dilutions on Brain Heart Infusion (BHI) agar plates (j). Lta4h−/− mice and littermate controls infected intranasally with 1 × 107 Hib were administered vehicle or RTR peptide, and the concentration of PGP in BALF was determined by ESI–LC/MS/MS (k). Total cell numbers in the airways (l) and lung tissue (m) enumerated at 24 h post infection. Bacterial burden at this time point was assessed by performing serial dilutions of lung homogenate (n) on BHI agar plates. The number of neutrophils recruited into the airways (o) and lung tissue (p) of Hib-infected mice was determined by flow cytometry. The concentration of TNF-α (q) and IL-6 (r) in the BALF was determined by ELISA. Data (mean±s.e.m.) are combined from two separate experiments with 4–5 mice per group and are representative of 3–4 experiments (a–h) or are representative of at least two experiments with 5–6 mice per group (i–r). *P<0.05; **P<0.01 using the Mann–Whitney test.
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f4: Failure to degrade PGP drives an exacerbated neutrophilic inflammation in response to Hib infection.Lta4h−/− mice and littermate controls were infected intranasally with 1 × 107 Hib and the concentration of LTB4 (a), KC (b), MIP-2 (c), TNF-α (d) and IL-6 (e) in the BALF was determined. The concentration of PGP in BALF was determined by ESI–LC/MS/MS (f). BALF from different time points post Hib infection was incubated with PGP and degradation was assessed after 2 h by mass spectrometry (g) or release of free proline (h). Mice were infected intranasally with 1 × 107 Hib and 2 h later treated intranasally with AcPGP or control peptide, AcPGG, and at 24 h post infection the number of neutrophils recruited into airways was determined by flow cytometry (i) and the bacterial burden in the BALF was assessed by performing serial dilutions on Brain Heart Infusion (BHI) agar plates (j). Lta4h−/− mice and littermate controls infected intranasally with 1 × 107 Hib were administered vehicle or RTR peptide, and the concentration of PGP in BALF was determined by ESI–LC/MS/MS (k). Total cell numbers in the airways (l) and lung tissue (m) enumerated at 24 h post infection. Bacterial burden at this time point was assessed by performing serial dilutions of lung homogenate (n) on BHI agar plates. The number of neutrophils recruited into the airways (o) and lung tissue (p) of Hib-infected mice was determined by flow cytometry. The concentration of TNF-α (q) and IL-6 (r) in the BALF was determined by ELISA. Data (mean±s.e.m.) are combined from two separate experiments with 4–5 mice per group and are representative of 3–4 experiments (a–h) or are representative of at least two experiments with 5–6 mice per group (i–r). *P<0.05; **P<0.01 using the Mann–Whitney test.
Mentions: The augmented neutrophilic inflammation observed in Hib-infected lta4h−/− mice, despite the absence of LTB4 (Fig. 4a), was not attributable to an elevation in KC and MIP-2 since levels in BALF (Fig. 4b,c) were comparable between WT and lta4h−/− mice. Other neutrophil chemoattractants C5a, lungkine/CXCL15 and ENA-78/CXCL5 were also comparable between WT and lta4h−/− mice (Supplementary Fig. 4A–C). Levels of pro-inflammatory cytokines tumour-necrosis factor (TNF)-α (Fig. 4d) and IL-6 (Fig. 4e), which can regulate neutrophil recruitment, were elevated at 24 h in Hib-infected lta4h−/− mice, but seemed insufficient alone to drive the observed phenotype. However, while no PGP was detectable in the BALF of Hib-infected WT mice, significant quantities were present in lta4h−/− animals (Fig. 4f). Accordingly, the capacity of BALF to degrade PGP was absent in Hib-infected lta4h−/− mice (Fig. 4g,h). PGP administration to Hib-infected WT mice augmented airway neutrophilia (Fig. 4i) and promoted bacterial clearance (Fig. 4j), supporting the notion that the phenotype of the lta4h−/− animals could be attributable to PGP accumulation.

Bottom Line: The physiological significance of this secondary anti-inflammatory activity remains unknown.Here we show, using readily resolving pulmonary inflammation models, that loss of this secondary activity leads to more pronounced and sustained inflammation and illness owing to PGP accumulation.This highlights a critical role for the secondary anti-inflammatory activity of LTA4H and thus has consequences for the generation of global LTA4H inhibitors currently being developed.

View Article: PubMed Central - PubMed

Affiliation: Leukocyte Biology Section, National Heart and Lung Institute, Imperial College London, London SW7 2AZ, UK.

ABSTRACT
Bioactive matrix fragments (matrikines) have been identified in a myriad of disorders, but their impact on the evolution of airway inflammation has not been demonstrated. We recently described a pathway where the matrikine and neutrophil chemoattractant proline-glycine-proline (PGP) could be degraded by the enzyme leukotriene A4 hydrolase (LTA4H). LTA4H classically functions in the generation of pro-inflammatory leukotriene B4, thus LTA4H exhibits opposing pro- and anti-inflammatory activities. The physiological significance of this secondary anti-inflammatory activity remains unknown. Here we show, using readily resolving pulmonary inflammation models, that loss of this secondary activity leads to more pronounced and sustained inflammation and illness owing to PGP accumulation. PGP elicits an exacerbated neutrophilic inflammation and protease imbalance that further degrades the extracellular matrix, generating fragments that perpetuate inflammation. This highlights a critical role for the secondary anti-inflammatory activity of LTA4H and thus has consequences for the generation of global LTA4H inhibitors currently being developed.

No MeSH data available.


Related in: MedlinePlus