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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

Augmented macrophage inflammation in Hib-infected lta4h−/− mice secondary to PGP accumulation and protease discord.Lta4h−/− mice and littermate controls were infected intranasally with 1 × 107 Hib and levels of total MMP-9 (a) and NE (b) were assessed by ELISA in the BALF. Levels of MMP-9 mRNA were assessed in lung tissue by real-time PCR (c). Bone marrow neutrophils were incubated with media alone, IL-8 or AcPGP, and levels of MMP-9 and NE were assessed in the supernatant after 15 min (d). Levels of MMP-12 protein in the BALF were assessed by ELISA (e) and MMP-12 mRNA levels in lung tissue assessed by real-time PCR (f). Lta4h−/− mice and littermate controls infected intranasally with 1 × 107 Hib were administered vehicle or RTR peptide, and the concentration of MMP-9 (g), NE (h) and MMP-12 (i) in the BALF was determined by ELISA at 24 h post infection. To determine the role of elastin-derived chemotactic fragments in driving cellular recruitment, lta4h−/− mice and littermate controls infected intranasally with 1 × 107 Hib were administered control or BA4 (anti-elastin) antibody, and total cell numbers in the airways (j) and lung tissue (k) enumerated at 4 days post infection. In the same experiment, the numbers of infiltrating monocytes/macrophages in the airways (l) and lung tissue (m) was determined by flow cytometry at 4 days post infection. 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,b,e) or are representative of at least two experiments with 5–6 mice per group (g–m). Data (mean±s.d.) are representative of three experiments with at least triplicates (d). *P<0.05; **P<0.01 using the Mann–Whitney test.
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f5: Augmented macrophage inflammation in Hib-infected lta4h−/− mice secondary to PGP accumulation and protease discord.Lta4h−/− mice and littermate controls were infected intranasally with 1 × 107 Hib and levels of total MMP-9 (a) and NE (b) were assessed by ELISA in the BALF. Levels of MMP-9 mRNA were assessed in lung tissue by real-time PCR (c). Bone marrow neutrophils were incubated with media alone, IL-8 or AcPGP, and levels of MMP-9 and NE were assessed in the supernatant after 15 min (d). Levels of MMP-12 protein in the BALF were assessed by ELISA (e) and MMP-12 mRNA levels in lung tissue assessed by real-time PCR (f). Lta4h−/− mice and littermate controls infected intranasally with 1 × 107 Hib were administered vehicle or RTR peptide, and the concentration of MMP-9 (g), NE (h) and MMP-12 (i) in the BALF was determined by ELISA at 24 h post infection. To determine the role of elastin-derived chemotactic fragments in driving cellular recruitment, lta4h−/− mice and littermate controls infected intranasally with 1 × 107 Hib were administered control or BA4 (anti-elastin) antibody, and total cell numbers in the airways (j) and lung tissue (k) enumerated at 4 days post infection. In the same experiment, the numbers of infiltrating monocytes/macrophages in the airways (l) and lung tissue (m) was determined by flow cytometry at 4 days post infection. 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,b,e) or are representative of at least two experiments with 5–6 mice per group (g–m). Data (mean±s.d.) are representative of three experiments with at least triplicates (d). *P<0.05; **P<0.01 using the Mann–Whitney test.

Mentions: In keeping with elevated neutrophilic inflammation in Hib-infected lta4h−/− mice, there was a significant increase in BALF levels of neutrophil-rich proteases MMP-9 (Fig. 5a) and NE (Fig. 5b). Furthermore, there was an augmentation in MMP-9 messenger RNA (mRNA) reflective of the substantial influx of neutrophils richly expressing this protease (Fig. 5c). Stimulation of bone marrow neutrophils with PGP elicited the release of MMP-9 and NE (Fig. 5d), demonstrating that the peptide was not only capable of recruiting neutrophils but also driving the secretion of their products. Intriguingly, Hib-infected lta4h−/− mice also displayed elevated macrophage elastase, MMP-12, levels in BALF (Fig. 5e). MMP-12 is predominantly expressed by alveolar macrophages and not neutrophils. There was no difference in MMP-12 mRNA levels between lta4h−/− mice and littermate controls (Fig. 5f), suggestive that increased levels in the BALF of knockout animals was not due to increased expression but rather release from alveolar macrophages.


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)

Augmented macrophage inflammation in Hib-infected lta4h−/− mice secondary to PGP accumulation and protease discord.Lta4h−/− mice and littermate controls were infected intranasally with 1 × 107 Hib and levels of total MMP-9 (a) and NE (b) were assessed by ELISA in the BALF. Levels of MMP-9 mRNA were assessed in lung tissue by real-time PCR (c). Bone marrow neutrophils were incubated with media alone, IL-8 or AcPGP, and levels of MMP-9 and NE were assessed in the supernatant after 15 min (d). Levels of MMP-12 protein in the BALF were assessed by ELISA (e) and MMP-12 mRNA levels in lung tissue assessed by real-time PCR (f). Lta4h−/− mice and littermate controls infected intranasally with 1 × 107 Hib were administered vehicle or RTR peptide, and the concentration of MMP-9 (g), NE (h) and MMP-12 (i) in the BALF was determined by ELISA at 24 h post infection. To determine the role of elastin-derived chemotactic fragments in driving cellular recruitment, lta4h−/− mice and littermate controls infected intranasally with 1 × 107 Hib were administered control or BA4 (anti-elastin) antibody, and total cell numbers in the airways (j) and lung tissue (k) enumerated at 4 days post infection. In the same experiment, the numbers of infiltrating monocytes/macrophages in the airways (l) and lung tissue (m) was determined by flow cytometry at 4 days post infection. 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,b,e) or are representative of at least two experiments with 5–6 mice per group (g–m). Data (mean±s.d.) are representative of three experiments with at least triplicates (d). *P<0.05; **P<0.01 using the Mann–Whitney test.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4595997&req=5

f5: Augmented macrophage inflammation in Hib-infected lta4h−/− mice secondary to PGP accumulation and protease discord.Lta4h−/− mice and littermate controls were infected intranasally with 1 × 107 Hib and levels of total MMP-9 (a) and NE (b) were assessed by ELISA in the BALF. Levels of MMP-9 mRNA were assessed in lung tissue by real-time PCR (c). Bone marrow neutrophils were incubated with media alone, IL-8 or AcPGP, and levels of MMP-9 and NE were assessed in the supernatant after 15 min (d). Levels of MMP-12 protein in the BALF were assessed by ELISA (e) and MMP-12 mRNA levels in lung tissue assessed by real-time PCR (f). Lta4h−/− mice and littermate controls infected intranasally with 1 × 107 Hib were administered vehicle or RTR peptide, and the concentration of MMP-9 (g), NE (h) and MMP-12 (i) in the BALF was determined by ELISA at 24 h post infection. To determine the role of elastin-derived chemotactic fragments in driving cellular recruitment, lta4h−/− mice and littermate controls infected intranasally with 1 × 107 Hib were administered control or BA4 (anti-elastin) antibody, and total cell numbers in the airways (j) and lung tissue (k) enumerated at 4 days post infection. In the same experiment, the numbers of infiltrating monocytes/macrophages in the airways (l) and lung tissue (m) was determined by flow cytometry at 4 days post infection. 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,b,e) or are representative of at least two experiments with 5–6 mice per group (g–m). Data (mean±s.d.) are representative of three experiments with at least triplicates (d). *P<0.05; **P<0.01 using the Mann–Whitney test.
Mentions: In keeping with elevated neutrophilic inflammation in Hib-infected lta4h−/− mice, there was a significant increase in BALF levels of neutrophil-rich proteases MMP-9 (Fig. 5a) and NE (Fig. 5b). Furthermore, there was an augmentation in MMP-9 messenger RNA (mRNA) reflective of the substantial influx of neutrophils richly expressing this protease (Fig. 5c). Stimulation of bone marrow neutrophils with PGP elicited the release of MMP-9 and NE (Fig. 5d), demonstrating that the peptide was not only capable of recruiting neutrophils but also driving the secretion of their products. Intriguingly, Hib-infected lta4h−/− mice also displayed elevated macrophage elastase, MMP-12, levels in BALF (Fig. 5e). MMP-12 is predominantly expressed by alveolar macrophages and not neutrophils. There was no difference in MMP-12 mRNA levels between lta4h−/− mice and littermate controls (Fig. 5f), suggestive that increased levels in the BALF of knockout animals was not due to increased expression but rather release from alveolar macrophages.

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