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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

Dual-LTA4H activities are functional during Hib infection.129/S6 mice were infected with Hib and weight loss assessed daily (a). Total cell numbers in the airways (b) and lung tissue (c) of Hib-infected mice were measured. Bacterial burden was assessed by performing serial dilutions of BALF (d) and lung homogenate (e) on Brain Heart Infusion agar. The number of neutrophils recruited into the airways (f) and lung tissue (g) of Hib-infected mice was determined by flow cytometry. Mice infected with 1 × 107 Hib were administered control (2A3) or neutrophil-depleting (1A8) antibody, and neutrophil numbers (h) and c.f.u. (i) were assessed at 24 h post infection. The concentration of KC (j) and MIP-2 (k) in the BALF was determined by ELISA. Intracellular epoxide hydrolase activity of BAL cells (l). LTB4 levels in BALF of Hib-infected mice (m). Mice infected with 1 × 107 Hib were administered 2A3 or 1A8 antibody and intracellular epoxide hydrolase activity of BAL cells determined at 24 h post infection (n). Amounts of total MMP-9 (o) in BALF were assessed by ELISA and MMP-9 gelatinolytic activity (p) was assessed by gelatin zymography (representative image depicted: lane 1=naive; 2=1 × 106 6 h; 3=1 × 107 6 h; 4=1 × 106 24 h; 5=1 × 107 24 h; 6=1 × 106 day 3; 7=1 × 107 day 3; 8=1 × 106 day 7; 9=1 × 107 day 7). (q) PE activity in BALF at different times after Hib infection. Mice infected with 1 × 107 Hib were administered 2A3 or 1A8 antibody, and total MMP-9 levels (r) and PE activity (s) in the BALF were determined at 24 h post infection. Total LTA4H levels in BALF were assessed by ELISA at different times post infection (t). BALF, from different time points post Hib infection, was incubated with PGP and degradation was assessed after 2 h by mass spectrometry (u) or release of free proline (v). Mice infected with 1 × 107 Hib were administered 2A3 or 1A8 antibody and PGP degradation by BALF at 24 h was assessed by mass spectrometry (w) or release of free proline (x). Data (mean±s.e.m.) are representative of at least two experiments with 5–6 mice per group.*P<0.05; **P<0.01 using the Mann–Whitney test.
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f1: Dual-LTA4H activities are functional during Hib infection.129/S6 mice were infected with Hib and weight loss assessed daily (a). Total cell numbers in the airways (b) and lung tissue (c) of Hib-infected mice were measured. Bacterial burden was assessed by performing serial dilutions of BALF (d) and lung homogenate (e) on Brain Heart Infusion agar. The number of neutrophils recruited into the airways (f) and lung tissue (g) of Hib-infected mice was determined by flow cytometry. Mice infected with 1 × 107 Hib were administered control (2A3) or neutrophil-depleting (1A8) antibody, and neutrophil numbers (h) and c.f.u. (i) were assessed at 24 h post infection. The concentration of KC (j) and MIP-2 (k) in the BALF was determined by ELISA. Intracellular epoxide hydrolase activity of BAL cells (l). LTB4 levels in BALF of Hib-infected mice (m). Mice infected with 1 × 107 Hib were administered 2A3 or 1A8 antibody and intracellular epoxide hydrolase activity of BAL cells determined at 24 h post infection (n). Amounts of total MMP-9 (o) in BALF were assessed by ELISA and MMP-9 gelatinolytic activity (p) was assessed by gelatin zymography (representative image depicted: lane 1=naive; 2=1 × 106 6 h; 3=1 × 107 6 h; 4=1 × 106 24 h; 5=1 × 107 24 h; 6=1 × 106 day 3; 7=1 × 107 day 3; 8=1 × 106 day 7; 9=1 × 107 day 7). (q) PE activity in BALF at different times after Hib infection. Mice infected with 1 × 107 Hib were administered 2A3 or 1A8 antibody, and total MMP-9 levels (r) and PE activity (s) in the BALF were determined at 24 h post infection. Total LTA4H levels in BALF were assessed by ELISA at different times post infection (t). BALF, from different time points post Hib infection, was incubated with PGP and degradation was assessed after 2 h by mass spectrometry (u) or release of free proline (v). Mice infected with 1 × 107 Hib were administered 2A3 or 1A8 antibody and PGP degradation by BALF at 24 h was assessed by mass spectrometry (w) or release of free proline (x). Data (mean±s.e.m.) are representative of at least two experiments with 5–6 mice per group.*P<0.05; **P<0.01 using the Mann–Whitney test.

Mentions: Infection of 129/S6 mice with Hib elicited a transient, mild weight loss peaking at 24–48 h post infection, which correlated with the size of the inoculating dose of bacteria (Fig. 1a). Coinciding with peak illness was a robust, readily resolving inflammation observed in the airways (Fig. 1b) and lungs (Fig. 1c). Consequently, bacteria were promptly cleared from the airways (Fig. 1d) and lung parenchyma (Fig. 1e) of infected mice. The pulmonary infiltrate was predominantly neutrophilic, with Hib inducing a rapid, dose-dependent, influx of neutrophils peaking at 24 h post infection (Fig. 1f,g). Secondary to this neutrophilic inflammation was a relatively modest infiltration of monocytes/macrophages, natural killer cells and T cells (Supplementary Fig. 1A–E, respectively). Within this system, alveolar macrophages (Supplementary Fig. 1F–H) and neutrophils (Fig. 1h,i) were critical to the clearance of Hib, as their depletion significantly compromised bacterial clearance.


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)

Dual-LTA4H activities are functional during Hib infection.129/S6 mice were infected with Hib and weight loss assessed daily (a). Total cell numbers in the airways (b) and lung tissue (c) of Hib-infected mice were measured. Bacterial burden was assessed by performing serial dilutions of BALF (d) and lung homogenate (e) on Brain Heart Infusion agar. The number of neutrophils recruited into the airways (f) and lung tissue (g) of Hib-infected mice was determined by flow cytometry. Mice infected with 1 × 107 Hib were administered control (2A3) or neutrophil-depleting (1A8) antibody, and neutrophil numbers (h) and c.f.u. (i) were assessed at 24 h post infection. The concentration of KC (j) and MIP-2 (k) in the BALF was determined by ELISA. Intracellular epoxide hydrolase activity of BAL cells (l). LTB4 levels in BALF of Hib-infected mice (m). Mice infected with 1 × 107 Hib were administered 2A3 or 1A8 antibody and intracellular epoxide hydrolase activity of BAL cells determined at 24 h post infection (n). Amounts of total MMP-9 (o) in BALF were assessed by ELISA and MMP-9 gelatinolytic activity (p) was assessed by gelatin zymography (representative image depicted: lane 1=naive; 2=1 × 106 6 h; 3=1 × 107 6 h; 4=1 × 106 24 h; 5=1 × 107 24 h; 6=1 × 106 day 3; 7=1 × 107 day 3; 8=1 × 106 day 7; 9=1 × 107 day 7). (q) PE activity in BALF at different times after Hib infection. Mice infected with 1 × 107 Hib were administered 2A3 or 1A8 antibody, and total MMP-9 levels (r) and PE activity (s) in the BALF were determined at 24 h post infection. Total LTA4H levels in BALF were assessed by ELISA at different times post infection (t). BALF, from different time points post Hib infection, was incubated with PGP and degradation was assessed after 2 h by mass spectrometry (u) or release of free proline (v). Mice infected with 1 × 107 Hib were administered 2A3 or 1A8 antibody and PGP degradation by BALF at 24 h was assessed by mass spectrometry (w) or release of free proline (x). Data (mean±s.e.m.) are representative of at least two experiments with 5–6 mice per group.*P<0.05; **P<0.01 using the Mann–Whitney test.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Dual-LTA4H activities are functional during Hib infection.129/S6 mice were infected with Hib and weight loss assessed daily (a). Total cell numbers in the airways (b) and lung tissue (c) of Hib-infected mice were measured. Bacterial burden was assessed by performing serial dilutions of BALF (d) and lung homogenate (e) on Brain Heart Infusion agar. The number of neutrophils recruited into the airways (f) and lung tissue (g) of Hib-infected mice was determined by flow cytometry. Mice infected with 1 × 107 Hib were administered control (2A3) or neutrophil-depleting (1A8) antibody, and neutrophil numbers (h) and c.f.u. (i) were assessed at 24 h post infection. The concentration of KC (j) and MIP-2 (k) in the BALF was determined by ELISA. Intracellular epoxide hydrolase activity of BAL cells (l). LTB4 levels in BALF of Hib-infected mice (m). Mice infected with 1 × 107 Hib were administered 2A3 or 1A8 antibody and intracellular epoxide hydrolase activity of BAL cells determined at 24 h post infection (n). Amounts of total MMP-9 (o) in BALF were assessed by ELISA and MMP-9 gelatinolytic activity (p) was assessed by gelatin zymography (representative image depicted: lane 1=naive; 2=1 × 106 6 h; 3=1 × 107 6 h; 4=1 × 106 24 h; 5=1 × 107 24 h; 6=1 × 106 day 3; 7=1 × 107 day 3; 8=1 × 106 day 7; 9=1 × 107 day 7). (q) PE activity in BALF at different times after Hib infection. Mice infected with 1 × 107 Hib were administered 2A3 or 1A8 antibody, and total MMP-9 levels (r) and PE activity (s) in the BALF were determined at 24 h post infection. Total LTA4H levels in BALF were assessed by ELISA at different times post infection (t). BALF, from different time points post Hib infection, was incubated with PGP and degradation was assessed after 2 h by mass spectrometry (u) or release of free proline (v). Mice infected with 1 × 107 Hib were administered 2A3 or 1A8 antibody and PGP degradation by BALF at 24 h was assessed by mass spectrometry (w) or release of free proline (x). Data (mean±s.e.m.) are representative of at least two experiments with 5–6 mice per group.*P<0.05; **P<0.01 using the Mann–Whitney test.
Mentions: Infection of 129/S6 mice with Hib elicited a transient, mild weight loss peaking at 24–48 h post infection, which correlated with the size of the inoculating dose of bacteria (Fig. 1a). Coinciding with peak illness was a robust, readily resolving inflammation observed in the airways (Fig. 1b) and lungs (Fig. 1c). Consequently, bacteria were promptly cleared from the airways (Fig. 1d) and lung parenchyma (Fig. 1e) of infected mice. The pulmonary infiltrate was predominantly neutrophilic, with Hib inducing a rapid, dose-dependent, influx of neutrophils peaking at 24 h post infection (Fig. 1f,g). Secondary to this neutrophilic inflammation was a relatively modest infiltration of monocytes/macrophages, natural killer cells and T cells (Supplementary Fig. 1A–E, respectively). Within this system, alveolar macrophages (Supplementary Fig. 1F–H) and neutrophils (Fig. 1h,i) were critical to the clearance of Hib, as their depletion significantly compromised bacterial clearance.

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