A novel proteolytic cascade generates an extracellular matrix-derived chemoattractant in chronic neutrophilic inflammation.
Chronic neutrophilic inflammation is a manifestation of a variety of lung diseases including cystic fibrosis (CF). There is increasing evidence that fragments of extracellular matrix proteins, such as collagen and elastin, play an important role in inflammatory cell recruitment to the lung in animal models of airway inflammation. Unfortunately, the association of these peptides with human disease and the identification of therapeutic targets directed toward these inflammatory pathways have remained elusive. In this study, we demonstrate that a novel extracellular matrix-derived neutrophil chemoattractant, proline-glycine-proline (PGP), acts through CXC receptors 1 and 2 on neutrophils, similar to N-acetylated proline-glycine-proline (N-alpha-PGP). We describe the specific multistep proteolytic pathway involved in PGP generation from collagen, involving matrix metalloproteases 8 and 9 and prolyl endopeptidase, a serine protease for which we identify a novel role in inflammation. PGP generation correlates closely with airway neutrophil counts after administration of proteases in vivo. Using CF as a model, we show that CF sputum has elevated levels of PGP peptides and that PGP levels decline during the course of CF inpatient therapy for acute pulmonary exacerbation, pointing to its role as a novel biomarker for this disease. Finally, we demonstrate that CF secretions are capable of generating PGP from collagen ex vivo and that this generation is significantly attenuated by the use of inhibitors directed toward matrix metalloprotease 8, matrix metalloprotease 9, or prolyl endopeptidase. These experiments highlight unique protease interactions with structural proteins regulating innate immunity and support a role for these peptides as novel biomarkers and therapeutic targets for chronic, neutrophilic lung diseases.
Gaggar
Amit
A
Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA. agaggar@uab.edu
Jackson
Patricia L
PL
Noerager
Brett D
BD
O'Reilly
Philip J
PJ
McQuaid
D Brent
DB
Rowe
Steven M
SM
Clancy
J P
JP
Blalock
J Edwin
JE
D000818:Animals; D002630:Chemotactic Factors / Q000276:immunology / Q000378:metabolism; D002634:Chemotaxis, Leukocyte; D002908:Chronic Disease; D003550:Cystic Fibrosis / Q000276:immunology / Q000378:metabolism*; D005109:Extracellular Matrix / Q000276:immunology / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D006801:Humans; D007249:Inflammation / Q000276:immunology / Q000378:metabolism*; D020784:Matrix Metalloproteinase 8 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D051379:Mice; D018375:Neutrophil Activation; D009504:Neutrophils / Q000276:immunology / Q000378:metabolism*; D009842:Oligopeptides / Q000378:metabolism*; D011392:Proline / Q000031:analogs & derivatives* / Q000378:metabolism; D000085822:Prolyl Oligopeptidases; D023062:Receptors, Interleukin-8A / Q000378:metabolism; D023063:Receptors, Interleukin-8B / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism*; D013183:Sputum / Q000276:immunology / Q000378:metabolism
D002630:Chemotactic Factors; D016326:Extracellular Matrix Proteins; D009842:Oligopeptides; D023062:Receptors, Interleukin-8A; D023063:Receptors, Interleukin-8B; C113164:prolyl-glycyl-proline; D011392:Proline; D012697:Serine Endopeptidases; C000705287:PREPL protein, human; D000085822:Prolyl Oligopeptidases; D020784:Matrix Metalloproteinase 8; D020780:Matrix Metalloproteinase 9