A Novel Proteolytic Cascade Generates an Extracellular Matrix-Derived Chemoattractant in Chronic Neutrophilic Inflammation

Abstract

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-α-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.

Increased Expression of Matrix Metalloproteinase-1 in Systemic Vessels of Preeclamptic Women

“…31,32 Interleukin-8 secretion by VSMCs was significantly increased by 0.25-, 2.5-, and 25-ng/ml MMP-1 (P Ͻ 0.01) and collagen type 1 fragments by 2.5-and 25-ng/ml MMP-1 (P Ͻ 0.05 and P Ͻ 0.001, respectively) compared with control ( Figure 3, B and C). Interleukin-8 was primarily responsible for neutrophil migration because migration was significantly inhibited by 82% to 86% in the presence of an IL-8 - neutralizing antibody (P Ͻ 0.001) ( Figure 3A).…”

The effect of the decoy molecule PA401 on CXCL8 levels in bronchoalveolar lavage fluid of patients with cystic fibrosis

“…It is however only one of a number of chemoattractants found in the CF airways. Leukotriene B 4 , formyl peptides, C5a, platelet activating factor (Mackerness et al, 2008) and more recently prolineglycine-proline (Gaggar et al, 2008) are among other chemoattractants that contribute to GAG:CXCL8 interactions in CF BALF samples by PA401 was sufficient to significantly decrease the number of migrating neutrophils in vitro, with the potential for an effective antiinflammatory outcome in vivo.…”

The extracellular matrix in myocardial injury, repair, and remodeling

“…The collagen-derived tripeptide proline-glycine-proline (PGP) and its acetylated form have been demonstrated as acting as neutrophil chemoattractants in models of pulmonary inflammation, signaling through activation of the chemokine receptor CXCR2 (34). PGP generation requires activation of a multistep cascade that involves MMP8, MMP9, and prolyl endopeptidase (35). Proteolytic processing of laminins by MMP2 and MMP14 has also been demonstrated as yielding fragments with potent neutrophil chemoattractant properties (36).…”