Abstract
Introduction: Our group has previously characterized N-acetyl-Pro-Gly-Pro (Ac-PGP) as an important neutrophil (PMN) chemoattractant generated through collagen degradation by matrix metalloproteinase-9 (MMP-9). MMP-9 is present in PMN granules but whether Ac-PGP regulates MMP-9 release from these cells is unknown.
Aims: The aim of this study was to determine if Ac-PGP can mediate MMP-9 release from PMNs and to highlight the pathways which regulate this response.
Methods: Primary human blood PMNs were pretreated with and without an ERK1/2 MAPK inhibitor (U0126) or the CXCR1/CXCR2 inhibitor Repertaxin and then incubated with Ac-PGP. The cell supernatants and lysates were analyzed for MMP-9 levels and intracellular pathway activation, respectively. In addition, after stimultating PMNs with C13, N15 labeled Ac-PGP, supernatants were incubated overnight with type I collagen to measure the ongoing generation of Ac-PGP.
Results: We found that Ac-PGP induced significant release of MMP-9 (in a dose- and time-dependent manner) and activated the ERK1/2 MAPK pathway. This MMP-9 release was attenuated by an inhibitor of ERK1/2 and upstream blockade of CXCR1/CXCR2 with Repertaxin led to decreased MMP-9 release and ERK 1/2 activation. Supernatants obtained from PMNs stimulated by C13 N15 labeled Ac-PGP generated increased endogenous Ac-PGP when incubated with intact collagen; this effect was inhibited by an ERK1/2 pathway inhibitor.
Conclusions: These data indicate that ECM-derived Ac-PGP results in MMP-9 release from activated PMNs through the ligation of CXCR1 and CXCR2 and subsequent activation of the ERK1/2 MAPK, demonstrating a new pathway of matrikine-mediated protease regulation and subsequent “feed-forward” Ac-PGP production.
- © 2011 ERS