PLoS ONE (Jan 2014)

Mononuclear phagocytes and airway epithelial cells: novel sources of matrix metalloproteinase-8 (MMP-8) in patients with idiopathic pulmonary fibrosis.

  • Vanessa J Craig,
  • Francesca Polverino,
  • Maria E Laucho-Contreras,
  • Yuanyuan Shi,
  • Yushi Liu,
  • Juan C Osorio,
  • Yohannes Tesfaigzi,
  • Victor Pinto-Plata,
  • Bernadette R Gochuico,
  • Ivan O Rosas,
  • Caroline A Owen

DOI
https://doi.org/10.1371/journal.pone.0097485
Journal volume & issue
Vol. 9, no. 5
p. e97485

Abstract

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OBJECTIVES:Matrix metalloproteinase-8 (MMP-8) promotes lung fibrotic responses to bleomycin in mice. Although prior studies reported that MMP-8 levels are increased in plasma and bronchoalveolar lavage fluid (BALF) samples from IPF patients, neither the bioactive forms nor the cellular sources of MMP-8 in idiopathic pulmonary fibrosis (IPF) patients have been identified. It is not known whether MMP-8 expression is dys-regulated in IPF leukocytes or whether MMP-8 plasma levels correlate with IPF outcomes. Our goal was to address these knowledge gaps. METHODS:We measured MMP-8 levels and forms in blood and lung samples from IPF patients versus controls using ELISAs, western blotting, and qPCR, and assessed whether MMP-8 plasma levels in 73 IPF patients correlate with rate of lung function decline and mortality. We used immunostaining to localize MMP-8 expression in IPF lungs. We quantified MMP-8 levels and forms in blood leukocytes from IPF patients versus controls. RESULTS:IPF patients have increased BALF, whole lung, and plasma levels of soluble MMP-8 protein. Active MMP-8 is the main form elevated in IPF lungs. MMP-8 mRNA levels are increased in monocytes from IPF patients, but IPF patients and controls have similar levels of MMP-8 in PMNs. Surprisingly, macrophages and airway epithelial cells are the main cells expressing MMP-8 in IPF lungs. Plasma and BALF MMP-8 levels do not correlate with decline in lung function and/or mortality in IPF patients. CONCLUSION:Blood and lung MMP-8 levels are increased in IPF patients. Active MMP-8 is the main form elevated in IPF lungs. Surprisingly, blood monocytes, lung macrophages, and airway epithelial cells are the main cells in which MMP-8 is upregulated in IPF patients. Plasma and BALF MMP-8 levels are unlikely to serve as a prognostic biomarker for IPF patients. These results provide new information about the expression patterns of MMP-8 in IPF patients.