The roles of urokinase-type plasminogen activator in leukocyte infiltration and inflammatory responses in mice corneas treated with lipopolysaccharide

Invest Ophthalmol Vis Sci. 2014 Jul 24;55(8):5338-50. doi: 10.1167/iovs.14-14867.

Abstract

Purpose: Urokinase-type plasminogen activator (u-PA) plays an important role in corneal wound healing, yet its role in corneal inflammation remains poorly understood. We investigated the role of u-PA in a murine model of lipopolysaccharide (LPS)-induced corneal inflammation.

Methods: The corneal epithelium was scraped and LPS was applied to u-PA wild-type (u-PA(+/+)) and u-PA-deficient (u-PA(-/-)) mice. Corneal re-epithelialization and opacity were measured by stereomicroscopy. Fibrin zymography was performed to detect plasminogen activators in corneas from u-PA(+/+) and u-PA(-/-) mice. Neutrophil, macrophage, and u-PA receptor (u-PAR) expression were determined by immunohistochemistry. Gene expression of corneal macrophage chemoattractant protein (MCP)-1 and macrophage inflammatory protein (MIP)-2 was assessed with reverse transcription-polymerase chain reaction. The in vitro effects of endogenous u-PA on MCP-1, MIP-2, matrix metalloproteinase (MMP)-2, and MMP-9 expression, and macrophage migration activity in mouse ocular fibroblasts stimulated by LPS, were examined.

Results: The u-PA(+/+) mice showed enhanced corneal inflammation as compared with u-PA(-/-) mice. The u-PA expression was increased by LPS stimulation. Immunohistochemical analyses indicated that more neutrophils and macrophages were present in corneas from u-PA(+/+) mice than u-PA(-/-) mice. The u-PAR expression was detected in inflammatory cells and in the leading edges of the epithelial migrating cells. Enhanced mRNA expression of MCP-1 and MIP-2 was observed in corneas from u-PA(+/+) mice compared to u-PA(-/-) mice. Macrophage chemoattractant protein-1, MIP-2, and MMP-9, but not MMP-2, significantly increased in corneal fibroblasts from u-PA(+/+) mice compared with u-PA(-/-) mice.

Conclusions: These data indicate that u-PA promotes LPS-induced leukocyte infiltration in cornea and that u-PA is an important component in LPS-induced corneal inflammatory responses.

Keywords: LPS; cornea; leukocyte; u-PA; wound healing.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chemokine CCL2 / metabolism
  • Chemokine CXCL2 / metabolism
  • Cornea / drug effects*
  • Disease Models, Animal
  • Immunohistochemistry
  • Keratitis / pathology
  • Keratitis / physiopathology*
  • Leukocytes / cytology*
  • Leukocytes / immunology
  • Lipopolysaccharides
  • Macrophages / metabolism
  • Matrix Metalloproteinase 2 / metabolism
  • Matrix Metalloproteinase 9 / metabolism
  • Mice
  • Neutrophils / metabolism
  • Receptors, Urokinase Plasminogen Activator / metabolism
  • Urokinase-Type Plasminogen Activator / physiology*

Substances

  • Chemokine CCL2
  • Chemokine CXCL2
  • Lipopolysaccharides
  • Receptors, Urokinase Plasminogen Activator
  • Urokinase-Type Plasminogen Activator
  • Matrix Metalloproteinase 2
  • Matrix Metalloproteinase 9