Matrix Metalloproteinase-9 Amplifies the Immune Response toPseudomonas aeruginosaCorneal Infection
Investigative Ophthalmology and Visual Science
PURPOSE. The purpose of this study was to determine the role of matrix metalloproteinases (MMP) in Pseudomonas aeruginosa keratitis. METHODS. Gene array and selective real-time PCR examined MMP expression in the cornea of susceptible (C57BL/6, B6) versus resistant (BALB/c) mice before and after infection; zymography tested enzyme activity for MMP-2 and -9. Clinical score, Langerhans cell (LC), and Neutrophil (PMN) quantitation were done in recombinant (r) MMP-9, antibody neutralized, and MMP-9
... /mice. The chemotactic potential of MMP-9 was tested in a Boyden chamber assay; light and transmission microscopy and immunostaining for collagen IV and MMP-9 were used to examine the effects and the source of MMP-9 after infection. ELISA was used to assess IL-1␤ and MIP-2 levels. RESULTS. Gene array (confirmed by PCR) revealed sixfold more MMP-9, and zymography showed greater enzyme activity in the infected cornea of B6 over BALB/c mice. rMMP-9 injection of BALB/c mice enhanced, whereas MMP-9 antibody neutralization in B6 mice and its absence in MMP-9 -/mice decreased corneal disease. MMP-9 -/and antibody neutralized mice had fewer LCs in cornea; rMMP-9-treated mice had more. A myeloperoxidase (MPO) assay showed a similar pattern for PMN. MMP-9 was not chemotactic for LC or PMN. The basement membrane was more intact in MMP-9 -/over wild-type infected mice and correlated with staining for collagen IV; PMN was a source of MMP-9. IL-1␤ and MIP-2 were increased in rMMP-9 but decreased in MMP-9 antibody neutralized and MMP-9 -/over control groups. CONCLUSIONS. MMP-9 regulates immune function in cornea by proteolysis, potentiating P. aeruginosa keratitis by degrading collagen IV and upregulating chemotactic cytokines/chemo-Disease was graded as before, 18 from 0 to 4, with 0 being clear or slight opacity partially covering the pupil and ϩ4, corneal perforation. A clinical score was recorded for each mouse for statistical comparison (n ϭ 10/group/treatment).