Matrix metalloproteinase-9 amplifies the immune response to Pseudomonas aeruginosa corneal infection.
OBJECTIVE
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-1beta 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-1beta 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/chemokines IL-1beta and MIP-2.
McClellan
Sharon A
SA
Department of Anatomy/Cell Biology, Wayne State University School of Medicine, 540 East Canfield Avenue, Detroit, Michigan 48201, USA.
Huang
Xi
X
Barrett
Ronald P
RP
Lighvani
Shahrzad
S
Zhang
Yunfan
Y
Richiert
Dawn
D
Hazlett
Linda D
LD
D000818:Animals; D000917:Antibody Formation; D054426:Chemokine CXCL2; D018925:Chemokines / Q000378:metabolism; D002634:Chemotaxis, Leukocyte / Q000502:physiology; D024141:Collagen Type IV / Q000378:metabolism; D003320:Corneal Ulcer / Q000201:enzymology / Q000276:immunology*; D004198:Disease Susceptibility; D004797:Enzyme-Linked Immunosorbent Assay; D015818:Eye Infections, Bacterial / Q000201:enzymology / Q000276:immunology*; D005260:Female; D007113:Immunity, Innate; D007375:Interleukin-1 / Q000378:metabolism; D007801:Langerhans Cells / Q000276:immunology*; D020780:Matrix Metalloproteinase 9 / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009504:Neutrophils / Q000276:immunology*; D020411:Oligonucleotide Array Sequence Analysis; D011552:Pseudomonas Infections / Q000201:enzymology / Q000276:immunology*; D011550:Pseudomonas aeruginosa / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation
D054426:Chemokine CXCL2; D018925:Chemokines; D024141:Collagen Type IV; C404915:Cxcl2 protein, mouse; D007375:Interleukin-1; D020780:Matrix Metalloproteinase 9