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Infect. Immun., 07 1997, 2754-2758, Vol 65, No. 7
JA Hobden, SA Masinick, RP Barrett and LD Hazlett
Corneal clarity in young adult Swiss (HSD:ICR) mice is restored after
Pseudomonas aeruginosa infection. Previous data showed that this response
involves a rapid up-regulation of constitutive intercellular cell adhesion
molecule-1 (ICAM-1) and migration of inflammatory cells into the cornea. In
contrast, in aged mice, there is no up-regulation of corneal ICAM-1,
inflammatory cell infiltration into the cornea is delayed, and the cornea
perforates. Therefore, the aim of this study was to test whether specific
cytokines which up-regulate ICAM-1 expression differ in young and aged
mice. Corneas of young (6- to 8- week-old) and aged (1- to 2-year-old) mice
were scarified and inoculated with P. aeruginosa. The eyes were graded for
pathologic changes (score 0 to +4); at 6, 12, 24, and 48 h postinfection
(p.i.), six mice from each age group were sacrificed. Three corneas from
each respective group were excised for quantitation of interleukin-1beta
(IL- 1beta), tumor necrosis factor alpha, and gamma interferon (IFN-gamma)
by enzyme-linked immunosorbent assay. The remaining three corneas from each
age group were harvested for quantitation of viable bacteria by direct
plate count determination and for infiltrating polymorphonuclear leukocytes
(PMNs) by a myeloperoxidase (MPO) assay. Compared to those of young mice,
the corneas of infected aged mice had less IL-1beta at 6 h p.i. (P < or
= 0.04) and less IFN-gamma at 12 to 48 h p.i. (P < or = 0.05). Also,
compared to those of young mice, corneas of aged mice had fewer PMNs (P
< or = 0.008) by the MPO assay at 6 h p.i. and more viable bacteria (P
< or = 0.01) per cornea by plate count determination at 24 h p.i. These
data suggest that the lack of up-regulation of ocular ICAM-1 in aged mice
may reflect a reduction in both IL-1beta and IFN-gamma levels in the
infected cornea. Consequently, a sufficient number of PMNs and other
inflammatory cells fail to rapidly migrate into the infected corneas of
aged mice, the bacterial load is initially greater than that in young mice,
and the cornea perforates.
Copyright © 1997, American Society for Microbiology
Proinflammatory cytokine deficiency and pathogenesis of Pseudomonas aeruginosa keratitis in aged mice
Department of Anatomy/Cell Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
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