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Bacterial proteases and adherence of Pseudomonas aeruginosa to mouse cornea
S K Gupta1, S A Masinick, J A Hobden
1Department of Anatomy/Cell Biology, Wayne State University, Detroit, MI 48201, USA.
Abstract:
The goal of this study was to test whether bacterial exoproducts, such as elastase or alkaline protease contribute to the initial binding of Pseudomonas aeruginosa to mouse corneal epithelium. Each protease, purified from P. aeruginosa, when applied exogenously at concentrations of either 25 or 50 ng ml-1, elevated binding of Pseudomonas to mouse cornea in organ culture. Polyclonal antibodies against bacterial alkaline protease, but not elastase, interfered with bacterial binding and reduced significantly the number of organisms bound to cornea in an organ culture binding inhibition assay. Zymographic analysis of conditioned media from additional organ culture experiments showed that the P. aeruginosa strain used, which is highly virulent in cornea in vivo, secretes detectable levels of alkaline protease, but not elastase in vitro and that secretion was enhanced if the corneal epithelium was wounded. Lastly, how alkaline protease enhanced bacterial binding to the corneal epithelium of the organ cultured eye was examined. Data from this study suggest that exposure of lipase-sensitivity epithelial receptors represents at least one mechanism.
Insights
Bacterial alkaline protease enhances Pseudomonas aeruginosa binding to the cornea. Antibodies against this protease reduced bacterial adhesion, suggesting it
Area of Science:
- Ophthalmology
- Microbiology
- Bacterial Pathogenesis
Background:
- Pseudomonas aeruginosa is a significant cause of bacterial keratitis.
- Bacterial exoproducts may play a role in the initial adhesion of P. aeruginosa to the corneal epithelium.
Purpose of the Study:
- To investigate the role of bacterial exoproducts, specifically elastase and alkaline protease, in the initial binding of P. aeruginosa to mouse corneal epithelium.
Main Methods:
- Organ culture model of mouse cornea.
- Exogenous application of purified proteases.
- Binding inhibition assays using polyclonal antibodies.
- Zymographic analysis of bacterial-secreted proteases.
- Examination of alkaline protease's mechanism of enhancing bacterial binding.
Main Results:
- Exogenous elastase and alkaline protease increased P. aeruginosa binding to corneal epithelium.
- Antibodies against alkaline protease, but not elastase, significantly reduced bacterial binding.
- The virulent P. aeruginosa strain secreted alkaline protease, but not elastase, in vitro.
- Secretion of alkaline protease was enhanced by wounded corneal epithelium.
- Alkaline protease enhances binding by exposing lipase-sensitive epithelial receptors.
Conclusions:
- Bacterial alkaline protease is a key factor in the initial adhesion of P. aeruginosa to the mouse corneal epithelium.
- The mechanism involves the exposure of lipase-sensitive epithelial receptors.
- Alkaline protease represents a potential therapeutic target for P. aeruginosa keratitis.