Koji Sugioka1, Aya Kodama-Takahshi1, Tomoko Sato1, Kiyotaka Okada2, Junko Murakami1, Ah-Mee Park3, Hiroshi Mishima1, Yoshikazu Shimomura1, Shunji Kusaka1, Teruo Nishida4. 1. Department of Ophthalmology, Kindai University Faculty of Medicine, Osakasayama City, Osaka, Japan. 2. Division of Basic Medical Science, Kindai University Faculty of Medicine, Osakasayama City, Osaka, Japan. 3. Department of Microbiology, Kindai University Faculty of Medicine, Osakasayama City, Osaka, Japan. 4. Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, Ube City, Yamaguchi, Japan.
Abstract
Purpose: Staphylococcus aureus is a common cause of corneal ulceration, and staphylokinase (SAK) produced by this bacterium is a plasminogen activator. To investigate the pathogenesis of corneal ulceration induced by S. aureus, we examined the effects of bacterial culture broth and SAK on collagen degradation in a culture model in which human corneal fibroblasts are embedded in a collagen gel. Methods: Corneal fibroblasts embedded in collagen were exposed to S. aureus culture broth or SAK. Collagen degradation was assessed by measurement of hydroxyproline in acid hydrolysates of culture supernatants. Expression of pro-matrix metalloproteinase-1 (pro-MMP-1) was detected by immunoblot analysis as well as reverse transcription and real-time polymerase chain reaction analysis. Results: Both S. aureus culture broth and SAK markedly increased collagen degradation in the presence of corneal fibroblasts and plasminogen. This effect of the culture broth was dependent on cell number to a greater extent than was that of SAK. Whereas the culture broth also increased the expression of pro-MMP-1 in corneal fibroblasts at both mRNA and protein levels, SAK did not. Conclusions: Our results suggest that S. aureus may promote collagen degradation both by upregulating pro-MMP1 expression in corneal fibroblasts, with pro-MMP-1 then being converted to active MMP-1 by plasmin, and by directing plasmin activity toward collagen in a SAK-dependent manner.
Purpose: Staphylococcus aureus is a common cause of corneal ulceration, and staphylokinase (SAK) produced by this bacterium is a plasminogen activator. To investigate the pathogenesis of corneal ulceration induced by S. aureus, we examined the effects of bacterial culture broth and SAK on collagen degradation in a culture model in which human corneal fibroblasts are embedded in a collagen gel. Methods: Corneal fibroblasts embedded in collagen were exposed to S. aureus culture broth or SAK. Collagen degradation was assessed by measurement of hydroxyproline in acid hydrolysates of culture supernatants. Expression of pro-matrix metalloproteinase-1 (pro-MMP-1) was detected by immunoblot analysis as well as reverse transcription and real-time polymerase chain reaction analysis. Results: Both S. aureus culture broth and SAK markedly increased collagen degradation in the presence of corneal fibroblasts and plasminogen. This effect of the culture broth was dependent on cell number to a greater extent than was that of SAK. Whereas the culture broth also increased the expression of pro-MMP-1 in corneal fibroblasts at both mRNA and protein levels, SAK did not. Conclusions: Our results suggest that S. aureus may promote collagen degradation both by upregulating pro-MMP1 expression in corneal fibroblasts, with pro-MMP-1 then being converted to active MMP-1 by plasmin, and by directing plasmin activity toward collagen in a SAK-dependent manner.
Authors: Marina E Brown; Micaela L Montgomery; Manali M Kamath; Sarah Nicholas; Yutao Liu; Dimitrios Karamichos; Kevin K Fuller Journal: Exp Eye Res Date: 2021-04-15 Impact factor: 3.770