Abstract
Purpose :
One of the most frequent ocular pathologies worldwide is keratitis, which may be associated with infectious processes. Fungal keratitis is caused by a broad spectrum of microorganisms, which differs depending on the geographical area involved. The identification of the epithelial receptors which enable adherence and colonization is key with respect to fungal keratitis. Previous studies have shown that, in bacterial keratitis, pathogens specifically bind to certain regions of the glycosaminoglycans (GAGs) chains, which are usually highly sulphated. This study tested the hypothesis that GAGs can act as receptors of yeasts in corneal infection and possible changes in the gene expression of the modifying enzymes of the GAGs chains.
Methods :
The adherence inhibition assays were performed on immortalized corneal epithelial cells (HCE-2) monolayers. Firstly, FITC-labeled yeast (Candida albicans, Candida glabrata or Candida parapsilosis) were co-incubated with heparan sulfate (HS), chondroitin sulfate A (CSA), chondroitin sulfate B (CSB), chondroitin sulfate C (CSC), or a mixture of the four, and then all incubated with HCE-2. Variations in the transcription levels of the GAGs chains modifying enzymes were analysed by RT-PCR. The data were analysed with statistical analysis. The mean values of two samples were compared using the Mann-Whitney U test with p<0.05 being considered as significant.
Results :
The inhibition of adherence showed a decrease in the adherence of the 3 yeasts to the corneal cells although there are differences between fungal species and the interfering molecule used. HS and CSB showed the greatest inhibition in C. albicans, contrary to what occurs in C. parapsilosis, which were CSA and CSC. In C. glabrata, HS and CSC were those with the highest inhibitory capacity. The adherence of the fungus induced significant alterations in the expression levels of both HS and CS chains modifying enzymes. Among modifying enzymes of CS, 6 out of 9 enzymes showed sub-expressions induced by C. glabrata. In the case of modifying enzymes of HS, 10 out of 14 enzymes showed sub-expressions, although depending on the gene and yeast used.
Conclusions :
Corneal surface GAGs are involved in the adherence of C. albicans, C. glabrata and C. parapsilosis. The interaction of the microorganism with cells induces alterations in the transcription levels of the GAGs chains modifying enzymes that are dependent at the yeast species.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.