ABSTRACT
PURPOSE: A role for a bacterium, Bacillus oleronius, originally isolated from a Demodex mite, in the induction of ocular rosacea has been proposed. The aim of this work was to characterize the response of a corneal epithelial cell line to Bacillus proteins, as this might give an insight into how such proteins contribute to the symptoms of ocular rosacea in vivo. METHODS: The effect of exposing Bacillus protein preparation on human telomerase-immortalized corneal epithelial cells (hTCEpi) was measured by monitoring changes in cell proliferation and the expression of a number of genes associated with inflammation. The production of inflammatory cytokines was measured and the expression and activity of MMP-9 was quantified. RESULTS: Exposure of hTCEpi cells to 2 or 6 µg/mL Bacillus protein resulted in a dose-dependent reduction in cell proliferation. Exposure of cells to 6 µg/mL Bacillus protein did not induce apoptosis, but there was an increase in the expression of genes coding for IL-6 (13.8-fold), IL-1ß (4.0-fold), IL-8 (11.1-fold), and TNF-α (4.1-fold). Increased expression of genes coding for the defensins, CCL20 (4.5-fold) and S100A7 (6.8-fold) also was observed. Elevated production of IL-6 and IL-8 was evident from cells exposed to 2 and 6 µg/mL Bacillus protein. The hTCEpi cells demonstrated increased MMP-9 expression (3.2-fold, P = 0.003) and activity (2.2-fold, P = 0.0186) after 48 hours of exposure to 6 µg/mL Bacillus protein preparation. CONCLUSIONS: The results suggest that interaction of Demodex-associated Bacillus proteins with the corneal surface could lead to tissue degradation and inflammation, possibly leading to corneal scarring.
