Impact of Exposure to Benzalkonium Chloride on Corneal Mucin

Abstract

Abstract: : Purpose: To investigate the effect of one of the most frequently used preservative, benzalkonium chloride (BAC), on transmembranous mucin, and MUC1 and MUC16 in immortalized corneal cells and pre–corneal mucous layer in the rabbit corneal epithelium. Methods: Immortalized corneal cells (HCLE) were incubated for 15 minutes in 6 different conditions and expression of MUC1 and MUC16 were compared by western blotting: 1) serum–free media as a control group 2) 0.01% BAC 3) commercially available ocuflox^® antibiotic eyedrop (0.3% ofloxacin with 0.0025% BAC) 4) 0.3% ofloxacin 5) commercially available topical alcaine^® anesthetic eyedrop (0.5% proparacaine with 0.01% BAC) 6) 0.5% proparacaine. Healthy female albino rabbits were euthanised at 15.00 hours. The dissected corneas were treated with 0.01% BAC over a period of 1, 5, 10, 15, 30 and 60 minutes, and fixed with buffered glutaraldehyde fixative PH 7.4 at 35°C with tannic acid staining. As a control group, cornea was immediately fixed with buffered glutaraldehyde fixative. Specimens of cornea were critical point dried out of propylene oxide and embedded in Epon. The sectioned materials were examined by transmission electron microscopy (TEM). Results: The expression of MUC1 and MUC16 in group treated with 0.01% BAC was decreased compare to that of the control group that was incubated with serum–free media. Also the expression of MUC1 and MUC16 in two groups treated with commercially available eyedrops were decreased compare to that of their separate agents: 0.3% ofloxacin and 0.5% proparacaine. Specimens treated with 0.01% BAC from over a period of 5 minutes to 60 minutes showed dense mucous layer. However, little or no mucus were retained on the surface of cornea in control and treated for 1–minute groups. Conclusions: Commercially available ocuflox^® antibiotic eyedrop, alcaine^® anesthetic eyedrop and BAC decreased the expression of MUC1 and MUC16 in immortalized corneal cells. With the treatment of 0.01% BAC even for 5 minutes, dense mucous layer was evident on the corneal surface by TEM. These changes would prevent membranous mucin, MUC1 and MUC 16, from properly working resulting unstable tear film and dry eye symptoms.

Keywords: cornea: epithelium • drug toxicity/drug effects