In vitro comparison of cytoprotective and antioxidative effects of latanoprost, travoprost, and bimatoprost on conjunctiva-derived epithelial cells.

PURPOSE: In a previous study, it was demonstrated that in vitro in a human conjunctiva-derived cell line, latanoprost in its commercial presentation appeared to be less toxic than the benzalkonium chloride (BAC) it contains as a preservative. Through a microplate cytometry technique, the investigation was furthered by study of whether the three commercially available antiglaucoma prostaglandin analogs could protect the same cell line in vitro against BAC toxicity and whether an antioxidative mechanism could be involved in such prostaglandin effects.
METHODS: Human conjunctiva-derived epithelial cells from the Chang cell line were exposed to three prostaglandins in their commercial presentation (latanoprost, travoprost, and bimatoprost) and to three concentrations of BAC (0.02%, 0.015%, and 0.005%), corresponding to the concentrations contained in the three prostaglandin eyedrops. Each solution was diluted to 1/10 and was applied for 30 minutes Cellular membrane integrity, cytosolic H2O2, cytosolic O2*- and apoptosis were evaluated using neutral red, H2DCF-DA, hydroethidine, and Yopro-1 probes, respectively.
RESULTS: Cellular viability decreased as BAC concentration increased, but it was accompanied by concentration-dependent toxicity. Toxicity of latanoprost and travoprost commercial solutions was statistically significantly lower than their respective BAC concentrations (P < 0.01), whereas bimatoprost induced no significant effects. There was a statistically significant decrease in H2O2 detection with cells exposed to latanoprost (P < 0.01) and travoprost (P < 0.01) and a lower detection of O2*- with cells exposed to latanoprost (P < 0.01) compared with the corresponding BAC concentration alone. The Yopro-1 test showed a BAC-induced apoptotic effect that increased with its concentration. Latanoprost and travoprost produced proapoptotic effects compared with control (P < 0.01), but these were lower than their respective preservative concentrations (statistically significant difference; P < 0.01).
CONCLUSIONS: Latanoprost and travoprost were responsible for significant protective effects against BAC toxicity on conjunctiva-derived epithelial cells in vitro, probably related to their antioxidative properties. The low toxicity of the bimatoprost solution did not reveal a possible antioxidative effect. Reduced reactive oxygen species production could be the main mechanism by which prostaglandin analogs protect epithelial cells from the proapoptotic effects of BAC. Further studies will be useful to confirm this hypothesis.