Evaluation of cytotoxicity of various ophthalmic drugs, eye drop excipients and cyclodextrins in an immortalized human corneal epithelial cell line

Purpose. An immortalized human corneal epithelial cell line (HCE) was tested as a screening tool for prediction of topical ocular irritation/toxicity by pharmaceuticals. Methods. Effects of various drugs, excipients and cyclodextrins (CDs) on viability of HCE cells were evaluated using two in vitro cytotoxicity tests, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) dye reduction assay and propidium iodide assay. Results. Mitochondrion-based MTT test was a more sensitive indicator of cytotoxicity than the plasma membrane-based propidium iodide test. The tests revealed following cytotoxic rankings for ophthalmic drugs: dipivefrin > timolol > pilocarpine approximate to dexamethasone; for excipients: benzalkonium chloride (BAC) > sodium edetate (NA(2) EDTA) > polyvinyl alcohol (PVA) > methylparaben; and for CDs: alpha-CD > dimethyl-beta-cyclodextrin (DM-P-CD) > sulfobutyl ether P-cyclodextrin ((SBE)(7m)-beta-CD) approximate to hydroxypropyl-beta-cyclodextrin (HP-beta-CD)> gamma-CD. In consideration of the in vivo clinical situation, the short exposure time (5 min) is more relevant even though toxic effects of some test substances were seen only after longer exposure times (30 and 60 min). Conclusions, Immortalized HCE cells are a promising tool for rapid cytotoxicity assays of ocular medications. The cell line is potentially useful in predicting the in vivo corneal toxicity of ocularly applied compounds.