Abstract: To define the cytotoxicity of ofloxacin(OFX), a widely used antibiotic drug in eye clinic, to human corneal epithelium and the possible cellular and molecular mechanisms, the cytotoxic effect, apoptosis-inducing effect and apoptosis-triggering pathways of OFX were investigated using an in vitro model of HCEP cells in this study. After in vitro cultured HCEP cells were treated with different concentrations of OFX for different time, the morphology, cytopathic effect(CPE)and viability were assessed by light microscopy and MTT assay, the cell cycle arrest and apoptosis were detected by flow cytometry(FCM), AO/EB double-staining, gel electrophoresis and transmission electron microscopy, and caspase activation, cytoplasmic amount of mitochondrion-specific apoptosis-triggering proteins and mitochondrial transmembrane potential(MTP)disruption were quantified using ELISA, Western blot and FCM. Our results revealed that OFX above concentrations of 0.375 g/L induced morphological abnormality, CPE formation, viability decline and plasma membrane permeability elevation of HCEP cells in a dose-and time-dependent manner. Moreover, OFX could arrest the cells at S phase of the cell cycle and induce phosphatidylserine externalization, DNA fragmentation, apoptotic body formation, activations of caspase-2, -9, and-3, up-regulation of cytoplasmic cytochrome c and apoptosis inducing factor, and disruption of MTP. In conclusion, OFX above 1/8 of its clinical therapeutic concentration 山 东 大 学 学 报 (理 学 版)第51卷 - 第5期王德平,等:氧氟沙星对人角膜上皮细胞的毒性作用及其细胞与分子机理研究 \=-has a significant cytotoxicity to HCEP cells by inducing cell cycle arrest and apoptosis which is regulated by a death receptor-mediated mitochondrion-dependent signaling pathway.

Key words: cytotoxicity, apoptosis, mitochondrion-dependent signaling pathway, ofloxacin, human cornel epithelial cells