In Vitro Toxicity of Cetalkonium Chloride on Corneal Epithelial Cells

Objective: To investigate the toxicity of cetalkonium chloride (CKC) on primary cultured human corneal epithelial cells (HCECs). Methods: HCECs were subjected to various concentrations (0.03125 × 10^-4 to 2.0 × 10^-4% (w/v)) of CKC for durations ranging from 24 to 72 h. Cell viability was evaluated using the CCK-8 kit along with live and dead cell staining. Intracellular reactive oxygen species (ROS) levels were measured 20 min following CKC exposure. Observations of changes in cell morphology, cytoplasmic actin filaments, and mitochondrial distribution were conducted using immunocytochemistry and MitoTracker assays. Protein expression levels related to cell survival pathways, including mTOR, ERK, Akt, Bcl-xL, and BAX, were examined via Western blot analysis. Results: CKC exhibited dose-dependent toxicity in HCECs. Exposure to CKC concentrations below 0.125 × 10^-4% resulted in no significant decrease in HCEC viability for up to 72 h. Conversely, exposure to CKC at concentrations of 1.0 × 10^-4% or higher led to significantly decreased HCEC viability. Following exposure to higher concentrations of CKC, elevated levels of intracellular ROS and LDH release were observed. This toxicity was further characterized by decreased levels of phosphorylated mTOR, phosphorylated Akt, phosphorylated ERK, and Bcl-xL, as well as an increase in BAX expression. As the CKC concentration increased, HCECs decreased in size, and mitochondria displayed a loss of characteristic punctate staining. Conclusions: Our findings indicated that exposure to CKC caused significant toxicity in HCECs, which varied with concentration and duration of exposure. This toxicity was associated with an increase in ROS, mitochondrial alterations, and a decline in activity of the cell survival pathways.