Cytotoxic properties of tyloxapol

Purpose. Tyloxapol, a viscous polymer of the alkyl aryl polyether alcohol type, is classified as a nonionic surfactant and is widely used in biomedical applications. Although tyloxapol has been reported to be cytotoxic in various cell lines, there is no published information about its possible mechanisms of cell death. Hence, the objective of this study was to determine whether tyloxapol causes apoptosis or necrosis. These data could be helpful for a better understanding of the action of tyloxapol in cellular systems. Methods. RAW 264.7 (murine macrophage-like) cells and NIH/3T3 (mouse fibroblast) cells were treated with tyloxapol, and the activity of dehydrogenases in those cells, an indicator of cell viability, was assessed. The cell morphology changes induced by tyloxapol treatment were detected using propidium iodide nuclear staining. The hallmarks of apoptotic cells were characterized using DNA fragmentation assays, DNA fluorescence staining, and then flow analysis. Results. Tyloxapol treatment produced dose- and time-dependent cytotoxicity. Tyloxapol treatment damaged RAW 264.7 cells more than it damaged NIH/3T3 cells. All the cells exposed to tyloxapol showed some morphological features of apoptosis, such as chromatin condensation and cell shrinkage. Typical apoptotic ladders were observed in DNA extracted from tyloxapol-treated cells. Flow cytometric analysis revealed an increase in the hypodiploid DNA population (sub-G1), indicating that DNA cleavage occurred after tyloxapol treatment. In addition, we showed that pretreating cells with zVAD-fmk, a general caspase inhibitor, did not prevent tyloxapol-induced apoptosis. The cytotoxicity of tyloxapol can be reduced by adding a nontoxic lipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine to attenuate the interaction of tyloxapol with the cell membrane. Conclusions. Our results indicate that tyloxapol induces apoptosis in RAW 264.7 and NIH/3T3 cells. These data provide a novel insight into the cytotoxic action of tyloxapol at the molecular level.