Abstract
Abstract: :
Purpose:Benzalkonium chloride is a quaternary ammonium molecule that is used as a preservative in ophthalmic solutions and is thought to be responsible for the toxic effects observed in conjunctival cells of some patients exposed to a prolonged topical treatment. Ultraviolet radiation also has toxic effects on conjunctival cells. We showed the molecular mechanisms of apoptosis induced by both UVB and benzalkonium chloride in immortalized conjunctival cells (Chang cells). Materials and Methods:Apoptosis was detected by examining morphological changes, chromatin condensation and DNA fragmentation. Furthermore, mechanisms – i.e. cytochrome c–mediated and caspase activation – were compared for both agents. Results:Both agents were observed to trigger apoptosis. In addition, Chang cells exposed to benzalkonium chloride developed large cytoplasmic vesicles, which were identified as autophagic vesicles The molecular mechanisms involved in Chang cell death in response to each stimulus appeared to be very similar and involved cytochrome c–mediated, time–dependent caspase activation under the control of Bcl–2 proteins, leading to intracellular protein cleavage, e.g. PARP cleavage. Interestingly, both agents also triggered Fas–ligand–independent, Fas clustering in the rafts of the plasma membrane. Conclusions:Altogether, these results demonstrate that both UV–B and benzalkonium chloride are able to trigger conjunctival cell apoptosis through both intrinsic and extrinsic pathways.
Keywords: apoptosis/cell death • conjunctiva