Purpose: To investigate the cytotoxicity of triamcinolone acetonide (TA) and dexamethasone (DXM) in various types of cells in retinal cell culture.
Methods: Primary rat retinal cell cultures were treated with 25 to 800 microg/mL TA (58 microM-1.8 mM) or DXM (48 microM-1.6 mM) for 12 to 24 hours. Cell survival and death were assessed chemically by measuring cellular DNA contents using DNA-binding fluorescent dye and morphologically by propidium iodide staining. Standard methods were used for immunocytochemistry, immunoblots, and ELISA measurements. Retinal cellular oxidative stress was measured under a fluorescence microscope using 5-(and-6)-carboxy-2',7'-difluorodihydrofluorescein diacetate. Changes in the level of several antioxidative proteins were investigated using immunoblots.
Results: Exposure to 100 to 800 microg/mL TA (0.23-1.8 mM) or 800 microg/mL DXM (1.6 mM) for 24 hours caused a significant reduction in the number of retinal cells in culture, in a glucocorticoid receptor-independent manner. Of cell types in retinal cell cultures, astrocytes were most sensitive to TA and DXM. TA-induced cytotoxicity was mediated by oxidative stress. p38 kinase, c-Jun N-terminal kinase (JNK), caspase-1, and caspase-3 were involved in oxidative injury by TA. In addition, levels of antioxidative proteins increased after TA exposure.
Conclusions: TA induces oxidative injury to cultured retinal cells in a glucocorticoid receptor-independent manner. These results suggest that TA has a significantly higher toxic potential in retinal cell culture than more water-soluble DXM. For long-term anti-inflammatory effects, devices that are designed for the sustained release of water-soluble steroids may be safer.