Effects of daunorubicin, mitomycin C, azathioprine and cyclosporin A on human retinal pigmented epithelial, corneal endothelial and conjunctival cell lines

Background: We wished to investigate the toxicity of four immunosuppressant and antimetabolic drugs, which are known to influence postoperative wound healing, on three different human ocular cell lines. Methods: Acute toxicity to cyclosporin A, azathioprine, mitomicyn C and daunorubicin was assessed in Chang cells by monitoring their uptake of propidium iodide during a 3-h period. Chronic toxicity was assessed by monitoring the proliferation and viability of subconfluent cultures of Chang cells, human corneal endothelial cells (HCECs) and retinal pigmented epithelial (RPE) cells after continuous exposure to the drugs for 7 days. Results: Acute toxicity testing revealed no obvious effects. However, the chronic toxicity tests disclosed a narrow concentration range over which cell proliferation decreased dramatically but calcein metabolism was sustained. Although the three lines reacted similarly to each agent, HCECs were the most vulnerable to daunorubicin and mitomycin. At a daunorubicin concentration of 0.05 μg/ml, a 75% decrease in calcein metabolism (P<0.001) and a ≥95% cell loss (P<0.001) were observed. At a mitomycin concentration of 0.01μg/ml, cell density decreased by 61% (P<0.001) without a change in calcein metabolism, but at 0.1 μg/ml, the latter parameter decreased to 12% (P=0.00014). At this concentration the proliferation of Chang and RPE cells decreased by more than 50%, whilst calcein metabolism was largely sustained. Cyclosporin inhibited cell proliferation moderately at lower concentrations (<5 μg/ml; P=0.05) and substantially at higher ones, with a corresponding decline in calcein metabolism. Azathioprine induced a profound decrease in both parameters at concentrations above 5 μg/ml. Conclusion: Daunorubicin, cyclosporin and azathioprine could be used to inhibit excessive intraocular scarring after glaucoma and vitreoretinal surgery without overly reducing cell viability. The attributes of immunosuppressants lie in their combined antiproliferative and immunomodulatory effects.