Hypothermia protects cultured human retinal pigment epithelial cells against indocyanine green toxicity

Purpose: The aim of this study was to determine whether indocyanine green (ICG) is toxic to cultured human retinal pigment epithelial (ARPE-19) cells, and whether hypothermia can protect the ARPE-19 cells against the ICG toxicity. Methods: Cultured ARPE-19 cells were exposed to 0.25, 0.5, 1, 2.5, and 5 mg/mL of ICG dye at 37 and 4°C for 30 min. The percentage of ARPE-19 cells that survived was determined by resazurin 1 day after the exposure. Results: Exposure of the RPE cells to a hypotonic saline solution with an osmolarity equal to 5 mg/mL of ICG did not induce a statistically significant decrease in the percentage of RPE cells that survived. Exposure of the ARPE-19 cells to ICG induced a significant decrease in the percentage of cell survival at all concentrations of ICG (P < 0.05), except in 0.25 mg/mL at 37°C. At 4°C, on the other hand, ICG induced a statistically significant decrease in the percentage of RPE cell survival only at 5 mg/mL of ICG (P < 0.05). Conclusions: These results indicate that ICG is toxic to human RPE cells in culture, and that cell death cannot be attributed to the low osmolarity. Hypothermia of 4°C has a protective effect against ICG toxicity.