Roles of Leukocyte Adhesion in Retinal Phototoxicity After Indocyanine Green Injection

Abstract

Abstract: : Purpose:Recently, indocyanine green (ICG) has been used for vitreous surgery besides angiography, and the possibility of retinal phototoxicity with ICG has been pointed out. Since adhesion of leukocytes to blood vessel is recognized as the initial step to retinal tissue damage, we examined adhesion of leukocytes to retinal vessel wall after light exposure of ICG–infused retinas to elucidate mechanisms of the retinal phototoxicity with ICG. Methods: Light exposure is delivered to mice retinas immediately after injection of ICG into their tail vein. Twenty four hours after the injection, mice were anesthetized, perfused with saline to wash out leukocytes, and the leukocytes adhering to retinal vessel wall were labeled with FITC–concanavalin A lectin. The number of leukcytes adhering to the retinal vessels were counted under fluorescent microscope. Results:Light exposure without ICG or ICG infusion without light exposure did not cause significant increase in leukocyte adhesion to retinal vessel wall. Three minutes light exposure after injection of ICG (0.05∼12.5mg/kg) increased leukocyte adhesion significantly. Although the degree of leukocyte adhesion increase were not significantly different among 0.05∼1.25mg/kg injection of ICG, high dose of ICG (12.5mg/kg) caused much more increase in leukocyte adhesion than low dose. In other experiments with light exposure for 3, 5, and 10 minutes after injection of 1.25mg/kg ICG, amount of adhering leukocytes were increased depending on the duration of the light exposure. Conclusions: Light exposure after ICG injection caused significant increase in leukocyte adhesion to retinal vessel. The retinal phototoxicity after ICG injection would be mediated by leukocyte adhesion to retinal vessel wall. Considering that leukocyte adhesion increased depending on the duration of the light exposure in contrast to its independency to the dose of ICG among low dose, shortening of the light exposure duration might be important to prevent the retinal damage.

Keywords: drug toxicity/drug effects • radiation damage: light/UV • vascular cells