Lens epithelial cell protection by aminothiol WR-1065 and anetholedithiolethione from ionizing radiation

Abstract

Lens epithelium disorganization, glutathione (GSH) depletion, and epithelial cell death have been incriminated in the cytopathogenic mechanisms that lead to cataract formation following UVB and x-ray exposures. The objective of this study was to determine the in vitro capacity of the aminothiol WR-1065, the active metabolite of amifostine, and anetholedithiolethione (ADT or Sulfarlem) to protect bovine lens epithelial cells against x-ray irradiation. WR-1065 and ADT were used at a concentration of 20 microM. A single dose of 10 Gy was delivered at a rate of 2 Gy/min. Fluorimetric assays were then performed using a neutral red probe to evaluate cell viability, a Hoechst 33342 probe (HO) to evaluate nuclear condensation and apoptosis, and a monobromobimane probe to estimate the intracellular GSH pool. Twenty-four hours after x-ray exposure, cells pretreated with WR-1065 showed increased GSH levels, improved cell viability, and decreased HO fluorescence in addition to a lesser proportion of cells with apoptotic nuclear modifications. Between 72 and 120 hr postirradiation, ADT-pretreated cells also showed increased intracellular GSH levels and cell viability and decreased HO fluorescence and apoptotic cell morphology. This in vitro study demonstrates that WR-1065 and ADT protects lens epithelial cells from x-ray injury; thus, ADT and amifostine are appropriate candidates for clinical trials in humans. They are currently used in preventing radiation-induced xerostomia and should be further tested in the prevention of late radiation-induced ocular complications such as sicca syndrome and cataract.