Lens Epithelial Cell Protection by Aminothiol WR-1065 and Anetholedithiolethione from Ionizing Radiation Yazid Belkace ´mi, M.D., Ph.D., 1,2 Patrice Rat, Ph.D., 1 Gae ¨lle Piel, M.S., 3 Marie-Odile Christen, Ph.D., 4 Emmanuel Touboul, M.D., 2 and Jean-Michel Warnet, Ph.D. 1 1 Cell Pharmacotoxicology Unit, Department of Pharmacy, CHNO des XV-XX, and Laboratory of Toxicology, UFR Pharmacy, University of Paris V, France 2 Department of Radiation-Oncology, Tenon Hospital, Paris, France 3 MedPass International – Biostatistics, Paris, AL-HL, France 4 Solvay Pharma, Suresnes, France SUMMARY 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 M. 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 cur- rently 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. © 2002 Wiley-Liss, Inc. Key words: lens cells; ionizing radiation; cytofluorimetric assay; WR-1065; anetholedithiolethione INTRODUCTION Cataract formation is a frequent and well-documented late effect in patients treated by radiation when tumor volume coverage prohibits adequate eye protection. The risk of lens opacification depends on irradiation parameters [1– 4]. A cataract rate as high as 100% at 3.5 years has been reported in patients conditioned with a single fraction total body irradiation prior to bone marrow transplantation [5]. Currently, patients transplanted for hematologi- cal malignancies receive no prophylactic medical *Correspondence to: Yazid Belkace ´mi, M.D., Ph.D., Radiation-Oncology Department, Tenon Hospital, 4 rue de la Chine F-75970, Paris Cedex 20, France. Phone: +331.56.01.79.60; Fax: +331.56.01.79.33; E-mail: yazid.belkacemi@tnn.ap-hop-paris.fr Received 27 June 2001; Revised 30 October 2001; Accepted 2 November 2001 DOI 10.1002/ijc.10346 Published online 11 March 2002 in Wiley InterScience (www.interscience.wiley.com). Int. J. Cancer (Radiat. Oncol. Invest): 96 (Suppl.) 15–26 (2001) © 2002 Wiley-Liss, Inc. Publication of the International Union Against Cancer