Protection of Thymocytes from Radiation-Induced Interphase Death by Dihydrolipoic Acid and WR-1065

Abstract

Radiation-induced cell death can be divided into two classes, reproductive death and interphase death (1). In reproductive death the irradiated cell functions until it attempts one or more cell divisions, whereupon it dies. In interphase death, the radiation damage manifests itself in the absence of mitosis. Most mammalian cells undergo reproductive death at clinically relevant radiation doses. In contrast, thymocytes, lymphocytes and intestinal crypt cells undergo interphase death at clinically relevant doses of 2–4 Gy or less (1). Radiation-induced interphase death is an example of apoptosis. The most characteristic early biochemical event in apoptosis is nuclear DNA fragmentation into oligonucleosomal subunits (2), which can be distinguished from the random cleavage observed in cells undergoing necrosis. In this paper, we describe the effects of dihydrolipoic acid and N-(2-mercaptoethyl)-1,3- propanediamine (WR-1065) on DNA fragmentation and cell viability in thymocytes exposed to ionizing radiation.