Impact evaluation of a-lipoic acid in gamma-irradiated erythrocytes Omar S. Desouky a,n , Nabila S. Selim a , Eman M. Elbakrawy a , Rezk A. Rezk b a Biophysics Lab, Radiation Physics Department, National Center for Radiation Research and Technology (NCRRT), AEA, POB 29, Madinat Nasr, Cairo, Egypt b Physics Department, Faculty of Science, Helwan University, Cairo, Egypt article info Article history: Received 30 August 2010 Accepted 30 September 2010 Keywords: Erythrocyte Gamma radiation Viscosity Osmotic fragility Lipoic acid abstract This work is intended to study in vitro the ability of lipoic acid to protect erythrocytes against the oxidative damage resulting from exposure to gamma radiation through measurement of their rheological properties and to study the effects of detergent on their membrane solubility and permeability. Different doses of gamma radiation were applied: the most recommended and applied dose (25 Gy), and two higher doses, namely 50 and 100 Gy. The effect of addition of lipoic acid as well as its effect as a radioprotector was tested. The obtained results show changes in structural integrity of the erythrocyte cell membrane components as a result of oxidative damage due to gamma radiation that could be improved by pre-treatment with the antioxidant lipoic acid. & 2010 Elsevier Ltd. All rights reserved. 1. Introduction The study of antioxidants as radioprotective agents has been introduced by Patt et al. (1949). They carried an in vivo study of the radioprotective effect of cysteine against a lethal dose of X-rays. Since that time, several studies have been conducted to test the efficiency of natural and synthetic antioxidants in protection against radiation effects both in vitro and in vivo. Now, it has become an indispensable concept in the field of radiation applica- tion as was reported by Prasad et al. (2004); in order to protect normal tissues from potential radiation damage, it would be important to apply biological or chemical agents that when given before radiation exposure, could protect all normal tissues. Such radioprotective agents would help extend the concept of ALARA from dose to biological damage. They would also protect patients against radiation damage during diagnostic procedures. Irradiation of blood bags was also applied in blood banks and hospitals as an effective method for sterilization. However, the use of gamma radiation is limited by its damaging effects on erythrocytes. The recommended dose is 25 Gy, as it is considered safe for erythro- cytes (Jacob, 1998). However, some authors reported that this dose is not enough for complete sterilization (Fagiolo and Toriani- Terenzi, 2002). In this study we will focus on the use of a-lipoic acid (ALA; one of the powerful antioxidants) as a radioprotector for packed erythrocytes at the current applied dose (25 Gy) and explore its effect at higher doses (50 and 100 Gy). Although sufficient evidence is available to support the anti- oxidant function of ALA, reports on its radioprotective activity are insufficient and most of the findings are concerned with its role in diabetic neuropathy. Lipoic acid is a medium chain fatty acid naturally occurring in the body. It consists of 8 carbon atoms, with two sulfur atoms forming a disulfide link between carbons 6 and 8. It is a predominantly lipophilic molecule having an amphipathic character due to its carboxylic acid group attached to the ring structure (Akkas et al., 2007). It is described as a universal antioxidant because of the following criteria: it is the only antioxidant that is both fat- and water-soluble; it is easily absorbed and transported across cell membranes and hence it can exert its activity both inside and outside the cell; it is a small molecule, possessing antioxidant properties in its original form and also in its reduced form. Dihydrolipoic acid (DHLA) is an even more potent antioxidant than ALA. The protective effects of both forms might involve a modification of membrane polarity induced by modifica- tions of the membrane proteins conformation or fluidity of the membrane (Lahet et al., 2007). The superior antioxidant effect of the reduced form of ALA that was observed with both EPR experiments and erythrocyte membrane protection could be explained by the presence of two free thiol groups within the DHLA structure, which are available for the reducing reactions (Cremer et al., 2006). Naturally, it is a coenzyme in the metabolic process, especially in the conversion of glucose to energy (ATP). Its reduced form acts synergistically with other antioxidants, indicating that it is capable of regenerating other antioxidants from their radical or inactive forms (Packer et al., 1995). Several researchers studied the effect of ALA both in vivo and in vitro and found that ALA played a role in the detoxification of activated oxygen species (Navari-Izzo et al., 2002), and attenuates oxidative stress in mice induced by X-ray exposure (Manda et al., 2007). Combination of ALA with vitamin E has shown beneficial effects in reducing damage in oxidation-related Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/radphyschem Radiation Physics and Chemistry 0969-806X/$ - see front matter & 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.radphyschem.2010.09.017 n Corresponding author. E-mail address: omardesouky@yahoo.com (O.S. Desouky). Please cite this article as: Desouky, O.S., et al., Impact evaluation of a-lipoic acid in gamma-irradiated erythrocytes. Radiat. Phys. Chem. (2010), doi:10.1016/j.radphyschem.2010.09.017 Radiation Physics and Chemistry ] (]]]]) ]]]–]]]