A comparative study of effects of aversectin C, abamectin and ivermectin on apoptosis of rat thymocytes induced by radiation and dexamethasone

The effects of avermectins on radiation- and dexamethasone-induced apoptosi s of rat thymocytes have been studied. In particular, the properties of aba mectin (avermectin B-1), ivermectin (22,23-dihydroavermectin B-1, H2B1) and aversectin C were examined. Aversectin C is a mixture of eight naturally o ccurring avermectins of the following composition: B-1 (42%), B-2 (22%), A( 1) (13%) and A(2) (23%). This mixture is currently widely used as active in gredient in veterinary antiparasitic formulations produced by Pharmbiomed C o. Apoptosis was estimated by membrane damage, nuclear pycnosis (or chromat in condensation), DNA fragmentation and percentage of cells with subdiploid DNA. It was shown that aversectin C inhibits thymocyte apoptosis induced b y both agents. The IC50 dose was in the range of 0.1-0.3 mu g/ml for averse ctin C, whereas abamectin and ivermectin produced no effect up to 1 mu g/ml . It is suggested that avermectins of the A series are responsible for the high anti-apoptotic activity exhibited by aversectin C. Thus, aversectin C is not only an effective antiparasitic drug but is also capable of exhibiti ng some other useful activities, e.g. a cytoprotective effect exerted on th e mammalian immune cells.