Doxorubicin induced apoptosis in oocytes—Mechanism and possible executers

Abstract

9611 Background: Premature ovarian failure and infertility are well-known side-effects observed in young girls and reproductive-age women treated for cancer. Long-term consequences of chemotherapy observed on non-target tissues, such as ovaries are substantial. Oocytes are among the cells most sensitive to collateral damage from chemotherapy, raising concern and potential health risks for women surviving diseases such as breast cancer, Hodgkin’s disease and leukemia. Our study aims at exploring the lethal effect doxorubicin exerts on oocytes. Methods: Retrieved ovulated or ovarian mouse oocytes, served as our biological model. Oocytes were exposed to doxorubicin and studied at several time-intervals. Using state of the art confocal microscopy, we performed fluorescent immunohistochemistry to follow doxorubicin localization within the oocytes as well as possible cellular targets at various post-treatment intervals. To evaluate doxorubicin induced apoptosis, we also used specific activity assays to trace potential effectors such as caspases and calpain. Results: Doxorubicin appears to be localized simultaneously at two cellular compartments - the nucleus (being the known original target site, as expected), where it induces acute obliteration of the DNA, and the mitochondria. We demonstrated activation of the mitochondria by doxorubicin as reflected by changes in its membrane potential. The effect on the mitochondria appears to be direct and is not inhibited by caspase2-inhibitor, an effector that mediates signals of the nuclear pathway. Exploring the apoptotic cascade within the oocyte, we showed that doxorubicin induces caspase-12 activation, probably via calpain activation. Conclusions: Our results imply that doxorubicin elicits a unique apoptotic signal transduction pathway within the oocyte via direct co-localization within the mitochondria and its activation. Possible cellular effectors appeared to be caspase12 and calpain, as formerly described in cardiomyocytes. Revealing the cellular mechanisms by which doxorubicin executes oocyte destruction might shed light on chemotherapy- induced infertility and could serve in discovering biological keys needed for protecting the germ cells against chemotherapy-induced damage. No significant financial relationships to disclose.