Apoptosis-associated signaling pathways are required for chemotherapy-mediated female germ cell destruction

Abstract

Female sterility resulting from oocyte destruction is an unfortunate, and in many cases inevitable, consequence of chemotherapy. We show that unfertilized mouse oocytes exposed to therapeutic levels of the antitumor drug, doxorubicin (DXR), undergo apoptosis; however, fertilized oocytes do not initiate apoptosis, but enter cell-cycle arrest, when treated with DXR. Apoptosis induced by DXR in oocytes is blocked by sphingosine-1-phosphate, an inhibitor of ceramide-promoted cell death. Oocytes from Bax-deficient, but not p53-null, female mice display complete resistance to DXR-induced apoptosis in vivo and in vitro. Pretreatment of oocytes with a specific peptide inhibitor of caspases also abrogates the apoptotic response to DXR. These findings indicate that oocyte destruction caused by chemotherapy can be prevented by manipulation of apoptosis-associated signaling pathways.

Molecular requirements for doxorubicin-mediated death in murine oocytes

“…Lack of p53 transcript recruitment observed in the present study as well as its dispensability in the DXR-mediated death reported previously, 10 further supports the hypothesis that, other members of p53 surveillance proteins may be involved in DXR modulations. Discovery of two other p53 family members (p63 and p73) which share many molecular features of p53 apoptosis induction makes these molecules excellent candidates for modulating DXRmediated death pathways in oocytes.…”

“…In this study, as in our previous report, 10 DXR induced high rate of oocyte fragmentation (5374.8%, n ¼ 397; Po0.001), whereas spontaneous rate of cytoplasmic fragmentation was low in unexposed oocytes (6.472.5%, n ¼ 414).…”

“…10,20 Because sphingolipids play key roles in the regulation of several fundamental biological events including uptake and movement of molecules within the cells, 23 we next assessed the role of S1P in modulating the intracellular trafficking of DXR. By exploiting the autofluorescent nature of DXR, we monitored its accumulation in both the cytoplasm and on the chromatin by computer-aided analysis of fluorescence intensity using deconvolution microscopy.…”

“…[7][8][9] It is unclear in those papers whether the induction agent(s) failed to trigger cytoplasmic fragmentation or whether the researches refrained from reporting this observation. In the process of our work to elucidate the mechanisms of chemotherapy-induced oocyte depletion, we observed that doxorubicin (DXR) (anthracycline-derived chemotherapeutical agent) induces both cellular and DNA fragmentation of murine oocytes 3,10 and thus represents an ideal model to study molecular events associated with cell death in oocytes.…”

“…Those experiments confirmed the importance of Bax, Caspase-2 and ceramide, but excluded p53 and Caspase-3 as important effectors in cytoplasmic fragmentation. 3,10,[20][21][22] In the current report, we attempted to further dissect some mechanistic aspects of the molecular pathways underlying cytoplasmic fragmentation of oocytes during the course of treatment with DXR, including: requirements of spindle checkpoints; exit from meiosis; analysis of gene expression; as well as the role of sphingolipids.…”