The protective mechanism of cetrorelix acetate in a chemotherapy-induced murine model of ovarian damage

We previously demonstrated that the GnRH antagonist, cetrorelix acetate, reduced loss of primordial follicles in mice treated with cyclophosphamide. In this murine model, cetrorelix acetate reduced granulosa cell death but the protective mechanism remained unclear. The objective of this study was to examine cell-death pathways in a murine model to elucidate the mechanism(s) involved. Laboratory study in a murine model. Sixty 6-8 week old BALB/c mice (15 per group) were treated with saline (group 1), antagonist only (group 2), cyclophosphamide only 100mg/kg (group 3), and cyclophosphamide 100mg/kg + antagonist (group 4). Mice were treated with saline or cetrorelix acetate (0.5mg/kg) for 15 days followed by cyclophosphamide or saline on day 9. Ovarian tissue was obtained under an approved animal protocol. Expression of three proteins in the cell death pathway was quantified by immunohistochemical staining (H-SCORE): 1) cleaved caspase-3 (cCASP3), a cysteine peptidase that functions as an active and immediate mediator of substrate breakdown in apoptosis; 2) Bax, a pro-apoptotic protein; and 3) LAMP-1, lysosome-associated membrane protein-1, a protein present in autophagosomes. Expression of cCASP3 in granulosa cells was reduced in antagonist-treated mice (groups 2 and 4) compared to mice not treated with antagonist (groups 1 and 3). Bax expression was increased in the combined antagonist + cyclophosphamide, and antagonist only mice (groups 2 and 4). LAMP-1 expression was greatest in antagonist only-treated mice (group 2). The classic apoptotic pathway was partially inhibited in GnRH antagonist-treated mice as demonstrated by the reduction in staining for cCASP3. Autophagy may play a role in the protective effect mediated by a GnRH antagonist as demonstrated by increased LAMP-1 expression.