Effects of Echinomycin on Follicular Development in the Ovary of Postnatal Rats

Echinomycin (Ech) is a small-molecule inhibitor of hypoxia-inducible factor-1 DNA-binding activity, which plays a crucial role in the regulation of ovarian functions in mammals. The present study was designed to test the hypothesis that hypoxia-inducible factor (HIF)-1alpha-mediated proliferation cell nuclear antigen (PCNA) expressions contributed to the follicular development in the ovary of postnatal rats. Through the histological examination, the decrease of growing and antral follicle numbers was found in Ech-treated group. And then PCNA mRNA and protein expressions were detected by real time PCR and western blot and the significant decreases of these were found. While the levels of HIF-1alpha mRNA and protein expression were no obviously changes. Further analysis of HIF-1 binding activity found Ech significantly inhibited HIF-1 binding activities in Ech-treated group. These results indicated Ech inhibites follicular development though HIF-1alpha signaling pathway and HIF-1alpha plays an important role in this developmental process in PCNA-dependent manner. Granulosa cell culture experiment further identified the above findings. Taken together, these results demonstrated this HIF-1alpha-mediated PCNA expression is one of the important mechanisms regulating the ovarian follicular development in mammals.