Regulations And Mechanisms Of Prostaglandin F_2α And Progesterone On Slit/Robo Expression During Luteolysis In The Mouse Ovary

The corpus luteum (CL) is a transient endocrine gland, the main function of the CL is to regulate the estrous cycle and maintain the pregnancy. If pregnancy does not occur, the CL regresses in a process termed luteolysis. Prostaglandin F2α (PGF2α) is a key factor to trigger the regression of CL. In addition, it has been reported that Slit/Robo signaling involves in regulating luteolysis. However, the interactions between PGF2α and Slit/Robo in the luteolysis progress remain to be established.The present study was designed to identify whether the luteolysis is regulated by the interactions of PGF2α and Slit/Robo signaling in mouse CL. Here, our in vitro and in vivo results demonstrate that PGF2α has functions on Slits/Robos expressions and Slit/Robo signaling mediates PGF2α’effect on luteolysis. Furthermore, we investigate the signaling pathways and molecular mechanisms of PGF2α in regulating Slits/Robos expressions. The important findings in our study include the following points:1. Real-time PCR and immunohistochemistry results showed that Slit2and Robol are highly and specifically co-expressed in mouse CL, and the functional studies showed that Slit/Robo signaling participated in mouse luteolysis by enhancing cell apoptosis and upregulating Caspase3expression. These demonstrate that the Slit/Robo plays important roles in the luteolysis of mouse.2. PGF2α increased Slits/Robos expressions in luteal cells in vitro in a dose-dependent and time-dependent manner. Cloprostenol, a synthetic analog of PGF2α, up-regulated Slits/Robos expressions in CL in vivo both at mRNA and protein levels. These data infer that Slit/Robo signaling has a function on PGF2α-induced luteolysis.3. PGF2α induced Slits/Robos expression in luteal cells through the PKC-dependent ERK1/2and P38MAPK signaling pathways, which subsequently enhanced cell apoptosis in CL.4. In order to assess whether the effect of PGF2α on luteolysis depends on Slit/Robo signaling, we examined PGF2α-induced luteal cell apoptosis with Slit/Robo signaling inhibitor. Our results revealed that Slit/Robo signaling inhibitor significantly decreased the levels of PGF2α-induced luteal cell apoptosis. These findings demonstrate that PGF2α and Slit/Robo signaling are involved in regulating mouse luteolysis by their interactions.5. We also investigated the effect of progesterone on Slit/Robo signaling, and the results revealed that progesterone significantly decreased Slits/Robos mRNA and protein levels both in vitro and in vivo condition.In conclusion, our data support the notion that PGF2α and progesterone play role in regulating the Slits/Robos expression. Furthermore, Slit/Robo signaling mediates the effects of PGF2α on luteolysis. These results provide a new perspective of the relationship between reproductive hormone and luteolysis.