Local effects of the sphingosine 1-phosphate on PGF2alpha-induced luteolysis in the pregnant rat

PELUFFO, MC; HERNANDEZ, SF; IRUSTA, G; STOUFFER, RL; TESONE, M

Kailua-Kona, Hawaii

Congreso; 41st SSR Annual Meeting; 2008

SSR (Society for the Study of Reproduction)

Since apoptosis is associated with regression of the corpus luteum (CL) in many species, studies were designed to determine if local administration of the antiapoptotic agent sphingosine-1-phosphate (S1P) effectively blocks the luteolytic action of PGF-2alpha. On day 19 of pregnancy, 2 h before systemic PGF-2alpha administration, rats were injected with either S1P or vehicle (control) into the bursa of both ovaries. The activity of four caspases, which contribute to the initial (caspase-2, -8 and -9) and final (caspase-3) events in apoptosis, was measured in pooled CL from 4 individual ovaries at 0 h (pretreatment) and 4 h after PGF-2alpha injection in both control and S1P groups. The expression of the phosphorylated form of AKT was analyzed in CL using an ELISA. In addition, cell death was evaluated by electronic microscopy (EM) in CL 36 h after PGF-2alpha injection. The activity of caspase-2, -3 and -8 was significantly greater by 4h after PGF-2alpha administration (0h vs 4h: 8491±1406 vs 36702±3155; 45049±5679 vs 155053±7391; 1895±283 vs 9888±585 RFU respectively, p<0.05), but not caspase-9 activity. In contrast, expression of the phosphorylated form of AKT decreased (0h vs 4h: 22.5±0.5 vs 19.5±0.2 U/ml; p<0.05). Administration with S1P suppressed these effects, decreasing caspase activities and increasing the phosphorylated form of AKT (p<0.05). EM studies revealed ultrastructural indices of apoptotic and non-apoptotic cell death in the CL at day 19 of pregnancy. PGF-2alpha treatment increased luteal cells with advanced signs of apoptosis (i.e. containing multiple nuclear fragments, chromatin condensation or apoptotic bodies) by 36h post-injection. S1P treatment suppressed these changes and increased the blood vessel density. These results suggest that S1P can block the luteolytic effect of the PGF-2alpha by decreasing caspase-2, -3 and -8 activities and increasing the phosphorylation of AKT. Supported by: ANPCYT (BID 1201 OC-AR PICT 99:05-06384), NIH-FIRCA RO3-TW007041 and NIH-NCCR RR00163.