Involvement of pro-inflammatory cytokines, mediators of inflammation, and basic fibroblast growth factor in prostaglandin F2α-induced luteolysis in bovine corpus luteum

The process of luteolysis requires very subtly modulated coordination of different factors and regulation systems. Immune cells and cytokines were shown to be relevant for bovine luteolysis. The aim of this study was to investigate the detailed pattern of mRNA expression of the pro-inflammatory cytokines tumor necrosis factor alpha (TNFalpha), TNF receptor type 1 (TNF-R1), interleukin 1beta (IL-1beta), and interferon gamma (IFNgamma), and of the inducible nitric oxide synthase (iNOS) and the basic fibroblast growth factor (FGF-2) during prostaglandin (PG) F-2alpha-induced luteolysis in the bovine corpus luteum (CL). In addition, the mRNA expression for the LH-receptor (LH-R) and the steroidogenic enzyme P450scc was determined. Cows in the midluteal phase (Days 8-12) were injected with the PGF(2alpha) analogue cloprostenol, and CL were collected by transvaginal ovariectomy before and 2, 4, 12, 48, and 64 h after PGF(2alpha) injection. Conventional and real-time reverse transcription polymerase chain reaction RT-PCR (LightCycler) using SYBR Green I detection were employed to determine the mRNA expression for the investigated factors. All cytokines were significantly up-regulated during induced luteolysis. LH-R and P450scc mRNA were down-regulated (P < 0.05) during structural luteolysis (after 12 h), and P450scc in addition at 2 h after PGF(2alpha) (P < 0.05). FGF-2 expression increased (P < 0.001) during functional luteolysis (until 12 h after PGF(2alpha)) and diminished thereafter. The mRNA expression for iNOS decreased (P < 0.05) after induction of luteolysis. In conclusion, cytokines may be involved not only in structural but also in functional luteolysis and the deprivation of luteal survival factors, leading to a situation where apoptosis can occur. FGF-2 may participate in the suppression of cytokine-induced iNOS mRNA expression and in the prevention of an inflammatory reaction in the surrounding tissues.