Effect of pre-implantation factor on the secretion of prostaglandin F2α and prostaglandin E2 from bovine endometrial tissue following a lipopolysaccharide challenge in vitro.

Implications New treatments are needed for bovine endometritis. Preimplantation factor (PIF) has the potential to be a candidate; however, the present study shows that PIF did not alter the prostaglandin response in an endometritis model. Nonetheless, the effect of sPIF on other innate immune pathways integral to the response of bovine endometrium to LPS remains to be investigated.

Introduction Endometritis is a common inflammatory uterine disease in dairy cattle caused by entry of bacteria into the uterus. Secretion of prostaglandin F2α (PGF2α¬) and prostaglandin E2 (PGE2) from endometrial tissue is increased during the pro-inflammatory immune response caused by bacteria. Current treatments are antibiotics and hormones, however, with growing resistance to antibiotics (Santos et al., 2010) and the ineffectiveness of hormone treatment (Haimerl et al., 2012), new treatments are needed. Preimplantation factor (PIF) is a pregnancy specific peptide secreted by the embryo that has immune modulatory roles during pregnancy and has been shown to exert its effects in models of inflammatory based autoimmune diseases (Weiss et al., 2012). The aim was to assess if synthetic PIF (sPIF) has immune modulatory roles in a lipopolysaccharide (LPS; a component of the cell wall of Escherichia coli) model of endometritis.

Material and methods Bovine endometrial tissue from cows (n=12) with a stage I corpus luteum present (CL cows) was weighed and cultured in media alone or stimulated with LPS (1µg/ml), sPIF (50, 100, 500nM) or LPS (1µg/ml) and sPIF (50, 100, 500nM). Media were sampled at 24, 48 and 72h and analysed by radioimmunoassay (RIA) for PGF2α and PGE2 concentrations. Serum was obtained for all cows from blood samples taken immediately after slaughter and analysed by ELISA for progesterone concentration. The experiment was then repeated using endometrial tissue from follicular cows, cow type was recorded so that both dairy (n=3) and beef cows were used (n=4). Media was analysed by RIA for PGF2α concentrations. Data was expressed as production of prostaglandin per mg of tissue and analysed using a repeated measures ANOVA, with the following factors: CL data: sPIF, LPS and progesterone; follicular data: sPIF, LPS and cow type.

Results CL cows: CL cows were split into two groups based on progesterone concentration at slaughter: low progesterone (1.93±0.34ng/ml; n=8) and high progesterone (10.39±2.43ng/ml; n=4). There was no effect of progesterone on PGF2α or PGE2 secretion (P>0.05). There was a significant increase in PGF2α and PGE2 secretion over time in culture (P<0.001). LPS treatment induced a significant increase in PGF2α and PGE2 secretion from explants (P<0.001). There was a significant interaction between LPS treatment and progesterone group with explants within the high progesterone group secreting less PGF2α than those in the low progesterone group when not challenged with LPS (P<0.05). There was also an interaction between LPS and time, with explants stimulated with LPS secreting more PGE2 between each time point compared to those not stimulated with LPS (<0.001). sPIF had no effect on PGF2α or PGE2 secretion at any time point with or without LPS treatment (P>0.05). Variation between cows in response to sPIF was large, therefore cow type was recorded for follicular animals and samples were split into groups based on cow type. Follicular cows: There was no overall effect of cow type (beef or dairy) on PGF2α¬ secretion (P>0.05). There was a significant increase in PGF2α secretion over time (P<0.001). LPS treatment induced a significant increase in PGF2α secretion from explants (P<0.001). There was a significant interaction between LPS treatment and cow type; explants from beef cows secreted more PGF2α in response to LPS treatment than dairy cow explants (P<0.01). Furthermore there was a significant interaction between time point and cow type; explants from beef cows secreted greater concentrations of PGF2α between each time point than dairy cows (P<0.001). There was no effect of sPIF and high variability was seen in both dairy and beef cow explants in response to sPIF treatment (P<0.05).

Conclusion LPS significantly increased PGF2α and PGE2 production, demonstrating a clear pro-inflammatory immune response from both luteal and follicular tissue. However, the effect of sPIF was highly variable and had no overall effect on the pro-inflammatory response to LPS challenge in bovine endometrial tissue. It was hypothesised that this variability was due to cow type (beef or dairy, not recorded for the CL cows), however when cow type was recorded in follicular cows, breed did not affect results.