Effect of preimplantation factor in response to a LPS challenge on bovine endometrial IL-6 secretion and expression

Preimplantation factor (PIF) is a 15 amino acid peptide that is secreted by viable foetuses as early as the two cell stage. PIF is able to alter the maternal immune response for the benefit of the embryo and translated to models of inflammation-based auto-immune disease has immune modulatory properties. The aim of this study was to investigate the use of PIF as an immune modulator within a model of bovine E. coli endometritis. The study used three different concentrations of lipopolysaccharide (LPS) to mimic different levels of E. coli infection. Bovine endometrial tissue (n=4) was cultured from uteri with a stage IV corpus luteum. Tissue was initially pre-treated for 24 hours with PIF (100 nM) or media alone before subsequent PIF and LPS treatment. Thereafter tissue was treated for 6 and 24 hours with: Control (medium alone), LPS (5, 50 and 500 ng/mL), PIF (100 nM) or LPS (5, 50 and 500 ng/mL) with PIF (100 nM). Tissue was collected post-treatment at 6 hours for RT-PCR analysis for IL6 expression. Culture media samples were collected from separate wells at 24 hours for ELISA analysis of IL-6 secretion. There was a significant increase in IL6 mRNA expression when tissue was stimulated with 50 and 500 ng/mL LPS (P<0.05). When PIF was added with 500 ng/mL LPS, IL6 gene expression was increased compared to the expression induced by 500 ng/mL LPS alone (P<0.05). There was no effect of PIF on IL6 expression with any other concentration of LPS (P>0.05). All concentrations of LPS significantly increased IL-6 secretion from explants (P<0.001). However, there was no effect of PIF on IL-6 secretion from explants (P>0.05). In conclusion, at gene expression level, PIF increased IL6 expression relative to the highest concentration of LPS alone, displaying a pro-inflammatory effect of PIF. However at a protein level, it was shown that PIF had no effect on IL-6 secretion from explants. It is possible that changes in protein secretion may be seen at earlier time points.