LPS-mediated effects and spatio-temporal expression of TLR2 and TLR4 in the bovine corpus luteum

When given intravenously (iv), lipopolysaccharide (LPS) transiently suppresses the structure and function of the bovine corpus luteum (CL). This is associated with increased release of prostaglandin (PG) F2α metabolite (PGFM). The underlying regulatory mechanisms of this process remain, however, obscure. Therefore, the aims of this study were: (1) to investigate the expression of the LPS receptor toll-like receptor (TLR) 4 and TLR2 in the bovine CL during early, mid, and late luteal phases; (2) to further dissect the mechanisms of LPS-mediated suppression of luteal function. As revealed by semi-quantitative qPCR and immunohistochemistry, both receptors were detectable throughout the luteal lifespan. Their mRNA levels increased from the early towards the mid-luteal phase; no further changes were observed thereafter. The TLR4 protein seemed more highly represented than TLR2. The cellular localization of TLRs was in blood vessels; weaker signals were observed in luteal cells. Additionally, cows were treated either with LPS (iv, 0.5 µg/kgBW) or with saline on Day 10 after ovulation. Samples were collected 12 h after treatment, and on Day 10 of the respective subsequent (untreated) cycle. The mRNA expression of several possible regulatory factors was investigated, revealing the suppression of PGF2α receptor (PTGFR), steroidogenic acute regulatory protein (STAR) and 3β-hydroxysteroid dehydrogenase (3βHSD), compared with controls and subsequent cycles. The expression of TLR2 and TLR4, interleukin (IL) 1α and IL1β, and of PGF2α and PGE2 synthases (20αHSD/PGFS and mPTGES, respectively) was increased. The results demonstrate the presence of TLR2 and TLR4 in the bovine CL, and implicate their possible involvement in the deleterious effects of LPS on its function

Gene expressions in the persistent corpus luteum of postpartum dairy cows: distinct profiles from the corpora lutea of the estrous cycle and pregnancy

Persistence of the corpus luteum (CL) in cattle usually occurs during the puerperium and is associated with interference of prostaglandin (PG) F(2α) release from the uterus. The objective of the present study was to determine for the first time the gene expressions in the persistent CL compared with the CL of pregnancy and cyclic CL. Three types of CL biopsy samples were collected from 32 lactating Holstein cows: (1) CL persisting for 29 to 33 days after the first ovulation postpartum (persistent CL, n=9), (2) CL between days 29 and 33 of early pregnancy (CL of pregnancy, n=8) and (3) CL between days 10 and 13 of the estrous cycle (cyclic CL, n=27). mRNA expression of 2',5'-oligoadenylate synthetase-1 was upregulated only in the CL of pregnancy, confirming exposure to interferon-τ (IFNT) produced by trophoblasts in pregnant cows. mRNA expressions of immune tolerance-related factors (PGES and forkhead/winged helix transcription factor 3) were upregulated in the CL of pregnancy but not in the persistent CL, suggesting that IFNT controls upregulation of these genes. mRNA expression relating to some of the major systems such as lymphangiogenesis, inflammation and apoptosis were similarly upregulated in the persistent CL and the CL of pregnancy but not in the cyclic CL. The results suggest that the persistent CL may survive for a long period without changes in local immune tolerance but develops several major systems required for CL maintenance similar to the CL of pregnancy