Unravelling the role of 17β-estradiol on advancing uterine luteolytic cascade in cattle

In cattle, 17β-estradiol (E2) stimulates prostaglandin F2α (PGF2α) synthesis, which causes luteolysis. Except for the well-established upregulation of oxytocin receptor gene (OXTR), molecular mechanisms of E2-induced PGF2α release in vivo remain unknown. We hypothesized that E2-induced PGF2α release requires de novo transcription of components of the PGF2α synthesis machinery. Beef cows (n = 52) were assigned to remain untreated (Control; n = 10), to receive 50% ethanol infusion intravenously (Placebo; n = 21), or 3 mg E2 in 50% ethanol infusion intravenously (Estradiol; n = 21) on day 15 (D15) after estrus. We collected a single endometrial biopsy per animal at the time of the treatment (0h; Control B0h group), 4 hours (4h; Placebo B4h group and Estradiol B4h group), or 7 hours (7h; Placebo B7h group and Estradiol B7h group) post-treatment. Compared to the Placebo group, the Estradiol group presented significantly greater 13,14-dihydro-15-keto-PGF2α concentrations between 4h and 7h and underwent earlier luteolysis. At 4h, the qPCR analysis showed a lower abundance of ESR1, ESR2 and aldo-keto reductase family 1 member B1 (AKR1B1) genes in the Estradiol B4h group, and a greater abundance of OXTR compared to the Placebo B4h group. Similarly, the E2 treatment significantly reduced the abundance of AKR1B1, and AKR1C4 in the Estradiol B7h group, compared to the placebo group. Overall, E2-induced PGF2α release and luteolysis involved an unexpected and transient downregulation of components of the PGF2α-synthesis cascade, except for OXTR, which was upregulated. Collectively, our data suggest that E2 connects newly-synthesized OXTR to pre-existing cellular machinery to synthesize PGF2α and cause luteal regression.

64 Prediction of pregnancy and early embryo loss through OAS-1 expression, concentrations of pregnancy-associated glycoproteins, and Doppler ultrasonography in beef cattle

We aimed to compare three methods to detect pregnancy based on interferon-tau stimulated gene expression in peripheral blood polymorphonuclear cells and Doppler ultrasonography (Doppler-US) 20 days after timed AI and the concentrations of pregnancy associated glycoproteins (PAGs) 25 days after timed AI. Our second objective was to compare interferon-tau stimulated genes and PAGs as early embryo loss (EEL) predictors. Nelore cows (n=144) and heifers (n=103) were submitted to timed AI (Day (D) 0). On D20, polymorphonuclear cells were isolated from blood samples by Ficoll gradient (GE Healthcare), and the RNA was extracted. Expression of the interferon-tau stimulated gene (OAS-1) was quantified by qPCR and normalized to reference genes (GAPDH and ACTB). On D25, blood was collected from the jugular vein and PAG concentrations were measured by an in-house enzyme-linked immunosorbent assay. Pregnancy diagnoses were performed on D20 by luteolysis detection with Doppler-US and on D30 by detection of an embryo by heartbeat. Animals were classified as pregnant (P; fetus on D30), non-P (NP; no active corpus luteum on D20), and EEL (active corpus luteum on D20 but NP on D30). Expression of OAS-1 and PAG concentrations were analysed by analysis of variance using PROC MIXED of SAS considering the effects of group, category, and their interaction. Receiver operating characteristic curves were created, and the area under the curve (AUC), accuracy, specificity, and sensitivity were calculated for pregnancy predictions on D20 (OAS-1 and Doppler-US) and D25 (PAGs) compared with the standard diagnosis method on D30. Expression of OAS-1 and PAG concentrations were greater (P<0.01) in the P (2.4±0.2 and 4.8±0.2ngmL−1, respectively) compared with the NP (0.50±0.1 and 1.2±0.2ngmL−1, respectively) and EEL (0.8±0.2 and 1.0±0.2ngmL−1, respectively) groups. Receiver operating characteristic analysis indicated that OAS-1, Doppler, and PAGs were significant (P<0.01) predictors of pregnancy in heifers (AUC=0.86, 0.92, and 0.94, respectively) and cows (AUC=0.82, 0.94, and 0.95, respectively). The PAGs and Doppler-US presented higher accuracy on diagnosing pregnancy (92 and 89% for heifers, 94 and 93% for cows, respectively) than OAS-1 (81% for heifers and 75% for cows). Doppler-US was 100% sensitive to detect nonpregnant females, which avoided false negative results, whereas PAG concentrations presented a higher specificity (86% for heifers and cows) when compared with Doppler-US and OAS-1 (76 and 65% for heifers, 85 and 75% for cows, respectively). On D25, PAGs were 90% accurate to detect heifers and cows that would experience EEL, whereas on D20, OAS-1 was 50% accurate. In conclusion, Doppler-US can be used as early as D20 with high accuracy and sensitivity. Likely, the use of PAG concentrations on D25 is highly accurate and is more effective at detecting EEL. Pregnancy diagnosis through OAS-1 expression is not as accurate as the other methods and could not efficiently predict EEL. This research was supported by FAPESP (2015/106069; 2017/134729).

Supplemental progesterone induces temporal changes in luteal development and endometrial transcription in beef cattle

Long-acting injectable progesterone (iP4) supplementation during early diestrus is a strategy to increase conception rates in cow-calf beef operations. However, iP4 treatment causes early functional and structural regression of the corpus luteum (CL) in a proportion of iP4-treated animals, resulting in pregnancy loss. The hypothesis evaluated was that iP4 accelerates downregulation of sex-steroid receptors (PGR, ESR1, ESR2) during early to mid-diestrus and the upregulation of genes controlling PGF₂α secretion (OXTR, PTGS2, AKR1B1) during late diestrus in the endometrium. Ovulations of cyclic, multiparous Nelore (Bos indicus) cows were synchronized, and cows were divided to receive placebo or 300 mg iP4 3 d postovulation (D3). Growth and vascularization of luteal tissue were evaluated by ultrasonography. Blood samples were collected from 3 d postovulation to 3 d after luteolysis, and P4 plasma concentrations were measured by radioimmunoassay. On days 3, 5, 7, 9, 11, 13, and 16 luminal endometrial samples were taken using a cytologic brush. Transcript abundance was measured by qPCR. Structural luteolysis occurred 3 d earlier in cows receiving iP4 compared to the control group. Analyzing only cows that received iP4, those that presented early luteolysis (ie, ≤ D16) showed a decrease in CL area and P4 concentration after D5, compared to the control group. Cows that presented early luteolysis showed a reduced abundance of transcripts on D5 for the ESR2 gene and a greater abundance of transcripts for OXTR and ESR1 on D16, compared to cows that did not present early luteolysis. The iP4-induced early luteolysis can be explained by two nonexclusive possibilities: the activation of uterine mechanisms that trigger early secretion of endometrial PGF pulses and the formation of a subfunctional CL that is prone to early regression.

Supplementation with long-acting progesterone in early diestrus in beef cattle: I. effect of artificial insemination on onset of luteolysis

Progesterone (P4) supplementation in early diestrus advances changes in the endometrial transcriptome, stimulating embryonic development. However, it also induces early onset of luteolysis. Occurrence of luteolysis before D16 postmating can be detrimental to fertility. A potential counteracting role of the elongating conceptus on early luteolysis is understood poorly. The aim of the study was to evaluate the effect of artificial insemination (AI; ie, pregnancy) on the temporal dynamics of luteolysis of cows supplemented with P4. Nonsuckled beef cows were inseminated at 12 h after estrus (D0: ovulation) or were not inseminated (no-AI). On D3, the AI cows were assigned to receive a single dose of 150 mg of injectable long-acting P4 via intramuscular injection (AI + iP4; n = 23), and the no-AI cows were assigned to receive iP4 (iP4; n = 21) or saline (control, n = 22). Corpus luteum (CL) development and regression were determined by ultrasonography (US) between D3 and D21. Plasma P4 concentrations were measured on D3 and every other day from D9 to D21. Pregnancy status was determined by US (D28‒D32). iP4 supplementation reduced luteal development (D5-D10) compared to the control group and increased incidence of luteolysis between D14 and D15. On D15, the proportion of cows that underwent luteolysis and plasma P4 concentrations differed between the iP4 group (47.6; 2.10 ± 0.47) and the control group (13.6; 4.40 ± 0.46) and was intermediate in the AI + iP4 group, respectively (26.1%; 3.70 ± 0.45 ng/mL; P < 0.05). The AI effects were due to the pregnant cows (n = 7). Considering nonpregnant cows only, the proportion of early luteolysis in the AI + iP4 group (37.5%) was similar to the iP4 group. Pregnancy was not established in cows having a shortened luteal lifespan. Indeed, interval to luteolysis in the AI + iP4 group (15.50 ± 0.66 d) was similar to the iP4 group (16.38 ± 0.46 d), but less than the control group (17.38 ± 0.40 d; P = 0.05). In conclusion, the effect of AI on extending luteal lifespan occurred exclusively in cows that maintained pregnancy.

PRAME/EZH2-mediated regulation of TRAIL: a new target for cancer therapy

The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) exerts a cancer cell-specific pro-apoptotic activity. This property made the TRAIL associated pathway one of the most promising strategies aimed at inducing tumor-selective death. In fact, several approaches have been considered to explore this pathway for cancer therapy, such as recombinant TRAIL, agonist antibodies for TRAIL receptors, and adenoviral TRAIL. However, all of these approaches have certain disadvantages that limit their clinical use. Our recent discovery that the complex PRAME/EZH2 is able to repress TRAIL expression, in a cancer-specific manner, suggests an alternative approach for combined cancer therapy. A genetic or pharmacological inhibition of TRAIL repressors in cancer cells could restore endogenous TRAIL expression, thereby overcoming some of the limitations of and/or cooperating with previous approaches.