RESUMEN
The objective of the current study was to evaluate the effects of 2 intramammary infusions of lipopolysaccharide (LPS) on inflammatory and reproductive parameters and endometrial gene expression of lactating Holstein cows. At 35 ± 7 d in milk, 20 cows were submitted to a Double Ovsynch program and randomly assigned to control (n = 11) and LPS (n = 9) treatments. Cows from the LPS treatment received 2 intramammary infusions of 25 µg of LPS after morning milking on d 5 and 10 post-AI, whereas control cows were infused with only saline. Blood samples were taken and ultrasound scanning of the ovaries was performed during the entire study before and after AI to determine haptoglobin, tumor necrosis factor-α, and progesterone concentrations as well as response to the hormonal protocol and corpus luteum diameter. Milk yield was evaluated and samples were taken for somatic cell count at 0, 10, 24, 34, and 96 h relative to each infusion. Rumen-reticular temperature was recorded using a rumen-reticular bolus logger and summarized hourly. On d 15 post-AI, uterine flushing for conceptus recovery and endometrial biopsies were performed. Samples of endometrium from cows with positive embryo recovery (control = 5; LPS = 6) were submitted to mRNA extraction and quantitative reverse-transcription PCR analysis of 96 target genes. Haptoglobin concentrations in plasma were greater for LPS treatment (control = 0.24 ± 0.07, LPS = 0.89 ± 0.06 optical density), but tumor necrosis factor-α concentrations were similar (control = 0.67 ± 0.11, LPS = 0.46 ± 0.11 ng/mL) between treatments. Lipopolysaccharide reduced milk yield after treatment (control = 34.3 ± 1.5, LPS = 29.4 ± 1.6 kg/d), whereas somatic cell count (log) was greater in LPS-treated cows until 34 h after infusions (control = 2.3 ± 0.1, LPS = 3.3 ± 0.1 cells/mL of milk). Rumen-reticular temperature of LPS cows was elevated between 5 and 10 h after each infusion compared with control cows (control = 39.5 ± 0.1, LPS = 40.1 ± 0.1°C). Progesterone concentration after AI was unaffected by treatment or pregnancy status as well as corpus luteum diameter and conceptus length on d 15. Lipopolysaccharide treatment altered the expression of 13 key genes in the endometrium (mostly upregulated), whereas another 17 tended to be modulated. Modified gene expression included genes related to immune response (PTX3 = 2.34-fold increase; IL6 = 3.42-fold increase; and TCN1 = 2.52-fold increase), adhesion molecules (CADM3 = 1.93-fold increase; MMP19 = 1.49-fold increase; EMMPRIN = 1.20-fold increase; SELL = 1.91-fold increase), Wnt signaling pathway (WNT2, FZD4, and FZD7, all <1.5-fold increase), and interferon-stimulated genes (BMP15 = 0.27-fold decrease; ISG15 = 2.17-fold increase, and MX2 = 2.23-fold increase). In summary, intramammary infusions of LPS were able to trigger an inflammatory response with no effect on corpus luteum diameter and concentration of progesterone in plasma. However, a limited but important set of modulations in the endometrium gene expression at d 15 of gestation was found.