Ovarian steroids do not affect bovine endometrial cytokine or chemokine responses to Escherichia coli or LPS in vitro

Abstract

The risk of bacterial infection of the endometrium causing uterine disease in cattle is increased in the progesterone-dominated luteal phase of the ovarian cycle, while oestrogens or oestrus are therapeutic or protective against disease. The first line of defence against bacteria, such as Escherichia coli that cause inflammation of the endometrium, is the innate immune system, which recognises bacterial lipopolysaccharide (LPS). This study tested the hypothesis that cyclic variation in ovarian hormone concentrations alters innate immune responses within the bovine endometrium. Ex vivo organ cultures of endometrium, and in vitro cultures of endometrial epithelial and stromal cells, and peripheral blood mononuclear cells (PBMCs), all mounted inflammatory responses to E. coli or LPS, with secretion of inflammatory mediators interleukin 1b (IL1b), IL6 and IL8, and increased expression of mRNA encoding IL1B, IL6, CXCL8 (IL8) and CCL5. However, these inflammatory responses, typical of innate immunity, were not affected by the stage of ovarian cycle in which the endometrium was collected for organ culture, or by exogenous oestradiol or progesterone. Although a dexamethasone-positive control reduced inflammation stimulated by E. coli or LPS, treatment with oestradiol or progesterone, or inhibitors of oestradiol or progesterone nuclear receptors, did not affect endometrial cell or PBMC secretion of IL1b, IL6 or IL8, or IL1B, IL6, CXCL8 and CCL5 gene expression. In conclusion, the stage of the oestrus cycle or ovarian steroids did not modulate the innate immune response in the bovine endometrium in vitro.

Polarized Epithelial Cells Secrete Interleukin 6 Apically in the Bovine Endometrium1

“…Furthermore, culturing cells for several days likely modulates steroid receptor expression and physiological function, although the same model of polarized bovine endometrial epithelial cells do secrete prostaglandins as expected [24]. The present study also supports the recent findings that stage of VECTORIAL IL6 FROM ENDOMETRIAL EPITHELIUM estrous cycle, exogenous steroids, or inhibitors for the steroid nuclear receptors did not affect IL6 secretion from conventional bovine endometrial epithelial or stromal cell cultures [38]. In mice, stage of estrous cycle also had little impact on the predominant apical secretion of IL6 from polarized epithelial cells, although exogenous estradiol reduced IL6 release [25].…”

“…In the present study, exogenous progesterone, estradiol, or a combination of the steroids had little effect on TER or on IL6 secretion, although inflammation was suppressed by dexamethasone as expected [38]. However, caution is required when comparing the in vitro data from the present study with the in vivo situation.…”

“…However, use of different breeds of the same species also provides a wider range of evidence. Furthermore, the epithelial and stromal cell secretion of IL6 or CXCL8 in response to E. coli or LPS does not differ significantly between beef and dairy breeds, at least in vitro [38]. In addition, the preferential secretion of inflammatory mediators to the apical surface of polarized epithelial cells is not unusual in other species [1,2].…”

“…Dexamethasone is the prototypical glucocorticoid anti-inflammatory steroid and is effective with endometrial cells [38,39]. Thus, to examine if dexamethasone modulated inflammatory responses of polarized epithelial cells, cells were incubated for 24 h in control medium or in medium containing 5 ng/ml of dexamethasone.…”

Toll‐like receptor and related cytokine mRNA expression in bovine corpora lutea during the oestrous cycle and pregnancy

“…Lipopolysaccharide (LPS), produced by E. coli , a common causative agent of uterine infections in dairy cows, binds to TLR4 on uterine epithelial cells. This induces a pro‐inflammatory cascade of cytokines leading to altered prostaglandin (PG) production (increased PGE‐2:PGF2α ratio) by the uterus (Davies et al., ; Sheldon et al., ) which causes delayed luteolysis and extended cycles in animals with uterine infections (Davies et al., ; Saut, Healey, Borges, & Sheldon, ; Sheldon et al., ). In other studies, it was shown that LPS concentrations in peripheral blood (Mateus, Lopes da Costa, Diniz, & Ziecik, ), and within the ovarian follicular fluid (Herath et al., ), are elevated in animals with uterine infections, suggesting that LPS may also have direct effects on ovarian function.…”