Abstract
After parturition, cows frequently develop uterine bacterial infections, resulting in the onset of endometritis. To eliminate the bacteria, bovine endometrial cells secrete chemokines, such as IL‐6 and MCP1, which attract macrophages (MΦs) to the subepithelial stroma. These attracted MΦs are not only involved in bacterial elimination but also the orchestration of inflammation and tissue repair. These immune responses aid in the recovery from endometritis; however, the recovery from endometritis takes longer in summer than in any other season. Based on these findings, we hypothesized that heat stress (HS) affects the chemokine production in endometrial cells. To confirm this hypothesis, we compared IL‐6 and MCP1 production induced by lipopolysaccharide (LPS) in bovine endometrial epithelial and stromal cells under normal (38.5°C) and HS conditions (40.5°C). In the endometrial epithelial cells, IL‐6 production stimulated by LPS was significantly (p < .05) suppressed under HS conditions. MCP1 production in endometrial epithelial cells was not detected under both the control and HS conditions regardless of the presence of LPS. Moreover, LPS significantly (p < .05) stimulated IL‐6 and MCP1 production in endometrial stromal cells. Moreover, HS significantly (p < .05) enhanced their production compared to that under the control conditions. In addition, HS did not affect the migration ability of MΦs; however, the supernatant of the endometrial stromal cells cultured under the HS condition significantly (p < .05) attracted the MΦs when compared to the control condition. These results suggest that HS disrupts chemokine production in two types of endometrial cells and alters the distribution of MΦs in the endometrium during the summer.
Highlights
The bovine endometrium is a major contributor to the regulation of reproduction and is involved in processes such as the estrous cycle, implantation, and placenta formation (Bazer et al, 2009; Poyser, 1995; Roberts et al, 1992)
To determine whether heat stress (HS) affects the immune responses in bovine endometrium at the cellular level, we examined the chemokine production in bovine endometrial cells in vitro under HS conditions
3.4 | Experiment 4: Effect of HS and LPS on the mRNA expression of Toll-like receptor 4 (TLR4), CD14, and MD2 in cultured bovine endometrial epithelial and stromal cells In Experiment 4, to determine whether HS affects the recognition of LPS in bovine endometrial epithelial and stromal cells, we examined the mRNA expression of the pattern-recognition receptor and its related factors
Summary
The bovine endometrium is a major contributor to the regulation of reproduction and is involved in processes such as the estrous cycle, implantation, and placenta formation (Bazer et al, 2009; Poyser, 1995; Roberts et al, 1992). | 2 of 14 bovine cervix becomes softer and the endometrial epithelial layer is exfoliated in the postpartum period, the uterine anatomical barrier functions are disrupted, resulting in bacterial infections in the bovine endometrium (Bondurant, 1999; Bromfield et al, 2015). In the case of bovine endometritis, because almost all of E. coli are present in the uterine lumen and endometrial epithelial layer, immune cells need to be recruited there to eliminate the bacteria and promote recovery from endometritis (Karstrup et al, 2017). To determine whether HS affects the immune responses in bovine endometrium at the cellular level, we examined the chemokine production in bovine endometrial cells in vitro under HS conditions
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