Heat stress affects prostaglandin synthesis in bovine endometrial cells

Abstract

Heat stress (HS) negatively affects reproduction in cattle; however, its effect on endocrine function in bovine endometrial cells remains unclear. In this study, we examined the effects of HS on the production of prostaglandin (PG) E2 and PGF2α in the cultured bovine endometrial epithelial and stromal cells separately. To evaluate the effect of HS on endocrine function, the cells were cultured at 38.5°C (control) or 40.5°C (HS). After treatment, PGE2 and PGF2α levels were measured via enzyme immunoassay (EIA) and mRNA expressions of enzymes involved in PG synthesis were examined via quantitative reverse transcription polymerase chain reaction (RT-PCR). HS did not influence the production of PGE2 or PGF2α in the epithelial cells; however, HS significantly enhanced the production of both PGE2 and PGF2α in the stromal cells (P < 0.05). In addition, HS significantly increased phospholipase A2 (PLA2), cyclooxygenase 2 (COX2), prostaglandin F synthase (PGFS), prostaglandin E synthase (PGES), and carbonyl reductase 1 (CBR1) mRNA expression in the stromal cells (P < 0.05). The overall results suggest that HS induces mRNA expression of enzymes involved in PG synthesis, resulting in the upregulation of PGE2 and PGF2α production in the stromal cells, but not in the epithelial cells. The HS-induced increase of PGE2 and PGF2α secretion in bovine endometrial stromal cells may disrupt the normal estrous cycle and cause infertility in cows during summer.

Keywords: Bovine; Endometrial cell; Heat stress; Prostaglandin.

Fig. 1.

Expressions of HSP70 and HSP90 mRNA (A and C) and protein (B and D) in the bovine endometrium in the mid luteal stages in winter (December 2013 – April 2014; n = 5 uteri) and summer (July – August 2014 and August 2015; n = 6 uteri). Different superscripts indicate significant difference (P < 0.05), as determined by Student’s t-test.

Fig. 2.

Effects of elevated incubation temperature (38.5°C, 39.5°C, and 40.5°C) on HSP70 and HSP90 mRNA and protein expressions in the cultured bovine endometrial epithelial (A, B, C and D) and stromal (E, F, G and H) cells (mean ± S.E.M, n = 8–13 uteri). Different superscripts indicate significant differences (P < 0.05), as determined by ANOVA followed by Dunnett’s multiple comparisons test.

Fig. 3.

Effect of elevated temperature on the production of PGE2 and PGF2α in the cultured bovine endometrial epithelial (A, B) and stromal (C, D) cells (mean ± S.E.M., n = 4–6 uteri). Different superscripts indicate significant differences (P < 0.05), as determined by Student’s t-test.

Fig. 4.

Effect of elevated temperature on the expressions of PLA2, COX2, PGFS, cPGES, and CBR1 mRNA in the cultured bovine endometrial epithelial (A, B, C, D and E) and stromal (F, G, H, I, and J) cells (mean ± S.E.M., n = 6–13 uteri). Different superscripts indicate significant differences (P < 0.05), as determined by Student’s t-test.