Endocrine Abstracts

Corpus luteum lifespan is regulated by the secretion of prostaglandins (PGF and PGE) from the endometrium. which are synthesized by cyclo-oxygenase 2 (COX-2). However. corpus luteum lifespan is altered by uterine bacterial infections. causing infertility. Uterine infection is common after parturition in cattle. often involving Escherichia coli. The pathogenic ligand of E. coli. lipopolysaccharide (LPS). is detected by Toll-like Receptor 4 (TLR4). predominantly found on immune cells. The aims of this study were to determine whether endometrial cells express TLR4 mRNA and respond to LPS in vitro. Epithelial and stromal cells cultured from bovine endometrium were challenged with heat-killed E. coli (10² to 10⁵ CFU/ml) or LPS (0.1 to 3 μg/ml). reflecting their ranges during spontaneous uterine infections. After 24 h. cells were collected for RT-PCR. and supernatants aspirated for PGF and PGE measurement using radioimmunoassay. Stromal and epithelial cells expressed TLR4 mRNA. and respond to E. coli or LPS stimulation by up-regulation of COX-2 mRNA. Compared with control. addition of 10⁵ E. coli CFU/ml increased secretion of stromal cell PGE (28.9±10.2 vs 112.2±8.4 ng/ml. P<0.05). and epithelial cell PGF (5.1±0.6 vs 12.7±1.4 ng/ml. P<0.05). Addition of LPS. even at 0.1 μg/ml. increased secretion of stromal cell PGE (11.5±1.4 vs 49.5±4.0 ng/ml. P<0.05). and epithelial cell PGF (7.2±1.9 vs 10.6±0.9 ng/ml. P<0.05). This functional response was likely to be TLR4 mediated since addition of LPS antagonist. polymixin B. abrogated the production of prostaglandins. In summary. endometrial stromal and epithelial cells express TLR4 mRNA. and E. coli or LPS stimulate secretion of PGE and PGF. which may disrupt corpus luteum function.

This work was supported by BBSRC.