TLR2/4 signaling pathway mediates sperm-induced inflammation in bovine endometrial epithelial cells in vitro

PLoS One. 2019 Apr 17;14(4):e0214516. doi: 10.1371/journal.pone.0214516. eCollection 2019.

Abstract

We have recently shown that sperm attachment to bovine endometrial epithelial cells (BEECs) triggers uterine local innate immunity with induction of a pro-inflammatory response in vitro, however details of the mechanism remain unknown. Here, we investigated the involvement of Toll-like receptor 2/4 (TLR2/4) pathway in mediating sperm-BEECs inflammatory process. Immunohistochemistry of the uterine tissue revealed that TLR2 and TLR4 proteins were present in the luminal and glandular epithelia of bovine endometrium. Moreover, BEECs monolayers were treated with TLR2 agonist (Pam; 0, 10, 100, and 1000 ng/ml) or TLR4 agonist (LPS; 0, 0.1, 1, and 10 ng/ml) for 0, 1, 3, or 6 h, followed by evaluating mRNA expression of the pro-inflammatory genes (TNFA, IL-1B, IL-8, and PGES) in BEECs using a real-time PCR. Both Pam and LPS treatments showed a dose-dependent stimulation of mRNA expression of the pro-inflammatory genes. To elucidate the functional role of TLR2/4 in sperm-BEECs interaction, BEECs monolayers were incubated with either TLR2 antagonist or TLR4 antibody for 2 h prior to the co-culture with sperm for 3 h. Importantly, pre-incubation of BEECs with TLR2 antagonist or TLR4 antibody prevented the stimulatory effect of sperm on the transcription of pro-inflammatory genes in BEECs. Furthermore, sperm increased the phosphorylation levels of TLR2/4 downstream targets (p38MAPK and JNK) in BEECs within 1 h of the co-culture. Treatment of BEECs with TLR2 antagonist prior to sperm addition inhibited JNK phosphorylation, while TLR4 antibody inhibited the phosphorylation of both p38MAPK and JNK. In conclusion, the present in vitro findings strongly suggest that bovine endometrial epithelial cells respond to sperm via TLR2/4 signal transduction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cattle
  • Cells, Cultured
  • Coculture Techniques
  • Dose-Response Relationship, Drug
  • Endometritis / metabolism
  • Endometrium / cytology*
  • Epithelial Cells / metabolism*
  • Female
  • Immunity, Innate
  • Immunohistochemistry
  • Inflammation / metabolism*
  • Insemination, Artificial
  • Lipopolysaccharides
  • MAP Kinase Kinase 4 / metabolism
  • Male
  • Phosphorylation
  • Signal Transduction
  • Spermatozoa / metabolism*
  • Toll-Like Receptor 2 / agonists
  • Toll-Like Receptor 2 / metabolism*
  • Toll-Like Receptor 4 / agonists
  • Toll-Like Receptor 4 / metabolism*
  • p38 Mitogen-Activated Protein Kinases / metabolism

Substances

  • Lipopolysaccharides
  • Toll-Like Receptor 2
  • Toll-Like Receptor 4
  • p38 Mitogen-Activated Protein Kinases
  • MAP Kinase Kinase 4

Grants and funding

This work was supported by Grant-in Aid for Scientific Research (16H05013, 17F17407 and 18K19259) of Japan Society for the Promotion of Science (JSPS), Kieikai Research Foundation (2018C015), and Livestock Promotional Funds of Japan Racing Association (JRA). Mohamed Aboul Ezz received a scholarship for his PhD program from the Ministry of Higher Education, Egypt. Mohamed Ali Marey received a post-doctoral fellowship from JSPS.