Activation of sperm Toll-like receptor 2 induces hyperactivation to enhance the penetration to mucus and uterine glands: a trigger for the uterine inflammatory cascade in cattle

Ihshan Akthar; Yejin Kim; Takashi Umehara; Chihiro Kanno; Motoki Sasaki; Mohamed Ali Marey; Mohamed Samy Yousef; Shingo Haneda; Masayuki Shimada; Akio Miyamoto

doi:10.3389/fimmu.2023.1319572

Activation of sperm Toll-like receptor 2 induces hyperactivation to enhance the penetration to mucus and uterine glands: a trigger for the uterine inflammatory cascade in cattle

Front Immunol. 2023 Dec 19:14:1319572. doi: 10.3389/fimmu.2023.1319572. eCollection 2023.

Authors

Affiliations

¹ Global Agromedicine Research Center (GAMRC), Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan.
² Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Japan.
³ School of Veterinary Medicine, Kitasato University, Towada, Japan.
⁴ Department of Basic Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan.
⁵ Department of Theriogenology, Faculty of Veterinary Medicine, Damanhur University, Behera, Egypt.
⁶ Department of Theriogenology, Faculty of Veterinary Medicine, Assiut University, Assiut, Egypt.
⁷ Department of Clinical Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan.

Abstract

It is known that sperm and seminal plasma (SP) affect uterine immunity. In cattle, artificial insemination enables breeding by depositing frozen and largely diluted sperm with a negligible amount of SP into the uterus. Thus, the present study focused on the impact of frozen-thawed sperm on bovine uterine immunity. We have previously shown that in the bovine uterus, sperm swim smoothly over the luminal epithelium and some sperm interact with uterine glands to induce a weak inflammatory response mainly via the endometrial Toll-like receptor 2 (TLR2) signaling. However, the process by which sperm is encountered in the uterine glands is not completely clear. The present study intended to evaluate the role of sperm-TLR2 in sperm-uterine mucus penetration for reaching the glandular epithelium to induce the uterine immune response. To activate and block sperm-TLR2, they were treated with TLR2 agonist and antagonist, respectively. TLR2 activation enhanced sperm hyperactivation and improved its capacity to penetrate the artificial viscoelastic fluid and estrous-uterine-mucus. In contrast, TLR2-blocked sperm showed completely opposite effects. It is noteworthy, that the TLR2-activated sperm that penetrated the uterine mucus exhibited increased motile activity with hyperactivation. In the sperm-endometrial ex-vivo model, a greater amount of TLR2-activated sperm entered the uterine glands with an immune response, which was seen as the upregulation of mRNA expression for TNFA, IL1B, IL8, PGES, and TLR2 similar to those in control sperm. On the other hand, a lesser amount of TLR2-blocked sperm entered the uterine glands and weakened the sperm-induced increase only in PGES, suggesting that penetration of a certain number of sperm in the uterine gland is necessary enough to trigger the inflammatory response. Altogether, the present findings indicate that activation of sperm-TLR2 promotes their hyperactivation and mucus penetration with greater motility, allowing them to enter into the uterine glands more. This further suggests that the hyperactivated sperm contributes to triggering the pro-inflammatory cascade partly via TLR2 in the uterus.

Keywords: Toll-like receptor 2; cattle; hyperactivation; immune response; mucus; sperm; uterine gland.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Cattle
Female
Male
Mucus / physiology
Semen*
Spermatozoa / metabolism
Toll-Like Receptor 2* / metabolism
Uterus / metabolism

Substances

Toll-Like Receptor 2

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. The present research work was funded by a Grant-in-Aid for Scientific Research (20H03122, 22KF0018, and 23H02356) of Japan Society for the Promotion of Science (JSPS), and, in part, by the Livestock Promotional Funds of Japan Racing Association (JRA).