Neurotensin stimulates the sperm acrosome reaction and reduces percentages of fertilization in vitro

Abstract

Objective: To determine the impact of neurotensin (NTS), a naturally occurring peptide, on the function of human and nonhuman primate sperm. Design: Experimental study. Setting: University-based research laboratory. Patient(s)/Animal(s): Consenting normozoospermic human donors and cynomolgus macaques. Intervention(s): None. Main Outcome Measure(s): Sperm acrosome status was assessed. Computer-assisted semen analysis assessed sperm motility, progression, and velocity. Immunocytochemistry and receptor selective agonists were used to identify specific NTS receptors on sperm. Monkey oocytes were obtained after ovarian stimulation, and NTS-treated monkey sperm were used for in vitro fertilization. Results: Neurotensin treatment of human sperm stimulated the acrosome reaction in both a dose-dependent (0.1-10 mmol/L) and timedependent (5-30 minutes) manner. Neurotensin treatment did not alter sperm motility or progression. Both a general NTS receptor antagonist (SR142948) and a NTSR1 selective antagonist (SR48692) reduced the ability of NTS to stimulate the acrosome reaction. The neurotensin receptor NTSR1, but not NTSR2 or SORT1, was detected in monkey sperm using immunostaining. Neurotensin treatment also compromised the ability of sperm to fertilize an oocyte. Percentage of fertilization with untreated monkey sperm and monkey oocytes was 72%. Sperm pre-treated with NTS yielded a significantly lower fertilization rate of 18%. Conclusion(s): Neurotensin effectively stimulates the acrosome reaction in human and monkey sperm. Neurotensin produced by the oviduct or cumulus cells may promote natural fertilization. Pretreatment of sperm with NTS significantly reduces fertilization. Exposure of sperm to NTS prior to reaching the oviduct has the potential for contraceptive development. Identification of NTSR1 as the mediator of NTS action provides a specific target for future studies.

Neurotensin: A novel mediator of ovulation?

“…NTSR1 mRNA was consistently detected in pancreas, and NTSR1 immunodetection was noted in pancreatic islets, which served as a positive control (Figure 4J). 29,30 We have previously confirmed that this NTSR1 antibody detects NTSR1 in monkey testis 31 …”

“…29,30 We have previously confirmed that this NTSR1 antibody detects NTSR1 in monkey testis. 31 NTSR2 immunodetection in granulosa cells was strong before hCG administration, then was low to undetectable at 36 hour hCG, or just before ovulation ( Figure 4K-N). Strong NTSR2 immunodetection was noted in the intercalated duct cells of the exocrine pancreas, which served as a positive control ( Figure 4O).…”

Neurotensin modulates ovarian vascular permeability via adherens junctions

“…On the following day, surgery was performed to inject the ovulatory follicle with either sterile water ( n = 2), rabbit IgG with no known antigen (Abbiotec 254513, San Diego, CA; n = 3), a rabbit antibody against NTS (ImmunoStar 20072, Hudson, WI; n = 4), or the general NTS receptor antagonist SR142948 (Tocris Bioscience 2309, Bristol, UK; 100 μM, n = 4) 21 . The final concentration of SR142948 in the follicle was selected based on prior reports 22–25 . Sterile water was used as the vehicle for the SR142948 injection solution.…”

“…21 The final concentration of SR142948 in the follicle was selected based on prior reports. [22][23][24][25] Sterile water was used as the vehicle for the SR142948 injection solution. Directly after surgery, 1000 IU hCG was administered to initiate ovulation.…”