PROBLEM: Interleukin-18 (IL-18) strongly induces interferon-gamma productio
n and is produced not only by types of immune cells but also by types of no
n-immune cells. Ovulation is thought to be an inflammation-like reaction in
which many pro-inflammatory cytokines are involved. We investigated whethe
r IL-18 is involved in the functions of ovary.
METHOD OF STUDY: The 4-week-old immature female mice were examined for IL-1
8 and IL-18 receptor (IL-18R) expression on their ovaries under stimulation
with pregnant mare's serum gonadotropin (PMSG) and human chorionic gonadot
ropin (hCG) by immunohistochemical staining, Western blotting and reverse t
ranscript-polymerase chain reaction. The IL-18R was blocked by the injectio
n of anti-IL-18R monoclonal antibody to immature mice during PMSG-hCG stimu
lation, and the number of ovulated ova was counted.
RESULTS: The expression of both proteins and mRNA of IL-18 and IL-18R were
very low in immature ovaries before stimulation, but after PMSG injection b
oth IL-18 and IL-18R increased dramatically in theca cells and reached a ma
ximum level at the peri-ovulatory phase then slightly lowered, but still ke
pt a high level during the luteal phase in the corpus luteum. The treatment
of IL-18R monoclonal antibody to the mice during ovarian stimulation reduc
ed the number of ovulated ova and inhibited the expansion of cumulus cells
surrounding the ovum.
CONCLUSION: IL-18 and IL-18R play roles in various kinds of function of ova