RAT OVARIAN PROSTAGLANDIN-ENDOPEROXIDE-SYNTHASE-1 AND PROSTAGLANDIN-ENDOPEROXIDE-SYNTHASE-2 - PERIOVULATORY EXPRESSION OF GRANULOSA CELL-BASED INTERLEUKIN-1-DEPENDENT ENZYMES

This laboratory has previously shown that interleukin-l (IL-l), a puta tive intermediary in the ovulatory process, is capable of up-regulatin g PG biosynthesis by cultured whole ovarian dispersates from immature rats. In part, this phenomenon was attributable to the stimulation of ovarian phospholipase A(2) activity. In this communication we examine the possibility that the PG-promoting property of IL-1 is also due to the up-regulation of PG endoperoxide synthase (PGS), the rate-limiting step in prostanoid biosynthesis. The in vivo expression of ovarian PG S-2 transcripts in the course of a simulated estrous cycle rose abrupt ly to a peak (35-fold increase over the control value; P < 0.05) 8-12 h after hCG administration (i.e. before or during projected ovulation) . PGS-1 transcripts, in turn, were not signifi cantly altered during t he periovulatory period. Treatment of cultured whole ovarian dispersat es with IL-1 beta resulted in dose-and time-dependent up-regulation of PGS-2 transcripts las well as of immunoreactive PGS-2 protein and PGE (2) accumulation), characterized by an ED50 of 2 ng/ml and a maximal ( 72-fold) increase at 10 ng/ml. Although treatment with IL-1 beta also led to an increase in PGS-1 transcripts and immunoreactive PGS-1 prote in, the relative magnitude of the effect was markedly reduced compared with that of PGS-2. Cotreatment with an IL-1 receptor antagonist comp letely reversed the IL-I effects, thereby suggesting mediation via the IL-1 receptor. The ability of IL-1 to up-regulate PGS-2 transcripts p roved relatively specific, in that other cellular regulators (insulin- like growth factor I, activin A, endothelin-l, transforming growth fac tor-alpha, tumor necrosis factor-alpha, vascular endothelial growth fa ctor, leukemia inhibitor factor, hepatocyte growth factor, or keratino cyte growth factor) were not effective. The optimal IL-1 effect requir ed heterologous contact-dependent coculturing of granulosa and thecal- interstitial cells. Taken together, these observations 1) reaffirm (by molecular probing) the granulosa cell as the primary site of ovarian PGS-1 and PGS-2 expression, 2) document an increase in ovarian PGS-2 t ranscripts before ovulation, and 3) reveal a marked dependence of ovar ian PGS (2 much greater than 1) transcripts, proteins, and activity on IL-1. The effects of IL-1 proved relatively specific, contingent upon somatic cell-cell cooperation, dose and time dependent, and IL-1 rece ptor mediated. These results are compatible with the proposition that the PG-promoting property of IL-1 is due, in large measure, to the act ivation of ovarian PGS transcription and translation. The ability of I L-1 to up-regulate ovarian PGS, an obligatory component of ovulation, is in keeping with the idea that IL-1 may constitute an intermediary i n the ovulatory process.