ENDOCRINE- AND AUTOCRINE-MEDIATED REGULATION OF RAT OVARIAN (THECA-INTERSTITIAL) INTKRLEUKIN-βGENE EXPRESSION: GONADOTROPIN-DEPENDENT PREOVIILATORY ACQUISITION

Abstract

We, and others have recently demonstrated the ovary to be a site of interleukin-1 (IL-1) reception and action. Since IL-1 is an established mediator of inflammation and since ovulation may constitute an inflammatory-like reaction, consideration was given to the possibility that IL-1 may play an intermediary role in the ovulatory process. To begin to evaluate the above hypothesis, we have set out to evaluate rat ovarian IL-1 beta gene expression, to determine its cellular localization, and to study its modulation by key endocrine and autocrine regulatory signals. To this end, use was made of a solution hybridization/RNase protection assay in which rat ovarian total RNA (20 micrograms) was hybridized with a [32P]-labeled 272 base rat IL-1 beta antisense riboprobe. To assess rat ovarian IL-1 beta gene expression under in vivo circumstances, use was made of an established experimental model capable of simulating naturally-occurring follicular maturation, ovulation, and corpus luteum formation. Specifically, a single subcutaneous injection of PMSG (15IU/rat) was followed (48h) later by an ovulatory dose (15IU) of human chorionic gonadotropin (hCG). A faint protected fragment 222 bases long corresponding to the IL-1 beta message was detectable in whole ovarian material prior to gonadotropic stimulation. Treatment with PMSG for 48h resulted in a modest, albeit measurable increase in the densitometrically-quantified steady state levels of the ovarian IL-1 beta message. Most striking, however, were the increments noted in the relative abundance of ovarian IL-1 beta transcripts following a 6h exposure to hCG producing a 4 to 5-fold increase (P less than 0.05) over the untreated state at a time point approximately 6h prior to projected follicular rupture. Subsequent evaluation of ovarian IL-1 beta transcripts, 24 and 48h following hCG administration, revealed significant (P less than 0.05) decrements (relative to the 6h peak) to a level comparable to that seen at the conclusion of 48h of treatment with PMSG. Cellular localization studies revealed the gonadotropin-dependent IL-1 beta mRNA to be theca-interstitial cell-exclusive. To assess rat ovarian IL-1 beta gene expression under in vitro circumstances, we have set out to determine whether IL-1 itself may influence the relative level of its own message. Treatment of whole ovarian dispersates with rhIL-1 beta (10ng/ml) for 4 and 24h resulted in a marked (P less than 0.05) time-dependent increase (up to 12-fold) in the relative abundance of IL-1 beta transcripts when compared with untreated controls.(ABSTRACT TRUNCATED AT 400 WORDS)

Transforming growth factor-beta1 is a potent inhibitor of interleukin-1beta action in whole ovarian dispersates

“…Furthermore, IL-1 is capable of promoting a number of ovulation-associated phenomena in cultured ovarian cells, including an increase in prostaglandin production (Kokia et al 1992, Townson & Pate 1994, stimulation of nitric oxide synthesis (Ben-Shlomo et al 1994b), induction of collagenase activity (Hurwitz et al 1993) and a metabolic shift towards aerobic glycolysis as evidenced by increased lactate accumulation and glucose consumption (Ben-Shlomo et al 1997). Additionally, IL-1 appears to enhance the production of mRNA transcripts encoding for itself (Hurwitz et al 1991). Taken together, these data provide evidence in support of the notion that ovulation is akin to an inflammatory response, a concept originally put forward by Espey (1994).…”

“…In contrast, the function of TGF in ovarian physiology is uncertain (Shull & Doetschman 1994), but evidence suggests that TGF may act as a general regulator of follicle cell differentiation (Dodson & Schomberg 1987). Given the pattern of expression of IL-1 mRNAs during a narrow periovulatory window (Hurwitz et al 1991, Simon et al 1994 and the periovulatory rise and sustained elevation of TGF mRNA levels throughout the luteal phase (GaddyKurten et al 1989), we hypothesize that IL-1 mediates inflammatory-like phenomena at midcycle, while TGF may play a role in the healing process and in the development of the corpus luteum.…”

“…A 222 bp PstI fragment of the original cDNA was sub-cloned into pGEM2. T7-driven transcription of the EcoRI-linearized plasmid yielded a 272 nt riboprobe which upon hybridization was projected to generate a 222 nt protected fragment (Hurwitz et al 1991).…”

“…IL-1 synergizes with luteinizing hormone in bringing about ovulation (Brannstrom et al 1993, Takehara et al 1994, and components of the intraovarian IL-1 system (IL-1 and the type I IL-1 receptor (IL-1R)) are only expressed during a narrow periovulatory window (Hurwitz et al 1991, Simon et al 1994, Wang et al 1997. Furthermore, IL-1 is capable of promoting a number of ovulation-associated phenomena in cultured ovarian cells, including an increase in prostaglandin production (Kokia et al 1992, Townson & Pate 1994, stimulation of nitric oxide synthesis (Ben-Shlomo et al 1994b), induction of collagenase activity (Hurwitz et al 1993) and a metabolic shift towards aerobic glycolysis as evidenced by increased lactate accumulation and glucose consumption (Ben-Shlomo et al 1997).…”

Inhibition by gonadotropins of interleukin-1 production by rabbit granulosa and theca cells: effects on gonadotropin-induced progesterone production

“…It is likely that macrophages act as a source of intraovarian IL-1 (5). On the other hand, it has been reported that in the rat theca-interstitial cells are sites of IL-1b gene expression (5), and that cultured human granulosa cells produce IL-1b (6,7).…”