Periovulatory and interleukin (IL)-1-dependent regulation of IL-6 in the immature rat ovary: a specific IL-1 receptor-mediated eicosanoid-dependent effect.
Interleukin (IL)-6, traditionally an IL-1-induced immune regulator, is nevertheless synthesized by a variety of tissues including the ovary. The purposes of this communication were to assess the ovarian expression of IL-6, examine its cyclic variation, and study its regulation by IL-1, a putative intermediary in the ovulatory process. Molecular probing revealed IL-6 transcripts to be most abundant in the thymus, liver, and ovary, which suggests that, in relative terms, untreated immature whole ovarian tissue is a significant site of IL-6 gene expression. Treatment of immature rats with pregnant mare serum gonadotropins resulted in a measurable, statistically significant (P <.05) increase in ovarian IL-6 mRNA compared with untreated controls. Isolated and indeed transient increments in the relative abundance of IL-6 transcripts were noted 4 hours after exposure to hCG, a point in time 8 hours from projected follicular rupture, a pattern highly reminiscent of that previously recognized for IL-1 beta transcripts. Treatment of whole ovarian dispersates from immature rats with IL-1 beta for 48 hours resulted in a significant (P <.05) increase (11-fold) over control in IL-6 transcripts. The IL-1 effect proved dose dependent; the first significant increase was noted at the 1-ng/mL dose level. Evaluation of the time requirements revealed IL-1 beta to significantly (P <.05) up-regulate (4.5-fold) IL-6 transcripts as early as 24 hours into the culture period. Cotreatment with the IL-1 receptor antagonist completely reversed the IL-1 effect, which suggests mediation through a specific IL-1 receptor. Treatment with indomethacin (10 microg/mL), an established inhibitor of prostaglandin biosynthesis, resulted in a significant (P <.05) decrease (79%) in the ability of IL-1 beta to up-regulate IL-6 transcripts. Importantly, the addition of prostaglandin E(2) (10 microg/mL) to untreated or indomethacin-treated cells significantly (P <.05) augmented the IL-1 beta effect. This suggests a role for eicosanoid signaling in IL-1 beta action. Treatment with aminoguanidine, an established inhibitor of nitric oxide synthase, significantly (P <.05) decreased (85%) the IL-1 beta effect. However, the addition of S-nitroso-n-acetyl-penicilamine, an established nitrite generator, failed to reverse the aminoguanidine effect, which suggests that the inhibitor effect of aminoguanidine may be nitrite independent. Treatment with cycloheximide produced dose-dependent inhibition of the ability of IL-1 to up-regulate IL-6 transcripts; the maximal inhibitory effect was 89%. Taken together, these findings (1) reaffirm the rat ovary as a site of IL-6 expression; (2) document an in vivo increase in IL-6 transcripts before ovulation; (3) disclose a marked dependence of IL-6 on IL-1 beta; and (4) reveal the IL-1 beta effect to be dose and time dependent, receptor mediated, contingent upon de novo protein biosynthesis, and eicosanoid dependent but nitric oxide independent. These findings suggest that IL-1 action in the ovary may require the intermediacy of IL-6 in a manner like that encountered in extraovarian sites.
Chung
K W
KW
Division of Reproductive Endocrinology, Department of Obstetrics and Gynecology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
Ando
M
M
Adashi
E Y
EY
D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D046508:Culture Techniques; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000494:pharmacology; D015777:Eicosanoids / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004971:Estrus; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006064:Gonadotropins, Equine / Q000494:pharmacology; D006146:Guanidines / Q000494:pharmacology; D007213:Indomethacin / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology*; D015850:Interleukin-6 / Q000235:genetics*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052247:Nitric Oxide Synthase Type II; D010053:Ovary / Q000378:metabolism*; D010060:Ovulation / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017472:Receptors, Interleukin-1 / Q000502:physiology*; D014018:Tissue Distribution
D006063:Chorionic Gonadotropin; D016861:Cyclooxygenase Inhibitors; D015777:Eicosanoids; D004791:Enzyme Inhibitors; D006064:Gonadotropins, Equine; D006146:Guanidines; D007375:Interleukin-1; D015850:Interleukin-6; D012333:RNA, Messenger; D017472:Receptors, Interleukin-1; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D015232:Dinoprostone; C004479:pimagedine; D007213:Indomethacin