Mats Brännström

Tumor necrosis factor α in the human ovary: presence in follicular fluid and effects on cell proliferation and prostaglandin production

OBJECTIVEnTo examine the concentration of tumor necrosis factor alpha (TNF alpha) in human follicular fluid (FF) and its effects on cultured human granulosa-lutein cells.nnnDESIGNnThe concentration of TNF alpha in FF from hyperstimulated cycles and in conditioned media from cultured granulosa-lutein cells was measured by radioimmunoassay (RIA) and bioassay using L929 cells. The effects of recombinant human TNF alpha (rTNF alpha) on proliferation and production of progesterone (P) and prostaglandin (PG, PGE2, and PGF2 alpha) by cultured human granulosa-lutein cells were assessed.nnnSETTINGnIn vitro fertilization and embryo transfer (IVF-ET) program at Reproductive Medicine Unit, The Queen Elizabeth Hospital, Woodville, South Australia, Australia.nnnPATIENTSnTwenty-five women undergoing IVF-ET for tubal factor infertility.nnnRESULTSnThe concentration of immunoreactive TNF alpha in FF was 0.36 +/- 0.02 microgram/L, and there were no significant correlations between levels of TNF alpha and steroids or FF volume. Bioactivity for TNF alpha was considerably less. Immunoreactive or bioactive TNF alpha was not detected in conditioned media from granulosa-lutein cell culture. Recombinant human TNF alpha dose-dependently stimulated proliferation of cultured granulosa-lutein cells as measured by incorporation of 3H-thymidine, but in contrast to earlier reports, we were not able to demonstrate any effect of rTNF alpha on basal or human chorionic gonadotropin-stimulated P accumulation during culture periods of up to 72 hours. The accumulation of both PGE2 and PGF2 alpha was dose-dependently increased by rTNF alpha during a 48-hour incubation period. Time course studies revealed that maximal levels of both PGE2 and PGF2 alpha were reached within 12 hours of culture.nnnCONCLUSIONnImmunoreactive and bioactive TNF alpha is present in FF. Tumor necrosis factor alpha may have a physiological role in stimulating proliferation of follicular cells and PG production at the time of ovulation and formation of the corpus luteum.

Cytokines in rodent reproduction and the cytokine-endocrine interaction

Insights derived from recent studies employing rodent models demonstrate that the synthesis of pluripotent cytokines is an important function of resident cells in the female reproductive tract. Through steroid hormone regulated secretion of these mediators, resident cells appear to coordinate the recruitment and action of leukocytes that are centrally implicated in the dramatic remodelling processes characteristic of reproductive events.

Interleukin-1β inhibits luteinizing hormone-induced plasminogen activator activity in rat preovulatory folliclesin vitro

The effects of interleukin-1β (IL-1β) and tumour necrosis factor-α (TNFα) on ovulation-associated plasminogen activator (PA) activity were investigated using preovulatory follicles excised 48h after equine chorionic gonadotrophin (16IU)-priming of immature rats. Follicles were incubated for 6 and 14h with a single dose of LH (1 μg/ml) only, or various cytokine doses in the presence or absence of LH. PA activity in follicular homogenates was determined by a radioactively labelled fibrin-coated plate method and secreted levels of the ovulatory mediators progesterone (P) and prostaglandin E (PGE) were measured by radioimmunoassay. LH induced timedependent rises in PA (2.5-fold over control at 6h and fourfold over control at 14h), while IL-1β and TNFα alone had no effect over either time period. LH and cytokine coincubations over 14h revealed that IL-1β dosedependently inhibited the LH-induced increase in PA activity, up to 85%. The effects of TNFα on LH-induced PA activity were not significant. Both IL-1β and TNFα increased P and PGE secretion time- and dose-dependently. In summary, IL-1β dose-dependently inhibits the LH-induced increase in PA activity in rat preovulatory folliclesin vitro while, as with TNFα, increasing P and PGE synthesis. This study, shows that the earlier reported pro-ovulatory action of IL-1β is not likely to be mediated by activation of the PA-system and suggests that IL-1β may mediate a regulatory loop controlling the extent and distribution of LH-induced PA activity in rat preovulatory follicles.

Inhibitory effect of mifepristone (RU 486) on ovulation in the isolated perfused rat ovary.

The antigestagen mifepristone (RU 486) acts by blocking the progesterone receptor. Mifepristone has been used clinically for medical termination of pregnancy. It has recently also been shown that it can be used as an effective contraceptive agent in many species including the human. This contraceptive effect is acquired through prolonged exposure to mifepristone during the follicular phase and has been linked to disrupted folliculogenesis and inhibition of the LH surge. In the present study it is tested if mifepristone inhibits ovulation by a direct action on the ovary at the time of the LH surge. Preovulatory rat ovaries from immature Sprague-Dawley rats primed with 20IU of equine CG were perfused in vitro for 20 h in the presence of LH and 3-isobutyl-1-methylxanthine (IBMX) to induce ovulations. Mifepristone was added to study the effect on ovulation rate and ovarian steroidogenesis. Unstimulated control ovaries did not ovulate whereas addition of ovine LH (0.1 microgram/ml) and IBMX (0.2mM) resulted in 17.6 +/- 2.7 ovulations per treated ovary. Presence of mifepristone at 1 microM did not significantly inhibit LH+IBMX-induced ovulation (13.0 +/- 1.2) whereas mifepristone at 50 microM significantly (p < 0.01) inhibited ovulation (2.8 +/- 1.4). When the latter dosage of mifepristone (50 microM) was added 4h after LH+IBMX, no inhibitory effect was seen (17.2 +/- 3.0). Progesterone and estradiol release was significantly increased by LH+IBMX over the control group. Presence of mifepristone at any tested dose or time of addition did not significantly change the LH+IBMX-stimulated steroid release. It is concluded that mifepristone inhibits ovulation in the rat at the ovarian level when present just before LH stimulation but not when administered 4h into the ovulatory process.