Lipopolysaccharide inhibits in vitro luteinizing hormone-stimulated rat ovarian granulosa cell estradiol but not progesterone secretion

Female reproductive tract-organ axes

The female reproductive tract (FRT) and remote/versatile organs in the body share bidirectional communication. In this review, we discuss the framework of the "FRT-organ axes." Each axis, namely, the vagina-gut axis, uterus-gut axis, ovary-gut axis, vagina-bladder axis, vagina-oral axis, uterus-oral axis, vagina-brain axis, uterus-brain axis, and vagina-joint axis, is comprehensively discussed separately. Each axis could be involved in the pathogenesis of not only gynecological diseases but also diseases occurring apart from the FRT. Although the microbiota is clearly a key player in the FRT-organ axes, more quantitative insight into the homeostasis of the microbiota could be provided by host function measurements rather than current microbe-centric approaches. Therefore, investigation of the FRT-organ axes would provide us with a multicentric approach, including immune, neural, endocrine, and metabolic aspects, for understanding the homeostatic mechanism of women's bodies. The framework of the FRT-organ axes could also provide insights into finding new therapeutic approaches to maintain women's health.

Lipid Polysaccharides have a Detrimental Effect on the Function of the Ovaries and Uterus in Mice through Increased Pro-Inflammatory Cytokines

As the number of coronavirus disease 2019 (COVID-19) vaccinations increases, various side effects are being reported, and menstrual abnormalities have been reported as a side effect in women. However, it is still unclear whether the COVID-19 vaccine has detrimental effects on the female reproductive system. Therefore, we investigated the effect of excessive immune response on reproductive function by administering Lipopolysaccharides (LPS) instead of the COVID-19 vaccine. The immune response in mice was induced by injection of LPS. Mice injected with saline 5 times were used as a control group, and mice injected with LPS 5 times were used as an experimental group. Repeated administration of LPS significantly reduced the number of corpus luteum (CL). On the other hand, the injection of LPS did not affect the development of follicles leading before the CL. The expression of the apoptosis-related genes Fas and Fas-L increased in the experimental group. In addition, the expression of the inflammation-related genes increased in the experimental group. In this study, we confirmed that LPS had detrimental effects on the uterus and ovaries in mice. These results suggest that injection of LPS can cause immune reactions within the uterus and ovaries and cause hormonal changes, which can have adverse effects such as abnormal operation or bleeding of the menstrual cycle. These results are expected to help determine the cause of decreased reproductive function, infertility, or physiological disorders caused by the COVID-19 vaccine.

Lipopolysaccharide alters CEBPβ signaling and reduces estradiol production in bovine granulosa cells

Background

Bacterial infection of the uterus in postpartum dairy cows limits ovarian follicle growth, reduces blood estradiol concentrations, and leads to accumulation of bacterial lipopolysaccharide (LPS) in ovarian follicular fluid. Although treating granulosa cells with LPS in vitro decreases the expression of the estradiol synthesis enzyme CYP19A1 and reduces estradiol secretion, the molecular mechanisms are unclear. The transcription factor CCAAT enhancer binding protein beta (CEBPβ) not only facilitates the transcription of LPS regulated cytokines, but also binds to the promoter region of CYP19A1 in humans, mice, and buffalo. We hypothesized that LPS alters CEBPβ signaling to reduce CYP19A1 expression, resulting in decreased estradiol secretion.

Methods

Bovine granulosa cells were isolated from small/medium or large follicles and treated with LPS in the presence of FSH and androstenedione for up to 24 h.

Results

Treatment with LPS increased CXCL8 and IL6 gene expression and reduced estradiol secretion in granulosa cells from both small/medium and large follicles. However, LPS only reduced CYP19A1 expression in granulosa cells from large follicles. Treatment with LPS increased CEBPB expression and reduced CEBPβ nuclear localization in granulosa cells from small/medium follicles, but not granulosa cells from large follicles.

Conclusions

Although LPS reduces estradiol synthesis in bovine granulosa cells, the effects of LPS on CYP19A1 and CEBPβ are dependent on follicle size.

Dimethyl itaconic acid improves viability and steroidogenesis and suppresses cytokine production in LPS-treated bovine ovarian granulosa cells by regulating TLR4/nfkβ, NLRP3, JNK signaling pathways

The stimulation of pro-inflammatory pathways by lipopolysaccharide (LPS) endotoxins is a key player in the pathological mechanisms involved in the development of ovarian dysfunctions in dairy cows. Dimethyl itaconate acid (DMIA) is a novel immunometabolite that has recently emerged as a regulator of inflammatory responses in mammals. The present study was undertaken to determine the anti-inflammatory effects of DMIA on bovine granulosa cells (GCs) and to explore its possible molecular mechanisms. The ovarian GCs were obtained from small follicles of dairy cows. The GCs were stimulated with 1 μg/mL LPS for 4 h and then treated with 250 μM DMIA for 12 h. The viability, production of pro-inflammatory cytokines, activation of inflammatory signaling pathways and synthesis of steroid hormones were evaluated in treated GCs. Our results showed that DMIA reduced the inflammatory responses in LPS stimulated GCs by down-regulating the expression of nod-like receptor family pyrin domain containing 3 inflammasome, and toll-like receptor 4 and by suppressing the phosphorylation of nuclear factor kappa B and c-Jun N-terminal kinase proteins. DMIA also attenuated the increased production of pro inflammatory cytokines (interleukin 6, tumor necrosis factor α and interleukin 1 beta (p < 0.01) in LPS stimulated GCs. Exposure of LPS stimulated GCs to DMIA improved the impaired steroidogenesis by up-regulation of steroid synthesis genes including 3-beta-hydroxysteroid dehydrogenase, follicle stimulating hormone receptor and cytochrome P450 aromatase. The results of the present study highlight the potential role of itaconic acid for the improvement of GCs inflammation in dairy cows with ovarian dysfunctions.

COVID-19 in Africa: an ovarian victory?

Coronavirus disease 2019 (COVID-19) caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) mainly attacks the respiratory system and is characterized by pneumonia, cytokine storm, coagulation disorders and severe immune downregulation. Although public health experts predicted worst outcomes in Africa, the incidence, hospitalization and mortality rates have been lower in Africa compared to other continents. Interestingly, lower incidence and mortality rates have been observed in women from Africa compared to their cohorts from other continents. Also, in the US non-Hispanic Black females have lower COVID-19 and death rates compared to their white counterparts. It's unclear why this significant difference exists; however, the ovarian function, genetics and immunological statuses could play a major role. Women of African descent have elevated levels of estrogen compared with Caucasians hence we anticipate that estrogen might offer some protection against the SARS-CoV-2 infections. The racial differences in lifestyle, age and inaccessibility to contraceptive usage might also play a role. Here, we provide insight on how the high levels of estrogen in African women might contribute to the lower cases and fatalities in Africa. Specifically, estrogen might offer protection against COVID-19 by suppressing hyper-production of cytokines, promoting anti-inflammatory cytokines, stimulating antibody production and suppressing endoplasmic reticulum (ER) stress. This will as well provide useful information on how future pandemics could be managed using Africa as a case study.

The effects of CLP-induced sepsis on proliferation and apoptosis of granulosa and theca cells in rat ovary: A histochemical and ultrastructural study

Sepsis is defined as a systemic inflammatory response to infection. This study is aimed to evaluate the effects of experimental sepsis on the proliferation and apoptosis of granulosa and theca cells in the rat ovary. 28-day-old immature Wistar-Albino female rats were treated with pregnant mare serum gonadotrophin to develop the first generation of preovulatory follicles. Sepsis was induced by cecal ligation and puncture (CLP). Following in vivo 5-Bromo-2-deoxyuridine (BrdU) labeling, animals were sacrificed and ovaries were embedded in paraffin and Epon. Besides electron microscopic evaluation, BrdU, cleaved caspase-3, p27 immunostaining, and TUNEL labeling were performed. In CLP-operated animals, cleaved caspase-3 immunoreactivity was significantly increased in Graafian follicles. TUNEL and BrdU labeling in the ovarian follicles were not statistically different between CLP and sham-operated rats. In septic animals, p27 immunoreactivity was increased significantly in the nuclei of oocytes and decreased in the cytoplasm of granulosa and theca cells in multilaminar primary follicles compared to the sham group. In ultrastructural evaluation, increased apoptosis was observed in theca interna and granulosa cells in both the early and late stages of follicles in the CLP group. In conclusion, experimentally-induced sepsis leads to apoptosis in ovarian follicles at advanced stages of development. Our data suggest that although sepsis may not cause a potential threat to developing follicles at least in the short term, more severe damage may occur during advanced stages of follicle development.

Virus analog decreases estradiol secretion in FSH-treated human ovarian granulosa cells

The aim of this study was to evaluate the effect of virus infection on estradiol (E₂) production in human ovarian granulosa cells. Polyriboinosinic polyribocytidylic acid [Poly (I: C)], a synthetic analog of viral double stranded RNA that can be recognized by Toll like receptor 3 (TLR3), was used to imitate virus infection. Granulosa cells (GCs) obtained from patients undergoing in vitro fertilization and embryo transfer (IVF-ET) were cultured in vitro and treated with Poly (I: C), FSH, or both. Concentration of E₂ was assayed by electrochemiluminescence. The mRNA and protein expression of TLR3 and aromatase were determined by real-time quantitative PCR (qPCR) and Western blot, respectively. The results showed that expression of TLR3 mRNA was significantly increased after Poly (I: C) stimulation. Poly (I: C) decreased E₂ synthesis in FSH-treated GCs. Poly (I: C) inhibited the expression of aromatase in FSH-treated GCs. This study demonstrated that Poly (I: C) inhibits the synthesis of estradiol by granulosa cells under the stimulation of FSH, which might contribute to disturbance of follicular development and ovulation.

Antimicrobial peptide expression in swine granulosa cells in response to lipopolysaccharide

Antimicrobial peptides (AMP) are host defense peptides present in all species examined. The objective of the current study was to characterize the expression of a group of antimicrobial peptides in ovarian cells, and to investigate their expression response to pathogen ligands. It was found that while PG1 transcript was not detected in the ovary, the expression of BD2 is the highest in small follicle derived granulosa cells (SGC), and its expression decreases during follicular development to large follicle stage (LGC; p < 0.05). The expression of BD2 in cumulus cells also decreased from GV to MII stage of oocyte maturation. ANG4 expression increased in granulosa cells during follicular development from SGC to LGC stage (p < 0.05), although no significant difference was observed in cumulus cells from different stages of oocyte maturation. We further examined AMP expression in follicle cells treated with different toll-like receptor (TLR) ligands which mimic pathogen exposure in the ovary. Of the four TLR ligands examined, lipopolysaccharide (LPS) exposure resulted in a 11.5 fold increase of BD2 expression, and a significant decrease of LYZ in LGC. A similar response pattern in BD2 and LYZ expression was also observed in SGC. These responses of AMP expression to LPS are associated with increased TLR4 signaling pathway component in mRNA and protein level, such as MyD88 and NFkB, and pro-inflammatory cytokines/chemokines, such as IL-6, TNFα and IL-8 (p < 0.05). Our data suggest that AMPs may play a role in innate defense as well as other physiological functions during ovarian follicular development and oocyte maturation.

Human granulosa-luteal cells initiate an innate immune response to pathogen-associated molecules

The microenvironment of the ovarian follicle is key to the developmental success of the oocyte. Minor changes within the follicular microenvironment can significantly disrupt oocyte development, compromising the formation of competent embryos and reducing fertility. Previously described as a sterile environment, the ovarian follicle of women has been shown to contain colonizing bacterial strains, whereas in domestic species, pathogen-associated molecules are concentrated in the follicular fluid of animals with uterine infection. The aim of this study is to determine whether human granulosa-luteal cells mount an innate immune response to pathogen-associated molecules, potentially disrupting the microenvironment of the ovarian follicle. Human granulosa-luteal cells were collected from patients undergoing assisted reproduction. Cells were cultured in the presence of pathogen-associated molecules (LPS, FSL-1 and Pam3CSK4) for 24h. Supernatants and total RNA were collected for assessment by PCR and ELISA. Granulosa-luteal cells were shown to express the molecular machinery required to respond to a range of pathogen-associated molecules. Expression of TLR4 varied up to 15-fold between individual patients. Granulosa-luteal cells increased the expression of the inflammatory mediators IL1B, IL6 and CXCL8 in the presence of the TLR4 agonist E. coli LPS. Similarly, the TLR2/6 ligand, FSL-1, increased the expression of IL6 and CXCL8. Although no detectable changes in CYP19A1 or STAR expression were observed in granulosa-luteal cells following challenge, a significant reduction in progesterone secretion was measured after treatment with FSL-1. These findings demonstrate the ability of human granulosa-luteal cells to respond to pathogen-associated molecules and generate an innate immune response.

Effect of Lipopolysaccharide (LPS) Exposure on the Reproductive Organs of Immature Female Rats

Lipopolysaccharide (LPS), an endotoxin, elicits strong immune responses in mammals. Several lines of evidence demonstrate that LPS challenge profoundly affects female reproductive function. For example, LPS exposure affects steroidogenesis and folliculogenesis, resulting in delayed puberty onset. The present study was conducted to clarify the mechanism underlying the adverse effect of LPS on the delayed puberty in female rats. LPS was daily injected for 5 days (50 μg/kg, PND 25-29) to treated animals and the date at VO was evaluated through daily visual examination. At PND 39, animals were sacrificed, and the tissues were immediately removed and weighed. Among the reproductive organs, the weights of the ovaries and oviduct from LPS-treated animals were significantly lower than those of control animals. There were no changes in the weights of uterus and vagina between the LPS-treated and their control animals. Immunological challenge by LPS delayed VO. Multiple corpora lutea were found in the control ovaries, indicating ovulations were occurred. However, none of corpus luteum was present in the LPS-treated ovary. The transcription level of steroidogenic acute regulatory protein (StAR), CYP11A1, CYP17A1 and CYP19 were significantly increased by LPS treatment. On the other hand, the levels of 3β- HSD, 17β-HSD and LH receptor were not changed by LPS challenge. In conclusion, the present study demonstrated that the repeated LPS exposure during the prepubertal period could induce multiple alterations in the steroidogenic machinery in ovary, and in turn, delayed puberty onset. The prepubertal LPS challenge model used in our study is useful to understand the reciprocal regulation of immune (stress) - reproductive function in early life.

Innate immunity and the sensing of infection, damage and danger in the female genital tract

Tissue homeostasis in the female genital tract is challenged by infection, damage, and even physiological events during reproductive cycles. We propose that the evolutionarily ancient system of innate immunity is sufficient to sense and respond to danger in the non-pregnant female genital tract. Innate immunity produces a rapidly inducible, non-specific response when cells sense danger. Here we provide a primer on innate immunity and discuss what is known about how danger signals are sensed in the endometrium and ovary, the impact of inflammatory responses on reproduction, and how endocrinology and innate immunity are integrated. Endometrial epithelial and stromal cells, and ovarian granulosa cells express pattern recognition receptors, similar to cells of the innate immune system. These pattern recognition receptors, such as the Toll-like receptors, bind pathogen-associated or damage-associated molecular patterns. Activation of pattern recognition receptors leads to inflammation, recruitment of immune cells from the peripheral circulation, and phagocytosis. Although the inflammatory response helps maintain or restore endometrial health, there may also be negative consequences for fertility, including perturbation of oocyte competence. The intensity of the inflammatory response reflects the balance between the level of danger and the systems that regulate innate immunity, including the endocrine environment. Understanding innate immunity is important because disease and inappropriate inflammatory responses in the endometrium or ovary cause infertility.

Effects of Coculture With Immune Cells on the Developmental Competence of Mouse Preimplantation Embryos in Vitro and in Utero

The aim of this study was to establish a coculture system using immune cells as well as an in vitro model for inflammatory conditioning using RAW 264.7 mouse macrophages activated by lipopolysaccharide. The direct and indirect coculture systems were applied to evaluate the influence of embryo-to-cell direct or indirect secretory molecules from the cocultured cells. Blastulation rate in vitro (94.6% vs 76.9%, P < .05) and implantation rate in utero (43.3% vs 17.6%, P < .01) were significantly increased in direct coculture with activated RAW 264.7 cells compared to control. We also found the embryotrophic effects in vitro in the indirect coculture system. Our results indicate that coculture of mouse preimplantation embryos with immune cells could improve the developmental competence in vitro and in utero. Taken together, RAW 264.7 cells secret embryotrophic molecules, and it suggests the valuable insights that immune cells could improve in vitro culture conditions of preimplantation embryos.

Low-dose gold nanoparticles exert subtle endocrine-modulating effects on the ovarian steroidogenic pathway ex vivo independent of oxidative stress

Gold nanoparticles (GNPs) have gained considerable attention for application in science and industry. However, the untoward effects of such particles on female fertility remain unclear. The objectives of this study were to (1) examine the effects of 10-nm GNPs on progesterone and estradiol-17β accumulation by rat ovaries ex vivo and (2) to identify the locus/loci whereby GNPs modulate steroidogenesis via multiple-reference gene quantitative real-time RT-PCR. Regression analyses indicated a positive relationship between both Star (p < 0.05, r(2) = 0.278) and Cyp11a1 (p < 0.001, r(2) = 0.366) expression and P4 accumulation upon exposure to 1.43 × 10(6) GNPs/mL. Additional analyses showed that E2 accumulation was positively associated with Hsd3b1 (p < 0.05, r(2) = 0.181) and Cyp17a1 (p < 0.01, r(2) = 0.301) expression upon exposure to 1.43 × 1(3) and 1.43 × 10(9) GNPs/mL, respectively. These results suggest a subtle treatment-dependent impact of low-dose GNPs on the relationship between progesterone or estradiol-17β and specific steroidogenic target genes, independent of oxidative stress or inhibin.

Associations of prepartum body condition score with occurrence of clinical endometritis and resumption of postpartum ovarian activity in dairy cattle

This study was performed to investigate the effect of periparturient body condition score on the occurrence of clinical endometritis and postpartum resumption of ovarian activity in dairy cows. Eighty-seven lactating Holstein cows, fed with a total mixed ration diet, were included into the study. Body condition scoring (using a 5-point scale with quarter-point divisions) was performed by the same investigator using the visual technique every 2 weeks, from 2 weeks before until 6 weeks after calving. Palpation of the reproductive tract and ultrasonographic assessment of ovaries for detection of corpus luteum using a rectal linear probe was also performed at 2, 4, and 6 weeks after calving. Cows with clinical endometritis had significantly lower body condition score (BCS) than normal cows at all weeks pre- and postcalving, and cows that did not ovulate until 45 days after calving had a significantly lower BCS pre- and postpartum. Cows that did not ovulate until 45 days after calving also lost more BCS from 2 weeks before to 4 weeks after calving. Besides, first ovulation after calving take occurred later in cows with clinical endometritis compared to normal cows (P < 0.05). In conclusion, low BCS is a risk factor for postpartum endometritis and delayed cyclicity in dairy cows. BCS loss from dry-off to early lactation and occurrence of clinical endometritis can significantly affect postpartum ovarian activity.

Preventing Microbial Contamination during Long-Term In Vitro Culture of Human Granulosa-Lutein Cells: An Ultrastructural Analysis

Purpose. To investigate whether the addition of antibiotic/antimycotic during human granulosa-lutein cells (GLCs) isolation and cell-plating procedures prevents microbial contamination after 144 h of culture and also evaluate the effects of contamination on GLCs ultrastructure and steroid secretion. Methods. GLCs obtained from five women submitted to assisted reproductive techniques (ARTs) were isolated with PBS supplemented with antibiotic/antimycotic or PBS nonsupplemented and cultured for 144 h. GLCs were evaluated by transmission electron microscopy (TEM), and estradiol (E2) and progesterone (P4) secretion was assayed by chemiluminescence. Results. Although no contaminating microorganisms were identified by light microscopy, TEM analyses revealed several bacterial colonies in culture dishes of GLCs isolated with only PBS. Bacterial contamination disrupted the adherence of the GLCs to the culture plate interfering with monolayer formation affecting the growth pattern of GLCs. Various cellular debris and bacteria were observed, and no organelles were found in the cytoplasm of infected cells. While bacterial contamination decreased estradiol media levels, it increased progesterone, as compared with noncontaminated group. Conclusion. Taken together, our data showed that the addition of a high dose of antibiotic/antimycotic during the isolation and cell-plating procedures prevents microbial contamination of long-term GLCs culture as its effects on cells growth and function in vitro.

Effect of resistin on granulosa and theca cell function in cattle

Resistin is an adipokine that has not been extensively studied in cattle but is produced by adipocytes in greater amounts in lactating versus non-lactating cattle. Seven experiments were conducted to determine the effect of resistin on proliferation, steroidogenesis, and gene expression of theca and granulosa cells from small (1-5mm) and/or large (8-22 mm) cattle follicles. Resistin had no effect on IGF-I-induced proliferation of large-follicle theca cells or small-follicle granulosa cells, but decreased IGF-I-induced proliferation of large-follicle granulosa cells. Resistin weakly stimulated FSH plus IGF-I-induced estradiol production by large-follicle granulosa cells, but had no effect on IGF-I- or insulin-induced progesterone and androstenedione production by theca cells or progesterone production by granulosa cells of large follicles. In small-follicle granulosa cells, resistin attenuated the stimulatory effect of IGF-I on progesterone and estradiol production of small-follicle granulosa cells. RT-PCR measuring abundance of side-chain cleavage enzyme (CYP11A1), aromatase (CYP19A1), FSH receptor (FSHR) and LH receptor (LHCGR) mRNA in large- and small-follicle granulosa cells indicated that resistin reduced the stimulatory effect of IGF-I on CPY11A1 mRNA abundance in large-follicle granulosa cells but had no effect on CYP19A1, FSHR or LHCGR mRNA abundance in large- or small-follicle granulosa cells. Resistin had no effect on CYP11A1, CYP17A1 or LHCGR mRNA abundance in theca cells. These results indicate that resistin preferentially inhibits steroidogenesis of undifferentiated (small follicle) granulosa cells and inhibits proliferation of differentiated (large follicle) granulosa cells, indicating that the ovarian response to resistin is altered during follicular development.

Reproductive axis response to repeated lipopolysaccharide administration in peripubertal female rats

Immune system disorders are often accompanied by alterations in the reproductive axis. Several reports have shown that administration of bacterial lipopolysaccharide (LPS) has central inflammatory effects and activates cytokine release in the hypothalamus where the luteinizing hormone releasing hormone (Gn-RH) neurons are located. The present study was designed to investigate the effect of repeated LPS administration on the neuroendocrine mechanisms of control of the reproductive axis in peripubertal female rats (30-day-old rats). With this aim, LPS (50 mug/kg weight) was administered to the animals during 25, 27 and 29 days of age and sacrificed on 30 day of life. Gn-RH, gamma-amino butyric acid (GABA) and glutamic acid (GLU), two amino acids involved in the regulation of Gn-RH secretion, hypothalamic content were measured. LH and estradiol serum levels were also determined and the day of vaginal opening examined. The results showed a significant increase in Gn-RH and GLU content (p < 0.0001), shared by a reduction of GABA one (p < 0.0001). LH and estradiol serum levels were decreased (p < 0.01, p < 0.001) and delay in the day of vaginal opening was also observed in treated animals. Present results show that repeated LPS administration impaired reproductive function, modifying the neuroendocrine mechanisms of control of the axis in peripubertal female rats.

The effect of Escherichia coli lipopolysaccharide and tumour necrosis factor alpha on ovarian function

PROBLEM

Pelvic inflammatory disease and metritis are important causes of infertility in humans and domestic animals. Uterine infection with Escherichia coli in cattle is associated with reduced ovarian follicle growth and decreased estradiol secretion. We hypothesized that this effect could be mediated by the bacterial lipopolysaccharide (LPS) or cytokines such as tumour necrosis factor alpha (TNFalpha).

METHOD OF STUDY

In vitro, bovine ovarian theca and granulosa cells were treated with LPS or TNFalpha and steroid secretion measured. In vivo, the effect of LPS or TNFalpha intrauterine infusion was determined by ovarian ultrasonography and measurement of hormones in cattle.

RESULTS

Lipopolysaccharide reduced granulosa cell estradiol secretion, whilst TNFalpha decreased theca and granulosa cell androstenedione and estradiol production, respectively. In vivo, fewer animals ovulated following intrauterine infusion with LPS or TNFalpha.

CONCLUSION

Lipopolysaccharide and TNFalpha suppress ovarian cell function, supporting the concept that pelvic inflammatory disease and metritis are detrimental for bovine ovarian health.

The Src tyrosine kinase pathway regulates thecal CYP17 expression and androstenedione secretion

In order to evaluate the role of Src tyrosine kinase in thecal cell steroidogenesis, a pharmacological approach was utilized by treating enriched populations of mouse ovarian theca-interstitial cells in vitro with a direct Src kinase inhibitor, PP2. Inhibition of Src with PP2 increased both basal and forskolin-stimulated androstenedione secretion, and increased cytochrome P450 17-alpha hydroxylase-lyase (CYP17) promoter activity and steady state mRNA. PP2 did not change thecal levels of StAR mRNA. Inhibition of mitogen-activated protein kinase kinase, a downstream regulator of Src activity, using PD98059 also increased forskolin-stimulated secretion of androstenedione above forskolin alone, but had no effect on basal secretion of androstenedione. Src inhibition increased mitogen-activated protein kinase phosphatase-1 protein and decreased phosphorylation of SF-1, which correlated with increased CYP17 promoter activity and mRNA levels. These results implicate Src tyrosine kinase in the regulation of CYP17 and thecal androgen secretion.

Ovarian follicular cells have innate immune capabilities that modulate their endocrine function

Oestrogens are pivotal in ovarian follicular growth, development and function, with fundamental roles in steroidogenesis, nurturing the oocyte and ovulation. Infections with bacteria such as Escherichia coli cause infertility in mammals at least in part by perturbing ovarian follicle function, characterised by suppression of oestradiol production. Ovarian follicle granulosa cells produce oestradiol by aromatisation of androstenedione from the theca cells, under the regulation of gonadotrophins such as FSH. Many of the effects of E. coli are mediated by its surface molecule lipopolysaccharide (LPS) binding to the Toll-like receptor-4 (TLR4), CD14, MD-2 receptor complex on immune cells, but immune cells are not present inside ovarian follicles. The present study tested the hypothesis that granulosa cells express the TLR4 complex and LPS directly perturbs their secretion of oestradiol. Granulosa cells from recruited or dominant follicles are exposed to LPS in vivo and when they were cultured in the absence of immune cell contamination in vitro they produced less oestradiol when challenged with LPS, although theca cell androstenedione production was unchanged. The suppression of oestradiol production by LPS was associated with down-regulation of transcripts for aromatase in granulosa cells, and did not affect cell survival. Furthermore, these cells expressed TLR4, CD14 and MD-2 transcripts throughout the key stages of follicle growth and development. It appears that granulosa cells have an immune capability to detect bacterial infection, which perturbs follicle steroidogenesis, and this is a likely mechanism by which ovarian follicle growth and function is perturbed during bacterial infection.

CD4+ T lymphocyte subsets express connexin 43 and establish gap junction channel communication with macrophages in vitro

Gap junction channels constructed of connexins (Cxs) are expressed by peripheral and secondary lymphoid organ-derived lymphocytes. These channels in the plasma membrane play key roles in a range of lymphocyte functions exemplified by the synthesis and secretion of Igs and cytokines and during transmigration across the endothelium. Most recently, their involvement in antigen cross-presentation has also been established. We report here for the first time the expression of mRNA and protein encoding Cx43 in mouse-derived CD4+ Th0, Th1, and Th2 lymphocyte subpopulations and demonstrate the establishment gap junction channel formation with primary macrophages in vitro. We show that this mode of direct communication is particularly favored in Th1-macrophage interactions and that LPS inhibits lymphocyte-macrophage cross-talk independently of the subset of lymphocyte involved. Our work suggests that gap junction-mediated communication can be modulated in the absence of specific antigenic stimulation. Therefore, a further mechanism featuring gap junction-mediated communication may be implicated in immune regulation.

Bacterial lipopolysaccharide induces apoptosis in the trout ovary

BACKGROUND

In mammals it is well known that infections can lead to alterations in reproductive function. As part of the innate immune response, a number of cytokines and other immune factors is produced during bacterial infection or after treatment with lipopolysaccharide (LPS) and acts on the reproductive system. In fish, LPS can also induce an innate immune response but little is known about the activation of the immune system by LPS on reproduction in fish. Therefore, we conducted studies to examine the in vivo and in vitro effects of lipopolysaccharide (LPS) on the reproductive function of sexually mature female trout.

METHODS

In saline- and LPS -injected brook trout, we measured the concentration of plasma steroids as well as the in vitro steroidogenic response (testosterone and 17alpha-hydroxyprogesterone) of ovarian follicles to luteinizing hormone (LH), the ability of 17alpha,20beta-dihydroxy-4-pregnen-3-one to induce germinal vesicle breakdown (GVBD) in vitro, and that of epinephrine to stimulate follicular contraction in vitro. We also examined the direct effects of LPS in vitro on steroid production, GVBD and contraction in brook trout ovarian follicles. The incidence of apoptosis was evaluated by TUNEL analysis. Furthermore, we examined the gene expression pattern in the ovary of saline- and LPS-injected rainbow trout by microarray analysis.

RESULTS

LPS treatment in vivo did not affect plasma testosterone concentration or the basal in vitro production of steroids, although a small but significant potentiation of the effects of LH on testosterone production in vitro was observed in ovarian follicles from LPS-treated fish. In addition, LPS increased the plasma concentration of cortisol. LPS treatment in vitro did not affect the basal or LH-stimulated steroid production in brook trout ovarian follicles. In addition, we did not observe any effects of LPS in vivo or in vitro on GVBD or follicular contraction. Therefore, LPS did not appear to impair ovarian steroid production, oocyte final maturation or follicular contraction under the present experimental conditions. Interestingly, LPS administration in vivo induced apoptosis in follicular cells, an observation that correlated with changes in the expression of genes involved in apoptosis, as evidenced by microarray analysis.

CONCLUSION

These results indicate that female trout are particularly resistant to an acute administration of LPS in terms of ovarian hormone responsiveness. However, LPS caused a marked increase in apoptosis in follicular cells, suggesting that the trout ovary could be sensitive to the pro-apoptotic effects of LPS-induced inflammatory cytokines.

Influence of the estrous cycle on tolerance development to LPS-induced sickness behaviors in rats

The relations between the estrous cycle, inflammatory responses and the development of tolerance to endotoxin were examined. Female Long-Evans rats were injected intraperitoneally with lipopolysaccharide (LPS; 200 microg/kg) or saline vehicle at 08:00h on either diestrus (D) or proestrus (P). Ninety-five minutes after injection locomotor activity was assessed in an automated non-novel open-field for 20 min. To assess tolerance development to LPS, rats were re-injected at the next identical stage (i.e. 4 days later; groups: DD, PP) or at the alternate stage (i.e. 6 days later; groups: DP, PD) of the estrous cycle and locomotor activity was again assessed. On Test Day 1 all groups injected with LPS exhibited similar significant activity decrements, regardless of the stage of the estrous cycle. However, on Test Day 2 rats which received both injections of LPS during proestrus (PP) showed no signs of tolerance development, whereas rats in all other groups were tolerant to LPS. In a follow up study, the time between injections was extended to 8 days. Still the animals injected both times at proestrus showed no signs of tolerance to LPS after the second injection. Thus, the stages of the estrous cycle both at the time of initial exposure and of re-exposure appear critical in the formation of behavioral tolerance to LPS in rats.

Response of rat fasciculata-reticularis cells in primary culture to bacterial lipopolysaccharide

The aim of this study was to determine the direct effect of a wide range of concentrations of lipopolysaccharide (LPS) of Escherichia coli O111:B4 on fasciculata-reticularis cells in primary cultures. In short-term cultures of fasciculata-reticularis cells, the presence of low (1-10 microg/ml) doses of LPS in the medium produced a decrease in ACTH-induced corticosterone secretion, in a dose-dependent manner and independent of the culture medium. The corticosterone production stimulated by db-cAMP was slightly decreased by the presence of LPS in culture medium, while the pregnenolone induced corticosterone biosynthesis was not modified. LPS modified the binding of [125I]-Tyr23-ACTH to the fasciculata-reticularis cell membrane and the signal transduction pathway, as LPS reduced ACTH-induced cAMP production. In long-term cultures, the presence of LPS in the medium produces a decrease in the specific binding of [125I]-Tyr23-ACTH, while the presence of ACTH in the culture medium produced an increase in its specific binding. The use of high doses of LPS (100-250 microg/ml) has helped to clarify some aspects of the LPS action. These doses of LPS severely inhibited ACTH-induced corticosterone production, and clearly reduced the corticosterone production stimulated by db-cAMP and the binding of ACTH to its receptors. In long-term cultures, LPS decreased the number of ACTH receptors, an effect that was reversed by subsequent exposure to ACTH. These results indicate that LPS exerts a direct action on fasciculata-reticularis cells and a model of the mechanism of LPS action is proposed.

Escherichia coli derived factors modulate human granulosa cell steroidogenesis

AIM

In order to identify bacterial compounds which directly affect granulosa cell steroidogenesis, the effect of culture-supernatants and extracts from Escherichia coli were tested in an in vitro granulosa cell culture model.

METHODS

Samples were drawn from the culture-supernatant of E. coli ATCC25922 cultured in Luria-broth medium. Bacterial extract was prepared by incubation of freshly harvested bacteria in buffer. The bacterial culture-supernatants and extracts were added to human granulosa cells in culture. The granulosa cells collected from the follicular aspirates from women undergoing in-vitro fertilization were cultured for 17-53 h and progesterone or oestradiol was assayed in the spent culture medium.

RESULTS

The E. coli culture-supernatant stimulated the basal granulosa cell progesterone production demonstrating its maximum activity reached after 200-240 min of bacterial growth. The heat denaturated bacterial extract as well as its low-molecular-weight fraction (<10 kDa) stimulated both the basal and the hCG-stimulated progesterone production; the oestradiol production was slightly inhibited. Stimulation of progesterone production was time dependent increasing from 125 +/- 18% of control within the first 3 h to 205 +/- 35% within 17-53 h. The high-molecular-weight fraction (>30 kDa) of the bacterial extract inhibited progesterone production. The inhibitory activity was significantly diminished by heat denaturation.

CONCLUSIONS

The present study demonstrates the existence of various compounds which are secreted by E. coli and could also be extracted out of E. coli bacteria. These bacterial compounds modulate ovarian steroidogenesis. Further studies are needed to clarify how far these compounds contribute to menstrual disturbance observed in chronic pelvic inflammation.

A ‘minimum dose’ of lipopolysaccharide required for implantation failure: assessment of its effect on the maternal reproductive organs and interleukin-1α expression in the mouse

Genital tract infections caused by gram-negative bacteria induce abortion and are one of the most common complications of human pregnancy. This study was carried out to decipher the mechanism of gram-negative bacterial lipopolysaccharide (LPS)-induced pregnancy loss, using a mouse (Park strain) model. Since many of the biological effects of LPS are mediated by interleukin (IL)-1α, the role of IL-1α in LPS-induced pregnancy loss was studied. Pregnant female animals were injected intra-peritoneally (i.p.) with different doses (1 to 50 μg) of LPS from Salmonella minnesota Re-595, on day 0.5 of pregnancy. We found that 250 μg/kg body weight (i.e. 5 μg/female mouse) of LPS when given on day 0.5 of pregnancy was the ‘minimum dose’ (MD) required to completely inhibit the implantation of the blastocyst in the mouse. The effect of this dose on the pathophysiology of the various reproductive organs (i.e. uterus, ectoplacental cones, developing fetus, ovaries etc.) was assessed on day 14 of pregnancy. The effects of this dose on the level and pattern of expression of the proinflammatory cytokine IL-1α in the maternal uterine horns and preimplantation stage embryos were studied by RT-PCR. A single dose (100 ng/mouse) of recombinant mouse IL-1α was given i.p. to pregnant females on day 1 of pregnancy to study its effect on implantation. Our results show that treatment of the pregnant animals with LPS may alter cell proliferation and induce leukocyte infiltration, degeneration of luminal glandular epithelium, and hyperplasia in the various reproductive organs, and may also alter both embryonic and uterine IL-1α expression. IL-1α administration also caused implantation failure similar to that of LPS. The observations suggest that the determined MD of LPS may alter the expression of developmentally important proinflammatory cytokines such as IL-1α, which could, in turn, inhibit the normal processes of blastocyst implantation. Therefore, it is proposed that the LPS-induced histopathological alterations in the various reproductive organs of pregnant animals could be mediated by IL-1α and this may be one of the causes of failure of blastocyst implantation in the mouse.

Comprehending the role of LPS in Gram-negative bacterial vaginosis: ogling into the causes of unfulfilled child-wish

INTRODUCTION

Intrauterine infection is frequently associated with pregnancy loss in pregnant women.

DISCUSSION

This article reviews the role of Gram-negative bacterial infection in various complications related to early pregnancy and subsequent pregnancy loss. Here we discuss the pathways of ascending intrauterine infection, microbiology and the pathophysiology of such infections. The clinical impact, therapy, consequences, prevention and implications of Gram-negative bacterial infections in women during their reproductive life span is also discussed. This article also makes an attempt to discuss our studies and findings, related to the effect of the LPS component of the Gram-negative bacterial endotoxin on preimplantation stage embryonic development and implantation. This early phase of pregnancy remains mostly unnoticed by the mother as well as the health care provider, and therefore holds more threat to the life of the fetus and the mother. The molecular mechanisms of LPS-induced pregnancy losses through abnormal embryonic development, implantation failure, and preterm labor and birth with specific references to the role of proinflammatory cytokines like IL-1 and TNF are discussed.

CONCLUSION

Once these inflammatory mediators have increased in the feto-maternal tissues, it may be too late or harmful to try and prevent the adverse outcomes of pregnancy.

Gram-Negative Bacterial Endotoxin- Induced Infertility: A Birds Eye View

Alleviation of infertility on the one hand and development of improved methods of contraception on the other are global concerns to woman's health. The molecular signals that regulate implantation are of clinical relevance since understanding the nature of these signals may lead to strategies to correct implantation failure and to develop novel contraceptive approaches. The other pressing concern is the poor pregnancy rate resulting from in vitro fertilization (IVF). The pregnancy rate in IVF programs remains about 20-30% in spite of the high rate of successful fertilization. This has led to the proposition that additional uterine factors, critical for the implantation process, must be limiting. Identification of such parameters could help in determining the appropriate physiological state of the uterus for embryo transfer. Several factors are known to have a direct or indirect impact on the ability of the uterus to develop to a functionally receptive state. This would disrupt the normal coordination between embryonic and uterine development even though all molecular players may seem otherwise normal.

Rat glomerulosa cells in primary culture and E. coli lipopolysaccharide action

During endotoxic shock there is a dysfunction of the adrenal gland; both corticosterone and aldosterone secretion are altered. The aim of the present study is to use glomerulosa cells in primary culture as a target of lipopolysaccharide (LPS) action. Glomerulosa cells cultured in basal conditions are able to proliferate; bFGF and ACTH have antagonic effects, bFGF increases proliferation whereas ACTH is antimitogenic. LPS has a biphasic effect, in the short term it is antimitogenic and in the long term increases the proliferation rate. LPS inhibits ACTH-induced corticosterone secretion in a dose-dependent manner in glomerulosa cells in culture similar to that in fasciculata cells, but it does not exert an important direct effect on aldosterone secretion. These results show that LPS exerts different effects in ACTH and ANG II signal transduction pathways and in the two enzymes which catalyze the late step in the steroidogenesis, 11beta-hydroxylase and aldosterone synthase, which could be in agreement with the existence of both enzymes, regulated independently, in rat zona glomerulosa cells.

Herbimycin, a tyrosine kinase inhibitor with Src selectivity, reduces progesterone and estradiol secretion by human granulosa cells

The purpose of the present study was to investigate whether the tyrosine kinase inhibitor herbimycin with some selectivity to block Src would alter the stimulatory effects of follicle-stimulating hormone (FSH) and cyclic adenosine monophosphate (cAMP) on estradiol secretion by human granulosa cells. Granulosa cells were taken from ovaries of premenopausal women undergoing oophorectomy for reasons unrelated to ovarian pathology. Granulosa cells from follicles ranging from 5-20 mm in diameter were subjected to culture. Granulosa cells were cultured with human FSH (2 ng/mL) or cAMP (0-1 mM) and testosterone (1 microM) in the presence and absence of herbimycin (0-2 pM). Media were collected at 24, 48, and 72 h. Accumulation of cAMP, progesterone, and estradiol in the media was determined by radioimmunoassay. Herbimycin dose dependently inhibited the ability of FSH to induce increases in progesterone and estradiol secretion. Although herbimycin increased (p < 0.0001) the accumulation of cAMP in response to FSH, this was evident only at the high concentrations of herbimycin (2 microM). To determine whether herbimycin would inhibit the ability of exogenous cAMP to induce estradiol and progesterone secretion, granulosa cells were incubated with 0-1 mM cAMP in the presence and absence of various doses of herbimycin. Herbimycin inhibited cAMP-induced estradiol and progesterone secretion in granulosa cells. The results from seven experiments indicate that herbimycin inhibits FSH stimulation of estradiol and progesterone secretion and that this inhibition may be, in part, at post-cAMP site(s).

Prolactin and lipopolysaccharide treatment increased apoptosis and atresia in rat ovarian follicles

Follicular atresia is associated with the presence of increased macrophages within the follicle. What is not known is whether, in the adult rat, macrophages are instrumental in inducing apoptosis and/or atresia or whether they are simply secondary to a hormonally mediated event. As prolactin is an immunoreactive hormone and stimulates the expression of monocyte chemoattractant, the present experiments compared the effects of prolactin treatment with that of an immune challenge with lipopolysaccharide (LPS) on the invasion of macrophages into the follicular and luteal compartments of the ovary and the occurrence of apoptosis/atresia in relation to macrophage invasion. Rats were treated for 3 days with either prolactin or LPS and ovaries obtained at pro-oestrus or oestrus. Prolactin and LPS increased the number of atretic vs. healthy follicles (P < 0.008, chi2) in pro-oestrus ovaries and increased the mean number of apoptotic cells and macrophages (P < 0.05 for some groups). Macrophages were typically observed in the thecal layer, apoptotic cells in the granulosa cell layer, although 84% follicles which had macrophages within the granulosa cell layer also contained relatively high numbers of apoptotic nuclei. Prolactin and LPS treatment in vivo reduced the progesterone response to follicle stimulating hormone (FSH) (P < 0.001) in cultures of ovarian dispersates but did not inhibit the response to forskolin. In contrast, prolactin or LPS added in vitro to the cultures inhibited the progesterone response to forskolin. Results show that both prolactin and LPS increase follicular apoptosis and atresia and reduce the progesterone response to FSH.

Endotoxin induces delayed ovulation following endocrine aberration during the proestrous phase in Holstein heifers

The effect of endotoxin on follicular growth and on secretion of LH, estradiol-17beta, progesterone and cortisol during the proestrous phase in cattle was investigated. Holstein heifers were treated with PGF2alpha at 11-13 d after ovulation to induce luteolysis. At 42 hr after PGF2alpha treatment, heifers were administered either lipopolysaccharide (LPS; Escherichia coli, O111:B4, 5 microg/kg, n = 6) or saline (control; n = 6) by i.v. bolus injection. Ovarian structures were monitored daily by transrectal ultrasonography, and blood samples were collected at various times for hormonal analysis. The duration from PGF2alpha treatment to ovulation was significantly longer in the LPS group (8.0 +/- 1.3 d) than in the control group (4.2 +/- 0.2 d). LPS significantly reduced the pulse frequency of LH for 6 hr after the administration, and increased the mean concentration and pulse amplitude of LH from 3 to 6 hr after the administration. The plasma concentrations of progesterone and cortisol were transiently increased after LPS administration. The plasma concentration of estradiol-17beta was significantly decreased at 24 hr after LPS administration compared to that in the controls. Five of six LPS-treated heifers exhibited no preovulatory LH surge until 120 hr after PGF2alpha treatment and the remaining heifer exhibited the surge at 108 hr after PGF2alpha treatment, while the LH surge was observed at 54-78 hr after PGF2alpha treatment in control heifers. These results suggest that endotoxin disrupts progression of the proestrous phase of cattle, interrupting the preovulatory estradiol rise and thus delaying the LH surge and the subsequent ovulation.

Diametric effects of bacterial endotoxin lipopolysaccharide on adrenal and Leydig cell steroidogenic acute regulatory protein

Immune activation results in the activation of adrenal steroidogenesis and inhibition of gonadal steroidogenesis. Previous studies indicated that these effects were caused primarily by activation and suppression of the secretion of ACTH and LH, respectively. However, other evidence indicated a direct effect of the immune system on the gonads. In this study, serum testosterone, quantitated by RIA after lipopolysaccharide injection, showed a significant decrease within 2 h. Parallel measurement of serum LH showed no change. There were no differences in LH receptor or cAMP produced in Leydig cells between vehicle- and lipopolysaccharide-injected mice. The 30-kDa form of the steroidogenic acute regulatory (StAR) protein was quantitated, by Western blot, in Leydig cells and was found to decrease in a time-dependent manner. No change in StAR protein messenger RNA (mRNA) was detected by Northern analysis during this time, nor were any changes found in the levels of mRNA for the steroidogenic enzymes P450scc, 3beta-hydroxysteroid dehydrogenase delta4-delta5-isomerase, or P450c17. In the adrenal, StAR protein was increased, as was StAR protein mRNA. No changes were observed in the levels of mRNA for P450scc, 3beta-hydroxysteroid dehydrogenase delta4-delta5-isomerase, or P450c21. Thus, although the mechanisms of regulation differ, changes in the levels of StAR protein are a sensitive indicator of the steroidogenic capacity of these two tissues.

Endocrine alterations that underlie endotoxin-induced disruption of the follicular phase in ewes

Two experiments were conducted to investigate endocrine mechanisms by which the immune/inflammatory stimulus endotoxin disrupts the follicular phase of the estrous cycle of the ewe. In both studies, endotoxin was infused i.v. (300 ng/kg per hour) for 26 h beginning 12 h after withdrawal of progesterone to initiate the follicular phase. Experiment 1 sought to pinpoint which endocrine step or steps in the preovulatory sequence are compromised by endotoxin. In sham-infused controls, estradiol rose progressively from the time of progesterone withdrawal until the LH/FSH surges and estrous behavior, which began approximately 48 h after progesterone withdrawal. Endotoxin interrupted the preovulatory estradiol rise and delayed or blocked the LH/FSH surges and estrus. Experiment 2 tested the hypothesis that endotoxin suppresses the high-frequency LH pulses necessary to stimulate the preovulatory estradiol rise. All 6 controls exhibited high-frequency LH pulses typically associated with the preovulatory estradiol rise. As in the first experiment, endotoxin interrupted the estradiol rise and delayed or blocked the LH/FSH surges and estrus. LH pulse patterns, however, differed among the six endotoxin-treated ewes. Three showed markedly disrupted LH pulses compared to those of controls. The three remaining experimental ewes expressed LH pulses similar to those of controls; yet the estradiol rise and preovulatory LH surge were still disrupted. Our results demonstrate that endotoxin invariably interrupts the preovulatory estradiol rise and delays or blocks the subsequent LH and FSH surges in the ewe. Mechanistically, endotoxin can interfere with the preovulatory sequence of endocrine events via suppression of LH pulsatility, although other processes such as ovarian responsiveness to gonadotropin stimulation appear to be disrupted as well.

Role of cytokines in testicular function

Inflammatory disease has been established to affect male reproductive function and fertility. Relevant inflammatory diseases include general and chronic infectious diseases as well as localized acute or chronic infections of the male genitourinary tract. Male accessory gland infections account for almost 15% of all cases of male infertility seen in infertility clinics while fertility usually is not a clinical objective among patients with acute systemic infections such as Gram-negative sepsis. Infections of the male accessory glands frequently are associated with increased counts of white blood cells in semen and elevated levels of proinflammatory cytokines in semen and the testis. There is a mounting body of evidence that demonstrates the importance of cytokines and chemokines in the regulation of testicular and glandular function during pathophysiological states as well as under normal physiological conditions when cytokines act as growth and differentiation factors. The purpose of this review is to examine the role of cytokines in the regulation of steroidogenesis and spermatogenesis in the testis under physiological and pathophysiological conditions and considers clinical investigations that help to improve the evaluation and treatment of male infertility.

The expression of interleukin-6 in the pregnant rat corpus luteum and its regulation by progesterone and glucocorticoid

Interleukin (IL)-6, a multifunctional cytokine originally described as a T cell-derived factor, is also produced by different cell types, and it influences a wide variety of physiological and pathophysiological processes. Recent studies further suggest that IL-6 has a role in down-regulating hormone production by endocrine organs and can negatively affect the steroidogenic capacity of both ovaries and testes. Thus, the aims of this investigation were to examine whether IL-6 plays a role in luteolysis and, more specifically, to determine whether luteal cells express the IL-6 gene, whether this expression is developmentally and hormonally regulated in pregnancy, and whether the corpus luteum could be a target for IL-6 action. Using semiquantitative RT-PCR, messenger RNA (mRNA) encoding both components of the IL-6 receptor [the ligand-binding subunit (IL-6 R) and the IL-6 R-associated signal transducer (gp130)] were found to be highly expressed in corpora lutea throughout pregnancy. In contrast, IL-6 mRNA expression was barely detectable from day 4 through the end of pregnancy, whereas a sharp and abrupt expression of IL-6 mRNA occurred immediately after parturition. Although the corpus luteum does not express IL-6 mRNA during most of pregnancy, it could be induced to express this gene with an in vivo injection of the bacterial endotoxin, lipopolysaccharide. In addition, when corpora lutea from day-15 pregnant rats were isolated and maintained in culture, IL-6 mRNA that was undetectable at 0 h increased in a time-related manner and reached significant levels after 4 h of incubation, followed by a similar increase in IL-6 protein secreted in the culture media. Isolation of the small and large luteal cells by elutriation indicated that both cell populations can secrete IL-6 in culture. The apparent ability of luteal cells to spontaneously express IL-6 in vitro, together with the lack of IL-6 expression during most of pregnancy, led us to examine whether the IL-6 gene is silenced throughout pregnancy by luteotropic hormones. Corpora lutea from day-15 pregnant rats were cultured in the presence of different doses of progesterone; the synthetic glucocorticoid, dexamethasone; 17beta-estradiol; and PRL. Progesterone and dexamethasone markedly inhibited IL-6 mRNA expression, whereas 17beta-estradiol had a minimal inhibitory effect, and PRL did not affect IL-6 mRNA expression. In summary, results of this investigation have revealed that the rat corpus luteum expresses the IL-6 receptor system and that luteal cells are able to secrete IL-6. However, IL-6 gene expression is silenced during most of pregnancy, probably by the high levels of progesterone locally produced in the corpus luteum. The salient finding that progesterone and glucocorticoid strongly inhibit the expression of IL-6 in the corpus luteum suggests that one important luteotropic role of progesterone and glucocorticoids could be to prevent the expression of IL-6, which might have a deleterious effect on luteal function.

Different receptor mechanisms mediate the effects of endotoxin and interleukin-1 on female sexual behavior

Activation of the immune system by lipopolysaccharide (LPS) produces physiological, neuroendocrine and behavioral effects, some of which are mediated by cytokine production. We have previously shown that the cytokine interleukin-1 (IL-1) inhibits sexual behavior in female, but not male rats, while producing a comparable suppression of locomotion in both sexes. The present study examined the effects of LPS on sexual behavior and locomotion of male and female rats, and the involvement of IL-1 receptors in mediating the effects of IL-1 and LPS on females' behavior. Peripheral (i.p.) administration of LPS (50 or 250 microg/kg) significantly decreased sexual behavior in females, up to 6 h after administration, while it had no effect on male sexual behavior. However, locomotor activity, measured in the open-field test, was similarly reduced by LPS in both males and females. Pretreatment with the IL-1 receptor antagonist (IL-1ra) either i.p. (10 mg/kg) or intracerebroventricularly (i.c.v.) (50 microg/rat) did not prevent the inhibition of female sexual behavior and locomotion induced by either i.p. (50 microg/kg) or i.c.v. (200 or 400 ng/rat) administration of LPS, respectively. However, identical doses of IL-1ra significantly reversed the effects of IL-1beta, administered either i.p. (5 microg/kg) or i.c.v. (50 ng/rat), respectively. These results demonstrate that both LPS and IL-1beta produce marked inhibition of sexual behavior in female, but not in male rats. However, IL-1 receptors are not required for the effects of LPS on sexual behavior in female rats.

Review: cytokine involvement in ovarian processes

PROBLEM

Expression of tumor necrosis factor-alpha (TNF) and interleukins 1 alpha and 1 beta (IL-1) have been reported in ovaries of several species and humans and are implicated in ovarian follicular development and atresia, ovulation, steroidogenesis, and corpus luteum function (including formation, development, and regression). The principal abnormal processes affected by these cytokines are ovarian cancer and reduction of ovarian function during sepsis.

METHODS

A literature review.

RESULTS

Numerous studies indicate that TNF and IL-1 inhibit gonadotropin-stimulated steroidogenesis of undifferentiated ovarian cells due to inhibition of adenylyl cyclase and post-cAMP sites. In differentiated ovarian cells, these cytokines either stimulate progesterone synthesis or have little to no effect on steroidogenesis. Both cytokines participate in ovulation and levels of these cytokines increase during the preovulatory period. Endotoxin inhibits gonadotropin-stimulated ovarian steroidogenesis and follicular development and these effects are mediated, in part, by TNF and by direct effects of endotoxin on ovarian cells. IN newly formed corpora lutea, progesterone secretion is inhibited by TNF and IL-1, although each has proliferative effects. TNF also has been implicated in regression of corpora lutea because TNF stimulates prostaglandin synthesis and luteal TNF increases after initiation of the decline in progesterone secretion. TNF and IL-1 are secreted by some ovarian cancer cells and stimulate growth of these cells.

CONCLUSIONS

Thus, TNF and IL-1 are multifunctional factors affecting various ovarian processes.