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

Crosstalk between reproductive and immune systems: the teleostean perspective

The bidirectional interaction between the hypothalamic-pituitary-gonadal (HPG) axis and the immune system plays a crucial role in the adaptation of an organism to its environment, its survival and the continuance of a species. Nonetheless, very little is known about this interaction among teleost, the largest group of extant vertebrates. Fishes being seasonal breeders, their immune system is exposed to seasonally changing levels of HPG hormones. On the contrary, the presence and infiltration of leukocytes, the expression of pattern recognition receptors as well as cytokines in gonads suggest their key role in teleostean gametogenesis as in the case of mammals. Moreover, the modulation of gametogenesis and steroidogenesis by lipopolysaccharide implicates the pathological significance of inflammation on reproduction. Thus, it is important to engage in the understanding of the interaction between these two important physiological systems, not only from a phylogenetic perspective but also due to the importance of fish as an important economic resource. In view of this, the authors have reviewed the crosstalk between the reproductive and immune systems in teleosts and tried to explore the importance of this interaction in their survival and reproductive fitness.

Molecular Mechanisms of Lipopolysaccharide (LPS) Induced Inflammation in an Immortalized Ovine Luteal Endothelial Cell Line (OLENDO)

Escherichia coli (E. coli) is the most common Gram-negative bacterium causing infection of the uterus or mammary gland and is one of the major causes of infertility in livestock. In those animals affected by E. coli driven LPS-mediated infections, fertility problems occur in part due to disrupted follicular and luteal functionality. However, the molecular mechanisms by which LPS induces inflammation, and specifically, the role of LPS in the disruption of capillary morphogenesis and endothelial barrier function remain unclear. Here, we hypothesized that LPS may lead to alterations in luteal angiogenesis and vascular function by inducing inflammatory reactions in endothelial cells. Accordingly, OLENDO cells were treated with LPS followed by evaluation of the expression of selected representative proinflammatory cytokines: NF-kB, IL6, IL8, TNFα, and ICAM 1. While TNFα was not affected by treatment with LPS, transcripts of NF-kB, IL6, and IL8 were affected in a dosage-dependent manner. Additionally, the activity of TLR2 and TLR4 was blocked, resulting in suppression of the LPS-induced expression of ICAM 1, NF-kB, IL6, and IL8. Inhibition of the PKA or MAPK/ERK pathways suppressed the LPS-stimulated expression of NF-kB, IL6, and IL8, whereas blocking the PKC pathway had the opposite effect. Furthermore, LPS-induced phosphorylation of Erk1 and Erk2 was inhibited when the TLR4 or MAPK/ERK pathways were blocked. Finally, LPS seems to induce inflammatory processes in OLENDO cells via TLR2 and TLR4, utilizing different signaling pathways.

The Release of Peripheral Immune Inflammatory Cytokines Promote an Inflammatory Cascade in PCOS Patients via Altering the Follicular Microenvironment

Background

Hormones and immune imbalance are critical factors in polycystic ovary syndrome (PCOS). The alternation of immune microenvironment of oocytes may play a significant role in infertility of PCOS patients.

Objective

This study explores the role of follicular fluid microenvironment change in inflammatory pathways activation of granulosa cells (GCs) in PCOS women infertility.

Methods

We enrolled 27 PCOS patients and 30 controls aged 22 to 38 years who underwent IVF and collected their luteinized granulosa cells (LGCs). Meanwhile, a granulosa-like tumor cell line (KGN) as a cell-model assisted this study. Key inflammatory markers in human ovarian GCs and follicular fluid were detected by RT-qPCR, Western blotting, or ELISA. The KGN cells were treated with follicle supernatant mixed with normal medium to simulate the microenvironment of GCs in PCOS patients, and the inflammation indicators were observed. The assembly of NLRP3 inflammasomes was detected by immunofluorescence techniques. Dihydroethidium assay and EdU proliferation assay were used to detect ROS and cell proliferation by flow cytometry.

Results

Compared with normal controls (n = 19), IL-1β (P = 0.0005) and IL-18 (P = 0.021) in the follicular fluid of PCOS patients (n = 20) were significantly increased. The NF-κB pathway was activated, and NLRP3 inflammasome was formatted in ovarian GCs of PCOS patients. We also found that inflammation of KGN cells was activated with LPS irritation or stimulated by follicular fluid from PCOS patients. Finally, we found that intracellular inflammation process damaged mitochondrial structure and function, which induced oxidative stress, affected cellular metabolism, and impaired cell proliferation.

Conclusion

Inflammatory microenvironment alteration in the follicular fluid of PCOS patients leads to activated inflammatory pathway in GCs, serving as a crucial factor that causes adverse symptoms in patients. This study provides a novel mechanism in the inflammatory process of PCOS.

TNFα-Erk1/2 signaling pathway-regulated SerpinE1 and SerpinB2 are involved in lipopolysaccharide-induced porcine granulosa cell proliferation

Lipopolysaccharide (LPS) is an inhibitory factor that causes hormonal imbalance and subsequently affects ovarian function and fertility in mammals. Previous studies have shown that the exposure of granulosa cells (GC) to LPS leads to steroidogenesis dysfunction. However, the effects of LPS on the viability of GC remain largely unclear. In the present study, we aimed to address this question and unveil the underlying molecular mechanisms using cultured porcine GC. Results showed that GC proliferation and tumor necrosis factor α (TNFα) secretion were significantly increased after exposure to LPS, and these effects were completely reversed by blocking the TNFα sheddase, ADAM17. Moreover, GC proliferation induced by LPS was mimicked by treatment with recombinant TNFα. In addition, SerpinE1 and SerpinB2 expression levels increased in GC after treatment with LPS or recombinant TNFα, whereas blocking the Erk1/2 pathway completely abolished these effects and also inhibited GC proliferation. Further, consistent with the effects of blocking the Erk1/2 pathway, cell proliferation was completely inhibited by knocking down SerpinE1 or SerpinB2 in the presence of LPS or recombinant TNFα. Mitochondrial membrane potential (MMP) polarization in GC was increased by LPS or recombinant TNFα treatment, and these changes were completely negated by Erk1/2 inhibition, but not by SerpinE1 or SerpinB2 knockdown. Taken together, these results suggested that the TNFα-mediated upregulation of SerpinE1 and SerpinB2, through activation of the Erk1/2 pathway plays a crucial role in LPS-stimulated GC proliferation, and the increase in GC MMP may synergistically influence this process.

Lipopolysaccharide and tumor necrosis factor-alpha alter gene expression of oocytes and cumulus cells during bovine in vitro maturation

Communication between the oocyte and cumulus facilitates oocyte growth, cell cycle regulation, and metabolism. This communication is mediated by direct contact between oocytes and cumulus cells, and soluble secreted molecules. Secreted molecules involved in this process are known inflammatory mediators. Lipopolysaccharide (LPS) is detected in follicular fluid and is associated with reduced fertility, whereas accumulation of inflammatory mediators in follicular fluid, including tumor necrosis factor-α (TNF-α), is associated with female infertility. Maturation of oocytes in the presence of LPS or TNF-α reduces meiotic maturation and the capacity to develop to the blastocyst. Here we evaluated the abundance of 92 candidate genes involved immune function, epigenetic modifications, embryo development, oocyte secreted factors, apoptosis, cell cycle, and cell signaling in bovine cumulus cells or zona-free oocytes after exposure to LPS or TNF-α during in vitro maturation. We hypothesize that LPS or TNF-α will alter the abundance of transcripts in oocytes and cumulus cell in a cell type dependent manner. Exposure to LPS altered abundance of 31 transcripts in oocytes (including ACVR1V, BMP15, DNMT3A) and 12 transcripts in cumulus cells (including AREG, FGF4, PIK3IP1). Exposure to TNF-α altered 1 transcript in oocytes (IGF2) and 4 transcripts in cumulus cells (GJA1, PLD2, PTGER4, STAT1). Cumulus expansion was reduced after exposure to LPS or TNF-α. Exposing COCs to LPS had a marked effect on expression of targeted transcripts in oocytes. We propose that altered oocyte transcript abundance is associated with reduced meiotic maturation and embryo development observed in oocytes cultured in LPS or TNF-α.

Lipopolysaccharide disrupts gap junctional intercellular communication in an immortalized ovine luteal endothelial cell line

Gram-negative bacteria, in particular Escherichia coli with its cell wall lipopolysaccharide (LPS), often cause metritis and mastitis in domestic animals. Ovarian LPS accumulation may initiate local inflammatory reactions mediated through cell surface Toll-like receptors (TLRs). This may disrupt ovarian functionality leading to infertility. Possible adverse effects of LPS on luteal activity are not yet well explored. We hypothesized that LPS could lead to alterations in luteal vascular functionality. Therefore, we established an in vitro cell line model (OLENDO) by immortalizing microvascular endothelial cells isolated from ovine corpus luteum (CL) with a potent Simian Virus 40 T-antigen (SV40-Tag). OLENDO exhibit endothelial cell characteristics, like low-density lipoprotein (LDL) uptake, express BSL-I, and VEGFR2, as well as TLR2 and TLR4 receptors. LPS-treatment of OLENDO altered in vitro tube formation, had no effects on cell viability and decreased gap junctional intercellular communication (GJIC). LPS did not impair GJA1/Cx43 protein expression, but altered its cellular localization showing signs of internalization. Taken together, we demonstrated the mechanisms underlying LPS induced impairment of luteal GJIC and immune processes in a novel and well-characterized OLENDO cell line.

Effects of LPS on the accumulation of lipid droplets, proliferation, and steroidogenesis in goat luteinized granulosa cells

Lipopolysaccharide (LPS) can cause ovarian dysfunction and infertility in mammals. The purpose of this study was to investigate the effects of LPS on the accumulation of lipid droplets (LDs), proliferation, and steroidogenesis in goat luteinized granulosa cells (LGCs). GCs isolated from the ovarian follicles were spontaneously luteinized under media with fetal bovine serum, resulting in increased progesterone and shifted shape from spherical to star with multiple prolongations. Then, LGCs were treated with LPS (0-10 μg/mL) for 0-48 hours. Oil Red O staining was performed to observe LDs accumulation and commercial kit was applied to detect intracellular triglyceride (TG) content. The cell proliferation were detected by cell counting kit-8. Expressions of cell-cycle-related genes were determined by real-time polymerase chain reaction. Estradiol (E ₂ ) and progesterone (P ₄ ) from cell supernatants were determined by enzyme-linked immunosorbent assay, and expressions of STAR, P450scc, 3β-hydroxysteroid dehydrogenase (3β-HSD) and CYP19A1 were detected by Western blot. Results showed that LPS treatment significantly increased LDs accumulation after 24 hours, and 5 μg/mL LPS increased TG content ( P < 0.05). LPS treatment for 24 hours stimulated the LGCs activities ( P<0.05), which was confirmed by the increases in the expressions of proliferating cell nuclear antigen (PCNA), cyclinB1 and cyclinD1, while 48 hours treatment had no effect. LPS treatment suppressed E ₂ and P ₄ output of LGCs ( P < 0.05). Western blot results showed that 10 μg/mL LPS decreased the protein expression of 3β-HSD in LGCs ( P < 0.05). In conclusion, LPS increased LDs accumulation and cell proliferation, and LPS-mediated P ₄ reduction could be attributed to the decreased 3β-HSD protein expression, which provide new information for the regulation of ovarian function in goats.

Inflammatory markers in human follicular fluid correlate with lipid levels and Body Mass Index

The detrimental consequences of obesity on female fertility are well known, but the functional changes that occur in the ovary in response to elevated BMI are not clear. Obesity induces multiple components of a systemic inflammatory state that is a key pathway by which it initiates tissue dysfunction in adipose, liver and muscle; however whether obesity induces similar inflammatory changes in the ovary has not been fully investigated. This is important to understand because it is increasingly clear that obesity at conception impacts not only pregnancy rates but also influences pre-implantation embryo development. To further understand the characteristics of inflammation in the ovaries of obese women we analysed a panel of cytokines (IL6, IL10 and TNFα), adipokines (adiponectin, leptin and monocyte chemotactic factor 1 (MCP-1)) and acute phase proteins (C-Reactive Protein (CRP) and sICAM-1) in the ovarian follicular fluid obtained at oocyte aspiration from women (n = 48) who were lean, overweight or obese. We hypothesised that adipokines and pro-inflammatory cytokines would be correlated with and/or dysregulated by increasing Body Mass Index (BMI). Surprisingly however, the majority were not related to BMI but instead were positively correlated with lipid levels in follicular fluid, namely triglycerides and free fatty acids. Further, as is typical of metabolic inflammation, the inflammatory markers that were associated with intra-follicular lipids included both pro-inflammatory (CRP, IL6, TNFα) and anti-inflammatory (adiponectin, IL10) mediators. The direct consequences of an ovarian microenvironment containing high levels of lipids and inflammatory mediators are not known but could impact luteinisation, ovulation and/or oocyte developmental competence.

Age-related changes in the bovine corpus luteum function and progesterone secretion

Decreased fertility associated with maternal ageing is a well-known critical problem, and progesterone (P4) concentration decreases during the menopause transition in women. The corpus luteum (CL) secretes P4, thereby supporting the implantation and maintenance of pregnancy. It is proposed that a bovine model is suitable for studying age-associated decline of fertility in women because the physiology of cows is similar to that of women and cows have a greater longevity compared with other animal models. Thus, we investigated the age-dependent qualitative changes and inflammatory responses in the bovine CL. In vivo experiment: Cows were divided into three groups, namely, young (mean age: 34.8 months), middle (80.1 months) and aged (188.9 months). Blood samples were collected on days 7 and 12 during the estrous cycle. In vitro experiments: Cows were divided into young (mean age: 27.6 months) and aged (183.1 months). The CL tissues of these groups were collected from a local slaughterhouse and used for tissue culture experiments. An in vivo experiment, plasma P4 concentration in aged cows was significantly lower than that in young cows, whereas no difference was found regarding the area of CL. An in vitro examination in the bovine CL tissues showed that the luteal P4 concentration, P4 secretion, and mRNA expression of StAR and 3β-HSD were lower in aged cows compared with young cows, especially in the early luteal phase. However, no differences were detected in the mRNA expression of inflammation- and senescence-related factors and inflammatory responses to lipopolysaccharides between the CL tissues from young and aged cows, indicating that an age-dependent increase in inflammation is not involved in the luteal function. P4 production and secretion from the bovine CL diminish in old cows, especially during the early luteal phase, suggesting that senescence may affect the luteal function in cows.

Influence of follicular fluid and cumulus cells on oocyte quality: clinical implications

An equilibrium needs to be established by the cellular and acellular components of the ovarian follicle if developmental competence is to be acquired by the oocyte. Both cumulus cells (CCs) and follicular fluid (FF) are critical determinants for oocyte quality. Understanding how CCs and FF influence oocyte quality in the presence of deleterious systemic or pelvic conditions may impact clinical decisions in the course of managing infertility. Given that the functional integrities of FF and CCs are susceptible to concurrent pathological conditions, it is important to understand how pathophysiological factors influence natural fertility and the outcomes of pregnancy arising from the use of assisted reproduction technologies (ARTs). Accordingly, this review discusses the roles of CCs and FF in ensuring oocyte competence and present new insights on pathological conditions that may interfere with oocyte quality by altering the intrafollicular environment.

Evaluating lipopolysaccharide-induced oxidative stress in bovine granulosa cells

PURPOSE

The purpose of this study was to evaluate the capacity of bovine granulosa cells to generate reactive oxygen intermediates in response to lipopolysaccharide. We hypothesized that granulosa cells increase reactive oxygen intermediates in response to Gram-negative lipopolysaccharide in a similar manner to immune cells.

METHODS

Bovine peripheral blood mononuclear cells and granulosa cells were cultured in the presence of lipopolysaccharide. Oxidative stress was evaluated using the fluorescent marker dye CellROX, and oxidative stress-related genes were measured using real-time RT-PCR.

RESULTS

As expected, peripheral blood mononuclear cells increased oxidative stress in response to lipopolysaccharide as measured by accumulation of the fluorescent marker dye CellROX. While granulosa cells demonstrate the capacity to increase accumulation of CellROX dye in response to a positive control menadione, lipopolysaccharide had no effect on accumulation of CellROX dye. The expression of GSR, SOD1, and SOD2 were variable in peripheral blood mononuclear cells treated with lipopolysaccharide but were consistently upregulated when co-incubated with the antioxidant, N-acetyl cysteine. The expression of oxidative stress-related genes was not altered in granulosa cells, with the exception of elevated SOD1 following lipopolysaccharide exposure in the absence of antioxidant.

CONCLUSIONS

Combined, these data suggest that while reactive stress is important in pathogen killing and inflammation in immune cells, granulosa cells do not increase oxidative stress in response to lipopolysaccharide.

Follicular expression of pro-inflammatory cytokines tumour necrosis factor-α (TNFα), interleukin 6 (IL6) and their receptors in cattle: TNFα, IL6 and macrophages suppress thecal androgen production in vitro

Pro-inflammatory cytokines secreted by macrophages and other cell types are implicated as intraovarian factors affecting different aspects of ovarian function including follicle and corpus luteum 'turnover', steroidogenesis and angiogenesis. Here, we compared granulosal (GC) and thecal (TC) expression of TNF, IL6 and their receptors (TNFRSF1A, TNFRSF1B and IL6R) during bovine antral follicle development; all five mRNA transcripts were detected in both GC and TC and statistically significant cell-type and follicle stage-related differences were evident. Since few studies have examined cytokine actions on TC steroidogenesis, we cultured TC under conditions that retain a non-luteinized 'follicular' phenotype and treated them with TNFα and IL6 under basal and LH-stimulated conditions. Both TNFα and IL6 suppressed androgen secretion concomitantly with CYP17A1 and LHCGR mRNA expression. In addition, TNFα reduced INSL3, HSD3B1 and NOS3 expression but increased NOS2 expression. IL6 also reduced LHCGR and STAR expression but did not affect HSD3B1, INSL3, NOS2 or NOS3 expression. As macrophages are a prominent source of these cytokines in vivo, we next co-cultured TC with macrophages and observed an abolition of LH-induced androgen production accompanied by a reduction in CYP17A1, INSL3, LHCGR, STAR, CYP11A1 and HSD3B1 expression. Exposure of TC to bacterial lipopolysaccharide also blocked LH-induced androgen secretion, an effect reduced by a toll-like receptor blocker (TAK242). Collectively, the results support an inhibitory action of macrophages on thecal androgen production, likely mediated by their secretion of pro-inflammatory cytokines that downregulate the expression of LHCGR, CYP17A1 and INSL3. Bovine theca interna cells can also detect and respond directly to lipopolysaccharide.