The role of oxygen radical-mediated signaling pathways in endometrial function

Visfatin Affects the Transcriptome of Porcine Luteal Cells during Early Pregnancy

Visfatin/NAMPT (VIS), the hormone exerting a pleiotropic effect, is also perceived as an important factor in the regulation of reproductive processes and pregnancy maintenance. Previous studies confirmed its involvement in the control of porcine pituitary and ovary function. In this study, we hypothesized that VIS may affect the global transcriptome of luteal cells and thus regulate the functioning of the ovaries. Illumina's NovaSeq 6000 RNA sequencing was performed to investigate the differentially expressed genes (DEGs) and long non-coding RNAs (DELs) as well as the occurrence of differential alternative splicing events (DASs) in the porcine luteal cells exposed to VIS (100 ng/mL) during the implantation period. The obtained results revealed 170 DEGs (99 up- and 71 downregulated) assigned to 45 functional annotations. Moreover, we revealed 40 DELs, of which 3 were known and 37 were described for the first time. We identified 169 DASs events. The obtained results confirmed a significant effect of VIS on the transcriptome and spliceosome of luteal cells, including the genes involved in the processes crucial for successful implantation and pregnancy maintenance as angiogenesis, steroidogenesis, inflammation, cell development, migration, and proliferation.

Decidualization dampens toll-like receptor mediated inflammatory responses in human endometrial stromal cells by upregulating IκBα

Endometrial stromal cells (EnSCs) are the major cell type of the human endometrium and they undergo dramatic differentiation, termed decidualization, every month that enables them to be receptive to implantation. Appropriate decidualization and EnSC function is key for a successful pregnancy. EnSC function may be affected when the uterus is exposed to bacterial and viral infection. However, how human EnSCs respond to viral and bacterial components have not been well-studied and it remains unclear whether uterine innate immune responses change during decidualization. This study demonstrated that viral double-stranded RNA [Poly(I:C)] and bacterial lipopolysaccharide (LPS) upregulated undecidualized human EnSC production of a large array of proinflammatory cytokines and chemokines, and revealed that these immune responses were significantly dampened during decidualization in vitro and in vivo. This dampened response was associated with increased NFKBIA transcription during decidualization that leads to the accumulation of this negative regulator in decidualizing EnSCs that can bind to NFκB p65 and prevents its nuclear translocation and downstream Toll-like receptor signaling. These findings highlight that endometrial responses to infection may vary at different stages of the menstrual cycle which may be important for preparing the endometrium to support the growth of the semi-allogenic blastocyst. This work emphasizes the need to consider menstrual cycle stage, sex hormone levels and the differentiation status of cells when examining inflammatory responses in the future.

The Relationship of Preconception and Early Pregnancy Isoprostanes with Fecundability and Pregnancy Loss

BACKGROUND

Although redox stress likely plays an important role in reproductive health, the utility of peripheral biomarkers of oxidative stress, such as isoprostanes, during the periconception period remains underexplored. We evaluated the relationship between isoprostanes during preconception and gestational week 4 and women's reproductive health outcomes.

METHODS

The Effects of Aspirin in Gestation and Reproduction trial (2007-2011) enrolled 1228 women attempting pregnancy and followed them for up to 6 menstrual cycles and throughout pregnancy if they became pregnant. We measured creatinine-adjusted, log-transformed isoprostanes 8-iso-prostaglandin F 2α (8-iso-PGF2α), its metabolite 2,3-dinor-iPF2α-III, and stereoisomers 5-iso-PGF2α-VI and 8,12-iso-iPF2α-VI in urine during preconception and 4 weeks gestation. We evaluated pregnancy among participants in each menstrual cycle using human chorionic gonadotropin (hCG) and defined pregnancy loss as observed loss following positive hCG. We calculated fecundability odds ratios (FOR) and 95% confidence intervals (CI) using discrete-time Cox proportional hazards models and relative risk of pregnancy loss using adjusted log-binomial models.

RESULTS

Higher preconception isoprostane levels were associated with lower fecundability [e.g., FOR = 0.89; 95% CI = 0.81, 0.97 per interquartile range (IQR) increase in 8-iso-PGF2α]. Among 797 pregnancies, isoprostane levels increased from preconception to 4 weeks gestation (e.g., mean difference = 0.12; 95% CI = 0.10, 0.14 ng/mL for 8-iso-PGF2α) and higher isoprostanes at 4 weeks gestation were associated with lower risk of pregnancy loss (e.g., RR = 0.79; 95% CI = 0.62, 1.00 per IQR increase in 8-iso-PGF2α).

CONCLUSIONS

Preconception urinary isoprostanes may identify redox stress pathways associated with lower fecundability. However, the increase in isoprostanes into gestational week 4 and the associated lower risk of pregnancy loss may suggest confounding by latent factors in early pregnancy.

Reduced Glutathione-Modified Electrode for the Detection of Hydroxyl Free Radicals

Hydroxyl radicals (•OH) are known as essential chemicals for cells to maintain their normal functions and defensive responses. However, a high concentration of •OH may cause oxidative stress-related diseases, such as cancer, inflammation, and cardiovascular disorders. Therefore, •OH can be used as a biomarker to detect the onset of these disorders at an early stage. Reduced glutathione (GSH), a well-known tripeptide for its antioxidant capacity against reactive oxygen species (ROS), was immobilized on a screen-printed carbon electrode (SPCE) to develop a real-time detection sensor with a high selectivity towards •OH. The signals produced by the interaction of the GSH-modified sensor and •OH were characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The CV curve of the GSH-modified sensor in the Fenton reagent exhibited a pair of well-defined peaks, demonstrating the redox reaction of the electrochemical sensor and •OH. The sensor showed a linear relationship between the redox response and the concentration of •OH with a limit of detection (LOD) of 49 µM. Furthermore, using EIS studies, the proposed sensor demonstrated the capability of differentiating •OH from hydrogen peroxide (H2O2), a similar oxidizing chemical. After being immersed in the Fenton solution for 1 hr, redox peaks in the CV curve of the GSH-modified electrode disappeared, revealing that the immobilized GSH on the electrode was oxidized and turned to glutathione disulfide (GSSG). However, it was demonstrated that the oxidized GSH surface could be reversed back to the reduced state by reacting with a solution of glutathione reductase (GR) and nicotinamide adenine dinucleotide phosphate (NADPH), and possibly reused for •OH detection.

OXIDATIVE STRESS AND REPRODUCTIVE FUNCTION: The impact of oxidative stress on reproduction: a focus on gametogenesis and fertilization

In brief

Many aspects of the reproductive process are impacted by oxidative stress. This article summarizes the chemical nature of reactive oxygen species and their role in both the physiological regulation of reproductive processes and the pathophysiology of infertility.

Abstract

This article lays out the fundamental principles of oxidative stress. It describes the nature of reactive oxygen species (ROS), the way in which these potentially toxic metabolites interact with cells and how they impact both cellular function and genetic integrity. The mechanisms by which ROS generation is enhanced to the point that the cells' antioxidant defence mechanisms are overwhelmed are also reviewed taking examples from both the male and female reproductive system, with a focus on gametogenesis and fertilization. The important role of external factors in exacerbating oxidative stress and impairing reproductive competence is also examined in terms of their ability to disrupt the physiological redox regulation of reproductive processes. Developing diagnostic and therapeutic strategies to cope with oxidative stress within the reproductive system will depend on the development of a deeper understanding of the nature, source, magnitude, and location of such stress in order to fashion personalized treatments that meet a given patient's clinical needs.

Progress of oxidative stress in endometrium decidualization

The difficulty in maintaining the balance between oxides and antioxidants causes a phenomenon named oxidative stress. Oxidative stress often leads to tissue damage and participates in the pathogenesis of a series of diseases. Decidua provides the 'soil' for embryo implantation, and the normal decidualization shows the characteristics of strong antioxidation. Once the mechanism of antioxidant stress goes awry, it will lead to a series of pregnancy-related diseases. In recent years, more and more studies have shown that oxidative stress is involved in pregnancy-related diseases caused by abnormal decidualization of the endometrium. In order to have a more comprehensive understanding of the role of oxidative stress in decidual defect diseases, this paper reviews the common decidual defect diseases in conjunction with relevant regulatory molecules, in order to arouse thinking about the importance of oxidative stress, and to provide more theoretical basis for the aetiology of decidual defects.

The investigation of the role of sirtuin-1 on embryo implantation in oxidative stress-induced mice

PURPOSE

Implantation is essential for a successful pregnancy. Despite the increasing number of studies, implantation is still an unknown process. This study aimed to determine whether sirtuin-1 has a role in embryo implantation in oxidative stress-induced mice.

METHODS

Pregnant mice were separated into 5 groups: control, vehicle, paraquat, SRT1720, and SRT1720+Paraquat. Paraquat is a herbicide and is used to induce oxidative stress. SRT1720 is a specific sirtuin-1 activator. Implantation and inter-implantation sites were removed in the morning of the 5th day of pregnancy after Chicago blue injection was performed. Sirtuin-1 and Forkhead box O1 (FoxO1) were detected by immunohistochemistry and Western blot while acetylated lysine was evaluated by Western blot analysis. Reactive oxygen and nitrogen species (ROS/RNS) and superoxide dismutase (SOD) activity were determined by fluorometric and spectrometric methods, respectively.

RESULTS

Although there was no embryo implantation in paraquat-treated mice, 5 out of 9 SRT1720+Paraquat-treated mice had implantation sites which were significantly higher compared to the paraquat-treated group. Sirtuin-1 and FoxO1 expressions were increased at implantation sites of SRT1720-treated mice. ROS/RNS levels were decreased, while deacetylated FoxO1 levels and SOD activity were increased in SRT1720-treated mice.

CONCLUSION

Our findings suggest that sirtuin-1 may play a role in embryo implantation against oxidative stress through FoxO1-SOD signaling.

Detection of Hydroxyl Radicals Using Cerium Oxide/Graphene Oxide Composite on Prussian Blue

A composite sensor consisting of two separate inorganic layers of Prussian blue (PB) and a composite of cerium oxide nanoparticles (CeNPs) and graphene oxide (GO), is tested with •OH radicals. The signals from the interaction between the composite layers and •OH radicals are characterized using cyclic voltammetry (CV). The degradation of PB in the presence of H₂O₂ and •OH radicals is observed and its impact on the sensor efficiency is investigated. The results show that the composite sensor differentiates between the solutions with and without •OH radicals by the increase of electrochemical redox current in the presence of •OH radicals. The redox response shows a linear relation with the concentration of •OH radicals where the limit of detection, LOD, is found at 60 µM (100 µM without the PB layer). When additional composite layers are applied on the composite sensor to prevent the degradation of PB layer, the PB layer is still observed to be degraded. Furthermore, the sensor conductivity is found to decrease with the additional layers of composite. Although the CeNP/GO/PB composite sensor demonstrates high sensitivity with •OH radicals at low concentrations, it can only be used once due to the degradation of PB.

Increased dietary calcium inclusion in fully acidified prepartum diets improved postpartum uterine health and fertility when fed to Holstein cows

The objective of this study was to determine the effects of prepartum negative dietary cation-anion difference diet (DCAD) fed at two dietary Ca inclusion rates on postpartum uterine health and ovulation dynamics of multiparous Holstein cows (n = 76). Treatments began at 28 days before expected calving until parturition and were: CON: DCAD = +6 mEq/100g of DM with low dietary Ca (46.2 ± 15.2 g Ca/d; 0.4% DM; n = 26); ND: DCAD = -24 mEq/100g of DM with low dietary Ca (44.1 ± 16.1 Ca/d; 0.4% DM; n = 24); NDCA: DCAD = -24 mEq/100g of DM with high dietary Ca (226.6 ± 96.0 g Ca/d; 2.0% DM; n = 26). Vaginal discharge was evaluated through the fresh period via Metricheck (MC) for presence of purulent material. Polymorphonuclear (PMN) cell concentration in the uterus was evaluated at 15 and 30 days relative to calving (DRC). Endometrial tissue was harvested at 30 DRC for glandular morphology, presence of tight-junctions and adheren-junctions proteins, as well as assessment of superoxide dismutase (SOD) and glutathione peroxidase (GPX) activity. Blood plasma and serum samples were harvested in the prepartum and postpartum phase and were assessed for concentrations of lipopolysaccharide binding protein (LBP), serum amyloid A (SAA), and haptoglobin (HP). Ovarian dynamics were assessed through the fresh period until first timed artificial insemination (TAI). Cows fed CON had a lower MC score (P = 0.06) than the average of cows fed ND and cows fed NDCA. Cows fed ND had a higher MC score than cows fed NDCA. Cows fed NDCA had greater uterine gland epithelial height (P = 0.02) than cows fed ND. Cows fed NDCA also had a greater number of epithelial cells per gland (P = 0.05) than cows fed ND. Cows fed NDCA had greater intensity of occludin expression (P = 0.15) than cows fed ND. Cows fed NDCA had increased activity of SOD (P = 0.05) and decreased activity of GPX (P < 0.001) than cows fed ND. Cows fed ND had higher plasma HP concentrations than cows fed NDCA in the prepartum (P = 0.01) and post-partum (P = 0.03) periods. Cows fed ND and NDCA had lower (P = 0.01) postpartum plasma HP concentration than cows fed CON. In conclusion, cows fed NDCA had an improved uterine environment most likely due to alleviation of oxidative stress, an enhanced immune response to parturition and uterine discharge comparable to cows fed CON.

HB-EGF Ameliorates Oxidative Stress-Mediated Uterine Decidualization Damage

HB-EGF is essential for uterine decidualization, but its antioxidant function remains largely unclear. Here, we found that HB-EGF promoted the proliferation of stromal cells followed by the accelerated transition of the cell cycle from G1 to S phase and enhanced the expression or activity of Prl8a2, Prl3c1, and ALP which were well-established markers for uterine stromal cell differentiation during decidualization. Under oxidative stress, stromal cell differentiation was impaired, but this impairment was abrogated by rHB-EGF accompanied with the reduced levels of ROS and MDA which were regarded as the biomarkers for oxidative stress, indicating an antioxidant role of HB-EGF. Further analysis revealed that HB-EGF enhanced the activities of antioxidant enzymes SOD, CAT, and GPX, where addition of GPX inhibitor MS attenuated the induction of rHB-EGF on Prl8a2, Prl3c1, and ALP. Meanwhile, HB-EGF rescued the content of GSH and restored the ratio of GSH/GSSG after exposure to H2O2 but did not alter NOX activity. Along with a decline for mitochondrial superoxide, exogenous rHB-EGF improved the damage of oxidative stress on mtDNA copy number, ATP level, mitochondrial membrane potential, and activities of mitochondrial respiratory chain complex I and III whose blockage by ROT and AA led to a failure of rHB-EGF in protecting stromal cell differentiation against injury. Moreover, HB-EGF prevented stromal cell apoptosis by inhibiting Caspase-3 activity and Bax expression and recovering the level of Bcl-2 mRNA. Collectively, HB-EGF might ameliorate oxidative stress-mediated uterine decidualization damage.

Endometrial stromal cell proteome mapping in repeated implantation failure and recurrent pregnancy loss cases and fertile women

RESEARCH QUESTION

Are there proteomic differences between endometrial stromal cells of repeated implantation failure (RIF), recurrent pregnancy loss (RPL) and normal fertile women, and is there differential protein expression upon decidualization?

DESIGN

This exploratory study investigated the proteome of in-vitro cultured endometrial stromal cells of women with RIF (n = 4), women with RPL (n = 3) and normal fertile women (n = 4), comparing day 0 with 5 days of decidualization. Total proteins extracted from cell lysates were analysed by high-definition mass spectrometry. Data analysis was performed using significance analysis of microarray in R (P < 0.05; false discovery rate [FDR] 10%).

RESULTS

In the RIF group, ANXA6, PSMC5 and FSCN1 were up-regulated (1.9-fold, 2.5-fold and 1.9-fold, respectively), whereas PBXIP1 was down-regulated (7.7-fold) upon decidualization. In the RPL group, RPS25 and ACADVL were down-regulated (1.9-fold and 2.4-fold, respectively; FDR 10%) between the non-decidualized and the decidualized samples. In the normal fertile group VIM and RPL23A were down-regulated (1.9-fold and 2.4-fold, respectively). Comparing ratios of expression of decidualized over non-decidualized samples in the different groups revealed six differentially expressed proteins: DUX4L2, CNPY4, PDE7A, CTSK, PCBP2 and PSMD4. Comparison of RPL versus normal fertile in the decidualized condition revealed serotransferrin to be differentially expressed. The changes in expression levels for serotransferrin, ANX6, ACDVL and VIM were confirmed by western blot.

CONCLUSIONS

Results show a varying response of endometrial stromal cells in distinct clinical groups (RIF, RPL and normal fertile) upon in-vitro decidualization. Serotransferrin could serve as a marker for the aberrant decidualization process in RPL.

Decidualization of the human endometrium

BACKGROUND

Decidualization of the human endometrium, which involves a dramatic morphological and functional differentiation of human endometrial stromal cells (ESCs), is essential for the establishment of a successful pregnancy. Decidualization results from a complex interplay of transcription factors, morphogens, cytokines, cell cycle regulators, and signaling pathways.

METHODS

Based on a literature review, the regulation of, and the molecular mechanisms involved in, the decidualization of the endometrium are described.

MAIN FINDINGS

Progesterone, together with proteins that are regulated by progesterone and/or cyclic adenosine monophosphate, including homeobox A10, forkhead box O1, signal transducers and activators of transcription, and heart and neural crest derivatives expressed transcript 2, forms a critical network for ESC decidualization and is a prerequisite to successful implantation. Decidualized ESCs contribute to the microenvironment at the feto-maternal interface and its direct or indirect influence on extracellular matrix remodeling, regulation of the local immune response, anti-oxidative stress, and angiogenesis (vascular maturation). Impairment of this process is associated with a variety of pregnancy disorders, including infertility, recurrent miscarriages, and uteroplacental disorders.

CONCLUSION

A deeper understanding of the process of decidualization is expected to provide new insights into the fields of reproductive biology and reproductive medicine.

Distinct changes in the proteome profile of endometrial tissues in polycystic ovary syndrome compared with healthy fertile women

RESEARCH QUESTION

What is the molecular basis of infertility related to uterine dysfunction in women with polycystic ovary syndrome (PCOS)?

DESIGN

In this study, differences in protein expression between PCOS and normal endometrium were identified using a proteomic approach based on two-dimensional electrophoresis (2-DE) coupled with mass spectrometry (MS). The proteome of endometrium were analysed during the proliferative (on day 2 or 3 before ovulation, n = 6) and luteal phases (on day 3-5 after ovulation, n = 6) from healthy women and PCOS patients (12-14 days after spontaneous bleeding, n = 12). The differentially expressed proteins were categorized based on the biological process using the DAVID bioinformatics resources.

RESULTS

Over 803 reproducible protein spots were detected on gels, and 150 protein spots showed different intensities between PCOS and normal women during the proliferative and luteal phases. MS analysis detected 70 proteins out of 150 spots. For four of the 70 proteins, 14-3-3 protein, annexin A5, SERPINA1 and cathepsin D, 2-DE results were validated and localized by Western blot and immunohistochemistry, respectively, and their gene expression profiles were confirmed by real-time quantitative PCR. The obtained results corresponded to the proteomic analysis. The differentially expressed proteins identified are known to be involved in apoptosis, oxidative stress, inflammation and the cytoskeleton.

CONCLUSIONS

The processes related to the differentially expressed proteins play important roles in fecundity and fecundability. The present study may reveal the cause of various endometrial aberrations as a limiting factor for achieving pregnancy in PCOS women.

Bud extracts from Salix caprea L. inhibit voltage gated calcium channels and catecholamines secretion in mouse chromaffin cells

BACKGROUND

Salix caprea L. is an ornamental plant with prominent antioxidant activity. In the last decades Salix caprea bud extracts (SCBEs) have been used for the treatment of oxidative stress related disorders.

PURPOSE

A large part of cellular functions depends on the amount of intracellular Ca²⁺ concentration which in turn is mainly determined by Ca²⁺ ions movements across plasma membrane as well as by Ca²⁺ released from the stores. For better evaluating the mechanism of action of SCBEs, we focused on the effect of SCBEs on voltage gated Ca²⁺ channels (VGCCs) functioning and related catecholamines secretion in mouse chromaffin cells (MCCs). These latter are neuroendocrine cells that share a wide variety of functions with neurons. They are particularly interesting for studying the relationship between VGCCs activation and catecholamines secretion both in control and under stressful conditions.

STUDY DESIGN AND METHODS

We focused on the effect of SCBEs on VGCCs being these latter considered one of the main pathway of Ca²⁺ influx across plasma membrane. Ca²⁺ currents and capacitance changes were measured in patch clamp experiments performed in voltage clamp configuration.

RESULTS

We show that SCBEs inhibited VGCCs in a dose dependent manner. On average, the saturating concentration of SCBEs (SCBEs_max) is able to block 36% of the maximum Ca²⁺ current amplitude (I_Ca) without selectivity for L (I_{Ca, L}) or non-L type (I_{Ca, non-L}) Ca²⁺ channels. Furthermore, I_Ca inhibition is not followed by alteration of VGCCs gating kinetics, but is responsible for a marked decrease of Ca²⁺ dependent catecholamines secretion.

CONCLUSION

We conclude that the ability of SCBEs to inhibit VGCCs function, known to be potentiated during oxidative stress, could contribute to the already known antioxidant properties of Salix caprea L. We finally suggest that the inhibitory effect of SCBEs on catecholamines secretion may contribute to treat stress dependent cellular dysfunctions.

The protective mechanism of QGC in feline esophageal epithelial cells by interleukin-1β treatment

In a previous study, Quercetin-3-O-β-D-glucuronopyranoside (QGC) has anti-oxidative and anti-inflammatory effects in vivo. QGC is a flavonoid glucoside extracted from Rumex Aquaticus. We investigated the downstream target proteins involved in IL-1β-stimulated ROS production and the ability of QGC to inhibit ROS production. Cell viability was determined using the MTT reduction assay. Western blot analysis was performed with antibodies to investigate the activation of three MAPKs, NF-κB, and phosphorylated IκB-α (pIB), and the expression of COX-2. 2',7'-dichlorofluorescin diacetate was used to detect the generation of intracellular ROS species. When the cells were exposed to media containing IL-1β for 18 h, cell viability was not affected. QGC did not reduce the COX-2 expression induced by IL-1β. However; QGC attenuated the production of intracellular ROS induced by IL-1β. IL-1β increased the expression of ERK, p38 MAPK, and pIB, and nuclear translocation of NF-κB were recovered by the ROS scavenger N-acetyl-L-cysteine (NAC) and QGC, but not by the NADPH oxidase inhibitor diphenylene iodonium. Pretreatment of cells with the ERK inhibitor PD98059, the p38 MAPK inhibitor SB202190, NAC, and QGC attenuated nuclear translocation of NF-κB and activation of pIB. QGC has a scavenging effect on cytokine-induced ROS production, thereby preventing its downstream effects, nuclear translocation of NF-κB, and activation of pIB is mediated by activation of ERK and p38 MAPK, although QGC does not inhibit IL-1β-stimulated COX-2 expression in feline esophageal epithelial cells. The data suggest that QGC exerts anti-oxidative effects and inhibitory effects against esophageal epithelial cells signals by the action of IL-1β treatment.

Oxidative stress biomarkers in endometrial secretions: A comparison between successful and unsuccessful in vitro fertilization cycles

A potential role of oxidative stress has been implicated in the outcome of various steps of assisted reproductive technology (ART). In a prospective cohort study, a total of 100 patients undergoing IVF/ICSI procedure due to male factor infertility were recruited based on the inclusion criteria. In all patients, 1-2ml of endometrial secretions was aspirated prior to embryo transfer. The oxidative stress markers in endometrial secretions, including superoxide dismutase (SOD), catalase (CAT) activities, lipid peroxidation (LPO), total thiol groups (TTG), and total antioxidant power (TAP) were investigated and compared among study groups including term pregnancy, failed IVF cycle, and miscarriage. P<0.05 was considered statistically different. Of the 100 patients, 28 cases (28%) resulted in ongoing pregnancy (biochemical pregnancy followed by clinical pregnancy), 11 cases (11%) resulted in miscarriage, and 61 cases (61%), resulted in failed IVF cycle. SOD, LPO, CAT, and TAP levels in the endometrial secretions of the three groups were statistically different (P-value <0.01, <0.001, <0.001, and <0.001, respectively). TTG levels in endometrial secretion of three groups were not statistically different (P-value=0.837). Our results indicated that higher levels of antioxidants such as SOD, CAT, or TAP, and lower levels of oxidative stress markers such as LPO in the endometrial secretions were associated with successful IVF outcome.

A pilot study to search possible mechanisms of ultralong gonadotropin-releasing hormone agonist therapy in IVF-ET patients with endometriosis

Background

Additional treatment with a gonadotropin-releasing hormone (GnRH) agonist (GnRHa) before IVF-ET (ultralong GnRHa therapy) has been reported to improve the outcome of IVF-ET in endometriosis patients. However, the mechanism of ultralong GnRHa therapy is unclear. It is suggested that inflammatory cytokines and oxidative stress contribute to infertility in endometriosis patients. Therefore, in order to search a possible mechanism of ultralong GnRHa therapy, we investigated the effect of ultralong GnRHa therapy on intrafollicular concentrations of tumor necrosis factor alpha (TNFα), oxidative stress markers, and antioxidants in patients with endometriosis.

Methods

Twenty-three infertile women with Stage III or IV endometriosis were recruited for this study. Eleven patients received three courses of GnRHa (1.8 mg s.c. every 28 days), followed by a standard controlled ovarian hyperstimulation (COH) for IVF-ET (ultralong group). The other 12 patients received a standard COH with mid-luteal phase GnRHa down-regulation (control group). The numbers of matured follicles and retrieved oocytes, fertilization rates, implantation rates, clinical pregnancy rate, and intrafollicular concentrations of TNFα, 8-hydroxy-2’-deoxyguanosine (8-OHdG) and hexanoyl-lysine adduct (HEL) as oxidative stress markers, and melatonin and Cu,Zu-superoxide dismutase (Cu,Zn-SOD) as antioxidants were compared between the two groups.

Results

The numbers of mature follicles and retrieved oocytes, and fertilization rates did not differ between the two groups. Implantation rates and pregnancy rates tended to be higher in the ultralong group (21.4% and 27.3%, respectively) compared with the control group (8.3% and 8.3%, respectively). TNFα concentrations in the follicular fluid were significantly lower in the ultralong group (5.8 ± 3.2 pg/ml) than those in the control group (10.6 ± 3.2 pg/ml). Follicular concentrations of 8-OHdG concentrations were significantly lower in the ultralong group (5.7 ± 1.6 ng/ml) than those in the control group (6.6 ± 1.5 ng/ml), while melatonin concentrations were significantly higher in the ultralong group (139 ± 46 pg/ml) compared with the control group (86 ± 27 pg/ml).

Conclusions

Ultralong GnRHa therapy reduces the detrimental effects of cytotoxic cytokines and oxidative stress in the ovary in patients with endometriosis.

Effect of sodium arsenite on reproductive organs of female Wistar rats

The present study was performed to investigate the subchronic effect of sodium arsenite on female Wistar rats. Mature female rats were divided into 4 groups of 12 animals each. Group I received distilled water, whereas the other 3 groups received sodium arsenite at 10, 30, and 50 µg/L doses for 60 days through drinking water. Half of the animals from each group were dissected after 30 days and the remaining after 60 days. A disruption in estrous cycle was observed with prolonged diestrous and metestrous phases. A significant increase in ovarian surface epithelium and follicular atresia was observed in treated rats (p ≤ .05). A significant decrease (p ≤ .05) in the uterine myometrium was observed. A significant increase (p ≤ .05) in the levels of lipid peroxidation along with decrease in the activities of antioxidant enzymes was observed. The results revealed that subchronic exposure of sodium arsenite causes degenerative changes in reproductive organs and induces oxidative stress in female rats.

Importance of C/EBPβ binding and histone acetylation status in the promoter regions for induction of IGFBP-1, PRL, and Mn-SOD by cAMP in human endometrial stromal cells

Dynamic changes of gene expressions occur in human endometrial stromal cells (ESCs) during decidualization. CCAAT/enhancer-binding proteinβ (C/EBPβ) regulates the expression of a number of decidualization-related genes. In addition to transcription factors, it is important to know the role of epigenetic mechanisms, such as histone modifications in the regulation of decidualization-related genes. This study investigated the molecular and epigenetic mechanisms by which cAMP up-regulates the expression of IGF-binding protein-1 (IGFBP-1), prolactin (PRL), and manganese superoxide dismutase (Mn-SOD) in ESC. ESCs isolated from proliferative phase endometrium were incubated with cAMP to induce decidualization. IGFBP-1, PRL, and Mn-SOD mRNA expressions were determined by real-time RT-PCR. The C/EBPβ binding and histone modification status (acetylation of histone-H3 lysine-27 [H3K27ac]) in the promoter were examined by chromatin immunoprecipitation assay. Knockdowns of C/EBPβ were performed using the small interfering RNA method. cAMP induced mRNA expressions of IGFBP-1 and PRL accompanied by the increases in both C/EBPβ binding activities and H3K27ac levels in the promoters. The stimulatory effects of cAMP on mRNA levels and H3K27ac levels were completely abolished by C/EBPβ knockdown. cAMP increased Mn-SOD mRNA levels and C/EBPβ binding activities in the enhancer region. C/EBPβ knockdown inhibited Mn-SOD mRNA levels. The H3K27ac levels in the enhancer were high before cAMP stimulus but were not further increased by cAMP and were not inhibited by C/EBPβ knockdown. These results show that C/EBPβ regulates the expression of IGFBP-1 and PRL by altering the histone acetylation status of their promoters but differently regulates Mn-SOD gene expression in human ESC during decidualization.

Increased serum oxidative stress markers in women with uterine leiomyoma

Background

Uterine leiomyomas (fibroids) are the most common gynaecological benign tumors in premenopausal women. Evidences support the role of oxidative stress in the development of uterine leiomyoma. We have analysed oxidative stress markers (thiols, advanced oxidized protein products (AOPP), protein carbonyls and nitrates/nitrites) in preoperative sera from women with histologically proven uterine leiomyoma.

Methodology/Principal Findings

We conducted a laboratory study in a tertiary-care university hospital. Fifty-nine women with histologically proven uterine leiomyoma and ninety-two leiomyoma-free control women have been enrolled in this study. Complete surgical exploration of the abdominopelvic cavity was performed in each patient. Preoperative serum samples were obtained from all study participants to assay serum thiols, AOPP, protein carbonyls and nitrates/nitrites.

Concentrations of serum protein carbonyl groups and AOPP were higher in leiomyoma patients than in the control group (p=0.005 and p<0.001, respectively). By contrast, serum thiol levels were lower in leiomyoma patients (p<0.001). We found positive correlations between serum AOPP concentrations and total fibroids weight (r=0.339; p=0.028), serum AOPP and serum protein carbonyls with duration of infertility (r=0.762; p=0.006 and r=0.683; p=0.021, respectively).

Conclusions/Significance

This study, for the first time, reveals a significant increase of protein oxidative stress status and reduced antioxidant capacity in sera from women with uterine leiomyoma.

Oxidative stress and DNA damage in utero and embryo implantation of mice exposed to carbon disulfide at peri-implantation

Carbon disulfide (CS2) has reproductive toxicity but the mechanism remains unclear. The aim of the present study was to investigate the effect of oxidative stress and DNA damage on embryo implantation of mice exposed to CS2 at peri-implantation. CS2 exposure was on gestational day 3 (GD3), GD4, GD5 and GD6, separately, and the number of embryonic day 9 (E9) mouse embryos was obtained. DNA damage of endometrial cells, oxidative stress and 8-hydroxy-2′-deoxyguanosine (8-OH-dG) level in uterus tissues were tested with time series at different end points after exposure. The number of E9 mouse embryos significantly decreased in all CS2 exposure groups, especially on GD4 exposure. The rates of embryo implantation decreased by 43.05%, 63.74%, 60.45% and 47.26% for CS2 exposure on GD3, GD4, GD5 and GD6, respectively. Oxidative stress significantly increased within 24 h and reached the top level at 18 h after exposure. The same time-dependent trend was observed no matter when the exposure happened at peri-implantation. 8-OH-dG significantly increased at 18 h and 24 h after exposure by 893.8% and 647.4%, respectively, when compared with the control. The indexes of DNA damage significantly increased at 6 h after exposure, which appeared earlier than the changes of oxidative stress and 8-OH-dG. Besides, both oxidative stress and DNA damage showed a strong negative correlation with the number of E9 mouse embryos. The present study illustrated that CS2 directly induced DNA damage in endometrial cells and enhanced the action through oxidative stress, both of which were responsible for CS2-induced embryo loss.

Anti-Oxidative and Anti-Inflammatory Effects of QGC in Cultured Feline Esophageal Epithelial Cells

Quercetin-3-O-β-D-glucuronopyranoside (QGC) is a flavonoid glucoside extracted from Rumex Aquaticus Herba. In the present study, anti-oxidative and anti-inflammatory effects of QGC were tested in vitro. Epithelial cells obtained from cat esophagus were cultured. When the cells were exposed to acid for 2 h, cell viability was decreased to 36%. Pretreatment with 50 µM QGC for 2 h prevented the reduction in cell viability. QGC also inhibited the productions of intracellular ROS by inflammatory inducers such as acid, lipopolysaccharide, indomethacin and ethanol. QGC significantly increased the activities of superoxide dismutase (SOD) and catalase, and also induced the expression of SOD2, while it restored the decrease of catalase expression in cells exposed to acid. QGC inhibited NF-κB translocation, cyclooxygenase-2 expression and PGE₂ secretion in cells exposed to acid, which plays an important role in the pathogenesis of esophagitis. The data suggest that QGC may well be one of the promising substances to attenuate oxidative epithelial cell injury and inflammatory signaling in esophagus inflammation.

Elevated blood plasma antioxidant status is favourable for achieving IVF/ICSI pregnancy

The aim of the study was to determine the roles of intrafollicular and systemic oxidative stress and antioxidant response in ovarian stimulation and intracytoplasmic sperm injection (ICSI) outcomes. For this purpose, 102 ICSI patients undergoing controlled ovarian stimulation were enrolled and samples were collected on the day of follicle puncture. Total peroxide (TPX) concentrations and total antioxidant response (TAR) were measured in follicular fluid and blood plasma, and an oxidative stress index (OSI) was calculated based on these two parameters. Urinary concentrations of 8-iso-prostaglandin F2a (F2IsoP) were measured. Elevated intrafollicular oxidative stress was positively correlated with ovarian stimulation outcome: less FSH per retrieved oocyte was used, more oocytes were collected and higher serum oestradiol concentrations were measured in patients with higher follicular OSI. However, high urinary F2IsoP related to lower embryo quality and F2IsoP was also elevated in smoking patients. Patients with endometriosis had lower follicular antioxidant status. Most importantly, higher systemic blood TAR was significantly favourable for achieving clinical pregnancy (P=0.03). In conclusion, the findings suggest clear associations between oxidative stress, antioxidant status and several aspects of ovarian stimulation and IVF/ICSI outcome, including pregnancy rate. Several oxygen-dependent biochemical reactions produce reactive oxygen species as by-products that may eventually lead to oxidative stress, which is detrimental to cells and tissues. Total antioxidant status, on the other hand, comprises several agents that balance the excess of these reactive oxygen species and reduce potential damage to the body. The aim of the current work was to study this balance in 102 patients participating in an ICSI programme and to examine the degree to which total peroxide content and antioxidant status influence infertility and pregnancy outcome. During the study, several tests were performed to characterize oxidative stress levels in ovarian follicular fluid, blood plasma and urine. We found a significantly higher oxidative stress environment in the ovary when compared with blood plasma. This suggests a prominent role of oxidative stress in the ovaries of these patients. The elevated oxidative stress levels were correlated to a higher number of oocytes that could be obtained via the procedure and to a lower amount of FSH needed to mature the oocytes, suggesting that oxidative stress, to some degree, is favourable for hormone stimulation outcome. A high level of lipid peroxidation products in the urine, another marker of oxidative stress, was observed in smokers and this marker was elevated in patients with embryos that had lower developmental potential. A higher overall antioxidant status in blood plasma was advantageous for achieving pregnancy.

Inhibitory Effects of ECQ on Indomethacin-Induced Gastric Damage in Rats

We investigated inhibitory effects of extract containing quercetin-3-O-β-D-glucuronopyranoside (ECQ) extracted from Rumex Aquaticus Herba on indomethacin-induced gastric damage in Rats. Gastritis was induced in male Sprague-Dawley rats (200~220 g) by oral administration of indomethacin at a dose of 40 mg/kg. One hour before administration of indomethacin, animals were orally pretreated with ECQ at doses of 0.3, 1, 3 or 10 mg/kg. Six hours after indomethacin administration, the rats were sacrificed and the stomach was excised and opened along the greater curvature, and the surface area of gastric lesion was measured using optical microscope. Superoxide dismutase (SOD), catalase (CAT), myeloperoxidase (MPO) activities and malondialdehyde (MDA) levels were measured by ELISA. Western blot analysis was performed to detect protein expression of SOD-2. Linear hemorrhagic mucosal lesions were observed in the stomach 6 hours after oral administration of indomethacin. Pretreatment with ECQ significantly reduced the severity of the lesions in a dose-dependent manner. It also inhibited the reductions in SOD and CAT activities and SOD expression by the indomethacin-induced gastric damage. In addition, the pretreatment with ECQ significantly suppressed the elevation of the MPO activity and the MDA levels induced by indomethacin. These results suggest that ECQ has the inhibitory effects via antioxidative action against indomethacin-induced gastritis in rats.

Inflammation, leukocytes and menstruation

Menstruation has many of the features of an inflammatory process. The complexity and sequence of inflammatory-type events leading to the final tissue breakdown and bleeding are slowly being unravelled. Progesterone has anti-inflammatory properties, and its rapidly declining levels (along with those of estrogen) in the late secretory phase of each non-conception cycle, initiates a sequence of interdependent events of an inflammatory nature involving local inter-cellular interactions within the endometrium. Intracellular responses to loss of progesterone (in decidualized stromal, vascular and epithelial cells) lead to decreased prostaglandin metabolism and loss of protection from reactive oxygen species (ROS). Increased ROS results in release of NFκB from suppression with activation of target gene transcription and increased synthesis of pro-inflammatory prostaglandins, cytokines, chemokines and matrix metalloproteinases (MMP). The resultant leukocyte recruitment, with changing phenotypes and activation, provide further degradative enzymes and MMP activators, which together with a hypoxic environment induced by prostaglandin actions, lead to the tissue breakdown and bleeding characteristic of menstruation. In parallel, at sites where shedding is complete, microenvironmentally-induced changes in phenotypes of neutrophils and macrophages from pro- to anti-inflammatory, in addition to induction of growth factors, contribute to the very rapid re-epithelialization and restoration of tissue integrity.

DNA damage and repair in endometrial cancer in correlation with the hOGG1 and RAD51 genes polymorphism

The cellular reaction to the DNA-damaging agents may modulate individual's cancer susceptibility. This reaction is mainly determined by the efficacy of DNA repair, which in turn, may be influenced by the variability of DNA repair genes, expressed by their polymorphism. The hOGG1 gene encodes a glycosylase of base excision repair and RAD51 specifies a key protein in homologues recombination repair. Both proteins can be involved in the repair of DNA lesions, which are known to contribute to endometrial cancer. In the present work we determined the extent of basal DNA damage and the efficacy of removal of DNA damage induced by hydrogen peroxide and N-methyl-N'-nitro N-nitrosoguanidyne (MNNG) in peripheral blood lymphocytes of 30 endometrial cancer patients and 30 individuals without cancer. The results from DNA damage and repair study were correlated with the genotypes of two common polymorphisms of the hOGG1 and RAD51 genes: a G>C transversion at 1245 position of the hOGG1 gene producing a Ser → Cys substitution at the codon 326 (the Ser326Cys polymorphism) and a G>C substitution at 135 position of the RAD51 gene (the 135G>C polymorphism). DNA damage and repair were evaluated by alkaline single cell gel electrophoresis and genotypes were determined by restriction fragment length polymorphism PCR. We observed a strong association between endometrial cancer and the C/C genotype of the 135G>C polymorphism of the RAD51 gene. Moreover, there was a strong correlation between that genotype and endometrial cancer occurrence in subjects with a high level of basal DNA damage. We did not observe any correlation between the Ser326Cys polymorphism of the hOGG1 gene and endometrial cancer. Our result suggest that the 135G>C polymorphism of the RAD51 gene may be linked to endometrial cancer and can be considered as an additional marker of this disease.

Mitochondrial manganese superoxide dismutase mRNA expression in human chorioamniotic membranes and its association with labor, inflammation, and infection

OBJECTIVE

Human parturition is characterized by the activation of genes involved in acute inflammatory responses in the fetal membranes. Manganese superoxide dismutase (Mn SOD) is a mitochondrial enzyme that scavenges reactive oxygen species (ROS). Mn SOD is up-regulated in sites of inflammation and has an important role in the down-regulation of acute inflammatory processes. Therefore, the aim of this study was to determine the differences in Mn SOD mRNA expression in the fetal membranes in patients with term and preterm labor (PTL) as well as in acute chorioamnionitis.

STUDY DESIGN

Fetal membranes were obtained from patients in the following groups: (1) term not in labor (n = 29); (2) term in labor (n = 29); (3) spontaneous PTL with intact mebranes (n = 16); (4) PTL with histological chorioamnionitis (n = 12); (5) preterm prelabor rupture of the membranes (PPROM; n = 17); and (6) PPROM with histological chorioamnionitis (n = 21). Mn SOD mRNA expression in the membranes was determined by quantitative real-time reverse transcription-polymerase chain reaction.

RESULTS

(1) Mn SOD mRNA expression was higher in the fetal membranes of patients at term in labor than those not in labor (2.4-fold; p = 0.02); (2) the amount of Mn SOD mRNA in the fetal membranes was higher in PTL than in term labor or in PPROM (7.2-fold, p = 0.03; 3.2-fold, p = 0.03, respectively); (3) Mn SOD mRNA expression was higher when histological chorioamnionitis was present both among patients with PPROM (3.8-fold, p = 0.02) and with PTL (5.4-fold, p = 0.02) than in patients with these conditions without histological chorioamnionitis; (4) expression of Mn SOD mRNA was higher in PTL with chorioamnionitis than in PPROM with chorioamnionitis (4.3-fold, p = 0.03).

CONCLUSION

The increase in Mn SOD mRNA expression by fetal membranes in term labor and in histological chorioamnionitis in PTL and PPROM suggests that the fetus deploys anti-oxidant mechanisms to constrain the inflammatory processes in the chorioamniotic membranes.

Antioxidant status and selected biochemical parameters of porcine ovarian granulosa cells exposed to lead in vitro

The objective of this study was to determine the activity of superoxide dismutase (SOD), total antioxidant status (TAS) and release of calcium, phosphorus, magnesium, sodium, potassium, total lipids, totals proteins, glucose, cholesterol and triglycerides by porcine ovarian granulosa cells cultured in vitro after lead acetate administration. The parameters were analyzed using semi-automated clinical chemistry analyzer Microlab 300, microprocessor-controlled analyzer EasyLite and spectrophotometer Genesys 10. Cells were cultured with lead acetate trihydrate [Pb(CH(3)COO)(2).3H(2)O] as follows: group Max (5 mg Pb(CH(3)COO)(2).3H(2)O/10 mL), group A (2.5 mg/10 mL), group B (0.83 mg/10 mL), group C (0.625 mg/10 mL), group D (0.455 mg/10 mL) and the control group without lead exposure for 18 hrs. The highest TAS was estimated in the control group without lead treatment in comparison with other groups (MAX, A, B, C, D). Statistical analyses showed significantly lower value (P < 0.05) in group B. The activity of SOD was the lowest in the control group in comparison to those exposed to in vitro lead culture. A significant decrease (P < 0.05) of calcium content in group MAX in comparison with control group was determined. Release of phosphorus by ovarian granulosa cells was significantly lower (P < 0.05; 0.01; 0.001) in all the treated groups in comparison with control group. Lead was found to stimulate the release of magnesium and potassium by granulosa cells, but the increase remained statistically insignificant. The highest concentration of glucose was noted in control group, but the differences were not significant either. No significant differences (P > 0.05) were detected in concentration of other studied parameters among observed groups, too.

Retinoic acid is a cofactor for translational regulation of vascular endothelial growth factor in human endometrial stromal cells

Vascular endothelial growth factor (VEGF) and endometrial angiogenesis play a critical role in successful embryonic implantation. Despite many studies of the effects of estrogen and progesterone on VEGF expression, its focal regulation at the site of implantation is unknown. Retinoic acid (RA) has been reported to regulate VEGF in a variety of cell types. Because localized RA synthesis occurs within the periimplantation endometrium, we tested the possibility that RA regulates VEGF production in endometrial stromal cells. Using primary and telomerase-immortalized human endometrial stromal cells, we determined that RA alone did not alter constitutive levels of VEGF production, but markedly amplified secretion when the cells were cotreated with activators of VEGF gene transcription (12-O-tetradecanoyl phorbol-13-acetate, TPA; TGF-beta; and IL-1beta). Whereas TPA or TGF-beta alone stimulated VEGF promoter activity and up-regulated mRNA levels, significant protein secretion was detected only after RA was added to the culture systems. Analysis of retinoids in secretory phase endometrial biopsies indicated that endogenous RA accumulated at concentrations sufficient to induce VEGF secretion. Polyribosome profile analysis showed that the addition of RA to transcriptional activators of VEGF shifted the translational suppressed VEGF mRNA transcripts into larger polyribosome complexes engaged in active translation. Although the precise mechanism(s) of the RA effect remains to be defined, it appears to be mediated by reactive oxygen species; the antioxidant N-acetylcysteine inhibited RA+TPA-stimulated secretion of VEGF by more than 80%. Together, our results demonstrate that in human endometrial stromal cells, RA can combine with transcriptional activators of VEGF to augment VEGF secretion through a translational mechanism of action mediated by reactive oxygen species. These findings suggest a link between the spatiotemporal changes of retinoid synthesis in the periimplantation stroma and the capacity to quickly up-regulate focal VEGF secretion needed to induce early angiogenic events of pregnancy.

Impact of oxidative stress on female fertility

PURPOSE OF REVIEW

To review the role of oxidative stress in the context of female fertility.

RECENT FINDINGS

Oxidative stress is associated with decreased female fertility in animal and in-vitro models, but no studies to date have directly assessed the relationship in women. Exposures associated with oxidative stress and with evidence to influence the timing and maintenance of a viable pregnancy include pregnancy complications (e.g. preeclampsia), extremes of body weight, alcohol, tobacco, and caffeine intake. Intake of antioxidant nutrients, including use of multivitamins, impacts the generation of reactive oxygen species and may play a beneficial role in female fertility.

SUMMARY

Infertility is a significant public health problem and diagnosis and treatment are stressful, invasive, and costly. The role of oxidative stress in female fertility is an understudied and compelling area for investigation. Identifying modifiable factors to decrease oxidative stress in the gynecologic environment may be an inexpensive and noninvasive therapy for increasing fertility.

Downregulation of cell survival signalling pathways and increased cell damage in hydrogen peroxide-treated human renal proximal tubular cells by alpha-erythropoietin

OBJECTIVE

Erythropoietin has been shown to have a protective effect in certain models of ischaemia-reperfusion, and in some cases the protection has been correlated with activation of signalling pathways known to play a role in cell survival and proliferation. We have studied whether erythropoietin would overcome direct toxic effects of hydrogen peroxide (H(2)O(2)) treatment to human renal proximal tubular (HK-2) cells.

MATERIALS AND METHODS

HK-2 cells were incubated with H(2)O(2) (2 mm) for 2 h with or without erythropoietin at concentrations of 100 and 400 U/ml, and cell viability/proliferation was assessed by chemical reduction of MTT. Changes in phosphorylation state of the kinases Akt, glycogen synthase kinase-3beta (GSK-3beta), mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinase 1 and 2 (ERK1/ERK2) were also analysed.

RESULTS

Cells incubated with H(2)O(2) alone showed a significant decrease in viability, which did not significantly change by addition of erythropoietin at concentration of 100 U/ml, but was further reduced when concentration of erythropoietin was increased to 400 U/ml. Phosphorylation state of the kinases Akt, GSK-3beta, mTOR and ERK1/ERK2 of H(2)O(2)-treated HK-2 cells was slightly altered in the presence of erythropoietin at concentration of 100 U/ml, but was significantly less in the presence of erythropoietin at a concentration of 400 U/ml. Phosphorylation of forkhead transcription factor FKHRL1 was diminished in cells incubated with H(2)O(2) and erythropoietin at a concentration of 400 U/ml.

CONCLUSIONS

Erythropoietin, at high concentrations, may significantly increase cellular damage in HK-2 cells subjected to oxidative stress, which may be due in part to decrease in activation of important signalling pathways involved in cell survival and/or cell proliferation.

A role for menstruation in preconditioning the uterus for successful pregnancy

Menstruation is widely viewed as serving no purpose other than to reinitiate the endometrial cycle in the absence of pregnancy. Yet, it is striking that cyclic endometrial decidualization followed by menstrual shedding is confined to the few species, including human beings, where placenta formation entails deep trophoblast invasion of maternal tissues and its vasculature. Both menstruation and pregnancy are inflammatory conditions that cause a degree of physiological ischemia-reperfusion tissue injury, albeit much more so in pregnancy. Thus, the emergence of cyclic menstruation may not have been an evolutionary coincidence but serves to protect uterine tissues from the profound hyperinflammation and oxidative stress associated with deep placentation, a process known as preconditioning. The concept of menstrual preconditioning provides a novel paradigm for understanding how reproductive disorders impact on pregnancy outcome. For example, endometriosis could be viewed as a disorder of exaggerated menstrual preconditioning that confers protection against placentation-related disorders, such as preeclampsia.

Oxidative stress and antioxidants: exposure and impact on female fertility

BACKGROUND

Reproductive failure is a significant public health concern. Although relatively little is known about factors affecting fertility and early pregnancy loss, a growing body of literature suggests that environmental and lifestyle factors play an important role. There is sufficient evidence to hypothesize that diet, particularly its constituent antioxidants, and oxidative stress (OS) may influence the timing and maintenance of a viable pregnancy. We hypothesize that conditions leading to OS in the female affect time-to-pregnancy and early pregnancy loss.

METHODS

We review the epidemiology of female infertility related to antioxidant defenses and oxidation and examine potential sources of OS from the ovarian germ cell through the stages of human pregnancy and pregnancy complications related to infertility. Articles were identified through a search of the PubMed database.

RESULTS

Female OS is a likely mediator of conception and threshold levels for OS exist, dependent on anatomic location and stage of preconception.

CONCLUSIONS

Prospective pregnancy studies with dietary assessment and collection of biological samples prior to conception with endpoints of time-to-pregnancy and early pregnancy loss are needed.