Is a high serum copper concentration a risk factor for implantation failure?

Environmental copper exposure, placental cuproptosis, and miscarriage

Copper pollution has become global environmental concern. Widespread Cu pollution results in excessive Cu exposure in human. Epidemiological studies and animal experiments revealed that Cu exposure might have reproductive toxicity. Cuproptosis is a newly reported Cu-dependent and programmed cell death formTsvetkov et al., 2022. However, whether copper exposure at real environmental exposure dose might cause placental cuproptosis and induce miscarriage was completely unexplored. In this study, we found that Cu exposure during pregnancy induced miscarriage or complete pregnancy loss by inducing placenta cuproptosis in CuCl2-exposed pregnant mice. Notably, Cu exposure at 1.3 mg/kg/d (a real environmental exposure dose) was enough to cause placenta cuproptosis. CuCl2 exposure disrupts the TCA cycle, causes proteotoxic stress, increases Cu2+ ion import/decreases Cu2+ export, and results in the loss of Fe-S cluster proteins in mouse placenta, which induces placenta cuproptosis. Moreover, we also identified that Cu exposure down-regulates the expression levels of mmu-miR-3473b, which interacts with Dlst or Rtel1 mRNA and simultaneously positively regulates Dlst or Rtel1 expression, thereby disrupting the TCA cycle and resulting in the loss of Fe-S cluster proteins, and thus epigenetically regulates placental cuproptosis. Treatment with TTM (a cuproptosis inhibitor) suppressed placental cuproptosis and alleviated miscarriage in CuCl2-exposed mice. This work provides novel reproductive toxicity of Cu exposure in miscarriage or complete pregnancy loss by causing placental cuproptosis. This study also provides new ways for further studies on other toxicological effects of Cu and proposes a new approach for protection against Cu-induced reproductive diseases.

Demystifying the landscape of endometrial immune microenvironment in luteal-phase from cuprotosis: Implications for the mechanism and treatment of RPL

BACKGROUND

Adaptive changes in the endometrial immune microenvironment during the luteal phase are essential for pregnancy, and their abnormalities are associated with recurrent pregnancy loss (RPL). Nevertheless, the specific mechanism is still unknown. Cuprotosis, an innovatively discovered type of programmed cell death, provides us with a pioneering perspective to decipher the landscape of luteal-phase endometrial immune microenvironment in RPL. This study aimed to analyze the immune landscape of luteal-phase endometrial microenvironment in RPL and explore the association of cuprotosis with it through integrative bioinformatics analysis.

METHODS

The microarrays involving the luteal phase endometrial tissue of RPL were obtained from the GEO database. Differentially expressed genes (DEGs) of RPL were screened and key modules were detected by WGCNA. GO, KEGG, and GSEA immune enrichment analyses were performed on the DEGs in the most relevant modules to RPL. Then, the endometrial immune microenvironment landscape of RPL was analyzed, including immune infiltration analysis and correlation analysis between immune cells or immune functions. The interaction of cuprotosis-related genes (CRGs), the expression level between groups, the immune localization and their correlation with immune cells and immune function were analyzed. LASSO regression and Nomogram evaluated the diagnostic value of immune-related CRGS in RPL. Functional enrichment analysis was performed on the RPL signature CRGs. And RPL samples were grouped according to the expression of 7 RPL signature CRGs through unsupervised clustering analysis. After that, we analyzed the expression level of CRGs and immune infiltration, as well as performed immune function enrichment analysis in subtypes. In addition, we also screened potential drugs that might act on CRGs to improve the pathological mechanism of RPL.

RESULTS

In this study, we uncovered that DEGs and genes in key modules derived from weighted gene co-expression network analysis (WGCNA) were involved in immune regulation. And the immune infiltration landscape of RPL was significantly different from healthy controls. Furthermore, six hub genes were screened from CRGs based on Cytohubba, and their expression profilings were verified in RPL and normal mouse samples. Besides, seven CRGs closely associated with the immune regulation of RPL were identified by Spearman correlation analysis, including SLC31A1, LIAS, DLD, DLAT, DBT, ATP7B, and ATP7A, named as immune-related CRGs. Furthermore, three subgroups clustered according to these seven genes showed significant differences in immune landscape, suggesting a remarkable effect of CRGs on immune regulation. Last but not least, we analyzed the regulation network of transcription factors, miRNAs, and CRGs, and screened potential compounds for the treatment of RPL by targeting CRGs.

CONCLUSIONS

The abnormal endometrial immune microenvironment in the luteal phase was associated with the pathomechanism of RPL, and cuprotosis was closely involved in the immune microenvironment in the luteal phase endometrium of RPL. Collectively, this study revealed the potential contribution of CRGs to the pathogenesis of RPL, providing a novel breakthroughs in insights into the pathogenesis, diagnosis, and treatment of RPL.

Copper exposure induces ovarian granulosa cell apoptosis by activating the caspase-dependent apoptosis signaling pathway and corresponding changes in microRNA patterns

Environmental copper (Cu) contamination is a complex worldwide public health problem. However, information on the effects of Cu pollution on human reproduction is limited. Although our previous studies have indicated that Cu exposure disrupts ovarian folliculogenesis, the underlying mechanism needs to be further explored. In this study, human luteinized ovarian granulosa cells and a rat animal model were used to investigate whether Cu exposure affects ovarian follicle development by inducing apoptosis and to elucidate the possible mechanisms. The results showed that Cu exposure from weaning to sexual maturity significantly decreased the proportion of preantral follicles but increased the proportion of atretic follicles (P < 0.05). In addition, 6 mg/kg Cu increased the proportion of antral follicles, while 12 and 25 mg/kg Cu decreased it (P < 0.05). We also found that 6 mg/kg Cu exposure inhibited apoptosis of ovarian granulosa cells, while 12 and 25 mg/kg Cu promoted apoptosis (P < 0.05). Experiments on primary human luteinized ovarian granulosa cells suggested that higher levels of Cu exposure induced a significant increase in the mRNA levels of Bcl2 Bax , Fas, Caspase8, and Caspase3 (P < 0.05), and the protein levels of BAX, BCL2, CASPASE3, CASPASE8, CLE-CASPASE3, CLE-CASPASE8 and BAX/BCL2 were also increased (P < 0.05). miRNA chip analyses identified a total of 95 upregulated and 10 downregulated miRNAs in human luteinized granulosa cells exposed to Cu. Hsa-miR-19b-3p, hsa-miR-19a-3p, miR-548ar-3p, hsa-miR-652-5p, and hsa-miR-29b-5p were decreased after Cu exposure (P < 0.05). Additionally, the level of hsa-miR-144-5p was increased (P < 0.05). Together, our results reveal that Cu exposure induces abnormal ovarian folliculogenesis by inducing ovarian granulosa cell apoptosis, which is triggered by the caspase-dependent apoptosis signaling pathway, and that miRNAs may be involved in this process.

Serum Essential Trace Element Status in Women and the Risk of Endometrial Diseases: a Case-Control Study : Serum Essential Trace Element Status in Women and the Risk of Endometrial Diseases: a Case-Control Study

Endometrial diseases, including uterine fibroids, polyps, intrauterine adhesion, endometritis, etc., are the major causes of infertility among women. However, the association between essential trace element status in women and the risk of endometrial disease is limited and unclear. This study aimed to investigate this association using a case-control study design; a total of 302 women patients with endometrial diseases and 302 healthy women were included. Compared to women in the control group, serum selenium (Se) (p = 0.024) and zinc (Zn) (p = 0.017) levels were significantly lower, while copper (Cu) (p = 0.004) and molybdenum (Mo) (p = 0.005) levels were significantly higher among women with endometrial diseases. In addition, compared to women in the first quartile of the copper/zinc (Cu/Zn) ratio value group, the adjusted ORs (95% CIs) of endometrial diseases were 1.50 (1.05, 2.14), 1.68 (1.18, 2.39), and 1.47 (1.02, 2.10), respectively, in the second, third, and fourth quartile of the Cu/Zn ratio value group (p trend = 0.047). In addition, the results from restricted cubic splines showed that the dose-response relationships of serum levels of these essential elements with the risk of endometrial diseases were nonlinear for Se, Cu, and Zn and relatively linear for Mo and Cu/Zn ratio. The present study showed serum levels of Zn and Se among women with endometrial diseases were significantly lower compared to that among healthy women, while serum levels of Cu and Mo were significantly higher, in addition, the serum Cu/Zn ratio value was also significantly and positively associated with the risk of endometrial diseases.

Copper/Zinc Ratio Can Be a Marker to Diagnose Ectopic Pregnancy and Is Associated with the Oxidative Stress Status of Ectopic Pregnancy Cases

It was aimed to evaluate serum zinc and copper levels and oxidative stress parameters in ectopic pregnancy cases, healthy pregnant women, and healthy non-pregnant women. In this cross-sectional case-control study, 30 patients diagnosed with tubal ectopic pregnancy in the gynecology clinic of a tertiary hospital constituted the study group. A healthy pregnant control group (n = 30) was formed of age, body mass index (BMI), and gestational week-matched subjects, and a healthy non-pregnant control group (n = 30) was formed of age and BMI-matched women. The groups were compared in terms of demographic characteristics and laboratory parameters including serum zinc (Zn) level, serum copper (Cu) level, serum malondialdehyde (MDA) level, serum catalase (CAT) activity, serum glutathione peroxidase (GPX) activity, and serum superoxide dismutase (SOD) activity. The groups were similar in respect of demographic characteristics. In the ectopic pregnancy group, serum GPX activity and Cu level were significantly lower, and serum SOD and CAT activity and Zn and MDA levels were higher compared with those of the healthy pregnant and healthy non-pregnant groups. The Cu/Zn ratio showed a significant, positive correlation with the serum GPX activity and serum progesterone level and a negative correlation with serum SOD and CAT activity. When 1.14 was taken as the cutoff value, sensitivity and specificity of the Cu/Zn ratio to determine ectopic pregnancy were 73.3% and 80.0%, respectively. Comparing the area under curve (AUC) in the ROC (receiver operating characteristic) curve analysis, the Cu/Zn ratio was determined to be more valuable than the Cu or Zn values alone in predicting ectopic pregnancy. In correlation analysis, serum beta hCG level showed a negative correlation with SOD and CAT activities and Zn levels. Serum progesterone level showed a negative correlation with serum CAT and SOD activities and MDA and zinc levels and a positive correlation with serum GPX activity and serum copper level (p < 0.05 for all). The current study can be considered of value as the first study in literature to show a significantly lower serum Zn level and higher serum Cu level in ectopic pregnancy cases compared with healthy pregnant control cases. This is also the first study to have revealed an association between the serum Cu/Zn ratio, oxidative status, and ectopic pregnancy. Furthermore, the serum Cu/Zn ratio was found to be useful in the diagnosis of ectopic pregnancy cases.

Oral exposure of pregnant rats to copper nanoparticles caused nutritional imbalance and liver dysfunction in fetus

Copper nanoparticles (Cu NPs) are increasingly used as an animal feed additive in China. In previous studies, it was determined that Cu NPs can penetrate the placental barrier, however, its toxic effects on the fetus have not yet been elucidated. Therefore, in this study, we investigated the potential fetal toxic effects of Cu NPs. Cu NPs were orally administered to pregnant Sprague-Dawley rats from gestation days (GDs) 3-18 at a dose of 60, 120, and 180 mg/kg/day. Cesarean sections were conducted on GD 19. During fetal examination, no toxicities were observed regarding general clinical signs, however, Cu NPs significantly decreased fetal body weight, body length, and liver weights. Cu ions and Cu MPs exhibited similar effects on the fetal development. Cu NPs increased the liver concentration of Cu, and decreased protein levels and Fe in fetuses. Cu NPs also increased oxidative stress and inflammation in the fetus after pregnant rats were exposed to high doses of Cu NPs. Oral exposure to Cu NPs during pregnancy increased Cu concentrations in the fetus, which not only affected fetal development, but also significantly induced oxidative stress and inflammatory responses in fetal liver. Taken together, these findings are valuable to evaluate fetal risk assessment after oral exposure of Cu NPs during pregnancy. Additional comprehensive toxicity studies are deemed necessary to clarify the underlying mechanisms involved.

Copper and lead exposures disturb reproductive features of primary endometrial stromal and epithelial cells

This study investigates if Cu and Pb act as endocrine disruptors affecting endometrial cells. Primary EnSCs and EnECs were exposed to Cu (0, 50, 100 and 200 μM) or Pb (0, 30, 100 and 500 μM) and assessed for viability, decidualization, apoptosis and proliferation on EnSCs, and wound healing and adhesion capabilities on EnECs. Cu exposure decreased significantly cell viability in a dose-dependent manner. Cu and Pb negatively affected in vitro decidualization, showing a significant decrease in PRL secretion. HOXA10 and ERα mRNA levels significantly decreased in decidualized cells (dEnSCs) exposed to Cu. Cu and Pb decreased adhesion and regeneration capability in EnEC. This study reveals that Cu and Pb could negatively affect endometrial functionality, compromising the decidualization process and disrupting endometrial regeneration and embryo adhesion. Therefore, special care should be taken considering heavy metals exposure if pregnancy is being pursued.

Serum levels of copper, iron, and manganese in women with pregnancy, miscarriage, and primary infertility

BACKGROUND

Iron (Fe), copper (Cu), and manganese (Mn) play a significant role in female reproduction and fetal development. At the same time, high levels of metals may exert toxic effects. Correspondingly, both excess and deficiency of essential trace elements were shown to be associated with female infertility and adverse pregnancy outcome, although the existing data are rather contradictory. Therefore, the objective of the present study was to reveal the potential role of altered iron, copper, and manganese status in female reproductive health problems through assessment of serum metal levels in healthy non-pregnant and pregnant women, as well as patients with miscarriage and primary infertility.

METHODS

A total of 150 healthy controls, 169 pregnant women (II trimester of pregnancy), 75 women with miscarriage, and 91 patients with primary infertility were enrolled. Serum metal levels were assessed using ICP-MS.

RESULTS

Pregnant women are characterized by a significant increase in serum Cu an Mn levels by 40% (p < 0.001) and 16% (p = 0.043) as compared to the controls, respectively. Serum Cu levels in women with miscarriage and infertility were 30% and 35% lower than those in pregnant women (p < 0.001). No significant difference in serum iron levels were observed between the control and pregnant women. Women who had miscarriage were characterized by 13% (p = 0.042) higher serum Fe levels as compared to the pregnant ones. Multiple regression analysis demonstrated that serum copper levels was significantly associated both with pregnancy (β = 0.436; p < 0.001) and reproductive health problems in women (β = -0.272; p < 0.001). The latter was improved significant after adjustment for serum Fe and Mn levels, age, and BMI (β = -0.431; p < 0.001). The model incorporating serum Cu, Fe, Mn, and anthropometric parameters accounted for 23% of variability in reproductive status (p < 0.001).

CONCLUSIONS

It is proposed that the lack of pregnancy-associated increase in metal levels in miscarriage and infertility may be indicative of at least partial role of metal insufficiency in impaired pregnancy and reproductive function in general. However, detailed clinical studies as well as experimental investigations are required for assessment of the potential causes and mechanisms of the observed associations.