Cadmium and proliferation in human uterine leiomyoma cells: evidence of a role for EGFR/MAPK pathways but not classical estrogen receptor pathways

Mechanisms of Heavy Metal Cadmium (Cd)-Induced Malignancy

The environmental pollution of cadmium is worsening, and its significant carcinogenic effects on humans have been confirmed. Cadmium can induce cancer through various signaling pathways, including the ERK/JNK/p38MAPK, PI3K/AKT/mTOR, NF-κB, and Wnt. It can also cause cancer by directly damaging DNA and inhibiting DNA repair systems, or through epigenetic mechanisms such as abnormal DNA methylation, LncRNA, and microRNA. However, the detailed mechanisms of Cd-induced cancer are still not fully understood and require further investigation.

Screening and validation of biomarkers for cadmium-induced liver injury based on targeted bile acid metabolomics

Although cadmium (Cd) is a toxic heavy metal that reportedly causes liver injury, few studies have investigated biomarkers of Cd-induced liver injury. The purpose of this study is to investigate the role of bile acid (BA) in Cd-induced liver injury and determine reliable and sensitive biochemical parameters for the diagnosis of Cd-induced liver injury. In this study, 48 Sprague-Dawley rats were randomly divided into six groups and administered either normal saline or 2.5, 5, 10, 20, and 40 mg/kg/d cadmium chloride for 12 weeks. A total of 403 subjects living in either a control area (n = 135) or Cd polluted area (n = 268) of Dongdagou-Xinglong (DDGXL) cohort were included, a population with long-term low Cd exposure. The BA profiles in rats' liver, serum, caecal contents, faeces, and subjects' serum were detected using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Changes in rats' and subjects' liver injury indices, rats' liver pathological degeneration, and rats' liver and subjects' blood Cd levels were also measured. Cadmium exposure caused cholestasis and an increase in toxic BAs, leading to liver injury in rats. Among them, glycoursodeoxycholic acid (GUDCA), glycolithocholic acid (GLCA), taurolithocholic acid (TLCA), and taurodeoxycholate acid (TDCA) are expected to be potential biomarkers for the early detect of Cd-induced liver injury. Serum BAs can be used to assess Cd-induced liver injury as a simple, feasible, and suitable method in rats. Serum GUDCA, GLCA, TDCA, and TLCA were verified to be of value to evaluate Cd-induced liver injury and Cd exposure in humans. These findings provided evidence for screening and validation of additional biomarkers for Cd-induced liver injury based on targeted BA metabolomics.

Prolonged Cadmium Exposure Alters Migration Dynamics and Increases Heterogeneity of Human Uterine Fibroid Cells—Insights from Time Lapse Analysis

Cadmium (Cd) is one of the most prevalent environmental heavy metal contaminants and is considered an endocrine disruptor and carcinogen. In women with uterine fibroids, there is a correlation between blood Cd levels and fibroid tumor size. In this study, fibroid cells were exposed to 10 µM CdCl2 for 6 months and a fast-growing Cd-Resistant Leiomyoma culture, termed CR-LM6, was recovered. To characterize the morphological and mechanodynamic features of uterine fibroid cells associated with prolonged Cd exposure, we conducted time lapse imaging using a Zeiss confocal microscope and analyzed data by Imaris and RStudio. Our experiments recorded more than 64,000 trackable nuclear surface objects, with each having multiple parameters such as nuclear size and shape, speed, location, orientation, track length, and track straightness. Quantitative analysis revealed that prolonged Cd exposure significantly altered cell migration behavior, such as increased track length and reduced track straightness. Cd exposure also significantly increased the heterogeneity in nuclear size. Additionally, Cd significantly increased the median and variance of instantaneous speed, indicating that Cd exposure results in higher speed and greater variation in motility. Profiling of mRNA by NanoString analysis and Ingenuity Pathway Analysis (IPA) strongly suggested that the direction of gene expression changes due to Cd exposure enhanced cell movement and invasion. The altered expression of extracellular matrix (ECM) genes such as collagens, matrix metallopeptidases (MMPs), secreted phosphoprotein 1 (SPP1), which are important for migration contact guidance, may be responsible for the greater heterogeneity. The significantly increased heterogeneity of nuclear size, speed, and altered migration patterns may be a prerequisite for fibroid cells to attain characteristics favorable for cancer progression, invasion, and metastasis.

Prolonged cadmium exposure alters benign uterine fibroid cell behavior, extracellular matrix components, and TGFB signaling

The heavy metal Cadmium (Cd), a widespread environmental contaminant, poses serious hazards to human health and is considered a metallohormone and carcinogen. In women with uterine fibroids, there is a significant association between blood Cd levels and increased fibroid tumor size. The aim of this study was to determine if benign human uterine leiomyoma (fibroid) cells could be malignantly transformed in vitro by continuous Cd exposure and, if so, explore a molecular mechanism by which this could occur. We found when fibroid cells were exposed to 10 µM CdCl₂ for 8 weeks, a robust and fast‐growing Cd‐Resistant Leiomyoma (CR‐LM) cell culture was established. The CR‐LM cells formed viable colonies in soft agar and had increased cytoplasmic glycogen aggregates, enhanced cell motility, a higher percentage of cells in G2/M phase, and increased expression of the proliferation marker Ki‐67. NanoString analysis showed downregulation of genes encoding for extracellular matrix (ECM) components, such as collagens, fibronectins, laminins, and SLRP family proteins, whereas genes involved in ECM degradation (MMP1, MMP3, and MMP10) were significantly upregulated. A volcano plot showed that the top differentially genes favored cancer progression. Functional analysis by ingenuity pathway analysis predicted a significant inhibition of TGFB1 signaling, leading to enhanced proliferation and attenuated fibrosis. Prolonged Cd exposure altered phenotypic characteristics and dysregulated genes in fibroid cells predicative of progression towards a cancer phenotype. Therefore, continuous Cd exposure alters the benign characteristics of fibroid cells in vitro, and Cd exposure could possibly pose a health hazard for women with uterine fibroids.

"Metalloestrogenic" effects of cadmium downstream of G protein-coupled estrogen receptor and mitogen-activated protein kinase pathways in human uterine fibroid cells

Cadmium (Cd) is a toxic metal reported to act as an estrogen "mimic" in the rat uterus and in vitro. We have reported that Cd stimulates proliferation of estrogen-responsive human uterine leiomyoma (ht-UtLM; fibroid) cells through nongenomic signaling involving the G protein-coupled estrogen receptor (GPER), with activation of epidermal growth factor receptor (EGFR) and mitogen-activated protein kinase (pMAPK44/42). In this study, we explored Cd-induced mechanisms downstream of MAPK and whether Cd could stimulate phosphorylation of Histone H3 at serine 10 (H3Ser10ph) through activated Aurora B kinase (pAurora B), a kinase important in activation of histone H3 at serine 10 during mitosis, and if this occurs via Fork head box M1 (FOXM1) and cyclin D1 immediately downstream of MAPK. We found that Cd increased proliferating cell nuclear antigen (PCNA) and H3Ser10ph expression by immunofluorescence, and that H3ser10ph and pAurora B were coexpressed along the metaphase plate in ht-UtLM cells. In addition, Cd-exposed cells showed higher expression of pMAPK44/42, FOXM1, pAurora B, H3ser10ph, and Cyclin D1 by western blotting. Immunoprecipitation and proximity ligation assays further indicated an association between FOXM1 and Cyclin D1 in Cd-exposed cells. These effects were attenuated by MAPK kinase (MEK1/2) inhibitor. In summary, Cd-induced proliferation of ht-UtLM cells occurred through activation of Histone H3 and Aurora B via FOXM1/Cyclin D1 interactions downstream of MAPK. This provides a molecular mechanism of how Cd acts as an "estrogen mimic" resulting in mitosis in hormonally responsive cells.

[Estradiol activates ERK phosphorylation by binding to ERβ to inhibit proliferation and promote apoptosis of human chondrocytes]

OBJECTIVE

To explore the effect of estradiol (E2) binding to its receptor ERβ on the proliferation and apoptosis of C28I2 cells.

OBJECTIVE

We cloned the sequence of ESR2 into a recombinant adenovirus plasmid (pAd-ESR2) and packaged the plasmid in HEK293 cells. Normal human chondrocyte C28I2 cells were transfected with Ad-ESR2 or small interfering RNA targeting ESR2-siRNA (ESR2-siRNA), and the effects of treatment with DMSO or E2 on the expression of the proteins associated with endoplasmic reticulum (ER) stress and cell apoptosis were determined using Western blotting. qRT-PCR was used to detect the expressions of proliferation-related marker genes, and an EdU kit and flow cytometry were used to assess cell proliferation and apoptosis. We also tested the effects of U0126 (an ERK pathway inhibitor) and E2, alone or in combination, on ER stress, apoptosis and the ERK signaling pathway in C28I2 cells infected with Ad-ESR2 using Western blotting.

OBJECTIVE

Overexpression of Ad-ESR2 in C28I2 cells significantly promoted the expressions of IRE1α, PERK, XBP1s, and cleaved caspase-12, inhibited proliferation related marker genes PCNA, cyclin B1, cyclin D1, and decreased the level of ERK phosphorylation following E2 treatment (all P < 0.05). Interference of ESR2 caused significant reduction in the expressions of ER stress-related proteins and apoptosis-related proteins, up-regulated the genes related to cell proliferation, and increased intracellular pERK/ERK ratio in C28I2 cells. The effect of E2 binding to ERβ, which promoted the expressions of ER stress associated proteins and apoptosis related proteins, was obviously antagonized by treatment of the cells with U0126.

OBJECTIVE

The binding of E2 to ERβ promotes ER stress and apoptosis in human chondrocytes by activating ERK pathway phosphorylation inhibit cell proliferation.

Environmental Factors Involved in Maternal Morbidity and Mortality

Nongenetic, environmental factors contribute to maternal morbidity and mortality through chemical exposures via air, water, soil, food, and consumer products. Pregnancy represents a particularly sensitive window of susceptibility during which physiological changes to every major organ system increase sensitivity to chemicals that can impact a woman's long-term health. Nonchemical stressors, such as low socioeconomic status, may exacerbate the effects of chemical exposures on maternal health. Racial/ethnic minorities are exposed disproportionately to both chemicals and nonchemical stressors, which likely contribute to the observed health disparities for maternal morbidities and mortality. Epidemiological studies linking exposures to adverse maternal health outcomes underscore the importance of environmental health impacts, and mechanistic studies in model systems reveal how chemicals perturb biological pathways and processes. Environmental stressors are associated with a variety of immediate maternal health impacts, including hypertensive disorders of pregnancy, fibroids, and infertility, as well as long-term maternal health impacts, such as higher risk of breast cancer and metabolic disorders. Identifying and reducing a pregnant woman's environmental exposures is not only beneficial to her offspring but also important to preserve her short- and long-term health.

Suppression of estrogen receptor-beta promotes gastric cancer cell apoptosis with induction of autophagy

Estrogen Receptor 2 (ESR2) is the protein-coding gene of estrogen receptor β (ERβ) and has been shown to be abundantly expressed in gastric carcinoma (GC), suggesting that it plays a role in GC pathogenesis. However, the underlying molecular mechanism remains elusive. In the present in vitro study, GC cell growth was found to be estrogen-dependent, and the expression level of ERβ was higher than that of ERα. Knocking down the endogenous expression of ESR2 in GC cells increased the apoptosis rate and the level of cleaved caspase-3, caspase-7 and poly ADP-ribose polymerase. The induced apoptosis was primarily related to GC cell growth arrest, accompanied with activation of DNA damage-inducible protein 45 alpha (GADD45α) in a p53-independent manner. Importantly, down-regulation of ESR2 also promoted autophagy. The autophagy inhibitor 3-MA or silencing ATG7 rescued the apoptosis by knocking down ESR2 via activation of the MAPK signaling pathway in AGS cells, leading to increased apoptosis. In conclusion, these results demonstrated that suppression of ESR2 gene expression could promote GC cell apoptosis, suggesting that it may prove to be a potential therapeutic target for GC.

Dietary cadmium chloride impairs shell biomineralization by disrupting the metabolism of the eggshell gland in laying hens

In this study, we identified cadmium (Cd) as a potential endocrine disruptor that impairs laying performance, egg quality, and eggshell deposition and induces oxidative stress and inflammation in the eggshell glands of laying hens. A total of 480 38-wk-old laying hens were randomly assigned into 5 groups that were fed a basal diet (control) or a basal diet supplemented with Cd (provided as CdCl2·2.5 H2O) at 7.5, 15, 30, and 60 mg Cd per kg feed for 9 wk. The results showed that, when compared with the control group, a low dose of dietary Cd (7.5 mg/kg) had positive effects on egg quality by improving albumen height, Haugh unit, yolk color, and shell thickness at the third or ninth week. However, with the increase in the dose and duration of Cd exposure, the laying performance, egg quality, and activities of eggshell gland antioxidant enzymes (catalase [CAT], glutathione peroxide [GSH-Px]), and ATPase (Na+/K+-ATPase, Ca2+-ATPase, and Mg2+-ATPase) deteriorated, and the activity of total nitric oxide synthase (T-NOS) and the level of malondialdehyde (MDA) increased significantly (P < 0.05). The histopathology and real-time quantitative PCR results showed that Cd induced endometrial epithelial cell proliferation accompanied by upregulation of the mRNA levels of progesterone receptor (PgR) and epidermal growth factor receptor (EGFR), downregulation of the mRNA levels of estrogen receptor α (ERα) and interleukin 6 (IL6), and inflammation of the eggshell gland accompanied by significantly increased expression of complement C3 and pro-inflammatory cytokine tumor necrosis factor α (TNFα) (P < 0.05). In addition, the ultrastructure of the eggshell showed that dietary supplementation with 7.5 mg/kg Cd increased the palisade layer and total thickness of the shell, but with the increase in dietary Cd supplementation (30 and 60 mg/kg) the thickness of the palisade layer and mammillary layer decreased significantly (P < 0.05), and the outer surface of the eggshell became rougher. Correspondingly, the expression of calbindin 1 (CALB1), ovocalyxin-32 (OCX-32), ovocalyxin-36 (OCX-36), osteopontin (SPP1), and ovocledidin-17 (OC-17) decreased significantly (P < 0.05) with increasing dietary Cd supplementation. Conclusively, the present study demonstrates that dietary supplementation with Cd negatively affects laying performance, egg quality, and eggshell deposition by disturbing the metabolism of eggshell glands in laying hens but has a positive effect on egg quality at low doses.

The influence of long-term cadmium exposure on the male advertisement call of Xenopus laevis

Cadmium (Cd) is a non-essential environmental endocrine-disrupting compound found in water and a potential threat to aquatic habitats. Cd has been shown to have various short-term effects on aquatic animals; however, evidence for long-term effects of Cd on vocal communications in amphibians is lacking. To better understand the long-term effects of low-dose Cd on acoustic communication in amphibians, male Xenopus laevis individuals were treated with low Cd concentrations (0.1, 1, and 10 μg/L) via aqueous exposure for 24 months. At the end of the exposure, the acoustic spectrum characteristics of male advertisement calls and male movement behaviors in response to female calls were recorded. The gene and protein expressions of the androgen receptor (AR) were determined using Western blot and RT-PCR. The results showed that long-term Cd treatment affected the spectrogram and formant of the advertisement call. Compared with the control group, 10 μg/L Cd significantly decreased the first and second formant frequency, and the fundamental and main frequency, and increased the third formant frequency. One and 10-μg/L Cd treatments significantly reduced the proportion of individuals responding to female calls and prolonged the time of first movement of the male. Long-term Cd treatment induced a downregulation in the AR protein. Treatments of 0.1, 1, and 10 μg/L Cd significantly decreased the expression of AR mRNA in the brain. These findings indicate that long-term exposure of Cd has negative effects on advertisement calls in male X. laevis.

A nongenomic mechanism for "metalloestrogenic" effects of cadmium in human uterine leiomyoma cells through G protein-coupled estrogen receptor

Cadmium (Cd) is a ubiquitous environmental metal that is reported to be a "metalloestrogen." Uterine leiomyomas (fibroids) are estrogen-responsive gynecologic neoplasms that can be the target of xenoestrogens. Previous epidemiology studies have suggested Cd may be associated with fibroids. We have shown that Cd can stimulate proliferation of human uterine leiomyoma (ht-UtLM) cells, but not through classical estrogen receptor (ER) binding. Whether nongenomic ER pathways are involved in Cd-induced proliferation is unknown. In the present study, by evaluating G protein-coupled estrogen receptor (GPER), ERα36, and phospho-epidermal growth factor receptor (EGFR) expression in human tissues, we found that GPER, ERα36 and phospho-EGFR were all highly expressed in fibroids compared to patient-matched myometrial tissues. In ht-UtLM cells, cell proliferation was increased by low doses of Cd (0.1 µM and 10 µM), and this effect could be inhibited by GPER-specific antagonist (G15) pretreatment, or silencing (si) GPER, but not by siERα36. Cd-activated MAPK was dependent on GPER/EGFR transactivation, through significantly increased phospho-Src, matrix metalloproteinase-2 (MMP2) and MMP9, and heparin-binding EGF-like growth factor (HB-EGF) expression/activation. Also, phospho-Src could interact directly to phosphorylate EGFR. Overall, Cd-induced proliferation of human fibroid cells was through a nongenomic GPER/p-src/EGFR/MAPK signaling pathway that did not directly involve ERα36. This suggests that Cd may be a risk factor for uterine fibroids through cross talk between hormone and growth factor receptor pathways.

Evidences for involvement of estrogen receptor induced ERK1/2 activation in ovarian cancer cell proliferation by Cadmium Chloride

Cadmium (Cd) as a human carcinogen and one of the most toxic industrial and environmental pollutant mimics the estrogenic effects in cell proliferation. So, it might have a role in the incidence and etiology of hormone-related cancers such as ovarian cancer as the most lethal gynecologic malignancy. This study aimed to evaluate the estrogenic effect and underlying mechanism of Cd in ovarian cancer cell line proliferation. OVCAR3 and SKOV3 cell lines were treated with different concentrations of CdCl₂ (0- 50 μM). Cell proliferation was analyzed using MTT and BrdU assay. To evaluate the estrogenic effect of Cd, the cells were pre-incubated with estrogen receptor (ER) antagonist ICI 182,780. The expression of ER was determined using western blotting method. Real-time RT-PCR method was used to assess c-fos, c-jun and FOXO3a mRNA level. The results showed that Cd has an estrogenic proliferative effect at nM concentration range and ICI 182,780 significantly reversed the CdCl₂-induced cell proliferation. Cd also increased the expression of ERs. Cd exposure induced activation of p-ERK1/2 in these cells. Cd also intensified c-jun, c-fos, and FOXO3a mRNA expression. Taken together, the current work suggests that Cd induces ovarian cancer cell proliferation in an ER-dependent mechanism induced ERK1/2 activation pathway. Understanding of downstream targets by which Cd deregulates cell proliferation can be noteworthy to define its underlying carcinogenesis mechanism.

Exposure to Pb and Cd alters MCT4/CD147 expression and MCT4/CD147-dependent lactate transport in mice Sertoli cells cultured in vitro

Sertoli cells (SCs) provide lactate as an energy substrate to develop germ cells during spermatogenesis. Lead (Pb) and cadmium (Cd) can induce SC toxicity. However, the mechanisms remain unclear. This study aimed to investigate the molecular mechanisms by which Pb and Cd alter lactate transport and production by SCs. Mouse SC line (15P-1 cells) were cultured in the absence and presence of lead acetate (PbAc, 1, 10, 20 and 30 μM) or cadmium chloride (CdCl₂, 0.5, 5, 10 and 15 μM) for 24 h. The results showed that PbAc exposure significantly decreased lactate dehydrogenase (LDH) activity and mRNA level, intracellular and extracellular lactate, and MCT4 and CD147 protein levels but increased MCT4 and CD147 mRNA levels. However, PbAc did not alter the glucose uptake, glucose transporters 1 (GLUT1) and 3 (GLUT3) mRNA expression of SCs. Thus, PbAc mainly decreased lactate production by inhibiting LDH activity. In CdCl₂-treated SCs, intracellular lactate content increased but extracellular lactate content decreased significantly, P < .05. The glucose uptake, LDH activity, and mRNA expression of GLUT1, GLUT3 and LDH, all significantly increased. But the mRNA and protein levels of MCT4 and CD147 significantly decreased. Moreover, the fluorescence intensity of co-localizations of the MCT4-CD147 complex dose-dependently decreased in the cell membrane. Thus, CdCl₂ may reduce lactate export by suppressing MCT4 and CD147 expression. These results suggest that PbAc and CdCl₂ disrupt lactate production and transport in mouse SCs by disturbing glycolysis or inhibiting MCT4-CD147 transporter expression and co-localizations.

Low-dose cadmium activates the JNK signaling pathway in human renal podocytes

Cadmium (Cd) is an environmental toxin. Our previous study demonstrated that low‑dose Cd damages the integrity of the glomerular filtration barrier (GFB); however, the underlying mechanisms are poorly understood. Podocytes are a major component of the GFB, which regulate the passage of proteins. The present study aimed to investigate the effects of low‑dose Cd on human renal podocytes (HRPs). HRPs were treated with Cd and activation of the c-Jun N-terminal kinase (JNK) pathway was examined by western blot analysis. Proliferation, viability and apoptosis of HRPs were evaluated by MTT assay, trypan blue exclusion assay and flow cytometry, respectively. The properties of HRPs were validated by immunofluorescence staining and Phalloidin‑labeling. The results indicated that 4 µM Cd may activate the JNK pathway, and increase the protein expression levels of c‑Jun and c‑Fos. However, proliferation, viability, apoptosis and alignment of the F‑actin cytoskeleton in HRPs were not significantly affected by Cd treatment, with or without SP600125 pretreatment. In addition, the expression levels of CD2‑associated protein and synaptopodin, which are differentiation markers of HRPs, remained unchanged following Cd treatment. These results indicated that low‑dose Cd activates the JNK pathway but does not significantly affect HRP function.

The protective role of melatonin in cadmium-induced proliferation of ovarian cancer cells

Cadmium (Cd), a ubiquitous environmental and occupational pollutant, acts as a metalloestrogen to induce cell proliferation. It is suggested that Cd may also contribute to the development of estrogen-related cancers like ovarian cancer which is the most lethal cancer in women. Furthermore, it was shown that melatonin has antiproliferative effect on estradiol (E2)-induced proliferation. The aim of the present study was to evaluate whether melatonin inhibits Cd-induced proliferation in ovarian cancer cell lines and also whether Cd and melatonin can modulate estrogen receptor α (ERα) expression. OVCAR3 and SKOV3 human ovarian cancer cell lines were treated with CdCl₂ (1-100 nM) and melatonin (1 μM) for 48 h. Cell proliferation evaluation was carried out by bromodeoxyuridine (BrdU) incorporation assay. ERα expression was detected by western blotting method 24 h after cell treatment. The results were demonstrated that Cd increased proliferation of ovarian cancer cell lines in a dose dependent manner. Melatonin inhibited Cd-induced proliferation of OVCAR3 and SKOV3 cell lines. Moreover, CdCl₂ significantly increased ERα expression in both OVCAR3 and SKOV3 cell lines compared to control. Melatonin significantly inhibited Cd inducing effect on ERα expression of OVCAR3 and SKOV3 cell. In conclusion, due to the proliferative effect on ovarian cancer cell lines, Cd could play an important role in the etiology of ovarian cancer by inducing cells ERα expression. Furthermore, melatonin has the protective role on Cd-induced cell proliferation by inhibition of ERα expression.

Blood cadmium and volume of uterine fibroids in premenopausal women

Background

A number of studies have found associations between heavy metals and uterine fibroids, but the results are inconsistent. Here, we conducted this research to demonstrate the relationships between blood heavy metal concentrations and uterine fibroid volume as well as the rate of uterine fibroid presence.

Methods

In a cross-sectional study, we collected data from 308 premenopausal women aged 30–49 years in Seoul; uterine fibroids are ascertained by past history of myomectomy and pelvic ultrasonography. In the analytic phase, we first analyzed the presence of the fibroids and the concentrations of heavy metals via logistic regression. In subgroup analysis, we used simple and multiple linear regression analyses to examine the associations between heavy metals and uterine fibroid volume.

Results

There was no connection between the heavy metal concentrations and the presence of uterine fibroids, but the odds of women having fibroids were higher with three particular metals. In subgroup analysis, the association between blood cadmium concentrations and uterine fibroid volume was statistically significant (adjusted beta coefficient = 2.22, 95% confidential interval: 0.06–4.37). In contrast, blood mercury and lead concentrations were not significantly associated with uterine fibroid volume.

Conclusions

Our findings are the first that we know to report the association of blood cadmium concentrations with the volume of uterine fibroids. We expect that our findings will be used as evidence for supporting policies to improve premenopausal Korean women’s health.

Involvement of Notch1 signaling in malignant progression of A549 cells subjected to prolonged cadmium exposure

Cadmium exposure is known to increase lung cancer risk, but the underlying molecular mechanisms in cadmium-stimulated progression of malignancy are unclear. Here, we examined the effects of prolonged cadmium exposure on the malignant progression of A549 human lung adenocarcinoma cells and the roles of Notch1, hypoxia-inducible factor 1α (HIF-1α), and insulin-like growth factor 1 receptor (IGF-1R)/Akt/extracellular signal-regulated kinase (ERK)/p70 S6 kinase 1 (S6K1) signaling pathways. Exposing A549 cells to 10 or 20 μm cadmium chloride (CdCl2) for 9-15 weeks induced a high proliferative potential, the epithelial-mesenchymal transition (EMT), stress fiber formation, high cell motility, and resistance to antitumor drugs. Of note, the CdCl2 exposure increased the levels of the Notch1 intracellular domain and of the downstream Notch1 target genes Snail and Slug. Strikingly, siRNA-mediated Notch1 silencing partially suppressed the CdCl2-induced EMT, stress fiber formation, high cell motility, and antitumor drug resistance. In addition, we found that prolonged CdCl2 exposure induced reduction of E-cadherin in BEAS-2B human bronchial epithelial cells and antitumor drug resistance in H1975 human tumor-derived non-small-cell lung cancer cells depending on Notch1 signaling. Moreover, Notch1, HIF-1α, and IGF-1R/Akt/ERK/S6K1 activated each other to induce EMT in the CdCl2-exposed A549 cells. These results suggest that Notch1, along with HIF-1α and IGF-1R/Akt/ERK/S6K1 signaling pathways, promotes malignant progression stimulated by prolonged cadmium exposure in this lung adenocarcinoma model.

A morphological study of uterine alterations in mice due to exposure to cadmium

We investigated the morphologic and molecular effects of exposure to cadmium (Cd) for 30 and 60 days on the uteri of mice. We assessed uterine morphometric measurements, eosinophilia, mast cell numbers, endometrial apoptosis, proliferation and estrogen receptor alpha (ERα) immunoreactivity. We examined vaginal smears that reflected the hormonal alterations in the female reproductive tract. Because the female reproductive tract exhibits different morphology at each stage of the estrous cycle, we sacrificed all animals at estrus to make appropriate comparisons. Female BALB/c mice were exposed to 200 ppm Cd in their drinking water for either 30 or 60 days. Cd exposure caused significant decreases in endometrial thickness and number of glands in estrus phase uteri. The endometrial eosinophilia in the groups exposed to Cd also decreased compared to controls. Cd exposure increased the number of mast cells. Luminal and glandular epithelia were examined using the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and by immunostaining proliferating cell nuclear antigen (PCNA) and estrogen receptor α (ERα). Compared to controls, the apoptotic index increased with time in both Cd exposed groups, while the proliferation index decreased. ERα immunoreactivity was decreased in both Cd exposed groups compared to controls; the decrease was most apparent in the 30 day Cd group. We found that 60 day Cd exposure increased apoptosis in the endometrium, which may affect the receptivity of the uterus for implantation.

The influence of low-dose cadmium on the laryngeal microstructure and ultrastructure of Pelophylax nigromaculata

Cadmium (Cd) is one of the common heavy metals dispersed throughout the modern environment that disrupts the development of aquatic organisms. Amphibians appear to be particularly vulnerable to this heavy metal contaminant since their eggs and aquatic larvae live in aquatic habitats and have permeable skin. During this critical sensitive period, amphibians live primarily in the water and are thus susceptible to the effects of environmental pollutants in water. Pelophylax nigromaculata completes their laryngeal development from Gosner stage 19 (GS 19, embryonic stage) to GS 46 (metamorphosis stage). To study whether long-term (from GS 19 to GS 46) exposure to low Cd concentrations (0, 4, 8, 16, 32, 64, and 128 μg/L) affects the development of the larynx in P. nigromaculata, a comparative study of microstructures and ultrastructures of female and male P. nigromaculata larynges was carried out. In histological structure, the larynx was composed of epithelial tissue, skeletal muscle, and hyaline cartilage, and there were no differences between male and female frogs except that males had a larger cross-section area than females. In contrast to controls, 64 and 128 μg/L Cd treatments caused a significant decrease in cross-sectional area, while other treatments showed no significant differences. Under the scanning electron microscope, the surface of the larynx could be seen to be attached to developed and evenly distributed cilia, with no significant differences between young male and female frogs, even among the Cd treatments. Under transmission electron microscopy, developed laryngeal epithelial cells could be observed, with obvious cross striations of skeletal muscle cells and mitochondria distributed around the muscle and skeletal muscle satellite cells. Compared with the control group, mitochondria around the skeletal muscle grew in size and decreased in number in the high-concentration treatment.

Cadmium promotes the proliferation of triple-negative breast cancer cells through EGFR-mediated cell cycle regulation

Cadmium (Cd) is a carcinogenic metal which is implicated in breast cancer by epidemiological studies. It is reported to promote breast cancer cell growth in vitro through membrane receptors. The study described here examined Cd-mediated growth of non-metastatic human breast cancer derived cells that lack receptors for estrogen, progesterone, and HER2. Treatment of triple-negative HCC 1937 cells with 0.1-0.5 μM Cd increased cell growth by activation of AKT and ERK. Accelerated cell cycle progression was achieved by increasing the levels of cyclins A, B, and E, as well as those of CDKs 1 and 2. Although triple negative cells lack estrogen receptor, they express high levels of EGFR. Therefore, further studies on HCC 1937 and another triple-negative cell line, HCC 38, were conducted using specific siRNA and an inhibitor of EGFR to determine whether EGFR was responsible for mediating the effect of Cd. The results revealed that in both cell types EGFR was not only activated upon Cd treatment, but was also essential for the downstream activation of AKT and ERK. Based on these observations, it is concluded that, in breast cancer cells lacking estrogen receptor, sub-micromolar concentration of Cd can promote cell proliferation. Furthermore, that EGFR plays a critical role in this process.

Requirement of ERα and basal activities of EGFR and Src kinase in Cd-induced activation of MAPK/ERK pathway in human breast cancer MCF-7 cells

Cadmium (Cd) is a common environmental toxicant and an established carcinogen. Epidemiological studies implicate Cd with human breast cancer. Low micromolar concentrations of Cd promote proliferation of human breast cancer cells in vitro. The growth promotion of breast cancer cells is associated with the activation of MAPK/ERK pathway. This study explores the mechanism of Cd-induced activation of MAPK/ERK pathway. Specifically, the role of cell surface receptors ERα, EGFR, and Src kinase was evaluated in human breast cancer MCF-7 cells treated with 1-3μM Cd. The activation of ERK was studied using a serum response element (SRE) luciferase reporter assay. Receptor phosphorylation was detected by Western blot analyses. Cd treatment increased both the SRE reporter activity and ERK1/2 phosphorylation in a concentration-dependent manner. Cd treatment had no effect on reactive oxygen species (ROS) generation. Also, blocking the entry of Cd into the cells with manganese did not diminish Cd-induced activation of MAPK/ERK. These results suggest that the effect of Cd was likely not caused by intracellular ROS generation, but through interaction with the membrane receptors. While Cd did not appear to activate either EGFR or Src kinase, their inhibition completely blocked the Cd-induced activation of ERK as well as cell proliferation. Similarly, silencing ERα with siRNA or use of ERα antagonist blocked the effects of Cd. Based on these results, it is concluded that not only ERα, but also basal activities of EGFR and Src kinase are essential for Cd-induced signal transduction and activation of MAPK/ERK pathway for breast cancer cell proliferation.

Cadmium induced apoptosis in mouse primary hepatocytes: the role of oxidative stress-mediated ERK pathway activation and the involvement of histone H3 phosphorylation

Time-delayed apoptosis induced by cadmium in primary hepatocytes through DNA damage, histone modification and ERK signaling cascade, which are all mediated by oxidative stress.