The endocrine disruptor cadmium alters human osteoblast-like Saos-2 cells homeostasis in vitro by alteration of Wnt/β-catenin pathway and activation of caspases

Rethinking Biomedical Titanium Alloy Design: A Review of Challenges from Biological and Manufacturing Perspectives

Current biomedical titanium alloys have been repurposed from other industries, which has contributed to several biologically driven implant failure mechanisms. This review highlights the added value that may be gained by building an appreciation of implant biological responses at the onset of alloy design. Specifically, the fundamental mechanisms associated with immune response, angiogenesis, osseointegration and the potential threat of infection are discussed, including how elemental selection can modulate these pivotal systems. With a view to expedite inclusion of these interactions in alloy design criteria, methods to analyze these performance characteristics are also summarized. While machine learning techniques are being increasingly used to unearth complex relationships between alloying elements and material properties, much is still unknown about the correlation between composition and some bio-related properties. To bridge this gap, high-throughput methods are also reviewed to validate biological response along with cutting edge manufacturing approaches that may support rapid discovery. Taken together, this review encourages the alloy development community to rethink their approach to enable a new generation of biomedical implants intrinsically designed for a life in the body, including functionality to tackle biological challenges thereby offering improved patient outcomes.

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.

The endocrine disruptor cadmium modulates the androgen-estrogen receptors ratio and induces inflammatory cytokines in luminal (A) cell models of breast cancer

PURPOSE

Breast cancer (BC) is the most common malignancy that affects women, and it is, to date, their leading cause of death. Luminal A molecular subtype accounts for 40% of BC and is characterized by hormone receptors positive/human epidermal growth factor 2 expression and current treatment consists of surgery plus aromatase inhibitor therapy. Interestingly, several studies demonstrated that the heavy metal cadmium (Cd), classified as a group 1 human carcinogen and widely spread in the environment, exerts estrogen-like activities in several tissues and suggested an intriguing relationship between increased Cd exposure and BC incidence. Thus, aim of this study was to evaluate effects of Cd on Luminal A BC estrogen receptor (ER) positive/progesterone receptor positive cell models in vitro to characterize the mechanism(s) involved in breast cell homeostasis disruption.

METHODS

T47D and MCF7 were exposed to Cd (0.5-1 µM) for 6-24 h to evaluate potential alterations in: cells viability, steroid receptors and intracellular signaling by western blot. Moreover, we evaluated the expression of inflammatory cytokines interleukin by RT-PCR.

RESULTS

Our results showed a significant induction of androgen receptor (AR) and an increased AR/ER ratio. Further, Cd exposure increased pro-inflammatory cytokines interleukin (IL)6, IL8 and tumor necrosis factor α levels. Finally, as previously demonstrated by our group, Cd alters pathways such as mitogen-activated protein kinase family and protein kinase B.

CONCLUSION

In conclusion, our study demonstrates that Cd modifies the expression and pattern of ERs and AR in BC cell lines, suggesting an alteration of BC cells homeostasis, likely predisposing to a carcinogenetic microenvironment.

Associations between smoke exposure and osteoporosis or osteopenia in a US NHANES population of elderly individuals

BACKGROUND

Tobacco exposure is considered to be a risk factor for reduced bone mineral density (BMD), which may result in osteopenia. Cotinine, a metabolite of nicotine, is commonly utilized as a marker of tobacco exposure. Nevertheless, there are limited clinical data on the associations between osteoporosis (OP) or osteopenia and smoking status or serum cotinine level.

METHODS

We thoroughly examined the NHANES cross-sectional data from 2005 to 2010, 2013 to 2014, and 2017 to 2018. Multivariate logistic regression models were applied to assess the associations among smoking status and serum cotinine levels as well as OP and osteopenia. The relationships between serum cotinine level and OP and osteopenia were also assessed using the restricted cubic spline (RCS) method.

RESULTS

A total of 10,564 participants were included in this cross-sectional study. The mean age of the study population was 64.85 ± 9.54 years, and the patients were predominantly male (51.9%). We found that the relationships between higher serum cotinine levels (≥3 ng/ml) and the prevalence of osteoporosis (Model 1: OR=2.27 [1.91-2.69]; Model 2: OR=2.03 [1.70-2.43]; Model 3: OR=2.04 [1.70-2.45]; all p for trend <0.001) remained significant after adjustment for covariates by applying the lowest serum cotinine levels (<0.05 ng/ml) as the reference. Similar results were observed for current smokers, who were more likely to develop OP compared with nonsmokers (Model 1: OR=2.30 [1.90-2.79]; Model 2: OR=2.16 [1.77-2.64]; Model 3: OR=2.16 [1.77-2.65]). Moreover, higher serum cotinine levels were found to be strongly and positively correlated with the prevalence of osteopenia (OR=1.60 [1.42-1.80]). A similar relationship was observed between current smokers and the prevalence of osteopenia compared with nonsmokers (OR=1.70 [1.49-1.94]). RCS regression also showed that serum cotinine levels were nonlinearly and positively correlated with OP and osteopenia, with inflection points of 5.82 ng/ml and 3.26 ng/ml, respectively.

CONCLUSION

This study showed that being a smoker was associated with the prevalence of OP or osteopenia compared with being a nonsmoker and that there was a strong nonlinear positive dose-response relationship between serum cotinine levels and OP and osteopenia.

Race and Gender Differences in the Associations Between Cadmium Exposure and Bone Mineral Density in US Adults

Several previous studies have found the deleterious effects of cadmium exposure on bone. However, studies on the effects of cadmium exposure on bone mineral density (BMD) in gender- and race-specific groups are still lacking. The aim of this study was to investigate the relationship between cadmium exposure and BMD in adults and the gender and racial differences therein. Weighted multivariate regression, generalized weighted model, and smoothed curve fitting were used to explore the relationship between lumbar BMD with blood cadmium (B-Cd) and urine cadmium (U-Cd) based on data from the National Health and Nutrition Examination Survey (NHANES). In addition, subgroup analyses were further used to investigate the differential associations across gender and race. Of the 4335 adult participants. After adjusting for primary demographic variables, B-Cd [- 0.018 (- 0.028, - 0.008)] and U-Cd [- 0.010 (- 0.020, - 0.001)] were shown to be negatively related to lumbar BMD. In the fully adjusted model, the negative association between B-Cd and lumbar BMD was maintained [- 0.010 (- 0.018, - 0.002)]. In the subgroup analysis stratified by gender and race, this relationship was retained in females and non-Hispanic blacks. Furthermore, these negative associations were most pronounced among non-Hispanic black women [B-Cd and lumbar BMD, - 0.046 (- 0.076, - 0.017); U-Cd and lumbar BMD, -0.034 (- 0.063, - 0.006)]. Our findings suggest that there are significant sex and race differences in the negative association between cadmium exposure and BMD. This negative association was most prominent in non-Hispanic black females.

Low levels of cadmium exposure affect bone by inhibiting Lgr4 expression in osteoblasts and osteoclasts

BACKGROUND

Cadmium exposure is associated with bone loss. However, the mechanisms involved have not yet been fully understood. Leucine-rich repeat containing GPCR-4 (LGR4) can bind with the receptor activator of nuclear factors κB ligand (RANKL) and inhibit osteoclast formation. In addition, Lgr4 plays an important role in maintaining osteoblast activity. In the present study the effect of cadmium exposure on bone was investigated in terms of Lgr4 expression.

METHODS

Raw 264.7 cells and primary osteoblasts were exposed to cadmium (0-60 nM/L). The effects of cadmium on osteoclast formation and osteoblast activity were investigated. Osteoclast differentiation-related (Traf6, NFATc1) and osteoblast-related (RANKL; osteoprotegerin, OPG) gene and protein expression were determined. Lgr4 expression in osteoclasts and osteoblasts were also determined. A rat model was established to show the effects of cadmium (50 mg/L) on bone loss and Lgr4 expression in vivo.

RESULTS

Cadmium exposure inhibited osteoblast activities and stimulated osteoclast formation. Cadmium exposure also inhibited Lgr4 expression in both osteoclasts and osteoblasts. Low dose of RANKL added to the culture medium could promote osteoclast formation in cadmium-pretreated RAW264.7 cells. Blocking Lgr4 in osteoclasts only slightly inhibited cadmium-induced osteoclast formation in cadmium-pretreated RAW264.7 cells. Cadmium significantly upregulated the AKT/ERK signaling pathway. An in vivo study showed that cadmium exposure promoted osteoclast formation and inhibited Lgr4 expression.

CONCLUSIONS

Our data indicates that cadmium may induce bone loss by inhibiting Lgr4-related bone formation and promoting Lgr4-related osteoclast formation.

Repercussions of Bisphenol A on the Physiology of Human Osteoblasts

(1) Background: Bisphenol A (BPA) is an endocrine disruptor that is widely present in the environment and exerts adverse effects on various body tissues. The objective of this study was to determine its repercussions on bone tissue by examining its impact on selected functional parameters of human osteoblasts. (2) Methods: Three human osteoblast lines were treated with BPA at doses of 10^-5, 10^-6, or 10^-7 M. At 24 h post-treatment, a dose-dependent inhibition of cell growth, alkaline phosphatase activity, and mineralization was observed. (4) Results: The expression of CD54 and CD80 antigens was increased at doses of 10^-5 and 10^-6 M, while the phagocytic capacity and the expression of osteogenic genes (ALP, COL-1, OSC, RUNX2, OSX, BMP-2, and BMP-7) were significantly and dose-dependently reduced in the presence of BPA. (5) Conclusions: According to these findings, BPA exerts adverse effects on osteoblasts by altering their differentiation/maturation and their proliferative and functional capacity, potentially affecting bone health. Given the widespread exposure to this contaminant, further human studies are warranted to determine the long-term risk to bone health posed by BPA.

Environmental Exposure to Heavy Metals Contributes to Diseases Via Deregulated Wnt Signaling Pathways

Wnt signaling plays a critical role during embryogenesis and is responsible for regulating the homeostasis of the adult stem cells and cells fate via a multitude of signaling pathways and associated transcription factors, receptors, effectors, and inhibitors. For this review, published articles were searched from PubMed Central, Embase, Medline, and Google Scholar. The search terms were Wnt, canonical, noncanonical, signaling pathway, β-catenin, environment, and heavy metals. Published articles on Wnt signaling pathways and heavy metals as contributing factors for causing diseases via influencing Wnt signaling pathways were included. Wnt canonical or noncanonical signaling pathways are the key regulators of stem cell homeostasis that control many mechanisms. There is an adequate balance between β-catenin dependent and independent Wnt signaling pathways and remain highly conserved throughout different development stages. Environmental heavy metal exposure may cause either inhibition or overexpression of any component of Wnt signaling pathways such as Wnt protein, transcription factors, receptors, ligands, or transducers to impede normal cellular function via negatively affecting Wnt signaling pathways. Environmental exposure to heavy metals potentially contributes to diseases via deregulated Wnt signaling pathways. 

Integrated metabolomics coupled with pattern recognition and pathway analysis to reveal molecular mechanism of cadmium-induced diabetic nephropathy

Diabetic nephropathy (DN) is becoming a worldwide public health problem and its pathophysiological mechanism is not well understood. Emerging evidences indicated that cadmium (Cd), an industrial material but also an environmental toxin, may be involved in the development and progression of diabetes and diabetes-related kidney disease. However, the underlying mechanism is still unclear. Herein, a DN animal model was constructed by exposing to Cd, the metabolomic profiling of DN mice were obtained by using ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS), pattern recognition and pathway analysis were performed to screen potential biomarker. Moreover, western blotting was employed to verify the possible mechanism involved in the occurrence of Cd-induced DN. A total of 66 metabolites in serum have been screened out and identified as biomarkers, including free fatty acids, phospholipids, sphingomyelins, glycerides, and others. Significant differences were demonstrated between the metabolic profiles, including decreased levels of phospholipid and increased content of triglyceride, diacylglycerols, ceramide, lysophosphatidylcholine in Cd-induced DN mice compared with control. Protein expression level of p38 MAPK and Wnt/β-catenin were significantly increased. UPLC-Q-TOF/MS-based serum metabolomics coupled with pattern recognition methods and pathway analysis provide a powerful approach to identify potential biomarkers and is a new strategy to predict the underlying mechanism of disease caused by environmental toxicant.

The endocrine disruptor cadmium: a new player in the pathophysiology of metabolic diseases

Cadmium (Cd), a highly toxic heavy metal, is found in soil, environment and contaminated water and food. Moreover, Cd is used in various industrial activities, such as electroplating, batteries production, fertilizers, while an important non-occupational source is represented by cigarette smoking, as Cd deposits in tobacco leaves. Since many years it is clear a strong correlation between Cd body accumulation and incidence of many diseases. Indeed, acute exposure to Cd can cause inflammation and affect many organs such as kidneys and liver. Furthermore, the attention has focused on its activity as environmental pollutant and endocrine disruptor able to interfere with metabolic and energy balance of living beings. Both in vitro and in vivo experiments have demonstrated that the Cd-exposure is related to metabolic diseases such as obesity, diabetes and osteoporosis even if human studies are still controversial. Recent data show that Cd-exposure is associated with atherosclerosis, hypertension and endothelial damage that are responsible for cardiovascular diseases. Due to the large environmental diffusion of Cd, in this review, we summarize the current knowledge concerning the role of Cd in the incidence of metabolic and cardiovascular diseases.

Burden of osteoporosis and costs associated with human biomonitored cadmium exposure in three European countries: France, Spain and Belgium

Cadmium (Cd) is a toxic heavy metal widespread in the environment leading to human exposure in particular through diet (when smoking is excluded), as documented by recent human biomonitoring (HBM) surveys. Exposure to Cd at environmental low-exposure levels has been associated with adverse effects such as renal toxicity and more recently bone effects. The implication, even if limited, of Cd in the etiology of osteoporosis can be of high importance at the population level given the significant prevalence of osteoporosis and the ubiquitous and life-long exposure to Cd. Therefore, the osteoporosis cases attributable to Cd exposure was estimated in three European countries (Belgium, France and Spain), based on measured urinary Cd levels from HBM studies conducted in these countries. The targeted population was women over 55 years old, for which risk levels associated with environmental Cd exposure were available. Around 23% of the cases were attributed to Cd exposure. Moreover, in a prospective simulation approach of lifelong urinary Cd concentrations assuming different intakes scenarios, future osteoporosis attributable cases were calculated, based on urinary Cd levels measured in women aged under 55. Between 6 and 34% of the considered populations under 55 years were at risk for osteoporosis. Finally, the costs associated to the burden of osteoporosis-related fractures attributable to Cd for each country targeted in this paper were assessed, standing for a major contributing role of Cd exposure in the overall social costs related to osteoporosis. Absolute costs ranged between 0.12 (low estimate in Belgium) and 2.6 billion Euros (high estimate in France) in women currently over 55 years old and at risk for fractures. Our results support the importance of reducing exposure of the general population to Cd.

Bone Disruption and Environmental Pollutants

BACKGROUND

Endocrine Disrupting Chemicals (EDCs) are ubiquitous and may significantly contribute in environmental pollution, thus contaminating humans and wildlife. Environmental pollutants could interfere with bone homeostasis by means of different mechanisms, which include hormonal imbalance, direct osteoblasts toxicity and enanchment of osteoclasts activity, thus leading to osteopenia or osteoporosis. Among these, bisphenols, dioxins, polycyclic aromatic hydrocarbons, polychlorobiphenyls, poly- and perfluoroalkyls, phthalates, parabens, organotins and cadmium may play a role in bone distuption.

METHODS

PubMed/MEDLINE, ISI-web of knowledge and Google scholar databases were searched for medical subject headings terms and free-text word related to the aforementioned classes of chemicals and bone metabolism and remodelling for better clarifying and understanding the main mechanisms of bone disruption.

RESULTS

Several of EDCs act as xenoestrogens. Considering that estrogens play a significant role in regulating bone remodeling, most of these chemicals generate hormonal imbalance with possible detrimental consequences on bone tissue structure and its mechanical and non-mechanical properties.

DISCUSSION

A lot of evidences about bone distruptors came from in vitro studies or animal models, and conduct to equivocal results. In addition, a few data derived form humans and most of these data focused on the impact of EDCs on bone mineral density without considering their influence on long-term fracture risk. Moreover, it should be taken into account that humans are exposed to a mixture of EDCs and the final effect on bone metabolism might be the result of either a synergism or antagonist effects among them. Age of first exposure, cumulative dose exposure over time, and the usually observed non-monotonic dose-response curve for EDCs should be considered as other important variable influencing the final effect on bone metabolism.

CONCLUSION

Taking into account these variables, observational studies are needed to better analyze this issue both for echological purpose and to preserve bone health.

Di-(2-ethylhexyl) phthalate-induced tumor growth is regulated by primary cilium formation via the axis of H2O2 production-thymosin beta-4 gene expression

Di-(2-ethylhexyl) phthalate (DEHP) that is one of the most commonly used phthalates in manufacturing plastic wares regulates tumorigenesis. Thymosin beta-4 (TB4), an actin-sequestering protein, has been reported as a novel regulator to form primary cilia that are antenna-like organelles playing a role in various physiological homeostasis and pathological development including tumorigenesis. Here, we investigated whether DEHP affects tumor growth via primary cilium (PC) formation via the axis of TB4 gene expression and the production of reactive oxygen species (ROS). Tumor growth was increased by DEHP treatment that enhanced TB4 expression, PC formation and ROS production. The number of cells with primary cilia was enhanced time-dependently higher in HeLa cells incubated in the culture medium with 0.1% fetal bovine serum (FBS). The number of cells with primary cilia was decreased by the inhibition of TB4 expression. The incubation of cells with 0.1% FBS enhanced ROS production and the transcriptional activity of TB4 that was reduced by ciliobrevin A (CilioA), the inhibitor of ciliogenesis. ROS production was decreased by catalase treatment but not by mito-TEMPO, which affected to PC formation with the same trend. H₂O₂ production was reduced by siRNA-based inhibition of TB4 expression. H₂O₂ also increased the number of ciliated cells, which was reduced by siRNA-TB4 or the co-incubation with CilioA. Tumor cell viability was maintained by ciliogenesis, which was correlated with the changes of intracellular ATP amount rather than a simple mitochondrial enzyme activity. TB4 overexpression enhanced PC formation and DEHP-induced tumor growth. Taken together, data demonstrate that DEHP-induced tumor growth might be controlled by PC formation via TB4-H₂O₂ axis. Therefore, it suggests that TB4 could be a novel bio-marker to expect the risk of DEHP on tumor growth.

Cadmium induces apoptosis via generating reactive oxygen species to activate mitochondrial p53 pathway in primary rat osteoblasts

Cadmium (Cd), a heavy metal produced by various industries, contaminates the environment and seriously damages the skeletal system of humans and animals. Recent studies have reported that Cd can affect the viability of cells, including osteoblasts, both in vivo and in vitro. However, the mechanism of Cd-induced apoptosis remains unclear. In the present study, primary rat osteoblasts were used to investigate the Cd-induced apoptotic mechanism. We found that treatment with 2 and 5 μM Cd for 12 h decreased osteoblast viability and increased apoptosis. Furthermore, Cd increased the generation of reactive oxygen species (ROS), and, thus, DNA damage measured via p-H2AX. The level of the nuclear transcription factor p53 was significantly increased, which upregulated the expression of PUMA, Noxa, Bax, and mitochondrial cytochrome c, downregulated the expression of Bcl-2, and increased the level of cleaved caspase-3. However, pretreatment with the ROS scavenger N-acetyl-l-cysteine (NAC) or the p53 transcription specific inhibitor PFT-α suppressed Cd-induced apoptosis. Our results indicate that Cd can induce apoptosis in osteoblasts by increasing the generation of ROS and activating the mitochondrial p53 signaling pathway, and this mechanism requires the transcriptional activation of p53.

Adverse Impact of Heavy Metals on Bone Cells and Bone Metabolism Dependently and Independently through Anemia

Mounting evidence is revealing that heavy metals can incur disordered bone homeostasis, leading to the development of degenerative bone diseases, including osteoporosis, osteoarthritis, degenerative disk disease, and osteomalacia. Meanwhile, heavy metal-induced anemia has been found to be intertwined with degenerative bone diseases. However, the relationship and interplay among these adverse outcomes remain elusive. Thus, it is of importance to shed light on the modes of action (MOAs) and adverse outcome pathways (AOPs) responsible for degenerative bone diseases and anemia under exposure to heavy metals. In the current Review, the epidemiological and experimental findings are recapitulated to interrogate the contributions of heavy metals to degenerative bone disease development which may be attributable dependently and independently to anemia. A few likely mechanisms are postulated for anemia-independent degenerative bone diseases, including dysregulated osteogenesis and osteoblastogenesis, imbalanced bone formation and resorption, and disturbed homeostasis of essential trace elements. By contrast, remodeled bone microarchitecture, inhibited erythropoietin production, and disordered iron homeostasis are speculated to account for anemia-associated degenerative bone disorders upon heavy metal exposure. Together, this Review aims to elaborate available literature to fill in the knowledge gaps in understanding the detrimental effects of heavy metals on bone cells and bone homeostasis through different perspectives.

Cancer risk and disease burden of dietary cadmium exposure changes in Shanghai residents from 1988 to 2018

Cadmium (Cd) is a widely distributed toxic metal, which is mainly exposed to humans through diet. The impact of dietary guidelines on the Chinese diet structure has indirectly led to changes in dietary Cd exposure. The Chinese Dietary Guidelines were issued in 1997 and revised in 2007. Based on the time between issuance and revision, this study examined the Cd contamination levels in Shanghai foods from 1988 to 2018 and evaluated cancer risk and disease burden of dietary Cd exposure accordingly. Over the time periods of 1988-1997, 1998-2007, and 2008-2018, it was found that Cd dietary exposure of Shanghai residents showed a trend of increasing and then decreasing (39.7, 44.7, and 36.4 μg/day, respectively). In contrast to cereals, the contribution rates of meat and vegetables to Cd exposure have gradually increased over time, and aquatic foods have become the main source of Cd exposure (40.6%). Although the non-cancer risk hazard quotients of dietary Cd exposure and the excess lifetime cancer risks (ELCR) are relatively low (HQ < 1, ELCR < 10^-4), 26.6% of Shanghai residents had a potential risk of kidney injury calculated by toxicokinetic model (TK model), and the disability adjusted life years (DALYs) have been rising (from 41.6 to 58.2). Results indicated that in the past three decades, changes of Cd contamination in food due to both limit standards and changes in dietary structure have influenced cancer risk and disease burden from Cd exposure in Shanghai residents. In summary, our study suggested that while regulating the contamination in foods, attention should also be paid to the potential impacts of dietary structure and guidelines on the exposure of pollutants.

Melatonin protects bone against cadmium-induced toxicity via activation of Wnt/β-catenin signaling pathway

Among heavy metals, cadmium (Cd) is one of the most toxic for health due to it accumulation in several tissues including bone. Since melatonin (MLT) favors new bone formation through several pathways including Wnt/β-catenin, here we assessed whether MLT has a protective role against Cd induced toxicity in the rat bone tissue. Adult male Wistar rats receiving 50 mg CdCl₂/L and/or 3 mg/L MLT were used and were sacrificed 30 days after the treatment. Femurs and plasma were collected and analyzed by various biochemicals, molecular and histological investigation. The results showed that Cd exposure induced bone disorder characterized by histopathological alterations, a decreased alkaline phosphatase activity and plasmatic concentration of osteocalcin. Moreover, also the expression levels of some osteogenic-related genes (Runx2, Ocn and Alp) were down-regulated after Cd treatment. Since mechanistically Cd toxicity reduced the Kinase activity of GSK3β and protein levels of Wnt3a and β-catenin, we observed that MLT administration significantly ameliorated the toxic effects induced by the metal. Our findings provide clues about a potential protective effect of MLT against Cd-induced bone metabolism destruction and that the protection was partially mediated via the Wnt/β-catenin signaling pathway.

Cadmium exposure alters steroid receptors and proinflammatory cytokine levels in endothelial cells in vitro: a potential mechanism of endocrine disruptor atherogenic effect

BACKGROUND

Cadmium (Cd) is a widespread environmental pollutant that causes alterations in human health acting as endocrine disruptor. Recent data suggest that cardiovascular system might be a contamination target tissue, since Cd is found in atheromatic plaques. Thus, the purpose of this study was to evaluate the consequence of Cd exposure of endothelial cells in vitro to evaluate detrimental effect in vascular system by a potential sex-steroid hormone receptor-dependent mechanism(s).

METHODS

To this aim, Human Umbilical Vein Endothelial Cells (HUVECs) were cultured and exposed to several concentrations of cadmium chloride (CdCl₂) for different interval times.

RESULTS

CdCl₂ exposure of HUVECs induced a significant increase of ERβ and Cyp19a1 at both mRNA and protein levels, while a drastic dose-dependent decrease of AR expression level was observed after 24 h of exposure. On the contrary, an increase of PhAR^ser308 as well as a reduction of PhGSK-3β^ser9 and PhAKT^ser473 was detected after 1 h treatment. This effect was consistently reduced by GSK inhibition. Furthermore, CdCl₂ abolished DHT-induced cell proliferation in HUVECs suggesting an antagonist-like effect of Cd on AR-mediated signaling. Remarkable, after 6 h CdCl₂-treatment, a relevant increase in TNF-α, IL-6 and IL-8 mRNA was observed and this effect was blocked by the presence of an ERβ-selective antagonist. Moreover, Cd-induced TxR1 overexpression, likely, correlated with the activation of p38 MAPK/NF-κB pathway.

CONCLUSION

In conclusion, our study demonstrates for the first time that Cd alters sex-steroid hormone receptors level and activity likely affecting intracellular signaling linked to a proinflammatory state in endothelial cells. This alteration might possibly lead to endothelial cell injury and vascular dysfunction and could be a mechanism of gender-specific atherogenic damages induced by endocrine disruptors and, thus, induce atherogenic events with increased risk of cardiovascular diseases in individuals exposed to this endocrine disruptor.

Anti-Osteogenic Activity of Cadmium in Zebrafish

Among the many anthropogenic chemicals that end up in the aquatic ecosystem, heavy metals, in particular cadmium, are hazardous compounds that have been shown to affect developmental, reproductive, hepatic, hematological, and immunological functions in teleost fish. There is also evidence that cadmium disturbs bone formation and skeletal development, but data is scarce. In this work, zebrafish was used to further characterize the anti-osteogenic/osteotoxic effects of cadmium and gain insights into underlying mechanisms. Upon exposure to cadmium, a reduction of the opercular bone growth was observed in 6-days post-fertilization (dpf) larvae and an increase in the incidence of skeletal deformities was evidenced in 20-dpf post-larvae. The extent and stiffness of newly formed bone was also affected in adult zebrafish exposed to cadmium while regenerating their caudal fin. A pathway reporter assay revealed a possible role of the MTF-1 and cAMP/PKA signaling pathways in mechanisms of cadmium osteotoxicity, while the expression of genes involved in osteoblast differentiation and matrix production was strongly reduced in cadmium-exposed post-larvae. This work not only confirmed cadmium anti-osteogenic activity and identified targeted pathways and genes, but it also suggested that cadmium may affect biomechanical properties of bone.

A Review of Metal Exposure and Its Effects on Bone Health

The presence of metals in the environment is a matter of concern, since human activities are the major cause of pollution and metals can enter the food chain and bioaccumulate in hard and soft tissues/organs, which results in a long half-life of the metal in the body. Metal intoxication has a negative impact on human health and can alter different systems depending on metal type and concentration and duration of metal exposure. The present review focuses on the most common metals found in contaminated areas (cadmium, zinc, copper, nickel, mercury, chromium, lead, aluminum, titanium, and iron, as well as metalloid arsenic) and their effects on bone tissue. Both the lack and excess of these metals in the body can alter bone dynamics. Long term exposure and short exposure to high concentrations induce an imbalance in the bone remodeling process, altering both formation and resorption and leading to the development of different bone pathologies.

Biochemical and transcriptional analyses of cadmium-induced mitochondrial dysfunction and oxidative stress in human osteoblasts

Cadmium (Cd) accumulation is known to occur predominantly in kidney and liver; however, low-level long-term exposure to Cd may also result in bone damage. Few studies have addressed Cd-induced toxicity in osteoblasts, particularly upon cell mitochondrial energy processing and putative associations with oxidative stress in bone. To assess the influence of Cd treatment on mitochondrial function and oxidative status in osteoblast cells, human MG-63 cells were treated with Cd (up to 65 μM) for 24 or 48 h. Intracellular reactive oxygen species (ROS), lipid and protein oxidation and antioxidant defense mechanisms such as total antioxidant activity (TAA) and gene expression of antioxidant enzymes were analyzed. In addition, Cd-induced effects on mitochondrial function were assessed by analyzing the activity of enzymes involved in mitochondrial respiration, membrane potential (ΔΨm), mitochondrial morphology and adenylate energy charge. Treatment with Cd increased oxidative stress, concomitantly with lipid and protein oxidation. Real-time polymerase chain reaction (qRT-PCR) analyses of antioxidant genes catalase (CAT), glutathione peroxidase 1 (GPX1), glutathione S-reductase (GSR), and superoxide dismutase (SOD1 and SOD2) exhibited a trend toward decrease in transcripts in Cd-stressed cells, particularly a downregulation of GSR. Longer treatment with Cd (48 h) resulted in energy charge states significantly below those commonly observed in living cells. Mitochondrial function was affected by ΔΨm reduction. Inhibition of mitochondrial respiratory chain enzymes and citrate synthase also occurred following Cd treatment. In conclusion, Cd induced mitochondrial dysfunction which appeared to be associated with oxidative stress in human osteoblasts.

Trace elements have beneficial, as well as detrimental effects on bone homeostasis

The protective role of nutrition factors such as calcium, vitamin D and vitamin K for the integrity of the skeleton is well understood. In addition, integrity of the skeleton is positively influenced by certain trace elements (e.g. zinc, copper, manganese, magnesium, iron, selenium, boron and fluoride) and negatively by others (lead, cadmium, cobalt). Deficiency or excess of these elements influence bone mass and bone quality in adulthood as well as in childhood and adolescence. However, some protective elements may become toxic under certain conditions, depending on dosage (serum concentration), duration of treatment and interactions among individual elements. We review the beneficial and toxic effects of key elements on bone homeostasis.

Thyroid disruption by perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA)

BACKGROUND

Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are two fluorinated compounds widely used in industry because of their useful chemical characteristics. They were identified as endocrine disruptors due to their ability to interfere with thyroid function. The resistance of PFOA and PFOS to environmental degradation, their bio-accumulation in food chains, and their long half-life raised concern in the scientific community, and several studies were performed with the aim to establish the real dangerousness of these compounds for the human health.

PURPOSE

The present review will focus on the effects of PFOA and PFOS on the thyroid gland taking into account in vitro experiments, animal studies, and human data. PFOS and PFOA reduce the circulating levels of thyroid hormones in diet-exposed animals, mainly by increasing their metabolic clearance rate.

CONCLUSIONS

An accumulation of PFOS and PFOA was documented in thyroid cells, and a cytotoxic effect was observed after exposure to extremely high concentrations of these compounds. In environmentally exposed communities and in the general population, the most consistent effect of exposure to PFOA, and to a less extent to PFOS, is the occurrence of hypothyroidism. Women and children appear to be more at risk of developing mild thyroid failure. Pregnant women with circulating thyroid antibodies might be at risk of developing subclinical hypothyroidism, mainly when exposed at high doses of PFOS. The relative risks for thyroid cancer in people exposed to PFOA and PFOS were low and based on a few cases. Moreover, there was no consistent finding across all or even most studies.

Environmental Factors Impacting Bone-Relevant Chemokines

Chemokines play an important role in normal bone physiology and the pathophysiology of many bone diseases. The recent increased focus on the individual roles of this class of proteins in the context of bone has shown that members of the two major chemokine subfamilies-CC and CXC-support or promote the formation of new bone and the remodeling of existing bone in response to a myriad of stimuli. These chemotactic molecules are crucial in orchestrating appropriate cellular homing, osteoblastogenesis, and osteoclastogenesis during normal bone repair. Bone healing is a complex cascade of carefully regulated processes, including inflammation, progenitor cell recruitment, differentiation, and remodeling. The extensive role of chemokines in these processes and the known links between environmental contaminants and chemokine expression/activity leaves ample opportunity for disruption of bone healing by environmental factors. However, despite increased clinical awareness, the potential impact of many of these environmental factors on bone-related chemokines is still ill defined. A great deal of focus has been placed on environmental exposure to various endocrine disruptors (bisphenol A, phthalate esters, etc.), volatile organic compounds, dioxins, and heavy metals, though mainly in other tissues. Awareness of the impact of other less well-studied bone toxicants, such as fluoride, mold and fungal toxins, asbestos, and chlorine, is also reviewed. In many cases, the literature on these toxins in osteogenic models is lacking. However, research focused on their effects in other tissues and cell lines provides clues for where future resources could be best utilized. This review aims to serve as a current and exhaustive resource detailing the known links between several classes of high-interest environmental pollutants and their interaction with the chemokines relevant to bone healing.

Pleiotropic roles of Ca+2/calmodulin-dependent pathways in regulating cadmium-induced toxicity in human osteoblast-like cell lines

The heavy metal cadmium is a widespread environmental contaminant that has gained public attention due to the global increase in cadmium-containing electronic waste. Human exposure to cadmium is linked to the pathogenesis of osteoporosis. We previously reported cadmium induces apoptosis and decreases alkaline phosphatase mRNA expression via extracellular signal-regulated protein kinase (ERK) activation in Saos-2 bone-forming osteoblasts. This study examines the mechanisms of cadmium-induced osteotoxicity by investigating roles of Ca⁺²/calmodulin-dependent protein kinase (CAMK) pathways. Saos-2 or MG-63 cells were treated for 24 or 48h with 5μM CdCl₂ alone or in combination with calmodulin-dependent phosphodiesterase (PDE) inhibitor CGS-9343β; calmodulin-dependent kinase kinase (CAMKK) inhibitor STO-609; or calmodulin-dependent kinase II (CAMKII) inhibitor KN-93. CGS-9343β protected against cadmium-induced toxicity and attenuated ERK activation; STO-609 enhanced toxicity and exacerbated ERK activation, whereas KN-93 had no detectable effect on cadmium-induced toxicity. Furthermore, CGS-9343β co-treatment attenuated cadmium-induced apoptosis; but CGS-9343β did not recover cadmium-induced decrease in ALP activity. The major findings suggest the calmodulin-dependent PDE pathway facilitates cadmium-induced ERK activation leading to apoptosis, whereas the CAMKK pathway plays a protective role against cadmium-induced osteotoxicity via ERK signaling. This research distinguishes itself by identifying pleiotropic roles for CAMK pathways in mediating cadmium's toxicity in osteoblasts.