Cadmium in blood of Tunisian men and risk of bladder cancer: interactions with arsenic exposure and smoking

Relationships between blood cadmium concentration and risk of nine cancers: evidence from the NHANES 1999-2018 and Mendelian randomization analyses

BACKGROUND

Previous observational studies examining the relationship between cadmium exposure and various cancers have yielded conflicting results. This study aims to comprehensively clarify the relationship between blood cadmium concentration (BCC) and nine specific cancers.

METHODS

A retrospective analysis of National Health and Nutrition Examination Survey (NHANES) 1999-2018 identified 36,991 participants. Multivariable logistic regression was used to assess the association between BCC and the risk of nine specific cancers. Additionally, Mendelian randomization (MR) analyses were conducted to investigate potential causal relationships.

RESULTS

Multivariable logistic regression analysis of the NHANES data indicated a positive association between BCC and the risk of bladder and lung cancers (P < 0.05) and a negative association with the risk of kidney and prostate cancers (P < 0.05). The MR analyses demonstrated a causal relationship between BCC and kidney cancer (P < 0.05). Additionally, it uncovered causal associations with breast, cervical, and colon cancers (P < 0.05).

CONCLUSION

Elevated BCC was associated with an increased risk of bladder and lung cancers while demonstrating an inverse relationship with kidney and prostate cancers. MR analysis revealed that cadmium exposure may act as a protective factor against breast, cervical, colon, and kidney cancers, that must be confirmed with new studies.

Elements in trace amount with a significant role in human physiology: a tumor pathophysiological and diagnostic aspects

Cancer has a devastating impact globally regardless of gender, age, and community, which continues its severity to the population due to the lack of efficient strategy for the cancer diagnosis and treatment. According to the World Health Organisation report, one out of six people dies due to this deadly cancer and we need effective strategies to regulate it. In this context, trace element has a very hidden and unexplored role and require more attention from investigators. The variation in concentration of trace elements was observed during comparative studies on a cancer patient and a healthy person making them an effective target for cancer regulation. The percentage of trace elements present in the human body depends on environmental exposure, food habits, and habitats and could be instrumental in the early diagnosis of cancer. In this review, we have conducted inclusive analytics on trace elements associated with the various types of cancers and explored the several methods involved in their analysis. Further, intricacies in the correlation of trace elements with prominent cancers like prostate cancer, breast cancer, and leukaemia are represented in this review. This comprehensive information on trace elements proposes their role during cancer and as biomarkers in cancer diagnosis.

Cadmium in biological samples and site-specific cancer risk and mortality: A systematic review of original articles and meta-analyses

BACKGROUND

Cadmium (Cd) is classified as a class 1 carcinogen by the IARC, yet uncertainty persists regarding the total burden of cancer (incidence and mortality) caused by exposure to it, due to the still limited evidence with regard to its aetiological role in cancer at several body sites.

OBJECTIVES AND METHODS

We searched PubMed and EMBASE for meta-analyses and original articles published by February 1st, 2024, that focused on the link between cadmium measured in biological samples (blood, urine, finger-/toe-nails, and hair) and site-specific cancer risk and mortality.

RESULTS

We included 9 meta-analyses and 57 original articles (of these, the design was retrospective in 38 and prospective in 19, and Cd levels were quantified in blood, n=33, urine, n=19, both blood and urine, n=2, or finger-/toenail, n=3). Current data consistently suggest a causal role of exposure to cadmium in pancreas, lung, and bladder carcinogenesis. Total cancer risk and mortality are also positively correlated with Cd levels in biological samples. The evidence is weak or inconclusive for the remaining cancer sites (including breast and prostate), mostly due to the limited number of studies available to date and/or methodological limitations.

DISCUSSION

Exposure to cadmium poses a risk for increased cancer incidence and mortality. Cadmium-related cancer burden might indeed be currently underestimated, as the amount of available evidence for most cancer sites and types is currently limited, and more research in the field is warranted. Continuing efforts to contain Cd pollution and mitigate associated health risk are also needed.

Does the Presence of Heavy Metals Influence the Gene Expression and Oxidative Stress in Bladder Cancer?

Heavy metal toxicity is associated with cancer progression. Studies have reported the relation between some metal ions and bladder cancer (BC). Direct influence of such agents in bladder carcinogenesis is still needed. Total 49 BC patients were included in the study. Level of Pb, Cr, Hg and Cd, oxidative stress markers, and gene expression of Bcl-2, Bax, IL-6, AKT, and P38 genes were detected in cancer and non-cancerous tissues obtained from bladder cancer patients. Concentrations of Pb, Cr, and Cd were significantly elevated in cancer tissues than normal, while Hg level was significantly increased in normal tissue than cancer. MDA level was significantly higher and SOD activity was lower in the cancer tissues compared to non-cancerous. The expressions of Bcl-2, IL-6, AKT, and P38 were significantly increased in the cancer tissues than in normal tissues while Bax level was significantly increased in non-cancerous tissue than in cancer tissue. In cancer tissue, there were significant correlations between Cr level with expression of Bax, AKT, and P38 while Cd level was significantly correlate with Bax, IL-6, AKT, and P38expression. The correlation between Cr and Cd with the expression of Bax, IL-6, AKT, and P38 may indicate a carcinogenic role of these metals on progression of bladder cancer.

Uncovering the epidemiology of bladder cancer in the Arab world: A review of risk factors, molecular mechanisms, and clinical features

Objective

Bladder cancer (BC) is a significant public health concern in the Middle East and North Africa, but the epidemiology and clinicopathology of the disease and contributors to high mortality in this region remain poorly understood. The aim of this systematic review was to investigate the epidemiological features of BC in the Arab world and compare them to those in Western countries in order to improve the management of this disease.

Methods

An extensive electronic search of the PubMed/PMC and Cochrane Library databases was conducted to identify all articles published until May 2022, following the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines. A total of 95 articles were included in the final analysis after title, abstract, and full-text screening, with additional data obtained from the GLOBOCAN and WHO 2020 databases.

Results

Most of the included articles were case-control studies examining the risk factors and molecular mechanisms of BC. These studies originated from 10 different countries, with Egypt being the most active contributor. While BC in the Arab world shares some common risk factors with Western countries, such as smoking and occupational exposure, it also exhibits unique features related to schistosomiasis. The high mortality rates in this region are alarming and can be attributed to various factors, including the prevalence of smoking, the impact of schistosomiasis, a combination of genetic and socioeconomic factors, treatment shortages, and limited access to care or inadequate assessment of the quality of care.

Conclusion

Despite the relatively low incidence of BC in Arab countries, the mortality rates are among the highest worldwide. BC tends to be more aggressive in the Arab world, making it essential to implement strategies to address this burden.

Unveiling an Association between Waterpipe Smoking and Bladder Cancer Risk: A Multicenter Case-Control Study in Iran

BACKGROUND

Limited data exist for the association between bladder cancers and waterpipe smoking, an emerging global public health concern.

METHODS

We used the IROPICAN database in Iran and used multivariable logistic regression, adjusting for cigarette smoking, opium use, and other confounding factors. In addition, we studied the association between exclusive waterpipe smoking and bladder cancer.

RESULTS

We analyzed 717 cases and 3,477 controls and a subset of 215 patients and 2,145 controls who did not use opium or cigarettes. Although the OR adjusted for opium, cigarettes, and other tobacco products was 0.92 [95% confidence interval (CI), 0.69-1.20], we observed a statistically significant elevated risk in exclusive waterpipe smokers (OR = 1.78; 95% CI, 1.16-2.72) compared with non-users of opium or any tobacco. Associations were strongest for smoking more than two heads/day (OR = 2.25; 95% CI, 1.21-4.18) and for initiating waterpipe smoking at an age less than 20 (OR = 2.73; 95% CI, 1.11-6.72). The OR for urothelial bladder cancer was higher in ex-smokers (OR = 2.35; 95% CI, 1.24-4.42) than in current smokers (OR = 1.52; 95% CI, 0.72-3.15). All observed associations were consistently higher for urothelial histology.

CONCLUSIONS

Waterpipe smoking may be associated with an increased risk of bladder cancer, notably among individuals who are not exposed to cigarette smoking and opium.

IMPACT

The study provides compelling evidence that waterpipe smoking is a confirmed human carcinogen, demanding action from policymakers. See related In the Spotlight, p. 461.

An exploratory study on the association of multiple metals in serum with preeclampsia

Background

Individual metal levels are potential risk factors for the development of preeclampsia (PE). However, understanding of relationship between multiple metals and PE remains elusive.

Purpose

The purpose of this study was to explore whether eight metals [zinc (Zn), manganese (Mn), copper (Cu), nickel (Ni), lead (Pb), arsenic (As), cadmium (Cd), and mercury (Hg)] in serum had a certain relationship with PE.

Methods

A study was conducted in Dongguan, China. The concentrations of metals in maternal serum were assessed using inductively coupled plasma mass spectrometry (ICP-MS). Data on various factors were collected through a face-to-face interview and hospital electronic medical records. The unconditional logistic regression model, principal component analysis (PCA) and Bayesian Kernel Machine Regression (BKMR) were applied in our study.

Results

The logistic regression model revealed that the elevated levels of Cu, Pb, and Hg were associated with an increased risk of PE. According to PCA, principal component 1 (PC1) was predominated by Hg, Pb, Mn, Ni, Cu, and As, and PC1 was associated with an increased risk of PE, while PC2 was predominated by Cd and Zn. The results of BKMR indicated a significant positive cumulative effect of serum metals on PE risk, with Ni and Cu exhibiting a significant positive effect. Moreover, BKMR results also revealed the nonlinear effects of Ni and Cd.

Conclusion

The investigation suggests a potential positive cumulative impact of serum metals on the occurrence of PE, with a particular emphasis on Cu as a potential risk factor for the onset and exacerbation of PE. These findings offer valuable insights for guiding future studies on this concern.

Exposure to cadmium and head and neck cancers: a meta-analysis of observational studies

Cadmium (Cd) is a widespread environmental pollutant. A number of observational studies have reported that Cd might be a cause of nasopharyngeal (NPC), pharyngeal (PC), or laryngeal cancers (LC). In this study evidence about the relation of Cd and NPC, PC, and LC has been summarized. A literature review was conducted until 20 June 2020 in PubMed, Ovid, Scopus, Web of Science and Google scholar databases to investigate the epidemiologic evidence for the relation between cadmium exposure and cancers of the nasopharynx, pharynx, and larynx. Ten articles were selected after careful screening of retrieved studies. All of these studies obtained a Newcastle-Ottawa Scale (NOS) quality score from 6 to 8. Due to high heterogeneity, in all analyses, random effect was used. The pooled results showed that cadmium levels in NPC (standard mean difference (SMD=0.55; 95% CI=0.20, 0.89; p=0.002) and PC (SMD=9.79; 95% CI=0.62, 18.96; p=0.036) patients/tissues were significantly higher than their controls. But cadmium levels were not significantly different between LC cases/tissues and their controls. (SMD=-0.05; 95% CI=-0.99, 0.89; p=0.921). Exposure to cadmium is likely to cause nasopharyngeal and pharyngeal cancer.

Association Between Serum Cadmium and Arsenic Levels with Bladder Cancer: A Case-control Study

Background: Bladder cancer is the second most common cancer of the genitourinary system and the eighth cause of cancer death. In addition to known risk factors such as smoking and urinary stones, trace elements are also effective in causing bladder cancer and other cancers. Objectives: This study was conducted to determine the association between bladder cancer and the carcinogens cadmium and arsenic. Methods: This case-control study was conducted on 40 patients with bladder cancer admitted to Shahid Bahonar Hospital and a control group of 40 healthy individuals in Kerman, Iran, in 2018. The serum levels of arsenic and cadmium were measured by atomic absorptiometry. The paired t-test and chi-square tests were employed to assess the difference between cases and controls groups. An unadjusted and 2 multivariable conditional regression models were separately adjusted on sex, family cancer history, residence, occupation, and smoking and were used to estimate odds ratios (OR) and 95% confidence intervals (95% CI) to assess the association between arsenic and cadmium levels and bladder cancer. The statistical software SPSS version 26 and R software version 3.6.3 were used to perform the statistical analyses. Results: The mean cadmium level was 2.99 ± 1.45 and 2.59 ± 0.46 in the case and control groups, respectively, with no statistically significant difference between the groups (P = 0.100). The mean arsenic level was 2.12 ± 1.04 and 1.43 ± 0.73 in the case and control groups, respectively, demonstrating a statistically significant difference between the groups (P = 0.001). Unadjusted and adjusted conditional logistic regression models indicated significant association between arsenic levels and bladder cancer (unadjusted: odds ratio (OR) (95% CI): 0.66 (0.46 - 0.94), P-value = 0.022; adjusted: OR (95% CI): 0.64 (0.44 - 0.92), P-value = 0.018). Conclusions: Overall, cadmium and arsenic levels are higher in patients with bladder cancer, with a statistically significant difference for arsenic. However, these elements are not interrelated and are not related to other factors.

Erythrocytes as a Model for Heavy Metal-Related Vascular Dysfunction: The Protective Effect of Dietary Components

Heavy metals are toxic environmental pollutants associated with severe ecological and human health risks. Among them is mercury (Hg), widespread in air, soil, and water, due to its peculiar geo-biochemical cycle. The clinical consequences of Hg exposure include neurotoxicity and nephrotoxicity. Furthermore, increased risk for cardiovascular diseases is also reported due to a direct effect on cardiovascular tissues, including endothelial cells, recently identified as important targets for the harmful action of heavy metals. In this review, we will discuss the rationale for the potential use of erythrocytes as a surrogate model to study Hg-related toxicity on the cardiovascular system. The toxic effects of Hg on erythrocytes have been amply investigated in the last few years. Among the observed alterations, phosphatidylserine exposure has been proposed as an underlying mechanism responsible for Hg-induced increased proatherogenic and prothrombotic activity of these cells. Furthermore, following Hg-exposure, a decrease in NOS activity has also been reported, with consequent lowering of NO bioavailability, thus impairing endothelial function. An additional mechanism that may induce a decrease in NO availability is the generation of an oxidative microenvironment. Finally, considering that chronic Hg exposure mainly occurs through contaminated foods, the protective effect of dietary components is also discussed.

The role of autophagy in metal-induced urogenital carcinogenesis

Environmental and/or occupational exposure to metals such as Arsenic (As), Cadmium (Cd), and Chromium (Cr) have been shown to induce carcinogenesis in various organs, including the urogenital system. However, the mechanisms responsible for metal-induced carcinogenesis remain elusive. We and others have shown that metals are potent inducers of autophagy, which has been suggested to be an adaptive stress response to allow metal-exposed cells to survive in hostile environments. Albeit few, recent experimental studies have shown that As and Cd promote tumorigenesis via autophagy and that inhibition of autophagic signaling suppressed metal-induced carcinogenesis. In light of the newly emerging role of autophagic involvement in metal-induced carcinogenesis, the present review focuses explicitly on the mechanistic role of autophagy and potential signaling pathways involved in As-, Cd-, and Cr-induced urogenital carcinogenesis.

Bioaccessibility of potentially toxic metals in soil, sediments and tailings from a north Africa phosphate-mining area: Insight into human health risk assessment

The risk assessment of phosphate mining/processing industrial activities on the environment and human health is crucial to properly manage and minimize the risks over time. In this work, we studied the inhalation and dermal bioaccessibility of potentially toxic metals (PTM) in different particle-size fractions of urban soil, sediments and tailings from Gafsa-Metlaoui phosphate mining area, to assess afterwards the non-carcinogenic (NCR) and carcinogenic (CR) risks for the health of local citizens and workers constantly exposed to airborne particulate matter (PM) originating from these sources of contamination. Samples were separated in particle-size fractions by centrifugation and consecutive cycles of sedimentation and decanting. The pseudo-total concentrations and bioaccessible fractions of PTM were extracted by aqua regia and in vitro bioaccessibility tests, respectively. Both sediments and tailings showed higher-than-background concentrations of PTM (mainly Cd, Zn and Cr), with a tendency to accumulate these metals in fine particles (<10 μm). In urban soil, only Cd was above the background concentration. The bioaccessibility of PTM via inhalation was significantly higher in artificial lysosomal fluid (ALF) than in simulated epithelial lung fluid (SELF): basically, Cd was the most bioaccessible metal (relative bioaccessibility up to 80%), followed by the medium-to-high bioaccessible Zn (47%), Pb (46%) and Cu (39%), and the least bioaccessible Cr (16%). In synthetic skin surface liquid (NIHS 96-10), only Cd was bioaccessible at worrying extent (20-44%). On the basis of US.EPA risk assessment, the exposure to PTM bioaccessible fractions or pseudo-total concentrations would not cause serious NCR and CR risks for human health. Significant health risks (Hazard Index >1 and CR > 10^-4), especially for children, can occur if ingestion route is also considered. The findings underline the need for adequate protection of contaminated soil, sediments and mine tailings laying nearby urban agglomerates, to reduce the health risks for inhabitants and workers of Gafsa-Metlaoui mining area.

Correlation between blood levels of cadmium and lead and the expression of microRNA-21 in Egyptian bladder cancer patients

Objective

To investigate the relationship between blood levels of cadmium (Cd) and lead (Pb) and the expression of miRNA-21 among bladder cancer (BC) patients.

Material and methods

The blood concentrations of Cd and Pb in 268 BC patients and 132 controls were determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The blood concentrations of Cd and Pb were interpreted according to the type and stage of the carcinoma. The expression of miRNA-21 was assessed by quantitative reverse transcription polymerase chain reaction in cancerous and adjacent non-cancerous bladder tissues among the patient groups.

Results

The blood concentrations of Cd and Pb were statistically elevated in BC patients compared to those of the controls. This elevation is more prevalent in groups with muscle-invasive bladder cancer (MIBC) than those with non-muscle invasive bladder cancer (NMIBC). Among the BC group, miRNA-21 was upregulated in cancerous tissues relative to adjacent non-cancerous tissues. Moreover, the expression was significantly higher in patients with MIBC compared to those with NMIBC. The expression of miRNA-21 in cancerous tissues was significantly associated with blood concentration of Cd and Pb among BC patients.

Conclusion

There is a relationship between Cd and Pb body burden and the tissue expression of miRNA-21 among BC patients. This indicates the role of miRNA-21 in Cd and Pb induced BC.

lncRNA OTUD6B-AS1 Exacerbates As2O3-Induced Oxidative Damage in Bladder Cancer via miR-6734-5p-Mediated Functional Inhibition of IDH2

Arsenic trioxide (As2O3) is a promising effective chemotherapeutic agent for cancer treatment; however, how and through what molecular mechanisms the oxidative damage of As2O3 is controlled remains poorly understood. Recently, the involvement of dysregulated long noncoding RNA ovarian tumor domain containing 6B antisense RNA1 (lncRNA OTUD6B-AS1) in tumorigenesis is established. Here, for the first time, we characterize the regulation of As2O3 in the oxidative damage against bladder cancer via lncRNA OTUD6B-AS1. As2O3 could activate lncRNA OTUD6B-AS1 transcription in bladder cancer cells, and these findings were validated in a xenograft tumor model. Functional assays showed that lncRNA OTUD6B-AS1 dramatically exacerbated As2O3-mediated oxidative damage by inducing oxidative stress. Mechanistically, As2O3 increased levels of metal-regulatory transcription factor 1 (MTF1), which regulates lncRNA OTUD6B-AS1, in response to oxidative stress. Further, lncRNA OTUD6B-AS1 inhibited mitochondrial NADP+-dependent isocitrate dehydrogenase 2 (IDH2) expression by stabilizing miR-6734-5p, which contributed to cytotoxicity by enhancing oxidative stress. Together, our findings offer new insights into the mechanism of As2O3-induced oxidative damage and identify important factors in the pathway, As2O3/lncRNA OTUD6B-AS1/miR-6734-5p/IDH2, expanding the knowledge of activity of As2O3 as cancer treatment.

A systems toxicology approach to compare the heavy metal mixtures (Pb, As, MeHg) impact in neurodegenerative diseases

Conventional toxicological risk assessment methods mainly working on single chemicals that fail to adequately address the simultaneous exposure and their potential toxicity in humans. We herein investigated the toxic heavy metals lead (Pb), arsenic (As), and methylmercury (MeHg) and their binary mixtures role in neurodegenerative diseases. To characterize the toxicity of metal mixtures at the molecular level, we established a non-animal omics-based organ relevant cell model system. The obtained experimental data was refined by using the statistical and downstream functional analysis. The protein expression information substantiates the previous findings of single metal (Pb, As, and MeHg) induced alterations to mitochondrial dysfunction, oxidative stress, mRNA splicing, and ubiquitin system dysfunction relation to neurodegenerative diseases. The functional downstream analysis of single and binary mixtures protein data is presented in a comparative manner. The heavy metals mixtures' outcome showed significant differences in the protein expression compared to single metals that indicate metal mixtures exposure is more hazardous than single metal exposure. These results suggest that more comprehensive strategies are needed to improve the mixtures risk assessment in the future.

Simultaneous cleanup of Reactive Black 5 and cadmium by a desert soil bacterium

Multi-contaminated industrial wastewaters pose serious environmental risks due to high toxicity and non-biodegradability. The work reported here evaluated the ability of Pseudomonas aeruginosa strain Gb30 isolated from desert soil to simultaneously remove cadmium (Cd) and Reactive Black 5 (RB5), both common contaminants in various industrial effluents. The strain was able to grow normally and decolorize 50 mg L^-1 RB5 within 24 h of incubation in the presence of 0.629 m mol L^-1 of Cd²⁺. In order to evaluate strain performance in RB5 detoxification, a cytotoxicity test using Human Embryonic Kidney cells (HEK293) was used. Cadmium removal from culture media was determined using atomic adsorption. Even in presence of (0.115 + 0.157 + 0.401 + 0.381) m mol L^-1, respectively, of Cr⁶⁺, Cd²⁺, Cu²⁺ and Zn²⁺ in the growth medium, strain Gb30 successfully removed 35% of RB5 and 44%, 36%, 59% and 97%, respectively, of introduced Zn²⁺, Cu²⁺, Cr⁶⁺ and Cd²⁺, simultaneously. In order to understand the mechanism of Cd removal used by P. aeruginosa strain Gb30, biosorption and bioaccumulation abilities were examined. The strain was preferentially biosorbing Cd on the cell surface, as opposed to intracellular bioaccumulation. Microscopic investigations using AFM, SEM and FTIR analysis of the bacterial biomass confirmed the presence of various structural features, which enabled the strain to interact with metal ions. The study suggests that Pseudomonas aeruginosa Gb30 is a potential candidate for bioremediation of textile effluents in the presence of complex dye-metal contamination.

Environmental Health Research in Africa: Important Progress and Promising Opportunities

The World Health Organization in 2016 estimated that over 20% of the global disease burden and deaths were attributed to modifiable environmental factors. However, data clearly characterizing the impact of environmental exposures and health endpoints in African populations is limited. To describe recent progress and identify important research gaps, we reviewed literature on environmental health research in African populations over the last decade, as well as research incorporating both genomic and environmental factors. We queried PubMed for peer-reviewed research articles, reviews, or books examining environmental exposures and health outcomes in human populations in Africa. Searches utilized medical subheading (MeSH) terms for environmental exposure categories listed in the March 2018 US National Report on Human Exposure to Environmental Chemicals, which includes chemicals with worldwide distributions. Our search strategy retrieved 540 relevant publications, with studies evaluating health impacts of ambient air pollution (n=105), indoor air pollution (n = 166), heavy metals (n = 130), pesticides (n = 95), dietary mold (n = 61), indoor mold (n = 9), per- and polyfluoroalkyl substances (PFASs, n = 0), electronic waste (n = 9), environmental phenols (n = 4), flame retardants (n = 8), and phthalates (n = 3), where publications could belong to more than one exposure category. Only 23 publications characterized both environmental and genomic risk factors. Cardiovascular and respiratory health endpoints impacted by air pollution were comparable to observations in other countries. Air pollution exposures unique to Africa and some other resource limited settings were dust and specific occupational exposures. Literature describing harmful health effects of metals, pesticides, and dietary mold represented a context unique to Africa. Studies of exposures to phthalates, PFASs, phenols, and flame retardants were very limited. These results underscore the need for further focus on current and emerging environmental and chemical health risks as well as better integration of genomic and environmental factors in African research studies. Environmental exposures with distinct routes of exposure, unique co-exposures and co-morbidities, combined with the extensive genomic diversity in Africa may lead to the identification of novel mechanisms underlying complex disease and promising potential for translation to global public health.

Specificity of the Metallothionein-1 Response by Cadmium-Exposed Normal Human Urothelial Cells

Occupational and environmental exposure to cadmium is associated with the development of urothelial cancer. The metallothionein (MT) family of genes encodes proteins that sequester metal ions and modulate physiological processes, including zinc homeostasis. Little is known about the selectivity of expression of the different MT isoforms. Here, we examined the effect of cadmium exposure on MT gene and isoform expression by normal human urothelial (NHU) cell cultures. Baseline and cadmium-induced MT gene expression was characterized by next-generation sequencing and RT-PCR; protein expression was assessed by Western blotting using isoform-specific antibodies. Expression of the zinc transporter-1 (SLC30A1) gene was also assessed. NHU cells displayed transcription of MT-2A, but neither MT-3 nor MT-4 genes. Most striking was a highly inducer-specific expression of MT-1 genes, with cadmium inducing transcription of MT-1A, MT-1G, MT-1H, and MT-1M. Whereas MT-1G was also induced by zinc and nickel ions and MT-1H by iron, both MT-1A and MT-1M were highly cadmium-specific, which was confirmed for protein using isoform-specific antibodies. Protein but not transcript endured post-exposure, probably reflecting sequestration. SLC30A1 transcription was also affected by cadmium ion exposure, potentially reflecting perturbation of intracellular zinc homeostasis. We conclude that human urothelium displays a highly inductive profile of MT-1 gene expression, with two isoforms identified as highly specific to cadmium, providing candidate transcript and long-lived protein biomarkers of cadmium exposure.

The crosstalk between trace elements with DNA damage response, repair, and oxidative stress in cancer

DNA damage response (DDR) is a regulatory system responsible for maintaining genome integrity and stability, which can sense and transduce DNA damage signals. The severity of damage appears to determine DDRs, which can include damage repair, cell-cycle arrest, and apoptosis. Furthermore, defective components in DNA damage and repair machinery are an underlying cause for the development and progression of various types of cancers. Increasing evidence indicates that there is an association between trace elements and DDR/repair mechanisms. In fact, trace elements seem to affect mediators of DDR. Besides, it has been revealed that oxidative stress (OS) and trace elements are associated with cancer development. In this review, we discuss the role of some critical trace elements in the risk of cancer. In addition, we provide a brief introduction on DDR and OS in cancer. Finally, we will further review the interactions between some important trace elements including selenium, zinc, chromium, cadmium, and arsenic, and DDR, and OS in cancer.

Response of soil microbial communities to red mud-based stabilizer remediation of cadmium-contaminated farmland

In this work, a field test was conducted to investigate the effects of heavy metal stabilizer addition on brown rice and microbial variables in a cadmium (Cd)-contaminated farmland from April to October in 2016. Compared with the control, red mud-based stabilizer (RMDL) effectively reduced the concentration of Cd in brown rice (with the removal rate of 48.14% in early rice, 20.24 and 47.62% in late rice). The results showed that adding 0.3 kg m^-2 RDML in early rice soil or soil for both early and late rice increased the microbial biomass carbon (MBC), the number of culturable heterotrophic bacteria and fungi, and the catalase activity in soil at different stages of paddy rice growth. Furthermore, there was no notable difference in the diversity of the bacterial species, community composition, and relative abundance at phylum (or class) or operational taxonomic unit (OTU) levels between the control and treatment (RMDL addition) groups. In a word, RMDL could be highly recommended as an effective remediation stabilizer for Cd-contaminated farmland, since its continuous application in paddy soil cultivating two seasons rice soil could effectively decrease the Cd content in brown rice and had no negative impact on soil microorganisms.

Risk assessment of occupational exposure to heavy metal mixtures: a study protocol

Background

Sfax is a very industrialized city located in the southern region of Tunisia where heavy metals (HMs) pollution is now an established matter of fact. The health of its residents mainly those engaged in industrial metals-based activities is under threat. Indeed, such workers are being exposed to a variety of HMs mixtures, and this exposure has cumulative properties. Whereas current HMs exposure assessment is mainly carried out using direct air monitoring approaches, the present study aims to assess health risks associated with chronic occupational exposure to HMs in industry, using a modeling approach that will be validated later on.

Methods

To this end, two questionnaires were used. The first was an identification/descriptive questionnaire aimed at identifying, for each company: the specific activities, materials used, manufactured products and number of employees exposed. The second related to the job-task of the exposed persons, workplace characteristics (dimensions, ventilation, etc.), type of metals and emission configuration in space and time.

Indoor air HMs concentrations were predicted, based on the mathematical models generally used to estimate occupational exposure to volatile substances (such as solvents).

Later on, and in order to validate the adopted model, air monitoring will be carried out, as well as some biological monitoring aimed at assessing HMs excretion in the urine of workers volunteering to participate.

Lastly, an interaction-based hazard index HI_int and a decision support tool will be used to predict the cumulative risk assessment for HMs mixtures.

Discussion

One hundred sixty-one persons working in the 5 participating companies have been identified. Of these, 110 are directly engaged with HMs in the course of the manufacturing process. This model-based prediction of occupational exposure represents an alternative tool that is both time-saving and cost-effective in comparison with direct air monitoring approaches. Following validation of the different models according to job processes, via comparison with direct measurements and exploration of correlations with biological monitoring, these estimates will allow a cumulative risk characterization.

Polymorphisms in XRCC1, ERCC2, and ERCC3 DNA repair genes, CYP1A1 xenobiotic metabolism gene, and tobacco are associated with bladder cancer susceptibility in Tunisian population

Other than the established environmental risk factors associated with bladder cancer (BC), little is known about the genetic variations determining the individual susceptibility of this complex disease. This study aimed to investigate the relationship of BC with environmental agents and polymorphisms in XRCC1, ERCC2, and ERCC3 DNA repair genes and CYP1A1, CYP2D6, NAT1, and NAT2 xenobiotic metabolism genes through a hospital-based case-control study in Tunisia. The selection of the single nucleotide polymorphisms (SNPs) (rs25487, rs 13181, rs415407, rs446421, rs1058172, rs4921880, and rs1208) was performed using the dbSNP database. DNA genotyping was determined by PCR-RFLP after DNA extraction from whole blood. The risks of BC associated with every polymorphism as well as the studied environmental factors were estimated by multivariate-adjusted logistic regression using R software. In addition, gene-gene interactions were analyzed using generalized multifactor dimensionality reduction (GMDR) methods. Results showed that tobacco smoking and chewing parameters were significantly associated with BC risk. Single-gene variant analysis showed significant associations of the TT genotype of CYP1A1 and the rare GG genotype of ERCC2 with bladder cancer susceptibility (OR = 1.34, 95% CI 1.22-1.40, P < 0.0001). According to GMDR analysis, our findings indicated a significant association between BC and gene-gene interaction among the CYP1A1, ERCC3, and XRCC1. The present results suggest a potential role of XRCC1, ERCC2, ERCC3, and CYP1A1 besides tobacco intake in susceptibility to BC.

Cancer risk in waterpipe smokers: a meta-analysis

Objectives

To quantify by meta-analysis the relationship between waterpipe smoking and cancer, including cancer of the head and neck, esophagus, stomach, lung and bladder.

Methods

We performed a systematic literature search to identify relevant studies, scored their quality, used fixed and random-effect models to estimate summary relative risks (SRR), evaluated heterogeneity and publication bias.

Results

We retrieved information from 28 published reports. Considering only highquality studies, waterpipe smoking was associated with increased risk of head and neck cancer (SRR 2.97; 95 % CI 2.26–3.90), esophageal cancer (1.84; 1.42–2.38) and lung cancer (2.22; 1.24–3.97), with no evidence of heterogeneity or publication bias. Increased risk was also observed for stomach and bladder cancer but based mainly on poor-quality studies. For colorectum, liver and for all sites combined risk estimates were elevated, but there were insufficient reports to perform a meta-analysis.

Conclusions

Contrary to the perception of the relative safety of waterpipe smoking, this meta-analysis provides quantitative estimates of its association with cancers of the head and neck, esophagus and lung. The scarcity and limited quality of available reports point out the need for larger carefully designed studies in well-defined populations.

A review of toxicity and mechanisms of individual and mixtures of heavy metals in the environment

The rational for the study was to review the literature on the toxicity and corresponding mechanisms associated with lead (Pb), mercury (Hg), cadmium (Cd), and arsenic (As), individually and as mixtures, in the environment. Heavy metals are ubiquitous and generally persist in the environment, enabling them to biomagnify in the food chain. Living systems most often interact with a cocktail of heavy metals in the environment. Heavy metal exposure to biological systems may lead to oxidation stress which may induce DNA damage, protein modification, lipid peroxidation, and others. In this review, the major mechanism associated with toxicities of individual metals was the generation of reactive oxygen species (ROS). Additionally, toxicities were expressed through depletion of glutathione and bonding to sulfhydryl groups of proteins. Interestingly, a metal like Pb becomes toxic to organisms through the depletion of antioxidants while Cd indirectly generates ROS by its ability to replace iron and copper. ROS generated through exposure to arsenic were associated with many modes of action, and heavy metal mixtures were found to have varied effects on organisms. Many models based on concentration addition (CA) and independent action (IA) have been introduced to help predict toxicities and mechanisms associated with metal mixtures. An integrated model which combines CA and IA was further proposed for evaluating toxicities of non-interactive mixtures. In cases where there are molecular interactions, the toxicogenomic approach was used to predict toxicities. The high-throughput toxicogenomics combines studies in genetics, genome-scale expression, cell and tissue expression, metabolite profiling, and bioinformatics.

Association between blood arsenic levels and nasal polyposis disease risk in the Tunisian population

Although the pathophysiology underlying nasal polyposis (NP) formation is not fully understood, systemic, local, and environmental factors appear to contribute to NP disease development. This study aimed to explore the relationship between metal blood levels and NP risk. To the best of our knowledge, the current research represents the first scientific contribution reporting levels of Cr and As in blood of NP patients. In this context, 90 NP patients and 171 controls were recruited and blood samples were analyzed to determine the concentrations of As and Cr. Metal blood levels of As in patients (2.1 μg/L) were significantly higher than those of controls (1.2 μg/L). However, no significant difference in blood Cr levels was found between cases and controls. Arsenic blood levels of cigarette smokers were significantly higher than those of non-smokers. Environmental exposure and shisha consumption presented the most significant association with NP disease (OR = 10.1 and 14.1, respectively). High levels of blood As were significantly associated with NP disease (OR = 2.1). Cr blood levels were found to be associated with the four stages of polyps in both nasal cavities. This study found a strong association between nasal polyposis disease and As blood levels. These findings merit further investigation.

Toxicity assessment due to sub-chronic exposure to individual and mixtures of four toxic heavy metals

Humans are exposed to a cocktail of heavy metal toxicants in the environment. Though heavy metals are deleterious, there is a paucity of information on toxicity of low dose mixtures. In this study, lead (Pb) (0.01mg/L), mercury (Hg) (0.001mg/L), cadmium (Cd) (0.005mg/L) and arsenic (As) (0.01mg/L) were administered individually and as mixtures to 10 groups of 40 three-week old mice (20 males and 20 females), for 120 days. The study established that low dose exposures induced toxicity to the brain, liver, and kidney of mice. Metal mixtures showed higher toxicities compared to individual metals, as exposure to low dose Pb+Hg+Cd reduced brain weight and induced structural lesions, such as neuronal degeneration in 30-days. Pb+Hg+Cd and Pb+Hg+As+Cd exposure induced hepatocellular injury to mice evidenced by decreased antioxidant activities with marginal increases in MDA. These were accentuated by increases in ALT, AST and ALP. Interactions in metal mixtures were basically synergistic in nature and exposure to Pb+Hg+As+Cd induced renal tubular necrosis in kidneys of mice. This study underlines the importance of elucidating the toxicity of low dose metal mixtures so as to protect public health.

Comparative Tissue Proteomics of Microdissected Specimens Reveals Novel Candidate Biomarkers of Bladder Cancer

More than 380,000 new cases of bladder cancer are diagnosed worldwide, accounting for ∼150,200 deaths each year. To discover potential biomarkers of bladder cancer, we employed a strategy combining laser microdissection, isobaric tags for relative and absolute quantitation labeling, and liquid chromatography-tandem MS (LC-MS/MS) analysis to profile proteomic changes in fresh-frozen bladder tumor specimens. Cellular proteins from four pairs of surgically resected primary bladder cancer tumor and adjacent nontumorous tissue were extracted for use in two batches of isobaric tags for relative and absolute quantitation experiments, which identified a total of 3220 proteins. A DAVID (database for annotation, visualization and integrated discovery) analysis of dysregulated proteins revealed that the three top-ranking biological processes were extracellular matrix organization, extracellular structure organization, and oxidation-reduction. Biological processes including response to organic substances, response to metal ions, and response to inorganic substances were highlighted by up-expressed proteins in bladder cancer. Seven differentially expressed proteins were selected as potential bladder cancer biomarkers for further verification. Immunohistochemical analyses showed significantly elevated levels of three proteins-SLC3A2, STMN1, and TAGLN2-in tumor cells compared with noncancerous bladder epithelial cells, and suggested that TAGLN2 could be a useful tumor tissue marker for diagnosis (AUC = 0.999) and evaluating lymph node metastasis in bladder cancer patients. ELISA results revealed significantly increased urinary levels of both STMN1 and TAGLN2 in bladder cancer subgroups compared with control groups. In comparisons with age-matched hernia urine specimens, urinary TAGLN2 in bladder cancer samples showed the largest fold change (7.13-fold), with an area-under-the-curve value of 0.70 (p < 0.001, n = 205). Overall, TAGLN2 showed the most significant overexpression in individual bladder cancer tissues and urine specimens, and thus represents a potential biomarker for noninvasive screening for bladder cancer. Our findings highlight the value of bladder tissue proteome in providing valuable information for future validation studies of potential biomarkers in urothelial carcinoma.

Reference values of cadmium, arsenic and manganese in blood and factors associated with exposure levels among adult population of Rio Branco, Acre, Brazil

This study aimed to investigate the distribution and factors influencing blood levels of Cadmium (Cd), Arsenic (As), and Manganese (Mn), and to determine their reference values in a sample of blood donors residing in Rio Branco, capital city of Acre State, Brazil. Blood samples were collected from all blood donors attending the Central Hemotherapic Unit in Rio Branco between 2010 and 2011. Among these, 1183 donors (98.9%) answered to a questionnaire on sociodemographic and lifestyle factors. Blood metal concentrations were determined by atomic spectrometry. Association between Cd, As and Mn levels and donors' characteristics was examined by linear regression analysis. Reference values were estimated as the upper limit of the 95% confidence interval of the 95th percentile of metal levels. References values were 0.87 μg L(-1) for Cd, 9.87 μg L(-1) for As, and 29.32 μg L(-1) for Mn. Reference values of Cd and As in smokers were 2.66 and 10.86 μg L(-1), respectively. Factors contributing to increase Cd levels were smoking, ethnicity (non-white), and lower education, whereas drinking tea and non-bottled water were associated with lower Cd. Lower levels of As were associated with higher household income, living near industrial facilities, working in a glass factory, a compost plant or in metal mining activities. Risk factors for Mn exposure were not identified. In general, blood Cd concentrations were in the range of exposure levels reported for other people from the general population, whereas levels of As and Mn were higher than in other non-occupationally exposed populations elsewhere.

Cadmium and nickel in blood of Tunisian population and risk of nasosinusal polyposis disease

Nasosinusal polyposis (NSP) is a chronic inflammatory disease of the nasal mucosa. Although the pathophysiology underlying NSP formation is not fully understood, environmental factors appear to be contributed the development of this disease. A case-control study of Tunisian patients was examined to assess the levels of cadmium (Cd) and nickel (Ni) in blood and reparse the association between the exposure to these metals and the risk of nasosinusal polyposis disease. Mean blood levels of Cd in patients (2.2 ± 12.8 μg/L) were significantly higher than those of controls (0.5 ± 0.7 μg/L). Levels of blood Cd were positively correlated with tobacco smoking and chewing among controls. The Cd and Ni concentrations among control (p = 0.001) and patient (p = 0.018) tobacco consumers (smoking, chewing, and shisha) were significantly higher than those nonconsumers. Additionally, Ni blood levels of patient and control smokers were significantly higher than those of nonsmokers. Cd levels in blood samples of NSP patients occupationally exposed for more than 14 years were eight times higher than that of nonexposed. Drinking water was also found to be incriminated as exposure sources. Among risk factors, shisha consumption, environmental exposure, and occupational exposure presented the most significant association with NSP disease (odds ratio (OR) = 14.1, 10.1, and 1.7, respectively). High levels of blood Cd (OR = 3.5) were strongly associated with NSP disease (p = 0.027). Ni blood levels were shown to be associated with the four stages of polyps in both nasal cavities (right and left) (p < 0.05). This investigation suggested a potential role of toxic metals in the mechanism of NSP disease development. Exposure assessment investigations encompassing a wider population are needed.

Interaction of four low dose toxic metals with essential metals in brain, liver and kidneys of mice on sub-chronic exposure

This study reports on interactions between low dose toxic and essential metals. Low dose Pb (0.01mg/L), Hg (0.001mg/L), Cd (0.005mg/L) and As (0.01mg/L) were administered singly to four groups of 3-week old mice for 120 days. Pb exposure increased brain Mg and Cu by 55.5% and 266%, respectively. Increased brain Mg resulted from metabolic activity of brain to combat insults, whiles Cu overload was due to alteration and dysfunction of CTR1 and ATP7A molecules. Reduction of liver Ca by 56.0% and 31.6% (on exposure to As and Cd, respectively) resulted from inhibition of Ca-dependent ATPase in nuclei and endoplasmic reticulum through binding with thiol groups. Decreased kidney Mg, Ca and Fe was due to uptake of complexes of As and Cd with thiol groups from proximal tubular lumen. At considerably low doses, the study establishes that, toxic metals disturb the homeostasis of essential metals.

Cytogenetic damage in the oral mucosa cells of bladder cancer patients exposed to tobacco in Southern Tunisia

Bladder cancer was associated to exposure to several pollutants which can be absorbed, inhaled, or possibly ingested. We analyzed the frequency of micronuclei (MNC) and binucleated cells (BNC) in exfoliated cells of the oral mucosa of 24 bladder cancer (BC) patients and 48 controls residing in Southern Tunisia. An assessment was carried out on the incidence of MNC and BNC in 1,000 cells per individual. The data were analyzed with SPSS, using the chi-square and the Mann-Whitney U test, α = 0.05. The frequency of MN cells in BC cases was 2.5-fold higher, than in the control group (P < 0.001), while the difference for BNC between both groups was not significant. The smoking habits, age, and gender significantly influenced the MN but not the BNC alterations. The results of our study showed significantly increased frequencies of MN but not of BNC in exfoliated oral cells of BC patients associated with the smoking status, sex, and age. This study provides preliminary evidence that the frequency of MN in oral mucosa could be a predictive biomarker for cancers in parts of the body other than the upper aerodigestive tract, such as BC. Further scrupulous investigations are certainly warranted in order to implement this assay as a routine test in the planning and validation of cancer surveillance and prevention programs.

Biomonitoring of cadmium, chromium, nickel and arsenic in general population living near mining and active industrial areas in Southern Tunisia

The human health impact of the historic and current mining and industrial activities in Tunisia is not known. This study assessed the exposure to metals in the population of Southern Tunisia, using biomonitoring. The aim of this pilot study was to evaluate metal exposure on 350 participants living near mining and active industrial areas in the South of Tunisia. Blood specimens were analyzed for metals (Cd, Cr, As, and Ni) by Atomic Absorption Spectrometer equipped with Zeeman background correction and AS-800 auto sampler by graphite furnace and graphite tubes with integrated L'vov platform. The sample population was classified according to different age groups, sex, smoking habit, sea food and water drinking consumption, occupational exposure, amalgam fillings and place of residence. The blood As, Cd, Cr and Ni values expressed as mean ± SD were 1.56 ± 2.49, 0.74 ± 1.15, 35.04 ± 26.02 and 30.56 ± 29.96 μg/l, respectively. Blood Cd and Ni levels in smokers were 2 and 1.2 times, respectively, higher than in non-smokers. Blood Cd levels increase significantly with age (p = 0.002). As, Cd and Ni were significantly correlated with gender and age (p < 0.05). Cd level in blood samples of subjects occupationally exposed was 1.3 times higher than that of non-exposed. Blood metals were not significantly affected by amalgam fillings, place of living and sea food and drinking water consumption. This first biomonitoring study of metal exposure in the South of Tunisia reveals a substantial exposure to several metals. The pathways of exposure and health significance of these findings need to be further investigated.

Metal-mediated DNA damage and cell death: mechanisms, detection methods, and cellular consequences

Metal ions cause various types of DNA damage by multiple mechanisms, and this damage is a primary cause of cell death and disease.

New insight into molecular interaction of heavy metal pollutant--cadmium(II) with human serum albumin

Cadmium (Cd) is an extremely toxic metal commonly found as an environmental contaminant from industrial and agricultural sources, posing severe risks to human health. In this study, the binding mechanism of Cd(II)-human serum albumin (HSA) complex and the effect of Cd(II) on the conformational stability and structural state of HSA were comprehensively investigated through a series of efficient and appropriate methods. X-ray photoelectron spectroscopy accurately described the microenvironmental changes around protein C, N, and O atoms in the presence of Cd(II). Fluorescence results indicated that the probable mechanism of Cd(II)-HSA interaction is a static quenching process. Fourier transform infrared spectroscopy and dynamic light scattering showed Cd(II) complexation altered HSA conformation and the microenvironments of Trp and Tyr residues, accompanied by the size increases of HSA aggregates. This research will be helpful for understanding the toxic effects of Cd(II) on protein function in vivo.