Non-renal effects and the risk assessment of environmental cadmium exposure

Prolonged Cadmium Exposure and Osteoclastogenesis: A Mechanistic Mouse and in Vitro Study

BACKGROUND

Cadmium (Cd) is a highly toxic and widespread environmental oxidative stressor that causes a myriad of health problems, including osteoporosis and bone damage. Although nuclear factor erythroid 2-related factor 2 (NRF2) and its Cap 'n' Collar and basic region Leucine Zipper (CNC-bZIP) family member nuclear factor erythroid 2-related factor 1 (NRF1) coordinate various stress responses by regulating the transcription of a variety of antioxidant and cytoprotective genes, they play distinct roles in bone metabolism and remodeling. However, the precise roles of both transcription factors in bone loss induced by prolonged Cd exposure remain unclear.

OBJECTIVES

We aimed to understand the molecular mechanisms underlying Cd-induced bone loss, focusing mainly on the roles of NRF2 and NRF1 in osteoclastogenesis provoked by Cd.

METHODS

Male wild-type (WT), global Nrf2-knockout (N r f 2 - / - ) and myeloid-specific Nrf2 knockout [Nrf2(M)-KO] mice were administered Cd (50 or 100  ppm ) via drinking water for 8 or 16 wk, followed by micro-computed tomography, histological analyses, and plasma biochemical testing. Osteoclastogenesis was evaluated using bone marrow-derived osteoclast progenitor cells (BM-OPCs) and RAW 264.7 cells in the presence of Cd (10 or 20  nM ) with a combination of genetic and chemical modulations targeting NRF2 and NRF1.

RESULTS

Compared with relevant control mice, global N r f 2 - / - or Nrf2(M)-KO mice showed exacerbated bone loss and augmented osteoclast activity following exposure to 100  ppm Cd in drinking water for up to 16 wk. In vitro osteoclastogenic analyses suggested that Nrf2-deficient BM-OPCs and RAW 264.7 cells responded more robustly to low levels of Cd (up to 20  nM ) with regard to osteoclast differentiation compared with WT cells. Further mechanistic studies supported a compensatory up-regulation of long isoform of NRF1 (L-NRF1) and subsequent induction of nuclear factor of activated T cells, cytoplasmic, calcineurin dependent 1 (NFATc1) as the key molecular events in the Nrf2 deficiency-worsened and Cd-provoked osteoclastogenesis. L-Nrf1 silenced (via lentiviral means) Nrf2-knockdown (KD) RAW cells exposed to Cd showed dramatically different NFATc1 and subsequent osteoclastogenesis outcomes compared with the cells of Nrf2-KD alone exposed to Cd, suggesting a mitigating effect of the Nrf1 silencing. In addition, suppression of reactive oxygen species by exogenous antioxidants N -acetyl-l-cysteine (2  mM ) and mitoquinone mesylate (MitoQ; 0.2 μ M ) mitigated the L-NRF1-associated effects on NFATc1-driven osteoclastogenesis outcomes in Cd-exposed Nrf2-KD cells.

CONCLUSIONS

This in vivo and in vitro study supported the authors' hypothesis that Cd exposure caused bone loss, in which NRF2 and L-NRF1 responded to Cd and osteoclastogenic stimuli in a cooperative, but contradictive, manner to coordinate Nfatc1 expression, osteoclastogenesis and thus bone homeostasis. Our study suggests a novel strategy targeting NRF2 and L-NRF1 to prevent and treat the bone toxicity of Cd. https://doi.org/10.1289/EHP13849.

Low dose cadmium inhibits syndecan-4 expression in glycocalyx of glomerular endothelial cells

Cadmium (Cd) is one of the most polluting heavy metal in the environment. Cd exposure has been elucidated to cause dysfunction of the glomerular filtration barrier (GFB). However, the underlying mechanism remains unclear. C57BL/6J male mice were administered with 2.28 mg/kg cadmium chloride (CdCl2) dissolved in distilled water by oral gavage for 14 days. The expression of SDC4 in the kidney tissues was detected. Human renal glomerular endothelial cells (HRGECs) were exposed to varying concentrations of CdCl2 for 24 h. The mRNA levels of SDC4, along with matrix metalloproteinase (MMP)-2 and 9, were analyzed by quantitative PCR. Additionally, the protein expression levels of SDC4, MMP-2/9, and both total and phosphorylated forms of Smad2/3 (P-Smad2/3) were detected by western blot. The extravasation rate of fluorescein isothiocyanate-dextran through the Transwell was used to evaluate the permeability of HRGECs. SB431542 was used as an inhibitor of transforming growth factor (TGF)-β signaling pathway to further investigate the role of TGF-β. Cd reduced SDC4 expression in both mouse kidney tissues and HRGECs. In addition, Cd exposure increased permeability and upregulated P-Smad2/3 levels in HRGECs. SB431542 treatment inhibited the phosphorylation of Smad2/3, Cd-induced SDC4 downregulation, and hyperpermeability. MMP-2/9 levels increased by Cd exposure was also blocked by SB431542, demonstrating the involvement of TGF-β/Smad pathway in low-dose Cd-induced SDC4 reduction in HRGECs. Given that SDC4 is an essential component of glycocalyx, protection or repair of endothelial glycocalyx is a potential strategy for preventing or treating kidney diseases associated with environmental Cd exposure.

Environmental cadmium inhibits testicular testosterone synthesis via Parkin-dependent MFN1 degradation

Low testosterone (T) levels are associated with many common diseases, such as obesity, male infertility, depression, and cardiovascular disease. It is well known that environmental cadmium (Cd) exposure can induce T decline, but the exact mechanism remains unclear. We established a murine model in which Cd exposure induced testicular T decline. Based on the model, we found Cd caused mitochondrial fusion disorder and Parkin mitochondrial translocation in mouse testes. MFN1 overexpression confirmed that MFN1-dependent mitochondrial fusion disorder mediated the Cd-induced T synthesis suppression in Leydig cells. Further data confirmed Cd induced the decrease of MFN1 protein by increasing ubiquitin degradation. Testicular specific Parkin knockdown confirmed Cd induced the ubiquitin-dependent degradation of MFN1 protein through promoting Parkin mitochondrial translocation in mouse testes. Expectedly, testicular specific Parkin knockdown also mitigated testicular T decline. Mito-TEMPO, a targeted inhibitor for mitochondrial reactive oxygen species (mtROS), alleviated Cd-caused Parkin mitochondrial translocation and mitochondrial fusion disorder. As above, Parkin mitochondrial translocation induced mitochondrial fusion disorder and the following T synthesis repression in Cd-exposed Leydig cells. Collectively, our study elucidates a novel mechanism through which Cd induces T decline and provides a new treatment strategy for patients with androgen disorders.

Foliar Application of Nanoparticles Reduced Cadmium Content in Wheat (Triticum aestivum L.) Grains via Long-Distance "Leaf-Root-Microorganism" Regulation

Foliar application of beneficial nanoparticles (NPs) exhibits potential in reducing cadmium (Cd) uptake in crops, necessitating a systematic understanding of their leaf-root-microorganism process for sustainable development of efficient nano-enabled agrochemicals. Herein, wheat grown in Cd-contaminated soil (5.23 mg/kg) was sprayed with different rates of four commonly used NPs, including nano selenium (SeNPs)/silica (SiO2NPs)/zinc oxide/manganese dioxide. SeNPs and SiO2NPs most effectively reduced the Cd concentration in wheat grains. Compared to the control, Cd concentration in grains was significantly decreased by 35.0 and 33.3% by applying 0.96 mg/plant SeNPs and 2.4 mg/plant SiO2NPs, and the grain yield was significantly increased by 33.9% with SeNPs application. Down-regulated gene expression of Cd transport proteins (TaNramp5 and TaLCT1) and up-regulated gene expression of vacuolar Cd fixation proteins (TaHMA3 and TaTM20) were observed with foliar SeNPs and SiO2NPs use. SeNPs increased the levels of leaf antioxidant metabolites. Additionally, foliar spray of SeNPs resulted in lower abundances of rhizosphere organic acids and reduced Cd bioavailability in rhizosphere soil, and soil microorganisms related to carbon and nitrogen (Solirubrobacter and Pedomicrobium) were promoted. Our findings underscore the potential of the foliar application of SeNPs and SiO2NPs as a plant and rhizosphere soil metabolism-regulating approach to reduce Cd accumulation in wheat grains.

PBA alleviates cadmium-induced mouse spermatogonia apoptosis by suppressing endoplasmic reticulum stress

OBJECTIVE

Endoplasmic reticulum (ER) stress mediates Cd-caused germ cell apoptosis in testis. The effects of 4-phenylbutyric acid (PBA), a classical chaperone, were investigated on Cd-induced apoptosis in mouse GC-1 spermatogonia cells.

METHODS

The cells were pretreated with PBA before Cd exposure. TUNEL and flow cytometry assays were applied to determine apoptosis. Some key biomarkers of ER stress were analyzed using RT-PCR and western blot.

RESULTS

as expected, the apoptotic cells exposed to Cd apparently increased. The mRNA and protein expression levels of GRP78 and ATF6α, were elevated in the Cd groups. Additional experiments displayed that Cd notably increased IRE1α and JNK phosphorylation, and upregulated XBP-1 mRNA and protein expression. Moreover, p-eIF2α and CHOP expressions were clearly elevated in the Cd groups. Interestingly, PBA almost completely inhibited ER stress and protected spermatogonia against apoptosis induced by Cd.

CONCLUSION

PBA alleviated Cd-induced ER stress and spermatogonia apoptosis, and may have the therapeutic role in Cd-induced male reproductive toxicity.

Total contents, fractionation and bioaccessibility of nine heavy metals in household dust from 14 cities in China

The potential health risk caused by long-term exposure to heavy metals in household dust is not only depended on their total content, but also bioaccessibility. In this study, twenty-one dust samples were collected from residential buildings, schools, and laboratories in 14 provincial-capital/industrial cities of China, aiming to evaluate the total contents, fractionation, bioaccessibility and health risks of nine heavy metals (As, Cd, Cr, Ni, Pb, Mn, Zn, Fe, and Cu). Results showed that the highest levels of Cd, Cr, Ni and Zn were found in laboratory dust, As, Pb and Mn in school dust, and Fe and Cu in residential dust, indicating different source profiles of the heavy metals. The mean bioaccessibility of the heavy metals across all samples as evaluated using SBRC (Solubility Bioavailability Research Consortium), IVG (In Vitro Gastrointestinal), and PBET (Physiologically Based Extraction Test) assays was 58.4%, 32.4% and 17.2% in gastric phase (GP), and 24.9%, 21.9% and 9.39% in intestinal phase (IP), respectively. Cadmium had the highest content in the fractions of E1+C2 (43.7%), as determined by sequential extraction, and Pb, Mn, and Zn had a higher content in E1+C2+F3 (64.2%, 67.2%, 78.8%), resulting in a higher bioaccessibility of these heavy metals than others. Moreover, the bioaccessibility of most heavy metals was inversely related to dust pH (R = -0.18 in GP; -0.18 in IP; P < 0.01) and particle size, while a positive correlation was observed with total organic carbon (R = 0.40 in GP; 0.38 in IP; P < 0.01). The exposure risk calculated by the highest bioaccessibility was generally lower than that calculated by the total content. However, Pb in one school dust sample had an unacceptable carcinogenic risk (adult risk = 1.19 × 10-4; child risk = 1.08 × 10-4). This study suggests that bioaccessibility of heavy metals in household dust is likely related to geochemical fractions and physical/chemical properties. Further research is needed to explore the sources of bioaccessible heavy metals in household dust.

Metals and arsenic distribution in stray dogs' tissues around a lead-zinc mine in Kabwe, Zambia

Metal contamination poses a threat to human, animal, and environmental health. The purpose of the current study was to assess the accumulation of toxic and trace metal concentrations in tissues of stray dogs in Kabwe, a town known for lead pollution due to a long history of lead and zinc mining. Brain, spleen, heart, stomach, stomach content, small intestine, kidney, liver, and bone samples were collected from 29 stray dogs (14 from locations within 3 km of the mine and 15 from sites 7 km away from the mine) after necropsy. Inductively coupled plasma mass spectrometry was used to analyze toxic metals, arsenic (As), cadmium (Cd), and lead (Pb), and trace elements, copper (Cu) and zinc (Zn). The lungs (0.117 ± 0.114 mg/kg dry weight), kidney (7.515 ± 8.830 mg/kg dry weight), and bone (41.68 ± 66.83 mg/kg dry weight) were found to have the highest concentrations of As, Cd, and Pb, respectively. In contrast, higher Cu and Zn concentrations were measured in the liver than in other tissues. In all tissues analyzed, tissues sampled from dogs near the mine had significantly higher mean concentrations of Cd and Pb than dogs far away. Neither sex nor age-related differences were observed in the distribution of metals in most tissues. There were significant associations among toxic (Pb and Cd) and trace metals (Cu and Zn). In the kidney, Cd positively correlated with Pb (ρ = 0.534) and Zn (ρ = 0.600), whereas in the liver, Cu correlated with Zn (ρ = 0.565). The current study's findings suggest that environmental pollution is still a problem in Kabwe, and environmental remediation is needed to address the pollution.

A protocol for the prospective study of urinary cadmium with risk of fracture, bone loss, and muscle loss

Cadmium (Cd) is a heavy metal and natural element found in soil and crops with increasing concentrations linked to phosphate fertilizers and sewage sludge applied to crop lands. A large fraction of older US men and woman have documented Cd exposure. Cd exposure has proven health concerns such as risk of lung cancer from inhalation and impaired renal function; however, growing evidence suggests it also influences bone and muscle health. Given that low levels of Cd could affect bone and muscle, we have designed prospective studies using the two largest and most detailed US studies of bone health in older men and women: the Osteoporotic Fractures in Men Study and the Study of Osteoporotic Fractures. We are investigating the association of urinary cadmium (U-Cd), as a surrogate for long-term Cd exposure, with bone and muscle health. Building off suggestive evidence from mechanistic and cross-sectional studies, this will be the first well-powered prospective study of incident fracture outcomes, bone loss, and muscle loss in relation to U-Cd, an established biomarker of long-term Cd exposure. The following is a proposed protocol for the intended study; if successful, the proposed studies could be influential in directing future US policy to decrease Cd exposure in the US population similar to recent policies adopted by the European Union to limit Cd in fertilizers.

Blood cadmium is associated with increased fracture risk in never-smokers - results from a case-control study using data from the Malmö Diet and Cancer cohort

BACKGROUND

Several studies have shown associations between cadmium (Cd) exposure and an increased risk of fractures. However, the size of the risk is still unclear and proper adjustment for smoking is a challenge. The aim of this study was to quantify the association between dietary cadmium measured in blood and fracture risk in the general Swedish population through a large population-based case-control study in never-smokers.

METHODS

The study included 2113 incident cases with osteoporosis-related fractures and the same number of age- and sex-matched controls in never-smokers from the Swedish population-based Malmö Diet and Cancer study cohort. Cd in blood (B-Cd) was analyzed at baseline (1991-1996). Incident osteoporosis-related fractures (of the hip, distal radius, and proximal humerus) up to the year 2014 were identified using the National Patient Register. Associations between B-Cd and fractures were analyzed using logistic regression.

RESULTS

Median B-Cd was 0.22 μg/L (P25 = 0.16, P75 = 0.31) among 2103 cases and 0.21 (P25 = 0.15, P75 = 0.30) among 2105 controls. The risk of fracture was significantly increased (OR 1.58; 95 % confidence interval 1.08-2.31, per μg/L of B-Cd), after adjustment for age, sex, BMI, physical activity, and fiber consumption. In analyses by cadmium quartiles, the OR increased monotonically and was significant in the highest quartile of B-Cd (for B-Cd > 0.31 versus B-Cd < 0.15 μg/L; OR 1.21; 95 % confidence interval 1.01-1.45).

CONCLUSION

Even modestly increased blood cadmium in never-smokers is associated with increased risk of incident osteoporosis-related fractures.

Sex-dependent effects of rice cadmium exposure on body weight, gut microflora, and kidney metabolomics based on a mouse model

Consumption of cadmium (Cd) contaminated rice is the main dietary source of Cd exposure and toxicity. To protect humans from Cd toxicity, it is pivotal to fully understand the sex-dependent toxicity of subchronic rice-Cd exposure. However, the sex-dependent effects of subchronic rice-Cd exposure on body weight gain, gut microflora, and kidney metabolomics are still unclear. In this study, a Cd-free and a Cd-contaminated rice (0.005 and 0.74 mg Cd kg-1) were fed to both female and male mice for one month, with changes in body weight gain, Cd accumulation in tissue, bone mineral concentration, expression of intestinal channels involving in Cd and calcium (Ca) absorption, gut microbiota, and kidney metabolites assessed for both genders. Results showed that female mice had normal body weight gain after rice-Cd exposure, while body weight of male mice was decreased from 19.8 to 17.5 g over the one-month consumption of the Cd-contaminated rice (0.74 mg kg-1), suggesting specific toxicity on growth of male mice. Rice-Cd exposure had limited effects on gut microbiota for both genders. However, higher Cd accumulation in liver and femur was observed in male mice than in females, which may be due to higher intestinal expression of Ca channels involving in intestinal Cd absorption in male mice with rice-Cd exposure. Greater risk of osteoporosis was also observed in male mice. In addition, kidney metabolomic profiling showed special disruption of adrenocortical hormone homeostasis for male mice with rice-Cd exposure. Particularly, expression of cortisol in kidneys of male mice was elevated 37.1-fold with rice-Cd exposure, likely resulting in Cushing's syndrome and contributing to growth retardation. This study advances our understanding of the sex-dependent toxicity of rice-Cd exposure, and highlights the priority of protecting males from the adrenocortical hormone disrupting effects of rice-Cd exposure.

Influence of dietary patterns on urinary excretion of cadmium in an Italian population: A cross-sectional study

INTRODUCTION

Cadmium is a toxic heavy metal with detrimental effects on human health. Apart from smoking and occupational factors, diet is the main source of cadmium. However, the relation between adherence to so-called "healthy" dietary patterns and cadmium exposure has not been investigated in detail. In this study, we aimed at assessing such association in a Northern Italian population.

METHODS

Using a cross-sectional study design, we investigated a population of non-smokers aged 30-60 years in the period 2017-2019. Each subject completed a validated food frequency questionnaire (FFQ) in order to estimate adherence to four dietary patterns, namely the Dietary Approach to Stopping Hypertension-DASH diet, Greek Mediterranean Index-GMI, the Italian Mediterranean Index-IMI, and the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet. We collected a fasting morning urinary sample to measure urinary levels of cadmium and cotinine. The association between increasing adherence to dietary patterns and cadmium exposure was evaluated using a cubic spline regression non-linear model and adjusting for relevant confounders (age, sex, body mass index, urinary cotinine levels, intake of fiber, and alcohol).

RESULTS

We recruited 137 participants (males/females: 62/75) with median (interquartile range-IQR) age of 47 (IQR: 43-53) years. Median scores for the investigated dietary patterns were 24 (IQR: 21-28), 4 (IQR: 3-6), 4 (IQR: 3-5), and 7.5 (IQR: 6.5-8.5) for DASH, GMI, IMI and MIND diets, respectively. The median urinary cadmium level was 0.21 μg/L (IQR: 0.11-0.34 μg/L). Spline regression analysis showed an inverse linear association between increasing adherence to the DASH and MIND diets and urinary cadmium levels, reaching a plateau at high adherence scores, approximately > 25 and > 9 for DASH and MIND diets, respectively. An increase of cadmium exposure with increasing MIND score also emerged. Conversely, the association was almost null for IMI, and slightly positive for GMI.

CONCLUSIONS

The present findings suggest that increasing adherence to the DASH and MIND diets are associated with decreased cadmium levels only at moderate level. Overall, these results indicate that public health strategies, including the decrease of cadmium contamination in healthy foods should be implemented.

Partition pattern and environmental consequences of the widespread coalmines and host rocks on the water of selected regions, China

The massive exploration and random dumping of coals in various regions of China create serious environmental and health problems because of the presence of toxic trace elements (TTEs), which possibly transfer to environment and cause serious health issues. This study was conducted to probe the environmental consequences of coalmines on the aquifer water and their association with health risks and the environment. For this purpose, 100 s of water samples was collected from the typical coalmine regions of Hancheng, Huanglong, Binxian, Handan, Langao, and Fusui and analyzed for various parameters. In Handan mining areas, Se, Mn, Fe, TDS, SO42-, and total hardness were higher than the WHO standard, while in Hancheng, SO42- was > 95%, Ca2+ 40-96%, and Mg2+ was 0-40%, which caused permanent hardness. In the Fusui and Huanglong areas, the SO42- concentration was > 95%, Ca2+ 60-100%, and Mg2+ 20%, causing permanent hardness. In Binxian, HCO3- was 70-90%, Ca2+ 60-80%, and Cl- and SO42- were 20%, causing temporary hardness. In the Kashin-Beck disease (KBD) area, Se in the Middle Triassic was 0.3, Upper Triassic 0.23, and Quaternary 0.01, while fluoride (F) was 124.7, 141.6, and 159 in μg L-1. The Handan water is included in rock-evaporation dominance (a mixed controlling mechanism), Hancheng, Binxian, Huanglong, and Langao water was included in rock dominance, while the Fusui water was included in rock-precipitation dominance. The average daily intake ((ADI) mg kg-1 d-1) of Ba, Cd, Co, Cr, Cu, Fe, Ti, Tl, Mo, Ni, Zn, Pb, Be, U, and Sr was comparably higher than No Observed Adverse Effect Level (NOAEL), which surely causes high health risk in selected regions. The elemental contaminants in the water were attributed to the geological environment, geochemical processes, ion exchanges, redox reactions, and dissolution of mineralized rock. For aquifer safety, coal mining, and other geological activities should be avoided to protect the water for future generations.

Reassessment of the cadmium toxicological reference value for use in human health assessments of foods

The U.S. Food and Drug Administration (FDA) developed an oral toxicological reference value (TRV) for characterizing potential health concerns from dietary exposure to cadmium (Cd). The development of the TRV leveraged the FDA's previously published research including (1) a systematic review for adverse health effects associated with oral Cd exposure and (2) a human physiological based pharmacokinetic (PBPK) model adapted from Kjellstrom and Nordberg (1978) for use in reverse dosimetry applied to the U.S. population. Adverse effects of Cd on the bone and kidney are associated with similar points of departure (PODs) of approximately 0.50 μg Cd/g creatinine for females aged 50-60 based on available epidemiologic data. We also used the upper bound estimate of the renal cortical concentration (50 μg/g Cd) occurring in the U.S. population at 50 years of age as a POD. Based on the output from our reverse dosimetry PBPK Model, a range of 0.21-0.36 μg/kg bw/day was developed for the TRV. The animal data used for the animal TRV derivation (0.63-1.8 μg/kg bw/day) confirms biological plausibility for both the bone and kidney endpoints.

A regional comparison of children's blood cadmium, lead, and mercury in rural, urban and industrial areas of six European countries, and China, Ecuador, and Morocco

OBJECTIVES

The authors aimed to evaluate whether blood cadmium (B-Cd), lead (B-Pb) and mercury (B-Hg) in children differ regionally in 9 countries, and to identify factors correlating with exposure.

MATERIAL AND METHODS

The authors performed a cross-sectional study of children aged 7-14 years, living in 2007-2008 in urban, rural, or potentially polluted ("hot spot") areas (ca. 50 children from each area, in total 1363 children) in 6 European and 3 non-European countries. The authors analyzed Cd, Pb, and total Hg in blood and collected information on potential determinants of exposure through questionnaires. Regional differences in exposure levels were assessed within each country.

RESULTS

Children living near industrial "hot-spots" had B-Cd 1.6 (95% CI: 1.4-1.9) times higher in the Czech Republic and 2.1 (95% CI:1.6-2.8) times higher in Poland, as compared to urban children in the same countries (geometric means [GM]: 0.13 μg/l and 0.15 μg/l, respectively). Correspondingly, B-Pb in the "hot spot" areas was 1.8 (95% CI: 1.6-2.1) times higher than in urban areas in Slovakia and 2.3 (95% CI: 1.9-2.7) times higher in Poland (urban GM: 19.4 μg/l and 16.3 μg/l, respectively). In China and Morocco, rural children had significantly lower B-Pb than urban ones (urban GM: 64 μg/l and 71 μg/l, respectively), suggesting urban exposure from leaded petrol, water pipes and/or coal-burning. Hg "hot spot" areas in China had B-Hg 3.1 (95% CI: 2.7-3.5) times higher, and Ecuador 1.5 (95% CI: 1.2-1.9) times higher, as compared to urban areas (urban GM: 2.45 μg/l and 3.23 μg/l, respectively). Besides industrial exposure, traffic correlated with B-Cd; male sex, environmental tobacco smoke, and offal consumption with B-Pb; and fish consumption and amalgam fillings with B-Hg. However, these correlations could only marginally explain regional differences.

CONCLUSIONS

These mainly European results indicate that some children experience about doubled exposures to toxic elements just because of where they live. These exposures are unsafe, identifiable, and preventable and therefore call for preventive actions. Int J Occup Med Environ Health. 2023;36(3):349-64.

Transcriptomic and Functional Analyses of Two Cadmium Hyper-Enriched Duckweed Strains Reveal Putative Cadmium Tolerance Mechanisms

Cadmium (Cd) is one of the most toxic metals in the environment and exerts deleterious effects on plant growth and production. Duckweed has been reported as a promising candidate for Cd phytoremediation. In this study, the growth, Cd enrichment, and antioxidant enzyme activity of duckweed were investigated. We found that both high-Cd-tolerance duckweed (HCD) and low-Cd-tolerance duckweed (LCD) strains exposed to Cd were hyper-enriched with Cd. To further explore the underlying molecular mechanisms, a genome-wide transcriptome analysis was performed. The results showed that the growth rate, chlorophyll content, and antioxidant enzyme activities of duckweed were significantly affected by Cd stress and differed between the two strains. In the genome-wide transcriptome analysis, the RNA-seq library generated 544,347,670 clean reads, and 1608 and 2045 differentially expressed genes were identified between HCD and LCD, respectively. The antioxidant system was significantly expressed during ribosomal biosynthesis in HCD but not in LCD. Fatty acid metabolism and ethanol production were significantly increased in LCD. Alpha-linolenic acid metabolism likely plays an important role in Cd detoxification in duckweed. These findings contribute to the understanding of Cd tolerance mechanisms in hyperaccumulator plants and lay the foundation for future phytoremediation studies.

Association between urinary cadmium level and subclinical myocardial injury in the general population without cardiovascular disease aged ≥ 50 years

Cadmium (Cd) is a toxic heavy metal linked to an increased risk of cardiovascular disease (CVD). But the relationship between urinary Cd (U-Cd) and electrocardiographic subclinical myocardial injury (SC-MI) in older people is unclear. This study evaluated the connection between U-Cd and SC-MI in people who did not have CVD. The study involved 4269 participants from the National Health and Nutrition Examination Survey III(NHANES III) aged ≥ 50 years and had no history of CVD. The relationship between U-Cd and cardiac infarction/injury score (CIIS) was assessed by multivariable linear regression. Whether U-Cd and SC-MI were correlated was determined by multivariate logistic regression, restricted cubic spline, and subgroup analysis. There was a significant association between U-Cd and CIIS (β, 1.04, 95% confidence interval (CI): 0.39-1.69; P = 0.003) in the highest quartile and fully adjusted model. After adjusting for relevant confounders, multivariable logistic regression showed that participants in the highest quartile of U-Cd had a greater chance of having SC-MI than those in the first ( OR (95% CI), 1.37(1.13,1.66), P for trend = 0.003), and this relationship was especially strong among hypertensive participants. And a positive linear correlation between U-Cd and the prevalence of SC-MI was shown by restricted cubic spline analysis. U-Cd may be a novel risk element for SC-MI because it is independently and linearly linked to CIIS and SC-MI.

Identification of high ecological risk areas with naturally high background value of soil Cd related to carbonate rocks

The characteristics of high concentrations or high activity levels of heavy metals, especially Cd, in soils caused by the pedogenesis of rocks are attracting increased attention. Carbonate rocks and black shales often coexist during geological deposition, but the risk characteristics of heavy metals are different after their weathering into the soil. The purpose of this study was to investigate the element concentrations of a naturally high background value area, to identify patterns of different risk areas, and to make recommendations for the safe usage of farmland. The results showed that, compared with the soil in the carbonate rock area, the soil in the black shale area was more acidified and most of the heavy metal elements were leached. Based on the soil pH value and the heavy metal concentrations, an identification method for land risk areas within naturally high background values was established, and land planning was carried out using this method. The exceeding rates of Cd in rice for the preferential protection area and strict control area were 0.0 and 50.0%, respectively. Therefore, in naturally high background area, the identified lithology can apply to maximize the use of farmland resources. This method provides a basis for preliminary ecological risk screening in naturally high background value areas using the results of the soil survey. A suggestion for the prevention and control of soil pollution in areas with naturally high background values was put forward. In carbonate rock areas, the soil should be closely monitored to prevent soil acidification.

Associations of urinary and blood cadmium concentrations with all-cause mortality in US adults with chronic kidney disease: a prospective cohort study

Epidemiological evidence for the relationship between cadmium exposure and mortality in specific chronic kidney disease (CKD) populations remains scarce. We aimed to explore the relationships between cadmium concentrations in urine and blood and all-cause mortality among CKD patients in the USA. This cohort study was composed of 1825 CKD participants from the National Health and Nutrition Examination Survey (NHANES) (1999-2014) who were followed up to December 31, 2015. All-cause mortality was ascertained by matching the National Death Index (NDI) records. We estimated hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause mortality in relation to urinary and blood cadmium concentrations by Cox regression models. During an average follow-up period of 82 months, 576 CKD participants died. Compared with the lowest quartiles, HRs (95% CIs) for all-cause mortality associated with the fourth weighted quartiles of urinary and blood cadmium concentrations were 1.75 (1.28 to 2.39) and 1.59 (1.17 to 2.15), respectively. Furthermore, the HRs (95% CIs) for all-cause mortality per ln-transformed IQR increment in cadmium concentrations in urine (1.15 μg/g U_Cr) and blood (0.95 μg/L) were 1.40 (1.21 to 1.63) and 1.22 (1.07 to 1.40), respectively. Linear concentration-response relationships between urinary and blood cadmium concentrations and all-cause mortality were also found. Our findings suggested that increased cadmium concentrations in both urine and blood significantly contributed to enhanced mortality risk in CKD patients, thus highlighting that efforts to reduce cadmium exposure may reduce mortality risk in high-risk populations with CKD.

Salt stress-induced changes in soil metabolites promote cadmium transport into wheat tissues

Soil salinity is known to improve cadmium (Cd) mobility, especially in arid soils. However, the mechanisms involved in how salt stress-associated metabolic profiles participate in mediating Cd transport in the soil-plant system remain poorly understood. This study was designed to investigate the effects of salinity-induced changes in soil metabolites on Cd bioavailability. Sodium salts in different combinations according to molar ratio (NaCl:Na₂SO₄=1:1; NaCl:Na₂SO₄:NaHCO₃=1:2:1; NaCl:Na₂SO₄:NaHCO₃:Na₂CO₃=1:9:9:1; NaCl:Na₂SO₄:NaHCO₃:Na₂CO₃=1:1:1:1) were applied to the Cd-contaminated soils, which increased soil Cd availability by 22.36% and the Cd content in wheat grains by 36.61%, compared to the control. Salt stress resulted in soil metabolic reprogramming, which might explain the decreased growth of wheat plants and increased Cd transport from the soil into wheat tissues. For example, down-regulation of starch and sucrose metabolism reduced the production of sugars, which adversely affected growth; up-regulation of fatty acid metabolism allowed wheat plants to maintain a normal intracellular environment under saline conditions; up-regulation of the tricarboxylic acid (TCA) cycle was triggered, causing an increase in organic acid synthesis and the accumulation of organic acids, which facilitated the migration of soil Cd into wheat tissues. In summary, salt stress can facilitate Cd transport into wheat tissues by the direct effect of salt-based ions and the combined effect of altered soil physicochemical properties and soil metabolic profiles in Cd-contaminated soils.

Multi-Element Assessment of Potentially Toxic and Essential Elements in New and Traditional Food Varieties in Sweden

With the global movement toward the consumption of a more sustainable diet that includes a higher proportion of plant-based foods, it is important to determine how such a change could alter the intake of cadmium and other elements, both essential and toxic. In this study, we report on the levels of a wide range of elements in foodstuffs that are both traditional and "new" to the Swedish market. The data were obtained using analytical methods providing very low detection limits and include market basket data for different food groups to provide the general levels in foods consumed in Sweden and to facilitate comparisons among traditional and "new" food items. This dataset could be used to estimate changes in nutritional intake as well as exposure associated with a change in diet. The concentrations of known toxic and essential elements are provided for all the food matrices studied. Moreover, the concentrations of less routinely analyzed elements are available in some matrices. Depending on the food variety, the dataset includes the concentrations of inorganic arsenic and up to 74 elements (Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cs, Cu, Fe, Ga, Ge, Hf, Hg, K, Li, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Rb, S, Sb, Sc, Se, Si, Sn, Sr, Ta, Te, Th, Ti, Tl, U, W, V, Y, Zn, Zr, rare Earth elements (REEs) (Ce, Dy, Er, Eu, Gd, Ho, La, Lu, Nd, Pr, Sm, Tb, Tm, and Yb), platinum group elements (PGEs) (Ir, Os, Pd, Pr, Pt, Re, Rh, Ru, and Pr), and halogens (Br, Cl, and I)). The main focus (and thus the most detailed information on variation within a given food group) is on foods that are currently the largest contributors to dietary cadmium exposure in Sweden, such as pasta, rice, potato products, and different sorts of bread. Additionally, elemental concentrations in selected food varieties regarded as relatively new or "novel" to the Swedish market are provided, including teff flour, chia seeds, algae products, and gluten-free products.

Reactive Oxygen Species Control Osteoblast Apoptosis through SIRT1/PGC-1α/P53Lys382 Signaling, Mediating the Onset of Cd-Induced Osteoporosis

The imbalance between osteogenesis and osteoclastogenesis is a feature of bone metabolic disease. Cadmium (Cd) exposure causes human bone loss and osteoporosis (OP) through bioaccumulation of the food chain. However, the impact of Cd on bone tissues and the underlying molecular mechanisms are not well-characterized. In the current study, we found that the Cd concentration in bone tissues of OP patients was higher than normal subjects; meanwhile, the nuclear silent information regulator of transcription 1 (SIRT1) protein expression level was significantly decreased, which is a new star molecule to treat OP. It is further revealed that SIRT1 activation markedly reprograms bone metabolic and stress-response pathways that incline with osteoblast (OB) apoptosis. Suppressing reactive oxygen species (ROS) release with N-acetyl-l-cysteine (NAC) abolished Cd-induced reduction of SIRT1 protein, deacetylation of P53, OB apoptosis, and attenuated OP. Conversely, overexpression of SIRT1 suppressed Cd-induced ROS release. SIRT1 overexpression in vivo and in vitro dampened PGC-1α protein, acetylation of P53 at lysine 382, and caspase-dependent apoptosis. These results reveal that ROS/SIRT1 controls P53 acetylation and coordinates OB apoptosis involved in the onset of OP.

Clinical features and shared mechanisms of chronic gastritis and osteoporosis

Chronic gastritis (CG) and osteoporosis (OP) are common and occult diseases in the elderly and the relationship of these two diseases have been increasingly exposed. We aimed to explore the clinical characteristics and shared mechanisms of CG patients combined with OP. In the cross-sectional study, all participants were selected from BEYOND study. The CG patients were included and classified into two groups, namely OP group and non-OP group. Univariable and multivariable logistic regression methods were used to evaluate the influencing factors. Furthermore, CG and OP-related genes were obtained from Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were identified using the GEO2R tool and the Venny platform. Protein-protein interaction information was obtained by inputting the intersection targets into the STRING database. The PPI network was constructed by Cytoscape v3.6.0 software again, and the key genes were screened out according to the degree value. Gene function enrichment of DEGs was performed by Webgestalt online tool. One hundred and thirty CG patients were finally included in this study. Univariate correlation analysis showed that age, gender, BMI and coffee were the potential influencing factors for the comorbidity (P < 0.05). Multivariate Logistic regression model found that smoking history, serum PTH and serum β-CTX were positively correlated with OP in CG patients, while serum P1NP and eating fruit had an negative relationship with OP in CG patients. In studies of the shared mechanisms, a total of 76 intersection genes were identified between CG and OP, including CD163, CD14, CCR1, CYBB, CXCL10, SIGLEC1, LILRB2, IGSF6, MS4A6A and CCL8 as the core genes. The biological processes closely related to the occurrence and development of CG and OP mainly involved Ferroptosis, Toll-like receptor signaling pathway, Legionellosis and Chemokine signaling pathway. Our study firstly identified the possible associated factors with OP in the patients with CG, and mined the core genes and related pathways that could be used as biomarkers or potential therapeutic targets to reveal the shared mechanisms.

Contrasting Cd accumulation of Arabidopsis halleri populations: a role for (1→4)-β-galactan in pectin

Cadmium (Cd) accumulation is highly variable among Arabidopsis halleri populations. To identify cell wall (CW) components that contribute to the contrasting Cd accumulation between PL22-H (Cd-hyperaccumulator) and I16-E (Cd-excluder), Cd absorption capacity of CW polysaccharides, CW mono- and poly- saccharides contents and CW glycan profiles were compared between these two populations. PL22-H pectin contained 3-fold higher Cd concentration than I16-E pectin in roots, and (1→4)-β-galactan pectic epitope showed the biggest difference between PL22-H and I16-E. CW-related differentially expressed genes (DEGs) between PL22-H and I16-E were identified and corresponding A. thaliana mutants were phenotyped for Cd tolerance and accumulation. A higher Cd translocation was observed in GALACTAN SYNTHASE1 A. thaliana knockout and overexpressor mutants, which both showed a lengthening of the RG-I sidechains after Cd treatment, contrary to the wild-type. Overall, our results support an indirect role for (1→4)-β-galactan in Cd translocation, possibly by a joint effect of regulating the length of RG-I sidechains, the pectin structure and interactions between polysaccharides in the CW. The characterization of other CW-related DEGs between I16-E and PL22-H selected allowed to identify a possible role in Zn translocation for BIIDXI and LEUNIG-HOMOLOG genes, which are both involved in pectin modification.

Ectopic Expression of PvHMA2.1 Enhances Cadmium Tolerance in Arabidopsis thaliana

Cadmium (Cd) in soil inhibits plant growth and development and even harms human health through food chain transmission. Switchgrass (Panicum virgatum L.), a perennial C4 biofuel crop, is considered an ideal plant for phytoremediation due to its high efficiency in removing Cd and other heavy metals from contaminated soil. The key to understanding the mechanisms of switchgrass Cd tolerance is to identify the genes involved in Cd transport. Heavy-metal ATPases (HMAs) play pivotal roles in heavy metal transport, including Cd, in Arabidopsis thaliana and Oryza sativa, but little is known about the functions of their orthologs in switchgrass. Therefore, we identified 22 HMAs in switchgrass, which were distributed on 12 chromosomes and divided into 4 groups using a phylogenetic analysis. Then, we focused on PvHMA2.1, which is one of the orthologs of the rice Cd transporter OsHMA2. We found that PvHMA2.1 was widely expressed in roots, internodes, leaves, spikelets, and inflorescences, and was significantly induced in the shoots of switchgrass under Cd treatment. Moreover, PvHMA2.1 was found to have seven transmembrane domains and localized at the cell plasma membrane, indicating that it is a potential transporter. The ectopic expression of PvHMA2.1 alleviated the reduction in primary root length and the loss of fresh weight of Arabidopsis seedlings under Cd treatment, suggesting that PvHMA2.1 enhanced Cd tolerance in Arabidopsis. The higher levels of relative water content and chlorophyll content of the transgenic lines under Cd treatment reflected that PvHMA2.1 maintained water retention capacity and alleviated photosynthesis inhibition under Cd stress in Arabidopsis. The roots of the PvHMA2.1 ectopically expressed lines accumulated less Cd compared to the WT, while no significant differences were found in the Cd contents of the shoots between the transgenic lines and the WT under Cd treatment, suggesting that PvHMA2.1 reduced Cd absorption from the environment through the roots in Arabidopsis. Taken together, our results showed that PvHMA2.1 enhanced Cd tolerance in Arabidopsis, providing a promising target that could be engineered in switchgrass to repair Cd-contaminated soil.

Independent association of blood cadmium with subclinical lower extremity atherosclerosis: An observational study based on dose-response analysis

BACKGROUND

Atherosclerosis is an increasingly public health issue globally. Previous studies have showed a causal link between heavy metal exposure and atherosclerosis. However, the association of cadmium concentration with subclinical lower extremity atherosclerosis (SLEA) remains unclear.

AIMS

To investigate the association of blood cadmium with SLEA and its extent, and further analyze the potential dose-response relationship.

METHODS

Blood cadmium concentration was measured using inductively coupled plasma mass spectrometry. SLEA and its extent were assessed by ultrasound diagnosis system. Multivariate models were applied to evaluate the association of blood cadmium with SLEA and its extent. Restricted cubic splines were performed to explore the potential dose-response relationship.

RESULTS

This observational study consisted of 1664 participants from cardiovascular outpatient, with an average age of 62.4 years and 1218 (73.2%) men. When blood cadmium was included as a categorical variable in multivariate models, logistic regression analysis showed that high quartile in blood cadmium was an independent risk factor of SLEA (OR = 2.704, 95%CI 1.866-3.919). After log-transformed for SLEA extent parameters, linear regression analysis indicated that high quartile in blood cadmium was significantly associated with higher Crouse score (GMR = 1.21, 95%CI 1.15-1.28), plaque maximum thickness (GMR = 1.13, 95%CI 1.09-1.18) and diseased vessel count (GMR = 1.14, 95%CI 1.10-1.19), respectively. When blood cadmium was used as a continuous variable in restricted cubic splines, the dose-response relationship presented a positive progression in SLEA (P = 0.302), plaque maximum thickness (P = 0.145) and diseased vessel count (P = 0.055) apparently that did not deviate from linearity.

CONCLUSIONS

Blood cadmium exhibited an independent association with SLEA, and this dose-response relationship was progressive without significant departure from linearity.

Iron, Zinc, Copper, Cadmium, Mercury, and Bone Tissue

The paper presents the current understanding on the effects of five metals on bone tissue, namely iron, zinc, copper, cadmium, and mercury. Iron, zinc, and copper contribute significantly to human and animal metabolism when present in sufficient amounts, but their excess or shortage increases the risk of developing bone disorders. In contrast, cadmium and mercury serve no physiological purpose and their long-term accumulation damages the osteoarticular system. We discuss the methods of action and interactions between the discussed elements as well as the concentrations of each element in distinct bone structures.

Urine metabolomic characteristics of female patients with occupational chronic cadmium poisoning after 15 years of treatment

Occupational chronic cadmium poisoning (OCCP) can cause irreversible organ damage. Currently, no effective treatment is available for OCCP, and effective and sensitive biomarkers for treatment evaluation are still lacking. In this study, metabolomics techniques were used to analyze changes in endogenous metabolites in the urine of patients with OCCP after 15 years of treatment. Thirty urine samples from female patients with OCCP and healthy female controls (n = 15 per group) were assessed using gas chromatography-time-of-flight mass spectrometry and ultra-high-performance liquid chromatography-Q-Exactive mass spectrometry. The OCCP group had higher concentrations of blood urea nitrogen and urinary cadmium but near-normal urinary concentrations of β₂ -microglobulin and retinol-binding protein. Compared with the control group, the OCCP group had 66 significantly different metabolites with a variable importance in projection score >1 and p < 0.05. These differential metabolites were involved in various metabolic pathways, such as creatine metabolism, nicotinate and nicotinamide metabolism, the pentose phosphate pathway, d-glutamine and d-glutamate metabolism, and amino acid metabolism. Compared with the control group, the OCCP group had significantly higher urinary concentrations of creatine, glutamic acid, quinolinic acid and nicotinic acid. In a receiver operator characteristic analysis, the area under the curve of creatine was higher than those for glutamic acid, quinolinic acid and nicotinic acid, indicating that urinary concentrations of creatine could be used as a sensitive biomarker for the diagnosis and prognosis of OCCP and for monitoring its treatment.

Interspecies differences in mammalian susceptibility to legacy POPs and trace metals using skin fibroblast cells

The susceptibility to trace metals and legacy POPs is different between terrestrial and marine mammals. In this study, we established the first cell line from Indo-Pacific finless porpoises and compared the cellular responses of skin fibroblast cells from Pygmy killer whales, Pantropic spotted dolphins, Indo-Pacific finless porpoises, mice, and humans following exposure to copper, methylmercury, cadmium, PCB126, PCB153, and BDE47 to better understand the interspecies sensitivities of mammals to chemical pollutants. We conducted a risk assessment by comparing no-observed effect concentrations (NOEC), lowest-observed effect concentrations (LOEC), and half maximal effective concentrations (EC50) from cell viability assays and previously reported pollutant body burdens in mammals. Based on the in vitro data, Indo-Pacific finless porpoises were more sensitive to copper and methylmercury than other mammals. PCB153 exposure reduced cell viability in all mammals except humans, while PCB126 was more potent, with 13.33 μg/mL exposure reducing cell viability in all mammals. In contrast, BDE47 exposure reduced cell viability only in terrestrial mammals in addition to pantropic spotted dolphin. Based on the in vitro data and the natural context of metal concentrations, both methylmercury and cadmium posed a higher risk to cetaceans than human, while copper posed a lower risk to cetaceans. All three legacy POPs (PCB126, PCB153, and BDE47) posed minor risk to cetaceans for short-term exposure. This study demonstrated that a species-specific in vitro model may provide more accurate information on the potential risk of pollutants to mammals. However, due to the bioamplification of POPs and their potential impact on the endocrine system and immune system of cetaceans, risk assessment with long-term exposure with more in vitro models should be further studied.

Distribution characteristics of selenium, cadmium and arsenic in rice grains and their genetic dissection by genome-wide association study

High selenium (Se) and low cadmium (Cd) and arsenic (As) contents in rice grains were good for human health. The genetic basis and relationship of Se, Cd and As concentrations in rice grains are still largely unknown. In the present study, large variations were observed in Se, Cd and As concentrations in brown and milled rice in normal and Se treatment conditions in 307 rice accessions from 3K Rice Genomes Project. Se fertilizer treatment greatly increased Se concentrations but had no obvious changes in concentrations of Cd and As both in brown and milled rice. Total of 237 QTL were identified for Se, Cd and As concentrations in brown and milled rice in normal and Se treatment conditions as well as ratio of concentrations under Se treatment to normal conditions. Only 19 QTL (13.4%) were mapped for concentrations of Se and Cd, Se and As, and Se, Cd and As in the same or adjacent regions, indicating that most Se concentration QTL are independent of Cd and As concentration QTL. Forty-three favorable alleles were identified for 40 candidate genes by gene-based association study and haplotype analysis in 14 important QTL regions. Se-enriched rice variety will be developed by pyramiding favorable alleles at different Se QTL and excluding undesirable alleles at Cd and As QTL, or combining favorable alleles at Se QTL with the alleles at Se-sensitive QTL by marker-assisted selection.

Cadmium exposure in population: alcoholic beverage consumption and health risk assessment

Risk assessment of cadmium (Cd) for human health play a key role because of toxic effect. Researchers are undergoing constant development for modelling approaches to make a risk assessment. It was carried out a central composite design combining with response surface modeling to optimize and modeling of Cd2+ ions in this study. Also, this study was performed to provide information about possible risk associated with alcoholic beverage consumption. Some independent process parameters including contact time and pH were chosen for optimization. Under optimal parameters, 142.9 mg g-1 was determined as Cd2+ ions removal effectiveness. Significance independent parameters and their interactions were checked using analysis of variance. These results were verified by correlation coefficients (R2 = 0.9967) of the statistical prediction. Estimated daily intake (EDI) and target hazard quotients (THQ) were calculated, to assess health risk. The Cd2+ ions EDI values (µg/day/person) were less than the recommended dietary allowance values and also, its THQ value was less than 1, also. When the obtained results compared with the levels set by regulatory authorities, the studied alcoholic beverages consumption do not pose a toxicological risk.

Graphical abstract

A systematic review of adverse health effects associated with oral cadmium exposure

Scientific data characterizing the adverse health effects associated with dietary cadmium (Cd) exposure were identified in order to make informed decisions about the most appropriate toxicological reference value (TRV) for use in assessing dietary Cd exposure. Several TRVs are available for Cd and regulatory organizations have used epidemiologic studies to derive these reference values; however, risk of bias (RoB) evaluations were not included in the assessments. We performed a systematic review by conducting a thorough literature search (through January 4, 2020). There were 1714 references identified by the search strings and 328 studies identified in regulatory assessments. After applying the specific inclusion and exclusion criteria, 208 studies (Human: 105, Animal: 103) were considered eligible for further review and data extraction. For the epidemiologic and animal studies, the critical effects identified for oral Cd exposure from the eligible studies were a decrease in bone mineral density (BMD) and renal tubular degeneration. A RoB analysis was completed for 49 studies (30 epidemiological and 19 animal) investigating these endpoints. The studies identified through the SR that were considered high quality and low RoB (2 human and 5 animal) can be used to characterize dose-response relationships and inform the derivation of a Cd TRV.

Advances in molecular mechanisms underlying cadmium uptake and translocation in rice

The increasing cadmium (Cd) pollution in paddy fields has severely threatened China's ecological and food safety. Cultivation of low Cd accumulation varieties to reduce Cd content in rice or cultivation of Cd-tolerant varieties for phytoremediation are considered effective methods to control Cd pollution in paddy fields. However, the underlying molecular mechanism of Cd absorption and transport by rice plants needs to be deciphered to cultivate these varieties. Here, we summarized the molecular mechanisms underlying Cd absorption and transport in rice, as well as the variation of Cd accumulation among rice varieties, the QTLs related to Cd accumulation in rice, and discusses the direction of future research.

Cadmium Toxicity Is Regulated by Peroxisome Proliferator-Activated Receptor δ in Human Proximal Tubular Cells

Cadmium (Cd) is a toxic heavy metal that is widely present in the environment. Renal proximal tubule disorder is the main symptom of Cd chronic poisoning. Our previous study demonstrated that Cd inhibits the total activities of peroxisome proliferator-activated receptor (PPAR) transcription factors in human and rat proximal tubular cells. In this study, we investigated the involvement of PPAR in Cd renal toxicity using the HK-2 human proximal tubular cell line. Among PPAR isoform genes, only PPARD knockdown significantly showed resistance to Cd toxicity in HK-2 cells. The transcriptional activity of PPARδ was decreased not only by PPARD knockdown but also by Cd treatment. DNA microarray analysis showed that PPARD knockdown changed the expression of apoptosis-related genes in HK-2 cells. PPARD knockdown decreased apoptosis signals and caspase-3 activity induced by Cd treatment. PPARD knockdown did not affect the intracellular Cd level after Cd treatment. These results suggest that PPARδ plays a critical role in the modification of susceptibility to Cd renal toxicity and that the apoptosis pathway may be involved in PPARδ-related Cd toxicity.

Deep learning approach identified a gene signature predictive of the severity of renal damage caused by chronic cadmium accumulation

Epidemiology studies have indicated that environmental cadmium exposure, even at low levels, will result in chronic cadmium accumulation in the kidney with profound adverse consequences and that the diabetic population is more susceptible. However, the underlying mechanisms are yet not fully understood. In the present study, we applied an animal model to study chronic cadmium exposure-induced renal injury and performed whole transcriptome profiling studies. Repetitive CdCl₂ exposure resulted in cadmium accumulation and remarkable renal injuries in the animals. The diabetic ob/ob mice manifested increased severity of renal injury compared with the wild type C57BL/6 J littermate controls. RNA-Seq data showed that cadmium treatment induced dramatic gene expression changes in a dose-dependent manner. Among the differentially expressed genes include the apoptosis hallmark genes which significantly demarcated the treatment effects. Pathway enrichment and network analyses revealed biological oxidation (mainly glucuronidation) as one of the major stress responses induced by cadmium treatment. We next implemented a deep learning algorithm in conjunction with cloud computing and discovered a gene signature that can predict the degree of renal injury induced by cadmium treatment. The present study provided, for the first time, a comprehensive mechanistic understanding of chronic cadmium-induced nephrotoxicity in normal and diabetic populations at the whole genome level.

Associations of urinary and dietary cadmium with urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine and blood biochemical parameters

Cadmium is a heavy metal with established adverse effects on human health, namely on bone, liver and kidney function and the cardiovascular system. We assessed cadmium exposure and its correlation with biomarkers of toxicity. We recruited 137 non-smoking blood donors without a history of chronic disease or cancer who resided in the Northern Italy province of Reggio Emilia (mean age 47 years, range 30-60 years) in the 2017-2019 period. We used a semi-quantitative food frequency questionnaire to estimate dietary cadmium intake and urine samples to assess concentrations of urinary cadmium and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG). Median urinary cadmium and 8-oxodG concentrations were 0.21 μg/L (interquartile range (IQR): 0.11-0.34 μg/L) and 3.21 μg/g creatinine (IQR: 2.21-4.80 μg/g creatinine), respectively, while median dietary cadmium intake was 6.16 μg/day (IQR: 5.22-7.93 μg/day). We used multivariable linear and spline regression models to estimate mean differences exposure concentrations. Dietary and urinary cadmium were positively correlated, and both were positively and linearly correlated with 8-oxodG. We found a positive association of urinary cadmium with blood alanine aminotransferase (ALT), total cholesterol, low-density lipoprotein (LDL)-cholesterol and thyroid-stimulating hormone (TSH) concentrations. We also observed a positive association with triglycerides, in both linear (beta regression coefficient = 77.03, 95% confidence interval 32.27-121.78) and non-linear spline regression analyses. Despite the positive correlation between dietary and urinary cadmium estimates, dietary cadmium intake showed inconsistent results with the study endpoints and generally weaker associations, suggesting a decreased capacity to reflect actual cadmium exposure. Overall, these findings suggest that even low levels of cadmium exposure may adversely alter hematological and biochemical variables and induce oxidative stress.

Mutation of NtNRAMP3 improves cadmium tolerance and its accumulation in tobacco leaves by regulating the subcellular distribution of cadmium

Cadmium (Cd) is a harmful element that affects plant growth and development. Genetic improvements could be applied for enhancing Cd tolerance and accumulation in plants. Here, a novel Cd stress-induced gene, NtNRAMP3, was identified in tobacco. We constructed two NtNRAMP3-knockout (KO) tobacco lines using the CRISPR/Cas9 system, which enhanced Cd tolerance and Cd accumulation in tobacco leaves compared with those in the wildtype (WT). Subcellular localization analysis suggested that NtNRAMP3 is a tonoplast protein and GUS (β-glucuronidase) histochemical analysis showed that NtNRAMP3 is highly expressed in the conductive tissue of leaves. NtNRAMP3-KO tobacco showed reduced Cd translation from vacuole to cytosol in leaves compared with the WT, and its vacuolar Cd concentration was significantly higher (20.78-22.81%) than that in the WT; in contrast, Cd concentration in the cytosol was reduced by 13.72-20.15%, preventing chlorophyll degradation and reducing reactive oxygen species accumulation in the leaves. Our findings demonstrate that NtNRAMP3 is involved in regulating Cd subcellular distribution (controlling Cd transport from vacuoles to the cytosol) and affects Cd tolerance and its accumulation in tobacco. This provides a key candidate gene to improve the phytoremediation efficiency of plants via genetic engineering.

Enhancing the Phytoremediation of Heavy Metals by Combining Hyperaccumulator and Heavy Metal-Resistant Plant Growth-Promoting Bacteria

Heavy metals (HMs) have become a major environmental pollutant threatening ecosystems and human health. Although hyperaccumulators provide a viable alternative for the bioremediation of HMs, the potential of phytoremediation is often limited by the small biomass and slow growth rate of hyperaccumulators and HM toxicity to plants. Here, plant growth-promoting bacteria (PGPB)-assisted phytoremediation was used to enhance the phytoremediation of HM-contaminated soils. A PGPB with HM-tolerant (HMT-PGPB), Bacillus sp. PGP15 was isolated from the rhizosphere of a cadmium (Cd) hyperaccumulator, Solanum nigrum. Pot experiments demonstrated that inoculation with strain PGP15 could significantly increase the growth of S. nigrum. More importantly, strain PGP15 markedly improved Cd accumulation in S. nigrum while alleviating Cd-induced stress in S. nigrum. Specifically, PGP15 inoculation significantly decreased the contents of H₂O₂, MDA, and O 2 · - in S. nigrum, while the activities (per gram plant fresh weight) of SOD, APX, and CAT were significantly increased in the PGP15-inoculated plants compared with the control sample. These results suggested that the interactions between strain PGP15 and S. nigrum could overcome the limits of phytoremediation alone and highlighted the promising application potential of the PGPB-hyperaccumulator collaborative pattern in the bioremediation of HM-contaminated soils. Furthermore, the PGP15 genome was sequenced and compared with other strains to explore the mechanisms underlying plant growth promotion by HMT-PGPB. The results showed that core genes that define the fundamental metabolic capabilities of strain PGP15 might not be necessary for plant growth promotion. Meanwhile, PGP15-specific genes, including many transposable elements, played a crucial role in the adaptive evolution of HM resistance. Overall, our results improve the understanding of interactions between HMT-PGPB and plants and facilitate the application of HMT-PGPB in the phytoremediation of HM-contaminated soils.

The Abundance of Trace Elements in Human Bone Relative to Bone Type and Bone Pathology

As the global population ages and the proportion of individuals afflicted with musculoskeletal disease spirals upward, there is an increasing interest in understanding and preventing bone-related diseases. Bone diseases, such as osteoporosis and osteoarthritis, are known to be influenced by a variety of factors including age, gender, nutrition, and genetics, but are also inherently linked to the human body's ability to produce biominerals of suitable quality. Because the crystal lattice structure and mineralogy of bone hydroxyapatite is surprisingly analogous to geological hydroxyapatite, trace element levels and exposure have long been proposed to influence the structure of biominerals as they do geological minerals (e.g., strontium substitution changes the crystal lattice of bone minerals, while toxic lead disrupt bone cellular processes leading to bone disease). Here, we explore the distribution of trace elements in human bones to evaluate the distribution of these elements with respect to bone type (cortical vs. trabecular) and bone disease (osteoarthritis vs. osteoporosis). We find higher concentrations of many metabolically active transition metals, as well as lead, in cortical bone compared to trabecular bone. When compared to patients who have osteoarthritis, and thus presumably normal bone minerals, osteoporosis patients have higher concentrations of scandium and chromium (Cr) in trabecular bone, and Cr and lead in cortical bone. Lower concentrations of barium and titanium are associated with osteoporotic trabecular bone. This survey is an exploratory cross-sectional geochemical examination of several trace element concentrations previously understudied in human bone minerals.

The association between hemoglobin level and osteoporosis in a Chinese population with environmental lead and cadmium exposure

Low hemoglobin (Hb) level or anemia is associated with osteoporosis and bone fracture. Cadmium (Cd) and lead (Pb) exposure are also risk factors of osteoporosis and anemia. However, the role of anemia in Cd/Pb related bone loss remains unclear. The aim of present study was to investigate the association between Hb level and bone loss in a population with environmental lead and cadmium exposure. One hundred and ninety-four women and 108 men with different levels of Cd/Pb exposure were included in our study. The Cd/Pb exposure was determined using graphite-furnace atomic absorption spectrometry. Forearm bone mineral density (BMD) was determined by peripheral dual-energy X-ray absortiometry. Hb concentration was determined using an automatic blood cellcounter. A logistic model was established to predict the risk of osteoporosis. The BMDs of women that had the highest quartile BCd and BPb were markedly lower than that with the lowest quartile (p < 0.05). The BMD and the prevalence of osteoporosis in men with anemia were lower and higher than that with normal Hb (p < 0.05), respectively. In men, age, BPb and anemia were independent risk factors for osteoporosis. The odds ratio (OR) of men with anemia was 11.28 (95%confidence interval (CI):1.94-65.54) and 19.56 (95%CI: 2.98-128.78) compared to those with normal Hb after adjusting for potential cofounders. No such association was found in women. The area under the curve was 0.88 (95%CI: 0.82-0.96) in predicting osteoporosis using the logistic model in men. Linear discriminant analysis also showed that 90.7% of osteoporosis was correctly classified. Our data show that anemia is associated with incident of osteoporosis in men but not in women that environmentally exposed to Pb and Cd.

Maternal exposure to cadmium during pregnancy is associated with changes in DNA methylation that are persistent at 9 years of age

BACKGROUND

Cadmium (Cd) exposure during gestation has been associated with altered DNA methylation at birth, but it is not known if the changes in methylation persist into childhood.

OBJECTIVES

To evaluate whether gestational Cd-related changes of DNA methylation persist from birth to 9 years of age.

METHODS

We studied mother-child dyads in a longitudinal cohort in rural Bangladesh. Cadmium concentrations in maternal blood (erythrocyte fraction; Ery-Cd) at gestational week 14 and in child urine (U-Cd, long-term exposure marker) at 9 years were measured using inductively coupled plasma mass spectrometry. The epigenome-wide DNA methylation was measured in mononuclear cells (PBMCs) prepared from cord blood and peripheral blood at 9 years in 71 children (hereafter referred to as the explorative group) by Infinium HumanMethylation450K BeadChip. Replication of one differentially methylated region (DMR; 9 CpG sites) was performed in PBMCs of 160 9-year-old children (validation group) by EpiTyper MALDI-TOF mass spectrometry.

RESULTS

The median maternal Ery-Cd concentration was 1.24 µg/kg (range 0.35, 4.55) in the explorative group and 0.83 µg/kg (0.08, 2.97) in the validation group. The median U-Cd concentration in the 9-year-old children was 0.26 µg/L (0.09, 1.06) in the explorative group and 0.32 µg/L (0.07, 1.33) in the validation group. In the explorative group, we identified ten DMRs, both in cord blood and in PBMCs at 9 years, that were associated with maternal Ery-Cd. Eight out of the ten DMRs were hypomethylated and three of the hypomethylated DMRs were located in the HLA region on chromosome 6. One of the DMRs (hypomethylated) in the HLA region (upstream of the zinc finger protein 57 homolog, ZFP57 gene) was replicated in the validation group, and we found that it was hypomethylated in relation to maternal Ery-Cd, but not child U-Cd.

CONCLUSION

Gestational exposure to Cd appears to be associated with regional changes, especially hypomethylated, in DNA methylation that linger from birth up to prepubertal age.

Cadmium inhibits signal transducer and activator of transcription 6 leading to pancreatic β cell apoptosis

The toxic heavy metal cadmium has been proven to cause pancreatic dysfunction and lead to the development of DM. However, the underlying mechanisms have not been completely elucidated. Here, we investigated the effects of cadmium on the pancreatic β cell line MIN6 and explored the underlying mechanisms. The Cell Counting Kit-8 (CCK8) assay and flow cytometry were used to determine cell viability and apoptosis in MIN6 cells. The expression levels of signal transducer and activator of transcription 6 (STAT6) were assessed by western blotting. We further assessed the effects of cadmium on the function of pancreatic β cells under high glucose levels using enzyme-linked immunosorbent assay (ELISA) and western blotting. Insulin secretion and expression were decreased by cadmium in MIN6 cells. In addition, cadmium suppressed cell viability and promoted apoptosis of MIN6 cells, downregulated insulin secretion and genesis of MIN6 cells under high glucose conditions, while inhibiting STAT6. Furthermore, after treatment with IL-4, the activator of STAT6, the MIN6 cell viability suppression and apoptosis promotion effect caused by cadmium were blocked. In conclusion, cadmium inhibits pancreatic β cell MIN6 growth by regulating the activation of STAT6. Our findings reveal a new mechanism of cadmium toxicity in pancreatic β cells.

Long-term cadmium exposure and fractures, cardiovascular disease, and mortality in a prospective cohort of women

BACKGROUND

Cadmium (Cd) is a toxic metal, which the non-smoking population is mainly exposed to through diet. Current health-based guidance values are based on renal toxicity; however, emerging evidence suggests that bone and the cardiovascular system might be more sensitive to Cd exposure.

OBJECTIVE

To assess the association of urinary Cd (U-Cd) with incidence of fractures, myocardial infarction, heart failure, ischemic stroke and mortality in postmenopausal women.

METHODS

We used data from 4024 women, aged 56-85 in the population-based prospective Swedish Mammography Cohort-Clinical. U-Cd was measured by ICP-MS at baseline (2004-2009) and categorized into tertiles. Incident cases of the outcomes were ascertained via register linkage through 2019. Multivariable-adjusted hazard ratios (HR) and 95% confidence intervals (CI) were estimated using Cox regression.

RESULTS

The median U-Cd at baseline was 0.33 µg/g creatinine (cr) (5-95 percentiles 0.15-0.77). We ascertained the following incident cases: 903 first fracture of any type, 149 myocardial infarction, 174 heart failure, 162 ischemic stroke and 545 total deaths during the approximately 11 years of follow-up. U-Cd was dose-dependently associated with risk of any fracture (HR: 1.20, 95% CI: 1.01 to 1.43, p_trend: 0.04) and all-cause mortality (HR: 1.38, 95% CI: 1.10 to 1.74, p_trend: <0.01) when comparing the highest tertile of U-Cd (median 0.54 µg/g cr) with the lowest (median 0.20 µg/g cr). No clear associations were observed for myocardial infarction, heart failure or stroke.

DISCUSSION

Long-term Cd exposure might be associated with risk of fractures and all-cause mortality at lower levels than previously suggested.

Gestational Cd Exposure in the CD-1 Mouse Sex-Specifically Disrupts Essential Metal Ion Homeostasis

In CD-1 mice, gestational-only exposure to cadmium (Cd) causes female-specific hepatic insulin resistance, metabolic disruption, and obesity. To evaluate whether sex differences in uptake and changes in essential metal concentrations contribute to metabolic outcomes, placental and liver Cd and essential metal concentrations were quantified in male and female offspring perinatally exposed to 500 ppb CdCl2. Exposure resulted in increased maternal liver Cd+2 concentrations (364 µg/kg) similar to concentrations found in non-occupationally exposed human liver. At gestational day (GD) 18, placental Cd and manganese concentrations were significantly increased in exposed males and females, and zinc was significantly decreased in females. Placental efficiency was significantly decreased in GD18-exposed males. Increases in hepatic Cd concentrations and a transient prenatal increase in zinc were observed in exposed female liver. Fetal and adult liver iron concentrations were decreased in both sexes, and decreases in hepatic zinc, iron, and manganese were observed in exposed females. Analysis of GD18 placental and liver metallothionein mRNA expression revealed significant Cd-induced upregulation of placental metallothionein in both sexes, and a significant decrease in fetal hepatic metallothionein in exposed females. In placenta, expression of metal ion transporters responsible for metal ion uptake was increased in exposed females. In liver of exposed adult female offspring, expression of the divalent cation importer (Slc39a14/Zip14) decreased, whereas expression of the primary exporter (Slc30a10/ZnT10) increased. These findings demonstrate that Cd can preferentially cross the female placenta, accumulate in the liver, and cause lifelong dysregulation of metal ion concentrations associated with metabolic disruption.

Cadmium exposure and risk of diabetes and prediabetes: A systematic review and dose-response meta-analysis

BACKGROUND

Cadmium exposure has been associated with increased diabetes risk in several studies, though there is still considerable debate about the magnitude and shape of the association.

OBJECTIVE

To perform a systematic review and meta-analysis of observational studies investigating the relation between cadmium exposure and risk of type 2 diabetes and prediabetes, and to summarize data on the magnitude and shape of the association.

DATA SOURCE

After conducting an online literature search through October 1, 2021, we identified 42 eligible studies investigating the association between cadmium exposure and risk of diabetes and prediabetes.

STUDY ELIGIBILITY CRITERIA

We included studies that assessed cadmium exposure through biomarker levels; examined type 2 diabetes or prediabetes among outcomes; and reported effect estimates for cadmium exposure for meta-analysis only.

STUDY APPRAISAL AND SYNTHESIS METHODS

Studies were evaluated using ROBINS-E risk of bias tool. We quantitively assessed the relation between exposure and study outcomes using one-stage dose-response meta-analysis with a random effects meta-analytical model.

RESULTS

In the meta-analysis, comparing highest-versus-lowest cadmium exposure levels, summary relative risks (RRs) for type 2 diabetes were 1.24 (95% confidence interval 0.96-1.59), 1.21 (1.00-1.45), and 1.47 (1.01-2.13) for blood, urinary, and toenail matrices, respectively. Similarly, there was an increased risk of prediabetes for cadmium concentrations in both urine (RR = 1.41, 95% CI: 1.15-1.73) and blood (RR = 1.38, 95% CI: 1.16-1.63). In the dose-response meta-analysis, we observed a consistent linear positive association between cadmium exposure and diabetes risk, with RRs of 1.25 (0.90-1.72) at 2.0 µg/g of creatinine. Conversely for blood cadmium, diabetes risk appeared to increase only above 1 µg/L. Prediabetes risk increased up to approximately 2 µg/g creatinine above which it reached a plateau with RR of 1.42 (1.12-1.76) at 2 µg/g creatinine.

LIMITATIONS AND CONCLUSIONS

This analysis provides moderate-certainty evidence for a positive association between cadmium exposure (measured in multiple matrices) and risk of both diabetes and prediabetes.

Plasma membrane-localized protein BcHIPP16 promotes the uptake of copper and cadmium in planta

Cadmium (Cd) is one of the toxic heavy metals in soil, which not only suppresses crop production but also threatens human health. In this study, we aim to clarify the biological function of Cd-related gene BcHIPP16, so as to provide potential genetic solutions to decrease the Cd levels of pak choi. Tissue expression analysis showed that BcHIPP16 expressed in almost all the plant bodies. The transcriptional level of BcHIPP16 in roots was higher than that in shoots, which was significantly induced by copper (Cu) deficiency and Cd exposure conditions. Subcellular localization revealed that BcHIPP16 localized in plasma membrane. Expressing BcHIPP16 in yeast cells improved the sensitivity to Cu and Cd and improved their accumulation in yeast. Furthermore, the Cu and Cd content of Arabidopsis seedlings were increased and complemented, respectively when expressing BcHIPP16 in wild type (WT) and hip16 mutants. Non-invasive Micro-test Technology (NMT) was used to measure the real-time Cd²⁺ influx from the root surface of BcHIPP16 transgenic Arabidopsis lines, and the result demonstrated that BcHIPP16 promoted Cd²⁺ influx into Arabidopsis root cells. Taken together, our study showed that BcHIPP16 contributed to absorbing nutrient metal Cu and heavy metal Cd in planta.

The Association Between Cadmium Exposure and Osteoporosis: A Longitudinal Study and Predictive Model in a Chinese Female Population

Objective: The association between cadmium exposure and osteoporosis has been rarely reported in longitudinal studies. In this study, we investigated the association between osteoporosis and cadmium exposure and developed predictive models in women in a longitudinal cohort. Materials and Methods: In total, 488 women living in southeastern China were included at baseline (1998). Cadmium in blood (BCd) and urine (UCd) and also renal dysfunction biomarkers and bone mineral density (BMD) were determined both at baseline and follow-up. A total of 307 subjects were finally included after excluding subjects that did not have exposure or effect biomarkers. Osteoporosis was defined based on T score ≤ -2.5. Multiple linear regression and multivariate logistic analysis were used to show the association between baseline data and follow-up osteoporosis. Based on the identified associated factors, nomograms were developed to graphically calculate the individual risk of osteoporosis. Results: The baseline BMD in subjects with osteoporosis was significantly lower than that in subjects without osteoporosis (0.59 vs. 0.71 g/cm², p < 0.05). The prevalence of low bone mass at baseline was higher in subjects with osteoporosis than in those without osteoporosis (23.5 vs. 7.2%, p = 0.001). Logistic regression analysis demonstrated that age [odds ratio (OR) = 1.21, 95% confidence interval (CI): 1.16-1.27], UCd (OR = 1.03, 95% CI: 1.002-1.06) and the presence of low BMD (OR = 3.84, 95% CI: 1.49-9.89) were independent risk factors for osteoporosis. For those subjects with normal baseline BMD, age, UCd, and baseline BMD were also independent risk factors for osteoporosis. The OR value was 1.16 (95% CI: 1.10-1.22) for age, 2.27 (95% CI: 1.03-4.99) for UCd > 10 μg/g creatinine, and 0.39 (95% CI: 0.21-0.72) for BMD_baseline. We developed two nomograms to predict the risk of osteoporosis. The area under the curve was 0.88 (95% CI: 0.84-0.92) for total population and was 0.88 (95% CI: 0.84-0.92) for subjects with normal baseline BMD, respectively. Conclusion: Baseline age, UCd, and BMD were associated with follow-up osteoporosis in women. Nomograms showed good performance in predicting the risk of osteoporosis.

Urinary cadmium in relation to bone damage: Cadmium exposure threshold dose and health-based guidance value estimation

Cadmium (Cd) is a widespread heavy metal with osteotoxicity, and bone mineral density (BMD) is often used as an early sensitive biomarker of bone damage. This study retrieved worldwide epidemiological studies to conduct a systematic meta-analysis to explore the association between Cd exposure and bone damage. A random effect model was used to establish the relationship between urinary Cd (U-Cd) and BMD and explore the influence of covariate factors. The benchmark dose method was used to calculate the safety threshold of U-Cd when the BMD decrease within an acceptable range. Toxicokinetic (TK) model was used to estimate the health-based guidance value (HBGV) of dietary Cd exposure based on the U-Cd threshold. The 95% lower confidence interval of benchmark dose of U-Cd derived in this study was 1.71 μg/g Cr, and the HBGV of dietary Cd exposure was determined to be 0.64 μg/kg bw/day. Gender had the greatest influence on BMD, followed by body mass index (BMI), age, and race. This study conducted a comprehensive systematic analysis of global research and was the first exploration to quantify the decreased BMD caused by Cd exposure in a large-scale population. The results provided reference for the risk assessment of Cd exposure and the formulation of dietary exposure standards.

Cadmium exposure induces osteoporosis through cellular senescence, associated with activation of NF-κB pathway and mitochondrial dysfunction

Cadmium (Cd) is a heavy metal toxicant as a common pollutant derived from many agricultural and industrial sources. The absorption of Cd takes place primarily through Cd-contaminated food and water and, to a significant extent, via inhalation of Cd-contaminated air and cigarette smoking. Epidemiological data suggest that occupational or environmental exposure to Cd increases the health risk for osteoporosis and spontaneous fracture such as itai-itai disease. However, the direct effects and underlying mechanism(s) of Cd exposure on bone damage are largely unknown. We used primary bone marrow-derived mesenchymal stromal cells (BMMSCs) and found that Cd significantly induced BMMSC cellular senescence through over-activation of NF-κB signaling pathway. Increased cell senescence was determined by production of senescence-associated secretory phenotype (SASP), cell cycle arrest and upregulation of p21/p53/p16^INK4a protein expression. Additionally, Cd impaired osteogenic differentiation and increased adipogenesis of BMMSCs, and significantly induced cellular senescence-associated defects such as mitochondrial dysfunction and DNA damage. Sprague-Dawley (SD) rats were chronically exposed to Cd to verify that Cd significantly increased adipocyte number, and decreased mineralization tissues of bone marrow in vivo. Interestingly, we observed that Cd exposure remarkably retarded bone repair and regeneration after operation of skull defect. Notably, pretreatment of melatonin is able to partially prevent Cd-induced some senescence-associated defects of BMMSCs including mitochondrial dysfunction and DNA damage. Although Cd activated mammalian target of rapamycin (mTOR) pathway, rapamycin only partially ameliorated Cd-induced cell apoptosis rather than cellular senescence phenotypes of BMMSCs. In addition, a selective NF-κB inhibitor moderately alleviated Cd-caused the senescence-related defects of the BMMSCs. The study shed light on the action and mechanism of Cd on osteoporosis and bone ageing, and may provide a novel option to ameliorate the harmful effects of Cd exposure.