Cadmium or cadmium compounds and chronic kidney disease in workers and the general population: a systematic review

Cornus officinalis var. koreana Kitam extracts alleviate cadmium-induced renal fibrosis by targeting matrix metallopeptidase 9

ETHNOPHARMACOLOGICAL RELEVANCE

Cornus officinalis var. koreana Kitam (Cornus officinalis) is a commonly used Chinese herbal medicine and has a good clinical efficacy in kidney and liver diseases. Recent years, a number of studies reported the significant effects of Cornus officinalis on renal fibrosis. However, it is still unclear about the underlying specific mechanism, the bioactive ingredients, and the target gene regulatory network.

AIM OF THE STUDY

We investigated the impact of Cornus officinalis extract on cadmium-induced renal fibrosis, screened the bioactive ingredients of Cornus officinalis using a pharmacological sub-network analysis, and explored the regulatory effects of Cornus officinalis extracts on target gene matrix metallopeptidase 9 (MMP9).

METHODS

Male C57BL/6N mice were treated with single or combinatorial agents such as saline, cadmium chloride, Cornus officinalis, Isoginkgetin and FSL-1. Isoginkgetin is a compound with anti-MMP9 activity. FSL-1 can induce MMP9 expression. Masson staining and Western blot and immunohistochemistry analyses were used for assessing renal fibrosis. In addition, wound healing model was established using BUMPT (Boston university mouse proximal tubular) cells to investigate how Cornus officinalis affected cadmium-induced cell migration. The main Cornus officinalis bioactive compounds were identified by UHPLC-MS (Ultra-high-performance liquid chromatography - mass spectrometry). The MMP9 target for Cornus officinalis active ingredients were confirmed through a pharmacological sub-network analysis.

RESULTS

Aqueous extracts of Cornus officinalis protected from renal dysfunction and kidney fibrosis induced by cadmium chloride in mice. In vitro experiments validated that Cornus officinalis extracts inhibited cell migration ability especially in cadmium chloride condition. The sub-network analysis and chemical components profiling technique revealed the active compounds of Cornus officinalis. Cellular thermal shift assay verified the binding abilities of three active components Daidzein, N-Acetyl-L-tyrosine or Swertisin with matrix metalloproteinase-9. Gelatin zymography assay revealed that the activity of MMP9 was inhibited by the three active components. We further confirmed that MMP9 was involved in the process of Cornus officinalis extracts reducing renal fibrosis. Cornus officinalis attenuated the cadmium-induced renal fibrosis was correlated with decreased expression of MMP9, collagen I, α-SMA (alpha-smooth muscle actin) and vimentin.

CONCLUSIONS

This study demonstrated that Cornus officinalis extracts could alleviate the cadmium chloride-induced renal fibrosis by targeting MMP9, and might provide new insights into the mechanism of treating renal fibrosis by Cornus officinalis.

Is Chronic Kidney Disease Due to Cadmium Exposure Inevitable and Can It Be Reversed?

Cadmium (Cd) is a metal with no nutritional value or physiological role. However, it is found in the body of most people because it is a contaminant of nearly all food types and is readily absorbed. The body burden of Cd is determined principally by its intestinal absorption rate as there is no mechanism for its elimination. Most acquired Cd accumulates within the kidney tubular cells, where its levels increase through to the age of 50 years but decline thereafter due to its release into the urine as the injured tubular cells die. This is associated with progressive kidney disease, which is signified by a sustained decline in the estimated glomerular filtration rate (eGFR) and albuminuria. Generally, reductions in eGFR after Cd exposure are irreversible, and are likely to decline further towards kidney failure if exposure persists. There is no evidence that the elimination of current environmental exposure can reverse these effects and no theoretical reason to believe that such a reversal is possible. This review aims to provide an update on urinary and blood Cd levels that were found to be associated with GFR loss and albuminuria in the general populations. A special emphasis is placed on the mechanisms underlying albumin excretion in Cd-exposed persons, and for an accurate measure of the doses-response relationships between Cd exposure and eGFR, its excretion rate must be normalised to creatinine clearance. The difficult challenge of establishing realistic Cd exposure guidelines such that human health is protected, is discussed.

Protective effect of quercetin on cadmium-induced kidney apoptosis in rats based on PERK signaling pathway

BACKGROUND

Cadmium (Cd) is a highly toxic environmental pollutant that can enter the body through bioaccumulation. The kidney is an important target organ for Cd poisoning. Quercetin (Que) is a natural flavonoid compound with free radical scavenging and antioxidant properties. Previous studies showed that Que can alleviate kidney damage caused by Cd poisoning in rats, but the specific mechanism is still unclear.

METHODS

Twenty-four male Sprague-Dawley (SD) rats were divided into four groups: normal saline-treated control group, Cd group treated by intraperitoneal injection of 2 mg/kg b.w. CdCl2, Cd + Que group treated by intraperitoneal injection of 2 mg/kg b.w. CdCl2 and 100 mg/kg b.w. Que, and Que group treated by 100 mg/kg b.w. Que. Four weeks later, the rats were anesthetized with diethyl ether, and blood was taken intravenously. The rats were executed with their necks cut off, and the kidneys were removed. Body weight, kidney organ weight, and glutathione (GSH) and malondialdehyde (MDA) levels were measured. The structure of kidney tissue was observed by hematoxylin and eosin staining, kidney cell apoptosis was detected by TUNEL assay, and the mRNA expression levels of genes related to the PERK signaling pathway were analyzed by RT-PCR.

RESULTS

Compared with the control group, the Cd-treated group exhibited a significant decrease in body weight (P < 0.01). Their kidneys showed a significant increase in the relative organ weight (P < 0.01). Moreover, the MDA and GSH levels increased. Kidney tissue damage and renal cell apoptosis were observed, and the mRNA expression levels of genes related to the PERK signaling pathway significantly increased (P < 0.01). Compared with the Cd-treated group, the Cd + Que group exhibited a significant increase in body weight (P < 0.01) and significant decreases in the relative organ weight, MDA and GSH levels, and mRNA expression levels of genes related to the PERK signaling pathway (P < 0.01). Furthermore, kidney tissue damage and renal cell apoptosis were observed.

CONCLUSION

Cd treatment resulted in rat weight loss, renal edema, and oxidative stress and caused renal tissue damage and cell apoptosis by activating the PERK signaling pathway. Que was able to restore the body weight and renal coefficient of rats. It also alleviated the oxidative stress and kidney tissue damage caused by Cd and the cell apoptosis caused by Cd through inhibiting the PERK signaling pathway. Thus, Que could be considered for the treatment of kidney diseases caused by Cd poisoning.

Efficient and safe use of a slow-release Mn material for three sequential crops of rice in Cd-contaminated paddy soils

Traditional passivators reduce the effectiveness of Cd by ion exchange, chemisorption, and complexation in soil. However, traditional passivators have defects such as easy aging and poor durability, which not only reduce the treatment efficiency but also increase the risk of primary soil environmental pollution. For this reason, considering that Mn and Cd have physiological antagonism in rice, sepiolite-supported manganese ferrite (SMF) was prepared in this study to improve passivation persistence. The passivation mechanism, effect and duration of SMF were explored. The results showed that SMF has a dense and small pore structure and that the surface is rough, which provides abundant adsorption sites for Cd2+ adsorption. When the SMF adsorbs Cd2+, ions or functional groups in the material, such as MnOOH*, will exchange with Cd2+ to form Cd(OH)2 and other internal complexes. Indoor pure soil cultivation experiments showed that 0.1 % SMF can reduce the effective Cd content of soil by 41.32 %, demonstrating the efficiency of SMF. The three-crop rice experiments in pots showed that SMF could increase soil pH and continuously increase the content of available Mn in soil. Increasing the content of available Mn reduces the ability of rice to absorb Cd. In addition, the three-cropping rice experiments also indicated that the passivation effect of SMF materials on Cd-contaminated paddy fields was long-lasting and stable and that SMF is a more efficient and safe Cd passivation agent.

Current Levels of Environmental Exposure to Cadmium in Industrialized Countries as a Risk Factor for Kidney Damage in the General Population: A Comprehensive Review of Available Data

The growing number of reports indicating unfavorable outcomes for human health upon environmental exposure to cadmium (Cd) have focused attention on the threat to the general population posed by this heavy metal. The kidney is a target organ during chronic Cd intoxication. The aim of this article was to critically review the available literature on the impact of the current levels of environmental exposure to this xenobiotic in industrialized countries on the kidney, and to evaluate the associated risk of organ damage, including chronic kidney disease (CKD). Based on a comprehensive review of the available data, we recognized that the observed adverse effect levels (NOAELs) of Cd concentration in the blood and urine for clinically relevant kidney damage (glomerular dysfunction) are 0.18 μg/L and 0.27 μg/g creatinine, respectively, whereas the lowest observed adverse effect levels (LOAELs) are >0.18 μg/L and >0.27 μg/g creatinine, respectively, which are within the lower range of concentrations noted in inhabitants of industrialized countries. In conclusion, the current levels of environmental exposure to Cd may increase the risk of clinically relevant kidney damage, resulting in, or at least contributing to, the development of CKD.

Health risk assessment of heavy metals (Zn, Pb, Cd, and Hg) in water and muscle tissue of farmed carp species in North Iran

This cross-sectional study was conducted to determine and compare the concentrations of heavy metals (Zn, Pb, Cd, and Hg) in carp-farming water and muscle of various carp species including common carp (Cyprinus carpio), bighead carp (Hypophthalmichthys nobilis), silver carp (Hypophthalmichthys molitrix), and grass carp (Ctenopharyngodon idella) collected from three major warm-water fish farms in Mazandaran Province (Iran) during March 2018 to March 2019. In addition, bioaccumulation of heavy metals (BCFs) and carcinogenic and non-carcinogenic risk assessments of consumers exposed to heavy metals through fish consumption were estimated. The water concentration of all metals in this study was lower than permissible limits. The concentration of Zn in the water (10.21-17.11 μg L^-1) was higher than that of other metals in all sites, followed by Pb > Cd > Hg. In fish muscle, Zn concentration in silver carp was the highest, and the lowest concentrations were related to Hg and Cd in common carp and grass carp, respectively. The target hazard quotients (THQ) indicated that the non-carcinogenic health risk to humans was relatively low by consuming four farmed carp species products. The carcinogenic risk of inorganic Pb was 1.24E-04 (common carp) to 2.11E-04 (grass carp) for adults, which is within the acceptable range. The values of BCFs for all metals demonstrated that farmed carp muscle could not be considered a bioaccumulative tissue for heavy metals. The results indicated that the concentrations of heavy metals in the farmed carp species in North Iran were relatively low and did not cause considerable human health risks.

Association of single and joint metals with albuminuria and estimated glomerular filtration longitudinal change in middle-aged adults from Spain: The Aragon workers health study

The nephrotoxicity of low-chronic metal exposures is unclear, especially considering several metals simultaneously. We assessed the individual and joint association of metals with longitudinal change in renal endpoints in Aragon Workers Health Study participants with available measures of essential (cobalt [Co], copper [Cu], molybdenum [Mo] and zinc [Zn]) and non-essential (As, barium [Ba], Cd, chromium [Cr], antimony [Sb], titanium [Ti], uranium [U], vanadium [V] and tungsten [W]) urine metals and albumin-to-creatinine ratio (ACR) (N = 707) and estimated glomerular filtration rate (eGFR) (N = 1493) change. Median levels were 0.24, 7.0, 18.6, 295, 3.1, 1.9, 0.28, 1.16, 9.7, 0.66, 0.22 μg/g for Co, Cu, Mo, Zn, As, Ba, Cd, Cr, Sb, Ti, V and W, respectively, and 52.5 and 27.2 ng/g for Sb and U, respectively. In single metal analysis, higher As, Cr and W concentrations were associated with increasing ACR annual change. Higher Zn, As and Cr concentrations were associated with decreasing eGFR annual change. The shape of the longitudinal dose-responses, however, was compatible with a nephrotoxic role for all metals, both in ACR and eGFR models. In joint metal analysis, both higher mixtures of Cu-Zn-As-Ba-Ti-U-V-W and Co-Cd-Cr-Sb-V-W showed associations with increasing ACR and decreasing eGFR annual change. As and Cr were main drivers of the ACR change joint metal association. For the eGFR change joint metal association, while Zn and Cr were main drivers, other metals also contributed substantially. We identified potential interactions for As, Zn and W by other metals with ACR change, but not with eGFR change. Our findings support that Zn, As, Cr and W and suggestively other metals, are nephrotoxic at relatively low exposure levels. Metal exposure reduction and mitigation interventions may improve prevention and decrease the burden of renal disease in the population.

Association of low cadmium and mercury exposure with chronic kidney disease among Chinese adults aged ≥80 years: A cross-sectional study

BACKGROUND

The heavy metals cadmium (Cd) and mercury (Hg) are known to be widespread environmental contaminants and high occupational exposure adversely affects the risk of chronic kidney disease (CKD). However, evidence from epidemiological studies linking low Cd and Hg exposure (or non-industrial) to the risk of progression to CKD are conflicting. This study aimed to explore the association of low Cd and Hg exposure with the risk of CKD in Chinese adults aged ≥80 years.

METHODS

The participants were recruited for the Healthy Aging and Biomarkers Cohort Study in 2017, an ongoing perspective survey conducted in longevity areas in China initially involving 3016 older adults. We used logistic regression models to estimate odds ratios (ORs) with 95% confidence intervals of CKD setting Cd and Hg as categorical variables. Logistic regression with restricted cubic spline was used to characterize a dose-response relationships between Cd or Hg concentrations and the risk of CKD in the study population.

RESULTS

The ORs for the risk of CKD comparing the fourth to the first quartile of blood Cd, blood Hg, urine Cd, and urine Hg were 1.77, 1.57, 2.03, and 1.50, respectively. Restricted cubic spline models showed that blood Cd and urine Hg were significantly linearly correlated with the risk of CKD, while blood Hg and urine Cd were non-linearly correlated with the risk of CKD with a steeper slope at concentrations <2.30 μg/L and 3.30 μg/g creatinine.

CONCLUSIONS

Our findings suggest that even low Cd and Hg exposure (or non-industrial) were associated with increased risk of CKD in Chinese oldest old, although we did not find a significant multiplicative and additive interaction between Cd and Hg levels in relation to the risk of CKD.

The Validity of Benchmark Dose Limit Analysis for Estimating Permissible Accumulation of Cadmium

Cadmium (Cd) is a toxic metal pollutant that accumulates, especially in the proximal tubular epithelial cells of kidneys, where it causes tubular cell injury, cell death and a reduction in glomerular filtration rate (GFR). Diet is the main Cd exposure source in non-occupationally exposed and non-smoking populations. The present study aimed to evaluate the reliability of a tolerable Cd intake of 0.83 μg/kg body weight/day, and its corresponding toxicity threshold level of 5.24 μg/g creatinine. The PROAST software was used to calculate the lower 95% confidence bound of the benchmark dose (BMDL) values of Cd excretion (E_Cd) associated with injury to kidney tubular cells, a defective tubular reabsorption of filtered proteins, and a reduction in the estimated GFR (eGFR). Data were from 289 males and 445 females, mean age of 48.1 years of which 42.8% were smokers, while 31.7% had hypertension, and 9% had chronic kidney disease (CKD). The BMDL value of E_Cd associated with kidney tubular cell injury was 0.67 ng/L of filtrate in both men and women. Therefore, an environmental Cd exposure producing E_Cd of 0.67 ng/L filtrate could be considered as Cd accumulation levels below which renal effects are likely to be negligible. A reduction in eGFR and CKD may follow when E_Cd rises from 0.67 to 1 ng/L of filtrate. These adverse health effects occur at the body burdens lower than those associated with E_Cd of 5.24 µg/g creatinine, thereby arguing that current health-guiding values do not provide a sufficient health protection.

The NOAEL Equivalent of Environmental Cadmium Exposure Associated with GFR Reduction and Chronic Kidney Disease

Cadmium (Cd) is a highly toxic metal pollutant present in virtually all food types. Health guidance values were established to safeguard against excessive dietary Cd exposure. The derivation of such health guidance figures has been shifted from the no-observed-adverse-effect level (NOAEL) to the lower 95% confidence bound of the benchmark dose (BMD), termed BMDL. Here, we used the PROAST software to calculate the BMDL figures for Cd excretion (E_Cd) associated with a reduction in the estimated glomerular filtration rate (eGFR), and an increased prevalence of chronic kidney disease (CKD), defined as eGFR ≤ 60 mL/min/1.73 m². Data were from 1189 Thai subjects (493 males and 696 females) mean age of 43.2 years. The overall percentages of smokers, hypertension and CKD were 33.6%, 29.4% and 6.2%, respectively. The overall mean E_Cd normalized to the excretion of creatinine (E_cr) as E_Cd/E_cr was 0.64 µg/g creatinine. E_Cd/E_cr, age and body mass index (BMI) were independently associated with increased prevalence odds ratios (POR) for CKD. BMI figures ≥24 kg/m² were associated with an increase in POR for CKD by 2.81-fold (p = 0.028). E_Cd/E_cr values of 0.38-2.49 µg/g creatinine were associated with an increase in POR for CKD risk by 6.2-fold (p = 0.001). The NOAEL equivalent figures of E_Cd/E_cr based on eGFR reduction in males, females and all subjects were 0.839, 0.849 and 0.828 µg/g creatinine, respectively. The BMDL/BMDU values of E_Cd/E_cr associated with a 10% increase in CKD prevalence were 2.77/5.06 µg/g creatinine. These data indicate that Cd-induced eGFR reduction occurs at relatively low body burdens and that the population health risk associated with E_Cd/E_cr of 2.77-5.06 µg/g creatinine was not negligible.

Mechanisms of Cd-induced Cytotoxicity in Normal Human Skin Keratinocytes: Implication for Human Health

Cadmium (Cd) is one of the toxic heavy metals found widely in the environment. Skin is an important target organ of Cd exposure. However, the adverse effects of Cd on human skin are still not well known. In this study, normal human skin keratinocytes (HaCaT cells) were studied for changes in cell viability, morphology, DNA damage, cycle, apoptosis, and the expression of endoplasmic reticulum (ER) stress-related genes (XBP-1, BiP, ATF-4, and CHOP) after exposure to Cd for 24 h. We found that Cd decreased cell viability in a concentration-dependent manner, with a median lethal concentration (LC₅₀) of 11 µM. DNA damage induction was evidenced by upregulation of the level of γ-H2AX. Furthermore, Cd induced G0/G1 phase cell cycle arrest and apoptosis in a dose-dependent manner and upregulated the mRNA levels of ER stress biomarker genes (XBP-1, BiP, ATF4, and CHOP). Taken together, our results showed that Cd induced cytotoxicity and DNA damage in HaCaT cells, eventually resulting in cell cycle arrest in the G0/G1 phase and apoptosis. In addition, ER stress may be involved in Cd-induced HaCaT apoptosis. Our data imply the importance of reducing Cd pollution in the environment to reduce its adverse impacts on human skin.

Associations of multiple plasma metals with chronic kidney disease in patients with diabetes

As common contaminants, metals are non-negligible risk factors for diabetes and chronic kidney disease. However, whether there is an association between multiple metals exposure and incident chronic kidney disease (CKD) risk in patients with diabetes is unclear. We conducted a prospective study to evaluate these associations. In total, 3071 diabetics with baseline estimated glomerular filtration rate (eGFR) ≥ 60 mL/min/1.73 m² from the Dongfeng-Tongji cohort were included. We measured baseline plasma concentrations of 23 metals and investigated the associations between plasma metal concentrations and CKD in diabetics using logistic regression, the least absolute shrinkage and selection operator (LASSO), and the Bayesian Kernel Machine Regression (BKMR) models. During average 4.6 years of follow-up, 457 diabetics developed CKD (14.9 %). The three models consistently found plasma levels of zinc, arsenic, and rubidium had a positive association with incident CKD risk in patients with diabetes, while titanium, cadmium, and lead had an inverse correlation. The results of BKMR showed a significant and positive overall effect of 23 metals on the risk of CKD, when all of the metals were above the 50th percentile as compared to the median value. In addition, potential interactions of zinc and arsenic, zinc and cadmium, zinc and lead, titanium and arsenic, and cadmium and lead on CKD risk were observed. In summary, we found significant associations of plasma titanium, zinc, arsenic, rubidium, cadmium, and lead with CKD in diabetes and interactions between these metals except for rubidium. Co-exposure to multiple metals was associated with increased CKD risk in diabetics.

Chain modeling for the biogeochemical nexus of cadmium in soil-rice-human health system

This paper presents a novel chain model named soil-food-human (SFH) for clarifying the biogeochemical cascades among the triple challenges of cadmium contamination, food safety, and related public health effect. The model was developed based on the integration of spatial distribution pattern of soil environment and the biogeochemical process of cadmium in soil-rice-human health, and it was validated through a case study. In soil environment terms, SFH predicted the spatial distribution of soil properties with an average prediction accuracy of 82.28%. In food production terms, the SFH can identify the safe production zones for planting rice and unsafe area for adjusting croppingsystems with a relative error of 39.41%. In food consumption terms, SFH mapped the high-resolution map of cadmium exposure dose, which gives a new solution to assess the food safety risks for self-sufficient populations. For the health effect of rice cadmium exposure, SFH simulated the spatiotemporal pattern of urinary cadmium based on toxicokinetic which revealed the health effect of rice cadmium exposure. The chain model provides a new insight in understanding the biogeochemical cascades between food production, food safety, and public health, making it possible to develop a comprehensive strategy to tackle cadmium pollution in soil-rice-human health system.

Dose-Response Analysis of the Tubular and Glomerular Effects of Chronic Exposure to Environmental Cadmium

We retrospectively analyzed data on the excretion of cadmium (E_Cd), β₂-microglobulin (E_β2M) and N-acetyl-β-D-glucosaminidase (E_NAG), which were recorded for 734 participants in a study conducted in low- and high-exposure areas of Thailand. Increased E_β2M and E_NAG were used to assess tubular integrity, while a reduction in the estimated glomerular filtration rate (eGFR) was a criterion for glomerular dysfunction. E_Cd, E_β2M and E_NAG were normalized to creatinine clearance (C_cr) as E_Cd/C_cr, E_β2M/C_cr and E_NAG/C_cr to correct for interindividual variation in the number of surviving nephrons and to eliminate the variation in the excretion of creatinine (E_cr). For a comparison, these parameters were also normalized to E_cr as E_Cd/E_cr, E_β2M/E_cr and E_NAG/E_cr. According to the covariance analysis, a Cd-dose-dependent reduction in eGFR was statistically significant only when E_cd was normalized to C_cr as E_Cd/C_cr (F = 11.2, p < 0.001). There was a 23-fold increase in the risk of eGFR ≤ 60 mL/min/1.73 m² in those with the highest E_Cd/C_cr range (p = 0.002). In addition, doubling of E_Cd/C_cr was associated with lower eGFR (β = -0.300, p < 0.001), and higher E_NAG/C_cr (β = 0.455, p < 0.001) and E_β2M/C_cr (β = 0.540, p < 0.001). In contrast, a covariance analysis showed a non-statistically significant relationship between E_Cd/E_cr and eGFR (F = 1.08, p = 0.165), while the risk of low eGFR was increased by 6.9-fold only among those with the highest E_Cd/E_cr range. Doubling of E_Cd/E_cr was associated with lower eGFR and higher E_NAG/E_cr and E_β2M/E_cr, with the β coefficients being smaller than in the C_cr-normalized dataset. Thus, normalization of Cd excretion to C_cr unravels the adverse effect of Cd on GFR and provides a more accurate evaluation of the severity of the tubulo-glomerular effect of Cd.

Myo-inositol oxygenase overexpression exacerbates cadmium-induced kidney injury via oxidant stress and necroptosis

Conceivably, like other forms of acute kidney injury, cadmium-induced renal injury may also be associated with oxidative stress and various forms of cell death, including necroptosis, a form of regulated necrosis-associated cell death. Myo-inositol oxygenase (MIOX), an enzyme localized in renal proximal tubules, regulates oxidative stress and programmed cell death in various forms of renal injuries. Herein, the role and potential mechanism(s) by which MIOX potentiates cadmium-induced renal tubular damage were investigated. Overexpression of MIOX exacerbated cadmium-induced cell death and proximal tubular injury in mice, whereas MIOX gene disruption attenuated cellular damage in vitro and in vivo. Furthermore, necroptosis was observed in the renal tubular compartment, and, more importantly, it was corroborated by inhibitor experiments with necrostatin-1 (Nec-1). Coadministration of Nec-1 dampened including receptor-interacting protein kinase (RIP)1/RIP3/mixed-lineage kinase domain-like signaling, which is relevant to the process of necroptosis. Interestingly, the necroptosis induced by cadmium in tubules was modulated by MIOX expression profile. Also, the increased reactive oxygen species generation and NADPH consumption were accelerated by MIOX overexpression, and they were mitigated by Nec-1 administration. These findings suggest that MIOX-potentiated redox injury and necroptosis are intricately involved in the pathogenesis of cadmium-induced nephropathy, and this may yield novel potential therapeutic targets for amelioration of cadmium-induced kidney injury.NEW & NOTEWORTHY This is a seminal article documenting the role of myo-inositol oxygenase (MIOX), a renal proximal tubule-specific enzyme, in the exacerbation of cadmium-induced acute kidney injury by perturbing redox balance and inducing necroptosis. MIOX gene disruption or administration of necrostatin-1 (a necroptosis inhibitor) diminished cadmium-induced renal damage, in both in vitro and in vivo systems, suggesting a therapeutic potential of MIOX to attenuate necroptosis and relevant signaling pathways in cadmium-induced renal injury.

Cadmium exposure in US adults, research based on the National Health and Nutrition Examination Survey from 1988 to 2018

Cadmium (Cd) is a widespread environmental contaminant that has a wide range of adverse effects on human health. We described the distribution of blood Cd levels (BCLs) and urinary Cd levels (UCLs) in US adults aging ≥ 18 years over a 30-year period by using data from the National Health and Nutrition Examination Survey (NHANES) III and continuous NHANES (1999-2018). Geometric mean (GM) and 95% confidence intervals (CI) were calculated among participants with valid BCLs (n=47889) or UCLs (n=33003). The prevalence of BCLs ≥ 0.5, ≥ 1.0 ug/L and UCLs ≥ 0.5, ≥ 1.0 ug/g creatinine were estimated. The results showed that for men and women, respectively, GM BCLs declined from 0.458 and 0.472 ug/L in 1999-2000 to 0.252 and 0.330 ug/L in 2017-2018, while GM UCLs declined from 0.266 and 0.376 ug/g creatinine in 1988-1991 to 0.145 and 0.231 ug/g creatinine in 2015-2016. The estimated prevalence of UCLs ≥ 0.5 ug/g creatinine among men and women declined from 31.96 and 45.34% during 1988-1991 to 7.88 and 18.73% in 2015-2016. Higher Cd exposure was associated with females, older age, poverty, lower education, and smoking. These results indicate that Cd exposure in US adults has declined over the past 30 years. However, there are still approximately 7.88% US men and 18.73% US women being exposed to Cd at levels reported to show toxic effects on kidneys.

Exposure to cadmium induces neuroinflammation and impairs ciliogenesis in hESC-derived 3D cerebral organoids

Cadmium (Cd) is an environmental heavy metal toxicant with central nervous system toxicity and has a greater negative impact on fetal neurodevelopment. However, the causative mechanisms for the neurodevelopmental toxicity of Cd have remained unclear. The human cerebral organoids can better mimic the three-dimensional structure of the early fetal nerve tissue, which can be used to study the developmental neurotoxicity under the condition of maternal exposure to Cd. Our study identified that Cd exposure specifically induced apoptosis in neurons and inhibited the proliferation of neural progenitor cells, but neural differentiation was not significantly affected in cerebral organoids. Cd exposure also elicited overexpression of GFAP, a marker of astrocytes and resulted in IL-6 release. This study revealed that mineral absorption was significantly disturbed with metallothioneins expression up-regulation. Moreover, we found Cd exposure inhibited cilium-related gene expression and reduced ciliary length with increasing dose. In conclusion, our study has shown that Cd exposure regulated neural cell proliferation and death, induced neuroinflammation, enhanced metal ion absorption, and impaired ciliogenesis, which hinder the normal development of the fetal brain.

Trace Elements in the Large Population-Based HUNT3 Survey

The Nord-Trøndelag Health Study (The HUNT Study) is a large health survey population study in the county of Trøndelag, Norway. The survey has been repeated four times in about 10-year intervals. In the HUNT3 survey (2006-2008), we collected 28,000 samples for trace element analysis. Blood samples from 758 healthy persons without known occupational exposure were selected for multielement analysis of a small sample of blood (0.25 mL). The aim of the study was to determine the minimum blood volume that can be used for the analytical procedure and to compare our results with previously published results of similar surveys in healthy populations. Samples were digested and the concentration of selected trace elements was determined by ICP-MS. We report results on essential elements (B, Co, Cu, Mn, Se and Zn) as well as non-essential elements (As, Be, Br, Cd, Cs, In, La, Pb, Hg, Nd, Ni, Nb, Pd, Pt, Sm, Ta and Sn). Results are similar to previous studies on the HUNT3 population, and with a few exceptions, our data compares very well with results obtained in recent studies from other countries. We wanted to test a minimum volume of blood in a large-scale analytical program. For a number of nonessential elements, our results were below the limit of detection. We suggest that future studies using similar ICP-MS equipment as analytical tool should use at least 0.5 mL of blood.

Association of microRNA expression with changes in immune markers in workers with cadmium exposure

Human exposure to cadmium (Cd) is known to produce severe health effects. Recently, molecular mechanism of Cd toxicity has revealed the role of Cd in causing epigenetic alterations. miRNAs are small, non-coding RNAs which are involved in translational repression of genes. Therefore, the aim of the present study was to evaluate the alterations in expression of miRNAs associated with inflammation, carcinogenesis and, further, study their possible correlation with immune profile, in occupationally Cd exposed workers of Jodhpur. 106 workers from metal handicraft and welding factories were recruited as subjects, while, 80 apparently healthy non-exposed individuals served as control for this study. Blood Cd levels (BCd) were determined by Graphite Furnace Atomic Absorption Spectroscopy (GFAAS). Lymphocyte cell subset were measured by flow cytometry, serum interleukins were assessed by ELISA and miRNA expression was determined by Real Time Polymerase Chain Reaction (RT-PCR). BCd levels were significantly higher in the exposed individuals when compared to the non-exposed, with welders reporting the highest amongst all. Among the lymphocyte subset, exposed group showed significantly higher percentage of Th17 and lower percentage of Treg population. Cytokine profile expressed by exposed workers were predominantly pro-inflammatory in nature. Among, the studied miRNAs, miR-221 was significantly higher in exposed group with a fold change of 3.05. Additionally, miR-221 and miR-155 showed significant positive correlation with Th17 cell %. Regression analysis showed duration of exposure and IL-17 to have significant effect on miR-221 in exposed group. In conclusion, miR-221 was significantly upregulated in exposed and was correlated with immune alteration making it a potential candidate for further exploration of mechanism underlying Cd toxicity.

The association between estimated glomerular filtration rate and cadmium exposure: An 8-year follow-up study

BACKGROUND

The associations between cadmium exposure and chronic kidney disease have rarely been reported in longitudinal studies. In this study, we investigated the associations between the estimated glomerular filtration rate and cadmium exposure in a cross-sectional study in a longitudinal cohort.

MATERIALS AND METHODS

In total, 790 subjects (≥35 years of age) living in southeastern China were included at 1998. Cadmium in blood (BCd) and urine (UCd) as well as renal dysfunction biomarkers, urinary N-acetyl-β d-glucosaminidase (UNAG) and albumin (UALB), were determined. 497 subjects were followed at 2006 and a total of 456 subjects were finally included after excluding subjects that did not have exposure or effects biomarkers. The BCd, UCd, UNAG and UALB were determined using baseline methods. At follow-up, the estimated glomerular filtration rate (eGFR) was computed using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. Single nucleotide polymorphisms (SNPs) in metallothioneins 1A (MT1A) rs11076161 and MT2A rs28366003 in blood sample were detected using TaqMan allelic discrimination assays.

RESULTS

The median of UCd and BCd at baseline was 5.38 μg/g cr and 4.69 μg/L, respectively, and the median UCd and BCd at follow-up was 4.88 μg/g cr and 2.20 μg/L at follow-up. The mean eGFR at follow-up was 88.0 mL/min/1.73 m² and 15 subjects had new onset of eGFR <60 mL/min/1.73 m². The eGFR at follow-up was associated with baseline age (β = -0.66, 95% confidence interval (CI): 0.80 to -0.52), BCd (β = -0.46, 95% CI: 0.68 to -0.25) and UALB (β = -0.29, 95% CI: 0.41 to -0.16) after adjusting for confounders. Subgroup analysis in subjects who had low baseline UALB or subjects with or without hypertension showed similar results. A logistic regression model further showed that baseline BCd and UALB were independent risk factors for follow-up CKD. The odds ratios (ORs) were 1.09 (95% CI:1.03-1.16) for UALB, 1.16 (95% CI:1.01-1.33) for BCd, and 6.74 (0.87-29.63) for current hypertension. Baseline BCd, UALB and current hypertension were used to construct the nomogram. Linear discriminant analysis (LCA) showed that 87.6% of CKD was accurately predicted based on the three factors.

CONCLUSION

Baseline age, BCd and UALB were associated with follow-up eGFR, and baseline BCd and UALB were predictive factors for incidence of CKD.

Associations between exposure to heavy metals and the risk of chronic kidney disease: a systematic review and meta-analysis

We performed a systematic review and meta-analysis to examine the relationship between heavy metals (HMs) exposure and the risk of chronic kidney disease (CKD). Databases of Web of Science, Embase, MEDLINE, and Scopus were searched through June 2020 to identify studies assessing the relationships between exposure to HMs (i.e. cadmium, lead, arsenic, mercury) and the risk of CKD, evaluated by decreased estimated glomerular filtration rate (eGFR) and/or increased proteinuria risks in adults (≥18 years). Data were pooled by random-effects models and expressed as weighted mean differences and 95% confidence intervals. The risk of bias was assessed by the Newcastle-Ottawa scale (NOS). Twenty-eight eligible articles (n = 107,539 participants) were included. Unlike eGFR risk (p = 0.10), Cadmium exposure was associated with an increased proteinuria risk (OR = 1.35; 95% CI: 1.13, 1.61; p < 0.001; I² = 79.7%). Lead exposure was associated with decreased eGFR (OR = 1.12; 95%CI: 1.03, 1.22; p = 0.008; I² = 87.8%) and increased proteinuria (OR = 1.25; 95% CI: 1.04, 1.49; p = 0.02; I² = 79.6) risks. Further, arsenic exposure was linked to a decreased eGFR risk (OR = 1.55; 95% CI: 1.05, 2.28; p = 0.03; I² = 89.1%) in contrast to mercury exposure (p = 0.89). Only two studies reported the link between arsenic exposure and proteinuria risk, while no study reported the link between mercury exposure and proteinuria risk. Exposure to cadmium, lead, and arsenic may increase CKD risk in adults, albeit studies were heterogeneous, warranting further investigations. Our observations support the consideration of these associations for preventative, diagnostic, monitoring, and management practices of CKD.

Cadmium exposure induces rat proximal tubular cells injury via p62-dependent Nrf2 nucleus translocation mediated activation of AMPK/AKT/mTOR pathway

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a nuclear transcription factor of great concern which is widely involved in physiological and pathological processes of the organism, but the role and regulatory mechanism of Nrf2 in kidney exposed to cadmium (Cd) remain largely unknown. Here we demonstrated that Cd exposure induced injury in primary rat proximal tubular (rPT) cells and NRK-52E cell line, which was accompanied by autophagic flux blockade and subsequent accumulation of p62. Cd-activated nucleus translocation of Nrf2 depended on p62, which promoted antioxidant genes transcription, but it failed to against Cd-induced cell injury and ultimately succumbed to Cd toxicity. CDDO Methyl Ester (CDDO-ME) or ML385 treatment aggravated or alleviated rPT cells injury induced by Cd respectively, indicating that Nrf2 nucleus translocation played a negative role during Cd-induced rPT cells injury. Phosphorylation of 5' AMP-activated protein kinase (AMPK) decreased together with enhanced Nrf2 nucleus translocation in rPT cells exposed to Cd. Dephosphorylation of AMPK induced by Cd were facilitated or restored by CDDO-ME or ML385 treatment, which confirmed AMPK is a downstream factor of Nrf2. Simultaneously, CDDO-ME further enhanced Phosphorylation of mTOR and AKT which increased during Cd exposure. While, Cd-induced phosphorylation of mTOR and AKT were reversed by ML385 treatment. These results illustrated that Cd mediated Nrf2 nucleus translocation depends on p62 accumulation which results from autophagic flux inhibition. The enhanced nucleus translocation of Nrf2 suppresses phosphorylation of AMPK to inactivate AKT/mTOR signaling, and results in rPT cells injury finally.

The current status of osteoporosis after 15 years of reduced cadmium exposure among residents living in cadmium-contaminated areas in northwestern Thailand

The purposes of this study were to determine the prevalence of osteoporosis after 15 years of reduced cadmium exposure and to determine the association between urinary cadmium (U-Cd) and osteoporosis. The study was conducted with 937 participants (109 males, 828 females) living in a cadmium-contaminated area in northwestern Thailand. All participants were required to respond to a questionnaire. Bone mineral density (BMD) was investigated by measurements taken at the calcaneus by dual-energy X-ray absorptiometry. U-Cd, which reflects the amount of cadmium contained in the body, was measured by atomic absorption spectrophotometry (AAS). The geometric mean of U-Cd was significantly higher in males than in females (p < 0.001). The mean level of BMD for females was found to be statistically significantly lower than that for males (p < 0.001). Increasing U-Cd levels were correlated with decreasing levels of BMD. The association between U-Cd and osteoporosis appeared to exist only at concentrations of U-Cd ≥ 10 μg/g creatinine (OR = 2.7, 95% CI = 1.2-5.9). It can be concluded that despite discontinued or reduced cadmium exposure for more than 10 years, the effect of cadmium toxicity on bone, which is stronger in women, continues, as cadmium, once absorbed, will accumulate in the human body for a long time due to its extremely long half-life.

The association between life-time dietary cadmium intake from rice and chronic kidney disease

The association between internal cadmium exposure and chronic kidney disease (CKD) has been investigated before. However, few studies have shown the association between dietary cadmium intake and CKD. In this study, we show the association between life-time dietary cadmium intake and CKD based on a follow-up study. At baseline, we collected blood and urine samples for assays of cadmium and renal effect biomarkers. A questionnaire and food survey was given to each subject to collect diet and lifestyle information for the estimation of cadmium intake. Dietary cadmium, cadmium in blood and urine were regarded as exposure markers. Life-time dietary cadmium intake was estimated based on an individual's daily cadmium intake and exposure time. At follow-up, 467 persons (163 men and 304 women) were finally included. CKD at follow-up was considered if the estimated glomerular filtration rate (eGFR) was less than 60 mL/min/1.73 m². The eGFR level in subjects in the highest quartile of total dietary cadmium intake (>9.34 g) was significantly lower than in those with a moderate or low intake (p < 0.01). eGFR was negatively associated with total dietary cadmium intake (β = -0.42, 95% confidence interval (CI): -0.77 to -0.07) after adjustment with confounders. Logistic regression further showed that the risk of CKD in subjects with a high total dietary cadmium intake (>2.2 g) was higher than in those with a low intake (odds ratio (OR) = 18.16, 95%CI: 1.75-188.85). A similar association was found between the baseline urinary albumin (UALB) level and CKD incidence. A predictive model based on UALB and life-time dietary cadmium intake showed an acceptable performance (the area under the curve was 0.77 (95%CI: 0.65-0.88)). Our data show that high dietary cadmium exposure was associated with CKD after controlling for renal tubular dysfunction and internal cadmium exposure.

Diagnosis and evaluation of the health status of sediment-water-farmland-rice system in Longtang

As one of the largest electronic waste (e-waste) disassembling sites in China, environmental quality and human health of Longtang town have always been the focus of concern and research. With the effective enforcement of relevant laws, most informal e-waste dismantling centers have been shut down, but heavy metals are non-biodegradable and easily enriched contaminants that are difficult to remove from the environment. This research investigated the heavy metal (Cd, Pb, Cu, Zn, As, and Cr) level in sediments, water, paddy soils, and the matched rice plants in Longtang, and assessed the potential ecological risk and human health risk of heavy metals. The results showed that the heavy metal content was highest in the sediment, followed by paddy soil and rice, the lowest in water, and the surface water was higher than groundwater. In the paddy soil, the heavy metal content in the topsoil was the highest, and all exceeded the soil background value of Guangdong Province, and the level of Cu (129.45 mg kg^-1), Cd (0.44 mg kg^-1), and Pb (100.63 mg kg^-1) exceeded the national risk screening value (GB 15618-2018). Compared with previous studies, the contents of Cd, Cu, and Zn in soil showed a downward trend. Potential ecological risk assessment showed that the risk level of Cd in the topsoil was high, and the risk levels of Cd and Cu in the sediment were very high and considerable, respectively, posing a major risk to human health. In rice plants, heavy metals mainly accumulated in the roots of rice, and their migration ability in rice tissues was poor. The heavy metal level in grain was within the threshold value set by the Codex Alimentarius Commission (CAC, CXS 193-1995) or China (GB 2762-2017), and the risk level to human health was low. Accordingly, it is imperative to continuously monitor the content of heavy metals in the sediment and soil of Longtang, especially Cu and Cd.

LncRNA-ENST00000446135 is a novel biomarker of cadmium toxicity in 16HBE cells, rats, and Cd-exposed workers and regulates DNA damage and repair

Cadmium (Cd) and its compounds are well-known human carcinogens, but the mechanisms underlying the carcinogenesis are not well understood. This study aimed to investigate whether long noncoding RNA (LncRNA)-ENST00000446135 could serve as a novel biomarker of Cd toxicity in cells, animals, and Cd-exposed workers and regulate DNA damage and repair. LncRNA-ENST00000446135 expression increased gradually in cadmium chloride-transformed 16HBE cells. Small interfering RNA-mediated knockdown of LncRNA-ENST00000446135 inhibited the growth of DNA-damaged cells and decreased the expressions of DNA damage-related genes (ATM, ATR, and ATRIP), whereas increased the expressions of DNA repair-related genes (DDB1, DDB2, OGG1, ERCC1, MSH2, XRCC1, and BARD1). Chromatin immunoprecipitation-sequencing showed that MSH2 is a direct transcriptional target of lncRNA-ENST00000446135. Cadmium increased lncRNA-ENST00000446135 expression in the lung of Cd-exposed rats in a dose-dependent manner. A significant positive correlation was observed between blood ENST00000446135 expression and urinary/blood Cd concentrations, and there were significant correlations of LncRNA-ENST00000446135 expression with the DNA damage cell and the expressions of target genes in the lung of Cd-exposed rats and the blood of Cd-exposed workers and significantly correlated with liver and renal function in Cd-exposed workers. These results indicate that the expression of LncRNA-ENST00000446135 is upregulated and may serve as a signature for DNA damage and repair related to the epigenetic mechanisms underlying the cadmium toxicity and become a novel biomarker of cadmium toxicity.

Activation of the Erk/MAPK signaling pathway is a driver for cadmium induced prostate cancer

PURPOSE

Cadmium (Cd) is reported to be associated with carcinogenesis. The molecular mechanisms associated with Cd-induced prostate cancer (PCa) remain elusive.

MATERIALS AND METHODS

RWPE1, PWR1E and DU 145 cells were used. RT2 Profiler Array, real-time-quantitative-PCR, immunofluorescence, cell cycle, apoptosis, proliferation and colony formation assays along with Gene Set Enrichment Analysis (GSEA) were performed.

RESULT

Chronic Cd exposure of non-malignant RWPE1 and PWR1E cells promoted cell survival, proliferation and colony formation with inhibition of apoptosis. Even a two-week Cd exposure of PCa cell line (DU 145) significantly increased the proliferation and decreased apoptosis. RT2 profiler array of 84 genes involved in the Erk/MAPK pathway revealed induction of gene expression in Cd-RWPE1 cells compared to RWPE1. This was confirmed by individual TaqMan gene expression analysis in both Cd-RWPE1 and Cd-PWR1E cell lines. GSEA showed an enrichment of the Erk/MAPK pathway along with other pathways such as KEGG-ERBB, KEGG-Cell Cycle, KEGG-VEGF, KEGG-Pathways in cancer and KEGG-prostate cancer pathway. We randomly selected upregulated genes from Erk/MAPK pathway and performed profile analysis in a PCa data set from the TCGA/GDC data base. We observed upregulation of these genes in PCa compared to normal samples. An increase in phosphorylation of the Erk1/2 and Mek1/2 was observed in Cd-RWPE1 and Cd-PWR1E cells compared to parental cells, confirming that Cd-exposure induces activation of the Erk/MAPK pathway.

CONCLUSION

This study demonstrates that Erk/MAPK signaling is a major pathway involved in Cd-induced malignant transformation of normal prostate cells. Understanding these dominant oncogenic pathways may help develop optimal therapeutic strategies for PCa.

Emerging Roles of MicroRNAs and Long Noncoding RNAs in Cadmium Toxicity

Metal cadmium (Cd) and its compounds are ubiquitous industrial and environmental pollutants and they have been believed to exert severe damage to multiple organs and tissues. MicroRNAs (miRNAs) and long noncoding RNAs (lncRNAs) are the two most common noncoding RNAs and have pivotal roles in various cellular and physiological processes. Since the importance of miRNAs and lncRNAs in Cd toxicity has been widely recognized, we focus our interests on the current researches of miRNAs and lncRNAs as well as their regulation roles in Cd toxicity. In this paper, the keywords "cadmium" in combination with "miRNA" or "LncRNA" or "noncoding RNA" was used to retrieve relevant articles in PubMed, EMbase, CNKI, Wan Fang, and CBM databases. The literatures which contained the above keywords and carried out in animals (in vivo and in vitro) have been collected, collated, analyzed, and summarized. Our summary results showed that hundreds of miRNAs and lncRNAs are involved in the Cd toxicity, which have been demonstrated as multiple organ injury, reproductive toxicity, malignant transformation, and abnormal repair of DNA damage. In this paper, we also discussed the blank in present research field of Cd toxicity as well as suggested some ideas for future study in Cd toxicity.

Isoorientin plays an important role in alleviating Cadmium-induced DNA damage and G0/G1 cell cycle arrest

Cadmium is a heavy metal pollutant that has been reported to cause oxidative stress, apoptosis, and autophagy in cells, while the flavone isoorientin is a traditional Chinese medicine extract that has proven antioxidant and anti-inflammatory properties. Accordingly, in this study we used the rat proximal tubular cell line NRK-52E and primary rat proximal tubular (rPT) cells as models to investigate the effects of isoorientin against Cadmium-induced cell injury and the mechanism of these effects. Comet assay, Western blot, flow cytometry, immunofluorescence, and transmission electron microscopy were used to evaluate cell damage and cell-cycle-related protein expression. Furthermore, real-time cell analysis, cell-counting kit-8, and ELISA were used to investigate the role of isoorientin in Cadmium-induced cell injury. The results revealed that treatment of rat renal tubular epithelial cells with 2.5 μM Cd for 12 h resulted in DNA damage and G0/G1 cell cycle arrest, while isoorientin attenuated this Cd-induced damage.

Prenatal and postnatal cadmium exposure and cellular immune responses among pre-school children

BACKGROUND

Experimental studies have demonstrated that cadmium exposure induces alterations on immune function, but epidemiological evidence is lacking.

OBJECTIVE

To examine the associations between prenatal and postnatal cadmium exposure and cellular immune responses among pre-school children.

METHODS

Pre-school aged children (n = 407) were followed from a prospective birth cohort study in Wuhan, China. Maternal urinary and children's plasma cadmium concentrations were measured as biomarkers of prenatal and postnatal cadmium exposure, respectively. Children's cellular immune responses were assessed by peripheral blood T lymphocyte subsets and plasma cytokines. Multivariable adjusted models were applied to estimate the associations of prenatal and postnatal cadmium exposure with T lymphocyte subsets and cytokines, and the effect modification by child gender were also examined.

RESULTS

Maternal urinary cadmium was associated with reduced absolute counts of CD3⁺CD4⁺ cells (-12.45%; 95% CI: -23.74%, 0.40% for the highest vs. lowest quartile; p for trend = 0.045). Inverse associations of maternal urinary cadmium with %CD3⁺CD4⁺ cells and CD4⁺/CD8⁺ ratio were only observed among females (both p-interaction < 0.050); whereas an inverse association with absolute counts of CD3⁺CD8⁺ cells was only observed among males (p-interaction = 0.057). Positive associations of maternal urinary cadmium with %CD3⁺CD4⁺ cells, interleukin-4 (IL-4), and IL-6 were only observed among females, although there were no significant interactions. We observed no clear associations of children's plasma cadmium with T lymphocyte subsets and cytokines.

CONCLUSION

Prenatal but not postnatal cadmium exposure was associated with sex-specific alterations on children's cellular immune responses.

Roles of different humin and heavy-metal resistant bacteria from composting on heavy metal removal

This study aims to assess the roles of different humin and heavy-metal resistant bacterial community from composting on heavy metal removal. The results showed that the concentration of Cu²⁺, Zn²⁺, Ni²⁺, Pb²⁺, Cr³⁺ and Cd²⁺ decreased with adding the compost-derived humin, but the removal rates were relatively low (<30% on average). The heavy metal resistant bacteria from composting have better metal binding capacities than humin, and the combined addition of humin and bacteria could further stimulate the biosorption of heavy metals with 60-80% removal of metals and improve the diversity and biomass of bacterial community. There was obviously increased synergy between the humin from maturity phase and bacteria for metal biosorption ("1 + 1 > 2"). Structural equation modeling showed that microbial biomass and humin humification are the key factors for the biosorption of heavy metals. Combining humin from maturity phase with heavy-metal resistant bacteria was suggested to control heavy metal pollution in composts.

High-throughput assessment of toxic effects of metal mixtures of cadmium(Cd), lead(Pb), and manganese(Mn) in nematode Caenorhabditis elegans

Heavy metals, a class of persistent environmental toxicants, are harmful to human health. Cd and Pb are two of the most common toxic heavy metals that have been linked with cancers and malfunction of the nervous system. Notably, contamination of Mn usually coexisted with Cd and Pb in environmental and occupational settings. Studies regularly examined the toxic effects on individual metals; however, potential health and toxic effects of mixtures containing two or more heavy metals are unknown. Here, we investigated toxic effects of Cd, Pb, Mn, and their binary and ternary mixtures in the nematode Caenorhabdities elegans. The toxic outcomes, including effects on growth, reproduction, and feeding, were measured via high-throughput platform analysis. The transgenic strain BY250 with GFP in dopaminergic neurons was used to explore the neurodegenerative effects induced by single metals or their mixtures. The combination index(CI) for mixtures effect was calculated using isobolograms methods. Following the exposure, we found significant toxic effects in C. elegans. For single metals, the toxicity order for growth, reproduction, and feeding were Pb > Cd > Mn. For mixtures, the mixture of Cd + Mn induced a less than addictive effect in C. elegans, whereas the mixtures of Cd + Pb, Pb + Mn, and Cd + Pb + Mn induced greater-than-additive effects. Both single metals and their mixtures induced abnormality in dopaminergic neurons. These results showed combinative toxic and neurodegenerative effects of heavy metal mixtures, and future studies will focus on characterization of concentration-response patterns and identification of potential molecular mechanisms in C. elegans model.

Toxic Metals and Chronic Kidney Disease: a Systematic Review of Recent Literature

PURPOSE OF REVIEW

Arsenic (As), cadmium (Cd), and lead (Pb) are ubiquitous toxicants with evidence of adverse kidney impacts at high exposure levels. There is less evidence whether environmental exposure to As, Cd, or Pb plays a role in development of chronic kidney disease (CKD). We conducted a systematic review to summarize the recent epidemiologic literature examining the relationship between As, Cd, or Pb with CKD.

RECENT FINDINGS

We included peer-reviewed studies published in English between January 2013 and April 2018 for As and Cd, and all dates prior to April 2018 for Pb. We imposed temporality requirements for both the definition of CKD (as per NKF-KDOQI guidelines) and environmental exposures prior to disease diagnosis. Our assessment included cohort, case-control or cross-sectional study designs that satisfied 5 inclusion criteria. We included a total of eight articles of which three, two, and four studies examined the effects of As, Cd, or Pb, respectively. Studies of As exposure consistently reported positive association with CKD incidence; studies of Pb exposure were mixed. We found little evidence of association between Cd exposure and CKD. Additional well-designed prospective cohort studies are needed and we present recommendations for future studies.

Risk factors for chronic kidney disease of non-traditional causes: a systematic review

OBJECTIVES

To evaluate the potential associations between chronic kidney disease of uncertain or non-traditional etiology (CKDnT) and agrochemicals, heat stress, heavy metals, and other factors identified in the literature in any region of the world and at any time.

METHODS

This was a systematic review of the most frequent exposures suspected to be possible causes of CKDnT. A search was conducted of PubMed, LILACS, World Wide Science electronic databases, among other sources. Only medium- and high-quality studies were included. The synthesis of evidence included a narrative synthesis, meta-analysis, and meta-regression.

RESULTS

Four systematic reviews and 61 primary studies were included. Results of the meta-analysis suggest that exposure to agrochemicals and working in agriculture increase the risk of CKDnT, but this only reached significance for working in agriculture. When cross-sectional studies were excluded, agrochemical exposure became significant. However, there is substantial heterogeneity in the effect sizes.

CONCLUSIONS

Based on the existing evidence and the precautionary principle, it is important to implement preventive measures to mitigate the damage caused by CKDnT to both agricultural workers and their communities (i.e., improvement of working conditions, cautious management of agrochemicals, etc.). More high-quality research is needed to measure impact and to build the evidence base.

Global burden of late-stage chronic kidney disease resulting from dietary exposure to cadmium, 2015

Chronic exposures to cadmium (Cd) are associated with reduced glomerular filtration rate (GFR), increasing the risk of chronic kidney disease (CKD). In support of the World Health Organization (WHO)'s initiative to estimate the global burden of foodborne diseases, a risk assessment was performed to estimate the Disability-Adjusted Life Years (DALYs) due to late-stage CKD associated with dietary exposures to cadmium. Using the distribution of population GFRs, the prevalence of CKD was calculated as the proportion of humans whose GFR fall in the ranges corresponding to Stage 4 or Stage 5 CKD. The increase in the CKD prevalence due to cadmium exposure was simulated based on a previously reported pharmacokinetic model describing the relationship between dietary cadmium intake and urinary cadmium (UCd), as well as a previously published dose-response relationship between UCd and GFR. Cadmium-related incidence rate, calculated as the change in the prevalence during a one-year period, were used to compute the mortality and DALY in all WHO regions. It is estimated that dietary cadmium would result in a median of 12,224 stage 4 and stage 5 new CKD cases per year worldwide, resulting in 2064 global deaths and 70,513 DALYs. These data translate into a median global burden of 1.0 DALY per 100,000 population, which account for 0.2% of the global DALYs of CKD. While these results suggest that the overall impact of dietary cadmium exposure on global CKD is low, they do indicate that reasonable efforts to reduce dietary exposure will result a positive public health impact. This would be particularly the case in areas with elevated levels of dietary cadmium.

Effect of combined application of lead, cadmium, chromium and copper on grain, leaf and stem heavy metal contents at different growth stages in rice

Most studies on plants' response to heavy metal toxicity have been focusing on single metals. However, soils are always contaminated by several kinds of heavy metals. In this study, pot experiments were carried out to investigate the effects of combined toxicity on two rice genotypes differing in Cd accumulation (Xiushui817, a low-grain-Cd-accumulation and Zheda821, a high-grain-Cd-accumulation genotype). Yield, heavy metal concentrations of grain and leaf/stem at different growth stages were measured under combined application of Cd, Cr, Pb and Cu. Yield was significantly decreased under higher Pb and Cd treatment in both genotypes with Xiushui817 showing greater reduction. Increasing soil Cu level showed no significant effect on grain yield. Zheda821 consistently showed a higher grain Cd content than Xiushui817. The application of Pb, Cd, Cr and Cu significantly affected grain Cd, Cr and Cu accumulations. Similar trends were also observed in leaves and stems at harvest stage. The critical levels of leaf/stem Cd and Cr for safe rice production were also estimated. Alleviation measures should be taken to decrease Cd or Cr accumulations in grain of rice if leaf or stem Cd or Cr concentrations at different growth stages exceed the critical levels.

Chemical Speciation and Characterization of Trace Metals in Dry Camellia sinensis and Herbal Tea Marketed in Nigeria

BACKGROUND

Trace metals from anthropogenic activities have been found to occur in tea brands and pose potential human health risks to consumers.

OBJECTIVES

The present study assessed the concentrations of trace metals in green, black and herbal tea brands using a modified Community Bureau of Reference sequential extraction method.

METHODS

Fifteen (15) Camellia sinensis and eight (8) herbal tea samples commonly consumed in Nigeria were collected and analyzed for trace metals. The concentrations of cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), vanadium (V), and zinc (Zn) in extract fractions were analyzed using microwave plasma atomic emission spectroscopy (MP-AES).

RESULTS

Trace metals were detected in all of the samples investigated. The concentrations of trace metals in 4 stages (soluble/exchangeable/carbonates bound fraction, reducible fraction, oxidizable fraction, residual fraction) of sequential and pseudo-total metal extraction procedures are presented. The concentrations of Cd, Cr, Cu, Mn, Ni, Pb, V, and Zn in the exchangeable/carbonate bound fraction for green tea ranged between 0.27-1.47, ND-0.33, ND-0.44, 7.05-33.04, 0.23-0.69, ND-0.51, ND-0.16 and 0.18-1.99 mg/kg, ND-0.73, 0.15-0.36, 0.36-0.59, 1.38-30.07, 0.15-0.54, 0.05-0.76, 0.15-0.34 and 0.27-0.77 mg/kg and 0.54-0.64, 0.25-0.41, 0.35-0.47, 18.72-23.98, 0.30-0.55, 0.15-0.21, 0.15-0.23 and 0.30-0.48 mg/kg for hebal tea, respectively.

CONCLUSION

The metal content in the investigated tea indicated low to enhanced concentrations. Locally produced black teas recorded relatively low trace metal contents compared to the green and herbal tea samples. The most bioavailable trace metal was Mn, while Zn was most preferably bound to the residual fraction. Cadmium, Cr, Cu, Ni, Pb, and V were distributed at varied concentrations among other extractable phases. Daily consumption of the investigated tea products may expose consumers to potentially toxic metals as well as essential elements.

COMPETING INTERESTS

The authors declare no competing financial interests.

Dietary cadmium exposure assessment in rural areas of Southwest China

Dietary exposure of cadmium (Cd) has not been studied in Southwest China. The objective of the study was to determine the pollution characteristics and contamination levels in various agriculture products in Southwest China and to conduct a comparison of dietary exposure assessment of Cd in polluted and non-polluted areas. Results showed that the mean Cd contents in rice were 0.53 and 0.52 mg/kg in the high-polluted and low-polluted areas, respectively, with the average value was 0.03 mg/kg in the control area. The mean dietary Cd exposure from rice and vegetables of the selected non-occupational residents in Southwest China was 113.10 μg/kg bodyweight (bw)/month, 88.80 μg/kg bw/month, and 16.50 μg/kg bw/month in the high-polluted, low-polluted, and control areas, respectively, which correspond to 4.5 times, 3.6 times, and 0.66 times of the provisional tolerable monthly intake (25 μg/kg bw/month) established by the Joint FAO/WHO Expert Committee on Food Additives. The findings indicated that the risk for Cd exposure of residents was high due to home-grown food (most especially rice) being near polluted areas and is of great concern.

Risk assessment of effects of cadmium on human health (IUPAC Technical Report)

Chemistry and Human Health, Division VII of the International Union on Pure and Applied Chemistry (IUPAC), provides guidance on risk assessment methodology and, as appropriate, assessment of risks to human health from chemicals of exceptional toxicity. The aim of this document is to describe dose-response relationships for the health effects of low-level exposure to cadmium, in particular, with an emphasis on causation. The term “cadmium” in this document includes all chemical species of cadmium, as well as those in cadmium compounds. Diet is the main source of cadmium exposure in the general population. Smokers and workers in cadmium industries have additional exposure. Adverse effects have been shown in populations with high industrial or environmental exposures. Epidemiological studies in general populations have also reported statistically significant associations with a number of adverse health effects at low exposures. Cadmium is recognized as a human carcinogen, a classification mainly based on occupational studies of lung cancer. Other cancers have been reported, but dose-response relationships cannot be defined. Cardiovascular disease has been associated with cadmium exposure in recent epidemiological studies, but more evidence is needed in order to establish causality. Adequate evidence of dose-response relationships is available for kidney effects. There is a relationship between cadmium exposure and kidney effects in terms of low molecular mass (LMM) proteinuria. Long-term cadmium exposures with urine cadmium of 2 nmol mmol−1 creatinine cause such effects in a susceptible part of the population. Higher exposures result in increases in the size of these effects. This assessment is supported by toxicokinetic and toxicodynamic (TKTD) modelling. Associations between urine cadmium lower than 2 nmol mmol−1 creatinine and LMM proteinuria are influenced by confounding by co-excretion of cadmium with protein. A number of epidemiological studies, including some on low exposures, have reported statistically significant associations between cadmium exposure and bone demineralization and fracture risk. Exposures leading to urine cadmium of 5 nmol mmol−1 creatinine and more increase the risk of bone effects. Similar associations at much lower urine cadmium levels have been reported. However, complexities in the cause and effect relationship mean that a no-effect level cannot be defined. LMM proteinuria was selected as the critical effect for cadmium, thus identifying the kidney cortex as the critical organ, although bone effects may occur at exposure levels similar to those giving rise to kidney effects. To avoid these effects, population exposures should not exceed that resulting in cadmium values in urine of more than 2 nmol mmol−1 creatinine. As cadmium is carcinogenic, a ‘safe’ exposure level cannot be defined. We therefore recommend that cadmium exposures be kept as low as possible. Because the safety margin for toxic effects in kidney and bone is small, or non-existent, in many populations around the world, there is a need to reduce cadmium pollution globally.

Effect of an Extract from Aronia melanocarpa L. Berries on the Body Status of Zinc and Copper under Chronic Exposure to Cadmium: An In Vivo Experimental Study

In an experimental model of low-level and moderate environmental human exposure to cadmium (Cd), it was investigated whether the consumption of a polyphenol-rich Aronia melanocarpa L. berries (chokeberries) extract (AE) may influence the body status of zinc (Zn) and copper (Cu). The bioelements' apparent absorption, body retention, serum and tissue concentrations, total pool in internal organs, excretion, and the degree of binding to metallothionein were evaluated in female rats administered 0.1% aqueous AE or/and Cd in their diet (1 and 5 mg/kg) for 3-24 months. The consumption of AE alone had no influence on the body status of Zn and Cu. The extract administration at both levels of Cd treatment significantly (completely or partially) protected against most of the changes in the metabolism of Zn and Cu caused by this xenobiotic; however, it increased or decreased some of the Cd-unchanged indices of their body status. Based on the findings, it seems that rational amounts of chokeberry products may be included in the daily diet without the risk of destroying Zn and Cu metabolisms; however, their potential prophylactic use under exposure to Cd needs further study to exclude any unfavourable impact of these essential elements on the metabolism.

Spatial distribution of kidney disease in the contaminated site of Taranto (Italy)

BACKGROUND

Exposure to heavy metals has been associated with kidney disease. We investigated the spatial distribution of kidney disease in the industrially contaminated site of Taranto.

METHODS

Cases were subjects with a first hospital discharge diagnosis of kidney disease. Cases affected by specific comorbidities were excluded. Standardized Hospitalization Ratios (SHRs) were computed for low/high exposure area and for modeled spatial distribution of cadmium and fine particulate matter.

RESULT

Using the high/low exposure approach, in subjects aged 20-59 years residing in the high exposure area a significant excess of hospitalization was observed in males and a non-significant excess in females. No excesses were observed in subjects aged 60 years and over. The analysis by the modeling approach did not show a significant association with the greatest pollution impact area.

CONCLUSION

Due to the excesses of hospitalization observed in the high/low exposure approach, a continuing epidemiological surveillance of residents and occupational groups is warranted.

Environmental exposures and pediatric kidney function and disease: A systematic review

BACKGROUND

Environmental chemical exposures have been implicated in pediatric kidney disease. No appraisal of the available evidence has been conducted on this topic.

METHODS

We performed a systematic review of the epidemiologic studies that assessed association of environmental exposures with measures of kidney function and disease in pediatric populations. The search period went through July 2016.

RESULTS

We found 50 studies that met the search criteria and were included in this systematic review. Environmental exposures reviewed herein included lead, cadmium, mercury, arsenic, fluoride, aflatoxin, melamine, environmental tobacco, bisphenol A, dental procedures, phthalates, ferfluorooctanoic acid, triclosan, and thallium/uranium. Most studies assessed environmental chemical exposure via biomarkers but four studies assessed exposure via proximity to emission source. There was mixed evidence of association between metal exposures, and other non-metal environmental exposures and pediatric kidney disease and other kidney disease biomarkers. The evaluation of causality is hampered by the small numbers of studies for each type of environmental exposure, as well as lack of study quality and limited prospective evidence.

CONCLUSION

There is a need for well-designed epidemiologic studies of environmental chemical exposures and kidney disease outcomes.

Low-Level Environmental Cadmium Exposure Induces Kidney Tubule Damage in the General Population of Korean Adults

Cadmium (Cd) is the most potent nephrotoxic heavy metal and may affect bone; it also has a long biological half-life in the human body. This study was designed to assess the effect of environmental low-level Cd exposure on kidney function and bone in the general population. The subjects of this cross-sectional study were 1907 healthy Korean adults who had not been exposed to Cd occupationally. We analyzed the concentrations of Cd in the urine, markers of renal tubule damage, such as β₂-microglobulin (β₂-MG) and N-acetyl-β-D-glucosaminidase (NAG) activity in the urine, calculated the estimated glomerular filtration rate (eGFR) using serum creatinine, and measured bone mineral density (BMD). Also, we analyzed malondialdehyde (MDA) levels in the urine. The geometric mean concentration of Cd in urine was higher in women (1.36 μg/g creatinine) than in men (0.82 μg/g creatinine). Urinary Cd was significantly positively correlated with urinary β₂-MG and NAG activity, whereas it was negatively correlated with eGFR and BMD. The risk of renal tubule damage was significantly associated with urine Cd level, and the association remained significant after controlling for various confounding variables. However, no association was observed between urinary Cd level and glomerular dysfunction or bone damage. The concentration of MDA was increased with urinary Cd level in a dose-dependent manner. These findings suggest that low-level environmental Cd exposure may cause microscopic damage to renal tubules through oxidative stress but might not impair kidney glomeruli or bones.

Single and combined removal of Cr(VI) and Cd(II) by nanoscale zero-valent iron in the absence and presence of EDDS

This study examined the feasibility of nanoscale zero-valent iron (nZVI) for the single and combined removal of Cr(VI) and Cd(II) with or without ethylene diamine disuccinic acid (EDDS). The effects of pH and dissolved oxygen (DO) on the removal process were investigated. Results show that the single removal of either Cr(VI) or Cd(II) by nZVI was pH dependent, where the higher Cr(VI) removal was achieved under acidic conditions, whereas the higher Cd(II) removal was achieved under alkaline conditions. The presence of DO enhanced Cd(II) removal but inhibited Cr(VI) removal under alkaline conditions. In the co-existence of Cr(VI) and Cd(II), it was found that Cd(II) exerted insignificant effect on Cr(VI) removal, while the presence of Cr(VI) remarkably enhanced the Cd(II) removal. The addition of EDDS exhibited different influences on Cr(VI) and Cd(II) removal, which were associated with pH and DO. The EDDS enhanced Cr(VI) removal at pH 5.6-9.0 in the absence of DO, but decreased Cr(VI) removal at pH 9.0 in the presence of DO. For the removal of Cd(II) at pH 5.6-7.0, either facilitation or inhibition effect of EDDS was observed, depending on EDDS concentration and the co-existence of Cr(VI). However, Cd(II) removal was always significantly inhibited by EDDS at pH 9.0.

Urine cadmium levels and albuminuria in a general population from Spain: A gene-environment interaction analysis

BACKGROUND

The interaction of cadmium with genes involved in oxidative stress, cadmium metabolism and transport pathways on albuminuria can provide biological insight on the relationship between cadmium and albuminuria at low exposure levels.

OBJECTIVES

We tested the hypothesis that specific genotypes in candidate genes may confer increased susceptibility to cadmium exposure.

METHODS

Cadmium exposure was estimated by inductively coupled plasma mass spectrometry (ICPMS) in urine from 1397 men and women aged 18-85years participating in the Hortega Study, a representative sample of a general population from Spain. Urine albumin was measured by automated nephelometric immunochemistry. Abnormal albuminuria was defined as urine albumin greater than or equal to 30mg/g.

RESULTS

The weighted prevalence of abnormal albuminuria was 6.3%. The median level of urine cadmium was 0.39 (IQR, 0.23-0.65) μg/g creatinine. Multivariable-adjusted geometric mean ratios of albuminuria comparing the two highest to the lowest tertile of urine cadmium were 1.62 (95% CI, 1.43-1.84) and 2.94 (95% CI, 2.58-3.35), respectively. The corresponding odds ratios of abnormal albuminuria were 1.58 (0.83, 3.02) and 4.54 (2.58, 8.00). The association between urine cadmium and albuminuria was observed across all participant subgroups evaluated including participants without hypertension, diabetes or chronic kidney disease. We observed Bonferroni-corrected statistically significant interactions between urine cadmium levels and polymorphisms in gene SLC30A7 and RAC1.

CONCLUSIONS

Increasing urine cadmium concentrations were cross-sectionally associated with increased albuminuria in a representative sample of a general population from Spain. Genetic variation in oxidative stress and cadmium metabolism and transport genes may confer differential susceptibility to potential cadmium effects.