Risk assessment of nephrotoxicity of cadmium

Associations of renal function with urinary excretion of metals: Evidence from NHANES 2003-2012

BACKGROUND

Urinary metals are considered measures of long-term exposures of metals, such as cadmium (Cd). Some studies indicate reduced renal function may affect the urinary excretion of several metals in general population making assessments difficult.

OBJECTIVES

To examine whether reduced renal function is associated with reduced urinary excretion of 12 metals or their metabolites and, in turn, an underestimated measure of Cd in general population.

METHODS

We conducted analyses using data from the National Health and Nutrition Examination Survey (NHANES) 2003-2012. Multiple linear regression models were used to examine the associations between urinary metal levels and estimated glomerular filtration rate (eGFR). Restricted cubic spline regression models were used to evaluate the nonlinearity.

RESULTS

Urinary metal levels significantly increased (p < 0.001) with increasing eGFR, except for antimony (p = 0.172). Urinary levels of arsenic, dimethylarsonic acid, cobalt, molybdenum and tungsten increased linearly with eGFR, while Cd, lead, mercury, barium, cesium and thallium increased nonlinearly (p < 0.001) with eGFR. Based on a restricted cubic spline regression model, we found, corresponding to a fixed blood Cd adverse cutpoint of 5 μg/L, predicted urinary Cd cutpoints substantially varied from 0.78-1.21 μg/g for urinary Cd between those aged <40 years and who had chronic kidney disease and those aged 60 years or over with normal renal function, respectively.

CONCLUSION

Reduced renal function is associated with reduced urinary metals; and associations are also observed across the eGFR range not just in the reduced range. Urinary abnormal cutpoints of metals are likely dependent on eGFR and age. The associations between urinary exposure of metals and disease risk are likely underestimated without considering the modifying effect of renal function.

Effects of Maternal Exposure to Cadmium Oxide Nanoparticles During Pregnancy on Maternal and Offspring Kidney Injury Markers Using a Murine Model

Nanoparticles (NP) are pervasive in many areas of modern life, with little known about their potential toxicities. One commercially important NP is cadmium oxide (CdO), which is used to synthesize other Cd-containing NP, such as quantum dots. Cadmium (Cd) is a well-known nephrotoxicant, but the nephrotoxic potential of CdO NP remains unknown, particularly when exposure occurs during pregnancy. Therefore, pregnant CD-1 mice were used to examine the effects of inhaled CdO NP (230 μg CdO NP/m(3)) on maternal and neonatal renal function by examining urinary creatinine and urinary biomarkers of kidney injury, including kidney injury molecule-1 (Kim-1) and neutrophil gelatinase-associated lipocalin (NGAL). Inhalation of CdO NP by dams produced a fivefold increase in urinary Kim-1 with no marked effect on urinary creatinine levels. Kim-1 mRNA expression peaked by gestational day (GD) 10.5, and NGAL expression increased from GD 10.5 to 17.5. In addition, histological analyses revealed proximal tubular pathology at GD 10.5. Neonatal Kim-1 mRNA expression rose between postnatal days (PND) 7 and 14, with mammary glands/milk being the apparent source of Cd for offspring. These studies demonstrate that, similar to what is seen with other Cd forms, Cd associated with inhaled CdO NP results in renal injury to both directly exposed dam and offspring. As commercial uses for nanotechnology continue to expand throughout the world, risks for unintentional exposure in the workplace increase. Given the large number of women in the industrial workforce, care needs to be taken to protect these already vulnerable populations.

Early biomarkers of cadmium exposure and nephrotoxicity

As the risks of cadmium (Cd)-induced kidney disease have become increasingly apparent, much attention has been focused on the development and use of sensitive biomarkers of Cd nephrotoxicity. The purpose of this review is to briefly summarize the current state of Cd biomarker research. The review includes overviews of the toxicokinetics of Cd, the mechanisms of Cd-induced proximal tubule injury, and mechanistic summaries of some of the biomarkers (N-acetyl-β-D-glucosamidase; β(2)-microglubulin, metallothionein, etc.) that have been most widely used in monitoring of human populations for Cd exposure and nephrotoxicity. In addition, several novel biomarkers (kidney injury molecule-1, α-glutathione-S-transferase and insulin) that offer the potential for improved biomonitoring of Cd-exposed populations are discussed.

Detection of Cd(II) using antibody-modified microcantilever sensors

This work demonstrated the feasibility of detecting divalent Cd(II) ions using antibody-modified microcantilever (MCL) sensors. Different surface modification methods were compared and multilayer approach was found superior than others for MCL surface modifications for antibody-based Cd(II) sensor development. When the Cd(II)-EDTA complex sample is injected into the fluid cell where the MCL is held, the MCL bends upon the recognition of the Cd(II) complex by the antibody on the surface of the MCL. Control experiments showed that complex that does not contain Cd(II) did not cause any bending of the MCL. The detection limit of the sensor was approximately 10(-9) M. The reaction rate analysis indicated that Langmuir adsorption model is appropriate to describe the absorption of Cd(II)-EDTA-BSA on the antibody-covered MCL surface.

Hsp27, Hsp70, and metallothionein in MDCK and LLC-PK1 renal epithelial cells: effects of prolonged exposure to cadmium

Cadmium is a widely distributed industrial and environmental toxin. The principal target organ of chronic sublethal cadmium exposure is the kidney. In renal epithelial cells, acute high-dose cadmium exposure induces differential expression of proteins, including heat shock proteins. However, few studies have examined heat shock protein expression in cells after prolonged exposure to cadmium at sublethal concentrations. Here, we assayed total cell protein, neutral red uptake, cell death, and levels of metallothionein and heat shock proteins Hsp27 and inducible Hsp70 in cultures of MDCK and LLC-PK1 renal epithelial cells treated with cadmium for 3 days. Treatment with cadmium at concentrations equal to or greater than 10 microM (LLC-PK1) or 25 microM (MDCK) reduced measures of cell vitality and induced cell death. However, a concentration-dependent increase in Hsp27 was detected in both cell types treated with as little as 5 microM cadmium. Accumulation of Hsp70 was correlated only with cadmium treatment at concentrations also causing cell death. Metallothionein was maximally detected in cells treated with cadmium at concentrations that did not reduce cell vitality, and further increases were not detected at greater concentrations. These results reveal that heat shock proteins accumulate in renal epithelial cells during prolonged cadmium exposure, that cadmium induces differential expression of heat shock protein in epithelial cells, and that protein expression patterns in epithelial cells are specific to the cadmium concentration and degree of cellular injury. A potential role for Hsp27 in the cellular response to sublethal cadmium-induced injury is also implicated by our results.

Effects of low-dose cadmium exposure on biological examinations

We conducted an epidemiological study to investigate the effects of low-dose cadmium (Cd) exposure on human health in a specific area of a town in Japan where low Cd concentration was detected in rice. We compared clinical findings, urinary and whole blood Cd concentrations, and indicators of renal dysfunction between the polluted area and the control area. The study employed 44 men and 54 women from the polluted area and 21 men and 29 women from the control area. In urine analysis, as indicators of Cd exposure and possible related renal dysfunction, Cd, beta(2)-microglobulin (beta(2)-MG), alpha(1)-microglobulin (alpha(1)-MG), N-acetyl-beta-D-glucosaminidase (NAG), total protein, inorganic phosphorus, lysozyme and creatinine were quantitatively measured. In blood analysis, serum IP and creatinine and whole blood Cd were measured. No case of renal dysfunction due to Cd exposure was confirmed. However, both the urinary and whole blood Cd of the polluted area were significantly higher than those of the control area for both sexes. Urinary beta(2)-MG did not differ between the two areas. For women, urinary alpha(1)-MG was significantly higher in the polluted area than in the control area. In correlation analysis, beta(2)-MG, alpha(1)-MG and NAG, were positively correlated with both of urinary and whole blood Cd for men and women in the polluted area except for between urinary beta(2)-MG and urinary Cd for men. In the control area, the sole positive correlation observed was between urinary beta(2)-MG and whole blood Cd for men. We then examined the determinants of variations of parameters in urinary and blood tests. Potential determinants were age, sex, body mass index, an indicator of smoking habits (cigarette index) and the index of estimated Cd intake from rice (Cd-rice-index). Cd-rice-index was expressed as the product of Cd concentrations in homegrown rice multiplied by daily frequency multiplied by duration (years) of residence in the polluted area. In multiple regression analysis, whole blood Cd was independently associated with Cd-rice-index, age and gender. Variations in whole blood Cd accounted for a substantial portion of the variations in urinary Cd, although they were less influential in older individuals. Whole blood Cd was the sole independent variable related to variations in urinary beta(2)-MG. Cd-rice-index accounted for a portion of the variance in urinary NAG, while age was a more powerful determinant. It was thus revealed that the consumption of homegrown rice polluted with Cd in low concentration resulted in an elevation of whole blood Cd level and consequent increase in urinary Cd level. However, it was not clearly elucidated that the excretion of urinary low-molecular microglobulins could increase significantly in response to slight elevation of Cd body load.

Preliminary report on the levels of elements in four fish species from the Arabian Gulf of Saudi Arabia

This manuscript presents preliminary information on the concentrations of heavy metals: cadmium, lead, nickel, vanadium and arsenic in 66 fish samples of four different species collected from three different sites on the Gulf coast of Saudi Arabia where there are agricultural, municipality and petroleum industrial activities. Fish species; highly consumed by the local population were selected: Emperors, Rabbitfish, Doublebar-bream and Greasy-grouper to ascertain the fish quality for human consumption. The concentration of metals was determined by atomic absorption spectrophotometry (AA). The average mean concentrations (ng/g wet wt.) of cadmium, lead, nickel, vanadium and arsenic in fish tissues were as follows: 4.6 +/- 7.2, 20.0 +/- 20.8, 60.6 +/- 63.2, 73.6 +/- 27.1 and 42.7 +/- 17.4 ng/g wet wt. respectively. The concentration of metals was significantly affected by the sampling site and fish species. In Maniefa site, the concentrations of all tested metals were higher than in Al-Dammam and Dareen sites with the exception of nickel where no significant differences were found. Levels of cadmium, lead, nickel, vanadium and arsenic varied depending on the fish species. The concentration of metals was below the maximum allowed limit by the Saudi and international legislations for fish human consumption permissible limit.

Alterations of serum hormone levels in male workers occupationally exposed to cadmium

In order to investigate the influence of occupational exposure to cadmium (Cd) on the levels of serum hormone, a cross-sectional study was undertaken in male workers. Creatinine-adjusted urinary cadmium (UCd) was used as the indicator of cadmium body burden in workers. The levels of serum testosterone (T), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) were determined by radioimmunoassay and enzyme immunoassay, respectively. The results showed that with cadmium exposure, the levels of serum testosterone and LH were significantly increased after controlling for confounding factors such as age, smoking habits, and alcohol consumption. However, no significant cadmium-associated changes in the levels of serum FSH were found. At the same time, a significant negative correlation of serum testosterone levels with age was detected. In contrast, the levels of serum FSH and LH were significantly elevated with increasing age. When taking the marital status into consideration, only significantly elevated FSH levels were noted in married workers after controlling for confounding factors. These results indicate that occupational cadmium exposure and other factors such as age and marital status may independently contribute to alterations in the levels of serum sex hormones in males.