CT Imaging Biomarkers of Bone Damage Induced by Environmental Level of Cadmium Exposure in Male Rats

Bioassimilation of lead and zinc in rabbits fed on spinach grown on contaminated soil

Accumulation of heavy metals in the environment can pose a potential risk to living organisms. Ingestion of leafy vegetables, containing heavy metals, is one of the main routes through which these elements enter the human body. The present study was conducted to assess the accumulation of lead (Pb) and zinc (Zn) in spinach grown on metal contaminated soil, and to examine the bioassimilation of these metals in spinach-fed rabbits. Spinach grown in the fields spiked with Pb (1000 mg kg-1 soil) and Zn (150 mg kg-1 soil), was fed to the rabbits for 14 days. Concentrations of Pb and Zn in the leaves of spinach were 39.1 and 113 mg kg-1, respectively. For the assessment of Pb and Zn concentration, blood samples were collected after 24 h, 7 days and 14 days of feeding, while the essential organs, i.e. liver and kidneys of rabbits were collected at the end of feeding trials. Concentrations (mg L-1) of Pb (3.28) and Zn (7.10) increased in blood after 24 h compared to control treatment and then decreased (Pb 1.12; Zn 3.32) to a steady state with the passage of time after 7 days. A significant increase in the concentrations of Pb (1.20%, 3.95% and 5.58%) and Zn (10.7%, 6.89% and 18.4%) as compared to control treatment was also found in liver, kidney and bones of the rabbits, respectively, which was further confirmed by multivariate analysis. The highest significant values of correlation coefficient (r) were observed for blood and bones, i.e. 0.992 followed by blood and liver, i.e. 0.989. The bioassimilation of Pb in the body of rabbits was in the order of bone > kidney > liver > blood, while for Zn the order was bone > liver > kidney > blood. The bioassimilation of Pb and Zn in the blood, essential organs and bones depicted the serious health risks associated by consuming the metal contaminated vegetable.

Blood lead and cadmium levels are negatively associated with bone mineral density in young female adults

Background

The organ toxicities of lead and cadmium have been extensively studied; however, studies of their toxic effects on bone remain limited, especially in young adults. The objective of this study was to examine the associations of blood lead levels (BLL) and blood cadmium levels (BCL) with bone mineral density (BMD) among young adults.

Methods

We performed a cross-sectional study using the National Health and Nutrition Examination Survey 2011–2018 database. Because of the skewed distribution, BLL and BCL were Ln-transformed for analysis. Weighted multivariate regressions were performed to evaluate the associations between LnBLL and LnBCL and lumbar BMD. Subgroup analyses were further performed.

Results

A total of 3234 participants aged 20–35 years were included in this study. No significant association between LnBLL and lumbar BMD was found (β = − 5.6, 95%CI: − 13.5–2.3). However, in the subgroup analysis stratified by sex, this association became negative in women (β = − 18.2, 95%CI: − 29.9– − 6.4). Moreover, this negative association was more prominent in female blacks (β = − 35.5, 95%CI: − 63.4– − 7.6). On the other hand, a negative association between LnBCL and lumbar BMD was found (β = − 7.4, 95%CI: − 14.0– − 0.8). In the subgroup analysis stratified by sex, this negative association only existed in women (β = − 18.7, 95%CI: − 28.0– − 9.5). Moreover, this negative association was more prominent in female whites (β = − 31.1, 95%CI: − 46.2– − 16.1).

Conclusions

Our finding showed that both BLL and BCL were independently and negatively associated with lumbar BMD among young females, but not among young males.

Low-level cadmium exposure is associated with decreased cortical thickness, cortical area and trabecular bone volume fraction in elderly men: The MrOS Sweden study

It is well known that high-level exposure to cadmium can cause bone disease such as osteoporosis, osteomalacia and fractures. However, the effect of low-level exposure, as found in the general population (mainly derived from diet and smoking), has only been assessed recently. The aim of this study was to examine if cadmium exposure in the general Swedish population causes other bone changes than decreased areal bone mineral density as measured by traditional DXA technology, e.g. changes in microstructure and geometry, such as cortical thickness or area, cortical porosity and trabecular bone volume. The study population consisted of 444 men, aged 70-81 years at inclusion year 2002-2004, from the Swedish cohort of the Osteoporotic Fractures in Men Study (MrOS). Cadmium was analyzed in baseline urine samples (U-Cd). Different parameters of bone geometry and microstructure were measured at the distal tibia at follow-up in 2009, including examination with high-resolution peripheral quantitative computed tomography (HR-pQCT). Associations between bone parameters and U-Cd in tertiles were estimated in multivariable analyses, including potential confounding factors (age, smoking, BMI, and physical activity). We found significant associations between U-Cd and several bone geometry or microstructure parameters, with 9% lower cortical thickness (p = 0.03), 7% lower cortical area (p = 0.04), and 5% lower trabecular bone volume fraction (p = 0.02) in the third tertile of U-Cd, using the first tertile as the reference. Furthermore, significant negative associations were found between log-transformed U-Cd and cortical thickness, cortical area, trabecular number and trabecular bone volume fraction, and a significant positive association with trabecular separation. The results indicate that low-level Cd exposure in the general population has negative effects on both cortical and trabecular bone.

Refinement of health-based guidance values for cadmium in the French population based on modelling

In France, part of the population is overexposed to cadmium by the diet. In our work, we first revised the tolerable daily intake (TDI) of 0.36 μg Cd.kg bw.d.^-1 proposed by the European Food Safety Authority (EFSA), derived from effects on kidneys and based on the critical urinary Cd concentration of 1.0 μg Cd.g^-1 creatinine for humans. After reviewing the epidemiological data on Cd toxicity published after 2011, bone effects were selected as the critical effects. Body burden data of 0.5 μg.g^-1 creatinine was chosen for the critical threshold for human urinary cadmium concentrations. To be used for the derivation of the new oral toxicological reference value, we used a modified physiologically based pharmacokinetic model (PBPK). The reverse calculation on the PBPK model gave a TDI of 0.35 μg Cd.kg bw^-1.day^-1. This TDI is compatible with a urinary Cd concentrations not exceeding 0.5 μg Cd.g^-1 creatinine, in a 60 year-old adult, assuming that ingestion is the only source of exposure to Cd at 60 years. After implementing the PBPK model with French physiological data, Cd biological reference values as a function of age were modelled so as to remain below the revised health-based guidance values.

Cadmium exposure negatively affects the microarchitecture of trabecular bone and decreases the density of a subset of sympathetic nerve fibers innervating the developing rat femur

Cadmium (Cd) is toxic to the skeletal system resulting in bone loss and pain. We aimed at determining the effect of chronic Cd exposure on bone density and microarchitecture along with changes in the density of a subset of sensory and sympathetic nerve fibers innervating the developing rat femur. Newborn male Wistar rats were injected daily for 49 days with CdCl₂ (1 mg/kg i.p.) or saline solution (control group). At the day of sacrifice, levels of Cd in the right femur, liver and kidney were determined by atomic absorption spectrophotometry. Additionally, microCT followed by immunohistochemical analyses were performed in the left femur. Results showed Cd accumulation in trabecular bone neared levels seen in liver and kidney. Cd concentration in cortical bone was significantly lower versus trabecular bone. MicroCT analysis revealed that Cd-exposed rats had a significant decrease in trabecular bone parameters at the distal femoral metaphysis; however, most of the cortical bone parameters were not significantly affected. Cd-exposed rats showed a significant loss of TH⁺ sympathetic nerve fibers, but not of CGRP⁺ sensory nerve fibers, at the level of bone marrow of the femoral diaphysis as compared to control rats. This study shows that Cd negatively affects bone density and microarchitecture of trabecular bone and decreases the density of sympathetic nerve fibers innervating rat femur. Future studies are warranted to determine the toxigenic mechanisms of Cd on sympathetic nerves and how sympathetic denervation influences bone loss in animals exposed to Cd.

Disruption of Bone Zinc Metabolism during Postnatal Development of Rats after Early Life Exposure to Cadmium

This current study was conducted to investigate whether bone tissue impairment induced by early life exposure to cadmium (Cd) during postnatal development could result from disruption to zinc (Zn) metabolism. For this reason, the offspring from mothers receiving either tap water, Cd, Zn or Cd + Zn during gestation and lactation periods were euthanized at PND21 and PND70. At the end of the lactation period (PND21), our results showed that exposure to Cd increased Cd accumulation and Zn depletion in the femur. Furthermore, calcium (Ca) level was reduced. At the molecular level, Cd induced an increase of MT-1 expression and caused an upregulation of ZIP2 accompanied with a down-regulation of ZnT5. Runx2, ALP, colα-1 and Oc mRNA levels were also decreased. In plasma, IGF-1 and osteocalcin concentrations were decreased. Further, Cd altered femoral growth by generating changes in the growth plate. Consequently, the toxic effect of Cd persisted at adult age (PND70) by decreasing bone volume (%BV/TV), bone mineral density (BMD) and Ca content and by increasing trabecular separation (Tb.Sp) in the distal femur. Interestingly, Zn supply provided total or partial corrections of several toxic effects of Cd. These data suggest that the increases of Zn bioavailability as well as the reduction of Cd accumulation in the femur following the changes in ZIP2 and ZnT5 expression are part of the mechanism involved in Zn protection against Cd toxicity on bone tissue.

Toxic Effect of Acute Cadmium and Lead Exposure in Rat Blood, Liver, and Kidney

Background: Cadmium and lead are widespread and non-biodegradable pollutants of great concern to human health. In real life scenarios, we are exposed to mixtures of chemicals rather than single chemicals, and it is therefore of paramount importance to assess their toxicity. In this study, we investigated the toxicity of Cd and Pb alone and as a mixture in an animal model of acute exposure. Methods: Experimental groups received a single treatment of aqueous solution of Cd-chloride (15 and 30 mg/kg body weight (b.w.) and Pb-acetate (150 mg/kg b.w.), while the mixture group received 15 mg Cd/kg b.w. and 150 mg Pb/kg b.w. Toxic effects of individual metals and their mixture were investigated on hematological and biochemical parameters, and the redox status in the plasma, liver, and kidneys of treated Wistar rats. Results: Tissue-specific changes were recorded in various parameters of oxidative damage, while the accumulation of metals in tissues accompanied the disturbances of both hematological and biochemical parameters. It was observed that the level of toxic metals in tissues had a different distribution pattern after mixture and single exposure. Conclusions: Comprehensive observations suggest that exposure to Cd and Pb mixtures produces more pronounced effects compared to the response observed after exposure to single metal solutions. However, further research is needed to confirm toxicokinetic or toxicodynamic interactions between these two toxic metals in the organisms.

Impact of occupational cadmium exposure on bone in sewage workers

Cadmium (Cd) is one of the environmental risk factors for bone loss. The present study included 40 sewage workers occupationally exposed to Cd. Forty nonexposed men were included as a control group. Current smokers represented 65% and 47.5% of the exposed and control groups, respectively. The study aimed to investigate the hazard of occupational Cd exposure on bone health. This was achieved through measuring serum and urinary Cd, and calcium (Ca), in addition to serum osteoprotegerin (OPG) and estrogen receptor-α gene. Results showed significant elevation in serum Cd, OPG, and urinary Ca levels in the exposed compared to the controls. Bony aches and joint pain were more prevalent among the exposed workers. Serum and urinary Cd increased in exposed smokers relative to control smokers. Also, serum OPG levels showed significant rise among exposed smoker and nonsmoker compared to control smoker and nonsmoker groups. Serum Cd level increased significantly in PP and pp genotypes in exposed workers compared to controls, while elevated levels of serum OPG was observed in PP and Pp genotypes in exposed workers relative to controls. Urinary Cd exhibited significant rise in both PP and pp genotypes in exposed workers, while Ca excretion was elevated in pp genotype only. The study reflected an association of genetic predisposition and Cd exposure in progression of osteoporosis. Further research is needed to explain the mechanisms of Cd impact on bone. The role of smoking is important and hence smoking cessation programs are essential for sewage workers.

Magnesium Lithospermate B Protects against Lipopolysaccharide-Induced Bone Loss by Inhibiting RANKL/RANK Pathway

Lipopolysaccharide (LPS) can induce bone loss by stimulating bone resorption. Natural compounds have great potential for the treatment of osteolytic bone diseases. Magnesium lithospermate B (MLB) plays an important role in protecting against oxidative damage and also has potential anti-inflammatory pharmacological properties. However, its role in LPS-induced bone loss is still unknown. In the present study, we observed the effects of MLB on LPS-induced bone damage and investigated the possible mechanisms. The bone loss models were established by LPS administration in male Sprague–Dawley rats. MLB (200 mg/kg body weight) was given by subcutaneous injection. MicroCT analysis, biomarker assay, histological examination and immunohistochemical staining were performed at the 8th weeks. In addition, RAW264.7 cells were treated with LPS in the presence or absence of MLB. The osteoclast formation, resorption activity and differentiation-related genes [(receptor activator of nuclear factor kappa-B (RANK), Traf6, Fra-1, and c-src)] expression were evaluated. LPS induced bone loss shown as the decrease in bone volume fraction and trabecular number, and increase in trabecular separation. LPS also markedly enhanced the osteoclast formation and resorption activity compared with the control. MLB significantly abolished the LPS-induced bone microstructure damage (p < 0.05) and osteoclast formation. MLB also inhibited the increases of serum tartrate-resistant acid phosphatase 5b, RANK ligand (RANKL) and TNF-α level enhanced by LPS (p < 0.05). Immunohistochemical staining indicated that MLB attenuated the high expression of RANKL and RANK stimulated by LPS. In addition, MLB significantly abolished the LPS-enhanced osteoclast formation, resorption activity, RANK, Traf6, Fra-1, and c-src expression in vitro. Our data demonstrate that MLB can suppress LPS-induced bone loss via inhibiting RANKL/RANK related osteoclast formation.

Emodin suppresses cadmium-induced osteoporosis by inhibiting osteoclast formation

Environmental level of cadmium (Cd) exposure can induce bone loss. Emodin, a naturally compound found in Asian herbal medicines, could influence osteoblast/osteoclast differentiation. However, the effects of emodin on Cd-induced bone damage are not clarified. The aim of this study was to investigate the role of emodin on Cd-induced osteoporosis. Sprague-Dawley male rats were divided into three groups which were given 0mg/L, 50mg Cd/L and 50mg Cd/L plus emodin (50mg/kg body weight). Bone histological investigation, microCT analysis, metabolic biomarker determination and immunohistochemical staining were performed at the 12th week. The bone mass and bone microstructure index of rats treated with Cd were obviously lower than in control. Cd markedly enhanced the osteoclast formation compared with control. Emodin significantly abolished the Cd-induced bone microstructure damage (p<0.05), osteoclast formation and increase of tartrate-resistant acid phosphatase 5b level (p<0.05). Our data further showed that emodin attenuated the Cd-induced inhibition of osteoprotegerin expression and stimulation of receptor activator for nuclear factor-κ B ligand expression. Our data show that emodin suppresses the Cd-induced osteoporosis by inhibiting osteoclast formation.