Characterisation of the effects of cadmium on the release of calcium and on the activity of some enzymes from neonatal mouse calvaria in culture

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

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

Levels of Cadmium in Human Mandibular Bone

Cadmium (Cd) is an environmental toxicant that accumulates in bone and alters bone turnover and metabolism. Periodontal disease is characterized by tooth loss and tissue destruction, specifically, loss of supporting bone around the teeth. We have previously shown that Cd causes loss of dental alveolar (tooth supporting) bone in a rodent model of long-term Cd poisoning. The overall goal of this study was to determine the possible association between levels of Cd in alveolar bone and evidence of periodontal disease in human cadavers. The extent of Cd accumulation in human mandible samples was analyzed. Levels of Cd in mandibular alveolar bone were compared to those in basal bone as well as the renal cortex in samples obtained from the cadavers. Alveolar bone contained significantly higher levels of Cd when compared to basal bone (p < 0.01). Cd levels in mandibular bone were significantly higher in female compared to male cadavers (p < 0.05). The kidney cortex had greater than 15-fold higher Cd levels compared to mandible bone. Additional analyses showed a possible association between levels of Cd in basal bone and the presence of periodontal disease in cadavers from which the samples were obtained. This study shows that Cd accumulates to relatively high levels within alveolar bone as compared to basal bone in the mandible and thus may have a significant and direct effect in the progression of changes in bone associated with periodontal disease.

Cadmium Exposure Disrupts Periodontal Bone in Experimental Animals: Implications for Periodontal Disease in Humans

Cadmium (Cd) is an environmental contaminant that damages the kidney, the liver, and bones. Some epidemiological studies showed associations between Cd exposure and periodontal disease. The purpose of this study was to examine the relationship between Cd exposure and periodontal disease in experimental animals. Male Sprague/Dawley rats were given daily subcutaneous injections of Cd (0.6 mg/kg/day) for up to 12 weeks. The animals were euthanized, and their mandibles and maxillae were evaluated for levels of periodontal bone by measuring the distance from the cementoenamel junction (CEJ) to the alveolar bone crest (ABC) of the molar roots. After 12 weeks of Cd exposure in animals, there was a significantly greater distance between the CEJ and ABC in the palatal aspect of the maxillary molars and the lingual aspect of the mandibular molars when compared with controls (p < 0.0001). This study shows that Cd has significant, time-dependent effects on periodontal bone in an animal model of Cd exposure. These findings support the possibility of Cd being a contributing factor to the development of periodontal disease in humans.

Maternal exposure to nanosized titanium dioxide suppresses embryonic development in mice

Although nanoscale titanium dioxide (nano-TiO2) has been extensively used in industrial food applications and daily products for pregnant women, infants, and children, its potential toxicity on fetal development has been rarely studied. The main objective of this investigation was to establish the effects of maternal exposure of nano-TiO2 on developing embryos. Female imprinting control region mice were orally administered nano-TiO2 from gestational day 0 to 17. Our findings showed that Ti concentrations in maternal serum, placenta, and fetus were increased in nano-TiO2-exposed mice when compared to controls, which resulted in reductions in the contents of calcium and zinc in maternal serum, placenta, and fetus, maternal weight gain, placental weight, fetal weight, number of live fetuses, and fetal crown-rump length as well as cauda length, and caused an increase in the number of both dead fetuses and resorptions. Furthermore, maternal nano-TiO2 exposure inhibited development of the fetal skeleton, suggesting a significant absence of cartilage, reduced or absent ossification, and an increase in the number of fetuses with dysplasia, including exencephaly, spina bifida, coiled tail, scoliosis, rib absence, and sternum absence. These findings indicated that nano-TiO2 can cross the blood-fetal barrier and placental barrier, thereby delaying the development of fetal mice and inducing skeletal malformation. These factors may be associated with reductions in both calcium and zinc in maternal serum and the fetus, and both the placenta and embryos may be major targets of developmental toxicity following maternal exposure to nano-TiO2 during the prenatal period. Therefore, the application of nano-TiO2 should be carried out with caution.

The role of Ca pathway in Cd uptake and translocation by the hyperaccumulator Sedum alfredii

Effect of Ca on plant growth, Cd uptake and translocation in the hyperaccumulator Sedum alfredii was investigated, as to reveal the possible pathway of Cd entry into the plants system. High Ca increased plant growth under Cd stress after 7 d, and significantly affected the total Cd influx and translocation rate. Short-term kinetics of (109)Cd influx performed using radiotracers confirmed a significant inhibition of (109)Cd influx into the roots induced by high Ca. Under exposure of 5.0 mM Ca, K(m) of (109)Cd influx into roots was 2-fold higher in the hyperaccumulator, although the V(max) value remained at similar level, when compared with the treatments of 0.5 mM Ca. Calcium concentrations in xylem sap of the hyperaccumulator decreased with the increasing Cd levels and significant negative correlationship between the two elements was observed. However, increased xylem loading of Cd was observed in the hyperaccumulator in response to the increasing exogenous Ca level from 0.5 to 4.0 mM, but reverse effect was observed when higher Ca levels (8-32 mM) were presented in the solutions. These results suggest that Cd uptake and translocation in the hyperaccumulator S. alfredii plants is positively associated with Ca pathway.

Cadmium-induced effects on bone in a population-based study of women

High cadmium exposure is known to cause bone damage, but the association between low-level cadmium exposure and osteoporosis remains to be clarified. Using a population-based women's health survey in southern Sweden [Women's Health in the Lund Area (WHILA) ] with no known historical cadmium contamination, we investigated cadmium-related effects on bone in 820 women (53-64 years of age) . We measured cadmium in blood and urine and lead in blood, an array of markers of bone metabolism, and forearm bone mineral density (BMD) . Associations were evaluated in multiple linear regression analysis including information on the possible confounders or effect modifiers: weight, menopausal status, use of hormone replacement therapy, age at menarche, alcohol consumption, smoking history, and physical activity. Median urinary cadmium was 0.52 microg/L adjusted to density (0.67 microg/g creatinine) . After multivariate adjustment, BMD, parathyroid hormone, and urinary deoxypyridinoline (U-DPD) were adversely associated with concentrations of urinary cadmium (p < 0.05) in all subjects. These associations persisted in the group of never-smokers, which had the lowest cadmium exposure (mainly dietary) . For U-DPD, there was a significant interaction between cadmium and menopause (p = 0.022) . Our results suggest negative effects of low-level cadmium exposure on bone, possibly exerted via increased bone resorption, which seemed to be intensified after menopause. Based on the prevalence of osteoporosis and the low level of exposure, the observed effects, although slight, should be considered as early signals of potentially more adverse health effects. Key words: biochemical bone markers, bone mineral density, cadmium, lead, osteoporosis, women.

Lactational Transfer of Cadmium from Meriones shawi shawi Mothers to Their Pups and Its Effects on Calcium Homeostasis and Bone Calcium in Pups

Cadmium (Cd) was given to Meriones shawi shawi dams in the diet (1 g CdCl2/1.5 kg of diet) from day 1 to day 21 of lactation. Pups were killed at 5, 10, 14 and 21 days of lactation. Thereafter, liver, kidney, femur and stomach content were removed and plasma was collected to element analyses. Cd in stomach content, kidney, liver and femur and calcium (Ca) in stomach content, femur and plasma were determined in pups by atomic absorption spectrophotometer. The results indicate that Cd was transferred to the suckling and it was detected in the liver, the kidney and the femur from the 5th, the 10th and the 14th days of age, respectively. Stomach content of Ca was increased significantly from the 10th day to the end of lactation, whereas Ca levels increase in plasma and femur only at day 10 of lactation.

Heavy metal toxicity: cadmium permeates through calcium channels and disturbs the plant water status

Because plant wilting has been described as a consequence of cadmium (Cd2+) toxicity, we investigate Cd2+ effects on plant water losses, gas exchanges and stomatal behaviour in Arabidopsis thaliana L. Effects of 1-week Cd2+ application in hydroponic condition (CdCl2 10-100 micro m) were analyzed. A 10- micro m Cd2+ concentration had no significant effect on the plant-water relationship and carbon assimilation. At higher Cd2+ concentrations, a Cd2+ -dependent decrease in leaf conductance and CO2 uptake was observed despite the photosynthetic apparatus appeared not to be affected as probed by fluorescence measurements. In epidermal strip bioassays, nanomolar Cd2+ concentrations reduced stomatal opening under light in A. thaliana, Vicia faba and Commelina communis. Application of 5 micro m ABA limited the root-to-shoot translocation of cadmium. However, the Cd2+-induced stomatal closure was likely ABA-independent, since a 5-day treatment with 50 micro m Cd2+ did not affect the plant relative water content. Additionally, a similar Cd2+-induced stomatal closure was observed in the ABA insensitive mutant abi1-1. Interestingly, this mutant displayed a higher transpiration rate than the wild type but did not accumulate more Cd2+, arguing that Cd2+ uptake is not dependent only on the transpiration flow. Application of putative calcium channels inhibitors suppressed the inhibitory effect of Cd2+ in epidermal strip experiments, suggesting that Cd2+ could enter the guard cell through calcium channels. Patch-clamp studies with V. faba guard cell protoplasts showed that plasma membrane K+ channels were insensitive to external Cd2+ application whereas Ca2+ channels were found permeable to Cd2+. In conclusion, we propose that Cd2+ affects guard cell regulation in an ABA-independent manner by entering the cytosol via Ca2+ channels.