Failure to produce hypertension in rats by chronic exposure to cadmium

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.

Endothelial Dysfunction Induced by Cadmium and Mercury and its Relationship to Hypertension

Hypertension is an important public health concern that affects millions globally, leading to a large number of morbidities and fatalities. The etiology of hypertension is complex and multifactorial, and it involves environmental factors, including heavy metals. Cadmium and mercury are toxic elements commonly found in the environment, contributing to hypertension. We aimed to assess the role of cadmium and mercury-induced endothelial dysfunction in the development of hypertension. A narrative review was carried out through database searches. In this review, we discussed the critical roles of cadmium and mercury in the etiology of hypertension and provided new insights into potential mechanisms of their effect, focusing primarily on endothelial dysfunction. Although the mechanisms by which cadmium and mercury induce hypertension have yet to be completely elucidated, evidence for both implicates impaired nitric oxide signaling in their hypertensive etiology.

Metabonomics analysis of kidneys in rats administered with chronic low-dose cadmium by ultra-performance liquid chromatography-mass spectrometry

This study aimed to investigate the nephrotoxicity in rats administered with chronic low-dose cadmium (Cd) by ultra-performance liquid chromatography-mass spectrometry. A total of 40 male Sprague-Dawley rats were randomly assigned to four groups, namely: control; low-dose (0.13 mg/kg·body weight [bw]); middle-dose (0.80 mg/kg·bw); and high-dose (4.89 mg/kg·bw). The rats received CdCl₂ daily via drinking water for 24 weeks. Rat kidneys were collected for metabonomics analysis. Principal components analysis and partial least-squares discriminant analysis were used to investigate the metabonomics profile changes in the kidney samples and to screen the potential biomarkers. Ten metabolites were identified in the positive and negative ion modes. Compared with the control group, the intensities of tetranor 12-HETE, uric acid, hypoxanthine, phenylacetylglycine, guanidinosuccinic acid and xanthosine significantly increased (P < 0.01), and those of imidazolelactic acid, lactose 6-phosphate, l-urobilinogen and arachidonic acid significantly decreased (P < 0.01) in the high-dose group. Results showed that exposure to Cd in rats induced oxidative stress to the kidneys and disrupted amino acid metabolism, fatty acid metabolism and energy metabolism.

Metabolomic analysis of the toxic effect of chronic exposure of cadmium on rat urine

This study aimed to assess the toxic effect of chronic exposure to cadmium through a metabolomic approach based on ultra-performance liquid chromatography/mass spectrometry (UPLC-MS). Forty male Sprague-Dawley rats were randomly assigned to the following groups: control, low-dose cadmium chloride (CdCl₂) (0.13 mg/kg body weight (bw)), middle-dose CdCl₂ (0.8/kg bw), and high-dose CdCl₂ (4.9 mg/kg bw). The rats continuously received CdCl₂ via drinking water for 24 weeks. Rat urine samples were then collected at different time points to establish the metabolomic profiles. Multiple statistical analyses with principal component analysis and partial least squares-discriminant analysis were used to investigate the metabolomic profile changes in the urine samples and screen for potential biomarkers. Thirteen metabolites were identified from the metabolomic profiles of rat urine after treatment. Compared with the control group, the treated groups showed significantly increased intensities of phenylacetylglycine, guanidinosuccinic acid, 4-pyridoxic acid, 4-aminohippuric acid, 4-guanidinobutanoic acid, allantoic acid, dopamine, LysoPC(18:2(9Z,12Z)), and L-urobilinogen. By contrast, the intensities of creatinine, L-carnitine, taurine, and pantothenic acid in the treated groups were significantly decreased. These results indicated that Cd disrupts energy and lipid metabolism. Meanwhile, Cd causes liver and kidney damage via induction of oxidative stress; serum biochemical indices (e.g., creatinine and urea nitrogen) also support the aforementioned results.

Metabonomics analysis of serum from rats given long-term and low-level cadmium by ultra-performance liquid chromatography-mass spectrometry

1. This study evaluated the toxicity of chronic exposure to low-level cadmium (Cd) in rats using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS). Forty male Sprague-Dawley rats were randomly assigned to four groups, namely, the control group, low-dose group (0.13 mg/kg·bw), middle-dose group (0.8 mg/kg·bw) and high-dose group (4.89 mg/kg·bw). The rats continuously received CdCl₂ via drinking water for 24 weeks. Serum samples were collected for metabonomics analysis. The data generated from the UPLC-MS was analysed using principal components analysis (PCA) and partial least-squares discriminant analysis (PLS-DA). PLS-DA model with satisfactory explanatory and predictive ability is capable of discriminating the treatment groups from the control group. 2. Finally, the 10 metabolites were identified and showed significant changes in some treatment groups compared with that in the control group (p < 0.0167 or p < 0.003). Exposure to Cd resulted in increased intensities of lysophosphatidic acid (P-16:0e/0:0), glycocholic acid, bicyclo-prostaglandin E2, lithocholyltaurine, sulfolithocholylglycine, lysophosphatidylethanolamine (20:5/0:0) and lysophosphatidylcholine (20:0), as well as decreased intensities of 3-indolepropionic acid, phosphatidylcholine (18:4/18:0) and 15S-hydroxyeicosatrienoic acid in rat serum. 3. Results suggest that exposure to Cd can cause disturbances in the lipid metabolism, amino acid metabolism, nervous system, antioxidant defence system, liver and kidney function.

The elderly as a sensitive population in environmental exposures: making the case

The US population is aging. CDC has estimated that 20% of all Americans will be 65 or older by the year 2030. As a part of the aging process, the body gradually deteriorates and physiologic and metabolic limitations arise. Changes that occur in organ anatomy and function present challenges for dealing with environmental stressors of all kinds, ranging from temperature regulation to drug metabolism and excretion. The elderly are not just older adults, but rather are individuals with unique challenges and different medical needs than younger adults. The ability of the body to respond to physiological challenge presented by environmental chemicals is dependent upon the health of the organ systems that eliminate those substances from the body. Any compromise in the function of those organ systems may result in a decrease in the body's ability to protect itself from the adverse effects of xenobiotics. To investigate this issue, we performed an organ system-by-organ system review of the effects of human aging and the implications for such aging on susceptibility to drugs and xenobiotics. Birnbaum (1991) reported almost 20 years ago that it was clear that the pharmacokinetic behavior of environmental chemicals is, in many cases, altered during aging. Yet, to date, there is a paucity of data regarding recorded effects of environmental chemicals on elderly individuals. As a result, we have to rely on what is known about the effects of aging and the existing data regarding the metabolism, excretion, and adverse effects of prescription medications in that population to determine whether the elderly might be at greater risk when exposed to environmental substances. With increasing life expectancy, more and more people will confront the problems associated with advancing years. Moreover, although proper diet and exercise may lessen the immediate severity of some aspects of aging, the process will continue to gradually degrade the ability to cope with a variety of injuries and diseases. Thus, the adverse effects of long-term, low-level exposure to environmental substances will have a longer time to be manifested in a physiologically weakened elderly population. When such exposures are coupled with concurrent exposure to prescription medications, the effects could be devastating. Public health officials must be knowledgeable about the sensitivity of the growing elderly population, and ensure that the use of health guidance values (HGVs) for environmental contaminants and other substances give consideration to this physiologically compromised segment of the population.

Dose- and route-dependent hormonal activity of the metalloestrogen cadmium in the rat uterus

The toxic heavy metal cadmium (Cd) is regarded as a potential endocrine disruptor, since Cd exerts estrogen-like activity in vitro and can elicit some typical estrogenic responses in rodents upon intraperitoneal (i.p.) injection. But estrogenic effects have not been documented in vivo with other more relevant routes of exposure, although it is known that Cd absorption and distribution in the body is strongly affected by the application route. Therefore, we investigated its hormonal activity in ovariectomized Wistar rats after oral administration of CdCl(2) (0.05-4 mg/kg b.w. on 3 days by gavage and 0.4-9 mg/kg b.w. for 4 weeks in drinking water) in comparison with i.p. injection of CdCl(2) (0.00005-2 mg/kg b.w.). Uterus wet weight, height of uterine epithelium, and modulation of estrogen-regulated gene expression, i.e. uterine complement component 3 (C3), were determined, and also Cd-levels in uterus and liver were measured by atomic absorption spectrometry. The analysis revealed pronounced differences in Cd tissue levels and hormonal potency for the two routes of administration: a single i.p. injection of Cd increased dose-dependently uterine wet weight and thickness of the uterine epithelium. Interestingly, C3 mRNA expression in the uterus was down regulated at low doses of CdCl(2) (0.00005-0.05 mg/kg b.w.), but strongly stimulated at the highest dose of 2 mg/kg b.w. Other than i.p. injection, oral treatment with Cd, by gavage or in drinking water, did neither increase uterine wet weights nor epithelial thickness. But, both 3-day- and 4-week oral Cd administration resulted in a dose-dependent stimulation of C3 expression in the uterus, significant at and above 0.5 mg/kg b.w. In summary, our data demonstrate an estrogenic effect in the uterus upon i.p. injection of Cd, but considerably lower hormonal potency with oral administration: short and long-term oral treatment with Cd did not affect uterus weight or histology, whilst on the molecular level, an induction of estrogen sensitive uterine gene expression was observed, albeit at dose levels far exceeding those of dietary exposure in humans.