Evaluation of cadmium-induced nephrotoxicity using urinary metabolomic profiles in sprague-dawley male rats

Effects of Cadmium on Kidney Function of the Freshwater Turtles Mauremys reevesii

This research studied the effects of cadmium on kidney function of the freshwater turtles Mauremys reevesii. Turtles were injected intraperitoneally with 0, 7.5, 15, and 30 mg kg^-1 cadmium separately for once. The samples were gathered to check the kidney index, the contents of TP in kidney tissue, and the levels of CRE and BUN in the plasma of the turtles. Results showed that the concentration of TP was overall decreased with the extension of cadmium exposure time and the increasing of the exposure dose of cadmium. The CRE content in the plasma of each treatment group increased with the prolongation of exposure time in a dose-dependent, and the BUN levels of all poisoned groups showed a trend of increasing. The kidney index of treated turtles increased. In summary, cadmium could induce the increase of turtle kidney index, the content of CRE and BUN in plasma, and the decrease of TP content in the kidney.

Metabolic effects of long-term cadmium exposure: an overview

Cadmium (Cd) is a toxic non-essential heavy metal. Chronic low Cd exposure (CLCE) has been associated with distinct pathologies in many organ systems, including liver and kidney damage, osteoporosis, carcinogenicity, or reproductive toxicity. Currently, about 10% of the global population is at risk of CLCE. It is urgent to find robust and effective biomarkers for early diagnosis of Cd exposure and treatment. Metabolomics is a high-throughput method based on mass spectrometry to study the dynamic changes in a series of endogenous small molecular metabolites (typically < 1000 Da) of tissues, cells, or biofluids. It can reflect the rich and complex biochemical changes in the body after exposure to heavy metals, which may be useful in screening biomarkers to monitor exposure to environmental pollutants and/or predict disease risk. Therefore, this review focuses on the changes in metabolic profiles of humans and rodents under long-term Cd exposure from the perspective of metabolomics. Furthermore, the relationship between the disturbance of metabolic pathways and the toxic mechanism of Cd is discussed. All these information will facilitate the development of reliable metabolic biomarkers for early detection and diagnosis of Cd-related diseases.

Using intracellular metabolic profiling to identify novel biomarkers of cisplatin-induced acute kidney injury in NRK-52E cells

The aim of this study was to investigate changes in the intracellular metabolism resulting from cisplatin (CDDP)-induced nephrotoxicity in normal kidney tubular epithelial NRK-52E cells. Cytotoxicity, cell cycle analysis, and apoptotic cell death were all evaluated in NRK-52E cells treated with CDDP. Subsequently, proton nuclear magnetic resonance (¹H-NMR) spectroscopy was used to investigate cellular metabolic profiles. CDDP-induced nephrotoxicity was determined in vivo model. Cytotoxicity in the NRK-52E cells significantly rose following treatment with CDDP and these increases were found to be concentration-dependent. Both p53 and Bax protein expression was increased in CDDP-treated NRK-52E cells, correlating with enhanced cellular apoptosis. In addition, a number of metabolites were altered in both media and cell lysates in these cells. In cell lysates, citrate, creatinine, and acetate levels were dramatically reduced following treatment with 20 µM CDDP concentrations, while glutamate level was elevated. Lactate and acetate levels were significantly increased in culture media but citrate concentrations were reduced following high 20 µM CDDP concentrations incubation. In addition, excretion of clusterin, calbindin, neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), selenium binding protein 1 (SBP1), and pyruvate kinase M2 (PKM2) into the culture media was significantly increased in CDDP-treated cells while expression of acetyl CoA synthetase 1 (AceCS1) was markedly reduced in these cells. These findings suggest that acetate-dependent metabolic pathway may be a reliable and useful biomarker for detecting CDDP-induced nephrotoxicity. Taken together, data demonstrate that the discovery of novel biomarkers by metabolite profiling in target cells may contribute to the detection of nephrotoxicity and new drug development.

Study on toxicity effects of environmental pollutants based on metabolomics: A review

In the past few decades, the toxic effects of environmental pollutants on non-target organisms have received more and more attention. As a new omics technology, metabolomics can clarify the metabolic homeostasis of the organism at the overall level by studying the changes in the relative contents of endogenous metabolites in the organism. Recently, a large number of studies have used metabolomics technology to study the toxic effects of environmental pollutants on organisms. In this review, we reviewed the analysis processes and data processes of metabolomics and its application in the study of the toxic effects of environmental pollutants including heavy metals, pesticides, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, polybrominated diphenyl ethers and microplastics. In addition, we emphasized that the combination of metabolomics and other omics technologies will help to explore the toxic mechanism of environmental pollutants and provide new research ideas for the toxicological evaluation of environmental pollutants.

Urinary metabolic characterization with nephrotoxicity for residents under cadmium exposure

Cadmium is a well-known hazardous pollutant that mainly comes from dietary, tobacco and occupational exposure, posing threat to kidney. However, there is still a lack of systematic study on metabolic pathways and urinary biomarkers related to its nephrotoxicity under cadmium exposure for both females and males. In this study, a mass spectrometry-based metabolomics investigation of a cohort of 144 volunteers was conducted to explore sex-specific metabolic alteration and to screen biomarkers related to cadmium-induced nephrotoxicity. When the concentration of urinary cadmium increased, creatine pathway, amino acid metabolism especially the tryptophan metabolism, aminoacyl-tRNA biosynthesis, and purine metabolism were primarily influenced regardless of the gender. Also, the most specific biomarkers linked with nephrotoxicity based on the statistical analysis were detected including creatine, creatinine, l-tryptophan, adenine and uric acid. The study outcome might provide information to reflect the body burden and help improve health policy for risk assessment.

Biomarkers of effect as determined in human biomonitoring studies on hexavalent chromium and cadmium in the period 2008-2020

A number of human biomonitoring (HBM) studies have presented data on exposure to hexavalent chromium [Cr(VI)] and cadmium (Cd), but comparatively few include results on effect biomarkers. The latter are needed to identify associations between exposure and adverse outcomes (AOs) in order to assess public health implications. To support improved derivation of EU regulation and policy making, it is of great importance to identify the most reliable effect biomarkers for these heavy metals that can be used in HBM studies. In the framework of the Human Biomonitoring for Europe (HBM4EU) initiative, our study aim was to identify effect biomarkers linking Cr(VI) and Cd exposure to selected AOs including cancer, immunotoxicity, oxidative stress, and omics/epigenetics. A comprehensive PubMed search identified recent HBM studies, in which effect biomarkers were examined. Validity and applicability of the markers in HBM studies are discussed. The most frequently analysed effect biomarkers regarding Cr(VI) exposure and its association with cancer were those indicating oxidative stress (e.g., 8-hydroxy-2'-deoxyguanosine (8-OHdG), malondialdehyde (MDA), glutathione (GSH)) and DNA or chromosomal damage (comet and micronucleus assays). With respect to Cd and to some extent Cr, β-2-microglobulin (B2-MG) and N-acetyl-β-D-glucosaminidase (NAG) are well-established, sensitive, and the most common effect biomarkers to relate Cd or Cr exposure to renal tubular dysfunction. Neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule (KIM)-1 could serve as sensitive biomarkers of acute kidney injury in response to both metals, but need further investigation in HBM studies. Omics-based biomarkers, i.e., changes in the (epi-)genome, transcriptome, proteome, and metabolome associated with Cr and/or Cd exposure, are promising effect biomarkers, but more HBM data are needed to confirm their significance. The combination of established effect markers and omics biomarkers may represent the strongest approach, especially if based on knowledge of mechanistic principles. To this aim, also mechanistic data were collected to provide guidance on the use of more sensitive and specific effect biomarkers. This also led to the identification of knowledge gaps relevant to the direction of future research.

Comparative study on protective effect of different selenium sources against cadmium-induced nephrotoxicity via regulating the transcriptions of selenoproteome

Cadmium (Cd) is a ubiquitous environmental pollutant, which mainly input to the aquatic environment through discharge of industrial and agricultural waste, can be a threat to human and animal health. Selenium (Se) possesses a beneficial role in protecting animals and ameliorating the toxic effects of Cd. However, the comparative antagonistic effects of different Se sources such as inorganic, organic Se and nano-form Se on Cd toxicity are still under-investigated. Hence, the purpose of this study was to evaluate the comparative of Se sources antagonism on Cd-induced nephrotoxicity via oxidative stress and selenoproteome transcription. In the present study, Cd-diet disturbed in the system balance of 5 trace elements (Zinc (Zn), copper (Cu), Iron (Fe), Se, Cd) and impaired renal function. Se sources, including nano- Se (NS), Se- yeast (SY), sodium selenite (SS) and mixed selenium (MS) significantly recovered the balance of 4 trace elements (Zn, Cu, Cd, Se) and renal impaired indexes (blood urea nitrogen (BUN) and creatinine (CREA)). Histological appearance of Cd-treated kidney indicated renal tubular epithelial vacuoles, particle degeneration and enlarged capsular space. Ultrastructure observation results illustrated that Cd-induced mitochondrial cristae reduction, membrane disappearance, and nuclear deformation. Treatment with Se sources, NS appeared a better impact on improving kidney tissues against the pathological alterations resulting from Cd administration. Meanwhile, NS reflected a significant impact on relieving Cd-induced kidney oxidative damage, and significantly restored the antioxidant defense system of the body. Our findings also showed NS ameliorated the Cd-induced downtrends expression of selenoproteome and selenoprotein synthesis related transcription factors. Overall, NS was the most effective Se source in avoiding of Cd cumulative toxicity, improving antioxidant capacity and regulating of selenoproteome transcriptome and selenoprotein synthesis related transcription factors expression, which contributes to ameliorate Cd-induced nephrotoxicity in chickens. These results demonstrated diet supplement with NS may prove to be an effective approach for alleviating Cd toxicity and minimizing Cd -induced health risk.

Identification of Novel Biomarker for Early Detection of Diabetic Nephropathy

Diabetic nephropathy (DN) is one of the most common complications of diabetes mellitus. After development of DN, patients will progress to end-stage renal disease, which is associated with high morbidity and mortality. Here, we developed early-stage diagnostic biomarkers to detect DN as a strategy for DN intervention. For the DN model, Zucker diabetic fatty rats were used for DN phenotyping. The results revealed that DN rats showed significantly increased blood glucose, blood urea nitrogen (BUN), and serum creatinine levels, accompanied by severe kidney injury, fibrosis and microstructural changes. In addition, DN rats showed significantly increased urinary excretion of kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL). Transcriptome analysis revealed that new DN biomarkers, such as complementary component 4b (C4b), complementary factor D (CFD), C-X-C motif chemokine receptor 6 (CXCR6), and leukemia inhibitory factor (LIF) were identified. Furthermore, they were found in the urine of patients with DN. Since these biomarkers were detected in the urine and kidney of DN rats and urine of diabetic patients, the selected markers could be used as early diagnosis biomarkers for chronic diabetic nephropathy.

Potential protective roles of curcumin against cadmium-induced toxicity and oxidative stress

Curcumin, used as a spice and traditional medicine in India, exerts beneficial effects against several diseases, owing to its antioxidant, analgesic, and anti-inflammatory properties. Evidence indicates that curcumin might protect against heavy metal-induced organ toxicity by targeting biological pathways involved in anti-oxidation, anti-inflammation, and anti-tumorigenesis. Curcumin has received considerable attention owing to its therapeutic properties, and the mechanisms underlying some of its actions have been recently investigated. Cadmium (Cd) is a heavy metal found in the environment and used extensively in industries. Chronic Cd exposure induces damage to bones, liver, kidneys, lungs, testes, and the immune and cardiovascular systems. Because of its long half-life, exposure to even low Cd levels might be harmful. Cd-induced toxicity involves the overproduction of reactive oxygen species (ROS), resulting in oxidative stress and damage to essential biomolecules. Dietary antioxidants, such as chelating agents, display the potential to reduce Cd accumulation and metal-induced toxicity. Curcumin scavenges ROS and inhibits oxidative damage, thus resulting in many therapeutic properties. This review aims to address the effectiveness of curcumin against Cd-induced organ toxicity and presents evidence supporting the use of curcumin as a protective antioxidant.

Developmental toxicity of cadmium in infants and children: a review

Several millions of people are exposed to cadmium worldwide due to natural and anthropogenic activities that led to their widespread distribution in the environment and have shown potential adverse effects on the kidneys, liver, heart and nervous system. Recently human and animal-based studies have been shown that In utero and early life exposure to cadmium can have serious health issues that are related to the risk of developmental disabilities and other outcomes in adulthood. Since, cadmium crosses the placental barrier and reaches easily to the fetus, even moderate or high-level exposure of this metal during pregnancy could be of serious health consequences which might be reflected either in the children’s early or later stages of life. Mortality from various diseases including cancer, cardiovascular, respiratory, kidney and neurological problems, correlation with In utero or early life exposure to cadmium has been found in epidemiological studies. Animal studies with strong evidence of various diseases mostly support for the human studies, as well as suggested a myriad mechanism by which cadmium can interfere with human health and development. More studies are needed to establish the mechanism of cadmium-induced toxicity with environmentally relevant doses in childhood and later life. In this review, we provide a comprehensive examination of the literature addressing potential long- term health issues with In utero and early life exposure to cadmium, as well as correlating with human and animal exposure studies.

Metabolomic biomarkers in urine of rats following long-term low-dose exposure of cadmium and/or chlorpyrifos

Heavy metals and pesticides can be easily enriched in food chains and accumulated in organisms, thus pose significant threat to human health. However, their combined effects for long-term exposure at low dose has not been thoroughly investigated; especially there was no biofluid biomarker available to noninvasively diagnose the toxicosis of the combined exposure of the two chemicals at their low levels. In this study, we investigated the change of urine metabolites of rats with 90-day exposure to heavy metal cadmium (Cd) and/or organophosphorus pesticide chlorpyrifos (CPF) using gas chromatography-mass spectrometry (GC-MS)-based metabolomics approach. Our results showed that the interaction of Cd and CPF mainly displayed an antagonistic effect. We identified the panels of metabolite biomarkers in urine: benzoic acid and mannose were unique biomarkers for Cd exposure; creatinine and N-phenylacetyl glycine were unique biomarkers for CPF exposure; anthranilic acid, ribitol, and glucose were unique biomarkers for Cd plus CPF exposure. Our results suggest that 90-day exposure to Cd and/or CPF could cause a disturbance in energy and amino acid metabolism. And urine metabolomics analysis can help understand the toxicity of low dose exposure to mixed environmental chemicals.

Nephroprotective effect of wogonin against cadmium-induced nephrotoxicity via inhibition of oxidative stress-induced MAPK and NF-kB pathway in Sprague Dawley rats

Oxidative stress (OS) is one of the responsible factors for causing renal diseases. For the treatment or prevention of the renal disease, antioxidants use could be a hopeful therapeutic mediation as they block the oxidative reaction along with inflammatory process. Wogonin (Wog) is a plant flavonoid, a pharmacologically active component of Scutellaria baicalensis Georgi (Huang Qui), which exhibits antioxidant activity. In this investigation, we explored the nephroprotective activity of Wog on cadmium (Cd)-induced nephron toxicity in rats. Administering (10 and 20 mg/kg) intraperitoneally diminished Cd-induced anomalies in kidney histology and creatinine and serum urea levels. Wog therapy reduced the Cd-influenced generation of inflammatory mediators, inclusive of tumor necrosis factor alpha, interleukin 6, and interleukin 1 beta. Western blot analysis demonstrated that Wog abolished proinflammatory nuclear factor-kappa B (NF-κB) p65 stimulation, phosphorylation of p38 mitogen-activated protein kinases (MAPKs). In all, Wog demonstrated antioxidative and anti-inflammatory effects in Cd- intoxicated rats by obstructing OS and activation of NF-κB via restricting the stimulation of upstream kinases inclusive of MAPKs.

Biomarkers of cadmium, lead and mercury exposure in relation with early biomarkers of renal dysfunction and diabetes: Results from a pilot study among aging Canadians

Cadmium (Cd), lead (Pb) and mercury (Hg) are known nephrotoxicants that have been associated with the risk of developing type-2 diabetes (T2D). The aim of this pilot study was to explore relations between biomarkers of Cd, Pb and Hg exposure, early urinary biomarkers of renal dysfunction (kidney-injured molecule-1 (KIM-1), N-acetylglucosaminidase and retinol-binding protein (RBP)) and plasma biomarkers deemed predictive of the risk of developing T2D (adiponectin, leptin, branched-chain and aromatic amino acids), among 70 participants (age range: (46-87 yrs)) from the Canadian Longitudinal Study on Aging (CLSA) with normal glycemic control (glycated haemoglobin ≤ 6.5%) in all but four of them. Significant (p < 0.05) Spearman correlation coefficients were obtained between: plasma adiponectin and RBP (r = 0.42), urinary Cd (r = 0.32), blood Cd (r = 0.36); KIM-1 and CdU (r = 0.33) as well as HgU (r = 0.37); RBP and isoleucine (r = -0.28), leucine (r = -0.33), tyrosine (r = -0.3) and valine (r = -0.44); CdU and isoleucine and valine (r = -0.27 for both). Multiple linear regression analyses showed that some T2D-related biomarkers are confounders of associations between RBP and Hg or Cd biomarkers. Path analyses support a mediating effect of adiponectin on the relation between urinary Cd and RBP. Concluding, this pilot study originally investigated a comprehensive set of biomarkers on complex interactions between toxic metal exposure, renal function and T2D in a group of aging Canadians. Its findings warrant further investigation of longitudinal data in a greater number of participants.

Royal jelly attenuates cadmium-induced nephrotoxicity in male mice

Cadmium exposure induces nephrotoxicity by mediating oxidative stress, inflammation, and apoptosis. The purpose of this study was to examine the protective effect of royal jelly on Cd-induced nephrotoxicity. Adult male mice were distributed randomly into 4 clusters: untreated, royal jelly-treated (85 mg/kg, oral), CdCl₂-treated (6.5 mg/kg, intraperitoneal), and pretreated with royal jelly (85 mg/kg) 2 h before CdCl₂ injection (6.5 mg/kg, intraperitoneal) for seven consecutive days. Cd concentration in the renal tissue and absolute kidney weight of the Cd-treated mice were significantly higher than those of control group. The levels of kidney function markers, kidney injury molecules-1 (KIM-1), metallothionein, lipid peroxidation, nitric oxide, tumor necrosis factor-α, interleukin-1β, and the apoptosis regulators Bax and caspases-3 also increased significantly in the renal tissue of Cd-treated mice, whereas the levels of glutathione, antioxidant enzyme activities, and the apoptosis inhibitor Bcl-2 were significantly reduced in the renal tissue of Cd-treated group. Histopathological studies showed vacuolation and congested glomeruli in the kidney tissue of Cd-treated mice. However, all aforementioned Cd-induced changes were attenuated by pretreatment with royal jelly. We therefore concluded that royal jelly attenuated Cd-induced nephrotoxicity and it is suggested that this nephroprotective effect could be linked to its ability to promote the nuclear factor erythroid 2–related factor 2 (Nrf2)/antioxidant responsive element (ARE) pathway.

On the oxidative damage by cadmium to kidney mitochondrial functions

In the kidney, the accumulation of heavy metals such as Cd2+ produces mitochondrial dysfunctions, i.e., uncoupling of the oxidative phosphorylation, inhibition of the electron transport through the respiratory chain, and collapse of the transmembrane electrical gradient. This derangement may be due to the fact that Cd2+ induces the transition of membrane permeability from selective to nonselective via the opening of a transmembrane pore. In fact, Cd2+ produces this injury through the stimulation of oxygen-derived radical generation, inducing oxidative stress. Several molecules have been used to avoid or even reverse Cd2+-induced mitochondrial injury, for instance, cyclosporin A, resveratrol, dithiocarbamates, and even EDTA. The aim of this study was to explore the possibility that the antioxidant tamoxifen could protect mitochondria from the deleterious effects of Cd2+. Our results indicate that the addition of 1 μmol/L Cd2+ to mitochondria collapsed the transmembrane electrical gradient, induced the release of cytochrome c, and increased both the generation of H2O2 and the oxidative damage to mitochondrial DNA (among other measured parameters). Of interest, these mitochondrial dysfunctions were ameliorated after the addition of tamoxifen.

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.

Identification of aldo-keto reductase (AKR7A1) and glutathione S-transferase pi (GSTP1) as novel renal damage biomarkers following exposure to mercury

The kidney is one of the main targets for toxicity induced by xenobiotics. Sensitive detection of early impairment is critical to assess chemical-associated renal toxicity. The aim of this study was to identify potential nephrotoxic biomarkers in rat kidney tissues after exposure to mercury (Hg), a representative nephrotoxicant, and to evaluate these new biomarkers employing in vivo and in vitro systems. Mercuric chloride was administered orally to Sprague-Dawley rats for 2 weeks. Proteomic analysis revealed that aldo-keto reductase (AKR7A1) and glutathione S-transferase pi (GSTP1) were significantly elevated in kidney after Hg exposure. While the levels of conventional nephrotoxic clinical markers including blood urea nitrogen and serum creatinine were not elevated, the mRNA and protein levels of AKR7A1 and GSTP1 were increased upon Hg exposure in a dose-dependent manner. The increases in AKR7A1 and GSTP1 were also observed in rat kidneys after an extended exposure for 6 weeks to low-dose Hg. In in vitro rat kidney proximal tubular cells, changes in AKR7A1 and GSTP1 levels correlated well with the extent of cytotoxicity induced by Hg, cadmium, or cisplatin. AKR7A1 and GSTP1 were identified as new candidates for Hg-induced nephrotoxicity, suggesting that these biomarkers have potential for evaluating or predicting nephrotoxicity.

Effects of long-term cadmium exposure on urinary metabolite profiles in mice

Cadmium (Cd) is a common environmental pollutant with known toxic effects on the kidney. Urinary metabolomics is a promising approach to study mechanism by which Cd-induced nephrotoxicity. The aim of this study was to elucidate the mechanism of Cd toxicity and to develop specific biomarkers by identifying urinary metabolic changes after a long-term of Cd exposure and with the critical concentration of Cd in the kidney. Urine samples were collected from wild-type 129/Sv mice after 67 weeks of 300 ppm Cd exposure and analyzed by ultra performance liquid chromatography connected with quadrupole time of flight mass spectrometer (UPLC-QTOF-MS) based metabolomics approach. A total of 40 most differentiated metabolites (9 down-regulated and 31 up-regulated) between the control and Cd-exposed group were identified. The majority of the regulated metabolites are amino acids (glutamine, L-aspartic acid, phenylalanine, tryptophan, and D-proline) indicating that amino acid metabolism pathways are affected by long-term exposure of Cd. However, there are also some nucleotides (guanosine, guanosine monophosphate, cyclic AMP, uridine), amino acid derivatives (homoserine, N-acetyl-L-aspartate, N-acetylglutamine, acetyl-phenylalanine, carboxymethyllysine), and peptides. Results of pathway analysis showed that the arginine and proline metabolism, purine metabolism, alanine, aspartate and glutamate metabolism, and aminoacyl-tRNA biosynthesis were affected compared to the control. This study demonstrates that metabolomics is useful to elucidate the metabolic responses and biological effects induced by Cd-exposure.

Metabonomic analysis of toxic action of long-term low-level exposure to acrylamide in rat serum

This study assessed the effects of long-term, low-dose acrylamide (AA) administration in rats using ultra-performance liquid chromatography–mass spectrometry. Forty male Wistar rats were randomly divided into the following four groups: control, low-dose AA (0.2 mg/kg BW), middle-dose AA (1 mg/kg BW), and high-dose AA (5 mg/kg BW). AA was administered to rats via drinking water ad libitum. After 16-week treatment, rat serum was collected for metabonomic analysis. Biochemical tests were further conducted to verify metabolic alterations. Eleven metabolites were identified with significant changes in intensities (increased or reduced) as a result of treatment. These metabolites included citric acid, pantothenic acid, isobutyryl-l-carnitine, eicosapentaenoic acid, docosahexaenoic acid, sphingosine 1-phosphate, LysoPC(20:4), LysoPC(22:6), LysoPE(20:3), undecanedioic acid, and dodecanedioic acid. Results indicate that chronic exposure to AA at no observed adverse effect level does not exert a toxic effect on rats at the body metabolism level. AA disturbed the metabolism of lipids and energy, affected the nervous system of rats, and induced oxidative stress and liver dysfunction.

Curcumin ameliorates cadmium-induced nephrotoxicity in Sprague-Dawley rats

Chronic exposure to cadmium (Cd) causes remarkable damage to the kidneys, a target organ of accumulated Cd after oral administration. The aim of the present study was to investigate the protective effect of curcumin against Cd-induced nephrotoxicity. Sprague-Dawley male rats were divided into the following four treatment groups: control, curcumin (50 mg/kg, oral), CdCl₂, (25 mg/kg, oral), and pre-treatment with curcumin (50 mg/kg) 1 h prior to the administration of CdCl₂ (25 mg/kg, oral) for 7 days. At 24 h after the final treatment, the animals were killed, and the biomarkers associated with nephrotoxicity were measured. Our data indicated that blood urea nitrogen (BUN) and serum creatinine (sCr) levels were significantly reduced by curcumin pre-treatment in CdCl₂-treated animals. Histopathological studies showed hydropic swelling and hypertrophy of the proximal tubular cells in the renal cortex after Cd treatment. Pretreatment with curcumin ameliorated the histological alterations induced by Cd. The urinary excretion of kidney injury molecule-1 (Kim-1), osteopontin (OPN), tissue inhibitor of metalloproteinases 1 (TIMP-1), neutrophil gelatinase-associated lipocalin (NGAL), and netrin-1 significantly reduced by curcumin treatment compared to that in the CdCl₂-treated group. The administration of curcumin provided a significant protective effect against Cd-induced nephrotoxicity.

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.

Identification of a sensitive urinary biomarker, selenium-binding protein 1, for early detection of acute kidney injury

Acute kidney injury (AKI) is associated with increased mortality rate in patients but clinically available biomarkers for disease detection are currently not available. Recently, a new biomarker, selenium-binding protein 1 (SBP1), was identified for detection of nephrotoxicity using proteomic analysis. The aim of this study was to assess the sensitivity of urinary SBP1 levels as an early detection of AKI using animal models such as cisplatin or ischemia/reperfusion (I/R). Sprague-Dawley rats were injected with cisplatin (6 mg/kg, once i.p.) and sacrificed at 1, 3, or 5 days after treatment. Ischemia was achieved by bilaterally occluding both kidneys with a microvascular clamp for 45 min and verified visually by a change in tissue color. After post-reperfusion, urine samples were collected at 9, 24, and 48 hr intervals. Urinary excretion of protein-based biomarkers was measured by Western blot analysis. In cisplatin-treated rats, mild histopathologic alterations were noted at day 1 which became severe at day 3. Blood urea nitrogen (BUN) and serum creatinine (SCr) levels were significantly increased at day 3. Levels of urinary excretion of SBP1, neutrophil gelatinase-associated lipocalin (NGAL), and a tissue inhibitor of metalloproteinase-1 (TIMP-1) were markedly elevated at day 3 and 5 following drug treatment. In the vehicle-treated I/R group, serum levels of BUN and SCr and AST activity were significantly increased compared to sham. Urinary excretion of SBP1 and NGAL rose markedly following I/R. The urinary levels of SBP1, NGAL, TIMP-1, and KIM-1 proteins excreted by AKI patients and normal subjects were compared. Among these proteins, a marked rise in SBP1 was observed in urine of patients with AKI compared to normal subjects. Based upon receiver-operator curves (ROC), SBP1 displayed a higher area under the curve (AUC) scores than levels of SCr, BUN, total protein, and glucose. In particular, SBP1 protein was readily detected in small amounts of urine without purification. Data thus indicate that urinary excretion of SBP1 may be useful as a reliable biomarker for early diagnosis of AKI in patients.

Integration of Traditional and Metabolomics Biomarkers Identifies Prognostic Metabolites for Predicting Responsiveness to Nutritional Intervention against Oxidative Stress and Inflammation

Various statistical approaches can be applied to integrate traditional and omics biomarkers, allowing the discovery of prognostic markers to classify subjects into poor and good prognosis groups in terms of responses to nutritional interventions. Here, we performed a prototype study to identify metabolites that predict responses to an intervention against oxidative stress and inflammation, using a data set from a randomized controlled trial evaluating Korean black raspberry (KBR) in sedentary overweight/obese subjects. First, a linear mixed-effects model analysis with multiple testing correction showed that four-week consumption of KBR significantly changed oxidized glutathione (GSSG, q = 0.027) level, the ratio of reduced glutathione (GSH) to GSSG (q = 0.039) in erythrocytes, malondialdehyde (MDA, q = 0.006) and interleukin-6 (q = 0.006) levels in plasma, and seventeen NMR metabolites in urine compared with those in the placebo group. A subsequent generalized linear mixed model analysis showed linear correlations between baseline urinary glycine and N-phenylacetylglycine (PAG) and changes in the GSH:GSSG ratio (p = 0.008 and 0.004) as well as between baseline urinary adenine and changes in MDA (p = 0.018). Then, receiver operating characteristic analysis revealed that a two-metabolite set (glycine and PAG) had the strongest prognostic relevance for future interventions against oxidative stress (the area under the curve (AUC) = 0.778). Leave-one-out cross-validation confirmed the accuracy of prediction (AUC = 0.683). The current findings suggest that a higher level of this two-metabolite set at baseline is useful for predicting responders to dietary interventions in subjects with oxidative stress and inflammation, contributing to the emergence of personalized nutrition.

Toxicology of metals and metalloids: Promising issues for future studies in environmental health and toxicology

The function and behavior of chemical elements in ecosystems and in human health probably comprise one of the most studied issues and a theme of great interest and fascination in science. Hot topics are emerging on an annual basis in this field. Bearing this in mind, some promising themes to explore in the field of metals and metalloids in the environment and in toxicology are highlighted and briefly discussed herein.

Discovery of urinary metabolomic biomarkers for early detection of acute kidney injury

The discovery of new biomarkers for early detection of drug-induced acute kidney injury (AKI) is clinically important. In this study, sensitive metabolomic biomarkers identified in the urine of rats were used to detect cisplatin-induced AKI. Cisplatin (10 mg kg(-1), i.p.) was administered to Sprague-Dawley rats, which were subsequently euthanized after 1, 3 or 5 days. In cisplatin-treated rats, mild histopathological alterations were noted at day 1, and these changes were severe at days 3 and 5. Blood urea nitrogen (BUN) and serum creatinine (SCr) levels were significantly increased at days 3 and 5. The levels of new urinary protein-based biomarkers, including kidney injury molecule-1 (KIM-1), glutathione S-transferase-α (GST-α), tissue inhibitor of metalloproteinase-1 (TIMP-1), vascular endothelial growth factor (VEGF), calbindin, clusterin, neutrophil, neutrophil gelatinase-associated lipocalin (NGAL), and osteopontin, were significantly elevated at days 3 and 5. Among urinary metabolites, trigonelline and 3-indoxylsulfate (3-IS) levels were significantly decreased in urine collected from cisplatin-treated rats prior to histological kidney damage. However, carbon tetrachloride (CCl4), a hepatotoxicant, did not affect these urinary biomarkers. Trigonelline is closely associated with GSH depletion and results in insufficient antioxidant capacity against cisplatin-induced AKI. The predominant cisplatin-induced AKI marker appeared to be reduced in urinary 3-IS levels. Because 3-IS is predominantly excreted via active secretion in proximal tubules, a decrease is indicative of tubular damage. Further, urinary excretion of 3-IS levels was markedly reduced in patients with AKI compared to normal subjects. The area under the curve receiver operating characteristics (AUC-ROC) for 3-IS was higher than for SCr, BUN, lactate dehydrogenase (LDH), total protein, and glucose. Therefore, low urinary or high serum 3-IS levels may be more useful for early detection of AKI than conventional biomarkers.

Selenium-binding protein 1: a sensitive urinary biomarker to detect heavy metal-induced nephrotoxicity

Identifying novel biomarkers to detect nephrotoxicity is clinically important. Here, we attempted to identify new biomarkers for mercury-induced nephrotoxicity and compared their sensitivity to that of traditional biomarkers in animal models. Comparative proteomics analysis was performed in kidney tissues of Sprague-Dawley rats after oral treatment with HgCl₂ (0.1, 1, or 5 mg/kg/day) for 21 days. Kidney cortex tissues were analyzed by two-dimensional gel electrophoresis/matrix-assisted laser desorption/ionization, and differentially expressed proteins were identified. The corresponding spots were quantitated by RT-PCR. Selenium-binding protein 1 (SBP1) was found to be the most markedly upregulated protein in the kidney cortex of rats after HgCl₂ administration. However, blood urea nitrogen, serum creatinine, and glucose levels increased significantly only in the 1 or 5 mg/kg HgCl₂-treated groups. A number of urinary excretion proteins, including kidney injury molecule-1, clusterin, monocyte chemoattractant protein-1, and β-microglobulin, increased dose-dependently. Histopathological examination revealed severe proximal tubular damage in high-dose (5 mg/kg) HgCl₂-exposed groups. In addition, urinary excretion of SBP1 significantly increased in a dose-dependent manner. To confirm the critical role of SBP1 as a biomarker for nephrotoxicity, normal kidney proximal tubular cells were treated with HgCl₂, CdCl₂, or cisplatin for 24 h. SBP1 levels significantly increased in conditioned media exposed to nephrotoxicants, but decreased in cell lysates. Our investigations suggest that SBP1 may play a critical role in the pathological processes underlying chemical-induced nephrotoxicity. Thus, urinary excretion of SBP1 might be a sensitive and specific biomarker to detect early stages of kidney injury.

Pyruvate Kinase M2: A Novel Biomarker for the Early Detection of Acute Kidney Injury

The identification of biomarkers for the early detection of acute kidney injury (AKI) is clinically important. Acute kidney injury (AKI) in critically ill patients is closely associated with increased morbidity and mortality. Conventional biomarkers, such as serum creatinine (SCr) and blood urea nitrogen (BUN), are frequently used to diagnose AKI. However, these biomarkers increase only after significant structural damage has occurred. Recent efforts have focused on identification and validation of new noninvasive biomarkers for the early detection of AKI, prior to extensive structural damage. Furthermore, AKI biomarkers can provide valuable insight into the molecular mechanisms of this complex and heterogeneous disease. Our previous study suggested that pyruvate kinase M2 (PKM2), which is excreted in the urine, is a sensitive biomarker for nephrotoxicity. To appropriately and optimally utilize PKM2 as a biomarker for AKI requires its complete characterization. This review highlights the major studies that have addressed the diagnostic and prognostic predictive power of biomarkers for AKI and assesses the potential usage of PKM2 as an early biomarker for AKI. We summarize the current state of knowledge regarding the role of biomarkers and the molecular and cellular mechanisms of AKI. This review will elucidate the biological basis of specific biomarkers that will contribute to improving the early detection and diagnosis of AKI.

Different mechanisms for lead acetate, aluminum and cadmium sulfate in rat corpus cavernosum

INTRODUCTION

Some heavy metals show adverse vascular and neurological effects, however, their effect on erection is underestimated. This study aims to investigate the effect of Pb, Cd and Al on erectile function and their potential mechanism of action in rats.

METHODS

Measurement of intracavernosal pressure/mean arterial pressure (ICP/MAP) changes elicited by electrical stimulation of cavernous nerve in anesthetized rats treated with Pb-acetate, Al-sulfate, or Cd-sulfate acutely, and subacutely for 7 days. Serum creatinine, testosterone, TBARs, GSH levels and metal accumulation in corpus cavernosum were measured.

RESULTS

Pb, Al and Cd significantly reduced ICP/MAP in rats after acute (2,10-2,10 and 1,3 mg/kg respectively) and sub-acute (3, 3, and 1mg/kg/day respectively) treatments. They selectively accumulated in the corpus cavernosum reaching 25.107 ± 2.081 μg/g wet weight for Pb, 1.029 ± 0.193 for Cd, 31.343 ± 1.991 for Al, compared to 7.084 ± 1.517, 0.296 ± 0.067, and 8.86 ± 1.115 as controls respectively. Serum creatinine levels were not altered. Cd and Al significantly reduced testosterone level to 0.483 ± 0.059 and 0.419 ± 0.037 ng/ml respectively compared to 0.927 ± 0.105 ng/ml as control. Aluminum elevated TBARs significantly by 27.843%. The acute anti-erectile action of Pb was blocked by non-selective NOS and GC inhibitors and potassium channel blocker. Lead also masked the potentiatory effect of l-arginine and diazoxide on ICP/MAP. No interaction with muscarinic or nicotinic modulators was observed.

CONCLUSIONS

Pb, Cd and Al show anti-erectile effect independent on renal injury. They don not modulate cholinergic nor ganglionic transmission in corpus cavernosum. Pb may inhibit NO/cGMP/K+channel pathway. The effect of Cd and Al but not Pb seems to be hormonal dependent.

Cytotoxic mechanism related to dihydrolipoamide dehydrogenase in Leydig cells exposed to heavy metals

Heavy metals are common environmental toxicants with adverse effects on steroid biosynthesis. The importance of mitochondria has been recognized in cytotoxic mechanism of heavy metals on Leydig cells these years. But it is still poorly known. Our previous study reported that dihydrolipoamide dehydrogenase (DLD) located on the mitochondria was significantly decreased in Leydig cells exposed to cadmium, which suggested that DLD might be involved in the cytotoxic effects. Therefore, the altered expression of DLD was validated in rats and R2C cells exposed to cadmium, manganese and lead, and the role of DLD in the steroid synthesis pathway cAMP/PKA-ERK1/2 was investigated in this study. With a low expression of DLD, heavy metals dramatically reduced the levels of steroid hormone by inhibiting the activation of cAMP/PKA, PKC signaling pathway and the steroidogenic enzymes StAR, CYP11A1 and 3β-HSD. After knockdown of DLD in R2C cells, progesterone synthesis was reduced by 40%, and the intracellular concentration of cAMP, protein expression of StAR, 3β-HSD, PKA, and the phosphorylation of ERK1/2 were also decreased. These results highlight that DLD is down-regulation and related to steroid biosynthesis in Leyig cells exposed to heavy metals; cAMP/PKA act as downstream effector molecules of DLD, which activate phosphorylation of ERK1/2 to initiate the steroidogenesis.

Phlda3, a urine-detectable protein, causes p53 accumulation in renal tubular cells injured by cisplatin

Measurable indicators of renal injury are required for the assessment of kidney function after toxicant challenge. In our previous study, pleckstrin homology-like domain, family A, member 3 (Phlda3) was a most greatly up-regulated molecule downstream from p53, culminating with kidney tubular injury. This study investigated the positive feedforward effect of Phlda3 on p53 in an effort to explain the largest increase of Phlda3 in injured tubules and the potential of its urine excretion. qRT-PCR assays confirmed a rapid and substantial increase in Phlda3 messenger RNA (mRNA) in the kidney cortex of mice treated with a single dose of cisplatin. Cisplatin overexpression of Phlda3 was verified by gene set analyses of three different microarray databases. In the immunohistochemistry, Phlda3 staining intensities were augmented in the tubules as kidney injury worsened. Moreover, the urinary content of Phlda3 was increased after cisplatin treatment, as were those of other kidney injury markers (Kim-1 and Timp-1). By contrast, cisplatin failed to increase Phlda3 mRNA in the liver despite hepatocyte necrosis and ensuing increases in serum transaminase activities. In NRK52E tubular cells, siRNA knockdown of Phlda3 enhanced the ability of cisplatin to increase p-Mdm2 presumably via Akt, enforcing the interaction between Mdm2 and p53. Consistently, a deficiency in Phlda3 abrogated p53 increase by cisplatin, indicating that Phlda3 promotes p53 accumulation. Phlda3 overexpression had the opposite effect. In addition, treatment with cyclosporine A or CdCl2, other nephrotoxicants, increased Phlda3 mRNA and protein levels in NRK52E cells, as did cisplatin treatment. Overall, Phlda3 may cause p53 accumulation through a feedforward pathway, facilitating tubular injury and its urine excretion.

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.