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PubMed1999

Genotoxicity and radioresistance in electroplating workers exposed to chromium.

A biomonitoring study was carried out to investigate the genetic risk associated to occupational exposure to chromium. The induction of genetic damage was measured by analysing the frequency of micronuclei (MN) in peripheral blood lymphocytes. In addition to the 40 electroplater exposed workers who participated in the study, a group constituted by 18 volunteer donors, without exposure to chromium, was analysed as a control group. Measures of chromium levels at working place and in erythrocytes and urine were obtained, as indicators of exposure. The results from this study indicate that the blood from exposed workers contained higher levels of chromium, when compared with those obtained in the control group, and that a significant increase in the frequency of both the total number of MN and the number of binucleated cells carrying MN (BNMN) was detected. Furthermore, a good direct relationship was obtained between the amount of chromium present in air, erythrocytes or urine and the frequency of MN. To determine the existence of radioresistance as consequence of chromium exposure, the response of lymphocytes to the in vitro gamma-radiation was studied. The results of this experiment show a lower induction in the increase of the frequency of MN after challenge irradiation in the lymphocytes of chromium exposed workers, which should be indicative of an adaptive response.

Adaptation, Physiological↗
PubMedDate not supplied

Synthesis of peptide-oligonucleotide conjugates for chromium coordination.

The synthesis of the first peptide-oligonucleotide conjugate designed to coordinate chromium(III) is reported. The overall goal of this work is to synthesize di-deoxynucleotides tethered with chromium(III)-coordinating appendages to model chromium-DNA-protein cross-links, which are a type of DNA lesion that may be involved in chromium-induced cancers. The conjugate dGp(NHCH(2)CH(2)S-Ac-Gly-Ser-Gly-OH)G was made by coupling the peptide, ClAc-Gly-Ser-Gly-OH, and dinucleotide, dGp(NHCH(2)CH(2)SH)G, through a thioether moiety. The conjugate was characterized by HPLC and mass spectrometry. Previously reported methods for small-scale solid-phase synthesis of peptides and dinucleotide were unsuitable; therefore, gram-scale solution-phase methods were developed. We also report the gram-scale syntheses of two other serine-containing peptides, ClAc-betaAla-Ser-Gly-OH and ClAc-Ser-Gly-OH, and three histidine-containing peptides, ClAc-Gly-His-Gly-OH, ClAc-betaAla-His-Gly-OH, and ClAc-His-Gly-OH. The synthesis and characterization of chromium-containing peptide-oligonucleotide conjugates will ultimately help us to understand chromium-DNA interactions at a molecular level, which is necessary before we can determine how chromium causes cancer.

Chromium↗
PubMed2005

Cellular chromium enhances activation of insulin receptor kinase.

Chromium has been recognized for decades as a nutritional factor that improves glucose tolerance by enhancing in vivo insulin action, but the molecular mechanism is unknown. Here we report pretreatment of CHO-IR cells with chromium enhances tyrosine phosphorylation of the insulin receptor. Different chromium(III) compounds were effective at enhancing insulin receptor phosphorylation in intact cells, but did not directly activate recombinant insulin receptor kinase. The level of insulin receptor phosphorylation in cells can be increased by inhibition of the opposing protein tyrosine phosphatase (PTP1B), a target for drug development. However, chromium did not inhibit recombinant human PTP1B using either p-nitrophenyl phosphate or the tyrosine-phosphorylated insulin receptor as the substrate. Chromium also did not alter reversible redox regulation of PTP1B. Purified plasma membranes exhibited insulin-dependent kinase activity in assays using substrate peptides mimicking sites of Tyr phosphorylation in the endogenous substrate IRS-1. Plasma membranes prepared from chromium-treated cells had higher specific activity of insulin-dependent kinase relative to controls. We conclude that cellular chromium potentiates insulin signaling by increasing insulin receptor kinase activity, separate from inhibition of PTPase. Our results suggest that nutritional and pharmacological therapies may complement one another to combat insulin resistance, a hallmark of type 2 diabetes.

Amino Acid Sequence↗
PubMed2005

Solid waste removes toxic liquid waste: adsorption of chromium(VI) by iron complexed protein waste.

The leather processing industry generates huge amounts of wastes, both in solid and liquid form. Fleshing from animal hides/skins is one such waste that is high in protein content. In this study, raw fleshing has been complexed with iron and is used for removal of chromium(VI). The effect of pH and the initial concentration of chromium(VI) on the removal of Cr(IV) by iron treated fleshing is presented. Iron treatment is shown to greatly improve adsorption of the fleshing for hexavalent chromium. The ultimate adsorption capacity of iron treated fleshing is 51 mg of chromium(VI) per gram of fleshing. That of untreated fleshing is 9 mg/g such that iron treatment increases the adsorption capacity of fleshing by 10-fold. The measured adsorption kinetics is well described by a pseudo-second-order kinetic model. The uptake of chromium(VI) by fleshing is best described by the Langmuir adsorption isotherm model. X-ray photoelectron spectroscopic (XPS) studies show that the iron is incorporated into the protein matrix. Shifts in XPS spectra suggest that dichromate binding occurs with iron at active adsorption sites and that iron treated fleshing removes chromium(VI) without reducing it to chromium(III).

Adsorption↗
PubMed2006

The contemporary anthropogenic chromium cycle.

Chromium is an essential engineering metal used in stainless and alloy steels, chemicals, and refractory products. Using material flow analysis, all major anthropogenic chromium flows are characterized for the year 2000, from mining through discard, on three spatial levels: fifty-four countries, nine world regions, and the planet. Included is the first detailed quantification of chromium in internationally traded finished products and diverse waste streams. Findings include (1) 78% of chromium flow entering final use is added as a net addition to stock on the global level; most countries are close to this figure; (2) the majority of mining occurs in Africa (2400 Gg Cr/yr) and the Commonwealth of Independent States (1090 Gg Cr/yr), while the major end-users are Asia, Europe, and North America at 1150, 1140, and 751 Gg Cr/yr, respectively; (3) waste flows of chromium are the greatest in Europe (420 Gg Cr/yr), Asia (370 Gg Cr/yr), and North America (290 Gg Cr/yr), but the composition of these waste flows varies greatly among the world regions; (4) releases of chromium by the global system, which total 2630 Gg Cr/yr, are nearly evenly divided among tailings, ferrochromium slag, downgraded scrap, and post-consumer losses; (5) many countries have a heavy foreign dependence on chromium in the all forms, as is demonstrated for the United States. The findings relating to in-use stock changes and finished product trade are relevant to industry, allowing for more accurate planning for future scrap availability. The quantification of releases due to discards and dissipation hold environmental and human health relevance, while the full life cycle international trade assessment addresses local scarcity.

Chromium↗
PubMed2000

Lack of effect of dietary chromium supplementation on glucose tolerance, plasma insulin and lipoprotein levels in patients with type 2 diabetes.

Chromium is essential for the regulation of insulin action, thereby influencing carbohydrate and lipid metabolism. An uncontrolled pilot study was designed to measure the habitual daily intake of chromium in a group of healthy individuals with type 2 diabetes and to monitor the effect of daily supplementation with high chromium yeast on glucose tolerance, plasma insulin and lipoproteins. Twelve free-living adults with type 2 diabetes underwent a glucose tolerance test (GTT) on recruitment, at 4 weeks (after a 7-d duplicate diet collection) and at 12 weeks (following 8 weeks daily supplementation with 100 micrograms of chromium). Urine samples were collected on the day before and the day of each GTT. Blood samples were taken at half hourly intervals for 3 hours during the GTT and the plasma glucose, cholesterol, triglyceride, HDL, LDL and insulin concentration measured. The chromium content of diets and urine samples was determined. Fasting glucose concentrations and glucose area under the curve profiles did not alter significantly post supplementation with the chromium rich yeast. No significant changes in insulin and lipoprotein concentrations were observed. The results of this study do not support the hypothesis that individuals with type 2 diabetes benefit from yeast-based chromium supplements (100 micrograms/day).

Aged↗
PubMed2004

Human nucleotide excision repair efficiently removes chromium-DNA phosphate adducts and protects cells against chromate toxicity.

Intracellular reduction of carcinogenic Cr(VI) leads to the extensive formation of Cr(III)-DNA phosphate adducts. Repair mechanisms for chromium and other DNA phosphate-based adducts are currently unknown in human cells. We found that nucleotide excision repair (NER)-proficient human cells rapidly removed chromium-DNA adducts, with an average t((1/2)) of 7.1 h, whereas NER-deficient XP-A, XP-C, and XP-F cells were severely compromised in their ability to repair chromium-DNA lesions. Activation of NER in Cr(VI)-treated human fibroblasts or lung epithelial H460 cells was manifested by XPC-dependent binding of the XPA protein to the nuclear matrix, which was also observed in UV light-treated (but not oxidant-stressed) cells. Intracellular replication of chromium-modified plasmids demonstrated increased mutagenicity of binary Cr(III)-DNA and ternary cysteine-Cr(III)-DNA adducts in cells with inactive NER. NER deficiency created by the loss of XPA in fibroblasts or by knockdown of this protein by stable expression of small interfering RNA in H460 cells increased apoptosis and clonogenic death by Cr(VI), providing genetic evidence for the role of monofunctional chromium-DNA adducts in the toxic effects of this metal. The rate of NER of chromium-DNA adducts under saturating conditions was calculated to be approximately 50,000 lesions/min/cell. Because chromium-DNA adducts cause only small changes in the DNA helix, rapid repair of these modifications in human cells indicates that the presence of major structural distortions in DNA is not required for the efficient detection of the damaged sites by NER proteins in vivo.

Cell Line↗
PubMed1999

Lipid peroxidation in workers exposed to hexavalent chromium.

The aim of this study was to investigate whether exposure to hexavalent chromium induces lipid peroxidation in human. This study involved 25 chrome-plating factory workers and a reference group of 28 control subjects. The whole-blood and urinary chromium concentrations were determined by graphite furnace atomic absorption spectrophotometry. Malondialdehyde (MDA), the product of lipid peroxidation, was determined by high-performance liquid chromatography, and the activities of protective enzymes were measured by ultraviolet-visible spectrophotometry. In the chrome-plating workers, the mean concentrations of chromium in blood and urine were 5.98 microg/L and 5.25 microg/g creatinine, respectively; the mean concentrations of MDA in blood and urine were 1.7 micromol/L and 2.24 micromol/g creatinine. The concentrations of both chromium and MDA in blood and urine were significantly higher in the chromium-exposed workers. The activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) were not markedly different between control and exposed workers. Data suggest that MDA may be used as a biomarker for occupational chromium exposure. Antioxidant enzymic activities are not a suitable marker for chromium exposure.

Adult↗
PubMed1998

Comparative effects of chromium, vanadium and gymnema sylvestre on sugar-induced blood pressure elevations in SHR.

OBJECTIVE: Effects on systolic blood pressure (SBP) of ingesting three agents reported to influence insulin metabolism, i.e., chromium polynicotinate, bis(maltolato)oxovanadium (BMOV), and the herb, Gymnema sylvestre, were assessed simultaneously in spontaneously hypertensive rats (SHR). METHODS: In the first study, SHR were fed either a starch, sugar, or sugar diet containing chromium polynicotinate, bis(maltolato)oxovanadium (BMOV), or G. sylvestre. Tail SBP was estimated indirectly and various blood chemistries were measured. TBARS formation was determined in hepatic and renal tissue. In a second study, tail SBP was measured in SHR ingesting diets containing different concentrations of BMOV. RESULTS: Compared to starch, SHR consuming sucrose showed a significant elevation of SBP within days that was maintained for the duration of study. Addition of chromium polynicotinate to the sucrose diet at the beginning of study prevented the sucrose-induced elevation of SBP for 2 weeks, but SBP rose significantly after that. BMOV at high concentrations overcame the sucrose-induced rise in SBP and even decreased SBP below values seen in SHR eating the starch diet, but marked weight loss was noted. A second study examined different concentrations of BMOV. At 0.01% w/w concentration of BMOV, SBP was still significantly decreased, even though SHR did not lose body weight (BW) early on. SHR consuming G. sylvestre showed no change or even elevated SBP. Hepatic thiobarbituric acid reacting substances (TBARS) formation, an estimate of lipid peroxidation, was decreased by chromium polynicotinate and BMOV, and renal TBARS by chromium polynicotinate. Circulating cholesterol concentrations were decreased in the SHR consuming G. sylvestre. CONCLUSIONS: Chromium decreases the portion of SBP elevated by high sucrose intake as shown previously, but high levels of sucrose ingestion can eventually overcome this. BMOV overcame sucrose-induced elevation of SBP as well as some of the "genetic hypertension." Different from chromium, this decrease was not overcome by high levels of dietary sucrose. The significant lowering of cholesterol with G. sylvestre ingestion indicates some effect on metabolism, but G. sylvestre did not lower and even raised SBP.

Animals↗
PubMed1997

Concentration and size distribution of airborne hexavalent chromium in electroplating factories.

Studies have shown that chromium from electroplating factories can cause respiratory problems to workers after prolonged exposure. Since Taiwan has a relatively high number of electroplating factories and minimal data regarding chromium's effect on workers, the authors undertook this study focusing on the size distribution of airborne hexavalent chromium and its concentration levels within the factory. Both area and personal sampling were conducted using a particle fractionating sampler. Samples were analyzed using visible spectrophotometry. A comparison of three types of factories-chromium, nickel-chromium, and zinc-showed that the highest concentrations were found in chromium electroplating factories near the electroplating tank. Hexavalent chromium particles obtained from area sampling had mass median diameters between 1.67-6.38 microns and 0.75-4.73 microns for personal sampling. Particles of this high concentration and small size can enter and cause considerable damage to the respiratory tract.

Air Pollutants, Occupational↗
PubMed2006

Exposure to chromium, cobalt and molybdenum from metal-on-metal total hip replacement and hip resurfacing arthroplasty.

BACKGROUND: All metal implants--and metal-on-metal bearings in particular--corrode and cause a release of metal ions. Because cobalt and chromium have been shown to be carcinogenic and mutagenic in human and animal models, systemic toxicity and cancer risk are considered to be possible disadvantages of the metal-on-metal articulation. This study was designed to investigate the serum concentration profiles of chromium, cobalt and molybdenum after implantation of a Birmingham hip resurfacing arthroplasty (BHR) and a cementless total hip replacement with a 28-mm Metasul articulation (MTHR), over the first 2 years after implantation. METHODS: We analyzed profiles of metal ion serum levels in 111 patients implanted with a BHR, in 74 patients implanted with an MTHR, and in 130 implant-free probands control subjects using atomic absorption spectrophotometry. RESULTS: Chromium and cobalt concentrations (in microg/L) of all BHR and MTHR patients differed significantly from those of control subjects (chromium: < 0.25; cobalt: 0.25). The median chromium and cobalt concentrations in BHR patients had increased to 5.1 and 4.3 microg/L 2 years after surgery. Concentrations in BHR patient exceeded those in the unilateral MTHR patients. Molybdenum serum concentrations hardly changed over time in either group and were not significantly different from the concentrations seen in the control subjects. INTERPRETATION: During the first 2 years after surgery, the Birmingham hip resurfacing arthroplasty leads to a significantly greater increase in serum chromium and cobalt levels than the 28-mm metal-on-metal MTHR. Observation of patients over a longer period will be necessary in order to evaluate any chronic adverse effects to the system due to elevated chromium and cobalt serum concentrations.

Aged↗
PubMed2004

Removal of chromium from tannery effluents by adsorption.

Tannery effluent is characterized not only by heavy loads but also with toxic heavy metals especially chromium ions. Chromium is considered an important source of contamination due to large volume of exhaust liquid discharged and solid sludge produced. Details on adsorption studies were carried out using synthetic chromium salts (chromium chloride) as adsorbate, and cement kiln dust (a waste from white cement industry) as adsorbent. Equilibrium isotherms have been determined for the adsorption of chromium ions on cement kiln dust. Kinetic study provided that the adsorption process is diffusion controlled. The experimental results have been fitted using Freundlich, Langmuir, and Redlich Peterson isotherms. The maximum adsorption capacity of cement kiln dust was found to be 33 mg/g. Industrial tannery effluent (22-mg/L chromium and COD 952 mg/L) was also treated by cement dust. The treated effluent (using 20 g cement dust per 1 L) contains only 0.6 mg/L chromium and COD 200 mg/L.

Adsorption↗
PubMedDate not supplied

Trivalent chromium inhibits protein glycosylation and lipid peroxidation in high glucose-treated erythrocytes.

Epidemiological studies have shown lower levels of chromium among men with diabetes and cardiovascular disease (CVD) compared with healthy control subjects. The mechanism by which chromium may decrease the incidence of CVD and insulin resistance is not known. Using erythrocytes as a model, this study demonstrates that chromium inhibits the glycosylation of proteins and oxidative stress, both risk factors in the development of CVD. Erythrocytes were treated with high levels of glucose (mimicking diabetes) in the presence or absence of chromium chloride in the medium at 37 degrees C for 24 hours. Chromium supplementation prevented the increases in protein glycosylation and oxidative stress caused by the high levels of glucose in erythrocytes. This study demonstrates for the first time that chromium supplementation inhibits protein glycosylation in erythrocytes exposed to high glucose medium, which appears to be mediated by its antioxidative effect. This provides evidence for a novel mechanism by which chromium supplementation may decrease incidence of CVD in diabetic patients.

Chlorides↗
PubMed1980

Effect of chromium on insulin secretion and glucose removal rate in the newborn.

The effect of chromium on glucose removal rate (GRR) was investigated in the first 48 hr of life in 22 full-term newborns. Intravenous glucose tolerance test was performed in all babies in the first 24 hr. GRR was found 1.22 +/- 0.17% min. Sixteen of 22 babies received orally 250 micrograms CrCl3 6 H2O and the other six served as controls (no chromium). Intravenous glucose tolerance test was repeated on the 2nd day in all subjects. In the chromium administered group GRR increased from 1.34 +/- 0.19 to 2.58 +/- 0.45% min (P less than 0.01). In the controls, GRR on 2 consecutive days were found 0.90 +/- 0.36 and 2.04 +/- 0.32% min, respectively (P less than 0.05). The ratio of the difference between two GRR values to initial GRR showed no significant difference between the chromium-administered group and the controls. Chromium did not cause a significant change in plasma insulin. The low GRR observed in the newborn irrespective of administered chromium may be taken as evidence that similar to the relative delay in insulin release, the active role of chromium in plasma as glucose tolerance factor may also be inadequate in the early newborn period.

Chromium↗
PubMed2005

Low toenail chromium concentration and increased risk of nonfatal myocardial infarction.

Chromium intake may increase insulin sensitivity, glucose tolerance, and the ratio of high density lipoprotein cholesterol to low density lipoprotein cholesterol. However, the epidemiologic evidence on the association between chromium and cardiovascular disease is very limited. To determine whether low toenail chromium concentrations were associated with risk of nonfatal myocardial infarction, the authors conducted an incident, population-based, case-control study in eight European countries and Israel in 1991-1992. Cases (n = 684) were men with a first diagnosis of myocardial infarction recruited from the coronary units of participating hospitals. Controls (n = 724) were men selected randomly from population registers (five study centers) or through other sources, such as hospitalized patients (three centers), general practitioners' practices (one center), or relatives or friends of cases (one center). Toenail chromium concentration was assessed by neutron activation analysis. Average toenail chromium concentrations were 1.10 mug/g in cases (95% confidence interval: 1.01, 1.18) and 1.30 mug/g in controls (95% CI: 1.21, 1.40). Multivariate odds ratios for quintiles 2-5 were 0.82 (95% CI: 0.52, 1.31), 0.68 (95% CI: 0.43, 1.08), 0.60 (95% CI: 0.37, 0.97), and 0.59 (95% CI: 0.37, 0.95). Toenail chromium concentration was inversely associated with the risk of a first myocardial infarction in men. These results add to an increasing body of evidence that points to the importance of chromium for cardiovascular health.

Case-Control Studies↗
PubMed1992

Mutational specificity of chromium(VI) compounds in the hprt locus of Chinese hamster ovary-K1 cells.

Chromium(VI) compounds exert their genotoxicity and mutagenicity by complex metabolic reducing pathways that generate a variety of reactive forms of chromium and free radicals. To investigate the molecular nature of chromium-induced mutations, we characterized the entire coding region of the hypoxanthine (guanine) phosphoribosyltransferase (hprt) gene of 27 independent mutants derived from chromium(VI) oxide (CrO3)-treated Chinese hamster ovary-K1 cells, by direct sequencing of PCR-amplified cDNA. Among these mutants, 10 consisted of single base substitutions, five contained two base substitutions, one had four base substitutions, six were splicing mutations, and five exhibited single base pair insertions or deletions. All of the base substitutions and most of the frameshift mutations observed were located at A/T-rich sequences. More than 90% of the base substitutions (22/24) occurred in A.T base pairs. Among them, T-->A and T-->G transversions (18/22) predominated. The mutational hotspots for single and double base substitutions were the 3' thymidine of 5'PuT and thymidines of 5'ATTT sequences respectively. This mutational specificity was also observed in CHO-K1 cells treated with two other chromium(VI) compounds, namely K2Cr2O7 and PbCrO4. Strand bias was noticed in chromium mutagenicity, since 77% of T base substitutions occurred on the non-transcribed strand. This highly sequence-specific mutation spectrum suggests that a particular form of chromium may directly interact with DNA at these hotspot sequences.

Amino Acids↗
PubMed1986

Chromium (VI)-induced DNA damage in chick embryo liver and blood cells in vivo.

Uptake of chromium (VI) and subsequent induction of DNA damage was examined in liver and blood cells of 14-day chick embryos after injection of sodium dichromate onto the inner shell membrane. Maximal loss of chromium from the inner shell membrane and distribution of chromium in liver, lung and blood was observed 2 h after injection. DNA strand breaks, interstrand cross-links and DNA--protein cross-links were measured using the alkaline elution technique. In chick embryo liver, chromium (VI) induced DNA cross-links in the absence of strand breaks. Maximal DNA cross-linking was detected in the liver 8 h after injection. Little or no DNA damage remained in the liver 10-24 h after injection. In contrast, chromium (VI) induced DNA strand breaks in the absence of cross-links in chick embryo blood cells. Maximal DNA strand breakage was observed in blood cells 8 h after injection. High levels of DNA strand breaks were present in blood cells even 24 h after treatment. These intra-embryonic tissue differences in chromium (VI)-induced DNA damage may be a result of the differences in glutathione, cytochrome P-450, other pathways of chromium (VI) metabolism or chromatin organization which exist in liver and blood cells.

Animals↗
PubMed1989

Effects of starch, sucrose, fructose and glucose on chromium absorption and tissue concentrations in obese and lean mice.

Forty-eight male genetically obese (OB) mice (C57BL/6J-OB) and 48 lean male littermates were randomly assigned within main plots (OB or lean) to one of eight diets. Diets were low chromium or supplemented with 1 mg chromium as CrCl3 per kg. Starch, sucrose, fructose or glucose comprised 50% of the diet, which met AIN recommendations except for chromium. Experimental diets and deionized water were available ad libitum for 26 d. Mice were fasted 10 h and were intubated 2 h before killing with 15 microCi of 51CrCl3 in a 25% carbohydrate solution (2 mg carbohydrate/g body wt) of either starch, sucrose, glucose or fructose corresponding to the diet previously fed. 51Cr concentrations were significantly higher in the blood, liver, spleen, epididymal fat pad, testes and femur of animals given their carbohydrate load as starch than in animals fed sucrose, fructose or glucose. Carbohydrate had a significant effect on chromium concentrations of testes, spleen, kidney and liver with values generally being higher with the starch diet. Chromium supplementation increased bone and kidney chromium concentrations and heart and muscle glycogen. These data indicate that the source of carbohydrate can alter chromium absorption and retention.

Adipose Tissue↗