Relationships between blood chromium exposure and liver injury: Exploring the mediating role of systemic inflammation in a chromate-exposed population.

Hexavalent chromium and its compounds are prevalent pollutants, especially in the work environment, pose a significant risk for multisystem toxicity and cancers. While it is known that chromium accumulation in the liver can cause damage, the dose-response relationship between blood chromium (Cr) and liver injury, as well as the possible potential toxic mechanisms involved, remains poorly understood. To address this, we conducted a follow-up study of 590 visits from 305 participants to investigate the associations of blood Cr with biomarkers for liver injury, including serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL), and direct bilirubin (DBIL), and to evaluate the mediating effects of systemic inflammation. Platelet (PLT) and the platelet-to-lymphocyte ratio (PLR) were utilized as biomarkers of systemic inflammation. In the linear mixed-effects analyses, each 1-unit increase in blood Cr level was associated with estimated effect percentage increases of 0.82% (0.11%, 1.53%) in TBIL, 1.67% (0.06%, 3.28%) in DBIL, 0.73% (0.04%, 1.43%) in ALT and 2.08% (0.29%, 3.87%) in AST, respectively. Furthermore, PLT mediated 10.04%, 11.35%, and 10.77% increases in TBIL, DBIL, and ALT levels induced by chromate, respectively. In addition, PLR mediated 8.26% and 15.58% of the association between blood Cr and TBIL or ALT. These findings shed light on the mechanisms underlying blood Cr-induced liver injury, which is partly due to worsening systemic inflammation.

[Effects on human peripheral erythrocytes of long-term occupational contact with chromate].

Objective: To investigate the effects on human peripheral blood erythrocytes of long-term occupational contact with chromate. Methods: A dynamic cohort study was conducted of chromate-exposed workers (343 cases) and non-chromate-exposed workers (73 cases) at a chromate production enterprise who were selected according to specific inclusion and exclusion criteria from 2010 to 2015. Personal information and chromate exposure information were obtained by questionnaire. A generalized estimating equation was employed to analyze the effects on human peripheral blood erythrocytes of long-term occupational contact with chromate, controlling for age, gender, smoking, alcohol consumption and body mass index. Results: The mean ages and working ages of those entering the cohort study were 36.67 ±6.78 and 38.47 ± 7.18, respectively, for the exposure group and 8.39 ± 6.02 and 12.86 ± 8.34, respectively, for the control group. The erythrocyte content [(4.73±0.46), (4.81±0.53), (4.41±0.45)]×1012/L in the peripheral blood in the chromate exposure group was lower than that [(4.76±0.42), (4.95±0.45), (4.47±0.39)]×1012/L in the control group for the years 2010, 2011, 2012 and 2014 (t values were 0.38, 1.96, 0.92 and 1.21; P values were 0.703, 0.051, 0.358 and 0.227, respectively). The correlations between the years 2010 and 2011, 2011 and 2012, 2012 and 2014, and 2014 and 2015 were 0.667, 0.464,-0.070 and 0.020, respectively (P<0.001). The RR for males and those that consumed alcohol were 0.661 (95% CI: 0.616-0.709) and 0.910 (95% CI: 0.811- 1.201), respectively. Compared with the control group, the risk of reduced erythrocyte levels in the peripheral blood was increased by 0.915 (95% CI: 0.852- 0.982) in the chromate-exposed group. Conclusions: The erythrocyte content of peripheral blood was reduced after long-term exposure to chromate. Maleness and alcohol consumption were factors that increased the risk of reduced peripheral blood erythrocytes in the chromate-exposed population.

THE ESTROGENS / CHROMIUM INTERACTION IN THE NITRIC OXIDE GENERATION.

The interaction of estrogens with environmental toxins in free radicals generation: reactive oxygen species (ROS) or reactive nitrogen species (RNS) which participates in cancerogenesis is not yet recognized. Chromium(VI) is widely present in environment. One of its toxicity pathway is free radicals generation. Estrogens have the ability to scavenge free radicals, but may also act as prooxidants. Both chromium(VI) and estrogens are classified by International Agency for Research on Cancer (IARC) as carcinogens, so synergistic effect seems very dangerous. The interaction of chromium and estrogens in ROS generation are partly described but there are no reports on estrogen/chromium interaction on nitric oxide (NO) generation. The aim of the study was to examine the interaction of chromium(VI) and 17-p-estradiol (E2) on NO level in human blood as well as the role of E2 metabolites: 4-hydroxyestradiol (4-OHE2) and 16a-hydroxyestrone (16α-OHE1) in these processes. The NO level was estimated with the diagnostic kit (Nitric Oxide Colorimetric Detection Kit from Arbor Assays) in human blood in vitm. The results showed that Cr(VI) in used concentration (0.5; 1.0 and 5.0 gg/mL) decreases significantly NO level in blood, acting antagonistically to E2 and 4-OHE2. Estrogens (E2, 4-OHE2 and 16α-OHEI) do not protect against inhibiting effect of Cr(VI) on nitric oxide generation in blood because after combined exposure the decreased production of NO in blood was noted. In conclusion, presented results provide the information about the character of estrogen/Cr(VI) interaction in NO level in human blood. It is important knowledge for cardio protected effect e.g., hormone replacement therapy in environmental or occupational exposure to Cr(VI), chromium supplementation, also important for cancer risk evaluation.

Assessing the suitability of 8-OHdG and micronuclei as genotoxic biomarkers in chromate-exposed workers: a cross-sectional study.

OBJECTIVES: We aimed to investigate suitable conditions of 8-hydroxy-2'-deoxyguanosine (8-OHdG) and micronucleus (MN) as genotoxic biomarkers at different levels of occupational chromate exposure. DESIGN: A cross-sectional study was used. PARTICIPANTS: 84 workers who were exposed to chromate for at least 1 year were chosen as the chromate exposed group, while 30 non-exposed individuals were used as controls. MAIN OUTCOME MEASURES: Environmental and biological exposure to chromate was respectively assessed by measuring the concentration of chromate in the air (CrA) and blood (CrB) by inductively coupled plasma mass spectrometer (ICP-MS) in all participants. MN indicators, including micronucleus cell count (MNCC), micro-nucleus count (MNC), nuclear bridge (NPB) and nuclear bud (NBUD) were calculated by the cytokinesis-block micronucleus test (CBMN), while the urinary 8-OHdG was measured by the ELISA method and normalised by the concentration of Cre. RESULTS: Compared with the control group, the levels of CrA, CrB, MNCC, MNC and 8-OHdG in the chromate-exposed group were all significantly higher (p<0.05). There were positive correlations between log(8-OHdG) and LnMNCC or LnMNC (r=0.377 and 0.362). The levels of LnMNCC, LnMNC and log (8-OHdG) all have parabola correlations with the concentration of CrB. However, there was a significantly positive correlation between log (8-OHdG) and CrB when the CrB level was below 10.50 µg/L (r=0.355), while a positive correlation was also found between LnMNCC or LnMNC and CrB when the CrB level was lower than 9.10 µg/L (r=0.365 and 0.269, respectively). CONCLUSIONS: MN and 8-OHdG can be used as genotoxic biomarkers in the chromate-exposed group, but it is only when CrB levels are lower than 9.10 and 10.50 µg/L, respectively, that they can accurately reflect the degree of genetic damage.

[Certain toxicodynamic and toxicokinetic features of combined subchronic intoxication with hexavalent chromium and nickel].

Repeated intraperitoneal injections of nickel and chromium (VI) into rats appeared to demonstrate that the combined subchronic toxicity can be additive or vary (mostly to subadditivity) in accordance with effect on which they are evaluated. With moderate general toxic effects, the studied combination has marked genotoxicity with additive effect. The studies demonstrated reciprocal influence of nickel and chromium on accumulation of the second metal in some organs (especially, in spleen), but not on its renal excretion.

Flower-like self-assembly of gold nanoparticles for highly sensitive electrochemical detection of chromium(VI).

We report here the fabrication of a flower-like self-assembly of gold nanoparticles (AuNPs) on a glassy carbon electrode (GCE) as a highly sensitive platform for ultratrace Cr(VI) detection. Two AuNP layers are used in the current approach, in which the first is electroplated on the GCE surface as anchors for binding to an overcoated thiol sol-gel film derived from 3-mercaptopropyltrimethoxysilane (MPTS). The second AuNP layer is then self-assembled on the surface of the sol-gel film, forming flower-like gold nanoelectrodes enlarging the electrode surface. When functionalized by a thiol pyridinium, the fabricated electrode displays a well-defined peak for selective Cr(VI) reduction with an unusually large, linear concentration range of 10-1200 ng L(-1) and a low detection limit of 2.9 ng L(-1). In comparison to previous approaches using MPTS and AuNPs on Au electrodes, the current work expands the use of AuNPs to the GCE. Subsequent functionalization of the secondary AuNPs by a thiol pyridinium and adsorption/preconcentration of Cr(VI) lead to the unusually large detection range and high sensitivity. The stepwise preparation of the electrode has been characterized by electrochemical impedance spectroscopy (EIS), scanning electronic microscopy (SEM), and IR. The newly designed electrode exhibits good stability, and has been successfully employed to measure chromium in a pre-treated blood sample. The method demonstrates acceptable fabrication reproducibility and accuracy.

Oxidative DNA damage and global DNA hypomethylation are related to folate deficiency in chromate manufacturing workers.

Exposure to hexavalent chromium [Cr (VI)] can cause DNA damage, genetic instability and increase the risk of cancer development. Folate deficiency affects DNA methylation and reduces the stability of the genetic material. However, the correlation between folate deficiency and DNA damage has never been clearly elucidated in chromate workers. In this study, we recruited one hundred and fifteen workers from chromate producing facilities as testing subjects and sixty local residents without chromium exposure history served as controls. The results showed an evident accumulation of Cr in peripheral red blood cells accompanied by a significantly decreased serum folate in chromate exposed workers. The decreased serum folate was associated with an increased urinary 8-hydroxy-2'-deoxyguanosine, DNA strand breaks and global DNA hypomethylation. These findings suggest that chronic occupational chromate exposure could induce folate depletion, which may further promote DNA damages and global DNA hypomethylation. Adequate folate supplement may provide benefit to chromate sufferers in stabilization of genetic material and reduce the risk of cancer development.

Effects of chronic chromate exposure on human serum prostate specific antigen: a cross sectional study.

The detrimental effect of chronic chromium (Cr) exposure on the prostate has never been studied. Here, we report the prostate specific antigen (PSA) changes in occupational chromate exposed workers. In this study, eighty six male occupational chromate exposed workers and forty five age-matched controls were recruited. The concentration of Cr in urine (U-Cr), serum total PSA (tPSA), free PSA (fPSA), high sensitive C reactive protein (Hs-CRP) and peripheral white blood cells count (WBC) were measured. The results show that the U-Cr, serum tPSA, Hs-CRP and WBC were significantly higher in Cr exposed workers when compared to the controls. Contrastively, the serum fPSA level in Cr exposed workers was lower than controls. A significant positive correlation between U-Cr and serum tPSA was observed. Multiple linear regression analysis revealed that serum tPSA and fPSA level was statistically associated with the serum Hs-CRP and U-Cr concentration in Cr exposed workers. These observations suggested that chronic Cr exposure could produce potential prostate injury and the nonspecific inflammation at least might be one of the reasons to explain the elevated concentration of tPSA in chronic occupational chromate exposed workers.

[Chromic acid burns: systematic prevention of systemic toxicity]. / Brûlure par acide chromique: prévention systématique de la toxicité systémique.

Chromic acid burns can lead to systemic toxicity by cutaneous absorption of the chrome seen surfaces more than 1% of the total body surface area. In order to illustrate the necessity of anticipate systematically this toxicity by a specific treatment, we describe the case of a patient with systemic toxicity in the least severe situation of chromic acid burn: the chromic acid was diluted to 0,02%, the burn was superficial second degree, both thermic and chemical, on the forearm, and extended only to 1% of the total body surface area. In spite of the specific treatment, our patient had a blood transfer of the chrome, however without any consequences on the renal and hepatic functions. He cicatrised in 2 weeks, and his blood and urinary chromium levels were normalised in 3 weeks. Without this specific early treatment, what would have been the consequences of a systemic toxicity even more important?

Clinical significance of optimal red cell mass and plasma volume estimation methods.

BACKGROUND: The aim of this study was to present and compare the results of proposed methods for optimal red cell mass and plasma volume (RCM&PV) estimation, and their influence on the interpretation of obtained results. MATERIAL AND METHODS: In 120/280 patients with polycythaemia rubra vera, subjected to RCM&PV determination with autologous erythrocytes in vitro labelled with 51Cr-sodium chromate, optimal volumes were determined using: 1. traditional ml/kg of: --the real body weight method (ml/kg RBW); --the optimal body weight method (ml/kg OBW). 2. the body weight, height, and sex based method (Retzlaff's tables), 3. the method recommended by the International Council for Standardization in Haematology (ICSH), based on body surface area. RESULTS: Different interpretation of the same results of 120 RCM&PV measurements was registered in 48/120 patients (40%). The greatest disagreement existed between ml/kg RBW and ml/kg OBW methods (in 39/120 subjects, 32.5%). In underweight patients the ml/kg RBW method, and in overweight patients the ml/kg OBW method, offered better agreement with ICSH&Retzlaff's methods. The ml/kg RBW method disagreed with ICSH&Retzlaff's methods and ml/kg OBW in 25% and 19.2% of patients respectively. ICSH and Retzlaff's methods disagreed in 10/120 patients (8.3%). The ICSH method yielded significantly lower optimal volumes than Retzlaff's. CONCLUSION: Three methods for optimal RCM&PV estimation lead to different interpretations of the same results of RCM&PV measurements with 51Cr-erythrocytes in 40% of patients. Two ml/kg body weight methods show greater disagreement in comparison with ICSH and Retzlaff's methods, which differ significantly. The ICSH method yields lower optimal values compared to Retzlaff's.

LLU-alpha, an endogenous metabolite of gamma-tocopherol, is more effective against metal nephrotoxicity in rats than gamma-tocopherol.

Antioxidants of the vitamin E family have protective effects against metal toxicity. We examined the protective effect of racemic LLU-alpha [2,7,8-trimethyl-2-(carboxyethyl)-6-hydroxychroman] a metabolite of gamma-tocopherol, in comparison to the effect of alpha- and gamma-tocopherol in rats treated with sodium dichromate (Cr) or thallium sulfate (Tl). We measured metal nephrotoxicity based on urinary protein excretion and discussed it with respect to the metal concentration in renal tissue. The ranking of antioxidant activity (iron stimulated lipid peroxidation, luminol and lucigenin amplified chemiluminescence) was determined in the following order: alpha-tocopherol

Acute, fatal, oral chromic acid poisoning.

CASE REPORT: We report a 35-year-old woman who developed severe acidosis, massive gastrointestinal hemorrhage, acute renal failure, and hepatic injury following ingestion of chromic acid (50 mL) and died 12 hours after ingestion. Postmortem liver biopsy revealed a fatty degeneration with chromium concentration 3.6 mumol/g. The kidney, with chromium concentration 2.6 mumol/g, had extensive necrosis and ischemic lesions. Erythrocyte chromium was 1903 mumol/L at 3 hours declining to 865 mumol/L at 11 hours.

Increased DNA-protein crosslinks in lymphocytes of residents living in chromium-contaminated areas.

It has been known for a number of years that chromium-containing mine slags were used as landfill in residential areas of Hudson County, New Jersey. Since one of the major lesions induced in intact cells by chromate is the DNA-Protein crosslink, we have used this lesion as a biomarker of biological effect of chromium (Cr) exposure. We have previously developed a sensitive and easy-to-perform assay to detect DNA-Protein crosslinks, based on the selective K SDS precipitation of DNA associated with protein. We examined the levels of DNA-Protein crosslinks in peripheral blood mononuclear cells of 33 individuals determined to be at risk for chromium exposure by virtue of their residence in Hudson County and their urinary Cr levels. These data were compared to the levels of DNA-Protein crosslinks among 49 controls who resided in noncontaminated areas. A complete clinical examination and urine analysis did not show any Cr-related abnormalities among the exposed population. The mean DNA-Protein crosslink level in the lymphocytes of the exposed group was 1.3 +/- 0.5% (SD), whereas the unexposed group had 0.8 +/- 0.4% (p < 0.001), after adjustment for age, gender, race, smoking, and weight. Further studies in this population are needed to confirm the possible association between the high levels of DNA-Protein crosslink and Cr exposure.

Elevated serum chromium in patients on total parenteral nutrition and the ionic species of contaminant chromium.

Chromium (Cr), an essential micronutrient required for glucose metabolism, was found in high concentrations in up to 94% of the patients on short-term total parenteral nutrition. Approximately 50% had serum levels > 10-fold of normal (upper reference value of 3.8 nmol/L), about 18% were > 20-fold, and about 2% were 40-fold higher. The major Cr contaminant was detected in the amino acid constituents, and was found to have the trivalent ionic form. Although trivalent Cr is reported to be less genotoxic, further study is required to determine the effects on cells exposed to high concentrations of this element during parenteral nutrition over an extended period of time.

Uptake of chromate in human red blood cells and isolated rat liver cells: the role of the anion carrier.

The transport of [51Cr]chromate into human erythrocytes and isolated rat hepatocytes has been investigated. It was found that uptake in both cell types could be inhibited by the established anion carrier inhibitor 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid. The uptake was very fast, and in kinetic studies a very low Km was found for both cell types, indicating either a high affinity of chromate for the carrier, and/or, more probably, an efficient intracellular reduction and trapping of 51Cr. The transport capacity, however, was of the same magnitude as for physiological substrates, such as lactate and sulfate. The uptake was temperature dependent and the activation energy was of the same magnitude as that for the physiological substrates. The uptake could be partly inhibited by high levels (mmol l-1) of lactate, pyruvate or sulfate. The uptake rate was greatly increased at lower pH (6.0 versus 7.4) which could indicate transport of the HCrO4- form or an increased intracellular rate of CrVI reduction. The results showed efficient uptake of 51CrO4(2-) by erythrocytes and hepatocytes. They were consistent with a mechanism of uptake which involved the cell membrane anion-exchange carrier in the transport and trapping of 51Cr within the cell.

Development of a pharmacokinetic model for chromium in the rat following subchronic exposure. I. The importance of incorporating long-term storage compartment.

A pharmacokinetic model of chromium depuration in the rat has been developed under subchronic exposure conditions. Rats were exposed to 100 ppm Cr(VI) in their drinking water for 6 weeks, followed by a 140-day period of depuration. Tissue concentrations of Cr at the end of the 6-week exposure period were greatest in the bone, spleen, and kidney, with lower concentrations present in the liver and blood. The overall kinetics of Cr depuration from the tissues were relatively slow, especially for the largest compartment which included bone. The results indicated that the half-life of Cr in bone exceeded 100 days. A three-compartment model was developed to fit the data. Liver, kidney, and spleen were grouped into a single compartment which was linked to a major storage compartment (i.e., bone, skin, hair, and muscle) via the blood. Using this model, the time to a 50% reduction of whole body Cr (i.e., loss of total Cr mass for the whole rat) was calculated to be about 80 days. The higher half-life for the storage compartment of 100 days is due to the relative weights of the compartments and the more rapid loss of Cr from the liver, kidney, and spleen compartment. The data suggest that Cr may be sequestered and release of Cr by the storage compartment over an extended period of time, thereby, may play an important role in maintaining elevated body burdens and tissue concentrations of Cr following long-term exposure to this toxic metal.

In vitro interaction of mutagenic chromium (VI) with red blood cells.

The interaction of mutagenic Cr(VI) with red blood cells has been studied by ESR spectroscopy. Signals of two Cr(V) species are observed almost immediately after contacting red cells with chromate(VI) aqueous solution at pH 7.4. The signal at go = 1.985, which decays within one hour, is attributed to a Cr(V) complex formed by glutathione due its reducing and chelating ability. The other signal at go = 1.979, which is distinctly more persistent, may indicate that some immobilization of the formed Cr(V) ions takes place on the macromolecular cell components, e.g. glycoproteins.

Chromate effects on human erythrocytes--investigations on sulphydryl groups, cross-linking of membrane proteins and electromechanical properties in the coulter-counter.

The carcinogen chromate inactivates its own carrier in the human erythrocyte membrane. This effect is paralleled by the inhibition of chromate uptake by the sulphydryl reagents N-ethylmaleimide and iodoacetate. However, no decrease in the sulphydryl content of erythrocyte membranes treated with up to 100 mM chromate was detected. By SDS gel electrophoresis, a limited cross-linking of red cell membrane proteins was found at 100 mM chromate, but not at cytotoxic concentrations up to 10 mM chromate. Erythrocytes treated with up to 100 mM chromate exhibited no change in the "dielectric breakdown", i.e. the sharp decrease of the apparent cellular volume at a critical detector current.

Uptake of 51Cr(VI) by human erythrocytes: evidence for a carrier-mediated transport mechanism.

Uptake of 20 micron 51Cr(VI) by resuspended red blood cells (RBC) (0.9% saline) was studied. Inhibition of the specific anion carrier system "band-3-protein" of RBC membrane with "SITS" (4-acetamido-4'-cyanatostilbene-2,2'-disulphonic acid) resulted in a non-competitive type of inhibition for chromium uptake. It is concluded that Cr(VI) is transported by participation with this system. Intracellularly, chromium is almost quantitatively bound to hemoglobin and trapped for the cell's lifetime. Glutathione (GSH) is possibly involved in this process as indicated by incubation experiments of RBC with 10 mM Na2(51)CrO4. In these experiments, a rapid decrease of GSH content of the cells was observed.

Modification of the erythrocyte anion carrier by chromate.

It was confirmed that chromate is taken up by human erythrocytes via the general anion carrier. The chromate flux is unidirectional and chromium is accumulated within red cells presumably due to intracellular reduction of Cr(VI) to Cr(III). The analysis of the initial rates of uptake of chromate revealed two distinct uptake mechanisms at low (0.001-0.01 mM) and at high (0.05-1.0 mM) chromate concentrations. After prolonged incubation with 1 mM chromate, the subsequent rate of uptake of chromate was decreased. It is suggested that the decreased uptake is due to a modification of the anion-transport protein by chromate.