Chemical properties and toxicity of chromium(III) nutritional supplements

Bioremoval of trivalent chromium using Bacillus biofilms through continuous flow reactor

Present study deals with the applicability of bacterial biofilms for the bioremoval of trivalent chromium from tannery effluents. A continuous flow reactor was designed for the development of biofilms on different substrates like glass beads, pebbles and coarse sand. The parameters for the continuous flow reactor were 20 ml/min flow rate at 30°C, pH4. Biofilm biomass on the substrates was in the following sequence: coarse sand>pebbles>glass beads (4.8 × 10(7), 4.5 × 10(7) and 3.5 × 10(5)CFU/cm(2)), which was confirmed by CLSM. Biofilms developed using consortium of Bacillus subtilis and Bacillus cereus on coarse sand had more surface area and was able to remove 98% of Cr(III), SEM-EDX proved 92.60% Cr(III) adsorption on biofilms supported by coarse sand. Utilization of Bacillus biofilms for effective bioremoval of Cr(III) from chrome tanning effluent could be a better option for tannery industry, especially during post chrome tanning operation.

Bioinorganics and biomaterials: bone repair

The field of bioinorganics is well established in the development of a variety of therapies. However, their application to bone regeneration, specifically by way of localized delivery from functional implants, is in its infancy and is the topic of this review. The toxicity of inorganics is species, dose and duration specific. Little is known about how inorganic ions are effective therapeutically since their use is often the result of serendipity, observations from nutritional deficiency or excess and genetic disorders. Many researchers point to early work demonstrating a role for their element of interest as a micronutrient critical to or able to alter bone growth, often during skeletal development, as a basis for localized delivery. While one can appreciate how a deficiency can cause disruption of healing, it is difficult to explain how a locally delivered excess in a preclinical model or patient, which is presumably of normal nutritional status, can evoke more bone or faster healing. The review illustrates that inorganics can positively affect bone healing but various factors make literature comparisons difficult. Bioinorganics have the potential to have just as big an impact on bone regeneration as recombinant proteins without some of the safety concerns and high costs.

Exposure to multiple metals from groundwater-a global crisis: geology, climate change, health effects, testing, and mitigation

This paper presents an overview of the global extent of naturally occurring toxic metals in groundwater. Adverse health effects attributed to the toxic metals most commonly found in groundwater are reviewed, as well as chemical, biochemical, and physiological interactions between these metals. Synergistic and antagonistic effects that have been reported between the toxic metals found in groundwater and the dietary trace elements are highlighted, and common behavioural, cultural, and dietary practices that are likely to significantly modify health risks due to use of metal-contaminated groundwater are reviewed. Methods for analytical testing of samples containing multiple metals are discussed, with special attention to analytical interferences between metals and reagents. An overview is presented of approaches to providing safe water when groundwater contains multiple metallic toxins.

Metal-based anti-diabetic drugs: advances and challenges

The current status and likely future directions of complexes of V(V/IV), Cr(III), Mo(VI), W(VI), Zn(II), Cu(II), and Mn(III) as potential oral drugs against type 2 diabetes are reviewed. We propose a unified model of extra- and intracellular mechanisms of anti-diabetic efficacies of V(V/IV), Mo(VI), W(VI), and Cr(III), centred on high-oxidation-state oxido/peroxido species that inhibit protein tyrosine phosphatases (PTPs) involved in insulin signalling. The postulated oxidative mechanism of anti-diabetic activity of Cr(III) via carcinogenic Cr(VI/V) (which adds to safety concerns) is consistent with recent clinical trials on Cr(III) picolinate, where activity was apparent only in patients with poorly controlled diabetes (high oxidative stress), and the correlation between the anti-diabetic activities and ease of oxidation of Cr(III) supplements and their metabolites in vivo. Zn(II) and Cu(II) anti-diabetics act via different mechanisms and are unlikely to be used as specific anti-diabetics due to their diverse and unpredictable biological activities. Hence, future research directions are likely to centre on enhancing the bioavailability and selectivity of V(V/IV), Mo(VI), or W(VI) drugs. The strategy of potentiating circulating insulin with metal ions has distinct therapeutic advantages over interventions that stimulate the release of more insulin, or use insulin mimetics, because of many adverse side-effects of increased levels of insulin, including increased risks of cancer and cardiovascular diseases.

The content of elements in rainwater and its relation to the frequency of hospitalization for chronic lymphocytic leukemia and chronic myeloid leukemia in Opole Voivodship, Poland, during 2000-2002

Environmental factors play an essential role in the etiology of diseases of the hematopoietic system. Such factors include soil and water pollution and the presence of metals and toxic compounds in the air. Measuring the content of metallic elements in rainwater has become an accepted procedure for environmental pollution monitoring. In accordance with the above, it was decided to study relations between the content of selected elements in rainwater and hospitalization frequency due to chronic lymphocytic leukemia (CLL, C91 on ICD-10) and chronic myeloid leukemia (CML, C92 on ICD-10). It can be assumed that hospitalization frequency is a reliable indicator of exacerbations of these diseases. The annual average of hospitalizations due to a given disease during the years 2000-2002 was correlated with the annual average content of a given element in rainwater using the Spearman's correlation indicator to describe the relationship between the element content and the disease that is possibly a consequence of the element's presence in rainwater. In cases of CLL for all the subjected population and for men, no statistically significant correlations were found. For women, statistically significant correlations were found for chromium (r = 0.66), lead (r = 0.58), copper (r = 0.58), and cadmium (r = 0.51). For CML in all the studied population significant, negative correlations were found for magnesium (r = -0.6) and zinc (r = -0.52). In men, significant negative correlations were seen for magnesium (r = -0.69 and zinc (r = -0.55). No significant correlations were found in women. These results indicate the need of taking into account the environmental and gender factors in research connected with these diseases, which can be probably of help in improvements of therapy efficiency.

Polyelectrolyte-modified multi-walled carbon nanotubes for the adsorption of

Multi-walled carbon nanotubes (MWNTs) are noncovalently wrapped by a cationic polyelectrolyte of poly(diallyldimethylammonium chloride) (PDDA) via π-π interactions between the unsaturated impurity in PDDA and MWNTs. The modified PDDA-MWNTs are characterized by FT-IR and surface charge analysis. The PDDA-MWNTs are packed into a mini-column and used for the adsorption of Cr(vi) in a sequential injection system with detection by electrothermal atomic absorption spectrometry (ETAAS). A 32% improvement on the adsorption efficiency of Cr(vi) by the PDDA-MWNTs at pH 6 is achieved with respect to that obtained by the bare MWNTs. The retained Cr(vi) is afterwards recovered by using 80 μL of ammonium nitrate solution (0.1 mol L-1) as stripping reagent producing an elution efficiency of 81%. The presence of a certain amount of Cr(iii) within a Cr(iii)/Cr(vi) concentration ratio of 6 : 1 causes no interfering effect for the adsorption of Cr(vi) by the PDDA-MWNTs mini-column. A sample loading volume of 1000 μL creates an enrichment factor of 8.6, along with a detection limit of 0.016 μg L-1 (3σ, n = 7) and a RSD of 3.9% (0.5 μg L-1) within a linear calibration range of 0.05-1.5 μg L-1. The procedure has been validated by analyzing a certified reference material of GBW08608 and a series of water samples.

Trace elements in glucometabolic disorders: an update

Many trace elements, among which metals, are indispensable for proper functioning of a myriad of biochemical reactions, more particularly as enzyme cofactors. This is particularly true for the vast set of processes involved in regulation of glucose homeostasis, being it in glucose metabolism itself or in hormonal control, especially insulin. The role and importance of trace elements such as chromium, zinc, selenium, lithium and vanadium are much less evident and subjected to chronic debate. This review updates our actual knowledge concerning these five trace elements. A careful survey of the literature shows that while theoretical postulates from some key roles of these elements had led to real hopes for therapy of insulin resistance and diabetes, the limited experience based on available data indicates that beneficial effects and use of most of them are subjected to caution, given the narrow window between safe and unsafe doses. Clear therapeutic benefit in these pathologies is presently doubtful but some data indicate that these metals may have a clinical interest in patients presenting deficiencies in individual metal levels. The same holds true for an association of some trace elements such as chromium or zinc with oral antidiabetics. However, this area is essentially unexplored in adequate clinical trials, which are worth being performed.

Formation and reactivity of chromium(V)-thiolato complexes: a model for the intracellular reactions of carcinogenic chromium(VI) with biological thiols

The nature of the long-lived EPR-active Cr(V) species observed in cells and biological fluids exposed to carcinogenic Cr(VI) has been definitively assigned from detailed kinetic and spectroscopic analyses of a model reaction of Cr(VI) with p-bromobenzenethiol (RSH) in the presence or absence of cyclic 1,2-diols (LH(2)) in aprotic or mixed solvents. The first definitive structures for Cr(V) complexes with a monodentate thiolato ligand, [Cr(V)O(SR)(4)](-) (g(iso) = 1.9960, A(iso) = 14.7 x 10(-4) cm(-1)), [Cr(V)OL(SR)(2)](-) (g(iso) = 1.9854, A(iso) = (15.8-16.2) x 10(-4) cm(-1)) and [Cr(V)(O)(2)(SR)(2)](-) (g(iso) = 1.9828, A(iso) = 6.8 x 10(-4) cm(-1)) were assigned by EPR spectroscopy and electrospray mass spectrometry. The unusually low A(iso) ((53)Cr) value for the latter species is consistent with its rare four-coordinate, bis-oxido structure. The [Cr(V)OL(SR)(2)](-) species are responsible for the transient g(iso) approximately 1.986 EPR signals observed in living cells and animals treated with Cr(VI) (where RSH and LH(2) are biological thiols and 1,2-diols, respectively). For the first time, concentrations of Cr(V) intermediates formed during the reduction of Cr(VI) were determined by quantitative EPR spectroscopy, and a detailed reaction mechanism was proposed on the basis of stochastic simulations of the kinetic curves for Cr(V) species. A key feature of the proposed mechanism is the regeneration of Cr(V) species in the presence of Cr(VI) through the formation of organic free radicals, followed by the rapid reactions of the formed radicals with Cr(VI). The concentration of Cr(V) grows rapidly at the beginning of the reaction, reaches a steady-state level, and then drops sharply once Cr(VI) is spent. Similar mechanisms are likely to operate during the reduction of Cr(VI) in biological environment rich in reactive C-H bonds, including the oxidative DNA damage by Cr(V) intermediates.

Imaging metals in proteins by combining electrophoresis with rapid x-ray fluorescence mapping

Growing evidence points toward a very dynamic role for metals in biology. This suggests that physiological circumstance may mandate metal ion redistribution among ligands. This work addresses a critical need for technology that detects, identifies, and measures the metal-containing components of complex biological matrixes. We describe a direct, user-friendly approach for identifying and quantifying metal-protein adducts in complex samples using native- or SDS-PAGE, blotting, and rapid synchrotron X-ray fluorescence mapping with micro-XANES (X-ray absorption near-edge structure) of entire blots. The identification and quantification of each metal bound to a protein spot has been demonstrated, and the technique has been applied in two exemplary cases. In the first, the speciation of the in vitro binding of exogenous chromium to blood serum proteins was influenced markedly by both the oxidation state of chromium exposed to the serum proteins and the treatment conditions, which is of relevance to the biochemistry of Cr dietary supplements. In the second case, in vivo changes in endogenous metal speciation were examined to probe the influence of oxygen depletion on iron speciation in Shewanella oneidensis.

The genotoxicity of physiological concentrations of chromium (Cr(III) and Cr(VI)) and cobalt (Co(II)): an in vitro study

Humans are exposed to chromium and cobalt in industry, from the environment and after joint replacement surgery from the CoCr alloy in the implant. In this study we have investigated whether Cr(III), Cr(VI), Co(II) and Cr in combination with Co could induce chromosome aberrations in human fibroblasts in vitro at the same concentrations that have been found in the peripheral blood of exposed humans. We used 24 colour M-FISH as a sensitive way to detect translocations and aneuploidy and examined the effects of a 24-h exposure and its consequences up to 30 days after the exposure in order to record genomic instability and/or repair. At these physiological doses the metals induced predominantly numerical rather than structural aberrations. Co was the least reactive and Cr(VI) especially in combination with Co the most. All metals at the highest physiological doses caused simple (gain or loss of 3 or less chromosomes) and complex (more than 49 chromosomes) aneuploidy. All metals at the lowest physiological dose caused a significant increase of total aberrations. Cr(VI) was much more effective than Cr(III) in causing chromosome fragments, which were only induced at the highest doses. There was a slow resolution of aneuploidy with time after exposure. This involved a reduction in the proportion of aneuploid cells and a reduction of the number of chromosomes within cells showing complex aneuploidy. We conclude that these metal ions can cause chromosome aberrations at physiological concentrations and that their main effect is aneugenic.

Chemical and biological properties of toxic metals and use of chelating agents for the pharmacological treatment of metal poisoning

Exposure to toxic metals is a well-known problem in industrialized countries. Metals interfere with a number of physiological processes, including central nervous system (CNS), haematopoietic, hepatic and renal functions. In the evaluation of the toxicity of a particular metal it is crucial to consider many parameters: chemical forms (elemental, organic or inorganic), binding capability, presence of specific proteins that selectively bind metals, etc. Medical treatment of acute and chronic metal toxicity is provided by chelating agents, namely organic compounds capable of interacting with metal ions to form structures called chelates. The present review attempts to provide updated information about the mechanisms, the cellular targets and the effects of toxic metals.

Autoschizis of T-cells is induced by the nutritional supplement, Cr(III)picolinate

In recent times, Cr(III)(picolinate)(3) [Cr(III)(pic)(3)] a nutritional supplement, is gaining attention because of its clastogenic and mutagenic properties. Earlier studies of ours indicated that Cr(III)(pic)(3) is cytotoxic to lymphocytes with ROS and mitochondrial events playing a role in bringing about apoptosis. Now, we report that, autoschizis is induced in lymphocytes in a concentration and time dependent manner which is confirmed through TEM and SEM. Lymphocytes treated with concentrations of 100microM of Cr(III)(pic)(3) exhibit features such as cytoplasmic bleb, self excision of cytoplasm, cytoplasmic leakage and membrane bound bodies formed from the excised pieces apart from apoptosis and necrosis. Though autoschizis has been described in tumor cell lines treated with menadione and ascorbate, occurrence of this cell death in normal T-lymphocytes is reported here. The cellular events that accompany autoschizis are found to be increase in intracellular Reactive Oxygen Species (ROS) and cytoplasmic lactate dehydrogenase, loss of mitochondrial membrane potential (MMP) and depletion of ATP. Further, autoschizis is effected through increases in DNase I and DNase II activity with a concomitant decrease in caspase-3 activity which leads to a random cleavage of the DNA as demonstrated by a smear like pattern after electrophoresis on agarose gel.

Recent developments in ruthenium anticancer drugs

Interest in Ru anticancer drugs has been growing rapidly since NAMI-A ((ImH(+))[Ru(III)Cl(4)(Im)(S-dmso)], where Im = imidazole and S-dmso = S-bound dimethylsulfoxide) or KP1019 ((IndH(+))[Ru(III)Cl(4)(Ind)(2)], where Ind = indazole) have successfully completed phase I clinical trials and an array of other Ru complexes have shown promise for future development. Herein, the recent literature is reviewed critically to ascertain likely mechanisms of action of Ru-based anticancer drugs, with the emphasis on their reactions with biological media. The most likely interactions of Ru complexes are with: (i) albumin and transferrin in blood plasma, the former serving as a Ru depot, and the latter possibly providing active transport of Ru into cells; (ii) collagens of the extracellular matrix and actins on the cell surface, which are likely to be involved in the specific anti-metastatic action of Ru complexes; (iii) regulatory enzymes within the cell membrane and/or in the cytoplasm; and (iv) DNA in the cell nucleus. Some types of Ru complexes can also promote the intracellular formation of free radical species, either through irradiation (photodynamic therapy), or through reactions with cellular reductants. The metabolic pathways involve competition among reduction, aquation, and hydrolysis in the extracellular medium; binding to transport proteins, the extracellular matrix, and cell-surface biomolecules; and diffusion into cells; with the extent to which individual drugs participate in various steps along these pathways being crucial factors in determining whether they are mainly anti-metastatic or cytotoxic. This diversity of modes of action of Ru anticancer drugs is also likely to enhance their anticancer activities and to reduce the potential for them to develop tumour resistance. New approaches to metabolic studies, such as X-ray absorption spectroscopy and X-ray fluorescence microscopy, are required to provide further mechanistic insights, which could lead to the rational design of improved Ru anticancer drugs.

Inner-sphere oxidation of ternary iminodiacetatochromium(III) complexes involving DL-valine and L-arginine as secondary ligands. Isokinetic relationship for the oxidation of ternary iminodiacetato-chromium(III) complexes by periodate

Background

In this paper, the kinetics of oxidation of [Cr^III(HIDA)(Val)(H₂O)₂]⁺ and [Cr^III(HIDA)(Arg)(H₂O)₂]⁺ (HIDA = iminodiacetic acid, Val = DL-valine and Arg = L-arginine) were studied. The choice of ternary complexes was attributed to two considerations. Firstly, in order to study the effect of the secondary ligands DL-valine and L-arginine on the stability of binary complex [Cr^III(HIDA)(IDA)(H₂O)] towards oxidation. Secondly, transition metal ternary complexes have received particular focus and have been employed in mapping protein surfaces as probes for biological redox centers and in protein capture for both purification and study.

Results

The results have shown that the reaction is first order with respect to both [IO₄^-] and the complex concentration, and the rate increases over the pH range 2.62 – 3.68 in both cases. The experimental rate law is consistent with a mechanism in which both the deprotonated forms of the complexes [Cr^III(IDA)(Val)(H₂O)₂] and [Cr^III(IDA)(Arg)(H₂O)₂] are significantly more reactive than the conjugate acids. The value of the intramolecular electron transfer rate constant for the oxidation of [Cr^III(HIDA)(Arg)(H₂O)₂]⁺, k₃ (1.82 × 10^-3 s^-1), is greater than the value of k₁ (1.22 × 10^-3 s^-1) for the oxidation of [Cr^III(HIDA)(Val)(H₂O)₂]⁺ at 45.0°C and I = 0.20 mol dm^-3. It is proposed that electron transfer proceeds through an inner-sphere mechanism via coordination of IO₄^- to chromium(III).

Conclusion

The oxidation of [Cr^III(HIDA)(Val)(H₂O)₂]⁺ and [Cr^III(HIDA)(Arg)(H₂O)₂]⁺ by periodate may proceed through an inner-sphere mechanism via two electron transfer giving chromium(VI). The value of the intramolecular electron transfer rate constant for the oxidation of [Cr^III(HIDA)(Arg)(H₂O)₂]⁺, k₃, is greater than the value of k₁ for the oxidation of [Cr^III(HIDA)(Val)(H₂O)₂]⁺. A common mechanism for the oxidation of ternary iminodiacetatochromium(III) complexes by periodate is proposed, and this is supported by an excellent isokinetic relationship between ΔH* and ΔS* values for these reactions.