Au(III), Pd(II), Ni(II), and Hg(II) alter NFκB signaling in THP1 monocytic cells

Interplay of Environmental, Individual and Genetic Factors in Rheumatoid Arthritis Provocation

In this review, we explore systemization of knowledge about the triggering effects of non-genetic factors in pathogenic mechanisms that contribute to the development of rheumatoid arthritis (RA). Possible mechanisms involving environmental and individual factors in RA pathogenesis were analyzed, namely, infections, mental stress, sleep deprivation ecology, age, perinatal and gender factors, eating habits, obesity and smoking. The non-genetic factors modulate basic processes in the body with the impact of these factors being non-specific, but these common challenges may be decisive for advancement of the disease in the predisposed body at risk for RA. The provocation of this particular disease is associated with the presence of congenital loci minoris resistentia. The more frequent non-genetic factors form tangles of interdependent relationships and, thereby, several interdependent external factors hit one vulnerable basic process at once, either provoking or reinforcing each other. Understanding the specific mechanisms by which environmental and individual factors impact an individual under RA risk in the preclinical stages can contribute to early disease diagnosis and, if the factor is modifiable, might be useful for the prevention or delay of its development.

Biosynthesis of Gold Nanoparticles by Vascular Cells in vitro

Biosynthesis of gold nanoparticles (AuNPs) for antimicrobial and chemotherapeutic applications is a well-established process in microbial hosts such as bacterial, fungi, and plants. However, reports on AuNPs biosynthesis in mammalian cells are scarce. In this study, bovine aortic endothelial cells (BAECs) and bovine aortic smooth muscle cells (BASMCs) were examined for their ability to synthesize AuNPs in vitro. Cell culture conditions such as buffer selection, serum concentration, and HAuCl4 concentration were optimized before the biosynthesized AuNPs were characterized through visible spectrometry, transmission electron microscopy, X-ray diffraction, and Fourier transform infrared (FTIR) spectroscopy. BAECs and BASMC produced small, spherical AuNPs that are semi-crystalline with a similar diameter (23 ± 2 nm and 23 ± 4 nm). Hydrogen peroxide pretreatment increased AuNPs synthesis, suggesting that antioxidant enzymes may reduce Au3+ ions as seen in microbial cells. However, buthionine sulfoximine inhibition of glutathione synthesis, a key regulator of oxidative stress, failed to affect AuNPs generation. Taken together, these results show that under the right synthesis conditions, non-tumor cell lines can produce detectable concentrations of AuNPs in vitro.

Toxicity assessment of electrochemical advanced oxidation process-treated groundwater from a gas station with petrochemical contamination

Electrochemical advanced oxidation process (EAOP) is known for its efficient and fast degradation of organic pollutants in polluted water treatment. In this study, the EAOP using a boron-doped diamond (BDD) anode was applied to treat two-season groundwater samples collected from four sampling wells (GS1 to GS4) with petrochemical contaminants including methyl tert-butyl ether (MTBE), benzene, toluene, chlorobenzene, total organic compounds (TOC), and total petroleum hydrocarbons (TPH) at a gas station in southern Taiwan. Moreover, toxicity tests (ATP, p53, and NF-κB bioassays) were performed to evaluate the biological responses of raw and EAOP-treated groundwater. Results show that the concentrations of chlorobenzene before and after EAOP treatment were all below its method detection limit. High degradation efficiencies were observed for MTBE (100%), benzene (100%), toluene (100%, except that of GS2 in the first season), TPH (94-97%, except that of GS4 in the first season), and TOC (85-99%). Cell viability for both the raw groundwater (81.2 ± 13.5%) and EAOP-treated samples (84.7 ± 11.7%) as detected using the ATP bioassay showed no significant difference (p = 0.715). A mean reduction in the DNA damage (739 to 165 ng DOX-equivalency L^-1 (ng DOX-EQ. L^-1)) and inflammatory response levels (460 to 157 ng TNFα-equivalency L^-1 (ng TNFα-EQ. L^-1)) were observed for EAOP-treated samples subjected to p53 and NF-κB bioassays. Overall, the significances of the average degradation efficiency, DNA damage, and inflammatory response before and after groundwater with EAOP treatment was observed to be significant (p < 0.05). p53 and NF-κB bioassays might be applied to assess ecotoxic risk in the environment.

Nuclear factor erythroid 2 - related factor 2 and its relationship with cellular response in nickel exposure: a systems biology analysis

Background

Nickel and nickel-containing compounds (NCC) are known human carcinogens. However, the precise molecular mechanisms of nickel-induced malignant transformation remain unknown. Proposed mechanisms suggest that nickel and NCC may participate in the dual activation/inactivation of enzymatic pathways involved in cell defenses against oxidative damage, where Nuclear factor-erythroid 2 related factor 2 (Nrf2) plays a central role.

Methods

For assessing the potential role of proteins involved in the Nrf2-mediated response to nickel and NCC exposure, we designed an interactome network using the STITCH search engine version 5.0 and the STRING software 10.0. The major NCC-protein interactome (NCPI) generated was analyzed using the MCODE plugin, version 1.5.1 for the detection of interaction modules or subnetworks. Main centralities of the NCPI were determined with the CentiScape 2.2 plugin of Cytoscape 3.4.0 and main biological processes associated with each cluster were assessed using the BiNGO plugin of Cytoscape 3.4.0.

Results

Water-soluble NiSO₄ and insoluble Ni₃S₂ were the most connected to proteins involved in the NCPI network. Nfr2 was detected as one of the most relevant proteins in the network, participating in several multifunctional protein complexes in clusters 1, 2, 3 and 5. Ontological analysis of cluster 3 revealed several processes related to unfolded protein response (UPR) and response to endoplasmic reticulum (ER) stress.

Conclusions

Cellular response to NCC exposure was very comparable, particularly concerning oxidative stress response, inflammation, cell cycle/proliferation, and apoptosis. In this cellular response, Nfr2 was highly centralized and participated in several multifunctional protein complexes, including several related to ER-stress. These results add evidence on the possible Ni²⁺ induced – ER stress mainly associated with insoluble NCC. In this scenario, we also show how protein degradation mediated by ubiquitination seems to play key roles in cellular responses to Ni.

De novo characterization of the liver transcriptome of javelin goby Synechogobius hasta and analysis of its transcriptomic profile following waterborne copper exposure

Previous studies have investigated the physiological responses to chronic copper (Cu) exposure in the liver of Synechogobius hasta; however, little information is available on the underlying molecular mechanisms. In an effort to better understand the mechanisms of Cu toxicity and to illuminate global gene expression patterns modulated by Cu exposure, we obtained the liver transcriptome information of S. hasta by RNA sequencing (RNA-seq) technology and also investigated the differential expression of genes following waterborne Cu exposure. Using the Illumina sequencing platform, as many as 60,217 unigenes were generated, with 815 bp of average length and 1298 bp of unigene N50 after filtering and assembly. For functional annotation analysis, 34,860, 31,526, 31,576, 25,808, 11,542, and 21,721 unigenes were annotated to the NR, NT, Swiss-Prot, KEGG, COG, and GO databases, respectively, and total annotation unigenes were 37,764. After 30 days of exposure to 55 μg Cu/l, a total of 292 and 1076 genes were significantly up- and down-regulated, respectively. By KEGG analysis, 660 had a specific pathway annotation. Subsequent bioinformatics analysis revealed that the differentially expressed genes were mainly related to lipid metabolism, immune system, apoptosis, and signal transduction, suggesting that these signaling pathways may be regulated by Cu exposure. The present study provides comprehensive sequence information for subsequent gene expression studies regarding S. hasta, and the transcriptome profiling after Cu exposure is also expected to improve our understanding of the molecular toxicology of Cu.

Potent selective inhibition of MMP-14 by chloroauric acid and its inhibitory effect on cancer cell invasion

Enzyme kinetics and Matrigel invasion assay indicated that the specific inhibition of HAuCl₄ on MMP-14 involves a non-competitive reversible inhibitory mechanism and HAuCl₄ inhibits HT-1080 cell invasion in a dose-dependent manner.

Nickel alloys in the oral environment

The use of nickel casting alloys for long-term restorations in dentistry has long been controversial. A 'tug-of-war' between economic, engineering and biological considerations is central to this controversy; nickel-casting alloys have low costs and favorable physical properties, but are corrosion-prone in the oral environment. Clinicians and researchers have questioned the safety of nickel-containing dental alloys because several nickel compounds are known to cause adverse biological effects in vivo and in vitro in contexts outside of dentistry. The debate revolves around the extent to which corrosion products from oral restorations cause intraoral or systemic biological problems. Current evidence suggests that nickel alloys may be used successfully and safely in dentistry if clinical risks are taken into account. However, these alloys may cause significant clinical problems, primarily allergenic and inflammatory, if the risks are ignored.

Nickel ion inhibits nuclear factor-kappa B activity in human oral squamous cell carcinoma

Background

The spontaneous IL-8 secretion observed in OSCC is partially dependent on the disregulated activity of transcription factor NF-κB. Nickel compounds are well established human carcinogens, however, little is known about the influence of nickel on the spontaneous secretion of IL-8 in oral squamous cell carcinoma (OSCC) cells. The aim of the present study was to investigate whether Ni²⁺ ions can influence on IL-8 secretion by OSCC.

Methods and Results

The IL-8 secretion was measured by ELISA. The expression of IL-8 mRNA was examined by real-time PCR. The NF-κB activity was measured by luciferase assay. The phosphorylation status and nuclear localization of NF-κB subunits were examined by Western blotting or Transfactor kit and immunofluorescence staining, respectively. The interaction of NF-κB p50 subunit and Ni²⁺ ions was examined by Ni²⁺-column pull down assay. The site-directed mutagenesis was used to generate a series of p50 mutants. Scratch motility assay was used to monitor the cell mobility. Our results demonstrated that, on the contrary to our expectations, Ni²⁺ ions inhibited the spontaneous secretion of IL-8. As IL-8 reduction was observed in a transcriptional level, we performed the luciferase assay and the data indicated that Ni²⁺ ions reduced the NF-κB activity. Measurement of p50 subunit in the nucleus and the immunofluorescence staining revealed that the inhibitory effect of Ni²⁺ ions was attributed to the prevention of p50 subunit accumulation to the nucleus. By Ni²⁺-column pull down assay, Ni²⁺ ions were shown to interact directly with His cluster in the N-terminus of p50 subunit. The inhibitory effect of Ni²⁺ ions was reverted in the transfectant expressing the His cluster-deleted p50 mutant. Moreover, Ni²⁺ ions inhibited the OSCC mobility in a dose dependent fashion.

Conclusions

Taken together, inhibition of NF-κB activity by Ni²⁺ ion might be a novel therapeutic strategy for the treatment of oral cancer.

Toll-like receptor 4 signaling pathway mediates proinflammatory immune response to cobalt-alloy particles

Metal orthopedic implant debris-induced osteolysis of hip bone is a major problem in patients with prosthetic-hips. Although macrophages are the principal targets for implant-wear debris, the receptor(s) and mechanisms underlying these responses are not fully elucidated. We examined whether the TLR4 pathway mediates immune response to metal-on-metal (MoM) implant-generated wear particles. Human monocytes (THP-1) were exposed to Co-alloy particles at increasing particle:cell ratio for 24 h. Challenge with particles caused up-regulation of IL-1β, TNF-α and IL-8, and mediated degradation of cytosolic I-κB and nuclear translocation of NF-κB. Blocking antibodies against TLR4 or gene silencing of MyD88 and IRAK-1 prevented particle-induced I-κB/NF-κB activation response and markedly inhibited IL-8 release. Particle-mediated IL-8 response was not observed in TLR4-negative HEK293T cells; whereas transfection-based TLR4-overexpression in HEK293T enabled particle-sensitivity, as observed by I-κB degradation and IL-8 expression in response to particles. Results demonstrate that Co-alloy particles trigger immune response via the TLR4-MyD88-dependent signaling pathway.

Predicting clinical biological responses to dental materials

OBJECTIVES

Methods used to measure and predict clinical biological responses to dental materials remain controversial, confusing, and to some extent, unsuccessful. The current paper reviews significant issues surrounding how we assess the biological safety of materials, with a historical summary and critical look at the biocompatibility literature. The review frames these issues from a U.S. perspective to some degree, but emphasizes their global nature and universal importance.

METHODS

The PubMed database and information from the U.S. Food and Drug Administration, International Standards Organization, and American National Standards Institute were searched for prominent literature addressing the definition of biocompatibility, types of biological tests employed, regulatory and standardization issues, and how biological tests are used together to establish the biological safety of materials. The search encompassed articles published in English from approximately 1965-2011. The review does not comprehensively review the literature, but highlights significant issues that confront the field.

RESULTS

Years ago, tests for biological safety sought to establish material inertness as the measure of safety, a criterion that is now deemed naive; the definition of biocompatibility has broadened along with the roles for materials in patient oral health care. Controversies persist about how in vitro or animal tests should be used to evaluate the biological safety of materials for clinical use. Controlled clinical trials remain the single best measure of the clinical response to materials, but even these tests have significant limitations and are less useful to identify mechanisms that shape material performance. Practice-based research networks and practitioner databases are emerging as important supplements to controlled clinical trials, but their final utility remains to be determined.

SIGNIFICANCE

Today we ask materials to play increasingly sophisticated structural and therapeutic roles in patient treatment. To accommodate these roles, strategies to assess, predict, and monitor material safety need to evolve. This evolution will be driven not only by researchers and manufacturers, but also by patients and practitioners, who want to use novel materials in new ways to treat oral disease.

Zinc, cadmium and nickel increase the activation of NF-κB and the release of cytokines from THP-1 monocytic cells

The sustained activation of the transcription factor nuclear factor κB (NF-κB) by metal-activated signalling pathways can lead to chronic inflammatory processes and related diseases, including carcinogenesis. The aim of the present work was to clarify the effect of zinc, nickel and cadmium on NF-κB activation in the THP-1 human monocytic leukemia cell line. The production of the NF-κB downstream pro-inflammatory mediators tumor necrosis factor (TNF)-α and interleukin (IL)-1β, IL-6 and IL-8 was also evaluated due to their important roles in the pathogenesis of chronic inflammatory and autoimmune diseases and, ultimately, in the development of cancer. The results obtained demonstrated that zinc, nickel and cadmium significantly activate NF-κB, and the release of the chemokine IL-8. Cadmium also induced the release of TNF-α and IL-6 in THP-1 monocytic cells, which may indicate some potential to induce deleterious effects through this pathway.

Inorganic mercury exposure in prairie voles (Microtus ochrogaster) alters the expression of toll-like receptor 4 and activates inflammatory pathways in the liver in a sex-specific manner

Environmental exposure to mercury can cause a number of adverse effects in humans including the disruption of endocrine function that may result in sex-specific effects. The present study was designed to characterize sex-specific effects of chronic inorganic mercury exposure on toll-like receptor (TLR) 2 and TLR4 and inflammatory signaling in the liver of prairie voles (Microtus ochrogaster). Following 10 weeks of exposure to mercury via drinking water, effects on protein expression levels of TLR2 and TLR4 and the downstream p38 mitogen-activated protein kinase (p38 MAPK) and nuclear factor-kappa (NF-κB) signaling pathways were assessed. Using immunoblot analysis, we found that mercury exposure significantly enhanced the expression of TLR4 and activated p38 MAPK and NF-κB pathways in vole livers. This is the first report indicating that TLR4 may serve as a sensor for chronic mercury exposure in the liver. Further, compared to females, mercury-treated male voles exhibited significant increases in activated p38 MAPK and a greater extent of liver damage. Together, these findings establish sex-specific liver immunomodulation and cellular signaling following chronic inorganic mercury exposure. Furthermore, this study also supports the use of voles as biomarkers of environmental mercury contamination and offers a promising in vivo tool to test various therapeutic strategies for mercury detoxification.

Palladium alloys for biomedical devices

In the biomedical field, palladium has primarily been used as a component of alloys for dental prostheses. However, recent research has shown the utility of palladium alloys for devices such as vascular stents that do not distort magnetic resonance images. Dental palladium alloys may contain minor or major percentages of palladium. As a minor constituent, palladium hardens, strengthens and increases the melting range of alloys. Alloys that contain palladium as the major component also contain copper, gallium and sometimes tin to produce strong alloys with high stiffness and relatively low corrosion rates. All current evidence suggests that palladium alloys are safe, despite fears about harmful effects of low-level corrosion products during biomedical use. Recent evidence suggests that palladium poses fewer biological risks than other elements, such as nickel or silver. Hypersensitivity to palladium alone is rare, but accompanies nickel hypersensitivity 90-100% of the time. The unstable price of palladium continues to influence the use of palladium alloys in biomedicine.

Exposure to lanthanum compound diminishes LPS-induced inflammation-associated gene expression: involvements of PKC and NF-kappaB signaling pathways

Lanthanum chloride, a rare earth compound, possesses antibacterial and cellular immunity regulating properties. However, the underlying molecular mechanisms remain largely unknown. In this study, we examined the effects of lanthanum chloride on the production of nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha), the expression of inducible NO synthase (iNOS) and TNF-alpha in RAW 264.7 cells, a mouse macrophage cell line. We found that the LPS-elicited excessive production of NO and TNF-alpha in RAW 264.7 cells was inhibited significantly in the presence of lanthanum chloride, and the attenuation of iNOS and TNF-alpha occurred at mRNA level. Furthermore, the possible signaling components affected by lanthanum chloride in the pathway that lead to LPS-induced iNOS and TNF-alpha expression were explored. The results indicated the involvements of PKC/Ca(2+) and NF-kappaB in the attenuation of NO and pro-inflammatory cytokine production by lanthanum chloride. Our observations suggest a possible therapeutic application of this agent for treating inflammatory diseases.

Soluble and particulate Co-Cr-Mo alloy implant metals activate the inflammasome danger signaling pathway in human macrophages: a novel mechanism for implant debris reactivity

Immune reactivity to soluble and particulate implant debris remains the primary cause of aseptic inflammation and implant loosening. However, the intracellular mechanisms that trigger immune cells to sense and respond to exogenous nonbiological agents such as metal particles or metal ions released from orthopedic implants remain unknown. Recent studies in immunology have outlined the importance of the intracellular inflammasome complex of proteins in sensing danger/stress signals triggered by nonbiological agents in the cytosol of macrophages. We hypothesized that metal implant debris can activate the inflammasome pathway in macrophages that causes caspase-1-induced cleavage of intracellular pro-IL-1beta into its mature form, resulting in IL-1beta secretion and induction of a broader proinflammatory response. We tested this hypothesis by examining whether soluble cobalt, chromium, molybdenum, and nickel ions and Co-Cr-Mo alloy particles induce inflammasome- mediated macrophage reactivity. Our results demonstrate that these agents stimulate IL-1beta secretion in human macrophages that is inflammasome mediated (i.e., NADPH-, caspase-1-, Nalp3-, and ASC-dependent). Thus, metal ion- and particle-induced activation of the inflammasome in human macrophages provides evidence of a novel pathway of implant debris-induced inflammation, where contact with implant debris is sensed and transduced by macrophages into a proinflammatory response.

Ni(II) ions dysregulate cytokine secretion from human monocytes

Nickel-containing alloys are used in dentistry because of their low cost, but poor corrosion behavior increases their risk of causing adverse biological responses. Intraorally, nickel-containing alloys accumulate bacterial plaque that triggers periodontal inflammation via toxins such as lipopolysaccharide (LPS). Recent evidence suggests that in monocytes, Ni(II) amplifies LPS-induced secretion of several cytokines that mediate periodontal destruction. Thus, we investigated the effects of Ni(II), with or without LPS, on the secretion of a broader array of cytokines from monocytes. We then measured monocytic expression of two proteins, Nrf2 and thioredoxin-1 (Trx1), that influence the regulation of cytokine secretion. Cytokine arrays were used to measure the effects of 0-50 microM Ni(II) on cytokine secretion from human THP1 monocytes, with or without LPS activation. Immunoblots were used to estimate Nrf2 and Trx1 levels. Our results indicate that both Ni(II) alone and Ni(II) with LPS have broad-based effects on cytokine secretion. Ni(II) increased Nrf2 levels by threefold, and LPS amplified the effects of Ni(II) by 10-fold. Trx1 levels did not change under any condition tested. Our results suggest that Ni(II)-induced changes in cytokine secretion by monocytes are diverse and may be influenced by Nrf2 but are not likely influenced by changes in whole-cell Trx1 levels.

Cytokine profiling using monocytes/macrophages cultured on common biomaterials with a range of surface chemistries

Cytokines, chemokines, and growth factors were assayed from the supernatants of monocytes and macrophages cultured on common biomaterials with a range of surface chemistries. TNF-alpha, MCP-1, MIP-1alpha, IL-8, IL-6, IL-1beta, VEGF, IL-1ra, and IL-10 were measured from monocyte/macrophage cultures at different stages of activation and differentiation seeded onto polyethylene, polyurethane, expanded polytetrafluoroethylene, polymethyl methacrylate, and a hydrogel copolymer of 2-hydroxyethyl methacrylate, 1-vinyl-2-pyrrolidinone, and polyethylene glycol acrylate in tissue culture polystyrene (TCPS) plates. Empty TCPS wells and organo-tin polyvinyl chloride served as "blanks" and positive controls, respectively. Results showed an overall increase in cytokine, chemokine, and growth factor production as monocytes are activated or differentiated into macrophages and that proinflammatory and anti-wound healing cytokines and chemokines dominate this profile. However, cytokine production was only modestly affected by the surface chemistry of these four stable and noncytotoxic biomaterials.

Dose-dependent effects of Ni (II) ions on production of three inflammatory cytokines (TNF-alpha, IL-1beta and IL-6), superoxide dismutase (SOD) and free radical NO by murine macrophage-like RAW264 cells with or without LPS-stimulation

The effect of Ni (II) ions on macrophages is not well understood. The purpose of this study was to examine the dose-dependent effects of Ni (II) ions up to 1,000 micromol/L on production of three inflammatory cytokines (TNF-alpha, IL-1beta and IL-6), superoxide dismutase (SOD) and nitric oxide (NO) by murine macrophage-like RAW264 cells with (+) or without (-) lipopolysaccharide (LPS) -stimulation. Ni (II) ions caused LPS (-) RAW264 cells to slightly increase production of TNF-alpha and IL-6, proportionally to the Ni (II) ion concentration while IL-1beta was not produced, and to slightly increase production of SOD and NO. It can be concluded that Ni (II) ions dose-dependently increased the inflammatory and oxidative stress conditions of LPS (-) RAW264 cells. LPS-stimulation caused RAW264 cells to produce in abundance the three inflammatory cytokines, SOD and NO. Ni (II) ions dose-dependently reduced the three cytokine quantities and NO amounts in LPS (+) RAW264 cells, while dose-independently increasing SOD amounts. It was noted that Ni (II) ions dose-dependently reduce the resistance power against bacteria of LPS (+) macrophages, because the production of volatile NO--bacteria killer is diminished proportionally to the Ni (II) ion concentration.

Relative calcium-binding strengths of amino acids determined using the kinetic method

We have measured the relative calcium-binding energies of amino acids using tandem mass spectrometry of Ca(2+)-bound trimeric amino acids. Although calcium-bound dimeric amino acid complexes coordinated too strongly to allow observation of the two competing dissociation products (calcium-bound monomeric ions) required for analysis of their metal binding affinities using the conventional kinetic method, the Ca(2+)-bound trimeric cluster ions dissociated readily to form dimeric cluster ions through simple ligand losses. The calcium-binding energies were obtained by comparing the ratio of the [Ca(2+)(A(1))(2) - H(+)](+) and [Ca(2+) (A(1))(A(2)) - H(+)](+) ions that dissociated from the [Ca(2+) (A(1))(2)(A(2)) - H(+)](+) ion and the ratio of the [Ca(2+)(A(2))(2) - H(+)](+) and [Ca(2+)(A(1)) (A(2)) - H(+)](+) ions that dissociated from the [Ca(2+)(A(1))(A(2))(2) - H(+)](+) ion, where A(1) and A(2) represent two amino acids. The energies deduced from this analysis represent the relative average binding energies of complexes having the form [Ca(2+)(A(1))(2) - H(+)](+). The relative Ca(2+)-binding strengths of the alpha-amino acid complexes follow the order Cys < Ser < Thr < Ile < Leu < Val < Gly < Ala < Pro < Phe < Met < Tyr < Asn < His < Gln < Trp < Lys < Arg. To our knowledge, this report provides the first example of using kinetic methods to determine the relative binding strengths of divalent metal-amino acid complexes.

Gold-induced reactive oxygen species (ROS) do not mediate suppression of monocytic mitochondrial or secretory function

The toxicity of anti-rheumatic gold compounds has limited their use and development, yet both the toxicological and therapeutic actions of these compounds remain unclear. In the current study, we tested the hypothesis that intracellular reactive oxygen species (ROS) induced by Au(I) or Au(III) compounds mediate their ability to suppress mitochondrial activity.

METHODS

Human THP1 monocytes were exposed to HAuCl(4) x 3H(2)O (Au(III)), or the anti-rheumatic compounds auranofin (AF) or gold sodium thiomalate (GSTM) for 6-72 h, after which mitochondrial activity (succinate dehydrogenase) was measured. To assess the role of cellular redox status as a mediator of mitochondrial suppression, monocytes were pre-treated with a pro-oxidant (t-butyl hydroquinone, t-BHQ) or antioxidant (N-acetyl cysteine, NAC ). ROS levels were measured 0-24h post-gold addition to determine their role as mediators of mitochondrial activity suppression.

RESULTS

AF was the most potent inhibitor of mitochondrial activity, followed by Au(III) and GSTM. Only Au(III) induced intracellular ROS; no ROS formation was observed in response to AF or GSTM exposure. Although anti- and pro-oxidants had some effects on mitochondrial suppression of Au compounds, collectively the data do not support redox effects or ROS formation as major mediators of Au-compound mitochondrial suppression.

CONCLUSIONS

Our results do not indicate that ROS and redox effects play major roles in mediating the cytotoxicity of AF, GSTM or Au(III).

Ni(II) activates the Nrf2 signaling pathway in human monocytic cells

Nickel is a component of biomedical alloys that is released during corrosion and causes inflammation in tissues by as yet unknown mechanisms. Recent data show that Ni(II) at concentrations of 10-50 microM amplifies lipopolysaccharide-triggered, NFkappaB-mediated cytokine secretion from monocytes. In the current study, we tested the hypothesis that Ni(II) amplifies cytokine secretion by activating the Nrf2 antioxidant pathway rather than by enhancing activity of the NFkappaB signaling pathway. Human THP1 monocytes were exposed to Ni(II) concentrations of 10-30 microM for 6-72 h, then immunoblots of whole-cell lysates or cytosolic and nuclear proteins were used to detect changes in Nrf2 or NFkappaB signaling. Our results show that Ni(II) increased (by 1-2 fold) whole-cell Nrf2 levels and nuclear translocation of Nrf2, and amplified lipopolysaccharide (LPS)-induction of Nrf2 (by 3-5 fold), but had no detectable effect on the initial activation or nuclear translocation of NFkappaB. Because Nrf2 target gene products are known regulators of NFkappaB nuclear activity, our results suggest that Ni(II) may affect cytokine secretion indirectly via modulation of the Nrf2 pathway.

Mercury as a risk factor for cardiovascular diseases

Mercury is a heavy metal that exists naturally in the environment. Major sources include the burning of fossil fuels (especially coal) and municipal waste incineration. Mercury can exist in several forms, with the most hazardous being organic methylmercury. In waterways (lakes, rivers, reservoirs, etc.), mercury is converted to methylmercury, which then accumulates in fish, especially in large predatory fish. Fish and fish products are the major--if not the only--source of methylmercury in humans. Mercury has long been recognized as a neurotoxin for humans, but in the last 10 years, its potentially harmful effects on cardiovascular diseases (CVD) have raised a cause for concern, mostly due to the proposed role of mercury in oxidative stress propagation. Some epidemiological studies have indeed found an association between increased levels of mercury in the body and risk of CVD. There are several plausible mechanisms to explain the association; these are discussed in this review. We also review the epidemiological studies that have investigated the association between mercury and CVD.