Effect of heavy metals on human rheumatoid synovial cell proliferation and collagen synthesis

Ultrasonographic Measurement of the Achilles and Supraspinatus Tendon Thicknesses in Patients with Chronic Lead Exposure

OBJECTIVE

The study aimed to assess tendon thickness in patients with chronic occupational lead exposure by using ultrasonography.

METHODS

Twenty-seven male workers (mean age 32.9 ± 6.2 years, range 25-44 years) with occupational lead exposure and 27 age- and body mass index (BMI)-matched healthy male subjects (mean age 33.1 ± 5.6 years, range 25-44 years) were enrolled. Ultrasonographic measurements were obtained from the supraspinatus and Achilles tendons by using a linear probe (5-10 MHz).

RESULTS

Mean Achilles tendon values at long axis (p = 0.034) and tendon cross-sectional area (p = 0.013) were significantly smaller in the lead-exposed group than the control group. On the other hand, no significant difference was found regarding the thickness of the supraspinatus tendon (p > 0.05).

CONCLUSION

Our preliminary results imply that subjects with occupational lead exposure have smaller Achilles tendons than healthy subjects. Chronic lead exposure may affect the tendons due to reduction of collagen synthesis. Further studies are definitely needed to confirm our initial findings.

Whole blood lead levels are associated with biomarkers of joint tissue metabolism in African American and white men and women: the Johnston County Osteoarthritis Project

PURPOSE

To examine associations between biomarkers of joint tissue metabolism and whole blood lead (Pb), separately for men and women in an African American and Caucasian population, which may reflect an underlying pathology.

METHODS

Participants in the Johnston County Osteoarthritis Project Metals Exposure Sub-Study (329 men and 342 women) underwent assessment of whole blood Pb and biochemical biomarkers of joint tissue metabolism. Urinary cross-linked N telopeptide of type I collagen (uNTX-I) and C-telopeptide fragments of type II collagen (uCTX-II), serum cleavage neoepitope of type II collagen (C2C), serum type II procollagen synthesis C-propeptide (CPII), and serum hyaluronic acid (HA) were measured using commercially available kits; the ratio of [C2C:CPII] was calculated. Serum cartilage oligomeric matrix protein (COMP) was measured by an in-house assay. Multiple linear regression models were used to examine associations between continuous blood Pb and biomarker outcomes, adjusted for age, race, current smoking status, and body mass index. Results are reported as estimated change in biomarker level for a 5-unit change in Pb level.

RESULTS

The median Pb level among men and women was 2.2 and 1.9μg/dL, respectively. Correlations were noted between Pb levels and the biomarkers uNTX-I, uCTX-II, and COMP in women, and between Pb and uCTX-II, COMP, CPII, and the ratio [C2C:CPII] in men. In adjusted models among women, a 5-unit increase in blood Pb level was associated with a 28% increase in uCTX-II and a 45% increase in uNTX-I levels (uCTX-II: 1.28 [95% CI: 1.04-1.58], uNTX-I: 1.45 [95% CI:1.21-1.74]). Among men, levels of Pb and COMP showed a borderline positive association (8% increase in COMP for a 5-unit change in Pb: 1.08 [95% CI: 1.00-1.18]); no other associations were significant after adjustment.

CONCLUSIONS

Based upon known biomarker origins, the novel associations between blood Pb and biomarkers appear to be primarily reflective of relationships to bone and calcified cartilage turnover among women and cartilage metabolism among men, suggesting a potential gender-specific effect of Pb on joint tissue metabolism that may be relevant to osteoarthritis.

Silver ions induce oxidative stress and intracellular zinc release in human skin fibroblasts

Silver compounds used as topical antimicrobial agents are known to exert toxic effects on skin cells. The aim of this study was to investigate whether the toxicity of silver ions, in analogy to other transition metal ions, depends on pro-oxidant effects. We treated human skin fibroblasts with concentrations of AgNO(3) not affecting cell proliferation, mitochondrial activity, or cell viability and found that Ag(+) strongly increases the production of reactive oxygen species, including superoxide anion radicals. These effects correspond to a strong decrease in intracellular reduced glutathione and to an increased susceptibility to H(2)O(2)-induced cell death. In addition, AgNO(3) down-regulates the expression of antioxidant genes such as the transcription factor Nrf2 and its target gene glutamate-cysteine ligase catalytic subunit. Furthermore Ag(+) induces a transient intracellular zinc release and increases the mRNA and protein expression of the zinc-binding protein metallothionein by activating the metal-responsive transcription factor 1, as verified by RNA interference. In conclusion, we show for the first time that Ag(+) induces oxidative stress and affects intracellular zinc homeostasis in human skin fibroblasts. The understanding of the mechanism involved in silver toxicity might contribute to new strategies for managing the therapy of skin infections.

Development of a high-throughput screening assay for chemical effects on proliferation and viability of immortalized human neural progenitor cells

There is considerable public concern that the majority of commercial chemicals have not been evaluated for their potential to cause developmental neurotoxicity. Although several chemicals are assessed annually under the current developmental neurotoxicity guidelines, time, resource, and animal constraints prevent testing of large numbers of chemicals using this approach. Thus, incentive is mounting to develop in vitro methods to screen chemicals for their potential to harm the developing human nervous system. As an initial step toward this end, the present studies evaluated an automated, high-throughput method for screening chemical effects on proliferation and viability using ReNcell CX cells, a human neural progenitor cell (hNPC) line. ReNcell CX cells doubled in approximately 36 h and expressed the neural progenitor markers nestin and SOX2. High-throughput assays for cell proliferation (5-bromo-2'-deoxyuridine incorporation) and viability (propidium iodide exclusion) were optimized and tested using known antiproliferative compounds. The utility of this in vitro screen was evaluated further using a set of compounds containing eight known to cause developmental neurotoxicity and eight presumably nontoxic compounds. Six out of eight developmental neurotoxicants significantly inhibited ReNcell CX cell proliferation and/or viability, whereas two out of eight nontoxic chemicals caused only minimal effects. These results demonstrate that chemical effects on cell proliferation and viability can be assessed via high-throughput methods using hNPCs. Further development of this approach as part of a strategy to screen compounds for potential effects on nervous system development is warranted.

Lead exposure and periodontitis in US adults

BACKGROUND AND OBJECTIVE

Lead is known to have significant effects on bone metabolism and the immune system. This study tested the hypothesis that lead exposure affects periodontitis in adults.

MATERIAL AND METHODS

This study used the data from the Third National Health and Nutrition Examination Survey (NHANES III, 1988-94). It analyzed data from 2500 men and 2399 women, 20-56 yr old, who received complete periodontal examination. Periodontitis was defined as the presence of > 20% of mesial sites with >or= 4 mm of attachment loss. Lead exposure was grouped into three categories: < 3; 3-7; and > 7 microg/dL. Covariates were cotinine levels, poverty ratio, race/ethnicity, education, bone mineral density, diabetes, calcium intake, dental visit, and menopause (for women). All analyses were performed separately for men and women and considering the effect design. Univariate, bivariate, and stratified analysis was followed by multivariable analysis by estimating prevalence ratios through poisson regression.

RESULTS

After adjustment for confounders, the prevalence ratios, comparing those with a lead blood level of > 7 microg/dL to those with a lead blood level of < 3 microg/dL was 1.70 (95% confidence interval (CI): 1.02, 2.85) for men and 3.80 (95% CI: 1.66, 8.73) for women.

CONCLUSION

The lead blood level was positively and statistically associated with periodontitis for both men and women. Considering the public health importance of periodontitis and lead exposure, further studies are necessary to confirm this association.

Mercuric chloride induces a strong immune activation, but does not accelerate the development of dermal fibrosis in tight skin 1 mice

In susceptible mice, mercuric chloride induces a systemic autoimmune disease characterized by increased serum levels of immunoglobulin (Ig) G1 and IgE, production of anti-nucleolar autoantibodies (ANolA) and formation of renal IgG deposits. We have previously hypothesized that mercury confers more adverse immunological effects on those mouse strains, which are genetically prone to develop spontaneous autoimmune diseases than on normal strains. In this study, we tested our hypothesis in tight skin 1 (Tsk1/+) mice, a murine model for human scleroderma. As a support for our hypothesis, we observed that in Tsk1/+ mice, B cells were spontaneously hyperactive and that treatment with mercury induced a strong immune/autoimmune response in these mice, but not in their non-Tsk (+/+) littermates. This response was characterized by the formation of high numbers of splenic IgG1, IgG2b and IgG3 antibody-secreting cells, increased serum levels of IgE, production of IgG1 antibodies against single-stranded DNA (ssDNA), trinitrophenol (TNP) as well as thyroglobulin and the development of renal IgG1 deposits. Neither Tsk1/+ mice nor F1 hybrid crosses between this strain, and mercury susceptible B10.S (H-2(s)) were able to produce IgG1-ANolA in response to mercury. Moreover, mercury-induced immune activation in Tsk1/+ was not able to potentiate the progression of skin fibrosis in this strain. Thus, exposure to mercury accelerates the immune dysregulation, but not the development of skin fibrosis in Tsk1/+ mice.

Microarray analysis of differential gene expression in lead-exposed astrocytes

The toxic metal lead is a widespread environmental health hazard that can adversely affect human health. In an effort to better understand the cellular and molecular consequences of lead exposure, we have employed cDNA microarrays to analyze the effects of acute lead exposure on large-scale gene expression patterns in immortalized rat astrocytes. Our studies identified many genes previously reported to be differentially regulated by lead exposure. Additionally, we have identified novel putative targets of lead-mediated toxicity, including members of the family of calcium/phospholipid binding annexins, the angiogenesis-inducing thrombospondins, collagens, and tRNA synthetases. We demonstrate the ability to distinguish lead-exposed samples from control or sodium samples solely on the basis of large-scale gene expression patterns using two complementary clustering methods. We have confirmed the altered expression of candidate genes and their encoded proteins by RT-PCR and Western blotting, respectively. Finally, we show that the calcium-dependent phospholipid binding protein annexin A5, initially identified as a differentially regulated gene by our microarray analysis, is directly bound and activated by nanomolar concentrations of lead. We conclude that microarray technology is an effective tool for the identification of lead-induced patterns of gene expression and molecular targets of lead.

Mercuric ion inhibits the activity and fidelity of the human cell DNA synthesome

Mercuric ion is cytotoxic and mutagenic to cells; however, the mechanisms of mercuric ion-induced cytotoxicity are not well understood. Numerous studies have suggested that these effects may be due in part to the alteration and inhibition of a variety of cellular processes including DNA replication, DNA repair, RNA transcription, and protein synthesis. Studies utilizing whole cells to examine these activities are not able to specifically identify the precise mechanism or site of the effect. Other studies carried out using whole cell extracts and variously purified DNA polymerases are not able to adequately represent the highly ordered environment in which DNA replication occurs in the intact cell. We report here, for the first time, the use of an intact human cell multiprotein complex (which we have termed the DNA synthesome) to carry out full-length DNA replication and DNA synthesis in the presence of Hg2+ ion in vitro. In this study we report that DNA replication and DNA polymerase activity, as well as DNA replication fidelity of the human cell DNA synthesome, are specifically inhibited by physiologically attainable concentrations of mercuric ion.

Toxicological aspects of topical silver pharmaceuticals

Silver is generally considered to present a relatively low toxic threat to humans because unintentional exposure to large doses of the noble metal is quite rare. However, as the intentional utilization of silver in pharmaceutical preparations and devices increases, subtle toxic effects of silver may be predictable and expected. The present review examines the scientific literature, primarily covering the past 10 years, dealing with reports describing various types of silver toxicity. These reports consist of both in vitro and in vivo data dealing with immunological, mesenchymal, neural, and parenchymal cell types. Particular emphasis is given to (1) the use of silver in topical antimicrobial preparations as toxicity relates to absorption through dermal wounds into the systemic circulation and possible effects on delayed wound healing, (2) possible local silver toxicity via iontophoretic devices, (3) current theories relating to the toxicological mechanism of action of silver.

Determination of lead in paired samples of blood and synovial fluid of bovines

Exposure of synovial fluid to lead allows the entrance of this metal into the systemic circulation. In this study we report lead concentrations measured in bovine paired samples of synovial fluid and whole blood withdrawn from the coxo-femoral joints and jugular vein, respectively. Lead was determined by atomic absorption spectrophotometry. This study provides the "normal" values for lead in synovial fluid 12.15 +/- 5.41 and blood 3.54 +/- 1.31 micrograms% (mean +/- SD). The data distribution fits the GAUSSIAN curve (p < 0.02). The difference of concentration between synovial fluid and blood can not be explained only in terms of the solubility of lead in both fluids; other factors must be considered.

Effects of lead acetate on DNA and RNA synthesis by intact HeLa cells, isolated nuclei and purified polymerases

The effects of lead acetate on DNA and RNA synthesis have been investigated with intact HeLa cells, isolated nuclei, and purified DNA and RNA polymerases. No inhibition of DNA or RNA synthesis in intact cells was found even after exposure to 0.5 mM lead acetate for 18 hr. In contrast, both DNA and RNA synthesis in isolated nuclei were inhibited by lead (with 50% inhibition at approximately 150 and 80 microM respectively). Similarly, both HeLa DNA polymerase alpha and RNA polymerase II were inhibited, with 50% inhibition obtained at approximately 150 and 20 microM lead acetate respectively. The inhibition of nucleic acid synthesis in isolated nuclei can thus be accounted for by inhibition of the polymerases. The sensitivity of Escherichia coli DNA polymerase I to lead acetate was found to be significantly greater than the HeLa DNA polymerase alpha (50% inhibition at only 10 microM), but the sensitivity of the E. coli RNA polymerase was the same as that of the HeLa enzyme.