Systemic serum amyloid A as a biomarker for exposure to zinc and/or copper-containing metal fumes

Long-term exposure to ambient air pollution and inflammatory response in the KORA study

Previous studies consistently showed an association between fine atmospheric particulate matter (PM2.5) and cardiovascular diseases. Concerns about adverse health effects of ultrafine particles (UFP) are growing but long-term studies are still scarce. In this study, we examined the association between long-term exposure to ambient air pollutants and blood biomarkers of inflammation and coagulation, including fibrinogen, high-sensitivity C-reactive protein (hs-CRP), serum amyloid A (SAA) adiponectin and interleukin-6 (IL-6), measured in the German KORA-S4 cohort study (1999-2001). IL-6 was available for older participants only, who were therefore considered as a subsample. Annual mean concentrations of UFP (as particle number concentration), particulate matter in different particles sizes (PM10, PMcoarse, PM2.5, PM2.5 absorbance), ozone (O3), and nitrogen oxides (NO2, NOX) were estimated by land-use regression models and assigned to participants' home addresses. We performed a multiple linear regression between each pollutant and each biomarker with adjustment for confounders. Per 1 interquartile range (IQR, 1945 particles/cm3) increase of UFP, fibrinogen increased by 0.70 % (0.04; 1.37) and hs-CRP increased by 3.16 % (-0.52; 6.98). Adiponectin decreased by -2.53 % (-4.78; -0.24) per 1 IQR (1.4 μg/m3) increase of PM2.5. Besides, PM2.5 was associated with increased IL-6 in the subsample. In conclusion, we observed that long-term exposure to air pollutants, including both fine and ultrafine particles, was associated with higher concentrations of pro-inflammatory and lower concentrations of an anti-inflammatory blood biomarkers, which is consistent with an increased risk for cardiovascular disease observed for long-term exposure to air pollutants.

Acute phase response following pulmonary exposure to soluble and insoluble metal oxide nanomaterials in mice

BACKGROUND

Acute phase response (APR) is characterized by a change in concentration of different proteins, including C-reactive protein and serum amyloid A (SAA) that can be linked to both exposure to metal oxide nanomaterials and risk of cardiovascular diseases. In this study, we intratracheally exposed mice to ZnO, CuO, Al₂O₃, SnO₂ and TiO₂ and carbon black (Printex 90) nanomaterials with a wide range in phagolysosomal solubility. We subsequently assessed neutrophil numbers, protein and lactate dehydrogenase activity in bronchoalveolar lavage fluid, Saa3 and Saa1 mRNA levels in lung and liver tissue, respectively, and SAA3 and SAA1/2 in plasma. Endpoints were analyzed 1 and 28 days after exposure, including histopathology of lung and liver tissues.

RESULTS

All nanomaterials induced pulmonary inflammation after 1 day, and exposure to ZnO, CuO, SnO₂, TiO₂ and Printex 90 increased Saa3 mRNA levels in lungs and Saa1 mRNA levels in liver. Additionally, CuO, SnO₂, TiO₂ and Printex 90 increased plasma levels of SAA3 and SAA1/2. Acute phase response was predicted by deposited surface area for insoluble metal oxides, 1 and 28 days post-exposure.

CONCLUSION

Soluble and insoluble metal oxides induced dose-dependent APR with different time dependency. Neutrophil influx, Saa3 mRNA levels in lung tissue and plasma SAA3 levels correlated across all studied nanomaterials, suggesting that these endpoints can be used as biomarkers of acute phase response and cardiovascular disease risk following exposure to soluble and insoluble particles.

The human long noncoding RNAs CoroMarker, MALAT1, CDR1as, and LINC00460 in whole blood of individuals after controlled short-term exposure with ultrafine metal fume particles at workplace conditions, and in human macrophages in vitro

Background

Short-term inhalation of occupationally relevant ultrafine zinc/copper (Zn/Cu) containing welding fumes has been shown to induce subclinical systemic inflammation, associated with an elevated risk for cardiovascular diseases. The involvement of noncoding RNAs (lncRNAs) in this setting is currently unknown. However, lncRNAs have been reported to fulfill essential roles in, e.g., cardiovascular diseases, inflammation, infectious diseases, and pollution-related lung disorders.

Methods

In this study, the specific lncRNAs levels of the 4 lncRNAs CoroMarker, MALAT1, CDR1as and LINC00460 were determined by RT-qPCR in THP-1 macrophages exposed to Zn/Cu metal fume suspensions for 1, 2, and 4 hours in vitro. Furthermore, 14 subjects were exposed to Zn/Cu containing welding fumes (at 2.5 mg/m³) for 6 hours. Before, 6, 10, and 29 hours after exposure start, whole blood cell lncRNAs levels were determined by RT-qPCR.

Results

In THP-1 macrophages, we observed a 2.3-fold increase of CDR1as at 1 h (Wilcoxon p = 0.03), a non-significant increase of CoroMarker at 1 h, and an increase of LINC00460 at 2 h (p = 0.03) and at 4 h (p = 0.06). In whole blood cells, we determined a non-significant upregulation of CDR1as at 6 h (p = 0.2), a significant downregulation of CoroMarker at 6 h (p = 0.04), and a significant upregulation of LINC00460 levels at 10 h (p = 0.04) and 29 h (p = 0.04). MALAT-1 remained unchanged in both settings.

Conclusion

The orientation of regulation of the lncRNAs is (except for CoroMarker) similar in the in vitro and in vivo experiments and in line with their described functions. Therefore, these results, e.g. the upregulation of the potential risk marker for cardiovascular diseases, CDR1as, contribute to understanding the underlying mechanisms of Zn/Cu-induced subclinical inflammation in metal workers.

Malondialdehyde and anion patterns in exhaled breath condensate among subway workers

BACKGROUND

Underground transportation systems can contribute to the daily particulates and metal exposures for both commuter and subway workers. The redox and metabolic changes in workers exposed to such metal-rich particles have yet to be characterized. We hypothesize that the distribution of nitrosative/oxidative stress and related metabolic biomarkers in exhaled breath condensate (EBC) are modified depending on exposures.

RESULTS

Particulate number and size as well as mass concentration and airborne metal content were measured in three groups of nine subway workers (station agents, locomotive operators and security guards). In parallel, pre- and post-shift EBC was collected daily during two consecutive working weeks. In this biological matrix, malondialdehyde, lactate, acetate, propionate, butyrate, formate, pyruvate, the sum of nitrite and nitrate (ΣNO_x) and the ratio nitrite/nitrate as well as metals and nanoparticle concentrations was determined. Weekly evolution of the log-transformed selected biomarkers as well as their association with exposure variables was investigated using linear mixed effects models with the participant ID as random effect. The professional activity had a strong influence on the pattern of anions and malondialdehyde in EBC. The daily number concentration and the lung deposited surface area of ultrafine particles was consistently and mainly associated with nitrogen oxides variations during the work-shift, with an inhibitory effect on the ΣNO_x. We observed that the particulate matter (PM) mass was associated with a decreasing level of acetate, lactate and ΣNO_x during the work-shift, suggestive of a build-up of these anions during the previous night in response to exposures from the previous day. Lactate was moderately and positively associated with some metals and with the sub-micrometer particle concentration in EBC.

CONCLUSIONS

These results are exploratory but suggest that exposure to subway PM could affect concentrations of nitrogen oxides as well as acetate and lactate in EBC of subway workers. The effect is modulated by the particle size and can correspond to the body's cellular responses under oxidative stress to maintain the redox and/or metabolic homeostasis.

Characterization of toxicological effects of complex nano-sized metal particles using in vitro human cell and whole blood model systems

Metal oxide fumes form at high temperatures, for instance, during welding or firing ammunition. Inhalation exposure to high levels of airborne metal oxide particles can cause metal fume fever, cardiovascular effects, and lung damage in humans, but the associated underlying pathological mechanisms are still not fully understood. Using human alveolar epithelial cells, vascular endothelial cells, and whole blood model systems, we aimed to elucidate the short-term effects of well-characterized metal particles emitted while firing pistol ammunition. Human lung epithelial cells exposed to gunshot smoke particles (0.1-50 μg/ml) produced reactive oxygen species (ROS) and pro-inflammatory cytokines (interleukin 8 (IL-8), granulocyte-macrophage colony-stimulating factor (GM-CSF)) that activate and recruit immune cells. Particles comprising high copper (Cu) and zinc (Zn) content activated human endothelial cells via a non-ROS-mediated mechanism that triggered immune activation (IL-8, GM-CSF), leukocyte adhesion to the endothelium (soluble intercellular adhesion molecule 1 (sICAM-1)), and secretion of regulators of the acute-phase protein synthesis (interleukin 6 (IL-6)). In human whole blood, metal oxides in gunshot smoke demonstrated intrinsic properties that activated platelets (release of soluble cluster of differentiation 40 ligand (sCD40L), platelet-derived growth factor B-chain homodimer(PDGF-BB), and vascular endothelial growth factor A (VEGF-A)) and blood coagulation and induced concomitant release of pro-inflammatory cytokines from blood leukocytes that further orchestrate thrombogenesis. The model systems applied provide useful tools for health risk assessment of particle exposures, but more studies are needed to further elucidate the mechanisms of metal fume fever and to evaluate the potential risk of long-term cardiovascular diseases.

Latent Toxoplasma gondii infections are associated with elevated biomarkers of inflammation and vascular injury

BACKGROUND

Toxoplasma gondii is a protozoan parasite that infects cats as definitive hosts and other warm-blooded animals including humans as intermediate hosts. It forms infectious cysts in the brain, muscle and other tissues establishing life-long latent infection. Approximately 10% of the US population is infected. While latent infections are largely asymptomatic, they are associated with neurological deficits and elevated risks of neuropsychiatric diseases.

METHODS

This cross-sectional epidemiological study investigated associations of T. gondii infections with biomarkers of inflammation and vascular injury: soluble intercellular adhesion molecule 1 (ICAM-1), soluble vascular cell adhesion molecule 1 (VCAM-1), C-reactive protein (CRP), and serum amyloid A (SAA). Serum samples from 694 adults in the Raleigh-Durham-Chapel Hill, North Carolina metropolitan area were tested for IgG antibody response to T. gondii, and for the above biomarkers using commercially available assays.

RESULTS

T. gondii seroprevalence rate in this sample was 9.7%. Seropositivity was significantly associated with 11% (95% confidence limits 4, 20%) greater median levels of VCAM-1 (p = 0.003), and marginally significantly with 9% (1, 17%), and 36% (1, 83%) greater median levels of ICAM-1, and CRP, respectively (p = 0.04 for each) after adjusting for sociodemographic and behavioral covariates, while the 23% (- 7, 64%) adjusted effect on SAA was not statistically significant (p = 0.15).

CONCLUSIONS

Latent infections with T. gondii are associated with elevated biomarkers of chronic inflammation and vascular injury that are also known to be affected by ambient air pollution.

The Effects of Exposure Time on Systemic Inflammation in Subjects With Exposure to Zinc- and Copper-Containing Brazing Fumes

INTRODUCTION

Inhalation of copper and zinc containing brazing fumes (2.5 mg/m for 6 hours) is able to induce asymptomatic systemic inflammation which is supposed to be connected with an increased risk for cardiovascular disease. In this study it was investigated if inflammation can be prevented by reducing the exposure time.

METHODS

A total of 15 healthy male subjects were exposed to such brazing fumes in a crossover design for 3, 4, and 5 hours in randomized order. Before and 24 hours after exposure, blood samples were taken and c-reactive protein (CRP) as marker for an acute phase reaction was measured.

RESULTS

Five-hour exposure induced an increase of CRP, whereas the shorter exposure times did not result in a significant inflammatory reaction.

CONCLUSIONS

Reducing daily exposure times below 5 hours is able to prevent systemic inflammatory reactions.

Pulmonary toxicity of synthetic amorphous silica - effects of porosity and copper oxide doping

Materials can be modified for improved functionality. Our aim was to test whether pulmonary toxicity of silica nanomaterials is increased by the introduction of: a) porosity; and b) surface doping with CuO; and whether c) these modifications act synergistically. Mice were exposed by intratracheal instillation and for some doses also oropharyngeal aspiration to: 1) solid silica 100 nm; 2) porous silica 100 nm; 3) porous silica 100 nm with CuO doping; 4) solid silica 300 nm; 5) porous silica 300 nm; 6) solid silica 300 nm with CuO doping; 7) porous silica 300 nm with CuO doping; 8) CuO nanoparticles 9.8 nm; or 9) carbon black Printex 90 as benchmark. Based on a pilot study, dose levels were between 0.5 and 162 µg/mouse (0.2 and 8.1 mg/kg bw). Endpoints included pulmonary inflammation (neutrophil numbers in bronchoalveolar fluid), acute phase response, histopathology, and genotoxicity assessed by the comet assay, micronucleus test, and the gamma-H2AX assay. The porous silica materials induced greater pulmonary inflammation than their solid counterparts. A similar pattern was seen for acute phase response induction and histologic changes. This could be explained by a higher specific surface area per mass unit for the most toxic particles. CuO doping further increased the acute phase response normalized according to the deposited surface area. We identified no consistent evidence of synergism between surface area and CuO doping. In conclusion, porosity and CuO doping each increased the toxicity of silica nanomaterials and there was no indication of synergy when the modifications co-occurred.

Effects of mild steel welding fume particles on pulmonary epithelial inflammation and endothelial activation

Welders have an increased risk for cardiovascular disease (CVD) following exposure to welding fumes. The underlying mechanisms are largely unknown; however, oxidative stress, systemic inflammation, and endothelial dysfunction have been suggested as contributing factors to particle-induced CVD. We investigated effects of mild steel welding fume (MSWF) on three target cell types: macrophages, pulmonary epithelial, and vascular endothelial cells. Cells were exposed to MSWF at nontoxic doses for 6 h/day, for five consecutive days. The expression of 40 genes involved in inflammation, fibrosis, and endothelial activation was analyzed. Moreover, changes in the reactive oxygen species production and migration capacity of cells were assessed. The expression of matrix metallopeptidase 1 (MMP1) was induced in both epithelial and endothelial cells following repeated exposure to MSWF. Although MMP1 is important in inflammatory responses in vivo, this effect was not concurrent with changes in the inflammatory status, cell proliferation, and migration capacities, nor did it induce oxidative stress in the cells. Thus, repeated exposure with low doses of MSWF was sufficient neither for inducing inflammatory stress in epithelial cells and macrophages nor for endothelial activation, and higher concentrations of MSWF or the nonparticle fraction of MSWF may be critical in causing the increased risk of CVD observed among welders.

Human Cytomegalovirus Infections Are Associated With Elevated Biomarkers of Vascular Injury

Background: Human cytomegalovirus (HCMV) infects ~50% of adults in the United States. HCMV infections may cause vascular inflammation leading to cardiovascular disease, but the existing evidence is inconsistent.

Objective: We investigated demographic predictors of HCMV infection and explored associations between HCMV infection status, the intensity of anti-HCMV Immunoglobulin G (IgG) antibody response, and biomarkers of inflammation and endothelial function which are known predictors of cardiovascular disease.

Methods: We conducted a cross-sectional study of 694 adults residing in the Raleigh-Durham-Chapel Hill, NC metropolitan area. Serum samples were tested for IgG antibody response to HCMV, and for biomarkers of vascular injury including soluble intercellular adhesion molecule 1 (sICAM-1), soluble vascular cell adhesion molecule 1 (sVCAM-1), C-reactive protein (CRP), and serum amyloid A (SAA). Associations between HCMV and biomarker levels were analyzed using two approaches with HCMV serostatus modeled as a binary variable and as an ordinal variable with five categories comprised of seronegative individuals and quartiles of anti-HCMV antibody responses in seropositive individuals.

Results: HCMV seroprevalence in the study population was 56%. Increased body mass index, increased age, female gender, racial/ethnic minority status, and current smoking were significantly associated with HCMV seropositivity in a multivariate regression analysis. HCMV seropositivity was also associated with 9% (95% confidence interval 4–15%) and 20% (0.3–44%) increases in median levels of sICAM-1 and CRP, respectively, after adjusting for covariates. The association between HCMV seropositivity and median levels of sVCAM-1 and SAA were positive but not statistically significant. Significant positive associations were observed between the intensity of anti-HCMV IgG responses and levels of sICAM-1 and sVCAM-1 (p-values 0.0008 and 0.04 for linear trend, respectively). To our knowledge, this is the first epidemiological study to show a relationship between anti-HCMV IgG responses and vascular injury biomarkers sICAM-1 and sVCAM-1 in the general population.

Conclusion: HCMV infections are associated with vascular injury and inflammation biomarkers in adult residents of North Carolina.

De novo Synthesis of SAA1 in the Placenta Participates in Parturition

Serum amyloid A1 (SAA1) is an acute phase protein produced mainly by the liver to participate in immunomodulation in both sterile and non-sterile inflammation. However, non-hepatic tissues can also synthesize SAA1. It remains to be determined whether SAA1 synthesized locally in the placenta participates in parturition via eliciting inflammatory reactions. In this study, we investigated this issue by using human placenta and a mouse model. We found that SAA1 mRNA and protein were present in human placental villous trophoblasts, which was increased upon syncytialization as well as treatments with lipopolysaccharides (LPS), tumor necrosis factor-α (TNF-α), and cortisol. Moreover, significant increases in SAA1 abundance were observed in the placental tissue or in the maternal blood in spontaneous deliveries without infection at term and in preterm birth with histological chorioamnionitis. Serum amyloid A1 treatment significantly increased parturition-pertinent inflammatory gene expression including interleukin-1β (IL-1β), IL-8, TNF-α, and cyclooxygenase-2 (COX-2), along with increased PGF2α production in syncytiotrophoblasts. Mouse study showed that SAA1 was present in the placental junctional zone and yolk sac membrane, which was increased following intraperitoneal administration of LPS. Intraperitoneal injection of SAA1 not only induced preterm birth but also increased the abundance of IL-1β, TNF-α, and COX-2 in the mouse placenta. Conclusively, SAA1 can be synthesized in the human placenta, which is increased upon trophoblast syncytialization. Parturition is accompanied with increased SAA1 abundance in the placenta. Serum amyloid A1 may participate in parturition in the presence and absence of infection by inducing the expression of inflammatory genes in the placenta.

Acute Phase Response as a Biological Mechanism-of-Action of (Nano)particle-Induced Cardiovascular Disease

Inhaled nanoparticles constitute a potential health hazard due to their size-dependent lung deposition and large surface to mass ratio. Exposure to high levels contributes to the risk of developing respiratory and cardiovascular diseases, as well as of lung cancer. Particle-induced acute phase response may be an important mechanism of action of particle-induced cardiovascular disease. Here, the authors review new important scientific evidence showing causal relationships between inhalation of particle and nanomaterials, induction of acute phase response, and risk of cardiovascular disease. Particle-induced acute phase response provides a means for risk assessment of particle-induced cardiovascular disease and underscores cardiovascular disease as an occupational disease.

Association between a urinary biomarker for exposure to PAH and blood level of the acute phase protein serum amyloid A in coke oven workers

BACKGROUND

Coke oven workers are exposed to both free and particle bound PAH. Through this exposure, the workers may be at increased risk of cardiovascular diseases. Systemic levels of acute phase response proteins have been linked to cardiovascular disease in epidemiological studies, suggesting it as a marker of these conditions. The aim of this study was to assess whether there was association between PAH exposure and the blood level of the acute phase inflammatory response marker serum amyloid A (SAA) in coke oven workers.

METHODS

A total of 87 male Polish coke oven workers from two different plants comprised the study population. Exposure was assessed by means of the individual post-shift urinary excretion of 1-hydroxypyrene, as internal dose of short-term PAH exposure, and by anti-benzo[a]pyrene diolepoxide (anti-B[a]PDE)-DNA), as a biomarker of long-term PAH exposure. Blood levels of acute phase proteins SAA and CRP were measured by immunoassay. C-reactive protein (CRP) levels were included to adjust for baseline levels of SAA.

RESULTS

Multiple linear regression showed that the major determinants of increased SAA levels were urinary 1-hydroxypyrene (beta = 0.56, p = 0.030) and serum CRP levels (beta = 7.08; p < 0.0001) whereas anti-B[a]PDE-DNA, the GSTM1 detoxifying genotype, diet, and smoking were not associated with SAA levels.

CONCLUSIONS

Urinary 1-hydroxypyrene as biomarker of short-term PAH exposure and serum levels of CRP were predictive of serum levels of SAA in coke oven workers. Our data suggest that exposure of coke oven workers to PAH can lead to increased systemic acute response and therefore potentially increased risk of cardiovascular disease.

Interaction of biologically relevant proteins with ZnO nanomaterials: A confounding factor for in vitro toxicity endpoints

The results of in vitro toxicological studies for manufactured nanomaterials (MNs) are often contradictory and not reproducible. Interference of the MNs with assays has been suggested. However, understanding for which materials and how these artefacts occur remains a major challenge. This study investigated interactions between two well-characterized ZnO MNs (NM-110 and NM-111) and lactate dehydrogenase (LDH), and two interleukins (IL-6 and IL-8). Particles (10 to 640 μg/mL) and proteins were incubated for up to 24 h in routine in vitro assays test conditions. LDH activity (OD_LDH), but not interleukins concentrations, decreased sharply in a dose-dependent manner within an hour after exposure (OD_LDH < 60% of OD_ref for both MNs at 10 μg/mL). A Freundlich adsorption isotherm was successfully applied, indicating multilayer adsorption of LDH. ZnO MNs and LDH had neutral to slightly negative surface charges in dispersion, precluding electrostatic attachment. Particle sedimentation was not a limiting factor. Fast dissolution of ZnO MNs was shown and Zn²⁺ could play a role in the OD_LDH drop. To summarize, ZnO MNs quickly reduced OD_LDH due to concentration-dependent adsorption and LDH inhibition by interaction with dissolved Zn. The control of particle interference in toxicological in vitro assays should become mandatory to avoid misleading interpretation of results.

Concentration-dependent systemic response after inhalation of nano-sized zinc oxide particles in human volunteers

Background

Inhalation of high concentrations of zinc oxide particles (ZnO) may cause metal fume fever. In an earlier human inhalation study, no effects were observed after exposure to ZnO concentrations of 0.5 mg/m³. Further data from experimental studies with pure ZnO in the concentration range between 0.5 and 2.5 mg/m³ are not available. It was the aim of this experimental study to establish the concentration-response relationship of pure nano-sized ZnO particles.

Methods

Sixteen healthy subjects were exposed to filtered air and ZnO particles (0.5, 1.0 and 2.0 mg/m³) for 4 h on 4 different days, including 2 h of cycling with a low workload. The effects were assessed before, immediately after, and about 24 h after each exposure. Effect parameters were symptoms, body temperature, inflammatory markers and clotting factors in blood, and lung function.

Results

Concentration-dependent increases in symptoms, body temperature, acute phase proteins and neutrophils in blood were detected after ZnO inhalation. Significant effects were detected with ZnO concentrations of 1.0 mg/m³ or higher, with the most sensitive parameters being inflammatory markers in blood.

Conclusion

A concentration-response relationship with nano-sized ZnO particles in a low concentration range was demonstrated. Systemic inflammatory effects of inhaled nano-sized ZnO particles were observed at concentrations well below the occpational exposure limit for ZnO in many countries. It is recommended to reassess the exposure limit for ZnO at workplaces.

Editorial: dose-dependent ZnO particle-induced acute phase response in humans warrants re-evaluation of occupational exposure limits for metal oxides

Epidemiological studies link inhalation of particles to increased risk of cardiovascular disease. Inhaled particles may induce cardiovascular disease by several different mechanisms including translocation of particles to systemic circulation, activation of airway sensory nerves resulting in autonomic imbalance and particle-induced pulmonary inflammation and acute phase response.The acute phase response is the systemic response to acute and chronic inflammatory states caused by for example bacterial infection, virus infection, trauma and infarction. It is characterized by differential expression of ca. 50 different acute phase proteins including C-reactive protein and Serum amyloid A, which are the most differentially up-regulated acute phase response proteins. Blood levels of these two acute phase proteins are closely associated with risk of cardiovascular disease in epidemiological studies and SAA has been causally related to the formation of plaques in the aorta in animal studies.In a recent paper in Particle and Fibre Toxicology, Christian Monsé et al. provide evidence that inhalation of ZnO nanoparticles induces dose-dependent acute phase response in humans at dose levels well below the current mass-based occupational exposure limits in a number of countries including Germany, The Netherlands, UK, Sweden, Denmark and the US.Given the evidence suggesting a causal relationship between increased levels of serum amyloid A and atherosclerosis, the current results call for a re-evaluation of occupational exposure limits for a number of particle exposures including ZnO taking induction of acute phase response into account. Furthermore, it underscores cardiovascular disease as an occupational disease.