Air pollution particles and iron homeostasis

Highly-fluorescent extracts from Pterocarpus wood for Fe3+ ion detection

At present, excessive Fe3+ in daily water has become a threat to human health. Among the conventional detection methods for Fe3+, fluorescent probes have been applied on a large scale due to their simplicity and efficiency. However, the currently available fluorescent probes are difficult to synthesize, costly and environmentally unfriendly, limiting their applications. In this work, a fluorescent extract of Pterocarpus wood was successfully obtained, and the structure of some coumarin-based molecules in this extract was determined by 2D-NMR. Subsequently, the intensity of this fluorescence was optimized using response surface methodology (RSM), resulting in a high-intensity fluorescent probe. The probe was sensitive to the concentrations of Fe3+ and MnO4-, and could efficiently detects Fe3+ in the range of 2.7 μM-8.0 μM, with LOD and LOQ reaching 1.06 μM and 3.20 μM, respectively. Moreover, based on the strong complexation property of EDTA on Fe3+, this work designed the "switch-on" fluorescent probes. The experiment shows that both static and dynamic quenching exist in this system. The mechanism of complexation and oxidation of fluorescent molecules by the quencher is interpreted in the quenching reaction. In addition, the fluorescent probe has a high yield and low cost, it also performs well in actual water sample tests. This method is expected to be developed as a new way on Fe3+ detection.

Ambient PM2.5 Components Are Associated With Bone Strength: Evidence From a China Multi-Ethnic Study

CONTEXT

The relationship between the components of particulate matter with an aerodynamic diameter of 2.5 or less (PM2.5) and bone strength remains unclear.

OBJECTIVE

Based on a large-scale epidemiologic survey, we investigated the individual and combined associations of PM2.5 and its components with bone strength.

METHODS

A total of 65 906 individuals aged 30 to 79 years were derived from the China Multi-Ethnic Cohort Annual average concentrations of PM2.5 and its components were estimated using satellite remote sensing and chemical transport models. Bone strength was expressed by the calcaneus quantitative ultrasound index (QUI) measured by quantitative ultrasound. The logistic regression model and weighted quantile sum method were used to estimate the associations of single and joint exposure to PM2.5 and its components with QUI, respectively.

RESULTS

Our analysis shows that per-SD increase (μg/m3) in 3-year average concentrations of PM2.5 (mean difference [MD] -7.38; 95% CI, -8.35 to -6.41), black carbon (-7.91; -8.90 to -6.92), ammonium (-8.35; -9.37 to -7.34), nitrate (-8.73; -9.80 to -7.66), organic matter (-4.70; -5.77 to -3.64), and soil particles (-5.12; -6.10 to -4.15) were negatively associated with QUI. In addition, these associations were more pronounced in men, and people older than 65 years with a history of smoking and chronic alcohol consumption.

CONCLUSION

We found that long-term exposure to PM2.5 and its components may lead to reduced bone strength, suggesting that PM2.5 and its components may potentially increase the risk of osteoporosis and even fracture. Nitrate may be responsible for increasing its risk to a greater extent.

Iron: Not Just a Passive Bystander in AITD

Autoimmune thyroid disease (AITD) is the most prevalent autoimmune disease all over the world and the most frequent cause of hypothyroidism in areas of iodine sufficiency. The pathogenesis of AITD is multifactorial and depends on complex interactions between genetic and environmental factors, with epigenetics being the crucial link. Iron deficiency (ID) can reduce the activities of thyroid peroxidase and 5′-deiodinase, inhibit binding of triiodothyronine to its nuclear receptor, and cause slower utilization of T3 from the serum pool. Moreover, ID can disturb the functioning of the immune system, increasing the risk of autoimmune disorders. ID can be responsible for residual symptoms that may persist in patients with AITD, even if their thyrometabolic status has been controlled. The human lifestyle in the 21st century is inevitably associated with exposure to chemical compounds, pathogens, and stress, which implies an increased risk of autoimmune disorders and thyroid dysfunction. To summarize, in our paper we discuss how iron deficiency can impair the functions of the immune system, cause epigenetic changes in human DNA, and potentiate tissue damage by chemicals acting as thyroid disruptors.

Can Iron Play a Crucial Role in Maintaining Cardiovascular Health in the 21st Century?

In the 21st century the heart is facing more and more challenges so it should be brave and iron to meet these challenges. We are living in the era of the COVID-19 pandemic, population aging, prevalent obesity, diabetes and autoimmune diseases, environmental pollution, mass migrations and new potential pandemic threats. In our article we showed sophisticated and complex regulations of iron metabolism. We discussed the impact of iron metabolism on heart diseases, treatment of heart failure, diabetes and obesity. We faced the problems of constant stress, climate change, environmental pollution, migrations and epidemics and showed that iron is really essential for heart metabolism in the 21st century.

Ultraviolet Light Protection: Is It Really Enough?

Our current understanding of the pathogenesis of skin aging includes the role of ultraviolet light, visible light, infrared, pollution, cigarette smoke and other environmental exposures. The mechanism of action common to these exposures is the disruption of the cellular redox balance by the directly or indirectly increased formation of reactive oxygen species that overwhelm the intrinsic antioxidant defense system, resulting in an oxidative stress condition. Altered redox homeostasis triggers downstream pathways that contribute to tissue oxinflammation (cross-talk between inflammation and altered redox status) and accelerate skin aging. In addition, both ultraviolet light and pollution increase intracellular free iron that catalyzes reactive oxygen species generation via the Fenton reaction. This disruption of iron homeostasis within the cell further promotes oxidative stress and contributes to extrinsic skin aging. More recent studies have demonstrated that iron chelators can be used topically and can enhance the benefits of topically applied antioxidants. Thus, an updated, more comprehensive approach to environmental or atmospheric aging protection should include sun protective measures, broad spectrum sunscreens, antioxidants, chelating agents, and DNA repair enzymes.

Cigarette Smoke Particle-Induced Lung Injury and Iron Homeostasis

It is proposed that the mechanistic basis for non-neoplastic lung injury with cigarette smoking is a disruption of iron homeostasis in cells after exposure to cigarette smoke particle (CSP). Following the complexation and sequestration of intracellular iron by CSP, the host response (eg, inflammation, mucus production, and fibrosis) attempts to reverse a functional metal deficiency. Clinical manifestations of this response can present as respiratory bronchiolitis, desquamative interstitial pneumonitis, pulmonary Langerhans’ cell histiocytosis, asthma, pulmonary hypertension, chronic bronchitis, and pulmonary fibrosis. If the response is unsuccessful, the functional deficiency of iron progresses to irreversible cell death evident in emphysema and bronchiectasis. The subsequent clinical and pathological presentation is a continuum of lung injuries, which overlap and coexist with one another. Designating these non-neoplastic lung injuries after smoking as distinct disease processes fails to recognize shared relationships to each other and ultimately to CSP, as well as the common mechanistic pathway (ie, disruption of iron homeostasis).

Deferoxamine Treatment Improves Antioxidant Cosmeceutical Formulation Protection against Cutaneous Diesel Engine Exhaust Exposure

Skin is one of the main targets of the outdoor stressors. Considering that pollution levels are rising progressively, it is not surprising that several cutaneous conditions have been associated with its exposure. Among the pollutants, diesel engine exhaust (DEE) represents one of the most toxic, as it is composed of a mixture of many different noxious chemicals generated during the compression cycle, for ignition rather than an electrical spark as in gasoline engines. The toxic chemicals of most concern in DEE, besides the oxides of nitrogen, sulfur dioxide and various hydrocarbons, are metals that can induce oxidative stress and inflammation. The present study aimed to evaluate the effects of topical application, singularly or in combination, of the iron-chelator deferoxamine and a commercially available formulation, CE Ferulic, in up to 4-day DEE-exposed skin. DEE induced a significant increase in the oxidative marker 4-hydroxy-nonenal (4HNE) and matrix-metallopeptidase-9 (MMP-9), the loss of cutaneous-barrier-associated proteins (filaggrin and involucrin) and a decrease in collagen-1, while the formulations prevented the cutaneous damage in an additive manner. In conclusion, this study suggests that iron plays a key role in DEE-induced skin damage and its chelation could be an adjuvant strategy to reinforce antioxidant topical formulations.

Effects of albumin, transferrin and humic-like substances on iron-mediated OH radical formation in human lung fluids

Inhalation of particulate matter is hypothesized to contribute to health effects by overproducing reactive oxygen species (ROS) and inducing oxidative stress. Fe(II) has been shown to contribute to ROS generation in acellular simulated lung fluids. Atmospheric humic-like substances (HULIS) have been shown to chelate Fe(II) and significantly enhance this ROS generation. Here, we investigate Fe(II)-mediated ^.OH generation from the iron active proteins in lung fluid, albumin and transferrin, and fulvic acid, a surrogate for HULIS, in human bronchoalveolar lavage fluid (BALF). We find that albumin enhances ^.OH generation from inorganic Fe(II) and that transferrin attenuates this enhancement. We estimate the rate constants for albumin-Fe(II) and fulvic acid-Fe(II) mediated O₂^.- reduction (1.9 ± 0.3) M^-1 s^-1 and (2.7 ± 0.3) M^-1s^-1 (pH = 5.5, T = 37 °C), 17-25 times the rate for free iron, which we measured to be (110 ± 20) × 10^-3 M^-1s^-1, in agreement with the literature. ^.OH generation measured from fulvic acid-Fe(II) in BALF from 8 individuals with added fulvic acid is successfully predicted rates of ^.OH generation by mixtures of Fe(II), albumin, transferrin, fulvic acid, and ascorbate in saline solution. This indicates that fulvic acid enhances ^.OH formation in BALF, and that albumin and transferrin in BALF moderate the effect. We propose that fulvic acid, and thereby HULIS, is capable of mobilizing Fe(II) away from albumin and transferrin and this increases the formation rate of O₂^.- and ultimately of ^.OH. Furthermore, we find that albumin and transferrin have significantly different impacts on Fe(II)-mediated ^.OH than citrate, a common component of simulated lung fluids, a factor that should be considered carefully in the interpretation of results obtained from solutions containing citrate.

Combined Toxicity of Metal Nanoparticles: Comparison of Individual and Mixture Particles Effect

Toxicity of metal nanoparticles (NPs) are closely associated with increasing intracellular reactive oxygen species (ROS) and the levels of pro-inflammatory mediators. However, NP interactions and surface complexation reactions alter the original toxicity of individual NPs. To date, toxicity studies on NPs have mostly been focused on individual NPs instead of the combination of several species. It is expected that the amount of industrial and highway-acquired NPs released into the environment will further increase in the near future. This raises the possibility that various types of NPs could be found in the same medium, thereby, the adverse effects of each NP either could be potentiated, inhibited or remain unaffected by the presence of the other NPs. After uptake of NPs into the human body from various routes, protein kinases pathways mediate their toxicities. In this context, family of mitogen-activated protein kinases (MAPKs) is mostly efficient. Despite each NP activates almost the same metabolic pathways, the toxicity induced by a single type of NP is different than the case of co-exposure to the combined NPs. The scantiness of toxicological data on NPs combinations displays difficulties to determine, if there is any risk associated with exposure to combined nanomaterials. Currently, in addition to mathematical analysis (Response surface methodology; RSM), the quantitative-structure-activity relationship (QSAR) is used to estimate the toxicity of various metal oxide NPs based on their physicochemical properties and levels applied. In this chapter, it is discussed whether the coexistence of multiple metal NPs alter the original toxicity of individual NP. Additionally, in the part of "Toxicity of diesel emission/exhaust particles (DEP)", the known individual toxicity of metal NPs within the DEP is compared with the data regarding toxicity of total DEP mixture.

Ozone Reacts With Carbon Black to Produce a Fulvic Acid-Like Substance and Increase an Inflammatory Effect

Exposure to ambient ozone has been associated with increased human mortality. Ozone exposure can introduce oxygen-containing functional groups in particulate matter (PM) effecting a greater capacity of the particle for metal complexation and inflammatory effect. We tested the postulate that (1) a fulvic acid-like substance can be produced through a reaction of a carbonaceous particle with high concentrations of ozone and (2) such a fulvic acid-like substance included in the PM can initiate inflammatory effects following exposure of respiratory epithelial (BEAS-2B) cells and an animal model (male Wistar Kyoto rats). Carbon black (CB) was exposed for 72 hours to either filtered air (CB-Air) or approximately 100 ppm ozone (CB-O₃). Carbon black exposure to high levels of ozone produced water-soluble, fluorescent organic material. Iron import by BEAS-2B cells at 4 and 24 hours was not induced by incubations with CB-Air but was increased following coexposures of CB-O₃ with ferric ammonium citrate. In contrast to CB-Air, exposure of BEAS-2B cells and rats to CB-O₃ for 24 hours increased expression of pro-inflammatory cytokines and lung injury, respectively. It is concluded that inflammatory effects of carbonaceous particles on cells can potentially result from (1) an inclusion of a fulvic acid-like substance after reaction with ozone and (2) changes in iron homeostasis following such exposure.

Inorganic particulate matter modulates non-typeable Haemophilus influenzae growth: a link between chronic bacterial infection and geogenic particles

Australian Aboriginal populations have unacceptably high rates of bronchiectasis. This disease burden is associated with high rates of detection of pathogenic bacteria, particularly non-typeable Haemophilus influenzae (NTHi). While there is evidence to suggest that exposure to inorganic particulate matter (PM) is associated with worse respiratory infections, no studies have considered the direct effect of this PM on bacterial growth. Nine clinical isolates of pathogenic NTHi were used for this study. Isolates were exposed to two common iron oxides, haematite (Fe₂O₃) or magnetite (Fe₃O₄), or quartz (SiO₂), as the main constituents of environmental inorganic PM. NTHi isolates were exposed to PM with varying levels of heme to identify whether the response to PM was altered by iron availability. The maximal rate of growth and maximum supported growth were assessed. We observed that inorganic PM was able to modify the maximal growth of selected NTHi isolates. Magnetite and quartz were able to increase maximal growth, while haematite could both increase and suppress the maximal growth. However, these effects varied depending on iron availability and on the bacterial isolate. Our data suggest that inorganic PM may directly alter the growth of pathogenic NTHi. This observation may partly explain the link between exposure to high levels of crustal PM and chronic bacterial infection in Australian Aboriginals.

Molecular and cellular mechanisms linking air pollution and bone damage

Air pollution is the second most important risk factor associated with noncommunicable diseases after smoking. The effects of pollution on health are commonly attributable to particulate matter (PM), a complex mixture of particles suspended in the air. PM can penetrate the lower respiratory tract and has harmful direct and indirect effects on different organs and tissues. Direct effects are caused by the ability of PM components to cross the respiratory membrane and enter the bloodstream; indirect effects are systemic consequences of the local airway response. Recent work suggests that PM is an independent risk factor for low bone mineral density and osteoporosis-related fractures. Osteoporosis is a common age-related disease closely linked to bone fractures, with severe clinical consequences affecting quality of life, morbidity, and mortality. In this review, we discuss potential mechanisms behind the association between outdoor air pollution, especially PM, and bone damage. The discussion features four main mechanisms: 1) several different atmospheric pollutants can induce low-grade systemic inflammation, which affects bone metabolism through a specific effect of cytokines such as TNFα, IL-1β, IL-6, and IL-17 on osteoblast and osteoclast differentiation and function; 2) some pollutants, particularly certain gas and metal compounds, can cause oxidative damage in the airway and bone cells; 3) different groups of pollutants can act as endocrine disruptors when binding to the receptors in bone cells, changing their functioning; and 4) air pollution can directly and indirectly cause vitamin D deficiency. Characterizing these mechanisms will better define the physiopathology of bone damage, and recognizing air pollution as a modifiable risk factor for osteoporosis will inform environmental policies. Such knowledge will also guide the prevention of fractures due to fragility and help reduce health-related costs.

The toxicology of air pollution predicts its epidemiology

The epidemiologic investigation has successively delineated associations of air pollution exposure with non-malignant and malignant lung disease, cardiovascular disease, cerebrovascular disease, pregnancy outcomes, perinatal effects and other extra-pulmonary disease including diabetes. Defining these relationships between air pollution exposure and human health closely parallels results of an earlier epidemiologic investigation into cigarette smoking and environmental tobacco smoke (ETS), two other particle-related exposures. Humic-like substances (HULIS) have been identified as a chemical component common to cigarette smoke and air pollution particles. Toxicology studies provide evidence that a disruption of iron homeostasis with sequestration of host metal by HULIS is a fundamental mechanistic pathway through which biological effects are initiated by cigarette smoke and air pollution particles. As a result of a common chemical component and a shared mechanistic pathway, it should be possible to extrapolate from the epidemiology of cigarette smoking and ETS to predict associations of air pollution exposure with human disease, which are currently unrecognized. Accordingly, it is anticipated that the forthcoming epidemiologic investigation will demonstrate relationships of air pollution with COPD causation, peripheral vascular disease, hypertension, renal disease, digestive disease, loss of bone mass/risk of fractures, dental disease, eye disease, fertility problems, and extrapulmonary malignancies.

Human lung injury following exposure to humic substances and humic-like substances

Among the myriad particles the human respiratory tract is exposed to, a significant number are distinctive in that they include humic substances (HS) and humic-like substances (HULIS) as organic components. HS are heterogeneous, amorphous, organic materials which are ubiquitous occurring in all terrestrial and aqueous environments. HULIS are a complex class of organic, macromolecular compounds initially extracted from atmospheric aerosol particles which share some features with HS including an aromatic, polyacidic nature. As a result of having a variety of oxygen-containing functional groups, both HS and HULIS complex metal cations, especially iron. Following particle uptake by cells resident in the lung, host iron will be sequestered by HS- and HULIS-containing particles initiating pathways of inflammation and subsequent fibrosis. It is proposed that (1) human exposures to HS and HULIS of respirable size (<10 µm diameter) are associated with inflammatory and fibrotic lung disease and (2) following retention of particles which include HS and HULIS, the mechanism of cell and tissue injury involves complexation of host iron. Human inflammatory and fibrotic lung injuries following HS and HULIS exposures may include coal workers' pneumoconiosis, sarcoidosis, and idiopathic pulmonary fibrosis as well as diseases associated with cigarette smoking and exposures to emission and ambient air pollution particles.

Airway surface liquid from smokers promotes bacterial growth and biofilm formation via iron-lactoferrin imbalance

Background

Smoking is a leading cause of respiratory infections worldwide. Tobacco particulate matter disrupts iron homeostasis in the lungs and increases the iron content in the airways of smokers. The airway epithelia secrete lactoferrin to quench iron required for bacteria to proliferate and cause lung infections. We hypothesized that smokers would have increased bacterial growth and biofilm formation via iron lactoferrin imbalance.

Methods

We collected bronchoalveolar lavage (BAL) samples from non-smokers and smokers. We challenged these samples using a standard inoculum of Staphylococcus aureus and Pseudomonas aeruginosa and quantified bacterial growth and biofilm formation. We measured both iron and lactoferrin in the samples. We investigated the effect of supplementing non-smoker BAL with cigarette smoke extract (CSE) or ferric chloride and the effect of supplementing smoker BAL with lactoferrin on bacterial growth and biofilm formation.

Results

BAL from smokers had increased bacterial growth and biofilm formation compared to non-smokers after both S. aureus and P. aeruginosa challenge. In addition, we found that samples from smokers had a higher iron to lactoferrin ratio. Supplementing the BAL of non-smokers with cigarette smoke extract and ferric chloride increased bacterial growth. Conversely, supplementing the BAL of smokers with lactoferrin had a concentration-dependent decrease in bacterial growth and biofilm formation.

Conclusion

Cigarette smoking produces factors which increase bacterial growth and biofilm formation in the BAL. We propose that smoking disrupts the iron-to-lactoferrin in the airways. This finding offers a new avenue for potential therapeutic interventions to prevent respiratory infections in smokers.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0743-x) contains supplementary material, which is available to authorized users.

Urban particulate matter triggers lung inflammation via the ROS-MAPK-NF-κB signaling pathway

Background

Particulate matter (PM) is a high risk factor for various respiratory diseases and triggers an inflammatory response in lung tissues. However, the molecular mechanism of the PM-induced inflammatory response is incompletely understood.

Methods

Human bronchial epithelial cells (HBECs) were treated with the urban PM 1649b for assessment of the inflammatory response. The intracellular level of reactive oxygen species (ROS) was measured by flow cytometry. PM-activated signaling pathways were addressed with specific inhibitors. In vivo, the C57 mice model of PM-induced acute lung inflammation was established with intratracheal instillation of PM for 2 consecutive days. The oxidant stress in lung tissues was assessed with dihydroethidium (DHE) staining, and malondialdehyde (MDA) activity and hydrogen peroxide (H₂O₂) assays. The histopathologic changes in lung tissues and number of inflammatory cells in bronchoalveolar lavage fluid (BALF) were examined. Expression of pro-inflammatory cytokines in BALF was measured by ELISA.

Results

PM increased the expression of interleukin (IL)-1β, IL-6, IL-8, matrix metalloproteinase (MMP)-9 and cyclooxygenase (COX)-2 in a dose-dependent manner. ROS generation and activation of MAPK (ERK, JNK, p38 MAPK) and NF-κB pathways were detected in PM-exposed HBECs. Pretreatment with N-acetylcysteine (NAC) led to the inflammatory response, ROS level and activation of the MAPK and NF-κB pathways to be attenuated. Blockade of ERK, JNK or p38 MAPK pathway with specific inhibitor prevented the release of pro-inflammatory cytokines and activation of the NF-κB pathway. Inhibition of the NF-κB pathway reduced the expression of pro-inflammatory cytokines. In vivo, PM exposure increased oxidant stress in lung tissues, infiltration of inflammatory cells around PM in lung tissues, the number of total cells and inflammatory cells in BALF, and the concentrations of IL-1β, IL-6, IL-8 and MMP-9 in BALF, all of which were reversed partially upon NAC treatment.

Conclusions

PM exposure enhanced the airway inflammatory response significantly through ROS-mediated activation of MAPK (ERK, JNK, p38 MAPK) and downstream NF-κB signaling pathways. Oxidative stress appeared to be the key regulator for PM-induced lung inflammation. These results suggested the molecular mechanism of lung inflammation caused by PM.

Indices of iron homeostasis correlate with airway obstruction in an NHANES III cohort

Cigarette smoking results in the accumulation of iron both systemically and locally, in the lung thereby causing imbalance in iron homeostasis. This disruption in iron homeostasis can be associated with oxidative stress and consequent tissue injury. Therefore, in this study, we tested the association between iron homeostasis and airway obstruction by examining a large cohort of smokers and non-smokers for relationships between 1) serum ferritin and iron concentrations and transferrin saturation and 2) forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁), and their ratio (FEV₁/FVC). Data from the National Health and Examination Survey III were analyzed. The study population included persons aged 20 years and above with their following data recorded: race, gender, serum ferritin and iron concentrations, and transferrin saturation; the final sample number was 7,251. In the total population, Pearson correlation coefficients between 1) serum ferritin and iron concentrations and transferrin saturation and 2) FVC and FEV₁ were significantly positive; whereas those between 1) serum ferritin concentrations and transferrin saturation and 2) FEV₁/FVC were significantly negative. With separate analyses, serum ferritin concentrations demonstrated positive associations with FVC and FEV₁ but an inverse relationship with FEV₁/FVC in smokers and non-smokers. Serum ferritin levels increased with worsening airway obstruction among smokers, and its highest concentrations were found among those with the lowest values of FEV₁/FVC ratio (<60%). Comparable to cigarette smokers, serum ferritin concentrations among non-smokers were greatest in those with the lowest FEV₁/FVC ratio. Furthermore, elevated levels of serum iron and saturation of transferrin also corresponded with decreased FEV₁/FVC ratio among non-smokers. Thus, we conclude that indices of iron homeostasis are associated with airway obstruction in both smokers and non-smokers.