Interaction of nano carbon particles and anthracene with pulmonary surfactant: The potential hazards of inhaled nanoparticles

Exposure to O3 and NO2 on the interfacial chemistry of the pulmonary surfactant and the mechanism of lung oxidative damage

Exposure to ozone (O3) and nitrogen dioxide (NO2) are related to pulmonary dysfunctions and various lung diseases, but the underlying biochemical mechanisms remain uncertain. Herein, the effect of inhalable oxidizing gas pollutants on the pulmonary surfactant (PS, extracted from porcine lungs), a mixture of active lipids and proteins that plays an important role in maintaining normal respiratory mechanics, is investigated in terms of the interfacial chemistry using in-vitro experiments; and the oxidative stress induced by oxidizing gases in the simulated lung fluid (SLF) supplemented with the PS is explored. The results showed that O3 and NO2 individually increased the surface tension of the PS and reduced its foaming ability; this was accompanied by the surface pressure-area isotherms of the PS monolayers shifting toward lower molecular areas, with O3 exhibiting more severe effects than NO2. Moreover, both O3 and NO2 produced reactive oxygen species (ROS) resulting in lipid peroxidation and protein damage to the PS. The formation of superoxide radicals (O2•-) was correlated with the decomposition of O3 and the reactions of O3 and NO2 with antioxidants in the SLF. These radicals, in the presence of antioxidants, led to the formation of hydrogen peroxide and hydroxyl radicals (•OH). Additionally, the direct oxidation of unsaturated lipids by O3 and NO2 further caused an increase in the ROS content. This change in the ROS chemistry and increased •OH production tentatively explain how inhalable oxidizing gases lead to oxidative stress and adverse health effects. In summary, our results indicated that inhaled O3 and NO2 exposure can significantly alter the interfacial properties of the PS, oxidize its active ingredients, and induce ROS formation in the SLF. The results of this study provide a basis for the elucidation of the potential hazards of inhaled oxidizing gas pollutants in the human respiratory system.

Interactions between inhalable aged microplastics and lung surfactant: Potential pulmonary health risks

The relationship between microplastics (MPs) and human respiratory health has garnered significant attention since inhalation constitutes the primary pathway for atmospheric MP exposure. While recent studies have revealed respiratory risks associated with MPs, virgin MPs used as plastic surrogates in these experiments did not represent the MPs that occur naturally and that undergo aging effects. Thus, the effects of aged MPs on respiratory health remain unknown. We herein analyzed the interaction between inhalable aged MPs with lung surfactant (LS) extracted from porcine lungs vis-à-vis interfacial chemistry employing in-vitro experiments, and explored oxidative damage induced by aged MPs in simulated lung fluid (SLF) and the underlying mechanisms of action. Our results showed that aged MPs significantly increased the surface tension of the LS, accompanied by a diminution in its foaming ability. The stronger adsorptive capacity of the aged MPs toward the phospholipids of LS appeared to produce increased surface tension, while the change in foaming ability might have resulted from a variation in the protein secondary structure and the adsorption of proteins onto MPs. The adsorption of phospholipid and protein components then led to the aggregation of MPs in SLF, where the aged MPs exhibited smaller hydrodynamic diameters in comparison with the unaged MPs, likely interacting with biomolecules in bodily fluids to exacerbate health hazards. Persistent free radicals were also formed on aged MPs, inducing the formation of reactive oxygen species such as superoxide radicals (O2•-), hydrogen peroxide (HOOH), and hydroxyl radicals (•OH); this would lead to LS lipid peroxidation and protein damage and increase the risk of respiratory disease. Our investigation was the first-ever to reveal a potential toxic effect of aged MPs and their actions on the human respiratory system, of great significance in understanding the risk of inhaled MPs on lung health.

Interactions between CuO NPs and PS: The release of copper ions and oxidative damage

Copper oxide nanoparticles (CuO NPs) can adversely affect lung health possibly by inducing oxidative damage through the release of copper ions. However, the migration and transformation processes of CuO NPs in lung lining fluid is still unclear, and there are still conflicting reports of redox reactions involving copper ions. To address this, we examined the release of copper ions from CuO NPs in simulated lung fluid supplemented with pulmonary surfactant (PS), and further analyzed the mechanisms of PS-CuO NPs interactions and the health hazards. The results showed that the phospholipid of PS was adsorbed on the particle surface, which not only induced aggregation of the particles but also provided a reaction environment for the interaction of PS with CuO NPs. PS was able to promote the release of ions from CuO NPs, of which the protein was a key component. Lipid peroxidation, protein destabilization, and disruption of the interfacial chemistry also occurred in the PS-CuO NPs interactions, during which copper ions were present only as divalent cations. Meanwhile, the contribution of the particle surface cannot be neglected in the oxidative damage to the lung caused by CuO NPs. Through reacting with biomolecules, CuO NPs accomplished ion release and induced oxidative damage associated with PS. This research was the first to reveal the mechanism of CuO NPs releasing copper ions and inducing lipid oxidative damage in the presence of PS, which provides a new idea of transition metal-induced health risk in human body.

The dependence of particle size on cell toxicity for modern mining dust

Progressive massive pulmonary fibrosis among coal miners has unexpectedly increased. It would likely due to the greater generation of smaller rock and coal particles produced by powerful equipment used in modern mines. There is limited understanding of the relationship between micro- or nanoparticles with pulmonary toxicity. This study aims to determine whether the size and chemical characteristics of typical coal-mining dust contribute to cellular toxicity. Size range, surface features, morphology, and elemental composition of coal and rock dust from modern mines were characterized. Human macrophages and bronchial tracheal epithelial cells were exposed to mining dust of three sub- micrometer and micrometer size ranges at varying concentrations, then assessed for cell viability and inflammatory cytokine expression. Coal had smaller hydrodynamic size (180–3000 nm) compared to rock (495–2160 nm) in their separated size fractions, more hydrophobicity, less surface charge, and consisted of more known toxic trace elements (Si, Pt, Fe, Al, Co). Larger particle size had a negative association with in-vitro toxicity in macrophages (p < 0.05). Fine particle fraction, approximately 200 nm for coal and 500 nm for rock particles, explicitly induced stronger inflammatory reactions than their coarser counterparts. Future work will study additional toxicity endpoints to further elucidate the molecular mechanism causing pulmonary toxicity and determine a dose–response curve.

A Deeper Insight into the Interfacial Behavior and Structural Properties of Mixed DPPC/POPC Monolayers: Implications for Respiratory Health

1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl-2-oleyl-sn-glycerol-3-phosphorcholine (POPC) are important components in pulmonary surfactants (PSs), of which the relative content is related to lung compliance. Herein, the phase behavior and thermodynamic structure of mixed DPPC/POPC monolayers were studied to elucidate the intermolecular interaction between DPPC and POPC molecules. Surface pressure-molecular area isotherms demonstrated that POPC significantly affected the phase behavior of the lipid domain structure as a function of its concentration. The compression modulus of the mixed monolayers reduced with the increase in POPC proportion, which can be attributed to the intermolecular repulsion between DPPC and POPC. Brewster angle microscopy analysis showed that the ordered structure of the monolayers trended toward fluidization in the presence of POPC. Raman spectroscopy results revealed that the change in C-C skeleton stretching vibration was the main cause of the decrease in the monolayer packing density. These findings provide new insights into the role of different phospholipid components in the function of PS film at a molecular level, which can help us to understand the synergy effects of the proportional relationship between DPPC and POPC on the formation and progression of lung disease and provide some references for the synthesis of lung surfactants.

Lung surfactant as a biophysical assay for inhalation toxicology

Lung surfactant (LS) is a mixture of lipids and proteins that forms a thin film at the gas-exchange surfaces of the alveoli. The components and ultrastructure of LS contribute to its biophysical and biochemical functions in the respiratory system, most notably the lowering of surface tension to facilitate breathing mechanics. LS inhibition can be caused by metabolic deficiencies or the intrusion of endogenous or exogenous substances. While LS has been sourced from animals or synthesized for clinical therapeutics, the biofluid mixture has also gained recent interest as a biophysical model for inhalation toxicity. Various methods can be used to evaluate LS function quantitatively or qualitatively after exposure to potential toxicants. A narrative review of the recent literature was conducted. Studies focused whether LS was inhibited by various environmental contaminants, nanoparticles, or manufactured products. A review is also conducted on synthetic lung surfactants (SLS), which have emerged as a promising alternative to conventional animal-sourced LS. The intrinsic advantages and recent advances of SLS make a strong case for more widespread usage in LS-based toxicological assays.

Silica nanoparticle exposure inhibits surfactant protein A and B in A549 cells through ROS-mediated JNK/c-Jun signaling pathway

Exposure to silica nanoparticles (SiNPs) is related to the dysregulation of pulmonary surfactant that maintains lung stability and function. Nevertheless, there are limited studies concerning the interaction and influence between SiNPs and pulmonary surfactant, and the damage and mechanism are still unclear. Herein, we used A549 cells to develop an in vitro model, with which we investigated the effect of SiNPs exposure on the expression of pulmonary surfactant and the potential regulatory mechanism. The results showed that SiNPs were of cytotoxicity in regarding of reduced cell viability and promoted the production of excessive reactive oxygen species (ROS). Additionally, the JNK/c-Jun signaling pathway was activated, and the expression of surfactant protein A (SP-A) and surfactant protein B (SP-B) was decreased. After the cells being treated with N-acetyl-L-cysteine (NAC), we found that the ROS content was effectively downregulated, and the expression of proteins related to JNK and c-Jun signaling pathways was suppressed. In contrast, the expression of SP-A and SP-B was enhanced. Furthermore, we treated the cells with JNK inhibitor and c-Jun-siRNA and found that the expression of protein related to JNK and c-Jun signaling pathways, as well as SP-A and SP-B, changed in line with that of NAC treatment. These findings suggest that SiNPs exposure can upregulate ROS and activate the JNK/c-Jun signaling pathway in A549 cells, thereby inhibiting the expression of SP-A and SP-B proteins.

Insights on the Dynamics and Toxicity of Nanoparticles in Environmental Matrices

The manufacturing rate of nanoparticles (10–100 nm) is steadily increasing due to their extensive applications in the fabrication of nanoproducts related to pharmaceuticals, cosmetics, medical devices, paints and pigments, energy storage etc. An increase in research related to nanotechnology is also a cause for the production and disposal of nanomaterials at the lab scale. As a result, contamination of environmental matrices with nanoparticles becomes inevitable, and the understanding of the risk of nanoecotoxicology is getting larger attention. In this context, focusing on the environmental hazards is essential. Hence, this manuscript aims to review the toxic effects of nanoparticles on soil, water, aquatic, and terrestrial organisms. The effects of toxicity on vertebrates, invertebrates, and plants and the source of exposure, environmental and biological dynamics, and the adverse effects of some nanoparticles are discussed.

Evaluating the Impact of Hydrophobic Silicon Dioxide in the Interfacial Properties of Lung Surfactant Films

The interaction of hydrophobic silicon dioxide particles (fumed silicon dioxide), as model air pollutants, and Langmuir monolayers of a porcine lung surfactant extract has been studied in order to try to shed light on the physicochemical bases underlying the potential adverse effects associated with pollutant inhalation. The surface pressure-area isotherms of lung surfactant (LS) films including increasing amounts of particles revealed that particle incorporation into LS monolayers modifies the organization of the molecules at the water/vapor interface, which alters the mechanical resistance of the interfacial films, hindering the ability of LS layers for reducing the surface tension, and reestablishing the interface upon compression. This influences the normal physiological function of LS as is inferred from the analysis of the response of the Langmuir films upon the incorporation of particles against harmonic changes of the interfacial area (successive compression-expansion cycles). These experiments evidenced that particles alter the relaxation mechanisms of LS films, which may be correlated to a modification of the transport of material within the interface and between the interface and the adjacent fluid during the respiratory cycle.

Pulmonary delivery nanomedicines towards circumventing physiological barriers: Strategies and characterization approaches

Pulmonary delivery of nanomedicines is very promising in lung local disease treatments whereas several physiological barriers limit its application via the interaction with inhaled nanomedicines, namely bio-nano interactions. These bio-nano interactions may affect the pulmonary fate of nanomedicines and impede the distribution of nanomedicines in its targeted region, and subsequently undermine the therapeutic efficacy. Pulmonary diseases are under worse scenarios as the altered physiological barriers generally induce stronger bio-nano interactions. To mitigate the bio-nano interactions and regulate the pulmonary fate of nanomedicines, a number of manipulating strategies were established based on size control, surface modification, charge tuning and co-delivery of mucolytic agents. Visualized and non-visualized characterizations can be employed to validate the robustness of the proposed strategies. This review provides a guiding overview of the physiological barriers affecting the in vivo fate of inhaled nanomedicines, the manipulating strategies, and the validation methods, which will assist with the rational design and application of pulmonary nanomedicine.

Inhalation Bioaccessibility of Polycyclic Aromatic Hydrocarbons in PM2.5 under Various Lung Environments: Implications for Air Pollution Control during Coronavirus Disease-19 Outbreak

Global spread of coronavirus disease-19 (COVID-19) is placing an unprecedented pressure on the environment and health. In this study, a new perspective is proposed to assess the inhalation bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) in PM2.5 for people with various lung health conditions. In vitro bioaccessibility (IVBA) was measured using modified epithelial lung fluids simulating the extracellular environment of patients with severe and mild lung inflammation. The average PAH IVBA in PM2.5 of 24.5 ± 4.52% under healthy conditions increased (p = 0.06) to 28.6 ± 3.17% and significantly (p < 0.05) to 32.3 ± 5.32% under mild and severe lung inflammation conditions. A mechanistic study showed that lung inflammation decreased the critical micelle concentrations of main pulmonary surfactants (i.e., from 67.8 (for dipalmitoyl phosphatidylcholine) and 53.3 mg/L (for bovine serum albumin) to 44.5 mg/L) and promoted the formation of micelles, which enhanced the solubilization and competitive desorption of PAHs from PM2.5 in the lung fluids. In addition, risk assessment considering different IVBA values suggested that PAH contamination levels in PM2.5, which were safe for healthy people, may not be acceptable for patients with lung inflammation. Because of the large number of COVID-19 infections, and the fact that some survivors of COVID-19 were observed to still show symptoms of interstitial lung inflammation, the finding here can provide important implications for both the scientific community and policy makers in addressing health risk and air pollution control during the COVID-19 outbreak.

Evaluation of the permeability and potential toxicity of polycyclic aromatic hydrocarbons to pulmonary surfactant membrane by the parallel artificial membrane permeability assay model

Polycyclic aromatic hydrocarbons (PAHs) can penetrate and accumulate in the pulmonary surfactant (PS) membranes, leading to abnormalities of biological macromolecules and the destruction of membrane structure and properties. In the present study, the bioavailability, apparent permeability, effective permeability and residual coefficient of 10 PAHs on PS membrane was assessed by the parallel artificial membrane permeability assay (PAMPA). The influence of various forces on permeability is obtained by analyzing the correlation between parameters and physicochemical properties. Research shows that octanol-water partition coefficient (K_ow) cannot directly predict permeability, and permeability has no significant relationship with polarity. Dispersion, induction, coupling/polarization promote permeation, while hydrogen bonded acid and n-n electron pair inhibit permeation. Further surface pressure-area (π-A) isotherms test and Brewster angle microscope observation manifested that there are huge differences in the transmembrane ability and effects on the membrane of PAHs with different structures. This work has considerable significance that will help to evaluate the bioavailability and human health risk of PAHs.

Fluid Films as Models for Understanding the Impact of Inhaled Particles in Lung Surfactant Layers

Pollution is currently a public health problem associated with different cardiovascular and respiratory diseases. These are commonly originated as a result of the pollutant transport to the alveolar cavity after their inhalation. Once pollutants enter the alveolar cavity, they are deposited on the lung surfactant (LS) film, altering their mechanical performance which increases the respiratory work and can induce a premature alveolar collapse. Furthermore, the interactions of pollutants with LS can induce the formation of an LS corona decorating the pollutant surface, favoring their penetration into the bloodstream and distribution along different organs. Therefore, it is necessary to understand the most fundamental aspects of the interaction of particulate pollutants with LS to mitigate their effects, and design therapeutic strategies. However, the use of animal models is often invasive, and requires a careful examination of different bioethics aspects. This makes it necessary to design in vitro models mimicking some physico-chemical aspects with relevance for LS performance, which can be done by exploiting the tools provided by the science and technology of interfaces to shed light on the most fundamental physico-chemical bases governing the interaction between LS and particulate matter. This review provides an updated perspective of the use of fluid films of LS models for shedding light on the potential impact of particulate matter in the performance of LS film. It should be noted that even though the used model systems cannot account for some physiological aspects, it is expected that the information contained in this review can contribute on the understanding of the potential toxicological effects of air pollution.

Potential hazards associated with interactions between diesel exhaust particulate matter and pulmonary surfactant

Long term exposure to diesel exhaust particulate matter (DEPM) can induce numerous adverse health effects to the respiratory system. Understanding the interaction between DEPM and pulmonary surfactant (PS) can be an essential step toward preliminary evaluation of the impact of DEPM on pulmonary health. Herein, DEPM was explored for its interaction with 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC), the major component of PS. The results indicated that the surface pressure-area (π-A) isotherms of DPPC monolayers shifted toward lower molecular areas and the compression modulus (C_S^-1) reduced in the presence of DEPM. Atomic force microscopy image showed that DEPM can disrupt the ultrastructure of DPPC monolayers along with the direction of lateral compression. In addition, DPPC can in turn condition the surface properties of DEPM, permitting its agglomeration in aqueous media, which was attributed to the adsorption of DEPM to DPPC. Furthermore, the particle-bound polycyclic aromatic hydrocarbons (PAHs) could be desorbed from DEPM by the solubilization of DPPC and it was positively correlated with the hydrophobicity of PAHs. These findings revealed the toxicity of DEPM-associated PAHs and the role of DPPC in facilitating the removal of the inhaled particles, which can provide a new insight into the potential hazards of airborne particles on lung health.

Interactions of model airborne particulate matter with dipalmitoyl phosphatidylcholine and a clinical surfactant Calsurf

HYPOTHESIS

Lung surfactant protects lung tissue and reduces the surface tension in the alveoli during respiration. Particulate matter with an aerodynamic diameter of less than 2.5 μm (PM_2.5), which invades primely through inhalation, can deposit on and interact with the surfactant layer, leading to changes in the biophysical and morphological properties of the lung surfactant.

EXPERIMENTS

Langmuir monolayers of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and clinical surfactant Calsurf were investigated with a PM_2.5 model injected into the water subphase, which were characterized by surface pressure-area isotherms, Brewster angle microscopy, atomic force microscopy, fluorescent microscopy, and x-ray photoelectron spectroscopy. The binding between DPPC/Calsurf and PM_2.5 was studied using isothermal titration calorimetry.

FINDINGS

PM_2.5 induced the expansion of the monolayers at low surface pressure (п) and film condensation at high п. Aggregation of PM_2.5 mainly occurred at the interface of liquid expanded/liquid condensed (LE/LC) phases. PM_2.5 led to slimmer and ramified LC domains on DPPC and the reduction of nano-sized condensed domains on Calsurf. Both DPPC and Calsurf showed fast binding with PM_2.5 through complex binding modes attributed to the heterogeneity and amphiphilic property of PM_2.5. This study improves the fundamental understanding of PM_2.5-lung surfactant interaction and shows useful implications of the toxicity of PM_2.5 through respiration process.

Interfacial interaction between benzo[a]pyrene and pulmonary surfactant: Adverse effects on lung health

Inhaled polycyclic aromatic hydrocarbons (PAHs) can directly interact with the lung surfactant (PS) lining of alveoli, thereby affecting the normal physiological functions of PS, which is a serious threat to lung health. In spite of the extensive study of benzo[a]pyrene (BaP, a representative of PAHs), its potential biophysical influence on the natural PS is still largely unknown. In this study, the interfacial interaction between PS (extracted from porcine lungs) and BaP is investigated in vitro. The results showed that the surface tension, phase behavior, and interfacial structure of the PS monolayers were obviously altered in the presence of BaP. A solubilization test manifested that PS and its major components (dipalmitoyl phosphatidylcholine, DPPC; bovine serum albumin, BSA) could in turn accelerate the dissolution of BaP, which followed the order: PS > DPPC > BSA, and mixed phospholipids were significantly responsible for the solubilization of BaP by PS. In addition, solubilization of BaP also enhanced the consumption of hydroxyl radicals (·OH) in the simulated lung fluid, which could disturb the balance between oxidation and antioxidation.

Interactions of particulate matter and pulmonary surfactant: Implications for human health

Particulate matter (PM), which is the primary contributor to air pollution, has become a pervasive global health threat. When PM enters into a respiratory tract, the first body tissues to be directly exposed are the cells of respiratory tissues and pulmonary surfactant. Pulmonary surfactant is a pivotal component to modulate surface tension of alveoli during respiration. Many studies have proved that PM would interact with pulmonary surfactant to affect the alveolar activity, and meanwhile, pulmonary surfactant would be adsorbed to the surface of PM to change the toxic effect of PM. This review focuses on recent studies of the interactions between micro/nanoparticles (synthesized and environmental particles) and pulmonary surfactant (natural surfactant and its models), as well as the health effects caused by PM through a few significant aspects, such as surface properties of PM, including size, surface charge, hydrophobicity, shape, chemical nature, etc. Moreover, in vitro and in vivo studies have shown that PM leads to oxidative stress, inflammatory response, fibrosis, and cancerization in living bodies. By providing a comprehensive picture of PM-surfactant interaction, this review will benefit both researchers for further studies and policy-makers for setting up more appropriate regulations to reduce the adverse effects of PM on public health.

Strong influence of surfactants on virgin hydrophobic microplastics adsorbing ionic organic pollutants

Microplastic (MP) pollution has become an area of increasing concern because MPs accumulate various types of pollutants. Many previous studies have explored the interactions between MPs and hydrophobic pollutants. However, little research has been conducted on hydrophilic pollutants, which are of much higher concentration and ubiquitous in environment. Surfactants cause hydrophobic MPs to become hydrophilic, which may significantly enhance their capacities to adsorb hydrophilic pollutants. This study explored the influence of co-existing surfactants on the adsorption of ionic organic pollutants by MPs, and found that the presence of an ionic surfactant could significantly enhance the capacity of polyvinyl chloride (PVC, 0.2 mm) MPs to adsorb pollutants with opposite charges. The Langmuir methylene blue adsorption capacity of PVC could be increased from 172 to 4417 ppm in the presence of a sodium dodecyl benzene sulfonate surfactant. Nonionic surfactants impeded the adsorption of both cationic and anionic pollutants due to the steric resistance of the hydrophilic polyethelene glycol chains. The electrostatic interaction mechanism dominated the interfacial behaviors of ionic pollutants on surfactant-adsorbed MP interfaces. The effects of the surfactants were further verified using four different model pollutants and six surfactants. The adsorption capacities of real environmental MPs, including PVC, polyethylene (PE), polypropylene (PP), and polystyrene (PS), increased by three to twenty-six times. The adsorption properties of MPs may be determined by the presence of co-existing surfactants, rather than their polymer species or additives.

Multi-walled carbon nanotubes (MWCNTs) transformed THP-1 macrophages into foam cells: Impact of pulmonary surfactant component dipalmitoylphosphatidylcholine

Pulmonary surfactant or its components can function as barriers toward nanomaterials (NMs) entering pulmonary systems. However, since pulmonary surfactant mainly consists of lipids, it may be necessary to investigate the effects of co-exposure to NMs and pulmonary surfactant or its components on lipid metabolism and related signaling pathways. Recently we found that multi-walled carbon nanotubes (MWCNTs) transformed THP-1 macrophages into lipid-laden foam cells via ER stress pathway. Here this study further investigated the impact of pulmonary surfactant component dipalmitoylphosphatidylcholine (DPPC) on this process. Up to 64 μg/mL hydroxylated or carboxylated MWCNTs induced lipid accumulation and IL-6 release in THP-1 macrophages, accompanying with increased oxidative stress and p-chop proteins (biomarker for ER stress). Incubation with 100 μg/mL DPPC led to MWCNT surface coating but did not significantly alter MWCNT internalization, lipid burden or IL-6 release. However, lipidomics indicated that DPPC altered lipid profliles in MWCNT-exposed cells. DPPC also led to a higher level of de novo lipogenesis regulator FASN in cells exposed to hydroxylated MWCNTs, as well as a higher level of p-chop and scavenger receptor MSR1 in cells exposed to carboxylated MWCNTs. Combined, DPPC did not significantly affect MWCNT-induced lipid accumulation but altered lipid components and ER stress in macrophages.

Transformation pathways and fate of engineered nanoparticles (ENPs) in distinct interactive environmental compartments: A review

The ever increasing production and use of nano-enabled commercial products release the massive amount of engineered nanoparticles (ENPs) in the environment. An increasing number of recent studies have shown the toxic effects of ENPs on different organisms, raising concerns over the nano-pollutants behavior and fate in the various environmental compartments. After the release of ENPs in the environment, ENPs interact with various components of the environment and undergoes dynamic transformation processes. This review focus on ENPs transformations in the various environmental compartments. The transformation processes of ENPs are interrelated to multiple environmental aspects. Physical, chemical and biological processes such as the homo- or hetero-agglomeration, dissolution/sedimentation, adsorption, oxidation, reduction, sulfidation, photochemically and biologically mediated reactions mainly occur in the environment consequently changes the mobility and bioavailability of ENPs. Physico-chemical characteristics of ENPs (particle size, surface area, zeta potential/surface charge, colloidal stability, and core-shell composition) and environmental conditions (pH, ionic strength, organic and inorganic colloids, temperature, etc.) are the most important parameters which regulated the ENPs environmental transformations. Meanwhile, in the environment, organisms encountered multiple transformed ENPs rather than the pristine nanomaterials due to their interactions with various environmental materials and other pollutants. Thus it is the utmost importance to study the behavior of transformed ENPs to understand their environmental fate, bioavailability, and mode of toxicity.

Interaction of industrial smelting soot particles with pulmonary surfactant: Pulmonary toxicity of heavy metal-rich particles

Inhalable particles can influence the interfacial behavior of pulmonary surfactant (PS) resulting in various pulmonary diseases. However, the effects of actually airborne particles on the interfacial behavior of PS and its role in the alteration for soluble metal fraction in particles are entirely unexplored. Herein, we investigated the interaction of PS extracted from porcine lungs with smelting soot fine particles as a model of inhaled heavy metal-rich particles. Our results showed that the phase behavior and foamability of PS were obviously altered in the presence of smelting soot fine particles. In addition, the soluble heavy metals in smelting soot fine particles notably increased in the presence of PS as compared to that of saline solution. Further experiments conducted by adding PS's major components (dipalmitoylphosphatidylcholine, DPPC; bovine serum albumin, BSA) demonstrated that comparison of DPPC, adsorbed BSA is beneficial for the dissolution of heavy metals in smelting soot fine particles. Dynamic light scattering experiments verified that the well dispersion of smelting soot fine particles in the presence of BSA may be responsible for the higher solubility of heavy metals. These findings indicate that PS's interfacial behavior change and PS-enhanced solubilization release of metal components may increase the potentially pulmonary risk in the exposure of airborne fine particles enriched with heavy metals.

Polycyclic aromatic hydrocarbons in soils and sediments in Southwest Nigeria

Polycyclic Aromatic Hydrocarbons are strongly associated with agricultural, residential, transportation, and industrial activities. This study determined by GC-MS the concentration of 15 PAHs in soil and sediments at different sites from the Awotan-Asunle dumpsite area in the Southwestern region of Nigeria, which is one of the largest dumpsites in Africa. The sources of contamination, toxicity and associated risks for human health were also evaluated. Total PAHs concentrations were from 489 to 5616 μg kg^-1, and 642-2159 μg kg^-1, for soil and sediment, respectively. For soils, the highest values were observed for indeno[1,2,3-c,d]pyrene, coronene, and phenanthrene, while for sediments, the most abundant species were pyrene, fluoranthene and phenanthrene. Diagnostic ratios were used to determine the sources of PAHs and suggested that the compounds were mainly emitted from non-traffic sources. The total BaP-TEQ and BaP-MEQ for soils did not exceed the value recommended by the Canadian guideline since the country does not present guidelines. The analysis of incremental lifetime cancer risk was high mostly for dermal and ingestion exposures in the population. This study might provide valuable information regarding exposure to PAHs in soils of a Nigerian community.

Evaluation of in vitro toxicity of silica nanoparticles (NPs) to lung cells: Influence of cell types and pulmonary surfactant component DPPC

Cultured human lung epithelial cells, particularly A549 cells, are commonly used as the in vitro model to evaluate the inhalational toxicity of nanoparticles (NPs). However, A549 cells are cancer cells that might not reflect the response of normal tissues to NP exposure. In addition, the possible influence of pulmonary surfactant also should be considered. This study used silica NPs as model NPs, and evaluated the toxicity of silica NPs to both 16HBE human bronchial epithelial cells and A549 adenocarcinomic cells, with or without the presence of pulmonary surfactant component dipalmitoyl phosphatidylcholine (DPPC). We found that silica NPs induced cytotoxicity at the concentration of 128 μg/mL in 16HBE cells but not A5490 cells, and the cytotoxicity of silica NPs to 16HBE cells was inhibited by DPPC. Intracellular reactive oxygen species (ROS) was only induced in 16HBE cells, accompanying with decreased thiol levels. Moreover, 16HBE cells internalized more silica NPs compared with A549 cells, and the internalization was reduced with the presence of DPPC in both types of cells. The retention of ABC transporter substrate Calcein was only significantly induced by silica NPs at high concentrations in 16HBE cells, and was partially reduced due to the presence of DPPC. In addition, ABC transporter inhibitor MK571 increased the toxicity of silica NPs to both types of cells, with 16HBE cells being more sensitive. Our data revealed that the cell types and pulmonary surfactant components could influence the toxicological consequences of silica NPs to human lung cells. Therefore, it is recommended that in vitro studies should carefully select suitable models to evaluate the inhalational toxicity of NPs.

The Lord of the Lungs: The essential role of pulmonary surfactant upon inhalation of nanoparticles

The rapid development of nanotechnology is opening a huge world of promising possibilities in healthcare, but this is also increasing the necessity to study the potential risk of nanoparticles on public health and the environment. Since the main route for airborne particles to enter into our organism is through the lungs, it has become essential to prove that the nanoparticles generated by human activities do not compromise the respiratory function. This review explains the key role of pulmonary surfactant to sustain the normal function of breathing, as well as the stability and immunity of lungs. Particular emphasis is made on the importance of analysing the features of nanoparticles, defining their interactions with surfactant and unravelling the mutual effects. The implication of the nanoparticle-surfactant interaction on the function and fate of both structures is described, as well as the main in vitro methodologies used to evaluate this interaction. Finally, the incorporation of pulmonary surfactant in appropriate in vitro models is used in order to obtain an extensive understanding of how nanoparticles may act in the context of the lung. The main goal of this review is to offer a general view on inhaled nanoparticles and their effects on the structure and function of lungs derived from their interaction with the pulmonary surfactant system.

Interaction of inhalable volatile organic compounds and pulmonary surfactant: Potential hazards of VOCs exposure to lung

Exposure of volatile organic compounds (VOCs) towards lung leads to pulmonary dysfunctions and various lung diseases. However, the interaction of VOCs with pulmonary surfactant (PS) that directly comes into contact with inhaled VOCs is unknown. Here, simulated PS extracted from porcine lungs (EPS) was used to study the interaction with BTEX (i.e., benzene, toluene, ethylbenzene, and p-xylene) as representatives of VOCs. Surface pressure-area (π-A) isotherms showed that in the presence of individual BTEX, EPS monolayer's phase conversion from gas to liquid expanded phase was dramatically influenced and its collapse pressure decreased greatly compared to those of EPS alone, which was attributed to the alteration of EPS monolayer's microstructure characterized by atomic force microscopy and Brewster angle microscopy. Solubilization experiments manifested that EPS and its major components (dipalmitoyl phosphatidylcholine, DPPC; bovine serum albumin, BSA) exhibited obvious solubilization effects on individual BTEX. The solubilization capacity followed an order: EPS > DPPC > BSA, which was positively correlated with hydrophobicity of individual BTEX. Synergistic solubilization test unveiled that the mixed phospholipid components were largely responsible for the solubilization capacity of EPS. These findings indicate that VOCs exposure may induce potential pulmonary health risk due to the alteration of gas-liquid interfacial properties of PS.

Interaction of pulmonary surfactant with silica and polycyclic aromatic hydrocarbons: Implications for respiratory health

Understanding the interaction between pulmonary surfactant (PS) and inhalable pollutants is vital for risk assessment of respiratory health. Here, PS extracted from porcine lung (EPS) was used to investigate the interaction of PS with nano-silica particles and polycyclic aromatic hydrocarbons (PAHs). Our results demonstrated that silica significantly affected the phase behavior and foaming ability of EPS; EPS and its major components (dipalmitoyl phosphatidylcholine, DPPC; bovine serum albumin, BSA) exhibited great enhancing effect on PAHs solubility, which follows the order: EPS > DPPC > BSA, and it was positively correlated with the hydrophobicity of PAHs. Further experiments demonstrated that mixed phospholipids of EPS were largely responsible for the solubilization of EPS on PAHs. In the presence of EPS, DPPC or BSA, adsorption of PAHs by silica was notably inhibited, indicating competitive adsorption between PAHs and PS components on silica. These findings provide evidence for the surface chemistry by which PS facilitates the solubilization of PAHs and reducing the adsorption of PAHs on silica, which may be helpful for deeply understanding the effects of particulate matter and PAHs on lung health.