Role of iron and oxidative stress in the exacerbation of allergic inflammation in murine lungs caused by urban particulate matter <2.5 μm and desert dust

The influence of long-range transported Saharan dust on the inflammatory potency of ambient PM2.5 and PM10

Although desert dust promotes morbidity and mortality, it is exempt from regulations. Its health effects have been related to its inflammatory properties, which can vary between source regions. It remains unclear which constituents cause this variability. Moreover, whether long-range transported desert dust potentiates the hazardousness of local particulate matter (PM) is still unresolved. We aimed to assess the influence of long-range transported desert dust on the inflammatory potency of PM2.5 and PM10 collected in Cape Verde and to examine associated constituents. During a reference period and two Saharan dust events, 63 PM2.5 and PM10 samples were collected at four sampling stations. The content of water-soluble ions, elements, and organic and elemental carbon was measured in all samples and endotoxins in PM10 samples. The PM-induced release of inflammatory cytokines from differentiated THP-1 macrophages was evaluated. The association of interleukin (IL)-1β release with PM composition was assessed using principal component (PC) regressions. PM2.5 from both dust events and PM10 from one event caused higher IL-1β release than PM from the reference period. PC regressions indicated an inverse relation of IL-1β release with sea spray ions in both size fractions and organic and elemental carbon in PM2.5. The PC with the higher regression coefficient suggested that iron and manganese may contribute to PM2.5-induced IL-1β release. Only during the reference period, endotoxin content strongly differed between sampling stations and correlated with inflammatory potency. Our results demonstrate that long-range transported desert dust amplifies the hazardousness of local air pollution and suggest that, in PM2.5, iron and manganese may be important. Our data indicate that endotoxins are contained in local and long-range transported PM10 but only explain the variability in inflammatory potency of local PM10. The increasing inflammatory potency of respirable and inhalable PM from desert dust events warrants regulatory measures and risk mitigation strategies.

The involvement of oxidative stress and the TLR4/NF-κB/NLRP3 pathway in acute lung injury induced by high-altitude hypoxia

OBJECTIVE

This study investigated the effect of oxidative stress and the TLR4/NF-κB/NLRP3 pathway on the pathogenesis of acute lung injury (ALI) induced by high-altitude hypoxia.

METHODS

Rats were placed in an animal hyperbaric oxygen chamber to establish a rat model of ALI induced by high-altitude hypoxia after treatment with N-acetylcysteine (NAC; a reactive oxygen species [ROS] inhibitor) or/and MCC950 (an NLPR3 inflammasome inhibitor). After modeling, the wet-to-dry weight ratio (W/D) of rat lung tissues was calculated. In lung tissues, ROS levels were detected with immunofluorescence, the enzyme activity was tested with the kit, and the expression of TLR4/NF-κB/NLRP3 pathway-related genes and proteins was measured with western blotting and qRT-PCR. The levels of inflammatory factors in the serum were quantified with ELISA.

RESULTS

After modeling, rats showed significantly increased W/D, ROS levels, and Malondialdehyde (MDA) concentrations and markedly diminished Superoxide dismutase (SOD) and Glutathione (GSH) concentrations in lung tissues (all P < 0.01), accompanied by substantially enhanced serum levels of TNF-α, IL-6, and IL-1β, significantly reduced serum levels of IL-10, and remarkably augmented TLR4, NLRP3, p-NF-κB p65, NF-κB p65 mRNA, and Caspase-1 expression in lung tissues (all P < 0.01). Furthermore, treatment with NAC or MCC950 alone or in combination prominently lowered the W/D of lung tissues (P < 0.01), serum levels of TNF-α (P < 0.05), IL-6 (P < 0.05), and IL-1β (P < 0.01), and NF-κB p65 expression and phosphorylation (P < 0.05, P < 0.01) while significantly increasing SOD and GSH concentrations (P < 0.05, P < 0.01) and serum levels of IL-10 (P < 0.01) in modeled rats. Meanwhile, treatment of NAC alone or combined with MCC950 significantly reduced MDA concentration and ROS levels (P < 0.05, P < 0.01) in modeled rats, and treatment of MCC950 alone or combined with NAC considerably declined TLR4, NLRP3, and Caspase-1 expression in modeled rats (P < 0.05, P < 0.01).

CONCLUSION

Inhibition of oxidative stress and the TLR4/NF-κB/NLRP3 pathway can ameliorate ALI in rats exposed to high-altitude hypoxia.

Atmospheric fine particulate matter (PM2.5) induces pulmonary fibrosis by regulating different cell fates via autophagy

The presence of respiratory diseases demonstrates a positive correlation with atmospheric fine particulate matter (PM2.5) exposure. The respiratory system is the main target organ affected by PM2.5, and exposure to PM2.5 elevates the likelihood of developing pulmonary fibrosis (PF). In this study, lung epithelial cell (BEAS-2B) and fibroblast (NIH-3T3) were used as in vitro exposure models to explore the mechanisms of PF. PM2.5 exposure caused mitochondrial damage in BEAS-2B cells and increased a fibrotic phenotype in NIH-3T3 cells. Epithelial cells and fibroblasts have different fates after PM2.5 exposure due to their different sensitivities to trigger autophagy. Exposure to PM2.5 inhibits mitophagy in BEAS-2B cells, which hinders the removal of damaged mitochondria and triggers cell death. In this process, the nuclear retention of the mitophagy-related protein Parkin prevents it from being recruited to mitochondria, resulting in mitophagy inhibition. In contrast, fibroblasts exhibit increased levels of autophagy, which may isolate PM2.5 and cause abnormal fibroblast proliferation and migration. Fibrotic phenotypes such as collagen deposition and increased α-actin also appear in fibroblasts. Our results identify PM2.5 as a trigger of PF and delineate the molecular mechanism of autophagy in PM2.5 induced PF, which provides new insights into the pulmonary injury.

Loranthus tanakae Franch. and Sav. Attenuates Respiratory Inflammation Caused by Asian Sand Dust

Asian sand dust (ASD), generally produced in East Asia, including China, Japan, and Korea, directly leads to the development of pulmonary disease and exacerbates underlying pulmonary diseases. Loranthus tanakae Franch. and Sav. is a traditional herbal medicine applied to improve various inflammatory conditions. Here, we evaluated the curative properties of L. tanakae ethanol extract (LTE) against pulmonary inflammation caused by ASD. Additionally, to investigate the mechanism of action of LTE, we performed network pharmacological analysis. ASD was administrated on day 1, 3, and 5 by intranasal instillation, and LTE was orally administered for 6 days. Administration of LTE significantly decreased inflammatory cytokines and the number of inflammatory cells in bronchoalveolar lavage fluid, which was accompanied by a decrease in inflammatory cell accumulation in pulmonary tissue. Administration of LTE decreased the expression of cyclooxygenase2 and matrix metalloproteinase-9 in mice exposed to ASD with the decline in p65 phosphorylation. Additionally, administration of LTE significantly elevated hemeoxygenase (HO)-1 expression in the pulmonary tissue of mice exposed to ASD. These results were consistent with the data of network pharmacological analysis. This experiment showed that LTE attenuated pulmonary inflammation caused by ASD via inhibition of NF-κB and elevation of HO-1. Therefore, LTE may have potential as a therapeutic agent to treat pulmonary inflammation caused by ASD.

Single-cell transcriptomics reveals the pulmonary inflammation induced by inhalation of subway fine particles

People generally take the subway and inevitably inhale the fine particles (PM2.5) on subway platforms. This study revealed whether and how subway PM2.5 causes lung inflammation. Herein, the pulmonary inflammatory response to subway PM2.5 was observed in mice, manifesting as the inflammatory cells infiltration and collagen deposition in tissue, inflammatory cytokine enhancement in bronchoalveolar lavage fluid and Toll-like receptors signal pathway activation in the lungs. Furthermore, single-cell RNA sequencing unearthed subway PM2.5-induced cell-specific responses in the lungs. Twenty immune subsets were identified by the molecular and functional properties. Specific cell populations of CD4+ T and γδ T cells were regarded as the predominant sources of pneumonitis induced by subway PM2.5. Moreover, we demonstrated that the lung inflammatory injury was significantly more attenuated in Rag1-/- mice lacking functional T cells and B cells than that in wild type mice. We proved the slight inflammation of lung tissue in Rag1-/- mice may be dependent on monocytes and neutrophils by activation of the intracellular molecular network. This is the first experimental study on subway PM2.5 causing pulmonary inflammatory damage. It will set an alarm for people who usually travel by subway and efficient measures to reduce PM2.5 should be developed in subway stations.

Dithiothreitol-Measured Oxidative Potential of Reference Materials of Mineral Dust: Implications for the Toxicity of Mineral Dust Aerosols in the Atmosphere

Oxidative stress is a mechanism that might raise the toxicity of mineral dust aerosols. We evaluated the oxidative potential (OP) of four reference materials (RMs) of mineral dusts using dithiothreitol assay. The OP of the water-soluble fraction of the dust RMs accounts for 40%-70% of the OP of the total fraction. The values of total and water-soluble OP normalized by the surface area of insoluble particles showed agreement among the different dust RMs. The surface area of insoluble dust particles was therefore inferred as an important factor affecting the OP of mineral dust. Using the relation between total OP and the surface area of insoluble particles of the dust RMs, we estimated the total OPs of fine and coarse atmospheric mineral dust aerosols assuming a typical particle size distribution of Asian dust aerosols observed in Japan. Mass-normalized total OPs were estimated at 44 and 23 pmol min^-1 μg^-1 for fine and coarse atmospheric mineral dust particles. They closely approximate the values observed for urban aerosols in Japan, which suggests that mineral dust plume advection can lead to a marked increase in human exposure to redox-active aerosols, even far downwind from mineral dust source regions.

Differential Pattern of Cell Death and ROS Production in Human Airway Epithelial Cells Exposed to Quinones Combined with Heated-PM2.5 and/or Asian Sand Dust

The combined toxicological effects of airborne particulate matter (PM), such as PM2.5, and Asian sand dust (ASD), with surrounding chemicals, particularly quinones, on human airway epithelial cells remain underexplored. In this study, we established an in vitro combination exposure model using 1,2-naphthoquinones (NQ) and 9,10-phenanthroquinones (PQ) along with heated PM (h-PM2.5 and h-ASD) to investigate their potential synergistic effects. The impacts of quinones and heated PM on tetrazolium dye (WST-1) reduction, cell death, and cytokine and reactive oxygen species (ROS) production were examined. Results revealed that exposure to 9,10-PQ with h-PM2.5 and/or h-ASD dose-dependently increased WST-1 reduction at 1 μM compared to the corresponding control while markedly decreasing it at 10 μM. Higher early apoptotic, late apoptotic, or necrotic cell numbers were detected in 9,10-PQ + h-PM2.5 exposure than in 9,10-PQ + h-ASD or 9,10-PQ + h-PM2.5 + h-ASD. Additionally, 1,2-NQ + h-PM2.5 exposure also resulted in an increase in cell death compared to 1,2-NQ + h-ASD and 1,2-NQ + h-PM2.5 + h-ASD. Quinones with or without h-PM2.5, h-ASD, or h-PM2.5 + h-ASD significantly increased ROS production, especially with h-PM2.5. Our findings suggest that quinones, at relatively low concentrations, induce cell death synergistically in the presence of h-PM2.5 rather than h-ASD and h-PM2.5 + h-ASD, partially through the induction of apoptosis with increased ROS generation.

Inhalable Saharan dust induces oxidative stress, NLRP3 inflammasome activation, and inflammatory cytokine release

Desert dust is increasingly recognized as a major air pollutant affecting respiratory health. Since desert dust exposure cannot be regulated, the hazardousness of its components must be understood to enable health risk mitigation strategies. Saharan dust (SD) comprises about half of the global desert dust and contains quartz, a toxic mineral dust that is known to cause severe lung diseases via oxidative stress and activation of the NLRP3 inflammasome-interleukin-1β pathway. We aimed to assess the physicochemical and microbial characteristics of SD responsible for toxic effects. Also, we studied the oxidative and pro-inflammatory potential of SD in alveolar epithelial cells and the activation of the NLRP3 inflammasome in macrophage-like cells in comparison to quartz dusts and synthetic amorphous silica (SAS). Characterization revealed that SD contained Fe, Al, trace metals, sulfate, diatomaceous earth, and endotoxin and had the capacity to generate hydroxyl radicals. We exposed A549 lung epithelial cells and wild-type and NLRP3^-/- THP-1 macrophage-like cells to SD, three well-investigated quartz dusts, and SAS. SD induced oxidative stress in A549 cells after 24 h more potently than the quartz dusts. The quartz dusts and SAS upregulated interleukin 8 expression after 4 h and 24 h while SD only caused a transient upregulation. SD, the quartz dusts, and SAS induced interleukin-1β release from wild-type THP-1 cells>20-fold stronger than from NLRP3^-/- THP-1 cells. Interleukin-1β release was lower for SD, in which microbial components including endotoxin were heat-destructed. In conclusion, microbial components in SD are pivotal for its toxicity. In the epithelium, the effects of SD contrasted with crystalline and amorphous silica in terms of potency and persistence. In macrophages, the strong involvement of the NLRP3 inflammasome emphasizes the acute and chronic health risks associated with desert dust exposure.

Identification of differentially expressed genes and pathways in BEAS-2B cells upon long-term exposure to particulate matter (PM2.5) from biomass combustion using bioinformatics analysis

BACKGROUND

Long-term exposure to PM2.5 from burning domestic substances has been linked to an increased risk of lung disease, but the underlying mechanisms are unclear. This study is to explore the hub genes and pathways involved in PM2.5 toxicity in human bronchial epithelial BEAS-2B cells.

METHODS

The GSE158954 dataset is downloaded from the GEO database. Differentially expressed genes (DEGs) were screened using the limma package in RStudio (version 4.2.1). In addition, DEGs analysis was performed by Gene Ontology (GO) functional analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. A protein-protein interaction (PPI) network was constructed, MCODE plug-in and the cytoHubba plug-in in Cytoscape software was used to identify the hub genes. Finally, CytoHubba and DEGs were used to integrate the hub genes, and preliminary validation was performed by comparing the toxicology genomics database (CTD). Differential immune cell infiltration was investigated using the CIBERSORT algorithm.

RESULTS

A total of 135 DEGs were identified, of which 57 were up-regulated and 78 were down-regulated. Functional enrichment analyses in the GO and KEGG indicated the potential involvement of DEGs was mainly enriched in the regulation of endopeptidase activity and influenza A. Gene Set Enrichment Analysis revealed that Chemical Carcinogenesis - DNA adducts were remarkably enriched in PM2.5 groups. 53 nodes and 198 edges composed the PPI network. Besides, 5 direct-acting genes were filtered at the intersection of cytohubba plug-in, MCODE plug-in and CTD database. There is a decreasing trend of dendritic cells resting after BEAS-2B cells long-term exposure to PM2.5.

CONCLUSIONS

The identified DEGs, modules, pathways, and hub genes provide clues and shed light on the potential molecular mechanisms of BEAS-2B cells upon long-term exposure to PM2.5.

Energy metabolism disorders and oxidative stress in the SH-SY5Y cells following PM2.5 air pollution exposure

Studies have shown that PM_2.5 exposure can induce neuronal apoptosis and neurobehavioral changes in animal experiments due partly to the mitochondria-mediated oxidative damage. How does it affect the mitochondrial energy metabolism as well as the neuronal damage, however, remain unclear. This study aimed to investigate the molecular processes of energy metabolism and oxidative damage induced by ambient PM_2.5 exposure in SH-SY5Y cells. SH-SY5Y cells were treated with PM_2.5 to establish a cytotoxicity model. A Seahorse Extracellular Flux Analyzer (XFp) was performed to evaluate the cellular mitochondrial respiratory and glycolysis after exposure to PM_2.5. The dose- and time-dependent effects of PM_2.5 on oxidative damage and apoptosis were analyzed. To further explore the relationship among oxidative damage, energy metabolism and apoptosis, SH-SY5Y cells were co-cultured with BHA and PM_2.5 for 24 h. The results demonstrated that the basic respiration and ATP production, the typical index of mitochondrial respiration as well as glycolysis, significantly reduced in SH-SY5Y cells with dose and time dependent. At the same time, the PM_2.5 could significantly decrease the cell viability and Mn-SOD activity, and increase the ROS levels and apoptosis rate as the escalation of dose and the extension of time. Importantly, the application of BHA could synchronously recover the PM_2.5 induced cell energy metabolism disorder, oxidative damage, and apoptosis. It seems that the abnormal cellular energy metabolism may be caused by oxidative damage following fine particles exposure, and further led to apoptosis.

Anti-Inflammatory Effects of the Iron Chelator, DIBI, in Experimental Acute Lung Injury

Iron plays a critical role in the immune response to inflammation and infection due to its role in the catalysis of reactive oxygen species (ROS) through the Haber-Weiss and Fenton reactions. However, ROS overproduction can be harmful and damage healthy cells. Therefore, iron chelation represents an innovative pharmacological approach to limit excess ROS formation and the related pro-inflammatory mediator cascades. The present study was designed to investigate the impact of the iron chelator, DIBI, in an experimental model of LPS-induced acute lung injury (ALI). DIBI was administered intraperitoneally in the early and later stages of lung inflammation as determined by histopathological evaluation. We found that lung tissues showed significant injury, as well as increased NF-κB p65 activation and significantly elevated levels of various inflammatory mediators (LIX, CXCL2, CCL5, CXCL10, IL-1𝛽, IL-6) 4 h post ALI induction by LPS. Mice treated with DIBI (80 mg/kg) in the early stages (0 to 2 h) after LPS administration demonstrated a significant reduction of the histopathological damage score, reduced levels of NF-κB p65 activation, and reduced levels of inflammatory mediators. Intravital microscopy of the pulmonary microcirculation also showed a reduced number of adhering leukocytes and improved capillary perfusion with DIBI administration. Our findings support the conclusion that the iron chelator, DIBI, has beneficial anti-inflammatory effects in experimental ALI.

Co-exposure of peptidoglycan and heat-inactivated Asian sand dust exacerbates ovalbumin-induced allergic airway inflammation in mice

AIMS

Asian sand dust (ASD) comprises soil particles, microorganisms, and various chemical components. We examined whether peptidoglycan (PGN), a structural cell wall component of Gram-positive bacteria, exacerbates ASD-induced allergic airway inflammation in mice.

METHODS

The ASD (median diameter ∼4 µm) used was a certified reference material from the National Institute for Environmental Studies in Japan, derived from Gobi Desert surface soil collected in 2011. BALB/c mice were intratracheally exposed to PGN, heat-inactivated ASD (H-ASD), and ovalbumin (OVA), individually and in combination. Twenty-four hours after the final intratracheal administration, bronchoalveolar lavage fluid (BALF) and serum samples were collected. Inflammatory cell count, cytokine levels in the BALF, OVA-specific immunoglobulin levels in the serum, and pathological changes in the lungs were analyzed.

RESULTS AND DISCUSSION

After OVA + PGN + H-ASD treatment, the number of eosinophils, neutrophils, and macrophages in the BALF and of eosinophils in the lung tissue was significantly higher than that after OVA + PGN or OVA + H-ASD treatment. Moreover, levels of chemokines and cytokines associated with eosinophil recruitment and activation were significantly higher in the BALF of this group than in that of the OVA + PGN group, and tended to be higher than those in the OVA + H-ASD group. Pathological changes in the lungs were most severe in mice treated with OVA + PGN + H-ASD.

CONCLUSIONS

Our results indicate that PGN is involved in the exacerbation of ASD-induced allergic airway inflammation in mice. Thus, inhalation of ASD containing Gram-positive bacteria may trigger allergic bronchial asthma.

Acute iron oxide nanoparticles exposure induced murine eosinophilic airway inflammation via TLR2 and TLR4 signaling

Iron oxide nanoparticles (Fe₂ O₃ NPs) is the main component of air pollution particles in urban rail transit environment. People are more exposed to Fe₂ O₃ NPs, however, the studies on relationship between Fe₂ O₃ NPs and respiratory health are limited. In the present study, acute airway inflammation caused by Fe₂ O₃ NPs and its possible mechanism were investigated. BALB/c mice were intratracheally challenged with different concentrations of Fe₂ O₃ NPs. Fe₂ O₃ NPs induced bronchial epithelial barrier function damage, infiltration of neutrophils and lymphocytes into the airway submucosa, secretion of mucus in the airway epithelium and elevated expression of eosinophil major basic protein (EMBP) in lungs. Compared with the control group, Fe₂ O₃ NPs increased eosinophils by 20 times in bronchoalveolar lavage fluid (BALF), and markedly increased eosinophils related cytokines and chemokines, including interleukin (IL) -5, IL-33, thymic stromal lymphopoietin (TSLP), monocyte chemotactic protein (MCP)-3, eotaxin, tumor necrosis factor (TNF)-α, keratinocyte chemoattractant (KC). Furthermore, Fe₂ O₃ NPs up-regulated levels of IL-5, MCP-3, eotaxin, and KC in serum. In vitro studies showed that Fe₂ O₃ NPs increased the genes and proteins expression of Toll-like receptors (TLR)-2, TLR4, TNF receptor associated factor 6 (TRAF6), myeloid differentiation factor 88 (MyD88), nuclear factor (NF)-κB, and TNF-α in RAW267.4 cells. The downstream inflammatory cytokine protein expression and release such as TNF-α was significantly decreased after using TLR2/TLR4 inhibitor OxPAPC, but not MyD88 inhibitor ST2825. These results suggest that TLR2 and TLR4 played important role in Fe₂ O₃ NPs inducing acute eosinophilic airway inflammation in the murine lung.

lncRNA AABR07005593.1 potentiates PM2.5-induced interleukin-6 expression by targeting MCCC1

BACKGROUND

Fine particle pollution, specifically pollution by fine particulate matter (PM_2.5), remains a significant concern in developing countries and plays an important role in the development and progression of respiratory diseases. Increasing evidences have demonstrated that long non-coding RNAs (lncRNAs) may act as vital molecules by binding to specific RNA-binding protein (RBP); however, their relationship with PM_2.5 pollution is largely unexplored.

OBJECTIVE

We investigated the association between lncRNA and respiratory system inflammation caused by PM_2.5.

METHODS

PM_2.5 components were detected by gas chromatography-mass spectrometry (GC-MS), inductively coupled plasma-mass spectrometry (ICP-MS), and ionic chromatography. We established an inflammation model of PM_2.5-induced toxicity in vivo (male and female SD rats, 0, 25, 50 and 100 mg/k PM_2.5, 1, 7 and 14 days, single non-invasive tracheal instillation) and in vitro (rat alveolar macrophage cell line (NR8383), 0, 50, 100, 200, 400 μM PM_2.5 for 24, 48, and 72 h). lncRNA high-throughput sequencing (lncRNA-seq) was used to investigate lncRNA profiles in PM_2.5-treated NR8383 cells, and RNA interference (RNAi) was applied to explore the function of the target lncRNA. The mechanisms associated with specific lncRNAs were explored using comprehensive identification of RNA-binding proteins by mass spectrometry (ChIRP-MS) and western blot.

RESULTS

PM_2.5-treated NR8383 cells and SD rats exhibited respiratory inflammation. lncRNA AABR07005593.1 was a pro-inflammatory factor that regulated IL-6 levels. Mechanistically, ChIRP-MS and western blot analyses revealed that highly expressed lncRNA AABR07005593.1 interacted with MCCC1 to involve in the activation of NF-κB pathway, and ultimately promoted the expression of IL-6.

CONCLUSION

This study demonstrated that PM_2.5 induced inflammation in vivo and in vitro. Furthermore, lncRNA AABR07005593.1 bound to MCCC1 to potentiated IL-6 expression. Therefore, lncRNA AABR07005593.1 may act as a potential biomarker for PM_2.5 inflammation.

Mechanisms underlying the health effects of desert sand dust

Desertification and climate change indicate a future expansion of the global area of dry land and an increase in the risk of drought. Humans may therefore be at an ever-increasing risk of frequent exposure to, and resultant adverse health effects of desert sand dust. This review appraises a total of 52 experimental studies that have sought to identify mechanisms and intermediate endpoints underlying epidemiological evidence of an impact of desert dust on cardiovascular and respiratory health. Toxicological studies, in main using doses that reflect or at least approach real world exposures during a dust event, have demonstrated that virgin sand dust particles and dust storm particles sampled at remote locations away from the source induce inflammatory lung injury and aggravate allergen-induced nasal and pulmonary eosinophilia. Effects are orchestrated by cytokines, chemokines and antigen-specific immunoglobulin potentially via toll-like receptor/myeloid differentiation factor signaling pathways. Findings suggest that in addition to involvement of adhered chemical and biological pollutants, mineralogical components may also be implicated in the pathogenesis of human respiratory disorders during a dust event. Whilst comparisons with urban particulate matter less than 2.5 μm in diameter (PM2.5) suggest that allergic inflammatory responses are greater for microbial element-rich dust- PM2.5, aerosols generated during dust events appear to have a lower oxidative potential compared to combustion-generated PM2.5 sampled during non-dust periods. In vitro findings suggest that the significant amounts of suspended desert dust during storm periods may provide a platform to intermix with chemicals on its surfaces, thereby increasing the bioreactivity of PM2.5 during dust storm episodes, and that mineral dust surface reactions are an unrecognized source of toxic organic chemicals in the atmosphere, enhancing toxicity of aerosols in urban environments. In summary, the experimental research on desert dust on respiratory endpoints go some way in clarifying the mechanistic effects of atmospheric desert dust on the upper and lower human respiratory system. In doing so, they provide support for biological plausibility of epidemiological associations between this particulate air pollutant and events including exacerbation of asthma, hospitalization for respiratory infections and seasonal allergic rhinitis.

Combined adjuvant effects of ambient vapor-phase organic components and particulate matter potently promote allergic sensitization and Th2-skewing cytokine and chemokine milieux in mice: The importance of mechanistic multi-pollutant research

Although exposure to ambient particulate matter (PM) is linked to asthma, the health effects of co-existing vapor-phase organic pollutants (vapor) and their combined effects with PM on this disease are poorly understood. We used a murine asthma model to test the hypothesis that exposure to vapor would enhance allergic sensitization and this effect would be further strengthened by co-existing PM. We found that vapor and PM each individually exerted adjuvant effects on OVA sensitization. Co-exposure to vapor and PM during sensitization further enhanced allergic lung inflammation and OVA-specific antibody production which was accompanied by pulmonary cytokine/chemokine milieu that favored T-helper 2 immunity (i.e. increased IL-4, downregulation of Il12a and Ifng, and upregulation of Ccl11 and Ccl8). TNFα, IL-6, Ccl12, Cxcl1 and detoxification/antioxidant enzyme responses in the lung were pollutant-dependent. Inhibition of lipopolysaccharide-induced IL-12 secretion from primary antigen-presenting dendritic cells correlated positively with vapor's oxidant potential. In conclusion, concurrent exposure to vapor and PM led to significantly exaggerated adjuvant effects on allergic lung inflammation which were more potent than that of each pollutant type alone. These findings suggest that the effects of multi-component air pollution on asthma may be significantly underestimated if research only focuses on a single air pollutant (e.g., PM).

Mineral Micronutrients in Asthma

Asthma represents one of the most common medical issues in the modern world. It is a chronic inflammatory disease characterized by persistent inflammation of the airways and disturbances in redox status, leading to hyperresponsiveness of bronchi and airway obstruction. Apart from classical risk factors such as air pollution, family history, allergies, or obesity, disturbances of the levels of micronutrients lead to impairments in the defense mechanisms of the affected organism against oxidative stress and proinflammatory stimuli. In the present review, the impact of micronutrients on the prevalence, severity, and possible risk factors of asthma is discussed. Although the influence of classical micronutrients such as selenium, copper, or zinc are well known, the effects of those such as iodine or manganese are only rarely mentioned. As a consequence, the aim of this paper is to demonstrate how disturbances in the levels of micronutrients and their supplementation might affect the course of asthma.

Protective effects of N-acetylcysteine on a chemical-induced murine model of asthma

INTRODUCTION

Oxidative stress is involved in the pathophysiology of inflammatory airway diseases, including asthma. In this study, we elucidated the possible protective effects of the antioxidant N-acetylcysteine (NAC) on a toluene diisocyanate (TDI)-induced murine asthma model.

METHODS

Male BALB/c mice were sensitized and challenged with TDI to generate a chemical-induced asthma model. NAC was given intraperitoneally to mice immediately after each TDI challenge. Airway reactivity to methacholine and bronchoalveolar lavage fluid was analyzed. Lungs were examined by histology.

RESULTS

NAC treatment dramatically reduced the increased airway hyperresponsiveness, inflammatory infiltration, and goblet cell metaplasia in TDI-exposed mice. Numbers of total cells, neutrophils, and eosinophils in the bronchoalveolar lavage fluid of TDI-challenged mice were significantly higher than vehicle control, but the administration of NAC decreased these inflammatory cell counts. TDI exposure led to significantly increased levels of interleukin 4 (IL-4) and IL-5, which were also suppressed by NAC. In addition, diminished lung reduced oxidized glutathione ratio and superoxide dismutase activity were observed after TDI challenge, and these changes were attenuated by NAC.

CONCLUSION

NAC treatment has beneficial effects in TDI-induced asthma.

Effects of N-acetylcysteine on oxidative stress and inflammation reactions in a rat model of allergic rhinitis after PM2.5 exposure

Particulate matter 2.5 (PM_2.5) exposure can increase the prevalence of allergic rhinitis (AR), the mechanism underlying which may include oxidative stress and inflammatory response. As a ROS quenching agent, N-acetylcysteine (NAC) can attenuate the accumulation of inflammatory cells and hyper-responsiveness in animal asthma models. To explore the effect of NAC on the oxidative stress and inflammatory reactions in AR rats exposed to PM_2.5, we analyzed the components of PM_2.5 and examined the nasal symptoms, redox level in nasal mucosa, Th1/Th2-related serum cytokines, nasal mucosal histopathology and ultrastructure in AR rat models with NAC intervention after PM_2.5 exposure. The results showed that the high concentrations of metal cations and PAHs in PM_2.5 could aggravate Th2-dominant allergic inflammation in AR model and cause redox imbalance, accompanied by nasal epithelial cell stripping and eosinophil infiltration, while NAC intervention could alleviate the clinical symptoms of AR model after PM_2.5 exposure, correct the redox imbalance, reduce the Th2 cytokines, reduce eosinophil infiltration, and promote the moderate regeneration of epithelial cells. The mechanism of NAC reversing PM_2.5-mediated action may be related to its anti-oxidant and anti-inflammatory effects, which may provide some new insights for the prevention of AR exacerbated by exposure to PM_2.5.

Indoor PM2.5, tobacco smoking and chronic lung diseases: A narrative review

The lung is one of the most important organs exposed to environmental agents. People spend approximately 90% of their time indoors, and risks to health may thus be greater from exposure to poor air quality indoors than outdoors. Multiple indoor pollutants have been linked to chronic respiratory diseases. Environmental tobacco smoke (ETS) is known as an important source of multiple pollutants, especially in indoor environments. Indoor PM_2.5 (particulate matter with aerodynamic diameter < 2.5 μm) was reported to be the most reliable marker of the presence of tobacco smoke. Recent studies have demonstrated that PM_2.5 is closely correlated with chronic lung diseases. In this paper, we reviewed the relationship of tobacco smoking and indoor PM_2.5 and the mechanism that underpin the link of tobacco smoke, indoor PM_2.5 and chronic lung diseases.

Current Status and Future Directions of Chronic Cough in China

Chronic cough is one of the most common complaints for which patients in China seek medical attention. However, there are no nationwide data on the prevalence and socioeconomic burden of chronic cough. Although approximately 50% of Chinese men smoke, the vast majority of patients presenting for evaluation of chronic cough are never smokers. An equal sex distribution and a middle-aged predominance have been observed in the Chinese chronic cough population, despite demonstration of a higher cough reflex sensitivity in females and older patients. The role of air pollution in the distinct age and sex distribution requires further study. In terms of the etiologies of chronic cough in China, cough-variant asthma, upper airway cough syndrome, nonasthmatic eosinophilic bronchitis, and atopic cough are the most common causes, comprising 75.2% to 87.6% of cases across different regions. Chinese Guidelines for Diagnosis and Treatment of Cough were initially published in 2005, and updated in 2009 and 2016. In addition, the China Cough Coalition was established in 2016. Great progress has been made in both cough-related clinical practice and research in recent years, however, there are still challenges ahead. To facilitate optimal management of chronic cough in China, efforts promoting the dissemination and application of published guidelines will be essential, especially in community-based healthcare and in rural regions. As chronic refractory cough has been identified as a huge challenge to clinicians worldwide, continued international cooperation will be essential in optimizing evaluation and management of chronic cough.

Co-exposure to lipopolysaccharide and desert dust causes exacerbation of ovalbumin-induced allergic lung inflammation in mice via TLR4/MyD88-dependent and -independent pathways

Background

Lipopolysaccharide (LPS) often presents in high concentrations in particulate matter (PM), few studies have reported the enhancing effects of both LPS and PM on airway inflammation in mice and the role of toll-like receptors (TLRs) in this process. Asian sand dust (ASD) is observed most frequently during the spring. This study aimed to clarify the role of TLRs in murine lung eosinophilia exacerbated by ASD and LPS.

Methods

The effects of LPS and ASD co-treatment on ovalbumin (OVA)-induced lung eosinophilia were investigated using wild-type (WT), TLR2^−/−, TLR4^−/−, and adaptor protein myeloid differentiation factor 88 (MyD88)^−/− BALB/c mice. ASD was heated (H-ASD) to remove the toxic organic substances. WT, TLR2^−/−, TLR4^−/− and MyD88^−/− BALB/c mice were intratracheally instilled with four different combinations of LPS, H-ASD and OVA treatment. Subsequently, the pathological changes in lungs, immune cell profiles in bronchoalveolar lavage fluid (BALF), inflammatory cytokines/chemokines levels in BALF and OVA-specific immunoglobulin (Ig) in serum were analyzed.

Results

In WT mice, H-ASD + LPS exacerbated OVA-induced lung eosinophilia. This combination of treatments increased the proportion of eosinophils and the levels of IL-5, IL-13, eotaxin in BALF, as well as the production of OVA-specific IgE and IgG1 in serum compared to OVA treatment alone. Although these effects were stronger in TLR2^−/− mice than in TLR4^−/− mice, the expression levels of IL-5, IL-13, eotaxin were somewhat increased in TLR4^−/− mice treated with OVA + H-ASD + LPS. In MyD88^−/− mice, this pro-inflammatory mediator-induced airway inflammation was considerably weak and the pathological changes in lungs were negligible.

Conclusions

These results suggest that LPS and H-ASD activate OVA-induced Th2 response in mice, and exacerbate lung eosinophilia via TLR4/MyD88, TLR4/TRIF and other TLR4-independent pathways.