Airborne Asian sand dust enhances murine lung eosinophilia

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.

Saharan dust induces the lung disease-related cytokines granulocyte-macrophage colony-stimulating factor and granulocyte colony-stimulating factor

Desert dust exposure is associated with adverse respiratory health effects. Desert dust is a complex pollutant mixtures that includes respirable crystalline and amorphous particles, metals, and microbial constituents. Given the health effects of desert dust and its heterogeneity, as yet unidentified harmful biological pathways may be triggered. Therefore, we exposed human in vitro air-liquid interface co-cultures of alveolar epithelial A549 cells and THP-1 macrophages to Saharan dust (SD). For comparison, we used the known pulmonary toxicant DQ12 quartz dust. Via RNA sequencing, we identified that SD but not DQ12 increased the gene expression of granulocyte-macrophage colony-stimulating factor (GMCSF) and granulocyte colony-stimulating factor (GCSF). These findings were confirmed by quantitative reverse transcriptase PCR. SD dose-dependently upregulated GMCSF and GCSF expression with significant 7 and 9-fold changes, respectively, at the highest tested concentration of 31 µg/cm2. Furthermore, we observed that SD significantly enhanced the secretion of GM-CSF and G-CSF by 2-fold. Both cytokines have previously been associated with lung diseases such as asthma and fibrosis. Hence, we present two molecular messengers that may contribute to the adverse health effects of desert dust and might serve as drug targets for this globally relevant non-anthropogenic air pollutant.

Saharan dust induces NLRP3-dependent inflammatory cytokines in an alveolar air-liquid interface co-culture model

BACKGROUND

Epidemiological studies have related desert dust events to increased respiratory morbidity and mortality. Although the Sahara is the largest source of desert dust, Saharan dust (SD) has been barely examined in toxicological studies. Here, we aimed to assess the NLRP3 inflammasome-caspase-1-pathway-dependent pro-inflammatory potency of SD in comparison to crystalline silica (DQ12 quartz) in an advanced air-liquid interface (ALI) co-culture model. Therefore, we exposed ALI co-cultures of alveolar epithelial A549 cells and macrophage-like differentiated THP-1 cells to 10, 21, and 31 µg/cm² SD and DQ12 for 24 h using a Vitrocell Cloud system. Additionally, we exposed ALI co-cultures containing caspase (CASP)1-/- and NLRP3-/- THP-1 cells to SD.

RESULTS

Characterization of nebulized DQ12 and SD revealed that over 90% of agglomerates of both dusts were smaller than 2.5 μm. Characterization of the ALI co-culture model revealed that it produced surfactant protein C and that THP-1 cells remained viable at the ALI. Moreover, wild type, CASP1-/-, and NLRP3-/- THP-1 cells had comparable levels of the surface receptors cluster of differentiation 14 (CD14), toll-like receptor 2 (TLR2), and TLR4. Exposing ALI co-cultures to non-cytotoxic doses of DQ12 and SD did not induce oxidative stress marker gene expression. SD but not DQ12 upregulated gene expressions of interleukin 1 Beta (IL1B), IL6, and IL8 as well as releases of IL-1β, IL-6, IL-8, and tumor necrosis factor α (TNFα). Exposing wild type, CASP1-/-, and NLRP3-/- co-cultures to SD induced IL1B gene expression in all co-cultures whereas IL-1β release was only induced in wild type co-cultures. In CASP1-/- and NLRP3-/- co-cultures, IL-6, IL-8, and TNFα releases were also reduced.

CONCLUSIONS

Since surfactants can decrease the toxicity of poorly soluble particles, the higher potency of SD than DQ12 in this surfactant-producing ALI model emphasizes the importance of readily soluble SD components such as microbial compounds. The higher potency of SD than DQ12 also renders SD a potential alternative particulate positive control for studies addressing acute inflammatory effects. The high pro-inflammatory potency depending on NLRP3, CASP-1, and IL-1β suggests that SD causes acute lung injury which may explain desert dust event-related increased respiratory morbidity and mortality.

Classification and sources of extremely severe sandstorms mixed with haze pollution in Beijing

Air quality has significantly improved in China; however, new challenges emerge when dust weather is combined with haze pollution during spring in northern China. On March 15, 2021, an extremely severe sandstorm occurred in Beijing, with hourly maximum PM₁₀ and PM_2.5 concentrations reaching 5267.7 μg m^-3 and 963.9 μg m^-3, respectively. Continuous sandstorm events usually lead to complicated pollution status in spring. Three pollution types were identified disregarding the time sequence throughout March. The secondary formation type was dominant, with high ratios of PM_2.5/PM₁₀ (mean 74%) and PM₁/PM_2.5 (mean 52%). This suggests that secondary transformations are the primary cause of heavy pollution, even during the dry seasons. Sandstorm type resulted in dramatic PM₁₀ levels, with a noticeable decrease in PM_2.5/PM₁₀ levels (27%), although PM_2.5 levels remain high. The transitional pollution type was distinguished by an independent increase in PM₁₀ levels, although PM_2.5 and PM₁ levels differed from the PM₁₀ levels. Throughout March, the sulfur oxidation rate varied considerably, with high levels during most periods (mean 0.52). A strong correlation indicated that relative humidity was the primary variable promoting the formation of secondary sulfate. Sandstorms promote heterogeneous reactions by providing abundant reaction surfaces from mineral particles, therefore aggravating secondary pollution. The sandstorm air mass from the northwest passing through the sand sources of Mongolia carried not only crustal matter but also organic components, such as bioaerosols, resulting in a sharp increase in the organic carbon in PM_2.5.

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.

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.

In vivo immune activation of splenocytes following exposure to tar from Asian sand dust

Air pollution, especially that initiated by particulate matter (PM), has been implicated as a risk factor for several inflammatory diseases. Previously, it was reported that PM enhances immune responses. PM includes the tar fraction that contains polycyclic aromatic hydrocarbons (PAHs), which produce adverse health effects in exposed individuals. However, the influence of the tar fraction (as a component of PM) on splenocytes is not fully understood. The aim of this study was to determine the effects of the tar fraction extracted from PM collected from the atmosphere in Fukuoka, Japan, on mouse splenocytes. ICR mice were administered tar (1 or 5 μg/mouse) intratracheally 4 times at 2-week intervals, and splenocytes from the tar-treated mice were extracted and examined. The parameters determined were proliferation, cytokine concentrations and transcription factors activation. Following tar treatment, splenocyte proliferation increased relative to controls. Concanavalin A (ConA)-induced interleukin (IL)-2 formation and ConA- or lipopolysaccharide (LPS)-induced interferon-γ production were elevated in splenocytes from tar-exposed mice. However, the production of tumor necrosis factor-α and IL-6 induced by LPS was not markedly changed following tar treatment. Further, nuclear factor of activated T cells, but not nuclear factor-κB, was enhanced in splenocytes of tar-exposed mice. Data indicate that tar-activated splenocytes and PM-bound PAHs might contribute to T cell activation in the spleen.

Global nature of airborne particle toxicity and health effects: a focus on megacities, wildfires, dust storms and residential biomass burning

Since air pollutants are difficult and expensive to control, a strong scientific underpinning to policies is needed to guide mitigation aimed at reducing the current burden on public health. Much of the evidence concerning hazard identification and risk quantification related to air pollution comes from epidemiological studies. This must be reinforced with mechanistic confirmation to infer causality. In this review we focus on data generated from four contrasting sources of particulate air pollution that result in high population exposures and thus where there remains an unmet need to protect health: urban air pollution in developing megacities, household biomass combustion, wildfires and desert dust storms. Taking each in turn, appropriate measures to protect populations will involve advocating smart cities and addressing economic and behavioural barriers to sustained adoption of clean stoves and fuels. Like all natural hazards, wildfires and dust storms are a feature of the landscape that cannot be removed. However, many efforts from emission containment (land/fire management practices), exposure avoidance and identifying susceptible populations can be taken to prepare for air pollution episodes and ensure people are out of harm's way when conditions are life-threatening. Communities residing in areas affected by unhealthy concentrations of any airborne particles will benefit from optimum communication via public awareness campaigns, designed to empower people to modify behaviour in a way that improves their health as well as the quality of the air they breathe.

Metagenomic Analysis of Airborne Bacterial Community and Diversity in Seoul, Korea, during December 2014, Asian Dust Event

Asian dust or yellow sand events in East Asia are a major issue of environmental contamination and human health, causing increasing concern. A high amount of dust particles, especially called as particulate matter 10 (PM10), is transported by the wind from the arid and semi-arid tracks to the Korean peninsula, bringing a bacterial population that alters the terrestrial and atmospheric microbial communities. In this study, we aimed to explore the bacterial populations of Asian dust samples collected during November-December 2014. The dust samples were collected using the impinger method, and the hypervariable regions of the 16S rRNA gene were amplified using PCR followed by pyrosequencing. Analysis of the sequencing data were performed using Mothur software. The data showed that the number of operational taxonomic units and diversity index during Asian dust events were higher than those during non-Asian dust events. At the phylum level, the proportions of Proteobacteria, Actinobacteria, and Firmicutes were different between Asian dust and non-Asian dust samples. At the genus level, the proportions of the genus Bacillus (6.9%), Arthrobacter (3.6%), Blastocatella (2%), Planomicrobium (1.4%) were increased during Asian dust compared to those in non-Asian dust samples. This study showed that the significant relationship between bacterial populations of Asian dust samples and non-Asian dust samples in Korea, which could significantly affect the microbial population in the environment.

Alterations in the airborne bacterial community during Asian dust events occurring between February and March 2015 in South Korea

During Asian dust events, a relatively high concentration of particulate matter is transported by wind from arid and semi-arid regions, such as the Gobi and Taklamakan deserts, to nearby countries, including China, Korea, and Japan. The dust particles contain various microorganisms, which can affect human health as well as the environmental microbe population. In the current study, we investigated the characteristics of the airborne bacterial community during Asian dust events between February and March 2015 in South Korea. Bacterial diversity indexes such as operational taxonomic units, Chao1 and Inverse Simpson index were increased, along with total 16S rRNA gene copy number during Asian dust events. The bacterial community structure during Asian dust events was clearly distinguishable from that during non-Asian dust days. The genera Bacillus and Modestobacter were increased 3.9- and 2.7-fold, respectively, while Escherichia-Shigella was decreased by 89.8%. A non-metric multidimensional scaling plot with metadata analysis revealed association of particulate matter concentration, but not temperature, humidity or wind speed, with bacterial community structure, suggesting that the newly transported dust particles contain various microorganisms that influence the airborne bacterial environment.

Co-exposure to zymosan A and heat-inactivated Asian sand dust exacerbates ovalbumin-induced murine lung eosinophilia

Background

Epidemiological studies have implicated Asian sand dust (ASD) in the increased prevalence of respiratory disorders, including asthma. It has been observed that fungal elements such as β-glucan can be adsorbed onto ASD. In the present study, the exacerbating effect of the combined exposure to zymosan A (ZymA) containing yeast β-glucan and heat-inactivated ASD on ovalbumin (OVA)-induced murine lung eosinophilia was investigated.

Methods

BALB/c mice were repeatedly instilled intratracheally with one of eight immunogenic formulations consisting of various combinations of (1) ZymA, (2) ASD that was briefly heated to remove organic substances (H-ASD), and (3) OVA in normal saline, or each of the above alone. Pathologic changes, cytological alterations in bronchoalveolar lavage fluid (BALF), changes in inflammatory cytokines and chemokines in BALF, and OVA-specific IgE and IgG₁ antibodies in serum were investigated.

Results

Exposure to ZymA with or without OVA had no effect on most indicators of lung inflammation. Exposure to H-ASD with OVA increased the recruitment of inflammatory cells to the lungs and the serum levels of OVA-specific IgE and IgG₁. The combination OVA + ZymA + H-ASD induced a marked recruitment of eosinophils and upregulation of T helper 2 (Th2) cytokines (interleukin [IL]-4 and IL-13), IL-6, eotaxin/CCL11, and monocyte chemotactic protein (MCP)-3/CCL7 in BALF and OVA-specific IgE in serum. This treatment also induced the most severe pathological changes in the lungs of mice. ZymA was found to boost the effects of H-ASD, thereby exacerbating the OVA-induced allergic inflammation, even though ZymA alone did not have such effect.

Conclusions

The results suggest that fungal elements such as β-1,3-glucan aggravate the allergic inflammation caused by ASD. Our findings may facilitate prophylaxis of some allergic diseases in Asia.

The Effect of Seasonal Variations in Airborne Particulate Matter on Asthma-Related Airway Inflammation in Mice

This study aimed to investigate the effects of winter and spring particulate matter (PM) on airway inflammation and allergies in a mouse asthma model. PM was collected during 7–28 February 2013 (winter) and during 7–28 April 2013 (spring) in Yonago, Japan. NC/Nga mice were co-sensitized using intranasal instillation of the PMs and Dermatophagoides farinae (Df) for 5 consecutive days, and were subsequently challenged using intranasal Df at 7 days after the last sensitization. At 24 h after the challenge, serum immunoglobulin levels, differential leukocyte counts, and inflammatory cytokines levels were measured in the mice’s bronchoalveolar lavage fluid (BALF). Compared to co-sensitization using spring PM and Df, winter PM and Df induced greater increases in the BALF neutrophil and eosinophil counts and total serum IgE and IgG2a levels. Furthermore, winter PM-sensitized mice exhibited higher BALF levels of interleukin-5, interleukin-13, interleukin-6, and keratinocyte-derived chemokine. Therefore, we observed seasonal variations in the effects of PM on asthma-related airway inflammation. These findings suggest that the compositions of PM vary according to season, and that it is important to evaluate PM compositions in order to understand the associations between asthma and PM.

Exposure to bisphenol A enhanced lung eosinophilia in adult male mice

Background

Bisphenol A (BPA) is useful in many manufacturing processes and is also found in commonly used consumer products. Previous experimental studies have reported that perinatal exposure to BPA promotes the development of allergic lung inflammation in childhood and even into adulthood. In this study, the effects of BPA on allergic lung inflammation in adults were investigated in murine lungs.

Methods

CD-1 mice were orally administrated with 1 mg of BPA/mouse four times at one-week intervals with or without ovalbumin (OVA). The pathologic changes in the airways, cytological alterations in bronchoalveolar lavage fluid (BALF), levels of inflammatory cytokines/chemokines in BALF, and OVA-specific IgE and IgG1 antibodies in serum were measured in the treated CD-1 mice. In vitro study using RAW264.7 cells, which are macrophage-like cells derived from BALB/c male mice, was conducted. The gene expression of cytokines and chemokines were measured.

Results

BPA enhanced eosinophil recruitment induced by OVA in the alveoli and in the submucosa of the airway, which has a goblet cell proliferation in the bronchial epithelium. BPA increased Th2 cytokines-interleukin-13 (IL-13), eosinophil-relevant cytokines and chemokines, such as IL-5, and CCL2 induced by OVA, in BALF. BPA induced adjuvant effects on OVA-specific IgG1 production. In the in vitro study using RAW264.7 cells, BPA increased the mRNA expression of IL-1β, IL-6, CCL2 and CCL3 compared with the control and OVA groups.

Conclusions

These results suggest that (1) the exposure of BPA could synergize with an OVA challenge to aggravate the severity of lung eosinophilia in adult mice, possibly by promoting a Th2-biased immune response and (2) the activation of macrophages and inflammatory cytokines released from these cells by BPA could be participating in this phenomenon.

Desert dust induces TLR signaling to trigger Th2-dominant lung allergic inflammation via a MyD88-dependent signaling pathway

Asian sand dust (ASD) is known to exacerbate asthma, although its mechanism is not yet well understood. In this study, when the effects on inflammatory response by LPS present in ASD was investigated by measuring the gene expression of cytokines and chemokines in RAW264.7 cells treated with ASD and/or polymyxin B (PMB), the ASD effects were attenuated by PMB, but not completely. When an in vitro study was performed using bone marrow-derived macrophages (BMDMs) from WT, TLR2(-/-), TLR4(-/-), and MyD88(-/-) BALB/c mice and BMDMs from WT, TLR2(-/-), TLR4(-/-), TLR2/4(-/-), TLR7/9(-/-), and MyD88(-/-) C57BL/6J mice, cytokine (IL-6, IL-12) production in BMDMs was higher in ASD-stimulated TLR2(-/-) cells than in TLR4(-/-) cells, whereas it was lower or undetectable in TLR2/4(-/-) and MyD88(-/-) cells. These results suggest that ASD causes cytokine production predominantly in a TLR4/MyD88-dependent pathway. When WT and TLRs 2(-/-), 4(-/-), and MyD88(-/-) BALB/c mice were intratracheally challenged with OVA and/or ASD, ASD caused exacerbation of lung eosinophilia along with Th2 cytokine and eosinophil-relevant chemokine production. Serum OVA-specific IgE and IgG1 similar to WT was observed in TLRs 2(-/-), 4(-/-) mice, but not in MyD88(-/-) mice. The Th2 responses in TLR2(-/-) mice were attenuated remarkably by PMB. These results indicate that ASD exacerbates lung eosinophilia in a MyD88-dependent pathway. TLRs 2 and 4 signaling may be important in the increase in lung eosinophilia. Also, the TLR4 ligand LPS and TLR2 ligand like β-glucan may be strong candidates for exacerbation of lung eosinophilia.

Silica-carrying particulate matter enhances Bjerkandera adusta-induced murine lung eosinophilia

Bjerkandera adusta (B. adusta) causes fungus-associated chronic cough. However, the inflammatory response is not yet fully understood. Recently, B. adusta was identified in Asian sand dust (ASD) aerosol. This study investigated the enhancing effects of ASD on B. adusta-induced lung inflammation. B. adusta was inactivated by formalin. ASD was heated to remove toxic organic substances. ICR mice were intratracheally instilled with saline, B. adusta 0.2 µg, or B. adusta 0.8 µg with or without heated ASD 0.1 mg (H-ASD), four times at 2-week intervals. Two in vitro experiments were conducted to investigate any enhancing effects using bone marrow-derived macrophages (BMDM) from Toll-like receptor (TLR) knockout mice and ICR mice. Co-exposure to H-ASD and B. adusta, especially at high doses, caused eosinophil infiltration, proliferation of goblet cells in the airway, and fibrous thickening of the subepithelial layer, and remarkable increases in expression of Th2 cytokines and eosinophil-related cytokine and chemokine expression in bronchoalveolar lavage fluid. In the in vitro study using BMDM from wild-type, TLR2-/-, and TLR4-/- mice, the TLR-signaling pathway for cytokine production caused by B. adusta was predominantly TLR2 rather than TLR4. H-ASD increased the expression of NF-κB and cytokine production by B. adusta in BMDM from ICR mice. The results suggest that co-exposure to H-ASD and B. adusta caused aggravated lung eosinophilia via remarkable increases of pro-inflammatory mediators. The aggravation of inflammation may be related, at least in part, to the activation of the TLR2-NF-κB signaling pathway in antigen presenting cells by H-ASD.

The Role of Toll-Like Receptors and Myeloid Differentiation Factor 88 in Bjerkandera adusta-Induced Lung Inflammation

BACKGROUND

Recently, a cluster of patients with an intractable allergic fungal cough who were characterized by sensitization to Bjerkandera adusta was reported. In the present study, the role of Toll-like receptors and myeloid differentiation factor 88 (MyD88) in B. adusta-induced lung inflammation was investigated.

METHODS

Wild-type (WT), TLR2-/-,TLR4-/-, and MyD88-/- BALB/c mice were intratracheally challenged with B. adusta 4 times at 2-week intervals. Lung pathology, bronchoalveolar lavage fluid (BALF) cytological profiles, and inflammatory mediators in BALF were investigated. Bone marrow-derived macrophages (BMDM) from TLR2-/-,TLR4-/-, TLR2/4-/-, TLR7/9-/-,MyD88-/-, and WT C57BL/6J mice were stimulated with B. adusta for 12 h, and inflammatory mediators in the culture medium were measured.

RESULTS

B. adusta caused lung inflammation along with Th2 cytokine [interleukin (IL)-5 and IL-13] and eosinophil-related chemokine [eotaxin and monocyte chemotactic protein (MCP-3)] production, an increase in eosinophils in BALF, and eosinophil infiltration in the airways in WT and TLR4-/- mice. However, Th2 and eosinophil-related responses in TLR2-/- and MyD88-/- mice were low or undetectable. The induction of neutrophils and IL-6, IL-12, IL-17A, and MCP-1 in the BALF of MyD88-/- mice was attenuated compared to that in WT mice. The induction of IL-6, TNF-α, MCP-1, and macrophage inflammatory protein-1α was reduced or undetectable in B. adusta-stimulated BMDM from TLR7/9-/- and MyD88-/- mice compared to WT mice.

CONCLUSIONS

These results suggest that TLR2 and the adapter protein MyD88 may play an important role in the induction of eosinophils by B. adusta. However, TLR7/9-MyD88 might be important in the induction of neutrophils and the relevant inflammatory mediators, especially IL-17A.

PM2.5-rich dust collected from the air in Fukuoka, Kyushu, Japan, can exacerbate murine lung eosinophilia

PM2.5 can exacerbate asthma. Organic substances adsorbed on PM2.5-rich dust (PM2.5rd) were inactivated by heating at 360 °C. To characterize the role of organic substances, the effects of PM2.5rd and heated PM2.5-rich dust (H-PM2.5 rd) on allergic lung inflammation were investigated. BALB/c mice were intratracheally administered PM2.5rd or H-PM2.5rd with or without ovalbumin (OVA) four times at 2-week intervals. PM2.5rd, but not H-PM2.5rd, caused neutrophilic alveolitis and bronchitis. In the presence of OVA, PM2.5rd caused severe eosinophil infiltration and goblet cells proliferation in airways, along with a marked induction of the Th2 cytokines interleukin (IL)-4 and IL-13, and the eosinophil-related cytokine IL-5 in bronchoalveolar lavage fluid (BALF). OVA + H-PM2.5rd caused a weaker response. PM2.5rd showed adjuvant effects on OVA-specific immunoglobulin E (IgE) and IgG1 production, but H-PM2.5rd showed minimal effects. These findings suggested that PM2.5rd-bound substances might aggravate lung eosinophilia. To clarify the roles of TLR2, TLR4, and MyD88 on cytokine production in PM2.5rd, murine bone marrow-derived macrophages (BMDMs) from wild-type (WT), TLR2(-/-), TLR4(-/-), and MyD88(-/-) BALB/c mice were stimulated with dust. Cytokine production was low or undetectable in TLR4(-/-) cells, but occurred from TLR2(-/-) cells, and production by MyD88(-/-) cells was higher than by TLR4(-/-) cells. These results suggest that TLR4 and TLR2 ligands (LPS and β-glucan, respectively) mainly contributed to cytokines production induced by PM2.5rd. In addition to chemical substances, PM2.5-bound microbial substances might act in inflammatory and allergic lung diseases.

Hemato-biochemical responses to packing in donkeys administered ascorbic acid during the harmattan season

Experiments were performed to investigate the effect of ascorbic acid (AA) in reducing hemato-biochemical changes in pack donkeys during the cold-dry (harmattan) season. Six experimental donkeys administered orally AA (200 mg/kg) and six control donkeys not administered ascorbic acid were subjected to packing. Blood samples were collected from all donkeys for hematological and biochemical analyses. In the control donkeys, packed cell volume (PCV), erythrocyte count and hemoglobin concentration (Hb) decreased significantly (P<0.05) at the end of packing. In the experimental donkeys, there was no significant difference between the pre- and post-packing values of PCV, erythrocyte count and Hb. In the control donkeys, the neutrophil and neutrophil:lymphocyte ratio increased significantly (P<0.05) post packing, but in the experimental donkeys, the pre- and post-packing values were not significantly different. The eosinophil count increased significantly (P<0.05) in experimental and control donkeys post packing. In conclusion, packing exerted significant adverse effects on the hematological parameters ameliorated by AA administration. AA may modulate neutrophilia and induce a considerable alteration of erythroid markers in donkeys subjected to packing during the harmattan season.

Asian sand dust aggregate causes atopic dermatitis-like symptoms in Nc/Nga mice

Background

Asian sand dust (ASD) originates from the arid and semiarid areas of China, and epidemiologic studies have shown that ASD exposure is associated with various allergic and respiratory symptoms. However, few studies have been performed to assess the relationship between skin inflammation and ASD exposure.

Methods

Twelve-week-old NC/Nga mice were divided into 6 groups (n = 8 for each group): hydrophilic petrolatum only (control); hydrophilic petrolatum plus ASD (ASD); hydrophilic petrolatum and heat inactivated-ASD (H-ASD); Dermatophagoides farinae extract (Df); Df and ASD (Df + ASD), and; Df and H-ASD (Df + H-ASD). The NC/Nga mice in each group were subjected to treatment twice a week for 4 weeks. We evaluated skin lesions by symptoms, pathologic changes, and serum IgE levels.

Results

ASD alone did not induce atopic dermatitis (AD)-like skin symptoms. However, Df alone, Df + H-ASD and Df + ASD all induced AD-like symptoms, and dermatitis scores in the group of Df + ASD group were significantly greater than that of the Df group (P = 0.0011 at day 21; and P = 0.017 at day 28). Mean serum IgE was markedly increased in the Df and Df + ASD groups, compared to the ASD and control groups (P < 0.0001), and serum IgE levels in the Df + ASD group were significantly higher compared to the Df group (P = 0.003).

Conclusions

ASD alone did not cause AD-like symptoms in NC/Nga mice. However, AD-like symptoms induced by Df, a major allergen, were enhanced by adding ASD. Although no epidemiological studies have been conducted for the association between ASD and symptoms of dermatitis, our data suggest that it is likely that ASD may contribute to the exacerbation of not only respiratory symptoms, but also skin diseases, in susceptible individuals.

Influence of Asian dust particles on immune adjuvant effects and airway inflammation in asthma model mice

OBJECTIVE

An Asian dust storm (ADS) contains airborne particles that affect conditions such as asthma, but the mechanism of exacerbation is unclear. The objective of this study was to compare immune adjuvant effects and airway inflammation induced by airborne particles collected on ADS days and the original ADS soil (CJ-1 soil) in asthma model mice.

METHODS

Airborne particles were collected on ADS days in western Japan. NC/Nga mice were co-sensitized by intranasal instillation with ADS airborne particles and/or Dermatophagoides farinae (Df), and with CJ-1 soil and/or Df for 5 consecutive days. Df-sensitized mice were stimulated with Df challenge intranasally at 7 days after the last Df sensitization. At 24 hours after challenge, serum allergen specific antibody, differential leukocyte count and inflammatory cytokines in bronchoalveolar lavage fluid (BALF) were measured, and airway inflammation was examined histopathologically.

RESULTS

Co-sensitization with ADS airborne particles and Df increased the neutrophil and eosinophil counts in BALF. Augmentation of airway inflammation was also observed in peribronchiolar and perivascular lung areas. Df-specific serum IgE was significantly elevated by ADS airborne particles, but not by CJ-1 soil. Levels of interleukin (IL)-5, IL-13, IL-6, and macrophage inflammatory protein-2 were higher in BALF in mice treated with ADS airborne particles.

CONCLUSION

These results suggest that substances attached to ADS airborne particles that are not in the original ADS soil may play important roles in immune adjuvant effects and airway inflammation.

Silica and double-stranded RNA synergistically induce bronchial epithelial apoptosis and airway inflammation

Silica crystals (silica), which are the main mineral component of volcanic ash and desert dust, can activate the caspase-1-activating inflammasome in phagocytic cells to secrete IL-1β. Although inhalation of silica-containing dust is known to exacerbate chronic respiratory diseases, probably through inflammasome activation, its direct effects on bronchial epithelial cells remain unclear. Here, we show that silica and double-stranded RNA (dsRNA) synergistically induces caspase-9-dependent apoptosis, but not inflammasome activation, of bronchial epithelial cells. Intranasal administration of silica and dsRNA to mice synergistically enhanced neutrophil infiltration in the airway without IL-1β release in the bronchoalveolar lavage fluid. Histopathological analysis revealed that silica or dsRNA alone induced slight airway inflammation, whereas combined administration significantly enhanced airway inflammation and epithelial damage. These novel findings suggest that inhalation of silica-containing dust may cause inflammasome-independent airway inflammation, possibly by damaging the epithelial barrier, especially at the time of viral infection. These responses may also be involved in acute lung injury caused by inhaled silica-containing dust.

Aggravation of ovalbumin-induced murine asthma by co-exposure to desert-dust and organic chemicals: an animal model study

BACKGROUND

The organic chemicals present in Asian sand dust (ASD) might contribute to the aggravation of lung eosinophila. Therefore, the aggravating effects of the Tar fraction from ASD on ovalbumin (OVA)-induced lung eosinophilia were investigated.

METHODS

The Tar fraction was extracted from ASD collected from the atmosphere in Fukuoka, Japan. ASD collected from the Gobi desert was heated at 360°C to inactivate toxic organic substances (H-ASD). ICR mice were instilled intratracheally with 12 different test samples prepared with Tar (1 μg and 5 μg), H-ASD, and OVA in a normal saline solution containing 0.02% Tween 80. The lung pathology, cytological profiles in the bronchoalveolar lavage fluid (BALF), inflammatory cytokines/chemokines in BALF and OVA-specific immunoglobulin in serum were investigated.

RESULTS

Several kinds of polycyclic aromatic hydrocarbons (PAHs) were detected in the Tar sample. H-ASD + Tar 5 μg induced slight neutrophilic lung inflammation. In the presence of OVA, Tar 5 μg increased the level of eosinophils slightly and induced trace levels of Th2 cytokines IL-5 and IL-13 in BALF. Also mild to moderate goblet cell proliferation and mild infiltration of eosinophils in the submucosa of airway were observed. These pathological changes caused by H-ASD + OVA were relatively small. However, in the presence of OVA and H-ASD, Tar, at as low a level as 1 μg, induced severe eosinophil infiltration and proliferation of goblet cells in the airways and significantly increased Th2 cytokines IL-5 and IL-13 in BALF. The mixture showed an adjuvant effect on OVA-specific IgG1 production.

CONCLUSIONS

These results indicate that H-ASD with even low levels of Tar exacerbates OVA-induced lung eosinophilia via increases of Th2-mediated cytokines. These results suggest that ASD-bound PAHs might contribute to the aggravation of lung eosinophila.

Effect of Asian sand dust on Japanese cedar pollinosis

OBJECTIVE

Asian sand dust (ASD), originating in the deserts of Mongolia and China, spreads over large areas and is associated with adverse effects on human health in East Asia, including asthma, heart disease, and some allergic diseases. However, the effect of ASD on patients with seasonal allergic rhinitis caused by Japanese cedar pollen (SAR-JCP), the most common form of allergic rhinitis, remains unclear. The aim of this study was to investigate the effect of ASD on SAR-JCP patients.

METHODS

A total of 41 patients with SAR-JCP recorded nasal and ocular allergic symptom scores in a diary. We assessed the influence of ASD events on patients with SAR-JCP during the JCP season and before and after the JCP season.

RESULTS

ASD events did not influence nasal and ocular allergy symptoms during the JCP season. Scores for sneezing and runny nose were significantly increased by ASD events in the pre-JCP season. Ocular symptom scores were significantly increased by ASD events in the post-JCP season.

CONCLUSION

Our results suggest that ASD may exacerbate allergy symptoms even before mass scattering of JCP, which usually does not cause allergic symptoms in patients with SAR-JCP. ASD also induced conjunctivitis symptoms after the JCP season. However, we did not observe any adverse effects of ASD on allergic symptoms during the JCP season.

Enhancement of OVA-induced murine lung eosinophilia by co-exposure to contamination levels of LPS in Asian sand dust and heated dust

Background

A previous study has shown that the aggravation of Asian sand dust (ASD) on ovalbumin (OVA)-induced lung eosinphilia was more severe in lipopolysaccharide (LPS)-rich ASD than in SiO₂-rich ASD. Therefore, the effects of different LPS contamination levels in ASD on the aggravation of OVA-induced lung eosinophilia were investigated in the present study.

Methods

Before beginning the in vivo experiment, we investigated whether the ultra-pure LPS would act only on TLR4 or not using bone marrow-derived macrophages (BMDMs) of wild–type, TLR2-/-, TLR4-/- and MyD88-/- BALB/c mice. ASD collected from the desert was heated to remove toxic organic substances (H-ASD). BALB/c mice were instilled intratracheally with 12 different testing samples prepared with LPS (1 ng and 10 ng), H-ASD, and OVA in a normal saline solution. The lung pathology, cytological profiles in the bronchoalveolar lavage fluid (BALF), the levels of inflammatory cytokines/chemokines in BALF and OVA-specific immunoglobulin in serum were investigated.

Results

The LPS exhibited no response to the production of TNF-α and IL-6 in BMDMs from TLR4-/-, but did from TLR2-/-. H-ASD aggravated the LPS-induced neutrophilic lung inflammation. In the presence of OVA, LPS increased the level of eosinophils slightly and induced trace levels of Th2 cytokines IL-5 and IL-13 at the levels of 1 ng and 10 ng. In the presence of OVA and H-ASD, LPS induced severe eosinophil infiltration and proliferation of goblet cells in the airways as well as remarkable increases in Th2 cytokines IL-5 and IL-13 in BALF. The mixture containing LPS (1 ng) showed adjuvant activity on OVA-specific IgE and IgG1 production.

Conclusions

The results suggest that H-ASD with naturally-occurring levels of LPS enhances OVA-induced lung eosinophilia via increases in Th2-mediated cytokines and antigen-specific immunoglobulin. These results indicate that LPS is a strong candidate for being a major aggravating substance in ASD.

Effects of two Asian sand dusts transported from the dust source regions of Inner Mongolia and northeast China on murine lung eosinophilia

The quality and quantity of toxic materials adsorbed onto Asian sand dust (ASD) are different based on dust source regions and passage routes. The aggravating effects of two ASDs (ASD1 and ASD2) transported from the source regions of Inner Mongolia and northeast China on lung eosinophilia were compared to clarify the role of toxic materials in ASD. The ASDs contained different amounts of lipopolysaccharides (LPS) and β-glucan (ASD1<ASD2) and SiO2 (ASD1>ASD2). CD-1 mice were instilled intratracheally with ASD1, ASD2 and/or ovalbumin (OVA) four times at 2-week intervals. ASD1 and ASD2 enhanced eosinophil recruitment induced by OVA in the submucosa of the airway, with goblet cell proliferation in the bronchial epithelium. ASD1 and ASD2 synergistically increased OVA-induced eosinophil-relevant cytokines interleukin-5 (IL-5), IL-13 (ASD1<ASD2) and chemokine eotaxin (ASD1>ASD2) in bronchoalveolar lavage fluid. ASD2 aggravating effects on lung eosinophilia were greater than ASD1. The role of LPS and β-glucan in ASD2 on the production of pro-inflammatory mediators was assessed using in vitro bone marrow-derived macrophages (BMDMs) from wild type, Toll-like receptor 2-deficient (TLR2-/-), TLR4-/-, and MyD88-/- mice (on Balb/c background). ASD2-stimulated TLR2-/- BMDMs enhanced IL-6, IL-12, TNF-α, MCP-1 and MIP-1α secretion compared with ASD2-stimulated TLR4-/- BMDMs. Protein expression from ASD2-stimulated MyD88-/- BMDM were very low or undetectable. The in vitro results indicate that lung eosinophilia caused by ASD is TLR4 dependent. Therefore, the aggravation of OVA-related lung eosinophilia by ASD may be dependent on toxic substances derived from microbes, such as LPS, rather than SiO2.

Induction of immune tolerance and reduction of aggravated lung eosinophilia by co-exposure to Asian sand dust and ovalbumin for 14 weeks in mice

Background

Atmospheric contamination caused by Asian sand-dust (ASD) storms aggravates asthma in both human adults and children. This study aims to investigate a series of manifestations in allergic airway disease caused by co-exposure to allergens and ASD for 6 weeks and 14 weeks.

Methods

CD-1 Mice were instilled intratracheally with 0.1 mg of ASD/mouse four times (6 weeks) or eight times (14 weeks) at 2-week intervals (total dose of 0.4 mg or 0.8 mg/mouse) with or without ovalbumin (OVA). The pathologic changes in the airway, cytological alteration in bronchoalveolar lavage fluid (BALF), and levels of inflammatory cytokines/chemokines in BALF, and OVA-specific IgE and IgG1 antibodies in serum were measured in the treated CD-1 mice.

Results

Four-time co-exposure to OVA and ASD aggravates allergic airway inflammation along with Th2-cytokine IL-13 and eosinophil-relevant cytokine/chemokines IL-5, Eotaxin and MCP-3 in BALF, and fibrous thickening of the subepithelial layer in the airway. On the other hand, eight-time co-exposure attenuates these changes along with a significant increase of TGF-β1 in BALF. Adjuvant effects of ASD toward IgG1 and IgE production in sera were, however, still seen in the eight-time co-exposure.

Conclusions

These results indicate that the immune responses in airways are exacerbated by four-time co-exposure to ASD with OVA, but that there is a shift to suppressive responses in eight-time co-exposure, suggesting that the responses are caused by TGF-β1-related immune tolerance.

Asian dust storm elevates children's respiratory health risks: a spatiotemporal analysis of children's clinic visits across Taipei (Taiwan)

Concerns have been raised about the adverse impact of Asian dust storms (ADS) on human health; however, few studies have examined the effect of these events on children’s health. Using databases from the Taiwan National Health Insurance and Taiwan Environmental Protection Agency, this study investigates the documented daily visits of children to respiratory clinics during and after ADS that occurred from 1997 to 2007 among 12 districts across Taipei City by applying a Bayesian structural additive regressive model controlled for spatial and temporal patterns. This study finds that the significantly impact of elevated children’s respiratory clinic visits happened after ADS. Five of the seven lagged days had increasing percentages of relative rate, which was consecutively elevated from a 2-day to a 5-day lag by 0.63%∼2.19% for preschool children (i.e., 0∼6 years of age) and 0.72%∼3.17% for school children (i.e., 7∼14 years of age). The spatial pattern of clinic visits indicated that geographical heterogeneity was possibly associated with the clinic’s location and accessibility. Moreover, day-of-week effects were elevated on Monday, Friday, and Saturday. We concluded that ADS may significantly increase the risks of respiratory diseases consecutively in the week after exposure, especially in school children.

Asian sand dust enhances allergen-induced th2 allergic inflammatory changes and mucin production in BALB/c mouse lungs

Purpose

Recent studies have reported that Asian sand dust (ASD) has a potential risk of aggravating airway inflammation. The purpose of this study was to investigate the effect of ASD on inflammation and mucin production in the airways of allergic mice.

Methods

Forty BALB/c female mice were divided into four groups: saline (group 1); ASD (group 2); ovalbumin (OVA) alone (group 3); and OVA+ASD (group 4). OVA-specific immunoglobulin E (IgE) in serum and interleukin (IL)-4, IL-5, IL-13, and interferon-gamma (IFN-γ) in bronchoalveolar lavage fluid (BALF) were measured by enzyme-linked immunosorbent assay (ELISA). Hematoxylin & eosin (H&E) and Periodic acid-Schiff (PAS) staining was performed on lung tissues. In addition, immunohistochemical staining for IL-4, IL-5, MUC5AC, and transforming growth factor alpha (TGF-α) was conducted.

Results

Serum IgE levels were significantly higher in group 4 than in group 3 (P<0.05). IL-4 and IL-5 in BALF were significantly higher in group 4 than in group 3 (P<0.05, respectively). Based on H&E staining, inflammatory cell numbers were significantly greater in group 4 than in the other groups (P<0.05). The number of PAS-positive cells was also significantly greater in groups 3 and 4 than in groups 1 and 2 (P<0.05). The numbers of IL-4 and IL-5-positive cells were higher in group 4 than in group 3 (P<0.05). The number of MUC5AC and TGF-α-positive cells were also higher in group 4 than in group 3 (P<0.05).

Conclusions

Our data suggest that ASD increases cytokine expression and mucin production in an allergic murine model. The increased inflammatory reactions were related to cytokine production.

The adverse effects of air pollution on the nervous system

Exposure to ambient air pollution is a serious and common public health concern associated with growing morbidity and mortality worldwide. In the last decades, the adverse effects of air pollution on the pulmonary and cardiovascular systems have been well established in a series of major epidemiological and observational studies. In the recent past, air pollution has also been associated with diseases of the central nervous system (CNS), including stroke, Alzheimer's disease, Parkinson's disease, and neurodevelopmental disorders. It has been demonstrated that various components of air pollution, such as nanosized particles, can easily translocate to the CNS where they can activate innate immune responses. Furthermore, systemic inflammation arising from the pulmonary or cardiovascular system can affect CNS health. Despite intense studies on the health effects of ambient air pollution, the underlying molecular mechanisms of susceptibility and disease remain largely elusive. However, emerging evidence suggests that air pollution-induced neuroinflammation, oxidative stress, microglial activation, cerebrovascular dysfunction, and alterations in the blood-brain barrier contribute to CNS pathology. A better understanding of the mediators and mechanisms will enable the development of new strategies to protect individuals at risk and to reduce detrimental effects of air pollution on the nervous system and mental health.

Transcriptional activation of inflammasome components by Libby amphibole and the role of iron

The induction of the NALP3 inflammasome complex is shown to be necessary for the development of fibrosis after asbestos exposure. Libby amphibole (LA) induces lung inflammation and fibrosis, while complexation of iron (Fe) on fibers inhibits inflammation. In this study we examined the ability of LA to induce the inflammasome cascade and the role of Fe in modulating inflammasome activity. Spontaneously hypertensive rats were exposed intratracheally to either saline (300 μl), deferoxamine (Def) (1 mg), FeCl(3) (21 μg), LA (0.5 mg), Fe-loaded LA (Fe + LA), or LA + Def. Activities of oxidative stress-sensitive enzymes, expression of inflammasome-specific genes, and cytokine proteins in bronchoalveolar lavage fluid were analyzed. Lung enzymes at 4 h and 24 h post-exposure were unchanged. LA increased lung expression of genes including interleukin-1β (IL-1β), cathepsin-B, ASC, NALP3, interleukin (IL)-6 and NFκB. LA+Fe significantly reduced IL-1β and NFκB with a trend of reduction in ASC, NALP3, cathepsin-B and IL-6 expression. Def treatment did not reverse the inhibitory effect of Fe on IL-1β and ASC but reversed IL-6 expression. CCL-7, CCL-12, CXCL-3 and COX-2 were induced by LA while LA+Fe tended to reduce these responses. Phosphorylation of ERK but not MEK was increased at 4 h after LA but not LA+Fe exposure. In conclusion, components of the NALP3 inflammasome are transcriptionally activated acutely during LA-induced inflammation. The key inflammatory regulators IL-1β and NFκB were inhibited in the presence of surface-complexed Fe possibly through decreased ERK signaling upstream of the NALP3 inflammasome. The inflammasome activation by LA may contribute to fibrosis, and Fe may reduce this response and alter compensatory mechanisms in individuals exposed to LA.