Gene Expression Analysis of Murine Lungs Following Pulmonary Exposure to Asian Sand Dust Particles

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.

A review of pulmonary neutrophilia and insights into the key role of neutrophils in particle-induced pathogenesis in the lung from animal studies of lunar dusts and other poorly soluble dust particles

The mechanisms of particle-induced pathogenesis in the lung remain poorly understood. Neutrophilic inflammation and oxidative stress in the lung are hallmarks of toxicity. Some investigators have postulated that oxidative stress from particle surface reactive oxygen species (psROS) on the dust produces the toxicopathology in the lungs of dust-exposed animals. This postulate was tested concurrently with the studies to elucidate the toxicity of lunar dust (LD), which is believed to contain psROS due to high-speed micrometeoroid bombardment that fractured and pulverized lunar surface regolith. Results from studies of rats intratracheally instilled (ITI) with three LDs (prepared from an Apollo-14 lunar regolith), which differed 14-fold in levels of psROS, and two toxicity reference dusts (TiO2 and quartz) indicated that psROS had no significant contribution to the dusts' toxicity in the lung. Reported here are results of further investigations by the LD toxicity study team on the toxicological role of oxidants in alveolar neutrophils that were harvested from rats in the 5-dust ITI study and from rats that were exposed to airborne LD for 4 weeks. The oxidants per neutrophils and all neutrophils increased with dose, exposure time and dust's cytotoxicity. The results suggest that alveolar neutrophils play a critical role in particle-induced injury and toxicity in the lung of dust-exposed animals. Based on these results, we propose an adverse outcome pathway (AOP) for particle-associated lung disease that centers on the crucial role of alveolar neutrophil-derived oxidant species. A critical review of the toxicology literature on particle exposure and lung disease further supports a neutrophil-centric mechanism in the pathogenesis of lung disease and may explain previously reported animal species differences in responses to poorly soluble particles. Key findings from the toxicology literature indicate that (1) after exposures to the same dust at the same amount, rats have more alveolar neutrophils than hamsters; hamsters clear more particles from their lungs, consequently contributing to fewer neutrophils and less severe lung lesions; (2) rats exposed to nano-sized TiO2 have more neutrophils and more severe lesions in their lungs than rats exposed to the same mass-concentration of micron-sized TiO2; nano-sized dust has a greater number of particles and a larger total particle-cell contact surface area than the same mass of micron-sized dust, which triggers more alveolar epithelial cells (AECs) to synthesize and release more cytokines that recruit a greater number of neutrophils leading to more severe lesions. Thus, we postulate that, during chronic dust exposure, particle-inflicted AECs persistently release cytokines, which recruit neutrophils and activate them to produce oxidants resulting in a prolonged continuous source of endogenous oxidative stress that leads to lung toxicity. This neutrophil-driven lung pathogenesis explains why dust exposure induces more severe lesions in rats than hamsters; why, on a mass-dose basis, nano-sized dusts are more toxic than the micron-sized dusts; why lung lesions progress with time; and why dose-response curves of particle toxicity exhibit a hockey stick like shape with a threshold. The neutrophil centric AOP for particle-induced lung disease has implications for risk assessment of human exposures to dust particles and environmental particulate matter.

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.

Microarray Analysis of Gene Expression Alteration in Human Middle Ear Epithelial Cells Induced by Asian Sand Dust

OBJECTIVES

The primary aim of this study is to evaluate the gene expression profile of Asian sand dust (ASD)-treated human middle ear epithelial cell (HMEEC) using microarray analysis.

METHODS

The HMEEC was treated with ASD (400 µg/mL) and total RNA was extracted for microarray analysis. Molecular pathways among differentially expressed genes were further analyzed. For selected genes, the changes in gene expression were confirmed by real-time polymerase chain reaction.

RESULTS

A total of 1,274 genes were differentially expressed by ASD. Among them, 1,138 genes were 2 folds up-regulated, whereas 136 genes were 2 folds down-regulated. Up-regulated genes were mainly involved in cellular processes, including apoptosis, cell differentiation, and cell proliferation. Down-regulated genes affected cellular processes, including apoptosis, cell cycle, cell differentiation, and cell proliferation. The 10 genes including ADM, CCL5, EDN1, EGR1, FOS, GHRL, JUN, SOCS3, TNF, and TNFSF10 were identified as main modulators in up-regulated genes. A total of 11 genes including CSF3, DKK1, FOSL1, FST, TERT, MMP13, PTHLH, SPRY2, TGFBR2, THBS1, and TIMP1 acted as main components of pathway associated with 2-fold down regulated genes.

CONCLUSION

We identified the differentially expressed genes in ASD-treated HMEEC. Our work indicates that air pollutant like ASD, may play an important role in the pathogenesis of otitis media.

The Effect of Therapeutic Blockades of Dust Particles-Induced Ca²⁺ Signaling and Proinflammatory Cytokine IL-8 in Human Bronchial Epithelial Cells

Bronchial epithelial cells are the first barrier of defense against respiratory pathogens. Dust particles as extracellular stimuli are associated with inflammatory reactions after inhalation. It has been reported that dust particles induce intracellular Ca(2+) signal, which subsequently increases cytokines production such as interleukin- (IL-) 8. However, the study of therapeutic blockades of Ca(2+) signaling induced by dust particles in human bronchial epithelial cells is poorly understood. We investigated how to modulate dust particles-induced Ca(2+) signaling and proinflammatory cytokine IL-8 expression. Bronchial epithelial BEAS-2B cells were exposed to PM10 dust particles and subsequent mediated intracellular Ca(2+) signaling and reactive oxygen species signal. Our results show that exposure to several inhibitors of Ca(2+) pathway attenuated the PM10-induced Ca(2+) response and subsequent IL-8 mRNA expression. PM10-mediated Ca(2+) signal and IL-8 expression were attenuated by several pharmacological blockades such as antioxidants, IP3-PLC blockers, and TRPM2 inhibitors. Our results show that blockades of PLC or TRPM2 reduced both of PM10-mediated Ca(2+) signal and IL-8 expression, suggesting that treatment with these blockades should be considered for potential therapeutic trials in pulmonary epithelium for inflammation caused by environmental events such as seasonal dust storm.

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.

Streamer discharge reduces pollen-induced inflammatory responses and injury in human airway epithelial cells

Although epidemiological studies have demonstrated that cedar pollen influences respiratory health, effective method for inactivating cedar pollen has not been established. Streamer discharge is a type of plasma discharge in which high-speed electrons collide with oxygen and nitrogen molecules. It reportedly has the ability to eliminate bacteria, mould, chemical substances and allergens. The present study investigated the influence of pollen on BEAS-2B cell line, derived from human airway epithelial cells, as well as the efficiency of streamer discharge on pollen-induced health effects. Airway epithelial cells were exposed to non-treated pollen and streamer-discharged pollen at doses of 100 and 1000 μg/mL for 6 or 24 h. Non-treated pollen at a dose of 1000 μg/mL significantly decreased cell viability and induced both mRNA and protein expression of interleukin-6, whereas streamer-discharged pollen showed the attenuated changes as compared with non-treated pollen. Further, scanning electron micrographs showed that streamer discharge caused the fine structural changes of pollen. These results provide the first experimental evidence that pollen at a high dose affects cell viability and inflammatory responses, and streamer discharge technology attenuates their influences by decomposing pollen.

Inflammatory and degranulation effect of yellow sand on RBL-2H3 cells in relation to chemical and biological constituents

Recent studie pointed out that allergic diseases have increased during the Asian dust storm event (ADSE) in Japan. Daily observations and the atmospheric concentrations of yellow sand (YS) aerosol have been increasing. In this study, YS samples collected from three sites of Japan during ADSE in 2009-2010 were used. The particles were analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence-energy dispersive spectrometer (XRF-EDS). We investigate ability of YS extract on enhancing the chemical mediator release and cytokine production from rat basophilic leukemia (RBL-2H3) cells. The dust particles at Fukuoka and Tsukuba were abundant in aluminum (Al), iron (Fe), potassium (K) and titan (Ti) than those at Naha. Concentration of the trace endotoxin and Cryptomeria japonica pollen allergen (Cry j 1) were measured in YS extract. After exposure of RBL-2H3 cells to YS extract, the β-hexosaminidase (β-hex) release, tumor necrosis factor-alpha (TNF-α) production were enhanced in RBL-2H3 cells. This process depends on endotoxin, Cry j 1 and other allergen present in the YS extract. YS water extract also show a strong cytotoxic effect on the cells. This data suggest that low levels of endotoxin and Cry j 1 in YS may cause allergy during the ADSE.

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.

Pathological Study of Chronic Pulmonary Toxicity Induced by Intratracheally Instilled Asian Sand Dust (Kosa)

Asian sand dust (ASD) events are associated with an increase in pulmonary morbidity and mortality. The number of ASD events has increased rapidly in the east Asian region since 2000. To study the chronic lung toxicity of ASD, saline suspensions of low doses (200 and 400 µg) and high doses (800 and 3,000 µg) of ASD were intratracheally instilled into ICR mice. Animals were sacrificed at 24 hr, 1 week, or 1, 2, or 3 months after instillation. Histopathological examination revealed that ASD induced acute inflammation at 24 hr after instillation. The acute inflammation was transient and subsided at 1 week and 1 month after instillation. At 2 and 3 months after instillation, focal infiltration of lymphocytes with accumulation of epithelioid macrophages, which is a suggestive finding of transformation to granuloma, and granuloma formation were occasionally observed. Aggregation of macrophages containing particles was observed in the pulmonary lymph nodes at 3 months after instillation in high-dose groups. Prolonged inflammatory foci (granuloma) and presence of ASD particles in pulmonary lymph nodes would have a chance to induce immunological modulation leading to adverse health effects in the exposed animals.

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 acute and long-term effects of Middle East sand particles on the rat airway following a single intratracheal instillation

Military personnel deployed in the Middle East have emphasized concerns regarding high levels of dust generated from blowing desert sand and the movement of troops and equipment. Airborne particulate matter levels (PM(10); PM < 10 μm) in the region may exceed 1500 μg/m(3), significantly higher than the military exposure guideline (MEG) of 50 μg/m(3). Increases in PM(10) have been linked to a rise in incidences of asthma, obstructive pulmonary disease, lung cancer, and cardiovascular diseases. Male Sprague-Dawley rats received a single intratracheal (IT) instillation of 1, 5, or 10 mg of Middle East PM(10) collected at a military occupied site in Kuwait, silica (positive control), or titanium dioxide (TiO(2); negative control) suspended in 400 μl sterile saline, or saline alone (vehicle control). Twenty-four hours, 3 d, 7 d and 6 mo postexposure (n = 15/group), organs including lung were evaluated for histopathological changes and for particle contaminants. Bronchoalveolar fluid (BALF) was also analyzed for cellular and biochemical parameters, including cytokines and chemokines. Instillation of silica resulted in early, pronounced, sustained inflammation indicated by significant increases in levels of total protein and neutrophils, and activities of lactate dehydrogenase activity and β-glucuronidase activity. Lower magnitude and transient changes using the same markers were observed in animals exposed to TiO(2) and Middle East PM(10). The results suggest that for acute exposures, this Middle East PM(10) is a nuisance-type dust with relatively low toxicity. However, since average deployment of military personnel to the Middle East is 180 d with potential for multiple follow-on tours, chronic exposure studies are needed to fully understand the pulmonary effects associated with Middle East PM exposure.

Asian dust storm particles induce a broad toxicological transcriptional program in human epidermal keratinocytes

Exposure to airborne dust particles originated from seasonal Asian dust storms in Chinese and Mongolian deserts results in increased incidence of a range of diseases including asthma, contact dermatitis and conjunctivitis. The areas affected by Asian dust particles extend from East China to the west coast of North America. In order to study toxicological mechanisms in human skin, we evaluated the effects of dust particles collected during Asian dust storms (Asian dust particles) on gene expression in human epidermal keratinocytes (HEK). In HEK, exposure to Asian dust particles significantly increased gene expressions of cytochrome P450 1A1 (CYP1A1), CYP1A2, and CYP1B1, which is an indication of aryl hydrocarbon receptor (AHR) activation. In addition, Asian dust particles increased gene transcription of the cytokines IL-6, IL-8, and GM-CSF, which have broad pro-inflammatory and immunomodulatory properties. Asian dust particles significantly up-regulated expression of caspase 14 in HEK, suggesting that Asian dust particles directly affect keratinocyte differentiation. We also demonstrated that protein extract of pollen, a material frequently adsorbed onto Asian dust particles, potentially contributes to the increased transcription of IL-6, CYP1A1, CYP1A2, and CYP1B1. Taken together, these studies suggest that Asian dust particles can exert toxicological effects on human skin through the activation of the cellular detoxification system, the production of pro-inflammatory and immunomodulatory cytokines, and changes in the expression of proteins essential in normal epidermal differentiation.

Pathological Study of Acute Pulmonary Toxicity Induced by Intratracheally Instilled Asian Sand Dust (Kosa)

The objective of this study was to investigate acute lung toxicity caused by Asian sand dust. Simulated Asian sand dust collected from the Tennger desert in China (CJ-2 particles) and Asian sand dust collected from the atmosphere in Japan (Tottori particles) were used. Saline suspensions of 50, 200, 800, and 3,000 µg Asian sand dust were intratracheally instilled to ICR mice. Localized accumulation of the dust particles was observed in the bronchioles and the alveoli of the lung tissues; acute inflammatory changes characterized by infiltration of macrophages and neutrophils were observed around the particles. Degenerated alveolar walls and bronchial epithelial cells, as well as a weakened positive immunolabeling for laminin, were observed to be associated with particle attachment. Positive immunolabelings for interleukin-6, tumor necrosis factor–α inducible nitric oxide synthase, and dimeric copper- and zinc-containing superoxide dismutase were observed mainly in the inflammatory cells in the lesions; these findings were not observed in the controls or in areas lacking lesions. These results suggest that Asian sand dust particles caused damage to the lung tissue through a direct physical effect. In addition, secondary released cytokines and oxidative stress generated in the lesion may be involved in the development of the acute lung toxicity.

Toxicogenomics: transcription profiling for toxicology assessment

Toxicogenomics, the application of transcription profiling to toxicology, has been widely used for elucidating the molecular and cellular actions of chemicals and other environmental stressors on biological systems, predicting toxicity before any functional damages, and classification of known or new toxicants based on signatures of gene expression. The success of a toxicogenomics study depends upon close collaboration among experts in different fields, including a toxicologist or biologist, a bioinformatician, statistician, physician and, sometimes, mathematician. This review is focused on toxicogenomics studies, including transcription profiling technology, experimental design, significant gene extraction, toxicological results interpretation, potential pathway identification, database input and the applications of toxicogenomics in various fields of toxicological study.