Organic dust induced inflammation--role of atopy and TLR-4 and CD14 gene polymorphisms

Key genes and immune infiltration in chronic spontaneous urticaria: a study of bioinformatics and systems biology

Background

Chronic spontaneous urticaria (CSU) is defined by the spontaneous occurrence of wheals and/or angioedema for >6 weeks. The pathogenesis involves skin mast cells, but the complex causes of their activation remain to be characterized in detail.

Objectives

To explore disease-driving genes and biological pathways in CSU.

Methods

Two microarray data sets, e.g., GSE57178 and GSE72540, with mRNA information of skin from CSU patients, were downloaded from the Gene Expression Omnibus (GEO) database. An integrated bioinformatics pipeline including identification of differentially expressed genes (DEGs), functional enrichment analysis, protein-protein interaction (PPI) network analysis, co-expression and drug prediction analysis, and immune and stromal cells deconvolution analyses were applied to identify hub genes and key drivers of CSU pathogenesis.

Results

In total, we identified 92 up-regulated and 7 down-regulated genes in CSU lesions. These were significantly enriched in CSU-related pathways such as TNF, NF-κB, and JAK-STAT signaling. Based on PPI network modeling, four genes, i.e., IL-6, TLR-4, ICAM-1, and PTGS-2, were computationally identified as key pathogenic players in CSU. Immune infiltration analyses indicated that dendritic cells, Th2 cells, mast cells, megakaryocyte-erythroid progenitor, preadipocytes, and M1 macrophages were increased in lesional CSU skin.

Conclusion

Our results offer new insights on the pathogenesis of CSU and suggest that TNF, NF-κB, JAK-STAT, IL-6, TLR-4, ICAM-1, and PTGS-2 may be candidate targets for novel CSU treatments.

Are In Vitro Cytotoxicity Assessments of Environmental Samples Useful for Characterizing the Risk of Exposure to Multiple Contaminants at the Workplace? A Systematic Review

In some occupational environments risk characterization is challenging or impossible to achieve due to the presence of multiple pollutants and contaminants. Thus, in vitro testing using the most relevant cell lines will provide information concerning health effects due to the co-exposure to multiple stressors. The aim of this review article is to identify studies where the cytotoxicity assessment was performed in environmental samples, as well as to describe the main outputs and challenges regarding risk characterization and management. This study is based on a study of the available information/data on cytotoxicity assessment performed on environmental samples following the PRISMA methodology. Different cell lines were used depending on the environment assessed and exposure routes implicated. The A549 alveolar epithelial cell line was applied in four studies for occupational exposure in the waste sorting industry and for outdoor environments; lymphocytes were used in two studies for occupational and outdoor environments; swine kidney cells were used in three studies performed in the waste industry and hepatocellular/Hep G2 in one study in the waste industry. Cytotoxicity assessments in environmental samples should have a more prominent role due to their contribution for identifying and better understanding the associations between co-exposure to environmental contaminants and adverse human health effects as a prioritization for risk management.

Bioaerosol Exposure and in vitro Activation of Toll-like Receptors in a Norwegian Waste Sorting Plant

Background

The global shift toward greener societies demands new technologies and work operations in the waste-management sector. However, progressive industrial methods do not necessarily consider workers’ health. This study characterized workers' exposure to bioaerosols and investigated the bioaerosols’ potential to engage the immune system in vitro.

Methods

Full shift personal aerosol sampling was conducted over three consecutive days. Dust load was analyzed by gravimetry, fungal and actinobacterial spores were analyzed by scanning electron microscopy, and endotoxin by limulus amebocyte lysate (LAL) assay. In vitro exposure of HEK cells to airborne dust samples was used to investigate the potential of inducing an inflammatory reaction.

Results

The total dust exposure level exceeded the recommended occupational exposure limit (OEL) of 5.0 mg/m³ in 3 out of 15 samples. The inhalable endotoxin level exceeded the recommended exposure level by a 7-fold, whereas the fungal spore level exceeded the recommended exposure level by an 11-fold. Actinobacterial spores were identified in 8 out of 14 samples. In vitro experiments revealed significant TLR2 activation in 9 out of 14 samples vs. significant TLR4 activation in all samples.

Conclusion

The present study showed that the dust samples contained potentially health-impairing endotoxin, fungi, and actinobacterial levels. Furthermore, the sampled dust contained microbial components capable of inducing TLR activation and thus have the potential to evoke an inflammatory response in exposed individuals.

Microcystis bloom containing microcystin-LR induces type 2 diabetes mellitus

Epidemiological data from Lake Taihu showed significantly higher incidences of type 2 diabetes mellitus (T2DM) than in other areas of China. This may be related to the occurrence of a Microcystis bloom in Lake Taihu in the summer and autumn every year. The objective of this study is to investigate whether the contaminated water from the Microcystis bloom and the derivative pollutant microcystin-LR (MC-LR) can explain the higher incidences of T2DM. Healthy male mice were fed with water from different regions of Lake Taihu, and were either acutely or chronically exposed to MC-LR through oral administration or intraperitoneal injection. Serum lipid profiles were determined, and the effects on T2DM-related gene expression and insulin receptor signaling pathway were investigated. Intraperitoneal glucose tolerance (IPGTT) and insulin resistance (IRT) tests were implemented, and the functions of pancreatic islet and β-cell were also evaluated. The results showed that both water sampled from the region with a Microcysis bloom and those containing MC-LR altered the serum glucide and lipid profiles in mice after exposure. The exposure to a Microcysis bloom water affected the expression T2DM-related genes: up-regulated the mRNA levels of FASn, ACACA, G6pc, LPL, and Insig2, and down-regulated the mRNA level of PEPCK and Gsk-3β. Both acute and chronic exposure of MC-LR, even at very low concentrations (1 μg/L), impaired the insulin receptor signalling pathway and induced hyperinsulinemia and insulin resistance in mice. In this study, the most important intracellular target of MC-LR was found to be hetapocellular mitochondria. Thus, exposure to Microcystis bloom water containing microcystin-LR can induce the incidence of T2DM, by impairing the function of mitochondria by microcystin-LR. The study suggests a review of the risk assessment concerning 1 μg/L MC-LR as the reference dose in surface water.

Inflammatory Markers and Genetic Polymorphisms in Workers Exposed to Flour Dust

OBJECTIVE

The aim of this study is to evaluate inflammatory markers and pro-inflammatory CD14 and Toll-like Receptor 4 (TLR4) polymorphisms in workers exposed to flour dust.

METHODS

Polymorphisms in TLR4 and CD14 were identified in our study population of 167 workers that included 63 healthy subjects (HS), 45 atopic subjects (A), and 59 subjects diagnosed clinically with occupational asthma/rhinitis (OAR). Endpoint measures in this study included fractional exhaled nitric oxide and serum concentrations of interleukin IL-6, IL-8, and tumor necrosis factor-alpha (TNF-α).

RESULTS

We identified a polymorphism in CD14 (rs2569190) that may be differentially expressed (P = 0.06). IL-6 concentrations in the serum were significantly higher in the A and OAR groups (P < 0.01) than in subjects in the HS group, while IL-8 concentrations were significantly elevated only in the OAR group (P < 0.01). Interestingly, TNF-α concentrations in the OAR group were significantly reduced when compared with subjects in the HS group (P < 0.01).

CONCLUSION

Cytokines are likely a defensive response in atopic and healthy workers. A protective genotype is hypothesized for occupational asthma.

Systemic and bronchial inflammation following LPS inhalation in asthmatic and healthy subjects

Background: Inhaled endotoxin is known to induce airway inflammation, causing bronchial hyper-reactivity.

Objective: We characterized the response to lipopolysaccharide-inhalation by measuring exhaled nitric oxide (eNO) and inflammatory mediators.

Patients and Methods : A total of 43 adult volunteers (13 asthmatics, 30 healthy controls) inhaled stepwise LPS every 30 min up to a cumulative dose of 100 µg (2.5, 10.5, 42, 45 µg). After each provocation and up to 24 h later, FEV1 was determined; the procedure was stopped when FEV1 declined more than 12.5%. We measured eNO, leucocytes, eosinophils, polymorphonuclear neutrophils (PMNs), C-reactive protein (CrP), lipopolysaccharide binding protein (LBP), eosinophilic cationic protein (ECP), leucotriene B4 (LTB4), thromboxane B2 (TXB2), and body temperature.

Results: Initial eNO values were higher in asthmatics ( P < 0.01), but only increased in an asthmatic subgroup. Marked differences were observed in the systemic response to LPS inhalation. Significant increases were found for CrP, LBP, and PMNs. There was no correlation between FEV1 decrease and basal eNO levels.

Conclusions: Inhalation of endotoxin was followed by clinical and laboratory signs of systemic inflammation, with asthmatics responding to the challenge similar as healthy subjects. Bronchial eNO increased only temporarily in asthmatics.

CD14 tobacco gene-environment interaction in atopic children

Studying gene-environment interactions may elucidate the complex origins of atopic diseases. The aim of this study was to evaluate the association of CD14 polymorphisms and atopy in Egyptian children and to study whether atopy is influenced by CD14 interaction with tobacco smoke exposure. CD14 -159 C/T and CD14 -550 C/T were genotyped in 500 asthmaic children, 150 allergic rhinitis children and 150 controls. We found that CD14 -159T allele, CD14 -550T allele and CD14 -159T/-550T haplotype were significantly associated with atopic asthma and allergic rhinitis groups. CD14 -159 TT and CD14 -550 TT genotypes associated with elevated IgE levels in children exposed to tobacco smoke. The TT genotype of CD14 -159 C/T and CD14 -550 C/T was associated with higher serum levels of sCD14. The present study indicated that CD14 gene polymorphisms may contribute to susceptibility to atopy in Egyptian children and influenced with tobacco smoke exposure.

Increased Nitric Oxide Production Prevents Airway Hyperresponsiveness in Caveolin-1 Deficient Mice Following Endotoxin Exposure

BACKGROUND

Caveolin-1, the hallmark protein of caveolae, is highly expressed within the lung in the epithelium, endothelium, and in immune cells. In addition to its classical roles in cholesterol metabolism and endocytosis, caveolin-1 has also been shown to be important in inflammatory signaling pathways. In particular, caveolin-1 is known to associate with the nitric oxide synthase enzymes, downregulating their activity. Endotoxins, which are are composed mainly of lipopolysaccharide (LPS), are found ubiquitously in the environment and can lead to the development of airway inflammation and increased airway hyperresponsiveness (AHR).

METHODS

We compared the acute responses of wild-type and caveolin-1 deficient mice after LPS aerosol, a well-accepted mode of endotoxin exposure, to investigate the role of caveolin-1 in the development of environmental lung injury.

RESULTS

Although the caveolin-1 deficient mice had greater lung inflammatory indices compared to wild-type mice, they exhibited reduced AHR following LPS exposure. The uncoupling of inflammation and AHR led us to investigate the role of caveolin-1 in the production of nitric oxide, which is known to act as a bronchodilator. The absence of caveolin-1 resulted in increased nitrite levels in the lavage fluid in both sham and LPS treated mice. Additionally, inducible nitric oxide synthase expression was increased in the lung tissue of caveolin-1 deficient mice following LPS exposure and administration of the potent and specific inhibitor 1400W increased AHR to levels comparable to wild-type mice.

CONCLUSIONS

We attribute the relative airway hyporesponsiveness in the caveolin-1 deficient mice after LPS exposure to the specific role of caveolin-1 in mediating nitric oxide production.

sCD14 in bronchoalveolar lavage 18, 42 and 162 hours after segmental allergen provocation

Lipopolysaccharides (LPS) have been associated with a protective role in the development of asthma while higher levels of endotoxin have been linked with more severe asthma. LPS recruit neutrophils and eosinophils and activate macrophages via the CD14 receptor. The soluble CD 14 receptor (sCD14) has been found in bronchoalveolar lavage fluid in different diseases including allergic asthma. To elucidate the kinetics and the regulation of sCD14 concentrations in BAL in asthma, 18 patients with allergic asthma underwent segmental allergen challenge at different time points (10 min, 18, 42 and 162 h). In addition, CD14(+) peripheral blood mononuclear cell (PBMC-CD14(+)) cultures from seven allergic and seven non-allergic subjects were stimulated with LPS, leukotrien D(4) (LTD(4)), a combination of LPS and LTD(4), IL-17 and LTD(4) in presence of the leukotriene-receptor antagonist (LTRA) Montelukast for 6, 12 and 24 h. sCD14 concentrations in BAL and the supernatants were measured by ELISA. sCD14 concentrations in BAL were significantly increased 18 h after allergen challenge and peaked at 42 h. At 162 h, concentrations had returned to baseline levels. In PBMC-CD14(+) cultures, sCD14 levels increased significantly 24 h after stimulation with LTD(4) and Montelukast was able to block LTD(4)-induced stimulation. Allergen challenge leads to a significant increase in sCD14 concentrations in BAL and might modulate the allergen-induced inflammation. In addition, LTD(4) might play a role in the release of sCD14, and it could be speculated that sCD14 reduction by LTRA might contribute to the mechanisms of LTRA in the treatment of allergic asthma.

Occupational exposures and adult asthma

Occupational exposures can cause a new onset of asthma in a subset of susceptible workers on the basis of sensitization to a specific work agent or a high-level irritant exposure. Epidemiologic studies give insight into the natural history of occupational asthma, including host factors and environmental factors leading to the development of occupational asthma, the progression, and the potential role of preventive measures. Work-exacerbated asthma has been a focus of studies only recently but is recognized as common among asthmatic workers and is a potential cause of significant morbidity and socioeconomic impact.