Effects of diesel exhaust particles on human neutrophil activation

Inhibitory effects of modified gamgil-tang in a particulate matter-induced lung injury mouse model

ETHNOPHARMACOLOGICAL RELEVANCE

The modified gamgil-tang (GGX) is a mixture of four herbal medicine including Platycodi Radix, Glycyrrhizae Radix, Lonicerae Flos and Mori Radicis Cortex which has been traditionally used to treat lung and airway diseases to relieve symptoms like sore throat, cough, and sputum in Korea. Its major component chlorogenic acid had been reported to have antioxidant, antibacterial, hepatoprotective, cardioprotective, anti-inflammatory, antiviral, and anti-microbial activity.

AIM OF THE STUDY

To identify the inhibitory effect of GGX in a particulate matter (PM) induced lung injury mouse model.

MATERIALS AND METHODS

We evaluated NO production, the release of TNF-α and IFN-γ in PM-induced MH-S cells, and the number of neutrophils, immune cell subtypes, and the secretion of TNF-α, IL-17, CXCL-1, MIP-2 in the PM-stimulated mouse model to assess the inhibitory effect of GGX against PM. In addition, as exposure to PM increases respiratory symptoms, typically cough and sputum, we attempted to evaluate the antitussive and expectorant activities of GGX.

RESULTS

Our study provided evidence that GGX has inhibitory effects in PM-induced lung injury by inhibiting the increase in neutrophil and inflammatory mediators, deactivating T cells, and ameliorating lung tissue damage. Notably, GGX reduced PM-induced neutrophilic inflammation by attenuating the number of neutrophils and regulating the secretion of neutrophil-related cytokines and chemokines, such as TNF-α, IL-17, MIP2, and CXCL-1. In addition, GGX demonstrated an antitussive activity by significantly reducing citric acid-induced cough frequency and delaying the latent period and expectorant activities by the increased phenol red secretion compared to the control group.

CONCLUSIONS

GGX is expected to be an effective herbal remedy to prevent PM-induced respiratory disease.

Quenching the fires: Pro-resolving mediators, air pollution, and smoking

Exposure to air pollution and other environmental inhalation hazards, such as occupational exposures to dusts and fumes, aeroallergens, and tobacco smoke, is a significant cause of chronic lung inflammation leading to respiratory disease. It is now recognized that resolution of inflammation is an active process controlled by a novel family of small lipid mediators termed "specialized pro-resolving mediators" or SPMs, derived mainly from dietary omega-3 polyunsaturated fatty acids. Chronic inflammation results from an imbalance between pro-inflammatory and pro-resolution pathways. Research is ongoing to develop SPMs, and the pro-resolution pathway more generally, as a novel therapeutic approach to diseases characterized by chronic inflammation. Here, we will review evidence that the resolution pathway is dysregulated in chronic lung inflammatory diseases, and that SPMs and related molecules have exciting therapeutic potential to reverse or prevent chronic lung inflammation, with a focus on lung inflammation due to inhalation of environmental hazards including urban particulate matter, organic dusts and tobacco smoke.

Morphometric analysis of inflammation in bronchial biopsies following exposure to inhaled diesel exhaust and allergen challenge in atopic subjects

Background

Allergen exposure and air pollution are two risk factors for asthma development and airway inflammation that have been examined extensively in isolation. The impact of combined allergen and diesel exhaust exposure has received considerably less attention. Diesel exhaust (DE) is a major contributor to ambient particulate matter (PM) air pollution, which can act as an adjuvant to immune responses and augment allergic inflammation. We aimed to clarify whether DE increases allergen-induced inflammation and cellular immune response in the airways of atopic human subjects.

Methods

Twelve atopic subjects were exposed to DE 300 μg.m⁻³ or filtered air for 2 h in a blinded crossover study design with a four-week washout period between arms. One hour following either filtered air or DE exposure, subjects were exposed to allergen or saline (vehicle control) via segmental challenge. Forty-eight hours post-allergen or control exposure, bronchial biopsies were collected. The study design generated 4 different conditions: filtered air + saline (FAS), DE + saline (DES), filtered air + allergen (FAA) and DE + allergen (DEA). Biopsies sections were immunostained for tryptase, eosinophil cationic protein (ECP), neutrophil elastase (NE), CD138, CD4 and interleukin (IL)-4. The percent positivity of positive cells were quantified in the bronchial submucosa.

Results

The percent positivity for tryptase expression and ECP expression remained unchanged in the bronchial submucosa in all conditions. CD4 % positive staining in DEA (0.311 ± 0.060) was elevated relative to FAS (0.087 ± 0.018; p = 0.035). IL-4 % positive staining in DEA (0.548 ± 0.143) was elevated relative to FAS (0.127 ± 0.062; p = 0.034). CD138 % positive staining in DEA (0.120 ± 0.031) was elevated relative to FAS (0.017 ± 0.006; p = 0.015), DES (0.044 ± 0.024; p = 0.040), and FAA (0.044 ± 0.008; p = 0.037). CD138 % positive staining in FAA (0.044 ± 0.008) was elevated relative to FAS (0.017 ± 0.006; p = 0.049). NE percent positive staining in DEA (0.224 ± 0.047) was elevated relative to FAS (0.045 ± 0.014; p = 0.031).

Conclusions

In vivo allergen and DE co-exposure results in elevated CD4, IL-4, CD138 and NE in the respiratory submucosa of atopic subjects, while eosinophils and mast cells are not changed.

Trial registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01792232.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-016-0114-z) contains supplementary material, which is available to authorized users.

The impact of low-dose carcinogens and environmental disruptors on tissue invasion and metastasis

The purpose of this review is to stimulate new ideas regarding low-dose environmental mixtures and carcinogens and their potential to promote invasion and metastasis. Whereas a number of chapters in this review are devoted to the role of low-dose environmental mixtures and carcinogens in the promotion of invasion and metastasis in specific tumors such as breast and prostate, the overarching theme is the role of low-dose carcinogens in the progression of cancer stem cells. It is becoming clearer that cancer stem cells in a tumor are the ones that assume invasive properties and colonize distant organs. Therefore, low-dose contaminants that trigger epithelial-mesenchymal transition, for example, in these cells are of particular interest in this review. This we hope will lead to the collaboration between scientists who have dedicated their professional life to the study of carcinogens and those whose interests are exclusively in the arena of tissue invasion and metastasis.

Diesel exhaust particles override natural injury-limiting pathways in the lung

Induction of effective inflammation in the lung in response to environmental and microbial stimuli is dependent on cooperative signaling between leukocytes and lung tissue cells. We explored how these inflammatory networks are modulated by diesel exhaust particles (DEP) using cocultures of human monocytes with epithelial cells. Cocultures, or monoculture controls, were treated with DEP in the presence or absence of LPS or flagellin. Production of cytokines was explored by Western blotting and ELISA; cell signaling was analyzed by Western blotting. Here, we show that responses of epithelial cells to DEP are amplified by the presence of monocytes. DEP amplified the responses of cellular cocultures to very low doses of TLR agonists. In addition, in the presence of DEP, the responses induced by LPS or flagellin were less amenable to antagonism by the physiological IL-1 antagonist, IL-1ra. This was paralleled by the uncoupling of IL-1 production and release from monocytes, potentially attributable to an ability of DEP to sequester or degrade extracellular ATP. These data describe a model of inflammation where DEP amplifies responses to low concentrations of microbial agonists and alters the nature of the inflammatory milieu induced by TLR agonists.

Pulmonary effects of inhaled diesel exhaust in aged mice

Pulmonary morbidity and mortality resulting from exposure to fine particulate matter (PM) increases with age. The present studies analyzed potential mechanisms underlying increased susceptibility of the elderly to PM using diesel exhaust (DE) as a model. Mice (2 m and 18 m) were exposed to DE (0, 300, and 1000 microg/m(3)) for 3 h once (single) or 3 h/day for 3 days (repeated). Bronchoalveolar lavage fluid (BAL), serum and lung tissue were collected 0 and 24 h later. Exposure to DE resulted in structural alterations in the lungs of older but not younger mice, including patchy thickening of the alveolar septa and inflammatory cell localization in alveolar spaces. These effects were most pronounced 24 h after a single exposure to the higher dose of DE. Significant increases in BAL nitrogen oxides were also noted in older mice, as well as expression of lipocalin 24p3, an oxidative stress marker in the lung with no effects in younger mice. Following DE inhalation, expression of Tumor Necrosis Factor alpha (TNFalpha) was upregulated in lungs of both younger and older mice; however, this was attenuated in older animals. Whereas exposure to DE resulted in increases in lung Interleukin-6 (IL-6) expression in both older and younger mice, IL-8 increased only in older animals. In younger mice, constitutive expression of manganese superoxide dismutase (MnSOD) decreased after DE exposure, while in older mice, constitutive MnSOD was not detectable and DE had no effect on expression of this antioxidant. Taken together, these results suggest that altered generation of inflammatory mediators and MnSOD may contribute to increased susceptibility of older mice to inhaled DE.

Epidermal growth factor receptor activation by diesel particles is mediated by tyrosine phosphatase inhibition

Exposure to particulate matter (PM) is associated with increased cardiopulmonary morbidity and mortality. Diesel exhaust particles (DEP) are a major component of ambient PM and may contribute to PM-induced pulmonary inflammation. Proinflammatory signaling is mediated by phosphorylation-dependent signaling pathways whose activation is opposed by the activity of protein tyrosine phosphatases (PTPases) which thereby function to maintain signaling quiescence. PTPases contain an invariant catalytic cysteine that is susceptible to electrophilic attack. DEP contain electrophilic oxy-organic compounds that may contribute to the oxidant effects of PM. Therefore, we hypothesized that exposure to DEP impairs PTPase activity allowing for unopposed basal kinase activity. Here we report that exposure to 30 microg/cm(2) DEP for 4 h induces differential activation of signaling in primary cultures of human airway epithelial cells (HAEC), a primary target cell in PM inhalation. In-gel kinase activity assay of HAEC exposed to DEPs of low (L-DEP), intermediate (I-DEP) or high (H-DEP) organic content showed differential activation of intracellular kinases. Exposure to these DEP also induced varying levels of phosphorylation of the receptor tyrosine kinase EGFR in a manner that requires EGFR kinase activity but does not involve receptor dimerization. We demonstrate that treatment with DEP results in an impairment of total and EGFR-directed PTPase activity in HAEC with a potency that is independent of the organic content of these particles. These data show that DEP-induced EGFR phosphorylation in HAEC is the result of a loss of PTPase activities which normally function to dephosphorylate EGFR in opposition to baseline EGFR kinase activity.