Proinflammatory and anti-inflammatory cytokine balance in gasoline exhaust induced pulmonary injury in mice

Toxicological effects of traffic-related air pollution on the lungs: Evidence, biomarkers and intervention

BACKGROUND

Numerous epidemiological studies have recently observed that exposure to traffic-related air pollution (TRAP) is associated with increased risk of various respiratory diseases. Major gaps in knowledge remain regarding the toxicological effects.

OBJECTIVES

We examined the toxicological effects of the gasoline exhaust particles (GEP), a paradigm of TRAP, in rats, with an objective to provide the evidence, obtain the biomarkers, and suggest effective intervention measure.

METHODS

We measured the airway hyperresponsiveness (AHR), inflammatory cells in the bronchoalveolar lavage (BAL) fluid, histological changes in the lung tissues, and the biomarkers so as to systematically examine the toxicological effects of GEPs at different dose levels (0.5, 2.5, 5 mg/kg BW). The intervention of vitamin E (VE), a natural antioxidant, on the toxicological effects was investigated.

RESULTS

The lung injury caused by GEP exposure was first indicated by the airway hyperresponsiveness (AHR). Compared with the control group, GEP exposure significantly increased the airway resistances and decreased the lung compliance; the higher the dose of GEP, the more serious the lung injury. Lung injury was also revealed by the increase of inflammatory cells, including the lymphocytes and neutrophils, in the BAL fluid. With the increase of GEP dose, histological changes in the lung tissues were further observed: inflammatory cell infiltration increased and alveolar wall thickened. The toxicology of GEP was demonstrated by the increase of the biomarkers of the oxidative stress, the pro-inflammatory cytokines and the apoptosis cytokine. However, administration of VE was found to be effective in restoring airway injury.

CONCLUSION

The toxicological effects of traffic-related air pollution (TRAP) on rat lungs are supported by evidence and biomarkers, and vitamin E intervention is feasible.

Oxido-inflammatory responses and histological alterations in rat lungs exposed to petroleum product fumes

Petroleum products-petrol, kerosene, and diesel-composed of volatile organic constituents contribute to air pollution. Exposure of gas station attendants (GSAs) to petroleum products fumes (PPFs) may account for occupation-related predisposition to respiratory toxicity and disease pathogenesis. We simulated GSA exposure to PPF inhalation and examined their effect on oxido-inflammatory responses, toxicity, and histopathological alterations in rat lungs, following 8-hours daily exposure for 60 and 90 days. Reactive oxygen and nitrogen species (RONS), oxidative stress and inflammatory biomarkers, namely: superoxide dismutase (SOD), reduced glutathione (GSH), glutathione peroxidase (GPx), glutathione-S-transferase (GST), TNF-α, IL-1β, xanthine oxidase (XO), nitric oxide (NO) activity were evaluated. Besides, histopathological examination of the lungs and trachea of exposed rats, PPF exposure resulted in significant (P < .05) increases in RONS, biomarkers of oxidative stress, pro-inflammation cytokines, and reduced (P < .05) GSH levels in rats, secondary to histopathological alteration in lungs and trachea cytoarchitecture examined in an exposure-duration-dependent manner. We conclude, therefore, that the observed biochemical and histological changes create a microenvironment that is permissive to diseases pathogenesis of the respiratory system via oxido-inflammatory mechanistic pathways.

Liver disorders related to exposure to gasoline fumes in male rats and role of fenugreek seed supplementation

Progressive effects of inhalation of gasoline fumes on the liver and the protective potential with fenugreek seed supplementation were evaluated in adult male rats. Twenty-four rats were divided into four groups, unexposed control and fenugreek groups, as well as exposed groups to gasoline fumes for 6 h/6 days/week for 10 weeks, with and without supplementation of fenugreek seed powder in food (5%w/w). Exposure to gasoline fumes resulted in a significant elevation in serum alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, gamma-glutamyl transferase, total bilirubin, total cholesterol, total triglycerides, and low-density lipoprotein, along with a significant decrease in high-density lipoprotein, total protein, and albumin contents compared to the control. Meanwhile, liver oxidative stress markers, malondialdehyde, hydrogen peroxide, and nitric oxide, were highly detected with decreased antioxidants, superoxide dismutase and catalase. Also, levels of inflammatory markers, interleukin(IL)-1β and IL-6, were significantly elevated with fibrotic markers, transforming growth factor (TGFβ1), fibroblast growth factor (FGF1), and collagen I. Histopathological studies illustrated that rats exposed to gasoline fumes have degenerated hepatocytes with cellular infiltration and necrotic areas, along with remarkable deposition of collagen fibers, suggesting an incidence of liver fibrosis. Administration of fenugreek seeds, rich with antioxidant and anti-inflammatory components, during gasoline exposure showed significant amelioration through suppressing oxidative stress and inflammation.

Acute peat smoke inhalation sensitizes rats to the postprandial cardiometabolic effects of a high fat oral load

Wildland fire emissions cause adverse cardiopulmonary outcomes, yet controlled exposure studies to characterize health impacts of specific biomass sources have been complicated by the often latent effects of air pollution. The aim of this study was to determine if postprandial responses after a high fat challenge, long used clinically to predict cardiovascular risk, would unmask latent cardiometabolic responses in rats exposed to peat smoke, a key wildland fire air pollution source. Male Wistar Kyoto rats were exposed once (1 h) to filtered air (FA), or low (0.36 mg/m³ particulate matter) or high concentrations (3.30 mg/m³) of peat smoke, generated by burning peat from an Irish bog. Rats were then fasted overnight, and then administered an oral gavage of a HF suspension (60 kcal% from fat), mimicking a HF meal, 24 h post-exposure. In one cohort, cardiac and superior mesenteric artery function were assessed using high frequency ultrasound 2 h post gavage. In a second cohort, circulating lipids and hormones, pulmonary and systemic inflammatory markers, and circulating monocyte phenotype using flow cytometry were assessed before or 2 or 6 h after gavage. HF gavage alone elicited increases in circulating lipids characteristic of postprandial responses to a HF meal. Few effects were evident after peat exposure in un-gavaged rats. By contrast, exposure to low or high peat caused several changes relative to FA-exposed rats 2 and 6 h post HF gavage including increased heart isovolumic relaxation time, decreased serum glucose and insulin, increased CD11 b/c-expressing blood monocytes, increased serum total cholesterol, alpha-1 acid glycoprotein, and alpha-2 macroglobulin (p = 0.063), decreased serum corticosterone, and increased lung gamma-glutamyl transferase. In summary, these findings demonstrate that a HF challenge reveals effects of air pollution that may otherwise be imperceptible, particularly at low exposure levels, and suggest exposure may sensitize the body to mild inflammatory triggers.

Genome Wide Identification of SARS-CoV Susceptibility Loci Using the Collaborative Cross

New systems genetics approaches are needed to rapidly identify host genes and genetic networks that regulate complex disease outcomes. Using genetically diverse animals from incipient lines of the Collaborative Cross mouse panel, we demonstrate a greatly expanded range of phenotypes relative to classical mouse models of SARS-CoV infection including lung pathology, weight loss and viral titer. Genetic mapping revealed several loci contributing to differential disease responses, including an 8.5Mb locus associated with vascular cuffing on chromosome 3 that contained 23 genes and 13 noncoding RNAs. Integrating phenotypic and genetic data narrowed this region to a single gene, Trim55, an E3 ubiquitin ligase with a role in muscle fiber maintenance. Lung pathology and transcriptomic data from mice genetically deficient in Trim55 were used to validate its role in SARS-CoV-induced vascular cuffing and inflammation. These data establish the Collaborative Cross platform as a powerful genetic resource for uncovering genetic contributions of complex traits in microbial disease severity, inflammation and virus replication in models of outbred populations.

Hydroxysafflor yellow A of Carthamus tinctorius attenuates lung injury of aged rats exposed to gasoline engine exhaust by down-regulating platelet activation

Long-term inhalation of gasoline engine exhaust (GEE) increases the risk of respiratory disease. Studies have suggested involvement of platelets in the development of some lung diseases. Hydroxysafflor yellow A (HSYA), a flavonoid compound, prevents hemostasis. Therefore, we investigated its effects on GEE-induced lung injury, and role of platelets in injury. Sixty-week-old male Sprague-Dawley rats were exposed to GEE for 4h/day for 6 weeks, and then grouped as follows: control, GEE, GEE+HSYA, GEE+HSYA+GW9662, and GEE+GW9662. Arterial oxygen tension (PaO2), carbon dioxide tension (PaCO2), pH, and the PaO2/fraction of inspired oxygen ratio (PaO2/FiO2) in the blood were detected using a blood gas analyzer. Wet/dry lung weight ratio, total protein in bronchoalveolar lavage fluid (BALF), and cytokine concentrations in serum and BALF were determined. Furthermore, cyclic adenosine monophosphate (cAMP) level and expression levels of target proteins were analyzed. Platelets were counted and their state was evaluated. HSYA attenuated GEE-mediated decreases in PaO2, PaO2/FiO2, platelet cAMP level, protein kinase A (PKA) activity, and peroxisome proliferator-activated receptor γ (PPARγ) expression. HSYA also attenuated GEE-mediated increases in lung permeability, cytokine levels in serum and BALF, plasma platelet count, and ADP-mediated platelet aggregation. Moreover, it suppressed GEE-induced increases in the expression of adhesion molecules and proinflammatory cytokines in platelets and lung tissue. Therefore, HSYA is therapeutically effective for GEE-mediated lung injury and acts by enhancing PKA activity and inhibiting platelet activation.

Anti-Inflammatory Potential of Ethanolic Leaf Extract of Eupatorium adenophorum Spreng. Through Alteration in Production of TNF-α, ROS and Expression of Certain Genes

Search for a novel anti-inflammatory agent from a herbal source, such as Eupatorium adenophorum Spreng., a plant from the Eastern Himalayas, is of prime interest in the present investigation. Inflammation causes tissue destruction and development of diseases such as asthma, rheumatoid arthritis, and so forth. The ethanolic leaf extract of E. adenophorum (EEA) was administered intravenously and in other cases topically at the site of delayed type hypersensitivity (DTH) reaction in mouse foot paw induced with dinitrofluorobenzene. EEA can effectively inhibit DTH reaction and bring back normalcy to the paw much earlier than the controls. Efficacy of EEA on regulatory mechanisms for inflammation has also been considered. Intravenous administration of EEA increased the number of CD4⁺ T cells in spleen and tumor necrosis factor (TNF)-α in serum of DTH mice. Initially it was difficult to reconcile with the anti-inflammatory role of EEA and simultaneous induction of TNF-α, an established pro-inflammatory cytokine. EEA induces higher expression of TNF-α gene and amount of the cytokine in serum. We discussed the other role of TNF-α, its involvement in repairing tissue damage incurred in course of inflammatory reaction. EEA also induces TGF-β encoding a cytokine involved in tissue repair mechanism. EEA inhibits expression of another pro-inflammatory cytokine gene IL-1β and downregulates cycloxygenase 2 (COX2) gene responsible for metabolism of inflammatory mediators like prostaglandins. Furthermore, anti-inflammatory role of EEA is also revealed through its inhibition of hydroxyl radical generation. Notably EEA does not necessarily affect the expression of other inflammation-related genes such as IL-6, IL-10 and IKK. The present study reports and analyzes for the first time the anti-inflammatory property of the leaf extract of E. adenophorum.

Identifying the pulmonary hazard of high aspect ratio nanoparticles to enable their safety-by-design

High aspect ratio, or fiber-shaped, nanoparticles (HARNs) represent a growth area in nanotechnology as their useful properties become more apparent. Carbon nanotubes, the best known and studied of the HARNs are handled on an increasingly large scale, with subsequent potential for human inhalation exposure. Their resemblance to asbestos fibers precipitated fears that they might show the same type of pathology as that caused by asbestos and there is emerging evidence to support this possibility. The large number of other HARNs, including nanorods, nanowires and other nanofibers, require similar toxicological scrutiny. In this article we describe the unusual hazard associated with fibers, with special reference to asbestos, and address the features of fibers that dictate their pathogenicity as developed in the fiber pathogenicity paradigm. This paradigm is a robust structure:toxicity model that identifies thin, long, biopersistent fibers as the effective dose for fiber-type pathogenic effects. It is likely that HARNs will in general conform to the paradigm and such an understanding of the features that make fibers pathogenic should enable us to design safer HARNs.

MMP-12 induces IL-8/CXCL8 secretion through EGFR and ERK1/2 activation in epithelial cells

Macrophage metalloelastase (MMP-12) is described to be involved in pulmonary inflammatory response. To determine the mechanisms linking MMP-12 and inflammation, we examined the effect of recombinant human MMP-12 (rhMMP-12) catalytic domain on IL-8/CXCL8 production in cultured human airway epithelial (A549) cells. Stimulation with rhMMP-12 resulted in a concentration-dependent IL-8/CXCL8 synthesis 6 h later. Similar results were also observed in cultured BEAS-2B bronchial epithelial cells. In A549 cells, synthetic matrix metalloproteinase (MMP) inhibitors prevented rhMMP-12-induced IL-8/CXCL8 release. We further demonstrated that in A549 cells, rhMMP-12 induced transient, peaking at 5 min, activation of ERK1/2. Selective MEK inhibitors (U0126 and PD-98059) blocked both IL-8/CXCL8 release and ERK1/2 phosphorylation. IL-8/CXCL8 induction and ERK1/2 activation were preceded by EGF receptor (EGFR) tyrosine phosphorylation, within 2 min, and reduced by selective EGFR tyrosine kinase inhibitors (AG-1478 and PD168393) by a neutralizing EGFR antibody and by small interfering RNA oligonucleotides directed against EGFR, implicating EGFR activation. In addition, we observed an activation of c-Fos in A549 cells stimulated by rhMMP-12, dependent on ERK1/2. Using small interfering technique, we showed that c-Fos is involved in rhMMP-12-induced IL-8/CXCL8 production. From these results, we conclude that one mechanism, by which MMP-12 induces IL-8/CXCL8 release from the alveolar epithelium, is the EGFR/ERK1/2/activating protein-1 pathway.