Inhibition of beta-defensin gene expression in airway epithelial cells by low doses of residual oil fly ash is mediated by vanadium

Host Defense Peptides in Nutrition and Diseases: A Contributor of Immunology Modulation

Host defense peptides (HDPs) are primary components of the innate immune system with diverse biological functions, such as antibacterial ability and immunomodulatory function. HDPs are produced and released by immune and epithelial cells against microbial invasion, which are widely distributed in humans, animals, plants, and microbes. Notably, there are great differences in endogenous HDP distribution and expression in humans and animals. Moreover, HDP expression could be regulated by exogenous substances, such as nutrients, and different physiological statuses in health and disease. In this review, we systematically assessed the regulation of expression and mechanism of endogenous HDPs from nutrition and disease perspectives, providing a basis to identify the specificity and regularity of HDP expression. Furthermore, the regulation mechanism of HDP expression was summarized systematically, and the differences in the regulation between nutrients and diseases were explored. From this review, we provide novel ideas targeted the immune regulation of HDPs for protecting host health in nutrition and practical and effective new ideas using the immune regulation theory for further research on protecting host health from pathogenic infection and excessive immunity diseases under the global challenge of the antibiotic-abuse-induced series of problems, including food security and microbial resistance.

SARS-CoV-2 infection, COVID-19 pathogenesis, and exposure to air pollution: What is the connection?

Exposure to air pollutants has been previously associated with respiratory viral infections, including influenza, measles, mumps, rhinovirus, and respiratory syncytial virus. Epidemiological studies have also suggested that air pollution exposure is associated with increased cases of SARS-CoV-2 infection and COVID-19-associated mortality, although the molecular mechanisms by which pollutant exposure affects viral infection and pathogenesis of COVID-19 remain unknown. In this review, we suggest potential molecular mechanisms that could account for this association. We have focused on the potential effect of exposure to nitrogen dioxide (NO2 ), ozone (O3 ), and particulate matter (PM) since there are studies investigating how exposure to these pollutants affects the life cycle of other viruses. We have concluded that pollutant exposure may affect different stages of the viral life cycle, including inhibition of mucociliary clearance, alteration of viral receptors and proteases required for entry, changes to antiviral interferon production and viral replication, changes in viral assembly mediated by autophagy, prevention of uptake by macrophages, and promotion of viral spread by increasing epithelial permeability. We believe that exposure to pollutants skews adaptive immune responses toward bacterial/allergic immune responses, as opposed to antiviral responses. Exposure to air pollutants could also predispose exposed populations toward developing COIVD-19-associated immunopathology, enhancing virus-induced tissue inflammation and damage.

NF-κB-regulation of miR-155, via SOCS1/STAT3, is involved in the PM2.5-accelerated cell cycle and proliferation of human bronchial epithelial cells

Air pollution, especially fine particulate matter (PM_2.5, particles <2.5 μm in size), induces adverse health effects on the respiratory system. Uncontrolled proliferation of bronchial epithelial cells, resulting from deregulated cell cycle progression, contributes to pulmonary homeostatic imbalance. Although dysregulation of miRNAs is involved in a variety of pathophysiologic processes, the role of miRNAs in lung injury caused by PM_2.5 is unclear. In the present study, we found that different concentrations of PM_2.5 caused a biphasic effect on proliferation of human bronchial epithelial (HBE) cells. PM_2.5 induced an aberrant cell cycle and proliferation of HBE cells, and up-regulated miR-155 levels with a concentration-dependent manner. High miR-155 expression, mediated by NF-κB activation, produced an accelerated G1/S phase and cell proliferation though the STAT3 pathway, which targeted SOCS1. These findings indicate that NF-κB-mediated miR-155 induces an altered cell cycle through epigenetic modulation of the SOCS1/STAT3 signaling pathway and provide a mechanism for the biphasic effect of different concentrations of PM_2.5 in inducing respiratory injury.

Effects of transportation on cattle health and production: a review

The goal of this review is to present a concise and critical assessment of the literature related to physiologic responses in cattle that are subjected to transportation. Over two-thirds of US cattle are transported. Understanding trends in circulating physiologic parameters is an important part of mitigating the negative effects of transportation. For the producer, linking these effects after transportation to morbidity outcomes within the first 45 days on feed (i.e. especially development of bovine respiratory disease) is critical. Physiologic parameters in circulation are of primary importance and may have value for prediction of bovine respiratory disease on arrival and for the understanding of disease pathogenesis. The results of our literature survey indicated that post-transportation immune function, increased acute phase proteins, glucocorticoids, and inflammation are a pivotal starting point for understanding disease. These potential biomarkers may have utility in identifying disease for targeted therapeutics so that traditional protocols that rely heavily on metaphylaxis can be avoided. Additional research is needed to develop strategies for physiological marker identification, treatment methods, or predictive behaviors to prevent respiratory disease before and after transport. This review examines the significant deleterious effects of transportation handling and stress, and current immune system translation and non-antimicrobial mitigation strategies.

Benzo(a)pyrene suppresses tracheal antimicrobial peptide gene expression in bovine tracheal epithelial cells

Respiratory disease is an important cause of morbidity and mortality in cetaceans, which are also threatened by environmental degradation caused by crude oil spills. Following oil spills, cetaceans at the water surface may inhale droplets of oil containing toxic polycyclic aromatic hydrocarbons (PAHs), which could potentially alter respiratory immunity via activation of the aryl hydrocarbon receptor (AHR) and its subsequent interaction with nuclear factor kappa B (NF-κB). β-defensins are antimicrobial peptides secreted by airway epithelial cells and their expression is known to be dependent on NF-κB. We hypothesized that PAHs may suppress the expression of β-defensins, and thereby contribute to the pathogenesis of pneumonia. This hypothesis was modeled by measuring the in vitro effects of benzo(a)pyrene (BAP), phenanthrene, and naphthalene on tracheal antimicrobial peptide (TAP) gene expression in bovine tracheal epithelial cells. Stimulation with lipopolysaccharide (LPS) induced 20 ± 17-fold (mean ± SD) increased TAP gene expression. Exposure of tracheal epithelial cells to 5 μM BAP for 4 or 8 h, followed by incubation with a combination of LPS and 5 μM BAP for another 16 h, significantly (P = 0.002) suppressed LPS-induced TAP gene expression by 40.6 ± 21.8% (mean ± SD) in tracheal epithelial cells from 9 calves tested. BAP-induced suppression of TAP gene expression coincided with induction of cytochrome P450 1A1 gene expression. In contrast, phenanthrene and naphthalene had no consistent effect, and exposure to PAHs did not significantly affect constitutive TAP gene expression (i.e. without LPS). These findings characterize the suppressive effects of BAP-a toxic pollutant found in crude oil-on this respiratory innate immune response.

LL-37 disrupts the Kaposi's sarcoma-associated herpesvirus envelope and inhibits infection in oral epithelial cells

Oral epithelial cells (OECs) represent the first line of defense against viruses that are spread via saliva, including Kaposi's sarcoma-associated herpesvirus (KSHV). Infection of humans by KSHV and viral pathogenesis begins by infecting OECs. One method OECs use to limit viral infections in the oral cavity is the production of antimicrobial peptides (AMPs), or host defense peptides (HDPs). However, no studies have investigated the antiviral activities of any HDP against KSHV. The goal of this study was to determine the antiviral activity of one HDP, LL-37, against KSHV in the context of infecting OECs. Our results show that LL-37 significantly decreased KSHV's ability to infect OECs in both a structure- and dose-dependent manner. However, this activity does not stem from affecting OECs, but instead the virions themselves. We found that LL-37 exerts its antiviral activity against KSHV by disrupting the viral envelope, which can inhibit viral entry into OECs. Our data suggest that LL-37 exhibits a marked antiviral activity against KSHV during infection of oral epithelial cells, which can play an important role in host defense against oral KSHV infection. Thus, we propose that inducing LL-37 expression endogenously in oral epithelial cells, or potentially introducing as a therapy, may help restrict oral KSHV infection and ultimately KSHV-associated diseases.

Urban particulate matter (PM) suppresses airway antibacterial defence

Background

Epidemiological studies have shown that urban particulate matter (PM) increases the risk of respiratory infection. However, the underlying mechanisms are poorly understood. PM has been postulated to suppress the activation of airway epithelial innate defence in response to infection.

Methods

The effects of PM on antibacterial defence were studied using an in vitro infection model. The levels of antimicrobial peptides were measured using RT-PCR and ELISA. In addition to performing colony-forming unit counts and flow cytometry, confocal microscopy was performed to directly observe bacterial invasion upon PM exposure.

Results

We found that PM PM increased bacterial invasion by impairing the induction of β-defensin-2 (hBD-2), but not the other antimicrobial peptides (APMs) secreted by airway epithelium. PM further increases bacteria-induced ROS production, which is accompanied by an accelerated cell senescence and a decrease in bacteria-induced hBD-2 production, and the antioxidant NAC treatment attenuates these effects. The PM exposure further upregulated the expression of IL-8 but downregulated the expression of IL-13 upon infection.

Conclusions

PM promotes bacterial invasion of airway epithelial cells by attenuating the induction of hBD-2 via an oxidative burst. These findings associate PM with an increased susceptibility to infection. These findings provide insight into the underlying mechanisms regarding the pathogenesis of particulate matter.

Newborn sex-specific transcriptome signatures and gestational exposure to fine particles: findings from the ENVIRONAGE birth cohort

BACKGROUND

Air pollution exposure during pregnancy has been associated with adverse birth outcomes and health problems later in life. We investigated sex-specific transcriptomic responses to gestational long- and short-term exposure to particulate matter with a diameter < 2.5 μm (PM_2.5) in order to elucidate potential underlying mechanisms of action.

METHODS

Whole genome gene expression was investigated in cord blood of 142 mother-newborn pairs that were enrolled in the ENVIRONAGE birth cohort. Daily PM_2.5 exposure levels were calculated for each mother's home address using a spatial-temporal interpolation model in combination with a dispersion model to estimate both long- (annual average before delivery) and short- (last month of pregnancy) term exposure. We explored the association between gene expression levels and PM_2.5 exposure, and identified modulated pathways by overrepresentation analysis and gene set enrichment analysis.

RESULTS

Some processes were altered in both sexes for long- (e.g. DNA damage) or short-term exposure (e.g. olfactory signaling). For long-term exposure in boys neurodevelopment and RhoA pathways were modulated, while in girls defensin expression was down-regulated. For short-term exposure we identified pathways related to synaptic transmission and mitochondrial function (boys) and immune response (girls).

CONCLUSIONS

This is the first whole genome gene expression study in cord blood to identify sex-specific pathways altered by PM_2.5. The identified transcriptome pathways could provide new molecular insights as to the interaction pattern of early life PM_2.5 exposure with the biological development of the fetus.

Regulation of tracheal antimicrobial peptide gene expression in airway epithelial cells of cattle

β-defensins are an important element of the mucosal innate immune response against bacterial pathogens. Tracheal antimicrobial peptide (TAP) has microbicidal activity against the bacteria that cause bovine respiratory disease, and its expression in tracheal epithelial cells is upregulated by bacterial products including lipopolysaccharide (LPS, a TLR4 agonist), Pam3CSK4 (an agonist of Toll-like receptor 2/1), and interleukin (IL)-17A. The objectives of this study were to identify the signalling pathway by which LPS, Pam3CSK4 and IL-17A induce TAP gene expression, and to determine the effect of glucocorticoid as a model of stress on this epithelial innate immune response. In primary cultures of bovine tracheal epithelial cells (bTEC), LPS, Pam3CSK4 and IL-17A each stimulated TAP gene expression. This effect was abrogated by caffeic acid phenylester (CAPE), an inhibitor of NF-κB. Similarly, western analysis showed that LPS, Pam3CSK4 and IL-17A each induced translocation of NF-κB p65 from the cytoplasm to the nucleus, but pre-treatment with CAPE inhibited this response. Finally, pre-treatment of bTEC with the glucocorticoid dexamethasone abolished the stimulatory effect of LPS, Pam3CSK4 and IL-17A on upregulation of TAP gene expression. These findings indicate that NF-κB activation is necessary for induction of TAP gene expression by LPS (a TLR4 agonist), Pam3CSK4 (a TLR2/1 agonist), or IL-17A. Furthermore, this stimulatory response is inhibited by glucocorticoid, suggesting this as one mechanism by which stress increases the risk of bacterial pneumonia. These findings have implications for understanding the pathogenesis of stress-associated bacterial pneumonia, and for developing methods to stimulate innate immune responses in the respiratory tract of cattle.

In vivo short-term exposure to residual oil fly ash impairs pulmonary innate immune response against environmental mycobacterium infection

Epidemiological studies have shown that pollution derived from industrial and vehicular transportation induces adverse health effects causing broad ambient respiratory diseases. Therefore, air pollution should be taken into account when microbial diseases are evaluated. Environmental mycobacteria (EM) are opportunist pathogens that can affect a variety of immune compromised patients, which impacts significantly on human morbidity and mortality. The aim of this study was to evaluate the effect of residual oil fly ash (ROFA) pre-exposure on the pulmonary response after challenge with opportunistic mycobacteria by means of an acute short-term in vivo experimental animal model. We exposed BALB/c mice to ROFA and observed a significant reduction on bacterial clearance at 24 h post infection. To study the basis of this impaired response four groups of animals were instilled with (a) saline solution (Control), (b) ROFA (1 mg kg(-1) BW), (c) ROFA and EM-infected (Mycobacterium phlei, 8 × 10(6) CFU), and (d) EM-infected. Animals were sacrificed 24 h postinfection and biomarkers of lung injury and proinflammatory madiators were examined in the bronchoalveolar lavage. Our results indicate that ROFA was able to produce an acute pulmonary injury characterized by an increase in bronchoalveolar polymorphonuclear (PMN) cells influx and a rise in O2 (-) generation. Exposure to ROFA before M. phlei infection reduced total cell number and caused a significant decline in PMN cells recruitment (p < 0.05), O2 (-) generation, TNFα (p < 0.001), and IL-6 (p < 0.001) levels. Hence, our results suggest that, in this animal model, the acute short-term pre-exposure to ROFA reduces early lung response to EM infection.

Air pollution particulate matter alters antimycobacterial respiratory epithelium innate immunity

Inhalation exposure to indoor air pollutants and cigarette smoke increases the risk of developing tuberculosis (TB). Whether exposure to ambient air pollution particulate matter (PM) alters protective human host immune responses against Mycobacterium tuberculosis has been little studied. Here, we examined the effect of PM from Iztapalapa, a municipality of Mexico City, with aerodynamic diameters below 2.5 μm (PM2.5) and 10 μm (PM10) on innate antimycobacterial immune responses in human alveolar type II epithelial cells of the A549 cell line. Exposure to PM2.5 or PM10 deregulated the ability of the A549 cells to express the antimicrobial peptides human β-defensin 2 (HBD-2) and HBD-3 upon infection with M. tuberculosis and increased intracellular M. tuberculosis growth (as measured by CFU count). The observed modulation of antibacterial responsiveness by PM exposure was associated with the induction of senescence in PM-exposed A549 cells and was unrelated to PM-mediated loss of cell viability. Thus, the induction of senescence and downregulation of HBD-2 and HBD-3 expression in respiratory PM-exposed epithelial cells leading to enhanced M. tuberculosis growth represent mechanisms by which exposure to air pollution PM may increase the risk of M. tuberculosis infection and the development of TB.

Respiratory and cardiovascular effects of metals in ambient particulate matter: a critical review

In this review, we critically evaluated the epidemiological and toxicological evidence for the role of specific transition metals (As. Cr. Cu. Fe. Mn. Ni. Sc. Ti. V and Zn) in causing or contributing to the respiratory and cardiovascular health effects associated with ambient PM. Although the epidemiologic studies arc suggestive. and both the in vivo and in vitro laboratory studies document the toxicity of specific metals (Fe. Ni. V and Zn). the overall weight of evidence does not convincingly implicate metals as major contributors to health effects. None of the epidemiology studies that we reviewed conclusively implicated specific transition metals as having caused the respiratory and cardiovascular effects associated with ambient levels of PM. However, the studies reviewed tended to be internal ly consistent in identifying some metals (Fe, Ni, V and Zn) more frequently than others (As, Cu, Mn and Sc) as having positive associations wi th health effects. The major problem wi th which the epidemiological studies were faced was classifying and quantifying exposure. Community and population exposures to metals or other components of ambient PM were inferred from centrally- located samplers that may not accurately represent individual level exposures. Only a few authors reported findings that did not support the stated premise of the study; indeed, statistic ally significant associations are not necessarily biologically significant. It is likely that ·'negative studies" are under-represented in the published literature, making it a challenge to achieve a balanced evaluation of the role of metals in causing health effects associated with ambient PM. Both the in vivo and in vitro study results demonstrated that individual metals (Cu. Fe. Ni. V and Zn) and extracts of metals from ambient PM sources can produce acute inflammatory responses. However. the doses administered to laboratory animals were many orders of magnitude greater than what humans experience from breathing ambient air. The studies that used intratracheal instillation have the advantage of delivering a known dose to a specific anatomical location. but arc not analogous to an inhaled dose that is distributed over the surface area of the respiratory tract. Studies. in which laboratory animals or human volunteers inhaled CAPs best represent exposures to the general human population. The in vivo and in vitro studies reviewed provide indications that the probable mechanisms involved in the respiratory and cardiac effects from high metal exposures include: an inflammatory response mediated by formation of ROS, upregulation of genes coding for inflammatory cytokines, altered expression of genes involved in cell signaling pathways and maintenance of metals homeostasis.The fact that doses of metals many orders of magnitude greater than those existing in ambient air were required to produce measurable adverse effects in animals makes it doubtful that metals play any major role in respiratory and cardiovascular effects produced from human exposure to ambient PM. We suggest that future research priorities should focus on testing at more environmentally relevant exposure levels and that any new toxicological studies be written to include dosages in units that can be easily compared to human exposure levels.

Vanadate from air pollutant inhibits hrs-dependent endosome fusion and augments responsiveness to toll-like receptors

There is a well-established association between exposure to air pollutants and pulmonary injuries. For example, metals found in ROFA (residual oil fly ash) increase susceptibility of mice as well as humans to microbial infections. In our research, we have found that vanadate substantially increased the response of several Toll-like receptors (TLRs) to stimulation with their ligands. Although vanadate caused generation of reactive oxygen species (ROS), the addition of ROS scavenger N-acetyl cysteine (NAC) had no effect on augmented lipopolysaccharide (LPS) stimulation. We further showed that vanadate inhibits endosome fusion. This effect was determined by measuring the size of endosomes, NF-κB activity and TLR4 degradation in Hrs (hepatocyte growth factor-regulated tyrosine kinase substrate) overexpressed cells. Moreover, we identified the role of Hrs phosphorylation in these processes. Based on our findings, we can conclude that vanadate potentiates TLR4 activity by increasing Hrs phosphorylation status, reducing the size of Hrs/TLR4-positive endosomes and impacting TLR4 degradation, thus contributing to the detrimental effects of air pollutants on human health.

Failure of respiratory defenses in the pathogenesis of bacterial pneumonia of cattle

The respiratory system is well defended against inhaled bacteria by a dynamic system of interacting layers, including mucociliary clearance, host defense factors including antimicrobial peptides in the epithelial lining fluid, proinflammatory responses of the respiratory epithelium, resident alveolar macrophages, and recruited neutrophils and monocytes. Nevertheless, these manifold defenses are susceptible to failure as a result of stress, glucocorticoids, viral infections, abrupt exposure to cold air, and poor air quality. When some of these defenses fail, the lung can be colonized by bacterial pathogens that are equipped to evade the remaining defenses, resulting in the development of pneumonia. This review considers the mechanisms by which these predisposing factors compromise the defenses of the lung, with a focus on the development of bacterial pneumonia in cattle and supplemented with advances based on mouse models and the study of human disease. Deepening our understanding of how the respiratory defenses fail is expected to lead to interventions that restore these dynamic immune responses and prevent disease.

Effects of Eyjafjallajökull volcanic ash on innate immune system responses and bacterial growth in vitro

BACKGROUND

On 20 March 2010, the Icelandic volcano Eyjafjallajökull erupted for the first time in 190 years. Despite many epidemiological reports showing effects of volcanic ash on the respiratory system, there are limited data evaluating cellular mechanisms involved in the response to ash. Epidemiological studies have observed an increase in respiratory infections in subjects and populations exposed to volcanic eruptions.

METHODS

We physicochemically characterized volcanic ash, finding various sizes of particles, as well as the presence of several transition metals, including iron. We examined the effect of Eyjafjallajökull ash on primary rat alveolar epithelial cells and human airway epithelial cells (20-100 µg/cm(2)), primary rat and human alveolar macrophages (5-20 µg/cm(2)), and Pseudomonas aeruginosa (PAO1) growth (3 µg/104 bacteria).

RESULTS

Volcanic ash had minimal effect on alveolar and airway epithelial cell integrity. In alveolar macrophages, volcanic ash disrupted pathogen-killing and inflammatory responses. In in vitro bacterial growth models, volcanic ash increased bacterial replication and decreased bacterial killing by antimicrobial peptides.

CONCLUSIONS

These results provide potential biological plausibility for epidemiological data that show an association between air pollution exposure and the development of respiratory infections. These data suggest that volcanic ash exposure, while not seriously compromising lung cell function, may be able to impair innate immunity responses in exposed individuals.

Toluene Exposure Leads to a Change in Expression Patterns of β Defensins in the Mouse Tracheal Epithelium

Defensins are generally implicated in the quick resistance of epithelial surfaces to microbials; however, recent reports have indicated that defensins also have unknown purposes in relation to noninfectious diseases. In this study, the localization patterns of anti-microbial peptides, β defensins (BDs), in the tracheal epithelium of male C3H mice under exposure to toluene were analyzed by immunohistochemistry. Mice were exposed one to ten times to toluene for 30 min by nose-only inhalation. Expression of BDs was revealed by immunohistochemistry in serial sections of trachea after the final exposure. Expression of BD-1 was usually observed at almost the same levels in all exposure groups, and expression of BD-2 was observed in the control group; however, the signals for BD-2 decreased gradually with frequency of exposure. In the group exposed ten times, expression of BD-2 decreased to far lower than that of the control group. No expression of BD-3 was detected in any groups. Interestingly, expression of BD-4 increased to the maximum in the group exposed four times and decreased to a level lower than that of the control in the group exposed ten times. The results of the present study indicated that toluene gas might change the expression pattern of BDs in the tracheal epithelial cells. The oscillation of expression of BD-4 was quite characteristic and might contribute to morphological damage in on the epithelial cells.

Comparison of five different in vitro assays for assessment of sodium metavanadate cytotoxicity in Chinese hamster ovary cells (CHO-K1 line)

This investigation was undertaken to compare five different in vitro cytotoxicity assays for their power in revealing vanadium-mediated toxicity in Chinese hamster ovary (CHO)-K1 cells. The cells were exposed to sodium metavanadate (NaVO3) in the range of 10–1000 µM for 24 h and thereafter the cytotoxic effects of NaVO3 were measured by colorimetric in vitro assays: the neutral red (NR) test, the 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxyanilide inner salt (XTT) assay, the resazurin assay, the sulforhodamine B (SR-B) assay, and by microscopic assessment of cell viability using the trypan blue (TB) staining method. Among the assays used, the NR test was the most sensitive, since it revealed metavanadate cytotoxicity at the lowest NaVO3 dose (=50 µM). Also, NaVO3 cytotoxicity expressed as inhibitory concentration (IC) showed the lowest values for the NR test. Three other tests XTT, resazurin, and SR-B assays showed intermediate sensitivity revealing the cytotoxicity of NaVO3 at 100 µM. The corresponding IC10 and IC50 values calculated for the XTT, resazurin, and SR-B tests were similar. The TB staining method was the least sensitive, since it recorded metavanadate cytotoxicity at the highest NaVO3 concentration tested (=600 µM). Based on the cytotoxicity end points measured with the above assays, it can be concluded that lysosomal/Golgi apparatus damage (measured by NR assay) may be the primary effect of NaVO3 on CHO-K1 cells. The disintegration of mitochondria (assessed with the XTT and resazurin assays) probably follows lysosomal impairment. Plasma membrane permeability (staining with TB) occurs at a late stage of NaVO3-induced cytotoxicity on CHO-K1 cells. The results obtained in this research work show that the NR test can be recommended as a very sensitive assay for the assessment of NaVO3 cytotoxicity in the CHO-K1 cell culture model. Considering the convenience of assay performance along with adequate sensitivity, the XTT and resazurin assays can also be advocated for NaVO3 cytotoxicity assessment.

Coal fly ash impairs airway antimicrobial peptides and increases bacterial growth

Air pollution is a risk factor for respiratory infections, and one of its main components is particulate matter (PM), which is comprised of a number of particles that contain iron, such as coal fly ash (CFA). Since free iron concentrations are extremely low in airway surface liquid (ASL), we hypothesize that CFA impairs antimicrobial peptides (AMP) function and can be a source of iron to bacteria. We tested this hypothesis in vivo by instilling mice with Pseudomonas aeruginosa (PA01) and CFA and determine the percentage of bacterial clearance. In addition, we tested bacterial clearance in cell culture by exposing primary human airway epithelial cells to PA01 and CFA and determining the AMP activity and bacterial growth in vitro. We report that CFA is a bioavailable source of iron for bacteria. We show that CFA interferes with bacterial clearance in vivo and in primary human airway epithelial cultures. Also, we demonstrate that CFA inhibits AMP activity in vitro, which we propose as a mechanism of our cell culture and in vivo results. Furthermore, PA01 uses CFA as an iron source with a direct correlation between CFA iron dissolution and bacterial growth. CFA concentrations used are very relevant to human daily exposures, thus posing a potential public health risk for susceptible subjects. Although CFA provides a source of bioavailable iron for bacteria, not all CFA particles have the same biological effects, and their propensity for iron dissolution is an important factor. CFA impairs lung innate immune mechanisms of bacterial clearance, specifically AMP activity. We expect that identifying the PM mechanisms of respiratory infections will translate into public health policies aimed at controlling, not only concentration of PM exposure, but physicochemical characteristics that will potentially cause respiratory infections in susceptible individuals and populations.

The roles of antimicrobial peptides in innate host defense

Antimicrobial peptides (AMPs) are multi-functional peptides whose fundamental biological role in vivo has been proposed to be the elimination of pathogenic microorganisms, including Gram-positive and -negative bacteria, fungi, and viruses. Genes encoding these peptides are expressed in a variety of cells in the host, including circulating phagocytic cells and mucosal epithelial cells, demonstrating a wide range of utility in the innate immune system. Expression of these genes is tightly regulated; they are induced by pathogens and cytokines as part of the host defense response, and they can be suppressed by bacterial virulence factors and environmental factors which can lead to increased susceptibility to infection. New research has also cast light on alternative functionalities, including immunomodulatory activities, which are related to their unique structural characteristics. These peptides represent not only an important component of innate host defense against microbial colonization and a link between innate and adaptive immunity, but also form a foundation for the development of new therapeutic agents.

A review of effects of particulate matter-associated nickel and vanadium species on cardiovascular and respiratory systems

Many epidemiological investigations indicate that excess risks of mortality and morbidity may vary among specific PM(2.5) components. Nickel (Ni) and vanadium (V) particulate metal species may potentially be related to increasing respiratory and cardiovascular mortality and morbidity. This review focuses on exposure concentrations of these two species in various settings, their health effects based on epidemiological and toxicological studies and the underlying mechanisms. The evidence shows that environmental exposure concentrations of Ni and V in general setting are lower than the World Health Organization standard (V, 1 microg/m(3)/day) in 2000, or the European Environment Agency standard (Ni, 1 microg/m(3)/day) in 2003, but their associations with cardiopulmonary diseases can still be found. The toxicological mechanism can be explained by laboratory-based studies. Updated safe guidelines on environmental and human exposure of Ni and V are necessary in order to clarify the associations between them and cardiopulmonary diseases and provide environmental intervention policies.

A review of current toxicological concerns on vanadium pentoxide and other vanadium compounds: gaps in knowledge and directions for future research

Vanadium pentoxide (V(2)O(5)) and other inorganic vanadium compounds have recently been evaluated by several occupational exposure limit (OEL) setting (occupational exposure limit, OEL) committees and expert groups in response to the publication of several new studies, including the U.S. National Toxicology Program (NTP, 2002) carcinogenicity study of inhaled V(2)O(5) in rats and mice, which concluded that clear evidence of lung tumors was seen in mice of both genders and that there was some evidence of carcinogenicity in male rats. This study reviews the expert evaluations of several OEL committees and expert groups and attempts to understand the strengths and weaknesses in their scientific arguments. This study also evaluates some key studies relating to potential genotoxicity, carcinogenicity, and respiratory effects of vanadium compounds and discusses how they might elucidate the mechanism(s) by which V(2)O(5) induces lung cancer in mice. All expert groups appear to agree that the lung tumors induced in mice in the NTP (2002) study are a site-specific response and, in general, verify that existing in vitro and in vivo studies suggest that tumors were induced by a secondary mechanism (presumably non-genotoxic), which is supported, though not conclusively, by a mechanistic data set. As some vanadium compounds produce a range of DNA and chromosome damage, there is no consensus on which of these changes is critical for the carcinogenic process for V(2)O(5) or whether the findings for the lung tumors seen in mice exposed to V(2)O(5) can be extrapolated to other inorganic vanadium compounds. As such, the various expert committees used the evidence differently, some to read across, i.e., to predict an endpoint for a substance based on the endpoint information of another with similar characteristics (e.g., physicochemical properties [solubility, bioaccessibility, bioavailability], structure, fate [toxicokinetics], and toxicology) for carcinogenicity from V(2)O(5) to other inorganic vanadium compounds. It is noteworthy that the toxicity of metals does not necessarily relate to carcinogenicity in a direct manner; thus, no assumptions should be made a priori when trying to extrapolate from V(2)O(5) to other inorganic vanadium compounds. Recent studies evaluated in this review provided some further insights into possible mechanisms but do not cover all relevant endpoints, address only a limited number of vanadium compounds, and have not established no-effect thresholds for carcinogenicity or respiratory tract irritation. Thresholds need to be established in order for arguments to be made for setting a health-based OEL for non-genotoxic or secondary genotoxic carcinogens. In conclusion, important knowledge gaps preclude confident classification and risk assessment for all vanadium compounds. Evidence suggests that further research that may address some of these critical gaps is needed.

Host defense peptides in the oral cavity and the lung: similarities and differences

Peptides with broad-spectrum antimicrobial activity are found in the mucosal surfaces at many sites in the body, including the airway, the oral cavity, and the digestive tract. Based on their in vitro antimicrobial and other immunomodulatory activities, these host defense peptides have been proposed to play an important role in the innate defense against pathogenic microbial colonization. The genes that encode these peptides are up-regulated by pathogens, further supporting their role in innate immune defense. However, the differences in the local microbial environments between the generally sterile airway and the highly colonized oral cavity suggest a more complex role for these peptides in innate immunity. For example, beta-defensin genes are induced in the airway by all bacteria and Toll-like receptor (TLR) agonists primarily through an NF-kappaB-mediated pathway. In contrast, the same genes are induced in the gingival epithelium by only a subset of bacteria and TLR ligands, via different pathways. Furthermore, the environments into which the peptides are secreted--specifically saliva, gingival crevicular fluid, and airway surface fluid--differ greatly and can effect their respective activities in host defense. In this review, we examine the differences and similarities between host defense peptides in the oral cavity and the airway, to gain a better understanding of their contributions to immunity.

Antimicrobial activity of human beta-defensins and induction by Francisella

The ability of human beta-defensins hBD-1, hBD-2, and hBD-3 to exert direct in vitro antimicrobial effects was evaluated using Francisella tularensis Live Vaccine Strain (LVS) and Francisella novicida. While hBD-2 showed some antimicrobial activity in these assays, only hBD-3 demonstrated significant potency against Francisella. Francisella tularensis LVS infection induced elevated levels of hBD-2 mRNA in human airway epithelial (A549) cells, while having no significant impact on the levels of hBD-3 and only a moderate effect on the level of hBD-1 mRNA. Francisella infection avoided stimulating the production of the most potent anti-Francisella host peptide, hBD-3, in A549 cells, although hBD-3 is stimulated by other treatments. The differential induction of beta-defensins in Francisella infected lung epithelial cells suggests a complex dynamic in the expression of antimicrobial peptides and the innate immune response.

Impairment of innate immune responses of airway epithelium by infection with bovine viral diarrhea virus

Bovine viral diarrhea virus (BVDV) infection is an important risk factor for development of shipping fever pneumonia in feedlot cattle, and infects but does not cause morphologic evidence of damage to airway epithelial cells. We hypothesized that BVDV predisposes to bacterial pneumonia by impairing innate immune responses in airway epithelial cells. Primary cultures of bovine tracheal epithelial cells were infected with BVDV for 48 h, then stimulated with LPS for 16 h. Expression of tracheal antimicrobial peptide (TAP) and lingual antimicrobial peptide (LAP) mRNA was measured by quantitative RT-PCR, and lactoferrin concentrations were measured in culture supernatant by ELISA. BVDV infection had no detectable effect on the constitutive expression of TAP and LAP mRNA or lactoferrin concentration in culture supernatant. LPS treatment provoked a significant increase in TAP mRNA expression and lactoferrin concentration in the culture supernatant (p<0.01), and these effects were significantly (p<0.02, p<0.01) abrogated by prior infection of the tracheal epithelial cells with the type 2 ncp-BVDV isolate. In contrast, infection with the type 1 ncp-BVDV isolate had no effect on TAP mRNA expression or lactoferrin secretion. LPS treatment induced a significant (p<0.001) upregulation of LAP mRNA expression, which was not significantly affected by prior infection with BVDV. These data indicate that infection with a type 2 BVDV isolate inhibits the LPS-induced upregulation of TAP mRNA expression and lactoferrin secretion by tracheal epithelial cells, suggesting a novel mechanism by which this virus abrogates respiratory innate immune responses and predisposes to bacterial pneumonia in cattle.

Effect of corticosteroids and neuropeptides on the expression of defensins in bovine tracheal epithelial cells

Susceptibility to bacterial pneumonia in cattle is enhanced by stressors such as transportation, weaning, and commingling, which trigger a physiologic stress response resulting in elevated levels of endogenous corticosteroids and catecholamines. To determine the effect of neuroendocrine mediators on the expression of innate defense peptides in the lung, bovine tracheal epithelial cells were exposed to dexamethasone, catecholamines, acetylcholine, or substance P, and then beta-defensin expression was quantified using real-time reverse transcription-PCR. Basal expression of tracheal antimicrobial peptide (TAP) mRNA was not affected by any of the mediators tested. However, induction of TAP expression by lipopolysaccharide was significantly inhibited by pretreatment with dexamethasone. Bronchial biopsy specimens from dexamethasone-treated calves had significantly lower expression of TAP and lingual antimicrobial peptide (LAP) mRNA than saline-treated controls following 48 h of treatment. Lipopolysaccharide-elicited neutrophil recruitment was enhanced in the lungs of dexamethasone-treated calves compared to saline-treated controls. These findings indicate that modulation of epithelial antimicrobial peptide expression is one mechanism through which corticosteroids and stress may impair innate pulmonary defenses.