Interleukin-8 induction by the environmental contaminant benzo(a)pyrene is aryl hydrocarbon receptor-dependent and leads to lung inflammation

Chemical constituents of tobacco smoke induce the production of interleukin-8 in human bronchial epithelium, 16HBE cells

Background

Interleukin-8 (IL-8) functions as a major chemoattractant and plays pivotal roles in the initiation and development of chronic obstructive pulmonary disease (COPD), and tobacco smoke is a most risk factor contributing to the development of COPD. Hence, we have screened some of the tobacco smoke-derived chemical compounds that potentially induce the production of IL-8 in human bronchial epithelium, 16HBE cells.

Methods

Twenty-eight hazardous smoke components belonging to 9 classes including nicotine, ammonia, aromatic amines, polycyclic aromatic hydrocarbons, phenols, carbonyls, hydrocyanic acid, nitrosamines and other volatile organics were used in the experiments. Proliferation of 16HBE cells was determined by cell counting kit-8 kit, luciferase activity was measured in IL-8 reporter gene-expressing 16HBE cells, and IL-8 levels in culture supernatants were quantified by enzyme-linked immunosorbent assay.

Results

At the non-toxic dosages, chemical compounds belonging to nicotine, aromatic amines, benzopyrene, phenols, aldehydes, and some other volatile organics dose-dependently increased IL-8 reporter gene expression. Consistently, the representative compounds belonging to nicotine, aromatic amines, benzopyrene, phenols, aldehydes, and some other volatile organics significantly and dose-dependently increased IL-8 levels in the culture supernatants of 16HBE cells, among these compounds, benzopyrene is a most potent stimulator for inducing IL-8 production.

Conclusions

The present study has identified particular tobacco smoke constituents responsible for inducing the IL-8 production in human bronchial epithelium, which might help shed light on the pathogenesis of tobacco smoke-induced COPD.

Diesel exhaust: current knowledge of adverse effects and underlying cellular mechanisms

Diesel engine emissions are among the most prevalent anthropogenic pollutants worldwide, and with the growing popularity of diesel-fueled engines in the private transportation sector, they are becoming increasingly widespread in densely populated urban regions. However, a large number of toxicological studies clearly show that diesel engine emissions profoundly affect human health. Thus the interest in the molecular and cellular mechanisms underlying these effects is large, especially concerning the nature of the components of diesel exhaust responsible for the effects and how they could be eliminated from the exhaust. This review describes the fundamental properties of diesel exhaust as well as the human respiratory tract and concludes that adverse health effects of diesel exhaust not only emerge from its chemical composition, but also from the interplay between its physical properties, the physiological and cellular properties, and function of the human respiratory tract. Furthermore, the primary molecular and cellular mechanisms triggered by diesel exhaust exposure, as well as the fundamentals of the methods for toxicological testing of diesel exhaust toxicity, are described. The key aspects of adverse effects induced by diesel exhaust exposure described herein will be important for regulators to support or ban certain technologies or to legitimate incentives for the development of promising new technologies such as catalytic diesel particle filters.

Activation of aryl hydrocarbon receptor signaling by extracts of teak and other wood dusts

Wood dusts, as a group, are categorized as known human carcinogens, but the risks of exposure to specific types of wood dusts and the carcinogenic chemicals they contain are not well studied. Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is linked to the carcinogenic action of specific classes of chemicals. Here we examined whether chemicals in various wood dusts had the potential to activate AhR signaling as a potential toxic mechanism of action. We found that methanol extracts of teak, walnut, mahogany, and poplar dusts contained a wide range of AhR ligand activity, whereas extracts of oak, pine, and other softwoods did not contain appreciable activity. Teak dust extract, being particularly potent, was subjected to chemical analysis. The 2-methylanthraquinone (2-MAQ) accounted for the AhR ligand activity and was present at an average concentration of 0.27 parts per hundred in teak dust. Pure 2-MAQ potently induced AhR signaling (EC50 115 nM), confirming that this was the active ligand. Aqueous extracts of teak dust made using yeast or mammalian cell culture medium also contained robust AhR activity, suggesting the 2-MAQ ligand is soluble at bioactive concentrations in physiologically relevant fluids. The high concentration and potency of 2-MAQ in teak wood suggest it may mediate toxic effects through activation of AhR signaling in exposed wood workers.

Induction of c-Jun by air particulate matter (PM₁₀) of Mexico city: Participation of polycyclic aromatic hydrocarbons

The carcinogenic potential of urban particulate matter (PM) has been partly attributed to polycyclic aromatic hydrocarbons (PAHs) content, which activates the aryl hydrocarbon receptor (AhR). Here we report the effect of PM with an aerodynamic size of 10 μm (PM10) on the induction of AhR pathway in A549 cells, evaluating its downstream targets CYP1B1, IL-6, IL-8 and c-Jun. Significant increases in CYP1B1 protein and enzyme activity; IL-6 and IL-8 secretion and c-Jun protein were found in response to PM10. The formation of PAH-DNA adducts was also detected. The involvement of AhR pathway was confirmed with Resveratrol as AhR antagonist, which reversed CYP1B1 and c-Jun induction. Nevertheless, in IL-6 and IL-8 secretion, the Resveratrol was ineffective, suggesting an effect independent of this pathway. Considering the role of c-Jun in oncogenesis, its induction by PM may be contributing to its carcinogenic potential through induction of AhR pathway by PAHs present in PM10.

Activation of Proinflammatory Responses in Cells of the Airway Mucosa by Particulate Matter: Oxidant- and Non-Oxidant-Mediated Triggering Mechanisms

Inflammation is considered to play a central role in a diverse range of disease outcomes associated with exposure to various types of inhalable particulates. The initial mechanisms through which particles trigger cellular responses leading to activation of inflammatory responses are crucial to clarify in order to understand what physico-chemical characteristics govern the inflammogenic activity of particulate matter and why some particles are more harmful than others. Recent research suggests that molecular triggering mechanisms involved in activation of proinflammatory genes and onset of inflammatory reactions by particles or soluble particle components can be categorized into direct formation of reactive oxygen species (ROS) with subsequent oxidative stress, interaction with the lipid layer of cellular membranes, activation of cell surface receptors, and direct interactions with intracellular molecular targets. The present review focuses on the immediate effects and responses in cells exposed to particles and central down-stream signaling mechanisms involved in regulation of proinflammatory genes, with special emphasis on the role of oxidant and non-oxidant triggering mechanisms. Importantly, ROS act as a central second-messenger in a variety of signaling pathways. Even non-oxidant mediated triggering mechanisms are therefore also likely to activate downstream redox-regulated events.

Effects of the inhalation of the m3 receptor antagonist bencycloquidium bromide in a mouse cigarette smoke-induced airway inflammation model

Bencycloquidium bromide (BCQB), a novel M3 receptor antagonist, alleviates airway hyperresponsiveness, inflammation, and airway remodeling in a murine model of asthma. The aim of this study was to investigate the anti-inflammatory activity of inhaled BCQB in a cigarette smoke (CS)-induced model of acute lung inflammation. Mice exposed to CS developed chronic obstructive pulmonary disease (COPD). Inhalation of BCQB suppressed the accumulation of neutrophils and macrophages in airways and lung and also inhibited the CS-induced increases in mRNA levels of keratinocyte-derived chemokine, monocyte chemotactic protein-1, tumor necrosis factor-alpha, and interleukin-1β in lung and protein expression levels in bronchoalveolar lavage fluid. Moreover, BCQB (300 μg/ml) inhibited the CS-induced changes in superoxide dismutase and myeloperoxidase activities in the lungs. Our study suggests that BCQB might be a potential therapy for inflammation in CS-induced pulmonary diseases, including COPD.

AhR-dependent secretion of PDGF-BB by human classically activated macrophages exposed to DEP extracts stimulates lung fibroblast proliferation

Lung diseases are aggravated by exposure to diesel exhaust particles (DEPs) found in air pollution. Macrophages are thought to play a crucial role in lung immune response to these pollutants, even if the mechanisms involved remain incompletely characterized. In the present study, we demonstrated that classically and alternative human macrophages (MΦ) exhibited increased secretion of PDGF-B in response to DEP extract (DEPe). This occurred via aryl hydrocarbon receptor (AhR)-activation because DEPe-induced PDGF-B overexpression was abrogated after AhR expression knock-down by RNA interference, in both M1 and M2 polarizing MΦ. In addition, TCDD and benzo(a)pyrene, two potent AhR ligands, also significantly increased mRNA expression of PDGF-B in M1 MΦ, whereas some weak ligands of AhR did not. We next evaluated the impact of conditioned media (CM) from MΦ culture exposed to DEPe or of recombinant PDGF-B onto lung fibroblast proliferation. The tyrosine kinase inhibitor, AG-1295, prevents phosphorylations of PDGF-Rβ, AKT and ERK1/2 and the proliferation of MRC-5 fibroblasts induced by recombinant PDGF-B and by CM from M1 polarizing MΦ, strongly suggesting that the PDGF-BB secreted by DEPe-exposed MΦ is sufficient to activate the PDGF-Rβ pathway of human lung fibroblasts. In conclusion, we demonstrated that human MΦ, whatever their polarization status, secrete PDGF-B in response to DEPe and that PDGF-B is a target gene of AhR. Therefore, induction of PDGF-B by DEP may participate in the deleterious effects towards human health triggered by such environmental urban contaminants.

Exposure to diesel exhaust particle extracts (DEPe) impairs some polarization markers and functions of human macrophages through activation of AhR and Nrf2

Macrophages (MΦ), well-known to play an important role in immune response, also respond to environmental toxic chemicals such as diesel exhaust particles (DEP). Potential effects of DEPs towards MΦ polarization, a key hall-mark of MΦ physiology, remain however poorly documented. This study was therefore designed to evaluate the effects of a reference DEP extract (DEPe) on human MΦ polarization. Human blood monocytes-derived MΦ were incubated with IFNγ+LPS or IL-4 to obtain M1 and M2 subtypes, respectively; a 24 h exposure of polarizing MΦ to 10 μg/ml DEPe was found to impair expression of some macrophagic M1 and M2 markers, without however overall inhibition of M1 and M2 polarization processes. Notably, DEPe treatment increased the secretion of the M1 marker IL-8 and the M2 marker IL-10 in both MΦ subtypes, whereas it reduced lipopolysaccharide-induced IL-6 and IL-12p40 secretion in M1 MΦ. In M2 MΦ, DEPe exposure led to a reduction of CD200R expression and of CCL17, CCL18 and CCL22 secretion, associated with a lower chemotaxis of CCR4-positive cells. DEPe activated the Nrf2 and AhR pathways and induced expression of their reference target genes such as Hmox-1 and cytochrome P-4501B1 in M1 and M2 MΦ. Nrf2 or AhR silencing through RNA interference prevented DEPe-related down-regulation of IL-6. AhR silencing also inhibited the down-secretion of IL-12p40 and CCL18 in M1- and M2-DEPe-exposed MΦ, respectively. DEPs are therefore likely to alter expression of some M1 and M2 markers in an AhR- and Nrf2-dependent manner; such regulations may contribute to deleterious immune effects of atmospheric DEP.

The aryl hydrocarbon receptor: a review of its role in the physiology and pathology of the integument and its relationship to the tryptophan metabolism

The aryl hydrocarbon receptor (AHR) is a cytosolic receptor for low molecular weight molecules, of which the most widely recognized ligand is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and the most widely recognized effect, chloracne. Adverse effects of manipulation were most recently and graphically demonstrated by the poisoning of Viktor Yushchenko during the Ukrainian presidential elections of 2004. However, recent research has revealed a receptor with wide-ranging, and at times, paradoxical actions. It was arguably among the first biological receptors to be utilized by dermatologists, dating from the time of topical tar preparations as a therapeutic agent. I provide a review outlining the role AHR plays in the development, cellular oxidation/antioxidation, responses to ultraviolet light, melanogenesis, epidermal barrier function, and immune regulation and its relationship to tryptophan metabolism. Finally, I will review the role of AHR in diseases of the integument.

Analysis of gene expression changes in A549 cells induced by organic compounds from respirable air particles

A number of toxic effects of respirable ambient air particles (genotoxic effects, inflammation, oxidative damage) have been attributed to organic compounds bound onto the particle surface. In this study, we analyzed global gene expression changes caused by the extractable organic matters (EOMs) from respirable airborne particles <2.5μm (PM2.5), collected at 3 localities from heavily polluted areas of the Czech Republic and a control locality with low pollution levels, in human lung epithelial A549 cells. Although the sampled localities differed in both extent and sources of air pollution, EOMs did not induce substantially different gene expression profiles. The number of transcripts deregulated in A549 cells treated with the lowest EOM concentration (10μg/ml) ranged from 65 to 85 in 4 sampling localities compared to the number of transcripts deregulated after 30μg/ml and 60μg/ml of EOMs, which ranged from 90 to 109, and from 149 to 452, respectively. We found numerous commonly deregulated genes and pathways related to activation of the aryl hydrocarbon receptor (AhR) and metabolism of xenobiotics and endogenous compounds. We further identified deregulation of expression of the genes involved in pro-inflammatory processes, oxidative stress response and in cancer and developmental pathways, such as TGF-β and Wnt signaling pathways. No cell cycle arrest, DNA repair or pro-apoptotic responses were identified at the transcriptional level after the treatment of A549 cells with EOMs. In conclusion, numerous processes and pathways deregulated in response to EOMs suggest a significant role of activated AhR. Interestingly, we did not observe substantial gene expression changes related to DNA damage response, possibly due to the antagonistic effect of non-genotoxic EOM components. Moreover, a comparison of EOM effects with other available data on modulation of global gene expression suggests possible overlap among the effects of PM2.5, EOMs and various types of AhR agonists.

The teleostean liver as an immunological organ: Intrahepatic immune cells (IHICs) in healthy and benzo[a]pyrene challenged rainbow trout (Oncorhynchus mykiss)

The existence of a resident population of intrahepatic immune cells (IHICs) is well documented for mammalian vertebrates, however, it is uncertain whether IHICs are present in the liver of teleostean fish. In the present study we investigated whether trout liver contains an IHIC population, and if so, what the relative cellular composition of this population is. The results provide clear evidence for the existence of an IHIC population in trout liver, which constitutes 15-29% of the non-hepatocytes in the liver, and with a cellular composition different to that of the blood leukocyte population. We also analyzed the response of IHICs to a non-infectious liver challenge with the hepatotoxic and immunotoxic chemical, benzo[a]pyrene (BaP). Juvenile trout were treated with BaP (25 or 100mg/kgbw) at levels sufficient to induce the molecular pathway of BaP metabolism while not causing pathological and inflammatory liver changes. The IHIC population responded to the BaP treatments in a way that differed from the responses of the leukocyte populations in trout blood and spleen, suggesting that IHICs are an independently regulated immune cell population.

Urinary 1-hydroxypyrene is associated with oxidative stress and inflammatory biomarkers in acute Myocardial Infarction

Several studies have associated exposure to environmental pollutants, especially polycyclic aromatic hydrocarbons (PAHs), with the development of cardiovascular diseases. Considering that 1-hydroxypyrene (1-OHP) is the major biomarker of exposure to pyrenes, the purpose of this study was to evaluate the potential association between 1-OHP and oxidative stress/inflammatory biomarkers in patients who had suffered an acute myocardial infarction (AMI). After adopting the exclusion criteria, 58 post-infarction patients and 41 controls were sub-divided into smokers and non-smokers. Urinary 1-OHP, hematological and biochemical parameters, oxidative stress biomarkers (MDA, SOD, CAT, GPx and exogenous antioxidants) and the inflammatory biomarker (hs-CRP) were analyzed. 1-OHP levels were increased in post-infarct patients compared to controls (p < 0.05) and were correlated to MDA (r = 0.426, p < 0.01), CAT (r = 0.474, p < 0.001) and β-carotene (r = -0.309; p < 0.05) in non-smokers. Furthermore, post-infarction patients had elevated hs-CRP, MDA, CAT and GPx levels compared to controls for both smokers and non-smokers. Besides, β-carotene levels and SOD activity were decreased in post-infarction patients. In summary, our findings indicate that the exposure to pyrenes was associated to lipid damage and alterations of endogenous and exogenous antioxidants, demonstrating that PAHs contribute to oxidative stress and are associated to acute myocardial infarction.

AhR and Arnt differentially regulate NF-κB signaling and chemokine responses in human bronchial epithelial cells

Background

The aryl hydrocarbon receptor (AhR) has gradually emerged as a regulator of inflammation in the lung and other tissues. AhR may interact with the p65-subunit of the nuclear factor (NF)-κB transcription factors, but reported outcomes of AhR/NF-κB-interactions are conflicting. Some studies suggest that AhR possess pro-inflammatory activities while others suggest that AhR may be anti-inflammatory. The present study explored the impact of AhR and its binding partner AhR nuclear translocator (Arnt) on p65-activation and two differentially regulated chemokines, CXCL8 (IL-8) and CCL5 (RANTES), in human bronchial epithelial cells (BEAS-2B).

Results

Cells were exposed to CXCL8- and CCL5-inducing chemicals, 1-nitropyrene (1-NP) and 1-aminopyrene (1-AP) respectively, or the synthetic double-stranded RNA analogue, polyinosinic-polycytidylic acid (Poly I:C) which induced both chemokines. Only CXCL8, and not CCL5, appeared to be p65-dependent. Yet, constitutively active unligated AhR suppressed both CXCL8 and CCL5, as shown by siRNA knock-down and the AhR antagonist α-naphthoflavone. Moreover, AhR suppressed activation of p65 by TNF-α and Poly I:C as assessed by luciferase-assay and p65-phosphorylation at serine 536, without affecting basal p65-activity. In contrast, Arnt suppressed only CXCL8, but did not prevent the p65-activation directly. However, Arnt suppressed expression of the NF-κB-subunit RelB which is under transcriptional regulation by p65. Furthermore, AhR-ligands alone at high concentrations induced a moderate CXCL8-response, without affecting CCL5, but suppressed both CXCL8 and CCL5-responses by Poly I:C.

Conclusion

AhR and Arnt may differentially and independently regulate chemokine-responses induced by both inhaled pollutants and pulmonary infections. Constitutively active, unligated AhR suppressed the activation of p65, while Arnt may possibly interfere with the action of activated p65. Moreover, ligand-activated AhR suppressed CXCL8 and CCL5 responses by other agents, but AhR ligands alone induced CXCL8 responses when given at sufficiently high concentrations, thus underscoring the duality of AhR in regulation of inflammation. We propose that AhR-signaling may be a weak activator of p65-signaling that suppresses p65-activity induced by strong activators of NF-κB, but that its anti-inflammatory properties also are due to interference with additional pathways.

Effects of an iron-based fuel-borne catalyst and a diesel particle filter on exhaust toxicity in lung cells in vitro

Metal-containing fuel additives catalyzing soot combustion in diesel particle filters are used in a widespread manner, and with the growing popularity of diesel vehicles, their application is expected to increase in the near future. Detailed investigation into how such additives affect exhaust toxicity is therefore necessary and has to be performed before epidemiological evidence points towards adverse effects of their application. The present study investigates how the addition of an iron-based fuel additive (Satacen®3, 40 ppm Fe) to low-sulfur diesel affects the in vitro cytotoxic, oxidative, (pro-)inflammatory, and mutagenic activity of the exhaust of a passenger car operated under constant, low-load conditions by exposing a three-dimensional model of the human airway epithelium to complete exhaust at the air-liquid interface. We could show that the use of the iron catalyst without and with filter technology has positive as well as negative effects on exhaust toxicity compared to exhaust with no additives: it decreases the oxidative and, compared to a non-catalyzed diesel particle filter, the mutagenic potential of diesel exhaust, but increases (pro-)inflammatory effects. The presence of a diesel particle filter also influences the impact of Satacen®3 on exhaust toxicity, and the proper choice of the filter type to be used is of importance with regards to exhaust toxicity. Figure ᅟ.

Test-methods on the test-bench: a comparison of complete exhaust and exhaust particle extracts for genotoxicity/mutagenicity assessment

With the growing number of new exhaust after-treatment systems, fuels and fuel additives for internal combustion engines, efficient and reliable methods for detecting exhaust genotoxicity and mutagenicity are needed to avoid the widespread application of technologies with undesirable effects toward public health. In a commonly used approach, organic extracts of particulates rather than complete exhaust is used for genotoxicity/mutagenicity assessment, which may reduce the reliability of the results. In the present study, we assessed the mutagenicity and the genotoxicity of complete diesel exhaust compared to an organic exhaust particle extract from the same diesel exhaust in a bacterial and a eukaryotic system, that is, a complex human lung cell model. Both, complete exhaust and organic extract were found to act mutagenic/genotoxic, but the amplitudes of the effects differed considerably. Furthermore, our data indicate that the nature of the mutagenicity may not be identical for complete exhaust and particle extracts. Because in addition, differences between the responses of the different biological systems were found, we suggest that a comprehensive assessment of exhaust toxicity is preferably performed with complete exhaust and with biological systems representative for the organisms and organs of interest (i.e., human lungs) and not only with the Ames test.

The occurrence of polycyclic aromatic hydrocarbons and their derivatives and the proinflammatory potential of fractionated extracts of diesel exhaust and wood smoke particles

Exposure to combustion emissions, including diesel engine exhaust and wood smoke particles (DEPs and WSPs), has been associated with inflammatory responses. To investigate the possible role of polycyclic aromatic hydrocarbons (PAHs) and PAH-derivatives, the DEPs and WSPs methanol extracts were fractionated by solid phase extraction (SPE), and the fractions were analyzed for more than ∼120 compounds. The pro-inflammatory effects of the fractionated extracts were characterized by exposure of bronchial epithelial lung cells (BEAS-2B). Both native DEPs and WSPs caused a concentration-dependent increase in IL-6 and IL-8 release and cytotoxicity. This is consistent with the finding of a rather similar total content of PAHs and PAH-derivatives. Yet, the samples differed in specific components, suggesting that different species contribute to the toxicological response in these two types of particles. The majority of the IL-6 release and cytotoxicity was induced upon exposure to the most polar (methanol) SPE fraction of extracts from both samples. In these fractions hydroxy-PAHs, carboxy-PAHs were observed along with nitro-amino-PAHs in DEP. However, the biological effects induced by the polar fractions could not be attributed only to the occurrence of PAH-derivatives. The present findings indicate a need for further characterization of organic extracts, beyond an extensive analysis of commonly suspected PAH and PAH-derivatives. Supplemental materials are available for this article. Go to the publisher's online edition of Journal of Environmental Science and Health, Part A, to view the supplemental file.

Activation of the NF κ B Pathway Enhances AhR Expression in Intestinal Caco-2 Cells

Recent data suggest that apart from its well-known role in the regulation of xenobiotic metabolizing enzymes, AhR is also involved in inflammation. However, the influence of inflammation on AhR expression remains unknown. Here, we demonstrated that proinflammatory conditions induced by either PMA or IL-1 β enhance AhR expression in Caco-2 cells. This was associated with an increase in AhR promoter activity. By means of directed mutagenesis experiments and the use of proteasome inhibitors, we demonstrated that inflammation-induced AhR expression involved the NF κ B pathway but not AP-1. Moreover, conditioned media from PMA-treated Caco-2 cells were also able to induce AhR expression, and this induction was repressed by anti-IL-1 β blocking antibodies. Similar results were obtained with conditioned media from PMA-treated THP-1 cells. Taken together, these data suggest that AhR could be involved in vivo in an inflammatory loop. AhR was recently suspected to be implicated in inflammatory bowel disease. Our results support this hypothesis and suggest that AhR could be a new target for inflammatory bowel disease patient management.

Biomarkers of occupational exposure to air pollution, inflammation and oxidative damage in taxi drivers

Exposure to environmental pollutants has been recognised as a risk factor for cardiovascular events. 1-hydroxypyrene (1-OHP) is a biomarker of exposure to polycyclic aromatic hydrocarbons (PAHs) from traffic-related air pollution. Experimental studies indicate that PAH exposure could be associated with inflammation and atherogenesis. Thus, the purpose of this study was to evaluate whether the biomarker of PAH exposure is associated with biomarkers of inflammation and oxidative stress and if these effects modulate the risk of developing cardiovascular diseases in workers exposed to air pollution. This study included 60 subjects, comprising 39 taxi drivers and 21 non-occupationally exposed persons. Environmental PM2.5 and benzo[a]pyrene (BaP) levels, in addition to biomarkers of exposure and oxidative damage, were determined. Inflammatory cytokines (IL-1β, IL-6, IL-10, TNF-α, IFN-γ and hs-CRP) and serum levels of oxidised LDL (ox-LDL), auto-antibodies (ox-LDL-Ab) and homocysteine (Hcy) were also evaluated. PM2.5 and BaP exhibited averages of 12.4±6.9 μg m(-3) and 1.0±0.6 ng m(-3), respectively. Urinary 1-OHP levels were increased in taxi drivers compared to the non-occupationally exposed subjects (p<0.05) and were positively correlated with pro-inflammatory cytokines and negatively correlated with antioxidants. Furthermore, taxi drivers had elevated pro-inflammatory cytokines, biomarkers of oxidative damage, and ox-LDL, ox-LDL-Ab and Hcy levels, although antioxidant enzymes were decreased compared to the non-occupationally exposed subjects (p<0.05). In summary, our findings indicate that taxi drivers showed major exposure to pollutants, such as PAHs, in relation to non-occupationally exposed subjects. This finding was associated with higher inflammatory biomarkers and Hcy, which represent important predictors for cardiovascular events. These data suggest a contribution of PAHs to cardiovascular diseases upon occupational exposure.

Using Immunotoxicity Information to Improve Cancer Risk Assessment for Polycyclic Aromatic Hydrocarbon Mixtures

Estimating cancer risk from environmental mixtures containing polycyclic aromatic hydrocarbons (PAHs) is challenging. Ideally, each mixture would undergo toxicity testing to derive a cancer slope factor (CSF) for use in site-specific cancer risk assessments. However, this whole mixture approach is extremely costly in terms of finances, time, and animal usage. Alternatively, if an untested mixture is “sufficiently similar” to a well-characterized mixture with a CSF, the “surrogate” CSF can be used in risk assessments. We propose that similarity between 2 mixtures could be established using an in vitro battery of genotoxic and nongenotoxic tests. An observed association between carcinogenicity and immunosuppression of PAHs suggests that the addition of immune suppression assays may improve this battery. First, using published studies of benzo[a]pyrene (BaP) and other PAHs, we demonstrated a correlation between the derived immune suppression relative potency factors (RPFs) for 9 PAHs and their respective cancer RPFs, confirming observations published previously. Second, we constructed an integrated knowledge map for immune suppression by BaP based on the available mechanistic information. The map illustrates the mechanistic complexities involved in BaP immunosuppression, suggesting that multiple in vitro tests of immune suppression involving different processes, cell types, and tissues will have greater predictive value for immune suppression in vivo than a single test. Based on these observations, research strategies are recommended to validate a battery of in vitro immune suppression tests that, along with tests for genotoxic and other nongenotoxic modes of cancer action, could be used to establish “sufficient similarity” of 2 mixtures for site-specific cancer risk assessments.

The aryl hydrocarbon receptor: a novel target for immunomodulation in organ transplantation

The aryl hydrocarbon receptor (AHR), which has been central to studies in toxicology for years as the receptor for the toxicant dioxin, is rapidly gaining interest in immunology based on its ability to influence T-cell differentiation. Multiple studies have documented that binding of this receptor with certain ligands favors T-cell differentiation toward regulatory T cells, and paradoxically, binding of this same receptor with different ligands enhances Th17 effector cell differentiation. This finding has been confirmed in both in vitro and in vivo models, where different ligands are able to either ameliorate or conversely aggravate autoimmunity in experimental autoimmune encephalomyelitis. The AHR has both an endogenous role that is important in development and normal physiology and an exogenous role as a receptor for manmade toxicants, with their binding leading to transcription of cytochrome P450 enzymes that metabolize these same ligands. Based on recent reports that will be summarized in this overview, we will consider the role that the AHR might play as a sensor to the outside environment, leading to alteration of the acquired immune system that might have relevance in transplantation or other medical conditions. In addition to describing the data in normal physiology and T-cell differentiation, we will present examples of the importance of this receptor in preclinical models of disease and highlight specific ligands that target the AHR and will have efficacy in treating transplant rejection and in tolerance protocols.

The role of inflammation in HPV infection of the Oesophagus

BACKGROUND

Several human cancers are known to be associated with inflammation and/or viral infections. However, the influence of tumour-related inflammation on viral uptake is largely unknown. In this study we used oesophageal squamous cell carcinoma (OSCC) as a model system since this type of cancer is associated with chronic irritation, inflammation and viral infections. Although still debated, the most important viral infection seems to be with Human Papillomavirus (HPV). The present study focused on a possible correlation between inflammation, OSCC development and the influence of HPV infection.

METHODS

A total of 114 OSCC biopsies and corresponding normal tissue were collected at Groote Schuur Hospital and Tygerberg Hospital, Cape Town (South Africa), that were subjected to RNA and DNA isolation. RNA samples were analysed by quantitative Light Cycler RT-PCR for the expression of selected genes involved in inflammation and infection, while conventional PCR was performed on the DNA samples to assess the presence of integrated viral DNA. Further, an in vitro infection assay using HPV pseudovirions was established to study the influence of inflammation on viral infectivity using selected cell lines.

RESULTS

HPV DNA was found in about 9% of OSCC patients, comprising predominantly the oncogenic type HPV18. The inflammatory markers IL6 and IL8 as well as the potential HPV receptor ITGA6 were significantly elevated while IL12A was downregulated in the tumour tissues. However, none of these genes were expressed in a virus-dependent manner. When inflammation was mimicked with various inflammatory stimulants such as benzo-α-pyrene, lipopolysaccharide and peptidoglycan in oesophageal epithelial cell lines in vitro, HPV18 pseudovirion uptake was enhanced only in the benzo-α-pyrene treated cells. Interestingly, HPV pseudovirion infectivity was independent of the presence of the ITGA6 receptor on the surface of the tested cells.

CONCLUSION

This study showed that although the carcinogen benzo-α-pyrene facilitated HPV pseudovirion uptake into cells in culture, HPV infectivity was independent of inflammation and seems to play only a minor role in oesophageal cancer.

Acute exposure to waterpipe tobacco smoke induces changes in the oxidative and inflammatory markers in mouse lung

CONTEXT

Tobacco smoking represents a global public health threat, claiming approximately 5 million lives a year. Waterpipe tobacco use has become popular particularly among youth in the past decade, buttressed by the perception that the waterpipe "filters" the smoke, rendering it less harmful than cigarette smoke.

OBJECTIVE

In this study, we examined the acute exposure of waterpipe smoking on lung inflammation and oxidative stress in mice, and compared that to cigarette smoking.

MATERIALS AND METHODS

Mice were divided into three groups; fresh air control, cigarette and waterpipe. Animals were exposed to fresh air, cigarette, or waterpipe smoke using whole body exposure system one hour daily for 7 days.

RESULTS

Both cigarette and waterpipe smoke exposure resulted in elevation of total white blood cell count, as well as absolute count of neutrophils, macrophages, and lymphocytes (P < 0.01). Both exposures also elevated proinflammatory markers such as TNF-α and IL-6 in BALF (P < 0.05), and oxidative stress markers including GPx activity in lungs (P < 0.05). Moreover, waterpipe smoke increased catalase activity in the lung (P < 0.05). However, none of the treatments altered IL-10 levels.

DISCUSSION AND CONCLUSION

Results of cigarette smoking confirmed previous finding. Waterpipe results indicate that, similar to cigarettes, exposure to waterpipe tobacco smoke is harmful to the lungs.

Cytokines as molecular targets for aryl hydrocarbon receptor ligands: implications for toxicity and xenobiotic detoxification

INTRODUCTION

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor historically known for regulating expression of several important drug-detoxifying proteins. Besides drug metabolism pathways, cytokines have been recently recognized as targeted by the AhR signaling cascade, which may contribute to toxicity and changes in xenobiotic detoxification caused by AhR agonists.

AREAS COVERED

This article summarizes the nature of the main cytokines regulated by AhR ligands and reviews their involvement in toxic effects of AhR ligands, especially in relation with inflammation. The article also discusses the potential implications for drug detoxification pathways.

EXPERT OPINION

Even if various cytokines, including inflammatory ones, have already been demonstrated to constitute robust targets for AhR, the exact role played by AhR with respect to inflammation remains to be determined. Further studies are also required to better characterize the molecular mechanisms implicated in regulation of cytokines by AhR ligands and to determine the role that may play AhR-targeted cytokines in alteration of xenobiotic detoxification. Finally, changes in cytokine receptor expression triggered by AhR ligands have additionally to be taken into account to better and more extensively comprehend the role played by AhR in the cytokine/inflammation area.

In utero exposure to benzo(a)pyrene predisposes offspring to cardiovascular dysfunction in later-life

In utero exposure of the fetus to benzo(a)pyrene [B(a)P], a polycyclic aromatic hydrocarbon, is thought to dysregulate cardiovascular development. To investigate the effects of in utero B(a)P exposure on cardiovascular development, timed-pregnant Long Evans Hooded (LEH) rats were exposed to diluent or B(a)P (150, 300, 600 and 1200 μg/kg/BW) by oral gavage on embryonic (E) days E14 (the metamorphosing embryo stage) through E17 (the 1st fetal stage). There were no significant effects of in utero exposure to B(a)P on the number of pups born per litter or in pre-weaning growth curves. Pre-weaning profiles for B(a)P metabolite generation from cardiovascular tissue were shown to be dose-dependent and elimination of these metabolites was shown to be time-dependent in exposed offspring. Systolic blood pressure on postnatal day P53 in the middle and high exposure groups of offspring were significantly elevated as compared to controls. Microarray and quantitative real-time PCR results were directly relevant to a biological process pathway in animal models for "regulation of blood pressure". Microarray and quantitative real-time PCR analysis revealed upregulation of mRNA expression for angiotensin (AngII), angiotensinogen (AGT) and endothelial nitric oxide synthase (eNOS) in exposed offspring. Biological network analysis and gene set enrichment analysis subsequently identified potential signaling mechanisms and molecular pathways that might explain the elevated systolic blood pressures observed in B(a)P-exposed offspring. Our findings suggest that in utero exposure to B(a)P predispose offspring to functional deficits in cardiovascular development that may contribute to cardiovascular dysfunction in later life.

Benzo(a)pyrene-induced pulmonary inflammation, edema, surfactant dysfunction, and injuries in rats: alleviation by farnesol

Benzo(a)pyrene (B(a)P) is a well-known environmental contaminant and carcinogen. Its sources include tobacco smoke, automobile exhaust, forest fire, and other combustion processes. Farnesol, an active principle of Vachellia farnesiana and other aromatic plants, possesses preventive properties against various toxicities. Present study was designed to estimate chemopreventive effects of farnesol against B(a)P-induced pulmonary injuries. To determine the protective effects of farnesol, it was administered orally at 2 doses (100 and 200 mg/kg body weight [b.w.]) once daily for 14 days. Rats were exposed intratracheally to B(a)P, 5 mg/kg b.w. on days 12 and 14, thereafter assessed for pulmonary toxicities 24 hours post last dose of B(a)P. B(a)P-induced edema, inflammation, oxidative stress, and consequent damages in lungs were assessed in terms of total protein, total cell count, nitric oxide (NO), lactate dehydrogenase (LDH), alkaline phosphatase, and in bronchoalveolar lavage fluid (BALF). B(a)P also reduced the levels of phospholipids (lung surfactants) in BALF. However, pretreatment with farnesol at both the doses significantly reduced the lung injuries and inflammatory responses. Farnesol also protected the levels of phospholipids to normal when compared with control. It also modified the activities of B(a)P metabolizing enzymes NADPH-cytochrome P450 reductase, microsomal epoxide hydrolase (mEH), and glutathione S-transferase (GST) in lung tissue of rats. Present findings suggest a prominent role of farnesol against B(a)P-induced lung inflammation, edema, surfactant dysfunction, and epithelial damages in Wistar rats. In conclusion, farnesol shows lung protection against B(a)P toxicities in Wistar rats.

Alleviation of lung injury by glycyrrhizic acid in benzo(a)pyrene exposed rats: Probable role of soluble epoxide hydrolase and thioredoxin reductase

Benzo(a)pyrene [B(a)P] is known to alter lung physiology by interfering in various intracellular pathways including alterations in NF-κB activities, cytokine release and cell survival. NF-κB suppression/activation plays a major role in cell survival status. Present investigation deals with such kind of effects of B(a)P on lungs in relation with soluble epoxide hydrolase (sEH) and thioredoxin reductase (TrxR) activities. Glycyrrhizic acid (GA), an active principle of Glycyrrhiza glabra (Licorice), is known to modulate various molecular processes. In the present study, we investigated the protective effects of GA against B(a)P induced debilities in lungs of Wistar rats. Intratracheal instillation of B(a)P significantly suppressed NF-κB translocation, sEH, TrxR and catalase activities in lung tissue. A marked induction of H(2)O(2) levels along with caspases activation (caspases-2, -3, -6, -8, and -9) in lung tissue after B(a)P exposure was observed. Lung injury was assessed by measuring lactate dehydrogenase (LDH), alkaline phosphatase (ALP), total cell count, total protein, neutrophil elastase activity in bronchoalveolar lavage fluid (BALF). Reduction in phospholipid content further potentiated these parameters. GA oral administration (50 and 100mg/kg b.wt.) significantly showed protection of lung epithelium by suppression of caspases activities in lung tissue and reduction of total protein, total cells, elastase activity, LDH and ALP activities along with fortification of phospholipids in BALF. Histological observations also confirm the findings in above mentioned parameters. Results indicate a strong correlation between amelioration of sEH and TrxR activities, and NF-κB activation. The present investigation gives an insight into probable mechanisms of lung injuries induced by short term exposures of B(a)P and prevention by glycyrrhizic acid.

Aryl hydrocarbon receptor-dependent induction of the IgA receptor FcαRI by the environmental contaminant benzo(a)pyrene in human macrophages

Polycyclic aromatic hydrocarbons (PAHs), such as benzo(a)pyrene (BaP), are widely distributed toxic environmental contaminants well known to regulate gene expression through activation of the aryl hydrocarbon receptor (AhR). In the present study, we demonstrated that the IgA receptor FcαRI/CD89 constitutes a molecular target for PAHs. Indeed, in vitro exposure to BaP markedly increased mRNA and protein expression of FcαRI in primary human macrophages; intratracheal instillation of BaP to rats also enhanced mRNA expression of FcαRI in alveolar macrophages. BaP concomitantly increased activity of the previously uncharacterized -1734 to -42 fragment of the FcaRI promoter that we subcloned in a luciferase reporter vector. Three-methylcholanthrene, a PAH known to activate AhR like BaP, induced FcαRI expression, in contrast to benzo(e)pyrene, a PAH known to poorly interact with AhR. Moreover, FcαRI induction in BaP-exposed human macrophages was fully prevented by down-regulating AhR expression through small interference RNA transfection. In addition, BaP increased nuclear protein binding to a consensus AhR-related xenobiotic-responsive element found in the FcαRI gene promoter, as revealed by electrophoretic mobility shift assay. Overall, these data highlight an AhR-dependent up-regulation of FcαRI in response to BaP, which may contribute to the deleterious effects of environmental PAHs toward the immune/inflammatory response and which also likely emphasizes the role played by AhR in the regulation of genes involved in immunity and inflammation.

Role of the xenobiotic receptor in inflammatory bowel disease

BACKGROUND

Gene-environment interplay modulates inflammatory bowel diseases (IBD). Dioxin-like compounds can activate the aryl hydrocarbon receptor (AhR) and alter macrophage function as well as T-cell polarization. We hypothesized that attenuation of the AhR signaling pathway will ameliorate colitis in a murine model of IBD.

METHODS

Dextran sulfate sodium (DSS) colitis was induced in C57BL/6 AhR null mice (AhR(-/-) ), heterozygous mice (AhR(-/+) ), and their wildtype (WT) littermates. Clinical and morphopathological parameters were used to compare the groups.

PATIENTS

AhR pathway activation was analyzed in biopsy specimens from 25 IBD patients and 15 healthy controls.

RESULTS

AhR(-/-) mice died before the end of the treatment. However, AhR(-/+) mice exhibited decreased disease activity compared to WT mice. The AhR(-/+) mice expressed less proinflammatory cytokines such as tumor necrosis factor alpha (TNF-α) (6.1- versus 15.7-fold increase) and IL17 (23.7- versus 67.9-fold increase) and increased antiinflammatory IL-10 (2.3-fold increase) compared with the AhR(+/+) mice in the colon. Colonic macrophage infiltration was attenuated in the AhR(-/+) group. AhR and its downstream targets were significantly upregulated in IBD patients versus control (CYP1A1 -19.9, and IL8- 10-fold increase).

CONCLUSIONS

Attenuation of the AhR receptor expression resulted in a protective effect during DSS-induced colitis, while the absence of AhR exacerbated the disease. Abnormal AhR pathway activation in the intestinal mucosa of IBD patients may promote chronic inflammation. Modulation of AhR signaling pathway via the diet, cessation of smoking, or administration of AhR antagonists could be viable strategies for the treatment of IBD.

Combined CXCR1/CXCR2 antagonism decreases radiation-induced alveolitis in the mouse

The mechanisms leading to the radiation-induced lung responses of alveolitis and fibrosis are largely unknown. Herein we investigated whether CXC receptor 1 and 2 antagonism with CXCL8((3-72))K11R/G31P (G31P), a protein that reduces neutrophil chemotaxis in acute inflammatory response models, decreases the lung response to radiation. Mice of the AKR/J (alveolitis/pneumonitis responding) and KK/HIJ (fibrosis) strains received 18 Gy whole-thorax irradiation and a subset of these mice were treated with G31P (500 µg/kg) three times per week from the day of irradiation until euthanasia due to respiratory distress symptoms or 20 weeks after radiation treatment. Irradiated mice of both strains receiving G31P survived longer than mice receiving radiation alone. Radiation- and G31P-treated AKR/J mice surviving to the end of the experiment developed significantly less alveolitis, as measured histologically, than mice receiving radiation alone, but this difference was not evident in KK/HIJ mice. Using immunohistochemistry, G31P treatment was shown to increase the numbers of Gr-1-positive cells (neutrophils) in the lungs of unirradiated mice relative to control mice injected with saline, but the antagonist did not alter the numbers of Gr-1-positive cells in the lungs of radiation-treated mice. We conclude that G31P treatment reduces radiation-induced alveolitis but not fibrosis in mice.

Tiotropium bromide exerts anti-inflammatory activity in a cigarette smoke mouse model of COPD

Tiotropium bromide is a long acting muscarinic antagonist (LAMA), marketed under the brand name Spiriva, for the treatment of chronic obstructive pulmonary disease (COPD). Besides its proven direct bronchodilatory activity, recent clinical studies demonstrated that tiotropium is able to reduce the exacerbation rate and impact the clinical course of COPD. One significant pathological feature believed to be causative for the progressive nature of COPD is chronic pulmonary inflammation. The aim of the present study was to investigate the anti-inflammatory activity of tiotropium on cigarette smoke-induced pulmonary inflammation in mice. C57Bl/6 mice were exposed to cigarette smoke (CS) for four days with increasing exposure time for up to 6h per day to elicit pulmonary inflammation and mediator release. One hour before smoke exposure, animals were treated with tiotropium by inhalation (0.01-0.3mg/mL) for 5 min; 18h after the last CS exposure a bronchoalveolar lavage was performed. Tiotropium concentration-dependently inhibited pulmonary neutrophilic inflammation with an IC(50) of 0.058 mg/mL and a maximum inhibition of 60% at 0.3mg/mL. Furthermore, the CS-induced pulmonary release of leukotriene B(4), interleukin-6, keratinocyte-derived chemokine, monocyte chemotactic protein-1, macrophage inflammatory protein-1 alpha and -2, and tumor necrosis factor alpha was dose-dependently reduced. The bronchodilatory activity of tiotropium against acetycholine-induced bronchoconstriction was found to be in the same dose range as the anti-inflammatory activity with an IC(50) of 0.045 mg/mL and a maximum bronchodilation of 90% at 0.3mg/mL. Our data suggest that the beneficial effects of tiotropium on the course of COPD shown in patients may be associated with an anti-inflammatory activity.

Benzo[a]pyrene diol epoxide stimulates an inflammatory response in normal human lung fibroblasts through a p53 and JNK mediated pathway

Cellular responses to carcinogens are typically studied in transformed cell lines, which do not reflect the physiological status of normal tissues. To address this question, we have characterized the transcriptional program and cellular responses of human lung WI-38 fibroblasts upon exposure to the ultimate carcinogen benzo[a]pyrene diol epoxide (BPDE). In contrast to observations in cell lines, we find that BPDE treatment induces a strong inflammatory response in these normal fibroblasts. Whole-genome microarrays show induction of numerous inflammatory factors, including genes that encode interleukins (ILs), growth factors and enzymes related to prostaglandin synthesis and signaling. Real-time reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA) revealed a time- and dose-dependent-induced expression and production of cyclooxygenase 2, prostglandin E2 and IL1B, IL6 and IL8. In parallel, cell cycle progression and DNA repair processes were repressed, but DNA damage signaling was increased via p53-Ser15 phosphorylation and induced expression levels of GADD45A, CDKN1A, BTG2 and SESN1. Network analysis suggested that activator protein 1 transcription factors may link the cell cycle response and DNA damage signaling with the inflammatory stress-response in these cells. We confirmed this hypothesis by showing that p53-dependent signaling through c-jun N-terminal kinase (JNK) led to increased cJun-Ser63 phosphorylation and that inhibition of JNK-mediated cJun activation using p53- or JNK-specific inhibitors significantly reduced IL gene expression and subsequent production of IL8. This is the first demonstration that a strong inflammatory response is triggered in normal fibroblasts by BPDE and that this occurs through coordinated regulation with other cellular processes.

Exposure of human skin to benzo[a]pyrene: role of CYP1A1 and aryl hydrocarbon receptor in oxidative stress generation

Exposure to benzo[a]pyrene (BaP) can induce inflammatory skin diseases and skin cancer, which are both associated to oxidative stress. BaP is known to bind with high specificity to the aryl hydrocarbon receptor (AhR), modifying the expression of CYP1A1, involved both in cancer and inflammation. While the current knowledge is based on murine skin and cell culture data, in this study human healthy skin has been treated with 5muM BaP in conditions simulating occupational and environmental exposure. AhR and CYP1A1 expression was evaluated by Western blotting, which revealed their presence even in control untreated skin; both enzyme and receptor increased more than twofold after exposure to BaP. AhR expression level was lower than CYP1A1 in basal conditions and following induction. Oxidative stress was evaluated in terms of MTT reduction, protein peroxidation and reactive oxygen species (ROS) formation. A significant increase in ROS and carbonyl compound production, as well as reduced tissue viability have been determined by BaP. The results of this experiment indicate that BaP, an AhR agonist, can significantly increase receptor and CYP1A1 expression and induce oxidative stress in human skin, confirming the involvement of this pathway in the pathogenesis of tissue damage due to polycyclic aromatic hydrocarbons.

The NF-kappaB activation pathways, emerging molecular targets for cancer prevention and therapy

IMPORTANCE OF THE FIELD

Nuclear factor kappa B (NF-kappaB) is activated by a variety of cancer-promoting agents. The reciprocal activation between NF-kappaB and inflammatory cytokines makes NF-kappaB important for inflammation-associated cancer development. Both the constitutive and anticancer therapeutic-induced NF-kappaB activation blunts the anticancer activities of the therapy. Elucidating the roles of NF-kappaB in cancer facilitates developing approaches for cancer prevention and therapy.

AREAS COVERED IN THIS REVIEW

By searching PubMed, we summarize the progress of studies on NF-kappaB in carcinogenesis and cancer cells' drug resistance in recent 10 years.

WHAT THE READER WILL GAIN

The mechanisms by which NF-kappaB activation pathways are activated; the roles and mechanisms of NF-kappaB in cell survival and proliferation, and in carcinogenesis and cancer cells' response to therapy; recent development of NF-kappaB-modulating means and their application in cancer prevention and therapy.

TAKE HOME MESSAGE

NF-kappaB is involved in cancer development, modulating NF-kappaB activation pathways has important implications in cancer prevention and therapy. Due to the complexity of NF-kappaB roles in different cancers, careful evaluation of NF-kappaB's in each cancer type is crucial in this regard. More cancer cell-specific NF-kappaB inhibiting means are desired for improving anticancer efficacy and reducing systemic toxicity.

Transcriptional signature of human macrophages exposed to the environmental contaminant benzo(a)pyrene

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed immunotoxic and carcinogenic environmental contaminants, known to affect macrophages. In order to identify their molecular targets in such cells, we have analyzed gene expression profile of primary human macrophages treated by the prototypical PAH benzo(a)pyrene (BaP), using pangenomic oligonucleotides microarrays. Exposure of macrophages to BaP for 8 and 24 h resulted in 96 and 1100 genes, differentially expressed by at least a twofold change factor, respectively. Some of these targets, including the chemokine receptor CXCR5, the G protein-coupled receptor 35 (GPR35), and the Ras regulator RASAL1, have not been previously shown to be affected by PAHs, in contrast to others, such as interleukin-1beta and the aryl hydrocarbon receptor (AhR) repressor. These BaP-mediated gene regulations were fully validated by reverse transcription-quantitative polymerase chain reaction assays for some selected genes. Their bioinformatic analysis indicated that biological functions linked to immunity, inflammation, and cell death were among the most affected by BaP in human macrophages and that the AhR and p53 signaling pathways were the most significant canonical pathways activated by the PAH. AhR and p53 implications were moreover fully confirmed by the prevention of BaP-related upregulation of some selected target genes by AhR silencing or the use of pifithrin-alpha, an inhibitor of PAH bioactivation-related DNA damage/p53 pathways. Overall, these data, through identifying genes and signaling pathways targeted by PAHs in human macrophages, may contribute to better understand the molecular basis of the immunotoxicity of these environmental contaminants.

Aryl hydrocarbon receptor-dependent induction of the NADPH oxidase subunit NCF1/p47 phox expression leading to priming of human macrophage oxidative burst

Polycyclic aromatic hydrocarbons such as benzo(a)pyrene (BaP) are toxic environmental contaminants known to regulate gene expression through activation of the aryl hydrocarbon receptor (AhR). In the present study, we demonstrated that acute treatment by BaP markedly increased expression of the NADPH oxidase subunit gene neutrophil cytosolic factor 1 (NCF1)/p47(phox) in primary human macrophages; NCF1 was similarly up-regulated in alveolar macrophages from BaP-instilled rats. NCF1 induction in BaP-treated human macrophages was prevented by targeting AhR, through its chemical inhibition or small interference RNA-mediated down-modulation of its expression. BaP moreover induced activity of the NCF1 promoter sequence, containing a consensus AhR-related xenobiotic-responsive element (XRE), and electrophoretic mobility shift assays and chromatin immunoprecipitation experiments indicated that BaP-triggered binding of AhR to this XRE. Finally, we showed that BaP exposure resulted in p47(phox) protein translocation to the plasma membrane and in potentiation of phorbol myristate acetate (PMA)-induced superoxide anion production in macrophages. This BaP priming effect toward NADPH oxidase activity was inhibited by the NADPH oxidase specific inhibitor apocynin and the chemical AhR inhibitor alpha-naphtoflavone. These results indicated that BaP induced NCF1/p47(phox) expression and subsequently enhanced superoxide anion production in PMA-treated human macrophages, in an AhR-dependent manner; such an NCF1/NADPH oxidase regulation by polycyclic aromatic hydrocarbons may participate in deleterious effects toward human health triggered by these environmental contaminants, including atherosclerosis and smoking-related diseases.

The functional significance behind expressing two IL-8 receptor types on PMN

PMN are critical to innate immunity and are fundamental to antibacterial defense. To localize to sites of infection, PMN possess receptors that detect chemoattractant stimuli elicited at the site, such as chemokines, complement split products, or bioactive lipids. Signaling through these receptors stimulates chemotaxis toward the site of infection but also activates a number of biochemical processes, with the result that PMN kill invading bacteria. PMN possess two receptors, CXCR1 and CXCR2, for the N-terminal ELR motif-containing CXC chemokines, although only two chemokine members bind both receptors and the remainder binding only CXCR2. This peculiar pattern in receptor specificity has drawn considerable interest and investigation into whether signaling through each receptor might impart unique properties on the PMN. Indeed, at first glance, CXCR1 and CXCR2 appear to be functionally redundant; however, there are differences. Considering these proinflammatory activities of activating PMN through chemokine receptors, there has been great interest in the possibility that blocking CXCR1 and CXCR2 on PMN will provide a therapeutic benefit. The literature examining CXCR1 and CXCR2 in PMN function during human and modeled diseases will be reviewed, asking whether the functional differences can be perceived based on alterations in the role PMN play in these processes.