Induction of cytochrome P-450 1A1 in human hepatoma HepG2 and lung carcinoma NCI-H322 cells by motorcycle exhaust particulate

Xenobiotica-metabolizing enzymes in the lung of experimental animals, man and in human lung models

The xenobiotic metabolism in the lung, an organ of first entry of xenobiotics into the organism, is crucial for inhaled compounds entering this organ intentionally (e.g. drugs) and unintentionally (e.g. work place and environmental compounds). Additionally, local metabolism by enzymes preferentially or exclusively occurring in the lung is important for favorable or toxic effects of xenobiotics entering the organism also by routes other than by inhalation. The data collected in this review show that generally activities of cytochromes P450 are low in the lung of all investigated species and in vitro models. Other oxidoreductases may turn out to be more important, but are largely not investigated. Phase II enzymes are generally much higher with the exception of UGT glucuronosyltransferases which are generally very low. Insofar as data are available the xenobiotic metabolism in the lung of monkeys comes closed to that in the human lung; however, very few data are available for this comparison. Second best rate the mouse and rat lung, followed by the rabbit. Of the human in vitro model primary cells in culture, such as alveolar macrophages and alveolar type II cells as well as the A549 cell line appear quite acceptable. However, (1) this generalization represents a temporary oversimplification born from the lack of more comparable data; (2) the relative suitability of individual species/models is different for different enzymes; (3) when more data become available, the conclusions derived from these comparisons quite possibly may change.

The use of a 0.20 μm particulate matter filter decreases cytotoxicity in lung epithelial cells following air-liquid interface exposure to motorcycle exhaust

This study was designed to investigate whether the use of a 0.20 μm particulate matter (PM) filter reduced the cytotoxicity induced by motorcycle exhaust (ME), a mixture of gases and particles, in lung epithelial cells cultured in air-liquid interface (ALI) inserts. The concentrations of PM, carbon monoxide, carbon dioxide, total hydrocarbons (THC), total volatile organic compounds, and nitrogen oxides in both filtered ME (fME) by a 0.20 μm filter and non-filtered ME (non-fME) were measured. Lung epithelial cells were exposed to clean air, fME, or non-fME in the ALI chamber. Cell relative viabilities (CRV) and the reactive oxygen species (ROS) generation were determined. Our results revealed that PM_2.5 was the main compound of PM in ME. After filtration, PM and THC levels were significantly reduced, as compared with non-fME. When compared with the clean air exposed group, the CRV in both fME and non-fME-exposed group was significantly reduced (p < 0.001), while their ROS generation were markedly increased (p < 0.001). When compared with non-fME-exposed group, the CRV and ROS generation were significantly improved following fME exposure (p < 0.05). As a result, of PM and THC concentrations were decreased approximately 90% and 22.71%, respectively, the CRV was improved from 40.4% (non-fME) to 55.7% (fME), and the increased ROS generation by non-fME was decreased about 51.6%. When BEAS-2B cells were exposed to fME, a time-dependent reduction in CRV was observed. In conclusion, our findings suggest that ME-exposure in the ALI system induces cytotoxicity and oxidative stress responses. The addition of a 0.20 μm PM filter significantly modifies the particulate composition in PM and the concentration of THC, and shows protective effects by improving the survival of exposed lung epithelial cells and reducing the ROS generation. Therefore, emission factors such as different size of PM and THC from motorcycles may play a role in ME-induced toxicity.

An assessment of exposure and effects of persistent organic pollutants in an urban Cooper's hawk (Accipiter cooperii) population

Among the stressors confronting urban wildlife, chemical contaminants pose a particular problem for high trophic feeding species. Previous data from fortuitous carcass collections revealed surprisingly high levels of persistent organic pollutants in raptor species, including the Cooper's hawk (Accipiter cooperii), from urbanized areas of southwestern British Columbia, Canada. Thus, in 2012 and 2013, we followed up on that finding by measuring POPs in blood samples from 21 adult and 15 nestling Cooper's hawks in Vancouver, a large urban area in southwestern Canada. Reproductive success and circulating thyroid hormones were measured to assess possible toxicological effects. Model comparisons showed concentrations of polychlorinated biphenyls (ΣPCBs) were positively influenced by the level of urbanization. Total thyroxin (TT4) was negatively associated with increases in ΣPCBs. Total triiodothyronine (TT3) was negatively associated with ΣPCBs and polybrominated diphenyl ethers (ΣPBDEs). The legacy insecticide, dieldrin, appeared to have some negative influence on reproductive success. There is some evidence of biochemical perturbation by PBDEs and lingering impact of legacy POPs which have not been used for at least 40 years, but overall Cooper's hawks have successfully populated this urban environment.

Aryl hydrocarbon receptor activation and overexpression upregulated fibroblast growth factor-9 in human lung adenocarcinomas

We had previously reported that aryl hydrocarbon receptors (AhRs) are overexpressed in lung adenocarcinomas. Benzo[a]pyrene (BaP), an AhR agonist, increased FGF-9 expression in human lung adenocarcinoma cells. Similarly, several AhR agonists increased FGF-9 mRNA levels, and BaP-induced FGF-9 expression was prevented by cotreatment with AhR antagonist in human lung adenocarcinoma cells. Furthermore, AhR agonists increased transcriptional activity of FGF-9 promoter. Modulation of AhR expression via RNA interference or transient overexpression respectively reduced or increased both constitutive and BaP-induced FGF-9 expression in human lung cells. These results suggested that AhR activation and overexpression increased FGF-9 expression in lung cells. FGF-9 increased growth of lung fibroblasts but not that of lung adenocarcinoma cells. However, conditioned media collected from FGF-9-treated fibroblasts increased cell growth of lung adenocarcinoma cells. Furthermore, lung adenocarcinoma cells expressed FGF receptor 2 and cotreatment with anti-FGF receptor 2 prevented the interaction between fibroblasts and tumor cells. It is likely that FGF-9-stimulated fibroblasts secreted unknown factors, which activated FGF receptor 2 and subsequently promoted growth of lung adenocarcinoma cells. We further compared AhR and FGF-9 expression in 146 non-small cell lung cancer (NSCLC) cases by immunohistochemistry. FGF-9 expression was more common in adenocarcinomas than in squamous cell carcinomas. Furthermore, FGF-9 and AhR expression were well correlated in lung adenocarcinomas. These results suggest that AhR expression correlated positively with FGF-9 expression in lung adenocarcinomas, which might promote tumor growth by modulating communication between tumor cells and fibroblasts. Preventing AhR overexpression or disturbing FGF-9 function may reduce the development of lung adenocarcinomas. (c) 2009 UICC.

A highly sensitive fluorogenic probe for cytochrome P450 activity in live cells

A derivative of rhodamine 110 has been designed and assessed as a probe for cytochrome P450 activity. This probe is the first to utilize a 'trimethyl lock' that is triggered by cleavage of an ether bond. In vitro, fluorescence was manifested by the CYP1A1 isozyme with k(cat)/K(M)=8.8x10(3)M(-1)s(-1) and K(M)=0.09microM. In cellulo, the probe revealed the induction of cytochrome P450 activity by the carcinogen 2,3,7,8-tetrachlorodibenzo-p-dioxin, and its repression by the chemoprotectant resveratrol.

Motorcycle exhaust induces reproductive toxicity and testicular interleukin-6 in male rats

Motorcycle exhaust (ME) from two-stroke engines contains many toxicants and poses a potential health hazard. The major objectives of the present study were to investigate the male reproductive toxicity of ME and the underlying mechanisms of toxicity. Male Wistar rats were exposed to ME by inhalation 1 h each in the morning and afternoon, Monday through Friday. Exposures to 1:50 diluted ME for 4 weeks or to 1:10 diluted ME for 2 and 4 weeks showed concentration- and time-dependent decreases of testicular weight, spermatid number, and cauda epididymal sperm number. Subsequent studies were done using 4-week exposure to 1:10 diluted ME. ME caused histopathological changes including testicular spermatocytic necrosis and seminiferous tubule atrophy and cauda epididymal formation of clusters of pyknotic and necrotic sperm cells. ME-exposed male rats mated with untreated females showed decreases of male mating index and female fertility index and an increase of implantation site loss. ME decreased 7-ethoxycoumarin O-deethylase and superoxide dismutase activities but induced proinflammatory cytokine interleukin-6 (IL-6) messenger RNA (mRNA) in the testis. Male rats were exposed to ME with or without cotreatment with 50 mg/kg vitamin E orally for 4 weeks. ME decreased serum testosterone concentration. This effect was reversed by cotreatment with vitamin E. ME decreased testicular spermatid number and induced IL-6 mRNA and protein. These effects were also reversed by the vitamin E cotreatment. The present findings show that ME causes male reproductive effects and induces testicular IL-6 in rats by mechanisms involving induction of oxidative stress and inhibition of steroidogenesis.

Motorcycle exhaust particles augment antigen-induced airway inflammation in BALB/c mice

Evidence indicates that environment pollutants from fossil fuel combustion compromise the immune system by enhancing allergic reactions and damaging the respiratory tract. This study was performed to investigate the effects of motorcycle exhaust particles (MEP), a major air pollutant especially in the urban areas of Taiwan, on allergen-induced airway inflammatory reactions in lab animals. BALB/c mice were intratracheally instilled with ovalbumin (OVA), MEP, or phosphate-buffered saline, 3 times every 2 wk. Airway hyperresponsiveness was measured in unrestrained mice by barometric plethsmography. Bronchoalveolar lavage fluid (BALF) and serum from treated animals were collected for cytokine and antibody determination by enzyme-linked immunosorbent assay (ELISA). Lung tissue stained with hematoxylin/eosin was examined. Data showed that MEP augmented OVA-induced airway inflammation; characterized by infiltration of eosinophils and neutrophils in BALF and lung tissue inflammation. The combination of OVA and MEP markedly increased interleukin-4 (IL-4), interleukin-5 (IL-5), and tumor necrosis factor-alpha (TNF-alpha) protein levels in BALF. In addition, MEP also augmented OVA-induced rise in OVA-specific immunoglobulin (Ig) G1 and IgE and airway hyperresponsiveness. Pretreated lavage cells with mitogen-activated protein kinase (MAPK) inhibitors showed that TNF-alpha release was significantly inhibited. This study found that MEP augmented antigen-induced allergic airway inflammation and airway hyperresponsiveness through a Th2-dominant pathway.

Human breast biomonitoring and environmental chemicals: use of breast tissues and fluids in breast cancer etiologic research

Extensive research indicates that the etiology of breast cancer is complex and multifactorial and may include environmental risk factors. Breast cancer etiology and exposure to xenobiotic compounds, diet, electromagnetic fields, and lifestyle have been the subject of numerous scientific inquiries, but research has yielded inconsistent results. Biomonitoring has been used to explore associations between breast cancer and levels of environmental chemicals in the breast. Research using breast tissues and fluids to cast light on the etiology of breast cancer is, for the most part, predicated on the assumption that the tissue or fluid samples either contain measurable traces of the environmental agent(s) associated with the cancer or that they retain biological changes that are biomarkers of such exposure or precursors of carcinogenic effect. In this paper, we review breast cancer etiology research utilizing breast biomonitoring. We first provide a brief synopsis of the current state of understanding of associations between exposure to environmental chemicals and breast cancer etiology. We then describe the published breast cancer research on tissues and fluids, which have been used for biomonitoring, specifically human milk and its components, malignant and benign breast tissue, nipple aspirate fluid (NAF) and breast cyst fluid. We conclude with a discussion on recommendations for biomonitoring of breast tissues and fluids in future breast cancer etiology research. Both human milk and NAF fluids, and the cells contained therein, hold promise for future biomonitoring research into breast cancer etiology, but must be conducted with carefully delineated hypotheses and a scientifically supportable epidemiological approach.

Upregulation of Cyclooxygenase-2 by Motorcycle Exhaust Particulate-Induced Reactive Oxygen Species Enhances Rat Vascular Smooth Muscle Cell Proliferation

Long-term exposure to particulate air pollution has been implicated as a risk factor for cardiovascular disease and mortality. Short-term exposure has also been suggested to contribute to complications of atherosclerosis. Aberrant regulation of smooth muscle cell proliferation is thought to associate with the pathophysiology of vascular disorders such as atherosclerosis. In this study, we investigate the influence of organic extracts of motorcycle exhaust particulates (MEPE) on rat vascular smooth muscle cell (VSMC) proliferation and related regulation signaling. Exposure of VSMCs to MEPE (10-100 microg/mL) enhanced serum-induced VSMC proliferation. The expression of proliferating cell nuclear antigen (PCNA) was also enhanced in the presence of MEPE. VSMCs treated with MEPE induced the increase in the extent of cyclooxygenase (COX)-2 mRNA and protein expression and prostaglandin E 2 production, whereas the level of COX-1 protein was unchanged. Moreover, MEPE increased the production of reactive oxygen species (ROS) in VSMCs in a dose-dependent manner. MEPE could also trigger time-dependently extracellular signal-regulated kinase (ERK)1/2 phosphorylation in VSMCs, which was attenuated by antioxidants N-acetylcysteine (NAC) and pyrrolidinedithiocarbamate (PDTC). The level of translocation of nuclear factor (NF)-kappaB-p65 in the nuclei of VSMCs was also increased under MEPE exposure. The potentiating effect of MEPE on serum-induced VSMC proliferation could be abolished by COX-2 selective inhibitor NS-398, specific ERK inhibitor PD98059, and antioxidants NAC and PDTC. Taken together, these findings suggest that MEPE may contribute to the enhancement of the pathogenesis of cardiovascular diseases by augmenting proliferation of VSMCs through a ROS-regulated ERK1/2-activated COX-2 signaling pathway.

Human milk biomonitoring data: interpretation and risk assessment issues

Biomonitoring data can, under certain conditions, be used to describe potential risks to human health (for example, blood lead levels used to determine children's neurodevelopmental risk). At present, there are very few chemical exposures at low levels for which sufficient data exist to state with confidence the link between levels of environmental chemicals in a person's body and his or her risk of adverse health effects. Human milk biomonitoring presents additional complications. Human milk can be used to obtain information on both the levels of environmental chemicals in the mother and her infant's exposure to an environmental chemical. However, in terms of the health of the mother, there are little to no extant data that can be used to link levels of most environmental chemicals in human milk to a particular health outcome in the mother. This is because, traditionally, risks are estimated based on dose, rather than on levels of environmental chemicals in the body, and the relationship between dose and human tissue levels is complex. On the other hand, for the infant, some information on dose is available because the infant is exposed to environmental chemicals in milk as a "dose" from which risk estimates can be derived. However, the traditional risk assessment approach is not designed to consider the benefits to the infant associated with breastfeeding and is complicated by the relatively short-term exposures to the infant from breastfeeding. A further complexity derives from the addition of in utero exposures, which complicates interpretation of epidemiological research on health outcomes of breastfeeding infants. Thus, the concept of "risk assessment" as it applies to human milk biomonitoring is not straightforward, and methodologies for undertaking this type of assessment have not yet been fully developed. This article describes the deliberations of the panel convened for the Technical Workshop on Human Milk Surveillance and Biomonitoring for Environmental Chemicals in the United States, held at the Hershey Medical Center, Pennsylvania State College of Medicine, on several issues related to risk assessment and human milk biomonitoring. Discussion of these topics and the thoughts and conclusions of the panel are described in this article.

Motorcycle exhaust particles induce IL-8 production through NF-kappaB activation in human airway epithelial cells

Motorcycle exhaust particles (MEP) are among the major air pollutants, especially in urban area of Taiwan. In our previous study, data showed that MEP induce proinflammatory and proallergic response profiles in BALB/c mice. Effects of MEP on interleukin (IL)-8 production in A549 human airway epithelial cells were further investigated in this study. It was found that MEP enhanced IL-8 protein and mRNA expression in human epithelial cells. Pretreatment with an NF-kappaB inhibitor (1 mM PDTC), extracellular signal-regulated kinase (ERK) inhibitor (50 microM PD98059), JNK inhibitor (25 microM SP600125), p38 inhibitor (2 microM SB203580), and three antioxidants (500 U/ml superoxide dismutase [SOD], 50 microM vitamin E, 10 mMN-acetylcysteine [NAC]) attenuated the MEP-induced increase in IL-8 production. Through further, direct detection of nuclear factor (NF)-kappaB activation in epithelial cells using immunoblotting of nuclear p65 and NF-kappaB reporter assay, data showed that MEP induced nuclear translocation of p65 and enhancement of NF-kappaB luciferase gene expression. MEP also induced activation of ERK, JNK, and p38 signaling pathways and produced an increase of oxidative stress in A549 cells. By using mitogen-activated protein kinase (MAPK) inhibitors and antioxidant, it was demonstrated that ERK inhibitor, JNK inhibitor, and antioxidants but not p38 inhibitor attenuated the MEP-induced increase in NF-kappaB reporter activity. In conclusion, evidence shows that filter-trapped particles emitted from unleaded gasoline-fueled, two-stroke motorcycle engines induce an increase in IL-8 production by activation of NF-kappaB in human airway epithelial cells.

Induction of fibroblast growth factor-9 and interleukin-1alpha gene expression by motorcycle exhaust particulate extracts and benzo(a)pyrene in human lung adenocarcinoma cells

Motorcycle exhaust particulates (MEP) contain carcinogenic polycyclic aromatic hydrocarbons including benzo(a)pyrene. This study has determined the ability of MEP to alter the expression of select genes from drug metabolism, cytokine, oncogene, tumor suppressor, and estrogen signaling families of human lung adenocarcinoma CL5 cells. cDNA microarray analyses and confirmation studies were performed using CL5 cells treated with 100 microg/ml MEP extract for 6 h. The results showed that MEP increased the mRNA levels of metabolic enzymes CYP1A1 and CYP1B1, proinflammatory cytokines interleukin (IL)-1alpha, IL-6, and IL-11, fibroblast growth factor (FGF)-6 and FGF-9, vascular endothelial growth factor (VEGF)-D, oncogene fra-1, and tumor suppressor p21. In contrast, MEP decreased tumor suppressor Rb mRNA in CL5 lung epithelial cells. Treatment with 10 microM benzo(a)pyrene for 6 h altered gene expression profiles, in a manner similar to those by MEP. Induction of IL-1alpha, IL-6, IL-11, and FGF-9 mRNA by MEP and benzo(a)pyrene was concentration and time dependent. Cotreatment with 2 mM N-acetylcysteine blocked the MEP- and benzo(a)pyrene-mediated induction. Treatment with MEP or benzo(a)pyrene increased IL-6 and IL-11 releases to CL5 cell medium. Incubation of human lung fibroblast WI-38 with MEP- or benzo(a)pyrene-induced CL5 conditioned medium for 4 days stimulated cell growth of the fibroblasts. Inhalation exposure of rats to 1:10 diluted motorcycle exhaust 2 h daily for 4 weeks increased CYP1A1, FGF-9, and IL-1alpha mRNA in lung. This present study shows that MEP and benzo(a)pyrene can induce metabolic enzyme, inflammatory cytokine, and growth factor gene expression in CL5 cells and stimulate lung epithelium-fibroblast interaction.

Metabolism and bioactivation of toxicants in the lung. The in vitro cellular approach

Lung is a target organ for the toxicity of inhalated compounds. The respiratory tract is frequently exposed to elevated concentrations of these compounds and become the primary target site for toxicity. Occupational, accidental or prolonged exposure to a great variety of chemicals may result in acute or delayed injury to cells of the respiratory tract. Nevertheless, lung has a significant capability of biotransforming such compounds with the aim of reducing its potential toxicity. In some instances, the biotransformation of a given compound can result in the generation of more reactive, and frequently more toxic, metabolites. Indeed, lung tissue is known to activate pro-carcinogens (i.e. polycyclic aromatic hydrocarbons or N-nitrosamines) into more reactive intermediates that easily form DNA adducts. Lungs express several enzymes involved in the metabolising of xenobiotics. Among them, cytochrome P450 enzymes are major players in the oxidative metabolism as well metabolic bioactivation of many organic toxicants, including pro-carcinogens. Xenobiotic-metabolising P450 enzymes are expressed in bronchial and bronchiolar epithelium, Clara cells, type II pneumocytes, and alveolar macrophages Individual CYP isoforms have different patterns of localisation within pulmonary tissue. With the aid of sensitive techniques (i.e. reverse transcriptase-polymerase chain reaction, RT-PCR) it has become possible to detect CYP1A1, CYP1B1, CYP2A6, CYP2B6, CYP2E1 and CYP3A5 mRNAs in lung cells. Less conclusive results have been obtained concerning CYP2Cs, CYP2D6 and CYP3A4. CYP3A5 protein appears to be widely present in all lung samples and is localised in the ciliated and mucous cells of the bronchial wall, bronchial glands, bronchiolar ciliated epithelium and in type I and type II alveolar epithelium. Lung cells also express Phase II enzymes such as epoxide hydrolase, UGT1A (glucuronyl transferase) and GST-P1 (glutathione S-transferase), which largely act as detoxifying enzymes. A key question concerning organ-specific chemical toxicity is whether the actual target has the capacity to activate (or efficiently inactivate) chemicals. Results of several studies indicate that the different xenobiotic-metabolising CYPs, present in the human lung and lung-derived cell lines, likely contribute to in situ activation of pulmonary toxins, among them, pro-carcinogens. Some CYPs, in particular CYP1A, are polymorphic and inducible. Interindividual differences in the expression of these CYPs may explain the different risk of developing lung toxicity (possibly cancer), by agents that require metabolic activation. Few cell lines, principally A549, have been used with variable success as an experimental model for investigating the mechanisms of toxicity. Although RT-PCR analysis has evidenced the presence of the major human pulmonary CYP mRNAs, the measurable P450 specific activities are, however, far below those present in human lungs. Detection of the toxicity elicited by reactive metabolites requires the use of metabolically competent cells; consequently, better performing cells are needed to ensure realistic in vitro prediction of toxicity. Genetic manipulation of lung-derived cells allowing them to re-express key biotransformation enzymes appear to be a promising strategy to improve their functionality and metabolic performance.

The occupational toxicologist: professionalism, morality and ethical standards in the context of legal and non-litigation issues

By its very nature, practice and intended applications, the profession of occupational toxicology has individual and collective responsibilities related to the design, conduct, interpretation and extrapolation of laboratory and controlled human clinical studies in order to determine the potential for industrial xenobiotics to produce adverse effects. The implications for health-related adverse effects in the workplace, and in the domestic and general environment carries many and various responsibilities for the toxicologist which are related to multiple and wide-ranging ethical issues. This review presents and discusses some of the major areas where the occupational toxicologist may experience potential ethical problems related to the conduct of routine professional activities. Emphasis is placed on the design, conduct, interpretation and reporting of laboratory studies; animal welfare; regulatory activities; human clinical volunteer studies; roles and responsibilities in defining workplace safety and protective measures; malpractices in various disciplines and work practices; misconduct in publication; and codes of ethical behavior.

Effects of motorcycle exhaust inhalation exposure on cytochrome P-450 2B1, antioxidant enzymes, and lipid peroxidation in rat liver and lung

The effects of motorcycle exhaust (ME) on metabolic and antioxidant enzymes and lipid peroxidation were determined using male rats exposed to 1:10 diluted ME by inhalation 2 h daily for 4 wk. For microsomal cytochrome P-450 enzymes, ME resulted in threefold increases of 7-ethoxyresorufin and pentoxyresorufin O-deethylase activities in liver and a sixfold increase of 7-ethoxyresorufin O-deethylase activity and an 80% decrease of pentoxyresorufin O-dealkylase activity in lung. The results of immunoblot analysis of microsomal proteins revealed that ME increased liver and lung cytochrome P-450 1A1 with minimal effects on cytochrome P-450 2E1. ME increased cytochrome P-450 2B1/2 proteins in liver but decreased cytochrome P-450 2B1 in lung. ME did not change microsomal cytochrome P-450 enzyme activity or protein level in kidney. For phase II enzymes, ME resulted in 53% and twofold increases of cytosolic NAD(P)H:quinone oxidoreductase activities in liver and lung, respectively, and no effect on microsomal UDP-glucuronosyltransferase activities. For antioxidant enzymes, ME produced 23% and 35% decreases of superoxide dismutase, 9% and 27% decreases of catalase, and no changes of glutathione peroxidase activities in liver and lung cytosols, respectively. For lipid peroxidation, the results of thiobarbituric acid assay showed that ME resulted in a twofold increase of formation of malondialdehyde by liver microsomes incubated with FeCl(3) -ADP. ME produced a threefold increase of malondialdehyde formation by lung microsomes. The present study demonstrates that ME inhalation exposure differentially modulates cytochrome P-450 2B1 and antioxidant enzymes and increases susceptibility to lipid peroxidation in rat liver and lung.

A review of experimental studies on diesel exhaust particles and nasal epithelium alterations

The aim of the present review is to summarize biological events in nasal epithelium after short-term exposure to diesel exhaust particles (DEP). Therefore human, animal, and in vitro studies carried out since 1987 are reviewed. Short-term exposure results included qualitative alterations characterized by immediate nasal hyperresponsiveness, antioxidant responses, marked epithelial inflammation, and a specific humoral response. In addition, studies on combined DEP/allergen challenge reported that, besides their intrinsic deleterious properties, DEP produced adjuvant-like effects on the immediate and late-phase response to allergen challenge, since they are able to mimic effects occurring after allergen challenge. DEP act deeply in nasal epithelium by (1) directing cytokine gene expression toward a Th2 profile, (2) enhancing local antigen-specific immunoglobulin E (IgE) production, and (3) driving in vivo isotype switch to IgE. Furthermore, DEP can induce in allergic subjects sensitization to a neoallergen, sensitization that did not occur with exposure to the neoantigen alone. Particulate pollutants such as DEP, encountered in urban areas, are therefore thought to be contributing causal factors to the exaggerated sensitization to allergens in subjects with appropriate genetic predisposition, sensitization that they might not otherwise have experienced. These findings add weight to the hypothesis that DEP are involved in the increased prevalence of airway allergic diseases.

Effect of frying-meat emission particulate on 17beta-estradiol 2- and 4-hydroxylation in human lung adenocarcinoma CL5 cells

The effect of airborne frying-meat emission particulate (FMEP) on metabolism of 17beta-estradiol (E(2)) to potentially toxic catechol estrogens 2- and 4-hydroxyestradiol (2- and 4-OH-E(2)) was determined using human lung adenocarcinoma CL5 cells treated with organic extracts of beef FMEP. E(2) was incubated with microsomes prepared from untreated CL5 cells or cells treated with 200 microg/ml FMEP extract for 6 h. E(2) metabolites formed were analyzed by high-performance liquid chromatography (HPLC). The results revealed that treatment with FMEP produced three-and twofold increases of 2- and 4-hydroxylation of E(2), respectively. Monooxygenase activity and immunoblot analyses showed that FMEP markedly induced microsomal 7-ethoxyresorufin O-deethylase (EROD) activity and cytochrome P-450 (CYP) IAI and CYPIBI protein levels. Similar increases in E(2) hydroxylation, EROD activity, and CYP protein levels were observed with HepG2 human hepatoma and MCF-7 human breast cancer cells treated with FMEP or 1 microM dibenz[a,h]anthracene. Cotreatment of CL5 cells with FMEP extract and 2 microM alpha-naphthoflavone, an arylhydrocarbon receptor antagonist, blocked the inductive effects of FMEP on E(2) hydroxylation and EROD activity. Additions of 0.01, 0.1, or 1 microM alpha-naphthoflavone, a CYP inhibitor, to microsomes produced concentration-dependent decreases in E(2) 2-hydroxylation and EROD activity of CL5 cells induced by dibenz[a,h]anthracene. The present finding demonstrates that FMEP can increase formation of 2-OH-E(2) and 4-OH-E(2) by human lung cells, and induction of CYP1A1 and CYP1B1 is a potential mechanism underlying increased E(2) metabolism. The toxicological significance of FMEP and estrogen interaction warrants further investigation.

Diesel exhaust particle-induced alterations of pulmonary phase I and phase II enzymes of rats

Although diesel exhaust particles (DEP) are known to produce pulmonary disorders, the xenobiotic metabolic pathways associated with DEP detoxification and bioactivation remain unclear. In this study, the effect of acute exposure of DEP on phase I and phase II enzymes of rat lung was investigated. Intratracheal administration of DEP produced an induction of cytochrome P-450 (CYP) 1A1 enzyme protein and activity at 1 d postexposure, with the enzyme level returning to control at 5 d postexposure. On the other hand, carbon black (CB), a particle control, did not show any induction of CYP1A1 protein or enzyme activity. However, both DEP and CB significantly decreased CYP2B1 protein and enzyme activity at 1 d postexposure. The decrease in CYP2B1 enzyme protein and activity by DEP or CB treatment was observed up to 7 d postexposure. DEP and CB treatments also significantly attenuated glutathione S-transferase (GST)-pi protein at 1 d postexposure. Both DEP and CB at 35 mg/kg significantly decreased the activities of GST and catalase at 1 and 7 d postexposure. DEP, but not CB, significantly induced quinone reductase (QR) activity at 7 d postexposure. This study suggests that DEP may induce CYP1A1 and QR enzymes via a chemical effect, while the carbonaceous core may be involved in the attenuation of CYP2B1, GST, and catalase proteins and enzyme activities.

Rapid communication: partitioning of persistent lipophilic compounds, including dioxins, between human milk lipid and blood lipid: an initial assessment

A systematic program of sampling and analysis of blood serum for dioxins, furans, and dioxinlike polychlorinated biphenyls (PCBs) has been initiated in the United States through the National Health and Nutrition Examination Survey (NHANES) program. While such data could potentially be used to estimate population-level changes in human milk lipid concentrations of chemicals, such estimates would depend on understanding the relationship between human blood lipid and milk lipid concentrations of the compounds of interest. For dioxins and furans, extremely limited data in humans currently exist for paired blood/milk samples. These data reviewed in this article, support the hypothesis that, over a population and across time, human milk lipid levels of these compounds generally reflect blood lipid levels. However, these data also suggest that significant variations in these ratios are possible among individuals and at various times.

Development and characterization of a stable epithelial cell line from Muta Mouse lung

We have isolated and characterized a stable epithelial cell line from Muta Mouse lung that is a suitable complement to the in vivo assay system. The cells are contact inhibited, forming a flat monolayer, and retain several epithelial/pulmonary characteristics. The genome is stable across more than 50 generations, with a modal chromosome number of 78. Spontaneous rates of micronuclei (19.2 +/- 1.4 per 1,000), sister chromatid exchanges (0.25 +/- 0.004 per chromosome), and chromosome aberrations ( approximately 4%) are lower than, or comparable to, other transgenic cell lines currently used in mutagenicity research. Fluorescence in situ hybridization analyses showed that 80% of cells contain three lambdagt10lacZ loci. Slot-blot analyses indicated that the average cell contains approximately 17 transgene monomers. Spontaneous mutant frequency at the lacZ transgene is stable (39.8 +/- 1.1 x 10(-5)), and the direct-acting mutagens N-ethyl-N-nitrosourea and ICR-191 yielded increases in mutant frequency of 6.3- and 3.2-fold above control, respectively. Benzo[a]pyrene (BaP) exposure increased mutant frequency more than 25-fold above control and did not require an exogenous metabolic activation mixture. Inhibition of Cyp1A1 by 5 microM alpha-naphthoflavone eliminated BaP mutagenesis. Activation and mutation induction by the heterocyclic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine required a low concentration (0.05% v/v) of exogenous rat liver S9. High activity of alpha, micro, and pi glutathione-S-transferase isozymes appears to confer resistance to the cytotoxic effects of xenobiotics. The cell line is a suitable complement to the in vivo Muta Mouse assay, and provides an opportunity for routine in vitro mutagenicity testing using an endpoint that is identical to that employed in vivo.

Iris colour of American kestrels varies with age, sex, and exposure to PCBs

For most species of birds, little is known about the pattern and significance of intraspecific variation in iris colour. In early winter, captive American kestrels could be subjectively placed into at least two age categories: 0.5-yr-old birds had all-brown irides, whereas those of older birds were red-brown. As part of a toxicological study on kestrels, we quantified iris colour objectively using a digital camera to examine potential variation due to age, sex, and exposure to polychlorinated biphenyls (PCBs). Red, green, and blue values, plus an overall measure of colour using principal components analysis (PC1), were derived for breeding and nonbreeding kestrels 1.5-6.5 yr old (fed PCBs), plus offspring 0.5 yr old (exposed to PCBs only in ovo). Age category (0.5, 1.5, and 2.5+ yr) and PCB exposure consistently had an effect on colour, while sex was significant only for red and almost so for PC1. ANOVA with age as a covariate revealed that the amount of red continued to increase throughout life, but PCBs suppressed the development of that colour.

Induction of cytochromes P-450 1A1 and 1B1 by motorcycle exhaust particulate in human breast cancer MCF-7 cells

The effects of motorcycle exhaust particulate (MEP) on cytochrome P-450-dependent monooxygenases were determined using MCF-7 human breast cancer cells treated with organic extracts of MEP. Treatment with MEP extract produced concentration- and time-dependent increases of monooxygenase activity in S9 fractions. Treatment with 50 microg/ml MEP extract for 24 h increased benzo[a]pyrene hydroxylase and 7-ethoxycoumarin, 7-ethoxyresorufin, and methoxyresorufin O-dealkylases activities in S9. Treatments with 1 and 10 microg/ml MEP extract for 24 h markedly enhanced catabolism of 17beta-estradiol in MCF-7 cells. Cotreatment of the cells with 2 microM alpha-naphthoflavone, a cytochrome P-450 inhibitor and arylhydrocarbon receptor antagonist, blocked the increase of benzo[a]pyrene hydroxylase activity induced by treatment with MEP extract alone. Immunoblot analyses of S9 proteins using a mouse monoclonal antibody 1-12-3 against rat cytochrome P-450 1A1 and a rabbit polyclonal antibody against human cytochrome P-450 1B1 revealed that MEP extract induced proteins immunorelated to cytochromes P-450 1A1 and 1B1. RNA blot analysis of total RNA using human cytochrome P-450 (CYP)1A1 3'-end and human CYP1B1 RT-PCR product cDNA probes showed that MEP extract increased the levels of cytochromes P-450 1A1 and 1B1 mRNA hybridizable to the respective cDNA probes. Treatment with 10 micro M benzo[a]pyrene, a component of MEP extract, for 24 h induced catalytic activity, protein, and mRNA of cytochromes P-450 1A1 and 1B1 in MCF-7 cells. Treatment with MEP extract increased cytochromes P-450 1A1 and 1B1 proteins and mRNA levels in NCI-H322 human lung carcinoma and CL5 human lung adenocarcinoma cells. The extract also increased cytochrome P-450 1A1, but not cytochrome P-450 1B1, protein, and mRNA, in HepG2 human hepatoma cells. The present findings demonstrate that MEP extract has the ability to induce cytochromes P-450 1A1 and 1B1 in the estrogen-responsive MCF-7 cells. Induction of the carcinogen- and estrogen-metabolizing cytochromes P-450 1A1 and 1B1 may be an important factor to consider in assessing the potential health effects associated with human exposure to MEP.

Alterations of motor nerve functions in animals exposed to motorcycle exhaust

The effect of motorcycle exhaust (ME) on the motor nerve was studied using animals exposed to the exhaust by inhalation, intratracheal, or intraperitoneal administration of ME particulate (MEP). A 4-wk ME inhalation and intratracheal instillation of MEP for 1 d in rats or intraperitoneal administration of MEP (0.5 g/kg/d for 1 d and 0.1 g/kg/d for 2 d) in mice significantly decreased both rota-rod performance and motor nerve conduction velocity. The effect of some polycyclic aromatic hydrocarbons on the motor nerve was also investigated. Treatment with benzo[a]pyrene (0.05 and 0.1 g/kg/d for 3 d), but not pyrene (0.1 g/kg/d for 3 d), resulted in significant decrease of motor nerve conduction velocity in mice. Moreover, the Na(+),K(+)-ATPase activities of sciatic nerves isolated from ME-, MEP-, or benzo[a]pyrene-exposed animals were decreased. Treatment with pyrene did not markedly affect the Na(+),K(+)-ATPase activity of sciatic nerve. The rats exposed to ME for 4 wk showed increases in blood and sciatic nerve manganese levels. Results indicate that motorcycle exhaust produces adverse effects on the motor nerve, which is associated with a fall in nerve Na(+),K(+)-ATPase activity.

Induction of cytochromes P450 1A1 and 1B1 in human lung adenocarcinoma CL5 cells by frying-meat emission particulate

The effect of airborne frying-meat emission particulate (FMEP) on cytochrome P450 (P450)-dependent monooxygenase was determined using human lung adenocarcinoma cell line CL5 treated with organic extract of FMEP prepared from beef, fish or pork. Treatment with fish FMEP extract caused greater increases of intracellular peroxide production and glutathione content than did beef and pork FMEP extracts. Treatment with 200 microg/ml beef, fish or pork FMEP extract for 6 h increased benzo[a]pyrene hydroxylase, 7-ethoxyresorufin and methoxyresorufin O-dealkylases activities in S9. Immunoblot analysis of S9 proteins from control cells and cells treated with FMEP extracts revealed that the airborne particulates increased proteins immunorelated to CYP1A1 and CYP1B1. Northern blot analysis of total cellular RNA from controls and cells treated with FMEP extracts showed that the cooking by-products increased the levels of CYP1A1 and CYP1B1 mRNA. Treatment with 1 microM dibenzo[a,h]anthracene for 6 h increased monooxygenase activities, CYP1A1 and CYP1B1 protein and mRNA levels in CL5 cells. Beef FMEP extract and dibenzo[a,h]anthracene also induced CYP1A1 and CYP1B1 in human lung carcinoma NCI-H322 cells. The present finding demonstrates that airborne particulates generated during the frying of beef, fish and pork can induce carcinogen-metabolizing CYP1A1 and CYP1B1 in the human lung-derived cell line CL5.

Summary of information on human CYP enzymes: human P450 metabolism data

This chapter is an update of the data on substrates, reactions, inducers, and inhibitors of human CYP enzymes published previously by Rendic and DiCarlo (1), now covering selection of the literature through 2001 in the reference section. The data are presented in a tabular form (Table 1) to provide a framework for predicting and interpreting the new P450 metabolic data. The data are formatted in an Excel format as most suitable for off-line searching and management of the Web-database. The data are presented as stated by the author(s) and in the case when several references are cited the data are presented according to the latest published information. The searchable database is available either as an Excel file (for information contact the author), or as a Web-searchable database (Human P450 Metabolism Database, www.gentest.com) enabling the readers easy and quick approach to the latest updates on human CYP metabolic reactions.

Toxicological, medical and industrial hygiene aspects of glutaraldehyde with particular reference to its biocidal use in cold sterilization procedures

Aqueous solutions of > or =5% glutaraldehyde (GA) are of moderate acute peroral toxicity and those of < or =2% are of slight toxicity. By single sustained skin contact, aqueous GA solutions of > or =45% are of moderate acute percutaneous toxicity, those of 25% are of slight toxicity and those of </=15% do not present an acute percutaneous hazard. Vapor generated at ambient temperature may cause sensory irritant effects to the eye and respiratory tract, but not acute respiratory tract injury. The 50% decrease in respiratory rate (rd(50)) is 13.86 ppm. A 0.1% solution of GA is not irritating to the eye; the threshold for conjunctival irritation is 0.2% and for corneal injury it is 1.0%. Eye injury is moderate at 2% and severe at > or =5%. Primary skin irritation depends on the duration and contact site, occlusion and solvent. By sustained contact, the threshold for skin irritation is 1%, above which erythema and edema are dose related. With 45% and higher, skin corrosion may occur. There is a low incidence of skin sensitizing reactions, with an eliciting threshold of 0.5% aqueous GA. However, GA is neither phototoxic nor photosensitizing. Subchronic repeated exposure studies by the peroral route show only renal physiological compensatory effects, secondary to reduced water consumption. Repeated skin contact shows only minor skin irritant effects without systemic toxicity. By subchronic vapor exposure, effects are limited to the nasal mucosa at 1.0 ppm, with a no-effect concentration generally at 0.1 ppm. There is no evidence for systemic target organ or tissue toxicity by subchronic repeated exposure by any route. A chronic drinking water study showed an apparent increase, in females only, of large granular cell lymphocytic leukemia but this was not dosage related. This is most likely the result of a modifying effect on the factor(s) responsible for the expression of this commonly occurring rat neoplasm. A chronic (2-year) inhalation toxicity/oncogenicity study showed inflammatory changes in the anterior nasal cavity but no neoplasms or systemic toxicity. In vitro genotoxicity studies--bacterial mutagenicity, forward gene mutation (HGPRT and TK loci), sister chromatid exchange, chromosome aberration, UDS and DNA repair tests--have given variable results, ranging from no effect through to weak positive. In vivo genotoxicity studies--micronucleus, chromosome aberration, dominant lethal and Drosophila tests--generally have shown no activity but one mouse intraperitoneal study showed bone marrow cell chromosome aberrations. Developmental toxicity studies show GA not to be teratogenic, and a two-generation study showed no adverse reproductive effects. Percutaneous pharmacokinetic studies showed low skin penetration, with lowest values measured in vitro in rats and human skin. Overexposure of humans produces typical sensory irritant effects on the eye, skin and respiratory tract. Some reports have described an asthmatic-like reaction by overexposure to GA vapor. In most cases this resembles reactive airways dysfunction syndrome, and the role of immune mechanisms is uncertain. Local mucosal effects may occur if medical instruments or endoscopes are not adequately decontaminated. Protection of individuals from the potential adverse effects of GA exposure requires that there be adequate protection of the skin, eyes and respiratory tract. The airborne concentration of GA vapor should be kept below the recommended safe exposure level (e.g. the threshold limit value) by the use of engineering controls. Those who work with GA should, through a training program, be aware of the properties of GA, its potential adverse effects, how to handle the material safely and how to deal with accidental situations involving GA. If effects develop in exposed workers, the reasons should be determined immediately and corrective methods initiated. (c) 2001 John Wiley & Sons, Ltd.